2020-07941. Approval and Promulgation of Implementation Plans; Wyoming; Regional Haze 5-Year Progress Report State Implementation Plan

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

The Environmental Protection Agency (EPA) is proposing to approve a regional haze progress report State Implementation Plan (SIP) revision submitted by the State of Wyoming on November 28, 2017. The revision addresses the requirements for states to submit periodic reports describing progress toward reasonable progress goals established for regional haze and a determination of adequacy of the State's existing regional haze SIP and federal implementation plan (FIP). The regional haze progress report SIP revision also includes a revision to the Best Available Retrofit Technology (BART) requirements for Unit 3 at the Naughton Power Plant. The EPA acted on the BART revision for the Naughton Power Plant in a previous rulemaking and is not proposing to act on the BART revision in this rulemaking. The EPA is taking this action pursuant to section 110 of the Clean Air Act (CAA).

DATES:

Written comments must be received on or before May 18, 2020.

ADDRESSES:

Submit your comments, identified by Docket ID No. EPA-R08-OAR-2019-0623, to the Federal Rulemaking Portal: https://www.regulations.gov. Follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from www.regulations.gov. The EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission (i.e., on the web, cloud, or other file sharing system). For additional submission methods, the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit http://www2.epa.gov/​dockets/​commenting-epa-dockets.

Docket: All documents in the docket are listed in the www.regulations.gov index. Although listed in the index, some information is not publicly available, e.g., CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, will be publicly available only in hard copy. Publicly available docket materials are available either electronically in www.regulations.gov or in hard copy at the Air and Radiation Division, Environmental Protection Agency (EPA), Region 8, 1595 Wynkoop Street, Denver, Colorado 80202-1129. The EPA requests that if at all possible, you contact the individual listed in the FOR FURTHER INFORMATION CONTACT section to view the hard copy of the docket. You may view the hard copy of the docket Monday through Friday, 8:00 a.m. to 4:00 p.m., excluding federal holidays.

FOR FURTHER INFORMATION CONTACT:

Jaslyn Dobrahner, Air and Radiation Division, EPA, Region 8, Mailcode 8ARD-IO, 1595 Wynkoop Street, Denver, Colorado 80202-1129, [phone], [e-mail].

SUPPLEMENTARY INFORMATION:

Throughout this document wherever “we,” “us,” or “our” is used, we mean the EPA.

I. What action is the EPA proposing?

On November 28, 2017, Wyoming submitted a Progress Report SIP revision (Progress Report) which: (1) Detailed the progress made toward achieving progress for improving visibility at Class I areas,^[1] and (2) declared a determination of adequacy of the State's regional haze plan to meet reasonable progress goals. The Progress Report also included a revision to the BART requirements for Unit 3 at the Naughton Power Plant. However, the EPA acted on the BART revision for the Naughton Power Plant in a previous rulemaking and is therefore not proposing to act on the BART revision in this rulemaking.^[2] The State provided an opportunity for public comment through public hearings held on January 15, 2014 and September 26, 2017, and provided Federal Land Managers (FLMs) an opportunity to comment on the Progress Report.^[3] The EPA is proposing to approve Wyoming's November 28, 2017 regional haze Progress Report SIP submittal.

II. Background

A. Requirements of the Clean Air Act and the EPA's Regional Haze Rule

In section 169A of the 1977 CAA Amendments, Congress created a program for protecting visibility in the nation's national parks and wilderness areas. This section of the CAA establishes “as a national goal the prevention of any future, and the remedying of any existing, impairment of visibility in mandatory Class I Federal areas which impairment results from manmade air pollution.”

The EPA promulgated a rule to address regional haze on July 1, 1999.^[4] The Regional Haze Rule revised the existing visibility regulations ^[5] to integrate provisions addressing regional haze and established a comprehensive visibility protection program for Class I areas. The requirements for regional haze, found at 40 CFR 51.308 and 40 CFR 51.309, are included in the EPA's visibility protection regulations at 40 CFR 51.300 through 40 CFR 51.309. The EPA revised the Regional Haze Rule on January 10, 2017.^[6]

The CAA requires each state to develop a SIP to meet various air quality requirements, including protection of visibility.^[7] Regional haze SIPs must assure reasonable progress toward the national goal of achieving natural visibility conditions in Class I areas. A state must submit its SIP and SIP revisions to the EPA for approval. Once approved, a SIP is enforceable by the EPA and citizens under the CAA. If a state elects not to make a required SIP submittal, fails to make a required SIP submittal, or if we find that a state's required submittal is incomplete or not approvable, then we must promulgate a FIP to fill this regulatory gap.^[8]

B. Requirements for Regional Haze SIPs Submitted Under 40 CFR 51.309

The EPA's Regional Haze Rule provides two paths to address regional haze. One is 40 CFR 51.308, requiring states to perform individual point source BART determinations and evaluate the need for other control strategies. The other method for addressing regional haze is through 40 CFR 51.309, and is an option for states termed the “Transport Region States” including Wyoming. Transport Region States can adopt regional haze strategies based on recommendations from the Grand Canyon Visibility Transport Commission (GCVTC) for protecting the 16 Class I areas on the Colorado Plateau.⁹ The GCVTC submitted an annex to the EPA, known as the SO₂ Backstop Trading Program, containing annual sulfur dioxide (SO₂) emissions reduction milestones and detailed provisions of a backstop trading program to be implemented automatically if measures failed to achieve the SO₂ milestones. Wyoming submitted a regional haze SIP under section 40 CFR 51.309 to address stationary source SO₂ emissions reductions through the SO₂ Backstop Trading Program and submitted a regional haze SIP under section 40 CFR 51.309(g) to address stationary source nitrogen oxide (NO_X) and particulate matter (PM) emissions reductions.

C. Requirements for the Five-Year Regional Haze Progress Report SIP

Under both 40 CFR 51.308 and 40 CFR 51.309, states are required to submit progress reports that evaluate progress towards the reasonable progress goals for each mandatory federal Class I area within the state and in each Class I area outside the state that may be affected by emissions from within the state. In addition, the provisions also require states to submit, at the same time as the progress report, a determination of adequacy of the state's existing regional haze plan. The first progress report must be in the form of a SIP revision and is due 5 years after submittal of the initial regional haze SIP.

As a Transport Region State, Wyoming submitted its Progress Report SIP under 40 CFR 51.309, and exercised the option to meet the requirements contained in 40 CFR 51.309 for regional haze implementation plans.^[10] The requirements for Transport Region State progress reports are similar to those for other states, but the requirements for the reports are codified at 40 CFR 51.309(d)(10).

