1

Memorandum 

Date: July 1, 2015

Re: EPA’s Adequacy Review of Motor Vehicle Emissions Budgets in Mammoth 

Lakes PM10 Maintenance Plan

To: Docket Number EPA-R09-OAR-2015-0279; Docket for the Mammoth Lakes, 

California PM10 Maintenance Plan and Redesignation Request; Proposed 

Approval Action

From: Jerry Wamsley, Air Planning Office, U.S. Environmental Protection AgencyRegion 9

Summary

Together with EPA’s proposed rulemaking, this memorandum provides the documentation for 

EPA’s adequacy determination for the Mammoth Lakes 2012 and 2030 PM10 Motor Vehicle 

Emissions Budgets (MVEBs, also referred to as budgets) in the Great Basin Unified Air 

Pollution Control District’s (GBUAPCD) “2014 Air Quality Maintenance Plan and 

Redesignation Request for the Town of Mammoth Lakes” (Mammoth Lakes PM10 Maintenance 

Plan), adopted on May 5, 2014 and later submitted by California to EPA on October 21, 2014.

The MVEB adequacy criteria are specified in 40 CFR 93.118(e)(4) and 93.118(e)(5). There are 

seven criteria EPA must certify in finding an MVEB adequate. In support of our proposed 

approval and finding of adequacy for the Mammoth Lakes area PM10 MVEBs, we have 

determined that the State has met all of these criteria. Our detailed discussion follows below. 

Where noted, more detail can be found in our proposed action and in the Mammoth Lakes PM10 

Maintenance Plan. 

Criterion #1, Sec. 93.118(e)(4)(i): The plan was endorsed by the Governor (or designee) 

and was subject to a public hearing.

The GBUAPCD and the California Air Resources Board (CARB) satisfied applicable statutory 

and regulatory requirements for reasonable public notice and hearing prior to adoption and 

submittal of “2014 Air Quality Maintenance Plan and Redesignation Request for the Town of 

Mammoth Lakes”. The GBUAPCD and the State both provided separate 30-day public 

comment periods, and held a public hearing prior to the adoption of the Plan on May 5, 2014 and 

September 18, 2014, respectively. Documentation accompanying the SIP and provided in the 

docket for our proposal describes a public and agency outreach effort. See, e.g., the respective 

Public Hearing Notices and Proof of Publication provided by GBUAPCD and CARB, as well as 

CARB’s partial hearing transcript. 
2

Criterion #2, 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.

GBUAPCD and CARB consulted with federal, state and local agencies in April, May, August 

and September of 2014. This consultation included EPA, CARB, and California Department of 

Transportation (Caltrans). EPA received several draft versions of the Mammoth Lakes PM10 

Maintenance Plan and provided comments prior to adoption. As result of EPA comments during 

GBUAPCD’s 30-day comment period prior to District Board adoption on May 5, 2014, District 

staff amended the budgets to include the entire non-attainment area as opposed to the Township 

of Mammoth Lakes area. Consequently, the budgets considered and adopted by the District 

Board and transmitted to CARB were not the budgets initially released to the general public at 

the start of the District’s public comment period. To comply fully with public notice 

requirements for SIP revisions prior to submittal by the State, CARB provided a full 30-day 

comment period and public hearing for GBUAPCD Board adopted version of the Mammoth 

Lakes PM10 Maintenance Plan and the budgets contained therein. For the budgets as presented 

and adopted by CARB, see their “Staff Report: Town of Mammoth Lakes PM10 Maintenance 

Plan and Redesignation Request”, dated August 18, 2014 at Table 3, page 10, provided in the 

docket for this action. Again, for evidence of CARB’s public notice and hearing see CARB’s 

documentation included in the docket for this action. 

In sum, issues raised by EPA on the draft Mammoth Lakes PM10 Maintenance Plan were fully

addressed by GBUAPCD in their adopted maintenance plan and CARB’s public hearing ensured 

the GBUAPCD amendments met public notice requirements for SIPs.

Criterion #3, Sec. 93.118(e)(4)(iii): The motor vehicle emission budgets are clearly 

identified and precisely quantified.

The motor vehicle emissions budgets for 2012 and 2030 are clearly identified and precisely 

quantified on page 47 of the Mammoth Lakes PM10 Maintenance Plan; see also Tables 5-7, 8-1, 

and 8-3, pages 22, 36, and 37, respectively. Also, see the CARB’s “Staff Report: Town of 

Mammoth Lakes PM10 Maintenance Plan and Redesignation Request”, dated August 18, 2014 

at Table 3, page 10. The budgets were developed using CARB’s EMFAC2011 motor vehicle 

emissions factor model and EPA’s Compilation of Air Pollutant Emission Factors (AP-42). 

Chapter 5 of the Maintenance Plan documents the methods and assumptions underlying the 

emission inventory estimates used in developing the budgets.

Table 1: Mammoth Lakes PM10 Maintenance Plan 2012 and 2030 PM10 Motor Vehicle Emissions Budgets 

(kilograms/day) 

Source Category 2012 2030

Entrained Road Dust Cinders/Paved Roads 3,455 4,305

On-road Mobile Sources (exhaust, tailpipe, tire and brake wear) 11 14

Total Motor Vehicle Emissions Budget 3,466 4,319

Peak 24-hour winter PM10 emissions calculated for the entire planning area. Source: Mammoth Lakes PM10 

Maintenance Plan, Tables 5-7, 8-1, and 8-3, pages 22, 36, and 37, respectively; also, see page 47. 
3

Criterion #4, 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).

