[Federal Register Volume 65, Number 72 (Thursday, April 13, 2000)]
[Proposed Rules]
[Pages 19964-19991]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-8833]



[[Page 19963]]

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Part II





Environmental Protection Agency





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40 CFR Part 52



Approval and Promulgation of Implementation Plans; Arizona--Maricopa 
County PM-10 Nonattainment Area; Serious Area Plan for Attainment of 
the Annual PM-10 Standard; Proposed Rule



Interim Final Determination That State Has Corrected the Plan 
Deficiency and Stay of Sanctions; Phoenix PM-10 Nonattainment Area, 
Arizona; Interim Rule

  Federal Register / Vol. 65, No. 72 / Thursday, April 13, 2000 / 
Proposed Rules  

[[Page 19964]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[AZ092-002; FRL-6575-3]


Approval and Promulgation of Implementation Plans; Arizona--
Maricopa County PM-10 Nonattainment Area; Serious Area Plan for 
Attainment of the Annual PM-10 Standard

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: EPA proposes to approve provisions of the Revised MAG 1999 
Serious Area Particulate Plan for PM-10 for the Maricopa County 
(Phoenix) Nonattainment Area, February 2000, and the control measures 
on which it relies, that address the annual PM-10 national ambient air 
quality standard. We also propose to grant Arizona's request to extend 
the Clean Air Act deadline for attaining the annual PM-10 standard in 
the Phoenix area from 2001 to 2006. Finally, we propose to approve two 
particulate matter rules adopted by the Maricopa County Environmental 
Services Department and Maricopa County's Residential Woodburning 
Restrictions Ordinance.

DATES: Comments on this proposal must be received in writing by June 
12, 2000. Comments should be addressed to the contact listed below.

ADDRESSES: Comments may be mailed to: Frances Wicher, Office of Air 
Planning (AIR-2), EPA Region 9, 75 Hawthorne Street, San Francisco, CA 
94105-3901.
    A copy of docket No. AZ-MA-00-001, containing the technical support 
document (TSD) and other material relevant to EPA's proposed action, is 
available for public inspection at EPA's Region 9 office during normal 
business hours.
    A copy of the docket is also available for inspection at: Arizona 
Department of Environmental Quality, Library, 3033 N. Central Avenue, 
Phoenix, Arizona 85012, (602) 207-2217. Maricopa Association of 
Governments, 302 North 1st Street, Phoenix, Arizona 85003, (602) 254-
6300.

Electronic Availability

    This document and the Technical Support Document (TSD) are also 
available as electronic files on EPA's Region 9 Web Page at http://www.epa.gov/region09/air.

FOR FURTHER INFORMATION CONTACT: Frances Wicher, Office of Air Planning 
(AIR-2), U.S. Environmental Protection Agency, Region 9, 75 Hawthorne 
Street, San Francisco, California 94105, (415) 744-1238, email: 
[email protected].

SUPPLEMENTARY INFORMATION:

Table of Contents

Summary of Today's Proposals

Summary of the MAG Plan

PM-10 Air Quality in the Phoenix Metropolitan Area

A. The Maricopa Nonattainment Area and its PM-10 Air Quality
B. PM-10 Air Quality Planning in the Phoenix Metropolitan Area
C. Clean Air Act Sanctions on the Phoenix Area

The Clean Air Act's Planning Requirements for Serious PM-10 Areas and 
EPA's Guidance on Meeting these Requirements

A. Implementation of Best Available Control Measures
B. Implementation of Reasonably Available Control Measures
C. Extension of the Attainment Date beyond 2001
    1. Apply for an attainment date extension
    2. Demonstrate that attainment by 2001 is impracticable
    3. Complied with all requirements and commitments in its 
implementation plan
    4. Demonstrate the inclusion of the most stringent measures
    5. Demonstrate attainment by the most expeditious alternative 
date practicable
D. Separating Our Rulemaking Actions on the Annual and 24-hour 
Standards

Discussion of the MAG Plan's Compliance with Clean Air Act Requirements

A. Completeness of the SIP Submittals
B. Adequacy of the Transportation Conformity Budgets
C. Emission Inventory
D. Adequate Monitoring Network
E. Contribution to PM-10 Exceedances of Major Sources of PM-10 
Precursors
F. Implementation of Reasonably Available and Best Available Control 
Measures
    1. Determination of significant sources
    2. Identification of potential BACM
    3. Implementation of RACM and BACM and inclusion of MSM for each 
significant source category
    a. Technology controls for on-road motor vehicle exhaust
    b. Transportation control measures (TCMs) for on-road motor 
vehicle exhaust and paved road dust
    c. Nonroad engines
    d. Paved road dust
    e. Unpaved parking lots
    f. Disturbed vacant lands
    g. Unpaved roads
    h. Construction sites and activities
    i. Agricultural sources
    j. Residential wood combustion
    k. Secondary ammonium nitrate
    l. MCESD's commitments to improve compliance and enforcement of 
its fugitive dust rules
G. Attainment Date Extension
    1. Apply for an extension
    2. Demonstrate the impracticability of attainment by December 
31, 2001
    3. Complied with the commitments and requirements in the SIP
    4. Include the most stringent measures
    5. Demonstrate expeditious attainment
    a. Air quality modeling b. Control measures relied on for 
attainment
    6. Other factors that EPA may consider
    a. Nature and extent of nonattainment
    b. Types and number of sources or other emitting activities
    c. Population exposure to concentrations above the standard
    d. Presence and concentration of potentially toxic substances in 
the particulate
    e. Technological and economic feasibility of controls
    7. Conclusion on the extension request
H. Reasonable Further Progress (RFP) and Quantitative Milestones
    1. Reasonable further progress
    2. Quantitative milestones
I. General SIP Requirements

Proposed Action on Maricopa County Rules

A. Rule 310
B. Rule 310.01
C. Residential Woodburning Restriction Ordinance
D. CAA Section 110(l) Finding

Administrative Requirements

Summary of Today's Proposals

    We are proposing to approve the serious area air quality plan for 
attainment of the annual PM-10 standard in the Phoenix, Arizona, 
metropolitan area.\1\ Our proposed actions are based on our initial 
determination that this plan complies with the Clean Air Act's 
requirements for attainment of the annual PM-10 standard in serious PM-
10 nonattainment areas.
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    \1\ There are two separate national ambient air quality 
standards (NAAQS) for PM-10, an annual standard of 50 g/
m3 and a 24-hour standard of 150 g/
m3.
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    Specifically, we propose to approve the following elements of the 
plan as they apply to the annual PM-10 standard:
     the base year emissions inventory of PM-10 sources,
     the demonstration that the plan provides for 
implementation of reasonably available control measures (RACM) and best 
available control measures (BACM),
     the demonstration that attainment of the PM-10 annual 
standard by the Clean Air Act deadline of December 31, 2001 is 
impracticable,
     the demonstration that attainment of the PM-10 annual 
standard will occur by the most expeditious alternative date 
practicable, in this case, December 31, 2006,

[[Page 19965]]

     the demonstration that the plan provides for reasonable 
further progress and quantitative milestones,
     the demonstration that the plan includes to our 
satisfaction the most stringent measures found in the implementation 
plan of another state or are achieved in practice in another state, and 
can feasibly be implemented in the area.
     the demonstration that major sources of PM-10 precursors 
such as nitrogen oxides and sulfur dioxide do not contribute 
significantly to violations of the annual PM-10 standard, and
     the transportation conformity budget.
    We are also proposing to grant Arizona's request to extend the 
attainment date for the annual PM-10 standard from December 31, 2001 to 
December 31, 2006.
    Finally, we are proposing to approve Maricopa County's fugitive 
dust rules, Rules 310 and 301.01, and its residential woodburning 
restriction ordinance.
    This preamble describes our proposed actions on the Phoenix area 
plan and provides a summary of our evaluation of the plan. Our detailed 
evaluation of the plan can be found in the technical support document 
(``EPA TSD'') that accompanies this proposal. A copy of the EPA TSD can 
be downloaded from our website or obtained by calling or writing the 
contact person listed above.

Summary of the MAG Plan

    We are evaluating and proposing action on the Revised Maricopa 
Association of Governments 1999 Serious Area Particulate Plan for PM-10 
for the Maricopa County Nonattainment Area, February 2000 (``MAG 
plan''). This plan was developed by the Maricopa Association of 
Governments (MAG), the lead air quality planning agency in Maricopa 
County, with the assistance of the Maricopa County Environmental 
Services Department (MCESD), the Arizona Department of Environmental 
Quality (ADEQ), and the cities and towns in the Maricopa County 
nonattainment area. ADEQ submitted the final plan as a revision to the 
Arizona State Implementation Plan (SIP) on February 16, 2000.
    We are also evaluating and proposing action on the December 11, 
1997 submittal of Serious Area Committed Particulate Control Measures 
for PM-10 for the Maricopa County Nonattainment Area and Support 
Technical Analysis, MAG, December 1997. This submittal contains 
additional control measures that are relied on in the MAG plan. We 
consider the measures in this submittal to be part of the MAG plan and 
have evaluated them as such.
    Finally, we are also evaluating and proposing to act on the most 
recent revisions to MCESD's Rule 310, Fugitive Dust Sources (adopted 
February 16, 2000) and Rule 310.01, Fugitive Dust from Open Areas, 
Vacant Lots, Unpaved Parking Lots, and Unpaved Roadways (adopted 
February 16, 2000). We are also proposing to approve the revised 
Maricopa County Residential Woodburning Restrictions Ordinance (adopted 
November 17, 1999).
    As submitted, the revised MAG plan consists of the main plan 
document, four volumes of technical appendices, and four volumes of 
commitments from various agencies to implement PM-10 controls. The plan 
contains a 1994 regional PM-10 emissions inventory and uses the urban 
airshed model/limited chemistry version (UAM/LC) to model air quality 
in 1995 as a base year and in 2006 as the attainment year. The plan 
includes a BACM analysis and a demonstration that attainment by 2001 is 
impracticable. It also includes the State's request for a five year 
extension of the attainment date, a demonstration that the plan 
provides for the most stringent measures found in other areas' plans or 
used in practice, and a demonstration of attainment by December 31, 
2006. The plan shows that the principal sources contributing to PM-10 
exceedances in the Phoenix area are fugitive dust sources, such as 
construction sites, vacant lots, paved and unpaved roads, and various 
other dust sources. The principal controls relied on for attainment are 
controls on these fugitive dust sources.
    The MAG plan addresses both the annual and 24-hour PM-10 standards. 
We are not at this time proposing any actions regarding the plan's 
compliance with the statutory requirements relating to the 24-hour 
standard. As we explain in more detail later, the annual PM-10 standard 
is a separate air quality standard from the 24-hour one; therefore, we 
can and must separately evaluate a plan's compliance with the statutory 
requirements for each standard. We do not need to do these reviews 
concurrently.
    The MAG plan also contains contingency measures as required by CAA 
section 172(c)(9). We are not proposing action on these contingency 
measures at this time. Contingency measures are a distinct provision of 
the Clean Air Act that we may act on separately from the attainment 
requirements.

PM-10 Air Quality in the Phoenix Metropolitan Area

A. The Maricopa Nonattainment Area and its PM-10 Air Quality

    The Maricopa County (Phoenix) PM-10 nonattainment area is located 
in the eastern portion of Maricopa County and encompasses the cities of 
Phoenix, Mesa, Scottsdale, Tempe, Chandler, Glendale as well as 17 
other jurisdictions and considerable unincorporated County lands.\2\ 40 
CFR 81.303. The area is home to almost 3 million people.
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    \2\ The Maricopa nonattainment area also includes the town of 
Apache Junction in Pinal County. Apache Junction is covered by a 
separate air quality plan and will be addressed in a later action.
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    The area violates both the annual and 24-hour PM-10 standards. In 
1990, the area was designated nonattainment for PM-10 and classified as 
moderate. In 1996, because of continuing violations of both PM-10 
standards, the area was reclassified to serious. 61 FR 21372 (May 10, 
1996).
    As noted before, the principal contributors to elevated PM-10 
levels in the Phoenix area are fugitive dust sources such as 
construction sites, unpaved roads, vacant lots and paved road dust. 
Also contributing to the PM-10 problem, but to a much lesser degree 
than fugitive dust, are internal and external combustion sources 
including directly-emitted PM-10 from automobiles, trucks, construction 
equipment, bus, residential woodburning and industrial, commercial, and 
residential use of natural gas and fuel oil. See MAG plan, 3-5.

B. PM-10 Air Quality Planning in the Phoenix Metropolitan Area

    The MAG plan is the latest in a series of air quality plans 
addressing the PM-10 problem in Phoenix. These previous plans are:
     1991 MAG Moderate Area Plan. Arizona submitted this plan 
in 1991 and revisions to it in 1993 and 1994. The 1991 plan contained a 
demonstration that attainment was impracticable by the CAA's deadline 
for moderate areas, December 31, 1994. We initially approved this plan 
in 1995 (60 FR 18010 (April 10, 1995)); however, the 9th Circuit Court 
of Appeals vacated our approval in 1996, finding among other things 
that the plan did not address the 24-hour PM-10 standard. Ober v. EPA, 
84 F.3d 304 (9th Cir. 1996). In 1998, we disapproved the 1991 plan's 
reasonably available control measure (RACM) demonstration for the 
annual standard because the plan failed to provide for the 
implementation of RACM on

[[Page 19966]]

number of significant sources of PM-10, including unpaved roads. The 
failure to provide for the implementation of RACM also meant that the 
plan could no longer conclusively demonstrate the impracticability of 
attainment of the annual standard by December 31, 1994, so we also 
disapproved the impracticability demonstration. 63 FR 15919, 15925 
(April 1, 1998).
     Microscale Plan. Arizona submitted this plan in 1997 as a 
response to the 9th Circuit's findings in Ober. The plan addressed the 
CAA's serious area PM-10 requirements for attaining the 24-hour 
standard around four representative air quality monitors (that is, at 
four localized or ``microscale'' sites) in the Phoenix area. It found 
that 24-hour exceedances in the Phoenix area are mainly caused by 
fugitive dust from construction, agriculture, unpaved roads and parking 
lots, and disturbed vacant land. We approved the plan in part but also 
disapproved it in part because it did not provide for the 
implementation of RACM or BACM on agricultural sources, unpaved roads, 
unpaved parking lots, and disturbed vacant lots and did not demonstrate 
attainment at two of the four sites. 62 FR 41856 (August 4, 1997).
     1998 Moderate Area Federal Implementation Plan (FIP). We 
promulgated this plan on August 3, 1998. It provided for the 
implementation of RACM on the significant sources--unpaved roads, 
unpaved parking lots, disturbed vacant lots, and agricultural sources--
left unaddressed by the 1991 MAG moderate area plan and the Microscale 
plan.\3\ The FIP demonstrated that the implementation of RACM was 
insufficient for attainment of the 24-hour and annual standards by 
Phoenix area's attainment deadline of December 31, 2001.\4\ 63 FR 41326 
(August 3, 1998).
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    \3\ The FIP's requirements for unpaved roads, unpaved parking 
lots and disturbed vacant lots are codified at 40 CFR 52.128. We 
withdrew the FIP's agricultural requirements, formerly codified at 
40 CFR 52.127, when we approved similar State requirement in 1999. 
64 FR 34726 (June 29, 1999).
    \4\ At the time we promulgated the FIP in 1998, the moderate PM-
10 area deadline of December 31, 1994 had passed and we had 
reclassified the Phoenix area to serious. As a result the only 
statutory attainment deadline then applicable to the Phoenix area, 
and thus the deadline applicable to our moderate area FIP, was the 
serious area deadline, i.e., as expeditiously as practicable but not 
later than December 31, 2001. See 63 FR 15919, 15926.
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    A more detailed history of PM-10 planning in the Phoenix area can 
be found in the EPA TSD.

C. Clean Air Act Sanctions on the Phoenix Area

    Our 1998 disapprovals of parts of the 1991 MAG moderate area plan 
started sanction clocks under CAA section 179(a). Under section 179(a), 
once we disapprove a SIP provision because it fails to meet a CAA 
requirement, a State has 18 months to correct the deficiency that 
resulted in the disapproval before the first of two sanctions goes into 
place. If the state still has not corrected the deficiency within 24 
months of the disapproval, the second sanction goes into place.
    The two CAA sanctions are a limitation on certain highway approvals 
and funding and an increase in the offset ratio to 2 to 1 for any major 
new stationary source or major modification. See CAA section 179(b). 
Our sanctions regulations provide that the first sanction to be imposed 
is the offset ratio unless we have established at the time of the 
disapproval that the highway sanction will be first. 40 CFR 52.31(d).
    On August 3, 1998, we published our disapprovals of the RACM and 
attainment demonstrations for the annual standard in the 1991 MAG 
moderate area plan. 63 FR 41326. When these disapprovals became 
effective 30 days later on September 2, 1998, the sanction clocks 
started. The first of these sanction clocks expired on March 2, 2000 
and the 2:1 offset sanction is now in place in the Phoenix area. The 
second sanction clock for the highway funding limitations is set to 
expire on September 2, 2000.
    Under section 179(a) and our sanctions regulations at 40 CFR 
52.31(d)(1), we must approve a SIP revision that corrects the 
deficiencies to permanently end the sanctions clocks and lift any 
imposed sanctions. However, we may temporarily stay the clocks and any 
imposed sanctions if we propose to approve a SIP revision that corrects 
the deficiencies and have issued an interim final determination that 
the State has corrected the deficiencies. 40 CFR 52.31(d)(2)(i).
    In a rule being published concurrently with this proposal, we are 
issuing an interim final determination that, based our proposed 
findings here, Arizona has more than likely corrected the deficiencies 
that resulted in our August 1998 disapprovals.

The Clean Air Act's Planning Requirements for Serious PM-10 Areas 
and EPA's Guidance on Meeting these Requirements

    The Phoenix area is a PM-10 nonattainment area that has been 
reclassified to serious because it failed to attain by the moderate 
area attainment date of December 31, 1994. Such an area must submit, 
within 18 months of the reclassification, revisions to its 
implementation plan that address the CAA requirements for serious PM-10 
nonattainment areas. CAA section 189(b)(2). These requirements are:
    (a) assurances that best available control measures (BACM) for the 
control of PM-10 shall be implemented no later than 4 years after the 
area is reclassified (CAA section 189(b)(1)(B)); \5\
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    \5\ When a moderate area is reclassified to serious, the 
requirement to implement RACM in section 189(a)(1)(C) remains and is 
augmented by the requirement to implement BACM. Thus, a serious area 
PM-10 plan must, in addition to BACM, provide for the implementation 
of RACM as expeditiously as practicable to the extent that the RACM 
requirement has not been satisfied in the area's moderate area plan.
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    (b) assurances that best available control technology (BACT) on 
major stationary sources of PM-10 precursors shall be implemented no 
later than 4 years after the area is reclassified except where EPA has 
determined that such sources do not contribute significantly to 
exceedances of the PM-10 standards (CAA section 189(e));
    (c) a demonstration (including air quality modeling) that the plan 
will provide for attainment as expeditiously as practicable but no 
later than December 31, 2001, or, where the State is seeking an 
extension of the attainment date under section 188(e), a demonstration 
that attainment by December 31, 2001 is impracticable (CAA sections 
188(c)(2) and 189(b)(1)(A));
    (d) quantitative milestones which are to be achieved every 3 years 
and which demonstrate reasonable further progress (RFP) toward 
attainment by the applicable attainment date (CAA sections 172(c)(2) 
and 189(c)); and
    (e) a comprehensive, accurate, current inventory of actual 
emissions from all sources of PM-10. (CAA sections 172(c)(3)).
    Serious area PM-10 plans must also meet the general requirements 
applicable to all SIPs including reasonable notice and public hearing 
under section 110(l), necessary assurances that the implementing 
agencies have adequate personnel, funding and authority under section 
110(a)(2)(E)(i) and 40 CFR 51.280; and the description of enforcement 
methods as required by 40 CFR 51.111.
    Except for the requirements for the implementation of RACM and BACM 
and for extension requests, we will discuss our policies for each of 
these requirements when we discuss our evaluation of that section of 
the MAG plan later in this preamble.

[[Page 19967]]

    We have issued a General Preamble, 57 FR 13498 (April 16, 1992) and 
57 FR 18070 (April 28, 1992), and Addendum to the General Preamble 
(``Addendum''), 59 FR 41998 (August 16, 1994), describing our 
preliminary views on how we intend to review SIPs submitted to meet the 
Clean Air Act's requirements for PM-10 plans. We have also issued other 
guidance documents related to PM-10 plans or provisions of these plans. 
These other guidance documents will be cited as appropriate.

