Federal Register / Vol. 86, No. 5 / Friday, January 8, 2021 / Proposed Rules 1347 

covering such items as the range of 

potential purchasers of the Enterprise’s 

core business lines and other significant 

assets, as well as measures that, if taken 

by the Enterprise, could minimize the 

risk that its resolution would have 

serious adverse effects on the national 

housing finance markets and minimize 

the amount of potential loss to the 

Enterprise’s investors and creditors. 

(b) Confidential treatment of 

resolution plan. (1) The confidentiality 

of each resolution plan and related 

materials shall be determined in 

accordance with applicable exemptions 

under the Freedom of Information Act 

(5 U.S.C. 552(b)), 12 CFR part 1202 

(FHFA’s regulation implementing the 

Freedom of Information Act), and 12 

CFR part 1214 (FHFA’s regulation on 

the availability of non-public 

information). 

(2) An Enterprise submitting a 

resolution plan or related materials 

pursuant to this part that desires 

confidential treatment of the 

information under 5 U.S.C. 552(b)(4), 12 

CFR part 1202 (Freedom of Information 

Act), and 12 CFR part 1214 (availability 

of non-public information) may file a 

request for confidential treatment in 

accordance with those rules. 

(3) To the extent permitted by law, 

information comprising the confidential 

section of a resolution plan will be 

treated as confidential. 

(4) To the extent permitted by law, the 

submission of any nonpublic data or 

information under this part shall not 

constitute a waiver of, or otherwise 

affect, any privilege arising under 

Federal or state law (including the rules 

of any Federal or state court) to which 

the data or information is otherwise 

subject. The submission of any 

nonpublic data or information under 

this part shall be subject to the 

examination privilege. 

§ 1242.7 Review of resolution plans; 

resubmission of deficient resolution plans. 

(a) FHFA acceptance of resolution 

plan; review for completeness. (1) After 

receipt of a resolution plan, FHFA will 

either acknowledge acceptance of the 

plan for review or return the resolution 

plan if FHFA determines that it is 

incomplete or that substantial 

additional information is required to 

facilitate review of the resolution plan. 

(2) If FHFA determines that a 

resolution plan is incomplete or that 

substantial additional information is 

necessary to facilitate review of the 

resolution plan: 

(i) FHFA shall provide notice to the 

Enterprise in writing of the area(s) in 

which the resolution plan is incomplete 

or with respect to which additional 

information is required; and 

(ii) Within 30 days after receiving 

such notice (or such other time period 

as FHFA may establish in the notice), 

the Enterprise shall resubmit a complete 

resolution plan or such additional 

information as requested to facilitate 

review of the resolution plan. 

(b) FHFA review of complete plan; 

determination regarding deficient 

resolution plan. (1) Following review of 

a complete resolution plan, FHFA will 

send a notification to each Enterprise 

that: 

(i) Identifies any deficiencies in the 

Enterprise’s resolution plan (or confirms 

that no deficiencies were identified); 

(ii) Identifies any planned actions or 

changes set forth by the Enterprise that 

FHFA agrees could facilitate a rapid and 

orderly resolution of the Enterprise; and 

(iii) Provides any other feedback on 

the resolution plan (including feedback 

on timing of actions or changes to be 

undertaken by the Enterprise). FHFA 

will send the notification no later than 

12 months after accepting a complete 

plan, unless FHFA determines in its 

discretion that extenuating 

circumstances exist that require delay. 

(2) A deficiency is an aspect of an 

Enterprise’s resolution plan that FHFA 

determines presents a weakness that, 

individually or in conjunction with 

other aspects, could undermine the 

feasibility of the Enterprise’s resolution 

plan. 

(c) Resubmission of a resolution plan. 

Within 90 days of receiving a notice of 

deficiency, or such shorter or longer 

period as FHFA may establish by 

written notice to the Enterprise, an 

Enterprise shall submit a revised 

resolution plan to FHFA that addresses 

all deficiencies identified by FHFA, and 

that discusses in detail: 

(1) Revisions to the plan made by the 

Enterprise to address the identified 

deficiencies; 

(2) Any changes to the Enterprise’s 

business operations and corporate 

structure that the Enterprise proposes to 

undertake to address a deficiency 

(including a timeline for completing 

such changes); and 

(3) Why the Enterprise believes that 

the revised resolution plan is feasible 

and would facilitate a rapid and orderly 

resolution by FHFA as receiver. 

§ 1242.8 No limiting effect or private right 

of action. 

(a) No limiting effect on resolution 

proceedings. A resolution plan 

submitted pursuant to this part shall not 

have any binding effect on FHFA when 

appointed as conservator or receiver 

under 12 U.S.C. 4617. 

(b) No private right of action. Nothing 

in this part creates or is intended to 

create a private right of action based on 

a resolution plan prepared or submitted 

under this part or based on any action 

taken by FHFA with respect to any 

resolution plan submitted under this 

part. 

Mark A. Calabria, 

Director, Federal Housing Finance Agency. 

[FR Doc. 2020–28812 Filed 1–7–21; 8:45 am] 

BILLING CODE 8070–01–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R09–OAR–2020–0618; FRL–10018– 

46–Region 9] 

Partial Approval and Partial 

Disapproval of Air Quality 

Implementation Plans; Arizona; West 

Pinal County; 1987 PM10

Nonattainment Area Requirements 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is proposing to approve 

in part and to disapprove in part the 

state implementation plan (SIP) revision 

submitted by the State of Arizona to 

meet Clean Air Act (CAA or ‘‘Act’’) 

requirements for the 1987 PM10 national 

ambient air quality standards (NAAQS 

or ‘‘standard’’) in the West Pinal County 

PM10 nonattainment area. The State of 

Arizona’s ‘‘2015 West Pinal Moderate 

PM10 Nonattainment Area SIP’’ (‘‘West 

Pinal County PM10 Plan’’) addresses the 

CAA nonattainment area requirements 

for the 1987 PM10 NAAQS, including 

requirements for an emissions 

inventory, an attainment demonstration, 

reasonable further progress, reasonably 

available control measures, contingency 

measures, and motor vehicle emissions 

budgets. The EPA is proposing to 

approve the base year 2008 emissions 

inventory for direct PM10 and to 

disapprove the remaining elements of 

the West Pinal County PM10 Plan. 

DATES: Written comments must arrive 

on or before February 8, 2021. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–R09– 

OAR–2020–0618 at https://

www.regulations.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. The EPA may publish 

any comment received to its public 


tkelley on DSKBCP9HB2PROD with PROPOSALS
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1 52 FR 24634 (July 1, 1987). 

2 71 FR 61144 (October 17, 2006). 

3See 40 CFR 50.6 and 40 CFR part 50, appendix 

K. 

4Letter from Laura Yoshii, Acting Regional 

Administrator to Governor Jan Brewer dated 

October 14, 2009. The EPA notified the tribal 

leaders of the Ak-Chin Indian Community, Gila 

River Indian Community, San Carlos Apache Tribe 

by letters dated December 30, 2009, and Tohono 

O’odham Nation by letter dated September 21, 

2010. 

5 77 FR 32024 (May 31, 2012). The precise 

boundaries for the West Pinal County 

nonattainment area are described in 40 CFR 81.303. 

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, or if 

you need assistance in a language other 

than English or if you are a person with 

disabilities who needs a reasonable 

accommodation at no cost to you, 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 

https://www.epa.gov/dockets/ 

commenting-epa-dockets. If you need 

assistance in a language other than 

English or if you are a person with 

disabilities who needs a reasonable 

accommodation at no cost to you, please 

contact the person identified in the FOR

FURTHER INFORMATION CONTACT section. 

FOR FURTHER INFORMATION CONTACT: Jerry 

Wamsley, Air Planning Office (ARD–2), 

EPA Region IX, 75 Hawthorne Street, 

San Francisco, CA 94105, (415) 947– 

4111, or by email at wamsley.jerry@

epa.gov. 

SUPPLEMENTARY INFORMATION: 

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

and ‘‘our’’ refer to the EPA. 

Table of Contents 

I. Regulatory Context 

A. PM10 Standard, Area Designations, and 

SIPs 

B. CAA and Regulatory Requirements for 

Moderate PM10 Nonattainment Area SIPs 

II. Submissions From the State of Arizona To 

Address 1987 PM10 Standard 

Requirements in the West Pinal County 

Nonattainment Area 

A. Summary of State Submissions 

B. CAA Procedural Requirements for 

Adoption and Submission of SIP 

Revisions 

III. Evaluation of the West Pinal County PM10

Plan 

A. Emissions Inventories 

B. PM10 Precursors 

C. Reasonably Available Control Measures 

Demonstration 

D. Attainment Demonstration 

E. Reasonable Further Progress 

Demonstration 

F. Contingency Measures 

G. Motor Vehicle Emissions Budgets for 

Transportation Conformity 

IV. Proposed Action 

V. Statutory and Executive Order Reviews 

I. Regulatory Context 

A. PM10 Standard, Area Designations, 

and SIPs 

The EPA sets the National Ambient 

Air Quality Standard (NAAQS) for 

certain ambient air pollutants at levels 

required to protect human health and 

the environment. Particulate matter 

with an aerodynamic diameter less than 

or equal to a nominal ten micrometers, 

or PM10, is one of these ambient air 

pollutants for which the EPA has 

established health-based standards. On 

July 1, 1987, the EPA promulgated two 

primary standards for PM10: A 24-hour 

standard of 150 micrograms per cubic 

meter (mg/m3); and an annual PM10

standard of 50 mg/m3. The EPA also 

promulgated secondary PM10 standards 

that were identical to the primary 

standards.1 Because they are identical, 

we refer to the primary and secondary 

standards using the singular term, 

NAAQS. Effective December 18, 2006, 

EPA revoked the annual PM10 NAAQS 

but retained the 24-hour PM10 NAAQS.2

An area attains the 24-hour PM10

NAAQS when the expected number of 

days per calendar year with a 24-hour 

concentration in excess of 150 

micrograms per cubic meter (mg/m3) 

(referred to herein as an ‘‘exceedance’’), 

is equal to or less than one as 

determined in accordance with 40 CFR 

part 50, appendix K.3 Conversely, a 

violation of the PM10 NAAQS occurs 

when the number of expected annual 

exceedances of the 24-hour NAAQS is 

greater than one. 

Most of Pinal County, Arizona, 

including what is now the West Pinal 

County PM10 nonattainment area, was 

included in the ‘‘rest of state’’ area, 

which was designated ‘‘unclassifiable’’ 

for the 24-hour PM10 NAAQS by 

operation of law upon enactment of the 

CAA, consistent with section 

107(d)(4)(B)(iii). Until recently, this area 

in Arizona remained designated 

‘‘unclassifiable’’ for the 1987 24-hour 

PM10 NAAQS. The CAA, under section 

107(d)(3), authorizes the EPA to revise 

the designation of, or ‘‘redesignate,’’ 

areas (or portions thereof) based on air 

quality data, planning and control 

considerations, or any other air-qualityrelated considerations that the EPA 

deems appropriate. 

On October 14, 2009, under CAA 

section 107(d)(3)(A), the EPA notified 

the Governor of Arizona and four tribal 

leaders (whose areas of Indian country 

are located entirely, or in part, within 

Pinal County) that the designation for 

Pinal County, and any nearby areas that 

may be contributing to the monitored 

violations in Pinal County, should be 

revised.4 Our decision to initiate the 

redesignation process was due to 

ambient data for 2006–2008 from PM10

monitoring sites within the County 

showing widespread, frequent, and in 

some instances, severe, violations of the 

PM10 standard. 

Effective July 2, 2012, the EPA 

designated a portion of state lands in 

Pinal County, Arizona (‘‘West Pinal 

County’’) as nonattainment for the 1987 

PM10 NAAQS based on monitoring data 

from 2006–2008.5 West Pinal County is 

located in central Arizona, southeast of 

the Phoenix metropolitan area and 

northwest of the city of Tucson. Pinal 

County covers 5,365 square miles and 

has two distinct western and eastern 

regions with different characteristics 

relevant to pollution formation. The 

West Pinal County PM10 nonattainment 

area is located within the western 

region, characterized by low desert 

valleys and an arid climate. The eastern 

region is mountainous, with elevations 

up to 6,441 feet. 

As a result of the nonattainment 

designation, EPA classified West Pinal 

County as a ‘‘Moderate’’ PM10

nonattainment area. Consequently, by 

January 2, 2014, Arizona was required 

to submit a nonattainment plan SIP 

revision for the 24-hour PM10 NAAQS 

meeting relevant CAA requirements. 

The State submitted a SIP revision 

intended to meet these requirements on 

December 21, 2015, and this ‘‘2015 West 

Pinal Moderate PM10 Nonattainment 

Area SIP’’ is the subject of this proposed 

action. For a PM10 nonattainment area 

classified as Moderate, section 188(c) of 

the CAA provides that the Moderate 

area attainment date is ‘‘as 

expeditiously as practicable, but no later 

than the end of the sixth calendar year 

after the area’s designation as 

nonattainment.’’ Consequently, the 

applicable attainment date for the West 

Pinal County area, designated 

nonattainment in 2012, was as 

expeditiously as practicable, but no later 

than December 31, 2018. 

CAA section 188(b)(2) requires the 

EPA to determine whether a state has 


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6 85 FR 37756 (June 24, 2020). 

7 57 FR 13498 (April 16, 1992) and 57 FR 18070 

(April 28, 1992). 

8Letter dated December 21, 2015, from Eric C. 

