COMMENTS ON 

PROPOSED REGIONAL 

HAZE RULE 

EPA’S PROPOSED RULE RELATED TO APPROVAL, 

DISAPPROVAL AND PROMULGATION OF AIR 

QUALITY IMPLEMENTATION PLANS; ARIZONA; 

REGIONAL HAZE STATE AND FEDERAL 

IMPLEMENTATION PLANS 

DOCKET ID NO: EPA-R09-OAR-2012-0021 

FRL-9700-1 

PREPARED BY: 

SALT RIVER PROJECT 

P. O. B OX 5 2 0 2 5 

MAIL STATION 352 

PHOENIX, ARIZONA 85072 

SEPTEMBER 2012 
SRP Comments on Proposed Regional Haze Rule Page i

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

Table of Contents

1.0 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  1‐1

2.0 Fundamental Issues with EPA’s Overall Approach. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2‐1

3.0 EPA’s Proposed Rule Fails to Give Adequate Deference to Arizona. . . . . . . . . . . . . . . . . . . . . . .  3‐1

3.1 EPA Must Defer to the BART Determinations Made by Arizona. . . . . . . . . . . . . . . . . . . . .  3‐1

3.2 Arizona’s BART Determinations are Fully Consistent with the Requirements  

of the CAA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  3‐3

3.3 EPA Must Take Action on Arizona’s SIP Proposal as a Whole. . . . . . . . . . . . . . . . . . . . . . .  3‐4

3.4 EPA Cannot Propose or Finalize a NOx BART FIP for CGS Until it has Taken Final  

Action on Arizona’s Regional Haze SIP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  3‐5

4.0 EPA Improperly Ignored the CGS Consent Decree and Presumptive BART Limits in its  

Selection of Recommended BART Controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  4‐1

4.1 CGS Consent Decree Controls are Better Than BART. . . . . . . . . . . . . . . . . . . . . . . . . . . . .   4‐1

4.2 EPA Must Consider Presumptive BART Limits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   4‐3

5.0 EPA’s Control Technology Evaluations are Not Consistent with BART Guidelines. . . . . . . . . . .   5‐1

5.1 EPA’s Proposed NOx Emission Rates Associated with Post Combustion Controls  

are Not Achievable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  5‐1

5.1.1 EPA’s Proposed SCR NOx Emission Limit of 0.050 lb/MMBtu is  

Unachievable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  5‐1

5.1.2 SNCR NOx Emission Rate Evaluated by EPA is Incorrect. . . . . . . . . . . . . . . . . . .   5‐6

5.2 EPA’s Selected Baseline Emissions Period Eliminated Consideration of LNB/OFA  

as a Viable BART Control Strategy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5‐7

6.0 EPA’s Cost of Compliance Analysis is Flawed and Must be Replaced with  

Site‐Specific Costs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   6‐1

6.1 EPA Improperly Ignored Site‐Specific Cost Estimates for CGS BART Control Options . . .  6‐1

6.2 EPA Inappropriately Relied on Flawed Data from the Control Cost Manual and IPM. . . . 6‐4

6.3 SRP’s Adjusted Inputs to EPA’s IPM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6‐5

6.3.1 Unit Size. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6‐5

6.3.2 Gross Heat Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6‐6

6.3.3 NOx Removal Factor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6‐6

6.3.4 NOx Removal Efficiency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6‐6

6.3.5 Ammonia Cost. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6‐7

6.3.6 Operating Labor Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6‐7

6.3.7 Base Module Costs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6‐7
SRP Comments on Proposed Regional Haze Rule Page ii

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

6.3.8 Urea Costs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6‐7

6.3.9 Property Taxes and Insurance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6‐8

6.4 SRP’s Adjusted IPM Results Still Underestimate Post Combustion Control Costs. . . . . . .  6‐8

6.4.1 Detailed SCR Cost Comparison. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6‐9

6.4.2 Detailed SNCR Cost Comparison. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6‐11

6.4.3 EPA’s Reliance on Generic Modeled Costs is Inappropriate and  

Significantly Lower Than SRP’s Site‐Specific Costs. . . . . . . . . . . . . . . . . . . . . . . 6‐13

6.5 EPA Must Consider the Incremental Costs Between the Control Options. . . . . . . . . . . . 6‐15

6.6 EPA Must Consider Costs as They Relate to Visibility Improvement. . . . . . . . . . . . . . . . . 6‐15

7.0 EPA’s Proposed NOx BART Determination Rests on a Flawed Assessment of  

Visibility Impacts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  7‐1

7.1 EPA’s Modeling Choices Overestimate the Visibility Benefits Associated with BART  

Control Options. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  7‐1

7.1.1 EPA’s Use of Outdated CALPUFF Model Chemistry Over‐Predicts  

Visibility Benefits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  7‐1

7.1.2 EPA Use of Constant Ammonia Background Concentration Over‐Predicts

Visibility Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7‐3

7.2 Case Study: Mohave Generating Station Plant Closure. . . . . . . . . . . . . . . . . . . . . . . . . . . . 7‐5

7.3 EPA Must Consider Visibility Benefits from NOx Controls within the Context of  

Nitrate Contributions to Regional Haze. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7‐6

7.4 EPA Improperly Dismisses Arizona’s Visibility Impacts Analysis. . . . . . . . . . . . . . . . . . . . . .7‐8

7.5 EPA’s 0.5 Deciview Threshold is Without Basis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7‐12

8.0 EPA Must Properly Account for Energy and Non‐Air Quality Environmental Impacts. . . . . . . .  8‐1

9.0 Full Approval of Arizona’s BART Determinations is the Only Appropriate Course of  

Action Available to EPA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9‐1

9.1 EPA Must Accept Arizona’s BART Determination for NOx. . . . . . . . . . . . . . . . . . . . . . . . . .  9‐1

9.2 EPA’s BART Determination for PM is Reasonable and Appropriate . . . . . . . . . . . . . . . . . . 9‐3

9.3 EPA’s BART Determination for SO2 is Reasonable and Appropriate . . . . . . . . . . . . . . . . . .9‐5  

10.0 SRP’s Review of EPA’s Proposed Enforceability Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . 10‐1

10.1 EPA Must Implement an Appropriate Compliance Schedule. . . . . . . . . . . . . . . . . . . . . . .10‐1

10.2 EPA Must Modify the Monitoring Requirements to be Consistent with Existing

Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10‐2

10.2.1 Use of 40 CFR Part 75 for SO2 and NOx. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10‐2

10.2.2 Proposed Additional Relative Accuracy Requirements. . . . . . . . . . . . . . . . . . . 10‐3

10.2.3 Proposed CEMS Data Availability Requirements. . . . . . . . . . . . . . . . . . . . . . . .  10‐6

10.2.4 Use of Methods 201A and 202 for Determining PM Emissions. . . . . . . . . . . . .10‐7
SRP Comments on Proposed Regional Haze Rule Page iii

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

10.3 EPA Must Modify the Quarterly Reporting Requirements to be Consistent with  

Existing Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10‐9

10.4 EPA Must Modify the Notification Requirements within the Proposed Rule. . . . . . . . . 10‐10

11.0 EPA’s Assertion of Health Benefits is Unsubstantiated by the Proposed Rule. . . . . . . . . . . . . . 11‐1

12.0 Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12‐1

List of Tables

5‐1   30‐Day Rolling Average NOx Emissions Including Unit Startups and Low‐Load Cycling. . . . . . . . .  5‐4

6‐1   IPM Version 4.10 Cost Estimate Outputs for SCR Costs for CGS Unit 1. . . . . . . . . . . . . . . . . . . . . .  6‐9

6‐2 IPM Version 4.10 Cost Estimate Outputs for SCR Costs for CGS Unit 2. . . . . . . . . . . . . . . . . . . . .  6‐10

6‐3   IPM Version 4.10 Cost Estimate Outputs for SNCR Costs for CGS. . . . . . . . . . . . . . . . . . . . . . . . . .6‐12

9‐1   Cost and Visibility Analysis for NOx Emissions from CGS Units 1 and 2 Using  

CALPUFF Version 5.8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9‐2

9‐2   Cost and Visibility Analysis for NOx Emissions from CGS Units 1 and 2 Using  

CALPUFF Version 6.42. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9‐4

List of Figures

5‐1   Actual Emission Trends for CGS Units 1 and 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5‐8

6‐1   Comparison of IPM Cost Estimates to Site‐Specific Cost Estimates for CGS. . . . . . . . . . . . . . . . . .6‐14

7‐1   Sources of Light Extinction Over the Grand Canyon National Park. . . . . . . . . . . . . . . . . . . . . . . . . .7‐7

List of Attachments

A RMB Consulting & Research Inc. – Technical Memorandum: Achievability of the Proposed FIP NOx

Limits for Coronado Generating Station

B Letter to Deborah Jordan, EPA Region IX, from Jim Pratt, SRP, Regarding SRP Response to EPA

Letter, Dated July 27, 2012

C   Sargent & Lundy LLC – SNCR Capital Cost Estimate Report for Salt River Project Coronado

Generating Station – Unit 1

D   Letter to Robert Olsen, SRP, from Douglas Kirk, FuelTech, Regarding Salt River Project Coronado

Generating Station SNCR NOx Control Performance, NOx OUT® and HERTTM SNCR System, Dated

September 12, 2012

E   AECOM – Visibility Improvement Modeling for the Coronado Generating Station

F   Gradient – Comments on Health Benefits from the Proposed Arizona Regional Haze Rule for the

Coronado Generating Station
SRP Comments on Proposed Regional Haze Rule Page iv

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

List of Abbreviations

$/ton     dollars per ton

$/dv    dollars per deciview

ACFM     actual cubic feet per minute

ADEQ      Arizona Department of Environmental Quality

BACT     best available control technology   

BART    best available retrofit technology

Btu/kW‐hr   British thermal units per kilowatt‐hour

CAA     Clean Air Act

CAMD    Clean Air Markets Division

CEMS     continuous emissions monitoring system

CFR     Code of Federal Regulations

CGS    Coronado Generating Station

CO2    carbon dioxide

CSAPR     Cross‐State Air Pollution Rule

dv     deciview

EPA     U.S. Environmental Protection Agency

ESP     electrostatic precipitator

FIP     federal implementation plan

FGD     flue gas desulfurization

fps     feet per second

GCNP     Grand Canyon National Park

GCVTC    Grand Canyon Visibility Transport Commission

IMPROVE   Interagency Monitoring of Protected Visual Environments

IPM     Integrated Planning Model

IWAQM   Interagency Workgroup on Air Quality Modeling

kW     kilowatt

lb/MMBtu   pound per million British thermal units

lb/MWh   pound per megawatt‐hour

LNB     low‐NOx burner

MATS     Mercury Air Toxics Standards

MGS     Mohave Generating Station

MOHAVE   Measurement of Haze and Visual Effects

MPP     Mohave Power Project

MW     megawatt

MWG      gross megawatt

NEEDS     National Electric Energy Database System

NGS     Navajo Generating Station

NOx    nitrogen oxides
SRP Comments on Proposed Regional Haze Rule Page v

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

NREL     National Renewable Environmental Laboratory

NSPS     New Source Performance Standards

NSR     New Source Review

O2     oxygen

O&M     operations and maintenance

OFA     overfire air

PM     particulate matter

PM10     particulate matter nominally less than 10 microns

ppb     parts per billion

ppm     parts per million

PSD     Prevention of Significant Deterioration

QA     quality assurance

RA     relative accuracy

RATA     relative accuracy test audit

RMB     RMB Consulting and Research, Inc.

S&L     Sargent & Lundy LLC

SCR     selective catalytic reduction

SIP    state implementation plan

SNCR     selective non‐catalytic reduction

SO2     sulfur dioxide

SRP    Salt River Project Agricultural Improvement and Power District

SUSD     startup and shutdown

TSD     technical support document

U1     Unit 1

U2     Unit 2

WRAP     Western Regional Air Partnership

yr     year
SRP Comments on Proposed Regional Haze Rule Page 1‐1

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

1.0 Introduction  

Section 169A of the Clean Air Act (CAA) provides for a visibility protection program and sets forth as a

national goal “the prevention of any future, and the remedying of any existing, impairment of visibility in

mandatory class I Federal areas [in] which impairment results from man‐made air pollution.”  Congress

subsequently addressed regional haze in the 1990 amendments to the CAA through the addition of

Section 169B.  In compliance with that statutory requirement, the United States Environmental

Protection Agency (EPA) published final regulations to address regional haze on July 1, 1999.1

  Under

these regulations, states are required to set periodic goals for improving visibility in Class I areas.  As

states work to reach these goals, they must develop regional haze implementation plans that include

enforceable measures and strategies for reducing visibility‐impairing pollution.

On February 28, 2011, the Arizona Department of Environmental Quality (ADEQ) submitted a

comprehensive State Implementation Plan (SIP) to address regional haze issues related to emissions

from sources located within Arizona.  This plan established reasonable progress goals for the first

planning period of the regional haze program, which ends on July 31, 2018.  One component of the

comprehensive plan is the assessment and determination of “best available retrofit technology” (BART)

for eligible stationary sources, resulting in enforceable emission limitations for certain visibility impairing

pollutants.  

BART determinations must rest on consideration of the five statutory BART factors and application of

EPA’s BART Guidelines, promulgated in 2005 and incorporated in the Code of Federal Regulations (CFR)

as Appendix Y to Title 40, Part 51.2

  The CAA and EPA’s BART Guidelines assign the task of evaluating and

weighing the BART consideration factors to the states, and states have considerable leeway in deciding

how to assess and weigh the information they develop in the course of a BART analysis.

Arizona based its SIP on a reasonable and well‐documented analysis of each of the BART factors – (1) the

costs of compliance, (2) the energy and non‐air quality environmental impacts of compliance, (3) any

existing pollution control technology in use at the source, (4) the remaining useful life of the source, and

(5) the degree of improvement in visibility that may reasonably be anticipated to result from the use of

such technology – and EPA may not simply ignore that analysis because it would have preferred a

different outcome.

                                                           

1 See 64 Fed. Reg. 35,714 (July 1, 1999).  The 1999 rules were challenged in the U.S. Court of Appeals for the

District of Columbia Circuit, and, on May 24, 2002, those rules were vacated in part and sustained in part.  EPA

responded to the court’s ruling by promulgating new regulations on July 6, 2005.  70 Fed. Reg. 39,104 (July 6,

2005).

2 See 70 Fed. Reg. 39,104 (July 6, 2005).  Use of the BART Guidelines is mandatory only for power plants exceeding

750 megawatts.  States are “encouraged” to follow the Guidelines for other types of sources.  Id. at 39,108.
SRP Comments on Proposed Regional Haze Rule Page 1‐2

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

However, on July 20, 2012, EPA published a proposed rule that would partially approve and partially

disapprove the State of Arizona’s SIP, but only as it relates to the BART determinations for three electric

generating facilities, including the Coronado Generating Station (CGS), a two‐unit, coal‐fired facility

owned and operated by Salt River Project Agricultural Improvement and Water District (SRP).3

With respect to CGS, EPA proposes to approve Arizona’s BART determinations for the facility’s emissions

of sulfur dioxide (SO2) and particulate matter (PM) and to disapprove the state’s BART determinations

for nitrogen oxides (NOx) for each of the CGS units.  EPA also proposes a Federal Implementation Plan

(FIP) to take the place of Arizona’s SIP with respect to BART for NOx.  That FIP would impose a NOx BART

limit for CGS Unit 1 of 0.050 pounds per million British thermal units (lb/MMBtu), based on installation

and operation of low‐NOx burners (LNB) and overfire air (OFA) along with selective catalytic reduction

(SCR) emission control technology, and a NOx BART limit for CGS Unit 2 of 0.080 lb/MMBtu, based on

installation and operation of LNB/OFA and SCR, consistent with existing CGS consent decree

obligations.4

These comments detail SRP’s concerns regarding EPA’s FIP proposal.  SRP believes the proposed rule is

legally flawed and technically unsupported by the record EPA has provided in conjunction with

publication of the rule.  In the following sections of this document, SRP provides evidence in support of

SRP’s continuing belief that Arizona’s regional haze SIP must be considered as a whole, and must be fully

approved by EPA.

                                                           

3 See 77 Fed. Reg. 42,834 (July 20, 2012).  The other affected facilities are the Apache Generating Station and the

Cholla Power Plant.

4 Each of these limits is based on a 30‐day rolling average including periods of startup, shutdown, and malfunction.  

In the proposed rule, EPA proposes that the NOx limit for Unit 1 be applicable no later than five years following the

effective date of the rule.  For Unit 2, the effective date is proposed as June 1, 2014, consistent with current

consent decree obligations.
SRP Comments on Proposed Regional Haze Rule   Page 2‐1

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

2.0   Fundamental Issues with EPA’s Overall Approach

SRP has several significant concerns with the proposed rule’s implementation of regional haze

requirements in Arizona, as summarized below:

 The consent decree entered into by SRP and EPA just four years ago, and currently being

implemented by SRP, was designed to settle an EPA allegation that emissions from CGS Units 1

and 2 failed to comply with the CAA’s “best available control technology” (BACT) requirements,

a component of the “prevention of significant deterioration” (PSD) requirements of the CAA that

is applicable to certain new or modified sources.  That agreement requires SRP to install and

operate LNB/OFA on both units, as well as an SCR system on Unit 2.  It also establishes a NOx

emission limit of 0.320 lb/MMBtu for Unit 1, a NOx emission limit of 0.080 lb/MMBtu for Unit 2,

and a plant‐wide NOx emission limit of 7,300 tons per year.  EPA’s BART Guidelines provide that

emission limits imposed pursuant to a PSD‐related consent decree, such as the consent decree

applicable to CGS, should be deemed to satisfy BART.  EPA should follow its own guidelines and

consider the weight of evidence presented in these comments, and as a result, acknowledge

that the consent decree limits not only satisfy all BART obligations for CGS Units 1 and 2, but

provide a level of control that is better than BART.  

 ADEQ determined that NOx BART for CGS Units 1 and 2 was LNB/OFA and an emission limit of

0.320 lb/MMBtu.  Under the CAA, the state’s BART determination is entitled to deference.5

  EPA

is not free to second‐guess the state’s determinations.

 EPA’s proposed NOx BART determination for CGS fails to take the presumptive BART limits into

account.  Soon‐to‐be‐installed controls at CGS Unit 2, which will result in a 0.080 lb/MMBtu NOx

emission limit for that unit, are far more stringent than the presumptive NOx limit applicable to

CGS.  Indeed, EPA in this proposed rule fails even to mention, much less evaluate, the type of

emission controls (i.e., combustion controls) on which the presumptive limit is based.  EPA is not

free to disregard its own presumptive BART limit and its rulemaking determination that, for all

units except cyclone units (which are not present at CGS), NOx BART is presumed to be based on

combustion controls only and excludes post‐combustion controls such as SCR.

 EPA’s decision to propose a NOx emission limit of 0.050 lb/MMBtu for SCR is unsupported.  

Indeed, the fact that SRP is installing SCR on CGS Unit 2 and is required to maintain compliance

with a 0.080 lb/MMBtu emission limit for that unit pursuant to a BACT‐related consent decree

confirms that a limit of 0.050 lb/MMBtu is unrealistic and unachievable on a continuous basis.

                                                           

5 Am. Corn Growers Ass’n v. EPA, 291 F.3d at 1 (D.C. Cir. 2002).
SRP Comments on Proposed Regional Haze Rule   Page 2‐2

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

 EPA argues that the emission control costs relied on by Arizona and those prepared by SRP were

not calculated in accordance with the BART Guidelines and that they are inconsistent with EPA’s

Control Cost Manual.  The Control Cost Manual is not binding and is recognized as only one

reference source for cost information by EPA’s BART rules.  Moreover, the D.C. Circuit held in

Corn Growers6 that site‐specific costs must be taken into account.  Furthermore, SRP has

completed installation of LNB/OFA on both units at CGS and has made significant progress

towards completing the installation of SCR on Unit 2 at CGS, and the actual costs incurred are

much higher than the costs used by EPA in its proposed BART determination.

 EPA’s own calculation of costs in support of its FIP is seriously flawed.  EPA’s cost assessment

relies on an Integrated Planning Model (IPM) base case for capital and annual operating costs

for each NOx control option.  BART requires a site‐specific analysis.  Use of IPM’s generic

information does not satisfy this requirement.  Regardless, the data inputs EPA selected in

implementing IPM are incorrect given the site‐specific characteristics of CGS.  This error by EPA

resulted in a significant underestimate of the NOx control costs used in EPA’s analysis.

 EPA argues that visibility impacts were not appropriately evaluated and considered in the SIP.  

Further, EPA claims that visibility benefits at all potentially impacted Class I areas must be

considered.  EPA’s BART Guidelines do not require that cumulative visibility impacts be used as

the basis for BART assessments and does not require that they be considered at all.  ADEQ’s

evaluation of visibility impacts is a valid alternate approach to the consideration of visibility

benefits associated with control options, and Arizona’s reliance on that analysis is within the

state’s discretion.

 EPA’s refusal to allow use of the most recent and most accurate CALPUFF model (version 6.42) is

unreasonable and arbitrary, and contradicts the principle that BART determinations should be

based on the best available science.  Use of CALPUFF version 6.42 demonstrates that the

visibility benefits EPA projects are overstated.

 SRP’s modeling of CGS’ visibility impacts relies on more appropriate monthly‐varying

background ammonia concentrations in the ambient air and is more realistic than EPA’s reliance

on an artificial, uniform “default” value.  ADEQ acted within its discretion by relying on the same

background ammonia concentrations.

In summary, EPA’s proposed rule is seriously flawed and cannot, at least with respect to NOx BART for

CGS, be finalized.  The proposal is unlawful because EPA has failed to give the level of deference to the

State of Arizona’s BART determinations that the CAA requires.  EPA has presented no legitimate grounds

for disapproving any part of Arizona’s SIP, and EPA cannot, therefore, promulgate its own NOx BART

                                                           

6 Id.
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EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

determinations for CGS.  Further, EPA’s proposed FIP and the analysis EPA relies on to support that FIP

are inconsistent with the CAA and EPA’s own regional haze regulations.  Accordingly, the proposed FIP

does not reflect a proper NOx BART determination for CGS, and EPA must withdraw it.  Full approval of

Arizona’s SIP is the only course of action that is consistent with the law and available to EPA.
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3.0   EPA’s Proposed Rule Fails to Give Adequate Deference to Arizona

Arizona’s regional haze SIP, and not EPA’s proposed FIP, is consistent with the CAA and must be fully

approved.  Arizona’s determinations, including its BART determinations for CGS, reflect a proper

consideration and weighing of the BART factors and the state’s conclusions are, thus, factually correct.  

Arizona’s determinations, moreover, are entitled to an exceptionally high level of deference under the

CAA.  EPA has ignored its obligation to defer to the state’s determinations, and for that reason alone,

the proposed rule is unlawful.  In addition, EPA’s proposed rule does not provide Arizona and affected

parties, including SRP, with the procedural safeguards to which the state is entitled under the CAA.  

Accordingly, for the reasons described below, EPA should withdraw the proposed rule.

