[Federal Register Volume 66, Number 191 (Tuesday, October 2, 2001)]
[Proposed Rules]
[Pages 50252-50285]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-24203]



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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 24-Hour PM-10 Standard and Contingency Measures; Proposed Rule

  Federal Register / Vol. 66, No. 191 / Tuesday, October 2, 2001 / 
Proposed Rules  

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[AZ092-002; FRL-7067-5]


Approval and Promulgation of Implementation Plans; Arizona--
Maricopa County PM-10 Nonattainment Area; Serious Area Plan for 
Attainment of the 24-Hour PM-10 Standard and Contingency Measures

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, including the revisions 
submitted in June 2001 that address attainment of the 24-hour 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 24-hour PM-10 standard in the Phoenix area from 2001 to 2006. 
Finally, we propose to find that the plan provides for the 
implementation of contingency measures for both the 24-hour and annual 
PM-10 standards and to make several revisions to our previous proposal 
on the MAG plan's provisions for the annual standard and our proposed 
policy on attainment date extensions for serious PM-10 nonattainment 
areas.

DATES: Comments on this proposal must be received in writing by 
November 1, 2001. Comments should be addressed to the contact listed 
below.

ADDRESSES: Comments should 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 EPA technical 
support document (EPA TSD) and other material relevant to this 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) 744-1248, email: 
[email protected].

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Summary of Today's Proposals
II. Background to Today's Proposals
    A. PM-10 Air Quality in the Phoenix Area
    B. Description of the MAG Plan's Provisions for Attaining the 
24-Hour PM-10 Standard
    C. Previous Actions on the Phoenix Serious Area PM-10 Plan
    1. Annual Standard Proposal
    2. Microscale Plan Partial Approval/Partial Disapproval
    3. Arizona's Agricultural BMP General Permit Rule Approval
III. The CAA's Planning Requirements for Serious PM-10 Nonattainment 
Areas
IV. The MAG Plan's Compliance with the CAA's Requirements for 
Serious PM-10 Nonattainment Areas
    A. Completeness of the SIP Submittals
    B. Adequacy of the Transportation Conformity Budget
    C. Emissions 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. Steps 1 and 2: Determination of significant sources
    2. Step 3: Identification of potential BACM
    3. Step 4: 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 and Quantitative Milestones
    1. Reasonable further progress
    2. Quantitative milestones
    I. Contingency Measures
    J. General SIP Requirements
V. CAA Requirements for BACM and Attainment Date Extension and EPA's 
Guidance on Meeting these Requirements
    A. Implementation of Best Available Control Measures
    B. 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
VI. Administrative Requirements

I. Summary of Today's Proposals

    First, we propose to approve the provisions in the Revised MAG 1999 
Serious Area Particulate Plan for PM-10 for the Maricopa County 
Nonattainment Area, February 2000, (``MAG plan'') including revisions 
to that plan submitted in Maricopa County PM-10 Serious Area State 
Implementation Plan Revision, Agricultural Best Management Practices, 
June 2001, (collectively, ``the Maricopa County serious area plan'' or 
``the plan'') that address attainment of the 24-hour PM-10 standard.\1\ 
Our proposed actions are based on our initial determination that the 
Maricopa County serious area plan complies with the Clean Air Act's 
(CAA) requirements for serious PM-10 nonattainment area plans.
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    \1\ There are two separate national ambient air quality 
standards for PM-10, an annual standardd of 50 g/m\3\ and a 
24-hour standard of 150 g/m\3\. We proposed approval of the 
MAG plan's annual standard provisions on April 13, 2000 at 65 FR 
19964.
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    Specifically, we propose to approve the following elements of the 
plan as they pertain to the 24-hour standard:
     The demonstration that the plan provides for 
implementation of reasonably available control measures (RACM) and best 
available control measures (BACM),

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     The demonstration that attainment by the CAA deadline of 
December 31, 2001 is impracticable,
     The demonstration that attainment will occur by the most 
expeditious alternative date practicable, in this case, December 31, 
2006,
     The demonstration that the plan provides for reasonable 
further progress and quantitative milestones,
     The demonstration that major sources of PM-10 precursors 
such as nitrogen oxides and sulfur dioxide do not contribute 
significantly to air quality standard violations, and
     The transportation conformity budget.
    Second, we are proposing to grant Arizona's request to extend the 
attainment date for the 24-hour PM-10 standard from December 31, 2001 
to December 31, 2006. We make this proposal based on our determination 
that the State has met the CAA's criteria for granting such extensions.
    Third, we propose to find that the plan provides for the 
implementation of contingency measures for both the 24-hour and annual 
standards as required by the CAA.
    Finally, we make several revisions to our April 13, 2000 proposed 
approval of the annual standard provisions in the Maricopa County 
serious area plan. These revisions involve:
     Clarifications to our proposed policy on granting 
attainment date extensions under CAA section 188(e),
     Changes to Maricopa County Environmental Services 
Department's (MCESD) commitments to further improve its fugitive dust 
rule, Rule 310,
     Changes to several other control measures, and
     Evaluation of the plan's compliance with the BACM 
requirement and most stringent measure requirement in CAA section 
188(e) for the agriculture source category based on the State's 
Agricultural Best Management Practices General Permit Rule.\2\
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    \2\ Except for these limited number of revisions, we are not 
reopening the comment period and are not soliciting comments on our 
April 13, 2000 proposal.
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    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 
that accompanies this proposal. See ``Technical Support Document, 
Notice of Proposed Rulemaking on the Serious Area PM-10 State 
Implementation Plan for the Maricopa County PM-10 Nonattainment Area 
Provisions for Attaining the 24-Hour Standard and Contingency 
Measures,'' September 14, 2001 (EPA TSD). The EPA TSD is an integral 
part of this proposal and should be reviewed prior to making comments. 
A copy of the EPA TSD can be downloaded from our website or obtained by 
calling or writing the contact person listed above.

II. Background to Today's Proposals

A. PM-10 Air Quality in the Phoenix Area

    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.\3\ 40 
CFR 81.303. The area is home to almost 3 million people.
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    \3\ The Maaricopa 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 and required to submit 
a serious area plan by December 10, 1997. 61 FR 21372 (May 10, 1996).
    The principal contributors to elevated PM-10 levels in the Phoenix 
area are fugitive dust sources such as construction sites, unpaved 
roads, vacant lots, agricultural sources, 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, buses, residential woodburning and industrial, commercial, 
and residential use of natural gas and fuel oil. See MAG plan, p. 3-5.
    There is a long and complex history to PM-10 air quality planning 
in the Phoenix area. A summary of this history can be found in the 
annual standard proposal at 65 FR 19964, 19965. A more detailed history 
can be found in section 1 of the EPA TSD.

B. Description of the MAG Plan's Provisions for Attaining the 24-Hour 
PM-10 Standard

    Arizona has made several submittals to address the CAA requirements 
for serious PM-10 nonattainment area plans for the Phoenix area. The 
provisions for attainming the 24-hour PM-10 standard are found mainly 
in three of these submittals: the 1997 Microscale plan,\4\ the 2000 MAG 
plan, and the 2001 Best Management Practices (BMP) submittal.\5\ The 
latter two documents are the subject of this proposal and are described 
in more detail below. We have already acted on the Microscale plan, see 
62 FR 41856 (August 4, 1997). We describe this plan and explain its 
relationship to today's proposal in the next section.
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    \4\ The 1997 Microscale plan is the Plan for Attainment of the 
24-hour PM-10 Standard--Maricopa County PM-10 Nonattainment Area, 
Arizona Department of Environmental Quality, May, 1997.
    \5\ The other submittals contain rules and other control 
measures relied on to provide for RACM, BACM, reasonable further 
progress an attainment. These submittals include the commitments by 
local jurisdictions to PM-10 control measures submitted in December 
1997, revised MCESD Rules 310 and 310.01 submitted in March 2000, 
Maricopa County's Residential Wood Burning Ordinance submitted in 
January 2000, and the Agricultural Best Management Practices (BMP) 
General Permit Rule submitted in July 2000.
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    The first submittal is the Revised Maricopa Association of 
Governments 1999 Serious Area Particulate Plan for PM-10 for the 
Maricopa County Nonattainment Area, February 2000. This plan was 
developed by the Maricopa Association of Governments (MAG), the lead 
air quality planning agency in Maricopa County. The Arizona Department 
of Environmental Quality (ADEQ) submitted this plan as a revision to 
the Arizona State Implementation Plan (SIP) on February 16, 2000. We 
refer to this plan in this document as the MAG plan or the revised MAG 
plan; however, we occasionally use these terms to refer to the set of 
documents that collectively comprise the Maricopa County serious area 
PM-10 plan.
    The second document is the Maricopa County PM-10 Serious Area State 
Implementation Plan Revision, Agricultural Best Management Practices, 
(BMP) June 2001, submitted in draft on April 26, 2001 and final on June 
13, 2001. This SIP revision was developed by ADEQ. We refer to this 
submittal as the BMP TSD.
    The MAG plan contains a 1994 inventory and uses the urban airshed 
model/limited chemistry version (UAM/LC) to model regional air quality 
in 1995 as a base year and in 2006 as the attainment year for both the 
annual and 24-hour standards. The MAG plan, however, relies primarily 
on air quality modeling performed in the Microscale plan to evaluate 
localized 24-hour exceedances.
    The MAG plan, as revised by the BMP TSD, includes a BACM analysis 
and a demonstration that attainment by 2001 is impracticable for both 
the 24-hour and annual PM-10 standards. It also

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includes, again for both PM-10 standards, the State's request for a 
five-year extension of the attainment date, a demonstration that the 
plan includes for the most stringent measures found in other states' 
plans, and a demonstration of attainment by December 31, 2006.
    The BMP TSD updates the MAG plan to reflect the State's adoption of 
the Agricultural General Permit rule to control PM-10 from agricultural 
sources in Maricopa County. It includes a background document which 
provides the BACM demonstration for agricultural sources for both 
standards, a revised demonstration of attainment and reasonable further 
progress (RFP) for the 24-hour standard at two monitoring sites, and 
revisions to the contingency measure provisions for both standards. It 
also includes documentation quantifying emission reductions from the 
Agricultural General Permit rule and documentation related to 
implementing this rule.

C. Previous Actions on the Phoenix Serious Area PM-10 Plan

    We have taken three actions related to the Phoenix Serious Area PM-
10 plan: the proposed approval of the MAG plan's provisions for the 
annual standard, the partial approval/ partial disapproval of the 1997 
Microscale plan, and the approval of Arizona's Agricultural BMP General 
Permit rule. With today's proposal, we have now proposed action on all 
elements of the Maricopa County serious area PM-10 plan.
1. Annual Standard Proposal
    On April 13, 2000, we proposed to approve the MAG plan's provisions 
for attainment of the annual PM-10 standard. See 65 FR 19964.\6\ 
Specifically, we proposed to approve for the annual standard the 
provisions for implementation of RACM and BACM, the demonstration that 
attainment by 2001 is impracticable, the demonstration that attainment 
will occur by the most expeditious alternative date, the RFP 
demonstration, the quantitative milestones, and the conformity budget. 
We also proposed to grant an extension of the attainment date from 2001 
to 2006 based on our proposed determination that Arizona had met the 
CAA criteria for granting such an extension.
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    \6\ In the annual standard propsoal and in the EPA TSD for 
today's proposal, we discuss the legal basis for separating the 
proposed approvals for the 24-hour and annual standards and the 
practical reasons we chose to do so. See 65 FR 19964, 19969 and 
section 3 of the EPA TSD. We intent, however, to finalize actions on 
both standards in a single rulemaking in early 2002.
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    In April 2000 preamble, we also proposed to approve the base year 
regional emissions inventory required by CAA section 172(c)(3), MCESD's 
Rules 310 and 310.01, Maricopa County's Residential Woodburning 
Ordinance, and the commitments by the cities, towns, and County of 
Maricopa, ADEQ, MAG, and other State and local agencies to implement 
various PM-10 control measures. These proposals were applicable to both 
the annual and 24-hour PM-10 standards and thus are not being repeated 
today.
2. Microscale Plan Partial Approval/Partial Disapproval
    The attainment demonstration for the 24-hour standard in the 
Maricopa County serious area plan has both a local modeling component 
and a regional modeling component. Portions of the local or microscale 
component are found in the Microscale plan, the 2000 MAG plan, and the 
BMP TSD. The regional component is contained completely within the 2000 
MAG plan.
    Most of the technical evaluation for the microscale component is 
contained in the Microscale plan which was submitted to us in May 1997. 
It evaluates exceedances of the 24-hour PM-10 standard at four Phoenix 
area monitoring sites: Salt River, Maryvale, Gilbert, and West 
Chandler.
    This evaluation involved developing local, day-specific inventories 
and dispersion modeling to determine source contributions to 
exceedances at each site. The evaluation showed that the primary 
contributors to 24-hour exceedances in the Phoenix area are local 
fugitive dust sources such as construction sites, agricultural fields 
and aprons, vacant lots, unpaved roads and parking lots, and 
earthmoving operations. The Microscale plan also described the type of 
controls necessary to show attainment at each site although the plan 
only assured the implementation of such controls on construction-
related sources.
    We approved the Microscale plan in part and disapproved it in part 
on August 4, 1997 (62 FR 41856). We approved the attainment and RFP 
demonstrations for the Salt River and Maryvale sites because the plan 
demonstrated expeditious attainment at these sites; however, we 
disapproved these demonstrations for the West Chandler and Gilbert 
sites because the plan did not demonstrate attainment at them. Because 
attainment demonstrations at the Salt River and Maryvale sites were 
already approved, ADEQ limited its subsequent microscale work to 
developing approvable demonstrations for the Gilbert and West Chandler 
sites. Our proposal today is also limited to these two sites.
    To evaluate the provisions for the 24-hour PM-10 standard in the 
MAG plan, we are relying to a large extent on our previous evaluation 
of the Microscale plan. Except for the findings related to the 
implementation of BACM, we have not reevaluated the 24-hour standard 
provisions that we have already found adequate or approved as part of 
our actions on the Microscale plan.
    More information on the Microscale plan can be found in section 1 
of the EPA TSD and our proposed and final rulemakings on it. 62 FR 
31025 (June 6, 1997) and 62 FR 41856 (August 4, 1997).
3. Arizona's Agricultural BMP General Permit Rule Approval
    The analysis done for the Microscale plan revealed for the first 
time how significant a contribution agricultural sources make to 
exceedances of the 24-hour PM-10 standard in the Phoenix area. See 
Microscale plan, pp. 18-19. In order to develop adequate controls for 
this source, Arizona passed legislation in 1997 establishing an 
Agricultural Best Management Practices (BMP) Committee and directing 
the Committee to adopt by rule by June 10, 2000, an agricultural 
general permit specifying best management practices for reducing PM-10 
from agricultural activities. The legislation also required that 
implementation of the agricultural controls begin by June 10, 2000 with 
an education program and full compliance with the rule be achieved by 
December 31, 2001. See Arizona Revised Statutes (A.R.S.) 49-457.
    In September 1998, the State submitted the legislation. On June 29, 
1999, we approved it as meeting the RACM requirements of the CAA.\7\ 64 
FR 34726.
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    \7\ In 1998, we promulgated a moderate area PM-10 federal 
implementation plan (FIP) for the Phoenix area. 63 FR 41326 (August 
3, 1998). One of the measures in this FIP was our commitment to 
adopt RCM for agricultural sources, RACM being the primary control 
requirement for moderate PM-10 nonattainment areas. Arizona 
submitted the BMP legislation in 1998 as, among other things, a 
substitute for our FIP RACM commitment. Before we could withdraw our 
FIP RACM commitment and replace it with the State's legislation, we 
had to first find that the legislation was at least RACM, hence our 
initial determination that it was at least RCM. For further 
information on this legislation and its relationship to the history 
of PM-10 planning in the Phoenix area, see the ``Implementation of 
BACM and Inclusion of MSM for Agricultural Sources'' section in the 
EPA TSD.
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    While we approved the legislation as RACM, it was the State's 
intent that it also serve as BACM and MSM for agricultural sources in 
the serious area

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PM-10 plan. Therefore, in our annual standard proposal, we evaluated 
and proposed to find that the legislation met the CAA BACM and MSM 
requirements for the agricultural source category. 65 FR 19964, 19981.
    After a series of meetings during 1999 and 2000, the Agricultural 
BMP Committee adopted the agricultural general permit rule and 
associated definitions, effective May 12, 2000, at Arizona 
Administrative Code (AAC) R18-2-610, ``Definitions for R18-2-611,'' and 
611, ``Agricultural PM-10 General Permit; Maricopa PM10 Nonattainment 
Area'' (collectively, general permit rule). The State submitted the 
general permit rule in July 2000 and its analysis quantifying the 
emission reductions expected from the rule and the demonstration that 
the rule meets the CAA's RACM, BACM and MSM requirements in the June 
2001 BMP TSD. We proposed to approve the rule as meeting the CAA 
requirement for RACM on June 29, 2001 and signed the final approval on 
September 10, 2001. See 66 FR 34598.
    We are today withdrawing our proposed finding in the annual 
standard proposal that the State legislation provides for the 
implementation of BACM and MSM for agricultural sources for the annual 
standard. 66 FR 19964, 19981. In its place we are proposing to find 
that the General Permit rule provides for the implementation of BACM 
and MSM for agricultural sources for the annual standard. This proposal 
is based on our analysis, summarized later, of the rule and the State's 
demonstrations in the BMP TSD and is in addition to our proposed 
finding that the rule provides for the implementation of BACM and MSM 
for the 24-hour standard.

