46852 Federal Register / Vol. 81, No. 138 / Tuesday, July 19, 2016 / Proposed Rules 

1Although states and tribes may designate as 

Class I additional areas which they consider to have 

visibility as an important value, the requirements of 

the visibility program set forth in section 169A of 

the CAA apply only to ‘‘mandatory Class I Federal 

areas.’’ 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R09–OAR–2016–0292; FRL–9949–06– 

Region 9] 

Approval and Revision of Air Plans; 

Arizona; Regional Haze State and 

Federal Implementation Plans; 

Reconsideration 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is proposing to approve a 

source-specific revision to the Arizona 

State Implementation Plan (SIP) that 

addresses requirements for best 

available retrofit technology (BART) at 

Cholla Generating Station (Cholla). The 

EPA proposes to find that the SIP 

revision fulfills the requirements of the 

Clean Air Act (CAA) and the EPA’s 

Regional Haze Rule (RHR) for BART at 

Cholla. In conjunction with this 

proposed approval, we propose to 

withdraw those portions of the federal 

implementation plan (FIP) that address 

BART for Cholla. We previously 

partially granted petitions for 

reconsideration of that FIP from Cholla’s 

owners, Arizona Public Service 

Company (APS) and PacifiCorp. We are 

now proposing to find that final 

withdrawal of the FIP, as it applies to 

Cholla, would constitute our action on 

APS’s and PacifiCorp’s petitions for 

reconsideration of the FIP. 

DATES: Written comments must be 

received on or before September 2, 

2016. Requests for public hearing must 

be received on or before August 3, 2016. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–R09– 

OAR–2016–0292 at http://

www.regulations.gov, or via email to 

limaye.vijay@epa.gov. For comments 

submitted at Regulations.gov, follow the 

online instructions for submitting 

comments. Once submitted, comments 

cannot be edited or removed from 

Regulations.gov. For either manner of 

submission, the EPA may publish any 

comment received to its public docket. 

Do not submit electronically any 

information you consider to be 

Confidential Business Information (CBI) 

or other information whose disclosure is 

restricted by statute. Multimedia 

submissions (audio, video, etc.) must be 

accompanied by a written comment. 

The written comment is considered the 

official comment and should include 

discussion of all points you wish to 

make. The EPA will generally not 

consider comments or comment 

contents located outside of the primary 

submission (i.e. on the web, cloud, or 

other file sharing system). For 

additional submission methods, please 

contact the person identified in the FOR

FURTHER INFORMATION CONTACT section. 

For the full EPA public comment policy, 

information about CBI or multimedia 

submissions, and general guidance on 

making effective comments, please visit 

http://www2.epa.gov/dockets/

commenting-epa-dockets. 

FOR FURTHER INFORMATION CONTACT: 

Vijay Limaye, U.S. EPA, Region 9, 

Planning Office, Air Division, Air–2, 75 

Hawthorne Street, San Francisco, CA 

94105. Vijay Limaye can be reached at 

telephone number (415) 972–3086 and 

via electronic mail at limaye.vijay@

epa.gov. 

SUPPLEMENTARY INFORMATION: 

Throughout this document, ‘‘we,’’ ‘‘us’’ 

and ‘‘our’’ refer to the EPA. 

Table of Contents 

I. General Information 

II. Background 

III. Summary of the Cholla SIP Revision 

IV. The EPA’s Evaluation of the Cholla SIP 

Revision 

V. Proposed Action 

VI. Environmental Justice Considerations 

VII. Incorporation by Reference 

VIII. Statutory and Executive Order Reviews 

I. General Information 

A. Definitions 

For the purpose of this document, we 

are giving meaning to certain words or 

initials as follows: 

• The words or initials Act or CAA 

mean or refer to the Clean Air Act, 

unless the context indicates otherwise. 

• The initials ADEQ mean or refer to 

the Arizona Department of 

Environmental Quality. 

• The initials AFUDC mean or refer to 

Allowance for Funds Used During 

Construction. 

• The initials APS mean or refer to 

Arizona Public Service Company. 

• The words Arizona and State mean 

the State of Arizona. 

• The initials BART mean or refer to 

Best Available Retrofit Technology. 

• The term Class I area refers to a 

mandatory Class I Federal area.1

• The initials CBI mean or refer to 

Confidential Business Information. 

• The initials CCM mean or refer to 

the EPA’s Control Cost Manual. 

• The words EPA, we, us or our mean 

or refer to the United States 

Environmental Protection Agency. 

• The initials FIP mean or refer to 

Federal Implementation Plan. 

• The initials LNB mean or refer to 

low-NOX burners. 

• The initials MMBtu mean or refer to 

million British thermal units 

• The initials NOX mean or refer to 

nitrogen oxides. 

• The initials OFA mean or refer to 

over fire air. 

• The initials PM10 mean or refer to 

particulate matter with an aerodynamic 

diameter of less than 10 micrometers. 

• The initials RHR mean or refer to 

the EPA’s Regional Haze Rule. 

• The initials RP mean or refer to 

Reasonable Progress. 

• The initials RPG or RPGs mean or 

refer to Reasonable Progress Goal(s). 

• The initials SCR mean or refer to 

Selective Catalytic Reduction. 

• The initials SIP mean or refer to 

State Implementation Plan. 

• The initials SNCR mean or refer to 

Selective Non-catalytic Reduction 

• The initials SOFA mean or refer to 

separated over fire air. 

• The initials SO2 mean or refer to 

sulfur dioxide. 

B. Docket 

The EPA has established docket 

number EPA–R09–OAR–2016–0292 for 

this action. Generally, documents in the 

docket for this action are available 

electronically at http://

www.regulations.gov or in hard copy at 

EPA Region IX, 75 Hawthorne Street, 

San Francisco, California 94105–3901. 

While all documents in the docket are 

listed at http://www.regulations.gov, 

some information may be publicly 

available only at the hard copy location 

(e.g., copyrighted material, large maps, 

multi-volume reports), and some may 

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

confidential business information 

(CBI)). To inspect the hard copy 

materials, please schedule an 

appointment during normal business 

hours with the contact listed in the FOR

FURTHER INFORMATION CONTACT section. 

C. Public Hearings 

If anyone contacts the EPA by August 

3, 2016 requesting to speak at a public 

hearing, the EPA will schedule a public 

hearing and announce the hearing in the 

Federal Register. Contact Vijay Limaye 

at (415) 972–3086 or at limaye.vijay@

epa.gov to request a hearing or to 

determine if a hearing will be held. 


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2 77 FR 42834, 42837–42839 (July 20, 2012), 

(Arizona Regional Haze ‘‘Phase 1’’ Rule) 77 FR 

75704, 75709–75712 (December 21, 2012), (Arizona 

Regional Haze ‘‘Phase 2’’ Rule). 

3 42 U.S.C. 7491(a)(1). 

4See CAA section 169B, 42 U.S.C. 7492. 

5Areas designated as mandatory Class I Federal 

areas consist of national parks exceeding 6000 

acres, wilderness areas and national memorial parks 

exceeding 5000 acres, and all international parks 

that were in existence on August 7, 1977. 42 U.S.C. 

7472(a). When we use the term ‘‘Class I area’’ in this 

action, we mean a ‘‘mandatory Class I Federal 

area.’’ 

6See generally 40 CFR 51.308. 

7 40 CFR 51.308(e). 

8 40 CFR 51.308(e)(2). 

9We note that, while ADEQ referred to its Step 

5 as an evaluation of energy and non-air quality 

environmental impacts, this step also includes 

consideration of the costs of compliance and the 

remaining useful life of the source, consistent with 

the BART Guidelines, 40 CFR part 51, appendix Y, 

section IV.D.4. 

10Arizona Regional Haze SIP Revision, Appendix 

D, section XI. 

11 77 FR 72511. 

II. Background 

A. Statutory and Regulatory Background 

This section provides a brief overview 

of the requirements of the CAA and 

RHR, as they apply to this particular 

action. Please refer to our previous 

rulemakings on the Arizona Regional 

Haze SIP for additional background 

regarding the visibility protection 

provisions of the CAA and the RHR.2

In section 169A of the 1977 

Amendments to the CAA, Congress 

created a program for protecting 

visibility in the nation’s national parks 

and wilderness areas. This section of the 

CAA establishes as a national goal the 

‘‘prevention of any future, and the 

remedying of any existing, impairment 

of visibility in mandatory Class I 

Federal areas which impairment results 

from manmade air pollution.’’ 3 It also 

directs states to evaluate the use of 

retrofit controls at certain larger, often 

uncontrolled, older stationary sources in 

order to address visibility impacts from 

these sources. Specifically, section 

169A(b)(2)(A) of the CAA requires states 

to revise their SIPs to contain such 

measures as may be necessary to make 

reasonable progress towards the natural 

visibility goal, including a requirement 

that certain categories of existing major 

stationary sources built between 1962 

and 1977 (known as ‘‘BART-eligible’’ 

sources) procure, install, and operate 

BART. In the 1990 CAA Amendments, 

Congress amended the visibility 

provisions in the CAA to focus attention 

on the problem of regional haze, which 

is visibility impairment produced by a 

multitude of sources and activities 

located across a broad geographic area.4

In 1999, we promulgated the RHR, 

which requires states to develop and 

implement SIPs to ensure reasonable 

progress toward improving visibility in 

mandatory Class I Federal areas (Class I 

areas) 5 by reducing emissions that 

cause or contribute to regional haze.6

Under the RHR, states are directed to 

conduct an analysis and make a BART 

determination for each BART-eligible 

source that may be anticipated to cause 

or contribute to any visibility 

impairment in a Class I area.7 In 

particular, under CAA section 

169A(g)(2) and 40 CFR 

51.308(e)(1)(ii)(A), states must analyze 

and consider the following five factors 

as part of each source-specific BART 

analysis: (1) The costs of compliance of 

each technically feasible control 

technology, (2) the energy and non-air 

quality environmental impacts of 

compliance of the control technologies, 

(3) any existing pollution control 

technology in use at the source, (4) the 

remaining useful life of the source, and 

(5) the degree of improvement in 

visibility which may reasonably be 

anticipated to result from the use of 

such technology (collectively known as 

the ‘‘five-factor BART analysis’’). 

In 2005, the EPA published the 

Guidelines for BART Determinations 

under the Regional Haze Rule at 

Appendix Y to 40 CFR part 51 (‘‘BART 

Guidelines’’) on July 6, 2005. The BART 

Guidelines assist states in determining 

which of their sources should be subject 

to the BART requirements and in 

determining appropriate emission limits 

for each such ‘‘subject-to-BART’’ source. 