3.1 EPA Must Defer to the BART Determinations Made by Arizona

As stated by the U.S. Court of Appeals for the District of Columbia Circuit in Corn Growers, the states,

not EPA, “play the lead role in designing and implementing [the] regional haze programs” of the CAA

and have “broad authority over BART determinations.”7

  The D.C. Circuit has recently confirmed this

principle, in litigation resulting in the invalidation of EPA’s Cross‐State Air Pollution Rule (CSAPR), stating

that the CAA establishes a strict “federalism bar” that “prohibits EPA from using the SIP process to force

States to adopt specific control measures.”8

   

EPA is required to defer to a state’s BART determinations where the state has considered the five

statutory BART factors.  The state is empowered to determine how best to weigh each factor, and once

the state has made its decision, EPA has no authority to second‐guess the conclusions the state has

reached, as is the case here.  In this proposed rule, EPA simply ignores the deference due to Arizona and

proposes to disapprove the state’s determinations and impose its own preferred NOx emission limit for

CGS simply because EPA happens to “disagree” with the state’s conclusions.9

   

For instance, EPA “disagree[s]” with the manner in which ADEQ evaluated costs and visibility impacts for

the various emission control options considered at CGS.10  EPA admits that ADEQ “developed

information regarding each of the five [BART] factors,” acknowledging that the state complied with its

obligation under the CAA.11  Nevertheless, because EPA has weighed the factors differently than the

state and has chosen to focus on different analyses, EPA proposes disapproval of the state’s NOx

emission limit determinations.  EPA does this despite recognizing correctly that “[a] state plan need not

                                                           

7 See Corn Growers, 291 F.3d at 2, 8.

8 See EME Homer City Generation, L.P. v. EPA, No. 11‐1302, slip op. at 42 (D.C. Cir. Aug. 21, 2012).

9 See 77 Fed. Reg. at 42,851.

10 Id.

11 Id.
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contain exactly the same provisions that EPA might require” and that EPA’s job is simply to “find that the

state plan is consistent with the requirements of the Act.”12   

For purposes of the regional haze program, all that is required for a SIP to be consistent with the CAA is

that the state consider each of the five BART factors in making its BART determinations.  This is exactly

what Arizona did.  Arizona is entitled to make its own decisions in weighing and assessing the BART

factors, and Arizona has done that exactly as the law requires.

EPA purports to acknowledge its statutory obligation to defer to the state’s BART determinations when

it states, “[i]f Arizona submits a SIP revision that addresses the deficiencies [alleged in EPA’s proposed

rule] in sufficient time for EPA to review the submission, then we would prefer to act on that submittal,

if such action is consistent with our obligations under the CAA and applicable court orders.”13  Of course,

it is not deference to the state for EPA, in essence, to invite Arizona to submit a new SIP that conforms

to EPA’s policy choices.  That is little more than an attempted distraction from the proposed rules’

infringement on the state’s statutorily assigned role as the BART‐determining authority under the

regional haze program.  It is the Arizona SIP submittal that is in front of EPA now – not some future

potential SIP revision – that merits EPA’s full approval.

Moreover, even if Arizona could revise its SIP in a manner that differs in substance from EPA’s proposed

FIP and that EPA would still approve, it is apparent that EPA’s schedule for finalization of its proposed

rule does not provide the state with any real opportunity to take advantage of this option.  EPA entered

into a 2012 consent decree in which the agency agreed to take final action on Arizona’s regional haze

SIP, with regards to the three facilities impacted by this proposed rule, by November 15, 2012.  Absent

amendment of that consent decree, that schedule would leave ADEQ with two months to prepare a

revised SIP, adopt it pursuant to the state’s administrative law requirements, and submit it to EPA

before EPA takes final action with respect to the current proposed SIP disapproval and proposed FIP – a

clearly impossible task for the state.14

                                                           

12 See 77 Fed. Reg. at 42,836. Luminant Generation Co. v. EPA, 675 F.3d 917, 921 (5th Cir. 2012) (“With regard to

implementation, the Act confines the EPA to the ministerial function of reviewing SIPs for consistency with the

Act's requirements.”) (emphasis added); see also id. at 926 (“EPA may consider only the requirements of the CAA

when reviewing SIP submissions ... This statutory imperative leaves the agency no discretion to do anything other

than ensure that a state's submission meets the CAA's requirements and, if it does, approve it before the passage

of its statutory deadline.”) (emphases added).

13 See id. at 42,839; see also id. at 42,834 (“We encourage the State to submit a revised SIP to replace all portions

of our FIP, and we stand ready to work with the State to develop a revised plan.”).

14 If EPA sincerely wishes to work with the state, it should take the steps necessary to ensure that Arizona would

have the time it needs to respond to EPA’s proposed disapproval of its NOx BART determinations.  As noted in the

proposed rule, EPA published a finding on January 15, 2009 that 37 states, including Arizona, had failed to make all

or part of their required regional haze SIP submissions.  This finding triggered a two‐year deadline, ending on

January 15, 2011, for EPA either to promulgate a FIP or to review and approve a submitted SIP to address Arizona’s

regional haze obligations.  See CAA § 110(c).  EPA missed that deadline and then did not propose action on regional
SRP Comments on Proposed Regional Haze Rule   Page 3‐3

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

In summary, state primacy in BART determinations is a central tenet of the CAA regional haze program.  

In contravention of the statute, EPA’s proposed rule simply ignores that the CAA does not allow EPA to

impose its judgment for that of the state.  Arizona’s action is consistent with its obligations under the

law, and EPA must approve the SIP NOx BART determinations.

3.2 Arizona’s BART Determinations are Fully Consistent with the Requirements of the CAA

EPA further attempts to bolster its proposed partial disapproval of Arizona’s SIP by arguing that

Arizona’s NOx BART determinations “are neither consistent with the requirements of the Act nor with

BART decisions that other states have made.”15  However, as these comments demonstrate, Arizona’s

BART determinations are consistent with the CAA, and, even assuming for the sake of argument that

Arizona’s BART determinations differ from BART determinations made by some other states (which,

tellingly, EPA does not identify), such a finding is irrelevant to the approvability of the state’s BART

determinations.

The centerpiece of the regional haze program is state primacy.  Each state must make its own BART

determinations, based on consideration of the statutory factors, none of which involve BART decisions

made by others.  Indeed, inherent in the concept of state primacy is the possibility that the states will

make decisions that differ from one another and that such differences are valid.  Under EPA’s proposed

contrary interpretation of the CAA, states would have no room to develop differing BART policies or to

exercise their independent judgment.  They would instead be constrained to adopt BART determinations

made by other states.  This undermines the CAA’s policy of deference to state decision‐making, contrary

to the statute, its legislative history, and Corn Growers.

16  Moreover, EPA fails to explain why – even

assuming for the sake of argument that “consistency” of Arizona’s BART determinations with other

states’ BART determinations is required – it is Arizona’s SIP rather than other states’ “inconsistent” SIPs

that merit disapproval.

                                                                                                                                                                                               

haze implementation plan requirements for Arizona until July 2012, one year and five months after that deadline.  

See 77 Fed. Reg. at 42,834.  [NOTE: EPA’s deadline for action was Jan 2011, as stated in the previous sentence.]  

Particularly in light of the fact that, at this point, the CAA § 110(c) deadline no longer governs EPA’s discretion

regarding timing, it is appropriate for EPA to take the time necessary to work with the state to resolve any relevant

issues – assuming that EPA does not, as it should, promulgate full approval of Arizona’s SIP – rather than proceed

immediately to final promulgation of a FIP.    

15 See 77 Fed. Reg. at 42,836.

16 In analyzing the legislative history of the 1977 CAA Amendments, in which Congress enacted the BART

provisions, Corn Growers makes clear that “Congress intended the states” – not EPA – “to decide which sources

impair visibility and what BART controls should apply to those sources.”  Corn Growers, 291 F.3d at 8 (discussing

legislative history) (emphasis added).  Thus, where EPA “attempts to deprive the states of ... this statutory

authority,” EPA acts “in contravention of the [CAA].”  Id.  
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In any event, Arizona’s BART determinations for CGS are entirely reasonable and, to the extent that

other states’ BART determinations may be relevant, consistent not only with the action of other states,

but with action that EPA has approved (or proposed to approve) for those states.  A number of states

have determined, rightly, that combustion controls (including LNB/OFA), as called for by Arizona’s BART

determinations for CGS, are BART for NOx emissions and that an emission limit in the vicinity of 0.320

lb/MMBtu (as determined by Arizona for CGS) represents BART for NOx.

17   

EPA’s suggestion that Arizona’s SIP contains unreasonable, unauthorized, or unprecedented BART

determinations is simply wrong.  Because the state’s determination is based on consideration of the five

BART factors and is consistent with the statute and EPA’s BART rules, EPA must approve Arizona’s NOx

BART determination for CGS.18

3.3 EPA Must Take Action on Arizona’s SIP Proposal as a Whole  

EPA is proceeding to address Arizona’s regional haze SIP by dissecting that plan and taking action on

various pieces at various times.  As noted by EPA, its proposed rule “addresses only the portion of the

SIP related to Arizona’s determination of Best Available Retrofit Technology (BART) to control emissions

from eight units at three electric generating stations: Apache Generating Station, Cholla Power Plant and

Coronado Generating Station.”19   

Pursuant to the consent decree EPA chose to execute that sets deadlines for final action on, among

other things, Arizona’s regional haze SIP, EPA committed to take final action on this proposed rule by

November 15, 2012.  That same consent decree establishes a July 15, 2013 deadline for final action on

the remaining elements of Arizona’s regional haze SIP.  This bifurcated approach to Arizona’s regional

haze SIP is inconsistent with the CAA.   

                                                           

17 See 77 Fed. Reg. 50,602, 50,604 (Aug. 22, 2012) (approving New Hampshire’s determination that NOx BART for

Merrimack Station is an emission limit of 0.30 lb/MMBtu); 77 Fed. Reg. 33,022, 33,032 (June 4, 2012) (approving

Wyoming’s determination that NOx BART for FMC Westvaco is LNB plus OFA and an emission rate of 0.35

lb/MMBtu); 77 Fed. Reg. 20,894, 20,898 (Apr. 6, 2012) (approving North Dakota’s determination that NOx BART for

the applicable limits for Milton R. Young Station are 0.36 lb/MMBtu for Unit 1 and 0.35 lb/MMBtu for Unit 2, and

that NOx BART for Leland Olds Station is 0.35 lb/MMBtu); 77 Fed. Reg. 18,052, 18,065 (Mar. 26, 2012) (proposing

to approve Colorado’s determination that NOx BART for CENC Unit 4 is 0.37 lb/MMBtu based on installation and

operation of LNB with separated OFA).

18 See CAA § 110(k)(3) (providing that EPA “shall approve [any SIP] submittal as a whole if it meets all of the

applicable requirements of this Act”); see also Train v. Natural Res. Def. Council, 421 U.S. 60, 79 (1975) (“[T]he Act

gives the Agency no authority to question the wisdom of a State’s choices of emission limitations if they ... satisf[y]

the standards of [CAA] § 110(a)(2), and the Agency may devise and promulgate a specific plan of its own only if a

State fails to submit an implementation plan which satisfies those standards.”) (emphases added).

19 See 77 Fed. Reg. at 42,834.
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Specifically, Section 110(k)(3) of the CAA requires EPA to act on all elements of Arizona’s regional haze

SIP submittal at the same time:

“In the case of any [SIP] submittal on which the Administrator is required to act ... the

Administrator shall approve such submittal as a whole if it meets all of the applicable

requirements of this [Act].  If a portion of the plan revision meets all the applicable

requirements of this [Act], the Administrator may approve the plan revision in part and

disapprove the plan revision in part.”20  

Thus, Section 110(k)(3) of the CAA requires EPA either to approve a SIP submittal “as a whole” or to

approve that SIP submittal in part and disapprove it in part in a single rulemaking that addresses in its

entirety “the plan revision.”  It is inconsistent with this provision for EPA to break apart a SIP submittal

and take final action on individual components of that SIP in a piecemeal fashion.  Such a requirement is

completely sensible, because it is the plan as a whole, with all its elements working together, that must

ensure that the CAA’s regional haze‐related goals are being reached.  

Any approach to SIP review and approval other than the approach under Section 110(k)(3) of the CAA

would fail to take into account the full array of regulatory choices that Arizona has made to address

regional haze.21  EPA should, therefore, take the necessary measures to ensure that Arizona’s SIP is

reviewed, and ultimately approved, as a whole.

3.4 EPA Cannot Propose or Finalize a NOx BART FIP for CGS Until it has Taken Final Action on

Arizona’s Regional Haze SIP  

EPA’s authority to propose and then take final action to promulgate a FIP comes into existence only

when a state has not submitted a SIP or when, in a case where a state has submitted a SIP, EPA has

made a final determination that that SIP is not approvable.  As the Supreme Court has held,

“[t]he Act gives the Agency no authority to question the wisdom of a State’s choices of emission

limitations if they are part of a plan which satisfies the standards of § 110(a)(2), and the Agency

may devise and promulgate a specific plan of its own only if a State fails to submit an

implementation plan which satisfies those standards.”22    

                                                           

20 See CAA § 110(k)(3) (emphases added).

21 This is not a case in which a state has made an incomplete SIP submittal.  See 77 Fed. Reg. at 42,839

(acknowledging that Arizona’s SIP “was determined complete by operation of law on August 28, 2011”).

22 Train v. NRDC, 421 U.S. 60, 79 (1975) (citing and describing CAA § 110(c)) (emphasis added); see CAA §

110(a)(2)(J) (including visibility requirements among the “standards of § 110(a)(2)”).
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This principle – that EPA may not propose, let alone promulgate in final form, a FIP in the presence of a

submitted SIP that EPA has not determined, after notice‐and‐comment rulemaking, is unapprovable – is

confirmed by sections 307(d)(1)(B), (3), and (6) of the CAA.23  Under those provisions, any proposed or

final FIP must be accompanied by a “statement of basis and purpose,” which must include a summary of

“the factual data on which the ... rule is based” and “the major legal interpretations and policy

considerations underlying the ... rule.”24  Because the legal and factual predicate for any FIP is the

absence of an approvable SIP submission, EPA cannot present the relevant factual, legal, and policy

information and rationale necessary to justify a proposed or final FIP rule until it has properly taken final

action on any relevant SIP before it.   

For the reasons discussed above, EPA cannot reasonably or lawfully propose and promulgate a regional

haze FIP for Arizona, which has submitted a complete regional haze SIP to EPA, until EPA has made a

final determination as to whether that submitted regional haze SIP “satisfies” the Act’s regional haze

“standards” in CAA sections 110(a)(2)(J) and 169A.25  EPA can make such a determination only after full

review of and – following notice‐and‐comment rulemaking – final action on that SIP.  Thus, EPA’s

proposal of a FIP for Arizona contravenes the requirements of the CAA and must be withdrawn.  Final

action on Arizona’s SIP must precede any proposed or final action on a FIP for the state.  

                                                           

23 The requirements of section 307(d) are more stringent than those of the Administrative Procedure Act.  See

Small Refiner Lead Phase‐Down Task Force v. EPA, 705 F.2d 506, 519 (D.C. Cir. 1983).

24 CAA § 307(d)(3)(A), (C), (6)(A).   

25 Train v. NRDC, 421 U.S. at 79.   
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4.0   EPA Improperly Ignored the CGS Consent Decree and Presumptive BART

Limits in its Selection of Recommended BART Controls

After considering and giving appropriate weight to each of the BART factors, ADEQ determined that NOx

BART for CGS Units 1 and 2 is LNB/OFA with a corresponding emission limit of 0.320 lb/MMBtu.26  Units

1 and 2 are currently subject to a 0.320 lb/MMBtu NOx limit, consistent with the state’s determination.  

Unit 2 will be subject to a 0.080 lb/MMBtu NOx emission limit as soon as the SCR for that unit is installed

and operational (i.e., by June 1, 2014), pursuant to the consent decree to which CGS is subject.  That

limit is clearly significantly more stringent – and is based on a more advanced and expensive emission

control technology – than what the state determined to be BART for CGS.   

4.1   CGS Consent Decree Controls are Better Than BART

Once SCR is installed on Unit 2, the facility, as a whole, will also be subject to a plant‐wide emission limit

of 7,300 tons of NOx per year under the consent decree.  This tonnage limit translates to an effective

emission rate of 0.20 lb/MMBtu for CGS, as a whole.  This limit also represents a level of control that is

more stringent than that reflected in the state’s NOx BART determination for CGS and EPA’s presumptive

NOx limits.27  Accordingly, the state’s analysis supports a conclusion that the existing NOx controls at

CGS, including the soon‐to‐be‐installed SCR at Unit 2 and the plant‐wide NOx emission limit in the

consent decree, are in fact better than BART and that no additional changes to the plant’s emission

control requirements are warranted.

EPA’s BART rules support the conclusion that existing and currently planned CGS controls are better

than NOx BART because those controls, and their associated emission rates, were agreed to by SRP and

EPA to resolve allegations of violations of certain requirements of the PSD program28 for both CGS units.  

As such, those limits are intended to reflect compliance with the PSD program’s BACT requirements.  

BACT is defined as:

“an emission limitation based on the maximum degree of reduction of each pollutant subject to

regulation under this [Act] emitted from or which results from any major emitting facility, which

the permitting authority, on a case‐by‐case basis, taking into account energy, environmental,

and economic impacts and other costs, determines is achievable for such facility through

                                                           

26 See 77 Fed. Reg. at 42,842.

27 It is appropriate to consider the emission rate achieved by CGS as a whole because the BART rules expressly

authorize plant‐wide averaging to demonstrate compliance with BART requirements.  See 70 Fed. Reg. at 39,172.  

28 The PSD program is one element of the CAA’s New Source Review requirements and applies in areas that meet

the national ambient air quality standards.
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application of production processes and available methods, systems, and techniques, including

fuel cleaning, clean fuels, or treatment or innovative fuel combustion techniques for control of

each such pollutant.”29  

BACT applies to newly constructed facilities or existing facilities that undergo a “major modification,”

whereas BART applies to existing facilities that do not undergo major modification and that are,

therefore, not subject to new‐source levels of control.  Accordingly, BACT, which requires the “maximum

degree of reduction” of emissions from new facilities, considering the factors listed in CAA § 169(3), is in

almost all circumstances a more stringent requirement than BART (or certainly not less stringent than

BART).30    

EPA recently discussed the relationship between BART for an existing facility, Four Corners Power Plant

(FCPP), and BACT for a new facility, Desert Rock Energy Facility:

“Commenters argue that if Desert Rock was required to meet a limit of 0.05 lb/MMBtu using the

same coal as FCPP, the ash content should not hinder FCPP from achieving similarly low NOx

emission rates.  EPA notes that if constructed, Desert Rock would have been a new, state‐of‐

the‐art facility specifically designed with boiler characteristics, combustion controls, and post‐

combustion controls to meet the Best Available Control Technology (BACT) requirements for

numerous criteria and non‐criteria pollutants.  FCPP is an existing, over 40‐year‐old power

plant.  The Regional Haze Rule requires a case‐by‐case BART (best available retrofit technology)

determination, which need not be equivalent to BACT for new facilities.”31

EPA’s BART rules reflect this understanding.  They provide that BACT determinations and “NSR [New

Source Review]/PSD settlement agreements” generally satisfy BART requirements.32  EPA recently

recognized this principle in its final regional haze rule for North Dakota.  That rule explained that,

subsequent to EPA’s original BART FIP proposal to require SCR at the Milton R. Young Station, a United

States District Court held that the State of North Dakota had reasonably determined that NOx BACT for

that facility was 0.36 lb/MMBtu for one of its units and 0.35 lb/MMBtu for the other.33  EPA concluded

that because emission control technology had not changed in any appreciable way since that BACT

                                                           

29 See CAA § 169(3) (emphasis added).

30 See R. 95‐564, Joint Explanatory Statement of the Committee of Conference (Aug. 3, 1977), reprinted in 3 Comm.

on Public Works, Legislative History of the Clean Air Act Amendments of 1977 at 535 (1978) (explaining that BART

is intended to apply to existing facilities and that the more stringent PSD program will address any visibility

impairment that results from emissions from new sources).

31 77 Fed. Reg. at 51,620, 51,636 (Aug. 24, 2012) (emphases added).   

32 See 70 Fed Reg. at 39,164.   

33 See 77 Fed. Reg. at 20,897.   
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determination was made, it was appropriate to rely on the BACT determination to satisfy BART.34  A

similar situation is present here – CGS is subject to a very recent NSR consent decree that should,

pursuant to EPA’s BART Guidelines, be deemed to also satisfy the facility’s BART obligations.35

4.2   EPA Must Consider Presumptive BART Limits

EPA’s presumptive BART limits provide further support for accepting the existing CGS emission controls

as better than BART.  The presumptive BART limits are not mere suggestions or illustrations that EPA can

freely ignore.  EPA adopted them pursuant to notice‐and‐comment rulemaking, and they are binding

regulatory presumptions that should only be deviated from based on a careful consideration of the

BART factors.36  The presumptive BART limits, moreover, are a part of the BART Guidelines.  Thus, their

consideration during the course of a BART analysis is compelled by the CAA for facilities such as CGS.  

The presumptive limits cannot, therefore, simply be ignored, as they are in the proposed rule.37   

It is important to emphasize that – except for cyclone units, which are not present at CGS – EPA

deliberately based the presumptive BART limits for NOx “on the use of current combustion control

technology” and rejected basing those limits on “post‐combustion controls such as SCRs.”38  An

assessment of the presumptive NOx limits, which EPA is required to undertake and which EPA failed to

                                                           

34 Id.

35 A report by J. Edward Cichanowicz submitted by Public Service Company of New Mexico to EPA as part of its

Supplement to a Petition for Reconsideration of EPA’s August 22, 2011 BART FIP for the San Juan Generating

Station in New Mexico, 76 Fed. Reg. at 52,388 (Aug. 22, 2011), describes in detail the development of SCR

technology from early applications to the current state of the art.  See Supplement to the Petition of Public Service

Company of New Mexico for Reconsideration and Stay of EPA’s Final Rule: “Approval and Promulgation of

Implementation Plans; New Mexico; Federal Implementation Plan for Interstate Transport of Pollution Affecting

Visibility and Best Available Retrofit Technology Determination,” Docket No. EPA‐R06‐OAR‐2010‐0846, Exhibit C, J.

Edward Cichanowicz, “Evaluation of Engineering and Analytical Studies To Assess the Cost of Selective Catalytic

Reduction (SCR) NOx Control Technology for the Public Service Company of New Mexico San Juan Generation

Station” (April 2012) (hereinafter “Cichanowicz Report”).  That report explains that SCR technology has become

increasingly complex since its early deployment at those facilities that presented the least challenging retrofit

scenarios, and that SCR retrofit installation costs have increased considerably as installation complexity at more

challenging facilities has increased.  That report also demonstrates that SCR has not developed in any significant

manner with respect to its ability to achieve deeper levels of control of NOx emissions since the time that SRP

entered into the 2008 consent decree.  Accordingly, EPA has no factual or legal basis for requiring more stringent

NOx emission controls or emission limits than those reflected in the consent decree.

36 See 70 Fed. Reg. at 39,171 (“You may determine that an alternative control level [to the presumptive NOx limit]

is appropriate based on a careful consideration of the statutory factors.”) (emphasis added).

37 See 77 Fed. Reg. at 42,838.  EPA explains that “[i]n making BART determinations for fossil fuel‐fired electric

generating plants with a total generating capacity in excess of 750 megawatts, states must use the approach set

forth in the BART Guidelines,” but EPA makes no mention of the presumptive BART limits that are a key element of

those Guidelines.     

38 See 70 Fed. Reg. at 39,134.   
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consider in the proposed rule, demonstrates that controls installed pursuant to the consent decree are

better than BART for NOx at CGS.

The presumptive NOx BART limit listed in the BART guidelines for the type of units present at CGS (i.e.,

dry‐bottom turbo‐fired boilers using sub‐bituminous coal) is 0.23 lb/MMBtu, based on the installation

and operation of combustion controls only.39  This limit was established based on an analysis of actual

emissions data for dry‐bottom wall‐fired boilers – a different source category – because there were no

turbo‐fired boilers equipped with LNB/OFA at the time EPA’s guidelines were published.  It has since

been well documented that turbo‐fired boilers cannot achieve NOx emission rates with combustion

controls as low as dry‐bottom wall‐fired boilers.  SRP believes that if EPA were to perform the same

analysis today, the presumptive limit for turbo‐fired boilers would be equivalent to the emission limit

that currently applies to the units at CGS – 0.32 lb/MMBtu.40

In any case, the plant‐wide emission limit that will soon apply to CGS translates to an effective NOx

emission rate of 0.20 lb/MMBtu, which is plainly below the presumptive NOx limit.  Further, this limit is

                                                           

39 See 70 Fed. Reg. at 39,172.

40 SRP conducted a detailed review of the procedure used by EPA to establish the presumptive limits for the turbo‐

fired boilers at CGS.  This review included an analysis of the spreadsheet developed by EPA to document the

calculation of the presumptive limit for this source category, and a review of the accompanying Technical Support

Document.   

