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ENVIRONMENTAL PROTECTION

AGENCY

40 CFR Part 52 [AZ092-002; FRL-6575-3]
Approval and Promulgation of Implementation Plans; ArizonaMaricopa County PM-10 Nonattainment Area; Serious Area Plan for Attainment ofthe Annual PM-10 Standard

AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.

SUMMARY: EPA proposes to approve provisions of the Revised MAG 1999 Serious Area Particulate Plan for PM-10 for the Maricopa County (Phoenix) Nonattainment Area, February 2000, and the control measures on which it relies, that address the annual PM-10 national ambient air quality standard. We also propose to grant Arizona's request to extend the Clean Air Act deadline for attaining the annual PM-10 standard in the Phoenix area from 2001
to 2006. Finally, we propose to approve two particulate matter rules adopted by the Maricopa County Environmental Services Department and Maricopa County's Residential Woodburning Restrictions Ordinance.
DATES: Comments on this proposal must be received in writing byJune 12, 2000. Comments shouldbe addressed to the

contact listed below.
ADDRESSES: Comments may be mailed

to: Frances Wicher, Office ofAir Planning (AIR-2), EPA Region 9, 75 Hawthorne Street, San Francisco, CA
94105-3901.

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

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

Electronic Availability

This document andthe Technical Support Document (TSD) are also available as electronic files on EPA's Region 9 Web Page at http:// www.epa.gov/regiono9/air.
FOR FURTHER INFORMATION CONTACT: Frances Wicher, Office ofAir Planning (AIR-2), U.S. Environmental Protection Agency, Region 9, 75 Hawthorne Street, San Francisco, California 94105, (415) 744-1238, email: wicher.frances@epa.gov.
SUPPLEMENTARY INFORMATION:

Table ofContents Summary ofToday's Proposals Summary ofthe MAG Plan

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

The CleanAir Act's PlanningRequirements for Serious PM-10 Areas and EPA's Guidance onMeeting these Requirements
A. Implementation ofBest Available Control Measures B. Implementation ofReasonably Available Control Measures C. Extension ofthe Attainment Datebeyond 2001 1.Apply for an attainment date extension 2. Demonstrate that attainment by2001 is

impracticable 3. Complied with allrequirements and

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

stringent measures 5. Demonstrate attainment by themost

expeditious alternative date practicable D. Separating Our Rulemaking Actions on the Annual and 24-hour Standards

Discussion ofthe MAG Plan's Compliance with Clean AirAct Requirements
A. Completeness ofthe SIP Submittals B. Adequacy of theTransportation Conformity Budgets C. Emission Inventory D. Adequate Monitoring Network E. Contribution to PM-10 Exceedances of Major Sources ofPM-10 Precursors F. Implementation ofReasonably Available and Best Available ControlMeasures 1.Determination ofsignificant sources 2. Identification ofpotential BACM 3. Implementation of RACM and BACM

and inclusion ofMSM for each significant source category

a. Technology controls for on-road motor

vehicle exhaust b. Transportation control measures (TCMs)

for on-road motor vehicle exhaust and paved road dust

c. Nonroad engines d. Paved road dust

e. 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 dust rules G. Attainment Date Extension 1.Apply for an extension 2. Demonstrate the impracticability of

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

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

a. Air quality modeling b. Control

measures relied on for attainment 6. Otherfactors thatEPA 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 (RFP) and Quantitative Milestones 1.Reasonable furtherprogress 2. Quantitative milestones I. General SIP Requirements
Proposed Action onMaricopa County Rules
A.Rule 310 B. Rule 310.01 C. Residential Woodburning Restriction Ordinance D. CAA Section 110(1) Finding

Administrative Requirements
Summary ofToday's Proposals

We are proposing to approve the serious area air quality plan for attainment ofthe annual PM-10 standard in the Phoenix, Arizona, metropolitan area.1 Our proposed actions are based on our initial determination that this plan complies with the CleanAir Act's requirements for attainment ofthe annual PM-10 standard in serious PM-10 nonattainment areas.

Specifically, we propose to approve the following elements ofthe plan as they apply to the annual PM-10 standard:

* the base year emissions inventory of PM-10 sources,

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

measures (BACM),

* the demonstration that attainment ofthe PM-10 annual standard by the Clean Air Act deadline ofDecember 31, 2001 is impracticable,

* the demonstration that attainment ofthe PM-10 annual standard will

occur by the most expeditious alternative date practicable, in this case, December 31, 2006,

'There are two separate national ambient air qualitystandards (NAAQS) for PM-10, an annual standard of50pg/m 3and a 24-hour standard of150 pg/m3

. 

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

* the demonstration that theplan includes to our satisfaction the most stringent measures found in the implementation plan ofanother state or

are achieved in practice in another state, and canfeasibly be implemented in the

area.

* the demonstration that major

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

* the transportation conformity budget.

We are also proposing to grant Arizona's request to extend the attainment date for the annual PM-10 standard from December 31, 2001 to December 31, 2006.

Finally, we are proposing to approve Maricopa County's fugitive dust rules, Rules 310 and 301.01, and itsresidential woodburning restriction ordinance.

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 ("EPA TSD") that accompanies this proposal. A copy of the EPATSD can be downloaded from

our website or obtained by calling or writing the contact person listed above. Summary ofthe MAG Plan

We are evaluating and proposing action on the Revised Maricopa Association ofGovernments 1999 Serious Area Particulate Plan for PM-10 for the Maricopa County Nonattainment Area, February 2000 ("MAGplan"). This plan was developed by the Maricopa Association ofGovernments (MAG), the lead air quality planning
agency in Maricopa County, with the assistance ofthe Maricopa County Environmental Services Department (MCESD), the Arizona Department of Environmental Quality (ADEQ), and the cities and towns in the Maricopa County nonattainment area. ADEQ submitted the final plan as a revision to the Arizona State Implementation Plan (SIP)

onFebruary 16,2000.

We are also evaluating and proposing action on the December 11, 1997 submittal ofSerious Area Committed Particulate Control Measures for PM-10 for the Maricopa County Nonattainment Area and Support Technical Analysis, MAG, December 1997. This submittal contains additional control measures that are relied on in the MAG plan. We consider the measures in this submittal
to be part ofthe MAGplan and have evaluated them as such. Finally, we are also evaluating and proposing to act onthe most recent revisions to MCESD's Rule 310, Fugitive Dust Sources (adopted February 16, 2000) and Rule 310.01, Fugitive Dust from Open Areas, Vacant Lots, Unpaved Parking Lots, and Unpaved Roadways (adoptedFebruary 16, 2000). We are alsoproposing to approve the revised Maricopa County Residential Woodburning Restrictions Ordinance (adoptedNovember 17, 1999).

As submitted, the revised MAG plan consists ofthe main plan document, four volumes oftechnical appendices, and four volumes ofcommitments from various agencies toimplement PM-10 controls. The plan contains a 1994 regional PM-10 emissions inventory anduses the urban airshed model/ limited chemistry version (UAM/LC)to model air quality in 1995 as abase year andin 2006 as the attainment year. The plan includes aBACM analysis and a demonstration that attainment by 2001 is impracticable. It also includes the State's request for afive year extension ofthe attainment date, a demonstration that the plan provides for the most stringent measures found in other areas' plans orused in practice, and a demonstration of attainment by December 31, 2006. The plan shows that the principal sources contributing to PM-10 exceedances in the Phoenix area

are fugitive dust sources, such as construction sites, vacant lots, paved andunpaved roads, and various other dust sources. The principal controls relied on for attainment are controls on these fugitive dust sources.

The MAGplan addresses both the annual and 24-hour PM-10 standards. We arenot atthis time proposing any actions regarding the plan's compliance with the statutory requirements relating
to the 24-hour standard. As we explain in more detail later, the annual PM-10 standard is a separate air quality standard from the 24-hour one; therefore, we can and must separately evaluate aplan's compliance with the statutory requirements for each standard. We donot need to dothese reviews concurrently.

The MAGplan also contains contingency measures asrequired by CAA section 172(c)(9). We arenot proposing action onthese contingency

measures atthis time. Contingency

measures are a distinctprovision ofthe Clean Air Act that we may act on separately from the attainment requirements. PM-10 AirQuality in thePhoenix MetropolitanArea

A. TheMaricopa Nonattainment Area anditsPM-10AirQuality

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.2 40 CFR 81.303. The area is home to almost 3 millionpeople.

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

area was designated nonattainment for PM-10 and classified asmoderate. In 1996, because ofcontinuing violations ofboth PM-10 standards, the area was reclassified to serious. 61 FR 21372 (May 10, 1996).

As noted before, the principal contributors to elevated PM-10 levels in the Phoenix area are fugitive dust

sources such as construction sites, unpaved roads, vacant lots andpaved road dust. Also contributing to the PM10 problem, but to a much lesser degree thanfugitive dust, are internal and external combustion sources including directly-emitted PM-10 from automobiles, trucks, construction equipment, bus,residential woodburning andindustrial, commercial, and residential use of natural gas and fuel oil. SeeMAG plan, 3-5.

B.PM-I0AirQualityPlanning in the PhoenixMetropolitan Area
The MAGplan is the latest in a series ofair quality plans addressing the PM10 problem in Phoenix. These previous plans are: * 1991 MAG Moderate AreaPlan. Arizona submitted this plan in 1991 and revisionsto itin 1993 and 1994. The 1991 plan contained a demonstration that attainment was impracticable by the CAA's deadline for moderate areas, December 31, 1994. We initially approved this plan in 1995 (60 FR 18010 (April 10, 1995)); however, the 9thCircuit Court ofAppeals vacated our approval in 1996, finding among other thingsthat the plan did not address the 24-hour PM-10 standard. Oberv.EPA, 84 F.3d 304 (9thCir. 1996). In 1998, we disapproved the 1991 plan's reasonably available control measure (RACM) demonstration for the annual standard because the plan failed to provide for the implementation ofRACM on

2The Maricopa nonattainment area also includes
the town ofApache Junction inPinal County. Apache Junction is covered bya separate air quality plan and willbe addressed in a later action.

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number ofsignificant sources ofPM-10, including unpaved roads. The failure to provide for the implementation of RACM alsomeant that theplan could

no longer conclusively demonstrate the impracticability of attainment ofthe annual standardby December 31, 1994,

so we also disapproved the impracticability demonstration. 63 FR 15919, 15925 (April 1, 1998).

* MicroscalePlan.Arizona submitted this plan in 1997 as a response to the 9thCircuit's findings in Ober.The plan addressed the CAA's serious area PM10 requirements for attaining the 24- hour standard around four representative air quality monitors (that is, atfour localized or "microscale" sites)in the Phoenix area. It found that 24-hour exceedances in the Phoenix

area are mainly caused by fugitive dust from construction, agriculture, unpaved roads andparking lots, and disturbed
vacant land. We approved the plan in part but also disapproved it in part because it did not provide for the implementation ofRACM orBACM on agricultural sources, unpaved roads, unpaved parking lots, and disturbed
vacant lots and did not demonstrate attainment at two ofthe four sites. 62 FR 41856 (August 4, 1997).
* 1998ModerateAreaFederal ImplementationPlan(FIP). We promulgated this plan on August 3, 1998. It provided for the implementation ofRACM onthe significant sources-unpaved roads, unpaved parking lots, disturbed vacant lots, and agricultural sources-left unaddressed by the 1991 MAG moderate area plan and the Microscale plan.3 The FIP demonstrated thatthe implementation ofRACM was insufficient for attainment ofthe 24- hour and annual standards by Phoenix area's attainment deadline ofDecember 31, 2001. 4 63 FR 41326 (August 3, 1998).

A more detailed history ofPM-10 planning in the Phoenix area canbe found in the EPATSD.

3The FIP's requirements for unpaved roads, unpaved parking lots and disturbed vacant lots are codified at40 CFR 52.128. We withdrew the FIP's agricultural requirements, formerly codified at 40
CFR 52.127, when we approved similar State requirement in 1999. 64 FR 34726 (June 29, 1999).

4At the time we promulgated the FIP in 1998, the moderate PM-10 area deadline ofDecember 31, 1994 had passed andwe hadreclassified the Phoenix area to serious. As aresult the only statutory attainment deadline then applicable to the Phoenix area, and thus the deadline applicable to

ourmoderate area FIP, was the serious area deadline, i.e., as expeditiously as practicable but
not laterthan December 31, 2001. See 63 FR 15919,
15926. C. CleanAirAct Sanctionson the PhoenixArea
Our 1998 disapprovals ofparts ofthe 1991 MAG moderate area plan started sanction clocks under CAA section 179(a). Under section 179(a), once we disapprove a SIP provision because it fails to meet aCAA requirement, a State has 18 months to correct the deficiency that resulted in the disapproval before the first oftwo sanctions goes into place. Ifthe state still has not corrected the deficiency within 24 months ofthe disapproval, the second sanction goes into place.

The two CAA sanctions are a limitation on certain highway approvals and funding and an increase in the offsetratio to 2to 1for any major new stationary source ormajor modification. See CAA section 179(b). Our sanctions regulations provide thatthe first sanction to be imposed is the offsetratio unless we have established at the time ofthe disapproval thatthe highway sanction will be first.40 CFR 52.31(d).

OnAugust 3, 1998, we published our disapprovals ofthe RACM and attainment demonstrations for the annual standard in the 1991 MAG moderate area plan. 63 FR 41326. When these disapprovals became effective 30 days later on September 2, 1998, the sanction clocks started. The first of these sanction clocks expired onMarch 2, 2000 and the 2:1 offset sanction is

now in place in the Phoenix area. The second sanction clock for thehighway funding limitations is setto expire on September 2, 2000.

Under section 179(a) and our sanctions regulations at40 CFR 52.31(d)(1), we must approve a SIP revision that corrects the deficiencies to permanently endthe sanctions clocks andlift any imposed sanctions. However, we may temporarily stay the clocks and any imposed sanctions ifwe propose to approve a SIP revision that
corrects the deficiencies and have issued an interim final determination that the State has corrected the deficiencies. 40 CFR 52.31(d)(2)(i).

In arule being published concurrently with this proposal, we areissuing an interim final determination that, based

ourproposed findings here, Arizona has

more than likely corrected the deficiencies that resulted in our August 1998 disapprovals.

The Clean Air Act'sPlanning Requirements for SeriousPM-10 Areas andEPA's Guidance on Meeting these Requirements

The Phoenix area is aPM-10 nonattainment area thathas been reclassified to serious because it failed to attain by 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 CAA requirements for serious PM10 nonattainment areas. CAA section 189(b)(2). Theserequirements are:

(a) assurances that best available control measures (BACM) forthe control ofPM-10 shall be implemented nolater than4 years after the area isreclassified (CAAsection 189(b)(1)(B)); 5

(b) assurances thatbest available control technology (BACT) on major stationary sources ofPM-10 precursors shall be implemented nolater than 4
years after the area isreclassified except where EPA has determined that such

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

(c) a demonstration (including air quality modeling) that the planwill provide for attainment as expeditiously

as practicable but no later than December 31, 2001, or, where the State is seeking an extension ofthe attainment date under section 188(e), a demonstration that attainment by December 31, 2001 is impracticable (CAAsections 188(c)(2) and 189(b)(1)(A));

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

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

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

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

assurances thatthe 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

as required by 40 CFR 51.111.

Except for the requirements for the implementation ofRACM and BACM and for extension requests, we will discuss ourpolicies for each ofthese requirements when we discuss our evaluation ofthat section ofthe MAG planlater inthis preamble.

5When a moderate area is reclassified to serious, therequirement 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 ofRACM as expeditiously as practicable to the extent that the RACM requirement has notbeen satisfied in the
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We have issued a General Preamble, 57 FR 13498 (April 16, 1992) and 57 FR 18070 (April 28, 1992), andAddendum
to the General Preamble ("Addendum"), 59 FR 41998 (August 16, 1994), describing ourpreliminary views on how we intend toreview SIPs submitted
to meetthe Clean Air Act's requirements for PM-10 plans. We have alsoissued other guidance documents related to PM-10 plans orprovisions of these plans. These other guidance documents will be cited as appropriate.

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 is June 10, 2000.

The Act does not define what constitutes BACM. We consider BACM
to be a particular level ofcontrol, in this

case the best, on a source or source category. More specifically, we have defined BACM to be, among other things, the maximum degree ofemission reductions achievable from a source or

source category which is determined on

a case-by-case basis, considering energy, economic and environmental impacts. Addendum at 42010. We also consider BACM as going beyond existing RACMlevel controls, such as expanding the

use ofRACM controls (e.g., paving more miles ofunpaved roads). Addendum at 42013. Additionally, we believe that BACM should emphasize prevention rather than remediation (e.g., preventing track out at construction sites rather than simply requiring clean up of tracked-out dirt). Addendum at42013.