A. Implementation of Best Available Control Measures

    Under section 189(b)(2), serious area PM-10 plans must provide 
assurances that BACM will be implemented in the area no later than four 
years after the area is reclassified as serious. For Phoenix, the BACM 
implementation deadline is June 10, 2000.
    The Act does not define what constitutes BACM. We consider BACM to 
be a particular level of control, in this case the best, on a source or 
source category. More specifically, we have defined BACM to be, among 
other things, the maximum degree of emission reductions achievable from 
a source or source category which is determined on a case-by-case 
basis, considering energy, economic and environmental impacts. Addendum 
at 42010. We also consider BACM as going beyond existing RACM-level 
controls, such as expanding the use of RACM controls (e.g., paving more 
miles of unpaved roads). Addendum at 42013. Additionally, we believe 
that BACM should emphasize prevention rather than remediation (e.g., 
preventing track out at construction sites rather than simply requiring 
clean up of tracked-out dirt). Addendum at 42013.
    A serious area plan must provide for the implementation of BACM on 
each significant (i.e., non-de minimis) source category. Addendum at 
42011. In guidance, we have established a presumption that a 
``significant'' source category is one that contributes 1 g/m 
\3\ or more of PM-10 to a location of an annual standard violation. 
Addendum at 42011. However, whether the threshold should be lower than 
this in any particular area depends upon the specific facts of that 
area's nonattainment problem. Specifically, in areas that are 
demonstrating attainment by December 31, 2001, it depends on whether 
requiring the application of BACM on source categories below a proposed 
de minimis level would meaningfully expedite attainment. In areas that 
are claiming the impracticability of attainment by December 31, 2001, 
it depends upon whether requiring the application of BACM on source 
categories below a proposed de minimis level would make the difference 
between attainment and nonattainment by the serious area deadline of 
December 31, 2001.\6\
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    \6\ This principle is best illustrated by an example: In Area A, 
attainment of the annual standard by December 31, 2001 requires that 
total PM-10 emissions in the area be reduced to 200 tons per day 
(tpd). After application of BACM to all source categories above the 
proposed de minimis level, total emissions in the area are reduced 
to 220 tpd. BACM on the proposed de minimis source categories would 
reduce total emissions a further 5 tons to 215 tpd. Since 
application of BACM to the proposed de minimis source categories 
still leaves emissions above the attainment level of 200 tpd, the 
proposed de minimis level is appropriate.
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    We have outlined in our guidance a multi-step process for 
identifying BACM. Addendum at 42010-42014. The steps are:
    1. develop a detailed emission inventory of PM-10 sources and 
source categories,
    2. model to evaluate the impact on PM-10 concentrations over the 
standards of the various sources and source categories to determine 
which are significant,
    3. identify potential BACM for significant source categories 
including their technological feasibility, costs, and energy and 
environmental impacts if needed to determine BACM, and
    4. provide for the implementation of the BACM or provide a reasoned 
justification for rejecting any potential BACM.

B. Implementation of Reasonably Available Control Measures

    When a moderate area is reclassified to serious, the requirement to 
implement RACM in section 189(a)(1)(C) remains. Thus, a serious area 
PM-10 plan must also provide for the implementation of RACM as 
expeditiously as practicable to the extent that the RACM requirement 
has not been satisfied in the area's moderate area plan.
    However, we do not normally conduct a separate evaluation to 
determine if a serious area plan's measures also meet the RACM 
requirements as interpreted by us in the General Preamble at 13540. 
This is because in our serious area guidance (Addendum at 42010), we 
interpret the BACM requirement, as generally subsuming the RACM 
requirement (i.e. if we determine that the measures are indeed the 
``best available,'' we have necessarily concluded that they are 
``reasonably available''). Therefore, a separate analysis to determine 
if the measures represent a RACM level of control is not necessary. 
Consequently, our proposed approval of the MAG plan's provisions 
relating to the implementation of BACM is also a proposed finding that 
the plan provides for the implementation of RACM.

C. Extension of the Attainment Date Beyond 2001

    Section 188(e) of the Act allows us to extend the attainment date 
for a serious area for up to five years beyond 2001 if attainment by 
2001 is impracticable. However, before we may grant an extension of the 
attainment date, the State must first:
    1. apply to us for an extension of the PM-10 attainment date beyond 
2001,
    2. demonstrate that attainment by 2001 is impracticable,
    3. have complied with all requirements and commitments applying to 
the area in its implementation plan,
    4. demonstrate to our satisfaction that its serious area plan 
includes the most stringent measures that are included in the 
implementation plan of any state and/or are achieved in practice in any 
state and are feasible for the area, and
    5. submit a demonstration of attainment by the most expeditious 
alternative date practicable.
    In determining whether to grant an extension and the appropriate 
length of the attainment date extension, we may consider:
    1. the nature and extent of the nonattainment problem,
    2. the types and number of sources or other emitting activities in 
the area (including the influence of uncontrollable natural sources and 
international transport),
    3. the population exposed to concentrations in excess of the 
standard,
    4. the presence and concentration of potentially toxic substances 
in the mix of particulate emissions in the area, and
    5. the technological and economic feasibility of various control 
measures.
    We may grant only one extension for an area and that extension 
cannot be for more than 5 years after 2001; that is, the extended 
attainment date can be no later than December 31, 2006. CAA section 
188(e).
    To date, we have not issued any policy or regulation interpreting 
the attainment date extension requirements for urban areas like 
Phoenix. Therefore, before reviewing Arizona's request for an 
extension, we will first discuss how we propose to interpret section 
188(e).
    The following is our preliminary interpretation of the section 
188(e) requirements and we request comment on it. We emphasize that 
this is our preliminary view and it is subject to modification as we 
gain more experience reviewing on extension requests from other areas.

[[Page 19968]]

    We have listed above the five requirements a State must meet before 
we can consider granting an attainment date extension. We discuss each 
requirement in order:
1. Apply for an Attainment Date Extension
    The State must apply in writing to EPA for an extension of the 
attainment deadline. The request should accompany the SIP submittal 
containing the most expeditious alternative attainment demonstration. 
The public must be provided reasonable notice and a public hearing on 
the request before it is submitted.
    Extension requests are not SIP submittals per se and are therefore 
not subject to the requirements of the Clean Air Act and our 
regulations for public notice and hearing on SIP revisions. However, 
because they can greatly affect the content and ultimate approvability 
of a serious area PM-10 plan, we believe a state must give the public 
an opportunity, consistent with the requirements for SIP revisions, to 
comment on an extension request prior to submitting it to us.
2. Demonstrate That Attainment by 2001 is Impracticable
    In order to demonstrate impracticability, the plan must show that 
the implementation of BACM (as determined by our guidance) on 
significant source categories will not bring the area into attainment 
by December 31, 2001. BACM is the required level of control for serious 
areas that must be in place before the 2001 attainment date; therefore, 
we believe that it is reasonable to interpret the Act to require that a 
state provide for at least the implementation of BACM on significant 
source categories before it can claim impracticability of attainment by 
2001. This interpretation parallels our interpretation of the 
impracticability option for moderate PM-10 nonattainment areas in 
section 189(a)(1)(B). In moderate areas, RACM was required before a 
moderate area plan could show impracticability of attainment by 1994, 
the moderate area attainment deadline. General Preamble at 13544.
    The statutory provision for demonstrating impracticability requires 
that the demonstration be based on air quality modeling. See section 
189(b)(1)(A).
3. Complied With all Requirements and Commitments in its Implementation 
Plan
    We interpret this criterion to mean that the State has implemented 
the control measures in the SIP revisions it has submitted to us to 
address the CAA requirements in sections 172 and 189 for PM-10 
nonattainment areas.
    We read this provision not to require the area to have a fully 
approved SIP that meets the CAA's requirements for moderate areas. We 
base this reading on the plain language of section 188(e) which 
requires the state to comply with all requirements and commitments 
pertaining to that area in the implementation plan but does not require 
that the state comply with all requirements pertaining to the area in 
the Act. For the same reason we also read this provision not to bar an 
extension if all or part of an area's moderate area plan is disapproved 
or has been promulgated as a FIP.
4. Demonstrate the Inclusion of the Most Stringent Measures
    The fourth extension criterion requires the State to ``demonstrate 
to the satisfaction of the Administrator that the plan for the area 
includes the most stringent measures that are included in the 
implementation plan of any State, or are achieved in practice in any 
State, and can feasiblely be implemented in the area.'' CAA section 
188(e).
    The requirement for most stringent measures (MSM) is similar to the 
requirement for BACM. We define BACM to be, among other things, the 
maximum degree of emission reduction achievable from a source or source 
category which is determined on a case by case basis considering 
energy, economic and environmental impacts. Addendum at 42010. The Act 
establishes the deadline for implementing BACM as four years after an 
area's reclassification to serious. CAA section 189(b)(1)(A).
    We proposed to define a ``most stringent measure'' in a similar 
manner: the maximum degree of emission reduction that has been required 
or achieved from a source or source category in other SIPs or in 
practice in other states and can feasiblely be implemented in the area. 
The Act does not specify an implementation deadline for MSM. Because 
the clear intent of section 188(e) is to minimize the length of any 
attainment date extension, we propose that the implementation of MSM 
should be as expeditiously as practicable.
    Given this similarity between the BACM implementation and MSM 
requirements, we believe that determining MSM should follow a process 
similar to determining BACM, but with one additional step, to compare 
the potentially most stringent measure against the measures already 
adopted in the area:
    1. develop a detailed emission inventory of PM-10 sources and 
source categories,
    2. model to evaluate the impact on PM-10 concentrations over the 
standards of the various source categories to determine which are 
significant for the purposes of adopting MSM,
    3. identify the potentially most stringent measures in other 
implementation plans or used in practice in other States for each 
significant source category and, for each measure, determine their 
technological and economic feasibility for the area,
    4. compare the potentially most stringent measures for each 
significant source category against the measures, if any, already 
adopted for that source category, and
    5. provide for the adoption and expeditious implementation of any 
MSM that is more stringent than existing measures or, in lieu of 
adoption, provide a reasoned justification for rejecting the potential 
MSM, i.e., why such measures cannot be feasiblely implemented in the 
area.
    The level of control resulting from a most stringent measure 
depends on how well other areas have chosen to control their sources. 
If a source category has not been well controlled in other areas then 
MSM may in fact result in a rather low level of control. This contrasts 
with BACM which is determined independently of what other areas have 
done and depends only on what is the best level of control feasible for 
an area.
    Because BACM is the best level of control feasible for an area, it 
would be easy for the MSM requirement to result in no more controls and 
no more emission reductions in an area than result from the 
implementation of BACM. Given the strategy in the nonattainment 
provisions of the Act to offset longer attainment time frames with more 
stringent control requirements, we need to interpret the MSM provision 
to assure that it results in additional controls beyond the set of 
measures adopted as BACM. The primary ways to do this are (1) to 
require that more sources and source categories be subject to MSM 
analysis than to BACM analysis, that is, by lowering the threshold for 
what is considered a de minimis source category and (2) to require 
reanalysis of any measures garnered from other areas that were rejected 
during the BACM analysis because they could not be implemented by the 
BACM-implementation deadline to see if they

[[Page 19969]]

are now feasible for the area given the longer attainment date.
    De Minimis Thresholds. What constitutes a de minimis source 
category for BACM is dependent upon the specific facts of the 
nonattainment problem under consideration. In particular, it depends 
upon whether requiring the application of BACM for such sources would 
make the difference between attainment and nonattainment by the serious 
area deadline. We propose to use a similar approach for judging what 
constitutes a de minimis source category for MSM but instead of the 
attainment/nonattainment test, we propose to use a test of whether MSM 
controls on the de minimis sources would result in more expeditious 
attainment.
    We would not review an MSM analysis in a plan if the plan did not 
demonstrate expeditious attainment since one prerequisite for granting 
an extension is that the plan demonstrate attainment. Therefore, any de 
minimis standard for MSM that relied on the difference between 
attainment and nonattainment would be meaningless because no additional 
controls are needed for attainment beyond those already in the plan. 
Our responsibility under section 188(e), however, is to grant the 
shortest practicable extension of the attainment date by assuring the 
plan provides for attainment as expeditiously as practicable. Thus, one 
means of determining an appropriate de minimis level is to determine if 
applying MSM to the proposed de minimis source categories would 
meaningfully expedite attainment. If it did, then the de minimis level 
is too high, and if it did not, then the de minimis level is 
appropriate.\7\
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    \7\ In extension areas, the applicable control requirement after 
the December 31, 2001 attainment date is the MSM and expeditious 
attainment requirements of section 188(e). Thus, for measures 
implemented after December 31, 2001, a state need only show that the 
measure meets at minimum the MSM level of control and, combined with 
all other measures, is sufficient for expeditious attainment. A 
state has no obligation to show that the measure meets a BACM-level 
of control.
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    Technological Feasibility. In the MSM analysis, a state must 
evaluate the application of controls from elsewhere to sources in its 
own area. In many cases, these sources are already subject to local 
control measures. In these situations, part of determining if a control 
is technologically feasible is determining if the new control can be 
integrated with the existing controls without reducing or delaying the 
emission reductions from the existing control. If it cannot, then we 
would not, in general, consider the measure to be technologically 
feasible for the area.
    Economic Feasibility. Because cost is rarely used to justify 
rejection of a measure in the MAG plan, we will not attempt to 
establish a general guide for evaluating when a measure is economically 
infeasible but instead will address the issue on a case-by-case basis 
as needed.
    We propose to use the following approach in evaluating the 
selection of the most stringent among multiple measures, i.e., 
evaluating the determination of when one is more stringent than 
another:
    1. The determination will be made on a source category basis. When 
only a single measure is applicable to a source category then we will 
compare the measures directly. However, in many cases multiple measures 
apply to a single source category (e.g., unpaved roads which in the MAG 
plan are controlled both by Rule 310.01 and through City and County 
commitments). In these cases, we will evaluate the impact of the 
overall control strategy on emissions in the source category against 
the impact of the overall control strategy on the source category in 
other areas and will not compare individual measures within the source 
category.
    2. We will review all the elements of a rule that apply to a 
specific type of source as an inseparable measure. A rule's 
applicability and emission limitations (as they apply to a single type 
of source) together define its stringency. They are not separable 
elements that can be compared in isolation to another rule.
    3. Because stringency is based on an emissions level, we will not 
use a measure's implementation mechanisms (e.g., rule versus 
commitment), funding level, compliance schedule, resources available 
for enforcement, or other similar items as criteria for judging 
relative stringency. (We do consider these items when judging whether 
the plan provides for implementation of MSM.)
    Finally, we address how we view the ``to the satisfaction of the 
Administrator'' qualifier on the requirement that the State demonstrate 
that its plan includes the most stringent measures. The presence and 
wording of this qualifier indicate that Congress granted us 
considerable discretion in determining whether a plan in fact includes 
MSM. Under the terms of section 188(e), we believe that we can still 
accept an MSM demonstration even if it falls short of having every MSM 
possible. To intuit the limits of this discretion, we again look to the 
overall intent of section 188(e), that we grant as short an extension 
as practicable. In concrete terms, this means that when judging the 
overall adequacy of the MSM demonstration, we will give more weight to 
a failure to include MSM for source categories that contribute the most 
to the PM-10 problem in Phoenix and to the failure to include measures 
that could provide for more expeditious attainment and less weight to a 
failure to include MSM for source categories that contribute little to 
the PM-10 problem and/or would not expedite attainment.
5. Demonstrate Attainment by the Most Expeditious Alternative Date 
Practicable
    Section 189(b)(1)(A) requires that a serious area plan demonstrate 
attainment, using air quality modeling, by the most expeditious date 
practicable after December 31, 2001. This demonstration is the final 
criterion that must be met before we may grant an extension request.
    Our determination of whether the plan provides for attainment by 
the most expeditious date practicable will depend on whether the plan 
provides for implementation of BACM by the BACM implementation deadline 
and MSM as expeditiously as practicable.
    Please see section 4 of the EPA TSD for an additional discussion of 
our proposed interpretation of the extension requirements.

D. Separating Our Rulemaking Actions on the Annual and 24-hour 
Standards

    As we discussed above, there are two PM-10 NAAQS, an annual 
standard of 50 g/m3 and a 24-hour standard of 150 
g/m3. In this proposed action, we are evaluating 
the MAG plan only for its compliance with the Clean Air Act's 
requirements for attaining the annual PM-10 standard. We are not, at 
this time, evaluating the plan for its compliance with the Act's 
requirements for the 24-hour PM-10 standard. Under section 110(k)(2), 
we have until February 25, 2001--one year after the completeness 
finding--to act on the balance of the plan that was submitted on 
February 16, 2000.
    The two PM-10 standards are independent and must be addressed 
independently by states in their SIPs. This independence was 
highlighted by the Ninth Circuit Court of Appeals in Ober v. EPA, 84 
F.3d 304 (9th Cir. 1996). In Ober, the Court was reviewing our approval 
of the MAG moderate area plan:

The general provisions of the Clean Air Act repeatedly emphasize 
that implementation plans must provide for attainment of the NAAQS 
as expeditiously as practicable. For PM-10, the EPA promulgated two 
separate NAAQS-the annual standard and the 24-hour standard-which 
differ in the following

[[Page 19970]]

respects. First, the 24-hour standard offers protection against 
dangerous short-term exposures to high PM-10 levels, a protection 
that is distinct from the protection against chronic degradation in 
lung function provided by the annual standard. Second, the sources 
of PM-10 violation differ for the annual and the 24-hour: violations 
of the 24-hour standard are generally caused by localized sources 
such as construction projects, whereas violations of the annual 
standard tend to be caused by more diverse, dispersed sources. 
Third, control measures differ in effectiveness for the 24-hour 
standard and the annual standard.
    These differences emphasize the importance of viewing PM-10's 
two NAAQS individually and of requiring independent treatment of 
them in an implementation plan. . . . . Such independent treatment 
furthers the Clean Air Act's goals of protecting health and achieve 
clean air.
    Ober at 309 (emphasis added).
    If a state must treat each PM-10 NAAQS independently in the 
implementation plan, then we also must treat each PM-10 NAAQS 
independently when reviewing the plan's compliance with the Clean Air 
Act. Therefore, it is necessary for us to review the MAG plan's 
compliance against the CAA requirements as they apply to the annual 
standard and again review them against the CAA requirements as they 
apply to the 24-hour standard. There is no mandate that we conduct 
these reviews concurrently even if Arizona submitted a single document 
to meet the requirements for both standards since, effectively, we must 
treat it as if it contained two separate plans.
    We have chosen not to act at this time on the 24-hour provisions of 
the revised MAG plan because the State is still working on quantifying 
emission reductions from the best management practice measures (BMPs) 
intended to reduce fugitive dust from agricultural sources. Attainment 
of the 24-hour standard in the Phoenix area, unlike the annual 
standard, depends in part on emission reductions from these BMPs. Once 
Arizona quantifies the reductions, it will revise the 24-hour 
attainment demonstrations and resubmit them to us. We expect these 
changes later this year. We do not believe it is an efficient use of 
our resources to act now on the 24-hour provisions currently in the MAG 
plan knowing that they will be substantially revised prior to our 
statutory deadline to act on them.

Discussion of the MAG Plan's Compliance with the Clean Air Act's 
Requirements

    The following sections present a condensed discussion of our 
evaluation of the MAG plan's compliance with the applicable CAA 
requirements for attainment of the annual PM-10 standard. Our complete 
evaluation is found in the EPA TSD for this proposal. We urge anyone 
wishing to comment on this proposal to first review the TSD before 
preparing comments. A copy of the TSD can be downloaded from our 
website or obtained by calling or writing the contact person listed 
above.

A. Completeness of the SIP Submittals

    The first step we take after receiving a SIP submittal is to 
determine if it is complete. CAA section 110(k)(1)(B) requires that we 
review all SIPs and SIP revisions for completeness within 60 days of 
receipt of the submittal. The completeness review allows us to quickly 
determine if a state has submitted a SIP revision, including all needed 
supporting material, on which we can take action. We make completeness 
determinations using criteria we have established in 40 CFR part 51, 
appendix V.
    We found ADEQ's February 16, 2000 submittal (received on February 
23, 2000) of the final revised MAG serious area PM-10 plan complete. We 
notified the State of our completeness determination on February 25, 
2000. See Letter, David P. Howekamp, EPA, to Jacqueline Schafer, ADEQ.
    If we do not make a completeness determination, a submittal becomes 
complete by default 6 months after we receive it. See 100(k)(1)(B). We 
did not review the 1997 submittal of control measures for completeness 
and it became complete by default on June 15, 1998.
    We found Arizona's submittals containing MCESD's Rule 310 and 
310.01 and the revised Maricopa County residential woodburning 
ordinance complete on March 31, 2000.

B. Adequacy of the Transportation Conformity Budgets

    Section 176(c) of the Clean Air Act requires that federally funded 
or approved transportation plans, programs, and projects in 
nonattainment areas ``conform'' to the area's air quality 
implementation plans. Conformity ensures that federal transportation 
actions do not worsen an area's air quality or interfere with its 
meeting the air quality standards. We have issued a conformity rule 
that establishes the criteria and procedures for determining whether or 
not transportation plans, programs, and project conform. See 40 CFR 
part 93, subpart A.
    One of the primary tests for conformity is to show transportation 
plans and improvement programs will not cause motor vehicle emissions 
higher than the levels needed to make progress toward and meet the air 
quality standards. The motor vehicle emissions levels needed to make 
progress toward and meet the air quality standards are set in an area's 
attainment and/or reasonable further progress (RFP) plans and are known 
as the ``emissions budget for motor vehicles.'' Emissions budgets are 
established for specific years and specific pollutants. See 40 CFR 
93.118(a).
    Before an emissions budget in a submitted SIP revision may be used 
in a conformity determination, we must first determine that it is 
adequate. The criteria by which we determine adequacy of submitted 
emission budgets are outlined in our conformity rule in 40 CFR 
93.118(e)(4).
    The MAG plan establishes a mobile source emissions budget of 59.7 
mtpd. This regional budget is applicable for both the annual and 24-
hour PM-10 standards. The on-road mobile portion of the budget, which 
includes emissions from reentrained road dust, vehicle exhaust, and 
travel on unpaved roads, is 58.6 mtpd. The road construction portion of 
the budget is 1.1 mtpd. MAG plan, p. 8-13.
    On March 30, 2000, we have found adequate for transportation 
conformity purposes this motor vehicle emission budget. As a result of 
our adequacy finding, MAG and the Federal Highway Administration are 
required to use this budget in future conformity analyses.