D. Regulatory and Legal History of the Wyoming Regional Haze SIP and FIP

On January 12, 2011, and April 19, 2012, Wyoming submitted regional haze SIP revisions addressing the requirements of 40 CFR 51.309 that superseded and replaced regional haze SIP revisions submitted on December 24, 2003, May 27, 2004 and November 21, 2008. On December 12, 2012, the EPA approved the SIP revisions as meeting the requirements of the Regional Haze Rule with the exception of 40 CFR 51.309(d)(4)(vii) and 40 CFR 51.309(g). On January 30, 2014, the EPA issued a final rule partially approving and partially disapproving the SIP revisions as meeting the requirements of 40 CFR 51.309(g), and promulgating a federal implementation plan (FIP) for those portions of the SIP that were disapproved (together referred to as the regional haze implementation plan).^[11] Several parties challenged various aspects of the 2014 final rule pertaining to NO_X BART emission limits.^[12] On September 9, 2014, the U.S. Court of Appeals for the Tenth Circuit stayed various NO_X BART emission limits.^[13] Subsequent revisions were made to the regional haze SIP on March 21, 2019, and to the regional haze SIP and FIP on May 20, 2019.^[14]

III. The EPA's Evaluation of Wyoming's Progress Report and Adequacy Determination

A. Regional Haze Progress Report

Wyoming's Progress Report must meet the requirements set forth in 40 CFR 51.309(d)(10)(i). Wyoming's Progress Report must also include a determination of the adequacy of the existing implementation plan to ensure reasonable progress. 40 CFR 51.309(d)(10)(ii).

1. Status of Implementation of Control Measures

Wyoming's Progress Report must include a description of the status of implementation of all control measures included in the implementation plans for achieving reasonable progress goals for Class I areas both within and outside of the State. 40 CFR 51.309(d)(10)(i)(A).

In its Progress Report, Wyoming summarized the regional haze measures that were relied upon in the regional haze implementation plan, as well as SO₂ emissions reduction strategies implemented by sources in New Mexico, Utah, and Wyoming under the SO₂ Backstop Trading Program. The State referenced the SO₂ emissions for sources associated with the SO₂ Backstop Trading Program ^[15] found within the 2011 Regional SO₂ Emissions and Milestones Report (Table 1).^[16]

Table 1—Reported Emissions for Sources Associated With the Backstop Trading Program ¹⁷

State	Plant name	Reported 2011 SO2 emissions (tons)
NM	Agave Energy Co./Agave Dagger Draw Gas Plant	0
NM	BP America Production/Empire Abo Plant	1,704
NM	DCP Midstream/Artesia Gas Plant	326
NM	DCP Midstream/Eunice Gas Plant	2,921
NM	DCP Midstream/Linam Ranch Gas Plant	1,304
NM	Duke—Magnum/Pan Energy—Burton Flats	0
NM	Duke Energy/Dagger Draw Gas Plant	0
NM	Targa Midstream Services, LP/Eunice Gas Plant	718
NM	Frontier Field Services/Maljamar Gas Plant	2,986
NM	Giant Industries/Ciniza Refinery (Gallup)	125
NM	J L Davis Gas Processing/Denton Plant	675
NM	Marathon Oil/Indian Basin Gas Plant	133
NM	Navajo Refining Co/Artesia Refinery	45
NM	Public Service Co of New Mexico/San Juan Generating Station	4,741
NM	Raton Pub. Service/Raton Power Plant	0
NM	Southern Union Gas/Jal #3	1,319
NM	Targa Midstream Services, LP/Eunice South Gas Plant	0
NM	Targa Midstream Services, LP/Monument Plant	771
NM	Targa Midstream Services, LP/Saunders Plant	251
NM	Tri-State Gen & Transmission/Escalante Station	1,257
NM	Western Gas Resources/San Juan River Gas Plant	621
NM	Western Refining Southwest Inc./Sand Juan Refinery (Bloomfield)	6
UT	Brigham Young University—Main Campus	99
UT	Chevron Products Co—Salt Lake Refinery	24
UT	Flying J Refinery—(Big West Oil Company)	192
UT	Graymont Western U.S. Inc—Cricket Mountain Plant	16
UT	Holcim—Devil's Slide Plant	344
UT	Holly Refining and Marketing Co—Phillips Refinery	131
UT	Intermountain Power Service Corporation—Intermountain Generating Station	4,934
UT	Kennecott Utah Copper Corp—Power Plant/Lab/Tailings Impoundment	1,704
UT	Kennecott Utah Copper Corp—Smelter and Refinery	696
UT	Materion Natural Resources—Delta Mill	0
UT	PacifiCorp—Carbon Power Plant	7,740
UT	PacifiCorp—Hunter Power Plant	4,661
UT	PacifiCorp—Huntington Power Plant	2,529
UT	Patara Midstream LLC—Lisbon Natural Gas Processing Plant	25
UT	Sunnyside Cogeneration Associates—Sunnyside Cogeneration Facility	544
UT	Tesoro West Coast—Salt Lake City Refinery	795
UT	Utelite Corporation—Shale Processing	130
WY	American Colloid Mineral Co—East Colony	63
WY	American Colloid Mineral Co—West Colony	50
WY	Basin Electric—Dry Fork Station	279
WY	Basin Electric—Laramie River Station	9,402
WY	Black Hills Corporation—Neil Simpson I	789
WY	Black Hills Corporation—Neil Simpson II	542
WY	Black Hills Corporation—Osage Plant	0
WY	Black Hills Corporation—Wygen I	559
WY	Cheyenne Light Fuel and Power Company—Wygen II	215
WY	Black Hills Corporation—Wygen III	256
WY	Burlington Resources—Bighorn Wells	223
WY	Burlington Resources—Lost Cabin Gas Plant	1,543
WY	Chevron USA—Carter Creek Gas Plant	100
WY	Chevron USA—Table Rock Field	0
WY	Chevron USA—Table Rock Gas Plant	44
WY	Chevron USA—Whitney Canyon/Carter Creek Wellfield	2
WY	Devon Energy Production Co., L.P.—Beaver Creek Gas Field	5
WY	Devon Gas Services, L.P.—Beaver Creek Gas Plant	158
WY	Encore Operating LP—Elk Basin Gas Plant	847
WY	Exxon Mobil Corporation—Labarge Black Canyon Facility	156
WY	Exxon Mobil Corporation—Shute Creek	946
WY	FMC Corp—Green River Sodium Products	2,876
WY	FMC Wyoming Corporation Granger Soda Ash Plant	189
WY	Frontier Oil & Refining Company—Cheyenne Refinery	253
WY	Hiland Partners, LLC—Hiland Gas Plant	45
WY	Marathon Oil Co—Oregon Basin Gas Plant	247
WY	Marathon Oil Co—Oregon Basin Wellfield	96
WY	Merit Energy Company—Brady Gas Plant	209
WY	Merit Energy Company—Whitney Facility	1
WY	Merit Energy Company—Whitney Canyon Wellfield	0
WY	Mountain Cement Company—Laramie Plant	283
WY	P4 Production, L.L.C.—Rock Springs Coal Calcining Plant	706
WY	PacifiCorp—Dave Johnston Plant	11,306
WY	PacifiCorp—Jim Bridger Plant	9,689
WY	PacifiCorp—Naughton Plant	20,461
WY	PacifiCorp—Wyodak Plant	2,387
WY	Simplot Phosphates LLC—Rock Springs Plant	1,502
WY	Sinclair Oil Company—Sinclair Refinery	505
WY	Sinclair Wyoming Refining Company—Casper Refinery	241
WY	Solvay Chemicals—Soda Ash Plant (Green River Facility)	46
WY	TATA Chemicals (Soda Ash Partners)—Green River Plant	5,098
WY	The Western Sugar Cooperative—Torrington Plant	182
WY	University of Wyoming—Heat Plant	187
WY	Wyoming Refining—Newcastle Refinery	324

