The EPA Administrator, Gina McCarthy, signed this final rule on 7/28/14, and EPA is submitting it for publication in the Federal Register (FR).

While we have taken steps to ensure the accuracy of this Internet version of the rule, it is not the official version of the rule. Please refer to the

official version in a forthcoming FR publication, which will appear on the Government Printing Office's FDsys website

(http://fdsys.gpo.gov/fdsys/search/home.action) and on Regulations.gov (http://www.regulations.gov) in Docket No. EPA‐R09‐OAR‐2013‐0009.

Once the official version of this document is published in the FR, this version will be removed from the Internet and replaced with a link to the

official version.

6560-50-P 

ENVIRONMENTAL PROTECTION AGENCY 

40 CFR Part 49 

[EPA-R09-OAR-2013-0009; FRL-9914-62-Region 9] 

Approval of Air Quality Implementation Plans; Navajo Nation; 

Regional Haze Requirements for Navajo Generating Station; Final 

Rule 

AGENCY: Environmental Protection Agency (EPA). 

ACTION: Final rule. 

SUMMARY: The Environmental Protection Agency (EPA) is 

promulgating a source-specific Federal Implementation Plan (FIP) 

requiring the Navajo Generating Station (NGS), a coal-fired 

power plant located on the Navajo Nation near Page, Arizona, to 

achieve reductions in oxides of nitrogen (NOX) required under the 

Best Available Retrofit Technology (BART) provisions of the 

Clean Air Act (CAA) and the Regional Haze Rule (RHR). On 

February 5, 2013, EPA issued a proposed BART determination for 

NGS and an alternative to BART. In a supplemental proposal on 

October 22, 2013, EPA proposed to approve a new alternative 

plan, based on an agreement developed by a group of stakeholders 

known as the Technical Work Group (TWG). EPA is finalizing the 

alternative to BART described in our supplemental proposal. This 

rule is consistent with the TWG Agreement, including a lifetime 

cap in total emissions of NOX from NGS over 2009-2044 (2009-2044 
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NOX Cap). Our final action will achieve greater emissions 

reductions than BART and is expected to significantly reduce the 

impact of NGS on visibility at 11 mandatory Class I Federal 

areas. The operator of NGS must implement one of several 

alternative operating scenarios to achieve the necessary 

emission reductions to comply with the 2009-2044 NOX Cap. 

DATES: Effective date: This rule is effective on [insert date 60 

days from date of publication in the Federal Register]. 

FOR FURTHER INFORMATION CONTACT: Anita Lee, EPA Region 9, (415) 

972-3958, lee.anita@epa.gov. 

SUPPLEMENTARY INFORMATION: EPA has established a docket for 

this action under Docket ID No. EPA-R09-OAR–2013-0009. The index 

to the docket for this action is available electronically at 

http://www.regulations.gov and in hard copy at EPA Region 9, 75 

Hawthorne Street, San Francisco, California. While documents in 

the docket are listed in the index, some information may be 

publicly available only at the hard copy location (e.g. 

copyrighted material, voluminous or oversized documents, etc.), 

and some may not be publicly available in either location (e.g. 

Confidential Business Information (CBI)). To inspect the hard 

copy materials, please schedule an appointment during normal 

business hours with the contact listed in the FOR FURTHER 

INFORMATION CONTACT section. A reasonable fee may be charged for 

copies. 
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Throughout this document, “we”, “us”, and “our” refer to 

EPA. 

Table of Contents 

I. Executive Summary 

II. Background for the Final Rule 

 A. History of NGS 

B. Summary of Statutory and Regulatory Framework for 

Addressing Visibility and Sources Located in Indian 

Country 

C. Summary of Proposed Rule and Supplemental Proposal 

D. Summary of Legal Rationale for Compliance Flexibility 

III. Summary of Final FIP Provisions 

IV. Summary of Major Issues Raised by Commenters 

V. Summary of Final Action 

VI. Administrative Requirements 

A. Executive Order 12866: Regulatory Planning and Review 

and Executive Order 13563: Improving Regulation and Regulatory 

Review 

B. Paperwork Reduction Act 

C. Regulatory Flexibility Act 

D. Unfunded Mandates Reform Act 

E. Executive Order 13132: Federalism 

F. Executive Order 13175: Consultation and Coordination 

with Indian Tribal Governments 
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G. Executive Order 13045: Protection of Children from 

Environmental Health Risks and Safety Risks 

H. Executive Order 13211: Actions Concerning Regulations 

That Significantly Affect Energy Supply, Distribution, or Use 

I. National Technology Transfer and Advancement Act 

J. Executive Order 12898: Federal Actions to Address 

Environmental Justice in Minority Populations and Low-Income 

Populations 

K. Congressional Review Act 

L. Petitions for Judicial Review 

I. Executive Summary 

 EPA is taking final action pursuant to the CAA and the RHR 

to require Units 1, 2, and 3 at NGS to reduce emissions of NOX in 

order to reduce the impact NGS has on visibility at 11 mandatory 

Class I Federal areas. We are finalizing an alternative to BART 

based on agreed-upon recommendations developed by a group of 

diverse stakeholders known as the Technical Work Group (TWG). 

Our final action limits emissions of NOX from NGS by establishing 

a long-term facility-wide cap on total NOX emissions from 2009 to 

2044 and requires the implementation of one of several 

alternative operating scenarios to ensure that the 2009-2044 cap 

is met. Generally, the alternative operating scenarios require 

the closure of one unit at NGS (or the curtailment of 

electricity generation by a similar amount) in 2019, and 
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compliance with a NOX emission limit that is achievable with the 

installation of selective catalytic reduction (SCR) on two units 

in 2030. 

As part of our final action, EPA is also setting a sourcespecific BART Benchmark against which to compare the TWG 

Alternative to ensure that it will achieve greater reasonable 

progress than BART. The BART Benchmark is consistent with the 

BART determination we proposed on February 5, 2013, requiring 

all three units at NGS to meet an emission limit achievable with 

SCR within five years of a final rule. EPA is not finalizing our 

proposed BART determination for NGS in the regulatory 

requirements of this Final Rule. 

EPA’s action to finalize an alternative to BART consistent 

with the TWG Agreement will achieve greater NOX emission 

reductions at lower cost than BART in exchange for flexibility 

in the timeframe for achieving NOX reductions. When fully 

implemented, this Final Rule requires over an 80 percent 

reduction in NOX emissions from NGS and is expected to 

significantly reduce the impact of NGS on visibility at 11 

mandatory Class I Federal areas. 

II. Background for the Final Rule 

A. History of NGS 

NGS is a coal-fired power plant located on the Navajo 

Nation Indian Reservation near Page, Arizona. The facility 
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consists of three 750 megawatt (MW) coal-fired electric utility 

steam generating units with a total capacity of 2250 MW 

constructed from 1974 to 1976. The three units at NGS are coowned by six entities: the United States Bureau of Reclamation 

(Reclamation) (24.3 percent); Salt River Project (21.7 percent), 

which also serves as the facility operator; Los Angeles 

Department of Water and Power (21.2 percent); Arizona Public 

Service (14 percent); NV Energy (11.3 percent); and Tucson 

Electric Power (7.5 percent). 

Federal participation in NGS was authorized in the Colorado 

River Basin Project Act of 1968 as a preferred alternative to 

building hydroelectric dams in the Grand Canyon for the purpose 

of providing power to the Central Arizona Project (CAP).1 The CAP 

is a 336-mile water distribution system that delivers about 1.5 

million acre-feet (AF) per year of Colorado River water from 

Lake Havasu in western Arizona to non-Indian agricultural (NIA) 

water users in central Arizona, Indian tribes located in 

Arizona, and municipal water users in Maricopa, Pinal, and Pima 

Counties in Arizona. The CAP water is used to meet the terms of 

a number of Indian water-rights settlements in central Arizona 

and to reduce groundwater usage in the region. A portion of 

1 For more detail and for citations or references to the information provided 

in this Background section, please see the Proposed Rule at 78 FR 8274 

(February 5, 2013). 
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Reclamation’s share of electricity from NGS powers the pumps 

that move CAP water to its destinations along the distribution 

system. 

Several tribes located in Arizona, including the Gila River 

Indian Community, the Ak-Chin Indian Community, the Tohono 

O’odham Nation, the San Carlos Apache Tribe, the White Mountain 

Apache Indian Tribe, the Fort McDowell Yavapai Nation, the Salt 

River Pima-Maricopa Indian Community, the Navajo Nation, the 

Yavapai-Apache Nation, the Hopi Tribe, the Pascua Yaqui Tribe, 

the Yavapai-Prescott Tribe, and the Tonto Apache Nation, have 

CAP water allocations or contracts. In exchange for allocations 

of CAP water at reduced cost and access to funds for the 

development of water infrastructure, the tribes with water 

settlement agreements have released their claims to other water 

in Arizona. Excess NGS power owned by Reclamation that is not 

used by CAP is sold and profits are deposited into the Lower 

Colorado River Basin Development Fund (Development Fund) to 

support the tribal water settlement agreements. The U.S. 

Department of the Interior (DOI or Interior), through 

Reclamation, plays an important role in the implementation of 

these settlement agreements and the management of the 

Development Fund. 

The coal used by NGS is supplied by the Kayenta Mine, 

operated by Peabody Energy and located on reservation lands of 
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both the Navajo Nation and the Hopi Tribe. Taxes and royalties 

from NGS and the Kayenta Mine are paid to the Navajo Nation and 

Hopi Tribe, contributing to the annual revenues for both 

governments. EPA understands that the process is underway to 

renew site leases for NGS and the Kayenta Mine, as well as 

associated rights of way agreements and contracts with the 

Navajo Nation and Hopi Tribe. 

Given the extent of federal and tribal interests in NGS, on 

January 4, 2013, EPA, DOI, and the Department of Energy (DOE) 

signed a joint federal agency statement (Joint Statement) 

committing to collaborate on several short- and long-term goals, 

including analyzing and pursuing strategies for providing clean, 

affordable, and reliable power, affordable and sustainable 

water, and sustainable economic development to key stakeholders 

who currently depend on NGS.2 The Joint Statement also recognizes 

the trust responsibility of the Federal government to Indian 

tribes. 

B. Summary of Statutory and Regulatory Framework for Addressing 

Visibility and Sources Located in Indian Country 

In our Proposed Rules, we provided a detailed discussion of 

the statutory and regulatory framework for addressing visibility 

2 See document title “2013_0104 Joint Federal Agency Statement on NGS” within 

document number 0005 in the docket for this proposed rulemaking at EPA-R09-

OAR-2013-0009, which can be found at www.regulations.gov. 
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impairment in the mandatory Class I Federal Areas, addressing 

sources located in Indian country under the statute and the 

Tribal Authority Rule (TAR), and developing BART determinations 

pursuant to the CAA and the BART Guidelines set forth in 

Appendix Y to 40 CFR Part 51.3 Here, we provide a brief summary 

of the statutory and regulatory framework. 

Title I, part C, subpart II of the CAA Amendments of 1977 

establishes a visibility protection program that 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 which impairment results from man-made air 

pollution.”4 EPA promulgated regional haze regulations 

implementing the program on April 22, 1999.5 Consistent with the 

statutory requirement in 42 U.S.C. 7491(b)(2)(a), EPA’s 1999 

regional haze regulations include a provision that States must 

require certain major stationary sources to procure, install, 

and operate BART. This provision covers sources in listed 

industrial categories with the potential to emit 250 or more 

tons per year of an air pollutant that were “in existence on 

August 7, 1977, but which ha[ve] not been in operation for more 

than fifteen years as of such date.” These sources are 

3 See 78 FR 8274 (February 5, 2013) and 78 FR 62509 (October 22, 2013). 

4 See 42 U.S.C. 7419A(a)(1). 

5 See 64 FR 35765 (April 22, 1999). 
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considered to be “BART-eligible.”6 NGS meets these criteria and 

is a BART-eligible source.7

BART-eligible sources that are reasonably anticipated to 

cause or contribute to visibility impairment are “subject” to 

the BART requirements.8 Generally speaking, a BART-eligible 

source with a predicted visibility impact of 0.5 deciviews (dv) 

or more in a Class I area is considered to “contribute” to 

visibility impairment.9 NGS contributes to visibility impairment 

at 11 surrounding Class I areas in excess of this threshold, and 

is thus subject to BART. 

In determining BART, States are required to take into 

account five factors identified in the CAA and EPA’s 

regulations.10 Those factors are: (1) the costs of compliance, 

(2) the energy and non-air quality environmental impacts of 

compliance, (3) any pollution control equipment in use or in 

existence at the source, (4) the remaining useful life of the 

source, and (5) the degree of improvement in visibility which 

may reasonably be anticipated to result from the use of such 

6 See 40 CFR 51.308(e)(1). 

7 See 74 FR 44314 (August 28, 2009); 78 FR 8279 (February 5, 2013); see also 

56 FR 50172 (October 3, 1991) addressing BART for SO2 based on Reasonably 

Attributable Visibility Impairment. 

8 See 70 FR 39104 at 39161 (July 6, 2005). 

9 Id. 10 42 U.S.C. 7491(g)(2) and 40 CFR 51.308(e)(1)(A)(ii)(A). 
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technology.11 EPA’s guidelines for evaluating BART provide more 

detail and are set forth in Appendix Y to 40 CFR Part 51. 

In 1998, EPA promulgated the Tribal Authority Rule (TAR) 

relating to implementation of CAA programs in Indian country.12

In the TAR, EPA determined that it has the discretionary 

authority to promulgate “such federal implementation plan 

provisions as are necessary or appropriate to protect air 

quality” consistent with CAA sections 301(a) and 301(d)(4) when 

a tribe has not submitted or EPA has not approved a Tribal 

Implementation Plan (TIP).13 EPA has previously promulgated FIPs 

under the TAR to regulate air pollutants emitted from NGS.14

Under the CAA, compliance with emission limits determined 

to be BART must be achieved as expeditiously as practicable but 

not later than 5 years after the effective date of the final 

BART determination (See CAA 169A(b)(2)(A) and (g)(4)). As 

discussed in greater detail in our Proposed Rule, EPA recognizes 

that the circumstances related to NGS create unusual and 

11 40 CFR 51.308(e)(1)(ii)(A). 

12 See 40 CFR part 49; see also 59 FR 43956 (August 25, 1994) (proposed rule); 

63 FR 7254 (February 12, 1998) (final rule); Arizona Public Service Company 

v. EPA, 211 F.3d 1280 (DC Cir. 2000), cert. den., 532 U.S. 970 (2001) 

(upholding the TAR). 

13 See 40 CFR 49.11(a). 

14 See 56 FR 50172 (October 3, 1991). In 1999, EPA proposed a FIP for NGS to 

fill the regulatory gap that existed because Arizona State permits and SIP 

rules are not applicable or enforceable in the Navajo Nation, and the Tribe 

had not sought approval of a TIP covering the plant. 64 FR 48731 (September 

8, 1999). EPA then re-proposed the FIP with some additional conditions in 

September 2006. 71 FR 53631 (September 12, 2006). EPA finalized that NGS FIP 

on March 5, 2010. 75 FR 10174. 
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significant challenges for a 5-year compliance schedule.15 Based 

on those challenges and our discretion under the TAR for 

implementing CAA requirements in Indian country, we considered 

other options that are consistent with the CAA and RHR, and that 

provide for a more flexible, extended compliance schedule. 

EPA’s BART regulations allow an alternative in lieu of 

BART, provided the alternative results in greater reasonable 

progress than would have been achieved through installation of 

BART.16 Generally, an alternative is considered to be approvable 

provided it results in greater emissions reductions and the 

geographic distribution in emissions from the alternative is not 

substantially different than the distribution of the emissions 

under BART.17 For a state that is subject to the submittal 

deadlines in the RHR, the regulations provide that alternatives 

to BART must ensure that all necessary emission reductions occur 

15 Because of its complicated history and its location on the Navajo Nation, 

NGS faces numerous unique complexities and the unusual requirement to comply 

with NEPA for lease and other rights-of-way approvals, which apply only to 

NGS and Four Corners Power Plant, the other coal-fired power plant located on 

the Navajo Nation. EPA also understands the importance of the continued 

operation of NGS and the Kayenta Mine to the Navajo Nation and Hopi Tribe as 

a source of direct revenues through lease payments and coal royalties, as 

well as the importance of Reclamation’s share of NGS to supply water to many 

tribes located in Arizona in accordance with several water settlement acts. 

EPA also recognizes that Reclamation may have fewer options compared to the 

other owners for financing pollution control or other large capital 

improvement projects at NGS. SRP expressed concern that the owners of NGS may 

choose to retire the facility if faced with the financial risk of making a 

large capital investment within 5 years without also having certainty that 

the lease and contract re-negotiations would conclude in a timely and 

favorable manner. 

16 40 CFR 51.308(e)(2). 

17 40 CFR 51.308(e)(3). 
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within the period of the first long-term strategy for regional 

haze (i.e., by 2018) for states that were required to submit 

regional haze SIPs in December 2007.18 Thus, if states had 

submitted timely regional haze SIPs in 2007 with BART compliance 

deadlines in 2012, the RHR provided more than 5 additional years 

for the implementation of alternatives to BART. 

C. Summary of Proposed Rule and Supplemental Proposal 

EPA published an advanced notice of proposed rulemaking 

(ANPR) concerning BART for NGS and the Four Corners Power Plant 

in August 2009.19 On February 5, 2013, EPA’s proposed BART 

determination for NGS was published in the Federal Register and 

provided a thorough discussion of the statutory and regulatory 

framework for addressing visibility through application of BART 

for sources located in Indian country, and of the factual 

background for our BART determination at NGS.20 The proposal 

analyzed the five BART factors and proposed to find that BART 

for NGS was installation of emissions controls to meet a NOX

emission limit of 0.055 lb/MMBtu based on a rolling average of 

30 boiler operating days (30-BOD average).21 However, in 

recognition of the important role that NGS and the Kayenta Mine 

play in providing employment and revenue to the Navajo Nation 

18 40 CFR 51.308(e)(2)(iii). 

19 See 74 FR 44314 (August 28, 2009). 

20 See 78 FR 8274 (February 5, 2013). 

21 Id. at 8288. 
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and Hopi Tribe, and the role of Reclamation’s share of 

electricity generated by NGS in fulfilling water settlement 

agreements with numerous tribes located in Arizona, we proposed 

that the potential economic impacts to tribes argue for 

thoughtful consideration of how flexibility in the compliance 

timeframe could be provided consistent with the air quality 

goals of the CAA.22 Therefore, as discussed in our Proposed Rule, 

EPA proposed to exercise our authority and discretion under 

section 301(d)(4) of the CAA and 40 CFR Part 49.11(a) to propose 

an appropriate timeframe for alternative measures to BART under 

the RHR for NGS. We provided a thorough discussion of the legal 

rationale for setting the compliance schedule for alternative 

measures in our Proposed Rule.23

Our Proposed Rule included a framework for evaluating 

alternatives to BART.24 As part of the framework, EPA proposed a 

NOX emission credit for the previous early and voluntary 

installation of low-NOX burners with separated over-fire air 

(LNB/SOFA) over the 2009-2011 timeframe (LNB/SOFA credit). We 

proposed that the LNB/SOFA credit supported setting a compliance 

timeframe based on the flexibility under section 301(d)(4) of 

the CAA and 40 CFR 49.11(a).25 EPA proposed to find that an 

22 Id. at 8284. 23 Id. at 8289. 24 Id. at 8290-92. 25 78 FR 62509 at 62511 (October 22, 2013). 
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alternative is “better than BART” if the total emissions over 

2009-2044 from the alternative measure, minus the LNB/SOFA 

credit, are less than the total emissions under our proposed 

BART determination for the same period (i.e., the BART 

Benchmark). Consistent with this framework, EPA proposed an 

alternative to BART, requiring compliance with an emission limit 

of 0.055 lb/MMBtu on one unit per year in 2021, 2022, and 2023 

(Alternative 1). We calculated that total emissions under 

Alternative 1 over 2009-2044, minus the LNB/SOFA credit, would 

be less than emissions based on the BART Benchmark. Thus, we 

proposed to find that Alternative 1 was “better than BART”. EPA 

recognized that there may be interest in additional flexibility 

beyond the 2021-2023 timeframe. EPA evaluated two additional 

compliance schedules but did not propose to approve them as 

“better than BART” alternatives because total emissions over 

2009-2044 under these compliance schedules exceeded the BART 

Benchmark. However, we noted that potential technologies or 

other options for achieving additional emission reductions could 

bridge the NOX emission reduction deficit for alternatives to 

BART with compliance schedules that do not, by themselves, meet 

the BART Benchmark.26 We invited stakeholders to submit 

26 78 FR 8274 at 8291 (February 5, 2013). 
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additional BART alternatives, consistent with our proposed 

framework, for EPA’s consideration. 

On July 26, 2013, a stakeholder group, known as the 

Technical Work Group on NGS (TWG), submitted an agreement that 

had been established among the seven diverse entities in the 

TWG. We refer to the July 26, 2013, document as the “TWG 

Agreement.” The TWG is composed of representatives from Central 

Arizona Water Conservation District (CAWCD), the Environmental 

Defense Fund (EDF), the Gila River Indian Community (Gila River 

or the Community), the Navajo Nation (Navajo), Salt River 

Project (SRP) on behalf of itself and the other non-federal 

owners, DOI, and Western Resource Advocates (WRA). Although EPA 

attended the opening session of a “kick-off” meeting for the TWG 

on March 21, 2013, at which we described our Proposed Rule, EPA 

did not otherwise participate in the TWG and was not involved in 

any of the discussions leading to submittal of the TWG 

Agreement. 

Appendix B to the TWG Agreement contained TWG’s 

recommendation for an alternative to BART. In general, the 

alternative plan in the TWG Agreement included closure of one 

unit at NGS, or curtailment of net generating capacity by an 

equivalent amount, in 2019 and compliance with a NOX emission 

limit of 0.07 lb/MMBtu on two units at NGS beginning in 2030. 

The TWG Agreement also included a provision requiring the 
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owner/operator of NGS to cease conventional coal-fired 

generation at NGS by the end of 2044. 

EPA independently evaluated Appendix B to the TWG Agreement 

to determine whether it complied with the framework we put forth 

in our Proposed Rule, as well as the statutory and regulatory 

requirements in the CAA and the RHR. On October 22, 2013, EPA 

published a Supplemental Proposal describing the TWG Agreement 

and requesting comment.27 Our Supplemental Proposal contained a 

detailed evaluation of Appendix B to the TWG Agreement along 

with a discussion of our legal rationale for proposing to 

approve requirements consistent with the TWG Agreement as 

meeting the requirements for an alternative to BART. Throughout 

this notice, we refer to the regulations we proposed in our 

Supplemental Proposal that are consistent with Appendix B of the 

TWG Agreement as the “TWG Alternative.” Thus, in this notice, 

the term TWG Alternative refers to EPA’s independent regulatory 

requirements for NGS consistent with the TWG Agreement, rather 

than to Appendix B of the TWG Agreement. 

In our Supplemental Proposal, we proposed to revise the 

numerical value of the BART Benchmark from our Proposed Rule. We 

also proposed a 2009-2044 NOX Cap based on the revised numerical 

value of the BART Benchmark. In our Proposed Rule, we calculated 

27 See 78 FR 62509 (October 22, 2013). 
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the BART Benchmark to be 358,974 tons of NOX. As discussed in our 

Supplemental Proposal, we proposed three changes to the BART 

Benchmark: (1) correction of a transcription error; (2) 

correction of the date that EPA anticipated would be 5 years 

following the effective date of the final rule (i.e., July 1, 

2019 instead of January 1, 2018); and (3) application of the 

LNB/SOFA credit to the BART Benchmark, rather than alternatives 

to BART, to represent emissions under BART if LNB/SOFA had been 

installed concurrently with selective catalytic reduction (SCR) 

to reduce NOX emissions.28 Based on these changes, EPA proposed a 

2009-2044 NOX Cap of 494,899 tons. Although EPA revised our 

accounting method for the LNB/SOFA credit in our Supplemental 

Proposal, EPA provided a demonstration that the method EPA used 

in our Proposed Rule to compare our proposed BART determination 

against BART alternatives was equivalent to the method in the 

Supplemental Proposal.29 The application of the LNB/SOFA credit 

to the BART Benchmark in the Supplemental Proposal represented 

what total emissions over 2009-2044 would have been under our 

proposed BART determination if the operator of NGS had elected 

to install LNB/SOFA concurrently with SCR, i.e., within 5 years 

of a final rule, rather than in 2009-2011. Calculation of the 

BART Benchmark and 2009-2044 NOX Cap in this manner is easier to 

28 Id. Tables 1 and 3 at 62515-6. 29 Id. Table 2 and footnote 32 at 62515. 
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apply and enforce in the context of a cap in NOX emissions 

because the LNB/SOFA credit is built into the BART Benchmark 

rather than subtracted each year from actual cumulative 

emissions.30

In addition to the enforceable 2009-2044 NOX Cap, our 

Supplemental Proposal defines the operating scenarios that would 

be required depending on the final outcome of NGS ownership 

after the expiration of the current lease term at the end of 

2019. In the TWG Agreement, the owners of NGS committed to 

maintain emissions from NGS below the 2009-2044 NOX Cap 

regardless of post-2019 ownership of NGS and the applicable 

operating scenario. As a result, the operating scenarios in the 

TWG Alternative include specific actions for achieving emission 

reductions in 2019 and in 2030. The TWG Alternative also 

provides for an operating scenario that is less well-defined in 

terms of specific actions but establishes a second NOX emissions 

30 In contrast, in our Proposed Rule, we calculated the BART Benchmark and 

emissions under BART alternatives using the actual early installation dates 

for LNB/SOFA and then applied the LNB/SOFA credit to BART alternatives for 

comparison against the BART Benchmark. Although this method would have 

resulted in a lower numerical value for the 2009-2044 NOX Cap, the LNB/SOFA 

credit (representing the early emission reductions achieved over 2009-2018) 

would have instead been subtracted from the calculations of cumulative 

emissions under the BART alternative. Although this is functionally 

equivalent to the method used in the Supplemental Proposal, this method would 

make annual comparisons of actual cumulative emissions under the BART 

alternative against the BART Benchmark more complicated because it would have 

required adjustments every year to total emissions to subtract out the 

LNB/SOFA credit. By accounting for the LNB/SOFA credit in the BART Benchmark, 

the actual annual emissions from NGS can be directly compared to the BART 

Benchmark without any further adjustments. 
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cap over the period of 2009-2029 (2009-2029 NOX Cap) that is 

equivalent to emission reductions that would be achieved by a 

more well-defined operating scenario. The 2009-2029 NOX Cap would 

apply in addition to the 2009-2044 NOX Cap. The Supplemental 

Proposal included requirements for annual emission reporting to 

EPA that would also be made publicly available as part of the 

compliance demonstration for the TWG Alternative. 

D. Summary of Legal Rationale for Compliance Flexibility 

In our February 5, 2013, proposal for NGS, EPA proposed an 

alternative to BART that we referred to as Alternative 1. EPA 

proposed to find that consideration of a compliance schedule 

beyond 2018 for Alternative 1 at NGS was appropriate for a 

number of reasons, including the importance of NGS to numerous 

Indian tribes located in Arizona and the federal government’s 

reliance on NGS to meet the requirements of water settlements 

with several tribes. Providing this timeframe for compliance 

would not, in itself, avoid or mitigate increases in water rates 

for tribes located in Arizona; however, it would provide time 

for the collaborating federal agencies to explore options to 

avoid or minimize potential impacts to tribes, including seeking 

funding to cover expenses for the federal portion of pollution 

control at NGS. 

In developing this framework, EPA proposed to exercise its 

authority and discretion under section 301(d)(4) of the CAA, 42 
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U.S.C. 7601(d)(4) and the TAR, 40 CFR 49.11(a), and proposed an 

appropriate timeframe for an alternative measure under the RHR 

for NGS. EPA considered this timeframe to be consistent with the 

general programmatic requirements. Under the RHR, States and 

regulated sources had almost 20 years from the issuance of the 

rule in 1999 to design and implement alternative measures to 

BART. For numerous reasons, including the myriad stakeholder 

interests and complex governmental interests unique to NGS, we 

are only now addressing the BART requirements for NGS. 

Our proposal to require emission reductions beyond 2018 was 

supported by CAA section 301(d)(4) and the TAR codified at 40 

CFR 49.11(a). The TAR reflects EPA’s commitment to promulgate 

“such Federal implementation plan provisions as are necessary or 

appropriate to protect air quality” in Indian country where a 

tribe either does not submit a Tribal Implementation Plan (TIP) 

or does not receive approval of a submitted TIP (emphasis 

added). 

The use of the term “provisions as are necessary or 

appropriate” indicates EPA’s determination that it may only be 

necessary or appropriate to promulgate a FIP of limited scope. 

The United States Court of Appeals for the Tenth Circuit has 

previously endorsed the application of this approach in a 

challenge to the FIP for the Four Corners Power Plant, stating: 

“[40 CFR 49.11(a)] provides the EPA discretion to determine what 
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rulemaking is necessary or appropriate to protect air quality 

and requires the EPA to promulgate such rulemaking.”31 The court 

went on to observe: “Nothing in section 49.11(a) requires EPA . 

. . to submit a plan meeting the completeness criteria of [40 

CFR part 51] Appendix V.”32 While the decision in the Tenth 

Circuit focused on 40 CFR part 51, Appendix V, EPA believes the 

same considerations apply to the promulgation of a FIP intended 

to address the objectives set forth in 40 CFR 51.308(e)(2). In 

particular, EPA has discretion to determine if and when a FIP 

addressing the objectives set forth in 40 CFR 51.308(e)(2) 

should be promulgated, which necessarily includes discretion to 

determine the timing for complying with the requirements of any 

such FIP. 

III. Summary of Final FIP Provisions 

EPA is finalizing our finding that it is necessary or 

appropriate to promulgate a source-specific FIP requiring NGS to 

achieve NOX emission reductions required by the BART provisions 

of the CAA and RHR. EPA is determining that our proposed NOX

emission limit of 0.055 lb/MMBtu, based on our analysis of the 

relevant factors, establishes the appropriate BART Benchmark for 

determining “better than BART.” Further, we are finalizing our 

assessment that the TWG Alternative, which establishes an 

31 See Ariz. Public Serv. Co. v. EPA, 562 F.3d 1116 (10th Cir. 2009). 32 Id.
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enforceable 2009-2044 cap on NOX emissions from NGS over the life 

of the facility is “better than BART.” Finally, we are 

finalizing the TWG Alternative as the FIP requirements for NGS. 

EPA is promulgating four possible operating scenarios under 

the TWG Alternative (see Table 1). The operator of NGS must 

implement one of the four enforceable operating scenarios in 

order to comply with the 2009-2044 NOX Cap. The applicable 

operating scenario will depend on the outcome of ownership 

changes related to LADWP, NV Energy, and Navajo Nation, as well 

as whether the operator of NGS can increase capacity (by no more 

than 189 MW) to accommodate ownership changes, without 

triggering New Source Review permitting requirements, as 

described in Table 1. Once the ownership outcomes are finalized, 

the operator of NGS must implement the applicable Alternative as 

shown in Table 1. For example, if LADWP and NV Energy both 

retire their ownership shares of NGS and the Navajo Nation does 

not elect to purchase an ownership share of NGS, TWG Alternative 

A1 applies and the operator of NGS must implement Alternative A1 

and may not elect to implement Alternatives A2, A3, or B. By 

December 1, 2019, the operator of NGS must notify EPA of the 

applicable Alternative (i.e., TWG Alternative A1, A2, A3, or B). 

In addition to the enforceable 2009-2044 NOX Cap, 

Alternatives A1, A2, and A3 each has enforceable emission 

reduction measures in 2019 and 2030 (see Table 1). Under 
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Alternative B, in addition to the enforceable 2009-2044 NOX Cap, 

the operator of NGS must also ensure that cumulative NOX

emissions over 2009-2029 comply with the 2009-2029 NOX Cap. The 

2009-2029 NOX Cap is calculated based on emissions that would 

have been emitted over that period under Alternative A1. Under 

all Alternatives, if, based on required annual reports submitted 

by the operator of NGS to EPA, cumulative emissions of NOX from 

NGS exceed the 2009-2044 NOX Cap at any time prior to December 

31, 2044, the operator of NGS must permanently cease operation 

of NGS. In addition, under Alternative B, if cumulative 

emissions of NOX exceed the 2009-2029 NOX Cap prior to 2029, the 

operator of NGS must temporarily cease operation of all units at 

NGS.33 Under all Alternatives, the operator must permanently 

cease operation of all units at NGS by December 22, 2044. 

