The EPA Acting Regional Administrator, Keith Takata, signed the following proposed rule on 03/30/2012, and EPA 

is submitting it for publication in the Federal Register (FR). While we have taken steps to ensure the accuracy of 

this Internet version of the rule, it is not the official version of the rule for purposes of public comment. Please refer 

to the official version in a forthcoming FR publication, which will appear on the Government Printing Office's 

FDsys website (http://fdsys.gpo.gov/fdsys/search/home.action) and on Regulations.gov 

(http://www.regulations.gov) in Docket No. EPA-R09-OAR-2012-0253. Once the official version of this document 

is published in the FR, this version will be removed from the Internet and replaced with a link to the official version. 

6560-50-P 

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2012-0253; FRL-]

Approval and Promulgation of Air Quality Implementation Plan for 

1997 8-hour Ozone Standard; Arizona

AGENCY: U.S. Environmental Protection Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: EPA is proposing to approve revisions to the Arizona 

state implementation plan (SIP) that demonstrate attainment of 

the 1997 8-hour ozone national ambient air quality standards in 

the Phoenix-Mesa nonattainment area by June 15, 2009. These SIP 

revisions are the 2007 Ozone Plan developed by the Maricopa 

Association of Governments and adopted and submitted to EPA by 

the Arizona Department of Environmental Quality on June 13, 

2007. EPA is proposing to approve the 2007 Ozone Plan based on 

our determination that the plan contains all the provisions 

required for areas classified as nonattainment under Part D, 

Subpart 1 of the Clean Air Act, including the demonstration of 

reasonably available control measures (RACM), reasonable further 

progress (RFP), emission inventories, transportation conformity 

motor vehicle emission budgets for 2008, and contingency 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

2 

measures to be implemented if the Phoenix-Mesa nonattainment 

area fails to attain by June 15, 2009. 

DATE: Written comments must be received on or before [Insert 

date 30 days from the date of publication in the Federal 

Register]. 

ADDRESSES: Submit comments, identified by docket number EPA-R09-

OAR-2012-0253, by one of the following methods: 

• Federal e-Rulemaking Portal: www.regulations.gov. Follow 

the on-line instructions. 

• E-mail: lee.anita@epa.gov. 

• Mail or deliver: Marty Robin, Office of Air Planning (AIR2), U.S. Environmental Protection Agency Region IX, 75 

Hawthorne Street, San Francisco, CA 94105. 

Instructions: All comments will be included in the public docket 

without change and may be made available online at 

www.regulations.gov, including any personal information 

provided, unless the comment includes Confidential Business 

Information (CBI) or other information whose disclosure is 

restricted by statute. Information that you consider CBI or 

otherwise protected should be clearly identified as such and 

should not be submitted through www.regulations.gov or e-mail. 

The www.regulations.gov website is an “anonymous access” system, 

and EPA will not know your identity or contact information 

unless you provide it in the body of your comment. If you send 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

3 

e-mail directly to EPA, your e-mail address will be

automatically captured and included as part of the public 

comment. If EPA cannot read your comments due to technical 

difficulties and cannot contact you for clarification, EPA may 

not be able to consider your comment. 

Docket: The index to the docket for this action is available 

electronically on the www.regulations.gov website and in hard 

copy at EPA Region IX, 75 Hawthorne Street, San Francisco, 

California, 94105. While all documents in the docket are listed 

in the index, some documents may be publicly available only at 

the hard copy location (e.g., copyrighted material), and some 

may not be publicly available at either location (e.g., CBI). To 

inspect the hard copy materials, please schedule an appointment 

during normal business hours with the contact listed in the FOR 

FURTHER INFORMATION CONTACT section below. 

Copies of the SIP materials are also available for inspection at 

the following location: 

• Arizona Department of Environmental Quality, 1110 W. 

Washington Street, First Floor, Phoenix, AZ 85007, Phone: 

(602) 771-2217. 

The SIP materials are also electronically available at: 

http://www.azmag.gov/Projects/Project.asp?CMSID2=1120. 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

4 

FOR FURTHER INFORMATION CONTACT: Anita Lee, Air Planning Office 

(AIR-2), U.S. Environmental Protection Agency, Region IX, (415) 

972-3958, lee.anita@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Table of Contents 

I. The 1997 8-Hour Ozone Standard and the Phoenix-Mesa Ozone 

Nonattainment Area 

A. Background on the 1997 8-Hour Ozone NAAQS 

B. The Phoenix-Mesa 8-Hour Ozone Nonattainment Area 

II. CAA and Regulatory Requirements for 1997 8-Hour Ozone 

Nonattainment Area SIPs 

III. Arizona’s State Implementation Plan Submittal to Address 

Ozone Attainment in the Phoenix-Mesa Nonattainment Area 

A. Arizona’s SIP Submittal 

B. CAA Procedural and Administrative Requirements for SIP 

Submissions 

IV. Review of the 2007 Ozone Plan for Phoenix-Mesa 

A. Emission Inventories 

B. Reasonably Available Control Measures Demonstration and 

Control Strategy 

C. Attainment Demonstration 

D. Reasonable Further Progress Demonstration 

E. Contingency Measures 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

5 

F. Motor Vehicle Emissions Budgets for Transportation 

Conformity 

V. EPA’s Proposed Action 

VI. Statutory and Executive Order Reviews 

Throughout this document, “we”, “us” and “our” refer to EPA. 

I. The 1997 8-Hour Ozone Standard and the Phoenix-Mesa Ozone 

Nonattainment Area 

A. Background on the 1997 8-Hour Ozone NAAQS 

Ground-level ozone pollution is formed in the atmosphere 

from the reaction of volatile organic compounds (VOC) and oxides 

of nitrogen (NOx) in the presence of sunlight. These two 

pollutants, referred to as ozone precursors, are emitted by many 

types of pollution sources including on- and off-road motor 

vehicles and engines, power plants and industrial facilities, 

and smaller area sources such as lawn and garden equipment and 

paints. 

Scientific evidence indicates that adverse public health 

effects occur following exposure to ozone, particularly in 

children and adults with lung disease. Breathing air containing 

ozone can reduce lung function and inflame airways, which can 

increase respiratory symptoms and aggravate asthma or other lung 

diseases. Ozone exposure also has been associated with increased 

susceptibility to respiratory infections, medication use, doctor 

visits, and emergency department visits and hospital admissions 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

6 

for individuals with lung disease. Ozone exposure also increases 

the risk of premature death from heart or lung disease. Children 

are at increased risk from exposure to ozone because their lungs 

are still developing and they are more likely to be active 

outdoors, which increases exposure. See “Fact Sheet, Proposal to 

Revise the National Ambient Air Quality Standards for Ozone”, 

January 6, 2010 and 75 FR 2938 (January 19, 2010). 

On July 18, 1997, EPA revised the primary and secondary 

national ambient air quality standards (NAAQS or standard) for 

ozone to replace the existing 1-hour ozone standard of 0.12 

parts per million (ppm) with an 8-hour standard of 0.08 ppm1. 62 

FR 33856. EPA revised the ozone standard after considering 

substantial evidence from numerous health studies demonstrating 

that serious health effects are associated with exposures to 

ozone concentrations above the levels of these revised 

standards. 

B. The Phoenix-Mesa 8-Hour Ozone Nonattainment Area

Following promulgation of a new or revised NAAQS, EPA is 

required by Clean Air Act (CAA) section 107(d) to designate 

areas throughout the nation as attaining or not attaining the 

NAAQS. Under the implementation rule for the 1997 8-hour ozone 

standard, EPA designated certain areas as nonattainment under 

 

1 In March 2008, EPA completed another review of the primary and secondary 

ozone standards and further tightened the standards by lowering the level for 

both to 0.075 ppm. 73 FR 16436 (March 27, 2008). 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

7 

title I, part D, subpart 1 of the CAA (subpart 1) if the area’s 

1-hour ozone design value was above the level of the standard 

but below 0.121 ppm. On April 15, 2004, EPA designated PhoenixMesa as “Subpart 1” nonattainment for the 1997 8-hour ozone 

standard under CAA section 172. See 69 FR 23858 (April 30, 2004) 

and 40 CFR 81.303. The designation became effective on June 15, 

2004. Under part D, subpart 1 of the Act, states must submit 

plans to come into attainment within 3 years of the effective 

date of the nonattainment designation, and must attain the 

standard as expeditiously as practicable, but no later than 5 

years after the effective date of the designation. Arizona 

Department of Environmental Quality (ADEQ) submitted the 2007 

Attainment Plan to EPA on June 13, 20072 to attain the 1997 8-

hour ozone standard by the attainment date of June 15, 2009, 

which is 5 years after the effective date of the area’s 

designation as nonattainment.3 

In June 2007, the United States Court of Appeals for the 

District of Columbia Circuit (D.C. Circuit Court) vacated the 

 

2 Letter from Stephen A. Owens, Director, Arizona Department of Environmental 

Quality to Wayne Nastri, Regional Administrator, U.S. Environmental 

Protection Agency, Region IX, dated June 13, 2007, plus three enclosures, 

including the “Eight-Hour Ozone Plan for the Maricopa Nonattainment Area, 

dated June 2007” and Appendices Volumes one and two, dated June 2007. 

