Technical Support Document

Evaluation of the Arizona Infrastructure SIP for

2008 O3 Transport (CAA 110(a)(2)(D))

Evaluation of the Arizona Infrastructure State Implementation Plan for the 2008 Ozone (O3) 

NAAQS for CAA 110(a)(2)(D) Prongs 1, 2, and 4

U.S. EPA, Region 9

March 15, 2016
1

Introduction

This document summarizes the U.S. Environmental Protection Agency’s (EPA’s) review of the 

Arizona State Implementation Plan (SIP) provisions and local provisions to meet the

requirements of §110(a)(2)(D) of the Clean Air Act (CAA) for the 2008 ozone National Ambient 

Air Quality Standard (NAAQS). Specifically, this Technical Support Document (TSD) examines 

information submitted by the Arizona Department of Environmental Quality (ADEQ) on behalf 

of ADEQ, Maricopa County Air Quality Department (MCAQD or Maricopa County), Pima 

County Department of Environmental Quality (PDEQ or Pima County), and Pinal County Air 

Quality Control District (PCAQCD or Pinal County) to EPA in 2012 and 2015.

On December 27, 2012, ADEQ submitted the “Arizona State Implementation Plan Revision 

under Clean Air Act Section 110(a)(2) and (2); 2008 8-hour Ozone NAAQS” (2012 submittal) to 

address all of the CAA section 110(a)(2) requirements for the 2008 8-hour Ozone NAAQS. On 

December 3, 2015 ADEQ submitted a supplemental submittal that included analysis for

“infrastructure” SIP (I-SIP) elements related to several different NAAQS, including a submission 

for the 2008 ozone NAAQS for CAA § 110(a)(2)(D).

1 ADEQ subsequently clarified that the 

portion of the submittal related to the 2008 ozone NAAQS only applied to prongs 1, 2, and 4.2

For the purposes of this action, we will refer to this as the “2015 submittal.”

 

1 Arizona State Implementation Plan Revisions for 2008 Ozone and 2010 Nitrogen Dioxide Under Clean Air Act 

Section 110(a)(2)(D) and Revision for All Previous and Future NAAQS Under CAA Section 110(a)(2)(K) signed 

December 3, 2015.

2 Email from Heidi Haggerty of ADEQ to Maeve Clancy of EPA Region 9. “AZ 2015 Ozone Transport I-SIP 

Submittal Clarification.” Sent December 9, 2015.
2

Evaluation Summary

Element Identification Meets Requirement? 

Element 

SubElement

Description 

ADEQ 

Maricopa 

County

Pima 

County 

Pinal 

County

D

i

Interstate transport - significant 

contribution to nonattainment (prongs 

1-2) 

YES

Interstate transport - interference with 

maintenance (prong 3) 

NO ACTION

Previous Approval/Disapproval

Interstate transport - visibility 

transport (prong 4) NO (Regional Haze FIP)

ii 

Interstate pollution abatement (§126, 

including requirement to notify states 

of potential impacts from new 

sources) 

NO ACTION

Previous Approval/Disapproval

International air pollution (§115) NO ACTION

Previous Approval

Background

CAA sections 110(a)(1) and (2) requires states to address basic SIP requirements to implement, 

maintain and enforce the NAAQS no later than three years after the promulgation of a new or 

revised standard. Section 110(a)(2) outlines the specific requirements that each state is required 

to address in this SIP submission that collectively constitute the "infrastructure" of a state's air 

quality management program. SIP submittals that address these requirements are referred to as 

“infrastructure SIPs” (I-SIP). In particular, CAA section 110(a)(2)(D)(i)(I) requires that each SIP 

for a new or revised NAAQS contain adequate provisions to prohibit any source or other type of 

emissions activity within the state from emitting air pollutants that will “contribute significantly 

to nonattainment” (prong 1) or “interfere with maintenance” (prong 2) of the applicable air 

quality standard in any other state. CAA section 110(a)(2)(D)(i)(II) requires SIP provisions that 

prevent interference with measures required to be included in the applicable implementation plan 

for any other State under part C to prevent significant deterioration of air quality (prong 3) or to 

protect visibility (prong 4). This action address the section 110(a)(2)(D)(i) requirements of 

prongs 1, 2 and 4 with respect to Arizona’s SIP submissions.