Massey, Director, Air Quality Division, Arizona 

Department of Environmental Quality, to Jared 

Blumenfeld, Regional Administrator, EPA Region 

IX. 

9 82 FR 20267 (May 1, 2017). 

attained the 24-hour PM10 NAAQS in a 

Moderate PM10 nonattainment area by 

the applicable attainment date and 

requires the EPA to make such a 

determination within six months after 

that date. If the EPA determines that a 

Moderate area has not attained the 

NAAQS by the relevant attainment date, 

then the area is reclassified as a Serious 

area by operation of law. On June 24, 

2020, the EPA determined that the West 

Pinal County nonattainment area had 

not attained the 1987 24-hour PM10

NAAQS by December 31, 2018, the 

outermost permissible statutory 

attainment date for the area.6 This 

determination was based on our 

calculation of the PM10 design value for 

the West Pinal County nonattainment 

area over the 2016–2018 period, using 

complete, quality-assured, and certified 

PM10 monitoring data. 

The basis for the EPA’s June 24, 2020 

finding of failure to attain the PM10

NAAQS and the margin by which the 

area failed to attain indicate that the 

Moderate plan’s modeled attainment 

demonstration, which incorrectly 

predicted attainment of the PM10

NAAQS by December 31, 2018, is not 

approvable. Because the modeled 

attainment demonstration is not 

approvable, as described in section III.D, 

other elements of the West Pinal County 

PM10 Plan that are dependent upon the 

modeled attainment demonstration are 

likewise not approvable, e.g., the 

emission controls imposed by the State 

to meet reasonably available control 

measure/reasonably available control 

technology (RACM/RACT) requirements 

based on the predicted sufficiency of 

those controls to result in attainment by 

the intended attainment date. If 

finalized as we propose, our disapproval 

of most elements of the Moderate plan 

will start sanctions and Federal 

implementation plan (FIP) clocks, 

which can be turned off by the EPA’s 

approval of new plan elements for the 

PM10 NAAQS that correct the 

deficiencies within the Moderate plan. 

With the EPA’s reclassification of the 

West Pinal County area to Serious, 

Arizona now has an obligation to 

submit, by January 24, 2022, a 

nonattainment plan SIP revision that 

complies with the statutory and 

regulatory requirements for Serious 

PM10 nonattainment plans and that 

demonstrates attainment of the PM10

NAAQS as expeditiously as practicable, 

but no later than December 31, 2022. 

Although reclassification of an area 

from Moderate to Serious does not 

eliminate a state’s obligation to meet 

Moderate area nonattainment plan 

requirements, the EPA anticipates that 

Arizona’s submission of an approvable 

Serious area nonattainment plan would 

also satisfy the State’s Moderate area 

nonattainment plan obligations. For 

example, an approvable Serious area 

nonattainment plan would satisfy the 

Act’s requirements for imposing best 

available control measures, including 

best available control technology 

(BACM/BACT), which would 

presumably satisfy the less stringent 

requirements for RACM/RACT. 

B. CAA and Regulatory Requirements 

for Moderate PM10 Nonattainment Area 

SIPs 

Along with the new designations, 

classifications, and attainment dates, the 

Clean Air Act Amendments of 1990 

established new nonattainment area 

planning requirements. The air quality 

planning requirements for Moderate 

PM10 nonattainment areas are set out in 

subparts 1 and 4 of the CAA, including 

sections 110, 172, and 189 of the statute. 

We discuss these sections of the Act in 

more detail later during our review of 

each plan element. Also, the EPA has 

issued guidance, in a document we refer 

to as the General Preamble, describing 

how we will review state nonattainment 

plan SIP submissions under Title I of 

the CAA, including such SIP 

submissions for Moderate PM10

nonattainment areas.7 In general, states 

must include the following elements in 

nonattainment plans for Moderate areas 

for purposes of the 1987 24-hour PM10

NAAQS: A comprehensive, accurate, 

and current emissions inventory of 

emissions sources in the nonattainment 

area; provisions to implement RACM/ 

RACT for the appropriate sources and 

pollutants in the nonattainment area; 

provisions demonstrating reasonable 

further progress (RFP), including 

quantitative milestones towards 

attainment of the PM10 NAAQS as 

expeditiously as practicable, along with 

quantitative milestones for evaluation of 

RFP at set times; contingency measures 

that will provide for additional 

emissions reductions automatically in 

the event that the state fails to meet RFP 

or to attain the NAAQS by the 

applicable attainment date in the area; 

and, a motor vehicle emissions budget 

for the purpose of determining the 

conformity of transportation programs 

and plans developed by state 

transportation agencies. 

II. Submissions From the State of 

Arizona To Address the 1987 PM10

Standard Requirements in the West 

Pinal County Nonattainment Area 

A. Summary of State Submissions 

As a result of the May 31, 2012 

nonattainment designation, West Pinal 

County was classified as a Moderate 

PM10 nonattainment area. Within 18 

months from the July 2, 2012 effective 

date of the designation, or January 2, 

2014, the State was required to submit 

a nonattainment plan meeting Moderate 

area plan requirements, including 

emission control measures for West 

Pinal County designed to attain the 1987 

24-hour PM10 NAAQS as expeditiously 

as practicable, but no later than 

December 31, 2018. 

On December 21, 2015, Arizona 

submitted the West Pinal County PM10

Plan, intended to address the Moderate 

area nonattainment requirements, to the 

EPA as a revision to the Arizona SIP.8

The West Pinal County PM10 Plan is 

organized into seven chapters and nine 

appendices. The nine appendices 

provide support for the plan and are 

divided into the following categories: 

Technical support and documentation 

(appendices A–D, F), SIP adoption 

authority and public notice and hearing 

documentation (appendix E) and control 

measure submittals (appendices G–I). 

Appendices G, H, and I contain 

control measures submitted with the 

West Pinal County PM10 Plan in the 

form of rules, statutes, and other 

supporting documents. We are not 

proposing to act on the submitted 

control measures in this proposed 

action on the West Pinal County PM10

Plan. Previously, the EPA approved into 

the Arizona SIP the submitted control 

measures that regulate fugitive dust, 

construction dust, and crop operations.9

In a separate Federal Register notice, we 

intend to take action on the remainder 

of the State’s submitted rules, namely, 

an update to its agricultural best 

management practices (AgBMP) statute, 

and the AgBMP rules for animal 

operations in Pinal County. 

B. CAA Procedural Requirements for 

Adoption and Submission of SIP 

Revisions 

CAA sections 110(a) and 110(l) 

require a state to provide reasonable 

public notice and opportunity for public 

hearing prior to the adoption and 

submission of a SIP revision to the EPA 


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10 ‘‘Arizona Department of Environmental Quality 

and Public Comment Period and Hearing on the 

Proposed Arizona State Implementation Plan 

Revision, Attainment Plan for the West Pinal 

County PM10 Planning Area (1987 NAAQS)’’ 

published in the Arizona Republic October 19 and 

20, 2015; Exhibit E–III, Appendix E, West Pinal 

County PM10 Plan. 

11 ‘‘Public Hearing Presiding Officer 

Certification’’ signed by Naveen Savarirvayan, 

Presiding Officer, November 19, 2015 and 

notarized; Exhibit E–VI, Appendix E, West Pinal 

County PM10 Plan. The hearing transcript and the 

public comments and State responses are found at 

Exhibit E–VIII and Exhibit E–VII, respectively, 

within Appendix E, West Pinal County PM10 Plan. 

12Letter dated December 21, 2015 from Eric C. 

Massey, Director, Air Quality Division, ADEQ to 

Jared Blumenfeld, Regional Administrator, EPA 

Region IX. 

13 42 U.S.C. 7410(k)(1)(B). 

14See 81 FR 58032 (August 24, 2016). 

15See 81 FR 58027–58032. 

16As needed, we will refer to the primary 

document as ‘‘Appendix B’’ and the secondary 

document as ‘‘Appendix B-Exhibits.’’ 

17Please refer to Appendices G, H, and I, West 

Pinal County PM10 Plan for rule adoption 

information. 

18Appendix B, 62. 

for evaluation under section 110(k) and 

other applicable substantive 

requirements. To meet this procedural 

requirement, a state must include 

evidence that it provided adequate 

public notice and an opportunity for a 

public hearing, consistent with the 

EPA’s implementing regulations in 40 

CFR 51.102. 

The Arizona Department of 

Environmental Quality (ADEQ) 

provided public notice and opportunity 

for public comment on the West Pinal 

County PM10 Plan. On October 19, 2015, 

ADEQ released the West Pinal County 

PM10 Plan for public review and 

published a notice of public meeting to 

be held on November 19, 2015, to 

consider adoption of the West Pinal 

County PM10 Plan.10 On November 19, 

2015, ADEQ held the public hearing and 

subsequently adopted the West Pinal 

County PM10 Plan as a revision to the 

Arizona SIP.11 Under authority 

provided by Arizona state law, on 

December 21, 2015, Eric Massey, 

Director of the Air Quality Division, 

ADEQ, submitted the West Pinal County 

PM10 Plan to the EPA.12 On June 21, 

2016, the West Pinal County PM10 Plan 

became complete by operation of law.13

Based on information provided in the 

SIP submissions summarized above, the 

EPA has determined that the public 

hearing was properly noticed. 

Therefore, we find that the submittal of 

the West Pinal County PM10 Plan meets 

the procedural requirements for public 

notice and hearing in CAA sections 

110(a) and 110(l) and 40 CFR 51.102. 

III. Evaluation of the West Pinal County 

PM10 Plan 

A. Emissions Inventories 

1. Statutory and Regulatory 

Requirements 

CAA section 172(c)(3) requires a state 

to submit for each PM10 nonattainment 

area a ‘‘base year inventory’’ that is a 

comprehensive, accurate, current 

inventory of actual emissions from all 

sources of the relevant pollutant or 

pollutants in the area. Also, the state 

should submit a second projected 

‘‘attainment year inventory’’ for the year 

in which the state projects that the area 

will attain the PM10 standards. The state 

should include documentation 

explaining how it calculated the 

emissions data. When estimating mobile 

source emissions, states should use the 

latest emissions models and planning 

assumptions available at the time the 

SIP is developed.14

The state must meet several general 

requirements for base year emissions 

inventories, consistent with CAA 

section 172(c)(3). First, the emissions 

inventory year must be one of the 3 

years used for the EPA PM10

nonattainment designation for the area, 

or an alternative year agreed upon by 

the EPA and the state as more reflective 

of the causes and sources of violations 

of the PM10 standard that meet the 

criteria in CAA section 172(c)(3). 

Second, the state must reflect actual 

emissions from all sources of PM10 in 

the inventory. Third, the state should 

report the emissions inventory in the 

form of the PM10 standard it is intended 

to address, e.g., in tons or pounds per 

day to be consistent with the averaging 

period of the 24-hour PM10 NAAQS.15

A state must meet similar CAA 

section 172(c)(3) requirements in the 

projected attainment year inventory for 

the most expeditious year in which the 

state can show attainment of the PM10

standard in the modeled attainment 

demonstration portion of the 

nonattainment plan. At a minimum, the 

state must choose an attainment year 

consistent with the outermost 

applicable deadline required by CAA 

section 188(c). As with the baseline year 

inventory, the state must reflect 

emissions from all sources of PM10 in 

this inventory and report them in the 

form of the PM10 standard. In addition, 

the attainment year inventory must be 

consistent with the source categories 

and level of detail reported by the state 

in the base year inventory. 

Future attainment year and related 

baseline emissions inventories must 

reflect the most recent population, 

employment, travel and congestion 

estimates for the area. In this context, 

‘‘baseline’’ emissions inventories refer 

to emissions estimates for a given year 

and area that reflect rules and 

regulations and other measures that are 

already adopted in a state’s EPA 

approved SIP and assumed within the 

attainment demonstration. Future 

baseline emissions inventories are 

necessary to show the projected 

effectiveness of SIP control measures 

designed to result in attainment by the 

applicable attainment year. Both the 

base year and future year, baseline and 

attainment inventories are necessary 

inputs to any modeling or other 

analyses required to demonstrate 

attainment of the PM10 standard, as 

required by section 189(a)(1)(B). 

2. Summary of State’s Submission 

The West Pinal County PM10 Plan 

includes a base year (2008) inventory, 

and future year (2018) baseline and 

attainment emissions inventories for 

direct PM10 in the West Pinal County 

area. The State provided documentation 

for the emissions inventories in Chapter 

5 (‘‘Annual Emissions Inventory’’) of the 

West Pinal County PM10 Plan and its 

two-part Appendix B (‘‘Pinal County 

PM10 Nonattainment Area Emissions 

Inventories for 2008 and 2018 Base 

Years and Design Days’’, and its 

supporting ‘‘Exhibits’’).16 The emissions 

inventories are provided in two parts, 

one representing windblown PM10

emissions on high-wind days (including 

both entrained dust and windblown 

dust from human activities), and the 

second representing PM10 emissions on 

low-wind days (including dust due to 

human activity that stagnates near its 

point of origin). The State presents the 

annual emissions inventories on a tons 

per year basis that it later converts to a 

tons or pounds per day basis for use 

within the attainment demonstration 

modeling for the 24-hour NAAQS at 

issue. 

