The EPA Regional Administrator, Jared Blumenfeld, signed the following supplemental proposal on 9/25/13, 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 for purposes of public comment. 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-] 

Approval of Air Quality Implementation Plans; Navajo Nation; 

Regional Haze Requirements for Navajo Generating Station; 

Supplemental Proposal 

AGENCY: Environmental Protection Agency (EPA). 

ACTION: Supplemental proposed rule and notice of public 

hearings. 

SUMMARY: On February 5, 2013, EPA published its proposed sourcespecific Federal Implementation Plan (FIP) requiring the Navajo 

Generating Station (NGS), located on the Navajo Nation, to 

reduce emissions of oxides of nitrogen (NOX) under the Best 

Available Retrofit Technology (BART) provision of the Clean Air 

Act (CAA or Act). EPA proposed the BART FIP to reduce visibility 

impairment caused by NGS at 11 National Parks and Wilderness 

Areas. EPA’s proposed FIP included: (1) a proposed BART 

determination;(2) a proposed “better than BART” alternative that 

achieves greater reasonable progress towards the national 

visibility goals than BART; and (3) a framework for evaluating 

additional alternatives to BART. This framework for evaluating 

additional alternatives was included in the proposal due to the 
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9/25/2013. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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unique purpose and history of NGS and the numerous stakeholder 

interests in it. On March 19, 2013 and June 19, 2013, EPA 

provided two extensions of the public comment period based on 

requests of several stakeholders who were actively working to 

develop an alternative to BART. On July 26, 2013, a group of 

stakeholders, known as the Technical Work Group (TWG), submitted 

to EPA their suggested alternative to BART (the “TWG 

Alternative”). The TWG Alternative establishes a lifetime cap in 

NOX emissions over 2009-2044 (the 2009-2044 NOX Cap) that is 

equivalent to the cumulative NOX emissions over 2009-2044 that 

NGS would emit under EPA’s proposed BART determination of 0.055 

lb/MMBtu achieved within five years of the final rule. Due to 

on-going lease and ownership uncertainties, the operators of NGS 

cannot yet commit to a single course of action for maintaining 

emissions below the 2009-2044 NOX Cap. The TWG Alternative 

therefore includes several alternative operating scenarios for 

meeting the 2009-2044 NOX Cap. EPA did not participate in the TWG 

or assist in developing the TWG Alternative, and has 

independently evaluated the TWG Alternative to determine if it 

meets the requirements of the CAA and the Regional Haze Rule 

(RHR). In this action, EPA is proposing to determine that the 

TWG Alternative is “better than BART” because maintaining 

emissions below the 2009-2044 NOX Cap, as provided in the TWG 
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Alternative, achieves greater reasonable progress than EPA’s 

proposed BART determination towards the national visibility 

goal. EPA is accepting comment concurrently on today’s 

Supplemental Proposal and our proposal from February 5, 2013. 

DATES: Comments on EPA’s February 5, 2013 proposal and today’s 

Supplemental Proposal for NGS must be postmarked no later than 

January 6, 2014. 

ADDRESSES: Submit comments, identified by docket number EPA-R09-

OAR-2013-0009, by one of the following methods: 

(1) Federal eRulemaking Portal: www.regulations.gov. Follow the 

on-line instructions. 

(2) E-mail: r9ngsbart@epa.gov. 

(3) Mail or deliver: Anita Lee (Air-2), U.S. Environmental 

Protection Agency Region 9, 75 Hawthorne Street, San Francisco, 

CA 94105-3901. 

For more detailed instructions concerning how to submit 

comments on this supplemental proposed rule, and for more 

information on our proposed rule, please see the notice of 

proposed rulemaking, published in the Federal Register on 

February 5, 2013 (78 FR 8274). 

Instructions: All comments will be included in the public 

docket without change and may be made available online at 

www.regulations.gov, including any personal information 
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provided, unless the comment includes Confidential Business 

Information (CBI) or other information whose disclosure is 

restricted by statute. Information that you consider CBI or 

otherwise protected should be clearly identified as such and 

should not be submitted through www.regulations.gov or e-mail. 

www.regulations.gov is an “anonymous access” system, and EPA 

will not know your identity or contact information unless you 

provide it in the body of your comment. If you send an e-mail 

directly to EPA, your e-mail address will be automatically 

captured and included as part of the public comment. If EPA 

cannot read your comment due to technical difficulties and 

cannot contact you for clarification, EPA may not be able to 

consider your comment. 

Hearings: EPA has scheduled five public hearings to accept 

oral and written comments on the proposed rulemaking. Prior to, 

or concurrent with, each public hearing, EPA will be holding an 

informal open house to allow members of the public additional 

time to review information related to EPA’s proposed BART 

determination and Supplemental Proposal, and to speak with 

representatives from EPA. Any comments made to EPA staff during 

the open houses must still be provided in writing or orally 

during the formal public hearing in order to be considered in 
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the record. The open house and public hearing schedule is as 

follows: 

1. LeChee Chapter House (Navajo Nation), located in LeChee, 

Arizona, three miles south of Page on Coppermine Road 

(Navajo Route 20), (928) 698-2805, November 12, 2013, 

concurrent Open House and Public Hearing from 10 AM – 1 

PM, local time; 

2. Page High School Cultural Arts Building, 434 Lake Powell 

Boulevard, located in Page, Arizona, (928) 608-4138, 

November 12, 2013, Open House from 3 – 5 PM, local time 

and Public Hearing from 6 – 9 PM, local time; 

3. Hopi Day School, Quarter-Mile East Main Street, located 

in Kykotsmovi, Arizona, (928) 734-2467, November 13, 

2013, Open House from 3 – 5 PM, local time and Public 

Hearing from 6 – 9 PM, local time; 

4. Phoenix Convention Center, 100 North 3rd Street, located 

in Phoenix, Arizona, (602) 262-6225, November 14, 2013, 

Open House from 3 – 5 PM, local time and Public Hearing 

from 6 – 10 PM, local time; 

5. Proscenium Theatre, Pima Community College West Campus, 

Center for the Arts Building located two miles west of 

Interstate-10 on St. Mary’s Road, (520) 206-6986, in 

Tucson, Arizona – November 15, 2013, Open House from 3 – 
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5 PM, local time and Public Hearing from 6 – 9 PM, local 

time. 

EPA will provide oral interpretation services between 

English and Diné at the open houses and public hearings in 

LeChee and Page. EPA may provide oral interpretation services 

between English and the Hopi language at the open house and 

public hearing in Kykotsmovi, pending availability of a Hopi 

interpreter. To request additional oral interpretation services 

or to request reasonable accommodation for a disability, please 

contact the person listed in the FOR FURTHER INFORMATION CONTACT

section, by October 21, 2013. Verbatim transcripts, in English, 

of the hearings and written statements provided at the hearings 

will be included in the docket for this rulemaking. 

Oral testimony may be limited to five minutes or less for 

each commenter to address the proposal or supplemental proposed 

rule. We will not be providing equipment for commenters to show 

overhead slides or make computerized presentations. The public 

hearings for the four evening events are scheduled to close at 9 

PM (in Page, Kykotsmovi, and Tucson) or 10 PM (in Phoenix), but 

may close later, if necessary, depending on the number of 

speakers wishing to participate. 

Written statements and supporting information submitted 

electronically or by mail during the comment period will be 
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9/25/2013. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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considered with the same weight as any oral comments and 

supporting information presented at the public hearings. If you 

are unable to attend the hearings but wish to submit comments on 

the proposed rule, you may submit comments as indicated in the 

ADDRESSES section above. 

Docket: The index to the docket for this action is 

available electronically at 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 EPA Region 9 

(e.g., maps, voluminous reports, copyrighted material), and some 

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

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

972-3958, r9ngsbart@epa.gov. 

SUPPLEMENTARY INFORMATION: Throughout this document, “we”, “us”, 

and “our” refer to EPA. 

Table of Contents 

I. Background 

 A. The Significance of the Navajo Generating Station 

 B. EPA’s February 5, 2013 Proposed BART Determination 
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 C. Technical Work Group Agreement 

II. Legal Background for Proposing the TWG Alternative to BART 

as Achieving Greater Progress Towards the National Visibility 

Goal 

III. EPA’s Technical Evaluation of Greater Reasonable Progress 

Towards the National Visibility Goal 

 A. Summary of TWG Alternative to BART 

 B. EPA’s Technical Evaluation of TWG Alternative to BART 

IV. EPA’s Supplemental Proposal 

V. Statutory and Executive Order Reviews 

A. Executive Order 12866: Regulatory Planning and Review 

and Executive Order 13563: Improving Regulation and 

Regulatory Review 13563B. 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 

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 
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I. National Technology Transfer and Advancement Act 

J. Executive Order 12898: Federal Actions to Address 

Environmental Justice in Minority Populations and LowIncome Populations 

I. Background 

A. The Significance of the Navajo Generating Station 

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

Nation Indian Reservation, just east of Page, Arizona, 

approximately 135 miles north of Flagstaff, Arizona. Emissions 

of NOX from NGS affect visibility at 11 National Parks and 

Wilderness Areas that are designated as Class I federal areas, 

mandated by Congress to receive heightened protection: Arches 

National Park (NP), Bryce Canyon NP, Canyonlands NP, Capitol 

Reef NP, Grand Canyon NP, Mazatzal Wilderness Area (WA), Mesa 

Verde NP, Petrified Forest NP, Pine Mountain WA, Sycamore Canyon 

WA, and Zion NP. These areas support an active tourism industry 

drawing over four million visitors to the Grand Canyon National 

Park alone in 2011.1

 NGS is subject to the BART requirements of 

the CAA and the RHR based on its age and its effects on 

visibility in Class I areas. For a more detailed discussion of 

our determination that NGS is subject to BART and the 

                                                           

1

 See document titled “Grand Canyon Annual Visitation.pdf” within 

document number 0005 in the docket for this proposed rulemaking 

at EPA-R09-OAR-2013-0009. 
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requirements of the RHR, please see our proposed FIP at 78 FR 

8274 and 8277 (February 5, 2013). 