On March 27, 2008, EPA issued a revised NAAQS for 8-hour ozone.

3 This action triggered a 

requirement for states to submit an infrastructure SIP to address the applicable requirements of 

section 110(a)(2) within three years of issuance of the revised NAAQS. On December 27, 2012, 

 

3 National Ambient Air Quality Standards for Ozone; Final Rule, 73 FR 16436 (March 27, 2008).
3

ADEQ submitted the 2012 Ozone I-SIP (2012 submittal) which included the SIP revision, 

completeness checklist, copies of authorizing statutes, and copies of public process 

documentation.

On September 13, 2013, EPA issued “Guidance on Infrastructure State Implementation Plan 

(SIP) Elements under Clean Air Act Sections 110(a)(1) and 110(a)(2),” which provides “advice 

on the development of infrastructure SIPs for the 2008 ozone NAAQS . . . as well as 

infrastructure SIPs for new or revised NAAQS promulgated in the future.”4 EPA followed that 

guidance with an additional memo specific to 110(a)(2)(D)(i)(I) (prongs 1 and 2) requirements 

for the 2008 ozone standard on January 22, 2015 entitled, “Information on the Interstate 

Transport “Good Neighbor” Provision for the 2008 Ozone NAAQS Under CAA Section 

110(a)(2)(D)(i)(I)” (2015 transport memo).5 While this memo did not provide specific guidance 

to western states on interstate transport, it did contain preliminary modeling information for 

western states. This 2015 transport memo, following the approach used in EPA’s prior CrossState Air Pollution Rule (CSAPR),

6

provided data identifying ozone monitoring sites that were

projected to be in nonattainment or have maintenance problems for the 2008 ozone NAAQS in 

2018. Also, EPA provided the projected contribution estimates from 2018 anthropogenic oxides 

of nitrogen (NOX) and volatile organic compound (VOC) emissions in each state to ozone 

concentrations to each of the projected sites. 

On August 4, 2015, EPA published a Federal Register Notice entitled, “Notice of Availability of 

the Environmental Protection Agency's Updated Ozone Transport Modeling Data for the 2008 

Ozone NAAQS.”7 This Notice of Data Availability (NODA) is an update of the preliminary air 

quality modeling data that was released January 22, 2015. The NODA provided data identifying 

ozone monitoring sites that are projected to be nonattainment or have maintenance problems 

(following the CSAPR approach) for the 2008 ozone NAAQS in 2017.

8 Also, EPA provided the 

projected ozone contribution estimates from 2017 anthropogenic NOX and VOC emissions in 

each state to ozone concentrations at each of the projected monitoring sites. The 2017 modeling 

released in the NODA was used to support EPA’s proposed update to CSAPR to address CAA 

section 110(a)(2)(D)(i)(I) requirements with respect to the 2008 ozone NAAQS in the eastern 

U.S. (“CSAPR Update Rule”).9 CSAPR and its predecessor transport rules, the NOX SIP Call 

and CAIR, were designed to address the collective contributions from the 37 states in the eastern 

U.S.; ozone contribution information was not calculated to or from the 11 states in the western 

U.S. The proposed CSAPR Update Rule and the supportive modeling released in the NODA 

include data relevant to the West but do not evaluate potential interstate transport impacts in 11 

western states, including Arizona. In this action today, we are utilizing this data to evaluate the 

state’s submittals and any interstate transport obligations under section 110(a)(2)(D)(i)(I).

 

4 Memorandum from Stephen D. Page, Director, Office of Air Quality Planning and Standards, to Regional Air 

Division Directors, Regions 1-10 (September 13, 2013).

5 Memorandum from Stephen D. Page, Director, Office of Air Quality Planning and Standards, to Regional Air 

Division Directors, Regions 1-10 (January 22, 2015).

