1

Technical Support Document (September 18, 2015)

Maricopa Association of Governments 2014 Eight-Hour Ozone Plan – Submittal of 

Marginal Area requirements for the Maricopa Nonattainment Area (June 2014)

Contents

I. Introduction ............................................................................................................................................. 2

II. Procedural Requirements for Adoption and Submittal of SIP Revisions................................................ 3

a) Statutory and Regulatory Requirements......................................................................................... 3

b) Summary of the State’s Submittal ............................................................................................... 3

c) EPA Evaluation of the State’s Submittal .......................................................................................... 4

III. Analysis of the State’s Submittal ........................................................................................................... 4

a) Base Year Emissions Inventory (section 182(a)(1)).......................................................................... 4

1) Statutory and Regulatory Requirements....................................................................................................4

2) Summary of the State’s Submittal..............................................................................................................5

3) EPA Evaluation of the State’s Submittal.....................................................................................................8

b) Emissions Statement (section 182(a)(3)(B))................................................................................. 9

1) Statutory and Regulatory Requirements....................................................................................................9

2) Summary of the State’s Submittal..............................................................................................................9

3) EPA Evaluation of the State’s Submittal.................................................................................................. 10

c) Pre-1990 Reasonably Available Control Technology Corrections (section 182(a)(2)(A)).............. 10

1) Statutory and Regulatory Requirements................................................................................................. 10

2) Summary of the State’s Submittal........................................................................................................... 10

3) EPA Evaluation of the State’s Submittal.................................................................................................. 10

d) Savings Clause: Pre-1990 Corrections to Previously Required Vehicle Inspection and 

Maintenance Programs (section 182(a)(2)(B)) ..................................................................................... 11

1) Statutory and Regulatory Requirements................................................................................................. 11

2) Summary of the State’s Submittal........................................................................................................... 11

3) EPA Evaluation of the State’s Submittal.................................................................................................. 11

e) Permit Programs: Nonattainment Area Preconstruction, New Source Review (section 

182(a)(2)(C)........................................................................................................................................... 11

1) Statutory and Regulatory Requirements................................................................................................. 11

2) Summary of the State’s Submittal........................................................................................................... 11

3) EPA Evaluation of the State’s Submittal.................................................................................................. 12
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f) Offset Requirements (section 182(a)(4))....................................................................................... 12

1) Statutory and Regulatory Requirements................................................................................................. 12

2) Summary of the State’s Submittal........................................................................................................... 12

3) EPA Evaluation of the State’s Submittal.................................................................................................. 12

g) Periodic Emissions Inventory (section 182(a)(3)(A)................................................................... 12

1) Statutory and Regulatory Requirements................................................................................................. 12

2) Summary of the State’s Submittal........................................................................................................... 12

3) EPA Evaluation of the State’s Submittal.................................................................................................. 13

h) Transportation Conformity (section 176(c)) .............................................................................. 13

V. Recommendation ................................................................................................................................. 13

I. Introduction

This technical support document (TSD) summarizes the U.S. Environmental Protection Agency’s (EPA’s) technical 

review of the “Maricopa Association of Governments 2014 Eight-Hour Ozone Plan – Submittal of Marginal Area 

requirements for the Maricopa Nonattainment Area (June 2014)” adopted by the Maricopa Association of 

Governments (MAG) on June 25, 2014, submitted by MAG to the Arizona Department of Environmental Quality 

(ADEQ) on June 27, 2014, and submitted by ADEQ to EPA on behalf of MAG on July 2, 2014. Any questions 

pertaining to this TSD should be directed to Nancy Levin at 415-972-3848 or levin.nancy@epa.gov.

On March 12, 2008, EPA strengthened the primary and secondary eight-hour ozone national ambient air quality 

standards (NAAQS) to 0.075 ppm (annual fourth-highest daily maximum 8-hour concentration, averaged over 3 

years)(73 FR 16436).1 In accordance with section 107(d) of the Clean Air Act (CAA or Act), EPA must designate an 

area “nonattainment” if it is violating the NAAQS or if it is contributing to a violation of the NAAQS in a nearby 

area.

EPA designated the Phoenix-Mesa (hereinafter referred to as Maricopa) area as nonattainment for the 2008 

ozone NAAQS on May 21, 2012, effective July 20, 2012 (77 FR 30088). The Maricopa nonattainment area (NAA), 

which includes a portion of Maricopa County and a portion of Pinal County, was classified by operation of law as 

a marginal nonattainment area (40 CFR 81.303). ADEQ submitted the “Maricopa Association of Governments 

2014 Eight-Hour Ozone Plan – Submittal of Marginal Area requirements for the Maricopa Nonattainment Area 

(June 2014)” (MAG 2014 Eight-hour Ozone Plan or Submittal) on July 2, 2014.

EPA proposed the 2008 ozone NAAQS SIP Requirements Rule (SRR) on June 6, 2013 (78 FR 34178) and finalized 

the SRR on March 6, 2015 (80 FR 12264, codified at 40 CFR part 51, subpart AA), effective April 6, 2015. The SRR 

both promulgated implementation requirements for the 2008 ozone NAAQS and revoked the 1997 ozone 

NAAQS.

2

On August 27, 2015, EPA proposed, among other things, to reclassify the Maricopa NAA as Moderate for the 

2008 ozone NAAQs because the Maricopa NAA failed to attain the 2008 ozone NAAQS by the marginal area 

 1 Since the 2008 primary and secondary NAAQS for ozone are identical, for convenience, we refer to both as "the 2008 

ozone NAAQS" or "the 2008 ozone standards."

