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BECKHAM, LISA

From: Rios, Gerardo

Sent: Monday, May 19, 2014 12:03 PM

To: david_campbell@fws.gov; joel_lusk@fws.gov

Cc: wally_murphy@fws.gov; McKaughan, Colleen; Lee, Anita; BECKHAM, LISA; Lyons, Ann

Subject: FW: Request for concurrence on EPA determination that installation of new air pollution 

controls at Four Corners Power Plant is not likely to adversely affect listed species

Attachments: FCPP BA for PSD_05-02-14.pdf; FCPP SCR PSD Application-April 2014.pdf

TAKE 2, with attachments. 

Dear Mr. Campbell and Mr. Lusk: 

EPA is requesting concurrence under Section 7 of the Endangered Species Act (ESA) with our finding that an increase in 

emissions of sulfuric acid mist (SAM) from the Four Corners Power Plant (FCPP), located on the Navajo Nation, near 

Farmington, New Mexico, is not likely to adversely affect listed species. 

Arizona Public Service Company (APS), the operator and co-owner of FCPP, has submitted an application to EPA for a 

federal permit allowing it to increase emissions of sulfuric acid mist (SAM) as a result of their plan to install selective 

catalytic reduction (SCR) on Units 4 and 5 at FCPP (Project). The installation of SCR will significantly reduce emissions of 

oxides of nitrogen (NOx) from FCPP. NOx is a criteria air pollutant that affects human health and visibility, and 

contributes to ozone formation and acid deposition. The Federal Action under consideration for this consultation is a 

Federal Prevention of Significant Deterioration (PSD) permit for SAM under the Clean Air Act. 

EPA is responsible for complying with ESA Section 7 requirements with respect to Federal PSD permitting and is the 

lead Federal Agency for Section 7(a)(2) compliance for this Project. Because the Project has the potential to affect 

listed species and/or critical habitat, final action on this PSD permit must not occur until EPA has determined that 

permit issuance will be consistent with the substantive and procedural requirements of the ESA.

On August 24, 2012, EPA promulgated a Federal Implementation Plan (FIP) that requires FCPP to reduce emissions of 

NOx by 80 to 87 percent under the Best Available Retrofit Technology (BART) requirement of the Clean Air Act and the 

Regional Haze Rule. The FIP requires APS to implement one of two options to reduce emissions of NOx: (1) install SCR on 

Units 1-5 by October 2017 (BART), or (2) close Units 1-3 by January 1, 2014 and install SCR on Units 4 and 5 by July 31, 

2018 (BART Alternative). To comply with the FIP, APS has elected to implement the BART Alternative, and accordingly, 

APS permanently retired Units 1-3 at FCPP by January 1, 2014, resulting in substantial emission reductions of numerous 

air pollutants from FCPP, including NOx, mercury, selenium, and sulfur dioxide (SO2). The operation of SCR on Units 4 

and 5 will result in an increase in emissions of SAM; therefore, APS must apply for a permit under the PSD program and 

install Best Available Control Technology (BACT) to control emissions of SAM. Because Units 4 and 5 are already 

equipped with wet scrubbers and baghouses, when EPA proposes a PSD permit for public review, EPA’s BACT 

determination will set an emission limit for SAM that will likely require sorbent injection to increase the capture and 

control of SAM in the baghouses. 

At our request, APS submitted a draft Biological Assessment (BA), developed by AECOM, to examine potential impacts 

from our issuance of the PSD permit to listed species and critical habitat (attached).The BA identified seven species and 

their critical habitat that are listed or proposed to be listed as federally endangered or threatened that have the 

potential to occur within the Action Area of the facility. The Action Area includes areas where potential direct and 

indirect impacts on listed species and critical habitat may occur. The BA refers to the Action Area as the Deposition Area, 

and is the area where the predicted increase in soil concentration of metals (as a proxy for deposition of acids and other 
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particulate matter) after 25 years of future full load operation of Units 4 and 5 with SCR, was modeled to be more than 

one percent of the current concentrations. The species that may occur within this area are the Mexican spotted owl 

(threatened), the Southwestern willow flycatcher (endangered), the yellow-billed cuckoo (proposed for listing as 

threatened), the Colorado pikeminnow (endangered), the razorback sucker (endangered), the Mancos milk-vetch 

(endangered), and the Mesa Verde cactus (threatened). 

Installation and operation of the SCR, including associated buildings, such as storage silos, will occur within the existing 

fenceline of FCPP, in the middle of disturbed areas or within existing buildings. Although delivery of the reagents 

necessary for the operation of SCR (and any additional controls that EPA requires as BACT for SAM) will increase truck 

traffic to FCPP, the deliveries will occur on existing roads and paved areas within the existing fenceline of the facility. 