In making BART determinations for 

fossil fuel-fired electric generating 

plants with a total generating capacity 

in excess of 750 megawatts, states must 

use the approaches set forth in the 

BART Guidelines. States are 

encouraged, but not required, to follow 

the BART Guidelines in making BART 

determinations for other types of 

sources. In lieu of requiring sourcespecific BART controls, states also have 

the flexibility to adopt an alternative 

measure as long as the alternative 

provides greater reasonable progress 

towards natural visibility conditions 

than BART (i.e., the alternative must be 

‘‘better than BART’’).8

In addition to the visibility protection 

requirements of the CAA and the RHR, 

SIP revisions concerning regional haze 

are also subject to the general 

requirements of CAA section 110. In 

particular, they are subject to the 

requirement in CAA section 110(l) that 

SIP revisions must not ‘‘interfere with 

any applicable requirement concerning 

attainment and reasonable further 

progress (as defined in [CAA section 

171]), or any other applicable 

requirement of [the CAA],’’ as well as 

the requirement in CAA section 

110(a)(2)(A) that SIPs must include 

enforceable emission limits. 

B. Cholla Generating Station 

Cholla Generating Station consists of 

four primarily coal-fired electricity 

generating units with a total plant-wide 

generating capacity of 1,150 megawatts. 

Unit 1 is a 126 MW tangentially-fired, 

dry-bottom boiler that is not BARTeligible. Units 2, 3 and 4 have capacities 

of 272 MW, 272 MW and 410 MW, 

respectively, and are tangentially-fired, 

dry-bottom boilers that are each BARTeligible. Units 1, 2, and 3 are owned and 

operated by APS and Unit 4 is owned 

by PacifiCorp and operated by APS. 

C. Summary of State Submittals and 

EPA Actions 

1. 2011 Arizona Regional Haze SIP 

On February 28, 2011, the Arizona 

Department of Environmental Quality 

(ADEQ) submitted a Regional Haze SIP 

under Section 308 of the RHR (‘‘Arizona 

Regional Haze SIP’’) to EPA. This 

submittal included BART analyses and 

determinations for nitrogen oxides 

(NOX), particulate matter with an 

aerodynamic diameter of less than 10 

micrometers (PM10), and sulfur dioxide 

(SO2) at Cholla Units 2, 3, and 4. 

ADEQ’s BART analyses for Cholla 

included the following seven steps: 

• Step 1: Identify the Existing Control 

Technologies in Use at the Source, 

• Step 2: Identify All Available 

Retrofit Control Options, 

• Step 3: Eliminate All Technically 

Infeasible Control Options, 

• Step 4: Evaluate Control 

Effectiveness of Remaining 

Technologies, 

• Step 5: Evaluate the Energy and 

Non-Air Quality Environmental Impacts 

and Document Results,9

• Step 6: Evaluate Visibility Impacts, 

and 

• Step 7: Select BART.10

2. 2012 EPA Action on Arizona Regional 

Haze SIP and FIP 

On December 5, 2012, we issued a 

final rule approving in part and 

disapproving in part ADEQ’s BART 

determinations for three sources, 

including Cholla.11 We found that 

ADEQ’s overall approach to conducting 

BART analyses and its implementation 

of the first four steps of its approach 

were generally reasonable and 

consistent with the RHR and the BART 

Guidelines. However, we found 

significant flaws in ADEQ’s 

implementation of the last three steps. 


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12See 77 FR 42834, 42840–42941. 

13Cholla BART SIP Revision, Appendix A 

Significant Permit Revision No. 61713 to Operating 

Permit No. 53399 for Arizona Public Service 

Company Cholla Generating Station (October 16, 

2015). 

14Cholla SIP Revision, section 2.2, page 4. 

In particular, under step 5, we found 

that the costs of compliance were not 

calculated in accordance with the BART 

Guidelines; under step 6, we found that 

the visibility benefits were not 

appropriately evaluated and considered; 

and under step 7, we found that ADEQ 

did not provide a sufficient explanation 

and rationale for its determinations.12

As a result of these flaws, we 

disapproved ADEQ’s BART 

determinations for NOX at Cholla Units 

2, 3, and 4. We also found that the SIP 

lacked enforceable emission limits for 

all units and pollutants. In the same 

action, we promulgated a FIP for the 

disapproved portions of the SIP, 

including NOX BART determinations for 

Units 2, 3, and 4. We determined that 

BART for NOX at Units 2, 3, and 4 was 

an emission limit of 0.055 pounds per 

million British thermal units (lb/

MMBtu) determined as an average 

across the three units, based on a rolling 

30-boiler-operating-day average, which 

is achievable with the use of low-NOX

burners (LNB), overfire air (OFA) and 

selective catalytic reduction (SCR). The 

compliance date for the NOX BART 

emission limit is December 5, 2017. In 

addition, we established an SO2 removal 

efficiency requirement of 95 percent for 

the scrubbers on Cholla Units 2, 3 and 

4. Cholla Units 3 and 4 were required 

to achieve this removal efficiency by 

December 5, 2013, and Cholla Unit 2 

was required to comply by April 1, 

2016. We also established requirements 

for equipment maintenance, monitoring, 

recordkeeping, and reporting for all 

units and all pollutants. 

3. 2015 APS Application for Significant 

Permit Revision for Cholla Generating 

Station 

On January 15, 2015, APS and 

PacifiCorp submitted an ‘‘Application 

for Significant Permit Revision and 

Five-Factor BART Reassessment for 

Cholla’’ to ADEQ. APS and PacifiCorp 

requested that ADEQ conduct a revised 

BART analysis and determination based 

on new facts (‘‘BART Reassessment’’) 

and submit this BART Reassessment to 

the EPA as a revision to the Arizona 

Regional Haze SIP. Under the Cholla 

BART Reassessment, APS and 

PacifiCorp would commit to the 

following measures in lieu of 

implementing the FIP requirements for 

the Cholla Generating Station: 

• Unit 2 would be permanently shut 

down by April 1, 2016; 

• Unit 3 and Unit 4 would continue 

to operate with currently installed LNB 

and separated over fire air (SOFA). In 

addition, by April 30, 2025, APS and 

PacifiCorp would permanently cease 

burning coal at both units with the 

option to convert to pipeline-quality 

natural gas by July 31, 2025, with a ≤20 

percent annual average capacity factor. 

4. 2015 Arizona Regional Haze SIP 

Revision for Cholla Generating Station 

On October 22, 2015, ADEQ 

submitted a revision to the Arizona 

Regional Haze SIP that incorporates the 

Cholla BART Reassessment (‘‘Cholla SIP 

Revision’’). The Cholla SIP Revision is 

the subject of this proposal. 

III. Summary of the Cholla SIP 

Revision 

The Cholla SIP Revision consists of a 

revised BART analysis and 

determination for NOX at Cholla, an 

analysis under CAA section 110(l), and 

a revision to Cholla’s operating permit 

(‘‘Cholla Permit Revision’’) 13 to 

implement both the revised BART 

determination for NOX and ADEQ’s 

prior BART determinations for SO2 and 

PM10 at Cholla. If fully approved by the 

EPA, the Cholla SIP Revision would fill 

the gap in the Arizona Regional Haze 

SIP that resulted from the EPA’s 

disapproval of ADEQ’s BART 

determinations for NOX at Cholla Units 

2, 3, and 4 and the lack of enforceable 

emission limits for all units and 

pollutants. Accordingly, full approval of 

the Cholla SIP Revision would enable 

the EPA to withdraw the provisions of 

the Arizona Regional Haze FIP that 

apply to Cholla. 

In the Cholla SIP Revision, ADEQ 

determined that, if Unit 2 were shut 

down by April 1, 2016, no BART 

determination for Unit 2 would be 

necessary ‘‘because the enforceable 

shutdown date is within the five-year 

BART window.’’ 14 For Units 3 and 4, 

ADEQ performed a revised BART 

analysis, taking into account the new 

requirements that would be imposed as 

part of the Cholla BART Reassessment. 

This re-analysis and the resulting BART 

determinations are summarized in the 

following sections. 

A. BART Re-Analysis for Cholla Units 3 

and 4 

ADEQ’s BART re-analysis for Units 3 

and 4 consists of an evaluation of each 

of the five BART factors, effectively 

replacing step 5 (evaluation of costs of 

compliance, energy and non-air quality 

environmental impacts, and remaining 

useful life) and step 6 (evaluation of 

visibility benefits) of ADEQ’s prior 

BART analysis for Cholla in the Arizona 

Regional Haze SIP. 

1. Cost of Compliance 

ADEQ evaluated the costs of 

compliance for three control options: (1) 

LNB and SOFA, (2) SNCR with LNB and 

SOFA, and (3) SCR with LNB and 

SOFA. Two fuel-use scenarios were 

used as a comparison: (1) Twenty years 

of operation on coal and (2) eight years 

of operation on coal followed by twelve 

years of operation on natural gas (as 

provided for under the BART 

Reassessment). The cost-effectiveness 

values for each control option under 

each of these scenarios are shown in 

Tables 1 and 2. For all options, the costs 

associated with the BART Reassessment 

are due to lower utilization periods 

(coal firing until 2025 instead of for 20 

years) as well as significantly lower 

NOX emissions after conversion to 

natural gas. 

TABLE 1—COST-EFFECTIVENESS OF NOX CONTROL OPTIONS AT CHOLLA ASSUMING 20 YEARS OF OPERATION ON COAL

Unit Control option 

Average Incremental a

Annual cost 

($/year) 

Emission 

reduction 

relative to 

baseline 

(ton/year) 

Average costeffectiveness 

($/ton) 

Incremental 

annual cost 

($/year) 

Incremental 

emission 

reduction 

(ton/year) 

Incremental 

costeffectiveness 

($/ton) 

3 ........ LNB and SOFA ......................... $483,300 1,219 $396 ........................ ........................ ........................

SNCR with LNB and SOFA ...... 3,070,443 1,911 1,607 2,587,143 691 3,742 

SCR with LNB and SOFA ......... 9,448,912 3,300 2,838 8,965,612 2,110 4,248 

4 ........ LNB and SOFA ......................... 673,550 1,756 384 ........................ ........................ ........................


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TABLE 1—COST-EFFECTIVENESS OF NOX CONTROL OPTIONS AT CHOLLA ASSUMING 20 YEARS OF OPERATION ON

COAL—Continued 

Unit Control option 

Average Incremental a

Annual cost 

($/year) 

Emission 

reduction 

relative to 

baseline 

(ton/year) 

Average costeffectiveness 

($/ton) 

Incremental 

annual cost 

($/year) 

Incremental 

emission 

reduction 

(ton/year) 

Incremental 

costeffectiveness 

($/ton) 

SNCR with LNB and SOFA ...... 4,086,366 2,643 1,546 3,412,816 887 3,848 

SCR with LNB and SOFA ......... 13,590,853 4,408 3,083 12,917,303 2,652 4,871 

aThe incremental cost effectiveness results for SNCR and SCR are based on the emission and cost differences between these technologies 

and the proposed LNB + SOFA option. 

