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

ENVIRONMENTAL PROTECTION

AGENCY

40 CFR Part 52 [AZ092-002; FRL-7067-5]
Approval and Promulgation of Implementation Plans; ArizonaMaricopa County PM-10 Nonattainment Area; Serious Area Plan for Attainment ofthe 24-Hour PM-10 Standard and Contingency Measures
AGENCY: Environmental Protection Agency (EPA). ACTION: Proposed rule.

SUMMARY: EPAproposes to approve provisions ofthe RevisedMAG 1999 Serious AreaParticulate Plan forPM-10 fortheMaricopaCounty(Phoenix) Nonattainment Area,February 2000, including the revisions submitted in June 2001 that address attainment ofthe 24-hour PM-10 national ambient air quality standard. We also propose to grant Arizona's request to extend the Clean Air Act deadline for attaining the 24-hour PM-10 standard in the Phoenix

area from 2001 to 2006. Finally, we propose to find thatthe plan provides for the implementation ofcontingency

measures for both the 24-hour and annual PM-10 standards and to make several revisions to our previous proposal on the MAG plan's provisions for the annual standard and our proposed policy on attainment date extensions for serious PM-10 nonattainment areas. DATES: Comments on this proposal must be received in writingby November 1, 2001. Comments should be addressed to the contact listed below. ADDRESSES: Comments should be mailed to: Frances Wicher, Office ofAir Planning (AIR-2), EPARegion 9, 75 Hawthorne Street, San Francisco, CA 94105-3901.

A copy ofdocket No. AZ-MA-00- 001, containing the EPA technical support document (EPATSD) and other material relevant to this proposed action, is available for public inspection
atEPA's Region 9 office during normal business hours.

A copy ofthe docket is also available for inspection at: Arizona Department ofEnvironmental Quality, Library, 3033 N. Central Avenue, Phoenix, Arizona 85012. (602) 207-2217 Maricopa Association ofGovernments, 302 North 1st Street, Phoenix, Arizona 85003. (602) 254-6300

Electronic Availability
This document andthe Technical SupportDocument (TSD) are also available as electronic files on EPA's Region 9 Web Page athttp:// www.epa.gov/region09/air.
FOR FURTHER INFORMATION CONTACT: Frances Wicher, Office ofAir Planning (AIR-2),U.S. Environmental Protection Agency, Region 9, 75 Hawthorne Street, SanFrancisco, California 94105. (415) 744-1248, email: wicher.frances@epa.gov.

SUPPLEMENTARY INFORMATION:
Table ofContents
I. Summary ofToday's Proposals II.Background to Today's Proposals

A. PM-10 Air Quality in the Phoenix Area B.Description ofthe MAG Plan's

Provisions for Attaining the 24-Hour PM-10 Standard C.Previous Actions on thePhoenix Serious

Area PM-10 Plan 1.Annual Standard Proposal 2.Microscale PlanPartial Approval/Partial

Disapproval 3.Arizona's Agricultural BMP General

Permit Rule Approval III. The CAA's Planning Requirements for SeriousPM-10 Nonattainment Areas IV. The MAG Plan's Compliance withthe CAA's Requirements for Serious PM-10 Nonattainment Areas A. Completeness ofthe SIP Submittals B.Adequacy oftheTransportation

Conformity Budget C.Emissions Inventory D.Adequate Monitoring Network E. Contribution toPM-10 Exceedances of

Major Sources ofPM-10 Precursors F. Implementation ofReasonably Available

andBest Available ControlMeasures 1.Steps 1and 2: Determination of

significant sources 2.Step 3: Identification ofpotential BACM 3.Step 4: Implementation ofRACM and

BACM and inclusion ofMSM for each significant source category

a. Technology controls for on-roadmotor

vehicle exhaust b. Transportation control measures (TCMs)

for on-road motorvehicle exhaust and paved road dust

c.Nonroad engines d.Pavedroad dust

e.Unpavedparking lots I. Disturbed vacant lands g.Unpavedroads h. Construction sites and activities i. Agricultural sources j.Residential wood combustion k. Secondary ammonium nitrate 1.MCESD's commitments to improve

compliance and enforcement ofits fugitive dustrules G. Attainment DateExtension 1.Apply foran extension 2.Demonstrate theimpracticability of

attainment byDecember 31, 2001 3.Complied with the commitments and

requirements in the SIP 4. Include themost stringent measures 5.Demonstrate expeditious attainment

a. Airquality modeling b. Control measures relied on for

attainment 6. Otherfactors that EPA may consider

a. Nature and extent ofnonattainment b. Types and number ofsources or other

emitting activities

c. Population exposure to concentrations

above the standard d. Presence and concentration of

potentially toxic substances in the particulate

e. Technological and economic feasibility

ofcontrols 7. Conclusion on the extension request H.Reasonable Further Progress and

Quantitative Milestones 1.Reasonable further progress 2. Quantitative milestones I. Contingency Measures J. General SIP Requirements V. CAA Requirements forBACM and Attainment Date Extension and EPA's Guidance on Meeting these Requirements A. Implementation ofBest Available

ControlMeasures B. Extension ofthe Attainment Date

beyond 2001 1.Apply for an attainment date extension 2. Demonstrate that attainment by 2001 is

impracticable 3. Complied with allrequirements and

commitments in its implementation plan 4.Demonstrate the inclusion ofthe most

stringent measures 5. Demonstrate attainment by the most

expeditious alternative date practicable VI. Administrative Requirements

I. Summary ofToday's Proposals

First, we propose to approve the provisions in the RevisedMAG 1999 SeriousAreaParticulate Plan forPM-I0 fortheMaricopaCountyNonattainment Area,February 2000, ("MAG plan") including revisions to that plan submitted inMaricopaCountyPM-I0 SeriousArea StateImplementationPlan Revision,AgriculturalBestManagement Practices, June 2001, (collectively, "the Maricopa County serious area plan" or "the plan") that address attainment of the 24-hour PM-10 standard.' Our proposed actions are based on our initial determination thatthe Maricopa County serious area plan complies with the Clean Air Act's (CAA)requirements for serious PM-10 nonattainment area plans.

Specifically, we propose to approve the following elements ofthe plan as they pertain to the 24-hour standard:

* The demonstration that the plan provides for implementation of reasonably available control measures (RACM) and best available control

measures (BACM),

1Thereare two separate national ambient air quality standards for PM-10, an annual standardd of50pg/m 3 and a 24-hour standard of150 ig/m 3

. Weproposed approval ofthe MAG plan's annual standard provisions on April 13, 2000 at 65 FR 19964. 

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* The demonstration that attainment by the CAA deadline ofDecember 31, 2001 isimpracticable,

* The demonstration that attainment will occur bythe mostexpeditious alternative date practicable, in this case, December 31, 2006,

* The demonstration that the plan provides for reasonable further progress and quantitative milestones,

* The demonstration that major

sources ofPM-10 precursors such as nitrogen oxides and sulfur dioxide do
not contribute significantly to air quality standard violations, and

* The transportation conformity budget.

Second, we are proposing to grant Arizona's request to extend the attainment date for the 24-hour PM-10 standard from December 31, 2001 to December 31, 2006. We make this proposal based on our determination that the State has met the CAA's criteria for granting such extensions.

Third, we propose to find thatthe plan provides for the implementation of contingency measures for both the 24- hour and annual standards as required by the CAA.

Finally, we make several revisions to

our April 13, 2000 proposed approval of the annual standard provisions in the Maricopa County serious area plan. These revisions involve:

* Clarifications to our proposed policy on granting attainment date extensions under CAA section 188(e),

* Changes to Maricopa County Environmental Services Department's (MCESD) commitments tofurther improve its fugitive dustrule, Rule 310,

* Changes to several other control
measures, and

* Evaluation ofthe plan's compliance with the BACM requirement and most stringent measure requirement in CAA section 188(e) for the agriculture source category based on the State's Agricultural Best Management Practices General Permit Rule.2

This preamble describes our proposed actions onthe Phoenix area plan and provides a summary ofour evaluation of the plan. Our detailed evaluation ofthe plan can be found in the technical support document that accompanies this proposal. See "Technical Support Document, Notice ofProposed Rulemaking on the Serious Area PM-10 State Implementation Plan for the Maricopa County PM-10 Nonattainment Area Provisions for Attaining the 24- Hour Standard and Contingency Measures," September 14, 2001 (EPA

2Except for these limitednumber ofrevisions, we
are notreopening the comment periodand arenot soliciting comments onour April 13, 2000 proposal. TSD). The EPATSD is an integral part ofthis proposal and should be reviewed prior to making comments. A copy of the EPATSD can be downloaded from

our website or obtained by calling or writing the contact person listed above.

II. Background toToday's Proposals

A. PM-10Air Qualityin thePhoenix Area

The Maricopa County (Phoenix)PM10 nonattainment area is located in the
eastern portion ofMaricopa County and
encompasses the cities ofPhoenix, Mesa, Scottsdale, Tempe, Chandler, Glendale as well as 17 other jurisdictions and considerable unincorporated County lands. 340 CFR 81.303. The area ishome to almost 3 million people.

The area violates both the annual and 24-hour PM-10 standards. In 1990, the

area was designated nonattainment for PM-10 and classified as moderate. In 1996, because ofcontinuing violations ofboth PM-10 standards, the area was reclassified to serious andrequired to submit a serious area plan byDecember 10, 1997. 61 FR 21372 (May 10, 1996).

The principal contributors to elevated PM-10 levels in the Phoenix area are fugitive dust sources such as construction sites, unpaved roads,
vacant lots, agricultural sources, and paved road dust. Also contributing to the PM-10 problem, but to amuch lesser degree than fugitive dust, are internal and external combustion

sources including directly-emitted PM10 from automobiles, trucks, construction equipment, buses, residential woodburning and industrial, commercial, and residential use of natural gas and fuel oil. See MAG plan, p. 3-5.

There is along and complex history
to PM-10 air quality planning in the Phoenix area. A summary ofthis history

canbe found in the annual standard proposal at 65 FR 19964, 19965. A more detailed history can be found in section 1ofthe EPATSD.

B. DescriptionoftheMAG Plan's Provisions forAttainingthe24-Hour PM-JOStandard

Arizona has made several submittals
to address the CAA requirements for serious PM-10 nonattainment area plans for the Phoenix area. The provisions for attainming the 24-hour PM-10 standard arefound mainly in three ofthese submittals: the 1997

3TheMaaricopa nonattainment area also includes the town ofApache Junction inPinal County. Apache Junction is covered by a separate air quality plan and willbe addressed in a later action. Microscale plan,4the 2000 MAG plan, and the 2001 BestManagement Practices (BMP) submittal.5The latter
two documents are the subject ofthis proposal and are described in more detail below. We have already acted on the Microscale plan, see 62 FR 41856 (August4, 1997). We describe this plan and explain itsrelationship to today's proposal in the next section.

The first submittal is the Revised Maricopa AssociationofGovernments 1999 SeriousAreaParticulate Plan for PM-10fortheMaricopaCounty Nonattainment Area,February 2000. Thisplan was developed by the Maricopa Association ofGovernments (MAG), the lead air quality planning agency in Maricopa County. The Arizona Department ofEnvironmental Quality (ADEQ) submitted this plan as

a revision to the Arizona State Implementation Plan (SIP) onFebruary 16, 2000. We refer tothis plan in this document as the MAGplan orthe revised MAGplan; however, we occasionally use these terms to refer to the set ofdocuments that collectively comprise the Maricopa County serious

area PM-10 plan.

The second document is theMaricopa CountyPM-IOSerious Area State ImplementationPlanRevision, AgriculturalBestManagement Practices, (BMP) June 2001, submitted in draft onApril 26, 2001 andfinal on June 13, 2001. This SIP revision was developed byADEQ. We refer to this submittal as the BMP TSD.

The MAGplan contains a 1994 inventory and uses the urban airshed model/limited chemistry version (UAM/ LC) to model regional air quality in 1995

as abase year and in 2006 asthe attainment year forboth the annual and 24-hour standards. The MAGplan, however, relies primarily on air quality modeling performed in the Microscale planto evaluate localized 24-hour exceedances.

The MAGplan, as revised by the BMP TSD, includes a BACM analysis and a demonstration that attainment by 2001 is impracticable for both the 24-hour and annual PM-10 standards. It also

4The 1997 Microscale plan is the Plan for Attainmentofthe24-hourPM-10StandardMaricopaCountyPM-10Nonattainment Area, Arizona Department ofEnvironmental Quality, May, 1997.

5The other submittals contain rules and other control measures relied on to provide for RACM, BACM, reasonable further progress an attainment. Thesesubmittals include the commitments by local jurisdictions to PM-10 control measures submitted inDecember 1997, revised MCESD Rules 310 and 310.01 submitted in March 2000, Maricopa County's Residential Wood Burning Ordinance submitted inJanuary 2000, and the Agricultural BestManagement Practices (BMP) General Permit Rule submitted in July 2000. 50253

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includes, again for both PM-10 standards, the State's request for a fiveyear extension ofthe attainment date, a demonstration thatthe plan includes for the most stringent measures found in other states' plans, and a demonstration ofattainment by December 31, 2006.

The BMP TSD updates the MAG plan
to reflect the State's adoption ofthe Agricultural General Permit rule to control PM-10 from agricultural sources in Maricopa County. Itincludes a background document which provides the BACM demonstration for agricultural sources for both standards,

arevised demonstration of attainment andreasonable further progress (RFP) for the 24-hour standard at two monitoring sites, and revisions to the contingency measure provisions for both standards. It also includes documentation quantifying emission reductions from the Agricultural General Permit rule and documentation related to implementing this rule.

C.PreviousActions on thePhoenix Serious AreaPM-IOPlan

We have taken three actions related to the Phoenix Serious Area PM-10 plan: the proposed approval ofthe MAG plan's provisions for the annual standard, the partial approval/ partial disapproval ofthe 1997 Microscale plan, and the approval ofArizona's Agricultural BMP General Permit rule. With today's proposal, we have now proposed action on all elements ofthe Maricopa County serious area PM-10 plan.

1.Annual Standard Proposal

On April 13, 2000, we proposed to approve the MAGplan's provisions for attainment ofthe annual PM-10 standard. See 65 FR 19964.6 Specifically, we proposed to approve for the annual standard the provisions for implementation ofRACM andBACM, the demonstration that attainment by 2001 isimpracticable, the demonstration that attainment will

occur bythe mostexpeditious alternative date, the RFP demonstration, the quantitative milestones, and the conformity budget. We alsoproposed to grant an extension ofthe attainment date from 2001 to 2006based on our proposed determination that Arizona

6In the annual standard propsoal and in theEPA
TSD for today's proposal, we discuss the legal basis for separating the proposed approvals for the 24- hour and annual standards and the practical

reasons we chose to do so. See 65 FR 19964, 19969 and section 3 ofthe EPA TSD. We intent, however,
to finalizeactions on both standards in a single rulemaking inearly 2002. had met the CAA criteria for granting such an extension.

In April 2000 preamble, we also proposed to approve thebase year regional emissions inventory required by CAA section 172(c)(3), MCESD's Rules 310 and 310.01, Maricopa County's Residential Woodburning Ordinance, and the commitments by the cities, towns, andCounty ofMaricopa, ADEQ, MAG, and other State and local agencies to implement various PM-10 control measures. These proposals were applicable toboth the annual and 24- hour PM-10 standards andthus are not being repeated today.

2.Microscale Plan Partial Approval/ Partial Disapproval

The attainment demonstration for the 24-hour standard in the Maricopa County serious area plan hasboth a local modeling component and a regional modeling component. Portions ofthe local or microscale component are found in the Microscale plan, the 2000 MAG plan, andthe BMP TSD. The regional component is contained completely within the 2000 MAG plan.

Most ofthe technical evaluation for the microscale component is contained in the Microscale plan which was submittedto us in May 1997. It evaluates exceedances ofthe 24-hour PM-10 standard atfour Phoenix area monitoring sites: Salt River, Maryvale, Gilbert, and West Chandler.

This evaluation involved developing local, day-specific inventories and dispersion modeling to determine

source contributions to exceedances at each site. The evaluation showed that the primary contributors to 24-hour exceedances in the Phoenix area are local fugitive dust sources such as construction sites, agricultural fields and aprons, vacant lots, unpaved roads andparking lots, and earthmoving operations. The Microscale plan also described the type of controls necessary to show attainment at each site although the plan only assured the implementation of such controls on construction-related sources.

We approved the Microscale plan in part and disapproved it in part on August 4, 1997 (62 FR 41856). We approved the attainment andRFP demonstrations for the Salt River and Maryvale sitesbecause the plan demonstrated expeditious attainment at these sites; however, we disapproved these demonstrations for the West Chandler and Gilbert sites because the plan did not demonstrate attainment at them. Because attainment demonstrations at the Salt River and Maryvale sites were already approved, ADEQ limited its subsequent microscale workto developing approvable demonstrations for the Gilbert and West Chandler sites. Our proposal today is also limited to these two sites.

To evaluate the provisions forthe 24- hourPM-10 standard in the MAGplan,

we are relying to a large extent on our previous evaluation ofthe Microscale plan. Except for the findings related to the implementation ofBACM, we have
notreevaluated the 24-hour standard provisions that we have already found adequate or approved as part ofour actions onthe Microscale plan.

More information on the Microscale plan canbe foundin section 1ofthe EPATSD and ourproposed and final rulemakings on it. 62 FR 31025 (June 6, 1997) and 62 FR41856 (August4, 1997).

3.Arizona's Agricultural BMP General Permit Rule Approval

The analysis done for the Microscale planrevealed for the first time how significant a contribution agricultural

sources make to exceedances ofthe 24- hourPM-10 standard in the Phoenix

area. SeeMicroscale plan, pp. 18-19. In order to develop adequate controls for this source, Arizona passed legislation in 1997 establishing an Agricultural Best Management Practices (BMP) Committee and directing the Committee
to adopt by ruleby June 10, 2000, an agricultural general permit specifying best management practices for reducing PM-10 from agricultural activities. The legislation also required that implementation ofthe agricultural controls begin by June 10, 2000with an education program and full compliance with the rulebe achieved byDecember 31, 2001. SeeArizona Revised Statutes (A.R.S.) 49-457.

In September 1998, the State submitted the legislation. On June 29, 1999, we approved it as meeting the RACM requirements ofthe CAA.7 64 FR 34726.

While we approved the legislation as RACM, itwas the State's intent thatit also serve asBACM andMSM for agricultural sources inthe serious area

7In 1998, we promulgated a moderate area PM10 federal implementation plan (FIP) forthe
Phoenix area. 63 FR 41326 (August 3, 1998). One ofthe measures inthis FIP was our commitment to adopt RCM for agricultural sources, RACM being the primarycontrol requirement for moderate PM10nonattainment areas. Arizona submitted the BMP legislation in 1998 as, among other things, a substitute for our FIPRACM commitment. Before

we could withdraw our FIP RACM commitment andreplace itwith the State's legislation, we had
to firstfind thatthe legislation was at leastRACM, henceour initial determination that it was atleast RCM. For further information on this legislation and itsrelationship to the history ofPM-10 planning in the Phoenix area, see the "Implementation ofBACM and Inclusion of MSM forAgricultural Sources" section inthe EPA TSD. 50254

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PM-10 plan. Therefore, in our annual standard proposal, we evaluated and proposed to findthat the legislation met the CAA BACM andMSM requirements for the agricultural source category. 65 FR 19964, 19981.

After a series ofmeetings during 1999 and 2000, the Agricultural BMP Committee adopted the agricultural general permit rule and associated definitions, effective May 12, 2000, at Arizona Administrative Code (AAC) R18-2-610, "Definitions for R18-2- 611," and 611, "Agricultural PM-10 General Permit; Maricopa PM10 Nonattainment Area" (collectively, general permit rule). The State submitted the general permit rule in July 2000 and its analysis quantifying the emission reductions expected from the rule and the demonstration thatthe rule meets the CAA's RACM, BACM and MSM requirements in the June 2001 BMP TSD. We proposed to approve the rule as meeting the CAA requirement for RACM onJune 29, 2001 and signed the final approval on September 10, 2001. See 66 FR 34598.

We are today withdrawing our proposed finding in the annual standard proposal thatthe State legislation provides for the implementation of BACM andMSM for agricultural

sources for the annual standard. 66 FR 19964, 19981. In its place we are proposing to find that the General Permit rule provides for the implementation ofBACM andMSM for agricultural sources for the annual standard. This proposal isbased on our analysis, summarized later, ofthe rule andthe State's demonstrations in the BMP TSD andis in addition to our proposed finding thatthe rule provides for the implementation ofBACM and MSM for the 24-hour standard.

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

The Phoenix area is a PM-10 nonattainment area thathasbeen reclassified to serious because it failed
to attainby the moderate area attainment date ofDecember 31, 1994. Such an area must submit, within 18 months ofthe reclassification, revisions
to its implementation plan that address the CAArequirements for serious PM10 nonattainment areas. CAAsection 189(b)(2). These requirements are:

(a) assurances that the BACM, including best available control technology (BACT) for stationary
sources, for the control ofPM-10 shall be implemented no later than 4years after the area is reclassified (CAA section 189(b)(1)(B)); 8

(b) assurances thatBACT on major stationary sources ofPM-10 precursors shall be implemented no later than 4 years afterthe area is reclassified except where EPA has determined that such

sources do not contribute significantly
to exceedances ofthe PM-10 standards (CAA section 189(e));

(c) a demonstration (including air quality modeling) that theplan will provide for attainment as expeditiously

aspracticable but no later than December 31, 2001 orwhere the State is seeking an extension ofthe attainment date under section 188(e), a demonstration that attainment by December 31, 2001 is impracticable and that the plan provides for attainment by the most expeditious alternative date practicable (CAA sections 188(c)(2) and 189(b)(1)(A));

(d) quantitative milestones which are to be achieved every 3years and which demonstrate reasonable further progress toward attainment bythe applicable attainment date (CAA sections 172(c)(2) and 189(c)); and

(e) a comprehensive, accurate, current inventory of actual emissions from all

sources ofPM-10 (CAA section 172(c)(3)).

Serious area plan must alsoprovide for the implementation ofcontingency

measures ifthe area fails to make RFP

or attainby its attainment deadline. These contingency measures are to take effect without further actionby the State

orthe Administrator. CAA section 172(c)(9).

Serious area PM-10 plans must also
meet the general requirements applicable to all SIPs including reasonable notice and public hearing under section 110(1), necessary

assurances that the implementing agencies have adequate personnel, funding and authority under section 110(a)(2)(E)(i) and 40 CFR 51.280; and the description ofenforcement methods

asrequired by40 CFR 51.111.

We have issued aGeneral Preamble9 andAddendum to the General Preamble-o describing our preliminary

8 When a moderate area is reclassified to serious,
the requirement to implement RACM in section 189(a)(1)(C) remains and is augmented by the requirement to implement BACM. Thus, a serious

area PM-10 plan must, in addition to BACM, provide for the implementation of RACM as expeditiously as practicable totheextent that the RACM requirement has notbeen satisfied in the area's moderate area plan.

9"State Implementation Plans; General Preamble for the Implementation ofTitle I ofthe Clean Air Act Amendments of 1990," 57 FR 13498 (April 16, 1992) and 57 FR 18070 (April 28, 1992).

10"State Implementation Plans for Serious PM10 Nonattainment Areas, andAttainment Date views on how the Agency intends to review SIPs submittedto meet the CAA's requirements forPM-10 plans. The General Preamble mainly addresses the requirements for moderate areas and the Addendum, the requirements for serious areas.
IV.The MAG Plan'sCompliance with the CAA's Requirements for Serious PM-10 NonattainmentArea

The following sections present a condensed discussion ofour evaluation ofthe MAGplan's compliance with the applicable CAA requirements for attaining the 24-hour PM-10 standard. Our complete evaluation is found in the EPATSD for this proposal. We strongly
urge anyone wishing to comment on this proposal to first review the TSD before preparing comments. A copy of the TSD canbe downloaded from our website or obtained by calling or writing the contact person listed above.

A. Completenessofthe SIPSubmittals

CAA section 110(k)(1)(B) requires us to determine ifa SIP submittal is complete within 60 days ofits receipt. This completeness review allows us to quickly determine ifthe submittal includes allthe necessary items and information we need totake action on it. Wemake completeness determinations using criteria we have established in 40 CFR part 51, appendix V.We foundADEQ's February 16, 2000 submittal ofthe final revised MAG serious area PM-10 plan complete on February 25, 2000. See letter,David P. Howekamp, EPA,to Jacqueline Schafer, ADEQ.

We also foundADEQ's June 13, 2001 submittal ofthe BMP TSD complete on August 10, 2001. See letter, Jack Broadbent, EPA, to Jacqueline Schafer, ADEQ.

B.Adequacy ofthe Transportation ConformityBudgets

CAA Section 176(c) requires that federally-funded or approved transportation plans, programs, and projects innonattainment areas "conform" to the area's air quality implementation plans. Conformity

ensures that federal transportation actions donot worsen an area's air quality or interfere with its meeting the air quality standards. Wehave issued a conformity rule that establishes the criteria and procedures for determining

Waiversfor PM-10 Nonattainment Areas, and Attainment DateWaivers for PM-10 Nonattainment Areas Generally; Addendum to the General Preamble forthe Implementation ofTitle I ofthe Clean AirAct Amendments of 1990," 59 FR 41998 (August 16, 1994) 

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whether or not transportation plans, programs, and projects conform to a SIP. See 40 CFR part 93, subpart A.