A serious area plan must provide for the implementation ofBACM on each significant (i.e.,non-de minimis) source category. Addendum at 42011. In guidance, we have established a presumption that a "significant" source category is one that contributes 1gLg/m 3

ormore ofPM-10 to a location ofan annual standardviolation. Addendum
at42011. However, whether the threshold shouldbe lower than this in
any particular area depends upon the specific facts ofthatarea's nonattainment problem. Specifically, in

areas thatare demonstrating attainment by December 31, 2001, it depends on whether requiring the application of BACM on source categories below a proposed de minimis level would meaningfully expedite attainment. In

areas thatare claiming the impracticability of attainment by December 31, 2001, it depends upon whether requiring the application of BACM on source categories below a proposed de minimis level would make the difference between attainment and nonattainment by the serious area deadline ofDecember 31, 2001. 6

We have outlined in our guidance a multi-step process for identifying BACM. Addendum at42010-42014. The steps are:

1. develop a detailed emission 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 their technological feasibility, costs, and
energy and environmental impacts if needed to determine BACM, and

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

B. Implementationof Reasonably Available ControlMeasures

When amoderate area isreclassified
to serious, the requirement to implement RACM in section 189(a)(1)(C) remains. Thus, a serious

area PM-10 plan must alsoprovide for the implementation ofRACM as expeditiously aspracticable to the
extentthat the RACM requirement has
not been satisfiedin the area's moderate

area plan.

However, we do not normally conduct

a separate evaluation to determine ifa serious area plan's measures also meet the RACM requirements as interpreted by us in the General Preamble at 13540. This is because in our serious area guidance (Addendum at 42010), we interpret the BACM requirement, as generally subsuming the RACM requirement (i.e.ifwe determine that the measures are indeed the "best available," we have necessarily concluded that they are "reasonably available"). Therefore, a separate analysis to determine ifthe measures represent aRACM level ofcontrol is not necessary. Consequently, our proposed approval ofthe MAG plan's provisions

6This principle isbest illustratedby an example:
In Area A, attainment ofthe annual standard by December 31, 2001 requires that total PM-10 emissions in the area bereduced to 200 tons per day (tpd). After application ofBACM to all source categories above the proposed de minimis level, total emissions inthe area are reduced to 220 tpd. BACM on the proposed de minimis source categories would reduce total emissions a further 5
tons to 215 tpd. Since application ofBACM to the proposed de minimis source categories still leaves emissions above the attainment level of200 tpd,the proposed de minimis level is appropriate. relatingto the implementation ofBACM is also a proposed finding thattheplan provides for the implementation of RACM.

C.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.

In determining whether to grant an extension and the appropriate length of the attainment date extension, we may consider:

1. the nature and extent ofthe nonattainment problem,

2. the types andnumber of sources or other emitting activities in the area (includingthe influence of uncontrollable natural sources and international transport),

3. the population exposed to concentrations in excess ofthe standard,

4. the presence and concentration of potentially toxic substances in the mix ofparticulate emissions in the area, and

5. the technological and economic feasibility ofvarious controlmeasures.

We maygrant only one extension for

an area and that extension cannot be for

more than 5years after 2001; thatis, the extended attainment date can be no later thanDecember 31, 2006. CAA section 188(e).

To date, we have not issued any policy or regulation interpreting the attainment date extension requirements for urban areas like Phoenix. Therefore, before reviewing Arizona's request for

an extension, we will first discuss how

we propose tointerpret section 188(e).

The following is ourpreliminary interpretation ofthe section 188(e) requirements andwe request comment

on it. We emphasize thatthis is our preliminary view and itis subject to modification as we gain more experience reviewing on extension requests from other areas. 

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We have listed above the five requirements a State must meetbefore

we can consider granting an attainment date extension.We discuss each requirement in order:

1.Apply for an Attainment Date Extension

The State must apply in writing to EPA for an extension ofthe attainment deadline. The request should accompany the SIP submittal containing the most expeditious alternative attainment demonstration. The public
must be provided reasonable notice and

apublic hearing on the request before it is submitted.

Extension requests are not SIP submittals per se 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 plan, we believe

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

In order to demonstrate impracticability, the plan must show that the implementation ofBACM (as determined by our guidance) on significant source categories will not bring the area into attainment by December 31, 2001. BACM isthe required level ofcontrol for serious

areas thatmust be in place before the 2001 attainment date; therefore, we believe that itis reasonable to interpret the Act to require that a state provide for
atleast the implementation ofBACM on significant source categories before it

can claim impracticability of attainment by 2001. 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 show impracticability of attainment by 1994, the moderate area attainment deadline. General Preamble
at 13544.

The statutory provision for demonstrating impracticability requires that the demonstration bebased on air quality modeling. See section 189(b)(1)(A).

3.Complied With all Requirements and Commitments in its Implementation Plan

We interpret this criterion tomean that the State has implemented the control measures in the SIP revisions it has submitted to us to address the CAA requirements in sections 172 and 189 for PM-10 nonattainment areas.

We read this provision not to require the area to have a fully approved SIP that meets the CAA's requirements for moderate areas. We base this reading on the plain language of section 188(e) which requires the state to comply with allrequirements and commitments pertaining to that area in the implementation plan but does not require that the state comply with all requirements pertaining to the area in the Act.For the same reason we also read this provision not tobar an extension ifall orpart ofan area's moderate area plan is disapproved or has been promulgated as a FIP.

4. Demonstrate the Inclusion ofthe Most Stringent Measures

The fourth extension criterion requires the State to "demonstrate tothe satisfaction ofthe Administrator thatthe plan for 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 canfeasiblely be implemented in the area." CAA section 188(e).

The requirement for most stringent

measures (MSM)is similar to the requirement forBACM. We define BACM to be, among otherthings, the maximum degree ofemission reduction achievable from a source or source category which is determined ona case by case basis considering energy, economic and environmental impacts. Addendum at 42010. The Act establishes the deadline for implementing BACM as fouryears after

an area's reclassification to serious. CAA section 189(b)(1)(A).

We proposed to define a "most stringent measure" in a similar manner: the maximum degree ofemission reduction thathas been required or achieved from a source or source category in other SIPs or in practice in other states and can feasiblely be implemented in the area. The Act does
not specify an implementation deadline for MSM. Because the clear intent of section 188(e) is tominimize the length ofany attainment date extension, we propose thatthe implementation of MSM shouldbe as expeditiously as practicable.

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

1. develop a detailed emission inventory 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 of adopting MSM,

3. identify the potentially most stringent measures in other implementation plans or used in practice in other States for each significant source category and, for each
measure, determine theirtechnological and economic feasibility forthe area,

4. compare the potentially most stringent measures for each significant

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

5. provide for the adoption and expeditious implementation ofany MSM thatis more stringent than existing measures or, in lieu of adoption, provide a reasoned justification for rejecting the potential MSM, i.e., why such measures cannot be feasiblely implemented in the area.

The level ofcontrol resulting from a most stringent measure depends onhow well other areas have chosen to control their sources. Ifa source category has
notbeen well controlled in other areas thenMSM may infact result in a rather low level ofcontrol. This contrasts with BACM which is determined independently ofwhat other areas have done and depends only on what is the best level of controlfeasible for an area.

Because BACM is the best level of control feasible for an area, itwould be easy for the MSMrequirement to result in no more controls and no more emission reductions in an area than result from the implementation of BACM. Given the strategy in the nonattainment provisions ofthe Act to offset longer attainment time frames with more stringent control requirements, we needto interpret the MSM provision to assure that itresults in additional controls beyond the set of

measures adopted as BACM. The primary ways to do this are (1)to require thatmore sources and source categories be subject to MSM analysis thanto BACM analysis, that is, by lowering the threshold for what is considered a de minimis source category and (2)to require reanalysis of
any measures garnered from other areas that were rejected duringthe BACM analysis because they could not be implemented bythe BACMimplementation deadline to see ifthey 

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are now feasible for the area given the longer attainment date.

DeMinimis Thresholds.What constitutes a de minimis source category for BACM is dependent upon the specific facts ofthe nonattainment problem under consideration. In particular, itdepends 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 ade minimis

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

We would not review an MSM analysis in a plan ifthe plan did not demonstrate expeditious attainment since one prerequisite for granting an extension is that theplan demonstrate attainment. Therefore, any de minimis standard for MSM thatrelied on the difference between attainment and nonattainment would be meaningless because no additional controls are needed for attainment beyond those already in the plan. Our responsibility under section 188(e), however, is to grant the shortest practicable extension ofthe attainment dateby assuring the plan provides for attainment as expeditiously as practicable. Thus, one
means ofdetermining an appropriate de minimis level isto determine if applying MSM to the proposed de minimis source categories would meaningfully expedite attainment. Ifit did,then the de minimis level istoo high, and ifit did not, then the de minimis level is appropriate. 7 TechnologicalFeasibility. 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 control measures. In these situations, part ofdetermining ifa control is technologically feasible is determining ifthe new control can be integrated with the existing controls without reducing or delaying the emission reductions from the existing control. Ifit cannot, then we would not, in general, consider the measure tobe technologically feasible for the area.

7 In extension areas, the applicable control requirement after the December 31, 2001 attainment date is the MSM and expeditious attainment requirements ofsection 188(e). Thus, formeasures implemented after December 31, 2001, a stateneed only show that the measure meets at minimum the MSM level ofcontrol and, combined with all other
measures, is sufficient for expeditious attainment. A statehas no obligation to show thatthe measure meets a BACM-level ofcontrol. EconomicFeasibility. Because cost is rarely used tojustify rejection ofa

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

asneeded.

We propose to use the following approach in evaluating the selection of the most stringent amongmultiple
measures, i.e., evaluating the determination ofwhen one is more stringent than another:

1.The determination will be made on

a source category basis.When only a single measure is applicable to a source category then we will compare the

measures directly. However, in many
cases multiple measures apply to a single source category (e.g., unpaved roads which in theMAG plan are controlled both by Rule 310.01 and through City and County commitments). In these cases, we will evaluate the impact ofthe overall control strategy on emissions in the source category against the impact ofthe overall control strategy

onthe source category in other areas and will not compare individual

measures withinthe source category. 2.We will review all the elements of

arule that apply to a specific type of

source as an inseparable measure. A rule's applicability and emission limitations (as they apply to a single type of source) together define its stringency. They are not separable elements that canbe compared in isolation to another rule. 3.Because stringency isbased on an emissions level, we will not use a measure's implementation mechanisms (e.g.,rule versus commitment), funding level, compliance schedule, resources available for enforcement, or other similar items as criteria forjudging relative stringency. (We do consider these items when judging whether the plan provides for implementationof MSM.)

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 indicate that Congress granted us considerable discretion in determining whether a plan in fact includes MSM. Under the terms of section 188(e), we believe that we can still accept an MSM demonstration even ifitfalls short ofhaving every MSM possible. To intuitthe limits ofthis discretion, we again lookto the overall intent ofsection 188(e), that we grant as short an extension as practicable. In
concrete terms, this means that when judging the overall adequacy ofthe MSM demonstration, we will give more weight to afailure toinclude MSMfor

source categories that contribute the
mosttothe PM-10 problem in Phoenix and to the failure to include measures that could provide formore expeditious attainment and lessweight to afailure
to include MSM for source categories that contribute little to the PM-10 problem and/or would not expedite attainment.

5.Demonstrate Attainment by the Most Expeditious Alternative Date Practicable

Section 189(b)(1)(A) requires that a serious area plan demonstrate attainment, using air quality modeling, by the most expeditious date practicable after December 31, 2001. This demonstration is the final criterion that
mustbe met before we may grant an extension request.

Our determination ofwhether the planprovides for attainment by the
mostexpeditious date practicable will depend on whether the plan provides for implementation ofBACM by the BACM implementation deadline and MSM as expeditiously aspracticable.

Please see section 4 ofthe EPATSD for an additional discussion ofour proposed interpretation ofthe extension requirements.

D.SeparatingOurRulemakingActions

on theAnnualand24-hourStandards

As we discussed above, there are two PM-10 NAAQS, an annual standard of 50 gg/m 3 and a 24-hour standard of 150 gLg/m 3-In this proposed action, we are evaluating the MAG plan only for its compliance with the Clean Air Act's requirements for attaining the annual PM-10 standard. We are not, atthis time, evaluating the plan for its compliance with the Act's requirements for the 24-hour PM-10 standard. Under section 110(k)(2), we have until February 25, 2001-one year after the completeness finding-to act on the balance ofthe planthat was submitted

on February 16, 2000.

The two PM-10 standards are independent and mustbe addressed independently by states in their SIPs. Thisindependence was highlighted by the Ninth Circuit Court ofAppeals in Oberv.EPA, 84 F.3d 304 (9th Cir. 1996). In Ober,the Courtwas reviewing our approval ofthe MAG moderate area plan:
The general provisions ofthe Clean AirAct repeatedly emphasize thatimplementation plans mustprovide forattainment ofthe NAAQS as expeditiously as practicable.For PM-10, theEPA promulgated two separate NAAQS-the annual standard andthe 24-hour standard-which differ in thefollowing 

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respects. First, the 24-hour standard offers protection against dangerous short-term exposures to highPM-10 levels, aprotection that isdistinct from the protection against chronic degradation in lung function provided bythe annual standard. Second, the

sources ofPM-10 violation differ forthe annual and the 24-hour: violations ofthe 24- hour standard are generally causedby localized sources suchas construction projects, whereas violations ofthe annual standardtend tobe causedby more diverse, dispersed sources. Third, control measures differin effectiveness for the 24-hour standardand theannual standard.

These differencesemphasizethe importanceofviewingPM- O's two NAAQS individuallyandofrequiringindependent
treatmentofthem in animplementation plan

..... Such independent treatment furthers the Clean AirAct's goals of protecting health and achieve clean air. Oberat 309 (emphasis added). Ifa state must treat each PM-10 NAAQS independently in the implementation plan, then we also must treat each PM-10 NAAQS independently when reviewing the plan's compliance with the Clean Air Act. Therefore, itis necessary for us to review the MAG plan's compliance against the CAA requirements as they apply to the annual standard and again review them against the CAA requirements as they apply tothe 24- hour standard. There isno mandate that

we conduct these reviews concurrently

evenifArizona submitted asingle document to meet the requirements for both standards since, effectively, we must treat it as ifit contained two separate plans.

We have chosen not to act at thistime

onthe 24-hour provisions ofthe revised MAG planbecause the State is still working on quantifying emission reductions from the bestmanagement practice measures (BMPs) intended to reduce fugitive dust from agricultural

sources. Attainment ofthe 24-hour standard in the Phoenix area, unlike the annual standard, depends in part on emission reductions from these BMPs. Once Arizona quantifies the reductions, it will revise the 24-hour attainment demonstrations and resubmit them to

us. We expect these changes later this year. We do not believe itis an efficient

use ofour resources to act now on the 24-hour provisions currently in the MAG plan knowing that theywill be substantially revised prior to our statutory deadline to act on them.

Discussion ofthe MAG Plan's Compliance with the CleanAir Act's Requirements

The following sections present a condensed discussion ofour evaluation oftheMAG plan's compliance with the applicable CAArequirements for attainment ofthe annual PM-10 standard. Our complete evaluation is found in the EPATSD for this proposal. We urge anyone wishing to comment on this proposal to first review the TSD before preparing comments. A copy of the TSD canbe downloaded from our website or obtained bycalling or writing the contact person listed above.

A. CompletenessoftheSIPSubmittals

The first step we take afterreceiving

a SIP submittal is to determine ifit is complete. CAA section 110(k)(1)(B) requires that we review all SIPs and SIP revisions for completeness within 60 days ofreceipt ofthe submittal. The completeness review allows us to quickly determine ifa state has submitted a SIP revision, including all needed supporting material, onwhich

we can take action. We make completeness determinations using criteria we have established in 40 CFR part 51, appendix V.

We found ADEQ's February 16, 2000 submittal (received onFebruary 23, 2000) ofthe final revised MAG serious

area PM-10 plan complete. We notified the State ofour completeness determination onFebruary 25, 2000. See Letter, David P. Howekamp, EPA, to Jacqueline Schafer, ADEQ.

Ifwe donot make a completeness determination, a submittal becomes complete by default 6 months after we receive it. See 100(k)(1)(B). We did not review the 1997 submittal ofcontrol

measures for completeness and it became complete by default onJune 15, 1998.