TABLE 2—COST-EFFECTIVENESS OF NOX CONTROL OPTIONS AT CHOLLA ASSUMING 8 YEARS OF OPERATION ON COAL

AND 12 YEARS OF OPERATION ON NATURAL GAS

Unit Control option 

Average Incremental 

Annual cost 

($/year) 

Emission 

reduction 

relative to 

baseline 

(ton/year) 

Average costeffectiveness 

($/ton) 

Incremental 

annual cost 

($/year) 

Incremental 

emission 

reduction 

(ton/year) 

Incremental 

costeffectiveness 

($/ton) 

3 ........ LNB and SOFA ......................... $411,300 488 $843 ........................ ........................ ........................

SNCR with LNB and SOFA ...... 2,497,743 786 3,177 2,086,443 299 6,989 

SCR with LNB and SOFA ......... 8,716,452 1,387 6,286 8,305,152 899 9,237 

4 ........ LNB and SOFA ......................... 571,550 702 814 ........................ ........................ ........................

SNCR with LNB and SOFA ...... 3,283,930 1,085 3,027 2,712,380 383 7,091 

SCR with LNB and SOFA ......... 12,480,744 1,833 6,810 11,909,194 1,130 10,539 

2. Energy and Non-Air Environmental 

Impacts 

ADEQ indicated that the energy 

impacts of LNB, SOFA, and SNCR are 

minimal and that there are no non-air 

quality environmental impacts 

associated with LNB and SOFA. ADEQ 

also noted that SNCR and SCR would 

result in ammonia slip and that the 

transport and handling of anhydrous 

ammonia presents potential safety 

hazards. 

3. Existing Air Pollution Controls 

ADEQ noted that, under the Cholla 

BART Reassessment, use of the existing 

LNB and SOFA would be continued at 

Units 3 and 4. ADEQ proposed no 

additional controls for these two units. 

Unit 2 would be shut down in April 

2016, while Unit 1 (the non-BART unit) 

would cease burning coal in 2025. 

4. Remaining Useful Life 

ADEQ used a 20-year amortization 

period in order to calculate the costs of 

compliance for Units 3 and 4 because 

neither unit is subject to an enforceable 

shutdown date. 

5. Degree of Visibility Improvement 

ADEQ included the results of 

modeling conducted by APS and 

PacifiCorp to predict the degree of 

visibility improvement associated with 

the three BART scenarios. This 

modeling predicted visibility impacts at 

the thirteen Class I areas within 300 km 

of the Cholla facility under a baseline 

scenario (based on 2001–2003 emissions 

with all four units operating), as well as 

the three BART control scenarios: 

• BART Option 1: Unit 1 with 2001– 

2003 baseline controls (pre-LNB), Unit 2 

shut down, LNB/SOFA on Units 3 and 

4; 

• BART Option 2: Unit 1 with 2001– 

2003 baseline controls (pre-LNB), Unit 2 

shut down, LNB/SOFA and SNCR on 

Units 3 and 4; and 

• BART Option 3: Unit 1 with 2001– 

2003 baseline controls (pre-LNB), Unit 2 

shut down, LNB/SOFA and SCR on 

Units 3 and 4. 

APS and PacifiCorp used CALPUFF 

version 5.8 and incorporated 

meteorological data for 2001–2003, an 

assumption of 1.0 part per billion 

background concentration for ammonia, 

and ‘‘Method 8b’’ 20 percent best days 

background conditions for all cases. The 

results of this modeling are shown in 

Tables 3 and 4. 

TABLE 3—PREDICTED VISIBILITY IMPACTS

[22nd highest delta-dv over 3-year period] 

Class I area Baseline BART Option 1 

(LNB/SOFA) 

BART Option 2 

(LNB/SOFA/

SNCR) 

BART Option 3 

(LNB/SOFA/

SCR) 

Petrified Forest NP .......................................................................... 5.31 4.33 4.05 3.55 

Grand Canyon NP ........................................................................... 3.40 1.79 1.62 1.20 

Capitol Reef NP ............................................................................... 2.19 1.04 0.91 0.62 

Mazatzal WA .................................................................................... 2.23 0.96 0.87 0.69 

Sycamore Canyon WA .................................................................... 2.27 1.00 0.88 0.67 

Mount Baldy WA .............................................................................. 2.10 0.97 0.85 0.62 

Gila WA ............................................................................................ 1.53 0.53 0.47 0.39 

Sierra Ancha WA ............................................................................. 2.28 1.05 0.97 0.81 


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TABLE 3—PREDICTED VISIBILITY IMPACTS—Continued 

[22nd highest delta-dv over 3-year period] 

Class I area Baseline BART Option 1 

(LNB/SOFA) 

BART Option 2 

(LNB/SOFA/

SNCR) 

BART Option 3 

(LNB/SOFA/

SCR) 

Mesa Verde NP ............................................................................... 2.08 0.88 0.78 0.60 

Galiuro WA ...................................................................................... 0.96 0.34 0.31 0.27 

Superstition WA ............................................................................... 2.00 1.00 0.93 0.73 

Saguaro NP ..................................................................................... 0.70 0.22 0.22 0.20 

Pine Mountain WA ........................................................................... 1.64 0.67 0.59 0.48 

TABLE 4—PREDICTED VISIBILITY IMPROVEMENT OVER THE BASELINE VISIBILITY IMPACTS

[22nd highest delta-dv over 3-year period] 

Class I area 

BART 

Option 1 

(LNB/SOFA) 

BART 

Option 2 

(LNB/SOFA 

/SNCR) 

BART 

Option 3 

(LNB/SOFA 

/SCR) 

Option 2 over 

Option 1 

Option 3 over 

Option 1 

Petrified Forest NP .......................................... 0.98 1.26 1.77 0.28 0.79 

Grand Canyon NP ........................................... 1.61 1.78 2.20 0.17 0.59 

Capitol Reef NP ............................................... 1.15 1.28 1.57 0.13 0.42 

Mazatzal WA .................................................... 1.27 1.36 1.54 0.09 0.27 

Sycamore Canyon WA .................................... 1.27 1.39 1.60 0.12 0.33 

Mount Baldy WA .............................................. 1.14 1.26 1.48 0.12 0.34 

Gila WA ............................................................ 1.00 1.06 1.14 0.06 0.14 

Sierra Ancha WA ............................................. 1.22 1.30 1.47 0.08 0.25 

Mesa Verde NP ............................................... 1.21 1.30 1.49 0.09 0.28 

Galiuro WA ....................................................... 0.62 0.65 0.69 0.03 0.07 

Superstition WA ............................................... 1.00 1.07 1.28 0.07 0.28 

Saguaro NP ..................................................... 0.48 0.49 0.50 0.01 0.02 

Pine Mountain WA ........................................... 0.97 1.04 1.16 0.07 0.19 

Cumulative ....................................................... 13.92 15.24 17.89 1.32 3.97 

Average ............................................................ 1.07 1.17 1.38 0.10 0.31 

B. BART Determination for Cholla Units 

3 and 4 

ADEQ’s BART determination for 

Cholla Units 3 and 4 in the Cholla SIP 

Revision effectively replaces step 7 

(select BART) of its prior BART analysis 

for NOX BART for Cholla in the Arizona 

Regional Haze SIP. In making this 

determination, ADEQ compared the 

three emission control options (LNB and 

SOFA, SNCR with LNB and SOFA, SCR 

with LNB and SOFA). For Option 1, it 

found that the LNB and SOFA controls 

could be installed at reasonable costeffectiveness and would deliver 

visibility improvements ranging from 

0.48 to 1.61 dv over baseline conditions 

across thirteen Class I areas. For Option 

2, it found the SNCR control option to 

be too costly in comparison to the small 

additional visibility benefits it would be 

expected to deliver. For Option 3, ADEQ 

noted that the visibility benefits of SCR 

(3.97 dv cumulative incremental 

visibility improvement) would only last 

until 2025 when coal firing would 

cease, after which the incremental 

benefits of SCR would be ‘‘negligible.’’ 

Based on its analysis, ADEQ found 

Option 1 (LNB with SOFA) to be BART 

for NOX at Cholla Units 3 and 4. The 

rolling 30-boiler-operating-day NOX

emission limits associated with this 

BART determination are 0.22 lb/MMbtu 

(effective until April 30, 2025), which 

reflects the use of coal, and 0.080 lb/

MMbtu (effective May 1, 2025), which 

reflects the use of natural gas. 

C. 110(l) Analysis 

In addition to the BART re-analysis 

and determinations, the Cholla SIP 

Revision also includes a demonstration 

of ‘‘noninterference’’ under CAA section 

110(l). In particular, ADEQ considered 

whether the Cholla SIP Revision would 

interfere with (1) any applicable 

requirement concerning attainment of 

any National Ambient Air Quality 

Standards (NAAQS) or (2) any other 

applicable requirement of the CAA. 

1. Demonstration of Noninterference 

With NAAQS Attainment 

ADEQ noted that Cholla is located in 

Navajo County, Arizona, which is 

currently designated as attainment or 

unclassifiable for the following NAAQS: 

Carbon monoxide (CO), lead (Pb), 

nitrogen dioxide (NO2), ozone (O3) 

(2008 NAAQS), PM2.5 (1997 and 2006 

NAAQS), PM10, and SO2 (1971 

NAAQS). ADEQ also noted that it has 

recommended an attainment/

unclassifiable designation for this area 

for the 2012 PM2.5 and 2010 SO2

standards. 

ADEQ’s demonstration of 

noninterference with attainment 

focused on the NAAQS for PM10, SO2, 

NO2, and O3 because ambient levels of 

these pollutants are affected by 

emissions of PM10, SO2, and/or NOX. 

Specifically, ADEQ analyzed emissions 

of PM10, SO2, and NOX under the 

control strategies in the Cholla BART 

Reassessment, as compared with the 

existing control requirements in the 

applicable SIP and FIP. This assessment 

was conducted by considering revised 

emissions limits included in the Cholla 

SIP Revision, summarized in Table 5. 


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TABLE 5—EMISSION LIMITS FOR CHOLLA BART REASSESSMENT

Unit Dates 

Emission limit 

(lb/MMbtu) 

NOX PM10 SO2

Unit 2 ................................ Unit shut down on April 1, 2016 

Unit 3 ................................ until April 30, 2025 ...................................................... 0.22 0.015 0.15

after April 30, 2025 ..................................................... 0.08 0.01 0.0006 

Unit 4 ................................ until April 30, 2025 ...................................................... 0.22 0.015 0.15

after April 30, 2025 ..................................................... 0.08 0.01 0.0006 

For its PM10 analysis, ADEQ found 

that the emission control strategies in 

the Cholla BART Reassessment will 

result in greater PM10 reductions than 

those in the Arizona Regional Haze SIP 

beginning in 2016 and continuing into 

the future, as shown in Table 6. 

