[Federal Register Volume 62, Number 109 (Friday, June 6, 1997)]
[Proposed Rules]
[Pages 31025-31037]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-14848]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[AZ 69-0012; FRL-5836-9]


Approval and Promulgation of Implementation Plans; Arizona--
Maricopa County PM-10 Nonattainment Area

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: EPA is proposing to approve in part and disapprove in part the 
final Plan for Attainment of the 24-hour PM-10 Standard--Maricopa 
County PM-10 Nonattainment Area, (May 1997) (plan or microscale plan) 
submitted by the Arizona Department of Environmental Quality on May 7, 
1997. The microscale plan evaluates attainment of the 24-hour 
particulate matter (PM-10) national ambient air quality standard at 
four monitoring locations in the Maricopa County (Phoenix), Arizona, 
PM-10 nonattainment area. EPA is proposing to approve the attainment 
and reasonable further progress (RFP) demonstrations for two of these 
sites (Salt River and Maryvale) and disapprove them for two other sites 
(West Chandler and Gilbert). EPA is also proposing to approve the 
reasonably available control measure/best available control measure 
(RACM/BACM) demonstrations in the

[[Page 31026]]

microscale plan for some significant source categories of PM-10, but 
disapprove them for others.

DATES: Comments on this proposal must be received in writing by June 
20, 1997.

ADDRESSES: Comments should be addressed to the contact listed below.
    Copies of the State's submittals, the technical support document, 
and other information are contained in the docket for this rulemaking. 
A copy of this notice and the TSD are also available in the air 
programs section of EPA Region 9's website, http://www.epa.gov/
region09. The docket is available for inspection during normal business 
hours at the following locations:

U.S. Environmental Protection Agency, Region 9, Office of Air Planning, 
Air Division, 17th Floor, 75 Hawthorne Street, San Francisco, 
California 94105, (415) 744-1248.
Arizona Department of Environmental Quality, Office of Outreach and 
Information, First Floor, 3033 N. Central Avenue, Phoenix, Arizona 
85012, (602) 207-2217.
Maricopa County Environmental Services Department, Technical Services 
Division, 1001 N. Central Avenue, Suite 201, Phoenix, Arizona 85004, 
(602) 506-6010.

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.

SUPPLEMENTARY INFORMATION:

I. Background

A. Clean Air Act Requirements

1. Designation and Classification
    On the date of enactment of the 1990 Clean Air Act Amendments, PM-
10 areas meeting the conditions of section 107(d) of the Act, including 
portions of Maricopa County (the Maricopa County PM-10 nonattainment 
area), were designated nonattainment for the PM-10 national ambient air 
quality standards (NAAQS) 1 by operation of law. Once an 
area is designated nonattainment, section 188 of the Clean Air Act 
(CAA) outlines the process for classification of the area and 
establishes the area's attainment date. In accordance with section 
188(a), at the time of designation, all PM-10 nonattainment areas were 
initially classified as ``moderate'' by operation of law. 56 FR 11101 
(March 15, 1991).
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    \1\ There are two PM-10 NAAQS, a 24-hour standard and an annual 
standard. 40 CFR 50.6.
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    A moderate area could subsequently be reclassified as ``serious'' 
under CAA section 188(b)(1), if at any time, EPA determined that the 
area could not practicably attain the PM-10 NAAQS by the applicable 
attainment date for moderate areas, December 31, 1994. Moreover, a 
moderate area was reclassified by operation of law if EPA determined 
after the applicable attainment date that, based on actual air quality 
data, the area was not in attainment after that date. CAA section 
188(b)(2).
    On May 10, 1996, EPA published a final reclassification of the 
Maricopa County PM-10 nonattainment area as a serious PM-10 
nonattainment area based on actual air quality data. 61 FR 21372. 
Having been reclassified, the area is required to meet the serious area 
requirements in the CAA, including a demonstration that the area will 
attain the PM-10 NAAQS as expeditiously as practicable but no later 
than December 31, 2001. CAA sections 188(c)(2) and 189(b). Pursuant to 
section 189(b)(2), the State of Arizona must submit a serious area plan 
addressing both PM-10 NAAQS for the area by December 10, 1997.
2. Moderate Area Planning Requirements
    The air quality planning requirements for PM-10 nonattainment areas 
are set out in subparts 1 and 4 of title I of the Clean Air Act. EPA 
has issued a ``General Preamble'' 2 describing EPA's 
preliminary views on how the Agency intends to review SIPs and SIP 
revisions submitted under Title I of the Act, including those state 
submittals containing moderate PM-10 nonattainment area SIP provisions.
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    \2\ See ``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).
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    Those states containing initial moderate PM-10 nonattainment areas 
were required to submit, among other things, the following provisions 
by November 15, 1991:
    (a) Provisions to assure that reasonably available control measures 
(RACM) (including such reductions in emissions from existing sources in 
the area as may be obtained through the adoption, at a minimum, of 
reasonably available control technology (RACT)) shall be implemented no 
later than December 10, 1993 (CAA sections 172(c)(1) and 189(a)(1)(C));
    (b) Provisions to assure implementation of RACT on major stationary 
sources of PM-10 precursors except where EPA has determined that such 
sources do not contribute significantly to exceedances of the PM-10 
standards (CAA section 189(e));
    (c) Either a demonstration (including air quality modeling) that 
the plan will provide for attainment as expeditiously as practicable 
but no later than December 31, 1994 or a demonstration that attainment 
by that date is impracticable (CAA sections 188(c)(1) and 
189(a)(1)(B));
    (d) For plan revisions demonstrating attainment, quantitative 
milestones which are to be achieved every 3 years and which demonstrate 
reasonable further progress (RFP) toward attainment by December 31, 
1994 (CAA section 189(c)); 3 and
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    \3\ As will be seen below, the moderate area PM-10 plan for the 
Maricopa area did not demonstrate attainment by December 31, 1994, 
but rather included the alternative demonstration that attainment by 
that date is impracticable. Therefore, section 189(c) did not apply 
to the State's moderate area plan.
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    (e) For plan revisions demonstrating impracticability, such annual 
incremental reductions in PM-10 emissions as are required by part D of 
the Act or may reasonably be required by the Administrator for the 
purpose of ensuring attainment of the PM-10 NAAQS by the applicable 
attainment date (CAA sections 172(c)(2) and 171(1)).
    Moderate area plans were also required to meet the generally 
applicable SIP requirements for 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 Sec. 51.280; and the description of 
enforcement methods as required by 40 CFR Sec. 51.111, and EPA guidance 
implementing these sections.
3. Serious Area Planning Requirements
    EPA has issued an Addendum to the General Preamble (Addendum) 
describing the Agency's preliminary views on how it intends to review 
SIPs and SIP revisions containing serious area plan 
provisions.4
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    \4\ See ``State Implementation Plans for Serious 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, 1996).
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    Moderate PM-10 areas that have been reclassified to serious, such 
as the Maricopa area, in addition to meeting the moderate area 
requirements outlined above, must submit a plan that includes 
provisions addressing additional requirements. The additional serious 
area requirements that are relevant to this proposed action include:
    (a) Provisions to assure that the best available control measures 
(BACM)

[[Page 31027]]