NGS is co-owned by six entities: the U.S. Bureau of 

Reclamation (Reclamation) – 24.3 percent, Salt River Project 

Agricultural Improvement and Power District (SRP), which also 

acts as the facility operator - 21.7 percent, Los Angeles 

Department of Water and Power (LADWP) - 21.2 percent, Arizona 

Public Service (APS) - 14 percent, Nevada Energy (NV Energy, 

also known as Nevada Power Company) - 11.3 percent, and Tucson 

Electric Power (TEP) - 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 providing 

power to the Central Arizona Project (CAP).2 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-tribal agricultural water users in 

central Arizona, Indian tribes located in Arizona, and municipal 

                                                           

2

 See information on the Central Arizona Project at 

http://www.usbr.gov/projects/Project.jsp?proj_Name=Central+Arizo

na+Project. See also report by the National Renewable Energy Lab 

(NREL), discussed in more detail in Section G.iii of this 

notice, titled “Navajo Generating Station and Air Visibility 

Regulations: Alternatives and Impacts”, revision dated March 

2012 (NREL report) within document number 0005 in the docket for 

this proposed rulemaking at EPA-R09-OAR-2013-0009. 
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water users in Maricopa, Pinal, and Pima counties.3 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.4 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.5 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 a fund to 

                                                           

3

 See Section titled “Welcome” on CAP homepage: http://www.capaz.com/ 

4

 See, for example, Section 4 of the NREL report and Comments 

from the Central Arizona Water Conservation District on the NREL 

report to DOI and EPA dated February 23, 201[2], within document 

number 0005 in the docket for this proposed rulemaking at EPAR09-OAR-2013-0009. 

5

 See Table 7, 78 FR at 8283 (February 5, 2013). 
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support the tribal water settlement agreements.6 The U.S. 

Department of the Interior (DOI or the Interior), through 

Reclamation, plays an important role in the implementation of 

these settlement agreements and the management of the funds set 

aside for water infrastructure development for tribes. 

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

operated by Peabody Energy and located on reservation lands of 

both the Navajo Nation and the Hopi Tribe. Taxes and royalties 

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

Tribe contribute to the annual revenues for both governments.7

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.8

 The Joint Statement also recognizes 

the trust responsibilities of the Federal government to Indian 

tribes. 

                                                           

6 Id.

7 Id.

8

 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.
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B. EPA’s February 5, 2013 Proposed BART Determination 

As previously stated, NGS is subject to the BART 

requirements of the CAA and the RHR based on its age and its 

effects on visibility in Class I areas. Because NGS is located 

in Indian country, and because the Navajo Nation has not 

developed a Tribal Implementation Plan to implement the BART 

requirement for NGS, on February 5, 2013, EPA proposed a BART 

determination to require NGS to meet a NOX emission limit of 

0.055 pound per million British thermal units of heat input 

(lb/MMBtu) within five years of the effective date of a final 

rule.9

 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 proposed an Alternative to 

BART (i.e., Alternative 1) within the “better than BART” 

framework we outlined. EPA recognized that there may be other 

approaches that could result in better visibility benefits over 

time and that there may be changes in energy demand, supply, or 

other developments over the next several decades that may change 

electricity generation on the Navajo Nation. 

                                                           

9

 Unless otherwise noted, the averaging period, for all emission 

limits, is based on a rolling average of 30 boiler operating 

days. 
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EPA’s proposed “better than BART” framework established 

total emissions of NOX over 2009-2044 as the “BART Benchmark” 

against which an Alternative to BART would be compared.10 EPA’s 

“better than BART” framework included a NOX emission credit for 

the early and voluntary installation of LNB/SOFA over the 2009-

2011 timeframe (LNB/SOFA credit).11 As discussed in our proposed 

rulemaking, EPA was exercising its authority and discretion 

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

propose an extended timeframe for an alternative measure under 

the RHR for NGS. We proposed the LNB/SOFA credit supporting an 

extended timeframe based on the flexibility under section 

301(d)(4) of the CAA, and 40 CFR 49.11(a).12 EPA applied the 

LNB/SOFA credit to each Alternative to BART (adjusted emissions) 

and compared those values against the BART benchmark. Total 

adjusted emissions of an Alternative to BART over 2009-2044 that 

were lower than the BART Benchmark were then determined to be 

“better than BART” and result in greater reasonable progress 

                                                           

10 In our proposed rulemaking, we use the term “BART threshold” 

to describe the total emissions of NOX over 2009-2044 against 

which Alternatives to BART would be compared. Although we use 

the term “BART benchmark” here, the two terms are intended to be 

identical in meaning. 

11 The NOX reductions achieved by installing the modern LNB/SOFA 

were not required under any regulatory program under the CAA and 

resulted in more NOX emission reductions during the period 

between 2009 and the BART compliance date than if LNB/SOFA were 

installed concurrently with SCR by the BART compliance date.

12 See 78 FR 8289 (February 5, 2013). 
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towards the national visibility goal than BART. Conversely, 

alternatives that result in total NOX emissions exceeding the 

BART Benchmark would not be acceptable unless those alternatives 

provided additional emission reductions to bridge the deficit in 

NOX emission reductions. 

To calculate the value of the LNB/SOFA credit, EPA first 

calculated the total NOX emissions over 2009-2044 that NGS would 

emit if NGS had waited until the proposed BART compliance date 

to install LNB/SOFA concurrently with SCR. EPA then calculated 

total NOX emissions over 2009-2044 with the actual installation 

date of LNB/SOFA in 2009-2011 and installation of SCR by the 

BART compliance date. The difference between the two values was 

calculated to be the LNB/SOFA credit.13 Under EPA’s proposed 

framework, EPA established, as the BART benchmark, the total NOX

emissions over 2009-2044 with the actual installation date of 

LNB/SOFA in 2009-2011 and installation of SCR by the BART 

compliance date. For a more detailed discussion of this 

approach, please see our proposed FIP at 78 FR at 8288-91. 

                                                           

13 As discussed in greater detail in our proposed rule (78 FR at 

8289, February 5, 2013), EPA notes that LNB with SOFA is a 

potential control option evaluated under BART and that these 

technologies are typically used in conjunction with SCR or other 

add-on controls to first reduce NOX formation during combustion. 

EPA recognizes that the owners of NGS could have waited until 

the compliance date of the final BART determination before 

installing any new controls, including LNB/SOFA, and that the 

early and voluntary NOX reductions achieved beginning in 2009 

were not required under any regulatory program under the CAA. 
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EPA applied this framework to several alternatives we 

developed. In the February 2013 proposal, we proposed one 

Alternative to BART that would provide an additional three to 

five years to NGS in the schedule for the installation of new 

post-combustion control equipment to meet the proposed BART 

limit of 0.055 lb/MMBtu (i.e., Alternative 1 requiring 

compliance with the proposed BART limit on one unit per year in 

2021, 2022, and 2023). Additional NOX emissions resulting from 

delayed compliance were offset by the emissions credit NGS 

achieved by its early and voluntary installation of LNB/SOFA. We 

calculated that under this proposed Alternative 1, total 

adjusted emissions of NOX over 2009-2044 were lower than total 

emissions of NOX under EPA’s proposed BART determination. 

Therefore, EPA proposed to find that Alternative 1 achieves 

greater reasonable progress than BART. 

In the February 2013 proposal, EPA also described, but did 

not propose, two additional alternatives (Alternatives 2 and 3) 

that would provide an additional five to eight years for NGS to 

meet the proposed BART limit of 0.055 lb/MMBtu (i.e., 

Alternatives 2 and 3 called for compliance with the BART limit 

on one unit per year over 2023-2025 and 2024-2026, 

respectively). Total NOX emissions over 2009-2044, after 

accounting for the LNB/SOFA early installation credit, from each 
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of these two additional alternatives both exceeded the BART 

Benchmark. However, under our proposed framework, these two 

additional alternatives would be viable if the owners of NGS 

achieved sufficient additional emission reductions to bridge the 

NOX reduction deficit. EPA requested comment on our proposed 

“better than BART” framework and how NGS might achieve the 

emission reduction bridge necessary for the longer compliance 

schedules under Alternatives 2 and 3 to qualify as “better than 

BART.” 

