Regional Administrator Jared Blumenfeld signed the following proposed rule on July 10, 2015 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 compliance. 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/search/home.action) and on Regulations.gov (http://www.regulations.gov) in Docket 

Number EPA-R09-OAR-2015-0279.

6560-50-P

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 52 and 81

EPA-R09-OAR-2015-0279; FRLAir Plan Approval; California; Mammoth Lakes; Redesignation 

Request; PM10 Maintenance Plan

AGENCY: Environmental Protection Agency.

ACTION: Proposed rule.

SUMMARY: The Environmental Protection Agency (EPA) is proposing 

to approve, as a revision to the California State Implementation 

Plan (SIP), California’s request to redesignate the Mammoth 

Lakes nonattainment area to attainment for the 1987 National 

Ambient Air Quality Standard (NAAQS) for particulate matter of 

ten microns or less (PM10). EPA is also proposing to approve the

maintenance plan for the Mammoth Lakes area and the associated 

motor vehicle emissions budgets for use in transportation 

conformity determinations. Finally, EPA is proposing to approve 

the attainment year emissions inventory. EPA is proposing these 

actions because the SIP revision meets the requirements of the 
This document is a prepublication version signed by Regional Administrator Jared Blumenfeld on July 10, 2015. 

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

2

Clean Air Act and EPA guidance for maintenance plans and motor 

vehicle emissions budgets.

DATES: Any comments must arrive by [INSERT DATE 30 DAYS AFTER 

DATE OF PUBLICATION IN THE FEDERAL REGISTER].

ADDRESSES: Submit comments, identified by docket number EPAR09-OAR-2015-0279 by one of the following methods:

1. Federal eRulemaking Portal: www.regulations.gov. Follow 

the on-line instructions.

2. E-mail: wamsley.jerry@epa.gov.

3. Mail or deliver: Jerry Wamsley (Air-2), U.S. Environmental 

Protection Agency Region IX, 75 Hawthorne Street, San 

Francisco, CA 94105-3901. 

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.

www.regulations.gov 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 e-mail 
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3

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

captured and included as part of the public comment. If EPA 

cannot read your comment due to technical difficulties and 

cannot contact you for clarification, EPA may not be able to 

consider your comment. Electronic files should avoid the use of 

special characters, any form of encryption, and be free of any 

defects or viruses.

Docket: Generally, documents in the docket for this action are 

available electronically at www.regulations.gov and in hard copy 

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

California. While all documents in the docket are listed at 

www.regulations.gov, some information may be publicly available 

only at the hard copy location (e.g., copyrighted material, 

large maps), and some may not be publicly available in 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.

FOR FURTHER INFORMATION CONTACT: Jerry Wamsley, EPA Region IX, 

(415) 947-4111, wamsley.jerry@epa.gov.

SUPPLEMENTARY INFORMATION: Throughout this document, “we,” “us” 

and “our” refer to EPA.

Table of Contents 
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I. Summary of Our Proposal

II. Background of This Action

A. The PM10 National Ambient Air Quality Standard

B. PM10 Planning Requirements Applicable to the Mammoth Lakes 

Area

C. Summary of the PM10 Attainment Plan for the Mammoth Lakes 

Area

III. Procedural Requirements for the Adoption and Submittal of 

SIP Revisions

IV. Substantive Requirements for Redesignation to Attainment of 

a NAAQS

V. Our Evaluation of California’s Redesignation Request for the

Mammoth Lakes PM10 Nonattainment Area

A. Our Determination That the Area Has Attained the Applicable 

NAAQS

B. The Area Has a Fully Approved SIP Meeting Requirements 

Applicable for Purposes of Redesignation Under Section 110 and 

Part D of the Clean Air Act 

1. Basic SIP Requirements Under Section 110 of the Clean Air Act

2. SIP Requirements Under Part D of the Clean Air Act

a. Permits for New and Modified Major Stationary Sources

b. Control of PM10 Precursor Pollutants

c. General and Transportation Conformity Requirements

C. The Area Must Show the Improvement in Air Quality Is Due to 

Permanent and Enforceable Emission Reductions

D. The Area Must Have a Fully Approved Maintenance Plan Under 

Clean Air Act Section 175A

1. Attainment and Projected Emissions Inventories 

2. Maintenance Demonstration

3. Monitoring Network and Verifying Continued Attainment

4. Verification of Continued Attainment

5. Contingency Provisions

E. Transportation Conformity and Motor Vehicle Emissions Budgets
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VI. Proposed Action and Request for Public Comment

VII. Statutory and Executive Order Reviews

I. Summary of Our Proposal

EPA is proposing approval of the Mammoth Lakes PM10

redesignation and maintenance plan. We are proposing this action 

because California’s SIP revision meets the Clean Air Act (CAA)

requirements and EPA guidance concerning redesignations to 

attainment of a National Ambient Air Quality Standard (NAAQS or 

standard) and maintenance plans. 

First, under CAA section 107(d)(3)(D), EPA is proposing to 

approve the State’s request to redesignate the Mammoth Lakes 

PM10 nonattainment area to attainment for the PM10 NAAQS. Our 

proposal is based on our conclusion that the area has met the 

five criteria for redesignation under CAA section 107(d)(3)(E): 

(1) the area has attained the PM10 NAAQS; (2) the required 

portions of the SIP are fully approved for the area; (3) the 

improvement in ambient air quality in the area is due to 

permanent and enforceable reductions in PM10 emissions; (4) 

California has met all requirements applicable to the Mammoth 

Lakes PM10 nonattainment area with respect to section 110 and 

part D of the CAA; and, (5) the Mammoth Lakes PM10 Maintenance 
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Plan, as described below, meets the requirements of CAA section 

175A.

Second, under section 110(k)(3) of the CAA, EPA is 

proposing to approve as a revision to the SIP, the maintenance 

plan developed by the Great Basin Unified Air Pollution Control 

District (GBUAPCD) entitled “2014 Update Air Quality Maintenance 

Plan and Redesignation Request for the Town of Mammoth Lakes” 

(herein referred to as the Mammoth Lakes PM10 Maintenance Plan),

dated May 5, 2014, submitted by California, through the 

California Air Resources Board (CARB), to EPA on October 21, 

2014.1 EPA is proposing to find that the Mammoth Lakes PM10

Maintenance Plan meets the requirements in section 175A of the 

CAA. The plan’s maintenance demonstration shows that the Mammoth 

Lakes area will continue to attain the PM10 NAAQS for at least 

10 years beyond redesignation (i.e. through 2030). The plan’s 

contingency provisions incorporate a process for identifying new 

or more stringent control measures in the event of a future 

monitored violation. Finally, EPA is proposing to approve the 

plan’s 2012 emission inventory as meeting the requirements of 

CAA section 172 and 175A.

 

1

 See Section III in this action for list of documents submitted by the 

California. See the docket for this action for copies of the submittal 

documents including the October 21, 2014 submittal letter from the State. 
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Third, EPA is proposing to approve the motor vehicle 

emission budgets (budgets) in the Mammoth Lakes PM10 Maintenance 

Plan because we find they meet the applicable transportation 

conformity requirements under 40 CFR 93.118(e). With this 

Federal Register notice, EPA is informing the public that we are 

reviewing the plan’s budgets for adequacy. With this action, we 

are starting the public comment period on adequacy of the 

proposed budgets. Please see the DATES section of this proposal 

for the closing date of the comment period.

II. Background of This Action

A. The PM10 National Ambient Air Quality Standard

EPA sets the NAAQS for certain ambient air pollutants at 

levels required to protect public health and welfare. 

Particulate matter with an aerodynamic diameter less than or 

equal to a nominal ten micrometers, or PM10, is one of the 

ambient air pollutants for which EPA has established healthbased standards. As discussed below, we have promulgated and 

revised the PM10 NAAQS several times. 

EPA revised the NAAQS for particulate matter on July 1, 

1987, replacing standards for total suspended particulates (TSP,

particulate less than 30 microns in diameter) with new standards 

applying only to particulate matter up to 10 microns in diameter 
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(PM10) (52 FR 24633). In 1987, EPA established two PM10

standards, an annual standard and a 24-hour standard. An area 

attains the 24-hour PM10 standard of 150 micrograms per cubic 

meter (μg/m3) when the expected number of days per calendar year 

with a 24-hour concentration exceeding the standard (referred to 

as an exceedance), is equal to or less than one.2 The annual PM10

standard is attained when the expected annual arithmetic mean of 

the 24-hour samples averaged over a three year period does not 

exceed 50 μg/m3. See 40 CFR 50.6 and 40 CFR part 50, Appendix K.

In a 2006 PM NAAQS revision, the 24-hour PM10 standards

were retained but the annual standards were revoked, effective 

December 18, 2006 (71 FR 61144, October 17, 2006). On January 

15, 2013, EPA announced that it was again retaining the 24-hour 

PM10 NAAQS as a 24-hour standard of 150 μg/m3 (78 FR 3086). 

California’s submittal of the Mammoth Lakes PM10 Maintenance 

Plan addresses the 1987 24-hour PM10 standard, as originally 

promulgated, and as reaffirmed on January 15, 2013.

 

2

 An exceedance is defined as a daily value that is above the level of the 24-

hour standard, 150 μg/m3, after rounding to the nearest 10 μg/m3 (i.e., values 

ending in five or greater are to be rounded up). Consequently, a recorded 

value of 154 μg/m3 would not be an exceedance because it would be rounded to 

150 μg/m3; whereas, a recorded value of 155 μg/m3 would be an exceedance 

because it would be rounded to 160 μg/m3. See 40 CFR part 50, Appendix K, 

section 1.0.
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B. PM10 Planning Requirements Applicable to the Mammoth Lakes

Area

On the date of enactment of the 1990 CAA Amendments, PM10

areas meeting the qualifications of section 107(d)(4)(B) of the 

amended Act, such as Mammoth Lakes, were designated 

nonattainment by operation of law (56 FR 11101, March 15, 1991). 

See 40 CFR 81.305. Once an area is designated nonattainment, 

section 188 of the CAA outlines the process for classification 

of the area and establishes the area's attainment date. 

Consistent with section 188(a), at the time of designation, all 

PM10 nonattainment areas were initially classified as moderate 

by operation of law, including the Mammoth Lakes PM10

nonattainment area.3

The 1990 CAA established new planning requirements and 

attainment deadlines for the PM10 NAAQS. A fundamental

nonattainment area requirement applicable to the Mammoth Lakes 

area is that the State submit a SIP demonstrating attainment of 

the PM10 NAAQS. This demonstration must be based upon 

enforceable control measures producing emission reductions and 

 

3

 For the designated boundaries of the Mammoth Lakes PM10 nonattainment area, 

see 40 CFR 81.305. The Mammoth Lakes PM10 nonattainment area is located in 

the southern portion of Mono County, California; see Figures 1-1 and 1-2 

within the Mammoth Lakes PM10 Maintenance Plan, pages 3 and 4.
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emissions at or below the level predicted to result in 

attainment of the PM10 NAAQS throughout the nonattainment area 

(see CAA section 189(a)). As stated in section 189(a)(1) of the 

CAA, the State was required to make the following SIP submittals

by November 15, 1991: the State had to submit a SIP ensuring 

implementation of all reasonably available control measures 

(RACM) no later than December 10, 1993, as required by CAA 

section 189(a)(1)(C); and, the State had to submit a SIP

providing for expeditious attainment by the applicable 

attainment date, December 31, 1994, as required by CAA sections 

188(c)(1)and 189(a)(1)(B).