One ofthe primary tests for conformity is to show transportation plans andimprovement programs will
not cause motor vehicle emissions higher than the levels needed to make progress toward and meetthe air quality standards. The motorvehicle emissions levels needed to make progress toward andmeet the air quality standards are setin an area's attainment and/or RFP plans and are known as the "emissions budget for motorvehicles." Emissions budgets are established for specific years and specific pollutants. See 40 CFR 93.118(a).

Before an emissions budget in a submitted SIP revision canbe used in a conformity determination, we must first determine thatit is adequate. The criteria by which we determine adequacy ofsubmitted emission budgets

are outlined in our conformity rule in 40 CFR 93.118(e)(4). A finding ofadequacy does not approve an emissionsbudget, it simply allows states to begin to use the budget in conformity determinations pending our action on the overall SIP.

The MAGplan establishes a mobile

source emissions budget of59.7 mtpd. This regional budget is applicable to both the annual and 24-hour PM-10 standards. The on-road mobile source portion ofthe budget, which includes emissions from reentrained road dust, vehicle exhaust, and travel on unpaved roads, is 58.6 mtpd. The road construction dust portion ofthe budget is 1.1 mtpd. MAGplan, p. 8-13.

On March 30, 2000, we found adequate for transportation conformity
purposes this motor vehicle emissions budget. Our adequacy finding is documented in section II ofthe EPA TSD for the annual standard. As a result ofour adequacy finding, MAG andthe Federal Highway Administration are

now required to use this budget in all conformity analyses.

As discussed later in this preamble,

we are proposing to approve both the attainment and reasonable further progress demonstrations for the 24-hour standard in the Maricopa County serious area PM-10 plan. The 59.7 mtpd budget is consistent withthese demonstrations. We, therefore, propose to approve itas the motorvehicle emissions budget for the 24-hour PM-10 standard under CAAsection 176(c).

C.EmissionsInventory

CAA section 172(c)(3) requires that nonattainment area plans include a comprehensive, accurate, and current inventory ofactual emissions from all

sources in the nonattainment area. To meet this requirement Arizona submitted a 1994 base year inventory as part oftheMAG plan. See MAG plan, Appendix A, Exhibit 6. We proposed to approve this inventory as meeting the requirements ofsection 172(c)(3) in our proposal on the annual standard provisions. See 65 FR 19964, 19970.

In the Phoenix nonattainment area, both regional andmicroscale modeling inventories are needed to accurately reflect the sources thatare contributing
to 24-hour PM-10 ambientlevels. The regional modeling inventories were derived from the 1994 base year inventory and are the same for the annual and 24-hour standards. We proposed to findthese regional modeling inventories to be acceptable as part ofannual standard provisions. See 65 FR 19964, 19985-19986.

ADEQ developed microscale and subregional inventories for 1995 (the modeling base year) for the West Chandler and Gilbert microscale sites. See Microscale plan, Appendix A, Chapter 4 and MAG plan, Appendix C, Exhibit 3, Chapter 3. In the 1997 Microscale plan, ADEQ also developed 1995 inventories for the two other microscale sites, Maryvale and Salt River. SeeMicroscale plan, Appendix A, Chapters 4 and 6. We evaluated the 1995 inventories for all four sites as part ofour action onthe overall Microscale plan. See 62 FR 31025, 31030 (June 6, 1997). These microscale inventories are specialized modeling inventory andis
not intended to satisfy the CAA section 172(c)(3) requirement."

We discuss emissions inventories in this preamble andin the EPATSD in order to present a complete technical review ofthe Maricopa County serious

area plan's provisions for attainment of the 24-hour standard. Emissions inventories play a fundamental role in air quality modeling, andCAA section 189(b)(1)(A) requires attainment demonstrations in PM-10 serious area plan to be based on modeling. We
cannot findthis modeling, orthe attainment demonstrations that are derived from it, approvable without first finding thatthe underlying emissions inventories are adequate. We are not, however, proposing any actions today

onthe inventories relied onin the Maricopa County serious area plan for demonstrating attainment ofthe 24-hour standard because, as discussed above,

we have already either proposed to approve them or found them to be acceptable.

11The microscale inventories include only

sources within a small area surrounding each monitor rather than all sources within the entire nonattainment area asrequirement in CAA section 172(c)(3). D.AdequateMonitoringNetwork
We discuss the adequacy ofthe monitoring network in thispreamble solelyto support our finding that the plan appropriately evaluates the PM-10 problem in the Phoenix area. Reliable ambient data is necessary to validate the base year air quality modeling which in
turn isnecessary to assure sound attainment demonstrations.

The CAA requires states to establish and operate air monitoring networks to compile data on ambient air quality for all criteria pollutants. Section 110(a)(2)(B)(i). Our regulations in 40 CFR 58 establishes specific regulatory requirements for operating air quality surveillance networks to measure ambient concentrations ofPM-10, including measurement method requirements, network design, quality

assurance procedures, andin the case of large urban areas, the minimum number ofmonitoring sites designated as National Air Monitoring Stations (NAMS).

Ambient networks, however, do not need tomeet all ourregulations tobe found adequate to support air quality modeling. Agood spatial distribution of sites, correct siting, and quality-assured and quality-controlled data are the most important factors we consider when evaluating the monitoring network for air quality modeling. Nonattainment

area plans developed undertitle I,part D ofthe Clean AirAct are not, in general, required to address how the area's air quality network meets our monitoring regulations. These plans are submitted too infrequently to serve as the vehicle for assuringthat monitoring networks remain current.

The baseyear forthe MAG planis 1995. In 1995, there were 16 monitoring sites operated by either MCESD or ADEQthat collected PM-10 data in the Phoenix area, three designated as NAMS, five designated as state/local monitoring stations, and eight designated as special purpose monitors. All ofthe sites were operated in accordance with ourregulations in 1995. Figure 3-2 in the MAG plan lists the names ofthe sites and their locations in the Phoenix area as ofApril 1999. Most ofthese PM-10 monitoring sites were sited asneighborhood scale with an objective of assessing population exposure. Given the nature ofthe emission sources in the Phoenix
area, which are mostly local fugitive dust sources, we believe thisis an appropriate focus ofthe network.

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were chosen to evaluate the type and mix ofsources thought tobe contributing to elevated 24-hour PM-10 levels: Salt River for its proximityto industrial sources; West Chandler for its nearby highway construction; Maryvale for its residential area coupled with land disturbing activities due to the construction ofa park, and Gilbert for its proximity to agricultural land. In 1995 these sites recorded the highest andmost frequent exceedances ofthe 24-hour PM-10 standard. They are also representative ofsimilar areas in the Phoenix area that may not have monitoring sites.

Based on our evaluation, we have concluded that the monitoring network operated bythe MCESD and ADEQ in 1995 was adequate to support the air quality modeling in the MAG plan. The network utilized EPA reference or equivalent method monitors andboth agencies have EPA-approved quality

assurance plans in place.

E.ContributiontoPM-IOExceedances of

MajorSourcesofPM-I0 Precursors
CAA section 189(e) requires a state to apply the control requirements applicable tomajor stationary sources of PM-10 to major stationary sources of PM-10 precursors, unless we determine such sources do not contribute significantly to PM-10 levels in excess ofthe NAAQS in the area. Forthe serious area plan, a major source is one that emits or has the potential to emit

over 70 English tons peryear (tpy)of sulfur oxides (SOx), nitrogen oxides (NOx), or ammonium.

PM-10 precursors react in the atmosphere toform secondary particulate, secondary because it isnot directly emitted from the source. The MAG plan does not provide specific information on the impact ofmajor
precursor sources on Phoenix PM-10 levels; however, itdoes provide sufficient information on the contribution oftotal secondary particulates to PM-10 levels and the emissions from major precursor sources to estimate the impact.

We estimate that major stationary

sources contribute at most0.61 gLg/m3 to 24-hour PM-10 levels in the Phoenix

area. See EPA TSD section, "BACT for Major Stationary Sources ofPM-10 Precursors." We estimated this contribution by assuming that the major stationary sources' contribution to secondary levels is proportional to their
presence in the inventory. Webelieve that this assumption is reasonable given the very small presence ofmajor stationary sources in the precursor inventory and the small contribution total secondaries make toPM-10 levels in Phoenix. Moreover, secondary particulate takes hours to form in ambient air from itsprecursors. Bythe time secondary particluate isformed, the precursors are well mixed in the ambient air, so localized, disproportionate impacts bymajor

sources ofPM-10 precursors are very unlikely.

This contribution is wellbelow our proposed 5gg/m 3 significance level.12 However, independent ofthis fact, we believe that so small a contributionless than 0.4percent ofthe 24-hour PM10 standard of150 gg/m3-is truly insignificant by any measure for the Phoenix area. PM-10 levels above the 24-hour standard in Phoenix are almost exclusively caused by afew large source categories offugitive dust.It iscontrols

onthese sources that are the key to expeditious attainment andnot controls

ontrivial contributors such as major stationary sources ofPM-10 precursors.

Based ontheir negligible impact on ambient PM-10 levels, we propose to determine thatmajor sources ofPM-10
precursors donot contribute significantly to PM-10 levels which exceed the 24-hour standard in the Phoenix area; therefore, pursuant to CAA section 189(e), BACT need not be applied to major sources ofPM-10 precursors.
F. Implementationof Reasonably AvailableandBestAvailable Control Measures

CAA section 189(b)(1)(B) requires that

a serious area PM-10 plan provide for the implementation ofBACM within four years ofreclassification to serious. For Phoenix, this deadline isJune 10, 2000. Under our applicable guidance, BACM must be appliedto each significant area-wide source category. Addendum at 42011. As discussed in sectionV ofthis preamble, we have established afour-step process for evaluating BACM in serious area PM-10 plans.

1. Steps 1and 2: Determination of Significant Sources

The first step in the BACM analysis is
to develop a detailed emissions inventory ofPM-10 sources and source categories that canbe used in modeling
to determine their impact on ambient air quality.Addendum at 42012. The second step is use this inventory in air quality modeling to evaluate the impact

onPM-10 concentrations over the standards ofthe various sources and

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

are significant.

The development ofthe detailed emissions inventories is discussed in a preceding section. The MAG planuses three modeling studies ofPM-10

sources in the Phoenix area to identify significant source categories. One of these studies evaluated significant

sources using chemical mass balance (CMB) modeling performed on monitoring samples collected at 6 sites in 1989-1990. The two other studies evaluated significant sources using dispersion modeling of sources around 6 monitoring sitesusing data from 1992 through 1995.13

From these evaluations, the MAG planidentifies 8 significant source categories and 12 insignificant source categories. MAG plan,p. 9-6.

The final list of significant source categories in the MAG plan does not distinguishbetween those categories that are significant for the 24-hour standard and those that are significant for the annual standard; although previous studies have shown that some

source categories are significant onlyfor

one or the other standard. Because the MAG plan does not distinguish significant source categories between the two standards, we treat each ofthe listed significant source categories as significant for the 24-hour standard.

For the 24-hour standard, the MAG plan demonstrates that its selection of significant source categories is appropriate by showing that controls on the de minimis source categories would
notresult in attainment ofthe 24-hour standard by 2001. For a detailed description ofthis demonstration, see MAG plan, pp. 9-12 to 9-15 and the EPATSD section "BACM AnalysisStep 2, Model to Identify Significant
Sources."14

13These studies are "The 1989-90 Phoenix PM10 Study", Desert Research Institute, April 1991; "Particulate Control Measure Feasibility Study," SierraResearch, January 1997; and the Microscale plan.

14Inthis deminimus demonstration, certain

sourcecategories vacant land, unpavedroads, agricultural sources, and unpaved parking-were assumed to beuncontrolled atthe end of 2001. See MAG plan, Tables 9-b and 9-c. These categories willin factbe subject to BACM bythen. Bynot including controls on thesecategories in the de minimis demonstration, the gap between nonattainment andattainment ofthe 24-hour standard in 2001 is much larger than itshould be and thus, the deminimis determination for the 24- hour standard is suspect.

To check ifthe selected deminimis categories are truly de minimis under the correct control assumptions, we redid the determination incorporating the appropriate level ofcontrol for each source category. We concluded from this reanalysis thatthe MAG plan's selected de minimis threshold is infact appropriate and the identified
Continued 

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The 8 significant source categories

are:

1.Paved road travel 2.Unpaved road travel (includes unpaved parking lots) 3.Industrial paved road travel (paved andunpaved)

4. Construction site preparation (includesdisturbed vacant lots that are not undergoing construction) 5.Agricultural tilling (includes all agricultural sources)

6. Residential wood combustion 7. On-road and non-road motor vehicle exhaust

8. Secondary ammonium nitrate MAG Plan, Table 9-1.

The 12 de minimis source categories

are:

1. Stationary point sources 2.Fuel combustion (excluding residential wood combustion) 3.Waste/open burning 4. Agricultural harvesting 5.Cattle feedlots 6. Structural/vehicle fires 7.Charbroiling/frying meat 8. Marine vessel exhaust 9. Airport ground support exhaust 10. Railroad locomotive exhaust 11. Windblown from fluvial channels 12.Wild fires MAG plan, Table 9-a. The plan notes that several de minimis source categories (e.g., stationary point sources, waste/open burning, agricultural harvesting, charbroiling) are already subject to control orwill be controlled in the future. MAG plan, p. 9-12.

We propose to find thatthe MAG plan has not excluded any source categories that should be considered significant from its list ofsignificant source categories. The plan presents acceptable modeling to evaluate the impact of various PM-10 sources and source categories on PM-10 levels and to derive a comprehensive and conservative list of significant source categories.

2.Step 3: Identification ofPotential BACM

In preparing the list ofcandidate BACM, MAGreviewed our guidance documents onBACM, other EPA documents onPM-10 control, as well as PM-10 plans from other serious PM-10 nonattainment areas in the western United States. MAG also evaluated controls proposed during public
comment. MAGplan, pp. 9-24 through 9-29;MAG Plan, Appendix D, Exhibit 1, "Response to Public Comments,

de minimis categories areindeed deminimis and

are appropriately excluded from the BACM analysis. See EPA TSD, section "BACM AnalysisStep 2, Model to Identify Significant Sources." January 31, 2000 Public Hearing"; and BMP TSD, pp. 9 through 27.

The MAGplan appropriately screened the list ofcandidate BACM to eliminate

measures that did not apply to significant source categories in the area,

were technologically infeasible forthe

area because they would not reduce PM-10 emissions, or duplicated other

measures onthe list. The plan also provides cost effectiveness estimates for each ofthe candidate BACM. MAG plan, pp. 9-30 through 9-39; andBMP TSD, pp. 9 through 27.

We propose to find thatthe Maricopa County serious area PM-10 plan identified and evaluated potential BACM for the Maricopa area consistent with our guidance. Aswe will discuss below in our evaluations ofthe implementation ofBACM for each significant source category, we do not believe that the plan left out any candidate BACM. Overall, the plan presents one ofthe mostcomprehensive lists ofpotential BACM ever produced.

3. Step 4: Implementation ofRACM and BACM andinclusion ofMSM for Each Significant Source Category

In the following sections, we review the results ofthe Maricopa County serious area plan's BACM analysis. To present these results, we have grouped the emission generating activities that comprise the MAG plan's significant categories slightly differently from the plan, e.g., we have addressed separately construction activities and disturbed
vacant lands which areboth included in the MAGplan's significant category of construction site preparation. 15 We have done this to make our evaluations ofthe plan's provisions for the implementation ofBACM andinclusion ofMSM clearer and thus, we believe,

more understandable. However, despite the method ofpresentation, we have addressed the MAGplan's provisions for implementing RACM and BACM for each ofthe plan's significant source categories.

Also, because ofthe substantial overlap in the source categories and controls evaluated for BACM and those evaluated for MSM, we present our evaluation ofthe MAG plan's provisions for including MSM alongside our evaluation ofthe provisions for implementing RACM and BACM for each significant source category.

Controls on a number ofsignificant

source categories are in MCESD's fugitive dustrules, Rule 310 andRule

15

MAG planuses this grouping despite thefact that disturbed vacantlands includelands thatare disturbedforreasonsother thanconstruction activity. 310.01. MCESD has made extensive commitments to improve compliance and enforcement ofthese rules to assure thatthey achieve the emission reductions necessary for expeditious attainment. These commitments are an important component ofourproposed finding thatthe MAG planprovides for implementation ofRACM and BACM and inclusion ofMSM. We discuss them
atthe end ofthis section.

As discussed above, the MAG plan made no distinction between significant

sources for the annual standard and those for the 24-hour standard and, as
a result, it made no distinction between BACM and MSM forthe annual standard and those for the 24-hour standard. Wehave already extensively reviewed the MAGplan's BACM and MSM provisions for the annual standard and these reviews are applicable to the 24-hour standard. Thus, except for clarifying and/or updating information

on a few measures, we have not revised

our evaluations ofBACM andMSM for
mostofthe significant source categories. Four categories-on-road engines (technology controls), nonroad engines, unpaved roads and construction dusthaveundergone moderate changes.

Our analysis ofthe agricultural source category has changed substantially from the annual standard proposal. As discussed above, we based ourreview in the annual standard proposal on the State's legislation requiring the adoption ofmeasures for agriculture. Since then, the State has adopted the agricultural general permit rule and has submitted revisionsto the Maricopa County serious area plan containing the demonstration thatthe general permit rule represents BACM andMSM. For today's proposal, we have based our review ofBACM andMSM for the agricultural sources on the general permit rule and the State's additional documentation. Our revised analysis applies toboth the annual and 24-hour standards.

a. Technology Controls for On-road Motor Vehicle Exhaust

This category includes tailpipe and tire wear emissions ofprimary PM-10 from on-road motor vehicles. On-road
motorvehicles include both gasoline and diesel-powered passenger cars, light, medium, and heavy duty trucks, buses, andmotorcycles.

The suggested technology-based

measures for controlling emissions from on-road motor vehicle exhaust fall into

one offive categories: new emission standards, inspection and maintenance (I/M)programs, fuels, programs to encourage alternative fueled vehicle
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turnover. In total, the MAGplan considers 22 technology-based control

measures. See MAG plan, Table 5-2. We believe this list iscomplete and propose to findthat theMAG plan evaluates a comprehensive set ofpotential technology-based controls for on-road
motor vehicle exhaust emissions including the potentially most stringent

measures from other states.

For gasoline vehicles, Arizona has implemented one ofthe nation's best andmost comprehensive enhanced I/M programs including expanding the
program to areas surrounding Phoenix; has adopted its own Cleaner Burning Gasoline program which mandates the

use ofeither Phase II federal reformulated gasoline or California reformulated gasoline; and mandates federal, state, county, andmunicipal governments to convert their fleets to alternative fuels. MAGplan, pp. 7-2 through 7-24.

Arizona has instituted a heavy-duty diesel I/M program, will require pre1988 HDDV registered in the Phoenix nonattainment area tomeet 1988 federal emission standards starting in 2004, has established avoluntary vehicle repair andretrofit program to encourage retrofitting and overhaul ofheavy duty diesel engines to reduce emissions, and has limited diesel sulfur content to 500 parts per million (ppm).MAG plan, Chapter 7.

As noted before, Arizona has in place

a comprehensive programs to address on-road motor vehicle emissions. With the additional measures in the MAG plan (including a more stringent diesel I/M program and measuresboth encouraging and requiring diesel fleet turnover), the overall mobile source program is strengthened and goes beyond the existing program. Both strengthening and expanding existing programs are key criteria for demonstrating the implementation of BACM. See Addendum at 42013. Where the MAGplan has rejected potential BACM, itprovides a reasoned and acceptable justification for the rejection. See EPA TSD, Table ORM-3 in the section "Implementation ofBACM and MSM for On-Road Motor Vehicle Exhaust and Paved Road Dust (Technology Standards andFuels)."

The MAGplan identified just a few

measures from other areas as potential MSM. These measures have either been adopted orwe have concluded thatthe

measure need notbe included to assure the inclusion ofMSM.

The California Air Resources Board's diesel fuel standards (CARB diesel) is

one ofthe few identified motor vehicle controls not adoptedby the State. 16The plan identifies this measure as a potential MSM. MAG plan, Table 10-7. The MAG plan claims thatthe measure is unreasonable on a costbasis. MAG plan, p. 9-46.

Based oninformation in the Microscale plan, emissions from onroad motor vehicle are not implicated in 24-hour exceedances inthe Phoenix

area. Microscale plan, pp. 17-19. All currently available evidence isthat 24- hour exceedances are causedby local fugitive dust sources and controls on these sources alone will result in the earliest practicable date for attainment ofthe 24-hour PM-10 standard in the Phoenix area. Microscale plan, pp. 17- 19. Because implementation ofCARB diesel would not result in earlier attainment andthus unnecessary for expeditious attainment, wepropose to find thatthe MAGplan provides for the inclusion ofMSM to our satisfaction absentthe adoption and implementation ofCARB diesel.

Except for one, all the adopted BACM andMSM were implemented by June 10, 2000, the BACM implementation deadline for the Phoenix area. The exception is therequirement that pre1988 heavy duty dieselvehicles registered in the nonattainment area meet 1988 federal emission standards. This measure will not be fully implemented until January 1, 2004 in order to provide sufficient lead time for modification or replacement ofthe noncomplying heavy duty dieselvehicles.

We, therefore, propose to findthat the combination ofon-road motor vehicle technology controls andtransportation control measures (described in the next section)in the MAG plan provides for the implementation ofRACM and BACM andthe inclusion ofMSM for onroad motor vehicle exhaust for the 24- hour standard. Since the annual standard proposal

was published in April 2000, changes have been made to two on-road motor vehicle controls that were included in that proposal: theremote sensing (RSD)
program in the State's vehicle emissions inspection program (VEIP) and changes
to the State's incentives for purchase of alternatively-fueled vehicles or conversions to alternatively-fueled vehicles.

16

Arizona has already adopted halfofthe CARB
diesel standards, the 500ppm sulfur limit.The other CARB diesel standard is a limit on the aromatic hydrocarbon content ofno more than 10 percent by volume. CARB, Fact Sheet on California Diesel Fuel, March 1997. Also, inJanuary 2001, we established a new dieselfuel sulfur limit of 15 ppm

as part ofour overall program to control emissions from heavy duty diesel vehicles. They newlimit which will apply to Arizona will befully in place by September, 2006. 66 FR 5002 (January 8, 2001). In 2000, the Arizona legislature converted the RSD program from a regulatory program to apilot program because ofitshigh cost perton of emissions reduced 17In July 2001, Arizona submitted a SIP revision that included all changes to State's VEIP
program thathad been made since we last approved it in 1995, including the changes to the RSD program. 2001 I/M SIP submittal, p. 26. We consider thisI/ M program submittal tobe Arizona's
current statement ofwhat elements constitute its VEIP.

The RSD program is not credited in the RFP or attainment demonstrations for the annual standard. The State justifies itsrevision tothis program based onthe implementation cost ofthe unrevised program, thatis, they have determined thatthe unrevised program

was economically infeasible. We believe thatthis change to the overall on-road
motorvehicle control program in the MAG plan do not adversely affect our previously proposed finding thatthe planprovides for the implementation of RACM and BACM andthe inclusion of MSM forthis source category for the annual standard found at 65 FR 19964, 19972.

b. Transportation Control Measures (TCMs)for On-road MotorVehicle Exhaust and Paved Road Dust

TCMs canreduce PM-10 emissions in both the on-road motor vehicle exhaust and paved road dust source categories by reducing vehicle miles traveled (VMT) and vehicle trips (VT). They can also reduce vehicle exhaust emissions through relieving congestion. Our serious area PM-10 guidance requires thatplans identifying on-road motor vehicles as a significant sources must also evaluate the TCMs listed in section 108(f) ofthe CAA. Addendum at42013.

In ourreview, we have primarily assessed the MAG plan's provisions for implementing RACM and BACM and including MSM through TCMs based on the measures' effectiveness in controlling directly-emitted PM-10 from vehicle exhaust. We have not assessed the plan based on the TCMs' potential benefit in controlling PM-10 precursors such asNOx and SOx because (1)from available ambient measurements, neither nitrates nor sulfates are important to overall 24-hour PM-10 concentrations in the Phoenix area (See EPATSD section, "BACT for Major Stationary Sources ofPM-10 Precursors" which shows thattotal

17ADEQ, FinalArizona State Implementation
Plan Revision, Basic andEnhanced Vehicle Emissions Inspection/Maintenance Program, June 2001 ("2001 I/M SIP submittal"), p. 26. 

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secondary particulates from all sources have a maximum impact of9.2 gg/m 3 in 1995) and (2)Arizona has already targeted mobile source NOx and SOx through an aggressive setofmobile

source controls which we believe cover the implementation ofRACM and BACM andinclusion ofMSM requirements for tailpipe NOx and SOx. See discussion immediately above on technology controls for on-road motor vehicle exhaust.

In total, the MAG plan identifies 19 TCMs for consideration, including the CAA section 108(f) measures. The plan does not identify any potential most stringent TCMs from other areas. See EPA TSD section "Implementation of BACM andMSM for On-Road Motor Vehicle Exhaust and Paved Road Dust (TCMs)." We believe thatthis list is complete and propose to findthat the MAG plan evaluates a comprehensive
set ofpotential TCMs for on-road motor vehicle exhaust emissions and the potential MSM from other States.