Additionally, Wyoming provided the status of control measures associated with PM, NO_X, and SO₂ and emissions on units subject to BART and reasonable progress within the regional haze implementation plan (Table 2).

Table 2—Control Measures and Updates for Sources Subject to BART and Reasonable Progress in Wyoming

Unit	PM control type	PM10 emission limit	NOX control type	NOX emission limit	SO2 emission limit
	SIP Emission Limits		FIP Emission Limits
Basin Electric—Laramie River Unit 1 (550 Mega Watt (MW))	Electrostatic Precipitator (ESP) (completed)	0.030 lb/MMBtu	Selective Catalytic Reduction (SCR) (completed)	0.06 lb/MMBtu (30-day rolling) *	0.12 lb/MMBtu (averaged annually across Units 1 and 2).
Basin Electric—Laramie River Unit 2 (550 MW)	ESP (completed)	0.030 lb/MMBtu	Selective Noncatalytic Reduction (SNCR) (completed)	0.15 lb/MMBtu (30-day rolling) *
Basin Electric—Laramie River Unit 3 (550 MW)	ESP (completed)	0.030 lb/MMBtu	SNCR 12/30/2018 * (completed)	0.15 lb/MMBtu (30-day rolling) *	N/A.
PacifiCorp—Dave Johnston Unit 3 (230 MW)	Fabric Filter (completed)	0.015 lb/MMBtu	New Low NOX Burners (LNB) + Overfire Air (OFA) and shut down by 12/31/2027; or New LNB + OFA and SCR no later than 3/4/2019 **	0.28 lb/MMBtu (30-day rolling) and shutdown; or 0.07 lb/MMBtu (30-day rolling)	N/A.
PacifiCorp—Wyodak Unit 1 (335 MW)	Fabric Filter (completed)	0.015 lb/MMBtu	SCR, no later than 3/4/2019 ‡	0.07 lb/MMBtu (30-day rolling) ‡	N/A.
SIP Emission Limits
PacifiCorp—Dave Johnston Unit 4 (330 MW)	Fabric Filter (completed)	0.015 lb/MMBtu	LNB + OFA (completed)	0.15 lb/MMBtu (30-day rolling)	N/A.
PacifiCorp—Naughton Unit 1 (160 MW)	ESP + Flue Gas Conditioning (FGC) (completed)	0.040 lb/MMBtu	LNB + OFA (completed)	0.26 lb/MMBtu (30-day rolling)	N/A.
PacifiCorp—Naughton Unit 2 (210 MW)	ESP + FGC (completed)	0.040 lb/MMBtu	LNB + OFA (completed)	0.26 lb/MMBtu (30-day rolling)	N/A.
PacifiCorp—Naughton Unit 3 (330 MW with max annual heat input of 40%) †	Natural Gas Conversion by 1/30/19	0.008 lb/MMBtu	Natural Gas Conversion by 1/30/19; new LNB + Flue Gas Recirculation (FGR) (in progress) ††	0.12 lb/MMBtu (30-day rolling)	N/A.
PacifiCorp—Jim Bridger Unit 1 (530 MW)	ESP + FGC (completed)	0.030 lb/MMBtu	LNB + OFA + SCR (to be completed 12/31/2022)	0.26 lb/MMBtu (30-day rolling) by 2019; 0.07 lb/MMBtu (SCR)	N/A.
PacifiCorp—Jim Bridger Unit 2 (530 MW)	ESP + FGC (completed)	0.030 lb/MMBtu	LNB + OFA + SCR (to be completed 12/31/2021)	0.26 lb/MMBtu (30-day rolling) by 2019; 0.07 lb/MMBtu (SCR)	N/A.
PacifiCorp—Jim Bridger Unit 3 (530 MW)	ESP + FGC (completed)	0.030 lb/MMBtu	LNB + OFA + SCR (completed)	0.07 lb/MMBtu (30-day rolling) (SCR)	N/A.
PacifiCorp—Jim Bridger Unit 4 (530 MW)	ESP + FGC (completed)	0.030 lb/MMBtu	LNB + OFA + SCR (completed)	0.07 lb/MMBtu (30-day rolling) (SCR)	N/A.
FMC—Westvaco Trona Plant Unit NS—1A	ESP (completed)	0.05 lb/MMBtu	LNB + OFA (completed)	0.35 lb/MMBtu (30-day rolling)	N/A.
FMC—Westvaco Trona Plant Unit NS—1B	ESP (completed)	0.05 lb/MMBtu	LNB + OFA (completed)	0.35 lb/MMBtu (30-day rolling)	N/A.
TATA Chemicals Green River Trona Plant Unit C	ESP (completed)	0.09 lb/MMBtu	LNB + SOFA (completed)	0.28 lb/MMBtu (30-day rolling average)	N/A.
TATA Chemicals Green River Trona Plant Unit D	ESP (completed)	0.09 lb/MMBtu	LNB + SOFA (completed)	0.28 lb/MMBtu (30-day rolling)	N/A.
* The NOX and SO2 emission limits and controls for Basin Electric Laramie River Units 1—3 reflect implementation plan revisions that became federally enforceable on June 19, 2019. 84 FR 22711 (May 20, 2019).
** The EPA's Clean Air Markets Division (CAMD) database indicates the operation of the new low NOX burners and separated overfire air began on May 23, 2010. Air Markets Program Data, https://ampd.epa.gov/​ampd/​ (last visited February 10, 2020). PacifiCorp appears to be planning to retire the unit by 2027.
‡ On September 9, 2014, the United States Court of Appeals for the Tenth Circuit stayed the NOX emission limits for Wyodak Unit 1 in the regional haze FIP. The NOX emission limits for Laramie River Station Units 1-3 were also stayed but were later revised as explained above.
† The PM and NOX emission limits and controls reflect a SIP revision that became federally enforceable on April 22, 2019. 84 FR 10433 (March 21, 2019).
†† PacifiCorp, 2019 Integrated Resource Plan (October 2019), https://www.pacificorp.com/​content/​dam/​pcorp/​documents/​en/​pacificorp/​energy/​integrated-resource-plan/​2019_​IRP_​Volume_​I.pdf (last visited February 20, 2020).