3 On March 23, 2009, ADEQ submitted to EPA a redesignation request and 

maintenance plan for Phoenix-Mesa for the 1997 8-hour ozone standard based on 

ambient ozone monitoring data for the 2006 – 2008 period. EPA has not yet 

acted on this submittal. The maintenance plan and redesignation request are 

available from the Maricopa Association of Governments at: 

http://www.azmag.gov/Projects/Project.asp?CMSID2=1120&MID=Environmental%20Pro

grams 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

8 

portion of the 2004 ozone implementation rule that allowed areas 

to be classified under subpart 1. See South Coast Air Quality 

Mgmt. Dist. v. EPA, 472 F. 3d 882 (D.C. Cir. 2006), reh’g denied 

489 F.3d 1245 (SCAQMD) (vacating certain elements of EPA’s Phase 

1 ozone implementation rule). On January 16, 2009 (74 FR 2936), 

EPA published a proposed rule to address, among other issues, 

the D.C. Circuit Court vacatur of the classification system that 

EPA used to designate a subset of initial 1997 8-hour ozone 

nonattainment areas under subpart 1. In that rulemaking, EPA 

proposed that all areas designated nonattainment for the 1997 8-

hour ozone NAAQS under subpart 1 would be classified as subpart 

2 areas (hereafter referred to as the Subpart 1/Subpart 2 

Rulemaking). The Phoenix-Mesa area is included in the areas that 

would be classified under subpart 2 if EPA's proposal is 

finalized. EPA has not yet taken final action on the Subpart 

1/Subpart 2 Rulemaking. Following completion of the Subpart 

1/Subpart 2 Rulemaking, EPA will address in a future rulemaking 

any additional requirements that become applicable to PhoenixMesa, if any, as a result of its classification under subpart 2. 

If, after Phoenix-Mesa is classified under subpart 2, EPA 

determines in a future rulemaking that the area is in attainment 

with the 1997 8-hour ozone standard, then the obligation to 

submit certain planning SIPs related to attainment of the 1997 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

9 

8-hour ozone standard pursuant to its subpart 2 classification 

would be suspended in accordance with 40 CFR 51.918. 

The Phoenix-Mesa nonattainment area is located in the 

central portion of Arizona and encompasses 4,880 square miles, 

including the urban portions of Maricopa and Pinal Counties, the 

Fort McDowell Yavapai Nation and the Salt River-Pima Maricopa 

Indian Community. For a precise description of the geographic 

boundaries of the Phoenix-Mesa nonattainment area, see 40 CFR 

81.303. The Maricopa Association of Governments (MAG) is the 

agency with primary responsibility for developing the plan to 

attain the 1997 8-hour ozone standard for Phoenix-Mesa. 

Ambient 8-hour ozone concentrations in Phoenix-Mesa vary 

depending on location and season, with the highest values 

generally occurring in May - September, in north Phoenix or the 

air quality monitors located in the mountainous northeastern 

region of the Phoenix-Mesa nonattainment area. Ozone design 

values4 from Phoenix-Mesa that exceeded the 1997 8-hour standard 

of 0.08 parts per million5 (ppm) ranged from 0.085 ppm (for the 

2000 – 2002, 2001 – 2003, and 2003 – 2005 periods) to 0.088 ppm 

(for the 1998 – 2000 and 1999 – 2001 periods). The ozone design 

 

4 A design value is an ambient concentration calculated using a specific 

methodology to evaluate monitored air quality data and is used to determine 

whether an area’s air quality meets a NAAQS. The methodology for calculating 

design values for the 8-hour ozone NAAQS is found in 40 CFR part 50, Appendix 

I. 

5 Based on the rounding conventions described in 40 CFR part 50, Appendix I, a 

design value of 0.085 ppm is the lowest value that exceeds the 1997 8-hour 

ozone NAAQS of 0.08 ppm. 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

10 

values for the Phoenix-Mesa nonattainment area for the 2004 – 

2006 period (highest design value was 0.083 ppm) and years 

thereafter were at or below the standard. See EPA Air Quality 

System (AQS) data available in the docket for this proposed 

rulemaking and Table 3 below. 

II. CAA and Regulatory Requirements for 1997 8-Hour Ozone 

Nonattainment Area SIPs 

Each area designated nonattainment for the 1997 8-hour 

ozone standard is subject to, at minimum, the general 

requirements for nonattainment area plans in subpart 1 of part 

D, title I of the CAA. Subpart 2 of part D contains more 

detailed requirements for ozone nonattainment areas classified 

under this subpart. The Phoenix-Mesa ozone nonattainment area is 

not currently classified under subpart 2.6 EPA has proposed to 

classify the Phoenix-Mesa area under subpart 2 as “marginal” 

nonattainment for the 1997 8-hour ozone NAAQS (see 74 FR 2936 at 

2944, January 16, 2009) but has not yet completed this 

rulemaking. Although a future final decision by EPA to classify 

the Phoenix-Mesa area under subpart 2 may trigger additional 

future requirements for the area, EPA believes that this does 

not prevent EPA from proposing or ultimately finalizing our 

action on the 2007 Ozone Plan in accordance with the subpart 1 

 

6 EPA now refers to these areas as “former subpart 1” nonattainment areas in 

light of the SCAQMD decision. 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

11 

requirements that currently apply to the area.7 Thus, for 

purposes of evaluating the 2007 Ozone Plan, we are reviewing it 

for consistency with the applicable requirements of part D, 

title I of the Act, which are contained in sections 172(c)(1)-

(9).8 

In order to assist states in developing effective plans to 

attain the ozone standard, EPA issued the 8-hour ozone 

implementation rule. This rule was finalized in two phases. The 

first phase of the rule addresses classifications for the 1997 

8-hour ozone standard, applicable attainment dates for the 

various classifications, and the timing of emissions reductions 

needed for attainment. See 69 FR 23951 (April 30, 2004). The 

second phase addresses SIP submittal dates and the requirements 

for reasonably available control technology and measures (RACT 

and RACM), reasonable further progress (RFP) demonstration, 

modeling and attainment demonstrations, contingency measures, 

and new source review. See 70 FR 71612 (November 29, 2005). The 

rule is codified at 40 CFR part 51, subpart X9. We discuss each 

 

7 EPA is currently obligated under the terms of a Consent Decree to take final 

action on the 2007 Ozone Plan by May 31, 2012. See WildEarth Guardians v. 

Jackson, Case No. 4:11-cv-02205-SI (N.D. CA). 

8 Although the D.C. Circuit Court in SCAQMD rejected EPA’s rationale for 

implementing the 1997 8-hour ozone standard in certain nonattainment areas 

solely under subpart 1, EPA does not believe that the Court’s ruling in this 

case alters any subpart 1 requirements that currently apply to the 2007 Ozone 

Plan. 

9 EPA has revised or proposed to revise several elements of the 8-hour ozone 

implementation rule since its initial promulgation in 2004. See, e.g., 74 FR 

2936 (January 16, 2009); 75 FR 51960 (August 24, 2010); and 75 FR 80420 

(December 22, 2010). None of these revisions affect any provision of the rule 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

12 

of the applicable CAA and regulatory requirements for 8-hour 

ozone nonattainment plans in more detail below. 

III. Arizona’s State Implementation Plan Submittal to Address 

Ozone Attainment in the Phoenix-Mesa Nonattainment Area 

A. Arizona’s SIP Submittal 

 On June 13, 2007, the Arizona Department of Environmental 

Quality (ADEQ) submitted the “Eight-Hour Ozone Plan for the 

Maricopa Nonattainment Area” (2007 Ozone Plan) to EPA as a 

revision to the Arizona SIP. The plan was deemed complete by 

operation of law on December 13, 2007. MAG developed the 2007 

Ozone Plan and the MAG Regional Council Executive Committee 

adopted the plan on June 11, 2007. ADEQ adopted the plan on June 

13, 200710. The 2007 Ozone Plan contains complete emission 

inventories for ozone precursors for 2002 and 2008,

photochemical modeling to demonstrate that the standard will be 

attained in 2008 through the continued implementation of 

federal, state, and local control measures, motor vehicle 

emission budgets (MVEBs) used for transportation conformity, and 

descriptions of the State’s compliance with CAA requirements for 

“Subpart 1” ozone nonattainment areas. We are proposing to 

 

that is applicable to our proposed action today on the Phoenix-Mesa 2007 8-

hour Ozone SIP. 

10 Letter from Stephen A. Owens, Director of Arizona Department of 

Environmental Quality, to Wayne Nastri, Regional Administrator, U.S. 

Environmental Protection Agency, Region IX, “Submittal of the Eight-Hour 

Ozone Plan for the Maricopa County Nonattainment Area”. June 13, 2007. 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

13 

approve the 2007 Ozone Plan for the Phoenix-Mesa nonattainment 

area. 

B. CAA Procedural and Administrative Requirements for SIP 

Submittals

CAA sections 110(a)(1) and (2) and 110(l) require a state 

to provide reasonable public notice and opportunity for public 

hearing prior to the adoption and submittal of a SIP or SIP 

revision. To meet this requirement, every SIP submittal should 

include evidence that adequate public notice was given and an 

opportunity for a public hearing was provided consistent with 

EPA’s implementing regulations in 40 CFR 51.102. 

MAG has satisfied the applicable statutory and regulatory 

requirements for reasonable public notice and hearing prior to 

adoption and submittal of the 2007 Ozone Plan. MAG and ADEQ 

jointly held two public hearings on June 1, 2007 and June 4, 

2007. As evidence of notification of public hearings consistent 

with 40 CFR 51.102, the SIP submittal includes proof of 

newspaper publication and copies of letters sent to EPA and 

affected federal, state, and local agencies notifying interested 

parties of the joint MAG and ADEQ public hearings. We find, 

therefore, that the 2007 Ozone Plan submittal meets the 

procedural requirements for public notice and hearing in 

sections 110(a) and 110(l) of the CAA. 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

14 

CAA section 110(k)(1)(B) requires EPA to determine whether 

a SIP submittal is complete within 60 days of receipt. This 

section also provides that any plan submittal that EPA has not 

affirmatively determined to be complete or incomplete will be 

deemed complete by operation of law six months after the date of 

submittal. EPA’s SIP completeness criteria are found in 40 CFR 

part 51, Appendix V. The 2007 Ozone Plan, submitted by ADEQ on 

June 13, 2007, was deemed complete by operation of law on 

December 13, 2007. 