III. The CAA's Planning Requirements for Serious PM-10 
Nonattainment Areas

    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 the BACM, including best available control 
technology (BACT) for stationary sources, 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)); \8\
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    \8\ 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 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 and that the plan 
provides for attainment by the most expeditious alternative date 
practicable (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 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 section 172(c)(3)).
    Serious area plan must also provide for the implementation of 
contingency measures if the area fails to make RFP or attain by its 
attainment deadline. These contingency measures are to take effect 
without further action by the State or the Administrator. CAA section 
172(c)(9).
    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.
    We have issued a General Preamble\9\ and Addendum to the General 
Preamble\10\ describing our preliminary views on how the Agency intends 
to review SIPs submitted to meet the CAA's requirements for PM-10 
plans. The General Preamble mainly addresses the requirements for 
moderate areas and the Addendum, the requirements for serious areas.
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    \9\ ``State Implementation Plans; General Preamble for the 
Implementation of Title I of the Clean Air Act Amendments of 1990,'' 
57 FR 13498 (April 16, 1992) and 57 FR 18070 (April 28, 1992).
    \10\ ``State Implementation Plans for Serious PM-10 
Nonattainment Areas, and Attainment Date Waivers for PM-10 
Nonattainment Areas, and Attainment Date Waivers for PM-10 
Nonattainment Areas Generally; Addendum to the General Preamble for 
the Implementation of Title I of the Clean Air Act Amendments of 
1990,'' 59 FR 41998 (August 16, 1994)
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IV. The MAG Plan's Compliance with the CAA's Requirements for 
Serious PM-10 Nonattainment Area

    The following sections present a condensed discussion of our 
evaluation of the MAG plan's compliance with the applicable CAA 
requirements for attaining the 24-hour PM-10 standard. Our complete 
evaluation is found in the EPA TSD for this proposal. We strongly 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

    CAA section 110(k)(1)(B) requires us to determine if a SIP 
submittal is complete within 60 days of its receipt. This completeness 
review allows us to quickly determine if the submittal includes all the 
necessary items and information we need to take action on it. We make 
completeness determinations using criteria we have established in 40 
CFR part 51, appendix V.
    We found ADEQ's February 16, 2000 submittal of the final revised 
MAG serious area PM-10 plan complete on February 25, 2000. See letter, 
David P. Howekamp, EPA, to Jacqueline Schafer, ADEQ.
    We also found ADEQ's June 13, 2001 submittal of the BMP TSD 
complete on August 10, 2001. See letter, Jack Broadbent, EPA, to 
Jacqueline Schafer, ADEQ.

B. Adequacy of the Transportation Conformity Budgets

    CAA Section 176(c) 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

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whether or not transportation plans, programs, and projects conform to 
a SIP. 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 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 can 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). A finding of adequacy does not approve an emissions 
budget, it simply allows states to begin to use the budget in 
conformity determinations pending our action on the overall SIP.
    The MAG plan establishes a mobile source emissions budget of 59.7 
mtpd. This regional budget is applicable to both the annual and 24-hour 
PM-10 standards. The on-road mobile source 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 dust 
portion of the budget is 1.1 mtpd. MAG plan, p. 8-13.
    On March 30, 2000, we found adequate for transportation conformity 
purposes this motor vehicle emissions budget. Our adequacy finding is 
documented in section II of the EPA TSD for the annual standard. As a 
result of our adequacy finding, MAG and the Federal Highway 
Administration are now required to use this budget in all conformity 
analyses.
    As discussed later in this preamble, we are proposing to approve 
both the attainment and reasonable further progress demonstrations for 
the 24-hour standard in the Maricopa County serious area PM-10 plan. 
The 59.7 mtpd budget is consistent with these demonstrations. We, 
therefore, propose to approve it as the motor vehicle emissions budget 
for the 24-hour PM-10 standard under CAA section 176(c).

C. Emissions Inventory

    CAA section 172(c)(3) requires that nonattainment area plans 
include a comprehensive, accurate, and current inventory of actual 
emissions from all sources in the nonattainment area. To meet this 
requirement Arizona submitted a 1994 base year inventory as part of the 
MAG plan. See MAG plan, Appendix A, Exhibit 6. We proposed to approve 
this inventory as meeting the requirements of section 172(c)(3) in our 
proposal on the annual standard provisions. See 65 FR 19964, 19970.
    In the Phoenix nonattainment area, both regional and microscale 
modeling inventories are needed to accurately reflect the sources that 
are contributing to 24-hour PM-10 ambient levels. The regional modeling 
inventories were derived from the 1994 base year inventory and are the 
same for the annual and 24-hour standards. We proposed to find these 
regional modeling inventories to be acceptable as part of annual 
standard provisions. See 65 FR 19964, 19985-19986.
    ADEQ developed microscale and subregional inventories for 1995 (the 
modeling base year) for the West Chandler and Gilbert microscale sites. 
See Microscale plan, Appendix A, Chapter 4 and MAG plan, Appendix C, 
Exhibit 3, Chapter 3. In the 1997 Microscale plan, ADEQ also developed 
1995 inventories for the two other microscale sites, Maryvale and Salt 
River. See Microscale plan, Appendix A, Chapters 4 and 6. We evaluated 
the 1995 inventories for all four sites as part of our action on the 
overall Microscale plan. See 62 FR 31025, 31030 (June 6, 1997). These 
microscale inventories are specialized modeling inventory and is not 
intended to satisfy the CAA section 172(c)(3) requirement.\11\
---------------------------------------------------------------------------

    \11\ The microscale inventories include only sources within a 
small area surrounding each monitor rather than all sources within 
the entire nonattainment area as requirement in CAA section 
172(c)(3).
---------------------------------------------------------------------------

    We discuss emissions inventories in this preamble and in the EPA 
TSD in order to present a complete technical review of the Maricopa 
County serious area plan's provisions for attainment of the 24-hour 
standard. Emissions inventories play a fundamental role in air quality 
modeling, and CAA section 189(b)(1)(A) requires attainment 
demonstrations in PM-10 serious area plan to be based on modeling. We 
cannot find this modeling, or the attainment demonstrations that are 
derived from it, approvable without first finding that the underlying 
emissions inventories are adequate. We are not, however, proposing any 
actions today on the inventories relied on in the Maricopa County 
serious area plan for demonstrating attainment of the 24-hour standard 
because, as discussed above, we have already either proposed to approve 
them or found them to be acceptable.

D. Adequate Monitoring Network

    We discuss the adequacy of the monitoring network in this preamble 
solely to support our finding that the plan appropriately evaluates the 
PM-10 problem in the Phoenix area. Reliable ambient data is necessary 
to validate the base year air quality modeling which in turn is 
necessary to assure sound attainment demonstrations.
    The CAA requires states to establish and operate air monitoring 
networks to compile data on ambient air quality for all criteria 
pollutants. Section 110(a)(2)(B)(i). Our regulations in 40 CFR 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).
    Ambient networks, however, do not need to meet all our regulations 
to be found adequate to support air quality modeling. A good spatial 
distribution of sites, correct siting, and quality-assured and quality-
controlled data are the most important factors we consider when 
evaluating the monitoring network for air quality modeling. 
Nonattainment area plans developed under title I, part D of the Clean 
Air Act are not, in general, required to address how the area's air 
quality network meets our monitoring regulations. These plans are 
submitted too infrequently to serve as the vehicle for assuring that 
monitoring networks remain current.
    The base year for the MAG plan is 1995. In 1995, there were 16 
monitoring sites operated by either MCESD or ADEQ that collected PM-10 
data in the Phoenix area, three designated as NAMS, five designated as 
state/local monitoring stations, and eight designated as special 
purpose monitors. All of the sites were operated in accordance with our 
regulations in 1995. Figure 3-2 in the MAG plan lists the names of the 
sites and their locations in the Phoenix area as of April 1999. Most of 
these PM-10 monitoring sites were sited as neighborhood scale with an 
objective of assessing population exposure. Given the nature of the 
emission sources in the Phoenix area, which are mostly local fugitive 
dust sources, we believe this is an appropriate focus of the network.
    The 24-hour attainment demonstration in the MAG plan relies, in 
part, on showing attainment at four specific monitoring sites. These 
sites

[[Page 50257]]

were chosen to evaluate the type and mix of sources thought to be 
contributing to elevated 24-hour PM-10 levels: Salt River for its 
proximity to industrial sources; West Chandler for its nearby highway 
construction; Maryvale for its residential area coupled with land 
disturbing activities due to the construction of a park, and Gilbert 
for its proximity to agricultural land. In 1995 these sites recorded 
the highest and most frequent exceedances of the 24-hour PM-10 
standard. They are also representative of similar areas in the Phoenix 
area that may not have monitoring sites.
    Based on our evaluation, we have concluded that the monitoring 
network operated by the MCESD and ADEQ in 1995 was adequate to support 
the air quality modeling in the MAG plan. The network utilized EPA 
reference or equivalent method monitors and both agencies have EPA-
approved quality assurance plans in place.

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

    CAA section 189(e) requires a state to 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.
    We estimate that major stationary sources contribute at most 0.61 
g/m\3\ to 24-hour PM-10 levels in the Phoenix area. See EPA 
TSD section, ``BACT for Major Stationary Sources of PM-10 Precursors.'' 
We estimated this contribution by assuming that the major stationary 
sources' contribution to secondary levels is proportional to their 
presence in the inventory. We believe that this assumption is 
reasonable given the very small presence of major stationary sources in 
the precursor inventory and the small contribution total secondaries 
make to PM-10 levels in Phoenix. Moreover, secondary particulate takes 
hours to form in ambient air from its precursors. By the time secondary 
particluate is formed, the precursors are well mixed in the ambient 
air, so localized, disproportionate impacts by major sources of PM-10 
precursors are very unlikely.
    This contribution is well below our proposed 5 g/m\3\ 
significance level.\12\ However, independent of this fact, we believe 
that so small a contribution--less than 0.4 percent of the 24-hour PM-
10 standard of 150 g/m\3\--is truly insignificant by any 
measure for the Phoenix area. PM-10 levels above the 24-hour standard 
in Phoenix are almost exclusively caused by a few large source 
categories of fugitive dust. It is controls on these sources that are 
the key to expeditious attainment and not controls on trivial 
contributors such as major stationary sources of PM-10 precursors.
---------------------------------------------------------------------------

    \12\ The MAG plan demonstrates that the 5g/m\3\ is the 
appropriate level for determining which categories are significant 
for the BACM requirement for the 24-hour standard; therefore, we 
believe that it is an appropriate level for us to adopt here.
---------------------------------------------------------------------------

    Based on their negligible impact on ambient PM-10 levels, we 
propose to determine that major sources of PM-10 precursors do not 
contribute significantly to PM-10 levels which exceed the 24-hour 
standard in the Phoenix area; therefore, pursuant to CAA section 
189(e), BACT need not be applied to major sources of PM-10 precursors.

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. Under our applicable guidance, BACM must be applied to each 
significant area-wide source category. Addendum at 42011. As discussed 
in section V of this preamble, we have established a four-step process 
for evaluating BACM in serious area PM-10 plans.
1. Steps 1 and 2: Determination of Significant Sources
    The first step in the BACM analysis is to develop a detailed 
emissions 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 second step is use this inventory in air quality 
modeling to evaluate the impact on PM-10 concentrations over the 
standards of the various sources and source categories to determine 
which are significant.
    The development of the detailed emissions inventories is discussed 
in a preceding section. 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.\13\
---------------------------------------------------------------------------

    \13\ 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 the 
Microscale plan.
---------------------------------------------------------------------------

    From these evaluations, the MAG plan identifies 8 significant 
source categories and 12 insignificant source categories. MAG plan, p. 
9-6.
    The final list of significant source categories in the MAG plan 
does not distinguish between those categories that are significant for 
the 24-hour standard and those that are 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 does not distinguish significant source categories between 
the two standards, we treat each of the listed significant source 
categories as significant for the 24-hour standard.
    For the 24-hour standard, the MAG plan demonstrates that its 
selection of significant source categories is appropriate by showing 
that controls on the de minimis source categories would not result in 
attainment of the 24-hour standard by 2001. For a detailed description 
of this demonstration, see MAG plan, pp. 9-12 to 9-15 and the EPA TSD 
section ``BACM Analysis--Step 2, Model to Identify Significant 
Sources.''\14\
---------------------------------------------------------------------------

    \14\ In this de minimus demonstration, certain source categories 
vacant land, unpaved roads, agricultural sources, and unpaved 
parking--were assumed to be uncontrolled at the end of 2001. See MAG 
plan, Tables 9-b and 9-c. These categories will in fact be subject 
to BACM by then. By not including controls on these categories in 
the de minimis demonstration, the gap between nonattainment and 
attainment of the 24-hour standard in 2001 is much larger than it 
should be and thus, the de minimis determination for the 24-hour 
standard is suspect.
    To check if the selected de minimis categories are truly de 
minimis under the correct control assumptions, we redid the 
determination incorporating the appropriate level of control for 
each source category. We concluded from this reanalysis that the MAG 
plan's selected de minimis threshold is in fact appropriate and the 
identified de minimis categories are indeed de minimis and are 
appropriately excluded from the BACM analysis. See EPA TSD, section 
``BACM Analysis--Step 2, Model to Identify Significant Sources.''

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[[Page 50258]]

    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 (e.g., stationary point sources, waste/open burning, 
agricultural harvesting, charbroiling) 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.
2. Step 3: 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 nonattainment areas in the western 
United States. MAG also evaluated controls proposed during public 
comment. MAG plan, pp. 9-24 through 9-29; MAG Plan, Appendix D, Exhibit 
1, ``Response to Public Comments, January 31, 2000 Public Hearing''; 
and BMP TSD, pp. 9 through 27.
    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 plan also provides cost effectiveness estimates for each of 
the candidate BACM. MAG plan, pp. 9-30 through 9-39; and BMP TSD, pp. 9 
through 27.
    We propose to find that the Maricopa County serious area PM-10 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 plan left out any candidate BACM. 
Overall, the plan presents one of the most comprehensive lists of 
potential BACM ever produced.
3. Step 4: Implementation of RACM and BACM and inclusion of MSM for 
Each Significant Source Category
    In the following sections, we review the results of the Maricopa 
County serious area 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.\15\ 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.
---------------------------------------------------------------------------

    \15\ 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.
    Controls on a number of significant source categories are 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 proposed 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.
    As discussed above, the MAG plan made no distinction between 
significant sources for the annual standard and those for the 24-hour 
standard and, as a result, it made no distinction between BACM and MSM 
for the annual standard and those for the 24-hour standard. We have 
already extensively reviewed the MAG plan's BACM and MSM provisions for 
the annual standard and these reviews are applicable to the 24-hour 
standard. Thus, except for clarifying and/or updating information on a 
few measures, we have not revised our evaluations of BACM and MSM for 
most of the significant source categories. Four categories--on-road 
engines (technology controls), nonroad engines, unpaved roads and 
construction dust--have undergone moderate changes.
    Our analysis of the agricultural source category has changed 
substantially from the annual standard proposal. As discussed above, we 
based our review in the annual standard proposal on the State's 
legislation requiring the adoption of measures for agriculture. Since 
then, the State has adopted the agricultural general permit rule and 
has submitted revisions to the Maricopa County serious area plan 
containing the demonstration that the general permit rule represents 
BACM and MSM. For today's proposal, we have based our review of BACM 
and MSM for the agricultural sources on the general permit rule and the 
State's additional documentation. Our revised analysis applies to both 
the annual and 24-hour standards.
 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.
    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 (I/M) programs, 
fuels, programs to encourage alternative fueled vehicle usage, and 
programs to accelerate fleet

[[Page 50259]]

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 Cleaner 
Burning Gasoline program which mandates the use of either Phase II 
federal reformulated gasoline or California reformulated gasoline; 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.
    As noted before, Arizona has in place a 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. See 
EPA TSD, Table ORM-3 in the section ``Implementation of BACM and MSM 
for On-Road Motor Vehicle Exhaust and Paved Road Dust (Technology 
Standards and Fuels).''
    The MAG plan identified just a few measures from other areas as 
potential MSM. These measures have either been adopted or we have 
concluded that the measure need not be included to assure the inclusion 
of MSM.
    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.\16\ 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.
---------------------------------------------------------------------------

    \16\ Arizona has already adopted half of the CARB diesel 
standards, the 500 ppm sulfur limit. 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. Also, in January 2001, we established a new diesel fuel sulfur 
limit of 15 ppm as part of our overall program to control emissions 
from heavy duty diesel vehicles. They new limit which will apply to 
Arizona will be fully in place by September, 2006. 66 FR 5002 
(January 8, 2001).
---------------------------------------------------------------------------