The EPA proposes to find that Wyoming has adequately addressed the applicable provisions under 40 CFR 51.309(d)(10)(i)(A) regarding the implementation status of control measures because the State's Progress Report provides documentation of the implementation of control measures within Wyoming, including the BART-eligible sources and reasonable progress sources in the State.

2. Summary of Emissions Reductions Achieved

Wyoming's Progress Report must include a summary of the emissions reductions achieved throughout the State through implementation of control measures mentioned in 40 CFR 51.309(d)(10)(i)(A). 40 CFR 51.309(d)(10)(i)(B).

In its Progress Report, Wyoming presents information on emissions reductions achieved from the pollution control strategies discussed above. The State provides regional SO₂ emissions from 2003 through 2015 (Table 3) as well as Statewide SO₂, NO_X, ammonia, volatile organic compounds, primary organic aerosol, elemental carbon, fine soil, and coarse mass emissions in 2002 and 2008 (Table 4).

Table 3—Regional SO₂ Emissions and Milestones ¹⁸

Year	Adjusted reported SO2 emissions (tons)	Adjusted regional milestone (tons)
2003	* 330,679	* 447,383
2004	* 337,970	* 448,259
2005	* 304,591	* 446,903
2006	** 279,134	** 420,194
2007	** 273,663	** 420,637
2008	** 244,189	378,398
2009	143,704	234,903
2010	131,124	200,722
2011	117,976	200,722
2012	96,246	200,722
2013	101,381	185,795
2014	92,533	170,868
2015	81,454	155,940
* Represents the adjusted SO2 emissions/milestone for Arizona, New Mexico, Oregon, Utah, Wyoming, and Albuquerque-Bernalillo County.
** Represents the adjusted SO2 emissions/milestone for Arizona, New Mexico, Utah, Wyoming, and Albuquerque-Bernalillo County. Figures with no asterisk represent the adjusted SO2 emissions/milestone for New Mexico, Utah, Wyoming, and Albuquerque-Bernalillo County.

 

Table 4 SO₂, NO_X, Ammonia, Volatile Organic Compounds, Primary Organic Aerosol, Elemental Carbon, Fine Soil, and Coarse Mass Emissions ¹⁹

Pollutant	2002 Emissions † (tons/year)	2008 Emissions ‡ (tons/year)	Difference between 2002 and 2008 emissions (tons/year)/ percent change
Sulfur Dioxide	145,840	112,655	−33,186/−23
Nitrogen Oxides	287,974	230,678	−57,296/−20
Ammonia	33,032	27,024	−6,007/−18
Volatile Organic Compounds	816,904	339,534	−477,370/−58
Primary Organic Aerosol	29,194	25,027	−4,167/−14
Elemental Carbon	8,066	6,105	−1,961/−24
Fine Soil	23,020	55,959	32,940/>100
Coarse Mass	102,660	366,673	264,014/>100
† Plan02d.
‡ WestJump2008.

The emissions data show that there were decreases in emissions of SO₂, NO_X, ammonia, volatile organic compounds, primary organic aerosol, and elemental carbon. Furthermore, regional SO₂ emissions have been below the milestone every year. According to the State, for coarse and fine particulate matter categories, the increases (>100%) in emissions between 2002 and 2008 may be due to enhancements in dust inventory methodology rather than changes in actual emissions.^[20]

The EPA proposes to conclude that Wyoming has adequately summarized the emissions reductions achieved throughout the State in its Progress Report as required under 40 CFR 51.309(d)(10)(i)(B). In meeting this requirement, the EPA does not expect states to quantify emissions reductions for measures which have not yet been implemented or for which the compliance date has not yet been reached. However, for purposes of future progress reports, we recommend that Wyoming include additional quantitative details on the reductions of each major specific visibility-impairing pollutant and utilize the EPA's Clean Air Market Division (CAMD) database,^[21] as appropriate.^[22]

3. Visibility Conditions and Changes

Pursuant to 40 CFR 51.309(d)(10)(i)(C), for each mandatory Class I area within the State, Wyoming must assess the following visibility conditions and changes, with values for most impaired and least impaired days ^[23] expressed in terms of five-year averages of these annual values:

i. Assess the current visibility conditions for the most impaired and least impaired days.

ii. Analyze the difference between current visibility conditions for the most impaired and least impaired days and baseline visibility conditions.

iii. Evaluate the change in visibility impairment for the most impaired and least impaired days over the past five years.

In its Progress Report, Wyoming provides information on visibility conditions for the Class I areas within its borders. There are seven Class I areas located in Wyoming: Bridger Wilderness, Fitzpatrick Wilderness, Grand Teton National Park, North Absaroka Wilderness, Teton Wilderness, Washakie Wilderness and Yellowstone National Park. Monitoring and data representing visibility conditions in Wyoming's seven Class I areas is based on the three Interagency Monitoring of Protected Visual Environments (IMPROVE) monitoring sites located across the State (Table 5).

Table 5—Wyoming's Class I Areas and IMPROVE Sites

Class I area	IMPROVE site
Bridger Wilderness	Bridger (BRID1).
Fitzpatrick Wilderness	Bridger (BRID1).
Grand Teton National Park	Yellowstone Lake Maintenance Building (YELL2).
North Absaroka Wilderness	North Absaroka (NOAB1).
Teton Wilderness	Yellowstone Lake Maintenance Building (YELL2).
Washakie Wilderness	North Absaroka (NOAB1).
Yellowstone National Park	Yellowstone Lake Maintenance Building (YELL2).

