Federal Register / Vol. 86, No. 103 / Tuesday, June 1, 2021 / Proposed Rules 29219 

1 52 FR 24634 (July 1, 1987). 

2 71 FR 61144 (October 17, 2006). 

3 42 U.S.C. 7407(d)(4)(B), 7513(a). 

4 52 FR 29383. 

5 55 FR 45799. 

6 56 FR 11101. 

7 56 FR 37654. 

8 56 FR 56694. 

material may be found in the AD docket on 

the internet at https://www.regulations.gov 

by searching for and locating Docket No. 

FAA–2021–0380. 

(2) For more information about this AD, 

contact Andrea Jimenez, Aerospace Engineer, 

COS Program Management Section, 

Operational Safety Branch, Compliance & 

Airworthiness Division, FAA, 1600 Stewart 

Ave., Mail Stop: Room 410, Westbury, NY 

11590; telephone (516) 228–7330; email 

andrea.jimenez@faa.gov. 

Issued on May 21, 2021. 

Lance T. Gant, 

Director, Compliance & Airworthiness 

Division, Aircraft Certification Service. 

[FR Doc. 2021–11187 Filed 5–28–21; 8:45 am] 

BILLING CODE 4910–13–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R09–OAR–2021–0249; FRL–10022– 

26–Region 9] 

Rescission of Clean Data 

Determination and Call for Attainment 

Plan Revision for the Yuma, AZ 1987 

PM10 Moderate Nonattainment Area 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is proposing to rescind its 

previously issued clean data 

determination for the Yuma, Arizona 

‘‘Moderate’’ nonattainment area for the 

1987 24-hour national ambient air 

quality standard (NAAQS) for 

particulate matter with an aerodynamic 

diameter less than or equal to a nominal 

10 micrometers (PM10) because recent 

complete, quality-assured monitoring 

data show that the area has 

subsequently violated this NAAQS. We 

are also proposing to find that the 

Arizona State Implementation Plan (SIP) 

is substantially inadequate to attain or 

maintain the PM10 standard and to call 

for Arizona to revise the SIP to address 

this inadequacy. 

DATES: Any comments must arrive by 

July 1, 2021. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–R09– 

OAR–2021–0249 at http://

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. For either manner of 

submission, the EPA may publish any 

comment received to its public docket. 

Do not submit electronically any 

information you consider to be 

Confidential Business Information (CBI) 

or other information whose disclosure is 

restricted by statute. Multimedia 

submissions (audio, video, etc.) must be 

accompanied by a written comment. 

The written comment is considered the 

official comment and should include 

discussion of all points you wish to 

make. The EPA will generally not 

consider comments or comment 

contents located outside of the primary 

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

other file sharing system). For 

additional submission methods, please 

contact the person identified in the FOR

FURTHER INFORMATION CONTACT section. 

For the full EPA public comment policy, 

information about CBI or multimedia 

submissions, and general guidance on 

making effective comments, please visit 

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: John 

J. Kelly, Air Planning Office (AIR–2), 

EPA Region IX, (415) 947–4151, 

kelly.johnj@epa.gov. 

SUPPLEMENTARY INFORMATION: 

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

and ‘‘our’’ refer to the EPA. 

Table of Contents 

I. Background 

A. The 1987 PM10 NAAQS 

B. Designation and Classification of the 

Yuma PM10 Nonattainment Area 

C. The Clean Data Policy and the 2006 

Clean Data Determination 

II. Current Monitoring Data 

III. Proposed Action and Request for Public 

Comment 

IV. Statutory and Executive Order Reviews 

I. Background 

A. The 1987 PM10 NAAQS 

The EPA sets NAAQS for certain 

ambient air pollutants at levels required 

to protect human health and the 

environment. The primary NAAQS 

represent ambient air quality standards 

the attainment and maintenance of 

which the EPA has determined are 

requisite to protect public health, 

including an adequate margin of safety. 

The secondary NAAQS represent 

ambient air quality standards the 

attainment and maintenance of which 

the EPA has determined are requisite to 

protect public welfare from any known 

or anticipated adverse effects associated 

with the presence of such air pollutant 

in the ambient air. PM10 is one of these 

ambient air pollutants for which the 

EPA has established NAAQS. 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

Effective December 18, 2006, the EPA 

revoked the annual PM10 NAAQS but 

retained the 24-hour PM10 NAAQS.2

Because they are identical, we refer to 

the primary and secondary 24-hour 

standards using the single term, 

NAAQS. 