Under all TWG Alternatives, the operator of NGS must report 

to EPA annual emissions and heat input data and must make this 

information publicly available on its website. In addition, 

under TWG Alternative B, the operator must also submit to EPA 

annual Emission Reduction Plans projecting year-by-year 

emissions covering the 2020-2029 and 2030-2044 periods so that 

there is a plan for operation of NGS that ensures that 

33 The combination of the 2009-2044 and 2009-2029 NOX Caps under TWG 

Alternative B means that if NGS exceeds the 2009-2029 NOX Cap prior to 2029 it 

must cease operation, but the operator may re-start operation after 2030 as 

long as cumulative emissions have not yet exceeded the 2009-2044 NOX Cap. 
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cumulative emissions of NOX do not exceed the 2009-2029 NOX Cap 

and the 2009-2044 NOX Cap. Although year-by-year emissions 

projected in the annual Emission Reduction Plans are not 

enforceable (i.e., emissions in a given year are not required to 

match projections for that year in an Emission Reduction Plan), 

the requirement to submit Emission Reduction Plans is 

enforceable, and provides the operator with a framework for 

planning for future emissions reductions. The requirement also 

provides EPA and the public the opportunity to monitor and 

evaluate progress of emission reductions under TWG Alternative 

B. 
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Table 1: Summary of the Major Regulatory Provisions of the TWG Alternative 

Applicability 

(Step 1) 

 If LADWP and NV Energy both exit NGS without selling their ownership 

interests (i.e., retire shares), or both exit by selling to an existing NGS participant; or one retires shares and the other sells to an existing NGS participant; and 

 I

s

d

(Step 2)  If Navajo Nation does 

not purchase ownership share by 12/31/19; 

 If Navajo Nation 

purchases up to 170 MW by 12/31/19; and 

 If Navajo Nation 

purchases up to 170 MW by 12/31/19; and 

 

(Step 3)  n/a  If Participants 

increase capacity without triggering permit requirements; 

 If Participants cannot 

increase capacity without triggering permitting); 

 n

Applicable Alternative 

Then TWG Alternative 

A1 applies 

Then TWG Alternative 

A2 applies 

Then TWG Alternative 

A3 applies 

Th

Applicable Requirements 

 Comply with 2009-2044 NOX Cap of 494,899 tons 

 Permanently cease operation of all units if cumulative emissions before 2044 ex

 Owner/operator permanently ceases conventional coal-fired generation 

Additional Emission Cap 

 n/a  C

N

Specific Requirements* 

 By 12/31/19 

permanently close 1 unit 

 By 12/31/30 meet NOX

limit of 0.07 lb/MMBtu on 2 units 

 By 12/31/19 

permanently close 1 unit 

 By 12/31/19 operator 

may increase capacity by no more than 189 MW 

 By 12/31/30 meet 0.07 

lb/MMBtu on 2 units 

 By 12/31/19 reduce net 

generating capacity by no less than 561 MW 

 By 12/31/30 meet NOX

limit of 0.07 lb/MMBtu on 2 units 

 T

oee

Reporting  By December 1, 2019, notify EPA of applicable Alternative (A1, A2, A3, or B) 

 Submit annual report summarizing heat input and annual and cumulative emissions o Make annual report publicly available on website  Submit application to revise Part 71 Operating Permit by December 31, 2020 

Additional Reporting 

 n/a  B

asRpec

* All units must comply with the existing NOX emission limit of 0.24 lb/MMBtu established i

permitting action. See discussion in Proposed Rule at 78 FR at 8284 (February 5, 2013). Thto each unit unless otherwise stated.
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In our final rule, EPA has included several revisions to 

the proposed regulatory text (40 CFR 49.5513(j)) put forth in 

the Supplemental Proposal. The substantive revisions include: 

1. Revision to §49.5513(j)(3) to clarify that EPA is 

finalizing a “better than BART” Alternative; 

2. Additions to §49.5513(j)(3) to specify that the operator 

must temporarily cease operation of NGS if cumulative 

emissions of NOX exceed the 2009-2029 NOX Cap of 416, 

865 tons at any time prior to December 31, 2029 (under 

Alternative B), and must permanently cease operation of 

NGS if cumulative emissions of NOX exceed the 2009-2044 

NOX Cap of 494,899 tons at any time prior to December 

31, 2044 (under all Alternatives); 

3. Additions to §49.5513(j)(3)(i)(A)(2), (B)(3), and 

(C)(2), to specify that the NOX emission limit of 0.07 

lb/MMBtu is to be calculated based on a rolling average 

basis of 30 boiler operating days; 

4. Correction to §49.5513(j)(3)(ii)(D), to specify that 

Alternative B shall also apply if either of the 

Departing Participants (i.e., LADWP or NV Energy) 

remains as a participant in NGS; 

5. Addition of §49.5513(j)(3)(iii), consistent with the TWG 

Agreement, to require the owners of NGS to cease its 
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operation of conventional coal-fired generation at NGS 

no later than December 22, 2044;34

6. Addition to §49.5513(j)(4)(ii), to change the annual 

reporting date to begin in 2015 instead of the specific 

date of January 31, 2015, and specify that the report 

must be submitted to EPA and also made publiclyavailable within 30 days of the submittal deadline 

associated with the annual emission inventory required 

by the Part 71 Operating Permit for NGS; 

7. Addition to §49.5513(j)(4)(iii), to clarify that the 

Part 71 Operating Permit for NGS shall incorporate 

practically enforceable limits for NOX of 0.24 lb/MMBtu, 

on a 30‐day rolling average basis, for each Unit 

equipped with LNB/SOFA, and 0.07 lb/MMBtu, on a rolling 

average basis of 30 boiler operating days, for each Unit 

equipped with SCR, as federally enforceable permit 

conditions; and 

34 See page 14 of the TWG Agreement (section IV.F). This section of the TWG 

Agreement also states that “[a]t its election, consistent with the Lease 

Amendment, the Navajo Nation may continue plant operations at NGS after 

December 22, 2044 consistent with EPA approval.” EPA is not including this 

provision into the regulatory requirements at §49.5513(j)(3)(iii), however, 

EPA expects that NGS would be substantially modified if the Navajo Nation 

elects to continue operation of the facility after NGS ceases conventional 

coal-fired generation in 2044, and that NGS must then meet all applicable 

regulatory and permitting requirements in existence at that time. 
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8. Addition of §49.5513(j)(4)(iv)(C), to specify that the 

requirement to submit annual Emission Reduction Plans 

beginning no later than December 31, 2019, must be 

incorporated into the Part 71 Operating Permit for NGS 

as a federally enforceable permit condition. 

9. Revision to §49.5513(j)(7) to require the owner or 

operator of NGS to maintain records that document 

compliance with the NOX Cap (e.g., daily emissions and 

heat input data) for the life of the facility, rather 

than at least five years. 

10. Deletion of §49.5513(j)(7)(vi) that required recordkeeping of all major maintenance activities conducted on 

emission units, air pollution control equipment, and 

CEMS because record-keeping of maintenance activities 

are not needed to ensure compliance with the 2009-2029 

and 2009-2044 NOX Caps. 

11. Revision to §49.5513(j)(11) to state that the 

affirmative defense provisions of paragraphs §49.5513 

(c)(2) and §49.5513(i) do not apply to paragraph 

§49.5513(j).35

35 We note that in our Supplemental Proposal, we reported the affirmative 

defense provisions as paragraphs (c)(1) and (g)(3) in error. The correct 

citations are to paragraph (c)(2) and paragraph (i) of 40 CFR 49.5513. 
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Revision (1) above is necessary to clarify that EPA is 

finalizing a “better than BART” alternative in lieu of BART. 

The BART Benchmark used to assess the “better than BART” 

alternative is based on our proposed BART determination for NGS, 

and the “better than BART” alternative is consistent with our 

Supplemental Proposal of the TWG Alternative. Revision (3) above 

is necessary because EPA inadvertently did not specify the 

averaging period associated with the emission limits for NOX in 

our Supplemental Proposal. Revisions (2) and (4) through (10) 

above are in response to comments submitted to EPA on our 

Supplemental Proposal. Revision (11) above amends a proposed 

provision in our Supplemental Proposal that limited the 

applicability of the existing affirmative defense provisions for 

startups, shutdowns, and malfunctions (from the previous FIP for 

NGS codified at 40 CFR 49.5513(c)(2) and 40 CFR 49.5513(i)) to 

malfunctions.36 In this Final Action, we are revising (j)(11) to 

make clear that the existing affirmative defense provisions do 

not apply to the emission limits established in the TWG 

Alternative. 

Following the close of the public comment period, the United 

States Court of Appeals for the D.C. Circuit issued a decision 

36 See final action for the previous FIP for NGS at 75 FR 10179 (March 5, 

2010). 
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concerning various aspects of the NESHAP for Portland cement 

plants issued by EPA in 2013, including the affirmative defense 

provision of that rule.37 The court found that EPA lacked 

authority to establish an affirmative defense for private civil 

suits and held that under the CAA, the authority to determine 

civil penalty amounts lies exclusively with the courts, not EPA. 

The court did not address whether such an affirmative defense 

provision could be properly included in a SIP. However, the 

court’s holding makes it clear that the CAA does not authorize 

promulgation of such a provision by EPA. In particular, the 

court’s decision turned on an analysis of CAA sections 113 

(Federal enforcement) and 304 (Citizen suits). These provisions 

apply with equal force to a civil action brought to enforce the 

provisions of a FIP. The logic of the court’s decision thus 

applies to the promulgation of a FIP and precludes EPA from 

including an affirmative defense provision in a FIP. Therefore, 

we are not including an affirmative defense provision in the 

final FIP. 

We note that, if a source is unable to comply with emission 

standards as a result of a malfunction, EPA may use case-by-case 

enforcement discretion, as appropriate. Further, as the D.C. 

37 NRDC v. EPA, 2014 U.S. App. LEXIS 7281 (D.C. Cir.), in the docket for this 

rulemaking. 
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Circuit recognized, in an EPA or citizen enforcement action the 

court has the discretion to consider any defense raised and 

determine whether penalties are appropriate.38

IV. Summary of Major Issues Raised by Commenters 

The public comment period for our Proposed Rule opened on 

February 5, 2013. On two occasions, we extended the comment 

period on our Proposed Rule at the request of stakeholders, with 

a final closing date of January 6, 2014. Although we posted the 

pre-publication version of our Supplemental Proposal to the 

docket and to our website on September 25, 2013, the public 

comment period for the Supplemental Proposal officially began 

when it was published in the Federal Register on October 22, 

2013.39 We accepted public comments on our Supplemental Proposal, 

concurrently with our Proposed Rule, until January 6, 2014. Our 

Supplemental Proposal also included notice of five public 

hearings, one on the Navajo Nation, one on the Hopi reservation 

and three in the State of Arizona. The public hearings occurred 

during the week of November 12, 2013. In all, 194 oral 

testimonies were presented at the public hearings. 

38 Id. at 24 (arguments that violations were caused by unavoidable technology 

failure can be made to the courts in future civil cases when the issue 

arises). 

39 See document number 0182 (Pre-publication version of Supplemental Proposal 

for NGS Signed on September 25, 2013), posted to docket on September 25, 2013 

and publication of Supplemental Proposal in Federal Register at 78 FR 62509 

(October 22, 2013). 
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We received over 77,000 written comments. Of these, over 

76,800 comments came from private individuals who submitted 

substantially similar comments by email or postcard. We received 

an additional 300 unique written comments (not including 

duplicates, requests for extension of the public comment period, 

or requests for additional hearings) from a variety of 

individuals and entities, including tribal governments, 

environmental or public interest advocacy groups, water interest 

groups, groups representing industry or commerce, the operator 

and participants in NGS and the Kayenta Mine, elected officials, 

and state and local governments. 

In this notice, EPA is providing an abbreviated summary of 

the major comments and EPA’s responses to those comments, 

grouped together by subject matter. The complete response to 

comments document (RTC) includes the full summary of all 

substantive comments and EPA’s full responses to those comments. 

The RTC is included in the docket for this rulemaking.40 We are 

not responding to comments unrelated to our Proposed Rule or 

Supplemental Proposal for NGS in this notice or in the RTC. 

A. General Comments from Public Hearings 

40 See document titled “EPA Responses to Comments on Final Rule for NGS” in 

the docket for this rule. 
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Comment: Contribution of NGS to the local and state economy and 

support for TWG Alternative 

 Many commenters at the public hearings preferred the TWG 

Alternative because they believe that EPA’s proposed BART 

determination would force NGS and the Kayenta Mine to close, 

causing economic harm to an area where the majority of residents 

are low-income and where opportunities for employment are 

limited. Many commenters stressed that NGS employs over 500 

people and the Kayenta Mine has over 400 employees, and the loss 

of these jobs would only exacerbate the unemployment rate in the 

area, which currently ranges from 47 percent to 60 percent. 

 A number of commenters noted that NGS supplies more than 

90 percent of the energy used by Central Arizona Water 

Conservation District (CAWCD), which operates the Central 

Arizona Project (CAP), which transfers water from the Colorado 

River throughout Arizona. A few commenters urged EPA to uphold 

its federal trust obligations and ensure that tribal communities 

continue to have access to affordable water, and advised EPA to 

make a decision consistent with the legal rights that the Gila 

River Indian Community and other stakeholders negotiated and 

that Congress granted under the Arizona Water Settlements Act of 

2004. 

 A few commenters support the TWG Alternative because they 

believe it is a fair compromise created by a diverse group of 
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stakeholders that provides a path for future operation at NGS by 

allowing for potential ownership changes and by providing an 

extension to install SCR technology, while still ensuring that 

the total emission reductions of NOX will be greater than those 

achieved under EPA’s proposed BART determination. 

Response:

 EPA recognizes the contribution of NGS and the Kayenta Mine 

to the economy of the Navajo Nation, the Hopi Tribe, the city of 

Page, and the state of Arizona. In our Proposed Rule, EPA 

discussed the history of NGS and the relationship between NGS, 

the Central Arizona Project, and numerous tribes located in 

Arizona.41 EPA notes that NGS is a facility that is subject to 

the BART requirement of the RHR, and emissions from NGS affect 

visibility at 11 national parks and wilderness areas in the 

Southwest. The analyses in our Proposed Rule and Supplemental 

Proposal determined that additional controls at NGS are costeffective, will significantly reduce the contribution of NGS to 

visibility impairment at numerous Class I areas, and should not 

cause NGS to retire. However, for a number of reasons, including 

the importance of NGS to numerous Indian tribes located in 

Arizona and the federal government’s reliance on NGS to meet the 

requirements of water settlements with several tribes, EPA also 

41 See 78 FR 8274, at 8275 (February 5, 2013). 
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outlined a framework for considering “better than BART” 

alternatives that ensures emission reductions while providing 

additional flexibility to the operator of NGS.42

 EPA agrees with comments that the TWG Agreement represents 

a compromise between diverse stakeholders, although we recognize 

that the members of the TWG did not invite all affected 

stakeholders to participate in their discussions. The TWG 

Alternative provides certainty for future operation of NGS, 

flexibility in the compliance timeframe, and more emission 

reductions of NOX than would have been achieved under EPA’s 

proposed BART determination. Based on our analysis in our 

Supplemental Proposal and consideration of all comments 

received, EPA is taking action to finalize requirements 

consistent with the TWG Agreement we put forth in our 

Supplemental Proposal, i.e., the TWG Alternative. 

Comment: Impact of air pollutants from NGS on public health and 

welfare and support for proposed BART determination

 Several commenters favor EPA’s proposed BART determination 

for NGS because they believe that emissions from NGS cause 

health problems in the area, including respiratory illness and 

heart disease. One commenter cited a Clean Air Task Force study 

which states that NGS is responsible for approximately 

42 Id. and 78 FR 62509 (October 22, 2013). 
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$127 million in health costs every year. Many of these 

commenters urged EPA to conduct health studies to determine the 

actual impact to health in these communities. 

 Some commenters favor stringent controls because they 

believe that emissions from NGS adversely affect native plant 

species and harm traditional dry land farming. Others assert 

that emissions from NGS can be linked to high levels of mercury 

found in fish species located in nearby lakes. Many commenters 

expressed concerns over the well-being of the Navajo Aquifer. A 

number of commenters favor stringent controls because they 

believe that emissions produced from NGS contribute to climate 

change. 

 In contrast, a few commenters questioned the extent to 

which emissions from NGS impact public health and the 

environment, asserting that the haze is a result of emissions 

from natural sources (e.g., volcanoes, wind/dust storms, and 

forest fires) and pollution produced from nearby cities (i.e., 

Phoenix, Los Angeles, and Las Vegas). Another commenter asserted 

that EPA’s website states that vehicles are the largest 

producers of NOX emissions in the country and concludes that EPA 

is ignoring mobile sources and unfairly targeting stationary 

sources. 

 Some commenters preferred EPA’s proposed BART determination 

over the TWG Alternative because they believe that the 
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alternative is based on a false premise. They asserted that the 

closure of a single unit is not equivalent to cleaning up all 

three units because the reduction in capacity will ultimately 

require new electricity generation elsewhere because the demand 

for power does not change. 

Response:

Protection of human health and the environment is EPA’s 

mission and forms the basis for many Agency actions, including 

establishing the National Ambient Air Quality Standards (NAAQS), 

and promulgation of regulations such as the New Source 

Performance Standards (NSPS) and the National Emission Standards 

for Hazardous Air Pollutants (NESHAP). In addition to Clean Air 

Act requirements to protect human health, in the 1977 Clean Air 

Act Amendments, Congress declared as a national goal the 

prevention of any future, and the remedying of any existing, 

impairment of visibility in mandatory class I Federal areas 

which impairment results from manmade air pollution (See CAA 

§169A). 

EPA agrees that visibility-impairing pollutants are among 

the same pollutants that affect human and ecosystem health; 

however, health studies are beyond the scope of this BART 

analysis. Similarly, hazardous air pollutants (HAPs), such as 
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mercury, are not visibility-impairing pollutants and therefore 

are beyond the scope of this BART analysis.43

EPA agrees that climate change is an important issue.44

However, the RHR addresses pollutants that impair visibility and 

is not intended to address pollutants that contribute to climate 

change. EPA has developed various programs and activities to 

address emissions of greenhouse gases.45 On June 2, 2014, EPA 

signed a proposal to cut greenhouse gas emissions from coalfired power plants by up to 30 percent by 2030.46 Although 

regulation of greenhouse gases is conducted under separate 

statutory requirements from regional haze, EPA is mindful that 

this BART determination for NGS is not the only regulatory 

program that affects this facility and the region. 

EPA agrees with comments that mining and combustion of coal 

affect the environment. EPA notes that Reclamation has started 

its process to develop an Environmental Impact Statement (EIS) 

required under the National Environmental Protection Act (NEPA) 

for activities resulting from the continued operation of NGS and 

the Kayenta Mine.47 The on-going NEPA process provides numerous 

43 Emissions of HAPs from various source categories are addressed generally 

through the NESHAP. EPA addressed mercury emissions from power plants 

specifically in the final Mercury and Air Toxics Standard (MATS). 77 FR 9304 

(February 16, 2012). 

44 http://www.epa.gov/climatechange/basics/. 

45 http://www.epa.gov/climatechange/EPAactivities.html. 

46 See http://www2.epa.gov/carbon-pollution-standards. 

47 For more information, please see www.ngskmc-eis.net. 
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opportunities and the appropriate forum to raise concerns 

related to the impacts of mining and use of water from the 

Navajo Aquifer. We further note that representatives of DOI 

attended all the public hearings on NGS held by EPA and are 

aware of the issues raised by commenters during the BART process 

regarding mining and the Navajo Aquifer. 

EPA disagrees with the assertion that EPA is unfairly 

targeting stationary sources of emissions and ignoring the 

significant contribution of motor vehicle emissions. Consistent 

with title II of the CAA, the EPA Office of Transportation and 

Air Quality protects public health and air quality by, among 

other things, regulating air pollution from motor vehicles, 

engines, and the fuels to operate them.48 New cars and sport 

utility vehicles sold today have emission levels of 

hydrocarbons, NOX, and carbon monoxide that are 98 – 99 percent 

lower than new vehicles sold in the 1960s on a per mile basis.49

Similarly, standards established for heavy-duty highway and nonroad sources require emission rate reductions on the order of 90 

percent or more for particulate matter and NOX. In 2014, EPA 

finalized new vehicle emission standards and reduced the fuel 

sulfur content of gasoline to achieve additional reductions in 

48 http://www.epa.gov/otaq/. 

49 See, e.g., 76 FR 74854, at 74900 (December 1, 2011). 
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tailpipe and evaporative emissions from passenger cars, lightduty vehicles, medium-duty passenger cars, and some heavy-duty 

vehicles starting in 2017.50

EPA agrees that forest fires and volcanic eruptions, when 

they occur, can impact visibility to a greater extent than 

anthropogenic sources of emissions. However, Congress directed 

EPA to develop rules to address on-going emissions from 

stationary sources subject to BART to remedy the existing 

impairment of visibility in Class I areas and restore visibility 

to natural conditions. 

EPA disagrees with assertions that the TWG Alternative is 

based on a false premise because the closure or curtailment of 

one unit would just result in electricity being produced 

elsewhere. Closure of one unit at NGS or the curtailment of an 

equivalent amount of electricity generation is possible based on 

LADWP and NV Energy’s intended divestiture from NGS. Consistent 

with state law in California and Nevada, additional electricity 

needed to replace lost generation from NGS, associated with 

LADWP and NV Energy’s divestiture, would come from energy 

50 See Fact Sheet for Tier 3 Standards available at 

http://www.epa.gov/otaq/documents/tier3/420f14010.pdf 
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sources that emit less air pollution than a conventional coalfired power plant operating with SCR on all units.51

Comments regarding specific aspects of the TWG Alternative 

are discussed in Section 9.0 of the RTC. 

Comment: Environmental and Social Justice

 Several commenters consider the presence of NGS and several 

other power plants in and around the Navajo Nation to represent 

an environmental and economic justice issue. One commenter noted 

that a Navajo water hauler in Kaibeto, a Navajo community near 

Page, pays 10 to 20 times more for water, or $13,000 per acre 

foot, than municipal CAP water users in Glendale or a farmer in 

Tempe, who pay $551 and $41 per acre feet, respectively. 

 Several commenters opined that the leaders of the Navajo 

Nation and EPA have not protected the interests of the local 

population. A few expressed concerns over how the alternatives 

were written, noting that many tribal residents do not 

understand the technical language used in the documents and 

therefore cannot adequately comment on the validity of the 

alternatives proposed. Some commenters argued that pollution can 

be controlled using existing technology and EPA should apply the 

same standard to NGS as other coal-burning power plants (e.g., 

51 See RTC and references therein. 
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Four Corners Power Plant). A few commenters argued that 

extending the compliance timeframe for NGS demonstrates that the 

federal government considers itself exempt from federal law. 

Several argued that tribal communities do not have the funds to 

develop proposals and/or conduct environmental assessments and 

urged that EPA uphold federal trust responsibilities and create 

an equal playing field. 

Response: 

 EPA defines Environmental Justice as “the fair treatment 

and meaningful involvement of all people regardless of race, 

color, national origin, or income with respect to the 

development, implementation, and enforcement of environmental 

laws, regulations, and policies. EPA has this goal for all 

communities and persons across the country. It will be achieved 

when everyone enjoys the same degree of protection from 

environmental and health hazards and equal access to the 

decision-making process to have a healthy environment in which 

to live, learn, and work.”52

 EPA takes fair treatment and meaningful involvement 

seriously and provided numerous opportunities for tribal 

governments, environmental and tribal non-governmental 

organizations, and other interested stakeholders to provide 

52 http://www.epa.gov/environmentaljustice/. 
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input in the development of our Proposed Rule, Supplemental 

Proposal, and Final Rule for NGS. EPA began our public 

involvement process for a BART determination for NGS in 2009, 

when we published an Advanced Notice of Proposed Rulemaking 

(ANPR). Although we initially provided a 30-day public comment 

period, at the request of tribal governments and other 

interested stakeholders, we extended the comment period for 

tribes another 30 days to October 28, 2009 and, to allow 

additional time for government-to-government consultation on 

NGS, agreed to accept comments from tribes until March 1, 2010. 

EPA received over 6,000 comments on the ANPR.53 During 2009 

through 2012, EPA met with various stakeholders, including 

tribal governments and tribal environmental groups, to discuss 

NGS and hear concerns related to a BART determination for this 

facility.54 We initially provided a 90-day comment period for the 

Proposed Rule on February 5, 2013, and at the request of various 

stakeholders, we provided several extensions of the public 

comment period, which closed on January 6, 2014. During the 11-

month comment period, EPA continued to meet with stakeholders, 

53 See page 25 of the TSD to the February 5, 2013 Proposed Rule. 

54 See, for example document number 0232 in the ANPR docket at EPA-R09-OAR2009-0598, and document numbers 0008 and 0009 in the docket for this rule. 
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at their request, to discuss our proposed BART determination for 

NGS and our framework for “better than BART” alternatives.55

On July 26, 2013, the TWG submitted Appendix B to the TWG 

Agreement to EPA for consideration. EPA posted the TWG Agreement 

to our docket on the same day to provide the public an 

opportunity to review it.56 On September 25, 2013, EPA posted our 

Supplemental Proposal, along with supporting documents, to the 

docket to allow for pre-publication review by interested 

parties.57 The Supplemental Proposal was published in the Federal 

Register on October 22, 2013. The comment period for the 

Supplemental Proposal closed on the same day as the BART 

proposal, on January 6, 2014. The Supplemental Proposal also 

included notice of five open house and public hearing events EPA 

scheduled throughout Arizona in November 2013. The open houses 

allowed members of the public an opportunity to talk with 

representatives from EPA and ask questions. EPA held events at 

the LeChee Chapter House, located on the Navajo Nation, as well 

as in Page, Arizona, and provided oral interpretation services 

between English and Diné (the Navajo language). EPA also held an 

event at the Hopi Day School, located in Kykotsmovi, the seat of 

55 See, for example, document number 0150, 0152, 0166, 0173, 0302, and 0303 in 

the docket for this rule. 

56 See document number 0122 in docket for this rule. 

57 See document numbers 0182, 0183, and 0184 in the docket for this rule. 
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the Hopi tribal government.58 Finally, we also held events in 

Phoenix and in Tucson, Arizona, to allow stakeholders in central 

and southern Arizona, representing CAP water interests and 

several tribes receiving CAP water, the opportunity to provide 

comment and talk with representatives from EPA. Although EPA 

understands that the TSD and Federal Register notices include 

technical information that may be difficult to understand, EPA 

provided Fact Sheets and handouts, written in plain language, at 

the open house and public hearing events.59 EPA representatives 

were also present at the events to discuss and explain our 

Proposals. EPA recognizes that many tribal communities do not 

have the funds to develop alternative proposals or hire experts 

on their behalf; however, this does not diminish such 

communities’ ability to participate in the rulemaking process in 

a meaningful way as EPA takes seriously its responsibility to 

explain its proposal to all interested parties and assesses all 

comments, regardless of the form of the comment or whether or 

not the commenter has a technical background. 

As stated in our Proposed Rule and Supplemental Proposal, 

EPA has determined that these proposed rules, if finalized, will 

58 EPA engaged with the government of the Hopi Tribe to search for an oral 

interpreter between English and the Hopi language, but the Hopi Tribe was 

unable to locate anyone to provide those services. 

59 See document 0219 in the docket for this rule. 
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not have disproportionately high and adverse human health or 

environmental effects on minority or low-income populations 

because they increase the level of environmental protection for 

all affected populations (i.e., require emission reductions from 

NGS).60 EPA recognizes that some commenters may view the 

timeframe for compliance under EPA’s framework for BART 

Alternatives as an environmental justice issue. We note that the 

LNB/SOFA credit, an important component of the extended 

timeframe, was based on real, actual emission reductions 

beginning in 2009 that were voluntary and not required by any 

rule or regulation. We also note that the TWG Alternative, which 

calls for closure of one unit in 2019 (or equivalent 

curtailment) will result not only in greater reductions of NOX 

than would have been achieved under BART, but also reductions of 

several other pollutants, including SO2, PM, CO2, and mercury. 

Thus, although the TWG Alternative includes a compliance 

timeframe for achieving additional reductions in 2030, over 

2009-2044, the TWG Alternative will result in reductions of 

additional pollutants that affect visibility or human health, 

and will provide an enforceable mechanism to ensure that the 

60 See discussions under Executive Order 12898 in 78 FR at 8793 (February 5, 

2013) and 78 FR at 62520 (October 22, 2013). 
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owner/operator of NGS ceases conventional coal-fired electricity 

generation at NGS by the end of 2044. 

EPA recognizes that numerous commenters expressed 

frustration regarding social inequities related to costs and 

benefits of coal mining and combustion and water availability 

and cost. We recommend participating in the EIS process for NGS 

and Kayenta Mine to raise any concerns related to costs, 

benefits, and the environmental and social justice of coal 

mining and coal combustion at the Kayenta Mine and NGS. 

B. Comments on Factor 1 – Cost of Controls 

Comment: EPA underestimated SCR costs 

 Several commenters asserted that EPA underestimated the 

cost of compliance by improperly reworking cost estimates 

developed for SRP by Sargent and Lundy (S&L) in 2010 and 

disregarding real costs that would be incurred. One commenter 

quoted the BART Guidelines and the final RHR to assert that 

although the use of the Control Cost Manual is encouraged, it is 

not mandated, and that EPA has discretion to use additional 

sources of cost information. The commenter believes, therefore, 

that the SRP estimates for the excluded cost items are 

appropriate to use because they are more precise than the 

generic statements that EPA relied upon in the Control Cost 

Manual. 

Response:
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EPA disagrees with the comment that we improperly reworked 

and underestimated the SCR cost estimates. We note, however, 

that even if we had relied only on the cost estimate provided by 

SRP, EPA still would have concluded that SCR is cost-effective 

at NGS. 

EPA used a hybrid approach for our cost analysis that 

relied primarily on the cost estimates provided by SRP, but also 

followed the BART Guidelines to determine whether S&L included 

cost estimates for services or equipment associated with SCR 

that were not allowed under the EPA Control Cost Manual. The 

BART guidelines state “[i]n order to maintain and improve 

consistency, cost estimates should be based on the OAQPS Control 

Cost Manual, where possible”.61 The capital cost estimate EPA 

presented in the proposed rulemaking for SCR plus LNB/SOFA ($541 

million total for Units 1-3) is only 8 percent lower than the 

SRP cost estimate ($589 million). SRP’s cost estimate would not 

have changed our conclusion that SCR is cost-effective at NGS. 

As discussed in the TSD to the proposed rulemaking, EPA 

made four adjustments to SRP’s cost estimates for SCR, namely, 

to exclude “Owners Construction Management, O&M Support and 

Contract Service,” “Owners Legal Support and Insurance,” and 

61 The OAQPS Control Cost Manual is now referred to as the EPA Control Cost 

Manual. 
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“Allowance for Funds Used During Construction,” and to use an 

interest rate of 7 percent.62 Our detailed, line-by-line analysis 

was included in the docket for this proposed rulemaking and 

provided an explanation for why we retained, modified, or 

rejected each line item.63 Please see the RTC for additional 

discussion of these four adjustments to the S&L cost analysis. 

In our proposed rule, we presented total capital and total 

annual cost estimates from EPA and SRP, as well as average and 

incremental cost-effectiveness values based on EPA and SRP 

assumptions for total annual cost and total annual NOX

reductions. Based on SRP’s analysis, average cost-effectiveness 

of SCR+LNB/SOFA at NGS was less than $3,000 per ton and 

incremental cost-effectiveness of SCR+LNB/SOFA (compared to 

SNCR+LNB/SOFA) was approximately $5,300 per ton.64 EPA stated 

that the cost-effectiveness values calculated by both EPA and 

SRP for SCR+LNB/SOFA are lower than or within the range of other 

BART evaluations where EPA or a state has determined that SCR is 

BART (ranging from approximately $2,000 to $6,000 per ton). 

EPA has accordingly determined that SCR is cost-effective at 

NGS.65 Therefore, even if EPA accepted the S&L cost estimates 

62 See Table 12 of the TSD to the February 5, 2013 Proposed Rulemaking, 

available as document number 0014 in the docket for this rule. 

63 See MS Excel document titled “EPA cost analysis for NGS” within document 

number 0004 in the docket for this rule. 

64 See Table 3 of our Proposed Rule, 78 FR at 8281 (February 5, 2013). 

65 See our Proposed Rule at 78 FR at 8281 (February 5, 2013). 
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submitted by SRP, as commenters suggest, EPA would still have 

determined that SCR is cost-effective for NGS. 

Comment: EPA overestimated SCR costs 

 One commenter asserted that EPA overestimated the cost of 

installing SCR at NGS. Although the commenter supported EPA’s 

adjustments to the S&L cost estimates, the commenter asserted 

that further revisions are appropriate. The commenter stated 

that EPA overestimated the following costs: outage costs 

associated with installation and “preinstallation” work; 

catalyst costs; and auxiliary power. In addition, the commenter 

asserted that EPA overestimated annual costs by assuming 20 

years as the basis for amortizing costs and using an inflated 

interest rate of 7 percent. 

Although the commenter concurs with EPA’s conclusion that 

SCR plus LNB/SOFA is cost-effective at $2,240 per ton of NOX

removed, the commenter re-calculated cost-effectiveness to be 

$1,412 per ton for Unit 1, $1,331 per ton for Unit 2, and $1,497 

per ton for Unit 3. 

Response:

EPA disagrees with the commenter that any revisions to 

EPA’s estimate of SCR costs are necessary. Even if some of the 

costs projected by S&L and used by EPA may be overestimated 

(e.g., the commenter points primarily to capital recovery, 

catalyst replacement costs, and costs for lost power 
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generation), EPA disagrees that we must correct every issue of 

concern raised by the commenters in order to support our 

determination of the BART Benchmark. EPA made four specific 

corrections to the estimates provided by S&L and SRP to make the 

cost calculation methodology consistent with methodologies used 

for BART cost calculations nationally.66 As noted in other 

responses even if we consider the average and incremental cost 

effectiveness of SCR using SRP and S&L’s full cost projections, 

EPA would still determine that SCR at NGS is cost-effective. The 

cost-effectiveness values cited by the commenter, below $1,500 

per ton, certainly suggest that SCR could be even more costeffective than the values we relied upon in our proposal, but 

this would not change our overall determination that SCR is 

cost-effective for NGS. 

Comment: Updated SCR cost estimate from SRP 

 SRP contracted with S&L in 2013 to review and update the 

SCR cost estimates that were prepared in 2010. S&L escalated 

costs for inflation, and incorporated other minor adjustments to 

reflect a lower NOX design target. SRP’s revised capital cost 

estimates for SCR installation on all three units total $650 

66 See, e.g., Final Regional Haze Plan for Arizona (Phase 1) at 77 FR 72512 at 

72531 (December 5, 2012); Final Regional Haze Plan for North Dakota at 77 FR 

20894 at 20916-17 (April 16, 2012); Final Regional Haze Plan for New Mexico 

at 76 FR 52388 at 52399-400 (August 22, 2011); Final Regional Haze Plan for 

Wyoming at 79 FR 5032 at 5082 (January 30, 2014). 
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million (in 2013 dollars) compared to SRP’s 2010 cost estimate 

of $544 million. 