    Based on information in the Microscale plan, emissions from on-road 
motor vehicle are not implicated in 24-hour exceedances in the Phoenix 
area. Microscale plan, pp. 17-19. All currently available evidence is 
that 24-hour exceedances are caused by local fugitive dust sources and 
controls on these sources alone will result in the earliest practicable 
date for attainment of the 24-hour PM-10 standard in the Phoenix area. 
Microscale plan, pp. 17-19. Because implementation of CARB diesel would 
not result in earlier attainment and thus unnecessary for expeditious 
attainment, we propose to find that the MAG plan provides for the 
inclusion of MSM to our satisfaction absent the adoption and 
implementation of CARB diesel.
    Except for one, all the adopted BACM and MSM were implemented by 
June 10, 2000, the BACM implementation deadline for the Phoenix area. 
The exception is the requirement that pre-1988 heavy duty diesel 
vehicles registered in the nonattainment area meet 1988 federal 
emission standards. This measure will not be fully 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 transportation control measures 
(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 for the 24-hour standard.
    Since the annual standard proposal was published in April 2000, 
changes have been made to two on-road motor vehicle controls that were 
included in that proposal: the remote sensing (RSD) program in the 
State's vehicle emissions inspection program (VEIP) and changes to the 
State's incentives for purchase of alternatively-fueled vehicles or 
conversions to alternatively-fueled vehicles.
    In 2000, the Arizona legislature converted the RSD program from a 
regulatory program to a pilot program because of its high cost per ton 
of emissions reduced \17\ In July 2001, Arizona submitted a SIP 
revision that included all changes to State's VEIP program that had 
been made since we last approved it in 1995, including the changes to 
the RSD program. 2001 I/M SIP submittal, p. 26. We consider this I/M 
program submittal to be Arizona's current statement of what elements 
constitute its VEIP.
---------------------------------------------------------------------------

    \17\ ADEQ, Final Arizona State Implementation Plan Revision, 
Basic and Enhanced Vehicle Emissions Inspection/Maintenance Program, 
June 2001 (``2001 I/M SIP submittal''), p. 26.
---------------------------------------------------------------------------

    The RSD program is not credited in the RFP or attainment 
demonstrations for the annual standard. The State justifies its 
revision to this program based on the implementation cost of the 
unrevised program, that is, they have determined that the unrevised 
program was economically infeasible. We believe that this change to the 
overall on-road motor vehicle control program in the MAG plan do not 
adversely affect our previously proposed finding that the plan provides 
for the implementation of RACM and BACM and the inclusion of MSM for 
this source category for the annual standard found at 65 FR 19964, 
19972.
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 (VT). 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 
24-hour PM-10 concentrations in the Phoenix area (See EPA TSD section, 
``BACT for Major Stationary Sources of PM-10 Precursors'' which shows 
that total

[[Page 50260]]

secondary particulates from all sources have a maximum impact of 9.2 
g/m\3\ 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 vehicle exhaust.
    In total, the MAG plan identifies 19 TCMs for consideration, 
including the CAA section 108(f) measures. The plan does not identify 
any potential most 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 
potential MSM from other States.
    Arizona has a long history of adopting and then enhancing programs 
to reduce emissions from on-road motor vehicles by reducing VMT, VT, 
and/or congestion.\18\ 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.
---------------------------------------------------------------------------

    \18\ 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 and acceptable 
justification for the rejection.
    All the adopted TCM BACM were implemented by June 10, 2000, the 
BACM implementation date for the Phoenix area, or have on-going 
implementation schedules because they are part of an 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 nonroad 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 potential most stringent measures from other 
States.
    We have adopted national emission standards for a broad range of 
nonroad engines. We consider that these standards, which apply to 
nonroad engines sold in Arizona constitute at minimum a 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. CAA section 209(e)(2)(B).
    Arizona legislation allows ADEQ to adopt certain California nonroad 
engine standards. MAG plan, p. 7-42. ADEQ originally committed to adopt 
these California nonroad standards; however, subsequently, we adopted 
federal nonroad engine standards that will achieve essentially the same 
PM-10 reductions in the Phoenix area that adoption of the California 
ones would. As a result, Arizona determined that adoption of the 
California standards would not justify the resources ADEQ would need to 
expend to adopt, implement, and enforce them and has now withdrawn its 
commitment. See letter, Jacqueline E. Schafer, ADEQ, to Laura Yoshii, 
EPA, ``Justification for not implementing CARB Off-road engine 
standards for the Maricopa County PM-10 SIP,'' September 7, 2001 
(``ADEQ Off-Road Letter'').
    Arizona has adopted and implemented a year-round Cleaner Burning 
gasoline program and limits on the sulfur content of diesel fuels. 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 nonroad 
engines but does not adopt it. MAG plan, Table 10-7. 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.
    Based on information in the Microscale plan, emissions from nonroad 
engines are not implicated in 24-hour exceedances in the Phoenix area. 
Microscale plan, pp. 17-19. All currently available evidence is that 
24-hour exceedances are caused by local fugitive dust sources and 
controls on these sources alone will result in the earliest practicable 
date for attainment of the 24-hour PM-10 standard in the Phoenix area. 
Microscale plan, pp. 17-19. Because implementation of CARB diesel would 
not result in earlier attainment and thus unnecessary for expeditious 
attainment, we propose to find that the MAG plan provides for the 
inclusion of MSM to our satisfaction absent the adoption and 
implementation of CARB diesel.
    We, therefore, propose to find that MAG plan provides for the 
implementation of RACM and BACM and inclusion of MSM for nonroad 
engines.
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

[[Page 50261]]

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 VMT and VT, 
preventing deposition of material onto a roadway, and cleaning material 
off the roadway. We have already discussed measures for reducing VMT 
and VT in the section on TCMs above.
    The MAG plan lists several potential BACM for paved road dust. It 
also lists a number of potential 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 potential 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 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 PM-10-efficient street sweepers measure 
described below, all the adopted BACM for paved roads were implemented 
by June 10, 2001, the BACM implementation deadline for the Phoenix 
area, or have on-going implementation schedules because they are part 
of an 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, 
a MSM, 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. MCESD Rule 310, sections 308.2(c) and 308.3 address dirt 
track out from construction/industrial sites requiring 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 to control 
and prevent track out by installing a track out control device. The 
rule also requires all work sites to clean up spillage or track out 
immediately when it extends a cumulative distance of 50 linear feet or 
more and, where track out extends less than 50 feet, to clean it up at 
the end of the work day.
    The MAG plan identifies, as a potential MSM for track out, South 
Coast (Los Angeles area) Air Quality Management District's (South Coast 
AQMD) 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 each other out. 
MSM Study, p. C-4.\19\ 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.
---------------------------------------------------------------------------

    \19\ The ``MSM Study'' is the ``Most Strigent PM-10 Control 
Measure Analysis,'' Sierrra 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 
simply 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. The commitments are set depending on the resources available 
to each jurisdiction to implement them.
    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 MCESD 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

[[Page 50262]]

in Imperial County (California) 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 roadways are track out, erosion, 
and spill removal requirements and road sweeping.
    The MAG plan includes each of these measures:
    Material spillage, erosion, or accumulation. MCESD 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 AQMD's Rule 1186 and Mojave 
Desert (San Bernadino, California) AQMD'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 either the South Coast or 
Mojave Desert 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, 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 and Air Quality (CMAQ)\20\ 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 in 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.''
---------------------------------------------------------------------------

    \20\ CMAQ funds are federal transportation funds awarded to 
certain nonattainment areas for congestion management of air 
quality-transportation projects such as paving unpaved roads.
---------------------------------------------------------------------------

    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.\21\ 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).\22\ MAG will use this information to estimate 
the emission reductions 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.''
---------------------------------------------------------------------------

    \21\ Some street sweepers may be additions to, as opposed to 
replacements of, existing equipment.
    \22\ See MAG, ``Methodology for Evaluating Congestion Mitigation 
and Air Quality Improvement Projects,'' Draft Revised, June 21, 
2001, pp. 18-22.
---------------------------------------------------------------------------

    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. In addition, 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 will be implemented 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 only as they replace existing equipment.
    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 being purchased and placed in

[[Page 50263]]

operation 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 be reduced 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 on unpaved parking lots and windblown dust entrained 
from the disturbed surface of unpaved parking lots.
    There are two principal ways to control emissions from unpaved 
parking lots: prohibit unpaved parking lots or treat existing lots. MAG 
plan identified both: a prohibition on unpaved haul road 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 potential MSM, South Coast's Rule 403 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, section 303 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's standards/test 
methods. 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, section 302.1 
applies the same stabilization requirements to parking lots on 
permitted facilities. 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 first specifically considering 
whether the plan provides for the implementation of RACM for these 
sources.\23\ In our 1998 moderate area PM-10 FIP for the Phoenix area, 
we promulgated a RACM fugitive dust rule applicable to unpaved parking 
lots in the Phoenix PM-10 nonattainment area. 40 CFR 52.128(d)(3). This 
rule provides a starting point for determining whether the MAG plan's 
measures for unpaved parking lots meet RACM. It is not necessary for 
them 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. 
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.
---------------------------------------------------------------------------

    \23\ While a serious area PM-10 plan must provide for both the 
implementation of RACM (to the extent that it has not already 
satisfied the requirement in its moderate area plan) 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 generally necessary. However, in this particular case, we have 
already established through our FIP rule what we consider to be a 
RACM-level of control for this source category. Thus our FIP rule 
provides us with a baseline against which we can review whether the 
MAG plan provides not only for RACM but also goes beyond that for 
BACM. We also intend to eventually withdraw the FIP rule in favor of 
local controls. In order to do this, we must determine under CAA 
section 110(1), that, among other things, withdrawing the FIP rule 
does not interfere with the RACM requirements in the CAA. An 
explicit determination now simplifies this future action.
---------------------------------------------------------------------------

    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 (located in the eastern third of the County). Rule 
310.01 requirements became effective when the rule was adopted on 
February 2000. In light of the fact that Rule 310.01 requirements are 
the same as the FIP rule requirements and MCESD has made enforceable 
commitments to improve compliance and enforcement of Rule 310.01, we 
propose that the MAG plan provides for the implementation of RACM. 
Given the additional city/town commitments in the MAG plan that 
collectively increase the stringency of control on unpaved parking 
lots, we propose that the MAG plan also provides for the implementation 
of BACM. Both Rule 310.01 and the city/town commitments were 
implemented prior to June 10, 2000, the BACM implementation deadline 
for the Phoenix area.
    As the only potential MSM, the MAG plan identifies South Coast's 
Rule 403 which requires sources to apply dust suppressants to stabilize 
at least 80 percent of unstabilized surface area and to comply with a 0 
percent opacity property line limit. The MAG plan deems the respective 
requirements roughly equivalent to Rule 310. MAG plan, p. 10-29. 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 such that it is at least equivalent to that of South 
Coast Rule 403. We, therefore, propose to find that the MAG plan 
correctly concludes that there are no MSM 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. MAG plan, Table 5-2. The 
plan also identified controls on weed abatement operations and off-road 
racing as potential MSM. MAG plan, Table 10-7. 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.
    Both MCESD rules 301 and 301.01 address vacant lots. Rule 310 
requirements apply to vacant lots

[[Page 50264]]

located at permitted facilities (including construction sites) and Rule 
310.01 requirements apply to nonpermitted sources.\24\ 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.
---------------------------------------------------------------------------

    \24\ 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 this 
source category. See Footnote 23. In our FIP, we promulgated a RACM 
fugitive dust rule applicable to disturbed vacant land in the Phoenix 
PM-10 nonattainment area. 40 CFR 52.128(d)(3). This rule provides a 
starting point for determining whether the MAG plan's measures for 
disturbed vacant lands meet the RACM requirement. It is not necessary 
for them 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. 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. 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 resemble the Phoenix FIP rule's weed abatement requirements, 
except that Rule 310's threshold for coverage is lower.\25\
---------------------------------------------------------------------------

    \25\ 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 and 40 CFR 
52.129(c)(3) and (d)(3)(i).
---------------------------------------------------------------------------

    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 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. See EPA TSD section 
``Implementation of BACM and Inclusion of MSM for Disturbed Vacant 
Land.''
    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 (as discussed below), 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 which collectively increase the stringency of 
control on vacant disturbed lands, we propose that the MAG plan also 
provides for the implementation of BACM. All measures for vacant 
disturbed lands were implemented prior to the June 10, 2000 BACM 
implementation deadline for the Phoenix area.
    For its MSM analysis, 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 and 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 MSM 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 does 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 
23. In our FIP, we promulgated a RACM fugitive dust rule applicable to 
unpaved roads in the Phoenix PM-10 nonattainment area. 40 CFR 
52.128(d)(3). This rule provides a starting point for determining 
whether the MAG plan's measures for unpaved roads meet the RACM 
requirement. It is not necessary for them 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. 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 
principal control measure 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 (VPD) 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 accomplished before June 10, 2000--paving all 
80 miles of its publicly-owned unpaved roads regardless of the level of 
vehicle travel. Phoenix Commitment, Measure 98-DC-

[[Page 50265]]

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).\26\
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    \26\ Pacific Environmental Service, ``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 VDT and 
meet criteria to become public highways, using $22 million in CMAQ and 
MCDOT funds. 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 
account for 40 percent of all VMT 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.
    As the County evaluates roads for paving, it may make exceptions to 
its commitment to pave roads with vehicle trips that exceed 150 VDT. 
The County's evaluation process takes into account whether estimated 
costs of paving are excessive (greater than $500,000 per mile).\27\ 
When MCDOT identifies a road that meets these criteria (i.e. the road 
can be declared a public highway and costs are not excessive), it will 
recommend that the Board of Supervisors open and declare the road a 
public highway.\28\
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    \27\ 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.
    \28\ Maricopa County provided an update to us of their efforts 
to identify and pave County minimal maintenance roads. Kelly 
McMullen, MCDOT, via email on May 4, 2001. The County identified 
approximately 68 miles of minimal maintenance roads (courtesy 
grading only) that potentially could have over 150 VPD traffic. Of 
those roads, the County was unable to gather traffic count 
information for approximately 3 miles due to repeated counter 
vandalism or theft. The County included remaining roads with traffic 
counts over 130 VPD (allowing for short term growth seasonal 
variation, etc.) in its program to pave, totaling approximately 65 
miles, consisting of approximately 186 segments. The first group of 
these roads was expected to have a bid awarded in June 2001 and be 
paved by Fall 2001. Design work for the second group was expected to 
begin in Summer 2001 and is expected to go to bid for construction 
within the next twelve months. Design work for the third group also 
expected to begin in Summer 2001 and is expected to be bid 
approximately 10-12 months following the second group. This third 
group reflects the most difficult engineering and environmental 
issues. Based on project engineer estimates at this time, the County 
believes that six segments totaling approximately 3.0 miles may 
exceed the reasonable cost threshold of $500,000 per mile, or have 
issues with adjoining property owners that are not possible to 
resolve within the SIP time frames. The County will evaluate whether 
another method of dust suppression may be viable for those segments.
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    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 little traffic on it.\29\ 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 24-hour 
standard.
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    \29\ Through MAG, we requested additional information on private 
unpaved roads from the cities of Chandler, Scottsdale, Gilbert, 
Glendale, Mesa, Phoenix, Tempe, Peoria, Avondale, Carefree, Cave 
Creek, El Mirage, Goodyear, and Surprise. Letter Colleen McKaughan, 
EPA, to Lindy Bauer, MAG, March 21, 2001. All but three cities 
responded to the survey. Five cities state that they currently have 
no private unpaved roads with greater than 150 VPD. Three cities 
indicate they do not believe there are private unpaved roads with 
greater than 150 VPD in their jurisdictions. The remaining cities 
either have a small number of private road miles identified with 
greater than 150 VPD or make no statement regarding the number of 
private road miles with greater than 150 VPD in their jurisdictions. 
Letter Lindy Bauer, MAG, to Colleen McKaughan, EPA, June 29, 2001.
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    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's 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 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 these roads will be stabilized.
    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 MSM 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 sites 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 earthmoving, represent some 
90 percent of the emissions in this source category.
    The suggested measure in the MAG plan for controlling emissions 
from construction sites are actually various means of improving 
compliance with controls rather than new control requirements for 
construction sites. See

[[Page 50266]]