More specifically, Subparts 1 and 4 of part D, title 1 of 

the CAA contain air quality planning requirements for PM10

nonattainment areas. Subpart 1 of part D, sections 172(c) and 

176 contain general requirements for areas designated as 

nonattainment. The subpart 1 requirements include, among other 

things, provisions for RACM, reasonable further progress (RFP), 

emissions inventories, contingency measures and conformity. 

Subpart 4 of part D contains specific planning and scheduling 

requirements for PM10 nonattainment areas. Section 189(a),(c),

and (e) detail requirements that apply specifically to moderate 

PM10 nonattainment areas such as Mammoth Lakes. These 

requirements include the following: (1) an approved permit 
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program for construction of new and modified major stationary 

sources; (2) an attainment demonstration; (3) provisions for 

RACM; (4) quantitative milestones demonstrating RFP toward 

attainment by the applicable attainment date; and, (5) 

provisions to ensure that the control requirements applicable to 

major stationary sources of PM10 also apply to major stationary 

sources of PM10 precursors except where the Administrator has 

determined that such sources do not contribute significantly to 

PM10 levels exceeding the NAAQS within the area.

C. Summary of the PM10 Attainment Plan for the Mammoth Lakes 

Area

GBUAPCD adopted its moderate area Air Quality Management 

Plan for PM10 in December 1990 (1990 AQMP). California submitted 

the 1990 AQMP for the Mammoth Lakes area on September 11, 1991 

with an addenda submitted on January 9, 1992. Subsequently, EPA 

approved the 1990 AQMP in 1996 (61 FR 32341, June 24, 1996). In 

our 1996 action, we approved the following components of the 

1990 AQMP: the emissions inventory; its provision for 

implementation of RACM; and, the demonstration of attainment. In 

support of the 1990 AQMP, the State submitted two local rules: 

GBUAPCD Rule 431 – Particulate Emissions; and Town of Mammoth 

Lakes Municipal Code, Chapter 8.3, Particulate Emissions 

Regulations. We also approved these rules, which control PM10 
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emissions from entrained road dust and wood burning fireplaces 

and appliances, into the SIP in our 1996 action (61 FR 32341).

GBUAPCD Rule 431 was revised on December 4, 2006 and 

subsequently approved into the SIP in 2007 (72 FR 61525, October 

31, 2007).

Because of the timing of the development of the 1990 AQMP, 

the plan did not address subsequent SIP requirements such as 

contingency measures and transportation conformity. We will 

review how these and other CAA requirements, such as a permit 

program for new and modified stationary sources, were met by the 

State in section V, below. 

III. Procedural Requirements for the Adoption and Submittal of 

SIP Revisions

The GBUAPCD governing Board adopted the “2014 Air Quality 

Maintenance Plan and Redesignation Request for the Town of 

Mammoth Lakes” on May 5, 2014 and forwarded it to CARB on May 

22, 2014. CARB held a Board Hearing on September 18, 2014 and

adopted the Mammoth Lakes PM10 Maintenance Plan.4 California 

 

4

 See Resolution 14-27, State of California, Air Resources Board, “Approval 

and Submittal of the Town of Mammoth Lakes PM10 Maintenance Plan and 

Redesignation Request”, dated September 18, 2014. 
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submitted their redesignation request and the Mammoth Lakes PM10

Maintenance Plan to EPA on October 21, 2014.5

CARB's SIP submittal includes the following documents: (1)

a submittal letter dated October 21, 2014, from Richard Corey, 

Executive Officer, CARB to Jared Blumenfeld, Regional 

Administrator, U.S. EPA Region 9 submitting the State’s 

redesignation request and Mammoth Lakes PM10 Maintenance Plan; 

(2) a transmittal letter dated May 22, 2014 from Duane Ono, 

Deputy Air Pollution Control Officer, GBUAPCD to Richard Corey, 

Executive Officer, CARB; (3) May 22, 2014 Affidavit from The 

Clerk of the GBUAPCD Board, providing Proof of Publication of 

Public Notice for Public Hearing on “2014 Update Air Quality 

Maintenance Plan and Redesignation Request for the Town of 

Mammoth Lakes” and the May 5, 2014 GBUAPCD Board Hearing; (4) 

GBUAPCD Board Order #140505-03 approving and adopting the 

Mammoth Lakes PM10 Maintenance Plan, dated May 5, 2014; (5) 

CARB's August 8, 2014 Notice of Public Hearing for consideration 

of the adoption and approval of the redesignation request and 

Mammoth Lakes PM10 Maintenance Plan and associated motor vehicle 

emissions budgets on September 18, 2014; (6) “2014 Update Air 

 

5

 See letter from Richard Corey, Executive Officer, CARB, to Jared Blumenfeld, 

Regional Administrator, EPA Region 9, dated October 21, 2014, with 

attachments.
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Quality Maintenance Plan and Redesignation Request for the Town 

of Mammoth Lakes” dated May 5, 2014; (7) CARB Board Resolution 

14-27 adopting the redesignation request and Mammoth Lakes PM10

Maintenance Plan; and, (8) the CARB Staff Report, dated August 

18, 2014, containing the motor vehicle emissions budgets adopted 

at the CARB Board hearing. All of these documents are available 

for review in the docket for today's proposed rule.

Sections 110(a)(1) and 110(l) of the Act require states to 

provide reasonable notice and public hearing prior to adoption 

of SIP revisions. CARB's submittal of the redesignation request 

and Mammoth Lakes PM10 Maintenance Plan documents the public 

review process followed by GBUAPCD in adopting the plan prior to 

transmittal to CARB for subsequent submittal to EPA as a 

revision to the SIP. The documentation listed above provides 

evidence that reasonable notice of a public hearing was provided 

to the public and that a public hearing was conducted prior to 

adoption. 

Both GBUAPCD and CARB satisfied applicable statutory and 

regulatory requirements for reasonable public notice and hearing 

prior to adoption of the SIP revisions. GBUAPCD conducted public 

workshops, and properly noticed the public hearing at which the 

Mammoth Lakes PM10 Maintenance Plan was adopted. The SIP 

submittal included proof of publication for notices of the 
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public hearings of CARB and GBUAPCD. Consequently, we conclude 

that the SIP submittals have met the public notice and 

involvement requirements of section 110(a)(1) of the CAA. Based 

on the documentation submitted with the Mammoth Lakes PM10 

Maintenance Plan, we find that the submittal satisfies the 

procedural requirements of section 110(l) of the Act for 

revising SIPs.

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 that we have not 

affirmatively determined to be complete or incomplete will 

become complete six months after the day of submittal by 

operation of law. A completeness review allows us to determine 

if the submittal includes all the necessary items and 

information we need to act on it. We make completeness 

determinations using criteria we have established in 40 CFR part 

51, Appendix V.6

 

6

 The completeness criteria fall into two categories: administrative 

information and technical support information. The administrative information 

provides documentation that the State has followed required administrative 

procedures during the SIP-adoption process; thus, ensuring that we have a 

legally-adopted SIP revision before us. The technical support information 

provides us the information we need to determine the impact of the proposed 

revision on attainment and maintenance of the air quality standards.
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We notify a state of our completeness determination by 

letter unless the submittal becomes complete by operation of 

law. Once a SIP submittal is determined to be complete, either 

by letter or by operation of law, EPA is under a 12 month time 

clock for EPA to act on the SIP submittal. See CAA section 

110(k)(2). A finding of completeness does not approve the 

submittal as part of the SIP nor does it indicate that the 

submittal is approvable. The redesignation request and Mammoth 

Lakes PM10 Maintenance Plan became complete by operation of law 

on April 21, 2015.

IV. Substantive Requirements for Redesignation to Attainment of 

a NAAQS

In section 107(d)(3)(E), the CAA establishes the 

requirements for redesignating an area from nonattainment to 

attainment of a NAAQS. The Administrator may not redesignate an 

area unless the following criteria are met: (1) EPA determines 

that the area has attained the applicable NAAQS; (2) EPA has 

fully approved the applicable implementation plan for the area 

under Section 110(k) of the CAA; (3) EPA determines that the 

improvement in air quality is due to permanent and enforceable 

reductions; (4) EPA has fully approved a maintenance plan for 

the area as meeting the requirements of Section 175A of the CAA; 

and, (5) the State containing such an area has met all 
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requirements applicable to the area under section 110 and part D 

of the CAA. Section 110 identifies a comprehensive list of 

elements that SIPs must include, and part D establishes the SIP 

requirements for nonattainment areas. Part D is divided into six 

subparts. The generally-applicable nonattainment SIP 

requirements are found in part D, subpart 1, and the particulate 

matter-specific SIP requirements are found in part D, subpart 4.

EPA provided guidance on redesignations to states in a 1992 

document entitled “State Implementation Plans; General Preamble 

for the Implementation of Title I of the Clean Air Act 

Amendments of 1990” (referred to herein as the “General 

Preamble”).7 Additional guidance was issued in a September 4, 

1992 memorandum entitled “Procedures for Processing Requests to 

Redesignate Areas to Attainment” from John Calcagni, Director, 

Air Quality Management Division, EPA Office of Air Quality 

Planning and Standards, (referred to herein as the Calcagni 

memorandum). Maintenance plan submittals are SIP revisions. 

Consequently, under section 110(k) of the Act, EPA is obligated 

to approve or disapprove a maintenance plan depending on whether 

it meets the applicable CAA requirements for such plans.

 

7

 The General Preamble was first published at 57 FR 13498 (April 16, 1992) and 

supplemented at 57 FR 18070 (April 28, 1992).
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As discussed in more detail below in section V, we have 

evaluated the State’s submittal and propose to approve CARB's 

request to redesignate the Mammoth Lakes PM10 nonattainment area 

to attainment for the PM10 NAAQS. Our proposal is based on our 

conclusion that all the criteria under CAA section 107(d)(3)(E) 

have been satisfied.

