[Federal Register Volume 71, Number 10 (Tuesday, January 17, 2006)]
[Proposed Rules]
[Pages 2710-2808]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 06-179]



[[Page 2709]]

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Part III





Environmental Protection Agency





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40 CFR Parts 53 and 58



Revisions to Ambient Air Monitoring Regulations; Proposed Rule

  Federal Register / Vol. 71, No. 10 / Tuesday, January 17, 2006 / 
Proposed Rules  

[[Page 2710]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 53 and 58

[EPA-HQ-OAR-2004-0018; FRL-8015-9]
RIN 2060-AJ25


Revisions to Ambient Air Monitoring Regulations

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule; amendments.

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SUMMARY: The EPA is proposing to revise the ambient air monitoring 
requirements for criteria pollutants. This proposal establishes ambient 
air monitoring requirements in support of the proposed revisions to the 
National Ambient Air Quality Standards (NAAQS) for particulate matter 
published elsewhere in today's Federal Register, including new minimum 
monitoring network requirements for PM10-2.5 and criteria 
for approval of Federal reference and equivalent methods for 
PM10-2.5 (to supplement the Federal reference method for 
PM10-2.5 proposed elsewhere in today's Federal Register). 
This proposal also requires each State to operate one to three 
monitoring stations that take an integrated, multipollutant approach to 
ambient air monitoring. The proposed amendments modify the requirements 
for ambient air monitors by focusing requirements on populated areas 
with air quality problems and significantly reducing the requirements 
for criteria pollutant monitors that have measured ambient air 
concentrations well below the applicable NAAQS. Other proposed 
amendments revise the requirements for reference and equivalent method 
determinations (including specifications and test procedures) for fine 
particulate monitors, monitoring network descriptions and periodic 
assessments, quality assurance, and data certification. The purpose of 
the proposed amendments is to enhance ambient air quality monitoring to 
better serve current and future air quality management and research 
needs.

DATES: Comments must be received on or before April 17, 2006.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2004-0018, by one of the following methods:
     http://www.regulations.gov: Follow the on-line 
instructions for submitting comments.
     E-mail: [email protected].
     Fax: (202) 566-1741.
     Mail: Revisions to Ambient Air Monitoring Regulations, 
Docket No. EPA-HQ-OAR-2004-0018, Environmental Protection Agency, 
Mailcode 6102T, 1200 Pennsylvania Ave., NW., Washington, DC 20460. 
Please include a total of two copies. In addition, please mail a copy 
of your comments on the information collection provisions to the Office 
of Information and Regulatory Affairs, Office of Management and Budget 
(OMB), Attn: Desk Officer for EPA, 725 17th St., NW., Washington, DC 
20503.
     Hand Delivery: EPA Docket Center, 1301 Constitution 
Avenue, NW., Room B102, Washington, DC 20460. Such deliveries are only 
accepted during the Docket's normal hours of operation, and special 
arrangements should be made for deliveries of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2004-0018. EPA's policy is that all comments received will be included 
in the public docket without change and may be made available online at 
http://www.regulations.gov, including any personal information 
provided, unless the comment includes information claimed to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Do not submit information that you 
consider to be CBI or otherwise protected through http://www.regulations.gov or e-mail. The http://www.regulations.gov Web site 
is an ``anonymous access'' system, which means EPA will not know your 
identity or contact information unless you provide it in the body of 
your comment. If you send an e-mail comment directly to EPA without 
going through http://www.regulations.gov your e-mail address will be 
automatically captured and included as part of the comment that is 
placed in the public docket and made available on the Internet. If you 
submit an electronic comment, EPA recommends that you include your name 
and other contact information in the body of your comment and with any 
disk or CD ROM you submit. If EPA cannot read your comment due to 
technical difficulties and cannot contact you for clarification, EPA 
may not be able to consider your comment. Electronic files should avoid 
the use of special characters, any form of encryption, and be free of 
any defects or viruses. For additional information about EPA's public 
docket, visit the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm.
    Docket: All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in http://www.regulations.gov or in hard copy at the Revisions to the 
Ambient Air Monitoring Regulations Docket, EPA/DC, EPA West, Room B102, 
1301 Constitution Ave., NW., Washington, DC. The Public Reading Room is 
open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding 
legal holidays. The telephone number for the Public Reading Room is 
(202) 566-1744, and the telephone number for the Air Docket is (202) 
566-1742.

FOR FURTHER INFORMATION CONTACT: For general questions concerning 
today's proposed amendments, please contact Mr. Lewis Weinstock, U.S. 
EPA, Office of Air Quality Planning and Standards, Emissions Monitoring 
and Analysis Division, Ambient Air Monitoring Group (D243-02), Research 
Triangle Park, North Carolina 27711; telephone number: (919) 541-3661; 
fax number: (919) 541-1903; e-mail address: [email protected]. 
For technical questions, please contact Mr. Tim Hanley, U.S. EPA, 
Office of Air Quality Planning and Standards, Emissions Monitoring and 
Analysis Division, Ambient Air Monitoring Group (D243-02), Research 
Triangle Park, North Carolina 27711; telephone number: (919) 541-4417; 
fax number: (919) 541-1903; e-mail address: [email protected].

SUPPLEMENTARY INFORMATION:

I. General Information

A. Does This Action Apply to Me?

    Categories and entities potentially regulated by this action 
include:

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                           Category                               NAIC code 1    Examples of regulated entities
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Industry......................................................          334513  Manufacturer, supplier,
                                                                        541380   distributor, or vendor of
                                                                                 ambient air monitoring
                                                                                 instruments; analytical
                                                                                 laboratories or other
                                                                                 monitoring organizations that
                                                                                 elect to submit an application
                                                                                 for a reference or equivalent
                                                                                 method determination under 40
                                                                                 CFR part 53.

[[Page 2711]]

 
Federal government............................................          924110  Federal agencies (that conduct
                                                                                 ambient air monitoring similar
                                                                                 to that conducted by States
                                                                                 under 40 CFR part 58 and that
                                                                                 wish EPA to use their
                                                                                 monitoring data in the same
                                                                                 manner as State data) or that
                                                                                 elect to submit an application
                                                                                 for a reference or equivalent
                                                                                 method determination under 40
                                                                                 CFR part 53.
State/local/tribal government.................................          924110  State, territorial, and local,
                                                                                 air quality management programs
                                                                                 that are responsible for
                                                                                 ambient air monitoring under 40
                                                                                 CFR part 58 or that elect to
                                                                                 submit an application for a
                                                                                 reference or equivalent method
                                                                                 determination under 40 CFR part
                                                                                 53. The proposal also may
                                                                                 affect Tribes that conduct
                                                                                 ambient air monitoring similar
                                                                                 to that conducted by States and
                                                                                 that wish EPA to use their
                                                                                 monitoring data in the same
                                                                                 manner as State monitoring
                                                                                 data.
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1 North American Industry Classification System.

    This table is not intended to be exhaustive, but rather provides a 
guide for readers regarding entities likely to be regulated by this 
action. To determine whether your facility or Federal, State, local, or 
territorial agency would be regulated by this action, you should 
examine the requirements for reference or equivalent method 
determinations in 40 CFR part 53, subpart A (General Provisions) and 
the applicability criteria in 40 CFR 51.1 of EPA's requirements for 
State implementation plans. If you have any questions regarding the 
applicability of this action to a particular entity, consult the person 
listed in the preceding FOR FURTHER INFORMATION CONTACT section.

B. What Should I Consider as I Prepare My Comments for EPA?

    Do not submit information containing Confidential Business 
Information (CBI) to EPA through www.regulations.gov or e-mail. Send or 
deliver information identified as CBI only to the following address: 
Roberto Morales, OAQPS Document Control Officer (C404-02), U.S. EPA, 
Office of Air Quality Planning and Standards, Research Triangle Park, 
North Carolina 27711, Attention Docket ID EPA-HQ-OAR-2004-0018. Clearly 
mark the part or all of the information that you claim to be CBI. For 
CBI information in a disk or CD ROM that you mail to EPA, mark the 
outside of the disk or CD ROM as CBI and then identify electronically 
within the disk or CD ROM the specific information that is claimed as 
CBI. In addition to one complete version of the comment that includes 
information claimed as CBI, a copy of the comment that does not contain 
the information claimed as CBI must be submitted for inclusion in the 
public docket. Information so marked will not be disclosed except in 
accordance with procedures set forth in 40 CFR part 2.

C. Where Can I Get a Copy of This Document and Other Related 
Information?

    In addition to being available in the docket, an electronic copy of 
today's proposed amendments is also available on the Worldwide Web 
(WWW) through the Technology Transfer Network (TTN). Following the 
Administrator's signature, a copy of the proposed amendments will be 
placed on the TTN's policy and guidance page for newly proposed or 
promulgated rules at http://www.epa.gov/ttn/oarpg. The TTN provides 
information and technology exchange in various areas of air pollution 
control.

D. Will There Be a Public Hearing?

    Public hearings will be held concurrently with the public hearings 
on the proposed amendments to the NAAQS for particulate matter 
published elsewhere in this Federal Register. The EPA intends to hold 
public hearings during February 2006 in Philadelphia, Pennsylvania; 
Chicago, Illinois; and San Francisco, California. The EPA will announce 
the date, location, and time of the public hearings in a separate 
Federal Register notice.

E. Did EPA Conduct a Peer Review Before Issuing This Notice?

    The EPA sought expert scientific review of the proposed methods, 
technologies, and approach for ambient air monitoring by the Clean Air 
Scientific Advisory Committee (CASAC). The CASAC is a Federal advisory 
committee established to review scientific and technical information 
and make recommendations to the EPA Administrator on issues related to 
the air quality criteria and corresponding NAAQS. CASAC constituted a 
National Ambient Air Monitoring Strategy (NAAMS) Subcommittee in 2003 
to provide advice for a strategy for the national ambient air 
monitoring programs. This subcommittee, which operated over a one-year 
period, and a new subcommittee on Ambient Air Monitoring and Methods 
(AAMM), formed in 2004, provided the input for CASAC on its 
consultations, advisories, and peer-reviewed recommendations to the EPA 
Administrator.
    In July 2003, the CASAC NAAMS Subcommittee held a public meeting to 
review EPA's draft National Ambient Air Monitoring Strategy document 
(dated September 6, 2002), which contained technical information 
underlying planned changes to the ambient air monitoring networks. The 
EPA continued to consult with the CASAC AAMM Subcommittee throughout 
the development of the proposed amendments. Public meetings were held 
in July 2004, December 2004, and September 2005 to discuss the CASAC 
review of nearly 20 documents concerning methods and technology for 
measurement of particulate matter (PM); data quality objectives for PM 
monitoring networks and related performance-based standards for 
approval of equivalent continuous PM monitors; reconfiguration of 
ambient air monitoring stations; \1\ and other technical aspects of the 
proposed amendments. These documents, along with CASAC review comments 
and other information are available at: http://www.epa.gov/ttn/amtic/casacinf.html.
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    \1\ ``Station'' and ``site'' are used somewhat interchangeably 
in this notice of proposed rulemaking. When there is a difference 
``site'' generally refers to the location of a monitor, while 
``station'' refers to a suite of measurements at a particular site.
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F. How Is This Document Organized?

    The information presented in this preamble is organized as follows:

I. General Information
    A. Does this action apply to me?
    B. What should I consider as I prepare my comments for EPA?
    C. Where can I get a copy of this document and other related 
information?
    D. Will there be a public hearing?
    E. Did EPA conduct a peer review before issuing this notice?
    F. How is this document organized?
II. Overview

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    A. What is the purpose of today's proposal?
    B. What are the major changes proposed to the ambient air 
monitoring regulations?
    C. When would the proposed amendments affect States, local 
governments, tribes, and other stakeholders?
    D. How would EPA implement the new requirements?
III. Background
    A. What is the role of ambient air monitoring in air quality 
management?
    B. What is the history of ambient air monitoring?
    C. What revisions to the National Ambient Air Quality Standards 
for particulate matter also are proposed today?
    D. How do the monitoring data apply to attainment or 
nonattainment designations and findings?
IV. Proposed Monitoring Amendments
    A. What are the proposed terminology changes?
    B. What are the proposed requirements for approval of reference 
or equivalent methods?
    C. What are the proposed requirements for quality assurance 
programs for the National Ambient Air Monitoring System?
    D. What are the proposed monitoring methods for the National 
Ambient Air Monitoring System?
    E. What are the proposed requirements for the number and 
location of monitors to be operated by State and local agencies?
    F. What are the proposed probe and monitoring path siting 
criteria?
    G. What are the proposed data reporting, data certification, and 
sample retention requirements?
V. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From 
Environmental Health and Safety Risks
    H. Executive Order 13211: Actions that Significantly Affect 
Energy Supply, Distribution, or Use
    I. National Technology Transfer Advancement Act
    J. Executive Order 12898: Federal Actions to Address 
Environmental Justice in Minority Populations and Low-Income 
Populations

II. Overview

A. What Is the Purpose of Today's Proposal?

    The EPA is proposing a number of changes to the ambient air quality 
monitoring requirements of 40 CFR parts 53 and 58 to ensure that the 
national network of air monitors will meet the current and future data 
needs of EPA (and other Federal), State, local, and tribal air quality 
management agencies. While much of today's proposed rule outlines 
changes to the monitoring requirements for particulate matter (PM), 
there are additional changes relating to all the other criteria 
pollutants (ozone (O3), carbon monoxide (CO), sulfur dioxide 
(SO2), nitrogen dioxide (NO2), and lead (Pb)) 
included in this proposal.
    Some of these proposed changes are in support of the proposed 
revisions to the National Ambient Air Quality Standards (NAAQS) for PM 
in 40 CFR part 50 published elsewhere in today's Federal Register.\2\ 
These changes are essential to implementation of the proposed NAAQS for 
PM. Included among these proposed PM-related changes are new provisions 
for addition to 40 CFR parts 53 and 58 which address approval of 
methods and PM10-2.5 monitoring requirements. The added 
provisions would address federal reference method (FRM) equivalency 
determinations for continuous PM10-2.5 monitors and the 
requirements for the number of PM10-2.5 monitors a State 
must deploy. Another important element of the provisions for 
PM10-2.5 is a proposal for the conditions under which a 
PM10-2.5 monitor may be compared to the PM10-2.5 
NAAQS.
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    \2\ The proposed amendments to the National Ambient Air Quality 
Standards include revised standards for PM2.5 
(particulate mater with an aerodynamic diameter less than or equal 
to a nominal 2.5 micrometers) and new standards for 
PM10-2.5 (particulate matter with an aerodynamic diameter 
less than or equal to a nominal 10 micrometers and greater than or 
equal to a nominal 2.5 micrometers).
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    A number of amendments to existing provisions for PM2.5 
monitoring are also proposed. These would be important to the 
implementation of the revised PM2.5 NAAQS because they take 
advantage of the experience and insight gained by EPA and the States 
during the past 7 years of PM2.5 monitoring. One of the 
proposed PM2.5 changes involves the criteria for FRM 
equivalency determinations for continuous PM2.5 monitors. We 
anticipate that this change would allow States to operate continuous 
monitors at more required monitoring sites, providing more robust data 
for the PM2.5 air quality program.
    Other proposed changes are based on EPA's assessment that the 
monitoring regulations are not fully aligned with current data needs 
and opportunities across all the NAAQS pollutants--including PM but 
also including O3, CO, SO2, NO2, and 
Pb. This misalignment has developed over time as ambient conditions 
have improved for some pollutants. Also, new monitoring technologies 
have been developed that provide attractive opportunities for obtaining 
more robust and useful data. The EPA recognized that changes were 
needed several years ago and since then, we have been developing the 
specifics of these changes with States and other stakeholders.\3\ This 
group of proposed changes includes relaxation of some long-standing 
monitoring requirements which we believe are outdated or unnecessarily 
inflexible. This group of proposed changes also includes a new 
requirement for States to operate a new type of multipollutant 
monitoring station, which we plan to call National Core (NCore) 
stations. Other proposed changes relate to quality assurance 
requirements, monitor siting, special purpose monitoring, and data 
management.
    We are proposing both the PM NAAQS review-related changes as well 
as the overarching NAAQS monitoring system changes together because 
they are strongly related in terms of regulatory language and in terms 
of implementation decision making. Resources for ambient monitoring are 
limited, and the cost of new types of monitoring to meet new 
requirements such as those for PM10-2.5 must be offset, at 
least in part, by reducing resources for lower value types of 
monitoring. The proposed revisions to the monitoring regulations, when 
finalized, will improve EPA's and our monitoring partners' abilities to 
manage available funds to support monitoring activities and create a 
coordinated, integrated, multipurpose, and flexible monitoring system. 
In addition, it will be easier for the public to comment on the 
proposed changes if they are presented together rather than in 
sequential proposals.
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    \3\ Our work with States and other monitoring program 
stakeholders has included the development of successive versions of 
a draft report, ``National Ambient Air Monitoring Strategy''. The 
most recent version, dated December 2005, is available in the public 
docket. The document describes in more depth the reasons for 
proposing many of the changes presented in this notice, excluding 
the changes related to PM10-2.5. It also discusses 
strategy elements that are related to, but separate from, the 
regulatory provisions in 40 CFR parts 53 and 58 such as funding, 
training, etc.
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    The EPA notes that in the proposed regulatory language for 40 CFR 
parts 53 and 58, we are reprinting a number of existing provisions 
without change (for example, a number of definitions in current 58.1). 
We are doing so solely for the readers' convenience in order that the 
provisions we are proposing can appear in a single context. The EPA is 
not reproposing, reconsidering, or otherwise reopening any of these 
reprinted provisions. We will regard any comments as to these 
provisions as outside the scope of this proposal.

[[Page 2713]]

B. What Are the Major Changes Proposed to the Ambient Air Monitoring 
Regulations?

    The summary of each proposed change given here ends with a 
reference to the part(s) of section IV of this preamble that describes 
that change in detail.
     We propose to require States to operate from one to three 
National Core (NCore) multipollutant monitoring sites.\4\ Monitors at 
NCore multipollutant sites would be required to measure particles 
(PM2.5, speciated PM2.5, PM10-2.5), 
O3, SO2, CO, nitrogen oxides (NO/NO2/
NOY), and basic meteorology. Monitors for all the gases 
except for O3 would be required to be more sensitive than 
standard Federal reference method (FRM)/Federal equivalent method (FEM) 
monitors, so they could accurately report concentrations that are well 
below the respective NAAQS but that can be important in the formation 
of O3 and PM. We are not proposing specific locations for 
these sites, but instead would collaborate on site selection with 
States individually and through multistate organizations. Our objective 
is that sites be located in broadly representative urban (about 55 
sites) and rural (about 20 sites) locations throughout the country to 
help characterize regional and urban patterns of air pollution. We 
expect that in many cases States would collocate these new stations 
with Photochemical Assessment Monitoring Station (PAMS) sites already 
measuring O3 precursors and/or National Air Toxic Trends 
Station (NATTS) sites measuring air toxics.
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    \4\ The National Core (NCore) multi-pollutant stations are part 
of an overall strategy to integrate multiple monitoring networks and 
measurements, including research grade sites and State and local air 
monitoring stations (SLAMS). Research grade sites would provide 
complex, research-grade monitoring data for special studies; the 
proposed amendments do not include requirements for these sites. 
SLAMS would include sites needed for National Ambient Air Quality 
Standard comparisons and other data needs of monitoring agencies. 
The number and placement of SLAMS monitors would vary according to 
the pollutant, population, and level of air quality problem. The 
April 2004 draft version of the National Ambient Air Monitoring 
Strategy presented a taxonomy in which monitoring stations belonged 
to three levels, called Level 1 (research sites), Level 2 (what are 
called NCore multipollutant sites in this notice), and Level 3 (what 
have been called SLAMS/NAMS (national air monitoring stations) in 
the past). The three Levels combined were referred to as the NCore 
System. We have decided to dispense with the three-level taxonomy 
because it does not encompass all relevant monitoring efforts. We 
now refer to the collection of all ambient air monitoring--including 
research sites, all types of monitoring by States and Tribes, and 
all types of ambient monitoring by Federal agencies--as the National 
Ambient Air Monitoring System (NAAMS). We are retaining the 
``NCore'' label for the multipollutant sites in particular, because 
the term with this meaning has become part of the vocabulary of the 
State/local monitoring community.
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    These sites would still create points of integration among the 
existing networks for criteria pollutants, each of which was originally 
designed with only a single pollutant in mind. Where collocated with 
sites already measuring O3 precursors or air toxics, the 
degree of integration across pollutants of concern would be even 
stronger. Data from these NCore sites would be used for several 
purposes that cannot be served as well using only data available from 
existing networks. Forecasting of the Air Quality Index (AQI) would be 
improved by feeding several collocated and interdependent pollutant 
concentration measurements into an air quality model in near real-time 
to better represent current conditions, from which the model could 
provide an improved forecast of O3 and particle levels for 
the public. Studies that track long-term trends of criteria pollutants, 
and thereby help demonstrate the accountability of implemented 
emissions control programs, would be improved by utilizing higher-
sensitivity monitoring equipment for pollutants whose measured levels 
are well below the NAAQS. Air quality model development and validation 
efforts would benefit by having a long-term network of several 
important and interdependent measurements at improved time-scales 
(e.g., hourly instead of daily sample concentrations on PM methods) at 
a network of sites expected to remain in place over many years to allow 
testing of how well models simulate co-pollutant interactions. Where 
applicable siting criteria for PM or O3 monitoring stations 
are met, NCore sites could also be used to satisfy minimum monitoring 
requirements for PM and O3 and data from these stations 
could be used in designation decisions and in development of control 
strategies.\5\ The NCore proposals are described more fully in section 
IV.E.1 of this preamble.
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    \5\ While not a part of our rationale for requiring States to 
operate these sites, we note that the data from them will also be of 
use in future health effects studies.
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     We propose monitoring requirements for PM10-2.5 
which are based on deploying a network of FEM monitors that would be 
approved based on criteria for comparability to monitors utilizing the 
FRM proposed elsewhere in today's Federal Register. Requirements for 
PM10-2.5 Class I, Class II, and Class III candidate 
equivalent methods would be established. The definition of a ``Class 
III equivalent method'' would allow for designation of continuous and 
semi-continuous ambient air monitoring methods for 
PM10-2.5.\6\ Because we intend that most of the monitors 
used in the PM10-2.5 network will use continuous or semi-
continuous equivalent methods, the proposal for Class III approval 
requirements is particularly important for PM10-2.5. We are 
also proposing minimum requirements for a PM10-2.5 
monitoring network, including criteria for the number of FRM/FEM 
monitoring sites in each metropolitan area (which would vary from zero 
to five) and criteria for how monitors should be placed within an area. 
Closely linked to the placement criteria is a proposed test for the 
suitability of a PM10-2.5 monitoring site for comparison 
with the PM10-2.5 NAAQS. We are also proposing that 
speciation monitoring of PM10-2.5 be required in some areas. 
These proposals appear in sections IV.B.2, IV.B.3, IV.B.5, and IV.B.6 
(dealing with equivalent methods) and section IV.E.2 (dealing with 
number of monitors, their placement, and the use of data from them in 
comparisons to the NAAQS) of this preamble.
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    \6\ Class I equivalent methods have only minor deviations or 
modifications from the specified reference method. Class II 
equivalent methods include other filter-based, integrated, 
gravimetric-type methods similar to the specified reference method 
but with greater deviations than allowed for a Class I method. Class 
III equivalent methods include all candidate PM2.5 and 
PM10-2.5 methods not classified as Class I or Class II. 
We expect that most candidate Class III equivalent methods will be 
continuous or semi-continuous methods.
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     We propose amendments to facilitate the wider use of 
continuous PM2.5 monitors by revising performance-based FEM 
equivalence standards for continuous PM2.5 monitors and 
allowing for approved regional methods (ARM) for continuous 
PM2.5 mass monitors. Existing requirements for 
PM2.5 Class I and Class II candidate equivalent methods 
would be revised, and new requirements for PM2.5 Class III 
candidate equivalent methods would be added. The definition of a Class 
III equivalent method would be revised to allow for designation of 
continuous and semi-continuous ambient air monitoring methods for 
PM2.5. These proposals appear in sections IV.B.4, IV.B.5, 
and IV.B.6 (FEM equivalence standards) and in section IV.D.2 (approved 
regional methods) of this preamble.
     In association with the proposed requirements for new 
PM10-2.5 stations and new NCore multipollutant stations, we 
propose to remove the existing requirements for certain numbers of 
State and local air FRM/FEM monitoring stations for CO, 
PM10, SO2, and NO2, and reduce them 
for Pb.

[[Page 2714]]

However, States would still need EPA approval to move or remove 
existing monitoring stations for these pollutants.\7\ To expedite 
reviews and provide more certainty to State planning, a specific 
process and several substantive criteria are proposed to govern EPA 
approval actions. Also, the requirement that EPA approval be obtained 
at the Administrator level (rather than the Regional Administrator 
level) for the subset of these monitors historically designated as NAMS 
would be eliminated, and all changes would be reviewed by the Regional 
Administrator.\8\ In addition, the requirements for monitoring of 
O3 precursors under the PAMS program would be reduced by 
about 50 percent. These proposed changes allow PAMS monitoring to be 
more customized to local data needs rather than meeting so many 
specific requirements common to all subject O3 nonattainment 
areas; the PAMS changes would also give States the flexibility to 
reduce the overall size of their PAMS programs--within limits--and to 
use the associated resources for other types of monitoring they 
consider more useful. Requirements for minimum numbers of O3 
and PM2.5 monitors would be retained, with small 
adjustments. The overall impact of these changes would be to retain 
comprehensive monitoring networks for PM2.5 and 
O3, and to reduce the number of SO2, CO, 
NO2, Pb, and PM10 monitors in areas that do not 
have air quality problems for these pollutants. PM2.5 and 
O3 monitoring would be mostly unaffected because 
PM2.5 and O3 are current nonattainment challenges 
and comprehensive monitoring is needed to support efforts to attain the 
NAAQS. Many existing monitors for SO2, CO, NO2, 
Pb, and PM10 can be discontinued because they are now well 
below the applicable NAAQS and the data from most of these monitors 
have low value for air quality management and research purposes. We 
expect reductions in the number of monitors for these pollutants 
nationally to be in the range of about 33 percent for SO2 to 
about 90 percent for NO2.\9\ This would free up resources to 
go beyond minimum requirements for O3, PM2.5, 
PM10-2.5, or other pollutants such as air toxics in areas 
where there are ongoing or new air quality management challenges. These 
proposed changes are described in sections IV.E.3 (number of 
PM2.5 monitors), IV.E.4 (PM10 monitors), IV.E.5 
(number of O3 monitors), IV.E.6 (number of CO, 
SO2, NO2, and Pb monitors), IV.E.7 (PAMS 
monitors), and IV.E.8 (process and criteria for moving or removing 
monitors) of this preamble.
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    \7\ Where the PM10 annual and 24-hour NAAQS have both 
been revoked, the proposed rule does not require prior EPA approval 
for discontinuing a PM10 monitor.
    \8\ EPA Administrator approval would continue to be required for 
changes to some PM2.5 speciation monitoring stations, to 
any required NCore multipollutant station, and to any PAMS station.
    \9\ Detailed estimates of the current and expected future number 
of each type of monitor over the 3 years following promulgation are 
given in the supporting statement to the Information Collection 
Request for this action, available in the docket.
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     We propose updated quality assurance (QA) requirements for 
all NAAQS pollutants, emphasizing the responsibility of each monitoring 
program for its data quality based on the use of data quality 
objectives for monitoring precision, data completeness, and bias. 
States would be required to provide for adequate, independent 
performance audits of FRM/FEM monitoring stations. We describe several 
options for how they could meet this audit responsibility. One way 
would be to agree to have appropriated State and Territorial Air Grant 
(STAG) funds retained by EPA to cover the cost of performing these 
audits; another option would be a partnership between State/local 
monitoring agencies (or independent subunits within one agency). The 
statistics for calculating precision and bias would also would be 
revised. Quality assurance requirements would be defined for 
PM10-2.5 monitoring. See section IV.C of this preamble for 
details.
     We propose to revise the provisions regarding special 
purpose monitors (SPM) for all NAAQS pollutants. In certain restricted 
situations, data from SPM would not be usable for nonattainment 
designations. SPM that are FRM, FEM, or ARM monitors would be required 
to meet standard quality assurance requirements for their monitor type, 
and States would be required to report data from such SPM to the Air 
Quality System (AQS). See section IV.E.9 of this preamble for details.
     We propose to require that States conduct in-depth network 
assessments every 5 years. These assessments are intended to ensure 
that future gaps between data needs and monitoring operations are 
identified and filled in a timely manner. See section IV.E.11 of this 
preamble for specifics.
     We propose to move requirements for reporting certain 
operational data from PM samplers from 40 CFR part 50 to 40 CFR part 
58, and to reduce the number of data elements required to be reported. 
This would put all similar data reporting requirements together in 40 
CFR part 58 and allow them to apply to both FRM and FEM monitors. See 
section IV.G.1 of this preamble.
     We propose a new requirement for the reporting of 
PM2.5 field blank data.\10\ Only the data from field blanks 
which States are already taking into the field and weighing in their 
laboratories would be required to be reported under this proposal. 
Having the data from these field blanks available to the national 
monitoring community would help EPA and other researchers understand 
the relationship between the mass of PM that is sampled and weighed on 
a regular PM filter and the PM that is actually present in ambient air. 
See section IV.G.2 of this preamble or details.
---------------------------------------------------------------------------

    \10\ Field blanks are filters which are handled in the field as 
much as possible like actual filters except that ambient air is not 
pumped through them, to help quantify contamination and sampling 
artifacts.
---------------------------------------------------------------------------

     We propose to require State or local agencies to submit 
annual data certification letters, by May 1 of each year, to certify 
that the ambient air concentration and QA data submitted to EPA's AQS 
for the previous year are complete and accurate. These letters are now 
required on July 1 of each year. See section IV.G.3 of this preamble.
     We propose to require States to archive PM2.5 
and PM10-2.5 filters for one year (the current requirement 
is only for PM2.5 filters).\11\ See section IV.G.4 of this 
preamble.
---------------------------------------------------------------------------

    \11\ A PM10-2.5 ``filter'' from a FRM monitor would 
actually consist of the separate PM10 and 
PM2.5 filters. Some equivalent methods, if approved, 
could involve a single PM10-2.5 filter. All filters from 
both types of monitors would be subject to the archiving 
requirement.
---------------------------------------------------------------------------

     We propose to increase the distance that ozone monitors 
should be placed downwind of roadways, to reduce the possibility that 
ozone readings will be artificially low due to ozone scavenging by NO 
emitted by vehicles on roadways. See section IV.F of this preamble.

C. When Would the Proposed Amendments Affect State and Local 
Governments, Tribes, and Other Stakeholders?

1. State and Local Governments
    Only State governments, and those local governments that have been 
assigned responsibility for ambient air monitoring by their States, are 
subject to the mandatory requirements of 40 CFR part 58.\12\
---------------------------------------------------------------------------

    \12\ Throughout this preamble, ``States'' is meant to also refer 
to local governments that have been assigned responsibility for 
ambient air monitoring within their respective jurisdiction by their 
States. We also use ``monitoring organization'' to refer to States, 
local agencies, and/or Tribes conducting monitoring under or guided 
by the provisions of 40 CFR part 58.
---------------------------------------------------------------------------

    The proposed compliance date for deployment of PM10-2.5 
monitors by States is January 1, 2009. A plan for this

[[Page 2715]]

deployment would be due January 1, 2008, unless an extension is granted 
to July 1, 2008. These plans would be subject to EPA approval at the 
Regional Office level.
    State (or local) agencies would also be required to submit earlier 
annual data certification letters and make electronic reports of QA 
data to the AQS, starting May 1, 2009.
    The proposed amendments require that State (or local) agencies 
fully implement the required NCore multipollutant sites by January 1, 
2011 (more than 4 years after the expected date of promulgation of the 
amendments). A plan for this implementation, including site selection, 
would be due July 1, 2009.
    Network assessments would be required every 5 years starting July 
1, 2009.
    State and local agencies would be required to comply with existing 
requirements in 40 CFR part 58 (including annual network review and 
data reporting), until the compliance date for each new requirement is 
reached.
    Some provisions in the proposed amendments to 40 CFR part 58 (those 
that do not involve deployment of new monitoring stations or new types 
of data handling) would be effective as of the effective date of the 
final rule.
2. Tribes
    Under the Tribal Authority Rule (TAR) (40 CFR part 49), which 
implements section 301(d) of the CAA, Tribes may elect to be treated in 
the same manner as a State in implementing sections of the CAA. 
However, the EPA determined in the TAR that it was inappropriate to 
treat Tribes in a manner similar to a State with regard to specific 
plan submittal and implementation deadlines for NAAQS-related 
requirements, including, but not limited to, such deadlines in CAA 
sections 110(a)(1), 172(a)(2), 182, 187, and 191. See 40 CFR 49.4(a). 
For example, an Indian tribe may choose, but is not required, to submit 
implementation plans for NAAQS related requirements, nor are they 
required to monitor. If a Tribe elects to do an implementation plan, 
the plan can contain program elements to address specific air quality 
problems in a partial program. The EPA will work with the Tribe to 
develop an appropriate schedule which meets the needs of each Tribe.
    Indian tribes have the same rights and responsibilities as States 
under the CAA to implement elements of air quality programs as they 
deem necessary. Tribes can choose to engage in ambient air monitoring 
activities. In many cases, Indian tribes are required by EPA regions to 
institute strict quality assurance programs, utilize FRM or FEM when 
comparing their data to the NAAQS, and to insure that the data 
collected is qualitative and representative of their respective 
airsheds. For FRM and FEM monitors used for NAAQS attainment or 
nonattainment determinations, quality assurance requirements of 40 CFR 
part 58 must be followed and would be viewed by EPA as an indivisible 
element of a regulatory air quality monitoring program.
3. Other Stakeholders
    Manufacturers of continuous PM2.5 and 
PM10-2.5 instruments would be able to apply for designation 
of their instruments as FEM as soon as the notice of final rulemaking 
is signed. The EPA is eager to receive such applications as soon as 
manufacturers can collect and analyze the necessary supporting data.

D. How Would EPA Implement the New Requirements?

    After promulgation, we would implement the new requirements using 
several mechanisms. We expect to work with each State to develop the 
monitoring plans for their new PM10-2.5 and NCore 
multipollutant monitoring stations. For example, we would negotiate the 
selection of required new monitoring sites (or new capabilities at 
existing sites) and their schedules for start up as well as plans to 
discontinue sites that were no longer needed. The EPA would negotiate 
with each State its annual grants for air quality management 
activities, including ambient monitoring work. We would negotiate 
grants that provide funding to meet minimum requirements and which have 
milestones for completion of necessary changes. Once States have 
established a new monitoring infrastructure to meet the new 
requirements, we would review State monitoring activities, submitted 
data, and plans for further changes on an annual basis.
    The EPA's support for and participation in enhancing the national 
ambient air monitoring system to serve current and future air quality 
management and research needs will extend beyond ensuring that States 
meet the minimum requirements of the monitoring rules, including the 
proposed amendments. We will work with each State or local air 
monitoring agency to determine what affordable monitoring activities 
above minimum requirements would best meet the diverse needs of the 
individual air quality management program as well as the needs of other 
data users. In particular, we may negotiate with some States, and 
possibly with some Tribes, for the establishment and operation of some 
additional rural NCore multipollutant monitoring stations to complement 
the multipollutant stations that would be required by the proposed 
changes to the monitoring regulations. We also expect to work with the 
States, and possibly with some Tribes, to establish and operate more 
PM10-2.5 speciation sites than the minimums that would be 
required by the proposed amendments. We expect to work with the States, 
and possibly with some Tribes, to establish and operate rural 
PM10-2.5 mass concentration sites in less urbanized 
locations.
    An important element of implementing the new requirements will be 
EPA's role in encouraging the development and application of Federal 
equivalent methods (FEM), in particular for continuous methods of 
measuring PM2.5 and PM10-2.5. We have determined 
that continuous monitoring of PM2.5 has many advantages over 
the filter-based Federal reference method. One of the proposed changes 
makes it more practical for manufacturers of continuous 
PM2.5 instruments to obtain designation for them as FEM or 
approved regional methods. To ensure objectivity and sound science, 
EPA's Office of Research and Development would continue to review 
applications for FEM designations based on the criteria proposed today 
and would recommend approval or disapproval to the EPA Administrator.
    We will also provide technical guidance documents and training 
opportunities for State, local, and Tribal monitoring staff to help 
them select, operate, and use the data from new types of monitoring 
equipment. We have already distributed a technical assistance document 
on the precursor gas monitors \13\ that will be part of the 
multipollutant sites and we have conducted three training workshops on 
these monitors. Additional guidance will be developed and provided on 
some other types of monitors with which many State monitoring staff are 
currently unfamiliar, and on network design, site selection, quality 
assurance, and other topics. While Tribes are not to be subject to the 
requirements of the proposed monitoring amendments,

[[Page 2716]]

these technical resources will also be available to them directly from 
EPA and via grantees, such as the Institute for Tribal Environmental 
Professionals and the Tribal Air Monitoring Support Center.
---------------------------------------------------------------------------

    \13\ Technical Assistance Document (TAD) for Precursor Gas 
Measurements in the NCore Multipollutant Monitoring Network. Version 
4. U.S. Environmental Protection Agency. EPA-454/R-05-003. September 
2005. Available at: http://www.epa.gov/ttn/amtic/pretecdoc.html.
---------------------------------------------------------------------------

    In partnership with States, we will also continue to plan and 
manage State technical assistance grants (STAG) to support the National 
Park Service's operation of the IMPROVE monitoring network, which 
provides important data for implementing both regional haze and 
PM2.5 attainment programs.\14\
---------------------------------------------------------------------------

    \14\ Additional information on EPA/National Park Service IMPROVE 
(Interagency Monitoring of Protected Visual Environments) Visibility 
Program is available at: http://www.epa.gov/ttn/amtic/visdata.html.
---------------------------------------------------------------------------

    We will also continue to operate the Clean Air Status and Trends 
Network (CASTNET), which monitors for O3, PM, and chemical 
components of PM in rural areas across the nation.\15\ We are in the 
process of revising CASTNET to upgrade its monitoring capabilities to 
allow it to provide even more useful data to multiple data users. We 
expect that about 20 CASTNET sites will have new capabilities at least 
equivalent to the capabilities envisioned for NCore multipollutant 
sites. Those sites would reduce the number of, and complement, rural 
multipollutant sites funded with limited State/local grant funds.
---------------------------------------------------------------------------

    \15\ Additional information on CASTNET is available at: http://www.epa.gov/castnet/.
---------------------------------------------------------------------------

    We recognize that some air quality management issues require 
ambient concentration and deposition data that cannot be provided by 
the types of monitoring required by the proposed monitoring amendments 
and other activities addressed in today's proposal. These issues 
include near-roadway exposures to emissions from motor vehicles and 
mercury deposition. We are actively researching these issues and 
developing plans for monitoring programs to address them, but these 
issues are outside the scope of this proposal.

III. Background

A. What Is the Role of Ambient Air Monitoring in Air Quality 
Management?

    Ambient air monitoring systems are a critical part of the nation's 
air quality management program infrastructure. We use the ambient air 
monitoring data for a wide variety of purposes as part of an iterative 
process in managing air quality. This iterative process involves a 
continuum of setting standards and objectives, designing and 
implementing control strategies, assessing the results of those control 
strategies, and measuring progress. The data have many uses throughout 
this system, such as: Determining compliance with the National Ambient 
Air Quality Standards (NAAQS); characterizing air quality status and 
trends; estimating health risks and ecosystem impacts; developing and 
evaluating emissions control strategies; and measuring overall progress 
for the air pollution control program. Ambient air monitoring data 
provide accountability for control strategy reductions by tracking 
long-term trends of criteria and noncriteria pollutants and their 
precursors. The data also form the basis for air quality forecasting 
and other public air quality reports.
    More detailed ambient monitoring data are needed to meet current 
and future program and research needs. The data collected by State and 
local agencies under the proposed monitoring amendments would:
     Provide more timely Air Quality Index reporting to the 
public by supporting continuous particle measurements needed for AIRNow 
air quality forecasting and other public reporting mechanisms;
     Improve the development of emissions control strategies 
through more effective air quality model evaluation and other 
observational methods; and
     Support long-term health assessments that contribute to 
ongoing reviews of the NAAQS and other scientific studies ranging 
across technological, health, and atmospheric process disciplines.

B. What Is the History of Ambient Air Monitoring?

1. Statutory Authority
    The EPA rules for ambient air monitoring are authorized under 
sections 110, 301(a), and 319 of the Clean Air Act (CAA). Section 
110(a)(2)(B) of the CAA requires that each State implementation plan 
(SIP) provide for the establishment and operation of devices, methods, 
systems, and procedures needed to monitor, compile, and analyze data on 
ambient air quality and for the reporting of air quality data to EPA. 
Section 301(a) of the CAA authorizes EPA to develop regulations needed 
to carry out the Agency's mission and establishes rulemaking 
requirements. Uniform criteria to be followed when measuring air 
quality and provisions for daily air pollution index reporting are 
required by CAA section 319.
2. Ambient Air Monitoring Regulations
    The EPA's procedures for determining and designating reference and 
equivalent methods (40 CFR part 53) have been in place since 1975 (40 
FR 7049, February 18, 1975). Reference methods for criteria pollutants 
provide uniform, reproducible measurements of concentrations in the 
ambient air. Equivalent methods allow for the introduction of new and 
innovative technologies for the same purpose, provided the technologies 
produce measurements comparable to reference methods under a variety of 
monitoring conditions.
    Subpart A of 40 CFR part 53 (General Provisions) establishes 
definitions; general requirements for designation of Federal reference 
methods (FRM) and Federal equivalent methods (FEM); procedures for 
submitting, processing, and approving applications; and associated 
provisions. The general requirements identify the applicable 
requirements or tests that a candidate method must meet to be approved 
as a FRM or FEM. All manual or automated methods must meet the 
applicable requirements in 40 CFR part 53, subpart C (Procedures for 
Determining Comparability Between Candidate Methods and Reference 
Methods). Automated equivalent methods for pollutants other than 
PM10 or PM2.5 also must meet the requirements in 
40 CFR part 53, subpart B (Procedures for Testing Performance 
Characteristics of Automated Methods for SO2, CO, 
O3, and NO2). A manual sampler or automated 
method for PM10, Class I equivalent method for 
PM2.5, or Class II equivalent method for PM2.5 
also must meet the requirements in 40 CFR part 53, subpart D 
(Procedures for Testing Performance Characteristics of Methods for 
PM10), subpart E (Procedures for Testing Physical (Design) 
and Performance Characteristics of Reference Methods and Class I 
Equivalent Methods for PM2.5), or subpart F (Procedures for 
Testing Performance Characteristics of Class II Equivalent Methods for 
PM2.5), as applicable. The existing rule adopts a case-by-
case approach for PM2.5 Class III candidate equivalent 
methods. The regulations in 40 CFR part 53 have been amended several 
times since 1975 to reflect the addition of new and revised reference 
methods and advances in monitoring methods and technologies for 
criteria pollutants.
    In 1979 (44 FR 27558, May 10, 1979), EPA issued the first 
regulations for ambient air quality surveillance (40 CFR part 58) for 
all pollutants subject to NAAQS. Within 40 CFR part 58, subpart A 
(General Provisions) establishes definitions, and subpart B (Monitoring 
Criteria) sets requirements for quality assurance, methods, siting, 
operating

[[Page 2717]]

schedules, and special purpose monitors. Subpart C (State and Local Air 
Monitoring Stations), subpart D (National Air Monitoring Stations), and 
subpart E (Photochemical Assessment Monitoring Stations) generally 
define the current monitoring networks. Appendices A through G to 40 
CFR part 58 contain more detailed requirements on quality assurance; 
monitoring methods, network design, and siting criteria; and air 
quality reporting. Subpart F (Air Quality Index Reporting), subpart G 
(Federal Monitoring), and appendices F and G to 40 CFR part 58 define 
annual and daily reporting requirements.
    Most of the major amendments to the monitoring regulations made 
after 1979 coincide with the NAAQS revisions and include the addition 
of provisions for PM10 (52 FR 24740, July 1, 1987) and 
PM2.5 (62 FR 38833, July 18, 1997). Photochemical assessment 
monitoring stations (PAMS) were established in 1993 to monitor ozone 
and visibility (58 FR 8468, February 12, 1993).
3. Monitoring Networks
    More than 5,500 monitors at about 3,000 sites in the State and 
local air monitoring stations (SLAMS) and national air monitoring 
stations (NAMS) networks comprise the majority of monitors measuring 
criteria pollutants using FRM or FEM for direct comparison to the 
NAAQS. The NAMS are a subset of SLAMS that are designated as national 
trends sites. The PM2.5 network consists of ambient air 
monitoring sites that make mass or chemical speciation measurements. 
Within the PM2.5 network operated by State and local 
agencies, there are approximately 1,200 FRM filter-based samplers and 
about 450 continuous monitors for mass measurements. Chemical 
speciation measurements are made at 54 ``Speciation Trends Network'' 
sites that are intended to remain in operation indefinitely and about 
200 other, potentially less permanent sites used to support SIP 
development and other monitoring objectives. These stations collect 
aerosol samples and analyze the filters for trace elements, major ions, 
and carbon fractions.
    Ambient air monitors in the PAMS network measure ozone precursors 
at 109 stations in 25 serious, severe, or extreme ozone nonattainment 
areas. The PAMS monitors use near-research-grade measurement 
technologies to produce continuous data for more than 50 volatile 
organic compounds during summer ozone seasons.
    In addition to the NAMS/SLAMS/PAMS sites, there are approximately 
310 ambient air toxics monitoring sites, the majority of which are 
Federally funded and report data to EPA's Air Quality System (AQS).
    Ambient air monitoring stations also are operated by Indian Tribes. 
Thirty-one Tribes are currently making data from 119 individual 
monitors available to EPA and others. Approximately 73 Tribal sites 
monitor for PM10 and PM2.5, and about 16 monitor 
for ozone.
    The Clean Air Status and Trends Network (CASTNET) is cooperatively 
operated and funded by EPA with the National Park Service. The EPA's 
Office of Air and Radiation operates a majority of the monitoring 
stations with contractor support; however, the National Park Service 
operates approximately 30 stations in cooperation with EPA. It the 
nation's primary source for data on dry acidic deposition and rural, 
ground-level ozone. Operating since 1987, CASTNET is used in 
conjunction with other national monitoring networks to provide 
information for evaluating the effectiveness of national emission 
control strategies. CASTNET consists of over 80 sites across the 
eastern and western U.S. The longest data records are primarily at 
eastern sites. CASTNET provides atmospheric data on the dry deposition 
component of total acid deposition, ground-level ozone and other forms 
of atmospheric pollution. More information is available from the 
CASTNET program Web site http://www.epa.gov/castnet/.
    The EPA is also one of many sponsors of the National Atmospheric 
Deposition Program/National Trends Network. The National Atmospheric 
Deposition Program/National Trends Network (NADP/NTN) is a nationwide 
network of precipitation monitoring stations. The NADP/NTN has over 200 
stations spanning the continental U.S., Alaska, and Puerto Rico, and 
the Virgin Islands. The purpose of the network is to collect data on 
the chemistry of precipitation for monitoring of geographical and 
temporal long-term trends. While distinct from ambient air monitoring, 
precipitation monitoring is related in that it shares same of the same 
objectives, including tracking the effects of emission reduction 
programs. More information on NADP is available at its Internet Web 
site, http://nadp.sws.uiuc.edu/.
    The EPA is a major funding sponsor of the Interagency Monitoring of 
Protected Visual Environments (IMPROVE) program. IMPROVE is a 
cooperative measurement effort governed by a steering committee 
composed of representatives from EPA, National Park Service, other 
Federal agencies, and Regional-State organizations. A total of 110 
monitoring stations in Class I visibility areas have particulate matter 
samplers to measure speciated PM2.5 and PM10 
mass. Select stations also deploy transmissometer and nephelometers to 
measure light extinction and scattering respectively, as well as 
automatic camera systems. Some IMPROVE stations include an 
O3 monitor. The objectives of IMPROVE are: (1) To establish 
current visibility and aerosol conditions in mandatory Class I areas; 
(2) to identify chemical species and emission sources responsible for 
existing man-made visibility impairment; (3) to document long-term 
trends for assessing progress towards the national visibility goal; (4) 
and with the enactment of the Regional Haze Rule, to provide regional 
haze monitoring representing all visibility-protected Federal Class I 
areas where practical. The IMPROVE stations provide very useful 
information on regional-scale particulate matter concentrations which 
can help States and EPA attribute urban concentrations of 
PM2.5 to local versus regional sources and to types of 
sources. More information on the IMPROVE program is available on its 
Internet Web site, http://vista.cira.colostate.edu/improve/.
4. Data Storage and Dissemination Systems
    a. Air Quality System. The AQS stores data collected from over 
10,000 monitors, about 5,500 of which are currently active for criteria 
pollutants. The AQS also contains meteorological data, air toxics data, 
descriptive information about each monitoring station (including its 
geographic location and its operator), and data quality assurance/
quality control information. The EPA and other AQS users rely upon the 
system data to assess air quality, assist in attainment and non-
attainment designations, evaluate SIP, perform modeling for permit 
review analysis, and other air quality management functions. The AQS 
information is also used to prepare reports for Congress as mandated by 
the CAA. The AQS Web site address is: http://www.epa.gov/ttn/airs/airsaqs/index.htm.
    b. AIRNow. AIRNow is a cross-government Web site (http://airnow.gov/) that provides the public with easy access to national air 
quality information. The Web site offers a daily forecast of conditions 
and associated health effects, known as the Air Quality Index (AQI), as 
well as real-time conditions for more than 300 cities across country. 
The AQI focuses on health effects that may occur within a

[[Page 2718]]

few hours or days after breathing polluted air. The EPA calculates the 
AQI for ground-level ozone, particulate matter, carbon monoxide, sulfur 
dioxide, and nitrogen dioxide. The AIRNow Web site displays nationwide 
and regional real-time PM2.5 and ozone air quality maps for 
48 States and parts of Canada. The air quality data used in these maps 
and to generate forecasts are collected using either FRM, FEM, or 
techniques approved by State monitoring agencies.
    c. Other existing data systems. Other existing data systems for 
ambient air quality-related data include EPA's National Emission 
Inventory (NEI) and AirData. The NEI database at http://www.epa.gov/ttn/chief/eiinformation.html provides information about sources that 
emit criteria air pollutants and estimates of annual air pollutant 
emissions from point, nonpoint, and mobile sources. The EPA compiles 
the NEI database from emissions inventories compiled by State and local 
environmental agencies based on State reporting requirements in 40 CFR 
part 51, agency rulemaking databases, and the Toxic Release Inventory 
data from industry. The EPA updates the NEI database every 3 years.
    The AirData Web site at http://www.epa.gov/air/data/ provides 
annual summaries of ambient monitoring and emissions inventory data 
from the AQS and NEI. The database includes emission estimates from all 
50 States plus the District of Columbia, Puerto Rico, and the U.S. 
Virgin Islands, and provides data in a variety of formats. Other web-
based data systems related to ambient air concentration data include 
VIEWS (http://vista.cira.colostate.edu/views/) to support analysis of 
visibility-related data from the IMPROVE network, and Web sites to 
support analysis of CASTNET (http://www.epa.gov/castnet/data.html) and 
NADP (http://nadp.sws.uiuc.edu/) data sets.
5. EPA Funding
    The EPA has historically funded part of the cost of installation 
and operation of monitors to meet Federal monitoring requirements to 
defray costs for State, local, and tribal governments. Sections 103 and 
105 of the CAA allow EPA to provide grant funding for programs for 
preventing and controlling air pollution and for some research and 
development efforts. States must apply for section 103 grants and State 
agencies must provide nonfederal matching funds for section 105 grants.

C. What Revisions to the National Ambient Air Quality Standards for 
Particulate Matter Also Are Proposed Today?

1. PM2.5: Primary Standards, Secondary Standard, and Federal 
Reference Method
    Elsewhere in this Federal Register, we are proposing revisions to 
the National Ambient Air Quality Standards (NAAQS) for particulate 
matter (PM). Under the proposal, the 24-hour primary standard for 
PM2.5 would be reduced from the current level of 65 
micrograms per cubic meter ([mu]g/m3) to 35 [mu]g/
m3 (based on the three-year average of the annual 98th 
percentile concentrations). We also are proposing to retain the level 
of the current annual PM2.5 standard at 15 [mu]g/
m3 and to add additional constraints to the use of spatial 
averaging to demonstrate compliance with that standard. The EPA is also 
proposing to revise the current secondary standards for 
PM2.5 by making them identical to the suite of proposed 
primary standards.
    The NAAQS proposal would also make several changes to the Federal 
reference method (FRM) for PM2.5 in 40 CFR part 50, appendix 
L. These changes would improve the operation and maintenance aspects of 
the PM2.5 monitoring network. Specifically, we are proposing 
to adopt the ``very sharp cut cyclone'' (VSCC) as an approved second-
stage impactor. The performance of the VSSC separator is equivalent to 
that of the WINS (Well Impactor Ninety Six) impactor currently 
specified in the proposed reference method and has a considerably 
longer service interval. We also are proposing to require dioctyl 
sebacate as an alternative oil approved for use in the WINS, to extend 
the maximum allowed time to recover filters from samplers, and to 
modify the filter transport temperature and post-sampling time 
requirements for final laboratory analysis.
2. PM10-2.5: Primary Standard, Secondary Standard, and 
Federal Reference Method
    The NAAQS proposal would also revise the current 24-hour primary 
standard for PM10 by replacing the indicator with a 
PM10-2.5 indicator. The proposed PM10-2.5 
indicator is qualified so as to include any ambient mix of 
PM10-2.5 that is dominated by resuspended dust from high-
density traffic on paved roads and PM generated by industrial sources 
and construction sources, and exclude any ambient mix of 
PM10-2.5 that is dominated by rural windblown dust and soils 
and PM generated by agricultural and mining sources. This standard 
shall not require control of agricultural sources and mining sources. 
The proposed level of the standard is 70 [mu]g/m3, based on 
the three-year average of the annual 98th percentile concentrations.
    Accordingly, the proposed revisions to the NAAQS include a new FRM 
for measuring PM10-2.5 (Reference Method for the 
Determination of Coarse Particulate Matter as PM10-2.5 in 
the Atmosphere) to be codified in a new appendix O to 40 CFR part 50. 
The proposed FRM is based on the combination of two low-volume, filter-
based methods, one for measuring PM10 and the other for 
measuring PM2.5, and determines the PM10-2.5 
measurement by subtracting the PM2.5 measurement from the 
concurrent PM10 measurement. The PM2.5 
measurement method is identical to the PM2.5 FRM currently 
specified in 40 CFR part 50, appendix L (Reference Method for the 
Determination of Fine Particulate Matter as PM2.5 in the 
Atmosphere), with the proposed changes described above. The 
PM10 measurement method is very similar and utilizes a 
sampler that is the same as the PM2.5 sampler, except that 
it has no PM2.5 particle size separator downstream of the 
PM10 separator. Thus, this proposed PM10-2.5 FRM 
is based on the same aerodynamic particle size separation and filter-
based, gravimetric technology that is also the basis of the FRM for 
PM2.5 (with the proposed changes described above).
3. Data Handling Procedures for PM2.5 and 
PM10-2.5
    In the PM NAAQS proposal published elsewhere in today's Federal 
Register, EPA is also proposing to revise the conditions under which 
spatial averaging of the annual primary PM2.5 NAAQS would be 
permitted. We also propose to move the criteria for determining if 
spatial averaging is acceptable from section 2.8.1.6.1 of appendix D to 
40 CFR part 58 to appendix N of 40 CFR part 50 (Interpretation of the 
National Ambient Air Quality Standards for PM2.5). We also 
propose to add a new appendix P to 40 CFR part 50 (Interpretation of 
the National Ambient Air Quality Standards for PM10-2.5) to 
provide data handling procedures for PM10-2.5.
4. Revocation of National Ambient Air Quality Standards for 
PM10
    In the PM NAAQS proposal, we are proposing to revoke the current 
annual PM10 standard immediately should we finalize the 
primary standards for PM10-2.5 proposed in that notice. 
Further, we propose that the current 24-hour PM10 standard 
be revoked in all

[[Page 2719]]

areas except for 20 areas listed in section III of the NAAQS proposal 
preamble.

D. How Do the Monitoring Data Apply to Attainment or Nonattainment 
Designations and Findings?

    The criteria for determining when it is appropriate to compare 
ambient monitoring data from a specific monitor and period to a 
National Ambient Air Quality Standard (NAAQS) is an important element 
of the air quality management system because it can identify what 
geographic areas have air quality problems and may be designated as 
nonattainment.
    Later sections of this preamble, discussing the proposed monitoring 
requirements for the proposed PM10-2.5 NAAQS and the 
proposed provisions for special purpose monitors (SPM), discuss the use 
of monitoring data for attainment or nonattainment designations. We are 
also proposing a change related to the required spacing between ozone 
(O3) monitors and roadways. Finally, we are proposing 
changes to some quality assurance requirements. This section of the 
preamble provides background information on current EPA policy and 
regulations in order to facilitate informed public comment on these 
aspects of today's proposal.
    There are some preconditions to use of data from an ambient monitor 
for comparison to an NAAQS that generally apply to the current NAAQS 
for O3, PM10, PM2.5, CO, 
SO2, NO2, and Pb, with a few exceptions and/or 
the opportunity for waiver by EPA.\16\ These include the following:
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    \16\ Monitors that have received waivers are eligible for 
comparison to their respective NAAQS.
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     The monitoring site must represent ambient air, as defined 
in 40 CFR 50.1 (i.e., ``that portion of the atmosphere, external to 
buildings, to which the general public has access''). In practical 
terms, this means that data from monitoring sites within the boundaries 
of a privately-owned facility to which public access is restricted, for 
example, a storage yard of a factory, are not eligible for comparison 
to the NAAQS. (On occasion, EPA has relied on data from such sites when 
the air sampled is ambient air, even though the monitor may be sited on 
a facility to which public access is restricted (e.g., the monitor is 
very close to a fence line and is monitoring the conditions that are 
present in the adjacent publicly accessible property.) Data from a 
monitor in ambient air as so defined can be compared to the NAAQS even 
if members of the public infrequently come near the monitor's location 
(e.g., O3 monitors that are located on the ground on high 
elevation mountain sites). However, data from monitors located high 
above standing/walking ground level, such as on a high roof or tower, 
are not eligible for comparison to an NAAQS. It should be noted that 
although monitors are often sited with the intention to represent an 
area of a certain geographic scale, in general, a monitor need not be 
representative of the ambient air quality across an area of any 
specific size to be eligible for comparison to most NAAQS. However, as 
described in section IV.E.2 of this preamble, the current annual 
PM2.5 NAAQS is an exception, and the proposed 24-hour 
PM10-2.5 NAAQS would be an exception. (See also the item in 
this list regarding proximity of O3 and CO monitors to 
roadways.)
     The monitor must use a Federal reference method (FRM) or 
Federal equivalent method (FEM).
     The monitoring data must be technically valid so as to be 
truly representative of the actual air quality at its location during 
the sampline period, subject to the normal limitations of the FRM or 
FEM when properly operating. Generally, this means that the monitor's 
operation and subsequent sample handling and laboratory analysis, if 
applicable, must observe minimum quality assurance (QA) procedures, as 
set forth in 40 CFR 58.10 and 40 CFR part 58, appendices A and B 
(consolidated into a single appendix A in the proposed amendments), to 
guard against equipment malfunction, miscalibration, drift, or operator 
error. When States document that these procedures have been followed, 
the data are presumed to be valid although specific evidence of 
instrument faults or procedural errors can cause EPA to disregard data 
from particular periods. When documentation on whether these specific 
procedures have been followed is not available to EPA, as may be the 
case if a State has not submitted QA data to the Air Quality System 
(AQS) or if the monitoring was performed by a non-State organization 
not subject to the QA requirements in 40 CFR part 58, appendices A and 
B, the validity of data is considered on a case-by-case basis if the 
issue is raised by EPA, the State, or another party during an NAAQS 
designation process.
     The monitoring probe inlet (or open path, for open path 
monitors) must meet certain requirements for distance from adjacent 
roadways. This is a feature of the current monitoring requirements in 
40 CFR part 58, appendix E (Probe and Monitoring Path Siting Criteria 
for Ambient Air Quality Monitoring) and the proposed amendments.\17\ 
Ozone monitors too close to a roadway may be measuring air in which 
O3 has been scavenged by nitric oxide (NO). Carbon monoxide 
and NO2 monitors that are too close to a roadway can measure 
concentrations that do not represent likely human exposures of any 
significant frequency or duration. Requirements regarding spacing from 
roadways can be waived if no other suitable site is available.
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    \17\ Minimum separation distance requirements in the current 
rule apply to O3, NO2, CO, Pb (for stations 
designed to assess concentrations from mobile sources) and PM 
(PM10 and PM2.5). Under the proposed 
amendments, minimum separation distance requirements would apply to 
O3, oxides of nitrogen (NO, NO2, 
NOX, NOy), CO, PM (PM10, 
PM2.5, PM10-2.5) and Pb for 
stations designed to assess concentrations from stationary or mobile 
sources.
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     The monitoring probe inlet (or open path, for open path 
monitors) must meet certain minimum distance limits for proximity to 
nearby obstructions, such as walls of buildings.
     The probe height above the surface on which the public 
would stand or walk nearby must be within a certain range so that the 
air it samples is reasonably representative of what the public breathes 
when near the monitor. This requirement can be waived for practicality 
reasons.
     The monitoring data must be sufficiently complete 
according to requirements defined for each NAAQS in 40 CFR part 50, 
appendices H, I, K, and N (a new appendix P proposed elsewhere in 
today's Federal Register would add completeness requirements for 
PM10-2.5).\18\
    In addition to these generally applicable preconditions or 
restrictions, the current requirements of 40 CFR part 58 contain the 
following special provisions for PM2.5:
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    \18\ Interpretation of the 1-Hour Primary and Secondary National 
Ambient Air Quality Standards for Ozone; Interpretation of the 8-
Hour Primary and Secondary National Ambient Air Quality Standards 
for Ozone; Interpretation of the National Ambient Air Quality 
Standards for PM10; Interpretation of the National 
Ambient Air Quality Standards for PM2.5; and 
Interpretation of the National Ambient Air Quality Standards for 
PM10-2.5, respectively.
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     Data from a PM2.5 monitor can be compared to 
the annual or 24-hour PM2.5 NAAQS only if its location is 
``population-oriented.'' \19\ ``Population-

[[Page 2720]]

oriented monitoring or sites'' is described in 40 CFR 50.1 as applying 
to residential areas, commercial areas, recreational areas, industrial 
areas, and other areas where a substantial number of people may spend a 
significant fraction of their day.
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    \19\ Section 2.8.1.2.3 of appendix D to 40 CFR part 58 states 
that PM2.5 data from state or local air monitoring 
systems (SLAMS) and special purpose monitors (SPM) that are ``* * * 
representative of relatively unique population-oriented microscale 
or localized hot spot or unique population-oriented middle scale 
impact sites are only eligible for comparison to the 24-hour 
PM2.5 NAAQS.'' However, under certain circumstances, the 
Regional Administrator may approve population-oriented microscale or 
middlescale impact sites for comparison to the annual NAAQS.
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     Data from a PM2.5 monitor that is located in a 
``microscale'' location, meaning it is influenced by a nearby emissions 
source while locations somewhat further away would be much less 
influenced, can be compared to the annual PM2.5 NAAQS only 
if its location is representative of many other locations in the 
surrounding urban area, such that significant numbers of people can be 
expected to have similar PM2.5 concentration exposures as 
people living, working, or visiting the location of the monitor in 
question (section 2.8.1.2.3 of appendix D to 40 CFR part 58).
     Under certain conditions, a State may, with the approval 
of EPA, average data from specified monitors for purposes of comparing 
the data to the annual PM2.5 NAAQS. To be approved for 
spatial averaging, as it is known, monitors must meet certain 
requirements for relative location and measure concentrations as 
specified in section 2.8 of appendix D to 40 CFR part 58 (section 4.7.5 
of proposed appendix D to 40 CFR part 58).\20\
---------------------------------------------------------------------------

    \20\ Changes to the requirements for spatial averaging are 
proposed elsewhere in this Federal Register.
---------------------------------------------------------------------------

     The first two complete calendar years of data from an SPM 
for PM2.5 may be excluded from comparisons to the 
PM2.5 NAAQS, but only if the monitor is not continued beyond 
those 2 years (section 2.8.1.2.2 of appendix D to 40 CFR part 58).
    The first three of these four special provisions for 
PM2.5 are tied to the reliance by EPA on community 
epidemiology studies in setting the form and levels of the annual and 
24-hour PM2.5 NAAQS. In simple terms, EPA determined that 
the levels of these NAAQS would be appropriately protective of public 
health based on a presumption that NAAQS compliance determinations 
would be made using data only from monitors that represented 
concentrations to which a large portion of the population would be 
exposed, even though some individuals would have higher or lower 
exposures.
    Finally, EPA has policies addressing situations in which natural 
events and exceptional events have, or may have, influenced monitored 
concentrations. Under these policies, States may make the case that 
data from an otherwise eligible monitor from a specific period should 
not be used in comparisons to the NAAQS. We expect to revise these 
policies and codify them in 40 CFR part 50 in a separate 
rulemaking.\21\
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    \21\ These policies on natural and exceptional events will be 
discussed in the preamble to the Natural and Exceptional Events rule 
to be published in the near future.
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IV. Proposed Monitoring Amendments

A. What Are the Proposed Terminology Changes?

    In 40 CFR 58.1, we propose to replace the definition of ``National 
Air Monitoring Stations (NAMS)'' with a new definition for the 
``National Core (NCore)'' network. The NCore designation \22\ structure 
would be based on a tiered system of measurements including complex 
research-oriented stations,\23\ multipollutant stations equipped to 
support a better understanding of ozone, particulate matter (PM), and 
PM precursors, and sites with as few as one measured pollutant 
identified as State and Local Air Monitoring Stations (SLAMS) that are 
primarily intended to support compliance with the National Ambient Air 
Quality Standards (NAAQS).
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    \22\ Because the terms, SLAMS and NAMS, are used extensively 
through the current rules, this terminology change results in 
numerous changes. For clarity, we are publishing the entire text of 
40 CFR part 58, appendix D (Network Design Criteria for Ambient Air 
Quality Monitoring).
    \23\ The NCore research grade station designation is defined in 
the proposed amendments in anticipation that these stations will be 
initiated at some time in the future. We are not proposing to 
require (or to fund) NCore research grade stations in this notice.
---------------------------------------------------------------------------

    We are proposing to add a definition for the term, ``approved 
regional methods'' (ARM) to 40 CFR 58.1. This term refers to 
alternative PM2.5 methods that have been approved by EPA for 
use specifically within a State, local, or tribal air monitoring 
network for purposes of comparison to the NAAQS and to meet other 
monitoring objectives, but which may not have been approved as Federal 
equivalent methods (FEM) for nationwide use. The proposed testing 
criteria for approval of ARM are specified in 40 CFR part 58, appendix 
C (Ambient Air Monitoring Methodology).
    In 40 CFR 53.1, we are proposing to revise the definition of the 
term ``Class III equivalent method'' to apply only to continuous or 
semi-continuous methods having 1-hour (or less) measurement resolution. 
The revised definition would read:

* * * an equivalent method for PM2.5 or PM10-2.5 
that is an analyzer capable of providing PM2.5 or 
PM10-2.5 ambient air measurements representative of 1-hour 
or less integrated PM2.5 or PM10-2.5 
concentrations as well as 24-hour measurements determined as, or 
equivalent to, the mean of 24 consecutive 1-hour measurements.
Restricting the Class III definition as proposed would offer a 
technical advantage by allowing the establishment of more tolerant 
minimum performance limits than would be necessary if non-continuous 
methods were included.
    We are also proposing to add a definition of the term 
``PM10c'' to 40 CFR 53.1. This term refers to 
PM10 measurements obtained with a specially-approved sampler 
that meets more demanding performance specifications than high-volume 
PM10 samplers described in 40 CFR part 50, appendix J 
(Reference Method for the Determination of Particulate Matter as 
PM10 in the Atmosphere). Measurements obtained with 
PM10c samplers are intended to be paired with 
PM2.5 measurements from Federal reference method (FRM) 
samplers as part of the difference measurement (PM10-2.5 
equals PM10c minus PM2.5) specified in the 
proposed appendix O to 40 CFR part 50 (Reference Method for the 
Determination of Coarse Particulate Matter as PM10-2.5 in 
the Atmosphere) published elsewhere in today's Federal Register.

