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Permit Request

On February 20, 2015, EPA Region 9 received an application from Salt River Project 

Agricultural Improvement and Power District (SRP) requesting a minor NSR permit for the 

Navajo Generating Station (NGS) in accordance the requirements of the Tribal Minor NSR 

permitting program at 40 CFR Part 49.151-161. The NGS is a facility with three existing coal 

fired electricity generating units (EGUs) located within the exterior boundaries of the Navajo 

Nation Indian Reservation in the northern part of the State of Arizona near the town of Page. The 

facility location is given below:

Sec 2 T40N R9E

Latitude: 36.903135 N

Longitude: -111.390242 W

Coconino County, Arizona

The proposed minor NSR permit would authorize SRP to construct and operate a refined 

coal treatment system (RCTS), including ancillary equipment, in order to treat coal with cement 

kiln dust and calcium bromide prior to combustion in existing boiler units 1, 2, and 3. The 

proposed permit for the RCTS Project would result in increases in emissions of particulate matter

(PM, PM10, and PM2.5). Increases in particulate matter emissions will originate primarily from 

increased truck delivery traffic on existing unpaved roads at NGS. There will also be some 

particulate matter emissions increases from new dust collectors to be installed on the RTCS

conveyor belt systems and new baghouses associated with cement kiln dust storage silos and day 

bins. A very small increase in emissions will originate from the existing Units 1, 2 and 3 due to 

the increased ash content of the coal, however, this increase will not result in changing the 

permitted emissions limits for the EGUs. Air pollution emissions from the RCTS Project are 

below Prevention of Significant Deterioration (PSD) thresholds and will not cause or contribute 

to violations of any National Ambient Air Quality Standards (NAAQS).

The existing PSD permit issued to SRP in 2008 for the installation of a Low-NOx burner 

project at NGS (see PSD Permit No. AZ 8-01A), is being amended under this action to 

incorporate the minor NSR permit conditions, including operational standards and recordkeeping 

requirements for cement kiln dust and calcium bromide deliveries, as well as testing and 

recordkeeping requirements for new equipment to be installed under the RCTS project. There are 

no changes in any established emission limits for the existing boiler units 1, 2, and 3.

Air Quality Review

The Tribal Minor NSR regulations at 40 CFR 49.154(d) require that an Air Quality 

Impact Assessment (AQIA) modeling analysis be performed if there is reason to ensure that new 

construction will not cause or contribute to a NAAQS or PSD increment violation. If an AQIA 

reveals that the proposed construction could cause or contribute to a NAAQS or PSD increment 

violation, such impacts must be addressed before a pre-construction permit can be issued.

For purposes of Executive Order 12898 on environmental justice, the EPA has 

recognized that compliance with the NAAQS is “emblematic of achieving a level of public 

health protection that, based on the level of protection afforded by a primary NAAQS, 

demonstrates that minority or low-income populations will not experience disproportionately 

high and adverse human health or environmental effects due to the exposure to relevant criteria 
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pollutants.” In re Shell Gulf of Mexico, Inc. & Shell Offshore, Inc., 15 E.A.D. 103, 156 (EAB 

2010). This is because the NAAQS are health-based standards, designed to protect public health 

with an adequate margin of safety, including sensitive populations such as children, the elderly, 

and asthmatics.

The proposed RCTS Project at NGS will result in increased emissions of PM, PM10, and 

PM2.5. Although all emission increases due to the proposed project are below PSD thresholds, 

increases in PM and PM10 exceed minor NSR permitting thresholds. An analysis for PM is not 

required because there is no longer a NAAQS for PM. A primary and secondary NAAQS exists 

for PM10, therefore, impacts due to PM10 are being analyzed to ensure that they do not contribute 

or cause any impacts on the annual and 24-hour PM10 NAAQS or a PSD increment violation.

SRP conducted a PM10 and PM2.5 modeling analysis for the RCTS Project to determine the 

impact of emissions increases on the annual and 24-hour PM10 and PM2.5 NAAQS. Although an 

analysis is not required for PM2.5, SRP submitted a modeling report for PM2.5 to demonstrate that 

PM2.5 emissions from the RCTS project are not expected to exceed the minor NSR threshold. 

The modeling showed that maximum concentrations of PM10 and PM2.5 occur within the existing 

facility boundary and that increases of these pollutants do not exceed the Significant Impact 

Levels (SILs) outside the facility boundary and do not result in ambient concentrations that 

exceed the NAAQS. Therefore, due to the fact that the emissions beyond the facility boundary 

are insignificant, we are proposing to grant the minor NSR permit because the construction and

operation of the proposed RCTS project will not have any adverse effect on ambient air quality.

Environmental Impacts to Potentially Overburdened Communities

This minor NSR permit action authorizes the construction of new equipment and changes 

in operational standards which will cause an increase in air emissions of particulate matter at the 

NGS facility. The increased air emissions at the existing facility will not contribute to or cause 

any violation of the NAAQS. All emissions due to the RTCS Project will be well controlled at all 

times and subject to federally enforceable permit conditions. This permit action will have no 

adverse ambient air quality impacts.

Furthermore, the existing PSD permit that was issued in 2008 contains provisions stating, 

“At all times, including periods of startup, shutdown and malfunction, Permittee shall, to the 

extent practicable, maintain and operate the facility including associated air pollution control 

equipment in a manner consistent with good air pollution control practices for minimizing 

emissions,” and “Permittee shall construct and operate this project in compliance with this PSD 

Permit, the application on which this Permit is based, and all other applicable federal, state, and 

local air quality regulations. This PSD Permit does not release the Permittee from any liability 

for compliance with other applicable federal, state and local environmental laws and 

regulations, including the Clean Air Act.” Noncompliance with these permit provisions is a 

violation of the permit and is grounds for enforcement action and for permit termination or 

revocation. As a result, the EPA concludes that proposed issuance of this minor NSR permit and 

incorporating its conditions into the existing PSD permit will not have disproportionately high or 

adverse human health effects on communities in the vicinity of the Navajo Nation Indian 

Reservation.

A report made using EPA’s EJSCREEN tool showing demographics based on the U.S. Census 

Bureau 2010 data in the area surrounding the NGS facility is attached to this memorandum.
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Public Participation

Given the presence of potentially overburdened communities in the vicinity of the NGS facility, 

we are providing an enhanced public participation process for this permit.

1. The minor source permit application was submitted to both the EPA and the Navajo Nation

EPA per the application instructions (see http://www3.epa.gov/air/tribal/tribalnsr.html).

2. Navajo Nation EPA had 10 business days to communicate to us any preliminary questions and 

comments on the application.

3. In the event an Air Quality Impact Analysis is necessary in addition to the initial application, 

we typically email a copy of that document to Navajo Nation EPA within 5 business days from 

the date we receive it. This step was not necessary because the applicant has attached the Air 

Quality Impact Analysis to the application and submitted it to Navajo Nation EPA.

4. We are notifying Navajo Nation EPA, other affected states and tribes, and other interested 

parties of the public comment period for the proposed minor NSR permit and providing copies of 

the notice of public comment opportunity to post in various locations on and around the 

Reservation. We will also notify Navajo Nation EPA, other affected states and tribes, and other 

interested parties, of the issuance of the final permit.

Attachments

(1) EJSCREEN Census 2010 Summary Report – Area within an 9-mile radius of Navajo 

Generating Station

(2) EJSCREEN Report of area within an 9-mile radius of Navajo Generating Station