V. Our Evaluation of California’s Redesignation Request for the 

Mammoth Lakes PM10 Nonattainment Area

A. Our Determination That the Area Has Attained the Applicable 

NAAQS

Section 107(d)(3)(E)(i) of the CAA requires that EPA 

determine that the area has attained the NAAQS. Generally, EPA 

determines whether an area's air quality is meeting the 24-hour 

PM10 NAAQS based upon complete, quality-assured, and certified 

data gathered at established state and local air monitoring 

stations (SLAMS) in the nonattainment area, and entered into the 

EPA Air Quality System (AQS) database.8 Data from air monitors 

operated by state, local, or tribal agencies in compliance with 

 

8

 For PM10, a complete set of data includes a minimum of 75 percent of the 

scheduled PM10 samples per quarter. See 40 CFR part 50, Appendix K, section 

2.3(a). Because the annual PM10 standard was revoked effective December 18, 

2006, our action and determination discusses only attainment of the 24-hour 

PM10 standard; see 71 FR 61144, October 17, 2006.
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EPA monitoring requirements must be submitted to the AQS. These 

monitoring agencies certify annually that these data are 

accurate to the best of their knowledge. Accordingly, EPA relies 

primarily on data in AQS when determining the attainment status 

of an area. See 40 CFR 50.6; 40 CFR part 50, appendices J and K; 

40 CFR part 53; and, 40 CFR part 58, appendices A, C, D, and E.

GBUAPCD is responsible for assuring that the Mammoth Lakes 

PM10 nonattainment area meets air quality monitoring 

requirements. Both CARB and GBUAPCD submit annual monitoring 

network plans to EPA. GBUAPCD’s network plans describe the air 

quality monitoring network they operate within the Mammoth Lakes 

nonattainment area and discuss the status of the monitoring 

network, as required under 40 CFR 58.10. In the Mammoth Lakes 

nonattainment area, GBUAPCD operates an air quality monitoring 

station for PM10 in the Gateway Center commercial area within 

the Town of Mammoth Lakes. As required by 40 CFR part 58, the 

District conducts an annual review of the air quality monitoring 

station that is forwarded to CARB and EPA for evaluation. EPA 

regularly reviews these annual plans for compliance with the 

applicable reporting requirements in 40 CFR part 58. With 

respect to PM10, EPA has found that GBUAPCD's network plans meet 
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the applicable requirements of 40 CFR part 58.9 Also, GBUAPCD 

annually certifies that the data it submits to AQS are complete 

and quality-assured. All data has been certified by GBUAPCD for 

the period under review, 2009 through 2014.10

From its 2007 Technical System Audit (TSA) of CARB, the 

Primary Quality Assurance Organization (PQAO), EPA concluded 

that the ambient air monitoring program operated by GBUAPCD in 

the Mammoth Lakes nonattainment area currently meets or exceeds

EPA requirements.11 A TSA is an on-site review and inspection of 

a state or local ambient air monitoring program to assess its 

compliance with established regulations governing the 

collection, analysis, validation, and reporting of ambient air 

quality data. See 40 CFR Part 58, Appendix A, Section 2.5.

EPA determines attainment of the 24-hour PM10 NAAQS by 

calculating the expected number of exceedances of the standard 

in a year. The 24-hour PM10 standard is attained when the 

expected number of exceedances averaged over a three year period 

 

9 See EPA letters to GBUAPCD reviewing the District’s annual network plans for 

the years 2009 to 2014, within the docket for this action.

10 For 2009 to 2014 annual certification letters see the docket for this 

action, e.g., letter from Theodore D. Schade, GBUAPCD, to Jared Blumenfeld, 

EPA Region IX, dated April 25, 2014.

11

 See the Technical System Audit of Primary Quality Assurance Organization, 

California Air Resources Board, dated August 18, 2008, conducted by Air 

Quality Analysis Office, US EPA Region 9, within the docket for this action.
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is less than or equal to one at each monitoring site within the 

nonattainment area. Generally, three consecutive years of 

complete, quality-assured, and certified air quality data is 

sufficient to show attainment of the 24-hour PM10 NAAQS. See 40 

CFR part 50 and appendix K. To demonstrate attainment of the 24-

hour PM10 standard at a given monitoring site, the monitor must 

provide sufficient data to perform the require calculations in 

40 CFR part 50, appendix K described above. The amount of data 

required varies with the sampling frequency, data capture rate 

and the number of years of record. In all cases, three years of 

representative monitoring data must be complete meaning a 

minimum of 75 percent of scheduled PM10 samples must be recorded 

during each calendar quarter of the three year period under 

review. The purpose of these calculations and data completeness 

review is to determine a valid design value for making a 

determination of attainment for the PM10 standard. 

At the Gateway Center monitoring site, GBUAPCD operates two 

PM10 monitors. The first monitor is a Federal Reference Method 

(FRM) monitor (POC 5) run at a sampling frequency of once every 

three days. The second monitor is a Federal Equivalent Method 

(FEM) continuous monitor (POC 6) run at a daily sampling 

frequency. The FEM/POC 6 monitor is the primary monitor we will 

focus on in our determination of attainment. Each monitor 
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produces its own data stream, and the data from the two monitors 

produce separate design values. Our calculations show the 

highest design value for the Mammoth Lakes Planning Area over 

the 2009 through 2014 timeframe is 0.7 expected exceedances, as 

determined by data from the POC 6 monitor. Usually, this design 

value would be sufficient to determine that the Mammoth Lakes 

area has attained the PM10 NAAQS, but we found that the POC 6 

data failed to meet the 75 percent completeness standard in the 

third quarter of 2012, showing a 61 percent completeness 

record.12 Table 1 provides the design values or expected annual 

exceedances of the PM10 standard for the Mammoth Lakes area over 

the year 2009 through 2014 for both monitors.13

Table 1: Design Values and Annual Average Expected Exceedances of PM10 NAAQS 

in Mammoth Lakes Nonattainment Area, 2009 through 2014

Monitor 2009-2011 2010-2012 2011-2013 2012-2014

Gateway Center monitor, Site ID 

06-051-0001 POC 5 0.0 0.0 0.0 0.0

Gateway Center monitor, Site ID 

06-051-0001 POC 6 0.0 0.0 0.7 0.7

Source: EPA Air Quality System, Design Value Report, April 30, 2015

Given the data completeness issue with the third quarter 

2012 data at POC 6, we conducted two analyses to determine if 

the missing data could reasonably change the design value from 

 

12 See AQS Design Value Reports dated April 30, 2015 and AQS Raw Data Reports 

dated May 7, 2015 for completeness information. The reports can be found in 

the docket for today's action.

13

 A design value is calculated using a specific methodology from monitored 

air quality data and is used to compare an area's air quality to a NAAQS. The 

methodologies for calculating expected exceedances for the 24-hour PM10 NAAQS 

are found in 40 CFR Part 50, Appendix K, Section 2.1(a).
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attaining to violating the PM10 NAAQS.14 In the first analysis, 

we compared the POC 5 data with the POC 6 data over the 2009 

through 2014 time period to see if the data correlated closely 

enough to allow the POC 5 data to represent the missing POC 6 

data. We found that the data correlated very well, and when POC 

6 was not operating during the third quarter of 2012, the

observed PM10 values at POC 5 were between 9 and 17 μg/m3, well 

below the 150 μg/m3 value of the PM10 NAAQS. The two monitors 

differ, however, in the frequency of their observations with POC 

5 making observations one day in three and POC 6 making daily 

observations. Consequently, our second analysis examined whether 

exceedances may have reasonably occurred on the days POC 5 was 

not collecting data. 

To determine whether it is reasonable to assume that 

exceedances did not occur on the days POC 5 was not sampling, we 

identified the highest PM10 values over the 2009 through 2014 

time period. Looking at POC 6, the winter months, December, 

January, and February, of 2009, 2010, 2011, and 2012 exhibit 

consistently elevated PM10 concentrations and the highest annual 

 

14 See “Technical Support Document for the Determination of Attainment and 

Redesignation of the Mammoth Lakes PM10 Nonattainment Area: Analyses 

Addressing 2012 Incomplete Data”, April 30, 2015, in the docket for this 

action. 
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concentrations at Mammoth Lakes.15 Then, in 2013 and 2014, the 

highest 24-hour PM10 concentrations at POC 6 were measured 

during the third quarter of 2013 and 2014; see Table 2. Of these 

highest concentrations, on two days, July 28, 2013 and July 29, 

2013, concentrations were higher than the 150 μg/m3 standard.

Table 2: Five Highest PM10 Concentrations Observed at Mammoth Lakes Gateway 

Center Monitor from 2009 through 2014 and Wildfire Events

Date Concentration 

(μg/m3)

Wildfire Event

July 28, 2013 166 Aspen Fire – Exceptional Event Flag

July 29, 2013 182 Aspen Fire – Exceptional Event Flag

July 30, 2013 122 Aspen Fire

August 1, 2013 133 Aspen Fire

August 2, 2014 130 French Fire

Source: EPA Air Quality System, Raw Data Report, May 7, 2015; all

observations are from Site ID 06-051-0001, POC 6.

Further examination shows that the July 28, 2013 and July 

29, 2013 exceedances measured at the Gateway Center monitoring 

site are flagged as wildfire exceptional events within AQS; 

however, an exceptional event demonstration package was not 

submitted for the two exceedances. The Aspen Wildfire occurred 

near the Mammoth Lakes area over an extended period from July 

22, 2013 to September 8, 2013, burning 22,992 acres

approximately 30 miles south southwest of Mammoth Lakes near 

Mammoth Pool Reservoir on the upper San Joaquin River in the 

Sierra National Forest; thus, reasonably accounting for four of 

 

15 Gateway Center monitors POC 5 and POC 6 24-hour concentration data and 

monthly mean summary statistics can be found in the Air Quality System, Raw 

Data Report, dated May 7, 2015, in the docket for today’s action. 
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the five highest observed concentrations of PM10. In a similar 

wildfire event, the French Fire burned from July 28, 2014 to 

August 18, 2014 consuming 13,838 acres west of and adjacent to 

the site of the Aspen Fire; again, reasonably accounting for the 

August 2, 2014 high concentration.16 As a check, we examined the 

2013 and 2014 data for the months with the highest average 

monthly concentration and confirmed that in these two years, 

similar to 2009 through 2012, January and December had the 

highest monthly average PM10 concentrations observed. In sum, 

the high summertime third quarter concentrations observed in 

2013 and 2014 are related to wildfire events and are not 

consistent with the remaining 2009 through 2014 data showing 

that the winter months, December to February, is the period 

during which high PM10 concentrations are most likely to be 

observed in Mammoth Lakes. As noted earlier, the State has 

submitted complete data for all first and fourth calendar 

quarters (i.e. winter season) during the 2009 through 2014 time 

frame and no exceedance of the PM10 NAAQS has occurred during 

 

16 For information concerning the Aspen wildfire, see the 2013 Cal Fire Large 

Fire List at 

www.cdfdata.fire.ca.gov/pub/cdf/images/incidentstatevents_250.pdf. 

For information concerning the French wildfire, see the 2014 Cal Fire Large 

Fire List at 

www.cdfdata.fire.ca.gov/pub/cdf/images/incidentstatevents_249.pdf. 