B. What Are the Proposed Requirements for Approval of Reference or 
Equivalent Methods?

    The provisions of 40 CFR part 50 and related appendices define 
certain ambient air monitoring methods (or methodology) as reference 
methods for the purpose of determining attainment of the National 
Ambient Air Quality Standards (NAAQS). Under 40 CFR part 53, EPA 
designates specific commercial instruments or other versions of methods 
as Federal reference methods (FRM). Furthermore, to foster the 
development of improved alternative air monitoring methods, EPA also 
designates alternative methods that are shown to have comparable 
performance as Federal equivalent methods (FEM). Explicit performance 
tests, performance standards, and other requirements for designation of 
both FRM and FEM are provided in 40 CFR part 53 for each of the 
criteria pollutants. Only designated reference or equivalent methods 
may be used in the States' air surveillance monitoring networks. A list 
of all methods that EPA has designated as either FRM or FEM for all 
criteria pollutants is available at www.epa.gov/ttn/amtic/criteria.html.
    Elsewhere in this Federal Register, EPA is proposing a new 
reference method (40 CFR part 50, appendix O) for the measurement of 
coarse

[[Page 2721]]

particulate matter (PM) in the ambient air. Concurrent with the 
proposal of this new reference method, EPA is also proposing amendments 
to 40 CFR part 53 to extend the designation provisions to methods for 
PM10-2.5. These proposed amendments would set forth explicit 
tests, performance standards, and other requirements for designation of 
specific commercial samplers, sampler configurations, or analyzers as 
either FRM or FEM for PM10-2.5, as appropriate.
    The EPA recognizes that the PM10-2.5 reference method, 
while providing a good standard of performance for comparison to other 
methods, is not itself optimal for routine use in large 
PM10-2.5 monitoring networks. Accordingly, EPA is 
specifically encouraging the development of alternative methods (and 
particularly continuous monitoring methods) for PM10-2.5 by 
focusing on the explicit test and qualification requirements necessary 
for designation of such types of methods as equivalent methods for 
PM10-2.5. Virtual-impactor technology provides a more direct 
measurement of PM10-2.5 and can provide an integrated 
PM10-2.5 sample filter for chemical species analyses that 
can be important in the development of PM10-2.5 control 
strategies. Continuous (or semi-continuous) methods for 
PM10-2.5 typically provide significant operational 
advantages over 24-hour integrated monitoring methods, such as a self-
contained automatic measurement process for output of nearly real-time 
measurements, reduced on-site service and off-site filter analysis and 
support requirements, and measurement resolution of one-hour or less. 
In addition, corresponding provisions for considering the designation 
of continuous or semi-continuous equivalent methods for 
PM2.5 are also being proposed, since such provisions are 
similar to those for PM10-2.5 and are not currently included 
in 40 CFR part 53. The nature of the proposed new provisions for 
automated methods, which can accommodate a wide range of potential 
PM10-2.5 or PM2.5 measurement technologies, is 
based primarily on ambient air testing at diverse monitoring sites to 
demonstrate that the level of comparability to collocated reference 
method measurements is adequate to meet established data quality 
objectives. Furthermore, some existing requirements for designation of 
alternative, non-continuous methods for PM2.5 would be 
modified to be more consistent with the more advanced new requirements 
for non-continuous methods for PM10-2.5 and for continuous 
methods.\24\
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    \24\ For this reason, we view our proposal as consistent with 
the objectives of section 6102 of the Transportation Equity Act for 
the 21st Century. See section VI.5 of the preamble for the proposed 
amendments to the National Ambient Air Quality Standards for 
particulate matter published elsewhere in this Federal Register.
---------------------------------------------------------------------------

1. Proposed Requirements for Candidate Reference Methods for 
PM10-2.5
    Because of the nearly complete similarity between the 
specifications of the proposed PM10-2.5 reference method and 
the existing PM2.5 reference method, the proposed 
designation requirements for PM10-2.5 reference methods are 
essentially the same as those for PM2.5 reference 
methods.\25\ In fact, EPA proposes that a PM10-2.5 sampler 
pair consisting of samplers that have been shown to meet the 
PM2.5 reference method requirements (except for the 
PM2.5 particle size separator in the case of the 
PM10c sampler) may be designated as a PM10-2.5 
reference method without further testing.
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    \25\ The proposed PM10-2.5 reference method specifies 
a pair of samplers consisting of a conventional PM2.5 
sampler and a special PM10 sampler. The PM2.5 
sampler must meet all requirements for a PM2.5 reference 
method in 40 CFR part 50, appendix L. However, the PM10 
sampler required by the proposed method is not a conventional 
PM10 sampler as described in 40 CFR part 50, appendix J; 
rather, it is a sampler specified to be identical to the 
PM2.5 sampler of the pair, except that the 
PM2.5 particle size separator is removed. This special 
PM10 sampler is identified as a ``PM10c'' 
sampler to differentiate it from conventional PM10 
samplers that meet the lesser requirements of 40 CFR part 50, 
appendix J.
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2. Proposed Requirements for Candidate Equivalent Methods for 
PM10-2.5
    As noted, EPA will strive to encourage the development of improved 
alternative air monitoring methods by providing for their designation 
as equivalent methods. But developing suitable qualification 
requirements for equivalent methods for PM10-2.5 is 
complicated by the complex physical and chemical nature of PM, the 
definition of PM10-2.5 that to some extent incorporates the 
nature of the measurement technique defined in the reference method, 
and a wide variety of alternative PM2.5 measurement 
techniques that are or may become available or may be technically 
feasible. Alternative methods must be shown to provide concentration 
measurements closely comparable to those obtained with reference 
methods. Thus, the requirements established for designation of 
equivalent methods must identify candidate methods that can achieve 
that goal, while also having reasonable testing protocols that are not 
so extensive or burdensome as to effectively inhibit approval of 
adequate and suitable improved or alternative candidate methods.
    In light of these constraints, EPA previously defined three classes 
of PM2.5 candidate equivalent methods in 40 CFR part 53 with 
progressively greater equivalent method qualification burdens. Class I 
equivalent methods are limited to methods having ``* * * only minor 
deviations or modifications * * *'' from the specified reference method 
and have the most modest requirements for equivalent method designation 
(in addition to the applicable reference method designation 
requirements). Class II equivalent methods include other filter-based, 
integrated, gravimetric-type methods similar to the reference method, 
but with greater deviation than allowed for Class I. Class III 
equivalent methods include all other candidate PM2.5 methods 
not classified as Class I or II. The proposed amendments would extend 
the definition of Class I, Class II, and Class III candidate equivalent 
methods to PM10-2.5.
    Because Class I equivalent methods for PM10-2.5 differ 
only very modestly from PM10-2.5 reference methods, 
designation requirements would also be very similar. The EPA is 
proposing that PM10-2.5 Class I equivalent methods be 
designated if the samplers of the PM10-2.5 sampler pair are 
shown to meet all requirements for either PM2.5 reference 
methods or Class I equivalent methods. As for PM10-2.5 
reference methods, no further tests would be required.
    One type of Class II equivalent sampler for PM10-2.5 
could be based on virtual impactor technology, which is designed to 
separate coarse mode aerosols from fine mode aerosols. The resulting 
size-segregated filter samples could be of great importance to State, 
local, and tribal agencies to obtain PM10-2.5 sample filters 
for chemical speciation analyses. Class II methods, having greater 
deviation from the reference method, would have more extensive 
designation requirements. These methods still typically have many 
similarities to the reference method, and therefore, many of the 
reference method designation requirements would apply to Class II 
candidate equivalent methods. Generally, these methods must be subject 
to extensive laboratory and wind-tunnel tests to determine their 
performance relative to the performance of the reference method. 
However, for methods that have only one substantial difference from the 
reference method specifications (such as a virtual impactor particle-
size separator), only those laboratory tests pertaining to the

[[Page 2722]]

performance of the deviating component would be required. Further, for 
methods that have more deviation from the reference method 
specifications, the proposed requirements would provide an option to 
substitute more extensive field comparison tests for some or all of the 
extensive laboratory tests that would otherwise be required. Since such 
additional field tests would be similar to field test requirements 
proposed for PM10-2.5 methods, concurrent field testing for 
PM2.5 and PM10-2.5 methods could be carried out. 
Concurrent testing would substantially reduce the testing burden for 
candidate equivalent methods that measure both PM2.5 and 
PM10-2.5 (such as a dichotomous, virtual impactor sampler), 
which could be tested simultaneously for designation as an equivalent 
method for both PM indicators.
3. Continuous Methods for PM10-2.5
    The EPA recognizes that filter-based measurement methods for either 
PM2.5 or PM10-2.5 that require manual gravimetric 
analysis, as embodied in the corresponding reference methods, as well 
as Class I and Class II equivalent methods, are by nature very labor 
intensive. They are expensive to operate in routine monitoring networks 
and can generally provide only delayed reporting of multiple-hour 
integrated measurements. Self-contained, continuous-type automated 
monitoring methods (analyzers), such as those that are commonly used 
for monitoring various gaseous pollutants, overcome many of these 
shortcomings. Various types of continuous (or nearly continuous) 
analyzers have been developed or are under development for 
PM2.5 and PM10-2.5 that offer substantial 
advantages over manual methods for implementation in routine air 
monitoring. These advantages include reduced operational cost, greater 
practicality for daily operation, availability of short-term 
measurements such as one-hour averages, and the possibility for near 
real-time, telemetered measurement acquisition. Accordingly, EPA is 
very interested in encouraging the further development of these 
continuous-type methods by providing requirements for designating such 
methods as Class III equivalent methods, so that they can be used in 
monitoring networks. Because no such explicit requirements exist, EPA 
is today proposing new Class III designation requirements for both 
PM2.5 and PM10-2.5.
    Unfortunately, the continuous-type methods for PM2.5 and 
PM10-2.5 often tend to have performance characteristics 
somewhat different than those of the corresponding reference method. 
Consequently, adequate comparability to the corresponding reference 
method measurements may be technically difficult to achieve. Thus, the 
comparability testing requirements for Class III candidate methods must 
be sufficiently sophisticated to effectively differentiate between a 
method that shows adequate comparability and one that does not. At the 
same time, the designation qualification requirements must not be 
impractically extensive or burdensome, such that monitoring instrument 
manufacturers seeking designation for their analyzers cannot afford or 
economically justify the testing regimen.
    We are proposing to narrow the definition of Class III equivalent 
methods to apply only to continuous or semi-continuous analyzer methods 
having one-hour (or less) measurement resolution, because such methods 
are of the most interest to the air quality monitoring community. While 
it would be possible to develop new, noncontinuous (or non-
semicontinuous) PM2.5 or PM10-2.5 methods that 
would be categorized as Class III as currently defined, there is 
little, if any, technical need or economic incentive for instrument 
manufacturers to do so. Restricting the Class III definition to 
continuous analyzers, as proposed, would offer a substantial technical 
advantage by allowing the establishment of somewhat more tolerant 
limits of adequate comparability than would be necessary if non-
continuous methods were included. This statistical advantage arises 
because the analyzers are operated continuously rather than on an 
intermittent, one-in-six day or one-in-three day schedule, which is 
typical of manually operated sampler methods.
    Any of the currently existing or proposed requirements for 
designation of reference methods and Class I and Class II equivalent 
methods for PM2.5 or PM10-2.5 that would or 
should reasonably apply to a specific Class III candidate method would 
be required for the candidate Class III equivalent method, as well. But 
because of the wide variety of measurement techniques or technologies 
possible for a Class III candidate method, many of these existing 
requirements would not, or may not, apply. Therefore, the proposed 
requirements for PM2.5 and PM10-2.5 Class III 
candidate equivalent methods are based largely on demonstrating 
comparability between candidate method measurements and concurrent 
reference method measurements when both methods are collocated at 
several diverse monitoring and during different seasonal periods. These 
proposed requirements would be added to subpart C of 40 CFR part 53. 
Because we intend that most of the PM10-2.5 monitors in the 
network use continuous or semi-continuous methods, the proposal of 
Class III approval requirements is particularly important for 
PM10-2.5.
    Although candidate PM2.5 and PM10-2.5 Class 
III equivalent methods would have hourly measurement resolution, this 
capability would not be subject to comparability requirements because 
both PM2.5 and PM10-2.5 FRM have only 24-hour 
measurement capability.
    In developing these proposed new requirements for PM2.5 
and PM10-2.5 Class III candidate equivalent methods, EPA has 
attempted to provide requirements that effectively reject inadequately 
comparable methods while minimizing the testing burden to the extent 
possible. Because the performance characteristics of Class III methods 
are likely to vary at monitoring sites having differing climatic and 
aerosol conditions, comparison tests would be required at sites in 
three specified areas of the continental U.S. during winter and summer 
seasons (winter in only one of the areas). The EPA believes these 
requirements would provide the minimum of test venues necessary to 
represent an adequate degree of monitoring site diversity for 
designation of a candidate equivalent method. However, EPA specifically 
solicits comments on the adequacy of the proposed geographical test 
areas, the appropriateness of the proposed seasonal requirements, and 
whether an additional test site may be needed (including the nature of 
such an additional site).
4. Specific Requirements for Class III Equivalent Methods
    The proposed amendments to 40 CFR part 53 would revise the 
requirements for comparison tests and the allowable quantitative 
deviation from reference method measurements that are based on 
statistical analyses. The EPA has previously used a documented 
procedure \26\ and a special computer software aid \27\ to establish 
data quality objectives (DQO) for PM2.5 monitoring data so 
that such data can be used effectively in making decisions regarding 
attainment of the NAAQS for PM. Using these established DQO and the 
software, statistical analyses of both

[[Page 2723]]

actual and simulated PM2.5 monitoring data 28 29 
were carried out to confirm the suitability of the statistical 
parameters selected to describe a comparison relationship between the 
candidate and reference methods and to set appropriate and optimal 
limits for their values in the proposed Class III equivalent method 
tests. These quantitative requirements then define the minimum 
candidate method comparability performance that would be necessary to 
provide PM2.5 monitoring data of sufficient quality to meet 
the established DQO.\30\ The DQO for PM10-2.5 monitoring 
data have recently been developed and are incorporated into 40 CFR part 
58, appendix A. These DQO are similar to the DQO for PM2.5. 
Accordingly, the requirements proposed for PM10-2.5 methods 
are similar to those proposed for PM2.5 methods.\31\ 
Furthermore, similar or parallel requirements are also proposed for 
Class II equivalent methods for PM10-2.5 as well as for 
PM2.5. However, the proposed requirements for Class II 
equivalent methods for PM10-2.5 are stricter with regard to 
additive bias (intercept) since this method would also support other 
monitoring objectives. These latter requirements proposed for 
PM2.5 Class II methods would replace the existing test 
requirements with the more advanced, DQO-based requirements.
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    \26\ U.S. Environmental Protection Agency. Guidance for the Data 
Quality Objectives Process. EPA QA/G-4, EPA/600/R-96/055. August 
2000.
    \27\ U.S. Environmental Protection Agency (2004b) DQO Companion 
Tool, Version 2.0. 2004. http://www.epa.gov/ttn/amtic/dqotool.html.
    \28\ Data Quality Objectives for PM Continuous Methods. Prepared 
for U.S. Environmental Protection Agency by ManTech Environmental 
Technology, Inc. EPA Contract 68-D-00-206, Report TR-4423-03-08, 
June 2003.
    \29\ Data Quality Objectives for PM Continuous Methods II. 
Prepared for U.S. Environmental Protection Agency by ManTech 
Environmental Technology, Inc. EPA Contract 68-D-00-206. Report TR-
CAN-04-02, June 2004.
    \30\ Criteria for Designation of Equivalence Methods for 
Continuous Surveillance of PM2.5 Ambient Air Quality. 
Prepared for U.S. Environmental Protection Agency by B. Coutant and 
J. Sanford, Battelle Columbus, EPA Contract 68-D-02-061, 2004.
    \31\ Method Equivalency Development for PM10-2.5. 
Prepared for U.S. Environmental Protection Agency by B. Coutant, 
Battelle Columbus, 2005.
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    The parameters selected to estimate the performance of 
PM2.5 and PM10-2.5 Class II and Class III 
candidate method measurements relative to the performance of the 
reference method in the proposed field tests are precision, 
correlation, and the linear regression slope and intercept of a linear 
plot fitted to corresponding candidate and reference method mean 
measurement data pairs. Statistical analyses based on the DQO model 
show that the precision of a candidate method is not, statistically, 
very important to annual concentration averages used for NAAQS 
attainment decisions, but would be important for a daily standard. 
Precision is also consequential for other important aspects and 
applications of the PM2.5 or PM10-2.5 monitoring 
data. Accordingly, the proposed amendments would include a minimum 
requirement for an estimate of the candidate method precision for 24-
hour measurements.
    A minimum requirement for an estimate of reference method precision 
in the tests, as well as a test for possible anomalous reference method 
measurement values, also are proposed to ensure that the quality of the 
reference method measurements used for the test meets the expected 
reference method performance. The proposed numerical limits for the 
Class II and III precision test requirements for both the reference and 
candidate methods are somewhat larger than those currently prescribed 
for Class I PM2.5 methods because the Class II and III 
precision would be calculated as the root mean square average, rather 
than the simple average, of the daily precision values determined from 
multiple samplers or instruments. This more statistically appropriate 
aggregation of precision is consistent with the way precision would be 
expressed under proposed revisions to the data quality assessment 
provisions in appendix A to 40 CFR part 58.
    As noted above, the proposed revision to the definition for Class 
III equivalent methods would require such methods to provide one-hour 
(or less) concentration measurements, because such short-term 
measurements are useful for a variety of applications. The EPA proposes 
that hourly measurements from Class III comparability tests be recorded 
and submitted as part of the required test data. No requirement for the 
precision of these hourly measurements is included in the proposed 
amendments because no one-hour DQO have been established for either 
PM2.5 or PM10-2.5 measurements and neither of the 
PM2.5 or PM10-2.5 reference methods provide one-
hour data or performance goals. Nevertheless, in view of the 
substantial potential utility of one-hour PM2.5 and 
PM10-2.5 measurements, EPA solicits comments on whether 
requirements for one-hour measurement precision should be included in 
the Class III equivalent method designation requirements. In 
particular, comments are requested on whether such requirements, if 
included, should provide merely an assessment of one-hour precision or 
a specified standard of performance, and if the latter, to what extent 
would it be appropriate to reject a candidate method that exhibited 
poor one-hour precision but adequate 24-hour precision.
    The regression comparability parameters proposed for Class II and 
Class III candidate methods would be interpreted in ways somewhat 
different from those now used for determining candidate method 
comparability for other types of candidate equivalent methods for PM. 
The slope (multiplicative bias) and intercept (additive bias) are the 
performance parameters most critical in achieving the DQO for making 
correct attainment decisions. However, these parameters are 
interrelated, and statistical analyses of simulated PM2.5 
data \32\ show that the allowable limits for the intercept can be 
somewhat less stringent if they are made to be variable and related to 
the value obtained for the slope. Accordingly, EPA is proposing 
variable, slope-dependant limits for the intercept.
---------------------------------------------------------------------------

    \32\ Battelle Columbus (2004).
---------------------------------------------------------------------------

    Further, because Class III PM2.5 and PM10-2.5 
equivalent methods would be redefined as continuous or semi-continuous 
methods, such methods would normally be operated continuously, just as 
continuous gaseous pollutant analyzers are, rather than on a one-day-
in-six sampling schedule typically used for PM2.5 reference 
method sampling. Again, statistical analyses \33\ show that this more 
frequent (daily) sampling allows the intercept limits to be set even 
wider than would be needed for one-in-six day sampling and still meet 
the established DQO. The actual intercept limits for 
PM10-2.5 methods proposed today are somewhat more 
restrictive than the analyses would indicate to provide a factor of 
safety to account for inherent differences between the way candidate 
methods would be operated in the proposed equivalent method tests and 
the way they would be operated routinely in State monitoring networks.
---------------------------------------------------------------------------

    \33\ ManTech Environmental Technology, Inc. (June 2003); ManTech 
Environmental Technology, Inc. (June 2004); Battelle Columbus 
(2004); Battelle Columbus (2005).
---------------------------------------------------------------------------

    Another difference in the way the conventional comparison 
parameters would be interpreted relates to the proposed lower limit 
requirement for the comparison correlation. The correlation test is 
instrumental in detecting longer-term method variability, such as 
seasonal bias. By its nature, the correlation value calculated for the 
comparison is quite dependent on the range of concentrations measured 
in the tests. The comparison tests are subject to the actual 
PM2.5 or PM10-2.5 concentrations available at the 
test site, which are generally related to variable atmospheric 
conditions during the test period and consequently may

[[Page 2724]]

sometimes occur in a rather narrow range. Therefore, the minimum value 
proposed for this statistic is not a fixed value but rather a variable 
that is related to the concentration coefficient of variation (CCV), 
which is a measure of the range of the concentrations measured in the 
test. This variable limit for correlation would provide a more 
effective test without unnecessarily failing test data representative 
of an unfortunately limited range of test concentrations.
    One minor difference from the reference method would be 
necessitated by the proposed Class III comparison tests. The proposed 
reference methods for PM2.5 and PM10-2.5 specify 
a sampling period tolerance of 23 to 25 hours. Experience has shown 
that in multiple-sampler candidate method tests, which may be 
frequently combined with tests of additional instruments to reduce 
overall testing costs, the time required to properly change sample 
filters and service the samplers and other instruments between sample 
periods often requires more than one hour. Accordingly, the proposed 
test protocol would allow a 22-hour minimum sample period for the 
reference method to allow complete sample set acquisition within a 24-
hour period. This proposed revision in the reference method protocol 
should have very little, if any, adverse impact on the results of the 
comparability tests.
    The proposed requirements for PM10-2.5 and 
PM2.5 Class II and Class III equivalent methods are the 
least stringent requirements that would provide reasonable assurance 
that candidate methods meeting these requirements will produce 
monitoring data of quality commensurate with the quality of reference 
method data and that the data will meet the DQO established for 
PM2.5 and the proposed DQO for PM10-2.5. While 
recent field studies suggest some potential PM10-2.5 
continuous methods look promising,\34\ it is not certain at this time 
whether any current commercial continuous or nearly continuous methods 
can yet meet the proposed requirements for Class III methods. However, 
EPA believes that the establishment of these requirements would provide 
a definitive goal which instrument manufacturers could achieve.
---------------------------------------------------------------------------

    \34\ U.S. Environmental Protection Agency. Multi-Site 
Evaluations of Candidate Methodlogies for Determining Coarse 
Particulate Matter (PM10-2.5) Concentrations: August 2005 
Updated Report Regarding Second-generation and New 
PM10-2.5 Samplers.
---------------------------------------------------------------------------

5. Proposed Changes to Requirements for PM10 and 
PM2.5 Class I and Class II Equivalent Methods
    The proposed amendments would revise the existing provisions for 
PM10 and PM2.5 Class I and II candidate 
equivalent methods. These changes would clarify or simplify current 
provisions or implement minor improvements to test protocols suggested 
by experience and information acquired in processing equivalent method 
applications for these methods. The proposed changes would have very 
little, if any, impact on the nature, efficacy, or extent of any of the 
test requirements.
    In the tests for PM10 and PM2.5 Class I and 
II candidate equivalent methods, the minimum separation distance 
between sampler or analyzer inlets is proposed to be reduced from 2 
meters to 1 meter for instruments having flow rates less than 200 
liters per minute. One meter separation has been found to be entirely 
adequate for such low-flow-rate instruments, and the change is 
consistent with a similar minimum separation allowance for audit 
samplers used in assessing the precision of network PM2.5 
samplers.\35\ An identical change is also proposed for appendix A to 40 
CFR part 58.
---------------------------------------------------------------------------

    \35\ Quality Assurance Guidance Document: Field Standard 
Operating Procedures for the PM2.5 Performance Evaluation 
Program. U.S. Environmental Protection Agency. Office of Air Quality 
Planning and Standards, November 1998, Section 4, page 8.
---------------------------------------------------------------------------

    Another proposed change would replace existing requirements for 
Class II PM2.5 equivalent methods with similar but new DQO-
based requirements. These proposed requirements are similar to the 
Class III requirements and would be based on daily sampling. Therefore, 
PM10-2.5 and PM2.5 Class II equivalent methods 
used for determining compliance with the PM NAAQS would generally be 
restricted to daily operation. However, as discussed previously, 
filter-based integrated methods (such as Class II equivalent methods) 
are not likely to be widely used for compliance monitoring. These 
methods would be used more for chemical analysis of samples to 
characterize the species of PM in a monitoring area, which would not 
require daily operation of the samplers. For Class II methods (for 
either PM2.5 and PM10-2.5 methods), the test 
sites would be similar in character to those for Class III methods, but 
only two test sites (one eastern and one western) rather than three, 
and tests in only one season at any time of year rather than two 
seasons, would be required. These requirements would allow tests for 
PM2.5 and PM10-2.5 methods (or for Class II and 
Class III method) to be tested simultaneously, to reduced testing 
costs. Flow rates in the existing PM2.5 FRM and proposed 
PM10-2.5 FRM would be operated under conditions of actual 
ambient temperature and barometric pressure, ensuring compatibility of 
the measured sample flows. The EPA solicits comments on the adequacy 
and appropriateness of these tests requirements for Class II methods.
    In addition, the proposed amendments would lower many of the 
minimum concentration limit specifications for various existing test 
requirements for PM10 and PM2.5 Class I and Class 
II candidate equivalent methods. These minimum limits were established 
either to avoid possible difficulties with interpretation of test 
results due to increased measurement variability that often occurs at 
very low concentrations or to require a wide range of concentration 
measurements for the test. However, experience has shown that these 
lower limits are unnecessarily conservative and can be decreased 
considerably without encountering undue variability in the measurements 
or an insufficient range of concentrations. Further, applicants often 
have difficulty obtaining a sufficient number of measurement sets that 
meet some of these minimum limits. The proposed decreases in these 
minimum limits would reduce the number of test measurement sets that 
are rejected as unacceptable due to test concentration levels failing 
to meet the test requirements without compromising the efficacy of the 
tests. These changes would reduce the costs to applicants of conducting 
the tests.
6. Other Proposed Changes
    The proposed amendments would make subpart C of 40 CFR part 53 
easier to understand by consolidating the provisions for the various 
types of candidate equivalent methods. This reorganization results in 
numerous minor editorial and section number changes of no technical 
impact. The entire text of 40 CFR part 53, subpart C is reprinted in 
the proposed amendments.
    We are proposing numerous minor changes which are needed to 
incorporate new provisions for PM10-2.5 methods into 
subparts A, C, E, and F of 40 CFR part 53, as well as a few minor 
changes that would apply to methods for PM2.5 or other 
pollutants. As noted above, the definition of a ``Class III equivalent 
method'' in 40 CFR 53.1 would be modified to include only methods that 
provide automated

[[Page 2725]]

continuous or semi-continuous measurements of PM2.5 and 
PM10-2.5 with one-hour or less resolution. We are also 
proposing definitions for the terms, ``PM'', ``PM10-2.5 
sampler'', and ``PM10C sampler''. Another proposed change, 
to paragraph (4) of 40 CFR 53.3 (General requirements for an equivalent 
method), would clarify that Class III PM10-2.5 and 
PM2.5 candidate equivalent methods would be subject to 
applicable requirements for PM10-2.5 or PM2.5 
reference methods contained in those reference methods (40 CFR part 50, 
appendixes L and O) and applicable requirements for Class I and Class 
II equivalent methods contained in subparts E and F of 40 CFR part 53, 
in addition to the proposed amendments to subpart C. The requirement in 
40 CFR 53.5 (Processing of applications) to publish a notice in the 
Federal Register upon receipt of an application would be deleted, as 
would the requirements in 40 CFR 53.51(f)(2) and 53.2(a) for 
manufacturers of PM2.5 designated method samplers to submit 
an annual Product Manufacturing Checklist. These requirements have 
proved to be of little value, and the significant cost burden to the 
Government and to applicants for these activities can therefore be 
eliminated. The proposed amendments would also delete the requirement 
in 40 CFR 53.8 (Designation of reference and equivalent methods) for 
publishing a notice of designation in the Federal Register no later 
than 15 days after the date of the determination. We are proposing to 
delete the 15-day requirement because it is not achievable within the 
confines of EPA's internal review process.

C. What Are the Proposed Requirements for Quality Assurance Programs of 
the National Ambient Air Monitoring System?

    A quality system provides a framework for planning, implementing 
and assessing work performed by an organization and for carrying out 
required quality assurance (QA) and quality control (QC) activities. 
The proposed amendments to 40 CFR part 58, appendix A would provide the 
requirements necessary to develop quality systems for the NCore, State 
and Local Air Monitoring Stations (SLAMS), and Prevention of 
Significant Deterioration (PSD) networks. The proposed revisions 
address responsibilities for implementing the quality system for both 
EPA and monitoring organizations, as well as adherence to the Agency's 
QA policy, data quality objectives (DQO), and the minimum QC 
requirements and performance evaluations needed to assess the data 
quality indicators of precision, bias, detectability, and completeness. 
In addition, the proposed amendments would describe the required 
frequency of the QC requirements and performance evaluations, the data 
to be collected, and the statistical calculations for estimates of the 
data quality indicators at various levels of aggregation. The revised 
statistical calculations would be used to determine attainment of the 
DQO. The proposed amendments would also identify national programs that 
help determine data quality comparability across individual monitoring 
programs.
    The EPA has not conducted a thorough review of the quality system 
for many years. Based on our review of the existing QA program in 40 
CFR part 58, appendices A and B, we are proposing changes to make the 
requirements consistent with our current QA policy, meet the objectives 
of the NCore, SLAMS, and PSD monitoring networks, and make the 
requirements more user-friendly. These proposed changes would produce a 
more consistent QA program across pollutant categories that fosters use 
of new technologies by more directly linking instrument performance 
with programmatic objectives. The proposed revisions were developed 
with the assistance of a stakeholder group (QA Strategy Workgroup) 
composed of QA representatives from EPA, State, local, and tribal 
monitoring organizations. Recommendations from the workgroup are 
provided in one of the draft versions of the National Ambient Air 
Quality Strategy document.\36\ We solicit comments on all of the 
following proposed amendments to 40 CFR part 58, appendix A.
---------------------------------------------------------------------------

    \36\ The National Ambient Air Monitoring Strategy (Final Draft). 
U.S. Environmental Protection Agency. Office of Air Quality Planning 
and Standards, APril 2004. Some of the detailed content of the April 
2004 draft, including some of the workgroup recommendations are not 
included in the subsequent December 2005 version.
---------------------------------------------------------------------------

1. Consolidation of Quality Assurance Requirements
    The requirements for State and local air monitoring stations 
(SLAMS) and prevention of significant deterioration (PSD) monitoring 
stations have been combined from two separate appendices, 40 CFR part 
58, appendices A and B, into one single appendix A because both 
programs have similar QA requirements.
2. Realignment to Current EPA Quality Assurance Policies
    EPA Order 5360.1 A2 requires agencies that accept Federal grant 
funding for their air monitoring programs to have a QA program with 
certain elements including quality management plans (QMP), quality 
assurance project plans (QAPP), and a person designated as the quality 
assurance manager. Many of these elements are not in the existing 
regulations, which predate EPA Order 5360.1 A2 (revised in 2000), but 
would now be added under today's proposal. Grantee agencies have been 
following the requirements of EPA Order 5360.1 A2 for several years, 
and as a result, we do not expect these proposed revisions would have a 
significant impact on resources beyond the existing program. Copies of 
EPA Order 5360.1 A2 are available in the docket for this proposal as 
well as on EPA's Internet site http://www.epa.gov/quality1.
    A QMP is a document that describes an organization's quality system 
including its policy and procedures, functional responsibilities of 
management and staff, and other general practices of its data 
collection program. Project-specific details are documented in a QAPP. 
A QAPP would document, for example, how the PM2.5 air 
monitoring network will be operated and how sampler performance will be 
controlled and data quality evaluated.
    EPA Order 5360.1 A2 requires grantee agencies involved with data 
collection activities to identify a quality assurance manager. The 
proposed amendments to 40 CFR part 58, appendix A would require each 
State (or delegated monitoring agency) to identify and maintain a ``QA 
management function''. This proposed language captures the essence of 
the requirements in EPA Order 5360.1A2, while befitting the nature of 
the ambient air monitoring community which is made up of large and 
small (local and tribal) organizations.
    The EPA also proposes to revise the QA program by emphasizing the 
DQO process. A DQO is a qualitative and quantitative statement that 
defines the appropriate quality of data needed for a particular 
decision--for example, the data quality necessary for EPA or a 
monitoring organization to make data comparisons against the National 
Ambient Air Quality Standards (NAAQS). The DQO help to establish the 
requirements for precision, bias, completeness, and detectability and 
the rationale for their acceptance criteria.
    The proposed amendments would require monitoring organizations to

[[Page 2726]]

evaluate PM10-2.5 and ozone monitoring system performance 
through the DQO process. This is consistent with the existing 
requirement for organizations to evaluate their PM2.5 
monitoring system performance using the DQO process. Priority for these 
evaluations is placed on PM2.5, PM10-2.5, and 
ozone as these are the pollutants of most concern across the country. 
Quality assurance procedures such as determining precision through 
collocated sampling and determining bias through an independent 
performance evaluation program for PM10-2.5 are proposed to 
follow the same basic approach as the PM2.5 monitoring 
network. The proposed precision and bias measurement uncertainty goals 
are identified in 40 CFR part 58, appendix A. The proposed amendments 
to appendix A would also specify that EPA is responsible for the 
development of the DQO for NCore multi-pollutant stations and State and 
local air monitoring stations (SLAMS).
3. Quality Assurance Requirements for PM10, 
PM10-2.5 and PM2.5
    The proposed QA requirements for PM10-2.5 would follow 
the same approach as the requirements that currently apply to both 
automated and manual PM10 and PM2.5 monitors. 
These requirements would include the implementation of flow rates 
audits conducted by the monitoring organization, collocated monitoring, 
and performance evaluations. Statistical evaluations have allowed us to 
reduce collocation and performance evaluation sampling frequencies 
without significant affects to data quality assessments.
    We are proposing to amend the PM2.5 and PM10 
collocation sampling frequency requirement. Statistical assessments of 
the collocated PM2.5 and PM10 data reveal that 
adequate estimates of precision at the primary quality assurance 
organization could be made at a reduced sampling frequency. 
Consequently, we are proposing to reduce the frequency from every 6 
days to every 12 days. This change would reduce the burden on the 
monitoring organization without a significant effect on precision 
estimates. This proposal does not include a reduction in the 
collocation requirements for total suspended particulate (TSP) or PSD 
monitors. In addition, we are proposing to revise the concentration 
limits applicable to collocated pairs of monitors that are used to 
provide precision estimates. The concentration limits would be reduced 
from 6 micrograms per cubic meter ([mu]g/m3) to 3 [mu]g/
m3 for PM2.5 and from 20 [mu]g/m3 to 
15 [mu]g/m3 for PM10 (high-volume samplers). 
Statistical evaluation of three years of PM2.5 and 
PM10 data revealed comparable estimates of precision using 
data from both of these reduced concentration ranges, and that the 
addition of the data at these lower ranges will increase the level of 
confidence in the precision estimates. This proposed change would make 
the collocation sampling frequency requirement consistent for 
PM2.5 PM10 and PM10-2.5. A document 
describing the possible new approach is available in the docket.\37\
---------------------------------------------------------------------------

    \37\ Proposal to Change the PM2.5 and PM10 
Collocation Sampling Frequency Requirement, http://www.epa.gov/ttn/amtic/pmqainf.html
---------------------------------------------------------------------------

    We are proposing to revise the sampling frequency for the 
implementation of the PM Performance Evaluation Program (PEP). This 
proposed approach used historical PM2.5 precision and bias 
data to identify the minimum number of performance evaluations required 
for all primary quality assurance organizations to provide an adequate 
assessment of bias, rather than the current requirement that a uniform 
25 percent of monitors in a primary quality assurance organization be 
evaluated each year. The revision would establish an equitable sampling 
frequency of five valid audits a year for organizations with less than 
or equal to five monitoring sites and eight valid audits a year for 
those organizations with greater than five monitoring sites. A valid 
performance evaluation audit means that both the primary monitor and 
PEP audit concentrations are valid and above 3 [mu]g/m3. As 
an example, if a primary quality assurance organization had 20 
monitoring sites, the current requirement would require five sites (25 
percent of network) to be audited four times each year (one each 
quarter) for a total of 20 audits. The new proposal would simply 
require eight audits be provided (distributed across each quarter) and 
that all monitoring sites be audited within a six year period in order 
to provide a representative estimate of bias for the monitoring 
network. This would equate to distributing eight audits (or five for 
networks less than or equal to 5) at 15 percent of the monitoring 
network sites. In addition, each method designation must be audited. 
Therefore, if a primary quality assurance organization had two 
different monitoring instruments in their network, both would need PEP 
audits each year. Since bias data quality objectives are evaluated on 3 
years of PEP audits, both sampling frequencies should provide us with 
reasonable assessments of bias. Preliminary assessments of the impact 
of the possible new method show that organizations with smaller 
networks would need more audits but fewer audits would be needed at 
organizations with larger networks. The net result across all primary 
quality assurance organizations would be fewer audits, comparable bias 
results, and reduced resource burden. A document describing this 
possible approach is available in the docket.\38\
---------------------------------------------------------------------------

    \38\ Review of the Potential to Reduce or Provide a More Cost 
Efficient Means to Implement the PM2.5 Performance 
Evaluation Program, http://www.epa.gov/ttn/amtic/pmpep.html.
---------------------------------------------------------------------------

4. Requirements to Ensure Adequate Independent Quality Assurance for 
All Pollutants Subject to National Ambient Air Quality Standards
    We are proposing to revise the current regulatory requirements 
dealing with responsibilities for independent assessments of monitoring 
system performance. These evaluations are the subject of sections 2.4 
and 3.5.3.1 of the current appendix A to 40 CFR part 58. Section 2.4 of 
appendix A to 40 CFR part 58 applies to all National Ambient Air 
Quality Standards (NAAQS) pollutants and section 3.5.3.1 is applicable 
only to PM2.5. Currently, section 2.4 of appendix A requires 
the monitoring organization to ``participate'' in EPA's National 
Performance Audit Program (NPAP). For the last few years, EPA has 
considered that monitoring organizations are in compliance with the 
requirements of section 2.4 if, at a minimum, the organizations made 
their monitoring sites and equipment accessible to EPA or contractors 
for conducting the performance evaluations. For continuous gas 
instruments, a performance evaluation involves the introduction of a 
gas or gases of independently known concentration to determine the bias 
of the local monitor.
    Section 3.5.3.1 of appendix A to 40 CFR part 58 describes the 
Performance Evaluation Program (PEP) for PM2.5. The PEP 
requirements are functionally similar to the NPAP requirements but 
differ in its specifics because of the nature of particulate matter 
sampling (i.e., it is not possible to introduce air with a known 
concentration of PM2.5 into a monitor). Under the PEP for 
PM2.5, a local monitor is evaluated by placing a second, 
independently-maintained Federal reference method (FRM) monitor next to 
the local monitor and allowing both monitors to sample for 24 hours. 
The filter from the independent FRM monitor is then shipped to an 
independent laboratory

[[Page 2727]]

where it is weighed and the resulting independently calculated 
concentration is compared to the concentration from the local monitor. 
The resulting difference in concentrations between the independent FRM 
monitor and local monitor is used to calculate the bias between the 
sampler results.
    The monitoring organization is responsible for having these 
PM2.5 performance evaluations take place, or only for giving 
access to its sites for EPA staff or contractors to perform them. In 
practice, most monitoring organizations comply with the requirements in 
section 3.5.3.1 by giving access to EPA staff or contractors and by 
accepting that EPA funds this activity by holding back part of the 
grant funding that might otherwise go directly to the monitoring 
organization. One State complies with requirements in section 3.5.3.1 
by having independent audits in one part of the State performed by 
personnel and laboratories from the monitoring organization that is 
responsible for daily operations in another part of the State.
    The EPA proposes to revise the text of 40 CFR part 58, appendix A 
to clearly provide that it is the responsibility of each monitoring 
organization to make arrangements for, and to provide any necessary 
funding for, the conduct of adequate independent performance 
evaluations of all its FRM or Federal equivalent method (FEM) criteria 
pollutant monitors. The proposed language would also clearly indicate 
that it is the monitoring organization's choice whether to obtain its 
independent performance evaluations through EPA's NPAP and 
PM2.5 PEP programs, or from some other independent 
organization. An independent organization could be another unit of the 
same agency that is sufficiently separated in terms of organizational 
reporting and which can provide for independent filter weighing and 
audit gas naming. This proposed approach would ensure that adequate and 
independent audits will be performed but would provide flexibility in 
the implementation approach.
    Monitoring organizations that choose to comply with the revised 
provisions of appendix A to 40 CFR part 58 regarding performance 
evaluations by relying on EPA audits, for PM2.5, 
PM10-2.5, and/or other NAAQS pollutants, would be required 
to agree that EPA hold back part of the grant funds they would 
otherwise receive directly. The EPA intends to develop guidance for 
monitoring organizations that choose to comply by obtaining audit 
services from elsewhere. To ensure national consistency and effective 
audits, this guidance will include provisions for EPA certification of 
data comparability for audit services not provided by EPA and for 
traceability of gases and other audit standards to national standards 
maintained by the National Institute for Standards and Technology.
5. Revisions to Precision and Bias Statistics
    We are also proposing to change the statistics for assessment of 
precision and bias for criteria pollutants. Two important data quality 
indicators that are needed to assess the achievement of DQO are bias 
and precision. Statistics in the current requirements of 40 CFR part 
58, appendix A (with the exception of PM2.5) combine 
precision and bias together into a probability limit at the primary 
quality assurance organization level of aggregation. In addition, the 
statistical calculations of precision and bias vary among criteria 
pollutants and between manual and automated methods within the same 
pollutant. Since the DQO process uses separate estimates of precision 
and bias, we examined assessment methods that were statistically 
reasonable and simple. The proposed assessment methods are based on the 
QA measurements that are currently required in 40 CFR part 58, appendix 
A.
    For sulfur dioxide (SO2), nitrogen dioxide 
(NO2), carbon monoxide (CO), and ozone (O3), we 
are proposing to estimate precision and bias on confidence intervals at 
the site level of data aggregation rather than the primary quality 
assurance organization. Estimates at the site level can be accomplished 
with the automated methods for SO2, NO2, CO and 
O3 because there is sufficient QC information collected at 
the site level to perform adequate assessments. Since the criteria 
pollutant data are used for very important decisions (comparison to the 
NAAQS), providing precision and bias estimates at upper confidence 
limits would provide a higher probability of making appropriate 
decisions. The intent of this proposed change is to move organizations 
to a ``performance-based'' quality system. Organizations that 
demonstrate acceptable performance would be allowed the flexibility to 
reduce the frequency of certain QC checks. These agencies are expected 
to shift resources used for these QC checks into higher priority QA 
work. A document describing this possible new approach is available in 
the docket.\39\
---------------------------------------------------------------------------

    \39\ Proposal: New Method for Estimating Precision and Bais for 
Gaseous Automated Methods for Ambient Air Monitoring Program, http://www.epa.gov/ttn/amtic/files/ambient/gagc/proprecision.pdf.
---------------------------------------------------------------------------

    The precision and bias statistics for PM measurements 
(PM10, PM10-2.5 and PM2.5) would be 
generated at a primary quality assurance organization level because, 
unlike the gaseous pollutants, only a percentage of the sites have 
precision and bias checks performed in any year. As with the gaseous 
pollutants, the statistics would use the confidence limit approach. 
Using a consistent set of statistics would simplify procedures by 
removing a significant number of equations and confusing language in 
the appendix.
    We are also proposing to change the precision and bias statistics 
for lead (Pb) to provide a framework for developing and assessing DQO. 
The QC checks for Pb come in three forms: flow rate audits, Pb audit 
strips, and collocation. The EPA proposes to combine information from 
the flow rate audits and the Pb audit strips to provide an estimate of 
bias. Precision estimates would still be made using collocated sampling 
but the estimates would be based on the upper 95 percent confidence 
limit of the coefficient of variation, similar to the method described 
for the automated instruments.
6. Program Updates
    We are also proposing several QA program changes to update the 
existing requirements in 40 CFR part 58 to reflect current program 
needs and terminology:
     We are proposing to remove SO2 and 
NO2 manual audit checks. A review of all SLAMS/NAMS/PAMS 
sites by monitor type revealed that no monitoring organizations are 
using manual SO2 or NO2 methods, nor are any 
monitoring organizations expected to use these older technologies. 
Instead of the old manual methods, monitoring sites are using 
continuous methods to perform these audit checks. We are proposing to 
remove the manual method QC checks because the continuous check methods 
are covered by the current QA procedures.
     We are proposing to change the concentration ranges for QC 
checks and annual audit concentrations. The one-point QC check 
concentrations for the gaseous pollutants SO2, 
NO2, O3 and CO would be expanded to include lower 
concentrations. Lower audit ranges would also be added to concentration 
ranges in the annual audit concentrations. Adding or expanding the 
required range to lower concentration ranges is appropriate due to the 
lower measured concentrations at many monitoring sites as well as the 
potential for NCore stations to monitor areas where concentrations are 
at trace ranges. In addition, EPA proposes that

[[Page 2728]]

the selection of QC check gas concentration must reflect the routine 
concentrations normally measured at sites within the monitoring network 
in order to appropriately estimate the precision and bias at these 
routine concentration ranges.
     We are proposing to revise the PM10 collocation 
requirement. Currently, 15 percent of all PM2.5 sites are 
required to maintain collocated samplers. For consistency, the proposed 
amendments would change the PM10 collocation requirement to 
match the PM2.5 requirement. This proposed change would make 
the collocation requirement consistent for PM2.5 
PM10 and PM10-2.5.
     We are proposing to amend the PM2.5 and 
PM10 collocation sampling frequency requirement. Statistical 
assessments of the collocated PM2.5 and PM10 data 
reveal that adequate estimates of precision at the primary quality 
assurance organization could be made at a reduced sampling frequency. 
Consequently, we are proposing to reduce the frequency from every 6 
days to every 12 days. This change would reduce the burden on the 
monitoring organization without a significant effect on precision 
estimates. This proposal does not include a reduction in the 
collocation requirements for total suspended particulate (TSP) or PSD 
monitors. In addition, we are proposing to revise the concentration 
limits applicable to collocated pairs of monitors that are used to 
provide precision estimates. The concentration limits would be reduced 
from 6 micrograms per cubic meter ([mu]g/m3) to 3 [mu]g/
m3 for PM2.5 and from 20 [mu]g/m3 to 
15 [mu]g/m3 for PM10 (high-volume samplers). 
Statistical evaluation of 3 years of PM2.5 and 
PM10 data revealed comparable estimates of precision using 
data from both of these reduced concentration ranges, and that the 
addition of the data at these lower ranges will increase the level of 
confidence in the precision estimates. This proposed change would make 
the collocation sampling frequency requirement consistent for 
PM2.5 PM10 and PM10-2.5.
     We are proposing to revise the requirements for 
PM2.5 flow rate audits. Based on an evaluation of flow rate 
data and discussions within the QA Strategy Workgroup, we are proposing 
to reduce the frequency of flow rate audits from quarterly to 
semiannually and remove the alternative method which allows for 
obtaining the precision check from the analyzers internal flow meter 
without the use of an external flow rate transfer standard. Most 
monitoring organizations participating in the QA Strategy Workgroup 
considered auditing with a external transfer standard to be the 
preferred method and believed that the quarterly audit data 
demonstrates the instruments are sufficiently stable to reduce the 
audit frequency. The proposed amendments would provide an efficient and 
effective approach by reducing audit frequency to an adequate level 
while ensuring the use of a preferred approach.

D. What Are the Proposed Monitoring Methods for the National Ambient 
Air Monitoring System?

1. Federal Reference Methods and Federal Equivalent Methods
    Monitoring methods used in the multi-pollutant NCore and SLAMS 
networks would include Federal reference methods (FRM), Federal 
equivalent methods (FEM), and other methods designed to meet the data 
quality objectives of the network being deployed. When appropriate, the 
proposed amendments place emphasis on continuous methods over filter-
based methods to provide for highly time-resolved data for better 
characterization of diurnal patterns of air pollution and for timely 
public availability of data. While more emphasis is placed on 
continuous methods, a limited number of filter-based methods would 
still be retained in most networks to tie together historical data sets 
with new monitoring data. EPA's strategy for selecting the proposed 
monitoring methods for the National ambient air monitoring system was 
to select methods that meet data quality objectives for each pollutant 
and that have the most utility to support multiple monitoring 
objectives. Specifics on the monitoring methods proposed for use at 
each type of site are described below.
     A wide variety of research, FRM/FEM or other routine 
methods could be used at NCore research-grade stations. Maximum 
flexibility is provided in the proposed amendments for these sites 
because they would be used to investigate the atmospheric processes and 
air chemistry that go beyond the capabilities of characterizing the air 
with routine monitoring methods.
     NCore multi-pollutant stations would use FRM or FEM for 
criteria pollutants when the expected concentration of the pollutants 
are at or near the level of the National Ambient Air Quality Standards 
(NAAQS). For criteria pollutant measurements of carbon monoxide (CO) 
and sulfur dioxide (SO2), where the level of the pollutant 
is well below the NAAQS, it may be more appropriate to operate higher 
sensitivity monitors than FRM or FEM. In these cases, the higher 
sensitivity methods are expected to support different monitoring 
objectives than the FRM or FEM. In some limited cases, higher-
sensitivity gas monitors have also been approved as FEM and can serve 
both NAAQS and other monitoring objectives. Options for high-
sensitivity measurements of CO, SO2, and total reactive 
nitrogen (NO) are described in the report, ``Technical Assistance 
Document for Precursor Gas Measurements in the NCore Multipollutant 
Monitoring Network.''
     State and local air monitoring stations would use FRM or 
FEM for criteria pollutants. For PM2.5, these sites could 
also use approved regional methods (ARM), which are described in 
section IV.D.2 of this preamble.
     Photochemical assessment monitoring stations (PAMS) would 
use the ozone (O3) ultraviolet photometry FEM and the nitric 
oxide (NO) and nitrogen dioxide (NO2) chemiluminescence FRM 
for criteria pollutant measurements. Methods for volatile organic 
compounds (VOC) including carbonyls, additional measurements of gaseous 
nitrogen, such as NOy, and meteorological measurements are 
routinely operated at PAMS. Because these measurements are not of 
criteria pollutants, the methods are not subject to the requirements 
for reference or equivalent methods. However, these methods are 
described in detail in the report, ``Technical Assistance Document 
(TAD) for Sampling and Analysis of Ozone Precursors.''\40\
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    \40\ Technical Assistance Document (TAD) for Sampling and 
Analysis of Ozone Precursors. U.S. Environmental Protection Agency. 
HUman Exposure and Atmospheric Sciences Division. EPA/600-R-98/161. 
September 1998. Available at: http://www.epa.gov/ttn/amtic/pams.html.
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     Special purpose monitoring (SPM) sites have no 
restrictions on the type of method to be utilized. While FRM and FEM 
can be employed at SPM sites, other methods, not limited to continuous, 
high-sensitivity, and passive methods, may also be utilized. Because 
SPM sites are designed to encourage monitoring, agencies are expected 
to design SPM sites with methods to meet specific monitoring objectives 
that may not be achievable with FRM or FEM. For instance, a community 
may be concerned with a source impacting their neighborhood. Because 
many PM FRMs are filter-based manual methods, having a 24-hour sample 
may not indicate if the source impacted the neighborhood because of the 
meteorological variability during the sample collection period. 
However, a continuous method may be able to provide the high-time 
resolution

[[Page 2729]]

necessary to detect the short-term impacts of a plume on a 
neighborhood. Another example could be the utilization of passive 
monitors deployed at many locations to determine the location of 
maximum concentrations within a neighborhood. Additional information on 
SPM is included in section IV.E.9 of this preamble.
2. Approved Regional Methods for PM2.5
    The proposed amendments also expand the use of alternative 
PM2.5 measurement methods through approved regional methods 
(ARM). The proposed amendments to 40 CFR part 58, appendix C extend the 
existing provisions for EPA approval of a nondesignated 
PM2.5 method as a substitute for a FRM or FEM at a specific 
individual site to a network of sites. This approval would be extended 
on a network basis to allow for flexibility in operating a hybrid 
network of PM2.5 FRM and continuous monitors. The size of 
the network, in which the ARM could be approved, would be based on the 
location of test sites operated during the testing of the candidate 
ARM. The proposed amendments require that test sites be located in 
urban and rural locations that characterize a wide range of aerosols 
expected across the network. A hybrid network of monitors would be 
operated to address monitoring objectives beyond just determining 
compliance with NAAQS. The hybrid network would lead to a reduced 
number of existing FRM samplers for direct comparison to NAAQS and an 
increase in continuous samplers that meet specified performance 
criteria related to their ability to produce sound comparisons to FRM 
data. Those ARM that meet the specified performance criteria would be 
approved for direct comparison to PM2.5 NAAQS.
    Performance criteria for approval of ARM would be used to determine 
whether the continuous measurements are sufficiently comparable for 
integration into the PM2.5 network used in NAAQS decisions. 
These criteria are the same criteria for precision, correlation, and 
additive and multiplicative bias that are proposed for approval of 
continuous PM2.5 Class III equivalent methods, described in 
section IV.B.3 of this preamble. These performance criteria would be 
demonstrated by monitoring agencies independently or in cooperation 
with instrument manufacturers under actual operational conditions using 
one to two FRM and one to two candidate monitors each. This would be a 
departure from the very tightly-controlled approach used for national 
equivalency demonstration in which three FRM and three candidate 
monitors are operated. The ARM would be validated periodically in 
recognition of changing aerosol composition and instrument performance. 
These validations would be performed on at least two levels: (1) 
Through yearly assessments of data quality provided for as part of the 
on-going quality assurance (QA) requirements in 40 CFR part 58, 
appendix A, and (2) through network assessments conducted at least 
every 5 years as described in section IV.E.11 of this preamble.
    The testing criteria EPA is proposing for approval of 
PM2.5 continuous methods as ARM are intended to be robust 
but not overly burdensome. The two main facets of testing are the 
duration and location(s) of testing. The duration is expected to be one 
year to provide understanding of the quality of the data on a seasonal 
basis. The locations for testing are expected to be a subset of sites 
in a network where the State desires the PM2.5 continuous 
monitor to be approved as an ARM. Testing would be carried out in 
multiple locations to include up to two Core-based Statistical Area/
Combined Statistical Areas (CBSA/CSA) and one rural area or small city 
for a new method. For methods that have already been approved by EPA in 
other networks, one CBSA/CSA and one rural area or small city would be 
required.
    To ensure that approvals of new methods are made consistently on a 
national basis, the procedures for approval of methods would be similar 
to the requirements specified in 40 CFR part 53, i.e., the EPA 
Administrator (or delegated office) would approve the application. 
However, to optimize flexibility in the approval process, all other 
monitoring agencies seeking approval of a method that is already 
approved in another agency's monitoring network may seek approval 
through their own EPA Regional Administrator. This approach should 
provide a streamlined approval process, as well as an incentive for 
consistency in selection and operation of PM2.5 continuous 
monitors across various monitoring agency networks.
    The proposed QA requirements for approval of continuous 
PM2.5 ARM at a network of sites would be the same as for FEM 
in 40 CFR part 58, appendix A, except that 30 percent of the required 
sites that utilize a PM2.5 ARM would be collocated with an 
FRM and required to operate at a sample frequency of at least a one-in-
six day schedule. The higher collocation requirement would support the 
main goal of the particulate matter continuous monitoring 
implementation plan, which is to have an optimized FRM and 
PM2.5 continuous monitoring network that can serve several 
monitoring objectives. The current 15 percent collocation requirement 
in 40 CFR part 58, appendix A is adequate to provide an estimate of 
site and network precision; however, a higher amount of collocation is 
necessary to retain a minimum number of FRM for continued validation of 
the ARM, direct comparison to NAAQS, and for long-term trends that are 
consistent with the historical data set archived in the Air Quality 
System. The collocated sites are to be located at the highest 
concentration sites, starting with one site in each of the largest 
population CBSA or CSA in the network and working to the next highest-
population CBSA or CSA with the second site and so forth.

E. What are the Proposed Requirements for the Number and Locations of 
Monitors To Be Operated by State and Local Agencies?

    The proposed amendments modify the requirements in appendix D to 40 
CFR part 58 for the number and locations of monitors necessary to 
support ambient air data objectives. This proposal requires States to 
deploy a new network of multipollutant monitoring stations called the 
National Core (NCore) network; requires States to maintain robust 
networks for PM2.5 and ozone (O3) and to 
establish a robust monitoring network for PM10-2.5; allows 
States to make major reductions in monitoring for other criteria 
pollutants, where concentration data are well below the applicable 
National Ambient Air Quality Standards (NAAQS) and are not expected to 
pose future air quality problems; and allows States to reduce the 
number of stations required for the NCore photochemical assessment 
monitoring stations (PAMS) network. We also propose to establish or 
modify certain monitoring frequency requirements.
    This proposal allows for reductions in air pollution monitoring for 
select pollutants in geographic areas that do not have or are not 
expected to have related air quality problems, while increasing or 
maintaining monitoring sites in areas with continuing or new air 
quality problems. The proposal allows for reductions in the carbon 
monoxide (CO), sulfur dioxide (SO2), nitrogen dioxide 
(NO2), PM10, and lead (Pb) air monitoring 
networks in geographic areas with historically low concentrations of 
these specific pollutants, except cases in which the State 
implementation plan (SIP) or source permits specifically require

[[Page 2730]]

certain monitoring. However, monitoring requirements that are part of a 
SIP or permit should be revisited as part of the network assessments 
described in section IV.E.11 of this preamble. Overall, a limited 
number of these monitors are still expected, but not required, to be 
operated to support studies of air quality trends, to allow 
accountability for emissions control programs, and for health effects 
studies.
    This proposal also requires States to increase or maintain 
monitoring sites in most areas with continuing or new air quality 
problems for O3 and PM2.5. However, with EPA 
agreement, States would be allowed to move some monitors to better 
characterize the spatial variability of these pollutants.
    As discussed in section IV.E.2 of this preamble, we also are 
proposing requirements for the minimum monitoring network for the 
proposed PM10-2.5 NAAQS published elsewhere in this Federal 
Register.\41\
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    \41\ Continuous PM2.5 and PM10-2.5 methods 
that can meet multiple monitoring objectives are being promoted by 
proposing new performance-based criteria for approval of these 
methods. See section IV.B of this preamble.
---------------------------------------------------------------------------

    Under the proposed monitoring amendments, the PAMS network would 
remain a requirement for serious, severe, and extreme ozone 
nonattainment areas. However, EPA is promoting the development of more 
individualized PAMS networks to suit the specific data needs for a PAMS 
area. We propose to make the PAMS requirements more flexible to allow 
for this redesign.
    Minimum criteria pollutant monitoring requirements, where proposed 
for retention or addition, would be based in part on population 
statistics. The Office of Management and Budget (OMB) has established 
standards for defining metropolitan and micropolitan statistical areas 
that replace metropolitan statistical areas defined in the 1990 
standards (65 FR 82227, December 27, 2000). The EPA has traditionally 
used the 1990 metropolitan statistical area definitions within many of 
the air monitoring requirements including the numbers of monitoring 
sites within a network and the Air Quality Index (AQI) reporting 
requirements. The proposed amendments use the new OMB standards for 
defining metropolitan and micropolitan areas, as well as the new 
standards for Core-based Statistical Areas (CBSA) and Combined 
Statistical Areas (CSA).
1. Proposed Requirements for Operation of Multipollutant Monitoring 
Stations Identified as the National Core Network (NCore).
    The EPA is proposing requirements applicable to States individually 
that may, in the aggregate, cause the deployment of a new network of 
monitors in approximately 60 mostly urban multipollutant stations. Most 
States would be required to operate at least one urban station; 
however, rural stations could be substituted in States that have 
limited dense urban exposures. States with Core-Based Statistical Areas 
(CBSA) often also have multiple air sheds with unique characteristics 
and, often, elevated air pollution. These States include, at a minimum, 
California, Florida, Illinois, Michigan, New York, North Carolina, 
Ohio, Pennsylvania, and Texas. These States would be required to 
identify one to two additional NCore stations in order to account for 
their unique situations. These stations, combined with about 20 
multipollutant rural stations, which are not specifically being 
required of the States, would form the new multipollutant NCore 
network. The rural NCore stations will be negotiated using grant 
authority as part of an overall design of the network that is expected 
to leverage existing rural networks such as IMPROVE, CASTNET and, in 
some cases, State-operated rural sites.
    These multipollutant NCore stations are intended to track long-term 
trends for accountability of emissions control programs and health 
assessments that contribute to ongoing reviews of the NAAQS; support 
development of emissions control strategies through air quality model 
evaluation and other observational methods; support scientific studies 
ranging across technological, health, and atmospheric process 
disciplines; and support ecosystem assessments. Of course, these 
stations together with the more numerous PM2.5 and 
O3 sites would also provide data for use in the NAAQS 
decision making process and for public reporting and forecasting of the 
AQI.
    The EPA proposes that these multipollutant NCore stations be 
required to measure O3; high-sensitivity measurements, where 
appropriate, of CO, SO2, and total reactive nitrogen 
(NOy); PM2.5 with both a Federal reference method 
(FRM) and a continuous monitor, PM2.5 chemical speciation, 
and PM10-2.5 with a continuous FEM; and meteorological 
measurements of temperature, wind speed, wind direction, and relative 
humidity. High-sensitivity measurements are necessary for CO, 
SO2, and NOy to adequately measure a signal for 
these pollutants in most air sheds for data purposes beyond NAAQS 
attainment determinations. For the other listed pollutants, 
conventional ambient air monitoring methods could be used.
    At least one NCore station would be required in each State, unless 
a State determines through the network design process that a site which 
meets their obligation can be reasonably represented by a site in a 
second State, and the second State has committed to establishing and 
operating that site. Any State, local, or tribal agency could propose 
modifications to these requirements for approval by the Administrator. 
While the proposed amendments do not specify the cities in which the 
States must place their multipollutant NCore Level 2 monitoring 
stations, EPA anticipates that the overall result will be a network 
that has a diversity of locations to support the purposes listed 
earlier. For example, there would be sites with different levels and 
compositions of PM2.5 and PM10-2.5, allowing air 
quality strategies to be evaluated under a range of conditions.
    These sites would be located in a manner that represents as large 
an area of relatively uniform land use and ambient air concentrations 
as possible (i.e., out of the area of influence of specific local 
sources, unless exposure to the local source(s) is typical of exposures 
across the urban area). Neighborhood-scale sites may be appropriate for 
multipollutant NCore monitoring stations in cases where the site is 
expected to be similar to many other neighborhood scale locations 
throughout the area. In some instances, State and local agencies may 
have a long-term record of several measurements at an existing location 
that deviates from the siting criteria in the proposed amendments. The 
State or local agency may propose utilizing these kinds of sites as the 
multipollutant NCore monitoring station to take advantage of that 
record. The EPA will approve these sites, considering both existing and 
expected new users of the data. The multipollutant NCore stations 
should be collocated, when appropriate, with other multipollutant air 
monitoring stations including PAMS, National Air Toxic Trends Station 
(NATTS) sites, and the PM2.5 chemical Speciation Trends 
Network (STN) sites. Collocation would allow use of the same monitoring 
platform and equipment to meet the objectives of multiple programs 
where possible and advantageous.
    The proposed amendments would require operation of the 60 NCore

[[Page 2731]]

stations by January 1, 2011. However, up to 35 of these stations are 
already being operated on a voluntary and EPA-funded basis with 
acquisition of high-sensitivity monitors for CO, SO2, and 
NOy. These three new measurements and other existing 
measurements for O3,PM2.5, and meteorology are 
the foundation of this highly leveraged network. PM10-2.5 
measurements would also be added to these stations once the continuous 
technologies are approved as FEM and are commercially available.
    Once these multipollutant NCore stations are established, it is 
EPA's intention that they operate for many years in their respective 
locations. Therefore, State and local agencies are encouraged to insure 
long-term accessability to the sites proposed for NCore monitoring 
stations. Relocating these stations would require EPA approval, which 
would be based on the data needs of the host State and other clients of 
the information.
    We may negotiate with some States, and possibly with some Tribes, 
for the establishment and operation of some additional rural NCore 
multipollutant monitoring stations to complement the multipollutant 
stations that would be required by the proposed changes to the 
monitoring regulations. We are in the process of revising CASTNET to 
upgrade its monitoring capabilities to allow it to provide even more 
useful data to multiple data users. We expect that about 20 CASTNET 
sites will have new capabilities at least equivalent to the 
capabilities envisioned for NCore multipollutant sites. Those sites 
would reduce the number of, and complement, rural multipollutant sites 
funded with limited State/local grant funds.
2. Proposed Monitoring Requirements for the Proposed Primary National 
Ambient Air Quality Standard for PM10-2.5
    The EPA is proposing elsewhere in today's Federal Register a new 
primary standard for coarse particulate matter (PM), and a new 
indicator for that standard: PM10-2.5, qualified so as to 
include any mix of PM10-2.5 dominated by resuspended dust 
from high-density traffic on paved roads and PM generated by industrial 
sources and construction sources, and excludes any ambient mix of 
PM10-2.5 that is dominated by rural windblown dust and soils 
and PM generated by agricultural and mining sources. See section III.D 
of the 40 CFR part 50 proposal.\42\
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    \42\ As explained in section III of the NAAQS proposal 
(published elsewhere in this Federal Register), the focus on coarse 
particles associated with these source types is derived from the 
available epidemiological studies that examined exposures to the 
ambient mix of PM10-2.5 in urban areas, and the study 
which examined exposure to unenriched natural crustal materials, as 
well as dosimetric evidence and toxicological studies. Adverse 
health effects associated with PM10-2.5 concentrations 
have been noted in studies conducted in urban areas, while limited 
evidence does not support the association of health effects with 
PM10-2.5 concentrations resulting from the suspension by 
wind of uncontaminated natural crustal materials of geologic origin. 
Furthermore, available evidence does not support either the 
existence or the lack of causative associations for community 
exposures to coarse particle emissions from agricultural or mining 
sources.
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    Accordingly, EPA is proposing new provisions in 40 CFR Part 58 to 
establish the minimum requirements for States to deploy and monitor for 
this proposed NAAQS. A main goal of the minimum required network will 
be the support of NAAQS designation decisions. Other data objectives 
include the improved characterization of the composition of coarse 
particles to support source apportionment studies and the development 
of control strategies; support of epidemiological and toxicological 
research efforts; public reporting of real-time concentration levels 
through the AQI and particle pollution forecasting programs; the 
quantification of coarse particle trends over time; and identifying and 
quantifying the factors that have contributed to changes over time for 
purposes of program accountability.
    Requirements for monitor placement by States that are specific, for 
example requirements regarding the target distances of monitors from 
sources of concern, will also ensure a level of consistency in network 
design that allows monitoring results to be generally comparable among 
areas where minimum monitoring requirements apply.
    This section begins with a discussion of the monitoring methods, 
types, and sampling frequencies to be used in the proposed network. We 
then turn to the description of the proposed minimum requirements for 
the PM10-2.5 monitoring network including the proposed 
number of monitors to be required in affected areas and proposed 
requirements for where those monitors should be located within the 
areas. States would have the discretion (and would be encouraged) to 
place additional monitors to supplement these minimum required 
monitors.
    Monitoring for an indicator described in qualified terms poses 
issues regarding how and when to determine the sites at which the 
ambient mix of PM10-2.5 would be dominated by resuspended 
dust from high-density traffic on paved roads and PM generated by 
industrial sources and construction sources, and where it would not be 
dominated by rural windblown dust and soils and PM generated by 
agricultural and mining sources. The proposed new provisions for 40 CFR 
part 58 described in this section address this issue.
    a. Monitor type, methods, and frequency of sampling.
    We are proposing a Federal reference method (FRM) for 
PM10-2.5 in a new appendix 0 to 40 CFR part 50 (Reference 
Method for the Determination of Coarse Particulate Matter in the 
Atmosphere), in section VI of the preamble to the Part 50 proposal 
elsewhere in this Federal Register. See also section IV.B above. The 
proposed FRM for measuring PM10-2.5 is based on the 
combination of two conventional low-volume filter-based methods, one 
for measuring PM10 and the other for measuring 
PM2.5, and determining the PM10-2.5 measurement 
by subtracting the PM2.5 measurement from the concurrent 
PM10 measurement.\43\
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    \43\ As noted in section VI.A.5 ``Relationship of Proposed FRM 
to Section 6012 of the Safe, Accountable, Flexible, Efficient 
Transportation Equity Act: A Legacy for Users (SAFETEA-LU) (PL 109-
59)'' of the part 50 NAAQS proposal, section 6012 of SAFETEA-LU 
requires the Administrator to ``develop a Federal reference method 
to measure directly particles that are larger than 2.5 micrometers 
in diameter without reliance on subtracting from coarse particle 
measurements those particles that are equal to or smaller than 2.5 
micrometers in diameter.''
    As explained above in section IV.B of this preamble and in the 
NAAQS proposal, EPA, consistent with Clean Air Scientific Advisory 
Committee (CASAC) Peer Review and recommendation, is proposing a 
difference method as the Federal reference method (FRM). We are 
doing so because other methods are not yet sufficiently developed to 
serve as an FRM. We have further explained, however, that we believe 
that other methods, notably certain types of continuous monitoring 
and dichotomous methods, are potential Federal equivalent methods, 
and indeed, that we expect actual monitoring networks to utilize 
these other means of monitoring. We are also continuing to 
investigate the possibility of promulgating the dichotomous method 
as an FRM, and if technically justified, will do so.
    We view these actions as consistent with the new statutory 
provisions. We are taking the steps necessary to develop a 
compliance network using non-difference, continuous methods as the 
principal means of monitoring for PM10-2.5. We are 
further devoting substantial effort to the possibility of 
promulgating dichotomous methods as an alternative FRM. The EPA will 
also submit the required reports by August 10, 2007, the deadline 
specified by SAFETEA-LU.
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    The new filter-based FRM would not be required to be widely 
deployed in the operational PM10-2.5 network, but rather 
would serve as the basis of comparison for the equivalency procedures 
in 40 CFR part 53 described in section IV.B of this preamble. The EPA 
intends (but would not require) that the majority of the monitors 
comprising the PM10-2.5 network be based on continuous 
methods that will provide an hourly

[[Page 2732]]

time resolution. At sites with locally measured wind data and 
continuous PM10-2.5 monitors, hourly time resolution will 
help States and EPA understand the emission sources that are most 
important to control, by relating wind direction and source locations 
in particular hours with peaks, and/or by matching the hourly pattern 
of concentrations with known temporal patterns of sources such as 
traffic. It may also, in some cases, help in understanding whether 
natural events have influenced a day's 24-hour concentration. Whatever 
method a State chooses to deploy, all PM10-2.5 monitors 
counted by a State as part of its compliance with the required minimum 
number of PM10-2.5 monitoring sites (proposed below) would 
be required to sample every day. The EPA's data quality objective 
process has found daily sampling to be a key factor in reducing 
statistical uncertainty at concentration levels near the proposed daily 
PM10-2.5 NAAQS. The automation inherent in continuous 
methods would provide a more cost-effective alternative to manual 
filter-based sampling for achieving this daily sampling frequency.
    The EPA is proposing January 1, 2009, as the deadline for 
deployment of PM10-2.5 monitors. This will provide over 2 
years from promulgation of the final rule for one or more continuous 
PM10-2.5 monitors to be approved by EPA as meeting the 
proposed Class III FEM requirements in 40 CFR part 53 and for the 
States to procure and deploy those instruments. We believe this will be 
sufficient time for the steps that are required by monitor vendors, 
EPA, and the States. At least two monitor vendors have already 
developed prototype continuous instruments expected to be candidates 
for approval as equivalent methods. These prototypes have already been 
the subject of field trials in cooperation with EPA. We expect vendors 
to make improvements based on this field experience so that final 
designs can be field tested in the winter of 2006/2007, after 
promulgation of the final rule, and in the summer of 2007. Under 40 CFR 
section 53.5, the Administrator has up to 120 days to act on 
equivalency applications. Thus, it is feasible for applications to be 
submitted and EPA to approve one or more applications in late 2007 or 
early 2008 and for States (or EPA on behalf of States) to place orders 
in time for monitors to be manufactured, shipped, and installed by 
January 1, 2009.
    A small percentage of continuous PM10-2.5 samplers 
(minimum of 15 percent) would be required to have a collocated filter-
based FRM sampler or collocated continuous FEM monitor at the same site 
for QA purposes (see proposed 40 CFR part 58, appendix A, Quality 
Assurance Requirements for SLAMS, NCore, and Prevention of Significant 
Deterioration (PSD) Air Monitoring. While we have determined that all 
of the PM10-2.5 monitors should be of the continuous type, 
except for these collocated FRM samplers, we are not requiring the sole 
use of continuous methods, in order to maintain flexibility in the use 
of manual sampling technology that can meet the proposed 
PM10-2.5 FRM or FEM requirements, and potentially address 
additional goals such as speciation.
    We have considered the issue of whether a State should be allowed 
to operate an appropriately sited PM10 monitor in lieu of a 
required PM10-2.5 monitor in a situation in which the 
probability of a PM10-2.5 NAAQS violation is small. Some 
State monitoring officials have expressed interest in such an option to 
save resources or to spread the need for monitor investments over 
time.\44\ We expect that in the types of areas where 
PM10-2.5 is dominated by emissions generated from high 
density traffic on paved roads, industrial sources, and construction 
activity, a substantial fraction of PM10 is likely to be 
PM2.5. While a PM10 monitor will capture this 
PM2.5 and thus would provide a conservative estimate (i.e., 
an overestimate) of PM10-2.5 concentrations, there are 
complicating considerations.
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    \44\ The Clean Air Scientific Advisory Committee (CASAC) also 
supported this concept, although without explicit discussion of the 
complicating implementation considerations discussed here.
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    Without data from FRM or FEM PM10-2.5 monitors, an area 
would be initially designated unclassifiable for 
PM10-2.5.\45\ Some designated PM10 FRM 
instruments have relatively poor precision compared to the proposed 
requirements for the PM10-2.5 FRM and FEMs. It is possible 
that an area might appear to meet the PM10-2.5 NAAQS based 
on PM10 monitor readings but actually not be in compliance. 
It is also possible that a PM10 monitor might unexpectedly 
indicate a high enough concentration of PM10 as to suggest a 
possible violation of the PM10-2.5 NAAQS. In such a 
situation, the result could be a delay in efforts to meet the 
PM10-2.5 NAAQS relative to what would have been the case had 
an approved FRM or FEM PM10-2.5 monitor been deployed 
initially.
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    \45\ An area without a PM10-2.5 monitor could in 
concept be included in an adjacent nonattainment area because of its 
contribution to concentrations in the latter area. Given the 
typically short transport distance of PM10-2.5, this 
would be unusual.
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    On balance, EPA believes it is appropriate to allow use of any 
PM10 FRM or FEM monitor in lieu of a required 
PM10-2.5 monitor, with restrictions, including the 
requirement for daily sampling at such PM10 monitors. This 
could only be initiated at monitoring sites where the 98th percentile 
value for the most recent complete calendar year of PM10 
monitoring data \46\, reported at local conditions of temperature and 
pressure as specified for PM10-2.5 , is less than the 
proposed PM10-2.5 NAAQS.\47\ During any calendar year of 
PM10 sampling in lieu of a required PM10-2.5 
sampler, if more than seven 24-hour average PM10 
concentrations exceed the numerical value of the proposed 
PM10-2.5 NAAQS, the State would have to deploy a FRM or FEM 
PM10-2.5 monitor within a one year period. We invite comment 
on this subject, including other possible provisions for more limited 
use of PM10 monitors in lieu of PM10-2.5 
monitors, such as limiting the use of PM10 monitors to a 
period of 3 years after the first approval of a continuous FEM 
PM10-2.5 method.
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    \46\ PM10 data used to qualify a site for 
PM10 monitoring in place of PM10-2.5 
monitoring must be based on a 1-in-3 day sampling frequency, or more 
frequent sampling.
    \47\ The EPA's intention regarding the substitution of 
PM10 monitors for required PM10-2.5 monitors 
is that siting criteria would not be affected, i.e., the 
PM10 monitor that will substitute for a 
PM10-2.5 monitor would have to be located at a site that 
would be appropriate for a required PM10-2.5 monitor. 
(What sites are appropriate for required PM10-2.5 
monitors is addressed below.) Also, PM10 data used to 
qualify a site for PM10 monitoring in place of 
PM10-2.5 monitoring must also be from--or clearly 
representative of--the site where a PM10 monitor will 
substitute for a PM10-2.5 monitor.
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    b. Network design.
    i. Number of required monitors. The discussion of network design 
requirements for PM10-2.5 begins with the questions of how 
to define the geographic units which should be separately subject to 
minimum monitoring requirements and how many monitors should be 
required in each such area. We propose that the geographic unit for 
individual application of monitoring requirements be the Metropolitan 
Statistical Area (MSA) (i.e., a CBSA which contains an urbanized area 
with a population of at least 50,000 persons).\48\ We also propose that 
only those MSAs that contain all or part of an urbanized area with a 
population of at least 100,000 or more be required to have monitors.
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    \48\ Defined metropolitan and micropolitan statistical areas 
based on application of 2000 standards (which appeared in the 
Federal Register on December 27, 2000) to 2000 decennial census 
data. http://www.census.gov/population/www/estimates/00-32997.txt.