MAG plan, Table 5-2. MCESD had already adopted controls for 
construction sites in its fugitive dust rule, Rule 310. The plan also 
identifies several potential MSM. See MAG plan, Table 10-7. We propose 
to find that the MAG plan evaluates a comprehensive set of potential 
controls for construction sites emissions including the potentially MSM 
from other states.
    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 \30\ and 
sources subject to title V permits,\31\ 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.
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    \30\ 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.
    \31\ Title V permits are operating permits required by Title V 
of the Clean Air Act for major stationary sources and certain other 
stationary sources.
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    For other permitted sources, Rule 310 requires that a 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.\32\
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    \32\ 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.
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    Specific Rule 310 requirements include:
     a 20 percent opacity requirement for any dust generating 
operation
     wind event controls
     implementation of controls before, after and while 
conducting any dust generating operation, including weekends, after 
work hours and holidays
     required controls 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 for all fugitive dust sources; the 
contingency measure is to be immediately implemented if the primary 
control 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 controls for earthmoving activities, 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.\33\ Test methods associated with 
stabilization and opacity standards are contained in Appendix C, which 
was submitted with Rule 310.
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    \33\ Unpaved roads must meet a 6 percent silt content standard 
or, alternatively, a 0.33 oz/ft\2\ silt loading standard, while 
unpaved parking lots must meet an 8 percent silt content standard 
or, alternatively, a 0.33 oz/ft\2\ silt loading standard.
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    The 1999 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 made three 
enforceable commitments to further strengthen requirements for 
construction sites in 1999. See Maricopa County Commitments, Revised 
Measure 6. MCESD has recently revised these commitments and will take 
the revisions to the Maricopa County Board of Supervisors in December, 
2001 for formal adoption as enforceable commitments. See Letter, Al 
Brown, MCESD to Jack Broadbent, EPA, September 13, 2001 (MCESD 
commitment letter). The commitments are to:
    1. Research and develop a standard(s) and test method(s) for earth 
moving sources, designed to be enforceable and meet BACM requirements 
as to stringency and the number of sources that it applies to. Revise 
Rule 310 and/or Appendix C by no later than December 2002 to modify the 
existing opacity standard/test method or add an additional opacity 
standard(s)/test method(s), tailored to non-process fugitive dust 
sources that create intermittent plumes. This commitment will be met in 
its entirety only if the standard(s)/test method(s) is approved by EPA. 
The County is also proposing to support and coordinate with Clark 
County, Nevada in the ongoing research to develop fugitive dust test 
methods through the appropriation of $25,000.
2. Part 1: Onsite Implementation of Dust Control Plan
    Raise awareness of onsite project supervisors to acquire and read 
approved site dust control plans thereby improving the implementation 
of the dust control plan at the construction site. This objective will 
be achieved through one-on-one contact at the time of inspection and 
through the development of a revised training curriculum and supporting 
materials for both a classroom setting and onsite aids for improved 
project management. Maricopa County inspectors will continue to go over 
dust control plans with construction site personnel during the initial 
site inspection and whenever issues arise during subsequent 
inspections. The training curriculum being developed by the Arizona 
Department of Transportation (ADOT) is scheduled for completion in 
winter of 2002 and implementation of the second level of dust control 
education will begin March--June 2003.
Part 2: Dust Control Plan Improvements
    Research, develop and incorporate additional requirements for dust 
suppression practices/equipment into dust control plans and/or Rule 310 
by March--December 2002. Based on the ADOT research, MCESD research or 
other alternative research, Maricopa County will develop a growing list 
of criteria for effective versus ineffective dust suppression practices 
that address various site circumstances.
    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

[[Page 50267]]

Rule 310 and the dust control plan. Distribute sample log sheets with 
issued permits and conduct outreach to sources by December 2001.
    The first 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.
    Field research is needed to identify an appropriate standard(s) and 
test method(s) to meet this commitment. MCESD originally committed to 
complete this research and revise the opacity method by July 2001 but 
was unable to do so. It now intends to work with Clark County which has 
recently conducted research on test methods for earthmoving sources and 
is planning to conduct a second phase of research. MCESD will 
contribute funding to these efforts. MCESD has requested a one-year 
extension of the deadline in its original commitment in order to 
monitor, validate and verify the resulting test method(s) performance 
in Maricopa County.
    The second commitment addresses our concern that 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. Also, for effective dust control, certain soil types may 
require substantial pre-wetting, thorough mixing of water into the soil 
for uniform penetration, and/or dust surfactant or tackifyer combined 
with water; neither Rule 310 nor DCPs currently require such measures 
for any sites.
    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 and has made it difficult to establish these 
criteria. Because of this difficulty MCESD has revised its original 
commitment to allow additional time to develop them.
    MCESD has also expanded its original commitment to include a 
program to work with on-site supervisors to assure that they obtain and 
review the DCP for their sites. In implementing Rule 310 during the 
last year, it found that site supervisors do not have or do not know 
what is in their DCPs and thus may not be implementing appropriate dust 
control methods.
    The third 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 revised its original commitment to 
allow additional time to work with its stakeholders to develop daily 
recordkeeping log sheets to provide sufficient detail documenting the 
implementation of dust controls.
    We propose to find that Rule 310 as adopted on February 16, 2000 
and combined with the commitments by MCESD to make certain additional 
changes to the Rule, provide for the implementation of RACM and BACM on 
construction sites for the 24-hour PM-10 standards.\34\ We have also 
determined that the revised commitments do not affect our previous 
proposed finding that Rule 310 combined with the commitments provide 
for the implementation of RACM and BACM on construction sites for the 
annual standard. 65 FR 19964, 19980. 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).
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    \34\ These revised commitments are currently unenforceable 
because they have not been adopted by Maricopa County's Board of 
Supervisors. We are, however, proposing to approve these commitments 
under CAA section 110(k)(3) as an enforceable element of the Arizona 
SIP because we fully expect that the Board will adopt these 
commitments as enforceable SIP commitments and the State will submit 
them as a complete SIP revision prior to our final action. However, 
if we do not receive the adopted commitments by the time we must 
take final action, we propose to conditionally approve them under 
CAA section 110(k)(4). If we take final action to conditionally 
approve these commitments, MCESD will have one year to fulfill the 
commitment or the approval will turn into a disapproval and we would 
no longer be able to find that the MAG plan provides for the 
implementation of BACM and the inclusion of MSM on construction 
sites for either the annual or 24-hour standards.
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    The MAG plan identifies several potential most stringent 
construction site fugitive dust measures either in or under 
consideration for inclusion in others SIPs. 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 controls 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 potential most 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 measures.\35\ 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.
---------------------------------------------------------------------------

    \35\ 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 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

[[Page 50268]]

handling or transferring bulk material, chemical/physical 
stabilization, or sheltering/enclosure of the operation and transfer 
line. While Maricopa County Rule 310 requires owners/operators to 
comply with a 20 percent opacity standard for any dust generating 
operation and DCP must include a control measure for every fugitive 
dust source (including bulk material handling/transfer), it does not 
contain specific requirements as Imperial County does for this 
activity. However, watering 15 minutes prior to handling may be overly 
prescriptive and not necessary in all cases to meet the rule's 
performance standards. We propose to find that Maricopa County's second 
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. See Footnote 34.
i. Agricultural Sources
    The agriculture source category covers all dust generating 
activities and sources on farms and ranches. These activities and 
sources include land planning, tilling, harvesting, fallow fields, 
prepared fields, field aprons, and unpaved roads. This source category 
is a very significant contributor to 24-hour PM-10 standard exceedances 
in the Phoenix area. At the West Chandler site, 55 percent of the 
modeled exceedance was due to agricultural sources (a cotton field and 
its apron). At the Gilbert site, 26 percent of the modeled exceedance 
was due to an agricultural source (a field apron). See Microscale plan, 
pp. 18-19.
    In order to develop adequate controls for this source category, 
Arizona passed legislation in 1997 establishing an Agricultural Best 
Management Practices (BMP) Committee and directing the Committee to 
adopt by rule by June 10, 2000, an agricultural general permit 
specifying best management practices for reducing PM-10 from 
agricultural activities. The legislation also required that the 
implementation of agricultural controls begin with an education program 
starting by June 10, 2000 with full implementation by December 31, 
2001. See Arizona Revised Statutes (A.R.S.) 49-457.
    After a series of meetings during 1999 and 2000, the Agricultural 
BMP Committee adopted the agricultural general permit and associated 
definitions, effective May 12, 2000, at Arizona Administrative Code 
(AAC) R18-2-610, ``Definitions for R18-2-611,'' and 611, ``Agricultural 
PM-10 General Permit; Maricopa PM10 Nonattainment Area'' (collectively, 
general permit rule). The State submitted the general permit rule in 
July 2000 and its analysis quantifying the emission reductions expected 
from the rule and the demonstration that the rule meets the CAA's RACM, 
BACM and MSM requirements in June 2001. We proposed to approve it as 
meeting the CAA requirement for RACM on June 29, 2001 and signed the 
approval on September 10, 2001. See 66 FR 34598.
    The general permit rule requires a commercial farmer to implement 
by December 31, 2001 at least one BMP for three categories of emission 
sources on a farm: tillage and harvest, non-cropland, and cropland. 
R18-2-610 defines commercial farmer as ``an individual, entity, or 
joint operation in general control of 10 or more continuous acres of 
land used for agricultural purposes within the boundary of the Maricopa 
County PM10 nonattainment area.'' R18-2-610 defines tillage and harvest 
as ``any mechanical practice that physically disturbs cropland or crops 
on a commercial farm.'' R18-2-610 defines non-cropland as ``any 
commercial farm land that: is no longer used for agricultural 
production; is no longer suitable for production of crops; is subject 
to a restrictive easement or contract that prohibits use for the 
production of crops; or includes a private farm road, ditch, ditch 
bank, equipment yard, storage yard, or well head.'' R18-2-610 defines 
cropland as ``land on a commercial farm that: is within the time frame 
of final harvest to plant emergence; has been tilled in a prior year 
and is suitable for crop production, but is currently fallow; is a 
turn-row.'' R18-2-610 defines a BMP as ``a technique verified by 
scientific research, that on a case-by-case basis is practical, 
economically feasible and effective in reducing PM-10 particulate 
emissions from a regulated agricultural activity.''
    For enforcement purposes, a commercial farmer is required to 
maintain a record demonstrating compliance with the general permit. A 
commercial farmer not in compliance with the general permit is subject 
to a series of compliance actions described in A.R.S. 49-457.I-K.
    The BMP Committee began implementing the general permit rule in 
June 2000 by means of an extensive educational outreach program 
informing growers about the BMPs. In addition, the BMP Committee 
developed a Guide to Agricultural PM-10 Best Management Practices to 
provide information and guidance on how to effectively implement 
BMPs.\36\ Farmers must be in compliance with the general permit rule by 
December 31, 2001.
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    \36\ ``Guide to Agricultural PM-10 Best Management Practices, 
Maricopa County, Arizona PM-10 Nonattainment Area,'' Governor's 
Agricultural BMP Committee, First edition, February, 2001.
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    For the reasons discussed below and more extensively in the section 
``Implementation of BACM and Inclusion of MSM for Agricultural 
Sources'' in the EPA TSD, we propose to find that the State's general 
permit rule meets the CAA's requirements to provide for the 
implementation of BACM by June 10, 2000 in CAA section 189(b)(1)(B) and 
to include MSM in section 188(e). Our proposed finding is applicable to 
both the annual and 24-hr standards. It revises our previously proposed 
finding in the annual standard proposal that the State's commitment in 
the MAG plan to adopt and implement agricultural best management 
practices meets the CAA's requirements for BACM and MSM by substituting 
the BMP general permit rule. 65 FR 19964, 19981.
    In September 1998, the Agricultural BMP Committee appointed an Ad-
hoc Technical Group to develop a comprehensive list of potential BMPs 
for regulated sources in the Maricopa County nonattainment area. 
Participants on the Ad-hoc Group included the USDA NRCS, USDA 
Agricultural Research Service, University of Arizona College of 
Agriculture, ADEQ, University of Arizona College of Agriculture and 
Cooperative Extension, Western Growers Association, Arizona Cotton 
Growers Association, Arizona Farm Bureau Federation, and EPA. BMP TSD, 
p. 15.
    The Ad-hoc Technical Group reviewed available dust control 
regulations, literature, and technical documents, and developed a list 
of 65 conservation practices potentially suitable to agricultural 
sources in the Maricopa County nonattainment area for further 
consideration. BMP TSD, p. 16. These 65 measures represented a broad 
spectrum of potential BMPs, many of which related to conservation 
practices used in the western United States that had never been 
evaluated in the context of reducing PM-10.
    The Agricultural BMP Committee thoroughly reviewed the potential 
practices presented by the Ad-hoc Technical Group and evaluated the 
potential BMPs using available information on technological 
feasibility, costs, and energy and environmental impacts. After an 
analysis of the limited

[[Page 50269]]

information available and numerous public discussions, the Committee 
decided to include 34 of the 65 BMPs in the general permit rule and 
divided these 34 BMPs into the three categories of farm activities 
specified in A.R.S. 49-457.N.: 10 BMPs applicable to the tillage and 
harvest category; 10 BMPs applicable to the non-cropland category; and 
14 BMPs applicable to the cropland category. See BMP TSD, 17. In 
selecting these BMPs, the Committee deemed them to be feasible, 
effective and common sense practices for the Phoenix area which 
minimized potential negative impacts on local agriculture.
    Of the 31 potential BMPs eliminated, the majority were dropped 
because they either duplicated another BMP or did not reduce PM-10. 
Other reasons for elimination included the impracticability of a BMP 
for the Maricopa County Area, lack of cost effectiveness, or 
infeasibility of implementation. See June 13, 2001 BMP submittal, 
Enclosure 3, Attachment 8.
    At the time the BMP Committee was developing the general permit 
rule, there was very limited available information concerning the 
technological feasibility, costs, and energy and environmental impacts 
of these BMPs. Although the Committee determined that all the selected 
BMPs were technologically feasible control requirements, it found that 
calculating the other impacts on a commercial farmer was difficult. 
Because of the variety, complexity, and uniqueness of farming 
operations in Maricopa County, the Committee concluded that farmers 
need a variety of BMPs in each of the three categories of agricultural 
activities to choose from in order to tailor PM-10 controls to their 
individual circumstances. Further, the BMP Committee acknowledged that 
there is a limited amount of scientific information available 
concerning the emission reduction and cost effectiveness of some BMPs, 
especially in relation to Maricopa County. The BMP Committee balanced 
the limited scientific cost effectiveness information with the common 
sense recognition that the BMPs would reduce wind erosion and the 
entrainment of agricultural soils, thereby reducing PM-10. As a result, 
and given the myriad factors that affect farming operations, the BMP 
Committee concluded that requiring more than one BMP for each of the 
three agricultural categories could not be considered technically 
justified and could cause an unnecessary economic burden to farmers. 
Instead, the BMP Committee and ADEQ agreed to monitor the effectiveness 
of the BMPs and adjust the program, if needed, in the future. BMP TSD, 
p. 18.
    The general permit rule, as finally adopted by the BMP Committee in 
May 2000 as BACM and MSM, requires that commercial farmers implement at 
least one BMP for the tillage and harvest, cropland, and non-cropland 
categories by December 31, 2001.
    We define a BACM-level of control 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. Based on 
the BMP committee's findings regarding technological feasibility and 
economic effects of requiring more than one BMP per category, we 
believe that the BMP rule provides the maximum degree of emission 
reductions achievable from the agriculture source category in the 
Phoenix area and, therefore, meets the BACM requirement in section 
189(b)(1)(B).\37\
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    \37\ We also considered a BACM-level control as going beyond 
existing RACM-level controls, such as expanding use of RACM (e.g., 
paving more miles of unpaved roads). Addendum at 42013. As noted 
previously, we have proposed to approve the general permit rule as 
meeting the RACM requirement in CAA section 189(a)(1)(C). 66 FR 
34598. In that proposal, we stated our belief ``that the general 
permit rule represents a comprehensive, sensible approach that 
meets, and in fact far exceeds, the RACM requirements of CAA section 
189(a)(1)(C) and EPA guidance interpreting those requirements.'' 66 
FR 34598, 34602. Moreover, we explained that the State also intended 
the general permit rule and its enabling legislation to meet the 
CAA's serious area requirements. 66 FR 34598, 34599. Thus today's 
proposal that the general permit rule meets the BACM and MSM 
requirements of the Act is consistent with our prior action.
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    A requirement that an individual source select one control method 
from a list, but allowing the source to select which is most 
appropriate for its situation, is a common and accepted practice for 
the control of dust. For example, in its PM-10 FIP for Phoenix, we 
promulgated a RACM rule applicable to, among other things, unpaved 
parking lots, unpaved roads and vacant lots. The rule allows owners and 
operators to choose one of several listed control methods (pave, apply 
chemical stabilizers or apply gravel). 40 CFR 52.128(d). In the case of 
the FIP, those subject to the fugitive dust rule were given a choice of 
control methods in order to accommodate their financial 
circumstances.\38\
    Allowing sources the discretion to choose from a range of specified 
options is particularly important for the agricultural sector because 
of the variable nature of farming. As a technical matter, neither we 
nor the State is in a position to dictate what precise control method 
is appropriate for a given farm activity at a given time in a given 
locale. The decision as to which control method from an array of 
methods is appropriate is best left to the individual farmer. Moreover, 
the economic circumstances of farmers vary considerably. As a result, 
it is imperative that flexibility be built into any PM-10 control 
measure for the agricultural source category whether that measure is 
required to meet the RACM or BACM requirements of the Act.
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    \38\ See, as examples, SCAQMD Rule 403 (providing for 
alternative compliance mechanisms for the control of fugitive dust 
from earthmoving, disturbed surface areas, unpaved roads etc.); and 
SCAQMD Rule 1186 (requiring owners/operators of certain unpaved 
roads the option to pave, chemically stabilize, or install signage, 
speed bumps or maintain roadways to inhibit speeds greater than 15 
mph). We proposed to approve these SCAQMD rules as meeting the RACM 
and/or BACM requirements of the CAA on August 11, 1998 (63 FR 42786) 
and took final action approving them on December 9, 1998 (63 FR 
67784). See also the approval of Maricopa County Environmental 
Services Department (MCESD) Rule 310 as meeting the RACM/BACM 
requirements (62 FR 41856, August 4, 1997) and the proposal to 
approve updated Rule 310 and MCESD Rule 310.01 as meeting the same 
requirements (65 FR 19964, April 13, 2000).
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    We believe that the work of the BMP Committee resulted in the 
timely adoption of the general permit and educational programs that 
requires BACM implementation on a schedule that will allow time for the 
agricultural community to understand and select appropriate BMPs and to 
transition to new practices, some of which may involve the purchase of 
new equipment. Based on these factors, we believe that the BMP 
implementation schedule is as expeditious as practicable and meets the 
BACM implementation deadline for the Phoenix area of June 10, 2000.
    The MAG plan identified two potentials MSM for agricultural sources 
(1) cessation of tilling on high winds days in South Coast's Rule 403.1 
and (2) soil erosion plans in South Coast's Rule 403. MAG plan, Table 
10-8. The plan concluded that neither is, by itself, MSM for the 
Phoenix area.
    South Coast's 403.1, ``Wind Entrainment of Fugitive Dust,'' applies 
only in the Coachella Valley (Palm Springs) portion of the South Coast 
Air Basin and requires that, when wind speeds exceed 25 miles per hour 
(mph), agricultural tilling and soil mulching activities should cease. 
While the measure applies throughout the year, the high wind days tend 
to occur during a high-wind season that extends between April and June. 
The Coachella Valley typically experiences high winds on 47 days of the 
year. MAG estimated that there were a total of 37 hours,