Arizona has along history of adopting andthen enhancing programs toreduce emissions from on-road motor vehicles by reducing VMT, VT, and/or congestion. 18The area has an employer trip reduction ordinance which applies
to employers of50 or more, a public outreach program to encourage people
to reduce driving, programs to improve bicycling and pedestrian travel, and an extensive program to synchronize traffic lights. In most instances, these programs

were adopted and implemented aspart ofcarbon monoxide and ozone control programs, but they alsoreduce PM-10.

With the additional measures in the MAG plan (including additional traffic light synchronization, transit improvements, andbicycle and pedestrian facility improvements), the overall TCM program is strengthened and goes beyond the existing program. See EPA TSD, Table TCM-3 in section "Implementation ofBACM and MSM for On-Road Motor Vehicle Exhaust and Paved Road Dust (TCMs)." Both strengthening and expanding existing
programs are key criteria for demonstrating the implementation of BACM. See Addendum at 42013. Where the MAGplan has rejected potential BACM, itprovides a reasoned and acceptable justification for the rejection.

All the adopted TCM BACM were implemented by June 10, 2000, the BACM implementation date for the Phoenix area, or have on-going implementation schedules because they

are part ofan on-going capital

18Theseplans include the MAG moderate and
serious area carbon monoxide plans and MAG moderate area ozone plan. improvement program (e.g., signal synchronization).

We propose to find thatthe combination ofon-road motor vehicle technology controls (described in the previous section) and TCMs in the MAG plan provides for the implementation of RACM andBACM andinclusion of MSM for on-road motor vehicle exhaust. We alsopropose to find thatthe combination ofTCMs andpaved road dust measures (described in the paved road sectionlater in this preamble) provides for the implementation of RACM andBACM andthe inclusion of MSM for paved road dust.

c. Nonroad Engines

The nonroad engine category covers a diverse collection ofengines, equipment and vehicles fueled by gasoline, diesel, electric, natural gas, and other alternative fuels, including outdoor
power equipment, recreational equipment, farm equipment, construction equipment, lawn and garden equipment, andmarine vessels.

The suggested measures for controlling emissions from nonroad engines fall into one offour categories:

new emission standards, programs to accelerate fleet turnover, programs affecting usage, orfuels. In total, the MAG plan evaluates 8 measures in addition to clean fuels measures for reducing PM-10 emissions from nonroad engines. We believe thatthis list is complete and propose to findthat the MAGplan evaluates a comprehensive set ofpotential measures for nonroad engines including the potential most stringentmeasures from other States.

We have adoptednational emission standards for a broad range ofnonroad engines. We consider thatthese standards, which apply tononroad engines soldin Arizona constitute at minimum a RACM-level program for controlling emissions from nonroad engines. The CAA preempts all states, except for California, from setting independent nonroad emission standards. CAA section 209(e). Other states,however, may adopt regulations identical to California's regulations, provided they notify us and give appropriate lead time, 2years, for implementation. CAA section 209(e)(2)(B).

Arizona legislation allows ADEQto adopt certain California nonroad engine standards. MAG plan, p. 7-42. ADEQ originally committed to adoptthese California nonroad standards; however, subsequently, we adopted federal nonroad engine standards that will achieve essentially the same PM-10 reductions in the Phoenix area that adoption ofthe California ones would. As a result, Arizona determined that adoption ofthe California standards would notjustify the resources ADEQ would need to expend to adopt, implement, and enforce them and has

nowwithdrawn its commitment. See letter,Jacqueline E. Schafer, ADEQ, to Laura Yoshii,EPA, "Justification for not implementing CARB Off-road engine standards for the Maricopa County PM10 SIP," September 7, 2001 ("ADEQ OffRoad Letter").

Arizona has adopted and implemented a year-round Cleaner Burning gasoline program and limits on the sulfur content ofdiesel fuels. With the addition ofthese measures, the overall nonroad engine program is strengthened and goes beyond the existing federal program. See EPATSD section "Implementation ofBACM and Inclusion ofMSM for Nonroad Engines." Both strengthening and expanding existingprograms are key criteria for demonstrating the implementation ofBACM. See Addendum at 42013. Where the MAG planhas rejected potential BACM, it provides a reasoned justification for the rejection.

The MAGplan identifies CARB diesel

as a potential MSM for nonroad engines but does not adopt it. MAGplan, Table 10-7. The plan identifies this measure

as a potential MSM. MAG plan,Table 10-7. The MAG plan claims thatthe

measure isunreasonable on a costbasis. MAG plan, p. 9-46.

Based on information in the Microscale plan, emissions from nonroad engines are notimplicated in 24-hour exceedances inthe Phoenix

area. Microscale plan, pp. 17-19. All currently available evidence is that 24- hour exceedances are causedby local fugitive dust sources and controls on these sources alone will result in the earliest practicable date for attainment ofthe 24-hour PM-10 standard in the Phoenix area. Microscale plan, pp. 17- 19. Because implementation ofCARB diesel would not result in earlier attainment andthus unnecessary for expeditious attainment, we propose to findthat the MAGplan provides for the inclusion ofMSM to our satisfaction absent the adoption andimplementation ofCARB diesel.

We, therefore, propose to findthat MAG plan provides for the implementation ofRACM and BACM and inclusion ofMSM for nonroad engines.

d. Paved Road Dust

Paved road dust is the largest source ofPM-10 inthe Maricopa area. It is fugitive dust that is deposited on a 50260

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paved roadway and then isre-entrained into the air by the action oftires grinding on the roadway. Dustis deposited onthe roadway frombeing blown onto the road from disturbed
areas; tracked onto the road from unpaved shoulders, unpaved roads, or otherunpaved access points; stirred up from unpaved shoulders bywind
currents created from traffic movement; spilled ontothe roadby haul trucks; and carried onto theroad by water runoffor erosion.

The suggested measures for controlling emissions from paved road dust fall into one ofthree categories: reductions in VMT and VT, preventing deposition ofmaterial onto a roadway, and cleaning material offthe roadway. We have already discussed measures for reducing VMT and VT in the section on TCMs above.

The MAGplan lists several potential BACM for paved road dust. Italso lists

anumber ofpotential MSM from other

areas. We believe these lists are complete and propose to findthat the MAG plan evaluates a comprehensive
set ofpotential controls for paved road dust including the potential MSM from other States.

Prior to the MAG plan, the cities and
towns in the Phoenix area and Maricopa County implemented anumber of

measures addressing paved road dust. See MAG plan,Table 10-5. With the additional measures in the MAGplan (describedbelow), the overall control program to reduce paved road dust is both strengthened and expanded beyond the existing program. See EPA TSD section "Implementation ofBACM andInclusion ofMSM for Paved Road Dust." Both strengthening and expanding existing programs are key criteria for demonstrating the implementation ofBACM. See Addendum at 42013.

For the potential MSM, the MAG plan shows thatthese measures are either adopted orare not in fact more stringent than existing Phoenix area programs.

With the exception ofthe PM-10- efficient street sweepers measure described below, all the adopted BACM for paved roads were implemented by June 10, 2001, the BACM implementation deadline for the Phoenix area, or have on-going implementation schedules because they

are part ofan on-going capital improvement program, e.g., curbing. For the reasons discussed below, we propose to find thatthe MAG plan provides for the implementation ofthe PM-10 efficient street sweeper measures, a MSM, as expeditiously as practicable, consistent with our proposed MSM policy. We, therefore, propose to findthat the MAG plan provides for the implementation ofRACM andBACM and for the inclusion ofMSM for paved road dust. Preventing Deposition ofMaterial Onto

a Roadway

Measures aimed at preventing track
out on apaved road include treating unpaved access points, preventing track
outfrom construction/industrial sites, treating shoulders onpaved roads, controlling emissions during material transport (e.g., truck covers, freeboard requirements), and preventing erosion
ontopaved roads.

The MAGplan includes each ofthese

measures. Unpavedaccesspoints:In the MAG moderate area plan, local jurisdictions focused on requiring new connections
to public paved streets to be paved. MAG plan, p. 9-74. In the serious area plan, the focus has shifted to addressing existing unpaved access points in addition to preventing new unpaved

access points while maintaining the previous programs. Most public entities committed to stabilize unpaved access points when a connecting road isbuilt, improved or reconstructed. See, for example, Glendale Commitment, "Reduce Particulate Emissions from Unpaved Shoulders and Unpaved Access Points on Paved Roads." Some cities have made explicit commitments for stabilizing existing access points without this prerequisite, such as Gilbert andMesa. We also anticipate that routine city/town/County road paving and stabilization projects will result in controlling anumber of existing unpaved access points. These projects combined with increased enforcement oftrack-out restrictions and additional PM-10 efficient street sweeping efforts shouldreduce paved road emissions attributable to unpaved

access points.

The only potential MSM that the MAG plan identifies for unpaved access points are track out control requirements for construction sites. See MAG plan, Table 10-7. We discuss these measures in the next section. Trackout.MCESD Rule 310, sections 308.2(c) and 308.3 address dirt track out from construction/industrial sites requiring all work sitesthat are five

acres or larger and all work sites where 100 cubic yards ofbulkmaterials are hauled on-site or off-site each day to control andprevent track outby installing a track out control device. The rule alsorequires allwork sites to clean
up spillage or track outimmediately when it extends a cumulative distance of50 linear feet or more and, where track out extends less than 50 feet, to clean itup at the end ofthe work day.

The MAGplan identifies, as a potential MSM for track out, South Coast (LosAngeles area) Air Quality Management District's (SouthCoast AQMD) Rule 403.MAG plan, Table 10- 7.The plan concludes that the tworules

are reasonably similar in several respects, and where differences exist, the relative impacts on control roughly balance each other out. MSM Study, p. C-4.19We agree. Both rules emphasize prevention and rapid removal oftrack
out. See EPA TSD section "Implementation ofBACM and Inclusion ofMSM for Paved Roads Dust," Note 2.

UnpavedRoadShoulders.As with unpaved access points, the MAGplan demonstrates a shift to dealingwith existing unpaved shoulders from simply preventing new ones. MAG plan, Table 9-11. Maricopa County has committed
to treat 100 miles ofshoulders along existing paved arterial and collector roadways with high volume truck traffic by 2003, in addition to its annual capital improvement projects for paving or treatingunpaved shoulders. Maricopa County commitment, 1999 revised

measure 5. Otherjurisdictions have also made commitments to treat shoulders. The commitments are set depending on the resources available to each jurisdiction to implement them.

A.R.S. 9-500.04(3) and 49-474.01(4), adoptedby the State legislature in 1998, require the cities, towns andCounty of Maricopa to develop and implement plans to stabilize targeted unpaved roads and alleys and to stabilize unpaved shoulders on targeted arterials beginning January 1,2000. Although this legislation does not specify how many shoulder miles tobe controlled,

we believe thatthe localjurisdictions' efforts tomeet this new legislation will result in the control ofunpaved shoulders where it is most needed.

MaterialTransport.Requirements for the control ofPM-10 emissions during material transport are found in MCESD Rule 310, sections 308.1 and 308.2. Whenhauling material off-site onto paved public roadways, sources are required to: 1) load trucks such thatthe freeboard is not less thanthree inches; 2)prevent spillage; 3) covertrucks with

a tarp or suitable enclosure; and4) clean

or cover the interior cargo compartment before leaving a site with an empty truck.

The MAGplan identifies requirements for bulk material transport

19The "MSM Study" is the "Most Strigent PM10 Control Measure Analysis," Sierrra Research, May 13, 1998 found inAppendix C, Exhibit4 of the MAG plan. 

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in Imperial County (California) Regulation VIII as a potential MSM. MAG plan, Table 10-7. The plan concludes thatMCESD's rule is equally stringent. We agree because Rule 310's requirements for bulkmaterial transport/hauling are essentially the

same as Imperial County's requirements. Cleaning MaterialOfftheRoadway
Measures for cleaning material off roadways are track out, erosion, and spillremoval requirements and road sweeping.

The MAGplan includes each ofthese

measures:

Materialspillage,erosion,or accumulation.MCESD Rule 310, section 308.2 and 308.3 address rapid clean up oftrack out from construction/industrial sites. Rule 310.01, section 306 requires property owners/operators toremediate erosion-caused deposits ofbulk materials onto paved surfaces. Erosioncaused deposits are tobe removed within 24 hours oftheir identification or prior to resumption oftraffic on the pavement.

The MAGplan identifies South Coast AQMD's Rule 1186 and Mojave Desert (SanBernadino, California) AQMD's Rule 403 as potential MSMs for material spillage, erosion, and accumulation onto roadways. MAGplan, Table 10-7. In both cases, theplan concludes that MCESD's rules are more stringent. We agree. MCESD's rules require the clean
up ofmore incidences ofspillage, etc. than does either the South Coast or Mojave Desertrule. See EPATSD, "Implementation ofBACM and Inclusion ofMSM for Paved Roads," Note 5. Streetsweeping.Most cities/towns andthe County have on-going street sweeping programs withvariable sweeping frequencies. With some exceptions, public entities implementing this measure have not explicitly committed to increase their existing sweeping frequencies. Phoenix, for example, approved a program in 1996 toincrease the frequency of residential street sweeping to match the uncontained trash pick-up schedule. Phoenix commitment, measure 97-DC5.However, sweeping frequency is appropriately evaluated in combination with other paved road measures because the emission-reducing potential of increased sweeping frequency is closely associated with other factors. These factors include whether the sweepers currently in use are PM-10 efficient (suchthat the act ofsweeping does not

cause increased emissions) and whether the public entity has identified roads that tend to experience higher silt loadings where more frequent sweeping is likely tomake an appreciable difference in PM-10 emissions. Because sweeping frequency is among the criteria included in MAG's PM-10 efficient street sweeper solicitation (see below), we believe this measure is largely incorporated into MAG's new program.

The MAGplan identifies as a MSM the PM-10 efficient street sweeping provisions in South Coast Rule 1186. MAG plan, Table 10-7. However, the plan's analysis pre-dates MAG's commitment for the purchase and distribution ofPM-10 efficient street sweepers and isno longer current.

The MAGplan includes commitments by MAG, cities, towns andthe County for the purchase and use ofPM-10 efficient street sweepers. This commitment involves the allocation of $3.8 million in Congestion Mitigation andAir Quality (CMAQJ 2 0 fundsfor the FY 2000-2004 Transportation Improvement Program (TIP)to purchase PM-10 certified street sweepers for the local jurisdictions to use. MAGhas recommended an additional $1.9 million in CMAQ funds be allocated to purchase PM-10 certified street sweepers in theFY 2001-2005 TIP. See MAG commitment, "PM-10 Efficient Street Sweepers."

The funds allocated byMAG for this
program shouldbe sufficient to replace approximately two-thirds ofthe 72 existing city/town/County street sweepers. 21Each fiscal year in which CMAQ funds are allocated for street sweepers, MAG will solicit requests for funding from cities, towns and the County in the PM-10 nonattainment

area. Funding requests must identify by facility type (i.e.freeway, arterial/ collector, local) the number of centerline miles to be swept with the PM-10 certified units, expected frequency of sweeping, and average daily traffic (ifavailable).22 MAG will

use this information to estimate the emission reductions associated with each sweeper request and rank the requests in priority order of effectiveness for consideration in the allocation ofCMAQ funds. See MAG commitment, "PM-10 Efficient Street Sweepers."

In evaluating this program, we considered not onlythe number ofPM20CMAQ funds are federal transportation funds
awarded to certain nonattainment areas for congestion management ofairqualitytransportation projects such as paving unpaved roads.

21Some street sweepers may be additions to, as opposed toreplacements of, existing equipment.

22See MAG, "Methodology for Evaluating Congestion Mitigation and Air Quality Improvement Projects," Draft Revised, June 21, 2001, pp. 18-22. 10 efficient street sweepers tobe purchased and distributed, but whether the program incorporates use factors thatinfluence emissions reductions. The greatest emissions reduction benefit for this mitigative measure will be achieved ifthe sweepers are used on a frequentbasis on-roads with high silt loadings or significant visible accumulations.

Each public entity has a monetary incentive to compete for the PM-10 efficient street sweepers, as the program is funded byMAG with alow cost share (5.7 percent) requirement. Also, the new street sweepers will either replace existing city-owned street sweeping equipment or contracted out services, or be added to existing street sweeper equipment/services. MAG's selection
process includes PM-10 emissions reduction potential, based on the types ofroads eachjurisdiction istargeting for sweeping and how frequently they will be swept. This data will assist MAG in distributing the street sweepers to local jurisdictions in a way thatmaximizes the regional air quality benefits ofthe
program. In addition, when the cities/ towns/County are awarded PM-10 efficient street sweepers, their submittals will incorporate use factors thatmaximize emission reductions from this measure.

We believe that implementation ofthe PM-10 efficient street sweeper program willbe implemented as expeditious as practicable. The funding necessary to purchase this equipment is available only over the course of several fiscal years and the purchase ofthe PM-10 efficient street sweepers can only proceed at the rate these funds become available.

South Coast's Rule 1186 requires any government or government agency which contracts to acquire street sweeping equipment or services for routine street sweeping onpublic roads thatit owns and/or maintains, where the contract date or purchase or lease date isJanuary 1, 2000 orlater, to acquire or use only certified street sweeping equipment. The rule establishes street sweeper testing and certification procedures. Unlike Maricopa's strategy, Rule 1186 requires thatPM-10 efficient street sweepers be usedwhenever street sweeping is contracted out as ofJanuary 2000, and itrequires public agencies to replace their existing street sweeping equipment with PM-10 efficient equipment only as theyreplace existing equipment.

MAG's PM-10 efficient street sweeper program isbeing funded over the next 4to 5fiscal years, which may result in

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operation in a shorter time frame than couldbe expected using South Coast's natural attrition approach. While it is possible that some cities/towns in Maricopa may continue to contract out for street sweeping services where PM10 efficient sweepers may notbe used,
most do not contract for street sweeping. Furthermore, due to the fact thatpublic entities will be competing for PM-10 efficient street sweepers funded by CMAQ dollars with only a low cost share requirement, we believe thatthe already limited reliance on contracted
out services in Maricopa County willbe reduced as new PM-10 efficient equipment becomes available and that
contractors will switch to PM-10 efficient equipment tomeet new demand. In addition, MAG's program

ensures that the cities/town/County develop plans for howthe street sweepers willbe used to maximize their emissions reduction potential. We, therefore, believe that overall the Maricopa program is equivalent to South Coast's Rule 1186.

e. Unpaved Parking Lots

This category includes emissions from re-entrained road dust from vehicle traffic on unpaved parking lots and windblown dust entrained from the disturbed surface ofunpaved parking lots.

There are two principal ways to control emissions from unpaved parking lots: prohibit unpaved parking lots or treat existing lots. MAG plan identified both: a prohibition onunpaved haul road and parking or staging areas and surface treatment to reduce dust from unpaved driveways and parking lots. MAG plan, Table 5-2. The MAG plan identified one potential MSM, South Coast's Rule 403 which controls fugitive dust from parking areas on construction sites. MSM Study, p. C-9 and 10. It did
not identify any potential MSM for nonconstruction site unpaved parking lots. We believe this list is complete and propose to find thatthe MAG plan evaluates a comprehensive set of potential BACM and MSM for unpaved parking lots.

Most local jurisdictions in Maricopa County identified ordinances that require paving ofnew parking lots. In addition,MCESD Rule 310.01, section 303 requires owners/operators ofan unpaved parking lotlarger than 5,000
square feetto pave, apply dust suppressants, or apply gravel, according
to the applicable rule's standards/test methods. Applicable standards include

a 20 percent opacity standard, and an 8 percent silt content standard and/or a 0.33 oz/square foot silt loading standard. Section 303.2. MCESD Rule 310, section 302.1 applies the same stabilization requirements toparking lots on permitted facilities. Finally,
many cities/towns have treated their

own parking lots or required treatment ofprivate lots belowMCESD's thresholds.

In determining whether the MAG plan provides for the implementation of BACM for unpaved parking lots, we are first specifically considering whether the plan provides for the implementation ofRACM for these

sources.23In our 1998 moderate area PM-10 FIP for the Phoenix area, we promulgated aRACM fugitive dust rule applicable tounpaved parking lots in the Phoenix PM-10 nonattainment area. 40 CFR 52.128(d)(3). This rule provides

a starting point for determining whether the MAGplan's measures for unpaved parking lots meet RACM. Itis not necessary for them to be identical to the FIP rule in order to meetthe CAA's RACM requirement, but only thatthey provide for the implementation of RACM. However, ifthe submitted

measures for aparticular source are identical to the FIP rule, we can determine without further analysis that the MAGplan has provided for RACM for that source.

MCESD requirements for unpaved parking lots found in Rule 310.01, section 303 are the same in terms of

source coverage and applicable standards/test methods for unpaved parking lots as the FIP rule, with the only difference being that Rule 310.01 applies county-wide while the FIP rule applies strictly to sources located in the PM-10 nonattainment area (located in

23While a serious area PM-10 plan must provide
for both the implementation ofRACM (tothe extent that ithas not already satisfied the requirement in its moderate area plan) and BACM, in determining whether such aplan provides forBACM implementation, we do not normallyconduct a separate evaluation to determine ifthe measures also meet the RACM requirements ofthe CAA as interpreted by EPA inits General Preamble. See 57 FR 13540. This is because in our serious area guidance (Addendumat 42010), we interpret the BACM requirement as generally subsuming the RACM requirement (i.e., ifwe determine that the

measures are indeed the "best available," we have necessarily concluded that they are "reasonably available"). See Addendum at 42012-42014. Therefore, a separate analysis to determine ifthe

measures also represent a RACM-level ofcontrol is
not generally necessary. However, inthis particular
case, we have already established through our FIP rule what we consider to be a RACM-level of control for this source category. Thus our FIP rule provides us witha baseline against which we can review whether the MAG plan provides not only for RACM butalso goes beyond that for BACM. We also intend to eventually withdraw the FIP rule in favor of local controls. In order to do this, we must determine under CAA section 110(1), that, among other things, withdrawing the FIP rule does not interfere withthe RACM requirements in the CAA. An explicit determination now simplifies this future action. the eastern third ofthe County). Rule 310.01 requirements became effective when the rule was adopted on February 2000. In light ofthe factthat Rule 310.01 requirements are the same as the FIP rule requirements and MCESD has made enforceable commitments to improve compliance and enforcement of Rule 310.01, we propose thatthe MAG planprovides for the implementation of RACM. Given the additional city/town commitments inthe MAG planthat collectively increase the stringency of control onunpaved parking lots, we propose that the MAGplan also provides for the implementation of BACM. Both Rule 310.01 andthe city/
town commitments were implemented prior to June 10, 2000, the BACM implementation deadline for the Phoenix area.

As the onlypotential MSM, the MAG planidentifies South Coast's Rule 403 which requires sources to apply dust suppressants to stabilize at least 80 percent ofunstabilized surface area and
to comply with a 0 percent opacity property line limit. The MAG plan deems the respective requirements roughly equivalent to Rule 310. MAG plan, p. 10-29. We believe that the addition ofa silt loading/content standard for unpaved parking lots for

sources covered under Rule 310 increases the rule's stringency suchthat itis atleast equivalent tothat ofSouth Coast Rule 403. We, therefore, propose to find thatthe MAG plan correctly concludes thatthere are no MSM in other State plans orused in practice elsewhere that are applicable to the Phoenix area.
f.DisturbedVacant Lands

This category includes windblown fugitive dust emissions from disturbed surfaces ofvacant lands. On vacant land, fugitive dust emissions are caused by virtually any activity which disturbs

an otherwise naturally stable parcel of land, including earth-moving activities, material dumping, weed abatement, and vehicle traffic. 63 FR 15919, 15937 (April 1, 1998).

The MAGplan includes three suggested measures for controlling fugitive dust from vacant disturbed lands. MAGplan, Table 5-2. The plan also identified controls onweed abatement operations and off-road racing aspotential MSM. MAG plan, Table 10-7. We believe this listis complete and propose to findthat the MAG plan evaluates a comprehensive
set ofpotential BACM andMSM for disturbed vacant lands.

Both MCESD rules 301 and 301.01 address vacant lots. Rule 310 requirements apply to vacant lots

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located at permitted facilities (including construction sites) and Rule 310.01 requirements apply to nonpermitted

sources.24Rule 310 and Rule 310.01 requirements apply toboth publicly and privately owned lots. Rule 310, section 302.3 andRule 310.01, section 301 and 302.

In determining whether the MAG plan provides for the implementation of BACM for disturbed vacant land, we are also specifically considering whether the plan provides for the implementation ofRACM for this source category. See Footnote 23. In our FIP,

we promulgated a RACM fugitive dust rule applicable to disturbed vacant land in the Phoenix PM-10 nonattainment

area. 40 CFR 52.128(d)(3). This rule provides a starting point for determining whether the MAG plan's measures for disturbed vacant lands meetthe RACM requirement. Itis not necessary for them
to be identical to the FIP rule in order
to meetthe CAA's RACM requirement, but only that theyprovide for implementation ofRACM. However, if the submitted measures for a particular

source are identical tothe FIPrule, we

can determine without further analysis that theMAG plan hasprovided for RACM for that source.

Rule 310.01 requirements forvacant lots and open areas are virtually identical to the Phoenix FIPrule's requirements for these sources. Rule 310.01, however, is more broadly applicable. It covers vacant lots and
open areas located anywhere in Maricopa County, in contrast to the Phoenix FIP rule, which only applies to lots in the Maricopa County portion of PM-10 nonattainment area. Rule 310.01, sections 301 and 302. Unlike the FIP rule, Rule 310.01 also applies to partially developed residential, industrial, institutional, governmental,

orcommercial lots in Maricopa County, and any tract ofland in the Maricopa County portion ofthe nonattainment

area adjoining agricultural property. Rule 310.01, section 211.