EPA identified only seven turbo‐fired boilers for this analysis, none of which were equipped with LNB/OFA.  

Therefore, EPA relied on information for dry‐bottom wall‐fired boilers to develop presumptive limits for the dry‐

turbo‐fired source category.

EPA calculated the level of control that would be expected to be achievable on dry‐turbo‐fired units (column

heading “Calculated Control Case 1a NOx Emission Rate” in the “Control Case 1a” tab of EPA spreadsheet) as

follows:

Post‐Controlled NOx Rate = Pre‐Controlled NOx Rate x (1 – Fraction of Removal)

The “Fraction of Removal” term in the above equation is calculated as follows:

Fraction of Removal = 0.285 + (0.541 x Pre‐Controlled NOx Rate)

In the “NOx Control Cost & Performance” tab of the EPA spreadsheet, the above “Fraction of Removal” equation is

listed as applicable to dry‐bottom wall‐fired boilers burning sub‐bituminous coal that are equipped with LNB/OFA.  

There is no equation listed for dry‐turbo‐fired boilers.  Therefore, it appears that in the absence of specific

information for the dry‐turbo‐fired source category, EPA applied the equation for dry bottom wall‐fired boilers to

calculate the expected removal efficiency of LNB/OFA for dry turbo‐fired boilers.

Using this assumption, EPA calculated the expected control efficiency from applying LNB/OFA to be approximately

60%, which is likely to be well beyond what can be achieved by installing this control technology.  In the CGS BART

analysis submitted in February 2008, SRP noted that maximum NOx emissions from Units 1 and 2, before installing

LNB/OFA, are typically 0.433 and 0.466 lb/MMBtu, respectively.  Based on information provided by equipment

vendors, it was estimated that LNB/OFA would reduce NOx emissions to a level of approximately 0.32 lb/MMBtu,

which would translate to a control efficiency of 35‐46%.  Actual emissions of NOx from the boilers at CGS have

been close to the 0.32 lb/MMBtu limit since installation of LNB/OFA.
SRP Comments on Proposed Regional Haze Rule	 Page	4‐5

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based on installation and operation of combustion controls (LNB/OFA) on Unit 1, consistent with the

presumptive limits, and installation and operation of combustion controls (i.e., LNB/OFA) and post‐

combustion controls (i.e., SCR) on Unit 2, which far exceeds in stringency what the presumptive limits

require.  Therefore, the limits the consent decree imposes at CGS should be viewed as better than BART,

particularly when considering the facility as a whole.41   

EPA’s proposed rule would require the NOx BART emission limits in the FIP be met on a unit‐by‐unit

basis.42  However, EPA’s own BART rules authorize and encourage application of BART emission limits on

a plant‐wide basis.43  The relative distribution of emission reductions across units at a given facility

makes no difference from a visibility improvement perspective.  Accordingly, EPA should not require the

unnecessarily restrictive burden of unit‐by‐unit BART limits and instead should allow for the option of

plant‐wide averaging at CGS.

In summary, application of EPA’s BART Guidelines supports the conclusion that compliance with the

consent decree more than satisfies BART for both CGS units by: (1) meeting the BART Guidelines’

presumption that NSR/PSD consent decrees such as the CGS consent decree satisfy BART, and (2)

imposing emissions reductions that are greater than the presumptive limits in the BART Guidelines.

                                                           

41 EPA should, in the alternative, recognize that the consent decree, which requires SCR and a 0.080 lb/MMBtu NOx

limit for Unit 2, at the very least resolves BACT for Unit 2 and that this limit also satisfies BART for Unit 2.   

42 77 Fed. Reg. at 42,865/1‐3.  

43 70 Fed. Reg. at 39,172/2 (stating that the BART‐determining authority “should consider allowing sources to

‘average’ emissions across any set of BART‐eligible emission units within a fenceline, so long as the emission

reductions from each pollutant being controlled for BART would be equal to those reductions that would be

obtained by simply controlling each of the BART‐eligible units that constitute [the] BART‐eligible source”); id. at

39,115/2 (explaining that states may “allow sources to ‘average’ emissions across a set of BART‐eligible emission

units within a fenceline, so long as the amount of emission reductions from each pollutant being controlled for

BART would be at least equal to those reductions that would be obtained by simply controlling each unit”).
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5.0   EPA’s Control Technology Evaluations are Not Consistent with BART

Guidelines  

EPA’s evaluation of available control technologies and their associated control effectiveness levels is

incorrect in several respects, as outlined in this section.

5.1 EPA’s Proposed NOx Emission Rates Associated with Post Combustion Controls are Not

Achievable

SRP contracted with multiple third‐parties to complete evaluations of the proposed control efficiencies,

emission limits, and costs associated with post combustion control implementation at CGS Units 1 and 2.  

These entities concluded that the NOx emission limits currently proposed or contemplated for CGS likely

will result in on‐going compliance issues resulting from CGS’s inability to meet these limits on a

continuous basis.  Unfortunately, EPA would likely perceive these on‐going compliance issues as excess

emissions that would likely result in enforcement action against CGS, rather than associate these issues

with the limits being set incorrectly to begin with.

5.1.1 EPA’s Proposed SCR NOx Emission Limit of 0.050 lb/MMBtu is Unachievable

EPA’s proposed BART determination for CGS Unit 1 would impose an exceptionally stringent NOx

emission limit of 0.050 lb/MMBtu, which is premised on the assumption that SCR can achieve this limit

continuously on a 30‐day rolling average, including periods of startup, shutdown and equipment

malfunctions as required by the consent decree.  Continuous compliance with such a limit has, however,

not been shown to be feasible, and EPA has failed to support either its proposed BART determination or

its reliance on this limit in its BART analysis.   

No emission limit can be determined to represent BART for a given facility unless it has been shown to

be “achievable” at that facility.44  EPA has not demonstrated through the development of an SCR

conceptual design or some other, similar site‐specific analysis that SCR can achieve this emission rate at

CGS.  On the contrary, EPA’s proposed rule merely cites “[e]xisting vendor literature and technical

studies [that] indicate that SCR systems are capable of achieving a 0.05 lb/MMBtu emission rate

(approximately 80–90% control efficiency) and that this emission rate can be achieved on a retrofit

basis, particularly when combined with combustion control technology such as LNB.”45  EPA’s TSD cites

only three documents to support this position.46  Such a limited level of documentation is not

                                                           

44 40 C.F.R. § 51.301 (definition of “BART”).   

45 77 Fed. Reg. at 42,853.

46 See EPA, Arizona Haze Rule Technical Support Document at 37 & n.69 (July 2012), EPA‐R09‐OAR‐2012‐0021‐0009

(hereinafter “TSD”).  TSD at 37 & n.69.   
SRP Comments on Proposed Regional Haze Rule	 Page	5‐2

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persuasive, and in any event fails to even approach compliance with the CAA’s requirement that BART

determinations be based on a site‐specific analysis.

In the TSD, EPA states that “[i]n the absence of source‐specific considerations warranting a less stringent

control level, we presume that an emissions limit of 0.05 lb/MMBtu is achievable by these units through

the use of SCR in addition to advanced combustion controls.”47  This approach is inconsistent with EPA’s

own Guidelines.  Instead of presuming an emission rate is achievable, especially in the presence of

evidence that proves that it is not achievable, EPA must affirmatively establish that its selected BART

limit is in fact achievable.

   

Of particular interest is the fact that EPA justifies its BART determination by citing examples of

purported compliance with a 0.05 lb/MMBtu emission limit.  However, this is not the limit that EPA is

proposing for CGS.  EPA has taken a more stringent stance in proposing 0.050 lb/MMBtu, but this limit is

not referenced in its feasibility documentation – just 0.05 lb/MMBtu.48  A 0.050 lb/MMBtu NOx emission

limit is unprecedented for retrofit facilities like CGS.   

EPA recently imposed a 0.05 lb/MMBtu NOx limit in a BART FIP applicable to the San Juan Generating

Station in New Mexico.49  A technical report on that final rule concluded that the limit “appears to be

the most stringent NOx emissions limit ever imposed on any new or existing pulverized coal unit in the

United States” and “does not represent a consistently achievable level of emissions for the units at [the

facility] even with the use of best available NOx emission controls and the lowest available emission rate

performance guarantee.”50  The legality of that FIP limit is currently subject to challenge in litigation

                                                           

47 Id. at 37 (emphasis added).   

48 For example, if NOx emissions were 0.054 lb/MMBtu over a 30‐day rolling average, the unit would be considered

in compliance with an emission limit of 0.05 lb/MMBtu (due to rounding), whereas the unit would be considered

out of compliance with an emission limit of 0.050 lb/MMBtu.  Clearly, the two limits are not interchangeable.

49 76 Fed. Reg. at 52,388 (Aug. 22, 2011), the EPA published a final rule disapproving a portion of the New Mexico

interstate transport SIP revision and promulgating a FIP requiring a 0.05 NOx emission limit for each of the facility’s

units.  [NOTE: The rule does not disapprove New Mexico’s regional haze SIP.  EPA takes no action on that SIP.]

50 RMB Consulting & Research, Inc., Technical Memorandum regarding Analysis of the Achievability of the FIP NOx

Limit for San Juan Generating Station and Comparison to Other Ultra‐Low NOx Units at 1, 7 (Oct. 21, 2011)

(hereinafter “San Juan RMB Report”) (Attachment 2 to Public Service Company of New Mexico’s Petition for

Reconsideration and Stay of EPA’s Final Rule: “Approval and Promulgation of Implementation Plans; New Mexico;

Federal Implementation Plan for Interstate Transport of Pollution Affecting Visibility and Best Available Retrofit

Technology Determination,” Docket ID No. EPA‐R06‐OAR‐2010‐0846 (Oct. 21, 2011)).  During the course of the

litigation over EPA’s final rule for New Mexico, EPA asserted that the RMB study is flawed because Havana Unit 9,

which the RMB Report references, purportedly achieved a 0.05 lb/MMBtu rate during an 18‐month period.  

Regardless of the merits of this assertion, the RMB conclusion that “there are a significant number of periods

where the 30‐day average exceeds 0.05 lb/MMBtu, which suggests that the unit would not be able to consistently

demonstrate compliance with a FIP‐equivalent limit” applying a 30‐day average, still stands.  Id. at 7.  Accordingly,

such a limit is not “achievable.”  
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pending in the U.S. Court of Appeals for the Tenth Circuit on the grounds that, among other things, the

0.05 lb/MMBtu rate is infeasible and unachievable, particularly on a continuous basis.  Even with this

pending litigation, EPA has proposed an even more stringent limit for CGS Unit 1 – 0.050 lb/MMBtu.   

SRP contracted with two entities, RMB Consulting & Research, Inc. (RMB) and Sargent and Lundy (S&L),

to review the ability of the CGS units to achieve the 0.050 lb/MMBtu emission limit proposed by EPA

using SCR control technology.  Both consultants concluded that a NOx BART limit of 0.050 lb/MMBtu on

a 30‐day rolling average is not achievable at CGS.  

Specifically, in RMB’s analysis, which is included in Attachment A to these comments, they conclude

that:

“Based on our analysis of projected emissions ... a NOx emission limit of 0.050 lb/MMBtu does

not represent a consistently achievable level of emissions for the units at CGS.    The data

suggests that both units will periodically exceed the proposed limit, which will be inaccurately

characterized and reported as excess emissions.   RMB also finds that EPA did not adequately

consider the impact of SUSD [startup and shutdown] emissions or the ability to measure such

emissions during SUSD events in their BART determination.  As a result, we conclude that the

proposed BART NOx emission limit of 0.050 lb/MMBtu should be rejected for both units.”51

In addition, as SRP explained in its July 27, 2012 letter responding to EPA’s request for further

information regarding the viability of achieving a lower NOx emission limit for CGS Unit 2, a 0.050

lb/MMBtu NOx limit cannot be achieved on a continuous basis, even if certain modifications are made to

the current design to allow SCR use at lower inlet temperatures.52  This determination was based on

work by S&L who conducted modeling with and without the use of a low‐load temperature control

system while accounting for typical operating scenarios.  S&L’s modeling demonstrated that Unit 2 could

not comply with a 0.050 lb/MMBtu NOx limit if there was even one start during the 30‐day averaging

period, as shown in Table 5‐1 on the following page.53  

                                                           

51 See R Barton, S. Norfleet, & B. White, RMB Consulting & Research, Inc., Technical Memorandum: Achievability of

the Proposed FIP NOx Limits for Coronado Generating Station at 12 (Sept. 2012) (emphasis added) (hereinafter

“RMB Coronado Report”) (Attachment A to these Comments).

52  See letter to Deborah Jordan, EPA, from Kelly Barr, SRP, regarding SRP Response to EPA Letter Dated July 27,

2012 (Attachment B to these comments).

53 See Sargent & Lundy, LLC, Final Report: Salt River Project (SRP) Coronado Generating Station Unit 2 SCR Review

at 10 (Aug. 24, 2012) (hereinafer “S&L Coronado Report”) (Attachment B to these Comments).  
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EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

Table 5‐1: 30‐Day Rolling Average NOx Emissions Including Unit Startups and Low‐Load Cycling

Modeled Scenario

1 Start Per 30

Operating Days

2 Starts Per 30

Operating Days

3 Starts Per 30

Operating Days

SCR system without low‐load

temperature control system

0.075 lb/MMBtu 0.083 lb/MMBtu 0.091 lb/MMBtu

SCR system with low‐load

temperature control system

0.053 lb/MMBtu 0.063 lb/MMBtu 0.072 lb/MMBtu

S&L correctly concluded that even with a low‐load temperature control system, Unit 2 could not

consistently achieve a NOx emission limit of 0.050 lb/MMBtu when periods of low‐load cycling, startup,

and shutdown are taken into account.  These types of operating scenarios are typical for both units at

CGS.

RMB’s analysis also found that the 0.050 lb/MMBtu NOx emission limit that is being contemplated by

EPA is inconsistent with BACT determinations that EPA has approved for new coal‐fired units.  

Specifically, RMB’s analysis states:

“[T]he recently issued BACT limits do not support the FIP NOx limit for the units at CGS.  Although

there have been several units permitted with similar emissions limits, none of these limits are

directly equivalent (same numeric limit and averaging time, including startup and shutdown

periods) to the FIP limit ... In addition, all of the above units are based on new construction, which,

unlike retrofit units, can be designed to optimize NOx reduction in other aspects of combustion

(i.e. pulverizer design, boiler height, etc.).  Notwithstanding, there is also inadequate data

available to confirm the long‐term achievability of the limits because the units have not begun

operation or only recently became operational.  These findings indicate that the proposed FIP

NOx limit issued for the units at CGS represents the most stringent emission limit suggested for

any new or retrofit unit.  In addition, the fact that there are no similar units with a long‐term

operating history at such low emissions levels confirms that EPA failed to adequately consider

the achievability of the FIP limit.”54

This is notable because BACT is a more stringent requirement than BART.  The fact that EPA has not

imposed a limit comparable to the limit it proposes as BART for CGS Unit 1 pursuant to the CAA’s BACT

provisions is compelling evidence that such a limit is far too stringent to reflect a proper BART

determination.

                                                           

54 See Attachment A, RMB Coronado Report at 11 (emphasis added).
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Moreover, other recent EPA actions support the conclusion that such a limit cannot generally be

achieved and cannot be assumed to be achievable at CGS.  For example, as part of CSAPR,55 EPA

concluded that a NOx limit below 0.06 lb/MMBtu is not achievable through retrofit of SCR on coal‐fired

electric generating units.56  EPA in fact stated that this “well‐controlled emission rate of ... 0.06

lbs/MMBtu for NOx represent[s] the lowest annual emission rate assumed achievable when state‐of‐the‐

art pollution control technologies are installed at coal units,” and that such a rate is “based on the floor

rate[s] used in [EPA] modeling and [is] intended to reflect the lower bound of emission rates that

suppliers are willing to guarantee when installing state‐of‐the‐art pollution control equipment (selective

catalytic reduction (SCR) ... ).” 57  

EPA similarly recognized that a 0.05 lb/MMBtu emission limit is unachievable in two recent regional

haze rulemakings involving North Dakota and South Dakota.  In EPA’s Proposed Rule for North Dakota,

EPA based its BART analysis on a 0.05 lb/MMBtu emission rate, but then proposed to adopt a 0.07

lb/MMBtu limit because EPA concluded the more stringent rate would not allow a sufficient margin of

compliance.58  And in its final rule for South Dakota, EPA went further and set a NOx limit of 0.10

lb/MMBtu for an electric generating plant – twice the limit EPA proposes for CGS – again, to allow for an

adequate margin of compliance.59  The proposed rule for Arizona provides no similar or effective

mechanism for allowing an adequate margin of compliance for CGS.  Even state‐of‐the‐art new facilities

have not been required to show continuous compliance with a 0.050 lb/MMBtu NOx emission rate on a

30‐day rolling average basis.60   

After analyzing purportedly “similar” new‐source emission limits, the San Juan RMB Report concluded

that not even one of those limits was “directly equivalent” to the 0.05 lb/MMBtu compliance limit

imposed by EPA at San Juan.61  Those “similar” limits were less stringent through various means,

including use of a higher numerical limit, exclusion of periods of startup and shutdown, and use of a

longer averaging period.62  Thus, EPA has no basis to impose such a continuous, low emission limit in a

retrofit application.   

                                                           

55 Although the D.C. Circuit in EME Homer City Generation, L.P. v. EPA, – F.3d – 2012 WL 3570721 (D.C. Cir. Aug. 21,

2012) vacated CSAPR, that court had no occasion to address this aspect of CSAPR.

56 76 Fed. Reg. at 1,109, 1,115 (Jan. 7, 2011); EPA, Transport Rule Engineering Feasibility Response to Comments,

Docket ID No. EPA‐HQ‐OAR‐2009‐0491‐4529, at 13 (July 6, 2011).

57 76 Fed. Reg. at 1,115 & n.3.  

58 76 Fed. Reg. at 58,570, 58,610 (Sept. 21, 2011).   

59 77 Fed. Reg. at 24,845, 24,848, 24,849 (Apr. 26, 2012).

60 See San Juan RMB Report at 1, 7‐10.   

61 Id. at 9.   

62 Id. at 8‐9.    
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Further, EPA’s proposed NOx limit for CGS Unit 1 is even more stringent than EPA’s recently promulgated

Subpart Da new source performance standard (NSPS) for electric utility steam generating units

constructed after May 3, 2011.63  This standard, which applies to new or reconstructed facilities that

were constructed more recently than BART‐eligible facilities, is 0.70 pounds per megawatt‐hour

(lb/MWh) gross energy input or 0.76 lb/MWh net energy input.  For a heat rate of 9,000 British thermal

units per kilowatt‐hour (typical of new units), a 0.70 lb/MWh limit is equivalent to 0.077 lb/MMBtu.  

However, an existing unit likely has a much higher heat rate.  Requiring a more stringent emission limit

pursuant to BART for units older than those covered by this recently promulgated NSPS is unreasonable

and unsupported.

In summary, EPA has not established that a 0.050 lb/MMBtu emission rate is achievable for CGS, and it

has not demonstrated that Arizona’s selection of a 0.08 lb/MMBtu rate for evaluating SCR was in error.  

EPA’s proposed rule, moreover, contradicts the best available evidence.  Accordingly, EPA’s FIP and its

BART analyses are flawed and invalid and must be withdrawn.

5.1.2 SNCR NOx Emission Rate Evaluated by EPA is Incorrect

An analysis completed by S&L indicates that typical NOx removal efficiencies with the use of an SNCR

system range from 15‐40 percent.64  The critical parameters that affect the overall performance of an

SNCR system include flue gas temperature, residence time within the temperature window, consistent

quality of the urea droplet size distribution, amount of reagent injected, reagent distribution within the

flue gas, inlet NOx emissions, and carbon monoxide and oxygen concentrations in the flue gas.

Based on an initial review of the impacts these parameters would have on SNCR implementation at CGS,

S&L estimated that the expected NOX reductions would be 25 percent,65 but noted that additional

studies would be needed to guarantee this performance.  S&L’s estimate also was verified by an

independent vendor, FuelTech, who agreed with this assessment.66

It appears that EPA evaluated an emission limit that is based on a higher reduction efficiency (i.e., 30

percent) being applied to a starting NOx emission limit of only 0.30 lb/MMBtu.  As EPA is aware, CGS is

currently subject to a NOx emissions limit of 0.320 lb/MMBtu in its Title V permit following the

installation of LNB/OFA on each of the units.  Given SRP’s current NOx emission limit and an SNCR

                                                           

63 77 Fed. Reg. at 9,304, 9,423 (Feb. 16, 2012).

64 See Sargent & Lundy, LLC, Salt River Project Coronado Generating Station – Unit 1: SNCR Capital Cost Estimate

Report at 2‐2 (Sept. 7, 2012) (hereinafter “S&L Coronado SNCR Cost Estimates”) (Attachment C to these

Comments).

65 Id. at 2‐1.

66 See letter to Robert Olsen, SRP, from Douglas Kirk, FuelTech, regarding Salt River Project Coronado Generation

Station SNCR NOx Control Performance (Attachment D to these comments).
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control efficiency of 25 percent, the appropriate NOx emission rate to use in the BART analysis would be

0.24 lb/MMBtu, rather than EPA’s assumed value of 0.21 lb/MMBtu.  This corrected NOx emission rate

(i.e., 0.24 lb/MMBtu) represents a level that can likely be achieved on a consistent basis based on input

from SRP’s vendors who have specific SNCR implementation experience.

5.2 EPA’s Selected Baseline Emissions Period Eliminated Consideration of LNB/OFA as a

Viable BART Control Strategy

EPA’s improper lack of deference to Arizona’s NOx BART determination for CGS is reflected throughout

the proposed rule and is highlighted by EPA’s decision to supplant even the state’s assessment of

baseline emissions with EPA’s own conflicting analysis.  As noted in the proposed rule, SRP and the state

relied on baseline NOx emissions developed from “continuous emission monitoring system (CEMS) data

from 2001 to 2003.”67  EPA further acknowledges that reliance on this baseline period and on the

associated “existing pollution control technology used in the BART analyses” is “reasonable and

generally consistent with the [Regional Haze Rule] and the BART Guidelines.”68   

Indeed, a memorandum cited in the preamble to EPA’s BART Rules states that “BART analyses should be

based on the 2000 to 2004 period.”69  Yet in preparing its proposed FIP for CGS, EPA opted to reassess

BART using a baseline for NOx (and SO2) “based on the maximum daily emissions from recent data in

EPA’s Clean Air Markets Division (CAMD) database, with data examined for 2008 to 2011.”70  EPA

acknowledges that it decided to use this updated baseline because “SRP ... installed LNB with OFA on

Coronado Units 1 and 2” after the 2000 to 2004 general baseline period.71   

EPA should have deferred to Arizona’s proper assessment of baseline emissions.  States have discretion

over such decisions, and EPA had no basis for discarding the state’s method or its decision to use a

baseline derived from data within the 2000 to 2004 period.   

In any event, EPA’s decision to alter the emission baseline did not necessitate its flawed proposed NOx

BART determination.  On the contrary, existing emission controls, reflected in the baseline, can and

                                                           

67 See 77 Fed. Reg. at 42,850.   

68 See Id. at 42,841 (emphasis added).  

69 See 70 Fed. Reg. at 39,143 & n.84; Memorandum from Lydia Wegman and Peter Tsirigotis, 2002 Base Year

Emission Inventory SIP Planning: 8‐hr Ozone, PM2.5, and Regional Haze Programs, Attachment at 3 (Nov. 8, 2002),

available at http://www.epa.gov/ttn/naaqs/pm/data/epa_m_20021118.pdf.   