The 2018 attainment year emissions 

inventories reflect State of Arizona and 

Pinal County rules adopted 

concurrently with the West Pinal 

County PM10 Plan in late 2015.17 The 

Plan’s emissions reductions are based 

on continuing implementation of 

existing Federal controls along with 

new state and local control measures 

submitted with the Plan. The 2008 base 

year and projected 2018 baseline and 

attainment year inventories use the most 

recent EPA-approved mobile source 

emissions model at the time the plan 

was developed, MOVES2014, for 

estimating on-road motor vehicle 

emissions.18 Future emissions forecasts 

in the West Pinal County PM10 Plan, 

particularly on-road mobile source 

emissions, are based primarily on 


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19West Pinal County PM10 Plan, 27–28, Table 3– 

3; Appendix B, 120, 132, and 132 at footnote 97. 

20Appendix B, 62–75. 

21Appendix B, 87–90. EPA NONROAD Model, 

Version 2008a, released July 2009. 

22Appendix B, 96. 

23Tables 5–1, 5–2, and 5–3, West Pinal County 

PM10 Plan. 24Appendix B, chapters 3 and 5. 

demographic and economic growth 

projections provided by Arizona 

Department of Administration and the 

Maricopa Association of Governments 

(MAG).19

In general, the term ‘‘point sources’’ 

typically refers to permitted facilities 

that have one or more identified and 

fixed pieces of equipment and 

emissions points. ‘‘Area sources’’ 

typically consist of widespread and 

numerous smaller emissions sources, 

such as small permitted facilities and 

households. The ‘‘mobile sources’’ 

category refers to vehicles and is 

typically divided into two major 

subcategories, ‘‘on-road’’ and ‘‘nonroad’’ mobile sources. On-road mobile 

sources include light-duty automobiles, 

light-, medium-, and heavy-duty trucks, 

and motorcycles. In addition to tailpipe, 

brake, and tire wear, on-road mobile 

emissions estimates for PM10 also 

include re-entrained dust from vehicles 

driven on paved and unpaved roads. 

Non-road mobile sources include 

aircraft and related support vehicles, 

locomotives, construction equipment, 

agricultural equipment, mobile 

equipment, and recreational vehicles. 

In the West Pinal County PM10 Plan, 

the State based the point source 

emissions for the 2008 base year 

emissions inventory on reported data 

from facilities using the permit file 

reporting programs of the Pinal County 

Air Quality Control District (PCAQCD). 

Area sources, as noted above, include 

smaller emissions sources distributed 

across the nonattainment area. ADEQ 

estimated emissions for area sources 

using established inventory methods, 

including publicly available emissions 

factors and activity information. The 

State derived activity data from national 

survey data, such as the Energy 

Information Administration or from 

local sources and PCAQCD databases. 

Emissions factors used for the estimates 

come from many sources, such as 

facility and equipment source tests, 

compliance reports, and the EPA’s 

compilation of emissions factors 

document known as ‘‘AP–42.’’ 

ADEQ calculated the 2008 base year 

on-road emissions inventories in the 

West Pinal PM10 Plan using the 

MOVES2014 model and a back-casting 

of 2015 modeling of vehicle travel 

activity data provided by MAG.20 ADEQ 

estimated emissions inventories for nonroad equipment using the EPA’s 

NONROAD Model, including 

construction and mining equipment, 

industrial and commercial equipment, 

lawn and garden equipment, 

agricultural equipment, and recreational 

vehicles.21 Locomotive emissions were 

estimated from EPA published emission 

factors and local track-mileage, train 

speed, and throughput data.22 The State 

developed aircraft and related ground 

support vehicle emissions estimates in 

conjunction with activity data from 

local airports in the region. 

As described previously, the State 

grouped direct PM10 emissions 

estimates in the West Pinal County PM10

Plan into two general categories and 

emissions inventories, windblown dust 

and human activity-based emissions; 23

we present these inventories in Tables 

1 and 2, respectively. In general, 

emission inventories can be broken into 

four basic categories: Stationary sources, 

area sources, non-road sources and 

mobile sources. Instead of a summary 

emissions inventory consisting of these 

four general categories, ADEQ provided 

a more detailed 2008 base year 

emissions inventory. In some cases, a 

source category will appear in both 

emissions inventories and tables. For 

example, an unpaved road and an 

agricultural field will emit PM10 when 

wind speeds become high enough to 

pick up and carry disturbed earth, as 

well as due to vehicle and equipment 

traffic on the unpaved road or 

agricultural activity in a field, such as 

harvesting or tilling. 

TABLE 1—WEST PINAL COUNTY PM10

PLAN, WINDBLOWN DUST/FUGITIVE

EMISSIONS INVENTORY

[Tons per year] 

Source category 2008 

base year 

Developed Urban Lands ............. 200.7 

Developed Rural Lands .............. 1,959.7 

Unpaved Roads .......................... 4,688.6 

Cleared Areas ............................. 398.1 

Residential Construction ............. 1,302.4 

Dairies ......................................... 449.6 

CAFOs ........................................ 273.7 

Desert Shrubland ........................ 38,276.7 

Agriculture ................................... 19,510.1 

Commercial Construction ........... 686.4 

Other ........................................... 4,243.9 

Site Development ....................... 858.7 

Total ..................................... 72,848.6 

Source: West Pinal County PM10 Plan, 

Table 5–3; Appendix B, Tables 5–31, 5–33. 

Table 2 presents ADEQ’s direct PM10

emissions inventory related to human 

activity. Stationary sources are broken 

out into permitted sources and fuel 

combustion. Area sources are 

disaggregated into several source 

categories: Fires, open burning, unpaved 

parking, and construction sites and 

activities. Agricultural sources are also 

disaggregated into several source 

categories: on field harvesting, on field 

tilling, confined animal feed operations 

(CAFOs), and dairies. In contrast, 

mobile sources are included within the 

‘‘unpaved roads’’ and ‘‘paved roads’’ 

source categories. Each of these two 

source categories aggregate direct 

(vehicle exhaust, tire and brake wear) 

and fugitive PM10 emissions from motor 

vehicles on unpaved and paved roads. 

Finally, nonroad equipment and 

railroad emissions are assigned to their 

own respective source categories. 

TABLE 2—WEST PINAL COUNTY PM10

PLAN, HUMAN ACTIVITY-BASED

EMISSIONS INVENTORY

[Tons per year] 

Source category 2008 

base year 

Ag Fields—Harvesting ................ 312.9 

Ag Fields—Tilling ........................ 2,540.3 

CAFOs ........................................ 2,614.3 

Paved Road * .............................. 1,180.7 

Unpaved Road—All Road 

Types * .................................... 45,127.8 

Fuel Combustion ........................ 28.3 

Fires ............................................ 19.9 

Open Burning ............................. 13.6 

Nonroad ...................................... 121.3 

Railroad ...................................... 85.9 

Construction ................................ 12,955.3 

Dairy ........................................... 186.6 

Permitted Sources ...................... 781.3 

Unpaved Parking ........................ 251.5 

Total ..................................... 66,219.7 

Source: West Pinal County PM10 Plan, 

Table 5–3; Appendix B, Tables 5–31, 5–33. 

* Paved and Unpaved Road emissions estimates include direct vehicle emissions and fugitive dust emissions from vehicle reentrainment. 

Tables 1 and 2 provide a summary of 

the West Pinal County 2008 base year 

direct PM10 emissions in tons per year. 

Appendix B, Chapters 3 and 5 also 

provide source category estimates in a 

pounds per day format consistent with 

the 24-hour PM10 NAAQS. Where 

appropriate, within the attainment 

demonstration, ADEQ used these daily 

estimates or developed more focused 

daily emissions estimates to provide the 

basis for the control measure analysis 

and the modeled attainment 

demonstrations in the West Pinal 

County PM10 Plan.24 Within the 

windblown PM10 emissions inventory, 

the largest source after desert shrubland 


tkelley on DSKBCP9HB2PROD with PROPOSALS
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25As discussed in Section III.G Motor Vehicle 

Emissions Budgets and Transportation Conformity, 

an annual emissions inventory introduces 

difficulties with determining and presenting a 

motor vehicle emissions budget. 

26Chapter 5 and Appendix B of the West Pinal 

County PM10 Plan. 

27See CAA requirements for states to demonstrate 

attainment ‘‘as expeditiously as practicable,’’ CAA 

section 188(c)(1) and section 172(a)(1). 

28See 81 FR 58010, 58018. 

29Clements, A.L., Fraser, M.P., Upadhyay, N., 

Herckes, P., Sundblom, M., Lantz, J., and Solomon, 

P.A., ‘‘Chemical characterization of coarse 

particulate matter in the Desert Southwest—Pinal 

County Arizona, USA’’, Atmospheric Pollution 

Research, 5 (2014) 52–61. 

30ADEQ focused their attainment demonstration 

on a set of ‘‘design days’’ and monitors that have 

experienced, or are conducive to, the highest 

concentrations. See EPA TSD, p. 11. Two design 

days were examined in ADEQ’s PM10 precursor 

demonstration. 

31Appendix B, Exhibit BXVI, Table BXVI–2. 

is agricultural emissions. Within the 

human activity-based emissions 

inventory, the largest source is unpaved 

roads, followed by construction fugitive 

emissions. 

3. The EPA’s Review of the State’s 

Submission 

We have reviewed the 2008 base year 

emissions inventory for direct PM10 in 

the West Pinal County PM10 Plan and 

emissions inventory estimation 

methodologies used by ADEQ for 

consistency with CAA requirements and 

EPA guidance. We address the State’s 

analysis for PM10 precursors in Section 

III.B. 

First, we find that although the 2008 

base year inventory reports annual PM10

emissions estimates, the Plan also 

provides and uses daily emissions 

estimates within the attainment 

demonstration modeling and the related 

modeling domain micro-emissions 

inventories; therefore, the Plan is 

consistent with the requirement that 

ADEQ must use an emissions inventory 

in a form consistent with the 24-hour 

PM10 standard.25 ADEQ has provided 

adequate documentation explaining 

how it calculated the 2008 base year 

emissions estimates, both as annual and 

daily inventories.26

Second, we find that the 2008 base 

year emissions inventory in the West 

Pinal County PM10 Plan used emissions 

models, emission factors, and 

methodologies for estimating PM10

emissions that were accurate and 

appropriate to the time that the Plan 

was written. Also, the 2008 base year 

inventory for direct PM10 is 

comprehensive in scope and coverage. 

Therefore, the submitted emissions 

inventory represents a comprehensive, 

accurate, and current inventory of actual 

emissions of direct PM10 during that 

year in the West Pinal County Area. 

Third, we find that ADEQ’s selection 

of 2008 for the base year emissions 

inventory is appropriate because it is 

chosen from one of the three years, 

2006–2008, in which the area was 

designated nonattainment. The 2008 

emissions inventory is representative of 

the sources of direct PM10 pollution 

contributing to exceedances of the PM10

NAAQS that caused the area to be 

designated nonattainment. 

Consequently, the EPA is proposing to 

approve the 2008 base year emissions 

inventory for direct PM10 in the West 

Pinal County PM10 Plan as meeting the 

requirements for a base year inventory 

set forth in CAA section 172(c)(3). 

B. PM10 Precursors 

1. Statutory and Regulatory 

Requirements 

Section 189(e) of the Act requires that 

the control requirements for major 

stationary sources of direct PM10 also 

apply to major stationary sources of 

PM10 precursors, except where the 

Administrator determines that such 

sources do not contribute significantly 

to PM10 levels that exceed the standard 

in the area. While CAA section 189(e) 

expressly requires control of precursors 

from major stationary sources, subpart 4 

and other CAA provisions collectively 

require the control of direct PM10 and 

PM10 precursors from all types of 

sources (i.e., stationary sources, area 

sources and mobile sources) as may be 

needed for the purposes of 

demonstrating attainment as 

expeditiously as practicable in a given 

nonattainment area.27

The provisions of subpart 4 of part D, 

title I of the CAA do not define the term 

‘‘precursor’’ for purposes of PM10, nor 

do they explicitly require the control of 

any specific PM precursor. The statutory 

definition of ‘‘air pollutant’’ in CAA 

section 302(g), however, provides that 

the term ‘‘includes any precursors to the 

formation of any air pollutant, to the 

extent the Administrator has identified 

such precursor or precursors for the 

particular purpose for which the term 

‘air pollutant’ is used.’’ EPA has 

identified sulfur dioxide (SO2), oxides 

of nitrogen (NOX), volatile organic 

compounds (VOC), and ammonia (NH3) 

as precursors to the formation of PM.28

Accordingly, a state must include 

emissions of direct PM emissions and 

these four precursors in emissions 

inventories and must control emissions 

from sources of all of these pollutants, 

unless the state demonstrates to EPA’s 

satisfaction that control of one or more 

of these pollutants is not needed for 

expeditions attainment of the NAAQS 

in the nonattainment area at issue. 

2. Summary of the State’s Submission 

Appendix B, Exhibit BXVI contains 

ADEQ’s demonstration that emissions of 

SO2, NOX, and NH3 from existing 

sources in the West Pinal County 

nonattainment area do not contribute 

significantly to PM10 levels that exceed 

the NAAQS. For this analysis, ADEQ 

estimated the impact of these three PM10

precursors on PM10 concentrations at 

two sites, Cowtown (CWT) and Pinal 

County Housing (PCH), using ‘‘worst 

impact day monitored data’’ from a 

year-long chemical mass balance 

characterization (CMBC) study (Desert 

Southwest Coarse Particulate Matter 

Study) and emissions data from the 

2008 National Emission Inventory 

(NEI).29 ADEQ evaluated these data to 

determine which, if any, source 

categories had precursor emissions that 

contribute more than 5 micrograms per 

cubic meter (mg/m3) on specific design 

days. 30

Appendix B, Exhibit BXVI, Table 

BXVI–1 provides the maximum particle 

mass concentration and chemical 

composition (i.e., crustal, organic 

material, nitrate, sulfate, ammonium, 

other species, and unidentified particle 

fractions) measured during the CMBC 

study for CWT and PCH. ADEQ then 

calculated the percentage of each 

chemical constituent to the summed 

total of the chemical constituent parts. 