(including such reductions in emissions from existing sources in the 
area as may be obtained through the adoption, at a minimum, of best 
available control technology (BACT)) 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));
    (b) Provisions to assure implementation of BACT on major stationary 
sources of PM-10 precursors 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 (CAA sections 188(c)(2) and 
189(b)(1)(A)(i)); 5 and
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    \5\ Section 189(b)(1)(A)(ii) provides for an alternative 
demonstration of impracticability similar to that available for 
moderate areas. Since the State did not make such a demonstration, 
this alternative requirement is not addressed in this notice.
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    (d) For plan revisions demonstrating attainment, quantitative 
milestones which are to be achieved every 3 years and which demonstrate 
RFP toward attainment by December 31, 2001 (CAA section 189(c)).
    As discussed above in connection with the moderate area plan 
requirements, SIPs submitted to meet the CAA's serious area 
requirements must conform to general requirements applicable to all 
SIPs.
B. EPA Approval of Arizona's Moderate Area PM-10 Plan
    On July 28, 1994, EPA proposed to approve the State's moderate area 
PM-10 implementation plan revision for the Maricopa area. 59 FR 38402. 
Among other elements in that plan, EPA proposed to approve the State's 
RFP and RACM demonstrations as meeting the requirements of sections 
171(1), 172(c)(1), 172(c)(2), and 189(a)(1)(C) of the CAA. Based on its 
approval of the RACM demonstration, EPA also proposed to approve, as 
meeting the requirements of section 189(a)(1)(B), the State's 
demonstration that even with the implementation of all RACM by December 
10, 1993, it was impracticable for the Maricopa area to attain the PM-
10 NAAQS by December 31, 1994.6
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    \6\ The reader should refer to both the proposed approval, 59 FR 
38402, and the final rule, 60 FR 18010 (April 10, 1995), for EPA's 
interpretation of the certain moderate area PM-10 requirements of 
the CAA and the Agency's application of these interpretations to the 
State's moderate area PM-10 plan. Those notices should also be 
consulted for the history of the State's PM-10 plan submittals and 
EPA's actions concerning them.
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    During the public comment period on the EPA's proposed action, the 
Arizona Center for Law in the Public Interest (ACLPI) submitted lengthy 
comments on many aspects of EPA's proposed approval of the State's 
moderate area PM-10 plan. Among ACLPI's comments were claims that the 
plan as submitted failed in numerous respects to meet the moderate area 
requirements of the CAA for RACM, RFP and attainment demonstrations. 
ACLPI further claimed that the State's impracticability and RACM 
demonstrations were additionally deficient in that the State had failed 
to address both the annual and 24-hour PM-10 standards as required by 
the CAA and EPA guidance. In response to this comment, EPA concluded 
that the State's demonstration that the Maricopa area could not 
practicably attain the annual standard was sufficient to meet the 
requirements of section 189(a)(1)(B) and therefore a separate analysis 
was not necessary for the 24-hour standard.
    On April 10, 1995, having considered ACLPI's comments, EPA 
published a final rule in the Federal Register approving the State's 
moderate area PM-10 SIP for the Maricopa area. 60 FR 18010. In its 
final action, EPA approved, among other elements of the plan, the 
State's RACM and RFP demonstrations, and the State's demonstration that 
even with the implementation of all RACM by December 10, 1993, it was 
not practicable for the Maricopa area to attain the PM-10 NAAQS by 
December 31, 1994.
C. Ninth Circuit Litigation
    On May 1, 1995, ACLPI filed, on behalf of two Phoenix residents, a 
petition for review, Ober v. EPA, No. 95-70352, of EPA's approval of 
Arizona's moderate area PM-10 plan for the Maricopa area in the United 
States Court of Appeals for the Ninth Circuit. On May 14, 1996, the 
court issued its opinion in the Ober case vacating EPA's approval of 
the State's plan. 7
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    \7\ The reader is referred to the text of the opinion for the 
court's disposition of the range of issues raised by ACLPI in its 
petition. 84 F.3d 304 (9th Cir. 1996). This notice addresses that 
disposition only as it relates to the 24-hour standard. See also 61 
FR 54972 (October 23, 1996) in which EPA preliminarily addresses the 
court's opinion as it relates to the RACM, RFP and attainment 
demonstrations for the annual standard.
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    As it relates to this proposed rulemaking, the court found that the 
State was required to address in its SIP the moderate area requirements 
in the CAA regarding RFP, RACM and attainment or impracticability for 
both the 24-hour and the annual PM-10 NAAQS. The court concluded that 
because there are two separate NAAQS for PM-10, the CAA requires an 
implementation plan to address each of them. In order to remedy the 
failure of the State to address the required demonstrations for the 24-
hour standard, the court required EPA to in turn require the State to 
submit those demonstrations. 84 F.3d at 311.
D. EPA's Response to the Ober Opinion
    In the wake of the Ninth Circuit's Ober opinion, EPA considered how 
to appropriately implement the court's directive in the context of the 
State's then prevailing PM-10 planning efforts for the Maricopa area. 
The Maricopa area was reclassified as a serious PM-10 nonattainment 
area just days before the case was decided and, as noted above, the 
State is now required to submit a new PM-10 plan meeting the serious 
area requirements by December 10, 1997. Simply put, EPA had to 
reconcile, with respect to both timing and content, the court's mandate 
that the State submit a plan correcting its moderate area plan 
deficiencies regarding the 24-hour standard concurrent with its 
responsibility to submit a plan meeting the serious area requirements 
for both NAAQS.
1. Timing
    As an initial matter, EPA concluded that, given the substantial 
overlap of the moderate and serious area planning requirements, it 
would not be in the public interest to require the State to divert its 
scarce resources into two independent planning exercises. At the same 
time the Agency recognized that deferring submittal of a plan 
addressing the moderate area plan deficiencies until the serious area 
submittal deadline of December 10, 1997 would not constitute a timely 
response to the court. Therefore EPA, in consultation with the Arizona 
Department of Environmental Quality (ADEQ) and the Maricopa County 
Environmental Services Department (MCESD), decided that the State would 
incorporate the moderate area plan elements for the 24-hour standard 
into the serious area plan, but would split that planning effort into 
two related parts. Accordingly, EPA required submittal of a limited, 
locally-targeted plan (microscale plan) meeting both the moderate and 
serious area requirements for the 24-hour standard by May 9, 1997 
(extended from an original deadline of April 18) and a full regional 
plan meeting those requirements for both the 24-hour and annual 
standards by December 10, 1997. Thus, the microscale and regional plans 
taken together would satisfy both the moderate area requirements 
mandated by the court and the serious area planning requirements for 
both

[[Page 31028]]

standards. Therefore, until the regional plan is submitted and reviewed 
by EPA, it is premature to conclude that the microscale plan fully 
meets or does not meet the CAA requirements discussed below. The 
subject of this proposed action is the microscale plan only.
    The submittal deadlines and statutory requirements applicable to 
the microscale plan are contained in letters dated September 18, 1996 
and March 5, 1997 from Felicia Marcus, Regional Administrator, EPA 
Region IX, to Russell Rhoades, Director, ADEQ (Marcus letter).
2. Content
    As specified in EPA's September 18, 1996 letter to ADEQ, the 
microscale plan was to address the 24-hour standard violations at five 
specific monitors and meet the statutory attainment, RACM and RFP 
requirements for moderate PM-10 areas and EPA guidance. In addition, 
the microscale plan was to meet the statutory attainment, BACM and RFP 
requirements for serious PM-10 areas and EPA guidance at 59 FR 41998. 
Further, the plan was to contain the air quality modeling and emissions 
inventory information necessary to support these attainment, RFP, RACM, 
and BACM demonstrations and must meet the general SIP requirements 
discussed above.
    Having concluded that the hybrid moderate/serious plans described 
above would effectuate the intent of the Ninth Circuit's mandate, EPA 
then turned to the issue of how to define the moderate area 
requirements applicable to the microscale plan after the moderate area 
attainment deadline, December 31, 1994, has passed. The following 
discussion addresses that issue and the interrelationship of those 
requirements with the serious area requirements as they apply to that 
plan.
    (a) Attainment Demonstration. EPA believes that because the 
Maricopa area was reclassified from a moderate to a serious 
nonattainment area, the moderate area requirements (demonstration of 
impracticability or attainment by no later than December 31, 1994) have 
been superseded by the serious area attainment requirement (attainment 
by no later than December 31, 2001) and are therefore now moot. Having 
reviewed the CAA's moderate and serious area PM-10 attainment 
provisions, EPA has concluded that when a moderate PM-10 area has been 
reclassified after the moderate area attainment deadline has passed and 
been replaced with a new deadline, the moderate area deadline no longer 
has any logical, practical or legal significance.
    Thus, under this interpretation, there would be no need for the 
State's microscale plan, to the extent that it is intended to meet the 
CAA's moderate area requirements, to demonstrate attainment. In other 
words, such an attainment demonstration would only be required when the 
State submits in late 1997 the complete serious area plan to comply 
with the section 189(b)(1) attainment demonstration requirement. EPA 
believes that its interpretation can be reconciled with the Ober 
court's directive that EPA require the State to address the moderate 
area attainment requirements for the 24-hour standard and that such an 
interpretation is reasonable given the legal and factual context in 
which that case was decided. EPA's reasoning is explained in detail at 
61 FR 54972, 54974-54975 (October 23, 1996). Nevertheless, EPA has 
chosen to comply with the court's remedies regarding the moderate area 
attainment requirements. 8
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    \8\ While EPA could have sought clarification from the Ninth 
Circuit in order to apply its interpretation in the context of 
compliance with the court's remedies in Ober, the Agency did not 
believe that it would have been in the public interest to do so. 
Such a review would necessarily have occurred without benefit of a 
thorough briefing on the issue and in the absence of an 
administrative record. The Agency does, however, reserve its right 
to assert its interpretation in any challenge to EPA's 
implementation of the court's remedies or in the context of other 
reclassifications. Because EPA is not applying this interpretation 
in this rulemaking, it does not constitute final agency action.
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    Having determined that it must require the State to meet the CAA's 
moderate attainment requirements for the 24-hour standard, EPA has 
concluded that since the December 31, 1994 deadline has passed and the 
Maricopa area has been reclassified, the only attainment deadline 
currently applicable to the area is the serious area deadline, that is, 
no later than December 31, 2001. Thus the attainment deadline for both 
the moderate and serious area components of the State's microscale PM-
10 plan would be as expeditiously as practicable but no later than 
December 31, 2001. Therefore, if the microscale plan demonstrates 
attainment of the 24-hour standard at each monitor specified in EPA's 
September 18, 1996 letter by no later than December 31, 2001, it will 
be deemed to comply with sections 189(a)(1)(B) and (b)(1)(A) of the 
CAA.
    (b) RACM/BACM Demonstration. Sections 172(c)(1) and 189(a)(1)(C) 
read together require that moderate area PM-10 SIPs include RACM and 
RACT for existing sources of PM-10. These SIPs were to provide for 
implementation of RACM/RACT no later than December 10, 1993. Since the 
moderate area deadline for the implementation of RACM/RACT has passed, 
EPA has concluded that the RACM/RACT required in the State's microscale 
plan must be implemented as soon as possible. Delaney v. EPA, 898 F.2d 
687, 691 (9th Cir. 1990).
    The methodology for determining RACM/RACT is described in detail in 
the General Preamble. 57 FR at 13540-13541. In summary, EPA suggests 
starting to define RACM with the list of available control measures for 
fugitive dust, residential wood combustion, and prescribed burning 
contained in Appendices C1, C2, and C3 of the General Preamble and 
adding to this list any additional control measures proposed and 
documented in public comments. The state can then cull from the list 
any measures for insignificant emission sources of PM-10 and any 
measures that are unreasonable for technological or economic reasons. 
The General Preamble does not define insignificant except to say that 
it would be unreasonable to apply controls to sources that are 
negligible (``de minimis'') contributors to ambient concentrations. 
However, EPA's serious area plan guidance does define, for use in BACM 
determinations, a ``significant contributor'' source category as one 
that contributes 5 g/m \3\ or more of PM-10 to a location of 
expected 24-hour exceedances. Addendum at 42011. For purposes of the 
microscale plan only, EPA is proposing to use this same definition to 
define significant in determining which source categories require the 
application of RACM.
    For any RACM that are rejected by the state, the plan must provide 
a reasoned justification for the rejection. Once the final list of RACM 
is defined, each RACM must be converted into a legally enforceable 
vehicle such as a rule, permit, or other enforceable document. General 
Preamble at 13541.
    Under section 189(b)(2), for moderate areas that have been 
reclassified as serious, the state must submit BACM 18 months after 
reclassification, i.e., December 10, 1997 for the Maricopa area, and 
must implement those measures four years after reclassification, i.e., 
by June 10, 2000 for the Maricopa area.
    BACM is defined as the ``maximum degree of emission reduction of 
PM-10 and PM-10 precursors from a [significant] source [category] which 
is determined on a case-by-case basis, taking into account energy, 
environmental, and economic impacts and other costs, to be achievable 
for such sources through application of