2 The SRR revokes the 1997 NAAQS, but not all of the requirements for implementing the 1997 NAAQS.
3

attainment deadline of July 20, 2015 (80 FR 51992). Comments on the proposed rule are due by September 28, 

2015. Should this action be finalized, the Maricopa NAA would be subject to additional requirements, including 

1) an attainment demonstration; 2) provisions for reasonably available control technology (RACT) and 

reasonably available control measures (RACM); 3) reasonable further progress (RFP) reductions in volatile 

organic compounds (VOC) and/or nitrogen oxide (NOx) emissions; 4) contingency measures; 5) a vehicle 

inspection and maintenance program; and 6) NOx and VOC emission offsets at a ratio of 1.15 to 1 for major 

source permits (see 40 CFR part 51, subpart AA and CAA sections 182(b) and 172(c)). A SIP revision addressing 

all of these requirements would be due to EPA by January 1, 2017.3

II. Procedural Requirements for Adoption and Submittal of SIP Revisions

a) Statutory and Regulatory Requirements 

CAA section 110(a)(1) and 110(l) require states to provide reasonable notice and public hearing prior to 

adoption of SIP revisions. Section 110(k)(1)(B) requires EPA to determine whether a SIP submittal is complete 

within 60 days of receipt. Any plan that we have not affirmatively determined to be complete or incomplete will 

become complete six months after the day of submittal by operation of law. A finding of completeness does not 

approve the submittal as part of the SIP nor does it indicate that the submittal is approvable. It does start a 12-

month clock for EPA to act on the SIP submittal (see CAA section 110(k)(2)).

b) Summary of the State’s Submittal 

ADEQ’s submittal to EPA documents the public review process followed by MAG and ADEQ in adopting the 

“MAG 2014 Eight-Hour Ozone Plan – Submittal of Marginal Area Requirements for the Maricopa Nonattainment 

Area” prior to submittal to EPA as a revision to the SIP (See Appendix B. 1). It includes the following 

documentation: 

• A copy of the notice to the public published on April 14 and 15, 2014, announcing a public hearing on 

the MAG 2014 Eight-Hour Ozone Plan to be held on May 15, 2014 at 5:30 p.m. 4

• Affidavit of publication of the public hearing and 30-day comment period published on April 14 and 15, 

2014 in The Arizona Republic, a newspaper of general circulation in Maricopa County. 

• A statement in the public notice that the draft document was available for public review at the MAG 

Offices in Phoenix, AZ and on the MAG website.

• The May 15, 2014 public hearing transcript.

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• A notarized affirmation that a public hearing was held by ADEQ and MAG on May 15, 2014 to receive 

public comment on the “MAG 2014 Eight-Hour Ozone Plan – Submittal of Marginal Area Requirements 

for the Maricopa Nonattainment Area.” 6

• Comments and responses to comments from public comment period.

7

 3

 80 FR 51992, 51999.

4 The public notice announced a jointly-held ADEQ-MAG public hearing at MAG offices, 302 North 1st Avenue, Phoenix, 

Arizona 85003. 

5 Public Hearing, MAG 2014 Eight-Hour Ozone Plan-Submittal of Marginal Area Requirements, Phoenix, Arizona, May 15, 

2014, 5:32 p.m., MAG Offices, Saguaro Room, 302 North 1st Avenue, Second Floor, Phoenix, Arizona 85003. 6 Certification of holding of Public Hearing on the MAG 2014 Eight-Hour Ozone Plan-Submittal of Marginal Area 

Requirements for the Maricopa Nonattainment Area, Lindy Bauer, MAG Environmental Director, May 16, 2014.

7 “Response to Public Comments on the Draft MAG 2014 Eight-Hour Ozone Plan – Submittal of Marginal Area Requirements 

for the Maricopa Nonattainment Area, May 15, 2014 Public Hearing,” and April 15, 2014 (7:54 AM) email from Lisa M 

Tomczak, ADEQ to Matthew Poppen re: FW: Transmittal of the Preliminary Draft MAF 2014 Eight-Hour Ozone Plan –

Submittal of Marginal Area Requirements.
4

In addition, ADEQ’s submittal documents the adoption of the MAG 2014 Eight-Hour Ozone Plan by the MAG 

Regional Council. It includes the following:

• A June 25, 2014 MAG Regional Council resolution approving the MAG 2014 Eight-Hour Ozone Plan, and

• A letter dated June 27, 2014 from Dennis Smith, MAG to Henry Darwin, ADEQ, requesting that ADEQ 

submit the MAG 2014 Eight-Hour Ozone Plan to the EPA for approval.

c) EPA Evaluation of the State’s Submittal 

Based on the documentation included in ADEQ’s submittal, we find that the submittal of the MAG 2014 EightHour Ozone Plan, as a SIP revision, satisfies the procedural requirements of sections 110(a)(1) and 110(l) of the 

Act requiring states to provide reasonable notice and public hearing prior to adoption of SIP revisions.

The MAG 2014 Eight-Hour Ozone Plan became complete by operation of law on January 2, 2015 pursuant to 

section 110(k)(1)(B).

III. Analysis of the State’s Submittal

For Marginal nonattainment areas, states are required to comply with sections 172(c) and 182(a) of the Act. 

