SALT RIVER PROJECT

P.O. Box 52025

Phoenix, AZ B5072·2025

(602) 236S262

Fox (602) 236-6690

Keffy. Barr@srpnet.com

January 20, 2012

Dr. Deborah Jord an

u.s. Environmental Protectio n Agency Region IX

75 Hawthorne Street

San Francisco, CA 94105

Re: Updated Best Available Retrafit Technology Analysis

Navajo Generating Station

Dear Dr. Jordan:

KELLY J. BARR, ESQ.

Senior Direc tor

Environmental Ma nagement,

Policy and Compliance

The Salt River Project Agricult ural Improvement and Power District (SRP), the operator of the Navajo

Generating Station (NGS), submitted a repo rt to the United States Environm ental Protection Agency

(EPA) in January 2009 containing a Best Available Retr ofit Technology (BART) analysis for NGS. Since the

submittal of thi s report, SRP has conducted several studies and addit ional analysis in support of th e

pending BART determination. Accordingly, SRP is submitting thi s report to provide a compre hensive

updat e to its BART analysis fo r NGS.

In this report, SRP conducte d an analysis of each of the five BART stat uto ry factors in light of this

additi onal informatio n. Based on th is analysis, SRP is proposing that a nit rogen oxide (NO,) emission

limit of 0.24 Ib/MMBtu, achievable by installing and operating Low-NO, Burners and Separated Overfire

Air (LNB/SOFA)on all three unit s, is BART for NGS.

While SRP's conclusion has not changed since the 2009 report, SRP has gathered significant additional

inform at ion to support th at conclusion, including economic st udies, emission control cost evaluations,

and additi onal visibility modelin g.

SRP appreciates EPA's considerat ion of th is additional information. If you have any quest ions regarding

this report, please feel free to call me at 602-236-5262.

Sincerely,

K

~~elly J. Barr

cc: Janet McCabe, Deputy Assistant Administ rator, EPAOffi ce of Air and Radiation

Stephen Etsitty, Executive Director, Navajo Nation Environmental Protection Agency

Enclosure
Updated Best Available Retrofit Technology Analysis

Submitted for Consideration in Developing Best Available Retrofit

Technology Proposal for Navajo Generating Station

Submitted to:

United States Environmental Protection Agency, Region 9

75 Hawthorne Street  

San Francisco, California 94105  

Prepared by:

Salt River Project

P.O. Box 52025 PAB352

Phoenix, Arizona 85072‐2025

January 2012
i

Executive Summary

The Navajo Generating Station (NGS) is a unique generating asset that plays a critical role in the 

Southwest. In addition to providing electricity for millions of customers in the Southwest, it also 

provides 95% of the power used by the Central Arizona Project (CAP) to pump water from the 

Colorado River to central Arizona. It provides funds for the repayment of the cost of 

constructing the CAP, and for water rights settlements with multiple central Arizona Indian 

Tribes. It also provides significant economic benefit to the Navajo Nation and the Hopi Tribe 

through employment, scholarships, lease payments, and coal royalties. 

There are several significant issues facing NGS that threaten its future viability. The plant site 

lease and other critical agreements expire in 2019, and need to be extended. The coal supply 

contract with Peabody Energy is currently being renegotiated. Perhaps most significantly, the 

United States Environmental Protection Agency (EPA) is currently considering whether to 

require additional emission controls at NGS as part of its pending Best Available Retrofit 

Technology (BART) determination. If EPA requires costly additional controls as BART, the 

plant’s six owners would have to justify a significant capital expense without any certainty that 

the plant could continue to operate beyond 2019. This could put the plant at a significant risk of 

closure, which could have devastating economic consequences. 

The Salt River Project Agricultural Improvement and Power District (SRP), the operator of 

NGS, submitted a report to EPA in January 2009 containing a BART analysis for NGS. Since 

the submittal of this report (hereafter referred to as the “2009 BART Report”), SRP has 

conducted several studies and additional analysis in support of the pending BART determination. 

Accordingly, SRP is submitting this report to provide a comprehensive update to its BART 

analysis for NGS. 

SRP conducted an analysis of each of the five BART statutory factors in light of this additional 

information. Based on this analysis, SRP is proposing that a nitrogen oxide (NOx) emission limit 

of 0.24 lb/MMBtu, achievable by installing and operating Low-NOx Burners and Separated 

Overfire Air (LNB/SOFA) on all three units, is BART for NGS. While SRP’s conclusion has 

not changed since the 2009 BART Report, SRP has gathered significant additional information 

to support this conclusion. In summary, SRP’s proposal is based on the following 

considerations: 

• LNB/SOFA achieves an emission rate that is well below the presumptive BART limit of 

0.28 lb/MMBtu established by EPA for the type of boilers at NGS. 

• LNB/SOFA achieves greater incremental visibility improvement than post-combustion 

controls, at a fraction of the cost. The cost of Selective Catalytic Reduction (SCR), the 

most expensive control option, exceeds that of LNB/SOFA by more than a factor of 10, 

and by more than a factor of 25 if baghouses are also required. 
ii

• The NGS owners voluntarily installed LNB/SOFA on all three units between 2009 and 

2011. By installing LNB/SOFA early, total NOx reductions achieved in the first regional 

haze planning period will exceed the reductions that would be required by even the most 

stringent EPA BART determination, as shown in Figure ES-1. 

Figure ES-1. Comparison of NOx Reductions in the First Regional Haze Planning Period 

0

20,000

40,000

60,000

80,000

100,000

120,000

2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019

NOx Emission Reductions(tons)

NOx Reductions from LNB/SOFA NOx Reductions if BART = SCR

Cumulative NOx Reductionsfrom LNB/SOFA

Cumulative NOx Reductionsif EPA BART = SCR

LNB/SOFA

onUnit 3

LNB/SOFA

onUnit 2

LNB/SOFA

onUnit 1

SCR on

Unit1

SCR on

Unit2

SCRon

Unit3

• The results obtained using the EPA’s CALPUFF model (Version 5.8) indicate that the 

incremental visibility improvement from installing SCR relative to LNB/SOFA is well 

below 1 deciview (dv) at all Class I areas. 1 dv is the level that EPA has indicated is a 

“small but noticeable change in haziness.” 

• The results obtained using the latest version of CALPUFF (Version 6.4), which is based 

on the best available science, indicate that the incremental visibility improvement from 

installing SCR relative to LNB/SOFA is significantly less than the improvement 

predicted by CALPUFF v5.8. In certain Class I areas, visibility is predicted to degrade 

due to the increase in sulfates that are produced by SCR. 