IV. Review of the 2007 Ozone Plan for Phoenix-Mesa 

 EPA evaluated the 2007 Ozone Plan according to the general 

subpart 1 nonattainment plan requirements contained in section 

172(c) of the Act. 

A. Emission Inventories 

1. Requirements for Emissions Inventories 

 CAA section 172(c)(3) requires each state with an ozone 

nonattainment area to submit plan provisions that include a 

“comprehensive, accurate, current inventory of actual emissions 

from all sources of the relevant pollutant or pollutants in such 

area, including such periodic revisions as the Administrator may 

determine necessary to assure that the requirements of this part 

are met”. EPA has issued the “Emissions Inventory Guidance for 

Implementation of Ozone and Particulate Matter National Ambient 

Air Quality Standards (NAAQS) and Regional Haze Regulations” (EI 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

15 

Guidance),11 which provides guidance on how to develop base year 

and future year baseline emission inventories for 8-hour ozone, 

PM2.5, and regional haze SIPs. For areas designated nonattainment 

for the 8-hour ozone standard in 2004, EPA recommends using 

calendar year 2002 as the base year for the inventory. EI 

Guidance, p. 8. 

 Emissions inventories for ozone should include emissions of 

VOC, NOx and carbon monoxide (CO) and represent an average summer 

week day during the ozone season. EI Guidance, pp. 14 and 17. 

States should include documentation in their submittals 

explaining how the emissions data were calculated. 70 FR at 

71664 and EI Guidance p. 40. In estimating mobile source 

emissions, states should use the latest emissions models and 

planning assumptions available at the time the SIP is developed. 

68 FR at 32854 and 70 FR 71666. 

2. Emission Inventories in the 2007 8-Hour Ozone Plan 

 The base year and future year baseline inventories for NOx, 

CO and VOC for the Phoenix-Mesa nonattainment area, together 

with additional documentation for the inventories, are found in 

Volume 1 of the Appendices to the 2007 Ozone Plan12. These 

 

11 “Emissions Inventory Guidance for Implementation of Ozone and Particulate 

Matter National Ambient Air Quality Standards (NAAQS) and Regional Haze 

Regulations”, EPA-454/R-05-001, November 2005. This document is available at: 

http://www.epa.gov/ttnchie1/eidocs/eiguid/index.html. 

12 By “future year baseline inventories” or “projected baseline inventories”, 

we mean projected emission inventories for future years that account for, 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

16 

inventories represent average summer day (ozone season) 

emissions. A base year inventory is provided for 2002 and the 

projected baseline inventory is provided for the attainment year 

of 2008.13 All inventories include NOx, CO, and VOC emissions 

from point, area, nonroad mobile, and onroad mobile sources, 

except that biogenic emission inventories include only NOx and 

VOC emissions. 

The 2002 Periodic Emission Inventory (PEI) emissions 

estimates for Maricopa County and the Phoenix-Mesa nonattainment 

area, which provided the basis for the 2002 base year inventory, 

were calculated in terms of annual emissions and ozone seasonday emissions. Emissions from point sources were estimated from 

each identified facility through permit system databases and 

annual emission reports submitted to the facility’s permitting 

authority. Emissions from area sources were estimated by source 

category using information from permit databases and previous 

SIP inventories. Nonroad mobile source emissions were estimated 

with the EPA NONROAD 2002 model and onroad mobile source 

emissions were estimated from emission factors for various 

vehicle classes from MOBILE6.2 combined with estimates of 

 

among other things, the ongoing effects of economic growth and adopted 

emission control requirements. 

13 EPA’s ozone implementation rule defines “attainment year ozone season” as 

“the ozone season immediately preceding a nonattainment area’s attainment 

date.” 40 CFR 51.900(g). Because the attainment date for Phoenix-Mesa is June 

15, 2009, we refer to 2008 as the attainment year, and the 2008 ozone season 

as the “attainment year ozone season.” 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

17 

vehicle miles traveled (VMT) using data submitted by the Arizona 

Department of Transportation to the U.S. Department of 

Transportation’s Federal Highway Administration for the 2002 

Highway Performance and Monitoring System. Biogenic emissions of 

NOx and VOC were calculated using MAGBEIS2, a modified version of 

the UAM-BEIS2 model developed specifically for use in Maricopa 

County, based on land use information, surface temperature data, 

and emission factors for land use categories. See 2002 Periodic 

Emissions Inventory for Ozone Precursors, June 2004 in Volume 1 

of the Appendices to the 2007 Ozone Plan. 

Ozone precursor emissions from point, area, onroad, and 

nonroad sources used in the modeling domain (Table 1) were 

developed from the Comprehensive Air Quality Model with 

Extensions (CAMx), version 4.40, and the Emissions Preprocessor 

System (EPS3.0), based on the 2002 Periodic Emission Inventory 

for the three ozone episodes modeled for 2002. Biogenic VOC 

emission estimates used for the 2002 modeling domain (e.g., 

451.3 metric tons per day in the June 2002 ozone episode) are 

significantly higher than biogenic VOC emissions estimated in 

the 2002 PEI (e.g., 41.7 metric tons per ozone season day). 

Section III of Appendix A, Exhibit 2 of the 2007 Ozone Plan 

describes the method used to estimate biogenic emissions for the 

modeling domain. MAG used a model developed in 2005, called 

Model of Emissions of Gases and Aerosols from Nature (MEGAN), 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

18 

that was determined to be more reliable and accurate for 

Maricopa County because it relies on local field studies that 

identified dominant plant species and emission factors, as well 

as locations and biomass densities, to estimate biogenic 

emissions of ozone precursors. In the 2002 base year inventory, 

biogenic sources contributed 65 percent to total VOC emissions. 

In contrast, anthropogenic onroad mobile sources dominated the 

total NOx emissions and accounted for 63 percent of total NOx. 

See Tables 5-3 and 5-4 of the 2007 Ozone Plan. 

 The 2002 inventory was projected to 2008 by accounting for 

expected growth factors, ongoing control programs, and 

retirement rates for obsolete sources of emissions. MAG 

accounted for known projects in 2008 (e.g., the Phoenix 

Expansion Project of the Transwestern Pipeline Company) and 

additionally applied a five percent increase to onroad mobile 

source emissions of NOx and a three percent increase to all other 

anthropogenic emissions of VOC and NOx. The three percent 

increase was based on population projections prepared by the 

Arizona Department of Economic Security, based on a 2005 special 

census in Maricopa County. MAG applied the five percent increase 

to onroad mobile source emissions of NOx to create a safety 

margin for transportation conformity. See 2007 Ozone Plan, p. 5-

5, and Appendices to Ozone Plan, Volume 1. 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

19 

 For biogenic emissions, the 2002 inventory was held 

constant for 2008. In additional information provided to EPA, 

MAG explained that no projected land use or land cover data was 

available for the 2008 attainment year, therefore biogenic 

emissions in the ozone modeling domain were held constant14. In 

the approved 1-hour ozone maintenance plan, MAG projected an 

increase in VOC emissions from the Phoenix Metropolitan 

nonattainment area due to changes in land use, i.e., increasing 

urbanization and residential land use and decreasing use of land 

for agriculture. See 70 FR at 13437. The 1-hour ozone 

maintenance plan relied on MAGBEIS2 to estimate biogenic 

emissions from the nonattainment area and modeling domain.15 As 

shown in the additional information provided by MAG on February 

8, 2012, the MAGBEIS2 VOC emission factor for urbanized land use 

is greater than the VOC emission factor for agricultural land 

use, therefore, based on the projected increased urbanization in 

the 1-hour ozone nonattainment area, VOC emissions projected by 

MAGBEIS2 increased from the 1999 base year to the 2015 

maintenance year. In contrast, as described above, the 2007 8-

hour ozone plan relied on a new biogenic emissions model (MEGAN) 

that is more representative of Maricopa County and its desert 

environment. The additional information provided by MAG shows 

 

14 Email from Cathy Arthur, MAG, to Anita Lee, EPA, re: “Biogenic VOCs” on 

February 8, 2012, plus two attachments on land use boundaries and emission 

factors. 

15 Ibid.
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

20 

the urbanized land use emission factors from MEGAN are lower 

than emission factors associated with agriculture or other 

undeveloped desert landscapes in Maricopa County. Therefore, 

using MEGAN, MAG expects that the trend of increasing 

urbanization (as projected in the 1-hour ozone maintenance plan) 

is expected to decrease VOC emissions from Maricopa County. 

Because MAG did not have 2008 land use data available, it 

determined that maintaining constant biogenic emissions of the 

ozone precursors would be more conservative than attempting to 

estimate the anticipated decrease in biogenic VOC emissions.16 

 

Table 1: Emission Inventories for the Phoenix-Mesa Modeling 

Domain for June Ozone Episode (metric tons per day)

 NOx VOC 

2002 2008 2002 2008 

Point 11.15 32.78 11.72 13.55 

Area 9.79 13.49 90.56 105.03 

Nonroad Mobile 79.97 86.58 50.73 57.55 

Onroad Mobile 182.36 145.52 91.84 72.34 

Biogenics 8.56 8.56 451.28 451.28 

Total 291.82 286.93 696.13 699.75 

Source: 2007 Ozone Plan at Tables 5-3 and 5-4. 