Marginal areas have up to three years from the effective date of designation to attain the NAAQS (40 CFR 

51.1103(a)). Unlike areas classified as Moderate and above, Marginal areas are not required to submit an 

attainment demonstration or RFP provisions (see CAA section 182(a) and 80 FR 12268). Below we discuss the 

CAA and SRR requirements, how they are addressed in the submittal, and our recommended action.

a) Base Year Emissions Inventory (section 182(a)(1)) 

1) Statutory and Regulatory Requirements 

CAA section 182(a)(1) and 40 CFR 51.1115(a) require states to submit a “base year inventory” for each 2008 

ozone nonattainment area within two years of the effective date of designation. This inventory must be “a 

comprehensive, accurate, current inventory of actual emissions from sources of VOC and NOX emitted within 

the boundaries of the nonattainment area as required by CAA section 182(a)(1)” (40 CFR 51.1100(bb), see also 

CAA section 172(c)(3)). In addition, 40 CFR 51.1115(a) requires that the inventory year be selected consistent 

with the baseline year for the RFP plan, which is usually the most recent calendar year for which a complete 

triennial inventory is required to be submitted to EPA under the Air Emissions Reporting Requirements (AERR) 

(40 CFR part 51, subpart A) (see 40 CFR 51.1110(b)).

40 CFR 51.1115(c) requires that the emission values in the base year shall be “actual ozone season day 

emissions,” as defined in 40 CFR section 51.1100(cc). 40 CFR 51.1100(cc) defines ozone season day emissions as:

“. . . an average day's emissions for a typical ozone season work weekday. The state shall select, subject 

to EPA approval, the particular month(s) in the ozone season and the day(s) in the work week to be 

represented, considering the conditions assumed in the development of RFP plans and/or emissions 

budgets for transportation conformity.”

The preamble to the final SRR explains that EPA changed the temporal basis for determining base year emissions

from “summer day emissions” to “ozone season day emissions” to account for ozone seasons that may become 

nonattainment from exceedances outside the summer months (80 FR 12290):
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“The EPA has concluded that ozone season day emissions are the most appropriate temporal basis for 

developing the emissions to be included in this inventory, rather than summer day emissions as required 

by past implementation rules or the AERR. The EPA believes that summer day emissions required 

previously are an insufficient nomenclature, since in some areas nonattainment may be due to ozone 

exceedances in months other than summer months (e.g., wintertime), and necessitate focusing planning 

efforts on emissions occurring during the more relevant time period. Ozone season day emissions 

means an average day’s emissions for a typical ozone season work weekday as defined in CAA section 

51.1100(cc). The state will select, subject to EPA approval, the particular month(s) in the ozone season 

and the day(s) in the work week to be represented...” 

40 CFR 51.1100(n) defines “Ozone season” as, “for each state, the ozone monitoring season as defined in 40 CFR 

part 58, appendix D, section 4.1(i) for that state.” Pursuant to 40 CFR part 58, appendix D, section 4.1(i), the 

ozone monitoring season for Maricopa NAA begins in January and ends in December.8

40 CFR 51.1115(d) requires the state to report emissions from point sources according to the point source 

emissions thresholds of the AERR (40 CFR part 51, subpart A), which are identical to the major source thresholds

under 40 CFR part 70 (see 40 CFR 51.30).

2) Summary of the State’s Submittal 

The Maricopa County Air Quality Department (MCAQD) prepared a base year emissions inventory, with the 

assistance of MAG, and MAG submitted the base year inventory as part of the MAG 2014 Eight-hour Ozone 

Plan.

9 MCAQD selected 2011 as the base year.

The base year inventory includes ozone season-day emissions from point sources, area sources, nonroad mobile 

sources, and on-road mobile sources. Appendix A, Exhibit 1 includes a description of the methods used to 

estimate emissions for each category (or subcategory). 

The following is a summary of the 2011 Maricopa NAA Emissions Inventory. 

Maricopa NAA 2011 Base Year 8-hour Ozone Season Day Emission Inventory (July-September)

Category VOC lbs/day 

% of 

total NOx lbs/day % of total

Point sources

 

4,908 1% 15,407 3.1%

Area sources

Fuel combustion 593 0.1% 23,484 4.8%

Industrial processes 17,452 4% 1,490 0.3%

Solvent use 166,557 34%

Storage/transport 28,766 6%

Waste treatment/disposal 838 0% 316 0.1%

Miscellaneous area sources 13,650 3% 6,532 1.3%

 8 Table D-3 of Appendix D to Part 58 – Ozone Monitoring Season by State. 9 MAG 2014 Eight-hour Ozone Plan, Table 1 – Summary Table of Nonattainment Area Emissions from the Maricopa County 

Air Quality Department 2011 Periodic Emissions Inventory for Ozone Precursors, February 2014, page 5. See also Appendix 

A, Exhibit 1.
6

MOBILE - Non road sources 111,798 23% 141,444 28.8%

MOBILE - On road sources 148,186 30% 301,824 61.5%

Total (excluding biogenic)* 492,748 100% 490,495 100.0%

*Differences due to rounding.

Point Sources

For the purpose of the emissions inventory (EI), MCAQD considers any major source, as defined under 40 CFR 

part 70, as a point source. The threshold for major sources in a marginal nonattainment area is 100 tons per year 

of VOC or NOx. The 18 point sources listed in the in the 2011 Maricopa NAA Emissions Inventory are primarily 

power generation facilities and large manufacturers. The inventory includes emission reduction credits as of 

December 31, 2011 for VOC (114.7 tpy) and NOx (9.8 tpy). Section 2 of the 2011 Maricopa NAA Emissions 

Inventory contains a detailed description of point source emission estimates.