[[Page 50270]]

representing 11 days, with wind speeds greater than 15 mph in 1995 in 
Maricopa County.
    The BMP general permit rule includes ``limited activity during high 
wind event'' as one of ten BMPs that a grower can choose for the 
Tillage and Harvest category. According to an analysis in the MAG plan, 
postponing tilling on high wind days would reduce emissions by 72 
percent on high-wind days. MSM study, p. 4-23. However, because only 15 
percent of the Maricopa County PM-10 nonattainment area tilling occurs 
during the high wind season (March through September) and because less 
than 4 percent of the days during this period experience winds greater 
than 15 mph, the air quality benefits of the measure would be small 
(i.e, 0.08 metric tons per average annual day in 1995) for the annual 
standard. MSM study, p. 4-23. Emissions from tilling are a very small 
contributor to total agricultural emissions on the 1995 design day 
(which was a high-wind day), representing just 1.6 percent of all 
agricultural emissions and are not implicated in 24-hour exceedances. 
URS, Technical Support Document for Quantification of Agricultural Best 
Management Practices, June 8, 2001 (Ag Quantification TSD), p. 3-11 and 
Microscale plan, pp. 18-19. Moreover, based on the limited amount of 
information available regarding the control efficiencies for the ten 
BMPs in the Tillage and Harvest category, the control efficiency for 
``limited activity during high-wind event'' is on average as effective 
or less effective than the other BMPs in this category. Ag 
Quantification TSD, pp. 2-8 to 2-10.
    South Coast's Rule 403, ``Fugitive Dust,'' requires the 
implementation of conservation practices to reduce PM-10 from 
agricultural sources in the South Coast PM-10 nonattainment area. Under 
Rule 403(h), agricultural operations exceeding 10 acres within the 
South Coast Air Basin are exempt from the rule's requirements for 
fugitive dust if the farmer implements the conservation practices in 
the most recent Rule 403 Agricultural Handbook. See ``Rule 403 
Agricultural Handbook: Measures to Reduce Dust from Agricultural 
Operations in the South Coast Air Basin,'' South Coast AQMD, December 
1998 (the Handbook). Because the requirements of Rule 403 are more 
stringent than the requirements for conservation practices in the 
Handbook, it is assumed that farmers will always choose to comply with 
the latter's provisions. Thus the Handbook, rather than Rule 403 
itself, is effectively the potential MSM.
    For a variety of reasons, it is difficult to directly compare the 
requirements in the general permit with the requirements in the 
Handbook. First, the South Coast did not attempt to estimate the 
reductions and cost from each conservation practice. Second, the types 
of crops grown in Maricopa County and the South Coast area differ 
significantly. For example, cotton is a dominant crop in Maricopa 
County but is not grown in the South Coast Air Basin. Third, the 
Handbook allows a grower to substitute a local ordinance for the three 
conservation practices required for ``inactive'' agricultural land; 
however, the minimum requirements for the local ordinance are not 
specified. Handbook, section II, p.4. Fourth, the general permit rule 
and the Handbook also differ in terms of exemption and waivers. The 
general permit rule does not exempt any crop types or provide a waiver 
option, but the Handbook exempts orchards, vine crops, nurseries, range 
land, and irrigated pastures from requiring a practice for the active 
and inactive categories. Finally, the Handbook also allows farmers to 
request a waiver if the farmer cannot apply the required practices or a 
verifiable alternative.
    While the general permit rule divides agricultural activities into 
three categories and the Handbook divides them into six, and the 
terminology used is different, the categories of activities covered are 
essentially coterminous. Cf. Handbook, section I and ACC R18-2-610.7, 
.12, .22, .33. However, depending on the type of farming operation, the 
general permit rule would require implementation of at least one BMP 
for each of the Tillage and Harvest, Cropland, and Non-Cropland 
categories and the Handbook requires from one to three practices for 
its six agricultural categories.
    As discussed above, in the BACM section of this TSD, the BMP 
Committee concluded that, because of the variety, complexity, and 
uniqueness of farming operations and because agricultural sources vary 
by factors such as regional climate, soil type, growing season, crop 
type, water availability, and relation to urban centers, agricultural 
PM-10 strategies must be based on local factors. Therefore, the general 
permit rule, as finally adopted by the BMP Committee in May 2000, 
reflects the conclusion of the BMP Committee that farmers need a 
variety of BMPs to choose from in order to tailor PM-10 controls to 
their individual circumstances. Further, the BMP Committee acknowledged 
that there is a limited amount of scientific information available 
concerning the emission reduction and cost effectiveness of some BMPs, 
especially in relation to Maricopa County. The BMP Committee balanced 
these limitations with the common sense recognition that the BMPs would 
reduce wind erosion and the entrainment of agricultural soils, thereby 
reducing PM-10.
    While the Committee surveyed measures adopted in other geographic 
areas, these measures were of limited utility in determining what 
measures are available for the Maricopa County area. Given the limited 
scientific information available and the myriad factors that affect 
farming operations, the BMP Committee concluded that requiring more 
than one BMP could not be considered technically justified and could 
cause an unnecessary economic burden to farmers.
    Adding to concerns about the economic feasibility of requiring more 
BMPs per farming activity is the general uncertainty regarding the cost 
of the BMPs and continued viability of agriculture in Maricopa County. 
Between 1987 and 1997, the number of farms operating in Maricopa County 
declined by approximately 30 percent and the amount of land farmed 
declined by approximately 50 percent. This trend is expected to 
continue. Finally, in order to justify additional requirements for 
farming operations in the area beyond those in the general permit rule, 
the BMP Committee determined that a significant influx of money and 
additional research would be needed. BMP TSD, p. 18.
    Based on all of these factors, the BMP Committee concluded that the 
Handbook's practices were neither technologically nor economically 
feasible for agricultural sources in Maricopa County. BMP TSD, p. 18.
    We agree with the analysis of the BMP Committee. As noted 
previously, the development of the general permit rule was a multi-year 
endeavor involving an array of agricultural experts familiar with 
Maricopa County agriculture. Maricopa County is only the second area in 
the country where formal regulation of PM-10 emissions from the 
agricultural sector has ever been attempted. For the reasons discussed 
above, we propose to conclude that the BMP general permit rule meets or 
exceeds the stringency of South Coast Rule 403.1's requirement for 
cessation of tilling during high winds. Based on the forgoing analysis 
of the Handbook, we also propose to conclude that the Handbook's 
requirements are neither technologically nor economically feasible for 
Maricopa County. Because all the identified potential MSM have either 
not been demonstrated to be more

[[Page 50271]]

stringent than existing Maricopa County controls or found to be 
infeasible for the area, we propose to find that the MAG plan provides 
for the inclusion of MSM as required by CAA section 188(e) to our 
satisfaction.
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 a 
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 lists 11 
potential BACM and 10 potential MSM. MAG plan Tables 5-2 and 1-7. We 
believe these list are 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/m\3\). 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/m\3\. We proposed to approve the revised 
ordinance as part of the annual standard proposal. 65 FR 19964, 19990. 
In addition, A.R.S. section 9-500.16 and A.R.S. section 11-875 (1998) 
required 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. All measures were implemented 
by June 10, 2000, the BACM implementation deadline for the Phoenix 
area. We, therefore, propose to find that the MAG plan provides for the 
implementation BACM for residential wood combustion.
    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 
(NH\3\). Ninety percent of NOX comes from motor vehicle 
exhaust (both on and off road) and 99.9 percent of NH\3\ 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 this 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 in the Phoenix 
area and therefore are not technologically feasible. \39\ The estimated 
reduction in ammonia from 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.
---------------------------------------------------------------------------

    \39\ We consider a measure technologically feasible for an area 
only if it has the potential to reduce emissions in a 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. See MAG plan, Table 3-1.
    Arizona has adopted a number of measures for controlling 
NOX emissions from motor vehicles and nationally, we have 
established emission standards for control of NOX from both 
on- and nonroad engines. The MAG plan does not identify any 
technologically feasible measures for the control of ammonia. For these 
reasons, 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.
1. 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 enforceable 
commitments are found in Maricopa County, 1999 Revised Measure 6, 
adopted December 15, 1999. A narrative description of them 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 E.3.h. 
``Construction Sites and Activities.''

[[Page 50272]]

    These improvements to the compliance and enforcement programs 
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.
    We review these enforceable commitments and their current status 
below:
Staffing
    Maricopa County committed to increasing its inspection staff to 8 
inspectors, 1 supervisor, 1 aide and 2 enforcement officers by the end 
of January 2000 and to add a coordinator to the Small Business 
Environmental Assistance Program to assist smaller builders and 
construction companies and to help develop and implement education 
programs. It also committed to hire an attorney in the County 
Attorney's office to expedite civil litigation and to assist with 
prosecuting Class One Misdemeanor cases by April 2000. Total resources 
devoted to the fugitive dust program were to be increased to 15 
positions, a 25 percent increase over previous levels. After reaching 
the committed staffing level, MCESD was to review the program in March 
2000 to evaluate its effectiveness and the potential need to add more 
staff.
    By the end of January 2000, inspection unit staffing increased to 8 
inspectors, 1 supervisor, 1 coordinator (to oversee permit issuance and 
track notices of violations), 2 aides and 2 enforcement officer. By May 
2000, the County Attorney's office hired an attorney, paralegal, and 
support staff. In 2000, the Department found that the existing staff in 
the Small Business Environmental Assistance Program was able to handle 
the workload for assisting smaller builders and construction companies 
and for helping to develop and implement education programs. MCESD will 
re-evaluated the need for an additional coordinator in the small 
business assistance program when the second generation outreach and 
education materials are completed. In total, resources devoted to the 
fugitive dust program during the past year were 17 positions, a 42 
percent increase over previous levels.
Organization
    MCESD created a new enforcement section 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, MCESD committed to locate inspectors in two new 
regional offices to provide quicker response times to dust-related 
complaints and allow more time in the field. It has in fact located 
inspectors in four regional offices.
Funding
    For FY 1999-2000, revenue for fugitive dust program was projected 
to be $1.12 million from annual earth moving permit fees, a $772,000 
increase over the previous level. The increase was due to the 1998 fee 
increase for earth moving permits.
    For FY 2000-2001, anticipated revenue for the fugitive dust program 
is approximately $1.7 million, generated from annual earth moving 
permit fees. This is a $1.35 million increase over the previous level.
Inspection Program
    MCESD committed to 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 committed to initially direct 
its inspections to cities lacking such programs and to track the city 
plans that are required by State statute to stabilize target unpaved 
roads, alleys and unpaved shoulders.
    Prior to its adopting additional commitments in December 1999, 
MCESD had already 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.
    MCESD did develop by April, 2000 inspection priorities for vacant 
lots and unpaved parking lots considering lot size and number of 
sources with larger lots being inspected first and smaller lots in 
succeeding years. EPA and MCESD initially attempted, but were 
unsuccessful, to convert an Assessor's Office database of vacant lots 
into a user-friendly format for identifying priority lots. Now, MCESD 
inspectors are assigned geographical districts and are compiling notes 
on the vacant lots and unpaved parking lots in each district during 
their routine surveillance activities. Under current MCESD policy, the 
inspectors are first directed to handle all complaints and then to 
begin to address the larger sites on the individual district lists. In 
2000, the inspectors made 499 inspections on vacant lots, unpaved 
parking lots, and unpaved roads.
Enforcement Program
    To meet its commitment to revise its enforcement program, MCESD 
issued a revised air quality enforcement policy on April 28, 2000. See 
Air Quality Violation Reporting and Enforcement Policy and Procedure, 
MCESD, April 28, 2000. This policy:
     Includes guidelines for initiating various enforcement 
actions
     Includes guidelines for reinspecting
     Defines 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
     Identifies priority violations
     Includes guidelines for when to seek penalties reflecting 
the economic benefit of noncompliance, if feasible
     Includes guidelines for seeking and determining higher 
penalties for repeat violators
     Includes 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 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 enables the enforcement 
officers to work on

[[Page 50273]]

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.
    In 2000, MCESD revised its dust control guidelines with its 
partners ADOT and Arizona State University. This year ADOT secured a 
research grant directed towards developing educational tools and 
outreach programs. This product will enhance the current guidelines, 
add information on the life cycle costs of controls and controls' 
impact on the construction process, and develop additional outreach 
tools. In addition, MCESD is currently working with two contractors to 
develop a model environmental management system for construction. These 
two efforts will add to the technical knowledge on dust control and 
offer additional tools for companies to increase compliance with 
regulations.
Program Evaluation and Tracking
    MCESD committed to track the number of inspections, number and type 
of enforcement actions, amount of penalties assessed, and amount of 
penalties collected. It also committed to conduct mid-year reviews of 
the program in September, 2000 and again in March 2001 to evaluate 
progress and future needs.
    MCESD conducted its reviews and will conduct then again in 
September, 2001 and again in March 2002 to evaluate progress and future 
needs. In 2000, MCESD conducted 6625 inspections. In the first year of 
operation under the new enforcement process, it issued 189 violations, 
processed 145 settlement cases and netted $425,000 in fines (May 1, 
2000 to April 30, 2001).

G. Attainment Date Extension

    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 SIP revisions containing a demonstration of attainment by 
the most expeditious alternative date practicable.
    We evaluate the Maricopa County serious area plan's compliance with 
each of these requirements below.
1. Apply for an Extension
    A state must apply for an extension and concurrently submit a SIP 
revision containing a demonstration that the area will attain by the 
most expeditious alternative date practicable. The state must provided 
the public reasonable notice and a hearing on the application before it 
is sent to EPA.
    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. The documentation 
supporting this request is found 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, including the 
demonstration that the area will attain the 24-hour standard by the 
earliest alternative date practicable.
2. Demonstrate the Impracticability of Attainment by December 31, 2001
    CAA section 189(b)(1)(a)(ii) and our proposed policy on extension 
requests require that the serious area 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 in order to claim that attainment by that date is 
impracticable.
    To evaluate the impracticability of attainment by 2001, the MAG 
plan evaluated the impact of BACM on sources at both the West Chandler 
and Gilbert sites in 2001. The evaluation showed these BACM-level 
controls left 24-hour PM-10 levels well above the 24-hour standard at 
both sites in 2001, thus demonstrating attainment is impracticable by 
then. MAG plan, Appendix C, Exhibit 3, pp. 3-10 and 3-11.
    In this demonstration, the MAG plan assumes controls only on the 
``permitted'' sources, that is, only on those sources that receive 
permits from MCESD. The plan assumes that all ``nonpermitted'' 
sources--unpaved roads, vacant lots, and unpaved parking lots--are 
uncontrolled in 2001. MAG plan, Appendix C, Exhibit 3, pp. 3-10 and 3-
11. This latter assumption does not reflect the efforts by MCESD to 
assure the implementation of BACM on these sources and is inconsistent 
with the assumptions made for these sources in the annual standard 
impracticability demonstration.
    To check to see if using consistent assumptions between the annual 
standard and 24-hour standard demonstrations would show that attainment 
of the 24-hour standard is practicable by 2001, we recalculated the 
2001 impacts at each monitor using the control assumptions from the 
annual standard demonstrations and additional control information from 
the BMP TSD. In these recalculations, we assume that the sources at the 
microscale site are in full compliance with the applicable rule. See 
the ``Extension Request--Demonstrate the Impracticability of Attainment 
by December 31, 2001'' in the EPA TSD.
    Our recalculations show that attainment of the 24-hour standard at 
the West Chandler site remains impracticable by 2001. The principal 
sources at this site are an agricultural field, its apron, and a 
construction site. The site needs substantial reductions, in excess of 
50 percent, in agricultural emissions in addition to controls on the 
construction site before the 24-hour standard can be attained. This 
level of emission reduction from agricultural sources is not expected 
until 2006.
    However, our recalculations show that attainment of the 24-hour 
standard at the Gilbert site is practicable by 2001. The site's primary 
source, an unpaved parking lot, is subject to full control under Rule 
310.01 by 2001 and controls on this source together with controls on 
the other major source at Gilbert, a vacant lot (also required by Rule 
310.01) result in the site showing attainment by 2001.
    In order to show attainment, a plan must show attainment at each 
location