For a map showing the relative location of the Aspen and French wildfires, 

see www.wildfiretoday.com/2014/07/30/california-french-fire/. 
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these quarters. Also, no exceedance occurred during the third 

quarter of the years 2009, 2010, and 2011. 

To summarize, it is reasonable to conclude that the missing 

third quarter 2012 PM10 data would not have an effect on the

design value and would not overturn our determination of 

attainment for the following reasons: (1) the only two 

exceedances and other high ambient values in the last six years 

were due to wildfire events; (2) data from the third quarters in 

2009, 2010, and 2011 show no exceedances and do not correspond 

with the observed summer time period of elevated PM10 

concentrations in 2013 and 2014; and, (3) the POC 5 data 

correlates well enough to be a valid representation of the 

missing third quarter POC 6 data. Consequently, we are proposing 

to find that the design values in Table 1 are accurate and 

representative design values for the Mammoth Lakes nonattainment 

area with no expected exceedances greater than 0.7 calculated 

over the 2009 through 2014 period. Twenty-four hour ambient PM10

levels in Mammoth Lakes meet the requirement of no more than 1.0 

expected annual average exceedance over a three year period.

Therefore, EPA proposes to determine that the Mammoth Lakes

PM10 nonattainment area has attained the 24-hour PM10 standard 

and continues to attain the standard to date based on the most 

recent available AQS data. In addition, preliminary air quality 
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data for 2015 show that the area is continuing to meet the PM10 

NAAQS. Before finalizing this proposal, EPA will include a

review of any available preliminary data for 2015.

B. The Area Has a Fully Approved SIP Meeting Requirements 

Applicable for Purposes of Redesignation Under Section 110 and 

Part D of the Clean Air Act

Section 107(d)(3)(E)(ii) and (v) require EPA to determine 

that the area has a fully-approved SIP under section 110(k) that 

meets all applicable requirements under section 110 and part D 

for the purposes of redesignation. EPA may rely on prior SIP 

approvals in approving a redesignation request as well as any 

additional measures it may approve in conjunction with a 

redesignation action.17

1. Basic SIP Requirements Under Section 110 of the Clean 

Air Act

The general SIP elements and requirements provided in 

section 110(a)(2) include, but are not limited to, the 

following: submittal of a SIP that has been adopted by the 

 

17

 See the following EPA guidance and court decisions: Calcagni memorandum at 

p. 3; Southwestern Pennsylvania Growth Alliance v. Browner, 144 F.3d 984, 

989-90 (6th Cir. 1998). See 68 FR 25418 and 25426 (May 12, 2003) and 

citations therein concerning EPA’s reliance on added measures approved with 

an action on a redesignation request.
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State after reasonable public notice and hearing; provisions for 

establishment and operation of appropriate procedures needed to 

monitor ambient air quality; implementation of a source permit 

program; provision for the implementation of part C requirements 

for prevention of significant deterioration (PSD) provisions; 

provisions for the implementation of part D requirements for 

nonattainment new source review (nonattainment NSR) permit 

programs; provisions for air pollution modeling; and, provisions 

for public and local agency participation in planning and 

emission control rule development.

We note that SIPs must be fully approved only with respect 

to the applicable requirements for redesignations consistent 

with section 107(d)(3)(E)(ii) of the Act. The section 110 (and 

part D) requirements that are linked to a particular 

nonattainment area's designation and classification are the 

relevant measures to evaluate in reviewing a redesignation 

request. Requirements that apply regardless of the designation 

of any particular area in the State are not applicable 

requirements for the purposes of redesignation, and the State 

will remain subject to these requirements after the Mammoth 

Lakes PM10 nonattainment area is redesignated to attainment. For 

example, CAA section 110(a)(2)(D) requires that SIPs contain 

certain measures to prevent sources in a State from 
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29

significantly contributing to air quality problems in another 

state, known as “transport SIPs.” Because the section 

110(a)(2)(D) requirements for transport SIPs are not linked to a 

particular nonattainment area's designation and classification 

but rather apply regardless of the attainment status, these are 

not applicable requirements for the purposes of redesignation 

under section 107(d)(3)(E).

Similarly, EPA believes that other section 110 (and part D) 

requirements that are not linked to nonattainment plan 

submittals or to an area's attainment status are not applicable 

requirements for purposes of redesignation. EPA believes that 

the section 110 (and part D) requirements relating to a 

particular nonattainment area's designation and classification 

are the relevant measures to evaluate in reviewing a 

redesignation request. This view is consistent with EPA's 

existing policy on applicability of the conformity SIP 

requirement for redesignations.18

Regarding Mammoth Lakes, CARB and GBUAPCD have submitted 

and EPA has approved provisions addressing the basic CAA section 

110 provisions. The GBUAPCD portion of the approved California 

SIP contains enforceable emissions limitations; requires 

 

18

 See discussion in 75 FR 36023 and 36026 (June 24, 2010).
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monitoring, compiling, and analyzing of ambient air quality 

data; requires preconstruction review of new or modified 

stationary sources; provides for adequate funding, staff, and 

associated resources necessary to implement its requirements; 

and, provides the necessary assurances that the State maintains 

responsibility for ensuring that the CAA requirements are 

satisfied in the event that GBUAPCD is unable to meet its CAA 

requirements. There are no outstanding or disapproved applicable 

section 110 SIP submittals with respect to the State, the 

GBUAPCD, and Mammoth Lakes.19 In sum, we propose to conclude that 

CARB and GBUAPD have met all applicable SIP requirements under 

section 110 of the CAA (General SIP Requirements) for the

Mammoth Lakes nonattainment area for purpose of redesignating 

the area to attainment of the PM10 NAAQS.

2. SIP Requirements Under Part D of the Clean Air Act

Subparts 1 and 4 of part D within title 1 of the CAA 

contain air quality planning requirements for PM10 nonattainment 

areas. Subpart 1 contains general requirements for all 

nonattainment areas of any NAAQS pollutant, including PM10. 

Among other provisions, the subpart 1 requirements include

provisions for RACM, RFP, emissions inventories, contingency 

 

19

 The applicable California SIP for all nonattainment areas can be found at: 

http://yosemite.epa.gov/r9/r9sips.nsf/Casips?readform&count=100&state=Califor

nia.
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measures, and conformity. Subpart 4 contains specific planning 

and scheduling requirements for PM10 nonattainment areas. 

Section 189(a), (c), and (e) requirements apply specifically to 

moderate PM10 nonattainment areas and include: (1) an approved 

permit program for construction of new and modified major 

stationary sources; (2) provisions for RACM; (3) an attainment 

demonstration; (4) quantitative milestones demonstrating RFP 

toward attainment by the applicable attainment date; and, (5) 

provisions to ensure that the control requirements applicable to 

major stationary sources of PM10 also apply to major stationary 

sources of PM10 precursors except where the Administrator has 

determined that such sources do not contribute significantly to 

PM10 levels that exceed the NAAQS in the area.

With respect to the subpart 4 requirements discussed above, 

California submitted a moderate area PM10 plan, the 1990 AQMP,

for the Mammoth Lakes nonattainment area on September 11, 1991. 

This attainment plan was developed and adopted by the GBUAPCD on 

December 12, 1990. The State submitted a revision to this plan 

on January 9, 1992, also previously adopted by the GBUAPCD on 

November 6, 1991. This 1990 AQMP for the Mammoth Lakes PM10

Planning Area relied on two control measures to reduce PM10

emissions sufficient to meet the PM10 standard: GBUAPCD, Rule 

431- Particulate Emissions, adopted on November 6, 1991; and, 
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32

Town of Mammoth Lakes Municipal Code Chapter (TMLMCC) 8.30 –

Particulate Matter Emissions Regulations, dated October 2, 1991. 

Both of these rules were submitted with the 1990 AQMP so as to 

reduce emissions from the primary sources of PM10 in the 

nonattainment area, fireplaces and woodstoves, and re-suspended 

road dust and pulverized cinders from motor vehicles driving on 

paved roads. 

EPA reviewed the 1990 AQMP and its companion control 

measures and in 1996 approved the moderate area plan, GBUAPCD 

Rule 431, and TMLMCC 8.30, incorporating them into the SIP (61 

FR 32341, June 24, 1996). In this approval action, we made the 

following findings concerning the 1990 AQMP: the plan provided 

a comprehensive, accurate, and current emissions inventory 

meeting the requirements of section 172(c)(3); the plan provided 

for all RACM to be implemented by December 10, 1993, as required 

by sections 172(c) and 189(a)(1)(C) of the Act; the plan 

provided a demonstration of attainment by December 31, 1994, the 

applicable attainment date, as required by section 189(a)(1)(B); 

and, we found that precursor pollutants of PM10 do not 

contribute significantly to PM10 levels in excess of the NAAQS. 

Regarding RFP, our General Preamble provides that initial 

moderate nonattainment areas, such as the Mammoth Lakes area,

could meet the RFP requirement by demonstrating attainment by 
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33

the applicable attainment date, December 31, 1994.20 As noted 

above, we approved the demonstration of attainment as meeting 

section 189(a)(1)(B).

 The 1990 AQMP did not provide for motor vehicle emissions 

budgets as required by section 176(c) of the Act because EPA’s 

guidance and regulations were not published at the time the plan 

was developed and adopted. The maintenance plan has provided for 

motor vehicle emission budgets. We review them later in this

action and propose to approve them.

The 1990 AQMP as approved in 1996 did not address 

contingency measures required by section 172(c)(9) of the CAA. 

Again, this was because the 1990 AQMP was developed prior to EPA 

guidance on contingency measures.

Since our 1996 action on GBUAPCD Rule 431, the State has 

submitted and EPA has approved into the SIP a subsequent 

revision to the rule (72 FR 61525, October 31, 2007). This 2006 

amendment to Rule 431 eliminated the operational exemption from 

no-burn day requirements granted to EPA-certified devices. These 

EPA-certified devices comprise 84 percent of the residential 

wood burning device inventory.21 Since 2007, all wood-burning 

 

20

 See our discussion concerning RFP/quantitative milestones in the General 

Preamble, (57 FR 13498 and 13539, April 16, 1992). 

21 See Mammoth Lakes PM10 Maintenance Plan, Table 5-1, page 18.
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devices in the Mammoth Lakes nonattainment area have been 

required to shut down on designated no-burn days, adding an 

additional increment of emission reductions when no-burn days 

are called for under the rule. In general, the 2006 revisions to 

GBUAPCD Rule 431 are surplus to the rule provisions in the 1990 

AQMP that represent the control strategy that has resulted in 

the Mammoth Lakes area meeting the PM10 standard. In this 

manner, GBUAPCD Rule 431 represents a pre-implemented 

contingency measure and fulfils the requirements of section 

172(c)(9).

