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.

Through notice and comment rulemaking to revise the Exceptional Events Rule in 2016, the EPA concluded that fires meeting the definition of 40 CFR 50.1(n) occuring on wildlands would be considered natural events. Since the comment takes issue with the definition of wildfire that was promulgated in 2016, the comment is beyond the scope of this action.

3. EPA failed to show that past activities contributing to wildfire severity (climate change, fire suppression, grazing, logging, introduction of invasive species, and intensive building at the wildland-urban interface) had been reasonably controlled or prevented.

EPA RESPONSE: Through notice and comment rulemaking, the Exceptional Events Rule promulgated in 40 CFR 50.14 and 40 CFR 51.930 was revised in 2016. 40 CFR 50.14(a)(4) states that:

(4) Wildfire. The Administrator shall exclude data from use in determinations of exceedances and violations where a State demonstrates to the Administrator's satisfaction that emissions from wildfires caused a specific air pollution concentration in excess of one or more national ambient air quality standard at a particular air quality monitoring location and otherwise satisfies the requirements of this section. Provided the Administrator determines that there is no compelling evidence to the contrary in the record, the Administrator will determine every wildfire occurring predominantly on wildland to have met the requirements identified in paragraph (c)(3)(iv)(D) of this section regarding the not reasonably controllable or preventable criterion.

40 CFR 50.14(c)(3)(iv)(D) states that the demonstration to justify data exclusion must include:

(D) A demonstration that the event was both not reasonably controllable and not reasonably preventable.

These sections, taken together, mean that there is a rebuttable presumption that the not reasonably controllable and not reasonably preventable demonstration requirements have been met for wildfires in the absence of compelling evidence to the contrary in the record. 81 FR 68248-50.

4. Fires in which human activity play at least a “little” direct causal role are not natural events.

EPA RESPONSE: 40 CFR 50.1(n) defines a wildfire as:

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.

The comment does not comport with the regulatory language promulgated in the 2016 Exceptional Events Rule revision where, in certain, limited situations (e.g., “unplanned ignition caused by . . . unauthorized activity; or accidental, human-caused activity” as well as fires that were deliberately ignited but developed into a wildfire) wildfires can be caused by human action. Accordingly, this comment is outside the scope of this rulemaking.

4.a Fires caused by human activity are preventable, and therefore not exceptional events.

EPA RESPONSE: Commenter suggests that fires caused by sparks from power lines are preventable, “through burying power lines underground, providing power lines with proper maintenance, properly managing vegetation for above ground power lines, and de-energizing power lines in dangerous situations.” Commenter does not show that these preventive measures are reasonable for all power lines crossing all wildlands. 40 CFR 50.14(b)(4) addresses the nature of wildfires caused by human activity by stating that:

Provided the Administrator determines that there is no compelling evidence to the contrary in the record, the Administrator will determine every wildfire occurring predominantly on wildland to have met the requirements . . . regarding the not reasonably controllable or preventable criterion.

Commenter has not provided “compelling evidence to the contrary in the record” to refute the presumption that these wildfires were not reasonably preventable. The information the commenter provided on de-energizing power lines in emergencies and long-term transition to underground lines are not generally applicable to all powerlines throughout the west. Further, Commenter’s issues with this provision of 40 CFR Part 50 should have been raised during the comment period for the 2016 Exceptional Events Rule revision and is outside the scope of this rulemaking.

-Criticisms of the EPA Technical Approach to Concurrence on the September 6, 2017 Exceptional Event

5. EPA failed to identify the specific fires causing the September 6, 2017 PM2.5 exceedance at the Rose Park monitor.

EPA RESPONSE: The EPA provided maps and satellite imagery of the extent of wildfire smoke in the northwestern United States on September 4-6, 2017, which showed the locations of contributing fires, and maps and analysis of regional weather patterns providing transport of wildfire emissions to the Salt Lake Valley and the Rose Park monitor. The EPA identified a selection of the very large fires burning in Oregon, Washington, Idaho, Northern California and British Columbia and characterized the lands burning as wildlands (National Forests, designated Wilderness Areas, and BLM lands). This information was sufficient to allow the EPA to conclude that wildfires burning on wildlands (and therefore natural events) emitted the smoke which was transported to the Rose Park monitor and caused the PM2.5 exceedance. Commenter finds the EPA’s collection of evidence lacking. The EPA disagrees, but provides the following additional detail in response to comments on the EPA’s technical support document (TSD).