In both the February 2013 proposal and in the accompanying 

fact sheet, EPA encouraged a robust public discussion of our 

proposed BART determination, our proposed Alternative 1, as well 

as our proposed “better than BART” framework and other possible 

alternatives that meet the framework. In addition, we recognized 

the potential need for a supplemental proposal if other 

approaches developed by other parties are identified as meeting 

the requirements of the CAA.14

After EPA published the proposed FIP on February 5, 2013, 

we received requests for a 90-day extension of the public 

comment period from the Navajo Nation, the Gila River Indian 

Community, SRP, and the Central Arizona Water Conservation 

District (CAWCD), the CAP operating entity, in order to allow 

                                                           

14 See Fact Sheet at 

http://www.epa.gov/region9/air/navajo/index.html#proposed 
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stakeholders additional time to develop alternatives to BART for 

EPA’s consideration. Recognizing the significant time and effort 

necessary to develop viable alternatives and the critical 

importance of active participation by affected parties in the 

development of alternatives to BART, on March 19, 2013, EPA 

extended the close of the public comment period to August 5, 

2013 (78 FR 16825). 

On June 10, 2013, EPA signed a notice, published on June 

19, 2013, of our intent to hold five public hearings throughout 

the state of Arizona (78 FR 36716), at one location each on 

reservation lands of the Navajo Nation and Hopi Tribe, and in 

Page, Phoenix, and Tucson, Arizona. 

On June 20, 2013, SRP submitted a letter, on behalf of 

itself and certain other stakeholders, requesting another 

extension of the comment period for NGS. The SRP letter 

described work that had been on-going for several months with 

representatives from several organizations (the TWG) to develop 

an Alternative to BART. On July 9, 2013, EPA extended the close 

of the public comment period again to October 4, 2013 (78 FR 

41012). On September 16, 2013, EPA signed a notice extending the 
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close of the public comment period a third time, to January 6, 

2014.15

C. Technical Work Group Agreement 

On July 26, 2013, a group of stakeholders known as the TWG 

and composed of the Central Arizona Water Conservation District 

(CAWCD), the Environmental Defense Fund (EDF), the Gila River 

Indian Community (Gila River, or the Community), the Navajo 

Nation, SRP, on behalf of itself and the other non-federal 

Participants, the Department of the Interior, and Western 

Resource Advocates, submitted a document memorializing a multiparty agreement (the TWG Agreement) to EPA for consideration.16

EPA had attended a “kick-off” meeting for the TWG on March 21, 

2013, at which we described our February 5, 2013 proposal, but 

EPA did not have any further participation in the TWG.17 As 

described in Section III of the TWG Agreement, “Summary of 

Agreement Elements; Reasonable Progress Alternative to BART, 

Obligations of Support, and Reservation Right”, the Agreement 

consists of seven elements: (1) a description of a “Reasonable 

                                                           

15 See document number 0172 in the docket for this proposed 

rulemaking at EPA-R09-OAR-2013-0009. 

16 See “Technical Work Group Agreement Related to Navajo 

Generating Station (NGS)” dated July 25, 2013, and submitted to 

EPA on July 26, 2013, in the docket for this proposed rulemaking 

at EPA-R09-OAR-2013-0009-0122. 

17 See document number 0033 in the docket for the proposed 

rulemaking at EPA-R09-OAR-2013-0009. 
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Progress Alternative to BART” (the TWG Alternative);18 (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. 

The TWG Agreement, in its entirety, is included in the 

docket for this proposed rulemaking. Appendix B to the TWG 

Agreement is the only component of the TWG Agreement that is 

applicable to today’s action. EPA is not requesting comment on 

the provisions of the TWG Agreement unrelated to Appendix B, and 

                                                           

18 The “Reasonable Progress Alternative to BART” is a term from 

the TWG Agreement. EPA interprets this term to have the same 

meaning as an Alternative to BART or a “better than BART” 

Alternative, however, we do not otherwise use this term in 

today’s Supplemental Proposal. 
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will not be responding to comments on aspects of the TWG 

Agreement that are not related to our authority under section 

169A of the CAA to require BART or an Alternative to BART. 

II. Legal Background for Proposing the TWG Alternative to BART 

as Achieving Greater Progress Towards the National Visibility 

Goal 

 In our proposed BART determination for NGS on February 5, 

2013 (78 FR 8274), we provided a detailed discussion of the 

statutory and regulatory framework for addressing visibility, 

addressing sources located in Indian country under 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. Please see 77 FR 8275 – 8277 for 

our discussion on these topics. In the following paragraphs, we 

describe the legal background and authority for evaluating 

Alternatives to BART and for providing additional compliance 

flexibility to NGS. 

Under the CAA, compliance with emission limits determined 

as BART must be achieved “as expeditiously as practicable but in 

no event later than five years” after the effective date of the 

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

Therefore, the BART compliance date for NGS would be no later 

than 2019 if the rule is finalized in 2014. As discussed in 
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greater detail in our proposed BART determination, EPA 

recognizes that the circumstances related to NGS create unusual 

and significant challenges for a five-year compliance schedule.19

Based on those challenges and our discretion under the TAR for 

implementing CAA requirements on tribal lands, 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 to BART 

provided the alternative results in greater reasonable progress 

than would have been achieved through installation of BART. 40 

CFR 51.308(e)(2). The regulations provide that an Alternative to 

BART must ensure that all necessary emission reductions occur 

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

                                                           

19 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 five years without also having 

certainty that the lease and contract re-negotiations would 

conclude in a timely and favorable manner. EPA understands that 

the owners of NGS face numerous uncertainties and the unusual 

requirement to comply with NEPA for lease and other rights-ofway 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 

or 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. 
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Thus, if states had submitted timely regional haze SIPs in 2007 

with BART compliance deadlines in 2012, the RHR provided over 

five additional years for the implementation of Alternatives to 

BART. 

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

Alternative to BART (Alternative 1). In particular, EPA proposed 

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. The 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 

U.S.C. § 7601(d)(4), and the TAR, 40 CFR 49.11(a) and proposed 

an extended timeframe for an alternative measure under the RHR 

for NGS. EPA considered this extension of time to be consistent 

with the general programmatic requirements. States and regulated 
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sources accordingly had almost 20 years under the RHR to design 

and implement alternative measures to BART. Because of the 

myriad stakeholder interests and complex governmental interests 

unique to NGS, we are only now addressing the BART requirements 

for NGS. For all the reasons explained above, we considered it 

appropriate to consider an extended compliance period for NGS. 

Our proposal to require emission reductions beyond 2018 was 

supported by the Tribal Authority Rule 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 C.F.R. 49.11(a)] provides the EPA discretion to determine 

what rulemaking is necessary or appropriate to protect air 

quality and requires the EPA to promulgate such rulemaking.” 
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Ariz. Public Serv. Co. v. EPA, 562 F.3d 1116 (10th Cir. 2009). 

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.” Id. While the decision 

in Arizona Public Service Company 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. EPA’s Technical Evaluation of Greater Reasonable Progress 

Towards the National Visibility Goal 

A. Summary of TWG Alternative to BART 

 Appendix B of the TWG Agreement contains the TWG 

Alternative that was submitted to EPA for consideration as a 

”better than BART” Alternative.20 The TWG Alternative was 

developed by the Technical Work Group, which did not include 

                                                           

20 The TWG Alternative is divided into distinct operating 

scenarios that the TWG calls Alternative A and Alternative B. 

The TWG Alternative further divides Alternative A into subscenarios. EPA refers to the sub-scenarios under Alternative A 

as A1, A2, and A3. EPA is reviewing all four scenarios 

(Alternatives A1, A2, A3, and B) together as one Alternative. 
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EPA, to satisfy the “better than BART” requirements of the RHR.21

The core element of the TWG Alternative is that the TWG 

Alternative establishes a cap in NOX emissions over the period 

2009-2044 (the 2009-2044 NOX Cap). The TWG Alternative then 

outlines 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. The 

                                                           

21 The TWG Agreement also states that the TWG Alternative is 

intended to satisfy any requirements of the Reasonably 

Attributable Visibility Impairment (RAVI) program. On May 5, 

2009, the National Parks Conservation Association (NPCA) 

petitioned the Department of the Interior to certify that 

emissions of NOx and particulate matter cause visibility 

impairment at the Grand Canyon National Park. This type of 

visibility impairment, reasonably attributable from a single 

stationary source, is known as Reasonably Attributable 

Visibility Impairment (RAVI). On January 20, 2011, NPCA filed a 

complaint in the United States District Court for the District 

of Columbia contending that the Department of the Interior was 

unreasonably delaying making a finding of reasonable attribution 

from NGS. In a letter dated March 8, 2011 to NPCA, the National 

Park Service (NPS) declined to make such a finding based on 

EPA’s on-going work related to a BART determination for NGS. On 

June 30, 2011, the Court dismissed the complaint holding the NPS 

letter refusing to make the finding of reasonable attribution 

constituted denying the Petitioner’s request for a RAVI finding. 