Separate and distinct from a finding of attainment of a 

standard, EPA has taken the position that CAA requirements 

associated with attainment of the NAAQS are not applicable for 

purposes of redesignation. In the General Preamble, EPA has 

stated that section 172(c)(9) requirements are directed at

ensuring reasonable further progress and attainment by the 

applicable attainment date specified by statute. These 

attainment related requirements no longer apply when an area has 

attained a standard and is eligible to be redesignated to 

attainment.22 The Calcagni memorandum states a similar position 

that requirements for reasonable further progress and other 

measures needed for attainment will not apply for redesignations 

 

22

 See the General Preamble at 57 FR 13498 and 13564, (April 16, 1992).
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35

because they only have meaning and applicability where areas do 

not meet the NAAQS.23 While the attainment related provisions of 

RFP and section 172(c)(9) are no longer relevant in the context 

of redesignation, the maintenance plan provisions in section 

175A of the CAA require that such plans incorporate contingency 

provisions sufficient for an area to expeditiously regain 

attainment of a NAAQS. We review the contingency provisions in 

the Mammoth Lakes PM10 Maintenance Plan later in this action and 

propose to approve them. 

a. Permits for New and Modified Major Stationary Sources

CAA sections 172(c)(5) and 189(a)(1)(A) require the State 

to submit SIP revisions that establish certain requirements for 

new or modified stationary sources in nonattainment areas, 

including provisions to ensure that major new sources or major 

modifications of existing sources of nonattainment pollutants 

incorporate the highest level of control, referred to as the 

Lowest Achievable Emission Rate (LAER), and that increases in 

emissions from such stationary sources are offset so as to 

provide for reasonable further progress towards attainment in 

the nonattainment area. The process for reviewing permit 

applications and issuing permits for new or modified stationary 

 

23

 See the Calcagni memorandum at page 6. 
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sources in nonattainment areas is referred to as “nonattainment 

New Source Review” (nonattainment NSR). With respect to the part 

D requirements for a nonattainment NSR permit program for 

construction of new and modified major stationary sources, EPA 

has previously approved the following nonattainment NSR rules 

for GBUAPCD which apply within the Mammoth Lakes nonattainment 

area: GBUAPCD Rule 209-A and 216.24

Final approval of the NSR program, however, is not a 

prerequisite to finalizing our proposed approval of the State's 

redesignation request. EPA has determined in past redesignations 

that a NSR program does not have to be approved prior to 

redesignation, provided that the area demonstrates maintenance 

of the standard without part D NSR requirements in effect. The 

rationale for this position is described in a memorandum from 

Mary Nichols, Assistant Administrator for Air and Radiation, 

dated October 14, 1994, entitled “Part D NSR Requirements for 

Areas Requesting Redesignation to Attainment.” See the more 

detailed explanations in the following redesignation 

rulemakings: Detroit, MI (60 FR 12459, March 7, 1995); 

Cleveland-Akron-Lorrain, OH (61 FR 20458, May 7, 1996); 

Louisville, KY (66 FR 53665, October 23, 2001); Grand Rapids, MI 

 

24 For Rule 209-A, see 47 FR 26379, June 18, 1982, and for Rule 216, see 41 FR 

53661, December 8, 1976.
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37

(61 FR 31831, June 21, 1996); and San Joaquin Valley, CA (73 FR 

22307, April 25, 2008 and 73 FR 66759, November 12, 2008).

The requirements of the PSD program under Part C will apply 

to PM10 once the area has been redesignated. Thus, new major 

sources of PM10 emissions and major modifications at major 

sources of PM10 as defined under 40 CFR 52.21 will be required 

to obtain a PSD permit or include PM10 emissions in their 

existing PSD permit. Currently, EPA is the PSD permitting 

authority in the Mammoth Lakes nonattainment area under a 

federal implementation plan; see 40 CFR 52.270(a)(3). GBUAPCD 

can implement the federal PSD program, however, either through a 

delegation agreement with EPA, or by making the necessary 

changes to its NSR rules and submitting those revisions to EPA 

for a SIP-approved PSD rule.

b. Control of PM10 Precursor Pollutants

Section 189(e) of the CAA requires that the control 

requirements applicable under the part D SIP for major 

stationary sources of PM10 also apply to major stationary 

sources of PM10 precursors, except where the Administrator 

determines that such sources do not contribute significantly to 

PM10 levels that exceed the standard in the area. As noted 

above, in our approval action on the 1990 AQMP, we found that 

PM10 precursors do not contribute significantly to exceedances 
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38

of the PM10 standard in the Mammoth Lakes PM10 area (61 FR 

32344, June 24, 1996). Using similar analytical techniques in 

developing the Mammoth Lakes PM10 Maintenance Plan, GBUAPCD 

confirmed that direct PM10 emissions are most likely to cause or 

contribute to future violations of the NAAQS and addressed these 

sources of direct PM10 in their maintenance plan discussed 

below. 

c. General and Transportation Conformity Requirements

Section 176(c) of the CAA requires states to establish 

criteria and procedures to ensure that federally supported or 

funded projects conform to the air quality planning goals in the 

applicable SIP. The requirement to determine conformity applies 

to transportation plans, programs and projects developed, funded 

or approved under Title 23 U.S.C. and the Federal Transit Act 

(transportation conformity), as well as to other federallysupported or funded projects (general conformity). State 

conformity regulations must be consistent with federal 

conformity regulations that the CAA required EPA to promulgate 

relating to consultation, enforcement and enforceability.

GBUAPCD's general conformity regulation, Regulation 13, was 

submitted to EPA on October 5, 1994 and approved on April 23, 

1999 (64 FR 19916).
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EPA has not approved a transportation conformity regulation

for Mammoth Lakes and the GBUAPCD. EPA believes, however, that 

it is reasonable to interpret the conformity SIP requirements as 

not applying for purposes of a redesignation request under 

section 107(d) because state conformity rules are still required

after redesignation, and federal conformity rules apply where 

state rules have not been approved.25

In conclusion, if EPA finalizes today's proposal approving 

the PM10 emissions inventory and motor vehicle emissions budgets 

for the Mammoth Lakes PM10 nonattainment area, then EPA will 

have determined the State has a fully-approved SIP meeting all 

requirements applicable under section 110 and part D for the 

Mammoth Lakes PM10 nonattainment area for purposes of 

redesignation, per section 107(d)(3)(E)(v) of the CAA.

C. The Area Must Show the Improvement in Air Quality Is Due to 

Permanent and Enforceable Emission Reductions

Before redesignating an area to attainment of a NAAQS, 

section 107(d)(3)(E)(iii) of the CAA requires EPA to determine 

that the air quality improvement in the Mammoth Lakes PM10 

nonattainment area is due to permanent and enforceable emission 

 

25 See Wall v. EPA, 265 F. 3d 426 (6th Cir. 2001), upholding this 

interpretation. Also, see 60 FR 62748 (December 7, 1995).
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40

reductions resulting from implementation of the applicable SIP 

and applicable federal air pollution control regulations and 

other permanent and enforceable regulations. Under this 

criterion, the State must reasonably be able to attribute the 

improvement in air quality to emissions reductions that are 

permanent and enforceable. Attainment resulting from temporary 

reductions in emissions rates (e.g., reduced production or 

shutdown) or unusually favorable meteorology would not qualify 

as an air quality improvement due to permanent and enforceable 

emission reductions.26 As discussed earlier, EPA may rely on 

prior SIP approvals in approving a redesignation request and any 

additional measures it may approve in conjunction with a 

redesignation action. As noted earlier, GBUAPCD has jurisdiction 

over air quality planning requirements for the Mammoth Lakes 

PM10 nonattainment area and produced a moderate area PM10 plan, 

the 1990 AQMP, and related rules designed to reduce PM10 

emissions in the Mammoth Lakes area so as to meet the PM10 

NAAQS.

As discussed, GBUAPCD developed and California submitted 

the 1990 AQMP for the Mammoth Lakes nonattainment area on 

September 11, 1991. The 1990 AQMP relied on two control measures 

 

26

 See the Calcagni memorandum, page 4.
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41

to reduce PM10 emissions sufficient to meet the PM10 standard: 

GBUAPCD Rule 431 - Particulate Emissions, adopted on November 6, 

1991; and, Town of Mammoth Lakes Municipal Code Chapter 8.30 –

Particulate Matter Emissions Regulations, dated October 2, 1991. 

Both of these rules were implemented so as to reduce emissions 

from the primary sources of PM10 in the nonattainment area, 

fireplaces and woodstoves, and re-suspended road dust and 

cinders from motor vehicles driving on paved roads. In 1996, EPA 

approved the 1990 AQMP, GBUAPCD Rule 431, and TMLMCC 8.30, 

incorporating them into the SIP (61 FR 32341, June 24, 1996). In 

this approval action, we found that the rules provided for RACM 

and were sufficient to reduce PM10 to levels necessary to meet 

the PM10 NAAQS. CARB cites figures from 1995 showing that from 

1990 to 1994 the percentage of cleaner burning EPA certified 

wood burning devices in the area increased from 1 percent to 35 

percent.27 Since 1994, the percentage of EPA-certified woodburning devices has increased to 84 percent in 2013.28 With 

regard to entrained road dust PM10 emissions on paved roads, the 

purchase and continued use of high efficiency vacuum street 

 

27 See “Staff Report: Town of Mammoth Lakes PM10 Maintenance Plan and 

Redesignation Request,” CARB, August 18, 2014, page 5. 

28 See Mammoth Lakes PM10 Maintenance Plan, Table 5-1, page 18.
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sweepers have resulted in reducing PM10 emissions by as much as 

68 percent from pre-1990 levels.29 

We are proposing to determine that the Mammoth Lakes area 

has attained the PM10 standard continuously since 2009 according 

to complete, quality-assured, and certified air quality data, 

per our discussion in section V.A. of this proposal. In addition 

to our review of air quality data supporting our proposed 

determination, the Mammoth Lakes PM10 Maintenance Plan provided 

data showing that over the period these two control measures 

were implemented and enforced, 1994 to the present, there have 

been no violations of the federal PM10 standard.30 Also, see 

Figures 4-1 and 4-2 of the Mammoth Lakes PM10 Maintenance Plan 

showing how winter time average and peak ambient PM10 levels 

have fallen since 1990.

In conclusion, EPA is proposing to find that the 

improvement in PM10 air quality for the Mammoth Lakes

nonattainment area is the result of permanent and enforceable 

 

29

 See “Staff Report: Town of Mammoth Lakes PM10 Maintenance Plan and 

Redesignation Request,” CARB, August 18, 2014, page 6.