Point sources in the Maricopa County are required to report their emission data and calculations to MCAQD (See 

MCAQD Rule 100, Section 500 and ADEQ Rule R18-2-327).10 Point sources in Pinal County are required to report 

their emissions data and calculations to the Pinal County Air Quality Control District (PCAQCD) (See PCAQCD 

Rule 3-1-103).11 There are no point sources in Pinal County.12

Appendix A of the Maricopa NAA Emissions Inventory includes detailed instructions for regulated sources, 

including sample forms, and an emission calculation method hierarchy. Each year, MCAQD prepares forms with 

pre-populated data from the prior year, sends out the forms and holds workshops for industry. Once received, 

MCAQD checks EI reports for errors, missing information, and completeness, and contact businesses for 

corrections if needed. (See section 2.7 of the 2011 Maricopa NAA Emissions Inventory - Quality 

assurance/quality control procedures).

Area Sources

Area sources collectively represent individual sources that are small and numerous, or activities, such as 

consumer and commercial products and pesticides, that have not been inventoried as specific point or mobile 

sources. They are generally grouped in a way that they can be estimated collectively using one methodology. A 

detailed description of area source emission estimates is found in section 3 of the 2011 Maricopa NAA Emissions 

Inventory. 

The Submittal lists each area source category according to its Source Classification Code (SCC) and description. 

The area sources are grouped into the follow categories: 1) Fuel combustion, 2) Industrial processes, 3) Solvent 

use, 4) Storage and transport; 5) Waste treatment and disposal; and 6) Miscellaneous area sources. The largest 

area sources of VOC emissions are consumer and commercial products (96,469 lbs/day), architectural coatings 

(30,973 lbs/day), residential portable gas cans (16,311 lbs/day), rubber/plastic product manufacturing (14,110 

lbs/day), wildfires (12,794 lbs/day) and auto refinishing (10,212 lbs/day). The largest area sources of NOx 

emissions are industrial distillate oil engines (11,733 lbs/day), wildfires (5,833 lbs/day), commercial/institutional 

natural gas (4,992 lbs/day) and industrial natural gas (4,285 lbs/day). (See Submittal Table 1).

MCAQD used various methodologies for estimating emissions from area source categories including:

• Surveys for data on local usage or using state-wide data (See, e.g., section 3.2.2. Industrial natural gas).

• Published per-capital or per-employee emission factors (See, e.g., section 3.4.6 Consumer and 

commercial products).

 10 EPA approved Rule 100, Section 500 and ADEQ R18-2-237 into the SIP on November 5, 2012 (77 FR 66405). 11 EPA approved PCAQCD Rules 3-1-103 into the SIP on December 20, 2000 (65 FR 79742). 12 Phone conversation with Bob Downing, MCAQD, May 29, 2015.
7

• Available data from annual emission reports and “scaling up” using employment data (See section 3.4.4 

Graphic Arts).

• Process-level and operation data from permits and emission reports for categories where there were no 

significant unpermitted sources (See section 3.3.3 Secondary metal production).

Seasonal and season-day emissions were calculated based on assumptions about when the emissions occurred 

during the year and how often the activity occurred (days/week). For example, MCAQD assumed that consumer 

and commercial product use occurs uniformly across the year, and calculated season-day emissions by dividing 

annual emissions by 365 days. For pesticide use, MCAQD determined that 36.4% of pesticides were applied 

during the ozone season. Total seasonal emissions were divided by 91 days (13 weeks, 7 days a week) to 

determine season-day emissions. Dry cleaning activities were assumed to occur 5 days a week throughout the 

year, so the season-day emissions were derived by dividing annual total emissions by 260 (5 days/week * 52 

weeks/year) (See section 3.4.3). The ozone season day emissions for industrial oil combustion were calculated 

by multiplying annual County emissions by 25% to convert to the three-month ozone season, and dividing by the 

number of days that activity occurs during the ozone season.

Since the NAA includes portions of Maricopa and Pinal Counties, the MCAQD developed a calculation to account 

for partial county and multi-county emissions. Section 1.5 of the inventory document describes this method. As 

most of the emission sources are located in Maricopa County, MCAQD applied a demographic “multiplier” to 

Maricopa County data to estimate emissions in the NAA. Specifically, MCAQD used a demographic or land use 

multiplier based on the ratio of population (or employment) in Maricopa County versus that in the 8-hour Ozone 

NAA. For example, for Auto refinishing emissions, MCAQD first calculated county-wide estimates based on 

county employment and a per employee emission factor, and then used the multiplier of industrial employment 

in the NAA v. County (372,731/374,338 or 99.57%) to calculate annual emissions for the NAA. (See section 

3.4.1.2)

The same approach was used for land use (e.g., acreage within Maricopa County/acreage within 8-hour Ozone 

NAA = Percentage within 8-hour Ozone NAA). For example, MCAQD used Maricopa County-wide National 

Emissions Inventory (NEI) data on pesticide use, and then multiplied it by the ratio of agricultural land in the 8-

hour NAA (161,371 acres) to Maricopa County (276,016 acres) emissions for agricultural pesticide usage 

(58.46%) to determine annual emissions in the NAA (See section 3.4.8) days/week and 13 weeks). 

Nonroad mobile sources

The EI contains nonroad mobile emission estimates for the following categories: agricultural equipment, airport 

ground support equipment (GSE) and auxiliary power units (APU), commercial equipment, construction and 

mining equipment, industrial equipment, lawn and garden equipment, pleasure craft, railway maintenance 

equipment, recreational equipment, aircraft, and locomotives. A detailed description of nonroad emission 

estimates is found in section 4 of the 2011 Maricopa NAA Emissions Inventory.