The 24-hour PM10 NAAQS is attained 

when the expected number of 

exceedances, averaged over a three-year 

period, is less than or equal to one. The 

expected number of exceedances 

averaged over a three-year period at any 

given monitor is known as the PM10

design value for that site. The PM10

design value for the nonattainment area 

is the highest design value from a 

monitor within that area. The 

methodologies for calculating expected 

exceedances for the 24-hour PM10

NAAQS are found in 40 CFR part 50, 

appendix K, Section 2.1(a). 

B. Designation and Classification of the 

Yuma PM10 Nonattainment Area 

Upon enactment of the 1990 

Amendments to the Clean Air Act (CAA 

or ‘‘Act’’), the Act itself designated 

specific areas as nonattainment by 

operation of law, and classified these 

areas as Moderate.3 These areas 

included all former Group I PM10

planning areas identified in Federal 

Register documents published on 

August 7, 1987,4 and October 31, 1990,5

and any other areas violating the 1987 

PM10 NAAQS prior to January 1, 1989. 

The EPA published a Federal Register 

document announcing the areas 

designated nonattainment for PM10

upon enactment of the 1990 CAA 

Amendments, known as ‘‘initial’’ PM10

nonattainment areas, on March 15, 

1991.6 The EPA published a subsequent 

Federal Register document correcting 

some of these areas on August 8, 1991.7

These nonattainment designations and 

Moderate area classifications were 

codified in 40 CFR part 81 on November 

6, 1991.8 The EPA designated as 

‘‘unclassifiable’’ all other areas in the 

Nation not designated nonattainment 


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9See CAA section 107(d)(4)(B)(iii). 

10 52 FR 29383 (August 7, 1987). 

11 56 FR 11101. 

12Arizona submitted a Moderate area plan for the 

Yuma NAA on November 14, 1991. The EPA found 

this plan to be incomplete on May 14, 1992. 

Arizona submitted a revised plan for the Yuma 

NAA on July 12, 1994, but withdrew this plan in 

2006, following the EPA’s issuance of a clean data 

determination for the Yuma NAA. 

13 71 FR 13021 (March 14, 2006). 

14The clean data determination also applied to 

the annual PM10 NAAQS, but that NAAQS was 

revoked later that year. See 71 FR 61144 (October 

17, 2006). 

15 In the same Federal Register document, the 

EPA also determined pursuant to CAA sections 

179(c)(1) and 188(b)(2) that the Yuma NAA had 

attained the NAAQS by the Moderate area 

attainment date of December 31, 1994. Because that 

determination was tied to that specific attainment 

date, it would not be affected by the rescission of 

the clean data determination proposed in this 

action. 

16 40 CFR part 50, appendix K, section 2.3(a). 

17EPA, AQS ‘‘Design Value Report,’’ dated March 

31, 2021. This report is included in the docket. 

18See, e.g., ‘‘State of Arizona Air Monitoring 

Network Plan for the Year 2020.’’ Copies of 

Arizona’s Annual Network Plans for 2018–2020 are 

included in the docket. 

19See, e.g., letter dated November 8, 2019, from 

Gwen Yoshimura, Manager, EPA Region IX, Air 

Quality Analysis Office, to Daniel Czecholinksi, 

Acting Director, Air Quality Division, ADEQ. 

Copies of EPA letters responding to Arizona’s 

Annual Network Plans for 2018–2020 are included 

in the docket. 20Letter dated April 25, 2019, from Elizabeth 

Adams, Director, EPA Region 9 Air Division to 

Timothy Franquist, Director, Air Quality Division, 

ADEQ, enclosure titled ‘‘Technical Systems Audit 

of the Ambient Air Monitoring Program: Arizona 

Department of Environmental Quality, April 2– 

April 6, 2018,’’ Network Requirements section, 8. 21See, e.g., letter dated April 13, 2020, from 

Daniel Czecholinksi, Director, Air Quality Division, 

ADEQ, to Gwen Yoshimura, Manager, EPA Region 

IX, Air Quality Analysis Office. Copies of ADEQ 

certifications and their respective transmittal letters 

for years 2017–2019 are included in the docket. 22EPA, AQS ‘‘Design Value Report,’’ dated March 

3, 2021. 

upon enactment of the 1990 CAA 

Amendments.9

The Yuma PM10 nonattainment area 

(‘‘Yuma NAA’’) was one of the areas 

specified by Congress and designated by 

the 1990 CAA Amendments. 