 

16Ibid.
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

21 

3. Proposed Action on the Emission Inventories 

 We have reviewed the 2002 base year inventory and the 

inventory methodologies used in the 2007 Ozone Plan and believe 

that the inventory was developed consistent with the CAA 

requirements as reflected in the 8-hour ozone implementation 

rule and EPA’s guidance. The 2002 base year inventory is a 

comprehensive inventory of actual emissions of ozone precursors 

in the Phoenix-Mesa nonattainment area. We therefore propose to 

approve the base year inventory as meeting the requirements of 

CAA section 172(c)(3) and EPA’s 8-hour ozone implementation 

rule. 

B. Reasonably Available Control Measures Demonstration and 

Control Strategy 

1. Requirements for RACM and Control Strategies 

 CAA Section 172(c)(1) requires that each attainment plan 

“provide for the implementation of all reasonably available 

control measures as expeditiously as practicable (including such 

reductions in emissions from existing sources in the area as may 

be obtained through the adoption, at a minimum, of reasonable 

available control technology), and shall provide for attainment 

of the national primary ambient air quality standards.” The 8-

hour ozone implementation rule requires that for each 

nonattainment area that is required to submit an attainment 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

22 

demonstration, the state must also submit concurrently a SIP 

revision demonstrating that it has adopted all RACM necessary to 

demonstrate attainment as expeditiously as practicable and to 

meet any RFP requirements. 40 CFR 51.912(d). 

 EPA has previously provided guidance interpreting the RACM 

requirement in the General Preamble at 1356017 and in a 

memorandum entitled “Guidance on the Reasonably Available 

Control Measure Requirement and Attainment Demonstration 

Submissions for Ozone Nonattainment Areas”, John Seitz, 

Director, OAQPS to Regional Air Directors, November 30, 1999 

(Seitz memo). In summary, EPA guidance provides that, to address 

the requirement to adopt all RACM, states should consider all 

potentially reasonable control measures for source categories in 

the nonattainment area to determine whether they are reasonably 

available for implementation in that area and whether they 

would, if implemented individually or collectively, advance the 

area’s attainment date by one year or more. See Seitz memo and 

General Preamble at 1356018. Any measures that are necessary to 

 

17 The “General Preamble for the Implementation of Title I of the Clean Air 

Act Amendments of 1990”, published at 57 FR 13498 on April 16, 1992, 

describes EPA’s preliminary view on how we would interpret various SIP 

planning provisions in title I of the CAA as amended in 1990, including those 

planning provisions applicable to the 1-hour ozone standard. EPA continues to 

rely on certain guidance in the General Preamble to implement the 8-hour 

ozone standard under title I. 

18 See also “State Implementation Plans; General Preamble for Proposed 

Rulemaking on Approval of Plan Revisions for Nonattainment Areas”, 44 FR 

20372 (April 4, 1979), and Memorandum dated December 14, 2000 from John S. 

Seitz, Director, Office of Air Quality Planning and Standards, “Additional 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

23 

meet these requirements that are not already either federally 

promulgated, part of the state’s SIP, or otherwise creditable in 

SIPs must be submitted in enforceable form as part of a state’s 

attainment plan for the area. 

 CAA section 172(c)(6) requires nonattainment plans to 

“include enforceable emission limitation, and such other control 

measures, means, or techniques (including economic incentives 

such as fees, marketable permits, and actions of emission 

rights), as well as schedules and timetables for compliance, as 

may be necessary or appropriate to provide for attainment of 

such standard in such area by the applicable attainment date * * 

*.” See also CAA section 110(a)(2)(A). The ozone implementation 

rule requires that all control measures needed for attainment be 

implemented no later than the beginning of the attainment year 

ozone season. 40 CFR 51.908(d). The attainment year ozone season 

is defined as the ozone season immediately preceding a 

nonattainment area’s attainment date. 40 CFR 51.900(g). 

2. RACM Demonstration and the Control Strategy in the 2007 Ozone 

Plan 

 The attainment demonstration for the Phoenix-Mesa 

nonattainment area, which we discuss further in section IV.D of 

this document, shows that implementation of all of the measures 

 

Submission on RACM from States with Severe One-Hour Ozone Nonattainment Area 

SIPs”. 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

24 

identified as RACM for the 1997 8-hour ozone NAAQS would enable 

the Phoenix-Mesa area to attain the 1997 8-hour ozone standard 

during the 2008 ozone season, preceding the 2009 attainment date 

for the area. EPA previously approved all of the key NOx and VOC 

control measures, including several dozen VOC RACT rules, as 

part of Arizona’s plans for attaining and maintaining the 1-hour 

ozone standard in Phoenix-Mesa.19 The 2007 Ozone Plan 

specifically relies on seven of these control measures to 

demonstrate attainment of the 1997 8-hour ozone standard by June 

15, 2009, and provides for implementation of these measures by 

the beginning of the attainment year ozone season (January 

2008), consistent with the requirements of 40 CFR 51.908(d). See 

2007 Ozone Plan at pp. 4-2 through 4-7.20 We discuss below the 

seven measures that the attainment demonstration in the 2007 

Ozone Plan relied on to reduce emissions of VOC and/or NOx (see 

Table 2). Emission reductions associated with each measure were 

estimated for the June 2008 ozone episode modeled for the 

attainment demonstration. Of these seven measures, phased-in 

 

19 See, e.g., 2007 Ozone Plan at Table 1-1; 68 FR 2912 (January 22, 2003); 69 

FR 10161 (March 4, 2004); 70 FR 30370 (May 26, 2005); 70 FR 13425 (March 21, 

2005) (proposed redesignation of Phoenix to attainment for the 1-hour 

standard) and 70 FR 34362 (June 14, 2005) (final redesignation). RACT rules 

for NOx were not required for purposes of attaining and maintaining the 1-hour 

ozone NAAQS in Phoenix-Mesa because EPA approved a petition for NOx exemption 

for this purpose. 60 FR 19510 (April 19, 1995). 

20 The 2007 Ozone Plan refers to these seven control measures as “attainment 

measures,” to be distinguished from “baseline measures,” which were taken 

into account in the base year and projection year emission inventories. See 

2007 Ozone Plan at 4-2 and Volume 1 of the Appendices to the 2007 Ozone Plan 

at Table III-1. 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

25 

emission test cutpoints and the development of intelligent 

transportation systems resulted in the greatest reduction in VOC 

emissions, and the summer fuel reformulation resulted in the 

greatest reduction in NOx emissions. 

Table 2: 2008 Emission Reductions from “Attainment Measures” 

 VOC NOx

 Metric 

ton/day 

reduction 

% change 

compared to 

2008 base 

case 

Metric 

ton/day 

reduction 

% change 

compared to 

2008 base 

case 

Summer Fuel 

Reformulation 

(0.1) 

(increase) 

< 0.1% 

(increase) 

10.3 3.5% 

Phased-in Emission Test 

Cutpoints 

3.1 1.2% 2.6 0.9% 

One Time Waiver from 

Vehicle Emissions Test 

0.1 < 0.1% < 0.1 < 0.1% 

Coordinate Traffic 

Signal Systems 

< 0.1 < 0.1% < 0.1 < 0.1% 

Develop Intelligent 

Transportation Systems 

2.2 0.9% 0.4 0.1% 

Tougher Enforcement of 

Vehicle Registration and 

Emission Test Compliance 

0.2 < 0.1% 0.1 < 0.1% 

Rule 358: Polystyrene 

Foam Operations 

0.5 0.2% N/A N/A 

Total 6.0 2.4% 13.4 4.6% 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

26 

 Source: 2007 Ozone Plan at Table 5-2. 

a. Summer Fuel Reformulation 

 The 2007 Ozone Plan relies on H.B. 2307, a Cleaner Burning 

Gasoline (CBG) program passed by the Arizona Legislature in 

1997. The CBG program contains requirements related to seasonal 

changes in gasoline formulation related to vapor pressure and 

oxygen content. Typically, fuel reformulation measures are 

designed to reduce summertime evaporative VOC emissions. 

However, the results of MAG’s emissions modeling analyses 

suggest that the summer reformulation measure would increase VOC 

emissions slightly and significantly reduce emissions of NOx. In 

Volume 2 of the Appendices to the 2007 Ozone Plan, in response 

to EPA comments, MAG explains that the slight increase in 

projected VOC emissions from the summer fuel reformulation 

measure occurred because the MOBILE6.2 input for the measure 

specified a Reid vapor pressure (RVP) of 7.0 pounds per square 

inch (psi). Actual fuel specifications for the 2002 base case 

used actual fuel specifications from the Arizona Department of 

Weights and Measures that were lower than 7.0 psi. The projected 

decrease in NOx emissions in 2008 from the summer fuel 

reformulation measure is a result of the removal of the 

summertime (April 1 through November 1) minimum oxygen content 

standard for Type 1 gasoline. Oxygenates in fuel are used to 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

27 

improve combustion as a control strategy for CO and other 

products of incomplete combustion, for example unburned VOCs; 

however improved combustion also tends to increase formation of 

NOx. Therefore, removal of the minimum summertime oxygenate 

standard is projected to reduce formation of NOx. See 2007 Ozone 

Plan at 4-2, 4-3. 

b. Phased-in Emission Test Cutpoints 

 The 2007 Ozone Plan describes two measures passed by the 

Arizona Legislature that comprise this attainment measure: H.B. 