6 Cross-State Air Pollution Rule, 76 Fed. Reg. 48208 (Aug. 8, 2011).

7 Notice of Availability of the Environmental Protection Agency's Updated Ozone Transport Modeling Data for the 

2008 Ozone National Ambient Air Quality Standard (NAAQS), 80 FR 46271 (August 4, 2015).

8 EPA adopted 2017 as the analytic year for the updated ozone modeling information. See 80 FR 46273.

9 Cross-State Air Pollution rule Update for the 2008 Ozone NAAQS, 80 FR 75706 (December 3, 2015).
4

EPA is obligated, pursuant to a judgement issued by the Northern District of California in Sierra 

Club vs. McCarthy, to take final action on 110(a)(2)(D) prongs 1, 2, and 4 of Arizona’s 

December 27, 2012 SIP revision by June 7, 2016.10 In our July 2015 partial approval and partial 

disapproval of the 2008 lead and ozone NAAQS for I-SIP elements C, D, J, and K, EPA partially 

approved and partially disapproved Arizona for 110(a)(2)(D)(i) prong 3 and partially approved 

and partially disapproved the SIP for purposes of 110(a)(2)(D)(ii) (relating to CAA 115 and 

126). We also stated our intention to propose action on the I-SIP for the 2008 ozone NAAQS

110(a)(2)(D)(i) prongs 1, 2, and 4 in a separate action.11 EPA subsequently took action on I-SIP 

elements A, B, E-H, L, and M for the 2008 Pb and 2008 ozone NAAQS in August 2015.12

On December 3, 2015, ADEQ submitted a supplement to the 2012 Ozone I-SIP for 

110(a)(2)(D)(i) prongs 1, 2, and 4, which included additional SIP revisions reflecting the 2013 ISIP guidance, 2015 transport memo, and 2015 NODA (2015 submittal).

13

We have evaluated the 2012 and 2015 submittals in relation to the infrastructure SIP 

requirements (or “elements”) of CAA section 110(a)(2)(D) for the 2008 Ozone NAAQS. In the 

following pages we discuss the requirements of the Act, summarize the State’s submittals, and 

present our evaluation for CAA section 110(a)(2)(D)(i) prongs 1, 2, and 4.

CAA Section 110(a)(2)(D) – Interstate Transport Overview

Section 110(a)(2)(D) of the Act requires that each SIP “contain adequate provisions—

(i) prohibiting, consistent with the provisions of this title, any source or other type of emissions 

activity within the State from emitting any air pollutant in amounts which will—(I) contribute 

significantly to nonattainment in, or interfere with maintenance by, any other State with respect 

to any such national primary or secondary ambient air quality standard, or (II) interfere with 

measures required to be included in the applicable implementation plan for any other State under 

part C to prevent significant deterioration of air quality or to protect visibility, and 

(ii) insuring compliance with the applicable requirements of sections 126 and 115 (relating to 

interstate and international pollution abatement).”

Section 126(a) of the Act requires notification to affected, nearby states of major proposed new 

or modified sources. Sections 126(b) and (c) pertain to petitions by affected states to EPA 

regarding sources violating the “interstate transport” provisions of CAA section 110(a)(2)(i). 

Section 115 of the Act similarly pertains to international transport of air pollution.

With respect to the first two “prongs” of CAA section 110(a)(D)(i) (regarding significant 

contribution to nonattainment or interference with maintenance in any other State), EPA 

 

10 See Judgment, Sierra Club v. McCarthy, Case 4:14-cv-05091-YGR (N.D. Cal. May 15, 2015).

11 Partial Approval and Partial Disapproval of Air Quality State Implementation Plans; Arizona; Infrastructure 

Requirements for Lead and Ozone. 80 FR 40905 (July 14, 2015).

12 Approval and Promulgation of State Implementation Plans; Arizona; Infrastructure Requirements for the 2008 

Lead (Pb) and the 2008 8-Hour Ozone National Ambient Air Quality Standards (NAAQS). 80 FR 47859 (August 

10, 2015).