70 See 77 Fed. Reg. at 42,854.   

71 See Id. at 42,861; cf. 77 Fed. Reg. at 20,894, 20,919 (Apr. 6, 2012) (EPA’s final regional haze rule for North

Dakota) (“[EPA] do[es] not agree ... that it is appropriate to lower the baseline emission rate based on ... voluntary

installation of combustion controls on Unit 2 in 2010, well after the State established the historic baseline of 2003‐

2004 for BART planning”).
SRP Comments on Proposed Regional Haze Rule	 Page	5‐8

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should be evaluated as BART candidates, and EPA has previously approved state determinations that

existing controls are BART.72   

In proposing to adjust the baseline, however, EPA has failed to give proper consideration to LNB/OFA as

a viable BART candidate.  EPA states, for instance, that it is “examining only one control scenario in our

analysis for [CGS] Unit 2, SCR at a more stringent emission rate of 0.050 lb/MMBtu ...”73  Similarly, EPA

states that, with respect to CGS Unit 1, EPA “evaluated SNCR ... and SCR at 0.05 lb/MMBtu.”74  EPA’s

decision to include LNB/OFA in its baseline NOx emissions estimate does not and cannot, consistent with

the BART rules, foreclose consideration of those controls as BART for CGS.  Regardless of whether EPA’s

rationale for failing to conduct a full assessment of LNB/OFA as a BART candidate is related to EPA’s

inclusion of these controls in its revised baseline, EPA’s improperly truncated BART assessment makes

the proposed rule invalid.

Furthermore, as shown in Figure 5‐1 below, installation of LNB/OFA on both units at CGS has already

resulted in substantial reductions in NOx emissions that are not contemplated or acknowledged in EPA’s

analysis.

Figure 5‐1: Actual Emission Trends for CGS Units 1 and 2

                                                           

72 See, e.g., 77 Fed. Reg. at 49,308, 49,314 (Aug. 15, 2012) (concluding that existing SO2 controls are BART); 77 Fed.

Reg. at 41,279, 41,283 (July 13, 2012) (concluding that existing PM controls are BART).   

73 See 77 Fed. Reg. at 42,861 to 62.   

74 See Id. at 42,863.   
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These emission reductions should not be ignored in EPA’s analysis simply because EPA delayed review of

Arizona’s SIP until 2012.  EPA should give deference to the baseline emissions period selected by ADEQ

in its SIP analysis and fully consider LNB/OFA as an appropriate basis for BART emission limitations for

CGS.
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6.0   EPA’s Cost of Compliance Analysis is Flawed and Must be Replaced with

Site‐Specific Costs

SRP provided, and ADEQ reviewed and utilized,75 site‐specific cost estimates for the installation of NOx

emission controls at CGS.  Rather than use these site‐specific costs, EPA substituted cost estimates

developed by its own contractor, without considering the unique characteristics of CGS, to prepare the

cost assessment provided in the technical support document that accompanied this proposed rule.  In

rejecting ADEQ’s site‐specific cost analysis and substituting EPA’s own analysis based on application of

its generic Control Cost Manual and flawed use of the Integrated Planning Model, EPA made significant

errors and excluded legitimate, real‐world costs, resulting in a proposed rule based on a drastic

underestimation of control costs.  Correction of these errors, as described in this section of SRP’s

comments, demonstrates that Arizona’s BART determination was correct and that EPA’s proposed NOx

BART determination must be withdrawn.  

6.1 EPA Improperly Ignored Site‐Specific Cost Estimates for CGS BART Control Options

In its proposed rule, EPA rejects Arizona’s assessment of BART control costs and substitutes its own

assessments.  EPA’s overreaching completely ignores that Arizona has “the lead role in designing and

implementing [its] regional haze program” and “broad authority over BART determinations.”76  The

assessment and weighing of “the costs of compliance” under CAA § 169A(g)(2), a significant component

of a BART determination, is therefore the proper province of the states, and ADEQ fulfilled that role on

behalf of Arizona, consistent with the CAA.77   

EPA attempts to justify its rejection of ADEQ’s cost determinations through various unmerited and

vague assertions, including, most prominently, EPA’s proposed conclusions that: (1) “there are certain

aspects of [ADEQ’s] cost calculations that we find inconsistent with the BART Guidelines and EPA’s

Control Cost Manual;”78 and (2) ADEQ did not have cost information “at a level of detail that allowed for

a comprehensive review.”79

Contrary to the first assertion, ADEQ fully complied with the BART Guidelines and was justified in any

deviation from the specific terms of the Control Cost Manual because ADEQ engaged in a reasoned, site‐

specific cost analysis.  As stated in the proposed rule:

                                                           

75 Indeed, as EPA’s proposed rule acknowledges, ADEQ requested additional cost information so as to ensure that

its own assessment of costs was fully and adequately supported.  See 77 Fed. Reg. at 42,841.

76 See Corn Growers, 291 F.3d at 3, 8.

77 See Id. at 6‐7.  

78 See 77 Fed. Reg. at 42,841.

79 See Id. at 42,851.  See also TSD at 35.
SRP Comments on Proposed Regional Haze Rule	 Page	6‐2

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

“ADEQ included information relating to costs of compliance in its RH [regional haze] SIP,

including information on total annualized costs, cost per ton of pollutant removed, and

incremental cost per ton of pollutant removed for the various control options considered.  Cost

calculations were prepared by consulting firms on behalf of the facilities as part of their BART

analyses that relied on a combination of vendor quotes, facility data, and internal cost

calculation methodology.  These BART analyses were subsequently submitted to ADEQ.  Upon

review, ADEQ requested certain clarifying information from the facilities regarding these cost

calculations, including greater detail on the underlying assumptions and additional supporting

documentation.  ADEQ received responses of varying detail to these requests, and included

this information as part of its RH SIP.”80  

Thus, it is apparent that Arizona considered the type of cost elements (e.g., total annualized costs, cost

per ton of pollutant removed, and incremental costs) that are the central components of a proper BART

cost assessment under the BART Guidelines.  In such circumstances, there can be no basis for suggesting

that the state has acted contrary to the BART Guidelines or the CAA.

Further, EPA’s assertion that ADEQ’s cost assessment is flawed because it is in some way inconsistent

with EPA’s Control Cost Manual also fails to justify rejection of the state’s cost conclusions and

associated BART determinations for CGS.  Contrary to EPA’s suggestion, the BART Guidelines promote,

rather than limit, state “flexibility in how they calculate costs.”81  The Guidelines explicitly state that, in

addition to considering cost elements discussed in the Control Cost Manual, “[t]he cost analysis should

also take into account any site‐specific design or other conditions ... that affect the cost of a particular

BART technology option.”82  The Guidelines thus indicate that the Control Cost Manual does not tie a

state’s hands in assessing control costs:

“[T]he Control Cost Manual provides a good reference tool for cost calculations, but if there are

[cost] elements or sources that are not addressed by the Control Cost Manual or there are

additional cost methods that could be used, we [EPA] believe that these could serve as useful

information.”83  

If a state adopts a different approach to cost considerations than the one set forth in the Control Cost

Manual, as Corn Growers directs, if site‐specific issues warrant considerations that differ from the

                                                           

80 See 77 Fed. Reg. at 42,841 (emphases added).

81 See 70 Fed. Reg. at 39,104, 39,127.

82 See Id. at 39,166 (emphases added).

83 See Id. at 39,127.
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EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

Control Cost Manual, the BART Guidelines indicate that the state “should include” documentation of the

information “used for the cost calculations,” such as:

“[A]ny information supplied by vendors that affects ... assumptions regarding purchased

equipment costs, equipment life, replacement of major components, and any other element of

the calculation that differs from the Control Cost Manual.”84  

This is precisely the sort of information that EPA’s own proposed rule indicates ADEQ sought and relied

on in assessing the cost‐of‐compliance BART factor for CGS and in reaching its BART determination for

that facility.85  Thus, EPA has no rational basis for rejecting Arizona’s BART analysis.

Neither the CAA nor the BART rules dictate specific documentation requirements for the presentation of

cost assessment information for a state’s BART determination.  If EPA was concerned that the state’s

cost assessment was not adequately detailed or documented, it should have requested additional

information from ADEQ before proposing to disapprove ADEQ’s analysis and developing a proposed FIP

that would substitute EPA’s judgment for that of the state.  Yet in comments EPA provided to ADEQ

regarding Arizona’s proposed regional haze SIP, EPA never mentioned any flaws perceived by EPA in the

state’s assessment of costs (or any other BART factor) applicable to the CGS assessment, and those

comments did not indicate that additional cost documentation would be a prerequisite to approval of

the state’s NOx BART determination for CGS.86   

Moreover, given ADEQ’s primacy in making BART determinations, ADEQ has discretion to conduct and

document its cost assessment at a level that it deems appropriate, and the documentation that supports

ADEQ’s BART determination is reasonable by any objective standard.  ADEQ engaged in a thorough

analysis, requesting more information from SRP when needed to inform a well‐reasoned decision,87 and

therefore, assessed costs at the level of detail it judged appropriate.  And indeed, the supplemental

information provided by SRP to the state includes detailed cost breakdowns for each control option

considered.88   

                                                           

84 See Id. at 39,166 n.15.

85 See 77 Fed. Reg. at 42,841 (noting that the information relied on by the state included “vendor quotes, facility

data, and internal cost calculation methodology”).

86 See Arizona Regional Haze State Implementation Plan Under Section 308 of Federal Regional Haze Rule,

Appendix E, Letter from Colleen McKaughan, EPA to Eric Massey, ADEQ (Dec. 2, 2010), available at

http://www.azdeq.gov/environ/air/haze/download/app_e.pdf.   

87 See 77 Fed. Reg. at 42,850.

88 See SRP Response to ADEQ Request for Additional BART Information (June 25, 2009), available at

http://www.azdeq.gov/environ/air/haze/download/110810m.pdf.  
SRP Comments on Proposed Regional Haze Rule	 Page	6‐4

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

EPA must respect and defer to Arizona’s primary authority and the state’s adequately detailed and

documented cost assessment.  Arizona properly determined costs, and EPA has no right to reject the

state’s analysis.  It is EPA’s analysis that does not withstand scrutiny and that cannot support a BART

determination.  Arizona’s NOx BART determination for CGS must therefore be approved and EPA’s FIP

withdrawn.

6.2 EPA Inappropriately Relied on Flawed Data from the Control Cost Manual and IPM  

In its cost analysis, EPA indicates that it “relied on facility data from a number of sources including ...

EPA’s Control Cost Manual,” which is now more than a decade old and therefore out of date.89  EPA’s

cost assessment departs from the CAA’s requirement, as confirmed by the D.C. Circuit in Corn Growers,

that a BART cost assessment be site‐specific.   

Instead of relying on information developed for the specific facilities at issue in this rule, as Arizona did,

EPA used the IPM to calculate the capital costs and annual operating costs associated with the various

NOx control options that EPA considered.90  The proposed rule and EPA’s TSD say almost nothing about

how IPM was used to calculate costs.  Instead, EPA directs the public to an EPA contractor report for

more information, but no contractor report in the docket for this rulemaking supplies additional detail

on precisely how IPM was used.  This failing alone renders EPA’s proposed rule inconsistent with the

CAA’s public notice requirements.  Moreover, it is apparent that no cost estimate derived from a model

designed to produce generalized information about utilities throughout the nation could possibly satisfy

the CAA requirement that BART be determined based on a site‐specific analysis.     

Regardless, SRP and its contractor, S&L, evaluated the costs associated with the post‐combustion

control equipment presented by EPA in the proposed rule and the supporting TSD to assess the

reasonableness of the costs used by EPA in its analysis.  SRP maintains that site‐specific costs for

installation of BART controls are appropriate for use in making a BART determination because neither

the Control Cost Manual nor IPM account for site‐specific issues that may substantially increase the cost

to install and operate NOx control equipment.  To provide EPA with an additional basis for review of

                                                           

89 See TSD at 35.  Even if EPA updates the dollar figures used in the Control Cost Manual on a regular basis, the

Manual is still out‐dated because its conception of reasonable costs to include in an assessment of emission

controls, like SCR, does not fit the complex retrofit sites that remain in 2012.  Further, standard utility accounting

procedures now reflect costs that EPA’s Control Cost Manual does not include.  Indeed, even EPA’s own, more

recently developed (initially in 2000) Coal Utility Environmental Cost program (CUECOST) accounting methodology

reflects current utility costs more realistically than the Control Cost Manual, which reflects utility accounting

practices as they were conceptualized over twenty years ago.  See J. Edward Cichanowicz, Evaluation of

Engineering and Analytical Studies To Assess the Cost of Selective Catalytic Reduction (SCR) NOx Control

Technology for the Public Service Company of New Mexico San Juan Generation Station at 4‐5 (April 2012).

90 See 77 Fed. Reg. at 42,852.   
SRP Comments on Proposed Regional Haze Rule	 Page	6‐5

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

SRP’s site‐specific costs, SRP also used historical data,91 and vendor input to revise the IPM inputs

utilized by EPA.   

Once the IPM costs are revised to reflect appropriate data inputs, the IPM outputs validate the site‐

specific costs provided by SRP.  As such, SRP’s site‐specific costs should be used as the cost basis for any

BART determinations.  EPA’s generalized approach, on the other hand, is not supported by the record,

and fails to even remotely satisfy the CAA’s requirement that such assessment be site‐specific.

6.3 SRP’s Adjusted Inputs to EPA’s IPM

6.3.1 Unit Size

EPA’s cost analysis used a value of 410.9 gross megawatts (MWG) for CGS Units 1 and 2, as taken from

the National Electric Energy Database System (NEEDS) version 4.10.  For the purposes of SRP’s model

run, SRP evaluated historical operating data where gross output was greater than 430 MWG to

determine an appropriate unit size.  Based on this analysis, SRP used a value of 431 MWG for CGS Units 1

and 2.

Additionally, in the revised IPM Appendix 5‐2A, it states that “the elevation of the site must be

considered separately and factored into the unit MW [megawatt] size accordingly due to its effects on

the flue gas volume.”92  The model provided along with the TSD does not appear to account for the fact

that CGS is located approximately 5,000 feet above sea level.  As such, SRP has added another factor

into the model that accounts for this change in elevation (i.e., an Elevation Factor).

At higher elevations, lower barometric pressure can increase the amount of flue gas generated during

combustion.  This results in the need to increase the size of equipment to compensate for this additional

flue gas flow.  The effects of elevation on flue gas requirements can be calculated by computing the

ratio of the flow rate in actual cubic feet per minute (ACFM) of the flue gas at sea level versus the ACFM

of the flue gas at elevation.  This ratio can be reduced to a ratio of absolute barometric pressure at sea

level versus absolute barometric pressure at elevation.  For this analysis, SRP used an absolute

barometric pressure at sea level of 29.9 inches of mercury and an absolute barometric pressure at 5,000

feet above sea level of 24.9 inches of mercury.  Accordingly, SRP used a value of 1.20 for the Elevation

Factor.  

                                                           

91 Where plant historical data is referenced, SRP evaluated plant historical data over an 18‐month window, from

January 2011 through July 2012, unless otherwise noted.

92 S & L, IPM Model – Revisions to Cost Performance for APC Technologies: SCR Cost Development Methodology,

Final, Appendix 5‐2A at 2 (Aug. 2010) (hereinafter “Revised IPM Appendix 5‐2A”), available at

http://www.epa.gov/airmarkt/progsregs/epa‐ipm/docs/v410/Appendix52A.pdf.
SRP Comments on Proposed Regional Haze Rule	 Page	6‐6

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

It is important to note, however, that SRP did not apply the Elevation Factor to fixed operating and

maintenance (O&M) costs, which are based upon actual unit size, not flue gas flow rate.

6.3.2 Gross Heat Rate

EPA’s cost analysis used a value of 10,503 British thermal units per kilowatt‐hour (Btu/kW‐hr) for CGS

Unit 1 and value of 9,695 Btu/kW‐hr for CGS Unit 2.  Both of these values were taken from the NEEDS

version 4.10 database.  In reviewing historical operating data for CGS, the gross heat rate for each unit

historically fluctuates between 9,000 and 9,400 Btu/kW‐hr, depending on a wide variety of conditions,

including unit load, ambient temperature, ambient pressure, and fuel content.   

SRP reviewed historical gross heat rate data for each unit when operating at full load.  Based on this

analysis, SRP used a gross heat rate value of 9,087 Btu/kW‐hr for CGS Unit 1 and 9,317 Btu/kW‐hr for

CGS Unit 2.

6.3.3 NOx Removal Factor

EPA’s cost analysis used a fixed value of 0.875 for the NOX removal factor.  This NOx removal factor is

consistent with the example provided in the revised IPM Appendix 5‐2A.  However, in EPA’s

documentation supplement for the EPA Base Case version 4.10 for the Mercury Air Toxics Standard

(MATS), EPA indicated that the NOx removal factor is equal to the NOx removal efficiency divided by

80.93  As such, SRP used this equation to calculate a NOx removal factor of 1.044 for Unit 1 based on a

NOx emission limit of 0.05 lb/MMBtu, and 1.061 and 0.948 for Unit 2 based on a NOx emission limit of

0.05 lb/MMBtu and 0.08 lb/MMBtu, respectively.

6.3.4 NOx Removal Efficiency

In EPA’s SCR cost analysis, the NOx removal efficiency is calculated on the basis that the target NOx

emissions are 0.05 lb/MMBtu (or 0.08 lb/MMBtu for the Unit 2 consent decree limit scenario), which is

consistent with the revised IPM Appendix 5‐2A where it provides “...the lower level of NOx removal.”94  

In calculating the NOx removal efficiency, EPA also used the average actual NOx emissions for each unit.  

This suggests to SRP that EPA’s model provides costs on an actual NOx reduction basis, instead of a

permitted basis.

Without a doubt, the actual costs associated with achieving a NOx emission limit of 0.050 lb/MMBtu

would be higher than those costs presented in the EPA cost analysis in order to account for a sufficient

                                                           

93 Support documentation for the MATS Rule at 10, available at http://www.epa.gov/airmarkets/progsregs/epa‐

ipm/docs/SuppDoc410MATS.pdf.  

94 Revised IPM Appendix 5‐2A, at 2.
SRP Comments on Proposed Regional Haze Rule	 Page	6‐7

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

compliance margin.  However, to be consistent with the revised IPM Appendix 5‐2A and EPA’s analysis,

SRP’s analysis also used a target NOx emission rate of 0.05 lb/MMBtu.   

6.3.5 Ammonia Cost

EPA’s cost analysis used a value of $400 per ton of ammonia.  SRP attempted to get vendor specific

quotes for delivery of ammonia to CGS by rail, but was unsuccessful at receiving budgetary pricing

within the comment period provided by EPA.   

In the absence of site‐specific data, SRP looked to Springerville Generating Station Unit 4 (Springerville

4), which uses anhydrous ammonia in its SCR equipment.95  Springerville 4 is located less than 30 miles

from CGS and utilizes the same rail delivery line, and, as such, SRP believes that ammonia pricing at CGS

would be comparable to ammonia pricing for Springerville 4.  For this reason, SRP used $752 per ton of

ammonia based on recent costs for use of ammonia at Springerville 4.

6.3.6 Operating Labor Rate

EPA’s cost analysis used a value of $60 per hour as the operating labor rate.  SRP evaluated the loaded

wage rates for operations and maintenance staff along with the current scheduling requirements for a

variety of staff.  Based on this evaluation, SRP used $75 per hour as the operating labor rate in its

analysis, as this figure better represents the actual costs.

6.3.7 Base Module Costs

EPA’s cost analysis assumed that the base module cost for a low‐dust SCR was 25 percent lower than the

base module cost for a high‐dust SCR, which is unsupported by IPM Appendix 5‐2A.  SRP disagrees with

this assessment as the cost model is based upon flue gas flow, which does not change with dust loading

into the SCR.  As such, SRP’s analysis does not reduce the base module costs due to a low‐dust SCR

configuration.

6.3.8 Urea Costs

EPA’s cost analysis for SNCR assumed urea costs to be approximately $400 per ton (at 50 percent

solution, by weight).  For the detailed cost estimate for SNCR installation at CGS Unit 1, S&L used $630

                                                           

95 SRP owns Springerville Unit 4, but the unit is operated by Tucson Electric Power.
SRP Comments on Proposed Regional Haze Rule	 Page	6‐8

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

per ton of urea (at 50 percent in solution, by weight)96 based on recent costs provided to them by urea

suppliers.97  This cost estimate is based on similar pricing used by S&L in recent SNCR studies.   

In addition, SRP notes that IPM Appendix 5‐2B correctly calculates urea consumption based on the

molar ratio of urea to NOx.  However, when determining the variable O&M costs associated with SNCR,

the model does not calculate urea costs on a dry basis, and, as such, predicts variable O&M costs to be

half of what they should be.  SRP believes it is appropriate to perform this calculation on a dry basis, and

SRP’s model includes an adjustment to annual urea costs based on using a 50 percent solution, by

weight.

6.3.9 Property Taxes and Insurance

EPA’s cost analysis, as presented in the proposed rule, included property taxes and insurance in its

calculation of annualized capital costs for both the SCR and SNCR model runs.  However, in its TSD, EPA

excluded these costs in its analysis.98  Regardless of EPA’s changing interpretations, SRP did not include

property taxes or insurance in its calculations when determining the annualized capital costs.  Even

though these costs are not necessary to sustain Arizona’s BART determination for CGS, they are

legitimate, real‐world costs that Corn Growers directs EPA to take into account.  EPA’s failure to do so

highlights EPA’s consistent failure to follow the BART Guidelines and the CAA.  

6.4 SRP’s Adjusted IPM Results Still Underestimate Post Combustion Control Costs

Comparing the EPA IPM costs as set forth in the proposed rule and the TSD to the SRP site‐specific costs,

the SRP site‐specific costs are approximately 55 to 77 percent higher than the costs used by EPA in

support of the proposed FIP.  Given EPA’s obvious refusal to use site‐specific costs, in contravention of

the requirements of the CAA, SRP also re‐ran the IPM estimates using more accurate data inputs.  These

revised IPM costs are 44 to 50 percent higher than the costs used by EPA in support of the proposed FIP.  

Even using EPA’s legally flawed approach to assessing costs, it is clear EPA’s cost estimates greatly

understate the actual costs that SRP will incur pursuant to EPA’s proposed rule.

                                                           

96 See Attachment C, S&L Cost Estimate Report, Appendix A.  September 7, 2012. Salt River Project Coronado

Generating Station – Unit 1: SNCR Capital Cost Estimate Report.  Sargent & Lundy, LLC.  Included as Attachment C

to these comments.

97 See Appendix A.  September 7, 2012. Salt River Project Coronado Generating Station – Unit 1: SNCR Capital Cost

Estimate Report.  Sargent & Lundy, LLC.  Included as Attachment C to these comments.

98 See TSD at 62.
SRP Comments on Proposed Regional Haze Rule	 Page	6‐9

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

6.4.1 Detailed SCR Cost Comparison

SRP’s IPM results for SCR are significantly closer than EPA’s cost assessment to the site‐specific SCR

installation costs provided by S&L.  For Unit 2, site‐specific SCR installation costs are approximately 7.4

percent higher than the SRP IPM results (at 0.080 lb/MMBtu).  These results are within the accuracy

indicated by IPM Appendix 5‐2A.99  For CGS Unit 1, site‐specific SCR installation costs are approximately

18.6 percent higher than the SRP IPM model results.

The relative agreement between SRP’s site‐specific installation costs and SRP’s IPM SCR results provide

further validation that EPA inappropriately relied on flawed data in support of its proposed FIP.  A

detailed comparison of these costs for Units 1 and 2 is provided in Tables 6‐1 and 6‐2, respectively.  