5.a EPA failed to provide back trajectories from the Rose Park monitor on September 6.

EPA RESPONSE: Back trajectories are not a required element (either in CFR or guidance) for wildfire smoke exceptional event demonstrations. The EPA provided maps and satellite imagery of the extent of wildfire smoke in the northwestern United States on September 4-6, 2017, and maps and analysis of regional weather patterns providing transport of wildfire emissions to the Salt Lake Valley and the Rose Park monitor. This evidence was sufficient for the EPA to conclude there was a clear causal relationship between wildfires in the Pacific Northwest and the Rose Park PM2.5 exceedance on September 6, 2017. Nonetheless, in response to this comment, back trajectories for each hour of September 6, 2017, are shown in Figure 1. Green trajectories end at a point 50 meters above the Rose Park monitor, blue trajectories end 500 meters above the monitor and red trajectories end 1000 meters above the monitor. From midnight until early to midmorning, trajectories indicate downslope flow from the east and northeast. In the morning, first with the 1000-meter trajectories, and later with the 500-meter trajectories as well, flow to the monitor begins to come from the northwest. The 72-hour trajectories (3 days) indicate that air in the Salt Lake Valley originate in extreme northern California, Oregon, Washington and Idaho over the three-day period. Satellite detected fire hot spots on September 6, 2017, are indicated by red triangles on the map. Trajectories contact numerous fire locations in extreme northern California, Oregon, Washington and Idaho. As the origin of the trajectories vary during the 24-hours of September 6, the trajectory paths cross essentially all of Oregon, Washington and Idaho, indicating that all the active fires in the 3 days prior to September 6, 2017 contributed smoke to the Salt Lake Valley.

Figure 1. Hourly 72-hour 50, 500 and 1000-meter elevation back trajectories from the Rose Park monitor on September 6, 2017.

Figure 2 and 3 show satellite imagery of wildfire smoke collected by the Moderate Resolution Imaging Spectroradiometers (MODIS) on the Terra and Aqua Earth Observing System (EOS) satellites. Again, red triangles indicate fires detected by the satellites.

Figure 2. MODIS Aqua Image, wildfire smoke, wildfire detects (red triangles) and 8:00 pm PM2.5 readings, September 5, 2017.

Figure 3. MODIS Aqua Image, wildfire smoke, wildfire detects (red triangles) and 8:00 pm PM2.5 readings, September 6, 2017.

5.b EPA failed to identify the specific wildfires which caused the September 6, 2017 PM2.5 exceedance at Rose Park.

EPA RESPONSE: The EPA identified a “selection” of large wildfires burning on wildlands in the Pacific Northwest during the first week of September 2017 in Table 1 of the Exceptional Event concurrence TSD. The EPA did not intend the table to be comprehensive, but to show that a clear causal relationship existed between the large wildfires and the exceedance at Rose Park. Nonetheless, in response to this comment, the EPA has prepared Table 1, below, to provide additional information on the contributing fires, shown along the back trajectories of Figure 1, burning in early September 2017 and contributing to the Rose Park exceedance. Each fire is identified by a label that indicates the location of the fire on the Sept. 5, 2017 fire detect map in Figure 4. The only significant fires in Figure 4 not listed in Table 1 are a group of relatively small fires in the Nez Perce National Forest. These relatively small fires in remote, rugged wildlands were not being actively suppressed, and so lack frequently updated burned area data during the 1st week of September. The acreage burned in that area is not included in Table 1. Compiling the early September fire consumption data, Table 1 shows fires upwind of the Rose Park monitor which burned more than 319,000 acres (500 square miles) in the period from September 1 through 10, 2017.