• Regardless of which version of the CALPUFF model is used, the results indicate that 

LNB/SOFA achieves greater incremental visibility improvement than Selective NonCatalytic Reduction (SNCR) or SCR, and at a significantly lower capital cost. This 

conclusion is illustrated graphically in Figure ES-2 below. 
iii

Figure ES-2. Cost vs. Visibility Benefit for BART Control Options 

$45 Million

$84 Million

$589 Million ‐ $1.1 Billion

0.25 dv

0.17 dv

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0

100

200

300

400

500

600

700

Low‐NOx Burners and

SeparatedOverfire Air

(LNB/SOFA)

LNB/SOFA and Selective

Non‐Catalytic Reduction (SNCR)

LNB/SOFA and Selective

Catalytic Reduction (SCR)

Visibility Improvement (Deciviews[dv]) *

Capital Cost ($million)

* Visibility improvement shown is the average over all Class I areas modeled, obtained using CALPUFF v5.8, 

assuming a NOx emission rate of 0.15 lb/MMBtu for SNCR. 

• If EPA requires SCR as BART, there is a significant risk that NGS could shutdown, 

which would result in the loss of a vital resource to the economies of the Navajo and 

Hopi Tribes. NGS has over 500 employees, more than 80% of whom are Navajo. NGS 

and the Kayenta Mine, which supplies it with coal, employ a total of almost 1,000 people. 

The plant and the mine provide significant economic benefit to the Navajo Nation and the 

Hopi Tribe through employment, scholarships, lease payments, and coal royalties. All of 

those benefits would be lost if NGS and the mine were to shutdown. 

• The shutdown of NGS would also have devastating economic consequences on the state 

of Arizona as a whole. In a recent study, Arizona State University’s Seidman Institute 

evaluated the economic contribution of NGS and the Kayenta Mine to the Arizona 

economy. ASU estimates that NGS and the Kayenta Mine will account for over 

$20 billion in Gross State Product between 2011 and 2044, and contribute to over 

3,000 jobs each year.

In light of the above considerations, SRP respectfully urges EPA to propose a NOx BART 

emission limit for NGS that is based on LNB/SOFA. The analysis presented in this report, 

which is based on a review of the five BART statutory factors, demonstrates that LNB/SOFA is 

the most cost-effective BART control option for NGS, and a BART proposal that is based on this 

technology would not introduce the risk of broader adverse economic consequences. 
Table of Contents

1 Background and Purpose of this Report .................................................................................. 1

2 Updated Emissions Data ......................................................................................................... 2

3 Updated Visibility Modeling ................................................................................................... 5

4 Updated Costs of Compliance ............................................................................................... 10

5 Remaining Useful Life .......................................................................................................... 16

6 Updated Five Factor Analysis and BART Proposal .............................................................. 17

Appendix A. Modeling Files 
1

1 Background and Purpose of this Report

SRP submitted a BART analysis to EPA in January 2009. The analysis included a thorough 

review of each emission control option in the context of the five BART statutory factors. Based 

on this analysis, SRP concluded that a NOx emission limit of 0.24 lb/MMBtu, achievable by 

installing and operating LNB/SOFA on all three units, is BART for NGS. 

Since the submittal of the 2009 BART Report, SRP has conducted several studies in support of 

the pending BART determination for NGS, and has submitted additional information to EPA: 

• Additional Information Letter (May 2009) 

• Comments on EPA’s Advanced Notice of Proposed Rulemaking (ANPR) (August 2009) 

• Sargent and Lundy (S&L) Cost Study (August 2010) 

• Ammonia Monitoring Report (September 2010) 

• Additional Information Letter (October 2010) 

• Modeling Update (February 2011) 

SRP has also more recently initiated several additional studies in support of the pending BART 

determination for NGS that have not yet been submitted to EPA: 

• ASU’s Seidman Institute conducted a study to quantify the value of NGS and the 

Kayenta Mine to the state of Arizona; 

• Harvey Economics conducted a study to evaluate the broader economic impacts within 

the state of Arizona associated with each of the BART control options, assuming that 

implementation of BART does not lead to plant closure; and 

• Fuel Tech, Incorporated (FTI), the largest commercial supplier of SNCR, conducted infurnace temperature and gas measurements in order to more accurately define the 

potential NOx emission rate achievable by installing and operating SNCR at NGS. The 

information from FTI suggests that SNCR can achieve greater NOx reductions and 

visibility benefits than were estimated in the 2009 BART Report. 

SRP is submitting this report to EPA in order to provide a consolidated and comprehensive 

update to SRP’s BART analysis for NGS. This report contains an updated analysis of the five 

statutory factors in light of all of the latest information available. 

This report focuses on the NOx BART determination for NGS. Sulfur dioxide (SO2) emissions 

were addressed under the 1991 visibility Federal Implementation Plan (FIP). In the case of 

particulate matter (PM), NGS is currently subject to a limit of 0.06 lb/MMBtu. In the 

2009 BART Report, SRP proposed a filterable PM limit of 0.05 lb/MMBtu, achievable using the 

existing electrostatic precipitators (ESPs) and wet scrubbers, as BART for NGS. SRP is not 

proposing any changes to its PM BART proposal in this report. 
2

2 Updated Emissions Data

This section provides the latest information regarding the potential emission rates achievable by 

each of the BART control options. 

2.1 LNB/SOFA

LNB/SOFA was voluntarily installed by the NGS owners on all three units between 2009 and 

2011. Actual NOx emissions recorded from each unit at NGS since commencement of operation 

of LNB/SOFA have been below the proposed BART permit limit of 0.24 lb/MMBtu, and well 

below the presumptive BART limit of 0.28 lb/MMBtu established by EPA for the type of boilers 

at NGS. 

2.2 Combustion Diagnostic and Optimization Tools

Combustion diagnostic and optimization tools provide automatic feedback and control of 

parameters that directly affect NOx emissions, such as excess oxygen, temperature, and moisture. 

These tools have the potential to further reduce emissions by optimizing several parameters 

simultaneously, which may not be as easily or effectively accomplished by a human operator. 

SRP has not conducted an evaluation of the potential NOx reductions achievable using 

combustion diagnostic and optimization tools. However, the NGS owners are planning to install 

a combustion diagnostic and optimization software package at NGS in calendar year 2012. 