Specifically, the Yuma NAA was 

designated nonattainment by section 

107(d)(4)(B)(i) of the Act and classified 

as Moderate because it had been 

previously categorized as a Group I 

area.10 The EPA announced the Yuma 

NAA designation, as required by section 

107(d)(2) of the Act, on March 15, 

1991.11 In accordance with CAA section 

189(a)(2), Arizona was required to 

submit a SIP revision meeting 

applicable nonattainment plan 

requirements by November 15, 1991, 

demonstrating attainment of the 1987 

p.m.10 NAAQS in the Yuma NAA by 

December 31, 1994.12

C. The Clean Data Policy and the 2006 

Clean Data Determination 

In nonattainment areas where 

monitored data demonstrate that the 

NAAQS has been attained, the EPA 

interprets certain requirements of the 

Act as no longer being applicable for so 

long as air quality continues to meet the 

NAAQS in the area. This interpretation 

is known as the ‘‘clean data policy,’’ and 

EPA findings issued under this policy 

are known as ‘‘clean data 

determinations.’’ On March 14, 2006, 

the EPA issued a clean data 

determination for the Yuma NAA for the 

1987 24-hour PM10 NAAQS, based on 

complete, quality-assured and certified 

PM10 monitoring data for 2002–2004.13

Because the data from 2002–2004 were 

complete and showed no exceedances of 

the relevant NAAQS, and because 

preliminary data for 2005 also indicated 

no such exceedances, the EPA 

concluded that the Yuma NAA was in 

attainment for the 1987 24-hour PM10

NAAQS.14 Based on this finding, the 

EPA determined that certain 

nonattainment plan requirements in the 

Yuma NAA were not applicable for so 

long as the Yuma NAA continued to 

monitor attainment of the 1987 24-hour 

PM10 and annual NAAQS.15

II. Current Monitoring Data 

In accordance with 40 CFR part 50, 

appendices J and K, a finding of 

whether an area has attained or is 

currently attaining the 1987 24-hour 

PM10 NAAQS must generally be based 

upon certified, complete, qualityassured data gathered at monitoring 

sites in the nonattainment area and 

entered into the EPA’s Air Quality 

System (AQS) database. For the 1987 

24-hour PM10 NAAQS, appendix K 

provides that all data produced by state 

and local air monitoring sites (SLAMS) 

and other sites submitted to the EPA in 

accordance with the part 58 

requirements be used for evaluating 

attainment.16

In order to assess whether an area is 

currently attaining the NAAQS, the 

PM10 ambient air quality monitoring 

data collected by the state within the 

area for the three-year period must meet 

data completeness criteria, or otherwise 

unambiguously establish nonattainment 

according to 40 CFR part 50, appendix 

K, section 2.3. The ambient air quality 

monitoring data completeness 

requirements are met when quarterly 

data capture rates for all four quarters in 

a calendar year over a three-year period 

are at least 75 percent. For purposes of 

this proposal, we reviewed the data for 

the 2017–2019 period for completeness 

and determined that the PM10 data met 

the completeness criterion for all 12 

quarters at the Yuma Supersite PM10

monitoring site in the Yuma NAA.17

The Arizona Department of 

Environmental Quality (ADEQ) is the 

governmental agency with the authority 

and responsibilities under the State’s 

laws for collecting ambient air quality 

data for the Yuma NAA. ADEQ submits 

annual monitoring network plans to the 

EPA.18 These plans discuss the status of 

the ambient air monitoring network, as 

required under 40 CFR part 58. The EPA 

reviews these annual network plans for 

compliance with the applicable 

reporting requirements in 40 CFR 58.10. 

With respect to PM10, the EPA has 

found that the 2018–2020 annual 

network plans submitted by ADEQ, 

which reflect the network during the 

2017–2019 design value period, met the 

applicable requirements under 40 CFR 

part 58.19 Furthermore, we concluded 

from our 2018 technical systems audit 

of ADEQ’s ambient air quality 

monitoring program that the ambient air 

monitoring network currently meets or 

exceeds the requirements for the 

minimum number of monitoring sites 

designated as SLAMS for PM10 in the 

Yuma NAA.20 ADEQ certifies annually 

that the data it submits to AQS are 

quality-assured and has done so for each 

year relevant to our proposed action, 

2017–2019.21

Table 1 provides the 2019 p.m.10

design value for the Yuma Supersite, the 

sole regulatory monitoring site 

measuring ambient PM10 within the 

Yuma NAA, expressed as a single value 

representing the average expected 

annual exceedances over the three-year 

period, 2017–2019. The PM10 data show 

that the design value is greater than 1.0 

estimated annual average exceedances 

of the 1987 24-hour PM10 NAAQS. 

