Docket ID Number EPA-HQ-OAR /9/2015 Page I. March 9, 2015 CERTIFIED MAIL#

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1 Docket ID Number EPA-HQ-OAR Page I March 9, 2015 CERTIFIED MAIL# EPA Docket Center (EPA/DC) ATTN: Docket ID Number EPA-HQ-OAR U.S. Environmental Protection Agency West Building Mail Code: 28221T 1200 Pennsylvania Ave. NW Washington, D.C Re: National Ambient Air Quality Standards for Ozone The Clark County Department of Air Quality in Las Vegas, Nevada, is pleased to have this opportunity to comment on the proposed National Ambient Air Quality Standards (NAAQS) for ozone published in the Federal Register on December 17, 2014 (vol. 79, p. 42). Clark County supports a health-based approach to establishing the NAAQS. Clark County also agrees that the standards should be set to protect children and at-risk populations, and to provide increased protection against ozone-related adverse impacts on vegetation and ecosystems. After reviewing the scientific studies, the Clean Air Scientific Advisory Committee concluded that "there is adequate scientific evidence to recommend a range of levels for a revised primary ozone standard from 70 ppb to 60 ppb." Clark County supports this range for the primary standard, as well as a scientifically based primary and secondary standard; however, if EPA implements a new secondary standard, this will be the first time the form of the primary and secondary standards are different. We believe EPA should take into consideration the additional resources needed to determine compliance with a W126 form regarding Prevention of Significant Deterioration (PSD) and Nonattainment New Source Review (NNSR), along with transportation and general conformity. There might be other implementation issues Clark County is not aware of. Lowering the standards w!ll create major challenges for Clark County, since natural background in some areas exceeds the proposed NAAQS. Local industry and communities may also face undue compliance burdens if EPA does not address the following areas of concern in implementation rules and guidance documents: I. The 4 1 h-highest three-year ( ) average for Jean, Clark County's background site, is 75 ppb. Jean lies in open desert, 30 miles south of the urbanized area of the Las Vegas Valley and 20 miles north of the California state line. Prevailing winds are from the southwest, so anthropogenic pollutants from the Las Vegas Valley have little or no impact on this site. Modeling suggests that natural background concentrations (including biogenic sources of precursor pollutants) range as high as 48 ppb. Natural background ozone concentrations,

2 Docket ID Number EPA-HQ-OAR Page 2 combined with transport of anthropogenic pollutants from neighboring states, will cause Clark County to exceed the proposed NAAQS without contributions from any local anthropogenic sources. Local and state air agencies need guidance on how to address background levels of ozone that approach and sometimes exceed the level of the proposed ozone NAAQS. 2. Clark County disagrees with the use of a mean seasonal average in modeling to assess background concentrations in the West. In the Regulatory Impact Analysis, the seasonal mean background ozone was reported by EPA to be between 30 and 35 ppb. These values are natural background, absent any anthropogenic ozone. Elevated ozone concentrations in Clark County often happen during episodes when background concentrations are unusually high, due to international or regional transport, and natural events such as wildfires and stratospheric ozone intrusions. We believe EPA should use this episodic background to assess overall concentrations in Clark County. 3. Regional transport of anthropogenic pollutants is signiticant in the Mountain West in general and Clark County in particular. This issue must be addressed in EPA's implementation rules and guidance documents, since it is not adequately addressed in the federal Clean Air Act (CAA). For example, Section 126 ("Interstate Pollution Abatement") discusses only proposed stationary sources of pollutants; in the West, area and mobile sources are often much more significant contributors to regional transport. State and local agencies in the West need assistance in modeling regional transport to identify sources of emissions and assess control strategies. (Clark County has conducted several studies on regional ozone transport into southern Nevada, and would willingly share the information with other agencies upon request.) EPA modeling results involving the CAA's "Good Neighbor" provisions show that regional and international transport significantly affect design values at Clark County ozone monitoring stations. Figure I shows that Jean, Clark County's background site, could exceed the proposed standard without any local contributions. The average local ozone contribution is approximately 20 percent; all other contributions are out of Clark County's control. Even if Clark County were to implement additional control measures, its jurisdiction would still violate the NAAQS.