Beginning in 2026, PM10 emissions will 

be further reduced under the Cholla 

BART Reassessment, due to the 20 

percent capacity factor limit and the 

more stringent emission limits (0.01 lb/ 

MMBtu rather than 0.015 lb/MMBtu) 

that will apply after the switch to 

natural gas at Units 3 and 4. Therefore, 

ADEQ found that the Cholla SIP 

Revision will not interfere with 

attainment and maintenance of the PM10

NAAQS. 

TABLE 6—COMPARISON OF ANNUAL PM10 EMISSIONS FOR 2011 ARIZONA SIP VS. CHOLLA BART REASSESSMENT

Time period Unit No. 

Annual PM10

(tons per year (tpy)) 

2011 AZ SIP Cholla SIP 

revision 

2016 ........................................................................ Unit 1 ...................................................................... 84 84 

Unit 2 ...................................................................... a 214 b 78 

Unit 3 ...................................................................... 197 197 

Unit 4 ...................................................................... 269 269 

Total ................................................................ 764 628 

2017–2025 .............................................................. Unit 1 ...................................................................... 84 84 

Unit 2 ...................................................................... 181 0 

Unit 3 ...................................................................... 197 197 

Unit 4 ...................................................................... 269 269 

Total ................................................................ 731 550 

2026 forward ........................................................... Unit 1 ...................................................................... 84 13 

Unit 2 ...................................................................... 181 0 

Unit 3 ...................................................................... 197 30 

Unit 4 ...................................................................... 269 39 

Total ................................................................ 731 82 

aBased on compliance date of April 1, 2016 for emissions limit of 0.015 lb/MMBtu. 

bBased on operation of Unit 2 until April 1, 2016. 

ADEQ also compared SO2 emission 

control strategies in the 2011 SIP with 

those in the Cholla BART Reassessment. 

As shown in Table 7, the control 

strategies in the Cholla BART 

Reassessment will result in greater SO2

reductions than those in the 2011 SIP 

beginning in 2016 and continuing into 

the future. Therefore, ADEQ found that 

the emissions reductions achieved by 

the control strategy outlined in the 

Cholla SIP Revision will not interfere 

with attainment and maintenance of the 

SO2 NAAQS. 

TABLE 7—COMPARISON OF ANNUAL SO2 EMISSIONS FOR 2011 ARIZONA SIP VS. CHOLLA BART REASSESSMENT

Time period Unit No. 

Annual SO2

(tpy) 

2011 AZ SIP Cholla SIP 

revision 

2016 .............................................................................. Unit 1 ............................................................................ 844 844 

Unit 2 ............................................................................ 1,614 a 452 

Unit 3 ............................................................................ 1,966 1,966 

Unit 4 ............................................................................ 2,688 2,688 


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TABLE 7—COMPARISON OF ANNUAL SO2 EMISSIONS FOR 2011 ARIZONA SIP VS. CHOLLA BART REASSESSMENT— 

Continued 

Time period Unit No. 

Annual SO2

(tpy) 

2011 AZ SIP Cholla SIP 

revision 

Total ....................................................................... 7,112 5,950 

2017–2025 .................................................................... Unit 1 ............................................................................ 844 844 

Unit 2 ............................................................................ 1,614 0 

Unit 3 ............................................................................ 1,966 1,966 

Unit 4 ............................................................................ 2,688 2,688 

Total ....................................................................... 7,112 5,498 

2026 forward ................................................................. Unit 1 ............................................................................ 844 1 

Unit 2 ............................................................................ 1,614 0 

Unit 3 ............................................................................ 1,966 2 

Unit 4 ............................................................................ 2,688 2 

Total ....................................................................... 7,112 5 

aBased on operation of Unit 2 until April 1, 2016. 

ADEQ also analyzed the emission 

control strategies for NOX in the Cholla 

BART Reassessment (Unit 2 shutdown 

and LNB/SOFA controls at Units 3 and 

4 until conversion to natural gas by 

2025 with a ≤20 percent annual average 

capacity factor) in comparison to the 

FIP, which requires the installation of 

SCR with LNB and SOFA at all units by 

December 5, 2017. As shown in Table 8, 

while the shutdown of Unit 2 results in 

lower NOX emissions than the FIP for 

2016, the Reassessment will allow for 

4,161 tpy more NOX emissions than the 

FIP between 2018 and 2025. However, 

after 2025, due to the conversion to 

natural gas, the Cholla BART 

Reassessment will result in greater 

annual NOX emission reductions than 

the FIP. ADEQ found that, because there 

are no nonattainment or maintenance 

SIPs that rely on emission reductions at 

Cholla to ensure continued attainment 

of the NO2 NAAQS and the Cholla 

BART Reassessment will result in NOX

emission reductions relative to the 

existing operating conditions of the 

facility, it will not interfere with 

attainment or maintenance of the 

current NO2 NAAQS. 

TABLE 8—COMPARISON OF NOX ANNUAL EMISSIONS FOR FIP VS. CHOLLA BART REASSESSMENT

Time period Unit No. 

Annual NOX

(tpy) 

EPA FIP Cholla BART 

reassessment 

Annual emission 

change (Cholla 

BART 

reassessment 

to EPA FIP) 

2016 ....................................................... Unit 1 ..................................................... 1,131 1,131 0 

Unit 2 ..................................................... 3,601 a 900 ¥2,701 

Unit 3 ..................................................... 2,766 2,766 0 

Unit 4 ..................................................... 3,548 3,548 0 

Total ............................................... 11,046 8,345 ¥2,701 

2017 ....................................................... Unit 1 ..................................................... 1,131 1,131 0 

Unit 2 ..................................................... 3,601 0 ¥3,601 

Unit 3 ..................................................... 2,766 2,766 0 

Unit 4 ..................................................... 3,548 3,548 0 

Total ............................................... 11,046 7,445 ¥3,601 

2018–2025 ............................................. Unit 1 ..................................................... 1,131 1,131 0 

Unit 2 ..................................................... 602 0 ¥602 

Unit 3 ..................................................... 655 2,766 2,111 

Unit 4 ..................................................... 896 3,548 2,652 

Total ............................................... 3,284 7,445 4,161 

2026 forward .......................................... Unit 1 ..................................................... 1,131 105 ¥1,026 

Unit 2 ..................................................... 602 0 ¥602 

Unit 3 ..................................................... 655 244 ¥411 

Unit 4 ..................................................... 896 308 ¥588 


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15 Id. 

16CAA section 169A(b)(2) and 40 CFR 

51.308(e)(1)(ii)(B) require that BART for each fossilfuel fired generating power plant having a total 

generating capacity in excess of 750 megawatts be 

determined pursuant to the BART Guidelines. 

Cholla has a total generating capacity in excess of 

750 megawatts, so the BART Guidelines are 

mandatory for the Cholla BART analysis and 

determination. 

TABLE 8—COMPARISON OF NOX ANNUAL EMISSIONS FOR FIP VS. CHOLLA BART REASSESSMENT—Continued 

Time period Unit No. 

Annual NOX

(tpy) 

EPA FIP Cholla BART 

reassessment 

Annual emission 

change (Cholla 

BART 

reassessment 

to EPA FIP) 

Total ............................................... 3,284 657 ¥2,627 

aBased on operation of Unit 2 until April 1, 2016. 

Similarly, with regard to ozone, for 

which NOX emissions are a precursor, 

ADEQ noted that there are no 

nonattainment or maintenance SIPs that 

rely on emission reductions at Cholla to 

ensure continued attainment of the 

NAAQS and that the Cholla BART 

Reassessment will result in greater longterm NOX emission reductions than the 

existing FIP. Accordingly, ADEQ 

concluded that the Cholla BART 

Reassessment will not interfere with the 

attainment or maintenance of the 2008 

ozone NAAQS. 

2. Demonstration of Noninterference 

With Other CAA Requirements 

With regards to the other applicable 

CAA requirements, ADEQ considered 

whether the Cholla BART Reassessment 

would interfere with (1) the 

requirements of the Regional Haze 

program or (2) the CAA’s air toxics 

requirements. 

In evaluating potential interference 

with the RHR, ADEQ relied primarily on 

the results of air quality modeling (using 

CALPUFF) performed by APS and 

PacifiCorp to assess the visibility 

impacts of Cholla under the Cholla SIP 

Revision compared to the existing SIP 

and FIP requirements.15 These results, 

summarized in Table 9, show that, 

compared with the existing SIP and FIP 

requirements, the Cholla SIP Revision 

would result in less visibility 

improvement at all affected Class I areas 

between 2018 and 2025, but would 

result in greater improvement starting in 

2026. Based on these results and taking 

into consideration the long-term goal of 

the Regional Haze Rule to achieve 

natural visibility conditions, ADEQ 

found that the BART Reassessment will 

not interfere with the requirements of 

the regional haze program. 

TABLE 9—MODELED VISIBILITY IMPACTS OF CHOLLA

Class I Area 

EPA FIP and 

existing SIP 

SIP Revision 

BART 

(2018–2025) 

SIP Revision 

BART 

(2026 forward) 

Visibility impacts 

(dv) Visibility impacts 

(dv) 

Visibility impacts 

(dv) 

Petrified Forest NP .................................................................................................... 2.64 3.75 1.45 

Grand Canyon NP ..................................................................................................... 1.11 1.48 0.45 

Capitol Reef NP ......................................................................................................... 0.62 0.92 0.29 

Mazatzal WA .............................................................................................................. 0.75 0.83 0.30 

Sycamore Canyon WA .............................................................................................. 0.73 0.94 0.29 

Mount Baldy WA ........................................................................................................ 0.69 0.87 0.28 

Gila WA ...................................................................................................................... 0.46 0.47 0.17 

Sierra Ancha WA ....................................................................................................... 0.82 0.94 0.36 

Mesa Verde NP ......................................................................................................... 0.63 0.84 0.30 

Galiuro WA ................................................................................................................ 0.29 0.30 0.09 

Superstition WA ......................................................................................................... 0.73 0.88 0.30 

Saguaro NP ............................................................................................................... 0.20 0.19 0.05 

Pine Mountain WA ..................................................................................................... 0.51 0.58 0.17 

Cumulative impacts ................................................................................................... 10.18 12.99 4.50 

Concerning air toxics, ADEQ noted 

that in addition to ceasing operation of 

Unit 2, the Cholla facility proposes to 

implement sorbent injection at Units 1, 

3, and 4 by March 2016 to reduce air 

toxics and achieve compliance with the 

EPA’s Mercury and Air Toxics (MATS) 

rule. Therefore, ADEQ concluded that 

the Cholla BART Reassessment will not 

interfere with any air toxics 

requirements of the CAA. 