C. Emission Inventory

    CAA section 172(c)(3) requires all nonattainment area plans to 
contain a comprehensive, accurate, and current inventory. Our policies 
require that the inventory be fully documented.
    The MAG plan describes annual and average annual day emissions for 
1994 from point, area, nonroad, on-road, and nonanthropogenic sources 
in the Maricopa County portion of the 2,880 square mile nonattainment 
area. The inventory includes emissions of PM-10, PM-2.5, ammonia 
(NH3), nitrogen oxides (NOX), and sulfur oxides 
(SOX).
    The inventory shows that the dominant sources of emissions in the 
Phoenix area are paved road dust (39.1 percent), unpaved roads, (21.6 
percent) and construction-related fugitive dust (20.1 percent). Much 
lower but still important contributors are directly-emitted PM-10 from 
non-road engines (7.0 percent) and on-road motor vehicles (3.3 
percent), all stationary area sources, e.g., woodburning (6.1 percent) 
and stationary point sources (2.7 percent). MAG plan, Table 3-1.
    Generally the inventories are very well documented with the

[[Page 19971]]

documentation exceeding our guidance requirements.
    Current: The base year, 1994, is a reasonably current year, 
considering the length of time needed to develop an inventory, perform 
the modeling, develop and adopt control measures, and hold public 
hearings on such a large and technically-complex plan like the MAG 
plan.
    Comprehensive: The MAG plan inventories are fairly complete, 
considering a few emission factors are unknown for some of the smaller 
sources of PM-10. The inventories did not include emissions of volatile 
organic compounds (VOC) which is a precursor of secondary PM-10 because 
the plan found there is a negligible impact on ambient measurements of 
PM-10 from VOC aerosol. We concur with this finding and that VOC 
sources need not be inventoried for the PM-10 plan.
    Accurate: In developing the inventory, MAG and MCESD closely 
followed our guidance relative to the use of emission factors, activity 
estimates, and growth and control factors, and the other source 
specific emission estimation methodologies (continuous emission 
monitoring, annual stack tests, and mass balance methods). Source 
specific methods were used to the maximum extent possible as they are 
inherently more accurate than emission factors. The relative accuracy 
of each estimate underwent the prescribed quality assurance procedures 
to eliminate all possible errors. The inventory is thus as accurate as 
inventories can be.
    Because we find that the inventory is current, comprehensive, and 
accurate, we propose to approve it under CAA section 172(c)(3).

D. Adequate Monitoring Network

    CAA section 110(a)(2)(B)(i) requires States to establish and 
operate air monitoring networks to compile data on ambient air quality 
for all criteria pollutants. Our regulations in 40 CFR part 58 
establishes specific regulatory requirements for operating air quality 
surveillance networks to measure ambient concentrations of PM-10, 
including measurement method requirements, network design, quality 
assurance procedures, and in the case of large urban areas, the minimum 
number of monitoring sites designated as National Air Monitoring 
Stations (NAMS).
    The MAG plan does not specifically address the adequacy of the PM-
10 monitoring network in the Phoenix area. There is no requirement that 
it does. We are reviewing the adequacy of the monitoring network here 
because the plan relies on ambient data to characterize the extent and 
severity of the PM-10 problem in the Phoenix area and we need to assure 
that the monitoring network is adequate for this purpose.
    In 1995, the base year for the air quality modeling, there were 18 
monitoring sites collecting data in the Phoenix area, all of which were 
operated in accordance with our regulations. Most of these PM-10 
monitoring sites were neighborhood scale sites with an objective of 
assessing population exposure. Given the widespread nature of the 
emission sources in the Phoenix area, we believe this focus was 
appropriate and that the network was adequate to characterize the 
extent and severity of the PM-10 problem in 1995.

E. Contribution to PM-10 Exceedances of Major Sources of PM-10 
Precursors

    Under CAA section 189(e), a state must apply the control 
requirements applicable to major stationary sources of PM-10 to major 
stationary sources of PM-10 precursors, unless we determine such 
sources do not contribute significantly to PM-10 levels in excess of 
the NAAQS in the area. For the serious area plan, a ``major source'' is 
one that emits or has the potential to emit over 70 English tons per 
year (tpy) of sulfur oxides (SOx), nitrogen oxides (NOx), or ammonium.
    PM-10 precursors react in the atmosphere to form ``secondary'' 
particulate, secondary because it is not directly emitted from the 
source. The MAG plan does not provide specific information on the 
impact of major precursor sources on Phoenix PM-10 levels; however, it 
does provide sufficient information on the contribution of total 
secondary particulates to PM-10 levels and the emissions from major 
precursor sources to estimate the impact.
    All major stationary sources of PM-10 precursors are estimated to 
contribute just 0.24 g/m3 to the annual levels of 
PM-10. See EPA TSD section, ``BACT for Major Stationary Sources of PM-
10 Precursors.'' This contribution is less than 0.5 percent of the 
annual PM-10 levels over the standard in the Phoenix area and less than 
0.5 percent of the annual standard of 50 g/m \3\.
    We believe that this small contribution is insignificant for the 
Phoenix area. PM-10 levels above the annual standard in Phoenix are 
almost exclusively caused by a few large source categories of fugitive 
dust, and it is BACM-level controls on these sources that are the key 
to expeditious attainment of the annual standard in the Phoenix area 
and not controls on small contributors such as major sources of PM-10 
precursors.
    We, therefore, propose to determine that major sources of PM-10 
precursors do not contribute significantly to PM-10 levels in excess of 
the PM-10 NAAQS in the Phoenix area. As a result, Arizona is not 
required to apply BACT to major sources of PM-10 precursors in the 
Phoenix area.

F. Implementation of Reasonably Available and Best Available Control 
Measures

    CAA section 189(b)(1)(B) requires that a serious area PM-10 plan 
provide for the implementation of BACM within four years of 
reclassification to serious. For Phoenix, this deadline is June 10, 
2000. BACM must be applied to each significant area-wide source 
category. Addendum at 42011. As discussed above, we have established a 
four-step process for evaluating BACM in serious area PM-10 plans.
1. Determination of Significant Sources
    The first step in the BACM analysis is to develop a detailed 
emission inventory of PM-10 sources and source categories that can be 
used in modeling to determine their impact on ambient air quality. 
Addendum at 42012.
    The MAG plan uses three modeling studies of PM-10 sources in the 
Phoenix area to identify significant source categories. One of these 
studies evaluated significant sources using chemical mass balance (CMB) 
modeling performed on monitoring samples collected at 6 sites in 1989-
1990. The two other studies evaluated significant sources using 
dispersion modeling of sources around 6 monitoring sites using data 
from 1992 through 1995.\8\
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    \8\ These studies are ``The 1989-90 Phoenix PM-10 Study,'' 
Desert Research Institute, April 1991; ``Particulate Control Measure 
Feasibility Study,'' Sierra Research, January 1997; and ``Plan for 
Attainment of the 24-hour PM-10 Standard, Maricopa County PM-10 
Nonattainment Area,'' ADEQ, May 1997.
---------------------------------------------------------------------------

    From these evaluations, the MAG plan identified 8 significant 
source categories and 12 insignificant source categories. MAG plan, p. 
9-6.
    The final list of significant source categories did not distinguish 
between those categories that are significant for the 24-hour standard 
and those significant for the annual standard; although previous 
studies have shown that some source categories are significant only for 
one or the other standard. Because the MAG plan did not distinguish 
significant source categories between the two standards, we will treat 
each of the listed significant source

[[Page 19972]]

categories as significant for the annual standard.
    For the annual standard, the MAG plan demonstrates that its 
selection of significant source categories is appropriate by showing 
that control on the de minimis source categories would not make the 
difference between attainment and nonattainment of the annual standard 
by 2001. According to the plan, total emissions in the area need to be 
reduced to 130 mtpd to attain the annual standard by 2001. After 
application of BACM, total emissions are reduced to 152 mtpd. MAG plan, 
p. 9-11. The 12 de minimis sources categories contribute in total 10.3 
mtpd. MAG plan, Table 9-a. Totally eliminating these source categories 
would reduce total regional emissions to 142 mtpd, still 12 mtpd above 
the regional emissions level needed for attainment. MAG plan, pp. 9-10 
through 9-12.
    The 8 significant source categories are:
    1. Paved road travel.
    2. Unpaved road travel (includes unpaved parking lots).
    3. Industrial paved road travel (paved and unpaved).
    4. Construction site preparation (includes disturbed vacant lots 
that are not undergoing construction).
    5. Agricultural tilling (includes all agricultural sources).
    6. Residential wood combustion.
    7. On-road and non-road motor vehicle exhaust.
    8. Secondary ammonium nitrate.
    MAG Plan, Table 9-1.
    The 12 de minimis source categories are:
    1. Stationary point sources.
    2. Fuel combustion (excluding residential wood combustion).
    3. Waste/open burning.
    4. Agricultural harvesting.
    5. Cattle feedlots.
    6. Structural/vehicle fires.
    7. Charbroiling/frying meat.
    8. Marine vessel exhaust.
    9. Airport ground support exhaust.
    10. Railroad locomotive exhaust.
    11. Windblown from fluvial channels.
    12. Wild fires.
MAG plan, Table 9-a. The plan notes that several de minimis source 
categories are already subject to control or will be controlled in the 
future. MAG plan, p. 9-12.
    We propose to find that the MAG plan has not excluded any source 
categories that should be considered significant from its list of 
significant source categories. The plan presents acceptable modeling to 
evaluate the impact of various PM-10 sources and source categories on 
PM-10 levels and to derive a comprehensive and conservative list of 
significant source categories.
    Our proposal here does not mean that we believe all the source 
categories identified as significant in the MAG plan needed to be 
considered significant for the purpose of evaluating BACM. We believe 
that the MAG plan is conservative in its selection of significant 
source categories, that is, it may have included more source categories 
in its significant source list than are strictly needed. Thus our use 
of negative wording in our proposed finding: no significant source 
categories were excluded as opposed to only the significant categories 
were included. In our 1998 FIP, we derived a narrower list of 
significant sources based on more recent modeling than was used to 
develop the list in the MAG plan. See 63 FR 15920, 15932 (Table 2 and 
text).
2. Identification of Potential BACM
    In preparing the list of candidate BACM, MAG reviewed our guidance 
documents on BACM, other EPA documents on PM-10 control, as well as PM-
10 plans from other serious PM-10 areas in the West. It also evaluated 
controls proposed during public comment. MAG plan, pp. 9-24 through 9-
29.
    The MAG plan appropriately screened the list of candidate BACM to 
eliminate measures that did not apply to significant source categories 
in the area, were technologically infeasible for the area because they 
would not reduce PM-10 emissions, or duplicated other measures on the 
list. The MAG plan also provides cost effectiveness estimates for each 
of the candidate BACM. MAG plan, pp. 9-30 through 9-39.
    We propose to find that the MAG plan identified and evaluated 
potential BACM for the Maricopa area consistent with our guidance. As 
we will discuss below in our evaluations of the implementation of BACM 
for each significant source category, we do not believe that the MAG 
plan left out any candidate BACM. We note that additional evaluation of 
control measures was done as part of the most stringent measure 
analysis. MAG plan, pp 10-25 & 10-26. Overall, the MAG plan presents 
one of the most comprehensive lists of potential BACM ever produced.
3. Implementation of RACM and BACM and Inclusion of MSM for Each 
Significant Source Category
    In the following sections, we review the results of the MAG plan's 
BACM analysis. To present these results, we have grouped the emission 
generating activities that comprise the MAG plan's significant 
categories slightly differently from the plan, e.g., we have addressed 
separately construction activities and disturbed vacant lands which are 
both included in the MAG plan's significant category of construction 
site preparation.\9\ We have done this to make our evaluations of the 
plan's provisions for the implementation of BACM and inclusion of MSM 
clearer and thus, we believe, more understandable. However, despite the 
method of presentation, we have addressed the MAG plan's provisions for 
implementing RACM and BACM for each of the plan's significant source 
categories.
---------------------------------------------------------------------------

    \9\ MAG plan uses this grouping despite the fact that disturbed 
vacant lands include lands that are disturbed for reasons other than 
construction activity.
---------------------------------------------------------------------------

    Also, because of the substantial overlap in the source categories 
and controls evaluated for BACM and those evaluated for MSM, we present 
our evaluation of the MAG plan's provisions for including MSM alongside 
our evaluation of the provisions for implementing RACM and BACM for 
each significant source category.
    Finally, controls on a number of significant source categories are 
found in MCESD's fugitive dust rules, Rule 310 and Rule 310.01. MCESD 
has made extensive commitments to improve compliance and enforcement of 
these rules to assure that they achieve the emission reductions 
necessary for expeditious attainment. These commitments are an 
important component of our finding that the MAG plan provides for 
implementation of RACM and BACM and inclusion of MSM. We discuss them 
at the end of this section.
    a. Technology controls for on-road motor vehicle exhaust. This 
category includes tailpipe and tire wear emissions of primary PM-10 
from on-road motor vehicles. On-road motor vehicles include both 
gasoline and diesel-powered passenger cars, light, medium, and heavy 
duty trucks, buses, and motorcycles.\10\
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    \10\ We will treat gasoline-and diesel-powered vehicles together 
here to preserve to the extent practicable the significant source 
groupings in the MAG plan; however, we believe they are in fact 
distinct categories. Almost 95 percent of diesel PM-10 emissions 
come from heavy-duty diesel trucks while 75 percent of gasoline PM-
10 comes from the family car, that is, light duty cars and trucks 
(which include sports utility vehicles). See Table ORM-1 in the EPA 
TSD section ``Implementation of BACM and Inclusion of MSM for On-
Road Motor Exhaust (Technology Standards).'' There is almost no 
overlap in the controls for the family car and those for heavy duty 
diesel trucks, key evidence that they are in fact distinct source 
categories. See Table ORM-4 in the EPA TSD.

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[[Page 19973]]

    The suggested technology-based measures for controlling emissions 
from on-road motor vehicle exhaust fall into one of five categories: 
new emission standards, inspection and maintenance programs, fuels, 
programs to encourage alternative fueled vehicle usage, and programs to 
accelerate fleet turnover. In total, the MAG plan considers 22 
technology-based control measures. See MAG plan, Table 5-2. We believe 
this list is complete and propose to find that the MAG plan evaluates a 
comprehensive set of potential technology-based controls for on-road 
motor vehicle exhaust emissions including the potentially most 
stringent measures from other states.
    For gasoline vehicles, Arizona has implemented one of the nation's 
best and most comprehensive enhanced I/M programs including expanding 
the program to areas surrounding Phoenix; has adopted its own Clean 
Burning Gasoline program which mandates the use of either Phase II 
federal reformulated gasoline or California reformulated gasoline; 
offers generous tax credits and deductions for conversion of vehicles 
to alternative fuels; and mandates federal, state, county, and 
municipal governments to convert their fleets to alternative fuels. MAG 
plan, pp. 7-2 through 7-24.
    Arizona has instituted a heavy duty diesel I/M program, will 
require pre-1988 HDDV registered in the Phoenix nonattainment area to 
meet 1988 federal emission standards starting in 2004, has established 
a voluntary vehicle repair and retrofit program to encourage 
retrofitting and overhaul of heavy duty diesel engines to reduce 
emissions, and has limited diesel sulfur content to 500 parts per 
million (ppm). MAG plan, Chapter 7.
    The California Air Resources Board's diesel fuel standards (CARB 
diesel) is one of the few identified motor vehicle controls not adopted 
by the State. The plan identifies this measure as a potential MSM. MAG 
plan, Table 10-7. The MAG plan claims that the measure is unreasonable 
on a cost basis. MAG plan, p. 9-46. We make no judgement on this claim 
given the great uncertainty regarding the potential cost of 
implementing CARB diesel in the Phoenix area. We do note that the State 
has already adopted half of the CARB diesel standards, the 500 ppm 
sulfur limit.\11\
---------------------------------------------------------------------------

    \11\ The other CARB diesel standard is a limit on the aromatic 
hydrocarbon content of no more than 10 percent by volume. CARB, Fact 
Sheet on California Diesel Fuel, March 1997.
---------------------------------------------------------------------------

    Under our proposed policy for MSM in extension requests, we believe 
that we can find that the MAG plan provides for the inclusion of MSM to 
our satisfaction absent the adoption and implementation of CARB diesel 
because, based on information in the MAG plan, the on-road engine 
category's contribution to nonattainment in the Phoenix area is 
relatively low compared to other PM-10 dust sources and implementation 
of CARB diesel would not advance the attainment date.
    According to the MAG plan, the on-road motor vehicle category 
contributes just 1.3 percent of the pre-control inventory in 2006, 
compared to construction dust at 43.8 percent, paved road dust at 20.4 
percent, unpaved road dust at 13.1 percent, and windblown dust at 8.7 
percent. MAG plan, Table 8-3. Adoption of CARB diesel would generate a 
total reduction of 0.8 mtpd in 2006. MAG plan, p. 10-37. It takes a 4 
mtpd reduction to advance the annual standard attainment date one year 
(the minimum needed because it is an annual standard), so reductions 
from implementation of this measure are insufficient to advance the 
attainment date. See section on RFP and Quantitative Milestones.
    As noted before, Arizona has in place one of the nation's most 
comprehensive programs to address on-road motor vehicle emissions. With 
the additional measures in the MAG plan (including a more stringent 
diesel I/M program and measures both encouraging and requiring diesel 
fleet turnover) the overall mobile source program is strengthened and 
goes beyond the existing program. Both strengthening and expanding 
existing programs are key criteria for demonstrating the implementation 
of BACM. See Addendum at 42013. Where the MAG plan has rejected 
potential BACM, it provides a reasoned and acceptable justification for 
the rejection.
    The MAG plan identified just a few measures from other areas as 
being more stringent than existing programs. These measures have either 
been adopted or we have concluded that the measures need not be 
included to assure the inclusion of MSM.
    All the adopted BACM and MSM are already implemented, except for 
one. The requirement that pre-1988 heavy duty diesel vehicles 
registered in the nonattainment area meet 1988 federal emission 
standards will not be implemented until January 1, 2004 in order to 
provide sufficient lead time for modification or replacement of the 
non-complying heavy duty diesel vehicles.
    We, therefore, propose to find that the combination of on-road 
motor vehicle technology controls and TCMs (described in the next 
section) in the MAG plan provides for the implementation of RACM and 
BACM and the inclusion of MSM for on-road motor vehicle exhaust.
    b. Transportation control measures (TCMs) for on-road motor vehicle 
exhaust and paved road dust. TCMs can reduce PM-10 emissions in both 
the on-road motor vehicle exhaust and paved road dust source categories 
by reducing vehicle miles traveled (VMT) and vehicle trips. They can 
also reduce vehicle exhaust emissions through relieving congestion. Our 
serious area PM-10 guidance requires that plans identifying on-road 
motor vehicles as a significant sources must also evaluate the TCMs 
listed in section 108(f) of the CAA. Addendum at 42013.
    In our review, we have primarily assessed the MAG plan's provisions 
for implementing RACM and BACM and including MSM through TCMs based on 
the measures' effectiveness in controlling directly-emitted PM-10 from 
vehicle exhaust. We have not assessed the plan based on the TCMs' 
potential benefit in controlling PM-10 precursors such as 
NOX and SOX because (1) from available ambient 
measurements, neither nitrates nor sulfates are important to overall 
PM-10 concentrations in the Phoenix area (See EPA TSD section, ``BACT 
for Major Stationary Sources of PM-10 Precursors'' which shows that 
total secondary particulates accounted for less than 4 g/
m3 in 1995) and (2) Arizona has already targeted mobile 
source NOX and SOX through an aggressive set of 
mobile source controls which we believe cover the implementation of 
RACM and BACM and inclusion of MSM requirements for tailpipe 
NOX and SOX. See discussion immediately above on 
technology controls for on-road motor exhaust.
    In total, the MAG plan identifies 19 TCMs for consideration 
including the CAA section 108(f) measures. The plan does not identify 
any potentially more stringent TCMs from other areas. See EPA TSD 
section ``Implementation of BACM and MSM for On-Road Motor Vehicle 
Exhaust and Paved Road Dust (TCMs).'' We believe that this list is 
complete and propose to find that the MAG plan evaluates a 
comprehensive set of potential TCMs for on-road motor vehicle exhaust 
emissions and the potentially most stringent measures from other 
States.
    Arizona has a long history of adopting and then enhancing programs 
to reduce emissions from on-road motor vehicles by reducing vehicle 
miles traveled,

[[Page 19974]]

vehicle trips, and/or congestion.\12\ The area has an employer trip 
reduction ordinance which applies to employers of 50 or more, a public 
outreach program to encourage people to reduce driving, programs to 
improve bicycling and pedestrian travel, and an extensive program to 
synchronize traffic lights. In most instances, these programs were 
adopted and implemented as part of carbon monoxide and ozone control 
programs, but they also reduce PM-10.
---------------------------------------------------------------------------

    \12\ These plans include the MAG moderate and serious area 
carbon monoxide plans and MAG moderate area ozone plan.
---------------------------------------------------------------------------

