UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION IX 

75 Hawthorne Street 

San Francisco, CA 94105

Memorandum 

To: Clark County Ozone Maintenance Plan SIP Proposed Approval Docket, Docket ID EPAR09-OAR-2012-0792 

From: Karina O'Connor, Air Planning Office, EPA Region 9 

Date: October 15, 2012 

RE: Adequacy Documentation for Motor Vehicle Emission Budgets in April 2011 Clark 

County Ozone Maintenance State Implementation Plan 

Attached to this memorandum is the adequacy documentation for the Motor Vehicle Emission Budgets 

in April 2011 Clark County Ozone Maintenance State Implementation Plan 
 

Table 1. Evaluation of the Motor Vehicle Emissions Budgets in the 

2011 Clark County Ozone Maintenance Plan 

October 2012 (reviewed by Karina O’Connor)

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 Clark County Redesignation Request and Maintenance Plan was submitted to 

EPA on April 11, 2011 by the Administrator of the Nevada Division of 

Environmental Protection (NDEP), the Governor of Nevada’s designee for all SIP 

revision submittals. This SIP submittal documents that the Clark County Board of 

County Commissioners, which is responsible for implementation of air quality 

management programs within the boundaries of Clark County, held a public 

hearing on the plan on March 15, 2011, and adopted the plan on that same date. 

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 

The plan was developed by Clark County Department of Air Quality through 

consultation with Federal, State, and local agencies. These agencies include: EPA 

Region IX; U.S. Department of Transportation; Nevada Department of 

Transportation; Nevada Division of Environmental Protection, Bureau of Air 

Quality Planning; Regional Transportation Commission of Clark County, other 

Clark County departments, and the cities of Las Vegas, North Las Vegas, 

Henderson, and Boulder City. Issues raised by EPA Region IX staff on the 

administrative draft were addressed through this process prior to publication of the 

proposed plan for public review. 

Sec. 

93.118(e)(4)(iii) 

The motor vehicle emission 

budgets are clearly identified and 

precisely quantified. 

Y 

The motor vehicle emissions budgets are clearly identified and precisely quantified 

for years 2008, 2015, and 2022 on page 7-1 of the Redesignation Request and 

Maintenance Plan.. These budgets reflect federal motor vehicle control measures 

that were already adopted at the time that Clark County adopted the SIP on March 

15, 2011 and were developed using EPA’s MOBILE6 model. 
 

Table 1. Evaluation of the Motor Vehicle Emissions Budgets in the 

2011 Clark County Ozone Maintenance Plan 

October 2012 (reviewed by Karina O’Connor)

Adequacy Review Criteria

(40 CFR part 93)

Is Criterion

Satisfied? Reference in SIP Document/Comments

Sec. 

93.118(e)(4)(iv) 

The motor vehicle emissions 

budget(s), when considered 

together with all other emission 

sources, is consistent with 

applicable requirements for 

reasonable further progress and 

attainment. 

Y 

The Redesignation Request and Maintenance Plan describes how the level of 

emissions contained in the motor vehicle emission budgets, with all other emission 

sources will show maintenance through the year 2022. See page 7-1 of the plan and 

Appendix A for a discussion of the derivation of the motor vehicle emissions 

budgets and how they are consistent with the maintenance demonstration provided 

in Chapter 6 of the plan. The plan uses a 2008 attainment-year emissions inventory 

to develop an emission budget and projects emissions to 2015 and 2022 to show 

continually decreasing emissions. 

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 Appendix A of the plan, as well as in Chapter 6. Chapter 4 describes the 

federally enforceable control measures and their respective emission reductions. 

Appendix A describes the emissions inventories and baselines used to project 

future year emissions. 

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 

vehicle miles traveled). 

Y 

Clark County was originally designated nonattainment in 2004 and submitted an 

early progress plan in 2008 to establish motor vehicle emission budgets for the year 

2008. EPA determined that these budgets, 64.2 tpd VOC and 76.1 tpd NOx, were 

adequate for conformity in May of 2009. See 74 FR 22738 (May 14, 2009). 

MOBILE6.2 was used to develop the updated motor vehicle emissions in both 

plans, however updated VMT estimates for the year 2008 was used in development 

of the updated, lower emissions for 2008 in this plan. .
 

Table 1. Evaluation of the Motor Vehicle Emissions Budgets in the 

2011 Clark County Ozone Maintenance Plan 

October 2012 (reviewed by Karina O’Connor)

Adequacy Review Criteria

(40 CFR part 93)

Is Criterion

Satisfied? Reference in SIP Document/Comments

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 

A notice of the public hearing was published in the Las Vegas Review-Journal and 

the Las Vegas Sun on December 12, 2010. The public hearing itself took place on 

March 15, 2011 by the Clark County Board of County Commissioners (BCC) in 

Las Vegas, Nevada. No comments were made by members of the public at the 

hearing.