Consequently, the EPA proposes to 

determine, based upon three years of 

complete, quality-assured and certified 

data from 2017–2019, that the Yuma 

NAA is no longer attaining the 1987 24- 

hour PM10 NAAQS. 

TABLE 1—2017–2019 DESIGN VALUE

FOR THE 1987 24-HOUR PM10

NAAQS FOR THE YUMA NAA 

Monitoring site 

AQS 

identification 

No. 

Design 

value 

Yuma Supersite ....... 04–027–8011 5.7 

Source: EPA, AQS ‘‘Design Value Report,’’ dated 

March 31, 2021, 15. 

We have also reviewed preliminary 

2020 data, which indicate that the Yuma 

NAA had a 2018–2020 design value of 

5.4.22 This preliminary design value 


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23 Id. 

24 Id. 

25See CAA section 110(k)(5) (‘‘Any finding under 

this paragraph shall, to the extent the Administrator 

deems appropriate, subject the State to the 

requirements of this chapter to which the State was 

subject when it developed and submitted the plan 

for which such finding was made . . .’’). 

26CAA section 189(a)(1)(A). 27CAA section 189(a)(1)(B). 28CAA section 189(a)(1)(C). 29CAA section 189(c). 30CAA section 189(e). 31CAA section 172(c)(2). 32CAA section 172(c)(3). 33CAA section 172(c)(6). 34CAA section 172(c)(9). 35 40 CFR 93.102(b)(1). Effective June 27, 2007 

(see 72 FR 32295, June 12, 2007), the EPA found 

adequate for transportation conformity purposes the 

motor vehicle emissions budgets in the Yuma PM10

Maintenance Plan (August 2006). However, if we 

take final action to withdraw the clean data 

determination and issue a SIP call, we expect also 

to reverse our previous finding to a finding of 

inadequacy pursuant to 40 CFR 93.118(f)(1)(vi). Our 

inadequacy finding for the motor vehicle emissions 

budget would require transportation agencies to 

determine conformity using interim emission tests 

pursuant to 40 CFR 93.119, instead of the current 

practice of using the past maintenance plan motor 

vehicle emissions budgets as part of a budgets test. 

36 57 FR 13498 (April 16, 1992). 

37CAA section 189(a)(2). 

38CAA section 188(c)(1). 

39CAA section 110(k)(5), ‘‘the Administrator may 

adjust any dates applicable under such 

requirements as appropriate (except that the 

Administrator may not adjust any attainment date 

prescribed under part D of this subchapter, unless 

such date has elapsed).’’ 

40 Given that exceedances of the 1987 24-hour 

PM10 NAAQS in the Yuma NAA are often 

associated with high wind that could potentially 

qualify for treatment as ‘‘natural events’’ under the 

EPA’s Exceptional Events Rule, we recommend 

RACM/RACT be fully implemented as early as 

January 1, 2023, so that anthropogenic sources 

would be reasonably controlled during the threeyear period preceding the proposed attainment 

date. See, e.g., 40 CFR 50.14(b)(5)(ii) (‘‘The 

Administrator will consider high wind dust events 

to be natural events in cases where windblown dust 

is entirely from natural undisturbed lands in the 

area or where all anthropogenic sources are 

reasonably controlled . . .’’). 

also does not show attainment of the 

1987 24-hour PM10 NAAQS and is 

therefore consistent with the proposed 

determination. We also reviewed 

preliminary data from the Yuma 

Supersite monitor for 2021, which is not 

a full year of data.23 As of March 31, 

2021, there were no exceedances in 

2021. We note, however, that even with 

no exceedances in 2021, given the 

number of expected exceedances in the 

certified year 2019, plus those in the 

preliminary year 2020, the 2021 threeyear preliminary design value violates 

the NAAQS and is therefore also 

consistent with our proposed 

determination. 

III. Proposed Action and Request for 

Public Comment 

Based on our proposed determination 

that the Yuma NAA is no longer 

attaining the 1987 24-hour PM10

NAAQS, we propose to rescind the 

clean data determination for the Yuma 

NAA and reinstate the requirements that 

were suspended under that 

determination. We anticipate that 

Arizona’s submission of a new, 

approvable Moderate nonattainment 

plan in response to the ‘‘SIP call’’ 

discussed below would satisfy these 

obligations. 

