U.S. Environmental Protection Agency 

Region 9 

Clean Air Act Permit 

Cultural Resources Report under the National Historic Preservation Act

Four Corners Power Plant SCR Project

1.0 Introduction

Pursuant to Section 106 of the National Historic Preservation Act (NHPA) the U.S. Environmental Protection 

Agency (EPA) must consider the effects of its permit actions on properties listed in or eligible for inclusion in the 

National Register of Historic Places. EPA Region 9 is currently reviewing a PSD permit application for the Four 

Corners Power Plant (FCPP) on Navajo Nation in Fruitland, New Mexico. As such, EPA must meet its obligations 

under Section 106 for this project prior to issuing a final permit decision. 

2.0 Description of the Undertaking

Arizona Public Service Company (APS) co-owns and operates the FCPP. The FCPP is a coal-fired power plant, 

utilizing pulverized coal-boilers, located on the Navajo Nation about 25 miles west of Farmington, New Mexico 

(see Figure 1). 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. 

On August 24, 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.1In a 

letter dated December 30, 2013, 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 by January 1, 2014. 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 systems 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 permit from EPA Region 9. The installation of SCR systems on 

Units 4 and 5 are expected to improve visibility at 16 nearby national parks and wilderness areas, such as Mesa 

Verde National Park. The new and affected emission units associated with the FCPP SCR Project are: 

· Units 4 and 5 will be modified by adding new SCR emissions controls. SCR will be added to substantially 

reduce NOX emissions. The SCR systems will be located after each EGU’s economizer and before the air 

preheater. 

· Because the SCR emissions controls will cause a significant net emissions increase in SAM emissions, APS 

is proposing to install and operate dry sorbent injection (DSI) system as BACT to minimize SAM 

emissions. The DSI system will be located after the air preheater and just before the baghouse and wet 

FGD. 

· Truck traffic will increase due to the delivery of reagent for the DSI system resulting in increased fugitive 

emissions from paved plant roads. 

· Truck traffic will also increase due to the delivery of urea pellets, 29% aqueous ammonia, or anhydrous 

ammonia for the SCR system resulting in increased fugitive emissions from paved plant roads. 

· A new pneumatic dry sorbent truck unloading system and silo will be installed; and 

· A new pneumatic urea pellet truck unloading system and silo may be installed if this reagent option is 

selected for the SCR system or a new ammonia truck unloading station and storage tank will be installed 

 

1

For more information on EPA’s BART FIP, please see 77 Fed. Reg. 51620 (Aug. 24, 2012). 
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NHPA - FCPP SCR Project 

EPA Region 9 

if either the aqueous or anhydrous ammonia option is selected for the SCR system. 

Construction of the FCPP SCR Project will involve the use of heavy equipment for site preparation and 

installation of SCR on Units 4 and 5 and for construction of associated structures such as silos for storage of the 

sorbents and reagents and baghouses on the silos for control of PM10 and PM2.5 emissions. Construction of the 

SCR systems is expected to start in mid-2015 or early 2016 with operation planned by July 2018. All projectrelated construction will be limited to industrial areas within the FCPP fenceline in the middle of paved, 

disturbed areas or within existing buildings. Construction will be performed with heavy equipment such as 

earth-movers, cranes, and trucks. 

3.0 Area of Potential Effects

The construction and operation of the FCPP SCR Project will occur only within the existing footprint of the FCPP. 

As such, the area of potential effects (APE) includes the existing footprint of the FCPP power plant as seen in 

Figure 2. In addition, the FCPP SCR Project will increase emissions of SAM to the atmosphere from the FCPP 

while reducing emissions of NOX. SAM and NOX emissions both have the potential to reduce visibility and 

increase acid deposition. As such, we are considering the APE to also include a 50 km radius around the FCPP as 

shown in Figure 3. This area encompasses the expected acid deposition area for the FCPP. 

4.0 Historic Properties within the APE

EPA was advised by the Navajo Nation Tribal Historic Preservation Officer (THPO) that the FCPP itself is eligible 

for inclusion in the National Register of Historic Places. The FCPP has been in existence since the late 1960’s and 

has been an integral part of the economy and community of Navajo Nation since that time. 