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[[Page 2733]]

    Some MSAs contain multiple urbanized areas with populations of 
100,000 people or more, each containing emission sources of interest 
for PM10-2.5, which could be separately subject to 
monitoring requirements; however, we believe applying minimums at the 
urbanized area level is not necessary to support implementation of the 
proposed NAAQS.\49\ Where more than one MSA is part of a Combined 
Statistical Area (CSA), each MSA would be treated separately. We 
believe separate treatment of MSAs is appropriate in light of the 
typically short transport distance of PM10-2.5 and the 
diversity of situations that can exist in a CSA. For comparison, 
PM2.5 and O3 monitoring, minimum requirements 
apply at the CSA level, because a broader geographic frame is 
appropriate for those photochemically formed pollutants.
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    \49\ Factors which contribute to this assessment include the 
consideration that multiple urbanized areas in a single Metropolitan 
statistical area (MSA) will tend to have similar situations 
affecting PM10-2.5 concentrations, for example similar 
meteorological conditions which can favor or suppress emissions of 
PM10-2.5 from paved roadways and construction sites. 
Also, applying monitoring requirements separately to urbanized areas 
would both increase the total number of required monitors and reduce 
State flexibility in siting the required monitors since any 
requirements would have to be met separately in each urbanized area.
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    Consistent with both the current State and Local Air Monitoring 
Station (SLAMS) minimum requirements for PM2.5 described in 
40 CFR part 58, appendix D and the proposed minimum requirements for 
PM2.5 described in section IV.E.3 of this preamble, EPA 
proposes that States be required to have more PM10-2.5 
monitors in higher-population MSA than in lower-population MSA. A 
higher-population MSA typically has more total roadway surface, higher 
traffic counts, more and larger industrial sources, and more ongoing 
construction at any given time, all of which make it more likely that 
the MSA contains more locations with high concentrations of coarse 
particles attributable to these sources. Also, a higher-population MSA 
potentially contains more distinct types of emissions situations 
causing PM10-2.5 nonattainment, i.e., more distinct mixes of 
emission sources affecting different locations, such that separate 
monitoring may be needed to identify these and to develop and track the 
success of control strategies for them. More monitors will also be 
useful in helping to define nonattainment boundaries in larger and 
potentially more complex MSAs. Accordingly, we are proposing minimum 
requirements for the number of PM10-2.5 monitoring stations 
in each MSA based, in part, on the total population of the MSA.\50\
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    \50\ April 1, 2000 population in Metropolitan and Micropolitan 
Statistical Areas in Alphabetical Order and Numerical and Percent 
Change for the United States and Puerto Rico: 1990 and 2000, Source: 
U.S. Census Bureau, Census 2000 and 1990 Census. Internet Release 
date: December 30, 2003. http://www.census.gov/population/cen2000/phc-t29/tab01a.xls.
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    We are proposing that the actual or estimated PM10-2.5 
design value (three-year average of 98th percentile 24-hour 
concentrations) of an MSA, where one can be calculated, be used as a 
second factor to increase the minimum number of monitors in MSA with 
higher estimated ambient coarse particle levels and to reduce 
requirements in MSA with lower estimated levels. Given the imprecision 
of current estimates of PM10-2.5 ambient concentrations and 
the resulting non-robust design value statistics that will initially be 
available to States when they develop their monitoring plans, we are 
proposing three categories of design values defined by percentages of 
the proposed 24-hour PM10-2.5 NAAQS. The proposed amendments 
categorize MSA design values as either low (less than 50 percent of the 
proposed PM10-2.5 NAAQS), medium (50 percent to 80 percent), 
or high (greater than 80 percent).
    The EPA will assist States with the development of 
PM10-2.5 design values by analyzing the concentrations from 
existing collocated or nearly collocated PM10 and 
PM2.5 monitors in each MSA and identifying which pairs meet 
the proposed siting criteria appropriate for comparison to the proposed 
PM10-2.5 NAAQS. Monitoring agencies may propose other 
procedures for calculating estimated PM10-2.5 design values 
as a substitute for EPA-calculated values, subject to Regional Office 
approval of the monitoring methods, site characteristics, and data 
handling procedures being used to calculate substitute estimated design 
values. PM10-2.5 design values for purposes of determining 
the number of required monitors would be calculated using data only 
from sites which are suitable for comparison to the NAAQS under the 
criteria presented later in this section. If no such sites exist, 
medium area MSA minimum requirements would apply. After actual data 
using FRM or FEM monitors is available to establish a true design value 
based on 3 years of data, a State would be allowed to reduce or be 
required to increase the number of monitors based on that design value. 
This process of adjustment would be ongoing, and would be a specific 
aspect of the periodic network assessment that would be required by the 
proposed amendments.
    Table 1 of this preamble presents the specifics of the proposed 
requirements for the minimum number of monitors in an MSA, relating the 
minimum number of PM10-2.5 monitors to total MSA population 
and design value. For example, an MSA with a total population of 
between 1 million and 5 million people that contains all or part of an 
urbanized area with a population of at least 100,000 people, with an 
actual or estimated PM10-2.5 design value of between 50 
percent and 80 percent of the proposed PM10-2.5 NAAQS would 
be required to have at least two monitors. In another example, an MSA 
with a total population between 100,000 and 500,000 people with an 
actual or estimated PM10-2.5 design value of less than 50 
percent of the proposed PM10-2.5 NAAQS would not be required 
to have any monitors, although States could deploy discretionary 
monitors.
    We invite comment on whether there should be a different minimum 
size for an MSA required to have monitors, rather than applying the 
criteria in Table 1 of this preamble to all MSA that contain all or 
part of an urbanized area with a population of at least 100,000 
persons. We also invite comment on whether factors in addition to MSA 
population and estimated design value should enter into the 
determination of the number of required monitors, for example, MSA or 
urbanized area(s) population density, and if so, in what way.

[[Page 2734]]



                               Table 1.--PM10-2.5 Minimum Monitoring Requirements
----------------------------------------------------------------------------------------------------------------
                                                                  Most recent  3- Most recent  3- Most recent  3-
                                                                    year design     year design     year design
                    MSA total population 1 5                       value 2 >80%    value 50%-80%   value <50% of
                                                                    of PM10-2.5     of PM10-2.5   PM10-2.5 NAAQS
                                                                      NAAQS 3        NAAQS 3 4           3
----------------------------------------------------------------------------------------------------------------
> 5,000,000.....................................................               5               3               2
1,000,000-<5,000,000............................................               4               2               1
500,000-<1,000,000..............................................               3               1               0
100,000-<500,000................................................               2               1              0
----------------------------------------------------------------------------------------------------------------
\1\ Metropolitan Statistical Area (MSA) as defined by the Office of Management of Budget. The requirements of
  this table apply only to MSAs that contain all or part of an urbanized area with a population of at least
  100,000 persons. Metropolitan and micropolitan statistical areas based on application of 2000 standards (which
  appeared in the Federal Register on December 27, 2000) to 2000 decennial census data.
\2\ A database of estimated PM10-2.5 design values will be provided by EPA until the network is fully deployed
  for 3 years.
\3\ The proposed PM10-2.5 National Ambient Air Quality Standards (NAAQS) levels and forms are defined in 40 CFR
  part 50.
\4\ These minimum monitoring requirements would apply in the absence of a design value.
\5\ Population based on latest available census figures.

    The EPA estimates that the size of the minimum required 
PM10-2.5 network will be approximately 250 monitors based on 
the proposed requirements and our current estimates of 
PM10-2.5 design values. Figure 1 of this preamble 
illustrates our current estimates of how many monitors would be 
required in each MSA based on the criteria in Table 1, census data on 
MSA populations, and current estimates of design value.\51\ We are not 
proposing a specific number of monitors for any MSA. The actual initial 
number of monitors required in a given MSA and the initial size of the 
minimum required national network may be different if monitoring 
agencies propose and we approve alternate approaches to estimating 
design values for this purpose. It may be that later review by States 
may determine that one or more of the PM10 monitors we have 
used to estimate PM10-2.5 design values is not appropriate. 
Also, consideration of exceptional events may be appropriate and may 
affect estimated design values. The size of the required network may 
vary after its startup depending on long-term changes in total MSA 
population and design values.
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    \51\ A document listing the current estimate of 
PM10-2.5 design values used in constructing figure 1 of 
this preamble is available in the docket.
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[[Page 2735]]

[GRAPHIC] [TIFF OMITTED] TP17JA06.000

BILLING CODE 6560-50-C
    Figure 1 of this preamble shows that the proposed minimum network 
criteria could (depending on estimated design values as of the time the 
States develop their monitor siting plans) have the effect of putting 
relatively more monitors in the eastern States than in western States. 
This occurs in part because of currently estimated design values but 
also in part because there are so many individual MSA in eastern States 
compared to western States. In western States, there are fewer small 
and medium-sized cities which are in separate MSA and thus qualify for 
separate monitoring under the proposed criteria, because the larger 
size of

[[Page 2736]]

counties in the western States means that many smaller cities are 
subsumed within relatively few MSA.
    We request comment on whether the proposed minimum requirements 
appropriately address the need for monitoring data in both eastern and 
western States, whether additional or fewer monitors could be needed, 
and whether additional monitors in some areas, if needed, should be 
required by the regulations or deployed through collaborative planning 
and grant support. A possibility on which we request comment is to not 
adhere to the formal county-based definition of MSA in the West and in 
some way to require separate monitoring of more urbanized areas that 
are not distinct MSA and, therefore, would not be separately subject to 
the minimum monitoring requirements as proposed. For example, some MSA 
in some western states are divided into distinct nonattainment areas 
for ozone, reflecting natural barriers to transport between air basins. 
This division or similar divisions of a large MSA in a western state 
could perhaps play a role in determining which population centers 
should require separate monitoring for PM10-2.5. We also 
request comment on approaches that would aggregate officially distinct 
MSAs in eastern States for the purpose of determining the required 
number of monitors.
    ii. Location of required monitors and comparability to the NAAQS. 
We now turn to the criteria that should be used to locate required 
monitoring sites within an MSA (the number of monitors to be sited 
being determined by the total MSA population and estimated design value 
criteria as just described). As stated in the introduction to this 
section, a main goal of the minimum required monitors in a given MSA 
will be to support NAAQS designation decisions, including decisions on 
nonattainment area boundaries. As detailed in the NAAQS proposal also 
in today's Federal Register, the purpose of the proposed qualified 
coarse particle indicator and standard is to protect against coarse 
particle mixes that are likely to be similar to those present in the 
urban epidemiological studies upon which the proposed standard is 
based. The indicator for the NAAQS includes any ambient mix of 
PM10-2.5 that is dominated by resuspended dust from high-
density traffic on paved roads and PM generated by industrial sources 
and construction sources, and excludes any ambient mix of 
PM10-2.5 that is dominated by rural windblown dust and soils 
and PM generated by agricultural and mining sources. In order to 
implement the proposed standard, it is necessary to separate where the 
mix is dominated by the emissions of PM from listed sources and where 
it is not. We have been mindful of this goal in developing the 
following proposals regarding monitor siting. In particular we have 
been mindful that the strategy for locating PM10-2.5 
monitors must be developed in light of the qualified indicator for the 
NAAQS. Monitors should therefore be placed in locations where 
concentrations of PM10-2.5 are dominated by PM emissions 
generated from high density traffic on paved roads, industrial sources, 
and construction activities.
    We have also been mindful that the strategy for locating 
PM10-2.5 monitors must be developed in light of the approach 
used to set the level of the proposed PM10-2.5 NAAQS. As 
explained in the NAAQS proposal notice elsewhere in today's Federal 
Register, the proposed level of 70 [mu]g/m3 for 
PM10-2.5 (98th percentile form) was selected to be of 
equivalent stringency to the current 24-hour PM10 NAAQS of 
150 [mu]g/m3 (one-expected exceedance form). As discussed 
below, the approach used to determine that these levels are equivalent 
in stringency has implications for PM10-2.5 monitor 
placement.
    The EPA recognizes that each MSA will be characterized by a unique 
mix of moderate to highly populated areas together with unique 
arrangements of paved roads, areas of construction, and industrial 
sources of coarse particles. Therefore, we are proposing network design 
requirements that leave room for later agreement between EPA and each 
State on specific sites but that provide the binding principles for 
those agreements.
    We envision that a typical PM10-2.5 monitoring network 
in a large MSA would include some sites with heavy impacts from PM 
emissions generated from highly traveled roadways and/or major 
industrial sources, but with a relatively small exposed population 
because the area around the site is not a dense residential or 
commercial area, and some sites in densely populated areas with 
somewhat less proximity to such sources. It could also include some 
sites in lower-density suburban-type population areas that are 
nonetheless affected by sources with emissions of concern. Within each 
of these three categories of sites, there are some sites that are not 
suitable for required monitors because the sites have a good 
possibility of not being dominated by PM emissions generated from high 
density traffic on paved roads, industrial sources, and construction 
activities, or because placement of monitors for comparison to the 
NAAQS in those locations would be inconsistent with the intended 
stringency of the NAAQS. The following proposal addresses both how the 
required number of monitors should be assigned to the three categories 
of sites, and what types of sites are suitable or unsuitable for 
placement of monitors.
    We are proposing a five-part test of whether a potential monitoring 
site is suitable for comparison to the NAAQS, and two rules for how 
required monitors should be assigned among such suitable sites. All 
five parts of the suitability test must be met. The suitability test 
also would be used to determine whether non-required or special purpose 
monitors are suitable for comparison with the proposed 
PM10-2.5 NAAQS.
    The first two parts of the five-part suitability test are based on 
using readily available Census data to help ensure that 
PM10-2.5 monitoring sites are located near and will be 
dominated by PM emissions from paved roads, construction, and 
industrial sources. The first part is that a monitoring site must be 
within a U.S. Census Bureau-defined urbanized area that has a 
population of at least 100,000 persons. Restricting suitable sites to 
only those within an urbanized area of this size increases the 
likelihood that the ambient mix of PM10-2.5 will be 
dominated by resuspended dust from high-density traffic on paved roads 
and PM generated by industrial sources and construction sources, rather 
than rural windblown dust and soils and PM generated by agricultural 
and mining sources which are more typical of rural areas.
    The second part of the suitability test is a minimum threshold for 
the population density of the block group containing the monitoring 
site. This provides more assurance that resuspended dust from high-
density traffic on paved roads and PM generated by industrial sources 
and construction sources will dominate in the vicinity of the 
monitoring site.
    We propose to employ population density in addition to simple 
presence within an urbanized area because population density is highly 
correlated to traffic density and is available on a relevant geographic 
scale. It is appropriate to expect that mixes of PM10-2.5 
monitored at sites located in areas of sufficiently high population 
density are dominated by resuspended dust from high-density traffic on 
paved roads and PM generated by industrial sources and construction 
sources.
    Accordingly, we have based the proposed suitability test for a 
candidate monitoring site on the population

[[Page 2737]]

density of the census block group in which the site is located. There 
is a strong correlation of county-level estimates of Vehicle Miles 
Traveled (VMT) density with county-based population density.\52\ It is 
reasonable to presume that this county-level correlation indicates an 
association between population density and vehicular traffic and 
resulting emissions of resuspended dust at smaller geographic scales 
also, although exceptions to the association no doubt become more 
common. To a lesser extent, there may also be associations between 
population density and the presence of other industrial sources and 
construction activities.\53\ It is thus appropriate to expect that 
mixes of PM10-2.5 monitored at sites located in areas of 
sufficiently high population density are dominated by resuspended dust 
from high-density traffic on paved roads and PM generated by industrial 
sources and construction sources, and are not dominated by rural 
windblown dust and soils and PM generated by agricultural and mining 
sources.
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    \52\ Review of the National Ambient Air Quality Standards for 
Particulate Matter: Policy Assessment of Scientific and Technical 
Information, OAQPS Staff Paper, EPA-452/R-05-005, June 2005, p. 5-
59. Counties are the geographic unit at which vehicle miles traveled 
(VMT) is most readily available from State departments of 
transportation. The Federal Highway Administration maintains VMT 
statistics at a higher level of aggregation.
    \53\ Manufacturing and service industry facilities, and areas of 
long-term construction such as commercial development and roadway 
construction, tend--with exceptions--to be in the general area of 
populated areas that create the demand for such activities and 
provide their workers.
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    The available census geographic entities for which population 
density is published by the U.S. Census are counties, urbanized areas, 
urban clusters, census tracts, and block groups. Block groups typically 
encompass one-half to two square miles, and thus they provide a spatial 
resolution of about one mile. On average, there are approximately 200 
block groups for each of the 370 MSA in the U.S. In a State such as 
Michigan, for example, the average land area in a county is 700 square 
miles as compared to just over 20 square miles for a census tract and 
to about 0.5 square miles for a block group. A large-scale unit of 
density analysis, say the urbanized area level, would not be as helpful 
for guiding monitor placement since it would be a mix of low and high 
density sub-units that could have quite different source mixes.
    We considered a range of block group population density thresholds 
for use in identifying block groups within an urbanized area that may 
be suitable for comparison to the NAAQS, depending on other parts of 
the suitability test. A low population density threshold would tend to 
identify as suitable low density ``edge'' block groups, which because 
of their proximity to surrounding non-urbanized lands could tend to 
have PM10-2.5 concentrations that are from emission sources 
that are not of concern, as these are explicitly rural sources 
(windblown rural dust and soil) or sources that are more typical in 
rural lands (agriculture and mining). A low population density 
threshold would also tend to identify internal or ``enclave'' low 
density block groups which may well have significant paved road, 
industrial, and construction emission sources but happen not to have 
many residences; later we return to such ``enclave'' block groups as an 
exceptional case. A population density threshold that is too high could 
leave out areas where PM10-2.5 concentrations are dominated 
by PM emissions from high density traffic on paved roads, industrial 
sources, and construction activities.
    We first noted that the U.S. Census Bureau uses a population 
density of 500 persons per square mile in one step of defining the 
``Initial Core'' of an urbanized area. The initial core of an urbanized 
area always includes core census block groups or blocks with a density 
of at least 1,000 persons per square mile and contiguous block groups 
that have a density of at least 500 persons per square mile.\54\
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    \54\ See Urban Area Criteria for Census 2000, March 15, 2002, 51 
FR 11663. The Census Bureau adds to each urbanized area additional 
non-contiguous block groups below and above 500 persons per square 
mile using detailed ``hop'' and ``jump'' criteria. Any additional 
block groups below 500 persons per square mile would not be included 
in our proposed suitability test because such areas are less likely 
to have a dense concentration of paved roads, construction, and 
industrial sources and may be in close proximity to sources of 
emissions that are not of concern.
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    We have investigated for comparison the population densities of 
block groups in which States and EPA have agreed in the past to place 
PM10 monitors. We observe that States have typically located 
PM10 monitors in block groups of population densities that 
are higher than 500 people per square mile. The median block group 
population density of the approximately 1,200 PM10 
monitoring sites active in the U.S. between 2002 and 2004 is 1,390 
people per square mile. Sixty-three percent of the approximately 1,200 
PM10 monitoring sites are in block groups with a density 
higher than 500 persons per square mile.
    We have also investigated for comparison the block group population 
densities for those PM10 monitors which are sited with or 
near a PM2.5 monitor. The PM2.5 monitoring 
program was set up to be more urban oriented than the PM10 
monitoring program. Thus, this smaller set is of more relevance to the 
structure of a PM10-2.5 monitoring program. Among the 710 
such monitors, the median block group density is 2,306 persons per 
square mile. Seventy-eight percent of the 710 monitoring sites are in 
block groups with a density higher than 500 persons per square mile.
    After examining on an empirical basis in a sampling of MSA the 
block groups identified by population density thresholds of 500 persons 
per square mile, values lower than 500, and values above 500, and in 
light of the practices of the U.S. Census Bureau, we selected 500 as 
the proposed threshold value for the second part of the suitability 
test because it appears to result in inclusion of most of the related 
urbanized area while omitting fringe areas where paved roads, 
construction sites, and industrial sources are few in number and/or low 
in emissions mass, and whose emissions and ambient impact could be 
exceeded by the impact of rural soil, dust, and emissions from 
agricultural and mining sources.
    Regarding the above-mentioned issue of enclaves within an urbanized 
area, we are concerned not to exclude low population density block 
groups that contain paved roads, construction sites, and/or industrial 
sources and do not contain significant agricultural or mining sources. 
The Census incorporates enclaves consisting of block groups with 
population density below 500 persons per square mile if certain 
conditions are satisfied. Enclaves of less than five square miles are 
always incorporated. Even larger enclaves can be included as well. We 
are concerned that such large enclaves may not be industrial zones or 
transportation corridors that happen to have little resident population 
(which could be appropriate for monitoring) but instead could contain 
agricultural or mining operations (which could make them inappropriate 
for monitoring). Therefore, we propose that block group(s) with 
population densities less than 500 persons per square mile, even if 
part of an urbanized area, will be considered to pass the second part 
of the suitability test if those block groups comprise an enclave of 
less than five square miles in land area. We invite comment on this 
special exception.
    We propose that the third necessary condition for siting a required 
monitor and comparing any PM10-2.5 monitor to the 
PM10-2.5 NAAQS be that the monitor be population-oriented. 
The term

[[Page 2738]]

``population-oriented sites'' is presently defined in 40 CFR 58.1 as 
sites in residential areas, recreational areas, industrial areas, and 
other areas where a substantial number of people may spend a 
significant fraction of their day.\55\ The concept plays an important 
role in the PM2.5 monitoring network in that a 
PM2.5 monitor must be population-oriented to be appropriate 
for comparison to either the annual or 24-hour PM2.5 NAAQS. 
We believe that this restriction is also appropriate for 
PM10-2.5 for the same reasons as for PM2.5.
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    \55\ Population density of a block group and population-
orientation of a monitoring site are distinct concepts. A monitoring 
site may not be population-oriented even though it is within a block 
group of high population density. Population-orientation refers to 
the presence of people in a geographic area around a monitoring site 
that may be much smaller than the block group. If there is not a 
substantial number of people spending a significant fraction of 
their day in the area around the monitor with ambient concentrations 
of about the magnitude indicated by a monitor, the monitor is not 
population oriented, regardless of the population density of the 
surrounding census block group. For example, there could be a 
portion of a high-density block group that is near a source but 
which has few residents or visitors because of its land use type, 
for example.
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    The fourth part of the five-part suitability test is a restriction 
against monitoring sites that are adjacent to a large emissions source 
or otherwise within the micro scale environment affected by a large 
source.\56\ This restriction is intended to help ensure that monitor 
siting is consistent with the intended stringency of the proposed 
NAAQS. The relatively large size of coarse particles and resulting high 
rate of deposition under most weather conditions, and the fact that 
nearly all coarse particles are primary\57\, mean that the ambient 
concentration of PM10-2.5 measured in a specific location 
will be more dependent on the distance of that monitor from coarse 
particle sources than would typically be the case for ambient 
PM2.5 and associated sources of fine particles.\58\ Monitors 
placed adjacent to coarse particle sources would typically measure 
higher ambient concentrations than monitors placed farther away. A 
PM10-2.5 monitoring site located adjacent to a high emitting 
industrial source or a heavily traveled highway, for example, might 
measure high ambient concentrations, but these concentrations could be 
characteristic only of the relatively small area around the monitor, 
notably a smaller area than in the case of a similarly sited 
PM2.5 monitor. Even if there are people living or working at 
the monitor site, thus qualifying it as population-oriented, applying 
the proposed NAAQS level to the concentration level measured at such a 
monitor would be inconsistent with the level of community protection 
intended through the proposed NAAQS. As explained in section III.G of 
the NAAQS preamble, the EPA intends that the proposed 24-hour 
PM10-2.5 NAAQS be equivalent in stringency to the current 
24-hour PM10 NAAQS. In determining the level for the 
PM10-2.5 NAAQS that would achieve this equivalency, we 
relied on the relationship between PM10-2.5 and 
PM10 observed at PM10 monitoring sites all or 
most of which were not adjacent to large emission sources. If 
PM10-2.5 monitors were placed at sites that are adjacent to 
emission sources, the effect would be to make the proposed NAAQS less 
community-oriented and more stringent than intended. The EPA therefore 
believes it is appropriate to have a restriction that 
PM10-2.5 monitors in source-influenced micro-environments, 
such as on facility fence lines or along the edge of traffic lanes, are 
not appropriate for comparison to the NAAQS even if there is some 
population subject to exposure in that location (even if EPA or the 
State believes that there are other micro-environments similarly 
affected by other sources of the same type). PM10-2.5 
monitors placed in such micro environment-types of situations thus 
would not be eligible for comparison to the NAAQS \59\ and would not 
count toward meeting minimum EPA monitoring requirements.
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    \56\ A microscale environment is one in which there are 
significant differences in concentrations between locations that are 
10 meters to 100 meters apart, and generally are areas that are 
impacted by immediately adjacent sources such as industrial sites, 
roadways, or construction sites.
    \57\ i.e., coarse particles typically are deposited in the form 
most recently emitted by their original source (or in the form they 
had when resuspended after having deposited to a roadway or 
construction site) rather than being created or modified by 
atmospheric chemical reactions during their generally short 
transport from the point of original emission (or resuspension). 
Particles that have been resuspended may have incorporated 
secondarily formed compounds at some time in their prior history.
    \58\ Air Quality Criteria for Particulate Matter, Volume I of 
II, EPA/600/P-99/002aF, October 2004, p. 2-49. See also section 
III.G in the NAAQS proposal elsewhere in today's Federal Register.
    \59\ We note that this proposed language is more restrictive for 
the proposed 24-hour PM10-2.5 NAAQS than parallel 
language for the 24-hour PM2.5 NAAQS (which allows such 
data to be used for comparison with the 24-hour PM2.5 
NAAQS, see present 40 CFR part 58, appendix D, section 2.8.1.2.3). 
As explained in the text above, this is because coarse PM is 
transported over shorter distances such that a microscale 
PM10-2.5 monitor would not be representative of 
community-wide conditions.
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    The fifth part of the suitability test, which would only need to be 
considered for sites that satisfy all of the first four parts, is that 
a site-specific assessment shows that the ambient mix of 
PM10-2.5 sampled at that site would be dominated by 
resuspended dust from high-density traffic on paved roads and PM 
generated by industrial sources and construction sources, and would not 
be dominated by rural windblown dust and soils and PM generated by 
agricultural and mining sources. The first four parts of the 
suitability test make it unlikely that a candidate site would be 
dominated by rural windblown dust (other than perhaps during 
exceptional events), but the site-specific assessment may determine 
otherwise. The site-specific assessment may also reveal the presence of 
a dominant agricultural or mining operation, for example, a gravel or 
sand extraction and material handling operation.
    As an example of how this five-part suitability test would work, 
consider the Riverside-San Bernardino-Ontario, California MSA. The 
first part of the test excludes any site outside the Census-designated 
urbanized areas within the MSA, of which there are several. The second 
part of the test would indicate that a monitoring site within a certain 
boundary around the densest parts of the Riverside-San Bernardino 
urbanized area, the Indio-Cathedral City-Palm Springs urbanized area, 
or any of the other urbanized areas in the MSA that have a population 
of at least 100,000 persons, is possibly suitable for comparison with 
the NAAQS, while a monitoring site in the small Yucca Valley urban 
cluster would definitely not be suitable. Each boundary would follow 
block group borders, and would leave out less dense parts of its 
associated urbanized area. The third part of the test (population-
orientation) would disqualify some sites within these boundaries 
because of the small number of people subject to exposure in the 
vicinity that has concentrations similar to what would be monitored at 
the site. The fourth part would disqualify sites adjacent to major 
roadways (a source-influenced microenvironment). The fifth part would 
assess the remaining candidate sites to verify that they are not 
exposed to windblown rural dust and soils or PM generated by 
agriculture and mining sources to such an extent that emissions from 
those sources would dominate the mix of PM10-2.5 sampled at 
that site.
    We invite comment on possible variations of the proposed test for 
suitability for comparison to the NAAQS, for example the use of census 
tracts in place of block groups or different values for population 
density or total population of a aggregation of block groups or tract 
groups. Census

[[Page 2739]]

tracts are defined as combinations of (usually a few) block groups, and 
would provide a somewhat larger scale of analysis around a candidate 
monitoring site.
    While the issue of setting boundaries for nonattainment areas is 
not a subject of this rulemaking, we note that the considerations that 
underlie the proposed suitability test, having to do with the influence 
of sources on measured concentrations, may also be relevant to the 
setting of such boundaries.
    The five-part suitability test will leave as suitable many sites in 
a MSA, falling into the three broad categories described earlier. We 
believe that States should be given further direction on placement of 
the required monitors among these sites. A network design strategy 
should not allow all required PM10-2.5 monitoring sites to 
be located so far from large emissions sources that they measure 
ambient concentrations lower than would be representative of the impact 
of coarse particle sources on well populated urban areas. We propose to 
address this issue by adopting some of the elements of the monitoring 
siting approach that has been used for the PM10 NAAQS. We 
propose that 50 percent of required PM10-2.5 monitors \60\ 
be required to represent population-oriented middle scale-sized areas 
\61\ \62\ near but not adjacent to large sources of PM (i.e., heavily 
traveled paved roadways, long-term construction sites, large industrial 
sources) to characterize air quality in significant-sized areas that 
are affected by emissions from these sources where people may spend a 
greater part of their day.\63\ The placement of a monitor on the 
grounds of a school within a residential community that is near but not 
adjacent to an industrial facility would be an example of such a site. 
With this requirement for middle scale PM10-2.5 sites, EPA's 
proposal provides the intended degree of protection in populated areas 
with high coarse particle concentrations by requiring sites that are 
likely to measure the maximum concentrations (among sites meeting the 
suitability test) in one or more of the populated areas that are 
impacted by the heaviest PM emissions from roadways and/or industrial/
construction sources.
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    \60\ Fractional monitor requirements would round up. MSA with 
one, two, three, four, or five required monitors would place one, 
one, two, two, or three monitors in this manner, respectively.
    \61\ A middle scale-sized area is one in which there are 
significant differences in concentrations between locations that are 
100 meters to 500 meters apart, and generally are areas that are 
impacted by nearly adjacent (but not immediately adjacent) sources, 
such as industrial sites, roadways, or construction sites. Middle 
scale sites are common in PM10 monitoring (see present 40 
CFR part 58, appendix D, section 2.8.0.2) and typical of the 
PM10 sites used to establish the equivalency of the 
proposed PM10-2.5 NAAQS to the current PM10 
NAAQS.
    \62\ Additional information on middle-scale siting, and on all 
such monitoring scales, can be found in the document: Guidance For 
Network Design and Optimum Site Exposure For PM2.5 and 
PM10. U.S. Environmental Protection Agency. EPA-454/R-99-
022. December 1997. Available on the web at: http://www.epa.gov/ttn/amtic/files/ambient/pm25/network/r-99-022.pdf.
    \63\ If only one monitor is required, then that monitor would 
need to conform to this siting requirement (if the monitor is to be 
considered as part of the minimum network design).
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    For those areas with monitoring requirements greater than one 
required monitor, we propose that at least one of the required monitors 
must be sited in a neighborhood scale-sized area \64\ that is highly 
populated and which may be somewhat further away from emission sources 
but is still expected to have elevated levels of coarse particles of 
concern. These sites would typically still be impacted by roadway and/
or industrial/construction source emissions, but to a lesser extent 
than sites expected to measure maximum concentrations. Among such 
sites, the State should select a site characterized by a very large 
number of people subject to exposure; typically, this population number 
would be higher than the population at sites expected to record maximum 
concentrations. A site located within a heavily populated residential 
and commercial area that is in proximity to roadways with high 
vehicular traffic would be an example of this type of monitor 
placement. A site of this type is useful for several reasons. It will 
help define the spatial gradients of PM10-2.5 
concentrations, which may be useful in setting nonattainment area 
boundaries. It likely will provide concentration data that are relevant 
for informing a large segment of the population of their exposure 
levels on a given day. Also, areas of this type may have 
PM10-2.5 nonattainment problems that are caused by a 
different source mix than problems found at the first type of site, and 
require a different approach to reducing concentrations. For example, 
the mix of industrial and paved road emissions may be different or the 
mix of types of vehicles on paved roads may be different.
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    \64\ A neighborhood scale-sized are is one in which there are 
not typically significant differences in concentrations between 
locations that are 500 meters to four kilometers apart, and 
generally are areas that are impacted by the more well-mixed 
emissions of urban industrial and mobile sources in the general 
vicinity of the site.
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    For MSA with a requirement for one, two, or three monitors, the 
above two siting provisions address the siting of all required monitors 
with respect to proximity to specific sources and populations. For MSA 
with a requirement for four or five monitors, there is one remaining 
required monitor not yet addressed. We propose that the siting of this 
monitor be left to the discretion of the State or local monitoring 
agency, subject to a restriction that the site satisfy the suitability 
test described above. This site could be placed in locations similar to 
those that would be eligible as monitoring sites for the other required 
monitors, i.e., at other sites that meet one of the above two proposed 
siting requirements. A State may also choose to place the site in a 
location that is somewhat more distant from downtown areas, main 
industrial source regions, or areas of highest traffic density, such as 
in a highly populated suburban residential community. The comparison of 
ambient PM10-2.5 concentrations between such suburban 
monitors and those monitors located at the previously described maximum 
exposure-type of sites would provide comparative data for assessing the 
spatial variation of PM10-2.5 concentrations over a 
metropolitan area.
    While we expect the proposed suitability test described above will 
appropriately identify areas where the ambient mix of 
PM10-2.5 is dominated by resuspended dust from high-density 
traffic on paved roads and PM generated by industrial sources and 
construction sources, it may not identify them all. We recognize that 
it does not address the possibility that high density traffic on paved 
roads, large industrial emission sources, and/or construction 
activities may be located outside an urbanized area (including outside 
any MSA) or in parts of an urbanized area that do not satisfy the 
second part of the suitability test (related to population density) 
such that monitoring sites near these sources would not meet the 
proposed test, yet persons living or working near the source could be 
exposed to concentrations of PM10-2.5 which are dominated by 
the PM emissions from these sources. We invite comment on alternative 
approaches that would examine areas where States may wish to place non-
required monitors that do not meet the proposed suitability test, but 
are locations of industrial emissions or high traffic on paved roads 
which create the potential for ambient mixes of coarse particles of the 
type intended to be included by the indicator. In particular, EPA 
solicits comment on a modification of the proposed test that would 
specify that a site meeting only the third, fourth, and fifth parts of 
the

[[Page 2740]]

suitability test could be compared to the NAAQS if it were close enough 
to an industrial source of coarse particles of a defined high enough 
emissions level (for example, 100 tons per year or more of emissions) 
that the ambient mix would be dominated by PM generated by that 
industrial source. The term ``industrial'' would be made operational by 
using a source's assigned industry code under the North American 
Industry Classification System (NAICS) and excluding sources with codes 
corresponding to agricultural or mining industries.\65\ As noted, the 
site would have to population-oriented and could not be in the micro-
scale environment affected by a large source. A site-specific 
assessment (the fifth part of the suitability test) would still be 
required, and would consider the local mix of emission source types and 
sizes, their relative locations to the potential monitoring site, and 
local factors affecting transport and deposition of 
PM10-2.5. Such monitors, even if determined to be comparable 
to the NAAQS through the site-specific assessment, would not count 
toward the minimum number of monitors required for each MSA.
---------------------------------------------------------------------------

    \65\ Information on the NAICS is avaialble at http://www.census.gov/epcd/naics02/.
---------------------------------------------------------------------------

    We also invite comment on the possibility of another, similar 
modification to the proposed suitability test as that just described 
for industrial sources, but addressing emissions from vehicle traffic 
on roadways. Non-required State sites otherwise excluded from 
comparison to the NAAQS, based on their location outside of a U.S. 
Census Bureau-defined urbanized area and/or their location in block 
groups with population density below the proposed threshold, but are 
population oriented and within some distance of a roadway with a 
certain traffic volume per day, could be the subject of site-specific 
analysis to determine if they are in fact suitable for comparison to 
the NAAQS based on the PM emissions from sources that dominate 
PM10-2.5 concentrations at those sites. Such sites would 
have to be population-oriented and could not be in the micro-scale 
environment affected by the roadway. The site-specific assessment would 
consider the local mix of emission source types and sizes, their 
relative locations to the potential monitoring site, and local factors 
affecting transport and deposition of PM10-2.5. We seek 
comment on whether such sites would be appropriate for comparison to 
the NAAQS, and, if so, what levels of VMT must occur and/or other 
conditions exist before comparison to the NAAQS could be considered. We 
note that traffic volume alone is not a direct predictor of emissions 
of resuspended dust and other PM10-2.5 emissions, since the 
load of dust on the highway and the mix of vehicle types matter also. 
Such monitors, even if determined to be comparable to the NAAQS through 
the site-specific assessment, would not count toward the minimum number 
of monitors required for each MSA.
    iii. Non-required monitoring. States may deploy PM10-2.5 
monitors in addition to those that would be required. For example, 
additional monitors in areas that are required to have one or more 
monitors may be very useful for determining nonattainment area 
boundaries. States might also want to site monitors near large point 
sources, if the final rule provides for the suitability of monitoring 
sites near such sources. The EPA will work with States as they consider 
what additional monitors to deploy and operate.
    The proposed suitability test for comparison with the 
PM10-2.5 NAAQS applies to all non-required monitors (as well 
as all required monitors). Data from monitors that do not meet the 
suitability test could not be used for nonattainment determinations. 
For example, as with required monitors, non-required monitors must also 
be population-oriented as defined above in order to be used for 
nonattainment designations. Also, as with required monitors, non-
required monitors could not be compared to the NAAQS if they are 
located in source-influenced micro-environments, such as on facility 
fence lines or along the edge of traffic lanes.
    iv. Speciation monitoring. In addition to sites measuring 
PM10-2.5 mass concentration, our experience with 
PM2.5 suggests that it would be useful to have a long-term 
PM10-2.5 speciation network of 50 to 100 sites to assess 
physical and chemical characteristics at a nationally diverse set of 
locations. Speciation data would help identify the specific source 
types, address the relative contribution of anthropogenic and natural 
sources to ambient concentrations, and support future research 
concerning the health risks of coarse particles of various compositions 
and source origins. We propose that one speciation site be located in 
each of the MSAs with total population greater than 500,000 people and 
that also have an estimated PM10-2.5 design value greater 
than 80 percent of the proposed PM10-2.5 NAAQS. We expect 
that approximately 25 MSAs will be required to have speciation monitors 
based on these proposed criteria. These sites will gather data in areas 
that have a higher probability of exceeding the proposed NAAQS and also 
have larger exposed populations at risk, and would support the 
characterization of coarse particles concentrations that control the 
attainment/nonattainment status of the area. States would be required 
to operate any of these speciation sites that were located inside their 
borders. In some cases, monitors could be collocated with 
PM2.5 speciation monitors at urban NCore multipollutant 
monitoring stations to provide comparative chemical characterization 
studies between fine and coarse particles. The PM10-2.5 mass 
concentration data obtained with speciation monitors would be 
comparable to the NAAQS only in situations where the underlying 
sampling method used to obtain the filters was an approved FRM or FEM 
and the site met the suitability test described earlier in this 
section.
    We will collaborate with States to select and fund additional sites 
based on data requirements, individual State needs, and availability of 
funds. The EPA solicits comment on all aspects of the 
PM10-2.5 speciation network including the number of required 
sites, the total size of the network, the criteria for choosing the 
number of required monitors in each area, the sampling method used to 
obtain filters, and frequency and types of analyses that would be 
performed on those filters.
    c. Monitoring plan requirements and approval process.
    We propose that each State be required to submit to the respective 
EPA Regional Administrator a plan proposing how all affected monitoring 
organizations within the State will comply with the requirements 
described above for the type, sampling schedule, number, and location 
of PM10-2.5 monitoring stations. The plan would also provide 
supporting information for why each monitoring site which the State 
proposes to count towards the requirement for a minimum number of 
monitors is suitable for comparison to the PM10-2.5 NAAQS, 
based on the criteria described above. In addition, for each non-
required monitoring site which the State intends to deploy and which 
the State considers would be appropriate for comparison to the proposed 
PM10-2.5 NAAQS, the plan would also provide evidence that 
the monitor is suitable for comparison, based on the criteria described 
above. The State would be required to make this plan available for 
public inspection for at least 30 days prior to submission to EPA.
    This plan would be due to EPA January 1, 2008. The EPA Regional 
Administrator may extend this due date

[[Page 2741]]

to July 1, 2008, for example to allow it to be consolidated with the 
overall annual monitoring review and plan due at that time.
    The EPA Regional Administrator will review the submitted plan and 
approve or disapprove it by a letter to the submitting State official 
within 120 days of submittal. The EPA Regional Administrator will be 
required to invite public comment; he/she must consider relevant public 
comments, if any are received in response to the invitation. We are not 
proposing a specific mechanism for the Regional Administrator to make 
the plan available for public comment, but we invite comment now on 
mechanisms that would be practical for the Regional Administrators and 
effective for persons likely to want to comment. The approval, if 
given, will include confirmation that EPA will treat each planned 
monitoring site as suitable or not suitable for comparison to the 
PM10-2.5 NAAQS, along with the reasons for each 
determination. This confirmation will be a final EPA action applicable 
to subsequent determinations of attainment or nonattainment. This 
status will then be recorded in AQS for each monitor by the State.
    Elsewhere in this notice (section IV.E.11), we are proposing a new 
requirement for States to conduct and submit to EPA a comprehensive 
monitoring system assessment at five-year intervals. The status of each 
PM10-2.5 monitoring site with respect to comparability to 
the NAAQS should be re-examined during these assessments, starting with 
the first assessment which is submitted not less than 5 years after EPA 
Regional Administrator approval of the initial PM10-2.5 
monitoring plan. The State may also propose a change in the status of a 
PM10-2.5 monitor whenever a large existing source of 
PM10-2.5 near the monitor ceases (or begins) operation and 
is expected to remain shut down (or to continue operation)for three or 
more years, if the type of source involved is such that its shut down 
or start up could materially affect what types of emissions dominate 
the PM10-2.5 measured at the site.
    We invite comment on this proposed process and possible 
alternatives or additions to it, for example on whether there should be 
review by the EPA Administrator before the approval or disapproval is 
considered a final Agency action, or an opportunity for appeal to the 
Administrator to alter the final action.
3. Monitoring Requirements for the Proposed Primary and Secondary 
National Ambient Air Quality Standards for PM2.5
    The current PM2.5 network includes over 1,200 FRM 
samplers at approximately 900 sites that are operated to determine 
compliance with the NAAQS; track trends, development, and 
accountability of emission control programs; and provide data for 
health and ecosystem assessments that contribute to periodic reviews of 
the NAAQS. Over 450 continuous PM2.5 monitors are operated 
to support public reporting and forecasting of the AQI.
    For PM2.5, EPA proposes to modify the network minimum 
requirements for PM2.5 monitoring so that multiple urban 
monitors in the same CBSA are not required if they are redundant or 
measuring concentrations well below the NAAQS. We propose to base 
minimum monitoring requirements for PM2.5 on 
PM2.5 concentrations as represented by a design value, and 
on the census population of the CBSA. Overall, this is expected to 
result in a lower number of required sites; however, we recommend and 
anticipate that States continue to operate a high percentage of the 
existing sites now utilizing FRM, but with FEM and ARM continuous 
methods replacing the FRM monitors at many of these sites.\66\
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    \66\ An approved regional method (ARM) is a PM2.5 
method that has been approved specifically within a State, local, or 
tribal air monitoring network for purposes of comparison to the 
National Ambient Air Quality Standards and to meet other monitoring 
objectives. See section IV.D.2 of this preamble.
---------------------------------------------------------------------------

    We are proposing to require that all sites counted by a State 
towards meeting the minimum requirement for the number of 
PM2.5 sites have an FRM, FEM, or ARM monitor. We are also 
proposing that at least one-half of all the required PM2.5 
sites be required to operate PM2.5 continuous monitors of 
some type even if not an FEM or ARM. This requirement would ensure that 
continuous methods continue to be well utilized throughout the network 
to support monitoring objectives such as public reporting and 
forecasting of the AQI not readily addressed by FRM and filter-based 
FEM.
    As noted, EPA proposes to use design value and population as inputs 
in deciding the minimum required PM2.5 monitoring sites in 
each CSA/CBSA. We are proposing these inputs so that monitoring 
resources are prioritized based on the number of people who may be 
exposed to a problem and the level of exposure of that population. 
Metropolitan areas with smaller populations would not be required to 
perform as much monitoring as larger areas. If ambient air 
concentrations as indicated by historical monitoring are low enough, 
these smaller population areas would not be required to continue to 
perform any PM2.5 monitoring.
    The proposed amendments would require fewer sites when design 
values are well above (rather than near) the NAAQS to allow more 
flexibility in the use of monitoring resources in these areas where 
States and EPA are already more certain of the severity and extent of 
the PM2.5 problem and possibly in more need of other types 
of data to address it. For instance, an agency may wish to operate more 
speciation samplers rather than FRM to get a better understanding of 
the atmospheric chemistry of an area. We invite comments on this 
approach, versus requiring more FRM/FEM monitors in areas well above 
the NAAQS.
    The proposed siting criteria for PM2.5 monitors would 
remain the same as current requirements, which have an emphasis on 
population-oriented sites at neighborhood scale and larger. Population-
oriented middle scale sites would remain a part of the network for 
comparison to both the daily and annual standard when a site can 
represent many other middle-scale locations where people are exposed. 
For middle-scale sites that are unique, only the daily NAAQS would be 
considered when comparing data to the standard.
    Background and transport sites would remain a required part of each 
State's network to support characterization of regional transport and 
regional scale episodes of PM2.5. To meet these 
requirements, IMPROVE samplers may be used even though they would not 
be eligible for comparison to the PM2.5 NAAQS; these 
samplers are currently used in visibility monitoring programs in Class 
I areas and national parks. Sites in other States which are located at 
places that make them appropriate as background and transport sites can 
also fulfill these minimum siting requirements.
    The proposed change in the primary 24-hour PM2.5 NAAQS 
from 65 [mu]g/m\3\ to 35 [mu]g/m\3\ raises the issue of whether any 
commensurate changes would be needed in the PM2.5 ambient 
monitoring network regulations. The current specific network design 
criteria for PM2.5 in appendix D to 40 CFR part 58 directs 
States to select sites mostly representative of community-oriented 
area-wide PM2.5 exposure levels at locations of neighborhood 
or larger scale, except in cases where a certain population-oriented 
microscale or middle-scale PM2.5 site is determined to 
represent similar locations that

[[Page 2742]]

collectively form a larger region of localized high ambient 
PM2.5 concentrations. The EPA believes that these current 
design criteria remain appropriate for implementation of the proposed 
primary PM2.5 NAAQS. The existing minimum requirements 
effectively ensure that monitors are placed in locations that 
appropriately reflect the community-oriented area-wide concentrations 
levels used in the epidemiological studies that support the proposed 
lowering of the 24-hour NAAQS.
    Most often, the current location of maximum monitors around 
PM2.5 concentrations is the same as the location of maximum 
monitored 24-hour PM2.5 concentrations, suggesting that no 
shifts in monitors would be needed to implement the proposed 24-hour 
NAAQS. In a relatively small number of cases \67\, certain microscale 
PM2.5 monitors that have not been eligible for comparison to 
the annual PM2.5 NAAQS and that have been complying with the 
24-hour PM2.5 NAAQS, and therefore have not impacted the 
attainment status, may become more influential to attainment status 
under a more stringent 24-hour form of the NAAQS. Some sites that have 
not measured high concentrations relative to the current 24-hour NAAQS 
may also become more influential to attainment status under the 
proposed more stringent 24-hour NAAQS. In these cases, States may 
choose to move accompanying speciation and continuous monitors to the 
new site of particular interest to get a better characterization of PM 
at that location. States and EPA may also agree on changing the 
location of some PM2.5 FRM/FEM sites to insure measurements 
at the population-oriented location(s) of most interest.
---------------------------------------------------------------------------

    \67\ EPA is presently aware of less than 10 PM2.5 
monitors that are sited in a manner that is unsuitable for 
comparison to the annual NAAQS.
---------------------------------------------------------------------------

    In proposed changes to 40 CFR 58.10 (Monitoring Network Description 
and Periodic Assessments), monitoring agencies would be required to 
provide a network plan that includes the identification of any 
PM2.5 sites that are not suitable for comparison against the 
annual PM2.5 NAAQS. The proposed requirements would also 
provide for a public hearing and review of changes to a 
PM2.5 monitoring network that impact the location of a 
violating PM2.5 monitor, prior to requesting EPA approval of 
the changes. Through this process, monitoring agencies would be able to 
consider changes to their PM2.5 monitoring networks made in 
response to the proposed NAAQS, and inform the public about the 
potential implications on design values and resulting attainment and 
nonattainment decisions.
    In today's NAAQS proposal (published elsewhere in this Federal 
Register), EPA requests comments on the alternative of basing a 
PM2.5 secondary standard on a shorter-term averaging 
interval of less than 24-hours to provide protection against visibility 
impairment primarily in urban areas.
    If the alternative short-term secondary standard is promulgated, 
EPA envisions that compliance would be assessed with data from 
continuous PM2.5 monitoring methods capable of providing 
hourly time resolution. Continuous monitors would be required to comply 
with FEM or ARM requirements. Hourly PM2.5 data values would 
be averaged over the appropriate short-term averaging interval (e.g., 
four to eight hours) to assess compliance with the proposed short-term 
secondary NAAQS. The alternative short-term secondary NAAQS would also 
require minor additions to the current PM2.5 siting 
requirements. Some continuous monitors would likely be required to be 
sited on a neighborhood and urban scale to form the basis of a network 
representing ambient PM2.5 conditions along corridors that 
influence visibility of important scenic resources in and around urban 
areas. Sites might also want to consider collocating such monitors with 
automated haze-cam systems to quantify local relationships between 
short-term PM2.5 concentrations and visual range.
4. Proposed Monitoring Requirements for PM10
    In the PM NAAQS proposal published elsewhere in this Federal 
Register, EPA proposes to revoke the PM10 annual standard. 
Further, consistent with the more targeted nature of the proposed new 
PM10-2.5 indicator, the Administrator proposes to revoke the 
current 24-hour PM10 standard everywhere except in areas 
where there is at least one monitor that violates the 24-hour 
PM10 standard. In areas where both applicable 
PM10 NAAQS are revoked, we propose to have no minimum 
PM10 monitoring requirements and to allow discontinuation of 
PM10 monitors without prior EPA approval, although 
monitoring organizations would have the option of funding and operating 
PM10 monitors as needed to satisfy any still-applicable SIP 
commitments or to monitor compliance with non-Federal air quality 
standards. In areas where the PM10 NAAQS are not both 
revoked, we propose to have no minimum requirements, but to require 
prior EPA approval for changes to existing monitors. See also section 
IV.E.8 of this preamble.
5. Proposed Requirements for Operation of Ozone Monitoring Sites
    Ozone (O3) monitoring sites are operated to determine 
compliance with the NAAQS; to track trends, development, and 
accountability of emission control programs; to provide data for health 
and ecosystem assessments that contribute to ongoing reviews of the 
NAAQS; and to support public reporting and forecasting of the AQI. For 
O3, EPA proposes to change the minimum network requirement 
from at least two sites in ``any urbanized area having a population of 
more than 200,000'' to an approach that considers the level of exposure 
of O3, as indicated by the design value and the census 
population of an area. Larger population CSA and CBSA with design 
values near the O3 NAAQS would be required to operate at 
least four sites. Smaller CSA and CBSA would be required to operate as 
few as one site, provided the design values were sufficiently low 
enough. Similar to the proposal for PM2.5, EPA proposes that 
areas with measured ambient concentrations significantly above the 
NAAQS be required to operate fewer sites than areas with measured 
ambient concentrations near the NAAQS to allow flexibility of resources 
in those areas. We invite comments on this approach.
    The O3 monitoring network is primarily based on 
continuous FEM using ultraviolet analysis. The network is well deployed 
throughout the country at about 1,100 sites with most metropolitan 
areas already operating more O3 monitors than would be 
required by today's proposed amendments. The EPA does not anticipate or 
recommend significant changes to the size of this network because 
O3 remains a pollutant with measured levels near or above 
the NAAQS in many areas throughout the country. However, the proposed 
amendments would help to better prioritize monitoring resources 
depending on the population and relative levels of O3 in an 
area.
6. Proposed Requirements for Operation of Carbon Monoxide, Sulfur 
Dioxide, Nitrogen Dioxide, and Lead Monitoring Sites
    Criteria pollutant monitoring networks for the measurement of CO, 
SO2, NO2, and Pb are primarily operated to 
determine compliance with the NAAQS and to track trends and 
accountability of emission control

[[Page 2743]]

programs as part of a SIP. Because these criteria pollutant 
concentrations are typically well below the NAAQS, there is limited use 
for public reporting to the AQI, except for a very small number of 
locations with on-going local air quality issues.
    Gas measurements of CO, SO2, and NO2 utilize 
continuous technologies. Lead (Pb) is sampled by collecting total 
suspended particulates (TSP) on a high-volume sampler and analyzed in a 
laboratory.
    We are proposing to revoke all minimum requirements for CO, 
SO2, and NO2, monitoring networks, and reduce the 
requirements for Pb. This proposal allows for reductions in ambient air 
monitoring for CO, SO2, NO2, and Pb, particularly 
where measured levels are well below the applicable NAAQS and air 
quality problems are not expected, except in cases with ongoing 
regulatory requirements for monitoring such as SIP or permit 
provisions. In these cases, EPA encourages States to comment on ways to 
reduce these potentially unnecessary monitors. We will also work with 
some States on a voluntary basis to make sure that at least some 
monitors for these pollutants remain in place in each EPA region. 
Measurement of CO, SO2, and NOy are being 
proposed as required measurements at NCore sites. There may be little 
regulatory purpose for keeping many other sites showing low 
concentrations, other than specific State, local, or tribal commitments 
to do so. However, in limited cases, some of these monitors may be part 
of a long-term record utilized in a health effects study. The EPA 
expects State and local agencies to seek input on which monitors are 
being used for heath effects studies prior to shutting down a monitor. 
See also section IV.E.8 of this preamble (Proposed criteria and process 
for discontinuing monitors).
7. Proposed Changes to Minimum Requirements for Ozone Precursor 
Monitoring
    Section 182(c)(1) of the CAA required us to promulgate rules 
requiring enhanced monitoring of ozone, oxides of nitrogen, and 
volatile organic compounds in ozone nonattainment areas classified as 
serious, severe, or extreme. On February 12, 1993, we promulgated 
requirements for State and local monitoring agencies to establish 
Photochemical Assessment Monitoring Stations (PAMS) as part of their 
SIP monitoring networks in ozone nonattainment areas classified as 
serious, severe, or extreme. During 2001, we formed a workgroup 
consisting of EPA, State, and local monitoring experts to evaluate the 
existing PAMS network. The PAMS workgroup recommended that the existing 
PAMS requirements be streamlined to allow for more individualized PAMS 
networks to suit the specific data needs for a PAMS area.
    We are proposing changes to the minimum PAMS monitoring 
requirements in 40 CFR part 58 to implement the recommendations of the 
PAMS workgroup. Specifically, we are proposing the following changes:
     The number of required PAMS sites would be reduced. Only 
one Type 2 site would be required per area regardless of population and 
Type 4 sites would not be required. Only one Type 1 or one Type 3 site 
would be required per area.
     The requirements for speciated VOC measurements would be 
reduced. Speciated VOC measurements would only be required at Type 2 
sites and one other site (either Type 1 or Type 3) per PAMS area.
     Carbonyl sampling would only be required in areas 
classified as serious or above for the 8-hour O3 standard.
     NO2/NOX monitors would only be 
required at Type 2 sites.
     NOy will be required at one site per PAMS area 
(either Type 1 or Type 3).
     Trace level CO would be required at Type 2 sites.
    Note that on April 15, 2004, we revised some O3 
nonattainment classifications, under the 8-hour O3 standard 
(69 FR 23951). While the number of areas classified as serious, severe, 
or extreme ozone nonattainment under the 8-hour O3 standard 
has been greatly reduced (69 FR 23857), areas that had previously been 
classified as serious, severe, or extreme ozone nonattainment under the 
1-hour O3 standard are required to comply with the PAMS 
monitoring requirements until they achieve compliance with the 8-hour 
ozone standard. See 40 CFR 51.900(f)(9). In addition, the PAMS 
requirements would apply to any new areas that are classified or 
reclassified as serious, severe, or extreme O3 nonattainment 
under the 8-hour O3 standard.
    We solicit comments on the proposed revisions to the PAMS 
monitoring program requirements including the measurements to be made, 
the sampling frequencies, and the location and numbers of required 
monitoring sites proposed.
8. Proposed Criteria and Process for Discontinuing Monitors
    The EPA has determined that many single-pollutant monitors operated 
by State and local agencies, specifically many of those measuring CO, 
Pb, PM10, SO2, and NO2, are providing 
data that have limited usefulness in air quality management. This is 
likely the case for monitors whose data indicate current attainment of 
the corresponding NAAQS with little prospect for future nonattainment. 
Accordingly, consistent with the draft National Ambient Air Monitoring 
Strategy (NAAMS), we are proposing to eliminate the current 
requirements for operation of a certain minimum number of monitors for 
CO, PM10, SO2, and NO2, and to reduce 
the requirements for Pb monitors, as described in section IV.E.6 of 
this preamble. We are also proposing changes to loosen the minimum 
requirements for monitoring of O3 precursors in the PAMS 
program, as described in section IV.E.7 of this preamble. We are also 
proposing changes to the minimum requirements for O3 and 
PM2.5 monitoring that may have the effect of reducing the 
minimum number of these monitors in some areas. We note that the 
remaining specific minimum requirements (limited to O3, 
PM2.5, and PM10-2.5) are intended to be necessary 
but are not always sufficient to meet the requirement in section 
110(a)(2)(B) of the Clean Air Act (CAA) that SIP provide for operation 
of appropriate systems to monitor, compile, and analyze data on ambient 
air quality. We intend to require many States to operate some monitors 
for these pollutants, but to determine what monitoring is appropriate 
on a more case-by-case basis. The EPA encourages, and in fact the 
proposed amendments to 40 CFR part 58 would require, all States to 
assess their monitoring networks periodically to determine what changes 
should be made, including which monitors should be discontinued and 
which retained. Local situations will differ, and should be considered 
individually. Reducing low-value monitoring expenditures would allow 
resources to be devoted to under-served and new monitoring purposes.
    Some monitors in excess of the remaining minimums may be necessary 
to the State/local air quality management process, or for other uses, 
such as development and validation of air quality models. We are 
proposing to continue to require States to propose changes in their 
monitoring networks and obtain EPA approval before making changes, even 
when the remaining minimum requirements for number of monitors would 
still be met. This EPA review and approval can take place through the 
mechanism of the annual monitoring plan. The current rule already 
requires State agencies to prepare and submit the plan on July 1

[[Page 2744]]

of each year for EPA approval at the Regional Office level. We are 
proposing to retain this current requirement. We will approve proposed 
changes to a monitoring plan provided the proposed network will still 
meet any applicable SIP provisions related to ambient monitoring and 
will provide data needed to support the air quality control program. 
Based on assessments that we and individual States have done to date, 
we generally expect to find that a large percentage--between 33 percent 
for SO2 and 90 percent for NO2--of current 
monitors for CO, PM10, SO2, and NO2 
can be removed; that most O3 monitors should continue 
although some should be moved to more productive locations; that some 
filter-based PM2.5 monitors can be removed; and that some 
filter-based PM2.5 monitors should be replaced by continuous 
instruments when models that have been approved as FEM or ARM are 
available.
    While local situations need to be considered individually, we 
believe that certain general principles can be articulated regarding 
reductions in monitoring networks. We have incorporated these 
principles in the proposed amendments to reduce uncertainties in the 
process and thereby facilitate an efficient and timely process for 
review and approval or disapproval of proposed changes. These 
principles would apply independently. A monitor meeting any one of them 
would qualify for EPA approval for discontinuation. Situations not 
addressed by these criteria would be considered on a case-by-case 
basis. The EPA Regional Offices would have more time to give this case-
by-case consideration to the exceptional cases because cases meeting 
one of the following criteria could be disposed of more quickly.
     Any PM2.5, O3, CO, PM10, 
SO2, Pb, or NO2 monitor which has shown 
attainment during the previous 5 years, that has a probability of less 
than 10 percent of exceeding 80 percent of the NAAQS during the next 3 
years based on the levels, trends, and variability observed in the 
past, and which is not specifically required by an attainment plan or 
maintenance plan, can be removed or moved to another 
location.68, 69 Few if any O3 monitors in urban 
areas would likely meet this criterion, but some PM2.5 
monitors may do so. This criterion would not apply to a 
PM2.5 monitor that is part of a spatial averaging plan.
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    \68\ The concept of using historical data to statistically 
predict the probability of a future violation is an element of EPA's 
current policy memo on ``Limited Maintenance Plan Option for 
Moderate PM10 Nonattainment Areas,'' August 9, 2001. See 
http://www.epa.gov/ttn/oarpg/t1/fact_sheets/lmp_fs.pdf and http://www.epa.gov/ttn/oarpg/t1/memoranda/cdv.pdf. EPA believes that this 
concept can be generalized to the other pollutants listed in this 
paragraph, but the details of the probability estimation method(s) 
will likely differ.
    \69\ Five years of historical data means five successive 
calendar years of data sufficient for making an attainment 
determination.
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     A monitor for CO, PM10, SO2, or 
NO2, which has consistently measured lower concentrations 
than another monitor for the same pollutant in the same county and same 
nonattainment area during the previous 5 years, and which is not 
specifically required by an attainment plan or maintenance plan, could 
be removed or moved to another location, if control measures scheduled 
to be implemented or discontinued during the next 5 years would apply 
to the areas around both monitors and have similar effects on measured 
concentrations, such that the retained monitor would remain the higher 
reading of the two monitors being compared.\70\
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    \70\ PM2.5 and O3 are not included in this 
proposed criterion because of the value of even low-reading monitors 
in understanding the causes of nonattainment and in informing the 
public about potential exposures. Lead (Pb) is not included because 
Pb concentrations are often very dependent on effective control of 
Pb emissions of individual sources very close to the monitor and we 
believe it would be too risky to depend on area-wide generalizations 
about the effect of scheduled controls. Also, we believe the 
effectiveness of emission controls on Pb sources may be more 
variable over time than of CO, SO2, PM10, and 
NO2 emission controls on sources of those pollutants.
---------------------------------------------------------------------------

     For any pollutant, the highest reading monitor (which may 
be the only monitor) in a county (or portion of a county within a 
distinct nonattainment or maintenance area) could be removed or moved 
to a new location provided the monitor has not measured NAAQS 
violations in the previous 5 years, the CBSA within which the county 
lies (if in any) would still meet requirements for the minimum number 
of monitors for the applicable pollutant if any, and the approved SIP 
provides for a specific, reproducible approach to representing the air 
quality of the affected county in the absence of actual monitoring 
data. For example, the SIP could provide that a continuing monitor in a 
neighboring county will always be taken by the State and EPA to 
represent both counties for purposes of nonattainment and other 
regulatory determinations. Because EPA would review and approve any SIP 
revision that provides such an approach to representing air quality in 
the affected county, EPA can ensure its technical validity and 
protectiveness. We intend to take a cautious approach to allowing 
removal of such monitors, particularly in urban areas. While approval 
of such SIP revisions would be delegated to the Regional Offices, EPA 
Headquarters officials would participate in the review of proposed 
revisions that present the first instance of specific approaches, and 
would resolve issues of national consistency if such issues arise.
     A monitor, which EPA has determined cannot be compared to 
the relevant NAAQS because of the siting of the monitor, could be moved 
or removed. For example, a PM2.5 monitor must be population-
oriented to be comparable to the daily or annual NAAQS, and one that is 
not population-oriented could be removed.\71\
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    \71\ Section 2.8.1.2.3 of appendix D to 40 CFR part 58 (Network 
Design for State and Local Air Monitoring Stations (SLAMS)).
---------------------------------------------------------------------------

     A monitor that is designed to measure concentrations 
upwind of an urban area for purposes of characterizing transport into 
the area and that has not recorded violations of the relevant NAAQS in 
the previous 5 years could be moved to another location where 
information on transport will be more useful to SIP development.
     A monitor not eligible for removal under any of the above 
criteria could be moved to a nearby location with the same scale of 
representation if logistical problems beyond the State's control make 
it impossible to continue operation at its current site. For example, 
the State may lose access to a monitoring site not owned by the State 
itself, and this criterion would ensure approval of a new site that was 
nearby and that had the same scale of representation (e.g., middle-
scale or neighborhood-scale). A move to a more distant site would 
require case-by-case EPA review of the appropriateness of the new 
location compared to other alternatives.
    In the situations covered by these proposed criteria, the State 
would need to make a factual showing that the specified conditions are 
met. Once the EPA Regional Office accepts that showing, the proposed 
amendments would require approval of the State's request as part of the 
Regional Office action on the annual monitoring plan. We may issue 
guidance suggesting appropriate ways these showings can be made.
    We invite comments on the specific details of these proposed 
criteria, and on other criteria that would be appropriate.
    In order to help information be available to the State and to EPA 
that could be relevant to the appropriateness of monitoring network 
changes, we propose that each State be required to make available for 
public inspection its draft annual monitoring plan for a

[[Page 2745]]

period of at least 30 days prior to submitting it to the EPA Regional 
Office for approval. The State could, for example, satisfy this 
proposed requirement by making the draft plan available for download 
via the air agency's Internet Web site. We also propose that when 
submitting the annual monitoring plan for EPA approval, the State 
provide evidence that: (1) The State has considered the ability of the 
proposed network to support air quality characterization for areas with 
relatively high populations of susceptible individuals (e.g., children 
with asthma); and (2) if the State proposes to discontinue any 
monitoring sites, the State has considered how discontinuing monitoring 
sites would affect data users other than the monitoring agency itself, 
such as nearby States and tribes or health effects research studies. We 
invite comment on where EPA should provide opportunity to examine and 
comment on monitoring plans after they are reviewed by the Regional 
Office.
9. Special Purpose Monitors
    The development of today's proposed amendments has given EPA 
occasion to re-examine the longstanding issue of whether the ambient 
air monitoring rules and current policies regarding use of monitoring 
data for regulatory determinations have the effect of creating undue 
and counterproductive disincentives to States and other organizations 
deploying discretionary monitors that overall and in the long run would 
benefit air quality management efforts. The EPA is proposing a limited 
change in the monitoring rules on this issue.
    At present, each State at any given time is required to operate a 
certain set of monitors under the monitoring regulations and its own 
approved monitoring plan, or to meet commitments it has made in its SIP 
and/or grant agreement(s) with EPA. If a State chooses to deploy an 
additional monitor, it may designate it as a special purpose monitor 
(SPM). Such designation can afford the State certain flexibility it 
would not have if the monitor were designated as an NCore station or 
State and local air monitoring station (SLAMS).\72\ However, regardless 
of whether a monitor is designated as an SPM, if it is an 
appropriately-sited FRM or FEM monitor and if its operation meets the 
QA requirements of 40 CFR part 58, or if the data are otherwise 
determined to be technically valid, EPA considers all available data 
from that monitor whenever we make a determination of attainment or 
nonattainment. The possibility that data from an SPM could result in a 
nonattainment designation of an area that would otherwise not be so 
designated may discourage the State from deploying a new monitor or 
supporting the deployment of a monitor by another organization, such as 
a university, even when the monitor would provide useful information 
for determining the extent, severity, causes, and possible solutions of 
a known or suspected air quality problem. Thus, a State that might have 
voluntarily addressed a nonattainment problem may never become aware of 
the problem. Also, affected persons may also be left unaware and unable 
to reduce their own exposures by modifying their behavior or to 
advocate for State action to address the problem.
---------------------------------------------------------------------------

    \72\ A special purpose monitor (SPM) is one which the State does 
not count when showing compliance with the minimum requirements for 
the number and siting of monitors and which it has designated as an 
SPM by so labeling it in the Air Quality System (AQS) data system 
and/or in its monitoring plan. In common practice EPA does not 
overrule such designations provided the rest of the monitoring 
network meets minium requirements. Monitors carrying special purpose 
status need not use Federal reference or equivalent methods, are not 
subject to the quality system requirements of 40 CFR part 58 that 
apply to State and local air monitoring stations (SLAMS), and are 
not subject to siting requirements such as probe height or distance 
from nearby obstructions (or, in this proposal, the proposed siting 
suitability requirements for monitors which can be used for 
comparison with the proposed 24-hour PM10-2.5 standard. 
Their data are not required to be submitted to AQS, and they may be 
discontinued at will by the State (assuming no grant commitment 
exists for their continued operation). States start up and designate 
monitors as special purpose as a flexible and economical way to meet 
various local monitoring objectives, such as exploring a possible 
air quality problem in response to citizen concerns.
---------------------------------------------------------------------------

    We addressed this issue in the 1997 rulemaking that established the 
current requirements for PM2.5 monitoring, and created a 
narrow exception to the practice that all known, good air quality data 
be considered in such determinations. (See preamble discussion at 62 FR 
38770, July 18, 1997 and in existing 40 CFR 58.14(b).) That narrow 
exception addressed only new SPM for PM2.5 concentrations. 
It provides that PM2.5 NAAQS violation determinations shall 
not be exclusively made based on data produced at a population-oriented 
SPM site during the first two complete years of its operation, but only 
if monitoring is not continued beyond those 2 years. More recently, 
during the development of the draft NAAMS and today's proposal, EPA has 
received input from various parties, including the Clear Air Act 
Advisory Committee, to the effect that EPA ``should promote policies to 
avoid disincentives to monitoring'' by limiting the regulatory use of 
data from such monitoring.\73\ A moratorium on any use of data from the 
first 3 years after the deployment of a discretionary monitor, 
applicable to all NAAQS pollutants, was a specific approach discussed 
in some of our consultations with State and local monitoring officials 
during the development of this proposal. Such a moratorium would give 
States time to address the air quality problem with more flexibility 
than it would have if the area were designated nonattainment and 
subject to CAA requirements for nonattainment areas.
---------------------------------------------------------------------------

    \73\ See recommendation 1.4 in Recommendations to the Clean Air 
Act Advisory Committee (CAAAC), Air Quality Management Workgroup, 
January 2005, transmitted by the CAAAC as a Committee recommendation 
to Administrator Michael O. Leavitt on January 19, 2005.
---------------------------------------------------------------------------

    We understand and, to some degree, sympathize with the States' 
perception that the current requirements create disincentives to 
monitoring. We agree that it is conceivable, and perhaps likely, that 
it might ultimately be more protective of public health to have more 
monitoring data in hand even if the early years of data from each 
additional, discretionary monitor could not be used for regulatory 
purposes, compared to never having that data at all. However, we 
believe we may not ignore technically valid air quality data from FRM 
and FEM monitors when making attainment or nonattainment 
determinations. If we know that an area is actually not meeting an 
NAAQS based on valid data, we cannot ignore those data. This is 
premised on the provisions of the CAA that the Agency must follow in 
determining whether an area is attainment or nonattainment. Section 
107(d)(1)(A)(i) of the CAA defines ``nonattainment'' as ``any area that 
does not meet'' an NAAQS and CAA section 107(d)(1)(A)(ii) defines 
``attainment'' as any area ``that meets'' an NAAQS. In light of this 
explicit language, EPA does not believe we could affirmatively 
determine an area to be an attainment area for a particular criteria 
pollutant, (i.e., an area ``that attains'' the NAAQS) if we had the 
requisite years of valid data from appropriately sited FRM or FEM 
monitors showing that the area was in fact not attaining the standard.
    In light of this legal requirement, we believe that two limited 
exclusions on use of data from SPM are possible. We are proposing that: 
(1) The limited two-year moratorium on the use of data from SPM in 
determinations of NAAQS violations established in the 1997 rulemaking 
for PM2.5 be extended to the annual PM10 NAAQS 
(if it is retained rather than revoked as proposed

[[Page 2746]]

elsewhere in today's Federal Register), the O3 NAAQS, and 
the proposed 24-hour PM10-2.5 NAAQS, rather than any more 
extensive data exclusion approach; and (2) for CO, SO2, 
NO2, Pb, and 24-hour PM10, that data from the 
first 2 years of a SPM would not be used for nonattainment designations 
but would be used in making findings of whether a nonattainment area 
has attained the NAAQS. In both cases, data from the first 2 years of 
operation of a new SPM would not be used provided the monitor does not 
continue operation beyond those 2 years. If the monitor does continue 
operation beyond 2 years, all years of data will be given full 
consideration. This policy would in some situations facilitate special 
purpose monitoring that would otherwise be discouraged by the risk of a 
nonattainment finding, but we acknowledge that these situations will be 
limited.
    This proposed approach would have no practical effect for those 
NAAQS for which three consecutive years of data are always required 
before a determination of attainment/nonattainment can be made, i.e., 
the 24-hour and annual PM2.5 NAAQS, the annual 
PM10 NAAQS, the proposed PM10-2.5 NAAQS, and the 
O3 NAAQS. For these NAAQS, the proposed rule provision would 
make it clear that there is no risk of a nonattainment outcome based on 
a two-year period of SPM operation.
    The CO, SO2, NO2, 24-hour PM10, 
and Pb NAAQS present a different issue, because under the form of these 
NAAQS a single year of data can be sufficient to make a finding of 
nonattainment. We note that until such time as we revise one of these 
NAAQS, we are under no mandatory duty to designate an area from 
attainment or unclassifiable to nonattainment, so it is within our 
discretion to simply not take such an action if the critical data 
indicating nonattainment is from the first 2 years of an SPM.
    However, if we are requested by a State to redesignate a 
nonattainment area to attainment, we do have a mandatory duty to act on 
that request. Consequently, we cannot overlook some SPM data that is 
contrary to the redesignation request by simply not taking an action. 
We must respond to a request for redesignation from nonattainment to 
attainment, and if there are valid data indicating that nonattainment 
still exists we could not approve the redesignation request. Therefore, 
we can use the fact that future designation of any new CO, 
SO2, NO2, 24-hour PM10, or Pb 
nonattainment areas is discretionary to protect States from use of 2 
years of data from a new SPM for one of these pollutants resulting in a 
nonattainment designation, but we cannot protect an area from use of 
such data in a finding on whether an already designated nonattainment 
area has subsequently attained the relevant NAAQS. Consequently, the 
proposed two-year data moratorium should remove the disincentive to 
place new monitors in attainment areas for CO, SO2, 
NO2, 24-hour PM10, or Pb, but may leave in place 
disincentives to add monitors in nonattainment areas that may appear to 
have reached attainment or be approaching attainment.
    Despite the limited nature of the proposed moratorium, States and 
other organizations would still be able to perform many useful types of 
discretionary monitoring without fear of triggering a near-term 
nonattainment designation. In the case of PM2.5, 
PM10, and the proposed PM10-2.5 NAAQS, many of 
the most useful types of monitors for purposes of understanding the 
causes and possible solutions to a nonattainment problem are not FRM, 
FEM, or ARM monitors, and therefore these monitors can be deployed for 
two or even more years without any concern about use of the data in 
nonattainment designations. This includes a number of filter-based 
sampler models including the samplers used in the IMPROVE program, all 
types of speciation samplers for PM2.5, PM10, and 
the proposed PM10-2.5, and all existing continuous monitors 
for PM2.5. There are also non-FRM/FEM for some of the other 
NAAQS that currently can be deployed indefinitely to characterize air 
quality problems better without fear of nonattainment designation 
consequences (e.g., passive monitors).
    Another situation in which the limited nature of the proposed two-
year moratorium would have no practical disincentive effect is when the 
siting of a monitor precludes comparison to the applicable NAAQS, even 
though it is an FRM or FEM monitor that meets quality system 
requirements. It could, for example, be placed in an location that is 
not ambient air and does not represent ambient air. It could also be 
placed inconsistently with siting criteria found in the rules which 
specify when monitoring data can be used for comparison with the NAAQS. 
See existing 40 CFR part 58, appendix D, section 2.8.1.2.3 and the 
suitability criteria proposed for the PM10-2.5 monitoring 
network discussed in section IV.E.2 of this preamble.
    The limited nature of the moratorium would have a disincentive 
effect on discretionary monitoring relative to a hypothetically more 
encompassing moratorium. For example, a State could still be 
discouraged from operating an O3 or PM2.5 monitor 
beyond 2 years, and thus may miss becoming aware of an actual public 
health problem. Therefore, we invite comment on the Agency's legal 
interpretation, which has shaped today's proposal for the described 
limited moratorium, and on what provisions for SPM data we should adopt 
if EPA was to change the legal interpretation in light of public 
comments. In particular, we invite comments on an approach in which the 
first 3 years of data from any SPM would be permanently protected from 
use in nonattainment determinations regardless of whether it operates 
beyond 3 years, but any monitor showing a violation in the first 3 
years would be required to continue operation unless its 
discontinuation is approved as part of EPA's review of the State's 
annual monitoring plan. This approach would result in the State having 
some time to address the NAAQS violation before three usable years of 
data became available to make an official nonattainment/attainment 
determination from the fourth through sixth year of operation.
    Special purpose monitors are presently not subject to the quality 
system requirements of 40 CFR part 58. With respect to data quality, 
EPA wishes to encourage all State and local monitoring agencies to 
adhere to the quality system requirements of 40 CFR part 58 for all 
FRM, FEM, and ARM monitors (the monitor types to which such 
requirements are applicable). Substandard quality system practices 
should not be deliberately used as a way to prevent EPA from using data 
from an SPM beyond the protection offered by the proposed two-year 
moratorium. However, under the current monitoring rules, States may do 
so and some have done so. Accordingly, EPA proposes to amend 40 CFR 
part 58 to require that all FRM, FEM, and ARM monitors operated by 
States (or delegated local agencies) comply with the quality system 
requirement in 40 CFR part 58 relevant to the monitor type(s) being 
used. We propose that this requirement take effect 2 years after the 
date of publication of the final rule, to provide States time to 
prepare to meet the requirement and to choose transition dates that fit 
with other network plans. We also invite comment on the alternative of 
using grant agreements to attempt to achieve quality system objectives 
for SPM instead of including a specific requirement in the proposed 
amendments.