We found Arizona's submittals containing MCESD's Rule 310 and 310.01 andthe revised Maricopa County residential woodburning ordinance complete on March 31, 2000.

B. Adequacy ofthe Transportation ConformityBudgets

Section 176(c) ofthe Clean Air Act requires that federally funded or approved transportation plans,
programs, and projects in nonattainment

areas "conform" tothe 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. We have issued a conformity rule that establishes the criteria andprocedures for determining whether or not transportation plans,
programs, and project conform. 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 thanthe levels needed tomake progress toward and meet the air quality standards. The motor vehicle emissions levels needed to make progress toward and meetthe air quality standards are set in an area's attainment and/or reasonable further progress (RFP) plans and are known asthe "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 may be used in

a conformity determination, we must first determine thatit is adequate. The criteria by which we determine adequacy of submitted emission budgets

are outlined in our conformity rulein 40 CFR 93.118(e)(4).

The MAGplan establishes a mobile

source emissions budget of59.7 mtpd. Thisregional budget is applicable for both the annual and 24-hour PM-10 standards. The on-road mobileportion ofthebudget, which includes emissions fromreentrained road dust,vehicle exhaust, and travel onunpaved roads, is 58.6 mtpd. The road construction portion ofthe budget is 1.1 mtpd. MAG plan, p. 8-13.

On March 30, 2000, we have found adequate for transportation conformity
purposesthis motor vehicle emission budget. As a result ofour adequacy finding, MAG and the Federal Highway Administration are required touse this budget in future conformity analyses.

C.EmissionInventory

CAA section 172(c)(3) requires all nonattainment area plans to contain a comprehensive, accurate, and current inventory. Our policies require thatthe inventory be fully documented.

The MAGplan describes annual and average annual day emissions for 1994 frompoint, area, nonroad, on-road, and nonanthropogenic sources in the Maricopa County portion ofthe 2,880
square mile nonattainment area. The inventory includes emissions ofPM-10, PM-2.5, ammonia (NH 3), nitrogen oxides (NOx), and sulfur oxides (SOx).

The inventory shows thatthe dominant sources ofemissions in the Phoenix area are paved road dust (39.1 percent), unpaved roads, (21.6 percent) and construction-related fugitive dust (20.1 percent). Much lower but still important contributors are directlyemitted PM-10 from non-road engines (7.0 percent) and on-road motor vehicles (3.3 percent), all stationary area sources, e.g., woodburning (6.1 percent) and stationary point sources (2.7 percent). MAG plan, Table 3-1.

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documentation exceeding our guidance requirements. Current: The base year, 1994, is a reasonably current year, considering the length oftime needed to develop an inventory, perform the modeling, develop and adopt control measures, andhold public hearings on such a large andtechnically-complex plan like the MAG plan. Comprehensive:The MAG plan inventories are fairly complete, considering a few emission factors are unknown for some ofthe smaller

sources ofPM-10. The inventories did
not include emissions ofvolatile organic compounds (VOC) which is a precursor ofsecondary PM-10 because the plan found there is a negligible impact on ambient measurements ofPM-10 from VOC aerosol. We concur with this finding and thatVOC sources need not be inventoried for the PM-10 plan.

Accurate:In developing the inventory, MAG and MCESD closely followed our guidance relative to the

use ofemission factors, activity estimates, and growth and control factors, and the other source specific emission estimation methodologies (continuous emission monitoring, annual stack tests, and mass balance methods). Source specific methods were used to the maximum extent possible as they are inherently more accurate than emission factors. The relative accuracy ofeach estimate underwent the prescribed quality assurance procedures
to eliminate all possible errors. The inventory is thus as accurate as inventories canbe.

Because we findthat the inventory is current, comprehensive, and accurate,

we propose to approve itunder CAA section 172(c)(3).

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

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

The MAGplan does not specifically address the adequacy ofthe PM-10 monitoring network in the Phoenix area. There isno requirement that itdoes. We

are reviewing the adequacy ofthe monitoring network here because the plan relies on ambient datato characterize the extent and severity of the PM-10 problem in the Phoenix area and we need to assure that the monitoring network is adequate for this
purpose.

In 1995, the base year for the air quality modeling, there were 18 monitoring sites collecting data in the Phoenix area, all ofwhich were operated in accordance with our regulations. Most ofthese PM-10 monitoring sites were neighborhood scale siteswith an objective ofassessing population exposure. Given the widespread nature ofthe emission

sources in the Phoenix area, we believe this focus was appropriate and thatthe network was adequate to characterize the extent and severity ofthe PM-10 problem in 1995.

E.Contributionto PM-IOExceedances of

MajorSourcesofPM-I0 Precursors
Under CAA section 189(e), a state must applythe 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. For the serious area plan, a "major source"is

one that emits orhas the potential to emit over 70 English tons per year (tpy) ofsulfur 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 onthe contribution oftotal secondary particulates to PM-10 levels and the emissions from major precursor sources to estimate the impact.

All major stationary sources ofPM-10 precursors are estimated to contribute just 0.24 gg/m3 to the annual levels of PM-10. SeeEPA TSD section, "BACT for Major Stationary Sources ofPM-10 Precursors." This contribution isless than 0.5 percent ofthe annual PM-10 levels over the standard in the Phoenix

area and less than 0.5 percent ofthe annual standard of50 gg/m 3.

We believe that this small contribution is insignificant for the Phoenix area. PM-10 levels above the annual standard in Phoenix are almost exclusively caused by afew large source categories offugitive dust, andit is BACM-level controls onthese sources that are thekey to expeditious attainment ofthe annual standard in the Phoenix area and not controls on small contributors such as major sources of PM-10 precursors.

We, therefore, propose to determine thatmajor sources ofPM-10 precursors do not contribute significantly to PM-10 levels in excess ofthe PM-10 NAAQS in the Phoenix area. As a result, Arizona is not required to apply BACT to major

sources ofPM-10 precursors in the Phoenix area.
F. Implementationof Reasonably AvailableandBestAvailableControl Measures

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

a serious area PM-10 planprovide for the implementation ofBACM within four years ofreclassification to serious. ForPhoenix, this deadline is June 10, 2000. BACM mustbe applied to each significant area-wide source category. Addendum at 42011. As discussed above, we have established a four-step
process for evaluating BACM in serious

area PM-10 plans.

1.Determination ofSignificant Sources

The first step inthe BACM analysis is
to develop a detailed emission inventory ofPM-10 sources and source categories that canbe usedin modeling
to determine theirimpact on ambient air quality.Addendum at 42012.

The MAGplan uses three modeling studies ofPM-10 sources in the Phoenix

area to identify significant source categories. One ofthese studies evaluated significant sources using chemical mass balance (CMB) modeling performed on monitoring samples collected at 6 sites in 1989-1990. The
two other studies evaluated significant

sources using dispersion modeling of

sources around 6 monitoring sites using data from 1992 through 1995.8

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

The final list of significant source categories did not distinguishbetween those categories that are significant for the 24-hour standard andthose significant for the annual standard; although previous studies have shown that some source categories are significant only for one or the other standard. Because the MAGplan did not distinguish significant source categories between the two standards, we will treat each ofthe listed significant source

8These studies are "The 1989-90 Phoenix PM10 Study," Desert Research Institute, April 1991; "Particulate Control Measure Feasibility Study," SierraResearch, January 1997; and "Plan for Attainment ofthe 24-hoar PM-10 Standard, Maricopa County PM-10 Nonattainment Area," ADEQ, May 1997. 

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categories as significant for the annual standard.

For the annual standard, the MAG plan demonstrates thatits selection of significant source categories is appropriate by showing that control on the de minimis source categories would
not make the difference between attainment and nonattainment ofthe annual standardby 2001. According to the plan, total emissions in the area need tobe reduced to 130 mtpd to attain the annual standard by 2001. After application ofBACM, total emissions

are reduced to 152 mtpd. MAG plan, p. 9-11. The 12 de minimis sources categories contribute in total 10.3 mtpd. MAG plan, Table 9-a. Totally eliminatingthese source categories would reduce total regional emissions to 142 mtpd, still 12 mtpd above the regional emissions level needed for attainment. MAG plan, pp. 9-10 through 9-12.

The 8 significant source categories

are:

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

Our proposal here does not mean that

we believe all the source categories identified as significant in the MAG plan needed tobe considered significant for the purpose ofevaluating BACM. We believe that the MAG plan is conservative in its selection of significant source categories, thatis, it may have included more source categories in its significant source list than are strictly needed. Thus our use ofnegative wording in ourproposed finding: no significant source categories

were excluded as opposed to onlythe significant categories were included. In

our 1998 FIP, we derived a narrower list ofsignificant sources based onmore recent modeling than was used to develop the list in theMAG plan. See 63 FR 15920, 15932 (Table 2and text).

2.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

areas in theWest. It also evaluated controls proposed during public
comment. MAGplan, pp. 9-24 through 9-29.

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 for the

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

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

We propose to find thatthe MAGplan identified and evaluated potential BACM for the Maricopa area consistent with our guidance. As we will discuss below in our evaluations ofthe implementation ofBACM for each significant source category, we do not believe that the MAG plan left out any candidate BACM. We note that additional evaluation ofcontrol

measures was done as part ofthe most stringent measure analysis. MAG plan,
pp 10-25 &10-26. Overall, the MAG plan presents one ofthe most comprehensive lists ofpotential BACM

everproduced.

3.Implementation ofRACM andBACM andInclusion ofMSM for Each Significant Source Category

In the following sections, we review the results ofthe MAGplan's BACM analysis. To present these results, we have grouped the emission generating activities that comprise the MAG plan's significant categories slightly differently fromthe plan, e.g., we have addressed separately construction activities and disturbed vacant lands which areboth included in the MAG plan's significant category ofconstruction site preparation.9We have donethis to make our evaluations oftheplan's provisions for the implementation of BACM and inclusion ofMSM clearer and thus,we believe, more understandable. However, despite the method ofpresentation, we have addressed theMAG plan'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.

Finally, controls on a number of significant source categories are found in MCESD'sfugitive dust rules, Rule 310 and Rule 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 ofour finding that the MAG planprovides for implementation of RACM and BACM and inclusion of MSM. We discuss them atthe end of this section.

a. Technologycontrols foron-road
motorvehicleexhaust.This category includes tailpipe and tire wear emissions ofprimary PM-10 from onroadmotor vehicles. On-road motor vehicles include both gasoline and diesel-powered passenger cars, light, medium, and heavy duty trucks, buses, and motorcycles.10

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

10We will treat gasoline-and diesel-powered
vehicles together here to preserve to the extent practicable the significant source groupings in the MAG plan; however, we believethey are in fact distinct categories. Almost 95 percent ofdiesel PM10 emissions come from heavy-duty diesel trucks while 75 percent ofgasoline PM-10 comes from the familycar, thatis, light duty cars and trucks (which include sports utility vehicles). See Table ORM-1 inthe EPA TSD section "Implementation ofBACM and Inclusion ofMSM for On-Road Motor Exhaust (Technology Standards)." There is almost no overlap inthe controls for the family car and those forheavy duty diesel trucks, key evidence that they

are in fact distinct source categories. See Table ORM-4 in theEPA TSD. 

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The suggested technology-based

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

one offive categories: new emission standards, inspection andmaintenance programs, fuels, programs to encourage alternative fueled vehicle usage, and
programs to accelerate fleet turnover. In total, the MAG plan considers 22 technology-based control measures. See MAG plan, Table 5-2. We believe this list is complete and propose to findthat the MAGplan 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 gasolinevehicles, 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 Clean Burning Gasoline program which mandates the

use ofeither Phase II federal reformulated gasoline or California reformulated gasoline; offers generous tax credits and deductions for conversion ofvehicles to alternative fuels; andmandates federal, state, county, and municipal governments to convert their fleets to alternative fuels. MAG plan, pp. 7-2 through 7-24.

Arizona has instituted a heavy duty diesel I/M program, will require 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.

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

one ofthe few identified motor vehicle controls not adopted by the State. The plan identifies this measure as a potential MSM. MAG plan, Table 10-7. The MAG plan claims thatthe measure is unreasonable on acost basis. MAG plan, p. 9-46. We make nojudgement

onthis claim given the great uncertainty regarding the potential cost of implementing CARB diesel in the Phoenix area. We do note that the State has already adopted halfofthe CARB diesel standards, the 500 ppm sulfur limit.l

Under ourproposed policy for MSM in extension requests, we believe that

11

Theother CARB diesel standard isalimiton the aromatic hydrocarbon content ofno more than 10 percent byvolume. CARB, Fact Sheet on CaliforniaDiesel Fuel,March 1997. we can findthat the MAG plan provides for the inclusion ofMSM to our satisfaction absent the adoption and implementation ofCARB diesel because, based on information in the MAG plan, the on-road engine category's contribution to nonattainment in the Phoenix area is relatively low compared to other PM-10 dust sources andimplementation of CARB diesel would not advance the attainment date.

According to the MAGplan, the onroad motor vehicle category contributes just 1.3 percent ofthepre-control inventory in 2006, compared to construction dust at43.8 percent, paved road dust at 20.4 percent, unpaved road dust at 13.1 percent, and windblown dust at 8.7 percent. MAGplan, Table 8- 3.Adoption ofCARB diesel would generate atotal reduction of0.8 mtpd in 2006. MAG plan, p. 10-37. Ittakes a 4 mtpd reduction to advance the annual standard attainment date one year (the minimum needed because it is an annual standard), so reductions from implementation ofthis measure are insufficient to advance the attainment date. See section on RFP and Quantitative Milestones.

As noted before, Arizona has in place

one ofthe nation's most comprehensive programs to address on-road motor vehicle emissions. With the additional

measures inthe MAG plan (including a

more stringent diesel I/Mprogram and

measures both encouraging and requiring diesel fleet turnover) the overall mobile source program is strengthened andgoes beyond the existing 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 reasoned and acceptable justification for the rejection.

The MAGplan identified just a few

measures from other areas as being more stringent than existing programs. These

measures have either been adopted or

we have concluded thatthe measures need not be included to assure the inclusion ofMSM.

All the adoptedBACM andMSM are already implemented, except for one. The requirement thatpre-1988 heavy duty diesel vehicles registered in the nonattainment area meet 1988 federal emission standards will not be implemented until January 1, 2004 in order to provide sufficient lead time for modification or replacement ofthe noncomplying heavy duty dieselvehicles.

We, therefore, propose to findthat the combination ofon-road motor vehicle technology controls andTCMs (described in the next section) in the MAG plan provides for the implementation ofRACM and BACM and the inclusion ofMSM for on-road
motorvehicle exhaust.

b. Transportationcontrolmeasures (TCMs) foron-roadmotorvehicle exhaustandpavedroaddust.TCMs can reduce PM-10 emissions in both the onroadmotor vehicle exhaust and paved road dust source categories by reducing vehicle miles traveled (VMT) and vehicle trips. They can also reduce vehicle exhaust emissions through relieving congestion. Our serious area PM-10 guidance requires that plans identifying on-road motor vehicles as a significant sources must also evaluate the TCMs listed in section 108(f) ofthe CAA. Addendum at 42013.

In ourreview, we haveprimarily 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 PM-10 concentrations in the Phoenix area (See EPATSD section, "BACT for Major Stationary Sources ofPM-10 Precursors" which shows thattotal secondary particulates accounted for less than4 gg/m 3in 1995) and (2) Arizona has already targeted mobile

source NOx and SOx through an aggressive set ofmobile source controls which webelieve coverthe implementation ofRACM and BACM and inclusion ofMSM requirements for tailpipe NOx and SOx. See discussion immediately above ontechnology controls for on-road motor exhaust.

In total, the MAG plan identifies 19 TCMs for consideration including the CAA section 108(f) measures. The plan does not identify any potentially more stringent TCMs from other areas. See EPATSD section "Implementation of BACM and MSM 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 potentially most stringent measures from other States.

Arizona has a longhistory ofadopting and then enhancing programs toreduce emissions from on-road motor vehicles by reducing vehicle miles traveled, 

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vehicle trips, and/or congestion.12 The

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 andpedestrian travel, and an extensive
program to synchronize traffic lights. In
most instances, these programs were adopted andimplemented as part of carbon 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 andMSM 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 justification for the rejection.