Table 6‐1:  IPM Version 4.10 Cost Estimate Outputs for SCR Costs for CGS Unit 1

EPA Contractor

IPM Costs  

for CGS U1 SCR

SRP

IPM Costs

for CGS U1 SCR

Target NOx Rate, lb/MMBtu 0.05 0.05

Base Module SCR Costs 36,515,317 54,583,868

Base Module Reagent Prep Costs 2,356,820 2,300,321

Base Module Air Preheater Costs  ‐ ‐

Base Module Balance of Plant Costs 4,959,112 5,141,364

Total Base Costs 43,831,249 62,025,553

Engineering & Construction Management 4,383,125 6,202,555

Labor Adjustment 4,383,125 6,202,555

Contractor Profit and Fees 4,383,125 6,202,555

Capital, Engineering, and Construction Costs Subtotal 56,980,624 80,633,219

Total Fixed O&M Costs, per year, per kilowatt (kW) $0.88/kW $0.76/kW

Total Variable O&M Costs, $/megawatt‐hour (MWh) $1.10/MWh $1.36/MWh

Annual O&M Costs 3,572,319 4,492,736

Annualized Capital Costs 6,062,335 7,611,205

Total Annual Costs 9,634,654 12,103,941

                                                           

99 See Revised IPM Appendix 5‐2A.  S&L indicated an expected accuracy of “approximately 11% at 600 MW.”
SRP Comments on Proposed Regional Haze Rule	 Page	6‐10

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1Table 6‐2: IPM Version 4.10 Cost Estimate Outputs for SCR Costs for CGS Unit 2

EPA Contractor

IPM Costs

for CGS U2 SCR

SRP

IPM Costs

for CGS U2 SCR

EPA Contractor

IPM Costs

for CGS U2 SCR

Target NOx Rate (lb/MMBtu) 0.05 0.05 0.Base Module SCR Costs 33,922,728 56,039,147 33,922,7Base Module Reagent Prep Costs 2,371,545 2,376,286 2,305,5Base Module Air Preheater Costs  ‐ ‐ ‐ Base Module Balance of Plant Costs 4,795,152 5,195,624 4,795,1Total Base Costs 41,089,425 63,611,057 41,023,4Engineering & Construction Management 4,108,943 6,361,106 4,102,3Labor Adjustment 4,108,943 6,361,106 4,102,3Contractor Profit and Fees 4,108,943 6,361,106 4,102,3Capital, Engineering, and Construction Costs Subtotal 53,416,253 82,694,375 53,330,4Total Fixed O&M Costs, per year, per kilowatt (kW) $0.88/kW $0.76/kW $0.88/kTotal Variable O&M Costs, $/megawatt‐hour (MWh) $1.12/MWh $1.50/MWh $1.04/MWAnnual O&M Costs 3,950,038 5,375,973 3,686,7Annualized Capital Costs 5,683,111 7,805,764 5,673,9Total Annual Costs 9,633,149 13,181,736 9,360,7
SRP Comments on Proposed Regional Haze Rule	 Page	6‐11

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

6.4.2 Detailed SNCR Cost Comparison

In determining costs for SNCR equipment at CGS, EPA appears to have used a substantially modified

approach.  In this approach, EPA does not use the model developed in IPM Appendix 5‐2B, but instead

assumes that SNCR capital installation costs were $20 per kilowatt.100  To support this assumption, EPA

appears to have adjusted the multiplier rate for Engineering and Construction Management, Labor

Adjustment, and Contractor Profit and Fees from 10 percent to 5 percent.101

In addition, it also appears that EPA included the use of owner’s costs in order to support the

assumption that SNCR capital installation costs are $20 per kilowatt.  In the TSD issued to support EPA’s

proposed FIP, EPA rejected costs provided for Arizona Electric Power Cooperative and Arizona Public

Service noting that “... certain line item costs not allowed by the EPA Control Cost Manual were

included, such as owner’s costs ...”102  The use of owner’s costs in EPA’s own cost calculations indicate an

inconsistent stance by EPA with respect to additional line item costs.  This provides further validation

that EPA inappropriately relied on flawed data in support of its proposed FIP.

In an effort to be consistent with the EPA Control Cost Manual, SRP’s IPM evaluation for SNCR does not

include purportedly disallowed costs, such as owner’s costs or allowance for funds used during

construction.  In addition, SRP used the recommended rate of 10 percent to calculate Engineering and

Construction Management, Labor Adjustment, and Contractor Profit and Fees, which is consistent with

the approach defined in IPM Appendix 5‐2B.  The results of this evaluation are detailed in Table 6‐3.

In comparing EPA’s SNCR cost estimate to SRP’s site‐specific costs for SNCR, the site‐specific costs are

more than twice EPA’s IPM results.  However, when comparing SRP’s IPM SNCR costs to SRP’s site‐

specific costs for SNCR, the site‐specific costs are only approximately 14 percent higher than SRP’s IPM

results.  The relative agreement between SRP’s IPM results and SRP’s site specific costs again supports

the conclusion that EPA improperly relied on flawed cost data to support its FIP.  

                                                           

100 Cell K52 of the “NOx‐SNCR” TSD cost spreadsheet included with the supporting materials for the proposed rule

states “it was assumed that SNCR capital cost was $20/kW for all applications.”

101 Ten percent of the base SNCR capital costs is applied to each Engineering and Construction Management, Labor

Adjustment, and Contractor Profit and Fees. See Revisions to Cost Performance for APC, Revised IPM Appendix 5‐

2B, at 2, available at http://www.epa.gov/airmarkt/progsregs/epa‐ipm/docs/v410/Appendix52B.pdf.

102 See TSD, pgs 22 and 27.
SRP Comments on Proposed Regional Haze Rule	 Page	6‐12

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1Table 6‐3: IPM Version 4.10 Cost Estimate Outputs for SNCR Costs for CGS

EPA Contractor

IPM Costs

for CGS U1 SNCR

SRP

IPM Costs

for CGS U1 SNCR

EPA Contractor

IPM Costs

for CGS U2 SNCR

Target NOx Rate (lb/MMBtu) 0.21 0.24 0.2Base Module SNCR Costs 6,805,797 2,817,346 6,805,79Base Module Air Preheater Costs  ‐ ‐ Base Module Balance of Plant Costs  ‐ 4,305,590 ‐ Total Base Costs 6,805,797 7,122,938 6,805,79Engineering & Construction Management 340,290 712,294 340,29Labor Adjustment 340,290 712,294 340,29Contractor Profit and Fees 340,290 712,294 340,29Capital, Engineering, and Construction Costs Subtotal 7,826,667 9,259,817 7,826,66Total Fixed O&M Costs, per year, per kilowatt (kW) $0.35/kW $0.35/kW $0.35/kW Total Variable O&M Costs, $/megawatt‐hour (MWh) $1.00/MWh $1.76/MWh $0.67/MWAnnual O&M Costs 3,048,958 5,546,407 2,289,87Annualized Capital Costs 832,702 874,061 832,70Total Annual Costs 3,881,660 6,420,468 3,122,57
SRP Comments on Proposed Regional Haze Rule	 Page	6‐13

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

SRP acknowledges that at $28.37 per kilowatt,103 the site‐specific installation costs for SNCR equipment

at CGS are substantially higher than EPA’s presumed rate of $20 per kilowatt.  That is because, in

developing their detailed cost estimate, S&L determined that additional water treatment equipment

and rail unloading equipment will be necessary if SNCR equipment is installed at CGS.104  Because IPM

Appendix 5‐2B does not include any consideration for additional water treatment equipment or rail

unloading equipment, SRP believes site‐specific costs must be used over any modeled costs.

6.4.3 EPA’s Reliance on Generic Modeled Costs is Inappropriate and Significantly Lower Than SRP’s

Site‐Specific Costs

SRP’s site‐specific costs for SCR are based on the actual cost projections associated with the current SCR

installation at CGS Unit 2.  SRP has already made substantial progress on the Unit 2 SCR installation with

more than 40 percent of the project already complete.  This percent completion accounts for the fact

that the engineering design effort is more than 90 percent complete, and the overall procurement

efforts for the project are more than 75 percent complete.  As such, these site‐specific costs are

appropriate for use in any evaluation of BART controls.   

As illustrated in Figure 6‐1, there is a substantial difference between IPM results and site‐specific costs,

which further proves that costs used by EPA to support the BART determination for CGS are inaccurate.  

Specifically, in looking at Figure 6‐1, it is important to note that the cost estimates associated with an

SCR system on Unit 1 are conservative in that they are based on the costs associated with the Unit 2

SCR, which was designed to comply with a 0.080 lb/MMBtu NOx emission limit – not a 0.050 lb/MMBtu

NOx emission limit.  The Unit 1 SCR costs could increase significantly due to additional investments that

may be required to meet a NOx emission limit of 0.050 lb/MMBtu, including:

 Additional catalyst and an increase to the ammonia injection rate.   

 A dry sorbent injection control system to address increased sulfuric acid mist and condensable

PM emissions.   

 A fabric filter baghouse and ID fans to address increased filterable PM emissions.

These additional investments could be as high as $117 million in addition to the estimated SCR

investment for each unit shown in Figure 6‐1.

                                                           

103 $28.37/kW is lower than the $33/kW stated in S&L’s Coronado SNCR Cost Estimate because SRP has removed

the contingency costs included in S&L’s estimate.  These costs were removed based on contingency being

purportedly disallowed by EPA’s Control Cost Manual.  Such costs are, however, real and should figure into a

proper, site‐specific BART analysis.

104 See Attachment C, S&L Cost Estimate Report at ES‐3.
SRP Comments on Proposed Regional Haze Rule	 Page	6‐14

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

Figure 6‐1: Comparison of IPM Cost Estimates to Site‐Specific Cost Estimates for CGS

Even without including these additional costs, the site‐specific cost estimate for an SCR system on Unit 1

is almost twice the value used by EPA in its BART determination.  For the SCR system on Unit 2, the

actual cost incurred by SRP is likewise almost twice the value used by EPA in its BART determination.  

This documentation clearly demonstrates the importance of using available site‐specific cost estimates

when conducting a BART determination for CGS.

0

10

20

30

40

50

60

70

80

90

100

110

U1 SNCR U1 SCR U2 SCR

Cost, in millions $

EPA IPM Estimates SRP IPM Estimates Site‐Specific Costs*

Based on actual costs incurred by SRP

with more than 90% of engineering

design and more than 75% of

procurement already complete.

Based on an emission rate of

0.080 lb/MMBtu, as they are

scaled from U2 actual costs.

*Site‐Specific costs do not include disallowed costs, such as AFUDC, contingency, insurance, or property

taxes, and do not include possible additional investments that may be required to meet PM emission limits.
SRP Comments on Proposed Regional Haze Rule	 Page	6‐15

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

6.5 EPA Must Consider the Incremental Costs Between the Control Options

The flaws in EPA’s own cost assessment do not result only from EPA’s use of the Control Cost Manual

and IPM.  They also spring from EPA’s failure to follow its own rules.  The BART Guidelines make clear

that the costs of complying with various candidate BART control options should be assessed on an

“incremental” basis, which requires “a comparison of the cost and performance level of a control option

to the next most stringent control method.”105  EPA did not conduct such an analysis for CGS.  

The proposed rule and accompanying TSD both provide, in a table prepared by EPA, a single entry for

incremental costs for each of the CGS units.  This entry apparently reflects the incremental cost of the

most stringent NOx BART control option compared to the baseline.  This is not a complete incremental

analysis as it ignores incremental comparisons between identified control options.  Accordingly, EPA’s

incremental cost assessment does not provide the sort of information that the BART Guidelines call for

in making BART determinations.   

In the absence of a proper NOx BART assessment, EPA’s proposed rule lacks an adequate foundation.  

The high incremental costs of post‐combustion NOx control technologies when compared to combustion

control technologies reinforces the conclusion that post‐combustion control technologies cannot be the

basis for BART for the units at CGS.

6.6 EPA Must Consider Costs as They Relate to Visibility Improvement

An example of ADEQ’s appropriate and tailored approach to cost considerations was its decision to

consider, in addition to the cost assessment elements specifically called for in the BART Guidelines,

information with respect to the ”dollars‐per‐deciview” cost‐effectiveness of different control options.106  

Given the visibility improvement goal of the regional haze program, this approach to choosing the most

cost‐effective BART control option is reasonable and entirely within the broad discretion afforded to the

states under the CAA.   

Notably, in the proposed rule, EPA failed to consider the dollars per deciview effectiveness of different

control options when it supplanted ADEQ’s cost analysis with its own.  EPA’s decision to exclude rational

considerations, such as site‐specific costs and cost‐effectiveness on a deciview basis, and instead look to

limited and outdated information, such as the Control Cost Manual and IPM, has resulted in an

unsupported supplanting of ADEQ’s BART determination for CGS.

                                                           

105 See 70 Fed. Reg. at 39,167.   

106 See, e.g., TSD at 30; see also 70 Fed. Reg. at 39,170 (recognizing that states may consider “$/deciview” as a

“cost‐effectiveness measure”).
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7.0   EPA’s Proposed NOx BART Determination Rests on a Flawed Assessment

of Visibility Impacts

As described previously in these comments, the state has broad discretion over the manner in which it

evaluates the BART factors, including the visibility improvement factor, and EPA lacks authority to

disapprove Arizona’s BART determination simply because EPA believes that the factor should have been

evaluated in a different manner.  EPA’s proposed rule acknowledges that “ADEQ assessed the degree of

improvement in visibility from candidate BART technologies using models and procedures generally in

accord with EPA guidance.”107  Nevertheless, EPA proposes to disapprove Arizona’s NOx BART

determination for CGS, in part, because the EPA “do[es] not agree” with the state’s evaluation of

visibility impacts.  EPA further says it does not believe that “the visibility impacts were ... appropriately

evaluated and considered.”108  By EPA’s own assessment, Arizona’s approach to assessing visibility

improvement was lawful and permissible; therefore, EPA has no authority to disapprove Arizona’s BART

determination without explicitly identifying the deficiencies in the state’s analysis.109   

As detailed below, SRP believes EPA’s own modeling is deficient because it fails to use the most

scientifically credible approach to assess visibility impacts and fails to consider the extensive evidence

that NOx emissions are not a significant contributor to haze in the Colorado Plateau region.  Moreover,

EPA, through the proposed FIP, seeks to restrict impermissibly Arizona’s significant discretion to

calculate or consider the visibility benefits across multiple Class I areas by introducing use “cumulative”

visibility metric in partial replacement of the state’s more reasoned analysis.110   

7.1   EPA’s Modeling Choices Overestimate the Visibility Benefits Associated with BART

Control Options

7.1.1 EPA’s Use of Outdated CALPUFF Model Chemistry Over‐Predicts Visibility Benefits

EPA’s BART Guidelines recommend use of the CALPUFF model for evaluating visibility impacts associated

with pollution control options included in BART analyses.  Over the past decade, several investigators111

                                                           

107 See 77 Fed. Reg. at 42,841.   

108 Id. (emphasis added).

109 See Train, 421 U.S. at 79.

110 See 77 Fed. Reg. at 42,841.   

111 See J. Scire,et al., Southwest Wyoming Regional CALPUFF Air Quality Modeling Study (Vol. I) (2001) (prepared

for the Wyoming Dept of Environmental Quality) (hereinafter “Southwest Wyoming Modeling Study”); R Morris.

et. al., Evaluation of the CALPUFF Chemistry Algorithms (2005) (presented at A&WMA 98th Annual Conference and

Exhibition, June 21‐25, 2005 Minneapolis, Minnesota); P. Karamchandani, et.al, Development of an Improved

Chemistry Version of CALPUFF and Evaluation Using the 1995 SWWYTAF Data Base (2009) (presented at the Air &
SRP Comments on Proposed Regional Haze Rule	 Page	7‐2

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

compared field measurements of sulfates and nitrates with corresponding values predicted by CALPUFF

version 5.8, the EPA‐approved version for use in BART applications.  Those studies concluded that

version of the model over‐predicts particulate nitrate formation by as much as a factor of 3 to 4 under

wintertime conditions.

EPA specifically acknowledged the shortcomings of the current CALPUFF model’s chemistry in the

preamble to the 2005 BART rule, as follows:   

(1) “[T]he simplified chemistry in the [CALPUFF] model tends to magnify the actual visibility

effects of that source,”112; and (2) “[w]e understand the concerns of commenters that the

chemistry modules of the CALPUFF model are less advanced than some of the more recent

atmospheric chemistry simulations.  In its next review of the Guideline on Air Quality Models,

EPA will evaluate these and other newer approaches.”113

Despite EPA’s recognition of the limitations of CALPUFF version 5.8, and its commitment to review

newer approaches, EPA has not yet conducted the promised evaluation of the CALPUFF model and

continues to rely on CALPUFF version 5.8 in BART visibility modeling.  However, model development has

advanced independently, and in November 2010, CALPUFF’s developer, TRC, released a new version of

CALPUFF (version 6.4; now version 6.42) to fix certain coding “bugs” in the EPA‐approved version of the

model (version 5.8) and to improve the chemistry module.   

Both versions of the CALPUFF model (version 5.8 and version 6.42 with the improved chemistry options)

were evaluated by AECOM using the 1995 Southwest Wyoming Technical Air Forum database,114

available from the Wyoming Department of Environmental Quality.  Sulfates and nitrates that were

predicted by the two models were compared with actual measured values obtained at the Bridger

Wilderness Area site and the Pinedale site.  For the two model configurations, the results for sulfates

were very similar.  However, the EPA‐approved CALPUFF model (version 5.8) was found to significantly

over‐predict nitrates by a factor of 2 to 3.  

These results are similar to an independent evaluation of CALPUFF conducted by Scire et al.115  The

performance of CALPUFF version 6.42 coupled with use of measured ammonia concentrations (similar

                                                                                                                                                                                               

Waste Management Association Specialty Conference on Guidelines on Air Quality Models: Next Generation of

Models, October 28‐30, 2009, Raleigh, North Carolina).

112  See 70 Fed. Reg. at 39,121 (emphasis added).

113  Id. at 39,123.

114 See Southwest Wyoming Technical Air Forum, Wyoming Long Term Strategy for Visibility Protection, 2003

Review Report, available at http://deq.state.wy.us/aqd/prop/2003AppF.pdf (background and database

description).

115 See Southwest Wyoming Modeling Study (Vol. I).
SRP Comments on Proposed Regional Haze Rule	 Page	7‐3

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

to the monthly varying background ammonia used in the 2008 CGS BART modeling) was much

improved, with an over‐prediction of approximately 4 percent at the Pinedale site and approximately 28

percent at the Bridger site.  These over‐predictions were 2 to 3 times less than the over‐predictions

produced when the EPA‐approved CALPUFF version 5.8 was used.116  This result makes CALPUFF version

6.42 nearly unbiased in the evaluation of nitrate concentrations for these databases.

The two models were also evaluated in a sensitivity analysis conducted by Atmospheric and

Environmental Research, Inc.117  Both CALPUFF version 5.8 and CALPUFF version 6.42 were run with the

Interagency Workgroup on Air Quality Modeling (IWAQM) default ammonia background concentration

of 1 part per billion (ppb).  The results showed the same trend as that noted above: the improved

CALPUFF predictions were about a factor of 2 lower than those from the EPA‐approved version of

CALPUFF.  These results indicated that with the same ammonia background, the more advanced

CALPUFF model (version 6.42) would be expected to predict lower nitrate concentrations than the

current EPA‐approved version 5.8.

The use of CALPUFF version 6.42 supports a state‐of‐the‐art upgrade to the chemistry that EPA indicated

was needed in its July 6, 2005 BART Rule.  Although EPA has not yet approved the use of CALPUFF

version 6.42, SRP had its contractor provide results for this version of the model for EPA’s consideration

in an important weight‐of‐evidence demonstration of the more likely visibility effects of NOX emission

reductions at CGS.  The results of this analysis are provided in Attachment E to these comments.118

7.1.2    EPA’s Use of Constant Ammonia Background Concentration Over‐Predicts Visibility Benefits

Another factor that leads to over‐prediction of nitrate effects on visibility is selection of the background

ammonia concentrations used as inputs to the CALPUFF model.  EPA used a default constant 1.0 ppb

value for background ammonia concentrations in the modeling performed in support of the proposed

FIP, rejecting Arizona’s use of variable background ammonia concentrations in its visibility modeling.119  

SRP believes Arizona was well within the bounds of its discretion in its choice to rely on variable

ammonia concentrations, and EPA has no basis for disapproving that determination.  EPA’s approach

fails to account for known variations in monthly or seasonal ammonia concentrations and is an

unrefined approach to visibility modeling.

                                                           

116 See J. Scire, et al., New Developments and Evaluations of the CALPUFF Model at 10, 11 (2012) (presented at 10th

Conference of Air Quality Models), available at http://www.epa.gov/ttn/scram/10thmodconf/presentations/3‐5‐

CALPUFF_Improvements_Final.pdf.  

117 P. Karamchandani, et al, Development of an Improved Chemistry Version of CALPUFF and Evaluation Using the

1995 SWWYTAF Data Base (2009) (presented at the Air & Waste Management Association Specialty Conference on

Guideline on Air Quality Models: Next Generation of Models, October 28‐30, 2009, Raleigh, North Carolina).		

118  AECOM, Visibility Improvement Modeling for the Coronado Generating Station (Sept. 2012).

119 See 77 Fed. Reg. at 42,849.   
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EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

The National Renewable Energy Laboratory (NREL) issued a report in March 2012 in which it evaluated

the Navajo Generating Station (NGS) and air visibility regulations.  Within this report, NREL found that:

“[B]ackground ammonia concentrations are a critical factor in predicting ammonia nitrate

formation.  The assumed ammonia concentrations input to SRP’s and EPA’s analyses differed

significantly ... and are likely responsible for the majority of the differences between the SRP and

EPA model results.  The high nitrate episodes measured at IMPROVE sites in the Colorado

Plateau are cold season, rather than warm season events.  Similarly, the high nitrate episodes

modeled for the Class I areas in the region are cold season, rather than warm season events.  

Therefore, it is most crucial to get the ammonia concentrations correct in the cool months, as

that is when both modeling and monitoring indicate that there can be relatively high nitrate

days.  Limited studies have been done to date to measure ambient air ammonia concentrations

in the Four Corners region ... The studies summarized above indicate that in more remote areas

of the southwest, especially during winter months, there is much less ammonia available in the

atmosphere.  The ammonia ranges used by EPA’s modeling, ranging from 0.7 ppb to 1 ppb in the

winter months, depending on modeled Class I area, are much higher than measured in the

above studies.  For example, winter month ammonia measured at Mesa Verde was in the 0.1 to

0.2 ppb range.  As pointed out in the referenced SRP ammonia study, use of EPA’s higher

ammonia values produces modeled ammonium nitrate concentrations an order of magnitude

higher than measured values for many cases.  On the other hand, use of the SRP ammonia

background values in CALPUFF produces a much better comparison between modeled and

measured values.”120

Similar to the analysis for NGS, the visibility analysis for CGS included in Arizona’s BART analysis used

higher ambient ammonia background concentrations in the summer months (May through September),

and lower ambient ammonia background concentrations in the winter months (December through

February).  Use of these factors is consistent with the trend in measured background ammonia

concentrations acknowledged in the NREL report.  

When the IWAQM Phase 2 guidance121 was issued fourteen years ago, CALPUFF did not have the

capability of accommodating monthly ammonia background concentrations and only allowed a single

input value.  Since then, CALPUFF has been updated to receive monthly varying ammonia

concentrations.  Unfortunately, the IWAQM guidance on the recommended input values has not kept

pace with the CALPUFF model’s capability.  It is clear at this time that EPA’s reliance on a constant value

                                                           

120 Hurlbut, D., et al. National Renewable Energy Laboratory. Navajo Generating Station and Air Visibility

Regulations: Alternatives and Impacts, at 80 (March 2012), available at www.nrel.gov/docs/fy12osti/53024.pdf.

(emphasis added).

121 EPA OAQPS, IWAQM Phase 2 Summary Report and Recommendations, EPA‐454/R‐98‐019 (Dec. 1998) available

at http://www.epa.gov/scram001/7thconf/calpuff/phase2.pdf.
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is an outdated approach that is not scientifically credible.

Using ammonia concentration inputs that best reflect ambient conditions results in more accurate

CALPUFF predictions, and is the best scientific approach for CALPUFF modeling.  Therefore, EPA has no

basis for rejecting Arizona’s use of variable background ammonia concentrations in disapproving the SIP.  