Although some additional NOx reduction may be achieved using these tools, SRP has not 

quantified the potential additional emission reductions that may be achievable at this time. 

Therefore, no credit is being taken for any potential additional NOx reduction achievable using 

combustion diagnostic and optimization tools in the BART analysis presented in this report. 

SRP will keep EPA informed as additional information becomes available on the performance of 

the diagnostic and optimization tools after installation. 

2.3 SNCR

In the 2009 BART Report, SRP conservatively assumed that a NOx emission rate of 

0.20 lb/MMBtu was achievable by installing and operating SNCR. The visibility modeling, 

which was performed by AECOM on behalf of SRP, was conservatively based on stack 

ammonia emissions of 5 parts per million by volume (ppmv) at 15% oxygen (O2). Although a 

sensitivity analysis was performed to explore the effect of changing stack ammonia emissions, at 

EPA Region 9’s request, all of the sensitivity modeling runs were based on a starting assumption 

of stack ammonia emissions of 5 ppmv. 
3

In the 2009 BART Report, SRP did not propose SNCR as BART because the visibility benefits 

expected to be achievable using SNCR were predicted to be minimal, and in certain Class I 

areas, SNCR was predicted to degrade visibility due to the adverse effect of ammonia slip under 

certain scenarios. 

Since the time of submittal of the 2009 BART Report, SRP has obtained information that 

suggests that SNCR can achieve greater NOx reductions and visibility benefits than were 

estimated in the 2009 analysis. The updated information relates to the potential NOx emission 

rate achievable using SNCR, and the ammonia slip assumptions, as described below. 

• NOx Emission Rate. SRP recently retained Fuel Tech Incorporated (FTI), the largest 

commercial supplier of SNCR, to conduct in-furnace temperature and gas measurements 

in order to more accurately define the potential NOx emission rate achievable by 

installing and operating SNCR at NGS. FTI is currently building a Computational Fluid 

Dynamics (CFD) model to develop a preliminary design for an SNCR system for NGS 

that would maximize NOx removal. This work has not yet been completed, but based on 

the information that FTI has provided to date, SRP used two NOx emission rates for the 

purpose of the cost effectiveness calculations and modeling performed in this report: 

1) 0.15 lb/MMBtu, and 2) 0.18 lb/MMBtu. SRP will keep EPA informed as additional 

information becomes available on the performance of SNCR at NGS. 

• Ammonia Slip. In 2009, EPRI issued a report containing recommended methodologies 

for quantifying ammonia emissions from power plants. In the report, EPRI indicated that 

wet scrubbers drastically reduce the amount of ammonia escaping the stack. EPRI 

expects that as a result of the high solubility of ammonia in water, approximately 99% of 

the gaseous ammonia remaining in the flue gas stream is assumed to be removed in wet 

scrubbers.1 In addition, 25% of the gaseous ammonia is expected to be combined with 

sulfur trioxide (SO3) in the air preheater, resulting in additional removal. Even if it is 

conservatively assumed that no gaseous ammonia is removed in the air preheater by 

combining with SO3, ammonia slip emissions would be negligible at the stack if the NGS 

wet scrubbers achieve 99% control. If the ammonia concentration is 5 ppmv at 6% O2 at 

the boiler exit, ammonia emissions would be 0.26 lb/hr if 99% control is achieved by the 

wet scrubber. In the modeling performed in the 2009 BART Report, an ammonia 

emission rate of 26 lb/hr was modeled in the worst-case scenario. 

In the updated modeling presented in this report, SRP assumed that the 5 ppm ammonia 

slip at the SNCR outlet is substantially reduced by contact with the air preheater and wet 

scrubbing. Although the 2009 EPRI report recommends a 99% control efficiency for wet 

scrubbers, the modeling presented in this report is based on a more conservative control 

efficiency of 90%. 

                                                           

1

  EPRI, Estimating Ammonia Emissions from Stationary Power Plants, Technical Update, Report #1017985, April 2009, 

Pg. A-14 and Table 4-6.
4

2.4 SCR

In previous submittals, including the 2009 BART Report and SRP’s comments on the 

August 2009 ANPR, SRP indicated that a NOx emission rate of at least 0.08 lb/MMBtu is needed 

as a permit limit if the installation and operation of SCR was required as BART for NGS. 

Sufficient margin for compliance is necessary to ensure that a permit limit is achievable on a 

continuous basis. 

Since the visibility modeling performed by SRP in the BART analysis for the other control 

options was based on the permit limits that those controls could achieve, the cost effectiveness 

calculations and modeling presented in this report for the SCR scenarios are based on an 

emission rate of 0.08 lb/MMBtu. 
5

3 Updated Visibility Modeling

3.1 Modeling Approach

The visibility modeling presented in SRP’s 2009 BART Report was based on a modeling 

protocol that EPA accepted in a letter dated July 1, 2008. The updated modeling presented in 

this report is also based on the approved protocol. The only differences are the refinements to 

the NOx and ammonia emissions from SNCR, and the use of the latest version of the CALPUFF 

model, as discussed below. 

SRP retained AECOM to perform the updated modeling presented in this report. The updated 

analysis is based on the following NOx emission rates for SNCR: 1) 0.15 lb/MMBtu, and 

2) 0.18 lb/MMBtu. In addition, SRP assumed that the 5 ppm ammonia slip is substantially 

reduced by contact with the air preheater and wet scrubbing. Although the 2009 EPRI report 

recommends a 99% control efficiency for wet scrubbers, the modeling presented in this report is 

based on a more conservative control efficiency of 90%. All of the other assumptions and inputs 

used in the modeling are the same as those that were used in the modeling presented in SRP’s 

comments on the August 2009 ANPR.

CALPUFF requires background ambient ammonia concentrations as input for visibility 

modeling, rather than stack ammonia emission rates. Therefore, for the SNCR scenarios, a 

separate analysis was conducted for each Class I area to determine the contribution of stack 

ammonia emissions to ambient background conditions. If this concentration exceeded 0.005 ppb 

at any Class I area, that value would be added to the ammonia background value used as input to 

the visibility modeling analysis. If the maximum concentration was less than 0.005 ppb, there 

would be no effect expected from adding this small value to the background concentration. 

To be consistent with previous modeling conducted for NGS, the updated modeling results 

presented in this report were obtained using two versions of the CALPUFF model: 

1) CALPUFF v5.8, which is currently approved for regulatory use. The unadjusted 

background ammonia values used as input are the same as those used in the 2009 BART 

Report. These background ammonia values were adjusted for the SNCR scenarios based 

on the ammonia slip analysis described above. 