13 See footnotes 1 and 2.
5

previously approved Arizona’s interstate transport SIP as satisfying the requirements of CAA 

section 110(a)(2)(D)(i)(I) for the 1997 8-hour ozone and 1997 PM2.5 NAAQS.14 As we stated in 

our July 2015 action on the 2008 O3 I-SIP, “EPA is proposing action on the I-SIP for the 2008 

ozone NAAQS with respect to these first two prongs of CAA section 110(a)(D)(i) in this 

separate rulemaking and will take final action on these SIP elements no later than June 7, 

2016.”

15

 

With respect to the third “prong” of CAA section 110(a)(D)(i) (regarding interference with 

measures required to be included in the applicable implementation plan for any other State to 

prevent significant deterioration of air quality), EPA’s evaluation of the Arizona SIP for 

purposes of the 2008 ozone NAAQS is contained in our July 2015 partial approval and partial 

disapproval action.

16 Finally, with respect to the fourth prong of CAA section 110(a)(2)(D)(i), 

EPA is proposing action and will take final action no later than June 7, 2016.17

With respect to the requirements in CAA section 110(a)(2)(D)(ii) regarding compliance with the 

applicable requirements of section 126 relating to interstate pollution abatement, EPA previously 

partially approved and partially disapproved this part of the Arizona SIP in July 2015.18 We are 

taking no further action on this portion of Arizona’s transport SIP in today’s action.

CAA section 115 authorizes the Administrator to require a state to revise its SIP, in the case of a 

belief or allegation that any air pollutant emitted in the United States causes or contributes to air 

pollution which may reasonably be anticipated to endanger public health or welfare in a foreign 

country. EPA previously approved this part of the Arizona SIP for the 2008 ozone NAAQS in 

July 2015.19

Summary of Arizona’s 110(a)(2)(D) Submittals

Arizona’s 2012 submittal briefly summarized the CAA requirements of sections 110(a)(2)(D)(i) 

and 110(a)(2)(D)(ii), but as to prongs 1, 2, and 4, did not address the 2008 ozone NAAQS or 

potential transport linkages between Arizona and other states.

Arizona’s 2015 submittal represents ADEQ’s comprehensive analysis of ozone transport from 

Arizona to surrounding states and discusses potential interstate transport linkages between 

Arizona and the El Centro and Los Angeles, CA nonattainment receptors that were identified in 

the 2015 ozone transport memo and/or the 2015 NODA. The 2015 submittal also addresses the 

requirements of prong 4 (interstate transport visibility requirements). 

 

14 Approval and Promulgation of Implementation Plans; States of Arizona and Nevada; Interstate Transport of 

Pollution, 72 FR 41629 (July 31, 2007).

15 See footnote 11.

16 Id.

17 See footnote 10.

18 See footnote 11.

19 Id.
6

Consistent with the 2015 NODA, Arizona notes that its impact on the El Centro and Los Angeles 

monitors is above 1%. However, Arizona only potentially impacts one of seven Los Angeles 

monitors, and contributes less than 1% to all other maintenance and nonattainment receptors. 

ADEQ also states that, “In eastern states, the EPA has chosen a 1% of the standard threshold as a 

significant contribution. However, Arizona considers the southwest to be different.” They go on 

to say that, “It is unclear at this point what threshold is significant for southwestern states.”

EPA’s assessment of these statements is in the next section.

ADEQ then summarizes sources of volatile organic compounds (VOCs) and nitrogen oxides

(NOx) statewide, aggregated from the 2011 National Emission Inventory. Biogenic contributions 

and fires are the large non-anthropogenic sector of VOC emissions with mobile sources, 

solvents, and gas stations as the largest anthropogenic sector. Electric generating units (EGUs), 

airports, and miscellaneous source categories are the largest point source contributors. For NOx, 

mobile sources, EGUs, and fires are the highest contributors. Airports and Portland cement 

operations are also large point sources of NOx emissions in the state. 