30 See Table 2-1 in the Mammoth Lakes PM10 maintenance plan, page 10. We note 

that while the data record shows falling PM10 levels and PM10 levels below 

the NAAQS over the period of control measure implementation and enforcement, 

the data record shown in Table 2-1 was not sufficient to determine attainment 

of the PM10 NAAQS, until recently. For instance, Table 2-1 shows periods 

where the PM10 monitor was not operating and therefore not providing a data 

record complete enough to determine attainment of the PM10 NAAQS. See our 

prior discussion of data requirements in our proposed determination that the 

area has attained the PM10 standard in section V.A above.
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reductions in emissions from significant sources of PM10 in the 

area and, in accordance with 107(d)(3)(E)(iii), is not the 

result of temporary reductions (e.g., economic downturns or 

shutdowns) or unusually favorable meteorology.

D. The Area Must Have a Fully Approved Maintenance Plan Under 

Clean Air Act Section 175A

Section 175A of the CAA describes the elements of a 

maintenance plan for areas seeking redesignation from 

nonattainment to attainment. We interpret this section of the

CAA to require the following elements: an attainment emissions

inventory; a maintenance demonstration; a monitoring network

capable of verification of continued attainment along with a 

commitment to do so; and, a contingency plan.31 Under CAA section 

175A, a maintenance plan must demonstrate continued attainment 

of the relevant NAAQS for at least ten years after EPA approves 

a redesignation to attainment. To address the possibility of 

future NAAQS violations, the maintenance plan must contain

contingency provisions that EPA finds sufficient to correct 

promptly any violation of the NAAQS that occurs after the area’s 

redesignation. Based on our review and evaluation provided 

below, we are proposing to approve the Mammoth Lakes PM10

 

31

 See Calcagni memorandum, pages 8 through 13.
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Maintenance Plan because it meets the requirements of CAA 

section 175A.

Before reviewing the Mammoth Lakes PM10 Maintenance Plan 

and its components in more detail, it is important to provide a 

description of the geography and the economy of the region. The 

Mammoth Lakes area sits on the eastern slopes of the Sierra 

Nevada mountain range on the western edge of the Long Valley 

Caldera in southwestern Mono County, California. At the western 

boundary of the nonattainment area, there is Mammoth Mountain at 

an elevation of 11,053 feet. From the foot of Mammoth Mountain 

and the developed portion of the Town of Mammoth Lakes at 7,891 

feet elevation, the Mammoth Creek Valley slopes to the east and 

down to the eastern edge of the PM10 nonattainment area near the 

Mammoth Lakes airport at 7,127 feet elevation.32 Much of the area 

surrounding the Town of Mammoth Lakes within and without the 

nonattainment area is public land, either national forest or 

national monument lands. 

The Town of Mammoth Lakes is the area’s only population 

center and the only incorporated community in Mono County with 

an estimated permanent population of 8,234 in 2010.33 Within the 

Mammoth Lakes PM10 nonattainment area and the boundaries of the 

 

32 See Mammoth Lakes PM10 Maintenance Plan, Figures 1-1 and 1-2, page 3 and 4. 

33 U. S. Census figure. 
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Town of Mammoth Lakes is the Mammoth Mountain ski area, west of 

the town center. The ski area attracts 1.2 to 1.5 million 

visitors every winter, swelling the Town of Mammoth Lakes 

population to approximately 35,000 people on a major winter 

weekend.34 The large number of winter time visitors contribute to 

PM10 emissions from residential wood burning and vehicle 

entrained dust from pulverized cinders that have been applied to 

the paved roads to provide better vehicle traction on snowcovered roads. In the 1990 AQMP and in the Maintenance Plan, 

these two sources were determined to be the overwhelming 

contributors of PM10 to potential exceedances of the NAAQS in 

the Mammoth Lakes area. 

1. Attainment and Projected Emissions Inventories

Section 172(c)(3) of the CAA requires plan submittals to 

include a comprehensive, accurate, and current inventory of 

emissions from all sources in the nonattainment area. In 

demonstrating maintenance according to CAA section 175A and the 

Calcagni memorandum, the State should provide an attainment 

emissions inventory for the area so as to identify the emissions 

level sufficient to attain the NAAQS. Where the State has made 

an adequate demonstration that air quality has improved as a 

 

34 See Mammoth Lakes PM10 Maintenance Plan at Section 1.3, page 2.
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result of the SIP, the attainment emissions inventory will 

generally be an inventory of actual emissions at the time the 

area attained the standard.35 A maintenance plan for the 24-hour 

PM10 standard must include an inventory of emissions of PM10 in 

the area to identify a level of emissions sufficient to attain 

the 24-hour PM10 NAAQS. This inventory must be consistent with 

EPA's most recent guidance on emissions inventories for 

nonattainment areas available at the time and should represent 

emissions during the time period associated with the monitoring 

data showing attainment. The inventory must also be 

comprehensive, including emissions from stationary point 

sources, area sources, and mobile sources.

The Mammoth Lakes PM10 Maintenance Plan provides an 

estimated daily PM10 emissions inventory for 2012 and 2030. The 

year 2012 provides an appropriate attainment year inventory 

because it is one of the years in the most recent three-year 

periods (2012 through 2014) in which attainment of the PM10

NAAQS was monitored. Table 3 presents the PM10 emissions 

inventories for 2012 and 2030 provided in the Mammoth Lakes PM10

Maintenance Plan.

 

35

 EPA's primary guidance for evaluating these emissions inventories is the 

document entitled, “PM10 Emissions Inventory Requirements,” EPA, Office of 

Air Quality Planning and Standards, EPA-454/R-94-033 (September 1994) which 

can be found at: http://www.epa.gov/ttn/chief/eidocs/PM10eir.pdf.
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Table 3: 2012 and 2030 Mammoth Lakes Nonattainment Area Peak 24 hour PM10 

Emissions (kilograms/winter day)

Source Category 2012 2030

Residential Wood Combustion Sources 850 802

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

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

Stationary – Point Sources 8 8

Total PM10 4,324 5,129

Source: Mammoth Lakes PM10 Maintenance Plan, Tables 5-7, 8-1, and 8-3, pages 

22, 36, and 37. 

The Mammoth Lakes PM10 Maintenance Plan's emissions 

inventory for sources within the Mammoth Lakes nonattainment 

area air basin is subdivided into four subcategories: 

residential wood combustion, entrained road dust and cinders, 

on-road mobile sources, and stationary sources. Because the most 

consistently elevated values of ambient PM10 concentrations 

occur in the winter, sources like construction dust and fugitive 

dust from unpaved roads are not accounted for in this inventory. 

In the Mammoth Lakes area, construction activity is seasonal and 

inactive during the winter due to the wet and cold climate. 

Similarly, unpaved roads are snow covered or rarely used due to 

wet conditions; in either case, little fugitive dust is 

generated by vehicle use on unpaved roads. As shown in Table 3, 

direct PM10 emissions in the Mammoth Lakes area are dominated by 

entrained road dust from paved roads and residential wood 

combustion. The estimates for peak winter day PM10 emissions 

incorporate the highest ski season visitors and vehicle miles 
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traveled (VMT) estimates in the calculation for both entrained 

paved road dust and on-road mobile emissions. GBUAPCD used a 

chemical mass balance (CMB) analysis to determine if PM10 

precursors were affecting PM10 values at the Gateway Center 

monitor/receptor. CMB uses chemical profiles of emission sources 

to apportion the monitored concentration between the various 

source types. The CMB study showed that on representative days 

of high PM10 concentrations the total contribution of nitrates, 

sulfates, and ammonium was approximately 1-2% of total mass 

collected. Consistent with the large contributions from 

entrained road dust and residential wood combustion the largest 

contributors to PM10 concentrations were organic carbon, 

elemental carbon, and soil.36

GBUAPCD projects that overall, direct PM10 emissions will 

increase from 2012 to 2030 because of a general and winter-time 

tourist population increase due to build out of the Town of 

Mammoth Lakes. While higher emitting wood combustion sources 

will be replaced by cleaner burning devices or removed entirely, 

population growth and resulting VMT growth will drive the 

predicted increase in entrained road dust. The District's 

maintenance demonstration modeling and supporting analyses

 

36

 See Mammoth Lakes PM10 Maintenance Plan, Appendix G, “Chemical Analysis of 

PM10 and PM2.5 Filters from Mammoth Lakes”, Desert Research Institute, May 

21, 2013; see Table 3, page 3.
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indicate that despite the population and VMT growth, the Mammoth 

Lakes nonattainment area will continue to attain the federal 24-

hour PM10 standard because of the relative importance and 

continuing decline of residential wood combustion emissions. The 

overall predicted result is a slight increase in ambient PM10

levels over the 2012 to 2030 timeframe. We will review the 

maintenance demonstration and 2030 predicted PM10 concentrations 

in greater detail in the next section of this action. 

In conclusion, GBUAPCD’s selection of 2012 as the 

attainment year inventory is appropriate since the area was 

determined to have attained the NAAQS during the 2011 to 2013

period. Based on our review of the Mammoth Lakes PM10 

Maintenance Plan, we propose to find that the emissions 

inventories for 2012 and 2030 are comprehensive, current, and 

accurate in that they include estimates of PM10 from all of the 

relevant source categories, residential wood combustion, 

entrained road dust, on-road mobile sources, and stationary

sources. Therefore, we are proposing to approve the 2012

emissions inventory, which serves as the Mammoth Lakes PM10

Maintenance Plan's attainment year inventory, as satisfying the 

requirements of section 172(c)(3) of the CAA for the purposes of 

redesignation of the Mammoth Lakes PM10 nonattainment area to 

attainment of the 24-hour PM10 NAAQS.
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2. Maintenance Demonstration

Section 175A(a) of the CAA requires a demonstration of 

maintenance of the NAAQS for at least 10 years after 

redesignation. Generally, a State may demonstrate maintenance of 

the NAAQS by either showing that future emissions of a pollutant 

or its precursors will not exceed the level of the attainment 

inventory, or by modeling to show that the future anticipated 

mix of sources and emission rates will not cause a violation of 

the NAAQS. For areas that are required under the CAA to submit 

modeled attainment demonstrations, the maintenance demonstration 

should use the same type of modeling.37

In the Mammoth Lakes PM10 Maintenance Plan, GBUAPCD chose 

to use modeling to demonstrate maintenance of the 24-hour PM10 

NAAQS and to show that the future anticipated mix of sources and 

emission rates will not cause a violation of the NAAQS in the 

Mammoth Lakes area. The maintenance demonstration builds upon

the previous 1990 AQMP attainment plan, and incorporates the

specifics of the Mammoth Lakes area, including geography, the 

winter-time peak visitor population, and the contribution of the 

two major sources of PM10, residential wood combustion and 

 

37 See Calcagni memorandum, page 9.
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entrained dust from paved roads. Below, we review the 

maintenance demonstration in more detail.

To be consistent with the 1990 AQMP attainment 

demonstration, GBUAPCD limited the area modeled in the 

maintenance demonstration to the Town of Mammoth Lakes boundary,

somewhat smaller than the larger nonattainment area boundary.38

This was done for two reasons. First, the land east of the Town 

boundary is mostly public lands, is sparsely populated, and is 

downhill from the PM10 monitoring station located within the 

Town. Almost all of the human population and developed land in 

the nonattainment area is situated and concentrated within a

smaller portion of the larger Township. The PM10 

monitor/receptor at Gateway Center, providing much of the data 

for the maintenance demonstration, is located there, too. 