All the adopted TCM BACM are already implemented or have on-going implementation schedules because they

are part ofa on-going capital 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 and inclusion of MSM for on-road motorvehicle exhaust. We also propose to find thatthe combination ofTCMs andpaved road dust measures (described in the paved road section later in this preamble) provides for the implementation of RACM andBACM and the inclusion of MSM for paved road dust.

c. Nonroadengines.The non-road 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

12Theseplans include the MAG moderate and
serious area carbon monoxide plans and MAG moderate area ozoneplan. 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 potentially most stringentmeasures from other States.

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

Arizona has committed to adopt California's non-road standards that are

more stringent than the federal standards. MAG plan, p. 7-42. In addition,the State has established and is currently running a voluntary retirement program for gasoline powered lawn and garden equipment which isrun by Maricopa County and

aprogram to encourage the use of temporary electrical power rather than portable generators at construction sites.
See MAG plan,pp. 7-41 and 7-43.

With the addition ofthese measures, the overall nonroad engine program is strengthened andgoes 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 plan has rejected potential BACM, it provides a reasonedjustification for the rejection.

The MAGplan identifies CARB diesel

as apotential MSM for non-road engines but does not adopt it. MAGplan, Table 10-7. Under our proposed policy for MSM in extension requests, we believe that we canfind thatthe MAGplan provides for the inclusion ofMSM to

our satisfaction absentthe adoption of CARB diesel because, based on information in the MAG plan,the nonroad engine category's contribution to nonattainment in the Phoenix area is relatively low compared to other PM-10 dust sources andimplementation of CARB diesel would not advance the attainment date. The nonroad motor vehicle category contributes 4.8percent ofthe precontrol inventory in 2006, compared to construction dust at 43.8percent, paved road dust at 20.4 percent, unpaved road dust at 13.1 percent, and windblown dust at 8.7 percent. MAGplan, Table 8- 3.Adoption ofCARB diesel would generate a totalreduction of0.8 mtpd in 2006. MAGplan, p. 10-37. Ittakes a 4 mtpdreduction to advance the annual standard attainment date one year (the minimum needed because it is an annual standard), so reductions from implementation ofthis measure are insufficient to advance the attainment date. See section on RFP and Quantitative Milestones.

We, therefore, propose to findthat MAG plan provides for the implementation ofRACM and BACM and inclusion ofMSM for on-road motor vehicle exhaust.

d.Pavedroaddust.Paved road dust is the largest source ofPM-10 in the Maricopa area. It is fugitive dust that is deposited on apaved roadway and then isre-entrained into the air bythe action oftires grinding on the roadway. Dust is deposited on theroadway from being blown onto the road from disturbed
areas; tracked onto the road from unpaved shoulders, unpaved roads, or other unpaved access points; stirred up fromunpaved shoulders by wind
currents created from traffic movement; spilled ontothe road byhaul trucks; and carried onto the roadby water runoffor erosion.

The suggested measures for controlling emissions from paved road dust fall into one ofthree categories: reductions in vehicle trips (VT) and vehicle miles traveled (VMT), preventing deposition ofmaterial onto a roadway and cleaning material offthe roadway. We have already discussed

measures for reducingVT and VMT in the section on TCMs above.

The MAGplan lists several potential BACM for paved road dust. It also lists

a number ofpotentially MSM from other

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

Prior tothe MAG plan, the cities and
towns in the Phoenix area and Maricopa County implemented a number of

measures addressing paved road dust. See MAG plan, Table 10-5. With the additional measures in the MAGplan (described below), the overall control program to reduce paved road dust is both strengthened and expanded beyond the existing program. See EPA TSD section "Implementation ofBACM 

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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 MSM for PM-10-efficient street sweepers described below, all the adopted BACM for paved roads are already implemented or have on-going implementation schedules because they

are part ofa on-going capital improvement program (e.g., curbing). For thereasons discussed below, we propose to find thatthe MAG plan provides for the implementation ofthe PM-10 efficient street sweeper measures
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.

Preventingdepositionofmaterialonto

aroadway. Measures aimed at preventing track out ona paved road include treating unpaved access points, preventing track out from construction/ industrial sites, treating shoulders on paved roads, controlling emissions duringmaterial transport (e.g., truck
covers, freeboard requirements), and preventing erosion ontopaved roads.

The MAGplan includes each ofthese

measures:

Unpaved access points: In the MAG moderate area plan, local jurisdictions focused on requiring new connections
to public paved streets tobe 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.

Track out. Rule 310, sections 308.2(c) and 308.3 address dirt track out from construction/industrial sites: All work sitesthat are five acres or larger and all work sites where 100 cubic yards of bulk materials are hauled on-site or offsite each day must control andprevent track outby installing atrack out control device. All work sites must also clean up spillage or track out immediately when it extends a cumulative distance of50 linear feet or more; where track out extends less than 50 feet, itmust be cleaned up atthe end ofthe work day.

The MAGplan identifies, as a potentially more stringentmeasure for track out, South Coast (Los Angeles area) Air Quality Management District's Rule 403. MAGplan, Table 10-7. The plan concludes thatthe two rules are reasonably similar in several respects, and where differences exist, therelative impacts on control roughly balance against each other. MSM Study, p. C4.13 We agree. Both rules emphasize prevention and rapid removal oftrack
out. See EPATSD section "Implementation ofBACM and Inclusion ofMSM for Paved Roads Dust," Note 2.

Unpaved Road Shoulders. As with unpaved access points, the MAGplan demonstrates a shift to dealing with existing unpaved shoulders from only preventing new ones. MAG plan, Table 9-11. Maricopa County has committed
to treat 100 miles 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 treating unpaved shoulders. Maricopa County commitment, 1999 revised

measure 5. Otherjurisdictions have also made commitments to treat shoulders.

A.R.S. 9-500.04(3) and 49-474.01(4), adopted by the State legislature in 1998, require the cities, towns and County of Maricopa to develop and implement plans to stabilize targeted unpaved roads and alleys and to stabilize unpaved shoulders on targeted arterials beginning January 1, 2000. Although

13The "MSM Study" is the "Most Stringent PM10 Control Measure Analysis," Sierra Research, May 13, 1998 foundin Appendix C, Exhibit 4 of the MAG plan. this legislation does not specify how many shoulder miles to be controlled,

we believe thatthe local jurisdictions' efforts tomeet this new legislation will result in the control ofunpaved shoulders where itis most needed.

Material Transport. Requirements for the control ofPM-10 emissions during material transport are found in Rule 310, sections 308.1 and 308.2. When haulingmaterial 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; and (4) clean or cover the interior cargo compartment before leaving a sitewith

an empty truck.

The MAGplan identifies requirements for bulk material transport in Imperial County 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 bulk material transport/hauling are essentially the same as Imperial County's requirements.

Cleaningmaterialoffthe roadway. Measures for cleaning material off roadway are track out, erosion, and spill removal requirements androad sweeping.

The MAGplan includes each ofthese

measures:

Material spillage, erosion, or accumulation. Rule 310, section 308.2 and 308.3 address rapid clean up of track outfrom construction/industrial sites. Rule 310.01, section 306 requires property owners/operators to remediate erosion-caused deposits ofbulk materials onto paved surfaces. Erosioncaused deposits are to be removed within 24 hours oftheiridentification or prior to resumption oftraffic on the pavement.

The MAGplan identifies South Coast's Rule 1186 and Mojave Desert's Rule 403 as potential MSMs for material spillage, erosion, and accumulation onto roadways. MAGplan, Table 10-7. In both cases, the plan concludes that MCESD's rules are more stringent. We
agree. MCESD's rules require the clean
up ofmore incidences of spillage, etc. than does South Coast's rule. See EPA TSD, "Implementation ofBACM and Inclusion ofMSM for Paved Roads," Note 5.

Street sweeping. Most cities/towns and the 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, 

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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 ofincreased sweeping frequency is closely associated with otherfactors. These factors include whether the
sweepers currently in use are PM-10 efficient (such thatthe act of sweeping does not cause increased emissions) and whether the public entity has identified roads that tend to experience higher silt loadings where more frequent sweeping is likely 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 and the County for the purchase and use ofPM-10 efficient street sweepers. This commitment involves the allocation of $3.8 million in Congestion Mitigation Air Quality (CMAQ) funds for theFY 2000-2004 Transportation Improvement Program (TIP)to purchase PM-10 certified street sweepers for the local jurisdictions to use. MAG has recommended an additional $1.9 million CMAQ funds be allocated to purchase PM-10 certified street sweepers in the FY 2001-2005 TIP. See MAG commitment, "PM-10 Efficient Street Sweepers."

The funds allocated by MAG for this program shouldbe sufficient to replace approximately two-thirds ofthe 72 existing city/town/County street sweepers. 14Each 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

14Some street sweepers maybe additions to, as opposedto replacements of, existing equipment. daily traffic (ifavailable). MAG will use this information to estimate the emissions reduction associated with each sweeper request and rank the requests in priority order of effectiveness for consideration in the allocation ofCMAQ funds. See MAG commitment, "PM-10 Efficient Street Sweepers."

In evaluating this program, we considered not onlythe number ofPM10 efficient street sweepers tobe purchased and distributed, but whether the program incorporates use factors that influence emissions reductions. The greatest emissions reduction benefit for this mitigative measure will be achieved ifthe sweepers are used on a frequent basis onroads with high silt loadings or significant visible accumulations. Each public entity has a monetary incentive to compete for the PM-10 efficient street sweepers, asthe 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, orbe added to existing street sweeper equipment/services. MAG's selection process includes PM-10 emissions reduction potential, based on the types ofroads eachjurisdiction is targeting for sweeping andhow frequently they will be swept. This data will assistMAG in distributing the
street sweepers tolocal jurisdictions in

away thatmaximizes the regional air quality benefits ofthe program. Plus, 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 is as expeditious as practicable. The funding necessary to purchase this equipment is available only over the

course of several fiscal years and the purchase 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 that it owns and/or maintains, where the contract date or purchase or lease date is January 1, 2000 or later, to acquire oruse only certified street sweeping equipment. The rule establishes street sweeper testing and certification procedures. Unlike Maricopa's strategy, Rule 1186 requires that PM-10 efficient street sweepers be used whenever street sweeping is contracted out as ofJanuary 2000, and itrequires public agencies to replace their existing street sweeping equipment with PM-10 efficient equipment by attrition.

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

a greater number ofstreet sweepers distributed in a shorter time frame than couldbe expected using South Coast's natural attrition approach. While itis possible that some cities/towns in Maricopa may continue to contract out for street sweeping services where PM10 efficient sweepers may not be used,
mostdo not contract for street sweeping. Furthermore, dueto the fact thatpublic entities will be competing forPM-10 efficient street sweepers fundedby CMAQ dollars with only a low cost share requirement, we believe that the already limited reliance on contracted
out services in Maricopa County will lessen asnew PM-10 efficient equipment becomes available and that
contractors will switch to PM-10 efficient equipment to meet new demand. In addition, MAG's program

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

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

There are two principle ways to control emissions from unpaved parking lots: prohibit unpaved parking lots or treatthe lot. MAGplan identified both:

a prohibition on unpaved haulroads and parking or staging areas and surface
treatment to reduce dust from unpaved driveways andparking lots.MAG plan, Table 5-2. The MAG plan identified one potentially more stringent measure from South Coast which controls fugitive dust from parking areas on construction sites. MSM Study, p. C-9 and 10. It did
notidentify any potential MSM fornonconstruction site unpaved parking lots. Webelieve this listis complete and
propose to find thatthe MAGplan evaluates a comprehensive set of potential BACM and MSM for unpaved parking lots.

Most localjurisdictions inMaricopa County identified ordinances that require paving ofnewparking lots.In addition,MCESD Rule 310.01 requires owners/operators ofan unpaved parking lotlarger than 5,000 square feettopave, apply dust suppressants, or apply gravel, according to the applicable rule 

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standards/test methods. Section 303. Applicable standards include a 20 percent opacity standard, and an 8 percent silt content standard and/or a 0.33 oz/square foot silt loading standard. Section 303.2. MCESD Rule 310 applies the same stabilization requirements to parking lots on permitted facilities. Rule 310, section 302.1. Finally, many cities/towns have treated their own parking lots or required treatment ofprivate lots below MCESD's thresholds.

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

sources. 15In our FIP, we promulgated a RACM fugitive dust rule applicable to unpaved parking lots in the Phoenix PM-10 nonattainment area andthus it provides a starting point for determining whether the MAG plan measures for unpaved parking lots meet RACM. It is
not necessary for the MAG plan

measures tobe identical tothe FIP rule in order tomeet the CAA's RACM requirement, but only thatthey provide for the implementation ofRACM.16 However, ifthe submitted measures for

aparticular source are identical tothe FIP rule, we can determine without further analysis that the MAG plan 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

15While a serious area PM-10 plan must provide for boththe implementation ofRACM and BACM, in determining whether such a plan provides for BACM implementation, we do not normally conducta 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 (Addendum at 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 if the

measures also represent a RACM level of control is

not necessary. However, in this particular case, we
are proposing to withdraw the FIP rule in conjunction with ourproposed approval ofthe MAG plan. Inorder to dothis, we must determine under CAA section 110(1), that, among other things, withdrawing the FIPrule does notinterfere with the RACM requirements inthe CAA.

16The State may submit one or more control

measures that collectively achieve a RACM level of control for aparticular source, regardless of whether they apply the same strategy as ourFIP rule. Furthermore, EPA's guidance indicates that a RACM evaluation includes considering "the impact ofthereasonableness ofthe measures on the municipal or other governmental entitythat must bear the responsibility for their implementation."
General Preamble at 13541. parking lots as the FIP rule, with the only difference being that Rule 310.01 applies county-wide while the FIP rule applies strictly to sources located in the PM-10 nonattainment area. Rule 310.01 requirements are effective upon adoption and were adopted onFebruary 2000, suchthat the timeframe for controls is equivalent to the FIP rule andis also as expeditious as practicable. In light ofthe factthat Rule 310.01 requirements arethe same asthe FIP rule requirements andMCESD's commitments to improve compliance and enforcement ofRule 310.01, we propose thatthe MAGplan provides for the implementation ofRACM. Given additional MAG plan city/town commitments that collectively increase the stringency ofcontrol on unpaved parking lots, we propose that the MAG plan alsoprovides for the implementation ofBACM. South Coast Rule 403 requires sources to apply dust suppressants to stabilize at least 80 percent ofunstabilized surface

area. Sources must comply with a 0 percent opacity property line limit. The MAG plan deems the respective requirements roughly equivalent to Rule 310. We believe that the addition ofa silt loading/content standard for unpaved parking lots for sources covered underRule 310 increases the rule's stringency to be at least equivalent to that ofSouth Coast Rule 403. We, therefore, propose to find that the MAGplan correctly concluded that there are no more stringentmeasures in other State plans or used in practice elsewhere that are applicable to the Phoenix area.

f. Disturbed vacantlands.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. The plan alsoidentified controls

onweed abatement operations and offroad racing aspotential most stringent

measures. We believe this listis complete and propose to findthat the MAG plan evaluates a comprehensive
set ofpotential BACM andMSM for disturbed vacant lands.

The MAGplan includes two MCESD rules that address BACM for vacant lots. Rule 310 requirements apply to vacant lots located atpermitted facilities (including construction sites) andRule 310.01 requirements apply to nonpermitted sources.1 7Rule 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 forthese

sources. See Footnote 15. In our FIP, we promulgated a RACM fugitive dust rule applicable to disturbed vacant land in the Phoenix PM-10 nonattainment area and thus itprovides a starting point for determining whether the MAG plan

measures for disturbed vacant lands
meet RACM. Itis notnecessary for the MAG plan measures tobe identical to the FIP rulein order to meet the CAA's RACM requirement, but only thatthey provide for implementation ofRACM. See footnote 16. However, ifthe submitted measures for aparticular

source are identical tothe FIP rule, we

can determine without further analysis thatthe MAG plan has provided for RACM for that source.

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

or commercial lots in Maricopa County, and any tract oflandin 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 that Rule 310 requires stabilization ofallinactive disturbed surface areas on permitted facilities, regardless oftheir size. Rule 310, section 302.3. Rule 310 also contains requirements for weed abatement that closely resembles the Phoenix FIP rule's weed abatement requirements, except

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

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that Rule 310's threshold for coverage is

more stringent.18

Vacant lots and open areas subject to Rule 310 and Rule 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, the MAG plan contains commitments made by several cities and towns to address vacant disturbed lots. For example, seven jurisdictions require or will require stabilization ofdisturbed vacant lots after 15 days ofinactivity (as compared
to Rule 310.01's 60-day compliance period); two (2)prohibit dumping of materials onvacant land; and two (2) will stabilize allcity-owned vacant lots.