Rule 310 requirements for vacant lots and open areas on permitted sources are

more stringent than those in Rule 310.01, in thatRule 310 requires stabilization ofall inactive disturbed surface areas on permitted facilities, regardless oftheir size. Rule 310, section 302.3. Rule 310 also contains requirements for weed abatement that closely resemble the Phoenix FIP rule's weed abatement requirements, except

24Permitted sources include any facility permitted by MCESD and are notlimited solely to those facilities with earthmoving permits, Rule 310, section 102. that Rule 310's threshold for coverage is lower.25

Vacant lots and open areas subject to Rule 310 andRule 310.01 are required
to meetthe same surface stabilization standards/test methods as required in the Phoenix FIP rule.

In addition torequirements in Rule 310 and Rule 310.01, theMAG plan contains commitments by several cities and towns to address vacant disturbed lots. For example, seven jurisdictions require orwill require stabilization of disturbed vacant lots after 15 days of inactivity (as compared toRule 310.01's 60-day compliance period); two (2) prohibit dumping ofmaterials onvacant land; and two (2)will stabilize all cityowned vacant lots. See EPA TSD section "Implementation ofBACM and Inclusion ofMSM for Disturbed Vacant Land."

Because Rules 310 and 310.01 requirements are atleast as stringent as the FIPrule requirements and MCESD has committed toimprove compliance and enforcement ofthese rules (as discussed below), we propose that the MAG plan provides for the implementation ofRACM on disturbed
vacant land. Because these rules increase the number oflots subject to control which collectively increase the stringency ofcontrol onvacant disturbed lands, we propose thatthe MAG plan also provides for the implementation ofBACM. All measures for vacant disturbed lands were implemented prior tothe June 10, 2000 BACM implementation deadline for the Phoenix area.

For itsMSM analysis, theMAG plan identifies measures in Clark County (Las Vegas, Nevada) Rule 41 and South Coast Rule 403. See MSM Study, pp. C-11 and C-16, 17. The plan concludes that neither measure is more stringent than the Maricopa measures because Rule 310 and 310.01 contain similar and equally ormore stringent requirements. We agree that the MCESD's rules are equally ormore stringent.

We, therefore, propose to findthat the MAG plan correctly concluded that there are no MSM in other State plans

orused in practice elsewhere that are applicable tothe Phoenix area.

g. Unpaved Roads

This category includes re-entrained dust from vehicle travel onunpaved roads. There are three classes of

25Rule 310 requires any earthmoving operation
that disturbs 0.1 acre ormore to have a dust control plan, including weed abatement by discing or blading, whereas the Phoenix FIP rule weed abatement requirements only apply to disturbances equal to orgreater than 0.5 acres. Rule 310, section
303 and 40 CFR 52.129(c)(3) and (d)(3)(i). unpaved roads in the Maricopa nonattainment area: public roads, private roads that are publicly maintained (alsoreferred to as minimally-maintained or courtesy grade), and private roadsthat are privately maintained.

The MAGplan includes three suggested measures for controlling fugitive dust from unpaved roads: Surface treatment to reduce dust from unpaved roads and alleys, traffic reduction/speed control plans for unpaved roads; and prohibition of unpaved haul roads. MAG plan, Table 5-2. The MAGplan does not identify any other State's measures that are more stringent than the ones already in the plan. We believe this listis complete and propose to find thatthe MAG plan evaluates a comprehensive set of potential BACM and MSM for unpaved roads.

In determining whether the MAG plan provides for the implementation of BACM for unpaved roads, we are also considering whether the Planprovides for the implementation ofRACM for these sources. See Footnote 23. In our FIP, we promulgated a RACM fugitive dust rule applicable to unpaved roadsin the Phoenix PM-10 nonattainment area. 40 CFR 52.128(d)(3). This rule provides

a starting pointfor determining whether the MAGplan's measures for unpaved roads meetthe RACM requirement. Itis
notnecessary for them to be identical to the FIP rulein order to meet the CAA's RACM requirement, but only thatthey provide for implementation ofRACM. However, ifthe submitted measures for

a particular source are identical to the FIP rule, we can determine without further analysis thatthe MAG plan has provided for RACM for that source.

As discussed below, we propose to findthat the MAGplan provides for the implementation ofRACM and BACM and the inclusion ofMSM for unpaved roads.

Surface treatment to reduce dust from unpaved roads and alleys. The principal control measure for public unpaved roads and alleys is Rule 310.01, section 304, whichrequires all publicly-owned unpaved roads and alleys with 250 vehicles per day (VPD) ormore tobe stabilized byJune 10, 2000 and those with 150 vehicles per day ormore tobe stabilized byJune 10, 2004.

Several cities have commitments that
gobeyond the requirements ofRule 310.01 for publicly-owned unpaved roads. For example, the City ofPhoenix committed to-and accomplished before June 10, 2000-paving all 80 miles ofits publicly-owned unpaved roads regardless ofthe level ofvehicle travel. Phoenix Commitment, Measure 98-DC50264

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7.Other cities, such as Tempe and Gilbert, have veryfew remaining miles ofpublic unpaved roads/alleys. See Tempe Commitments, Measure 98-DC-7 and Gilbert Commitments, Measure 98- DC-7.

For private roads, Rule 310, section 308.6, requires that easements, rights-ofway, and access roads for utilities (electricity, natural gas, oil, water, and
gas transmission) that receive 150 or

more VPD must be paved, chemically stabilized, or graveled in compliance with therule's standards.

Private unpaved roads are scattered throughout Maricopa County, within both County and cityjurisdictions. A
survey performed for us ofunpaved roads in Maricopa County determined that the great majority ofidentified unpaved road mileage consists of privately-owned roads thatreceive minimal maintenance by the Maricopa County Department ofTransportation (MCDOT).26

MAG and MCDOT have committed to pave County minimal maintenance roads within the nonattainment area that currently exceed 150 VDT and meet criteria to become public highways, using $22 million in CMAQ and MCDOT funds. MAG Commitment; Maricopa County Commitment, 1999 Revised Measure 17. This program will
pave an estimated 60 miles ofunpaved roadways in fiscal years 2001-2003 which is approximately 20 percent of the privately-owned, publiclymaintained County-jurisdiction roads and account for 40 percent ofall VMT

onthese roads. Maricopa County has also committed to continue to evaluate otherroads for funding when traffic levels increase above 150 vehicle trips
per day. Maricopa County Commitment, 1999 Revised Measure 17. We interpret this commitment to apply to any private roads within County jurisdiction, whether they currently receive minimal maintenance or not.

As the County evaluates roads for paving, it may make exceptions to its commitment to pave roads with vehicle trips that exceed 150 VDT. The County's evaluation process takes into account whether estimated costs ofpaving are excessive (greater than $500,000 per mile).27 When MCDOT identifies a road that meets these criteria (i.e.the road

canbe declared apublic highway and
costs are not excessive), it will

26Pacific Environmental Service, "Survey for Fugitive Dust Emission Sources", April 15, 1999.

27Aprivate road begins to bear other than local
traffic through extensions ofothernearby public roads orthe construction ofanindirect source that
attracts external drivers using theroad as a short

cut. SeeMaricopa County Commitments, 1999 Revised Measure 17. recommend thatthe Board of Supervisors open and declare the road

apublic highway.28

Because BACM implementation properly takes costs into account, we believe that MCDOT's criteria for selecting private roads topave are suitable in the context ofa strategy to implement BACM and will result in control ofthe great majority ofhigh traffic unpaved roads. Although available information onprivate roads in cityjurisdictions islimited, our existing information suggests that a typical privately-owned unpaved road has little traffic on it.29 As a result, we believe that the vastmajority ofprivate unpaved roads do not need to be controlled in order for us to determine that the MAG plan provides for the implementation ofBACM for unpaved roads for the 24-hour standard.

Traffic reduction/speed control plans for unpaved roads. Somejurisdictions committed to evaluate this measure. Twojurisdictions committed to posting 15 mph speed limit signs on private and

28Maricopa Countyprovided an update to us of
their efforts to identify and pave County minimal maintenance roads. Kelly McMullen, MCDOT, via email on May 4, 2001. The County identified approximately 68 miles ofminimal maintenance roads (courtesygrading only)that potentially could have over 150 VPD traffic. Of those roads, the County was unable to gather traffic count information forapproximately 3 miles dueto repeated counter vandalism ortheft. The County included remaining roads with traffic counts over 130 VPD (allowing forshort termgrowth seasonal variation, etc.) inits program to pave, totaling approximately 65 miles, consisting of approximately 186 segments. Thefirst group of these roads was expected to have abid awarded in June 2001 and be paved by Fall 2001. Design work for the second group was expected tobegin in Summer 2001 and is expected to go to bidfor construction within the next twelve months. Design work for the third group also expected tobegin in Summer 2001 and is expected to bebid approximately 10-12 monthsfollowing the second
group. This third group reflects the most difficult engineering and environmental issues. Based on project engineer estimates at this time, the County believes that six segments totaling approximately 3.0 miles may exceed the reasonable cost threshold of $500,000 permile, or have issues with adjoining property owners that arenot possible to resolve within the SIP time frames. The County will evaluate whether another method of dust suppression may beviable forthose segments.

29Through MAG, we requested additional
information on private unpaved roads from the cities of Chandler, Scottsdale, Gilbert, Glendale, Mesa, Phoenix, Tempe, Peoria, Avondale, Carefree, Cave Creek, El Mirage, Goodyear, and Surprise. Letter Colleen McKaughan, EPA, to Lindy Bauer, MAG, March 21, 2001. All but three cities responded to the survey. Five cities statethat they currently have no private unpavedroads with greater than 150 VPD. Three cities indicate they do
not believe there are private unpaved roads with greater than 150 VPD in theirjurisdictions. The remaining cities either have a small number of private road miles identified with greater than 150 VPD ormake no statement regarding the number of private road miles withgreater than 150 VPD in their jurisdictions. Letter LindyBauer, MAG, to Colleen McKaughan, EPA, June 29, 2001. public unpaved roads and access ways;
onejurisdiction hasposted 15 mph speed limits in all alleys. SeeMAG plan, Table 10-9. Also, underRule 310, owners/operators ofunpaved haul roads and utilityroads who comply with the ruleby limitingvehicle trips to 20 per day, must also limitvehicle speeds to 15 mph. While speed limit controls are onlybeing implemented to a limited extent, we believe the plan's measures to pave or otherwise stabilize unpaved roads in the Phoenix PM-10 nonattainment area establish the critical commitments for the implementation of RACM and BACMbecause road stabilization ensures emission reductions whereas speed limits may or may notbe observed.

Prohibition ofunpaved haul roads. Rule 310 requires that unpaved haul roads meetboth a 20 percent opacity standard and a silt content or silt loading standard. Rule 310, section 302.2. We propose to find thatthis requirement is sufficient forthe implementation ofBACM forthese roads. We believe requiring compliance with both ofthese standards ensures thatthese roads will be stabilized.

Evaluation ofunpaved road measures in other areas found none that aremore stringent than the measures for unpaved roads in the MAGplan. MAG plan, Table 10-7. We agree and propose to findthat there are no other MSM for unpaved roads than are already included in the MAG plan.

Please see the TSD section "Implementation ofBACM and Inclusion ofMSM for Unpaved Roads" for amore detailed discussion ofour proposed findings.

h.Construction Sites andActivities

Sources offugitive dust emissions at construction sites include land clearing, earthmoving, excavating, construction, demolition, material handling, bulk material storage and/or transporting operations, material track out or spillage
ontopaved roads (whichwe have addressed in the paved road section), andvehicle use and movement on site (e.g., the operation ofany equipment on unpaved surfaces, unpaved roads and unpaved parking areas). Windblown emissions from disturbed areas on construction sites are also a source of PM-10. Construction operations, which

are mostly earthmoving, represent some 90 percent ofthe emissions in this

source category.

The suggested measure in the MAG planfor controlling emissions from construction sites are actually various

means ofimproving compliance with controls ratherthan new control requirements for construction sites. See 50265

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MAG plan, Table 5-2. MCESD had already adopted controls for construction sites in its fugitive dust rule, Rule 310. The plan also identifies several potential MSM. See MAGplan, Table 10-7. We propose to findthat the MAG plan evaluates a comprehensive
set ofpotential controls for construction sites emissions including the potentially MSM from other states.

Rule 310's requirements, effective on February 16, 2000, apply to any source required to obtain a permit under Maricopa County rules, which includes earthmoving operations of0.10 acre or

more 30 and sources subject to title V permits,3 1non-title V permits, or general permits. In addition to rule requirements for fugitive dust sources located at any permitted source, Rule 310 requires thata Dust Control Plan (DCP) be submitted for any earthmoving operations of0.10 acre or more, and that the DCP be approved prior to commencing any dust generating operation. The rule's definition ofa dust generating operation includes any activity capable ofgenerating fugitive dust including land clearing, earthmoving, weed abatement by discing or blading, excavating, construction, demolition, material handling, storage and/or transporting operations, vehicle use and movement, the operation ofany outdoor equipment

orunpaved parking lots.

For other permitted sources, Rule 310 requires that a DCP be submitted and approved prior to commencing any routine dust generating activity, defined

as any dust generating operation which

occurs more than 4 times peryear or lasts 30 cumulative days ormore per year. 32

Specific Rule 310 requirements include:

* a 20 percent opacity requirement for any dust generating operation

* wind event controls * implementation ofcontrols before, after and while conducting any dust generating operation, including weekends, after work hours and holidays

* required controls and standards for: * unpaved parking lots

30Earthmoving operations include cutting and filling, grading,leveling, excavating, trenching, loading or unloading ofbulk materials, demolishing, blasting, drilling,adding to or removing bulk materials from open storage piles, back filling, soil mulching, landfill operations, or weed abatement by discing or blading.

31Title V permits are operating permits required by Title V ofthe Clean AirAct for major stationary

sources and certain other stationary sources.

32This is in addition to the requirement to submit

a DCP for anyearthmoving operation that disturbs 0.10 acre ormore even ifthe operation is subject
to Title V orother permittingrequirements. * unpaved haul/access roads * disturbed open areas and vacant lots * bulk material hauling * bulk material spillage, carry-out, erosion andtrack out

* open storage piles * weed abatement byblading or discing

* arequirement in dust control plans for atleast one primary and one contingency control for allfugitive dust
sources; the contingency measure isto be immediately implemented ifthe primary control proves ineffective

In order to comply with the rule's 20 percent opacity standard and dust control plan requirements for implementing primary and/or contingency controls for earthmoving activities, sources need to apply one or

more controls, which in most cases includes applying water or another dust suppressant before and during operations. Inactive disturbed surfaces
must be stabilized tomeet at least one oftherule's stabilization standards (e.g. visible crusting, 10 percent rock cover, etc.). Unpaved roads and unpaved parking lots must also be stabilized to meet both a 20 percent opacity standard and a silt content/loading standard.3 a
Test methods associated with stabilization and opacity standards are contained in Appendix C, which was submitted with Rule 310.

The 1999 revisions to Rule 310 that have increased the rule's stringency include the addition ofspecific work practice standards, the addition of stabilization standards andtest methods for unpaved surfaces, andmodifications
to the opacity test method (addingan alternative opacity test method for unpaved roads and unpaved parking lots and modifying the opacity test method for other sources). We believe that the new and/or revised standards/
test methods provide for a greater degree ofcontrol than under theprevious SIPapproved version ofRule 310.

In addition tothese Rule 310 revisions, MCESD made three enforceable commitments to further strengthen requirements for construction sites in 1999. See Maricopa County Commitments, Revised Measure 6. MCESD hasrecently revised these commitments and will take the revisions to the Maricopa County Board ofSupervisors in December, 2001 for formal adoption as enforceable commitments. See Letter, Al Brown, MCESD toJack Broadbent, EPA,

33Unpaved roads must meet a 6percent silt
content standard or, alternatively, a 0.33 oz/ft2 silt loading standard, while unpaved parking lots must meet an 8percent silt content standard or, alternatively, a 0.33 oz/ft 2silt loading standard. September 13, 2001 (MCESD commitment letter). The commitments

are to:

1. Research and develop a standard(s) and testmethod(s) for earth moving
sources, designed tobe enforceable and
meet BACM requirements as to stringency and the number of sources thatit applies to. Revise Rule 310 and/

or Appendix Cbyno later than December 2002 to modify the existing opacity standard/test method or add an additional opacity standard(s)/test method(s), tailored to non-process fugitive dust sources that create intermittentplumes. This commitment willbe met inits entirety onlyifthe standard(s)/test method(s) is approved by EPA. The County is alsoproposing
to support and coordinate with Clark County, Nevada in the ongoing research
to develop fugitive dust test methods through the appropriation of$25,000.

2.Part 1: Onsite Implementation ofDust Control Plan

Raise awareness ofonsite project supervisors to acquire and read approved site dust control plans thereby improving the implementation ofthe dust control plan at the construction site. This objective willbe achieved through one-on-one contact at the time ofinspection and through the development ofa revised training curriculum and supporting materials for both a classroom setting and onsite aids for improved project management. Maricopa County inspectorswill continue to go over dust control plans with construction sitepersonnel during the initial site inspection andwhenever issues arise during subsequent inspections. The training curriculum being developed bythe Arizona Department ofTransportation (ADOT)is scheduled for completion in winter of 2002 and implementation ofthe second level ofdust control education will begin March-June 2003.

Part 2: Dust Control Plan Improvements

Research, develop and incorporate additional requirements for dust suppression practices/equipment into dust control plans and/or Rule 310 by March-December 2002. Based on the ADOT research, MCESD research or other alternative research, Maricopa County will develop agrowing list of criteria for effective versus ineffective dust suppression practices that address various site circumstances. 3. Revise the sample daily recordkeeping logs for new and renewed Rule 310 permits to be consistent with rule revisions andto provide sufficient detail documenting the implementation ofdust control measures required by 

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Rule 310 and the dust control plan. Distribute sample log sheets with issued permits and conduct outreach to sources by December 2001.

The first commitment addresses our
concern thatthe existing opacity standard and test method for earthmoving operations may not always be sufficient to control construction site dust to BACM levels. MCESD has already revised the opacity test method
to deal partially with this concern (see Rule 310, Appendix C), but webelieve that additional standards/test methods

are needed tofully assure that sources

are effectively controlled.

Field research is needed to identify an appropriate standard(s) and test method(s) to meet this commitment. MCESD originally committed to complete this research and revise the opacity method by July 2001 but was unable to do so. It nowintends to work with Clark County which has recently conducted research on test methods for earthmoving sources and is planning to conduct a second phase ofresearch. MCESD will contribute funding to these efforts. MCESD hasrequested a one-year extension ofthe deadline in its original commitment in order to monitor, validate andverify the resulting test method(s) performance in Maricopa County.

The second commitment addresses

our concern that DCPs lack specific criteria for dust suppressant application. For example, a source engaged in grading or cut-and-fill earthmoving for a multi-acre project may choose to comply with Rule 310 by applying
water. However, neither the rule nor DCPs establishes minimum criteria for the number ofwater trucks/water application systems and water truck capacity for any given size construction site or a ratio ofearthmoving equipment
to water trucks. Also, for effective dust control, certain soil types may require substantial pre-wetting, thorough mixing ofwater into the soil for uniform penetration, and/or dust surfactant or tackifyer combined with water; neither Rule 310 nor DCPs currently require suchmeasures for any sites.

Establishing criteria for dust control is complicated byvariations in soils, meteorological conditions, equipment size/use, project phase, and level of activity. All these factors can impact the
amount ofwater (orother controls) needed to control fugitive dust on a particular site on a particular day and has made it difficult to establish these criteria. Because ofthis difficulty MCESD hasrevised its original commitment to allow additional time to develop them. MCESD has also expanded its original commitment to include a program to work with on-site supervisors to assure that they obtain and review the DCP for their sites. In implementing Rule 310 duringthe last year,it found that site supervisors donot have or donot know what is in their DCPs and thus may not be implementing appropriate dust control methods.

The third commitment addresses our
concern that while Rule 310 currently contains an acceptable recordkeeping requirement, a more specific recordkeeping requirement would help improve compliance. Currently neither the rule norDCPs specify what information should be included in a daily log. MCESD hasrevised its original commitment to allow additional time to work with its stakeholders to develop daily recordkeeping log sheets
to provide sufficient detail documenting the implementation ofdust controls.

We propose to find thatRule 310 as adopted onFebruary 16, 2000 and combined with the commitments by MCESD tomake certain additional changes to the Rule, provide for the implementation ofRACM andBACM on construction sites for the 24-hour PM10 standards. 34 We have also determined that the revised commitments do not affect ourprevious proposed finding thatRule 310 combined with the commitments provide for the implementation of RACM andBACM on construction sites for the annual standard. 65 FR 19964, 19980. The rule is comprehensive in
scope in that each dust source is subject
to a set ofrequirements under Rule 310 (e.g. storage piles, dirt trackout, haul truck loads, disturbed areas, earthmoving operations).

The MAGplan identifies several potential most stringent construction site fugitive dust measures either in or under consideration for inclusion in others SIPs. SeeMSM Study, Table 1- 2and Table 3-1.

34Theserevised commitments are currently unenforceable because they have notbeen adopted by Maricopa County's Board ofSupervisors. We are, however, proposing to approve these commitments under CAA section 110(k)(3) as an enforceable element ofthe Arizona SIPbecause we fully expect that the Board will adopt these commitments as enforceable SIPcommitments and the State will submit them as a complete SIPrevision prior to our final action. However, ifwe do notreceive the adopted commitments bythetimewe musttake final action, wepropose toconditionally approve them under CAAsection 110(k)(4). Ifwetake final action toconditionally approve these commitments, MCESD will haveone yeartofulfill the commitment or the approval will turn intoa disapproval andwe wouldno longer be abletofind that the MAG planprovides for theimplementation ofBACMandtheinclusionofMSM onconstruction sites foreithertheannualor 24-hour standards. Most ofthe potential MSMs are provisions in South Coast fugitive dust rule, Rule 403. The MAGplan indicates that each ofthe SouthCoast and MCESD's rules are more stringent than the other in certain respects. MAG plan,
p. 10-35. The MAG plan acknowledges thatRule 403 contains more stringent control measure requirements than those imposed byRule 310. For example, Rule 403 requires that water be applied to soil notmore than 15 minutes priorto moving the soil and requires open storage piles to be watered twice per hour or covered. However, the MAGplan indicates that Rule 310's 20 percent opacity limitis generally more restrictive thanRule 403's property line standard because a 20 percent opacity fugitive dustplume typically disperses to zero visibility within 50 feet downwind ofa source. MSM Study, p. C-12. The MAG plan concludes that, on balance, Rule 310 is equally stringent compared to Rule 403's construction site requirements. We agree with this conclusion with the
caveat that we believe Rule 310 and/or dust control plans require additional controls for dust suppression. This
caveat is addressed in the MAGplan's commitment to research, develop and incorporate additional requirements for dust suppression practices/equipment for construction activities into dust control plans and/orRule 310.

The MAGplan does not discuss any construction site measures from other

areas as potential most stringent

measures. Based on our work with the Las Vegas area, we have identified requirements in Clark County Health Districtpermits that are potentially

more stringent than Maricopa County's

measures. 35These requirements include stand tanks on projects that are 10 acres

or more in size, an additional, separate water truck when using atrencher or when screening, a separate water truck

or pull during landscaping, maintaining all stockpiles in amoist condition, etc.

We propose to find thatRule 310's existing provisions andMaricopa County's second commitment to research, develop andincorporate additional requirements for dust suppression practices/equipment into Rule 310 and/orDCPs are consistent with Clark County's requirements.

We have also identified a requirement in Imperial County Regulation VIII that ispotentially more stringent than Maricopa County's measures. Imperial County Regulation VIII requires that
water be applied 15 minutes prior to

35These requirements are notin Clark County's fugitive dust rulebut rather are required practices indust control permits. 

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handling or transferring bulkmaterial, chemical/physical stabilization, or sheltering/enclosure ofthe operation andtransfer line. While Maricopa County Rule 310 requires owners/ operators to comply with a 20 percent opacity standard for any dust generating operation andDCP must include a control measure for every fugitive dust

source (includingbulk material handling/transfer), it does not contain specific requirements as Imperial County does for this activity. However, watering 15 minutes prior to handling
may be overly prescriptive and not necessary in all cases tomeet the rule's performance standards. We propose to find thatMaricopa County's second commitment to research, develop and incorporate additional requirements for dust suppression practices/equipment into Rule 310 and/or DCPs is consistent with Imperial County's requirements.

For these reasons, we propose to find that the MAG plan provides for the inclusion ofthe MSM applicable to the Phoenix area for construction sites and activities. See Footnote 34.

i. Agricultural Sources

The agriculture source category covers all dust generating activities and sources

onfarms and ranches. These activities and sources include land planning, tilling, harvesting, fallow fields, prepared fields, field aprons, and unpaved roads. This source category is

avery significant contributor to 24-hour PM-10 standard exceedances in the Phoenix area. Atthe West Chandler site, 55 percent ofthe modeled exceedance

was due to agricultural sources (acotton field and its apron). At the Gilbert site, 26 percent ofthe modeled exceedance

was due to an agricultural source (a field apron). See Microscale plan, pp. 18-19.