[[Page 2747]]

    We also propose that States be required to submit to the Air 
Quality System (AQS) all data collected by all FRM, FEM, and ARM 
special purpose monitors, starting no later than 2 years after the date 
of publication of the final amendments. In the past, when SPM were not 
required to follow quality system requirements, the uncertain data 
quality from such monitors was a reason to allow States discretion 
regarding submission of data to AQS. With the proposed requirement that 
FRM, FEM, and ARM special purpose monitors follow quality system 
requirements, there is no rationale for their data not being submitted 
to AQS to provide transparency in the air quality management process.
    We propose to retain and clarify that a State may discontinue use 
of an SPM at any time, without need for EPA approval. However, we 
encourage States to continue the use of monitors that have gone beyond 
the two-year point of operation if they have recorded a violation of a 
NAAQS. Otherwise, EPA may designate the area as nonattainment and the 
State would lack clear evidence to show subsequent attainment.
10. Flexibility and Resources for Non-Required Monitoring
    The EPA wishes to clarify that while 40 CFR part 58, including the 
proposed amendments, contains a number of minimum requirements for 
States to operate ambient monitors, ensure data quality, and report 
data, these requirements are not a complete blueprint for the 
monitoring networks that we believe should and we hope will be operated 
by State and local agencies. Many specific features of minimum 
requirements for these networks, such as selection of specific 
monitoring sites for PM10-2.5, are left to be made later at 
the State level with EPA Regional Office approval, so that the best 
information and local insights can be applied to deciding those 
features. Also, not every type of monitoring that is needed can be 
required through the provisions of 40 CFR part 58 in this rulemaking 
because, in some cases, the specific State that should be responsible 
for a monitoring activity cannot be identified with confidence at this 
time. For example, the proposed amendments to 40 CFR part 58 do not 
require any State to operate a rural NCore multipollutant NCore 
monitoring station, even though we estimate that the Nation needs about 
20 such sites, because it would be premature and too rigid at this time 
to select those sites. Instead, we will work with States as they 
determine the location of their required urban NCore multipollutant 
site or sites, and we will most likely negotiate for the voluntary 
operation of some rural sites as well.
    The provisions of 40 CFR part 58 can and should only require the 
number and types of monitoring activities that will surely be needed in 
any State over a reasonably long time period, to avoid the need for 
frequent amendments to allow States to stop the use of obsolete 
monitors. However, aggregation of hypothetical State networks that just 
met the minimum requirements of 40 CFR part 58, including the proposed 
amendments, would be inadequate to meet the needs of air quality 
management at the State and national levels. We will negotiate with 
States for monitoring activities that go beyond the minimum 
requirements of 40 CFR part 58 using the draft National Ambient Air 
Monitoring Strategy as a starting point for those negotiations. The EPA 
will generally provide at least partial funding for such additional 
monitoring through grants, sometimes very specifically and sometimes 
though more general air quality management support grants. Where 
current monitoring activities by a State exceed the final minimum 
requirements in 40 CFR part 58, EPA may need to negotiate reductions in 
is funding for those activities if the data they produce are not 
sufficiently valuable to the air quality management process.
    In particular, we anticipate that we will be negotiating with 
States in the next several years the specifics of the following 
directional changes in their networks:
     Creation and operation of rural NCore multipollutant 
stations. We expect that some of the need for rural monitoring data can 
be met by required stations that some states choose to place in 
suitable rural areas and/or by planned federally-operated rural 
monitoring stations. We will identify the remaining needed sites and 
recruit and fund specific States to establish and operate them.
     Creation and operation of more PM10-2.5 
speciation sites than the minimum required in the proposed amendments.
     Creation and operation of rural PM10-2.5 mass 
concentration sites. In addition to the urban PM10-2.5 sites 
required by this proposal, having some PM10-2.5 mass 
concentration sites in rural areas may be useful to provide ambient 
data to compare with the higher coarse particle concentrations that are 
typically found in urban locations. Since these rural sites would 
typically be located outside of any MSA and would be characterized by 
lower population densities than in metropolitan areas, most would 
likely not be appropriate for NAAQS comparisons. We may work with 
selected States to establish such rural sites, taking into account 
existing siting opportunities such as the CASTNET and IMPROVE networks, 
and we solicit comment on the need for and siting strategy for such 
rural monitors. We note that monitoring sites in rural areas may be 
useful in future health effects research.
     Reduction in the number of PM2.5 filter-based 
monitors and replacement of some such monitors with continuous 
instruments.
     Reduction in the number of CO, SO2, 
NO2, PM10, and Pb monitoring sites.
     Changes in the number and/or locations of PM2.5 
speciation monitoring sites. The EPA and the States have been assessing 
these sites in the last year or so, and some changes are underway. A 
new factor to consider will be the speciation data needs of areas that 
may now be attaining the current PM2.5 NAAQS but appear 
likely to be nonattainment with the proposed NAAQS.
     Changes in PAMS networks. The proposed minimum 
requirements for PAMS monitoring would mean that many current State 
networks exceed minimum requirements, providing the opportunity for 
reassessment and redesign to better meet local conditions and data 
needs.
     Other changes that would result in networks that better 
meet State data goals, which can be so individualistic that they cannot 
be given consideration in a rulemaking such as this, or even in a 
nonbinding national strategy.
11. Proposed Requirements for Network Assessments
    In addition to annual network reviews, EPA proposes to require 
periodic and detailed network assessments as a way to maintain 
relevancy of ambient air monitoring to emerging air program needs and 
scientific findings. The EPA proposes that State and local agencies 
conduct a technical network assessment every 5 years to consider 
whether stations should be removed or added, or whether new program 
elements should be adopted to account for changes in air quality, 
population growth, emission sources, and other parameters. The first 
assessments would be due July 1, 2009. These assessments would also 
evaluate the adequacy of existing technologies deployed in the network 
compared to commercially available methods that could potentially be 
deployed to improve the network. Network assessments are intended to 
probe the

[[Page 2748]]

current and expected relevancy of air monitoring networks through a 
combination of stakeholder participation and technical analyses. This 
would be accomplished, in part, by periodically questioning the overall 
usefulness of the existing sites and identifying locations where 
additional monitoring may be necessary. Typical topics addressed in 
network assessments would include reviewing data objectives and data 
quality, prioritizing measurement needs, identifying redundant 
monitoring, and identifying specific gaps in location and measurement 
parameters. The EPA anticipates developing non-binding guidance on how 
to conduct these proposed network assessments. We solicit comment on 
the proposed requirements and schedule for network assessments.
12. Related Federal Monitoring
    The EPA conducts or supports three ambient monitoring programs 
directly, related to but separate from, the State, local, and tribal 
monitoring programs that are the subject of today's proposal. These are 
CASTNET, NADP, and IMPROVE programs, described in section III.B.3 of 
this preamble. Today's proposals do not apply to these programs, but 
the following brief description of these programs may assist the public 
in commenting on today's proposal.
    The EPA plans to upgrade the monitoring capabilities of many of the 
CASTNET sites in the next couple of years in ways that would allow them 
to meet the same multipollutant monitoring objectives as the proposed 
State-operated rural NCore stations. As these plans become more 
developed, EPA expects to adjust its targets for the number of rural 
NCore stations that are voluntarily operated by States under grant 
agreements with EPA.
    The EPA is exploring with the National Atmospheric Deposition 
Network (NADP) sponsors the possibility of expanding NADP's objectives 
and monitoring infrastructure to investigate measurement of spatial 
monitoring concentrations, from which dry deposition could be 
estimated. Also, NADP stations potentially provide efficient 
opportunities to site ambient air monitors for other purposes.
    At present, the IMPROVE program employs different sampling hardware 
and laboratory analytical procedures to measure speciated 
PM2.5 compared to most PM2.5 speciation 
monitoring in urban areas. The EPA is working to achieve more 
consistency between the two programs, so that monitoring results at the 
two types of stations are more directly comparable. We are also 
reviewing the current IMPROVE site list to determine which are of 
higher versus lower priority for long-term continuation.

F. What Are the Proposed Probe and Monitoring Path Siting Criteria?

    The EPA is proposing minor organizational changes to 40 CFR 58, 
appendix E (Probe and Monitoring Path Siting Criteria for Ambient Air 
Quality Monitoring). The EPA also is proposing specific criteria for 
the placement of PM10-2.5 samplers. Current vertical 
placement requirements permit microscale PM10 and 
PM2.5 monitors to be located 2 to 7 meters above ground 
level to allow for security, instrument servicing, and operator safety, 
as well as sampling particulate matter at the breathing height. The EPA 
is proposing that the same 2- to 7-meter vertical placement 
requirements apply to microscale PM10-2.5 sites.\74\ The EPA 
is also proposing that the 2- to 7-meter vertical placement requirement 
apply to middle-scale PM10-2.5 sites, which differs from the 
existing PM2.5 vertical placement requirement permitting 
middle-scale sites to have samplers placed 2 to 15 meters above ground. 
We recognize that significant PM10-2.5 vertical 
concentration gradients may exist due to re-entrainment of coarse 
particles from the surfaces that typically surround monitoring sites, 
such as adjacent streets, parking lots, and landscaped surfaces, and 
such vertical gradients may introduce additional complexities in the 
comparison of data from samplers at widely varying heights. The EPA 
seeks to reduce this variability by restricting the vertical placement 
of PM10-2.5 samplers at middle-scale sites to the 2 to 7 
meter requirement while recognizing that PM10-2.5 monitors 
that would have been at a higher level (e.g., 15 meters above ground) 
would have likely measured lower ambient concentrations. The EPA 
proposes that PM10-2.5 sites with neighborhood, urban, and 
regional scales have identical horizontal and vertical requirements 
with PM2.5 sites in consideration of the lesser gradients of 
coarse particle ambient concentrations likely with sites representing 
larger, more homogeneous conditions. The EPA acknowledges the 
logistical complexity of having different vertical placement 
requirements for middle-scale PM10-2.5 and PM2.5 
sites, and solicits comment on all aspects of PM10-2.5 probe 
siting criteria.
---------------------------------------------------------------------------

    \74\ The proposed network design criteria for 
PM10-2.5 would consider such data to be ineligible for 
comparison to the NAAQS (see preamble section IV.E.2.B.ii).
---------------------------------------------------------------------------

    Motor vehicle nitric oxide emissions are known to scavenge ozone, 
and EPA recognizes the difficulty that monitoring agencies face when 
trying to locate ozone air monitors in areas with multiple roadways and 
streets. Based upon concern about the scavenging effects of motor 
vehicle emissions on ozone, EPA proposes to increase the minimum 
distances between ozone monitors and roadways in certain cases. Recent 
field studies have shown significant effects of roadway emissions at 
the distances currently listed in 40 CFR part 58, appendix E. Summary 
information on this work is included in the docket for this proposal. 
The EPA solicits comments on these proposed minimum distance 
requirements.

G. What Are the Proposed Data Reporting, Data Certification, and Sample 
Retention Requirements?

1. Reduction of PM2.5 Supplemental Data Reporting 
Requirements
    The EPA is proposing to reduce the data reporting requirements 
associated with PM2.5 Federal Reference Methods (FRM) to 
reduce the data management burden for monitoring agencies. The 
following Air Quality System (AQS) reporting requirements are proposed 
for elimination: Maximum and minimum ambient temperature, maximum and 
minimum ambient pressure, flow rate coefficient of variation 
(CV), total sample volume, and elapsed sample time. AQS 
reporting requirements are being retained for average ambient 
temperature and average ambient pressure, and any applicable sampler 
flags.
    Supplemental monitoring parameters were required to be reported to 
AQS along with FRM mass concentration data to evaluate the performance 
of the FRM as implemented through the newly developed sampler hardware 
that was purchased by EPA for State and local agencies at the beginning 
of the PM2.5 monitoring program. Since that time, these 
supplemental data, along with statistical analyses conducted on data 
from collocated sampling and independent Performance Evaluation Program 
(PEP) audits, have confirmed that the PM2.5 FRM samplers are 
producing data that meet or exceed the data quality objectives 
developed for the method. As a result, the AQS reporting requirement 
for many of the supplemental data parameters can be discontinued with 
no adverse effect on PM2.5 data quality. Monitoring agencies 
would still be expected to retain supplemental data as required by 
their

[[Page 2749]]

approved Quality Assurance Program Plans (QAPP).
    AQS reporting requirements for average ambient temperature and 
average ambient pressure are being retained to provide data useful for 
the comparison of mass concentrations based on actual and standard 
operating conditions.
    EPA is also proposing amendments to 40 CFR 58.16 (Data submittal) 
to add the remaining PM2.5 supplemental data reporting 
requirements, which presently are only found in the FRM requirements 
(Table L-1 of appendix L of part 50). This change will ensure that 
supplemental data are reported for future PM2.5 samplers 
designated as a Class I or Class II Federal equivalent method under the 
proposed amendments to 40 CFR part 53.
2. PM2.5 Field Blank Data Reporting Requirement
    We are proposing amendments to 40 CFR part 58.16 to require the 
submission of data on PM2.5 field blank mass in addition to 
PM2.5 filter-based measurements. Field blanks are filters 
which are handled in the field as much as possible like actual filters 
except that ambient air is not pumped through them, to help quantify 
contamination and sampling artifacts. Only the data from field blanks 
which States are already taking into the field and weighing in their 
laboratories would be required to be reported under this proposal. 
Quantifying field blank mass is important in order to complete the 
material balance of the major components of sampled PM2.5. 
In addition, fluctuations of the field blank value are a useful quality 
control metric which can be used to help evaluate the performance of 
filter-based samplers and the quality of the sampled PM2.5 
values. However, there is currently limited information available to 
EPA and other users of ambient air quality data on the magnitude and 
trends in the blank concentrations from PM2.5 Federal 
reference method (FRM) samplers. These data are produced by State and 
local air pollution agencies on a regular basis throughout the year, 
but the data are not currently submitted to EPA. Having the data from 
these field blanks available to the national monitoring community would 
help EPA and other researchers better understand the relationship 
between the mass of PM that is sampled and weighed on a regular PM 
filter and the PM that is actually present in ambient air. The EPA 
solicits comment on this additional PM2.5 reporting 
requirement.
3. Data Certification Schedule
    To enhance timely certification of each year's air quality data to 
allow more timely reporting to the public and more timely regulatory 
findings and actions based on those data, EPA proposes to speed up 
official certification of air quality data by moving the annual data 
certification date from July 1 to May 1 of each year. We believe it can 
be met through more expeditious administrative clearance processes with 
State/local agencies and will not require significant changes in 
monitoring practices or equipment. The EPA solicits comments on this 
proposed change to the certification schedule. The EPA solicits 
comments identifying possible barriers to meeting the proposed 
certification date and information on how agencies that presently 
certify their data ahead of the current schedule accomplish this.
4. Particulate Matter Filter Archive
    During the regulatory development process, various governmental 
agencies and health scientists indicated that archiving particulate 
matter filters for FRM and Federal equivalent methods would be useful 
for later chemical speciation analyses, mass analyses, or other 
analyses. Therefore, we propose to require archiving PM2.5, 
PM10-2.5, and PM10C filters for one year (the 
current requirement is only for PM2.5 filters). The EPA 
solicits comment on this proposed requirement, specifically from those 
agencies or scientists interested in using these filters.

V. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

    Under Executive Order 12866 (58 FR 51735, October 4, 1993), EPA 
must determine whether the regulatory action is ``significant'' and 
therefore subject to review by the Office of Management and Budget 
(OMB) and to the requirements of the Executive Order. The Executive 
Order defines a ``significant regulatory action'' as one that is likely 
to result in a rule that may:
    (1) Have an annual effect on the economy of $100 million or more or 
adversely affect in a material way the economy, a sector of the 
economy, productivity, competition, jobs, the environment, public 
health or safety, or State, local, or tribal governments or 
communities;
    (2) Create a serious inconsistency or otherwise interfere with an 
action taken or planned by another agency;
    (3) Materially alter the budgetary impact of entitlements, grants, 
user fees, or loan programs or the rights and obligations of recipients 
thereof; or
    (4) Raise novel legal or policy issues arising out of legal 
mandates, the President's priorities, or the principles set forth in 
the Executive Order.
    Pursuant to the terms of Executive Order 12866, OMB has notified 
EPA that it considers this a ``significant regulatory action'' within 
the meaning of the Executive Order. EPA has submitted this action to 
OMB for review. Changes made in response to OMB suggestions or 
recommendations will be documented in the public record.

B. Paperwork Reduction Act

    The information collection requirements in the proposed rule have 
been submitted for approval to the Office of Management and Budget 
(OMB) under the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. The 
Information Collection Request (ICR) documents prepared by EPA have 
been assigned EPA ICR No. 0559.09 (2080-0005) for 40 CFR part 53 and 
0940.19 (2060-0084) for 40 CFR part 58. The provisions in 40 CFR parts 
53 and 58 have been previously approved by OMB under control numbers 
2080-0005 (EPA ICR number 0559.07) and 2060-0084 (EPA ICR number 
0940.17), respectively.
    The monitoring, record keeping, and reporting requirements in 40 
CFR parts 53 and 58 are specifically authorized by section 319 of the 
CAA (42 U.S.C. 7619). All information submitted to EPA pursuant to the 
monitoring, record keeping, and reporting requirements for which a 
claim of confidentiality is made is safeguarded according to Agency 
policies in 40 CFR part 2, subpart B.
    The information collected under 40 CFR part 53 (e.g., test results, 
monitoring records, instruction manual, and other associated 
information) is needed to determine whether a candidate method intended 
for use in determining attainment of the National Ambient Air Quality 
Standards (NAAQS) in 40 CFR part 50 will meet the design, performance, 
and/or comparability requirements for designation as a Federal 
reference method (FRM) or Federal equivalent method (FEM). The proposed 
amendments would add requirements for PM10-2.5 FEM and FRM 
determinations, Class II equivalent methods for PM10-2.5 and 
Class III equivalent methods for PM2.5 and 
PM10-2.5; reduce certain monitoring and data collection 
requirements; and streamline EPA administrative requirements.

[[Page 2750]]

    The incremental annual reporting and record keeping burden for this 
collection of information under 40 CFR part 53 (averaged over the first 
3 years of this ICR) for one additional respondent per year is 
estimated to increase by a total of 2,774 labor hours per year with an 
increase in costs of $32,000/year. The capital/startup costs for test 
equipment and qualifying tests are estimated at $3,832 with operation 
and maintenance costs of $27,772.
    The information collected and reported under 40 CFR part 58 is 
needed to determine compliance with the NAAQS, to characterize air 
quality and associated health and ecosystems impacts, to develop 
emission control strategies, and to measure progress for the air 
pollution program. The proposed amendments would revise the technical 
requirements for certain types of sites, add provisions for monitoring 
of PM10-2.5, and reduce certain monitoring requirements for 
criteria pollutants of than particulate matter and ozone. Monitoring 
agencies would be required to submit annual monitoring network plans, 
establish PM2.5 sites by January 1, 2009, establish NCore 
sites by January 1, 2011, conduct network assessments every 5 years, 
and perform quality assurance activities.
    The annual average reporting burden for the collection under 40 CFR 
part 58 (averaged over the first 3 years of this ICR) for 168 
respondents is estimated to decrease by a total of 336,650 labor hours 
per year with a decrease in costs of $31,600,362. State, local, and 
tribal entities are eligible for State assistance grants provided by 
the Federal government under the CAA for monitors and related 
activities.
    Burden means the total time, effort, or financial resources 
expended by persons to generate, maintain, retain, or disclose or 
provide information to or for a Federal agency. This includes the time 
needed to review instructions; develop, acquire, install, and utilize 
technology and systems for the purposes of collecting, validating, and 
verifying information, processing and maintaining information, and 
disclosing and providing information; adjust the existing ways to 
comply with any previously applicable instructions and requirements; 
train personnel to be able to respond to a collection of information; 
search data sources; complete and review the collection of information; 
and transmit or otherwise disclose the information.
    An agency may not conduct or sponsor, and a person is not required 
to respond to a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for EPA's 
regulations in 40 CFR parts 53 and 58 are listed in 40 CFR part 9.
    To comment on the Agency's need for the information, the accuracy 
of the provided burden estimates, and any suggested methods for 
minimizing respondent burden, including the use of automated collection 
techniques, EPA has established a public docket for the proposed 
amendments, which includes the ICR for 40 CFR part 58, under Docket ID 
number EPA-HQ-OAR-2004-0018. Submit any comments related to the ICR for 
the proposed amendments to 40 CFR part 58 to EPA and OMB. See the 
ADDRESSES section at the beginning of this notice for where to submit 
comments to EPA. Send comments to OMB at the Office of Information and 
Regulatory Affairs, Office of Management and Budget, 725 17th Street, 
NW., Washington, DC 20503, Attention: Desk Office for EPA. Since OMB is 
required to make a decision concerning the ICR between 30 and 60 days 
after January 17, 2006, a comment to OMB is best assured of having its 
full effect if OMB receives it by February 16, 2006. The final 
amendments will respond to any OMB or public comments on the 
information collection requirements for 40 CFR part 58 contained in 
this proposal.

C. Regulatory Flexibility Act

    The Regulatory Flexibility Act generally requires an agency to 
prepare a regulatory flexibility analysis of any rule subject to notice 
and comment rulemaking requirements under the Administrative Procedure 
Act or any other statute unless the agency certifies that the rule will 
not have a significant economic impact on a substantial number of small 
entities. Small entities include small businesses, small not-for-profit 
enterprises, and small governmental jurisdictions.
    For the purposes of assessing the impacts of today's proposed 
amendments on small entities, small entity is defined as: (1) A small 
business as defined by the Small Business Administration; (2) a 
government jurisdiction that is a government of a city, county, town, 
school district or special district with a population of less than 
50,000; and (3) a small organization that is any not-for-profit 
enterprise which is independently owned and operated and that is not 
dominant in its field.
    After considering the economic impacts of today's proposed 
amendments on small entities, I certify that this action will not have 
a significant economic impact on a substantial number of small 
entities. The proposed requirements in 40 CFR part 53 for applications 
for designation of equivalent methods do not address small entities. 
The requirement to apply is voluntary and, the criteria for approval 
are the minimum necessary to ensure that alternative methods meet the 
same technical standards as the proposed federal method. The proposed 
amendments to 40 CFR part 58 would reduce annual ambient air monitoring 
costs for State and local agencies by approximately $8.5 million and 
40,000 labor hours from present levels. State assistance grant funding 
provided by the federal government can be used to defray the costs of 
new or upgraded monitors for the NCore and PM10-2.5 
networks. We continue to be interested in the potential impacts of the 
proposed amendments on small entities and welcome comments on issues 
related to such impacts.

D. Unfunded Mandates Reform Act

    Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public 
Law 104-4, establishes requirements for Federal agencies to assess the 
effects of their regulatory actions on State, local, and Tribal 
governments and the private sector. Under section 202 of the UMRA, EPA 
generally must prepare a written statement, including a cost-benefit 
analysis, for proposed and final rules with ``Federal mandates'' that 
may result in expenditures to State, local, and Tribal governments, in 
the aggregate, or to the private sector, of $100 million or more in any 
one year. Before promulgating an EPA rule for which a written statement 
is needed, section 205 of the UMRA generally requires EPA to identify 
and consider a reasonable number of regulatory alternatives and adopt 
the least costly, most cost-effective or least burdensome alternative 
that achieves the objectives of the rule. The provisions of section 205 
do not apply when they are inconsistent with applicable law. Moreover, 
section 205 allows EPA to adopt an alternative other than the least 
costly, most cost-effective or least burdensome alternative if the 
Administrator publishes with the final rule an explanation why that 
alternative was not adopted. Before EPA establishes any regulatory 
requirements that may significantly or uniquely affect small 
governments, including Tribal governments, it must have developed under 
section 203 of the UMRA a small government agency plan. The plan must 
provide for notifying potentially affected small governments, enabling 
officials of affected small governments to have meaningful and timely 
input in the development of EPA regulatory

[[Page 2751]]

proposals with significant Federal intergovernmental mandates, and 
informing, educating, and advising small governments on compliance with 
the regulatory requirements.
    EPA has determined that the proposed rule does not contain a 
Federal mandate that may result in expenditures of $100 million or more 
for State, local, and Tribal governments, in the aggregate, or the 
private sector in any one year. The proposed amendments to 40 CFR part 
58 would reduce annual ambient air monitoring costs for State and local 
agencies by approximately $8.5 million and 40,000 labor hours from 
present levels. The costs for reconfiguring the existing ambient air 
monitoring requirements to implement the NCore network would be borne 
by the Federal government in the form of State assistance grants. Thus, 
the proposed amendments are not subject to the requirements of sections 
202 and 205 of the UMRA.
    EPA has determined that the proposed rule contains no regulatory 
requirements that might significantly or uniquely affect small 
governments. Small governments that may be affected by the proposed 
amendments are already meeting similar requirements under the existing 
rules, the proposed amendments would substantially reduce the costs of 
the existing rules, and the costs of changing the network design 
requirements would be borne by the Federal government through State 
assistance grants. Therefore, the proposed rule is not subject to the 
requirements of section 203 of the UMRA.

E. Executive Order 13132: Federalism

    Executive Order 13132 (64 FR 43255, August 10, 1999), requires EPA 
to develop an accountable process to ensure ``meaningful and timely 
input by State and local officials in the development of regulatory 
policies that have federalism implications.'' ``Policies that have 
federalism implications'' is defined in the Executive Order to include 
regulations that have ``substantial direct effects on the States, on 
the relationship between the national government and the States, or on 
the distribution of power and responsibilities among the various levels 
of government.''
    This proposed rule does not have federalism implications. It will 
not have substantial direct effects on the States, on the relationship 
between the national government and the States, or on the distribution 
of power and responsibilities among the various levels of government, 
as specified in Executive Order 13132. States currently implement 
similar ambient air monitoring requirements under 40 CFR parts 53 and 
58, and the costs of implementing new requirements would be borne by 
the Federal government through State assistance grants. Thus, Executive 
Order 13132 does not apply to this proposed rule.
    Although section 6 of the Executive Order does not apply to this 
proposed rule, EPA did consult with representatives of State and local 
governments early in the process of developing this proposed rule. In 
2001, EPA organized a National Monitoring Steering Committee (NMSC) to 
provide oversight and guidance in reviewing the existing air pollution 
monitoring program and in developing a comprehensive national ambient 
air monitoring strategy. The NMSC membership includes representatives 
EPA, State and local agencies, State and Territorial Air Pollution 
Program Administrators/Association of Local Air Pollution Control 
Officials (STAPPA/ALAPCO), and tribal governments to reflect the 
partnership between EPA and governmental agencies that collect and use 
ambient air data. The NMSC formed workgroups to address quality 
assurance, technology, and regulatory review of the draft ambient air 
monitoring strategy (NAAMS). These workgroups met several times by 
phone and at least once in a face-to-face workshop to detail out 
recommendations for improving the ambient air monitoring program. A 
record of the Steering Committee members, workgroup members, and 
workshop are available on the web at: http://www.epa.gov/ttn/amtic/monitor.html.
    In the spirit of Executive Order 13132, and consistent with EPA 
policy to promote communications between EPA and State and local 
governments, EPA specifically solicits comments on the proposed rule 
from State and local officials.

F. Executive Order 13175: Consultation and Coordination With Indian 
Tribal Governments

    Executive Order 13175, entitled ``Consultation and Coordination 
with Indian Tribal Governments'' (65 FR 67249, November 9, 2000), 
requires EPA to develop an accountable process to ensure ``meaningful 
and timely input by tribal officials in the development of regulatory 
policies that have tribal implications.'' This proposed rule does not 
have tribal implications, as specified in Executive Order 13175. The 
proposed amendments would not directly apply to Tribal governments. 
However, a tribal government may elect to conduct ambient air 
monitoring and report the data to AQS. Since it is possible that tribal 
governments may choose to establish and operate NCore sites as part of 
the national monitoring program, EPA consulted with tribal officials 
early in the process of developing the proposed rule to permit them to 
have meaningful and timely input into its development. As discussed in 
section V.E of this preamble, tribal agencies were represented on both 
the NMSSC and the workgroups that developed the NAAMS document and 
proposed monitoring requirements. Tribal monitoring programs were 
represented on both the Quality Assurance and Technology work groups. 
Participation was also open to tribal monitoring programs on the 
regulatory review workgroup. EPA specifically solicits additional 
comment on the proposed amendments from tribal officials.

G. Executive Order 13045: Protection of Children From Environmental 
Health and Safety Risks

    Executive Order 13045 (62 FR 19885, April 23, 1997) applies to any 
rule that: (1) Is determined to be ``economically significant'' as 
defined under Executive Order 12866, and (2) concerns an environmental 
health or safety risk that EPA has reason to believe may have a 
disproportionate effect on children. If the regulatory action meets 
both criteria, the Agency must evaluate the environmental health or 
safety effects of the planned rule on children, and explain why the 
planned regulation is preferable to other potentially effective and 
reasonably feasible alternatives considered by the Agency.
    EPA interprets Executive Order 13045 as applying only to those 
regulatory actions that are based on health or safety risks, such that 
the analysis required under section 5-501 of the Order has the 
potential to influence the regulation. The proposed rule is not subject 
to Executive Order 13045 because it is based on technology and not on 
health or safety risks.

H. Executive Order 13211: Actions That Significantly Affect Energy 
Supply, Distribution, or Use

    The proposed rule is not a ``significant energy action'' as defined 
in Executive Order 13211, ``Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution or Use'' (66 FR 28355, 
May 22, 2001) because it is not likely to have a significant adverse 
effect on the supply, distribution, or use of energy. No significant 
change in the use of energy is expected because the total number of 
monitors for ambient air

[[Page 2752]]

quality measurements will not increase above present levels. Further, 
we have concluded that this proposed rule is not likely to have any 
adverse energy effects.

I. National Technology Transfer Advancement Act

    Section 12(d) of the National Technology Transfer Advancement Act 
of 1995 (NTTAA), Public Law 104-113, section 12(d) (15 U.S.C. 272 note) 
directs EPA to use voluntary consensus standards in its regulatory 
activities unless to do so would be inconsistent with applicable law or 
otherwise impractical. Voluntary consensus standards are technical 
standards (e.g., materials specifications, test methods, sampling 
procedures, and business practices) that are developed or adopted by 
voluntary consensus standards bodies. The NTTAA directs EPA to provide 
Congress, through OMB, explanations when the Agency decides not to use 
available and applicable voluntary consensus standards.
    The proposed amendments involve environmental monitoring and 
measurement. Ambient air concentrations of PM2.5 are 
currently measured by the Federal reference method in 40 CFR part 50, 
appendix L (Reference Method for the Determination of Fine Particulate 
as PM2.5 in the Atmosphere) or by an a Federal reference or 
equivalent method that meets the requirements in 40 CFR part 53. 
Ambient air concentrations of PM10-2.5 would be measured by 
the proposed Federal reference method in 40 CFR part 50, appendix O 
(Reference Method for the Determination of Coarse Particulate Matter as 
PM10-2.5 in the Atmosphere) published elsewhere in this 
Federal Register or by a Federal reference or equivalent method that 
meets the requirements in 40 CFR part 53. As discussed in section IV.B 
of this preamble, the proposed Federal reference method for 
PM10-2.5 is similar to the existing methods for 
PM2.5 and PM10.
    In the preamble to the proposed NAAQS revisions published elsewhere 
in this Federal Register, EPA requests comments on selection of an 
alternative filter-based dichotomous sampler as the Federal reference 
method for PM10-2.5. Procedures are included in the proposed 
monitoring amendments that would allow for approval of a candidate 
equivalent method for PM10-2.5 that is similar to the 
proposed Federal reference method or to the alternative method proposed 
for comment. Any method that meets the performance criteria for a 
candidate equivalent method could be approved for use as a Federal 
reference or equivalent method.
    This approach is consistent with the Agency's Performance-Based 
Measurement System (PBMS). The PBMS approach is intended to be more 
flexible and cost effective for the regulated community; it is also 
intended to encourage innovation in analytical technology and improved 
data quality. EPA is not precluding the use of any method, whether it 
constitutes a voluntary consensus standard or not, as long as it meets 
the specified performance criteria. EPA welcomes comments on this 
aspect of the proposed amendments and, specifically invites the public 
to identify potentially applicable voluntary consensus standards and to 
explain why such standards should be used in the regulation.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations

    Executive Order 12848 (58 FR 7629, February 11, 1994) requires that 
each Federal agency make achieving environmental justice part of its 
mission by identifying and addressing, as appropriate, 
disproportionately high and adverse human health or environmental 
effects of its programs, policies, and activities on minorities and 
low-income populations. These requirements have been addressed to the 
extent practicable in the Regulatory Impact Analysis for the proposed 
revisions to the NAAQS for particulate matter.

List of Subjects in 40 CFR Parts 53 and 58

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Intergovernmental relations, Reporting and 
recordkeeping requirements.

    Dated: December 20, 2005.
Stephen L. Johnson,
Administrator.
    For the reasons set out in the preamble, title 40, chapter I, parts 
53 and 58 of the Code of Federal Regulations are proposed to be amended 
as follows:

PART 53--[AMENDED]

    1. The authority citation for part 53 continues to read as follows:

    Authority: Sec. 301(a) of the Clean Air Act (42 U.S.C. sec. 
1857g(a)), as amended by sec. 15(c)(2) of Pub. L. 91-604, 84 Stat. 
1713, unless otherwise noted.

Subpart A--[Amended]

    2. Revise Sec. Sec.  53.1 through 53.5 to read as follows:


Sec.  53.1  Definitions.

    Terms used but not defined in this part shall have the meaning 
given them by the Act.
    Act means the Clean Air Act (42 U.S.C. 1857-1857l), as amended.
    Additive and multiplicative bias means the linear regression 
intercept and slope of a linear plot fitted to corresponding candidate 
and reference method mean measurement data pairs.
    Administrator means the Administrator of the Environmental 
Protection Agency (EPA) or his or her authorized representative.
    Agency means the Environmental Protection Agency.
    Applicant means a person or entity who submits an application for a 
reference or equivalent method determination under Sec.  53.4, or a 
person or entity who assumes the rights and obligations of an applicant 
under Sec.  53.7. Applicant may include a manufacturer, distributor, 
supplier, or vendor.
    Automated method or analyzer means a method for measuring 
concentrations of an ambient air pollutant in which sample collection 
(if necessary), analysis, and measurement are performed automatically 
by an instrument.
    Candidate method means a method for measuring the concentration of 
an air pollutant in the ambient air for which an application for a 
reference method determination or an equivalent method determination is 
submitted in accordance with Sec.  53.4, or a method tested at the 
initiative of the Administrator in accordance with Sec.  53.7.
    Class I equivalent method means an equivalent method for 
PM2.5 or PM10-2.5 which is based on a sampler 
that is very similar to the sampler specified for reference methods in 
appendix L or appendix O (as applicable) of part 50 of this chapter, 
with only minor deviations or modifications, as determined by EPA.
    Class II equivalent method means an equivalent method for 
PM2.5 or PM10-2.5 that utilizes a 
PM2.5 sampler or PM10-2.5 sampler in which 
integrated PM2.5 samples or PM10-2.5 samples are 
obtained from the atmosphere by filtration and subjected to a 
subsequent filter conditioning process followed by a gravimetric mass 
determination, but which is not a Class I equivalent method because of 
substantial deviations from the design specifications of the sampler 
specified for reference methods in appendix L or appendix O (as

[[Page 2753]]

applicable) of part 50 of this chapter, as determined by EPA.
    Class III equivalent method means an equivalent method for 
PM2.5 or PM10-2.5 that is an analyzer capable of 
providing PM2.5 or PM10-2.5 ambient air 
measurements representative of one-hour or less integrated 
PM2.5 or PM10-2.5 concentrations as well as 24-
hour measurements determined as, or equivalent to, the mean of 24 one-
hour consecutive measurements.
    CO means carbon monoxideide.
    Collocated means two or more air samplers, analyzers, or other 
instruments that are operated simultaneously while located side by 
side, separated by a distance that is large enough to preclude the air 
sampled by any of the devices from being affected by any of the other 
devices, but small enough so that all devices obtain identical or 
uniform ambient air samples that are equally representative of the 
general area in which the group of devices is located.
    Equivalent method means a method for measuring the concentration of 
an air pollutant in the ambient air that has been designated as an 
equivalent method in accordance with this part; it does not include a 
method for which an equivalent method designation has been canceled in 
accordance with Sec.  53.11 or Sec.  53.16.
    ISO 9001-registered facility means a manufacturing facility that is 
either:
    (1) An International Organization for Standardization (ISO) 9001-
registered manufacturing facility, registered to the ISO 9001 standard 
(by the Registrar Accreditation Board (RAB) of the American Society for 
Quality Control (ASQC) in the United States), with registration 
maintained continuously.
    (2) A facility that can be demonstrated, on the basis of 
information submitted to the EPA, to be operated according to an EPA-
approved and periodically audited quality system which meets, to the 
extent appropriate, the same general requirements as an ISO 9001-
registered facility for the design and manufacture of designated 
reference and equivalent method samplers and monitors.
    ISO-certified auditor means an auditor who is either certified by 
the Registrar Accreditation Board (in the United States) as being 
qualified to audit quality systems using the requirements of recognized 
standards such as ISO 9001, or who, based on information submitted to 
the EPA, meets the same general requirements as provided for ISO-
certified auditors.
    Manual method means a method for measuring concentrations of an 
ambient air pollutant in which sample collection, analysis, or 
measurement, or some combination thereof, is performed manually. A 
method for PM10 or PM2.5 which utilizes a sampler 
that requires manual preparation, loading, and weighing of filter 
samples is considered a manual method even though the sampler may be 
capable of automatically collecting a series of sequential samples.
    NO means nitrogen oxide.
    NO2 means nitrogen dioxide.
    NOX means oxides of nitrogen and is defined as the sum 
of the concentrations of NO2 and NO.
    O3 means ozone.
    Operated simultaneously means that two or more collocated samplers 
or analyzers are operated concurrently with no significant difference 
in the start time, stop time, and duration of the sampling or 
measurement period.
    Pb means lead.
    PM means PM10, PM10C, PM2.5, 
PM10-2.5, or particulate matter of unspecified size range.
    PM10 means particulate matter as defined in section 1.1 
of appendix J to part 50 of this chapter.
    PM2.5 means particulate matter as defined in section 1.1 
of appendix L to part 50 of this chapter.
    PM10-2.5 means particulate matter as defined in section 
1.1 of appendix O to part 50 of this chapter.
    PM10C means PM10 particulate matter or 
PM10 measurements obtained with a PM10C sampler.
    PM2.5 sampler means a device, associated with a manual 
method for measuring PM2.5, designed to collect 
PM2.5 from an ambient air sample, but lacking the ability to 
automatically analyze or measure the collected sample to determine the 
mass concentrations of PM2.5 in the sampled air.
    PM10 sampler means a device, associated with a manual 
method for measuring PM10, designed to collect 
PM10 from an ambient air sample, but lacking the ability to 
automatically analyze or measure the collected sample to determine the 
mass concentrations of PM10 in the sampled air.
    PM10C sampler means a PM10 sampler that meets 
the special requirements for a PM10C sampler that is part of 
a PM10-2.5 reference method sampler, as specified in 
appendix O to part 50 of this chapter, or a PM10 sampler 
that is part of a PM10-2.5 sampler that has been designated 
as an equivalent method for PM10-2.5.
    PM10-2.5 sampler means a sampler, or a collocated pair 
of samplers, associated with a manual method for measuring 
PM10-2.5 and designed to collect either PM10-2.5 
directly or PM10C and PM2.5 separately and 
simultaneously from concurrent ambient air samples, but lacking the 
ability to automatically analyze or measure the collected sample(s) to 
determine the mass concentrations of PM10-2.5 in the sampled 
air.
    Reference method means a method of sampling and analyzing the 
ambient air for an air pollutant that is specified as a reference 
method in an appendix to part 50 of this chapter, or a method that has 
been designated as a reference method in accordance with this part; it 
does not include a method for which a reference method designation has 
been canceled in accordance with Sec.  53.11 or Sec.  53.16.
    Sequential samples for PM samplers means two or more PM samples for 
sequential (but not necessarily contiguous) time periods that are 
collected automatically by the same sampler without the need for 
intervening operator service.
    SO2 means sulfur dioxide.
    Test analyzer means an analyzer subjected to testing as part of a 
candidate method in accordance with subparts B, C, D, E, or F of this 
part, as applicable.
    Test sampler means a PM10 sampler, PM2.5 
sampler, or PM10-2.5 sampler subjected to testing as part of 
a candidate method in accordance with subparts C, D, E, or F of this 
part.
    Ultimate purchaser means the first person or entity who purchases a 
reference method or an equivalent method for purposes other than 
resale.


Sec.  53.2  General requirements for a reference method determination.

    The following general requirements for a reference method 
determination are summarized in table A-1 of this subpart.
    (a) Manual methods. (1) Sulfur dioxide (SO2) and lead. 
For measuring SO2 and lead, appendices A and G of part 50 of 
this chapter specify unique manual reference methods for measuring 
these pollutants. Except as provided in Sec.  53.16, other manual 
methods for SO2 and lead will not be considered for 
reference method determinations under this part.
    (2) PM10. A reference method for measuring 
PM10 must be a manual method that meets all requirements 
specified in appendix J of part 50 of this chapter and must include a 
PM10 sampler that has been shown in accordance with this 
part to meet all requirements specified in this subpart A and subpart D 
of this part.
    (3) PM2.5. A reference method for measuring 
PM2.5 must be a manual method that meets all requirements 
specified in appendix L of part 50 of

[[Page 2754]]

this chapter and must include a PM2.5 sampler that has been 
shown in accordance with this part to meet the applicable requirements 
specified in this subpart A and subpart E of this part. Further, 
reference method samplers must be manufactured in an ISO 9001-
registered facility, as defined in Sec.  53.1 and as set forth in Sec.  
53.51.
    (4) PM10-2.5. A reference method for measuring 
PM10-2.5 must be a manual method that meets all requirements 
specified in appendix O of part 50 of this chapter and must include 
PM10C and PM2.5 samplers that have been shown in 
accordance with this part to meet the applicable requirements specified 
in this subpart A and subpart E of this part. Further, 
PM10-2.5 reference method samplers must be manufactured in 
an ISO 9001-registered facility, as defined in Sec.  53.1 and as set 
forth in Sec.  53.51.
    (b) Automated methods. An automated reference method for measuring 
CO, O3, or NO2 must utilize the measurement 
principle and calibration procedure specified in the appropriate 
appendix to part 50 of this chapter and must have been shown in 
accordance with this part to meet the requirements specified in this 
subpart A and subpart B of this part.


Sec.  53.3  General requirements for an equivalent method 
determination.

    (a) Manual methods. A manual equivalent method must have been shown 
in accordance with this part to satisfy the applicable requirements 
specified in this subpart A and subpart C of this part. In addition, a 
PM sampler associated with a manual equivalent method for 
PM10, PM2.5, or PM10-2.5 must have 
been shown in accordance with this part to satisfy the following 
additional requirements, as applicable:
    (1) PM10. A PM10 sampler associated with a 
manual method for PM10 must satisfy the requirements of 
subpart D of this part.
    (2) PM2.5 Class I. A PM2.5 Class I equivalent 
method sampler must also satisfy all requirements of subpart E of this 
part, which shall include appropriate demonstration that each and every 
deviation or modification from the reference method sampler 
specifications does not significantly alter the performance of the 
sampler.
    (3) PM2.5 Class II. (i) A PM2.5 Class II 
equivalent method sampler must also satisfy the applicable requirements 
of subparts E and F of this part or the alternative requirements in 
paragraph (a)(3)(ii) of this section.
    (ii) In lieu of the applicable requirements specified for Class II 
PM2.5 methods in subparts C and F of this part, a Class II 
PM2.5 equivalent method sampler may alternatively meet the 
applicable requirements in paragraphs (b)(3)(i) through (iii) of this 
section and the testing, performance, and comparability requirements 
specified for Class III equivalent methods for PM2.5 in 
subpart C of this part.
    (4) PM10-2.5 Class I. A PM10-2.5 Class I 
equivalent method sampler must also satisfy the applicable requirements 
of subpart E of this part (there are no additional requirements 
specifically for Class I PM10-2.5 methods in subpart C of 
this part).
    (5) PM10-2.5 Class II. (i) A PM10-2.5 Class 
II equivalent method must also satisfy the applicable requirements of 
subpart C of this part and also the applicable requirements and 
provisions of paragraphs (b)(3)(i) through (iii) of this section, or 
the alternative requirements in paragraph (a)(5)(ii) of this section.
    (ii) In lieu of the applicable requirements specified for Class II 
PM10-2.5 methods in subpart C of this part and in paragraph 
(b)(3)(iii) of this section, a Class II PM10-2.5 equivalent 
method sampler may alternatively meet the applicable requirements in 
paragraphs (b)(3)(i) and (ii) of this section and the testing, 
performance, and comparability requirements specified for Class III 
equivalent methods for PM10-2.5 in subpart C of this part.
    (6) ISO 9001. All designated equivalent methods for 
PM2.5 or PM10-2.5 must be manufactured in an ISO 
9001-registered facility, as defined in Sec.  53.1 and as set forth in 
Sec.  53.51.
    (b) Automated methods. All types of automated equivalent methods 
must have been shown in accordance with this part to satisfy the 
applicable requirements specified in this subpart A and subpart C of 
this part. In addition, an automated equivalent method must have been 
shown in accordance with this part to satisfy the following additional 
requirements, as applicable:
    (1) An automated equivalent method for pollutants other than PM 
must be shown in accordance with this part to satisfy the applicable 
requirements specified in subpart B of this part.
    (2) An automated equivalent method for PM10 must be 
shown in accordance with this part to satisfy the applicable 
requirements of subpart D of this part.
    (3) A Class III automated equivalent method for PM2.5 or 
PM10-2.5 must be shown in accordance with this part to 
satisfy the requirements in paragraphs (b)(3)(i) through (iii) of this 
section, as applicable.
    (i) All pertinent requirements of 40 CFR part 50, appendix L, 
including sampling height, range of operational conditions, ambient 
temperature and pressure sensors, outdoor enclosure, electrical power 
supply, control devices and operator interfaces, data output port, 
operation/instruction manual, data output and reporting requirements, 
and any other requirements that would be reasonably applicable to the 
method, unless adequate (as determined by the Administrator) rationale 
can be provided to support the contention that a particular requirement 
does not or should not be applicable to the particular candidate 
method.
    (ii) All pertinent tests and requirements of subpart E of this 
part, such as instrument manufacturing quality control; final assembly 
and inspection; manufacturer's audit checklists; leak checks; flow rate 
accuracy, measurement accuracy, and flow rate cut-off; operation 
following power interruptions; effect of variations in power line 
voltage, ambient temperature and ambient pressure; and aerosol 
transport; unless adequate (as determined by the Administrator) 
rationale can be provided to support the contention that a particular 
test or requirement does not or should not be applicable to the 
particular candidate method.
    (iii) Candidate methods shall be tested for and meet any 
performance requirements, such as inlet aspiration, particle size 
separation or selection characteristics, change in particle separation 
or selection characteristics due to loading or other operational 
conditions, or effects of surface exposure and particle volatility, 
determined by the Administrator to be necessary based on the nature, 
design, and specifics of the candidate method and the extent to which 
it deviates from the design and performance characteristics of the 
reference method. These performance requirements and the specific 
test(s) for them will be determined by Administrator for each specific 
candidate method or type of candidate method and may be similar to or 
based on corresponding tests and requirements set forth in subpart F of 
this part or may be special requirements and tests tailored by the 
Administrator to the specific nature, design, and operational 
characteristics of the candidate method. For example, a candidate 
method with an inlet design deviating substantially from the design of 
the reference method inlet would likely be subject to an inlet 
aspiration test similar to that set forth in Sec.  53.63. Similarly, a 
candidate method having an inertial fractionation system substantially 
different from that of the reference method would likely be

[[Page 2755]]

subject to a static fractionation test and a loading test similar to 
those set forth in Sec. Sec.  53.64 and 53.65, respectively. A 
candidate method with more extensive or profound deviations from the 
design and function of the reference method may be subject to other 
tests, full wind-tunnel tests similar to those described in Sec.  
53.62, or to special tests adapted or developed individually to 
accommodate the specific type of measurement or operation of the 
candidate method.
    (4) All designated equivalent methods for PM2.5 or 
PM10-2.5 must be manufactured in an ISO 9001-registered 
facility, as defined in Sec.  53.1 and as set forth in Sec.  53.51.


Sec.  53.4  Applications for reference or equivalent method 
determinations.

    (a) Applications for reference or equivalent method determinations 
shall be submitted in duplicate to: Director, National Exposure 
Research Laboratory, Reference and Equivalent Method Program (MD-D205-
03), U.S. Environmental Protection Agency, Research Triangle Park, 
North Carolina 27711 (Commercial delivery address: 4930 Old Page Road, 
Durham, North Carolina 27703).
    (b) Each application shall be signed by an authorized 
representative of the applicant, shall be marked in accordance with 
Sec.  53.15 (if applicable), and shall contain the following:
    (1) A clear identification of the candidate method, which will 
distinguish it from all other methods such that the method may be 
referred to unambiguously. This identification must consist of a unique 
series of descriptors such as title, identification number, analyte, 
measurement principle, manufacturer, brand, model, etc., as necessary 
to distinguish the method from all other methods or method variations, 
both within and outside the applicant's organization.
    (2) A detailed description of the candidate method, including but 
not limited to the following: The measurement principle, manufacturer, 
name, model number and other forms of identification, a list of the 
significant components, schematic diagrams, design drawings, and a 
detailed description of the apparatus and measurement procedures. 
Drawings and descriptions pertaining to candidate methods or samplers 
for PM2.5 or PM10-2.5 must meet all applicable 
requirements in reference 1 of appendix A of this subpart, using 
appropriate graphical, nomenclature, and mathematical conventions such 
as those specified in references 3 and 4 of appendix A of this subpart.
    (3) A copy of a comprehensive operation or instruction manual 
providing a complete and detailed description of the operational, 
maintenance, and calibration procedures prescribed for field use of the 
candidate method and all instruments utilized as part of that method 
(under Sec.  53.9(a)).
    (i) As a minimum this manual shall include:
    (A) Description of the method and associated instruments.
    (B) Explanation of all indicators, information displays, and 
controls.
    (C) Complete setup and installation instructions, including any 
additional materials or supplies required.
    (D) Details of all initial or startup checks or acceptance tests 
and any auxiliary equipment required.
    (E) Complete operational instructions.
    (F) Calibration procedures and descriptions of required calibration 
equipment and standards.
    (G) Instructions for verification of correct or proper operation.
    (H) Trouble-shooting guidance and suggested corrective actions for 
abnormal operation.
    (I) Required or recommended routine, periodic, and preventative 
maintenance and maintenance schedules.
    (J) Any calculations required to derive final concentration 
measurements.
    (K) Appropriate references to any applicable appendix of part 50 of 
this chapter; reference 6 of appendix A of this subpart; and any other 
pertinent guidelines.
    (ii) The manual shall also include adequate warning of potential 
safety hazards that may result from normal use and/or malfunction of 
the method and a description of necessary safety precautions. (See 
Sec.  53.9(b).) However, the previous requirement shall not be 
interpreted to constitute or imply any warranty of safety of the method 
by EPA. For samplers and automated methods, the manual shall include a 
clear description of all procedures pertaining to installation, 
operation, preventive maintenance, and troubleshooting and shall also 
include parts identification diagrams. The manual may be used to 
satisfy the requirements of paragraphs (b)(1) and (2) of this section 
to the extent that it includes information necessary to meet those 
requirements.
    (4) A statement that the candidate method has been tested in 
accordance with the procedures described in subparts B, C, D, E, and/or 
F of this part, as applicable.
    (5) Descriptions of test facilities and test configurations, test 
data, records, calculations, and test results as specified in subparts 
B, C, D, E, and/or F of this part, as applicable. Data must be 
sufficiently detailed to meet appropriate principles described in part 
B, sections 3.3.1 (paragraph 1) and 3.5.1 and part C, section 4.6 of 
reference 2 of appendix A of this subpart; and in paragraphs 1 through 
3 of section 4.8 (Records) of reference 5 of appendix A of this 
subpart. Salient requirements from these references include the 
following:
    (i) The applicant shall maintain and include records of all 
relevant measuring equipment, including the make, type, and serial 
number or other identification, and most recent calibration with 
identification of the measurement standard or standards used and their 
National Institute of Standards and Technology (NIST) traceability. 
These records shall demonstrate the measurement capability of each item 
of measuring equipment used for the application and include a 
description and justification (if needed) of the measurement setup or 
configuration in which it was used for the tests. The calibration 
results shall be recorded and identified in sufficient detail so that 
the traceability of all measurements can be determined and any 
measurement could be reproduced under conditions close to the original 
conditions, if necessary, to resolve any anomalies.
    (ii) Test data shall be collected according to the standards of 
good practice and by qualified personnel. Test anomalies or 
irregularities shall be documented and explained or justified. The 
impact and significance of the deviation on test results and 
conclusions shall be determined. Data collected shall correspond 
directly to the specified test requirement and be labeled and 
identified clearly so that results can be verified and evaluated 
against the test requirement. Calculations or data manipulations must 
be explained in detail so that they can be verified.
    (6) A statement that the method, analyzer, or sampler tested in 
accordance with this part is representative of the candidate method 
described in the application.
    (c) For candidate automated methods and candidate manual methods 
for PM10, PM2.5, and PM10-2.5 the 
application shall also contain the following:
    (1) A detailed description of the quality system that will be 
utilized, if the candidate method is designated as a reference or 
equivalent method, to ensure that all analyzers or samplers offered for 
sale under that designation will have essentially the same

[[Page 2756]]

performance characteristics as the analyzer(s) or samplers tested in 
accordance with this part. In addition, the quality system requirements 
for candidate methods for PM2.5 and PM10-2.5 must 
be described in sufficient detail, based on the elements described in 
section 4 of reference 1 (Quality System Requirements) of appendix A of 
this subpart. Further clarification is provided in the following 
sections of reference 2 of appendix A of this subpart: part A 
(Management Systems), sections 2.2 (Quality System and Description), 
2.3 (Personnel Qualification and Training), 2.4 (Procurement of Items 
and Services), 2.5 (Documents and Records), and 2.7 (Planning); part B 
(Collection and Evaluation of Environmental Data), sections 3.1 
(Planning and Scoping), 3.2 (Design of Data Collection Operations), and 
3.5 (Assessment and Verification of Data Usability); and part C 
(Operation of Environmental Technology), sections 4.1 (Planning), 4.2 
(Design of Systems), and 4.4 (Operation of Systems).
    (2) A description of the durability characteristics of such 
analyzers or samplers (see Sec.  53.9(c)). For methods for 
PM2.5 and PM10-2.5 the warranty program must 
ensure that the required specifications (see Table A-1 to this subpart) 
will be met throughout the warranty period and that the applicant 
accepts responsibility and liability for ensuring this conformance or 
for resolving any nonconformities, including all necessary components 
of the system, regardless of the original manufacturer. The warranty 
program must be described in sufficient detail to meet appropriate 
provisions of the ANSI/ASQC and ISO 9001 standards (references 1 and 2 
in appendix A of this subpart) for controlling conformance and 
resolving nonconformance, particularly sections 4.12, 4.13, and 4.14 of 
reference 1 in appendix A of this subpart.
    (i) Section 4.12 in reference 1 of appendix A of this subpart 
requires the manufacturer to establish and maintain a system of 
procedures for identifying and maintaining the identification of 
inspection and test status throughout all phases of manufacturing to 
ensure that only instruments that have passed the required inspections 
and tests are released for sale.
    (ii) Section 4.13 in reference 1 of appendix A of this subpart 
requires documented procedures for control of nonconforming product, 
including review and acceptable alternatives for disposition; section 
4.14 in reference 1 of appendix A of this subpart requires documented 
procedures for implementing corrective (4.14.2) and preventive (4.14.3) 
action to eliminate the causes of actual or potential nonconformities. 
In particular, section 4.14.3 requires that potential causes of 
nonconformities be eliminated by using information such as service 
reports and customer complaints to eliminate potential causes of 
nonconformities.
    (d) For candidate reference or equivalent methods for 
PM2.5 and Class II or Class III equivalent methods for 
PM10-2.5, the applicant, if requested by EPA, shall provide 
to EPA for test purposes one sampler or analyzer that is representative 
of the sampler or analyzer associated with the candidate method. The 
sampler or analyzer shall be shipped FOB destination to Director, 
National Exposure Research Laboratory, Reference and Equivalent Method 
Program (MD-D205-03), U.S. Environmental Protection Agency, 4930 Old 
Page Road, Durham, North Carolina 27703, scheduled to arrive concurrent 
with or within 30 days of the arrival of the other application 
materials. This analyzer or sampler may be subjected to various tests 
that EPA determines to be necessary or appropriate under Sec.  53.5(f), 
and such tests may include special tests not described in this part. If 
the instrument submitted under this paragraph malfunctions, becomes 
inoperative, or fails to perform as represented in the application 
before the necessary EPA testing is completed, the applicant shall be 
afforded an opportunity to repair or replace the device at no cost to 
EPA. Upon completion of EPA testing, the analyzer or sampler submitted 
under this paragraph shall be repacked by EPA for return shipment to 
the applicant, using the same packing materials used for shipping the 
instrument to EPA unless alternative packing is provided by the 
applicant. Arrangements for, and the cost of, return shipment shall be 
the responsibility of the applicant. EPA does not warrant or assume any 
liability for the condition of the analyzer or sampler upon return to 
the applicant.


Sec.  53.5  Processing of applications.

    After receiving an application for a reference or equivalent method 
determination, the Administrator will, within 120 calendar days after 
receipt of the application, take one or more of the following actions:
    (a) Send notice to the applicant, in accordance with Sec.  53.8, 
that the candidate method has been determined to be a reference or 
equivalent method.
    (b) Send notice to the applicant that the application has been 
rejected, including a statement of reasons for rejection.
    (c) Send notice to the applicant that additional information must 
be submitted before a determination can be made and specify the 
additional information that is needed (in such cases, the 120-day 
period shall commence upon receipt of the additional information).
    (d) Send notice to the applicant that additional test data must be 
submitted and specify what tests are necessary and how the tests shall 
be interpreted (in such cases, the 120-day period shall commence upon 
receipt of the additional test data).
    (e) Send notice to the applicant that the application has been 
found to be substantially deficient or incomplete and cannot be 
processed until additional information is submitted to complete the 
application and specify the general areas of substantial deficiency.
    (f) Send notice to the applicant that additional tests will be 
conducted by the Administrator, specifying the nature of and reasons 
for the additional tests and the estimated time required (in such 
cases, the 120-day period shall commence 1 calendar day after the 
additional tests have been completed).
    2a. Revise Sec. Sec.  53.8 and 53.9 to read as follows:


Sec.  53.8  Designation of reference and equivalent methods.

    (a) A candidate method determined by the Administrator to satisfy 
the applicable requirements of this part shall be designated as a 
reference method or equivalent method (as applicable) by and upon 
publication of a notice of the designation in the Federal Register.
    (b) Upon designation, a notice indicating that the method has been 
designated as a reference method or an equivalent method shall be sent 
to the applicant.
    (c) The Administrator will maintain a current list of methods 
designated as reference or equivalent methods in accordance with this 
part and will send a copy of the list to any person or group upon 
request. A copy of the list will be available for inspection or copying 
at EPA Regional Offices and may be available via the Internet or other 
sources.


Sec.  53.9  Conditions of designation.

    Designation of a candidate method as a reference method or 
equivalent method shall be conditioned to the applicant's compliance 
with the following requirements. Failure to comply with any of the 
requirements shall constitute a ground for

[[Page 2757]]

cancellation of the designation in accordance with Sec.  53.11.
    (a) Any method offered for sale as a reference or equivalent method 
shall be accompanied by a copy of the manual referred to in Sec.  
53.4(b)(3) when delivered to any ultimate purchaser, and an electronic 
copy of the manual suitable for incorporating into user specific 
standard operating procedure documents shall be readily available to 
any users.
    (b) Any method offered for sale as a reference or equivalent method 
shall generate no unreasonable hazard to operators or to the 
environment during normal use or when malfunctioning.
    (c) Any analyzer, PM10 sampler, PM2.5 
sampler, or PM10-2.5 sampler offered for sale as part of a 
reference or equivalent method shall function within the limits of the 
performance specifications referred to in Sec.  53.20(a), Sec.  
53.30(a), Sec.  53.50, or Sec.  53.60, as applicable, for at least 1 
year after delivery and acceptance when maintained and operated in 
accordance with the manual referred to in Sec.  53.4(b)(3).
    (d) Any analyzer, PM10 sampler, PM2.5 
sampler, or PM10-2.5 sampler offered for sale as a reference 
or equivalent method shall bear a prominent, permanently affixed label 
or sticker indicating that the analyzer or sampler has been designated 
by EPA as a reference method or as an equivalent method (as applicable) 
in accordance with this part and displaying any designated method 
identification number that may be assigned by EPA.
    (e) If an analyzer is offered for sale as a reference or equivalent 
method and has one or more selectable ranges, the label or sticker 
required by paragraph (d) of this section shall be placed in close 
proximity to the range selector and shall indicate clearly which range 
or ranges have been designated as parts of the reference or equivalent 
method.
    (f) An applicant who offers analyzers, PM10 samplers, 
PM2.5 samplers, or PM10-2.5 samplers for sale as 
reference or equivalent methods shall maintain an accurate and current 
list of the names and mailing addresses of all ultimate purchasers of 
such analyzers or samplers. For a period of 7 years after publication 
of the reference or equivalent method designation applicable to such an 
analyzer or sampler, the applicant shall notify all ultimate purchasers 
of the analyzer or sampler within 30 days if the designation has been 
canceled in accordance with Sec.  53.11 or Sec.  53.16 or if adjustment 
of the analyzer or sampler is necessary under Sec.  53.11(b).
    (g) If an applicant modifies an analyzer, PM10 sampler, 
PM2.5 sampler, or PM10-2.5 sampler that has been 
designated as a reference or equivalent method, the applicant shall not 
sell the modified analyzer or sampler as a reference or equivalent 
method nor attach a label or sticker to the modified analyzer or 
sampler under paragraph (d) or (e) of this section until the applicant 
has received notice under Sec.  53.14(c) that the existing designation 
or a new designation will apply to the modified analyzer or sampler or 
has applied for and received notice under Sec.  53.8(b) of a new 
reference or equivalent method determination for the modified analyzer 
or sampler.
    (h) An applicant who has offered PM2.5 or 
PM10-2.5 samplers or analyzers for sale as part of a 
reference or equivalent method may continue to do so only so long as 
the facility in which the samplers or analyzers are manufactured 
continues to be an ISO 9001-registered facility, as set forth in 
subpart E of this part. In the event that the ISO 9001 registration for 
the facility is withdrawn, suspended, or otherwise becomes 
inapplicable, either permanently or for some specified time interval, 
such that the facility is no longer an ISO 9001-registered facility, 
the applicant shall notify EPA within 30 days of the date the facility 
becomes other than an ISO 9001-registered facility, and upon such 
notification, EPA shall issue a preliminary finding and notification of 
possible cancellation of the reference or equivalent method designation 
under Sec.  53.11.
    (i) An applicant who has offered PM2.5 or 
PM10-2.5 samplers or analyzers for sale as part of a 
reference or equivalent method may continue to do so only so long as 
updates of the Product Manufacturing Checklist set forth in subpart E 
of this part are submitted annually. In the event that an annual 
Checklist update is not received by EPA within 12 months of the date of 
the last such submitted Checklist or Checklist update, EPA shall notify 
the applicant within 30 days that the Checklist update has not been 
received and shall, within 30 days from the issuance of such 
notification, issue a preliminary finding and notification of possible 
cancellation of the reference or equivalent method designation under 
Sec.  53.11.
    Table A-1 to subpart A of part 53 is revised to read as follows:

  Table A-1 to Subpart A of Part 53.--Summary of Applicable Requirements for Reference and Equivalent Methods for Air Monitoring of Criteria Pollutants
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                               Applicable subparts of part 53
            Pollutant               Ref. or equivalent   Manual or automated   Applicable part 50 ------------------------------------------------------
                                                                                    appendix          A       B       C       D       E          F
--------------------------------------------------------------------------------------------------------------------------------------------------------
SO\2\............................  Reference...........  Manual.............  A..................  ......  ......  ......  ......  ......  .............
                                   Equivalent..........  Manual.............  ...................  [bchec  ......  [bchec  ......  ......  .............
                                                                                                       k]              k]
                                                         Automated..........  ...................  [bchec  [bchec  [bchec  ......  ......  .............
                                                                                                       k]      k]      k]
CO...............................  Reference...........  Automated..........  C..................  [bchec  [bchec  ......  ......  ......  .............
                                                                                                       k]      k]
                                   Equivalent..........  Manual.............  ...................  [bchec  ......  [bchec  ......  ......  .............
                                                                                                       k]              k]
                                                         Automated..........  ...................  [bchec  [bchec  [bchec  ......  ......  .............
                                                                                                       k]      k]      k]
O3...............................  Reference...........  Automated..........  D..................  [bchec  [bchec  ......  ......  ......  .............
                                                                                                       k]      k]
                                   Equivalent..........  Manual.............  ...................  [bchec  ......  [bchec  ......  ......  .............
                                                                                                       k]              k]
                                                         Automated..........  ...................  [bchec  [bchec  [bchec  ......  ......  .............
                                                                                                       k]      k]      k]
NO2..............................  Reference...........  Automated..........  F..................  [bchec  [bchec  ......  ......  ......  .............
                                                                                                       k]      k]
                                   Equivalent..........  Manual.............  ...................  [bchec  ......  [bchec  ......  ......  .............
                                                                                                       k]              k]
                                                         Automated..........  ...................  [bchec  [bchec  [bchec  ......  ......  .............
                                                                                                       k]      k]      k]
Pb...............................  Reference...........  Manual.............  G..................  ......  ......  ......  ......  ......  .............
                                   Equivalent..........  Manual.............  ...................  [bchec  ......  [bchec  ......  ......  .............
                                                                                                       k]              k]
PM10.............................  Reference...........  Manual.............  J..................  [bchec  ......  ......  [bchec  ......  .............
                                                                                                       k]                      k]
                                   Equivalent..........  Manual.............  ...................  [bchec  ......  [bchec  [bchec  ......  .............
                                                                                                       k]              k]      k]
                                                         Automated..........  ...................  [bchec  ......  [bchec  [bchec  ......  .............
                                                                                                       k]              k]      k]
PM2.5............................  Reference...........  Manual.............  L..................  [bchec  ......  ......  ......  [bchec  .............
                                                                                                       k]                              k]
                                   Equivalent Class I..  Manual.............  L..................  [bchec  ......  [bchec  ......  [bchec  .............
                                                                                                       k]              k]              k]
                                   Equivalent Class II.  Manual.............  L\1\...............  [bchec  ......  \2\[bc  ......  [bchec     \1\
                                                                                                       k]           heck]              k]  \2\[bcheck]

[[Page 2758]]

 
                                   Equivalent Class III  Automated..........  L\1\...............  [bchec  ......  [bchec  ......  \1\[bc  \1\[bcheck]
                                                                                                       k]              k]           heck]
PM10-2.5.........................  Reference...........  Manual.............  O\2\...............  [bchec  ......  ......  ......  [bchec  .............
                                                                                                       k]                              k]
                                   Equivalent..........  ...................  ...................  ......  ......  ......  ......  ......  .............
                                   Equivalent Class II.  Manual.............  O\2\...............  [bchec  ......  \2\[bc  ......  \1\[bc     \1\
                                                                                                       k]           heck]           heck]  \2\[bcheck]
                                   Equivalent Class III  Automated..........  L\1\, O\1\ \2\.....  [bchec  ......  [bchec  ......  \1\[bc  \1\[bcheck]
                                                                                                       k]              k]           heck]
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Some requirements may apply, based on the nature of each particular candidate method, as determined by the Administrator.
\2\ Alternative Class III requirements may be substituted.

