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Regional Haze in Utah

In 1999, the U.S. Environmental Protection Agency announced a major effort to improve air quality in national parks and wilderness areas designated as Class I areas.The Regional Haze Rule calls for state and federal agencies to work together to improve visibility in 156 national parks and wilderness areas. Use the map below to see where these areas are located.

  • Arches National Park
  • Bryce Canyon National Park
  • Canyonlands National Park
  • Capitol Reef National Park
  • Zion National Park

The Regional Haze program requires the states to consult with EPA and Federal Land Management agencies to develop and implement air quality protection plans to reduce the pollution that causes visibility impairment. The first State plans for regional haze were due in December 2007. Utah submitted its first plan in 2003.

States, tribes, and five multi-jurisdictional regional planning organizations worked together to develop the technical basis for these plans. Comprehensive periodic revisions to these initial plans are currently due in July 2021, 2028, and every 10 years thereafter.

Utah’s Regional Haze SIP for the second planning period is due July 31, 2021. There are eight major steps, outlined in EPA guidance, to create a Regional Haze plan. While these eight steps (illustrated below) are not necessarily sequential, they represent necessary elements of an approvable Regional Haze plan.

Step 1

Ambient Data Analysis

Step 2

Determine affected Class I Areas in Other States

Step 3

Source Selection

Step 4

Characterize Control Measure Factors

Step 5

Select Control Measures for Reasonable Progress

Step 6

Regional Modeling of LTS to 2028 RPGs

Step 7

URP Glidepath Check

Step 8

Additional SIP Requirements

Planning Information


Control Measure Analysis for Reasonable Progress

In the second Regional Haze planning period, the focus is on the requirement to make continued reasonable progress, but there are no BART (Best Available Retrofit Technology) requirements nor distinctions between BART and non-BART sources, as there were in the first planning period.

A reasonable progress analysis begins by using the four factors in Section 169A(g)(1) of the Clean Air Act to evaluate potential control measures. Those four factors are:

  1. cost of compliance;
  2. time necessary to achieve compliance;
  3. energy and non-air quality environmental impact of compliance; and
  4. the remaining useful life of any existing source subject to such requirements.

In accordance with 40 CFR 51.308(f)(2), states are required to consider any potentially affected anthropogenic source of visibility impairment and should consider evaluating major and minor stationary sources or groups of sources, mobile sources, and area sources. Guidance provided by the U.S. Environmental Protection Agency indicates that the identification of potential control measures does not create a presumption that one of them will be determined to be necessary to make reasonable progress. Sources in Utah were selected based on a Q/d analysis. The analysis is a ratio of a source’s 2014 emissions in tons per year (Q) divided by the distance (d) in kilometers to any Class I area. Pollutants included in the analysis included SO2, NOx, and Particulate Matter. If a source’s Q/d ratio was six or greater, Utah requested that it provide a 4-factor analysis.

Sources initially selected to perform a Four-Factor analysis

Facility NameCombined Q/dTotal Q tpy*Distance to Nearest Class I area in km (D)Q/d NOxQ/D SO2Q/D PM10NOx tons per year (Q)SO2 tons per year (Q)PM10 tons per year (Q)
Ash Grove Cement Company- Leamington Cement Plant6.9930.5134.
Cci Paradox Midstream, Llc: Lisbon Natural Gas Processing Plant†20.9747.135.85.314.01.6188.6499.659.0
Graymont Western Us Incorporated- Cricket Mountain Plant9.01,180.7130.
Intermountain Power Service Corporation- Intermountain Generation Station†193.628,945.7149.5153.329.211.122,909.24,371.51,665.0
Kennecott Utah Copper Llc- Mine & Copperton Concentrator†22.15,234.5237.,199.62.01,032.9
Kennecott Utah Copper Llc- Power Plant, Lab, and Tailings Impoundment†11.82,949.7250.,322.51,500.3126.8
Pacificorp- Hunter Power Plant216.116,177.974.9153.552.610.011,491.23,939.3747.4
Pacificorp- Huntington Power Plant105.510,106.295.871.725.97.96,871.62,479.2755.4
Sunnyside Cogeneration Associates- Sunnyside Cogeneration Facility15.21,477.197.03.610.90.8348.91,054.873.4
Us Magnesium Llc- Rowley Plant7.42,124.2288.,052.117.91,054.2

*Tons per year:Data is from version 2 of the 2014 National Emissions Inventory

† Additional data from these sources, including 2018 emissions, projected 2028 emissions, and planned closure, allowed them to be exempt from a 4-factor analysis

Utah Four-Factor Analysis Submittals

Utah Four-Factor Analysis Evaluations

Utah Four-Factor Analysis Evaluation Responses

Additional Control Measure Information

Comments Received During Public Comment Period

Watch the Regional Haze Public Hearing May 26, 2022 meeting recording.

EPA’s Regional Haze Page



In the 2022 RH SIP revision, UDAQ used an emissions over distance (Q/d) analysis to determine which facilities had the highest potential visibility impact on Utah’s Class I Areas (CIAs) and control potential.These facilities include the Ash Grove Cement Company Leamington Cement Plant, the Graymont Western US Inc. Cricket Mountain Plant, the PacifiCorp Hunter and Huntington Plants, the Sunnyside Cogeneration Associated Sunnyside Cogeneration Facility, and the US Magnesium LLC Rowley Plant. UDAQ required each facility to conduct a four-factor analysis of the following criteria: 1) cost of compliance, 2) time necessary for compliance, 3) energy and non-air quality environmental impacts, and 4) remaining useful life.