D. Cholla Permit Revision 

The Cholla Permit Revision, which is 

incorporated as Appendix A to the 

Cholla SIP Revision, was issued by 

ADEQ on October 16, 2015. The Permit 

Revision incorporates emission limits 

and compliance dates as well as 

monitoring, recordkeeping, and 

reporting requirements to implement 

both the Cholla BART Reassessment and 

ADEQ’s prior BART determinations for 

SO2 and PM10 at Cholla. 

IV. The EPA’s Evaluation of the Cholla 

SIP Revision 

We have evaluated the Cholla SIP 

Revision for compliance with the 

requirements of the CAA, the RHR, and 

the BART Guidelines.16 Our evaluation 

of each of the major components of the 


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17Cholla Permit Revision section I.C.1. 

18See 40 CFR 51.145(f)(4). 

19Letter from Edward Seal, APS, to Kathleen 

Johnson, EPA, and Eric Massey, ADEQ (October 28, 

2015). 

20Cholla Permit Revision section I.A. 

21See 77 FR 42840–42941 and 42849, 77 FR 

72565–72566. 

22EPA Air Pollution Control Cost Manual, 

available at https://www3.epa.gov/ttn/ecas/cost_

manual.html. 

23See 77 FR 42849. 

24See, e.g., Cholla SIP Revision, Appendix B, 

Table B–1, footnote (a). 

25See 77 FR 42852. 

26CCM (7th Edition), Section 4, Chapter 2— 

Selective Catalytic Reduction (May 2016), available 

at https://www3.epa.gov/ttn/ecas/docs/

SCRCostManualchapter7thEdition_2016.pdf. 

27See id. at 2–78 (‘‘broadly speaking, a 

representative value of the equipment life for SCR 

at power plants can be considered as 30 years.’’) 

28CCM (6th edition), Section 4.2, Chapter 2— 

Selective Catalytic Reduction (October 2000), 

available at https://www3.epa.gov/ttn/ecas/docs/

cs4-2ch2.pdf, at 2–48 (‘‘An economic lifetime of 20 

years is assumed for the SCR system.’’) 

29See 77 FR 42854. 

30See Cholla_SCR_costs (30 yr life).xlsx. 

31 Id. 

32See 77 FR 42849. 

33See, e.g., Cholla SIP Revision, Table 4 and 5. 

34 In particular, the BART Guidelines explain 

that, ‘‘[i]f the emissions from the list of emissions 

units at a stationary source exceed a potential to 

emit of 250 tons per year for any visibilityimpairing pollutant, then that collection of 

emissions units is a BART-eligible source.’’ 40 CFR 

part 51, appendix Y, section II.A.4. In other words, 

the BART-eligible source (the list of BART 

emissions units at a source) is the collection of 

units for which one must make a BART 

determination. The BART Guidelines also state 

‘‘you must conduct a visibility improvement 

determination for the source(s) as part of the BART 

determination.’’ Id, section IV.D.5. This requires 

consideration of the visibility improvement from 

BART applied to the BART-eligible source as a 

whole. 

35See Cholla SIP Revision section 2.3. 

Cholla SIP Revision is summarized in 

the following sections. 

A. The EPA’s Evaluation of the 

Enforceable Retirement Provision for 

Cholla Unit 2 

The Cholla Permit Revision requires 

Unit 2 to be permanently retired by no 

later than April 1, 2016.17 This date 

coincides with the compliance 

deadlines for SO2 and PM10 in the 

Arizona Regional Haze FIP and precedes 

the deadline for NOX by over a year.18

In fact, the unit was shut down on 

October 1, 2015.19 If Unit 2 were not 

retired, APS would have been required 

to install additional controls to meet the 

SO2 and PM10 limits in the SIP, as well 

as the NOX limit in the FIP, which is 

achievable with SCR. The requirement 

for permanent retirement will become 

effective and federally enforceable when 

the Cholla SIP Revision is approved into 

the SIP and the FIP provisions 

applicable to Cholla are withdrawn.20

Accordingly, we agree with ADEQ that 

no further analysis is required for Cholla 

Unit 2, and we propose to approve the 

requirement for permanent retirement as 

satisfying the requirements of the CAA 

and RHR for Cholla Unit 2. 

B. The EPA’s Evaluation of ADEQ’s 

BART Analysis for Cholla Units 3 and 

4 

We find that ADEQ’s BART analysis 

for Cholla Units 3 and 4 is consistent 

with the requirements of the CAA, RHR, 

and the BART Guidelines. In particular, 

we find that ADEQ’s BART re-analysis 

addresses the flaws that were the basis 

for our disapproval of ADEQ’s prior 

BART analysis for Cholla.21

With regard to the cost of compliance, 

in its previous BART analysis for 

Cholla, ADEQ included certain line item 

costs not allowed by the EPA Control 

Cost Manual (CCM),22 such as owner’s 

costs, surcharge, and Allowance for 

Funds Used During Construction 

(AFUDC).23 This approach did not 

comply with BART Guidelines’ 

direction that cost estimates should be 

based on the CCM. In the Cholla SIP 

revision, by contrast, ADEQ used the 

cost estimates that the EPA developed 

as part of the Regional Haze FIP,24

which were calculated using the CCM 

methodology.25

We note that in May 2016, EPA 

revised the CCM chapter that concerns 

SCR systems.26 The revised CCM 

recommends use of a 30-year equipment 

life for SCR systems,27 whereas the 

previous version recommended a 20- 

year life.28 As noted above, ADEQ used 

a 20-year remaining useful life in its 

cost calculations in the Cholla SIP 

Revision, which was consistent with the 

current CCM recommendation at the 

time of SIP submittal in October 2015. 

Given that the majority of other BART 

analyses, including the EPA’s analysis 

for Cholla in the Arizona Regional Haze 

FIP,29 have used a 20-year remaining 

useful life for SCR, we believe that this 

remains an appropriate assumption in 

this instance in order to ensure a 

consistent comparison with the cost 

estimates for SCR in other BART 

determinations. Nonetheless, we have 

also conducted an additional analysis to 

evaluate how use of a 30-year remaining 

useful life would affect the costeffectiveness values for SCR at Cholla 

Units 3 and 4. We found that use of a 

30-year remaining useful life would 

increase the average cost-effectiveness 

of SCR at Unit 3 from $6,286/ton to 

$7,864/ton and the ‘‘incremental’’ costeffectiveness (as compared with 

LNB+SOFA) from $9,237/ton to 

$11,295/ton.30 The average and 

‘‘incremental’’ (as compared with 

LNB+SOFA) cost-effectiveness of SCR at 

Unit 4 would be increased from $6,810/ 

ton to $8,401/ton and from $10,539 to 

$12,674, respectively.31 Thus, if ADEQ 

had calculated the average and 

incremental cost-effectiveness of SCR 

based on a 30-year remaining useful life, 

it would have provided further support 

for ADEQ’s determination that the 

incremental costs of compliance for SCR 

are not warranted by the incremental 

benefits. 

With regard to visibility modeling, in 

its previous BART analysis for Cholla, 

ADEQ considered the benefits from 

controls on only one emitting unit at a 

time and overlooked significant benefits 

at multiple Class I areas, thereby 

understating the full visibility benefits 

of the candidate controls.32 By contrast, 

in the Cholla SIP revision, ADEQ looked 

at the visibility impacts and potential 

improvements from all three BARTeligible units together and also 

considered impacts and potential 

improvements at all 13 Class I areas 

within 300 km of Cholla, based on 

modeling performed by APS and 

PacifiCorp.33

In considering the results of this 

modeling, it should be noted that the 

baseline scenario included emissions 

from Unit 2, but the control scenarios 

did not include any emissions from Unit 

2. As a result, the total visibility 

improvement anticipated under each of 

the control scenarios represents not only 

the visibility benefits of controls on 

Units 3 and 4, but also the visibility 

benefits of the closure of Unit 2. We 

consider this to be a reasonable 

approach because it is consistent with 

the requirement of the BART Guidelines 

for states to consider the visibility 

improvement from controls applied to 

the entire BART-eligible source.34

However, given that ADEQ is not 

making a BART determination for Unit 

2 in this instance, we believe it is 

appropriate to also consider the 

visibility improvement expected to 

result from controls on Units 3 and 4 

only. ADEQ’s evaluation of the 

‘‘incremental’’ visibility benefits of 

SNCR (‘‘Option 2 over Option 1’’ in 

Table 4) and SCR (‘‘Option 3 over 

Option 1’’ in Table 4) effectively 

excludes the benefits of the Unit 2 

shutdown because Options 1, 2, and 3 

all exclude emissions from Unit 2. 

Given that ADEQ relied heavily on these 

‘‘incremental’’ visibility benefits in 

reaching its ultimate BART 

determination,35 we find that ADEQ 

appropriately considered the visibility 


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36See Cholla_SCR_vs_NG rev2.xlsx. 

37 40 CFR part 51 appendix Y, section IV.D.4.e 

(emphasis added). The BART Guidelines do not 

specify a method for calculating incremental 

visibility benefits. We consider it appropriate to 

calculate these benefits in the same manner as 

incremental costs, i.e. by comparing the expected 

benefits of a control option to those of the next most 

stringent option. 

38Cholla Units 3 and 4 Incremental Costs and 

Benefits.xlsx. 

39 Id. 

40As described in the previous section, if ADEQ 

had calculated the incremental benefits of SCR in 

accordance with the BART Guidelines, the per area 

incremental benefits would have ranged from 0.01 

dv to 0.51 dv, and the cumulative incremental 

benefit would have been 2.65 dv. 

benefits of controls on Units 3 and 4 

only, as well as the benefits of the 

Cholla BART Reassessment as a whole. 

We also note that ADEQ did not 

quantify the expected visibility benefits 

of SCR and SNCR on Units 3 and 4 after 

these units are converted to gas in 2025, 

but characterized these benefits as 

‘‘negligible.’’ In order to evaluate 

ADEQ’s characterization, we scaled the 

modeled visibility benefits of SCR under 

the coal-fired scenario to roughly 

estimate what the benefits would be 

under the gas-fired scenario. The results 

of this scaling indicate that, under the 

gas-fired scenario, the approximate 

benefits of SNCR would be 0.07 dv at 

the most-improved Class I area and 0.31 

dv cumulatively over all affected Class 

I areas, while the approximate benefits 

of SCR would be 0.15 dv at the mostimproved Class I area and 0.77 dv 

cumulatively over all affected Class I 

areas.36 Thus, the benefits of SNCR or 

SCR under the gas-fired scenario would 

be significantly less than under the coalfired scenario, for which the expected 

‘‘incremental’’ benefits over LNB+SOFA 

are 0.28 dv at the most-improved area 

and 1.32 dv cumulative for SNCR and 

0.79 dv at the most-improved Class I 

area and 3.97 dv cumulative for SCR. 