2237, passed in 1997, that appropriates funds from the State 

General Fund to develop and implement an alternative test 

protocol to reduce false failure rates associated with the more 

stringent standards for the Vehicle Emissions Testing Program, 

and S.B. 1427, which requires vehicles in certain areas to be 

emission tested and requires owners of the newest five model 

year vehicles to be exempt from testing but to pay an in lieu 

fee that is deposited into the Arizona Clean Air Fund, effective 

December 31, 1998. Using MOBILE6.2, MAG estimated that this 

measure reduces NOx emissions by 2.6 metric tons per day in the 

June 2008 ozone episode and VOC emissions by 3.1 metric tons per 

day. See 2007 Ozone Plan at 4-3, 4-4. 

c. One Time Waiver from Vehicle Emissions Test 

The Arizona Legislature passed S.B. 1002 which limits 

issuance of a waiver for failure to comply with emission testing 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

28 

requirements to one-time only, effective January 1, 1997. MAG 

modeled this measure in MOBILE6.2 by adjusting the percentage of 

waivers allowed and estimated that this measure reduces NOx

emissions by less than 0.1 metric tons per day in the June 2008 

ozone episode and VOC emissions by 0.1 metric tons per day. See 

2007 Ozone Plan at 4-4. 

d. Coordinate Traffic Signal Systems 

 House Bill 2237 passed by the Arizona Legislature contains 

appropriations for fiscal years 1997-1998 and 1998-1999 to 

Arizona Department of Transportation for distribution to cities 

and counties for synchronization of traffic signals within and 

across jurisdictional boundaries. MAG modeled this measure in 

MOBILE6.2 by adjusting the input for idling time at traffic 

signals and estimated that this measure reduces NOx emissions by 

less than 0.1 metric tons per day in the June 2008 ozone episode 

and VOC emissions by less than 0.1 metric tons per day. See 2007 

Ozone Plan at 4-4, 4-5. 

e. Develop Intelligent Transportation Systems 

 The 2007 Ozone Plan cites three committed control measures 

in the 1-hour Ozone Maintenance Plan that serve to reduce 

traffic congestion: “Coordinate Traffic Signal Systems”, 

“Develop Intelligent Transportation Systems”, and “Reduce 

Traffic Congestion at Major Intersections”. The 2007 Ozone Plan 

describes these measures as technologies implemented on the 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

29 

local level over fiscal years 2003-2006 that reduce VOC and NOx

emissions by reducing congestion. MAG estimated emission 

reductions from these measures to be 0.4 metric tons of NOx per 

day in the June 2008 ozone episode and 2.2 metric tons of VOC 

per day. See 2007 Ozone Plan at 4-5. 

f. Tougher Enforcement of Vehicle Registration and Emission Test 

Compliance 

 The 2007 Ozone Plan cites two measures from the Arizona 

Legislature and a program implemented by the Arizona Motor 

Vehicle Division of the Arizona Department of Transportation 

that collectively improve enforcement of vehicle registration 

and compliance with vehicle testing requirements: S.B. 1427 

passed in 1998 that requires school and special districts in 

certain areas to prohibit employees who have not complied with 

emission testing requirements from parking in employee parking 

lots, and H.B. 2254 passed in 1999 that requires vehicles owned 

by federal, state, or political state subdivisions in Arizona 

to comply with A.R.S 49-542. MAG modeled this measure in 

MOBILE6.2 by adjusting the weighting between inspection and 

maintenance (I/M) and non-I/M emission factors, and estimated 

that this measure reduces NOx emissions by 0.1 metric tons per 

day in the June 2008 ozone episode and VOC emissions by 0.2 

metric tons per day. See 2007 Ozone Plan at 4-5, 4-6. 

g. Maricopa County Rule 358: Polystyrene Foam Operations 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

30 

 Rule 358 adopted by Maricopa County on April 20, 2005 

limits VOC emissions from the manufacturing of expandedpolystyrene products. MAG relied on information provided by the 

Maricopa County Air Quality Department that Rule 358 would 

result in 80 percent control effectiveness and 80 percent rule 

effectiveness. MAG estimated VOC emission reductions to be 0.5 

metric tons per day in the June 2008 ozone episode, with no 

effect on emissions of NOx. See 2007 Ozone Plan at 4-6, 4-7. 

3. Proposed Actions on the RACM Demonstration and Control 

Strategy 

 Based on our review of the RACM analysis and Arizona’s 

adopted rules, we propose to find that the 2007 Ozone Plan 

provides for implementation of all reasonably available control 

measures necessary to demonstrate expeditious attainment of the 

1997 8-hour ozone standard and to meet any related RFP 

requirements in the Phoenix-Mesa nonattainment area, consistent 

with the applicable requirements of CAA section 172(c)(1) and 40 

CFR 51.912. 

C. Attainment Demonstration 

1. Requirements for Attainment Demonstration 

CAA section 172(c)(1) requires states with ozone 

nonattainment areas to submit plan provisions that provide for 

attainment of the national ambient air quality standards. See 

also 40 CFR 51.908. The attainment demonstration should include: 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

31 

(1) Technical analyses to locate and identify sources of 

emissions that are causing violations of the 8-hour ozone NAAQS 

within the nonattainment area; 

 (2) Adopted measures with schedules for implementation and 

other means and techniques necessary and appropriate for 

attainment; and 

 (3) Contingency measures required under section 172(c)(9) 

of the CAA. 

 See 70 FR 71612 at 71615. 

 The requirements for the first two items are described in 

the sections on emission inventories and RACM/RACT above 

(sections IV.A and IV.B) and in the sections on air quality 

modeling and attainment demonstration that follow immediately 

below. Requirements for the third item are described in the 

section on contingency measures (IV.F.). 

2. Air Quality Modeling in the Phoenix-Mesa 2007 Ozone Plan 

 Under EPA’s ozone implementation rule, an attainment 

demonstration must meet the air quality modeling and other 

requirements of 40 CFR 51.112 and must be supported “by means of 

a photochemical grid model or any other analytical method 

determined by [EPA] to be at least as effective.” 40 CFR 51.908. 

Air quality modeling is used to establish attainment emissions 

targets, that is, a combination of ozone precursor emission 

levels that the area can accommodate without exceeding the 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

32 

NAAQS, and to assess whether the proposed control strategy will 

result in attainment of the NAAQS. 

Air quality modeling is performed for a base year and 

compared to air quality monitoring data from that year in order 

to evaluate model performance. Once the performance is 

determined to be acceptable, future year changes to the 

emissions inventory are simulated with the model to determine 

the effect of emissions reductions on ambient air quality. The 

procedures for modeling ozone as part of an attainment 

demonstration are contained in EPA's “Guidance on the Use of 

Models and Other Analyses for Demonstrating Attainment of Air 

Quality Goals for the 8-Hour Ozone and PM2.5 NAAQS and Regional 

Haze” (Guidance). The Guidance also recommends that 

supplemental analyses be performed, and used in combination with 

the modeling in a Weight of Evidence determination that the 

control strategy will result in attainment of the NAAQS. 

Guidance p. 17. 

The air quality modeling is described in Chapter 3 of the 

2007 Ozone Plan and documented in Volume One of the Appendices 

to the 2007 Ozone Plan, in Appendix A, Exhibit 2 (“Modeling 

TSD”). We provide a brief description of the modeling and a 

summary of our evaluation of it below. 

MAG performed the air quality modeling for the 2007 Ozone 

Plan using the Comprehensive Air Quality Model with Extensions 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

33 

(CAMx) photochemical model, incorporating meteorological fields 

from the Mesoscale Model version 5 (MM5). These models have 

been extensively used in developing SIP attainment 

demonstrations and are identified in EPA Guidance as candidate 

models. Guidance pp. 139 & 160. While there was no intensive 

field study for this modeling effort, 31 ozone stations and 56 

meteorological stations provided an ample database of routinely 

collected data for use in model application development and 

performance evaluation. 

EPA recommends that States prepare modeling protocols as 

part of their modeled attainment demonstrations. Guidance, p. 

133. The Guidance at pp. 133-134 describes the topics to be 

addressed in this modeling protocol. A modeling protocol should 

detail the procedures for conducting the modeling analysis, such 

as the background and objectives, the schedule and 

organizational structure, selection of ozone episodes to model, 

meteorological and emissions input data preparation, model 

performance evaluation, interpreting modeling results, and 

procedures for using the model to demonstrate whether proposed 

strategies are sufficient to attain the NAAQS. The 2007 Ozone 

Plan’s modeling protocol is contained in Volume Two of the 

Appendices to the 2007 Plan, in Appendix I-i, and covers all of 

the topics recommended in the Guidance. 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

34 

A key part of the modeling protocol is the selection of 

ozone episodes to be modeled. An attainment demonstration that 

is robust despite natural variability should include modeling of 

multiple days with high ozone concentrations, spanning the range 

of meteorological conditions that lead to exceedances of the 

NAAQS in the area. Guidance p. 146. Volume two of the Appendices 

to the 2007 Ozone Plan, Attachment II, has a thorough 

description of the episode selection process. A climatology of 

high ozone days for 1987-2004 was prepared, considering synoptic 

meteorological conditions, temperature, wind speed, wind 

direction, and frequency of high ozone by month, day of week, 

and hour of day. For the more recent 2000-2004 period, ozone 

spatial patterns were examined, and back trajectories prepared 

to help assess whether ozone was locally generated or partly due 

to transport from outside the domain. High temperature occurred 

on summer days whether they exceeded the standard or not, and so 

was not useful in selecting episodes. Typical features of 

episodes are high ozone concentrations northeast of central 

Phoenix and winds from the east in the morning, shifting to 

south at midday, and then southwesterly in the afternoon. Based 

on the analysis, MAG identified three meteorological regimes 

leading to high ozone concentrations, and six candidate recent 

ozone episodes. On the basis of ozone episode severity and 

duration, MAG chose three of the episodes for modeling. Regime 1 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