Response:

EPA reviewed the updated 2013 cost estimates developed by 

S&L and provided by SRP.67 In its 2013 cost report, S&L explains 

that it escalated labor and material costs, and updated cost 

estimates based on a revised design target of 0.03 lb/MMBtu (so 

that the SCR system is deployed as a 3+1 system rather than a 

2+2 catalyst layer system), and other design features, including 

a low-load temperature control system to operate SCR at lower 

loads. S&L escalated several costs at rates above 6.7 or 8 

percent (e.g., freight, scaffolding). S&L did not make any 

revisions to the components of variable annual costs, including 

maintenance labor, auxiliary power, steam, and catalyst 

replacement. To be consistent with the cost estimates in our 

Proposed Rule, EPA accepted most of the line item costs as 

adjusted by S&L and made the same four adjustments to the 2013 

cost estimates as we had applied to the 2010 cost estimates. 

These changes result in an 8 percent difference in total capital 

costs of SCR between EPA’s 2013 estimate and SRP’s 2013 estimate 

and a 21 percent difference in the total annual costs of SCR 

between the 2013 estimates from EPA and SRP (see Table 2). 

67 See RTC and references therein. 
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Table 2: Cost Estimates for SCR in 2010 and 2013 Dollars 

Total Capital 

Cost in 2010$ 

Total Capital 

Cost in 2013$ 

Total Annual 

Cost in 2010$ 

Total Annual 

Cost in 2013$ 

EPA Estimate $496 million $598 million $59 million $69 million 

SRP Estimate $544 million $650 million $75 million $88 million 

 In our proposed BART determination, EPA also presented the 

average and incremental cost-effectiveness of controls, based on 

the combination of combustion controls (LNB/SOFA) and postcombustion controls (i.e., SNCR or SCR). Therefore, costeffectiveness values presented in our Proposed Rule were based 

on total annual cost of SCR in combination with annual cost of 

LNB/SOFA (SCR+LNB/SOFA), SNCR in combination with LNB/SOFA 

(SNCR+LNB/SOFA) or LNB/SOFA alone.68 Based on the updated 2013 

cost estimates for SCR, Table 3 shows the average and 

incremental cost-effectiveness of controls, in both 2010 and 

2013 dollars, based on EPA and SRP assumptions for total annual 

cost and annual NOX reductions achieved by SCR. See RTC for 

further detail on cost-effectiveness of SNCR+LNB/SOFA and 

LNB/SOFA. 

Table 3: Cost Effectiveness of Controls in 2010 and 2013 dollars 

2010 $ 2013 $ 

EPA SRP EPA SRP 

SCR+ 

LNB/SOFA Total Annual Cost* $67.5 million 

$80.2 

million 

$74.4 

million 

$92.6 

million 

68 78 FR at 8281, February 5, 2013. 
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Annual NOx reduced 

(tpy) 28,573 26,180 28,573 26,180 

NOx Limit (lb/MMBtu) 0.055 0.080 0.055 0.080 

Average Cost 

Effectiveness ($/ton) $2,369 $3,069 $2,605 $3,537 

Incremental Cost 

Effectiveness (vs. 

LNB/SOFA) ($/ton) 

$3,522 $4,889 $3,899 $5,695 

Incremental Cost 

Effectiveness (vs. 

SNCR+LNB/SOFA) 

($/ton) 

$3,239 $5,357 $3,798 $6,647 

* EPA’s cost effectiveness calculations represent SCR in combination with 

LNB/SOFA, rather than SCR alone. 

Based on the revised 2013 cost estimates for SCR+LNB/SOFA, 

the revised average cost-effectiveness of SCR+LNB/SOFA is 

roughly 10 percent higher (based on EPA’s estimates) than the 

average cost-effectiveness values reported in our Proposed Rule, 

and roughly 15 percent higher based on SRP’s estimates.69 The 

2013 values for average cost-effectiveness of SCR+LNB/SOFA based 

on EPA and SRP estimates are still comparable to the range of 

values determined cost-effective for SCR in other BART 

determinations. For these reasons, EPA continues to consider 

SCR+LNB/SOFA as cost-effective at NGS. 

Comment: Cost-Effectiveness of Presumptive BART 

 One commenter stated that in establishing presumptive 

limits in the BART Guidelines, EPA recognized that SCR is not 

69 For informational purposes, EPA included the incremental cost-effectiveness 

values of SCR+LNB/SOFA (estimated in 2010 and 2013) compared to LNB/SOFA and 

SNCR+LNB/SOFA, but we note that a comparison of the percent change in 

incremental cost-effectiveness between 2010 and 2013 is not informative 

because SRP did not provide updated cost estimates (in 2013 dollars) for the 

other control technologies. 
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cost-effective and that combustion controls such as LNB/SOFA 

represent the most cost-effective control options for most 

boiler types. The commenter pointed out that in establishing 

presumptive limits, EPA considered controls that cost less than 

$1,500 per ton to be cost-effective, and that the costeffectiveness for SCR at NGS, which ranges from $3,000 to $6,000 

per ton based on 2010 estimates, is well above this threshold. 

The commenter concluded that EPA should have rejected SCR and 

proposed LNB/SOFA as BART for NGS. 

Response:

EPA disagrees with the assertion that the BART Guidelines 

established a threshold for cost-effectiveness against which all 

future BART determinations must compare. In developing the 

presumptive NOX limits for BART in 2005, EPA did not set the 

cost-effectiveness values estimated for combustion controls as 

the threshold for determining whether a given control technology 

was or was not cost-effective. If EPA had intended the costeffectiveness values estimated in 2005 to represent a threshold 

for BART, it is reasonable to assume that the BART Guidelines 

would have included those cost-effectiveness values as 

thresholds in Appendix Y, and would have required future cost 

estimates to be presented in 2005 dollars for appropriate 

comparison to the thresholds. The BART Guidelines do not set a 

numerical definition for “cost-effective”, and the analysis of 
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presumptive limits uses cost-effectiveness as a means to broadly 

compare control technologies, not as a threshold for rejecting 

controls for an individual unit or facility that exceed the 

average cost-effectiveness of combustion controls. In addition, 

as discussed in the RTC, a value of $1,500 per ton is not an 

appropriate or relevant value for determining costeffectiveness. 

Comment: Indirect costs should also be considered under Factor 1

 The Gila River Indian Community asserted that EPA conducted 

the analysis of cost-effectiveness incorrectly by not including 

the indirect costs of the requirements and only considering the 

direct cost of the requirements. The commenter stated that EPA 

did not give sufficient consideration to the high costs to 

tribes associated with indirect impacts of its proposed BART 

determination. 

Response:

 EPA disagrees with the assertion that our costeffectiveness analysis was incorrect because it did not include 

indirect costs in the assessment of the costs of compliance. The 

BART Guidelines, which States and EPA must follow in BART 

determinations for fossil-fuel fired power plants greater than 
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750 MW,70 focus on the direct costs of the pollution control 

equipment and other capital and annual costs associated with the 

control technology alternatives. The BART Guidelines do not 

require consideration of the cost of potential indirect effects 

of BART control options when assessing the costs of compliance. 

Therefore, EPA disagrees that our analysis for Factor 1 was 

incorrect or incomplete because it did not include indirect 

costs to tribes. EPA further notes that under Factor 2, the 

energy and non-air quality environmental impacts analysis, the 

BART Guidelines specifically require the energy impact analysis 

to consider direct energy impacts (e.g., parasitic load from 

certain control technologies) and to generally exclude indirect 

energy impacts of controls (e.g., energy to produce raw 

materials for construction of control equipment) unless the 

indirect impact is unusual or significant. 

However, because of the unique relationship between NGS, 

tribes, and tribal water settlement agreements, and to inform 

our government-to-government consultation with tribes, EPA did 

consider potential indirect effects of control options to tribes 

under Factor 2. EPA quantified the impact to electricity rates 

and CAP water rates, and also assessed whether installation of 

70 40 CFR 51.308(e)(1)(ii)(B). 
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SCR would result in electricity generation costs at NGS that 

exceed the cost to purchase power on the wholesale market. 

Therefore, although EPA appropriately did not consider indirect 

costs in our analysis of Factor 1, EPA did include consideration 

of indirect impacts to tribes and other entities in our analysis 

of Factor 2. 

C. Comments on Factor 2 – Energy and Non-Air Quality 

Environmental Impacts, including Economic Impacts 

Comment: EPA’s Affordability Analysis relied on invalid 

assumptions

One commenter submitted a report, prepared by Management 

Information Services, Inc. (MISI report), asserting that EPA 

made several assumptions that underestimated the cost of 

continuing to operate NGS with additional controls, including 

the assumption that no new capital would be deployed at NGS over 

the next 25 years, the assumption that the increase in the 

annual NGS lease cost would be $15 million per year (which is 

lower than actual increase in lease cost of $43 million per year 

that was released after publication of our Proposed Rule), and 

the use of EPA’s capital cost estimates for SCR instead of the 

cost estimated by S&L. 

Other commenters asserted that EPA underestimated the cost 

of closing NGS and purchasing power on the wholesale market, by 
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not accounting for costs associated with stranded investments 

and decommissioning NGS. 

Response:

EPA recognizes the economic importance of NGS to the State 

of Arizona, the Navajo Nation, and the Hopi Tribe. The purpose 

of the Affordability Analysis in our docket was to determine 

whether the control options for BART would have a detrimental 

impact on the competitiveness of NGS in the western power 

market, affecting whether the NGS owners would continue to 

operate NGS or replace NGS generation with less expensive market 

power. The Affordability Analysis indicated that, even if SCR 

installation was required on all three units at NGS, power 

produced at NGS would remain less expensive than the cost to 

replace power through wholesale purchases. Because utilities 

will generally provide power to their customers in a least-cost 

manner and because NGS, with the installation and operation of 

SCR, remained the less expensive option, EPA determined that the 

operation and installation of SCR, in and of itself, was not 

likely to force NGS to close. 

 In response to multiple comments expressing concern related 

to simplifying assumptions or outdated data, EPA updated the 

Affordability Analysis with the most current power market price 

curves from the U.S. Energy Information Administration (EIA) and 

recent forward power market prices in March 2014 and other more 
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current modeling variables. These revisions are discussed in 

more detail in the RTC as well as in additional supporting 

documents.71 The updated model results, comparing the net present 

value (NPV) of electricity generation costs with air pollution 

controls installed compared to the costs to purchase an 

equivalent amount of power on the wholesale market, are 

summarized in the RTC. Overall, the combined changes do not 

change the conclusions from the original Affordability Analysis 

that installing and operating SCR at NGS would be less costly 

than closing NGS and purchasing replacement power from the 

wholesale market. 

Comment: EPA’s failure to appropriately consider the impacts to 

non-Indian agricultural (NIA) water users renders its Factor 2 

analysis arbitrary, capricious, and an abuse of discretion 

One commenter stated that, as a result of errors and 

omissions, EPA’s Factor 2 analysis is arbitrary, capricious, and 

an abuse of discretion. The commenter asserted that there are 

several problems with the EPA analysis related to NIA users of 

CAP water, including erroneous assumptions, insufficient support 

for conclusions, failure to consider decreased farming 

profitability and increased unemployment, failure to acknowledge 

71 See RTC and references therein. 
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the inability of NIA water users to pass along cost increases as 

compared to municipal users, and other factors. 

Response:

 EPA recognizes that CAP water is an important resource for 

NIA and other users of water in Arizona. As a result, as one of 

a number of discretionary analyses EPA conducted on the indirect 

impacts on major stakeholders, EPA calculated water rate 

increases to NIA users of CAP water and municipal and industrial 

users of CAP water. 

EPA disagrees that our discussion of impacts to NIA users of 

CAP water renders our Factor 2 analysis arbitrary, capricious, 

and an abuse of discretion. Neither the CAA nor the BART 

Guidelines require consideration of indirect costs or indirect 

impacts of controls in a BART analysis. EPA, nevertheless, 

included an evaluation of impacts to some of the major 

stakeholders in NGS in our BART analysis under Factor 2, 

including NIA users, as consistent with the statement in the 

BART Guidelines that “the energy impacts analysis may consider . 

. . whether a given alternative would result in significant 

economic disruption or unemployment” (emphasis added).72

EPA recognizes that the information we had available to us 

about NIA users of CAP water was limited, and we acknowledged in 

72 See BART Guidelines at 70 FR at 39169 (July 6, 2005). 
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the TSD to our Proposed Rule that we had several questions about 

CAP and groundwater availability to NIA water users. EPA 

appreciates the clarifications and additional information 

provided by NIA users of CAP water during the comment period for 

our proposals. The additional information provided during the 

comment period about NIA users of CAP water does not change our 

conclusion under Factor 2, that the potential economic impacts 

to tribes argue for flexibility in the compliance timeframe for 

NGS, because this compliance flexibility also benefits other 

stakeholders, including the NIA users of CAP water. 

Comment: EPA must evaluate cumulative economic impact of other 

rulemakings 

 One commenter asserted that the BART proposal must take 

into account the context in which the regional haze rules are 

being implemented and conduct a cumulative impact analysis of 

all EPA rulemakings. The commenter noted that the two remaining 

copper smelters in Arizona are already subject to BART for SO2

and they also have to make significant capital investments to 

comply with other regulatory programs and initiatives such as 

the revised SO2 NAAQS. 

Response:

 EPA disagrees with the assertion that we must consider the 

total cost impact of all EPA regulatory requirements in a BART 

analysis. EPA recognizes that other facilities, whose water and 
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electricity rates may be affected by our BART determination for 

NGS, may also be subject to BART for their own emissions of 

visibility-impairing pollutants. As a general matter, EPA is 

mindful that facilities may be affected by multiple regulatory 

and program activities. We note that BART is a case-by-case 

determination that is based on a source-specific analysis of 

five factors, which include considerations of the unique 

circumstances of each affected facility, as required under the 

CAA. 

Comment: Impact to the Development Fund

One commenter stated that the increased cost of electricity 

generation associated with SCR would reduce the competitiveness 

of the price of NGS power on the wholesale market and therefore 

reduce the revenue that flows into the Development Fund. 

Response:

 As discussed in our Proposal Rule and TSD, EPA recognizes 

that any electricity owned by Reclamation based on its 24.3 

percent participation in NGS that is not used by CAP is sold and 

revenues are deposited into the Development Fund.73 This fund is 

authorized to pay the delivery portion of the cost of CAP water 

for certain Indian tribes and to pay the cost of constructing 

73 See Proposed Rule at 78 FR at 8282 (February 5, 2013) and TSD at pages 71-

72. 
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delivery systems to bring CAP water to certain Indian tribes.74

EPA considers the potential economic impacts to tribes, 

including potential impacts to the Development Fund, as part of 

BART factor 2 to support the appropriateness of flexibility in 

the compliance timeframe for NGS. 

Comment: No basis for public health claim 

 One commenter asserted that EPA has no basis for claiming 

that the NOX reductions from NGS would lead to a public health 

benefit. The commenter noted that EPA establishes NAAQS at 

levels that are protective of public health and welfare with an 

adequate margin of safety that accounts for sensitive 

populations such as children and the elderly, and that EPA has 

never found that any of the areas around NGS fail to attain the 

NAAQS. The commenter asserted that EPA must conduct a health 

risk evaluation that follows the four basic steps of the risk 

assessment process: hazard identification, dose‐response, 

exposure assessment, and risk characterization. 

Response:

EPA agrees that the purpose of this rule is to reduce 

visibility impairment caused by emissions of NOX from NGS. EPA 

has not conducted a health risk evaluation for this rulemaking 

that attempts to characterize or quantify a public health 

74 See Proposed Rule at 78 FR at 8283 (February 5, 2013). 
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benefit. Because NOX is itself a criteria pollutant that affects 

public health and is also a precursor to ozone and fine 

particulate matter, which are also criteria pollutants that 

affect public health, we consider it reasonable to state that 

other benefits could exist. We also note that EPA does not agree 

that there are no health benefits from reductions in ozone and 

fine particulate matter below the level of the NAAQS. On the 

contrary, EPA’s practice of quantifying these benefits in 

regulatory impact assessments has been strongly supported by 

peer-reviewed science.75

D. Comments on Factor 3 – Existing Controls at NGS 

Comment: EPA failed to consider existing controls 

 Based on EPA’s statement in the Proposed Rule that the 

early installation of LNB/SOFA would not influence EPA’s BART 

determination and EPA’s use of a baseline scenario in the 

visibility modeling that did not include LNB/SOFA, the operator 

of the Kayenta Mine concluded that EPA failed to consider 

existing controls. 

Response:

75 See EPA, 2010, “Summary of Expert Opinions on the Existence of a Threshold 

in the Concentration-Response Function for PM2.5-related Mortality Technical 

Support Document.” Available from 

http://www.epa.gov/ttn/ecas/regdata/Benefits/thresholdstsd.pdf. 
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EPA disagrees with the assertion that we failed to consider 

existing controls. As described in our Proposed Rule and 

consistent with the BART Guidelines (directing BART 

determinations to conduct the five-factor analysis generally 

using a 2001-2003 baseline) EPA evaluated LNB/SOFA as a separate 

control technology in our BART analysis, as well as a technology 

that can be used in combination with post-combustion control 

technologies (i.e., SNCR and SCR).76 We also discussed the 

voluntary installation of LNB/SOFA in 2009-2011 under Factor 3: 

Existing Controls at NGS.77

As discussed in section 8.5 of the RTC, EPA properly 

considered baseline emissions over the period 2001-2003 in our 

analysis of cost-effectiveness and anticipated visibility 

benefits of controls. Therefore, although we did not “consider 

existing controls” in the exact manner preferred by the 

commenter, we appropriately considered the existence of LNB/SOFA 

in Factor 3 of our BART analysis. In addition, the “better than 

BART” framework that we used to assess and finalize BART 

alternatives explicitly accounts for the existing LNB/SOFA. 

76 See Proposed Rule at 78 FR at 8280, 8284 and 8285 (February 5, 2013). 

77 Id. at 8284. 
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Comment: EPA should determine existing controls to be BART 

 Several commenters noted that NGS spent millions of dollars 

on LNB/SOFA to reduce NOx emissions to levels below the 

presumptive NOX emission levels in the BART Guidelines. 

 One commenter stated that installing LNB/SOFA prior to a 

requirement to do so under the RHR or any other CAA requirement 

has resulted in greater total NOX emission reductions in the 

first regional haze planning period than would be required by 

the most stringent EPA BART determination. 

Response: 

 EPA recognizes that the early and voluntary installation of 

LNB/SOFA on one unit per year in 2009-2011 at NGS resulted in 

significant emission reductions from NGS. EPA agrees that the 

early installation of LNB/SOFA on one unit per year was 

voluntary and resulted in significant NOX reductions in the first 

planning period for Regional Haze. However, based on our fivefactor analysis, we have determined that SCR+LNB/SOFA is also 

cost-effective and would result in significant additional 

visibility improvement at a number of Class I areas. We 

therefore disagree that LNB/SOFA should be determined BART for 

NGS. 

E. Comments on Factor 5 – Anticipated Visibility Benefits 

Comment: General Comments on Visibility 
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 Numerous commenters questioned the extent to which NGS 

impacts visibility at Class I areas or disputed EPA’s analysis 

that installation of SCR at NGS would improve visibility. Many 

commenters asserted that the haze is produced from emissions 

from other sources. 

Some commenters stated that the wind near and around the 

Grand Canyon blows predominantly west to east; thus, emissions 

from the NGS are pushed away from several Class I areas, not 

towards them. 

Response:

 We are aware of the studies cited by commenters purporting 

to show that controls on NGS would yield little visibility 

improvement, and we address them in section 7.0 of the RTC. We 

are also aware of work performed by the Western Regional Air 

Partnership (WRAP) suggesting that the relative contribution of 

nitrate from point sources to visibility impacts is relatively 

small.78 The CAA and RHR require that BART be installed on 

certain old, large stationary sources as part of the overall 

approach to improving visibility at Class I areas. No control at 

an individual source will be sufficient to meet the goal of 

remedying existing impairment of visibility in mandatory class I 

78 See, e.g. WRAP PM Source Apportionment Technology (PSAT) results, available 

on WRAP Technical Support System, Source Apportionment web page at 

http://vista.cira.colostate.edu/TSS/Results/SA.aspx. 
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Federal areas which result from manmade air pollution, as set 

out in section 169A of the CAA. 

 On the issue of wind direction, we note that the CALPUFF 

modeling uses three years of hourly meteorological input, which 

is based on meteorological modeling as well as observational 

data from stations throughout a large area. The input includes 

wind speed and direction, and would include the particular wind 

direction patterns noted by the commenter. The more 

sophisticated meteorological treatment in CALPUFF enables it to 

track the pollutant plume from NGS, including its twists and 

turns over multiple days. We consider this approach to 

adequately account for variability in winds noted by the 

commenter. 

Comment: EPA underestimated visibility benefits of SCR 

 One commenter, an organization representing several 

environmental and Navajo non-governmental groups, stated that 

the visibility benefits of SCR are greater than those modeled by 

EPA because EPA underestimated SCR performance and because EPA 

overestimated the potential increase in sulfate emissions that 

may come with the addition of SCR controls by assuming an SO2 to 

SO3 conversion rate that is too high and using an erroneous value 

for the coal sulfur content. The commenter stated that its own 

modeling shows greater visibility improvement than demonstrated 

by EPA. 
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Response:

 We disagree that EPA underestimated the visibility benefits 

of SCR and we note that the commenter’s assertion that the 

visibility benefits are even better would not change our 

proposed determination under Factor 5 that the anticipated 

visibility benefits of SCR+LNB/SOFA are significant and support 

our proposed BART limit for NOX, achievable with SCR+LNB/SOFA. 

Please see the RTC for a detailed discussion of EPA’s responses 

to the commenter’s specific assertions. 

Comment: EPA overestimated visibility impact of NGS by using 

background ammonia concentrations that were too high 

 Several commenters argued that EPA’s assumed ammonia 

background concentration of 1 part per billion (ppb), the 

default value recommended by the Interagency Workgroup on Air 

Quality Modeling (IWAQM), is unrealistically high compared to 

measured values in the area, resulting in artificially high 

model projections of visibility impacts, particularly in the 

winter.79 The commenter noted that the use of a constant value of 

1.0 ppb for background ammonia concentration fails to account 

79 Interagency Workgroup On Air Quality Modeling (IWAQM) Phase 2 Summary 

Report And Recommendations For Modeling Long Range Transport Impacts (EPA454/R-98-019), EPA OAQPS, December 1998, 

http://www.epa.gov/scram001/7thconf/calpuff/phase2.pdf. 
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for known variations in monthly or seasonal ammonia 

concentration. 

 One commenter cited an analysis conducted on behalf of SRP 

by AECOM and Dr. Ivar Tombach. The commenter stated that the 

Tombach study compared modeled predictions of ammonium nitrates 

using both EPA’s and AECOM’s ammonia background concentrations 

to measured ammonia values, demonstrating that the EPA’s 

assumptions over-predict actual measured values by a factor of 

10 or more in some cases. 

One commenter noted that when the IWAQM guidance was issued 

14 years ago, CALPUFF did not have the capability of 

accommodating monthly ammonia background concentrations as it 

has since been updated to do. The commenter asserted that EPA’s 

reliance on a constant value is an outdated approach. 

Response:

EPA has already considered and addressed the same arguments 

and data provided by commenters related to background ammonia 

concentrations in other rulemakings, including our final rule 

for Four Corners Power Plant.80 As summarized briefly below, EPA 

disagrees that our use of the IWAQM default background ammonia 

concentration for arid areas of 1 ppb was inappropriate. Please 

see the RTC for the full response to this comment.

80 See RTC and references therein. 
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We have carefully reviewed the comments and concluded that, 

on balance, the evidence does not support using lower values for 

background ammonia concentrations, as argued by the commenters, 

in estimating the visibility impacts from NGS. Much of the 

existing measured data cited by the commenters is from other 

states and may not be representative for evaluating visibility 

impacts from NGS.81 Further, existing data sometimes represent 

ammonia alone rather than total ammonia and ammonium. Because 

ammonium represents part of the pool of ammonia that could be 

available to interact with the SO2 and NOX emitted from 

stationary sources, it should be accounted for in the value for 

background ammonia concentrations used in the model. In several 

of the research papers cited by commenters, the amount of 

measured ammonium is comparable to and at times much greater 

than the amount of ammonia.82 Measurements made by SRP closer to 

NGS over December 2009 to April 2010, which included ammonia and 

ammonium, showed that depending on time and location, typical 

ammonia concentrations ranged from 0.2 ppb to 0.8 ppb and the 

concentration of total ammonia and ammonium ranged from 0.6 to 

1.2 ppb, which is considerably higher than the 0.2 ppb winter 

81 See e.g., SRP comments Appendix G, “Measurements of Ambient Background 

Ammonia on the Colorado Plateau and Visibility Modeling Implications”, 

Prepared by Salt River Project, Contributors: Ivar Tombach and Robert Paine, 

September 2010. Referred to here as “SRP monitoring report”, or Tombach & 

Paine 2010. 

82 See RTC and references therein. 
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values used in SRP’s modeling.83 Although some of the ammonium 

may not be available to interact with pollutants from NGS, the 

sum of ammonia and ammonium provides an upper bound estimate of 

background ammonia concentrations, and represents a conservative 

estimate for modeling. 

We further note that there are measurements of gaseous 

ammonia alone that show concentrations close to or greater than 

the concentration of 1 ppb, even in winter when ammonia 

concentrations are expected to be lowest. Winter measurements, 

representing 3-week averages, ranged from 1.1 ppb to 1.8 ppb at 

a monitor at the Farmington Airport in northwestern New Mexico.84

Measurements from the winters of 2011-2013 from the AMoN network 

ranged from 1.1 to 1.3 ppb for Farmington, and 0.7 – 0.9 ppb for 

Chiricahua, in southeastern Arizona.85

We further note that there is significant variability in 

the concentrations of ammonia measured at different times and 

places. Even the SRP monitoring report (Tombach & Paine, 2010, 

cited above) describes a surprisingly high spatial variability 

in ammonia concentrations. Because of the variability and its 

unknown causes, the data collected for SRP did not lead to a 

83 SRP monitoring report, or Tombach & Paine 2010, and SRP comments Appendix 

C. “Revised BART Analysis for the Navajo Generation Station Units 1-3” 

(January 2009) and Appendix I. “Visibility Modeling Using Upgraded CALPUFF 

Model” (February 2011). 

84 See RTC and references therein. 

85 Id.
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clear picture of appropriate and representative background 

ammonia concentrations to use with CALPUFF. 

Finally, we note that using the background ammonia 

concentrations recommended by commenters does not change our 

conclusion under Factor 5 because CALPUFF modeling of SCR shows 

substantial visibility benefits even using the alternative 

assumptions.86 Using a background ammonia concentration of 1 ppb 

ammonia, EPA modeled the greatest benefit from SCR+LNB/SOFA to 

be 5.4 deciviews at Capitol Reef NP, and modeled a visibility 

benefit exceeding 1 to 2 deciviews at ten additional Class I 

areas. Using the ammonia concentration recommended by some 

commenters (ranging from 0.2 ppb in winter to 1.0 ppb in 

summer), EPA modeled the greatest benefit of SCR to be 2.3 dv, 

and modeled a visibility benefit exceeding 1 deciview at nine 

Class I areas, with three of these nine areas having a benefit 

of approximately two deciviews. Even assuming a lower ammonia 

concentration, the modeling demonstrates that the installation 

of SCR+LNB/SOFA at NGS would have a significant beneficial 

impact on visibility at a number of Class I areas. Our 

conclusion as to the appropriate BART Benchmark for NGS would 

not accordingly change. 

Comment: EPA should have used an updated version of CALPUFF 

86 See RTC and references therein. 
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 Several commenters asserted that EPA erred in using CALPUFF 

version 5.8 in its modeling rather than the more recent CALPUFF 

version 6.42, released by TRC. One commenter argued that CALPUFF 

version 6.42 predicts lower visibility benefits than version 

5.8. 

Response: 

We disagree with the commenters that a new CALPUFF version 

should be used for the BART determination. We relied on version 

5.8 of CALPUFF because it is the version approved by EPA through 

a public notice and comment rulemaking, in accordance with the 

Guideline on Air Quality Models (“GAQM”, 40 CFR 51, Appendix W, 

section 6.2.1.e).87 CALPUFF version 6.4 is not approved by EPA 

for regulatory purposes, and we do not agree that the changes 

made to this most recent version of CALPUFF were simple model 

updates to address bugs. A full evaluation of a new model such 

as CALPUFF version 6.4 is needed before it should be used for 

regulatory purposes as errors that are not immediately apparent 

can be introduced along with new model features. 

Comment: Closure of Mohave Project did not improve visibility 

and shows CALPUFF is unreliable 

 One commenter discussed the findings of an analysis 

conducted after the closure of the Mohave Power Project (MPP) (a 

87 See RTC and references therein. 
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1,580 MW coal-fired power plant) to evaluate whether the closure 

had resulted in improved visibility in Grand Canyon National 

Park.88 The commenter indicated that although CALPUFF version 5.8 

modeling predicted that the plant had a significant impact on 

visibility in the Grand Canyon, this study concluded that there 

was “virtually no evidence that the MPP closure improved 

visibility in the Grand Canyon.” The commenter asserted that 

this study raises questions about the reliability of CALPUFF. 

Response: 

We disagree that the Terhorst & Berkman (T&B) study cited 

by the commenters raises questions about CALPUFF’s reliability. 

The conclusion in the T&B study on the effect of MPP closure is 

actually similar to that from earlier analyses, which also 

predicted improvements less than the human perceptibility 

threshold of 1 dv. A response to the T&B study written by White 

et al., stated that the T&B analysis is “misleadingly presented 

as discrediting previous studies and their interpretation by 

regulators. In reality the T&B analysis validates a consensus on 

MPP’s visibility impact that was established years before its 

closure.”89

88 See RTC and references therein. 

89 W.H. White, R.J. Farber, W.C. Malm, M. Nuttall, M.L. Pitchford, B.A. 

Schichtel, Comment on “Effect of coal-fired power generation on visibility in 

a nearby national park (Terhorst and Berkman, 2010)”, Atmospheric Environment 

55 (2012) 173-178. doi:10.1016/j.atmosenv.2012.02.076. Also available at: 

http://www.dri.edu/marc-pitchford?showall=&start=2.
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White et al., explicitly addressed the purported 

disagreement between the T&B methodology and results from 

CALPUFF, pointing out that the comparison was flawed in several 

ways. First, the ambient data relied upon by T&B are collected 

only every third day; this results in an insufficient number of 

days for a valid statistical comparison to the 98th percentile 

results reported from CALPUFF. Another important flaw is that 

when T&B translated visibility extinction into deciviews, they 

used recent polluted conditions as the background for 

comparison, whereas the BART Guidelines and the CALPUFF results 

use natural conditions as background.90 When the T&B results are 

computed using natural background, they are substantially 

larger, and generally in agreement with CALPUFF results. 

F. Comments on BART Determination for NOX

Comment: BART limit for NGS should be 0.04 lb/MMBtu

One commenter argued that the final BART emission limit 

should be more stringent and no higher than 0.04 lb/MMBtu. The 

comment noted that permitting authorities have required lower NOX

limits than 0.055 lb/MMBtu in recent BACT determinations based 

on SCR in combination with combustion controls. 

90 EPA considered and rejected comments on the proposed BART Guidelines that 

visibility impacts should be evaluated relative to current degraded 

visibility conditions and concluded that “[u]sing existing conditions as the 

baseline for single source visibility impact determinations would create the 

following paradox: the dirtier the existing air, the less likely it would be 

that any control is required.” (70 FR 39104 at 39124, July 6, 2005). 
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Response:

EPA disagrees with the commenter that the BART Benchmark 

for NGS should be 0.04 lb/MMBtu. We note that the commenter has 

not provided any specific information to show that NGS could 

demonstrate continuous compliance with an emission limit of 0.04 

lb/MMBtu. The commenter generally argued that SCR systems are 

typically designed to achieve 90 percent removal. EPA notes that 

although an SCR system can be designed to a specific target, the 

design target is typically not equivalent to the actual emission 

limit.91 EPA proposed a limit of 0.055 lb/MMBtu achievable with 

SCR+LNB/SOFA, and using a baseline emission rate of 0.35 

lb/MMBtu, this represents a removal efficiency of 84 percent.92

However, as noted elsewhere in the RTC, the limit of 0.055 

lb/MMBtu, which accommodates startup, shutdown, and low-load 

operation, is based on a design target of 0.03 lb/MMBtu. This 

represents a design target removal efficiency of 91 percent for 

SCR+LNB/SOFA (from a baseline of 0.35 lb/MMBtu), or 88 percent 

for SCR alone (i.e., from 0.24 lb/MMBtu). 

91 EPA’s Environmental Appeals Board has recognized that PSD emission limits 

must be set to allow fluctuations in operations, stating: “To account for 

these possibilities, a permitting authority must be allowed a certain degree 

of discretion to set the emissions limitation at a level that does not 

necessarily reflect the highest possible control efficiency, but will allow 

the permittee to achieve compliance consistently.” In Re Masonite 

Corporation, 5 E.A.D. 551, 560-61 (1994). 

92 See RTC and references therein. 
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EPA disagrees with the commenter’s assertion that emission 

limits associated with BART must meet BACT or the lowest 

emission rate ever achieved with that technology at any coalfired power plant. The BART Guidelines state that: “[i]n 

assessing the capability of the control alternative, latitude 

exists to consider special circumstances pertinent to the 

specific source under review, or regarding the prior application 

of the control alternative”, (70 FR at 39166) and that “[t]o 

complete the BART process, you must establish enforceable 

emission limits that reflect the BART requirements . . .” (70 FR 

at 39172). The five-factor BART analysis described in the 

Guidelines is a case-by-case analysis that considers site 

specific factors in assessing the best technology for continuous 

emission controls. After a technology is determined as BART, the 

BART Guidelines require establishment of an emission limit that 

reflects the BART requirements, but does not specify that the 

emission limit must represent the maximum level of control 

achieved by the technology selected as BART. For these reasons, 

EPA is not using the lower limit recommended by the commenter in 

setting the BART Benchmark. 