    With the additional measures in the MAG plan (including additional 
traffic light synchronization, transit improvements, and bicycle and 
pedestrian facility improvements), the overall TCM program is 
strengthened and goes beyond the existing program. See EPA TSD, Table 
TCM-3 in section ``Implementation of BACM and MSM for On-Road Motor 
Vehicle Exhaust and Paved Road Dust (TCMs).'' Both strengthening and 
expanding existing programs are key criteria for demonstrating the 
implementation of BACM. See Addendum at 42013. Where the MAG plan has 
rejected potential BACM, it provides a reasoned justification for the 
rejection.
    All the adopted TCM BACM are already implemented or have on-going 
implementation schedules because they are part of a on-going capital 
improvement program (e.g., signal synchronization).
    We propose to find that the combination of on-road motor vehicle 
technology controls (described in the previous section) and TCMs in the 
MAG plan provides for the implementation of RACM and BACM and inclusion 
of MSM for on-road motor vehicle exhaust. We also propose to find that 
the combination of TCMs and paved road dust measures (described in the 
paved road section later in this preamble) provides for the 
implementation of RACM and BACM and the inclusion of MSM for paved road 
dust.
    c. Nonroad engines. The non-road engine category covers a diverse 
collection of engines, equipment and vehicles fueled by gasoline, 
diesel, electric, natural gas, and other alternative fuels, including 
outdoor power equipment, recreational equipment, farm equipment, 
construction equipment, lawn and garden equipment, and marine vessels.
    The suggested measures for controlling emissions from nonroad 
engines fall into one of four categories: new emission standards, 
programs to accelerate fleet turnover, programs affecting usage, or 
fuels. In total, the MAG plan evaluates 8 measures in addition to clean 
fuels measures for reducing PM-10 emissions from nonroad engines. We 
believe that this list is complete and propose to find that the MAG 
plan evaluates a comprehensive set of potential measures for nonroad 
engines including the potentially most stringent measures from other 
States.
    We have adopted national emission standards for a broad range of 
nonroad engines. These standards apply to nonroad engines sold in 
Arizona and are the base, RACM-level, program for controlling emissions 
from nonroad engines. The CAA preempts all states, except for 
California, from setting independent nonroad emission standards. CAA 
section 209(e). Other states, however, may adopt regulations identical 
to California's regulations, provided they notify us and give 
appropriate lead time, 2 years, for implementation. Section 
209(e)(2)(B).
    Arizona has committed to adopt California's non-road standards that 
are more stringent than the federal standards. MAG plan, p. 7-42. In 
addition, the State has established and is currently running a 
voluntary retirement program for gasoline powered lawn and garden 
equipment which is run by Maricopa County and a program to encourage 
the use of temporary electrical power rather than portable generators 
at construction sites. See MAG plan, pp. 7-41 and 7-43.
    With the addition of these measures, the overall nonroad engine 
program is strengthened and goes beyond the existing federal program. 
See EPA TSD section ``Implementation of BACM and Inclusion of MSM for 
Nonroad Engines.'' Both strengthening and expanding existing programs 
are key criteria for demonstrating the implementation of BACM. See 
Addendum at 42013. Where the MAG plan has rejected potential BACM, it 
provides a reasoned justification for the rejection.
    The MAG plan identifies CARB diesel as a potential MSM for non-road 
engines but does not adopt it. MAG plan, Table 10-7. Under our proposed 
policy for MSM in extension requests, we believe that we can find that 
the MAG plan provides for the inclusion of MSM to our satisfaction 
absent the adoption of CARB diesel because, based on information in the 
MAG plan, the non-road engine category's contribution to nonattainment 
in the Phoenix area is relatively low compared to other PM-10 dust 
sources and implementation of CARB diesel would not advance the 
attainment date.
    The nonroad motor vehicle category contributes 4.8 percent of the 
pre-control inventory in 2006, compared to construction dust at 43.8 
percent, paved road dust at 20.4 percent, unpaved road dust at 13.1 
percent, and windblown dust at 8.7 percent. MAG plan, Table 8-3. 
Adoption of CARB diesel would generate a total reduction of 0.8 mtpd in 
2006. MAG plan, p. 10-37. It takes a 4 mtpd reduction to advance the 
annual standard attainment date one year (the minimum needed because it 
is an annual standard), so reductions from implementation of this 
measure are insufficient to advance the attainment date. See section on 
RFP and Quantitative Milestones.
    We, therefore, propose to find that MAG plan provides for the 
implementation of RACM and BACM and inclusion of MSM for on-road motor 
vehicle exhaust.
    d. Paved road dust. Paved road dust is the largest source of PM-10 
in the Maricopa area. It is fugitive dust that is deposited on a paved 
roadway and then is re-entrained into the air by the action of tires 
grinding on the roadway. Dust is deposited on the roadway from being 
blown onto the road from disturbed areas; tracked onto the road from 
unpaved shoulders, unpaved roads, or other unpaved access points; 
stirred up from unpaved shoulders by wind currents created from traffic 
movement; spilled onto the road by haul trucks; and carried onto the 
road by water runoff or erosion.
    The suggested measures for controlling emissions from paved road 
dust fall into one of three categories: reductions in vehicle trips 
(VT) and vehicle miles traveled (VMT), preventing deposition of 
material onto a roadway and cleaning material off the roadway. We have 
already discussed measures for reducing VT and VMT in the section on 
TCMs above.
    The MAG plan lists several potential BACM for paved road dust. It 
also lists a number of potentially MSM from other areas. We believe 
these lists are complete and propose to find that the MAG plan 
evaluates a comprehensive set of potential controls for paved road dust 
including the potentially MSM from other States.
    Prior to the MAG plan, the cities and towns in the Phoenix area and 
Maricopa County implemented a number of measures addressing paved road 
dust. See MAG plan, Table 10-5. With the additional measures in the MAG 
plan (described below), the overall control program to reduce paved 
road dust is both strengthened and expanded beyond the existing 
program. See EPA TSD section ``Implementation of BACM

[[Page 19975]]

and Inclusion of MSM for Paved Road Dust.'' Both strengthening and 
expanding existing programs are key criteria for demonstrating the 
implementation of BACM. See Addendum at 42013.
    For the potential MSM, the MAG plan shows that these measures are 
either adopted or are not in fact more stringent than existing Phoenix 
area programs.
    With the exception of the MSM for PM-10-efficient street sweepers 
described below, all the adopted BACM for paved roads are already 
implemented or have on-going implementation schedules because they are 
part of a on-going capital improvement program (e.g., curbing). For the 
reasons discussed below, we propose to find that the MAG plan provides 
for the implementation of the PM-10 efficient street sweeper measures 
as expeditiously as practicable, consistent with our proposed MSM 
policy.
    We, therefore, propose to find that the MAG plan provides for the 
implementation of RACM and BACM and for the inclusion of MSM for paved 
road dust.
    Preventing deposition of material onto a roadway. Measures aimed at 
preventing track out on a paved road include treating unpaved access 
points, preventing track out from construction/industrial sites, 
treating shoulders on paved roads, controlling emissions during 
material transport (e.g., truck covers, freeboard requirements), and 
preventing erosion onto paved roads.
    The MAG plan includes each of these measures:
    Unpaved access points: In the MAG moderate area plan, local 
jurisdictions focused on requiring new connections to public paved 
streets to be paved. MAG plan, p. 9-74. In the serious area plan, the 
focus has shifted to addressing existing unpaved access points in 
addition to preventing new unpaved access points while maintaining the 
previous programs. Most public entities committed to stabilize unpaved 
access points when a connecting road is built, improved or 
reconstructed. See, for example, Glendale Commitment, ``Reduce 
Particulate Emissions from Unpaved Shoulders and Unpaved Access Points 
on Paved Roads.'' Some cities have made explicit commitments for 
stabilizing existing access points without this prerequisite, such as 
Gilbert and Mesa. We also anticipate that routine city/town/County road 
paving and stabilization projects will result in controlling a number 
of existing unpaved access points. These projects combined with 
increased enforcement of track-out restrictions and additional PM-10 
efficient street sweeping efforts should reduce paved road emissions 
attributable to unpaved access points.
    The only potential MSM that the MAG plan identifies for unpaved 
access points are track out control requirements for construction 
sites. See MAG plan, Table 10-7. We discuss these measures in the next 
section.
    Track out. Rule 310, sections 308.2(c) and 308.3 address dirt track 
out from construction/industrial sites: All work sites that are five 
acres or larger and all work sites where 100 cubic yards of bulk 
materials are hauled on-site or off-site each day must control and 
prevent track out by installing a track out control device. All work 
sites must also clean up spillage or track out immediately when it 
extends a cumulative distance of 50 linear feet or more; where track 
out extends less than 50 feet, it must be cleaned up at the end of the 
work day.
    The MAG plan identifies, as a potentially more stringent measure 
for track out, South Coast (Los Angeles area) Air Quality Management 
District's Rule 403. MAG plan, Table 10-7. The plan concludes that the 
two rules are reasonably similar in several respects, and where 
differences exist, the relative impacts on control roughly balance 
against each other. MSM Study, p. C-4.\13\ We agree. Both rules 
emphasize prevention and rapid removal of track out. See EPA TSD 
section ``Implementation of BACM and Inclusion of MSM for Paved Roads 
Dust,'' Note 2.
---------------------------------------------------------------------------

    \13\ The ``MSM Study'' is the ``Most Stringent PM-10 Control 
Measure Analysis,'' Sierra Research, May 13, 1998 found in Appendix 
C, Exhibit 4 of the MAG plan.
---------------------------------------------------------------------------

    Unpaved Road Shoulders. As with unpaved access points, the MAG plan 
demonstrates a shift to dealing with existing unpaved shoulders from 
only preventing new ones. MAG plan, Table 9-11. Maricopa County has 
committed to treat 100 miles of shoulders along existing paved arterial 
and collector roadways with high volume truck traffic by 2003, in 
addition to its annual capital improvement projects for paving or 
treating unpaved shoulders. Maricopa County commitment, 1999 revised 
measure 5. Other jurisdictions have also made commitments to treat 
shoulders.
    A.R.S. 9-500.04(3) and 49-474.01(4), adopted by the State 
legislature in 1998, require the cities, towns and County of Maricopa 
to develop and implement plans to stabilize targeted unpaved roads and 
alleys and to stabilize unpaved shoulders on targeted arterials 
beginning January 1, 2000. Although this legislation does not specify 
how many shoulder miles to be controlled, we believe that the local 
jurisdictions' efforts to meet this new legislation will result in the 
control of unpaved shoulders where it is most needed.
    Material Transport. Requirements for the control of PM-10 emissions 
during material transport are found in Rule 310, sections 308.1 and 
308.2. When hauling material off-site onto paved public roadways, 
sources are required to: (1) load trucks such that the freeboard is not 
less than three inches; (2) prevent spillage; (3) cover trucks with a 
tarp or suitable enclosure; and (4) clean or cover the interior cargo 
compartment before leaving a site with an empty truck.
    The MAG plan identifies requirements for bulk material transport in 
Imperial County Regulation VIII as a potential MSM. MAG plan, Table 10-
7. The plan concludes that MCESD's rule is equally stringent. We agree 
because Rule 310's requirements for bulk material transport/hauling are 
essentially the same as Imperial County's requirements.
    Cleaning material off the roadway. Measures for cleaning material 
off roadway are track out, erosion, and spill removal requirements and 
road sweeping.
    The MAG plan includes each of these measures:
    Material spillage, erosion, or accumulation. Rule 310, section 
308.2 and 308.3 address rapid clean up of track out from construction/
industrial sites. Rule 310.01, section 306 requires property owners/
operators to remediate erosion-caused deposits of bulk materials onto 
paved surfaces. Erosion-caused deposits are to be removed within 24 
hours of their identification or prior to resumption of traffic on the 
pavement.
    The MAG plan identifies South Coast's Rule 1186 and Mojave Desert's 
Rule 403 as potential MSMs for material spillage, erosion, and 
accumulation onto roadways. MAG plan, Table 10-7. In both cases, the 
plan concludes that MCESD's rules are more stringent. We agree. MCESD's 
rules require the clean up of more incidences of spillage, etc. than 
does South Coast's rule. See EPA TSD, ``Implementation of BACM and 
Inclusion of MSM for Paved Roads,'' Note 5.
    Street sweeping. Most cities/towns and the County have on-going 
street sweeping programs with variable sweeping frequencies. With some 
exceptions, public entities implementing this measure have not 
explicitly committed to increase their existing sweeping frequencies. 
Phoenix,

[[Page 19976]]

for example, approved a program in 1996 to increase the frequency of 
residential street sweeping to match the uncontained trash pick-up 
schedule. Phoenix commitment, measure 97-DC-5. However, sweeping 
frequency is appropriately evaluated in combination with other paved 
road measures, because the emission-reducing potential of increased 
sweeping frequency is closely associated with other factors. These 
factors include whether the sweepers currently in use are PM-10 
efficient (such that the act of sweeping does not cause increased 
emissions) and whether the public entity has identified roads that tend 
to experience higher silt loadings where more frequent sweeping is 
likely to make an appreciable difference in PM-10 emissions. Because 
sweeping frequency is among the criteria included in MAG's PM-10 
efficient street sweeper solicitation (see below), we believe this 
measure is largely incorporated into MAG's new program.
    The MAG plan identifies as a MSM the PM-10 efficient street 
sweeping provisions in South Coast Rule 1186. MAG plan, Table 10-7. 
However, the plan's analysis pre-dates MAG's commitment for the 
purchase and distribution of PM-10 efficient street sweepers and is no 
longer current.
    The MAG plan includes commitments by MAG, cities, towns and the 
County for the purchase and use of PM-10 efficient street sweepers. 
This commitment involves the allocation of $3.8 million in Congestion 
Mitigation Air Quality (CMAQ) funds for the FY 2000-2004 Transportation 
Improvement Program (TIP) to purchase PM-10 certified street sweepers 
for the local jurisdictions to use. MAG has recommended an additional 
$1.9 million CMAQ funds be allocated to purchase PM-10 certified street 
sweepers in the FY 2001-2005 TIP. See MAG commitment, ``PM-10 Efficient 
Street Sweepers.''
    The funds allocated by MAG for this program should be sufficient to 
replace approximately two-thirds of the 72 existing city/town/County 
street sweepers.\14\ Each fiscal year in which CMAQ funds are allocated 
for street sweepers, MAG will solicit requests for funding from cities, 
towns and the County in the PM-10 nonattainment area. Funding requests 
must identify by facility type (i.e. freeway, arterial/collector, 
local) the number of centerline miles to be swept with the PM-10 
certified units, expected frequency of sweeping, and average daily 
traffic (if available). MAG will use this information to estimate the 
emissions reduction associated with each sweeper request and rank the 
requests in priority order of effectiveness for consideration in the 
allocation of CMAQ funds. See MAG commitment, ``PM-10 Efficient Street 
Sweepers.''
---------------------------------------------------------------------------

    \14\ Some street sweepers may be additions to, as opposed to 
replacements of, existing equipment.
---------------------------------------------------------------------------

    In evaluating this program, we considered not only the number of 
PM-10 efficient street sweepers to be purchased and distributed, but 
whether the program incorporates use factors that influence emissions 
reductions. The greatest emissions reduction benefit for this 
mitigative measure will be achieved if the sweepers are used on a 
frequent basis on roads with high silt loadings or significant visible 
accumulations. Each public entity has a monetary incentive to compete 
for the PM-10 efficient street sweepers, as the program is funded by 
MAG with a low cost share (5.7 percent) requirement. Also, the new 
street sweepers will either replace existing city-owned street sweeping 
equipment or contracted out services, or be added to existing street 
sweeper equipment/services. MAG's selection process includes PM-10 
emissions reduction potential, based on the types of roads each 
jurisdiction is targeting for sweeping and how frequently they will be 
swept. This data will assist MAG in distributing the street sweepers to 
local jurisdictions in a way that maximizes the regional air quality 
benefits of the program. Plus, when the cities/towns/County are awarded 
PM-10 efficient street sweepers, their submittals will incorporate use 
factors that maximize emission reductions from this measure.
    We believe that implementation of the PM-10 efficient street 
sweeper program is as expeditious as practicable. The funding necessary 
to purchase this equipment is available only over the course of several 
fiscal years and the purchase of the PM-10 efficient street sweepers 
can only proceed at the rate these funds become available.
    South Coast's Rule 1186 requires any government or government 
agency which contracts to acquire street sweeping equipment or services 
for routine street sweeping on public roads that it owns and/or 
maintains, where the contract date or purchase or lease date is January 
1, 2000 or later, to acquire or use only certified street sweeping 
equipment. The rule establishes street sweeper testing and 
certification procedures. Unlike Maricopa's strategy, Rule 1186 
requires that PM-10 efficient street sweepers be used whenever street 
sweeping is contracted out as of January 2000, and it requires public 
agencies to replace their existing street sweeping equipment with PM-10 
efficient equipment by attrition.
    MAG's PM-10 efficient street sweeper program is being funded over 
the next 4 to 5 fiscal years, which may result in a greater number of 
street sweepers distributed in a shorter time frame than could be 
expected using South Coast's natural attrition approach. While it is 
possible that some cities/towns in Maricopa may continue to contract 
out for street sweeping services where PM-10 efficient sweepers may not 
be used, most do not contract for street sweeping. Furthermore, due to 
the fact that public entities will be competing for PM-10 efficient 
street sweepers funded by CMAQ dollars with only a low cost share 
requirement, we believe that the already limited reliance on contracted 
out services in Maricopa County will lessen as new PM-10 efficient 
equipment becomes available and that contractors will switch to PM-10 
efficient equipment to meet new demand. In addition, MAG's program 
ensures that the cities/town/County develop plans for how the street 
sweepers will be used to maximize their emissions reduction potential. 
We, therefore, believe that overall the Maricopa program is equivalent 
to South Coast's Rule 1186.
    e. Unpaved parking lots. This category includes emissions from re-
entrained road dust from vehicle traffic in unpaved parking lots and 
windblown dust entrained from the disturbed surface of unpaved parking 
lots.
    There are two principle ways to control emissions from unpaved 
parking lots: prohibit unpaved parking lots or treat the lot. MAG plan 
identified both: a prohibition on unpaved haul roads and parking or 
staging areas and surface treatment to reduce dust from unpaved 
driveways and parking lots. MAG plan, Table 5-2. The MAG plan 
identified one potentially more stringent measure from South Coast 
which controls fugitive dust from parking areas on construction sites. 
MSM Study, p. C-9 and 10. It did not identify any potential MSM for 
non-construction site unpaved parking lots. We believe this list is 
complete and propose to find that the MAG plan evaluates a 
comprehensive set of potential BACM and MSM for unpaved parking lots.
    Most local jurisdictions in Maricopa County identified ordinances 
that require paving of new parking lots. In addition, MCESD Rule 310.01 
requires owners/operators of an unpaved parking lot larger than 5,000 
square feet to pave, apply dust suppressants, or apply gravel, 
according to the applicable rule

[[Page 19977]]

standards/test methods. Section 303. Applicable standards include a 20 
percent opacity standard, and an 8 percent silt content standard and/or 
a 0.33 oz/square foot silt loading standard. Section 303.2. MCESD Rule 
310 applies the same stabilization requirements to parking lots on 
permitted facilities. Rule 310, section 302.1. Finally, many cities/
towns have treated their own parking lots or required treatment of 
private lots below MCESD's thresholds.
    In determining whether the MAG plan provides for the implementation 
of BACM for unpaved parking lots, we are also specifically considering 
whether the plan provides for the implementation of RACM for these 
sources.\15\ In our FIP, we promulgated a RACM fugitive dust rule 
applicable to unpaved parking lots in the Phoenix PM-10 nonattainment 
area and thus it provides a starting point for determining whether the 
MAG plan measures for unpaved parking lots meet RACM. It is not 
necessary for the MAG plan measures to be identical to the FIP rule in 
order to meet the CAA's RACM requirement, but only that they provide 
for the implementation of RACM.\16\ However, if the submitted measures 
for a particular source are identical to the FIP rule, we can determine 
without further analysis that the MAG plan has provided for RACM for 
that source.
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    \15\ While a serious area PM-10 plan must provide for both the 
implementation of RACM and BACM, in determining whether such a plan 
provides for BACM implementation, we do not normally conduct a 
separate evaluation to determine if the measures also meet the RACM 
requirements of the CAA as interpreted by EPA in its General 
Preamble. See 57 FR 13540. This is because in our serious area 
guidance (Addendum at 42010), we interpret the BACM requirement, as 
generally subsuming the RACM requirement (i.e. if we determine that 
the measures are indeed the ``best available,'' we have necessarily 
concluded that they are ``reasonably available''). See Addendum at 
42012-42014. Therefore, a separate analysis to determine if the 
measures also represent a RACM level of control is not necessary. 
However, in this particular case, we are proposing to withdraw the 
FIP rule in conjunction with our proposed approval of the MAG plan. 
In order to do this, we must determine under CAA section 110(l), 
that, among other things, withdrawing the FIP rule does not 
interfere with the RACM requirements in the CAA.
    \16\ The State may submit one or more control measures that 
collectively achieve a RACM level of control for a particular 
source, regardless of whether they apply the same strategy as our 
FIP rule. Furthermore, EPA's guidance indicates that a RACM 
evaluation includes considering ``the impact of the reasonableness 
of the measures on the municipal or other governmental entity that 
must bear the responsibility for their implementation.'' General 
Preamble at 13541.
---------------------------------------------------------------------------

    MCESD requirements for unpaved parking lots found in Rule 310.01, 
section 303 are the same in terms of source coverage and applicable 
standards/test methods for unpaved parking lots as the FIP rule, with 
the only difference being that Rule 310.01 applies county-wide while 
the FIP rule applies strictly to sources located in the PM-10 
nonattainment area. Rule 310.01 requirements are effective upon 
adoption and were adopted on February 2000, such that the timeframe for 
controls is equivalent to the FIP rule and is also as expeditious as 
practicable. In light of the fact that Rule 310.01 requirements are the 
same as the FIP rule requirements and MCESD's commitments to improve 
compliance and enforcement of Rule 310.01, we propose that the MAG plan 
provides for the implementation of RACM. Given additional MAG plan 
city/town commitments that collectively increase the stringency of 
control on unpaved parking lots, we propose that the MAG plan also 
provides for the implementation of BACM.
    South Coast Rule 403 requires sources to apply dust suppressants to 
stabilize at least 80 percent of unstabilized surface area. Sources 
must comply with a 0 percent opacity property line limit. The MAG plan 
deems the respective requirements roughly equivalent to Rule 310. We 
believe that the addition of a silt loading/content standard for 
unpaved parking lots for sources covered under Rule 310 increases the 
rule's stringency to be at least equivalent to that of South Coast Rule 
403. We, therefore, propose to find that the MAG plan correctly 
concluded that there are no more stringent measures in other State 
plans or used in practice elsewhere that are applicable to the Phoenix 
area.
    f. Disturbed vacant lands. This category includes windblown 
fugitive dust emissions from disturbed surfaces of vacant lands. On 
vacant land, fugitive dust emissions are caused by virtually any 
activity which disturbs an otherwise naturally stable parcel of land, 
including earth-moving activities, material dumping, weed abatement, 
and vehicle traffic. 63 FR 15919, 15937 (April 1, 1998).
    The MAG plan includes three suggested measures for controlling 
fugitive dust from vacant disturbed lands. The plan also identified 
controls on weed abatement operations and off-road racing as potential 
most stringent measures. We believe this list is complete and propose 
to find that the MAG plan evaluates a comprehensive set of potential 
BACM and MSM for disturbed vacant lands.
    The MAG plan includes two MCESD rules that address BACM for vacant 
lots. Rule 310 requirements apply to vacant lots located at permitted 
facilities (including construction sites) and Rule 310.01 requirements 
apply to nonpermitted sources.\17\ Rule 310 and Rule 310.01 
requirements apply to both publicly and privately owned lots. Rule 310, 
section 302.3 and Rule 310.01, section 301 and 302.
---------------------------------------------------------------------------