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, we propose thatthe MAGplan provides for the implementation ofRACM on disturbed vacant land.Because these rules increase the number oflots subject
to control thus collectively increasing the stringency ofcontrol on vacant disturbed lands, we propose thatthe MAG plan also provides for the implementation ofBACM.

For itsMSM comparison, the MAG plan identifies measures in Clark County (Las Vegas, Nevada) Rule 41 and South Coast Rule 403. See MSM Study,
pp. C-11 and C-16,17. The plan concludes thatneither measure is more stringent than the Maricopa measures because Rule 310 and 310.01 contain similar, equally, or more stringent requirements. We agree thatthe MCESD's rules are equally or more stringent.

We, therefore, propose to findthat the MAG plan correctly concluded that there are no more stringent measures in other State plans or used in practice elsewhere that are applicable to the Phoenix area.

g. Unpavedroads.This category includes re-entrained dust from vehicle travel onunpaved roads. There are three classes ofunpaved roads in the Maricopa nonattainment area: public roads, private roads that are publicly maintained (also referred to as minimally-maintained or courtesy grade), and private roads that are privately maintained.

18Rule 310 requires any earthmoving operation
that disturbs 0.1 acre or more to have a dust control plan, includingweed abatementby discing or blading, whereas the Phoenix FIP rule weed abatement requirements only apply to disturbances equal to or greater than 0.5 acres. Rule 310, section
303. The MAGplan includes three suggested measures for controlling fugitive dust from unpaved roads: Surface treatment toreduce dust from unpaved roads and alleys, traffic reduction/speed controlplans for unpaved roads; andprohibition of unpaved haul roads. MAG plan, Table 5-2. The MAGplan did not identify any other State's measures that aremore stringent than the ones already in the plan. We believe this listis complete andpropose 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 Plan provides for the implementation ofRACM for these sources. See Footnote 15. In our FIP, we promulgated a RACM fugitive dust rule applicable to unpaved roads in the Phoenix PM-10 nonattainment area andthus itprovides a starting point for determining whether the MAG plan

measures forunpaved roads meet RACM. Itis not necessary for the MAG plan measures to be identical to the FIP rule in order to meet the CAA's RACM requirement, but only thatthey provide for implementation ofRACM. See footnote 16. 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.

As discussed below, wepropose to find thatthe MAGplan provides for the implementation ofRACM andBACM andthe inclusion ofMSM for unpaved roads. Surface treatment to reduce dust from unpaved roads and alleys. The principle control for public unpaved roads and alleys isRule 310.01, section 304, which requires allpublicly-owned unpaved roads and alleys with 250 vehicles per day or more to be stabilized by June 10, 2000 and those with 150 vehicles per day or more to be stabilized by June 10, 2004.

Several cities have commitments that go beyond the requirements ofRule 310.01 for publicly-owned unpaved roads. For example, the City ofPhoenix committed to, andrecently accomplished, paving all 80 miles ofits publicly-owned unpaved roads regardless ofthe level ofvehicle travel. Phoenix Commitment, Measure 98-DC7. Other cities, such as Tempe and Gilbert, have veryfew remaining miles ofpublic unpaved roads/alleys. See Tempe Commitments, Measure 98-DC7and 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) thatreceive 150 or

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

Private unpaved roads are scattered throughout Maricopa County, within both County and city jurisdictions. A survey performed for us ofunpaved roads in Maricopa County determined thatthe great majority ofidentified unpaved road mileage consists of privately-owned roads that receive minimal maintenance by the Maricopa County Department ofTransportation (MCDOT). 19

MAG and MCDOT have committed to pave County minimal maintenance roads within the nonattainment area that currently exceed 150 ADT and meet criteria tobecome public highways, using $22 million from Congestion Management/Air Quality andMCDOT funds.20 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 40 percent ofvehicle miles traveled

on these roads. Maricopa County has also committed to continue to evaluate other roads forfunding 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 Countyjurisdiction, whether they currently receive minimal maintenance or not.

As the County evaluates roads for paving,it may make exceptions to its commitment topave roads withvehicle trips that exceed 150 ADT. The County's evaluation process takes into account whether a road meets the proper criteria
to become a public highway and whether estimated costs ofpaving are excessive (greaterthan $500,000 per mile).21 When MCDOT identifies a road thatmeets these criteria (i.e.the road

canbe declared a public highway and

19Pacific Environmental Services, "Survey for Fugitive DustEmission Sources," April 15, 1999.

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

21Aprivate road begins tobear other than local trafficthrough extensions ofother nearbypublic roads or the construction ofan indirect source that
attracts external drivers using the road as a short
cut. See Maricopa County Commitments, 1999 Revised Measure 17. 

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costs are not excessive), it will recommend thatthe Board of Supervisors open and declare the road

apublic highway.

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 low ADT.22 As aresult, webelieve that the vast majority ofprivate unpaved roads donot need tobe controlled in order for us to determine thatthe MAG plan provides for the implementation of BACM for unpaved roads for the annual 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 public unpaved roads and access ways;

onejurisdiction has posted 15 mph speed limits in all alleys. See MAG plan, Table 10-9. Also, under Rule 310, owners/operators ofunpaved haul roads andutility roads who comply with the rule by 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 measures to pave or otherwise stabilize unpaved roads in the Phoenix PM-10 nonattainment area establish the critical commitments for the implementation of RACM andBACM. This isbecause road stabilization ensures emission reductions whereas speed limits may or may not be 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 findthat this requirement is sufficient for the implementation ofBACM for these roads. We believe requiring compliance with both ofthese standards ensures that the BACM applied will have a stabilizing effect.

Evaluation ofunpaved road measures in other areas found none that are more stringent than the measures for unpaved

22Among the over 100 segments ofunpaved privately-owned and maintained roads that were identified inthe PES survey, the contractor estimated, using aerial photographs, that only 6 of these have ADTs that exceed 150. Tube counts, which are more accurate than other methods to estimate ADT, were notconducted on theseroads. roads in the MAGplan. MAG plan, Table 10-7. We agree and propose to find thatthere are no other more stringent measures 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. Constmuctionsitesandactivities. Sources offugitive dust emissions at construction site sources include land clearing, earthmoving, excavating, construction, demolition, material handling, bulk material storage and/or transporting operations, material track
out or spillage onto paved roads (which

we have addressed in the paved road section), and vehicle use and movement

on site (e.g., the operation ofany equipment onunpaved surfaces, unpaved roads and unpaved parking areas). Windblown emissions from disturbed areas on construction sites are also a source ofPM-10. Construction operations, which aremostly various forms ofearthmoving, represent some 90 percent ofthe emissions in this

source category.

The suggested measures in the MAG plan are actually various means of improving compliance with controls as opposed to new controls for construction sites. The controls for construction sites are found in MCESD's fugitive dustrule, Rule 310, revised on February 16, 2000.

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

more and sources subject toTitle V permits, 23Non-Title V permits, or General Permits. In addition torule requirements for fugitive dust sources located at any permitted source, Rule 310 requires that aDust Control Plan (DCP) be submitted for any earthmoving operations of0.10 acre or more, andthat 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. Forother

23Title V permits are operating permits required by Title V ofthe Clean Air Act for major stationary

sources and certain other stationary sources. permitted sources, Rule 310 requires that a DustControl Plan (DCP) be submitted and approved prior to commencing any routine dust generating activity, defined as any dust generating operation which occurs more than4 times per year or lasts 30 cumulative days or more per year. 2 4 Specific Rule 310 requirements include:

* a 20 percent opacity requirement for any dust generating operation

* wind event control measures * implementation ofcontrol measures before, after and while conducting any dust generating operation, including weekends, after workhours and holidays

* required control measures and standards for:

* unpaved parking lots * unpaved haul/access roads * disturbed open areas and vacant lots

* bulk material hauling * bulk material spillage, carry-out, erosion andtrack out

* open storage piles * weed abatement byblading or discing a requirement in dust control plans for at least one primary and one contingency control measure for all fugitive dust sources; the contingency

measure is tobe immediately implemented ifthe primary control

measure proves ineffective

In order to comply with the rule's 20 percent opacity standard and dust control plan requirements for implementing primary and/or contingency control measures for earthmoving activities, 25sources need
to apply one ormore controls, which in
mostcases includes applying water or another dust suppressant before and during operations. Inactive disturbed surfaces mustbe stabilized tomeet at least one ofthe rule's stabilization standards (e.g.visible crusting, 10 percent rock cover, etc.). Unpaved roads and unpaved parking lots must alsobe stabilized to meet both a 20 percent opacity standard and a silt content/ loading standard.26 Test methods associated with stabilization and

24This is in addition to the requirement to submit

a DCP for any earthmoving operation that disturbs 0.10 acre or more even ifthe operation is subject
to Title V or otherpermitting requirements.

25Earthmoving operations include cutting and filling, grading, leveling, excavating, trenching, loading orunloading ofbulkmaterials, demolishing, blasting, drilling, adding to or removing bulkmaterials from open storage piles, back filling, soilmulching, landfill operations, or weed abatementby discing orblading.

26Unpaved roads must meet a 6percent silt

content standard or, alternatively, a 0.33 oz/ft 2 silt loading standard,while unpaved parking lots must meet an 8percent silt content standard or, alternatively, a 0.33 oz/ft 2silt loading standard. 

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

The February 2000 revisions toRule 310 thathave increased the rule's stringency include the addition of specific workpractice standards, the addition ofstabilization standards and
test methods for unpaved surfaces, and modifications 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/orrevised standards/test methods provide for a greater degree ofcontrol than under the previous SIP-approved version ofRule 310.

In addition tothese Rule 310 revisions, MCESD has made three enforceable commitments to further strengthen requirements for construction sites thatmust be met by July 2001. These commitments, which all are part ofRevised Measure 6 in Maricopa County's commitments, are to: 1.Research and develop a standard(s) andtest method(s) for earthmoving
sources, considering our field research, that are enforceable and meet BACM requirements on stringency and source coverage.

Currently, activities on construction sites must meet an opacity standard of 20 percent. Ifresearch on the standards andtest methods find problems with the existing opacity standard's enforceability, feasibility, or stringency for some or all earthmoving operations, MCESD will revise the rule to modify the existing opacity test method to address the problems as warranted or adopt anew standard(s) and test method(s) to deal with any problems that cannot be addressed by modifying the opacity test method; 2.Research, develop and incorporate additional requirements for dust suppression practices/equipment for construction activities into dust control plans and/orRule 310; 3.Revise the sample daily recordkeeping logs for new and renewed Rule 310 permits to be consistent with rule revisions and to provide sufficient detail documenting the implementation ofdust control measures required by Rule 310 and the dust control plan. Distribute sample log sheets with issued permits and conduct outreach to

sources.

The first enforceable commitment addresses our concern 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 we believe that additional standards/test methods

are needed to fully assure that sources
are effectively controlled. We have already sponsored afield study to address this issue and are considering additional field work in Summer, 2000. We believe that additional time is needed for Maricopa County to investigate options in coordination with
us, and then revise the rule. Therefore,

a commitment is the appropriate method ofaddressing this issue.

The second enforceable commitment addresses our concern that dust control plans (DCPs)lack specific criteria for dust suppressant application. For example, a source engaged in grading or cut-and-fill earthmoving for a multi-acre project may choose to comply with Rule 310 by applying water. However, neither the rule nor DCPs establishes minimum criteria for the number of
water trucks/water application systems and water truck capacity for any given size construction site or aratio of earthmoving equipment to water trucks. The rule also does not contain a prewetting requirement, althoughresearch may show this to be necessary to successfully control dust on certain soil types.

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 aparticular day, making it difficult to establish criteria that apply to all sites at alltimes. This explains why more time is needed for MCESD to develop criteria to address a multitude ofcircumstances.

The third enforceable commitment addresses our concern that while Rule 310 currently contains an acceptable recordkeeping requirement, amore specific recordkeeping requirement would help improve compliance. Currently neither the rule nor DCPs specify what information should be included in a daily log. MCESD has committed to revising and distributing
to permitted sources daily recordkeeping log sheets to provide sufficient detail documenting the implementation ofdust control

measures.

Based on our evaluation ofrevised Rule 310 andthe additional commitments madeby MCESD, we propose to find thatthe rule and commitments together include a comprehensive set ofBACM level controls for construction sites. The rule is comprehensive in scope in that each dust source is subject to a set of requirements under Rule 310 (e.g. storage piles, dirt trackout,haul truck loads, disturbed areas, earthmoving operations). In addition, the Rule 310 requirements are sufficiently stringent
to provide for the implementation of RACM and BACM, with the exception ofcertain aspects ofthe rule that are addressed in the commitments made by MCESD. Thus,between the submitted rule requirements and commitments, we propose to find thatthe MAG Plan
meets the CAA's RACM andBACM requirements for construction sites.

The MAGplan identifies potentially

more stringent construction site fugitive dust measures either in or under consideration for inclusion in others SIP. See MSM Study, Table 1-2 and Table 3-1.

Most 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 prior to 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 control measures for dust suppression. This caveat is addressed inthe MAG plan's commitment to research, develop and incorporate additional requirements for dust suppression practices/ equipment for construction activities into dust control plans and/or Rule 310.

The MAGplan does not discuss any construction site measures from other

areas as potentially more stringent

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

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measures. 27These requirements include standtanks on projects that are 10 acres

ormore in size, an additional, separate water truck when using a trencher or when screening, a separate water truck

orpull during landscaping, maintaining all stockpiles in amoist condition, etc.

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

We have also identified a requirement in Imperial County Regulation VIII that is potentially more stringent than Maricopa County's measures. Imperial County Regulation VIII requires that
water be applied 15 minutes prior to handling or transferring bulkmaterial, chemical/physical stabilization, or sheltering/enclosure ofthe operation andtransfer line. We propose to find that Maricopa County's second enforceable commitment to research, develop and incorporate additional requirements for dust suppression practices/equipment into Rule 310 and/

orDCPs isconsistent 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.

i.Agriculturalsources.The agriculture source category covers all dust generating activities and sources on farms and ranches in the Maricopa nonattainment area. These activities and

sources include land planning, tilling, harvesting, fallow fields, prepared fields, field aprons, and unpaved roads.

Maricopa County is rapidly urbanizing with agricultural land being converted into other uses at a rate of approximately 6,000 acres per year. Cathy Arthur, MAG, December, 1997. Despite the conversion ofagricultural lands to other uses, agricultural sources

are expected to continue to contribute to PM-10 emissions for the foreseeable future, especially in relation tothe PM10 24-hour standard.

The MAGplan identifies a number of potential BACM for agricultural sources. MAG plan, pp. 5-66 thru 5-72 and pp. 6-12 through 6-13.

In 1998, Arizona passed legislation establishing an Agricultural Best Management Practices (BMP) committee for the purpose ofadopting by ruleby

27Theserequirements are notin Clark County's fugitive dustrule, but rather are required practices in dust control permits. June 10, 2000, an agricultural general permit specifying BMPs for regulated agricultural activities to reduce PM-10 emissions in the Maricopa PM-10 nonattainment area. The Committee also is required to adopt and implement an education program byJune 10, 2000, and affected agricultural sources are required to implement at least one BMP by December 31, 2001. A.R.S. 49- 457.A-H, M. OnJune 29, 1999, we approved this legislation as a SIP revision meeting the requirement for the implementation ofRACM in 189(a)(1)(C) and atthe same time withdrew our commitment to adopt RACM controls for agricultural that we included in the 1998 PM-10 FIP. 64 FR 34726.

The MAGplan relies onthe State's commitment in A.R.S. 49-457 to adopt andimplement BMPs to meetthe requirement to provide for the implementation ofBACM for agricultural sources. MAGplan, p. 7- 156 and Letter from ADEQ toEPA, September, 1998, submitting the commitment as a SIP revision. The plan alsorelies onthe statutory commitment
to meetthe MSM requirement in CAA section 188(e). MAGplan, p.10-25.

Arizona's statutoryBMP commitment is similar to the commitment we made in our 1998 PM-10 FIP. 63 FR 41326 (August 3, 1998). As part ofthe RACM demonstration in the FIP, we promulgated a commitment, codified at 40 CFR 52.127, to ensure thatRACM for agricultural sources will be expeditiously adopted and implemented. For agricultural sources, the State isusing a similar strategy to address the RACM, BACM andMSM requirements.

We propose to find thatthe State's commitment to adopt and implement agricultural BMPs adequately addresses requirement to implement BACM and include MSM. The potential BACM explicitly identified in the MAGplan will be considered duringthe BMP development process.

