U.S. Environmental Protection Agency, Region 9 

Public Information Sheet 

Proposed Clean Air Act Permit 

Four Corners Power Plant 

Summary of the Proposed Permit 

On July 24, 2014, the United States Environmental Protection Agency (EPA) Region 9 provided notice of, 

and requested public comment on, a proposed permit that would grant conditional approval, in accordance 

with the Prevention of Significant Deterioration (PSD ) regulations (40 CFR 52.21), to the Arizona Public 

Service Company (APS) to construct and operate selective catalytic reduction (SCR) systems for controlling 

emissions of nitrogen oxides (NOX), as well as other ancillary equipment (the Project) to the Four Corners 

Power Plant (FCPP). The public comment period for this proposed permit will close on September 24, 

2014. 

APS co-owns and operates the FCPP. The FCPP is a coal-fired power plant, utilizing pulverized coalboilers, located on the Navajo Nation about 25 miles west of Farmington, New Mexico. The FCPP 

currently consists of two 750 megawatt (MW) coal-fired electric steam-generating units (EGUs), with a total 

capacity of approximately 1,500 MW, and other ancillary equipment such as coal storage, lime handling 

operations and dry ash handling operations. Previously, the FCPP consisted of five coal-fired EGUs. In 

2012, EPA promulgated a source-specific Federal Implementation Plan (FIP) requiring the FCPP to achieve 

emission reductions required by the CAA’s best available retrofit technology (BART) requirements. APS 

notified EPA that as part of the compliance strategy for the BART FIP it would permanently shut down 

three existing EGUs – Units 1, 2, and 3. As of January 2014, the FCPP now consists of the two remaining 

750 MW EGUs – Units 4 and 5 – and the existing ancillary equipment. APS will further comply with the 

requirements of EPA’s BART FIP by installing SCR on Units 4 and 5 to reduce emissions of nitrogen 

oxides (NOX) by approximately 80% from current levels. The installation of SCR to comply with EPA’s 

BART FIP is causing a significant net emission increase of sulfuric acid mist (SAM), which is the reason this 

Project must obtain a PSD permit from EPA Region 9. Because the Project causes a significant net 

emissions increase only for SAM emissions, SAM is the only pollutant subject to PSD review for the 

Project. 

This document is intended to provide a brief, informal summary of information to assist members of the 

public attending the public hearings scheduled for August 27 and 28, 2014 for EPA’s proposed permit for 

the Project. For more details about the permit requirements, refer to EPA’s public notice, the proposed 

permit, and the Fact Sheet for this proposed permit action, which are available on the EPA Region 9 permit 

website: http://www.epa.gov/region9/air/permit/r9-permits-issued.html. The administrative record for the 

proposed permit may be viewed in person at the EPA Region 9 office in San Francisco, California; for more 

information, or to obtain copies of relevant documents, please contact Lisa Beckham at (415) 972-3811 or 

via email at R9AirPermits@epa.gov. Lisa Beckham can also be reached through EPA Region 9’s toll-free 

general information line at (866) 372-9378. 

What Laws and Regulations Apply to EPA’s Proposed Permit? 

We prepared the proposed permit based on our PSD regulations issued under the Clean Air Act at 40 Code 

of Federal Regulations (CFR) 52.21 and our Minor New Source Review (NSR) regulations for Indian 

Country at 40 CFR 49.151-161. We believe that the proposed Project will comply with PSD and Minor NSR 

requirements, including the installation and operation of Best Available Control Technology (BACT) for 

SAM emissions. We made this determination based on the information supplied by the applicant, our review 

of the analyses contained in the permit application, and other relevant information contained in the 
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administrative record for this proposed action. EPA has provided the proposed permit and Fact Sheet to 

the public for review, and will make a final decision on the Project’s permit application after considering all 

public comments submitted during the public comment period. 

Environmental requirements from other federal, tribal, or local laws are not included in EPA’s proposed 

permit unless they are also part of the Clean Air Act PSD program or Minor NSR program for Indian 

Country. However, the Project is required to comply with all other environmental requirements. 

What Does EPA’s Proposed Permit Regulate? 