If NPS were to certify RAVI at Grand Canyon from NGS, EPA must 

determine whether visibility impairment at Grand Canyon is 

indeed reasonably attributable to NGS. If EPA were to make a 

positive attribution determination, then EPA would be required 

to conduct a BART determination for NGS. We note, however, that 

while the process for determining whether a given stationary 

source causes or contributes to RAVI or regional haze are 

different, the process for determining BART under both programs 

is essentially the same. In other words, a BART determination 

for RAVI would likely be the same as a BART determination for 

regional haze. The 2009 NPCA petition, the 2011 NPCA complaint, 

the 2011 letter from NPS, and the 2011 Court decision are all 

included in the docket for this proposed rulemaking. 
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owners of NGS commit to maintaining emissions from NGS below the 

2009-2044 NOX Cap regardless of the post-2019 ownership of NGS 

and the applicable operating scenario. In general, the operating 

scenarios include specific actions for achieving emission 

reductions by 2019 and 2030 to ensure compliance with the 2009-

2044 NOX Cap. The TWG Alternative also provides for an operating 

scenario that is less well-defined but establishes a second NOX

emissions cap over the period of 2009-2029 (the 2009-2029 NOX

Cap) that is equivalent to emission reductions that would be 

achieved by the more well-defined operating scenarios. The 2009-

2029 NOX Cap would apply in addition to the 2009-2044 NOX Cap. 

The TWG Alternative also includes annual reporting requirements 

to EPA. 

The 2009-2044 NOX Cap is calculated based on expected 

emissions that would result if NGS complied with EPA’s proposed 

BART emission limit of 0.055 lb/MMBtu on each unit within five 

years of the effective date of a final rule. The TWG Alternative 

also incorporates EPA’s proposed credit to NGS for the emission 

reductions achieved from the early and voluntary installation of 

LNB/SOFA beginning in 2009 (the LNB/SOFA credit). 

 The TWG Alternative puts forth two main operating 

scenarios, with additional sub-options, for limiting NOX

emissions below the 2009-2044 NOX Cap. These scenarios are called 
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TWG Alternatives A and B. The TWG Alternative provides different 

operating scenarios because of current uncertainty over the 

ownership interests in NGS following the expiration of the 

initial NGS lease term at the end of 2019. Specifically, two 

owners, LADWP and NV Energy, have announced plans to divest from 

any continuing ownership interest in NGS after 2019. These 

owners may retire or sell their interest in NGS. In addition, 

the recent Lease Amendment with the Navajo Nation that extends 

the NGS lease to 2044 includes an option for the Navajo Nation 

to purchase up to a 170 MW ownership share in NGS.22 

Each of the three scenarios under TWG Alternative A (i.e., 

A1, A2, or A3) requires two significant emission reductions, one 

to occur by December 31, 2019 and the other by December 31, 

2030. The emission reductions in the first step, by December 31, 

2019, under TWG Alternative A1 would be achieved through closure 

of one unit. Alternative A2 would entail closure of one unit 

with an increase in capacity, not to exceed 189 MW, at the 

remaining two units; Alternative A3 would entail the curtailment 

of energy production across all three units such that the 

                                                           

22 See Section XI of the “Amendment No. 1 to Indenture of Lease 

Navajo Units 1, 2, and 3 Between the Navajo Nation and Arizona 

Public Service Company, Department of Water and Power of the 

City of Los Angeles, Nevada Power Company dba NV Energy, Salt 

River Project Agricultural Improvement and Power District, and 

Tucson Electric Company”, within document number 0150 in the 

docket for this proposed rulemaking at EPA-R09-OAR-2013-0009. 
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emission reductions are equivalent to the closure of 

approximately one unit. The emission reductions to occur in the 

second step, under Alternatives A1-3, would occur by December 

31, 2030, and would be achieved by compliance of two units at 

NGS with an emission limit of 0.07 lb/MMBtu, achievable with the 

installation of SCR. Under the TWG Alternative, although the 

2009-2044 NOX Cap is calculated based on EPA’s proposed BART 

emission limit of 0.055 lb/MMBtu, the owners of NGS commit to 

meeting a limit of 0.07 lb/MMBtu from the installation of SCR. 

The operator states that a limit of 0.055 lb/MMBtu is not 

achievable for a retrofit application when startup, shutdown, 

and load following emissions are included.23 

Alternative A1 would be triggered if LADWP and NV Energy 

retire their ownership shares of NGS without selling, or if 

LADWP and NV Energy sell their ownership shares to an existing 

NGS participant and the Navajo Nation does not elect to purchase 

an interest in NGS. Alternative A2 is triggered if LADWP or NV 

                                                           

23 See Appendix B.1.A.3 of the Technical Work Group Agreement on 

NGS, document number 0122 in the docket for this proposed 

rulemaking. EPA does not consider the limit of 0.07 lb/MMBtu to 

be a BART emission limit, rather, a component of the TWG 

Alternative. Under the TWG Alternative, this higher emission 

rate is offset by the closure of one unit, or the curtailment of 

generation. In other words, despite the higher emission rate 

under the TWG Alternative compared to EPA’s proposed BART 

emission limit, NGS would comply with the 2009-2044 NOX Cap 

because additional emission reductions are achieved from closure 

or curtailment. 
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Energy sell their ownership shares to an existing NGS 

participant, the Navajo Nation elects to purchase an interest in 

NGS, and the NGS participants can increase the capacity of NGS 

by no more than 189 MW24 without triggering major source preconstruction permitting requirements.25 Alternative A3 is 

triggered if LADWP or NV Energy sell their ownership shares to 

an existing NGS Participant, the Navajo Nation elects to 

purchase an interest in NGS, and the NGS Participants cannot 

increase the capacity of NGS without triggering major source 

pre-construction permitting requirements.

TWG Alternative B would be triggered if LADWP and/or NV 

Energy sell their ownership interest to a third party (i.e., a 

party that is not an existing NGS participant). TWG Alternative 

B establishes similar emission reductions to Alternative A by 

                                                           

24 LADWP owns approximately 477 MW of NGS, while NV Energy owns 

approximately 254 MW. The sum of their shares is 731 MW, which 

is 19 MW short of one 750 MW unit at NGS. The Navajo Nation has 

the option to purchase up to a 170 MW interest in NGS. A 189 MW 

limit in the capacity increase is based on making up the 19 MW 

shortfall and the maximum amount the Navajo Nation can purchase 

(i.e., the sum of 19 MW and 170 MW). 

25 The Prevention of Significant Deterioration (PSD) Program 

generally requires pre-construction permitting for major sources 

if the intended modification increases emissions of certain air 

pollutants above the PSD significance thresholds. The TWG 

Alternative also cites the Nonattainment New Source Review 

Program, a pre-construction permitting program for areas that 

are not in attainment with the National Ambient Air Quality 

Standards (NAAQS). Currently, this program does not apply to NGS 

as it is not located in an area that is out of attainment with 

any of the NAAQS. 
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setting a second NOX emission cap over the 2009-2029 period, 

i.e., the 2009-2029 NOX Cap (calculated to be equivalent to the 

closure of one unit in 2020), in addition to the 2009-2044 NOX

Cap. Alternative B specifies that NOX emissions must be 

maintained below the cap during each applicable period (2009-

2029 and 2009-2044), but does not specify how the NGS owners 

must operate NGS to meet each cap. The TWG Alternative outlines 

annual emissions reporting and planning requirements both to the 

public and to EPA to ensure progress towards emissions goals and 

maintenance of emissions below the 2009-2044 NOX Cap. 

B. EPA’s Technical Evaluation of TWG Alternative to BART 

EPA is proposing to include the TWG Alternative as a second 

“better than BART” Alternative to achieve compliance with the 

RHR.26 We are proposing to determine that the TWG Alternative 

satisfies the requirements of the RHR as discussed below. 

As stated previously, the TWG Alternative establishes a 

2009-2044 NOX Cap based on expected emissions that would result 

if NGS complied with EPA’s proposed BART determination. The TWG 

Alternative also incorporates EPA’s proposed LNB/SOFA credit 

into the 2009-2044 NOX Cap. In our February 5, 2013 proposed 

                                                           

26 In our proposed action on February 5, 2013, EPA proposed a 

BART determination for NGS and Alternative 1 as a “better than 

BART” Alternative. In today’s action, we are proposing that the 

TWG Alternative also meets our “better than BART” framework. 

Taken together, EPA has proposed a BART determination for NGS, 

Alternative 1, and the TWG Alternative. 
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rule, EPA established our proposed BART determination as a BART 

Benchmark based on actual emissions and applied the LNB/SOFA 

credit to each Alternative to BART (to calculate “adjusted” 

emissions). Adjusted emissions, from each Alternative, were then 

compared against the BART Benchmark. As discussed in the 

following paragraphs, these two methods of applying credit for 

the early and voluntary installation of LNB/SOFA beginning in 

2009 are equivalent.27 

As shown in our proposed rulemaking, EPA’s proposed BART 

Benchmark was 358,974 tons of NOX over 2009-2044.28 This value 

was calculated assuming compliance with EPA’s proposed BART 

emission limit of 0.055 lb/MMBtu on January 1, 2018, based on a 

final rule effective date of January 1, 2013. A final rule 

effective date of January 1, 2013 is no longer appropriate for 

NGS because EPA will not issue a final BART rule by that date. 

                                                           

27 See also Spreadsheet titled “Supplemental Better than BART 

Alternatives.xlsx” in the docket for this proposed rulemaking. 