[[Page 50274]]

within the nonattainment area. Because the West Chandler site is still 
unable to show attainment of the 24-hour standard by 2001, the Phoenix 
nonattainment area as a whole is unable to show attainment by that 
date. Thus the MAG plan's conclusion that attainment of the 24-hour 
standard in the Phoenix area is impracticable by December 31, 2001 is 
correct. We, therefore, propose to find that attainment of the 24-hour 
standard is impracticable by December 31, 2001.
3. Complied With Commitments and Requirements in the SIP
    We interpret this criterion to mean that the state has implemented 
the emissions reducing measures in the plan revisions it has submitted 
to address the CAA requirements in sections 172 and 189 for PM-10 
nonattainment areas.
    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 
principal controls in this plan were Rule 310 and the County 
woodburning ordinances. The 1991 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 plan 
also contained a large number of commitments from the local 
jurisdictions to implement 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 earlier 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
    In our proposed policy for granting extension requests under CAA 
section 188(e), we suggest a 5-step process for identifying and 
adopting MSM. See section V.B.4. of this preamble. This process is 
similar to the one we have established for determining BACM, but with 
one additional step, to compare the potential MSM against measures 
already adopted in the area to determine if the existing measures are 
most stringent.
    The first two steps in our proposed MSM policy are to develop a 
detailed emissions inventory of PM-10 sources and source categories and 
to 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. The MAG plan, however, 
excludes no source categories of directly-emitted PM-10 from its MSM 
analysis and moves directly to the third step in the MSM determination, 
identifying potential MSM in other implementation plans or used in 
practice in other states for each source categories 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.
    The fourth step in our proposed policy for MSM is to compare the 
potential MSM for each significant source category against the 
measures, if any, already adopted for that source category in the local 
area. In the MAG plan, 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 lists of affected sources, fewer exemptions, and/or one 
or more substantive regulatory provisions not found in the Maricopa 
measure.
    The final step in our proposed policy for MSM is to provide for the 
adoption of any MSM that is more stringent than existing similar local 
measures and provide for implementation as expeditiously as practicable 
or, in lieu of providing for adoption, provide a reasoned justification 
for rejecting the potential MSM, i.e., why such measures cannot be 
feasibly implemented in the area. In the MAG plan, MSM that remained 
after the screening in step 4 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, MAG plan, p. 10-46, and 
BMP TSD, pp. 19 to 27.
    Based on our analysis of the MAG plan's provisions for identifying 
and adopting MSM, we propose to find that the MAG plan demonstrates 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 potential MSM for commercial feedlots/
livestock areas. However, the two rules control different emission 
activities 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 fewer than 80 dairies (most of which are actually 
outside the nonattainment area). 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 and are not necessary for expeditious attainment. We, therefore, 
propose to 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

[[Page 50275]]

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. Since then, 
the medical waste incinerators in this category have shut down and 
today there are even fewer emissions. Because incinerators are a 
trivial source and controls on them would not advance the attainment 
date and are not necessary for expeditious attainment, we propose to 
find that the MAG plan provides 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 be 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 AQMD is developing a new rule to deal 
with underfired charbroilers and MCESD will wait until South Coast 
completes its rulemaking, now scheduled for late 2001, to adopt this 
measure. 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 establish MSM for controls 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 CAA section 189(b)(1)(A)(ii). We also 
propose to find that the attainment demonstration relies on control 
measures that either are approved or have been proposed for approval 
and meet our SIP enforceability criteria; that the emissions estimates 
credited to 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.
    The following is a brief summary of our evaluation of the modeling 
in the MAG plan. Our full evaluation is in the EPA TSD section 
``Extension Request-Demonstrate Attainment by the Most Expeditious 
Alternative Date Practicable after December 31, 2001.''

a. Air Quality Modeling

    The attainment demonstration for the 24-hour standard is divided 
into two parts, a microscale analysis and a regional analysis. The 
microscale part evaluates 24-hour exceedances at four monitoring sites 
in the Phoenix area using a version of the industrial source complex 
(ISC) model. The regional part evaluates 24-hour levels throughout the 
rest of the Maricopa County nonattainment area using the Urban Airshed 
Model-Linear Chemistry version (UAM-LC).
    As discussed previously, Arizona has made three submittals that 
contain elements of the attainment demonstration for the 24-hour PM-10 
standard: the 1997 Microscale plan, the 2000 revised MAG plan, and the 
2001 BMP TSD. A more complete description of these submittals can be 
found in section 2 of this preamble and in section 1 of the EPA TSD. We 
briefly describe here how these submittals fit together to create the 
overall attainment demonstration for the 24-hour standard.
    The first of the three submittals, the 1997 Microscale plan, 
contains a microscale, or localized, inventory and modeling analysis 
using the ISCST model of 24-hour standard exceedances at four 
monitoring sites in the Phoenix area: Maryvale, Salt River, West 
Chandler and Gilbert. It shows attainment of the standard at the 
Maryvale and Salt River sites but does not demonstrate attainment for 
the Gilbert and West Chandler sites, both of which were substantially 
affected by agricultural sources.\40\
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    \40\ Because we have already approved the attainment 
demonstrations at the Maryvale and Salt River sites, we do not 
further discuss these sites in this proposal. See 62 FR 41856, 
41863.
---------------------------------------------------------------------------

    The second submittal, the 2000 revised MAG plan contains a regional 
modeling analysis of 24-hour standard exceedances using UAM-LC. It also 
uses the ISCST model to determine that a 58 percent reduction in 
agricultural emissions is needed to attain the 24-hour standard at the 
West Chandler site and 20 percent at the Gilbert site.\41\ However, at 
the time of its submittal, Arizona had not yet completed adoption of 
its BMP general permit rule and also had not yet quantified the 
expected reductions from rule and thus was unable to model the impact 
of the rule at these two sites.
---------------------------------------------------------------------------

    \41\ See p. 3-9 in ADEQ, ``Evaluation for Compliance with the 
24-hour PM-10 Standard for the West Chandler and Gilbert Microscale 
Sites,'' June 1999 (ADEQ TSD), found in Appendix C, Exhibit 3 of the 
MAG plan.
---------------------------------------------------------------------------

    The third submittal, the 2001 BMP TSD, documents the expected 
emission reductions from the BMP general permit rule. This submittal 
does not contain new modeling but rather shows that the rule's emission 
reductions, together with a reasonable estimate of land use change, 
provide greater reductions than needed for attainment at the Gilbert 
and West Chandler sites.
1. Modeling Approach to the 24-Hour PM-10 Standard Attainment 
Demonstration
    Our guidance on attainment demonstrations generally assumes that 
the entire nonattainment area will be modeled using a dispersion 
model.\42\ However, emissions inventory development and modeling for 
areas with substantial fugitive dust problems, such as the Phoenix 
area, have proved difficult, because of fugitive dust emissions' marked 
uncertainty and their temporal and spatial variability. Accurately 
estimating emissions for input to dispersion modeling of fugitive dust 
over a large area is much more difficult than for point sources of 
gaseous pollutants, which were the archetypes for development of much 
of our modeling guidance.
---------------------------------------------------------------------------

    \42\ A dispersion model models how emissions from sources are 
dispersed into the atmosphere based on local wind patterns and 
speeds and other meteorological parameters. The two principal inputs 
into a dispersion model are temporally- and spatially-distributed 
emissions and meteorological information.
---------------------------------------------------------------------------

    Thus, in areas dominated by fugitive dust sources, the approach of 
intensively inventorying and modeling a small area is a reasonable one. 
This approach is also more reflective of the nature of fugitive dust. 
Fugitive dust PM-10 is emitted near ground level and has relatively 
sharp spatial gradients as dust settles out with distance from the 
source, and hence has more localized effects than the other criteria 
pollutants, which are typically buoyant and gaseous.
    Under the microscale approach used in the MAG plan, the areas 
around the exceeding monitors are deemed to be representative of 
locations throughout the nonattainment area. Attainment is

[[Page 50276]]

demonstrated at locations representing the various mixes of emission 
sources that occur in the area. Although a specific emitting activity, 
such as new housing construction, will eventually decline in a given 
location, it will reappear elsewhere as the metropolitan area grows. A 
location that is currently experiencing a lot of construction can thus 
be used to represent locations where construction will occur in the 
future. Moreover, in the MAG plan all locations exceeding the 24-hour 
PM-10 standard in 1995 were subjected to analysis. A demonstration of 
attainment at these locations will show that the mixes of sources that 
caused exceedances in the Phoenix area will be controlled sufficiently 
to meet the standard.
    Although there is solid reasoning underpinning the microscale 
approach in a fugitive dust-dominated area such as Phoenix, there is 
concern that for a large urban area the sheer number of sources, 
especially fugitive dust area sources, could make for a pervasive 
regional component of PM-10 in addition to the more localized or 
microscale component. Additionally, a portion of PM-10 is fine 
particles, which can stay suspended longer and so can be transported 
greater distances than coarse particulate.
    Fine particulate includes secondary particulate, which forms 
chemically in the air from precursors like ammonia and oxides of sulfur 
and nitrogen. Secondary particulate is formed by chemical reactions in 
a mixture of emissions from various sources, spread over hours and a 
spatial scale of 10's of kilometers. Like ozone, it is a regional 
pollutant, and so needs to be modeled on a larger scale. Although only 
a small fraction (4 percent) of the total PM in the Maricopa area, 
secondary particulate is present. While this regional component could 
partly be addressed by adding a background concentration to microscale 
modeling, the determination of a background is ambiguous since it 
includes the effect of sources similar to those in the microscale 
domain. For these reasons, the MAG plan include regional modeling in 
addition to the microscale analysis.
2. EPA's Review of the Air Quality Modeling in the MAG Plan
    In today's proposal, we focus our discussion on the supplemental 
microscale modeling for the Gilbert and West Chandler sites in the ADEQ 
TSD and the evaluation of the agricultural general permit rule in the 
BMP TSD. We have already extensively reviewed both the microscale 
modeling and the regional modeling in previous proposals and found them 
acceptable. See our proposal on the Microscale plan at 62 FR 31025, 
31029 and the proposal on the annual standard at 65 FR 19964, 
19985.\43\ See also the EPA TSD section on ``Extension Request-
Demonstrate Attainment by the Most Expeditious Alternative Date 
Practicable after December 31, 2001.''
---------------------------------------------------------------------------

    \43\ For the regional model, 65 individual days were analyzed in 
the base year and attainment year, that is, MAG ran the UAM-LC model 
for each of these 65 24-day days. To evalute the 24-hour standard, 
the individual results from each one of these modeling runs are 
used. To evaluate the annual standard, the results from all the 
modeling runs for each year are averaged together. Thus, in 
reviewing the modeling for the annual standard demonstrations, we 
necessarily also reviewed the modeling for the regional 24-hour 
standard demonstrations.
---------------------------------------------------------------------------

    The approach used for the supplemental modeling in the ADEQ TSD is 
essentially the same approach used in the Microscale plan. They differ 
in just three ways. First, the ADEQ TSD uses a new calculation of 
background concentrations (that is, the impact on ambient PM-10 levels 
in the microscale area of sources outside the microscale area). Second, 
it evaluates PM-10 concentrations at multiple locations within the 
microscale domain. Finally, it evaluated various levels of reductions 
from agricultural controls, in order to determine the emission 
reductions needed for attainment.
    New background values were calculated in order to reflect the 
regional implementation of controls. These controls reduce the 
contribution to ambient PM-10 levels in the microscale area of sources 
outside the microscale area. To recalculate the background values, ADEQ 
split the background between windblown and non-windblown contributions, 
applying controls only to the windblown contribution. See ADEQ TSD, p. 
3-7.
    The evaluation of PM-10 concentrations at multiple locations within 
the microscale area is an improvement to the previous microscale 
modeling. In the Microscale plan, the evaluation was limited to the 
actual location of the ambient air quality monitor within the 
microscale domain.
    The evaluation of the emissions reductions needed for attainment in 
2006 at the West Chandler site (assuming a 90 percent level of control 
on the construction site) showed that a 58 percent reduction in 
emissions from agricultural aprons and fields was needed. For the 
Gilbert site, a 20 percent emission reduction is shown to be needed 
from the agricultural apron. ADEQ TSD, pp. 3-9.
    The BMP TSD shows that BMP general permit rule, together with a 
reasonable estimate of land use changes, provide a 60.3 percent 
reduction by 2006. This reduction is sufficient to demonstrate 
attainment by 2006 at West Chandler. For the Gilbert site, the rule 
provides more than the 20 percent needed for attainment by 2006. BMP 
TSD, p. 9.
    This 60.3 percent reduction at the West Chandler site is a 
combination of a 36.6 percent emissions reduction from the BMP general 
permit and a 37 percent emissions from the conversion of agricultural 
land to residential and commercial use.\44\ This land use conversion 
rate is derived from a land use model for the overall nonattainment 
area and represents the reduction regionally in agricultural lands 
between 1995 and 2006. BMP TSD p. 28.
---------------------------------------------------------------------------

    \44\ The reductions are not additive because the BMP general 
permit rule reduces emissions only from the land left in 
agricultural production. The overall control effectiveness is 
calculated as the percent lost agricultural lands + BMP rule 
effectiveness * percent remaining agricultural lands or 37% + 
0.366*63%.
---------------------------------------------------------------------------

    Under the microscale approach, the areas around the exceeding 
monitors are deemed to be representative of locations throughout the 
nonattainment area. Thus, applying regionally the controls needed for 
attainment at these representative sites is assumed to assure 
attainment at similar sites throughout the nonattainment area. One 
aspect of this approach, which was not adequately explored in earlier 
submittals, is to how to treat the inevitable changes in land uses and 
activities within the microscale domains. For example, construction 
activity, like that at the West Chandler site, will eventually be 
completed and no longer contribute to emissions in the area.\45\
---------------------------------------------------------------------------

    \45\ In fact, at the West Chandler site, the construction is 
complete and agricultural land has been converted to residential and 
commercial uses.
---------------------------------------------------------------------------

    A land use and socioeconomic model, in conjunction with a 
dispersion model, could legitimately show that exceedances no longer 
occur in the area simply based on this change in land use. However, 
just waiting for land use changes alone to reduce emissions is not an 
acceptable method of demonstrating attainment at the individual 
microscale sites because once again, the premise underlying the 
microscale approach is that each site is representative of other 
similar areas in the nonattainment area. In a growing metropolitan area 
like that of Phoenix, there will always be areas with on-going 
construction.
    On the other hand, the opposite extreme of assuming no conversion 
of agricultural lands at all does not seem reasonable either. The 
reality is that the

[[Page 50277]]

metropolitan area is growing and agricultural land is rapidly being 
converted. Such changes have been observed over the past decades and 
are projected to continue.
    In this situation, using an estimate from the area's land use model 
of the conversion of agricultural lands to occur by 2006 is a 
reasonable approach to use. This approach is a compromise between the 
extremes of the no-conversion and the total-conversion assumptions. It 
is driven by the area's socioeconomic projections that are used for 
many purposes and represent the best available information about the 
land use changes the overall area will experience.
    Also, using an area average figure is consistent with the area wide 
application of control measures required under the submittal's 
approach. Reliably predicting the conversion for a particular small 
area (several square miles in the microscale approach) would be 
problematic in any case, since it would depend on knowing individuals' 
purchase decisions and development plans. Aggregate conversion figures, 
driven by larger economic forces and representing the average of many 
actions, should be more reliable.
    Assuming some land use change is more in line with the traditional 
use of microinventories in EPA's PM-10 attainment demonstration 
guidance, and also is in line with how attainment demonstrations are 
performed in general. Typically the projections for land use, 
employment, industrial production, population, vehicle traffic, etc. 
are part of the baseline conditions assumed in projecting future air 
quality; in an attainment demonstration they are independent of, but 
used in conjunction with, estimates of control measure effectiveness. 
In other words, reductions that occur naturally because of 
socioeconomic changes are implicitly counted in attainment 
demonstrations. Conversely, growth in emission sources, e.g., vehicle 
traffic, are also implicitly counted and must be compensated for by 
additional emission reductions.
    In summary, we believe that the approach used in 2001 BMP TSD, 
while not completely consistent with how the microscale approach was 
implemented in the 1997 Microscale plan, nevertheless, is a reasonable 
balance between different possible implementations of a microscale 
approach. Overall, we propose to find that technical evaluation in the 
MAG plan is adequate to support the attainment demonstration for the 
24-hour standard at the West Chandler and Gilbert sites.