ADEQ assumed the design days for each 

monitor had the same relative chemical 

composition as the ‘‘worst impact day’’ 

identified in the CMBC study. The State 

calculated design day concentrations for 

each chemical constituent by 

multiplying the study-derived 

percentages by a design day 

concentration for CWT (244.5 mg/m3) 

and PCH (178.0 mg/m3). The CMBC 

study estimated that summed nitrate, 

sulfate, and ammonium impacts on the 

CWT and PCH monitors were 3.4 

percent and 4.0 percent, respectively. 

These percentages suggest that 8.4 mg/ 

m3 and 7.2 mg/m3 of the design day 

ambient PM10 concentrations at the 

CWT and PCH monitors resulted from 

emissions of the three PM10 precursors 

examined. 

Next, ADEQ processed Pinal County 

2008 EPA NEI reported emissions for 

NOX, SO2, and NH3 to determine the 

percent contribution of each source 

sector to the total emissions of these 

pollutants for the county. 31 ADEQ 

apportioned the precursor 

concentrations derived above to 

individual source sectors based on the 

relative contribution of each sector to 

the annual emission inventory. Based 


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32Appendix B, Exhibit BXVI, Table BXVI–3. 

33Appendix B, Exhibit BXVI, BXVI–2. See 59 FR 

at 42011. 

34For more recent guidance on precursor 

significance, see Memorandum from Scott Mathias, 

Acting Director, Air Quality Policy Division and 

Richard Wayland, Director, Air Quality Assessment 

Division, ‘‘Fine Particulate Matter (PM2.5) Precursor 

Demonstration Guidance’’ (May 30, 2019). 

35 44 FR 20372 (April 4, 1979) and 57 FR 13498 

(April 16, 1992). 

on this analysis, no precursor emissions 

from any source category exceeded the 

5 mg/m3 threshold.32 The largest 

contributing source category was ‘‘Onroad Mobile,’’ contributing less than 3.5 

mg/m3 of PM10 from precursor emissions 

to either monitor on the design days. 

3. The EPA’s Review of the State’s 

Submission 

We identified several issues with the 

analysis that ADEQ presented. First, 

SO2, NOX, VOC, and ammonia are 

precursors to the formation of PM10. 

ADEQ does not address VOC emissions 

in its analysis; therefore, we cannot 

evaluate whether sources of VOC 

emissions contribute significantly to 

PM10 levels that exceed the NAAQS in 

the West Pinal County PM10

nonattainment area. 

Second, it is unclear whether the 

chemical composition values presented 

in Appendix B, Exhibit BXVI, Table 

BXVI–1 reflect one maximum day 

sample, or the maximum chemical 

composition measured for each 

individual component during the entire 

CMBC study. If the latter approach was 

used, then the resulting percentages 

would not reflect percentages measured 

on any actual exceedance day and could 

overrepresent or underrepresent the 

various chemicals when compared to 

actual exceedance days. If the chemical 

composition values represent one 

maximum day sample, then: (a) The 

individual components listed in Table 

BXVI–1 when totaled together should 

equal that day’s total mass, which they 

do not; and (b) this would only 

represent a single day—therefore, a 

single type of exceedance day. ADEQ 

modeled two meteorological scenarios 

causing exceedances, high wind 

conditions and stagnant or low wind 

conditions. The emission sources 

affecting the PM10 composition would 

vary between these two scenarios, 

making use of a single maximum value 

at each site for each chemical 

component likely insufficient. 

Therefore, ADEQ’s approach of 

assuming the chemical composition of 

the two design days match those 

reported in the study likely does not 

address all conditions affecting 

nonattainment for the area. 

Third, ADEQ applied the 5 mg/m3

threshold from the Serious PM10

nonattainment area addendum to the 

General Preamble.33 The Serious area 

addendum states that, for purposes of 

evaluating best available control 

measures (BACM), a source category 

will be presumed to contribute 

significantly to a violation of the 

NAAQS if its PM10 impact at the 

location of the expected violation would 

exceed 5 mg/m3. This guidance is not 

precursor guidance and was intended to 

apply to the total impact of a source 

category (including direct PM and 

precursor emissions). It is not clear from 

the State’s submission why the 

application of this threshold to the 

impact of precursor emissions from 

individual source categories is an 

appropriate method of evaluating the 

significance of PM10 precursor 

emissions for the West Pinal County 

PM10 nonattainment area.34

Finally, ADEQ used an annual 

inventory to partition the source 

category contribution to PM10. High 

wind affected days would likely have a 

different composition of sources than 

what would be reflected in an annual 

inventory, potentially by a substantial 

margin. ADEQ did not address this 

issue, and used the annual inventory 

composition to represent all exceedance 

days. 

The State has not adequately shown 

that PM10 precursors do not contribute 

significantly to concentrations above the 

NAAQS in the West Pinal County PM10

nonattainment area. As described 

elsewhere in this notice, due to the 

deficiencies with the State’s precursor 

analysis, the State has not shown that it 

was unnecessary to regulate emissions 

of precursors in its RACM and modeled 

attainment demonstration. As explained 

in Section III.C., the State has only 

evaluated sources of direct PM 

emissions within the West Pinal County 

PM10 Plan. The EPA anticipates that 

ADEQ could develop an improved 

precursor analysis for the area, and this 

analysis may ultimately confirm that it 

is not necessary to regulate one or all of 

the PM10 precursors; however, we find 

that the precursor analysis submitted 

with the Plan does not provide a 

sufficient basis for that conclusion. 

In conclusion, because of the 

omissions and uncertainties in ADEQ’s 

PM10 precursor analysis, we are unable 

to determine whether precursor 

emissions contribute significantly to 

PM10 levels that exceed the NAAQS in 

the West Pinal County nonattainment 

area. Consequently, we are proposing to 

disapprove the precursor demonstration 

in the West Pinal County PM10 Plan 

because the demonstration is inadequate 

to show that emissions reductions from 

all PM10 precursors do not contribute 

significantly to PM10 levels exceeding 

the NAAQS, as required by CAA 

Section 189(e). As explained in section 

III.C, the deficiencies in the State’s 

precursor analysis mean that the State 

failed to establish in its RACM/RACT 

analysis that it was unnecessary to 

regulate PM10 precursor emissions. 

C. Reasonably Available Control 

Measures Demonstration 

1. Statutory and Regulatory 

Requirements 

CAA section 172(c)(1) requires that 

each attainment plan provide for the 

implementation of all RACM/RACT as 

expeditiously as practicable (including 

such reductions in emissions from 

sources in the area through 

implementation of reasonably available 

control technology) and for attainment 

of the NAAQS. Consistent with section 

189(a)(1)(C), each state with a Moderate 

PM10 nonattainment area is required to 

submit provisions to assure 

implementation of reasonably available 

control measures no later than 4 years 

after the date of designation of the area. 

Taken together, these CAA provisions 

require that Moderate area attainment 

plans must provide for the 

implementation of RACM and RACT in 

the nonattainment area as expeditiously 

as practicable but no later than 4 years 

after designation. 

Section 189(a)(1)(B) of the CAA 

requires states to demonstrate 

attainment of the PM10 standard by the 

applicable attainment date (or 

demonstrate that attainment by such 

date is impracticable) and Section 

188(c)(1) requires that the attainment 

date for a Moderate area shall be as 

expeditiously as practicable, but no later 

than the end of the sixth calendar year 

after the year of the nonattainment 

area’s designation. 

To address this requirement to adopt 

all RACM/RACT and meet the PM10

NAAQS as expeditiously as practicable, 

states should consider all potentially 

reasonable control measures for source 

categories in the nonattainment area to 

determine whether they are reasonably 

available for implementation in that 

area and whether they would, if 

implemented individually or 

collectively, advance the area’s 

applicable attainment date by one year 

or more.35 Any measures that are 

necessary to meet these requirements 

that are not either federally 

promulgated, or part of the state’s SIP, 

must be submitted in enforceable form 


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36 57 FR 18070. 

37 57 FR 13540, 13541. 

38Appendix F, Chapters 2 and 3. 

39Appendix F, 4–12. 

40Appendix F, Chapter 2 and Table 1. 

41Appendix F, Chapters 2–4. 

42Appendix F, Chapter 4; Exhibit F–I, Available 

Measures; Exhibit F–II, Construction Comparison; 

Exhibit F–III, Agricultural Comparison; and, Exhibit 

F–IV, Fugitive Dust Comparison. 

43West Pinal County PM10 Plan, Chapter 7; Table 

7–4; Appendix D, Table D5–1. 

44Appendix F, 29, 47, 51. 

45West Pinal County PM10 Plan, Chapters 6 and 

7. 

46West Pinal County PM10 Plan, Chapter 6; 

Chapter 7, Table 7–4. 

47West Pinal County PM10 Plan, Chapters 6 and 

7. 

48West Pinal County PM10 Plan, Chapter 6; 

Chapter 7, Table 7–4. 

as part of the state’s nonattainment plan 

SIP submission for the area. 

The EPA has provided guidance 

interpreting the RACM requirement in 

the General Preamble for the 

Implementation of the Clean Air Act 

Amendments of 1990 (‘‘General 

Preamble’’). This guidance includes the 

following elements and concepts: A 

recommended list of potential PM10

measures for states to consider; 36 an 

emphasis on a state’s evaluation of the 

technological and economic feasibility 

of potential control measures to 

determine if such measures are 

reasonably available for implementation 

in a given nonattainment area; an 

expectation that the state will provide a 

reasoned explanation for a decision not 

to adopt a given control measure, 

including a review of any control 

measures recommended to the state 

during public comment or public 

hearing; and, a discussion that in some 

cases partial implementation of an 

emissions reduction program may be 

considered RACM when full 

implementation would be infeasible 

within the given Moderate area 

timeframe.37

2. Summary of the State’s Submission 

For the West Pinal County PM10 Plan, 

ADEQ worked through a process to 

identify and evaluate potential RACM/ 

RACT that could contribute to 

expeditious attainment of the PM10

NAAQS in the West Pinal County 

nonattainment area. Chapter 6 of the 

West Pinal County PM10 Plan provides 

an overview and description of the 

Plan’s constituent control measures. 

ADEQ’s RACM/RACT analysis for the 

PM10 standard is described in Appendix 

F—RACM Analysis for the West Pinal 

County PM10 Nonattainment Area 

(‘‘Appendix F’’). Appendix F contains 

summary analyses of potential control 

measures for emissions reduction 

opportunities, as well as the economic 

and technological feasibility and 

comparability with control requirements 

in other states and localities. 

As a first step in the RACM/RACT 

analysis, ADEQ prepared a detailed 

inventory of direct PM10 emissions 

sources to identify source categories 

from which emissions reductions would 

contribute to attaining the PM10

standard.38 In this analysis, ADEQ 

identified point sources, unpaved roads 

and agriculture on tribal land, dairy 

operations, nonroad vehicles, 

residential fuel combustion, and open 

burning as insignificant sources of 

emissions in the area.39 Then, ADEQ 

identified agricultural operations, 

confined animal feeding operations, 

fugitive dust from cleared area and 

unpaved parking lots, construction 

fugitive dust, and re-entrained dust from 

paved and unpaved roads as significant 

sources in the nonattainment area and 

determined a list of available control 

measures. ADEQ determined that a 

source category was significant if those 

sources contributed more than 5 mg/m3

on a 24-hour basis on a given design 

day. Conversely, ADEQ determined that 

source categories contributing less than 

the 5 mg/m3 threshold were 

insignificant; furthermore, ADEQ 

determined these insignificant sources 

would not advance attainment of the 

NAAQS, given their small collective 

contribution to nonattainment.40

Finally, ADEQ evaluated the efficacy, 

cost, and technical feasibility of these 

identified control measures within the 

nonattainment area.41 As part of this 

review, ADEQ also compared the 

control requirements of its proposed 

rules with those requirements in other 

PM10 nonattainment areas or similar 

state and local provisions.42 ADEQ did 

not identify sources or analyze potential 

RACM/RACT for PM10 precursors 

because it concluded that such 

precursors did not contribute 

significantly to a violation of the 

NAAQS. 

With this process, ADEQ attempted to 

evaluate and analyze the universe of 

potential RACM/RACT level controls for 

sources of direct PM10 emissions and 

identify the subset of control measures 

that were available to include within the 

West Pinal County PM10 Plan. ADEQ 

identified a set of control measures that 

it determined would be sufficient to 

enable the area to attain by December 

31, 2018, and additional controls that it 

determined were not necessary for 

attainment or RFP to serve as 

contingency measures.43 ADEQ based 

this conclusion on: (1) The practical 

feasibility of adopting control measures 

over the latter half of 2015 with the 

State’s desired implementation date of 

no later than January 1, 2016; and (2) 

the ability of these control measures to 

produce immediate emissions 

reductions and contribute to attainment 

of the PM10 NAAQS by 2018.44 As 

discussed earlier, the State submitted 

the following control measures with the 

West Pinal County PM10 Plan: The 

AgBMP Rules for Pinal County, the 

Pinal County Fugitive Dust Rule, and 

the Pinal County Construction Dust 

Rule. ADEQ relied only on the following 

portions of the AgBMP Rules for Pinal 

County to meet the RACM/RACT 

requirements and demonstrate 

attainment of the PM10 standard: 

AgBMP rule R18–2–610 and –610.03, 

commercial farms; AgBMP rule R18–2– 

611 and –611.03, commercial animal 

operations (except for dairy operations); 

and R18–2–612 and –612.01, irrigation 

districts.45

ADEQ did not provide a complete or 

systematic analysis of whether the 

control measures it did not adopt based 

on concerns about a lack of immediate 

emission reduction effect, if taken 

together, would advance the area’s 

attainment date. Nonetheless, ADEQ did 

adopt those control measures, 

implemented them over the 2016–2018 

timeframe, and allocated them to serve 

as contingency measures in the Plan. 

