UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION IX 

75 Hawthorne Street 

San Francisco, CA 94105

Memorandum

To: Clark County PM10 Maintenance Plan SIP Proposed Approval Docket, Docket ID EPAR09-OAR-2013-0735

From: Karina OConnor, Air Planning Office, EPA Region 9

Date: October 28, 2013

RE: Adequacy Documentation for Plan Motor Vehicle Emission Budgets in August 2012

Clark County PM10 Maintenance State Implementation Plan

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

in the Redesignation Request and Maintenance Plan for Particulate Matter (PM10), Clark County, 

Nevada (August 2012)(“Clark County PM10 Maintenance Plan”).

The Clark County PM10 Maintenance Plan was adopted by the Clark County Board of County 

Commissioners on August 21, 2012 and submitted by the Nevada Division of Environmental Protection 

(NDEP) to EPA on September 7, 2012. The Clark County PM10 Maintenance Plan identifies MVEBs for 

the BLM disposal area portion of the Las Vegas Valley nonattainment area for PM10 for 2008, 2015, and 

2023. We announced receipt of the Clark County PM10 Maintenance Plan on the Internet on November 

7, 2012, and requested public comment by December 7, 2012. We did not receive any comments on the 

budgets and Clark County PM10 Maintenance Plan during the comment period. 

This memo contains our analysis of the MVEBs in the Clark County PM10 Maintenance Plan for BLM 

disposal area portion of the Las Vegas Valley PM10 nonattainment area. The budgets are listed in the 

following table.

Budget Year PM10 (tons per designday)

2008 141.40

2015 141.40

2023 141.40
 

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

Clark County PM10 Maintenance Plan (August 2012)

October 2013 (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 PM10 Maintenance Plan was submitted to EPA on September 7, 

2012 by the NDEP Administrator, 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 under Nevada law for 

implementation of air quality management programs within the boundaries of 

Clark County, held a public hearing on the plan on August 21, 2012, 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

Clark County Department of Air Quality (DAQ) developed the Clark County PM10

Maintenance Plan in consultation from Federal, State, and local agencies. These 

agencies include: EPA Region IX; Federal Highway Administration; Nevada 

Department of Transportation; Nevada Division of Environmental Protection, 

Bureau of Air Quality Planning; Regional Transportation Commission of Clark 

County; Public Works Departments of Clark County and the City of Las Vegas. 

EPA submitted comments during the initial comment period on the draft 

maintenance plan, held from January 16th through February 15th, 2012. Issues 

raised by EPA Region IX staff on the draft PM10 maintenance plan were discussed 

by Clark County DAQ and EPA in several meetings and responded to by Clark 

County DAQ in the final adopted maintenance plan (see appendix B 

(“Documentation of the Public Review Process”) to the Clark County PM10

Maintenance Plan).

Sec. 

93.118(e)(4)(iii)

The motor vehicle emission 

budgets are clearly identified and 

precisely quantified.

Y

The MVEBs are clearly identified and precisely quantified for years 2008, 2015, 

and 2023 in tables 7-1 and 7-3 of the Clark County PM10 Maintenance Plan. The

MVEBs for all three years are 141.41 tons per day. The information in tables 7-1 

and 7-3 show that the MVEBs represent the sum of certain emissions source 

categories included in the plan inventory, including vehicle (exhaust, brake wear, 

and tire wear), paved road dust, unpaved road dust, road construction, construction 

track-out, and wind erosion (road construction), plus a safety margin. Appendix A 

to the plan documents the methods and assumptions used to develop the emission 

inventory estimates used to develop the MVEBs.
 

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

Clark County PM10 Maintenance Plan (August 2012)

October 2013 (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, 

attainment, or maintenance

(whichever is relevant to a given 

implementation plan submission).

Y

The Clark County PM10 Maintenance Plan describes how the MVEBs, when 

considered together with all other emission sources, are consistent with 

maintenance of the PM10 NAAQS in Las Vegas Valley through 2023. The plan 

uses a 2008 attainment-year emissions inventory to develop an emission inventory

and projects emissions to 2015 and 2023 to show continually decreasing emissions. 