28 See Table 12 at 78 FR at 8290 and document titled “BART 

Alternatives.xlsx” in document number 0005 in the docket for 

this proposed rulemaking at EPA-R09-OAR-2013-0009. In our BART 

proposal, and in calculating the 2009-2044 NOX Cap in this 

Supplemental Proposal, EPA used the average annual NOX emissions 

from NGS over 2001-2008 (34,152 tons) to estimate future annual 

emissions before compliance with the 0.055 lb/MMBtu NOX limit. 

The TWG Alternative also used this value in estimating its cap. 

Estimates for annual emissions in 2020 and thereafter were based 

on the 0.055 lb/MMBtu NOX limit for BART and the average heat 

input over 2001-2008. This method was similarly used by EPA in 

our BART proposal and this Supplemental Proposal, as well as the 

TWG Alternative. 
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The TWG Alternative provided an example calculation for the 

2009-2044 NOX Cap assuming a final rule effective date of 

December 31, 2013, an emission limit of 0.055 lb/MMBtu, and the 

application of the LNB/SOFA credit to the cap.29 The LNB/SOFA 

credit, as applied to the cap, assumes that LNB/SOFA are 

installed at NGS concurrently with SCR, rather than using the 

actual early installation dates on one unit per year over 2009-

2011. The example in the TWG Alternative calculates a 2009-2044 

NOX Cap of 480,490 tons and acknowledges that the cap would 

change depending on the actual effective date of the final rule. 

The difference between the BART Benchmark from EPA’s proposed 

rulemaking (of 358,974 tons) and the example calculated in the 

TWG Alternative (of 480,490 tons) is based on the application of 

the LNB/SOFA credit to the 2009-2044 NOX Cap and the use of a 

different final rule effective date, i.e., 2014 instead of 2013. 

Additionally, in our proposed rulemaking, EPA included a 

transcription error in our calculation of the BART Benchmark, 

which contributes nominally to the difference.30 

                                                           

29 Regarding the final rule effective date, see Infra. at 

footnote 33. 

30 EPA erroneously used the value 5,343 tons per year to 

represent NOX emissions from NGS after installation of SCR. The 

correct value was 5,345 tons per year. See, for example, 

comparison of cells B23 and C23 in “emissions” tab of the 

spreadsheet entitled “BART Alternatives.xlsx” in document number 

0005 in the docket for this proposed rulemaking at EPA-R09-OAR2013-0009. 
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Table 1: Differences between BART Benchmark and Example 

Calculation of NOX Cap from TWG Alternative 

 BART Benchmark 

for NOX

Assumptions 

As reported in 2/5/13 

Proposed Rulemaking 

358,974 tons BART compliance by January 1, 

2018 (final rule effective 

January 1, 2013) 

Step 1: Correction 

for Transcription 

Error 

359,028 tons Transcription Error of 2 tpy 

for 27 years = addition of 54 

tons 

Step 2: Plus 

Correction for 

Revised BART 

Compliance Date 

377,015 tons Change BART Compliance date 

from January 1, 2018 to January 

1, 2019 = Difference between 

LNB/SOFA and SCR+LNB/SOFA for 

one year = 23,325 tons minus 

5,345 tons = 17,980 tons 

Step 3: Plus 

Application of 

LNB/SOFA Credit 

480,489 tons Early emission reductions over 

2009-2018 achieved from 

LNB/SOFA installation = (34,152 

tpy * 10 years) – (30,500 + 

24,427 + 19,837 + (23,325 * 7 

years) = 103,481 tons 

Table 1 shows that the correction for EPA’s transcription error, 

a revised BART compliance date, and the application of the 

LNB/SOFA credit to the BART Benchmark instead of alternatives, 

account for the full difference between EPA’s BART Benchmark, as 

reported in our proposed rulemaking, and the example calculation 

from the TWG Alternative.31

 Using the value from Table 1 of 480,489 tons, representing 

total NOX emissions over 2009-2044 if LNB/SOFA were installed 

concurrently with SCR by 2019, and the value of 377,015 tons, 

representing total NOX emissions over 2009-2044 with actual 

installation years for LNB/SOFA, the LNB/SOFA credit is 103,481 

                                                           

31 Id. 
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tons. As discussed previously, in our proposed rulemaking, EPA 

set, as the BART Benchmark, the value of total NOX emissions over 

2009-2044 based on the actual early installation years for 

LNB/SOFA (i.e., 377,015 tons), and applied the LNB/SOFA credit 

to BART Alternatives to calculated a value for “adjusted 

emissions”. If the “adjusted emissions” were lower than the BART 

Benchmark, the BART Alternative was determined to be “better 

than BART”. The TWG Alternative, instead, applied the LNB/SOFA 

credit to the 2009-2044 NOX Cap (i.e., resulting in 480,489 tons, 

very close to the value reported by TWG of 480,490 tons), and 

calculated total emissions from Alternatives based on the actual 

early installation years for LNB/SOFA. If emissions from the 

BART Alternative are lower than the 2009-2044 NOX Cap, the 

Alternative is “better than BART”. Using Alternative 1 from our 

February 5, 2013 proposed rulemaking, i.e., compliance with the 

proposed BART emission limit in 2021, 2022, and 2023, as an 

example, Table 2 shows that these two methods of comparing 

Alternatives against BART are equivalent.32

 

                                                           

32 See also Spreadsheet titled “Supplemental Better than BART 

Alternatives.xlsx” in the docket for this proposed rulemaking.
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Table 2: EPA and TWG Methods of Comparing Alternatives Against 

BART 

EPA Method

 BART Alternative 1 

Compliance Years By 2019 2021, 2022, 2023 

Total Emissions (tons) 377,008 tons 430,948 tons 

LNB/SOFA Credit n/a 103,481 tons 

Adjusted Emissions n/a 327,467 tons 

Better than BART? n/a Yes, by 49,541 tons 

(377,008 – 327,467 tons) 

TWG Method

 BART Alternative 1 

Compliance Years By 2019 2021, 2022, 2023 

Total Emissions (tons) 377,008 tons 430,948 tons 

LNB/SOFA Credit 103,481 tons n/a 

Adjusted Emissions 480,489 tons n/a 

Better than BART? n/a Yes, by 49,541 tons 

(480,489 – 430,948 tons) 

As discussed previously, EPA anticipates that the 

compliance date for BART would be based on the effective date of 

the final rule, which is typically 60 days following publication 

of the final rule in the Federal Register. Therefore, in 

calculating the 2009-2044 NOX Cap, EPA assumes that an effective 

date of July 1, 2014 is reasonable and justified.33 Based on a 

July 1, 2014 effective date, compliance with the BART emission 

limit must occur by July 1, 2019. Using this compliance date, as 

well as correcting for the transcription error in our proposed 

rulemaking and applying the LNB/SOFA credit to the BART 

                                                           

33 The comment period for EPA’s proposed BART determination and 

Supplemental Proposal will close in January 2013. EPA 

anticipates that a final rule that considers and responds to all 

comments cannot be completed until Spring 2014. Because a final 

rule is typically effective 60 days following publication in the 

Federal Register, EPA anticipates the effective date of the 

final rule will occur no earlier than mid-summer 2014. 
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Benchmark instead of BART Alternatives, EPA calculates the 2009-

2044 NOX Cap to be 494,899 tons.34

 In our proposed BART determination on February 5, 2013, we 

established a framework for evaluating other Alternatives to 

BART, centered on our proposed BART determination that 

calculated a BART benchmark for total NOX emissions over 2009-

2044. We compared total emissions from our proposed alternative, 

Alternative 1 (adjusted for the emission reductions associated 

with the early installation of LNB/SOFA) against the BART 

benchmark to determine that Alternative 1 was “better than 

BART”. The TWG Alternative to BART uses EPA’s BART benchmark to 

establish an emission cap and commits to operate NGS in a manner 

such that total NOX emissions over 2009-2044 remain below the 

2009-2044 NOX Cap, which we calculate to be 494,899 tons. In 

ensuring that total NOX emissions over 2009-2044 from NGS remain 

below the 2009-2044 NOX Cap, the TWG Alternative meets the 

criteria of our proposed “better than BART” framework. 

EPA’s technical evaluation has also focused on whether the 

four potential operating scenarios in the TWG Alternative 

(Alternatives A1 – A3 and B) provide a reasonable basis to 

ensure the NOX emissions will remain below the 2009-2044 NOX Cap 

of 494,899 tons. 

                                                           

34 See also Spreadsheet titled “Supplemental Better than BART 

Alternatives.xlsx” in the docket for this proposed rulemaking.
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 The four possible operating scenarios under the TWG 

Alternative (Alternatives A1, A2, A3, and B) are summarized in 

section III.A of this Supplemental Proposal. These four 

scenarios are also shown in Table 3 and compared against the 

2009-2044 NOX Cap. The 2009-2044 NOX Cap reflects the final rule 

effective date that EPA estimates is reasonable and justified 

for this rulemaking (July 1, 2014), resulting in a BART 

compliance date of July 1, 2019. As discussed above, the 2009-

2044 NOX Cap incorporates the LNB/SOFA early installation credit. 

EPA calculates the 2009-2044 NOx Cap to be 494,899 tons. 