In order to develop adequate controls for this source category, Arizona passed legislation in 1997 establishing an Agricultural Best Management Practices (BMP) Committee and directing the Committee to adopt by ruleby June 10, 2000, an agricultural general permit specifying best management practices for reducing PM-10 from agricultural activities. The legislation also required that the implementation ofagricultural controls begin with an education program startingby June 10, 2000 with full implementation byDecember 31, 2001. See Arizona Revised Statutes (A.R.S.) 49-457.

After a series ofmeetings during 1999 and 2000, the Agricultural BMP Committee adopted the agricultural general permit and associated definitions, effective May 12, 2000, at Arizona Administrative Code (AAC) R18-2-610, "Definitions for R18-2- 611," and 611, "Agricultural PM-10 General Permit; Maricopa PM10 Nonattainment Area" (collectively, general permit rule). The State submitted the general permit rule in July 2000 and its analysis quantifying the emission reductions expected from the rule and the demonstration thatthe rule meets the CAA's RACM, BACM and MSM requirements in June 2001. We proposed to approve itas meeting the CAA requirement for RACM onJune 29, 2001 and signed the approval on September 10, 2001. See 66 FR 34598.

The general permit rule requires a commercial farmer toimplement by December 31, 2001 atleast one BMP for three categories ofemission sources on

afarm: tillage andharvest, noncropland, and cropland. R18-2-610 defines commercial farmer as "an individual, entity, orjoint operation in general control of 10 or more continuous acres ofland used for agricultural purposes within the boundary ofthe Maricopa County PM10 nonattainment area." R18-2-610 defines tillage and harvest as "any mechanical practice thatphysically disturbs cropland or crops on a commercial farm." R18-2-610 defines non-cropland as "any commercial farm land that: is no longer used for agricultural production; is no longer suitable for production ofcrops; is subject to arestrictive easement or contract that prohibits use for the production ofcrops; or includes a private farm road, ditch, ditchbank, equipment yard, storage yard, or well head." R18-2-610 defines cropland as "land on a commercial farm that: is within the time frame offinal harvest to plant emergence; has been tilled in a prior year andis suitable for crop production, but is currently fallow; is a turn-row." R18-2-610 defines a BMP as "a technique verified by scientific research, that on acase-by-case basis is practical, economically feasible and effective in reducing PM-10 particulate emissions from a regulated agricultural activity."

For enforcement purposes, a commercial farmer isrequired to maintain a record demonstrating compliance with the general permit. A commercial farmer not in compliance with the general permit is subject to a series ofcompliance actions described in A.R.S. 49-457.1-K.

The BMP Committee began implementing the general permit rule in June 2000 bymeans ofan extensive educational outreach program informing
growers about the BMPs. In addition, the BMP Committee developed aGuide
to Agricultural PM-10 Best Management Practices to provide information and guidance on how to effectively implement BMPs.36 Farmers must be in compliance with the general permit rule by December 31, 2001.

For the reasons discussed below and

more extensively in the section "Implementation ofBACM and Inclusion ofMSM for Agricultural Sources" in the EPA TSD, we propose to find thatthe State's general permit rule meets the CAA'srequirements to provide for the implementation of BACMby June 10, 2000in CAA section 189(b)(1)(B) and to include MSM in section 188(e). Our proposed finding is applicable toboth the annual and 24-hr standards. It revises our previously proposed finding in the annual standard proposal thatthe State's commitment in the MAGplan to adopt and implement agricultural best management practices
meets the CAA'srequirements for BACM and MSMby substituting the BMP general permit rule. 65 FR 19964, 19981.

In September 1998, the Agricultural BMP Committee appointed an Ad-hoc Technical Group to develop a comprehensive list ofpotential BMPs for regulated sources in the Maricopa County nonattainment area. Participants

on the Ad-hoc Group included the USDANRCS, USDA Agricultural Research Service, University ofArizona College ofAgriculture, ADEQ, University ofArizona College of Agriculture and Cooperative Extension, Western Growers Association, Arizona Cotton Growers Association, Arizona Farm Bureau Federation, and EPA. BMP TSD, p. 15.

The Ad-hoc Technical Group reviewed available dust control regulations, literature, andtechnical documents, and developed a list of65 conservation practices potentially suitable to agricultural sources in the Maricopa County nonattainment area for further consideration. BMP TSD, p. 16. These 65 measures represented a broad spectrum ofpotential BMPs, many of which related to conservation practices usedin the western United States that had never been evaluated in the context ofreducing PM-10.

The Agricultural BMP Committee thoroughly reviewed the potential practices presented bythe Ad-hoc Technical Group and evaluated the potential BMPs using available information on technological feasibility, costs, and energy and environmental impacts. After an analysis ofthe limited

36

"Guide to Agricultural PM-10 Best Management Practices, Maricopa County, Arizona PM-10 Nonattainment Area," Governor's Agricultural BMP Committee, First edition, February, 2001. 50268

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information available andnumerous public discussions, the Committee decided toinclude 34 ofthe 65 BMPs in the general permit rule and divided these 34 BMPs into the three categories offarm activities specified in A.R.S. 49- 457.N.: 10 BMPs applicable to the tillage andharvest category; 10 BMPs applicable tothe non-cropland category; and 14 BMPs applicable tothe cropland category. See BMP TSD, 17. In selecting these BMPs, the Committee deemed them tobe feasible, effective and

common sense practices for the Phoenix

area which minimized potential negative impacts on local agriculture.

Ofthe 31 potential BMPs eliminated, the majority were dropped because they either duplicated another BMP or did
not reduce PM-10. Other reasons for elimination included the impracticability ofaBMP for the Maricopa County Area, lack ofcost effectiveness, or infeasibility of implementation. See June 13, 2001 BMP submittal, Enclosure 3, Attachment 8.

At the time the BMP Committee was developing the general permit rule, there was very limited available information concerning the technological feasibility, costs, and energy and environmental impacts of these BMPs. Although the Committee determined that all the selected BMPs

were technologically feasible control requirements, itfound that calculating the other impacts on a commercial farmer was difficult. Because ofthe variety, complexity, anduniqueness of farming operations in Maricopa County, the Committee concluded that farmers need avariety ofBMPs in each of the three categories ofagricultural activities
to choose from in order to tailor PM-10 controls to their individual circumstances. Further, the BMP Committee acknowledged thatthere is a limited amount ofscientific information available concerning the emission reduction and cost effectiveness of some BMPs, especially in relation to Maricopa County. The BMP Committee balanced the limited scientific cost effectiveness information with the common sense recognition thatthe BMPs would reduce wind erosion and the entrainment of agricultural soils, thereby reducing PM10. As a result, and given the myriad factors that affect farming operations, the BMP Committee concluded that requiring more than one BMP for each ofthe three agricultural categories could
not be considered technically justified and could cause an unnecessary economic burden to farmers. Instead, the BMP Committee and ADEQagreed
to monitor the effectiveness ofthe BMPs and adjust the program, ifneeded, in the future. BMP TSD, p. 18. The general permit rule, as finally adopted by the BMP Committee in May 2000 as BACM and MSM, requires that commercial farmers implement atleast

one BMP for the tillage and harvest, cropland, andnon-cropland categories by December 31, 2001.

We define a BACM-level ofcontrol to be, among other things, the maximum degree of emission reduction achievable from a source or source category which is determined on a case-by-case basis, considering energy, economic and environmental impacts. Addendum at 42010. Based onthe BMP committee's findings regarding technological feasibility and economic effects of requiring more than one BMP per category, webelieve that the BMP rule provides the maximum degree of emission reductions achievable from the agriculture source category in the Phoenix area and, therefore, meets the BACM requirement in section 189(b)(1)(B). 37

A requirement that an individual

source select one control method from

alist, but allowing the source to select which ismost appropriate for its situation, is a common and accepted practice for the control ofdust. For example, in its PM-10 FIP for Phoenix,

we promulgated a RACM rule applicable to, among other things, unpaved parking lots, unpaved roads and vacant lots. The rule allows owners and operators to choose one ofseveral listed control methods (pave, apply chemical stabilizers or apply gravel). 40 CFR 52.128(d). In the case ofthe FIP, those subject to the fugitive dust rule

were given a choice ofcontrol methods in order to accommodate their financial circumstances. 38

37We also considered a BACM-level control as going beyond existing RACM-level controls, such as expanding use ofRACM (e.g., pavingmore miles of unpaved roads). Addendum at42013. As noted previously, we have proposed to approve the general permit rule as meeting the RACM requirement in CAA section 189(a)(1)(C). 66 FR 34598. Inthat proposal,we stated ourbelief "that the general permit rule represents a comprehensive, sensible approach that meets, and in factfar exceeds, the RACM requirements ofCAA section 189(a)(1)(C) and EPA guidance interpreting those requirements." 66 FR 34598, 34602. Moreover, we explained that the State also intended the general permit ruleand its enabling legislation to meet the CAA's serious area requirements. 66 FR 34598, 34599. Thus today's proposal that the general permit rulemeets the BACM andMSM requirements ofthe Act is consistent with our prior action.

38 See, as examples, SCAQMD Rule 403 (providingfor alternative compliance mechanisms for the control offugitive dust from earthmoving, disturbed surface areas, unpaved roads etc.); and SCAQMD Rule 1186 (requiring owners/operators of certain unpaved roads the option to pave, chemically stabilize, or install signage, speed bumps or maintain roadways to inhibit speeds greater than 15 mph). We proposedto approve these Allowing sources the discretion to choose from a range ofspecified options isparticularly important forthe agricultural sector because ofthe variable nature offarming. As a technical matter, neither we northe State is in a position to dictate what precise controlmethod is appropriate for agiven farm activity at agiven time in a given locale. The decision as to which control method from an array of methods is appropriate isbest left to the individual farmer. Moreover, the economic circumstances offarmers vary considerably. As a result, it is imperative that flexibility be built into any PM-10 control measure for the agricultural source category whether thatmeasure isrequired tomeet the RACM orBACM requirements ofthe Act.

We believe that the work ofthe BMP Committee resulted in the timely adoption ofthe general permit and educational programs thatrequires BACM implementation on a schedule that will allow time for the agricultural community tounderstand and select appropriate BMPs andto transition to

new practices, some ofwhich may involve the purchase ofnew equipment. Based onthese factors, webelieve that the BMP implementation schedule is as expeditious as practicable and meets the BACM implementation deadline for the Phoenix area ofJune 10, 2000.

The MAGplan identified two potentials MSM for agricultural sources (1)cessation oftilling onhigh winds days in South Coast's Rule 403.1 and (2) soil erosion plans in South Coast's Rule 403. MAGplan, Table 10-8. The plan concluded that neither is, byitself, MSM forthe Phoenix area.

South Coast's 403.1, "Wind Entrainment ofFugitive Dust," applies onlyin the Coachella Valley (Palm Springs) portion ofthe SouthCoast Air Basin and requires that, when wind speeds exceed 25 milesper hour (mph), agricultural tilling and soil mulching activities should cease. While the

measure applies throughout the year, the high wind days tend to occur during

a high-wind season that extends between April and June. The Coachella Valley typically experiences high winds

on 47 days ofthe year. MAG estimated thatthere were a total of 37 hours,

SCAQMID rules as meeting the RACM and/or BACM requirements ofthe CAA on August 11, 1998 (63 FR42786) and took final action approving them on December 9, 1998 (63 FR 67784). See alsothe approval ofMaricopa County Environmental Services Department (MCESD) Rule 310 as meeting the RACM/BACM requirements (62 FR41856, August 4, 1997) and the proposal to approve updated Rule 310 and MCESD Rule 310.01 as meeting the samerequirements (65 FR 19964, April 13, 2000). 

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representing 11 days, with wind speeds greater than 15 mph in 1995 in Maricopa County.

The BMP general permit rule includes "limited activity during high wind event" as one often BMPs that agrower

can choose for the Tillage and Harvest category. According to an analysis in the MAG plan, postponing tilling on high wind days would reduce emissions by 72 percent on high-wind days. MSM study,p. 4-23. However,because only 15 percent ofthe Maricopa County PM10 nonattainment area tilling occurs duringthe high wind season (March through September) and because less than 4 percent ofthe days during this period experience winds greater than 15 mph, the air quality benefits ofthe

measure would be small (i.e,0.08 metric
tons per average annual day in 1995) for the annual standard. MSM study, p. 4- 23. Emissions from tilling are a very small contributor to total agricultural emissions on the 1995 design day (whichwas ahigh-wind day), representing just 1.6 percent ofall agricultural emissions and are not implicated in 24-hour exceedances. URS, Technical SupportDocument for Quantification ofAgricultural Best Management Practices, June 8, 2001 (Ag Quantification TSD), p. 3-11 and Microscale plan, pp. 18-19. Moreover, based onthe limited amount of information available regarding the control efficiencies for the ten BMPs in the Tillage and Harvest category, the control efficiency for "limited activity duringhigh-wind event" is on average

as effective or less effective than the otherBMPs in this category. Ag Quantification TSD, pp. 2-8 to 2_10.

South Coast's Rule 403, "Fugitive Dust," requires the implementation of conservation practices to reduce PM-10 from agricultural sources in the South Coast PM-10 nonattainment area. Under Rule 403(h), agricultural operations exceeding 10 acres within the South Coast Air Basin are exempt from the rule's requirements for fugitive dust if the farmer implements the conservation practices in the most recent Rule 403 Agricultural Handbook. See "Rule 403 Agricultural Handbook: Measures to Reduce Dust from Agricultural Operations in the South Coast Air Basin," South Coast AQMD, December 1998 (the Handbook). Because the requirements ofRule 403 are more stringent than the requirements for conservation practices in the Handbook, it is assumed thatfarmers will always choose to comply with the latter's provisions. Thus the Handbook, rather than Rule 403 itself, iseffectively the potential MSM. For a variety ofreasons, it is difficult
to directly compare the requirements in the general permit with the requirements in the Handbook. First, the South Coast did not attempt to estimate the reductions and costfrom each conservation practice. Second, the types ofcrops grown in Maricopa County and the South Coast area differ significantly. For example, cotton is a dominant crop in Maricopa Countybut is not grown in the South Coast Air Basin. Third, the Handbook allows a grower to substitute

alocal ordinance for the three conservation practices required for "inactive" agricultural land; however, the minimum requirements for the local ordinance are not specified. Handbook, sectionII, p.4. Fourth, the general permit rule andthe Handbook also differin terms ofexemption and waivers. The general permit rule does
not exempt any crop types orprovide a waiver option, but the Handbook exempts orchards, vine crops, nurseries, range land, and irrigated pastures from requiring a practice for the active and inactive categories. Finally, the Handbook also allows farmers to request

awaiver ifthe farmer cannot apply the required practices or averifiable alternative.

While the general permit rule divides agricultural activities into three categories and the Handbook divides them into six, and the terminology used is different, the categories of activities covered are essentially coterminous. Cf. Handbook, section I andACC R18-2- 610.7, .12, .22, .33. However, depending

onthe type offarming operation, the general permit rule would require implementation ofatleast one BMP for each ofthe Tillage and Harvest, Cropland, and Non-Cropland categories andthe Handbook requires from one to three practices for its six agricultural categories.

As discussed above, in the BACM section ofthis TSD, the BMP Committee concluded that,because ofthe variety, complexity, and uniqueness offarming operations andbecause agricultural

sources vary by factors such as regional climate, soil type, growing season, crop type, water availability, andrelation to urban centers, agricultural PM-10 strategies must be based on local factors. Therefore, the general permit rule, as finally adopted bythe BMP Committee in May 2000, reflects the conclusion of the BMP Committee thatfarmers need a variety ofBMPs to choose from in order
to tailor PM-10 controls totheir individual circumstances. Further, the BMP Committee acknowledged that there is alimited amount of scientific information available concerning the emission reduction and cost effectiveness of some BMPs, especially in relation to Maricopa County. The BMP Committee balanced these limitations with the common sense recognition that the BMPs would reduce wind erosion andthe entrainment of agricultural soils, thereby reducingPM10.

While the Committee surveyed

measures adopted in other geographic
areas, these measures were oflimited utilityin determining what measures
are available for the Maricopa County

area. Given the limited scientific information available and the myriad factors that affect farming operations, the BMP Committee concluded that requiring more than one BMP could not be considered technicallyjustified and could cause an unnecessary economic burden tofarmers.

Adding to concerns about the economic feasibility ofrequiring more BMPs per farming activity is the general uncertainty regarding the cost ofthe BMPs and continued viability of agriculture in Maricopa County. Between 1987 and 1997, the number of farms operating in Maricopa County declined by approximately 30 percent and the amount ofland farmed declined by approximately 50 percent. This trend is expected to continue. Finally, in order tojustify additional requirements for farming operations in the area beyond those in the general permit rule, the BMP Committee determined that a significant influx ofmoney and additional research would be needed. BMP TSD, p. 18.

Based on all ofthese factors, the BMP Committee concluded thatthe Handbook's practices were neither technologically nor economically feasible for agricultural sources in Maricopa County. BMP TSD, p. 18.

We agree with the analysis ofthe BMP Committee. As noted previously, the development ofthe general permit rule

was a multi-year endeavor involving an array of agricultural experts familiar with Maricopa County agriculture. Maricopa County isonly the second

area in the country where formal regulation ofPM-10 emissions from the agricultural sector has everbeen attempted. For the reasons discussed above, we propose to conclude that the BMP general permit rule meets or exceeds the stringency ofSouth Coast Rule 403.1's requirement for cessation oftilling during highwinds. Based on the forgoing analysis ofthe Handbook,

we also propose to conclude that the Handbook's requirements are neither technologically nor economically feasible for Maricopa County. Because all the identified potential MSM have either not been demonstrated tobe more 

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stringent than existing Maricopa County controls orfound to be infeasible for the
area, we propose to findthat the MAG plan provides for the inclusion ofMSM

asrequired byCAA section 188(e) to our satisfaction. j. Residential Wood Combustion

The residential wood combustion (RWC) category includes emissions from the burning ofsolid fuel in residential fireplaces and woodstoves as well as barbecues and firepits.

Measures to control PM-10 from residential woodburning include a public education program, woodburning curtailment programs, retrofit requirements and restrictions or bans on the installation ofwoodburning stoves and/orfireplace. In total the MAG plan lists 11 potential BACM and 10 potential MSM. MAG plan Tables 5-2 and 1-7. We believe these list are complete and propose to findthat the MAG plan evaluates a comprehensive
set ofresidential woodburning

measures.

MCESD Rule 318, Approval of Residential Woodburning Devices, establishes standards for the approval of residential woodburning devices that

canbe used during restricted-burn periods. Maricopa County's Residential Woodburning Restriction Ordinance provides thatrestricted-burn periods are declared by the Control Officer when the Control Officer determines that air pollution levels could exceed the CO standard and/or the PM standard (150 gLg/m3). We approved Rule 318 and an earlierversion ofthe ordinance (revised April 21, 1999) as providing for the implementation ofRACM. See 64 FR 60678 (November 8, 1999).

MCESD revised the ordinance on November 17, 1999 to allow the Control Officer to declare restricted-burn periods when the particulate matter pollution levels could exceed the "particulate matter no-burn standard'of 120 gLg/m 3

. We proposed to approve the revised ordinance as part ofthe annual standard proposal. 65 FR 19964, 19990. In addition, A.R.S. section 9-500.16 and A.R.S. section 11-875 (1998) required cities and the County to adopt by December 31, 1998, an ordinance that prohibits the installation or construction ofa fireplace orwood stove unless itis

afireplace with a permanently installed
gas or electric log insert, a fireplace or wood stove thatmeets EPA's Phase II wood stove requirements, ora fireplace with a wood stove insert that meets EPA's Phase II stoverequirements. Most jurisdictions have adopted or have committed to or indicated that State law requires them to adopt the required ordinance. See MAG Plan, pp, 7-55 to 7-64.

With these additional controls, the overall residential woodburning restriction program is strengthened and goes beyond the existingRACM-level program. Both strengthening and expanding existingprograms are key criteria for demonstrating the implementation ofBACM. See Addendum at 42013. Where the MAG plan has rejected potential BACM, it provides a reasonedjustification for the rejection. All measures were implemented byJune 10, 2000, the BACM implementation deadline for the Phoenix area. We, therefore, propose to find thatthe MAGplan provides for the implementation BACM for residential wood combustion.

The MAGplan identified anumber of potential MSM for residential wood combustion. Except for the adoption of

alower threshold for calling noburn episodes, the plan does not provide for the adoption ofany ofthese measures butprovides reasoned and acceptable justifications for their rejection. Therefore, we propose to findthat the MAG plan provides for the inclusion of MSM.

k. Secondary Ammonium Nitrate Secondary ammonium nitrate is formed by a chemical reaction in the atmosphere between oxides ofnitrogen (NOx)and ammonia (NH3).Ninety percent ofNOx comes from motor vehicle exhaust (both on and offroad) and 99.9percent ofNH3 comes from animal wastes. See MAG plan, Table 3- 1.Two potential BACM were identified for ammonia nitrate control: reduce emissions of ammonia andnitrates from agricultural operations and require animal waste management plans for farms/ranches with more than 50 animals. The first measure involves tilling in ofmanure used as fertilizer within 48 hours ofapplication. MAG plan, Table 6-1, measure 97-AG-3. The second measure would focus on reducing ammonia emissions from livestock waste during the winter months when conditions are most conducive to ammonium nitrate formation. MAGplan, Appendix B, Exhibit 5, p. 5-70. For MSM, no

measures were found thatrequired animal waste management plans for farms or ranches andno other measures

were identified. SeeMAG plan, Table 10-7. A large number ofmeasures that couldreduce NOx emissions were identified andhave been evaluated for on-road motor vehicles andnonroad engines. We believe this list ofmeasures is complete andpropose to find thatthe MAG plan evaluates a comprehensive
set ofpotential controls for ammonium nitrate.

Data from earlier studies indicate that ammonia emissions would need to be reducedby 80 percent tohave an appreciable impact on ambient concentrations of ammonium nitrate. MAG plan, Appendix B, Exhibit 5, p. C1.Essentially all ammonia emissions in the inventory are fromlivestock and not fromthe application ofmanure to agricultural fields. As result, controls on the application ofmanure are very unlikely to have any impact onPM-10 levels in the Phoenix area andtherefore

are not technologically feasible. 39 The estimated reduction in ammonia from implementing waste management plans is 30 percent, far short ofthe 80 percent needed to show impact on PM-10 levels (MAGplan, Appendix B, Exhibit 5, p. 5-72), so we alsobelieve that this

measure is currently not technologically feasible.

Other than the on-road vehicle and nonroad engine categories, we do not believe thatthere are any other sources ofNOx that should be called significant in terms ofcontributing to ammonium nitrate levels. See MAGplan, Table 3- 1.Arizona has adopted a number of

measures for controlling NOx emissions frommotor vehicles and nationally, we have established emission standards for control ofNOx from both on- and nonroad engines. The MAGplan does
notidentify any technologically feasible

measures for the control of ammonia. Forthese reasons, we propose tofind thatthe MAG plan provides for the implementation ofRACM and BACM and for the inclusion ofMSM for secondary ammonium nitrates.

1.MCESD's Commitments to Improve Compliance andEnforcement ofits Fugitive DustRules

MCESD has committed to expanding and improving the compliance and enforcement program forits fugitive dust rules. These enforceable commitments are foundin Maricopa County, 1999 Revised Measure 6, adopted December 15, 1999. Anarrative description ofthem and other program changes are found in Appendix IV, Exhibit 3to the MAG plan's modeling TSD. MCESD has also committed to continuing to improve Rule 310 and Rule 310.01. These commitments are described in Section E.3.h. "Construction Sites and Activities."

39We consider a measure technologically feasible foran area only ifit has the potentialto reduce emissions in a manner that reduces ambient concentrations inthe area. 

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These improvements to the compliance and enforcement programs include increased public outreach and education, increased funding and staffing, increased inspection frequency, revised enforcement policies, and commitments to program evaluations andimprovements. They address many oftheprogram areas that are key to improving compliance and we believe form a solid program for increasing the effectiveness ofthe County's fugitive dust program.

We review these enforceable commitments and their current status below: Staffing

Maricopa County committed to increasing its inspection staffto 8 inspectors, 1 supervisor, 1aide and 2 enforcement officers by the end of January 2000 and to add a coordinator
to the Small Business Environmental Assistance Program to assist smaller builders and construction companies andto help develop and implement education programs. It also committed
to hire an attorney in the County Attorney's office to expedite civil litigation and to assist with prosecuting Class One Misdemeanor cases by April 2000. Total resources devoted to the fugitive dust program were tobe increased to 15 positions, a 25 percent increase over previous levels. After reaching the committed staffing level, MCESD was to review the program in March 2000 to evaluate its effectiveness andthe potential need to add more staff.

By the end ofJanuary 2000, inspection unit staffing increased to 8 inspectors, 1 supervisor, 1coordinator (tooversee permit issuance and track notices ofviolations), 2aides and 2 enforcement officer. ByMay 2000, the County Attorney's office hired an attorney,paralegal, and support staff.In 2000, the Department found thatthe existing staffin the Small Business Environmental Assistance Program was able to handle the workload for assisting smallerbuilders and construction companies and for helping to develop andimplement education programs. MCESD will re-evaluated the need for

an additional coordinator in the small business assistance program when the second generation outreach and education materials are completed. In total, resources devoted tothe fugitive dust program during the past year were 17 positions, a 42 percent increase over previous levels. Organization

MCESD created a new enforcement sectionunder the direct supervision of the MCESD Director/Air Pollution Control Officer (APCO). This position streamlines enforcement by reducing senior management review and approval ofenforcement actions and allows enforcement officers to submit directly
to the APCO's desk all enforcement actions requiring APCO approval.