ADEQ designated the portion of the 

AgBMP Rules for Pinal County 

applicable to dairy operations (R18–2– 

611 and –611.03), along with the Pinal 

County Fugitive Dust Rule and the Pinal 

County Construction Dust Rule, as 

contingency measures because these 

rules provided additional emissions 

reductions not relied upon within the 

Plan’s attainment demonstration.46

3. The EPA’s Review of the State’s 

Submission 

As described above, ADEQ evaluated 

a wide range of potentially available 

measures for the West Pinal County 

PM10 Plan. ADEQ identified portions of 

the AgBMP Rules for Pinal County as 

RACM/RACT and the State adopted 

them to provide for attainment of the 

PM10 standard.47 The remaining 

adopted control measures, some of 

which were identified as significant 

sources and potential RACM/RACT, 

were assigned to provide for 

contingency measures within the 

Plan.48 In sum, all source categories 

identified as significant were covered by 

controls either as a control measure for 

attainment, or as contingency measures, 

and implemented over the 2016–2018 

timeframe. As has been confirmed by 

subsequent monitoring data, however, 


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49Appendix F, Chapter 4. 

50See 81 FR 58010, 58035. Although such 

controls should be evaluated to determine if their 

adoption could advance attainment. 51West Pinal PM10 Plan County, Section 7.1. 

these adopted control measures were 

insufficient to attain the PM10 NAAQS 

by the applicable attainment date, in 

part because the State overestimated the 

effectiveness of the RACM/RACTdesignated adopted controls. As an 

example, ADEQ assumed high and 

insufficiently conservative compliance 

rates for agricultural operations that had 

either no previous experience 

implementing control measures, or little 

to no reliable documented compliance 

history. We review the State’s analysis 

and attainment demonstration in 

Section III.D and provide detailed 

discussion in the Technical Support 

Document (TSD). 

The Plan described the adopted 

control measures and concluded that a 

subset was reasonable and would 

achieve the NAAQS by the attainment 

date; therefore, the State concluded that 

the RACM/RACT-designated subset of 

adopted control measures constituted 

the necessary RACM/RACT for the 

area.49 The State adopted several 

additional measures beyond the RACM/ 

RACT measures to serve as contingency 

measures in the Plan. If the RACM/ 

RACT-designated adopted controls 

actually sufficed to achieve attainment, 

then these control measures could have 

constituted sufficient RACM, as 

additional measures beyond those 

necessary for attainment need not 

necessarily be considered as RACM/ 

RACT.50 Because the adopted controls 

designated as RACM/RACT in the West 

Pinal County PM10 Plan were 

insufficient, however, to achieve 

attainment, due in part to overestimates 

of the control efficiency of these rules, 

we find that the State terminated its 

RACM/RACT analysis prematurely. The 

control measures reserved for 

contingency measures that the State did 

not include as RACM/RACT should 

have been included and justified as 

RACM. Furthermore, because the State’s 

determination regarding PM10

precursors failed to demonstrate that 

precursors do not contribute 

significantly to a violation of the 

NAAQS, the State remains obligated to 

demonstrate that additional PM10

precursor control measures are not 

required RACM/RACT. 

Despite the RACM/RACT-designated 

rules and contingency measures 

adopted and implemented by the State, 

we find that the State failed to adopt 

RACM/RACT sufficient to achieve the 

PM10 NAAQS, due in part, to 

overestimating the control effectiveness 

of these RACM/RACT control measures. 

Our conclusion is confirmed by the 

failure of the Plan’s adopted and 

designated measures to result in 

attainment of the PM10 NAAQS by the 

applicable attainment date of December 

31, 2018. Because the adopted controls 

were insufficient to meet the PM10

NAAQS by the attainment date, and the 

State excluded source categories, 

including sources of precursors, from its 

RACM/RACT demonstration without 

sufficient justification, we propose to 

disapprove the RACM/RACT 

demonstration in the West Pinal County 

PM10 Plan and determine that the Plan 

does not provide for the implementation 

of all RACM/RACT as required by CAA 

section 172(c)(1) and section 

189(a)(1)(C). 

D. Attainment Demonstration 

1. Statutory and Regulatory 

Requirements 

Section 189(a)(1)(B) of the CAA 

requires that a plan for a Moderate PM10

nonattainment area include a 

‘‘demonstration (including air quality 

modeling) that the plan will provide for 

attainment [of the PM10 NAAQS] by the 

applicable attainment date.’’ An 

attainment demonstration consists of 

several elements including technical 

analyses, such as base year and future 

year modeling, to locate and identify 

sources of emissions that are 

contributing to violations of the PM10

NAAQS within the nonattainment area 

(i.e., analyses related to the emissions 

inventory for the nonattainment area 

and the emissions reductions necessary 

to attain the standard). Section 188(c)(1) 

of the CAA requires Moderate areas to 

meet the PM10 standard as expeditiously 

as practicable, but no later than the 

sixth calendar year from the area 

designation. 

In addition to reviewing the 

attainment demonstration modeling and 

related analyses, we evaluate the Plan’s 

control strategy and the efficacy of the 

Plan’s adopted controls to meet the 

PM10 NAAQS by the applicable date. 

2. Summary of the State’s Submission 

ADEQ applied a form of proportional 

roll back and dispersion modeling using 

a micro-emissions inventory method to 

model attainment of the PM10 NAAQS. 

ADEQ modeled two meteorological 

scenarios causing ambient air values in 

excess of the 24-hour PM10 NAAQS of 

150 mg/m3, high wind conditions and 

stagnant or low wind conditions, at a 

representative subset of the monitoring 

sites in the nonattainment area.51 Under 

‘‘stagnation’’ conditions, wind speeds 

are typically below 3 mph and particles 

accumulate in the air without any 

meteorological reprieve. Under ‘‘high 

wind’’ conditions, elevated wind speeds 

(e.g., over 12 mph) generate dust from 

disturbed soil surfaces, elevating PM10

concentrations. Each selected 

monitoring site in each modeling 

scenario had design day specific microemissions inventories consistent with 

the chosen areal modeling domain and 

application. ADEQ calculated the 2008 

Base, 2018 Base, and 2018 Attainment 

micro-emissions inventories for the 

given requirements of the modeling 

application at the respective monitoring 

site domain and meteorological day 

scenario. 

The State’s attainment demonstration 

approach is described in the Plan within 

the following documents: Chapter 7, 

‘‘Attainment Demonstration and 

Reasonable Further Progress’’; 

Appendix A, ‘‘Pinal County PM 

Inventory Preparation Plan’’ (‘‘IPP’’); 

Appendix B, ‘‘Pinal County PM10

Nonattainment Area Emissions 

Inventories for 2008 and 2018 Base 

Years and Design Days’’ (‘‘Modeling 

EI’’); Appendix C, ‘‘Pinal County PM10

Nonattainment Area Source 

Apportionment Modeling for 2008 and 

2018 Base Scenario Design Days’’ 

(‘‘Modeling TSD’’); and, Appendix D, 

‘‘Pinal County PM10 Nonattainment 

Area 2018 Attainment Demonstration 

and Controlled Emissions Inventories.’’ 

The West Pinal County PM10 Plan 

discusses the control strategy within 

Chapter 6 of the Plan and in more detail 

within Appendix D of the Plan. 

a. Modeling 

As noted, the West Pinal County PM10

Plan’s attainment demonstration 

considers two specific problems 

contributing to nonattainment of the 

PM10 standard in West Pinal County: (1) 

PM10 emissions from windblown dust 

and human activity on days with 

elevated wind speeds; and (2) PM10

emissions from human activity, 

particularly on days with very low wind 

or ‘‘stagnant’’ meteorological conditions. 

• ADEQ developed a high wind day 

scenario for Cowtown, Maricopa, Pinal 

County Housing, and Stanfield monitors 

and surrounding area micro-emissions 

inventories. Each monitor has its own 

two domain micro-emissions inventory 

for modeling: High wind hours/ 

windblown dust; and, low wind hours/ 

activity-based emissions. The high wind 

scenario used a proportional rollback 

approach that accounts for the timing 


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52The term ‘‘rollback’’ refers to the assumption 

that the PM10 concentrations are directly 

proportional to emissions. To predict the ambient 

effect of an emissions change, the concentration can 

be scaled, or ‘‘rolled back,’’ by the same percentage 

by which emissions are reduced. In ‘‘proportional 

rollback,’’ each source category is rolled back 

separately, since emissions from each will have a 

different level of control, and in general a different 

degree of dispersion. As in simple rollback, the 

ambient contribution of each individual source 

category scales with its emissions. For the 

‘‘weighted proportional rollback,’’ source-tomonitor distance was accounted for via an inverse 

distance factor (1/d). For example, a source with 

only small emissions may nevertheless have a large 

contribution to the concentration if it was very 

close to the monitor. A change in a source’s 

emissions causes a change in total concentration in 

proportion to that source’s contribution to that 

particular monitor. 

53West Pinal County PM10 Plan, Chapters 6 and 

7. 

and geographic location of emissions 

contributing to NAAQS exceedances.52

• ADEQ developed a stagnation day 

scenario for Cowtown, Pinal County 

Housing, and Stanfield monitors and 

surrounding area micro-emissions 

inventories. The stagnant day scenarios 

used dispersion modeling from the 

American Meteorological Society 

(AMS)/EPA Regulatory Model 

(AERMOD). ADEQ chose design days 

from the fall season, September through 

November 2008 for this analysis. 

b. Control Strategy for Attainment 

ADEQ relied on the following 

portions of the AgBMP Rules for Pinal 

County to provide for attainment of the 

PM10 standard: R18–2–610 and –610.03, 

commercial farms; AgBMP rule R18–2– 

611 and –611.03, commercial animal 

operations (except for dairy operations); 

and, R18–2–612 and –612.01, irrigation 

districts.53 Tables 3 and 4 show the 

annual nonattainment area emissions 

inventories for the 2018 baseline 

estimate and the 2018 attainment 

estimate by source category and the 

control strategies’ predicted emissions 

reductions. Within the windblown 

fugitive dust emissions inventories, 

ADEQ predicted almost all the emission 

reductions, 93 percent, to come from 

soil stabilization control measures on 

agricultural land. Within the activitybased emissions inventories, ADEQ 

predicted most of the emission 

reductions, 87 percent, to come from 

control measures applied to unpaved 

road operations on private agricultural 

land and canal roads; the remainder of 

predicted emission reductions come 

from control measures to reduce PM10

emissions from on-field agriculture and 

animal feeding operations. As noted, the 

regulatory vehicle for these emissions 

reductions is the AgBMP rule provisions 

the State relied on to provide for 

attainment of the PM10 standard and to 

implement RACM/RACT in the area. 

TABLE 3—WINDBLOWN DUST/FUGITIVE EMISSIONS, 2018 BASE AND ATTAINMENT EMISSIONS INVENTORIES WITH

ESTIMATED EMISSION REDUCTIONS

[tpy] 

Source category Base 2018 Attainment 2018 Emission reductions 

Developed Urban Lands .............................................................................................. 248.1 248.1 ....................................

Developed Rural Lands (low density) ......................................................................... 1,959.7 1,959.7 ....................................

Unpaved Roads ........................................................................................................... 4,653.0 3,803.1 849.9 

Cleared Areas .............................................................................................................. 457.0 457.0 ....................................

Residential Construction .............................................................................................. 837.5 837.5 ....................................

Dairies .......................................................................................................................... 449.6 449.6 ....................................

CAFOs ......................................................................................................................... 155.2 125.3 29.9 

Desert Shrubland ......................................................................................................... ........................ ............................ ....................................

Agriculture .................................................................................................................... 19,510.1 7,122.0 12,388.1 

Commercial Construction ............................................................................................ 441.4 441.4 ....................................

Other ............................................................................................................................ 4,243.9 4,243.9 ....................................

Site Development ........................................................................................................ 552.2 552.2 ....................................

Total ...................................................................................................................... 33,507.7 20,239.8 13,267.9 

Source: West Pinal County PM10 Plan, Table 5–3; Appendix B, Tables 5–31, 5–32, 5–33, 5–34. 

TABLE 4—ACTIVITY BASED EMISSIONS, 2018 BASE AND ATTAINMENT EMISSIONS INVENTORIES WITH ESTIMATED EMISSION

REDUCTIONS

[tpy] 

Source category Base 2018 Attainment 2018 Emission reductions 

Ag—Harvesting ............................................................................................................ 312.9 207.1 105.8 

Ag—Tilling .................................................................................................................... 2,540.3 1,658.0 882.3 

CAFOs ......................................................................................................................... 1,620.6 1,369.2 251.4 

Paved Road * ............................................................................................................... 1,408.0 1,408.0 ....................................

Unpaved Road * ........................................................................................................... 45,105.3 37,186.4 7,918.9 

Fuel Combustion .......................................................................................................... 34.9 34.9 ....................................

Fires ............................................................................................................................. 22.2 22.2 ....................................

Open Burning ............................................................................................................... 16.8 16.8 ....................................