The Progress Report addressed current visibility conditions and the difference between current visibility conditions and baseline visibility conditions with values for the most impaired (20 percent worst days) and least impaired and/or clearest days (20 percent best days). Table 6: Visibility Progress in Wyoming's Class I Areas, shows the difference between the current period (represented by 2005-2009 data) and the baseline visibility data (represented by 2000-2004 data).^[24] The EPA supplemented the data provided by the State by including more current data (2012-2016) for both the worst 20 percent and best 20 percent days.^[25] We also supplemented the data provided by the State by including visibility data for the baseline period (2000-2004) and more current period (2012-2016) using the revised visibility tracking metric described in the EPA's December 2018 guidance document.^[26] The revised visibility tracking metric selects the 20 percent most “impaired” days (as opposed to haziest days) based only on anthropogenic impairment so that days with large impacts from extreme, episodic natural events such as fires and dust storms are no longer selected. Although this revised visibility tracking metric is applicable to the second and future implementation periods for regional haze (and therefore not retroactively required for progress reports for the first regional haze planning period), the revised tracking metric's focus on the days with the highest daily anthropogenic impairment shifts focus away from days influenced by fire and dust events, and is therefore a more accurate metric for showing visibility progress especially for Class I areas heavily impacted by wildfire. This supplemental data is shown in square brackets in Table 6. Table 7: Visibility Rolling 5-Year Averages in Wyoming's Class I Areas, shows the rolling 5-year average visibility from 2000-2014 as well as the change from the first 5-year rolling average period (2000-2004) to the last 5-year rolling average period (2010-2014).^[27]

Table 6—Visibility Progress in Wyoming's Class I Areas

Class I area	IMPROVE site	Baseline period 2000-04	Current period 2005-09	More current period 2012-16	Difference (current- baseline)	Difference (more current- baseline)
			Deciview
	20% Worst Days [20% Most Anthropogenically Impaired Days]
Bridger Wilderness	BRID1	11.1 [8.0]	10.7	10.8 [6.6]	−0.4	−0.3 [−1.4]
Fitzpatrick Wilderness	BRID1	11.1 [8.0]	10.7	10.8 [6.6]	−0.4	−0.3 [−1.4]
Grand Teton National Park	YELL2	11.8 [8.3]	11.5	12.3 [7.7]	−0.3	0.5 [−0.6]
North Absaroka Wilderness	NOAB1	11.5 [8.8]	11.0	11.3 [7.2]	−0.5	−0.2 [−1.6]
Teton Wilderness	YELL2	11.8 [8.3]	11.5	12.3 [7.7]	−0.3	0.5 [−0.6]
Washakie Wilderness	NOAB1	11.5 [8.8]	11.0	11.3 [7.2]	−0.5	−0.2 [−1.6]
Yellowstone National Park	YELL2	11.8 [8.3]	11.5	12.3 [7.7]	−0.3	0.5 [−0.6]
	20% Best Days
Bridger Wilderness	BRID1	2.1	1.5	0.8	−0.6	−1.3
Fitzpatrick Wilderness	BRID1	2.1	1.5	0.8	−0.6	−1.3
Grand Teton National Park	YELL2	2.6	2.0	1.4	−0.6	−1.2
North Absaroka Wilderness	NOAB1	2.0	1.2	1.0	−0.8	−1.0
Teton Wilderness	YELL2	2.6	2.0	1.4	−0.6	−1.2
Washakie Wilderness	NOAB1	2.0	1.2	1.0	−0.8	−1.0
Yellowstone National Park	YELL2	2.6	2.0	1.4	−0.6	−1.2

Table 7—Visibility Rolling 5-Year Averages in Wyoming's Class I Areas

Class I area	IMPROVE site	2000-04	2005-09	2006-10	2007-11	2008-12	2009-13	2010-14	Change from baseline
		Deciview
	20% Worst Days
Bridger Wilderness	BRID1	11.1	10.7	10.6	10.0	10.8	10.2	10.3	−0.8
Fitzpatrick Wilderness	BRID1	11.1	10.7	10.6	10.0	10.8	10.2	10.3	−0.8
Grand Teton National Park	YELL2	11.8	11.5	11.6	11.7	12.5	12.0	12.0	0.2
North Absaroka Wilderness	NOAB1	11.4	11.0	*—	*—	*—	*—	11.6	0.2
Teton Wilderness	YELL2	11.8	11.5	11.6	11.7	12.5	12.0	12.0	0.2
Washakie Wilderness	NOAB1	11.4	11.0	*—	*—	*—	*—	11.6	0.2
Yellowstone National Park	YELL2	11.8	11.5	11.6	11.7	12.5	12.0	12.0	0.2
	20% Best Days
Bridger Wilderness	BRID1	2.1	1.5	1.4	1.3	1.1	1.0	1.0	−1.1
Fitzpatrick Wilderness	BRID1	2.1	1.5	1.4	1.3	1.1	1.0	1.0	−1.1
Grand Teton National Park	YELL2	2.6	2.0	1.8	1.7	1.5	1.5	1.4	−1.2
North Absaroka Wilderness	NOAB1	2.0	1.2	*—	*—	*—	*—	1.2	−0.8
Teton Wilderness	YELL2	2.6	2.0	1.8	1.7	1.5	1.5	1.4	−1.2
Washakie Wilderness	NOAB1	2.0	1.2	*—	*—	*—	*—	1.2	−0.8
Yellowstone National Park	YELL2	2.6	2.0	1.8	1.7	1.5	1.5	1.4	−1.2
* Data recovery issues in 2007, 2009, 2010 and 2011 nullified 5-year averages.

As shown in Table 6, all the IMPROVE monitoring sites within the State show improvement in visibility conditions between the baseline (2000-2004) and current (2005-2009) periods on both the 20 percent worst visibility and 20 percent best visibility days. When considering only anthropogenic impairment within the baseline (2000-2004) and most current (2012-2016) periods, all of the IMPROVE monitoring sites within the State also show improvement in visibility on the 20 percent most impaired days. Deciview improvement was consistent over the 2000-2014 time period, using 5-year rolling averages, on the 20 percent best days (Table 7).^[28]

In its Progress Report, Wyoming demonstrates that particulate organic matter was the largest contributor to light extinction on the 20 percent worst days.^[29] According to the State, the largest contributions of particulate organic matter generally occurred between June and September consistent with the period for increased wildfire activity, especially for the year 2012, when wildfires burned nearly 130,000 acres in June 2012 in Wyoming.^[30] Indeed, when uncontrollable, non-anthropogenic sources are removed from the selection of most of the worst visibility days, visibility improves by almost 40 percent at all Class I areas thereby demonstrating the significant contributions of non-anthropogenic sources on visibility, particularly organic mass from wildfires.

The EPA proposes to conclude that Wyoming has adequately addressed the requirements under 40 CFR 51.309(d)(10)(i)(C) to include summaries of monitored visibility data as required by the Regional Haze Rule.

4. Emissions Tracking Analysis

Wyoming's Progress Report must include an analysis tracking the change over the past five years in emissions of pollutants contributing to visibility impairment from all sources and activities within the State. 40 CFR 51.309(d)(10)(i)(D).