Comment: BART limit for NGS should be in the range of 0.07-0.08 

lb/MMBtu

Several commenters asserted that the NOX emission limit EPA 

proposed for NGS is unachievable. One commenter noted that the 
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averaging period for the proposed limit of 0.055 lb/MMBtu 

includes periods when the SCR is unable to operate such as 

startup, shutdown, and periods of load-cycling. The commenter 

made the following arguments: (1) the S&L analysis submitted by 

the commenter shows that the proposed emission limit is 

unachievable on a continuous basis; (2) the NOX emissions 

achieved in other SCR retrofit situations do not justify the 

proposed emission limit. 

Response:

EPA disagrees with the commenter that the limit used in 

setting the BART Benchmark for NGS should be higher than our 

proposed limit of 0.055 lb/MMBtu, in the range of 0.07 to 0.08 

lb/MMBtu.93

The S&L report generally argues that because the emission 

limit is established based on a 30-BOD average basis, the 

proposed emission limit of 0.055 lb/MMBtu is not consistently 

achievable at NGS. The S&L analysis is based on a design target 

of 0.03 lb/MMBtu and suggests an emission limit in the range of 

0.07-0.08 lb/MMBtu would be required to accommodate periods of 

load-cycling operation, startups, and shutdowns. S&L is 

93 The response included in this Final Rule is abbreviated and excludes the 

graphs and tables EPA generated to support our response. For additional 

detail, please see the RTC. 
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recommending a limit that is 2.3 to 2.7 times higher than the 

design target, or a compliance margin of 133 to 167 percent. 

 The S&L report discusses the temperature limitations 

associated with SCR and explains that at temperatures below a 

specific minimum operating temperature, a component of the SCR 

system (i.e., ammonia injection) must cease to prevent ammonium 

salt formation on the catalyst. S&L asserts that a minimum 

operating temperature of 580F is typical for retrofit SCR 

control systems installed on coal-fired electric generating 

units with similar coal sulfur content and states that this 

temperature corresponds with a gross load of approximately 650 

MW (650 gross MW, or MWg). S&L further assumes that SRP will 

likely modify the units to increase flue gas temperatures at 

lower operating loads by installing one of several options for 

low load temperature control. In their analysis, S&L assumes the 

low load temperature control would be achieved with a water-side 

bypass (to allow water to bypass the economizer tube bundles 

during low-load operation). The S&L report states “[b]ased on a 

preliminary review of the available systems, a water-side bypass 

system should be capable of increasing the temperature of the 

bulk flue gas by approximately 25F to 65F during low-load 

operation. For this evaluation, a low-load temperature control 

system capable of achieving a temperature increase of 65F during 
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low-load operations was assumed for modeling purposes.” S&L 

further estimates that this would correspond to a minimum gross 

load of 450 MWg for the SCR to operate, or operation at 55 

percent capacity. 

Using the assumption that the SCR would not operate at 

loads below 450 MWg, S&L used 2012 operations data at NGS to 

estimate emission rates at NGS assuming a design target of 0.03 

lb/MMBtu with actual steady-state operations achieving 0.04 

lb/MMBtu. S&L modeled eighteen different operating scenarios and 

identified seven scenarios, which included periods of low load 

cycling along with unit startup and shutdowns, that resulted in 

the maximum 30-BOD average for each unit and facility-wide, that 

exceeded 0.055 lb/MMBtu. The highest 30-BOD average S&L modeled 

was 0.077 lb/MMBtu for Unit 2, achieved under 3 different 

operating scenarios involving low-load cycling. 

SRP and S&L did not provide the underlying data used in the 

S&L analysis. Therefore, EPA evaluated the S&L report by 

reviewing emissions data from the EPA Air Markets Program Data 

(AMPD) for multiple years, as well as emissions data from other 

facilities that were constructed or retrofit with SCR. EPA 

sought to understand 2012 operations at NGS within the context 

of longer term operational trends at the facility, as well as 

understand the minimum operating load assumed by S&L for NGS 
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within the context of minimum operating loads at other 

facilities with SCR. 

EPA evaluated the reported hourly gross load operating data 

for Units 1-3 at NGS for the years 2001, 2003, 2010, 2011, 2012, 

and 2013.94 Emission data from AMPD show that NGS, and in 

particular, Unit 2, spent a higher percentage of operating hours 

at gross loads below 450 MWg in 2012 compared to other years. 

The 2012 gross load profiles for Unit 2 (as well as Units 1 and 

3) are characteristic of load-cycling units, with significant 

periods of time below the purported SCR minimum operating load 

of 450 MWg, particularly in the spring. Please see the RTC for 

more detail. In 2010, Unit 2 also operated for significant 

periods of time at loads below 450 MWg. However, these periods 

in 2010 occurred following the major outage on Unit 2 (following 

installation of LNB/SOFA on that unit). Although Units 1-3 at 

NGS did appear to operate as load-cycling units and operated 

below 450 MWg for significant periods of time in 2012, this type 

of operation does not appear to be characteristic of typical 

operation at NGS, based on our evaluation of previous years, as 

well as 2013. 

Based on the gross load operating profiles for six years, 

EPA estimated the rolling 30-BOD averages for each BOD to 

94 See RTC and references therein. 
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determine whether the operating profiles (which included actual 

startup, shutdown, and load-cycling in each year) would result 

in 30-BOD averages that would exceed 0.055 lb/MMBtu. Based on 

our analysis, EPA projected the highest 30-BOD average to be 

0.079 lb/MMBtu (Unit 2 in 2010). Using 2012 data, representative 

of load-cycling operation, EPA projected the highest 30-BOD 

average to also occur on Unit 2 (0.075 lb/MMBtu). Similarly, S&L 

projected the highest 30-BOD average in 2012 was from Unit 2, at 

0.077 lb/MMBtu. Therefore, although the scenarios modeled by S&L 

and EPA were not identical, the highest 30-BOD averages 

projected by EPA and S&L, using similar starting assumptions, 

were comparable. Our analysis, of projected SCR performance, 

which included emission and operating profiles of actual startup 

and shutdown events, and load-cycling in various years, showed 

that Unit 3 was not projected to exceed 0.055 lb/MMBtu in any of 

the evaluated years, and that there were several years within 

these six selected years that Units 1 and 2 would also not 

exceed 0.055 lb/MMBtu. 

 The analysis of projected 30-BOD average emission rates 

assumes that S&L’s value of 450 MWg (or 55 percent capacity) for 

the minimum operating load to operate SCR at NGS is correct. EPA 

notes that 450 MWg was a value that S&L assumed based on 

preliminary analysis of available low load temperature control 

systems. SRP submitted a similar S&L analysis to EPA for Units 1 
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and 3 at Coronado Generating Station (CGS).95 Units 1 and 2 at 

CGS are 430 MWg Riley-Turbo units that typically operate as 

load-cycling units. CGS burns low-sulfur coal from the Powder 

River Basin (PRB coal). With the application of low-load 

temperature controls on these units, S&L’s analysis suggests 

that the minimum operation load for SCR on Units 1 and 2 at CGS 

would be 138 MWg (or 32 percent capacity). This is significantly 

lower than the 55 percent capacity S&L assumed for NGS. S&L 

stated that the coal sulfur content will affect the minimum 

operating load for SCR. NGS does not burn PRB coal; however, NGS 

does burn low-sulfur coal from the Kayenta Mine. AECOM, SRP’s 

consultant for visibility modeling, reported the maximum sulfur 

content of the coal as 0.593 percent based on daily data for the 

2001-2003 period. For comparison, various sources reference PRB 

coal as generally low-sulfur coal with a sulfur content of less 

than 1 percent, or a mean of 0.5 percent.96 In contrast, high 

sulfur coal is typically above 3 percent.97

EPA evaluated emission data of eight well-performing units 

burning PRB coal and generated empirical estimates for minimum 

operating loads and capacity requirements for SCR operation at 

95 See RTC and references therein. 

96 See, for example, publication from the U.S. Geological Survey, figure PQ-4 

and Table PQ-1, available at http://pubs.usgs.gov/pp/p1625a/Chapters/PQ.pdf. 

97 Id.
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those facilities. Based on this analysis (see RTC for further 

detail), EPA estimated capacity requirements for SCR operation 

that ranged from 35 percent to 46 percent, with an average value 

of 40 percent. Using the average (40 percent) and the maximum 

(46 percent) capacity requirement to operate SCR, EPA projected 

that NGS would meet a limit of 0.055 lb/MMBtu (on a 30-BOD 

average) for all but 3 cases (i.e., Units 1 and 2 in 2012, and 

Unit 2 in 2010) under the 46 percent capacity requirement. Under 

the 40 percent capacity requirement to run SCR, Units 1 and 2 in 

2012 would remain below 0.055 lb/MMBtu and for Unit 2 in 2012 

the highest 30-BOD average was projected to be exactly 0.055 

lb/MMBtu. Operation of Unit 2 in 2010 was not typical of normal 

operation. Please see RTC for more detail on this analysis. 

The S&L report concludes that even with a design target for 

SCR of 0.03 lb/MMBtu, a limit of 0.07-0.08 lb/MMBtu is required 

to accommodate periods of startup, shutdown, and load-cycling 

operation. EPA agrees that load-cycling operation appears to be 

an important factor; however, EPA concludes that the critical 

S&L assumption, that the units at NGS must operate at 

approximately 55 percent capacity in order for the SCR to 

operate, was not sufficiently supported and was acknowledged by 

S&L to be an assumption based on a preliminary review of 

available low-load temperature control systems. EPA also notes 

that in the S&L revised 2013 cost analysis, S&L included costs 
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for hot water recirculation systems which “maintains SCR in 

operation at all plant operating loads” (emphasis added).98

In summary, EPA is finalizing a BART Benchmark based on an 

emission limit for NGS of 0.055 lb/MMBtu on a rolling 30-BOD 

basis. In determining the achievability of this limit, EPA has 

conducted an analysis that considers actual periods of startup, 

shutdown, and low-load cycling. Based on the understanding that 

S&L would design the SCR system at NGS to a design target of 

0.03 lb/MMBtu, the BART limit of 0.055 lb/MMBtu represents an 

adequate compliance margin to accommodate periods of startup, 

shutdown, and load-cycling operation. 

Comment: Presumptive Limit for NOX

 Several commenters noted that with existing LNB/SOFA 

controls, NGS emits NOX at rates below the presumptive limit of 

0.28 lb/MMBtu established by the EPA in the BART Guidelines. A 

commenter stated that to properly justify departure from the 

presumptive BART limit, EPA must evaluate the impacts of the 

presumptive BART limit in its five-factor analysis. 

Response: 

EPA disagrees with the comment that installation of 

LNB/SOFA at NGS should satisfy BART simply because it meets the 

98 See page 1-2 of the Sargent and Lundy report prepared for SRP, dated 

January 2, 2014, included as Appendix U to the SRP comment letter in the 

docket for this rulemaking. 
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presumptive limit for NOX of 0.28 lb/MMBtu in the BART Guidelines 

for tangential-fired boilers burning bituminous coal. 

Presumptive BART limits, and the corresponding technology upon 

which those limits are based, do not preclude states or EPA from 

setting limits that differ from those presumptions based on 

case-specific consideration of the relevant BART factors. The 

presumptive limits generally represent a minimum level of 

control for BART for various types of power plants, based on 

EPA’s assessment of the typical costs of controls and likely 

visibility benefits.99 EPA further disagrees with the assertion 

that we did not evaluate the impacts of the presumptive BART 

limit in our five-factor analysis. The presumptive BART limit of 

0.28 lb/MMBtu is based on the installation and operation of 

modern combustion controls. EPA evaluated LNB/SOFA (at a limit 

of 0.24 lb/MMBtu, which is each unit’s existing permitted NOX

limit for operation with LNB/SOFA) in the five-factor analysis 

on which our proposed rule was based. Please see our RTC for a 

detailed discussion. 

Comment: Install SCR within 3.5 years 

 One commenter , an organization representing several 

environmental and Navajo non-governmental groups, stated that 

99 See 77 FR 14604, 14608-14610 (March 12, 2012) for a detailed discussion of 

the presumptive limits. 
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the CAA requirement for BART to be installed “as expeditiously 

as practicable” requires installation and full implementation of 

SCR on all three units at NGS within 3.5 years rather than five 

years. The commenter stated that EPA provided no site-specific 

factors at NGS that would require a longer-than-average 

installation time for SCR (particularly in light of the fact 

that it appears contractors in the region will not be 

overwhelmed). 

Response: 

 EPA disagrees with the commenter that a 3.5-year compliance 

deadline for the installation of SCR would be practicable for 

NGS. EPA agrees that there are numerous sources of information, 

including EPA’s response to comments on its BART determination 

for SJGS, to suggest that on average, the time required to 

design and construct an SCR system can range from 37 to 43 

months. The commenter also cites EPA documents suggesting that 

it generally takes 21 months to design, install, and test one 

SCR unit, and 35 months for SCR installation at power plants 

with multiple SCR units, and another publication that suggests 

that SCR can be installed in less than five years (i.e., 

document from The Brattle Group). Our RTC contains a detailed 

discussion of our conclusion that the Brattle Group estimate of 
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47 months (nearly 4 years) applies to one unit, not multiple 

units at one facility.100

In addition, although EPA cited one facility where the 

retrofit of seven units required 35 months, EPA also stated 

“ideally, longer than 35 months would allow for all the 

retrofits to occur over a period of several years so that 

facility owners can properly plan outages and suppliers can 

properly plan for resource availability.”101

The commenter also states that “it appears contractors in 

the region will not be overwhelmed” to justify why installation 

time for SCR should not be longer than average.102 We note that 

“installation time” is one part of compliance, and that EPA must 

also consider time for design, procurement, and permitting. We 

also note that the commenter did not provide any support for its 

statement that contractors in the region will not be 

overwhelmed. We note that several EGUs in the southwest have 

compliance dates for the installation of SCR around 2018.103

Therefore, EPA anticipates that leading up to 2018, numerous 

100 See May 2012 Brattle Group document, page 12 and page 17, in the docket for 

this rule. 

101 See EPA 2002 Multipollutant Strategies document, page 22, in the docket for 

this rule. 

102 See page 17 of the EarthJustice comment letter, in the docket for this 

rule. 

103 See Final BART FIP for Four Corners Power Plant an compliance dates under 

the BART Alternative at 77 FR 51620 at 51648 (August 24, 2012) and Final 

Regional Haze FIP for Arizona (phase 1) at 77 FR 72512 at 72578 (December 5, 

2012). 
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coal-fired EGUs in the region will be retrofitted with postcombustion controls. 

In taking action to finalize a BART Benchmark, EPA is 

retaining the five year compliance period as proposed. Because 

BART compliance at NGS involves the design, procurement, and 

installation of SCR on three units and upcoming ownership 

changes at NGS as discussed in our proposed rule, EPA is 

determining that a five-year BART compliance timeframe at NGS is 

as expeditious as practicable. This is within the range cited by 

the commenter and the facility operator (i.e., average of 21 to 

47 months per unit, or 35 months to 67 months for multiple units 

at one facility) and is consistent with the CAA which requires 

BART compliance as expeditiously as practicable but no later 

than five years following the effective date of the final 

rule.104

G. Comments on BART for PM 

Comment: Support/opposition for finding not to establish PM BART 

 Several commenters supported EPA’s statement in the 

Proposed Rule that “[b]ecause emissions of PM are well 

controlled at NGS through federally enforceable limits, EPA is 

not proposing that it is “necessary or appropriate” under the 

TAR to determine BART for PM emissions at NGS.” 

104 See section 169A of the CAA (§169A(b)(2)(A) and (g)(4)). 
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 Some commenters noted that implementation of the Mercury 

and Air Toxics Standards (MATS) in the near future will 

establish an additional federally enforceable limit for PM of 

0.03 lb/MMBtu. The commenters added that the BART Guidelines 

provide that one can generally rely on MACT standards for 

purposes of BART. 

 In contrast, two commenters asserted that EPA was incorrect 

to determine that it need not evaluate BART for control of PM at 

NGS. The commenter asserts that the existing PM limit of 0.06 

lb/MMBtu was not based on a BART analysis and does not reflect a 

well-controlled PM emission rate for a coal-fired EGU. 

 One commenter asserted that the electrostatic precipitators 

(ESPs) at NGS do not represent the best system of control for 

PM. The commenter believes that EPA’s determination is 

inconsistent with recent BART and BACT determinations for coalfired utility boilers that set emissions limits for PM of 0.015 

lb/MMBtu or lower based on the use of fabric filter baghouses. 

The commenter concluded that EPA should revise its determination 

and complete a BART analysis for PM that includes evaluation of 

fabric filter baghouses. 

Response:

EPA agrees with the comment that it is not necessary or 

appropriate to require BART for PM emissions from NGS at this 

time. As we stated in our proposed rule: “Emissions of PM and SO2
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are controlled by hot-side electrostatic precipitators (HS-ESPs) 

and wet scrubbers, respectively.”105 Because NGS will be required 

to comply with the PM emissions limits in the MATS rule, EPA 

continues to find that it is not necessary or appropriate at 

this time to promulgate a BART emission limit for PM from NGS. 

EPA is not determining that the existing PM emission limit for 

NGS is BART. Instead, it is EPA’s position that it is not 

necessary or appropriate under our discretionary authority under 

the TAR, promulgated at 40 CFR 49.11, to conduct a BART 

determination for PM emissions because they are currently wellcontrolled and will be further reduced by compliance with the 

0.03 lb/MMBtu emission limit in the MATS rule. 

One commenter asserted that EPA should require fabric 

filter baghouses as BART for PM. EPA cannot agree or disagree 

that baghouses would be required as BART for PM because, as 

described above, we have determined that it is not necessary or 

appropriate at this time to conduct a BART determination for PM 

at NGS. 

H. Comments on BART for SO2

Comment: Support for finding that Reasonable Progress is met for 

SO2 

105 78 FR at 8279 (February 5, 2013). 
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 Several commenters noted that EPA recognized in the 

Proposed Rule that the emission limits EPA established for SO2 in 

1991 were determined to achieve greater reasonable progress than 

would BART. Several commenters agreed that no additional 

emission limits or controls should be required as a result of 

BART for SO2 emissions. One commenter noted that the existing SO2

limit at NGS is more stringent than the BART Guidelines’ 

presumptive SO2 limit. 

Response:

EPA agrees with these comments. As EPA stated in our 

proposal in February 2013, the SO2 emissions limit established in 

EPA’s 1991 SO2 FIP was determined to be better than BART under 

the visibility regulations addressing reasonably attributable 

visibility impairment. Specifically, EPA determined that 

promulgating a SO2 emission limit of 0.10 lb/MMBtu on an annual 

average basis would result in greater cumulative SO2 emissions 

reductions and visibility improvement over time than would the 

SO2 BART limit that EPA had proposed for NGS. NGS installed a wet 

flue gas desulfurization system to reduce SO2 emissions on each 

of its boilers in 1997-1999.106. 

I. Comments on EPA’s BART Alternative 

106 EPA initially codified the requirements for NGS to meet an SO2 emission 

limit in an existing FIP for the State of Arizona. See 40 CFR 52.145. After 

promulgation of the TAR, EPA moved the NGS SO2 FIP to 40 CFR 49.5513 
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Comment: Support for EPA’s authority for “better than BART” 

 Several commenters discussed and supported EPA’s policy and 

legal rationale for its discretion to approve “better than BART” 

alternatives and to provide an extended period for 

implementation of such an alternative at NGS. One commenter also 

opined that the 5‐year compliance period for BART that is defined 

in section 169A(g)(4) of the CAA applies by its terms only to: 

(1) SIPs, by providing that the BART compliance date shall be no 

later than “five years after the date of approval of a plan 

revision under this section”; and (2) FIPs promulgated under CAA 

section 110(c), by providing that the BART compliance date under 

any such FIP shall be no later than “five years after . . . the 

date of promulgation of such a plan revision in the case of 

action by the Administrator under section 110(c).” The commenter 

concluded that because the FIP for NGS is not promulgated under 

section 110(c) of the CAA, the 5-year timeframe for BART does 

not apply to NGS. 

Response:

EPA agrees with the comment in support of our action to 

find that the TWG Alternative meets the framework established in 

our Proposed Rule. EPA agrees that we have the legal authority 

under the CAA and RHR to implement a “better than BART” 
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alternative.107 EPA agrees that we have the authority under the 

CAA and the TAR to extend the compliance date that will apply to 

the “better than BART” alternative pursuant to CAA Section 

301(d)(4) and 40 CFR 49.11(a), as discussed in detail below. 

 We also note that regardless of whether the commenter is 

correct that the CAA does not require compliance with the BART 

requirements within five years for sources subject to a FIP in 

Indian country, we consider five years to be a reasonable 

timeframe for the installation and operation of SCR at NGS. To 

the extent the commenter is correct that the timing provisions 

of section 169A(g)(4) are outside the scope of EPA’s action to 

implement a FIP in Indian country under section 301 and the TAR, 

this further supports EPA’s determination that extending the 

compliance deadline beyond 2018 for a BART alternative at NGS is 

appropriate. 

EPA also agrees with the comment that approving the TWG 

Alternative for NGS will not compromise the ultimate goal of the 

RHR based on progress toward eliminating human‐caused visibility 

impairment in Class I areas by 2064.108 The TWG Agreement 

provides that the owner/operator of NGS will cease conventional 

107 See 40 CFR 51.308(e)(2); CAWCD v. EPA, 990 F.2d 1531 (9th Cir. 1993); CEED 

v. EPA, 398 F.3d 653 (D.C. Cir. 2005); UARG v. EPA, 471 F.3d 1333 (D.C. Cir. 

2006). 

108 See CAA section 169A(1)(a). 
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coal-fired generation in 2044. Because the TWG Agreement 

included this provision, we are including a provision in the 

Final Rule that requires the owner/operator of NGS to cease 

conventional coal-fired generation by December 22, 2044.109 The 

TWG Agreement further states that the Navajo Nation may elect to 

operate NGS after December 22, 2044 consistent with EPA 

approval. EPA is not including this provision in the regulatory 

requirements at §49.5513(j)(3)(iii); however, EPA expects that 

NGS would be substantially modified if the Navajo Nation were to 

elect to continue operation of the facility after NGS ceases 

conventional coal-fired generation in 2044, and that NGS would 

then need to meet all applicable regulatory and permitting 

requirements in existence at that time. In addition, any power 

generating units that may be built to replace NGS would also be 

subject to environmental review and air permitting requirements. 

Comment: General opposition to EPA’s “better than BART” 

determinations 

 One commenter stated that EPA may approve an alternative to 

BART only under certain limited circumstances, with the 

fundamental legal requirement being a demonstration that the 

109 See 79 FR 12944, 12950 (March 7, 2014). “While it is true that the Regional 

Haze Rule and BART Guidelines do not contemplate unit retirements as a 

potential BART option, neither rule prohibits states or EPA from considering 

a shutdown as part of a BART determination if the strategy is proposed by the 

owner of a BART-eligible source.” 
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alternative will “achieve greater reasonable progress toward 

natural visibility conditions” as supported by the clear weight 

of evidence. The commenter indicated that there are two ways EPA 

can make such a demonstration: (1) showing that the distribution 

of emissions is substantially similar under BART and the 

alternative measure, and that the alternative measure provides 

greater emissions reductions; or (2) performing modeling to 

demonstrate that visibility does not decline in any affected 

Class I area and there is an overall improvement in visibility. 

The commenter stated that the EPA may not use the first prong of 

the above test because the TWG Alternative distributes emissions 

over time differently than BART. Because the TWG Alternative 

also results in reductions of SO2 and PM, the commenter states 

that the pollutants reduced are also distributed differently. 

The commenter added that a BART alternative must ensure that all 

necessary emission reductions occur in the first planning 

period, which ends in 2018, and that any emission reductions 

resulting from the alternative measure must be surplus to 

reductions required under other provisions of the CAA. 

Response: 

EPA disagrees with the commenter’s statement that the TWG 

Alternative fails to demonstrate that it will “achieve greater 

reasonable progress toward natural visibility conditions.” As 

explained below, we disagree with the various comments 
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underlying the argument that our framework for analyzing the TWG 

Alternative is flawed. 

EPA appropriately focused on a comparison of the emissions 

reductions from BART and the TWG Alternative, rather than using 

visibility modeling to compare the two approaches. As the 

commenter noted, EPA’s regulations provide a specific twopronged test that may be used to demonstrate that a BART 

alternative achieves greater reasonable progress. In this 

rulemaking, EPA has applied the first prong of that test to 

demonstrate that the TWG Alternative provides for greater 

reasonable progress. The first prong of the test, set out in 40 

CFR 51.308(e), states that if the distribution of emissions is 

not substantially different under BART and the alternative, and 

“the alternative measure results in greater emission 

reductions,” the alternative may be deemed to achieve greater 

reasonable progress. Because both BART and the TWG Alternative 

apply to the same source the geographic distribution of 

emissions is similar.110 EPA therefore applied this test to 

110 In providing states with the flexibility to adopt alternative measures in 

lieu of BART, EPA assumed that under the BART alternative provisions, states 

would most likely adopt a trading program rather source specific BART 

controls. See, e.g., 40 CFR 308(e)(a regional haze SIP must contain BART 

limits unless the State demonstrates that “an emissions trading program or 

other alternative will achieve greater reasonable progress...”). The geographic 

distribution of emissions under a trading program is unlikely to be similar 

to that under source-specific BART. In contrast, the geographic distribution 

of emissions under a “better than BART” alternative that applies only to the 

BART source in question would be similar. 
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determine whether the TWG Alternative provided for greater 

reasonable progress, taking into account total NOX emissions over 

the 2009 to 2044 period from both BART and the TWG Alternative. 

The commenter argues, however, that the emissions must be 

temporally similar in order for this test to apply. When EPA 

added §51.308(e)(3) to the regional haze regulations in 2005, 

however, we made clear that EPA intended this test to apply 

where the geographic distribution of emissions between the BART 

and an alternative were similar.111 This approach is reasonable, 

as visibility modeling is not needed to demonstrate that a 

greater reduction in emissions from a source will result in 

greater visibility benefits than a lesser reduction in emissions 

from the same source. Accordingly, to the extent that the 

regulations are not clear that the test applies where the 

geographic distribution of emissions is similar, our 

interpretation is a reasonable one. In concluding that this test 

is the appropriate one to apply, EPA is not ignoring the 

commenter’s argument that the TWG Alternative distributes 

emissions over time very differently than would BART, and that 

in the near term, visibility would improve more rapidly if EPA 

were to require the installation of BART controls sooner. It is 

111 70 FR at 39136. 
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not necessary to model the visibility impacts of the TWG 

Alternative and BART, however, to reach that conclusion.112

EPA is accordingly determining that the provisions for 

retiring capacity and installing SCR under the TWG Alternative 

achieve a similar geographic distribution of emissions and that 

the appropriate test to apply is whether the alternative 

provides for greater emissions reductions than BART. In applying 

that test, EPA considers it reasonable to consider the 

cumulative emissions under BART and the BART alternative, rather 

than to simply compare annual emissions in some future year 

under the two scenarios. This approach provides a reasonable 

112 Although the commenter argues that visibility modeling is required to 

demonstrate that the TWG Alternative makes greater reasonable progress, the 

commenter notes only in passing the second test set out in the regulations at 

40 CFR 51.308(e)(3) governing situations where BART and a BART alternative 

will result in dissimilar distributions of emissions. In such situations, 

greater reasonable progress may be shown if visibility modeling shows that 

(i) visibility does not decline in any Class I area, and (ii) there is an 

overall improvement in visibility by comparing the average differences 

between BART and the alternative over all affected Class I areas. Even absent 

visibility modeling, it seems clear that the TWG Alternative, which requires 

NGS to reduce emissions from current levels, will not cause visibility to 

decline in any Class I area. Visibility modeling done by EPA in response to 

comments regarding the limited benefits of SO2 and PM reductions suggests that 

the TWG Alternative also passes the second half of this test. As explained in 

the RTC, EPA modeled the visibility impacts of TWG Alternatives A1, A2, and 

A3 (the operating scenarios that include reductions in alternative 

pollutants). See RTC for further discussion. This modeling shows that the 

cumulative visibility benefits of the TWG Alternative outweigh those 

associated with BART. Although we have not modeled the visibility impacts of 

Alternative B, compliance with the 2009-2044 and 2009-2029 NOx Caps will 

require NGS to achieve emission reductions similar to those required under 

Alternative A1 because the 2009-2029 NOX Cap is based on emissions that would 

be expected to occur under Alternative A1 (closure of one unit in 2019) and 

the 2009-2044 NOX Cap applies to all alternatives under the TWG Alternative.
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mechanism to give credit to NGS for its early reduction in NOX

emissions from the installation of combustion controls. 

 The commenter also objects to EPA’s decision to approve a 

BART alternative that will not be fully implemented by 2018. EPA 

agrees that the regional haze rule requires BART alternatives to 

be fully implemented by states by 2018, the end of the first 

planning period for states that were required to submit regional 

haze plans.113 As noted in the Proposed Rule, given the deadline 

for the submittal of regional haze SIPs, EPA’s regulations 

accordingly built in an additional five years beyond the BART 

compliance date for the implementation of BART alternatives.114

We note that in this action, although the TWG Alternative 

will not be fully implemented until 2044, NOx emissions from NGS 

have already declined from historical levels, and significant 

additional declines in emissions are expected in 2019 and again 

in 2030. Nonetheless, we acknowledge that we are looking 

forward to 2044 for full implementation of the TWG alternative, 

well beyond the 2018 date in the RHR. We explained the basis for 

our proposed decision to set the compliance period for the TWG 

Alternative in the Supplemental Proposal. EPA’s reasoning on 

this issue is grounded in CAA section 301 and the TAR. The TAR 

113 40 CFR 51.308(e)(2)(iii). 114 78 FR at 8288. 
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generally exempted Tribes from the CAA submittal deadlines that 

applied to States. EPA interprets the requirement in 40 CFR 

51.308(e)(2)(iii) to constitute a reasonably severable RHR 

submittal deadline that applies to States but not to Tribes. If 

the alternative measure is promulgated by the State, it must 

“submit[s] an implementation plan containing the following plan 

elements and include[s] documentation for all required analyses: 

. . . (iii) A requirement that all necessary emission reductions 

take place during the period of the first long-term strategy for 

regional haze.” Therefore, it is a required “plan element” for a 

State-only required implementation plan submittal. See 40 CFR 

51.308(b)(3)(requirements for States to submit long-term 

strategies). Because it is not mandatory for the Tribe to submit 

a long-term strategy, there is no mandatory requirement for the 

Tribe to ensure that all emissions reductions from a better than 

BART alternative occur within some deadline. 

This result is equitable as well as reasonable. States were 

required to submit SIPs in 2007, allowing 11 years for a “better 

than BART” alternative to be achieved in 2018. Because this is a 

FIP for a source in Indian country, and we are only now 

implementing the requirement in 2014, it is equitable to extend 

the compliance time as well. Please see the RTC for a more 

detailed discussion. 
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In summary, EPA is determining that the TWG Alternative is 

“better than BART” based on achieving greater NOX emissions 

reductions over a similar geographic distribution, within the 

date of the goal specified in the RHR of achieving natural 

conditions in 2064. Given the requirement for the owner/operator 

to cease conventional coal-fired generation at NGS in 2044, and 

with cumulative emissions over 2009 to 2044 being less than the 

BART Benchmark, the TWG Alternative satisfies the requirements 

of the RHR with respect to NOX BART as applied to Navajo Nation 

based on the TAR. 

Comment: EPA overestimated the BART Benchmark 

 Aside from its assertions that an approach using a BART 

Benchmark based on total emissions is not lawful under the CAA, 

one commenter (an organization representing itself and several 

other non-governmental organizations) stated that EPA’s 

assumptions in calculating a numerical value for the BART 

Benchmark included errors and improper credits. Specifically, 

the commenter asserted that: (1) EPA’s credit for the early 

installation of LNB/SOFA runs counter to the Regional Haze Rule, 

EPA’s longstanding policies, and EPA’s specific statements 

regarding the haze determination for NGS, (2) EPA’s proposal to 

delay BART due to the LNB/SOFA credit creates a dangerous 

precedent that threatens to significantly undermine the regional 

haze program, (3) EPA made a number of errors in its 
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calculations that all have the effect of artificially inflating 

the BART Benchmark. The specific errors purported by the 

commenter are outlined in more detail in the RTC. The commenter 

asserts that in total, assuming a final rule by July 1, 2014, 

their recommended revisions to the BART Benchmark would reduce 

the estimated emissions under BART during EPA’s chosen timeframe 

(2009-2044) by nearly 100,000 tons, a reduction of approximately 

26 percent. The commenter asserted that if EPA persists in using 

the emission cap framework, EPA must correct the NOX cap to 

prevent alternatives from being compared to an artificially 

inflated estimate of total NOX emissions. 

Response: 

 The commenter questions the use of LNB/SOFA credit in the 

BART Benchmark and cites three sources to support its assertion 

that the LNB/SOFA credit runs counter to the RHR and EPA’s longstanding policies: (1) page 18 of a report written by Victoria 

Stamper (Stamper Report), which was commissioned by the 

commenter and submitted as part of its comments,115 (2) page 

35,728 of the July 1, 1999 Regional Haze Rule, and (3) section 

IV.D.4.d of the BART Guidelines.116 EPA disagrees with these 

assertions. 

115 See document number 0372 in the docket for this rule. 116 Id. page 21. 
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The three citations provided by the commenter do not 

support its assertions that our proposal to credit NGS for the 

early installation of LNB/SOFA runs counter to the Regional Haze 

Rule or EPA’s long-standing policies. These three citations 

merely address the appropriate baseline period to use in the 

five-factor BART analysis. Page 18 of the Stamper Report 

supports our use of 2001-2003 as the baseline period for our 

BART determination for NGS and cites to 64 FR at 35,728 of the 

July 1, 1999 Regional Haze Rule that discusses EPA’s 

determination that the most appropriate baseline period would be 

over the 2001 to 2004 timeframe. The baseline period is used for 

evaluating the costs and visibility benefits of controls. The 

Stamper Report also cites Section IV.D.4.d of the BART 

Guidelines at 40 CFR Part 51 Appendix Y, that states baseline 

emissions should generally represent a realistic depiction of 

anticipated emissions for the source based on actual emissions 

from a baseline period. 