 The three operating scenarios under Alternative A represent 

emission reductions that occur during three distinct periods of 

time: over 2009-2011 (through the early installation of 

LNB/SOFA), by 2020 (from closure or curtailment of one unit, and 

by 2031 (through compliance with a NOX limit of 0.07 lb/MMBtu on 

two units). Similarly, Alternative B represents emission 

reduction that would occur during three distinct periods of 

time: over 2009-2011 (through the early installation of 

LNB/SOFA), any time prior to 2029 (to maintain compliance with 

the 2009-2029 NOX Cap), and any time between 2029 and 2044 (to 

maintain compliance with the 2009-2044 NOX Cap). 

EPA notes that the closure or curtailment of one unit at 

NGS in 2020 would result not only in NOX reductions, but also in 
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reductions of other criteria and hazardous air pollutants, such 

as sulfur dioxide (SO2), particulate matter, and mercury. 

 
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Table 3: Summary of EPA Analysis of TWG Alternative35

TWG Alternative: Maintain Emissions below 2009-2044 NOx Cap u

following operating scenarios: 

A1 A2 A3 

Ownership Possibilities 

If: 

LADWP and NV Energy exit without selling ownership interest or by selling to an existing NGS Participant. 

And: Navajo Nation does 

not purchase ownership interest. 

Navajo Nation purchases interest (up to 170 MW). 

Navajo Nation purchases interest (up to 170 MW). 

And: Owners increase 

capacity (does not trigger permit). 

Owners do not increase capacity (triggers permit). 

Summary of Cap or Operating Scenarios 

2009-2044 NOX

Cap = 494,899 

tons: By 

7/1/2019, meet limit of 0.055 lb/MMBtu through installation of LNB/SOFA concurrently with SCR. 

By 12/31/2019, close one unit. By 12/31/2030, meet NOx limit of 0.07 

lb/MMBtu on two units. 

By 12/31/2019, close one unit. By 12/31/2019, increase net capacity by no more than 189 MW. By 12/31/2030, meet NOx limit of 0.07 

lb/MMBtu on two units. 

Three units could remain open. By 12/31/2019, curtail generation by at least 561 MW. By 12/31/2030, meet NOx limit of 

0.07 lb/MMBtu on two units. 

Estimate of Total NOx over 

2009-2044 435,819 tons 461,816 tons 

35 Graphical representation of these Alternatives against the 2009-2044 NOX 

in Spreadsheet titled “Supplemental Better than BART Alternatives.xlsx” in this proposed rulemaking. 
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 In order to better understand whether the three potential 

operating scenarios under Alternative A provide reasonable 

assurance that emissions from NGS will remain below the 2009-

2044 NOX Cap, EPA estimated annual NOX emissions for each 

potential operating scenario.36 These estimates were based on the 

specific requirements for each scenario and the average heat 

input and average emission rates for each unit operating with 

LNB/SOFA.37 EPA used actual emission data, as reported to the EPA 

Clean Air Markets Program, for 2001 – 2012.38 To estimate tons of 

NOX emitted in the future, EPA calculated the product of annual 

heat input (in MMBtu/year) and the annual average NOX emission 

rate (in lb/MMBtu). In Table 3, estimates for total NOX emissions 

over 2009-2044 were calculated based on the average annual heat 

input over 2001-2012, and the average annual NOX emission rate 

achieved over 2011-2012 (when all three units were operating 

with LNB/SOFA) for the 2013-2018 period, and 0.07 lb/MMBtu for 

the 2020-2044 period. 

 As shown in Table 3, estimates for total NOX emissions 

over 2009-2044 for Alternatives A1, A2, and A3 are all below the 

2009-2044 NOX Cap. This indicates that under TWG Alternative A, 

                                                           

36 Id.

37 Under EPA PSD permit AZ 08-01, November 20, 2008, Units 1-3 at 

NGS operate with modern LNB/SOFA with an emission limit of 0.24 

lb/MMBtu. See documents within EPA-R09-OAR-2013-0009-0005. 

38 Id. See also http://ampd.epa.gov/ampd/. 
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NGS can be reasonably expected to remain below the 2009-2044 NOX

Cap. The TWG Alternative requires the operator of NGS to submit 

an annual report to EPA, which it must also make publicly 

available, that includes annual emissions of SO2 and CO2, and 

annual and cumulative emissions of NOX. In addition, EPA is 

including a provision to require reporting of annual heat input 

at NGS to assess operation and utilization of capacity at NGS. 

Consistent with 40 CFR 51.308(e), the enforceable 2009-2044 

NOX Cap will ensure that total emissions of NOX are less than 

those that would be emitted under our proposed BART 

determination. The weight of evidence, including the operating 

scenarios and annual reporting requirements as discussed above, 

suggest that NGS can be reasonably expected to remain below the 

2009-2044 NOX Cap. 

 As indicated in Table 3, and as discussed previously, the 

operating scenario under TWG Alternative B does not specify the 

exact process that would be used to comply with the 2009-2044 NOX

Cap. To ensure that NOX emission reductions are achieved under 

TWG Alternative B in a manner similar to TWG Alternative A1-A3, 

the TWG Alternative imposes a nested NOX emission cap for the 

2009-2029 period (the 2009-2029 NOX Cap) that would apply in 

addition to the 2009-2044 NOX Cap. Under TWG Alternative B, the 

2009-2029 NOX Cap would be equivalent to total NOX emissions over 
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2009-2029 that would be achieved under TWG Alternative A1, i.e., 

closure of one unit by December 31, 2019. Thus, under TWG 

Alternative B, NGS must still reduce NOX emissions over 2009-2029 

and 2030-2044 in order to comply with the 2009-2029 and 2009-

2044 NOX Caps, but the operator would have flexibility to 

determine the timing and method of reducing emissions. 

To evaluate TWG Alternative B, EPA estimated potential 

emission reduction timeframes that would be needed to comply 

with the 2009-2029 and 2009-2044 NOX Caps assuming the owners of 

NGS elect to install SCR on all three units at NGS.39 Using the 

average annual heat input over 2001-2012, and the average annual 

NOX emission rate achieved over 2011-2012 (when all three units 

were operating with LNB/SOFA), if NGS achieves emission rates of 

0.07 lb/MMBtu or below after installation of SCR, the owners of 

NGS would need to install SCR on one unit each in 2026, 2027, 

and 2028 in order to comply with the 2009-2029 and 2009-2044 NOX

Caps. If NGS achieves emission rates of 0.055 lb/MMBtu or below, 

the owners of NGS would need to install SCR on one unit each in 

2028, 2029, and 2030 in order to comply with the 2009-2029 and 

                                                           

39 Although Alternative B does not specify how the caps will be 

maintained, installation of SCR on all units at NGS is a 

reasonable compliance option, and therefore, EPA is using this 

as an example for further examination of Alternative B. See 

spreadsheet, titled “Supplemental Better than BART 

Alternatives.xlsx”. 
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2009-2044 NOX Caps. In addition to the option of installing SCR 

on each unit, under TWG Alternative B, the owners of NGS could 

elect to implement any operating scenario (including 

curtailment, installation of other technologies to reduce 

emissions of NOX, or a combination of options or technologies) as 

long as the operational changes result in reduced emissions of 

NOX sufficient to maintain emissions below the applicable NOX

Cap. 

To ensure compliance, the annual reporting requirements 

that apply to TWG Alternative A would also apply under TWG 

Alternative B. In addition, if TWG Alternative B is triggered, 

the operator of NGS would be required to submit annual Emission 

Reduction Plans to EPA that would identify the potential 

emission reductions measures and operating scenarios to comply 

with the 2009-2029 or 2009-2044 NOX Caps. Each potential 

operating scenario in each annual Emission Reduction Plan must 

show compliance with the applicable NOX Cap. 

Consistent with 40 CFR 51.308(e), the enforceable 2009-2029 

and 2009-2044 NOX Caps will ensure that total emission reductions 

of NOX are greater than those that would be achieved under our 

proposed BART determination. The weight of evidence, including 

possible operating scenarios and the reporting requirements as 
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discussed above, indicate that NGS can be reasonably expected to 

remain below the 2009-2029 and 2009-2044 NOX Caps. 

Based on our analysis of the operating scenarios under TWG 

Alternatives A1-A3 and B, EPA is proposing to determine that the 

TWG Alternative meets EPA’s “better than BART” framework 

outlined in our February 5, 2013 proposed BART determination for 

NGS. 

IV. EPA’s Supplemental Proposal 

 In addition to our proposed BART determination and 

Alternative 1 for NGS dated February 5, 2013, in today’s action, 

EPA is supplementing our proposal with the TWG Alternative 

submitted to EPA on July 26, 2013 as an additional “better than 

BART” Alternative. Because we are supplementing our February 5, 

2013 proposed rulemaking with today’s proposal, after 

considering public comments, EPA may finalize provisions from 

either or both proposals, i.e., our proposed BART determination, 

proposed Alternative 1, or the TWG Alternative. 