In addition,MCESD committed to locate inspectors in two new regional offices to provide quicker response times to dust-related complaints and allow more time in the field. Ithas in fact located inspectors in four regional offices. Funding

For FY 1999-2000, revenue for fugitive dustprogram was projected to be $1.12 million from annual earth moving permit fees, a $772,000 increase

over theprevious level. The increase

was due to the 1998 fee increase for earth moving permits.

For FY 2000-2001, anticipated

revenue for the fugitive dust program is approximately $1.7 million, generated from annual earth movingpermit fees. This is a $1.35 million increase over the previous level. Inspection Program

MCESD committed to develop by April, 2000 inspection priorities for
vacant lots andunpaved parking lots that consider lot size and number of
sources, with larger lotsbeing inspected first and smaller lots in succeeding years. Anumber ofcities have municipal programs to address these
sources; therefore, the Department committed to initially direct its inspections to cities lacking such
programs andto track the city plans that

are required by State statute to stabilize target unpaved roads, alleys and unpaved shoulders.

Prior to its adopting additional commitments inDecember 1999, MCESD had already increased inspection rates andimproved procedures for permitted sources such

as construction sites including:

* Proactively inspecting sites larger than 10 acres, 3to 6 times per year and inspect smaller sites once within 30 days ofproject start date.

* Scheduling weekend inspections randomly once per month. * Providing a shortened complaint
response time with a goal of8 hours for high priority complaints and maintaining the current goal of24 hours for others * Revising standard operating procedures and checklists for fugitive dust inspections tobe consistent with the revised rules. * Revising inspection standard operating procedures to have inspectors check for records and inspect fugitive dust sources atpermitted stationary

sources.

MCESD did develop by April, 2000 inspection priorities for vacant lots and unpaved parking lots considering lot size and number ofsources with larger lotsbeing inspected first and smaller lots in succeeding years. EPA and MCESD initially attempted, but were unsuccessful, to convert an Assessor's Office database ofvacant lots into a user-friendly format for identifying prioritylots. Now,MCESD inspectors

are assigned geographical districts and

are compiling notes on the vacant lots and unpaved parking lots in each district during theirroutine surveillance activities. Under current MCESD policy, the inspectors are first directed to handle all complaints and then tobegin
to address the larger sites onthe individual district lists.In 2000, the inspectors made 499 inspections on vacant lots, unpaved parking lots, and unpaved roads.

Enforcement Program

To meet its commitment torevise its enforcement program, MCESD issued a revised air quality enforcement policy

on April 28, 2000. See Air Quality Violation Reporting and Enforcement Policy and Procedure, MCESD, April 28, 2000. Thispolicy:

* Includes guidelines for initiating various enforcement actions * Includes guidelines for reinspecting * Defines timely and appropriate actionby laying out guidelines for which type ofviolationis appropriate for specific enforcement actions and for the time frames for escalating enforcement actions when appropriate

* Identifies priority violations * Includes guidelines for when to seek penalties reflecting the economic benefit ofnoncompliance, iffeasible * Includes guidelines for seeking and determining higherpenalties forrepeat violators * Includes guidelines for inspectors
to handle predetermined citation categories form observation tojustice
court

Enforcement action options include issuing an Order ofAbatement, filing a Misdemeanor Complaintin Justice court, or asking the County Attorney to seek a civil penalty in Superior Court.

Inspectors handle certain predetermined citation category violations and will be responsible for

case development from observance ofa violation to filing ofthe actual citation in thejustice court. Having the inspectors handle routine cases enables the enforcement officers to work on 

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resolving cases involving more serious and complicated violations.

Public Outreach/Education

Public outreach and education consists ofstafftraining, educating the regulated parties, developing good working relationships with other involved parties such as the cities, and making the program more understandable. Increased education of both inspectors and the regulated industry increases compliance.

Among the public outreach and education efforts will be:

* Inspector training on case development.

* Inspector training onrevised test methods.

* City stafftraining on preparing inspection reports and notices of violation.

* On-going training at the local community college.

* Making information available on MCESD website.

* Distribution ofinformation through citybuilding departments and other

sources.

In 2000, MCESD revised its dust control guidelines withits partners ADOT and Arizona State University. This year ADOT secured a research grant directed towards developing educational tools and outreach programs. This product will enhance the current guidelines, add information

onthe life cycle costs ofcontrols and controls' impact on the construction
process, and develop additional outreach tools. In addition, MCESD is currently working with two contractors to develop a model environmental management system for construction. These two efforts will add tothe technical knowledge on dust control and offer additional tools for companies
to increase compliance with regulations. Program Evaluation andTracking

MCESD committed to track the number ofinspections, number and type ofenforcement actions, amount of penalties assessed, and amount of penalties collected. Italso committed to conductmid-year reviews ofthe program in September, 2000 and again in March 2001 to evaluate progress and future needs.

MCESD conducted itsreviews and will conductthen again in September, 2001 and again in March 2002 to evaluate progress andfuture needs. In 2000, MCESD conducted 6625 inspections. In the first year ofoperation under the new enforcement process, it issued 189violations, processed 145 settlement cases and netted $425,000 in fines (May 1, 2000 toApril 30, 2001). G. AttainmentDateExtension
Section 188(e) ofthe Act allows us to extend the attainment date for a serious

area for up to five years beyond 2001 if attainment by 2001 is impracticable. However, before we may grant an extension ofthe attainment date, the State must first:

1. apply to us for an extension ofthe PM-10 attainment date beyond 2001, 2. demonstrate that attainment by 2001 isimpracticable,

3.have complied with all requirements and commitments applying to the area in its implementation plan,

4. demonstrate to our satisfaction that its serious area plan includes the most stringent measures that are included in the implementation plan ofany state and/or are achieved in practice in any state and are feasible for the area, and

5. submit SIP revisions containing a demonstration of attainment by the most expeditious alternative date practicable.

We evaluate the Maricopa County serious area plan's compliance with each ofthese requirements below.

1.Apply for an Extension

A state must apply for an extension and concurrently submit a SIP revision containing a demonstration that the area will attainby the most expeditious alternative date practicable. The state must provided the public reasonable notice and ahearing on the application before it is sent toEPA.

MAG, asthe lead air quality planning agency for the Phoenix metropolitan
area, formally requested an extension of the PM-10 nonattainment deadline to December 31, 2006. The documentation supporting this request is found in Chapter 10 ofthe MAG plan and Appendix C, Exhibit 5 ofthe MAG plan. MAG plan, p. 10-2. This extension request is an integral part ofthe MAG plan andwas subject to public hearing alongwith therest ofthe plan, including the demonstration thatthe

area will attain the 24-hour standard by the earliest alternative date practicable.

2.Demonstrate the Impracticability of Attainment by December 31, 2001

CAA section 189(b)(1)(a)(ii) and our proposed policy on extension requests require that the serious area plan must show thatthe implementation ofBACM (as determined by our guidance) on significant sources categories will not bring the area into attainment by December 31, 2001 in order to claim that attainment bythat date is impracticable.

To evaluate the impracticability of attainment by 2001, the MAG plan evaluated the impact ofBACM on
sources at both the WestChandler and Gilbert sites in 2001. The evaluation showed these BACM-level controls left 24-hour PM-10 levels well above the 24-hour standard at both sites in 2001, thus demonstrating attainment is impracticable by then. MAG plan, Appendix C, Exhibit 3, pp. 3-10 and 3- 11.

In this demonstration, the MAGplan

assumes controls only onthe "permitted" sources, thatis, only on those sources that receive permits from MCESD. The plan assumes that all "nonpermitted" sources-unpaved roads, vacant lots, andunpaved parking lots-are uncontrolled in 2001. MAG plan, Appendix C, Exhibit 3, pp. 3-10 and 3-11. Thislatter assumption does
notreflect the efforts byMCESD to

assure the implementation ofBACM on these sources and is inconsistent with the assumptions made for these sources in the annual standard impracticability demonstration.

To check to see ifusing consistent assumptions between the annual standard and 24-hour standard demonstrations would show that attainment ofthe 24-hour standard is practicable by 2001, we recalculated the 2001 impacts at each monitor using the control assumptions from the annual standard demonstrations and additional control information from the BMP TSD. In these recalculations, we assume that the sources atthe microscale site are in full compliance with the applicable rule. See the "Extension RequestDemonstrate the Impracticability of Attainment by December 31, 2001" in the EPA TSD.

Our recalculations show that attainment ofthe 24-hour standard at the West Chandler siteremains impracticable by 2001. The principal

sources at this site are an agricultural field, its apron, and a construction site. The site needs substantial reductions, in

excess of50 percent, in agricultural emissions in addition to controls on the construction site before the 24-hour standard can be attained. This level of emission reduction from agricultural

sources is not expected until 2006.

However, ourrecalculations show that attainment ofthe 24-hour standard
atthe Gilbert site ispracticable by 2001. The site's primary source, an unpaved parking lot, is subject to full control underRule 310.01 by 2001 and controls

on this source together with controls on the other major source atGilbert, a vacant lot (alsorequired by Rule 310.01) result in the site showing attainment by 2001.

In order to show attainment, aplan
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within the nonattainment area. Because the West Chandler site is still unable to show attainment ofthe 24-hour standard by 2001, the Phoenix nonattainment area as a whole isunable
to show attainment by that date. Thus the MAGplan's conclusion that attainment ofthe 24-hour standard in the Phoenix area isimpracticable by December 31, 2001 is correct. We, therefore, propose to find that attainment ofthe 24-hour standard is impracticable by December 31, 2001.

3.Complied With Commitments and Requirements in the SIP

We interpret this criterion tomean that the state has implemented the emissions reducing measures in the plan revisions it has submitted to address the CAArequirements in sections 172 and 189 for PM-10 nonattainment areas.

The two SIP revisions that Arizona has submitted to address PM-10 are the 1991 MAG moderate area plan and the 1997 Microscale plan.

The 1991 MAG plan includes abroad range ofmeasures to address PM-10 including controls for constructions sites, paved road, unpaved roads, unpaved parking areas, vacant lots, and woodburning. The principal controls in this plan were Rule 310 and the County woodburning ordinances. The 1991 plan alsoincluded reasonably available control technology for stationary

sources and a wide range of transportation control measures. The implementation ofthe measures in this plan are described in theMAG plan at pp. 10-10 to 10-25. The plan also contained a large number of commitments from the local jurisdictions to implement various

measures. Most ofthe measures represented "business as usual" actions by thejurisdictions to do infrastructure (e.g.,road) improvements, to implement existing building codes or take actions already underway for the carbon monoxide plan. MAG plan, pp. 10-13 through 10-24.

The 1997 Microscale plan focused on fugitive dust sources such as construction sites, vacant lots, unpaved roads, unpaved parking lots, and agriculture. The principal controls in this plan were improvements to the implementation ofRule 310 and coordination with the cities to improve fugitive dust control. Implementation of the measures in the Microscale plan are discussed in Maricopa County commitments, 1998 Revised Measure 6.

From available information in the MAG plan, we believe thatthe commitments and requirements in these earlierplans have been met. We, therefore, propose to find thatthe State has complied with the requirements and commitments inits implementation plan.

4. Include the Most Stringent Measures

In ourproposed policy for granting extension requests under CAA section 188(e), we suggest a 5-step process for identifying and adopting MSM. See sectionV.B.4. ofthis preamble. This
process is similar to the one we have established for determining BACM, but with one additional step, to compare the potential MSM against measures already adopted in the area to determine ifthe existing measures aremost stringent.

The first two steps in our proposed MSM policy are to develop a detailed emissions inventory ofPM-10 sources and source categories andto model to evaluate the impact on PM-10 concentrations over the standards ofthe various source categories to determine which are significant for the purposes of adopting MSM. The MAG plan, however, excludes no source categories ofdirectly-emitted PM-10 from its MSM analysis andmoves directly to the third step in the MSM determination, identifying potential MSM in other implementation plans or used in practice in other states for each source categories present in the Phoenix area. MAG plan, p 10-25.

To identify candidate MSM, MAG's
contractor Sierra Research interviewed people knowledgeable about PM-10 controls, reviewed the documents used
to develop the candidate list ofBACM and obtained copies ofcurrent air quality control measures from most other States including both SIP andnonSIP measures. MSM Study, p. 1-2.

The fourth step in our proposed policy for MSM is to compare the potential MSM for each significant

source category against the measures, if any, already adopted for that source category in the local area. In the MAG plan, after a comprehensive list of candidate MSM was developed, each

measure was screened against the corresponding Maricopa measure to identify those withmore restrictive emission limitations, more extensive lists ofaffected sources, fewer exemptions, and/or one or more substantive regulatory provisions not found in the Maricopa measure.

The final step in our proposed policy for MSM is toprovide for the adoption ofany MSM that ismore stringent than existing similar local measures and provide for implementation as expeditiously aspracticable or, in lieu ofproviding for adoption, provide a reasoned justification for rejecting the potential MSM, i.e., why such measures cannot be feasibly implemented in the

area. In the MAG plan, MSM that remained after the screening in step 4

were grouped by source category and

were either included in the plan or a reasonedjustification for rejecting the

measure was provided. MSM study, Table 3-1, MAGplan, p. 10-46, and BMP TSD, pp. 19 to 27.

Based on our analysis ofthe MAG plan's provisions for identifying and adopting MSM, we propose to find that the MAGplan demonstrates to our satisfaction that itincludes the most stringent measures that are included in the implementation plan ofany State, or

are achieved in practice in any State, and canbe feasibly be implemented in the Phoenix area.

We have discussed identification and adoption ofMSM andthe rejection of any MSM for each category deemed significant for BACM earlier in this preamble. The MAGplan identifies three MSMs for categories considered de minimis in the BACM analysis. These categories are cattle feed lots, incinerators, and charbroilers.

Cattle feed lots: MCESD Rule 310.01 requires that owners/operators of commercial feedlots and/or livestock

areas apply dust suppressants, apply gravel, or install shrubs and/or trees within 50 to 100 feet ofanimal pens. The MAG planidentifies South Coast Rule 1186 requirements for livestock operations as apotential MSM for commercial feedlots/livestock areas. However, the two rules control different emission activities at commercial feedlots/livestock areas. South Coast Rule 1186 requires controlling unpaved roads and hay grinding at dairy and horse farms but does not address fugitive dust emissions from disturbed
open areas. MCESD Rule 310.01 controls fugitive dust emissions from disturbed open areas at dairies and cattle lotsbut not unpaved roads and hay grinding.

In the Maricopa County PM-10 nonattainment area, there is only one cattle feedlot and fewer than 80 dairies (mostofwhich are actually outside the nonattainment area). Unpaved roads at dairies are low travel (10 to 20 ADT) and represent avery small source of emissions in the Phoenix area and controls on them would not advance the attainment date and are not necessary for expeditious attainment. We, therefore, propose to find thatthe MAG planprovides for the implementation of MSM to our satisfaction without Rule 1186 provisions for unpaved roads at cattle feedlots.

In Maricopa County, hay grinding activities occur primarily atfeed mills (as opposed to dairies) which are 

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permitted sources and thus already subject to control requirements.

Incinerators: The MAG plan identifies Clark County's Rule 26 as having a more stringent opacity limit than MCESD's Rule 313. Clark County limits opacity from existing incinerators to 5percent while Maricopa's limit is 20 percent. MAG plan, Table 10-7. Incinerators are
avery small source in the Phoenix nonattainment area. In 1994 there were 32 incinerators thattogether emitted 2.56 metric tons peryear(7.1 kg per day). 1994 Regional PM-10 Inventory, p. 4-17. Since then, the medical waste incinerators in this category have shut down andtoday there are even fewer emissions. Because incinerators are a trivial source and controls on them would not advance the attainment date and are not necessary for expeditious attainment, we propose to find thatthe MAG plan provides for the inclusion of MSM to our satisfaction without including Clark County's opacity limit for incinerators.

Charbroiling: Emissions from charbroiling and frying meat are estimated to be 0.6 mtpd or 227 mtpy. 1994 Regional PM-10 Inventory, p. 4- 25. This is 0.4 percent ofthe daily directly-emitted PM-10 inventory in 1994 and 0.4 percent ofthe annual inventory in 1994. MCESD has committed to develop a new rule to require existing andnew chain-driven andunderfired charbroilers, typically found in restaurants specializing in grilled meatproducts, to be equipped with emission control equipment. South Coast AQMD is developing a new rule
to deal withunderfired charbroilers and MCESD will waituntil South Coast completes itsrulemaking, now scheduled for late 2001, to adopt this

measure. Maricopa County commitments, Revised Measure 23. We
propose to find thatimplementation of this rule is expeditious. Waiting on South Coast to complete its rulemaking, which will establish control requirements for underfired charbroilers, is appropriate given that the South Coast rule when adopted will establish MSM for controls on these types ofcharbroilers.

5.Demonstrate Expeditious Attainment

For the reasons discussed below, we propose to find thatthe MAG plan demonstrates attainment bythe earliest date practicable after December 31, 2001

asrequired byCAA section 189(b)(1)(A)(ii). We also propose tofind that the attainment demonstration relies

on control measures that either are approved or have been proposed for approval and meet our SIP enforceability criteria; that the emissions estimates credited to these

measures inthe attainment demonstration are reasonable; and the

measures are being implemented on a schedule thatis as expeditious as practicable and will result in attainment by the earliest practicable date.

The following is abrief summary of

our evaluation ofthe modeling in the MAG plan. Our full evaluation is in the EPA TSD section "Extension RequestDemonstrate Attainment by the Most Expeditious Alternative Date Practicable after December 31, 2001."

a.Air Quality Modeling

The attainment demonstration for the 24-hour standard is divided into two parts, a microscale analysis and a regional analysis. The microscale part evaluates 24-hour exceedances atfour monitoring sites in the Phoenix area using aversion ofthe industrial source complex (ISC)model. The regional part evaluates 24-hour levels throughout the
rest ofthe Maricopa County nonattainment area using the Urban Airshed Model-Linear Chemistry version (UAM-LC).

As discussed previously, Arizona has made three submittals that contain elements ofthe attainment demonstration for the 24-hour PM-10 standard: the 1997 Microscale plan, the 2000 revised MAG plan, andthe 2001 BMP TSD. Amore complete description ofthese submittals canbe found in section 2ofthis preamble and in section 1ofthe EPATSD. We briefly describe here howthese submittals fittogether to create the overall attainment demonstration for the 24-hour standard.

The first ofthe three submittals, the 1997 Microscale plan, contains a microscale, or localized, inventory and modeling analysis using the ISCST model of24-hour standard exceedances
atfour monitoring sites in the Phoenix

area: Maryvale, Salt River, West Chandler and Gilbert. It shows attainment ofthe standard at the Maryvale and SaltRiver sites but does
not demonstrate attainment for the Gilbert andWest Chandler sites, both of which were substantially affected by agricultural sources.4 0
The second submittal, the 2000 revised MAGplan contains a regional modeling analysis of24-hour standard exceedances using UAM-LC. It also

uses the ISCST model to determine that

a 58 percent reduction in agricultural emissions is needed to attain the 24- hour standard at theWest Chandler site

40Because we have already approved the
attainment demonstrations atthe Maryvale and Salt River sites, we do not further discuss these sites in this proposal. See 62 FR 41856, 41863. and 20 percent at the Gilbert site.41 However, atthe time ofits submittal, Arizona had not yet completed adoption ofits BMP general permit rule and also had notyet quantified the expected reductions from rule and thus was unable to model the impact oftherule
atthese two sites.

The third submittal, the 2001 BMP TSD, documents the expected emission reductions from the BMP general permit rule. This submittal does not contain

new modeling butrather shows thatthe rule's emission reductions, together with a reasonable estimate ofland use change, provide greater reductions than needed for attainment at the Gilbert and West Chandler sites.

1.Modeling Approach to the 24-Hour PM-10 Standard Attainment Demonstration

Our guidance on attainment demonstrations generally assumes that the entire nonattainment area will be modeled using a dispersion model.42 However, emissions inventory development and modeling for areas with substantial fugitive dust problems, such asthe Phoenix area, have proved difficult, because offugitive dust emissions' marked uncertainty and their temporal and spatial variability. Accurately estimating emissions for input to dispersion modeling offugitive dust over alarge area is much more difficult thanfor point sources of gaseous pollutants, which were the archetypes for development ofmuch of

our modeling guidance.

Thus, in areas dominated byfugitive dust sources, the approach of intensively inventorying and modeling a small area is areasonable one. This approach is also more reflective ofthe
nature offugitive dust. Fugitive dust PM-10 is emittednear ground level and hasrelatively sharp spatial gradients as dust settles outwith distance from the
source, and hence has more localized effects than the other criteria pollutants, which are typically buoyant and gaseous.

Under the microscale approach used in the MAGplan, the areas around the exceeding monitors are deemed to be representative oflocations throughout the nonattainment area. Attainment is

41

See p. 3-9 inADEQ, "Evaluation for Compliance with the 24-hour PM-10 Standard for the WestChandler and Gilbert Microscale Sites," June 1999 (ADEQTSD), found in Appendix C, Exhibit 3 ofthe MAG plan.

42

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

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demonstrated at locations representing the various mixes ofemission sources that occur in the area. Although a specific emitting activity, such as new housing construction, will eventually decline in agiven location, itwill
reappear elsewhere as the metropolitan

area grows. A location thatis currently experiencing alot ofconstruction can thus be used torepresent locations where construction will occur in the future. Moreover, in the MAG plan all locations exceeding the 24-hour PM-10 standard in 1995 were subjected to analysis. Ademonstration ofattainment
atthese locations will show thatthe mixes of sources that caused exceedances in the Phoenix area willbe controlled sufficiently tomeet the standard.

Although there is solid reasoning underpinning the microscale approach in a fugitive dust-dominated area such

as Phoenix, there is concern thatfor a large urban area the sheer number of
sources, especially fugitive dust area sources, could make for a pervasive regional component ofPM-10 in addition to the more localized or microscale component. Additionally, a portion ofPM-10 is fine particles, which can stay suspended longer and so

canbe transported greater distances than coarse particulate.

Fine particulate includes secondary particulate, which forms chemically in the air from precursors like ammonia and oxides ofsulfur and nitrogen. Secondary particulate is formed by chemical reactions in amixture of emissions fromvarious sources, spread

over hours and a spatial scale of10's of kilometers. Like ozone, itis a regional pollutant, and so needs to be modeled

on alarger scale. Although only a small fraction (4 percent) ofthe total PMin the Maricopa area, secondary particulate is present. While this regional component couldpartly be addressed by adding abackground concentration to microscale modeling, the determination ofabackground is ambiguous since it includes the effect ofsources similar to those in the microscale domain. For these reasons, the MAGplan include regional modeling in addition to the microscale analysis.

2.EPA's Review ofthe Air Quality Modeling in the MAG Plan

In today's proposal, we focus our discussion on the supplemental microscale modeling for the Gilbert and West Chandler sites in the ADEQ TSD andthe evaluation ofthe agricultural general permit rule in the BMP TSD.We have already extensively reviewed both the microscale modeling andthe regional modeling in previous proposals and found them acceptable. See our proposal on the Microscale plan at 62 FR 31025, 31029 and theproposal on the annual standard at 65 FR 19964, 19985. 43 See also the EPATSD section

on "Extension Request-Demonstrate Attainment bythe Most Expeditious Alternative Date Practicable after December 31, 2001."

The approach used for the supplemental modeling in the ADEQ TSD isessentially the same approach used in the Microscale plan. They differ injust three ways. First, the ADEQTSD

uses a new calculation ofbackground concentrations (thatis, the impact on ambient PM-10 levels in the microscale

area of sources outside the microscale area). Second, it evaluates PM-10 concentrations at multiple locations within the microscale domain. Finally, it evaluated various levels ofreductions from agricultural controls, in order to determine the emission reductions needed for attainment.

New background values were calculated in order to reflect the regional implementation ofcontrols. These controls reduce the contribution
to ambient PM-10 levels in the microscale area of sources outside the microscale area. To recalculate the background values, ADEQ splitthe background between windblown and non-windblown contributions, applying controls onlyto the windblown contribution. See ADEQTSD, p. 3-7.

The evaluation ofPM-10 concentrations at multiple locations within the microscale area is an improvement to the previous microscale modeling. In the Microscale plan, the evaluation was limited to the actual location ofthe ambient air quality monitor within the microscale domain.

The evaluation ofthe emissions reductions needed for attainment in 2006 at the West Chandler site (assuming a 90 percent level ofcontrol

onthe construction site)showed that a 58 percent reduction in emissions from agricultural aprons andfields was needed. For the Gilbert site, a 20 percent emission reduction is shown to be needed from the agricultural apron. ADEQ TSD, pp. 3-9.

The BMP TSD shows that BMP general permit rule, together with a

43 Forthe regional model, 65 individual days

were analyzed inthe base year and attainment year, that is, MAG ran the UAM-LC model for each of these 65 24-day days. To evalute the 24-hour standard, the individual results from each one of these modeling runs areused. To evaluate the annual standard, the results from all the modeling

runs for eachyear are averaged together. Thus, in reviewing the modeling for the annual standard demonstrations, we necessarily also reviewed the modeling for theregional 24-hoar standard demonstrations. reasonable estimate ofland use changes, provide a 60.3 percent reduction by 2006. Thisreduction is sufficient to demonstrate attainment by 2006 at West Chandler. Forthe Gilbert site, therule provides more thanthe 20 percent needed for attainment by 2006. BMP TSD, p. 9.