    \17\ Permitted sources include any facility permitted by MCESD 
and are not limited solely to those facilities with earthmoving 
permits. Rule 310, section 102.
---------------------------------------------------------------------------

    In determining whether the MAG plan provides for the implementation 
of BACM for disturbed vacant land, we are also specifically considering 
whether the Plan provides for the implementation of RACM for these 
sources. See Footnote 15. In our FIP, we promulgated a RACM fugitive 
dust rule applicable to disturbed vacant land in the Phoenix PM-10 
nonattainment area and thus it provides a starting point for 
determining whether the MAG plan measures for disturbed vacant lands 
meet RACM. It is not necessary for the MAG plan measures to be 
identical to the FIP rule in order to meet the CAA's RACM requirement, 
but only that they provide for implementation of RACM. See footnote 16. 
However, if the submitted measures for a particular source are 
identical to the FIP rule, we can determine without further analysis 
that the MAG plan has provided for RACM for that source.
    Rule 310.01 requirements for vacant lots and open areas are 
virtually identical to the Phoenix FIP rule's requirements for these 
sources. Rule 310.01, however, is more broadly applicable. It covers 
vacant lots and open areas located anywhere in Maricopa County, in 
contrast to the Phoenix FIP rule, which only applies to lots in the 
Maricopa County portion of PM-10 nonattainment area (located in the 
eastern third of the County). Rule 310.01, sections 301 and 302. Unlike 
the FIP rule, Rule 310.01 also applies to partially developed 
residential, industrial, institutional, governmental, or commercial 
lots in Maricopa County, and any tract of land in the Maricopa County 
portion of the nonattainment area adjoining agricultural property. Rule 
310.01, section 211.
    Rule 310 requirements for vacant lots and open areas on permitted 
sources are more stringent than those in Rule 310.01, in that Rule 310 
requires stabilization of all inactive disturbed surface areas on 
permitted facilities, regardless of their size. Rule 310, section 
302.3. Rule 310 also contains requirements for weed abatement that 
closely resembles the Phoenix FIP rule's weed abatement requirements, 
except

[[Page 19978]]

that Rule 310's threshold for coverage is more stringent.\18\
---------------------------------------------------------------------------

    \18\ Rule 310 requires any earthmoving operation that disturbs 
0.1 acre or more to have a dust control plan, including weed 
abatement by discing or blading, whereas the Phoenix FIP rule weed 
abatement requirements only apply to disturbances equal to or 
greater than 0.5 acres. Rule 310, section 303.
---------------------------------------------------------------------------

    Vacant lots and open areas subject to Rule 310 and Rule 310.01 are 
required to meet the same surface stabilization standards/test methods 
as required in the Phoenix FIP rule.
    In addition to requirements in Rule 310 and Rule 310.01, the MAG 
plan contains commitments made by several cities and towns to address 
vacant disturbed lots. For example, seven jurisdictions require or will 
require stabilization of disturbed vacant lots after 15 days of 
inactivity (as compared to Rule 310.01's 60-day compliance period); two 
(2) prohibit dumping of materials on vacant land; and two (2) will 
stabilize all city-owned vacant lots.
    Because Rules 310 and 310.01 requirements are at least as stringent 
as the FIP rule requirements and MCESD has committed to improve 
compliance and enforcement of these rules, we propose that the MAG plan 
provides for the implementation of RACM on disturbed vacant land. 
Because these rules increase the number of lots subject to control thus 
collectively increasing the stringency of control on vacant disturbed 
lands, we propose that the MAG plan also provides for the 
implementation of BACM.
    For its MSM comparison, the MAG plan identifies measures in Clark 
County (Las Vegas, Nevada) Rule 41 and South Coast Rule 403. See MSM 
Study, pp. C-11 and C-16,17. The plan concludes that neither measure is 
more stringent than the Maricopa measures because Rule 310 and 310.01 
contain similar, equally, or more stringent requirements. We agree that 
the MCESD's rules are equally or more stringent.
    We, therefore, propose to find that the MAG plan correctly 
concluded that there are no more stringent measures in other State 
plans or used in practice elsewhere that are applicable to the Phoenix 
area.
    g. Unpaved roads. This category includes re-entrained dust from 
vehicle travel on unpaved roads. There are three classes of unpaved 
roads in the Maricopa nonattainment area: public roads, private roads 
that are publicly maintained (also referred to as minimally-maintained 
or courtesy grade), and private roads that are privately maintained.
    The MAG plan includes three suggested measures for controlling 
fugitive dust from unpaved roads: Surface treatment to reduce dust from 
unpaved roads and alleys, traffic reduction/speed control plans for 
unpaved roads; and prohibition of unpaved haul roads. MAG plan, Table 
5-2. The MAG plan did not identify any other State's measures that are 
more stringent than the ones already in the plan. We believe this list 
is complete and propose to find that the MAG plan evaluates a 
comprehensive set of potential BACM and MSM for unpaved roads.
    In determining whether the MAG plan provides for the implementation 
of BACM for unpaved roads, we are also considering whether the Plan 
provides for the implementation of RACM for these sources. See Footnote 
15. In our FIP, we promulgated a RACM fugitive dust rule applicable to 
unpaved roads in the Phoenix PM-10 nonattainment area and thus it 
provides a starting point for determining whether the MAG plan measures 
for unpaved roads meet RACM. It is not necessary for the MAG plan 
measures to be identical to the FIP rule in order to meet the CAA's 
RACM requirement, but only that they provide for implementation of 
RACM. See footnote 16. However, if the submitted measures for a 
particular source are identical to the FIP rule, we can determine 
without further analysis that the MAG plan has provided for RACM for 
that source.
    As discussed below, we propose to find that the MAG plan provides 
for the implementation of RACM and BACM and the inclusion of MSM for 
unpaved roads.
    Surface treatment to reduce dust from unpaved roads and alleys. The 
principle control for public unpaved roads and alleys is Rule 310.01, 
section 304, which requires all publicly-owned unpaved roads and alleys 
with 250 vehicles per day or more to be stabilized by June 10, 2000 and 
those with 150 vehicles per day or more to be stabilized by June 10, 
2004.
    Several cities have commitments that go beyond the requirements of 
Rule 310.01 for publicly-owned unpaved roads. For example, the City of 
Phoenix committed to, and recently accomplished, paving all 80 miles of 
its publicly-owned unpaved roads regardless of the level of vehicle 
travel. Phoenix Commitment, Measure 98-DC-7. Other cities, such as 
Tempe and Gilbert, have very few remaining miles of public unpaved 
roads/alleys. See Tempe Commitments, Measure 98-DC-7 and Gilbert 
Commitments, Measure 98-DC-7.
    For private roads, Rule 310, section 308.6, requires that 
easements, rights-of-way, and access roads for utilities (electricity, 
natural gas, oil, water, and gas transmission) that receive 150 or more 
VPD must be paved, chemically stabilized, or graveled in compliance 
with the rule's standards.
    Private unpaved roads are scattered throughout Maricopa County, 
within both County and city jurisdictions. A survey performed for us of 
unpaved roads in Maricopa County determined that the great majority of 
identified unpaved road mileage consists of privately-owned roads that 
receive minimal maintenance by the Maricopa County Department of 
Transportation (MCDOT).\19\
---------------------------------------------------------------------------

    \19\ Pacific Environmental Services, ``Survey for Fugitive Dust 
Emission Sources,'' April 15, 1999.
---------------------------------------------------------------------------

    MAG and MCDOT have committed to pave County minimal maintenance 
roads within the nonattainment area that currently exceed 150 ADT and 
meet criteria to become public highways, using $22 million from 
Congestion Management/Air Quality and MCDOT funds.\20\ MAG Commitment; 
Maricopa County Commitment, 1999 Revised Measure 17. This program will 
pave an estimated 60 miles of unpaved roadways in fiscal years 2001-
2003 which is approximately 20 percent of the privately-owned, 
publicly-maintained County-jurisdiction roads and 40 percent of vehicle 
miles traveled on these roads. Maricopa County has also committed to 
continue to evaluate other roads for funding when traffic levels 
increase above 150 vehicle trips per day. Maricopa County Commitment, 
1999 Revised Measure 17. We interpret this commitment to apply to any 
private roads within County jurisdiction, whether they currently 
receive minimal maintenance or not.
---------------------------------------------------------------------------

    \20\ Congestion Management/Air Quality (CMAQ) funds are federal 
transportation funds awarded to certain nonattainment areas for 
congestion management or air quality-transportation projects such as 
paving unpaved roads.
---------------------------------------------------------------------------

    As the County evaluates roads for paving, it may make exceptions to 
its commitment to pave roads with vehicle trips that exceed 150 ADT. 
The County's evaluation process takes into account whether a road meets 
the proper criteria to become a public highway and whether estimated 
costs of paving are excessive (greater than $500,000 per mile).\21\ 
When MCDOT identifies a road that meets these criteria (i.e. the road 
can be declared a public highway and

[[Page 19979]]

costs are not excessive), it will recommend that the Board of 
Supervisors open and declare the road a public highway.
---------------------------------------------------------------------------

    \21\ A private road begins to bear other than local traffic 
through extensions of other nearby public roads or the construction 
of an indirect source that attracts external drivers using the road 
as a short cut. See Maricopa County Commitments, 1999 Revised 
Measure 17.
---------------------------------------------------------------------------

    Because BACM implementation properly takes costs into account, we 
believe that MCDOT's criteria for selecting private roads to pave are 
suitable in the context of a strategy to implement BACM and will result 
in control of the great majority of high traffic unpaved roads. 
Although available information on private roads in city jurisdictions 
is limited, our existing information suggests that a typical privately 
owned unpaved road has low ADT.\22\ As a result, we believe that the 
vast majority of private unpaved roads do not need to be controlled in 
order for us to determine that the MAG plan provides for the 
implementation of BACM for unpaved roads for the annual standard.
---------------------------------------------------------------------------

    \22\ Among the over 100 segments of unpaved privately-owned and 
maintained roads that were identified in the PES survey, the 
contractor estimated, using aerial photographs, that only 6 of these 
have ADTs that exceed 150. Tube counts, which are more accurate than 
other methods to estimate ADT, were not conducted on these roads.
---------------------------------------------------------------------------

    Traffic reduction/speed control plans for unpaved roads. Some 
jurisdictions committed to evaluate this measure. Two jurisdictions 
committed to posting 15 mph speed limit signs on private and public 
unpaved roads and access ways; one jurisdiction has posted 15 mph speed 
limits in all alleys. See MAG plan, Table 10-9. Also, under Rule 310, 
owners/operators of unpaved haul roads and utility roads who comply 
with the rule by limiting vehicle trips to 20 per day, must also limit 
vehicle speeds to 15 mph. While speed limit controls are only being 
implemented to a limited extent, we believe the plan measures to pave 
or otherwise stabilize unpaved roads in the Phoenix PM-10 nonattainment 
area establish the critical commitments for the implementation of RACM 
and BACM. This is because road stabilization ensures emission 
reductions whereas speed limits may or may not be observed.
    Prohibition of unpaved haul roads. Rule 310 requires that unpaved 
haul roads meet both a 20 percent opacity standard and a silt content 
or silt loading standard. Rule 310, section 302.2. We propose to find 
that this requirement is sufficient for the implementation of BACM for 
these roads. We believe requiring compliance with both of these 
standards ensures that the BACM applied will have a stabilizing effect.
    Evaluation of unpaved road measures in other areas found none that 
are more stringent than the measures for unpaved roads in the MAG plan. 
MAG plan, Table 10-7. We agree and propose to find that there are no 
other more stringent measures for unpaved roads than are already 
included in the MAG plan.
    Please see the TSD section ``Implementation of BACM and Inclusion 
of MSM for Unpaved Roads'' for a more detailed discussion of our 
proposed findings.
    h. Construction sites and activities. Sources of fugitive dust 
emissions at construction site sources include land clearing, 
earthmoving, excavating, construction, demolition, material handling, 
bulk material storage and/or transporting operations, material track 
out or spillage onto paved roads (which we have addressed in the paved 
road section), and vehicle use and movement on site (e.g., the 
operation of any equipment on unpaved surfaces, unpaved roads and 
unpaved parking areas). Windblown emissions from disturbed areas on 
construction sites are also a source of PM-10. Construction operations, 
which are mostly various forms of earthmoving, represent some 90 
percent of the emissions in this source category.
    The suggested measures in the MAG plan are actually various means 
of improving compliance with controls as opposed to new controls for 
construction sites. The controls for construction sites are found in 
MCESD's fugitive dust rule, Rule 310, revised on February 16, 2000.
    Rule 310's requirements, effective on February 16, 2000, apply to 
any source required to obtain a permit under Maricopa County rules, 
which includes earthmoving operations of 0.10 acre or more and sources 
subject to Title V permits,\23\ Non-Title V permits, or General 
Permits. In addition to rule requirements for fugitive dust sources 
located at any permitted source, Rule 310 requires that a Dust Control 
Plan (DCP) be submitted for any earthmoving operations of 0.10 acre or 
more, and that the DCP be approved prior to commencing any dust 
generating operation. The rule's definition of a dust generating 
operation includes any activity capable of generating fugitive dust 
including land clearing, earthmoving, weed abatement by discing or 
blading, excavating, construction, demolition, material handling, 
storage and/or transporting operations, vehicle use and movement, the 
operation of any outdoor equipment or unpaved parking lots. For other 
permitted sources, Rule 310 requires that a Dust Control Plan (DCP) be 
submitted and approved prior to commencing any routine dust generating 
activity, defined as any dust generating operation which occurs more 
than 4 times per year or lasts 30 cumulative days or more per year.\24\
---------------------------------------------------------------------------

    \23\ Title V permits are operating permits required by Title V 
of the Clean Air Act for major stationary sources and certain other 
stationary sources.
    \24\ This is in addition to the requirement to submit a DCP for 
any earthmoving operation that disturbs 0.10 acre or more even if 
the operation is subject to Title V or other permitting 
requirements.
---------------------------------------------------------------------------

    Specific Rule 310 requirements include:
     a 20 percent opacity requirement for any dust generating 
operation
     wind event control measures
     implementation of control measures before, after and while 
conducting any dust generating operation, including weekends, after 
work hours and holidays
     required control measures and standards for:
     unpaved parking lots
     unpaved haul/access roads
     disturbed open areas and vacant lots
     bulk material hauling
     bulk material spillage, carry-out, erosion and track out
     open storage piles
     weed abatement by blading or discing a requirement in dust 
control plans for at least one primary and one contingency control 
measure for all fugitive dust sources; the contingency measure is to be 
immediately implemented if the primary control measure proves 
ineffective
    In order to comply with the rule's 20 percent opacity standard and 
dust control plan requirements for implementing primary and/or 
contingency control measures for earthmoving activities,\25\ sources 
need to apply one or more controls, which in most cases includes 
applying water or another dust suppressant before and during 
operations. Inactive disturbed surfaces must be stabilized to meet at 
least one of the rule's stabilization standards (e.g. visible crusting, 
10 percent rock cover, etc.). Unpaved roads and unpaved parking lots 
must also be stabilized to meet both a 20 percent opacity standard and 
a silt content/loading standard.\26\ Test methods associated with 
stabilization and

[[Page 19980]]

opacity standards are contained in Appendix C, which was submitted with 
Rule 310.
---------------------------------------------------------------------------

    \25\ Earthmoving operations include cutting and filling, 
grading, leveling, excavating, trenching, loading or unloading of 
bulk materials, demolishing, blasting, drilling, adding to or 
removing bulk materials from open storage piles, back filling, soil 
mulching, landfill operations, or weed abatement by discing or 
blading.
    \26\ Unpaved roads must meet a 6 percent silt content standard 
or, alternatively, a 0.33 oz/ft2 silt loading standard, 
while unpaved parking lots must meet an 8 percent silt content 
standard or, alternatively, a 0.33 oz/ft2 silt loading 
standard.
---------------------------------------------------------------------------

    The February 2000 revisions to Rule 310 that have increased the 
rule's stringency include the addition of specific work practice 
standards, the addition of stabilization standards and test methods for 
unpaved surfaces, and modifications to the opacity test method (adding 
an alternative opacity test method for unpaved roads and unpaved 
parking lots and modifying the opacity test method for other sources). 
We believe that the new and/or revised standards/test methods provide 
for a greater degree of control than under the previous SIP-approved 
version of Rule 310.
    In addition to these Rule 310 revisions, MCESD has made three 
enforceable commitments to further strengthen requirements for 
construction sites that must be met by July 2001. These commitments, 
which all are part of Revised Measure 6 in Maricopa County's 
commitments, are to: 1. Research and develop a standard(s) and test 
method(s) for earthmoving sources, considering our field research, that 
are enforceable and meet BACM requirements on stringency and source 
coverage.
    Currently, activities on construction sites must meet an opacity 
standard of 20 percent. If research on the standards and test methods 
find problems with the existing opacity standard's enforceability, 
feasibility, or stringency for some or all earthmoving operations, 
MCESD will revise the rule to modify the existing opacity test method 
to address the problems as warranted or adopt a new standard(s) and 
test method(s) to deal with any problems that cannot be addressed by 
modifying the opacity test method;
    2. Research, develop and incorporate additional requirements for 
dust suppression practices/equipment for construction activities into 
dust control plans and/or Rule 310;
    3. Revise the sample daily recordkeeping logs for new and renewed 
Rule 310 permits to be consistent with rule revisions and to provide 
sufficient detail documenting the implementation of dust control 
measures required by Rule 310 and the dust control plan. Distribute 
sample log sheets with issued permits and conduct outreach to sources.
    The first enforceable commitment addresses our concern that the 
existing opacity standard and test method for earthmoving operations 
may not always be sufficient to control construction site dust to BACM 
levels. MCESD has already revised the opacity test method to deal 
partially with this concern (see Rule 310, Appendix C), but we believe 
that additional standards/test methods are needed to fully assure that 
sources are effectively controlled. We have already sponsored a field 
study to address this issue and are considering additional field work 
in Summer, 2000. We believe that additional time is needed for Maricopa 
County to investigate options in coordination with us, and then revise 
the rule. Therefore, a commitment is the appropriate method of 
addressing this issue.
    The second enforceable commitment addresses our concern that dust 
control plans (DCPs) lack specific criteria for dust suppressant 
application. For example, a source engaged in grading or cut-and-fill 
earthmoving for a multi-acre project may choose to comply with Rule 310 
by applying water. However, neither the rule nor DCPs establishes 
minimum criteria for the number of water trucks/water application 
systems and water truck capacity for any given size construction site 
or a ratio of earthmoving equipment to water trucks. The rule also does 
not contain a pre-wetting requirement, although research may show this 
to be necessary to successfully control dust on certain soil types.
    Establishing criteria for dust control is complicated by variations 
in soils, meteorological conditions, equipment size/use, project phase, 
and level of activity. All these factors can impact the amount of water 
(or other controls) needed to control fugitive dust on a particular 
site on a particular day, making it difficult to establish criteria 
that apply to all sites at all times. This explains why more time is 
needed for MCESD to develop criteria to address a multitude of 
circumstances.
    The third enforceable commitment addresses our concern that while 
Rule 310 currently contains an acceptable recordkeeping requirement, a 
more specific recordkeeping requirement would help improve compliance. 
Currently neither the rule nor DCPs specify what information should be 
included in a daily log. MCESD has committed to revising and 
distributing to permitted sources daily recordkeeping log sheets to 
provide sufficient detail documenting the implementation of dust 
control measures.
    Based on our evaluation of revised Rule 310 and the additional 
commitments made by MCESD, we propose to find that the rule and 
commitments together include a comprehensive set of BACM level controls 
for construction sites. The rule is comprehensive in scope in that each 
dust source is subject to a set of requirements under Rule 310 (e.g. 
storage piles, dirt trackout, haul truck loads, disturbed areas, 
earthmoving operations). In addition, the Rule 310 requirements are 
sufficiently stringent to provide for the implementation of RACM and 
BACM, with the exception of certain aspects of the rule that are 
addressed in the commitments made by MCESD. Thus, between the submitted 
rule requirements and commitments, we propose to find that the MAG Plan 
meets the CAA's RACM and BACM requirements for construction sites.
    The MAG plan identifies potentially more stringent construction 
site fugitive dust measures either in or under consideration for 
inclusion in others SIP. See MSM Study, Table 1-2 and Table 3-1.
    Most of the potential MSMs are provisions in South Coast fugitive 
dust rule, Rule 403. The MAG plan indicates that each of the South 
Coast and MCESD's rules are more stringent than the other in certain 
respects. MAG plan, p. 10-35. The MAG plan acknowledges that Rule 403 
contains more stringent control measure requirements than those imposed 
by Rule 310. For example, Rule 403 requires that water be applied to 
soil not more than 15 minutes prior to moving the soil and requires 
open storage piles to be watered twice per hour or covered. However, 
the MAG plan indicates that Rule 310's 20 percent opacity limit is 
generally more restrictive than Rule 403's property line standard 
because a 20 percent opacity fugitive dust plume typically disperses to 
zero visibility within 50 feet downwind of a source. MSM Study, p. C-
12. The MAG plan concludes that, on balance, Rule 310 is equally 
stringent compared to Rule 403's construction site requirements. We 
agree with this conclusion with the caveat that we believe Rule 310 
and/or dust control plans require additional control measures for dust 
suppression. This caveat is addressed in the MAG plan's commitment to 
research, develop and incorporate additional requirements for dust 
suppression practices/equipment for construction activities into dust 
control plans and/or Rule 310.
    The MAG plan does not discuss any construction site measures from 
other areas as potentially more stringent measures. Based on our work 
with the Las Vegas area, we have identified requirements in Clark 
County Health District permits that are potentially more stringent than 
Maricopa County's

