Endangered Species Act Analysis

Navajo Generating Station

Boiler Burner Modification Project

The Endangered Species Act of 1973 requires the examination of impacts to all federally

listed threatened or endangered species. According to the United States Fish and Wildlife

Service, there are 21 species in Coconino County that are listed as endangered,

threatened, proposed for listing, or candidate species (refer to the 2007 Navajo

Generating Station Water Intake Environmental Assessment provided in Appendix E of

the permit application). Because the proposed project occurs on the Navajo Nation,

species of concern for the Navajo Nation also were investigated. The Navajo Department

of Fish and Wildlife has no records of species of concern occurring at or near the

proposed project site, but it provided a list of species from the Navajo Endangered

Species List that could potentially occur in the proposed project area (refer to the

Environmental Assessment provided in Appendix E of the permit application). There are

no National Park Service sensitive species in the project area.

Salt River Project (SRP) understands that the proposed project area for the water intake

project is different from that of the proposed project. The proposed project is occurring 

on the active plant site, which is located approximately 6 miles away from the water

intake project impact area. However, because of the proximity of the areas and the fact

that the habitat conditions are similar, it is anticipated that there would be no additional

species that would be identified for this proposed project as compared to what was

identified for the water intake project.

Based on the habitat conditions surrounding the project area, only two species from the

Coconino County threatened and endangered species list would be expected to occur in 

the proposed project vicinity. Bald eagles (Haliaeetus leucocephalus), which are listed as

threatened, have been seen at Antelope Island, across the lake and north of the water

intake project area, in the winter months. There have not been any nests on Antelope

Island or in the water intake project area. California condors (Gymnogyps californianus),

which are listed as endangered (Experimental Population, Non-Essential), have been

observed year-round in Page, Arizona, and at Wahweap Marina, both approximately 5

miles west of the water intake project area. No breeding or nesting was observed.

Condors have not been observed in the proposed project area.

Of the species on the Navajo Endangered Species List, only the peregrine falcon has been 

recorded near the proposed project area. The AGFD Heritage Data Management System

has recorded the peregrine falcon within 3 miles of the water intake site. Peregrine

falcons may occasionally forage near the water intake project area. Generally, peregrines

require very tall cliffs for nesting and wetlands that support their prey, which consists

largely of waterfowl. These conditions are present below Glen Canyon Dam, within

approximately 10 miles of the water intake project area. Peregrines from this part of the

Colorado River may sometimes forage over Lake Powell.

It is important to note that the proposed project is occurring on the active plant site,

which is already an industrial area. The species listed in this analysis generally avoid
human contact so it can be expected that the species would continue to avoid this area.

Therefore, construction activities associated with the proposed project would not affect

any endangered species.

In order to ensure that any increase in air emissions resulting from the proposed project

does not adversely impact listed species, SRP conducted a cumulative modeling analysis

that took into account the emissions from the proposed project, existing background

levels, and other nearby sources. The only air pollutant with emission increases

associated with this proposed project is carbon monoxide (CO) so this is the only

pollutant for which SRP conducted a comprehensive cumulative modeling analysis. The

maximum CO concentrations identified in the modeling analysis were compared against

the appropriate screening concentrations provided in a study by A.E. Smith and J.B.

Levenson that was prepared for the United States Environmental Protection Agency 

(EPA) Office of Air Quality Planning and Standards1. This document lists the screening 

concentrations as being equivalent to the National Ambient Air Quality Standards

(NAAQS).

Table 1 presents a summary of the cumulative CO modeling results and the

corresponding NAAQS. Even though the highest-second high concentrations could have

been used for the short-term cumulative analysis because of the length of the

meteorological data set, the analysis was made more conservative by reporting the

highest modeled short-term concentrations. In addition, higher CO background

concentrations from Phoenix, Arizona were conservatively used in the NAAQS impact

analysis as requested by EPA Region 9. Phoenix is a large urban area with far higher CO

emissions and resulting air concentrations than would be expected in the remote area of

Page. Therefore, the results provided in Table 1 represent a very conservative analysis of

potential air quality impacts from the proposed project.

Table 1 – CO Cumulative Analysis Results

Avg.

Period

Maximum

Modeled

Impact

(μg/m3)

Background

Concentration

(μg/m3)

Total Ambient

Concentration

(μg/m3)

NAAQS

(μg/m3)

Impact as

percent of

NAAQS

1-Hr 10,486 8,931 19,417 40,000 49%

8-Hr 1,749 6,069 7,818 10,000 78%

μg/m3 = micrograms per cubic meter

NAAQS = National Ambient Air Quality Standard

As the modeling analysis results show, the maximum CO concentrations are below the

corresponding screening concentrations (i.e., the NAAQS). Therefore, there is no 

indication that a more detailed review would be required for CO impacts on plants, soils,

and animals.

 1 Smith, A.E. and J.B. Levenson. “A Screening Procedure for the Impacts of Air Pollution Sources on Plants, Soils, and

Animals”. December 12, 1980. Screening concentrations provided in Table 5.3 in this document.