In the Cholla SIP Revision, ADEQ also 

appropriately accounted for the 

requirements that will apply to Units 3 

and 4 as of 2025, i.e., the permanent 

cessation of coal burning by April 30, 

2025, with the option to convert to 

pipeline-quality natural gas and comply 

with a 20 percent annual average 

capacity factor limit by July 31, 2025. 

These new requirements significantly 

decrease the emission reductions 

achievable by SCR or SNCR beginning 

in 2025 and thus increase the average $/ 

ton of both SCR and SNCR over the 

remaining useful life of the units, as 

shown in Tables 1 and 2 above. 

Similarly, these requirements limit the 

timeframe in which significant visibility 

benefits would result from either SCR or 

SNCR to less than eight years. 

We note that ADEQ did diverge 

slightly from the BART Guidelines in its 

calculation of the incremental costeffectiveness of SCR. In particular, 

ADEQ calculated the incremental cost, 

as well as incremental visibility 

benefits, based on a comparison 

between SCR with LNB+SOFA and 

LNB+SOFA only. This differs from the 

approach to calculating incremental 

cost-effectiveness that is set forth in the 

BART Guidelines, under which 

incremental cost-effectiveness is 

calculated by comparing ‘‘the costs and 

performance level of a control option to 

those of the next most stringent option 

. . . .’’ 37 In this case, SNCR with 

LNB+SOFA is the next most stringent 

option compared to SCR with 

LNB+SOFA. Had ADEQ compared SCR 

with LNB+SOFA to SNCR with 

LNB+SOFA, the incremental costeffectiveness using a 20-year remaining 

useful life would have been $10,347/ton 

for Unit 3 and $12,295/ton for Unit 4,38

rather than $9,237/ton for Unit 3 and 

$10,539/ton for Unit 4. Similarly, had 

ADEQ calculated the incremental 

visibility benefits of SCR with 

LNB+SOFA based on a comparison to 

SNCR with LNB+SOFA, the per area 

incremental benefits would have ranged 

from 0.01 dv to 0.51 dv, rather than 0.07 

dv to 0.79 dv, and the cumulative 

incremental benefit would have been 

2.65 dv rather than 3.97 dv.39 Thus, if 

ADEQ had calculated the incremental 

costs and benefits of SCR in accordance 

with the BART Guidelines, it would 

have resulted in higher incremental 

cost-effectiveness values and lower 

incremental visibility benefits compared 

with the figures provided in the Cholla 

SIP Revision, which would provide 

further support for ADEQ’s 

determination that the incremental costs 

of compliance for SCR are not warranted 

by the incremental benefits. 

Accordingly, in reviewing the 

reasonableness of ADEQ’s re-analysis of 

BART for these units, we find that 

ADEQ’s diversion from the BART 

Guidelines in this regard was of no 

consequence. 

Based on our findings that the Cholla 

SIP Revision addresses the flaws that 

were the basis for our disapproval of 

ADEQ’s prior BART analysis for Cholla 

and otherwise meets the requirements of 

the CAA, RHR, and the BART 

Guidelines, we propose to approve 

ADEQ’s BART re-analysis for Cholla 

Units 3 and 4. 

C. The EPA’s Evaluation of ADEQ’s 

BART Determination for Cholla Units 3 

and 4 

We also find that ADEQ’s BART 

determination for NOX at Cholla Units 

3 and 4 is consistent with the 

requirements of the CAA, RHR, and the 

BART Guidelines. In particular, we find 

that ADEQ appropriately considered 

and weighed the five BART factors in 

relation to the available control options 

and reached a reasonable BART 

determination based on its 

consideration of the factors. 

With regard to SCR, we find that it 

was reasonable for ADEQ to conclude 

that the costs of SCR were not warranted 

by the visibility benefits in this 

instance. In particular, with regard to 

costs, we are not aware of any instance 

in which the EPA has determined SCR 

to be BART where the average costeffectiveness of SCR was greater than 

$6,000/ton and the incremental costeffectiveness (calculated in accordance 

with the BART Guidelines) was greater 

than $10,000/ton, as is the case with 

Cholla Units 3 and 4. Similarly, we are 

not aware of any instance in which the 

EPA has disapproved a state’s BART 

determination that rejected SCR as 

BART based on similar costeffectiveness values. Furthermore, while 

the total visibility benefits of the SCRbased control scenario (‘‘BART Option 

3’’) are large (2.20 dv at the most 

improved area and 17.89 dv cumulative 

across all affected areas), as noted in the 

previous section, these benefits include 

not only the effect of SCR installation on 

Units 3 and 4, but also the retirement of 

Unit 2. Thus, we believe it was 

appropriate for ADEQ to focus primarily 

on what it characterized as the 

‘‘incremental’’ visibility benefits, i.e., 

the relative degree of visibility 

improvement expected under Option 3 

(Unit 2 retired and SCR with 

LNB+SOFA on Units 3 and 4) compared 

with Option 1 (Unit 2 retired and 

LNB+SOFA on Units 3 and 4), which 

were 0.07 dv to 0.79 dv per area and 

3.97 dv cumulative.40 While these 

benefits are significant, we believe it 

was reasonable for ADEQ to determine 

that the benefits were not warranted in 

light of the high costs of SCR and the 

fact that benefits of this magnitude 

would only last for approximately eight 

years, after which the benefits of SCR 

would be far less (roughly 0.15 dv at the 

most-improved Class I area and 0.77 dv 

cumulatively over all affected Class I 

areas). 

With regard to SNCR, we find that it 

was reasonable for ADEQ to conclude 

that the costs of SNCR were not 

warranted by the visibility benefits. In 

particular, with regard to costs, we are 

not aware of any instance in which the 

EPA has determined SNCR to be BART 

where the average cost-effectiveness of 

SNCR was greater than $3,000/ton and 


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41CAA Section 110(l), 42 U.S.C. 7410(l). 

42As shown in Table 8, ADEQ projected that total 

NOX emissions at Cholla Unit 2 would be 900 tpy 

in 2016, based on a Unit 2 shutdown date of April 

1, 2016. Because Unit 2 was retired in October 

2015, 2016 emissions from Unit 2 will actually be 

zero, so we anticipate the total NOX emissions from 

the facility will be roughly 7,445 tpy for all years 

between 2016 and 2025. 

43Cholla SIP Revision, pages 12–13, Table 7. 

44See 40 CFR 81.303. 

45 40 CFR part 51, subpart BB. 

46See Letter from Eric Massey, ADEQ, to Doris 

Lo, EPA (January 13, 2016). 

47 80 FR 65292 (October 26, 2015). 

48 Id. at 65438. 

49See, e.g., CAA section 110(a)(2)(F) and 40 CFR 

51.212(c). 

the incremental cost-effectiveness was 

roughly $7,000/ton, as is the case with 

Cholla Units 3 and 4. Similarly, we are 

not aware of any instance in which the 

EPA has disapproved a state’s BART 

determination that rejected SNCR as 

BART based on similar costeffectiveness values. Furthermore, while 

the total visibility benefits of the SNCRbased control scenario (‘‘BART Option 

2’’) are large (1.78 dv at the most 

improved area and 15.24 dv cumulative 

across all affected areas), as noted 

above, these benefits include not only 

the effect of SNCR installation on Units 

3 and 4, but also the retirement of Unit 

2. Thus, we believe it was appropriate 

for ADEQ to focus primarily on 

incremental visibility benefits, i.e., the 

relative degree of visibility 

improvement expected under Option 2 

(Unit 2 retired and SNCR with 

LNB+SOFA on Units 3 and 4) compared 

with Option 1 (Unit 2 retired and 

LNB+SOFA on Units 3 and 4), which 

were 0.01 dv to 0.28 dv per area and 

1.32 dv cumulative. While these 

benefits are not insignificant, we believe 

it was reasonable for ADEQ to 

determine that the benefits were not 

warranted in light of the relatively high 

costs of SNCR and the fact that benefits 

of this magnitude would only last for 

approximately eight years, after which 

the benefits of SNCR would be far less 

(roughly 0.07 dv at the most-improved 

Class I area and 0.31 dv cumulatively 

over all affected Class I areas). 

Therefore, we propose to approve 

ADEQ’s determination that BART for 

NOX at Cholla Units 3 and 4 consists of 

LNB+SOFA with associated emission 

limits of 0.22 lb/MMbtu (rolling 30- 

boiler-operating-day average) for each 

unit. As explained above, these 

emission limits will remain in effect 

until April 30, 2025, at which point 

both units will be permanently retired 

or converted to natural gas with NOX

emission limits of 0.08 lb/MMBtu 

(rolling 30-boiler-operating-day 

average). 

D. The EPA’s Evaluation Under CAA 

Section 110(l) 

CAA section 110(l) requires that any 

revision to an implementation plan 

shall not be approved by the EPA 

Administrator if the revision would 

interfere with any applicable 

requirement concerning attainment and 

reasonable further progress (RFP) or any 

other applicable requirement of the 

Act.41 In evaluating whether the Cholla 

SIP Revision would interfere with any 

CAA requirements, we note that overall, 

the Cholla SIP Revision will result in 

reduced emissions of both SO2 and 

PM10 compared to the existing SIP and 

FIP requirements beginning in 2016 (see 

Tables 6 and 7 above) due to the 

retirement of Unit 2. While the Cholla 

SIP Revision will require fewer NOX

reductions than the FIP between 2018 

and 2025, it will ensure that NOX

emissions remain at or below current 

levels (i.e., levels consistent with nonoperation of Unit 2 42 and operation of 

LNB and SOFA on Units 1, 3 and 4) 

until 2025, after which it will require a 

substantial reduction in NOX emissions 

compared to both current levels and the 

FIP (see Table 8 above). 