Further, EPA’s reliance on a constant default value disregards actual advances in the CALPUFF model

and renders EPA’s own visibility modeling an improper basis on which to make a BART determination.  

The visibility modeling analysis conducted in support of these comments uses monthly varying

background ammonia concentrations (refer to Attachment E to these comments).  

7.2 Case Study: Mohave Generating Station Plant Closure

EPA places great reliance on the outcomes of visibility modeling to support BART determinations, but it

is clear that CALPUFF is an imperfect modeling tool.  This is demonstrated by a recent evaluation of the

actual visibility benefits associated with the closing of a large coal‐fired power plant in the southwest,

the Mohave Generating Station (MGS).  MGS was a 1,580 megawatt coal‐fired power plant located in

Laughlin, Nevada, approximately 75 miles southwest of the Grand Canyon National Park (GCNP).  The

plant closed on December 31, 2005 following the promulgation of FIP requirements in which MGS was

required to install emission controls to reduce emissions of SO2, NOx and PM.  As stated in EPA’s FIP Fact

Sheet, “EPA believes that adopting the requirements ... is an appropriate way to address concerns

regarding the impact of SO2 emissions from MGS on visibility impairment at the Grand Canyon National

Park (GCNP) and will allow for reasonable progress toward the national visibility goal with respect to

such impact.”122

Terhorst and Berkman conducted an analysis after the plant closed to determine whether, in the

prolonged absence of plant operations, air quality in the GCNP has improved.123  The results were as

follows:

“We compared pre‐ and post‐closure visibility in the Canyon and at nearby unaffected sites in

order to identify the level of degradation attributable solely to MPP [Mohave Power Project].  

After controlling for the prevailing environmental and anthropogenic factors in the region, we

found virtually no evidence that the MPP closure improved visibility in the Grand Canyon; or,

equivalently, that the plant’s operation degraded it.  Mean visibility (deciviews) and light

extinction in GCNP did not respond to the closure in a statistically significant fashion.  Sulfate

levels did drop throughout the park, but not by an amount sufficient to induce a perceptible

                                                           

122 See EPA, Fact Sheet, Revision of the Visibility FIP for Nevada: Final Rule (June 6, 2001), available at

http://www.epa.gov/region9/air/mohave/nevadafipfact0202.pdf.  

123 J., Terhorst, et al, Effect of Coal‐Fired Power Generation on Visibility in a Nearby National Park. 44 Atmospheric

Environment (April 2010) (emphasis added).
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improvement in visibility.  We are thus unable to conclude that the closure improved visibility

in the Grand Canyon.  Our findings are consistent with, and indeed were predicted by, the

results of tracer/receptor analyses performed over the past two decades, which consistently

noted low correlation between MPP emissions and GCNP visibility.  They stand in contrast to the

various atmospheric transport models employed by Project MOHAVE [Measurement of Haze

and Visual Effects], which predicted that visibility would have improved by 5% or more after the

closure.  Since recent applications of CALPUFF (Nevada Division of Environmental Protection,

2009; Paine and Kostrova, 2008) continue to predict that retrofitting MPP will improve visibility

in the Grand Canyon, our results raise questions about the reliability of CALPUFF .  These

concerns are especially pertinent in light of EPA’s designation of CALPUFF as the preferred

model for assessing the effects of long‐range pollution transport on air quality in Class I visibility

areas under the Regional Haze Rule.”124

This analysis found that, contrary to the predictions of the CALPUFF model, a significant reduction in

pollutants from a large power plant did not “induce a perceptible improvement in visibility.”  This study

provides further evidence that there is substantial over‐prediction bias associated with the CALPUFF

model that EPA did not take into account when considering the visibility improvement factor in

evaluating BART control options for CGS.

  

7.3 EPA Must Consider Visibility Benefits from NOx Controls within the Context of Nitrate

Contributions to Regional Haze

EPA’s focus on NOx emission reductions in the proposed FIP gives the impression that NOx emissions are

a significant contributor to haze in the Colorado Plateau region, where CGS is located.  This assertion is

contrary to the extensive analysis of haze contributors that has been conducted in this region.  Visibility

in the Colorado Plateau region, as measured by the Interagency Monitoring of Protected Visual

Environments (IMPROVE) monitoring network,125 is generally excellent and the visibility impairment that

does occur is largely attributable to natural sources, including Rayleigh scattering, wind‐blown dust, and

smoke from wildfires.  The significance of natural source contribution to haze was illustrated by the

                                                           

124 Id. (emphasis added).

125 The IMPROVE program is a cooperative measurement effort governed by a steering committee composed of

representatives from federal and regional‐state organizations.  The IMPROVE monitoring program was established

in 1985 to aid the creation of federal and state implementation plans for the protection of visibility in Class I areas

(156 national parks and wilderness areas) as stipulated in the 1977 amendments to the Clean Air Act.  The

objectives of IMPROVE are to: (1) establish current visibility and aerosol conditions in mandatory class I areas; (2)

identify chemical species and emission sources responsible for existing man‐made visibility impairment; (3)

document long‐term trends for assessing progress towards the national visibility goal; and (4) with the enactment

of the regional haze rule, provide regional haze monitoring representing all visibility‐protected federal class I areas

where practical.  See WESTAR Council RA BART Phase II Working Group.  Recommendations for Making Attribution

Determinations in the Context of Reasonably Attributable BART, (May, 2003), available at

http://www.wrapair.org/forums/mtf/documents/ravi_bart/Final_RA_BART_Report.pdf.  
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Grand Canyon Visibility Transport Commission (GCVTC) in their detailed analysis of the relative

contributions of emission sources to light extinction (or visibility impairment) over GCNP.126  The

technical analyses performed by the GCVTC further showed that nitrate aerosols are a very small

relative contributor to light extinction in GCNP, as shown in Figure 7‐1 below.

Figure 7‐1: Sources of Light Extinction Over the Grand Canyon National Park

Subsequent analyses conducted by the Western Regional Air Partnership (WRAP) also looked at haze

related to nitrate aerosols, including an analysis of NOx emissions from stationary sources to support

state development of long‐term strategies for PM and NOx.

127  The study included analysis of current

and future emissions, ambient monitoring data, and limited modeling data.  The WRAP concluded that

stationary source emissions of PM probably cause less than 2 percent of the region’s visibility

impairment and that stationary source emissions of NOx, which produce nitrate aerosols, probably cause

only about 2 to 5 percent of the impairment on the Colorado Plateau.128

                                                           

126 See Grand Canyon Visibility Transport Commission.  Recommendations for Improving Western Vistas (June 10,

1996), available at http://www.wrapair.org/WRAP/reports/GCVTCFinal.PDF.   

127 See 40 CFR 51.309 (d)(4)(v).

128 WRAP Market Trading Forum.  Stationary Source NOx and PM Emissions in the WRAP Region: An Initial

Assessment of Emissions, Controls, and Air Quality Impacts.  Final Report, at I‐3 (Oct. 1, 2003), available at  

http://www.cabq.gov/airquality/pdf/appendixho.pdf.  

Elemental

Carbon

6%

Nitrate

4%

Sulfate

18%

Rayleigh

Scattering

40%

Organics

14%

Coarse

Particles

14%

Soil Dust

4%

Source: CGVTC
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In the 1999 regional haze rule, EPA directed states to consider all sources of man‐made haze in

developing long‐term strategies.129  While there is a significant focus on BART for major stationary

sources in the first planning period, it is clear that there are numerous other contributors to regional

haze, and EPA’s FIP fails to recognize this bigger picture.  While imposition of new NOx emission control

requirements under the FIP will result in a quantitative reduction in emissions, actual achievement of

any appreciable visibility benefits will not occur because NOx from power plants is a very small

contributor to regional haze impairment.  

Arizona properly determined that combustion controls satisfy BART requirements for CGS, following

EPA’s direction in the regional haze regulations for states to “base their decisions on the need for, and

levels of, emissions targets for these pollutants on the degree to which such pollutants contribute to

regional haze impairment in the Class I areas addressed by their SIPs”.130  Arizona’s proposed NOx BART

emission limits recognize that costly post‐combustion controls are not justified given the negligible

degree to which stationary source NOx emissions contribute to regional haze visibility impairment.

7.4 EPA Improperly Dismisses Arizona’s Visibility Impacts Analysis  

The proposed rule correctly acknowledges that, “the RHR [regional haze rule] and the BART Guidelines

do not prescribe a particular approach to calculating or considering visibility benefits across multiple

Class I areas.”131  Indeed, the CAA and the BART rules leave states with considerable discretion as to the

manner in which they will take visibility impacts, including impacts that may occur in more than one

Class I area, into account.  EPA’s proposed rule seeks impermissibly to restrict that congressionally

granted state discretion, and it is, therefore, unlawful.

EPA’s proposed rejection of Arizona’s visibility impacts analysis for CGS is also irreconcilably at odds with

EPA’s own rules and its guidance to the states.  The BART Guidelines make clear that, in assessing

projected visibility improvements from candidate BART controls, a state is to:

“[A]ssess the visibility improvement based on the modeled change in visibility impacts for the

pre‐control and post‐control emission scenarios.  You [the state] have flexibility to assess

visibility improvements due to BART controls by one or more methods.  You may consider the

frequency, magnitude, and duration components of impairment.”132  

                                                           

129 See 64 Fed. Reg. at 35,735.

130 See Id. at 35,752.  

131 See 77 Fed. Reg. at 42,841.   

132 See 70 Fed. Reg. at 39,170 (emphasis added).
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There is, in short, no prescribed method for states to consider and weigh this factor.  Thus, EPA has no

legal grounds for disapproving a SIP based on the “method” the state has chosen to consider visibility

impacts or improvements.

In assessing projected visibility impacts associated with emissions from CGS and possible BART

candidate controls, Arizona decided to evaluate a visibility index derived from an average of modeled

visibility improvements at the nine Class I areas closest to CGS.  This approach to evaluating this BART

factor was well within the state’s extraordinarily broad discretion to assess visibility under the BART

rules, and the proposed rule itself describes the method chosen by Arizona as “somewhat similar to the

sum of benefits over the nine areas,” (i.e., the cumulative methodology that EPA now appears to

prefer).133  Moreover, at one point in the preamble to the proposed rule, EPA appears to acknowledge

that the methodology Arizona used for CGS is acceptable even under EPA’s improperly limited view of

state discretion in this area.  Specifically, EPA stated:

“[A] more complete assessment of the degree of visibility improvement for candidate BART

controls would include consideration of the number of areas affected and the degree of visibility

improvement expected in all areas.  One could conduct this type of analysis by summing the

benefits over the areas, or by some other quantitative or qualitative procedure.”134  

EPA does not explain how or why Arizona’s “quantitative ... procedure” of averaging deciview (dv)

impacts associated with CGS emissions is in any way inconsistent with the statute, EPA’s rules, or even

EPA’s own statement in this proposed rule as to what it expects from states.

In conducting its own visibility assessment to support its proposed FIP for CGS, EPA decided to “rel[y]

heavily on the maximum dv improvement and the number of areas showing improvement, with

cumulative improvement providing a supplemental measure that combines information on the number

of areas and on individual area improvement.”135  But whatever EPA’s preference, EPA has no discretion

to substitute its method or its conclusion for those of the state, which is precisely what EPA has done in

its proposed rule.  

The BART rules provide no support for the conclusion that such a cumulative‐impact approach is

required of states.  On the contrary, the rules make clear that the initial focus is expected to be – and

that at a minimum the states have authority to rest their analysis on – the most impacted area, which

                                                           

133 See 77 Fed. Reg. at 42,850.   

134 See Id. at 42,841 (emphasis added).

135 See Id. at 42,857.   
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often will be the “nearest Class I area” to the facility in question.136  The rules then indicate that it is

appropriate to take account of not only impacts at the nearest Class I area but also impacts at other

nearby Class I areas, for the purpose of “determin[ing] whether effects at those [other] areas may be

greater than at the nearest Class I area.”137  Of critical importance is that EPA’s rules then state: “If the

highest modeled effects are observed at the nearest Class I area, you [i.e., the state] may choose not to

analyze the other Class I areas any further as additional analyses might be unwarranted.”138   

Even EPA’s own proposed rule for Arizona confirms that EPA’s cumulative approach has not traditionally

been applied, characterizing the maximum‐impacted‐area approach as “the typical visibility metric.”139  

Likewise, in another recent regional haze rulemaking, EPA itself relied exclusively on a maximum impact

area approach to assessing visibility impairment.  EPA’s final rule establishing a BART FIP for the Reid

Gardner Generating Station in Nevada is based on consideration of visibility in the maximum impact

area alone even though EPA found that Reid Gardner’s emissions affected visibility in five Class I

areas.140  If EPA is free to deviate from the cumulative visibility assessment methodology, then Arizona

surely is as well.

It is thus abundantly clear that EPA’s BART rules envision – or, at a minimum, allow – a visibility

improvement analysis that is focused on visibility impacts in the most impacted area.  Arizona’s

consideration of an average visibility impacts index is, if anything, an even more thorough type of

evaluation than that required by the BART rules.  EPA’s own proposed rule and its BART Guidelines

demonstrate that Arizona’s consideration of visibility impacts associated with CGS emissions not only is

fully consonant with the BART rules, but is an even more searching assessment than what is required by

the law.

Although EPA makes clear its policy preference for the use of a “cumulative” visibility impacts

assessment (which in any event it has no grounds for imposing on Arizona), there is no sound public

policy reason for adopting such a methodology.  EPA explains its rationale for attempting to require

adoption of the cumulative impacts approach in the following manner:

“Note that the issue here is not whether an individual in a given time and place would perceive

the deciview benefits occurring at different Class I areas and under possibly different

                                                           

136 See 70 Fed. Reg. at 39,170 (“One important element of the [modeling] protocol is in establishing the receptors

that will be used in the model.  The receptors that [the state] use[s] should be located in the nearest Class I area

with sufficient density to identify the likely visibility effects of the source.”).   

137 Id. at 39,162 (emphasis added).

138 Id. (emphasis added).

139 See 77 Fed. Reg. at 42,851.   

140 See 77 Fed. Reg. at 50,936 and 50,945; EPA “did not rely on the specific metric advocated by the commenters,

i.e. the sum of benefits over the areas.”
SRP Comments on Proposed Regional Haze Rule	 Page	7‐11

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

meteorological conditions.  Rather, the issue is accounting in some way for the full set of

expected visibility benefits.  A national program for addressing regional haze must inherently

address the multiple areas that occur in a region.”141  

To be relevant to the environmental effect that the regional haze program addresses, the metric by

which visibility improvement is determined for purposes of assessing BART for a particular facility must

reflect actual human perception of visibility.142  Indeed, human perceptibility is the only metric that

actually can account for the full set of expected visibility benefits because it is the only metric that can

differentiate between actual benefits and de minimis or hypothetical changes in visibility conditions.  

The cumulative‐impact approach has no tie to human perception and can only distort a BART analysis.  It

arbitrarily magnifies the benefit that might be associated with emission limitations at a single source.   

The cumulative‐impact approach’s artificial inflation of projected visibility benefits is demonstrated by

the fact that this methodology would yield different results if a given Class I area were subdivided into

two or more areas, increasing the benefit simply by increasing the number of locations to which the

analysis applies.  Similarly, the arbitrary nature of this approach is illustrated by the fact that it would

equate an accumulation of vanishingly small – indeed, merely theoretical – visibility “benefits” in several

different areas with a much larger and plainly perceptible improvement in a single area.  It cannot

reasonably be asserted that visibility improvements that are imperceptible in each of several Class I

areas can be the equivalent of – or even deemed more significant than – a much larger and humanly

perceptible improvement in a single area.

Accordingly, EPA’s reliance on purported cumulative visibility impacts to support its proposed

disapproval of Arizona’s NOx BART determination for CGS is unjustified and unsound.  This approach

cannot be imposed on a state, and a state’s decision not to use it is no basis for disapproving the state’s

SIP.

                                                           

141 See 77 Fed. Reg. at 42,841 n.26.

142 The fact sheet accompanying the proposed rule asserts that “[a] difference of 0.5 deciviews is generally

considered a perceptible change.” See EPA, Fact Sheet, Proposed Partial Approval and Partial Disapproval of

Arizona’s Regional Haze Plan and Proposed Federal Plan (July 27, 2012), available at

http://www.epa.gov/region9/air/actions/pdf/az/az‐haze‐factsheet.pdf. This assertion is unsupported.  The

regional haze rules and BART Guidelines indicate that 1.0 dv may generally be considered the threshold for human

perceptibility.  See 64 Fed. Reg. at 35,726‐27; 70 Fed. Reg. at 39,120.  Moreover, the most recent science confirms

that a 0.5 dv change in visibility conditions is not humanly perceptible.  Indeed, the best available evidence

establishes that a much more significant change is required before the human eye can detect a shift in conditions.  

See, e.g., Development and Applications of a Standard Visual Index, 28 Atmospheric Environment, 1049‐1054

(1994) (finding that a change of approximately 1 to 2 dv is necessary for human perception); Just‐Noticeable

Differences in Atmospheric Haze, 52 Journal of the Air &Waste Management Association, 1238‐1243 (2002)

(finding that a change of at least 1.8 dv is necessary for human perception).  Accordingly, EPA’s assertion that a 0.5

dv change is perceptible to a human observer is unjustified and inconsistent with the best available scientific

information.
SRP Comments on Proposed Regional Haze Rule	 Page	7‐12

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

7.5 EPA’s 0.5 Deciview Threshold is Without Basis

EPA cannot possibly justify its proposed disapproval of the Arizona SIP with respect to CGS NOx BART

requirements on the basis of the magnitude of projected visibility improvements from candidate BART

controls.  First, like the CAA itself, EPA’s own BART rules give states essentially unlimited discretion in

determining appropriate “thresholds” to use in considering whether projected visibility improvements

do or do not warrant a particular control.  The BART Guidelines merely make a “[s]uggestion” that

states “[u]se ... a comparison threshold, as is done for determining if BART‐eligible sources should be

subject to a BART determination.”143  Thus, there is not even a requirement that states use any sort of

comparison threshold in considering the visibility‐improvement BART factor for a given facility.   

If a state does choose to use a comparison threshold, it may do so “in a number of ways,” which may

take into account, “e.g.[,] the number of days or hours that the threshold was exceeded, a single

threshold for determining whether a change in impacts is significant, or a threshold representing an x

percent change in improvement.”144  EPA stated, in promulgating the BART Guidelines, that using a

comparison threshold is “an” – not necessarily “the” – “appropriate way to evaluate visibility

improvement,” but emphasized that:

“[T]he States have flexibility in setting absolute thresholds, target levels of improvement, or de

minimis levels since the deciview improvement must be weighed among the five [BART] factors,

and States are free to determine the weight and significance to be assigned to each factor.  For

example, a 0.3, 0.5, or even 1.0 deciview improvement may merit stronger weighting in one

case versus another, so one “bright line” may not be appropriate.”145  

Thus, EPA is without basis for establishing in the proposed rule a 0.5 dv comparison threshold146 as a

touchstone for analysis of impacts from CGS BART controls.  Even if EPA could impose a 0.5 dv

comparison threshold, it is only by substituting its own preferred modeling methodology (something

EPA cannot lawfully do, as discussed herein) that EPA can project that requiring SCR at Unit 1147 at an

unprecedented low emission rate would barely yield a projected improvement of more than 0.5 dv at

one area.148  But, as discussed above, EPA cannot impose any comparison threshold on a state – let

                                                           

143 See 70 Fed. Reg. at 39,129‐30, 39,170 (emphasis added).   

144 Id. at 39,130.

145 Id.

146 See 77 Fed. Reg. at 42,851 and 42,863‐64 & Table 23.

147 In this EPA control case, the Unit 1 SCR is in addition to SCR with a 0.080 lb/MMBtu BART limit at Unit 2.

148 See 77 Fed. Reg. at 42,863‐64 & Table 23.   
SRP Comments on Proposed Regional Haze Rule	 Page	7‐13

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

alone one as low as 0.5 dv – which even EPA has acknowledged can be considered below the level of

human perceptibility.149   

                                                           

149 See 64 Fed. Reg. at 35,726‐27; 70 Fed. Reg. at 39,120.
SRP Comments on Proposed Regional Haze Rule	 Page	8‐1

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

8.0   EPA Must Properly Account for Energy and Non‐Air Quality Environmental

Impacts  

In the proposed rule, EPA describes, in general terms, Arizona’s analysis of the energy and non‐air

quality environmental impacts of BART controls for CGS.  EPA states, for instance, that Arizona identified

“only minor energy and non‐air quality impacts for SO2 or PM10 [particulate matter nominally less than

10 microns] control strategies.”150  The proposed rule also notes, however, that the state’s analysis

identified more significant energy and non‐air quality environmental effects associated with various NOx

control options.  For instance, the state concluded that SCR “will cause an additional pressure drop in

the flue gas system due to the catalyst, increasing power requirements.”151  The state also concluded

that the use of either SCR or SNCR will affect the ammonia levels in fly ash and “could affect the decision

of facility managers to sell or dispose of fly ash” and that SCR and SNCR “may involve potential safety

hazards associated with the transportation and handling of anhydrous ammonia.”152

It is appropriate and necessary to consider each of these significant impacts in the course of completing

a five‐factor analysis to select BART.  However, EPA’s proposed rule states only that “ADEQ did not cite

any of these potential energy and non‐air impacts as the basis for eliminating any otherwise feasible

control strategies for NOx,” and that “EPA concurs that these impacts do not warrant elimination of any

of the control options.”153  And in the proposed rule’s specific assessment of Arizona’s BART

determinations for CGS, EPA fails even to mention the energy and non‐air quality environmental impacts

factor.154   

EPA similarly downplays this factor in its revised BART determination in the proposed FIP,155 presenting

the narrow conclusion that “potential energy and non‐air quality impacts do not warrant elimination of

any of the otherwise feasible control options for NOx at any of the sources.”156   

                                                           

150 See 77 Fed. Reg. at 42,841.   

151 See Id.

152 See Id.

153 See Id.

154 See Id. at 42,849‐52.   

155 See Id. at 42,853, (stating that SCR and other NOx emission controls at CGS “may also have modest energy

impacts” and that the costs of such impacts “are included in the cost analyses and are not considered further in

this section”); Id. at 42,853‐54, (suggesting that SCR and SNCR will not have a significant impact on fly ash

ammonia content and that such an impact can be mitigated); Id. at 42,854, (“EPA concludes that the use of

ammonia does not pose any additional safety concern as long as established safety procedures are followed.”).

156 See Id. at 42,854.
SRP Comments on Proposed Regional Haze Rule	 Page	8‐2

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

EPA’s assessment of energy and non‐air environmental impacts and its narrow evaluation of whether

consideration of this factor, in isolation, “eliminat[es]” any control option are untenable.  The state

identified significant energy and non‐air quality environmental impacts associated with requiring SNCR

or SCR at CGS.  These impacts are not only relevant in cases where they are an independent reason for

eliminating a particular control option from consideration.  On the contrary, this factor must be weighed

and considered in conjunction with the other BART factors in the overall assessment of what control

option constitutes BART for a particular source.  EPA’s approach minimizes the role that this factor can

conceivably play in a BART analysis, which is beyond EPA’s authority.157   

                                                           

157 Cf. Corn Growers, 291 F.3d at 6‐7 (finding that EPA’s original 1999 regional haze rules had improperly divorced

consideration of the BART visibility benefits factor from the other BART factors).
SRP Comments on Proposed Regional Haze Rule	 Page	9‐1

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

9.0   Full Approval of Arizona’s BART Determinations is the Only Appropriate

Course of Action Available to EPA

SRP agrees with EPA’s proposed approval of Arizona’s BART determinations for PM and SO2.  However,

after detailed review of the proposed rule, SRP believes EPA’s proposed BART determination for NOx is

unsupported by EPA’s analysis of the five BART factors.  Use of LNB/OFA on both CGS units meets the

BART requirements for CGS, as demonstrated by Arizona’s BART assessment.  