EPA is proposing to determine that the TWG Alternative 

ensures that total emissions of NOX from NGS over 2009-2044 will 

remain below the total emissions from NGS over 2009-2044 that 

would have occurred under BART. In today’s action, EPA is 

proposing to establish enforceable requirements to comply with 

the proposed 2009-2044 NOX Cap, and if applicable, a 2009-2029 
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NOX Cap, including annual reporting requirements related to heat 

input, emissions of SO2 and CO2, and annual and cumulative 

emissions of NOX. In addition, if the final ownership outcome 

triggers the operating scenarios under Alternatives A1-A3, EPA 

is proposing to establish the emission reduction milestones 

under A1-A3 (closure of one unit or curtailment of electricity 

generation by December 31, 2019, and installation of SCR on two 

units by December 31, 2030) as enforceable requirements. If the 

final ownership outcome triggers Alternative B, EPA is proposing 

to require the owners of NGS to submit annual Emission Reduction 

Plans to EPA to achieve the NOX emission reductions necessary to 

assure compliance with the 2009-2029 and 2009-2044 NOX Caps. EPA 

is also proposing to require the owners of NGS to notify EPA no 

later than December 1, 2019, of the final ownership outcome and 

the resulting applicable operating scenario that it will 

implement. For the reasons outlined above, EPA is supplementing 

our February 5, 2013 proposed rulemaking to also propose the TWG 

Alternative as a “better than BART” Alternative that ensures 

greater reasonable progress towards the national visibility goal 

than BART. 

EPA is accepting public comment concurrently on our 

February 5, 2013 proposed BART determination and proposed 

Alterative 1 and the TWG Alternative put forth in today’s 
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Supplemental Proposal. From November 12-15, 2013, EPA will be 

holding five open house and public hearing events throughout 

Arizona to accept written and oral comment on our proposed 

rulemaking and Supplemental Proposal. The comment period for our 

February 5, 2013 proposed rulemaking and today’s Supplemental 

Proposal closes on January 6, 2014. 

V. Statutory and Executive Order Reviews 

A. Executive Order 12866: Regulatory Planning and Review and 

Executive Order 13563: Improving Regulation and Regulatory 

Review 13563 

This action supplements our proposed source-specific 

Federal Implementation Plan for the Navajo Generating Station to 

propose and take comment on an additional Alternative to BART 

that was developed by and agreed upon by a group of seven 

stakeholders. Under the terms of Executive Order (EO) 12866 (58 

FR 51735, October 4, 1993) and EO 13563 (76 FR 3821, January 21, 

2011), because this proposed rule applies to only one facility, 

it is not a rule of general applicability. This proposed rule, 

therefore, is exempt from review under EO 12866 and EO 13563. 

B. Paperwork Reduction Act 

This action does not impose an information collection 

burden under the provisions of the Paperwork Reduction Act, 44 
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U.S.C. 3501 et seq. Burden is defined at 5 CFR 1320.3(b). Under 

the Paperwork Reduction Act, a “collection of information” is 

defined as a requirement for “answers to . . . identical 

reporting or recordkeeping requirements imposed on ten or more 

persons . . . .” 44 U.S.C. 3502(3)(A). Because the Supplemental 

Proposal applies to a single facility, Navajo Generating 

Station, the Paperwork Reduction Act does not apply. 

C. Regulatory Flexibility Act 

The Regulatory Flexibility Act (RFA) generally requires an 

agency to prepare a regulatory flexibility analysis of any rule 

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 proposed 

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-for-
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profit enterprise which is independently owned and operated and 

is not dominant in its field. 

After considering the economic impacts of this proposed 

action on small entities, I certify that this proposed 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 

proposed 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 continue to be interested in 

the potential impacts of the proposed rule and this Supplemental 

Proposal on small entities and welcome comments on issues 

related to such impacts. 

D. Unfunded Mandates Reform Act (UMRA) 

Title II of the Unfunded Mandates Reform Act of 1995 

(UMRA), 2 U.S.C. 1531-1538, requires Federal agencies, unless 

otherwise prohibited by law, to assess the effects of their 

regulatory actions on State, local, and tribal governments and 

the private sector. Federal agencies must also develop a plan to 

provide notice to small governments that might be significantly 

or uniquely affected by any regulatory requirements. The plan 

must enable officials of affected small governments to have 

meaningful and timely input in the development of EPA regulatory 
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proposals with significant Federal intergovernmental mandates 

and must inform, educate, and advise small governments on 

compliance with the regulatory requirements. 

This rule does not contain a Federal mandate that may 

result in expenditures of $100 million or more for state, local, 

and tribal governments, in the aggregate, or the private sector 

in any one year. EPA anticipates the annual cost to the private 

sector of this Supplemental Proposal, which involves compliance 

with BART emission limits by two units, rather than three units, 

to be lower than the anticipated cost of EPA’s proposed BART 

determination of $64 million per year (see Table 2 of EPA’s 

proposed BART determination at 78 FR 8274, February 5, 2013). 

Thus, this Supplemental Proposal is not subject to the 

requirements of sections 202 or 205 of UMRA. This proposed rule 

will not impose direct compliance costs on state, local or 

tribal governments. This proposed action will, if finalized, 

reduce the emissions of NOX from a single source, the Navajo 

Generating Station. 

In developing this rule, EPA consulted with small 

governments pursuant to a plan established under section 203 of 

UMRA to address impacts of regulatory requirements in the rule 

that might significantly or uniquely affect small governments. 

EPA put forth an Advanced Notice of Proposed Rulemaking on 
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August 28, 2009 regarding our intention to propose a BART 

determination for NGS and the Four Corners Power Plant. We 

received comments from numerous small governments, including 

tribal governments, and governments of several towns in Arizona. 

This proposed rule will not impose direct compliance costs on 

any small governments. However, increased electricity and water 

costs associated with this proposed rule may indirectly affect 

small governments. 

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 action proposes 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 

Under 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 
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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. 

EPA has concluded that this proposed action will have 

tribal implications, and consequently EPA has consulted with 

tribal officials during the process of developing the proposed 

regulation and will continue to consult with tribal officials 

during the process to take final action. EPA notes that the TWG 

Alternative, on which this Supplemental Proposal is based, was 

developed by a group of seven stakeholders that included the 

Navajo Nation and the Gila River Indian Community. However, we 

also note that not all tribes that may be affected by this 

proposed alternative were among the stakeholders. Other tribes 

may have views on this alternative and EPA welcomes their 

comments. The proposed regulation will not pre-empt tribal law. 

The proposed regulation will also not impose direct compliance

costs on a tribal government, because the direct compliance 

costs of this proposed rule, if finalized, will be borne by the 

owners of NGS. However, because several tribes located in 

Arizona rely directly or indirectly on NGS, there may be 

indirect impacts of this proposed rule on these tribes. The 
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Navajo Nation and Hopi Tribe receive coal-related royalties, 

taxes and employment at NGS and the Kayenta Mine that contribute 

to their economies. Several tribes in Arizona have allocations 

of CAP water under existing water settlement agreements. Because 

of the inter-relationship of CAP and NGS, impacts to NGS may 

also impact CAP and the tribes that use CAP water or otherwise 

benefit from CAP according to Congressionally-approved water 

settlement agreements. The importance to tribes of continued 

operation of NGS and affordable water costs cannot be 

overemphasized. In Section II.B.ii of EPA’s proposed BART 

determination dated February 5, 2013 (78 FR8274), EPA explains 

in detail the tribal information that we received and considered 

in this proposed rulemaking. 

In addition to our consultation with tribes discussed in 

our February 5, 2013 proposed rulemaking, EPA has had additional 

meetings and conference calls with tribes at their request since 

the time we received the TWG Alternative, and during our process 

of evaluating the TWG Alternative. On August 22, 2013, we met 

with Governor Gregory Mendoza and other representatives from the 

Gila River Indian Community.40 On August 28, 2013, EPA met with 

President Ben Shelly and other representatives from the Navajo 

                                                           

40 See document number 0152 in the docket for the proposed 

rulemaking at EPA-R09-OAR-2013-0009. 
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Nation.41 We held a conference call on September 13, 2013 with 

Chairman LeRoy Shingoitewa and another representative from the 

Hopi Tribe.42 Chairman Shingoitewa also submitted a letter to 

EPA, dated August 19, 2013, expressing several concerns related 

to the TWG Alternative.43 An updated timeline of all 

correspondence and consultation with tribes on NGS is included 

in the docket for this proposed rulemaking.44 

EPA recognizes that the Navajo Nation and the Gila River 

Indian Community participated in the development of the TWG 

Agreement on NGS and were signatories on the Agreement. However, 

EPA also understands from discussions with President Shelly and 

Governor Mendoza that concerns, related to potential impacts to 

their respective tribes from BART and the TWG Alternative, still 

exist. EPA understands that Chairman Shingoitewa has numerous 

concerns related to the TWG Agreement and Alternative, including 

the exclusion of the Hopi Tribe from the TWG and the development 

of the TWG Agreement, and the extended timeframe for the 

installation of new air pollution controls at NGS under the TWG 

                                                           

41 See document number 0150 in the docket for the proposed 

rulemaking at EPA-R09-OAR-2013-0009. 

42 See document number 0166 in the docket for the proposed 

rulemaking at EPA-R09-OAR-2013-0009.

43 See document number 0134 in the docket for the proposed 

rulemaking at EPA-R09-OAR-2013-0009. 