With regard to applicable 

requirements concerning attainment and 

RFP, as explained by ADEQ, Cholla is 

located in north central Navajo County, 

Arizona, which is designated as 

unclassifiable/attainment for all of the 

NAAQS for which the EPA has issued 

designations.43 ADEQ also indicated 

that it has recommended an attainment/ 

unclassifiable designation for this area 

for the 2012 PM2.5 and 2010 SO2

standards. With regard to the 2012 PM2.5

standard, the EPA has finalized a 

designation of unclassifiable/attainment 

for Navajo County.44 With regard to the 

2010 SO2 standard, we note that, under 

the EPA’s Data Requirements Rule,45

ADEQ is required to develop and submit 

air quality data characterizing ambient 

concentrations of SO2 in the area around 

Cholla.46 The EPA will take these data 

into consideration in finalizing a 

designation for the area. Finally, we 

note that, on October 1, 2015, the EPA 

promulgated revised primary and 

secondary ozone NAAQS.47 State 

designation recommendations for the 

2015 ozone NAAQS are due to the EPA 

by October 1, 2016.48

In summary, Cholla is located in area 

that is designated unclassifiable/

attainment or has not yet been 

designated for each of the current 

NAAQS. Thus, the Arizona SIP does not 

currently rely on emission limitations at 

Cholla to satisfy any attainment or RFP 

requirements. Given that the Cholla SIP 

Revision will result in equivalent or 

lower emissions of NOX, PM10 and SO2

for all future years, compared to current 

emission levels, in an area that is 

designated unclassifiable/attainment or 

has not yet been designated for all 

NAAQS, we propose to find that the 

Cholla SIP Revision would not interfere 

with any applicable requirements 

concerning attainment or RFP. 

The other requirements of the CAA 

that apply to Cholla are: 

• Standards of Performance for New 

Stationary Sources (NSPS), 40 CFR part 

60, subpart D; 

• National Emission Standards for 

Hazardous Air Pollutants (NESHAP), 40 

CFR part 63, subpart UUUUU (also 

known as MATS); 

• Compliance Assurance Monitoring 

(CAM), 40 CFR part 64; and 

• BART and other visibility 

protection requirements under CAA 

section 169A and the RHR. 

The Cholla SIP Revision would not 

affect the applicable NESHAP, NSPS 

and CAM requirements. Therefore, we 

propose to find that the Cholla SIP 

Revision would not interfere with the 

applicable NESHAP, NSPS and CAM 

requirements. 

We also propose to find that Cholla 

SIP Revision would not interfere with 

the visibility protection requirements of 

the CAA and the RHR. Our proposed 

approval of the BART Reassessment is 

based on our determination that, taking 

into consideration the differences in the 

facts underlying the EPA’s prior BART 

analysis for NOX in Arizona Regional 

Haze FIP and the Cholla BART 

Reassessment, ADEQ’s revised BART 

analysis and determination for Cholla 

meet the BART requirements of the 

CAA and RHR. Furthermore, the Cholla 

SIP Revision would result in greater 

visibility improvement than the existing 

SIP and FIP requirements beginning in 

2026, which is consistent with the longterm national goal of restoring natural 

visibility conditions at Class I areas. 

Thus, we propose to find that the Cholla 

SIP Revision would not interfere with 

the visibility protection requirements of 

the CAA. 

E. The EPA’s Evaluation of Enforceable 

Emission Limits 

CAA section 110(a)(2)(A) requires 

SIPs to include enforceable emission 

limitations as necessary or appropriate 

to meet the applicable requirements of 

the Act. In addition, SIPs must contain 

regulatory requirements related to 

monitoring, recordkeeping, and 

reporting for applicable emission 

limitations.49 The Cholla Permit 

Revision includes such enforceable 


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50Cholla Permit Revision section I.A. 

emission limits, as well as associated 

monitoring, recordkeeping, and 

reporting requirements, for all units and 

pollutants. These requirements will 

become effective and federally 

enforceable when the Cholla SIP 

Revision is approved into the SIP and 

the FIP provisions applicable to Cholla 

are withdrawn.50 Therefore, we propose 

to find that the Cholla SIP Revision 

meets the requirements of the CAA and 

the EPA’s implementing regulations for 

enforceable emission limitations. 

V. Proposed Action 

For the reasons described above, the 

EPA proposes to approve the Cholla SIP 

Revision. Because this approval would 

fill the gap in the Arizona Regional Haze 

SIP left by the EPA’s prior partial 

disapproval with respect to Cholla, we 

propose to withdraw the provisions of 

the Arizona Regional Haze FIP that 

apply to Cholla. We also propose to find 

that withdrawal of the FIP would 

constitute our action on APS’s and 

PacifiCorp’s petitions for 

reconsideration of the Arizona Regional 

Haze FIP. 

VI. Environmental Justice 

Considerations 

As shown in Tables 6 and 7, the 

Cholla SIP Revision will result in 

reduced emissions of both SO2 and 

PM10 compared to the existing SIP and 

FIP requirements beginning in 2016. As 

shown in Table 8, while the Cholla SIP 

Revision will result in fewer NOX

reductions than the FIP between 2018 

and 2025, it will ensure that NOX

emissions remain at or below current 

levels until 2025, after which it will 

require a substantial reduction in NOX

emissions compared to both current 

levels and to the existing Arizona 

Regional Haze FIP. Therefore, the EPA 

believes that this action will not have 

potential disproportionately high and 

adverse human health or environmental 

effects on minority, low-income, or 

indigenous populations. 

VII. Incorporation by Reference 

In this rule, the EPA is proposing to 

include in a final EPA rule, regulatory 

text that includes incorporation by 

reference. In accordance with 

requirements of 1 CFR 51.5, the EPA is 

proposing to incorporate by reference 

‘‘Significant Permit Revision No. 61713 

to Operating Permit No. 53399’’ issued 

by ADEQ on October 16, 2015. The EPA 

has made, and will continue to make, 

this document available electronically 

through www.regulations.gov and in 

hard copy at U.S. Environmental 

Protection Agency Region IX, Air-2, 75 

Hawthorne Street, San Francisco, CA, 

94105–3901. 

VIII. Statutory and Executive Order 

Reviews 

A. Executive Order 12866: Regulatory 

Planning and Review and Executive 

Order 13563: Improving Regulation and 

Regulatory Review 

This action is not a significant 

regulatory action and was therefore not 

submitted to the Office of Management 

and Budget (OMB) for review. This rule 

applies to only one facility and is 

therefore not a rule of general 

applicability. 

B. Paperwork Reduction Act (PRA) 

This action does not impose an 

information collection burden under the 

PRA. This rule applies to only one 

facility. Therefore, its recordkeeping 

and reporting provisions do not 

constitute a ‘‘collection of information’’ 

as defined under 44 U.S.C. 3502(3) and 

5 CFR 1320.3(c). 

C. Regulatory Flexibility Act (RFA) 

I certify that this action will not have 

a significant economic impact on a 

substantial number of small entities. 

This action will not impose any 

requirements on small entities. Firms 

primarily engaged in the generation, 

transmission, and/or distribution of 

electric energy for sale are small if, 

including affiliates, the total electric 

output for the preceding fiscal year did 

not exceed 4 million megawatt hours. 

Both owners of Cholla, APS and 

PacifiCorp, exceed this threshold. 

D. Unfunded Mandates Reform Act 

(UMRA) 

This action does not contain an 

unfunded mandate of $100 million or 

more as described in UMRA, 2 U.S.C. 

1531–1538, and does not significantly or 

uniquely 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 on the 

distribution of power and 

responsibilities among the various 

levels of government. 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

This action does not have tribal 

implications, as specified in Executive 

Order 13175. It will not have substantial 

direct effects on any Indian tribes, on 

the relationship between the Federal 

Government and Indian tribes, or on the 

distribution of power and 

responsibilities between the Federal 

Government and Indian tribes. Thus, 

Executive Order 13175 does not apply 

to this action. 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

Risks and Safety Risks 

The EPA interprets EO 13045 as 

applying only to those regulatory 

actions that concern health or safety 

risks that the EPA has reason to believe 

may disproportionately affect children, 

per the definition of ‘‘covered regulatory 

action’’ in section 2–202 of the 

Executive Order. This action is not 

subject to Executive Order 13045 

because it does not concern an 

environmental health risk or safety risk. 

H. Executive Order 13211: Actions 

Concerning Regulations That 

Significantly Affect Energy Supply, 

Distribution, or Use 

This action is not subject to Executive 

Order 13211 because it is not a 

significant regulatory action under 

Executive Order 12866. 

I. National Technology Transfer and 

Advancement Act 

This rulemaking does not involve 

technical standards. The EPA is not 

revising any technical standards or 

imposing any new technical standards 

in this action. 

J. Executive Order 12898: Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations 

The EPA believes the human health or 

environmental risk addressed by this 

action will not have potential 

disproportionately high and adverse 

human health or environmental effects 

on minority, low-income, or indigenous 

populations. The results of this 

evaluation are contained in section VI 

above. 

K. Determination Under Section 307(d) 

Pursuant to CAA section 307(d)(1)(B), 

the EPA proposes to determine that this 

action is subject to the provisions of 

section 307(d). Section 307(d) 

establishes procedural requirements 

specific to certain rulemaking actions 

under the CAA. Pursuant to CAA 

section 307(d)(1)(B), the withdrawal of 

the provisions of the Arizona Regional 

Haze FIP that apply to Cholla is subject 

to the requirements of CAA section 

307(d), as it constitutes a revision to a 

FIP under CAA section 110(c). 

Furthermore, CAA section 307(d)(1)(V) 

provides that the provisions of section 


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307(d) apply to ‘‘such other actions as 

the Administrator may determine.’’ The 

EPA proposes that the provisions of 

307(d) apply to the EPA’s action on the 

Cholla SIP revision. 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air 

pollution control, Incorporation by 

reference, Intergovernmental relations, 

Nitrogen dioxide, Particulate matter, 

Reporting and recordkeeping 

requirements, Sulfur dioxide, Visibility. 

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

Dated: June 30, 2016. 

Deborah Jordan, 

Acting Regional Administrator, EPA Region 

IX. 

PART 52—APPROVAL AND 

PROMULGATION OF 

IMPLEMENTATION PLANS 

■ 1. The authority citation for part 52 

continues to read as follows: 

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

Subpart D—Arizona 

■ 2. In § 52.145, revise paragraphs (f)(1), 

(2), (3), (4), (5), and (10) to read as 

follows: 

§ 52.145 Visibility protection. 

* * * * * 

(f) * * * 

(1) Applicability. This paragraph (f) 

applies to each owner/operator of the 

following coal-fired electricity 

generating units (EGUs) in the state of 

Arizona: Coronado Generating Station, 

Units 1 and 2. The provisions of this 

paragraph (f) are severable, and if any 

provision of this paragraph (f), or the 

application of any provision of this 

paragraph (f) 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 (f), shall not be affected 

thereby. 

(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. For purposes of this paragraph (f): 

ADEQ means the Arizona Department 

of Environmental Quality. 

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 

unit. 

Coal-fired unit means any of the EGUs 

identified in paragraph (f)(1) of this 

section. 

Continuous emission monitoring 

system or CEMS means the equipment 

required by 40 CFR part 75 and this 

paragraph (f). 