[[Page 31029]]

production processes and available methods, systems, and techniques * * 
*.'' Addendum at 42010. BACM/BACT must be determined and documented 
consistent with the Addendum (59 FR at 42012-14) and must be applied to 
each significant area-wide source category and individual stationary 
source. Addendum at 42010, footnote 33. A ``significant'' source 
category is defined as one that contributes 5 g/m \3\ or more 
of PM-10 to a location of expected 24-hour violation. Addendum at 
42011.
    The state must document its selection of BACM by showing what 
control measures applicable to each significant source category were 
considered. See Addendum at 42014. BACM should go beyond existing RACM 
controls and can include expanded use of RACM controls (e.g., paving 
more miles of unpaved roads). Addendum at 42013. Additionally, BACM 
should emphasize prevention pf PM-10 emissions where possible over 
remediation. Addendum at 42013.
    For the microscale plan, EPA required that Arizona submit RACM and 
BACM demonstrations by May 9, 1997 as they relate to exceedances of the 
24-hour standard at the five specified monitors. RACM and BACM were to 
be identified, documented, and realistically evaluated for 
effectiveness for contributing sources to each modeled exceedance. 
Marcus letter. Evaluation of RACM/BACM in the microscale plan is 
limited to controls for sources that are contributing significantly and 
directly to the localized violations rather than to sources 
contributing to background PM-10 levels. A full analysis of RACM/BACM 
for sources that significantly contribute to PM-10 levels in the 
Maricopa County PM-10 nonattainment area but are not directly 
implicated in the localized exceedances is to be conducted as part of 
the regional serious area plan, due December 10, 1997.
    (c) RFP/Quantitative Milestones. Both PM-10 moderate and serious 
area nonattainment SIPs demonstrating attainment must include 
quantitative milestones to be achieved every three years until the area 
is designated attainment and must demonstrate RFP toward attainment by 
the applicable date. CAA section 189(c)(1). EPA has addressed these 
requirements in several guidance documents. See the General Preamble at 
13539, the Addendum at 42015-42017, and the memorandum from Sally 
Shaver, EPA, to EPA Division Directors, ``Criteria for Granting 1-Year 
Extensions of Moderate PM-10 Nonattainment Area Attainment Dates, 
Making Attainment Determinations, and Reporting on Quantitative 
Milestones,'' November 14, 1994 (Shaver memorandum). Of these guidance 
documents, the most comprehensive is the Addendum which discusses both 
the RFP annual incremental reduction requirement and the appropriate 
interpretation of the milestone requirement as it relates to moderate 
areas that have been reclassified to serious.
    With respect to RFP, EPA determined that SIPs must indicate the 
annual emission reductions that correspond to the compliance schedules 
for the control measures in the plan. EPA then has considerable 
discretion in reviewing the SIP to determine whether the annual 
incremental emission reductions to be achieved are reasonable in light 
of the statutory objective of timely attainment. Addendum at 42015.
    With respect to the quantitative milestone requirement, for initial 
moderate areas, EPA concluded that the SIP should initially address at 
least two milestones and that the starting point for the first 3-year 
period would be the SIP submittal due date, i.e. November 15, 1991. EPA 
further concluded that since the time lag between that date and the 
December 31, 1994 attainment deadline was de minimis, emission 
reduction progress made between the submittal date and December 31, 
1994 would satisfy the first milestone. The second milestone to be 
addressed by these initial moderate area SIPs was November 15, 1997. 
General Preamble at 131539, Addendum at 42016, and Shaver memorandum. 
For moderate areas that are reclassified as serious, the third 
milestone achievement date is November 15, 2000. Addendum at 42016. The 
quantitative milestones should consist of elements that allow progress 
to be quantified or measured, e.g., percent compliance with implemented 
control measures. Addendum at 42016.
    EPA will assess whether an area has achieved RFP in conjunction 
with determining compliance with the quantitative milestone 
requirement. Thus a state should address compliance with both 
requirements in its RFP/milestone reports. The contents of these 
reports is discussed in the General Preamble, its Addendum, and the 
Shaver memorandum.
    Since the Ober court found that Arizona had failed to submit a 
moderate area SIP addressing the 24-hour PM-10 standard in 1991 and the 
regional plan addressing both the moderate and serious area 
requirements for both PM-10 NAAQS is now due on December 10, 1997, EPA 
believes that it is reasonable to conclude, by applying the de minimis 
reasoning above, that the November 15, 1997 milestone can be satisfied 
by the December plan submittal. Therefore, the microscale plan need not 
address the CAA section 189(c)(1) quantitative milestone requirement 
and it is not discussed further in this notice.

II. Evaluation of the State's Submittal

    The Plan for Attainment of the 24-hour PM-10 Standard--Maricopa 
County PM-10 Nonattainment Area (May, 1997) (microscale plan) was 
submitted to EPA by the Arizona Department of Environmental Quality 
(ADEQ) in draft on March 28, 1997 and in final on May 9, 1997. EPA has 
found both submittals complete pursuant to CAA section 110(k) and 40 
CFR part 51, Appendix V. Letter, David P. Howekamp, EPA, to Russell F. 
Rhoades, ADEQ, May 23, 1997.9
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    \9\ ADEQ requested that EPA propose action on the draft plan in 
parallel with the State's public comment period (see March 28, 1997 
submittal letter); however, the final plan was submitted before EPA 
could do so. Therefore, EPA's evaluation of the microscale plan, as 
described in this notice, is based on the final plan and all 
references in this notice are to that plan.
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    EPA has evaluated the plan for compliance with the applicable 
statutory, regulatory, and policy requirements described above. This 
evaluation is summarized here, and the detailed analysis can be found 
in the technical support document which is located in the docket for 
this proposed rulemaking.
A. Air Quality Modeling
1. The Microscale Approach
    CAA section 189(b)(1)(A)(i) requires serious area plans to include 
air quality modeling as part of their attainment demonstrations. For 
the microscale plan, base case air quality modeling was required for 
exceedances at the (East) Chandler,10 West Chandler, 
Gilbert, and Maryvale monitors. For the Salt River monitor, air quality 
modeling was required for each unique emissions scenario leading to an 
exceedance. In addition, all modeling inputs had to be fully documented 
and the air quality

[[Page 31030]]