2) CALPUFF v6.4, which incorporates updated nitrate chemistry. The unadjusted 

background ammonia values used as input were derived using the EPA’s Community 

Multi-Scale Air Quality (CMAQ) model, consistent with SRP’s February 2010 submittal. 

These background ammonia values were adjusted for the SNCR scenarios based on the 

ammonia slip analysis described above. 
6

3.2 Results

The results obtained in the updated visibility analysis are presented in Tables 1 and 2. The 

model input and output files generated in this analysis are included on a Compact Disk (CD) in 

Appendix A of this report. Consistent with the approved modeling protocol, the results shown in 

the tables represent the visibility improvement predicted by the CALPUFF model for each of the 

different emission control scenarios, in delta dv. Consistent with the approved modeling 

protocol, the tabulated results represent the average of the 8th highest (i.e., 98th percentile) days 

of visibility impairment over the years 2001-2003, relative to natural background conditions. 

In other state BART proceedings, certain commenters have noted that if visibility improvements 

are averaged over a number of Class I areas, the true potential for improvement is 

underestimated, since lower improvements at more distant parks could reduce the average. 

Those same commenters have suggested that instead of looking at average improvement, the 

improvements over each Class I area should be summed. As SRP has stated in previous reports, 

supported by opinions from experts in visibility science, the concept of adding improvements 

over multiple Class I areas has no connection to physical reality, and should not be used as a 

means of evaluating a BART control option. A more appropriate approach would be to consider 

the improvements that can be achieved on average, and then at the most impacted Class I area. 

The tabulated values presented in this report include the improvements at the most impacted 

Class I area, as well as the average over all Class I areas. In Tables 1 and 2, the row labeled 

“Average” is the average improvements over all 11 Class I areas modeled. The row labeled 

“Maximum” is the largest improvement over any of the 11 Class I areas modeled. In Tables 1 

and 2, the ranges associated with the scenarios that involve SNCR reflect the two different 

emission rates that were modeled (0.15 lb/MMBtu and 0.18 lb/MMBtu). For example, the 

average visibility improvement predicted by the model from installing SNCR compared to 

LNB/SOFA ranges from 0.15 dv to 0.25 dv. The 0.15 dv improvement is based on an SNCR 

NOx emission rate of 0.18 lb/MMBtu. The 0.25 dv improvement is based on an SNCR NOx

emission rate of 0.15 lb/MMBtu. 

The visibility modeling results are displayed graphically relative to the capital cost of each 

control option in Figures 1 and 2 below. Figure 1 shows the incremental visibility improvement 

from installing each BART control, relative to the capital cost of each control, which is discussed 

in greater detail in Section 4. The visibility improvements in Figure 1 are based on the average 

improvement over all Class I areas modeled using CALPUFF v5.8. Figure 2 displays the same 

information, but for the Class I area for which the model predicts the maximum visibility 

improvement (Canyonlands National Park). 

Regardless of which model is used, the incremental visibility improvement associated with 

installing LNB/SOFA over the baseline configuration exceeds the incremental improvement 

from installing SNCR over LNB/SOFA, or SCR over SNCR. Given the significantly lower cost 

of LNB/SOFA, as discussed in the following section of this report, this analysis demonstrates 

that LNB/SOFA is the most cost-effective technology for achieving visibility improvement in the 

first regional haze planning period. 
7

Table 1. CALPUFF v5.8 Modeling Results

Baseline to LNB/SOFA LNB/SOFA to SNCR SNCR to SCR

Arches 0.54 0.21 - 0.34 0.25 - 0.37

Bryce Canyon 0.42 0.18 - 0.28 0.19 - 0.29

Canyonlands 0.51 0.29 - 0.47 0.23 - 0.41

Capitol Reef 0.37 0.14 - 0.27 0.31 - 0.44

Grand Canyon 0.27 0.08 - 0.18 0.07 - 0.16

Mazatzal 0.25 0.06 - 0.09 0.03 - 0.07

Mesa Verde 0.38 0.20 - 0.30 0.21 - 0.31

Petrified Forest 0.38 0.15 - 0.24 0.18 - 0.27

Pine Mountain 0.19 0.07 - 0.10 0.06 - 0.09

Sycamore Canyon 0.39 0.11 - 0.17 0.15 - 0.21

Zion 0.37 0.16 - 0.26 0.20 - 0.31

Average 0.37 0.15 - 0.25 0.17 - 0.27

Maximum 0.54 0.29 - 0.47 0.31 - 0.44

Incremental Visibility Benefits (delta dv)

Table 2. CALPUFF v6.4 Modeling Results 

Baseline to LNB/SOFA LNB/SOFA to SNCR SNCR to SCR

Arches NP 0.51 0.14 - 0.18 0.04 to 0.09

Bryce Canyon NP 0.53 0.19 - 0.28 -0.12 - -0.03

Canyonlands NP 0.55 0.15 - 0.24 0.06 - 0.15

Capitol Reef NP 0.93 0.35 - 0.53 0.04 - 0.21

Grand Canyon NP 0.53 0.11 - 0.19 -0.19 - -0.10

Mazatzal W 0.09 0.00 - 0.00 -0.04 - -0.04

Mesa Verde NP 0.33 0.07 - 0.10 -0.02 - 0.01

Petrified Forest NP 0.42 0.08 - 0.10 -0.03 - -0.01

Pine Mountain W 0.02 0.00 - 0.00 -0.04 - -0.04

Sycamore Canyon W 0.18 0.03 - 0.03 0.01 - 0.01

Zion NP 0.44 0.05 - 0.07 -0.09 - -0.07

Average 0.41 0.11 - 0.16 -0.03 - 0.01

Maximum 0.93 0.35 - 0.53 0.06 - 0.21

Incremental Visibility Benefits (delta dv)
8

Figure 1. Cost vs. Visibility Improvement for BART Control Options 

(Based on Average Visibility Improvement over all Class I Areas) 

$45 Million

$84 Million

$589 Million ‐ $1.

0.25 dv

0.17 dv

0

100200300400500600700

Low‐NOx Burners and

SeparatedOverfire Air

(LNB/SOFA)

LNB/SOFA and Selective

Non‐Catalytic Reduction (SNCR)

LNB/SOFA and Se

Catalytic Reducti

Capital Cost ($million)

* Visibility improvement shown is the average over all Class I areas modeled, obtained using CALPUFF v5.8, assuming a NOx emission rate of 0.15 
9

Figure 2. Cost vs. Visibility Improvement for BART Control Options 

(Canyonlands National Park) 

$45 Million

$84 Million

$589 Million ‐ $1.