In addition, the area in which the construction of the FCPP SCR Project and associated infrastructure, such as the 

urea storage and processing facilities and dry storage injection silos, is within the built-up environment of the 

power plant. The area shown in Figure 2 has been mechanically excavated and leveled and contains an 

established complex of structures, roads, parking areas, and electrical lines to the degree that the area no longer 

resembles natural conditions. 

APS contracted with Statistical Research, Inc. (SRI), to perform a Class I cultural resources investigation and a 

Class III pedestrian survey of the FCPP lease area. The survey of the built-up area was performed from 

November 9 to November 25, 2013, during a Class III intensive pedestrian survey of the full FCPP plant lease. 

This survey covered everything that is not occupied by existing ash disposal structures or inundated by Morgan 

Lake. In the built-up areas, a systematic survey was conducted where the ground surface was visible and less 

disturbed. 

Several archaeological sites in the area were recorded in 1961 and reported by Sciscenti and Greminger in 1962. 

As part of the Class I cultural resources records search, SRI reviewed previous archaeological reports and records 

and tried to locate previously documented sites. No archaeological sites were recorded in the vicinity of the 

proposed construction area for the SCRs and associated infrastructure prior to FCPP construction during the 

1961 survey, and no sites were documented in this area during the 2013 survey. 

There are numerous other properties with 50 km (or potentially within 50 km) of the FCPP that are already listed 

on the National Register of Historic Places. See Table 1. Further there is the potential for other properties that 

are eligible for inclusion in the National Register to be located within 50 km of the FCPP. However, as discussed 

below the potential effects on these properties, other than to the FCPP, relates only to impacts of SAM and NOX

emissions on visibility and acid deposition. EPA’s evaluation applies to any area or property within 50 km of the 
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NHPA - FCPP SCR Project 

EPA Region 9 

FCPP and all properties of cultural significance that may exist are expected to incur that same effects. As such, a 

detailed review of other potentially affected historic properties was not conducted. 

5.0 Effects on Historic Properties

Four Corners Power Plant 

The onsite construction and operation of the FCPP SCR Project will not diminish the integrity of the location, 

design, setting, materials, workmanship, feeling, or association of the FCPP. This undertaking is necessary to 

ensure the FCPP is able to continue operating into the future in compliance with the Clean Air Act. While the 

undertaking will result in additional equipment at the plant, these changes are expected to be minimal and will 

not change the overall significance of the FCPP to the Navajo Nation. 

Visibility Impacts on Historic Properties 

Emissions of SAM and NOX – which are associated with the FCPP SCR Project – have the potential to impact 

visibility in the nearby area. Reduced visibility could adversely affect visual elements of nearby historic 

properties. As such, EPA evaluated visibility impacts associated with the FCPP. 

As stated above, on August 24, 2012, EPA promulgated a source-specific FIP requiring the FCPP to achieve 

emission reductions required by the Clean Air Act’s BART requirements. The installation of SCR to comply with 

EPA’s BART FIP, is causing a significant net emission increase of SAM, which is the reason this Project must 

obtain a permit from EPA Region 9. However, the FCPP SCR Project involves the installation of SCR to reduce 

approximately 80% of the NOX emissions from Units 4 and 5 to improve visibility at 16 nearby national parks and 

wilderness areas, such as Mesa Verde National Park. 

So while the FCPP SCR Project may result in an increase of up to 237 tons per year in SAM emissions it will also 

cause over 19,000 tpy reductions in nitrogen oxides emissions. SAM and NOX emission both have the potential 

to affect visibility. Given the overall large reductions in visibility impacting pollutants from the FCPP SCR Project, 

EPA expects a net improvement in visibility. 

Acid Deposition on Historic Properties 

Acid deposition (also known as acid rain) has the potential to adversely affect historic properties. Acid rain and 

the dry deposition of acidic particles contribute to the corrosion of metals (such as bronze) and the deterioration 

of paint and stone (such as marble and limestone). These effects can significantly reduce the societal value of 

buildings, bridges, other items of cultural significance. As required by the Clean Air Act, EPA implements the Acid 

Rain Program, of which FCPP is a part, to reduce the cumulative effects of acid rain. 