modeling protocols must conform to EPA guidance or be approved in 
advance by EPA. Marcus letter.
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    \10\ The East Chandler site was dropped from the microscale plan 
because there was insufficient source activity information to 
develop a useable inventory for modeling the exceedances at the 
site. Plan, Appendix A, p. 3-1. From the information that is 
available about the East Chandler site, it appears that exceedances 
there have similar causes to those at the modeled West Chandler 
site, that is, they are related to windblown dust during high winds 
from a mix of urban and agricultural sources. See facsimiles, Randy 
Sedlacek, ADEQ, to Frances Wicher, EPA, May 21, 1997 (found in the 
docket). The Gilbert site also had similar source characteristics. 
Plan, Appendix A, p. 4-7. Therefore, RACM/BACM implemented for the 
West Chandler and Gilbert sites should also contribute to emission 
reductions at the East Chandler site. Consequently there will be no 
further reference to this site in this notice.
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    Base case air quality modeling attempts to replicate observed PM-10 
NAAQS exceedances using historical observations of air quality, 
meteorology, and emissions. The modeling results indicate what sources 
are contributing to the exceedances and what level of emissions 
reductions are needed to eliminate these exceedances.
    The modeling approach used in the microscale plan is significantly 
different than default approaches in EPA guidelines and approaches used 
in other areas. The main concept of the approach used in the microscale 
plan is that if PM-10 exceedances are caused mainly by relatively 
nearby sources, then an attainment demonstration can be based on 
modeling over a relatively small (microscale) geographic domain, i.e., 
over sub-areas of the nonattainment area. The microscale approach is 
more fully described in Microscale Monitoring and Modeling Protocol for 
the Maricopa PM-10 Nonattainment Area, Harding Lawson Associates, 
August 31, 1994.
    Normally, attainment demonstrations should address attainment for 
the entire nonattainment area; however, emission inventory development 
and modeling for areas with substantial fugitive dust problems, such as 
the Maricopa area, have proved difficult because of the marked 
uncertainty and temporal and spatial variability of fugitive dust 
emissions. Fugitive PM-10 has more localized effects than the other 
criteria pollutants because it is emitted near ground level and has 
relatively sharp spatial gradients as dust settles out with distance 
from the source. These considerations suggest that effort should be 
focused on intensive inventorying and modeling of small areas and short 
episodes. The approach in the microscale plan can be viewed as an 
extension of the microinventory method cited in early EPA guidance on 
PM-10 (Receptor Model Technical Series, Volume I, Overview of Receptor 
Model Application to Particulate Source Apportionment, EPA-450-4-81-
016a, July 1981, p. 27) but goes a step further in using that emission 
inventory as input into a dispersion model to enable a more precise 
apportionment of the various sources' effects.
    Nevertheless, sources can have effects farther away than is implied 
by the term ``microscale.'' The finer component of fugitive PM-10 can 
settle out relatively slowly, and during high wind conditions, at least 
some of the larger component can be carried long distances. These 
effects create a regional component that is not captured in the 
emissions of a small area near a monitor. This regional component can 
be dealt with as part of a regional modeling exercise or as part of a 
``background'' to be added to the microscale results. The latter 
approach is taken in the microscale plan. The fact that the background 
levels in the plan are relatively high relative compared to the total 
concentrations indicates a limitation of the microscale approach. Plan, 
pp. 24-26. On the other hand, since fugitive dust control measures 
derived from the microscale analysis area to be applied over the entire 
nonattainment area, the background will likely also be reduced because 
it too is made up primarily of fugitive dust. Therefore, keeping the 
background constant between uncontrolled and controlled scenarios, as 
is done in the microscale plan, makes for a conservative microscale 
attainment demonstration, partly compensating for shortcomings in the 
microscale approach.
    EPA guidance for ozone and carbon monoxide modeling (e.g., 
Guideline for the Regulatory Application of the Urban Airshed Model, 
EPA-450/4-91-013, July 1991) describes the selection of pollution 
episodes to model; there is no comparable guidance for PM-10, but the 
reasoning would be the same. Basically, the day(s) chosen should be 
representative of the meteorological conditions and emissions scenarios 
that lead to NAAQS exceedances and have an adequate database for the 
development of model inputs. In addition, a microscale approach must 
ensure that the particular sites chosen for modeling are worst case or 
representative of PM-10 exceedances in the area.
2. Evaluation of the Microscale Plan's Air Quality Modeling
    While documentation in the plan is sparse in places, enough 
information is provided to assess the adequacy of the approaches used. 
The following summarizes EPA's evaluation of the microscale modeling. 
The complete evaluation can be found in the TSD.
    The rationale for the choice of monitoring sites to model with the 
microscale approach is given in Appendix A to the plan. Past emission 
inventory and modeling work for the Maricopa ara have identified 
several fugitive dust source categories as being especially important 
for PM-10 exceedances including urban lots, highway and other 
construction activities, agricultural activities, and some industrial 
sources. Study sites were chosen in areas of high emissions density: 
South Phoenix for its mix of urban sources; 11 Salt River 
for its proximity to industrial sources; West Chandler for its nearby 
highway construction; and East Chandler for its mix of urban and 
agricultural sources. The Gilbert and Maryvale sites were later added 
because they recorded 24-hour exceedances during 1995. These sites are 
characterized by nearby agricultural land and by park construction/
landscaping, respectively.
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    \11\ The South Phoenix site was not included in the microscale 
plan because it did not record any 24-hour PM-10 exceedances in 
1995. EPA's criterion for determining which sites were to be 
analyzed in the microscale plan was whether the site had recorded 
exceedances of the 24-hour NAAQS during 1995.
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    Together, all these sites present a representative cross-section of 
the emission sources in the Maricopa area that are suspected of 
contributing to PM-10 exceedances.
    The microscale study took place throughout 1995. In addition to the 
EPA's standard AP-42 emission methodologies and some other prior 
special studies for particular source categories, the microscale study 
included field surveys, aerial photography, examination of activity 
logs, and interviews with source operators. This study resulted in a 
substantially better emissions inventory data than is usually 
available.
    To help define the geographic domains to be included in the final 
modeling, initial screening modeling was performed to determine the 
distance beyond which sources have an insignificant impact at the 
monitors. Concentrations observed at neighborhood scale monitors, and 
information on the land uses that affect these, were used to develop 
background concentrations for each portion of the modeling domain. 
Background concentrations were then added to the results of the EPA-
recommended ISCST model to yield total predicted concentrations.
    Episodes for modeling were chosen from among exceedance days that 
occurred during the 1995 study. Because of the importance to the 
microscale approach of an intensive emission inventory database, some 
days had to be discarded for lack of adequate emission source activity 
data.
    The Sunday, April 9, 1995 high wind episode day was chosen for the 
Gilbert, West Chandler, and Maryvale sites.12 For the Salt 
River site, October 16, 1995

[[Page 31031]]

was selected since all the relevant sources were in operation, the 
model validated well, and an October day was desirable since many of 
the exceedances were in that month. Plan, Appendix A, pp. 7-18 to 7-19. 
Multiple days could have been used and would have been desirable given 
the seasonal shifts in the daily times of high concentration noted in 
the plan. However, these varying concentrations were mainly dependent 
on wind direction, and the chosen October 16, 1995 day exhibits fairly 
high values in both morning and evening. Thus, the modeled phenomena 
are similar enough to the other episodes that this single design day is 
sufficient for the Salt River site.
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    \12\ For the Gilbert and Maryvale sites, the April 9, 1995 
exceedance was the only 24-hour exceedance recorded in 1995. The 
West Chandler site recorded a second exceedance on July 30, 1995. 
Plan, p. 15. This exceedance also appears to be related to a high 
wind event. Plan, Appendix A, p. 3-4.
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    Overall, the episodes modeled are representative of the conditions 
under which exceedances of the 24-hour PM-10 NAAQS occur. Model 
performance was generally good, especially for the Salt River site, and 
well within what can be expected from the type of model used, a 
Gaussian dispersion model.
    The microscale plan's approach for demonstrating attainment within 
each sub-area or modeling domain was proportional rollback. The basic 
assumption in proportional rollback is that a given percentage 
reduction in emissions yields the same percentage reduction in 
concentration at the receptor. Every attainment demonstration for a 
chemically-inert pollutant (that is, a pollutant that does not react in 
the atmosphere) such as primary PM-10 is implicitly based on 
proportional rollback, so the plan's approach is acceptable.
    Air quality modeling should evaluate the effectiveness of controls 
throughout the entire modeling domain. A control strategy sufficient 
for attainment at the monitor or at the maximum modeled receptor might 
not be sufficient at other receptor points within the domain where 
source contributions could be different because of the varying 
distances between the receptors and the sources. For the microscale 
plan, this variation is probably not important for the Maryvale or Salt 
River sub-areas, where a single source category at each site is so 
dominant, but could be important for the Gilbert and West Chandler sub-
areas with their more equal mix of sources.13
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    \13\ The microscale plan does not demonstrate attainment at the 
Gilbert and West Chandler sites; therefore, this point is moot. When 
additional controls are analyzed for these sites, an array of points 
within each modeling domain should be evaluated. Evaluation of 
controls at a single point will not be adequate for an attainment 
demonstration.
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    As the sub-areas are representative of the sources and conditions 
that lead to exceedances, the air quality modeling in the microscale 
plan is adequate for demonstrating attainment of the 24-hour PM-10 
NAAQS for the Maryvale and Salt River sites within the context of the 
microscale approach.

B. Evaluation of RACM/BACM

1. RACM/BACM Analysis
    (a) Maryvale Site. The Maryvale PM-10 monitoring site is located 
next to the Desert West Park which was under construction in early 
1995. Plan, Appendix A, p. 4-2. The air quality modeling evaluation of 
the Sunday, April 9, 1995 exceedance at the monitor showed that 
windblown fugitive dust, all from the area cleared for the park (that 
is, a disturbed cleared area), was the single largest contributor to 
the exceedance. Plan, p. 18.
    The microscale plan includes a list of potential control measures 
for the disturbed cleared area category including wind fences, chemical 
stabilizers, watering to maintain adequate soil moisture, and water to 
maintain a crust. Plan, p. 22. This source category is also subject to 
MCESD's Rule 310, Open Fugitive Dust Sources, which requires the 
application of RACM to open sources of fugitive dust. RACM is defined 
in the Rule 310 (section 221) and is detailed on the rule's dust 
control plan checklist and handbook ``A Guide for Reducing Air 
Pollution from Construction.'' See Plan, Appendix E, Letter, Joy Bell, 
MCESD, to Joe Gibbs, ADEQ, May 6, 1997 (Bell letter).14 
These measures include EPA's suggested RACM for this source 
category.15 See General Preamble, Appendix C1.
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    \14\ The Maricopa County Board of Supervisors adopted on May 14, 
1997 a resolution committing to implement improvements to the 
administration of the fugitive dust control program and to foster 
interagency cooperation to address fugitive dust. The microscale 
plan included the draft resolution, and ADEQ transmitted the adopted 
resolution to EPA on May 27, 1997. See letter from Nancy Wrona, 
ADEQ, to John Kennedy, EPA.
    \15\ Background concentrations at each of the monitoring sites 
were substantial (80 to 90 g/m3). Analysis of the causes of 
the high background levels was not part of the microscale protocol. 
It is possible, therefore, that there are other significant sources 
contributing to the exceedances at the monitors that have not been 
identified because they only contribute to the background.
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    The microscale plan also identifies BACM enhancements, including 
revising the dust control plan checklist to make permit holders aware 
of the importance of preventing wind-blown dust even when areas are 
inactive and the requirement to stabilize disturbed surfaces at all 
times, and revising the handbook to encourage them to plan their 
projects to minimize the amount of land disturbed at one time. Plan, p 
27. These types of enhancements meet EPA's guidance for BACM by going 
beyond existing RACM controls, expanding the use of RACM controls, and 
emphasizing prevention over remediation.
    (b) Salt River Site. The Salt River monitor is located on the 
grounds of the City of Phoenix's Salt River Service Center Yard. The 
site is surrounded by a number of industrial operations (including pre-
cast concrete manufacturing and sand and gravel operations), landfills 
(the 19th Avenue Landfill superfund site and the 27th Avenue Landfill), 
and other fugitive dust sources such as unpaved parking lots and roads. 
Plan, Appendix A, pp. 6-3 and 6-4. The modeling showed that fugitive 
dust from earth moving activities at 19th Avenue Landfill was the 
single largest contributor to the modeled October 16, 1995 exceedance 
and was the result of not watering to the depth of the cut during earth 
moving operations. Plan, pp. 17 and 23. Fugitive dust from unpaved 
parking lots, industrial haul roads and other unpaved roads also 
contributed significantly to the exceedance. Plan, p. 17. See also 
footnote 15 of this notice.
    All these significant source categories are subject to the RACM 
requirements in Rule 310. The microscale plan also includes a list of 
controls for earth moving and unpaved parking lots,16 many 
of which duplicate RACM required by Rule 310. Plan, p. 21. These 
measures include EPA's suggested RACM for these source categories. 
General Preamble, Appendix C1.
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    \16\ The identified control measures for unpaved parking lots 
are also applicable to unpaved roads.
---------------------------------------------------------------------------