0.47 dv

0.23 dv

0

100200300400500600700

Low‐NOx Burners and

SeparatedOverfire Air

(LNB/SOFA)

LNB/SOFA and Selective

Non‐Catalytic Reduction (SNCR)

LNB/SOFA and Se

Catalytic Reducti

Capital Cost ($ million)

* Visibility improvements shown were obtained using CALPUFF v5.8, assuming a NOx emission rate of 0.15 lb/MMBtu for SNCR. 
10

4 Updated Costs of Compliance

NGS is a unique generating asset that plays a critical role in the delivery of reliable and 

affordable electricity and water to millions of customers in the Southwest. Depending on which 

NOx control option is selected for this power plant, the costs of compliance associated with more 

stringent BART control options will have substantial economic implications. Since the submittal 

of the 2009 BART Report, SRP has conducted a number of studies to refine the cost estimates 

for each of the BART control options under consideration. This section contains the latest 

information regarding the cost of compliance associated with each BART control option. 

4.1 Relationship of BART Controls to Water Cost and Supply

One of the unique attributes of NGS is its critical role in the delivery of reliable and affordable 

water to customers in central Arizona. Through an arrangement with the United States Bureau of 

Reclamation (BOR) as part owner of the Plant, NGS provides 95% of the power used by the 

Central Arizona Water Conservation District (CAWCD) to pump water through the CAP, which 

delivers water from the Colorado River to central Arizona. 

The importance of NGS in the delivery of water through the CAP cannot be overstated. 

Providing power for CAWCD's delivery of water was one of the primary reasons for 

constructing the plant, and NGS was built as an alternative to two hydroelectric dams that were 

proposed on both ends of the Grand Canyon. The CAP provides a renewable source of water to 

users in central Arizona, which reduces their dependence on groundwater. 

In 1980, Arizona passed the Groundwater Management Act (GMA) to address declining 

groundwater tables in the state. The intent of the GMA, which imposes limits on the quantity of 

groundwater that can be pumped in central Arizona, is to reduce groundwater overdraft with the 

management goal of achieving safe-yield by 2025. Significant increases in the cost of CAP 

water, which could occur if EPA requires SCR or baghouses, could jeopardize the state’s ability 

to achieve the goals outlined in the GMA. 

The BOR also uses proceeds from the sale of NGS power not needed for CAP pumping to fund 

Federal Indian water rights settlements. Those proceeds are currently directed to a fund called 

the Lower Colorado River Basin Development Fund (LCRBDF). The LCRBDF is used to 

subsidize water rates for Arizona Indian Tribes with CAP entitlements, as well as to fulfill other 

commitments made to Arizona Indian Tribes as part of the Arizona Water Settlements Act of 

2004.2

 

Because of the unique connection between NGS, the delivery of affordable water and electricity 

to customers in the Southwest, and the role it plays in Indian water rights settlements, the cost of 

compliance associated with the more expensive BART control option will likely have significant 

adverse economic impacts to many different population segments and groups that depend on the 

                                                           

2

  Public Law 108-451.
11

power produced at NGS. Furthermore, if the plant were to shutdown, which could occur if EPA 

imposes the most stringent control options as BART, the impacts to those same population 

segments and groups would be even more substantial. The shutdown of the plant would also 

adversely affect the Navajo Nation and Hopi Tribe, who receive significant economic benefit 

from the plant through employment, lease fees, coal royalty payments. 

The downstream implications associated with additional control costs are critical and merit 

further consideration in EPA’s BART determination for NGS. To provide EPA with specific 

information regarding the potential economic impacts of each control option, this section 

contains information from several cost and economic studies recently performed for NGS. 

4.2 Economic Studies

The economic impacts of additional controls were assessed in two studies that were recently 

performed for NGS: 

1. An analysis of the broader economic impacts within the state of Arizona associated with 

each of the BART control options, assuming that implementation of BART does not lead 

to plant closure, conducted by Harvey Economics (“Harvey Study”) 

2. An analysis of the value of NGS and the Kayenta Mine to the state of Arizona, conducted 

by Arizona State University’s Seidman Institute (“ASU Study”) 

The Harvey Study assesses the total economic impact of additional controls on different 

population segments and affected groups within the state of Arizona. For this updated BART 

report, the economic impacts are broken down as follows: 

1. Impact on Arizona Indian Tribes with CAP Contract Entitlements. The tribes that 

receive water from the CAP could be impacted in two ways: 1) Tribes would be directly 

responsible for additional CAP energy costs associated with the higher cost of producing 

power at NGS due to additional emission controls; and 2) Tribes could also be affected 

by reduced revenues to the LCRBDF, which funds Indian water rights settlements. 

2. Impact on Arizona Economy. The recovery of costs associated with additional controls 

would fall on all users of CAP water, including non-Indian agricultural users, industry, 

the non-Indian population residing in Central Arizona, as well as the Indian tribes. 

Higher water costs could affect CAP water users by reducing their disposable income and 

potentially the amount of money that they spend on sales of goods and services within 

their local economies. In addition, all customers of the electric utilities that are coowners of NGS would be impacted by higher electric power rates, which would reduce 

their disposable income and the amount of money they spend on sales of goods and 

services within their local economies. 

The ASU study evaluates the economic benefit of NGS, and the Kayenta mine that supplies coal 

to NGS, to the entire state of Arizona. This is particularly important because if costly additional 

controls are required, the NGS owners may not be able to justify the significant capital 
12

expenditure, which could force the closure of NGS. If NGS were to shutdown, the economic 

impacts would be much more significant. The shutdown of NGS would have a devastating 

economic impact on the Navajo Nation and the Hopi Tribes, who receive significant economic 

benefit from the plant through employment, lease fees, and coal royalty payments. 

Both the Harvey Study and ASU Study are still being finalized. In the interest of submitting this 

updated BART report to EPA in a timely manner, preliminary results from those studies are 

presented in this section, since they are critical factors in assessing the cost of compliance. 

Although the results are not final, the conclusions are clear. The imposition of the most stringent 

control option as BART for NGS would have significant adverse economic consequences. SRP 

will submit final versions of both studies to EPA under separate cover as soon as they are 

complete. 