The commenter also cited the discussion in our Proposed 

Rule under Factor 3, where we described, in 2008, how the early 

installation of LNB/SOFA would not prejudice the implementation 

of more effective controls for BART. As stated previously, we 

did not use the LNB/SOFA credit to justify a less stringent 

determination of BART for NGS. The commenter characterizes the 
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credit as a shift in course from the agreements and 

understandings established in 2008 during the PSD permit process 

for the installation of LNB/SOFA. EPA disagrees. As stated in 

our Proposed Rule, citing the Ambient Air Quality Impact Report 

from the 2008 Proposed PSD Permit, EPA stated that the early 

installation of LNB/SOFA systems would not affect the baselines 

for cost or visibility improvements, and therefore will not 

influence EPA’s determination of the NOX reductions required for 

BART.117 EPA’s BART analysis for NGS was consistent with this 

statement. As previously noted, EPA used the 2001-2003 period as 

the baseline for determining cost-effectiveness and visibility 

benefits of controls, and determined, based on our analysis of 

all five factors, that SCR+LNB/SOFA is an appropriate BART 

Benchmark for NGS. 

The commenter relies on EPA’s statements about the 

appropriate baseline period to support an assertion that in a 

BART analysis, EPA should not give consideration or credit for 

controls installed after the baseline period. As stated in 

section 5.0 of the RTC, although we appropriately acknowledged 

the installation of LNB/SOFA after the baseline period at NGS 

under Factor 3 (existing controls at the facility), our analysis 

of cost-effectiveness and anticipated visibility benefits 

117 See 78 FR at 8284 (February 5, 2013). 
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appropriately compared SCR+LNB/SOFA against the 2001-2003 

baseline period.118

EPA’s proposed credit for early installation of LNB/SOFA 

was not associated with our five-factor analysis or BART 

determination for NGS. Rather, EPA discussed the LNB/SOFA credit 

in our framework for evaluating alternatives to BART. 

Specifically, in discussing our framework for BART Alternatives, 

EPA calculated the cumulative NOX reductions achieved early 

because the operator of NGS elected to install LNB/SOFA on one 

unit per year over 2009-2011, instead of waiting for the 

compliance period for BART. In our Proposed Rule and 

Supplemental Proposal we used this value, the LNB/SOFA credit, 

when comparing BART Alternatives to BART. As discussed elsewhere 

in the RTC, EPA’s proposal to allow BART Alternatives to take 

credit for the early installation of LNB/SOFA at NGS is a 

reasonable use of our discretion under the TAR.119

EPA disagrees with the assertion that this credit creates a 

dangerous precedent that threatens to significantly undermine 

the regional haze program. EPA notes that part of our rationale 

118 We note that in State of North Dakota v. EPA, the U.S. Court of Appeals for 

the Eighth Circuit vacated and remanded EPA’s promulgation of a FIP for Coal 

Creek Station because EPA did not consider the existing pollution control 

technologies in use at Coal Creek Station that were voluntarily installed 

after the baseline period. This document is included in the docket for this 

rule. 

119 See 78 FR at 62511 (October 22, 2013). 
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for the better than BART framework for NGS (including the credit 

for the early installation of LNB/SOFA and the adjusted 

compliance timeframe for BART Alternatives) was the potential 

impacts to numerous tribes that rely on NGS and/or CAP, as well 

as EPA’s regulations specifying that SIP submittal deadlines 

that apply to states do not apply to Tribes (or to EPA when 

implementing FIPs in Indian country). Further, EPA notes that 

the relationship between NGS and CAP is unique, the only other 

BART-eligible source in Indian country is the Four Corners Power 

Plant, and EPA has already completed the BART determination and 

FIP for this facility.120

The commenter alleges that “EPA’s claimed reliance on 

“early” LNB/SOFA as an excuse to avoid or delay what is legally 

required is misplaced and without foundation in the facts or 

law.”121 EPA disagrees with the assertion that we are delaying 

BART. As stated elsewhere in the RTC, as well as in our Proposed 

Rule and Supplemental Proposal, EPA did not propose to “delay 

BART.” EPA proposed to provide additional flexibility in the 

compliance timeframe for alternatives to BART.122

120 See 77 FR 51620 (August 24, 2012). 121 See page 22 of the EarthJustice comment letter dated January 3, 2014 

(document 0367 in the docket for this rule). 

122 See 78 FR at 8288, column 1, describing our proposed BART determination. 

See also 78 FR at 8289, section titled “Legal Rationale for Extending 

Compliance Schedule for Alternative Measures for NGS.” 
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The commenter’s use of quotation marks around the word 

“early” implies that the LNB/SOFA modifications were not, as a 

factual matter, installed early. However, EPA notes that in 

2008, when the operator of NGS began discussions with EPA 

regarding the permitting requirements associated with the 

significant increase in carbon monoxide (CO) emissions that 

would result from the installation of LNB/SOFA, EPA had already 

begun our process for evaluating BART for NGS, but had not yet 

proposed a BART determination or put forth our ANPR. Therefore, 

no requirement existed that mandated the installation of 

LNB/SOFA at NGS. In addition, the operator of NGS was aware that 

a BART determination, that would likely involve but may not be 

limited to LNB/SOFA, was forthcoming. As noted in our Proposed 

Rule, the operator of NGS could have waited until the compliance 

date for BART to initiate any reductions in NOX emissions; 

however, the operator elected in 2008 to seek the necessary 

permit to install LNB/SOFA on one unit per year over 2009-

2011.123 Thus, because the LNB/SOFA modifications were made in 

2009-2011, NOX emissions from NGS declined from a high of over 

35,000 tons in 2002 to less than 20,000 tons after 2011.124

123 See Proposed Rule at 78 FR at 8289 (February 5, 2013). 124 See RTC and references therein. In 2011, NGS emitted 19,900 tons of NOX, in 

2012, NGS emitted nearly 16,500 tons of NOX and in 2013, nearly 17,500 tons of 

NOX. 
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Although some of the decline in total NOX emissions can be 

attributed to a decrease in capacity utilization (i.e., decline 

in heat input of approximately 13 percent when comparing 2002 to 

2013), the dominant contributor to the decline in NOX emissions 

from NGS was from the installation of LNB/SOFA over 2009-2011. 

EPA considers these emission reductions to be real reductions 

that were not required (i.e., voluntary and surplus) and were 

achieved in advance of any actual requirement to reduce 

emissions (i.e., early). 

EPA also disagrees with the assertion that we made errors 

in calculating the BART Benchmark and NOX Cap. The commenter 

argues that SCR can meet a lower emission limit than proposed by 

EPA and that EPA should have set a compliance date within 3.5 

years. As discussed in Section 8.1 of the RTC, EPA disagrees 

that the BART Benchmark should be based on an emission limit of 

0.040 lb/MMBtu and that compliance should be required in 3.5 

years. EPA is finalizing a BART Benchmark based on our 

determination requiring NGS to meet a limit of 0.055 lb/MMBtu 

within five years of the effective date of the Final Rule. 

Therefore, EPA is not revising the BART Benchmark or NOX Cap to 

assume a limit of 0.040 lb/MMBtu or a shorter compliance time 

for BART. 

 In addition, the commenter recommends that EPA use average 

heat input over the baseline period (i.e., over 2001-2003) 
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rather than the average over the pre-LNB/SOFA time period (i.e., 

average over 2001-2008) to calculate future emissions. The 

commenter notes that our calculations for cost-effectiveness use 

baseline heat input over 2001-2003 to calculate pre- and postcontrol emissions (approximately 5,264 tons per year). The 

commenter asserts that this inconsistency is arbitrary. The 

commenter correctly notes that EPA used the average heat input 

over 2001-2008 (the pre-LNB/SOFA time period) to estimate 

emissions over 2009-2019 that would have occurred if the 

operator of NGS had not installed LNB/SOFA early, and emissions 

over 2019 to 2044 under BART (5,345 tons per year). The average 

heat input over the baseline period of 2001-2003 was 191,505,266 

MMBtu, while the average heat input over 2001-2008 was 

194,373,910 MMBtu. This is a difference of about 1.5 percent. 

EPA agrees that use of the same 2001-2003 baseline heat input 

value for estimating pre- and post-control emission rates is 

appropriate and consistent with the RHR and BART Guidelines, 

particularly in light of the goal of understanding the effect of 

a given control technology on emissions (i.e., assume identical 

values for baseline and future heat input to isolate the impact 

of control technologies). However, this approach does not mean 

that an average from the three-year baseline period (2001-2003) 

is most appropriate for estimating future emissions in 

determining the BART Benchmark. EPA notes that the use of 
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average heat input for 2001-2008 includes the baseline period 

recommended by the commenters and provides a larger data set, 

and therefore a more robust average value for estimating future 

emissions. EPA considers the use of an average value based on 

three years to be less robust than an average value based on 

eight years of data for representing potential future operation; 

therefore, EPA is retaining our use of the average heat input 

over 2001-2008 for estimating emissions over 2009-2044. EPA 

further notes that emission caps in permit requirements are 

typically established based on the facility’s potential to emit 

(PTE) and would thus be calculated using maximum heat input 

values. The highest observed annual heat input value was 

199,398,687 MMBtu and, if used in the NOX cap, would result in a 

significantly higher BART Benchmark. 

 The commenter also argues that in calculating the NOX cap, 

EPA should use a value that reflects an annual average for postcontrol emission rates rather than a rate based on a 30-day 

average limit of 0.055 lb/MMBtu. The commenter reviewed daily 

data from 2000 to 2013 and calculated the ratio of the maximum 

30-day average rate to the annual rate for each year and 

determined an average ratio of 1.135. Based on this ratio, the 

commenter recommended that the BART emission limit of 0.055 

lb/MMBtu (on a rolling average of 30 boiler operating days) be 

reduced by a factor of 1.135 as an estimate of what the annual 
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average post-control emission rate would be at NGS (i.e., 0.048 

lb/MMBtu). EPA agrees that generally, emission rates averaged 

over an annual basis are lower than emission rates averaged over 

a 30-day basis. However, EPA did not propose setting a BART 

limit for NGS on an annual average basis and EPA did not receive 

any comments suggesting that we do so. Without an enforceable 

annual limit, EPA considers it inappropriate to assume a lower 

emission rate in our calculation of the NOX Cap. We note that the 

BART Guidelines require that BART limits for EGUs be set on a 

rolling average of 30 boiler operating days. Therefore, although 

the BART Guidelines would not preclude establishing multiple 

emission limits over different averaging periods, the BART 

Guidelines do not require it. 

 Separately, the commenter also asserts that EPA 

overestimated the 2009-2044 NOX Cap. The commenter represents 

EPA’s NOX Cap as the scenario it calls “CAP-1” with a value of 

494,899 tons. This value is consistent with the 2009-2044 NOx Cap 

EPA proposed in our Supplemental Proposal.125 The commenter 

asserts that this value is overestimated because (1) actual heat 

input data should be used to calculate the NOX Cap; and (2) the 

125 See Table 3 of our Supplemental Proposal at 78 FR at 62516 (October 22, 

2013). 
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LNB/SOFA could be installed in two years.126 EPA disagrees with 

these assertions. 

 The commenter argues that for the period of 2009-2013, 

actual heat input data should be used to calculate the NOX Cap 

instead of the average heat input value over 2001-2008. EPA 

acknowledges that actual heat input data is available for the 

2009-2013 period; however, EPA considers using the average value 

to be appropriate, recognizing that years of lower than average 

capacity utilization will be balanced with years of higher than 

average capacity utilization at NGS. 

The commenter also asserts that LNB/SOFA could have been 

required in two years, on a separate compliance timeframe than 

installation of SCR and that this should have been incorporated 

in our calculation of the NOX Cap. EPA is not aware of any BART 

determination that required combustion controls on a different 

schedule than post-combustion controls. Although the commenter 

correctly notes that LNB/SOFA was installed in three years (on 

one unit per year over 2009-2011), EPA notes that the operator 

began the permitting process in 2008 and installed the LNB/SOFA 

during periods of major outage for each unit, which occurs at 

126 See Table 3 of the report written by Nathan Miller and Raijit Sahu 

(Miller/Sahu Report) commissioned by the commenter and submitted with its 

comments. See document number 0370 in the docket for this rule. 
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NGS every six years for each unit.127 EPA expects that it would 

not have been practicable to require installation of LNB/SOFA 

within two years following the final rule because, in order to 

accommodate one year for permitting, it would have required 

major outages on all three units in the same year. Therefore, 

EPA does not consider it practicable to assume the LNB/SOFA 

would or could have been installed on a separate track from the 

SCR. 

Although the commenter makes assertions related to 

purported overestimations of the BART Benchmark and the 2009-

2044 NOX Cap separately, the commenter combines all of the 

assertions together to argue that the 2009-2044 NOX Cap should be 

373,029 tons (121,870 tons, or 25 percent, lower than EPA’s 

proposed 2009-2044 NOX Cap of 494,899 tons). As outlined above, 

EPA disagrees than any of the purported corrections suggested by 

the commenter are necessary or appropriate for projecting annual 

emissions to calculate the 2009-2044 NOX Cap. 

Comment: EPA double-counted the benefits of LNB/SOFA 

One commenter asserted that EPA double-counted the benefits 

of the early installation of LNB/SOFA, stating that EPA 

calculated cumulative emissions for the BART alternatives 

127 See tab titled “Outage Cycle” in the document titled “EPA Analysis of BART 

Alternatives” in document number 0004 in the docket for this rule. 
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including the benefits of early reductions, then subsequently 

applied a LNB/SOFA credit again to BART alternatives. 

Response: 

EPA disagrees with the assertion that we double-counted 

emission reductions associated with the early installation of 

LNB/SOFA. 

In our February 5, 2013 proposed rule, EPA calculated the 

value of the LNB/SOFA credit based on the difference between 

total emissions under the BART scenario where LNB/SOFA is 

installed concurrently with SCR and the actual scenario when 

LNB/SOFA was installed early. The value of this credit was then 

applied to total emissions over 2009-2044 under Alternative 1.128

Although our calculation of emissions under Alternative 1 did 

account for actual emissions with early installation of 

LNB/SOFA, and thus applying the LNB/SOFA credit to the BART 

Alternative may appear to be double counting, it is not doublecounting because the BART Alternatives were compared against a 

BART Benchmark that also accounted for actual emissions with 

early installation of LNB/SOFA. Thus, both the BART Benchmark 

and Alternative 1 were calculated the same way (actual emissions 

accounting for early LNB/SOFA installation), and the LNB/SOFA 

128 See document titled “EPA Analysis of BART Alternative.xlsx” in document 

0004 in the docket for the rule. 
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credit was only applied to Alternative 1. An example of doublecounting would have been if EPA had applied the LNB/SOFA credit 

to cumulative emissions over 2009-2044 under Alternative 1 and 

then compared that value to total emissions over the same period 

under BART assuming LNB/SOFA and SCR were installed 

concurrently. 

 In our October 22, 2013 Supplemental Proposal, EPA 

approached the calculation from a different but equivalent 

perspective. The new calculation approach was used because it 

was more intuitive to apply and understand in the context of an 

enforceable cap on NOX emissions. In the Supplemental Proposal, 

the BART Benchmark was established as the total emissions over 

2009-2044 that would have occurred if LNB/SOFA and SCR were 

installed concurrently, five years following the effective date 

of the final rule. Total emissions under BART Alternatives were 

then calculated using actual emissions beginning in 2009 (i.e., 

accounting for the early installation of LNB/SOFA) and 

projections for future emissions. Thus, in the methodology used 

in the Supplemental Proposal, the LNB/SOFA credit was applied to 

the BART Benchmark and NOX Cap, rather than to the TWG 

Alternative. This method is equivalent to the one used in the 

Proposed Rule but does not give the appearance of doublecounting. In our Supplemental Proposal and supporting documents, 

EPA included calculations to show that these two methods are 
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equivalent.129 The two methods are equivalent because what 

matters in the “better than BART” context is the difference 

between total emissions under BART and total emissions under the 

BART Alternative. Whether the LNB/SOFA credit is applied to BART 

or BART Alternatives will affect the absolute value of a total 

(e.g., using the numbers in Table 2 of the Supplemental 

Proposal, the LNB/SOFA credit represents a difference of 377,008 

tons or 480,489 tons), but it does not affect the difference 

between BART and BART Alternatives. The method used in the 

Supplemental Proposal is more intuitive because BART and the 

BART Benchmark reflect total emissions over 2009-2044 that would 

have occurred if LNB/SOFA were installed concurrently with SCR, 

and the BART Alternatives reflect actual emissions without 

further credit or modification. Because no credits or 

modifications are made to actual emissions under the BART 

Alternatives, this method is the more logical accounting 

methodology for determining compliance with the 2009-2044 NOX

Cap. 

Comment: BART Alternatives would interfere with reasonable 

progress goals in other states 

129 See Table 2 of the Supplemental Proposal (78 FR at 62515, October 22, 2013) 

and document number 0191 titled “Supplemental Better than BART 

Alterntives.xlsx” in the docket for this rule. 
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 One commenter stated delaying the compliance date for BART 

will allow NGS to continue emitting pollutants in excess of the 

levels modeled by the WRAP and will interfere with the ability 

of Arizona, Utah, and Colorado to meet their reasonable progress 

goals for 2018. 

Response: 

The issue raised by the commenter is outside the scope of 

our rulemaking addressing the NOX BART requirements for NGS. 

Although 40 CFR 51.308(d)(3) requires states to submit long-term 

strategies that are sufficient to ensure that the state has 

included all measures needed to achieve its share of emission 

reductions agreed to through the regional planning process, the 

Navajo Nation has not yet submitted a long-term regional haze 

strategy. In addition, EPA has not yet found it necessary or 

appropriate to address these requirements through a FIP. If EPA 

determines it is necessary or appropriate to do so, we will take 

appropriate action. 

Meanwhile, we note that for NGS, the WRAP assumed that NOX

emissions in 2018 would equal 10,611 tons per year. NOX emissions 

under the TWG Alternative, in turn, will range from 

approximately 13,000 to 15,000 tons per year following the 

closure of one unit (or equivalent curtailment) at the end of 

2019. We also note that the closure of one unit (or equivalent 

curtailment) by the end of 2019 would reduce not only NOX, but 
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also emissions of SO2. Given the overall changes in emissions 

from the various regional haze actions since the WRAP made its 

projections, we will be better able to assess the need, if any, 

for further action once Arizona, Utah, and Colorado have 

prepared regional haze SIPs for the second planning period. 

J. Comments on the TWG Alternative and EPA’s Supplemental 

Proposal 

Comment: TWG Alternative should not be premised on SCR as BART 

One commenter argued that the 2009-2044 NOX Cap used for the 

TWG Alternative is unduly and arbitrarily stringent because it 

is based on a limit of 0.055 lb/MMBtu, which the commenter 

believes is too stringent because (1) EPA should not have 

determined that SCR is BART and (2) even if SCR were the 

appropriate basis for BART, 0.055 lb/MMBtu is not achievable. 

The commenter stated that because Arizona agricultural users 

will phase out their use of CAP Ag Pool water by December 2030 

pursuant to the 2004 Arizona Water Settlement Act (AWSA), 

capital costs that are collected in advance of SCR operation 

will be imposed on NIA users in exchange for no benefit. The 

commenter asserted that if EPA finalizes either of the “better 

than BART” alternatives without modification, it would be 

arbitrarily and capriciously apportioning compliance costs to 

NIA water users for which they are not responsible. Given EPA's 

acknowledgment of the compliance flexibility that exists with 
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respect to the TAR, the commenter believes that the failure to 

consider potential “better than BART” alternatives that would 

afford compliance flexibility to all NGS stakeholders on an 

evenhanded basis constitutes an abuse of discretion on the part 

of EPA. 

Response: 

 EPA disagrees with the assertion that the TWG Alternative 

is unduly and arbitrarily stringent because it is based on a 

BART limit of 0.055 lb/MMBtu. We consider the limit of 0.055 

lb/MMBtu to appropriate for establishing the BART Benchmark for 

NGS. EPA addressed specific comments related to the BART limit 

in section 8.1 of the RTC. We also note that the TWG Alternative 

was developed as an agreement between diverse stakeholders, 

including SRP, the operator of NGS on behalf of itself and other 

co-owners, and the CAWCD. Although both entities submitted 

comments in opposition to the proposed BART limit of 0.055 

lb/MMBtu, both parties signed the TWG Agreement that establishes 

the NOX Cap based on the proposed BART limit of 0.055 lb/MMBtu. 

The commenters indicate that their access to CAP Ag Pool 

water is expected to end in 2030, and assert that the timeframes 

for compliance with the limit of 0.07 lb/MMBtu in 2030 would 

necessitate water rate increases prior to 2030. The commenter 

asserts that it is arbitrary and capricious for NIA water users 

to pay a few years of higher CAP water rates for controls that 
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will not be operational until after their access to the CAP Ag 

Pool expires. EPA notes that the direct impact of compliance 

with the limit of 0.07 lb/MMBtu in 2030 under the TWG Agreement, 

presumably with installation and operation of SCR, would be on 

the cost of electricity generation. Increasing water rates are 

indirect impacts that result from the relationship between NGS 

and CAP. EPA does not set or determine water rates charged by 

CAWCD to the CAP Ag Pool or any other classes of CAP customers. 

EPA’s proposed and final approval of requirements consistent 

with the TWG Agreement as a “better than BART” alternative is 

based on our review of the anticipated emission reductions 

associated with the TWG Alternative compared to BART. Although 

EPA, DOI, and DOE have committed to work together on many issues 

related to NGS, including funding for the federal portion of 

capital improvements at NGS, EPA does not determine how controls 

would be financed and how and when electricity or water rates 

would be adjusted to recover costs. 

Comment: TWG Alternative does not fully meet EPA’s obligations 

to the Gila River Indian Community 

 The Gila River Indian Community said that even though it 

fully supports the TWG Alternative, it is concerned that EPA has 

not met its obligations to the Community because of the 

significant costs to NGS and associated impacts on the 

Community. Rather, the commenter views the TWG Alternative as 
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the first step in a process that will limit the impacts on the 

Community because only under the TWG Alternative will key U.S. 

commitments contained in the TWG Agreement be realized. 

Specifically, under the TWG Agreement, and as outlined by the 

commenter, DOI will work with the Community and other tribes in 

the area around NGS, to evaluate the actual impacts the 

regulatory requirements will have on NGS over time. The 

commenter specifically referred to the U.S. commitment to 

allocate $10 million annually for 10 years starting in 2020, 

from the Reclamation Water Settlements Fund to reduce impacts to 

the Development Fund. 

Response: 

EPA acknowledges the comment and is aware that costs 

associated with implementing the TWG Alternative will have 

implications for numerous Tribes, including the Gila River 

Indian Community. EPA is committed to continuing to work with 

the Department of the Interior and the Department of Energy in 

the Interagency Working Group on NGS, as laid out in the Joint 

Statement signed in January 2013 by the heads of the three 

agencies, to work with tribes to address long-term issues 

related to NGS. The provisions in the TWG Agreement that are not 

related to EPA’s authority to evaluate BART or a “better than 

BART” alternative, however, are beyond the scope of this 

rulemaking. 
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Comment: TWG Alternative is vague and unenforceable 

 One commenter stated that a BART determination must include 

clear requirements for emissions reductions and a clear timeline 

for those reductions, to ensure continuing visibility 

improvements in Class I areas. The commenter indicated that 

without specific emission limits and/or commitments to retire 

specific amounts of capacity from specific units, as of a date 

certain, it is impossible to calculate the visibility 

improvements that will result from the TWG Alternative, 

particularly TWG Alternatives A3 and B, and it will be 

impossible for individuals or EPA to assess whether NGS is on 

track to meet the emission reductions necessary to ensure 

reasonable progress toward natural visibility in affected Class 

I areas. 

Response:

 EPA disagrees with the assertion that the TWG Alternative 

is vague and unenforceable. EPA acknowledges that the TWG 

Alternative provides flexibility in a manner that appears 

complex. This complexity is a result of the role future 

ownership outcomes will have in determining the most reasonable 

compliance options in the future. Once the ownership issues are 

resolved, the scope of options under the TWG Alternative 

narrows. Although some flexibility still remains in the TWG 

Alternative, particularly under TWG Alternative B, the options 
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for future operation of NGS are bounded by the limitations 

provided by the 2009-2044 and 2009-2029 NOX Caps. 

 Contrary to the assertions by commenters, EPA included 

proposed regulatory language in our Supplemental Proposal that 

provided specific and enforceable timelines for achieving 

emission reductions under the TWG Alternative. The proposed 

language under 40 CFR 49.5513(j)(3)(i), “Operating Scenarios to 

Comply with 2009-2044 NOX Cap,” defines the timeframes and 

requirements under TWG Alternatives A1, A2, A3, and B, all of 

which must be implemented in a manner that ensures total NOx

emissions over 2009-2044 remain below the 2009-2044 NOx Cap. 

Specifically, §49.5513(j)(3)(i)(A) defines Alternative A1, and 

specifies the following requirements: (1) by December 31, 2019, 

the owner/operator shall permanently cease operation of one 

coal-fired unit and (2) by December 31, 2030, the owner/operator 

shall comply with a NOx emission limit of 0.07 lb/MMBtu on each 

of the two remaining coal-fired units. Alternative A1 is the 

simplest of the possible operating scenarios under the TWG 

Alternative and §49.5513(j)(3)(ii)(A) specifies that Alternative 

A1 applies under three potential future ownership possibilities. 

 TWG Alternative A2 is defined in §49.5513(j)(3)(i)(B) and 

requires (1) by December 31, 2019, the owner/operator shall 

permanently cease operation of one coal-fired unit, and (2) by 

December 31, 2019, the owner/operator may elect to increase net 
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generating capacity of the remaining two coal-fired units by a 

combined total of no more than 189 MW. The actual increase in 

net generating capacity shall be limited to the sum of 19 MW and 

the ownership interest, in net MW capacity of up to 170 MW, 

purchased by the Navajo Nation by December 31, 2019. The 

owner/operator shall ensure that any increase in the net 

generating capacity is in compliance with all pre-construction 

permitting requirements, as applicable, and (3) by December 31, 

2030, the owner/operator shall comply with a NOX emission limit 

of 0.07 lb/MMBtu on each of the two remaining coal-fired units. 

The future ownership possibilities that would trigger 

Alternative A2 are defined in §49.5513(j)(3)(ii)(B). 

 TWG Alternative A3 is defined in §49.5513(j)(3)(i)(C) and 

requires (1) by December 31, 2019, the owner/operator shall 

reduce net generating capacity of NGS by no less than 561 MW. 

The actual reduction in net generating capacity of NGS shall be 

determined by the difference between 731 MW and the ownership 

interest, in net MW capacity of up to 170 MW, purchased by the 

Navajo Nation by December 31, 2019, and (2) by December 31, 

2030, the owner/operator shall comply with a NOX emission limit 

of 0.07 lb/MMBtu on two units. The future ownership 

possibilities that would trigger Alternative A2 are defined in 

§49.5513(j)(3)(ii)(C). 
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 TWG Alternative B is defined in §49.5513(j)(3)(i)(D) and 

requires that in addition to the 2009-2044 NOX Cap, the 

owner/operator shall ensure compliance with the 2009-2029 NOX

Cap. The 2009-2044 NOX Cap is defined in §49.5513(j)(2)(ii) as no 

more than 494,899 tons of NOX, and the 2009-2029 NOX Cap is 

defined in §49.5513(j)(2)(i) as no more than 416,865 tons of NOX. 

The 2009-2029 NOX Cap is based on closure of one unit by December 

31, 2019 and the 2009-2044 NOX Cap is based on compliance with 

the BART emission limit of 0.055 lb/MMBtu by July 1, 2019. The 

future ownership possibilities that would trigger Alternative B 

are defined in §49.5513(j)(3)(ii)(D). As described in 

§49.5513(j)(4)(iv), if TWG Alternative B is triggered, the 

owner/operator must submit annual Emission Reduction Plans that 

contain the anticipated year-by-year emissions to ensure 

compliance with the 2009-2029 and 2009-2044 NOX Caps. 

Comment: EPA did not evaluate other possible outcomes under TWG 

Alternative

The commenter asserts that under the scenario of reduced 

capacity (three units remain open, i.e., TWG Alternative A3), 

EPA ignored other possible outcomes and simplistically assumed 

that two units would continue to operate at full capacity with 

SCR and the unit whose operation is curtailed would operate only 

with LNB/SOFA. The commenter asserts that there is no guarantee 

that the operator will choose to comply with TWG Alternative A3 
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in this manner. The commenter also asserts that there are an 

infinite number of ways the operator could comply with the 2009-

2029 and 2009-2044 NOX Caps under TWG Alternative B. 

Response: 

Although the specific arrangement under TWG Alternative A3 

that EPA evaluated is not required, EPA disagrees that nothing 

compels the operator to comply with this operating scenario in a 

manner that reduces emissions comparably with the assumption 

that two units would operate at full capacity with SCR and the 

unit that is curtailed would operate with LNB/SOFA. EPA notes 

that under TWG Alternative A3, as well as all other TWG 

Alternatives, the owner/operator must operate the units at NGS 

so that total emissions remain below the 2009-2044 NOX Cap (as 

well as the 2009-2029 NOX Cap under Alternative B). For example, 

under TWG Alternative A3, if the operator chose to curtail all 

three units by a total of 561 MW equally and comply with a limit 

of 0.07 lb/MMBtu on two units and 0.24 lb/MMBtu on one unit, 

total emissions over 2009-2044 are not likely to comply with the 

2009-2044 NOX Cap.130 Thus, the operator would be prohibited from 

operating in this manner and would need to, for example, 

significantly curtail operations to reduce emissions further, or 

risk violating the FIP. 

130 See RTC and references therein. 
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As noted in our Supplemental Proposal, EPA estimated total 

NOX emissions over 2009-2044 for TWG Alternatives A1, A2, and A3 

to provide assurance that the owner/operator could reasonably 

meet the 2009-2044 NOX Cap under the specific terms of those 

alternatives. EPA does not need to determine that all operating 

possibilities that are consistent with the requirements of TWG 

Alternative A1, A2, and A3 would also meet the 2009-2044 NOX Cap. 

The regulatory requirements EPA is finalizing for the TWG 

Alternative provide specific dates on which the owner/operator 

must close a unit, curtail operations, and meet emission limits. 

While there is some flexibility in how emissions might be 

curtailed under TWG Alternative A3, the 2009-2044 NOX Cap ensures 

that the operator does not implement a strategy that results in 

substantially more emissions than would be achieved by 

installing SCR on the two units that are operated at full 

capacity and curtailing operations on the unit that was not 

retrofit with SCR. 

 The commenter further states that the two possibilities 

EPA considered in our Supplemental Proposal are not likely to be 

the outcomes under TWG Alternative B. EPA agrees that TWG 

Alternative B provides more flexibility than TWG Alternative A. 

However, EPA disagrees that TWG Alternative B is so open-ended 

that it would not be enforceable or result in emission 

reductions at NGS. We note that the 2009-2029 NOX Cap was 
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calculated based on the closure of one unit with no additional 

increase in capacity (i.e., equivalent to emissions under TWG 

Alternative A1). Thus, the operator cannot maintain the status 

quo (operation of all three units at full capacity at a limit of 

0.24 lb/MMBtu) and meet the 2009-2029 NOX Cap. We recognize that 

several commenters are concerned about the flexibility under TWG 

Alternative B. However, as discussed further in the RTC, we note 

that the range of possible operating choices for TWG Alternative 

B is substantially constrained by the requirement to comply with 

the 2009-2029 and 2009-2044 NOX Caps. 

Although we disagree with commenters that the TWG 

Alternative is vague and unenforceable, in response to the 

concerns expressed by these commenters, to provide additional 

assurance that cumulative emissions of NOX from NGS under the TWG 

Alternative will not exceed the BART Benchmark, EPA is adding 

the following provisions to the Final Rule. Under all 

Alternatives, if cumulative emissions of NOX from NGS exceed the 

2009-2044 NOX Cap prior to 2044, the operator of NGS must 

permanently cease operation of NGS. In addition, under 

Alternative B, if cumulative emissions of NOX exceed the 2009-
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2029 NOX Cap prior to 2029, the operator of NGS must temporarily 

cease operation of all units at NGS.131

EPA is finalizing the requirements of the TWG Alternative, 

consistent with Appendix B of the TWG Agreement, which require, 

among other things, emission reductions in 2019 and 2030. EPA is 

also adding as an enforceable requirement, the commitment in the 

TWG Agreement for the owner/operator to cease conventional coalfired electricity generation at NGS by 2044. EPA considers these 

timeframes to be consistent with the stated goal of section 169A 

of the CAA. EPA has addressed comments regarding consistency 

with EPA’s regulations, including the RHR and the TAR, in 

section 8.5 of the RTC. 

Comment: Relationship between TWG Alternative and Reasonably 

Attributable Visibility Impairment

One commenter asserted that EPA was incorrect to claim that 

the TWG Alternative would absolve NGS of obligations related to 

a Reasonably Attributable Visibility Impairment (RAVI) finding 

that may be made for NGS. 

Response:

131 The combination of the 2009-2044 and 2009-2029 NOX Caps under TWG 

Alternative B means that if NGS exceeds the 2009-2029 NOX Cap prior to 2029 it 

must cease operation, but the operator may re-start operation after 2030 as 

long as cumulative emissions have not yet exceeded the 2009-2044 NOX Cap. 
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EPA disagrees that we claimed that the TWG Alternative 

would absolve NGS of obligations related to RAVI. The commenter 

cited to footnote 21 in our Supplemental Proposal.132 In that 

footnote, we acknowledged that the TWG had intended their 

alternative to satisfy both the “better than BART” requirements 

of the RHR as well as any requirements of the RAVI program. Our 

footnote merely noted that there was no outstanding petition to 

certify impairment from NGS at any Class I area and outlined the 

process and requirements for triggering a BART determination 

under RAVI. Although we stated that a BART determination under 

RAVI would likely be the same as a BART determination under 

regional haze (i.e., an analysis of the five factors listed in 

the CAA), EPA did not make any conclusions or absolve NGS of any 

obligations related to RAVI because there is currently no action 

before EPA to make an attribution finding related to NGS. 

