2015-18531. Air Plan Approval; California; Mammoth Lakes; Redesignation Request; PM10

AGENCY:

Environmental Protection Agency (EPA).

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 Clean Air Act and EPA guidance for maintenance plans and motor vehicle emissions budgets.

DATES:

Any comments must arrive by August 31, 2015.

ADDRESSES:

Submit comments, identified by docket number EPA-R09-OAR-2015-0279 by one of the following methods:

1. Federal eRulemaking Portal:http://www.regulations.gov. Follow the online instructions.

2. Email: 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 http://www.regulations.gov or email. http://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 email directly to EPA, your email 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, [phone], wamsley.jerry@ epa.gov.

SUPPLEMENTARY INFORMATION:

Throughout this document, “we,” “us” and “our” refer to EPA.

Table of Contents

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. Contingency Provisions

E. Transportation Conformity and Motor Vehicle Emissions Budgets

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 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.

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 PM ₁₀ 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 health-based 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 (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/m^[3] ) 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 p.m. 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.

B. PM ₁₀ 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 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 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 PM ₁₀ 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 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 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 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 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]

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 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.

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 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 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 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 required 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 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 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 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 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 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 p.m.10 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 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 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 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 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 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, 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 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 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 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 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 (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 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 federally-supported 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).

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 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 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 wood-burning 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 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 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 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 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 snow-covered 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 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.

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 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 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.

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 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 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 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/m^[3] ; a PM₁₀ design value concentration of 99 μg/m^[3] 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 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/m^[3] .^[44] In the second scenario of highest entrained road dust emissions, the predicted 2030 PM₁₀ concentration was 104.8 μg/m^[3] .^[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 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 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.

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 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 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 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 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 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 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 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/m^[3] , 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 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 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 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);
• 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 (Pub. L. 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,
• 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).

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: July 10, 2015.

Jared Blumenfeld,

Regional Administrator, Region IX.

Footnotes

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.

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.

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.

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.

5.  See letter from Richard Corey, Executive Officer, CARB, to Jared Blumenfeld, Regional Administrator, EPA Region 9, dated October 21, 2014, with attachments.

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.

7.  The General Preamble was first published at 57 FR 13498 (April 16, 1992) and supplemented at 57 FR 18070 (April 28, 1992).

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.

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.

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).

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.

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.

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/​.

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.

18.  See discussion in 75 FR 36023 and 36026 (June 24, 2010).

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=​California.

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.

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

23.  See the Calcagni memorandum at page 6.

24.  For Rule 209-A, see 47 FR 26379, June 18, 1982, and for Rule 216, see 41 FR 53661, December 8, 1976.

25.  See Wall v. EPA, 265 F. 3d 426 (6th Cir. 2001), upholding this interpretation. Also, see 60 FR 62748 (December 7, 1995).

26.  See the Calcagni memorandum, page 4.

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.

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.

31.  See Calcagni memorandum, pages 8 through 13.

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

33.  U. S. Census figure.

34.  See Mammoth Lakes PM₁₀ Maintenance Plan at Section 1.3, page 2.

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.

36.  See Mammoth Lakes PM₁₀ Maintenance Plan, Appendix G, “Chemical Analysis of PM₁₀ and PM_2.5 Filters from Mammoth Lakes”, Desert Research Institute, May 21, 2013; see Table 3, page 3.

37.  See Calcagni memorandum, page 9.

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

39.  See Mammoth Lakes PM₁₀ Maintenance Plan, Chapter 5.0 page 17.

40.  See Mammoth Lakes PM₁₀ Maintenance Plan, Table 8-3, page 37.

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.

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.

46.  See Calcagni memorandum, page 11.

47.  See Mammoth Lakes PM₁₀ Maintenance Plan, Chapter 9.2.2, page 45.

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.

51.  See 40 CFR part 93 for the federal conformity regulations and 40 CFR 93.118 specifically for how budgets are used in conformity.

52.  Transportation-related emissions of volatile organic compounds (VOC) and/or oxides of nitrogen (NO_X) 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.

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.

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.

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.

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.

59.  See EPA memorandum titled, “EPA's Adequacy Review of Motor Vehicle Emissions Budgets in Mammoth Lakes PM₁₀ Maintenance Plan”, dated July 1, 2015.