35 

is characterized by stagnant winds and purely local generation 

of ozone; it includes some weekend exceedances. It is 

represented by the July 8-14, 2002 episode with a maximum ozone 

concentration of 107 ppb at Maryvale, and eight other exceeding 

sites; this was the episode with the highest ozone concentration 

during the 2000-2004 period. Regime 2 is characterized by light 

winds, with potential for transport from the south and 

southwest. It is represented by the June 3-7, 2002 episode with 

a maximum ozone concentration of 92 ppb at Fountain Hills, and 

eleven other exceeding sites. Regime 3 is characterized by a 

non-calm winds from other directions. It is represented by the 

August 5-11, 2001 episode with a maximum ozone concentration of 

99 ppb at Cave Creek, and four other exceeding sites. (Both 

regimes 2 and 3 occur in this episode.) The regimes had in 

common low wind speeds, partial cloud cover, and a low pressure 

system in the southwest of the State and a high pressure system 

in the northeast. EPA finds the selection process to be welldocumented and well-reasoned, and the selected episodes to be a 

good basis for the attainment demonstration. 

Section IV of the Modeling TSD in Volume one of the

Appendices to the 2007 Ozone Plan includes extensive statistical 

and graphical analysis demonstrating adequate overall model 

performance for the June 2002 episode, but also shows consistent 

underprediction for the August 2001 and July 2002 episodes. 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

36 

Under EPA Guidelines, models are used in a relative sense (see 

discussion on Relative Response Factors below), so although 

underpredictions in model performance do not necessarily mean 

that future design values would be underpredicted, they do 

suggest that these two episodes may be less reliable for 

predicting the effect of emissions changes. Thus, primary weight 

was given to the June 2002 episode in the attainment 

demonstration. CAMx model diagnostic sensitivity tests were 

performed by MAG to provide assurance that the model is 

adequately simulating the physical and chemical processes 

leading to ozone in the atmosphere and that the model responds 

in a scientifically reasonable way to emissions changes. The 

tests included zeroing out boundary condition concentrations, 

initial condition concentrations, and various categories of 

emissions. The model responded in a physically reasonable way in 

each of these tests. MAG also undertook sensitivity tests for 

MM5, which provides meteorological input to the CAMx air quality 

model. These are described in Appendix III to the Modeling TSD, 

and included incorporation of alternative observational data 

sets, and an alternative convection scheme to avoid

overestimating convective rainfall in this dry southwestern 

area. The meteorological model was found to perform adequately 

for wind speed, wind direction, temperature, and humidity. EPA 

finds the procedures MAG followed to be well-documented and 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

37 

reasonable, and to be acceptable for supporting the modeled 

attainment demonstration. 

For the modeled attainment test, the model is used to 

predict the air quality effect of changes in emissions due to 

land use changes, growth, and the effect of control measures. 

Under current EPA Guidance, the model is used to develop 

Relative Response Factors (RRFs) that give the model’s response 

to emission changes, and the RRFs are applied to monitored 

design value concentrations to arrive at the predicted future 

concentrations. The particulars of the calculation, and which 

model grid cells and modeled days are to be included, are 

specified in the EPA Guidance. Guidance pp. 15, 25, and 155. 

MAG assessed the 2008 effect of the seven control measures using 

the EPA-specified procedure, and found the maximum predicted 

ozone design value to be 84 ppb, which is in attainment of the 

ozone NAAQS. It should be noted that this result includes 5 

percent additional NOx to create a safety margin for the 

transportation conformity motor vehicle emissions budget. EPA 

agrees that MAG’s modeling demonstrates attainment of the ozone 

NAAQS by summer 2008. 

In addition to a modeled attainment demonstration, which 

focuses on locations with an air quality monitor, EPA generally 

requires an Unmonitored Area Analysis. This analysis is intended 

to ensure that a control strategy leads to reductions in ozone 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

38 

at other locations that have no monitor but that might have base 

year (and/or future year) ambient ozone levels exceeding the 

NAAQS. The unmonitored area analysis uses a combination of model 

output and ambient data to identify areas that might exceed the 

NAAQS if monitors were located there. In order to examine 

unmonitored areas in all portions of the modeling domain, EPA 

recommends use of interpolated spatial fields of ambient data 

combined with gridded modeled outputs. Guidance, p. 29. MAG used 

a variation of the EPA-described approach, described in section 

V of the modeling TSD, as a corroboratory screening test. The 

attainment demonstration passed this corroboratory screening 

test. EPA notes that concentration gradients in the supplied 

spatial isopleth maps appear to be weak except in the downtown 

area where the monitoring network is fairly dense and the RRFs 

themselves have only weak spatial variation. We believe the 

plan’s Unmonitored Area Analysis is adequate. 

Finally, the Weight of Evidence Analysis in Appendix V of 

the Modeling TSD, in Volume two of the Appendices to the 2007 

Ozone Plan, includes several supplemental analyses in support of 

the attainment demonstration. These include ozone air quality 

trends and precursor emission trends, both of which show 

continued progress and support the conclusion that the 

attainment demonstration is sound. Appendix G of Attachment II 

to the modeling protocol, in Volume two of the Appendices to the 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

39 

2007 Ozone Plan also illustrated the downward ozone trends at 

all ozone monitors. Other analyses examined the sensitivity of 

the model to NOx reductions, the representation of VOC speciation 

in the model, the VOC:NOx ratio as a photochemical indicator, 

Process Analysis, and examination of Weekday vs. Weekend 

effects. These analyses provided observational and modeling 

evidence that the model is correctly replicating the ozone 

photochemistry of the area, and that the Weight of Evidence 

supports the conclusion that the Phoenix-Mesa will attain the 

ozone NAAQS in 2008. Additionally, Table 3 below shows that 

design values (DV) in ppm from all monitors in the Phoenix-Mesa 

nonattainment area, operated by three different agencies (Pinal 

County Air Quality Control District (PCAQCD), Maricopa County 

Air Quality Division (MCAQD), and ADEQ), appear to have been 

meeting the 1997 ozone NAAQS based on monitored ozone 

concentrations since 2005. 

EPA proposes to find that the modeling provides an adequate 

basis for the RACM/RACT, RFP, and attainment demonstrations in 

the Phoenix-Mesa 2007 8-Hour Ozone Plan. 

Table 3: Ozone Design Values from 2005 – 2010 Monitoring Data in 

Phoenix-Mesa Nonattainment Area* 

Site Site ID Agency 2005-07 2006-08 2007-09 2008-10

Apache 

Junction 

04-013- PCAQCD DV (ppm) 0.076 0.080 0.075 0.073 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

40 

3001 % complete 99 99 99 99 

Buckeye 04-013-

4011 

MCAQD DV (ppm) 0.065 0.066 0.064 0.064 

% complete 100 100 100 100 

Blue Point 04-013-

9702 

MCAQD DV (ppm) 0.067 0.064 0.067 0.070 

% complete 100 94 99 99 

Cave Creek 04-013-

4008 

MCAQD DV (ppm) 0.079 0.078 0.075 0.074 

% complete 100 100 100 100 

Central 

Phoenix 

04-013-

3002 

MCAQD DV (ppm) 0.075 0.074 0.070 0.071 

% complete 99 97 100 100 

Dysart 04-013-

4010 

MCAQD DV (ppm) 0.067 0.067 0.066 0.068 

% complete 97 100 100 100 

Falcon 

Field 

04-013-

1010 

MCAQD DV (ppm) 0.076 0.075 0.071 0.070 

% complete 97 98 100 100 

Fountain 

Hill 

04-013-

9704 

MCAQD DV (ppm) 0.082 0.079 0.074 0.074 

% complete 98 100 99 100 

Glendale 04-013-

2001 

MCAQD DV (ppm) 0.075 0.074 0.071 0.072 

% complete 100 100 100 100 

Humboldt 

Mountain 

04-013-

9508 

MCAQD DV (ppm) 0.081 0.078 0.074 0.071 

% complete 100 100 99 100 

North 

Phoenix 

04-013-

1004 

MCAQD DV (ppm) 0.082 0.081 0.076 0.077 

% complete 99 95 100 100 

Pinnacle 

Peak 

04-013-

2005 

MCAQD DV (ppm) 0.078 0.074 0.072 0.073 

% complete 99 99 100 99 

Rio Verde 04-013-

9706 

MCAQD DV (ppm) 0.083 0.080 0.075 0.072 

% complete 99 92 96 100 

South 

Phoenix 

04-013-

4003 

MCAQD DV (ppm) 0.072 0.072 0.071 0.072 

% complete 99 99 99 100 

South 

Scottsdale 

04-013-

3003 

MCAQD DV (ppm) 0.078 0.077 0.075 0.074 

% complete 98 97 99 99 

JLG 

Supersite 

04-013- ADEQ DV (ppm) 0.076 0.076 0.075 0.075 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

41 

9997 % complete 100 98 100 99 

Tempe 04-013-

4005 

MCAQD DV (ppm) 0.077 0.077 0.073 0.071 

% complete 97 97 100 98 

West 

Chandler 

04-013-

4004 

MCAQD DV (ppm) 0.076 0.076 0.073 0.073 

% complete 100 98 100 100 

West 

Phoenix 

04-013-

0019 

MCAQD DV (ppm) 0.074 0.078 0.073 0.073 

% complete 100 99 99 99 

* The data in this table has been certified in EPA’s Air Quality 

System (AQS) database in accordance with the requirements of 40 

CFR part 58. We provide these data only to support our 

evaluation of the modeling and attainment demonstration and not 

to support a determination regarding attainment, which is not 

part of today’s proposed action. 