In its Progress Report, Wyoming presents data from a 2008 emissions inventory, which leverages inventory development work performed by the Western Regional Air Partnership (WRAP) for the West-wide Jumpstart Air Quality Modeling Study (WestJumpAQMS) ^[31] and the Deterministic & Empirical Assessment of Smoke's Contribution to Ozone (DEASCO₃) modeling projects, termed WestJump2008, and compares it to the baseline emissions inventory for 2002 (Plan02d). The pollutants inventoried include the following source classifications: SO₂, NO_X, ammonia, volatile organic compounds, primary organic aerosol, elemental carbon, fine soil and coarse mass from both anthropogenic and natural sources (Table 8).

Table 8—Emissions Progress in Wyoming

[tons/year]

Pollutant (anthropogenic, natural, and total sources)	2002 emissions (Plan02d)	2008 emissions (WestJump2008)	Difference (percent change)
SO2:
Anthropogenic	143,554	111,604	−31,950 (−22)
Natural	2,286	1,051	−1,235 (−54)
Total	145,840	112,655	−33,186 (−23)
NOX:
Anthropogenic	263,677	216,321	−47,356 (−18)
Natural	24,297	14,357	−9,940 (−41)
Total	287,974	230,678	−57,296 (−20)
Ammonia:
Anthropogenic	31,257	21,848	−9,409 (−30)
Natural	1,775	5,177	3,402 (>100)
Total	33,032	27,024	−6,007 (−18)
Volatile Organic Compounds:
Anthropogenic	193,158	157,134	−36,024 (−19)
Natural	623,747	182,401	−441,346 (−71)
Total	816,904	339,534	−477,370 (−58)
Primary Organic Aerosol:
Anthropogenic	5,401	8,686	3,285 (61)
Natural	23,793	16,341	−7,452 (−31)
Total	29,194	25,027	−4,167 (−14)
Elemental Carbon:
Anthropogenic	3,144	3,772	628 (20)
Natural	4,922	2,333	−2,589 (−53)
Total	8,066	6,105	−1,961 (−24)
Fine Soil:
Anthropogenic	15,646	44,382	28,736 (>100)
Natural	7,374	11,577	4,204 (57)
Total	23,020	55,959	32,940 (>100)
Coarse Mass:
Anthropogenic	44,745	312,867	268,122 (>100)
Natural	57,915	53,806	−4,108 (−7)
Total	102,660	366,673	264,014 (>100)

Overall, Wyoming's emissions that affect visibility were reduced in all sectors for all pollutants (total) except for coarse and fine particulate matter categories. Wyoming cites increases in windblown and fugitive dust and enhancements in dust inventory methodologies as reasons for the increase in fine and coarse particulate matter emissions over the time period analyzed in the Progress Report.^[32] A state adjacent to Wyoming, Montana, with similar increases in fine and coarse particulate matter also cited larger-than-expected amounts of emissions in anthropogenic and natural fires as another reason for the increase in fine and coarse particulate matter.^[33] The largest differences in point source inventories were decreases in SO₂ emissions, which can be attributed to the implementation of the SO₂ Backstop Trading Program in December 2003.

The EPA proposes to conclude that Wyoming has adequately addressed the requirements under 40 CFR 51.309(d)(10)(i)(D) to track changes in emissions of pollutants contributing to visibility impairment from all sources and activities within the State.

5. Assessment of Changes Impeding Visibility Progress

Wyoming's Progress Report must include an assessment of any significant changes in anthropogenic emissions within or outside the State that have occurred over the past five years that have limited or impeded progress in reducing pollutant emissions and improving visibility in Class I areas impacted by the State's sources. 40 CFR 51.309(d)(10)(i)(E).

In its Progress Report, Wyoming provided an assessment of any significant changes in anthropogenic emissions within or outside the State. On the 20% worst days over the 5-year period from 2005-2009, particulate organic matter and SO₂ were the two highest contributors to haze in Class I areas in Wyoming.^[34] According to the State, the primary sources of anthropogenic particulate organic matter in Wyoming include prescribed forest and agricultural burning, vehicle exhaust, vehicle refueling, solvent evaporation (e.g. paints), food cooking, and various commercial and industrial sources. The primary anthropogenic sources of SO₂ include coal-burning power plants and other industrial sources. In their Progress Report, the State concludes that both particulate organic matter and SO₂ are covered by existing regional haze long-term control strategies, including the SO₂ Backstop Trading Program and other control strategies discussed in Section III.A.1. Furthermore, the State concludes that there do not appear to be any other anthropogenic emissions within Wyoming that would have limited or impeded progress in reducing pollutant emissions or improving visibility.

Although not cited in Wyoming's Progress Report, at the time of the analysis done by the State for the Progress Report, not all BART and reasonable progress controls had been installed because compliance dates had not yet occurred for all facilities subject to BART and reasonable progress requirements at that time (Table 2). Thus, the impacts of the emissions reductions from those additional controls have not been fully realized and are therefore not evident or accounted for in the State's Progress Report. Once realized, we anticipate that these additional anthropogenic emissions reductions will further improve visibility in Wyoming's Class I areas.

The EPA proposes to find that Wyoming has adequately addressed the requirements under 40 CFR 51.309(d)(10)(i)(E) to assess significant changes in anthropogenic emissions of visibility impairing pollutants.

6. Assessment of Current Implementation Plan Elements and Strategies

Wyoming's Progress Report must include an assessment of whether the current regional haze implementation plan elements and strategies are sufficient to enable the State, or other states with mandatory Class I areas affected by emissions from the State, to meet all established reasonable progress goals. 40 CFR 51.309(d)(10)(i)(F).

In its Progress Report, Wyoming provided an assessment of whether the current regional haze implementation plan elements and strategies are sufficient to enable the State, and other states with Class I areas affected by emissions from the State, to meet the reasonable progress goals established by the State. However, the EPA disapproved Wyoming's reasonable progress goals, and instead promulgated reasonable progress goals consistent with the emission limits finalized in the approved SIP and FIP.^[35] Due to time and resource constraints, the EPA did not re-run the modeling necessary to quantify reasonable progress goals in deciviews, but anticipated that additional controls imposed by the FIP would result in visibility improvement on the 20% worst days.^[36] Thus, for the purpose of evaluating this section of the progress report requirements, we propose to rely on the fact that all controls required by the regional haze implementation plan or modified by subsequent action have been installed or are on track to be complete by the relevant compliance date, except those stayed by litigation. We also propose to rely on other quantitative and qualitative metrics to assess the current implementation plan elements and strategies.