Meteorologically, an analysis of wind speeds and wind directions 

on high winter PM10 days shows that hourly wind speeds are low 

(less than 2 meters/second) and primarily from the west.39 In 

these near stagnant air mass conditions, the observed wind 

direction and speed most likely result from cold air flows 

moving downhill from higher to lower elevations. As a result, on 

design days of likely high PM10 observations, PM10 emissions 

 

38 See Mammoth Lakes PM10 Maintenance Plan, Figure 1-2, page 4.

39

 See Mammoth Lakes PM10 Maintenance Plan, Chapter 5.0 page 17.
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east of the Town of Mammoth Lakes are unlikely to affect the 

levels observed at the PM10 monitor/receptor because those 

emissions would be moving away, further downhill and to the 

east. Consequently, an in-Town emissions inventory is the more 

appropriate inventory of PM10 sources contributing to high PM10 

values observed at the Gateway Center PM10 monitor. This in-Town 

emissions inventory accounts for 78 percent of the total area 

emissions inventory described in the preceding section of this 

notice.40 The excluded PM10 emissions are almost entirely 

entrained road dust produced east and downhill from the PM10 

monitor/receptor at Gateway Center in the Town of Mammoth Lakes. 

The second point of comparison with the 1990 AQMP 

attainment demonstration and maintenance demonstration is the 

use of a chemical mass balance (CMB) analysis to determine the 

emissions sources affecting PM10 values at the monitor/receptor. 

CMB uses chemical profiles of emission sources to apportion the 

monitored concentration between the various source types. The 

1990 AQMP’s attainment demonstration and emissions inventory 

showed that the primary sources contributing to exceedances of 

the PM10 NAAQS were residential wood combustion and entrained 

dust from vehicle traffic. Using a second CMB study and a new 

emissions inventory, GBUAPCD confirmed that the same two sources 

 

40 See Mammoth Lakes PM10 Maintenance Plan, Table 8-3, page 37. 
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continue to disproportionately affect PM10 levels in the Mammoth 

Lakes area.41 The 2013 CMB analysis done for the maintenance 

demonstration also provides critical inputs for the linear 

rollback analysis described next.

The maintenance demonstration modeling is based on a linear 

rollback methodology. In a linear rollback model, a fundamental 

assumption is that the ambient concentration attributed to a 

given source is proportional to emissions from that source. The 

rollback model used by GBUAPCD incorporated the following 

parameters: a background PM10 concentration of 5 μg/m3; a PM10 

design value concentration of 99 μg/m3 based on 2010 through 2012 

observations at the Gateway Center monitoring site; peak winter 

season VMT based on peak winter season visitor population 

consistent with a 2025 Town build out under the 2007 Town of 

Mammoth Lakes General Plan; and, in-Town peak winter PM10 

emissions estimated for residential wood combustion and 

entrained road dust on paved roads.42 The maintenance 

demonstration analyzed two worst case design day scenarios: (1) 

a day indicative of highest residential wood smoke conditions; 

and, (2) a day indicative of highest entrained road dust 

 

41

 See Mammoth Lakes PM10 Maintenance Plan, Chapter 6, page 23; Table 6-4, page 

26; and Appendix G. 

42

 See the Mammoth Lakes PM10 Maintenance Plan, Chapter 8, pages 36-42; Table 

8-4, page 38; and, the Executive Summary at page x for population and VMT 

discussion. 
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emissions.43 The proportionalities for residential wood sources 

and entrained road dust used within the rollback model scenarios 

are derived from the 2013 CMB source apportionment studies 

discussed in Chapter 6 and Appendix G of the maintenance plan. 

In the first scenario of highest residential wood smoke 

emissions, the predicted 2030 PM10 concentration was 100 μg/m3.44

In the second scenario of highest entrained road dust emissions, 

the predicted 2030 PM10 concentration was 104.8 μg/m3.45 In 

either scenario, PM10 concentrations are predicted to remain 

below the PM10 NAAQS of 150 μg/m3 and are slightly higher than 

the 2010-2012 attainment design value concentration of 99 μg/m3.

To conclude, EPA proposes to find that the forecasted 

increases in PM10 levels from 2012 to 2030 are consistent with 

the control measures currently implemented and are not 

anticipated to result in PM10 levels above the PM10 NAAQS, as 

shown in the maintenance demonstration described above. Based on 

our review of the information presented in the Mammoth Lakes 

PM10 Maintenance Plan, we propose to find that the State has 

shown that attainment of the PM10 standard will be maintained in 

 

43

 See the Mammoth Lakes PM10 Maintenance Plan Chapter 8.3, page 39, for 

calculations. 

44

 See the Mammoth Lakes PM10 Maintenance Plan Chapter 8.4, page 40, and Table 

8-6, page 41. 

45

 See the Mammoth Lakes PM10 Maintenance Plan Chapter 8.4, page 40, and Table 

8-7, page 42. 
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the Town of Mammoth Lakes and the larger Mammoth Lakes area for 

at least 10 years after redesignation.

3. Monitoring Network and Verifying Continued Attainment

Continued attainment of the NAAQS can be verified through 

operation of an appropriate air quality monitoring network. The 

Calcagni memorandum states that the maintenance plan should 

contain provisions for continued operation of air quality 

monitors that will provide such verification.46 GBUAPCD has 

committed to continue to operate an appropriate air quality 

monitoring network in accordance with 40 CFR part 58, to 

continue daily monitoring of PM10 at the existing monitoring 

site so as to verify the ongoing attainment status of the area.47

As we discussed in Section V.A. of this proposal, GBUAPCD’s

monitoring network for PM10 and the Mammoth Lakes PM10 monitors 

are part of an EPA-approved air quality monitoring network.

4. Contingency Provisions

Under section 175A of the CAA, contingency provisions are 

required for maintenance plans to correct promptly any 

violations of the NAAQS that occur after the area is

redesignated to attainment. These contingency provisions must 

 

46 See Calcagni memorandum, page 11.

47

 See Mammoth Lakes PM10 Maintenance Plan, Chapter 9.2.2, page 45.
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include a requirement that the State will implement all measures 

with respect to the control of the air pollutant concerned that 

were contained in the SIP for the area before redesignation of 

the area to attainment. These contingency provisions are 

distinguished from those generally required for nonattainment

areas under section 172(c)(9) because they are not required to 

be fully-adopted measures that will take effect without further 

action by the State before the maintenance plan can be approved. 

The contingency plan is considered, however, to be an 

enforceable part of the SIP and should ensure that the 

contingency measures are adopted expeditiously once they are 

triggered by a specified event.

The Calcagni memorandum states that the contingency 

provisions of the maintenance plan should identify the measures 

to be adopted, a schedule and procedure for adoption and 

implementation, and a time limit for action by the State. The 

memo also states that the contingency provisions should identify 

indicators or triggers which will be used to determine when the 

contingency measures need to be implemented. While the memo 

suggests inventory or monitoring indicators, it states that 

contingency provisions will be evaluated on a case-by-case 

basis.
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In several actions, EPA has long approved contingency 

provisions that rely on reductions from measures that are 

already in place but are over and above those relied on for 

attainment and RFP under section 172(c)(9) of the CAA (62 FR 

15844, April 3, 1997), (62 FR 6627, December 18, 1997), (66 FR 

30811, June 8, 2001), (66 FR 586 and 66 FR 634, January 3, 

2001). This interpretation has been upheld in LEAN v. EPA, 382 

F.3d 575 (5th Cir. 2004), where the court set forth its 

reasoning for accepting excess reductions from already adopted 

measures as contingency measures.

Our interpretation that excess emission reductions can 

appropriately serve as section 172(c)(9) contingency measures is 

equally applicable to section 175A(d) contingency measures. EPA 

has approved maintenance plans under section 175A that included 

contingency provisions relying on measures to be implemented 

prior to any post-redesignation NAAQS violation (60 FR 27028,

May 22, 1995) and (73 FR 66759, November 12, 2008).

As required by section 175A of the CAA, GBUAPCD adopted a 

contingency plan to address possible future PM10 air quality 

problems. The contingency provisions in the Mammoth Lakes PM10

Maintenance Plan are contained in Chapter 9.1.2 of the plan. In 

the event of a violation of the PM10 NAAQS, the District commits 

to adopt additional control measures to meet the PM10 NAAQS 
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within 18 months of the violation; the measures cited may 

include reducing the “no burn day” trigger threshold, or 

improving roadway clean-up procedures.48 Also, the District 

commits to track the progress of the maintenance plan and the 

continuing validity of its analyses and assumptions, such as an 

updated peak winter day emissions inventory and an analysis of 

air quality trends.49 Finally, the District commits to continued 

implementation of plan’s control measures, continued performance 

of ambient air quality monitoring, as well as the progress 

reports described previously.50 

To summarize, given the commitments described above, EPA is 

proposing to find that the Mammoth Lakes PM10 Maintenance Plan 

is consistent with the maintenance plan contingency provision 

requirements of the CAA and EPA guidance. The contingency 

provisions of the maintenance plan contain tracking and 

triggering mechanisms to determine when contingency measures are 

needed, and specific timelines for action. Thus, we conclude 

that the contingency provisions of the Mammoth Lakes PM10 

Maintenance Plan are adequate to ensure prompt correction of a 

 

48 See the Mammoth Lakes Maintenance Plan Chapter 9.1.2, page 44.

49 See the Mammoth Lakes Maintenance Plan Chapter 9.2.1, pages 44-45.

50 See the Mammoth Lakes Maintenance Plan Chapter 9.3, page 45.
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violation of the PM10 NAAQS and comply with section 175A(d) of 

the Act.

E. Transportation Conformity and Motor Vehicle Emissions Budgets

Under section 176(c) of the CAA, transportation plans, 

programs and projects in the nonattainment or maintenance areas 

that are funded or approved under title 23 U.S.C. and the 

Federal Transit Laws (49 U.S.C. chapter 53) must conform to the 

applicable SIP. In short, a transportation plan and program 

conforms to the applicable SIP if the emissions resulting from 

the implementation of that transportation plan and program are 

less than or equal to the motor vehicle emissions budgets 

(budgets) established in the SIP for the attainment year, 

maintenance year and other years.51 The budgets serve as a 

ceiling on emissions that would result from an area's planned 

transportation system. The budget concept is explained in the 

preamble to the transportation conformity rule (58 FR 62188, 

November 24, 1993). The preamble describes how to establish 

budgets in the SIP and how to revise the budgets.