Emissions limitation or emissions 

limit means any of the Federal Emission 

Limitations required by this paragraph 

(f) or any of the applicable PM10 and 

SO2 emissions limits for Coronado 

Generating Station submitted to EPA as 

part of the Arizona Regional Haze SIP in 

a letter dated February 28, 2011, and 

approved into the Arizona State 

Implementation Plan on December 5, 

2012. 

Flue Gas Desulfurization System or 

FGD means a pollution control device 

that employs flue gas desulfurization 

technology, including an absorber 

utilizing lime, fly ash, or limestone 

slurry, for the reduction of sulfur 

dioxide emissions. 

lb means pound(s). 

NOX means nitrogen oxides expressed 

as nitrogen dioxide (NO2). 

Owner(s)/operator(s) means any 

person(s) who own(s) or who operate(s), 

control(s), or supervise(s) one or more of 

the units identified in paragraph (f)(1) of 

this section. 

MMBtu means million British thermal 

unit(s). 

Operating hour means any hour that 

fossil fuel is fired in the unit. 

PM10 means filterable total particulate 

matter less than 10 microns and the 

condensable material in the impingers 

as measured by Methods 201A and 202 

in 40 CFR part 51, appendix M. 

Regional Administrator means the 

Regional Administrator of EPA Region 

IX or his/her authorized representative. 

SO2 means sulfur dioxide. 

SO2 removal efficiency means the 

quantity of SO2 removed as calculated 

by the procedure in paragraph 

(f)(5)(iii)(B) of this section. 

Unit means any of the EGUs identified 

in paragraph (f)(1) of this section. 

Valid data means data recorded when 

the CEMS is not out-of-control as 

defined by 40 CFR part 75. 

(3) Federal emission limitations—(i) 

NOX emission limitations. The owner/

operator of each coal-fired unit subject 

to this paragraph (f) shall not emit or 

cause to be emitted NOX in excess of the 

following limitations, in pounds per 

million British thermal units (lb/

MMBtu) from any coal-fired unit or 

group of coal-fired units. Each emission 

limit shall be based on a rolling 30- 

boiler-operating-day average, unless 

otherwise indicated in specific 

paragraphs. 

Coal fired unit or group of coalfired units 

Federal 

emission 

limitation 

Coronado Generating Station 

Unit 1 ..................................... 0.065 

Coal fired unit or group of coalfired units 

Federal 

emission 

limitation 

Coronado Generating Station 

Unit 2 ..................................... 0.080 

(ii) [Reserved] 

(4) Compliance dates. (i) The owners/ 

operators of each unit subject to this 

paragraph (f) shall comply with the NOX

emissions limitations and other NOXrelated requirements of this paragraph 

(f) no later than December 5, 2017. 

(ii) The owners/operators of each unit 

subject to this paragraph (f) shall 

comply with the applicable PM10 and 

SO2 emissions limits submitted to EPA 

as part of the Arizona Regional Haze SIP 

in a letter dated February 28, 2011, and 

approved into the Arizona State 

Implementation Plan on December 5, 

2012, as well as the related compliance, 

recordkeeping and reporting of this 

paragraph (f) no later than June 3, 2013. 

(5) Compliance determinations for 

NOX and SO2—(i) Continuous emission 

monitoring system. 

(A) At all times after the compliance 

date specified in paragraph (f)(4) of this 

section, the owner/operator of each 

coal-fired unit shall maintain, calibrate, 

and operate a CEMS, in full compliance 

with the requirements found at 40 CFR 

part 75, to accurately measure SO2, 

NOX, diluent, and stack gas volumetric 

flow rate from each unit. In addition, 

the owner/operator of Cholla Units 2, 3, 

and 4 shall calibrate, maintain, and 

operate a CEMS, in full compliance with 

the requirements found at 40 CFR part 

75, to accurately measure SO2 emissions 

and diluent at the inlet of the sulfur 

dioxide control device. All valid CEMS 

hourly data shall be used to determine 

compliance with the emission 

limitations for NOX and SO2 in 

paragraph (f)(3) of this section for each 

unit. When the CEMS is out-of-control 

as defined by 40 CFR part 75, that CEMs 

data shall be treated as missing data, 

and not used to calculate the emission 

average. Each required CEMS must 

obtain valid data for at least 90 percent 

of the unit operating hours, on an 

annual basis. 

(B) 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 40 CFR part 

75 requirements, relative accuracy test 

audits shall be calculated for both the 

NOX and SO2 pounds per hour 

measurement and the heat input 

measurement. The CEMs monitoring 

data shall not be bias adjusted. The inlet 

SO2 and diluent monitors required by 

this rule shall also meet the Quality 

Assurance/Quality Control (QA/QC) 


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requirements of 40 CFR part 75. The 

testing and evaluation of the inlet 

monitors and the calculations of relative 

accuracy for lb/hr of NOX, SO2 and heat 

input shall be performed each time the 

40 CFR part 75 CEMS undergo relative 

accuracy testing. 

(ii) Compliance determinations for 

NOX. 

(A) [Reserved] 

(B) Coronado Generating Station. 

Compliance with the NOX emission 

limits for Coronado Unit 1 and 

Coronado Unit 2 in paragraph (f)(3)(i) of 

this section shall be determined on a 

rolling 30 boiler-operating-day basis. 

The 30-boiler-operating-day rolling NOX

emission rate for each unit shall be 

calculated in accordance with the 

following procedure: Step one, sum the 

total pounds of NOX emitted from the 

unit during the current boiler operating 

day and the previous twenty-nine (29) 

boiler operating days; Step two, sum the 

total heat input to the unit in MMBtu 

during the current boiler operating day 

and the previous twenty-nine (29) boiler 

operating days; Step three, divide the 

total number of pounds of NOX emitted 

from that unit during the thirty (30) 

boiler operating days by the total heat 

input to the unit during the thirty (30) 

boiler operating days. A new 30-boileroperating-day rolling average NOX

emission rate shall be calculated for 

each new boiler operating day. Each 30- 

boiler-operating-day average NOX

emission rate shall include all emissions 

that occur during all periods within any 

boiler operating day, including 

emissions from startup, shutdown, and 

malfunction. 

(C) 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 of the 30-day rolling 

average. 

(iii) Compliance determinations for 

SO2. (A) The 30-day rolling average SO2

emission rate for each coal-fired unit 

shall be calculated in accordance with 

the following procedure: Step one, sum 

the total pounds of SO2 emitted from the 

unit during the current boiler-operating 

day and the previous twenty-nine (29) 

boiler-operating days; step two, sum the 

total heat input to the unit in MMBtu 

during the current boiler-operating day 

and the previous twenty-nine (29) 

boiler-operating day; and step three, 

divide the total number of pounds of 

SO2 emitted during the thirty (30) 

boiler-operating days by the total heat 

input during the thirty (30) boileroperating days. A new 30-day rolling 

average SO2 emission rate shall be 

calculated for each new boiler-operating 

day. Each 30-day rolling average SO2

emission rate shall include all emissions 

and all heat input that occur during all 

periods within any boiler-operating day, 

including emissions from startup, 

shutdown, and malfunction. 

(B) [Reserved] 

(C) If a valid SO2 pounds per hour at 

the outlet of the FGD system or heat 

input is not available for any hour for 

a unit, that heat input and SO2 pounds 

per hour shall not be used in the 

calculation of the 30-day rolling 

average. 

(D) If both a valid inlet and outlet SO2

lb/MMBtu and an outlet value of lb/hr 

of SO2 are not available for any hour, 

that hour shall not be included in the 

efficiency calculation. 

* * * * * 

(10) Equipment operations. 

(i) [Reserved] 

(ii) Coronado Generating Station. At 

all times, including periods of startup, 

shutdown, and malfunction, the owner 

or operator of Coronado Generating 

Station Unit 1 and Unit 2 shall, to the 

extent practicable, maintain and operate 

each unit in a manner consistent with 

good air pollution control practices for 

minimizing emissions. The owner or 

operator shall continuously operate 

pollution control equipment at all times 

the unit it serves is in operation, and 

operate pollution control equipment in 

a manner consistent with technological 

limitations, manufacturer’s 

specifications, and good engineering 

and 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 which may include, but 

is not limited to, monitoring results, 

review of operating and maintenance 

procedures, and inspection of each unit. 

* * * * * 

[FR Doc. 2016–16959 Filed 7–18–16; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R08–OAR–2016–0221; FRL–9948–88– 

Region 8] 

Approval and Promulgation of State 

Implementation Plan Revisions to 

Permits, Rules and Approval Orders; 

Utah 

AGENCY: Environmental Protection 

Agency. 

ACTION: Proposed rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is proposing to approve 

State Implementation Plan (SIP) 

revisions submitted by the State of Utah 

on February 10, 2012 and August 29, 

2014. These submittals request SIP 

revisions to remove changes to the 

major source baseline date that were 

disapproved by the EPA on July 15, 

2011. The submittals also address the 

EPA’s February 6, 2014 disapproval of 

several permit rules related to the public 

availability of good engineering practice 

stack height demonstrations in the 

public comment process for an approval 

order, and the process for making 

emission reductions enforceable in an 

approval order. The EPA is taking this 

action in accordance with section 110 of 

the Clean Air Act (CAA). 

DATES: Written comments must be 

received on or before August 18, 2016. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–R08– 

OAR–2016–0221, at http://

www.regulations.gov. Follow the online 

instructions for submitting comments. 

Once submitted, comments cannot be 

edited or removed from Regulations.gov. 

The EPA may publish any comment 

received to its public docket. Do not 

submit electronically any information 

you consider to be Confidential 

Business Information (CBI) or other 

information whose disclosure is 

restricted by statute. Multimedia 

submissions (audio, video, etc.,) must be 

accompanied by a written comment. 

The written comment is considered the 

official comment and should include 

discussion of all points you wish to 

make. The EPA will generally not 

consider comments or comment 

contents located outside of the primary 

submission (i.e., on the web, cloud, or 

other file sharing system). For 

additional submission methods, the full 

EPA public comment policy, 

information about CBI or multimedia 

submissions, and general guidance on 

making effective comments, please visit 

http://www2.epa.gov/dockets/

commenting-epa-dockets. 

FOR FURTHER INFORMATION CONTACT: Jody 

Ostendorf, Air Program, U.S. 

Environmental Protection Agency 

(EPA), Region 8, Mail Code 8P–AR, 

1595 Wynkoop Street, Denver, Colorado 

80202–1129, (303) 312–7814, 

ostendorf.jody@epa.gov. 

Incorporation by Reference 

In this rule, the EPA is finalizing 

regulatory text that includes 

incorporation by reference. In 

accordance with requirements of 1 CFR 

51.5, the EPA is proposing to 

incorporate by reference the Utah rules 


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