Arizona outlines the controls on anthropogenic emission sources in Arizona in the narrative and 

in tables included as Appendix B. They focus on their efforts to reduce NOx as a precursor 

pollutant for downwind ozone through controls implemented through Arizona's Regional Haze 

SIP and EPA's Regional Haze FIP and Maricopa County stationary source rules included in the 

Arizona SIP. The Regional Haze Rule controls NOx emissions from smelters, cement plants, and 

coal-fired EGUs through Best Available Retrofit Technologies (BART) to reduce haze. The cost 

of control ranges from $2400-$3400 per tons of NOx reduced for EGUs and $800-$1100 per ton

for cement kilns. Maricopa County is the most populous county in the state and has controls in 

place on many different NOx and VOC source categories including EGUs, gas stations, and 

various industrial processes, amongst others. Maricopa County was recently reclassified as a 

moderate nonattainment area for the 2008 ozone NAAQS,

20 and is updating its NOx rules to 

meet Reasonably Available Control Technology (RACT), so a more stringent level of control 

will be in place by January 1, 2017.

EPA’s Analysis

110(a)(2)(D)(i)(I) Prong 1 and Prong 2

CAA section 110(a)(2)(D)(i), requires SIPs to contain so called “good neighbor” provisions to 

prohibit certain adverse air quality effects on neighboring states due to interstate transport of 

pollution. There are four sub-elements (or prongs) within CAA section 110(a)(2)(D)(i). Prongs 1 

and 2 require that each SIP for a new or revised NAAQS contain adequate provisions to prohibit 

any source or other type of emissions activity within the state from emitting air pollutants that 

will “contribute significantly to nonattainment” (prong 1) or “interfere with maintenance” (prong 

2) of the applicable air quality standard in any other state.

 

20 Determinations of Attainment by the Attainment Date, Extensions of the Attainment Date, and Reclassification of 

Several Areas Classified as Marginal for the 2008 Ozone National Ambient Air Quality Standards. 80 FR 51992 

(August 27, 2015).
7

The January 2015 transport memo modeling showed a 1.47 ppb, or 1.96% contribution from 

Arizona to a monitor projected to violate the 2008 ozone NAAQS located in El Centro, CA

(receptor ID: 60251003).21 The updated ozone transport modeling released with the August 2015 

NODA continued to show the transport linkage between Arizona and El Centro, CA, but this 

time at a slightly higher level of contribution: 1.78 ppb, or 2.4% of the NAAQS.22 It also showed 

a new linkage between Arizona and a monitor in Los Angeles, CA (receptor ID: 60379033) at a 

contribution of 0.86 ppb, or 1.1% of the NAAQS.23

To determine whether the CAA section 110(a)(2)(D)(i)(I), prongs 1 and 2 requirement is 

satisfied, EPA first must determine whether a state's emissions will contribute significantly to 

nonattainment or interfere with maintenance of a NAAQS in another state. If a state is 

determined not to make such contribution or interfere with maintenance of the NAAQS, then

EPA can conclude that the state’s SIP complies with the requirements of section 

110(a)(2)(D)(i)(I). In several prior federal rulemakings interpreting section 110(a)(2)(D)(i)(I), 

EPA has evaluated whether a state will significantly contribute to nonattainment or interfere with 

maintenance of a NAAQS by first identifying downwind receptors that are expected to have 

problems attaining or maintaining the NAAQS.24 EPA has then determined which upwind states 

contribute to these identified air quality problems in amounts sufficient to warrant further 

evaluation to determine if the state can make emission reductions to reduce its contribution. 

CSAPR and the proposed CSAPR Update used a screening threshold (1% of the NAAQS) to 

identify such contributing upwind states warranting further review and analysis. EPA’s NODA 

used air quality modeling to evaluate contributions from upwind states to downward receptors. 

Applying the methodology used in CSAPR, the NODA modeling information indicates that 

emissions from Arizona contribute amounts exceeding the CSAPR 1% threshold at two projected 

downwind nonattainment sites in El Centro, California and Los Angeles, California. 