3. Proposed Action on the Attainment Demonstration 

 In order to approve a SIP’s attainment demonstration, EPA 

must make several findings: 

 First, we must find that the demonstration’s technical 

bases, emission inventories and air quality modeling, are 

adequate. As discussed in section IV.A and IV.C.2, we are 

proposing to approve the base year emission inventory and to 

find the air quality modeling adequate to support the attainment 

demonstration. 

 Second, we must find that the SIP provides for expeditious 

attainment through the implementation of all RACM. As discussed 

above in section III.B, we propose to find that the 2007 Ozone 

Plan provides for implementation of all reasonably available 

control measures necessary for expeditious attainment of the 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

42 

1997 8-hour ozone NAAQS and any related RFP requirements in the 

Phoenix-Mesa nonattainment area. 

 Third, we must find that the emission reductions that are 

relied on for attainment are creditable and are sufficient to 

provide for attainment. All of the key attainment measures 

relied on in the 2007 Ozone Plan to attain the 1997 8-hour ozone 

standard by June 15, 2009 have been adopted and approved into 

the SIP. 

 For the foregoing reasons, we propose to approve the 

attainment demonstration in the 2007 Ozone Plan for the PhoenixMesa nonattainment area. 

D. Reasonable Further Progress Demonstration 

 CAA section 172(c)(2) requires that plans for nonattainment 

areas provide for reasonable further progress (RFP). RFP is 

defined in section 171(1) as “such annual incremental reductions 

in emissions of the relevant air pollutant as are required by 

[title 1, part D] or may reasonably be required by the 

Administrator for the purpose of ensuring attainment of the 

applicable [standard] by the applicable date.” The ozone 

implementation rule interprets the RFP requirements for the 

purposes of the 1997 ozone standards, establishing requirements 

for RFP that depend on the area’s classification. For areas with 

attainment dates on or before June 15, 2009, RFP would be met by 

ensuring emissions reductions needed for attainment are 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

43 

implemented by the beginning of the ozone season prior to the 

attainment date. 40 CFR 51.910(b) and 70 FR 71612. 

 The attainment date for the Phoenix-Mesa ozone 

nonattainment area is June 15, 2009, and as discussed in the 

RACM demonstration and control strategy (section IV.B) and the 

attainment demonstration (section IV.C) sections above, all of 

the control measures needed for the attainment demonstration 

were being implemented prior to the 2008 ozone season. We 

propose, therefore, to approve the RFP demonstration in the 2007 

Ozone Plan. 

E. Contingency Measures 

1. Requirements for Contingency Measures 

 CAA section 172(c)(9) requires plans to provide for the 

implementation of contingency measures, that achieve additional 

emission reductions, to be undertaken if the area fails to meet 

RFP milestones or fails to attain by its attainment date. These 

contingency measures must be rules or measures that are ready 

for implementation quickly upon failure to meet milestones or 

attainment. The SIP should define trigger mechanisms for the 

contingency measures, specify a schedule for implementation, and 

indicate that the measures will be implemented without 

significant further action by the State or EPA. See 68 FR 32802, 

32837 and 70 FR 71612, 71650. 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

44 

 Additional guidance on the CAA contingency measure

provisions is found in the General Preamble at 13510-13512 and 

13520. The guidance indicates that states should adopt and 

submit contingency measures sufficient to provide a 3 percent 

emission reduction from the adjusted RFP base year. This level 

of reduction is generally acceptable to offset emission increase 

while States are correcting their SIPs. These reductions would 

be beyond what is needed to meet the attainment and/or RFP 

requirement. States may use reductions of either VOC or NOx or a 

combination of both to meet the contingency measure

requirements. General Preamble at 13520, footnote 6. EPA 

guidance also provides that contingency measures could be 

implemented early, i.e., prior to the milestone or attainment 

date21. Consistent with this policy, states are allowed to use 

excess reductions from already adopted measures to meet the CAA 

section 172(c)(9) and 182(c)(9) contingency measure requirement. 

This is because the purpose of contingency measures is to 

provide extra reductions that are not relied on for RFP or 

attainment that will provide for continued progress while the 

plan is being revised to fully address the failure to meet the 

required milestone. Nothing in the CAA precludes a State from 

implementing such measures before they are triggered. This 

 

21 Memorandum, G.T. Helms, Chief, Ozone/Carbon Monoxide Programs Branch to Air 

Directors, “Contingency Measures for Ozone and Carbon Monoxide 

Redesignations”, June 1, 1992. 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

45 

approach has been approved in numerous SIPs. See 62 FR 

15844(April 3, 1997) (approval of the Indiana portion of the 

Chicago area 15 percent Rate of Progress plan); 66 FR 30811 

(June 8, 2001) (proposed approval of the Rhode Island post-1996 

ROP plan); and 66 FR 586 and 66 FR 634 (January 3, 2001) 

(approval of the Massachusetts and Connecticut 1-hour ozone 

attainment demonstrations). In the only adjudicated challenge to 

this approach, the court upheld it. See LEAN v. EPA, 382 F.3d 

575 (5th Cir. 2004). 70 FR 71611, 71651. 

2. Contingency Measures in the 2007 Ozone Plan 

 Contingency measure provisions for the Phoenix-Mesa 

nonattainment area and the methodologies used to estimate the 

emission reductions from these measures are described in 

Chapters 4 and 5 of the 2007 Ozone Plan and Section V of Volume 

1 of the Appendices to the 2007 Ozone Plan. Table 4 lists the 

five contingency measures and the estimated reductions in VOC 

and NOx emissions from each measure. All five contingency 

measures have already been implemented in the Phoenix-Mesa 

nonattainment area, but credit for these measures were not 

needed or used to demonstrate attainment. See 2007 Ozone Plan at 

pp. 4-7 through 4-10 and 5-15 through 5-17. 

Table 4: Emission Reductions from Individual Contingency 

Measures in the Phoenix-Mesa 8-Hour Ozone Modeling Domain 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

46 

VOC NOx

Base Case Emissions 

on June 6, 2002 

696.13 

metric tons/day 

291.82 

metric tons/day 

Contingency Measure Reduction 

(metric 

ton/day) 

Percent 

Reduction 

Reduction 

(metric 

ton/day) 

Percent 

Reduction 

Expansion of Area A 

Boundaries 

1.3 0.2% 0.7 0.2% 

Gross Polluter Option 

for I/M Waivers 

<0.1 <0.1% <0.1 <0.1% 

Increased Waiver 

Repair Limit Options 

<0.1 <0.1% <0.1 <0.1% 

Federal Heavy Duty 

Diesel Vehicle 

Standards 

<0.1 <0.1% 2.5 0.9% 

Federal Nonroad 

Equipment Standards 

14.6 2.1% 15.6 5.3% 

Total 15.9 2.3% 18.8 6.4% 

Source: 2007 Ozone Plan at Table 5-6. 

a. Expansion of Area A Boundaries 

 In 2001, the Arizona legislature passed H.B. 2538 to expand 

the boundaries of Area A, adding additional portions of Maricopa 

County west of Goodyear and Peoria and a small area on the north 

side of Lake Pleasant. The implementation of air quality 

measures within the new Area A boundaries began on January 1, 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

47 

2002, except for public sector alternative fuel requirements to 

be phased in over a seven-year period. MAG modeled this 

contingency measure by increasing the number of registered 

vehicles in Area A that will be required to participate in the 

I/M program. MAG estimated the emission reductions from this 

contingency measure to be 1.3 metric tons per day of VOC and 0.7 

metric tons per day of NOx, but did not take credit for this 

measure in the attainment demonstration. See 2007 Ozone Plan at 

4-7 and 4-8. 

b. Gross Polluter Option for I/M Waivers 

 The Arizona legislature passed S.B. 1427 in 1998 to require 

vehicle owners with vehicles emitting more than twice the 

emission standard to repair the vehicle sufficiently to reduce 

the emission levels to less than twice the standard in order to 

obtain a compliance waiver from the Vehicle Emissions Inspection 

Program. ADEQ modeled the emission reductions for this measure 

and estimated the emission reductions from this contingency 

measure to be less than 0.1 metric tons per day of VOC and less 

than 0.1 metric tons per day of NOx. MAG but did not take credit 

for this measure in its attainment demonstration. See 2007 Ozone 

Plan at 4-9. 

c. Increased Waiver Repair Limit Options 

 In 1998, the Arizona legislature passed S.B. 1427 to 

increase the amount a person must spend to repair a failing 1967 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

48 

– 1974 vehicle in Area A in order to qualify for a waiver from 

$100 to $200. MAG modeled this measure using MOBILE6.2 by 

reducing the pre-1981 vehicle waiver rate from 4 to 2.6 percent. 

The emission reductions from this contingency measure were 

estimated to be less than 0.1 metric tons per day of VOC and 

less than 0.1 metric tons per day of NOx. MAG did not take credit 

for this measure in its attainment demonstration. See 2007 Ozone 

Plan at 4-9. 

d. Federal Heavy Duty Diesel Vehicle Standards 

 On January 18, 2001, EPA issued a final rule that set more 

stringent emission standards for new heavy duty diesel vehicles 

(66 FR 5001). The rule requires high-efficiency catalytic 

convertors or comparable technologies be installed on 2007 and 

later model year diesel vehicles, and requires ultra-low sulfur 

fuel be used in all onroad diesel vehicles beginning in 2006. 