The largest nonroad sources of VOC emissions in the Maricopa NAA are lawn and garden equipment (52,584.9 

lbs/day), commercial equipment (14,474.7 lbs/day), construction & mining equipment pleasure craft (13,534.5 

lbs/day), aircraft (8,385.8 lbs/day) and recreational equipment (8,020.9 lbs/day). The largest sources of nonroad 

NOx emissions are construction and mining equipment (90,774.0 lbs/day), aircraft (12,535.3 lbs/day), 

commercial equipment (8,299.0 lbs/day) and lawn and garden equipment (7,078.4 lbs/day). 

MCAQD used EPA’s NONROAD2008a model (July 2009) to estimate emissions from nonroad mobile source 

categories with the exception of aircraft, airport GSE, and locomotives. NONROAD2008a (2009) is EPA’s latest 

published version of the NONROAD model. Arizona Department of Weights and Measures provided monthly 

temperature and fuel data inputs for NONROAD2008a. Temporal allocations included the most conservative 
8

(use the highest allocation) fraction in each nonroad equipment class to calculate season-day emissions (See 

Table 4.1-2). MCAQD made local adjustments to EPA default numbers for commercial lawn and garden 

equipment (See section 4.1). The construction and mining emissions were calculated using NONROA2008a, and 

emissions for the nonattainment area were based on the ratio of construction employment in the 

nonattainment area to that in Maricopa County.

MCAQD used Federal Aviation Administration’s Emission Dispersion Modeling System model (Ver. 5.1.1.) for 

aircraft and airport GSE emission estimates. Maricopa County locomotive emissions were calculated by 

multiplying diesel fuel usage provided by three railroad operations by published EPA emission factors. 13 The 

nonattainment area locomotive emissions were determined by multiplying the Maricopa County emissions by 

the percent of track in the nonattainment area (See 2011 Maricopa NAA Emissions Inventory section 4.12).

Onroad mobile sources

MAG estimated onroad mobile emissions using EPA’s Motor Vehicle Emission Simulator (MOVES) version 2010b, 

which was the latest version available at the time of EI preparation.14 The modeling accounted of oxygenated 

fuel and the Arizona Vehicle Inspection/Maintenance (I/M) programs applied in Maricopa County in 2011. The 

2011 vehicle miles traveled (VMT) was estimated based on 2011 Highway Performance Monitoring System 

(HPMS) data provided by the Arizona Department of Transportation. A detailed description of on-road emission 

estimates is found in section 5 of the 2011 Maricopa NAA Emissions Inventory.

3) EPA Evaluation of the State’s Submittal 

EPA has reviewed the 2011 season-day EI including emission estimates for point source, area source, nonroad 

and onroad sources. We find that MCAQD’s selection of 2011 as the base year is appropriate.

15 We also find that 

the data elements in the base year inventory are “consistent with the detail” required by the AERR. 

Generally, MCAQD used published emission factors from EPA’s National Emissions Inventory,

16 made 

assumptions consistent with EPA’s Emission Inventory Improvement Program Guidance,17 and the used most 

recent EPA models available at the time of inventory preparation. In addition, the submittal provides sufficient 

documentation and explanation to allow EPA to make a determination on the acceptability of the EI. 

 13 Data provided by Burlington Northern/Santa Fe Railway, Union Pacific Railway and Amtrak. 14 Per March 13, 2015 email from Taejoo Shin, MAG to Nancy Levin, EPA. MAG developed onroad emission inventory in 

December 2012. MOVES2010b has subsequently been replaced by MOVES2014. MOVES2014 was released in July 2014 and 

updated in October 2014. For more information see “EPA Releases MOVES2014 Mobile Source Emissions Model, Questions 

and Answers, Office of Transportation and Air Quality U.S. EPA, EPA-420-F-14-049, July 2014 at 

http://www.epa.gov/otaq/models/moves/documents/420f14049.pdf.

15As noted above, the base year must be the same as the baseline year for RFP, which is the most recent calendar year for 

which a complete triennial inventory is required under the AERR, unless an alternative year is demonstrated to be 

appropriate. Because Maricopa is classified as a marginal nonattainment area, no RFP plan is required at this time. 

Nonetheless, given that Maricopa was designated nonattainment for the 2008 ozone standard in 2012, the presumptive 

baseline year for such a plan would be 2011 because 2011 was the most recent calendar year for which a complete triennial 

inventory was required to be submitted to EPA under the AERR (see 40 CFR 51.30(b)(1)). 

16 The National Emissions Inventory (NEI) is a comprehensive and detailed estimate of air emissions of both Criteria and 

Hazardous air pollutants from all air emissions sources. The NEI is prepared every three years by the EPA based primarily 

upon emission estimates and emission model inputs provided by State, Local and Trival air agencies for sources in their 

jurisdictions, and supplemented by data developed by the EPA. See 

http://www3.epa.gov/ttn/chief/net/2011inventory.html.