This 60.3 percent reduction atthe West Chandler site is a combination of

a 36.6 percent emissions reduction from the BMP general permit and a 37 percent emissions from the conversion ofagricultural landto residential and commercial use.44This land use conversion rate is derived from a land

use model for the overall nonattainment

area and represents the reduction regionally in agricultural lands between 1995 and 2006. BMP TSD p. 28.

Under the microscale approach, the

areas around the exceeding monitors are deemed to be representative oflocations throughout the nonattainment area. Thus, applying regionally the controls needed for attainment at these representative sites is assumed to assure attainment at similar sites throughout the nonattainment area. One aspect of this approach, which was not adequately explored in earlier submittals, is to howtotreat the inevitable changes in landuses and activities within the microscale domains. For example, construction activity, like that at the WestChandler site, will eventually be completed and

no longer contribute to emissions in the

area.45

A land use and socioeconomic model, in conjunction with a dispersion model, could legitimately show that exceedances no longer occur inthe area simplybased onthis change in land use. However, justwaiting for land use changes alone to reduce emissions is not

an acceptable method ofdemonstrating attainment atthe individual microscale sitesbecause once again, the premise underlying the microscale approach is that each siteis representative ofother similar areas inthe nonattainment area. In a growingmetropolitan area like that ofPhoenix, there will always be areas with on-going construction.

On the other hand, the opposite
extreme of assuming no conversion of agricultural lands at all does not seem reasonable either. The reality is thatthe

44The reductions are not additive because the BMP general permit rule reduces emissions only from the land left in agricultural production. The overall control effectiveness is calculated as the percent lostagricultural lands +BMP rule effectiveness * percentremaining agricultural lands

or 37% + 0.366*63%.

45Infact, at the WestChandler site, the construction is complete and agricultural land has been converted to residential and commercialuses. 

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metropolitan area isgrowing and agricultural land israpidly being converted. Such changes have been observed over the past decades and are projected to continue.

In this situation, using an estimate from the area's land use model ofthe conversion ofagricultural lands to occur by 2006 is a reasonable approach to use. This approach is a compromise between the extremes ofthe no-conversion and the total-conversion assumptions. It is drivenby the area's socioeconomic projections that are used for many purposes and represent the best available information about the land use changes the overall area will experience.

Also, using an area average figure is consistent with the area wide application ofcontrol measures required under the submittal's approach. Reliably predicting the conversion for a particular small area (several square miles in the microscale approach) would be problematic in any case, since it would depend on knowing individuals' purchase decisions and development plans. Aggregate conversion figures, driven bylarger economic forces and representing the average ofmany actions, shouldbe more reliable.

Assuming some land use change is

more in line with the traditional use of microinventories in EPA's PM-10 attainment demonstration guidance, and alsois in line with how attainment demonstrations are performed in general. Typically the projections for land use, employment, industrial production, population, vehicle traffic,
etc. are part ofthebaseline conditions assumed in projecting future air quality; in an attainment demonstration they are independent of,but used in conjunction with, estimates ofcontrol measure effectiveness. In other words, reductions that occur naturally because of socioeconomic changes are implicitly counted in attainment demonstrations. Conversely, growth in emission sources, e.g., vehicle traffic, are also implicitly counted andmust be compensated for by additional emission reductions.

In summary, we believe that the approach used in 2001 BMP TSD, while
not completely consistent with howthe microscale approach was implemented in the 1997 Microscale plan, nevertheless, is a reasonable balance between different possible implementations ofa microscale approach. Overall, we propose to find that technical evaluation in the MAG plan is adequate to support the attainment demonstration for the 24- hour standard at theWest Chandler and Gilbert sites. b. ControlMeasures Relied onfor Attainment

For demonstrating attainment ofthe 24-hour PM-10 standard, the MAG plan relies onreductions in directly-emitted PM-10 from 3measures: MCESD's Rules 310 and 310.01 andthe agricultural BMP general permit rule. ADEQ TSD, pp. 3-3 to 3-6 andBMP TSD, p. 8. We have proposed to approve all ofthese measures. See 65 FR 19992, 19989 and 66 FR 34598.

As part ofthese proposed approvals,

we have evaluated each ofthese

measure to ensure thatit meets our SIP enforceability criteria. These criteria

ensure that the measure's compliance requirements-applicability, performance standards, compliance schedule, and monitoring methods-are clear.For MCESD's rules, see sections on proposed approval ofRule 310 and 310.01 in the TSD supporting the annual standard proposal. Forthe agricultural general permit rule, see 66 FR 34598.

We have also evaluated the emissions reductions credited to each measure in the attainment demonstrations to ensure they are reasonable. In performing the microscale analysis, ADEQfirst determined that each significant, nonagricultural source atthe microscale sites (e.g., the unpaved parking lot at the Gilbert site)was large enough to be subject to Rules 310 or 310.01.46 For each ofthese sources, ADEQ then applied the control factor used in the Microscale plan for that source. Except for the agricultural sources, it did not

use rule effectiveness factors for either the sources in the microscale component orthe sources in the windblown background component in the attainment demonstrations.

Rule effectiveness (RE) accounts for emission reductions lost because of noncompliance, control equipment downtime, failure to apply adequate controls, or failure to use control equipment properly. One hundred percent rule effectiveness is the ability ofa regulatory program to achieve all the emission reductions thatcould be achieved byfull compliance withthe applicable regulations at all sources at alltimes. Because RE factors are intended toreflect the variations in compliance among large numbers of
sources, they are applied to source categories rather than to individual

sources.

We agree that itis appropriate not to apply an RE factor tothe individual

4 6Rule 310 and Rule 310.01 do not apply to

sources under a certain size. For example, Rule 310.01 does not apply to vacant lots under 0.1

acres. Rule 310.01, section 301. sources at each microscale site;47 however, we believe that an RE factor shouldbe applied to the windblown background source categories because each category represents multiple

sources. To determine the effect of applying the RE factor to sources in the windblown background, we reevaluated the attainment demonstrations at both Gilbert and West Chandler. We found thatthe plan still demonstrates attainment ofthe 24-hour standard as expeditiously as practicable. See EPA TSD section "Extension Request-Demonstrate Attainment by the Most Expeditious Alternative Date Practicable after December 31, 2001,"

We findthatthe emission reduction estimates for each source category are consistent with research on the applicable control methods and are appropriately applied in the attainment demonstrations. For more information

on the quantification ofemission reductions from Rules 310 and 310.01

see the section "Extension RequestDemonstrate Attainment by the Most Expeditious Alternative Date Practicable after December 31, 2001" in the EPA TSD for the annual standard proposal. Formore information on the quantification ofemission reductions fromthe agricultural general permit rule, see the section "Implementation of BACM and Inclusion ofMSM for Agricultural Sources" in the EPA TSD for this proposal.

We have also determined thatthe

measures relied on for attainment are being expeditiously implemented. Rule 310 and 310.01 are effective now. Implementation ofthe agricultural general permit rule began in July 2000 and willbe completed by December 31, 2001.

6. Other Factors ThatEPA May Consider

CAA section 188(e) listfive additional factors thatwe may consider in deciding whether to grant an extension and the length ofthat extension.

The MAGplan provides information addressing each ofthe factors in Chapter 10 ofthe plan. Nothing inthis additional information presented on the five factors suggests that granting an extension ofthe attainment date for the Phoenix area to 2006is inappropriate.

a.Nature and Extent ofNonattainment

In the Phoenix area, elevated 24-hour levels ofPM-10 occur mainly in areas with large fugitive dust sources orwith

a concentration offugitive dust sources.

47Ateach microscale site, there is only a single

sourcein each category, that is there is a single
vacantlot, a single construction site, a single agricultural field withits apron, a single unpaved parkinglot. 

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Areas such as this can be found throughout the Phoenix nonattainment
area, so we would expect thatthere are elevated 24-hour PM-10 levels throughout the Phoenix area. In order to attain the 24-hour standard in this situation, controls needto be uniformly implemented throughout the area, a task that generally requires longer to achieve than implementing controls in a few localized areas.
b. Types and Numbers ofSources or Other Emitting Activities

Primary contributors to elevated PM10 levels are fugitive dust sources including paved road dust,unpaved roads, construction activities, disturbed
vacant lands,unpaved parking lots, and agricultural sources. MAGplan, p. 10- 51. These sources are ubiquitous in the nonattainment area and collectively number in the thousands. Forexample, MCESD issued 2500 construction permits in 1999; we mailed 50,000 letters to owners ofvacant lots in the nonattainment area toinform them of

our FIP fugitive dust rule; there are 12,000 miles ofroadway in the nonattainment area.

c. Population Exposure to Concentrations Above the Standard

The MAGplan estimates population
exposure to elevated levels ofPM-10 (both annual and 24-hr) tobe from 78,000 to 163,000 (1995 figure), p. 10- 13. This population exposure is calculated using estimates ofdisturbed land versus population in subareas of the nonattainment area. According to this calculation, 84 percent of Maricopa's population lives in areas where 10 percent orless ofthe land is
open. MAG plan, Table 10-13. However, the plan does provide for implementation ofRACM, BACM, and MSM on disturbed land (including construction) and paved andunpaved roads with much ofthe emission reductions being achieved in the first few years. All these factors will reduce population exposure as quickly as practicable.

d.Presence and Concentration of Potentially Toxic Substances in the Particulate

The primary source ofairborne cancer risk in the Maricopa area is internal combustion engine exhaust fromboth

on andnonroad engines. This risk is from all pollutants emitted from these

sources (gaseous and particulate). MAG plan, p. 10-61. The MAGplan concludes thatthe cancer risk in the Phoenix area is comparable to thatin California cities, p. 10-61. The MAG plan and other Arizona programs (e.g., cleaner burning gasoline, national emission standards for nonroad engines) target emissions from on andnonroad engines.

Almost all ofthe PM-10 emission reductions in the outyears ofthe MAG plan (2003 and later) are and needto be from fugitive dust sources in order to show attainment ofthe 24-hour PM-10 standard and not from on- and nonroad engines; therefore, extending the attainment date does not affect the degree ofpublic exposure to the major

source oftoxic riskbecause shortening the extension would not accelerate controls onthe major source oftoxic risk, on- and nonroad engines.

e. Technological and Economic Feasibility ofControls

Fugitive dust sources dominate the emissions inventory in the Maricopa nonattainment area and are the most significant contributors to 24-hour PM10 exceedances. Controls for these

sources are well known (paving,wetting surfaces, etc.) and have been adopted; however, the number of sources and
nature ofsources make education and outreach necessary to assure full compliance with those controls. In addition, costsfor paving roads and other capital improvements needed to reduce PM-10 emissions are high and necessary funds are only available over

anumber ofyears. These factors generally support alonger time frame for attainment.

7.Conclusion on Extension Request

Based on ourreview ofthe MAG plan and our proposed determination thatit
meets the requirements necessary for granting an extension ofthe attainment date under CAA section 188(e), we are proposing to grant a five-year extension ofthe attainment date for the 24-hour PM-10 standard in the Phoenix PM-10 serious nonattainment area from December 31, 2001 to December 31, 2006.

H. ReasonableFurther Progress and Quantitative Milestones
CAA section 172(c)(2) requires nonattainment plans to provide for reasonable further progress (RFP). Section 171(1) ofthe Act defines RFP as "such annual incremental reductions in emissions ofthe relevant air pollutant as

are required bythis part [part D oftitle I] or may reasonably be required by the Administrator for the purpose of ensuring attainment ofthe applicable national ambient air quality standard by the applicable date."

CAA section 189(c) also requires PM10 plans demonstrating attainment to contain quantitative milestones which are to be achieved every 3years until the area is redesignated attainment and which demonstrate RFP. These quantitative milestones should consist ofelements that allow progress to be quantified or measured. Addendum at 42016.

1.ReasonableFurther Progress
The MAGplan provides for annual progress toward attaining the 24-hour standard. This demonstration shows thatmost ofthe projectedreductions

occur after 2001; however, this is an artifact ofthe assumption that there are

no controls on agricultural sources, vacant lots andunpaved parking prior
to December 31, 2001. This assumption does not reflect the efforts by MCESD to

assure the implementation ofBACM on these sources and the requirement for BMPs tobe implemented bythen. Ifthe RFP demonstration is revised to include emission reductions from BACM on these sources, thenthe majority ofthe emission reductions occur before 2001. See the "Reasonable Further Progress and Quantitative Milestones" section in the EPA TSD.

In order to demonstrate RFP, the plan first regionalizes the inventories at the
two microscale sitesby multiplying emissions from each source by afactor of360, which is the ratio ofthe size of the nonattainment area (2,880 square miles)to the size ofthe microscale sites (8 square miles). It then calculates the emission reductions from the application ofthe adopted measures to these sources. Next, it annualizes these emission reductions by multiplying the sources-which are all windblown sources-by 11, the number ofwindy days in 1995. Finally, the annualized figure is divided by 365 days to getan average annual day emission reductions. See BMP TSD, pp. 29-31.48

Regionalizing and annualizing the microscale inventories is a good approach to demonstrating RFP and establishing milestones for the 24-hour standard in the Phoenix area. Just a few

source categories are explicitly identified contributors to exceedances ofthis standard, and itis effective controls on these categories that are necessary for progress and attainment. Therefore, closely tracking the effect of

48There was anerror in the originalRFP
calculation on pages 29 to 31 inthe BMP TSD. ADEQ corrected this error and provided us a revised RFP and contingency measure demonstrations and quantitative milestones in a letter. See letter, Jacqueline E. Schafer, ADEQ, to Laura Yoshii,EPA, "Addendum to June 13, 2001, Submittal ofState Implementation Plan revision for the Agricultural BestManagement Practices
program in the Maricopa County PM-10 Nonattainment Area," September 7, 2001 ("ADEQ RFP Addendum Letter") 

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those controls on these source categories is essential. Regionalizing and annualizing the microscale inventories allows this tobe done.

The plan does not provide emission reduction information for each year between the base modeling year of 1995 andthe attainment year of2006. We do
not believe that this level ofdetail is necessary or meaningful given the evidence thatprogress is being made

over time and the implementation of controls are not being delayed. Therefore, we propose to findthat the MAG plan provides for "such annual incremental reductions in emissions of the relevant air pollutant as are required by this part [part D oftitle I] ormay reasonably be required bythe Administrator for the purpose of ensuring attainment ofthe [24-hour PM-10] national ambient air quality standard bythe applicable date" as required by section 172(c)(2) ofthe Act.

2. Quantitative Milestones Quantitative milestones based on regionalized and annualized microscale inventories are provided for 2001, 2003, and 2006. See RFP Addendum Letter, Enclosure 2. These are the same milestone years used for the annual standard. See 65 FR 19964, 19988. The assumptions regarding control measures' implementation and effectiveness thatunderlie the quantitative milestones are reasonable and consistent with the RFP demonstration.

The plan does not provide milestones for each ofthe two microscale sites. Milestones are intended as checks along the way, a means ofjudging actual emission reductions and control

measure implementation against those projected in the plan. Arguably, given the microscale analysis thatis thebasis for the Phoenix area's 24-hour standard plan, quantitative milestones shouldbe established for both the West Chandler and Gilbert sites. However, this approach would actually defeat the
purpose ofthe quantitative milestones rather than fulfill it.

In order to report on a quantitative milestone atthe microscale sites, Arizona would needto evaluate the implementation ofcontrols ateach site. However, land uses and activities around each ofthese microscale sites have changed significantly since 1995. For example, at theWest Chandler site, the road construction has been completed and the agricultural field and its apron have been converted into
stores. Thus, reporting on each site's quantitative milestones would tell us
more about the land use changes around each site than about the implementation ofcontrols. Because ofthis,the quantitative milestones for the 24-hour plan need to reflect regional implementation ofcontrols. The MAG plan's approach ofregionalizing and annualizing the emissions inventories from the microscale sites and then basing its RFP demonstration and milestones onthe resulting inventory is

an appropriate way to deal with these requirements for the 24-hour standard.

For these reasons, we propose to find that the MAG plan meets the quantitative milestone requirement in CAA section 189(c)(1) for the 24-hour standard.

L Contingency Measures
Section 172(c)(9) ofthe Clean Air Act requires that implementation plans provide for the implementation of specific measures tobe undertaken if the area fails to make RFP or attainby its attainment deadline. These contingency measures areto take effect without further actionby the State or the Administrator. The Act does not specifyhow many contingency

measures are necessary nor does it specifythe level ofemission reductions they must produce.

We interpret the "take effect without further actionby the State orthe Administrator" to mean thatno further rulemaking actions bythe State or EPA would be needed to implement the contingency measures. Addendum at 42015.

The purpose ofcontingency measures is to ensure that additional emission reductions beyond those relied on in the attainment andRFP demonstrations are available ifthere is afailure to make RFP or attain bythe applicable attainment date. These additional emission reductions will assure continued progress towards attainment while the SIP isbeing revised to fully
correct the failure. To ensure this continued progress, we recommend that contingency measures provide emission reductions equivalent ofoneyear's
average increment ofRFP. Addendum at 42016.

Certain core control measure requirements such asRACM, BACM, andMSM may result in a state adopting and expeditiously implementing more

measures than are strictly necessary for expeditious attainment and/orRFP. Because ofthis and because these core requirements effectively require the implementation ofallnon-trivial

measures that are technologically and economically feasible for the area, states

are left with few, ifany, substantive unimplemented control measures. In fact, under the Act's PM-10 planning provisions, ifthere were ameasure or set ofmeasures thatwere technologically and economically feasible and could collectively generate substantial emission reductions, e.g.,
one year's worth ofRFP, then a state wouldbe hard pressed tojustify withholding their implementation. 49

Ifwe read the CAA to demandthat the only acceptable contingency

measure are those that are adopted but
notimplemented, then states face a difficult choice: adopt the controls for immediate implementation and clearly
meetthe core controlmeasure requirements but failthe contingency

measure requirement or adopt the control measuresbut hold implementation in reserve to meetthe contingency measure requirement but potentially fail the core control measure requirements.

However, states do not need to face this difficult choice ifwe read the CAA
to allow adopted andimplemented

measures to serve as contingency
measures, provided that those measures' emission reductions are not needed to demonstrate expeditious attainment and/or RFP. There is nothing in the language ofsection 172(c)(9) that prohibitsthis interpretation. This approach to the contingency measure requirement also has thebenefit of allowing states to builduncredited cushions into their attainment and RFP demonstrations, which makes actual failures to make progress or attain less likely, while still obtaining the air quality and public health benefits from the implemented measures.

We have allowed this approach, which is effectively the early implementation ofcontingency measures, in ozone and carbon monoxide plans. See memorandum,G. T. Helms, Chief,Ozone/Carbon Monoxide Programs Brand, OAQPS to AirBranch Chiefs, Regions I-X, "Early Implementation ofContingency Measures for Ozone and Carbon Monoxide (CO) Nonattainment Areas," August 13, 1993. Inthis memorandum,

we note that several states wished to implement their contingency measures early eventhough they were not needed for their attainment orRFP demonstrations and that "[i]t seems illogical to penalize nonattainment areas that are taking extra steps to ensure attainment ofthe NAAQS by having them adopt additional [replacement] contingency measures now." This rationale applies with equal force to PM-10 plans.

49Wedonot believethatStates are obligatedby section 172(c)(9) to adoptinfeasible or unreasonable

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Annual Standard

The revised MAG plan as submitted in February 2000 identifies 5measures

as contingency measures with a collective emission reduction of5.5 mtpd: the agricultural BMP general permit rule, off-road engine standards, the clean burning fireplace ordinance, and additional dust controls from the cities ofTempe and Phoenix. MAG plan, p. 8-19.

Since theMAG plan was submitted, Arizona has made changes toits contingency measure package for the annual standard. First, Arizona has withdrawn its commitment to adopt California's offroadvehicle standards because the federal nonroad program produces essentially the same emission reductions. ADEQ Off-Road Letter. Second, the emission reductions from the agriculture contingency measure have been recalculated based on the BMP general permit rule as adopted. The emission reductions from the revised contingency measures package

are now 6.9 mtpd. See EPATSD "Contingency Measures" for more details onthe emission calculations.

All the measures that havebeen identified in the MAG plan as contingency measures have been adopted and are being implemented but

are not credited in the attainment, RFP

ormilestone demonstrations for the annual standard and are not necessary to demonstrate expeditious attainment ofthat standard. Under our applicable policies, states are allowed touse implemented but uncredited measures

as contingency measures.

Under our contingency measure policy, we recommend contingency

measures have total emission reductions equal to or more than the annual RFP increment. For the Phoenix area, the average annual increment in RFP for the annual standard is 5.5 mtpd/year for the full 11-year period, 1995 to 2006. See EPA TSD, "Reasonable Further Progress and Quantitative Milestones." Collectively, the specified contingency

measures generate 6.9 mtpd.

Based onthis analysis, we propose to find thatthe MAGplan provides for the implementation ofcontingency

measures for the annual standard as required byCAA section 172(c)(9).

24-Hour Standard

The identified contingency measure for the 24-hour standard is controls for unpaved roads and alleys. BMP TSD, p. 30. This measure comprises not only the unpaved road provisions in MCESD Rule 310.01 but also the commitments by localjurisdictions to control unpaved roads. See MAG plan, pp. 7-75 to 7-94. This measure is estimated to reduce emissions by 12.19 mtpd in 2006. MAG plan, p. 8-9.The average annual increment in RFP for the 24-hour standard is 10.9 mtpd/year. See ADEQ RFP Addendum Letter, Enclosure 1.

The unpaved road measure that is identified in the MAGplan as contingency measure for the 24-hour standard hasbeen adopted andis being implemented but is not credited in the attainment, RFP ormilestone demonstrations for the 24-hour standard andis not necessary to demonstrate expeditious attainment ofthat standard. Under our applicable policies, states are allowed to use implemented but uncredited measures as contingency

measures.

Based onthis analysis, we propose to find thatthe MAGplan provides for the implementation ofcontingency

measures forthe 24-hour standard as required byCAA section 172(c)(9).

J.GeneralSIPRequirements
Section 110(a)(2)(E)(i) ofthe Clean Air Act requires that implementation plan provide necessary assurances that the State (orthe general purpose local government) will have adequate personnel, funding and authority under State law. Requirements for legal authority are further defined in 40 CFR part 51, subpart L (51.230-51.232) and for resources in 40 CFR 51.280. States andresponsible local agencies
must demonstrate thatthey have the legal authority to adopt and enforce provisions ofthe SIP and to obtain information necessary to determine compliance. SIPs must also describe the

resources that are available or willbe available tothe State and local agencies
to carry outthe plan, both at the time ofsubmittal and duringthe 5-year period following submittal ofthe MAG plan. Other thanrevisions to Maricopa County's revised commitments to improve Rule 310, we are not proposing
to approve any controlmeasures in this proposal. All commitments and rules relied on in the MAG plan to meet the CAA requirements for the 24-hour PM10 standard are already approved, were proposed for approval in the annual standard proposal, or proposed for approval in a subsequent notice. In these notices, we have already proposed
to findthat the implementing agencies for the MAGplan have adequate

resources for implementing their respective commitments and provided

an opportunity for comment. We are not reproposing these findings.

Finally, we initially proposed to find in the annual standard proposal that all agencies andjurisdictions have adequate authority underArizona state lawto implement their respective commitments and, where applicable, to obtain information necessary to determine compliance. 65 FR 19964, 19989. While minor changes have been made to several control measures (e.g., the remote sensing program), the State continues to have adequate authority to implement the measures. No other changes have been made to any agencies and/or jurisdictions authority since we proposed the annual standard.

Section 110(a)(2)(C) requires SIPs to include aprogram to provide for the enforcement ofSIP measures. The implementing regulation for this section is found at 40 CFR 51.111(a) and requires control strategies to include a description ofenforcement methods including (1)procedures for monitoring compliance with each ofthe selected control measures, (2)procedures for handling violations, and (3)the designation ofthe agency responsible for enforcement.

The principle controlmeasures in the plan are MCESD'sRules 310 and 310.01 and the BMP General Permit. Procedures for monitoring compliance (i.e.,the inspection strategy) with these rules are described in Maricopa County's commitments and the BMP TSD. See Maricopa County commitment, 1999 Revised Measure 6 and BMP TSD, pp 33-34.

Based on the review ofMCESD's enforcement procedures, we propose to findthat the MAGplan adequately provides for the enforcement ofthe principle measures relied on for attainment andthat theplan includes an adequate description ofenforcement methods as required by ourregulations.

Section 110(a)(2)(E)(iii) requires SIPs
to include necessary assurances that where a State has relied on alocal or regional government, agency or instrumentality for the implementation ofany plan provision, the State has responsibility for ensuring adequate implementation ofthe such plan provision.

We havepreviously found that Arizona lawincludes the necessary

assurances that where a State hasrelied

on a local or regional government, agency or instrumentality for the implementation ofany plan provision, the State has responsibility for ensuring adequate implementation ofthe such planprovision. 60 FR 18010, 18019 (April 10, 1995). 

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V. CAA Requirements forBACM and Attainment Date Extension andEPA's Guidance onMeeting These Requirements

A. ImplementationofBestAvailable ControlMeasures

Under section 189(b)(2), serious area PM-10 plans must provide assurances that BACM will be implemented in the

area no later than four years after the

area isreclassified as serious. For Phoenix, the BACM implementation deadline was June 10, 2000.