EPA has concluded that the budgets for the years 2012 and 2030 when considered together with 

all other emission sources is consistent with the requirement to demonstrate maintenance of the 

24-hour PM10 standard in the Mammoth Lakes area. This finding is based on our review of 

GBUAPCD’s maintenance demonstration and budgets in the Mammoth Lakes PM10 

Maintenance Plan. 

For reasons related to the topography, economy, and winter time meteorology of the Mammoth 

Lakes area, GBUAPCD modeled within the maintenance demonstration an area equivalent to the 

Township of Mammoth Lakes boundaries and smaller than the total nonattainment area. 

Nominally, this resulted in budgets approximately 22 percent smaller than the calculated total 

nonattainment area budgets. GBUAPCD modeled two scenarios in its Township-based 

maintenance demonstration with the second scenario involving highest PM emissions from 

entrained road dust on paved roads being most relevant to the adopted budgets. Within the 

maintenance demonstration and the second scenario of highest entrained road dust emissions, the 

predicted 2030 PM10 concentration was 104.8 micrograms per cubic meter (μg/m3), well below 

the standard of 150 μg/m3. 

In response to EPA comments, GBUAPCD revised their budgets for 2012 and 2030 to include 

vehicle miles traveled and resulting direct and fugitive mobile source PM10 emissions from 

mobile sources east of the Township and representing the entire nonattainment area. Using the 

same background and proportionality inputs to the model from the second scenario of highest 

entrained road dust emissions provided in Chapter 8.3 of the Mammoth Lakes PM10 

Maintenance Plan, we modeled the 2030 PM10 ambient concentration using the total 

nonattainment area budgets provided by GBUAPCD and the result was 104.8 μg/m3; the same 

predicted concentration as the plan’s maintenance demonstration. 

The calculation is as follows: 

Cd = design day concentration = 99 μg/m3;

Cb = background concentration = 5 μg/m3(resulting in 94 μg/m3for allocation among emission 

sources); 

Cd RWB = design day concentration attributed to residential wood burning = (94 μg/m3)(0.61) = 

57.3 μg/m3;

Cd MS = design day concentration attributed to mobile sources (direct PM10 and entrained road 

dust) = (94 μg/m3)(0.39) = 36.7 μg/m3;

CRWB = 2030 concentration due to residential wood burning = (Cd RWB) (E2030/E2012) = (57.3 

μg/m3)(802 kilograms/day (kg/day) / 850 kg/day) = 53.9 μg/m3, where Exxxx is estimated 

emissions;

CMS = 2030 concentration due to entrained road dust = (Cd MS) (E2030/E2012) = (36.7 μg/m3)(4319 

kg/day / 3466 kg/day) = 45.9 μg/m3, where Exxxx is estimated emissions;
4

CTotal = total 2030 concentration = Cb + CRWB + CMS = 5 μg/m3 + 53.9 μg/m3 + 45.9 μg/m3 = 

104.8 μg/m3(all other source contributions were neglible, e.g., very low stationary source 

emissions are not predicted to change).

To conclude, we found that the predicted concentration was well below the standard and 

consistent with the concentration calculated in the maintenance demonstration for the same 

scenario. See our proposed action on the Mammoth Lakes PM10 Maintenance Plan for our 

detailed review of the emissions inventory and maintenance demonstration. 

Criterion #5, Sec. 93.118(e)(4)(v): The plan shows a clear relationship among the emissions 

budget(s), control measures and the total emissions inventory.

The emission inventories for all point, area, and mobile sources within the Mammoth Lakes 

nonattainment area are contained in Chapter 5 of the Mammoth Lakes PM10 Maintenance Plan. 

Chapter 7 describes the control measures implemented in the Mammoth Lakes area and Chapter 

8 details control measure effects in the maintenance demonstration. Tables 5-7, 8-1 and 8-3 best 

illustrate the relationships between the 2012 base year emissions inventory, the projected 2030 

emissions inventory, and the implemented control measures. 

The motor vehicle emissions budgets for PM10 represent the sum of emissions estimates for 

certain motor vehicle related source categories including emissionsfrom entrained road dust 

(paved), vehicle exhaust, brake wear, and tire wear. Where applicable, these emissions estimates 

show the effect of control measures implemented previously and maintained as part of the 

Maintenance Plan, particularly those related to entrained road dust. As discussed in the 

Mammoth Lakes PM10 Maintenance Plan and our proposed action, due to the wet and cold 

wintertime conditions, the budgets do not include entrained dust from unpaved roads, 

construction dust.

Criterion 6, 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).

The 1990 PM10 Air Quality Management Plan for Mammoth Lakes, previously approved by 

EPA in 1996, did not contain motor vehicle emissions budgets, as EPA had not promulgated the 

conformity regulations required by the 1990 Clean Air Act Amendments. So while the October 

2014 submitted Mammoth Lakes PM10 Maintenance Plan provides for 2012 and 2030 emissions 

budgets, it does not update or revise any budget for conformity purposes.
5

Criterion 7, 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.

Besides EPA, no one commented on the Mammoth Lakes PM10 Maintenance Plan and 

redesignation request during either the State’s, or the District’s public review process. See the 

docket for the public comments summary or CARB’s partial hearing transcript. EPA’s 

comments were fully addressed by GBUAPCD and CARB.