17 See, e.g., EPA, Emissions Inventory Improvement Program (EIIP), Volume III, Chapter 1. Introduction to Area Source 

Emission Inventory Development (Revised Final January 2001), Chapter 11. Gasoline Marketing (Stage I and Stage II) 

(Revised Final January 2001); Chapter 18. Structure Fires (Revised Final January 2001), and Area Source Category Method 

Abstract - Leaking Underground Storage Tanks, May 2001.
9

However, we believe that MCAQD’s initial selection of July – September as the basis for calculating the “ozone 

season day emissions,” based on 1981-1991 exceedance data,18 was not appropriate. Accordingly, we requested 

that MCAQD review more recent ozone monitoring data. Upon review of these data, MCAQD determined that 

the appropriate months to use to calculate ozone season day emissions are June-August.19 Therefore, MCAQD 

provided a “recast” ozone season day EI for June-August.20 The MCAQD’s “recast” analysis shows that, 

compared with the July-September EI, the June-August EI showed a small net increase in season day emissions 

for anthropogenic sources: VOC increased 0.41% and NOx increased 2.15%. MCAQD also added emission 

reduction credits (ERCs) to the June-August EI for point sources.21 Total VOC ERCs were adjusted from 114.7 to 

213.03 tons/year (1,167 lbs/season day) and total NOx ERCs were adjusted from 9.8 to 14.14 tons/year (77.5 

lbs/season day) to account for additional VOC and NOx ERCs.22

We agree with MCAQD that using June – August to calculate ozone season day emissions is appropriate for the 

Maricopa NAA, given that it was the three-month period with the highest average Air Quality Index value and 

the greatest number of exceedances of the 2008 ozone standard in the NAA in 2011. However, in light of the 

relatively small differences in total anthropogenic emissions between the June-August 2011 and July –

September 2011 periods, we do not believe it is necessary for MCAQD, MAG and ADEQ to submit a formal SIP 

revision reflecting the June-August period at this time. Accordingly, we find that the base year emission 

estimates approaches and methodologies are acceptable and that the state has met the requirements of the Act 

and the SRR with respect to base year inventories. We recommend that a revised 2011 season-day EI based on

June-August data be included as part of a subsequent SIP revision to meet the CAA's Moderate ozone 

nonattainment area requirements, as described above.

b) Emissions Statement (section 182(a)(3)(B))

1) Statutory and Regulatory Requirements 

Section 182(a)(3)(B)(i) of the Act requires States to submit a SIP revision requiring owners or operators of 

stationary sources of VOC or NOX to provide the State with statements of actual emissions from such sources.

Statements must be submitted at least every year and must contain a certification that the information 

contained in the statement is accurate to the best knowledge of the individual certifying the statement. Section 

182(a)(3)(B)(ii) allows states to waive the emission statement requirement for any class or category of stationary 

sources which emit less than 25 tons per year of VOCs or NOX, if the state provides an inventory of emissions 

from such class or category of sources as part of the baseline or periodic inventory. This inventory must be 

based on the use of the emission factors established by EPA or other methods acceptable to EPA.

2) Summary of the State’s Submittal 

ADEQ references three SIP-approved rules as meeting the requirements of CAA section 182(a)(3)(B): Maricopa 

County Rule 100, Section 500 – Monitoring and Records, ADEQ Rule 18-2-327 - Annual Emissions Inventory 

Questionnaire and Pinal County rule PG3-1-103 - Annual EI questionnaire.

 18 Appendix A, Exhibit 1: 2011 Periodic Emissions Inventory for Ozone Precursors for the Maricopa County, Arizona, EightHour Ozone Nonattainment Area. Maricopa County Air Quality Department. February 2014. An “exceedance” is an ambient 

concentration that exceeds the relevant NAAQS. 

19 Maricopa County Air Quality Department, 2011 Periodic Emissions Inventory for Ozone Precursors for the Maricopa 

County, Arizona, Eight-Hour Ozone Nonattainment Area, Addendum, August 2015, section 3.1. 20 Ibid. section 3.2. 21 Total VOC ERCs are 1,167.3 lbs/season day. Total NOx ERCs are 77.5 lbs/season day. 22 ERCs from Penn Racquet Sports Inc. (March 6, 2009). See Addendum, Table A.1.
10

3) EPA Evaluation of the State’s Submittal

Maricopa County Rule 100 (Section 500, Subsection 503) (approved into the Arizona SIP on November 5, 2012 

(77 FR 66405)) requires owners/operators of sources that emit or emit NOx or VOC to submit, upon request of 

the Control Officer, emission statements showing actual or estimated actual emissions of NOx and VOC, 

containing (at a minimum) all information required by Consolidated Emissions Reporting Rule,23 40 CFR, Subpart 

A, Appendix A, Table 2a.24 Section 503 also requires that Emissions Statements be submitted annually. The 

Control Officer may waive this requirement for the owner/operator of any source which emits less than 25 tons 

per year of NOx or VOC with an approved emission inventory for sources based on AP-42 or other 

methodologies approved by EPA. 

ADEQ Rule 18-2-327, Annual Emissions Inventory Questionnaire (approved into the Arizona SIP on November 5, 

2012 (77 FR 66405)), requires every source subject to air permit requirements to complete and submit an annual 

emissions inventory questionnaire including facility contact information, process and control device 

descriptions, and a quantification of actual emissions of regulated air pollutants25 using the appropriate 

quantification method as described in the rule. 

PG3-1-103 (approved into the Arizona SIP on December 20, 2000 (65 FR 79742)) requires every source that is 

subject to a permit or obtains an authorization to operate, to complete and submit to the Control Officer an 

annual emissions inventory questionnaire. The questionnaire must include the source’s name, address, contact 

information, address, and process information (e.g., including design capacity, operations schedule, emission 

control devices).26

Based on the contents of these rules, we find that Arizona has met the requirements of CAA section 182(a)(3)(B) 

for emission statements.

c) Pre-1990 Reasonably Available Control Technology Corrections (section 182(a)(2)(A))

1) Statutory and Regulatory Requirements 

Section 182(a)(2)(A) of the CAA requires the State to submit, within 6 months of classification under section 

181(a), all rules and corrections to existing RACT rules that were required under section 172(b) of the old (pre1990 Amendments) CAA. Newly designated nonattainment areas are not subject to the RACT "fix-ups" required 

by section 182(a)(2)(A) because they were not subject to section 172(b) of the old law (see 57 FR 13498, 13503). 