EPA notes that it disagrees with ADEQ’s contention that it is unclear what screening threshold is 

significant for southwestern states when addressing interstate transport contributions. EPA 

believes contribution from an individual state equal to or above 1% of the NAAQS could be 

considered significant where the collective contribution of emissions from one or more upwind 

states is responsible for a considerable portion of the downwind air quality problem regardless of 

where the receptor is geographically located.25

Accordingly, although EPA’s modeling indicates that emissions from Arizona contribute above 

the 1% threshold to two projected downwind air quality problems, EPA examined several factors

to determine whether Arizona should be considered to significantly contribute to nonattainment 

 

21 Air Quality Modeling Technical Support Document for Memorandum from Stephen D. Page, Director, Office of 

Air Quality Planning and Standards, to Regional Air Division Directors, Regions 1-10 (September 13, 2013).

22 Data file with 2017 Ozone Contributions. Included in docket for: Notice of Availability of the Environmental 

Protection Agency's Updated Ozone Transport Modeling Data for the 2008 Ozone National Ambient Air Quality 

Standard (NAAQS), 80 FR 46271 (August 4, 2015).

23 Id.

24 NOx SIP Call, Final Rule, 63 FR 57371 (October 27, 1998); Clean Air Interstate Rule (CAIR), Final Rule, 70 FR 

25172 (May 12, 2005); Cross-State Air Pollution Rule (CSAPR), Final Rule, 76 FR 48208 (August 8, 2011); 

CSAPR Update Rule, Proposed Rule, 80 FR 75706 (Dec. 3, 2015).

25 However, EPA has previously noted there may be additional criteria to evaluate regarding collective contribution 

of transported air pollution at certain locations in the West. See footnotes 5 and 7.
8

or interfere with maintenance of the NAAQS at those sites, including the air quality and 

contribution modeling, receptor data, and the statewide measures reducing emissions of VOCs 

and NOx. EPA notes that no single piece of information is by itself dispositive of the issue for 

purposes of this analysis. Instead, EPA has considered the total weight of all the evidence taken 

together to evaluate whether Arizona significantly contributes to nonattainment or interferes with 

maintenance of the 2008 ozone NAAQS in those areas.

One such factor that EPA considers relevant to determining the nature of a projected receptor’s 

interstate transport problem is the magnitude transported ozone from all upwind states

collectively contributing to the air quality problem. In CSAPR and the CSAPR Update Rule, 

EPA used the 1% air quality threshold to identify linkages between upwind states and downwind 

maintenance receptors. States whose contributions to a specific receptor that meet or exceed the 

threshold were considered to be linked to that receptor. The linked states emissions (and 

available emission reductions) were then analyzed further as a second step to EPA’s contribution 

analysis. States whose contributions to all receptors were below the 1% threshold did not require 

further evaluation to address interstate transport and therefore, we found those states were 

determined to make insignificant contributions to downwind air quality air quality. Therefore, 

the states below the threshold do not significantly contribute to nonattainment or interfere with 

maintenance of the NAAQS in other states. EPA used the 1% threshold in the East because prior 

analysis showed that, in general, nonattainment problems result from a combined impact of 

relatively small individual contributions from upwind states, along with contributions from instate sources. EPA has observed that a relatively large portion of the air quality problem at most 

ozone nonattainment and maintenance receptors in the East is the result of the collective 

contribution from a number of upwind states. 

Specifically, EPA found the total upwind states’ contribution to ozone concentration (from 

linked and unlinked states) based on modeling for 2017 ranges from 17% to 67% to identified 

downwind air quality problems, with between 4 and 12 states each contributing above 1% to the 

downwind air quality problem.26,27 Thus, irrespective of the 1% air quality threshold in the East, 

EPA has found that the collective contributions from upwind states represent a large portion of 

the ozone concentrations at projected air quality problems. Further in the East, EPA found that 

the 1% threshold is appropriate to capture a high percentage of the total pollution transport 

affecting downwind receptors. By comparison, according to EPA’s modeling, the total upwind 

(linked or unlinked) states’ contribution to ozone concentration at the projected nonattainment 

sites in El Centro, California, and Los Angeles, California, is comparatively small with only one 

state contributing above the 1% threshold.