9.1 EPA Must Accept Arizona’s BART Determination for NOx  

Arizona’s NOx BART analysis – a complete and thorough five‐factor analysis conducted in accordance

with the BART Guidelines – resulted in a reasonable and appropriate determination for NOx BART for

CGS.  In response to EPA’s proposed alternate BART determination in the proposed FIP, SRP performed

an assessment of the critical components of a BART analysis for CGS, including control costs and the

visibility improvements associated with the control options.  The results of this analysis are summarized

in Table 9‐1.   

SRP evaluated the Class I area with the highest visibility impacts when considering modeled baseline

emissions – Petrified Forest National Park – which is also the closest Class I area to CGS.  Petrified Forest

is the appropriate focus of analysis because EPA’s rules state “if the highest modeled effects are

observed at the nearest Class I area, you [i.e., the state] may choose not to analyze the other Class I

areas any further as additional analyses might be unwarranted.”158

Because BART is a component of the CAA’s visibility program, it is more crucial to evaluate control costs

in relation to the visibility improvements that may be expected using a dollars per deciview ($/dv)

metric.  Such an analysis is presented in Table 9‐1.

EPA’s BART regulations do not establish (nor do they require states to establish) any specific thresholds

for cost‐effectiveness, and EPA should defer to Arizona’s approach on this issue.  However, it is clear

that the incremental cost per deciview of each control scenario is significantly higher than the cost per

deciview presented in ADEQ’s proposal.  In looking at the costs on a $/dv basis, it is clear that LNB/OFA

represents a reasonable level of control under BART.   

                                                           

158 See 70 Fed. Reg. at 39,170.
SRP Comments on Proposed Regional Haze Rule	 Page	9‐2

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1Table 9‐1: Cost and Visibility Analysis for NOx Emissions from CGS Units 1 and 2 Using CALPUFF Version 5.8

Control Option1

Emission

Rate

(lb/MMBtu)2

Emissions

Removed

from

Baseline

(tons/yr)

Total

Annualized

Cost ($/yr)

Cost Effectiveness

($/ton)

Visibility Improvement

at Class I Area with

Maximum Impact3

(deciviews)

Average

Incremental

from

Previous

Change

from

Baseline

Incremental

from

Previous

Baseline

U1 = 0.433

U2 = 0.466

‐‐‐‐‐  ‐‐‐‐‐  ‐‐‐‐‐  ‐‐‐‐‐  ‐‐‐‐‐  ‐‐‐‐‐  

U1 = LNB/OFA

U2 = LNB/OFA

U1 = 0.320

U2 = 0.320 5,840 $3,887,623 $666  ‐‐‐‐‐  0.58  ‐‐‐‐‐  

U1 = LNB/OFA

U2 = LNB/OFA/SCR

U1 = 0.320

U2 = 0.080 11,005 $14,419,323 $1,310 $2,039 0.76 0.18 

U1 = LNB/OFA/SNCR

U2 = LNB/OFA/SCR

U1 = 0.240

U2 = 0.080 12,912 $20,502,986 $1,588 $3,190 0.85 0.09 

U1 = LNB/OFA/SCR

U2 = LNB/OFA/SCR

U1 = 0.050

U2 = 0.080 17,449 $28,053,1464 $1,608 $1,664 1.12 0.27 

1 LNB = low‐NOx burners; OFA = overfire air; SCR = selective catalytic reduction; SNCR = selective non‐catalytic reduction2 lb/MMBtu = pounds per million British thermal unit3 Petrified Forest National Park was the Class I area with the highest estimated baseline visibility impacts at 1.69 deciviews, based on 4 This figure does not include additional particulate matter controls that may be necessary to ensure the particulate matter emission 

permit can be continuously achieved. If additional particulate matter controls are required, negligible visibility improvement would b

would escalate significantly as previously described in SRP’s letter to EPA dated August 24, 2012 (refer to Attachment B to these comm
SRP Comments on Proposed Regional Haze Rule	 Page	9‐3

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

Even without considering other energy and non‐air quality environmental impacts associated with the

implementation of SNCR or SCR, it is clear that the negligible visibility benefits realized from

implementation of post‐combustion controls are not justified by the exorbitant cost.

In support of SRP’s continuing belief that CALPUFF version 6.42 is the more scientifically credible model

to use for BART visibility analyses, SRP also evaluated visibility improvement based on this updated

model.  The results from this analysis are summarized in Table 9‐2 and echo the results obtained with

CALPUFF version 5.8.  However, CALPUFF version 6.42 provides a more realistic estimate of the potential

visibility improvements that may be achieved with additional emission controls.  As such, use of

CALPUFF version 6.42 results in cost‐effectiveness values that provide even stronger evidence that

selection of post combustion controls as BART for CGS is inappropriate and unsupportable.

Regardless of which CALPUFF model version is used, the results remain the same – LNB/OFA represents

NOx BART for CGS Units 1 and 2.  EPA should, therefore, withdraw its proposed rule with respect to NOx

BART at CGS and affirm Arizona’s NOx BART determination for CGS.

9.2 EPA’s BART Determination for PM is Reasonable and Appropriate

SRP supports EPA’s proposed approval of Arizona’s PM BART determination for CGS.  That proposed

determination is consistent with the CAA, and is supported by the technical record in this rulemaking.  

Within the proposed rule, EPA specifically requested comment on “whether additional cost‐effective

upgrades to the existing electrostatic precipitators (ESPs) are available that would warrant a lower

emission limit.”159  SRP does not believe any upgrades to the ESPs are warranted as part of the BART

determination, as SRP has in place a plan to optimize performance of the existing equipment.  As part of

the consent decree between SRP and EPA for CGS, SRP is required to operate the ESPs “at all times

when the Unit it serves is in operation to maximize PM emission reductions, provided that such

operation of the ESP is consistent with the technological limitations, manufacturers’ specifications, and

good engineering and maintenance practices for the ESP.”160  This requirement also is reflected in CGS’

current Title V operating permit.

                                                           

159 See 77 Fed. Reg. at 42,851.

160 See Civil Action No. 2:08‐cv‐1479‐JAT.  Consent Decree ¶ 63, United States of America v. Salt River Project

Agricultural Improvement and & Power District, No. 08‐1479 (D. Ariz. Dec. 22, 2008).  Filed August 12, 2008.
SRP Comments on Proposed Regional Haze Rule	 Page	9‐4

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1Table 9‐2: Cost and Visibility Analysis for NOx Emissions from CGS Units 1 and 2 Using CALPUFF Version 6.42

Control Option1

Emission

Rate

(lb/MMBtu)2

Emissions

Removed

from

Baseline

(tons/yr)

Total

Annualized

Cost ($/yr)

Cost Effectiveness

($/ton)

Visibility Improvement

at Class I Area with

Maximum Impact3

(deciviews)

Average

Incremental

from

Previous

Change

from

Baseline

Incremental

from

Previous

Baseline

U1 = 0.433

U2 = 0.466

‐‐‐‐‐  ‐‐‐‐‐  ‐‐‐‐‐  ‐‐‐‐‐  ‐‐‐‐‐  ‐‐‐‐‐  

U1 = LNB/OFA

U2 = LNB/OFA

U1 = 0.320

U2 = 0.320 5,840 $3,887,623 $666  ‐‐‐‐‐  0.84  ‐‐‐‐‐  

U1 = LNB/OFA

U2 = LNB/OFA/SCR

U1 = 0.320

U2 = 0.080 11,005 $14,419,323 $1,310 $2,039 1.02 0.18 

U1 = LNB/OFA/SNCR

U2 = LNB/OFA/SCR

U1 = 0.240

U2 = 0.080 12,912 $20,502,986 $1,588 $3,190 1.09 0.07 

U1 = LNB/OFA/SCR

U2 = LNB/OFA/SCR

U1 = 0.050

U2 = 0.080 17,449 $28,053,1464 $1,608 $1,664 1.29 0.20 

1 LNB = low‐NOx burners; OFA = overfire air; SCR = selective catalytic reduction; SNCR = selective non‐catalytic reduction2 lb/MMBtu = pounds per million British thermal unit3 Petrified Forest National Park was the Class I area with the highest estimated baseline visibility impacts at 1.69 deciviews, based on 4 This figure does not include additional particulate matter controls that may be necessary to ensure the particulate matter emission 

permit can be continuously achieved. If additional particulate matter controls are required, costs would escalate as previously descri

dated August 24, 2012 (refer to Attachment B to these comments).
SRP Comments on Proposed Regional Haze Rule	 Page	9‐5

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

SRP also notes that the PM limit in the recently promulgated MATS Rule161 will be more stringent than

the PM limit that EPA rightly proposed to approve as BART.  As it makes sense for BACT to be more

stringent than BART, it likewise is appropriate for the MATS requirements to impose more stringent

compliance obligations on utilities than a BART determination.  The MATS are intended to protect the

public health from hazardous air pollutants, while BART is aimed at aesthetic concerns that Congress

intended the states to address very gradually.

Accordingly, EPA’s proposed approval of Arizona’s PM BART determination is consistent with both EPA’s

obligation to defer to state’s BART determinations and objectively reasonable when viewed in light of

what is required under MATS.

9.3 EPA’s BART Determination for SO2 is Reasonable and Appropriate

SRP supports EPA’s proposed approval of Arizona’s SO2 BART determination for CGS, and the technical

record demonstrates that approval is warranted.  

In the proposed rule, EPA specifically requested comment on “whether a lower emission limit may be

achievable when the units are burning a lower‐sulfur coal.”162  It is entirely inappropriate for EPA to

establish a BART limit that would be premised on any restriction of SRP’s fuel supply.  This type of

restriction would increase unit operating costs and reduce operational flexibility, and EPA provides no

technical record to support consideration of this emissions reduction option.  Furthermore, for reasons

discussed above in Section 9.2, the effective SO2 emission rate established in the MATS rule will be more

stringent than Arizona’s SO2 BART determination.   

Accordingly, EPA’s proposed approval of Arizona’s SO2 BART determination is both consistent with EPA’s

obligation to defer to state’s BART determinations and objectively reasonable when viewed in light of

what is required under MATS.

                                                           

161 See Fed. Reg. Vol. 77, No. 32.  National Emission Standards for Hazardous Air Pollutants from Coal‐ and Oil‐Fired

Electric Utility Steam Generating Units and Standards of Performance for Fossil‐Fuel‐Fired Electric Utility,

Industrial‐Commercial‐Institutional, and Small Industrial‐Commercial‐Institutional Steam Generating Units.  

February 16, 2012.

162 See 77 Fed. Reg. at 42,852.
SRP Comments on Proposed Regional Haze Rule	 Page	10‐1

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

10.0   SRP’s Review of EPA’s Proposed Enforceability Requirements

EPA’s proposed rule fails to adequately consider a number of issues that will impact the enforcement of

the proposed BART emission limits, including the proposed compliance schedule, monitoring

requirements, reporting requirements, and notification requirements.  Each of these issues is described

in more detail in this section.

10.1 EPA Must Implement an Appropriate Compliance Schedule

EPA’s proposed rule would require CGS Unit 1 to comply with EPA’s proposed 0.050 lb/MMBtu NOx

emission limit “within five years of final promulgation of this FIP consistent with the compliance times

for the NOx limits at the other units.”163  EPA requested comment on whether a shorter compliance

schedule “may be practicable for this unit.”164  SRP reiterates its opposition to EPA’s NOx limit for CGS

Unit 1.  However, should EPA proceed to impose SCR control on this unit, a five‐year compliance period

is certainly warranted.

The CAA and EPA’s regional haze rules provide in general for a five‐year compliance period after EPA’s

SIP approval or FIP promulgation.165  EPA may require compliance within a specified shorter time only if,

and to the extent, that compliance within that shorter period is shown to be “practicable.”166  No such

demonstration has been made by EPA, and considering the complex nature of an SCR control installation

project, the record supports allowing the full five‐year period for compliance with a FIP limit premised

on use of SCR technology.   

SRP currently estimates the total duration of time required to install SCR on CGS Unit 2 to be 48 months.  

Installation of the SCR equipment on CGS Unit 2 reduces the available space for installation of SCR

equipment on CGS Unit 1, and as such, increases even more the complexity of such an installation for

that unit.  In addition, as noted in SRP’s Response to EPA Dated July 27, 2012 (refer to Attachment B to

these comments), installation of an SCR system on CGS Unit 1 would likely require the installation of

low‐load temperature control equipment on both units in order to allow SRP to meet load cycling

demands.  This additional equipment, combined with the increased complexity of installing SCR

equipment on Unit 1, supports the need for a full five‐year compliance period.

                                                           

163 See 77 Fed. Reg. at 42,864.   

164 Id.

165 See CAA § 169A(g)(4); 40 CFR § 51.308(e)(1)(iv).

166 See 40 CFR § 51.308(e)(1)(iv).   
SRP Comments on Proposed Regional Haze Rule	 Page	10‐2

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

10.2 EPA Must Modify the Monitoring Requirements to be Consistent with Existing

Requirements

In several instances, monitoring requirements set out in the proposed rule are not consistent with

existing requirements that apply to the CGS units.  If EPA proceeds to impose additional controls at CGS

beyond those specified in the consent decree and already included in the CGS permit, EPA must align

these requirements to eliminate unnecessary and unreasonable compliance burdens.

10.2.1 Use of 40 CFR Part 75 for SO2 and NOx

EPA proposes to require coal‐fired units, like CGS Units 1 and 2, to operate, maintain, and calibrate an

SO2, NOx and diluent (oxygen (O2) or carbon dioxide (CO2)) CEMS, and a stack gas volumetric flow rate

monitor (stack flow monitor) according to 40 CFR Part 75.167  Data from those monitoring systems would

be considered “valid” and must be used in determining compliance with the applicable SO2 and NOx

limits, as long as all of the CEMS required to calculate lb/MMBtu are not “out‐of‐control” as defined in

40 CFR Part 75.168  When any CEMS is “out‐of‐control,” EPA proposes to treat the data as missing.169

SRP supports and appreciates the use of the monitoring system certification and quality assurance (QA)

procedures in 40 CFR Part 75.  SRP also agrees that failure to obtain valid data should simply be treated

as missing data, without use of any data substitution procedures.  However, EPA’s proposed definition

of “valid” data is broader than 40 CFR Part 75.  Under 40 CFR Part 75, data that are not “out‐of‐control”

(as defined in 40 CFR § 72.2 and 40 CFR Part 75) may also be considered “invalid” under certain

circumstances.   

For example, if a QA test is not performed within the specified data validation window or grace period,

the data recorded by the monitoring system are considered invalid for 40 CFR Part 75 reporting unless

the Administrator approves use of the data by petition.170  On the other hand, data that might otherwise

be considered invalid under § 75.20(b), following a change to a monitoring system, also can be

retroactively validated using procedures specified in that rule.  Although such events do not occur

frequently, and do not necessarily mean that data from the monitoring system are unreliable, adopting

a different definition of “valid” data for this rule than under 40 CFR Part 75 would create data

                                                           

167 See proposed § 52.145(e)(5); 77 Fed. Reg. at 42,870.   

168 Although 40 CFR Part 75 does not contain a definitions section, the substantive provisions in 40 CFR Part 75

(e.g., § 75.24 and App. B) make clear when a monitoring system is “out‐of‐control.”  The term “out‐of‐control” also

is defined for 40 CFR Part 75 purposes in 40 C.F.R. § 72.2.

169 See proposed § 52.145(e)(5); 77 Fed. Reg. at 42,870.

170 See, e.g., 40 CFR Part 75, App. B §§ 2.1.5, 2.2.4(b) & 2.3.3(c), § 75.66.   
SRP Comments on Proposed Regional Haze Rule	 Page	10‐3

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

management issues that are not justified.171  As a result, SRP requests that EPA define “valid” data as

those data recorded by a monitoring system that are valid for reporting under 40 CFR Part 75 either as

specified by the rule or, at the source’s option, as otherwise approved by the Administrator.172

EPA also should make clear that the “bias” adjustment procedures in 40 CFR Part 75 do not apply to data

used to calculate the 30‐day rolling averages.  Use of the 40 CFR Part 75 “bias” adjustment procedure is

not appropriate in this context because 40 CFR Part 75 does not allow downward adjustment of data

that are determined to be “biased” high.  For this reason, EPA has never required sources to use 40 CFR

Part 75 bias‐adjusted data in any command‐and‐control rule.173  Allowing use of unadjusted data also

would be consistent with SRP’s obligations under its consent decree.174    

In sum, EPA should utilize 40 CFR Part 75 under this rule in the same way it has used 40 CFR Part 75 in

other non‐market‐based contexts.

10.2.2 Proposed Additional Relative Accuracy Requirements

40 CFR Part 75 requires each SO2, NOx and diluent concentration monitor and each stack flow monitor to

meet relative accuracy test audit (RATA) requirements on an individual basis.  Rather than rely on 40

CFR Part 75 to ensure accuracy, EPA proposes to impose an additional 20 percent relative accuracy (RA)

specification to both SO2 and NOx, measured in pounds per hour, and to heat input.175  Because neither

the preamble nor any other document in the docket discusses these additional specifications, the

sampling requirements associated with these additional tests are not clear.  However, because stack

flow data are required to calculate both pounds per hour and heat input, and RATAs generally require

simultaneous sampling of required parameters, it appears that EPA intends to require reference method

sampling of stack flow (e.g., using EPA Method 2) simultaneously with each SO2,NOx and diluent

                                                           

171 If EPA adopts a different definition of “valid” for this rule, SRP will have to design software that can maintain

two separate databases of “valid” data – one for the FIP and one for 40 CFR Part 75 – even if EPA relies solely on 40

CFR Part 75 QA specifications to validate data, as SRP suggests below.   

172 In some instances where data would otherwise be considered invalid under 40 CFR Part 75 (e.g., because a QA

test was performed late), sources have filed, and the Administrator has granted, petitions requesting validation of

data recorded by the monitoring system without any adjustment based on other technical assessments (e.g., the

subsequent passing of the required QA test without any adjustment).  In such cases, EPA should allow use of the

data under the FIP as well without any additional petition requirement.   

173 See 40 CFR §§ 60.48Da(j)(2), 60.49Da(b)(4)(iii), (c)(2), (d) & (m) (prohibiting use of bias‐adjusted SO2, NOx,

diluent, and volumetric flow data in Subpart Da).   

174 See Consent Decree ¶¶ 45, 58, United States v. Salt River Project Agric. Improvement & Power Dist., No. 08‐

1479 (D. Ariz. Dec. 22, 2008) (declaring that SO2 and NOx emissions “data need not be bias adjusted”).

175 See proposed § 52.145(e)(5)(i)(B); 77 Fed. Reg. at 42,870.  EPA does not propose a pound per hour RA

specification for SO2, but does propose recordkeeping for such a specification.  Proposed § 52.145(e)(7); 77 Fed.

Reg. at 42,870.   
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concentration reference method run.  Reference method testing of stack flow to meet 40 CFR Part 75

RATA requirements generally is not conducted simultaneously with pollutant concentration reference

method measurements.

SRP objects to these proposed additional requirements.  Imposing additional RATA specifications will not

increase the accuracy of any monitoring system, but would increase the difficulty and cost of testing.  It

also could result in additional missing data if tests must be repeated to meet the specifications.   

Consider an example in which both of the monitoring systems needed to calculate NOx in pounds per

hour (the NOx CEMS and stack flow monitor) and both of the monitoring systems needed to calculate

heat input (the diluent CEMS and stack flow monitor) pass their RA specifications and thus have

adequate performance individually, but do not pass the combined pounds per hour and heat input

specifications.  Because all three individual monitors are working well, the only realistic option will be to

rerun the RATAs.   

If EPA has data to suggest that the proposed combined specifications are consistently achievable, or that

imposing a combined specification would provide necessary and significant improvement in RATA

results for individual monitoring systems, EPA must provide that information and solicit comment on it.  

EPA also must address the increased burdens and how the potential loss of data associated with failure

of the RA specifications might affect compliance with the proposed emission limitations and data

availability specifications.

When EPA first proposed 40 CFR Part 75 in 1991, EPA also proposed to impose a combined RA

specification for SO2 and flow monitoring systems (SO2 in pounds per hour) starting in January 2000.176  

However, EPA did not finalize that proposed specification and, after more than 20 years, the section

remains “reserved.”177  Later, when EPA adopted trading programs for NOx in pounds per hour under

CSAPR, EPA never even proposed (let alone finalized) such combined specifications.   

Similarly, although EPA has recently imposed output‐based standards under the NSPS that require

calculation of SO2 and NOx in pounds per hour, EPA also has relied on the individual RA specifications in

40 CFR Parts 60 and 75 to quality assure the relevant data.178  If combined RA specifications were

necessary to ensure the accuracy of mass emissions data, EPA surely would have adopted them in those

contexts.

                                                           

176 See 56 Fed. Reg. at 63,002 (Dec. 3, 1991).  In that proposal, EPA made clear that reference method testing of

stack flow and SO2 had to be performed simultaneously.  Proposed 40 CFR Part 75, App. A § 6.6.3; 56 Fed. Reg. at

63,311.

177 See 40 CFR Part 75, App. A § 3.3.5.   

178 See 40 CFR §§ 60.43Da, 60.44Da; 77 Fed. Reg. at 9,450‐53.   
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EPA’s failure to adopt combined specifications cannot be explained by a lack of data.  Utilities have been

reporting initial and annual SO2, NOx, diluent, and stack flow monitor RATA results to EPA since 1994.  

However, the lack of such specifications might be explained by EPA’s prior conclusions that existing

RATA performance likely cannot be significantly improved.  When EPA last examined RATA results

reported under 40 CFR Part 75, the reported values were significantly better than the existing 40 CFR

Part 75 RA specifications.  However, at least for SO2, NOx and CO2, EPA expressed concern that

promulgating specifications closer to the achieved results would approach the variability in the

reference methods themselves, and thus, might be beyond the limits of current monitoring

technology.179  

In short, because sources already were doing what is necessary to obtain the best RA results they could

reasonably achieve, EPA determined that imposing more stringent specifications would not improve

accuracy and could result in additional failures due solely to reference method variability.  If sources

already are doing the best they can, imposing additional combined RA specifications would be similarly

unjustified.

EPA’s proposed combined RATA specifications also are flawed in that they fail to provide the necessary

alternative specifications for low‐emitters.  The current SO2, NOx and diluent CEMS and flow monitor RA

specifications are ±10.0 percent, or ±7.5 percent to qualify for an annual RATA.  However, for SO2 and

NOx RATAs with average reference method results ≤150.0 parts per million (ppm), 40 CFR Part 75

provides an alternative RA specification of ±15.0 ppm, or ±12.0 ppm to qualify for an annual RATA.180  

For CO2 and O2, 40 CFR Part 75 provides an alternative RA specification of ±1.0 percent, or ±0.7 percent

to quality for an annual RATA.181  Finally, for RATAs with an average volumetric flow rate ≤10.0 feet per

second (fps), 40 CFR Part 75 provides an alternative specification of ±2.0 fps, or ±1.5 fps to qualify for an

annual RATA.182   

The 40 CFR Part 75 low‐emitter specifications, which have been in the regulations since initial

promulgation, are patterned after similar alternative specifications in 40 CFR Part 60 and are necessary

to account for the manner in which the mean emissions value during the RATA is used in the RA

equation (because the mean emissions value is used in the denominator of the RA equation, lower

                                                           

179 Acid Rain Program: Determinations Under EPA Study of Bias Test and Relative Accuracy and Availability

Analysis: Notice of Proposed Determinations and Proposed Rulemaking, 63 Fed. Reg. at 28,195, 28,198 (May 21,

1998).   

180 See 40 CFR Part 75, App. A §§ 3.3.1, 3.3.7 &App. B. § 2.3.1.2(e).   

181 See 40 CFR Part 75, App. A § 3.3.3 & App. B § 2.3.1.2(h).   

182 See 40 CFR Part 75, App. A § 3.3.4 & App. B § 2.3.1.2(d).
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average emissions result in a larger relative percentage error).183  Notably, when EPA proposed a

combined SO2/flow RA specification in 1991, EPA exempted low‐emitting units from that specification.184   

To proceed with combined RA specifications, EPA also would need to either propose (and solicit

comment on) alternative low‐emitter combined specifications that have been demonstrated to be

consistently achievable, or exempt units meeting any of the applicable 40 CFR Part 75 low‐emitter

thresholds from those specifications.  SRP notes the importance of such specifications to CGS Units 1

and 2, given the units’ low SO2 and NOx emission rates.