2) Summary of the State’s Submittal

The Submittal lists the SIP-approved Rules that apply to source categories subject to CAA section 182(a)(2)(A) 

and notes that EPA approved Arizona’s RACT demonstration for the Maricopa County 1-hour Serious Area 

Ozone NAA on June 14, 2005 (70 FR 34362). 

3) EPA Evaluation of the State’s Submittal

As noted in the Submittal, EPA previously determined that Arizona had met the VOC RACT requirements under 

section 182(a)(2)(A) for the Maricopa one-hour ozone NAA (see 70 FR 13435 and 70 FR 34363). Although the NAA 

 23 The Consolidated Emissions Reporting Rule is now part of the AERR (see 73 FR 76539). 24 Appendix G of the Maricopa County Air Pollution Control Rules, section 4, specifies that 40 CFR, Subpart A, Appendix A, 

Table 2a is incorporated by reference as of July 1, 2014. Table 2a was revised on February 19, 2015 (80 FR 8787, 8790) 25 Regulated air pollutant is defined by SIP-approved ADEQ rule R18-2-101, section 120 to include NOx and VOC. (See 40 

CFR 52.120(c)(162)(i)(A)(2), 26 On September 27, 2006 ADEQ submitted an amendment to PG Rule 3-1-103, however, the change does not substantively 

change the rule. Rather it reflected ADEQ’s reclassification of Class A and Class B permits to Class I, Class II, and Class III. 

Under this amendment, the term “Class B permits” is replaced by “Class II or Class II permits.”
11

for the 2008 eight-hour ozone standard is larger than that the one-hour NAA, only the original one-hour area is 

subject to the RACT correction requirement of 182(a)(2)(A). Therefore, we find that Arizona has met the 

requirements of CAA section 182(a)(2)(A) with respect to the Maricopa 2008 eight-hour ozone NAA.

d) Savings Clause: Pre-1990 Corrections to Previously Required Vehicle Inspection and 

Maintenance Programs (section 182(a)(2)(B))

1) Statutory and Regulatory Requirements 

Section 182(a)(2)(B)(i) of the Act requires the State to submit a revision, immediately after November 15, 1990, 

to correct any pre-1990 schedules for vehicle emission control inspection and maintenance programs, 

immediately after November 15, 1990. In addition, section 182(a)(2)(B)(ii) requires that the State shall review, 

revise, update, and republish in the Federal Register the guidance for the States for motor vehicle inspection and 

maintenance programs (I/M) within 1 year of November 15, 1990. EPA's I/M regulations are codified at 40 CFR 

part 51, subpart S ("Inspection/Maintenance Program Requirements"), sections 51.350 through 51.373. As 

explained in the preambles to proposed and final SRR, no new vehicle I/M programs are currently required for 

purposes of the 2008 ozone NAAQS (78 FR 34194-34196, 80 FR 12283).

2) Summary of the State’s Submittal

The Submittal notes that EPA approved ADEQ’s Basic and Enhanced Vehicle Emissions Inspection and 

Maintenance Programs on January 22, 2003, and approved a statutory provision extending the State’s vehicle 

emissions inspection program on December 21, 2009 (74 FR 67819).

3) EPA Evaluation of the State’s Submittal

As noted in the Submittal, EPA previously approved, an "enhanced" I/M program that exceeds the requirements 

of section 182(a)(2)(B) for the Phoenix-Mesa nonattainment area (69 FR 2912 (January 22, 2003)). Therefore, we 

find that Arizona has met the requirements of CAA section 182(a)(2)(B) with respect to the Maricopa 2008 eighthour ozone NAA.

e) Permit Programs: Nonattainment Area Preconstruction, New Source Review (section 

182(a)(2)(C)

1) Statutory and Regulatory Requirements 

Section 182(a)(2)(C) of the Act, requires states to submit a SIP revision within 2 years after November 15, 1990

to require pre-construction permits for new or modified major stationary sources in the NAA, and to correct 

requirements regarding pre-1990 permit programs. However, as explained in the preambles to EPA’s final Phase 

2 implementation rule for the 1997 eight-hour standard and the final SRR, EPA considers the submission of new 

source review (NSR) SIPs due on November 15, 1992 to have fulfilled this CAA requirement (See 75 FR 71683, n. 

110, and 80 FR 12267). Therefore, EPA has concluded that the 2-year deadline contained in CAA section 

182(a)(2)(C)(i) does not apply to subsequent NSR SIPs for revised ozone standards, including the nonattainment 

NSR SIPs for implementing the 8-hour ozone NAAQS. (Id.) Accordingly, the SRR at 40 CFR 51.1114 sets a deadline 

of 3 years from the date of designation for states to submit their nonattainment NSR program SIPs for the 2008 

ozone NAAQS.

2) Summary of the State’s Submittal 

The submittal describes the roles of ADEQ, MCAQD and PCAQCD in implementing the preconstruction permit 

program in the Maricopa NAA. In particular, the submittal explains that ADEQ has permitting jurisdiction for the 

following stationary source categories: smelting of metal ores, coal-fired electric generating stations, petroleum 

refineries, Portland cement plants, and portable sources. ADEQ also has permitting jurisdiction over other major 
12

sources in Pinal County, but has delegated implementation of the major source program to PCAQCD, which

implements ADEQ’s major NSR rules. MCAQD has jurisdiction over other sources in Maricopa County. The 

Submittal also described various SIP revisions submitted by ADEQ to meet nonattainment NSR requirements.