3 Docket 10 Number EPA-HQ-OAR Page 3 EPA projected 2018 Design Values Source Apportionment 60- Source NV ('t') CA Other SlOG Boundary Other States o- I BC I I I I I I I JD JM JN JO PM PV WJ site Figure 1. EPA Modeling Results for Clark County. 4. Gaps in the ambient air monitoring network throughout the West must be fi lled to support regional ozone modeling and provide a complete picture of the interstate transport of ozone and its precursor pollutants. for example, rural areas from southern California to Clark County to southern Utah have significant gaps between monitoring sites. 5. Smoke from wildfires or other exceptional events frequently cause ozone levels in Clark County to exceed the NAAQS. Elevated ozone concentrations associated with these events are uncontrollable and unpreventable. 6. Guidance on exceptional events packages for wildfires will not be finalized before 20 17, and we understand that no packages submitted will be reviewed until then. However, EPA' s concurrence or nonconcurrence on flagging an event could mean the difference between Clark County being designated as a marginal or a moderate nonattainrnent area. The difference between the two designations is significant, since a higher designati on could put unnecessary burdens on Clark County. Faster review and resolution of exceptional event

4 Docket 1D Number EPA-HQ-OAR Page 4 demonstrations is needed. Timely approval of these packages is essential for state and local governments to develop state implementation plans under mandated time frames. 7. Clark County is concerned about the timing of designations against the submittal of exceptional event packages. It is almost impossible to flag certain exceptional events because of the range of the proposed primary NAAQS and the uncertainty of the form (and level) of the secondary NAAQS: "... [u]ntil the EPA promulgates the level and form of the NAAQS, a state does not know whether the criteria for excluding data (which are tied to the' level and form of the NAAQS) were met for a given event..." (79 FR 75353). There might not be enough time for EPA to receive and review complex exceptional events packages before a assigning an ozone designation. As mentioned in Item 6, guidance for wildfire exceptional events will not be finalized until Clark County is concerned about the timing of the release of the implementation rule for the proposed standards. It is important that EPA release the rule in a timely matter. Seven years after the promulgation of the 2008 NAAQS, the implementation rule was finally published in the Federal Register in early March. Ideally, the proposed implementation rule should be released when the final NAAQS is promulgated, and the final rule should be published one year later. This would allow the areas designated as marginal to use the guidance to comply with the new NAAQS. 9. Clark County does not support the requirement to install Photochemical Assessment Monitoring Stations at the NCore site of an area in violation of any ozone standard. In Clark County are issues with funding, NCore site limitations, staffing, administrative burdens, and concems related to the collected data. Funding would have to be complete, not part of a match. Funding is projected at nearly $500,000 for startup and potentially $150,000 per year to operate. Clark County does not have the staff with the requisite education and background to operate these instruments. Clark County does not have the instruments or standards to implement this effort. The NCore site would likely have to be modified at significant costs to accommodate this effort. Clark County is located in a high desert environment. Previous studies have not identified a significant presence of the compounds typically measured with this type of instrumentation. The largest volatile organic compound present in our inventory is creosote, a compound not commonly measured with this instrumentation. In addition, the NCore site is located central cast of the Las Vegas Valley and most of the significant ozone measurements are in the northwest. I 0. Clark County supports the proposal for a grandfathered clause for PSD applications. However, we believe this clause can only apply (I) to a proposed facility that has a complete application on record on or before the signature date of the revised NAAQS, or (2) when the permitting agency has published a public notice of a draft permit or preliminary determination before the effective date of the revised NAAQS.

5 Docket ID Number EPA-HQ-OAR Page 5 Thank you for the opportunity to comment on this proposal. If you have any questions or need more information on these comments, please contact Jean-Paul Huys at (702) Sincerely, Lewis Wallenmeyer, Director

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