The Act does not define what level of control constitutes a BACM-level of control. In guidance, we have defined it
to be, among otherthings, the maximum degree ofemission reduction achievable from a source or source category which is determined on a case-by-case basis, considering energy, economic and environmental impacts. Addendum at 42010. This level ofcontrol is dependent on the deadline by which BACM must be implemented. 5

We also considered aBACM-level control asgoing beyond existing RACMlevel controls, such as expanding use of RACM (e.g,paving more miles of unpaved roads). Addendum at 42013. Additionally, we believe thatBACM should emphasize prevention rather than remediation (e.g., preventing track
outat construction sites rather than simplyrequiring clean up oftracked-out dirt). Addendum at 42013.

BACM is a best available control

measure.A control measure is a combination ofa statement of applicability andthe control requirement, thatis, what sources in the category are subject tothe measure and what the measure require the sources to doto reduce emissions. 51Both these elements must be specified before the measure's level ofcontrol (i.e., its stringency) canbe determined, thus in setting outa BACM, a state must specify both the measure's control requirement

5oWehave long held that anotherwise available

measure is reasonable and thus not an available

measure if itcannot beimplemented on a schedule that will advance the attainment date. See, for example, 57FR 13498, 13560 (April 16, 1992). See, also Delaneyv.EPA 898 F.2d 695 (9th Cir. 1990) which required the adoption of "all available control measures" to attain "as soon as possible" and not simply all available control measures. The
most clear example of this is a measure thatcannot be implemented until after the applicable attainment date.

51 Anexample: a measure requires all unpaved roads withADT over 150 be stabilizedby either paving, graveling, or treating with chemical stabilizers. The control requirement here is "Stabilize using oneofthese three methods: paving, graveling, or chemical stabilization" and the applicability is "all unpaved roads withADT over
150." andits applicability. The control requirement alone is not sufficient.

BACM must be applied to each significant (i.e.,non-de minimis) source category. Addendum at42011. In guidance, we have established a presumption that a "significant" source category is one that contributes 5gLg/m 3

ormore ofPM-10 to alocation of24- hour violation. Addendum at 42011. However, whether the threshold should be lower than this in any particular area depends upon the specific facts ofthat area's nonattainment problem. Specifically, in areas that are demonstrating attainment by December 31, 2001, it depends onwhether requiring the application ofBACM on
source categories below a proposed de minimis level would meaningfully expedite attainment. In areas that are claiming the impracticability of attainment by December 31, 2001, it depends upon whether requiring the application ofBACM on source categories below aproposed de minimis level would make the difference between attainment andnonattainment by the serious area deadline of December 31, 2001. 5 2

The recent decision by the Ninth Circuit Court ofAppeals in Oberv. Whitman 243 F.3d 1190 (9thCir. 2001) (OberI) supports the use ofa de minimis exemption in BACM analyses. OberI was a challenge to our 1998 PM10 moderate area FIP for the Phoenix

area in which we exempted from the RACM requirement, source categories with de minimis impacts onPM-10 levels. In the FIP, we established a de minimis threshold of1gLg/m 3for the annual standard and 5gLg/m 3for the 24- hour standard, borrowing these thresholds from our new source review
program for attainment areas to as a starting point in the de minimis analysis. In evaluating the appropriateness ofthese thresholds, we showed thatthey did not eliminate controls that would make the difference between attainment andnonattainment by the applicable attainment deadline, andtherefore were the appropriate thresholds. See 63 FR 41326, 41330 (August 3, 1998).

52 This principle is bestillustrated by an example:
In Area A, attainment ofthe 24-hour standard by December 31, 2001 requires that PM-10 ambient levels at exceeding locations bereduced by 40pg/

m 3 to 150 pg/m 3

. After application ofBACM to all

source categories above the proposed de minimis level, PM-10 levels arereduced by 32 pg/m 3

. BACM on the proposed de minimis source categories would reduce levels by a further 3pg/ M 3

,but still leaves ambient levels 5 ig/m 3 short of the reduction needed to show attainment. Since application ofBACM to the proposed deminimis

source categories still leaves ambient levels above the attainment level of 150 pg/m 3

, the proposed de minimis level is appropriate. In itsruling, the courtheld that we havethe power to make de minimis exemptions to control requirements underthe Clean Air Act and that our

use ofthe de minimis levels from the NSRprogram was appropriate. OberIIat 1195 and 1197. In addition, the court determined thatitwas appropriate for

us to use, as a criterion for identifying de minimis sources, whether controls

on the sources would resultin attainment by the attainment deadline. OberIIat 1198. Ober11dealtwith a de minimis exemption from the RACM requirement, but its reasoning applies equally to the BACM requirement.

We have outlined in our guidance a multi-step process for identifying BACM. Addendum at 42010-42014. The steps are:

1. develop a detailed emissions inventory ofPM-10 sources and source categories,

2. model to evaluate the impact on PM-10 concentrations over the standards ofthe various sources and

source categories to determine which

are significant,

3. identify potential BACM for significant source categories including theirtechnological feasibility, costs, and energy and environmental impacts when itbears onthe BACM determination, and

4. provide for the implementation of the BACM or provide a reasoned justification for rejecting any potential BACM.

B.ExtensionoftheAttainmentDate Beyond2001

Section 188(e) ofthe Act allows us to extend the attainment date for a serious

area for up to five years beyond 2001 if attainment by 2001 is impracticable. However,before we may grant an extension ofthe attainment date, the State mustfirst:

1. apply to us for an extension ofthe PM-10 attainment date beyond 2001,

2. demonstrate that attainment by 2001 is impracticable,

3. have complied with all requirements and commitments applying to the area in its implementation plan,

4. demonstrate to our satisfaction that its serious area plan includes the most stringent measures that are included in the implementation plan ofany state and/or are achieved in practice in any state and are feasible for the area, and

5. submit a demonstration of attainment by the most expeditious alternative date practicable.

6. the technological and economic feasibility ofvarious controlmeasures.

We maygrant only one extension for

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more than 5years after 2001; that is, the extended attainment date canbe no later than December 31, 2006. CAA section 188(e).

We first presented our preliminary interpretation ofthe attainment date extension provision in ourproposed approval ofthe annual standard provisions in the MAGplan. See 66 FR 19992, 19967. Based on comments we received on itduring that proposal's
commentperiod, we have clarified certain aspects ofthe policybut have made no substantive changes to it.We will provide our full response to comments received on the annual standard proposal when we take final action.

This interpretation isour preliminary view ofthe section 188(e) requirements and we again request comment on it. We emphasize thatthese are our preliminary views andthey are subject
to modification as we gain more experience reviewing extension requests from other areas.

In the following sections we discuss the five requirements a State must meet before we can consider granting an attainment date extension.

1.Apply for an Attainment Date Extension

Under CAA section 188(e), a State
must apply for an extension ofthe attainment deadline. The request should be accompanied by the SIP submittal containing the most expeditious alternative attainment date demonstration required by CAA section 189(b)(1)(A)(ii). The state must be provided the public withreasonable notice and a hearing on the request before it is sent toEPA.

Extension requests are not SIP submittals per se 53 and are therefore not subject to the requirements ofthe Clean Air Act and our regulations for public notice and hearing on SIP revisions. However, because they can greatly affect the content andultimate approvability ofa serious area PM-10 SIP, we believe

a state must give the public an opportunity, consistent with the requirements for SIP revisions, to comment on an extension request prior
to submitting itto us. 2.Demonstrate ThatAttainment by 2001 isImpracticable

In order to demonstrate impracticability, the plan must show

53 This is clear from the wording ofsection 188(e) which makes a distinction between the application for an extension and the SIP revision that must accompany it: "at the time ofthe such application, the Statemust submit arevision to the implementation plan that includes a demonstration of attainment by the mostexpeditious alternative date practicable." This attainment demonstration is the one required by section 189(b)(1)(A)(ii). that the implementation ofBACM on significant (thatis, non-de minimis)

source categories will not bring the area into attainment by December 31, 2001. In serious areas, BACM is required tobe in place in advance ofthe 2001 attainment date; therefore, we believe that itis reasonable to interpret the Act
to require that a state provide atleast for the implementation ofBACM on significant source categories before it

can claim impracticability ofattainment by 2001. 54 This interpretation parallels

our interpretation ofthe impracticability option for moderate PM-10 nonattainment areas in section 189(a)(1)(B). In moderate areas, RACM

was required before a moderate area plan could claim impracticability of attainment by 1994, the moderate area attainment date. See 57 FR 13498, 13544 (April 16, 1992). The Ober II court found this approach reasonable. OberII
at 1198.

The statutory provision for demonstrating impracticability requires that the demonstration bebased on air quality modeling. See section 189(b)(1)(A). We have established minimum requirements for air quality modeling. See discussion on air quality modeling later in this TSD. 3.Have Complied With all Requirements and Commitments in its Implementation Plan

We interpret this criterion tomean that the state has implemented the emission reducing measures in theplan revisions it has submittedto address the CAA requirements in sections 172 and 189 for PM-10 nonattainment areas.

The purpose ofthis criterion is to

assure that astate is not receiving additional time to attainbecause it failed to implement already-adopted or already-committed-to control measures. Given this purpose, webelieve our review under this criterion shouldbe limited tothe implementation status of control measures from earlierPM-10 plans andnot be an expansive review of the implementation status ofevery provision in submitted implementation plans, whether ornot it is an emission reducing measure.

We read this provision not torequire the area to have a fully approved plan that meets the CAA's requirements for moderate areas. We base this reading on the plain language of section 188(e)

54 As described in the section on the BACM requirement, ifapplying BACM-level controls to

one or more ofthe proposed de minimis source categories would result inattainment by December 31, 2001, then those categories arenot de minimis (i.e., they are significant) and must have BACM applied to them. Therefore, states cannot use the de minimis exemption to BACM to avoid applying controls that would resultin attainment by 2001. which requires the state to comply with all requirements and commitments pertaining to that area in the implementation planbut does not require thatthe state comply with all requirements pertaining to the area in theAct.For the same reason, we also read this provision not to bar an extension ifall orpart ofan area's moderate area plan is disapproved or hasbeen promulgated as a FIP orifthe

area has failed to meet aRFP milestone.

Part ofdetermining whether a state has implemented its commitments and requirements in earlier plans is assessing whether the state retains the legal authority for them andis funding, staffing, and enforcing them at the level assumed or committed to in those plans. Thus any determination thatthe state has met its commitments and requirements in earlier plans is also a finding thatit hasretained its legal authority and has met its commitments regarding enforcement, funding, and staffing.

4. Demonstrate the Inclusion ofthe Most Stringent Measures

The fourth extension criterion requires the State to "demonstrate tothe satisfaction ofthe Administrator thatthe planfor the area includes the most stringent measures that are included in the implementation plan ofany State, or

are achieved in practice in any State, and canbe feasibly be implemented in the area." CAA section 188(e).

The requirement for most stringent

measures (MSM) is similar to the requirement for BACM. We define a BACM-level ofcontrol to be, among other things, the maximum degree of emission reduction achievable from a

source or source category which is determined on a caseby case basis considering energy, economic and environmental impacts. Addendum at 42010. The Act establishes the deadline for implementing BACM as four years after an area's reclassification to serious. CAA section 189(b)(1)(A).

We propose to define a "most stringent measure" level ofcontrol in a similar manner: the maximum degree of emission reduction that hasbeen required or achieved from a source or

source category in other SIPs orin practice in other states and canbe feasibly implemented in the area. A MSM thenis a control measure that delivers this level ofcontrol.

The Act does not specify an implementation deadline for MSM. Because the clear intent ofsection 188(e) is to minimize the length ofany attainment date extension, we propose thatthe implementation ofMSM should be as expeditiously aspracticable. 

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Given this similarity between the BACM requirement and the MSM requirement, we believe that determining MSM should follow a process similar to determining BACM, but with one additional step, to compare the potentially most stringent measure against the measures already adopted in the area to determine ifthe existing

measures are most stringent: 1.Develop a detailed emissions inventory ofPM-10 sources and source categories,

2.Model to evaluate the impact on PM-10 concentrations over the standards ofthe various source categories to determine which are significant for the purposes ofadopting MSM, 3.Identify the potentially most stringent measures in other implementation plans or used in practice in other states for each significant source category and for each

measure determine their technological and economic feasibility for the area as necessary,

4. Compare thepotentially most stringent measures for each significant

source category against the measures, if any, already adopted for that source category, and

5.Provide for the adoption ofany MSM that is more stringent than existing similar local measures and provide for implementation as expeditiously as practicable or, in lieu ofproviding for adoption, provide a reasoned justification for rejecting the potential MSM, i.e., why such measures cannot be feasibly implemented in the

area.

The MSM provision only requires that

a state consider thebest controls from elsewhere in the country for implementation in the area requesting

an attainment date extension. Itlooks to see-and the results are completely dependent on-how well other areas have controlled their PM-10 sources. If other areas have not controlled a particular source or source category well, then the resulting level ofcontrol from the MSM will notbe the maximum feasible level ofcontrol for that source

orsource category in the local area. Even iftheyhave controlled them well, the resulting level ofcontrol may still
not be the maximum feasible level because local conditions may allow a higher degree ofcontrol than hasbeen achieved elsewhere.

The MSM provision does not require

a state to consider iflocal sources or

source categories canbe controlled at a level greater than the most stringent level from other areas. In other words, it does not require states to determine and adopt the maximum feasible level ofcontrol that couldbe applied to a

source or a source category given local conditions and the additional implementation time afforded by an extension.

In considering the MSM provision, the inclination isto assume thatthere

are always better controls in other areas than there are in the local area. This assumption isunwarranted, especially for areas thathave already gone through the process ofidentifying and adopting BACM for their significant sources in order to meet the section 189(b)(1)(B) requirement. These areas arelikely to have already evaluated the best controls from other areas and either adopted them as BACM or rejected them as not feasible for their area. As a result, the likelihood offinding substantial new controls during aMSM evaluation in

one ofthese areas is low. 5 5

DeMinimisThresholds.What constitutes a de minimis source category for BACM is dependent upon the specific facts ofthe nonattainment problem under consideration. In particular, it depends upon whether requiring the application ofBACM for such sources would make the difference between attainment andnonattainment by the serious area deadline. We propose to use a similar approach for judging what constitutes a de minimis

source category for MSM but instead of the attainment/nonattainment test,we propose to use the test ofwhether MSM controls onthe de minimis sources would result in more expeditious attainment.

We would not review an MSM analysis in aplan ifthe plan did not demonstrate expeditious attainment since one prerequisite for granting an extension request is thatthe plan demonstrate attainment. Therefore, any de minimis standard for MSM that relied on the difference between attainment andnonattainment would be meaningless because no additional controls are needed for attainment beyond those already in theplan. Our

55 There is alsoan inclination to assume that the MSM requirement is the provision in section 188(e) that implements the Act's general strategy of offsetting longer attainment time frames withmore stringer control and therefore, the MSM requirement mustbe interpreted toresult in the adoption ofmeasures more stringent than BACM. We believe, however, that this offsetting function is actually served by the CAA section 189(b)(i)(A)(ii) requirement for PM-10 plans to demonstrate attainment by the mostexpeditious date practicable, ifattainment by 2001 is impracticable. Because we arerequired to grant the shortest possible extension, a state must demonstrate that it has adopted the set ofcontrol measures that will result inthe most expeditious date practicable for attainement. This requirement mayvery well require that a state adopt controls thatgobeyond the most stringent measures adopted or implemented elsewhere. responsibility under section 188(e), however, is to grant the shortest practicable extension ofthe attainment dateby assuring the planprovides for attainment as expeditiously as practicable. Thus, one means of determining an appropriate de minimis level is to determine ifapplying MSM
to the proposed de minimis source categories would meaningfully expedite attainment. Ifit did, then the de minimis level is too high, andifit did not,then the de minimis level is appropriate.

Like the RACM andBACM requirements, there is no explicit provision inthe Act prohibiting an exemption from the MSM requirement for de minimis sources ofPM-10 pollution. We are using here the same principles for determining when a

source is considered de minimis under the MSM requirement thatwe used for the RACM requirement thatthe OberII
court upheld and thus we have constructed the de minimis exemption for the MSM requirement toprevent states from eliminating any controls on

sources or source categories that alone

or togetherwould result in more expeditious attainment ofthe PM-10 standards.

Technological feasibility.In the MSM analysis, a state must evaluate the application ofcontrols from elsewhere
to sources in its own area. In many cases, these sources are already subject
to local controlmeasures. In these situations, part ofdetermining ifa control istechnologically feasible is determining ifthe new control canbe integrated with the existing controls without reducing or delaying the emission reductions from the existing control. Ifitcannot, then we would not, in general, consider the measure tobe technologically feasible for the area unless the emission benefit ofthe new

measure is substantially greater than the existing measure.

Economic feasibility.Because costis rarely used tojustify rejection ofa

measure in the MAGplan, we will not attemptto establish a general guide for evaluating when a measure is economically infeasible but instead will address the issue on a case-by-case basis

as needed.

Judgingstringency.The stringency of

a control measure is determined primarily by a combination ofits applicability and its control requirement, that is, who in the source category is subject to the measure and what does the measure requires them to do to reduce emissions. When we use the term "measure" inthe context ofthe MSM requirement, we are referringto this combination; we are not referring to 50283

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just the control requirement or to individual methods ofcontrol.

The approach we propose touse in evaluating the selection ofthe most stringent among multiple measures, i.e., evaluating the determination ofwhen

one control measure is more stringent than another, is: 1.Ifthere is only a single measure applicable to asource category then we will compare the measures directly. If there are multiple control measures with diverse controls requirements applicable to asource category (e.g., tailpipe emissions are controlled through fuels, emission standards, inspection and maintenance programs, andtransportation control measures) then we will compare measures with similar control requirements against one another. Ifseveral measures apply the

same orvery similar control requirements to a source category, that is theyhave the same control requirement but different applicablities (e.g., MCESD Rule 310.01 and City and County commitments all require similar controls onunpaved roads), then will

use the collective stringency ofall the

measures in the stringency analysis. 2.We will review all theprovisions ofa rule thatapply to a specific type of

source (e.g., all the rule provision that apply to vacant lots) as an inseparable

measure. As discussed above a rule's stringency is defined by a combination ofits applicability and control requirements (as they apply to a single type of source). They are not separable elements that can be compared in isolation to another rule.56

3.In a MSM analysis, a measure's stringency shouldbe determined assuming thatit is appropriately adopted, implemented and enforced. Thus, we will not use a measure's implementation mechanisms (e.g., rule

versus commitment), funding level, compliance schedule, test method,

resources available for enforcement, or other similar items as criteria for judging relative stringency. 57

A state may determine which measure
ormeasures are most stringent either

56 Forexample, SouthCoast Rule 403 covers vacant lots, construction sites, and agriculture among otherfugitive dust sources. MCESD's Rule 310.01 coversvacant lots andRule 310covers construction sites.TheArizona BMPrulecovers agricultural sources. Underthistestwewould evaluate Rule 403'sprovisions forvacant lots against Rule 310.01 provisions forvacant lots;Rule 403's provisions for construction sitesagainst Rule 310's provision for construction sites; Rule 403's provisions for agricultural sources against theBMP rule's ones.

57 However, once a State determines a measure is

a feasible most stringent measure, itmust convert the measure into a legally enforceableform and provide the necessary level ofresources, etc. to

ensure itsimplementation. qualitatively or quantitatively. It isthe state's responsibility, however, to assure that any determination is well documented andpersuasive.

Once a state has identified a potential
most stringent measure, it must provide for the adoption ofany MSM that is

more stringent than existing measures andprovide for implementation as expeditiously aspracticable or, in lieu ofproviding for adoption, provide a reasoned justification for rejecting the potential MSM, i.e., why suchmeasures cannot be feasibly implemented in the

area.

Finally, we address how we view the "to the satisfaction ofthe Administrator" qualifier on the requirement thatthe State demonstrate that itsplan includes the most stringent

measures. The presence andwording of this qualifier indicates that Congress granted us considerable discretion in determining whether a plan in fact provides for MSM. Under the terms of section 188(e), we believe that we can still accept an MSM demonstration even ifitfalls short ofhaving every MSM possible. To intuitthe limits ofthis discretion, we again lookto the overall intent ofsection 188(e) thatwe grant as short an extension as practicable and to how we have interpreted the CAA's other general control requirements, RACM andBACM.

In concrete terms, this means that when judging the overall adequacy of the MSM demonstration, we will give

more weight to a failure to include MSM for source categories that contribute the
most tothe PM-10 problem andto the failure to include measures that could provide for more expeditious attainment and less weight tothose measures for

source categories that contribute little to the PM-10 problem and would not expedite attainment.

5.Demonstrate Attainment by the Most Expeditious Alternative Date Practicable. Section 189(b)(1)(A) requires that a serious area plan demonstrate attainment by the most expeditious date practicable using air quality modeling after December 31, 2001. This demonstration isthe final criterion that
must be met before we may grant an extension request.

There are two parts to reviewing a modeled attainment demonstration: evaluating the technical adequacy ofthe modeling itself, and evaluating the control measures that are relied on to demonstrate attainment.

We have established technical requirements for modeling PM-10 in SIP attainment demonstrations. Please

see discussion later in this TSD on modeling requirements for PM-10 SIPs. In order to evaluate the control

measures relied on in the attainment demonstration to determine if:

1. Wehave approved itinto the SIP

or the State has submitted itto us for approval into the SIP.

2. Itis enforceable under our SIPenforceability standards or qualifies to be credited under our mobile source voluntary measures policy. 58

3. The plan provides reasonable
assurances, including funding and other

resource commitments, that itwill be implemented and enforced.

4. Itwill be implemented onthe most expedient schedule practicable.

5. The emission reductions credited to itare reasonable and consistent withthe implementation resources and schedule, and for any reductions comingfrom mobile source voluntary measures, that they do not collectively exceed 3 percent ofthe total reductions needed for attainment. 59

Our determination ofwhether the planprovides for attainment by the
mostexpeditious date practicable will depend on whether we findthat the planprovides for appropriate BACM, MSM, and any othertechnologically and economically feasible measures that will resultin attainment as expeditiously aspracticable andthat these measures are implemented on an expeditious schedule.

Please see section 3ofthe EPATSD for additional discussion ofour proposed interpretation ofthe extension requirements.

VI.Administrative Requirements

Under Executive Order 12866 (58 FR 51735, October 4, 1993), this proposed action is not a "significant regulatory action" andtherefore is not subject to review by the Office ofManagement and Budget.For this reason, this proposed action is also not subject to Executive Order 32111, "Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, or Use" (66
FR 28355, May 22, 2001). This proposed action merely approves state law as meeting federal requirements and imposes no additional requirements beyond those imposed by state law. Accordingly, the Administrator certifies thatthis proposed rule will not have a significant economic impact on a substantial number ofsmall entities underthe Regulatory Flexibility Act (5 U.S.C. 601 etseq.). Because this rule

53Memorandum, Richard D. Wilson, Acting
Assistant Administrator forAir and Radiation, to EPA Regional Administrators, 1-10, "Guidance on Incorporating Voluntary Mobile Source Reduction Programs in State Implementation Plans (SIPs),"
October 24, 1997.

59

Ibid., page 5. 50284

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proposes to approve pre-existing requirements under state law and does
not impose any additional enforceable dutybeyond thatrequired by state law, it does not contain any unfunded mandate or significantly oruniquely affect small governments, as described in the Unfunded Mandates Reform Act of1995 (PublicLaw 104-4). This rule also does not have a substantial direct effect on one or more Indian tribes, on the relationship between the Federal Government and Indian tribes, or onthe distribution ofpower and responsibilities between the Federal Government and Indian tribes, as specified by Executive Order 13175 (65 FR 67249, November 9, 2000), nor will it have substantial direct effects on the States, on the relationship between the national government and the States, or

onthe distribution ofpower and responsibilities among the various levels ofgovernment, as specified in Executive Order 13132 (64 FR 43255, August 10, 1999), because it merely
approves a state rule implementing a federal standard, and does not alter the relationship or the distribution ofpower andresponsibilities established in the Clean Air Act. This proposed rule also is not subject to Executive Order 13045 (62 FR 19885, April 23, 1997), because it is not economically significant.

In reviewing SIP submissions, EPA's role is to approve state choices, provided that theymeet the criteria of the Clean Air Act. In this context, in the absence ofa prior existing requirement for the State touse voluntary consensus standards (VCS), EPAhas no authority
to disapprove aSIP submission for failure to use VCS. Itwould thus be inconsistent with applicable law for EPA, when itreviews a SIP submission,
to use VCS in place ofa SIP submission that otherwise satisfies the provisions of the Clean Air Act. Thus, the requirements ofsection 12(d) ofthe National Technology Transfer and Advancement Act of1995 (15 U.S.C. 272 note) donot apply. As required by section 3ofExecutive Order 12988 (61 FR 4729, February 7, 1996), in issuing this proposed rule, EPAhas taken the necessary steps to eliminate drafting

errors and ambiguity, minimize potential litigation, andprovide a clear legal standard for affected conduct. EPA has complied with Executive Order 12630 (53 FR 8859, March 15, 1988) by examining the takings implications of the rule in accordance with the "Attorney General's Supplemental Guidelines for the Evaluation ofRisk and Avoidance ofUnanticipated Takings" issued under the executive order.This proposed rule does not impose an information collection burden under the provisions ofthe Paperwork Reduction Act of1995 (44 U.S.C. 3501 etseq.).

List ofSubjects in 40 CFR Part52

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

Authority: 42 U.S.C. 7401 etseq. Dated: September 14, 2001. Mike Schulz, ActingRegional Administrator,RegionIX. [FR Doc. 01-24203 Filed 10-1-01; 8:45 am]

BILLING CODE 6560-50-P 

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