In particular, Arizona is the only state that contributes greater than the 1% threshold to the 

projected 2017 levels of the 2008 ozone NAAQS at the El Centro receptor. 28 The total 

contribution from all states to the El Centro receptor is 4.4% of the total ozone concentration at 

 

26 The stated range is based on the highest nonattainment or maintenance receptor in each area. All nonattainment 

and maintenance receptors had upwind contributions of well over 17%, except for some receptors in Dallas and 

Houston.

27 Memo to Docket from EPA, Air Quality Policy Division. “Contribution Analysis of Receptors in the Updated 

CSAPR Proposal.” March 10, 2016.

28 See footnote 22.
9

this receptor. Arizona is also the only state that contributes greater than 1% to the projected 2017 

levels of the 2008 ozone NAAQS at the Los Angeles receptor, and the total contribution from all 

states is 2.5% of the ozone concentration at this receptor. EPA believes that a 4.4% and 2.5% 

cumulative ozone contribution from all upwind states is negligible, particularly when compared 

to the relatively large contributions from upwind states in the East or in certain other areas of the 

West. For these reasons, EPA believes the emissions that result in transported ozone from 

upwind states have limited impacts on the projected air quality problems in El Centro, California, 

and Los Angeles, California, and therefore should not be treated as receptors for purposes of 

determining the interstate transport obligations of upwind states under section 110(a)(2)(D)(i)(I). 

In Arizona, the largest sources of VOC emissions are gasoline terminals, commercial cooking, 

fires, commercial/industrial fuel combustion, EGU fuel combustion, industrial boilers fuel 

combustion, residential fuel combustion, gas stations, waste disposal, solvents, aircraft, 

locomotives, non-road equipment, and on-road mobile sources. In Appendix B of the 2015 

submittal, ADEQ lists the statewide controls and programs for these sources and they include 

permits that limit operations and specify controls, source specific rules, vehicle emissions 

testing, fuel standards, and implementation of federal programs like NSPS, NESHAPs, and NSR 

and PSD permitting. The state also list Maricopa County source specific rules and ordinances in 

addition to rules that incorporate federal NSPS and NESHAP requirements. Finally, they list 

NSPS rules not incorporated into the state SIP that regulate residential fuel combustion and gas 

stations; Regional Haze FIP controls; and federal engine, emissions, and fuel standards for 

mobile sources. 

The largest sources of NOx emissions statewide are fires, commercial/industrial fuel combustion, 

EGU fuel combustion, industrial boilers fuel combustion, residential fuel combustion, industrial 

processes, waste disposal, solvents, aircraft, locomotives, non-road equipment, and on-road 

mobile sources. Similar to VOC emissions, in Appendix B of the 2015 submittal, ADEQ lists the 

statewide controls and programs for these sources and they include permits that limit operations 

and specify controls, source specific rules, vehicle emissions testing, fuel standards, and 

implementation of federal programs like NSPS, NESHAPs, and NSR and PSD permitting. They 

also list Maricopa County source specific rules and ordinances in addition to rules that 

incorporate federal NSPS and NESHAP requirements. Finally, they list NSPS rules not 

incorporated into the state SIP that regulate residential fuel combustion and gas stations; 

Regional Haze FIP controls; and federal engine, emissions, and fuel standards for mobile 

sources. Additionally, EPA notes that the Apache Generating Station will be retrofitting 2 units 

by December 5, 2017, further reducing NOx emissions—for one, Selective Non-Catalytic 

Reduction controls will be installed and the other will replace coal with pipeline natural gas as 

the primary fuel.29

EPA finds that where Arizona contributes above 1% of the NAAQS to a projected downwind air 

quality problem in California, the receptors are not significantly impacted by transported ozone 

from upwind states. Therefore, additional emission reductions from upwind states are not 

necessary to address interstate transport because the total collective upwind state ozone 

contribution to these areas is relatively low compared to the air quality problems typically 

 

29 “Approval and Promulgation of Air Quality Implementation Plans; Arizona; Regional Haze State and Federal 

Implementation Plans; Reconsideration” Final Rules (80 FR 19220, April 10, 2015)
10

addressed by the good neighbor provision. Additionally, Arizona has demonstrated that 

emissions from both VOC and NOx sources are going down and will continue to go down. EPA 

therefore believes that Arizona’s contributions to downwind receptors in California are 

considered insignificant. EPA proposes to find that Arizona does not significantly contribute to 

nonattainment or interfere with maintenance of the 2008 ozone NAAQS in other states. 