As part of this permit action, EPA also consulted with the U.S. Fish and Wildlife Service regarding endangered 

species and a biological assessment (BA) was prepared. The BA evaluates acid deposition from the FCPP SCR 

Project.2 Acid deposition associated with the FCPP can occur as a result of emissions of SAM, sulfur dioxide, 

nitrogen dioxide, sulfur, nitrogen, hydrochloric acid, and hydrofluoric acid. The BA considers total acid 

deposition from all of these emissions at FCPP. However, similar to the impacts on visibility, the FCPP SCR 

Project is expected to result in overall decreases in acid deposition forming pollutants (decrease of 19,000 tpy of 

 

2 The BA for this action and other information relating to EPA’s consultation with the USFWS is a part of EPA’s 

administrative record for its permit decision. 
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NHPA - FCPP SCR Project 

EPA Region 9 

NOX and an increase in 237 tpy of SAM). As such, no adverse effects of acid deposition are expected to occur as a 

result of the FCPP SCR Project. 

6.0 Conclusion

Based on the information reviewed, EPA is proposing a finding of no adverse effect for the FCPP SCR Project. 
Table 1 – List of Properties on the National Register of Historic Places within 50km of Four Corners Power Plant 

State County City Resource Address Listed

NEW MEXICO S an Juan Az tec Ab ra m s, H. D., House 4 03 N . C hu rc h St . 1 9 85 0 2 21 

NEW MEXICO S an Juan Az tec Am e rica n Hotel 3 00 S. M ai n 1 9 85 0 2 21 

NEW MEXICO S an Juan Fr uitland A rch e ol ogical Site OCA-CGP-56 Add re ss R es tric ted 19 78 02 23 

NEW MEXICO S an Juan Az tec Au st in -McDonald House 5 01 R io Gra nd e 1 9 85 0 2 21 

NEW MEXICO S an Juan Az tec Az te c M ain Street Historic District B o und ed by M ai n E. , C hu s ka S. , 

alley between Park and Main W., 

and Chaco N. 

1985 02 21

NEW MEXICO S an Juan Az tec Az te c M otor Company Building 30 1 S. M ai n 1 9 85 0 2 21 

NEW MEXICO S an Juan Az tec Az te c Ruins Administration Building--

Museum 

Approximately .75 mi. N of US 550, 

on outskirts of Aztec, Aztec Ruins 

National Monument 

1996 1 011

NEW MEXICO S an Juan Az tec Az te c Ruins National Monument 1 m i. N of Az te c 1 9 66 1 0 15 

NEW MEXICO S an Juan Az tec Ball, D . C., House 3 00 S an Ju an 1 9 85 0 2 21 

NEW MEXICO S an Juan Az tec Bu ild ing at 202 Park Avenue 20 2 P ark Ave . 19 85 02 21 

NEW MEXICO S an Juan Az tec Bu ild ing at 500 White Avenue 50 0 W h it e A ve . 19 85 02 21 

NEW MEXICO S an Juan Far mington C hris tm a sTree Ruin (LA 11097) Add re ss R es tric t ed 19 87 01 21 

NEW MEXICO S an Juan Az tec Chu rch Avenue-Lovers Lane Historic 

District 

Bounded by Rio Grande E., Zia S., 

Park W. and NM hwy 550 

1985 02 21

NEW MEXICO S an Juan Far mington C ot to nw o od Divide Site (LA 55829) Add r ess R es tric t ed 19 87 01 21 

NEW MEXICO S an Juan Az tec Da ws - Keys House 4 21 N . Chu rc h 19 85 02 21 

NEW MEXICO S an Juan Az tec De n ve r and Rio Grande Western Railway 

Depot 

314 Rio Grande 1 9 85 0 2 21 

NEW MEXICO S an Juan Far mington Eas t S id e Rincon Site Add re ss R est ric t ed 198 512 15

NEW MEXICO S an Juan Az tec Eng l em an-Thomas Building 2 00 S. M ai n 1 9 85 0 2 21 

NEW MEXICO S an Juan Far mington F ar m ing t on Historic Downtown 

Commercial District 

Approx. 8 blks, along Main St. and 

Broadway, from Auburn Ave. to 

Miller Ave. 