When the safety margins are added to the motor-vehicle and road-constructionrelated emissions from the inventory, overall PM10 emissions in 2015 (i.e., 694.35 

tons per day) and 2023 ( i.e., 563.53 tons per day) would still be less than the 2008 

attainment-year inventory (i.e., 706.55 tons per day). See table 7-2 of the Clark 

County PM10 Maintenance Plan. As such, inclusion of the identified safety margins 

as part of the MVEBs is consistent with continued maintenance of the standard in 

Las Vegas Valley.
 

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

Clark County PM10 Maintenance Plan (August 2012)

October 2013 (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)(v)

The plan shows a clear 

relationship among the emissions 

budget(s), control measures and 

the total emissions inventory.

Y

Chapter 6 (“Maintenance Plan”) and appendix A (“Technical Support Document”)

to the Clark County PM10 Maintenance Plan document the relationship among the 

MVEBs, control measures and total emissions inventory. Specifically, chapter 6 

presents the overall emissions within the BLM disposal area in terms of point,

nonpoint, on-road, and nonroad emissions, and also includes certain emission 

reduction credits (ERC). The MVEBs represent the sum of emissions estimates for 

certain motor vehicle related source categories, including vehicle (exhaust, tire 

wear and brake wear), paved and unpaved road dust, construction track-out, and 

road construction (including wind erosion at road construction sites). 

Documentation for the emissions estimates for each of the individual source 

categories that, when added together with the safety margins, comprise the MVEBs 

is found in the following chapters of appendix A: chapter 5 (“Fugitive Nonpoint 

Source Emissions”), including subsections 5.1.4.3 (“Road Construction”), 5.1.4.4 

(“Construction Track-Out”), and 5.1.4.5 (“Wind Erosion”)(particularly, table 5-

20); subsection 5.3 (“Unpaved Roads”); and chapter 8 (“On-Road Mobile 

Emissions”)(includes vehicle exhaust, tire wear and brake wear, and PM10 from 

vehicle entrainment over paved roads). Where applicable, these emissions 

estimates show the effect of control measures approved as part of the plan, 

particularly those related to fugitive dust sources. The sum of the estimates 

emissions from these source categories were then increased by safety margins 

sufficient to result in MVEBs for 2008, 2015, and 2023 equal to a level of 141.41 

tons per day, which matches the existing attainment plan budget for 2006. 
 

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

Clark County PM10 Maintenance Plan (August 2012)

October 2013 (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)(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 DAQ developed the Clark County PM10 Attainment Plan in 2001 

which established MVEBs for the years 2001, 2003 and 2006. EPA determined 

that these budgets were adequate for conformity in January of 2002 and approved 

that plan in June of 2004. See 69 FR 32273 (June 9, 2004). Clark County DAQ 

used MOBILE5B and PART5 to develop the motor vehicle emissions in the 2001 

attainment plan, but appropriately used EPA’s updated motor vehicle emissions 

factor model (MOVES) and the updated 2011 version of AP-42 to estimate motorvehicle-related emissions for the PM10 maintenance plan. In addition, Clark County 

DAQ used updated VMT estimates for the later years (2008, 2015 and 2023) 

provided by the Regional Transportation Commission of Southern Nevada (RTC) 

to develop the updated emissions estimates in the PM10 maintenance plan. A safety 

margin was also allocated to the budgets established in the maintenance plan. The 

impact of all these changes results in maintenance plan MVEBs that are equal to 

that of the 2006 attainment budget, 141.41 tons per day.

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 initial public comment period was published in the Las Vegas 

Review-Journal and the Las Vegas Sun on January 15, 2012. Notice for the public 

workshop was published on January 27, 2012. Notices were also published on the 

Clark County website. The only comments Clark County DAQ received on the 

draft maintenance plan were from EPA. The public hearing itself took place on 

August 21, 2012 by the Clark County Board of County Commissioners (BCC) in 

Las Vegas, Nevada. At the public hearing, a commenter expressed support for the 

draft plan. No adverse comments were made at the public hearing from members 

of the public. The PM10 maintenance plan submittal includes a copy of EPA’s 

comments on the draft plan and Clark County DAQ’s response to those comments. 

See appendix B (“Documentation of the Public Review Process”) to the Clark 

County PM10 Maintenance Plan.