As a result, UDAQ identified several existing measures necessary for reasonable progress, including federal on-road and non-road vehicle and equipment standards, Best Available Control Measures (BACM) measures and Best Available Control Technology (BACT) controls included in the recently completed Serious Area PM2.5 SIP for the Salt Lake Nonattainment Area, as well as the following first implementation period regional haze controls:

  • Existing NOx control rate-based limits and Hunter power plant
  • Existing NOx control rate-based limits and Huntington power plant
  • Existing SO2 limits for Hunter power plant (Section 309 control added to SIP in round 2)
  • Existing SO2 limits for Huntington power plant (Section 309 control added to SIP in round 2)
  • Closure of the Carbon power plant

UDAQ also identified and included the following existing control measures to ensure ongoing enforceability in the second implementation period:

  • Ash Grove
  • Graymont
  • Sunnyside
  • US Magnesium
  • Intermountain Generation Station

Finally, UDAQ identified and included the following new control measures as necessary for reasonable progress:

  • A plantwide enforceable mass-based NOx limit on Hunter power plant
  • A plantwide enforceable mass-based NOx limit on Huntington power plant
  • Installation of Flue Gas Recirculator on the US Magnesium Rowley Plant Riley Boiler
  • An enforceable closure date for Units 1 and 2 of the Intermountain Generation Station


In the 2019 SIP revision, Utah used dispersion modeling and the two prong test prescribed by the Regional Haze rule in 40 CFR 51.308(e)(3) to demonstrate that the proposed alternative to BART (Best Available Retrofit Technology) does show greater progress than the most stringent NOx controls (installation of SCR). The two prongs are:

  1. Visibility does not decline in any Class I area, and
  2. There is an overall improvement in visibility, determined by comparing the average differences between BART and the alternative over all affected Class I areas.

The two-prong test is a simple, objective pass-fail test which Utah’s BART alternative meets. EPA proposed approval of this latest SIP on January 22, 2020.


On June 4, 2015, Utah resubmitted its SIP for PM BART and submitted an alternative to BART for NOx for PacifiCorp’s Electrical Generating Units. On January 14, 2016, EPA issued a proposed rule containing a proposal to approve the PM BART and a co-proposal to either approve or disapprove the BART Alternative for NOx and to impose a FIP requiring BART for NOx in the event of the disapproval. On July 5, 2016, EPA issued the final rule disapproving the BART alternative for NOx and approving the BART for PM portion of the June 4, 2015 SIP. To replace the disapproved BART alternative, EPA promulgated a FIP, requiring installation of Selective Catalytic Reduction (SCR) controls on the subject EGUs by August of 2021.

Utah filed a lawsuit against EPA challenging the July 5, 2016 disapproval of BART Alternative for NOx in the Tenth Circuit on September 1, 2106. This litigation has been in abeyance since September 11, 2017, and the final rule requiring SCR installation is stayed.


The SO2 milestones were updated in 2011 to reflect a reduced number of states participating in the program (Arizona elected to pursue a SIP under section 308 of the regional haze rule). In addition, the growth estimates for coal-fired utilities and the estimates for emission reductions due to BART were revised.


While most of the 2003 SIP remained unchanged, in 2008 the Air Quality Board adopted revisions to the stationary source provisions of the SIP to meet the requirements of the revised regional haze rule and to reflect changes in the number of states participating in the program. In addition to these changes, the rule required an update to the SIP in 2008 to address the Best Available Retrofit Technology (BART) requirement for NOx and PM as well as an analysis of the impact of sources in Utah on Class I areas outside of the Colorado Plateau.


When the EPA adopted the Regional Haze Rule in 1999, it incorporated the 1996 recommendations of the Grand Canyon Visibility Transport Commission (GCVTC). In September, 2000 the WRAP, a regional planning organization that was established to address regional haze, submitted an Annex to the GCVTC recommendations that provided the details for regional milestones and a backstop trading program for stationary sources that emit sulfur dioxide. On June 5, 2003, EPA approved the Annex and incorporated the stationary source provisions into the Regional Haze Rule. In December, 2003 the Air Quality Board adopted Section XX of the SIP to address regional haze. This plan was based on the GCVTC recommendations and the Annex and contained a broad-based strategy to address the many source categories and pollutants that contributed to regional haze in Utah.

  • Clean Air Corridors
  • Fire
  • Mobile Sources
  • Paved and Unpaved Road Dust
  • Pollution Prevention and Renewable Energy Programs
  • Stationary Sources

EPA’s approval of the Annex was challenged, and on February 18, 2005 the DC Circuit Court of Appeals vacated EPA’s 2003 rules (Center for Energy and Economic Development (CEED) vs. Environmental Protection Agency, February 18, 2005). The Court determined that EPA had required a Best Available Retrofit Technology (BART) demonstration in the Annex that was based on a methodology that had been vacated by the Court in 2002 (American Corn Growers Association vs. Environmental Protection Agency, May 24, 2002). On October 13, 2006 EPA revised the regional haze rule to establish the methodology for states to develop an alternative to BART that was consistent with the Court’s decision.

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