    4. Paragraph (6) of appendix A to subpart A of part 53 is revised 
to read as follows:

Appendix A to Subpart A of Part 53--References

* * * * *
    (6) Quality Assurance Guidance Document 2.12. Monitoring 
PM2.5 in Ambient Air Using Designated Reference or Class I 
Equivalent Methods. U.S. EPA, National Exposure Research Laboratory, 
Research Triangle Park, NC, November 1998 or later edition. Currently 
available at http://www.epa.gov/ttn/amtic/pmqainf.html.

Subpart C--[Amended]

    5. Section 53.30 is revised to read as follows:


Sec.  53.30  General provisions.

    (a) Determination of comparability. The test procedures prescribed 
in this subpart shall be used to determine if a candidate method is 
comparable to a reference method when both methods measure pollutant 
concentrations in ambient air. Minor deviations in testing requirements 
and acceptance requirements set forth in this subpart, in connection 
with any documented extenuating circumstances, may be determined by the 
Administrator to be acceptable, at the discretion of the Administrator.
    (b) Selection of test sites. (1) Each test site shall be in an area 
which can be shown to have at least moderate concentrations of various 
pollutants. Each site shall be clearly identified and shall be 
justified as an appropriate test site with suitable supporting evidence 
such as a description of the surrounding area, characterization of the 
sources and pollutants typical in the area, maps, population density 
data, vehicular traffic data, emission inventories, pollutant 
measurements from previous years, concurrent pollutant measurements, 
meteorological data, and other information useful in supporting the 
suitability of the site for the comparison test or tests.
    (2) If approval of one or more proposed test sites is desired prior 
to conducting the tests, a written request for approval of the test 
site or sites must be submitted to the address given in Sec.  53.4. The 
request should include information identifying the type of candidate 
method and one or more specific proposed test sites along with a 
justification for each proposed specific site as described in paragraph 
(b)(1) of this section. The EPA will evaluate each proposed site and 
approve the site, disapprove the site, or request more information 
about the site. Any such pre-test approval of a test site by the EPA 
shall indicate only that the site meets the applicable test site 
requirements for the candidate method type; it shall not indicate, 
suggest, or imply that test data obtained at the site will necessarily 
meet any of the applicable data acceptance requirements. The 
Administrator may exercise discretion in selecting a different site (or 
sites) for any additional tests the Administrator decides to conduct.
    (c) Test atmosphere. Ambient air sampled at an appropriate test 
site or sites shall be used for these tests. Simultaneous concentration 
measurements shall be made in each of the concentration ranges 
specified in tables C-1, C-3, or C-4 of this subpart, as appropriate.
    (d) Sampling or sample collection. All test concentration 
measurements or samples shall be taken in such a way that both the 
candidate method and the reference method obtain air samples that are 
alike or as nearly identical as practical.
    (e) Operation. Set-up and start-up of the test analyzer(s), test 
sampler(s), and reference method analyzers or samplers shall be in 
strict accordance with the applicable operation manual(s).
    (f) Calibration. The reference method shall be calibrated according 
to the appropriate appendix to part 50 of this chapter (if it is a 
manual method) or according to the applicable operation manual(s) (if 
it is an automated method). A candidate method (or portion thereof) 
shall be calibrated according to the applicable operation manual(s), if 
such calibration is a part of the method.
    (g) Submission of test data and other information. All recorder 
charts, calibration data, records, test results, procedural 
descriptions and details, and other documentation obtained from (or 
pertinent to) these tests shall be identified, dated, signed by the 
analyst performing the test, and submitted. For candidate methods for 
PM2.5 and PM10-2.5, all submitted information 
must meet the requirements of the ANSI/ASQC E4 Standard, sections 
3.3.1, paragraphs 1 and 2 (reference 1 of appendix A of this subpart).


Sec.  53.31  [Removed]

    6. Section 53.31 is removed and reserved.
    7. Section 53.32 is revised to read as follows:


Sec.  53.32  Test procedures for methods for SO2, CO, 
O3, and NO2.

    (a) Comparability. Comparability is shown for SO2, CO, 
O3, and NO2 methods when the differences between:
    (1) Measurements made by a candidate manual method or by a test 
analyzer representative of a candidate automated method, and;
    (2) Measurements made simultaneously by a reference method are less 
than or equal to the values for maximum discrepancy specified in table 
C-1 of this subpart.
    (b) Test measurements. All test measurements are to be made at the 
same test site. If necessary, the concentration of pollutant in the 
sampled ambient air may be augmented with artificially generated 
pollutant to facilitate measurements in the specified ranges, as 
described under paragraph (f)(4) of this section.
    (c) Requirements for measurements or samples. All test measurements 
made or test samples collected by means of a

[[Page 2759]]

sample manifold as specified in paragraph (f)(4) of this section shall 
be at a room temperature between 20[deg] and 30[deg]C, and at a line 
voltage between 105 and 125 volts. All methods shall be calibrated as 
specified in Sec.  53.30(f) prior to initiation of the tests.
    (d) Set-up and start-up. (1) Set-up and start-up of the test 
analyzer, test sampler(s), and reference method shall be in strict 
accordance with the applicable operation manual(s). If the test 
analyzer does not have an integral strip chart or digital data 
recorder, connect the analyzer output to a suitable strip chart or 
digital data recorder. This recorder shall have a chart width of at 
least 25 centimeters, a response time of 1 second or less, a deadband 
of not more than 0.25 percent of full scale, and capability of either 
reading measurements at least 5 percent below zero or offsetting the 
zero by at least 5 percent. Digital data shall be recorded at 
appropriate time intervals such that trend plots similar to a strip 
chart recording may be constructed with a similar or suitable level of 
detail.
    (2) Other data acquisition components may be used along with the 
chart recorder during the conduct of these tests. Use of the chart 
recorder is intended only to facilitate visual evaluation of data 
submitted.
    (3) Allow adequate warmup or stabilization time as indicated in the 
applicable operation manual(s) before beginning the tests.
    (e) Range. (1) Except as provided in paragraph (e)(2) of this 
section, each method shall be operated in the range specified for the 
reference method in the appropriate appendix to part 50 of this chapter 
(for manual reference methods), or specified in table B-1 of subpart B 
of this part (for automated reference methods).
    (2) For a candidate method having more than one selectable range, 
one range must be that specified in table B-1 of subpart B of this 
part, and a test analyzer representative of the method must pass the 
tests required by this subpart while operated on that range. The tests 
may be repeated for a broader range (i.e., one extending to higher 
concentrations) than the one specified in table B-1 of subpart B of 
this part, provided that the range does not extend to concentrations 
more than two times the upper range limit specified in table B-1 of 
subpart B of this part and that the test analyzer has passed the tests 
required by subpart B of this part (if applicable) for the broader 
range. If the tests required by this subpart are conducted or passed 
only for the range specified in table B-1 of subpart B of this part, 
any equivalent method determination with respect to the method will be 
limited to that range. If the tests are passed for both the specified 
range and a broader range (or ranges), any such determination will 
include the broader range(s) as well as the specified range. 
Appropriate test data shall be submitted for each range sought to be 
included in such a determination.
    (f) Operation of automated methods. (1) Once the test analyzer has 
been set up and calibrated and tests started, manual adjustment or 
normal periodic maintenance, as specified in the manual referred to in 
Sec.  53.4(b)(3), is permitted only every 3 days. Automatic adjustments 
which the test analyzer performs by itself are permitted at any time. 
The submitted records shall show clearly when manual adjustments were 
made and describe the operations performed.
    (2) All test measurements shall be made with the same test 
analyzer; use of multiple test analyzers is not permitted. The test 
analyzer shall be operated continuously during the entire series of 
test measurements.
    (3) If a test analyzer should malfunction during any of these 
tests, the entire set of measurements shall be repeated, and a detailed 
explanation of the malfunction, remedial action taken, and whether 
recalibration was necessary (along with all pertinent records and 
charts) shall be submitted.
    (4) Ambient air shall be sampled from a common intake and 
distribution manifold designed to deliver homogenous air samples to 
both methods. Precautions shall be taken in the design and construction 
of this manifold to minimize the removal of particulate matter and 
trace gases, and to insure that identical samples reach the two 
methods. If necessary, the concentration of pollutant in the sampled 
ambient air may be augmented with artificially generated pollutant. 
However, at all times the air sample measured by the candidate and 
reference methods under test shall consist of not less than 80 percent 
ambient air by volume. Schematic drawings, physical illustrations, 
descriptions, and complete details of the manifold system and the 
augmentation system (if used) shall be submitted.
    (g) Tests. (1) Conduct the first set of simultaneous measurements 
with the candidate and reference methods:
    (i) Table C-1 of this subpart specifies the type (1- or 24-hour) 
and number of measurements to be made in each of the three test 
concentration ranges.
    (ii) The pollutant concentration must fall within the specified 
range as measured by the reference method.
    (iii) The measurements shall be made in the sequence specified in 
table C-2 of this subpart, except for the 1-hour SO2 
measurements, which are all in the high range.
    (2) For each pair of measurements, determine the difference 
(discrepancy) between the candidate method measurement and reference 
method measurement. A discrepancy which exceeds the discrepancy 
specified in table C-1 of this subpart constitutes a failure. Figure C-
1 of this subpart contains a suggested format for reporting the test 
results.
    (3) The results of the first set of measurements shall be 
interpreted as follows:
    (i) Zero failures: The candidate method passes the test for 
comparability.
    (ii) Three or more failures: The candidate method fails the test 
for comparability.
    (iii) One or two failures: Conduct a second set of simultaneous 
measurements as specified in table C-1 of this subpart. The results of 
the combined total of first-set and second-set measurements shall be 
interpreted as follows:
    (A) One or two failures: The candidate method passes the test for 
comparability.
    (B) Three or more failures: The candidate method fails the test for 
comparability.
    (iv) For SO2, the 1-hour and 24-hour measurements shall 
be interpreted separately, and the candidate method must pass the tests 
for both 1- and 24-hour measurements to pass the test for 
comparability.
    (4) A 1-hour measurement consists of the integral of the 
instantaneous concentration over a 60-minute continuous period divided 
by the time period. Integration of the instantaneous concentration may 
be performed by any appropriate means such as chemical, electronic, 
mechanical, visual judgment, or by calculating the mean of not less 
than 12 equally-spaced instantaneous readings. Appropriate allowances 
or corrections shall be made in cases where significant errors could 
occur due to characteristic lag time or rise/fall time differences 
between the candidate and reference methods. Details of the means of 
integration and any corrections shall be submitted.
    (5) A 24-hour measurement consists of the integral of the 
instantaneous concentration over a 24-hour continuous period divided by 
the time period. This integration may be performed by any appropriate 
means such as chemical, electronic, mechanical, or by calculating the 
mean

[[Page 2760]]

of twenty-four (24) sequential 1-hour measurements.
    (6) For O3 and CO, no more than six 1-hour measurements 
shall be made per day. For SO2, no more than four 1-hour 
measurements or one 24-hour measurement shall be made per day. One-hour 
measurements may be made concurrently with 24-hour measurements if 
appropriate.
    (7) For applicable methods, control or calibration checks may be 
performed once per day without adjusting the test analyzer or method. 
These checks may be used as a basis for a linear interpolation-type 
correction to be applied to the measurements to correct for drift. If 
such a correction is used, it shall be applied to all measurements made 
with the method, and the correction procedure shall become a part of 
the method.
    8. Section 53.33 is revised to read as follows:


Sec.  53.33  Test procedure for methods for Pb.

    (a) Comparability. Comparability is shown for Pb methods when the 
differences between:
    (1) Measurements made by a candidate method, and
    (2) Measurements made by the reference method on simultaneously 
collected Pb samples (or the same sample, if applicable), are less than 
or equal to the value specified in table C-3 of this subpart.
    (b) Test measurements. Test measurements may be made at any number 
of test sites. Augmentation of pollutant concentrations is not 
permitted, hence an appropriate test site or sites must be selected to 
provide Pb concentrations in the specified range.
    (c) Collocated samplers. The ambient air intake points of all the 
candidate and reference method collocated samplers shall be positioned 
at the same height above the ground level, and between 2 meters (1 
meter for samplers with flow rates less than 200 liters per minute (L/
min)) and 4 meters apart. The samplers shall be oriented in a manner 
that will minimize spatial and wind directional effects on sample 
collection.
    (d) Sample collection. Collect simultaneous 24-hour samples 
(filters) of Pb at the test site or sites with both the reference and 
candidate methods until at least 10 filter pairs have been obtained. A 
candidate method which employs a sampler and sample collection 
procedure that are identical to the sampler and sample collection 
procedure specified in the reference method, but uses a different 
analytical procedure, may be tested by analyzing common samples. The 
common samples shall be collected according to the sample collection 
procedure specified by the reference method and each shall be divided 
for respective analysis in accordance with the analytical procedures of 
the candidate method and the reference method.
    (e) Audit samples. Three audit samples must be obtained from the 
address given in Sec.  53.4(a). The audit samples are 3/4 x 8-inch 
glass fiber strips containing known amounts of Pb at the following 
nominal levels: 100 micrograms per strip ([mu]g/strip); 300 [mu]g/
strip; 750 [mu]g/strip. The true amount of Pb, in total [mu]g/strip, 
will be provided with each audit sample.
    (f) Filter analysis. (1) For both the reference method samples and 
the audit samples, analyze each filter extract three times in 
accordance with the reference method analytical procedure. The analysis 
of replicates should not be performed sequentially, i.e., a single 
sample should not be analyzed three times in sequence. Calculate the 
indicated Pb concentrations for the reference method samples in 
micrograms per cubic meter ([mu]g/m\3\) for each analysis of each 
filter. Calculate the indicated total Pb amount for the audit samples 
in [mu]g/strip for each analysis of each strip. Label these test 
results as R1A, R1B, R1C, 
R2A, R2B, * * *, Q1A, Q1B, 
Q1C, * * * ., where R denotes results from the reference 
method samples; Q denotes results from the audit samples; 1, 2, 3 
indicate the filter number, and A, B, C indicate the first, second, and 
third analysis of each filter, respectively.
    (2) For the candidate method samples, analyze each sample filter or 
filter extract three times and calculate, in accordance with the 
candidate method, the indicated Pb concentration in [mu]g/m\3\ for each 
analysis of each filter. Label these test results as C1A, 
C1B, C2C, . . ., where C denotes results from the 
candidate method. For candidate methods which provide a direct 
measurement of Pb concentrations without a separable procedure, 
C1A=C1B=C1C, 
C2A=C2B=C2C, etc.
    (g) Average Pb concentration. For the reference method, calculate 
the average Pb concentration for each filter by averaging the 
concentrations calculated from the three analyses using equation 1 of 
this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.005


where, i is the filter number.
    (h) Accuracy. (1)(i) For the audit samples, calculate the average 
Pb concentration for each strip by averaging the concentrations 
calculated from the three analyses using equation 2 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.006


where, i is audit sample number.
    (ii) Calculate the percent difference (Dq) between the 
indicated Pb concentration for each audit sample and the true Pb 
concentration (Tq) using equation 3 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.007

    (2) If any difference value (Dqi) exceeds 5 
percent, the accuracy of the reference method analytical procedure is 
out-of-control. Corrective action must be taken to determine the source 
of the error(s) (e.g., calibration standard discrepancies, extraction 
problems, etc.) and the reference method and audit sample 
determinations must be repeated according to paragraph (f) of this 
section, or the entire test procedure (starting with paragraph (d) of 
this section) must be repeated.
    (i) Acceptable filter pairs. Disregard all filter pairs for which 
the Pb concentration, as determined in paragraph (g) of this section by 
the average of the three reference method determinations, falls outside 
the range of 0.5 to 4.0 [mu]g/m\3\. All remaining filter pairs must be 
subjected to the tests for precision and comparability in paragraphs 
(j) and (k) of this section. At least five filter pairs must be within 
the 0.5 to 4.0 [mu]g/m\3\ range for the tests to be valid.
    (j) Test for precision. (1) Calculate the precision (P) of the 
analysis (in percent) for each filter and for each method, as the 
maximum minus the minimum divided by the average of the three 
concentration values, using equation 4 or equation 5 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.008


or

[[Page 2761]]

[GRAPHIC] [TIFF OMITTED] TP17JA06.009

where, i indicates the filter number.
    (2) If any reference method precision value (PRi) 
exceeds 15 percent, the precision of the reference method analytical 
procedure is out-of-control. Corrective action must be taken to 
determine the source(s) of imprecision, and the reference method 
determinations must be repeated according to paragraph (f) of this 
section, or the entire test procedure (starting with paragraph (d) of 
this section) must be repeated.
    (3) If any candidate method precision value (PCi) 
exceeds 15 percent, the candidate method fails the precision test.
    (4) The candidate method passes this test if all precision values 
(i.e., all PRi's and all PCi's) are less than 15 
percent.
    (k) Test for comparability. (1) For each filter or analytical 
sample pair, calculate all nine possible percent differences (D) 
between the reference and candidate methods, using all nine possible 
combinations of the three determinations (A, B, and C) for each method 
using equation 6 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.010


where, i is the filter number, and n numbers from 1 to 9 for the nine 
possible difference combinations for the three determinations for each 
method (j = A, B, C, candidate; k = A, B, C, reference).
    (2) If none of the percent differences (D) exceeds 20 
percent, the candidate method passes the test for comparability.
    (3) If one or more of the percent differences (D) exceed 20 percent, the candidate method fails the test for 
comparability.
    (4) The candidate method must pass both the precision test 
(paragraph (j) of this section) and the comparability test (paragraph 
(k) of this section) to qualify for designation as an equivalent 
method.
    9. Section 53.34 is revised to read as follows:


Sec.  53.34  Test procedure for methods for PM10 and Class I 
methods for PM2.5.

    (a) Comparability. Comparability is shown for PM10 
methods and for Class I methods for PM2.5 when the 
relationship between:
    (1) Measurements made by a candidate method, and
    (2) Measurements made by a corresponding reference method on 
simultaneously collected samples (or the same sample, if applicable) at 
each of one or more test sites (as required) is such that the linear 
regression parameters (slope, intercept, and correlation coefficient) 
describing the relationship meet the requirements specified in table C-
4 of this subpart.
    (b) Methods for PM10. Test measurements must be made, or derived 
from particulate samples collected, at not less than two test sites, 
each of which must be located in a geographical area characterized by 
ambient particulate matter that is significantly different in nature 
and composition from that at the other test site(s). Augmentation of 
pollutant concentrations is not permitted, hence appropriate test sites 
must be selected to provide the minimum number of test PM10 
concentrations in the ranges specified in table C-4 of this subpart. 
The tests at the two sites may be conducted in different calendar 
seasons, if appropriate, to provide PM10 concentrations in 
the specified ranges.
    (c) PM10 methods employing the same sampling procedure as the 
reference method but a different analytical method. Candidate methods 
for PM10 which employ a sampler and sample collection 
procedure that are identical to the sampler and sample collection 
procedure specified in the reference method, but use a different 
analytical procedure, may be tested by analyzing common samples. The 
common samples shall be collected according to the sample collection 
procedure specified by the reference method and shall be analyzed in 
accordance with the analytical procedures of both the candidate method 
and the reference method.
    (d) Methods for PM2.5. Augmentation of pollutant concentrations is 
not permitted, hence appropriate test sites must be selected to provide 
the minimum number of test measurement sets to meet the requirements 
for PM2.5 concentrations in the ranges specified in table C-
4 of this subpart. Only one test site is required, and the site need 
only meet the PM2.5 ambient concentration levels required by 
table C-4 of this subpart. A total of 10 valid measurement sets is 
required.
    (e) Collocated measurements. (1) Set up three reference method 
samplers collocated with three candidate method samplers or analyzers 
at each of the number of test sites specified in table C-4 of this 
subpart.
    (2) The ambient air intake points of all the candidate and 
reference method collocated samplers or analyzers shall be positioned 
at the same height above the ground level, and between 2 meters (1 
meter for samplers or analyzers with flow rates less than 200 L/min) 
and 4 meters apart. The samplers shall be oriented in a manner that 
will minimize spatial and wind directional effects on sample 
collection.
    (3) At each site, obtain as many sets of simultaneous 
PM10 or PM2.5 measurements as necessary (see 
table C-4 of this subpart), each set consisting of three reference 
method and three candidate method measurements, all obtained 
simultaneously.
    (4) Candidate PM10 method measurements shall be nominal 
24-hour (1 hour) integrated measurements or shall be 
averaged to obtain the mean concentration for a nominal 24-hour period. 
PM2.5 measurements may be either nominal 24- or 48-hour 
integrated measurements. All collocated measurements in a measurement 
set must cover the same nominal 24- or 48-hour time period.
    (5) For samplers, retrieve the samples promptly after sample 
collection and analyze each sample according to the reference method or 
candidate method, as appropriate, and determine the PM10 or 
PM2.5 concentration in [mu]g/m3. If the conditions of 
paragraph (c) of this section apply, collect sample sets only with the 
three reference method samplers. Guidance for quality assurance 
procedures for PM2.5 methods is found in ``Quality Assurance 
Document 2.12'' (reference (2) in appendix A to this subpart).
    (f) Sequential samplers. For sequential samplers, the sampler shall 
be configured for the maximum number of sequential samples and shall be 
set for automatic collection of all samples sequentially such that the 
test samples are collected equally, to the extent possible, among all 
available sequential channels or utilizing the full available 
sequential capability.
    (g) Calculation of reference method averages and precisions. (1) 
For each of the measurement sets, calculate the average PM10 
or PM2.5 concentration obtained with the reference method 
samplers, using equation 7 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.011


Where:


[[Page 2762]]


R = The concentration measurements from the reference methods;
i = The sampler number; and
j = The measurement set number.
    (2) For each of the measurement sets, calculate the precision of 
the reference method PM10 or PM2.5 measurements 
as the standard deviation, PRj, using equation 8 of this 
section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.012

    (3) For each measurement set, also calculate the precision of the 
reference method PM10 or PM2.5 measurements as 
the relative standard deviation, RPRj, in percent, using 
equation 9 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.013

    (h) Acceptability of measurement sets. Each measurement set is 
acceptable and valid only if the three reference method measurements 
and the three candidate method measurements are obtained and are valid, 
Rj falls within the acceptable concentration range specified 
in table C-4 of this subpart, and either PRj or 
RPRj is within the corresponding limit for reference method 
precision specified in table C-4 of this subpart. For each site, table 
C-4 of this subpart specifies the minimum number of measurement sets 
required having Rj above and below specified concentrations 
for 24- or 48-hour samples. Additional measurement sets shall be 
obtained, as necessary, to provide the minimum number of acceptable 
measurement sets for each category and the minimum total number of 
acceptable measurement sets for each test site. If more than the 
minimum number of measurement sets are collected that meet the 
acceptability criteria, all such measurement sets shall be used to 
demonstrate comparability.
    (i) Candidate method average concentration measurement. For each of 
the acceptable measurement sets, calculate the average PM10 
or PM2.5 concentration measurements obtained with the 
candidate method samplers, using equation 10 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.014


Where:

C = The concentration measurements from the candidate methods;
i = The measurement number in the set; and
j = The measurement set number.

    (j) Test for comparability. (1) For each site, plot all of the 
average PM10 or PM2.5 measurements obtained with 
the candidate method (Cj) against the corresponding average 
PM10 or PM2.5 measurements obtained with the 
reference method (Rj). For each site, calculate and record 
the linear regression slope and intercept, and the correlation 
coefficient.
    (2) To pass the test for comparability, the slope, intercept, and 
correlation coefficient calculated under paragraph (j)(1) of this 
section must be within the limits specified in table C-4 of this 
subpart for all test sites.
    10. Section 53.35 is added to read as follows:


Sec.  53.35  Test procedure for Class II and Class III methods for 
PM2.5 and PM10-2.5.

    (a) Overview. Class II and Class III candidate equivalent methods 
shall be tested for comparability of PM2.5 or 
PM10-2.5 measurements to corresponding collocated 
PM2.5 or PM10-2.5 reference method measurements 
at each of multiple field sites, as required. Comparability is shown 
for the candidate method when simultaneous collocated measurements made 
by candidate and reference methods meet the comparability requirements 
specified in this section Sec.  53.35 and in table C-4 of this subpart 
at each of the required test sites.
    (b) Test sites and seasons. (1) Test sites. Comparability testing 
is required at each of the applicable test sites required by this 
paragraph (b). Each test site must also meet the general test site 
requirements specified in Sec.  53.30(b).
    (i) PM2.5 Class II and Class III candidate methods. Test sites 
should be chosen to provide representative chemical and meteorological 
characteristics with respect to nitrates, sulfates, organic compounds, 
and various levels of humidity, wind, and elevation. For Class III 
methods, one test site shall be selected in each of the following 
general locations. For Class II methods, two test sites, one eastern 
site and one western site, shall be selected from these locations. Test 
site A shall be in the Los Angeles basin area in a location that is 
characterized by relatively high PM2.5, nitrates, and semi-
volatile organic pollutants. Test site B shall be in a northeastern or 
mid-Atlantic U.S. city that is seasonally characterized by high sulfate 
concentrations, high relative humidity, and wintertime conditions. Test 
site C shall be in a western U.S. city such as Denver, Salt Lake City, 
or Albuquerque in a location that is in an area characterized by cold 
weather, higher elevation, winds, and dust.
    (ii) PM10-2.5 Class II and Class III candidate methods. Test sites 
shall be chosen to provide modest to high levels of PM10-2.5 
representative of locations in proximity to urban sources of 
PM10-2.5 such as high-density traffic on paved roads, 
industrial sources, and construction activities. For Class III methods, 
one test site shall be selected in each of the following general 
locations. At least one of the test sites shall have characteristic 
wintertime temperatures of 0[deg]C or lower. For Class II methods, two 
test sites, one eastern site and one western site, shall be selected 
from these locations. Test site A shall be in the Los Angeles basin or 
the California Central Valley area. Test site B shall be in a large 
U.S. city east of the Mississippi River, having characteristically high 
humidity levels. Test site C shall be in a western U.S. city 
characterized by a high ratio of PM10-2.5 to 
PM2.5, with exposure to rural windblown dust, such as Las 
Vegas or Phoenix.
    (2) Test seasons. (i) For PM2.5 and PM10-2.5 
Class III candidate methods, test campaigns are required in both summer 
and winter seasons at test sites A and B. A test campaign is required 
only in the winter season at test site C. (A total of 5 test campaigns 
is required.) The summer season shall be defined as the typically 
warmest 3 or 4 months of the year at the site; the winter season shall 
be defined as the typically coolest 3 or 4 months of the year at the 
site.
    (ii) For Class II PM2.5 and PM10-2.5 
candidate methods, only one test campaign is required at each site, at 
any time of year (total of 2 test campaigns).
    (3) Test concentrations. The test sites should be selected to 
provide ambient concentrations within the concentration limits 
specified in table C-4 of this subpart, and also to provide a wide 
range of test concentrations. A narrow range of test concentrations may 
result in a low concentration coefficient of variation statistic for 
the test measurements, making the test for correlation coefficient more 
difficult to pass (see paragraph (h) of this section, test for 
comparison correlation).

[[Page 2763]]

    (4) Pre-approval of test sites. The EPA recommends that the 
applicant seek EPA approval of each proposed test site prior to 
conducting test measurements at the site. To do so, the applicant 
should submit a request for approval as described in Sec.  53.30(b)(2).
    (c) Collocated measurements. (1) For each test campaign, three 
reference method samplers and three candidate method samplers or 
analyzers shall be installed and operated concurrently at each test 
site within each required season (if applicable), as specified in 
paragraph (b) of this section. All reference method samplers shall be 
of single-filter design (not multi-filter, sequential sample design). 
Each candidate method shall be setup and operated in accordance with 
its associated manual referred to in Sec.  53.4(b)(3) and in accordance 
with applicable guidance in ``Quality Assurance Document 2.12'' 
(reference (2) in appendix A to this subpart). All samplers or 
analyzers shall be placed so that they sample or measure air 
representative of the surrounding area (within one kilometer) and are 
not unduly affected by adjacent buildings, air handling equipment, 
industrial operations, traffic, or other local influences. The ambient 
air inlet points of all samplers and analyzers shall be positioned at 
the same height above the ground level and between 2 meters (1 meter 
for instruments having sample inlet flow rates less than 200 L/min) and 
4 meters apart.
    (2) A minimum of 23 valid and acceptable measurement sets of 
PM2.5 or PM10-2.5 24-hour (nominal) concurrent 
concentration measurements shall be obtained during each test campaign 
at each test site. To be considered acceptable for the test, each 
measurement set shall consist of at least two valid reference method 
measurements and at least two valid candidate method measurements, and 
the PM2.5 or PM10-2.5 measured concentration, as 
determined by the average of the reference method measurements, must 
fall within the acceptable concentration range specified in table C-4 
of this subpart. Each measurement set shall include all valid 
measurements obtained. For each measurement set containing fewer than 
three reference method measurements or fewer than three candidate 
method measurements, an explanation and appropriate justification shall 
be provided to account for the missing measurement or measurements.
    (3) More than 23 valid measurement sets may be obtained during a 
particular test campaign to provide a more advantageous range of 
concentrations, more representative conditions, additional higher or 
lower measurements, or to otherwise improve the comparison of the 
methods. All valid data sets obtained during each test campaign shall 
be submitted and shall be included in the analysis of the data.
    (4) The integrated-sample reference method measurements shall be of 
at least 22 hours and not more than 25 hours duration. Each reference 
method sample shall be retrieved promptly after sample collection and 
analyzed according to the reference method to determine the 
PM2.5 or PM10-2.5 measured concentration in 
[mu]g/m3. Guidance and quality assurance procedures 
applicable to PM2.5 or PM10-2.5 reference methods 
are found in ``Quality Assurance Document 2.12'' (reference (2) in 
appendix A to this subpart).
    (5) Candidate method measurements shall be timed or processed and 
averaged as appropriate to determine an equivalent mean concentration 
representative of the same time period as that of the concurrent 
integrated-sample reference method measurements, such that all 
measurements in a measurement set shall be representative of the same 
time period. In addition, hourly average concentration measurements 
shall be obtained from each of the Class III candidate method analyzers 
for each valid measurement set and submitted as part of the application 
records.
    (6) In the following tests, all measurement sets obtained at a 
particular test site, from both seasonal campaigns if applicable, shall 
be combined and included in the test data analysis for the site. Data 
obtained at different test sites shall be analyzed separately. All 
measurements should be reported as normally obtained, and no 
measurement values should be rounded or truncated prior to data 
analysis. In particular, no negative measurement value, if otherwise 
apparently valid, should be modified, adjusted, replaced, or eliminated 
merely because its value is negative. Calculated mean concentrations or 
calculated intermediate quantities should retain at least one order-of-
magnitude greater resolution than the input values. All measurement 
data and calculations shall be recorded and submitted in accordance 
with Sec.  53.30(g), including hourly test measurements obtained from 
Class III candidate methods.
    (d) Calculation of mean concentrations. (1) Reference method 
outlier test. For each of the measurement sets for each test site, 
check each reference method measurement to see if it might be an 
anomalous value (outlier) as follows, where Ri,j is the 
measurement of reference method sampler i on test day j. In the event 
that one of the reference method measurements is missing or invalid due 
to a specific, positively-identified physical cause (e.g., sampler 
malfunction, operator error, accidental damage to the filter, etc.; see 
paragraph (c)(2) of this section), then substitute zero for the missing 
measurement, for the purposes of this outlier test only.
    (i) Calculate the quantities 2 x R1, j/(R1, j 
+ R2, j) and 2 x R1, j/(R1, j + 
R3, j). If both quantities fall outside of the interval, 
(0.93, 1.07), then R1, j is an outlier.
    (ii) Calculate the quantities 2 x R2, j/
(R2, j + R1, j) and 2 x R2, j/
(R2, j + R3, j). If both quantities fall outside 
of the interval, (0.93, 1.07), then R2, j is an outlier.
    (iii) Calculate the quantities 2 x R3,j/(R3,j 
+ R1,j) and 2 x R3,j/(R3,j + 
R2,j). If both quantities fall outside of the interval, 
(0.93, 1.07), then R3,j is an outlier.
    (iv) If this test indicates that one of the reference method 
measurements in the measurement set is an outlier, the outlier 
measurement shall be eliminated from the measurement set, and the other 
two measurements considered valid. If the test indicates that more than 
one reference method measurement in the measurement set is an outlier, 
the entire measurement set (both reference and candidate method 
measurements) shall be excluded from further data analysis for the 
tests of this section.
    (2) For each of the measurement sets for each test site, calculate 
the mean concentration for the reference method measurements, using 
equation 11 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.015


Where:
Rj = The mean concentration measured by the reference method 
for the measurement set;
Ri,j = The measurement of reference method sampler i on test 
day j; and
n =The number of valid reference method measurements in the measurement 
set (normally 3).
    (3) Any measurement set for which Rj does not fall in 
the acceptable concentration range specified in table C-4 of this 
subpart is not valid, and the entire measurement set (both reference 
and candidate method measurements) must be eliminated from further data 
analysis.

[[Page 2764]]

    (4) For each of the valid measurement sets at each test site, 
calculate the mean concentration for the candidate method measurements, 
using equation 12 of this section. (The outlier test in paragraph 
(d)(1) of this section shall not be applied to the candidate method 
measurements.)
[GRAPHIC] [TIFF OMITTED] TP17JA06.016


where:

Cj = The mean concentration measured by the candidate method 
for the measurement set;
Ci, j = The measurement of candidate method analyzer i on 
test day j; and
m = The number of valid candidate method measurements in the 
measurement set (normally 3).

    (e) Test for reference method precision. (1) For each of the 
measurement sets for each site, calculate an estimate for the relative 
precision of the reference method measurements, RPj, using 
equation 13 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.017

    (2) For each site, calculate an estimate of reference method 
relative precision for the site, RP, using the root mean square 
calculation of equation 14 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.018


where, J is the total number of valid measurement sets for the site.
    (3) Verify that the estimate for reference method relative 
precision for the site, RP, is not greater than the value specified for 
reference method precision in table C-4 of this subpart. A reference 
method relative precision greater than the value specified in table C-4 
of this subpart indicates that quality control for the reference method 
is inadequate, and corrective measures must be implemented before 
proceeding with the test.
    (f) Test for candidate method precision. (1) For each of the 
measurement sets, for each site, calculate an estimate for the relative 
precision of the candidate method measurements, CPj, using 
equation 15 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.019

    (2) For each site, calculate an estimate of candidate method 
relative precision for the site, CP, using the root mean square 
calculation of equation 16 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.020


where, J is the total number of valid measurement sets for the site.
    (3) To pass the test for precision, the mean candidate method 
relative precision at each site must not be greater than the value for 
candidate method precision specified in table C-4 of this subpart.
    (g) Test for additive and multiplicative bias (comparative slope 
and intercept). (1) For each test site, calculate the mean 
concentration measured by the reference method, R, using equation 17 of 
this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.021

    (2) For each test site, calculate the mean concentration measured 
by the candidate method, C, using equation 18 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.022

    (3) For each test site, calculate the linear regression slope and 
intercept of the mean candidate method measurements (Cj) 
against the mean reference method measurements (Rj), using 
equations 19 and 20 of this section, respectively:
[GRAPHIC] [TIFF OMITTED] TP17JA06.023

[GRAPHIC] [TIFF OMITTED] TP17JA06.024

    (4) To pass this test, at each test site:
    (i) The slope must be in the interval specified for regression 
slope in table C-4 of this subpart; and
    (ii) The intercept must be in the interval specified for regression 
intercept in table C-4 of this subpart.
    (iii) The slope and intercept limits are illustrated in figures C-2 
and C-3 of this subpart.
    (h) Tests for comparison correlation. (1) For each test site, 
calculate the (Pearson) correlation coefficient, r (not the coefficient 
of determination, r \2\), using equation 21 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.025

    (2) For each test site, calculate the concentration coefficient of 
variation, CCV, using equation 22 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.026

    (3) To pass the test, the correlation coefficient, r, for each test 
site must not be less than the values, for various values of CCV, 
specified for correlation in table C-4 of this subpart. These limits 
are illustrated in figure C-4 of this subpart.
    11. Tables C-1, C-2, C-3, and C-4 to subpart C are revised to read 
as follows:

[[Page 2765]]



   Table C-1 to Subpart C of Part 53.--Test Concentration Ranges, Number of Measurements Required, and Maximum
                                            Discrepancy Specification
----------------------------------------------------------------------------------------------------------------
                                                              Simultaneous measurements required
                                                             ------------------------------------     Maximum
                                        Concentration range         1-hr              24-hr         discrepancy
              Pollutant                  parts per million   ------------------------------------ specification,
                                                               First    Second   First    Second     parts per
                                                                set      set      set      set        million
----------------------------------------------------------------------------------------------------------------
Ozone...............................  Low 0.06 to 0.10......        5        6  .......  .......            0.02
                                      Med 0.15 to 0.25......        5        6  .......  .......             .03
                                      High 0.35 to 0.45.....        4        6  .......  .......             .04
                                      Total.................       14       18  .......  .......  ..............
Carbon monoxide.....................  Low 7 to 11...........        5        6  .......  .......            1.5
                                      Med 20 to 30..........        5        6  .......  .......            2.0
                                      High 35 to 45.........        4        6  .......  .......            3.0
                                      Total.................       14       18  .......  .......  ..............
Sulfur dioxide......................  Low 0.02 to 0.05......  .......  .......        3        3            0.02
                                      Med 0.10 to 0.15......  .......  .......        2        3             .03
                                      High 0.30 to 0.50.....        7        8        2        2             .04
                                      Total.................        7        8        7        8  ..............
Nitrogen dioxide....................  Low 0.02 to 0.08......  .......  .......        3        3            0.02
                                      Med 0.10 to 0.20......  .......  .......        2        3             .03
                                      High 0.25 to 0.35.....  .......  .......        2        2             .03
                                      Total.................  .......  .......        7        8  ..............
----------------------------------------------------------------------------------------------------------------


    Table C-2 to Subpart C of Part 53.--Sequence of Test Measurements
------------------------------------------------------------------------
                                            Concentration range
           Measurement           ---------------------------------------
                                       First set          Second set
------------------------------------------------------------------------
1...............................  Low...............  Medium.
2...............................  High..............  High.
3...............................  Medium............  Low.
4...............................  High..............  High.
5...............................  Low...............  Medium.
6...............................  Medium............  Low.
7...............................  Low...............  Medium.
8...............................  Medium............  Low.
9...............................  High..............  High.
10..............................  Medium............  Low.
11..............................  High..............  Medium.
12..............................  Low...............  High.
13..............................  Medium............  Medium.
14..............................  Low...............  High.
15..............................  ..................  Low.
16..............................  ..................  Medium.
17..............................  ..................  Low.
18..............................  ..................  High.
------------------------------------------------------------------------


 Table C-3 to Subpart C of Part 53.--Test Specifications for Pb Methods
------------------------------------------------------------------------
              Concentration range, [mu]g/m\3\                  0.5-4.0
------------------------------------------------------------------------
Minimum number of 24-hr measurements.......................            5
Maximum analytical precision, percent......................           15
Maximum analytical accuracy, percent.......................       5
Maximum difference, percent of reference method............       20
------------------------------------------------------------------------


                                             Table C-4 to Subpart C.--Test Specifications for PM10, PM2.5 and PM10-2.5 Candidate Equivalent Methods
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                   PM2.5                                                           PM10-2.5
          Specification                       PM10           -----------------------------------------------------------------------------------------------------------------------------------
                                                                       Class I                    Class II                  Class III                 Class II                  Class III
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Acceptable concentration range     15-300...................  3-200....................  3-200....................  3-200...................  3-200...................  3-200
 (Rj), [mu]g/m\3\.
Minimum number of test sites.....  2........................  1........................  2........................  3.......................  2.......................  3
Minimum number of candidate        3........................  3........................  3 \1\....................  3 \1\...................  3 \1\...................  3 \1\
 method samplers or analyzers per
 site.
Number of reference method         3........................  3........................  3 \1\....................  3 \1\...................  3 \1\...................  3 \1\
 samplers per site.
Minimum number of acceptable
 sample sets per site for PM10
 methods:.
Rj < 60 [mu]g/m\3\...............  3
Rj > 60 [mu]g/m\3\...............  3
    Total........................  10
    Minimum number of acceptable
     sample sets per site for
     PM2.5 and PM10-2.5 candidate
     equivalent methods:.
Rj < 30 [mu]g/m\3\ for 24-hr or    .........................  3
 Rj < 20 [mu]g/m\3\ for 48-hr
 samples.

[[Page 2766]]

 
Rj > 30 [mu]g/m\3\ for 24-hr or    .........................  3
 Rj > 20 [mu]g/m\3\ for 48-hr
 samples.
Each season......................  .........................  10.......................  23.......................  23......................  23......................  23
    Total, each site.............  .........................  10.......................  23.......................  46 (23 for single season  23......................  46 (23 for single season
                                                                                                                     site).                                              site)
Precision of replicate reference   5 [mu]g/m\3\ or 7%.......  2 [mu]g/m\3\ or 5%.......  10% \2\..................  10% \2\.................  10% \2\.................  10% \2\
 method measurements, PRj or
 RPRj, respectively; RP for Class
 II or III PM2.5 or PM10-2.5,
 maximum.
Precision of PM2.5 or PM10-2.5     .........................  .........................  10% \2\..................  15% \2\.................  15% \2\.................  15% \2\
 candidate method, CP, each site.
Slope of regression relationship.  10.1.........  10.05........  10.10........  10.10.......  10.10.......  10.12
Intercept of regression            05...........  01...........  Between: 13.55-(15.05 x    Between: 15.05-(17.32 x   Between: 59.93-(70.50 x   Between: 70.50-(82.93 x
 relationship, [mu]g/m\3\.                                                                slope), but not less       slope); and 15.05-        slope), but not less      slope); and 70.50-
                                                                                          than -1.5; and 16.56-      (13.20 x slope).          than -7.0; and 81.08-     (61.16 x slope)
                                                                                          (15.05 x slope), but not                             (70.50 x slope), but
                                                                                          more than +1.5.                                      not more than +7.0.
Correlation of reference method    >=0.97...................  >=0.97...................                >=0.93 for CCV<=0.4; >=0.85+0.2xCCV for 0.4<=CCV<=0.5; >=0.95 for CCV>=0.5
 and candidate method
 measurements.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Some missing daily measurement values may be permitted; see test procedure.
\2\ Calculated as the root mean square over all measurement sets.

    11. Figure C-1 to subpart C is revised to read as follows:
BILLING CODE 6560-50-U

[[Page 2767]]

[GRAPHIC] [TIFF OMITTED] TP17JA06.072

    13. Figures C-2, C-3, and C-4 are added to subpart C to read as 
follows:


[[Page 2768]]


[GRAPHIC] [TIFF OMITTED] TP17JA06.001


[[Page 2769]]


[GRAPHIC] [TIFF OMITTED] TP17JA06.002


[[Page 2770]]


[GRAPHIC] [TIFF OMITTED] TP17JA06.003

BILLING CODE 6560-50-C
    14. Appendix A to subpart C is amended by adding reference (2) to 
read as follows:

Appendix A to Subpart C--References

* * * * *
    (2) Quality Assurance Guidance Document 2.12. Monitoring 
PM2.5 in Ambient Air Using Designated Reference or Class I 
Equivalent Methods. U.S. EPA, National Exposure Research Laboratory, 
Research Triangle Park, NC, November 1998 or later edition. Currently 
available at http://www.epa.gov/ttn/amtic/pmqainf.html.

Subpart E--Procedures for Testing Physical (Design) andPerformance 
Characteristics of Reference Methods and Class I and Class II 
Equivalent Methods for PM2.5 or PM10-2.5

    15. The heading for subpart E is revised as set out above.
    16. Section 53.50 is revised to read as follows:


Sec.  53.50  General provisions.

    (a) A candidate method for PM2.5 or PM10-2.5 
described in an application for a reference or equivalent method 
determination submitted under Sec.  53.4 shall be determined by the EPA 
to be a reference method or a Class I, II, or III equivalent method on 
the basis of the definitions for such methods given in Sec.  53.1. This 
subpart sets forth the specific tests that must be carried out and the 
test results, evidence, documentation, and other materials that must be 
provided to EPA to demonstrate that a PM2.5 or 
PM10-2.5 sampler associated with a candidate reference 
method or Class I or Class II equivalent method meets all design and 
performance specifications set forth in appendix L or O, respectively, 
of part 50 of this chapter as well as additional requirements specified 
in this subpart E. Some or all of these tests may also be applicable to 
a candidate Class III equivalent method or analyzer, as may be 
determined under Sec.  53.3(b)(3).
    (b) PM2.5 methods. (1) Reference method. A sampler associated with 
a candidate reference method for PM2.5 shall be subject to 
the provisions, specifications, and test procedures prescribed in 
Sec. Sec.  53.51 through 53.58.
    (2) Class I method. A sampler associated with a candidate Class I 
equivalent method for PM2.5 shall be subject to the 
provisions, specifications, and test procedures prescribed in all 
sections of this subpart.
    (3) Class II method. A sampler associated with a candidate Class II 
equivalent method for PM2.5 shall be subject to the 
provisions, specifications, and test procedures prescribed in all 
applicable sections of this subpart, as specified in subpart F of this 
part or as specified in Sec.  53.3(a)(3).
    (c) PM10-2.5 methods. (1) Reference method. A sampler associated 
with a reference method for PM10-2.5, as specified in 
appendix O to part 50 of this chapter, shall be subject to the 
requirements in this paragraph (c)(1).
    (i) The PM2.5 sampler of the PM10-2.5 sampler 
pair shall be verified to be either currently designated under this 
part 53 as a reference method for PM2.5, or shown to meet 
all requirements for designation as a reference method for 
PM2.5, in accordance with this part 53.
    (ii) The PM10c sampler of the PM10-2.5 
sampler pair shall be verified to be of like manufacturer, design, 
configuration, and fabrication to the PM2.5 sampler of the 
PM10-2.5 sampler pair, except for replacement of the 
particle size separator specified in

[[Page 2771]]

section 7.3.4 of appendix L to part 50 of this chapter with the 
downtube extension as specified in Figure O-1 of appendix O to part 50 
of this chapter.
    (iii) For samplers that meet the provisions of paragraphs (c)(1)(i) 
and (ii) of this section, the candidate PM10-2.5 reference 
method may be determined to be a reference method without further 
testing.
    (2) Class I method. A sampler associated with a Class I candidate 
equivalent method for PM10-2.5 shall meet the requirements 
in this paragraph (c)(2).
    (i) The PM2.5 sampler of the PM10-2.5 sampler 
pair shall be verified to be either currently designated under this 
part 53 as a reference method or Class I equivalent method for 
PM2.5, or shown to meet all requirements for designation as 
a reference method or Class I equivalent method for PM2.5, 
in accordance with this part 53.
    (ii) The PM10c sampler of the PM10-2.5 
sampler pair shall be verified to be of similar design to the 
PM10-2.5 sampler and to meet all requirements for 
designation as a reference method or Class I equivalent method for 
PM2.5, in accordance with this part 53, except for 
replacement of the particle size separator specified in section 7.3.4 
of appendix L to part 50 of this chapter with the downtube extension as 
specified in Figure O-1 of appendix O to part 50 of this chapter.
    (iii) For samplers that meet the provisions of paragraphs (c)(2)(i) 
and (ii) of this section, the candidate PM10-2.5 method may 
be determined to be a Class I equivalent method without further 
testing.
    (3) Class II method. A sampler associated with a Class II candidate 
equivalent method for PM10-2.5 shall be subject to the 
applicable requirements of this subpart E, as described in Sec.  
53.3(a)(5).
    (d) The provisions of Sec.  53.51 pertain to test results and 
documentation required to demonstrate compliance of a candidate method 
sampler with the design specifications set forth in 40 CFR part 50, 
appendix L or O, as applicable. The test procedures prescribed in 
Sec. Sec.  53.52 through 53.59 pertain to performance tests required to 
demonstrate compliance of a candidate method sampler with the 
performance specifications set forth in 40 CFR part 50, appendix L or 
O, as applicable, as well as additional requirements specified in this 
subpart E. These latter test procedures shall be used to test the 
performance of candidate samplers against the performance 
specifications and requirements specified in each procedure and 
summarized in table E-1 of this subpart.
    (e) Test procedures prescribed in Sec.  53.59 do not apply to 
candidate reference method samplers. These procedures apply primarily 
to candidate Class I or Class II equivalent method samplers for 
PM2.5 or PM10-2.5 that have a sample air flow 
path configuration upstream of the sample filter that is modified from 
that specified for the reference method sampler, as set forth in 40 CFR 
part 50, appendix L, Figures L-1 to L-29 or 40 CFR part 50 appendix O, 
Figure O-1, if applicable, such as might be necessary to provide for 
sequential sample capability. The additional tests determine the 
adequacy of aerosol transport through any altered components or 
supplemental devices that are used in a candidate sampler upstream of 
the filter. In addition to the other test procedures in this subpart, 
these test procedures shall be used to further test the performance of 
such an equivalent method sampler against the performance 
specifications given in the procedure and summarized in table E-1 of 
this subpart.
    (f) A 10-day operational field test of measurement precision is 
required under Sec.  53.58 for both reference and Class I equivalent 
method samplers for PM2.5. This test requires collocated 
operation of 3 candidate method samplers at a field test site. For 
candidate equivalent method samplers, this test may be combined and 
carried out concurrently with the test for comparability to the 
reference method specified under Sec.  53.34, which requires collocated 
operation of three reference method samplers and three candidate 
equivalent method samplers.
    (g) All tests and collection of test data shall be performed in 
accordance with the requirements of reference 1, section 4.10.5 (ISO 
9001) and reference 2, part B, section 3.3.1, paragraphs 1 and 2 and 
Part C, section 4.6 (ANSI/ASQC E4) in appendix A of this subpart. All 
test data and other documentation obtained specifically from or 
pertinent to these tests shall be identified, dated, signed by the 
analyst performing the test, and submitted to EPA in accordance with 
subpart A of this part.
    17. Section 53.51 is revised to read as follows:


Sec.  53.51  Demonstration of compliance with design specifications and 
manufacturing and test requirements.

    (a) Overview. (1) The subsequent paragraphs of this section specify 
certain documentation that must be submitted and tests that are 
required to demonstrate that samplers associated with a designated 
reference or equivalent method for PM2.5 or 
PM10-2.5 are properly manufactured to meet all applicable 
design and performance specifications and have been properly tested 
according to all applicable test requirements for such designation. 
Documentation is required to show that instruments and components of a 
PM2.5 or PM10-2.5 sampler are manufactured in an 
ISO 9001-registered facility under a quality system that meets ISO-9001 
requirements for manufacturing quality control and testing.
    (2) In addition, specific tests are required by paragraph (d) of 
this section to verify that critical features of reference method 
samplers--the particle size separator and the surface finish of 
surfaces specified to be anodized--meet the specifications of 40 CFR 
part 50, appendix L or appendix O, as applicable. A checklist is 
required to provide certification by an ISO-certified auditor that all 
performance and other required tests have been properly and 
appropriately conducted, based on a reasonable and appropriate sample 
of the actual operations or their documented records. Following 
designation of the method, another checklist is required initially to 
provide an ISO-certified auditor's certification that the sampler 
manufacturing process is being implemented under an adequate and 
appropriate quality system.
    (3) For the purposes of this section, the definitions of ISO 9001-
registered facility and ISO-certified auditor are found in Sec.  53.1. 
An exception to the reliance by EPA on ISO-certified auditors is the 
requirement for the submission of the operation or instruction manual 
associated with the candidate method to EPA as part of the application. 
This manual is required under Sec.  53.4(b)(3). The EPA has determined 
that acceptable technical judgment for review of this manual may not be 
assured by ISO-certified auditors, and approval of this manual will 
therefore be performed by EPA.
    (b) ISO registration of manufacturing facility. The applicant must 
submit documentation verifying that the samplers identified and sold as 
part of a designated PM2.5 or PM10-2.5 reference 
or equivalent method will be manufactured in an ISO 9001-registered 
facility and that the manufacturing facility is maintained in 
compliance with all applicable ISO 9001 requirements (reference 1 in 
appendix A of this subpart). The documentation shall indicate the date 
of the original ISO 9001 registration for the facility and shall 
include a copy of the most recent certification of continued ISO 9001 
facility registration. If the manufacturer

[[Page 2772]]

does not wish to initiate or complete ISO 9001 registration for the 
manufacturing facility, documentation must be included in the 
application to EPA describing an alternative method to demonstrate that 
the facility meets the same general requirements as required for 
registration to ISO-9001. In this case, the applicant must provide 
documentation in the application to demonstrate, by required ISO-
certified auditor's inspections, that a quality system is in place 
which is adequate to document and monitor that the sampler system 
components and final assembled samplers all conform to the design, 
performance and other requirements specified in this part and in 40 CFR 
part 50, appendix L.
    (c) Sampler manufacturing quality control. The manufacturer must 
ensure that all components used in the manufacture of PM2.5 
or PM10-2.5 samplers to be sold as part of a reference or 
equivalent method and that are specified by design in 40 CFR part 50, 
appendix L or O (as applicable), are fabricated or manufactured exactly 
as specified. If the manufacturer's quality records show that its 
quality control (QC) and quality assurance (QA) system of standard 
process control inspections (of a set number and frequency of testing 
that is less than 100 percent) complies with the applicable QA 
provisions of section 4 of reference 4 in appendix A of this subpart 
and prevents nonconformances, 100 percent testing shall not be required 
until that conclusion is disproved by customer return or other 
independent manufacturer or customer test records. If problems are 
uncovered, inspection to verify conformance to the drawings, 
specifications, and tolerances shall be performed. Refer also to 
paragraph (e) of this section-final assembly and inspection 
requirements.
    (d) Specific tests and supporting documentation required to verify 
conformance to critical component specifications. (1) Verification of 
PM2.5 (WINS) impactor jet diameter. For samplers utilizing 
the WINS impactor particle size separator specified in paragraphs 
7.3.4.1, 7.3.4.2, and 7.3.4.3 of appendix L to part 50 of this chapter, 
the diameter of the jet of each impactor manufactured for a 
PM2.5 or PM10-2.5 sampler under the impactor 
design specifications set forth in 40 CFR part 50, appendix L, shall be 
verified against the tolerance specified on the drawing, using 
standard, NIST-traceable ZZ go/no go plug gages. This test shall be a 
final check of the jet diameter following all fabrication operations, 
and a record shall be kept of this final check. The manufacturer shall 
submit evidence that this procedure is incorporated into the 
manufacturing procedure, that the test is or will be routinely 
implemented, and that an appropriate procedure is in place for the 
disposition of units that fail this tolerance test.
    (2) VSCC separator. For samplers utilizing the BGI 
VSCCTM Very Sharp Cut Cyclone particle size separator 
specified in paragraph 7.3.4.4 of appendix L to part 50 of this 
chapter, the VSCC manufacturer shall identify the critical dimensions 
and manufacturing tolerances for the device, develop appropriate test 
procedures to verify that the critical dimensions and tolerances are 
maintained during the manufacturing process, and carry out those 
procedures on each VSCC manufactured to verify conformance of the 
manufactured products. The manufacturer shall also maintain records of 
these tests and their results and submit evidence that this procedure 
is incorporated into the manufacturing procedure, that the test is or 
will be routinely implemented, and that an appropriate procedure is in 
place for the disposition of units that fail this tolerance test.
    (3) Verification of surface finish. The anodization process used to 
treat surfaces specified to be anodized shall be verified by testing 
treated specimen surfaces for weight and corrosion resistance to ensure 
that the coating obtained conforms to the coating specification. The 
specimen surfaces shall be finished in accordance with military 
standard specification 8625F, Type II, Class I (reference 4 in appendix 
A of this subpart) in the same way the sampler surfaces are finished, 
and tested, prior to sealing, as specified in section 4.5.2 of 
reference 4 in appendix A of this subpart.
    (e) Final assembly and inspection requirements. Each sampler shall 
be tested after manufacture and before delivery to the final user. Each 
manufacturer shall document its post-manufacturing test procedures. As 
a minimum, each test shall consist of the following: Tests of the 
overall integrity of the sampler, including leak tests; calibration or 
verification of the calibration of the flow measurement device, 
barometric pressure sensor, and temperature sensors; and operation of 
the sampler with a filter in place over a period of at least 48 hours. 
The results of each test shall be suitably documented and shall be 
subject to review by an ISO-certified auditor.
    (f) Manufacturer's audit checklists. Manufacturers shall require an 
ISO-certified auditor to sign and date a statement indicating that the 
auditor is aware of the appropriate manufacturing specifications 
contained in 40 CFR part 50, appendix L or O (as applicable), and the 
test or verification requirements in this subpart. Manufacturers shall 
also require an ISO-certified auditor to complete the checklists, shown 
in figures E-1 and E-2 of this subpart, which describe the 
manufacturer's ability to meet the requirements of the standard for 
both designation testing and product manufacture.
    (1) Designation testing checklist. The completed statement and 
checklist as shown in figure E-1 of this subpart shall be submitted 
with the application for reference or equivalent method determination.
    (2) Product manufacturing checklist. Manufacturers shall require an 
ISO-certified auditor to complete a Product Manufacturing Checklist 
(figure E-2 of this subpart), which evaluates the manufacturer on its 
ability to meet the requirements of the standard in maintaining quality 
control in the production of reference or equivalent devices. The 
completed checklist shall be submitted with the application for 
reference or equivalent method determination.
    18. Section 53.52 is amended by revising paragraph (e)(1) to read 
as follows:


Sec.  53.52  Leak check test.

* * * * *
    (e) Test setup. (1) The test sampler shall be set up for testing as 
described in the sampler's operation or instruction manual referred to 
in Sec.  53.4(b)(3). The sampler shall be installed upright and set up 
in its normal configuration for collecting PM samples, except that the 
sample air inlet shall be removed and the flow rate measurement adaptor 
shall be installed on the sampler's downtube.
* * * * *
    19. Section 53.53 is amended by revising paragraph (e)(1) to read 
as follows:


Sec.  53.53  Test for flow rate accuracy, regulation, measurement 
accuracy, and cut-off.

* * * * *
    (e) Test setup. (1) Setup of the sampler shall be as required in 
this paragraph (e) and otherwise as described in the sampler's 
operation or instruction manual referred to in Sec.  53.4(b)(3). The 
sampler shall be installed upright and set up in its normal 
configuration for collecting PM samples. A sample filter and (or) the 
device for creating an additional 55 mm Hg pressure drop shall be 
installed for the duration of these tests. The sampler's ambient 
temperature, ambient pressure, and flow rate measurement

[[Page 2773]]

systems shall all be calibrated per the sampler's operation or 
instruction manual within 7 days prior to this test.
* * * * *
    20. Section 53.54 is amended by revising paragraph (d)(1) to read 
as follows:


Sec.  53.54  Test for proper sampler operation following power 
interruptions.

* * * * *
    (d) Test setup. (1) Setup of the sampler shall be performed as 
required in this paragraph (d) and otherwise as described in the 
sampler's operation or instruction manual referred to in Sec.  
53.4(b)(3). The sampler shall be installed upright and set up in its 
normal configuration for collecting PM samples. A sample filter and 
(or) the device for creating an additional 55 mm Hg pressure drop shall 
be installed for the duration of these tests. The sampler's ambient 
temperature, ambient pressure, and flow measurement systems shall all 
be calibrated per the sampler's operating manual within 7 days prior to 
this test.
* * * * *
    21. Section 53.55 is amended as follows:
    a. By revising paragraphs (a)(1) introductory text and (a)(2).
    b. By revising paragraph (e)(1).
    c. By revising paragraph (g)(5)(i).


Sec.  53.55  Test for effect of variations in power line voltage and 
ambient temperature.

    (a) Overview. (1) This test procedure is a combined procedure to 
test various performance parameters under variations in power line 
voltage and ambient temperature. Tests shall be conducted in a 
temperature controlled environment over four 6-hour time periods during 
which reference temperature and flow rate measurements shall be made at 
intervals not to exceed 5 minutes. Specific parameters to be evaluated 
at line voltages of 105 and 125 volts and temperatures of -20 [deg]C 
and +40 [deg]C are as follows:
* * * * *
    (2) The performance parameters tested under this procedure, the 
corresponding minimum performance specifications, and the applicable 
test conditions are summarized in table E-1 of this subpart. Each 
performance parameter tested, as described or determined in the test 
procedure, must meet or exceed the associated performance specification 
given. The candidate sampler must meet all specifications for the 
associated PM2.5 or PM10-2.5 method (as 
applicable) to pass this test procedure.
* * * * *
    (e) * * * (1) Setup of the sampler shall be performed as required 
in this paragraph (e) and otherwise as described in the sampler's 
operation or instruction manual referred to in Sec.  53.4(b)(3). The 
sampler shall be installed upright and set up in the temperature-
controlled chamber in its normal configuration for collecting PM 
samples. A sample filter and (or) the device for creating an additional 
55 mm Hg pressure drop shall be installed for the duration of these 
tests. The sampler's ambient temperature, ambient pressure, and flow 
measurement systems shall all be calibrated per the sampler's operating 
manual within 7 days prior to this test.
* * * * *
    (g) * * *
    (5) * * * (i) Calculate the absolute value of the difference 
between the mean ambient air temperature indicated by the test sampler 
and the mean ambient (chamber) air temperature measured with the 
ambient air temperature recorder as:
[GRAPHIC] [TIFF OMITTED] TP17JA06.027


Where:

Tind,ave = mean ambient air temperature indicated by the 
test sampler,[deg]C; and
Tref,ave = mean ambient air temperature measured by the 
reference temperature instrument,[deg]C.
* * * * *
    22. Section 53.56 is amended by revising paragraphs (a)(2) and 
(e)(1) to read as follows:


Sec.  53.56  Test for effect of variations in ambient pressure.

    (a) * * *
    (2) The performance parameters tested under this procedure, the 
corresponding minimum performance specifications, and the applicable 
test conditions are summarized in table E-1 of this subpart. Each 
performance parameter tested, as described or determined in the test 
procedure, must meet or exceed the associated performance specification 
given. The candidate sampler must meet all specifications for the 
associated PM2.5 or PM10-2.5 method (as 
applicable) to pass this test procedure.
* * * * *
    (e) * * * (1) Setup of the sampler shall be performed as required 
in this paragraph (e) and otherwise as described in the sampler's 
operation or instruction manual referred to in Sec.  53.4(b)(3). The 
sampler shall be installed upright and set up in the pressure-
controlled chamber in its normal configuration for collecting PM 
samples. A sample filter and (or) the device for creating an additional 
55 mm Hg pressure drop shall be installed for the duration of these 
tests. The sampler's ambient temperature, ambient pressure, and flow 
measurement systems shall all be calibrated per the sampler's operating 
manual within 7 days prior to this test.
* * * * *
    23. Section 53.57 is amended by revising paragraphs (a), (b), and 
(e)(1) to read as follows:


Sec.  53.57  Test for filter temperature control during sampling and 
post-sampling periods.

    (a) Overview. This test is intended to measure the candidate 
sampler's ability to prevent excessive overheating of the PM sample 
collection filter (or filters) under conditions of elevated solar 
insolation. The test evaluates radiative effects on filter temperature 
during a 4-hour period of active sampling as well as during a 
subsequent 4-hour non-sampling time period prior to filter retrieval. 
Tests shall be conducted in an environmental chamber which provides the 
proper radiant wavelengths and energies to adequately simulate the 
sun's radiant effects under clear conditions at sea level. For 
additional guidance on conducting solar radiative tests under 
controlled conditions, consult military standard specification 810-E 
(reference 6 in appendix A of this subpart). The performance parameters 
tested under this procedure, the corresponding minimum performance 
specifications, and the applicable test conditions are summarized in 
table E-1 of this subpart. Each performance parameter tested, as 
described or determined in the test procedure, must meet or exceed the 
associated performance specification to successfully pass this test.
    (b) Technical definition. Filter temperature control during 
sampling is the ability of a sampler to maintain the temperature of the 
particulate matter sample filter within the specified deviation (5 
[deg]C) from ambient temperature during any active sampling period. 
Post-sampling temperature control is the ability of a sampler to 
maintain the temperature of the particulate matter sample filter within 
the specified deviation from ambient temperature during the period from 
the end of active sample collection by the sampler until the filter is 
retrieved from the sampler for laboratory analysis.
* * * * *

[[Page 2774]]

    (e) * * * (1) Setup of the sampler shall be performed as required 
in this paragraph (e) and otherwise as described in the sampler's 
operation or instruction manual referred to in Sec.  53.4(b)(3). The 
sampler shall be installed upright and set up in the solar radiation 
environmental chamber in its normal configuration for collecting PM 
samples (with the inlet installed). The sampler's ambient and filter 
temperature measurement systems shall be calibrated per the sampler's 
operating manual within 7 days prior to this test. A sample filter 
shall be installed for the duration of this test. For sequential 
samplers, a sample filter shall also be installed in each available 
sequential channel or station intended for collection of a sequential 
sample (or at least 5 additional filters for magazine-type sequential 
samplers) as directed by the sampler's operation or instruction manual.
* * * * *
    24. Section 53.58 is revised to read as follows:


Sec.  53.58  Operational field precision and blank test.

    (a) Overview. This test is intended to determine the operational 
precision of the candidate sampler during a minimum of 10 days of field 
operation, using three collocated test samplers. Measurements of PM are 
made at a test site with all of the samplers and then compared to 
determine replicate precision. Candidate sequential samplers are also 
subject to a test for possible deposition of particulate matter on 
inactive filters during a period of storage in the sampler. This 
procedure is applicable to both reference and equivalent methods. In 
the case of equivalent methods, this test may be combined and conducted 
concurrently with the comparability test for equivalent methods 
(described in subpart C of this part), using three reference method 
samplers collocated with three candidate equivalent method samplers and 
meeting the applicable site and other requirements of subpart C of this 
part.
    (b) Technical definition. (1) Field precision is defined as the 
standard deviation or relative standard deviation of a set of PM 
measurements obtained concurrently with three or more collocated 
samplers in actual ambient air field operation.
    (2) Storage deposition is defined as the mass of material 
inadvertently deposited on a sample filter that is stored in a 
sequential sampler either prior to or subsequent to the active sample 
collection period.
    (c) Test site. Any outdoor test site having PM2.5 (or 
PM10-2.5, as applicable) concentrations that are reasonably 
uniform over the test area and that meet the minimum level requirement 
of paragraph (g)(2) of this section is acceptable for this test.
    (d) Required facilities and equipment. (1) An appropriate test site 
and suitable electrical power to accommodate three test samplers are 
required.
    (2) Teflon sample filters, as specified in section 6 of 40 CFR part 
50, appendix L, conditioned and preweighed as required by section 8 of 
40 CFR part 50, appendix L, as needed for the test samples.
    (e) Test setup. (1) Three identical test samplers shall be 
installed at the test site in their normal configuration for collecting 
PM samples in accordance with the instructions in the associated manual 
referred to in Sec.  53.4(b)(3) and also in accordance with applicable 
supplemental guidance provided in reference 3 in appendix A of this 
subpart. The test samplers' inlet openings shall be located at the same 
height above ground and between 2 (1 for samplers with flow rates less 
than 200 L/min.) and 4 meters apart horizontally. The samplers shall be 
arranged or oriented in a manner that will minimize the spatial and 
wind directional effects on sample collection of one sampler on any 
other sampler.
    (2) Each test sampler shall be successfully leak checked, 
calibrated, and set up for normal operation in accordance with the 
instruction manual and with any applicable supplemental guidance 
provided in reference 3 in appendix A of this subpart.
    (f) Test procedure. (1) Install a conditioned, preweighed filter in 
each test sampler and otherwise prepare each sampler for normal sample 
collection. Set identical sample collection start and stop times for 
each sampler. For sequential samplers, install a conditioned, 
preweighed specified filter in each available channel or station 
intended for automatic sequential sample filter collection (or at least 
5 additional filters for magazine-type sequential samplers), as 
directed by the sampler's operation or instruction manual. Since the 
inactive sequential channels are used for the storage deposition part 
of the test, they may not be used to collect the active PM test 
samples.
    (2) Collect either a nominal 24-hour or 48-hour atmospheric PM 
sample simultaneously with each of the three test samplers.
    (3) Following sample collection, retrieve the collected sample from 
each sampler. For sequential samplers, retrieve the additional stored 
(blank, unsampled) filters after at least 5 days (120 hours) storage in 
the sampler if the active samples are 24-hour samples, or after at 
least 10 days (240 hours) if the active samples are 48-hour samples.
    (4) Determine the measured PM mass concentration for each sample in 
accordance with the applicable procedures prescribed for the candidate 
method in appendix L or appendix O, as applicable, of part 50 of this 
chapter, or in accordance with the associated manual referred to in 
Sec.  53.4(b)(3) and supplemental guidance in reference 2 in appendix A 
of this subpart. For sequential samplers, also similarly determine the 
storage deposition as the net weight gain of each blank, unsampled 
filter after the 5-day (or 10-day) period of storage in the sampler.
    (5) Repeat this procedure to obtain a total of 10 sets of any 
combination of (nominal) 24-hour or 48-hour PM measurements over 10 
test periods. For sequential samplers, repeat the 5-day (or 10-day) 
storage test of additional blank filters once for a total of two sets 
of blank filters.
    (g) Calculations. (1) Record the PM concentration for each test 
sampler for each test period as Ci, j, where i is the 
sampler number (i = 1,2,3) and j is the test period (j = 1,2, * * * 
10).
    (2)(i) For each test period, calculate and record the average of 
the three measured PM concentrations as Cave, j where j is 
the test period using equation 26 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.028

    (ii) If Cave, j <3 [mu]g/m\3\ for any test period, data 
from that test period are unacceptable, and an additional sample 
collection set must be obtained to replace the unacceptable data.
    (3)(i) Calculate and record the precision for each of the 10 test 
periods, as the standard deviation, using equation 27 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.029

    (ii) For each of the 10 test periods, also calculate and record the 
precision as the relative standard deviation, in

[[Page 2775]]

percent, using equation 28 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.030

    (h) Test results. (1) The candidate method passes the precision 
test if either Pj or RPj is less than or equal to 
the corresponding specification in table E-1 of this subpart for all 10 
test periods.
    (2) The candidate sequential sampler passes the blank filter 
storage deposition test if the average net storage deposition weight 
gain of each set of blank filters (total of the net weight gain of each 
blank filter divided by the number of filters in the set) from each 
test sampler (six sets in all) is less than 50 [mu]g.
    25. Section 53.59 is amended by revising paragraphs (a) and (b)(5) 
to read as follows:


Sec.  53.59  Aerosol transport test for Class I equivalent method 
samplers.

