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Federal Register / Vol. 86, No. 145 / Monday, August 2, 2021 / Proposed Rules https www.epa.gov/dockets/
commenting-epa-dockets. If you need assistance in a language other than English or if you are a person with disabilities who needs a reasonable accommodation at no cost to you, please contact the person identified in the FOR
FURTHER INFORMATION CONTACT section.
FOR FURTHER INFORMATION CONTACT:
Jonathan Szeto, Air Planning Office AIR2, EPA Region IX, 415 947
4278, szeto.jonathan@epa.gov.
SUPPLEMENTARY INFORMATION:
Throughout this document, we, us, and our refer to the EPA.
Table of Contents
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I. Background II. Nevadas SIP Submittal III. The EPAs Evaluation of Nevadas SIP
Submittal A. Procedural Requirements B. LMP Requirements IV. Transportation Conformity V. Proposed Action and Public Comment VI. Statutory and Executive Order Reviews
I. Background Carbon monoxide is a colorless, odorless gas that is generally emitted from the incomplete combustion of carbon-containing fuels. The largest sources of CO in ambient environments are cars, trucks, and other vehicles and machineries that burn fossil fuels.
Inhalation of CO can impair oxygen delivery to vital organs and tissues.
Those with pre-existing heart disease or other conditions that make one unable to compensate for tissue hypoxia are particularly vulnerable to the cardiovascular effects of ambient CO, especially during exercise or when under increased stress. At high levels, CO exposure can also lead to dizziness, confusion, and unconsciousness.1
In 1971 the EPA established primary and secondary NAAQS for CO at 9 parts per million ppm, averaged over an 8hour period, and at 35 ppm, averaged over a 1-hour period.2 On September 13, 1985, the EPA retained the primary standards without revision and revoked the secondary standards.3 The EPA
retained the primary standards without revision again in both 1994 4 and 2011.5
The EPA retained the primary standards based on scientific evidence demonstrating that the existing standards are requisite to protect public health with an adequate margin of safety. The EPA also found that analysis of both the non-climate and climate welfare effects of CO are insufficient to 1 76

FR 54294 August 31, 2011.
FR 8186 April 30, 1971.
3 50 FR 37484 September 13, 1985.
4 59 FR 38906 August 1, 1994.
5 75 FR 54194 August 31, 2011.
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provide support for a secondary standard.
Following the enactment of the Clean Air Act CAA or Act Amendments of 1990, the EPA designated the Las Vegas Valley area as a Moderate nonattainment area.6 The area was reclassified as a Serious nonattainment area on October 2, 1997, when the EPA determined the area had not attained the standard after receiving a one-year extension of the 1995
attainment date.7 Under the CAA, states are required to adopt and submit SIPs to attain the NAAQS in nonattainment areas within their state.
Under CAA section 175A, one of the criteria for an area to be redesignated from nonattainment to attainment is the approval of a maintenance plan. The maintenance plan must, among other requirements, ensure control measures are in place such that the area will continue to maintain the standard for the period extending 10 years after redesignation, and include contingency provisions to assure that violations of the NAAQS will be promptly remedied.
In 1994, the EPA set forth new guidelines establishing a streamlined process for certain nonattainment areas to meet CAA section 175A maintenance plan requirements.8 This process provides for maintenance by demonstrating that future violations of the standard are unlikely to occur because the areas design values 9 are well below the NAAQS, and based on the historical stability of the areas air quality. A design value is considered well below the NAAQS when it is less than or equal to 85 percent of the standard. For CO specifically, this would be 85 percent of the 9 ppm 8hour CO standard, or 7.65 ppm. The EPA refers to this streamlined demonstration as a limited maintenance plan LMP. Although the LMP
guidelines originally addressed the ozone NAAQS, the EPA extended the provisions to apply to other pollutants and issued guidance specific for CO
nonattainment areas.10 The LMP must be submitted as a SIP revision and FR 56694 November 6, 1991.
FR 51604 October 2, 1997.
8 Memorandum dated November 16, 1994, from Sally L Shaver, Director, Air Quality Strategies &
Standards Divisions MD15 to Air Branch Directors, Regions IX, Limited Maintenance Plan Option for Nonclassifiable Ozone Nonattainment Areas.
9 A design value is a statistic that describes the air quality status of a certain pollutant for a given location relative to its NAAQS.
10 Memorandum dated October 6, 1995, from Joseph W. Paisie, Group Leader, Air Quality Management Division MD15 to Air Branch Chiefs, Regions IX, Limited Maintenance Plan Option for Nonclassifiable CO Nonattainment Areas Paisie Memo.

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should include an attainment emissions inventory, maintenance demonstration, provisions for the continued operation of the ambient air quality monitoring network for verification of continued attainment, a contingency plan in the event of a future violation of the NAAQS, and conformity determination provisions.11 12
In September 2010, the EPA approved the Carbon Monoxide Redesignation Request and Maintenance Plan, Las Vegas Valley Nonattainment Area, Clark County, Nevada September 2008 for the Las Vegas Valley area and redesignated the area to attainment.13
Under CAA section 175A, at the end of the eighth year after the effective date of redesignation, the state must submit a second maintenance plan to ensure ongoing maintenance of the standard for an additional ten years. On June 18, 2019, the State of Nevada submitted the Second 10-Year Carbon Monoxide Limited Maintenance Plan: Las Vegas Valley Maintenance Area, Clark County, Nevada May 2019 2019 LMP for the Las Vegas Valley area to fulfill the second maintenance plan requirement in CAA section 175A.14 The 2019 LMP
includes a demonstration that the area is expected to remain in attainment of the CO NAAQS through the last year of the second 10-year maintenance period, that is, through the remainder of the areas full 20-year maintenance period.
II. Nevadas SIP Submittal On June 18, 2019, NDEP submitted the 2019 LMP to the EPA as a revision to the Nevada SIP. The submittal includes the LMP and appendices.
Appendices to the plan include air quality data, emissions inventory information, air quality monitoring information, and documentation of the public review process.
III. The EPAs Evaluation of Nevadas SIP Submittal A. Procedural Requirements Sections 110a2 and 110l of the CAA require that a reasonable notice and public hearing occur before revisions to a SIP can be adopted by the state. Specifically, under 40 CFR part 51, subpart F, the EPA requires that 11 Id.

at 35.

12 Memorandum
dated September 4, 1992, from John Calcagni, Director, Air Quality Management Division MD15, Regional Air Division Directors, Regions IX, Procedures for Processing Requests to Redesignate Areas to Attainment.
13 75 FR 59090 September 27, 2010.
14 Letter of submittal dated June 13, 2019, from Greg Lovato, Administrator, Nevada Division of Environmental Protection, to Elizabeth Adams, Air Division Director, U.S. Environmental Protection Agency Region IX submitted electronically June 18, 2019.

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