Table 1. Fires in N California, Oregon, Washington, Idaho and W Montana with Significant Acreage Consumed September 2-6, 2017. Map Fire Name Location Total Fire Acreage Burned in Ignition Land Use Label Acreage Early Sept. 2017 Cause CA-1 Modoc July Complex Modoc NF 83,120 Minimal Lightning National Forest Wildland CA-2 Orleans Complex Marble Mtn. Wilderness 27,276 5,912 (9/2-9/7) Lightning National Forest Wilderness CA-3 Salmon Aug. Complex Marble Mtn. Wilderness 65,888 14,854 (9/4-9/6) Lightning National Forest Wilderness ID-1 Highline Payette NF 84,619 14,191 (9/5-9/10) Lightning National Forest Wildland and Wilderness ID-2 Bearskin Boise NF 30,251 6,808 (9/3-9/9) Lightning National Forest Wildland and Wilderness ID-3 Ibex Salmon-Challis NF – 16,869 2,427 (9/3-9/6) Lightning National Forest Wildland and Frank Church Wilderness Wilderness MT-1 Rice Ridge Lolo NF 160,187 18,857 (9/4-9/6) Lightning National Forest Wildland MT-2 Meyers Fire Beverhead-Deerlodge NF 62,034 18.684 (9/3-9/6) Lightning National Forest Wildland MT-3 Caribou Fire Kootenai NF 24,753 6,218 (9/3-9/6) Lightning National Forest Wildland MT-4 Gibraltar Ridge Fire Kootenai NF 12,938 506 (9/3-9/6) Lightning National Forest Wildland MT-5 Lolo Peak Bitterroot and Lolo NF 53,902 8,618 (9/1-9/6) Lightning National Forest Wildland 2 homes destroyed MT-6 Saphire Complex Beverhead-Deerlodge and 43,733 2,858 (9/3-9/7) Lightning National Forest Wildland Lolo NF MT-7 Alice Creek Helena-Lewis & Clark NF 43,733 10,556 (9/3-9/6) Lightning National Forest Wildland MT-8 Liberty Lolo NF 28,689 5,586 (9/3-9/6) Lightning National Forest Wildland MT-9 Highway 200 Complex Kaniksu NF 47,118 17,000 (9/2-9/8 est.) Lightning National Forest Wildland MT-10 West Fork Kootenai NF 20,072 4,168 (9/3-9/6) Lightning National Forest Wildland MT-11 Bob Marshall Wilderness Bob Marshall Wilderness 20,810 1,000 (9/3-9/6 est.) Lightning National Forest Wilderness OR-1 Chetco Bar Rogue-River-Siskiyou NF 191,125 34,444 (9/3-9/6) Lightning National Forest Wildland and Wilderness OR-2 Eagle Creek Columbia Gorge Nat. 48,831 30,182 (9/4-9/8) Human National Forest Wildland Scenic Area OR-3 Umpqua N. Complex Umpqua NF 43,148 4,224 (9/3-9/6) Unknown National Forest Wildland OR-4 Horse Creek Complex Willamette NF 42,489 10,656 (9/3-9/6) Lightning National Forest Wildland OR-5 Miller Complex Rogue-River-Siskiyou NF 39,715 10,705 (9/3-9/6) Lightning National Forest Wildland and Wilderness OR-6 High Cascade Complex National Forest and Crater 79,309 28,942 (9/3-9/6) Lightning National Forest and National Lake NF Park Wildland OR-7 Milli Fire Deschutes NF 24,079 1,552 (9/3-9/7) Lightning National Forest Wildland OR-8 Whitewater Fire Willamette NF 24,079 337 (9/3-9/6) Lightning National Forest Wildland and Wilderness OR-9 Jones Fire Willamette NF 10,114 806 (9/1-9/7) Lightning National Forest Wildland OR-10 North Pelican Fremont-Winema NF 3450 1600 (9/1-9/6) Lightning National Forest Wildland and Wilderness OR-11 Horse Prairie BLM & Private Forest 16,436 3,603 (9/1-9/6) Lightning BLM and Private Wildland Forest WA-1 Diamond Creek Okanogan-Wenatchee NF 128,272 36,206 (9/2-9/6) Human National Forest Wilderness WA-2 Jolly Mountain Wenatchee NF 36,808 6,429 (9/3-9/6) Lightning National Forest Wildland, Residential (0 structures lost) WA-3 Norse Peak Okanogan- 52,056 26,067 (9/3-9/6) Lightning National Forest Wildland, Wenatchee NF NF Residential (0 structures lost) WA-4 Uno Peak Okanogan- 9,500 4,500 (9/3-9/6) Lightning National Forest Wildland, Wenatchee NF NF Residential (0 structures lost)

Figure 4. Fire Detections (red triangles) in Northern California, Oregon, Washington, Idaho and Western Montana on September 5, 2017. Labels Refer to Fires Listed in Table 1.