Nonroad ....................................................................................................................... 144.4 144.4 ....................................

Railroad ........................................................................................................................ 45.4 45.4 ....................................

Construction ................................................................................................................. 8,499.8 8,499.8 ....................................

Dairy ............................................................................................................................. 184.0 184.0 ....................................

Permitted Sources ....................................................................................................... 781.3 781.3 ....................................

Unpaved Parking ......................................................................................................... 251.5 251.5 ....................................

Total ...................................................................................................................... 60,967.4 51,809.0 9,158.4 

Source: West Pinal County PM10 Plan, Table 5–3; Appendix B, Tables 5–31, 5–32, 5–33, 5–34 

* Paved and Unpaved Road emissions estimates include direct vehicle emissions and fugitive dust emissions from vehicle re-entrainment. 


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54West Pinal County PM10 Plan, Chapter 6; 

Chapter 7, Table 7–4. 

55 85 FR 37756. 

56See Table 2 in the TSD. 

57See Table 1 in the TSD. 

58See Table 3 and further discussion in Section 

II.B of the TSD. 

59TSD, Table 2; EPA AQS Quick Look Report, 

December 10, 2020, in the docket for this 

rulemaking action. 

The State adopted and preimplemented control measures to meet 

the contingency measures requirement 

within the Plan: The portion of the 

AgBMP Rules for Pinal County 

applicable to dairy operations (R18–2– 

611 and –611.03), along with the Pinal 

County Fugitive Dust Rule and the Pinal 

County Construction Dust Rule.54 We 

address the contingency measures 

requirement of the Act more completely 

in Section III.F, where we point out that 

pre-implemented contingency measures 

are not approvable under CAA section 

172(c)(9). Here, we mention the control 

measures, adopted and subsequently 

implemented as contingency measures, 

to emphasize two points: (1) Given the 

shortfall in attaining the PM10 NAAQS, 

these control measures designated for 

contingency should have been evaluated 

and designated RACM/RACT, as we 

discussed in Section III.C; and (2) 

despite implementing the RACM/RACT 

control measures for attainment and the 

designated contingency measures, the 

West Pinal County area still failed to 

attain the PM10 NAAQS, by a large 

margin. 

3. The EPA’s Review of the State’s 

Submission 

As previously discussed, the EPA 

issued a finding that the West Pinal 

County area failed to attain the PM10

NAAQS by the outermost statutory 

attainment date of December 31, 2018.55

In addition to our previous regulatory 

review of the air monitoring data from 

2016–2018, detailed in our June 24, 

2020 notice, we reviewed ambient air 

monitoring data collected from 2006– 

2018 to examine PM10 values over time 

and recent trends over the 2016–2018 

control strategy period of Plan 

implementation. Our detailed review of 

PM10 data is included in our TSD 

provided in the docket for this proposal. 

We provide two general conclusions 

from our data review. 

First, when considering the number of 

exceedances of the PM10 standard, the 

data show that the West Pinal County 

monitoring sites have consistently 

measured many exceedances in every 

year between the start of the base year 

period, 2006–2008, and in 2018, the 

attainment year. While the number of 

exceedances each year has generally and 

gradually decreased over time, there is 

no clear evidence of a sustained 

decrease in recent years as ADEQ 

implemented control measures. For 

example, over the 2016 through 2018 

period that would have been relevant to 

attainment by December 31, 2018, the 

annual number of exceedances of the 

24-hour PM10 NAAQS ranged from 29 to 

38.56 The form of the NAAQS allows for 

no more than one exceedance per year, 

averaged over a three year period. 

Furthermore, all eight monitors in the 

West Pinal County nonattainment area 

showed violations of the PM10 NAAQS 

as determined by their 2018 design 

values.57

Second, design value trends show that 

the number of expected exceedances 

remain well above the PM10 NAAQS of 

one exceedance per year. The high 

concentrations and number of 

exceedances clearly show that PM10

concentrations well above the level of 

the NAAQS (150 mg/m3) continue to be 

a major air quality problem in the West 

Pinal County nonattainment area 

despite the implementation of control 

measures meant to reduce PM10 levels. 

For example, the design concentration 

for 2016–2018, the period in which 

values should be at or under 150 mg/m3

to show attainment by 2018, is 403 mg/ 

m3, or 269 percent of the standard.58

TABLE 5—THREE-YEAR PM10 MONITORING DATA STATISTICS FOR THE COWTOWN AND HIDDEN VALLEY MONITORING

SITES a

3-Year period 2006– 

2008 

2007– 

2009 

2008– 

2010 

2009– 

2011 

2010– 

2012 

2011– 

2013 

2012– 

2014 

2013– 

2015 

2014– 

2016 

2015– 

2017 

2016– 

2018 

Design Concentration (μg/m3) 916 653 539 1064 1064 1064 521 510 b 357 b 303 403 

3-year Design Value ............. 201.2 139.8 86.1 60.7 63 75.7 64 50.5 b 38.3 b 29.8 32.8 

Sources: EPA AQS Quick Look Report, December 10, 2020, and EPA AQS Design Value Report, December 10, 2020. The design concentration for these sites is 

the 4th highest 24-hour concentration measured over each three-year period, as detailed in Section 6.3.1 of the PM10 SIP Development Guideline, EPA–450/2–86– 

001 (June 1987). a Data collected prior to 2016 were collected from the Cowtown monitoring site; data since 2016 were collected at the Hidden Valley monitoring site, as described in 

our TSD, page 6, within the docket for this rulemaking. bThe EPA’s relocation approval letter stated that the data from Cowtown and Hidden Valley would be combined to form one continuous data record for design 

value calculations. Consequently, the 2014–2016 and 2015–2017 design values are each a composite data record consisting of 2014 and/or 2015 data from the 

Cowtown monitoring site, and 2016 and/or 2017 data from the Hidden Valley monitoring site, as applicable. 

The West Pinal County 2015 PM10

design value was 50.5 exceedances. For 

the area to meet the PM10 standard by 

2018, it could not have more than three 

exceedances of the PM10 NAAQS across 

the three years, 2016–2018, to show a 

design value of 1.0 exceedances, 

averaged over three years. Instead, the 

Plan’s control strategy resulted in the 

following number of primary 

exceedances: 30 in 2016; 38 in 2017; 

and 29 in 2018.59 Not only did the 

Plan’s control strategy fail to produce 

the effect intended in 2016, the 

designated control strategy rules and 

pre-implemented contingency measures 

failed to reduce PM10 exceedances to a 

level needed to attain the PM10 standard 

by December 31, 2018. 

Given the ambient monitoring data 

unequivocally indicate that the Plan 

was insufficient to achieve attainment 

by the 2018 attainment date, we do not 

provide an exhaustive evaluation of the 

attainment demonstration analyses in 

the West Pinal County PM10 Plan. 

Instead, we focused our review on two 

major deficiencies that preclude our 

approval of this Plan element. Our 

review of these two deficiencies is 

illustrative of the insufficiently 

conservative analyses or assumptions 

underlying the Plan’s failed attainment 

demonstration. Specifically, we 

evaluated the ‘‘design days’’ ADEQ 

selected to conduct the modeling 

exercises and the specific design day 

micro-emissions inventories and rule 

control effectiveness assumptions ADEQ 

made to model the Plan’s control 

strategy within the 2018 attainment 

modeling analyses. Next, we provide a 

short summary of our review. We also 

provide a more detailed review in our 

TSD. 

First, we find the design days that 

ADEQ selected for modeling the 

Cowtown monitor under stagnation 


tkelley on DSKBCP9HB2PROD with PROPOSALS
1358 Federal Register / Vol. 86, No. 5 / Friday, January 8, 2021 / Proposed Rules 

60 ‘‘Low wind/stagnation exceedance days’’ for 

purposes of this document are the exceedance days 

that remain once days identified by ADEQ as high 

wind day exceedances in IPP, Appendix C, Table 

C–1 are removed. See ‘‘Cowtown 2008 

Exceedances.xlxs’’ in the docket for this action. 61See Section III.B.1. of the TSD for our complete 

review of design day selection for stagnation 

scenario at the Cowtown monitor. Also, see Section 

III.B.2 of the TSD for our complete review of design 

day selection for the high wind scenario. 

62See Section III.C. of the TSD for our complete 

review of control effectiveness estimates. 

63 57 FR at 13539. 

64 Ibid. 

65 81 FR 58063–64. 

66West Pinal County PM10 Plan, 99 and Figure 7– 

1, 101; Appendix D, 45. 

67West Pinal County PM10 Plan, 100. Expected 

emission reductions from 2015 to 2018, 22,426 tons 

per year, are divided into 3 annual increments of 

7,475 tons per year. 

conditions, and several monitors under 

high wind conditions, were chosen with 

inconsistent criteria and/or have data 

inaccuracies. In turn, these 

inconsistencies and inaccuracies led to 

design day concentration values that 

were likely too low to address 

adequately the range of exceedances 

experienced in the nonattainment area. 

For example, in selecting the stagnation 

scenario design day for Cowtown, 

ADEQ limited selection to fall 2008 

(September to November) exceedance 

days despite the higher PM10

concentrations and a comparable 

number of exceedance days in the 

spring season (March to May). 

Ultimately, the selected 2008 design day 

was the 68th highest out of the 137 total 

low wind/stagnation exceedance days 

identified by the State (i.e., 

approximately 49% of the low wind/ 

stagnation exceedance days had higher 

concentrations than the design day 

selected).60 This middle range day was 

insufficiently conservative and was 

inadequate to represent the attainment 

issues during stagnation conditions and 

to address the range and severity of 

exceedances experienced at CWT.61

Second, we conclude that several data 

inputs and assumptions associated with 

modeling the control strategy were 

unsupported, overstated, or 

insufficiently conservative leading to an 

overestimate of the overall efficacy of 

the control strategy within the 

attainment demonstration. Specifically, 

in calculating the control effectiveness 

of the rules in the control strategy, two 

component assumptions or estimates 

were the primary cause of this 

overestimate: (1) Rule effectiveness, i.e., 

the percentage of compliant facilities; 

and, (2) aggregate or net best 

management practices (BMP) control 

efficiencies. For example, we found that 

despite limited or no compliance data, 

the lack of compliance assistance 

program efficacy figures, the lack of 

automatic reporting requirements, and 

little to no farm experience 

implementing BMPs, ADEQ assumed 

high compliance rates with the AgBMP 

rule; in turn, this unjustifiably inflated 

the overall control effectiveness 

calculations. In addition, we found that 

the domain modeling micro-emissions 

inventory estimates that ADEQ derived 

from this limited BMP implementation 

data were not appropriately 

documented or supported and were 

insufficiently conservative due to overly 

optimistic or simplifying assumptions 

used to aggregate BMP control efficiency 

estimates, such as assuming that farms 

will either choose not to operate or will 

routinely implement higher cost and 

higher control efficiency BMPs on high 

risk days. Consequently, ADEQ assumed 

farms reduced emissions from cropland 

operations and unpaved roads to a 

greater extent than what could be 

supported by the documentation in the 

Plan.62

Based on our evaluation of the design 

days and modeling and control 

effectiveness assumptions in the Plan, 

we find that these several deficiencies 

in the analyses preclude approval of the 

attainment demonstration. In addition, 

after reviewing past and recent PM10

data against the West Pinal County PM10

Plan’s attainment demonstration 

predictions, we conclude that: 

• There is no clear evidence of a 

sustained decrease in the number of 

exceedances in recent years as control 

measures have been implemented 

(2015–2018); 

• PM10 concentrations well above the 

level of the 24-hour PM10 NAAQS (150 

mg/m3) continue to be a major air quality 

problem in the West Pinal County 

nonattainment area despite the 

implementation of control measures 

designed to reduce PM10 levels thus far; 

and 

• The Plan’s control strategy, whether 

considered as adopted RACM/RACT or 

as the entire suite of rules submitted 

with the Plan, was inadequate to attain 

the PM10 NAAQS by December 31, 

2018, as evidenced by the ambient PM10

data. 

Consequently, we propose to 

disapprove the modeled attainment 

demonstration in the West Pinal County 

PM10 Plan because it does not meet the 

requirements of CAA section 

189(a)(1)(B) and section 188(c)(1). 

E. Reasonable Further Progress 

Demonstration 

1. Statutory and Regulatory 

Requirements 

The requirement for RFP in PM10

nonattainment areas is specified in CAA 

section 172(c)(2) and is described in the 

General Preamble.63 Under CAA section 

171(1), RFP is defined as meaning such 

annual incremental reductions in 

emissions of the relevant air pollutant as 

are required under part D (‘‘Plan 

Requirements for Nonattainment 

Areas’’) of the CAA or as may 

reasonably be required by the EPA for 

the purpose of ensuring attainment of 

the applicable NAAQS by the applicable 

date. In addition, CAA section 189(c)(1) 

requires quantitative milestones that 

demonstrate RFP and must be achieved 

every 3 years until the nonattainment 

area is redesignated to attainment, 

beginning 4.5 years after a Moderate 

area’s designation to nonattainment of 

the PM10 NAAQS.64 Therefore, 

Moderate area plans should contain 

quantitative milestones for 4.5 and 7.5 

years after designation. These 

quantitative milestones should be 

constructed so that they can be tracked, 

quantified and/or measured adequately, 

and provide for an objective evaluation 

of RFP toward attainment of the 

NAAQS, particularly as part of 

milestone reporting.65

2. Summary of the State’s Submission 

The West Pinal County PM10 Plan 

discusses how the Plan provides for RFP 

in Section 7.2 and Appendix D and 

provides visual representation in Figure 

7–1 and Figure D 5–1.66 For the 

purposes of calculating annual 

increments of emission reductions for 

RFP, ADEQ assumed a linear 

‘‘glidepath’’ with equal annual 

emissions reductions over the 2016– 

2018 implementation timeframe. This 

annual increment representing RFP is 

7,475 tons per year.67 The 

implementation of the Plan’s control 

strategy is projected to produce almost 

all the needed emissions reductions in 

the first year, 2016, with slight and 

incremental emission reductions to 

follow in 2017 and 2018. Because ADEQ 

projected that most of the emissions 

reductions would come in the first year, 

the projected emissions were below the 

‘‘glidepath’’ and ADEQ concluded that 

RFP was demonstrated. 