    (a) Overview. This test is intended to verify adequate aerosol 
transport through any modified or air flow splitting components that 
may be used in a Class I candidate equivalent method sampler such as 
may be necessary to achieve sequential sampling capability. This test 
is applicable to all Class I candidate samplers in which the aerosol 
flow path (the flow path through which sample air passes upstream of 
sample collection filter) differs significantly from that specified for 
reference method samplers as specified in 40 CFR part 50, appendix L or 
appendix O, as applicable. The test requirements and performance 
specifications for this test are summarized in table E-1 of this 
subpart.
    (b) * * *
    (5) An added component is any physical part of the sampler which is 
different in some way from that specified for a reference method 
sampler in 40 CFR part 50, appendix L or appendix O, as applicable, 
such as a device or means to allow or cause the aerosol to be routed to 
one of several channels.
* * * * *
    26. Table E-1 to subpart E is revised to read as follows:

Table E-1 to Subpart E.--Summary of Test Requirements for Reference and Class I Equivalent Methods for PM2.5 and
                                                    PM10-2.5
----------------------------------------------------------------------------------------------------------------
                                                   Performance                               Part 50, Appendix L
 Subpart E procedure      Performance test        specification         Test conditions           reference
----------------------------------------------------------------------------------------------------------------
Sec.   53.52 Sample    Sampler leak check     External leakage: 80   Controlled leak flow   Sec. 7.4.6.
 leak check test        facility               mL/min, max            rate of 80 mL/min
                                              Internal leakage: 80
                                               mL/min, max
Sec.   53.53 Base      Sample flow rate       1. 67.67 5% L/min         operational test       7.4.2, Sec. 7.4.3,
                       2. Regulation          2. 2%, max              plus flow rate cut-    Sec. 7.4.4, Sec.
                       3. Meas accuracy       3. 2%, max              off test               7.4.5.
                       4. CV accuracy         4. 0.3% max            (b) Norman conditions
                       5. Cut-off             5. Flow rate cut-off   (c) Additional 55 mm
                                               if flow rate           Hg pressure drop to
                                               deviates more than     simulate loaded
                                               10% from design flow   filter
                                               rate for >6030 seconds       restrictions used
                                                                      for cut-off test
Sec.   53.54 Power     Sample flow rate:      1. 16.67   (a) 6-hour normal      Sec. 7.4.1, Sec.
 interruption test     1. Mean                 5% L/min               operational test       7.4.2, Sec. 7.4.3,
                       2. Regulation          2. 2%, max             (b) Nominal             Sec. 7.4.5, Sec.
                       3. Meas. accuracy      3. 2%, max              conditions             7.4.12, Sec.
                       4. CV accuracy         4. 0.3 max             (c) Additional 55 mm    7.4.13, Sec.
                       5. Occurrence time of  5. 2 min    Hg pressure drop to    7.4.15.4, Sec.
                        power interruptions    if >60 seconds         simulate loaded        7.4.15.5.
                       6. Elapsed sample      6. 20       filter
                        time                   seconds               (d) 6 power
                       7. Sample volume       7. 2%,      interruptions of
                                               max                    various durations
Sec.   53.55           Sample flow rate       1. 16.67   (a) 6-hour normal      Sec. 7.4.1, Sec.
 Temperature and line  1. Mean                 5% L/min               operational test       7.4.2, Sec. 7.4.3,
 voltage test          2. Regulation          2. 2%, max             (b) Normal conditions   Sec. 7.4.5, Sec.
                       3. Meas. accuracy      3. 2%, max             (c) Additional 55 mm    7.4.8, Sec.
                       4. CV accuracy         4. 0.3 max              Hg pressure drop to    7.4.15.1.
                       5. Temperature meas.   5 2 [deg]C              simulate loaded
                        accuracy                                      filter
                       6. Proper operation                           (d) Ambient
                                                                      temperature at -20
                                                                      and +40 [deg]C
                                                                     (e) Line voltage: 105
                                                                      Vac to 125 Vac
Sec.   53.56           Sample flow rate       1. 16.67   (a) 6-hour normal      Sec. 7.4.1, Sec.
 Barometric pressure   1. Mean                 5% L/min               operational test       7.4.2, Sec. 7.4.3,
 effect test           2. Regulation          2. 2%, max             (b) Normal conditions   Sec. 7.4.5, Sec.
                       3. Meas. accuracy      3. 2%, max             (c) Additional 55 mm    7.4.9.
                       4. CV accuracy         4. 0.3% max             Hg pressure drop to
                       5. Pressure meas.      5. 10 mm Hg             simulate loaded
                        accuracy                                      filter
                       6. Proper operation                           (d) Barometer
                                                                      pressure at 600 and
                                                                      800 mm Hg

[[Page 2776]]

 
Sec.   53.57 Filter    1. Filter temp meas.   1. 2 [deg]C            (a) 4-hour simulated   Sec. 7.4.8, Sec.
 temperature control    accuracy              2. 2 [deg]C             solar radiation,       7.4.10, Sec.
 test                  2. Ambient temp.       3. Not more than 5      sampling               7.4.11.
                        meas. accuracy         [deg]C above ambient  (b) 4-hour simulated
                       3. Filter temp.         temp. for more than    solar radiation, non-
                        control accuracy,      30 min.                sampling
                        sampling and non-                            (c) Solar flux of
                        sampling                                      1000 50
                                                                      W/m2
Sec.   53.58 Field     1 Measurement          1. Pj <2 [mu]g/m3 or   (a) 3 collocated       Sec. 5.1, Sec.
 precision test         precision              RPj <5%                samples at 1 site      7.4.5, Sec. 8, Sec.
                       2. Storage deposition  2. 50 [mu]g max.        for at least 10        9, Sec. 10.
                        test for sequential    average weight gain/   days;
                        samplers               blank filter          (b) PM2.5 conc. > 3
                                                                      [mu]g/m3
                                                                     (c) 25- or 48-hour
                                                                      samples
                                                                     (d) 5- or 10-day
                                                                      storage period for
                                                                      inactive stored
                                                                      filters
----------------------
              The Following Requirement Is Applicable to Class I Candidate Equivalent Methods Only
----------------------------------------------------------------------------------------------------------------
Sec.   53.59 Aerosol   Aerosol transport      97%, min. for all      Determine aerosol      ....................
 transport test                                channels               transport through
                                                                      any new or modified
                                                                      components with
                                                                      respect to the
                                                                      reference method
                                                                      sampler before the
                                                                      filter for each
                                                                      channel.
----------------------------------------------------------------------------------------------------------------

    27. References (3) and (5) in appendix A to subpart E of part 53 
are revised to read as follows:

Appendix A to Subpart E of Part 53--References

* * * * *
    (3) Quality Assurance Guidance Document 2.12. Monitoring 
PM2.5 in Ambient Air Using Designated Reference or Class I 
Equivalent Methods. U.S. EPA, National Exposure Research Laboratory, 
Research Triangle Park, NC, November 1998 or later edition. Currently 
available at http://www.epa.gov/ttn/amtic/pmgainf.html.
* * * * *
    (5) Quality Assurance Handbook for Air Pollution Measurement 
Systems, Volume IV: Meteorological Measurements. Revised March, 1995. 
EPA-600/R-94-038d. Available from National Technical Information 
Service, Springfield, VA 22161, (800-553-6847, http://www.ntis.gov). 
NTIS number PB95-199782INZ.
* * * * *

Subpart F--[Amended]

    28. Section 53.60 is amended by revising paragraphs (b), (c), (d) 
introductory text, and (f)(4) to read as follows:


Sec.  53.60  General provisions.

* * * * *
    (b) A candidate method described in an application for a reference 
or equivalent method determination submitted under Sec.  53.4 shall be 
determined by the EPA to be a Class II candidate equivalent method on 
the basis of the definition of a Class II equivalent method given in 
Sec.  53.1.
    (c) Any sampler associated with a Class II candidate equivalent 
method (Class II sampler) must meet all applicable requirements for 
reference method samplers or Class I equivalent method samplers 
specified in subpart E of this part, as appropriate. Except as provided 
in Sec.  53.3(a)(3), a Class II PM2.5 sampler must meet the 
additional requirements as specified in paragraph (d) of this section.
    (d) Except as provided in paragraphs (d)(1), (2), and (3) of this 
section, all Class II samplers are subject to the additional tests and 
performance requirements specified in Sec.  53.62 (full wind tunnel 
test), Sec.  53.65 (loading test), and Sec.  53.66 (volatility test). 
Alternative tests and performance requirements, as described in 
paragraphs (d)(1), (2), and (3) of this section, are optionally 
available for certain Class II samplers which meet the requirements for 
reference method or Class I equivalent method samplers given in 40 CFR 
part 50, appendix L, and in subpart E of this part, except for specific 
deviations of the inlet, fractionator, or filter.
* * * * *
    (f) * * *
    (4) Loading test. The loading test is conducted to ensure that the 
performance of a candidate sampler is not significantly affected by the 
amount of particulate deposited on its interior surfaces between 
periodic cleanings. The candidate sampler is artificially loaded by 
sampling a test environment containing aerosolized, standard test dust. 
The duration of the loading phase is dependent on both the time between 
cleaning as specified by the candidate method and the aerosol mass 
concentration in the test environment. After loading, the candidate's 
performance must then be evaluated by Sec.  53.62 (full wind tunnel 
evaluation), Sec.  53.63 (wind tunnel inlet aspiration test), or Sec.  
53.64 (static fractionator test). If the results of the appropriate 
test meet the criteria presented in table F-1 of this subpart, then the 
candidate sampler passes the loading test under the condition that it 
be cleaned at least as often as the cleaning frequency proposed by the 
candidate method and that has been demonstrated to be acceptable by 
this test.
* * * * *
    29. The section heading of Sec.  53.61 is revised to read as 
follows.


Sec.  53.61  Test conditions.

* * * * *
    30. Section 53.66 is amended by revising paragraph (e)(2)(iii) to 
read as follows:

[[Page 2777]]

Sec.  53.66  Test procedure: Volatility test.

* * * * *
    (e) * * *
    (2) * * *
    (iii) Operate the candidate and the reference samplers such that 
they simultaneously sample the test aerosol for 2 hours for a candidate 
sampler operating at 16.7 L/min or higher, or proportionately longer 
for a candidate sampler operating at a lower flow rate.
* * * * *
    31. Table F-1 to subpart F is revised to read as follows:

 Table F-1 to Subpart F.--Performance Specifications for PM2.5 Class II
                           Equivalent Samplers
------------------------------------------------------------------------
      Performance test           Specifications      Acceptance criteria
------------------------------------------------------------------------
Sec.   53.62 Full Wind        Solid VOAG produced   Dp50 = 2.5 [mu]m
 Tunnel Evaluation.            aerosol at 2 km/hr     0.2
                               and 24 km/hr.         [mu]m
                                                    Numerical Analysis
                                                     Results: 95%
                                                     <=Rc<=105%.
Sec.   53.63 Wind Tunnel      Liquid VOAG produced  Relative Aspiration:
 Inlet Aspiration Test.        aerosol at 2 km/hr   95% <=A<=105%.
                               and 24 km/hr.
Sec.   53.64 Static           Evaluation of the     Dp50 = 2.5 [mu]m
 Fractionator Test.            fractionator under     0.2
                               static conditions.    [mu]m
                                                    Numerical Analysis
                                                     Results: 95%
                                                     <=Rc<=105%.
Sec.   53.65 Loading Test...  Loading of the clean  Acceptance criteria
                               candidate under       as specified in the
                               laboratory            post-loading
                               conditions.           evaluation test
                                                     (Sec.   53.62, Sec.
                                                       53.63, or Sec.
                                                     53.64).
Sec.   53.66 Volatility Test  Polydisperse liquid   Regression
                               aerosol producted     Parameters
                               by air nebulization  Slope = 1  0.1,
                               grade glycerol,      Intercept = 0  0.15 mg r >=
                               purity.               0.97.
------------------------------------------------------------------------

    32. In Figure E-1 to subpart F, the figure number ``E-1'' is 
revised to read ``F-1.''

PART 58--[AMENDED]

    33. The authority citation for part 58 continues to read as 
follows:

    Authority: 42 U.S.C. 7410, 7601(a), 7613, and 7619.

Subpart A--[Amended]

    34. Sections 58.1, 58.2 and 58.3 are revised to read as follows:


Sec.  58.1  Definitions.

    As used in this part, all terms not defined herein have the meaning 
given them in the Act.
    Act means the Clean Air Act as amended (42 U.S.C. 7401, et seq.)
    Additive and multiplicative bias means the linear regression 
intercept and slope of a linear plot fitted to corresponding candidate 
and reference method mean measurement data pairs.
    Administrator means the Administrator of the Environmental 
Protection Agency (EPA) or his or her authorized representative.
    Air Quality System (AQS) means EPA's computerized system for 
storing and reporting of information relating to ambient air quality 
data.
    Approved regional method (ARM) means a continuous PM2.5 
method that has been approved specifically within a State or local air 
monitoring network for purposes of comparison to the NAAQS and to meet 
other monitoring objectives.
    AQCR means air quality control region.
    CO means carbon monoxide.
    Combined statistical area (CSA) is defined by the U.S. Office of 
Management and Budget as a geographical area consisting of two or more 
adjacent Core Based Statistical Areas (CBSA) with employment 
interchange of at least 15 percent. Combination is automatic if the 
employment interchange is 25 percent and determined by local opinion if 
more than 15 but less than 25 percent (http://www.census.gov/population/estimates/metro-city/List6.txt).
    Community monitoring zone (CMZ) means an optional averaging area 
with established, well defined boundaries, such as county or census 
block, within an MPA that has relatively uniform concentrations of 
annual PM2.5 as defined by appendix N of part 50 of this 
chapter. Two or more community-oriented SLAMS monitors within a CMZ 
that meet certain requirements as set forth in appendix N of part 50 of 
this chapter may be averaged for making comparisons to the annual 
PM2.5 NAAQS.
    Core-based statistical area (CBSA) is defined by the U.S. Office of 
Management and Budget, as a statistical geographic entity consisting of 
the county or counties associated with at least one urbanized area/
urban cluster of at least 10,000 population, plus adjacent counties 
having a high degree of social and economic integration. Metropolitan 
and micropolitan statistical areas (MSA) are the two categories of CBSA 
(metropolitan areas have populations greater than 50,000; and 
micropolitan areas have populations between 10,000 and 50,000). In the 
case of very large cities where two or more CBSA are combined, these 
larger areas are referred to as combined statistical areas (http://www.census.gov/population/estimates/metro-city/List1.txt).
    Corrected concentration pertains to the result of an accuracy or 
precision assessment test of an open path analyzer in which a high-
concentration test or audit standard gas contained in a short test cell 
is inserted into the optical measurement beam of the instrument. When 
the pollutant concentration measured by the analyzer in such a test 
includes both the pollutant concentration in the test cell and the 
concentration in the atmosphere, the atmospheric pollutant 
concentration must be subtracted from the test measurement to obtain 
the corrected concentration test result. The corrected concentration is 
equal to the measured concentration minus the average of the 
atmospheric pollutant concentrations measured (without the test cell) 
immediately before and immediately after the test.
    Design value means the calculated concentration according to the 
applicable appendix of part 50 of this chapter for the highest site in 
an attainment or nonattainment area.
    EDO means environmental data operations.
    Effective concentration pertains to testing an open path analyzer 
with a high-concentration calibration or audit standard gas contained 
in a short test cell inserted into the optical measurement beam of the 
instrument. Effective concentration is the equivalent ambient-level 
concentration that would produce the same spectral absorbance over the 
actual atmospheric monitoring path length as produced by the high-
concentration gas in the short test cell. Quantitatively, effective 
concentration is equal to the actual concentration of the gas standard 
in the test cell multiplied by the ratio of the path length of the test 
cell to the actual atmospheric monitoring path length.
    Equivalent method means a method of sampling and analyzing the 
ambient air

[[Page 2778]]

for an air pollutant that has been designated as an equivalent method 
in accordance with part 53 of this chapter; it does not include a 
method for which an equivalent method designation has been canceled in 
accordance with Sec.  53.11 or Sec.  53.16 of this chapter.
    HNO3 means nitric acid.
    Local agency means any local government agency, other than the 
State agency, which is charged by a State with the responsibility for 
carrying out a portion of the plan.
    Meteorological measurements means measurements of wind speed, wind 
direction, barometric pressure, temperature, relative humidity, solar 
radiation, ultraviolet radiation, and precipitation.
    Metropolitan Statistical Area (MSA) means a CBSA associated with at 
least one urbanized area of at least 50,000 population. The central 
county plus adjacent counties with a high degree of integration 
comprise the area.
    Monitor means an instrument, sampler, analyzer, or other device 
that measures or assists in the measurement of atmospheric air 
pollutants and which is acceptable for use in ambient air surveillance 
under the applicable provisions of appendix C to this part.
    Monitoring agency means a State or local agency responsible for 
meeting the requirements of this part.
    Monitoring organization means a State, local, or other monitoring 
organization responsible for operating a monitoring site for which the 
quality assurance regulations apply.
    Monitoring path for an open path analyzer means the actual path in 
space between two geographical locations over which the pollutant 
concentration is measured and averaged.
    Monitoring path length of an open path analyzer means the length of 
the monitoring path in the atmosphere over which the average pollutant 
concentration measurement (path-averaged concentration) is determined. 
See also, optical measurement path length.
    Monitoring planning area (MPA) means a contiguous geographic area 
with established, well defined boundaries, such as a CBSA, county or 
State, having a common area that is used for planning monitoring 
locations for PM2.5. An MPA may cross State boundaries, such 
as the Philadelphia PA-NJ MSA, and be further subdivided into community 
monitoring zones. MPA are generally oriented toward CBSA or CSA with 
populations greater than 200,000, but for convenience, those portions 
of a State that are not associated with CBSA can be considered as a 
single MPA.
    NATTS means the national air toxics trends stations. This network 
provides hazardous air pollution ambient data.
    NCore means the National Core multipollutant monitoring stations. 
Monitors at these sites are required to measure particles 
(PM2.5, speciated PM2.5, PM10-2.5), 
O3, SO2, CO, nitrogen oxides (NO/NO2/
NOY), and basic meteorology.
    Network means all stations of a given type or types.
    NH3 means ammonia.
    NO2 means nitrogen dioxide. NO means nitrogen oxide. NOX 
means oxides of nitrogen and is defined as the sum of the 
concentrations of NO2 and NO.
    NOy means the sum of all total reactive nitrogen oxides, including 
NO, NO2, and other nitrogen oxides referred to as 
NOZ.
    O3 means ozone.
    Open path analyzer means an automated analytical method that 
measures the average atmospheric pollutant concentration in situ along 
one or more monitoring paths having a monitoring path length of 5 
meters or more and that has been designated as a reference or 
equivalent method under the provisions of part 53 of this chapter.
    Optical measurement path length means the actual length of the 
optical beam over which measurement of the pollutant is determined. The 
path-integrated pollutant concentration measured by the analyzer is 
divided by the optical measurement path length to determine the path-
averaged concentration. Generally, the optical measurement path length 
is:
    (1) Equal to the monitoring path length for a (bistatic) system 
having a transmitter and a receiver at opposite ends of the monitoring 
path;
    (2) Equal to twice the monitoring path length for a (monostatic) 
system having a transmitter and receiver at one end of the monitoring 
path and a mirror or retroreflector at the other end; or
    (3) Equal to some multiple of the monitoring path length for more 
complex systems having multiple passes of the measurement beam through 
the monitoring path.
    PAMS means photochemical assessment monitoring stations.
    Pb means lead.
    Plan means a implementation plan approved or promulgated pursuant 
to section 110 of the Act.
    PM2.5 means particulate matter with an aerodynamic diameter less 
than or equal to a nominal 2.5 micrometers as measured by a reference 
method based on appendix L of part 50 of this chapter and designated in 
accordance with part 53 of this chapter, by an equivalent method 
designated in accordance with part 53 of this chapter, or by an 
approved regional method designated in accordance with appendix C to 
this part.
    PM10 means particulate matter with an aerodynamic diameter less 
than or equal to a nominal 10 micrometers as measured by a reference 
method based on appendix J of part 50 of this chapter and designated in 
accordance with part 53 of this chapter or by an equivalent method 
designated in accordance with part 53 of this chapter.
    PM10C means particulate matter with an aerodynamic diameter less 
than or equal to a nominal 10 micrometers as measured by a reference 
method based on appendix O of part 50 of this chapter and designated in 
accordance with part 53 of this chapter or by an equivalent method 
designated in accordance with part 53 of this chapter.
    PM10-2.5 means particulate matter with an aerodynamic diameter less 
than or equal to a nominal 10 micrometers and greater than a nominal 
2.5 micrometers as measured by a reference method based on appendix O 
to part 50 of this chapter and designated in accordance with part 53 of 
this chapter or by an equivalent method designated in accordance with 
part 53 of this chapter.
    Point analyzer means an automated analytical method that measures 
pollutant concentration in an ambient air sample extracted from the 
atmosphere at a specific inlet probe point and that has been designated 
as a reference or equivalent method in accordance with part 53 of this 
chapter.
    Population-oriented monitoring (or sites) means residential areas, 
commercial areas, recreational areas, industrial areas where workers 
from more than one company are located, and other areas where a 
substantial number of people may spend a significant fraction of their 
day.
    Primary quality assurance organization means a monitoring 
organization or other organization that is responsible for a set of 
stations that monitors the same pollutant and for which data quality 
assessments can be pooled. Each criteria pollutant sampler/monitor at a 
monitoring station in the SLAMS and SPM networks must be associated 
with one, and only one, primary quality assurance organization.
    Probe means the actual inlet where an air sample is extracted from 
the atmosphere for delivery to a sampler or point analyzer for 
pollutant analysis.
    PSD station means any station operated for the purpose of 
establishing the effect on air quality of the emissions from a proposed 
source for purposes of prevention of significant deterioration as 
required by Sec.  51.24(n) of this chapter.

[[Page 2779]]

    Reference method means a method of sampling and analyzing the 
ambient air for an air pollutant that is specified as a reference 
method in an appendix to part 50 of this chapter, or a method that has 
been designated as a reference method in accordance with this part; it 
does not include a method for which a reference method designation has 
been canceled in accordance with Sec.  53.11 or Sec.  53.16 of this 
chapter.
    Regional Administrator means the Administrator of one of the ten 
EPA Regional Offices or his or her authorized representative.
    Reporting organization means an entity, such as a State, local, or 
Tribal monitoring agency, that collects and reports air quality data to 
EPA.
    Site means a geographic location. One or more stations may be at 
the same site.
    SLAMS means State or local air monitoring stations. The SLAMS make 
up the ambient air quality monitoring sites that are primarily needed 
for NAAQS comparisons, but may serve other data purposes. SLAMS exclude 
special purpose monitor (SPM) stations and include NCore, PAMS, and all 
other State or locally operated stations that have not been designated 
as SPM stations.
    SO2 means sulfur dioxide.
    Special purpose monitor (SPM) station means a monitor included in 
an agency's monitoring network that the agency has designated as a 
special purpose monitor station in its monitoring network plan and in 
the Air Quality System, and which the agency does not count when 
showing compliance with the minimum requirements of this subpart for 
the number and siting of monitors of various types.
    State agency means the air pollution control agency primarily 
responsible for development and implementation of a plan under the Act.
    State speciation site means a supplemental PM2.5 
speciation station that is not part of the speciation trends network.
    Station means a single monitor, or a group of monitors with a 
shared objective, located at a particular site.
    STN station means a PM2.5 speciation station designated 
to be part of the speciation trends network. This network provides 
chemical species data of fine particulate.
    Traceable means that a local standard has been compared and 
certified, either directly or via not more than one intermediate 
standard, to a National Institute of Standards and Technology (NIST)-
certified primary standard such as a NIST-traceable Reference Material 
(NTRM) or a NIST-certified Gas Manufacturer's Internal Standard (GMIS).
    TSP (total suspended particulates) means particulate matter as 
measured by the method described in appendix B of part 50 of this 
chapter.
    Urbanized area means an area with a minimum residential population 
of at least 50,000 people and which generally includes core census 
block groups or blocks that have a population density of at least 1,000 
people per square mile and surrounding census blocks that have an 
overall density of at least 500 people per square mile. The Census 
Bureau notes that under certain conditions, less densely settled 
territory may be part of each Urbanized Area.
    VOC means volatile organic compounds.


Sec.  58.2  Purpose.

    (a) This part contains requirements for measuring ambient air 
quality and for reporting ambient air quality data and related 
information. The monitoring criteria pertain to the following areas:
    (1) Quality assurance procedures for monitor operation and data 
handling.
    (2) Methodology used in monitoring stations.
    (3) Operating schedule.
    (4) Siting parameters for instruments or instrument probes.
    (5) Minimum ambient air quality monitoring network requirements 
used to provide support to the State implementation plans (SIP), 
national air quality assessments, and policy decisions. These minimums 
are described as part of the network design requirements, including 
minimum numbers and placement of monitors of each type.
    (6) Air quality data reporting, and requirements for the daily 
reporting of an index of ambient air quality.
    (b) The requirements pertaining to provisions for an air quality 
surveillance system in the SIP are contained in this part.
    (c) This part also acts to establish a national ambient air quality 
monitoring network for the purpose of providing timely air quality data 
upon which to base national assessments and policy decisions.


Sec.  58.3  Applicability

    This part applies to:
    (a) State air pollution control agencies.
    (b) Any local air pollution control agency to which the State has 
delegated authority to operate a portion of the State's SLAMS network.
    (c) Owners or operators of proposed sources.

Subpart B--Monitoring Network

    35. The heading for subpart B is revised as set forth above.
    36. Sections 58.10 through 58.14 are revised and Sec. Sec.  58.15 
and 58.16 are added to read as follows:


Sec.  58.10  Annual monitoring network plan and periodic network 
assessment.

    (a)(1) Beginning July 1, 2007, the State, or where applicable 
local, agency shall adopt and submit to the Regional Administrator an 
annual monitoring network plan which shall provide for the 
establishment and maintenance of an air quality surveillance system 
that consists of a network of monitoring stations including Federal 
reference method (FRM), Federal equivalent method (FEM), and approved 
regional method (ARM) monitors that are part of SLAMS, NCore stations, 
STN stations, State speciation stations, SPM stations, and/or, in 
serious, severe and extreme ozone nonattainment areas, PAMS stations. 
The plan shall include a statement of purpose for each monitor and 
evidence that siting and operation of each monitor meets the 
requirements of appendices A, C, D, and E of this part, where 
applicable. The annual monitoring network plan must be made available 
for public inspection for at least 30 days prior to submission to EPA.
    (2) Any annual monitoring network plan that proposes SLAMS network 
modifications including new monitoring sites is subject to the approval 
of the EPA Regional Administrator, who shall provide opportunity for 
public comment and shall approve or disapprove the plan and schedule 
within 120 days.
    (3) PM10-2.5 stations.
    (i) The plan for establishing a network of PM10-2.5 
stations is due not later than January 1, 2008, as an addendum to the 
annual monitoring network plan required to be submitted July 1, 2007, 
unless the Regional Administrator extends this due date to July 1, 
2008, in which case it shall be part of the annual monitoring network 
plan due by that date.
    (ii) The plan shall provide for required PM10-2.5 
stations to be operational by January 1, 2009.
    (iii) The plan shall identify whether each planned 
PM10-2.5 station is suitable for comparison with the 
PM10-2.5 NAAQS under the criteria of Sec.  58.30(b), and 
shall include evidence for that identification including the 
information obtained and conclusions reached in each site-specific 
assessment.
    (iv) Identification of existing and proposed sites as suitable for 
comparison against the 24-hour PM10-2.5

[[Page 2780]]

NAAQS are subject to approval by the EPA Regional Administrator as part 
of the approval of the plan for the PM10-2.5 monitoring 
network. Such approval will constitute a final action by EPA.
    (4) The plan for establishing required NCore multipollutant 
stations is due July 1, 2009. The plan shall provide for all required 
stations to be operational by January 1, 2011.
    (b) The annual monitoring network plan must contain cost 
information for the network and the following information for each 
existing and proposed site:
    (1) The AQS site identification number.
    (2) The location, including street address and geographical 
coordinates.
    (3) The sampling and analysis method(s) for each measured 
parameter.
    (4) The operating schedules for each monitor.
    (5) Any proposals to remove or move a monitoring station within a 
period of 18 months following plan submittal.
    (6) The monitoring objective and spatial scale of 
representativeness for each monitor as defined in appendix D to this 
part.
    (7) The identification of any sites that are suitable and sites 
that are not suitable for comparison against the annual 
PM2.5 NAAQS or 24-hour PM10-2.5 NAAQS as 
described in Sec.  58.30.
    (8) Information supporting the basis for determining that 
PM10-2.5 sites are either suitable or not suitable for 
comparison to the 24-hour PM10-2.5 NAAQS as described in 
Sec.  58.30(b).
    (9) The MSA, CBSA, CSA or other area represented by the monitor.
    (c) The annual monitoring network plan must consider the ability of 
existing and proposed sites to support air quality characterization for 
areas with relatively high populations of susceptible individuals 
(e.g., children with asthma), and, for any sites that are being 
proposed for discontinuance, the effect on data users other than the 
agency itself, such as nearby States and Tribes or health effects 
studies.
    (d) The annual monitoring network plan must document how States and 
local agencies provide for the review of changes to a PM2.5 
monitoring network that impact the location of a violating 
PM2.5 monitor or the creation/change to a community 
monitoring zone, including a description of the proposed use of spatial 
averaging for purposes of making comparisons to the annual 
PM2.5 NAAQS as set forth in appendix N to part 50 of this 
chapter. The affected State or local agency must document the process 
for providing public hearings and include any comments received through 
the public notification process within their submitted plan.
    (e) The State, or where applicable local, agency shall perform and 
submit to the EPA Regional Administrator an assessment of the air 
quality surveillance system every 5 years to determine, at a minimum, 
if the network meets the monitoring objectives defined in appendix D to 
this part, whether new sites are needed, whether existing sites are no 
longer needed and can be terminated, and whether new technologies are 
appropriate for incorporation into the ambient air monitoring network. 
For PM2.5, the assessment also must identify needed changes 
to population-oriented sites. The State, or where applicable local, 
agency must submit a copy of this 5-year assessment, along with a 
revised annual network plan, to the Regional Administrator. The first 
assessment is due July 1, 2009. For PM10-2.5, each 
assessment due on or after July 1, 2014 must identify needed changes to 
the identification of whether each site is suitable or unsuitable for 
comparison to the NAAQS under the criteria of Sec.  58.30(b), based on 
changes in emissions sources affecting the site or better information 
about these sources.
    (f) All proposed additions and discontinuations of monitors in 
annual monitoring network plans and periodic network assessments are 
subject to approval according to Sec.  58.14.


Sec.  58.11  Network technical requirements.

    (a) State and local governments shall follow the applicable quality 
assurance criteria contained in appendix A to this part when operating 
the SLAMS and SPM networks. The owner or operator of an existing or a 
proposed source shall follow the quality assurance criteria in appendix 
A to this part that apply to PSD monitoring when operating a PSD site.
    (b) State and local governments must follow the criteria in 
appendix C to this part to determine acceptable monitoring methods or 
instruments for use in SLAMS networks. Appendix C criteria are optional 
at SPM stations.
    (c) State and local governments must follow the network design 
criteria contained in appendix D to this part in designing and 
maintaining the SLAMS stations. The final network design and all 
changes in design are subject to approval of the Regional 
Administrator. NCore, STN, and PAMS network design and changes are also 
subject to approval of the Administrator. Changes in SPM stations do 
not require approvals, but a change in the designation of a monitoring 
site from SLAMS to SPM requires approval of the Regional Administrator.
    (d) State and local governments must follow the criteria contained 
in appendix E to this part for siting monitor inlets, paths or probes 
at SLAMS stations. Appendix E adherence is optional for SPM stations 
that do not use appendix C methods.


Sec.  58.12  Operating schedules.

    State and local governments shall collect ambient air quality data 
at any SLAMS station on the following operational schedules:
    (a) For continuous analyzers, consecutive hourly averages must be 
collected except during:
    (1) Periods of routine maintenance,
    (2) Periods of instrument calibration, or
    (3) Periods or monitoring seasons exempted by the Regional 
Administrator.
    (b) For Pb and PM10 manual methods, at least one 24-hour 
sample must be collected every 6 days except during periods or seasons 
exempted by the Regional Administrator.
    (c) For PAMS VOC samplers, samples must be collected as specified 
in section 5 of appendix D to this part. Area-specific PAMS operating 
schedules must be included as part of the PAMS network description and 
must be approved by the Regional Administrator.
    (d) For manual PM2.5 samplers:
    (1) Manual PM2.5 samplers at other SLAMS stations must 
operate on at least a 1-in-3 day schedule at sites without a collocated 
continuously operating PM2.5 monitor. For SLAMS 
PM2.5 sites with both manual and continuous PM2.5 
monitors operating, the PM2.5 manual sampler may be operated 
with a 1-in-6 day sampling frequency under certain conditions. A 
monitoring agency may request approval for a reduction to 1-in-6 day 
PM2.5 sampling at SLAMS stations or for seasonal sampling 
from the EPA Regional Administrator. The EPA Regional Administrator may 
grant sampling frequency reductions after consideration of the 
historical PM2.5 data quality assessments, the location of 
current PM2.5 design value sites, and their regulatory data 
needs. Sites that have design values that are within 10 
percent of the NAAQS; and sites where the 24-hour values exceed the 
NAAQS for a period of 3 years are required to maintain at least a 1-in-
3 day sampling frequency.
    (2) Manual PM2.5 samplers at NCore stations and required 
regional background and regional transport sites must operate on at 
least a 1-in-3 day sampling frequency.

[[Page 2781]]

    (3) Manual PM2.5 speciation samplers at STN stations 
must operate on a 1-in-3 day sampling frequency.
    (e) Manual PM10-2.5 samplers at SLAMS stations must 
operate on a daily schedule at sites without a collocated continuously 
operating equivalent PM10-2.5 method that has been 
designated in accordance with part 53 of this chapter.


Sec.  58.13  Monitoring network completion.

    (a) The network of PM10-2.5 sites must be physically 
established no later than January 1, 2009, and at that time, operating 
under all of the requirements of this part, including the requirements 
of appendices A, C, D, E, and G to this part.
    (b) The network of NCore multipollutant sites must be physically 
established no later than January 1, 2011, and at that time, operating 
under all of the requirements of this part, including the requirements 
of appendices A, C, D, E, and G to this part.


Sec.  58.14  System modification.

    (a) The State, or where appropriate local, agency shall develop and 
implement a plan and schedule to modify the ambient air quality 
monitoring network that complies with the findings of the network 
assessments required every 5 years by Sec.  58.10(e). The State or 
local agency shall consult with the EPA Regional Administrator during 
the development of the schedule to modify the monitoring program, and 
shall make the plan and schedule available to the public for 30 days 
prior to submission to the EPA Regional Administrator. The final plan 
and schedule are subject to the approval of the EPA Regional 
Administrator, who shall provide opportunity for public comment and 
shall approve or disapprove the plan and schedule within 120 days.
    (b) Nothing in this section shall preclude the State, or where 
appropriate local, agency from making modifications to the SLAMS 
network for reasons other than those resulting from the periodic 
network assessments. These modifications must be reviewed and approved 
by the Regional Administrator. Each monitoring network may make or be 
required to make changes between the 5-year assessment periods, 
including for example, site relocations or the addition of PAMS 
networks in bumped-up ozone nonattainment areas. These modifications 
must address changes invoked by a new census and changes due to 
changing air quality levels. The State, or where appropriate local, 
agency shall provide written communication describing the network 
changes to the Regional Administrator for review and approval as these 
changes are identified.
    (c) State, or where appropriate, local agency requests for monitor 
station discontinuation, subject to the review of the Regional 
Administrator, will be approved if any of the following criteria are 
met. Other requests for discontinuation may also be approved on a case 
by case basis if discontinuance does not compromise data collection 
needed for implementation of a NAAQS.
    (1) Any PM2.5, O3, CO, PM10, 
SO2, Pb, or NO2 monitor which has shown 
attainment during the previous five years, that has a probability of 
less than 10 percent of exceeding 80 percent of the applicable NAAQS 
during the next three years based on the levels, trends, and 
variability observed in the past, and which is not specifically 
required by an attainment plan or maintenance plan.
    (2) Any monitor for CO, PM10, SO2, or 
NO2 which has consistently measured lower concentrations 
than another monitor for the same pollutant in the same county and same 
nonattainment area during the previous five years, and which is not 
specifically required by an attainment plan or maintenance plan, if 
control measures scheduled to be implemented or discontinued during the 
next five years would apply to the areas around both monitors and have 
similar effects on measured concentrations, such that the retained 
monitor would remain the higher reading of the two monitors being 
compared.
    (3) For any pollutant, the highest reading monitor (which may be 
the only monitor) in a county (or portion of a county within a distinct 
nonattainment or maintenance area) provided the monitor has not 
measured violations of the applicable NAAQS in the previous five years, 
the MSA or CSA within which the county lies (if in any) would still 
meet requirements for the minimum number of monitors for the applicable 
pollutant if any, and the approved SIP provides for a specific, 
reproducible approach to representing the air quality of the affected 
county in the absence of actual monitoring data.
    (4) A monitor which EPA has determined cannot be compared to the 
relevant NAAQS because of the siting of the monitor, in accordance with 
Sec.  58.30.
    (5) A monitor that is designed to measure concentrations upwind of 
an urban area for purposes of characterizing transport into the area 
and that has not recorded violations of the relevant NAAQS in the 
previous five years, if discontinuation of the monitor is tied to 
start-up of another station also characterizing transport.


Sec.  58.15  Annual air monitoring data certification.

    (a) Beginning May 1, 2009, the State, or where appropriate local, 
agency shall submit to the EPA Regional Administrator an annual air 
monitoring data certification letter to certify data collected at all 
SLAMS and at all SPM stations that meet appendix C and appendix E 
criteria from January 1 to December 31 of the previous year. The senior 
air pollution control officer in each agency, or their designee, shall 
certify that the previous year of ambient concentration and quality 
assurance data are completely submitted to AQS and that the ambient 
concentration data are accurate to the best of her or his knowledge, 
taking into consideration the quality assurance findings.
    (b) Along with each certification letter, the State shall submit to 
the Administrator (through the appropriate Regional Office) an annual 
summary report of all the ambient air quality data from all monitoring 
stations designated as SLAMS. The State also shall submit an annual 
summary to the appropriate Regional Administrator of all the ambient 
air quality monitoring data from all FRM, FEM, and ARM at SPM stations 
that are described in the State's current monitoring network 
description. The annual report(s) shall be submitted for data collected 
from January 1 to December 31 of the previous year. The annual summary 
report(s) must contain all information and data required by the State's 
approved plan and be submitted by July 1 of each year, unless an 
approved alternative date is included in the plan. The annual summary 
serves as the record of the specific data that is the object of the 
certification letter.


Sec.  58.16  Data submittal.

    (a) The State, or where appropriate, local agency, shall report to 
the Administrator, via AQS all ambient air quality data and associated 
quality assurance data for SO2, CO, O3, 
NO2, NO, NOY, Pb, PM10, 
PM2.5 mass concentration, for filter-based PM2.5 
FRM/FEM (field blank mass, sampler-generated average daily temperature, 
sampler-generated average daily pressure), chemically speciated 
PM2.5 mass concentration data, PM10-2.5 (mass 
concentration and chemically speciated data), meteorological data from 
NCore and PAMS sites, and metadata records and information specified by 
the AQS Data Coding Manual (http://www.epa.gov/ttn/airs/airsaqs/manuals/manuals.htm). Such air quality data and

[[Page 2782]]

information must be submitted directly to the AQS via electronic 
transmission on the specified quarterly schedule described in paragraph 
(b) of this section.
    (b) The specific quarterly reporting periods are January 1-March 
31, April 1-June 30, July 1-September 30, and October 1-December 31. 
The data and information reported for each reporting period must 
contain all data and information gathered during the reporting period, 
and be received in the AQS within 90 days after the end of the 
quarterly reporting period. For example, the data for the reporting 
period January 1-March 31 are due on or before June 30 of that year.
    (c) Air quality data submitted for each reporting period must be 
edited, validated, and entered into the AQS (within the time limits 
specified in paragraph (b) of this section) pursuant to appropriate AQS 
procedures. The procedures for editing and validating data are 
described in the AQS Data Coding Manual and in each monitoring agency's 
quality assurance project plan.
    (d) The State shall report VOC and if collected, carbonyl, 
NH3, and HNO3 data, from PAMS sites to AQS within 
6 months following the end of each quarterly reporting period listed in 
paragraph (b) of this section.
    (e) The State shall also submit any portion or all of the SLAMS and 
SPM data to the appropriate Regional Administrator upon request.

Subpart C--Special Purpose Monitors

    37. The heading for subpart C is revised as set forth above.
    38. Section 58.20 is revised to read as follows:


Sec.  58.20  Special purpose monitors (SPM).

    (a) An SPM is defined as any monitor included in an agency's 
monitoring network that the agency has designated as a special purpose 
monitor in its annual monitoring network plan and in AQS, and which the 
agency does not count when showing compliance with the minimum 
requirements of this subpart for the number and siting of monitors of 
various types. Any SPM operated by an air monitoring agency must be 
included in the periodic assessments and annual monitoring network plan 
required by Sec.  58.10. The plan shall include a statement of purpose 
for each SPM monitor and a evidence that siting and operation of each 
monitor meets the requirements of appendix A where applicable. The 
monitoring agency may designate a monitor as an SPM after January 1, 
2007 only if it is a new monitor not previously included in the 
monitoring plan.
    (b) Any SPM data collected by an air monitoring agency using a 
Federal reference method (FRM), Federal equivalent method (FEM), or 
approved regional method (ARM) must meet the requirements of Sec.  
58.11, Sec.  58.12, and appendices A and C to this part. Compliance 
with appendix E to this part is optional but encouraged except when the 
monitoring agency's data objectives are inconsistent with those 
requirements. Data collected at an SPM meeting these requirements must 
be submitted to AQS according to the requirements of Sec.  58.16. The 
monitoring agency must also submit to AQS an indication of whether the 
monitor meets the requirements of appendix E to this part.
    (c) All data from an SPM using an FRM, FEM, or ARM which has 
operated for more than 24 months is eligible for comparison to the 
relevant NAAQS, subject to the conditions of Sec.  58.30, unless the 
air monitoring agency demonstrates in the documentation required in 
paragraph (a) of this section that the data from a particular period 
does not meet the requirements in paragraph (b) of this section.
    (d) If an SPM using an FRM, FEM, or ARM is discontinued within 24 
months of start-up, the Administrator will not use data from the SPM 
for NAAQS violation determinations for the PM2.5, 
PM10-2.5, ozone, or the annual PM10 NAAQS.
    (e) If an SPM using an FRM, FEM, or ARM is discontinued within 24 
months of start-up, the Administrator will not use data from the SPM 
for NAAQS violation determinations for purposes of designating an area 
as nonattainment, for the CO, SO2, NO2, Pb, or 
24-hour PM10 NAAQS. Such data are eligible for use in 
determinations of whether a nonattainment area has attained one of 
these NAAQS.
    (f) Prior approval from EPA is not required for discontinuance of 
an SPM.
    39. Sections 58.21 through 58.28 are removed.

Subpart D--Comparability of Ambient Data to NAAQS

    40. The heading for subpart D is revised as set forth above.
    41. Section 58.30 is revised to read as follows:


Sec.  58.30  Special considerations for data comparisons to the NAAQS.

    (a) Comparability of PM2.5 data. (1) There are two forms 
of the PM2.5 NAAQS described in part 50 of this chapter. The 
PM2.5 monitoring site characteristics (see appendix D, 
section 4.7.1) impact how the resulting PM2.5 data can be 
compared to the annual PM2.5 NAAQS form. PM2.5 
data that are representative, not of areawide but rather, of relatively 
unique population-oriented microscale, or localized hot spot, or unique 
population-oriented middle-scale impact sites are only eligible for 
comparison to the 24-hour PM2.5 NAAQS. For example, if the 
PM2.5 monitoring site is adjacent to a unique dominating 
local PM2.5 source or can be shown to have average 24-hour 
concentrations representative of a smaller than neighborhood spatial 
scale, then data from a monitor at the site would only be eligible for 
comparison to the 24-hour PM2.5 NAAQS.
    (2) There are cases where certain population-oriented, microscale 
or middle scale PM2.5 monitoring sites are determined by the 
Regional Administrator to collectively identify a larger region of 
localized high ambient PM2.5 concentrations. In those cases, 
data from these population-oriented sites would be eligible for 
comparison to the annual PM2.5 NAAQS.
    (b) Comparability of PM10-2.5 data. To be eligible (or suitable) 
for comparison to the PM10-2.5 NAAQS, PM10-2.5 
data must be from a monitoring site that meets all five of the 
following conditions.
    (1) The site must be within the boundaries of an urbanized area as 
defined by the U.S. Bureau of the Census which has a population of at 
least 100,000 persons.
    (2) The site must be in a census block group with a population 
density of 500 or more persons per square mile. Alternatively, the site 
may be in a census block group with a lower population density if the 
block group is part of an enclave that is not more than five square 
miles in land area.
    (3) The site must be population-oriented.
    (4) The site may not be in source-influenced microenvironments 
(such as a microscale or localized hot spot site) not eligible for 
comparison to the annual PM2.5 NAAQS under the conditions of 
paragraph (a) of this section. For example, if the PM10-2.5 
monitoring site is located on the fenceline of a dominating local 
PM10-2.5 source, then data from a monitor at the site would 
not be eligible for comparison to the 24-hour PM10-2.5 
NAAQS.
    (5) PM10-2.5 concentrations at the site must be 
dominated by resuspended dust from high-density traffic on paved roads 
and PM generated by industrial sources and construction sources, and 
must not be dominated by rural windblown dust and soils and PM 
generated by

[[Page 2783]]

agricultural and mining sources, as determined by the State (and 
approved by the Regional Administrator) in a site-specific assessment. 
The site-specific assessment shall consider the types and sizes of 
sources that may impact the site, the impact of meteorological 
conditions on site-source relationships, verification that the site is 
not exposed to windblown rural dust and soil or emissions from 
agriculture and mining to such an extent that those sources would 
dominate the mix of PM10-2.5 sampled at that site, and other 
factors necessary for completing the assessment.
    42. Sections 58.31 through 58.36 are removed.

Subpart E--[Removed and Reserved]

    43. Subpart E of part 58 is removed and reserved.

Subpart F--[Amended]

    44. Section 58.50 is revised to read as follows:


Sec.  58.50  Index reporting.

    (a) The State or where applicable, local agency shall report to the 
general public on a daily basis through prominent notice an air quality 
index that complies with the requirements of appendix G to this part.
    (b) Reporting is required for all individual MSA with a population 
exceeding 350,000.
    (c) The population of a MSA for purposes of index reporting is the 
most recent decennial U.S. census population.

Subpart G--[Amended]

    45. Sections 58.60 and 58.61 are revised to read as follows:


Sec.  58.60  Federal monitoring.

    The Administrator may locate and operate an ambient air monitoring 
site if the State or local agency fails to locate, or schedule to be 
located, during the initial network design process, or as a result of 
the 5-year network assessments required within Sec.  58.10, a SLAMS 
station at a site which is necessary in the judgement of the Regional 
Administrator to meet the objectives defined in appendix D to this 
part.


Sec.  58.61  Monitoring other pollutants.

    The Administrator may promulgate criteria similar to that 
referenced in subpart B of this part for monitoring a pollutant for 
which an NAAQS does not exist. Such an action would be taken whenever 
the Administrator determines that a nationwide monitoring program is 
necessary to monitor such a pollutant.
    49. Appendix A to part 58 is revised to read as follows:

Appendix A to Part 58--Quality Assurance Requirements for SLAMS, NCore, 
and PSD Air Monitoring

    1. General Information.
    2. Quality System Requirements.
    3. Measurement Quality Check Requirements.
    4. Calculations for Data Quality Assessments.
    5. Reporting Requirements.
    6. References.
    1. General Information.
    This appendix specifies the minimum quality system requirements 
applicable to SLAMS air monitoring data and PSD data submitted to 
EPA. In this section, NCore stations and SPM stations (using FRM, 
FEM, or ARM methods) are considered a subset of the SLAMS network. 
Monitoring organizations are encouraged to develop and maintain 
quality systems more extensive than the required minimums. The 
permit-granting authority for PSD may require more frequent or more 
stringent requirements. Monitoring organizations may, based on their 
quality objectives, be required to develop and maintain quality 
systems beyond the required minimum. Additional guidance for the 
requirements reflected in this appendix can be found in the 
``Quality Assurance Handbook for Air Pollution Measurement 
Systems'', volume II, part 1 (see reference 10 of this appendix) and 
at a national level in references 1, 2, and 3 of this appendix.
    1.1 Similarities and Differences Between SLAMS and PSD 
Monitoring. In most cases, the quality assurance requirements for 
SLAMS and PSD are the same. Table A-1 of this appendix summarizes 
the major similarities and differences of the requirements for SLAMS 
and PSD. Both programs require:
    (a) The development, documentation, and implementation of an 
approved quality system;
    (b) The assessment of data quality;
    (c) The use of reference, equivalent, or approved methods 
(optional for SPM);
    (d) The use of calibration standards traceable to NIST or other 
primary standard;
    (e) Performance evaluations and systems.
    1.1.1 The monitoring and quality assurance responsibilities for 
SLAMS are with the State or local agency, hereafter called the 
monitoring organization, whereas for PSD they are with the owner/
operator seeking the permit. The monitoring duration for SLAMS is 
indefinite, whereas for PSD the duration is usually 12 months. 
Whereas the reporting period for precision and accuracy data is on 
an annual or calendar quarter basis for SLAMS, it is on a continuing 
sampler quarter basis for PSD--since the monitoring may not commence 
at the beginning of a calendar quarter.
    1.1.2 The performance evaluations for PSD must be conducted by 
personnel different from those who perform routine span checks and 
calibrations, whereas for SLAMS, it is the preferred but not the 
required condition. For PSD, the evaluation rate is 100 percent of 
the sites per reporting quarter whereas for SLAMS it is 25 percent 
of the sites or instruments quarterly. Note that monitoring for 
sulfur dioxide (SO2) and nitrogen dioxide 
(NO2) for PSD must be done with automated analyzers--the 
manual bubbler methods are not permitted.
    1.1.3 The requirements for precision assessment for the 
automated methods are the same for both SLAMS and PSD. However, for 
manual methods, only one collocated site is required for PSD.
    1.1.4 The precision, accuracy and bias data for PSD are reported 
separately for each sampler (site), whereas for SLAMS, the report 
may be by sampler (site) or primary quality assurance organization, 
depending on the pollutant. SLAMS data are required to be reported 
to the AQS, PSD data are required to be reported to the permit-
granting authority. Requirements in this appendix, with the 
exception to the differences discussed in this section, and in Table 
A-1 of this appendix will be expected to be followed by both SLAMS 
and PSD networks unless directly specified in a particular section.
    1.2 Measurement Uncertainty. Measurement uncertainty is a term 
used to describe deviations from a true concentration or estimate 
that are related to the measurement process and not to spatial or 
temporal population attributes of the air being measured. Monitoring 
organizations must develop quality assurance project plans (QAPP) 
which describe how the organization intends to control measurement 
uncertainty to an appropriate level in order to achieve the data 
quality objectives. Data quality indicators associated with 
measurement uncertainty include:
    (a) Precision. A measurement of mutual agreement among 
individual measurements of the same property usually under 
prescribed similar conditions, expressed generally in terms of the 
standard deviation.
    (b) Bias. The systematic or persistent distortion of a 
measurement process which causes errors in one direction.
    (c) Accuracy. The degree of agreement between an observed value 
and an accepted reference value. Accuracy includes a combination of 
random error (imprecision) and systematic error (bias) components 
which are due to sampling and analytical operations.
    (d) Completeness. A measure of the amount of valid data obtained 
from a measurement system compared to the amount that was expected 
to be obtained under correct, normal conditions.
    (e) Detectability. The low critical range value of a 
characteristic that a method specific procedure can reliably 
discern.
    1.3 Measurement Quality Checks. The SLAMS measurement quality 
checks described in sections 3.2 and 3.3 of this appendix shall be 
reported to AQS and are included in the data required for 
certification. The PSD network is required to implement the 
measurement quality checks and submit this information quarterly 
along with assessment information to the permit-granting authority.
    1.4 Assessments and Reports. Periodic assessments and 
documentation of data quality are required to be reported to EPA or 
to the permit granting authority (PSD). To

[[Page 2784]]

provide national uniformity in this assessment and reporting of data 
quality for all networks, specific assessment and reporting 
procedures are prescribed in detail in sections 3, 4, and 5 of this 
appendix. On the other hand, the selection and extent of the quality 
assurance and quality control activities used by a monitoring 
organization depend on a number of local factors such as field and 
laboratory conditions, the objectives for monitoring, the level of 
data quality needed, the expertise of assigned personnel, the cost 
of control procedures, pollutant concentration levels, etc. 
Therefore, quality system requirements in section 2 of this appendix 
are specified in general terms to allow each monitoring organization 
to develop a quality system that is most efficient and effective for 
its own circumstances while achieving the data quality objectives 
required for the SLAMS sites.
    2. Quality System Requirements.
    A quality system is the means by which an organization manages 
the quality of the monitoring information it produces in a 
systematic, organized manner. It provides a framework for planning, 
implementing, assessing and reporting work performed by an 
organization and for carrying out required quality assurance and 
quality control activities.
    2.1 Quality Management Plans and Quality Assurance Project 
Plans. All monitoring organizations must develop a quality system 
that is described and approved in quality management plans (QMP) and 
quality assurance project plans (QAPP) to ensure that the monitoring 
results:
    (a) Meet a well-defined need, use, or purpose;
    (b) Provide data of adequate quality for the intended monitoring 
objectives;
    (c) Satisfy stakeholder expectations;
    (d) Comply with applicable standards specifications;
    (e) Comply with statutory (and other) requirements of society; 
and
    (f) Reflect consideration of cost and economics.
    2.1.1 The QMP describes the quality system in terms of the 
organizational structure, functional responsibilities of management 
and staff, lines of authority, and required interfaces for those 
planning, implementing, assessing and reporting activities involving 
environmental data operations (EDO). The QMP must be suitably 
documented in accordance with EPA requirements (reference 2 of this 
appendix), and approved by the appropriate Regional Administrator, 
or Regional Administrator's designee. The quality system will be 
reviewed during the systems audits described in section 2.5 of this 
appendix. Organizations that implement long-term monitoring programs 
with EPA funds should have a separate QMP document. Smaller 
organizations or organizations that do infrequent work with EPA 
funds may combine the QMP with the QAPP based on negotiations with 
the funding agency. Additional guidance on this process can be found 
in reference 10 of this appendix. Approval of the recipient's QMP by 
the appropriate Regional Administrator, or the Regional 
Administrator's designee, may allow delegation of the authority to 
review and approve QAPP to the recipient, based on adequacy of 
quality assurance procedures described and documented in the QMP. 
The QAPP will be reviewed by EPA during systems audits or 
circumstances related to data quality.
    2.1.2 The QAPP is a formal document describing, in sufficient 
detail, the quality system that must be implemented to ensure that 
the results of work performed will satisfy the stated objectives. 
The quality assurance policy of the EPA requires every EDO to have 
written and approved QAPP prior to the start of the EDO. It is the 
responsibility of the monitoring organization to adhere to this 
policy. The QAPP must be suitably documented in accordance with EPA 
requirements (reference 3 of this appendix).
    2.1.3 The monitoring organizations' quality system must have 
adequate resources both in personnel and funding to plan, implement, 
assess and report on the achievement of the requirements of this 
appendix and its approved QAPP.
    2.2 Independence of Quality Assurance. The monitoring 
organization must provide for a quality assurance management 
function; that aspect of the overall management system of the 
organization that determines and implements the quality policy 
defined in a monitoring organization's QMP. Quality management 
includes strategic planning, allocation of resources and other 
systematic planning activities (e.g. planning, implementation, 
assessing and reporting) pertaining to the quality system. The 
quality assurance management function must have sufficient technical 
expertise and management authority to conduct independent oversight 
and assure the implementation of the organization's quality system 
relative to the Ambient Air Quality Monitoring Program and should be 
organizationally independent of environmental data generation 
activities.
    2.3 Data Quality Performance Requirements.
    2.3.1 Data Quality Objectives. Data quality objectives (DQO) or 
the results of other systematic planning processes are statements 
that define the appropriate type of data to collect and specify the 
tolerable levels of potential decision errors that will be used as a 
basis for establishing the quality and quantity of data needed to 
support the objectives of the SLAMS stations. DQO will be developed 
by EPA to support the primary SLAMS objectives for each criteria 
pollutant. As they are developed they will be added to the 
regulation. DQO or the results of other systematic planning 
processes for PSD or other monitoring will be the responsibility of 
the monitoring organizations. The quality of the conclusions made 
from data interpretation can be affected by population uncertainty 
(spatial or temporal uncertainty) and measurement uncertainty 
(uncertainty associated with collecting, analyzing, reducing and 
reporting concentration data). This appendix focuses on assessing 
and controlling measurement uncertainty.
    2.3.1.1 Measurement Uncertainty for Automated and Manual 
PM2.5 Methods. The goal for acceptable measurement 
uncertainty is defined as 10 percent coefficient of variation (CV) 
for total precision and  10 percent for total bias.
    2.3.1.2 Measurement Uncertainty for Automated Ozone Methods. The 
goal for acceptable measurement uncertainty is defined for precision 
as an upper 90 percent confidence limit for the coefficient 
variation (CV) of 7 percent and for bias as an upper 95 percent 
confidence limit for the absolute bias of 7 percent.
    2.3.1.3 Measurement Uncertainty for PM10-2.5 Methods. 
The goal for acceptable measurement uncertainty is defined for 
precision as an upper 90 percent confidence limit for the 
coefficient variation (CV) of 15 percent and for bias as an upper 95 
percent confidence limit for the absolute bias of 15 percent.
    2.4 National Performance Evaluation Programs. Monitoring plans 
or QAPP shall provide for the implementation of a program of 
independent and adequate audits of all monitors providing data for 
SLAMS and PSD including the provision of adequate resources for such 
audit programs. A monitoring plan (or QAPP) which provides for 
monitoring organization participation in EPA's National Performance 
Audit Program (NPAP) and the PM Performance Evaluation Program (PEP) 
program and which indicates the consent of the monitoring 
organization for EPA to apply an appropriate portion of the grant 
funds, which EPA would otherwise award to the monitoring 
organization for monitoring activities, will be deemed by EPA to 
meet this requirement. For clarification and to participate, 
monitoring organizations should contact either the appropriate EPA 
Regional Quality Assurance (QA) Coordinator at the appropriate EPA 
Regional Office location, or the NPEP Coordinator, Emissions 
Monitoring and Analysis Division (D205-02), U.S. Environmental 
Protection Agency, Research Triangle Park, NC 27711.
    2.5 Technical Systems Audit Program. Technical systems audits of 
each ambient air monitoring organization shall be conducted at least 
every 3 years by the appropriate EPA Regional Office and reported to 
the AQS. Systems audit programs are described in reference 10 of 
this appendix. For further instructions, monitoring organizations 
should contact the appropriate EPA Regional QA Coordinator.
    2.6 Gaseous and Flow Rate Audit Standards.
    2.6.1 Gaseous pollutant concentration standards (permeation 
devices or cylinders of compressed gas) used to obtain test 
concentrations for carbon monoxide (CO), sulfur dioxide 
(SO2), nitrogen oxide (NO), and nitrogen dioxide 
(NO2) must be traceable to either a National Institute of 
Standards and Technology (NIST) Traceable Reference Material (NTRM) 
or a NIST-certified Gas Manufacturer's Internal Standard (GMIS), 
certified in accordance with one of the procedures given in 
reference 4 of this appendix. Vendors advertizing certification with 
the procedures provided in reference 4 of this appendix and 
distributing gasses as ``EPA Protocol Gas'' must participate in the 
EPA Protocol Gas Verification Program or not use ``EPA'' in any form 
of advertizing.
    2.6.2 Test concentrations for ozone (O3) must be 
obtained in accordance with the

[[Page 2785]]

ultra violet photometric calibration procedure specified in appendix 
D to part 50 of this chapter, or by means of a certified 
O3 transfer standard. Consult references 7 and 8 of this 
appendix for guidance on primary and transfer standards for 
O3.
    2.6.3 Flow rate measurements must be made by a flow measuring 
instrument that is traceable to an authoritative volume or other 
applicable standard. Guidance for certifying some types of 
flowmeters is provided in reference 10 of this appendix.
    2.7 Primary Requirements and Guidance. Requirements and guidance 
documents for developing the quality system are contained in 
references 1 through 10 of this appendix, which also contain many 
suggested procedures, checks, and control specifications. Reference 
10 of this appendix describes specific guidance for the development 
of a quality system for SLAMS. Many specific quality control checks 
and specifications for methods are included in the respective 
reference methods described in part 50 of this chapter or in the 
respective equivalent method descriptions available from EPA 
(reference 6 of this appendix). Similarly, quality control 
procedures related to specifically designated reference and 
equivalent method analyzers are contained in the respective 
operation or instruction manuals associated with those analyzers.
    3. Measurement Quality Check Requirements.
    This section provides the requirements for performing the 
measurement quality checks that can be used to assess data quality 
and with the exception of the flow rate verifications (sections 
3.2.3 and 3.3.2 of this appendix) are required to be submitted to 
the AQS within the same time frame requirements as routine data. 
Section 3.2 of this appendix describes checks of automated or 
continuous instruments while section 3.3 describe checks associated 
with manual sampling instruments. Other quality control samples are 
identified in the various references described earlier and can be 
used to control certain aspects of the measurement system.
    3.1 Primary Quality Assurance Organization. Estimates of data 
quality will be calculated on the basis of single monitors, and 
primary quality assurance organizations. A primary quality assurance 
organization is defined as a monitoring organization or other 
organization that is responsible for a set of stations that monitors 
the same pollutant and for which data quality assessments can be 
pooled. Each criteria pollutant sampler/monitor at a monitoring 
station in the SLAMS network must be associated with one, and only 
one, primary quality assurance organization.
    3.1.1 Each primary quality assurance organization shall be 
defined such that measurement uncertainty among all stations in the 
organization can be expected to be reasonably homogeneous, as a 
result of common factors. Common factors that should be considered 
by monitoring organizations in defining primary quality assurance 
organizations include:
    (a) Operation by a common team of field operators according to a 
common set of procedures;
    (b) Use of a common QAPP or standard operating procedures;
    (c) Common calibration facilities and standards;
    (d) Oversight by a common quality assurance organization; and
    (e) Support by a common management, laboratory or headquarters.
    3.1.2 Primary quality assurance organizations are not 
necessarily related to the organization reporting data to the AQS. 
Monitoring organizations having difficulty in defining the primary 
quality assurance organizations or in assigning specific sites to 
primary quality assurance organizations should consult with the 
appropriate EPA Regional Office. All definitions of primary quality 
assurance organizations shall be subject to final approval by the 
appropriate EPA Regional Office during scheduled network reviews or 
systems audits.
    3.1.3 Assessment results shall be reported as specified in 
section 5 of this appendix.
    3.2 Measurement Quality Checks of Automated Methods. Table A-2 
of this appendix provides a summary of the types and frequency of 
the measurement quality checks that will be described in this 
section.
    3.2.1 One-Point Quality Control Check for SO2, 
NO2, O3, and CO. A one-point quality control 
(QC) check must be performed at least once every 2 weeks on each 
automated analyzer used to measure SO2, NO2, 
O3 and CO. The frequency of QC checks may be reduced 
based upon review, assessment and approval of the EPA Regional 
Administrator. However, with the advent of automated calibration 
systems more frequent checking is encouraged. See Reference 10 of 
this appendix for guidance on the review procedure. The QC check is 
made by challenging the analyzer with a QC check gas of known 
concentration (effective concentration for open path analyzers) 
between 0.01 and 0.10 parts per million (ppm) for SO2, 
NO2, and O3, and between 1 and 10 ppm for CO 
analyzers. The ranges allow for appropriate check gas selection for 
SLAMS sites that may be sampling for different objectives, i.e., 
trace gas monitoring vs. comparison to National Ambient Air Quality 
Standards (NAAQS). It is suggested that the QC check gas 
concentration selected should be related to the routine 
concentrations normally measured at sites within the monitoring 
network in order to appropriately reflect the precision and bias at 
these routine concentration ranges. To check the precision and bias 
of SLAMS analyzers operating at ranges either above or below the 
levels identified, use check gases of appropriate concentrations as 
approved by the appropriate EPA Regional Administrator or their 
designee. The standards from which check concentrations are obtained 
must meet the specifications of section 2.6 of this appendix.
    3.2.1.1 Except for certain CO analyzers described below, point 
analyzers must operate in their normal sampling mode during the QC 
check, and the test atmosphere must pass through all filters, 
scrubbers, conditioners and other components used during normal 
ambient sampling and as much of the ambient air inlet system as is 
practicable. If permitted by the associated operation or instruction 
manual, a CO point analyzer may be temporarily modified during the 
QC check to reduce vent or purge flows, or the test atmosphere may 
enter the analyzer at a point other than the normal sample inlet, 
provided that the analyzer's response is not likely to be altered by 
these deviations from the normal operational mode. If a QC check is 
made in conjunction with a zero or span adjustment, it must be made 
prior to such zero or span adjustments.
    3.2.1.2 Open path analyzers are tested by inserting a test cell 
containing a QC check gas concentration into the optical measurement 
beam of the instrument. If possible, the normally used transmitter, 
receiver, and as appropriate, reflecting devices should be used 
during the test and the normal monitoring configuration of the 
instrument should be altered as little as possible to accommodate 
the test cell for the test. However, if permitted by the associated 
operation or instruction manual, an alternate local light source or 
an alternate optical path that does not include the normal 
atmospheric monitoring path may be used. The actual concentration of 
the QC check gas in the test cell must be selected to produce an 
effective concentration in the range specified earlier in this 
section. Generally, the QC test concentration measurement will be 
the sum of the atmospheric pollutant concentration and the QC test 
concentration. If so, the result must be corrected to remove the 
atmospheric concentration contribution. The corrected concentration 
is obtained by subtracting the average of the atmospheric 
concentrations measured by the open path instrument under test 
immediately before and immediately after the QC test from the QC 
check gas concentration measurement. If the difference between these 
before and after measurements is greater than 20 percent of the 
effective concentration of the test gas, discard the test result and 
repeat the test. If possible, open path analyzers should be tested 
during periods when the atmospheric pollutant concentrations are 
relatively low and steady.
    3.2.1.3 Report the audit concentration (effective concentration 
for open path analyzers) of the QC gas and the corresponding 
measured concentration (corrected concentration, if applicable, for 
open path analyzers) indicated by the analyzer. The percent 
differences between these concentrations are used to assess the 
precision and bias of the monitoring data as described in sections 
4.1.2 (precision) and 4.1.3 (bias) of this appendix.
    3.2.2 Performance evaluation for SO2, NO2, 
O3, or CO. Each calendar quarter (during which analyzers 
are operated), evaluate at least 25 percent of the SLAMS analyzers 
that monitor for SO2, NO2, O3, or 
CO such that each analyzer is evaluated at least once per year. If 
there are fewer than four analyzers for a pollutant within a primary 
quality assurance organization, it is suggested to randomly evaluate 
one or more analyzers so that at least one analyzer for that 
pollutant is evaluated each calendar quarter. Where possible, EPA 
strongly encourages more frequent evaluations, up to a frequency of 
once per quarter for each SLAMS analyzer. It is also suggested that 
the evaluation be

[[Page 2786]]

conducted by a trained experienced technician other than the routine 
site operator.
    3.2.2.1 (a) The evaluation is made by challenging the analyzer 
with audit gas standard of known concentration (effective 
concentration for open path analyzers) from at least three 
consecutive ranges that are applicable to the analyzer being 
evaluated:

----------------------------------------------------------------------------------------------------------------
                                                                     Concentration range, ppm
                   Audit level                   ---------------------------------------------------------------
                                                        O3              SO2             NO2             CO
----------------------------------------------------------------------------------------------------------------
1...............................................  0.02-0.05       0.0003-0.005    0.0002-0.002    0.08-0.10
2...............................................  0.06-0.10       0.006-0.01      0.003-0.005     0.50-1.00
3...............................................  0.11-0.20       0.02-0.10       0.006-0.10      1.50-4.00
4...............................................  0.21-0.30       0.11-0.40       0.11-0.30          5-15
5...............................................  0.31-0.90       0.41-0.90       0.31-0.60         20-50
----------------------------------------------------------------------------------------------------------------

    (b) An additional 4th range is encouraged for those monitors 
that have the potential for exceeding the concentration ranges 
described by the initial three selected.
    3.2.2.2(a) NO2 audit gas for chemiluminescence-type 
NO2 analyzers must also contain at least 0.08 ppm NO. NO 
concentrations substantially higher than 0.08 ppm, as may occur when 
using some gas phase titration (GPT) techniques, may lead to 
evaluation errors in chemiluminescence analyzers due to inevitable 
minor NO-NOX channel imbalance. Such errors may be 
atypical of routine monitoring errors to the extent that such NO 
concentrations exceed typical ambient NO concentrations at the site. 
These errors may be minimized by modifying the GPT technique to 
lower the NO concentrations remaining in the NO2 audit 
gas to levels closer to typical ambient NO concentrations at the 
site.
    (b) To evaluate SLAMS analyzers operating on ranges higher than 
0 to 1.0 ppm for SO2, NO2, and O3 
or 0 to 50 ppm for CO, use audit gases of appropriately higher 
concentration as approved by the appropriate EPA Regional 
Administrator or the Administrators's designee.
    3.2.2.3 The standards from which audit gas test concentrations 
are obtained must meet the specifications of section 2.6 of this 
appendix. The gas standards and equipment used for evaluations must 
not be the same as the standards and equipment used for calibration 
or calibration span adjustments. For SLAMS sites, the auditor should 
not be the operator or analyst who conducts the routine monitoring, 
calibration, and analysis. For PSD sites the auditor must not be the 
operator or analyst who conducts the routine monitoring, 
calibration, and analysis.
    3.2.2.4 For point analyzers, the evaluation shall be carried out 
by allowing the analyzer to analyze the audit gas test atmosphere in 
its normal sampling mode such that the test atmosphere passes 
through all filters, scrubbers, conditioners, and other sample inlet 
components used during normal ambient sampling and as much of the 
ambient air inlet system as is practicable. The exception provided 
in section 3.2.1 of this appendix for certain CO analyzers does not 
apply for evaluations.
    3.2.2.5 Open path analyzers are evaluated by inserting a test 
cell containing the various audit gas concentrations into the 
optical measurement beam of the instrument. If possible, the 
normally used transmitter, receiver, and, as appropriate, reflecting 
devices should be used during the evaluation, and the normal 
monitoring configuration of the instrument should be modified as 
little as possible to accommodate the test cell for the evaluation. 
However, if permitted by the associated operation or instruction 
manual, an alternate local light source or an alternate optical path 
that does not include the normal atmospheric monitoring path may be 
used. The actual concentrations of the audit gas in the test cell 
must be selected to produce effective concentrations in the 
evaluation level ranges specified in this section of this appendix. 
Generally, each evaluation concentration measurement result will be 
the sum of the atmospheric pollutant concentration and the 
evaluation test concentration. If so, the result must be corrected 
to remove the atmospheric concentration contribution. The corrected 
concentration is obtained by subtracting the average of the 
atmospheric concentrations measured by the open path instrument 
under test immediately before and immediately after the evaluation 
test (or preferably before and after each evaluation concentration 
level) from the evaluation concentration measurement. If the 
difference between the before and after measurements is greater than 
20 percent of the effective concentration of the test gas standard, 
discard the test result for that concentration level and repeat the 
test for that level. If possible, open path analyzers should be 
evaluated during periods when the atmospheric pollutant 
concentrations are relatively low and steady. Also, the monitoring 
path length must be reverified to within 3 percent to 
validate the evaluation, since the monitoring path length is 
critical to the determination of the effective concentration.
    3.2.2.6 Report both the evaluation concentrations (effective 
concentrations for open path analyzers) of the audit gases and the 
corresponding measured concentration (corrected concentrations, if 
applicable, for open path analyzers) indicated or produced by the 
analyzer being tested. The percent differences between these 
concentrations are used to assess the quality of the monitoring data 
as described in section 4.1.4 of this appendix.
    3.2.3 Flow Rate Verification for Particulate Matter. A one-point 
flow rate verification check must be performed at least once every 
month on each automated analyzer used to measure PM10, 
PM10-2.5 and PM2.5. The verification is made 
by checking the operational flow rate of the analyzer. If the 
verification is made in conjunction with a flow rate adjustment, it 
must be made prior to such flow rate adjustment. Randomization of 
the flow rate verification with respect to time of day, day of week, 
and routine service and adjustments is encouraged where possible. 
For the standard procedure, use a flow rate transfer standard 
certified in accordance with section 2.6 of this appendix to check 
the analyzer's normal flow rate. Care should be used in selecting 
and using the flow rate measurement device such that it does not 
alter the normal operating flow rate of the analyzer. Report the 
flow rate of the transfer standard and the corresponding flow rate 
measured (indicated) by the analyzer. The percent differences 
between the audit and measured flow rates are used to assess the 
bias of the monitoring data as described in section 4.2.2 of this 
appendix (using flow rates in lieu of concentrations).
    3.2.4 Semi-Annual Flow Rate Audit for Particulate Matter. Every 
6 months, audit the flow rate of the PM10, 
PM10-2.5 and PM2.5 particulate analyzers. 
Where possible, EPA strongly encourages more frequent auditing. It 
is also suggested that the audit be conducted by a trained 
experienced technician other than the routine site operator. The 
audit is made by measuring the analyzer's normal operating flow rate 
using a flow rate transfer standard certified in accordance with 
section 2.6 of this appendix. The flow rate standard used for 
auditing must not be the same flow rate standard used to calibrate 
the analyzer. However, both the calibration standard and the audit 
standard may be referenced to the same primary flow rate or volume 
standard. Great care must be used in auditing the flow rate to be 
certain that the flow measurement device does not alter the normal 
operating flow rate of the analyzer. Report the audit flow rate of 
the transfer standard and the corresponding flow rate measured 
(indicated) by the analyzer. The percent differences between these 
flow rates are used to validate the one-point flow rate verification 
checks used to estimate bias as described in section 4.2.3 of this 
appendix.
    3.2.5 Collocated Procedures for PM10-2.5 and 
PM2.5. For each pair of collocated monitors, designate 
one sampler as the primary monitor whose concentrations will be used 
to report air quality for the site, and designate the other as the 
audit monitor.
    3.2.5.1 Each EPA designated Federal reference method (FRM) or 
Federal equivalent method (FEM) within a primary quality assurance 
organization must:
    (a) Have 15 percent of the monitors collocated (values of .5 and 
greater round up); and
    (b) Have at least 1 collocated monitor (if the total number of 
monitors is less than 3).