We have, beginning with the proposed rulemaking for our 1998 PM10 FIP and culminating in Ninth Circuit litigation onboth the FIP and our SIP approval, explained atlength our reasoning that a commitment to implement PM-10 controls beginning in June 2000 for agricultural fields and aprons in the Phoenix PM-10 nonattainment area rather than the immediate implementation offullydeveloped regulations for those sources meets the RACM requirement in CAA section 189(a)(1)C). See 63 FR 15920, 15935-15936 (April 1, 1998); 63 FR 41332-41334; 63 FR 71817. See also Brieffor Respondents in Oberv. Browner,No. 98-71158, at 43-59 (9th Cir., filed Oct. 2, 1998) (petitionfor review challenging EPA's FIP commitment to adopt and implement RACM for agricultural sources), and Brieffor Respondents in Oberv. Browner,No. 99-71107, at 16-40 (9th Cir., filed Aug. 26, 1999) (petitionfor review challenging EPA's approval of the State's commitment to adopt and implement agricultural BMPs as meeting the RACM requirement ofthe CAA).

In the context ofthis proposed action,

ourreasoning in short is that a legally binding commitment-embodied in the State statute establishing a committee thatisrequired to adopt ageneral permit specifying BMPs and identifying specific deadlines for their implementation-meets the statutory requirement inCAA section 189(b)(1)(C) since itis a "provision to assure that best available control measures" are implemented by afixed deadline. While in preparing the FIP, we reviewed

measures adopted by the South Coast for the control ofPM-10 emissions from agricultural sources, we concluded that agricultural sources inthe United States vary byfactors such asregional climate, soil type, growing season, crop type, water availability, andrelation to urban centers, therefore, each PM-10 agricultural strategy is uniquely based

on local circumstances. As aresult, we could not,without further analysis, conclude that the South Coast controls shouldbe immediately implemented in the Maricopa area.

Furthermore, we determined that the goal of attaining the PM-10 standards in Maricopa County with respect to agricultural sources wouldbe best served by engaging allinterested stakeholders in ajoint comprehensive process on the appropriate mix of agricultural controls to implement in Maricopa County. We stated our belief thatthis process, despite the additional timeneeded to work through it, will ultimatelyresult inthe best and most cost-effective controls on agricultural

sources in the County.

While A.R.S. 49-457 does notuse the
term "best available control measure," its definition ofBMPs is consistent with the criteria in EPA's guidance. "Best management practices" are defined in A.R.S. 49-457.N.3 as "techniques verified by scientific research, that on a

caseby case basis are practical, economically feasible and effective in reducingPM-10 particulate emissions from aregulated agricultural activity." The broad definition ofBMPs in the Arizona statute authorizes the BMP committee to adopt measures that will comply with our definition ofBACM. 

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Moreover, as noted above, the statute provides for BMP implementation that begins with an education programby June 10, 2000 and culminates in full implementation ofthe BMPs by December 31, 2001.28

Similarly, we have concluded that the definition ofBMPs in the Arizona
statute isbroad enough to authorize the BMP committee to adopt measures that
meet the level ofcontrol in the requirement to include MSM in CAA section 188(e) as we propose to interpret it in this proposed action. In reviewing

measures in other SIPs and/or thathave been adopted elsewhere, MAG determined that cessation ofhigh wind tilling and soil erosion control plans

were the most stringent measures available thathad potential application for agricultural sources in Maricopa County. MAG plan p. 10-47. These

measures are included in South Coast Rule 403 which requires PM-10 controls for allfugitive dust sources, including agricultural sources. In December 1998, South Coast adopted a set ofconservation practices for agricultural sources to use to reduce fugitive dust. These practices were developed in consultation with affected stakeholder groups. See Guide to Agricultural PM-10 Dust Control Practices. The BMP task force will consider these measures during the development ofthe BMPs. MAGplan p. 10-47. After the BMPs and supporting technical documents are submitted to EPA, we will review them to determine iftheir level ofcontrol is as stringent as the South Coast rule or adequately justifies why such level would not be feasible in the Maricopa area.

As discussed elsewhere in this TSD,

we propose to interpret section 188(e) to require implementation ofMSM as expeditiously as practicable. For the

reasons stated above, in our FIP, and in

our approval ofthe State legislation as meeting the RACM requirements ofthe CAA, we conclude that the implementation schedule in the State
statute meets thattest. Finally, we conclude thatthe commitment in the State legislation meets the requirement that "the plan include[s]the most stringent measures * * *" Emphasis added.

j. Residentialwood combustion.The residential wood combustion (RWC) category includes emissions from the burning of solid fuel in residential

28Ofcourse, once adopted and submitted to EPA

as a SIP revision, the individual BMPs will have to be evaluated to determine ifthey comply intheir specifics with the BACM requirement. Here we need only determine that the Arizona statute provides sufficient authorityto assure that BACM will be implemented by June 10, 2000. fireplaces and woodstoves as well as barbecues and firepits.

Measures to control PM-10 from residential woodburning include public education program, woodburning curtailment programs, retrofit requirements andrestrictions orbans on the installation ofwoodburning stoves and/orfireplace. In total the MAGplan list 11 potential BACM and 10 potential MSM. MAGplan Tables 5-2 and 1-7. We believe this list is complete and propose to find thatthe MAG plan evaluates a comprehensive set of residential woodburning measures.

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

canbe used duringrestricted-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 gg/m 3).We approved Rule 318 and an earlierversion ofthe ordinance (revised April 21, 1999) asproviding 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 gg/m 3

. In addition, A.R.S. section 9-500.16 andA.R.S. section 11-875 (1998) require cities andthe County to adoptby December 31, 1998, an ordinance that prohibits the installation

or construction of afireplace or wood
stoveunless it is afireplace with a permanently installed gas orelectric log insert, a fireplace orwood stove that
meets EPA's Phase II wood stove requirements, or a fireplace with a wood
stove insert that meets EPA's Phase II
stoverequirements. Mostjurisdictions have adopted orhave 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.

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

a lowerthreshold for calling no burn episodes, the plan does not provide for the adoption ofany ofthese measures butprovides reasoned and acceptable justifications fortheir rejection. Therefore, we propose to findthat the MAG plan provides for the inclusion of MSM.

k. Secondaryammoniumnitrate. 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 (bothon and offroad) and 99.9 percent ofNH 3comes from animal wastes. See MAGplan, Table 3- 1.Two potential BACM were identified for ammonia nitrate control: Reduce emissions of ammonia andnitrates from agricultural operations and require animal wastemanagement plans for farms/ranches with more than 50 animals. The firstmeasure involves tilling in ofmanure used as fertilizer within 48 hours of application. MAG plan, Table 6-1, measure 97-AG-3. The second measure would focus on reducing ammonia emissions from livestock waste during the winter months when conditions are most conducive to ammonium nitrate formation. MAGplan, Appendix B, Exhibit 5, p. 5-70. For MSM, no

measures were found that required animal wastemanagement plans for farms or ranches andno othermeasures

were identified. See MAG plan, Table 10-7. Alarge number ofmeasures that could reduce NO, emissions were identified and havebeen evaluated for on-road motor vehicles and nonroad engines. We believe these list of

measures is complete and propose to findthat the MAGplan 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 the Phoenix area and therefore are nottechnologically feasible. 29 The estimated reduction in ammonia from

29We consider a measure technologically feasible
foran area only ifit has the potentialto reduce emissions in manner that reduces ambient concentrations inthe area. 19982

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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 also believe that this

measure is currently not technologically feasible.

Other than the on-road vehicle and nonroad engine categories, we do not believe that there are any other sources ofNO, that should be called significant in terms ofcontributing to ammonium nitrate levels.

Because the MAG plan includes an extensive number ofmeasures for controlling NO, sources and no measure
are identified for the control of ammonia as technologically feasible, we propose to find thatthe MAG plan provides for the implementation of RACM andBACM and for the inclusion ofMSM for secondary ammonium nitrates.

1.MCESD'scommitmentsto improve complianceandenforcementofits fugitivedustrules.MCESD has committed to expanding and improving the compliance and enforcement program for its fugitive dust rules. These commitments are found in Maricopa County, 1999 Revised Measure 6, adopted December 15, 1999. Anarrative description ofthe commitments and otherprogram 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 F.3.g. "Construction Sites and Activities."

These improvements include increased public outreach and education, increased funding and staffing, increased inspection frequency, revised enforcement policies, and commitments to program evaluations 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.

Staffing.Bythe end ofJanuary, 2000, the inspection staffwill increase to eight inspectors, 1 supervisor, 1aide and 2 enforcement officers. ByApril, 2000, the County Attorney's office will hire an attorney to expedite civil litigation and
to assist withprosecuting Class One Misdemeanor cases. Acoordinator will be added to the Small Business Environmental Assistance Program to assist smallerbuilders and construction companies and to help develop and implement education programs. In total,

resources devoted to the fugitive dust program will be 15 positions, a 25 percent increase over previous levels. This level ofstaffing is in contrast to the less than 1 staffposition devoted tothe
program in 1996.

After reaching the committed staffing level, MCESD will review the program in March 2000 to evaluate its effectiveness and the potential need to addmore staff.

Organization.Anew enforcement sectionhas been created under the direct supervision ofthe MCESD Director/Air PollutionControl Officer (APCO). This position streamlines enforcement by reducing senior management review and approval of enforcement actions and allows enforcement officers to submit directly
to the APCO's desk all enforcement actions requiring APCO approval.

In addition,inspectors will be located in two new regional offices toprovide quicker response times to dust-related complaints and allow more time in the field.

Funding.Revenue for fugitive dust program is estimated at $1.12 million from annual earth movingpermit fees,

a $772,000 increase over the previous level thatis due to the permit fee increases adopted in 1998.

Inspectionprogram.MCESD will develop byApril, 2000 inspection priorities for vacant lots and unpaved parking lots that consider lot size and number of sources, with larger lots being inspected first and smaller lots in succeeding years. A number ofcities have municipal programs to address these sources; therefore, the Department will initially direct its inspections to cities lacking suchprograms. Itwill also track the city plans that are required by State statute to stabilize target unpaved roads, alleys andunpaved shoulders.

MCESD has alsoincreased 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 of 8 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. Enforcementprogram.ByApril 2000, MCESD will revise itfugitive dust enforcement policy to

* include guidelines for initiating various enforcement actions * include guidelines for reinspecting define timely and appropriate actionby laying out guidelines for which type of violation is appropriate for specific enforcement actions and forthe time frames for escalating enforcement actions when appropriate

* identify priorityviolations * include guidelines for when to seek penalties reflecting the economic benefit ofnoncompliance, iffeasible

* include guidelines for seeking and determining higherpenalties forrepeat violators * guidelines for inspectors to handle predetermined citation categories form observation to justice court Enforcement action options include issuing an Order ofAbatement, filing a Misdemeanor Complaintin Justice court, or asking the County Attorney to seeka civil penalty in Superior Court.

Inspectors will 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 will enable the enforcement officers to work

on resolving cases involving more serious and complicated violations.

Publicoutreach/education. Public outreach and education consists of staff training, educating the regulatedparties, developing good working relationships with other involved parties such asthe cities, andmaking the program more understandable. Increased education of both inspectors and the regulated industry increases compliance.

Among the public outreach and education efforts willbe:

* Inspector training on case development.

* Inspector training on revised 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.

Programevaluationandtracking. MCESD will track the number of inspections, number andtype of enforcement actions, amount of penalties assessed, and amount of penalties collected. It will also conduct mid-year reviews ofthe program in 

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

G.AttainmentDateExtension

1.Apply for an Extension

We interpret this requirement to mean that the State must apply in writing for

an extension andthat the extension request must accompany the SIP submittal containing the demonstration that the area will attain bythe most expeditious alternative date practicable. The public mustbe provided reasonable notice and a public hearing on the request before itis submitted.

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 based on documentation in Chapter 10 ofthe MAG plan and Appendix C, Exhibit 5of the MAGplan. MAG plan, p. 10-2. This extension request is an integral part of the MAGplan and was subject to public hearing along withthe rest ofthe plan.

2.Demonstrate the Impracticability of Attainment byDecember 31, 2001

In order to demonstrate impracticability, the plan must show that the implementation ofBACM (as determined by our guidance) on significant sources categories will not bring the area into attainment by December 31, 2001.

To demonstrate the impracticability of attainment by 2001, the MAG plan derived from the airquality modeling a change in PM-10 concentrations per change in emissions using the modeled concentration for the year 2006 and observed concentration for the year 1995 at Greenwood monitor and the overall change in emissions between the
two years. MAG plan, p. 8-10. Using this information, the plan estimates that the annual concentration in 2001 will be 52.21 gLg/m 3 after implementation of BACM. Because the projected 2001 annual concentration is still above the 50 gLg/m 3 annual NAAQS, the MAG plan concluded that itwas impracticable to attainby 2001.30 MAG plan,p. 8-10.

Based on our analysis ofcontrol

measures in the MAG plan as described in the preceding sections, wepropose to find thatthe MAGplan provides for implementation ofBACM asrequired by CAA section 189(b)(1)(C). Based on the modeling analysis in theplan, we also
propose to find thatthe MAG plan also

3 01n addition the MAG plan shows that implementation ofcontrols on the de minimis

source categories would notproduce enough emission reductions to show attainment in 2001. MAG plan, p. 9-11. demonstrates that attainment by 2001 is impracticable with the implementation ofBACM.

3.Complied With Commitments and Requirements in the SIP

We interpret this criterion tomean that the State has implemented the control measures in prior SIP revisions it has submittedto address the CAA requirements in sections 172 and 189 for PM-10 nonattainment areas. It does
not include measures being approved in this action.

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

The 1991 MAG plan includes a broad
range ofmeasures to address PM-10 including controls for constructions sites, paved road, unpaved roads, unpaved parking areas, vacant lots, and woodburning. The plan alsoincluded reasonably available control technology for stationary sources and awide range oftransportation control measures. The implementation ofthe measures in this plan are described in theMAG plan at pp. 10-10 to 10-25. The principal controls in this plan were Rule 310 and the County woodburning ordinances. The plan also contained a large number ofcommitments from the local jurisdictions to various measures. Most ofthe measures represented "business

asusual" actionsby thejurisdictions to doinfrastructure (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 tothe 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 andrequirements in these plans 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

The MAGplan excluded no source categories ofdirectly-emitted PM-10 from its MSM analysis instead simply started its evaluation ofMSM by identifying candidate measures for any
source category ofPM-10 present in the Phoenix area. MAGplan, 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.

After a comprehensive list of candidate MSM was developed, each

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

were grouped by source category and

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

measure was provided. MSM study, Table 3-1 and MAG plan, p. 10-46.

We propose to find that the MAGplan demonstrate to our satisfaction that it includes the most stringent measures that are included inthe implementation plan ofany State, or are achieved in practice in any State, and can be feasibly be implemented in the Phoenix

area.

We have discussed identification and adoption 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 apotentially more stringent requirements thanRule 310.01. However, the two rules control different sources at commercial feedlots/livestock areas. South Coast Rule 1186 requires controlling unpaved roads and hay grinding at dairy and horse farms but does not address fugitive dust emissions from disturbed open areas. MCESD Rule 310.01 controls fugitive dust emissions from disturbed open areas at dairies and cattle lots,but notunpaved roads and hay grinding.

In the Maricopa County PM-10 nonattainment area, there is only one cattle feedlot and less thanhalfthe 

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number ofdairies compared to those subject to South Coast Rule 1186. Similar to South Coast, unpaved roads
atdairies are low travel (10 to 20 ADT) andrepresent a very small source of emissions in the Phoenix area and controls onthem would not advance the attainment date. We, therefore, believe

we can findthat the MAG plan provides for the implementation ofMSM to our satisfaction without Rule 1186 provisions for unpaved roads at cattle feed lots. In Maricopa County, hay grinding activities occur primarily at feed mills (as opposed to dairies) which

are permitted sources and thus already subject to control requirements.

Incinerators: The MAG plan identifies Clark County's Rule 26 as having a more stringent opacity limit than MCESD's Rule 313. Clark County limits opacity from existing incinerators to 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. Because incinerators are so small a source and controls on them would not advance the attainment date,

we propose to findthat the MAG plan provide for the inclusion ofMSM to our satisfaction without including Clark County's opacity limit for incinerators.