Comment: TWG Alternative should specify the technology required 

for compliance

The Hopi Tribe indicated that it has serious concerns with 

the proposed TWG Alternative for several reasons, including 

because the TWG Alternative does not specify the technology, 

i.e., either SCR or an equivalent that will be used to achieve 

the same level of NOX reductions as the BART proposal. The 

132 See Supplemental Proposal, 78 FR at 62513, footnote 21 (October 22, 2013). 
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commenter states the TWG Alternative is ambiguous because both 

scenarios are vague and do not include the same level of 

assurance that the NOX reductions will be the same as under the 

BART proposal. Also, because the time NGS would be permitted to 

operate without SCR (or equivalent alternative) would be 

adjusted under the TWG Alternative, the commenter believes the 

TWG Alternative jeopardizes the goal of the CAA and the purpose 

of this regulation. 

Response: 

Our proposed BART determination did not specify what 

technology must be used because BART is defined as an emission 

limit that represents the level of control representing BART, 

not a particular technology. Thus, our Proposed Rule and the 

Supplemental Proposal both imposed emission limits for NOx. The 

limits for BART (0.055 lb/MMBtu) and the TWG Alternative (0.07 

lb/MMBtu) are based on what is achievable using a specific 

technology. Both limits are achievable with SCR, but the 

operator may consider using newer technologies, if available, as 

long as each unit complies with its applicable emission limit by 

its compliance date. The compliance period under the TWG 

Alternative is consistent with the goal of the CAA and the 
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purpose of the RHR, which are to restore visibility in Class I 

areas to natural conditions by 2064.133

Comment: “Arbitrary” 2044 end date 

 One commenter stated that the 2009-2044 period analyzed for 

the TWG Alternative is arbitrary because it is quite likely that 

one or more NGS units will operate beyond that time frame. The 

commenter asserted that if NGS units continue to operate for 

even 3 additional years, until 2047, the TWG Alternative permits 

outcomes that will result in greater total NOX emissions than the 

2009-2044 NOX Cap. 

Response:

 EPA disagrees with the comment that the 2044 end date for 

the NOX Cap is arbitrary. EPA used 2044 as the end date in our 

calculations of the BART Benchmark. We selected 2009-2044 as 

most appropriate because it includes the early installation 

dates for LNB/SOFA and extends until the anticipated 2044 

termination date of the renewed site lease that was approved by 

the Navajo Nation.134 Under the TWG Agreement signed by six 

entities including the Navajo Nation and SRP, the NGS Co-Tenants 

shall cease their operation of conventional coal-fired 

generating at NGS no later than December 22, 2044. At its 

133 40 CFR 51.308(d). 134 See Footnote 60 in the Proposed Rule, 78 FR at 8290 (February 5, 2013). 
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election, consistent with the Lease Amendment, the Navajo Nation 

may continue plant operations at NGS after December 22, 2044 

consistent with EPA approval.135 Thus, the Navajo Nation may seek 

to operate NGS after 2044, however, EPA expects that operation 

of NGS after the owner/operator ceases conventional coal-fired 

generation would involve substantial modification to NGS and NGS 

would be required to meet all applicable regulatory and 

permitting requirements in existence at that time. To make this 

end date federally-enforceable, EPA is adding it as a 

requirement to the regulatory language in today’s final action. 

EPA is adding the following requirement to the regulatory 

language in the Final Rule under 40 CFR 49.5513(j)(3)(iii): 

By December 22, 2044, the owner/operator 

shall permanently cease operation of all 

coal-fired units at NGS. At its election, 

the Navajo Nation may continue plant 

operation at NGS after December 22, 2044, 

consistent with EPA approval under the New 

Source Review program. 

Comment: Emissions under the TWG Alternative 

 One commenter, an organization representing several 

environmental and non-governmental groups, stated that neither 

EPA nor TWG have provided a comprehensive technical analysis of 

the emissions that are possible under the TWG Alternative. The 

135 See Section VII.F of the TWG Agreement (page 14). 
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commenter asserted that it is EPA’s responsibility to provide an 

administrative record that contains comprehensive modeling and 

analysis for any BART proposal, but EPA left this critical 

component of the alternatives analysis undone. 

 The commenter provided its own calculations of emissions 

under TWG Alternative A and B and compared those estimates with 

its own calculation of a NOX Cap and BART Benchmark, and 

concluded that cumulative emissions from possible scenarios 

under the TWG Alternative are not lower than its NOX Cap or BART 

Benchmark. 

Response: 

 EPA disagrees with the comment that we have failed to 

provide a comprehensive technical analysis of the TWG 

Alternative. We also disagree with the assertion that our 

administrative record for this rulemaking is incomplete. As 

stated elsewhere in the RTC, EPA’s analysis of the TWG 

Alternative is consistent with the required analyses for 

alternatives to BART outlined in the RHR. 

The comment relies on a report prepared by Nathan Miller 

and Ranijit Sahu (Miller/Sahu) for the commenter contending that 

EPA’s evaluation of the TWG Alternative is incorrect. But the 

report changes the central inputs underlying our calculations 

for BART and the TWG Alternative. The specific technical reasons 

that we disagree with the inputs that Miller/Sahu changed (e.g., 
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NOX emissions limit achievable with SCR, heat input values from 

baseline period, annual vs. 30-day emission rates) are explained 

in detail in section 8.5 of the RTC. 

Table 2 in the Miller/Sahu report depicts BART-1 as “EPA 

BART (No Corrections),” showing a value of 379,152 tons of 

cumulative NOX emissions over 2009-2044 that is nowhere traceable 

to EPA’s documents.136 The Miller/Sahu report then makes several 

“corrections” to reach a value of 280,554 tons of NOX emissions. 

EPA has explained in detail why we disagree with each of the 

Miller/Sahu “corrections” in section 8.5 of the RTC and 

references therein. For the reasons set forth in section 8.5, we 

also continue to disagree that our calculation of the BART 

Benchmark or the NOX Cap has relied on any incorrect inputs. 

Because we disagree with the “corrections” and the values 

presented in the Miller/Sahu report, we also disagree with the 

conclusions of Miller/Sahu that the TWG Alternative fails to 

satisfy our requirements for demonstrating an alternative is 

“better than BART”. The commenter cannot change the fact that 

its alternative preferences on the inputs for calculating BART 

are just preferences by simply calling them “corrections.” 

136 Miller/Sahu Report, Table 2 at p. 7. 
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Comment: Visibility modeling under the TWG Alternative 

 One commenter, an organization representing several 

environmental and Navajo non-governmental organizations, stated 

that the TWG Alternative distributes emissions over time very 

differently than BART: while BART would require NOX reductions 

within 5 years, the bulk of the reductions in the TWG 

Alternative might not come until the end of the 2009-2044 

period. The commenter stated that the additional analysis and 

modeling it conducted reveals that the TWG Alternative is likely 

substantially worse than BART. 

Response:

As discussed elsewhere in this notice, because emission 

reductions achieved under the TWG Alternative will have the same 

geographic distribution as emission reductions under BART, EPA 

disagrees that visibility modeling is required for our 

evaluation of the TWG Alternative. We note that the commenter 

provided its own visibility modeling and EPA disagrees with 

methodologies used and conclusions drawn by the commenter. 

The Miller/Sahu Report compared anticipated visibility 

impacts from the TWG Alternative against the anticipated 

visibility impacts based on its own preferences for the NOX Cap 

and BART Benchmark. Although the commenter asserts that its 

analysis shows that visibility under the TWG Alternative is 

substantially worse than under its preferences for the BART 
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Benchmark and NOX Cap, their analysis also shows that when the 

TWG Alternative is compared to the BART Benchmark and NOX Cap as 

proposed by EPA, the TWG Alternative scenarios it explored that 

meet the 2009-2044 and 2009-2029 NOX Caps (as applicable) 

generally result in lower or comparable visibility impacts as 

BART.137

EPA conducted visibility modeling to compare TWG 

Alternatives A1, A2, and A3 in 2019 and 2030 against the BART 

Benchmark.138 As indicated by commenters, other possibilities 

exist beyond the scenarios for the TWG Alternatives we 

considered explicitly in our Supplemental Proposal. EPA has 

stated elsewhere that we need not consider potential emissions 

under all possible scenarios in setting the NOX Cap, but must 

verify that NGS can reasonably be expected to comply with 2009-

2044 NOX Cap under the various constraints imposed under the TWG 

Alternatives (i.e., closure, curtailment, and a secondary 2009-

2029 NOX cap). However, EPA explored two other possibilities 

under TWG Alternative A3 that included reducing capacity on all 

three units equally or reducing capacity on two units and 

installing SCR on the two units that operate at reduced 

capacity.139 EPA did not include those two additional 

137 See Exhibit 2 to the Miller/Sahu report and RTC and references therein. 138 See RTC and references therein. 139 Id. 
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possibilities under TWG Alternative A3 in our visibility 

modeling analysis because those scenarios do not reduce 

emissions sufficiently to meet the 2009-2044 NOX Cap. 

 Our visibility modeling of the TWG Alternatives compared to 

our proposed BART determination shows that, as expected, during 

the approximate 10-year period between 2019 and 2030, the 

visibility impacts of NGS under the TWG Alternatives are higher 

than the visibility impacts of NGS under BART. After 2030, when 

NGS achieves additional emission reductions through compliance 

with a limit of 0.07 lb/MMBtu on two units, our modeling 

indicates that the visibility impacts under the TWG Alternatives 

are comparable to or lower than visibility impacts under BART 

(see RTC for further detail). These results are not surprising 

and mirror the comparative reduction in NOX emissions under the 

TWG Alternatives and the BART Benchmark over time, showing 

greater overall visibility improvement under the TWG Alternative 

than under the BART Benchmark. 

 As noted elsewhere in the RTC, EPA is including as part of 

the TWG Alternative, in the regulatory language in the Final 

Rule, a provision consistent with the TWG Agreement that the 

owner/operator of NGS permanently ceases conventional coal-fired 

generation by the end of 2044. Thus, under the TWG Alternative, 

the visibility impact of NGS is likely to be zero or near zero 
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in 2045 and thereafter.140 Under BART, there would be no 

commitment or enforceable requirement to close after 2044, 

therefore, visibility impacts of NGS at all 11 Class I areas 

would be expected to continue in 2045 and thereafter. 

Comment: Economic Impacts of the TWG Alternative 

The Hopi Tribe expressed concern that EPA did not assess 

the potential economic impacts of the TWG Alternative to the 

Hopi Tribe. The commenter opined that EPA recognized the 

significance of NGS to the Hopi Tribe in its analysis under 

Factor 2. Because the TWG Alternative includes closure of at 

least one unit in 2019, and EPA did not address the potential 

economic impacts of partial closure of NGS on the Hopi Tribe, 

the commenter contended that the Agency has not complied with 

the RHR and BART Guidelines. The Hopi Tribe noted that in the 

event capacity is reduced at NGS under the Supplemental 

Proposal, the amount of coal and water purchases from the Tribe 

would decrease leading to a decrease in income to the tribe from 

the sale of these. The commenter also stated that the 

Supplemental Proposal is not as effective in improving air 

quality and visibility for the Hopi Reservation. Extending the 

140 EPA expects that if the Navajo Nation elects to operate NGS after the 

owners have ceased conventional coal-fired generation, this would likely 

involve substantial modifications to NGS and NGS would be subject to all 

applicable regulatory and permitting requirements in existence at that time. 
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timeframe during which NGS can continue to operate without SCR 

or an equivalent technology would cause a continued air quality 

burden on the Hopi Tribe. 

Response: 

 EPA recognizes that the TWG Alternative, which includes 

closure of one unit at NGS or equivalent curtailment of 

operation, may change the royalties and other payments related 

to coal and water that are paid to the Hopi Tribe. Although EPA 

evaluated cost-effectiveness and affordability of the options in 

our analysis of BART controls, we disagree that we must also 

conduct an economic impact analysis for alternatives to BART. 

The BART Guidelines provide little guidance on the evaluation of 

alternatives to BART and the RHR does not require an analysis of 

economic impacts of BART Alternatives. EPA’s evaluation of 

potential impacts to tribes in our analysis of BART controls was 

used to inform our government-to-government consultation with 

tribes and is consistent with BART. In addition, we have held 

numerous government-to-government consultation meetings with 

tribes to discuss NGS during this rulemaking. EPA continues to 

recognize the issues and concerns of tribes located in Arizona 

regarding NGS and is committed to continuing to work with our 

federal partners and the tribes through the Joint Federal Agency 

Work Group on NGS to help address these issues. 
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 The Hopi Tribe also expressed concern that the TWG 

Alternative is less effective than BART at improving air quality 

and visibility on the Hopi Reservation. EPA notes that the 

purpose of the RHR is to reduce visibility impairment at Class I 

areas; however, EPA disagrees that the TWG Alternative is less 

effective than BART. Although the timeframe for implementation 

of the TWG Alternative (new reductions in 2019 and 2030) is 

longer than the timeframe for BART (in 2019), we note that BART 

would only reduce emissions of NOX, whereas the TWG Alternative, 

in 2019, would also reduce emissions of SO2, PM, CO2, and 

hazardous air pollutants as a result of the closure of one unit 

(or equivalent curtailment). 

Comment: Support for some changes EPA made to the TWG Agreement 

in the Supplemental Proposal 

 The TWG noted that there were several differences between 

Appendix B to the TWG Agreement and EPA’s Supplemental Proposal 

of the TWG Alternative. The commenters expressed support for 

some of the differences, and expressed concern with others. One 

commenter agreed with the methodology that EPA used to calculate 

the 2009-2044 NOX Cap of 494,899 tons. 

 The commenter supported the additional requirement to 

report annual heat input, although this information is already 

reported through the Acid Rain Program. However, the commenters 

requested that additional time be provided to ensure that the 
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data submitted in the annual report are consistent with the data 

that the NGS operator submits to the Clean Air Markets Database 

(CAMD), in the annual emission inventory, and in the greenhouse 

gas (GHG) report required by 40 CFR part 98, which are not due 

until March 31st. 

Response:

 EPA recognizes that the TWG supports some of the changes 

EPA made to Appendix B to the TWG Agreement, including EPA’s 

revisions to the 2009-2044 NOX Cap and the requirement to report 

annual heat input. EPA agrees that it is reasonable to require 

the timeframe for the reporting requirements under BART to 

generally be more consistent with other reporting requirements. 

Therefore, EPA is revising the regulatory language accordingly. 

Comment: Suggested addition to §§49.5513(j)(4)(iv)(A) and (B) 

 The TWG requested that EPA clarify the scope and content of 

the title V permit revision that is necessary to incorporate 

elements of the BART alternative by adding the language from 

Appendix B of the TWG Agreement to the requirements of the TWG 

Alternative. 

Response: 

EPA did not include the language from the TWG Agreement 

related to the title V (part 71) operating permit in the 

regulatory language in our Supplemental Proposal because the 

title V (part 71) regulations require that the operating permits 
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include all applicable requirements, which for NGS would include 

the permit limits that exist in its PSD permit (i.e., the limit 

of 0.24 lb/MMBtu when operating with LNB/SOFA) as well as the 

final requirements in this FIP (e.g., the limit of 0.07 lb/MMBtu 

on two units in 2030). Therefore, a specific requirement in the 

FIP that directs the operating permit to incorporate applicable 

requirements is not necessary. Although EPA considers it 

unnecessary, EPA will amend §49.5513(j)(4)(iii) as suggested by 

the commenter. 

We further note that in the proposed regulatory language in 

our Supplemental Proposal, EPA inadvertently did not specify an 

averaging period for the emission limits under the TWG 

Alternative Operating Scenarios (§49.5513(j)(3)). Therefore, EPA 

is adding to the regulatory language that emission limits apply 

over a rolling average of 30 boiler operating days, to 40 CFR 

§49.5513(j)(3), (j)(3)(i)(A)(2), (j)(3)(i)(B)(3), and 

(j)(3)(i)(C)(2). 

Comment: Another suggested addition to §§49.5513(j)(4)(iv)(A) 

and (B) 

 The TWG stated that the Supplemental Proposal specified a 

short‐term NOX limit of 0.07 lb/MMBtu for TWG Alternative A, but 

not for Alternative B as was included in the TWG Agreement. 

Response: 
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EPA agrees that if the owners of NGS elect to install SCR 

in order to comply with the applicable NOX Caps under TWG 

Alternative B, then it is useful to specify the emission limit 

that would apply. Although the limit of 0.07 lb/MMBtu (on a 

rolling average basis of 30 boiler operating days) would apply 

under TWG Alternatives A1, A2, A3, or B, EPA notes that the 

operator of NGS may need to operate SCR at an emission rate that 

is lower than 0.07 lb/MMBtu depending on their compliance with 

the NOX Cap, but the addition of this provision would prohibit 

emissions of NOX, when operating with SCR, to exceed 0.07 

lb/MMBtu (on a rolling average basis of 30 boiler operating 

days). EPA will amend the regulatory text accordingly.

Comment: Omitted ownership outcome 

 The TWG stated that the EPA described the NGS ownership 

outcomes in a manner that is different from the scenarios 

outlined in the TWG Agreement. The commenter indicated that the 

ownership outcomes appear to be consistent, except that one 

potential outcome was omitted – the scenario in which one or 

more of the existing NGS Participants (LADWP or NV Energy) 

remain in NGS, which would trigger Alternative B. 

Response: 

 EPA agrees that we inadvertently omitted from 

§49.5513(j)(3)(ii)(D) the potential scenario where one or both 

of the Departing Participants (i.e., LADWP or NV Energy) do not 
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exit NGS as expected. EPA is updating the language to 

incorporate the omitted ownership possibility. 

Comment: Describe details of TWG Agreement more fully in the 

preamble to the Final Rule 

The TWG expressed concern that EPA only briefly described 

the elements of the TWG Agreement in the Supplemental Proposal. 

One member of the TWG asserted that the limited discussion does 

not accurately present the provisions of the Agreement as it 

relates to clean energy economic development for affected 

Tribes, the rigorous development and consideration of clean 

energy alternatives to NGS, mitigation of CO2 emissions, and 

Local Benefit Fund to address concerns of the public in the 

vicinity of NGS and the Kayenta-Black Mesa Mine Complex. Should 

EPA proceed with this alternative in the Final Rule, the 

commenter requested that the Agency fully describe the key 

elements in the preamble to the Final Rule. 

Response:

EPA acknowledges that the TWG Agreement contains additional 

provisions that will be beneficial to the tribes in the area and 

to the environment. However, EPA does not consider it 

appropriate to provide a detailed discussion of these additional 

provisions of the TWG Agreement in our Final Rule. EPA was not a 

signatory to the TWG Agreement and did not participate in the 

TWG Stakeholder group. The TWG Agreement speaks for itself and 
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the participants and signatories are the appropriate entities to 

interpret the provisions of the TWG Agreement. EPA is finding 

that it is necessary or appropriate to regulate NOX emissions 

from NGS to reduce visibility impairment at the GCNP and 10 

other Class I areas. The other measures described by the 

commenter are outside the scope of our authority for this 

action. Therefore, EPA is declining to provide any further 

discussion of the provisions in the TWG Agreement that go beyond 

addressing regional haze concerns associated with NOx emissions 

from NGS. 

The comment also requests EPA to add certain language 

to the Final Rule. Specifically, the comment asks EPA to 

add: “Nothing in this final rule shall preclude the NGS 

Participants from seeking to obtain greenhouse gas emission 

reduction credits, or similar commodities associated with 

activities committed to in the TWG Agreement, under any 

Federal or State law or policy to the extent permitted 

under such applicable law or policy.” 

EPA is also declining to add the requested language to 

our Final Rule. EPA is not exercising any authority in this 

action other than implementing the BART provisions in CAA 

section 169A and the RHR, through our discretion in the 

TAR. It would be inappropriate in this action to take any 
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position on the future use or regulation of GHG emission 

reductions or “similar commodities.” 

Comment: TWG Alternative meets Reasonable Progress requirements 

 One member of the TWG stated that the TWG Alternative was 

intended to meet not only BART requirements, but also reasonable 

progress requirements applicable to NGS through 2044. The 

commenter requested that EPA acknowledge, in the preamble to the 

Final Rule, that the TWG Alternative satisfies both the BART and 

reasonable progress requirements of the CAA through 2044. 

Response: 

Today’s final rule addresses the NOX BART requirements of 

the RHR for NGS. We have not considered whether the TWG 

Alternative meets the reasonable progress requirements for NGS. 

We note that EPA has not made any finding pursuant to 40 CFR 

49.11(a) that it is necessary or appropriate at this time to 

promulgate a FIP to meet the reasonable progress or other 

requirements under the RHR. The requirement for states to 

develop reasonable progress goals and long-term strategies to 

achieve those goals is set out in CAA section 169A and 40 CFR 

51.308(d). There is no requirement that EPA address these 

requirements for sources on the Navajo Nation unless EPA makes a 

determination that it is necessary or appropriate for EPA to do 

so. 

Comment: Delete requirement to keep records of maintenance 
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 One member of the TWG requested that EPA delete the 

requirement that the NGS operator keep records of all major 

maintenance activities that occur at NGS. According to the 

commenter, the existing title V permit, which requires that the 

operator maintain and operate emission control equipment in a 

manner that is consistent with good engineering practices to 

keep emissions at or below applicable emissions limitations, 

provides sufficient assurance that emission control equipment 

will be operated and maintained in accordance with best 

practices. 

Response: 

 EPA is deleting the requirement proposed under 

§49.5513(j)(7)(vi) to require the operator of NGS to keep 

records of all major maintenance activities at NGS because 

records of major maintenance activities are not needed for 

demonstrating compliance with the 2009-2044 or 2009-2029 NOX Caps 

or other provisions of the TWG Alternative. 
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Comment: Require recordkeeping for the life of the plant 

One commenter indicated that the requirement to maintain 

records for 5 years is insufficient and inappropriate for the 

compliance schedule associated with NGS and recommended that 

records be maintained from 2009 through the remaining operating 

life of the plant. 

Response: 

 EPA agrees that because the operator of NGS must ensure 

compliance with the 2009-2044 NOX Cap, the operator of NGS should 

also maintain records for the life of the facility to 

demonstrate compliance with the TWG Alternative. In the 

regulatory language in our Final Rule, EPA is amending 

§49.5513(j)(7) to require the owner or operator of each unit to 

maintain records, as required under §49.5513(j)(7)(i) to (vi), 

until the earlier of December 22, 2044 or the date that the 

owner/operator ceases conventional coal-fired operation at NGS. 

Comment: Concern that affected parties were excluded from TWG

 Numerous commenters expressed frustration that all affected 

parties were not included in the development of the TWG 

Alternative. The Hopi Tribe noted that they have a Generating 

Performance Agreement with SRP that should have mandated their 

involvement. The White Mountain Apache Tribe also noted that it 

was not party to the TWG Agreement. Another commenter noted that 

Executive Order (EO) 13175 requires that all tribal nations be 
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consulted on these types of regulations, and asserted that EPA 

and DOI violated this EO. Another commenter argued that the TWG 

did not include grassroots organizations and discouraged their 

participation in TWG public forums. 

 One commenter stated that the EPA did not give the public 

enough time to comment on the TWG Alternative before proposing 

approval of it and, on that basis, demanded that the EPA 

withdraw its proposed approval. The commenter added that the TWG 

Agreement assumes that the Hopi will support the Kayenta Mine 

Lease extension when it expires in 2025, but the Hopi have yet 

to discuss the extension with the 12 Hopi independent villages, 

which is a requirement in the Hopi Constitution. Furthermore, 

the commenter noted that the TWG Agreement ignores the 

requirement of completing an EIS and ROD before the NGS site 

lease with the Navajo Nation expires in 2019. The commenter 

argued that DOI’s signing of the TWG Agreement, without the 

fulfillment of these requirements, violates NEPA. The commenter 

added that in 1989, the Hopi Tribe rejected the Draft Kayenta 

Mine-Black Mesa Mine EIS in its entirety, and implied that the 

decision to accept the TWG proposal could compromise EPA’s final 

decision. 

Response:

 EPA recognizes that there are affected tribes and other 

stakeholders that were not invited to participate in the 
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Technical Work Group. EPA was not involved in the formation of 

the TWG and not involved in any meetings or discussions of the 

TWG.141 As discussed in section 10.0 of the Response to Comments 

document, consistent with Executive Order 13175: Consultation 

and Coordination with Indian Tribal Governments, EPA consulted 

with tribes early and regularly during the development of this 

rulemaking for NGS. We note that the Regional Administrator for 

Region 9 spoke with Chairman of the Hopi Tribe, LeRoy 

Shingoitewa, on September 13, 2013 about the TWG Alternative and 

notified elected leaders or legal counsel for five tribes when 

EPA signed the Supplemental Proposal. EPA also held individual 

and joint consultation meetings with tribal leaders in Phoenix, 

Arizona on December 9 and 10, 2013. 

EPA disagrees that we did not provide the public enough 

time to review the TWG Alternative. EPA posted the TWG 

Alternative to the public docket on July 26, 2013, the same day 

it was submitted to EPA.142 EPA reviewed the TWG Alternative and 

on September 25, 2013, signed a Supplemental Proposal that put 

forth the TWG Alternative as an additional better than BART 

alternative for public comment. On October 22, 2013, the 

141 At the request of the TWG, at their kick-off meeting, EPA presented a 

summary of our Proposed Rule and framework for BART Alternatives. The 

presentation at the TWG kick-off meeting was generally the same presentation 

EPA provided to other stakeholders. See document 0033 in the docket for the 

rule. 

142 See document number 0122 in the docket for this rule. 
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Supplemental Proposal was published in the Federal Register.143

The public had nearly six months to review the TWG Agreement and 

Alternative as submitted to EPA and approximately three months 

to review and comment on EPA’s Supplemental Proposal. EPA also 

notes that EPA’s rulemaking is not subject to NEPA. 

Comment: EPA’s relationship to the TWG is confusing 

 The White Mountain Apache Tribe stated that although EPA 

stated it was not involved in the Technical Work Group, EPA was 

a signatory of the “Joint Federal Agency Statement Regarding 

Navajo Generating Station,” the scope of which includes numerous 

elements that reference EPA’s commitments, along with the 

Departments of the Interior and Energy, in relation to NGS. The 

commenter suggests that EPA was involved in a legal 

triangulation with the TWG signatories and that such action is 

an extra-jurisdictional exercise by EPA, to which the Tribe does 

not consent. The commenter concludes that the Tribe cannot 

consider the TWG Alternative unless its published form is 

changed by EPA to fully disentangle the proposal from the 

signatory group and all non-BART Agreement terms, and additional 

public comment is thereafter allowed. 

Response:

143 See document number 0182 and 0186 in the docket for this rule. 
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We disagree that the Joint Federal Agency Statement 

Regarding Navajo Generating Station indicates that EPA was 

involved in the TWG. The Joint Federal Agency Statement was 

signed by the Administrator of EPA and the Secretaries of the 

Interior and Energy on January 4, 2013. Among other things, that 

document acknowledged that each of the three federal agencies 

has an interest in the operation of NGS and set forth the goals 

of the agencies with respect to NGS and energy production in the 

region served by NGS. 

Although EPA clearly has an interest in reducing the 

visibility impacts of NGS, EPA was not part of the TWG. EPA did 

not participate in any of the substantive discussions and 

negotiations of the TWG. Two representatives of EPA attended the 

beginning of the first meeting of the TWG but only to present a 

summary of EPA’s February 5, 2013 Proposed Rule.144 After the 

initial meeting, EPA was not involved with the TWG until the TWG 

Agreement was completed. As such, EPA disagrees with the 

commenter that EPA is “entangled” with the TWG. 

The TWG was not primarily composed of federal agencies. The 

TWG had two Tribes (Gila River Indian Community and the Navajo 

144 At the request of the TWG, at their kick-off meeting, EPA presented a 

summary of our Proposed Rule and framework for BART Alternatives. The 

presentation at the TWG kick-off meeting was generally the same presentation 

EPA provided to other stakeholders. See document 0033 in the docket for the 

rule. 
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Nation), two environmental organizations (Environmental Defense 

Fund and Western Resource Advocates), two Arizona utilities 

(CAWCD and SRP) and DOI. Appendix B of the TWG Agreement 

contains provisions relating to BART but there were several 

other provisions of the TWG Agreement that are beyond the scope 

of BART and are not part of EPA’s rulemaking in this action.For 

all the above reasons, EPA does not agree with the assumption 

underlying the comment that the White Mountain Apache Tribe 

“cannot consider the TWG Alternative unless its published form 

is changed by EPA to fully disentangle the proposal from the 

signatory group and all non-BART Agreement terms.” EPA does not 

agree that any further public comment is warranted. 

K. Other BART Alternatives 

Comment: Suggested BART Alternative to require earlier emission 

reductions 

 Despite its objections to the proposed BART alternatives, 

an environmental organization representing several environmental 

and Navajo non-governmental groups suggested an alternative that 

includes (1) an enforceable requirement that one NGS unit shut 

down by 2020 and (2) an enforceable requirement that the 

remaining two units install SCR and meet a NOx emission limit of 

0.065 lb/MMBtu by the beginning of 2020. The commenter 

recognized that other alternatives may exist, but asserted that 

for any alternative to comply with the minimum legal 
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requirements, it must produce better visibility outcomes in 

Class I areas than BART and demonstrate that it does so through 

the use of visibility modeling. 

Response:

Neither the BART requirements nor the provisions in the RHR 

governing alternatives to BART requires that BART sources cease 

operation. As such, EPA does not consider it appropriate for the 

Agency to require the shutdown of one unit of NGS by 2020 absent 

the consent of the owners. Regardless of whether the suggested 

alternative would provide for earlier and greater visibility 

improvement, it is not an option at this time. As explained in 

this rulemaking, the TWG Alternative does comply with the legal 

requirements for BART alternatives. 

Comment: Suggested BART Alternative from CAP NIA Users: New 

controls should not be required until after 2030

 One commenter presented a table purporting to show EPA’s 

calculations of the NOX caps that would apply for a range of 

potential BART emission limits: 0.055, 0.06, 0.07, and 0.15 

lb/MMBtu. According to the commenter, the NOX cap that would 

apply under limits of 0.06 and 0.07 lb/MMBtu would exceed the 

proposed 2009-2044 NOX CAP by 2.5 and 7.5 percent, respectively. 

The commenter asserted that these differences would have 

imperceptible impacts on visibility and that, therefore, the use 

of the NOX cap based on a limit of 0.055 lb/MMBtu unduly 
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constrained TWG Alternative A and resulted in an unwarranted 

requirement to install SCR on two NGS units by 2030, which would 

impose inequitable compliance costs on agricultural water users. 

The commenter stated that a NOX cap based on a BART limit of 0.06 

or 0.07 lb/MMBtu would be very similar to the proposed 2009-2044 

NOX Cap, but would provide enough of an incremental increase to 

add 3 years of additional compliance flexibility for the 

installation of SCR on two units. 

 The same commenter also stated that based on the 2009-2044 

NOX Cap as proposed in the Supplemental Proposal, TWG Alternative 

A contains unused “headroom” that renders the operation of SCR 

by 2030 unnecessary. According to the commenter, TWG Alternative 

A has the effect of forcing NOX emissions to a level that is at 

least 33,000 tons below the NOX cap, which the commenter believes 

makes the requirement to install and operate SCR by 2030 

artificially stringent and unnecessary, and therefore arbitrary 

and capricious. The commenter indicated that the headroom under 

TWG Alternative A1 would yield more than 6 years of additional 

compliance flexibility for the operation of SCR, and TWG 

Alternatives A2 and A3 would yield more than 3 years. The 

commenter concluded that EPA should revise the TWG Alternatives 

to provide the maximum amount of compliance flexibility for 

installation of SCR on NGS so as to not unnecessarily impose 

costs on NIA water users. 
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Response:

 EPA disagrees with the assertion that new controls should 

not be required until after 2030. As stated previously, the TWG 

Agreement was a negotiated agreement, submitted to EPA, 

representing diverse interests. EPA evaluated the TWG 

Alternative to determine whether it was consistent with our 

framework for better than BART alternatives. Thus, although a 

few commenters may believe that the timeframes for compliance in 

the TWG Alternative are too stringent, the TWG Alternative is 

consistent with our proposed framework and it is consistent with 

the level of control in Appendix B to the TWG Agreement, which 

the operator and owners of NGS, as well as CAP, two tribes and 

two environmental organizations, have determined is acceptable. 

 As stated elsewhere in the RTC, we disagree with the 

assertion that BART for NGS is an emission limit associated with 

SNCR (0.15 lb/MMBtu) or a less stringent limit associated with 

SCR (0.06 or 0.07 lb/MMBtu). Therefore, the additional time for 

compliance suggested by the commenters using higher BART 

Benchmarks or NOX Caps is not appropriate. The commenters further 

assert that NGS could comply with a limit of 0.07 lb/MMBtu in 

2032 and 2033 and still maintain total emissions below the 2009-

2044 NOX Cap. EPA disagrees with commenters that the “unused 

headroom” warrants additional time to comply with the limit of 

0.07 lb/MMBtu. The emission estimates that EPA presented in our 
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Supplemental Proposal for the TWG Alternative involved 

projecting future emissions to 2044 based on average heat input 

at NGS over 2001-2008. Heat input in the future is expected to 

be variable and could possibly remain higher than average over 

an extended period of time, significantly affecting the total 

flexibility or compliance margin. EPA’s analysis was provided 

simply to assess whether operation consistent with the 

requirements under each TWG Alternative (A1-A3) could reasonably 

be determined to maintain emissions below the 2009-2044 NOX Cap 

and were not intended to represent actual year-by-year emissions 

in the future. Thus, the “unused headroom” is theoretical and 

could be smaller or larger than cited by the commenters. 