Analysis in the BA indicates that listed species and critical habitat do not occur within the fenceline of FCPP. 

The BA evaluates the effect of acid deposition to soils and surface water to determine whether the installation and 

operation of SCR would decrease the pH of soils and surface water to make existing metals more biologically available. 

Based on the analysis, the BA concludes that deposition of acid gases from FCPP would not significantly alter the pH of 

soil or surface water in the Deposition Area. The BA also considered direct deposition of acid mist, and pollutants that 

contribute to acid deposition (SO2 and NOx), on vegetation in general. The BA cites to a study by the World Health 

Organization (WHO) that concludes deposition of SAM tends to be greater on forested areas and vegetation at higher 

altitudes, and estimates critical load guidelines for SO2 and NOx to be 250 sulfur equivalents per hectare per year, and 5 

kilograms of nitrogen per hectare per year. The modeling analysis in the BA predicts a maximum annual average of 29.9 

sulfur equivalents per hectare per year and 0.037 kilograms of nitrogen per hectare per year in the Deposition Area. 

Based on documents from the US FWS, including recovery plans, goals, and listing documents, the primary threats to all 

of the eight species that may occur within the Deposition Area relate to extensive habitat loss or modification resulting 

from anthropogenic activities. Establishment of non-native invasive species and competition and predation were also 

identified as threats to the Southwestern willow flycatcher, the yellow-billed cuckoo, the Colorado pikeminnow, the 

razorback sucker, and the roundtail chub. Although pollutants associated with coal combustion, e.g., mercury and 

selenium, are listed as potential threats to the fish species, the closure of Units 1-3 at FCPP have reduced overall 

emissions of all pollutants, including mercury and selenium, and acid deposition (associated with the increase in SAM 

from the installation of SCR on Units 4 and 5) has not been identified as a potential threat to fish species. However, in 

the 1989 Final Recovery Plan for the Mancos milk-vetch (1989 Recovery Plan), acid deposition from power plants was 

identified as a potential threat. The 1989 Recovery Plan stated “Presently, there are no data to suggest that acidic wet or 

dry deposition pose any threat to the Mancos milkvetch, though no data have been collected. However, northwestern 

New Mexico is a center for power production in the region. Two power plants are already on line, and another is 

scheduled for construction. Particulate and chemical fallout from power plants is often acidic, and thus acidic deposition 

is a potential threat to the species.” More recent information from the US FWS, i.e., the 2011 five-year review of the 

Mancos milk-vetch (2011 five-year review), does not provide further discussion of, or any data related to, the potential 

threat of acid deposition to the species. On May 9, 2014, EPA conducted a literature search on the effects of acid 

deposition on milk-vetch (i.e., search terms Mancos milk vetch, Mancos milk-vetch, Astragalus humullimus, or milk 

vetch; and acid deposition, acid uptake, or acid rain, or sulfuric acid) on the Science Direct “Web of Science” database 

and Google Scholar. The only relevant documents from the search were the 1989 Recovery Plan, the 2011 five-year 

review, and the April 2007 Biological Assessment for the Desert Rock Energy Project (DREP), prepared by Ecosphere 

Environmental Services for the Bureau of Indian Affairs and the US FWS, with general references to the potential for acid 

rain to affect vegetation. We note that the draft Biological Opinion for DREP, prepared by the US FWS, did not focus on 

or address potential impacts of acid gases on the Mancos milk-vetch. 

The installation of SCR on Units 4 and 5 at FCPP to reduce emissions of NOx by 18,600 tons per year will result in a 

projected increase in emissions of SAM of 230 tons per year. The primary threats to the listed or proposed species relate 

to habitat destruction or modification, and the installation and operation of SCR will occur within the existing fenceline 

and disturbed areas of FCPP. The increase in SAM emissions is not expected to alter the pH of soils or surface water in 

the Deposition Area, and acid deposition rates of sulfur and nitrogen are expected to be well below critical load 

guidelines put forth by the WHO. Although acid deposition was previously identified as a potential threat to the Mancos 
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milk-vetch, there is no data to suggest that acid deposition poses an actual threat to the species. Therefore, we find that 

if EPA issues a PSD permit to FCPP to install and operate SCR on Units 4 and 5, the increase in emissions of SAM is not 

likely to adversely affect federally-listed species or their critical habitats, in accordance with 50 CFR 402.13 and 

402.14(b). EPA requests concurrence from the Service with this finding. 

Thank you in advance for your attention to this request. If you have any questions, please contact Anita Lee at (415) 972-

3958 or lee.anita@epa.gov. 

Gerardo C. Rios 

Chief, Permits Office 

(415) 972-3974