    The microscale plan also identifies an enhancement to RACM for 
earth moving operations. This enhancement requires watering to the 
depth of the cut or other equivalent technique. Plan, p. 23. This type 
of enhancement meets EPA's guidance for BACM by going beyond existing 
RACM controls, expanding the use of RACM controls, and emphasizing 
prevention over remediation. The microscale plan does not explicitly 
identify BACM for unpaved parking lots, industrial haul roads, and 
unpaved roads although clarifications to Rule 310 to make permit 
holders aware of the importance of preventing wind-blown dust even when 
areas are inactive and of the requirement to stabilize disturbed 
surfaces at all times should improve control on these types of sources 
when they are located at permitted facilities.
    (c) Gilbert Site. The Gilbert monitoring site is located on the 
grounds of the City of Gilbert's

[[Page 31032]]

wastewater treatment plant and has agriculture fields and aprons to its 
north, paved and unpaved parking to the north and west, and a city park 
to the south. Plan, Appendix A, pp. 4-5. The modeling showed that 
windblown fugitive dust from agriculture aprons and unpaved parking 
lots was the largest contributor to the Sunday, April 9, 1995 
exceedance. Plan, p. 18. Fugitive dust from disturbed cleared areas was 
also a significant contributor to the exceedance. Plan, p. 18. See also 
footnote 15 of this notice. All these source categories are subject to 
the RACM requirements in Rule 310.17 The RACM in Rule 310 
include EPA's suggested RACM for these source category. General 
Preamble, Appendix C1.
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    \17\ Application of Rule 310 to agricultural sources including 
fields and aprons is affected by the provision in section 102 
(incorporating A.R.S. 49-504.4) that the rule ``shall not be 
construed so as to prevent normal farm cultural practices.'' 
Therefore, applicability of the rule to such sources depends on what 
dust-generating operation is occurring at the source. In other 
words, Rule 310 applies to some operations on agricultural fields 
and aprons and not to others.
---------------------------------------------------------------------------

    The BACM enhancement identified for these categories are 
clarifications to the dust control requirements in Rule 310 and 
improved enforcement of Rule 310. Plan, p. 23. These types of 
enhancements meet EPA's guidance for BACM by going beyond existing RACM 
controls, expanding the use of RACM controls, and emphasizing 
prevention over remediation. The microscale plan also includes 
development of a partnering process with the U.S. Natural Resources 
Conservation Service (NRCS) to address fugitive dust from agricultural 
sources (Plan, p. 36) and with the local jurisdictions in Maricopa 
County to address unpaved parking (Plan, p 35); however, no potential 
controls are identified for these sources, nor is there any analysis as 
to why controls are not available.
    (d) West Chandler Site. The West Chandler monitoring site is 
located near the corner of Price and Frye Roads and is bordered on the 
west by agriculture fields (which were idle on April 9, 1995) and the 
right of way for Price Road/Freeway which was under construction in 
early 1995. Plan, Appendix A, p. 4-4. The modeling showed that 
windblown fugitive dust, mainly from agricultural fields and road 
construction (disturbed cleared area), was the largest contributor to 
the April 9, 1995 exceedance. Fugitive dust from vacant lands and 
agricultural aprons was also a significant contributor. Plan, p. 19. 
See also footnote 15 of this notice. All these source categories are 
subject to the RACM requirements in Rule 310 (see footnote 17 of this 
notice). These measures include EPA's suggested RACM for all these 
source category except agricultural fields. General Preamble, Appendix 
C1.
    The BACM enhancements to RACM for these categories are similar to 
those recommended for Gilbert and Maryvale. Plan, p. 28. These types of 
enhancements meet EPA's guidance for BACM by going beyond existing RACM 
controls, expanding the use of RACM controls, and emphasizing 
prevention over remediation.
    (e) PM-10 Precursors. CAA section 189(e) states that the control 
requirements applicable under PM-10 plans for major stationary sources 
of PM-10 are also applicable to major stationary sources of PM-10 
precursors (such as NOX and SOX sources) except 
where EPA determines that such sources do not contribute significantly 
to PM-10 levels. General Preamble at 13541-13542. ``Significant'' is 
not defined in the General Preamble, rather for moderate areas, the 
determination was to be made on a case-by-case basis. General Preamble 
at 13539. For serious areas, a ``significant'' source category is 
defined as one that contributes 5 g/m3 or more of 
PM-10 to a location of expected 24-hour violation. Addendum at 42001. 
For this rulemaking only, EPA is proposing to apply the serious area 
definition to both the RACT and BACT necessity determinations.
    It is clear from the modeling that primary-emitted PM-10 (i.e., 
fugitive dust) is the only significant contributor to the 24-hour PM-10 
exceedances at the four modeled sites. Based on this evidence, EPA is 
proposing to determine under section 189(e) that sources of PM-10 
precursors do not contribute significantly to PM-10 levels which exceed 
the 24-hour standard at the Gilbert, West Chandler, Maryvale, and Salt 
River monitors and therefore no RACM/BACM controls are necessary for 
these sources. This proposed finding applies only to the microscale 
plan and will need to be evaluated again for the full regional plan.
2. RACM/BACM Implementation
    (a) MCESD Rules and Commitments. The primary conclusion of the air 
quality modeling is that the 24-hour PM-10 exceedances at the four 
evaluated sites are related solely to fugitive dust. The eight source 
categories of fugitive dust that were identified as significant (that 
is, had an impact of 5 g/m3 or more) at one or more 
monitoring sites are regulated wholly or in part by MCESD's Rule 310 
(Open Sources of Fugitive Dust). See footnote 17 of this notice. These 
significant source categories are disturbed cleared area, earth moving, 
unpaved parking lots, unpaved roads, industrial haul roads, vacant 
land, agricultural fields, and agricultural aprons.
    (i) Rule 310. Rule 310 was adopted by Maricopa County in 1988, 
substantially revised in 1993, and revised again in 1994. The rule was 
initially submitted to EPA in 1994 as part of the moderate area PM-10 
plan for the Maricopa area, and EPA approved the rule on April 10, 1995 
(60 FR 18010) in conjunction with its approval of the overall moderate 
area plan. This plan's approval was subsequently vacated by the Ninth 
Circuit in Ober. Although the court's opinion did not address the SIP 
approvability of Rule 310, its disposition had the incidental effect of 
also vacating EPA's approval of Rule 310.
    In the 1994 proposed approval of the moderate area plan, EPA found 
that Rule 310 met the CAA's enforceability requirements and proposed to 
approve the rule except for a ``director's discretion'' 
provision.18 59 FR 38402 (July 28, 1994). Several comments 
questioning the enforceability of Rule 310 were received on the 
proposal but none changed EPA's conclusion that the rule was 
enforceable. 60 FR 18018. Neither the rule nor EPA's finding that the 
rule meets the SIP enforceability criteria has changed since that time. 
Therefore EPA is reaffirming its previous finding that Rule 310 meets 
the requirements of CAA sections 110(a)(2)(A) and 172(c)(6) for 
enforceable emission limitations. As a result, EPA is proposing to 
reapprove Rule 310 as an element of the Arizona SIP for the Maricopa 
PM-10 nonattainment area.
---------------------------------------------------------------------------

    \18\ This provision was subsequently deleted from the rule.
---------------------------------------------------------------------------

    Implementation of Rule 310. Rule 310 requires the application of 
reasonably available control measures to open sources of fugitive dust. 
RACM is defined in the rule (section 221) and is detailed on the dust 
control plan checklist and in the Rule 310 handbook ``A Guide for 
Reducing Air Pollution from Construction.'' The microscale plan 
includes revisions to the checklist and handbook to reflect BACM. Plan, 
Appendix E, Bell letter. These revisions include making clear that the 
dust control plan must be implemented throughout the life of the 
project until all roads and disturbed areas are stabilized and that 
watering is required to the depth of an earth moving cut.
    Rule 310 also requires that an earth moving permit be obtained 
prior to

[[Page 31033]]

engaging in any commercial, industrial or institutional earth moving or 
dust generating operation that disturbs a total surface area of 0.10 
acres or more.\19\ Rule 310, section 302 (dust generating operations--
permits required). A dust control plan must be submitted with the 
permit application. Rule 310, section 303 (control plans). Earth moving 
permits must be renewed every year. Rule 200 (Permit Requirements), 
section 305.4. No permit is required for other fugitive dust sources 
regulated by Rule 310 such as unpaved parking lots, unpaved roads, 
vacant lots, agricultural fields, and agricultural aprons.
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    \19\ Maricopa County's interpretation of the prohibition in 
A.R.S. 49-504.4 that county air pollution control agencies cannot 
``prevent [] normal farm cultural practices which cause dust'' has 
effectively exempted agricultural sources from the permit 
requirements of Rule 310. Plan, p. 31.
---------------------------------------------------------------------------

    To help permit applicants develop dust control plans, MCESD has 
developed a general dust control plan or checklist that lists RACM by 
category (e.g., earth moving, disturbed surface areas). Permit 
applicants can simply check off the RACM they will use but must check 
off at least one measure per category. Alternatively, applicants may 
craft their own dust control plans provided they meet the requirements 
of Rule 310. See Plan, p. 34 (revised dust control plan checklist).
    Review of earth moving permit applications and dust control plans 
as well as the inspection of permitted earth moving sites is done 
primarily by the MCESD's Earthmoving/Burn Permit 
Coordinator.20 Inspections are conducted for all projects 
greater than 10 acres in size and smaller operations are inspected 
based on several factors including the compliance history of the 
contractor/developer or complaints. Some inspections are performed by 
the Department's regional offices when time allows. Plan, Appendix B, 
p. 2-5. MCESD inspectors also note earth moving operations when they 
are out in the field and stop to check if the required permit is 
posted. Plan, Appendix G, p. 18. Historically, stationary sources have 
not been inspected for Rule 310 violations even when they have fugitive 
dust sources subject to the rule.21 Plan, Appendix B, p. 2-
5.
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    \20\ During the fall and winter this Coordinator is also 
responsible for implementing the County's residential wood burning 
restriction rule. Given the demonstrated contribution of earth 
moving sources to Maricopa area PM-10 exceedances, MCESD may want to 
re-evaluate splitting the Coordinator's time between the fugitive 
dust and no burn programs.
    \21\ MCESD is addressing the permitting process for stationary 
sources subject to dust control plan requirements in a work flow 
review and analysis of the Department's permitting process. 
Recommendations from this review (such as revised permitting 
procedures) will be implemented in July, 1997. Plan, Appendix E, 
Bell letter. Improved permitting of these sources should result in 
better inspections.
---------------------------------------------------------------------------