44 See document titled “Timeline of All Tribal Consultations on 

Navajo BART FIPs as of September 17 2013” in the docket for this 

proposed rulemaking. 
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Alternative. EPA will continue to consult with Tribal officials 

during and following the public comment period on the proposed 

FIP. 

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 proposed rule is not subject to Executive Order 13045 

because it requires emissions reductions of NOx from a single 

stationary source. Because this proposed action only applies to 

a single source and is not a proposed 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 extent that 
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the rule will reduce emissions of NOx, which contribute to ozone 

and fine particulate matter formation as well as visibility 

impairment, 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 exempt 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. 
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Consistent with the NTTAA, the Agency conducted a search to 

identify potentially applicable VCS. For the measurements 

listed 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 proposed 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 
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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 

environmental effects of their programs, policies, and 

activities on minority populations and low-income populations in 

the United States. 

EPA has determined that this proposed rule, if finalized, 

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. 

This proposed rule requires emissions reductions of NOx from a 

single stationary source, Navajo Generating Station. 

List of Subjects in 40 CFR Part 49 

 Environmental protection, Air pollution control, Indians, 

Intergovernmental relations, Nitrogen Dioxide. 

Authority: 42 U.S.C. 7401 et seq. 

September 25, 2013 /s/ 
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9/25/2013. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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Dated: Jared Blumenfeld, 

 Regional Administrator, Region 9.

Title 40, chapter I of the Code of Federal Regulations is 

proposed to be amended as follows: 

PART 49--[AMENDED] 

 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 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), shall not be affected thereby. 
This document is a prepublication version, signed by the EPA Regional Administrator, Jared Blumenfeld, on

9/25/2013. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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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. 

(2) Definitions. Terms not defined below shall 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 is no more than 416,865 tons of NOX. 

This value is calculated based on the sum of annual emissions 

over January 1, 2009 to December 31, 2029, and closure of one 

unit by December 31, 2019. 

(ii) 2009-2044 NOX Cap is no more than 494,899 tons of NOX. 

This value is calculated based on the sum of annual emissions 

over January 1, 2009 to December 31, 2044, and compliance with a 

BART emission limit of 0.055 lb/MMBtu on each Unit by July 1, 

2019. 

(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. 
This document is a prepublication version, signed by the EPA Regional Administrator, Jared Blumenfeld, on

9/25/2013. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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(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. 

(vi) Emission limitation or emission limit means the 

federal emissions limitation required by this paragraph. 

(vii) 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 

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 one Unit each over 2009-

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 
This document is a prepublication version, signed by the EPA Regional Administrator, Jared Blumenfeld, on

9/25/2013. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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(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(s)/operator(s) 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. 

(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) BART Determination. BART for NGS is a NOX emission limit 

of 0.055 lb/MMBtu on each Unit with a compliance date of July 1, 

2019, and is used to establish a cap in NOX emissions, known as 

the 2009-2044 NOX Cap. The owner/operator shall demonstrate BART 

compliance by ensuring that total NOX emissions from NGS, over 

January 1, 2009 to December 31, 2044, do not exceed the 2009-

2044 NOx Cap. The owner/operator shall implement the applicable 

operating scenario, under paragraph (j)(3)(i), to ensure NOX
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9/25/2013. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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emission reductions sufficient to maintain total NOX emissions 

below the 2009-2044 NOx Cap. 

(i) Operating Scenarios to Comply with 2009-2044 NOX Cap. 

(A) Alternative A1. 

(1) By December 31, 2019, the owner/operator shall 

permanently cease operation of one coal-fired Unit. 

(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. 

(B) Alternative A2. 

(1) By December 31, 2019, the owner/operator shall 

permanently cease operation of one coal-fired Unit.

(2) By December 31, 2019, the owner/operator may elect to 

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. The 

owner/operator shall ensure that any increase in the net 

generating capacity is in compliance with all pre-construction 

permitting requirements, as applicable. 
This document is a prepublication version, signed by the EPA Regional Administrator, Jared Blumenfeld, on

9/25/2013. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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(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.

(C) Alternative A3. 

(1) By December 31, 2019, the owner/operator shall 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, purchased by the Navajo Nation by 

December 31, 2019. 

(2) By December 31, 2030, the owner/operator shall comply 

with a NOX emission limit of 0.07 lb/MMBtu on two Units. 

(D) Alternative B. In addition to the 2009-2044 NOx Cap that 

applies between January 1, 2009 to December 31, 2044, during the 

January 1, 2009 to December 31, 2029 period, the owner/operator 

shall ensure compliance with the 2009-2029 NOX Cap. 

(ii) Applicability of Alternatives. 

(A) Alternative A1 shall apply if both of the Departing 

Participants retire their ownership interests in NGS by December 

31, 2019, and the Navajo Nation does not purchase an ownership 

share of NGS by December 31, 2019; or if both of the Departing 

Participants sell their ownership interests to Existing 

Participants, and the Navajo Nation does not purchase an 
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9/25/2013. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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ownership share of NGS by December 31, 2019; or if one of the 

Departing Participants retires its ownership interest and the 

other Departing Participant sells its ownership interest to an 

Existing Participant, and the Navajo Nation does not purchase an 

ownership share of NGS by December 31, 2019. 

(B) Alternative A2 shall apply if both of the Departing 

Participants sell their ownership interests to Existing 

Participants, the Navajo Nation elects to purchase an ownership 

share of NGS by December 31, 2019, and the owner/operator elects 

to increase net generating capacity of the two remaining Units; 

or if one of the Departing Participants retires its ownership 

interest and the other Departing Participant sells its ownership 

interest to an Existing Participant, the Navajo Nation elects to 

purchase an ownership share of NGS by December 31, 2019, and the 

owner/operator elects to increase net generating capacity of the 

two remaining Units. 

(C) Alternative A3 shall apply if both of the Departing 

Participants sell their ownership interests to Existing 

Participants, the Navajo Nation elects to purchase an ownership 

share of NGS by December 31, 2019, and the owner/operator does 

not elect to increase net generating capacity; or if one of the 

Departing Participants retires its ownership interest and the 

other Departing Participant sells its ownership interest to an 
This document is a prepublication version, signed by the EPA Regional Administrator, Jared Blumenfeld, on

9/25/2013. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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Existing Participant, the Navajo Nation elects to purchase an 

ownership share of NGS by December 31, 2019, and the 

owner/operator does not elect to increase net generating 

capacity. 

(D) Alternative B shall apply if, by December 31, 2019, any 

of the Departing Participants sell their ownership interests to 

a Party that is not an Existing Participant. 

(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 January 31, 2015, and annually thereafter 

until the earlier of December 22, 2044 or the date on which the 

owner/operator ceases conventional coal-fired generation at NGS, 

the owner/operator shall submit to the Regional Administrator, a 

report summarizing the annual heat input, the annual emissions 

of sulfur dioxide, carbon dioxide, and annual and cumulative 

emissions of NOX from NGS for the previous full calendar year. 

The owner/operator shall make this report available to the 

public, either through a link on its website or directly on its 

website. 

(iii) No later than December 31, 2020, the owner/operator 

shall submit an application to revise its existing Part 71 
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9/25/2013. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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Operating Permit to incorporate the requirements and emission 

limits of the applicable Alternative to BART under paragraph 

(j)(3). 

(iv) In addition to the requirements of paragraphs 

(j)(4)(i), (ii) and (iii), if Alternative B applies, the 

owner/operator shall 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 shall submit an 

Emission Reduction Plan containing anticipated year-by-year 

emissions covering the period from 2020 to 2029 that will assure 

that the operation of NGS will result 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, 
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9/25/2013. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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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 

forth in the Emission Reduction Plan, provided the revised plan 

ensure that NOX emissions remain below the 2009-2044 NOX Cap. 

(5) Continuous emission monitoring system (CEMS). 

(i) At all times, the owner/operator of each unit shall 

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. 

Valid data means data recorded when the CEMS is not out-ofcontrol as defined by Part 75, as defined in paragraph (j)(2) of 

this section. All valid CEMS hourly data shall be used to 
This document is a prepublication version, signed by the EPA Regional Administrator, Jared Blumenfeld, on

9/25/2013. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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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 

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) 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 twentynine (29) Boiler Operating Days; (2) sum the total heat input to 

the Unit in MMBtu during the current Boiler Operating Day and 
This document is a prepublication version, signed by the EPA Regional Administrator, Jared Blumenfeld, on

9/25/2013. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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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. 

(7) Recordkeeping. The owner or operator of each unit shall 

maintain the following records for at least five years: 

(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 calendar day rolling average group emission rates 

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. 
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9/25/2013. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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(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) Records of all major maintenance activities conducted 

on emission units, air pollution control equipment, and CEMS. 

(vii) Any other records required by 40 CFR Part 75. 

(8) Reporting. All reports and notifications under this 

paragraph (j) shall 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. 

(i) The owner/operator shall 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 shall 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), for each unit’s last 
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9/25/2013. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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30 boiler operating days. Included in this report shall be 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). 

(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 

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 or 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 
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9/25/2013. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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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)(1) and (g)(3) of this section, 

related only to malfunctions, apply to this paragraph (j).