Response to Comments on Clean Data Determination; Salt Lake City, Utah 2006 Fine Particulate Matter Standards Nonattainment Area. On June 5, 2019 (84 FR 26053), we published a proposed rule pertaining to a proposed approval of a clean data determination (CDD) for the 2006 24-hour fine particulate matter (PM2.5) Salt Lake City, Utah (UT) nonattainment area (NAA) and requested comments by July 5, 2019. Specifically, the proposed determination is based upon quality-assured, quality-controlled, and certified ambient air monitoring data for the period 2016–2018, available in the EPA’s Air Quality System (AQS) database, showing the area has monitored attainment of the 2006 24-hour PM2.5 National Ambient Air Quality Standards (NAAQS). Based on our proposed determination that the Salt Lake City, UT NAA is currently attaining the 24-hour PM2.5 NAAQS, the EPA also proposed to determine that the obligation for Utah to make submissions to meet certain Clean Air Act (CAA or the Act) requirements related to attainment planning for this area is not applicable for as long as the area continues to attain the NAAQS. We received a request from the Center for Biological Diversity to extend the comment period and, in response, we extended the comment period to July 22, 2019 (84 FR 29455). We received six comments on the proposal prior to the close of the public comment period,1 including the Center for Biological Diversity’s request for an extension. The second comment agreed that the Salt Lake City, UT CDD should be considered. We agree with this comment and will be finalizing the CDD for the Salt Lake City NAA. The third comment mentions that the strictest standards should be enforced and that the Utah legislators should be held accountable. Specifically, that for every day that the air is below the strictest standards, each legislator would be fined. EPA RESPONSE: Sections 108 and 109 of the CAA govern the establishment, review, and revision, as appropriate, of the NAAQS for each criteria air pollutant (carbon monoxide (CO), lead (Pb), nitrogen oxide (NOx), sulfur dioxide (SO2), ozone (O3), coarse particulate matter (PM10), and PM2.5) to provide protection for the nation’s public health and the environment. Once a standard is established, each state is required to develop a plan for how the state will control air pollution within its jurisdiction, which is called a state implementation plan (SIP). SIPs must include, among other things, emission limitations and other control measures, means, or techniques, as well as schedules, and timetables for compliance, as may be necessary or appropriate to meet applicable CAA requirements, including timely attainment and subsequent maintenance of the NAAQS. CAA section 110(a)(2); see also Train v. NRDC, 421 US 60, 67 (1975). “[S]o long as the ultimate effect of a State’s choice of emission limitations is compliance with the [NAAQS],” the State generally may adopt its preferred mix of controls deemed best suited to its particular situation. See Train, 421 US at 79. The CAA does not authorize, however, the levying of fines against state legislators for violations of the NAAQS. On the other hand, 1 On August 30, 2019, the EPA received a supplemental comment letter from the Utah Petroleum Association responding to comments made by the Center for Biological Diversity and other groups. The comment letter was placed in the docket for this action and labeled a late comment. mandatory sanctions (i.e., offset sanctions and highway sanctions) may be applied to a state in certain situations. See, e.g., 40 CFR 52.31. Nevertheless, the comment does not give a basis for the EPA to change its proposed action. The fourth comment discussed the Salt Lake Tribune’s article about the Salt Lake City PM2.5 NAA having better air quality and how this is due, partly, to better weather. Additionally, the fourth commenter discusses wildfire smoke causing problems in the airshed and that an independent air quality monitoring system (PurpleAir) should be reviewed. EPA RESPONSE: The commenter does not provide any specific concerns with the information found within the Salt Lake Tribune’s article on Salt Lake City PM2.5 NAA’s air quality. Due to this the EPA has no obligation to review or respond to any aspect of the Salt Lake Tribune’s article. Per the commenter’s brief discussion that air quality in the Salt Lake City PM2.5 NAA is only better due to more favorable weather, the October 17, 2006 (71 FR 61144) final rule, titled “National Ambient Air Quality Standards for Particulate Matter,” the EPA th established the form of the 24-hour PM2.5 standard as the 98 percentile of the annual 24-hour concentrations and the averaging time as over three years. The form and averaging time set in this final rule provides a means of averaging out any emissions data peaks and valleys so that trends are easily recognizable. This provides greater stability and reduces volatility in the data set so that the State can develop more accurate control measures. As the commenter describes, to the extent that favorable weather influences air quality, these