[[Page 2787]]

The first collocated monitor must be a designated FRM monitor.
    3.2.5.2 In addition, monitors selected for collocation must also 
meet the following requirements:
    (a) A primary monitor designated as an EPA FRM shall be 
collocated with an audit monitor having the same EPA FRM method 
designation.
    (b) For each primary monitor designated as an EPA FEM, 50 
percent of the monitors designated for collocation shall be 
collocated with an audit monitor having the same method designation 
and 50 percent of the monitors shall be collocated with an FRM audit 
monitor. If the primary quality assurance organization only has one 
FEM monitor it shall be collocated with an FRM audit monitor. If 
there are an odd number of collocated monitors required, the 
additional monitor shall be an FRM audit monitor. An example of this 
procedure is found in Table A-3 of this appendix.
    3.2.5.3 The collocated monitors should be deployed according to 
the following protocol:
    (a) 80 percent of the collocated audit monitors should be 
deployed at sites with annual average or daily concentrations 
estimated to be within  20 percent of the applicable 
NAAQS and the remainder at what the monitoring organizations 
designate as high value sites;
    (b) If an organization has no sites with annual average or daily 
concentrations within  20 percent of the annual NAAQS 
(or 24-hour NAAQS if that is affecting the area), 60 percent of the 
collocated audit monitors should be deployed at those sites with the 
annual mean concentrations (or 24-hour NAAQS if that is affecting 
the area) among the highest 25 percent for all sites in the network.
    3.2.5.4 In determining the number of collocated sites required 
for PM2.5, monitoring networks for visibility assessments 
should not be treated independently from networks for particulate 
matter, as the separate networks may share one or more common 
samplers. However, for Class I visibility areas, EPA will accept 
visibility aerosol mass measurement instead of a PM2.5 
measurement if the latter measurement is unavailable. Any 
PM2.5 monitoring site which does not have a monitor which 
is an EPA FRM or FEM is not required to be included in the number of 
sites which are used to determine the number of collocated monitors.
    3.2.5.5 For each PSD monitoring network, one site must be 
collocated. A site with the predicted highest 24-hour pollutant 
concentration must be selected.
    3.2.5.6 The two collocated monitors must be within 4 meters of 
each other and at least 2 meters apart for flow rates greater than 
200 liters/min or at least 1 meter apart for samplers having flow 
rates less than 200 liters/min to preclude airflow interference. 
Calibration, sampling, and analysis must be the same for both 
collocated samplers and the same as for all other samplers in the 
network.
    3.2.5.7 Sample the collocated audit monitor for SLAMS sites on a 
12-day schedule; sample PSD sites on a 6-day schedule or every third 
day for PSD daily monitors. If a primary quality assurance 
organization has only one collocated monitor, higher sampling 
frequencies than the 12-day schedule may be needed in order to 
produce ~25 valid sample pairs a year. Report the measurements from 
both primary and collocated audit monitors at each collocated 
sampling site. The calculations for evaluating precision between the 
two collocated monitors are described in section 4.3.1 of this 
appendix.
    3.2.6 Performance Evaluation Procedures for PM10-2.5 
and PM2.5. (a) The performance evaluation is an 
independent assessment used to estimate total measurement system 
bias. These evaluations will be performed under the PM Performance 
Evaluation Program (PEP) (section 2.4 of this appendix) or a 
comparable program. Performance evaluations will be performed on the 
SLAMS monitors annually within each primary quality assurance 
organization. For primary quality assurance organizations with less 
than or equal to five monitoring sites, five valid performance 
evaluation audits must be collected and reported each year. For 
primary quality assurance organizations with greater than five 
monitoring sites, eight valid performance evaluation audits must be 
collected and reported each year. A valid performance evaluation 
audit means that both the primary monitor and PEP audit 
concentrations are valid and above 3 [mu]g/m\3\. Additionally, each 
year, every designated FRM or FEM within a primary quality assurance 
organization must:
    (1) Have each method designation evaluated each year; and,
    (2) Have all FRM or FEM samplers subject to an PEP audit at 
least once every six years; which equates to approximately 15 
percent of the monitoring sites audited each year.
    (b) Additional information concerning the Performance Evaluation 
Program is contained in reference 10 of this appendix. The 
calculations for evaluating bias between the primary monitor and the 
performance evaluation monitor for PM2.5 are described in 
section 4.3.2 of this appendix. The calculations for evaluating bias 
between the primary monitor(s) and the performance evaluation 
monitors for PM10-2.5 are described in section 4.1.3 of 
this appendix.
    3.3 Measurement Quality Checks of Manual Methods. Table A-2 of 
this appendix provides a summary of the types and frequency of the 
measurement quality checks that will be described in this section.
    3.3.1 Collocated Procedures for PM10. For each 
network of manual PM10 methods, select 15 percent (or at 
least one) of the monitoring sites within the primary quality 
assurance organization for collocated sampling. For purposes of 
precision assessment, networks for measuring total suspended 
particulate (TSP) and PM10 shall be considered separately 
from one another. PM10 and TSP sites having annual mean 
particulate matter concentrations among the highest 25 percent of 
the annual mean concentrations for all the sites in the network must 
be selected or, if such sites are impractical, alternative sites 
approved by the EPA Regional Administrator may be selected.
    3.3.1.1 In determining the number of collocated sites required 
for PM10, monitoring networks for lead (Pb) should be 
treated independently from networks for particulate matter (PM), 
even though the separate networks may share one or more common 
samplers. However, a single pair of samplers collocated at a common-
sampler monitoring site that meets the requirements for both a 
collocated Pb site and a collocated PM site may serve as a 
collocated site for both networks.
    3.3.1.2 The two collocated monitors must be within 4 meters of 
each other and at least 2 meters apart for flow rates greater than 
200 liters/min or at least 1 meter apart for samplers having flow 
rates less than 200 liters/min to preclude airflow interference. 
Calibration, sampling, analysis and verification/validation 
procedures must be the same for both collocated samplers and the 
same as for all other samplers in the network.
    3.3.1.3 For each pair of collocated samplers, designate one 
sampler as the primary sampler whose samples will be used to report 
air quality for the site, and designate the other as the audit 
sampler. Sample SLAMS sites on a 12-day schedule; sample PSD sites 
on a 6-day schedule or every third day for PSD daily samplers. If a 
primary quality assurance organization has only one collocated 
monitor, higher sampling frequencies than the 12-day schedule may be 
needed in order to produce 25 valid sample pairs a year. Report the 
measurements from both samplers at each collocated sampling site. 
The calculations for evaluating precision between the two collocated 
samplers are described in section 4.2.1 of this appendix.
    3.3.2 Flow Rate Verification for Particulate Matter. Follow the 
same procedure as described in section 3.2.3 of this appendix for 
PM2.5, PM10, PM10-2.5 and TSP 
instruments. The percent differences between the audit and measured 
flow rates are used to assess the bias of the monitoring data as 
described in section 4.2.2 of this appendix.
    3.3.3 Semi-Annual Flow Rate Audit for Particulate Matter. Follow 
the same procedure as described in section 3.2.4 of this appendix 
for PM2.5, PM10, PM10-2.5 and TSP 
instruments. The percent differences between these flow rates are 
used to validate the one-point flow rate verification checks used to 
estimate bias as described in section 4.2.3 of this appendix. Great 
care must be used in auditing high-volume particulate matter 
samplers having flow regulators because the introduction of 
resistance plates in the audit flow standard device can cause 
abnormal flow patterns at the point of flow sensing. For this 
reason, the flow audit standard should be used with a normal filter 
in place and without resistance plates in auditing flow-regulated 
high-volume samplers, or other steps should be taken to assure that 
flow patterns are not perturbed at the point of flow sensing.
    3.3.4 Pb Methods.
    3.3.4.1 Annual Flow Rate. For the Pb Reference Method (40 CFR 
part 50, appendix G), the flow rates of the high-volume Pb samplers 
shall be verified and audited using the same procedures described in 
sections 3.3.2 and 3.3.3 of this appendix.
    3.3.4.2 Pb Strips. Each calendar quarter or sampling quarter 
(PSD), audit the Pb

[[Page 2788]]

Reference Method analytical procedure using glass fiber filter 
strips containing a known quantity of Pb. These audit sample strips 
are prepared by depositing a Pb solution on unexposed glass fiber 
filter strips of dimensions 1.9 centimeters (cm) by 20.3 cm (3/4 
inch by 8 inch) and allowing them to dry thoroughly. The audit 
samples must be prepared using batches of reagents different from 
those used to calibrate the Pb analytical equipment being audited. 
Prepare audit samples in the following concentration ranges:

------------------------------------------------------------------------
                                                            Equivalent
                                                Pb          ambient Pb
                  Range                   concentration,  concentration,
                                            [mu]g/strip   [mu]g/m\3\ \1\
------------------------------------------------------------------------
1.......................................         100-300         0.5-1.5
2.......................................        400-1000        3.0-5.0
------------------------------------------------------------------------
\1\ Equivalent ambient Pb concentration in [mu]g/m\3\ is based on
  sampling at 1.7 m\3\/min for 24 hours on a 20.3 cm x 25.4 cm (8 inch x
  10 inch) glass fiber filter.

    (a) Audit samples must be extracted using the same extraction 
procedure used for exposed filters.
    (b) Analyze three audit samples in each of the two ranges each 
quarter samples are analyzed. The audit sample analyses shall be 
distributed as much as possible over the entire calendar quarter.
    (c) Report the audit concentrations (in [mu]g Pb/strip) and the 
corresponding measured concentrations (in [mu]g Pb/strip) using AQS 
unit code 077. The relative percent differences between the 
concentrations are used to calculate analytical accuracy as 
described in section 4.4.2 of this appendix.
    (d) The audits of an equivalent Pb method are conducted and 
assessed in the same manner as for the reference method. The flow 
auditing device and Pb analysis audit samples must be compatible 
with the specific requirements of the equivalent method.
    3.3.5 Collocated Procedures for PM10-2.5 and 
PM2.5. Follow the same procedure as described in section 
3.2.5 of this appendix.
    3.3.6 Performance Evaluation Procedures for PM10-2.5 
and PM2.5. Follow the same procedure as described in 
section 3.2.6 of this appendix.
    4. Calculations for Data Quality Assessment.
    (a) Calculations of measurement uncertainty are carried out by 
EPA according to the following procedures. Primary quality assurance 
organizations should report the data for all appropriate measurement 
quality checks as specified in this appendix even though they may 
elect to perform some or all of the calculations in this section on 
their own.
    (b) The EPA will provide annual assessments of data quality 
aggregated by site and primary quality assurance organization for 
SO2, NO2, O3 and CO and by primary 
quality assurance organization for PM10, 
PM2.5, PM10-2.5 and Pb.
    (c) At low concentrations, agreement between the measurements of 
collocated samplers, expressed as relative percent difference or 
percent difference, may be relatively poor. For this reason, 
collocated measurement pairs are selected for use in the precision 
and bias calculations only when both measurements are equal to or 
above the following limits:
    (1) TSP: 20 [mu]g/m3.
    (2) Pb: 0.15 [mu]g/m3.
    (3) PM10 (Hi-Vol): 15 [mu]g/m3.
    (4) PM10 (Lo-Vol): 3 [mu]g/m3.
    (5) PM10-2.5 and PM2.5: 3 [mu]g/
m3.
    4.1 Statistics for the Assessment of QC Checks for 
SO2, NO2, O3 and CO.
    4.1.1 Percent Difference. All measurement quality checks start 
with a comparison of an audit concentration or value (flowrate) to 
the concentration/value measured by the analyzer and use percent 
difference as the comparison statistic as described in equation 1 of 
this section.
For each single point check, calculate the percent difference, di, 
as follows:
[GRAPHIC] [TIFF OMITTED] TP17JA06.031

where, meas is the concentration indicated by the monitoring 
organization's instrument and audit is the audit concentration of 
the standard used in the QC check being measured.
    4.1.2 Precision Estimate. The precision estimate is used to 
assess the one-point QC checks for SO2, NO2, 
O3, or CO described in section 3.2.1 of this appendix. 
The precision estimator is the coefficient of variation upper bound 
and is calculated using equation 2 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.032

where, X 0.1,n-1 is the 10th percentile of a chi-squared 
distribution with n-1 degrees of freedom.
    4.1.3 Bias Estimate. The bias estimate is calculated using the 
one-point QC checks for SO2, NO2, 
O3, or CO described in section 3.2.1 of this appendix and 
the performance evaluation program for PM10-2.5 described 
in section 3.2.6 of this appendix. The bias estimator is an upper 
bound on the mean absolute value of the percent differences as 
described in equation 3 of this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.033

where, n is the number of single point checks being aggregated; 
t0.95,n-1 is the 95th quantile of a t-distribution with 
n-1 degrees of freedom; the quantity AB is the mean of the absolute 
values of the di's and is calculated using equation 4 of 
this section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.034

and the quantity AS is the standard deviation of the absolute value 
of the di's and is calculated using equation 5 of this 
section:
[GRAPHIC] [TIFF OMITTED] TP17JA06.035

    4.1.3.1 Assigning a sign (positive/negative) to the bias 
estimate. Since the bias statistic as calculated in equation 3 of 
this appendix uses absolute values, it does not have a tendency 
(negative or positive bias) associated with it. A sign will be 
designated by rank ordering the percent differences of the QC check 
samples from a given site for a particular assessment interval.
    4.1.3.2 Calculate the 25th and 75th percentiles of the percent 
differences for each site. The absolute bias upper bound should be 
flagged as positive if both percentiles are positive and negative if 
both percentiles are negative. The absolute bias upper bound would 
not be flagged if the 25th and 75th percentiles are of different 
signs.
    4.1.4 Validation of Bias Using Performance Evaluations. The 
annual performance evaluations for SO2, NO2, 
O3, or CO described in section 3.2.2 of this appendix are 
used to verify the results obtained from the one-point QC checks and 
to validate those results across a range of concentration levels. To 
quantify this annually at the site level and at the 3-year

[[Page 2789]]

primary quality assurance organization level, probability limits 
will be calculated from the one-point QC checks using equations 6 
and 7 of this appendix:
[GRAPHIC] [TIFF OMITTED] TP17JA06.036

[GRAPHIC] [TIFF OMITTED] TP17JA06.051

Where, m is the mean (equation 8 of this appendix):
[GRAPHIC] [TIFF OMITTED] TP17JA06.037

where, k is the total number of one point QC checks for the interval 
being evaluated and S is the standard deviation of the percent 
differences (equation 9 of this appendix) as follows:
[GRAPHIC] [TIFF OMITTED] TP17JA06.038

    4.1.5 Percent Difference. Percent differences for the 
performance evaluations, calculated using equation 1 of this 
appendix can be compared to the probability intervals for the 
respective site or at the primary quality assurance organization 
level. Ninety-five percent of the individual percent differences 
(all audit concentration levels) for the performance evaluations 
should be captured within the probability intervals for the primary 
quality assurance organization.
    4.2 Statistics for the Assessment of PM10.
    4.2.1 Precision Estimate from Collocated Samplers. Precision is 
estimated via duplicate measurements from collocated samplers of the 
same type. It is recommended that the precision be aggregated at the 
primary quality assurance organization level quarterly, annually, 
and at the 3-year level. The data pair would only be considered 
valid if both concentrations are greater than the minimum values 
specified in section 4(c) of this appendix. For each collocated data 
pair, calculate the relative percent difference, di, 
using equation 10 of this appendix:
[GRAPHIC] [TIFF OMITTED] TP17JA06.039

where, Xi is the concentration from the primary sampler 
and Yi is the concentration value from the audit sampler. 
The coefficient of variation upper bound is calculated using the 
equation 11 of this appendix:
[GRAPHIC] [TIFF OMITTED] TP17JA06.040

where, n is the number of valid data pairs being aggregated, and X 
0.1,n-1 is the 10th percentile of a chi-squared 
distribution with n-1 degrees of freedom. The factor of 2 in the 
denominator adjusts for the fact that each di is 
calculated from two values with error.
    4.2.2 Bias Estimate Using One-Point Flow Rate Verifications. For 
each one-point flow rate verification described in sections 3.2.3 
and 3.3.2 of this appendix, calculate the percent difference in 
volume using equation 1 of this appendix where meas is the value 
indicated by the sampler's volume measurement and audit is the 
actual volume indicated by the auditing flow meter. The absolute 
volume bias upper bound is then calculated using equation 3, where n 
is the number of flow rate audits being aggregated; 
t0.95,n-1 is the 95th quantile of a t-distribution with 
n-1 degrees of freedom, the quantity AB is the mean of the absolute 
values of the di's and is calculated using equation 4 of 
this appendix, and the quantity AS in equation 3 of this appendix is 
the standard deviation of the absolute values of the di's 
and is calculated using equation 5 of this appendix.
    4.2.3 Assessment Semi-Annual Flow Rate Audits. The flow rate 
audits described in sections 3.2.4 and 3.3.3 of this appendix are 
used to assess the results obtained from the one-point flow rate 
verifications and to provide an estimate of flow rate acceptability. 
For each flow rate audit, calculate the percent difference in volume 
using equation 1 of this appendix where meas is the value indicated 
by the sampler's volume measurement and audit is the actual volume 
indicated by the auditing flow meter. To quantify this annually and 
at the 3-year primary quality assurance organization level, 
probability limits are calculated from the percent differences using 
equations 6 and 7 of this appendix where m is the mean described in 
equation 8 of this appendix and k is the total number of one-point 
flow rate verifications for the year and S is the standard deviation 
of the percent differences as described in equation 9 of this 
appendix.
    4.2.4 Percent Difference. Percent differences for the annual 
flow rate audit concentration, calculated using equation 1 of this 
appendix, can be compared to the probability intervals for the one-
point flow rate verifications for the respective primary quality 
assurance organization. Ninety-five percent of the individual 
percent differences (all audit concentration levels) for the 
performance evaluations should be captured within the probability 
intervals for primary quality assurance organization.
    4.3 Statistics for the Assessment of PM2.5 and 
PM10-2.5.
    4.3.1 Precision Estimate. Precision for collocated instruments 
for PM2.5 and PM10-2.5 may be estimated where 
both the primary and collocated instruments are the same method 
designation and when the method designations are not similar. Follow 
the procedure described in section 4.2.1 of this appendix. In 
addition, one may want to perform an estimate bias when the primary 
monitor is an FEM and the collocated monitor is an FRM. Follow the 
procedure described in section 4.1.3 of this appendix in order to 
provide an estimate of bias using the collocated data.
    4.3.2 Bias Estimate. Follow the procedure described in section 
4.1.3 of this appendix for the bias estimate of PM10-2.5. 
The PM2.5 bias estimate is calculated using the paired 
routine and the PEP monitor data described in section 3.2.6 of this 
appendix. Calculate the percent difference, di, using 
equation 1 of this appendix, where meas is the measured 
concentration from agency's primary monitor and audit is the 
concentration from the PEP monitor. The data pair would only be 
considered valid if both concentrations are greater than the minimum 
values specified in section 4(c) of this appendix. Estimates of bias 
are presented for various levels of aggregation, sometimes 
aggregating over time, sometimes aggregating over samplers, and 
sometimes aggregating over both time and samplers. These various 
levels of aggregation are achieved using the same basic statistic.
    4.3.2.1 This statistic averages the individual biases described 
in equation 1 of this appendix to the desired level of aggregation 
using equation 12 of this appendix:
[GRAPHIC] [TIFF OMITTED] TP17JA06.041

where, nj is the number of pairs and d1, 
d2, . . ., dnj are the biases for each of the 
pairs to be averaged.

[[Page 2790]]

    4.3.2.2 Confidence intervals can be constructed for these 
average bias estimates in equation 12 of this appendix using 
equations 13 and 14 of this appendix:
[GRAPHIC] [TIFF OMITTED] TP17JA06.042

[GRAPHIC] [TIFF OMITTED] TP17JA06.043

    Where, t0.95,df is the 95th quantile of a t-
distribution with degrees of freedom df=nj-1 and s is an 
estimate of the variability of the average bias calculated using 
equation 15 of this appendix:
[GRAPHIC] [TIFF OMITTED] TP17JA06.044

    4.4 Statistics for the Assessment of Pb.
    4.4.1 Precision Estimate. Follow the same procedures as 
described for PM10 in section 4.2.1 of this appendix 
using the data from the collocated instruments. The data pair would 
only be considered valid if both concentrations are greater than the 
minimum values specified in section 4(c) of this appendix.
    4.4.2 Bias Estimate. In order to estimate bias, the information 
from the flow rate audits and the Pb strip audits needs to be 
combined as described below. To be consistent with the formulas for 
the gases, the recommended procedures are to work with relative 
errors of the lead measurements. The relative error in the 
concentration is related to the relative error in the volume and the 
relative error in the mass measurements using equation 16 of this 
appendix:
[GRAPHIC] [TIFF OMITTED] TP17JA06.045

As with the gases, an upper bound for the absolute bias is desired. 
Using equation 16 above, the absolute value of the relative 
(concentration) error is bounded by equation 17 of this appendix:
[GRAPHIC] [TIFF OMITTED] TP17JA06.046

The quality indicator data collected are then used to bound each 
part of equation 17 separately.
    4.4.2.1 Flow rate calculations. For each flow rate audit, 
calculate the percent difference in volume by equation 1 of this 
appendix where meas is the value indicated by the sampler's volume 
measurement and audit is the actual volume indicated by the auditing 
flow meter. The absolute volume bias upper bound is then calculated 
using equation 3 of this appendix where n is the number of flow rate 
audits being aggregated; t0.95,n-1 is the 95th quantile 
of a t-distribution with n-1 degrees of freedom; the quantity AB is 
the mean of the absolute values of the di's and is 
calculated using equation 4, and the quantity AS in equation 3 of 
this appendix is the standard deviation of the absolute values of 
the di's and is calculated using equation 5 of this 
appendix.
    4.4.2.2 Lead strip calculations. Similarly for each lead strip 
audit, calculate the percent difference in mass by equation 1 where 
meas is the value indicated by the mass measurement and audit is the 
actual lead mass on the audit strip. The absolute mass bias upper 
bound is then calculated using equation 3 of this appendix where n 
is the number of lead strip audits being aggregated; 
t0.95,n-1 is the 95th quantile of a t-distribution with 
n-1 degrees of freedom; the quantity AB is the mean of the absolute 
values of the di's and is calculated using equation 4 of 
this appendix and the quantity AS in equation 3 of this appendix is 
the standard deviation of the absolute values of the di's 
and is calculated using equation 5 of this appendix.
    4.4.2.3 Final bias calculation. Finally, the absolute bias upper 
bound is given by combining the absolute bias estimates of the flow 
rate and Pb strips using equation 18 of this appendix:

[[Page 2791]]

[GRAPHIC] [TIFF OMITTED] TP17JA06.047

where, the numerator and denominator have been multiplied by 100 
since everything is expressed as a percentage.
    4.5 Time Period for Audits. The statistics in this section 
assume that the mass and flow rate audits represent the same time 
period. Since the two types of audits are not performed at the same 
time, the audits need to be grouped by common time periods. 
Consequently, the absolute bias estimates should be done on annual 
and 3-year levels. The flow rate audits are site-specific, so the 
absolute bias upper bound estimate can be done and treated as a 
site-level statistic.
    5. Reporting Requirements.
    5.1 SLAMS Reporting Requirements. For each pollutant, prepare a 
list of all monitoring sites and their AQS site identification codes 
in each primary quality assurance organization and submit the list 
to the appropriate EPA Regional Office, with a copy to AQS. Whenever 
there is a change in this list of monitoring sites in a primary 
quality assurance organization, report this change to the EPA 
Regional Office and to AQS.
    5.1.1 Quarterly Reports. For each quarter, each primary quality 
assurance organization shall report to AQS directly (or via the 
appropriate EPA Regional Office for organizations not direct users 
of AQS) the results of all valid measurement quality checks it has 
carried out during the quarter. The quarterly reports must be 
submitted consistent with the data reporting requirements specified 
for air quality data as set forth in Sec.  58.16. EPA strongly 
encourages early submission of the quality assurance data in order 
to assist the monitoring organizations control and evaluate the 
quality of the ambient air data.
    5.1.2 Annual Reports.
    5.1.2.1 When the monitoring organization has certified their 
data for the calendar year, EPA will calculate and report the 
measurement uncertainty for the entire calendar year. These limits 
will then be associated with the data submitted in the annual report 
required by Sec.  58.15.
    5.1.2.2 Each primary quality assurance organization shall 
submit, along with its annual report, a listing by pollutant of all 
monitoring sites in the primary quality assurance organization.
    5.2 PSD Reporting Requirements. At the end of each sampling 
quarter, the organization must report the appropriate statistical 
assessments in section 4 of this appendix for the pollutants 
measured. All data used to calculate reported estimates of precision 
and bias including span checks, collocated sampler and audit results 
must be made available to the permit granting authority upon 
request.
    6.0 References.
    (1) American National Standard--Specifications and Guidelines 
for Quality Systems for Environmental Data Collection and 
Environmental Technology Programs. ANSI/ASQC E4-2004. February 2004. 
Available from American Society for Quality Control, 611 East 
Wisconsin Avenue, Milwaukee, WI 53202.
    (2) EPA Requirements for Quality Management Plans. EPA QA/R-2. 
EPA/240/B-01/002. March 2001. Office of Environmental Information, 
Washington DC 20460. http://www.epa.gov/quality/qs-docs/r2-final.pdf.
    (3) EPA Requirements for Quality Assurance Project Plans for 
Environmental Data Operations. EPA QA/R-5. EPA/240/B-01/003. March 
2001. Office of Environmental Information, Washington DC 20460. 
http://www.epa.gov/quality/qs-docs/r5-final.pdf.
    (4) EPA Traceability Protocol for Assay and Certification of 
Gaseous Calibration Standards. EPA-600/R-97/121. September 1997. 
Available from U.S. Environmental Protection Agency, ORD 
Publications Office, Center for Environmental Research Information 
(CERI), 26 W. Martin Luther King Drive, Cincinnati, OH 45268.
    (5) Guidance for the Data Quality Objectives Process. EPA QA/G-
4. EPA/600/R-96/055. August 2000. Office of Environmental 
Information, Washington DC 20460. http://www.epa.gov/quality/qs-docs/g4-final.pdf.
    (6) List of Designated Reference and Equivalent Methods. 
Available from U.S. Environmental Protection Agency, National 
Exposure Research Laboratory, Human Exposure and Atmospheric 
Sciences Division, MD-D205-03, Research Triangle Park, NC 27711. 
http://www.epa.gov/ttn/amtic/criteria.html.
    (7) McElroy, F.F. Transfer Standards for the Calibration of 
Ambient Air Monitoring Analyzers for Ozone. EPA-600/4-79-056. U.S. 
Environmental Protection Agency, Research Triangle Park, NC 27711, 
September, 1979. http://www.epa.gov/ttn/amtic/cpreldoc.html.
    (8) Paur, R.J. and F.F. McElroy. Technical Assistance Document 
for the Calibration of Ambient Ozone Monitors. EPA-600/4-79-057. 
U.S. Environmental Protection Agency, Research Triangle Park, NC 
27711, September, 1979. http://www.epa.gov/ttn/amtic/cpreldoc.html.
    (9) Quality Assurance Handbook for Air Pollution Measurement 
Systems, Volume 1--A Field Guide to Environmental Quality Assurance. 
EPA-600/R-94/038a. April 1994. Available from U.S. Environmental 
Protection Agency, ORD Publications Office, Center for Environmental 
Research Information (CERI), 26 W. Martin Luther King Drive, 
Cincinnati, OH 45268. http://www.epa.gov/ttn/amtic/qabook.html.
    (10) Quality Assurance Handbook for Air Pollution Measurement 
Systems, Volume II: Part 1--Ambient Air Quality Monitoring Program 
Quality System Development. EPA-454/R-98-004. http://www.epa.gov/ttn/amtic/qabook.html.

       Table A-1 of Appendix A to Part 58.--Difference and Similarities Between SLAMS and PSD Requirements
----------------------------------------------------------------------------------------------------------------
                 Topic                                 SLAMS                                 PSD
----------------------------------------------------------------------------------------------------------------
Requirements..........................  1. The development, documentation,
                                         and implementation of an approved
                                         quality system.
                                        2. The assessment of data quality.
                                        3. The use of reference,
                                         equivalent, or approved methods.
                                        4. The use of calibration standards
                                         traceable to NIST or other primary
                                         standard.
                                        5. The participation in EPA
                                         performance evaluations and the
                                         permission for EPA to conduct
                                         system audits.
Monitoring and QA Responsibility......  State/local agency via the           Source owner/operator.
                                         ``primary quality assurance
                                         organization''.
Monitoring Duration...................  Indefinitely.......................  Usually up to 12 months.
Annual Performance Evaluation (PE)....  Standards and equipment different    Personnel, standards and equipment
                                         from those used for spanning,        different from those used for
                                         calibration, and verifications.      spanning, calibration, and
                                         Prefer different personnel.          verifications.
PE audit rate:
    --Automated.......................  100% per year......................  100% per quarter.
    --Manual..........................  Varies depending on pollutant. See   100% per quarter.
                                         Table A-2 of this appendix.
Precision Assessment:
    --Automated.......................  One-point QC check biweekly but      One point QC check biweekly.
                                         data quality dependent.

[[Page 2792]]

 
    --Manual..........................  Varies depending on pollutant. See   One site: 1 every 6 days or every
                                         Table A-2 of this appendix.          third day for daily monitoring
                                                                              (TSP and Pb).
Reporting:
    --Automated.......................  By site--EPA performs calculations   By site--source owner/operator
                                         annually.                            performs calculations each
                                                                              sampling quarter.
    --Manual..........................  By reporting organization--EPA       By site--source owner/operator
                                         performs calculations annually.      performs calculations each
                                                                              sampling quarter.
----------------------------------------------------------------------------------------------------------------


            Table A-2 of Appendix A to Part 58.--Minimum Data Assessment Requirements for SLAMS Sites
----------------------------------------------------------------------------------------------------------------
                                   Assessment                            Minimum
            Method                   method           Coverage          frequency         Parameters reported
----------------------------------------------------------------------------------------------------------------
                                                Automated Methods
----------------------------------------------------------------------------------------------------------------
1-Point QC: for SO2, NO2, O3,   Response check    Each analyzer...  Once per 2 weeks  Audit concentration \1\
 CO.                             at                                                    and measured
                                 concentration                                         concentration \2\.
                                 0.01-0.1 ppm
                                 SO2, NO2, O3,
                                 and 1-10 ppm CO.
Performance Evaluation for      See section       Each analyzer...  Once per year...  Audit concentration \1\
 SO2, NO2, O3, CO.               3.2.2 of this                                         and measured
                                 appendix.                                             concentration \2\ for
                                                                                       each level.
Flow rate verification PM10,    Check of sampler  Each sampler....  Once every month  Audit flow rate and
 PM2.5, PM10-2.5.                flow rate.                                            measured flow rate
                                                                                       indicated by the sampler.
Semi-annual flow rate audit     Check of sampler  Each sampler....  Once every 6      Audit flow rate and
 PM10, PM2.5, PM10-2.5.          flow rate using                     months.           measured flow rate
                                 independent                                           indicated by the sampler.
                                 standard.
Collocated Sampling PM2.5,      Collocated        15%.............  Every twelve      Primary sampler
 PM10-2.5.                       samplers.                           days.             concentration and
                                                                                       duplicate sampler
                                                                                       concentration.
Performance Evaluation PM2.5,   Collocated        1. 5 valid        over all 4        Primary sampler
 PM10-2.5.                       samplers.         audits for        quarters.         concentration and
                                                   primary QA                          performance evaluation
                                                   orgs, with <=5                      sampler concentration.
                                                   sites.
                                                  2. 8 valid
                                                   audits for
                                                   primary QA
                                                   orgs, with >5
                                                   sites..
                                                  3. All samplers
                                                   in 6 years..
-------------------------------
                                                 Manual Methods
----------------------------------------------------------------------------------------------------------------
Collocated Sampling PM10, TSP,  Collocated        15%.............  Every 12 days,    Primary sampler
 PM10-2.5, PM2.5,.               samplers.                           TSP--every 6      concentration and
                                                                     days.             duplicate sampler
                                                                                       concentration.
Flow rate verification PM10,    Check of sampler  Each sampler....  Once every month  Audit flow rate and
 TSP, PM10-2.5 PM2.5.            flow rate.                                            measured flow rate
                                                                                       indicated by the sampler.
Semi-annual flow rate audit     Check of sampler  Each sampler,      Once every 6     Audit flow rate and
 PM10, TSP, PM10-2.5 PM2.5.      flow rate using   all locations.    months.           measured flow rate
                                 independent                                           indicated by the sampler.
                                 standard.
Manual Methods Lead...........  1. Check of       1. Each sampler.  1. Include with   1. Same as for TSP.
                                 sample flow                         TSP.
                                 rate as for TSP.
                                2. Check of       2. Analytical     2. Each quarter.  2. Actual concentration
                                 analytical        system.                             and measured (indicated)
                                 system with Pb                                        concentration of audit
                                 audit strips.                                         samples ([mu]g Pb/strip).
Performance Evaluation PM2.5,   Collocated        1. 5 valid        Over all 4        Primary sampler
 PM10-2.5.                       samplers.         audits for        quarters.         concentration and
                                                   primary QA                          performance evaluation
                                                   orgs, with <=5                      sampler concentration.
                                                   sites..
                                                  2. 8 valid
                                                   audits for
                                                   primary QA
                                                   orgs, with >=5
                                                   sites..
                                                  3. All samplers
                                                   in 6 years..
----------------------------------------------------------------------------------------------------------------
\1\ Effective concentration for open path analyzers.
\2\ Corrected concentration, if applicable, for open path analyzers.


[[Page 2793]]


     Table A-3 to Appendix A of Part 58.--Summary of PM2.5 or PM10-2.5. Number and Type of Collocation (15%
 Collocation Requirement) Needed as an Example of a Primary Quality Assurance Organization That Has 54 Monitors
                            and Procured FRMs and Three Other Equivalent Method Types
----------------------------------------------------------------------------------------------------------------
                                                                                                    Number of
                                                                                                   collocated
                                           Total number of    Total number        Number of     monitors of same
   Primary sampler method designation         monitors         collocated      collocated FRM        method
                                                                                                 designation as
                                                                                                     primary
----------------------------------------------------------------------------------------------------------------
FRM.....................................                20                 3                 3               N/A
FEM (A).................................                20                 3                 2                 1
FEM (C).................................                 2                 1                 1                 0
FEM (D).................................                12                 2                 1                 1
----------------------------------------------------------------------------------------------------------------

    50. Appendix C is revised to read as follows:

Appendix C to Part 58--Ambient Air Quality Monitoring Methodology

    1.0 Purpose.
    2.0 SLAMS Ambient Air Monitoring Stations.
    3.0 NCore Ambient Air Monitoring Stations.
    4.0 Photochemical Assessment Monitoring Stations (PAMS).
    5.0 Particulate Matter Episode Monitoring.
    6.0 References.

    1.0 Purpose.
    This appendix specifies the criteria pollutant monitoring 
methods (manual methods or automated analyzers) which must be used 
in the State and local air monitoring stations (SLAMS) and the 
National Core (NCore) stations that are a subset of SLAMS.
    2.0 SLAMS Ambient Air Monitoring Network.
    2.1 Except as otherwise provided in this appendix, a criteria 
pollutant monitoring method used for making NAAQS decisions at a 
SLAMS site must be a reference or equivalent method as defined in 
Sec.  50.1 of this chapter.
    2.2 Through December 31, 2012, data produced from any 
PM10 method approved under part 53 of this chapter may be 
used in lieu of a required PM10-2.5 monitor to determine 
attainment of the PM10-2.5 NAAQS according to the 
following stipulations.
    2.2.1 At any sites proposed for monitoring in lieu of 
PM10-2.5 monitoring, the 98th percentile value for the 
most recent complete calendar year of PM10 monitoring 
data must be less than the PM10-2.5 NAAQS, based on a 
sample frequency of at least 1 in 3 sample days, and reported at 
local conditions of temperature and pressure.
    2.2.2 PM10 data used in lieu of required 
PM10-2.5 monitoring must be based on a daily sampling 
frequency.
    2.2.3 During any calendar year of sampling in lieu of a required 
PM10-2.5 sampler, if more than seven 24-hour average 
PM10 concentrations exceed the numerical value of the 
PM10-2.5 NAAQS, as reported at local conditions of 
temperature and pressure, the State must deploy a Federal reference 
method (FRM) or Federal equivalent method (FEM) PM10-2.5 
monitor within a 1-year period.
    2.3 Any manual method or analyzer purchased prior to 
cancellation of its reference or equivalent method designation under 
Sec.  53.11 or Sec.  53.16 of this chapter may be used at a SLAMS 
site following cancellation for a reasonable period of time to be 
determined by the Administrator.
    2.4 Approval of Non-designated Continuous PM2.5 
Methods as Approved Regional Methods (ARM) Operated Within a Network 
of Sites. A method for PM2.5 that has not been designated 
as an FRM or FEM as defined in Sec.  50.1 of this chapter may be 
approved as an approved regional method (ARM) for purposes of 
section 2.1 of this appendix at a particular site or network of 
sites under the following stipulations.
    2.4.1 The candidate ARM must be demonstrated to meet the 
requirements for PM2.5 Class III equivalent methods as 
defined in subpart C of part 53 of this chapter. Specifically the 
requirements for precision, correlation, and additive and 
multiplicative bias apply. For purposes of this section 2.4, the 
following requirements shall apply:
    2.4.1.1 The candidate ARM shall be tested at the site(s) in 
which it is intended to be used. For a network of sites operated by 
one reporting agency, the testing shall occur at a subset of sites 
to include one site in each MSA/CSA, up to the first 2 highest 
population MSA/CSA and at least one rural area or Micropolitan 
Statistical Area site. If the candidate ARM for a network is already 
approved for purposes of this section in another agency's network, 
subsequent testing shall minimally occur at one site in a MSA/CSA 
and one rural area or Micropolitan Statistical Area. There shall be 
no requirement for tests at any other sites.
    2.4.1.2 For purposes of this section, a full year of testing may 
begin and end in any season, so long as all seasons are covered.
    2.4.1.3 No PM10 samplers shall be required for the 
test, as determination of the PM2.5/PM10 ratio 
at the test site shall not be required.
    2.4.1.4 The test specification for PM2.5 Class III 
equivalent method precision defined in subpart C of part 53 of this 
chapter applies; however, there is no specific requirement that 
collocated continuous monitors be operated for purposes of 
generating a statistic for coefficient of variation (CV). To provide 
an estimate of precision that meets the requirement identified in 
subpart C of part 53 of this chapter, agencies may cite peer-
reviewed published data or data in AQS that can be presented 
demonstrating the candidate ARM operated will produce data that 
meets the specification for precision of Class III PM2.5 
methods.
    2.4.1.5 A minimum of 90 valid sample pairs per site for the year 
with no less than 20 valid sample pairs per season must be generated 
for use in demonstrating that additive bias, multiplicative bias and 
correlation meet the comparability requirements specified in subpart 
C of part 53 of this chapter. A valid sample pair may be generated 
with as little as one valid FRM and one valid candidate ARM 
measurement per day.
    2.4.1.6 For purposes of determining bias, FRM data with 
concentrations less than 3 micrograms per cubic meter [mu]g/
m3) may be excluded. Exclusion of data does not result in 
failure of sample completeness specified in this section.
    2.4.2 The monitoring agency wishing to use an ARM must develop 
and implement appropriate quality assurance procedures for the 
method. Additionally, the following procedures are required for the 
method:
    2.4.2.1 The ARM must be consistently operated throughout the 
network. Exceptions to a consistent operation must be approved 
according to section 2.8 of this appendix;
    2.4.2.2 The ARM must be operated on an hourly sampling frequency 
capable of providing data suitable for aggregation into daily 24-
hour average measurements;
    2.4.2.3 The ARM must use an inlet and separation device, as 
needed, that are already approved in either the reference method 
identified in appendix L to part 50 of this chapter or under part 53 
of this chapter as approved for use on a PM2.5 reference 
or equivalent method. The only exceptions to this requirement are 
those methods that by their inherent measurement principle may not 
need an inlet or separation device that segregates the aerosol; and
    2.4.2.4 The ARM must be capable of providing for flow audits, 
unless by its inherent measurement principle, measured flow is not 
required. These flow audits are to be performed on the frequency 
identified in appendix A to this part.
    2.4.3 The monitoring agency wishing to use the method must 
develop and implement appropriate procedures for assessing and 
reporting the precision and accuracy of the method comparable to the 
procedures set forth in appendix A of this part for designated 
reference and equivalent methods.
    2.4.4 Assessments of data quality shall follow the same 
frequencies and calculations

[[Page 2794]]

as required under section 3 of appendix A to this part with the 
following exceptions:
    2.4.4.1 Collocation of ARM with FRM/FEM samplers must be 
maintained at a minimum of 30 percent of the SLAMS sites with a 
minimum of 1 per network;
    2.4.4.2 All collocated FRM/FEM samplers must maintain a sample 
frequency of at least 1 in 6 sample days;
    2.4.4.3 Collocated FRM/FEM samplers shall be located at the 
design value site, with the required FRM/FEM samplers deployed among 
the largest MSA/CSA in the network, until all required FRM/FEM are 
deployed; and
    2.4.4.4 Data from collocated FRM/FEM are to be substituted for 
any calendar quarter that an ARM method has incomplete data.
    2.4.4.5 Collocation with an ARM under this part for purposes of 
determining the coefficient of variation of the method shall be 
conducted at a minimum of 7.5 percent of the sites with a minimum of 
1 per network. This is consistent with the requirements in appendix 
A to this part for one-half of the required collocation of FRM/FEM 
(15 percent) to be collocated with the same method.
    2.4.4.6 Assessments of bias with an independent audit of the 
total measurement system shall be conducted with the same frequency 
as an FEM as identified in appendix A to this part.
    2.4.5 Request for approval of a candidate ARM, that is not 
already approved in another agency's network under this section, 
must meet the general submittal requirements of section 2.7 of this 
appendix. Requests for approval under this section when an ARM is 
already approved in another agency's network are to be submitted to 
the EPA Regional Administrator. Requests for approval under section 
2.4 of this appendix must include the following requirements:
    2.4.5.1 A clear and unique description of the site(s) at which 
the candidate ARM will be used and tested, and a description of the 
nature or character of the site and the particulate matter that is 
expected to occur there.
    2.4.5.2 A detailed description of the method and the nature of 
the sampler or analyzer upon which it is based.
    2.4.5.3 A brief statement of the reason or rationale for 
requesting the approval.
    2.4.5.4 A detailed description of the quality assurance 
procedures that have been developed and that will be implemented for 
the method.
    2.4.5.5 A detailed description of the procedures for assessing 
the precision and accuracy of the method that will be implemented 
for reporting to AQS.
    2.4.5.6 Test results from the comparability tests as required in 
section 2.4.1 through 2.4.1.4 of this appendix.
    2.4.5.7 Such further supplemental information as may be 
necessary or helpful to support the required statements and test 
results.
    2.4.6 Within 120 days after receiving a request for approval of 
the use of an ARM at a particular site or network of sites under 
section 2.4 of this appendix, the Administrator will approve or 
disapprove the method by letter to the person or agency requesting 
such approval. When appropriate for methods that are already 
approved in another SLAMS network, the EPA Regional Administrator 
has approval/disapproval authority. In either instance, additional 
information may be requested to assist with the decision.
    2.5 [Reserved]
    2.6 Use of Methods With Higher, Nonconforming Ranges in Certain 
Geographical Areas.
    2.6.1 [Reserved]
    2.6.2 An analyzer may be used (indefinitely) on a range which 
extends to concentrations higher than two times the upper limit 
specified in table B-1 of part 53 of this chapter if:
    2.6.2.1 The analyzer has more than one selectable range and has 
been designated as a reference or equivalent method on at least one 
of its ranges, or has been approved for use under section 2.5 (which 
applies to analyzers purchased before February 18, 1975);
    2.6.2.2 The pollutant intended to be measured with the analyzer 
is likely to occur in concentrations more than two times the upper 
range limit specified in table B-1 of part 53 of this chapter in the 
geographical area in which use of the analyzer is proposed; and
    2.6.2.3 The Administrator determines that the resolution of the 
range or ranges for which approval is sought is adequate for its 
intended use. For purposes of this section (2.6), ``resolution'' 
means the ability of the analyzer to detect small changes in 
concentration.
    2.6.3 Requests for approval under section 2.6.2 of this appendix 
must meet the submittal requirements of section 2.7. Except as 
provided in section 2.7.3 of this appendix, each request must 
contain the information specified in section 2.7.2 in addition to 
the following:
    2.6.3.1 The range or ranges proposed to be used;
    2.6.3.2 Test data, records, calculations, and test results as 
specified in section 2.7.2.2 of this appendix for each range 
proposed to be used;
    2.6.3.3 An identification and description of the geographical 
area in which use of the analyzer is proposed;
    2.6.3.4 Data or other information demonstrating that the 
pollutant intended to be measured with the analyzer is likely to 
occur in concentrations more than two times the upper range limit 
specified in table B-1 of part 53 of this chapter in the 
geographical area in which use of the analyzer is proposed; and
    2.6.3.5 Test data or other information demonstrating the 
resolution of each proposed range that is broader than that 
permitted by section 2.5 of this appendix.
    2.6.4 Any person who has obtained approval of a request under 
this section (2.6.2) shall assure that the analyzer for which 
approval was obtained is used only in the geographical area 
identified in the request and only while operated in the range or 
ranges specified in the request.
    2.7 Requests for Approval; Withdrawal of Approval.
    2.7.1 Requests for approval under sections 2.4, 2.6.2, or 2.8 of 
this appendix must be submitted to: Director, National Exposure 
Research Laboratory, (MD-D205-03), U.S. Environmental Protection 
Agency, Research Triangle Park, North Carolina 27711. For ARM that 
are already approved in another agency's network, subsequent 
requests for approval under section 2.4 are to be submitted to the 
applicable EPA Regional Administrator.
    2.7.2 Except as provided in section 2.7.3 of this appendix, each 
request must contain:
    2.7.2.1 A statement identifying the analyzer (e.g., by serial 
number) and the method of which the analyzer is representative 
(e.g., by manufacturer and model number); and 2.7.2.2 Test data, 
records, calculations, and test results for the analyzer (or the 
method of which the analyzer is representative) as specified in 
subpart B, subpart C, or both (as applicable) of part 53 of this 
chapter.
    2.7.3 A request may concern more than one analyzer or 
geographical area and may incorporate by reference any data or other 
information known to EPA from one or more of the following:
    2.7.3.1 An application for a reference or equivalent method 
determination submitted to EPA for the method of which the analyzer 
is representative, or testing conducted by the applicant or by EPA 
in connection with such an application;
    2.7.3.2 Testing of the method of which the analyzer is 
representative at the initiative of the Administrator under Sec.  
53.7 of this chapter; or
    2.7.3.3 A previous or concurrent request for approval submitted 
to EPA under this section (2.7).
    2.7.4 To the extent that such incorporation by reference 
provides data or information required by this section (2.7) or by 
sections 2.4, 2.5, or 2.6 of this appendix, independent data or 
duplicative information need not be submitted.
    2.7.5 After receiving a request under this section (2.7), the 
Administrator may request such additional testing or information or 
conduct such tests as may be necessary in his judgment for a 
decision on the request.
    2.7.6 If the Administrator determines, on the basis of any 
available information, that any of the determinations or statements 
on which approval of a request under this section was based are 
invalid or no longer valid, or that the requirements of section 2.4, 
2.5, or 2.6, as applicable, have not been met, he/she may withdraw 
the approval after affording the person who obtained the approval an 
opportunity to submit information and arguments opposing such 
action.
    2.8 Modifications of Methods by Users.
    2.8.1 Except as otherwise provided in this section, no reference 
method, equivalent method, or ARM may be used in a SLAMS network if 
it has been modified in a manner that could significantly alter the 
performance characteristics of the method without prior approval by 
the Administrator. For purposes of this section, ``alternative 
method'' means an analyzer, the use of which has been approved under 
section 2.4, 2.5, or 2.6 of this appendix or some combination 
thereof.
    2.8.2 Requests for approval under this section (2.8) must meet 
the submittal

[[Page 2795]]

requirements of sections 2.7.1 and 2.7.2.1 of this appendix.
    2.8.3 Each request submitted under this section (2.8) must 
include:
    2.8.3.1 A description, in such detail as may be appropriate, of 
the desired modification;
    2.8.3.2 A brief statement of the purpose(s) of the modification, 
including any reasons for considering it necessary or advantageous;
    2.8.3.3 A brief statement of belief concerning the extent to 
which the modification will or may affect the performance 
characteristics of the method; and
    2.8.3.4 Such further information as may be necessary to explain 
and support the statements required by sections 2.8.3.2 and 2.8.3.3.
    2.8.4 The Administrator will approve or disapprove the 
modification by letter to the person or agency requesting such 
approval within 75 days after receiving a request for approval under 
this section and any further information that the applicant may be 
asked to provide.
    2.8.5 A temporary modification that could alter the performance 
characteristics of a reference, equivalent, or ARM may be made 
without prior approval under this section if the method is not 
functioning or is malfunctioning, provided that parts necessary for 
repair in accordance with the applicable operation manual cannot be 
obtained within 45 days. Unless such temporary modification is later 
approved under section 2.8.4 of this appendix, the temporarily 
modified method shall be repaired in accordance with the applicable 
operation manual as quickly as practicable but in no event later 
than 4 months after the temporary modification was made, unless an 
extension of time is granted by the Administrator. Unless and until 
the temporary modification is approved, air quality data obtained 
with the method as temporarily modified must be clearly identified 
as such when submitted in accordance with Sec.  58.16 and must be 
accompanied by a report containing the information specified in 
section 2.8.3 of this appendix. A request that the Administrator 
approve a temporary modification may be submitted in accordance with 
sections 2.8.1 through 2.8.4 of this appendix. In such cases the 
request will be considered as if a request for prior approval had 
been made.
    2.9 Use of IMPROVE Samplers at a SLAMS Site. ``IMPROVE'' 
samplers may be used in SLAMS for monitoring of regional background 
and regional transport concentrations of fine particulate matter. 
The IMPROVE samplers were developed for use in the Interagency 
Monitoring of Protected Visual Environments (IMPROVE) network to 
characterize all of the major components and many trace constituents 
of the particulate matter that impair visibility in Federal Class I 
Areas. Descriptions of the IMPROVE samplers and the data they 
collect are available in references 4, 5, and 6 of this appendix.
    3.0 NCore Ambient Air Monitoring Stations.
    3.1 Methods employed in NCore multipollutant sites used to 
measure SO2, CO, NO2, O3, 
PM2.5, or PM10-2.5 must be reference or 
equivalent methods as defined in Sec.  50.1 of this chapter, or an 
ARM as defined in section 2.4 of this appendix, for any monitors 
intended for comparison with applicable NAAQS.
    3.2 If alternative SO2, CO, NO2, 
O3, PM2.5, or PM10-2.5 monitoring 
methodologies are proposed for monitors not intended for NAAQS 
comparison, such techniques must be detailed in the network 
description required by Sec.  58.10 and subsequently approved by the 
Administrator.
    4.0 Photochemical Assessment Monitoring Stations (PAMS).
    4.1 Methods used for O3 monitoring at PAMS must be 
automated reference or equivalent methods as defined in Sec.  50.1 
of this chapter.
    4.2 Methods used for NO, NO2 and NOX 
monitoring at PAMS should be automated reference or equivalent 
methods as defined for NO2 in Sec.  50.1 of this chapter. 
If alternative NO, NO2 or NOX monitoring 
methodologies are proposed, such techniques must be detailed in the 
network description required by Sec.  58.10 and subsequently 
approved by the Administrator.
    4.3 Methods for meteorological measurements and speciated VOC 
monitoring are included in the guidance provided in references 2 and 
3 of this appendix. If alternative VOC monitoring methodology 
(including the use of new or innovative technologies), which is not 
included in the guidance, is proposed, it must be detailed in the 
network description required by Sec.  58.10 and subsequently 
approved by the Administrator.
    5.0 Particulate Matter Episode Monitoring.
    5.1 For short-term measurements of PM10 during air 
pollution episodes (see Sec.  51.152 of this chapter) the 
measurement method must be:
    5.1.1 Either the ``Staggered PM10'' method or the 
``PM10 Sampling Over Short Sampling Times'' method, both 
of which are based on the reference method for PM10 and 
are described in reference 1: or
    5.1.2 Any other method for measuring PM10:
    5.1.2.1 Which has a measurement range or ranges appropriate to 
accurately measure air pollution episode concentration of 
PM10,
    5.1.2.2 Which has a sample period appropriate for short-term 
PM10 measurements, and 5.1.2.3 For which a quantitative 
relationship to a reference or equivalent method for PM10 
has been established at the use site. Procedures for establishing a 
quantitative site-specific relationship are contained in reference 
1.
    5.2 PM10 methods other than the reference method are 
not covered under the quality assessment requirements of appendix A 
to this part. Therefore, States must develop and implement their own 
quality assessment procedures for those methods allowed under this 
section 4. These quality assessment procedures should be similar or 
analogous to those described in section 3 of appendix A to this part 
for the PM10 reference method.
    6.0 References.
    1. Pelton, D. J. Guideline for Particulate Episode Monitoring 
Methods, GEOMET Technologies, Inc., Rockville, MD. Prepared for U.S. 
Environmental Protection Agency, Research Triangle Park, NC. EPA 
Contract No. 68-02-3584. EPA 450/4-83-005. February 1983.
    2. Technical Assistance Document For Sampling and Analysis of 
Ozone Precursors. Atmospheric Research and Exposure Assessment 
Laboratory, U.S. Environmental Protection Agency, Research Triangle 
Park, NC 27711. EPA 600/8-91-215. October 1991.
    3. Quality Assurance Handbook for Air Pollution Measurement 
Systems: Volume IV. Meteorological Measurements. Atmospheric 
Research and Exposure Assessment Laboratory, U.S. Environmental 
Protection Agency, Research Triangle Park, NC 27711. EPA 600/4-90-
0003. August 1989.
    4. Eldred, R.A., Cahill, T.A., Wilkenson, L.K., et al., 
Measurements of fine particles and their chemical components in the 
IMPROVE/NPS networks, in Transactions of the International Specialty 
Conference on Visibility and Fine Particles, Air and Waste 
Management Association: Pittsburgh, PA, 1990; pp 187-196.
    5. Sisler, J.F., Huffman, D., and Latimer, D.A.; Spatial and 
temporal patterns and the chemical composition of the haze in the 
United States: An analysis of data from the IMPROVE network, 1988-
1991, ISSN No. 0737-5253-26, National Park Service, Ft. Collins, CO, 
1993.
    6. Eldred, R.A., Cahill, T.A., Pitchford, M., and Malm, W.C.; 
IMPROVE--a new remote area particulate monitoring system for 
visibility studies, Proceedings of the 81st Annual Meeting of the 
Air Pollution Control Association, Dallas, Paper 88-54.3, 1988.

    51. Appendix D to part 58 is revised to read as follows:

Appendix D to Part 58--Network Design Criteria for Ambient Air Quality 
Monitoring

    1. Monitoring Objectives and Spatial Scales.
    2. General Monitoring Requirements.
    3. Design Criteria for NCore Sites.
    4. Pollutant-Specific Design Criteria for SLAMS Sites.
    5. Design Criteria for Photochemical Assessment Monitoring 
Stations (PAMS).
    6. References.
    1. Monitoring Objectives and Spatial Scales.
    The purpose of this appendix is to describe monitoring 
objectives and general criteria to be applied in establishing the 
required SLAMS ambient air quality monitoring stations and for 
choosing general locations for additional monitoring sites. This 
appendix also describes specific requirements for the number and 
location of FRM, FEM, and ARM sites for specific pollutants, NCore 
multipollutant sites, PM10-2.5 mass sites, chemically-
speciated PM10-2.5 sites, continuous PM2.5 
mass sites, chemically-speciated PM2.5 sites, and 
O3 precursor measurements sites (PAMS). These criteria 
will be used by EPA in evaluating the adequacy of the air pollutant 
monitoring networks.
    1.1 Monitoring Objectives. The ambient air monitoring networks 
must be designed to

[[Page 2796]]

meet three basic monitoring objectives. These basic objectives are 
listed below. The appearance of any one objective in the order of 
this list is not based upon a prioritized scheme. Each objective is 
important and must be considered individually.
    (a) Provide air pollution data to the general public in a timely 
manner. Data can be presented to the public in a number of 
attractive ways including through air quality maps, newspapers, 
Internet sites, and as part of weather forecasts and public 
advisories.
    (b) Support compliance with ambient air quality standards and 
emissions strategy development. Data from FRM, FEM, and ARM monitors 
will be used for comparing an area's air pollution levels against 
the National Ambient Air Quality Standards (NAAQS). Data from 
monitors of various types can be used in the development of 
attainment and maintenance plans. SLAMS, and especially NCore 
station data, will be used to evaluate the regional air quality 
models used in developing emission strategies, and to track trends 
in air pollution abatement control measures' impact on improving air 
quality. In monitoring locations near major air pollution sources, 
source-oriented monitoring data can provide insight into how well 
industrial sources are controlling their pollutant emissions.
    (c) Support for air pollution research studies. Air pollution 
data from the NCore network can be used to supplement data collected 
by researchers working on health effects assessments and atmospheric 
processes, or for monitoring methods development work.
    1.1.1 In order to support the air quality management work 
indicated in the three basic air monitoring objectives, a network 
must be designed with a variety of types of monitoring sites. 
Monitoring sites must be capable of informing managers about many 
things including the peak air pollution levels, typical levels in 
populated areas, air pollution transported into and outside of a 
city or region, and air pollution levels near specific sources. To 
summarize some of these sites, here is a listing of six general site 
types:
    (a) Sites located to determine the highest concentrations 
expected to occur in the area covered by the network.
    (b) Sites located to measure typical concentrations in areas of 
high population density.
    (c) Sites located to determine the impact of significant sources 
or source categories on air quality.
    (d) Sites located to determine general background concentration 
levels.
    (e) Sites located to determine the extent of Regional pollutant 
transport among populated areas; and in support of secondary 
standards.
    (f) Sites located to measure air pollution impacts on 
visibility, vegetation damage, or other welfare-based impacts.
    1.1.2 This appendix contains criteria for the basic air 
monitoring requirements. The total number of monitoring sites that 
will serve the variety of data needs will be substantially higher 
than these minimum requirements provide. The optimum size of a 
particular network involves trade-offs among data needs and 
available resources. This regulation intends to provide for national 
air monitoring needs, and to lend support for the flexibility 
necessary to meet data collection needs of area air quality 
managers. EPA, State, and local agencies will periodically 
collaborate on network design issues through the network assessment 
process outlined in Sec.  58.10.
    1.1.3 This appendix focuses on the relationship between 
monitoring objectives, site types, and the geographic location of 
monitoring sites. Included are a rationale and set of general 
criteria for identifying candidate site locations in terms of 
physical characteristics which most closely match a specific 
monitoring objective. The criteria for more specifically locating 
the monitoring site, including spacing from roadways and vertical 
and horizontal probe and path placement, are described in appendix E 
to this part.
    1.2 Spatial Scales. (a) To clarify the nature of the link 
between general monitoring objectives, site types, and the physical 
location of a particular monitor, the concept of spatial scale of 
representativeness is defined. The goal in locating monitors is to 
correctly match the spatial scale represented by the sample of 
monitored air with the spatial scale most appropriate for the 
monitoring site type, air pollutant to be measured, and the 
monitoring objective.
    (b) Thus, spatial scale of representativeness is described in 
terms of the physical dimensions of the air parcel nearest to a 
monitoring site throughout which actual pollutant concentrations are 
reasonably similar. The scales of representativeness of most 
interest for the monitoring site types described above are as 
follows:
    (1) Microscale--defines the concentrations in air volumes 
associated with area dimensions ranging from several meters up to 
about 100 meters.
    (2) Middle scale--defines the concentration typical of areas up 
to several city blocks in size with dimensions ranging from about 
100 meters to 0.5 kilometer.
    (3) Neighborhood scale--defines concentrations within some 
extended area of the city that has relatively uniform land use with 
dimensions in the 0.5 to 4.0 kilometers range. The neighborhood and 
urban scales listed below have the potential to overlap in 
applications that concern secondarily formed or homogeneously 
distributed air pollutants.
    (4) Urban scale--defines concentrations within an area of city-
like dimensions, on the order of 4 to 50 kilometers. Within a city, 
the geographic placement of sources may result in there being no 
single site that can be said to represent air quality on an urban 
scale.
    (5) Regional scale--defines usually a rural area of reasonably 
homogeneous geography without large sources, and extends from tens 
to hundreds of kilometers.
    (6) National and global scales--these measurement scales 
represent concentrations characterizing the nation and the globe as 
a whole.
    (c) Proper siting of a monitor requires specification of the 
monitoring objective, the types of sites necessary to meet the 
objective, and then the desired spatial scale of representativeness. 
For example, consider the case where the objective is to determine 
NAAQS compliance by understanding the maximum ozone concentrations 
for an area. Such areas would most likely be located downwind of a 
metropolitan area, quite likely in a suburban residential area where 
children and other susceptible individuals are likely to be 
outdoors. Sites located in these areas are most likely to represent 
an urban scale of measurement. In this example, physical location 
was determined by considering ozone precursor emission patterns, 
public activity, and meteorological characteristics affecting ozone 
formation and dispersion. Thus, spatial scale of representativeness 
was not used in the selection process but was a result of site 
location.
    (d) In some cases, the physical location of a site is determined 
from joint consideration of both the basic monitoring objective and 
the type of monitoring site desired, or required by this appendix. 
For example, to determine PM2.5 concentrations which are 
typical over a geographic area having relatively high 
PM2.5 concentrations, a neighborhood scale site is more 
appropriate. Such a site would likely be located in a residential or 
commercial area having a high overall PM2.5 emission 
density but not in the immediate vicinity of any single dominant 
source. Note that in this example, the desired scale of 
representativeness was an important factor in determining the 
physical location of the monitoring site.
    (e) In either case, classification of the monitor by its type 
and spatial scale of representativeness is necessary and will aid in 
interpretation of the monitoring data for a particular monitoring 
objective (e.g., public reporting, NAAQS compliance, or research 
support).
    (f) Table D-1 of this appendix illustrates the relationship 
between the various site types that can be used to support the three 
basic monitoring objectives, and the scales of representativeness 
that are generally most appropriate for that type of site.

Table D-1 of Appendix D to Part 58.--Relationship Between Site Types and
                      Scales of Representativeness
------------------------------------------------------------------------
               Site type                    Appropriate siting scales
------------------------------------------------------------------------
1. Highest concentration...............  Micro, middle, neighborhood
                                          (sometimes urban or regional
                                          for secondarily formed
                                          pollutants).
2. Population oriented.................  Neighborhood, urban.
3. Source impact.......................  Micro, middle, neighborhood.

[[Page 2797]]

 
4. General/background & regional         Urban, regional.
 transport.
5. Welfare-related impacts.............  Urban, regional.
------------------------------------------------------------------------

    2. General Monitoring Requirements.
    (a) The National ambient air monitoring system includes several 
types of monitoring stations, each targeting a key data collection 
need and each varying in technical sophistication.
    (b) Research grade sites are platforms for scientific studies, 
either involved with health or welfare impacts, measurement methods 
development, or other atmospheric studies. These sites may be 
collaborative efforts between regulatory agencies and researchers 
with specific scientific objectives for each. Data from these sites 
might be collected with both traditional and experimental 
techniques, and data collection might involve specific laboratory 
analyses not common in routine measurement programs. The research 
grade sites are not required by regulation; however, they are 
mentioned here due to their important role in supporting the air 
quality management program.
    (c) The NCore multipollutant sites are sites that measure 
multiple pollutants in order to provide support to integrated air 
quality management data needs. NCore sites include urban scale 
measurements in general, in a selection of metropolitan areas and a 
limited number of more rural locations. Continuous monitoring 
methods are to be used at the NCore sites when available for a 
pollutant to be measured, as it is important to have data collected 
over common time periods for integrated analyses. NCore 
multipollutant sites are intended to be long-term sites useful for a 
variety of applications including air quality trends analyses, model 
evaluation, and tracking metropolitan area statistics. As such, the 
NCore sites should be placed away from direct emission sources that 
could substantially impact the ability to detect area-wide 
concentrations. NCore sites will also supplement other SLAMS sites 
in reporting to the public in major metropolitan areas. It is not 
the intent of the NCore sites to monitor in every area where the 
NAAQS are violated, rather they provide only a subset of the total 
monitoring effort necessary to accomplish air quality management 
goals. The total number of monitoring sites that will serve the 
variety of national, State, and local governmental needs will be 
substantially higher than these NCore requirements. The 
Administrator must approve the NCore sites.
    (d) Monitoring sites designated as SLAMS sites, but not as NCore 
sites, are intended to address specific air quality management 
interests, and as such, are frequently single-pollutant measurement 
sites. The EPA Regional Administrator must approve the SLAMS sites.
    (e) This appendix uses the statistical-based definitions for 
metropolitan areas provided by the Office of Management and Budget 
and the Census Bureau. These areas are referred to as metropolitan 
statistical areas (MSA), micropolitan statistical areas, core-based 
statistical areas (CBSA), and combined statistical areas (CSA). A 
CBSA associated with at least one urbanized area of at least 50,000 
population is termed a Metropolitan Statistical Area. A CBSA 
associated with at least one urbanized cluster of at least 10,000 
population is termed a Micropolitan Statistical Area. CSA consist of 
two or more adjacent CBSA. In this appendix, the term MSA is used to 
refer to a Metropolitan Statistical Area. By definition, both MSA 
and CSA have a high degree of integration; however, many such areas 
cross State or other political boundaries. MSA and CSA may also 
cross more than one air shed. EPA recognizes that State or local 
agencies must consider MSA/CSA boundaries and their own political 
boundaries and geographical characteristics in designing their air 
monitoring networks. EPA recognizes that there may be situations 
where the EPA Regional Administrator and the affected State or local 
agencies may need to augment or to divide the overall MSA/CSA 
monitoring responsibilities and requirements among these various 
agencies to achieve an effective network design. Full monitoring 
requirements apply separately to each affected State or local agency 
in the absence of an agreement between the affected agencies and the 
EPA Regional Administrator.
    3. Design Criteria for NCore Sites.
    (a) Each State is required to operate one NCore site. States may 
delegate this requirement to a local agency. States with many MSA 
often also have multiple air sheds with unique characteristics and, 
often, elevated air pollution. These States include, at a minimum, 
California, Florida, Illinois, Michigan, New York, North Carolina, 
Ohio, Pennsylvania, and Texas. These States are required to identify 
one to two additional NCore sites in order to account for their 
unique situations. Any State or local agency can propose additional 
candidate NCore sites or modifications to these requirements for 
approval by the Administrator. The NCore locations should be 
leveraged with other multipollutant air monitoring sites including 
PAMS sites, NATTS sites, CASTNET sites, and STN sites. Site 
leveraging includes using the same monitoring platform and equipment 
to meet the objectives of the variety of programs where possible and 
advantageous.
    (b) The NCore sites must measure, at a minimum, PM2.5 
particle mass using continuous and integrated/filter-based samplers, 
speciated PM2.5, PM10-2.5 particle mass using 
continuous samplers, O3, SO2, CO, NO/
NOY wind speed, wind direction, relative humidity, and 
ambient temperature. EPA recognizes that, in some cases, the 
physical location of the NCore site may not be suitable for 
representative meteorological measurements due to the site's 
physical surroundings. It is also possible that nearby 
meteorological measurements may be able to fulfill this data need. 
In these cases, the requirement for meteorological monitoring can be 
waived by the Administrator.
    (c) In addition to the continuous measurements listed above, 10 
of the NCore locations (either at the same sites or elsewhere within 
the MSA/CSA boundary) must also measure lead (Pb). These ten Pb 
sites are included within the NCore networks because they are 
intended to be long-term in operation, and not impacted directly 
from a single lead source. These locations for Pb monitoring must be 
located in the most populated MSA/CSA in each of the 10 EPA Regions. 
Alternatively, it is also acceptable to use the Pb concentration 
data provided at urban air toxics sites. In approving any 
substitutions, the Administrator must consider whether these 
alternative sites are suitable for collecting long-term lead trends 
data for the broader area.
    4. Pollutant-Specific Design Criteria for SLAMS Sites.
    4.1 Ozone (O3) Design Criteria. (a) State, and where 
appropriate, local Agencies must operate O3 sites for 
various locations depending upon area size (in terms of population 
and geographic characteristics) and typical peak concentrations 
(expressed in percentages above, below, or near the O3 
NAAQS). Specific SLAMS O3 site minimum requirements are 
included in Table D-2 of this appendix. Typically, most of these 
required ozone sites will be SLAMS. The NCore sites are expected to 
compliment the O3 data collection that takes place at 
SLAMS sites, and both types of sites can be used to meet the network 
minimum requirements. The total number of O3 sites needed 
to support the basic monitoring objectives of public data reporting, 
air quality mapping, compliance, and understanding O3-
related atmospheric processes will include more sites than these 
minimum numbers required in Table D-2 of this appendix. The EPA 
Regional Administrator and the responsible State or local air 
monitoring agency must work together to design and/or maintain the 
most appropriate O3 network to service the variety of 
data needs in an area.

[[Page 2798]]



                  Table D-2 of Appendix D to Part 58.--SLAMS Minimum O3 Monitoring Requirements
----------------------------------------------------------------------------------------------------------------
                                                                               Most recent  3-
                                                             Most recent  3-     year design     Most recent  3-
                                                               year design          value          year design
              MSA or CSA population \3,\ \5\                      value        concentrations         value
                                                             concentrations    15%   concentrations
                                                             >115% of any O3   of any O3 NAAQS   <85% of any O3
                                                                NAAQS \1\            \1\         NAAQS \1,\ \2\
----------------------------------------------------------------------------------------------------------------
>10 million...............................................                 3                 4                 2
4-10 million..............................................                 2                 3                 1
1-4 million...............................................                 2                 2                 1
350,000-1 million.........................................                 2                 2                 1
200,000-350,000...........................................                 1                 1                 0
50,000-<200,000 \4\.......................................                 1                 1                0
----------------------------------------------------------------------------------------------------------------
\1\ The ozone (O3) National Ambient Air Quality Standards (NAAQS) levels and forms are defined in 40 CFR part
  50.
\2\ These minimum monitoring requirements apply in the absence of a design value.
\3\ Minimum monitoring requirements apply to the Combined statistical area (CSA) as a whole, if applicable.
\4\ Metropolitan statistical areas (MSA) must contain an urbanized area of 50,000 or more population.
\5\ Population based on latest available census figures.