L. Other Comments 

Comment: Disproportionate impacts to tribes 

The Tonto Apache Tribe and the San Carlos Apache Tribe 

commented that both the original BART proposal and the proposed 

TWG Alternative are contrary to the obligations of the United 

States and its trust responsibilities to Indian Tribes under 

CAP. The commenters stated that both regulatory programs would 

have disproportionate impacts on tribes with CAP contracts. The 

commenters noted that environmental quality is of utmost 

importance to the tribes, but that clean air is the 

responsibility of all citizens. Therefore, the commenters assert 

that because the United States owns 24.3 percent of NGS, the 
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costs of compliance for that 24.3 percent share should be shared 

among all American people, who will benefit from cleaner air. 

The commenters urged EPA to develop an alternative regulation 

that does not place additional burden on Indian Tribes. 

Response: 

 EPA agrees that our proposed BART determination and the TWG 

Alternative will impact tribes with CAP water contracts. We note 

that the Joint Federal Agency Statement on NGS reflects the U.S. 

Government’s recognition of its responsibilities related to NGS 

and trust responsibility to Indian tribes affected by NGS. 

Although EPA is finalizing a BART Benchmark for NGS, the 

regulatory requirements of this Final Rule will include only the 

requirements and compliance timeframes for the TWG Alternative 

as proposed in our Supplemental Proposal. Under the TWG 

Alternative, emission reductions at NGS would be achieved in 

phases, including closure of one unit or the equivalent in 2019, 

and compliance with an emission limit achievable with SCR in 

2030. We note that the closure of one unit was possible because 

of the planned divestment of LADWP and NV Energy from NGS by 

2019. Because LADWP and NV Energy are unrelated to CAP, EPA does 

not expect substantial compliance costs to be borne by 

Reclamation (and thus, tribes or other CAP water users) due to 

the first phase of emission reductions at NGS in 2019. EPA 

further notes that the 2030 compliance date for meeting an 
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emission limit achievable with SCR on two units at NGS is 

approximately 16 years from the present day. As stated elsewhere 

in the RTC, the requirements under BART and the TWG Alternative 

include emission limits, rather than technology requirements. 

Thus, 16 years from now, although SCR will be capable of meeting 

the emission limit, other technologies or options may become 

available for the operator of NGS to more cost-effectively meet 

the NOX emission limit of 0.07 lb/MMBtu. 

EPA recognized the potential impacts to tribes of our 

proposed BART determination and sought ways to provide 

flexibility and a framework for affected stakeholders to develop 

alternative approaches to BART. EPA has determined that the TWG 

Alternative achieves greater emission reductions than would 

otherwise be achieved under our BART determination, while 

providing additional time for compliance. This additional time 

allows the DOI, DOE, and EPA time to work with tribal 

stakeholders to identify and implement strategies for achieving 

the goals outlined in the Joint Federal Agency Statement on NGS. 

Comment: EPA lacks authority to regulate NGS

 Several commenters indicated that EPA overstepped its 

authority and stated that EPA’s proposal hinders the state’s 

ability to deal with environmental issues on a local level. One 

commenter stated that EPA’s regulations are an attack on free 

enterprise, and believes that the agenda of the current 
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administration is to ban all coal-fired power plants regardless 

of the economic effect. 

Response: 

EPA disagrees that it has overstepped its regulatory 

authority and disagrees that any State has authority to regulate 

air pollution from sources located on the Navajo reservation. 

EPA’s authority to regulate NGS is established in sections 

301(a) and 301(d)(4) of the CAA and the TAR. Section 301(d)(4) 

authorizes EPA to directly administer provisions of the CAA in 

Indian country under certain circumstances. The State of Arizona 

lacks authority to regulate air pollution sources located on the 

Navajo reservation. 

EPA disagrees that the regulations promulgated in this 

action, which are requirements consistent with the TWG 

Agreement, constitutes an attack on free enterprise. EPA 

developed the framework used by the TWG specifically to allow 

stakeholders, including the business enterprises most directly 

affected, to formulate an alternative that they believed would 

better serve their interests in continued operation, employment, 

and environmental quality. The TWG Alternative was submitted to 

EPA by a stakeholder group that had determined it was a more 

cost-effective approach to continuing to operate NGS than a 

prior proposal by EPA. EPA considered the direct costs of 

compliance in our five-factor BART analysis, and although not 
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specifically required in the BART Guidelines, EPA also 

considered numerous indirect impacts and costs in our analysis 

of Factor 2. The comment provides no information other than 

conclusory statements that EPA failed to adequately consider the 

cost of compliance. Far from banning coal burning, this rule 

allows continued operation of NGS as a conventional coal-fired 

power plant until 2044, when its lease with the Navajo Nation 

expires. 

Comment: Lack of Consultation with Tribes 

The Navajo Nation commented that EPA should improve 

communication at the start of any rulemakings to ensure that the 

Navajo Nation can provide meaningful information. The commenter 

said that even when the Agency develops supporting rule 

information like the RIA the Navajo Nation would like to be 

involved as it could impact the Nation. The commenter pointed 

out that EPA has known for decades that the Navajo Nation would 

be impacted by regulation of NGS and FCPP. The commenter quoted 

excerpts from Executive Order 13175 - Consultation and 

Coordination with Indian Tribal Governments and said that the 

standard for determining if a regulation has tribal implication 

is not whether it “impose[s] substantial direct compliance costs 

on tribal governments,” but rather a regulation has “substantial 

direct effects on one or more Indian tribes.” 
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The Navajo Nation stated that it was not consulted during 

the development of the ANPR and indicated that in August of 

2009, one day prior to the ANPR for NGS and FCPP, EPA made a 

courtesy call to the President of the Navajo Nation. The Navajo 

Nation believes that if early and meaningful consultation with 

the Nation had occurred this could have led to an adequate 

analysis of BART controls and careful examination of non-air 

quality impacts. 

The Gila River Indian Community expressed similar concerns 

regarding the lack of consultation. During a consultation on 

August 7, 2012, the commenter stated that it was their 

understanding that EPA would describe to the Community the 

proposed regulation prior to the rulemaking being issued. 

Instead, the commenter said, EPA called the night before issuing 

the rule, which the commenter said was inadequate and 

inconsistent with the expectations regarding consultation. The 

commenter also understood that the rule was to be proposed in 

September 2012 but it was not proposed until January 2013 and in 

the meantime several stakeholders provided additional input to 

the Agency. However, the Community was not consulted during this 

time. In addition, the Community expects an explanation of the 

final rule after it is issued by EPA. 

 The Hopi Tribe also commented on the lack of consultation 

and involvement of tribes in developing the regulation. The 
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commenter submitted multiple letters to EPA indicating its 

concern about not being involved in the development of the rule 

or consulted but without providing pertinent information. In one 

of the letters, the commenter said that the government 

acknowledged the Hopi Tribe as a stakeholder and the intention 

to work with the Tribe; however, contrary to statements in the 

Joint Federal Agency Statement on NGS to work with tribes, the 

Hopi Tribe was not included in the TWG. 

 The Hopi Tribe specifically indicated that it was denied 

information regarding the TWG Alternative and the development of 

the alternative, something the commenter pointed out is 

essential in order to provide relevant and useful comments to 

EPA. The commenter said that it has submitted two Freedom of 

Information Act (FOIA) requests to DOI, which included 

documentation related to NGS and information documenting DOI’s 

representation of the Hopi Tribe during the negotiation of the 

TWG Alternative. The commenter said that until it has the 

information requested via FOIA, it is not able to provide 

written comments on the TWG Alternative. 

The Hopi Tribe asserted that it is has been treated 

differently than other tribal stakeholders in the TWG Agreement. 

For example, the TWG Agreement states that SRP will advocate to 

EPA the Navajo Nation’s treatment as state (TAS) status. The 

Hopi Tribe indicated that the TWG Alternative protects the 
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economic interests of the Navajo Nation and the Gila Indian 

Community but compromises the coal revenues of the Hopi Tribe 

and contains no mitigation measures for the significant and 

adverse economic impact. The Hopi Tribe indicated that it will 

be disproportionately and adversely affected by the reduced 

capacity at NGS. 

The Kaibab Band of Paiute Indians expressed similar 

concerns regarding the lack of involvement of Indian Tribes and 

demanded that EPA consider the requests of the Kaibab Paiute. 

The commenter referred to the TWG Agreement and requested that 

the Kaibab Paiute Indian Reservation receive $2.5 million of the 

$5 million Local Benefit Fund designated for community projects 

within 100 miles of NGS (the reservation is 60 miles from NGS). 

Also, the commenter said that the TWG Agreement promotes the 

development of clean energy, and based on that provision of the 

agreement, the commenter requested a 250 MW solar farm. 

The Tohono O’odham Nation objected that a number of Indian 

nations that would be substantially affected by the rule were 

excluded from the TWG. The commenter noted that it is 

particularly concerned with maintaining CAP water delivery under 

whatever rule is finalized by EPA. 

Response:

EPA understands that NGS is important to numerous tribes 

located in Arizona and we take seriously our trust 
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responsibility to Indian tribes affected by NGS. As a result, we 

have attempted to ensure that these tribes were consulted 

throughout the rulemaking process. We respectfully disagree that 

there was a lack of consultation with tribes. 

EPA agrees with the Navajo Nation that Executive Order 

13175 defines “policies that have tribal implications” to refer 

to regulations or other actions that have substantial direct 

effects on one or more Indian tribes.145 In our discussion of EO 

13175, we included consideration of substantial direct 

compliance costs to tribal governments, as well as the broader 

consideration of substantial direct effects on one or more 

Indian tribes. We conclude that our proposed action on NGS will

have tribal implications and may have substantial indirect 

effects on tribes, but will not impose substantial direct 

compliance costs on Indian tribal governments. We also conclude 

that this rule is appropriate under the CAA because NGS is a 

facility that is subject to BART. 

 In our proposed rule, EPA provided a document that listed 

all written or telephone correspondence as well as consultation 

meetings between EPA and Tribes on NGS. Although the commenter 

suggests that EPA’s telephone call to the President of the 

145 http://www.gpo.gov/fdsys/pkg/WCPD-2000-11-13/pdf/WCPD-2000-11-13-Pg2806-

2.pdf 
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Navajo Nation one day prior to the signature of the ANPR in 

August 2009 was our first communication with the Nation on the 

subject, we note that the timeline includes a meeting between 

EPA and the Navajo Nation that occurred two months prior to the 

ANPR to discuss EPA’s plans to move forward on an ANPR related 

to our ongoing BART analyses for FCPP and NGS.146 EPA further 

notes that the ANPR was not a proposed rule. The ANPR was an 

Advanced Notice of Proposed Rulemaking where we provided the 

public advance notice of our intention to develop rulemakings 

for FCPP and NGS. EPA included some initial analysis of two of 

the BART factors and stated that the “specific purpose of this 

ANPR is for EPA to collect additional information.”147 Subsequent 

to the publication of the ANPR in the Federal Register on August 

28, 2009, and prior to our proposed rule on NGS, EPA held four 

consultation meetings with tribes in 2009, eight consultation 

meetings with tribes in 2010, eight consultation meetings in 

2011, and ten consultation meetings with tribes in 2012.148 Of 

146 See listed item indicating consultation meeting on June 10, 2009 between 

Laura Yoshii, Acting Regional Administrator of EPA Region 9, and President 

Joe Shirley, Jr., of the Navajo Nation, to discuss moving forward on the ANPR 

for Four Corners Power Plant and NGS. See document titled “2013_0109 Timeline 

of all tribal consultations on NGS.docx” in document number 0005 in the 

docket for this rule. 

147 See 74 FR 44313 at 44314 (August 28, 2009). 148 See document titled “2013_0109 Timeline of all tribal consultation on 

NGS.pdf” in document number 0005 in the docket for the rule at and document 

titled “Updated Timeline of all Tribal Consultation on NGS_for Final 

Rule.pdf” in the docket for the rule. 
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these meetings, at least eight were held as group consultation 

sessions where all tribes in Arizona were invited to participate 

and were provided the opportunity to request individual 

consultation meetings as well.149

The Navajo Nation, the Hopi Tribe, the Gila River Indian 

Community, the Tohono O’odham Nation, the Ak-Chin Indian 

Community, the Pascua Yaqui Tribe, the Fort McDowell Yavapai 

Nation, and the Yavapai-Apache Nation, and the Inter Tribal 

Council of Arizona submitted comments to EPA on the ANPR. EPA 

summarized and provided responses to comments received from 

tribal governments in the TSD for our proposed rule on NGS.150

The primary concerns expressed by the tribal governments related 

to the economic importance of NGS and the relationship of NGS 

with CAP and Indian Water Settlement Agreements. The Navajo 

Nation also commented on specific aspects of the five-factor 

analysis for BART, and the Hopi Tribe submitted an economic 

study it had commissioned that expresses concern that regulatory 

actions would force NGS to close. In our proposed rule and in 

our development of our proposed framework for BART Alternatives, 

including the credit for early installation of LNB/SOFA, EPA 

recognized the importance of NGS to tribes in Arizona, both in 

149 Id., and see, e.g., document 0008 in the docket for the rule 150 See page 25 and 26 of the TSD to the Proposed Rule, document 0014 in the 

docket for this rule. 
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contributing to the economies of the Navajo Nation and Hopi 

Tribe, and in serving as a source of electrical power for CAP 

and a source of revenue to the Lower Colorado River Basin 

Development Fund, as related to water settlement agreements with 

numerous tribes in Arizona. Based on this recognition, EPA put 

forth additional options for greater flexibility in the 

compliance timeframe and invited stakeholders to develop and 

submit additional BART Alternatives to EPA for consideration. 

Following the publication of our proposed rule on February 

5, 2013, EPA engaged in 17 consultation meetings with tribes 

prior to the January 2014 close of the public comment period.151

Of these meetings, at least two were held as group consultation 

sessions where all tribes in Arizona were invited to participate 

and were provided the opportunity to request individual 

consultation meetings as well.152 EPA received comment letters on 

our proposal and Supplemental Proposal from the Navajo Nation, 

the Gila River Indian Community, the Tohono O’odham Nation, the 

Ak-Chin Indian Community, the Tonto Apache Tribe, the San Carlos 

Apache Tribe, and the Kaibab Band of Paiute Indians.153 At the 

request of two tribes for additional time beyond January 6, 2014 

151 See document titled “Updated Timeline of all Tribal Consultation on NGS_for 

Final Rule.pdf” in the docket for the rule. 

152 Id. 153 See comment numbers 0340, 0317, 0387, 0402, 0419, and 0421 in the docket 

for the rule. 
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to submit comments, EPA agreed that we would consider comments 

from tribal governments submitted after the close of the comment 

period. The White Mountain Apache Tribe submitted comments on 

February 5, 2014.154 In addition, in response to their request to 

EPA for information related to NGS, we provided responsive 

documents to the Hopi Tribe on January 7, 2014.155 As shown in 

additional correspondence, the Hopi Tribe requested additional 

time to submit comments, and EPA again agreed to consider late 

comments from the Hopi Tribe.156 EPA did not receive any further 

comments from the Hopi Tribe. 

Several tribes also expressed concern that the Technical 

Work Group included only two tribes, the Navajo Nation and the 

Gila River Indian Community, and excluded numerous other tribes 

that also have a significant economic interest in NGS. EPA 

recognizes that many tribes were not included in the development 

of the TWG Agreement. EPA was not involved in the formation of 

the TWG or any of the negotiations between the members of the 

TWG in developing the TWG Agreement. In addition, our evaluation 

of the TWG Agreement was for the sole purpose of determining 

whether Appendix B to the TWG Agreement meets our framework for 

154 See comment number 0440 in the docket for the rule. 155 See document titled “2014_0107 EPA Letter to Chairman Honanie with 

Enclosure 1.pdf” in the docket for this rule. 

156 See document titled “2014_0131 Letter from Chairman Honanie.pdf” and 

document titled “2014_0206 EPA Response to Chairman Honanie_Hopi Tribe.pdf” 

in the docket for this rule. 
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a “better than BART” Alternative. Therefore, although EPA agrees 

that many tribes have economic interest in NGS and CAP, EPA does 

not have any role in the distribution of funds described in the 

TWG Agreement. 

Based on numerous consultation meetings between high-level 

officials from EPA and elected tribal leaders, beginning in 2009 

and extending into 2013, and our development of flexible options 

for BART Alternatives in response to comments from tribes, EPA 

considers our consultation on NGS to be consistent with EO 13175 

and EPA’s policy to engage in early and meaningful consultation 

with tribes.157 EPA will provide notification of our Final Rule, 

in writing, to all tribal governments that submitted comments to 

EPA on our Proposed Rule or Supplemental Proposal and will 

provide our written responses to their specific comments. All 

written correspondence from tribal governments to EPA regarding 

NGS and our proposed BART determination is available in the 

docket for this rulemaking.158

V. Summary of Final Action

 On February 5, 2013, EPA issued a proposed BART analysis of 

NOX controls at NGS. Based on that analysis, EPA proposed a NOX

157 The EPA policy on Consultation and Coordination with Indian Tribes is 

posted on the following website: 

http://www.epa.gov/tribal/consultation/consult-policy.htm 

158 See Appendix A (List of Written Comments) to the RTC and the docket for 

this rulemaking. 
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emission limit of 0.055 lb/MMBtu for all three units within five 

years of a Final Rule. Our proposed rule also set out a 

framework for evaluating BART alternatives at NGS. EPA proposed 

a “better than BART” alternative (Alternative 1), consistent 

with this proposed framework, requiring compliance with a NOX

emission limit of 0.055 lb/MMBtu on one unit per year in 2021, 

2022, and 2023. EPA invited stakeholders to submit additional 

alternatives, consistent with our proposed framework for “better 

than BART” alternatives, to EPA for consideration. 

On July 26, 2013, a stakeholder group, known as the TWG, 

submitted an agreement among seven diverse entities (TWG 

Agreement) that included an additional BART alternative 

(Appendix B to the TWG Agreement). In general, this alternative 

includes closure of one unit at NGS, or curtailment of net 

generating capacity by an equivalent amount, in 2019 and 

compliance with an emission limit of 0.07 lb/MMBtu on two units 

at NGS in 2030. The TWG Agreement also included a provision 

requiring the owner/operator of NGS to cease conventional coalfired generation at NGS by the end of 2044. EPA independently 

evaluated Appendix B to the TWG Agreement to determine whether 

it complied with the framework we put forth in our Proposed 

Rule, as well as the statutory and regulatory requirements in 

the CAA and the RHR. 
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On October 22, 2013, EPA published a Supplemental Proposal. 

Our Supplemental Proposal contained a detailed evaluation of 

Appendix B to the TWG Agreement along with a discussion of our 

legal rationale for proposing to approve requirements consistent 

with the TWG Agreement as a “better than BART” alternative. Our 

Supplemental Proposal and this Final Rule refer to our 

regulations that are generally consistent with Appendix B to the 

TWG Agreement as the ”TWG Alternative”. The Supplemental 

Proposal (i.e. the TWG Alternative) included regulatory 

requirements to achieve substantial NOX reductions over time, as 

well as a cap in cumulative NOX emissions from NGS over 2009-2044 

(2009-2044 NOX Cap) to ensure that lifetime emissions from NGS 

under the TWG Alternative do not exceed lifetime emissions that 

would have otherwise occurred under our proposed BART 

determination for NGS (BART Benchmark). 

Based on our review of all comments we received on the 

Proposed Rule and Supplemental Proposal, EPA is taking action to 

finalize requirements consistent with the TWG Agreement, as a 

“better than BART” Alternative (TWG Alternative) put forth in 

our Supplemental Proposal. EPA is also taking final action to 

determine that a BART Benchmark, consistent with our proposed 

BART determination, is appropriate for establishing the 2009-

2044 NOX Cap under the TWG Alternative. EPA is not finalizing our 

proposed BART determination for NGS in the regulatory 
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requirements of this Final Rule, and EPA is not taking action to 

finalize Alternative 1, the “better than BART” Alternative we 

put forth in our Proposed Rule. 

This Final Action is expected to result in over an 80 

percent reduction in NOX emissions and to significantly reduce 

the impact of NGS on visibility at 11 mandatory Class I Federal 

areas. EPA’s action to finalize requirements consistent with the 

TWG Agreement as a “better than BART” alternative for NGS will 

ensure that lifetime NOX emissions from NGS do not exceed the 

BART Benchmark. 

VI. Administrative Requirements 

A. Executive Order 12866: Regulatory Planning and Review and 

Executive Order 13563: Improving Regulation and Regulatory 

Review 

This action will finalize a source-specific FIP for a 

single generating source. This type of action is exempt from 

review under Executive Orders 12866 (58 FR 51735, October 4, 

1993) and 13563 (76 FR 3821, January 21, 2011). 

B. Paperwork Reduction Act 

This action does not impose an information collection 

burden under the provisions of the Paperwork Reduction Act, 44 

U.S.C. 3501 et seq. Under the Paperwork Reduction Act, a 

“collection of information” is defined as a requirement for 

“answers to . . . identical reporting or recordkeeping 
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requirements imposed on ten or more persons . . . .” 44 U.S.C. 

3502(3)(A). Because the final FIP applies to a single facility, 

Navajo Generating Station, the Paperwork Reduction Act does not 

apply. See 5 CFR 1320(c). 

Burden means the total time, effort, or financial resources 

expended by persons to generate, maintain, retain, or disclose 

or provide information to or for a Federal agency. This includes 

the time needed to review instructions; develop, acquire, 

install, and utilize technology and systems for the purposes of 

collecting, validating, and verifying information, processing 

and maintaining information, and disclosing and providing 

information; adjust the existing ways to comply with any 

previously applicable instructions and requirements; train 

personnel to be able to respond to a collection of information; 

search data sources; complete and review the collection of 

information; and transmit or otherwise disclose the information. 

An agency may not conduct or sponsor, and a person is not 

required to respond to a collection of information unless it 

displays a currently valid OMB control number. The OMB control 

numbers for EPA's regulations in 40 CFR are listed in 40 CFR 

Part 9. 

C. Regulatory Flexibility Act 

The Regulatory Flexibility Act (RFA) generally requires an 

agency to prepare a regulatory flexibility analysis of any rule 
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subject to notice and comment rulemaking requirements under the 

Administrative Procedure Act or any other statute unless the 

agency certifies that the rule will not have a significant 

economic impact on a substantial number of small entities. Small 

entities include small businesses, small organizations, and 

small governmental jurisdictions. 

For purposes of assessing the impacts of today's rule on 

small entities, small entity is defined as: (1) a small business

as defined by the Small Business Administration’s (SBA) 

regulations at 13 CFR 121.201; (2) a small governmental 

jurisdiction that is a government of a city, county, town, 

school district or special district with a population of less 

than 50,000; and (3) a small organization that is any not-forprofit enterprise which is independently owned and operated and 

is not dominant in its field. 

After considering the economic impacts of this action on 

small entities, I certify that this final action will not have a 

significant economic impact on a substantial number of small 

entities. The Navajo Generating Station is not a small entity 

and the FIP for Navajo Generating Station being finalized today 

does not impose any compliance requirements on small entities. 

See Mid-Tex Electric Cooperative, Inc. v. FERC, 773 F.2d 327 

(D.C. Cir. 1985). We recognize that several tribes located in 

Arizona have expressed concerns regarding potential indirect 
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effects of this Final Rule; however, these indirect effects are 

not direct compliance costs or requirements on small entities. 

D. Unfunded Mandates Reform Act (UMRA)

This rule will impose an enforceable duty on the private 

sector owners of Navajo Generating Station. However, this rule 

does not contain a Federal mandate that may result in 

expenditures of $100 million (in 1996 dollars) or more for 

State, local, and tribal governments, in the aggregate, or the 

private sector in any one year. EPA’s estimate for the total 

annual cost to install and operate SCR on all three units at NGS 

if it had been required to comply with BART does not exceed $100 

million (in 1996 dollars) in any one year. Because we are 

finalizing requirements consistent with Appendix B to the TWG 

Agreement, which provides more flexibility than EPA’s proposed 

BART determination and would, at most, require installation and 

operation of SCR on two units, rather than three units at NGS, 

EPA expects the total annual cost of implementing the TWG 

Alternative to also not exceed $100 million (in 1996 dollars). 

Thus, this rule is not subject to the requirements of sections 

202 or 205 of UMRA. This action is also not subject to the 

requirements of section 203 of UMRA because it contains no 

regulatory requirements that might significantly or uniquely 

affect small governments. This rule will not impose direct 

compliance costs on the Navajo Nation, and will not preempt 
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Navajo law. This final action will reduce the emissions of NOX

from a single source, the Navajo Generating Station. 

E. Executive Order 13132: Federalism 

This action does not have federalism implications. It will 

not have substantial direct effects on the States, on the 

relationship between the national government and the States, or 

in the distribution of power and responsibilities among the 

various levels of government, as specified in Executive Order 

13132. This final action requires emission reductions of NOx at a 

specific stationary source located in Indian country. Thus, 

Executive Order 13132 does not apply to this action. 

F. Executive Order 13175: Consultation and Coordination With 

Indian Tribal Governments 

Subject to the Executive Order 13175 (65 FR 67249, November 

9, 2000) EPA may not issue a regulation that has tribal 

implications, that imposes substantial direct compliance costs, 

and that is not required by statute, unless the Federal 

government provides the funds necessary to pay the direct 

compliance costs incurred by tribal governments, or EPA consults 

with tribal officials early in the process of developing the 

proposed regulation and develops a tribal summary impact 

statement. EO 13175 defines “policies that have tribal 

implications” to refer to regulations or other actions that have 

substantial direct effects on one or more Indian tribes. 
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EPA has concluded that this Final Action will have tribal 

implications based on the direct relationship between NGS and 

the Navajo Nation. In addition, EPA anticipates that the 

following direct and indirect effects may result from the TWG 

Alternative and Reclamation’s ownership interest in NGS: 

decreased revenues to the Hopi Tribe and the Navajo Nation 

associated with the closure of one unit or curtailment of 

electricity generation in 2019; and increased water costs to 

tribes associated with the installation of controls to meet an 

emission limit of 0.07 lb/MMBtu in 2030. However, it will 

neither pre-empt Tribal law nor impose substantial direct 

compliance costs on tribal governments (no tribal government is 

an owner or participant in NGS and therefore no tribal 

government will be required to pay direct costs of compliance). 

We note that the Navajo Nation has the option to purchase up to 

a 170 MW share of NGS in 2019. EPA understands that the Navajo 

Nation has not yet made its decision and therefore, currently, 

no tribal government is a Participant in NGS. 

The owners of NGS, together with the Navajo Nation, the 

Gila River Indian Community, and several other stakeholders, 

submitted the TWG Agreement to EPA that would provide compliance 

flexibility to the owners and result in greater reasonable 

progress than BART toward the national visibility goal. This TWG 

Alternative involves closure or curtailment of production on one 
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unit of NGS and installation of add-on pollution controls to the 

remaining two units. EPA issued a Supplemental Proposal 

proposing to find that the TWG Alternative met the requirements 

of the CAA and RHR. Today, EPA is finalizing requirements 

consistent with the TWG Agreement. Because the TWG Alternative 

involves the closure or curtailment of production on one unit 

and an associated decline in the amount of coal mined and 

combusted, to the extent that taxes or royalties paid to the 

Hopi Tribe and the Navajo Nation by the operators of Navajo 

Generating Station and the Kayenta Mine, are tied to the amount 

of coal that is mined or the amount of electricity that is 

generated at NGS, the revenues to the Hopi Tribe and Navajo 

Nation may be expected to decline. In addition, under the TWG 

Alternative, when the installation of add-on pollution controls 

occurs in 2030, EPA expects the CAWCD variable OM&R water rate 

to increase, affecting tribes with allocations of CAP water. 

EPA consulted with tribal officials early in the process of 

developing this regulation to permit them to have meaningful and 

timely input into its development. EPA first put forth an ANPR 

on August 28, 2009 to accept comment on preliminary information 

provided by FCPP and NGS and to begin the consultation process 

with the Federal Land Managers and affected tribes. 

EPA received numerous comments on the ANPR from tribes and 

tribal organizations, including the Navajo Nation, Hopi Tribe, 
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Gila River Indian Community, Ak-Chin Indian Community, Tohono 

O’odham Nation, Pascua Yaqui Tribe, Fort McDowell Yavapai 

Nation, Yavapai-Apache Nation, and the Inter Tribal Council of 

Arizona. Comments from the Navajo Nation on NGS and from the 

Hopi Tribe focused on the significant contribution of coalrelated royalties, taxes, and employment at NGS and the Kayenta 

Mine to the economies of the Navajo Nation and the Hopi Tribe. 

Comments from the Gila River Indian Community, the Tohono 

O’odham Nation, and other tribes located in Arizona focused on 

the importance of continued operation of NGS as a source of 

power to CAP, in order for the federal government to meet 

obligations under existing water settlement agreements. The 

importance to tribes of continued operation of NGS and 

affordable water costs cannot be overemphasized. 

Given the extent of federal and tribal interests in NGS and 

the federal government’s trust responsibility to Indian tribes, 

on January 4, 2013, EPA, DOI, and DOE signed a joint federal 

agency statement committing to collaborate on several short- and 

long-term goals, including analyzing and pursuing strategies for 

providing clean, affordable and reliable power, affordable and 

sustainable water, and sustainable economic development to key 
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stakeholders who currently depend on NGS.159 The partner agencies 

have already begun to work together with stakeholders to 

identify and undertake actions that support implementation of 

BART, including seeking funding to cover expenses for pollution 

control or other necessary upgrades for the federal portion of 

NGS. The agencies have also begun work to jointly support a 

phase 2 report to analyze a full range of clean energy options 

for NGS. Finally, the agencies intend to work with stakeholders 

to develop a roadmap for achieving long-term, innovative clean 

energy solutions for NGS. 

In our February 5, 2013 Proposed Rule, EPA exercised 

discretion to include in our analysis of Factor 2 (Energy and 

Non-Air Quality Impacts), an examination of the viability of 

continued operation of NGS if new NOX controls are required, to 

address the concern expressed by numerous tribes that a BART 

determination requiring SCR would force NGS to close. Our 

analysis showed that although SCR would increase the cost of 

electricity generation at NGS, installing and operating SCR at 

NGS would still be less costly than replacing NGS with power 

purchased from elsewhere in the West.160 However, we also 

recognized that the timing of regulatory compliance is an 

159 See Joint Federal Agency Statement Regarding Navajo Generating Station, 

dated January 4, 2013, in the docket for this proposed rulemaking. 160 See Factor 2 analysis, 78 FR at 8281-8284 (February 5, 2013). 
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important consideration given potential ownership changes and 

other requirements related to the extension of the NGS lease and 

other rights-of-way agreements. As part of our Factor 2 

analysis, we also estimated potential water rate increases to 

tribes.161 As discussed in our proposed rule, EPA considers the 

potential economic impacts to tribes to argue for flexibility in 

the compliance timeframe for NGS. 

In addition to our proposed BART determination for NGS, EPA 

also proposed a framework for evaluating alternatives to BART 

that provide options for flexibility in achieving emission 

reductions at NGS. EPA proposed an alternative to BART 

consistent with our proposed framework and invited stakeholders 

to submit other alternatives to BART that reduce NOX emissions at 

NGS while providing long-term, sustainable benefits for 

tribes.162 We noted that the extended timeframe for compliance 

would not, in itself, avoid or mitigate increases in water rates 

for tribes located in Arizona; however, it would provide time 

for the collaborating federal agencies to explore options to 

avoid or minimize potential impacts to tribes, including seeking 

funding to cover the expenses for the federal portion of 

pollution control at NGS.163

161 Id. 162 Id. at 8291. 163 Id. at 8289. 
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Following our Proposed Rule, the TWG, which included the 

Navajo Nation, the Gila River Indian Community, and the 

Interior, together with four additional groups, submitted their 

agreement (TWG Agreement) that contained an additional BART 

alternative for consideration (Appendix B to the TWG Agreement). 

Although EPA was not part of the TWG, we note that the TWG 

Agreement included seven elements, including elements directly 

or indirectly related to tribes, i.e., commitments by Interior 

to mitigate potential impacts from EPA’s final BART rule to 

Affected Tribes and a commitment by SRP to make funds available 

for a Local Benefit Fund for community improvement projects 

within 100 miles of NGS or the Kayenta Mine.164

EPA has met with tribes on numerous occasions to discuss 

the significance of NGS to tribal economies and tribal water 

interests in Arizona.165 Consultations with tribes included 

164 As described in our Supplemental Proposal (78 FR at 62512, October 22, 

2013), the seven elements of the TWG Agreement were (1) a description of a 

“Reasonable Progress Alternative to BART” (Appendix B to the TWG Agreement); 

(2) a study of options by Reclamation for replacing the federal share of 

energy being generated from NGS with low-emitting energy; (3) commitments by 

Interior to reduce or offset emissions of carbon dioxide (CO2) by three 

percent per year and facilitate the development of clean energy resources; 

(4) commitments by Interior to mitigate potential impacts from EPA’s final 

BART rule to Affected Tribes; (5) a commitment by Interior to carry out the 

Phase 2 Study by the National Renewable Energy Laboratory (NREL) for the 

purposes of studying options for the future of NGS; (6) a commitment by SRP 

to make funds available for a Local Benefit Fund for community improvement 

projects within 100 miles of NGS or the Kayenta Mine; and (7) a summary of 

obligations of the Parties to the Agreement and miscellaneous legal 

provisions. 

165 See document titled “Updated Timeline of All Tribal Consultations on NGS 

for Final Rule.docx” in the docket for this rulemaking. 
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potential economic impacts associated with a BART determination 

for NGS, as well as potential impacts from EPA’s Mercury and Air 

Toxics Standards (MATS) rulemaking. 

 In recognition of the unusual complexity of regulating NGS, 

representatives from EPA, including the Assistant Administrator 

and the Deputy Assistant Administrator for the Office of Air and 

Radiation and the Regional Administrator for Region 9, visited 

NGS and affected communities in the area. EPA officials have 

also met with additional stakeholders, at various locations, 

including EPA offices in San Francisco, California and 

Washington, D.C., and offices of individual tribal governing 

councils and the Inter Tribal Council of Arizona.