4.3 Updated Control Costs and Economic Impacts

4.3.1 LNB/SOFA

The NGS owners completed the installation of LNB/SOFA on all three units at NGS between 

2009 and 2011. The actual capital cost of installing LNB/SOFA on all three units at NGS was 

approximately $45 million. Annual Operation and Maintenance (O&M) cost associated with 

LNB/SOFA are negligible. Harvey Economics estimates that the costs associated with 

LNB/SOFA will translate to the following impacts: 

• Impact on Arizona Indian Tribes with CAP Contract Entitlements. The five Arizona 

Indian Tribes that substantially depend on affordable CAP water could see increases in 

CAP energy charges and a reduction in funds available to subsidize water rates in the 

LCRBDF. Between 2012 and 2044, this could translate to a total reduction in Gross 

Product of $12 million, including personal income losses of $6 million. 

• Impact on Arizona Economy. The higher costs of water and power, and the losses to the 

LCRBDF, could translate to a total reduction in Gross State Product of $73 million, 

including personal income losses of $27 million, between 2012 and 2044. 

4.3.2 SNCR

SRP is currently working with FTI to develop more accurate estimates for the potential cost of 

installing and operating SNCR at NGS. Based on the most recent cost estimates provided by 

FTI, and estimates of additional costs developed by SRP, the capital cost of installing SNCR on 

all three units at NGS would be approximately $39 million. Annual O&M costs associated with 

SNCR would be approximately $19 million. Harvey Economics estimates that the costs 

associated with SNCR will translate to the following impacts: 

• Impact on Arizona Indian Tribes with CAP Contract Entitlements. The five Arizona 

Indian Tribes that depend on affordable CAP water could see increases in CAP energy 
13

charges and a reduction in funds available to subsidize water rates in the LCRBDF. 

Between 2012 and 2044, this could translate to a total reduction in Gross Product of 

$163 million, including personal income losses of $90 million. 

• Impact on Arizona Economy. The higher costs of water and power, and the losses to the 

LCRBDF, could translate to a total reduction in Gross State Product of $820 million, 

including personal income losses of $310 million, between 2012 and 2044. 

4.3.3 SCR

In 2010, SRP retained S&L to perform a thorough cost study for the purpose of more accurately 

quantifying the potential direct costs associated with installing and operating SCRs at NGS. The 

study was submitted to EPA in August 2010. The study was based on a site-specific assessment 

that took into consideration factors such as the logistics of bringing in the heavy machinery 

needed to construct the SCRs. S&L also evaluated the cost of an EPA requirement to install both 

SCRs and baghouses on each unit. S&L estimated that the capital cost of installing SCR on all 

units would be approximately $544 million. Annual O&M costs associated with SCR would be 

approximately $12 million. Harvey Economics estimates that the costs associated with SCR will 

translate to the following impacts: 

• Impact on Arizona Indian Tribes with CAP Contract Entitlements. The five Arizona 

Indian Tribes that substantially depend on affordable CAP water could see increases in 

CAP energy charges and a reduction in funds available to subsidize water rates in the 

LCRBDF. Between 2012 and 2044, this could translate to a total reduction in Gross 

Product of $264 million, including personal income losses of $145 million. 

• Impact on Arizona Economy. The higher costs of water and power, and the losses to the 

LCRBDF, could translate to a total reduction in Gross State Product of $1.4 billion, 

including personal income losses of $536 million, between 2012 and 2044. 

If baghouses were required in addition to SCR on all three units, S&L estimated that the total 

capital cost would be approximately $1.1 billion. Annual O&M costs associated with SCR and 

baghouses would be approximately $21 million. Harvey Economics estimates that the costs 

associated with SCR and baghouses will translate to the following impacts: 

• Impact on Arizona Indian Tribes with CAP Contract Entitlements. The five Arizona 

Indian Tribes that substantially depend on affordable CAP water could see increases in 

CAP energy charges and a reduction in funds available to subsidize water rates in the 

LCRBDF. Between 2012 and 2044, this could translate to a total reduction Gross 

Product of $504 million, including personal income losses of $277 million. 

• Impact on Arizona Economy. The higher costs of water and power, and the losses to the 

LCRBDF, could translate to a total reduction in Gross State Product of $2.8 billion, 

including personal income losses of $1.0 billion, between 2012 and 2044. 
14

If EPA requires SCR as BART, there is a significant risk that NGS could shutdown, for the 

reasons described in Section 5 of this report. If NGS were to shutdown, this would have a 

significant adverse impact on the Navajo and Hopi Tribes. NGS has over 500 employees, more 

than 80% of whom are Navajo. NGS and the Kayenta Mine, which supplies it with coal, employ 

a total of almost 1,000 people. The plant and the mine provide significant economic benefit to 

the Navajo Nation and the Hopi Tribe through employment, scholarships, lease payments, and 

coal royalties. 

ASU developed an estimate of the value of NGS and the Kayenta mine to the state of Arizona as 

a whole. ASU estimates that NGS and the Kayenta mine will account for over $20 billion in 

Gross State Product between 2011 and 2044, and contribute to over 3,000 jobs each year. 

Clearly, the shutdown of NGS would have devastating economic consequences on the state of 

Arizona as a whole. 

4.4 Cost Comparison

Table 3 below contains a comparison of the direct costs of each control option. Table 4 shows 

the average and incremental cost per ton associated with each control option, as well as the 

estimates for the broader economic impacts associated with each option. 

4.5 Conclusions Regarding Costs of Compliance

It is clear from Tables 3 and 4 that LNB/SOFA is a far more cost effective control option for 

NGS than post-combustion controls. Even without considering the broader economic impacts, 

the cost of SCR exceeds that of LNB/SOFA by more than a factor of 10, and by more than a 

factor of 25 if baghouses were required. 

The broader economic impacts associated with the SCR control option are significantly higher 

than those associated with LNB/SOFA or SNCR. Harvey Economics estimates that if the EPA 

were to require SCR as BART, the reduction in Arizona’s Gross State Product would be more 

than $1.4 billion, and more than $2.8 billion if both SCR and baghouses were required, between 

the years 2012 and 2044. If SCR were required as BART and NGS were to shutdown for the 

reasons described previously, the broader economic impacts would be even more significant. 