3. The EPA’s Review of the State’s 

Submission 

Based in part on our review of the 

2016–2018 ambient data and in part on 

the flaws identified in the West Pinal 

County PM10 Plan attainment 

demonstration, we find that ADEQ did 

not adequately provide for annual 

increments of emissions reductions 

needed to attain the PM10 NAAQS by 

2018. Because the West Pinal County 


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68 81 FR 58066 (August 24, 2016). 

69 57 FR 13498, 13543–13544. 

70 Id. at 13511. 

71Bahr v. EPA, 836 F.3d 1218, 1235–1237 (9th 

Cir. 2016). 

72 Id. at 1235–1237. 

73The Bahr v. EPA decision involved a challenge 

to an EPA approval of contingency measures under 

the general nonattainment area plan provisions for 

contingency measures in CAA section 172(c)(9), 

but, given the similarity between the statutory 

language in section 172(c)(9) and the ozone-specific 

contingency measure provision in section 182(c)(9), 

we find that the decision affects how both sections 

of the Act must be interpreted. 

74West Pinal County PM10 Plan, Chapter 6; 

Chapter 7, Table 7–4. 

75Appendix D, 45, Table D5–1. 

PM10 plan failed to achieve attainment 

by the attainment date, the RFP 

demonstration based on the rate by 

which these reductions were to occur is 

also necessarily deficient. This was 

borne out by the monitoring data; no 

real rate of reduction of exceedances can 

be demonstrated over the period of 

implementation of the Plan’s control 

measures, 2016–2018. Indeed, even with 

the early implementation of additional 

controls designated by the State as 

contingency measures to provide 

emissions reductions in the event of a 

failure to show RFP or to attain, West 

Pinal County still exceeded the PM10

standard by a large margin as evidenced 

by the data in Table 5. 

Regarding quantitative milestones, 

given the EPA’s 2012 designation of 

nonattainment for West Pinal County, 

the State should have included 

quantitative milestones for mid-2016 

and mid-2019 within the West Pinal 

County PM10 Plan. Aside from the two 

glidepath depictions in Figure 7–1, the 

Plan provides no further discussion of 

quantitative milestones. What is 

presented in Figure 7–1 does not meet 

the criteria that the Plan’s quantitative 

milestones should be trackable, 

quantified, and provide for an objective 

evaluation of RFP toward attainment of 

the NAAQS, by mid-2016. The West 

Pinal County PM10 Plan does not 

address RFP or quantitative milestones 

in mid-2019. 

For these reasons, we have 

determined that the West Pinal County 

PM10 Plan fails to demonstrate RFP, 

consistent with applicable CAA 

requirements and EPA guidance. 

Therefore, we propose to disapprove the 

RFP demonstration and quantitative 

milestones for the West Pinal County 

area for the 24-hour PM10 NAAQS under 

sections 172(c)(2) and 189(c)(1). 

F. Contingency Measures 

1. Statutory and Regulatory 

Requirements 

Under the CAA, states must include 

contingency measures consistent with 

section 172(c)(9) in their nonattainment 

plan SIP submissions. Contingency 

measures are additional controls or 

measures to be implemented in the 

event the area fails to meet RFP or to 

attain the NAAQS by the applicable 

attainment date. The SIP should contain 

trigger mechanisms for the contingency 

measures, specify a schedule for 

implementation, and indicate that the 

measure will be implemented without 

significant further action by the state or 

the EPA.68

Neither the CAA nor the EPA’s 

implementing regulations establish a 

specific level of emissions reductions 

that implementation of contingency 

measures must achieve, but the General 

Preamble reiterates the EPA’s guidance 

recommendation that contingency 

measures should generally provide for 

emissions reductions approximately 

equivalent to one year’s worth of RFP in 

the area.69 Where a failure to attain or 

to meet RFP can be corrected in less 

than one year, the EPA may accept a 

proportionally lesser amount sufficient 

to correct the identified failure.70

It has been the EPA’s longstanding 

interpretation of CAA section 172(c)(9) 

that states may meet the contingency 

measure requirement by relying on 

Federal measures (e.g., Federal mobile 

source measures based on the 

incremental turnover of the motor 

vehicle fleet each year) and state or local 

measures already scheduled for 

implementation that provide emissions 

reductions in excess of those needed to 

meet any other nonattainment plan 

requirements, such as RACM/RACT, 

RFP, or expeditious attainment. The key 

is that the Act requires that contingency 

measures provide for additional 

emissions reductions that are not relied 

on for RFP or attainment and that are 

not included in the RFP or attainment 

demonstrations as meeting part of or all 

the contingency measure requirements. 

The purpose of contingency measures is 

to provide continued emissions 

reductions while a plan is being revised 

to meet the missed milestone or 

attainment date. 

In Bahr v. EPA, the Ninth Circuit 

Court of Appeals rejected the EPA’s 

interpretation of CAA section 172(c)(9) 

as allowing for early implementation of 

contingency measures.71 The Ninth 

Circuit concluded that contingency 

measures must take effect at the time the 

area fails to make RFP or attain by the 

applicable attainment date, not before.72

Consequently, within the geographic 

jurisdiction of the Ninth Circuit, states 

cannot rely on early-implemented 

measures to comply with the 

contingency measure requirements 

under CAA section 172(c)(9).73

2. Summary of the State’s Submission 

ADEQ developed the West Pinal 

County PM10 Plan prior to the Bahr v. 

EPA decision, and the plan relies solely 

upon surplus emissions reductions from 

already implemented control measures 

during the 2016–2018 period to 

demonstrate compliance with the 

contingency measure requirements of 

CAA section 172(c)(9). The West Pinal 

County PM10 Plan included the 

following early implemented state and 

local regulations to meet the 

contingency measures requirement for 

the PM10 standard: The portion of the 

AgBMP Rules for Pinal County 

applicable to dairy operations (R18–2– 

611 and –611.03), and the Pinal County 

Fugitive Dust Rule and Construction 

Dust Rule.74 Contingency Measures are 

also discussed in Appendix D.75

3. The EPA’s Review of the State’s 

Submission 

Arizona is within the geographic 

jurisdiction of the Ninth Circuit Court of 

Appeals; therefore, after the Bahr v. EPA 

decision, the State cannot rely on 

already-implemented control measures 

to comply with the contingency 

measure requirement of CAA section 

172(c)(9). To comply with CAA section 

172(c)(9), as interpreted in the Bahr v. 

EPA decision, a state must develop, 

adopt and submit contingency measures 

to be triggered upon a failure to meet 

RFP milestones or failure to attain the 

NAAQS by the applicable attainment 

date regardless of the extent to which 

already-implemented measures would 

achieve surplus emissions reductions 

beyond those necessary to meet RFP 

milestones and beyond those predicted 

to achieve attainment of the NAAQS. 

Arizona’s adopted and pre-implemented 

contingency measures do not comply 

with these requirements for failure to 

make RFP and failure to meet 

attainment contingency measures. 

Section 172(c)(9) requires contingency 

measures to address potential failures to 

achieve RFP milestones or failure to 

attain the NAAQS by the applicable 

attainment date. For these reasons, we 

propose to disapprove the contingency 

measures element of the West Pinal 

County PM10 Plan as failing to meet the 

contingency measure requirements of 

CAA sections 172(c)(9). 


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76 40 CFR 93.102(b)(1). 

77 40 CFR 93.118(e)(4)(iii), (iv) and (v). For more 

information on the transportation conformity 

requirements and applicable policies on MVEBs, 

please visit our transportation conformity website 

at: http://www.epa.gov/otaq/stateresources/ 

transconf/index.htm. 

78 40 CFR 93.118(f)(2). 

79Appendix B, 120–137, and 166–180. 

80Appendix B, 120. 

81ADEQ used the appropriate AP–42 guidance in 

sections 13.2.1 and 13.2.2 to calculate fugitive dust 

from paved and unpaved roads. The AP–42 

emission factor equation inputs for estimating 

unpaved road fugitive dust emissions can be found 

in Appendix B, Table 5–11. The most recent EPA 

revision and approval of these AP–42 emission 

factor equations occurred in 2011 and are reflected 

in the Plan’s estimates; 76 FR 6328 (February 4, 

2011). 

82West Pinal County PM10 Plan, 62. 

83 40 CFR 93.118(e)(4) and (5). 

84West Pinal County PM10 Plan, Table 5–4; 

Appendix D, Table D4–4. 

G. Motor Vehicle Emissions Budgets for 

Transportation Conformity 

1. Statutory and Regulatory 

Requirements 

Section 176(c) of the CAA requires 

Federal actions in nonattainment and 

maintenance areas to conform to the 

goals of the state’s SIP to eliminate or 

reduce the severity and number of 

violations of the NAAQS and achieve 

timely attainment of the standards. 

Conformity to the goals of the SIP means 

that such actions will not: (1) Cause or 

contribute to violations of a NAAQS, (2) 

worsen the severity of an existing 

violation, or (3) delay timely attainment 

of any NAAQS or any interim 

milestone. 

Actions involving Federal Highway 

Administration (FHWA) or Federal 

Transit Administration (FTA) funding 

or approval are subject to the EPA’s 

transportation conformity rule, codified 

at 40 CFR part 93, subpart A. Under this 

rule, metropolitan planning 

organizations (MPOs) in nonattainment 

and maintenance areas coordinate with 

state and local air quality and 

transportation agencies, the EPA, the 

FHWA, and the FTA to demonstrate that 

an area’s regional transportation plans 

and transportation improvement 

programs conform to the applicable SIP. 

This demonstration is typically done by 

showing that estimated emissions from 

existing and planned highway and 

transit systems are less than or equal to 

the motor vehicle emissions budgets 

(MVEBs or ‘‘budgets’’) contained in all 

control strategy attainment plans 

designed to attain the NAAQSs. Budgets 

are generally established for specific 

years and specific pollutants or 

precursors. Attainment plans for PM10

nonattainment areas should identify 

budgets for mobile source emissions of 

PM10, i.e., vehicle and fugitive dust 

emissions, in the area for each RFP 

milestone year, as appropriate, and the 

attainment year, if the plan 

demonstrates attainment.76

For budgets to be approvable, they 

must meet, at a minimum, the EPA’s 

adequacy criteria at 40 CFR 93.118(e)(4). 

To meet these requirements, the budgets 

must be consistent with the attainment 

and RFP requirements and reflect all the 

motor vehicle control measures 

contained in the attainment and RFP 

demonstrations.77 Budgets may include 

a safety margin representing the 

difference between projected emissions 

and the total amount of emissions 

estimated to satisfy any requirements for 

attainment or RFP. 

The EPA’s process for determining 

adequacy of a budget consists of three 

basic steps: (1) Providing public 

notification of a SIP submission; (2) 

providing the public the opportunity to 

comment on the budget during a public 

comment period; and (3) making a 

finding of adequacy or inadequacy.78

2. Summary of the State’s Submission 

The West Pinal County PM10 Plan 

includes a budget for the 2018 

attainment year. As discussed in Section 

III.E, we are proposing to disapprove the 

RFP and quantitative milestones 

elements of the Plan. No interim RFP 

budget was submitted for 2016. The 

State’s submitted 2018 conformity 

budget for PM10 for the West Pinal 

County Area is provided in Table 6. 

TABLE 6—2018 MOTOR VEHICLE

EMISSIONS BUDGET FOR THE WEST

PINAL COUNTY PM10 NONATTAINMENT AREA

[Tons per year] 

Source Emissions 

Direct On-Road Mobile Sources 

(exhaust, tire and brake wear) 173.7 

Unpaved Road Fugitive Dust ..... 26,433.5 

Paved Road Fugitive Dust ......... 1,211.1 

Road Construction/Maintenance 168.8 

Total ..................................... 27,987.1 

Source: West Pinal County PM10 Plan, 

Table 5–4. 

The methodologies ADEQ used to 

develop the motor vehicle emissions 

budget are provided in Appendix B of 

the West Pinal County PM10 Plan.79 As 

discussed in section III.A. of this 

proposal, ADEQ used MOVES2014 in 

the development of this budget; this 

emissions factor model was the latest 

EPA approved version at the time the 

West Pinal County PM10 Plan was 

developed. Paved road vehicle miles 

traveled (VMT) estimates for estimating 

direct and fugitive PM10 emissions were 

provided by MAG using an 

interpolation methodology where 2018 

VMT was estimated from 2015 and 2025 

regional transportation modeling runs.80

ADEQ used the most recently approved 

EPA provided AP–42 emissions factor 

equations to develop paved and 

unpaved road fugitive dust emissions 

estimates.81 In addition to the line item 

source categories in the 2018 budget 

presented in Table 6, ADEQ specified 

that the budget includes an 81 ton per 

year safety margin.82

The EPA has neither found this 2018 

budget to be adequate, nor have we 

acted on it in the past. 

