UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION IX 75 Hawthorne Street San Francisco, CA 94105



### October 31, 2013

Memorandum

To: Docket for the EPA Action on the Maricopa Association of Governments’ 2009 Ozone

Maintenance Plan

- Docket ID EPA

- R09

- OAR

- 2013

- 0686

From: Ginger Vagenas , Air Planning Office, EPA Region 9

RE: Adequacy D ocumentation for M otor Vehicle Emission Budgets in the February 2009

Ozone Maintenance State Implementation Plan for the Phoenix

- Mesa Nonattainment
Area

Attached to this memorandum is the adequacy documentation for the motor vehicle emission budgets in the Maricopa Association of Governments’ February 2009 Eight

- Hour Ozone Redesignation Request
and Maintenance Pla n for the Maricopa Nonattainment Area . Note that the official name (i.e., the name appearing in 40 CFR 81.303) for the nonattainment area is “Phoenix

- Mesa

. ”Evaluation of the Motor Vehicle Emissions Budgets in the

Maricopa Association of Government’s Eight

- Hour Ozone Redesignation Request and Maintenance Plan for the Maricopa Nonattainment Area February 2009 (1997 8

- hour Ozone NAAQS)

Reviewed by Ginger Vagenas, October 2013

Adequacy Review Criteria 40 CFR part 93 Is Criterion
Satisfied? Reference in SIP Document/Comments

Sec. 93.118(e)(4)(i) The plan was endorsed by the

Governor (or designee) and was subject to a public hearing. Y The March 23, 2009 transmittal letter, which serves to adopt and submit MAG’s Eight

- hour Ozone Redesignation Request and Maintenance Plan for the Maricopa County Nonattainment Area, was signed by ADEQ’s acting director, Patrick J. Cunningham, who is the Go vernor’s designee.

A public hearing was held on January 22, 2009 and is documented in Encl osure 3
of the submittal letter. See Appendix B of MAG’s Eight

- hour Ozone Redesignation Request and Maintenance Plan for the Maricopa County

Nonattainment Area. Sec. 93.118(e)(4)(ii) The plan was developed through

consultation with federal, state and local agencies; full implementation plan documentation was provided and EPA’s stated concerns, if any,
were addressed. Y Documentation accompanying the plan describe s the manner in which the public and governmental agencies are consulted. The Maricopa Association of Governments (MAG), which is the regio nal air quality planning agency for Maricopa County, coordinates with the Arizona Department of Environmental Qualit y (ADEQ), the Arizona Department of Transportation (ADOT) and the Maricopa County Air Quality Department in developing air quality plans. The plan was reviewed and approved by the Maricopa Association of Government’s Air Quality Technical Advisory Committe e, the MAG Management Committee, and the MAG Regional Council. See Chapter 1, Introduction. EPA , ADEQ, Maricopa County

, and ADOT received a copy of the draft plan in November

2008 . EPA’s comments were addressed. Sec. 93.118(e)(4)(iii) The motor vehicle emission

budgets are clearly identified and precisely quantified. Y The motor vehicle emissions budgets (MVEBs) are included in Chapter 3 of the maintenance plan. The current maintenance plan establishes budgets for the year 2025 (VOC = 43.8 metric tons per day; NOx = 101.8 metric tons per day). See pages 3

- 19 and 3

- 20 of the maintenance plan and section IV.9 of the technical support document (Appendix A, Exhibit 2).Sec. 93.118(e)(4)(iv) The motor vehicle emissions budgets, when considered together with all other emission sources, is consistent with applicable requirements for

maintenance. Y MAG increased the the 2025 VOC and NOx emissions from onroad mobile sources in the eight

- hour ozone modeling domain in order to address the
“inherent uncertainties associated with the use of th e latest planning assumptions in conformity analyses.” MAG dist ributed the increase spatially based on the proportion of onroad mobile emissions assigned to each four kilometer grid cell. See page 3

- 20 of the Ozone Maintenance Plan. While the
MVEBs are de rived from the modeling domain, they reflect only the motor
vehicle emissions from within the nonattainment area.

Even with the 10 percent safety margin added to the on

- road emissions, the
overall projected emissions in the Phoenix

- Mesa area are consiste nt with
continued maintenance of the 1997 ozone standard.

The Ozone Maintenance Plan demonstrates that the level of emissions contained in the motor vehicle emissions budgets, with all other emissions sources, will provide for maintenance of the 1997 ozone NAAQS through 2025. See Chapter 3.

Sec. 93.118(e)(4)(v) The plan shows a clear

relationship among the emissions budget(s), control measures and the total emissions inventory. Y The emissions inventory for all point, area, and motor vehicle sources is
described in Section IV.2. of MAG’s Techni cal Support Document (included in the submittal as Appendix A, Exhibit 2), as well as in Chapter 3. See, for example,
tables 3

- 6, 3

- 7, and 3

- 8 . The documentation in these portions of the plan clearly shows the relationship among the inventories, control measures, and MVEBs

, which are used in the modeling of continued maintenance.

Emission factors for vehicle classes were calculated using MOBILE6.2, which was
the th en

- current version of the model that is used to estimate motor vehicle emission factors. The calculated emission factors were multiplied by the estimates of vehicle miles of travel (VMT) to generate emission estimates for
onroad mobile sources. ADOT’s 2005 Highway Performance Monitoring System (HPMS) 1 and the 2 005 traffic assignment prepared by MAG using the EMME/2 travel demand model provided data for the VMT estimates.

The projected emissions inventory and MVEBs take into account reductions from the maintenance measures, but do not include reductions from imp lementation

1 http://tpd.azdot.gov/data/reports/vmt2005.phpof the contingency measures.

Sec. 93.118(e)(4)(vi) Revisions to previously submitted

control strategy or maintenance plans explain and document any changes to any previous submitted budgets and control measures; impacts on point and

area source emissions; any changes to established safety margins (see §93.101 for definition), and reasons for the changes (including the basis for any changes to emission factors
or estimates of VMT. N/A EPA previously approved 2008 budgets for VOC (67.9 met ric tons per day) and NOx (138.3 metric tons per day) that were included in the attainment plan. See 77 FR 35285; June 13, 2012.This maintenance plan does not revise previously submitted plans or budgets. The budgets established in this plan are for t he ye ar 2025, and d o not modify the currently approved 2008 budgets for VOC and NO
x .

Sec. 93.118(e)(5) EPA has reviewed the State’s

compilation of public comments and response to comments that are required to be submitted with any implementation plan. Y No written comments were received during the comment period on the draft plan. One commenter presented verbal testimony at the public hearing held on January 22, 2009. Those comments and MAG’s responses are included in Appendix B, Exhibit 1 of the submitted maintenance plan.

We have reviewed the compilation of comments and responses and find the responses to be acceptable. No issues that might have affected our adequacy finding remain unanswered.