Even without considering the broader economic impacts, a comparison of costs in dollars-per-ton 

and dollars-per-deciview shows that LNB/SOFA is the most cost-effective option for improving 

visibility in the first regional haze planning period. When the economic impacts are taken into 

consideration, the costs of compliance associated with SCR far exceed those of LNB/SOFA, and 

should compel EPA to propose a BART emission limit that is based on LNB/SOFA. 
15

Table 3. Cost of NOx Control Options 

BART Control Option Capital Cost Annual O&M Cost Total Annual Cost 

LNB/SOFA $45,000,000 0 $5,214,000 

SNCR $39,200,000 $19,000,000 $23,542,000 

SCR $544,161,000 $11,946,000 $75,015,000 

SCR + Baghouses $1,130,972,000 $20,634,000 $151,714,000 

Table 4. Compliance Cost Summary 

LNB/SOFA SNCR (0.15 lb/MMBtu) SNCR (0.18 lb/MMBtu) SCR 

Cost Metrics

Average Cost ($/ton) $519 $1,251 $1,481 $2,926 Incremental Cost ($/ton) 1 $519 $2,090 $3,135 $5,282 / $7,546 

Incremental Cost - CALPUFF v5.8 ($/dv) 1 $14,000,000 $73,000,000 $122,000,000 $191,000,000 / $303,000,000 

Incremental Cost - CALPUFF v6.4 ($/dv) 1 $13,000,000 $115,000,000 $167,000,000 $5,147,000,000 / < $0 

Impact on Indian Tribes with CAP Water Entitlements

Peak Annual Job Losses Between 2012 and 2044 9 132 Average Annual Job Losses, 2012-2044 4 83 Total Personal Income Loss (2012-2044, 2011 dollars) $6,400,000 $145,100,000 Reduction in Gross Product (2012-2044, 2011 dollars) $11,700,000 $263,900,000 

Impact on Arizona Economy

Peak Annual Job Losses Between 2012 and 2044 30 472 Average Annual Job Losses, 2012-2044 16 316 Total Personal Income Loss (2012-2044, 2011 dollars) $27,100,000 $535,600,000 Reduction in Gross State Product (2012-2044, 2011 dollars) $73,400,000 $1,425,900,000 

$820,000,000

$89,500,000

58

$162,900,000

204

$310,000,000

51

183

1. The incremental cost of the SNCR options are shown relative to the costs of LNB/SOFA. The incremental cost of the SCR op

the costs of both SNCR options (0.18 lb/MMBtu / 0.15 lb/MMBtu). 

2. “Impact on Arizona Economy” includes the effects on Indian tribes, non-Indian agriculture, industry and residents of cities or 

entitlements, as well as power customers in central Arizona. 
16

5 Remaining Useful Life

Despite the economic importance of NGS, the plant faces a number of significant challenges that 

threaten its future viability. Those challenges include, but are not limited to, the following: 

• The plant site lease and several other critical agreements that are required for NGS to 

continue to operate begin to expire in 2019. The extension of the plant site lease will 

trigger a review under the National Environmental Policy Act (NEPA), which could 

require the preparation of an Environmental Impact Statement (EIS). The development 

of an EIS could take several years to complete, and the outcome of that assessment is 

uncertain. 

• NGS is co-owned by six participants: The United States Bureau of Reclamation (24.3%), 

Salt River Project (21.7%), Los Angeles Department of Water and Power (21.2%), 

Arizona Public Service (14%), NV Energy (11.3%), and Tucson Electric Power (7.5%). 

As a result of the recent emphasis on reducing greenhouse gas emissions and increasing 

utility renewable portfolio standards, several of the participants are uncertain about their 

continued ownership of coal-fired generating facilities. In the case of LADWP, for 

example, there is a California law that could prohibit the company from making 

investments that will extend the life of coal-fired facilities. 

• Future ownership uncertainty creates a substantial challenge because any significant 

capital investment, such as the investment that would be necessary if additional emission 

controls are required, must be unanimously approved by all six participants. If any of the 

current owners decides not to continue to participate, another buyer would need to be 

found, or the remaining participants would need to absorb the additional costs, in order to 

keep the plant operating. 

• The NGS participants are currently renegotiating the coal supply contract with Peabody 

Energy, and the terms of the plant site lease agreement with the Navajo Nation. 

Assuming that they can be successfully extended, the renegotiated agreements will result 

in higher future operating costs for the NGS participants, which could change the 

economics of NGS compared to other resource alternatives. 

If the EPA requires costly additional emission controls such as SCR as BART, the NGS 

participants would be forced to decide whether to make large capital investments without any 

certainty that the plant could continue to operate beyond 2019, and without certainty regarding 

the future costs of operating NGS due to the potentially higher lease and coal costs. This could 

put the plant at a significant risk of closure, which could have devastating economic 

consequences, as described in the previous section of this report. 

The report provides the information above because the NGS participants are concerned that EPA 

may not be giving sufficient weight to the possibility of plant closure. If EPA proposes a 

BART emission limit for NGS that requires SCR, there is a significant risk that the plant

could shutdown.
17

6 Updated Five Factor Analysis and BART Proposal

6.1 Factor 1:  Cost of Compliance

The information presented in this report clearly demonstrates that LNB/SOFA is the most costeffective BART control option. The cost of SCR exceeds that of LNB/SOFA by more than a 

factor of 10, and by more than a factor of 25 if baghouses are required. LNB/SOFA achieves the 

most incremental visibility improvement of any of the control options under consideration, at the 

lowest cost. 

This conclusion is further reinforced by the analysis of the broader economic impacts that could 

occur if additional controls are required at NGS. Harvey Economics estimates that if the EPA 

were to require SCR as BART, the reduction in Arizona’s Gross State Product would be more 

than $1.4 billion, and more than $2.8 billion if both SCR and baghouses were required, between 

the years 2012 and 2044. 

If EPA requires SCR as BART, there is a significant risk that NGS could be forced to close, for 

the reasons discussed in Section 5 of this report. The broader economic impacts associated with 

the shutdown of NGS would be even more significant. The closure of NGS would represent the 

loss of a vital resource to the economies of the Navajo and Hopi Tribes. ASU estimated that 

NGS and the Kayenta mine will account for over $20 billion in Gross State Product between 

2011 and 2044, and contribute to over 3,000 jobs each year. 

An analysis of the costs of each control option, the potential visibility benefits that can be 

achieved, and the broader economic implications, clearly points to LNB/SOFA as the most costeffective approach for improving visibility in the first regional haze planning period. 