6. EPA did not include mention of the Weber/Uintah fire in its clear causal discussion.

EPA RESPONSE: The commenter suggests that the 619-acre Uintah fire, 25 miles north of the Rose Park monitor on September 5, 2017 contributed to the exceedance at Rose Park on September 6, 2017, yet the EPA did not include a discussion of that fire in the exceptional event concurrence. The commenter did not provide any evidence that the Uintah fire contributed to the Rose Park PM2.5 exceedance on September 6, 2017. Commenter notes that the fire occurred on September 5, 2017, and, due to stagnant conditions, emissions should have been trapped in the Salt Lake Valley airshed and contributed to the exceedance on September 6, 2017. News reports state that the Uintah Fire consumed 619 acres by the evening of September 5, 2017. Later news reports more than one week later also state its size as 619 acres, indicating that the fire did not grow after September 5. Satellite imagery on September 5, 2017, show hot spots due to burning at the fire, but no discernable smoke plume at the fire location. Figure 5 shows the September 5, 2017 view from the MODIS instrument on the EOS Terra satellite at 11:45 am MST. The perimeter of the Uintah Fire is shown in red. Figure 6 shows the 1:25 pm MST image from the EOS Aqua MODIS instrument. Both images show a regional band of smoke moving southward across the IMAGE, with no obvious local enhancement from the Uintah fire. Wider views, as in Figure 7, show that band to be continuous from northwest Utah to central Wyoming, indicating that it is a regional transport plume, and not a local product of the Uintah fire.

Figure 5. 11:45 am MST Sept. 5, 2017 MODIS Terra Image, Uintah Fire Boundary in Red.

Figure 6. 1:25 pm MST Sept. 5, 2017 MODIS Aqua Image, Uintah Fire Boundary in Red.

Figure 7. 1:25 pm MST Sept. 5, 2017 MODIS Aqua Image, Regional Smoke Front Moving South Highlighted by Red Line.

Figure 8 shows pollution roses for the Rose Park and Bountiful PM2.5 monitors on September 5, 2017. Pollution roses indicate the fraction of hours of the day with winds coming from a given direction by the length of the wedge in that direction, and the concentration of PM2.5 measured in the same hours by the color of the wedge. The Bountiful monitor is located 16 miles south of the Uintah fire location, while the Rose Park monitor is located 23.5 miles south of the fire location. The pollution rose for Bountiful on September 5 shows the most common wind direction to the monitor as coming directly from the direction of the Uintah fire. Peak hourly PM2.5 for winds from that direction are in the 30 to 50 micrograms per cubic meter 3 3 (µg/m ) range. Actual peak hourly PM2.5 at Bountiful on September 5 was 44 µg/m at 7:00 pm MST when winds were from the southeast, but peak PM2.5 while winds were from the north occurred at 5:00 pm MST at 37.8 µg/m3. The pollution rose for Rose Park, in contrast, shows a dominant wind direction from the northeast, the direction of the Farmington Bay arm of the Great Salt Lake. The Bountiful pollution rose suggests contribution of smoke to the September 5 PM2.5, while the pollution rose for Rose Park does not show a clear relationship between Rose Park PM2.5 and the Uintah fire.

Figure 8. PM2.5 Pollution Roses for Bountiful and Rose Park, September 5, 2017.

Figure 9 shows the PM2.5 pollution roses for Bountiful and Rose Park on September 6, 2017. Neither rose shows much wind directly from the direction of the Uintah Fire. Both show 3 hourly PM2.5 greater than 30 µg/m nearly every hour of the day, independent of wind direction. Contribution from the Uintah fire is not clear for either monitor.

Figure 9. PM2.5 Pollution Roses for Bountiful and Rose Park, September 6, 2017.