    MCESD only inspects sources that do not require permits (such as 
vacant land and unpaved parking lots) on a complaint basis and has no 
proactive inspection or compliance assurance program for these types of 
sources. Plan, p. 12.
    The microscale plan identifies a number of recommended changes to 
improve implementation of Rule 310. MCESD has or will undertake a 
number of internal program modifications to implement these 
recommendations and will lead a regional program to foster interagency 
cooperation to reduce particulate pollution.
    Some of the internal program modifications the Department has 
already made are revising a number of documents that support 
implementation of Rule 310 including the dust control plan, the Rule 
310 handbook, the guideline for earth moving inspection checklist, and 
the standard operating procedures (SOP) for earth moving permit 
application processing and site inspection. In addition, MCESD is 
revising the SOP for air pollution inspection procedures.22 
Plan, Appendix E, Bell letter. Other changes include updating staff 
training on Rule 310 (target completion date: May 31, 1997), initiating 
a weekend inspection program for Rule 310 sources (target date: May, 
1997), and linking the earth moving permit, complaint, and enforcement 
databases to improve access to information on permitted sources (target 
completion date: February, 1998). Plan, Appendix E, Bell letter. A 
complete description of MCESD's commitments can be found in the Plan, 
Appendix E, Bell letter.
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    \22\ EPA recently complete a review of permit files at MCESD. 
One of the focuses of this file review was to evaluate the effect of 
the SOPs on the completeness and quality of inspections. The review 
showed that the SOPs have resulted in more thorough and higher 
quality inspections. Memorandum, Colleen McKaughan to Doug McDaniel, 
``File Review at Maricopa County Environmental Services Department 
April 7-10, 1997'' May 19, 1997 (found in the docket).
---------------------------------------------------------------------------

    Regional Program. MCESD has also committed to a regional program to 
foster interagency cooperation including designating a MCESD staff 
person as a coordinator, holding Rule 310 workshops for cities and 
contractors, creating material on Rule 310 for distributing to City/
County staff and contractors, continuing to conduct workshops in 1997 
on studying and improving the current dust control program, expanding 
public awareness programs for particulate pollution, and publicizing 
MCESD's public complaint line number. The regional program will be 
fully implemented in 1997. A complete description of MCESD's 
commitments can be found in the Plan, Appendix E, Bell letter.
    In total, MCESD's commitments clearly identify the actions required 
and the deadlines for those actions and thus constitute enforceable 
control measures under CAA sections 110(a)(2)(A) and 172(c)(6). EPA, 
therefore, proposes to approve them as elements of the Arizona SIP.
    Resources for Rule 310 Implementation. MCESD will continue to 
implement Rule 310 through a program of reviewing and evaluating dust 
control plans, inspection of sources with earthmoving permits, and 
responding to complaints. The Earthmoving/Burn Permit Coordinator has 
primary responsibility for reviewing dust control plans and inspections 
and is aided in inspections by four dedicated stationary source 
inspectors in the main office. In addition, MCESD has recently hired a 
public involvement coordinator and an assistant to the Earthmoving/Burn 
Permit Coordinator. Finally, the Department's Small Business Assistance 
Program also assists in implementing Rule 310 through outreach and 
compliance assistance. Plan, Appendix E, Bell letter.
    Complaints are handled by the appropriate regional office. Each 
regional office has one supervising inspector and two staff inspectors. 
The regional offices also do earth moving inspections as time allows 
during the summer months. These non-complaint inspections are limited 
to permitted sites from 5 to 10 acres. Plan, Appendix B, pp. 2-4 and 2-
5.
    In all, there are 1.75 full time equivalent (FTE) positions working 
directly on Rule 310 implementation, plus the Department has 19 
inspectors, aides, engineers, and supervisors available to perform 
field observations and respond to complaints. Plan, Appendix E, Bell 
letter. This level of staffing (when combined with the support from the 
rest of the Department's inspection staff) is sufficient to ensure 
implementation of Rule 310 at the level assumed and committed to in the 
microscale plan, that is, a reasonable level of implementation on 
permitted sources but minimal implementation on nonpermitted 
sources.23
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    \23\ The microscale plan only assumes emission reductions from 
sources subject to permitting (e.g., earth moving, disturbed cleared 
areas). No reductions are assumed for nonpermitted sources (e.g., 
vacant lots, unpaved parking). See Plan, pp. 37-40.

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[[Page 31034]]

    (ii) Rules 311 and 316. Individual point sources (e.g., several 
concrete manufacturers and sand and gravel operations) whose emissions 
are accounted for within several of the source categories at the Salt 
River site are also covered by MCESD's Rule 311 (Particulate Matter 
from Process Industries) and Rule 316 (Nonmetallic Mineral Mining and 
Processing). These rules were approved by EPA as RACT for PM-10 sources 
as part of the approval of the moderate area plan. 60 FR 18009. While 
not at issue in the litigation regarding that plan's approval, EPA's 
approval of these rules was also incidently vacated by the Ober 
decision. EPA, therefore, will be restoring its approval of these rules 
in its final action on this proposal.
    (b) City Resolutions. The microscale plan includes resolutions 
adopted by the Cities of Phoenix, Tempe, Chandler, Glendale, 
Scottsdale, and Mesa and the Town of Gilbert (collectively, city or the 
cities). Plan, Appendix E, ``Resolutions Adopted by Various Cities and 
Towns within Maricopa County'' (resolutions). The resolutions commit 
each city to participate in a regional program led by MCESD to foster 
interagency cooperation to reduce particulate pollution. This 
participation requires the city to (1) designate a staff person to 
coordinate the city's participation in the regional dust control 
program, (2) participate in workshops (to be held by MCESD) to study 
current dust control programs and to evaluate options for additional 
efforts, (3) distribute MCESD information on dust control to grading 
and certain building permit applicants, (4) ensure appropriate city 
personnel receive training on Rule 310 requirements, and (5) distribute 
information on particulate pollution to the public. The resolutions do 
not commit the cities to adopt any additional dust control 
requirements.
    The cities will undertake these actions using current staffing and 
funding. Plan, p. 35 and Appendix E, resolutions. Because these actions 
are easily integrated into on-going city activities, these staffing and 
funding levels are adequate to implement the commitments. MCESD has 
complemented the cities' efforts by committing to designate a staff 
person as the regional program coordinator, to hold workshops, develop 
material for distribution, and provide training on Rule 310. Plan, 
Appendix E, Bell letter.
    The commitment to address fugitive dust is an important additional 
step by the cities to help solve Maricopa's PM-10 problem in the long 
term.24 The air quality modeling clearly shows that fugitive 
dust from nonpermitted sources such as vacant lands, unpaved parking 
lots, and unpaved roads are significant contributors to exceedances. 
Given the size of the Maricopa PM-10 nonattainment area and MCESD's 
limited resources, the cities and towns will need to take a more active 
role in reducing fugitive dust from these nonpermitted sources.
---------------------------------------------------------------------------

    \24\ Many of the cities and towns in Maricopa County have 
already committed to undertake other PM-10 control measures such as 
paving unpaved roads. See MAG 1991 Particulate Plan.
---------------------------------------------------------------------------

    The cities' resolutions clearly identify the actions required and 
the deadlines for those actions and thus constitute enforceable 
commitments. As such, EPA proposes to approve them into the Arizona SIP 
for the Maricopa PM-10 nonattainment area.
    (c) Agricultural Sources. As discussed previously, the air quality 
modeling demonstrated that control of fugitive dust from agricultural 
fields and field aprons is necessary for attainment of the 24-hour PM-
10 standard at the Gilbert and West Chandler sites. Rule 310, while 
nominally applicable to agricultural sources, is not in general 
enforced against them. Plan, p. 31. See also footnote 17 of this 
notice. The microscale plan contains no controls for these source 
categories but does include an agreement by ADEQ, MCESD, and the 
federal Natural Resources Conservation Services (NRCS) to develop a 
protocol to address fugitive dust on agricultural land and refine 
roles, objectives and schedule. Plan, p. 36 and Appendix E, ``Agreement 
of ADEQ, U.S. NRCS, and MCESD'' (NRCS agreement).
    EPA appreciates the agreement of the three agencies to develop a 
protocol to address fugitive dust from agricultural sources and fully 
supports this effort. However, given the impact of these sources on PM-
10 levels in the Maricopa area, it is important that the protocol and 
the work that follows it are focused on getting appropriate RACM and 
BACM measures in place by the applicable deadlines.
    (d) Proposed Finding on RACM/BACM Implementation. There are eight 
source categories of fugitive dust identified in the microscale plan as 
significant at one or more monitoring sites: disturbed cleared area, 
earth moving, unpaved parking lots, unpaved roads, industrial haul 
roads, vacant land, agricultural field aprons, and agricultural 
fields.25 Plan, pp. 17-19. These sources divide into three 
categories. In the first category are sources subject to permitting: 
disturbed cleared areas, earth moving, and industrial haul 
roads.26 In the second category are sources that are not 
subject to permitting (i.e., nonpermitted sources): unpaved parking 
lots, unpaved roads, and vacant land. Finally, in the third category 
are the two sources that are essentially unregulated by Rule 310: 
agricultural fields and agricultural aprons.
---------------------------------------------------------------------------