    (b) At least one O3 site in each MSA/CSA's 
O3 network must be designed to record the maximum 
concentration for that particular metropolitan area. More than one 
maximum concentration site may be necessary in some areas. Table D-2 
of this appendix does not account for the full breadth of additional 
factors that would be considered in designing a complete ozone 
monitoring program for an area. Some of these additional factors 
include geographic size, population density, complexity of terrain 
and meteorology, adjacent ozone monitoring programs, air pollution 
transport from neighboring areas, and measured air quality in 
comparison to all forms of the O3 NAAQS (i.e., 8-hour and 
1-hour forms). Networks must be designed to account for all of these 
area characteristics. Network designs must be re-examined in 
periodic network assessments. Deviations from the above 
O3 requirements are allowed if approved by the EPA 
Regional Administrator.
    (c) The appropriate spatial scales for ozone sites are 
neighborhood, urban, and regional. Since ozone requires appreciable 
formation time, the mixing of reactants and products occurs over 
large volumes of air, and this reduces the importance of monitoring 
small scale spatial variability.
    (1) Neighborhood scale--Measurements in this category represent 
conditions throughout some reasonably homogeneous urban subregion, 
with dimensions of a few kilometers. Homogeneity refers to pollutant 
concentrations. Neighborhood scale data will provide valuable 
information for developing, testing, and revising concepts and 
models that describe urban/regional concentration patterns. These 
data will be useful to the understanding and definition of processes 
that take periods of hours to occur and hence involve considerable 
mixing and transport. Under stagnation conditions, a site located in 
the neighborhood scale may also experience peak concentration levels 
within a metropolitan area.
    (2) Urban scale--Measurement in this scale will be used to 
estimate concentrations over large portions of an urban area with 
dimensions of several kilometers to 50 or more kilometers. Such 
measurements will be used for determining trends, and designing 
area-wide control strategies. The urban scale sites would also be 
used to measure high concentrations downwind of the area having the 
highest precursor emissions.
    (3) Regional scale--This scale of measurement will be used to 
typify concentrations over large portions of a metropolitan area and 
even larger areas with dimensions of as much as hundreds of 
kilometers. Such measurements will be useful for assessing the ozone 
that is transported to and from a metropolitan area, as well as 
background concentrations. In some situations, particularly when 
considering very large metropolitan areas with complex source 
mixtures, regional scale sites can be the maximum concentration 
location.
    (d) EPA's technical guidance documents on ozone monitoring 
network design should be used to evaluate the adequacy of each 
existing O3 monitor, to relocate an existing site, or to 
locate any new O3 sites.
    (e) For locating a neighborhood scale site to measure typical 
city concentrations, a reasonably homogeneous geographical area near 
the center of the region should be selected which is also removed 
from the influence of major NOX sources. For an urban 
scale site to measure the high concentration areas, the emission 
inventories should be used to define the extent of the area of 
important nonmethane hydrocarbons and NOX emissions. The 
meteorological conditions that occur during periods of maximum 
photochemical activity should be determined. These periods can be 
identified by examining the meteorological conditions that occur on 
the highest ozone air quality days. Trajectory analyses, an 
evaluation of wind and emission patterns on high ozone days, can 
also be useful in evaluating an ozone monitoring network. In areas 
without any previous ozone air quality measurements, meteorological 
and ozone precursor emissions information would be useful.
    (f) Once the meteorological and air quality data are reviewed, 
the prospective maximum concentration monitor site should be 
selected in a direction from the city that is most likely to observe 
the highest ozone concentrations, more specifically, downwind during 
periods of photochemical activity. In many cases, these maximum 
concentration ozone sites will be located 10 to 30 miles or more 
downwind from the urban area where maximum ozone precursor emissions 
originate. The downwind direction and appropriate distance should be 
determined from historical meteorological data collected on days 
which show the potential for producing high ozone levels. Monitoring 
agencies are to consult with their EPA Regional Office when 
considering siting a maximum ozone concentration site.
    (g) In locating a neighborhood scale site which is to measure 
high concentrations, the same procedures used for the urban scale 
are followed except that the site should be located closer to the 
areas bordering on the center city or slightly further downwind in 
an area of high density population.
    (h) For regional scale background monitoring sites, similar 
meteorological analysis as for the maximum concentration sites may 
also inform the decisions for locating regional scale sites. 
Regional scale sites may be located to provide data on ozone 
transport between cities, as background sites, or for other data 
collection purposes. Consideration of both area characteristics, 
such as meteorology, and the data collection objectives, such as 
transport, must be jointly considered for a regional scale site to 
be useful.
    (i) Since ozone levels decrease significantly in the colder 
parts of the year in many areas, ozone is required to be monitored 
at SLAMS monitoring sites only during the ``ozone season'' as 
designated in the AQS files on a State-by-State basis and described 
below in Table D-3 of this appendix. Deviations from the ozone 
monitoring season must be approved by the EPA Regional 
Administrator, documented within the annual monitoring network plan, 
and updated in AQS. Information on how to analyze ozone data to 
support a change to the ozone season in support of the 8-hour 
standard for a specific State can be found in reference 8 to this 
appendix.

[[Page 2799]]



                      Table D-3 to Appendix D of Part 58.--Ozone Monitoring Season by State
----------------------------------------------------------------------------------------------------------------
                  State                              Begin month                          End month
----------------------------------------------------------------------------------------------------------------
Alabama.................................  March...........................  October.
Alaska..................................  April...........................  October.
Arizona.................................  January.........................  December.
Arkansas................................  March...........................  November.
California..............................  January.........................  December.
Colorado................................  March...........................  September.
Connecticut.............................  April...........................  September.
Delaware................................  April...........................  October.
District of Columbia....................  April...........................  October.
Florida.................................  March...........................  October.
Georgia.................................  March...........................  October.
Hawaii..................................  January.........................  December.
Idaho...................................  May.............................  September.
Illinois................................  April...........................  October.
Indiana.................................  April...........................  September.
Iowa....................................  April...........................  October.
Kansas..................................  April...........................  October.
Kentucky................................  March...........................  October.
Louisiana AQCR 019,022..................  March...........................  October.
Louisiana AQCR 106......................  January.........................  December.
Maine...................................  April...........................  September.
Maryland................................  April...........................  October.
Massachusetts...........................  April...........................  September.
Michigan................................  April...........................  September.
Minnesota...............................  April...........................  October.
Mississippi.............................  March...........................  October.
Missouri................................  April...........................  October.
Montana.................................  June............................  September.
Nebraska................................  April...........................  October.
Nevada..................................  January.........................  December.
New Hampshire...........................  April...........................  September.
New Jersey..............................  April...........................  October.
New Mexico..............................  January.........................  December.
New York................................  April...........................  October.
North Carolina..........................  April...........................  October.
North Dakota............................  May.............................  September.
Ohio....................................  April...........................  October.
Oklahoma................................  March...........................  November.
Oregon..................................  May.............................  September.
Pennsylvania............................  April...........................  October.
Puerto Rico.............................  January.........................  December.
Rhode Island............................  April...........................  September.
South Carolina..........................  April...........................  October.
South Dakota............................  June............................  September.
Tennessee...............................  March...........................  October.
Texas AQCR 106,153, 213, 214, 216.......  January.........................  December.
Texas AQCR 022, 210, 211, 212, 215, 217,  March...........................  October.
 218.
Utah....................................  May.............................  September.
Vermont.................................  April...........................  September.
Virginia................................  April...........................  October.
Washington..............................  May.............................  September.
West Virginia...........................  April...........................  October.
Wisconsin...............................  April 15........................  October 15.
Wyoming.................................  April...........................  October.
American Samoa..........................  January.........................  December.
Guam....................................  January.........................  December.
Virgin Islands..........................  January.........................  December.
----------------------------------------------------------------------------------------------------------------

    4.2 Carbon Monoxide (CO) Design Criteria. (a) There are no 
minimum requirements for the number of CO monitoring sites. 
Continued operation of existing SLAMS CO sites using FRM or FEM 
methods is required until discontinuation is approved by the EPA 
Regional Administrator. Where SLAMS CO monitoring is required, at 
least one site must be a maximum concentration site for that area 
under investigation.
    (b) Microscale and middle scale measurements are useful site 
classifications for SLAMS sites since most people have the potential 
for exposure on these scales. Carbon monoxide maxima occur primarily 
in areas near major roadways and intersections with high traffic 
density and often poor atmospheric ventilation.
    (1) Microscale--This scale applies when air quality measurements 
are to be used to represent distributions within street canyons, 
over sidewalks, and near major roadways. In the case with carbon 
monoxide, microscale measurements in one location can often be 
considered as representative of other similar locations in a city.
    (2) Middle scale--Middle scale measurements are intended to 
represent areas with dimensions from 100 meters to 0.5 kilometer. In 
certain cases, middle scale measurements may apply to areas that 
have a total length of several kilometers, such as ``line'' emission 
source areas. This type of emission sources areas would include air 
quality along a commercially developed

[[Page 2800]]

street or shopping plaza, freeway corridors, parking lots and feeder 
streets.
    (c) After the spatial scale and type of site has been determined 
to meet the monitoring objective for each location, the technical 
guidance in reference 2 of this appendix should be used to evaluate 
the adequacy of each existing CO site and must be used to relocate 
an existing site or to locate any new sites.
    4.3 Nitrogen Dioxide (NO2) Design Criteria. (a) There 
are no minimum requirements for the number of NO2 
monitoring sites. Continued operation of existing SLAMS 
NO2 sites using FRM or FEM methods is required until 
discontinuation is approved by the EPA Regional Administrator. Where 
SLAMS NO2 monitoring is required, at least one 
NO2 site in the area must be located to measure the 
maximum concentration of NO2.
    (b) NO/NOY measurements are included within the NCore 
multipollutant site requirements and the PAMS program. These NO/
NOY measurements will produce conservative estimates for 
NO2 that can be used to track continued compliance with 
the NO2 NAAQS. NO/NOY monitors are used at 
these sites because it is important to collect data on total 
reactive nitrogen species for understanding ozone photochemistry.
    4.4 Sulfur Dioxide (SO2) Design Criteria. (a) There 
are no minimum requirements for the number of SO2 
monitoring sites. Continued operation of existing SLAMS 
SO2 sites using FRM or FEM methods is required until 
discontinuation is approved by the EPA Regional Administrator. Where 
SLAMS SO2 monitoring is required, at least one of the 
SLAMS SO2 sites must be a maximum concentration site for 
that specific area.
    (b) The appropriate spatial scales for SO2 SLAMS 
monitoring are the microscale, middle, and possibly neighborhood 
scales. The multi-pollutant NCore sites can provide for metropolitan 
area trends analyses and general control strategy progress tracking. 
Other SLAMS sites are expected to provide data that are useful in 
specific compliance actions, for maintenance plan agreements, or for 
measuring near specific stationary sources of SO2.
    (1) Micro and middle scale--Some data uses associated with 
microscale and middle scale measurements for SO2 include 
assessing the effects of control strategies to reduce concentrations 
(especially for the 3-hour and 24-hour averaging times) and 
monitoring air pollution episodes.
    (2) Neighborhood scale--This scale applies where there is a need 
to collect air quality data as part of an ongoing SO2 
stationary source impact investigation. Typical locations might 
include suburban areas adjacent to SO2 stationary sources 
for example, or for determining background concentrations as part of 
these studies of population responses to exposure to SO2.
    (c) Technical guidance in reference 1 of this appendix should be 
used to evaluate the adequacy of each existing SO2 site, 
to relocate an existing site, or to locate new sites.
    4.5 Lead (Pb) Design Criteria. (a) State, and where appropriate, 
local agencies are required to conduct Pb monitoring for all areas 
where Pb levels have been shown or are expected to be of concern 
over the most recent 2 years. As a minimum, there must be two SLAMS 
sites in any area where Pb concentrations currently exceed or have 
exceeded the Pb NAAQS in the most recent 2 years, and at least one 
of these two required sites must be a maximum concentration site. 
Where the Pb air quality violations are widespread or the emissions 
density, topography, or population locations are complex and varied, 
the EPA Regional Administrator may require more than two Pb ambient 
air monitoring sites.
    (b) The most important spatial scales to effectively 
characterize the emissions from point sources are the micro, middle, 
and neighborhood scales.
    (1) Microscale--This scale would typify areas in close proximity 
to lead point sources. Emissions from point sources such as primary 
and secondary lead smelters, and primary copper smelters may under 
fumigation conditions likewise result in high ground level 
concentrations at the microscale. In the latter case, the microscale 
would represent an area impacted by the plume with dimensions 
extending up to approximately 100 meters. Data collected at 
microscale sites provide information for evaluating and developing 
``hot-spot'' control measures.
    (2) Middle scale--This scale generally represents Pb air quality 
levels in areas up to several city blocks in size with dimensions on 
the order of approximately 100 meters to 500 meters. The middle 
scale may for example, include schools and playgrounds in center 
city areas which are close to major Pb point sources. Pb monitors in 
such areas are desirable because of the higher sensitivity of 
children to exposures of elevated Pb concentrations (reference 3 of 
this appendix). Emissions from point sources frequently impact on 
areas at which single sites may be located to measure concentrations 
representing middle spatial scales.
    (3) Neighborhood scale--The neighborhood scale would 
characterize air quality conditions throughout some relatively 
uniform land use areas with dimensions in the 0.5 to 4.0 kilometer 
range. Sites of this scale would provide monitoring data in areas 
representing conditions where children live and play. Monitoring in 
such areas is important since this segment of the population is more 
susceptible to the effects of Pb. Where a neighborhood site is 
located away from immediate Pb sources, the site may be very useful 
in representing typical air quality values for a larger residential 
area, and therefore suitable for population exposure and trends 
analyses.
    (c) Technical guidance is found in references 4 and 5 of this 
appendix. These documents provide additional guidance on locating 
sites to meet specific urban area monitoring objectives and should 
be used in locating new sites or evaluating the adequacy of existing 
sites.
    4.6 Particulate Matter (PM10) Design Criteria. (a) 
There are no minimum requirements for the number of PM10 
monitoring sites. In areas where the PM10 NAAQS has not 
been revoked, continued operation of existing SLAMS PM10 
sites using FRM or FEM methods is required until discontinuation is 
approved by the EPA Regional Administrator. In areas for where the 
PM10 NAAQS has been revoked, there is no requirement for 
continued operation of existing sites.
    (b) The most important spatial scales to effectively 
characterize the emissions of PM10 from both mobile and 
stationary sources are the middle scales and neighborhood scales. 
For purposes of establishing monitoring sites to represent large 
homogenous areas other than the above scales of representativeness 
and to characterize regional transport, urban or regional scale 
sites would also be needed.
    (1) Microscale--This scale would typify areas such as downtown 
street canyons, traffic corridors, and fence line stationary source 
monitoring locations where the general public could be exposed to 
maximum PM10 concentrations. Microscale particulate 
matter sites should be located near inhabited buildings or locations 
where the general public can be expected to be exposed to the 
concentration measured. Emissions from stationary sources such as 
primary and secondary smelters, power plants, and other large 
industrial processes may, under certain plume conditions, likewise 
result in high ground level concentrations at the microscale. In the 
latter case, the microscale would represent an area impacted by the 
plume with dimensions extending up to approximately 100 meters. Data 
collected at microscale sites provide information for evaluating and 
developing hot spot control measures.
    (2) Middle scale--Much of the short-term public exposure to 
coarse fraction particles (PM10) is on this scale and on 
the neighborhood scale. People moving through downtown areas or 
living near major roadways or stationary sources, may encounter 
particulate pollution that would be adequately characterized by 
measurements of this spatial scale. Middle scale PM10 
measurements can be appropriate for the evaluation of possible 
short-term exposure public health effects. In many situations, 
monitoring sites that are representative of micro-scale or middle-
scale impacts are not unique and are representative of many similar 
situations. This can occur along traffic corridors or other 
locations in a residential district. In this case, one location is 
representative of a neighborhood of small scale sites and is 
appropriate for evaluation of long-term or chronic effects. This 
scale also includes the characteristic concentrations for other 
areas with dimensions of a few hundred meters such as the parking 
lot and feeder streets associated with shopping centers, stadia, and 
office buildings. In the case of PM10, unpaved or 
seldomly swept parking lots associated with these sources could be 
an important source in addition to the vehicular emissions 
themselves.
    (3) Neighborhood scale--Measurements in this category represent 
conditions throughout some reasonably homogeneous urban subregion 
with dimensions of a few kilometers and of generally more regular 
shape than the middle scale. Homogeneity refers to the particulate 
matter concentrations, as well as the land use and

[[Page 2801]]

land surface characteristics. In some cases, a location carefully 
chosen to provide neighborhood scale data would represent not only 
the immediate neighborhood but also neighborhoods of the same type 
in other parts of the city. Neighborhood scale PM10 sites 
provide information about trends and compliance with standards 
because they often represent conditions in areas where people 
commonly live and work for extended periods. Neighborhood scale data 
could provide valuable information for developing, testing, and 
revising models that describe the larger-scale concentration 
patterns, especially those models relying on spatially smoothed 
emission fields for inputs. The neighborhood scale measurements 
could also be used for neighborhood comparisons within or between 
cities.
    (4) Urban scale--This class of measurement would be made to 
characterize the particulate matter concentration over an entire 
metropolitan or rural area ranging in size from 4 to 50 kilometers. 
Such measurements would be useful for assessing trends in area-wide 
air quality, and hence, the effectiveness of large scale air 
pollution control strategies.
    (5) Regional scale--These measurements would characterize 
conditions over areas with dimensions of as much as hundreds of 
kilometers. As noted earlier, using representative conditions for an 
area implies some degree of homogeneity in that area. For this 
reason, regional scale measurements would be most applicable to 
sparsely populated areas. Data characteristics of this scale would 
provide information about larger scale processes of particulate 
matter emissions, losses and transport.
    4.7 Fine Particulate Matter (PM2.5) Design Criteria.
    4.7.1 General Requirements. (a) State, and where applicable 
local, agencies must operate the minimum number of required 
PM2.5 SLAMS sites listed in Table D-4 of this appendix. 
The NCore sites are expected to complement the PM2.5 data 
collection that takes place at non-NCore SLAMS sites, and both types 
of sites can be used to meet the minimum PM2.5 network 
requirements. Deviations from these PM2.5 monitoring 
requirements must be approved by the EPA Regional Administrator.

                   Table D-4 of Appendix D to Part 58.--PM2.5 Minimum Monitoring Requirements
----------------------------------------------------------------------------------------------------------------
                                                                                  Most recent  3-
                                                                  Most recent  3-   year design   Most recent  3-
                                                                    year design    value =115%    minus>15% of   value <=85% of
                                                                   of any PM2.5     PM2.5 NAAQS      any PM2.5
                                                                     NAAQS \1\          \1\          NAAQS1 2
----------------------------------------------------------------------------------------------------------------
> 1,000,000.....................................................               2               3               2
500,000-1,000,000...............................................               1               2               1
250,000-500,000.................................................               1               1               0
100,000-250,000.................................................               1               1               0
50,000-<100,000 \4\.............................................               1               1              0
----------------------------------------------------------------------------------------------------------------
\1\ The PM2.5 National Ambient Air Quality Standards (NAAQS) levels and forms are defined in 40 CFR part 50.
\2\ These minimum monitoring requirements apply in the absence of a design value.
\3\ Minimum monitoring requirements apply to the Combined statistical area (CSA) as a whole, where applicable.
\4\ Metropolitan statistical areas (MSA) must contain an urbanized area of 50,000 or more population.
\5\ Population based on latest available census figures.

    (b) The technical guidance in references 6 and 7 of this 
appendix should be used for siting PM2.5 monitors.
    (c) The most important spatial scale to effectively characterize 
the emissions of particulate matter from both mobile and stationary 
sources is the neighborhood scale for PM2.5. For purposes 
of establishing monitoring sites to represent large homogenous areas 
other than the above scales of representativeness and to 
characterize regional transport, urban or regional scale sites would 
also be needed. Most PM2.5 monitoring in urban areas 
should be representative of a neighborhood scale.
    (1) Microscale--This scale would typify areas such as downtown 
street canyons and traffic corridors where the general public would 
be exposed to maximum concentrations from mobile sources. In some 
circumstances, the microscale is appropriate for particulate sites; 
community-oriented SLAMS sites measured at the microscale level 
should, however, be limited to urban sites that are representative 
of long-term human exposure and of many such microenvironments in 
the area. In general, microscale particulate matter sites should be 
located near inhabited buildings or locations where the general 
public can be expected to be exposed to the concentration measured. 
Emissions from stationary sources such as primary and secondary 
smelters, power plants, and other large industrial processes may, 
under certain plume conditions, likewise result in high ground level 
concentrations at the microscale. In the latter case, the microscale 
would represent an area impacted by the plume with dimensions 
extending up to approximately 100 meters. Data collected at 
microscale sites provide information for evaluating and developing 
hot spot control measures. Unless these sites are indicative of 
population-oriented monitoring, they may be more appropriately 
classified as special purpose monitors (SPMs). Microscale 
PM2.5 sites would be excluded from comparison with the 
annual PM2.5 NAAQS in accordance with Sec.  58.30(a)(1).
    (2) Middle scale--People moving through downtown areas, or 
living near major roadways, encounter particle concentrations that 
would be adequately characterized by this spatial scale. Thus, 
measurements of this type would be appropriate for the evaluation of 
possible short-term exposure public health effects of particulate 
matter pollution. In many situations, monitoring sites that are 
representative of microscale or middle-scale impacts are not unique 
and are representative of many similar situations. This can occur 
along traffic corridors or other locations in a residential 
district. In this case, one location is representative of a number 
of small scale sites and is appropriate for evaluation of long-term 
or chronic effects. This scale also includes the characteristic 
concentrations for other areas with dimensions of a few hundred 
meters such as the parking lot and feeder streets associated with 
shopping centers, stadia, and office buildings.
    (3) Neighborhood scale--Measurements in this category would 
represent conditions throughout some reasonably homogeneous urban 
subregion with dimensions of a few kilometers and of generally more 
regular shape than the middle scale. Homogeneity refers to the 
particulate matter concentrations, as well as the land use and land 
surface characteristics. Much of the PM2.5 exposures are 
expected to be associated with this scale of measurement. In some 
cases, a location carefully chosen to provide neighborhood scale 
data would represent the immediate neighborhood as well as 
neighborhoods of the same type in other parts of the city. 
PM2.5 sites of this kind provide good information about 
trends and compliance with standards because they often represent 
conditions in areas where people commonly live and work for periods 
comparable to those specified in the NAAQS. In general, most 
PM2.5 monitoring in urban areas should have this scale.
    (4) Urban scale--This class of measurement would be used to 
characterize the particulate matter concentration over an entire 
metropolitan or rural area ranging in size from 4 to 50 kilometers. 
Such measurements would be useful for assessing trends in area-wide 
air quality, and hence, the effectiveness of large scale air 
pollution control strategies. Community-oriented PM2.5 
sites may have this scale.
    (5) Regional scale--These measurements would characterize 
conditions over areas with dimensions of as much as hundreds of 
kilometers. As noted earlier, using representative conditions for an 
area implies some degree of homogeneity in that area. For

[[Page 2802]]

this reason, regional scale measurements would be most applicable to 
sparsely populated areas. Data characteristics of this scale would 
provide information about larger scale processes of particulate 
matter emissions, losses and transport. PM2.5 transport 
contributes to elevated particulate concentrations and may affect 
multiple urban and State entities with large populations such as in 
the eastern United States. Development of effective pollution 
control strategies requires an understanding at regional 
geographical scales of the emission sources and atmospheric 
processes that are responsible for elevated PM2.5 levels 
and may also be associated with elevated ozone and regional haze.
    4.7.2 Requirement for Continuous PM2.5 Monitoring. 
State, or where appropriate, local agencies must operate continuous 
fine particulate analyzers at one-half (round up) of the minimum 
required sites listed in Table D-4 of this appendix. State and local 
air monitoring agencies must use methodologies and quality 
assurance/quality control (QA/QC) procedures approved by the EPA 
Regional Administrator for these sites.
    4.7.3 Requirement for PM2.5 Background and Transport 
Sites. Each State shall install and operate at least one 
PM2.5 site to monitor for regional background and at 
least one PM2.5 site to monitor regional transport. These 
monitoring sites may be at community-oriented sites and this 
requirement may be satisfied by a corresponding monitor in an area 
having similar air quality in another State. State and local air 
monitoring agencies must use methodologies and QA/QC procedures 
approved by the EPA Regional Administrator for these sites. Methods 
used at these sites may include non-federal reference method 
samplers such as IMPROVE or continuous PM2.5 monitors.
    4.7.4 PM2.5 Chemical Speciation Site Requirements. 
Each State shall continue to conduct chemical speciation monitoring 
and analyses at sites designated to be part of the PM2.5 
Speciation Trends Network (STN). The selection and modification of 
these STN sites must be approved by the Administrator. The 
PM2.5 chemical speciation urban trends sites shall 
include analysis for elements, selected anions and cations, and 
carbon. Samples must be collected using the monitoring methods and 
the sampling schedules approved by the Administrator. Chemical 
speciation is encouraged at additional sites where the chemically 
resolved data would be useful in developing State implementation 
plans and supporting atmospheric or health effects related studies.
    4.7.5 Special Network Considerations Required When Using 
PM2.5 Spatial Averaging Approaches. (a) The 
PM2.5 NAAQS, specified in 40 CFR 50, provides State and 
local air monitoring agencies with an option for spatially averaging 
PM2.5 air quality data. More specifically, two or more 
community-oriented (i.e., sites in populated areas) PM2.5 
monitors may be averaged for comparison with the annual 
PM2.5 NAAQS. This averaging approach is directly related 
to epidemiological studies used as the basis for the 
PM2.5 annual NAAQS. Spatial averaging does not apply to 
comparisons with the daily PM2.5 NAAQS.
    (b) State and local agencies must carefully consider their 
approach for PM2.5 network design when they intend to 
spatially average the data for compliance purposes. These State and 
local air monitoring agencies must define the area over which they 
intend to average PM2.5 air quality concentrations. This 
area is defined as a Community Monitoring Zone (CMZ), which 
characterizes an area of relatively similar annual average air 
quality. State and local agencies can define a CMZ in a number of 
ways, including as part or all of a metropolitan area. These CMZ 
must be defined within a State or local agencies network 
description, as required in Sec.  58.10 of this part and approved by 
the EPA Regional Administrator. When more than one CMZ is described 
within an agency's network design plan, CMZs must not overlap in 
their geographical coverage. The criteria that must be used for 
evaluating the acceptability of spatial averaging are defined in 
Appendix N of 40 CFR Part 50.
    4.8 Coarse Particulate Matter (PM10-2.5) Design 
Criteria.
    4.8.1 General Monitoring Requirements. (a) Consistent with the 
indicator for the proposed PM10-2.5 NAAQS, required 
PM10-2.5 monitoring will address areas where the mix of 
PM10-2.5 is dominated by resuspended dust from high-
density traffic on paved roads and PM generated by industrial 
sources and construction sources, and will not address areas where 
it is dominated by rural windblown dust and soils and PM generated 
by agricultural and mining sources.
    (b) State, and where applicable, local Agencies must operate, at 
a minimum, the number of required PM10-2.5 SLAMS sites 
listed in Table D-5 of this appendix. The minimum requirements of 
Table D-5 apply only to MSAs that contain all or part of an 
urbanized area with a population of at least 100,000 persons. NCore 
sites are expected to complement the PM10-2.5 data 
collection that takes place at SLAMS Sites. Data from urban NCore 
sites can be used to meet minimum PM10-2.5 network 
requirements if those sites meet the NAAQS comparability criteria in 
Sec.  58.30(b). Modifications from the PM10-2.5 
monitoring requirements must be approved by the Regional 
Administrator.

                  Table D-5 of Appendix D to Part 58.--PM10-2.5 Minimum Monitoring Requirements
----------------------------------------------------------------------------------------------------------------
                                                                  Most recent  3- Most recent  3- Most recent  3-
                                                                    year design     year design     year design
                       MSA population 1, 5                         value \2\ >=    value 50%-80%  value < 50% of
                                                                   80% of PM10-     of PM10-2.5   PM10-2.5 NAAQS
                                                                   2.5 NAAQS \3\     NAAQS 3 4          \3\
----------------------------------------------------------------------------------------------------------------
> 5,000,000.....................................................               5               3               2
1,000,000-< 5,000,000...........................................               4               2               1
500,000-< 1,000,000.............................................               3               1               0
100,000-< 500,000...............................................               2               1              0
----------------------------------------------------------------------------------------------------------------
\1\ Metropolitan Statistical Area (MSA) as defined by the Office of Management of Budget. The minimum
  requirements of this table apply only to MSAs that contain all or part of an urbanized area with a population
  of at least 100,000 persons. Multiple MSA in a Combined statistical area (CSA) are separately subject to these
  requirements based on their population and design value.
\2\ A database of estimated PM10-2.5 design values will be provided by EPA until the network is fully deployed
  for three years. States may propose alternate estimates for EPA Regional Administrator approval.
\3\ The PM10-2.5 National Ambient Air Quality Standards (NAAQS) levels and forms are defined in part 50 of this
  chapter.
\4\ These minimum monitoring requirements apply in the absence of a design value.
\5\ Population based on latest available census figures.

    (c) Middle and neighborhood scale measurements are the most 
important station classifications for PM10-2.5 to assess 
the variation in coarse particle concentrations that would be 
expected across populated areas that are in proximity to large 
emissions sources. Sites that represent larger spatial scales would 
characterize concentrations in the suburban, highly populated areas 
of larger MSA's that are more distant from the zones of most 
concentrated industrial activity.
    (1) Microscale--This scale would typify relatively small areas 
immediately adjacent to: Industrial sources; locations experiencing 
ongoing construction, redevelopment, and soil disturbance; and 
heavily traveled roadways. Data collected at microscale stations 
would characterize exposure over areas of limited spatial extent and 
population exposure, and may provide information useful for 
evaluating and developing source-oriented control measures. 
Microscale sites would be excluded from comparison with the NAAQS in 
accordance with Sec.  58.30(b)(4), and may be more appropriately 
classified as SPMs.
    (2) Middle scale--People living or working near major roadways 
or industrial districts encounter particle concentrations that would

[[Page 2803]]

be adequately characterized by this spatial scale. Thus, 
measurements of this type would be appropriate for the evaluation of 
public health effects of coarse particle exposure. Monitors located 
in populated areas that are nearly adjacent to large industrial 
point sources of coarse particles provide suitable locations for 
assessing maximum population exposure levels and identifying areas 
of potentially poor air quality. Similarly, monitors located in 
populated areas that border dense networks of heavily-traveled 
traffic are appropriate for assessing the impacts of resuspended 
road dust. This scale also includes the characteristic 
concentrations for other areas with dimensions of a few hundred 
meters such as school grounds and parks that are nearly adjacent to 
major roadways and industrial point sources, locations exhibiting 
mixed residential and commercial development, and downtown areas 
featuring office buildings, shopping centers, and stadiums.
    (3) Neighborhood scale--Measurements in this category would 
represent conditions throughout some reasonably homogeneous urban 
subregion with dimensions of a few kilometers and of generally more 
regular shape than the middle scale. Homogeneity refers to the 
particulate matter concentrations, as well as the land use and land 
surface characteristics. This category includes suburban 
neighborhoods dominated by residences that are somewhat distant from 
major roadways and industrial districts but still impacted by urban 
sources, and areas of diverse land use where residences are 
interspersed with commercial and industrial neighborhoods. In some 
cases, a location carefully chosen to provide neighborhood scale 
data would represent the immediate neighborhood as well as 
neighborhoods of the same type in other parts of the city. The 
comparison of data from middle scale and neighborhood scale sites 
would provide valuable information for determining the variation of 
PM10-2.5 levels across urban areas and assessing the 
spatial extent of elevated concentrations caused by major industrial 
point sources and heavily traveled roadways. Neighborhood scale 
sites would provide concentration data that are relevant to 
informing a large segment of the population of their exposure levels 
on a given day.
    4.8.2 PM10-2.5 Specific Siting Requirements.
    4.8.2.1 A minimum of 50 percent of the PM10-2.5 sites 
required in Table D-5 of this appendix must characterize middle 
scale-sized areas (values of 0.5 monitors and greater round up). 
Middle-scale sites must be situated in areas of expected maximum 
concentration among sites eligible for comparison to the NAAQS.
    4.8.2.2 For those areas with monitoring requirements greater 
than one required monitor, at least one of the required monitors 
must be at a population-oriented site in a neighborhood scale-sized 
area that is highly populated and which may be somewhat further away 
from emission sources than the required middle-scale sites, subject 
to the requirement that the site must meet the comparability 
criteria in Sec.  58.30(b). Among such sites, the State should 
select a site characterized by a large number of people subject to 
exposure; typically, this population number would be higher than the 
population at middle-scale sites expected to record maximum 
concentrations.
    4.8.2.3 For MSA's with a requirement for four or five monitors, 
the siting of the remaining unspecified monitor is left to the 
discretion of the State or local monitoring agency, subject to the 
requirement that the site must meet the comparability criteria in 
Sec.  58.30(b). This site could be placed in middle-scale or 
neighborhood scale locations similar to those that would be eligible 
as monitoring sites for the other required monitors. A State may 
also choose to place the site in a location that is somewhat more 
distant from downtown areas, main industrial source regions, or 
areas of highest traffic density, such as in a suburban residential 
community.
    4.8.3 PM10-2.5 Chemical Speciation Site Requirements. 
One chemical speciation monitoring site is required in each MSA with 
total population over 500,000 people that also has an estimated 
PM10-2.5 design value greater than 80% of the NAAQS. 
These sites will gather data in areas that have a higher probability 
of exceeding the proposed NAAQS and also have larger exposed 
populations at risk, and will support the characterization of coarse 
particles concentrations that control the attainment/nonattainment 
status of the area. Samples must be collected using monitoring 
methods and the sampling schedules approved by the EPA Regional 
Administrator. Chemical speciation is encouraged at additional sites 
to support development of State implementation plans and atmospheric 
or health effects related studies. These additional locations may 
include STN, NCore, CASTNET, and IMPROVE sites to provide coverage 
of sources typical of urban core locations, suburban regions 
typified by predominantly residential districts, and less densely-
settled rural locations that may be characterized by naturally 
occurring geologic materials. The selection and modification of 
PM10-2.5 chemical speciation sites must be approved by 
the EPA Regional Administrator.
    4.9 Filter Archive Requirements for PM2.5, 
PM10, and PM10-2.5. Air pollution control 
agencies shall archive PM2.5, PM10, and 
PM10-2.5 filters from all SLAMS sites for 1 year after 
collection. These filters shall be made available during the course 
of that year for supplemental analyses at the request of EPA or to 
provide information to State and local agencies on PM2.5 
composition. Other Federal Agencies may request access to filters 
for purposes of supporting air quality management or community 
health--such as biological assay--through the applicable EPA 
Regional Administrator. The filters shall be archived according to 
procedures approved by the Administrator. EPA recommends that 
particulate matter filters be archived for longer periods, 
especially for key sites in making NAAQS related decisions or for 
supporting health-related air pollution studies.
    5. Network Design for Photochemical Assessment Monitoring 
Stations (PAMS).
    The PAMS program provides more comprehensive data on 
O3 air pollution in areas classified as serious, severe, 
or extreme nonattainment for ozone than would otherwise be achieved 
through the NCore and SLAMS sites. More specifically, the PAMS 
program includes measurements for ozone, oxides of nitrogen, 
volatile organic compounds, and meteorology.
    5.1 PAMS Monitoring Objectives. PAMS design criteria are site 
specific. Concurrent measurements of O3, oxides of 
nitrogen, speciated VOC, CO, and meteorology are obtained at PAMS 
sites. Design criteria for the PAMS network are based on locations 
relative to O3 precursor source areas and predominant 
wind directions associated with high O3 events. Specific 
monitoring objectives are associated with each location. The overall 
design should enable characterization of precursor emission sources 
within the area, transport of O3 and its precursors, and 
the photochemical processes related to O3 nonattainment. 
Specific objectives that must be addressed include assessing ambient 
trends in O3, oxides of nitrogen, VOC species, and 
determining spatial and diurnal variability of O3, oxides 
of nitrogen, and VOC species. Specific monitoring objectives 
associated with each of these sites may result in four distinct site 
types. Detailed guidance for the locating of these sites may be 
found in reference 9 of this appendix.
    (a) Type 1 sites are established to characterize upwind 
background and transported O3 and its precursor 
concentrations entering the area and will identify those areas which 
are subjected to transport.
    (b) Type 2 sites are established to monitor the magnitude and 
type of precursor emissions in the area where maximum precursor 
emissions are expected to impact and are suited for the monitoring 
of urban air toxic pollutants.
    (c) Type 3 sites are intended to monitor maximum O3 
concentrations occurring downwind from the area of maximum precursor 
emissions.
    (d) Type 4 sites are established to characterize the downwind 
transported O3 and its precursor concentrations exiting 
the area and will identify those areas which are potentially 
contributing to overwhelming transport in other areas.
    5.2 Monitoring Period. PAMS precursor monitoring must be 
conducted annually throughout the months of June, July and August 
(as a minimum) when peak O3 values are expected in each 
area. Alternate precursor monitoring periods may be submitted for 
approval to the Administrator as a part of the annual monitoring 
network plan required by Sec.  58.10.
    5.3 Minimum Monitoring Network Requirements. A Type 2 site is 
required for each area. Overall, only two sites are required for 
each area, providing all chemical measurements are made. For 
example, if a design includes two Type 2 sites, then a third site 
will be necessary to capture the NOy measurement. The 
minimum required number and type of monitoring sites and sampling 
requirements are listed in Table D-6 of this appendix. Any 
alternative plans may be put in place in lieu of these requirements, 
if approved by the Administrator.

[[Page 2804]]



  Table D-6 of Appendix D to Part 58.--Minimum Required PAMS Monitoring
                        Locations and Frequencies
------------------------------------------------------------------------
                                                     Sampling frequency
                                                      (all daily except
         Measurement             Where required         for upper air
                                                       meteorology)\1\
------------------------------------------------------------------------
Speciated VOC \2\...........  Two sites per area,   During the PAMS
                               one of which must     monitoring period:
                               be a Type 2 site.     (1) Hourly auto GC,
                                                     or (2) Eight 3-hour
                                                     canisters, or (3) 1
                                                     morning and 1
                                                     afternoon canister
                                                     with a 3-hour or
                                                     less averaging time
                                                     plus Continuous
                                                     Total Non-methane
                                                     Hydrocarbon
                                                     measurement.
Carbonyl Sampling...........  Type 2 site in areas  3-hour samples every
                               classified as         day during the PAMS
                               serious or above      monitoring period.
                               for the 8-hour
                               ozone standard.
NOX.........................  All Type 2 sites....  Hourly during the
                                                     ozone monitoring
                                                     season.\3\
NOY.........................  One site per area at  Hourly during the
                               the Type 3 or Type    ozone monitoring
                               1 site.               season.
CO (ppb level)..............  One site per area at  Hourly during the
                               a Type 2 site.        ozone monitoring
                                                     season.
Ozone.......................  All sites...........  Hourly during the
                                                     ozone monitoring
                                                     season.
Surface met.................  All sites...........  Hourly during the
                                                     ozone monitoring
                                                     season.
Upper air meteorology.......  One representative    Sampling frequency
                               location within       must be approved as
                               PAMS area.            part of the PAMS
                                                     Network Description
                                                     described in 40 CFR
                                                     58.41.
------------------------------------------------------------------------
\1\ Daily or with an approved alternative plan.
\2\ Speciated VOC is defined in the ``Technical Assistance Document for
  Sampling and Analysis of Ozone Precursors'', EPA/600-R-98/161,
  September 1998.
\3\ Approved ozone monitoring season as stipulated in 40 CFR part 58,
  Table D-3 of this appendix.

    5.4 Transition Period. A transition period is allowed for 
phasing in the operation of newly required PAMS programs (due 
generally to reclassification of an area into serious, severe, or 
extreme nonattainment for ozone). Following the date of 
redesignation or reclassification of any existing O3 
nonattainment area to serious, severe, or extreme, or the 
designation of a new area and classification to serious, severe, or 
extreme O3 nonattainment, a State is allowed one year to 
develop plans for its PAMS implementation strategy. Subsequently, a 
minimum of one Type 2 site must be operating by the first month of 
the following approved PAMS season. Operation of the remaining 
site(s) must, at a minimum, be phased in at the rate of one site per 
year during subsequent years as outlined in the approved PAMS 
network description provided by the State.
    6. References.
    1. Ball, R.J. and G. E. Anderson. Optimum Site Exposure Criteria 
for SO2 Monitoring. The Center for the Environment and 
Man, Inc., Hartford, CT. Prepared for U.S. Environmental Protection 
Agency, Research Triangle Park, NC. EPA Publication No. EPA-450/3-
77-013. April 1977.
    2. Ludwig, F.F., J.H.S. Kealoha, and E. Shelar. Selecting Sites 
for Carbon Monoxide Monitoring. Stanford Research Institute, Menlo 
Park, CA. Prepared for U.S. Environmental Protection Agency, 
Research Triangle Park, NC. EPA Publication No. EPA-450/3-75-077, 
September 1975.
    3. Air Quality Criteria for Lead. Office of Research and 
Development, U.S. Environmental Protection Agency, Washington, DC. 
EPA Publication No. 600/8-89-049F. August 1990. (NTIS document 
numbers PB87-142378 and PB91-138420.)
    4. Optimum Site Exposure Criteria for Lead Monitoring. PEDCo 
Environmental, Inc. Cincinnati, OH. Prepared for U.S. Environmental 
Protection Agency, Research Triangle Park, NC. EPA Contract No. 68-
02-3013. May 1981.
    5. Guidance for Conducting Ambient Air Monitoring for Lead 
Around Point Sources. Office of Air Quality Planning and Standards, 
U.S. Environmental Protection Agency, Research Triangle Park, NC. 
EPA-454/R-92-009. May 1997.
    6. Koch, R.C. and H.E. Rector. Optimum Network Design and Site 
Exposure Criteria for Particulate Matter. GEOMET Technologies, Inc., 
Rockville, MD. Prepared for U.S. Environmental Protection Agency, 
Research Triangle Park, NC. EPA Contract No. 68-02-3584. EPA 450/4-
87-009. May 1987.
    7. Watson et al. Guidance for Network Design and Optimum Site 
Exposure for PM2.5 and PM10. Prepared for U.S. 
Environmental Protection Agency, Research Triangle Park, NC. EPA-
454/R-99-022, December 1997.
    8. Guideline for Selecting and Modifying the Ozone Monitoring 
Season Based on an 8-Hour Ozone Standard. Prepared for U.S. 
Environmental Protection Agency, RTP, NC. EPA-454/R-98-001, June 
1998.
    9. Photochemical Assessment Monitoring Stations Implementation 
Manual. Office of Air Quality Planning and Standards, U.S. 
Environmental Protection Agency, Research Triangle Park, NC. EPA-
454/B-93-051. March 1994.

    52. Appendix E to part 58 is revised to read as follows:

Appendix E to Part 58--Probe and Monitoring Path Siting Criteria for 
Ambient Air Quality Monitoring

    1. Introduction.
    2. Horizontal and Vertical Placement.
    3. Spacing from Minor Sources.
    4. Spacing From Obstructions.
    5. Spacing From Trees.
    6. Spacing From Roadways.
    7. Cumulative Interferences on a Monitoring Path.
    8. Maximum Monitoring Path Length.
    9. Probe Material and Pollutant Sample Residence Time.
    10. Waiver Provisions.
    11. Summary.
    12. References.
    1. Introduction.
    (a) This appendix contains specific location criteria applicable 
to SLAMS, NCore, and PAMS ambient air quality monitoring probes, 
inlets, and optical paths after the general location has been 
selected based on the monitoring objectives and spatial scale of 
representation discussed in appendix D to this part. Adherence to 
these siting criteria is necessary to ensure the uniform collection 
of compatible and comparable air quality data.
    (b) The probe and monitoring path siting criteria discussed in 
this appendix must be followed to the maximum extent possible. It is 
recognized that there may be situations where some deviation from 
the siting criteria may be necessary. In any such case, the reasons 
must be thoroughly documented in a written request for a waiver that 
describes how and why the proposed siting deviates from the 
criteria. This documentation should help to avoid later questions 
about the validity of the resulting monitoring data. Conditions 
under which the EPA would consider an application for waiver from 
these siting criteria are discussed in section 11 of this appendix.
    (c) The pollutant-specific probe and monitoring path siting 
criteria generally apply to all spatial scales except where noted 
otherwise. Specific siting criteria that are phrased with a ``must'' 
are defined as requirements and exceptions must be approved through 
the waiver provisions. However, siting criteria that are phrased 
with a ``should'' are defined as goals to meet for consistency but 
are not requirements.
    2. Horizontal and Vertical Placement.
    The probe or at least 80 percent of the monitoring path must be 
located between 2 and 15 meters above ground level for all ozone, 
sulfur dioxide and nitrogen dioxide monitoring sites, and for 
neighborhood scale Pb, PM10, PM10-2.5, 
PM2.5, and carbon monoxide sites. Middle scale 
PM10-2.5 sites are required to have sampler inlets 
between 2 and 7 meters above ground level. Microscale Pb, 
PM10, and PM2.5 sites are required to have 
sampler inlets between 2 and 7 meters above ground level. The inlet

[[Page 2805]]

probes for microscale carbon monoxide monitors that are being used 
to measure concentrations near roadways must be 3\1/2\ 
meters above ground level. The probe or at least 90 percent of the 
monitoring path must be at least 1 meter vertically or horizontally 
away from any supporting structure, walls, parapets, penthouses, 
etc., and away from dusty or dirty areas. If the probe or a 
significant portion of the monitoring path is located near the side 
of a building, then it should be located on the windward side of the 
building relative to the prevailing wind direction during the season 
of highest concentration potential for the pollutant being measured.
    3. Spacing from Minor Sources.
    (a) It is important to understand the monitoring objective for a 
particular location in order to interpret this particular 
requirement. Local minor sources of a primary pollutant, such as 
SO2, lead, or particles, can cause high concentrations of 
that particular pollutant at a monitoring site. If the objective for 
that monitoring site is to investigate these local primary pollutant 
emissions, then the site is likely to be properly located nearby. 
This type of monitoring site would in all likelihood be a microscale 
type of monitoring site. If a monitoring site is to be used to 
determine air quality over a much larger area, such as a 
neighborhood or city, a monitoring agency should avoid placing a 
monitor probe, path, or inlet near local, minor sources. The plume 
from the local minor sources should not be allowed to 
inappropriately impact the air quality data collected at a site. 
Particulate matter sites should not be located in an unpaved area 
unless there is vegetative ground cover year round, so that the 
impact of wind blown dusts will be kept to a minimum.
    (b) Similarly, local sources of nitric oxide (NO) and ozone-
reactive hydrocarbons can have a scavenging effect causing 
unrepresentatively low concentrations of O3 in the 
vicinity of probes and monitoring paths for O3. To 
minimize these potential interferences, the probe or at least 90 
percent of the monitoring path must be away from furnace or 
incineration flues or other minor sources of SO2 or NO. 
The separation distance should take into account the heights of the 
flues, type of waste or fuel burned, and the sulfur content of the 
fuel.
    4. Spacing From Obstructions.
    (a) Buildings and other obstacles may possibly scavenge 
SO2, O3, or NO2, and can act to 
restrict airflow for any pollutant. To avoid this interference, the 
probe, inlet, or at least 90 percent of the monitoring path must 
have unrestricted airflow and be located away from obstacles. The 
distance from the obstacle to the probe, inlet, or monitoring path 
must be at least twice the height that the obstacle protrudes above 
the probe, inlet, or monitoring path. An exception to this 
requirement can be made for measurements taken in street canyons or 
at source-oriented sites where buildings and other structures are 
unavoidable.
    (b) Generally, a probe or monitoring path located near or along 
a vertical wall is undesirable because air moving along the wall may 
be subject to possible removal mechanisms. A probe, inlet, or 
monitoring path must have unrestricted airflow in an arc of at least 
180 degrees. This arc must include the predominant wind direction 
for the season of greatest pollutant concentration potential. For 
particle sampling, a minimum of 2 meters of separation from walls, 
parapets, and structures is required for rooftop site placement.
    (c) Special consideration must be devoted to the use of open 
path analyzers due to their inherent potential sensitivity to 
certain types of interferences, or optical obstructions. A 
monitoring path must be clear of all trees, brush, buildings, 
plumes, dust, or other optical obstructions, including potential 
obstructions that may move due to wind, human activity, growth of 
vegetation, etc. Temporary optical obstructions, such as rain, 
particles, fog, or snow, should be considered when siting an open 
path analyzer. Any of these temporary obstructions that are of 
sufficient density to obscure the light beam will affect the ability 
of the open path analyzer to continuously measure pollutant 
concentrations. Transient, but significant obscuration of especially 
longer measurement paths could occur as a result of certain 
meteorological conditions (e.g., heavy fog, rain, snow) and/or 
aerosol levels that are of a sufficient density to prevent the open 
path analyzer's light transmission. If certain compensating measures 
are not otherwise implemented at the onset of monitoring (e.g., 
shorter path lengths, higher light source intensity), data recovery 
during periods of greatest primary pollutant potential could be 
compromised. For instance, if heavy fog or high particulate levels 
are coincident with periods of projected NAAQS-threatening pollutant 
potential, the representativeness of the resulting data record in 
reflecting maximum pollutant concentrations may be substantially 
impaired despite the fact that the site may otherwise exhibit an 
acceptable, even exceedingly high overall valid data capture rate.
    5. Spacing From Trees.
    (a) Trees can provide surfaces for SO2, 
O3, or NO2 adsorption or reactions, and 
surfaces for particle deposition. Trees can also act as obstructions 
in cases where they are located between the air pollutant sources or 
source areas and the monitoring site, and where the trees are of a 
sufficient height and leaf canopy density to interfere with the 
normal airflow around the probe, inlet, or monitoring path. To 
reduce this possible interference/obstruction, the probe, inlet, or 
at least 90 percent of the monitoring path must be at least 10 
meters or further from the drip line of trees.
    (b) The scavenging effect of trees is greater for O3 
than for other criteria pollutants. Monitoring agencies must take 
steps to consider the impact of trees on ozone monitoring sites and 
take steps to avoid this problem.
    (c) For microscale sites of any air pollutant, no trees or 
shrubs should be located between the probe and the source under 
investigation, such as a roadway or a stationary source.
    6. Spacing From Roadways.
    6.1 Spacing for Ozone and Oxide of Nitrogen Probes and 
Monitoring Paths. In siting an O3 analyzer, it is 
important to minimize destructive interferences from sources of NO, 
since NO readily reacts with O3. In siting NO2 
analyzers for neighborhood and urban scale monitoring, it is 
important to minimize interferences from automotive sources. Table 
E-1 of this appendix provides the required minimum separation 
distances between a roadway and a probe or, where applicable, at 
least 90 percent of a monitoring path for various ranges of daily 
roadway traffic. A sampling site having a point analyzer probe 
located closer to a roadway than allowed by the Table E-1 
requirements should be classified as middle scale rather than 
neighborhood or urban scale, since the measurements from such a site 
would more closely represent the middle scale. If an open path 
analyzer is used at a site, the monitoring path(s) must not cross 
over a roadway with an average daily traffic count of 10,000 
vehicles per day or more. For those situations where a monitoring 
path crosses a roadway with fewer than 10,000 vehicles per day, one 
must consider the entire segment of the monitoring path in the area 
of potential atmospheric interference from automobile emissions. 
Therefore, this calculation must include the length of the 
monitoring path over the roadway plus any segments of the monitoring 
path that lie in the area between the roadway and the minimum 
separation distance, as determined from Table E-1 of this appendix. 
The sum of these distances must not be greater than 10 percent of 
the total monitoring path length.

Table E-1 to Appendix E of Part 58.--Minimum Separation Distance Between
 Roadways and Probes or Monitoring Paths for Monitoring Neighborhood and
    Urban Scale Ozone (O3) and Oxides of Nitrogen (NO, NO2, NOX, NOY)
------------------------------------------------------------------------
                                                               Minimum
      Roadway average daily traffic, vehicles per day        distance\1\
                                                               (meters)
------------------------------------------------------------------------
<=1,000....................................................           10
10,000.....................................................           20
15,000.....................................................           30
20,000.....................................................           40
40,000.....................................................           60
70,000.....................................................          100
110,000....................................................         250
------------------------------------------------------------------------
\1\ Distance from the edge of the nearest traffic lane. The distance for
  intermediate traffic counts should be interpolated from the table
  values based on the actual traffic count.

    6.2 Spacing for Carbon monoxide Probes and Monitoring Paths. (a) 
Street canyon and traffic corridor sites (microscale) are intended 
to provide a measurement of the influence of the immediate source on 
the pollution exposure of the population. In order to provide some 
reasonable consistency and comparability in the air quality data 
from microscale sites, a minimum distance of 2 meters and a maximum 
distance of 10 meters from the edge of the nearest traffic lane must 
be maintained for these CO monitoring inlet probes. This should give 
consistency to the

[[Page 2806]]

data, yet still allow flexibility of finding suitable locations.
    (b) Street canyon/corridor (microscale) inlet probes must be 
located at least 10 meters from an intersection and preferably at a 
midblock location. Midblock locations are preferable to intersection 
locations because intersections represent a much smaller portion of 
downtown space than do the streets between them. Pedestrian exposure 
is probably also greater in street canyon/corridors than at 
intersections.
    (c) In determining the minimum separation between a neighborhood 
scale monitoring site and a specific roadway, the presumption is 
made that measurements should not be substantially influenced by any 
one roadway. Computations were made to determine the separation 
distance, and Table E-2 of this appendix provides the required 
minimum separation distance between roadways and a probe or 90 
percent of a monitoring path. Probes or monitoring paths that are 
located closer to roads than this criterion allows should not be 
classified as a neighborhood scale, since the measurements from such 
a site would closely represent the middle scale. Therefore, sites 
not meeting this criterion should be classified as middle scale.

Table E-2 to Appendix E of Part 58.--Minimum Separation Distance Between
   Roadways and Probes or Monitoring Paths for Monitoring Neighborhood
                          Scale Carbon Monoxide
------------------------------------------------------------------------
                                                               Minimum
                                                               distance
      Roadway average daily traffic, vehicles per day            \1\
                                                               (meters)
------------------------------------------------------------------------
<=10,000...................................................           10
15,000.....................................................           25
20,000.....................................................           45
30,000.....................................................           80
40,000.....................................................          115
50,000.....................................................          135
>=60,000...................................................         150
------------------------------------------------------------------------
\1\ Distance from the edge of the nearest traffic lane. The distance for
  intermediate traffic counts should be interpolated from the table
  values based on the actual traffic count.

    6.3 Spacing for Particulate Matter (PM2.5, 
PM10, Pb) Inlets. (a) Since emissions associated with the 
operation of motor vehicles contribute to urban area particulate 
matter ambient levels, spacing from roadway criteria are necessary 
for ensuring national consistency in PM sampler siting.
    (b) The intent is to locate localized hot-spot sites in areas of 
highest concentrations whether it be from mobile or multiple 
stationary sources. If the area is primarily affected by mobile 
sources and the maximum concentration area(s) is judged to be a 
traffic corridor or street canyon location, then the monitors should 
be located near roadways with the highest traffic volume and at 
separation distances most likely to produce the highest 
concentrations. For the microscale traffic corridor site, the 
location must be between 5 and 15 meters from the major roadway. For 
the microscale street canyon site the location must be between 2 and 
10 meters from the roadway. For the middle scale site, a range of 
acceptable distances from the roadway is shown in figure E-1 of this 
appendix. This figure also includes separation distances between a 
roadway and neighborhood or larger scale sites by default. Any site, 
2 to 15 meters high, and further back than the middle scale 
requirements will generally be neighborhood, urban or regional 
scale. For example, according to Figure E-1 of this appendix, if a 
PM sampler is primarily influenced by roadway emissions and that 
sampler is set back 10 meters from a 30,000 ADT (average daily 
traffic) road, the site should be classified as microscale, if the 
sampler height is between 2 and 7 meters. If the sampler height is 
between 7 and 15 meters, the site should be classified as middle 
scale. If the sample is 20 meters from the same road, it will be 
classified as middle scale; if 40 meters, neighborhood scale; and if 
110 meters, an urban scale.

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BILLING CODE 6560-50-C
    7. Cumulative Interferences on a Monitoring Path.
    (This paragraph applies only to open path analyzers.) The 
cumulative length or portion of a monitoring path that is affected 
by minor sources, trees, or roadways must not exceed 10 percent of 
the total monitoring path length.
    8. Maximum Monitoring Path Length.
    (This paragraph applies only to open path analyzers.) The 
monitoring path length must not exceed 1 kilometer for analyzers in 
neighborhood, urban, or regional scale. For middle scale monitoring 
sites, the monitoring path length must not exceed 300 meters. In 
areas subject to frequent periods of dust, fog, rain, or snow, 
consideration should be given to a shortened monitoring path length 
to minimize loss of monitoring data due to these temporary optical 
obstructions. For

[[Page 2807]]

certain ambient air monitoring scenarios using open path analyzers, 
shorter path lengths may be needed in order to ensure that the 
monitoring site meets the objectives and spatial scales defined in 
appendix D to this part. The Regional Administrator may require 
shorter path lengths, as needed on an individual basis, to ensure 
that the SLAMS sites meet the appendix D requirements. Likewise, the 
Administrator may specify the maximum path length used at NCore 
monitoring sites.
    9. Probe Material and Pollutant Sample Residence Time.
    For the reactive gases, SO2, NO2, and 
O3, special probe material must be used for point 
analyzers. (a) Studies 20-24 have been conducted to 
determine the suitability of materials such as polypropylene, 
polyethylene, polyvinyl chloride, Tygon[supreg], aluminum, brass, 
stainless steel, copper, Pyrex[supreg] glass and Teflon[supreg] for 
use as intake sampling lines. Of the above materials, only 
Pyrex[supreg] glass and Teflon[supreg] have been found to be 
acceptable for use as intake sampling lines for all the reactive 
gaseous pollutants. Furthermore, the EPA25 has specified 
borosilicate glass or FEP Teflon[supreg] as the only acceptable 
probe materials for delivering test atmospheres in the determination 
of reference or equivalent methods. Therefore, borosilicate glass, 
FEP Teflon[supreg], or their equivalent must be used for existing 
and new NCore monitors.
    (b) For volatile organic compound (VOC) monitoring at PAMS, FEP 
Teflon[supreg] is unacceptable as the probe material because of VOC 
adsorption and desorption reactions on the FEP Teflon[supreg]. 
Borosilicate glass, stainless steel, or its equivalent are the 
acceptable probe materials for VOC and carbonyl sampling. Care must 
be taken to ensure that the sample residence time is kept to 20 
seconds or less.
    (c) No matter how nonreactive the sampling probe material is 
initially, after a period of use reactive particulate matter is 
deposited on the probe walls. Therefore, the time it takes the gas 
to transfer from the probe inlet to the sampling device is also 
critical. Ozone in the presence of nitrogen oxide (NO) will show 
significant losses even in the most inert probe material when the 
residence time exceeds 20 seconds.26 Other studies 
27-28 indicate that a 10-second or less residence time is 
easily achievable. Therefore, sampling probes for reactive gas 
monitors at NCore must have a sample residence time less than 20 
seconds.
    10. Waiver Provisions.
    Most sampling probes or monitors can be located so that they 
meet the requirements of this appendix. New sites with rare 
exceptions, can be located within the limits of this appendix. 
However, some existing sites may not meet these requirements and yet 
still produce useful data for some purposes. EPA will consider a 
written request from the State agency to waive one or more siting 
criteria for some monitoring sites providing that the State can 
adequately demonstrate the need (purpose) for monitoring or 
establishing a monitoring site at that location.
    10.1 For establishing a new site, a waiver may be granted only 
if both of the following criteria are met:
    10.1.1 The site can be demonstrated to be as representative of 
the monitoring area as it would be if the siting criteria were being 
met.
    10.1.2 The monitor or probe cannot reasonably be located so as 
to meet the siting criteria because of physical constraints (e.g., 
inability to locate the required type of site the necessary distance 
from roadways or obstructions).
    10.2 However, for an existing site, a waiver may be granted if 
either of the criteria in sections 10.1.1 and 10.1.2 of this 
appendix are met.
    10.3 Cost benefits, historical trends, and other factors may be 
used to add support to the criteria in sections 10.1.1 and 10.1.2 of 
this appendix, however, they in themselves, will not be acceptable 
reasons for granting a waiver. Written requests for waivers must be 
submitted to the Regional Administrator.
    11. Summary.
    Table E-4 of this appendix presents a summary of the general 
requirements for probe and monitoring path siting criteria with 
respect to distances and heights. It is apparent from Table E-4 that 
different elevation distances above the ground are shown for the 
various pollutants. The discussion in this appendix for each of the 
pollutants describes reasons for elevating the monitor, probe, or 
monitoring path. The differences in the specified range of heights 
are based on the vertical concentration gradients. For CO, the 
gradients in the vertical direction are very large for the 
microscale, so a small range of heights are used. The upper limit of 
15 meters is specified for consistency between pollutants and to 
allow the use of a single manifold or monitoring path for monitoring 
more than one pollutant.

                                Table E-4 of Appendix E to Part 58.--Summary of Probe and Monitoring Path Siting Criteria
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                         Horizontal and
                                                                                       vertical distance
                                         Scale  (maximum      Height from ground to        supporting        Distance from trees       Distance from
             Pollutant                   monitoring path     probe, inlet or 80% of  structures2 to probe,    to probe, inlet or     roadways to probe,
                                         length, meters)         monitoring path1       inlet or 90% of       90% of  monitoring    inlet or monitoring
                                                                                        monitoring path1        path1 (meters)        path1  (meters)
                                                                                            (meters)
--------------------------------------------------------------------------------------------------------------------------------------------------------
SO2 3, 4, 5, 6.....................  Middle (300 m)          2-15..................  >1...................  >10..................  N/A.
                                      Neighborhood Urban,
                                      and Regional (1 km).
CO4, 5, 7..........................  Micro, middle (300 m),  3\1/2\: 2-  > 1..................  > 10.................  2-10; see Table E-2
                                      Neighborhood (1 km).    15.                                                                   of this appendix for
                                                                                                                                    middle and
                                                                                                                                    neighborhood scales.
NO2, O33, 4, 5.....................  Middle (300 m)          2-15..................  > 1..................  > 10.................  See Table E-1 of this
                                      Neighborhood, Urban,                                                                          appendix for all
                                      and Regional (1 km).                                                                          scales.
Ozone precursors (for PAMS)3, 4, 5.  Neighborhood and Urban  2-15..................  > 1..................  > 10.................  See Table E-4 of this
                                      (1 km).                                                                                       appendix for all
                                                                                                                                    scales.
PM, Pb3, 4, 5, 6, 8................  Micro: Middle,          2-7 (micro); 2-7        > 2 (all scales,       > 10 (all scales)....  2-10 (micro); see
                                      Neighborhood, Urban     (middle PM10-2.5); 2-   horizontal distance                           Figure E-1 of this
                                      and Regional.           15 (all other scales).  only).                                        appendix for all
                                                                                                                                    other scales.
--------------------------------------------------------------------------------------------------------------------------------------------------------
N/A--Not applicable.
1 Monitoring path for open path analyzers is applicable only to middle or neighborhood scale CO monitoring and all applicable scales for monitoring
  SO2,O3, O3 precursors, and NO2.
2 When probe is located on a rooftop, this separation distance is in reference to walls, parapets, or penthouses located on roof.
3 Should be >20 meters from the dripline of tree(s) and must be 10 meters from the dripline when the tree(s) act as an obstruction.
4 Distance from sampler, probe, or 90% of monitoring path to obstacle, such as a building, must be at least twice the height the obstacle protrudes
  above the sampler, probe, or monitoring path. Sites not meeting this criterion may be classified as middle scale (see text).

[[Page 2808]]

 
5 Must have unrestricted airflow 270 degrees around the probe or sampler; 180 degrees if the probe is on the side of a building.
6 The probe, sampler, or monitoring path should be away from minor sources, such as furnace or incineration flues. The separation distance is dependent
  on the height of the minor source's emission point (such as a flue), the type of fuel or waste burned, and the quality of the fuel (sulfur, ash, or
  lead content). This criterion is designed to avoid undue influences from minor sources.
7 For microscale CO monitoring sites, the probe must be >10 meters from a street intersection and preferably at a midblock location.
8 Collocated monitors must be within 4 meters of each other and at least 2 meters apart for flow rates greater than 200 liters/min or at least 1 meter
  apart for samplers having flow rates less than 200 liters/min to preclude airflow interference.

    12. References.
    1. Bryan, R.J., R.J. Gordon, and H. Menck. Comparison of High 
Volume Air Filter Samples at Varying Distances from Los Angeles 
Freeway. University of Southern California, School of Medicine, Los 
Angeles, CA. (Presented at 66th Annual Meeting of Air Pollution 
Control Association. Chicago, IL., June 24-28, 1973. APCA 73-158.)
    2. Teer, E.H. Atmospheric Lead Concentration Above an Urban 
Street. Master of Science Thesis, Washington University, St. Louis, 
MO. January 1971.
    3. Bradway, R.M., F.A. Record, and W.E. Belanger. Monitoring and 
Modeling of Resuspended Roadway Dust Near Urban Arterials. GCA 
Technology Division, Bedford, MA. (Presented at 1978 Annual Meeting 
of Transportation Research Board, Washington, DC. January 1978.)
    4. Pace, T.G., W.P. Freas, and E.M. Afify. Quantification of 
Relationship Between Monitor Height and Measured Particulate Levels 
in Seven U.S. Urban Areas. U.S. Environmental Protection Agency, 
Research Triangle Park, NC. (Presented at 70th Annual Meeting of Air 
Pollution Control Association, Toronto, Canada, June 20-24, 1977. 
APCA 77-13.4.)
    5. Harrison, P.R. Considerations for Siting Air Quality Monitors 
in Urban Areas. City of Chicago, Department of Environmental 
Control, Chicago, IL. (Presented at 66th Annual Meeting of Air 
Pollution Control Association, Chicago, IL., June 24-28, 1973. APCA 
73-161.)
    6. Study of Suspended Particulate Measurements at Varying 
Heights Above Ground. Texas State Department of Health, Air Control 
Section, Austin, TX. 1970. p. 7.
    7. Rodes, C.E. and G.F. Evans. Summary of LACS Integrated 
Pollutant Data. In: Los Angeles Catalyst Study Symposium. U.S. 
Environmental Protection Agency, Research Triangle Park, NC. EPA 
Publication No. EPA-600/4-77-034. June 1977.
    8. Lynn, D.A. et. al. National Assessment of the Urban 
Particulate Problem: Volume 1, National Assessment. GCA Technology 
Division, Bedford, MA. U.S. Environmental Protection Agency, 
Research Triangle Park, NC. EPA Publication No. EPA-450/3-75-024. 
June 1976.
    9. Pace, T.G. Impact of Vehicle-Related Particulates on TSP 
Concentrations and Rationale for Siting Hi-Vols in the Vicinity of 
Roadways. OAQPS, U.S. Environmental Protection Agency, Research 
Triangle Park, NC. April 1978.
    10. Ludwig, F.L., J.H. Kealoha, and E. Shelar. Selecting Sites 
for Monitoring Total Suspended Particulates. Stanford Research 
Institute, Menlo Park, CA. Prepared for U.S. Environmental 
Protection Agency, Research Triangle Park, NC. EPA Publication No. 
EPA-450/3-77-018. June 1977, revised December 1977.
    11. Ball, R.J. and G.E. Anderson. Optimum Site Exposure Criteria 
for SO2 Monitoring. The Center for the Environment and 
Man, Inc., Hartford, CT. Prepared for U.S. Environmental Protection 
Agency, Research Triangle Park, NC. EPA Publication No. EPA-450/3-
77-013. April 1977.
    12. Ludwig, F.L. and J.H.S. Kealoha. Selecting Sites for Carbon 
Monoxide Monitoring. Stanford Research Institute, Menlo Park, CA. 
Prepared for U.S. Environmental Protection Agency, Research Park, 
NC. EPA Publication No. EPA-450/3-75-077. September 1975.
    13. Ludwig, F.L. and E. Shelar. Site Selection for the 
Monitoring of Photochemical Air Pollutants. Stanford Research 
Institute, Menlo Park, CA. Prepared for U.S. Environmental 
Protection Agency, Research Triangle Park, NC. EPA Publication No. 
EPA-450/3-78-013. April 1978.
    14. Lead Analysis for Kansas City and Cincinnati, PEDCo 
Environmental, Inc., Cincinnati, OH. Prepared for U.S. Environmental 
Protection Agency, Research Triangle Park, NC. EPA Contract No. 66-
02-2515, June 1977.
    15. Barltrap, D. and C. D. Strelow. Westway Nursery Testing 
Project. Report to the Greater London Council. August 1976.
    16. Daines, R.H., H. Moto, and D. M. Chilko. Atmospheric Lead: 
Its Relationship to Traffic Volume and Proximity to Highways. 
Environ. Sci. and Technol., 4:318, 1970.
    17. Johnson, D.E., et al. Epidemiologic Study of the Effects of 
Automobile Traffic on Blood Lead Levels, Southwest Research 
Institute, Houston, TX. Prepared for U.S. Environmental Protection 
Agency, Research Triangle Park, NC. EPA-600/1-78-055, August 1978.
    18. Air Quality Criteria for Lead. Office of Research and 
Development, U.S. Environmental Protection Agency, Washington, DC 
EPA-600/8-83-028 aF-dF, 1986, and supplements EPA-600/8-89/049F, 
August 1990. (NTIS document numbers PB87-142378 and PB91-138420.)
    19. Lyman, D.R. The Atmospheric Diffusion of Carbon monoxide and 
Lead from an Expressway, Ph.D. Dissertation, University of 
Cincinnati, Cincinnati, OH. 1972.
    20. Wechter, S.G. Preparation of Stable Pollutant Gas Standards 
Using Treated Aluminum Cylinders. ASTM STP. 598:40-54, 1976.
    21. Wohlers, H.C., H. Newstein and D. Daunis. Carbon Monoxide 
and Sulfur Dioxide Adsorption On and Description From Glass, Plastic 
and Metal Tubings. J. Air Poll. Con. Assoc. 17:753, 1976.
    22. Elfers, L.A. Field Operating Guide for Automated Air 
Monitoring Equipment. U.S. NTIS. p. 202, 249, 1971.
    23. Hughes, E.E. Development of Standard Reference Material for 
Air Quality Measurement. ISA Transactions, 14:281-291, 1975.
    24. Altshuller, A.D. and A.G. Wartburg. The Interaction of Ozone 
with Plastic and Metallic Materials in a Dynamic Flow System. 
Intern. Jour. Air and Water Poll., 4:70-78, 1961.
    25. Code of Federal Regulations. Title 40 part 53.22, July 1976.
    26. Butcher, S.S. and R.E. Ruff. Effect of Inlet Residence Time 
on Analysis of Atmospheric Nitrogen Oxides and Ozone, Anal. Chem., 
43:1890, 1971.
    27. Slowik, A.A. and E.B. Sansone. Diffusion Losses of Sulfur 
Dioxide in Sampling Manifolds. J. Air. Poll. Con. Assoc., 24:245, 
1974.
    28. Yamada, V.M. and R.J. Charlson. Proper Sizing of the 
Sampling Inlet Line for a Continuous Air Monitoring Station. 
Environ. Sci. and Technol., 3:483, 1969.
    29. Koch, R.C. and H.E. Rector. Optimum Network Design and Site 
Exposure Criteria for Particulate Matter, GEOMET Technologies, Inc., 
Rockville, MD. Prepared for U.S. Environmental Protection Agency, 
Research Triangle Park, NC. EPA Contract No. 68-02-3584. EPA 450/4-
87-009. May 1987.
    30. Burton, R.M. and J.C. Suggs. Philadelphia Roadway Study. 
Environmental Monitoring Systems Laboratory, U.S. Environmental 
Protection Agency, Research Triangle Park, N.C. EPA-600/4-84-070 
September 1984.
    31. Technical Assistance Document For Sampling and Analysis of 
Ozone Precursors. Atmospheric Research and Exposure Assessment 
Laboratory, U.S. Environmental Protection Agency, Research Triangle 
Park, NC 27711. EPA 600/8-91-215. October 1991.
    32. Quality Assurance Handbook for Air Pollution Measurement 
Systems: Volume IV. Meteorological Measurements. Atmospheric 
Research and Exposure Assessment Laboratory, U.S. Environmental 
Protection Agency, Research Triangle Park, NC 27711. EPA 600/4-90-
0003. August 1989.
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Modeling Applications. Office of Air Quality Planning and Standards, 
U.S. Environmental Protection Agency, Research Triangle Park, NC 
27711. EPA 450/4-87-013. June 1987.
[FR Doc. 06-179 Filed 1-13-06; 8:45 am]
BILLING CODE 6560-50-U