[[Page 19981]]

measures.\27\ These requirements include stand tanks on projects that 
are 10 acres or more in size, an additional, separate water truck when 
using a trencher or when screening, a separate water truck or pull 
during landscaping, maintaining all stockpiles in a moist condition, 
etc.
---------------------------------------------------------------------------

    \27\ These requirements are not in Clark County's fugitive dust 
rule, but rather are required practices in dust control permits.
---------------------------------------------------------------------------

    We propose to find that Rule 310's existing provisions and Maricopa 
County's second enforceable commitment to research, develop and 
incorporate additional requirements for dust suppression practices/
equipment into Rule 310 and/or DCPs are consistent with Clark County's 
requirements.
    We have also identified a requirement in Imperial County Regulation 
VIII that is potentially more stringent than Maricopa County's 
measures. Imperial County Regulation VIII requires that water be 
applied 15 minutes prior to handling or transferring bulk material, 
chemical/physical stabilization, or sheltering/enclosure of the 
operation and transfer line. We propose to find that Maricopa County's 
second enforceable commitment to research, develop and incorporate 
additional requirements for dust suppression practices/equipment into 
Rule 310 and/or DCPs is consistent with Imperial County's requirements.
    For these reasons, we propose to find that the MAG plan provides 
for the inclusion of the MSM applicable to the Phoenix area for 
construction sites and activities.
    i. Agricultural sources. The agriculture source category covers all 
dust generating activities and sources on farms and ranches in the 
Maricopa nonattainment area. These activities and sources include land 
planning, tilling, harvesting, fallow fields, prepared fields, field 
aprons, and unpaved roads.
    Maricopa County is rapidly urbanizing with agricultural land being 
converted into other uses at a rate of approximately 6,000 acres per 
year. Cathy Arthur, MAG, December, 1997. Despite the conversion of 
agricultural lands to other uses, agricultural sources are expected to 
continue to contribute to PM-10 emissions for the foreseeable future, 
especially in relation to the PM-10 24-hour standard.
    The MAG plan identifies a number of potential BACM for agricultural 
sources. MAG plan, pp. 5-66 thru 5-72 and pp. 6-12 through 6-13.
    In 1998, Arizona passed legislation establishing an Agricultural 
Best Management Practices (BMP) committee for the purpose of adopting 
by rule by June 10, 2000, an agricultural general permit specifying 
BMPs for regulated agricultural activities to reduce PM-10 emissions in 
the Maricopa PM-10 nonattainment area. The Committee also is required 
to adopt and implement an education program by June 10, 2000, and 
affected agricultural sources are required to implement at least one 
BMP by December 31, 2001. A.R.S. 49-457.A-H, M. On June 29, 1999, we 
approved this legislation as a SIP revision meeting the requirement for 
the implementation of RACM in 189(a)(1)(C) and at the same time 
withdrew our commitment to adopt RACM controls for agricultural that we 
included in the 1998 PM-10 FIP. 64 FR 34726.
    The MAG plan relies on the State's commitment in A.R.S. 49-457 to 
adopt and implement BMPs to meet the requirement to provide for the 
implementation of BACM for agricultural sources. MAG plan, p. 7-156 and 
Letter from ADEQ to EPA, September, 1998, submitting the commitment as 
a SIP revision. The plan also relies on the statutory commitment to 
meet the MSM requirement in CAA section 188(e). MAG plan, p.10-25.
    Arizona's statutory BMP commitment is similar to the commitment we 
made in our 1998 PM-10 FIP. 63 FR 41326 (August 3, 1998). As part of 
the RACM demonstration in the FIP, we promulgated a commitment, 
codified at 40 CFR 52.127, to ensure that RACM for agricultural sources 
will be expeditiously adopted and implemented. For agricultural 
sources, the State is using a similar strategy to address the RACM, 
BACM and MSM requirements.
    We propose to find that the State's commitment to adopt and 
implement agricultural BMPs adequately addresses requirement to 
implement BACM and include MSM. The potential BACM explicitly 
identified in the MAG plan will be considered during the BMP 
development process.
    We have, beginning with the proposed rulemaking for our 1998 PM-10 
FIP and culminating in Ninth Circuit litigation on both the FIP and our 
SIP approval, explained at length our reasoning that a commitment to 
implement PM-10 controls beginning in June 2000 for agricultural fields 
and aprons in the Phoenix PM-10 nonattainment area rather than the 
immediate implementation of fully-developed regulations for those 
sources meets the RACM requirement in CAA section 189(a)(1)C). See 63 
FR 15920, 15935-15936 (April 1, 1998); 63 FR 41332-41334; 63 FR 71817. 
See also Brief for Respondents in Ober v. Browner, No. 98-71158, at 43-
59 (9th Cir., filed Oct. 2, 1998) (petition for review challenging 
EPA's FIP commitment to adopt and implement RACM for agricultural 
sources), and Brief for Respondents in Ober v. Browner, No. 99-71107, 
at 16-40 (9th Cir., filed Aug. 26, 1999) (petition for review 
challenging EPA's approval of the State's commitment to adopt and 
implement agricultural BMPs as meeting the RACM requirement of the 
CAA).
    In the context of this proposed action, our reasoning in short is 
that a legally binding commitment--embodied in the State statute 
establishing a committee that is required to adopt a general permit 
specifying BMPs and identifying specific deadlines for their 
implementation--meets the statutory requirement in CAA section 
189(b)(1)(C) since it is a ``provision to assure that best available 
control measures'' are implemented by a fixed deadline. While in 
preparing the FIP, we reviewed measures adopted by the South Coast for 
the control of PM-10 emissions from agricultural sources, we concluded 
that agricultural sources in the United States vary by factors such as 
regional climate, soil type, growing season, crop type, water 
availability, and relation to urban centers, therefore, each PM-10 
agricultural strategy is uniquely based on local circumstances. As a 
result, we could not, without further analysis, conclude that the South 
Coast controls should be immediately implemented in the Maricopa area.
    Furthermore, we determined that the goal of attaining the PM-10 
standards in Maricopa County with respect to agricultural sources would 
be best served by engaging all interested stakeholders in a joint 
comprehensive process on the appropriate mix of agricultural controls 
to implement in Maricopa County. We stated our belief that this 
process, despite the additional time needed to work through it, will 
ultimately result in the best and most cost-effective controls on 
agricultural sources in the County.
    While A.R.S. 49-457 does not use the term ``best available control 
measure,'' its definition of BMPs is consistent with the criteria in 
EPA's guidance. ``Best management practices'' are defined in A.R.S. 49-
457.N.3 as ``techniques verified by scientific research, that on a case 
by case basis are practical, economically feasible and effective in 
reducing PM-10 particulate emissions from a regulated agricultural 
activity.'' The broad definition of BMPs in the Arizona statute 
authorizes the BMP committee to adopt measures that will comply with 
our definition of BACM.

[[Page 19982]]

Moreover, as noted above, the statute provides for BMP implementation 
that begins with an education program by June 10, 2000 and culminates 
in full implementation of the BMPs by December 31, 2001. \28\
---------------------------------------------------------------------------

    \28\ Of course, once adopted and submitted to EPA as a SIP 
revision, the individual BMPs will have to be evaluated to determine 
if they comply in their specifics with the BACM requirement. Here we 
need only determine that the Arizona statute provides sufficient 
authority to assure that BACM will be implemented by June 10, 2000.
---------------------------------------------------------------------------

    Similarly, we have concluded that the definition of BMPs in the 
Arizona statute is broad enough to authorize the BMP committee to adopt 
measures that meet the level of control in the requirement to include 
MSM in CAA section 188(e) as we propose to interpret it in this 
proposed action. In reviewing measures in other SIPs and/or that have 
been adopted elsewhere, MAG determined that cessation of high wind 
tilling and soil erosion control plans were the most stringent measures 
available that had potential application for agricultural sources in 
Maricopa County. MAG plan p. 10-47. These measures are included in 
South Coast Rule 403 which requires PM-10 controls for all fugitive 
dust sources, including agricultural sources. In December 1998, South 
Coast adopted a set of conservation practices for agricultural sources 
to use to reduce fugitive dust. These practices were developed in 
consultation with affected stakeholder groups. See Guide to 
Agricultural PM-10 Dust Control Practices. The BMP task force will 
consider these measures during the development of the BMPs. MAG plan p. 
10-47. After the BMPs and supporting technical documents are submitted 
to EPA, we will review them to determine if their level of control is 
as stringent as the South Coast rule or adequately justifies why such 
level would not be feasible in the Maricopa area.
    As discussed elsewhere in this TSD, we propose to interpret section 
188(e) to require implementation of MSM as expeditiously as 
practicable. For the reasons stated above, in our FIP, and in our 
approval of the State legislation as meeting the RACM requirements of 
the CAA, we conclude that the implementation schedule in the State 
statute meets that test. Finally, we conclude that the commitment in 
the State legislation meets the requirement that ``the plan include[s] 
the most stringent measures * * *.'' Emphasis added.
    j. Residential wood combustion. The residential wood combustion 
(RWC) category includes emissions from the burning of solid fuel in 
residential fireplaces and woodstoves as well as barbecues and 
firepits.
    Measures to control PM-10 from residential woodburning include 
public education program, woodburning curtailment programs, retrofit 
requirements and restrictions or bans on the installation of 
woodburning stoves and/or fireplace. In total the MAG plan list 11 
potential BACM and 10 potential MSM. MAG plan Tables 5-2 and 1-7. We 
believe this list is complete and propose to find that the MAG plan 
evaluates a comprehensive set of residential woodburning measures.
    MCESD Rule 318, Approval of Residential Woodburning Devices, 
establishes standards for the approval of residential woodburning 
devices that can be used during restricted-burn periods. Maricopa 
County's Residential Woodburning Restriction Ordinance provides that 
restricted-burn periods are declared by the Control Officer when the 
Control Officer determines that air pollution levels could exceed the 
CO standard and/or the PM standard (150 g/m3). We 
approved Rule 318 and an earlier version of the ordinance (revised 
April 21, 1999) as providing for the implementation of RACM. See 64 FR 
60678 (November 8, 1999).
    MCESD revised the ordinance on November 17, 1999 to allow the 
Control Officer to declare restricted-burn periods when the particulate 
matter pollution levels could exceed the ``particulate matter no-burn 
standard'' of 120 g/m3. In addition, A.R.S. section 
9-500.16 and A.R.S. section 11-875 (1998) require cities and the County 
to adopt by December 31, 1998, an ordinance that prohibits the 
installation or construction of a fireplace or wood stove unless it is 
a fireplace with a permanently installed gas or electric log insert, a 
fireplace or wood stove that meets EPA's Phase II wood stove 
requirements, or a fireplace with a wood stove insert that meets EPA's 
Phase II stove requirements. Most jurisdictions have adopted or have 
committed to or indicated that State law requires them to adopt the 
required ordinance. See MAG Plan, pp. 7-55 to 7-64.
    With these additional controls, the overall residential woodburning 
restriction program is strengthened and goes beyond the existing RACM-
level program. Both strengthening and expanding existing programs are 
key criteria for demonstrating the implementation of BACM. See Addendum 
at 42013. Where the MAG plan has rejected potential BACM, it provides a 
reasoned justification for the rejection.
    The MAG plan identified a number of potential MSM for residential 
wood combustion. Except for the adoption of a lower threshold for 
calling no burn episodes, the plan does not provide for the adoption of 
any of these measures but provides reasoned and acceptable 
justifications for their rejection. Therefore, we propose to find that 
the MAG plan provides for the inclusion of MSM.
    k. Secondary ammonium nitrate. Secondary ammonium nitrate is formed 
by a chemical reaction in the atmosphere between oxides of nitrogen 
(NOX) and ammonia (NH3). Ninety percent of 
NOX comes from motor vehicle exhaust (both on and off road) 
and 99.9 percent of NH3 comes from animal wastes. See MAG 
plan, Table 3-1.
    Two potential BACM were identified for ammonia nitrate control: 
Reduce emissions of ammonia and nitrates from agricultural operations 
and require animal waste management plans for farms/ranches with more 
than 50 animals. The first measure involves tilling in of manure used 
as fertilizer within 48 hours of application. MAG plan, Table 6-1, 
measure 97-AG-3. The second measure would focus on reducing ammonia 
emissions from livestock waste during the winter months when conditions 
are most conducive to ammonium nitrate formation. MAG plan, Appendix B, 
Exhibit 5, p. 5-70. For MSM, no measures were found that required 
animal waste management plans for farms or ranches and no other 
measures were identified. See MAG plan, Table 10-7. A large number of 
measures that could reduce NOx emissions were identified and 
have been evaluated for on-road motor vehicles and nonroad engines. We 
believe these list of measures is complete and propose to find that the 
MAG plan evaluates a comprehensive set of potential controls for 
ammonium nitrate.
    Data from earlier studies indicate that ammonia emissions would 
need to be reduced by 80 percent to have an appreciable impact on 
ambient concentrations of ammonium nitrate. MAG plan, Appendix B, 
Exhibit 5, p. C-1. Essentially all ammonia emissions in the inventory 
are from livestock and not from the application of manure to 
agricultural fields. As result, controls on the application of manure 
are very unlikely to have any impact on PM-10 levels the Phoenix area 
and therefore are not technologically feasible. \29\ The estimated 
reduction in ammonia from

[[Page 19983]]

implementing waste management plans is 30 percent, far short of the 80 
percent needed to show impact on PM-10 levels (MAG plan, Appendix B, 
Exhibit 5, p. 5-72), so we also believe that this measure is currently 
not technologically feasible.
---------------------------------------------------------------------------

    \29\ We consider a measure technologically feasible for an area 
only if it has the potential to reduce emissions in manner that 
reduces ambient concentrations in the area.
---------------------------------------------------------------------------

    Other than the on-road vehicle and nonroad engine categories, we do 
not believe that there are any other sources of NOx that 
should be called significant in terms of contributing to ammonium 
nitrate levels.
    Because the MAG plan includes an extensive number of measures for 
controlling NOx sources and no measure are identified for 
the control of ammonia as technologically feasible, we propose to find 
that the MAG plan provides for the implementation of RACM and BACM and 
for the inclusion of MSM for secondary ammonium nitrates.
    l. MCESD's commitments to improve compliance and enforcement of its 
fugitive dust rules. MCESD has committed to expanding and improving the 
compliance and enforcement program for its fugitive dust rules. These 
commitments are found in Maricopa County, 1999 Revised Measure 6, 
adopted December 15, 1999. A narrative description of the commitments 
and other program changes are found in Appendix IV, Exhibit 3 to the 
MAG plan's modeling TSD. MCESD has also committed to continuing to 
improve Rule 310 and Rule 310.01. These commitments are described in 
section F.3.g. ``Construction Sites and Activities.''
    These improvements include increased public outreach and education, 
increased funding and staffing, increased inspection frequency, revised 
enforcement policies, and commitments to program evaluations and 
improvements. They address many of the program areas that are key to 
improving compliance and we believe form a solid program for increasing 
the effectiveness of the County's fugitive dust program.
    Staffing. By the end of January, 2000, the inspection staff will 
increase to eight inspectors, 1 supervisor, 1 aide and 2 enforcement 
officers. By April, 2000, the County Attorney's office will hire an 
attorney to expedite civil litigation and to assist with prosecuting 
Class One Misdemeanor cases. A coordinator will be added to the Small 
Business Environmental Assistance Program to assist smaller builders 
and construction companies and to help develop and implement education 
programs. In total, resources devoted to the fugitive dust program will 
be 15 positions, a 25 percent increase over previous levels. This level 
of staffing is in contrast to the less than 1 staff position devoted to 
the program in 1996.
    After reaching the committed staffing level, MCESD will review the 
program in March 2000 to evaluate its effectiveness and the potential 
need to add more staff.
    Organization. A new enforcement section has been created under the 
direct supervision of the MCESD Director/Air Pollution Control Officer 
(APCO). This position streamlines enforcement by reducing senior 
management review and approval of enforcement actions and allows 
enforcement officers to submit directly to the APCO's desk all 
enforcement actions requiring APCO approval.
    In addition, inspectors will be located in two new regional offices 
to provide quicker response times to dust-related complaints and allow 
more time in the field.
    Funding. Revenue for fugitive dust program is estimated at $1.12 
million from annual earth moving permit fees, a $772,000 increase over 
the previous level that is due to the permit fee increases adopted in 
1998.
    Inspection program. MCESD will develop by April, 2000 inspection 
priorities for vacant lots and unpaved parking lots that consider lot 
size and number of sources, with larger lots being inspected first and 
smaller lots in succeeding years. A number of cities have municipal 
programs to address these sources; therefore, the Department will 
initially direct its inspections to cities lacking such programs. It 
will also track the city plans that are required by State statute to 
stabilize target unpaved roads, alleys and unpaved shoulders.
    MCESD has also increased inspection rates and improved procedures 
for permitted sources such as construction sites including:
     Proactively inspecting sites larger than 10 acres, 3 to 6 
times per year and inspect smaller sites once within 30 days of project 
start date.
     Scheduling weekend inspections randomly once per month.
     Providing a shortened complaint response time with a goal 
of 8 hours for high priority complaints and maintaining the current 
goal of 24 hours for others.
     Revising standard operating procedures and checklists for 
fugitive dust inspections to be consistent with the revised rules.
     Revising inspection standard operating procedures to have 
inspectors check for records and inspect fugitive dust sources at 
permitted stationary sources.
    Enforcement program. By April 2000, MCESD will revise it fugitive 
dust enforcement policy to
     include guidelines for initiating various enforcement 
actions
     include guidelines for reinspecting define timely and 
appropriate action by laying out guidelines for which type of violation 
is appropriate for specific enforcement actions and for the time frames 
for escalating enforcement actions when appropriate
     identify priority violations
     include guidelines for when to seek penalties reflecting 
the economic benefit of noncompliance, if feasible
     include guidelines for seeking and determining higher 
penalties for repeat violators
     guidelines for inspectors to handle predetermined citation 
categories form observation to justice court Enforcement action options 
include issuing an Order of Abatement, filing a Misdemeanor Complaint 
in Justice court, or asking the County Attorney to seek a civil penalty 
in Superior Court.
    Inspectors will handle certain predetermined citation category 
violations and will be responsible for case development from observance 
of a violation to filing of the actual citation in the justice court. 
Having the inspectors handle routine cases will enable the enforcement 
officers to work on resolving cases involving more serious and 
complicated violations.
    Public outreach/education. Public outreach and education consists 
of staff training, educating the regulated parties, developing good 
working relationships with other involved parties such as the cities, 
and making the program more understandable. Increased education of both 
inspectors and the regulated industry increases compliance.
    Among the public outreach and education efforts will be:
     Inspector training on case development.
     Inspector training on revised test methods.
     City staff training on preparing inspection reports and 
notices of violation.
     On-going training at the local community college.
     Making information available on MCESD website.
     Distribution of information through city building 
departments and other sources.
    Program evaluation and tracking. MCESD will track the number of 
inspections, number and type of enforcement actions, amount of 
penalties assessed, and amount of penalties collected. It will also 
conduct mid-year reviews of the program in

[[Page 19984]]

September, 2000 and again in March 2001 to evaluate progress and future 
needs.