The PSD program (40 CFR 52.21) applies to “major” new sources and “major” modifications at existing 

major sources of attainment pollutants. Based on potential emissions from the FCPP, it is considered an 

existing major source. This Project must comply with the PSD program if it meets the definition of a major 

modification. The PSD program will apply for each pollutant that results in a significance net emissions 

increase. 

In accordance with 40 CFR 52.21(j), a major modification is required to apply best available control 

technology (BACT) for each PSD pollutant that would result in a significant net emissions increase. This 

requirement applies to each proposed emissions unit at which a net emissions increase in the pollutant 

would occur. With respect to the Project, increases of SAM cause a significant net emissions increase, and 

therefore the proposed permit requires the Project to apply BACT for SAM emissions to all equipment that 

is being modified as part of the Project. 

For any pollutant not subject to the PSD program, the Project must also comply with the Minor NSR 

Program in Indian Country for each pollutant that results in a net emissions increase above the Minor NSR 

thresholds. The Minor NSR thresholds are lower than the thresholds for the PSD program. With respect to 

the Project, there are no pollutants that cause a net emissions increase (other than SAM emissions, which 

are already subject to the PSD program). However, there are increases in allowable emissions of particulate 

matter (PM), PM10 and PM2.5 that the Minor NSR Program requires to be included in an NSR permit. Our 

proposed permit includes these requirements. 

How Would EPA’s Proposed Permit Affect Air Quality? 

The PSD regulations require an examination of the impacts of the proposed Project on ambient air quality 

for the pollutants regulated under the PSD permit. However, the pollutant regulated under the PSD permit 

– SAM – does not have a National Ambient Air Quality Standard. Based on the technical information that 

we have reviewed to date, the Project’s impacts on air quality and visibility are consistent with limits allowed 

under the Clean Air Act. 

The PSD regulations require that EPA evaluate other potential impacts on 1) soils and vegetation; 2) 

visibility impairment; and 3) growth. Based on our review of the analyses provided by the applicant and the 

maximum potential concentrations of the visibility-related criteria pollutants -- NO2, SAM5 -- we do not 

expect any adverse impacts on visibility, nor do we expect this project to result in any adverse impacts on 

plants and soils or significant growth. The purpose of this Project is to reduce NOX emissions from the 

FCPP to improve visibility at 16 national parks and wilderness areas near the FCPP. 

What Other Actions is EPA Taking in Connection with Its Decision making Process? 

EPA engaged in consultation with the U.S. Fish and Wildlife Service (Service) under section 7 of the l 

Endangered Species Act (ESA) to ensure the proposed permit decision for the Project is not likely to 
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jeopardize the continued existence of any federally-listed endangered or threatened species or result in the 

destruction or adverse modification of critical habitat for such species. EPA has received concurrence from 

the Service that the Project complies with the ESA requirements. 

In addition, EPA must consult with the Navajo Nation Tribal Historic Preservation Officer (THPO) to 

comply with section 106 of the National Historic Preservation Act (NHPA) and consider the effects this 

action will have on historic sites and cultural resources listed in or eligible for the National Register of 

Historic Places. EPA prepared a draft Cultural Resources Report for this action, which is available to the 

public as part of the administrative record for this action. EPA also invited other tribes, THPOs and state 

historic preservation officers to consult with EPA in this process. Any interested party is welcome to bring 

particular concerns or information to our attention regarding this project’s potential effect on historic 

properties. EPA will consult with any tribes requesting to join consultation and review any comments 

received prior to seeking concurrence from the Navajo Nation THPO. 

Finally, in accordance with Executive Order 12898, “Federal Actions to Address Environmental Justice in 

Minority Populations and Low-Income Populations,” EPA determined that it would be appropriate to 

prepare an analysis to consider environmental justice issues in connection with the issuance of this federal 

permit. In our Environmental Justice Analysis, we conclude that the emissions of SAM associated with this 

Project and regulated under EPA’s proposed permit will not result in adverse human health impacts to any 

population, and that there will not be disproportionately high and adverse human health or environmental 

effects with respect to this air pollutant on minority or low-income populations residing near the proposed 

Project or the community as a whole. In addition, we determined that we should provide English-Diné 

translation services at both public hearings. The Environmental Justice Analysis is available to the public as 

part of the administrative record supporting EPA’s proposed permit for the Project.