110(a)(2)(D)(i)(II) Prong 4

Prong 4 requires SIP provisions that prevent interference with measures required to be included 

in the applicable implementation plan for any other State under part C to prevent significant 

deterioration of air quality or to protect visibility.

EPA believes that ozone precursor emissions of NOx may contribute to visibility impairment in 

Class I areas. EPA’s 2013 I-SIP guidance clarifies that a state can rely upon a fully EPAapproved Regional Haze SIP to satisfy the requirements of this sub-element. Arizona’s Regional 

Haze SIP shows that sources in Arizona impact visibility in Colorado (Great Sand Dunes 

National Monument, Mesa Verde National Park, Black Canyon of the Gunnison National Park, 

La Garita Wilderness, and Weminuche Wilderness), New Mexico (Bandelier National 

Monument, San Pedro Parks Wilderness, Pecos Wilderness, Bosque del Apache National 

Wildlife Reserve, and Gila Wilderness), and Utah (Zion National Park, Bryce Canyon National 

Park, Capitol Reef National Park, Canyonlands National Park, and Arches National Park)30

Arizona’s Regional Haze SIP is not fully approved by EPA. Instead Arizona’s 2012 and 2015 

submittals rely, in part, on regulations imposed by FIPs to address visibility impairment in Class 

1 Areas caused by NOx, SO2, and PM. These regulations include control technologies or 

emission limits on the following facilities: Arizona Public Service Cholla,31 Salt River Project 

Coronado Generating Station,32 Freeport McMoran Miami Smelter,33 ASARCO Hayden 

Smelter,34 Sundt Station Unit 4,35 and Nelson Lime Plant Kilns 1 and 2.

36 Emissions limits and 

control technology requirements have been implemented through the state SIP, or initially 

through a FIP, but then incorporated into the SIP, at AEPCO Apache Station Units 1, 2, and 3.37

Because Arizona’s 2012 and 2015 submittals rely in part on FIPs to address interstate transport 

visibility requirements, they do not meet the requirements of prong 4 for the 2008 ozone 

NAAQS. However, because FIPs are already in place, no additional FIP obligation would be 

triggered by a final disapproval of this portion of Arizona’s infrastructure SIP. EPA will continue 

 

30 Arizona State Implementation Plan, Regional Haze Under Section 308 of the Federal Regional Haze Rule 

(January 2011), section 12.4.1.

31 FIP promulgated at 77 FR 72514 (December 5, 2012).

32 Id.

33 FIP promulgated at 79 FR 5240 (September 3, 2014).

34 Id.

35 Id.

36 Id.

37 SIP approval promulgated for Unit 1 and FIP promulgated for Units 2 and 3 at 77 FR 72511 (December 5, 2012). 

SIP revision for emissions limits for Unit 1 and SIP approval for Units 2 and 3 promulgated at 80 FR 19220 (April 

10, 2015).
11

to work with Arizona to incorporate emission limits to address the requirements of the Regional 

Haze Rule into the Arizona SIP.

Conclusion as to 110(a)(2)(D)

EPA is proposing to approve the first two prongs of 110(a)(2)(D)(i)(I) for the 2008 ozone 

NAAQS for Arizona. With respect to 110(a)(2)(D)(i)(II), EPA is proposing to disapprove 

Arizona’s 2012 and 2015 submittals due to their reliance on FIPs to address interstate transport 

visibility requirements. However, because FIPs are already in place, no additional FIP obligation 

would be triggered by a final disapproval of this portion of Arizona’s infrastructure SIP.

38

 

38 EPA previously partially approved and partially disapproved the Arizona SIP for 110(a)(2)(D)(i)(I) prong 3. EPA 

also previously partially approved and partially disapproved the Arizona state SIP for purposes of 110(a)(2)(D)(ii).

See footnote 11.