Maintenance plan submittals must specify the maximum 

emissions of transportation-related PM10 and PM10 precursor 

 

51 See 40 CFR part 93 for the federal conformity regulations and 40 CFR 93.118 

specifically for how budgets are used in conformity.
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emissions allowed in the last year of the maintenance period, 

i.e., the budgets.52 Budgets may also be specified for additional 

years during the maintenance period. The submittal must also 

demonstrate that these emissions levels, when considered with 

emissions from all other sources, are consistent with

maintenance of the NAAQS. For EPA to find these emissions levels 

or budgets adequate and approvable, the submittal must meet the 

conformity adequacy provisions of 40 CFR 93.118(e)(4) and (5).

EPA's process for determining adequacy of a budget consists 

of three basic steps: (1) notifying the public of a SIP 

submittal; (2) providing the public the opportunity to comment 

on the budget during a public comment period; and, (3) making a 

finding of adequacy or inadequacy. The process for determining 

the adequacy of a submitted budget is codified at 40 CFR 

93.118(f). EPA can notify the public by either posting an 

announcement that EPA has received SIP budgets on EPA's adequacy 

 

52

 Transportation-related emissions of volatile organic compounds (VOC) and/or 

oxides of nitrogen (NOx) emissions must also be specified in PM10 areas if EPA 

or the state finds that transportation-related emissions of one or both of 

these precursors within the nonattainment area are a significant contributor 

to the PM10 nonattainment problem and has so notified the metropolitan 

planning organization (MPO) and the U.S. Department of Transportation (DOT), 

or if the applicable SIP revision or SIP revision submittal establishes an 

approved or adequate budget for such emissions as part of the RFP, attainment 

or maintenance strategy. See 40 CFR 93.102(b)(2)(iii). Neither of these 

conditions apply to the Mammoth Lake PM10 nonattainment area. Consequently, 

the Mammoth Lakes PM10 Maintenance Plan establishes motor vehicle emissions 

budgets for PM10 only and does not include PM10 precursors.
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Web site (40 CFR 93.118(f)(1)), or via a Federal Register notice 

of proposed rulemaking when EPA reviews the adequacy of an 

implementation plan budget simultaneously with its review and 

action on the SIP itself (40 CFR 93.118(f)(2)).53

Today, we are notifying the public that EPA will be 

reviewing the adequacy of the 2012 and 2030 budgets in the 

Mammoth Lakes PM10 Maintenance Plan. The public has a 30-day 

comment period as described in the DATES section of this notice. 

After this comment period, EPA will indicate whether the budgets 

are adequate via the final rulemaking on this proposed action or 

on the adequacy Web site, according to 40 CFR 93.118(f)(2)(iii).

EPA’s adequacy review is provided in the subject Memorandum 

accompanying today's Federal Register notice and included in the 

docket for this action. 

During GBUAPCD’s 30-day comment period prior to the 

District Board adopting the Mammoth Lakes PM10 Maintenance Plan, 

District staff amended the budgets in a response to comments 

from EPA. Consequently, the budget considered and adopted by the 

District Board and transmitted to CARB was not the budget 

 

53 The availability of the SIP submittal with budgets can be announced for 

public comment on EPA's adequacy Web site at

http://www.epa.gov/otaq/stateresources/transconf/currsips.htm which provides 

a 30-day public comment period. The public can then comment directly on this 

Web site.
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released to the general public at the start of the District’s 

public comment period. To fully comply 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 the GBUAPCD Board adopted version of the Mammoth Lakes PM10 

Maintenance Plan and the budgets contained therein.54

The Mammoth Lakes PM10 Maintenance Plan submitted by the 

State contains PM10 budgets for the entire Mammoth Lakes PM10 

nonattainment area for the years 2012 and 2030. The PM10 budgets 

for the Mammoth Lakes nonattainment area are as follows: 2012 -

3,466 kilograms per day; and, 2030 – 4,319 kilograms per day.55

These budgets include direct PM10 emissions from vehicle 

exhaust, tire and brake wear emissions, and entrained dust on 

paved roads due to vehicle travel. See Table 4. These budgets do 

not include road construction dust or fugitive dust from vehicle 

travel on unpaved roads because emissions from these sources are 

minimal during the winter; see our earlier review of the Mammoth 

Lakes PM10 Maintenance Plan emissions inventory. As noted in our 

emission inventory review, PM10 precursors are a very small 

component of the overall inventory and a negligible contribution 

 

54 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. For evidence of CARB’s public notice and 

hearing see our earlier discussion of procedural requirements and CARB’s 

documentation included in the docket for this action. 

55

 See the Mammoth Lakes PM10 Maintenance Plan Chapter 10, page 47. 
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to the budgets. The on-road mobile source PM10 emissions (motor 

vehicle exhaust, tire and brake wear) were calculated using the 

latest approved emission factor model, EMFAC2011.56 The fugitive 

dust emissions for paved roads were calculated using the latest 

version of the Compilation of Air Pollutant Emission Factors

(AP-42).57

Table 4: 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 (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. 

 

As previously discussed in our review of the maintenance 

demonstration for 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. Although EPA concurs with the rationale for 

using an in-town PM10 emissions inventory in the maintenance 

 

56

 See the Mammoth Lakes PM10 Maintenance Plan Chapter 5.7, page 21. Also see 

78 FR 14533 (March 6, 2013) for our approval of EMFAC2011.

57 January 2011 Version of AP42, Fifth Edition, Volume I, Chapter 13.2.1 

Miscellaneous Sources, Paved Roads: 

http://www.epa.gov/ttn/chief/ap42/ch13/final/c13s0201.pdf
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demonstration, EPA also modeled the total area emissions shown 

in Table 4 to ensure that the higher estimated emissions do not, 

as we anticipate, cause or contribute to future violations of 

the ambient 24-hour PM10 standard. Using the same methodology as 

the maintenance demonstration and the modeling scenario of 

highest ambient contribution of entrained road dust emissions, 

we found that the predicted 2030 ambient PM10 concentration was 

104.8 μg/m3, well below the standard and consistent with the 

concentration calculated in the maintenance demonstration for 

the same scenario.58 

Based on the information presented in the Mammoth Lakes 

PM10 Maintenance Plan and our adequacy review to date, we 

propose to approve the motor vehicle emissions budgets in the 

Mammoth Lakes PM10 Maintenance Plan as meeting the requirements 

of the CAA and EPA regulations. EPA has determined that the 

budgets are consistent with control measures in the SIP and are 

consistent with maintenance of the 24-hour PM10 standard within 

the Mammoth Lakes area through 2030. The details of EPA’s 

evaluation of the budget for compliance with the budget adequacy 

 

58

 See the Mammoth Lakes Maintenance Plan, Chapter 8.3, page 39 for the 

maintenance demonstration methodology and model equation. Also, see our prior 

discussion of the emissions inventory and maintenance demonstration for model 

equation inputs, such as background concentration and residential wood smoke 

emissions. For our calculations, see the Memorandum regarding our 

documentation supporting our budgets adequacy determination in the docket for 

this action. 
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criteria of 40 CFR 93.118(e) are provided in a separate 

memorandum included within the docket for this rulemaking.59 As 

noted earlier, the public comment period for EPA’s adequacy 

finding will be concurrent with the public comment period for

this proposed action on the Mammoth Lakes PM10 Maintenance Plan.

VI. Proposed Action and Request for Public Comment

Based on our review of the Mammoth Lakes PM10 Maintenance 

Plan and redesignation request submitted by California, air 

quality monitoring data, and other relevant materials contained 

on our docket, EPA is proposing to find that the State has 

addressed all the necessary requirements for redesignation of 

the Mammoth Lakes nonattainment area to attainment of the PM10

NAAQS, pursuant to CAA sections 107(d)(3)(E) and 175A.

First, under CAA section 107(d)(3)(D), we are proposing to 

approve the State's request, which accompanied the submittal of 

the Mammoth Lakes PM10 Maintenance Plan, to redesignate the 

Mammoth Lakes PM10 nonattainment area to attainment for the 24-

hour PM10 NAAQS. We are doing so based on our conclusion that 

the area has met the five criteria for redesignation under CAA 

section 107(d)(3)(E): (1) the area has attained the 24-hour PM10

 

59 See EPA memorandum titled, “EPA’s Adequacy Review of Motor Vehicle 

Emissions Budgets in Mammoth Lakes PM10 Maintenance Plan”, dated July 1, 

2015.
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NAAQS; (2) the relevant portions of the SIP are fully approved; 

(3) the improvement in air quality in the Mammoth Lakes area is 

due to permanent and enforceable reductions in PM10 emissions; 

(4) California has met all requirements applicable to the 

Mammoth Lakes PM10 nonattainment area with respect to section 

110 and part D of the CAA; and, (5) our proposed approval of the 

Mammoth Lakes PM10 Maintenance Plan, as part of this action.

Second, under section 110(k)(3) of the CAA, EPA proposes to

approve the Mammoth Lakes PM10 Maintenance Plan and find that it 

meets the requirements of Section 175A. We propose to find that 

the maintenance demonstration shows that the area will continue 

to attain the 24-hour PM10 NAAQS for at least 10 years beyond 

redesignation (i.e., through 2030). We propose to find that the 

Maintenance Plan provides a contingency process for identifying 

and adopting new or more stringent control measures if a 

monitored violation of the PM10 NAAQS occurs. Finally, we are 

proposing to approve the 2012 emissions inventory as meeting 

applicable requirements for emissions inventories in Section 172

of the CAA.

Last, we propose that the Maintenance Plan’s motor vehicle 

emissions budgets meet applicable CAA requirements for 

maintenance plans and transportation conformity requirements 

under 40 CFR 93.118(e). With this action, we are starting the 
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67

public comment period on the adequacy of these proposed motor 

vehicle emissions budgets. 

We are soliciting comments on this proposed action. We will 

accept comments from the public on this proposal for 30 days 

following publication of this proposal in the Federal Register. 

We will consider these comments before taking final action.

VII. 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 proposed 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:

• 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);
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68

• 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,
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• does not provide EPA with the discretionary authority to 

address disproportionate human health or environmental 

effects with practical, appropriate, and legally 

permissible methods under Executive Order 12898 (59 FR 

7629, February 16, 1994).

In addition, this proposed action does not apply on any Indian 

reservation land or in any other area where EPA or an Indian 

tribe has demonstrated that a tribe has jurisdiction. In those 

areas of Indian country, the rule does not have tribal 

implications and will not impose substantial direct costs on 

tribal governments or preempt tribal law as specified by 

Executive Order 13175 (65 FR 67249, November 9, 2000).
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List of Subjects

40 CFR Part 52

Environmental protection, Air pollution control, Incorporation 

by reference, Intergovernmental relations, Particulate matter, 

Reporting and recordkeeping requirements.

40 CFR Part 81

Environmental protection, Air pollution control, National parks, 

Wilderness areas.

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

____________________ _______________________________

Dated: Jared Blumenfeld

Regional Administrator,

Region IX.