3) EPA Evaluation of the State’s Submittal

EPA recently finalized a limited approval and limited disapproval of various rules that comprise ADEQ’s NSR 

program.27 We expect that ADEQ will revise these rules in the near future.

With regard to MCAQD’s rules, we note that ADEQ had submitted MCAQD Rule 240 – Permits for New Major 

Sources and Major Modifications to Existing Major Sources to EPA on August 31, 1995, but withdrew it on April 

25, 2014 in order to revise and resubmit it to EPA for SIP approval. ADEQ published a proposed notice of 

rulemaking for amendments to Rule 240 and other related rules on August 31, 2015.

28

Given the expected submittal of revised ADEQ and MCAQD NSR rules in the near future, we recommend 

deferring action on this element of the MAG 2014 Eight-Hour Ozone Plan at this time.

f) Offset Requirements (section 182(a)(4)) 

1) Statutory and Regulatory Requirements 

CAA Section 173 requires new and modified major sources in nonattainment areas to secure emissions 

reductions (i.e., "offsets") to compensate for a proposed emissions increase. For Marginal areas, section 

182(a)(4) of the Act sets a general offset ratio of 1.1 to 1 for total VOC and NOx emission reductions as 

compared to VOC and NOx emission increases. 

2) Summary of the State’s Submittal 

The Submittal references ADEQ Rule R18-2-404(J) and Maricopa County Air Pollution Control Regulations, Rule

240, Section 306.3 as fulfilling the requirements of CAA section 182(a)(4).

3) EPA Evaluation of the State’s Submittal

Given the expected submittal of revised ADEQ and MCAQD NSR rules in the near future, we recommend 

deferring action on this element of the MAG 2014 Eight-Hour Ozone Plan at this time.

g) Periodic Emissions Inventory (section 182(a)(3)(A)

1) Statutory and Regulatory Requirements 

CAA section 182(a)(3)(A) and the SRR at 40 CFR 51.1115(b) require the State to submit a periodic inventory by 

the end of each 3-year period after required submission of the base year inventory. Other than the inventory 

year and timing of submittal, the same requirements apply to periodic inventories as to the base year inventory, 

as described in section III(a)(1) above (see 40 CFR 51.1115(b), (c), (d), (e).

2) Summary of the State’s Submittal 

In the submittal, the MCAQD commits to prepare a 2014 periodic inventory to meet the requirements of section 

182(a)(3)(A). 

 27 Final rule, Revisions to Air Plan; Arizona; Stationary Sources; New Source Review (pre-publication version, signed June 29, 

2015). 28 On July 31, 2015 the Arizona Secretary of State published a notice of proposed rulemaking to amend MCAQD’s rules 

relating to NSR, including Rule 240. See Arizona Administrative Register (AAR) Vol. 21, Issue 31, page 1302 (July 31, 2015), 

available at: http://apps.azsos.gov/public_services/register/2015/31/28_county_notices.pdf. It also announced a 30 day 

comment period that ended August 31, 2015. 
13

3) EPA Evaluation of the State’s Submittal

The deadline for submittal of the base year inventory for the Maricopa NAA was July 20, 2014 (24 months after 

designation). Accordingly, the deadline for the first periodic inventory is July 20, 2017. EPA will evaluate the first 

periodic inventory following its submission. 

h) Transportation Conformity (section 176(c))

The Submittal lists "Meet Transportation Conformity Requirements - CAA Section 176(c)" as a marginal area 

requirement. We note that motor vehicle emission budgets, used in transportation conformity determinations, 

are not required for marginal areas because such areas are not required to submit a “control strategy 

implementation plan revision.”29 However, as noted above, EPA has proposed to reclassify (or "bump up") the 

Maricopa NAA to Moderate nonattainment. If the reclassification is finalized, MAG would be required to 

develop emission budgets as part of a Moderate area attainment demonstration. In the meantime, MAG may

rely on the emission budgets for another NAAQS of the same pollutant (see 40 CFR 93.109(c)(2)). EPA approved 

Maricopa NAA emission budgets for the 1997 Ozone NAAQS on September 17, 2014 (79 FR 55645). Accordingly, 

we are not taking further action on these budgets at this time. 

V. Recommendation

For the reasons described above, we recommend full approval of the MAG 2014 Eight-Hour Ozone Plan with 

respect to the requirements of CAA section 182(a)(1), (2)(A) and (B), and (3)(B) and deferral of action with 

respect to the requirements of CAA sections 176(c) 182(a)(2)(C) and (4).

 29 See 40 CFR 93.101 (“Motor vehicle emissions budget is that portion of the total allowable emissions defined in the 

submitted or approved control strategy implementation plan revision or maintenance plan for a certain date for the 

purpose of meeting reasonable further progress milestones or demonstrating attainment or maintenance of the NAAQS, for 

any criteria pollutant or its precursors, allocated to highway and transit vehicle use and emissions”; “ Control strategy 

implementation plan revision is the implementation plan which contains specific strategies for controlling the emissions of 

and reducing ambient levels of pollutants in order to satisfy CAA requirements for demonstrations of reasonable further 

progress and attainment (including implementation plan revisions submitted to satisfy CAA sections 172(c), 182(b)(1), 

182(c)(2)(A), 182(c)(2)(B), 187(a)(7), 187(g), 189(a)(1)(B), 189(b)(1)(A), and 189(d); sections 192(a) and 192(b), for nitrogen 

dioxide; and any other applicable CAA provision requiring a demonstration of reasonable further progress or attainment).”)