6.2 Factor 2:  Energy and Non­Air Quality Impacts

LNB/SOFA and SNCR do not have any significant adverse energy or non-air quality 

environmental consequences. SCR consumes significantly more energy, and introduces several 

significant non-air quality environmental problems, including most notably: 1) an increase in 

cost of water to customers that rely on the CAP; 2) reduced revenues to the LCRBDF, which 

funds Indian water rights settlements; 3) the loss of access to renewable surface water and 

increased dependence on groundwater; and, as identified in the 2009 BART Report 4) the risk 

associated with the transportation and storage of anhydrous ammonia that would be needed by 

SCR. 
18

6.3 Factor 3:  Existing Controls at the Facility

LNB/SOFA was installed on all three units at NGS between 2009 and 2011. By installing 

LNB/SOFA early, total NOx reductions achieved in the first regional haze planning period will 

far exceed the reductions that would be required by even the most stringent EPA BART 

determination (SCR on all three units), as shown in Figure 3. In addition, LNB/SOFA would 

achieve an emission rate that is well below the presumptive BART limit of 0.28 lb/MMBtu 

established by EPA for this source category. 

Figure 3. Comparison of NOx Reductions in the First Regional Haze Planning Period 

0

20,000

40,000

60,000

80,000

100,000

120,000

2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019

NOx Emission Reductions(tons)

NOx Reductions from LNB/SOFA NOx Reductions if BART = SCR

Cumulative NOx Reductionsfrom LNB/SOFA

Cumulative NOx Reductionsif EPA BART = SCR

LNB/SOFA

onUnit 3

LNB/SOFA

onUnit 2

LNB/SOFA

onUnit 1

SCR on

Unit1

SCR on

Unit2

SCRon

Unit3

6.4 Factor 4:  Remaining Useful Life of Facility

As discussed in Section 5 of this report, the NGS participants are currently in the process of 

extending the plant site lease and other critical agreements that are necessary to ensure continued 

operation of NGS beyond 2019. The NGS participants are also working to extend the coal 

supply contract, which will result in higher future operating costs. If the EPA imposes 

requirements to install costly additional emission controls such as SCR as BART, the NGS 

participants would be forced to decide whether to make large capital investments without any 

certainty that the plant could continue to operate beyond 2019, and without certainty regarding 

the future costs of operating NGS due to the potentially higher lease and coal costs. This could 

put the plant at a significant risk of closure, which could have devastating economic 

consequences. 
19

LNB/SOFA achieves progress towards national visibility goals in the first planning period, while 

allowing the NGS participants time to secure the agreements necessary to ensure the continued 

operation of this valuable generating asset. 

6.5 Factor 5:  Degree of Visibility Improvement

As discussed in detail in Section 3 of this report, regardless of which version of the CALPUFF 

model is used, the incremental visibility improvement associated with installing LNB/SOFA 

over the baseline configuration exceeds the incremental improvement from installing SNCR over 

LNB/SOFA, or SCR over SNCR. Given the significantly lower cost of LNB/SOFA, this 

analysis demonstrates that LNB/SOFA is the most cost-effective BART control option for NGS. 

6.6 Conclusion:  BART Proposal

Based on an updated evaluation of the five statutory factors considering the latest information 

presented in this report, SRP is proposing that a NOx emission rate of 0.24 lb/MMBtu, 

achievable by installing and operating LNB/SOFA on all three units, is BART for NGS. While 

this conclusion has not changed since the 2009 BART report, SRP has gathered significant 

additional information to support that conclusion. In summary, SRP’s proposal is based on the 

following considerations: 

• LNB/SOFA achieves an emission rate that is well below the presumptive BART limit of 

0.28 lb/MMBtu established by EPA for the type of boilers at NGS. 

• LNB/SOFA achieves greater incremental visibility improvement than post-combustion 

controls, at a fraction of the cost. The cost of Selective Catalytic Reduction (SCR), the 

most expensive control option, exceeds that of LNB/SOFA by more than a factor of 10, 

and by more than a factor of 25 if baghouses are also required. 

• The NGS owners voluntarily installed LNB/SOFA on all three units between 2009 and 

2011. By installing LNB/SOFA early, total NOx reductions achieved in the first regional 

haze planning period will exceed the reductions that would be required by even the most 

stringent EPA BART determination, as shown in Figure 3. 

• The results obtained using the EPA’s CALPUFF model (Version 5.8) indicate that the 

incremental visibility improvement from installing SCR relative to LNB/SOFA is well 

below 1 deciview (dv) at all Class I areas. 1 dv is the level that EPA has indicated is a 

“small but noticeable change in haziness.” 

• The results obtained using the latest version of CALPUFF (Version 6.4), which is based 

on the best available science, indicate that the incremental visibility improvement from 

installing SCR relative to LNB/SOFA is significantly less than the improvement 

predicted by CALPUFF v5.8. In certain Class I areas, visibility is predicted to degrade 

due to the increase in sulfates that are produced by SCR. 
20

• Regardless of which version of the CALPUFF model is used, the results indicate that 

LNB/SOFA achieves greater incremental visibility improvement than Selective NonCatalytic Reduction (SNCR) or SCR, and at a significantly lower capital cost. This 

conclusion is illustrated graphically in Figures 1 and 2. 

• If EPA requires SCR as BART, there is a significant risk that NGS could shutdown, 

which would result in the loss of a vital resource to the economies of the Navajo and 

Hopi Tribes. NGS has over 500 employees, more than 80% of whom are Navajo. NGS 

and the Kayenta Mine, which supplies it with coal, employ a total of almost 1,000 people. 

The plant and the mine provide significant economic benefit to the Navajo Nation and the 

Hopi Tribe through employment, scholarships, lease payments, and coal royalties. All of 

those benefits would be lost if NGS and the mine were to shutdown. 

• The shutdown of NGS would also have devastating economic consequences on the state 

of Arizona as a whole. In a recent study, Arizona State University’s Seidman Institute 

evaluated the economic contribution of NGS and the Kayenta Mine to the Arizona 

economy. ASU estimates that NGS and the Kayenta Mine will account for over 

$20 billion in Gross State Product between 2011 and 2044, and contribute to over 

3,000 jobs each year.

In light of the above considerations, SRP respectfully urges EPA to propose a NOx BART 

emission limit for NGS that is based on LNB/SOFA. The analysis presented in this report, 

which is based on a review of the five BART statutory factors, demonstrates that LNB/SOFA is 

the most cost-effective BART control option for NGS, and a BART proposal that is based on this 

technology would not introduce the risk of broader adverse economic consequences.
Attachment A. Modeling Files