G. Attainment Date Extension

1. Apply for an Extension
    We interpret this requirement to mean that the State must apply in 
writing for an extension and that the extension request must accompany 
the SIP submittal containing the demonstration that the area will 
attain by the most expeditious alternative date practicable. The public 
must be provided reasonable notice and a public hearing on the request 
before it is submitted.
    MAG, as the lead air quality planning agency for the Phoenix 
metropolitan area, formally requested an extension of the PM-10 
nonattainment deadline to December 31, 2006 based on documentation in 
Chapter 10 of the MAG plan and Appendix C, Exhibit 5 of the MAG plan. 
MAG plan, p. 10-2. This extension request is an integral part of the 
MAG plan and was subject to public hearing along with the rest of the 
plan.
2. Demonstrate the Impracticability of Attainment by December 31, 2001
    In order to demonstrate impracticability, the plan must show that 
the implementation of BACM (as determined by our guidance) on 
significant sources categories will not bring the area into attainment 
by December 31, 2001.
    To demonstrate the impracticability of attainment by 2001, the MAG 
plan derived from the air quality modeling a change in PM-10 
concentrations per change in emissions using the modeled concentration 
for the year 2006 and observed concentration for the year 1995 at 
Greenwood monitor and the overall change in emissions between the two 
years. MAG plan, p. 8-10. Using this information, the plan estimates 
that the annual concentration in 2001 will be 52.21 g/m\3\ 
after implementation of BACM. Because the projected 2001 annual 
concentration is still above the 50 g/m3 annual 
NAAQS, the MAG plan concluded that it was impracticable to attain by 
2001.\30\ MAG plan, p. 8-10.
---------------------------------------------------------------------------

    \30\ In addition the MAG plan shows that implementation of 
controls on the de minimis source categories would not produce 
enough emission reductions to show attainment in 2001. MAG plan, p. 
9-11.
---------------------------------------------------------------------------

    Based on our analysis of control measures in the MAG plan as 
described in the preceding sections, we propose to find that the MAG 
plan provides for implementation of BACM as required by CAA section 
189(b)(1)(C). Based on the modeling analysis in the plan, we also 
propose to find that the MAG plan also demonstrates that attainment by 
2001 is impracticable with the implementation of BACM.
3. Complied With Commitments and Requirements in the SIP
    We interpret this criterion to mean that the State has implemented 
the control measures in prior SIP revisions it has submitted to address 
the CAA requirements in sections 172 and 189 for PM-10 nonattainment 
areas. It does not include measures being approved in this action.
    The two SIP revisions that Arizona has submitted to address PM-10 
are the 1991 MAG moderate area plan and the 1997 microscale plan.
    The 1991 MAG plan includes a broad range of measures to address PM-
10 including controls for constructions sites, paved road, unpaved 
roads, unpaved parking areas, vacant lots, and woodburning. The plan 
also included reasonably available control technology for stationary 
sources and a wide range of transportation control measures. The 
implementation of the measures in this plan are described in the MAG 
plan at pp. 10-10 to 10-25. The principal controls in this plan were 
Rule 310 and the County woodburning ordinances. The plan also contained 
a large number of commitments from the local jurisdictions to various 
measures. Most of the measures represented ``business as usual'' 
actions by the jurisdictions to do infrastructure (e.g., road) 
improvements, to implement existing building codes or take actions 
already underway for the carbon monoxide plan. MAG plan, pp. 10-13 
through 10-24.
    The 1997 Microscale plan focused on fugitive dust sources such as 
construction sites, vacant lots, unpaved roads, unpaved parking lots, 
and agriculture. The principal controls in this plan were improvements 
to the implementation of Rule 310 and coordination with the cities to 
improve fugitive dust control. Implementation of the measures in the 
Microscale plan are discussed in Maricopa County commitments, 1998 
Revised Measure 6.
    From available information in the MAG plan, we believe that the 
commitments and requirements in these plans have been met. We, 
therefore, propose to find that the State has complied with the 
requirements and commitments in its implementation plan.
4. Include the Most Stringent Measures
    The MAG plan excluded no source categories of directly-emitted PM-
10 from its MSM analysis instead simply started its evaluation of MSM 
by identifying candidate measures for any source category of PM-10 
present in the Phoenix area. MAG plan, p. 10-25. To identify candidate 
MSM, MAG's contractor Sierra Research interviewed people knowledgeable 
about PM-10 controls, reviewed the documents used to develop the 
candidate list of BACM and obtained copies of current air quality 
control measures from most other States including both SIP and non-SIP 
measures. MSM Study, p. 1-2.
    After a comprehensive list of candidate MSM was developed, each 
measure was screened against the corresponding Maricopa measure to 
identify those with more restrictive emission limitations, more 
extensive list of affected sources, fewer exemptions, and/or one or 
more substantive regulatory provisions not found in the Maricopa 
measure. The remaining MSM were grouped by source category and were 
either included in the plan or a reasoned justification for rejecting 
the measure was provided. MSM study, Table 3-1 and MAG plan, p. 10-46.
    We propose to find that the MAG plan demonstrate to our 
satisfaction that it includes the most stringent measures that are 
included in the implementation plan of any State, or are achieved in 
practice in any State, and can be feasibly be implemented in the 
Phoenix area.
    We have discussed identification and adoption of MSM and the 
rejection of any MSM for each category deemed significant for BACM 
earlier in this preamble. The MAG plan identifies three MSMs for 
categories considered de minimis in the BACM analysis. These categories 
are cattle feed lots, incinerators, and charbroilers.
    Cattle feed lots: MCESD Rule 310.01 requires that owners/operators 
of commercial feedlots and/or livestock areas apply dust suppressants, 
apply gravel, or install shrubs and/or trees within 50 to 100 feet of 
animal pens. The MAG plan identifies South Coast Rule 1186 requirements 
for livestock operations as a potentially more stringent requirements 
than Rule 310.01. However, the two rules control different sources at 
commercial feedlots/livestock areas. South Coast Rule 1186 requires 
controlling unpaved roads and hay grinding at dairy and horse farms but 
does not address fugitive dust emissions from disturbed open areas. 
MCESD Rule 310.01 controls fugitive dust emissions from disturbed open 
areas at dairies and cattle lots, but not unpaved roads and hay 
grinding.
    In the Maricopa County PM-10 nonattainment area, there is only one 
cattle feedlot and less than half the

[[Page 19985]]

number of dairies compared to those subject to South Coast Rule 1186. 
Similar to South Coast, unpaved roads at dairies are low travel (10 to 
20 ADT) and represent a very small source of emissions in the Phoenix 
area and controls on them would not advance the attainment date. We, 
therefore, believe we can find that the MAG plan provides for the 
implementation of MSM to our satisfaction without Rule 1186 provisions 
for unpaved roads at cattle feed lots. In Maricopa County, hay grinding 
activities occur primarily at feed mills (as opposed to dairies) which 
are permitted sources and thus already subject to control requirements.
    Incinerators: The MAG plan identifies Clark County's Rule 26 as 
having a more stringent opacity limit than MCESD's Rule 313. Clark 
County limits opacity from existing incinerators to 5 percent while 
Maricopa's limit is 20 percent. MAG plan, Table 10-7. Incinerators are 
a very small source in the Phoenix nonattainment area. In 1994 there 
were 32 incinerators that together emitted 2.56 metric tons per year 
(7.1 kg per day). 1994 Regional PM-10 Inventory, p. 4-17. Because 
incinerators are so small a source and controls on them would not 
advance the attainment date, we propose to find that the MAG plan 
provide for the inclusion of MSM to our satisfaction without including 
Clark County's opacity limit for incinerators.
    Charbroiling: Emissions from charbroiling and frying meat are 
estimated to 0.6 mtpd or 227 mtpy. 1994 Regional PM-10 Inventory, p. 4-
25. This is 0.4 percent of the daily directly-emitted PM-10 inventory 
in 1994 and 0.4 percent of the annual inventory in 1994. MCESD has 
committed to develop a new rule to require existing and new chain-
driven and underfired charbroilers, typically found in restaurants 
specializing in grilled meat products, to be equipped with emission 
control equipment. South Coast is developing a new rule to deal with 
underfired charbroilers and MCESD will wait until South Coast completes 
its rulemaking to adopt this measure. MCESD is projecting adoption of 
its rule in Spring, 2001. Maricopa County commitments, Revised Measure 
23. We propose to find that implementation of this rule is expeditious. 
Waiting on South Coast to complete its rulemaking, which will establish 
control requirements for underfired charbroilers, is appropriate given 
that the South Coast rule when adopted will set the standard for 
control on these types of charbroilers.
5. Demonstrate Expeditious Attainment
    For the reasons discussed below, we propose to find that the MAG 
plan demonstrates attainment by the earliest date practicable after 
December 31, 2001 as required by section 189(b)(1)(A)(ii) of the CAA. 
We also propose to find that the attainment demonstration relies on 
control measures that either are approved or are being proposed for 
approval and meet our SIP enforceability criteria; that the emissions 
estimates assigned these measures in the attainment demonstration are 
reasonable; and the measures are being implemented on a schedule that 
is as expeditious as practicable and will result in attainment by the 
earliest practicable date. See discussion below.
    a. Air quality modeling. A modeled attainment demonstration for the 
PM-10 annual standard should first estimate the temporal and spatial 
distribution of PM-10 and PM-10 precursor emissions that result from 
the adopted control measures by the attainment date. It should then 
simulate the ambient air concentration of these emissions in an air 
quality model and show that all locations within the nonattainment area 
have annual average PM-10 concentrations below the level of the annual 
PM-10 standard of 50 g/m3. See ``Guidelines on Air Quality 
Models,'' 40 CFR part 51 appendix W, section 7.2.2. and ``PM-10 SIP 
Development Guideline,'' EPA-450/2-86-001, June 1987.
    To provide context for our evaluation of the air quality modeling 
in the MAG plan, we will first briefly describe the steps in developing 
a modeled attainment demonstration and how the MAG plan performed each 
step.
    Step 1. A modeling base case is developed to replicate PM-10 
concentrations for specific recent days by simulating the emissions and 
meteorology that occurred for those days, by hour and by location 
throughout the area being modeled (that is, the model domain). For some 
input parameters, alternative plausible values are tried in a 
diagnostic process to ensure that the model is performing in a 
physically reasonable way. PM-10 concentrations from the model output 
are compared to monitored values to evaluate the performance of the 
model.
    The base case for the MAG plan consisted of the application of the 
urban airshed model with the limited chemistry module (UAM/LC) to each 
of 65 days during 1995. The results from modeling each of these days 
are then averaged together to get the modeled annual PM-10 
concentration. 1995 was used as the base year because an intensive 
inventory and monitoring study was performed during it; the 65 days 
coincided with the available PM-10 24-hour average monitoring data, 
which are collected once every 6 days. During 1995 the peak monitored 
annual PM-10 concentration was 60.01 g/m3 at the 
Greenwood monitor while the model predicted a peak concentration of 
75.91 g/m3 at a location away from the Greenwood 
monitor. MAG TSD, Chapter III.\31\
---------------------------------------------------------------------------

    \31\ The MAG TSD is the ``Revised Technical Support Document for 
Regional PM-10 Modeling in Support of the Revised MAG 1999 Serious 
Area Particulate Plan for PM-10 for the Maricopa County 
Nonattainment Area,'' MAG, February 2000 found in Appendix A, 
Exhibit 7 of the MAG plan.
---------------------------------------------------------------------------

    Step 2. After the base case model is developed, emissions are 
projected into the future. Projections are based on particular 
facilities's expansion plans, business and socioeconomic projections, 
and projections of the effect of changing technology and of the control 
measures that are already in place. The model simulation is repeated 
with these future emissions but with the same meteorological inputs as 
before. This simulation shows how a day meteorologically conducive to 
high PM-10 concentrations will look in the future if no new controls 
are implemented. The resulting modeled concentrations can be used to 
derive an estimate of the additional emission reductions needed to 
attain the air quality standard.
    For the MAG plan, emissions are projected to 2006 (which MAG found 
to be the earliest practicable attainment year). Before additional 
controls, the 2006 future peak PM-10 annual average was simulated to be 
86.72 g/m3. Because this was above the NAAQS of 50 
g/m3, the modeling showed that additional control 
measures were needed. MAG plan, p. 8-6.
    Step 3. The effect of control measures on ambient concentrations 
are simulated by changing the model emission inputs for future years to 
reflect higher implementation rates or larger emission reductions from 
additional controls. Additional measures are tried if PM-10 
concentrations are still above the standards.
    Attainment is demonstrated when sufficient emission reductions are 
in place so that modeled concentrations in every grid square are below 
the standard.
    MAG showed that with additional controls, the peak annual PM-10 
concentration in 2006 is 49.70 g/m3, which is below 
the annual PM-10 NAAQS of 50 49.70 g/m3, thus

[[Page 19986]]

demonstrating attainment. MAG plan, p. 8-12.
    In evaluating the air quality modeling in the MAG plan, we reviewed 
the choice of models; the selection of episodes to model, the selection 
of the modeling domain and grid resolution, the methods of preparing 
wind, temperature, and mixing height fields data; the selected initial 
and boundary conditions values; the modeling emission inventories; the 
procedures for and results of quality assurance, diagnostic testing and 
sensitivity testing; and selected modeling performance goals and model 
results vis a vis these goals. We have found them all generally 
acceptable. See our detailed evaluation in EPA TSD section 
``Demonstrate Attainment by the Most Expeditious Alternative Date 
Practicable after December 31, 2001.''
    The modeling performed for the MAG plan is as sophisticated as any 
that has been performed for a PM-10 SIP. While there are several 
problems associated with the model's performance for secondary 
particulates and several other shortcomings of the modeling and its 
documentation, the dominance of the contribution of primary 
particulates from fugitive dust to PM-10 concentrations in the Phoenix 
area obviates these concerns. At worst the MAG plan's modeling is akin 
to modified rollback, an approach that is acceptable under EPA modeling 
guidance for PM-10. We therefore propose to approve the modeling for 
the annual NAAQS because it provides a credible demonstration that the 
credited control measures will provide for attainment of the annual 
standard by 2006.
    b. Control measures relied on for attainment. For demonstrating 
attainment, the MAG plan relies on reductions in directly-emitted PM-10 
from 12 measures. MAG plan, Table 8-2. We have listed each measure; the 
rule, commitment or state statute through which it is implemented, and 
its emission reductions in Table 1-1.

 Table 1-1.--Control Measures Relied on in the Attainment Demonstration
------------------------------------------------------------------------
                                                              Emission
             Measure              Implementation mechanism    reduction
                                                               (mtpd)
------------------------------------------------------------------------
Strengthening and Better          Rule 310 and Maricopa            60.6
 Enforcement of Fugitive Dust      County Commitments,
 Rules (Construction sites).       1999 Revised Measure 6.
Unpaved roads and alleys........  Rules 310 and 310.01,            12.2
                                   Maricopa County
                                   Commitments, 199
                                   Revised Measures 6 &
                                   17, City/Town
                                   Commitments for Unpaved
                                   Roads and Alleys.
Unpaved parking lots............  Rules 310 and 310.01 and          3.7
                                   Maricopa County
                                   Commitments, 1999
                                   Revised Measure.
Vacant disturbed lots...........  Rules 310 and 310.01 and          1.8
                                   Maricopa County
                                   Commitments, 1999
                                   Revised Measure 6.
                01PM-10           MAG Commitment, ``PM-10           1.1
                 efficient         Efficient Street
                 street sweepers   Sweepers'' City/Town/
                 (MAG).            County Commitments for
                                   Street Sweeping.
Curbing, paving, or stabilizing   City/Town/County                  1
 shoulders on paved roads.         Commitments for
                                   Stabilizing Shoulders.
Curbing paving or stabilizing     City/Town/County                  0.4
 unpaved access points.            Commitments for
                                   Stabilizing Unpaved
                                   Access Points.
PM-10 episode thresholds........  Maricopa County                   0.07
                                   Residential Woodburning
                                   Restriction Ordinance.
Restaurant charbroiler controls   Maricopa County                   0.07
 (Maricopa County commitment).     Commitment, 1999
                                   Revised Measure 23.
Cleaner Burning Gasoline........  ADEQ Regulations                  0.03
                                   (already SIP approved).
Pre-1988 Heavy-Duty Diesel        A.R.S. 49-542 F.7.......          0.02
 Vehicle Standards.
Coordinate traffic signals......  City/Town/County                  0.01
                                   Commitments for
                                   synchronizing traffic
                                   lights..
------------------------------------------------------------------------

    We have evaluated each of these measure to ensure that it meets our 
SIP enforceability criteria. These criteria ensure that the measure's 
compliance requirements'applicability, performance standards, 
compliance schedule, and monitoring methods--are clear.
    We have also evaluated the emission reductions credited to each 
measure to ensure they are reasonable. In particular, we looked at the 
reduction estimates for Rules 310 and 310.01.
    The MAG plan assumes an incremental increase in rule effectiveness 
for these rules from 66 percent in 1998 to 80 percent in 2006. MAG TSD, 
Appendix IV, Exhibit 1, Committed Measure 1. Rule effectiveness (RE) 
accounts for emission reductions lost because of noncompliance, control 
equipment downtime, failure to apply adequate controls, or failure to 
use control equipment properly. One hundred percent rule effectiveness 
is the ability of a regulatory program to achieve all the emission 
reductions that could be achieved by full compliance with the 
applicable regulations at all sources at all times.
    We have established policies on applying rule effectiveness factors 
for both base year and projected year inventories of volatile organic 
compounds (VOC), a precursor to ozone. See General Preamble at 13503 
and ``Rule Effectiveness Guidance: Integration of Inventory, 
Compliance, and Assessment Applications.'' USEPA, OAQPS, EPA-452/R-94-
001, January 1994, (RE Guidance). In general, we encourage states to 
derive local category-specific RE factors. If there are no such local 
RE factors, we require the use of an 80 percent effectiveness default 
value in VOC inventories. General Preamble at 13503.
    We have not established any explicit guidance for applying RE to 
particulate matter sources. We know, however, that PM sources like VOC 
sources are not in full compliance with applicable rules at all times; 
therefore, some RE factor needs to be applied. For this rulemaking, we 
have applied the existing Agency RE guidance for VOC sources to 
emission reduction estimates for Rule 310 and Rule 310.01.
    The items that influence compliance with a rule and thus the 
appropriate RE factor are the clarity of the rule, its compliance 
requirements and the complexity of the controls required by the rule; 
the source's actions; and the implementing agency's actions. See RE 
Guidance, pp. Table 1-1 and Appendix C.
    Under our guidance, a state is allowed and required to use a 80 
percent RE factor absent evidence to the contrary. General Preamble at 
13503. In this case,

[[Page 19987]]

the evidence that we have is that compliance for Rule 310 was below 
this level as of early 1998. MAG, with concurrence of MCESD, assumed a 
30 percent compliance rate for the Rule 310 in the 1995 base year 
modeling. Inspections by MCESD in early 1998 indicated that the 
compliance rate with the rule was 66 percent. MAG TSD, Appendix II, 
Exhibit 6, ``Documentation on Assumption of Rule 310 Control Efficiency 
and Compliance Rate.''
    Over the last few years, MCESD has made substantial changes to its 
fugitive dust control program, many designed to improve compliance. 
MCESD has also committed to a number of additional changes which we 
have described earlier. We believe that an 80 percent rule 
effectiveness in 2006 is appropriate given these changes and MCESD's 
commitments to improve compliance with Rules 310 and 310.01. These 
improvements cover rule and test method revisions, increased public 
outreach and education, increased funding and staffing, increased 
inspection frequency, revised enforcement policies, and commitments to 
program evaluations and improvements. They address many of the program 
areas that are key to improving compliance.
    In our TSD (in the section ``Extension Request-Demonstrate 
Attainment by the Most Expeditious Alternative Date Practicable after 
December 31, 2001''), we have compared the MCESD's fugitive dust 
program in 1996 to the program that will be in place by 2006 based on 
MCESD's commitments in the MAG plan and its actions to date. This 
comparison clearly shows the scope of improvements to the MCESD's 
fugitive dust program and supports our proposed finding that an 80 
percent RE in 2006 for Rule 310 and Rule 310.01 is appropriate.\32\
---------------------------------------------------------------------------

    \32\ The cities and towns in Maricopa County are also increasing 
their efforts to address fugitive dust sources, such as unpaved 
parking lots and disturbed vacant lots. These efforts also support 
an overall 80 percent rule effectiveness.
---------------------------------------------------------------------------

    Finally, we have looked at the implementation schedule for each 
measure to assure that the MAG plan provides for expeditious 
implementation. Except for paving of some unpaved roads, adoption of 
the charbroiler rule, heavy duty diesel standards, and the purchase and 
deployment of the PM-10 efficient street sweepers, all the measures 
relied on in the attainment demonstration are currently in effect.
    However, attainment of the PM-10 annual standard in the Phoenix 
area depends on a high level of compliance with MCESD's fugitive dust 
rules. The MAG plan assumes this level increases from 66 percent in 
1998 to 80 percent in 2006. MAG TSD, Appendix IV, Exhibit 1, Committed 
Measure 1. This level of compliance depends in turn on education of the 
regulated community and increased enforcement modifying source 
behavior. Both of these take time to effect, therefore, we believe that 
it is reasonable to allow a period of time to achieve a high level of 
compliance with these rules. We thus believe that the emission 
reductions are being achieved as expeditiously as practicable.
6. Other Factors That EPA may Consider
    CAA section 188(e) list five additional factors that we may 
consider in deciding whether to grant an extension and the length of 
that extension.
    The MAG plan provides information addressing each of the factors in 
Chapter 10 of the plan. We have already proposed to determine that the 
MAG plan provides for the implementation of RACM and BACM, includes the 
MSM, and attainment of the annual PM-10 standard by the earliest 
practicable date of December 31, 2006. In the next section, we will 
also propose to find that the plan provides for reasonable further 
progress. Nothing in the additional information presented on the five 
factors suggest that granting an extension of the attainment date for 
the Phoenix area to 2006 is inappropriate.
    a. Nature and extent of nonattainment. Over the past 5 years, 
violations of the annual standard have occurred routinely at three 
sites (MAG plan, Table 10-11):
    1. Greenwood, an urban site heavily impacted by transportation 
sources,
    2. Chandler, an urban fringe site heavily impacted by fugitive dust 
sources such as construction and agriculture, and
    3. Salt River, a site heavily impacted by industrial sources.
    Areas similar to the first two sites can be found throughout the 
Phoenix nonattainment area, so we would expect that there are similarly 
elevated PM-10 levels throughout the Phoenix area; therefore, controls 
need to be uniformly implemented throughout the nonattainment area, a 
task that generally requires longer to achieve than implementing 
controls in few localized areas.
    b. Types and numbers of sources or other emitting activities. 
Primary contributors to elevated PM-10 levels are fugitive dust sources 
including paved road dust, unpaved roads, construction activities, 
disturbed vacant lands, unpaved parking lots, and agricultural sources. 
MAG plan, p. 10-51. These sources are ubiquitous in the nonattainment 
area and collectively number in the thousands. (For example, MCESD 
issued 2500 construction permits in 1999; we mailed 50,000 letters to 
owners of vacant lots in the nonattainment area; there are 12,000 miles 
of roadway in the nonattainment area.)
    c. Population exposure to concentrations above the standard. The 
MAG plan estimates population exposure to elevated levels of PM-10 
(both annual and 24-hr) to be from 78,000 to 163,000 (1995 figure), p. 
10-13. This population exposure is calculated using estimates of 
disturbed land versus population in subareas of the nonattainment area. 
According to this calculation, 84 percent of Maricopa's population 
lives in areas where 10 percent or less of the land is open. MAG plan, 
Table 10-13. This exposure number does not seem to include populations 
exposed to dust from paved and unpaved roads and therefore may 
underestimate overall population exposure. However, the plan does 
provide for implementation of RACM, BACM, and MSM on disturbed land 
(including construction) and paved and unpaved roads with much of the 
emission reductions being achieved in the first few years, all these 
factors will reduce population exposure as quickly as practicable.
    d. Presence and concentration of potentially toxic substances in 
the particulate. The primary source of airborne cancer risk in the 
Maricopa area is internal combustion engine exhaust from both on- and 
non-road engines. This risk is from all pollutants emitted from these 
sources (gaseous and particulate). MAG plan, p. 10-61. The MAG plan 
concludes that the cancer risk in the Phoenix area is comparable to 
that in California cities, p. 10-61. The MAG plan and other Arizona 
programs (e.g., cleaner burning gasoline, national emission standards 
for non-road engines) target emissions from on- and non-road engines.
    Almost all of the PM-10 emission reductions in the out years of the 
MAG plan (2003 and later) are and need to be from fugitive dust sources 
in order to show attainment of the annual PM-10 standard and not fron 
on- and non-road engines; therefore, extending the attainment date does 
not affect the degree of public exposure to the major source of toxic 
risk because shortening the extension would not accelerate controls on 
the major source of toxic risk, on- and nonroad engines.
    e. Technological and economic feasibility of controls. Fugitive 
dust sources dominate the emission inventory in the Maricopa

[[Page 19988]]

nonattainment area. Controls for these sources are well known (paving, 
wetting surfaces, etc.) and have been adopted; however, the number of 
sources and nature of sources make education and outreach necessary to 
assure full compliance with those controls. In addition, costs for 
paving roads, purchasing street sweepers, and other capital 
improvements necessary to reduce PM-10 emissions are high and necessary 
funds are only available over a number of years. These factors 
generally support a longer time frame for attainment.
7. Conclusion on Extension Request
    Based on our review of the MAG plan and our proposed determination 
that it meets the requirements necessary for granting an extension of 
the attainment date under CAA section 188(e), we are proposing to grant 
a five-year extension of the serious attainment date for the Phoenix 
PM-10 serious nonattainment area from December 31, 2001 to December 31, 
2006.