10.2.3 Proposed CEMS Data Availability Requirements

Although 40 CFR Part 75 requires the calculation of percent monitor data availability for each SO2, NOx

and diluent CEMS and each flow monitor, it does not establish any minimum availability requirement for

any monitoring system.  In the FIP, EPA proposes to require that each unit obtain valid (i.e., not “out‐of‐

control”) hourly SO2 and NOx emissions data (in lb/MMBtu) for at least 90 percent of the unit’s operating

hours for each calendar quarter.185  SRP does not believe that a data availability requirement is

necessary to provide incentives for collection of valid 40 CFR Part 75 data, and EPA has provided no

other rationale for its proposal.  

Source owners and operators already have sufficient incentive to obtain valid data in order to avoid the

increasingly conservative (and ultimately punitive) missing data substitution procedures that apply

under 40 CFR Part 75.186  Even without missing data substitution, sources have significant incentive to

have good data availability, since data loss reduces the amount of data available to compensate for

emissions variability (thus effectively making the proposed limit more stringent).

SRP also is concerned that EPA’s proposed quarterly availability specification is too stringent.  Even

properly maintained monitoring systems sometimes fail QA tests and are deemed “out‐of‐control.”  A

failed test (particularly a test like the RATA that takes hours to complete) sometimes can result in a

significant missing data period, despite the owners’ and operators’ best efforts.  If a unit has a significant

missing data event during a calendar quarter in which it also has a significant period of unit downtime

(e.g., as a result of an outage), the percent of operating hours during the quarter with valid data could

easily be less than 90 percent.  It is in part for this reason that 40 CFR Part 75 measures data availability

over each 8,760‐operating‐hour period.187   

                                                           

183 See 56 Fed. Reg. at 63,068‐69.   

184 Proposed 40 CFR Part 75, App. A. § 3; 56 Fed. Reg. at 63,309.   

185 Proposed § 52.145(e)(5)(ii)(B) & (iii)(B); 77 Fed. Reg. at 42,870.   

186 See 63 Fed. Reg. at 28,198 (evaluating percent monitor data availabilities under 40 CFR Part 75 to determine

whether to adjust the missing data thresholds).   

187 See 40 CFR § 75.32(a)(2).   
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Moreover, for monitoring systems that are used to calculate SO2 or NOx in pounds per hour, 40 CFR Part

75 data availability is based on a single CEMS, and not on collection of hourly values from multiple

CEMS.  Under EPA’s proposed calculation procedures for 30‐day rolling average emission rates, loss of

data from any one of the three monitoring systems required for that calculation (an SO2 or NOx CEMS, a

diluent CEMS, and a stack flow monitor) would result in loss of a valid hour.188   

In short, to the extent EPA based its evaluation of the reasonableness of the proposed 90 percent

criterion on 40 CFR Part 75 data availability, that evaluation is seriously flawed.  EPA should either

eliminate the unnecessary requirement or provide data to justify its proposed requirement that take

into account the differences described above.

10.2.4 Use of Methods 201A and 202 for Determining PM Emissions

To determine compliance with the PM limit in the proposed rule, EPA proposes to require annual

performance stack tests and compliance with the applicable Compliance Assurance Monitoring plan

developed under 40 CFR Part 64.  In the proposed regulatory language, EPA (like ADEQ’s plan) identifies

Methods 201A and 202 of 40 CFR Part 51, Appendix M, as the applicable methods for performance

tests.189  Method 201A uses a particle‐sizing device to collect filterable PM emissions with diameters of

either 10 or 2.5 micrometers for measurement.  Method 202 uses an impinger system to collect

condensable PM for measurement after filterable PM has been removed.  If used together, Methods

201A and 202 measure total PM (i.e., the combination of filterable PM of the chosen size cut‐off and

condensable PM).

In the preamble to the proposed rule, EPA solicits comment on whether other test methods should be

allowed or required in order to remain consistent with ADEQ’s BART determination and the resulting

proposed PM10 emission limit.  Specifically, EPA recognizes that the PM10 emission limit that ADEQ

adopted did not take into account the potential impacts on total PM emissions from the SCR that EPA

proposes to require under the FIP.  SCR can result in creation of sulfuric acid mist (a condensable PM),

which is not controlled by the required ESP.  With this increase, the PM limit would effectively be more

stringent than ADEQ intended.190   

To avoid that result, while still ensuring proper operation of the ESP, EPA asks whether another method

that does not capture condensable PM would be more appropriate.  As examples, EPA cites Methods 5

or 5e (in combination with Methods 1‐4) of 40 CFR Part 60, Appendix A, and Method 201.  Method 5 is a

                                                           

188 Proposed § 52.145(e)(5)(ii)(B) & (iii)(B); 77 Fed. Reg. at 42,870.   

189 Proposed § 52.145(e)(6); 77 Fed. Reg. at 42,870.   

190 See 77 Fed. Reg. at 42,851.
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filterable PM method typically used for utility sources without a wet scrubber.191  Method 5 does not

measure particle size.  Method 5e is a filterable PM method developed specifically for the wool

fiberglass insulation manufacturing industry.  SRP assumes the reference to Method 5e was in error, and

that EPA intended to reference Method 5I (which applies to low‐level filterable PM from a variety of

stationary sources).  Method 201 is the original method for collecting filterable PM10with a particle sizer.  

Method 201 was updated and expanded, but not replaced, by Method 201A.  EPA describes Method

201A as the “typical method used for filterable PM10.”192   

SRP shares EPA’s concerns regarding use of Method 202.  Not only will Method 202 collect condensable

PM that was not considered by ADEQ (or EPA) when establishing the proposed PM10 limit of 0.03

lb/MMBtu, the method also has been shown to have a high bias when used at sources with wet control

devices.193  CGS has recently installed new wet flue gas desulfurization (FGD) systems on both units at

CGS to meet the 2008 consent decree deadlines.194  Even if the actual condensable PM created by the

SCR was not sufficient to render the proposed limit unachievable with the ESP, SRP would have little

confidence that Method 202 could accurately measure the condensable fraction at CGS on a consistent

basis.  If the artifact EPA sought to reduce was not eliminated, CGS could fail to meet the emission limit

simply as a result of the test method.  SRP strongly believes no PM limit can be imposed that includes

condensable PM without conducting testing with the proposed test method (in this case Method 202) to

show that the proposed PM emission limit can be consistently achieved with that method.

CGS’s wet scrubbers also render Methods 201 and 201A inapplicable.  Although not explicit in Method

201, both methods rely on a particle sizing device that cannot be used in the presence of water droplets,

like those found in the stack following a wet FGD system.  EPA clarified this point in Method 201A and

discussed the limitations in the preamble to its final rule.195   

Although SRP expects sulfuric acid mist generation as a result of the SCR to be minimal (in part due to

CGS's use of low‐sulfur coal), some sulfuric acid mist may be created.  Because use of Method 202 not

only would include condensable PM sulfuric acid mist emissions that were not considered in establishing

                                                           

191 See 40 CFR § 60.46(d)(2) (Subpart D NSPS); Id. § 60.50Da(e) (Subpart Da NSPS).   

192 See 77 Fed. Reg. at 42,851.

193 Revisions by EPA to Method 202 in 2010 reduced, but did not eliminate, the “formation of reaction artifacts

that could lead to inaccurate measurements of condensable particulate matter.”  75 Fed. Reg. at 80,118, 80,118

(Dec. 21, 2010).

194 77 Fed. Reg. at 42,842, Table 3, Consent Decree ¶¶ 48‐49, United States v. Salt River Project Agric. Improvement

& Power Dist., No. 08‐1479 (D. Ariz. Dec. 22, 2008).   

195 See 40 CFR Part 51, App. M, Method 201A § 1.5 (“To measure filterable PM10 and PM2.5 in emissions where

water droplets are known to exist, we recommend that you use Method 5...”); 75 Fed. Reg. at 80,121 (“Method

201A cannot be used to measure emissions from stacks that have entrained moisture droplets (e.g., from a wet

scrubber stack)...”).
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the proposed PM limit, but also could overstate the actual emissions, SRP agrees with EPA’s suggestion

that only a filterable PM test method be used.  However, SRP does not agree that Method 201 or 201A

are valid options.  Both units have wet FGD systems and the resulting entrained moisture droplets in the

stack emissions render these methods inapplicable.

In the preamble to the proposed rule, EPA describes CGS’s PM emission limit under the consent decree

as a PM10 limit of 0.030 lb/MMBtu.196  That limit, however, is not a limit on PM10, but rather on filterable

PM measured with “Method 5, Method 5B, or Method 5I, App. A‐6, Method 17, or alternative stack

tests or methods that are requested by SRP and approved by EPA and Arizona DEQ.”197  CGS’s Title V

permit requires use of those methods as well.198   

Because of the above‐described issues with use of Methods 201A and 202, SRP requests that (consistent

with CGS’s consent decree and Title V permit) EPA specify use of Method 5, 5B, 5I, or an alternative

method requested by the source owner or operator and approved by EPA and ADEQ.  Although

Methods 5, 5B, and 5I would include in the measurement filterable PM above the PM10 size threshold,

ADEQ (and SRP) already have evaluated the achievability of the proposed limit with similar methods.  As

a result, SRP does not object to any additional conservativeness that use of those methods may impose.

10.3 EPA Must Modify the Quarterly Reporting Requirements to be Consistent with Existing

Requirements

EPA proposes to require submission of reports to EPA Region IX within 30 days of the end of each

calendar quarter listing (1) the daily 30‐day rolling emission rates for SO2 and NOx, and (2) the results of

any RATA performed during the quarter.199  Although SRP does not object to reporting of this

information to EPA, the proposed reporting duplicates (and is inconsistent with) the semi‐annual

reporting requirement under Title V and the RATA reporting required under 40 CFR Part 75.200   

Specifically, CGS’s Title V permit requires semi‐annual reporting of 30‐day rolling averages for SO2 and

NOx along with the compliance certification.  Those reports are due roughly 45 days after the end of the

semi‐annual period.201  SRP’s consent decree also requires semi‐annual reporting to the Director of the

                                                           

196 See 77 Fed. Reg. at 42,851.   

197 See Consent Decree ¶¶ 28, 65, United States v. Salt River Project Agric. Improvement & Power Dist., No. 08‐

1479 (D. Ariz. Dec. 22, 2008).

198 ADEQ, Title V Permit # 52639, Attachment B, Conditions II.D.1.b, II.D.1.c & II.D.5.   

199 See proposed § 52.145(e)(8); 77 Fed. Reg. at 42,870.   

200 Ordinarily, EPA must address such potential inconsistencies and duplication in its Information Collection

Request (ICR) to the Office of Management and Budget, but in this case EPA has asserted that no ICR is required

because EPA has limited this FIP to only three sources.  77 Fed. Reg. at 42,866.

201 ADEQ, Title V Permit # 52639, Attachment A Condition VII, Attachment B Conditions II.E.4 & II.G.3.f.   
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Air Division at U.S. EPA Region IX within 60 days after each half of the calendar year, and allows use of

the Title V reports.202   

SRP should not have to report on a quarterly basis information that SRP already is required to submit

semi‐annually to the same EPA Regional Office.  EPA has provided no reason for the duplication and

increase in reporting frequency.

With respect to RATA results, SRP already is electronically reporting detailed RATA data for the relevant

CGS monitoring systems to EPA under 40 CFR Part 75 at a similar frequency.203  EPA should allow SRP to

use the 40 CFR Part 75 reporting to satisfy any such reporting obligation under the FIP.  To the extent

EPA Region IX wants to view the results of a particular RATA in hard copy, 40 CFR Part 75 allows the

Region to request a hardcopy report within the later of 45 days after completing the RATA or 15 days

after receiving the request.  EPA should utilize this existing provision, which was designed to allow

access to hardcopy information without mandating automatic duplicative reporting of results.  In SRP’s

experience, EPA Regional Offices are rarely interested in reviewing RATA reports.

10.4 EPA Must Modify the Notification Requirements within the Proposed Rule

EPA proposes to require the owner or operator of a source to notify EPA within two weeks of

“completion of installation of combustion controls or Selective Catalytic Reactors on any of the units

subject to this section.”204  SRP does not object to providing notice of completion of actions required

under the final FIP.  However, the proposed notification is both overly broad and overly prescriptive.  

First, because there is no requirement under the proposed FIP or Arizona’s regional haze SIP for

installation of combustion controls at CGS, there is no basis for including in the FIP any requirement that

SRP provide notice to EPA with respect to installation of such controls.  Although ADEQ identified

LNB/OFA as BART for CGS, those systems already were installed at Units 1 and 2 under the consent

decree205 and therefore will not be installed under a FIP or regional haze SIP.  EPA should clarify the

proposed provision by requiring notice only of new controls that will be required to meet the FIP or

regional haze SIP.

Second, the proposed deadline is unclear and unreasonable.  Installation of controls is a complex

process, and the point at which that process is “complete” may not be immediately clear.  At a

                                                           

202 See Consent Decree ¶¶ 91, 92 & 142, United States v. Salt River Project Agric. Improvement & Power Dist., No.

08‐1479 (D. Ariz. Dec. 22, 2008).   

203 See 40 CFR §§ 75.59(a)(5), 75.64(a)(5).   

204 See proposed § 52.145(e)(8)(a); 77 Fed. Reg. at 42,870.    

205 See Consent Decree ¶¶ 23, 41 & 42, United States v. Salt River Project Agric. Improvement & Power Dist., No.

08‐1479 (D. Ariz. Dec. 22, 2008).
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minimum, EPA must revise the requirement to use a more objective term and allow sufficient time for

owners and operators to comply.  

Third, the proposed requirement duplicates reporting already required for a new add‐on NOx emission

control under 40 CFR Part 75.  Specifically, when an add‐on NOx emission control (or an FGD) is installed,

40 CFR Part 75 requires the designated representative to provide notice to EPA and to “the appropriate

EPA Regional Office” of “the date that reagent is first injected into” the control device.206  Although 40

CFR Part 75 does not provide a specific deadline for such notices,207 it makes little sense to require

owners and operators to provide notice of the same event (i.e., startup of the SCR) twice.  EPA should

rely on (and if necessary refer to) the notice required under Part 75.

                                                           

206 See 40 CFR §§ 75.4(e)(1)(ii), 75.61(a).   

207 The 40 CFR Part 75 provision that establishes deadlines for notice of the planned date of use (and, if different,

the actual date of use) of a new stack or FGD does not refer to add‐on NOx controls or injection of reagent.  See Id.

§ 75.61(a)(2).
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11.0   EPA’s Assertion of Health Benefits is Unsubstantiated by the Proposed

Rule

In its proposed rule, EPA states “to the extent this proposed rule will limit emissions of NOx, SO2, and

PM10, the rule will have a beneficial effect on children’s health by reducing air pollution.”208  

Additionally, in an accompanying fact sheet, EPA also stated that “pollutants that contribute to haze are

the same emissions that impair human health.”209

SRP contracted with Gradient to review EPA’s statements regarding health benefits associated with the

proposed rule.  Gradient concluded that it is inappropriate for EPA to make this claim as the rule

documentation does not provide any scientific evidence that current emissions from any of the facilities

that are the subject of this proposed rulemaking, including CGS, result in health impacts to communities

(including children) or that limiting emissions would provide health benefits to those communities (refer

to Attachment F to these comments).   

Before EPA may make a claim that the proposed rule will result in health benefits, EPA must conduct a

health risk evaluation that follows the four basic steps of any valid risk assessment process: hazard

identification, dose‐response, exposure assessment, and risk characterization.  The proposed rule’s

docket does not appear to include any evidence that such an evaluation has taken place.  As such, EPA

must acknowledge that the proposed rule has not been shown to have a beneficial effect on children’s

health or any other public health endpoint, and that EPA’s previous statements on this issue are

misleading and unsubstantiated.

                                                           

208 See Id. at 42,868.  

209 See U.S. EPA, Fact Sheet, Proposed Partial Approval and Partial Disapproval of Arizona’s Regional Haze Plan and

Proposed Federal Plan (updated July 27, 2012), available at http://www.epa.gov/region9/air/actions/pdf/az/az‐

haze‐factsheet.pdf.
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12.0   Conclusion

EPA proposes to approve Arizona’s BART determinations for emissions of SO2 and PM, and to disapprove

the Arizona’s BART determinations for NOx for each of the CGS units.  EPA also proposes a FIP to take

the place of Arizona’s SIP with respect to the NOx BART determination.  That FIP would impose a NOx

BART limit for CGS Unit 1 of 0.050 lb/MMBtu, based on installation of LNB/OFA and SCR, and a NOx BART

limit for CGS Unit 2 of 0.080 lb/MMBtu, based on installation and operation of LNB/OFA and SCR,

consistent with CGS’ existing consent decree obligations.

This document outlines SRP’s significant concerns with EPA’s proposed approach to implementation of

the regional haze regulations in Arizona.  These concerns are summarized below:

 Arizona’s BART determination established a NOx BART emissions limit of 0.320 lb/MMBtu based

on installation and use of LNB/OFA.  Under the CAA, the state’s BART determination is entitled

to deference.  EPA is not free to second‐guess the state’s determinations.  Arizona developed

and submitted a comprehensive SIP that included a large number of measures to address a

variety of sources that contribute to regional haze, including mobile sources, wildfires and

industrial facilities.  EPA should consider, and act on, all of these measures together rather than

single out three power plants for imposition of overly stringent NOx emission limits.

 The consent decree entered into by SRP and EPA just four years ago, and currently being

implemented by SRP, was designed to settle an EPA allegation that emissions from CGS Units 1

and 2 failed to comply with the CAA’s BACT requirements, a component of the PSD

requirements of the CAA that is applicable to certain new or modified sources.  That agreement

requires SRP to install and operate LNB/OFA on both units, as well as an SCR system on Unit 2.  

It also establishes a NOx emission limit of 0.320 lb/MMBtu for Unit 1, a NOx emission limit of

0.080 lb/MMBtu for Unit 2, and a plant‐wide NOx emission limit of 7,300 tons per year.  EPA’s

BART Guidelines provide that emission limits imposed pursuant to a PSD‐related consent

decree, such as the consent decree applicable to CGS, should be deemed to satisfy BART.  EPA

should follow its own guidelines and consider the weight of evidence presented in these

comments, and as a result, acknowledge that the consent decree limits not only satisfy all BART

obligations for CGS Units 1 and 2, but provide a level of control that is better than BART.  

 EPA’s proposed NOx BART determination for CGS fails to take the presumptive BART limits into

account.  Soon‐to‐be‐installed controls at CGS Unit 2, which will result in a 0.080 lb/MMBtu NOx

emission limit for that unit, are far more stringent than the presumptive NOx limit applicable to

CGS.  Indeed, EPA in this proposed rule fails even to mention, much less evaluate, the type of

emission controls (i.e., combustion controls) on which the presumptive limit is based.  EPA is not

free to disregard its own presumptive BART limit and its rulemaking determination that, for all
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units except cyclone units (which are not present at CGS), NOx BART is presumed to be based on

combustion controls only and excludes post‐combustion controls such as SCR.

 EPA’s proposed BART determination for CGS Unit 1 would impose an exceptionally stringent NOx

emission limit of 0.050 lb/MMBtu, which is premised on the assumption that implementation of

SCR technology can continuously achieve this limit on a 30‐day rolling average basis.  Continuous

compliance with such a limit, however, has not been shown to be feasible, and EPA has failed to

support either its proposed BART determination or its reliance on this limit in its BART analysis.  

A 0.050 lb/MMBtu NOx emission limit is unprecedented for retrofit facilities like CGS, and is

inconsistent with BACT determinations that EPA has approved for new coal‐fired units.

 EPA argues that the emission control costs relied on by Arizona and those prepared by SRP were

not calculated in accordance with the BART Guidelines and that they are inconsistent with EPA’s

Control Cost Manual.  The Control Cost Manual is not binding and is recognized as only one

reference source for cost information by EPA’s BART rules.  Furthermore, SRP has actual, site‐

specific cost information associated with the installation of LNB/OFA on both units at CGS and

installation of SCR on Unit 2 at CGS that demonstrates EPA estimation techniques do not

provide an accurate estimate of BART control costs.   

 EPA’s own calculation of costs in support of its FIP is seriously flawed.  EPA’s cost assessment

relies on an IPM base case for capital and annual operating costs for each NOx control option.  

BART requires a site‐specific analysis.  Use of IPM’s generic information does not satisfy this

requirement.  Regardless, the data inputs EPA selected in implementing IPM are incorrect given

the site‐specific characteristics of CGS.  This error by EPA resulted in a significant underestimate

of the NOx control costs used in EPA’s analysis.

 EPA failed to consider the dollars‐per‐deciview cost effectiveness of different control options

when it supplanted ADEQ’s cost analysis with its own analysis in the proposed rule.  EPA’s

decision to exclude rational considerations, such as site‐specific costs and cost‐effectiveness on

a deciview basis, and instead look to outdated and limited information, such as the Control Cost

Manual and IPM, has resulted in an unsupported supplanting of Arizona’s BART determination

for CGS.

 EPA’s refusal to allow use of the most recent and most accurate CALPUFF model (version 6.42) is

unreasonable and arbitrary, and contradicts the principle that BART determinations should be

based on the best available science.  Use of CALPUFF version 6.42 demonstrates that the

visibility benefits EPA projects in association with BART control options are overstated.

 SRP’s modeling of CGS’ visibility impacts relies on more appropriate monthly‐varying

background ammonia concentrations in the ambient air and is more realistic than EPA’s reliance
SRP Comments on Proposed Regional Haze Rule	 Page	12‐3

EPA‐R09‐OAR‐2012‐0021, FRL‐9700‐1

on an artificial, uniform “default” value.  Arizona acted within its discretion by relying on the

same background ammonia concentrations.

 EPA argues that visibility impacts were not appropriately evaluated and considered in the SIP.  

Further, EPA claims that visibility benefits at all potentially impacted Class I areas must be

considered.  EPA’s BART Guidelines do not require that cumulative visibility impacts be used as

the basis for BART assessments and does not require that they be considered at all.  ADEQ’s

evaluation of visibility impacts in support of Arizona’s BART determination is a valid alternate

approach to the consideration of visibility benefits associated with control options.  Arizona’s

reliance on that analysis is within the state’s discretion.

 EPA’s assessment of energy and non‐air quality environmental impacts must be weighed and

considered in conjunction with the other BART factors in the overall assessment of what control

option constitutes BART for a particular source.  EPA’s approach minimizes the role that this

factor can conceivably play in a BART analysis, which is beyond EPA’s authority.

 EPA’s proposed rule fails to adequately consider a number of issues that will impact the

enforcement of the proposed BART emission limits, including the proposed compliance

schedule, monitoring requirements, reporting requirements, and notification requirements.

 EPA must first conduct a health risk evaluation that follows the four basic steps of any valid risk

assessment process before EPA may make a claim that the proposed rule will result in health

benefits.  The proposed rule’s docket does not appear to include any evidence that such an

evaluation has taken place.   

In conclusion, EPA’s proposed rule is seriously flawed and cannot, at least with respect to the NOx BART

for CGS, be finalized.  EPA has failed to give the level of deference to the State of Arizona’s BART

determinations that the CAA requires.  EPA has presented no legitimate grounds for disapproving any

part of Arizona’s SIP, and EPA cannot, therefore, promulgate its own NOx BART determinations for CGS.  

Further, EPA’s proposed FIP and the analysis EPA relies on to support that FIP are inconsistent with the

CAA and EPA’s own regional haze regulations.  Accordingly, the proposed FIP does not reflect a proper

NOx BART determination for CGS, and EPA must withdraw it.  Full approval of Arizona’s SIP is the only

course of action that is consistent with the law and available to EPA.