Figure 10 shows the 24-hour average PM2.5 measured for all Wasatch Front monitoring stations on September 5 and 6, 2017. On both days, measured PM2.5 was highest at the north end of the Wasatch Front, with a general decrease in measured PM2.5 moving from north to south. This is consistent with wildfire smoke originating to the northwest of the Wasatch Front and dispersing southward with the dominant winds. On both days, the Bountiful monitor, 16 miles south of the Uintah fire location records PM2.5 above the linear regression trend line of the composite data, while the Rose Park monitor lies on or near the trend line of both days. This suggests that the Uintah fire may have contributed some PM2.5 to the Bountiful monitor, but there is no indication in the data trend that it contributed to the Rose Park monitor reading. This additional analysis of data on September 5 and 6, 2017, leads the EPA to conclude that there is no evidence of a clear causal relationship between the Uintah fire on September 5, 2017 and the Rose Park PM2.5 exceedance on September 6, 2017.

Figure 10. 24-hour PM2.5 Measured at Wasatch Front Monitors on September 5 and 6, 2017.

7. The Uintah fire burned in an urban area, and was not a natural event, as human activity played an overriding role in the existence and maintenance of the downed power line that started the fire.

EPA RESPONSE: As explained in the response to comment 6., there is no evidence of a clear causal relationship between the Uintah fire on September 5, 2017, and the PM2.5 exceedance at Rose Park on September 6, 2017. Therefore, the nature and cause of the Uintah fire are not relevant to the EPA decision on the Rose Park September 6, 2017 exceptional event claim.

8. Figure 1 [of the EPA’s TSD], which is the smoke plume map for September 5, 2017, seems to show that there is no connection between the fires in California and the Salt Lake City area.

EPA RESPONSE: Figure 1 of the EPA’s TSD is shown below (Figure 11 of this document). It shows on September 5, the day prior to the exceedance at Rose Park, an arc of wildfire detects by satellite (red triangles) extending from the coastal mountains in northern California and southern Oregon north along the Cascade mountains through Oregon and Washington, east along southern British Columbia, Canada, and then south along the Rocky Mountain ranges of Idaho and western Montana. Densest smoke detected by the satellites follows that arc of fires. Figure 15 of the EPA’s TSD (Figure 12 of this document) then shows an upper level (500 mb height) high pressure area centered over eastern Oregon. High pressure systems in the Northern hemisphere induce clockwise wind flow, as shown by wind barbs on Figure 15. The two figures, taken together show that the comment is in error, clockwise wind flow around eastern Oregon transported smoke from northeast California to Utah.

Figure 11. EPA TSD Figure 1 Of Fires and Smoke Plumes on September 5, 2017.

Figure 12. EPA TSD Figure 15 showing September 5, 2017 weather map and clockwise airflow around the high pressure system in eastern Oregon.

9. EPA uses Air Quality Index maps to claim that unidentified fires in Washington, Oregon and Idaho contributed smoke to the Wasatch Front and Cache Valley of Utah on September 4 – 5, 2017 but not September 6. See TSD at 8.

EPA RESPONSE: The EPA used Air Quality Index maps from September 6, 2017, in the same way it used those on September 4 and 5, 2017. The September 6 Air Quality Index map appeared in Figure 7 on page 7 of the EPA’s TSD. The EPA description of these figures read (TSD, p. 7):

The EPA Air Quality Index (AQI) maps from September 4 through 7 are below (Figure 6 through Figure 9). The AQI in northern Utah progressed from moderate air quality (yellow) to unhealthy for sensitive groups (orange) during this time period. The maps show continuity between the northern Utah degraded air quality and the upwind more severe air quality degradation (unhealthy and very unhealthy) in states closer to the wildfires.

10. In the section on whether the fires were reasonably controllable or preventable, EPA references fires in California, Montana and British Columbia, (TSD at 16) even though EPA does not seem to believe these fires had a causal relationship to the Rose Park Monitoring Station exceedances.

EPA RESPONSE: The commenter mistakenly concludes that the EPA does not believe fires in California, Montana and British Columbia had a causal relationship to the Rose Park monitoring station exceedance. The TSD established the clear causal relationship, and this RTC further clarifies the evidence of that clear causal relationship. The commenter did not provide any information refuting a clear causal relationship between fires in California, Montana and British Columbia, or refuting the EPA’s conclusion regarding the fires being not reasonably controllable or preventable.