trends of peaks and valleys are averaged out so that a more accurate trend of air quality is used in SIP development. The second point from the fourth commenter pertaining to wildfires impacting the airshed; on October 3, 2016 (81 FR68216) the EPA finalized revisions to the Exceptional Events Rule to establish criteria and procedures for use in determining if an exceptional event influenced air quality monitoring data. Exceptional events may include wildfires, high wind dust events, prescribed fires, stratospheric ozone intrusions, and volcanic and seismic activities. The Exceptional Events Rule relies on a “weight-of-evidence” approach for states when evaluating a demonstration to justify excluding air quality data influenced by an exceptional event. When “exceptional” events influence monitoring data and cause exceedances or violations of the NAAQS, air agencies can request the exclusion of event-influenced data, and the EPA can agree to exclude these data from the data set used for certain regulatory decisions, including a CDD. The third point from the fourth commenter pertains to PurpleAir data and a request for the EPA review this data. Most ambient air monitoring networks supporting air quality management are designed and operated by tribal, state, or local governments. The EPA develops requirements and guidance for the design and operation of these networks. The requirements related to methods are in the appendices of 40 CFR part 50 and part 53, and monitoring network requirements are found in 40 CFR part 58. For regulatory purposes, including CDDs, the EPA follows strict requirements found in 40 CFR parts 50, 53, and 58, to provide accurate data. PurpleAir and other monitoring devices used by the public provide ways to learn more about personal exposures to air pollutants and to understand the impact of emissions from traffic, industry or other sources at the local or even street level; however, even though these technologies have advanced tremendously, these monitors do not follow the requirements found in 40 CFR parts 50, 53, and 58, thus, they cannot be used for regulatory purposes. The fifth comment, from the Utah Petroleum Association (UPA), supports our proposed approval of the CDD for the Salt Lake City PM2.5 NAA. Additionally, UPA supports our concurrence on the two exceptional events that occurred at the Rose Park monitor in 2017; specifically, July 4, 2017 fireworks and September 6, 2017 wildfire impacts. We agree with this comment and are taking action to finalize the CDD for the Salt Lake City NAA. The sixth comment, from the Center of Biological Diversity, HEAL Utah, and Western Resource Advocates (hereafter, CBD), provided multiple points. The CBD raised a number of objections to EPA’s concurrence on a wildfire exceptional events demonstration regarding PM2.5 data from the Rose Park monitor in Salt Lake County on September 6, 2017. The CBD comments can roughly be separated into two groups: objections to provisions of the 2016 Exceptional Events Rule, codified in 40 CFR 50.14 and at 81 FR 68216 (October 3, 2016); and criticisms of the technical analysis the EPA provided to explain its concurrence conclusion. Below are the comments from CBD and the EPA’s responses. Comments regarding provisions of the 2016 Exceptional Events Rule 1. EPA relied on fires with natural or “unknown” causes and failed to address fires with anthropogenic causes. EPA RESPONSE: 40 CFR 50.1(n) defines wildfires for the purposes of exceptional events claims. It states that: Wildfire is any fire started by an unplanned ignition caused by lightning; volcanoes; other acts of nature; unauthorized activity; or accidental, human-caused actions, or a prescribed fire that has developed into a wildfire. A wildfire that predominantly occurs on wildland is a natural event. Under this definition, fires caused by unknown or accidental or unauthorized human activity can still be considered wildfires. Similarly, prescribed fires that escape containment, e.g., due to a sudden shift in prevailing winds, can also be considered wildfires. See 81 FR 68250. 2. EPA fails to adequately consider the effect of emissions of greenhouse gases, fire suppression policies and expansion of the wildland-urban interface in assessing whether wildfires cause anthropogenic or natural emissions. EPA RESPONSE: In proposing revisions to the Exceptional Events Rule in November 2015, the EPA noted that: The EPA anticipates receiving increasing numbers of fire-related demonstrations in the future due to the natural accumulation of fuels in the absence of fire, [and] due to climate change that is leading to increased incidence of wildfire After acknowledging that past human practices, both in wildfire management and in contribution to climate change, could contribute to increased fire related exceptional event claims in the future, the EPA went on to propose and then promulgate in the final rule the definition of wildfires provided in the response to comment 1., as well as a declaration in the 40 CFR 50.1(n) that: A wildfire that predominantly occurs on wildland is a natural event.