Charbroiling: Emissions from charbroiling and frying meat are estimated to 0.6 mtpd or 227 mtpy. 1994 Regional PM-10 Inventory, p. 4-25. This is 0.4 percent ofthe daily directlyemitted PM-10 inventory in 1994 and 0.4percent ofthe annual inventory in 1994. MCESD has committed to develop

anew rule to require existing and new chain-driven and underfired charbroilers, typically found in
restaurants specializing in grilled meat products, to be equipped with emission control equipment. South Coast is developing a new rule to deal with underfired charbroilers and MCESD will wait until South Coast completes its rulemaking to adopt this measure. MCESD isprojecting adoption ofits rule in Spring, 2001. 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
setthe standard for control 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 by section 189(b)(1)(A)(ii) of the CAA. We also propose to findthat the attainment demonstration relies on control measures that either are approved or are being proposed for approval andmeet our SIP enforceability criteria; that the emissions estimates assigned 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. See discussion below.

a.Airqualitymodeling.A modeled attainment demonstration for the PM-10 annual standard should first estimate the temporal and spatial distribution of PM-10 and PM-10 precursor emissions that result from the adopted control

measures by the attainment date. It shouldthen simulate the ambient air concentration ofthese emissions in an air quality model and show that all locations within the nonattainment area have annual average PM-10 concentrations belowthe level ofthe annual PM-10 standard of50 gg/m3. See "Guidelines on Air Quality Models," 40 CFR part 51 appendix W, section 7.2.2. and "PM-10 SIP Development Guideline," EPA-450/2- 86-001, June 1987.

To provide contextfor our evaluation ofthe air quality modeling in the MAG plan, we will first briefly describe the steps in developing amodeled attainment demonstration and howthe MAG plan performed each step. Step 1.A modeling base case is developed toreplicate PM-10 concentrations for specific recent days by simulating the emissions and meteorology that occurred for those days, by hour and bylocation throughout the area being modeled (that is, the model domain). For some input parameters, alternative plausible values

are tried in a diagnostic process to

ensure that the model isperforming in

aphysically reasonable way. PM-10 concentrations from the model output

are compared tomonitored values to evaluate the performance ofthe model.

The base case for the MAG plan consisted ofthe application ofthe urban airshed model with the limited chemistry module (UAM/LC) to each of 65 days during 1995. The results from modeling each ofthese days arethen averaged together to getthe modeled annual PM-10 concentration. 1995 was used asthe base year because an intensive inventory and monitoring study was performed during it; the 65 days coincided with the available PM10 24-hour average monitoring data, which are collected once every 6 days. During 1995 the peak monitored annual PM-10 concentration was 60.01 gg/m 3

atthe Greenwood monitor while the model predicted a peak concentration of 75.91 gg/m3 at a location away from the Greenwood monitor.MAG TSD, Chapter 111.31

Step 2.After thebase case model is developed, emissions are projected into the future. Projections arebased on particular facilities's expansion plans, business and socioeconomic projections, andprojections ofthe effect ofchanging technology and ofthe control measures that are already in place.The model simulation isrepeated with these future emissions but withthe

same meteorological inputs asbefore. This simulation shows how a day meteorologically conducive to high PM10 concentrations will look in the future ifno new controls are implemented. The resulting modeled concentrations

canbe used to derive an estimate ofthe additional emission reductions needed
to attain the air quality standard.

For the MAG plan, emissions are projected to 2006 (whichMAG found to be the earliest practicable attainment year). Before additional controls, the 2006 future peak PM-10 annual average

was simulated to be 86.72 gLg/m 3

- Because this was above the NAAQS of 50 gg/m 3

,the modeling showed that additional control measures were needed. MAG plan, p. 8-6.

Step 3.The effect ofcontrolmeasures
on ambient concentrations are simulated by changing the model emission inputs for future years to reflect higher implementation rates or larger emission reductions from additional controls. Additional

measures are tried ifPM-10 concentrations are still above the standards.

Attainment is demonstrated when sufficient emission reductions are in place so thatmodeled concentrations in every grid square are below the standard.

MAG showed that with additional controls, the peak annual PM-10 concentration in 2006 is 49.70 gg/m 3

, which isbelow the annual PM-10 NAAQS of50 49.70 jig/m 3

,thus

31The MAG TSD is the "Revised Technical SupportDocument for RegionalPM-10 Modeling in Support ofthe Revised MAG 1999 Serious Area Particulate Plan for PM-10 for the Maricopa County Nonattainment Area," MAG, February 2000 found inAppendix A, Exhibit 7 ofthe MAG plan.

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demonstrating attainment. MAGplan, p. 8-12.

In evaluating the air quality modeling in the MAG plan, we reviewed the choice ofmodels; the selection of episodes to model, the selection ofthe modeling domain and grid resolution, the methods ofpreparing wind, temperature, andmixing height fields data; the selected initial andboundary conditions values; the modeling emission inventories; the procedures for andresults ofquality assurance, diagnostic testing and sensitivity testing; and selected modeling performance goals andmodel resultsvis

avis these goals. We have found them allgenerally acceptable. See our detailed evaluation in EPA TSD section "Demonstrate Attainment by the Most Expeditious Alternative DatePracticable after December 31, 2001."

The modeling performed for the MAG plan is as sophisticated as any thathas been performed for a PM-10 SIP. While there are several problems associated with the model's performance for secondary particulates and several other shortcomings ofthe modeling and its documentation, the dominance ofthe contribution ofprimary particulates from fugitive dust toPM-10 concentrations in the Phoenix area obviates these concerns. Atworst the MAG plan's modeling is akin to modified rollback, an approach that is acceptable under EPAmodeling guidance for PM-10. We therefore
propose to approve the modeling forthe annual NAAQS because itprovides a credible demonstration thatthe credited control measures will provide for attainment ofthe annual standard by 2006.

b. Controlmeasuresreliedonfor attainment.For demonstrating attainment, the MAG plan relies on reductions in directly-emitted PM-10 from 12 measures. MAG plan, Table 8- 2.We have listed each measure; the rule, commitment or state statute through which it is implemented, and its emission reductions in Table 1-1.

TABLE 1-1.-CONTROL MEASURES RELIED ON IN THE ATTAINMENT DEMONSTRATION

Emission re- Measure Implementation mechanism duction (mtpd)
Strengthening and Better Enforcement of Fugitive Dust Rules Rule 310 and Maricopa County Commitments, 1999 Revised 60.6

(Construction sites). Measure 6. Unpaved roads and alleys

........................................................... Rules 310 and 310.01, Maricopa County Commitments, 199 12.2 Revised Measures 6 & 17, City/Town Commitments for Unpaved Roads and Alleys. Unpaved parking lots

................................................................... Rules 310 and 310.01 and Maricopa County Commitments, 3.7 1999 Revised Measure. Vacant disturbed lots

................................................................... Rules 310 and 310.01 and Maricopa County Commitments, 1.8 1999 Revised Measure 6. 01 PM-10 efficient street sweepers (MAG)

..... MAG Commitment, "PM-10 Efficient Street Sweepers" City/ 1.1 Town/County Commitments for Street Sweeping. Curbing, paving, or stabilizing shoulders on paved roads

.......... City/Town/County Commitments for Stabilizing Shoulders

........ 1 Curbing paving or stabilizing unpaved access points

................. City/Town/County Commitments for Stabilizing Unpaved Ac- 0.4

cess Points. PM-10 episode thresholds

.......................................................... Maricopa County Residential Woodburning Restriction Ordi- 0.07

nance. Restaurant charbroiler controls (Maricopa County commitment) Maricopa County Commitment, 1999 Revised Measure 23

...... 0.07 Cleaner Burning Gasoline

............................................................ ADEQ Regulations (already SIP approved)

............................... 0.03 Pre-1988 Heavy-Duty Diesel Vehicle Standards

....................... A.R.S. 49-542 F.7

. ..................................................................... 0.02 Coordinate traffic signals

............................................................. City/Town/County Commitments for synchronizing traffic lights. 0.01

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.

We have also evaluated the emission reductions credited to each measure to

ensure they are reasonable. In particular, we looked at thereduction estimates for Rules 310 and 310.01.

The MAGplan assumes an incremental increase in rule effectiveness for these rules from 66 percent in 1998 to 80 percent in 2006. MAG TSD, Appendix IV, Exhibit 1, Committed Measure 1.Rule effectiveness (RE) accounts for emission reductions lostbecause 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.

We have established policies on applying rule effectiveness factors for both base year and projected year inventories ofvolatile organic compounds (VOC), a precursor to ozone. See General Preamble at 13503 and "Rule Effectiveness Guidance: Integration ofInventory, Compliance, andAssessment Applications." USEPA, OAQPS, EPA-452/R-94-001, January 1994, (RE Guidance). In general, we encourage states to derive local category-specific RE factors. Ifthere are

no suchlocal RE factors, we require the

use ofan 80 percent effectiveness default value in VOC inventories. General Preamble at 13503. We have not established any explicit guidance for applying RE to particulate
matter sources. We know, however, that PM sources like VOC sources are not in full compliance with applicable rules at all times; therefore, some RE factor needs tobe applied. Forthis rulemaking, we have applied the existing Agency RE guidance for VOC

sources to emission reduction estimates for Rule 310 andRule 310.01.

The items thatinfluence compliance with a rule and thus the appropriate RE factor are the clarity ofthe rule, its compliance requirements and the complexity ofthe controls required by the rule; the source's actions; andthe implementing agency's actions. See RE Guidance, pp. Table 1-1 and Appendix C.Under our guidance, a state is allowed and required to use a 80 percent RE factor absent evidence tothe contrary. General Preamble at 13503. In this case, 

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the evidence that we have is that compliance for Rule 310 was below this level as ofearly 1998. MAG, with

concurrence ofMCESD, assumed a 30 percent compliance rate for the Rule 310 in the 1995 base year modeling. Inspections by MCESD in early 1998 indicated thatthe compliance rate with the rule was 66 percent. MAG TSD, Appendix II, Exhibit 6, "Documentation

onAssumption ofRule 310 Control Efficiency andCompliance Rate."

Over the last few years, MCESD has made substantial changes to its fugitive dust control program, many designed to improve compliance. MCESD has also committed to a number of additional changes which we have described earlier. Webelieve that an 80 percent rule effectiveness in 2006 is appropriate given these changes and MCESD's commitments to improve compliance with Rules 310 and 310.01. These improvements coverrule and test method revisions, increased public outreach and education, increased funding and staffing, increased inspection frequency, revised enforcement policies, and commitments
to program evaluations and improvements. They address many of the program areas that are key to improving compliance.

In our TSD (inthe section "Extension Request-Demonstrate Attainment bythe Most Expeditious Alternative Date Practicable after December 31, 2001"),

we have compared the MCESD's fugitive dust program in 1996 to theprogram that will be in place by 2006 based on MCESD's commitments in the MAG plan and its actions to date. This comparison clearly shows the scope of improvements to the MCESD's fugitive dust program and supports our proposed finding that an 80 percent RE in 2006 for Rule 310 and Rule 310.01 is appropriate.32

Finally, we have looked at the implementation schedule for each

measure to assure that the MAG plan provides for expeditious implementation. Except for paving of

someunpaved roads, adoption ofthe charbroiler rule, heavy duty diesel standards, and the purchase and deployment ofthe PM-10 efficient
street sweepers, allthe measures relied

onin the attainment demonstration are currently in effect.

However, attainment ofthe PM-10 annual standard in the Phoenix area depends on a high level ofcompliance with MCESD's fugitive dustrules. The

32The cities and towns in Maricopa County are also increasing their efforts to address fugitive dust
sources, such as unpaved parking lots and disturbed vacant lots. These efforts also support an overall 80 percent rule effectiveness. MAG plan assumes this level increases from 66 percent in 1998 to 80 percent in 2006. MAG TSD, Appendix IV, Exhibit 1, Committed Measure 1. This level ofcompliance depends in turn on education ofthe regulated community andincreased enforcement modifying

source behavior. Both ofthese take time
to effect, therefore, we believe thatit is reasonable to allow a period oftime to achieve ahigh level ofcompliance with these rules. We thusbelieve that the emission reductions are being achieved

as expeditiously aspracticable.

6. OtherFactors ThatEPA may Consider

CAA section 188(e) listfive additional factors that we 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. We have already proposed to determine that the MAG plan provides for the implementation of RACM andBACM, includes the MSM, and attainment ofthe annual PM-10 standard bythe earliest practicable date ofDecember 31, 2006. In the next section, we will alsopropose to find that the plan provides for reasonable further progress. Nothing in the additional information presented on the five factors suggest that granting an extension ofthe attainment date for the Phoenix area to 2006 is inappropriate.

a.Natureandextentof nonattainment.Over the past 5years, violations ofthe annual standard have occurred routinely at three sites (MAG plan, Table 10-11): 1.Greenwood, an urban site heavily impacted by transportation sources, 2.Chandler, an urban fringe site heavily impacted by fugitive dust

sources such as construction and agriculture, and

3. Salt River, a site heavily impacted by industrial sources.

Areas similar to the first two sites can be found throughout the Phoenix nonattainment area, so we would expect that there are similarly elevated PM-10 levels throughout the Phoenix area; therefore, controls need tobe uniformly implemented throughout the nonattainment area, atask that generally requires longer to achieve than implementing controls in fewlocalized

areas.

b. Types andnumbersofsourcesor otheremittingactivities.Primary contributors to elevated PM-10 levels

are fugitive dust sources including paved road dust, unpaved roads, construction activities, disturbed vacant lands, unpaved parking lots, and agricultural sources. MAGplan, p. 10- 51. These sources are ubiquitous in the nonattainment area and collectively number in the thousands. (Forexample, MCESD issued 2500 construction permitsin 1999; we mailed 50,000 letters to owners ofvacant lots in the nonattainment area; there are 12,000 miles ofroadway in the nonattainment area.)

c.Populationexposureto concentrations above thestandard. The MAG plan estimates population
exposure to elevated levels ofPM-10 (bothannual and 24-hr) tobe from 78,000 to 163,000 (1995 figure), p. 10- 13. This population exposure is calculated using estimates ofdisturbed landversus population in subareas of the nonattainment area. According to this calculation, 84 percent of Maricopa's population livesin areas where 10 percent or less ofthe land is
open. MAG plan, Table 10-13. This
exposure number does not seem to include populations exposed to dust frompaved and unpaved roads and therefore may underestimate overall population exposure. However, the plan does provide forimplementation of RACM, BACM, and MSM on disturbed land (including construction) andpaved and unpaved roads with much ofthe emission reductions being achieved in the first fewyears, all these factors will reduce population exposure as quickly

as practicable.

d.Presenceandconcentrationof potentiallytoxic substancesin the particulate. The primary source of airborne cancer risk in the Maricopa

area is internal combustion engine exhaust from both on- and non-road engines. This risk is from allpollutants emitted from these sources (gaseous and particulate). MAGplan, p. 10-61. The MAG plan concludes thatthe cancer risk inthe 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 non-road engines) target emissions from on- and non-road engines.

Almost all ofthe PM-10 emission reductions in the outyears ofthe MAG plan (2003 and later) are and need to be fromfugitive dust sources in order to show attainment ofthe annual PM-10 standard and not fron on- andnon-road 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 on the major source oftoxic risk,on- and nonroad engines.

e. Technologicalandeconomic feasibilityofcontrols.Fugitive dust

sources dominate the emission inventory in the Maricopa 

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nonattainment area. Controls for these

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

anumber ofyears. These factors generally support a longer time frame for attainment.

7.Conclusion on Extension Request

Based on our review 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 serious attainment date for the Phoenix PM-10 serious nonattainment

area from December 31, 2001 to December 31, 2006.

H. ReasonableFurther Progress(RFP) andQuantitative Milestones
We propose to find thatthe MAG plan provides for RFP and meets the quantitative milestone requirements of the Act.

1.Reasonable Further Progress

The MAGplan provides for annual
progress so that emissions levels in each year from 1995 to 2006 that are at or below the level needed to maintain linear progress toward attainment. It demonstrates thatregional PM-10 emission levels will drop from 191 mtpd in 1995 to 130 mtpd in 2006 with two-thirds ofthe reduction occurring before 2001. MAG plan,Figure 8-4. Total regional emissions decrease annually at arate ofapproximately 6.5 mtpd peryear from 1995 through 2001 and4.4 mtpd per year from 2002 to 2006. The assumptions that underlie the RFP demonstration regarding control measures' implementation and effectiveness are reasonable.

The plan does not provide emission reduction information for eachyear between the base modeling year of 1995 andthe attainment year of2006. We do
not believe that this level ofdetail is
necessary or meaningful. The principal control measures in the plan (such as improving compliance with the fugitive dust rules, progressive paving of unpaved roads, and annual replacement ofpart ofthe street sweeper fleet with PM-10 efficient units) produce year to year incremental increases in emission reductions sufficient to meetthe statutory requirement for RFP. See MAG plan, Figure 8-4 andEPA TSD, Figure RFP-1. Therefore, we propose to find that the MAG plan provides for "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" asrequired by section 172(c)(2) ofthe Act.