11. EPA’s attempt to use a generalization of all wildfires across the West contradicts the plain language of the regulation which requires identification of a specific event that is clearly causally related to the exceedance at the Rose Park monitor.

EPA RESPONSE: The EPA provided specific information on some of the largest contributing pacific Northwest wildfires which had clear causal relationships to the exceedance at the Rose Park monitor on September 6, 2017. Because the evidence that the extensive wildfire activity in the region caused the exceedance was so compelling, the EPA felt the data provided in the TSD was sufficient to meet the evidence requirements of 40 CFR 50.14. Additional specific evidence has been provided in this response document in the answers to comments 5., 5a. and 5b. The commenter did not provide evidence refuting the EPA’s determination regarding the clear causal relationship.

12. “Wildlands” are defined as “an area in which human activity … [is] essentially non- existent[.]” 40 C.F.R. § 50.1(o). A natural event is further defined as an “event and its resulting emissions … in which human activity plays little or no direct causal role.” 40 C.F.R. 50.1(k). Based on these definitions, EPA has failed to provide record evidence to support its proposal to deem the Rose Park exceedance an exceptional event.

EPA RESPONSE: Commenter has selectively extracted phrases from the definitions. The full definitions and record for the Exceptional Events Rule revision of 2016 help to place the complete definitions in context and support the EPA’s interpretation of these definitions. 40 CFR 50.1(o) provides in full:

(o) Wildland means an area in which human activity and development are essentially non- existent, except for roads, railroads, power lines, and similar transportation facilities. Structures, if any, are widely scattered.

The exceptions omitted by the commenter are significant enough that the omission of that exceptions clause fundamentally changes the definition by inaccurately narrowing its scope. In addition, at 81 FR 68248, October 3, 2016, promulgating the rule revisions, the EPA stated that:

This proposed definition of wildland includes lands that are predominantly wildland, such as land in the wildland-urban interface.

Footnote 63 of 81 FR 68248 describes the wildland-urban interface:

The wildland-urban interface is the line, area or zone where structures and other human development meet or intermingle with undeveloped wildland or vegetative fuels. The term describes an area within or adjacent to private and public property where mitigation actions can prevent damage or loss from wildfire.

Taken in context, this complete regulatory definition of wildlands includes significant departures from commenter’s definition that “wildland” means “human activity . . . is essentially non-existent”. For wilderness and national forest lands of the pacific Northwest, this definition of wildlands is generally applicable, including those small areas of national forest land considered wildland-urban interface. The EPA’s TSD identified the lands consumed in the identified fires as National Forest or wilderness lands, and the more complete Table 1 of this response document further clarifies that.

Regarding commenter’s statement that “A natural event is further defined as an “event and its resulting emissions … in which human activity plays little or no direct causal role”, 40 CFR 50.14(n) states:

(n) 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.

Thus, the definition of wildfire in 50.14(n) clarifies the interpretation of the definition of natural events in 50.14(k) in the specific case of wildfires caused by certain human-caused actions.

13. The wildfires the EPA identified in its TSD did not occur on wildlands as that term is defined by EPA, because human activity exists in these areas and that human activity contributed to these wildfires.

EPA RESPONSE: As in the response to question 12, the commenter selectively excludes human activities identified in the definition of wildlands from his recitation of the definition. 40 CFR 50.1(n) and the Federal Register notice promulgating the 2016 revisions to Part 50 make clear that the definition of wildlands for the Exceptional Events rule is consistent with interpreting wildfires occurring largely or entirely on National Forest lands or lands designated as wilderness areas are wildfires occurring on wildlands, regardless of the ignition cause of the fire.

14. There were human-caused fires burning during this time period. For example, the Eagle Creek Fire in Oregon burned from September 2 to November 30, 2017, consumed nearly 50,000 acres and was ignited by human activity. See https://inciweb.nwcg.gov/incident/5584/. It appears that EPA cherry-picked fires in its Table 1 to claim that fires were caused by natural ignition sources and left out human- caused fires like the Eagle Creek Fire.

EPA RESPONSE: The Eagle Creek Fire meets the definition in 40 CFR 50.1 of a wildfire burning on wildlands, and therefore is a natural event. Commenter points to the human cause of the fire as an issue, but human cause is explicitly included in the wildfire definition of 50.1(n), and does not preclude the EPA from considering the Eagle Creek Fire as a natural event.