    \25\ As noted previously (footnote 15), there may be other 
significant sources impacting the monitors that were not identified 
in the microscale modeling because they formed part of the 
background concentration.
    \26\ Haul roads are considered permitted sources in the 
microscale plan because, at the Salt River site where this category 
was significant, the haul roads are located on permitted sources.
---------------------------------------------------------------------------

    As discussed above, MCESD has an adequate implementation strategy 
for dealing with permitted sources including review and approval of 
dust control plans and proactive inspections and has sufficient 
resources to carry out that strategy. The Department adopted Rule 310 
in 1994 and is already implementing and improving the program. Plan, 
pp. 7-13 and 32-33. The BACM improvements to the Rule 310 program and 
the other commitments in the microscale plan will all be fully 
implemented within one year of submittal of the final plan, with many 
being implemented within one or two months. Plan, pp. 32-33. EPA, 
therefore, is proposing to find that the microscale plan assures 
implementation of RACM as soon as possible and BACM by December 10, 
2000 as required by CAA sections 189(a)(1)(C) and 189(b)(1)(B) for the 
significant source categories of: disturbed cleared areas, earth 
moving, and industrial haul roads. EPA is proposing to approve the 
RACM/BACM demonstrations for these source categories.
    For nonpermitted sources, MCESD seeks compliance with Rule 310 only 
when complaints are received. MCESD has adopted RACM controls for these 
sources in Rule 310 and is committed along with the seven cities to 
evaluate options to reduce particulate from vacant lands, unpaved 
roads, and unpaved parking areas. Plan, Appendix E, Bell Letter. The 
microscale plan, however, contains no commitments to assure RACM/BACM 
will be implemented for these sources at a meaningful level nor any 
analysis as to why RACM or BACM implementation on these sources is 
infeasible. As a result, the microscale plan does not claim any credit 
in the attainment demonstrations for these nonpermitted sources. Plan, 
pp. 37-40. EPA, therefore, is proposing to find that the microscale 
plan does not assure implementation of

[[Page 31035]]

either RACM or BACM as required by CAA sections 189(a)(1)(C) and 
189(b)(1)(B) and to disapprove the RACM/BACM demonstrations for the 
unpaved parking lots, unpaved roads, and vacant land source categories.
    As discussed previously, there are currently no effective controls 
on agricultural sources in the Maricopa area. The microscale plan 
provides for the development of a partnership to identify appropriate 
controls but does not contain any actual controls nor is there any 
analysis as to why RACM/BACM implementation on these sources is 
infeasible. EPA is, therefore, proposing to find that the microscale 
plan does not assure implementation of either RACM or BACM as required 
by CAA sections 189(a)(1)(C) and 189(b)(1)(B) and to disapprove the 
RACM/BACM demonstrations for these sources.
    These proposed findings are applicable only to the microscale plan 
and thus, if finalized, will not constitute EPA's final decision as to 
the State's full compliance with the requirements of CAA sections 
189(a)(1)(C) and 189(b)(1)(B) for RACM and BACM for the eight source 
categories. The State will need to re-evaluate appropriate RACM and 
BACM for these sources in the full regional plan.

C. Evaluation of Attainment and RFP Demonstrations

1. Salt River Site
    As discussed above, attainment of the 24-hour PM-10 standard at the 
Salt River site requires additional controls for earth moving 
activities, specifically watering to the depth of the cut or other 
equivalent techniques, in addition to the existing control provided by 
Rule 310. Plan, p. 37. These earth moving activities are subject to 
permitting under Rule 310. MCESD will revise its dust control plan 
checklist to clarify the earth moving requirement in May, 1997, and 
will begin including the requirement in all new earth moving permits 
and permit renewals by June 1, 1997. Plan, Appendix E, Bell letter. 
Permit renewals are required annually, thus full implementation will 
occur within one year of the submittal of the final plan. Plan, p. 38.
    Attainment is predicted based on acceptable air quality modeling. 
EPA will be restoring its approval of Rules 311 and 316. EPA is also 
proposing to reapprove Rule 310 and to approve the additional controls 
assumed in the attainment demonstration. Finally, EPA is also proposing 
to find that MCESD has adequate resources, personnel, and authority to 
assure implementation of the measures required for attainment at this 
site. EPA is, therefore, proposing to approve the attainment 
demonstration at the Salt River monitor pursuant to CAA sections 
189(a)(1)(B) and 189(b)(1)(A).
    Reasonable further progress is defined in CAA section 171(1) as 
``such annual incremental reductions in emissions of the relevant air 
pollutant as * * * may be reasonably be required by the Administrator 
for the purposes of ensuring attainment of the applicable [NAAQS].'' 
Because attainment will occur within one year of final plan submittal, 
the RFP and attainment demonstrations at this monitor are the same; 
that is the annual increment needed for progress toward attainment is 
the same as the emission reduction needed for attainment. Therefore, 
EPA is proposing to approve the RFP demonstration at this monitor 
pursuant to CAA section 189(c).
2. The Maryvale Site
    Attainment of the 24-hour PM-10 standard at the Maryvale site 
requires stabilization of disturbed cleared areas at all times. Plan, 
p. 38. Disturbed cleared areas is a source category subject to 
permitting under Rule 310. MCESD has revised its dust control plan 
checklist for Rule 310 to clarify the requirement to stabilize all 
disturbed areas at all times and will begin including the requirement 
in all new earth moving permits and permit renewals by June 1, 1997. 
Plan, Appendix E, Bell letter. Permit renewals are required annually, 
thus full implementation and attainment will occur within one year of 
the submittal of the final plan. Plan, p. 38.
    Attainment is predicted based on acceptable air quality modeling. 
EPA is proposing to reapprove Rule 310 and to approve the additional 
controls assumed in the attainment demonstration. Finally, EPA is 
proposing to find that MCESD has adequate resources, personnel, and 
authority to assure implementation of the measures to the extent 
required for attainment at this site. EPA is, therefore, proposing to 
approve the attainment demonstration at the Maryvale monitor pursuant 
to CAA sections 189(a)(1)(B) and 189(b)(1)(A).
    Because attainment will occur within one year of final plan 
submittal, the RFP and attainment demonstrations at this monitor are 
essentially the same; that is the annual increment needed for progress 
toward attainment is the same as the emission reductions needed for 
attainment. Therefore, EPA is proposing to approve the RFP 
demonstration at this monitor pursuant to CAA section 189(c).
3. The Gilbert Site
    The microscale plan does not demonstrate attainment or RFP at the 
Gilbert site because of uncontrolled fugitive dust emissions from 
agricultural aprons and unpaved parking lots. Plan, p. 38. As noted 
before, the microscale plan does include strategies to evaluate 
controls on these sources but, at this time, does not assure 
implementation of controls for them. EPA is, therefore, proposing to 
disapprove the attainment and RFP demonstrations for this site.
4. The West Chandler Site
    The microscale plan does not demonstrate attainment or RFP for the 
West Chandler site because of uncontrolled fugitive dust emissions from 
agricultural fields and aprons and vacant land. Plan, p. 39. As noted 
before, the microscale plan does include strategies to evaluate 
controls on these sources but, at this time, does not assure 
implementation of controls for them. EPA is, therefore, proposing to 
disapprove the attainment and RFP demonstrations for this site.
    These proposed approvals and disapprovals are applicable only to 
the microscale plan and thus, if finalized, will not constitute EPA's 
final decision as to the State's full compliance with the requirements 
of CAA sections 189(a)(1)(B), 189(b)(1)(A) and 189(c)(1) for attainment 
and RFP demonstrations at the Salt River, Maryvale, Gilbert and West 
Chandler monitoring sites. Because regional factors may influence 
attainment at these sites, the State will need to re-evaluate modeling 
at all four sites as part of the full regional plan.

D. General SIP Requirements

1. Section 110(l) Finding
    CAA section 110(l) states that the ``Administrator shall not 
approve a revision of a plan if the revision would interfere with any 
applicable requirement concerning attainment and reasonable further 
progress * * * or any other applicable requirement of this Act.''
    Pursuant to section 110(l) of the Act, EPA proposes to find that 
its proposed partial approval of the microscale plan does not interfere 
with any other requirements of the Act applicable to the Maricopa PM-10 
nonattainment area including the requirements for attainment and RFP. 
In fact, the control measures and commitments in the plan are essential 
elements in the demonstrations of attainment and RFP for the area for 
the 24-hour PM-10

[[Page 31036]]