2. Quantitative Milestones

Our guidance provides for a quantitative milestone for the year 2000. Addendum at 42016. Based on the statutory requirement for milestones everythree years, the years 2003 and 2006 are the next two milestones for

areas with an attainment date extension under section 188(e). The MAG plan provides milestones for 2003 and 2006 but substitutes 2001 for 2000. We believe this minor deviation from our guidance is appropriate and acceptable for the following reasons.

First, we set the milestone schedule in

our serious PM-10 area guidance assuming the area involved was one of the initial moderate areas and its moderate area plan demonstrates attainment by December 31, 1994. General Preamble at 13539 and Addendum at 42016. Although the Phoenix area was one ofthe initial moderate nonattainment areas, its moderate area plan did not demonstrate attainment. 33As aresult, our guidance

onthe appropriate milestone years is
not strictly applicable to the MAG serious area plan.

We alsobelieve that the statutory purpose for including milestones in PM-10 plans isbest served in the Phoenix area by having the milestone
year be 2001 rather than 2000. Under the Act, states are to submit a demonstration 90 days after a milestone date that the state has implemented all

measures inits approved plan and has
met the milestone. See CAA section 189(c)(2). Ifa state fails to submit a report or we determine thatthe area has
not met amilestone, then the state must submit aplan revision that assures that the nextmilestone will be met. See CAA section 189(c)(3).

It is clear from the statutory requirements, thatthe milestone requirement functions as a mid-course

33The moderate area plan submitted by the State in 1991 and revised in 1993 and 1994 demonstrated the impracticability ofattainment by December 31, 1994. While we have subsequently disapproved this impracticability demonstration because the plan didnot include RACM, we confirmed that attainment was impracticable in our 1998 FIP. 63

FR 41340. evaluation ofthe PM-10 plan and an opportunity to make corrections to the planto assure thatthere is no delay in attainment due to failures to implement

or achieve needed reductions. As such, the milestones should be keyed, to the
extentpossible, to major implementation deadlines in amanner that allows for arealistic and comprehensive look at the effectiveness ofthe implemented measures.

The BACM implementation deadline for Phoenix isJune 10, 2000. A December 31, 2000 milestone allows for the evaluation ofonly ahalf-year of implementation, which is littletime to

see ifimplementation isgoing to achieve the expected emission reductions. Setting the milestone one year later on December 31, 2001 as the MAG plan does, provides for afull year ofimplementation allowing for a more realistic assessment ofthe effectiveness ofBACM yet still leaving ample time to make any corrections needed to assure timely attainment. Therefore, webelieve that strict adherence to the 2000 milestone date in our guidance would be lessbeneficial to attainment in the Phoenix area than settingthe date at 2001.

The next milestone in the MAGplan after the 2001 one is in 2003. MAG plan, Figure 8-4. This second milestone is only 2years after the first, instead of3 years arguably required bythe Act. However, we believe thatthe 3-year milestone increment in CAA section 189(c) is the maximum allowable time between milestones and nothing in the section prohibits states from setting milestones dates that are closer together.

The assumptions regarding control measures' implementation and effectiveness that underlie the quantitative milestones are reasonable and consistent with the RFP demonstration.

For these reasons, we propose to find thatthe MAG plan meets the quantitative milestone requirement in CAA section 189(c)(1).

L GeneralSIPRequirements

Section 110(a)(2)(E)(i) ofthe CleanAir Act requires thatimplementation plan provide necessary assurances that the State (or the general purpose local government) will have adequate personnel, funding and authority under State law. Requirements for legal authority are further defined in 40 CFR part 51, subpart L (section 51.230-232) and for resources in 40 CFR 51.280.

States and responsible local agencies
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compliance. SIPs must also describe the

resources that are available or willbe available tothe State and local agencies
to carry out the plan, both at the time ofsubmittal and during the 5-year period following submittal.

We propose to find thatthe implementing agencies for the MAG plan have adequate resources for implementing their respective commitments. We also propose to find that the MAG plan adequately describes the resources that are available or will be available tothe State and local agencies to carry out the Plan,both now and over the next 5years. See discussion ofthe individual commitments and control measures in the TSD.

All agencies andjurisdictions appear to have adequate authority under Arizona state law to implement their respected commitments and, where applicable, to obtain information
necessary to determine compliance. We, therefore, propose to find thatthese agencies/jurisdictions have demonstrated that theyhave adequate legal authority to implement the MAG plan.

Section 110(a)(2)(C) requires SIPs to include a program 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 control measures in the plan are MCESD's Rules 310 and 310.01. Procedures for monitoring compliance (i.e.,the inspection strategy) with these rules are described in Maricopa County's commitments. See Maricopa County commitment, 1999 Revised Measure 6.

Based onthe review ofMCESD's enforcement procedures, we propose to find thatthe MAGplan adequately provides for the enforcement ofthe principle measures relied on for attainment and that theplan includes an adequate description ofenforcement methods asrequired byour regulations.

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

assurances that where a State hasrelied

on alocal or regional government, agency orinstrumentality for the implementation ofany plan provision, the State hasresponsibility for ensuring adequate implementation ofthe such plan provision. 60 FR 18010, 18019 (April 10, 1995). Proposed Actions onMaricopa County Rules

A. Rule 310

Rule 310 establishes requirements for fugitive dust sources onfacilities that have or are required to have air quality permits from MCESD. These facilities include construction sites, stationary
sources, and any other facility or operation that isrequired tohave a permit under MCESD rules. The rule requires earthmoving activities that disturb 0.10 acre or more to apply for and get approval ofaDust Control Plan (DCP) and requires other permitted

sources to obtain a DCP prior to commencing any routine dust generating activity. We have described
many ofthe Rule's specific requirements earlierin this preamble.

The current SIP approved version of Rule 310 is the version adopted on September 9, 1994. We approved this version ofRule 310 into the SIP on August 4, 1997 as part ofthe Microscale plan. 62 FR 41856

MCESD adopted a revised version of Rule 310 andAppendix C to MCESD rules onFebruary 16, 2000 andArizona submittedboth as arevision to the Arizona SIP onMarch 2, 2000. Appendix C contains the test methods relied on in Rule 310.

The revised Rule 310 is considerably different from the current SIP-approved version. The greatest change hasbeen to splitthe old rule into two new rules: the revised Rule 310 thataddresses permitted facilities and anew Rule 310.01 that addresses nonpermitted

sources. We evaluate Rule 310.01 in the
next section. MCESD also revised Rule 310 to strengthen it compared to the
current SIP-approved version. These rule improvements include: * Improved enforceability ofcontrol

measures and dust control permits (DCPs),

* Improvements to existing test methods (inAppendix C), * New performance standards and
test methods, * Clearer definitions, * More specific work practice requirements

MCESD has also committed to continue to strengthen and improve Rule 310 through research ontest methods, dust control methods, and revised recordkeeping requirements. See discussion in section F.3.g., "Construction Sites and Activities."

We believe that the revised Rule 310 is a considerable improvement over the SIP-approved version and, combined with MCESD commitments to continue
to improve the Rule and to improve enforcement and compliance with it, provides for implementation ofRACM and BACM and the inclusion ofthe MSM on the sources subject toit. We, therefore, propose to approve Rule 310 and Appendix C as adopted on February 16, 2000 and submitted on March 2, 2000, into the Arizona SIP.

We have described in more detail the improvements and other revisions to Rule 310 in section 6 ofour TSD.

B.Rule 310.01

Rule 310.01 establishes requirements for fugitive dust emitted from nonpermitted sources, including unpaved public roads, unpaved parking lots, open areas and vacant lots, erosioncaused deposits ofbulk materials onto paved surfaces, and commercial feedlots and/or commercial livestock areas.

The provision ofRule 310.01 are currently in the SIP as sections of former Rule 310. We approved this version ofRule 310 into the SIP on August 4, 1997 as part ofthe microscale plan. 62 FR 41856.

MCESD adopted Rule 310.01 on February 16, 2000 andArizona submitted itas a revision tothe Arizona SIP on March 2, 2000. As with Rule 310, Rule 310.01 relies on the test methods in Appendix C.

Rule 310.01's provisions are strengthened compared to the similar provisions in the SIP. These rule improvements and other rule changes include:

* The revised rule requires that unpaved roads and unpaved parking lots comply with both: (1)a 20 percent opacity standard; and (2)a silt content

or a silt loading standard.

* Anew opacity test method hasbeen added to Appendix C to determine compliance with the rule's 20 percent opacity standard for unpaved haul/

access roads and unpaved parking lots which isbetter tailored to these sources.

* Test methods for determining compliance with the new silt content/ loading standards has been added to Appendix C.

* Owners/operators ofdisturbed
vacant lots and open areas must maintain a visible crust or meet atleast

one other applicable stabilization standard, according to new test methods included in the rule andAppendix C. 

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* Specific controlmeasures for commercial feedlots and/or commercial livestock areas have been added, including: application ofdust suppressants orgravel, orinstallation of shrubs and/ortrees within 50 to 100 feet ofanimal pens.

* The revised rule specifies that unpaved roads with vehicular traffic of 250 or more must be stabilized by June 10, 2000 and unpaved roads with vehicular traffic of 150 or more must be stabilized byJune 10, 2004.

* The revised rule specifies that requirements to preventvehicle trespassing (section 301) apply to vacant lots and open areas that are 0.10 acre or larger andhave a cumulative of500 square feet or more that are driven over and/orused by motor vehicles and/or off-road vehicles.

* The revised rule specifies that requirements to stabilize disturbed
vacant lots and open areas (section 302) apply to lots/areas with 0.5 acre or more ofdisturbed surface.

We believe that Rule 310.01 is a considerable improvement over the SIPapproved version and, combined with MCESD's commitments to continue to improve the Rule and enforcement and compliance with it and the commitments by the County and local jurisdictions to address unpaved roads, unpaved parking lots, and vacant lots, provides for implementation ofRACM andBACM andthe inclusion ofthe MSM onthe sources subject to it. We, therefore, propose to approve Rule 310.01 as adopted on February 16, 2000 and submitted onMarch 2,2000, into the Arizona SIP.

We have described in more detail the strengthenings and other revisions to Rule 310.01 in section 6 ofour TSD.

C.ResidentialWoodburningRestriction Ordinance

Combined with MCESD Rule 318 "Approval ofResidential Woodburning Devices" (adopted April 21, 1999; approved November 8, 1999 (64 FR 60678)), Maricopa County's Residential Woodburning Restriction Ordinance implements a mandatory woodburning curtailment program. The curtailment
program restricts the types of woodburning devices that canbe used duringperiods ofhigh PM-10 concentrations. The ordinance allows the Control Officer to declare restrictedburn periods when the particulate
matter pollution levels could exceed the "particulate matter no-burn standard."

The SIP-approved ordinance provides that restricted-burn periods are declared by the Control Officer when the Control Officer determines that air pollution levels could exceed the 24-hour PM standard at 150 gLg/m 3

. The revised ordinance allows the Control Officer to declare restricted-burn periods when the particulate matter pollution levels could exceed the "particulate matter noburn standard" of 120 gg/m 3

. The lower oftheparticulate matter no burn standard to 120 gLg/m 3is the only change made tothe ordinance as itis currently approved in the SIP.

Because approving this revision will strengthen the SIP and when combined with theMAG plan's otherprovision for residential woodburning will provide for the implementation ofBACM and the inclusion ofthe MSM, we are proposing to approve itinto the SIP. See sectionF.3.j. "Residential Wood Combustion."

D. CAA Section 110(1)Finding

CAA section 110(1) prohibits us from approving a revision tothe applicable implementation plan ifthat revision would interfere with any applicable requirement concerning attainment and reasonable further progress (RFP) or any other applicable requirement ofthe Act. We interpret section 110(1) to mean that

we cannot approve aplan revision if that revision would mean thatthe plan would nolonger provide for attainment

orRFP as these are required by the CAA for that plan or ifthe revision would

mean that the plan would no longer
meet another requirement ofthe Act that applies to the plan. For afurther discussion ofthis interpretation, see 61 FR 51599, 51608 (October 3, 1996).

We are proposing to revise the Arizona SIP to incorporate therevised Rule 310, Rule 310.01 andthe Maricopa County Residential Woodburning Ordinance in replacement ofthe previous version ofRule 310 approved in August, 1997 and ofthe ordinance approved in November, 1999. In addition to the effect on attainment and RFP, the "other applicable requirement ofthe Act" that we must be concerned with for this proposal is the Act's requirements for implementation of RACM andBACM andthe inclusion of the MSM.

We are proposing to approve the expeditious attainment andRFP demonstrations in the MAG plan. These demonstrations are in part dependent

on approval ofthe revised Rule 310, Rule 310.01, andthe woodburning ordinance.

We are alsoproposing to findthat the MAG plan provides for the implementation ofRACM andBACM andthe inclusion ofthe MSM for construction sites, unpaved roads, unpaved parking lots, and disturbed
vacant lands. Again, these findings are in large part dependent on approval of the revised Rule 310 andRule 310.01. We, therefore, propose to findthat approval ofthe revised Rule 310 and Rule 310.01 will not interfere with plan's compliance with the CleanAir Act's requirements for attainment, RFP, implementation ofRACM and BACM, and inclusion ofthe MSM as they apply
to construction sites, unpaved roads, unpaved parking lots, and disturbed
vacant lands.

Finally, we are proposingto findthat the MAGplan provides for the implementation ofBACM and forthe inclusion ofMSM for residential woodburning. These proposed findings

are made in part based onthe revised ordinance. Therefore, we propose to findthat our approving the ordinance will notinterfere with the plan's compliance with the Act's requirements for the implementation ofBACM and the inclusion ofMSM as they apply to residential woodburning.

We have previously found that the Arizona SIP provided forthe implementation ofRACM forresidential woodburning. 64 FR 60678 (November 8, 1999). The State has now strengthened itsresidential woodburning program, in part with the revised ordinance; therefore, we propose that approval ofthe revised ordinance willnot interfere with the Arizona SIP's compliance with the requirement for the implementation of RACM asit applies to residential woodburning.

Administrative Requirements

Under Executive Order 12866 (58 FR 51735, October 4, 1993), this proposed action is not a "significant regulatory action" andtherefore is not subject to review by the Office ofManagement and Budget.This proposed action merely
approves state law as meeting federal requirements andimposes no additional requirements beyond those imposed by
state law. Accordingly, the Administrator certifies that this proposed rule will nothave a significant economic impact on a substantial number of small entities underthe Regulatory Flexibility Act (5U.S.C. 601
etseq.).

Because this rule proposes to approve pre-existing requirements under state law and does not impose any additional enforceable duty beyond thatrequired by state law, itdoes not contain any unfunded mandate or significantly or uniquely affect small governments, as described in the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4).

For the same reason, this proposed rule also does not significantly or uniquely affect the communities of tribal governments, as specified by 

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Executive Order 13084 (63 FR 27655, May 10, 1998). This proposed rule will
not have substantial direct effects on the States, on the relationship between the national government and the States, or

onthe distribution ofpower and responsibilities amongthe 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 itis not economically significant.

In reviewing SIP submissions, our role is to approve state choices, provided that they meet the criteria of the Clean Air Act. In this context, in the absence ofa prior existing requirement for the State touse voluntary consensus standards (VCS), we have no authority
to disapprove a SIP submission for failure to use VCS. Itwould thus be inconsistent with applicable law for us, when reviewing a SIP submission, to

use VCS in place ofaSIP 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) do not apply.

As required by section 3 ofExecutive Order 12988 (61 FR 4729, February 7, 1996), in issuing this proposed rule, we have taken the necessary steps to eliminate drafting errors and ambiguity, minimize potential litigation, and provide a clear legal standard for affected conduct.

We have complied withExecutive Order 12630 (53 FR 8859, March 15, 1988) by examining the takings implications ofthe rule in accordance with the "Attorney General's Supplemental Guidelines for the Evaluation ofRisk and Avoidance of Unanticipated Takings" issued under the executive order.

This proposed rule does not impose

an information collection burden under the provisions ofthe Paperwork Reduction Act of 1995 (44U.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:April 3,2000. LauraYoshii, ActingRegional Administrator,RegionIX. [FR Doc. 00-8833 Filed4-12-00; 8:45 am]

BILLING CODE 6560-50-U 

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