Wyoming asserts that even with wildfire emissions included in the assessment of visibility impacts on Class I areas, visibility continues to improve at the State's Class I areas from 2000 through 2009 and into 2010. Indeed, key visibility metrics described previously, show: (1) A decrease in SO₂ and NO_X emissions, which are associated with anthropogenic sources; (2) improvement in visibility conditions between the baseline (2000-2004) and current (2005-2009) periods on both the 20 percent worst visibility and 20 percent best visibility days; and (3) improvement in visibility conditions at all of the IMPROVE monitoring sites within the State on the 20 percent most impaired days. Furthermore, the State claims that conservative emissions estimates provided in its Progress Report show total emissions decreases for all major pollutant categories except coarse and fine particulate matter, which are likely due to enhancements in inventory methodology.^[37] Wyoming also expects further reductions in anthropogenic pollutant categories from a revised regional emissions inventory reflective of all final BART and reasonable progress controls.^[38]

Following the future implementation of remaining BART controls and the adjustment of the visibility metrics to account only for anthropogenic impairment, even greater visibility progress should be realized. Thus, Wyoming is confident that the current implementation plan elements and strategies are sufficient to make progress towards visibility goals and will not impede Class I areas outside of Wyoming from meeting their goals in the next planning period.^[39]

The EPA proposes to conclude that Wyoming has adequately addressed the requirements under 40 CFR 51.309(d)(10)(i)(F) and proposes to agree with the State's determination that implementation plan elements are sufficient to enable the State and other states affected by emissions from Wyoming to make progress towards the current reasonable progress goals. The EPA views the requirement of this section as a qualitative assessment that should evaluate emissions and visibility trends, including expected emissions reductions from measures that have not yet been implemented.

7. Review of Current Monitoring Strategy

Wyoming's Progress Report must include a review of the State's visibility monitoring strategy and any modifications to the strategy as necessary. 40 CFR 51.309(d)(10)(i)(G).

The monitoring strategy for regional haze in Wyoming relies upon participation in the IMPROVE network, which is the primary monitoring network for regional haze nationwide.

In its Progress Report, Wyoming summarizes the existing monitoring network, which includes three IMPROVE monitors, used to monitor visibility at the seven Class I areas in the State. The State relies solely on the IMPROVE monitoring network to track long-term visibility improvement and degradation and will continue to rely on the IMPROVE monitoring network, without modifications to the existing network, for complying with the regional haze monitoring requirements.

The EPA proposes to find that Wyoming adequately addressed the requirements of 40 CFR 51.309(d)(10)(i)(G) because the State reviewed its visibility monitoring strategy and determined that no further modifications to the strategy are necessary.

B. Determination of Adequacy of the Existing Regional Haze Plan

The provisions under 40 CFR 51.309(d)(10)(ii) require states to determine the adequacy of their existing implementation plan to meet existing reasonable progress goals and take one of the following actions:

(1) Submit a negative declaration to the EPA that no further substantive revision to the state's existing regional haze implementation plan is needed at this time.

(2) If the state determines that the implementation plan is or may be inadequate to ensure reasonable progress due to emissions from sources in another state(s) which participated in a regional planning process, the state must provide notification to the EPA and to the other state(s) which participated in the regional planning process with the state. The state must also collaborate with the other state(s) through the regional planning process for developing additional strategies to address the plan's deficiencies.

(3) Where the state determines that the implementation plan is or may be inadequate to ensure reasonable progress due to emissions from sources in another country, the state shall provide notification, along with available information, to the Administrator.

(4) If the state determines that the implementation plan is or may be inadequate to ensure reasonable progress due to emissions from sources within the state, then the state shall revise its implementation plan to address the plan's deficiencies within one year.

According to Wyoming, the IMPROVE data demonstrate that Wyoming is on track to either meet or exceed the State's reasonable progress goals. Thus, Wyoming's Progress Report provides a negative declaration to the EPA that no further substantive revisions to the regional haze implementation plan are needed to improve visibility in Class I areas beyond those controls already in place and scheduled to be installed in the future. The EPA proposes to conclude that Wyoming has adequately addressed 40 CFR 51.309(d)(10)(i)(G) because: (1) All controls required by the regional haze implementation plan or modified by subsequent action have been installed or are on track to be complete by the relevant compliance date, except those stayed by litigation; and (2) key visibility metrics described previously show a decrease in SO₂ and NO_X emissions, improvement in visibility conditions between the baseline (2000-2004) and current (2005-2009) periods on both the 20 percent worst visibility and 20 percent best visibility days, and improvement in visibility conditions at all of the IMPROVE monitoring sites within the State on the 20 percent most impaired days. Additionally, the EPA expects further visibility improvement to result from the future installation of controls required by the regional haze implementation plans and subsequent actions.

IV. Proposed Action

The EPA is proposing to approve Wyoming's November 28, 2017, Regional Haze Progress Report as meeting the applicable regional haze requirements set forth in 40 CFR 51.309(d)(10).

V. Statutory and Executive Order Reviews

Under the CAA, 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, the EPA's role is to approve state choices, provided that they meet the criteria of the CAA. Accordingly, this 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 action:

• Is not a “significant regulatory action” subject to review by the Office of Management and Budget under Executive Orders 12866 (58 FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 2011);
• Is not an Executive Order 13771 (82 FR 9339, February 2, 2017) regulatory action because SIP approvals are exempted under Executive Order 12866;
• 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 CAA; and
• Does not provide the EPA with the discretionary authority to address, as appropriate, disproportionate human health or environmental effects, using practicable and legally permissible methods, under Executive Order 12898 (59 FR 7629, February 16, 1994).

In addition, the SIP is not approved to apply on any Indian reservation land or in any other area where the EPA or an Indian tribe has demonstrated that a tribe has jurisdiction. In those areas of Indian country, the proposed 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 in 40 CFR Part 52

• Environmental protection
• Air pollution control
• Carbon monoxide
• Greenhouse gases
• Incorporation by reference
• Intergovernmental relations
• Lead
• Nitrogen dioxide
• Ozone
• Particulate matter
• Reporting and recordkeeping requirements
• Sulfur oxides
• Volatile organic compounds

Authority: 42 U.S.C. 7401 et seq.

Dated: April 9, 2020.

Gregory Sopkin,

Regional Administrator, EPA Region 8.