The Eagle Creek Fire was ignited by personal fireworks within the Columbia River Gorge National Scenic Area. Figure 16 shows the fire progression map for the fire. It ignited on September 2, and acreage burned on September 3 (purple), 4 (lavender) and 5 (light green), 2017 are labeled on the map. Figure 17 shows a Columbia Gorge National Scenic Area land use map for the same area. The majority of wildfire activity on June 3-5 was on lands identified as forest or open space. Figure 18 shows a GoogleEarth generated aerial view of the burn scar, looking upriver from the western edge of the fire. The areas burned on September 3-5 are largely the steep slopes of the southern wall of the gorge, lands accessible only by hiking trail. The lower elevations of the burn scar intersect with the urban wildland interface. However, actual structural damage was limited. The September 5, 2017 evening fire update indicated that “We lost one small residential structure and four outbuildings”.2 That was later updated to one occupied residence, and 3 unoccupied non-full-time residences.3 Indeed, the Oregon State Fire Marshall indicated that in the entire 2017 fire season, only 10 residences and 20 structures were lost to wildfire in 2017, with wildfire acreage totaling 665,000 (1,039 square miles).4 From this it can be concluded that fires within the wildland-urban interface formed only a small fraction of the total wildfire acreage in Oregon in 2017. This assessment further supports the EPA’s understanding that the Eagle Creek fire met the definitions of 40 CFR 50.1 of a wildfire burning on wildlands, and therefore a natural event.

2 Evening Update, Eagle Creek and Indan Creek Fires, 9/5/17, https://inciweb.nwcg.gov/incident/article/5584/40162/. 3 Eagle Creek Fire - Morning update - September 8, https://inciweb.nwcg.gov/incident/article/5584/40404/. 4 Impact of Oregon’s 2017 Wildfire Season, Oregon Forest Resource Institute, https://oregonforests.org/sites/default/files/2018- 01/OFRI%202017%20Wildfire%20Report%20-%20FINAL%2001-02-18.pdf. Figure 16. Eagle Creek Fire Progression; Burn Areas on September 3-5, 2017 Indicated.

Figure 17. Columbia Gorge National Scenic Area Land Use.

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Figure 18. Google Earth Generated View of Burned Terrain (top) on Sept. 3-5, 2017 and Pre-Burn conditions (bottom). 15. Other lapses in EPA’s analysis are event [sic]. The Whitewater Fire, for example, burned only 11,500 acres and therefore was not a fire greater than the 20,000 acres as the agency maintains.

EPA RESPONSE: The EPA has now provided specific information on all fires with significant acreage burned in early September in all upwind states, whether above or below the 20,000-acre threshold. The inclusion of the Whitewater fire in the previous 20,000 acre or larger fire table was inadvertent. Its inclusion in no way undermined the EPA’s conclusion that the exceedance at the Rose Park monitor on September 6, 2017 was caused by smoke from numerous large wildfires burning in California, Oregon, Washington, Idaho and Montana.

16. EPA does not adequately address whether the fires that it insists contributed to the Rose Park exceedance – both those the agency lists as well as other fires also burning at the time that the agency seems to ignore – actually ignited in and continued to burn in “wildlands.”

EPA RESPONSE: The EPA identified a selection of fires which contributed to the Rose Park exceedance adequate to justify a concurrence decision. The extreme severity of the 2017 wildfire season in the Pacific Northwest made detailed tabulation of fires laborious and unnecessary. Nevertheless, the EPA has now completed the evaluation of contributing fires, as shown in Table 1 of this response document, and has demonstrated that the contributing fires were wildfires burning on wildlands. Commenter has not identified any fires other than the Uintah fire burning near the monitor the day before the exceedance for which the wildland nature of the fire is in dispute. The EPA has shown that it is unlikely that this fire contributed to the Rose Park exceedance on September 6, 2017, in the response to comment 6.

17. EPA failed to evaluate whether the fires that contributed smoke to the Rose Park Monitoring Station ignited or burned in the WUI.

EPA RESPONSE: As explained in the response to comment 12, the EPA considers lands that are predominantly wildland, such as land in the wildland-urban interface, to be wildlands.