NAAQS and partially meet the statutory requirement for the adoption and 
implementation of RACM and BACM.
2. Adequate Personnel, Funding, and Authority
    Section 110(a)(2)(E)(i) of the Clean Air Act requires that 
implementation plans 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 (51.230-232) 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.
    Adequate Personnel and Funding. For Rule 310, the microscale plan 
reflects MCESD's current bifurcated implementation strategy of 
proactive compliance and enforcement on permitted sources and reactive 
enforcement on nonpermitted sources. This implementation strategy is 
assumed in the attainment demonstrations in which emission reductions 
are assumed only from permitted sources and not from nonpermitted 
sources. Plan, pp. 37-40. MCESD's available resources (both personnel 
and funding) for carrying out this bifurcated strategy for Rule 310 and 
its other commitments are discussed above and are adequate. MCESD 
expects to maintain this level of resource commitment over the next 
five years of plan implementation. Plan, p. 33.
    The cities' resources for implementing their respective commitments 
are also discussed above and are adequate. Each agency is expected to 
maintain this level of resource commitment over the next five years of 
plan implementation. Plan, pp. 35 and 36.
    Adequate Legal Authority. The primary implementing agency of the 
controls in the microscale plan is the County of Maricopa through its 
Environmental Services Department. A.R.S. 49-479 provides that the 
board of supervisors ``shall adopt such rules as it determines are 
necessary and feasible to control release into the atmosphere of air 
contaminants. * * *'' A.R.S. 49-476.01 provides the County control 
officer the authority to require sources to monitor, sample, or 
otherwise quantify their emissions and the board of supervisors the 
authority to adopt rules for source monitoring, sampling, etc. These 
sections provide the County and MCESD with sufficient authority under 
State law to adopt and enforce the proposed control measures and to 
obtain the information necessary to determine compliance.
    Legal authority for the cities to adopt and implement their 
resolutions are described in the microscale plan on pp. 35-36 and 
appears to be adequate.
    These proposed findings regarding adequate authority and resources 
are applicable only to the control strategy and commitments as 
submitted in the microscale plan.
3. Description of Enforcement Methods
    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.
    Procedures for monitoring compliance (i.e., the inspection 
strategy) with Rule 310 are discussed in the section on MCESD 
commitments above. MCESD is the designated agency for enforcing Rule 
310. See legal authority section above.
    MCESD has developed an Air Enforcement Policy (April 4, 1997). A 
summary of this strategy can be found in the microscale plan, Appendix 
E, Bell letter. Currently, the Department issues Notices of Violations 
(NOVs) whenever violations of rules are observed (Plan, p. 12) and will 
continue to do so. Orders of abatement will be issued after NOVs when 
compliance is not attainable within a reasonable time frame. Additional 
enforcement actions may be initiated based on several factors including 
actual or significant potential harm or willful noncompliance. The 
additional actions include filing criminal or civil complaints. 
Appropriate monetary penalties will be sought for criminal or civil 
complaints and the Department encourages Environmental Community Action 
Projects as part of settlements. Plan, Appendix E, Bell letter.
    EPA has also encouraged MCESD to take more enforcement actions with 
monetary penalties in order to make clear to the regulated community 
that compliance with Rule 310 should be a priority and to develop a 
system for tracking the number of NOVs and monetary penalties. See 
letter, Frances Wicher, EPA, to Joe Gibbs, ADEQ, April 30, 1997 (found 
in the Plan, Appendix D). In all, the Department's Air Enforcement 
Policy is adequate to meet the requirements of 40 CFR 51.111(a) and CAA 
section 110(a)(2)(C).

III. Summary of Proposed Action

A. Proposed Approvals and Disapprovals
    For the reasons discussed above, EPA is proposing to approve:
    (1) Under sections 172(c)(1), 189(a)(1)(C) and 189(b)(1)(B), the 
provisions for implementing RACM and BACM for the significant source 
categories of disturbed cleared areas, earth moving, and industrial 
haul roads; and
    (2) Under sections 189(a)(1)(B), 189(b)(1)(A), and 189(c), the 
attainment and RFP demonstrations for the Maryvale and Salt River 
sites.
    For the reasons discussed above, EPA is proposing to disapprove:
    (1) Under sections 172(c)(1), 189(a)(1)(C) and 189(b)(1)(B), the 
provisions for implementing RACM and BACM for the significant source 
categories of agricultural fields, agricultural aprons, vacant lands, 
unpaved parking lots, and unpaved roads; and
    (2) Under sections 189(a)(1)(B), 189(b)(1)(A), and 189(c)(1), the 
attainment and RFP demonstrations at the West Chandler and Gilbert 
sites.
    Finally, EPA is proposing to find that the microscale plan (1) 
provides the necessary assurances that the state and local agencies 
have adequate personnel, funding and authority under state law to carry 
out the submitted microscale plan, and (2) includes an adequate 
enforcement program, as required by CAA sections 110(a)(2)(E)(i) and 
110(a)(2)(C).
B. Consequences of the Proposed Disapprovals
    As noted before, EPA required submittal of a microscale plan 
meeting both the moderate and serious area requirements for the 24-hour 
PM-10 standard by May 9, 1997 and a full regional plan meeting those 
requirements for both the 24-hour and annual standards by December 10, 
1997. The microscale and regional plans taken together would satisfy 
both the moderate area requirements for the 24-hour standard mandated 
by the Ninth Circuit in Ober and the serious area planning requirements 
for both standards. The subject of this proposed action is the 
microscale plan only; the full regional plan is not due until late 
1997. It is, therefore, premature to

[[Page 31037]]

determine if the microscale plan, in and of itself, fully complies with 
the Clean Air Act requirements for moderate and serious PM-10 
nonattainment areas. Such a determination is not possible until the 
regional plan is submitted and reviewed.
    Because the microscale plan taken alone is not intended to fully 
comply with the RACM/BACM implementation, reasonable further progress 
and attainment demonstration requirements of the Clean Air Act, final 
disapprovals of portions of the microscale plan would not trigger 
sanctions under CAA section 179(a). CAA section 179(a) requires the 
imposition of one of the sanctions in section 179(b) within 18 months 
of a disapproval if EPA ``disapproves a [State] submission * * * based 
on the submission's failure to meet one or more of the elements 
required by [the CAA].'' Because the purpose of the microscale plan was 
to, in effect, provide a down payment towards meeting certain 
requirements of the Act, EPA is not, at this time, proposing to find 
that the State has failed to meet any of the applicable elements 
required by the CAA as contemplated by section 179(a).
    EPA is subject to the terms of a consent decree approved by the 
U.S. District Court for the District of Arizona on March 25, 1997. Ober 
v. Browner, No. CIV 94-1318 PHX PGR. The consent decree obligates EPA 
to propose a federal implementation plan (FIP) for PM-10 in the 
Maricopa nonattainment area by March 20, 1998 and finalize that FIP by 
July 18, 1998 27 if the Agency disapproves all or part of 
the microscale plan. Therefore, if EPA finalizes the proposed 
disapprovals described above, EPA will have an obligation to promulgate 
a regional moderate area PM-10 FIP that addresses the statutory 
requirements for attainment, RACM and RFP. Under the consent decree, 
the scope of this FIP obligation is reduced to the extent that EPA 
approves by July 18, 1998 SIP provisions meeting the statutory 
requirements for RACM, RFP and attainment for moderate PM-10 
nonattainment areas.
---------------------------------------------------------------------------

    \27\ The FIP deadlines each advance 2 months if EPA fails to act 
on the microscale plan by July 18, 1997.
---------------------------------------------------------------------------

    EPA believes, as is expressed in CAA section 101(a), that air 
pollution control is primarily the responsibility of states and local 
jurisdictions. Therefore, the Agency will work with the State of 
Arizona and the local agencies and jurisdictions responsible for PM-10 
planning and control in Maricopa County to develop SIP provisions that 
can reduce the scope of, or eliminate, any potential FIP. Considerable 
work is already underway or planned in the area to address the PM-10 
problem. As noted before, the full serious area regional PM-10 plan is 
due December 10, 1997. In addition, the microscale plan contains two 
initiatives, MCESD's regional program to address controls on 
nonpermitted sources and the ADEQ/MCESD/NRCS agreement to address 
fugitive dust from agricultural sources, that are targeted at 
significant but currently uncontrolled sources of PM-10.

IV. Administrative Requirements

A. Executive Order 12866

    This action has been classified as a Table 3 action for signature 
by the Regional Administrator under the procedures published in the 
Federal Register on January 19, 1989 (54 FR 2214-2225), as revised by a 
July 10, 1995 memorandum from Mary Nichols, Assistant Administrator for 
Air and Radiation. The Office of Management and Budget (OMB) has 
exempted this regulatory action from E.O. 12866 review.

B. Regulatory Flexibility Act

    Under the Regulatory Flexibility Act, 5 U.S.C. Sec. 600 et seq., 
EPA must prepare a regulatory flexibility analysis assessing the impact 
of any proposed or final rule on small entities. 5 U.S.C. Secs. 603 and 
604. Alternatively, EPA may certify that the rule will not have a 
significant impact on a substantial number of small entities. Small 
entities include small businesses, small not-for-profit enterprises, 
and government entities with jurisdiction over populations of less than 
50,000.
    SIP approvals under sections 110 and 301, and subchapter I, part D 
of the CAA do not create any new requirements but simply act on 
requirements that the State is already imposing. Therefore, because the 
Federal SIP approval does not impose any new requirements, I certify 
that it does not have a significant impact on any small entities 
affected. Moreover, due to the nature of the Federal-State relationship 
under the CAA, preparation of a flexibility analysis would constitute 
Federal inquiry into the economic reasonableness of State action. The 
Clean Air Act forbids EPA to base its action concerning SIPs on such 
grounds. Union Electric Co. v. U.S. EPA, 427 U.S. 246, 255-66 (1976); 
42 U.S.C. Sec. 7410(a)(2).

C. Unfunded Mandates

    Under section 202 of the Unfunded Mandates Reform Act of 1995 
(``Unfunded Mandates Act''), signed into law on March 22, 1995, EPA 
must prepare a budgetary impact statement to accompany any proposed or 
final rule that includes a Federal mandate that may result in estimated 
costs to State, local, or tribal governments in the aggregate; or to 
private sector, of $100 million or more. Under section 205, EPA must 
select the most cost-effective and least burdensome alternative that 
achieves the objectives of the rule and is consistent with statutory 
requirements. Section 203 requires EPA to establish a plan for 
informing and advising any small governments that may be significantly 
or uniquely impacted by the rule.
    EPA has determined that the approval/disapproval action proposed 
does not include a Federal mandate that may result in estimated costs 
of $100 million or more to either State, local, or tribal governments 
in the aggregate, or to the private sector. This Federal action 
approves pre-existing requirements under State or local law, and 
imposes no new Federal requirements. Accordingly, no additional costs 
to State, local, or tribal governments, or to the private sector, 
result from this action.

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Particulate 
matter, Incorporation by reference.

    Authority: 42 U.S.C. 7401.

    Dated: May 29, 1997.
Felicia Marcus,
Regional Administrator.
[FR Doc. 97-14848 Filed 6-5-97; 8:45 am]
BILLING CODE 6560-50-P