b. Control Measures Relied on for Attainment

    For demonstrating attainment of the 24-hour PM-10 standard, the MAG 
plan relies on reductions in directly-emitted PM-10 from 3 measures: 
MCESD's Rules 310 and 310.01 and the agricultural BMP general permit 
rule. ADEQ TSD, pp. 3-3 to 3-6 and BMP TSD, p. 8. We have proposed to 
approve all of these measures. See 65 FR 19992, 19989 and 66 FR 34598.
    As part of these proposed approvals, 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. For MCESD's rules, see sections on 
proposed approval of Rule 310 and 310.01 in the TSD supporting the 
annual standard proposal. For the agricultural general permit rule, see 
66 FR 34598.
    We have also evaluated the emissions reductions credited to each 
measure in the attainment demonstrations to ensure they are reasonable. 
In performing the microscale analysis, ADEQ first determined that each 
significant, non-agricultural source at the microscale sites (e.g., the 
unpaved parking lot at the Gilbert site) was large enough to be subject 
to Rules 310 or 310.01.\46\ For each of these sources, ADEQ then 
applied the control factor used in the Microscale plan for that source. 
Except for the agricultural sources, it did not use rule effectiveness 
factors for either the sources in the microscale component or the 
sources in the windblown background component in the attainment 
demonstrations.
---------------------------------------------------------------------------

    \46\ Rule 310 and Rule 310.01 do not apply to sources under a 
certain size. For example, Rule 310.01 does not apply to vacant lots 
under 0.1 acres. Rule 310.01, section 301.
---------------------------------------------------------------------------

    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. Because RE factors are intended to reflect the variations in 
compliance among large numbers of sources, they are applied to source 
categories rather than to individual sources.
    We agree that it is appropriate not to apply an RE factor to the 
individual sources at each microscale site; \47\ however, we believe 
that an RE factor should be applied to the windblown background source 
categories because each category represents multiple sources. To 
determine the effect of applying the RE factor to sources in the 
windblown background, we re-evaluated the attainment demonstrations at 
both Gilbert and West Chandler. We found that the plan still 
demonstrates attainment of the 24-hour standard as expeditiously as 
practicable. See EPA TSD section ``Extension Request-Demonstrate 
Attainment by the Most Expeditious Alternative Date Practicable after 
December 31, 2001,''
---------------------------------------------------------------------------

    \47\ At each microscale site, there is only a single source in 
each category, that is there is a single vacant lot, a single 
construction site, a single agricultural field with its apron, a 
single unpaved parking lot.
---------------------------------------------------------------------------

    We find that the emission reduction estimates for each source 
category are consistent with research on the applicable control methods 
and are appropriately applied in the attainment demonstrations. For 
more information on the quantification of emission reductions from 
Rules 310 and 310.01 see the section ``Extension Request-Demonstrate 
Attainment by the Most Expeditious Alternative Date Practicable after 
December 31, 2001'' in the EPA TSD for the annual standard proposal. 
For more information on the quantification of emission reductions from 
the agricultural general permit rule, see the section ``Implementation 
of BACM and Inclusion of MSM for Agricultural Sources'' in the EPA TSD 
for this proposal.
    We have also determined that the measures relied on for attainment 
are being expeditiously implemented. Rule 310 and 310.01 are effective 
now. Implementation of the agricultural general permit rule began in 
July 2000 and will be completed by December 31, 2001.
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. Nothing in this additional information 
presented on the five factors suggests that granting an extension of 
the attainment date for the Phoenix area to 2006 is inappropriate.

a. Nature and Extent of Nonattainment

    In the Phoenix area, elevated 24-hour levels of PM-10 occur mainly 
in areas with large fugitive dust sources or with a concentration of 
fugitive dust sources.

[[Page 50278]]

    Areas such as this can be found throughout the Phoenix 
nonattainment area, so we would expect that there are elevated 24-hour 
PM-10 levels throughout the Phoenix area. In order to attain the 24-
hour standard in this situation, controls need to be uniformly 
implemented throughout the area, a task that generally requires longer 
to achieve than implementing controls in a 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 to 
inform them of our FIP fugitive dust rule; 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. 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 nonroad 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 nonroad 
engines) target emissions from on and nonroad 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 24-hour PM-10 standard and not from 
on- and nonroad 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 emissions inventory in the 
Maricopa nonattainment area and are the most significant contributors 
to 24-hour PM-10 exceedances. 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 and other capital improvements needed 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 attainment date for the 24-hour PM-10 
standard in the Phoenix PM-10 serious nonattainment area from December 
31, 2001 to December 31, 2006.

H. Reasonable Further Progress and Quantitative Milestones

    CAA section 172(c)(2) requires nonattainment plans to provide for 
reasonable further progress (RFP). Section 171(1) of the Act defines 
RFP as ``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.''
    CAA section 189(c) also requires PM-10 plans demonstrating 
attainment to contain quantitative milestones which are to be achieved 
every 3 years until the area is redesignated attainment and which 
demonstrate RFP. These quantitative milestones should consist of 
elements that allow progress to be quantified or measured. Addendum at 
42016.

1. Reasonable Further Progress

    The MAG plan provides for annual progress toward attaining the 24-
hour standard. This demonstration shows that most of the projected 
reductions occur after 2001; however, this is an artifact of the 
assumption that there are no controls on agricultural sources, vacant 
lots and unpaved parking prior to December 31, 2001. This assumption 
does not reflect the efforts by MCESD to assure the implementation of 
BACM on these sources and the requirement for BMPs to be implemented by 
then. If the RFP demonstration is revised to include emission 
reductions from BACM on these sources, then the majority of the 
emission reductions occur before 2001. See the ``Reasonable Further 
Progress and Quantitative Milestones'' section in the EPA TSD.
    In order to demonstrate RFP, the plan first regionalizes the 
inventories at the two microscale sites by multiplying emissions from 
each source by a factor of 360, which is the ratio of the size of the 
nonattainment area (2,880 square miles) to the size of the microscale 
sites (8 square miles). It then calculates the emission reductions from 
the application of the adopted measures to these sources. Next, it 
annualizes these emission reductions by multiplying the sources--which 
are all windblown sources--by 11, the number of windy days in 1995. 
Finally, the annualized figure is divided by 365 days to get an average 
annual day emission reductions. See BMP TSD, pp. 29--31.\48\
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    \48\ There was an error in the original RFP calculation on pages 
29 to 31 in the BMP TSD. ADEQ corrected this error and provided us a 
revised RFP and contingency measure demonstrations and quantitative 
milestones in a letter. See letter, Jacqueline E. Schafer, ADEQ, to 
Laura Yoshii, EPA, ``Addendum to June 13, 2001, Submittal of State 
Implementation Plan revision for the Agricultural Best Management 
Practices program in the Maricopa County PM-10 Nonattainment Area,'' 
September 7, 2001 (``ADEQ RFP Addendum Letter'')
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    Regionalizing and annualizing the microscale inventories is a good 
approach to demonstrating RFP and establishing milestones for the 24-
hour standard in the Phoenix area. Just a few source categories are 
explicitly identified contributors to exceedances of this standard, and 
it is effective controls on these categories that are necessary for 
progress and attainment. Therefore, closely tracking the effect of

[[Page 50279]]

those controls on these source categories is essential. Regionalizing 
and annualizing the microscale inventories allows this to be done.
    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 given the evidence that progress is being made over time and 
the implementation of controls are not being delayed. 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 [24-hour PM-10] national ambient air quality standard by the 
applicable date'' as required by section 172(c)(2) of the Act.

2. Quantitative Milestones

    Quantitative milestones based on regionalized and annualized 
microscale inventories are provided for 2001, 2003, and 2006. See RFP 
Addendum Letter, Enclosure 2. These are the same milestone years used 
for the annual standard. See 65 FR 19964, 19988. The assumptions 
regarding control measures' implementation and effectiveness that 
underlie the quantitative milestones are reasonable and consistent with 
the RFP demonstration.
    The plan does not provide milestones for each of the two microscale 
sites. Milestones are intended as checks along the way, a means of 
judging actual emission reductions and control measure implementation 
against those projected in the plan. Arguably, given the microscale 
analysis that is the basis for the Phoenix area's 24-hour standard 
plan, quantitative milestones should be established for both the West 
Chandler and Gilbert sites. However, this approach would actually 
defeat the purpose of the quantitative milestones rather than fulfill 
it.
    In order to report on a quantitative milestone at the microscale 
sites, Arizona would need to evaluate the implementation of controls at 
each site. However, land uses and activities around each of these 
microscale sites have changed significantly since 1995. For example, at 
the West Chandler site, the road construction has been completed and 
the agricultural field and its apron have been converted into stores. 
Thus, reporting on each site's quantitative milestones would tell us 
more about the land use changes around each site than about the 
implementation of controls. Because of this, the quantitative 
milestones for the 24-hour plan need to reflect regional implementation 
of controls. The MAG plan's approach of regionalizing and annualizing 
the emissions inventories from the microscale sites and then basing its 
RFP demonstration and milestones on the resulting inventory is an 
appropriate way to deal with these requirements for the 24-hour 
standard.
    For these reasons, we propose to find that the MAG plan meets the 
quantitative milestone requirement in CAA section 189(c)(1) for the 24-
hour standard.

I. Contingency Measures

    Section 172(c)(9) of the Clean Air Act requires that implementation 
plans provide for the implementation of specific measures to be 
undertaken if the area fails to make RFP or attain by its attainment 
deadline. These contingency measures are to take effect without further 
action by the State or the Administrator. The Act does not specify how 
many contingency measures are necessary nor does it specify the level 
of emission reductions they must produce.
    We interpret the ``take effect without further action by the State 
or the Administrator'' to mean that no further rulemaking actions by 
the State or EPA would be needed to implement the contingency measures. 
Addendum at 42015.
    The purpose of contingency measures is to ensure that additional 
emission reductions beyond those relied on in the attainment and RFP 
demonstrations are available if there is a failure to make RFP or 
attain by the applicable attainment date. These additional emission 
reductions will assure continued progress towards attainment while the 
SIP is being revised to fully correct the failure. To ensure this 
continued progress, we recommend that contingency measures provide 
emission reductions equivalent of one year's average increment of RFP. 
Addendum at 42016.
    Certain core control measure requirements such as RACM, BACM, and 
MSM may result in a state adopting and expeditiously implementing more 
measures than are strictly necessary for expeditious attainment and/or 
RFP. Because of this and because these core requirements effectively 
require the implementation of all non-trivial measures that are 
technologically and economically feasible for the area, states are left 
with few, if any, substantive unimplemented control measures. In fact, 
under the Act's PM-10 planning provisions, if there were a measure or 
set of measures that were technologically and economically feasible and 
could collectively generate substantial emission reductions, e.g., one 
year's worth of RFP, then a state would be hard pressed to justify 
withholding their implementation.\49\
---------------------------------------------------------------------------

    \49\ We do not believe that States are obligated by section 
172(c)(9) to adopt infeasible or unreasonable measures or measures 
that individual or collectively have trivial benefit.
---------------------------------------------------------------------------

    If we read the CAA to demand that the only acceptable contingency 
measure are those that are adopted but not implemented, then states 
face a difficult choice: adopt the controls for immediate 
implementation and clearly meet the core control measure requirements 
but fail the contingency measure requirement or adopt the control 
measures but hold implementation in reserve to meet the contingency 
measure requirement but potentially fail the core control measure 
requirements.
    However, states do not need to face this difficult choice if we 
read the CAA to allow adopted and implemented measures to serve as 
contingency measures, provided that those measures' emission reductions 
are not needed to demonstrate expeditious attainment and/or RFP. There 
is nothing in the language of section 172(c)(9) that prohibits this 
interpretation. This approach to the contingency measure requirement 
also has the benefit of allowing states to build uncredited cushions 
into their attainment and RFP demonstrations, which makes actual 
failures to make progress or attain less likely, while still obtaining 
the air quality and public health benefits from the implemented 
measures.
    We have allowed this approach, which is effectively the early 
implementation of contingency measures, in ozone and carbon monoxide 
plans. See memorandum, G. T. Helms, Chief, Ozone/Carbon Monoxide 
Programs Brand, OAQPS to Air Branch Chiefs, Regions I-X, ``Early 
Implementation of Contingency Measures for Ozone and Carbon Monoxide 
(CO) Nonattainment Areas,'' August 13, 1993. In this memorandum, we 
note that several states wished to implement their contingency measures 
early even though they were not needed for their attainment or RFP 
demonstrations and that ``[i]t seems illogical to penalize 
nonattainment areas that are taking extra steps to ensure attainment of 
the NAAQS by having them adopt additional [replacement] contingency 
measures now.'' This rationale applies with equal force to PM-10 plans.

[[Page 50280]]

Annual Standard
    The revised MAG plan as submitted in February 2000 identifies 5 
measures as contingency measures with a collective emission reduction 
of 5.5 mtpd: the agricultural BMP general permit rule, off-road engine 
standards, the clean burning fireplace ordinance, and additional dust 
controls from the cities of Tempe and Phoenix. MAG plan, p. 8-19.
    Since the MAG plan was submitted, Arizona has made changes to its 
contingency measure package for the annual standard. First, Arizona has 
withdrawn its commitment to adopt California's off road vehicle 
standards because the federal nonroad program produces essentially the 
same emission reductions. ADEQ Off-Road Letter. Second, the emission 
reductions from the agriculture contingency measure have been 
recalculated based on the BMP general permit rule as adopted. The 
emission reductions from the revised contingency measures package are 
now 6.9 mtpd. See EPA TSD ``Contingency Measures'' for more details on 
the emission calculations.
    All the measures that have been identified in the MAG plan as 
contingency measures have been adopted and are being implemented but 
are not credited in the attainment, RFP or milestone demonstrations for 
the annual standard and are not necessary to demonstrate expeditious 
attainment of that standard. Under our applicable policies, states are 
allowed to use implemented but uncredited measures as contingency 
measures.
    Under our contingency measure policy, we recommend contingency 
measures have total emission reductions equal to or more than the 
annual RFP increment. For the Phoenix area, the average annual 
increment in RFP for the annual standard is 5.5 mtpd/year for the full 
11-year period, 1995 to 2006. See EPA TSD, ``Reasonable Further 
Progress and Quantitative Milestones.'' Collectively, the specified 
contingency measures generate 6.9 mtpd.
    Based on this analysis, we propose to find that the MAG plan 
provides for the implementation of contingency measures for the annual 
standard as required by CAA section 172(c)(9).
24-Hour Standard
    The identified contingency measure for the 24-hour standard is 
controls for unpaved roads and alleys. BMP TSD, p. 30. This measure 
comprises not only the unpaved road provisions in MCESD Rule 310.01 but 
also the commitments by local jurisdictions to control unpaved roads. 
See MAG plan, pp. 7-75 to 7-94. This measure is estimated to reduce 
emissions by 12.19 mtpd in 2006. MAG plan, p. 8-9. The average annual 
increment in RFP for the 24-hour standard is 10.9 mtpd/year. See ADEQ 
RFP Addendum Letter, Enclosure 1.
    The unpaved road measure that is identified in the MAG plan as 
contingency measure for the 24-hour standard has been adopted and is 
being implemented but is not credited in the attainment, RFP or 
milestone demonstrations for the 24-hour standard and is not necessary 
to demonstrate expeditious attainment of that standard. Under our 
applicable policies, states are allowed to use implemented but 
uncredited measures as contingency measures.
    Based on this analysis, we propose to find that the MAG plan 
provides for the implementation of contingency measures for the 24-hour 
standard as required by CAA section 172(c)(9).

J. 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 (51.230-51.232) 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 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 of the MAG 
plan.
    Other than revisions to Maricopa County's revised commitments to 
improve Rule 310, we are not proposing to approve any control measures 
in this proposal. All commitments and rules relied on in the MAG plan 
to meet the CAA requirements for the 24-hour PM-10 standard are already 
approved, were proposed for approval in the annual standard proposal, 
or proposed for approval in a subsequent notice. In these notices, we 
have already proposed to find that the implementing agencies for the 
MAG plan have adequate resources for implementing their respective 
commitments and provided an opportunity for comment. We are not 
reproposing these findings.
    Finally, we initially proposed to find in the annual standard 
proposal that all agencies and jurisdictions have adequate authority 
under Arizona state law to implement their respective commitments and, 
where applicable, to obtain information necessary to determine 
compliance. 65 FR 19964, 19989. While minor changes have been made to 
several control measures (e.g., the remote sensing program), the State 
continues to have adequate authority to implement the measures. No 
other changes have been made to any agencies and/or jurisdictions 
authority since we proposed the annual standard.
    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 and the BMP General Permit. Procedures for monitoring 
compliance (i.e., the inspection strategy) with these rules are 
described in Maricopa County's commitments and the BMP TSD. See 
Maricopa County commitment, 1999 Revised Measure 6 and BMP TSD, pp 33-
34.
    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).