MAG modeled emission reductions from this federal measure using 

MOBILE6.2 and estimated VOC reductions of less than 0.1 metric 

tons of VOC per day and 2.5 metric tons of NOx per day. MAG did 

not take credit for this measure in its attainment 

demonstration. See 2007 Ozone Plan at 4-9. 

e. Federal Nonroad Equipment Standards 

 On October 23, 1998, EPA issued a final rule to set more 

stringent Tier 2 and Tier 3 emission standards for new diesel 

nonroad equipment (63 FR 56967). The Tier 2 program phased in 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

49 

more stringent standards for all equipment between 2001 and 2006 

and Tier 3 imposed even more stringent standards for 50 to 750 

horsepower engines in 2006 to 2008. Additionally, on June 29, 

2004, EPA issued the Clean Air Nonroad Diesel – Tier 4 Final 

rule to require manufacturers to produce nonroad engines with 

emission controls that will reduce emissions by more than 90 

percent (69 FR 38958). The Tier 4 standards apply to nonroad 

engines less than 25 horsepower beginning in 2008 and will apply 

to larger engines over 2011 to 2015. MAG estimated emission 

reductions from this measure using the EPA NONROAD model and 

projected VOC emission reductions of 14.6 metric tons of VOC per 

day and 15.6 metric tons of NOx per day. MAG did not take credit 

for this measure in its attainment demonstration. See 2007 Ozone 

Plan at 4-9 and 4-10. 

3. Proposed Action on the Contingency Measures 

 We propose to approve the contingency measures in the 2007 

Ozone Plan. The contingency measures are consistent with EPA 

guidance that recommends a 3 percent emission reduction. All 

contingency measures have already been implemented but EPA 

guidance allows for the early implementation of contingency 

measures. 

F. Motor Vehicle Emissions Budgets for Transportation Conformity 

1. Requirements for Motor Vehicle Emission Budgets 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

50 

 CAA section 176(c) requires federal actions in 

nonattainment and maintenance areas to conform to the SIP’s 

goals of eliminating or reducing the severity and number of 

violations of the NAAQS and achieving expeditious attainment of 

the standards. Conformity to the SIP’s goals means that such 

actions will not: (1) cause or contribute to violations of a 

NAAQS, (2) worsen the severity of an existing violation, or (3) 

delay timely attainment of any NAAQS or any interim milestone. 

 Actions that involve Federal Highway Administration (FHWA) 

or Federal Transit Administration (FTA) funding or approval are 

subject to the EPA’s transportation conformity rule, codified in 

40 CFR part 93, subpart A. Under this rule, metropolitan 

planning organizations (MPOs) in nonattainment and maintenance 

areas coordinate with state and local air quality and 

transportation agencies, EPA, FHWA, and FTA to demonstrate that 

an area’s regional transportation plans (RTP) and transportation 

improvement programs (TIP) conform to the applicable SIP. This 

demonstration is typically done by showing that estimated 

emissions from existing and planned highway and transit systems 

are less than or equal to the motor vehicle emission budgets 

(budgets) contained in the SIP. An attainment, maintenance, or 

RFP SIP should establish budgets for the attainment year, each 

required RFP year, or last year of the maintenance plan, as 

appropriate. Budgets are generally established for specific 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

51 

years and specific pollutants or precursors. Ozone attainment 

and RFP plans should establish budgets for NOx and VOC. See 40 

CFR 93.102(b)(2)(i). 

 Before an MPO may use budgets in a submitted SIP, EPA must 

first determine that the budgets are adequate or approve the 

budgets. In order for EPA to find the budgets adequate and 

approvable, the submittal must meet the conformity adequacy 

requirements of 40 CFR 93.118(e)(4) and be approvable under all 

pertinent SIP requirements. To meet these requirements, the 

budgets must reflect all of the motor vehicle control measures 

contained in the attainment and RFP demonstrations. See 40 CFR 

93.118(e)(4)(v). 

2. Motor Vehicle Emission Budgets in the Phoenix-Mesa 2007 Ozone 

Plan 

 The 2007 Ozone Plan for Phoenix Mesa included budgets for 

VOC and NOx for the 2008 attainment year. On October 4, 2007, we 

notified ADEQ and MAG that we found the MVEB for the 2008 

attainment year adequate for transportation conformity purposes. 

See letter from Deborah Jordan, EPA Region 9, to Nancy Wrona, 

ADEQ, and Dennis Smith, MAG, “RE: Adequacy Status of Motor 

Vehicle Emissions Budgets in Eight-Hour Ozone Plan for the 

Maricopa Nonattainment Area (June 2007)”, October 4, 2007. We 

published a notice of our findings at 72 FR 60666 (October 25, 

2007). The budget for the 2008 attainment year is represented by 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

52 

onroad VOC and NOx emissions for the Phoenix-Mesa modeling domain 

on the peak episode day in June 2008 of 72.3 metric tons per day 

of VOC and 145.5 metric tons per day of NOx. MAG used geographic 

information systems (GIS) to separate the onroad mobile 

emissions from the Phoenix-Mesa 8-hour ozone nonattainment area 

from the modeling domain, resulting in the estimated 2008 MVEB 

of 67.9 metric tons per day of VOC and 138.2 metric tons per day 

of NOx. 

3. Proposed Action on the Motor Vehicle Emission Budgets 

 Based on our evaluation of the 2007 Ozone Plan and the 

budgets contained in it, which reflect all motor vehicle control 

measures contained in the attainment and RFP demonstration, we 

are proposing to approve the 2008 MVEB. 

V. EPA’s Proposed Action 

 For the reasons discussed above, EPA is proposing to 

approve Arizona’s submitted SIP for attaining the 1997 8-Hour 

Ozone Standard in the Phoenix-Mesa nonattainment area. 

 Specifically, EPA is proposing to approve under CAA section 

110(k)(3) the following elements of the 2007 Ozone Plan for 

Phoenix-Mesa: 

1. The 2002 base year emission inventory as meeting the 

requirements of CAA section 172(c)(3) and 40 CFR 51.915; 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

53 

2. The reasonably available control measures demonstration 

as meeting the requirements of CAA section 172(c)(1) and 40 CFR 

51.912(d); 

3. The reasonable further progress demonstration as meeting 

the requirements of CAA section 172(c)(2) and 40 CFR 51.910; 

4. The attainment demonstration as meeting the requirements 

of CAA section 172(c)(1) and 40 CFR 51.908; 

5. The contingency measures for failure to make RFP or to 

attain as meeting the requirements of CAA section 172(c)(9); and 

6. The motor vehicle emission budgets for the attainment 

year of 2008, which are derived from the attainment

demonstration, as meeting the requirements of CAA section 176(c) 

and 40 CFR part 93, subpart A. 

VI. Statutory and Executive Order Reviews 

Under the Clean Air Act, the Administrator is required to 

approve a SIP submission that complies with the provisions of 

the Act and applicable Federal regulations. 42 U.S.C. 7410(k); 

40 CFR 52.02(a). Thus, in reviewing SIP submissions, EPA’s role 

is to approve state choices, provided that they meet the 

criteria of the Clean Air Act. Accordingly, this action merely 

proposes to approve state law as meeting Federal requirements 

and does not impose additional requirements beyond those imposed 

by state law. For that reason, this proposed action: 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

54 

• is not a "significant regulatory action” subject to 

review by the Office of Management and Budget under Executive 

Order 12866 (58 FR 51735, October 4, 1993); 

• does not impose an information collection burden under 

the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et 

seq.); 

• is certified as not having a significant economic

impact on a substantial number of small entities under the 

Regulatory Flexibility Act (5 U.S.C. 601 et seq.); 

• does not contain any unfunded mandate or significantly 

or uniquely affect small governments, as described in the 

Unfunded Mandates Reform Act of 1995 (Public Law 104-4); 

• does not have Federalism implications as specified in 

Executive Order 13132 (64 FR 43255, August 10, 1999); 

• is not an economically significant regulatory action 

based on health or safety risks subject to Executive Order 13045 

(62 FR 19885, April 23, 1997); 

• is not a significant regulatory action subject to

Executive Order 13211 (66 FR 28355, May 22, 2001); 

• is not subject to requirements of Section 12(d) of the 

National Technology Transfer and Advancement Act of 1995 (15 

U.S.C. 272 note) because application of those requirements would 

be inconsistent with the Clean Air Act; and 
This document is a prepublication version, signed by the EPA Acting Regional Administrator, Keith Takata, on 

3/30/2012. We have taken steps to ensure the accuracy of this version, but it is not the official version.

55 

• does not provide EPA with the discretionary authority 

to address, as appropriate, disproportionate human health or 

environmental effects, using practicable and legally permissible 

methods, under Executive Order 12898 (59 FR 7629, February 16, 

1994). 

In addition, this proposed rule does not have tribal 

implications as specified by Executive Order 13175 (65 FR 67249, 

November 9, 2000), because the SIP is not approved to apply in 

Indian country located in the state, and EPA notes that it will 

not impose substantial direct costs on tribal governments or 

preempt tribal law. 

List of Subjects in 40 CFR Part 81 

 Environmental protection, Air pollution control, Ozone, 

Nitrogen Dioxide, Volatile Organic Compounds. 

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

_____________ ______________________________ 

Dated: Jared Blumenfeld 

 Regional Administrator, EPA Region IX 

Billing Code: 6560-50-P