2002 12 20
Table 1 – List of Properties on the National Register of Historic Places within 50km of Four Corners Power Plant 

State County City Resource Address Listed

NEW MEXICO S an Juan Far mington Gall e go s Wash Archeological District Add ress Restricted 19 75 11 20 

NEW MEXICO S an Juan Far mington H a dlo ck 's Crow Canyon No. 1 (LA 55830) Add r ess R est ric t ed 1 9 87 01 21 

NEW MEXICO S an Juan Blo omfield Half w a y House Archeological Site Add re ss R est ric t ed 19 80 10 10 

NEW MEXICO S an Juan Far mington Ja qu e z Si te Ruin Add re ss R est ric t ed 19 84 12 10 

NEW MEXICO S an Juan Az tec Lo we r Animas Ditch L owe r An imas D itc h fro m C hu rc h 

Ave. to Lovers Lane Historic District 

1987 03 19

NEW MEXICO S an Juan Az tec Mc C oy , Harvey, House 7 25 P io ne er 19 85 02 21 

NEW MEXICO S an Juan Az tec Mc C oy -Maddox House N W c or ne r o f M add o x and N E 

Aztec Blvd. 

1985 02 21

NEW MEXICO S an Juan Az tec McG ee House 5 01 S ab en a S t. 19 85 02 21 

NEW MEXICO S an Juan La Plata M orris ' No. 41 Archeological District Add r e ss R es tric t ed 1979 05 17

NEW MEXICO S an Juan La Plata Po nd , F lorence and John R., House 18 75 NM 17 0 2 0 13 0 9 25 

NEW MEXICO S an Juan Far mington P ri eta M e sa Site (LA 11251) Add re ss R es tric t ed 1987 01 21

NEW MEXICO S an Juan Far mington S al mo n R uin Add r ess R es tric t ed 19 70 09 04 

NEW MEXICO S an Juan Sh iprock S an Ju a n River Bridge at Shiprock U S 66 6 ov er Sa n Ju an R . 1 9 97 0 7 15 

NEW MEXICO S an Juan Far mington S imo n C a nyon (LA 5047) Add r ess R es tric t ed 19 87 01 21 

NEW MEXICO S an Juan Fr uitland Si te N o. OCA-CGP-54-1 Add re ss R est ric t ed 19 78 04 19 

NEW MEXICO S an Juan Fr uitland Si te OCA -CGP-605 Add r ess R es tric t ed 19 78 02 17 

NEW MEXICO S an Juan Far mington S tar R o ck Refuge (LA 55838) Add re ss R est ric te d 1987 01 21

NEW MEXICO S an Juan Blo omfield Tw in Ang els Archeological Site Add re ss R es tric ted 19 80 10 10 

COLORADO M ontezuma Ple asa nt 

View 

Lowry Ruin 30 m i. N W o f C o rte z via U . S. 160 19 66 1 0 15 

COLORADO M ontezuma Co rte z M itc he l l Springs Archeological Site Add re ss R es tric t ed 20 01 11 09 

COLORADO M ontezuma Co rte z M ud Sp rings Pueblo Add re ss R est ric t ed 19 82 10 29 

COLORADO M ontezuma Co rte z Ro y 's R uin Add r ess R es tric t ed 19 92 01 31 

COLORADO M ontezuma Co rte z Sa nd Ca nyon Archaeological District Add r e ss R es tric ted 2005 03 15
Table 1 – List of Properties on the National Register of Historic Places within 50km of Four Corners Power Plant 

State County City Resource Address Listed

COLORADO M ontezuma Do lo res S ou th e rn Hotel 10 1 S. F ift h S t. 1 9 89 0 2 23 

COLORADO M ontezuma Co rte z Wallac e Ruin Add re ss R est ric te d 20 05 03 24 

COLORADO M ontezuma Co rte z Yu cca H ouse National Monument 12 mi . S o f C or te z via U .S. 666 1 9 66 1 0 15 
Figure 1 Location of Four Corners Power Plant
Unit 4 Unit 5

Stack 4 & 5

DSI Silo

Urea

Facilities

SCR SCR

0 125 250 500

Feet

!( Point Source

Road Source

Fence

!(

!(

!(

! FCPP Lease

!

Urea Facilities

DSI Silo

Stacks 4 & 5

Inset Not to Scale

[

Location of Proposed SCRs

and Associated Facilities at the FCPP