[[Page 50281]]

V. CAA Requirements for BACM and Attainment Date Extension and 
EPA's Guidance on Meeting These Requirements

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 was June 10, 2000.
    The Act does not define what level of control constitutes a BACM-
level of control. In guidance, we have defined it 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. This level of control is dependent on the deadline by which BACM 
must be implemented.\50\
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    \50\ We have long held that an otherwise available measure is 
reasonable and thus not an available measure if it cannot be 
implemented on a schedule that will advance the attainment date. 
See, for example, 57 FR 13498, 13560 (April 16, 1992). See, also 
Delaney v. EPA 898 F.2d 695 (9th Cir. 1990) which required the 
adoption of ``all available control measures'' to attain ``as soon 
as possible'' and not simply all available control measures. The 
most clear example of this is a measure that cannot be implemented 
until after the applicable attainment date.
---------------------------------------------------------------------------

    We also considered a BACM-level control as going beyond existing 
RACM-level controls, such as expanding use of RACM (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.
    BACM is a best available control measure. A control measure is a 
combination of a statement of applicability and the control 
requirement, that is, what sources in the category are subject to the 
measure and what the measure require the sources to do to reduce 
emissions.\51\ Both these elements must be specified before the 
measure's level of control (i.e., its stringency) can be determined, 
thus in setting out a BACM, a state must specify both the measure's 
control requirement and its applicability. The control requirement 
alone is not sufficient.
---------------------------------------------------------------------------

    \51\ An example: a measure requires all unpaved roads with ADT 
over 150 be stabilized by either paving, graveling, or treating with 
chemical stabilizers. The control requirement here is ``Stabilize 
using one of these three methods: paving, graveling, or chemical 
stabilization'' and the applicability is ``all unpaved roads with 
ADT over 150.''
---------------------------------------------------------------------------

    BACM must be applied to 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 5 g/m\3\ or more of PM-10 to a location of 24-hour 
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.\52\
---------------------------------------------------------------------------

    \52\ This principle is best illustrated by an example: In Area 
A, attainment of the 24-hour standard by December 31, 2001 requires 
that PM-10 ambient levels at exceeding locations be reduced by 40 
g/m\3\ to 150 g/m\3\. After application of BACM to 
all source categories above the proposed de minimis level, PM-10 
levels are reduced by 32 g/m\3\. BACM on the proposed de 
minimis source categories would reduce levels by a further 3 
g/m\3\, but still leaves ambient levels 5 g/m\3\ 
short of the reduction needed to show attainment. Since application 
of BACM to the proposed de minimis source categories still leaves 
ambient levels above the attainment level of 150 g/m\3\, 
the proposed de minimis level is appropriate.
---------------------------------------------------------------------------

    The recent decision by the Ninth Circuit Court of Appeals in Ober 
v. Whitman 243 F.3d 1190 (9th Cir. 2001) (Ober II) supports the use of 
a de minimis exemption in BACM analyses. Ober II was a challenge to our 
1998 PM-10 moderate area FIP for the Phoenix area in which we exempted 
from the RACM requirement, source categories with de minimis impacts on 
PM-10 levels. In the FIP, we established a de minimis threshold of 1 
g/m\3\ for the annual standard and 5 g/m\3\ for the 
24-hour standard, borrowing these thresholds from our new source review 
program for attainment areas to as a starting point in the de minimis 
analysis. In evaluating the appropriateness of these thresholds, we 
showed that they did not eliminate controls that would make the 
difference between attainment and nonattainment by the applicable 
attainment deadline, and therefore were the appropriate thresholds. See 
63 FR 41326, 41330 (August 3, 1998).
    In its ruling, the court held that we have the power to make de 
minimis exemptions to control requirements under the Clean Air Act and 
that our use of the de minimis levels from the NSR program was 
appropriate. Ober II at 1195 and 1197. In addition, the court 
determined that it was appropriate for us to use, as a criterion for 
identifying de minimis sources, whether controls on the sources would 
result in attainment by the attainment deadline. Ober II at 1198. Ober 
II dealt with a de minimis exemption from the RACM requirement, but its 
reasoning applies equally to the BACM requirement.
    We have outlined in our guidance a multi-step process for 
identifying BACM. Addendum at 42010-42014. The steps are:
    1. develop a detailed emissions 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 when it bears on the BACM determination, and
    4. provide for the implementation of the BACM or provide a reasoned 
justification for rejecting any potential BACM.

B. 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.
    6. the technological and economic feasibility of various control 
measures.
    We may grant only one extension for an area and that extension 
cannot be for

[[Page 50282]]

more than 5 years after 2001; that is, the extended attainment date can 
be no later than December 31, 2006. CAA section 188(e).
    We first presented our preliminary interpretation of the attainment 
date extension provision in our proposed approval of the annual 
standard provisions in the MAG plan. See 66 FR 19992, 19967. Based on 
comments we received on it during that proposal's comment period, we 
have clarified certain aspects of the policy but have made no 
substantive changes to it. We will provide our full response to 
comments received on the annual standard proposal when we take final 
action.
    This interpretation is our preliminary view of the section 188(e) 
requirements and we again request comment on it. We emphasize that 
these are our preliminary views and they are subject to modification as 
we gain more experience reviewing extension requests from other areas.
    In the following sections we discuss the five requirements a State 
must meet before we can consider granting an attainment date extension.
    1. Apply for an Attainment Date Extension
    Under CAA section 188(e), a State must apply for an extension of 
the attainment deadline. The request should be accompanied by the SIP 
submittal containing the most expeditious alternative attainment date 
demonstration required by CAA section 189(b)(1)(A)(ii). The state must 
be provided the public with reasonable notice and a hearing on the 
request before it is sent to EPA.
    Extension requests are not SIP submittals per se \53\ 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 SIP, 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.
---------------------------------------------------------------------------

    \53\ This is clear from the wording of section 188(e) which 
makes a distinction between the application for an extension and the 
SIP revision that must accompany it: ``at the time of the such 
application, the State must submit a revision to the implementation 
plan that includes a demonstration of attainment by the most 
expeditious alternative date practicable.'' This attainment 
demonstration is the one required by section 189(b)(1)(A)(ii).
---------------------------------------------------------------------------

    2. Demonstrate That Attainment by 2001 is Impracticable
    In order to demonstrate impracticability, the plan must show that 
the implementation of BACM on significant (that is, non-de minimis) 
source categories will not bring the area into attainment by December 
31, 2001. In serious areas, BACM is required to be in place in advance 
of the 2001 attainment date; therefore, we believe that it is 
reasonable to interpret the Act to require that a state provide at 
least for the implementation of BACM on significant source categories 
before it can claim impracticability of attainment by 2001.\54\ 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 
claim impracticability of attainment by 1994, the moderate area 
attainment date. See 57 FR 13498, 13544 (April 16, 1992). The Ober II 
court found this approach reasonable. Ober II at 1198.
---------------------------------------------------------------------------

    \54\ As described in the section on the BACM requirement, if 
applying BACM-level controls to one or more of the proposed de 
minimis source categories would result in attainment by December 31, 
2001, then those categories are not de minimis (i.e., they are 
significant) and must have BACM applied to them. Therefore, states 
cannot use the de minimis exemption to BACM to avoid applying 
controls that would result in attainment by 2001.
---------------------------------------------------------------------------

    The statutory provision for demonstrating impracticability requires 
that the demonstration be based on air quality modeling. See section 
189(b)(1)(A). We have established minimum requirements for air quality 
modeling. See discussion on air quality modeling later in this TSD.
    3. Have Complied With all Requirements and Commitments in its 
Implementation Plan
    We interpret this criterion to mean that the state has implemented 
the emission reducing measures in the plan revisions it has submitted 
to address the CAA requirements in sections 172 and 189 for PM-10 
nonattainment areas.
    The purpose of this criterion is to assure that a state is not 
receiving additional time to attain because it failed to implement 
already-adopted or already-committed-to control measures. Given this 
purpose, we believe our review under this criterion should be limited 
to the implementation status of control measures from earlier PM-10 
plans and not be an expansive review of the implementation status of 
every provision in submitted implementation plans, whether or not it is 
an emission reducing measure.
    We read this provision not to require the area to have a fully 
approved plan 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 or if the area has failed to meet a 
RFP milestone.
    Part of determining whether a state has implemented its commitments 
and requirements in earlier plans is assessing whether the state 
retains the legal authority for them and is funding, staffing, and 
enforcing them at the level assumed or committed to in those plans. 
Thus any determination that the state has met its commitments and 
requirements in earlier plans is also a finding that it has retained 
its legal authority and has met its commitments regarding enforcement, 
funding, and staffing.
    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 be feasibly 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 a BACM-level of control 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 propose to define a ``most stringent measure'' level of control 
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 be feasibly implemented in 
the area. A MSM then is a control measure that delivers this level of 
control.
    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.

[[Page 50283]]

    Given this similarity between the BACM requirement and the MSM 
requirement, 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 to determine if the existing measures are most 
stringent:
    1. Develop a detailed emissions 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 as necessary,
    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 of any MSM that is more stringent than 
existing similar local measures and provide for implementation as 
expeditiously as practicable or, in lieu of providing for adoption, 
provide a reasoned justification for rejecting the potential MSM, i.e., 
why such measures cannot be feasibly implemented in the area.
    The MSM provision only requires that a state consider the best 
controls from elsewhere in the country for implementation in the area 
requesting an attainment date extension. It looks to see--and the 
results are completely dependent on--how well other areas have 
controlled their PM-10 sources. If other areas have not controlled a 
particular source or source category well, then the resulting level of 
control from the MSM will not be the maximum feasible level of control 
for that source or source category in the local area. Even if they have 
controlled them well, the resulting level of control may still not be 
the maximum feasible level because local conditions may allow a higher 
degree of control than has been achieved elsewhere.
    The MSM provision does not require a state to consider if local 
sources or source categories can be controlled at a level greater than 
the most stringent level from other areas. In other words, it does not 
require states to determine and adopt the maximum feasible level of 
control that could be applied to a source or a source category given 
local conditions and the additional implementation time afforded by an 
extension.
    In considering the MSM provision, the inclination is to assume that 
there are always better controls in other areas than there are in the 
local area. This assumption is unwarranted, especially for areas that 
have already gone through the process of identifying and adopting BACM 
for their significant sources in order to meet the section 189(b)(1)(B) 
requirement. These areas are likely to have already evaluated the best 
controls from other areas and either adopted them as BACM or rejected 
them as not feasible for their area. As a result, the likelihood of 
finding substantial new controls during a MSM evaluation in one of 
these areas is low.\55\
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    \55\ There is also an inclination to assume that the MSM 
requirement is the provision in section 188(e) that implements the 
Act's general strategy of offsetting longer attainment time frames 
with more stringer control and therefore, the MSM requirement must 
be interpreted to result in the adoption of measures more stringent 
than BACM. We believe, however, that this offsetting function is 
actually served by the CAA section 189(b)(i)(A)(ii) requirement for 
PM-10 plans to demonstrate attainment by the most expeditious date 
practicable, if attainment by 2001 is impracticable. Because we are 
required to grant the shortest possible extension, a state must 
demonstrate that it has adopted the set of control measures that 
will result in the most expeditious date practicable for 
attainement. This requirement may very well require that a state 
adopt controls that go beyond the most stringent measures adopted or 
implemented elsewhere.
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    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 the 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 request 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.
    Like the RACM and BACM requirements, there is no explicit provision 
in the Act prohibiting an exemption from the MSM requirement for de 
minimis sources of PM-10 pollution. We are using here the same 
principles for determining when a source is considered de minimis under 
the MSM requirement that we used for the RACM requirement that the Ober 
II court upheld and thus we have constructed the de minimis exemption 
for the MSM requirement to prevent states from eliminating any controls 
on sources or source categories that alone or together would result in 
more expeditious attainment of the PM-10 standards.
    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 unless the emission benefit of the new measure is 
substantially greater than the existing measure.
    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.
    Judging stringency. The stringency of a control measure is 
determined primarily by a combination of its applicability and its 
control requirement, that is, who in the source category is subject to 
the measure and what does the measure requires them to do to reduce 
emissions. When we use the term ``measure'' in the context of the MSM 
requirement, we are referring to this combination; we are not referring 
to

[[Page 50284]]

just the control requirement or to individual methods of control.
    The approach we propose to use in evaluating the selection of the 
most stringent among multiple measures, i.e., evaluating the 
determination of when one control measure is more stringent than 
another, is:
    1. If there is only a single measure applicable to a source 
category then we will compare the measures directly. If there are 
multiple control measures with diverse controls requirements applicable 
to a source category (e.g., tailpipe emissions are controlled through 
fuels, emission standards, inspection and maintenance programs, and 
transportation control measures) then we will compare measures with 
similar control requirements against one another. If several measures 
apply the same or very similar control requirements to a source 
category, that is they have the same control requirement but different 
applicablities (e.g., MCESD Rule 310.01 and City and County commitments 
all require similar controls on unpaved roads), then will use the 
collective stringency of all the measures in the stringency analysis.
    2. We will review all the provisions of a rule that apply to a 
specific type of source (e.g., all the rule provision that apply to 
vacant lots) as an inseparable measure. As discussed above a rule's 
stringency is defined by a combination of its applicability and control 
requirements (as they apply to a single type of source). They are not 
separable elements that can be compared in isolation to another 
rule.\56\
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    \56\ For example, South Coast Rule 403 covers vacant lots, 
construction sites, and agriculture among other fugitive dust 
sources. MCESD's Rule 310.01 covers vacant lots and Rule 310 covers 
construction sites. The Arizona BMP rule covers agricultural 
sources. Under this test we would evaluate Rule 403's provisions for 
vacant lots against Rule 310.01 provisions for vacant lots; Rule 
403's provisions for construction sites against Rule 310's provision 
for construction sites; Rule 403's provisions for agricultural 
sources against the BMP rule's ones.
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    3. In a MSM analysis, a measure's stringency should be determined 
assuming that it is appropriately adopted, implemented and enforced. 
Thus, we will not use a measure's implementation mechanisms (e.g., rule 
versus commitment), funding level, compliance schedule, test method, 
resources available for enforcement, or other similar items as criteria 
for judging relative stringency.\57\
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    \57\ However, once a State determines a measure is a feasible 
most stringent measure, it must convert the measure into a legally 
enforceable form and provide the necessary level of resources, etc. 
to ensure its implementation.
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    A state may determine which measure or measures are most stringent 
either qualitatively or quantitatively. It is the state's 
responsibility, however, to assure that any determination is well 
documented and persuasive.
    Once a state has identified a potential most stringent measure, it 
must provide for the adoption of any MSM that is more stringent than 
existing measures and provide for implementation as expeditiously as 
practicable or, in lieu of providing for adoption, provide a reasoned 
justification for rejecting the potential MSM, i.e., why such measures 
cannot be feasibly implemented in the area.
    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 indicates that Congress granted us 
considerable discretion in determining whether a plan in fact provides 
for 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 and to how we have interpreted the CAA's other 
general control requirements, RACM and BACM.
    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 and to the failure to include measures that could 
provide for more expeditious attainment and less weight to those 
measures for source categories that contribute little to the PM-10 
problem and 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 by the most expeditious date practicable using air quality 
modeling after December 31, 2001. This demonstration is the final 
criterion that must be met before we may grant an extension request.
    There are two parts to reviewing a modeled attainment 
demonstration: evaluating the technical adequacy of the modeling 
itself, and evaluating the control measures that are relied on to 
demonstrate attainment.
    We have established technical requirements for modeling PM-10 in 
SIP attainment demonstrations. Please see discussion later in this TSD 
on modeling requirements for PM-10 SIPs.
    In order to evaluate the control measures relied on in the 
attainment demonstration to determine if:
    1. We have approved it into the SIP or the State has submitted it 
to us for approval into the SIP.
    2. It is enforceable under our SIP-enforceability standards or 
qualifies to be credited under our mobile source voluntary measures 
policy.\58\
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    \58\ Memorandum, Richard D. Wilson, Acting Assistant 
Administrator for Air and Radiation, to EPA Regional Administrators, 
1-10, ``Guidance on Incorporating Voluntary Mobile Source Reduction 
Programs in State Implementation Plans (SIPs),'' October 24, 1997.
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    3. The plan provides reasonable assurances, including funding and 
other resource commitments, that it will be implemented and enforced.
    4. It will be implemented on the most expedient schedule 
practicable.
    5. The emission reductions credited to it are reasonable and 
consistent with the implementation resources and schedule, and for any 
reductions coming from mobile source voluntary measures, that they do 
not collectively exceed 3 percent of the total reductions needed for 
attainment.\59\
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    \59\ Ibid., page 5.
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    Our determination of whether the plan provides for attainment by 
the most expeditious date practicable will depend on whether we find 
that the plan provides for appropriate BACM, MSM, and any other 
technologically and economically feasible measures that will result in 
attainment as expeditiously as practicable and that these measures are 
implemented on an expeditious schedule.
    Please see section 3 of the EPA TSD for additional discussion of 
our proposed interpretation of the extension requirements.

VI. 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. For this reason, this proposed action is also not subject to 
Executive Order 32111, ``Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use'' (66 FR 
28355, May 22, 2001). 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

[[Page 50285]]

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 (Public Law 104-4). This rule also does not 
have a substantial direct effect on one or more Indian tribes, on the 
relationship between the Federal Government and Indian tribes, or on 
the distribution of power and responsibilities between the Federal 
Government and Indian tribes, as specified by Executive Order 13175 (65 
FR 67249, November 9, 2000), nor will it 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, EPA's 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), EPA has no authority 
to disapprove a SIP submission for failure to use VCS. It would thus be 
inconsistent with applicable law for EPA, when it reviews 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 note) do not apply. As required by section 3 
of Executive Order 12988 (61 FR 4729, February 7, 1996), in issuing 
this proposed rule, EPA has taken the necessary steps to eliminate 
drafting errors and ambiguity, minimize potential litigation, and 
provide a clear legal standard for affected conduct. EPA has 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: September 14, 2001.
Mike Schulz,
Acting Regional Administrator, Region IX.
[FR Doc. 01-24203 Filed 10-1-01; 8:45 am]
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