Footnotes

1.  42 U.S.C. 7491(a). Areas designated as mandatory Class I Federal areas consist of national parks exceeding 6000 acres, wilderness areas and national memorial parks exceeding 5000 acres, and all international parks that were in existence on August 7, 1977. 42 U.S.C. 7472(a). In accordance with section 169A of the CAA, EPA, in consultation with the Department of Interior, promulgated a list of 156 areas where visibility is identified as an important value. 44 FR 69122 (November 30, 1979). The extent of a mandatory Class I area includes subsequent changes in boundaries, such as park expansions. 42 U.S.C. 7472(a). Although states and tribes may designate as Class I additional areas whose visibility they consider to be an important value, the requirements of the visibility program set forth in section 169A of the CAA apply only to “mandatory Class I Federal areas.” Each mandatory Class I Federal area is the responsibility of a “Federal Land Manager.” 42 U.S.C. 7602(i). When we use the term “Class I area” in this section, we mean a “mandatory Class I Federal area.”

2.  84 FR 10433 (March 21, 2019).

3.  Due to new permit requirements for Unit 3 at the Naughton Power Plant added to the Progress Report in early 2017, a second public comment period was provided.

4.  64 FR 35714, 35714 (July 1, 1999) (codified at 40 CFR part 51, subpart P).

5.  The EPA had previously promulgated regulations to address visibility impairment in Class I areas that is “reasonably attributable” to a single source or small group of sources, i.e., reasonably attributable visibility impairment (RAVI). 45 FR 80084, 80084 (December 2, 1980).

6.  82 FR 3078 (January 10, 2017).

7.  42 U.S.C. 7410(a), 7491, and 7492(a); CAA sections 110(a), 169A, and 169B.

8.  42 U.S.C. 7410(c)(1).

9.  The Colorado Plateau is a high, semi-arid tableland in southeast Utah, northern Arizona, northwest New Mexico, and western Colorado. The 16 mandatory Class I areas are: Grand Canyon National Park, Mount Baldy Wilderness, Petrified Forest National Park, Sycamore Canyon Wilderness, Black Canyon of the Gunnison National Park Wilderness, Flat Tops Wilderness, Maroon Bells Wilderness, Mesa Verde National Park, Weminuche Wilderness, West Elk Wilderness, San Pedro Park Wilderness, Arches National Park, Bryce Canyon National Park, Canyonlands National Park, Capital Reef National Park and Zion National Park.

10.  Wyoming Department of Environmental Quality, Wyoming State Implementation Plan, 5-Year Progress Report. (Wyoming Progress Report), Governor's letter. (November 17, 2017).

11.  79 FR 5032 (January 30, 2014).

12.  Basin Electric, PacifiCorp, Powder River Basin Resource Council, National Parks Conservation Association, Sierra Club, and the State of Wyoming challenged various NO_X BART emission limits in the final rule. Basin Electric Cooperative v. EPA, No. 14-9533 (10th Cir.); Wyoming v. EPA, No. 14-9529 (10th Cir.); PacifiCorp v. EPA, No. 14.9534 (10th Cir.); Powder River Basin Resource Council, et al. v. EPA, No. 14-9530 (10th Cir.).

13.  Wyoming v. EPA, No. 14-9529, ECF No. 10204804.

14.  On March 21, 2019, the EPA approved a SIP revision to the BART requirements for Unit 3 at the Naughton Power Plant. 84 FR 10433 (March 21, 2019). On May 20, 2019, the EPA approved SIP revisions and revised the FIP to: (1) Modify the SO₂ emissions reporting requirements for Laramie River Station Units 1 and 2, (2) revise the NO_X emission limits for Laramie River Units 1, 2 and 3, and (3) establish an SO₂ emission limit averaged annually across both Laramie River Station Units 1 and 2. 84 FR 22711 (May 20, 2019).

15.  Wyoming Progress Report, pages 6, 10.

16.  Western Regional Air Partnership, 2011 Regional SO₂Emissions and Milestone Report. (February 20, 2013).

17.  In 2011, three states participated in the SO₂ Backstop Trading Program. SO₂ emissions from all three participating states are recorded and collectively compared to the milestone.

18.  See Wyoming Progress Report, page 10; see also Western Regional Air Partnership, 309 Committee: Documents, https://www.wrapair.org/​/forums/​309/​docs.html (last visited March 6, 2020). This Table represents the adjusted SO₂ emissions/milestone for New Mexico, Utah, Wyoming, and Albuquerque-Bernalillo County. Adjustments to reported emissions are required to allow the basis of current emissions estimates to account for changes in monitoring and calculation methods.

19.  Wyoming Progress Report, pages 30-37.

20.  Wyoming Progress Report, page 29.

21.  The EPA's Clean Air Markets Division (CAMD) database is available at: https://ampd.epa.gov/​ampd/​.

22.  U.S. Environmental Protection Agency, General Principles for the 5-Year Regional Haze Progress Reports for the Initial Regional Haze State Implementation Plans (Intended to Assist States and EPA Regional Offices in the Development and Review of the Progress Reports), pages 8-9 (April 2013).

23.  The “most impaired days” and “least impaired days” in the Regional Haze Rule refers to the average visibility impairment (measured in deciviews) for the 20% of monitored days in a calendar year with the highest and lowest amount of visibility impairment, respectively, averaged over a five-year period. See 40 CFR 51.301.

24.  Wyoming Progress Report, pages 18-19.

25.  Federal Land Manager Environmental Database, Visibility Status and Trends Following the Regional Haze Rule Metrics, http://views.cira.colostate.edu/​fed/​SiteBrowser/​Default.aspx?​appkey=​SBCF_​VisSum (last visited February 10, 2020).

26.  U.S. Environmental Protection Agency, Technical Guidance on Tracking Visibility Progress for the Second Implementation Period of the Regional Haze Program (December 20, 2018), https://www.epa.gov/​sites/​production/​files/​2018-12/​documents/​technical_​guidance_​tracking_​visibility_​progress.pdf (last visited February 10, 2020).

27.  Wyoming Progress Report, pages 24-27.

28.  Refer to the Wyoming Progress Report for pollutant contributions at each Class I area and 5-year rolling averages. Wyoming Progress Report, pages 24-27.

29.  Wyoming Progress Report, page 15.

30.  NOAA National Centers for Environmental Information, State of the Climate: Wildfires for June 2012, http://www.ncdc.noaa.gov/​sotc/​fire/​201206 (last visited February 10, 2020).

31.  WRAP Regional Technical Center and West Jump AQMS, https://www.wrapair2.org/​WestJumpAQMS.aspx (last visited February 10, 2020). Additional information on the WestJump study available in the docket for this action, “WestJump Fact Sheet.”

32.  Wyoming Progress Report, page 29.

33.  84 FR 32682 (July 9, 2019).

34.  Wyoming Progress Report, page 16.

35.  79 FR 5038 (January 30, 2014).

36.  77 FR 33022, 33057 (June 4, 2012).

37.  Wyoming Progress Report, pages 27-29.

38.  Wyoming Progress Report, page 41.

39.  Wyoming Progress Report, page 41.