Following the publication of our proposed rule on February 

5, 2013, EPA engaged in 17 consultation meetings with tribes 

prior to the January 2014 close of the public comment period.166

Of these meetings, at least two were held as group consultation 

sessions where all tribes in Arizona were invited to participate 

and were provided the opportunity to request individual 

consultation meetings as well.167 EPA received comment letters on 

our proposal and Supplemental Proposal from the Navajo Nation, 

the Gila River Indian Community, the Tohono O’odham Nation, the 

166 See document titled “Updated Timeline of all Tribal Consultation on NGS_for 

Final Rule.pdf” in the docket for the rule. 

167 Id.
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Ak-Chin Indian Community, the Tonto Apache Tribe, the San Carlos 

Apache Tribe, and the Kaibab Band of Paiute Indians.168 At the 

request of two tribes for additional time beyond January 6, 2014 

to submit comments, EPA exercised our discretion to accept 

comments from tribal governments after the close of the comment 

period. The White Mountain Apache Tribe submitted comments on 

February 5, 2014.169 In addition, in response to their request to 

EPA for information related to NGS, we provided responsive 

documents to the Hopi Tribe on January 7, 2014.170 As shown in 

additional correspondence, the Hopi Tribe requested additional 

time to submit comments, and EPA continued to exercise our 

discretion to accept late comments from the Hopi Tribe.171 Our 

separate response to comments document contains a summary of all 

substantive comments and EPA’s responses to those comments. 

Several tribes expressed concern that the Technical Work 

Group included only two tribes, the Navajo Nation and the Gila 

River Indian Community, and excluded numerous other tribes that 

also have a significant economic interest in NGS. Several tribes 

also asserted that the Proposed Rule and Supplemental Proposal 

168 See comment numbers 0340, 0317, 0387, 0402, 0419, and 0421 in the docket 

for the rule. 

169 See comment number 0440 in the docket for the rule. 170 See document titled “2014_0107 EPA Letter to Chairman Honanie with 

Enclosure 1.pdf” in the docket for this rule. 

171 See document titled “2014_0131 Letter from Chairman Honanie.pdf” and 

document titled “2014_0206 EPA Response to Chairman Honanie_Hopi Tribe.pdf” 

in the docket for this rule. 
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have disproportionate impacts on tribes with CAP water 

settlements and urged EPA to develop an alternative regulation 

that does not place an additional burden on Indian tribes. 

Another tribe requested that a portion of the funds identified 

in the TWG Agreement be designated to their tribe. 

EPA recognizes that many tribes did not participate in the 

development of the TWG Agreement. EPA was not involved in the 

formation of the Technical Work Group or any of the negotiations 

between the members of the TWG in developing the TWG Agreement. 

In addition, our evaluation of the TWG Agreement was for the 

sole purpose of determining whether the TWG Alternative 

(Appendix B to the TWG Agreement) meets our framework for a 

“better than BART” Alternative. Therefore, although EPA agrees 

that many tribes have economic interests in NGS and CAP, EPA did 

not have a role in the TWG Agreement and does not have any role 

in the distribution of funds described in the TWG Agreement. 

EPA recognizes that our final action will have tribal 

implications. Because we are taking action to finalize 

requirements consistent with the TWG Agreement, EPA anticipates 

that increases in CAP water costs as a result of the 

installation of new air pollution controls at NGS would not 

occur until 2030. In addition, as stated elsewhere, EPA has 

committed to collaborating with other federal agencies to 

explore options to avoid or minimize potential impacts to 
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tribes, including seeking funding to cover the expenses for the 

federal portion of pollution control at NGS. 

In summary, EPA has taken numerous steps, as described in 

the preceding paragraphs, to evaluate the potential impacts on 

Tribes and to identify and provide the flexibility for others to 

develop alternative approaches that would meet the requirements 

of the CAA and the RHR while being as sensitive as possible to 

concerns raised by Tribes. Through the Joint Federal Agency 

Statement on NGS, the federal government has recognized its 

obligations through its trust responsibility and through its 

specific historical and ongoing involvement with NGS and water 

rights settlements with Tribes. That agreement reflects our 

commitment to ongoing engagement with affected Tribes and to the 

pursuit of a long-term solution for electricity generation that 

is protective of the economic interests of Tribes and public 

health and the environment. 

Based on numerous consultation meetings between high-level 

officials from EPA and elected tribal leaders, beginning in 2009 

and extending into 2013, and our development of flexible options 

for BART Alternatives in response to comments from tribes, EPA 

considers our consultation on NGS to be consistent with EO 13175 
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and EPA’s policy to engage in early and meaningful consultation 

with tribes.172

G. Executive Order 13045: Protection of Children from 

Environmental Health Risks and Safety Risks 

Executive Order 13045: Protection of Children from 

Environmental Health Risks and Safety Risks (62 FR 19885, April 

23, 1997), applies to any rule that: (1) is determined to be 

economically significant as defined under Executive Order 12866, 

and (2) concerns an environmental health or safety risk that EPA 

has reason to believe may have a disproportionate effect on 

children. If the regulatory action meets both criteria, the 

Agency must evaluate the environmental health or safety effects 

of the planned rule on children, and explain why the planned 

regulation is preferable to other potentially effective and 

reasonably feasible alternatives considered by the Agency. 

This rule is not subject to Executive Order 13045 because 

it requires emissions reductions of NOX from a single stationary 

source. Because this action only applies to a single source and 

is not a rule of general applicability, it is not economically 

significant as defined under Executive Order 12866, and does not 

have a disproportionate effect on children. However, to the 

172 EPA’s policy on Consultation and Coordination with Indian Tribes is posted 

on the following website: http://www.epa.gov/tribal/consultation/consultpolicy.htm 
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extent that the rule will reduce emissions of NOX, which 

contributes to ozone formation, the rule will have a beneficial 

effect on children’s health by reducing air pollution that 

causes or exacerbates childhood asthma and other respiratory 

issues. 

H. Executive Order 13211: Actions Concerning Regulations That 

Significantly Affect Energy Supply, Distribution, or Use 

This action is not subject to Executive Order 13211 (66 FR 

28355 (May 22, 2001)), because it is not a significant 

regulatory action under Executive Order 12866. 

I. National Technology Transfer and Advancement Act 

Section 12(d) of the National Technology Transfer and 

Advancement Act of 1995 (NTTAA), Pub L. No. 104-113, 12 (10) (15 

U.S.C. 272 note) directs EPA to use voluntary consensus 

standards (VCS) in its regulatory activities unless to do so 

would be inconsistent with applicable law or otherwise 

impractical. VCS are technical standards (e.g., materials 

specifications, test methods, sampling procedures and business 

practices) that are developed or adopted by the VCS bodies. The 

NTTAA directs EPA to provide Congress, through annual reports to 

OMB, with explanations when the Agency decides not to use 

available and applicable VCS. 

Consistent with the NTTAA, the Agency conducted a search to 

identify potentially applicable VCS. For the measurements listed 
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below, there are a number of VCS that appear to have possible 

use in lieu of the EPA test methods and performance 

specifications (40 CFR Part 60, Appendices A and B) noted next 

to the measurement requirements. It would not be practical to 

specify these standards in the current rulemaking due to a lack 

of sufficient data on equivalency and validation and because 

some are still under development. However, EPA’s Office of Air 

Quality Planning and Standards is in the process of reviewing 

all available VCS for incorporation by reference into the test 

methods and performance specifications of 40 CFR Part 60, 

Appendices A and B. Any VCS so incorporated in a specified test 

method or performance specification would then be available for 

use in determining the emissions from this facility. This will 

be an ongoing process designed to incorporate suitable VCS as 

they become available. 

J. Executive Order 12898: Federal Actions to Address 

Environmental Justice in Minority Populations and Low-Income 

Populations

Executive Order 12898 (59 FR 7629, February 16, 1994),

establishes federal executive policy on environmental justice. 

Its main provision directs federal agencies, to the greatest 

extent practicable and permitted by law, to make environmental 

justice part of their mission by identifying and addressing, as 

appropriate, disproportionately high and adverse human health or 
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environmental effects of their programs, policies, and 

activities on minority populations and low-income populations in 

the United States. 

EPA has determined that this final rule will not have 

disproportionately high and adverse human health or 

environmental effects on minority or low-income populations 

because it increases the level of environmental protection for 

all affected populations without having any disproportionately 

high and adverse human health or environmental effects on any 

population, including any minority or low-income population. 

EPA recognizes that numerous commenters have stated that 

this rulemaking has environmental justice implications because 

NGS, which is among the largest coal-fired power plants in the 

country, is located on the Navajo Nation. Commenters have also 

expressed concern that the documents associated with this rule 

are too technical for community members to understand. Some 

commenters have also argued that EPA should apply the same 

standard to NGS as other coal-burning power plants (e.g., Four 

Corners Power Plant), and that the extended compliance timeframe 

for NGS is an environmental justice issue. 

Fair treatment and meaningful involvement are critical 

components of environmental justice and EPA takes fair treatment 

and meaningful involvement seriously. We provided numerous 

opportunities for tribal governments, environmental and tribal 
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non-governmental organizations, and other interested 

stakeholders to provide input in the development of our Proposed 

Rule, Supplemental Proposal, and Final Rule for NGS. 

As discussed in more detail in the RTC, EPA began our 

public involvement process for a BART determination for NGS in 

2009, when we published an Advanced Notice of Proposed 

Rulemaking (ANPR). During 2009 through 2012, EPA met with 

various stakeholders, including tribal governments and Navajo 

environmental groups to discuss NGS and hear concerns related to 

a BART determination for this facility.173 During the 11-month 

comment period for our Proposed Rule, EPA continued to meet with 

stakeholders to discuss our proposed BART determination for NGS 

and our framework for “better than BART” alternatives.174

On July 26, 2013, the TWG submitted the TWG Agreement to 

EPA for consideration. EPA posted the TWG Agreement to our 

docket on the same day to provide the public an opportunity to 

review it.175 On September 25, 2013, EPA posted a Supplemental 

Proposal, along with supporting documents, to the docket to 

allow for early review by interested parties.176 The Supplemental 

173 See, for example document number 0232 in the ANPR docket at EPA-R09-OAR2009-0598, and document numbers 0008 and 0009 in the docket for this rule at 

EPA-R09-OAR-2013-0009. 

174 See, for example, document number 0150, 0152, 0166, 0173, 0302, and 0303 in 

the docket for this rule. 

175 See document number 0122 in docket for this rulemaking. 176 See document numbers 0182, 0183, and 0184 in the docket for this 

rulemaking. 
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Proposal was published in the Federal Register on October 22, 

2013. The comment period for the Supplemental Proposal closed on 

the same day as the BART proposal, on January 6, 2014. The 

Supplemental Proposal also included notice of five open house 

and public hearing events EPA scheduled throughout Arizona in 

November 2013. The open houses allowed members of the public an 

opportunity to talk with representatives from EPA and ask 

questions. EPA held events at the LeChee Chapter House, located 

on the Navajo Nation, as well as in Page, Arizona, and provided 

oral interpretation services between English and Diné (the 

Navajo language). EPA also held an event at the Hopi Day School, 

located in Kykotsmovi, the seat of the Hopi tribal government.177

Finally, we also held events in Phoenix and in Tucson, Arizona, 

to allow stakeholders in central and southern Arizona, 

representing CAP water interests and several tribes receiving 

CAP water, the opportunity to provide comment and talk with 

representatives from EPA. 

EPA understands that the TSD and Federal Register notices 

include technical information that may be difficult to 

understand. EPA provided Fact Sheets and handouts, written in 

177 EPA engaged with the government of the Hopi Tribe to search for an oral 

interpreter between English and the Hopi language, but the Hopi Tribe was 

unable to locate anyone to provide those services. 
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plain language, at the open house and public hearing events.178

EPA representatives were also present at the events to discuss 

and explain our Proposals. 

EPA recognizes that some commenters may view the timeframe 

for compliance under EPA’s framework for BART Alternatives as an 

environmental justice issue. We note that the Navajo Nation and 

other Tribes expressed concern with the potential economic 

impacts of this rulemaking. The flexibility we provided has 

allowed for a balance between these considerations. 

We further note that the LNB/SOFA credit, an important 

component of the timeframe under our “better than BART” 

framework, was based on real, actual emission reductions 

beginning in 2009 that were voluntary and not required by any 

rule or regulation. We also note that the TWG Alternative, which 

calls for closure of one unit in 2019 (or equivalent 

curtailment), will result not only in reductions of NOX, but also 

reductions of several other pollutants, including SO2, PM, CO2, 

and hazardous air pollutants. Although the compliance date of 

emission limit for two units (achievable with the installation 

of SCR) under the TWG Alternative is in 2030, over 2009 to 2044, 

the TWG Alternative will result in greater NOX reductions than 

would have been achieved under BART, will result in step-wise 

178 See document 0219 in the docket for this rulemaking. 
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reductions of NOX and additional pollutants that affect 

visibility or human health, and will provide an enforceable 

mechanism to ensure that NGS ceases conventional coal-fired 

electricity generation at NGS by the end of 2044. All of these 

measures will increase the level of environmental protection for 

communities affected by NGS. 

K. Congressional Review Act 

The Congressional Review Act, 5 U.S.C 801 et seq., as added 

by the Small Business Regulatory Enforcement Fairness Act of 

1996, generally provides that before a rule may take effect, the 

agency promulgating the rule must submit a rule report, which 

includes a copy of the rule, to each House of the Congress and 

to the Comptroller General of the United States. Section 804 

exempts from section 801 the following types of rules (1) rules 

of particular applicability; (2) rules relating to agency 

management or personnel; and (3) rules of agency organization, 

procedure, or practice that do not substantially affect the 

rights or obligations of non-agency parties. 5 U.S.C 804(3). EPA 

is not required to submit a rule report regarding today’s action 

under section 801 because this action is a rule of particular 

applicability. This rule finalizes a source-specific FIP for a 

single generating source. 

L. Petitions for Judicial Review 
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Under section 307(b)(1) of the Clean Air Act, petitions for 

judicial review of this action must be filed in the United 

States Court of Appeals for the appropriate circuit by [insert 

date 60 days from publication in Federal Register]. Filing a 

petition for reconsideration by the Administrator of this final 

rule does not affect the finality of this rule for the purposes 

of judicial review nor does it extend the time within which a 

petition for judicial review may be filed, and shall not 

postpone the effectiveness of such rule or action. This action 

may not be challenged later in proceedings to enforce its 

requirements. See CAA section 307(b)(2). 
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List of Subjects in 40 CFR Part 49 

Environmental protection, Administrative practice and 

procedure, Air pollution control, Indians, Intergovernmental 

relations, Reporting and recordkeeping requirements. 

July 28, 2014 /s/ 

Dated: Gina McCarthy, 

Administrator. 
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Title 40, chapter I of the Code of Federal Regulations is 

amended as follows: 

PART 49--INDIAN COUNTRY: AIR QUALITY PLANNING AND MANGEMENT 

 1. The authority citation for part 49 continues to read as 

follows: 

Authority: 42 U.S.C. 7401, et seq. 

 2. Section 49.5513 is amended by adding paragraph (j) to 

read as follows: 

§ 49.5513 Federal Implementation Plan Provisions for Navajo 

Generating Station, Navajo Nation. 

* * * * * 

(j)(1) Applicability. Regional Haze Best Available Retrofit 

Technology limits for NOX for this plant are in addition to the 

requirements of paragraphs (a) through (i) of this section. The 

provisions of this paragraph (j) are severable, and if any 

provision of this paragraph (j), or the application of any 

provision of this paragraph (j) to any owner/operator or 

circumstance, is held invalid, the application of such provision 

to other owner/operators and other circumstances, and the 

remainder of this paragraph (j), will not be affected thereby. 

Nothing in this paragraph (j) allows or authorizes any Unit to 

emit NOX at a rate that exceeds its existing emission limit of 

0.24 lb/MMBtu as established by EPA permit AZ 08-01 issued on 

November 20, 2008. 
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(2) Definitions. Terms not defined below have the meaning 

given to them in the Clean Air Act or EPA’s regulations 

implementing the Clean Air Act and in paragraph (c) of this 

section. For purposes of this paragraph (j): 

(i) 2009-2029 NOX Cap means a limit on emissions from Units 

1, 2, and 3 of no more than 416,865 tons of NOX. 

(ii) 2009-2044 NOX Cap means a limit on emissions from Units 

1, 2, and 3 of no more than 494,899 tons of NOX. 

(iii) Boiler Operating Day means a 24-hour period between 

12 midnight and the following midnight during which any fuel is 

combusted at any time in the steam-generating unit. It is not 

necessary for fuel to be combusted the entire 24-hour period. 

(iv) Coal-Fired Unit means any of Units 1, 2, or 3 at 

Navajo Generating Station. 

(v) Continuous Emission Monitoring System or CEMS means the 

equipment required by 40 CFR Part 75 and this paragraph (j). 

(vi) Departing Participant means either Los Angeles 

Department of Water and Power or Nevada Energy, also known as NV 

Energy or Nevada Power Company. 

(vii) Emission limitation or emission limit means the 

federal emissions limitation required by this paragraph. 

(viii) Existing Participant means the existing owners of 

NGS: Los Angeles Department of Water and Power; Nevada Energy, 

also known as NV Energy or Nevada Power Company; Salt River 
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Project Agricultural Improvement and Power District; Arizona 

Public Service Company; and Tucson Electric Company, together 

with the United States, acting through the Bureau of 

Reclamation. 

(ix) lb means pound(s). 

(x) Low-NOx Burners and Separated Over-Fire Air or LNB/SOFA

means combustion controls installed on each Unit between 2009 

and 2011. 

(xi) Navajo Nation means the Navajo Nation, a federally 

recognized Indian Tribe. 

(xii) NGS or Navajo Generating Station means the steam 

electric generating station located on the Navajo Reservation 

near Page, Arizona, consisting of Units 1, 2, and 3, each 750 MW 

(nameplate rating), the switchyard facilities, and all 

facilities and structures used or related thereto. 

(xiii) NOX means nitrogen oxides expressed as nitrogen 

dioxide (NO2). 

(xiv) Owner/operator means any person(s) who own(s) or who 

operate(s), control(s), or supervise(s) one more of the Units of 

the Navajo Generating Station. 

(xv) MMBtu means million British thermal unit(s). 

(xvi) Operating hour means any hour that fossil fuel is 

fired in the unit. 
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(xvii) Unit means any of Units 1, 2, or 3 at Navajo 

Generating Station. 

(xviii) Valid Data means CEMs data that is not out of 

control as defined in 40 CFR Part 75. 

(3) “Better than BART” Alternative for NOX. Total cumulative 

NOX emissions from Units 1, 2, and 3, from January 1, 2009 to 

December 31, 2044, may not exceed the 2009-2044 NOX Cap. The 

owner/operator must implement the applicable operating scenario, 

under paragraph (j)(3)(i) of this section, to ensure NOX emission 

reductions sufficient to maintain total cumulative NOX emissions 

from Units 1, 2, and 3 below the 2009-2044 NOX Cap. 

(i) Operating Scenarios to Comply with 2009-2044 NOX Cap. 

The owner/operator must comply with one of the following 

operating scenarios based on the applicability provisions in 

paragraph (j)(3)(ii) of this section. 

(A) Alternative A1. 

(1) By December 31, 2019, the owner/operator must 

permanently cease operation of one coal-fired Unit; and 

(2) By December 31, 2030, the owner/operator must comply 

with a NOX emission limit of 0.07 lb/MMBtu, based on a rolling 

average of 30 boiler operating days, on each of the two 

remaining coal-fired Units. 

(3) The owner/operator must permanently cease operation of 

Units 1, 2, and 3 if total cumulative emissions of NOX from Units 
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1, 2, and 3, based on annual reports required under paragraph 

(j)(4)(ii) of this section, exceed the 2009-2044 NOX Cap at any 

time prior to December 31, 2044. 

(B) Alternative A2. 

(1) By December 31, 2019, the owner/operator must 

permanently cease operation of one coal-fired Unit; and

(2) By December 31, 2019, the owner/operator may increase 

net generating capacity of the remaining two coal-fired Units by 

a combined total of no more than 189 MW. The actual increase in 

net generating capacity shall be limited by the sum of 19 MW and 

the ownership interest, in net MW capacity, purchased by the 

Navajo Nation by December 31, 2019. Nothing in paragraph (j) of 

this section alters any regulatory requirements, including those 

for pre-construction permitting, associated with any increase in 

the net generating capacity of the Unit(s). 

(3) By December 31, 2030, the owner/operator must comply 

with a NOX emission limit of 0.07 lb/MMBtu, based on a rolling 

average of 30 boiler operating days, on each of the two 

remaining coal-fired Units. 

(4) The owner/operator must permanently cease operation of 

Units 1, 2, and 3 if total cumulative emissions of NOX from Units 

1, 2, and 3, based on annual reports required under paragraph 

(j)(4)(ii) of this section, exceed the 2009-2044 NOX Cap at any 

time prior to December 31, 2044. 
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(C) Alternative A3.

(1) By December 31, 2019, the owner/operator must reduce 

the net generating capacity of NGS by no less than 561 MW. The 

actual reduction in net generating capacity of NGS shall be 

determined by the difference between 731 MW and the ownership 

interest, in net MW capacity and limited to 170 MW, purchased by 

the Navajo Nation by December 31, 2019. 

(2) By December 31, 2030, the owner/operator must comply 

with a NOX emission limit of 0.07 lb/MMBtu, based on a rolling 

average of 30 boiler operating days, on two Units. 

(3) The owner/operator must permanently cease operation of 

Units 1, 2, and 3 if total cumulative emissions of NOX from Units 

1, 2, and 3, based on annual reports required under paragraph 

(j)(4)(ii) of this section, exceed the 2009-2044 NOX Cap at any 

time prior to December 31, 2044. 

(D) Alternative B.

(1) Total cumulative NOX emissions from Units 1, 2, and 3 

may not exceed the 2009-2044 NOx Cap or the 2009-2029 NOX Cap. 

(2) The owner/operator must cease operation of Units 1, 2, 

and 3 if total cumulative emissions of NOX from Units 1, 2, and 

3, based on annual reports required under paragraph (j)(4)(ii) 

of this section, exceed the 2009-2029 NOX Cap at any time prior 

to December 31, 2029. The owner/operator may restart operation 

of Units 1, 2, and 3 after January 1, 2030, as long as total 
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cumulative emissions of NOX from Units 1, 2, and 3, based on 

annual reports required under paragraph (j)(4)(ii) of this 

section, do not exceed the 2009-2044 NOX Cap. 

(3) The owner/operator must permanently cease operation of 

Units 1, 2, and 3 if total cumulative emissions of NOX from Units 

1, 2, and 3, based on annual reports required under paragraph 

(j)(4)(ii)), exceed the 2009-2044 NOX Cap at any time prior to 

December 31, 2044. 

(ii) Applicability of Alternatives. 

(A) Alternative A1 applies if by December 31, 2019, one of 

the following occurs: 

(1) Both of the Departing Participants retire their 

ownership interests in NGS by December 31, 2019, and the Navajo 

Nation does not purchase an ownership interest in NGS; or 

(2) Both of the Departing Participants sell their ownership 

interests in NGS to Existing Participants, and the Navajo Nation 

does not purchase an ownership interest in NGS; or 

(3) One of the Departing Participants retires its ownership 

interest in NGS and the other Departing Participant sells its 

ownership interest in NGS to an Existing Participant, and the 

Navajo Nation does not purchase an ownership interest in NGS. 

(B) Alternative A2 applies if by December 31, 2019, one of 

the following occurs: 
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(1) Both of the Departing Participants sell their ownership 

interests in NGS to Existing Participants, the Navajo Nation has 

purchased an ownership interest in NGS, and the owner/operator 

has increased net generating capacity of the two remaining Units 

by a combined total of no more than 189 MW; or 

(2) One of the Departing Participants retires its ownership 

interest in NGS and the other Departing Participant sells its 

ownership interest in NGS to an Existing Participant, the Navajo 

Nation has purchased an ownership interest in NGS, and the 

owner/operator has increased net generating capacity of the two 

remaining Units by a combined total of no more than 189 MW. 

(C) Alternative A3 applies if by December 31, 2019, one of 

the following occurs: 

(1) Both of the Departing Participants sell their ownership 

interests in NGS to Existing Participants, the Navajo Nation has 

purchased an ownership interest in NGS, and the owner/operator 

has not increased net generating capacity of the Units at NGS; 

or 

(2) One of the Departing Participants retires its ownership 

interest in NGS and the other Departing Participant sells its 

ownership interest in NGS to an Existing Participant, the Navajo 

Nation has purchased an ownership interest in NGS, and the 

owner/operator has not increased net generating capacity of the 

Units at NGS. 
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(D) Alternative B applies if, by December 31, 2019, if one 

of the following occurs: 

(1) Any of the Departing Participants sell their ownership 

interests in NGS to a Party other than the Navajo Nation that is 

not an Existing Participant, or 

(2) Any of the Departing Participants remains as a 

participant in NGS. 

(iii) By December 22, 2044, the owner/operator shall 

permanently cease conventional coal-fired electricity generation 

by all coal-fired Units at NGS. 

(4) Reporting and Implementation Requirements for BART. 

(i) No later than December 1, 2019, the owner/operator must 

notify EPA of the applicable Alternative for ensuring compliance 

with the 2009-2044 NOx Cap. 

(ii) Beginning in 2015, and annually thereafter until the 

earlier of December 22, 2044 or the date on which the 

owner/operator ceases conventional coal-fired electricity 

generation by all coal-fired Units at NGS, the owner/operator 

must report to EPA, the annual heat input, the annual emissions 

of sulfur dioxide, carbon dioxide, and NOX from the previous full 

calendar year. In addition, the owner/operator must also report 

total cumulative emissions of NOX from NGS to assure compliance 

with the 2009-2044 NOX Cap and the 2009-2029 NOX Cap (if 

applicable). The owner/operator must make this report available 
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to the public, either through a link on its website or directly 

on its website. The report must be made available within 30 days 

of the submittal deadline associated with the annual emission 

inventory required by the Part 71 Operating Permit for NGS. 

(iii) No later than December 31, 2020, the owner/operator 

must submit an application to revise its existing Part 71 

Operating Permit to incorporate the requirements and emission 

limits of the applicable Alternative to BART under paragraph 

(j)(3) of this section. The Part 71 Operating Permit for NGS 

must incorporate practically enforceable limits for NOX of 0.24 

lb/MMBtu, on a 30‐day rolling average basis, for each Unit 

equipped with LNB/SOFA, and 0.07 lb/MMBtu, on a rolling average 

basis of 30 boiler operating days, for each Unit equipped with 

SCR, as federally enforceable permit conditions. 

(iv) In addition to the requirements of paragraphs 

(j)(4)(i), (ii) and (iii) of this section, if Alternative B 

applies, the owner/operator must submit annual Emission 

Reduction Plans to the Regional Administrator. 

(A) No later than December 31, 2019 and annually thereafter 

through December 31, 2028, the owner/operator must submit an 

Emission Reduction Plan containing anticipated year-by-year 

emissions from Units 1, 2, and 3 covering the period from 2020 

to 2029 that will assure that the operation of NGS will result 
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in emissions of NOX that do not exceed the 2009-2029 NOX Cap. The 

Emission Reduction Plan may contain several potential operating 

scenarios and must set forth the past annual actual emissions 

and the projected emissions for each potential operating 

scenario. Each potential operating scenario must demonstrate 

compliance with the 2009-2029 NOX Cap. The Emission Reduction 

Plan shall identify emission reduction measures that may 

include, but are not limited to, the installation of advanced 

emission controls, a reduction in generation output, or other 

operating strategies determined by the owner/operator. The 

owner/operator may revise the potential operating scenarios set 

forth in the Emission Reduction Plan, provided the revised plan 

ensure that NOX emissions remain below the 2009-2029 NOX Cap. 

(B) No later than December 31, 2029 and annually 

thereafter, the owner/operator shall submit an Emission 

Reduction Plan containing year-by-year emissions covering the 

period from January 1, 2030 to December 31, 2044 that will 

assure that the operation of NGS will result in emissions of NOX

that do not exceed the 2009-2044 NOX Cap. The Emission Reduction 

Plan shall identify emission reduction measures that may 

include, but are not limited to, the installation of advanced 

emission controls, a reduction in generation output, or other 

operating strategies determined by the owner/operator. The 

owner/operator may revise the potential operating scenarios set 
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forth in the Emission Reduction Plan, provided the revised plan 

ensure that NOX emissions remain below the 2009-2044 NOX Cap. 

(C) The requirement to submit annual Emission Reduction 

Plans beginning no later than December 31, 2019, shall be 

incorporated into the Part 71 Operating Permit for NGS as 

federally enforceable permit conditions. 

(5) Continuous emission monitoring system (CEMS). 

(i) At all times, the owner/operator of each unit must 

maintain, calibrate, and operate a CEMS, in full compliance with 

the requirements found at 40 CFR part 75, to accurately measure 

NOX, diluent, and stack gas volumetric flow rate from each unit. 

All hourly valid data will be used to determine compliance with 

the emission limitations for NOX in paragraph (j)(3) of this 

section for each unit. If the CEMs data is not valid, that CEMs 

data shall be treated as missing data and not used to calculate 

the emission average. CEMs data does not need to be bias 

adjusted as defined in 40 CFR part 75. Each required CEMS must 

obtain valid data for at least 90 percent of the unit operating 

hours, on an annual basis. 

(ii) The owner/operator of each unit shall comply with the 

quality assurance procedures for CEMS found in 40 CFR part 75. 

In addition to these Part 75 requirements, relative accuracy 

test audits shall be calculated for both the NOX pounds per hour 

measurement and the heat input measurement. The calculation of 
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NOX pounds per hour and heat input relative accuracy shall be 

evaluated each time the CEMS undergo relative accuracy testing. 

(6) Compliance Determination for NOX Emission Limits. 

(i) Compliance with the NOX emission limits under paragraphs 

(j)(3)(i) of this section shall be determined on a rolling 

average basis of thirty (30) Boiler Operating Days on a unit by 

unit basis. Compliance shall be calculated in accordance with 

the following procedure: (1) sum the total pounds of NOX emitted 

from the Unit during the current Boiler Operating Day and the 

previous twenty-nine (29) Boiler Operating Days; (2) sum the 

total heat input to the Unit in MMBtu during the current Boiler 

Operating Day and the previous twenty-nine (29) Boiler Operating 

Days; and (3) divide the total number of pounds of NOX by the 

total heat input in MMBtu during the thirty (30) Boiler 

Operating Days. A new 30 Boiler Operating Day rolling average 

shall be calculated for each new Boiler Operating Day. Each 30 

Boiler Operating Day rolling average shall include all emissions 

that occur during periods within any Boiler Operating Day, 

including emissions from startup, shutdown, and malfunction. 

(ii) If a valid NOX pounds per hour or heat input is not 

available for any hour for a Unit, that heat input and NOX pounds 

per hour shall not be used in the calculation for that 30 boiler 

operating day period. 
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(7) Recordkeeping. The owner/operator of each Unit must 

maintain the following records until the earlier of December 22, 

2044 or the date that conventional coal-fired operation of all 

units at NGS permanently ceases: 

(i) All CEMS data, including the date, place, and time of 

sampling or measurement; parameters sampled or measured; and 

results as required by Part 75 and as necessary to calculate 

each units pounds of NOX and heat input for each hour. 

(ii) Each Boiler Operating Day rolling average emission 

rate for NOX calculated in accordance with paragraph (j)(6)(i) of 

this section. 

(iii) Each unit’s 30 Boiler Operating Day pounds of NOX and 

heat input. 

(iv) Records of quality assurance and quality control 

activities for emissions measuring systems including, but not 

limited to, any records required by 40 CFR part 75. 

(v) Records of the relative accuracy calculation of the NOX

lb/hr measurement and hourly heat input. 

(vi) Any other records required by 40 CFR part 75. 

(8) Reporting. All reports and notifications under this 

paragraph (j) must be submitted to the Director, Navajo 

Environmental Protection Agency, P.O. Box 339, Window Rock, 

Arizona 86515, and to the Director of Enforcement Division, U.S. 

EPA Region IX, at 75 Hawthorne Street, San Francisco, CA 94105. 
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(i) The owner/operator must notify EPA within two weeks 

after completion of installation of NOX control technology on any 

of the units subject to this section. 

(ii) Within 30 days after the first applicable compliance 

date in paragraph (j)(3) of this section and within 30 days of 

every second calendar quarter thereafter (i.e., semi-annually), 

the owner/operator must submit a report that lists for each 

calendar day, calculated in accordance with paragraph (j)(6) of 

this section, total lb of NOX and heat input (as used to 

calculate compliance per paragraph (j)(6) of this section, for 

each unit’s last 30 boiler operating days. The owner/operator 

must include the results of the last relative accuracy test 

audit and the calculated relative accuracy for lb/hr NOX and heat 

input performed 45 days prior to the end of that reporting 

period. The end of the year report shall also include the 

percent valid data for each NOX, diluent, and flow monitor used 

in the calculations of compliance with paragraph (j)(6) of this 

section. 

(9) Enforcement. Notwithstanding any other provision in 

this implementation plan, any credible evidence or information 

relevant as to whether the unit would have been in compliance 

with applicable requirements if the appropriate performance or 

compliance test had been performed, can be used to establish 

whether or not the owner or operator has violated or is in 
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violation of any standard or applicable emission limit in the 

plan. 

(10) Equipment Operations. At all times, including periods 

of startup, shutdown, and malfunction, the owner/operator shall, 

to the extent practicable, maintain and operate the unit 

including associated air pollution control equipment in a manner 

consistent with good air pollution control practices for 

minimizing emissions. Determination of whether acceptable 

operating and maintenance procedures are being used will be 

based on information available to the Regional Administrator, or 

their designee, which may include, but is not limited to, 

monitoring results, review of operating and maintenance 

procedures, and inspection of the unit. 

(11) Affirmative Defense. The affirmative defense 

provisions of paragraphs (c)(2) and (i) of this section do not 

apply to this paragraph (j).