H. Reasonable Further Progress (RFP) and Quantitative Milestones

    We propose to find that the MAG plan provides for RFP and meets the 
quantitative milestone requirements of the Act.
1. Reasonable Further Progress
    The MAG plan provides for annual progress so that emissions levels 
in each year from 1995 to 2006 that are at or below the level needed to 
maintain linear progress toward attainment. It demonstrates that 
regional PM-10 emission levels will drop from 191 mtpd in 1995 to 130 
mtpd in 2006 with two-thirds of the reduction occurring before 2001. 
MAG plan, Figure 8-4. Total regional emissions decrease annually at a 
rate of approximately 6.5 mtpd per year from 1995 through 2001 and 4.4 
mtpd per year from 2002 to 2006. The assumptions that underlie the RFP 
demonstration regarding control measures' implementation and 
effectiveness are reasonable.
    The plan does not provide emission reduction information for each 
year between the base modeling year of 1995 and the attainment year of 
2006. We do not believe that this level of detail is necessary or 
meaningful. The principal control measures in the plan (such as 
improving compliance with the fugitive dust rules, progressive paving 
of unpaved roads, and annual replacement of part of the street sweeper 
fleet with PM-10 efficient units) produce year to year incremental 
increases in emission reductions sufficient to meet the statutory 
requirement for RFP. See MAG plan, Figure 8-4 and EPA TSD, Figure RFP-
1. Therefore, we propose to find that the MAG plan provides for ``such 
annual incremental reductions in emissions of the relevant air 
pollutant as are required by this part [part D of title I] or may 
reasonably be required by the Administrator for the purpose of ensuring 
attainment of the applicable national ambient air quality standard by 
the applicable date'' as required by section 172(c)(2) of the Act.
2. Quantitative Milestones
    Our guidance provides for a quantitative milestone for the year 
2000. Addendum at 42016. Based on the statutory requirement for 
milestones every three years, the years 2003 and 2006 are the next two 
milestones for areas with an attainment date extension under section 
188(e). The MAG plan provides milestones for 2003 and 2006 but 
substitutes 2001 for 2000. We believe this minor deviation from our 
guidance is appropriate and acceptable for the following reasons.
    First, we set the milestone schedule in our serious PM-10 area 
guidance assuming the area involved was one of the initial moderate 
areas and its moderate area plan demonstrates attainment by December 
31, 1994. General Preamble at 13539 and Addendum at 42016. Although the 
Phoenix area was one of the initial moderate nonattainment areas, its 
moderate area plan did not demonstrate attainment.\33\ As a result, our 
guidance on the appropriate milestone years is not strictly applicable 
to the MAG serious area plan.
---------------------------------------------------------------------------

    \33\ The moderate area plan submitted by the State in 1991 and 
revised in 1993 and 1994 demonstrated the impracticability of 
attainment by December 31, 1994. While we have subsequently 
disapproved this impracticability demonstration because the plan did 
not include RACM, we confirmed that attainment was impracticable in 
our 1998 FIP. 63 FR 41340.
---------------------------------------------------------------------------

    We also believe that the statutory purpose for including milestones 
in PM-10 plans is best served in the Phoenix area by having the 
milestone year be 2001 rather than 2000. Under the Act, states are to 
submit a demonstration 90 days after a milestone date that the state 
has implemented all measures in its approved plan and has met the 
milestone. See CAA section 189(c)(2). If a state fails to submit a 
report or we determine that the area has not met a milestone, then the 
state must submit a plan revision that assures that the next milestone 
will be met. See CAA section 189(c)(3).
    It is clear from the statutory requirements, that the milestone 
requirement functions as a mid-course evaluation of the PM-10 plan and 
an opportunity to make corrections to the plan to assure that there is 
no delay in attainment due to failures to implement or achieve needed 
reductions. As such, the milestones should be keyed, to the extent 
possible, to major implementation deadlines in a manner that allows for 
a realistic and comprehensive look at the effectiveness of the 
implemented measures.
    The BACM implementation deadline for Phoenix is June 10, 2000. A 
December 31, 2000 milestone allows for the evaluation of only a half-
year of implementation, which is little time to see if implementation 
is going to achieve the expected emission reductions. Setting the 
milestone one year later on December 31, 2001 as the MAG plan does, 
provides for a full year of implementation allowing for a more 
realistic assessment of the effectiveness of BACM yet still leaving 
ample time to make any corrections needed to assure timely attainment. 
Therefore, we believe that strict adherence to the 2000 milestone date 
in our guidance would be less beneficial to attainment in the Phoenix 
area than setting the date at 2001.
    The next milestone in the MAG plan after the 2001 one is in 2003. 
MAG plan, Figure 8-4. This second milestone is only 2 years after the 
first, instead of 3 years arguably required by the Act. However, we 
believe that the 3-year milestone increment in CAA section 189(c) is 
the maximum allowable time between milestones and nothing in the 
section prohibits states from setting milestones dates that are closer 
together.
    The assumptions regarding control measures' implementation and 
effectiveness that underlie the quantitative milestones are reasonable 
and consistent with the RFP demonstration.
    For these reasons, we propose to find that the MAG plan meets the 
quantitative milestone requirement in CAA section 189(c)(1).

I. General SIP Requirements

    Section 110(a)(2)(E)(i) of the Clean Air Act requires that 
implementation plan provide necessary assurances that the State (or the 
general purpose local government) will have adequate personnel, funding 
and authority under State law. Requirements for legal authority are 
further defined in 40 CFR part 51, subpart L (section 51.230-232) and 
for resources in 40 CFR 51.280.
    States and responsible local agencies must demonstrate that they 
have the legal authority to adopt and enforce provisions of the SIP and 
to obtain information necessary to determine

[[Page 19989]]

compliance. SIPs must also describe the resources that are available or 
will be available to the State and local agencies to carry out the 
plan, both at the time of submittal and during the 5-year period 
following submittal.
    We propose to find that the implementing agencies for the MAG plan 
have adequate resources for implementing their respective commitments. 
We also propose to find that the MAG plan adequately describes the 
resources that are available or will be available to the State and 
local agencies to carry out the Plan, both now and over the next 5 
years. See discussion of the individual commitments and control 
measures in the TSD.
    All agencies and jurisdictions appear to have adequate authority 
under Arizona state law to implement their respected commitments and, 
where applicable, to obtain information necessary to determine 
compliance. We, therefore, propose to find that these agencies/
jurisdictions have demonstrated that they have adequate legal authority 
to implement the MAG plan.
    Section 110(a)(2)(C) requires SIPs to include a program to provide 
for the enforcement of SIP measures. The implementing regulation for 
this section is found at 40 CFR 51.111(a) and requires control 
strategies to include a description of enforcement methods including 
(1) procedures for monitoring compliance with each of the selected 
control measures, (2) procedures for handling violations, and (3) the 
designation of the agency responsible for enforcement.
    The principle control measures in the plan are MCESD's Rules 310 
and 310.01. Procedures for monitoring compliance (i.e., the inspection 
strategy) with these rules are described in Maricopa County's 
commitments. See Maricopa County commitment, 1999 Revised Measure 6.
    Based on the review of MCESD's enforcement procedures, we propose 
to find that the MAG plan adequately provides for the enforcement of 
the principle measures relied on for attainment and that the plan 
includes an adequate description of enforcement methods as required by 
our regulations.
    Section 110(a)(2)(E)(iii) requires SIPs to include necessary 
assurances that where a State has relied on a local or regional 
government, agency or instrumentality for the implementation of any 
plan provision, the State has responsibility for ensuring adequate 
implementation of the such plan provision.
    We have previously found that Arizona law includes the necessary 
assurances that where a State has relied on a local or regional 
government, agency or instrumentality for the implementation of any 
plan provision, the State has responsibility for ensuring adequate 
implementation of the such plan provision. 60 FR 18010, 18019 (April 
10, 1995).

Proposed Actions on Maricopa County Rules

A. Rule 310

    Rule 310 establishes requirements for fugitive dust sources on 
facilities that have or are required to have air quality permits from 
MCESD. These facilities include construction sites, stationary sources, 
and any other facility or operation that is required to have a permit 
under MCESD rules. The rule requires earthmoving activities that 
disturb 0.10 acre or more to apply for and get approval of a Dust 
Control Plan (DCP) and requires other permitted sources to obtain a DCP 
prior to commencing any routine dust generating activity. We have 
described many of the Rule's specific requirements earlier in this 
preamble.
    The current SIP approved version of Rule 310 is the version adopted 
on September 9, 1994. We approved this version of Rule 310 into the SIP 
on August 4, 1997 as part of the Microscale plan. 62 FR 41856
    MCESD adopted a revised version of Rule 310 and Appendix C to MCESD 
rules on February 16, 2000 and Arizona submitted both as a revision to 
the Arizona SIP on March 2, 2000. Appendix C contains the test methods 
relied on in Rule 310.
    The revised Rule 310 is considerably different from the current 
SIP-approved version. The greatest change has been to split the old 
rule into two new rules: the revised Rule 310 that addresses permitted 
facilities and a new Rule 310.01 that addresses nonpermitted sources. 
We evaluate Rule 310.01 in the next section. MCESD also revised Rule 
310 to strengthen it compared to the current SIP-approved version. 
These rule improvements include:
     Improved enforceability of control measures and dust 
control permits (DCPs),
     Improvements to existing test methods (in Appendix C),
     New performance standards and test methods,
     Clearer definitions,
     More specific work practice requirements
    MCESD has also committed to continue to strengthen and improve Rule 
310 through research on test methods, dust control methods, and revised 
recordkeeping requirements. See discussion in section F.3.g., 
``Construction Sites and Activities.''
    We believe that the revised Rule 310 is a considerable improvement 
over the SIP-approved version and, combined with MCESD commitments to 
continue to improve the Rule and to improve enforcement and compliance 
with it, provides for implementation of RACM and BACM and the inclusion 
of the MSM on the sources subject to it. We, therefore, propose to 
approve Rule 310 and Appendix C as adopted on February 16, 2000 and 
submitted on March 2, 2000, into the Arizona SIP.
    We have described in more detail the improvements and other 
revisions to Rule 310 in section 6 of our TSD.

B. Rule 310.01

    Rule 310.01 establishes requirements for fugitive dust emitted from 
nonpermitted sources, including unpaved public roads, unpaved parking 
lots, open areas and vacant lots, erosion-caused deposits of bulk 
materials onto paved surfaces, and commercial feedlots and/or 
commercial livestock areas.
    The provision of Rule 310.01 are currently in the SIP as sections 
of former Rule 310. We approved this version of Rule 310 into the SIP 
on August 4, 1997 as part of the microscale plan. 62 FR 41856.
    MCESD adopted Rule 310.01 on February 16, 2000 and Arizona 
submitted it as a revision to the Arizona SIP on March 2, 2000. As with 
Rule 310, Rule 310.01 relies on the test methods in Appendix C.
    Rule 310.01's provisions are strengthened compared to the similar 
provisions in the SIP. These rule improvements and other rule changes 
include:
     The revised rule requires that unpaved roads and unpaved 
parking lots comply with both: (1) a 20 percent opacity standard; and 
(2) a silt content or a silt loading standard.
     A new opacity test method has been added to Appendix C to 
determine compliance with the rule's 20 percent opacity standard for 
unpaved haul/access roads and unpaved parking lots which is better 
tailored to these sources.
     Test methods for determining compliance with the new silt 
content/loading standards has been added to Appendix C.
     Owners/operators of disturbed vacant lots and open areas 
must maintain a visible crust or meet at least one other applicable 
stabilization standard, according to new test methods included in the 
rule and Appendix C.

[[Page 19990]]

     Specific control measures for commercial feedlots and/or 
commercial livestock areas have been added, including: application of 
dust suppressants or gravel, or installation of shrubs and/or trees 
within 50 to 100 feet of animal pens.
     The revised rule specifies that unpaved roads with 
vehicular traffic of 250 or more must be stabilized by June 10, 2000 
and unpaved roads with vehicular traffic of 150 or more must be 
stabilized by June 10, 2004.
     The revised rule specifies that requirements to prevent 
vehicle trespassing (section 301) apply to vacant lots and open areas 
that are 0.10 acre or larger and have a cumulative of 500 square feet 
or more that are driven over and/or used by motor vehicles and/or off-
road vehicles.
     The revised rule specifies that requirements to stabilize 
disturbed vacant lots and open areas (section 302) apply to lots/areas 
with 0.5 acre or more of disturbed surface.
    We believe that Rule 310.01 is a considerable improvement over the 
SIP-approved version and, combined with MCESD's commitments to continue 
to improve the Rule and enforcement and compliance with it and the 
commitments by the County and local jurisdictions to address unpaved 
roads, unpaved parking lots, and vacant lots, provides for 
implementation of RACM and BACM and the inclusion of the MSM on the 
sources subject to it. We, therefore, propose to approve Rule 310.01 as 
adopted on February 16, 2000 and submitted on March 2, 2000, into the 
Arizona SIP.
    We have described in more detail the strengthenings and other 
revisions to Rule 310.01 in section 6 of our TSD.

C. Residential Woodburning Restriction Ordinance

    Combined with MCESD Rule 318 ``Approval of Residential Woodburning 
Devices'' (adopted April 21, 1999; approved November 8, 1999 (64 FR 
60678)), Maricopa County's Residential Woodburning Restriction 
Ordinance implements a mandatory woodburning curtailment program. The 
curtailment program restricts the types of woodburning devices that can 
be used during periods of high PM-10 concentrations. The ordinance 
allows the Control Officer to declare restricted-burn periods when the 
particulate matter pollution levels could exceed the ``particulate 
matter no-burn standard.''
    The SIP-approved ordinance provides that restricted-burn periods 
are declared by the Control Officer when the Control Officer determines 
that air pollution levels could exceed the 24-hour PM standard at 150 
g/m3. The revised ordinance allows the Control 
Officer to declare restricted-burn periods when the particulate matter 
pollution levels could exceed the ``particulate matter no-burn 
standard'' of 120 g/m3. The lower of the 
particulate matter no burn standard to 120 g/m3 is 
the only change made to the ordinance as it is currently approved in 
the SIP.
    Because approving this revision will strengthen the SIP and when 
combined with the MAG plan's other provision for residential 
woodburning will provide for the implementation of BACM and the 
inclusion of the MSM, we are proposing to approve it into the SIP. See 
section F.3.j. ``Residential Wood Combustion.''

D. CAA Section 110(l) Finding

    CAA section 110(l) prohibits us from approving a revision to the 
applicable implementation plan if that revision would interfere with 
any applicable requirement concerning attainment and reasonable further 
progress (RFP) or any other applicable requirement of the Act. We 
interpret section 110(l) to mean that we cannot approve a plan revision 
if that revision would mean that the plan would no longer provide for 
attainment or RFP as these are required by the CAA for that plan or if 
the revision would mean that the plan would no longer meet another 
requirement of the Act that applies to the plan. For a further 
discussion of this interpretation, see 61 FR 51599, 51608 (October 3, 
1996).
    We are proposing to revise the Arizona SIP to incorporate the 
revised Rule 310, Rule 310.01 and the Maricopa County Residential 
Woodburning Ordinance in replacement of the previous version of Rule 
310 approved in August, 1997 and of the ordinance approved in November, 
1999. In addition to the effect on attainment and RFP, the ``other 
applicable requirement of the Act'' that we must be concerned with for 
this proposal is the Act's requirements for implementation of RACM and 
BACM and the inclusion of the MSM.
    We are proposing to approve the expeditious attainment and RFP 
demonstrations in the MAG plan. These demonstrations are in part 
dependent on approval of the revised Rule 310, Rule 310.01, and the 
woodburning ordinance.
    We are also proposing to find that the MAG plan provides for the 
implementation of RACM and BACM and the inclusion of the MSM for 
construction sites, unpaved roads, unpaved parking lots, and disturbed 
vacant lands. Again, these findings are in large part dependent on 
approval of the revised Rule 310 and Rule 310.01. We, therefore, 
propose to find that approval of the revised Rule 310 and Rule 310.01 
will not interfere with plan's compliance with the Clean Air Act's 
requirements for attainment, RFP, implementation of RACM and BACM, and 
inclusion of the MSM as they apply to construction sites, unpaved 
roads, unpaved parking lots, and disturbed vacant lands.
    Finally, we are proposing to find that the MAG plan provides for 
the implementation of BACM and for the inclusion of MSM for residential 
woodburning. These proposed findings are made in part based on the 
revised ordinance. Therefore, we propose to find that our approving the 
ordinance will not interfere with the plan's compliance with the Act's 
requirements for the implementation of BACM and the inclusion of MSM as 
they apply to residential woodburning.
    We have previously found that the Arizona SIP provided for the 
implementation of RACM for residential woodburning. 64 FR 60678 
(November 8, 1999). The State has now strengthened its residential 
woodburning program, in part with the revised ordinance; therefore, we 
propose that approval of the revised ordinance will not interfere with 
the Arizona SIP's compliance with the requirement for the 
implementation of RACM as it applies to residential woodburning.

Administrative Requirements

    Under Executive Order 12866 (58 FR 51735, October 4, 1993), this 
proposed action is not a ``significant regulatory action'' and 
therefore is not subject to review by the Office of Management and 
Budget. This proposed action merely approves state law as meeting 
federal requirements and imposes no additional requirements beyond 
those imposed by state law. Accordingly, the Administrator certifies 
that this proposed rule will not have a significant economic impact on 
a substantial number of small entities under the Regulatory Flexibility 
Act (5 U.S.C. 601 et seq.).
    Because this rule proposes to approve pre-existing requirements 
under state law and does not impose any additional enforceable duty 
beyond that required by state law, it does not contain any unfunded 
mandate or significantly or uniquely affect small governments, as 
described in the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4).
    For the same reason, this proposed rule also does not significantly 
or uniquely affect the communities of tribal governments, as specified 
by

[[Page 19991]]

Executive Order 13084 (63 FR 27655, May 10, 1998). This proposed rule 
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 (64 FR 43255, August 
10, 1999), because it merely approves a state rule implementing a 
federal standard, and does not alter the relationship or the 
distribution of power and responsibilities established in the Clean Air 
Act.
    This proposed rule also is not subject to Executive Order 13045 (62 
FR 19885, April 23, 1997), because it is not economically significant.
    In reviewing SIP submissions, our role is to approve state choices, 
provided that they meet the criteria of the Clean Air Act. In this 
context, in the absence of a prior existing requirement for the State 
to use voluntary consensus standards (VCS), we have no authority to 
disapprove a SIP submission for failure to use VCS. It would thus be 
inconsistent with applicable law for us, when reviewing a SIP 
submission, to use VCS in place of a SIP submission that otherwise 
satisfies the provisions of the Clean Air Act. Thus, the requirements 
of section 12(d) of the National Technology Transfer and Advancement 
Act of 1995 (15 U.S.C. 272) do not apply.
    As required by section 3 of Executive Order 12988 (61 FR 4729, 
February 7, 1996), in issuing this proposed rule, we have taken the 
necessary steps to eliminate drafting errors and ambiguity, minimize 
potential litigation, and provide a clear legal standard for affected 
conduct.
    We have complied with Executive Order 12630 (53 FR 8859, March 15, 
1988) by examining the takings implications of the rule in accordance 
with the ``Attorney General's Supplemental Guidelines for the 
Evaluation of Risk and Avoidance of Unanticipated Takings'' issued 
under the executive order.
    This proposed rule does not impose an information collection burden 
under the provisions of the Paperwork Reduction Act of 1995 (44 U.S.C. 
3501 et seq.).

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Intergovernmental 
relations, Particulate matter, Reporting and recordkeeping 
requirements.

    Authority: 42 U.S.C. 7401 et seq.

    Dated: April 3, 2000.
Laura Yoshii,
Acting Regional Administrator, Region IX.
[FR Doc. 00-8833 Filed 4-12-00; 8:45 am]
BILLING CODE 6560-50-U