3. The EPA’s Review of the State’s 

Submission 

As part of our review of the 

approvability of the motor vehicle 

emissions budget in the West Pinal 

County PM10 Plan, we have evaluated 

the budget using the adequacy criteria 

specified in the transportation 

conformity rule.83 Reviewing the budget 

against the criteria in the transportation 

conformity rule informs the EPA’s 

decision to propose our action on the 

budget. We have determined that the 

2018 budget submitted by Arizona for 

the West Pinal County area has not met 

several of these criteria. 

First and foremost, § 93.118(e)(4)(iv) 

requires that a budget, when considered 

together with all other emissions 

sources, be consistent with applicable 

requirements for RFP, attainment, or 

maintenance (whichever is relevant to a 

given implementation plan submission). 

In this case, the West Pinal County area 

budget is not consistent with the 

requirements for attainment and RFP, as 

discussed in Sections III.D and E of this 

proposal and our proposed disapproval 

of these two Plan elements. Secondly, 

the West Pinal County budget is 

presented in a tons per year format for 

an attainment plan intended to meet the 

24-hour PM10 NAAQS. The budget must 

be consistent with the 24-hour 

timeframe of the attainment 

demonstration and PM10 standard, and 

therefore should be presented in a tons 

per day format. Finally, 

§ 93.118(e)(4)(iii) requires that the 

budget be clearly identified and 

precisely quantified. Although ADEQ 

describes an ‘‘allowance or safety 

margin’’ in the West Pinal County PM10

Plan, the submitted budget does not 

clearly and explicitly identify this safety 

margin in its presentations of the 

budget.84 Also, a safety margin, as 


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85 40 CFR 93.120(a)(3). 

86 40 CFR 93.120(a)(2). 

87 40 CFR 93.120(a)(1). 

defined in the Transportation 

Conformity rule, § 93.101, must be 

clearly presented and demonstrated to 

be outside and above the emissions 

level demonstrating attainment, but 

below the threshold of the applicable 

NAAQS. 

We have reviewed the motor vehicle 

emissions budget in the West Pinal 

County PM10 Plan and find that it does 

not meet applicable statutory and 

regulatory requirements including the 

adequacy criteria in 40 CFR 

93.1118(e)(4) and (5). The primary 

deficiency is that the submitted 2018 

budget is not consistent with, or derived 

from, a demonstration of attainment and 

RFP meeting the requirements of the 

Act. As discussed earlier in sections 

III.D and III.E, we are proposing herein 

to disapprove the Plan’s attainment and 

RFP demonstrations. Therefore, we are 

proposing to disapprove the 2018 

budget in the West Pinal County PM10

Plan. In addition, because we are 

disapproving the attainment and RFP 

demonstrations, the 2018 budget is not 

eligible for a protective finding.85

If our proposed disapproval of the 

2018 budget is finalized, upon the 

effective date of our final rule, the area 

would be subject to a conformity freeze 

under § 93.120 of the Transportation 

Conformity rule. No transportation 

project outside of the first four years of 

the currently conforming transportation 

plan and transportation improvement 

plan (TIP) or that meets the 

requirements of § 93.104(f) during the 

resulting conformity freeze may be 

found to conform until Arizona submits 

a new PM10 control strategy/attainment 

plan, the EPA finds the submitted 

budget adequate per § 93.118 or 

approves the new control strategy/ 

attainment plan and conformity to the 

new control/strategy implementation 

plan is determined.86 Furthermore, if, as 

a result of our final disapproval action, 

the EPA imposes highway sanctions 

under section 179(b)(1) of the Act two 

years from the effective date of our final 

rule, then the conformity status of the 

transportation plan and TIP will lapse 

on that date and no new transportation 

plan, TIP, or project may be found to 

conform until Arizona submits a new 

PM10 attainment plan, and conformity to 

this attainment plan is determined.87

IV. Proposed Action 

For the reasons discussed in this 

notice, under CAA section 110(k)(3), the 

EPA is proposing to approve and 

disapprove the following portions of the 

West Pinal County PM10 Plan, submitted 

by the State on December 21, 2015. Our 

proposed approval and disapproval 

actions are as follows: 

• We propose to approve the 2008 

base year emissions inventory element 

for direct PM10 in the West Pinal County 

PM10 Plan as meeting the requirements 

of CAA sections 172(c)(3) for the 1987 

p.m.10 NAAQS; 

• We propose to disapprove the 

precursor demonstration in the West 

Pinal County PM10 Plan because the 

demonstration is inadequate to show 

that emissions reductions from all PM10

precursors do not contribute 

significantly to PM10 levels exceeding 

the NAAQS, as required by CAA 

Section 189(e) for the 1987 p.m.10

NAAQS; 

• We propose to disapprove the 

RACM/RACT demonstration element in 

the West Pinal County PM10 Plan 

because it does not meet the 

requirements of CAA section 172(c)(1) 

and section 189(a)(1)(C) for the 1987 

p.m.10 NAAQS; furthermore, the 

deficiencies in the State’s precursor 

analysis mean that the State failed to 

establish in its RACM/RACT analysis 

that it was unnecessary to regulate PM10

precursor emissions; 

• We propose to disapprove the 

modeled attainment demonstration 

element for the 1987 p.m.10 NAAQS in 

the West Pinal County PM10 Plan 

because it does not meet the 

requirements of CAA section 

189(a)(1)(B) and section 188(c)(1) to 

demonstrate attainment of the 1987 

p.m.10 NAAQS; 

• We propose to disapprove the RFP 

demonstration element in the West 

Pinal County PM10 Plan because it does 

not meet the requirements of CAA 

sections 172(c)(2) for the 1987 p.m.10

NAAQS; 

• We propose to disapprove the 

quantitative milestones element in the 

West Pinal County PM10 Plan because it 

does not meet the requirements of CAA 

section 189(c)(1) for the 1987 p.m.10

NAAQS; 

• We propose to disapprove the 

contingency measures element of the 

West Pinal County PM10 Plan because it 

does not meet the requirements of CAA 

section 172(c)(9) for the 1987 p.m.10

NAAQS; and, 

• We propose to disapprove the 

motor vehicle emissions budget in West 

Pinal County PM10 Plan for the 

attainment year of 2018 (see Table 6) 

because it is not consistent with or 

derived from, approvable RFP or and 

attainment demonstrations for the 1987 

PM10 NAAQS meeting the requirements 

of the Act. 

The EPA is soliciting public 

comments on the issues discussed in 

this proposed rule. We will accept 

comments from the public on this 

proposal for the next 30 days and will 

consider those comments before taking 

final action. 

V. Statutory and Executive Order 

Reviews 

Additional information about these 

statutes and Executive orders can be 

found at http://www.epa.gov/lawsregulations/laws-and-executive-orders. 

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. 

B. Executive Order 13771: Reducing 

Regulations and Controlling Regulatory 

Costs 

This action is not an Executive Order 

13771 regulatory action because SIP 

approvals, including partial approvals, 

are exempted under Executive Order 

12866. 

C. Paperwork Reduction Act (PRA) 

This action does not impose an 

information collection burden under the 

PRA because this action does not 

impose additional requirements beyond 

those imposed by state law. 

D. Regulatory Flexibility Act (RFA) 

I certify that this action will not have 

a significant economic impact on a 

substantial number of small entities 

under the RFA. This action will not 

impose any requirements on small 

entities beyond those imposed by state 

law. 

E. Unfunded Mandates Reform Act 

(UMRA) 

This action does not contain any 

unfunded mandate as described in 

UMRA, 2 U.S.C. 1531–1538, and does 

not significantly or uniquely affect small 

governments. This action does not 

impose additional requirements beyond 

those imposed by state law. 

Accordingly, no additional costs to 

state, local, or tribal governments, or to 

the private sector, will result from this 

action. 

F. 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 


tkelley on DSKBCP9HB2PROD with PROPOSALS
1362 Federal Register / Vol. 86, No. 5 / Friday, January 8, 2021 / Proposed Rules 

distribution of power and 

responsibilities among the various 

levels of government. 

G. Executive Order 13175: Coordination 

With Indian Tribal Governments 

This action does not have tribal 

implications, as specified in Executive 

Order 13175, because the SIP is not 

approved to apply on any Indian 

reservation land or in any other area 

where the EPA or an Indian tribe has 

demonstrated that a tribe has 

jurisdiction, and will not impose 

substantial direct costs on tribal 

governments or preempt tribal law. 

Thus, Executive Order 13175 does not 

apply to this action. 

H. Executive Order 13045: Protection of 

Children From Environmental Health 

Risks and Safety Risks 

The EPA interprets Executive Order 

13045 as applying only to those 

regulatory actions that concern 

environmental 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 impose additional 

requirements beyond those imposed by 

state law. 

I. Executive Order 13211: Actions 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. 

J. National Technology Transfer and 

Advancement Act (NTTAA) 

Section 12(d) of the NTTAA directs 

the EPA to use voluntary consensus 

standards in its regulatory activities 

unless to do so would be inconsistent 

with applicable law or otherwise 

impractical. The EPA believes that this 

action is not subject to the requirements 

of section 12(d) of the NTTAA because 

application of those requirements would 

be inconsistent with the CAA. 

K. Executive Order 12898: Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations 

The EPA lacks the discretionary 

authority to address environmental 

justice in this rulemaking. 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air 

pollution control, Incorporation by 

reference, Intergovernmental relations, 

Particulate matter, Reporting and 

recordkeeping requirements. 

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

Dated: December 23, 2020. 

John Busterud, 

Regional Administrator, Region IX. 

[FR Doc. 2020–29092 Filed 1–7–21; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 63 

[EPA–HQ–OAR–2020–0560; FRL–10018–95– 

OAR] 

RIN 2060–AU59 

National Emission Standards for 

Hazardous Air Pollutants: Mercury Cell 

Chlor-Alkali Plants Residual Risk and 

Technology Review 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The U.S. Environmental 

Protection Agency (EPA) is proposing 

the results of the residual risk and 

technology review (RTR) of the National 

Emission Standards for Hazardous Air 

Pollutants (NESHAP) for mercury 

emissions from Mercury Cell ChlorAlkali Plants, as required by the Clean 

Air Act (CAA). The EPA is proposing to 

find risks due to emissions of hazardous 

air pollutants (HAP) to be acceptable 

from the Mercury Cell Chlor-Alkali 

Plants source category, and to determine 

that the current NESHAP provides an 

ample margin of safety to protect public 

health and that no more stringent 

standards are necessary to prevent, 

taking into consideration costs, energy, 

safety, and other relevant factors, an 

adverse environmental effect. The EPA 

is proposing to amend the requirements 

for cell room fugitive mercury emissions 

to require work practice standards for 

the cell rooms and to require 

instrumental monitoring of cell room 

fugitive mercury emissions under the 

technology review. Furthermore, under 

our technology review and maximum 

achievable control technology (MACT) 

analysis, we are proposing to not require 

conversion to non-mercury production 

technology and invite comments and 

data and information regarding this 

proposed determination. In addition, 

the EPA is proposing standards for 

fugitive chlorine emissions from 

mercury cell chlor-alkali plants, which 

are not currently regulated under the 

NESHAP. The EPA is proposing to 

address applicability for thermal 

mercury recovery units when chlorine 

and caustic are no longer produced in 

mercury cells. The EPA is also 

proposing revisions related to emissions 

during periods of startup, shutdown, 

and malfunction (SSM); provisions for 

electronic submission of performance 

test results, performance evaluation 

reports, and Notification of Compliance 

Status (NOCS) reports; and correction of 

various compliance errors in the current 

rule. 

DATES:

Comments. Comments must be 

received on or before February 22, 2021. 

Under the Paperwork Reduction Act 

(PRA), comments on the information 

collection provisions are best assured of 

consideration if the Office of 

Management and Budget (OMB) 

receives a copy of your comments on or 

before February 8, 2021. 

Public hearing: If anyone contacts us 

requesting a public hearing on or before 

January 13, 2021, we will hold a virtual 

public hearing. See SUPPLEMENTARY

INFORMATION for information on 

requesting and registering for a public 

hearing. 

ADDRESSES: You may send comments, 

identified by Docket ID No. EPA–HQ– 

OAR–2020–0560, by any of the 

following methods: 

• Federal eRulemaking Portal: 

https://www.regulations.gov/ (our 

preferred method). Follow the online 

instructions for submitting comments. 

• Email: a-and-r-docket@epa.gov. 

Include Docket ID No. EPA–HQ–OAR– 

2020–0560 in the subject line of the 

message. 

• Fax: (202) 566–9744. Attention 

Docket ID No. EPA–HQ–OAR–2020– 

0560. 

• Mail: U.S. Environmental 

Protection Agency, EPA Docket Center, 

Docket ID No. EPA–HQ–OAR–2020– 

0560, Mail Code 28221T, 1200 

Pennsylvania Avenue NW, Washington, 

DC 20460. 

• Hand Delivery or Courier (by 

scheduled appointment only): EPA 

Docket Center, WJC West Building, 

Room 3334, 1301 Constitution Avenue 

NW, Washington, DC 20004. The Docket 

Center’s hours of operation are 8:30 

a.m.–4:30 p.m., Monday–Friday (except 

Federal holidays). 

Instructions: All submissions received 

must include the Docket ID No. for this 

rulemaking. Comments received may be 

posted without change to https://

www.regulations.gov/, including any 

personal information provided. For 

detailed instructions on sending 

comments and additional information 

on the rulemaking process, see the 

SUPPLEMENTARY INFORMATION section of 

this document. Out of an abundance of 


tkelley on DSKBCP9HB2PROD with PROPOSALS