In addition, we propose to find, 

pursuant to CAA section 110(k)(5), that 

the Arizona SIP is substantially 

inadequate to attain or maintain the 

1987 24-hour PM10 NAAQS in the Yuma 

NAA. This proposed finding is based 

both on the most recent monitoring data 

discussed in section II of this document, 

as well as longer-term air quality trends 

in the Yuma NAA. In particular, we 

note that the Yuma NAA has had a 

violating design value for the 1987 24- 

hour PM10 NAAQSs every year since 

issuance of the clean data determination 

in 2006.24 Collectively, these recent and 

longer term monitoring data indicate 

that the current Arizona SIP is 

substantially inadequate to attain or 

maintain the 1987 24-hour PM10

NAAQS in the Yuma NAA. 

In order to address this inadequacy, 

we propose to issue a SIP call under 

CAA section 110(k)(5), requiring the 

State to submit a SIP revision 

establishing that the Yuma NAA meets 

the applicable nonattainment plan 

requirements of the CAA for Moderate 

PM10 NAAs.25 These requirements 

include: (i) An approved permit 

program for construction of new and 

modified major stationary sources; 26 (ii) 

a demonstration that the plan provides 

for attainment by no later than the 

applicable Moderate area attainment 

date or a demonstration that attainment 

by that date is impracticable; 27 (iii) 

provisions for the implementation of 

reasonably available control measures 

(RACM) and reasonably available 

control technology (RACT); 28 (iv) 

quantitative milestones that will be used 

to evaluate compliance with the 

requirement to demonstrate reasonable 

further progress (RFP); 29 (v) evaluation 

and regulation of PM10 precursors; 30 (vi) 

a description of the expected annual 

incremental reductions in emissions 

that will demonstrate RFP; 31 (vii) 

emissions inventories, as necessary; 32

(viii) other control measures besides 

RACM and RACT as may be needed for 

attainment; 33 (ix) contingency 

measures,34 and (x) a motor vehicle 

emissions budget for the purpose of 

determining the conformity of 

transportation programs and plans 

developed by state transportation 

agencies.35 The EPA’s longstanding 

guidance on these statutory 

requirements is embodied in the ‘‘The 

General Preamble for Implementation of 

Title I of the Clean Air Act (CAA) 

Amendments.’’ 36

We propose to require Arizona to 

submit this Moderate nonattainment 

plan SIP submission within 18 months 

of finalizing the SIP call, which is the 

maximum time permitted under CAA 

110(k)(5). This is longer than the 

original Moderate nonattainment plan 

submittal deadline of one year from the 

date of the 1990 CAA Amendments 

under CAA 189(a)(2)(A), but is in line 

with the deadline specified in CAA 

189(a)(2)(B) for other PM nonattainment 

areas.37 Similarly, because the original 

maximum attainment date for this area 

was December 31, 1994 (approximately 

four years from the original 

designation),38 we propose, pursuant to 

CAA 110(k)(5), that the new attainment 

date shall be as expeditious as 

practicable, but no later than December 

31, 2025.39 In line with this proposed 

attainment date, we propose to require 

implementation of RACM/RACT by no 

later than January 1, 2025.40 Lastly, in 

the event we finalize the above 

proposals, we propose to reverse our 

previous budget adequacy finding to a 

finding of inadequacy pursuant to 40 

CFR 93.118(f)(1)(vi). 

The EPA is soliciting public 

comments on the issues discussed in 

this document. We will accept 

comments from the public on this 

proposal until the date listed in the 

DATES section above. We will consider 

these comments before taking final 

action. 

IV. Statutory and Executive Order 

Reviews 

This action proposes a determination 

that the Yuma NAA is no longer 

attaining the 1987 PM10 NAAQS, based 

on the EPA’s review of air quality data, 

and a SIP call under section 110(k)(5) of 

the CAA. Upon a finding that a SIP is 

deficient, section 110(k)(5) of the CAA 

directs the Agency to require the state 

to correct the deficiency. Therefore, this 

action does not impose additional 

requirements beyond those required by 

the CAA itself. For that reason, this 

action: 

• Is not a ‘‘significant regulatory 

action’’ subject to review by the Office 

of Management and Budget under 

Executive Orders 12866 (58 FR 51735, 

October 4, 1993) and 13563 (76 FR 3821, 

January 21, 2011); 

• Does not impose an information 

collection burden under the provisions 


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of the Paperwork Reduction Act (44 

U.S.C. 3501 et seq.); 

• Is certified as not having a 

significant economic impact on a 

substantial number of small entities 

under the Regulatory Flexibility Act (5 

U.S.C. 601 et seq.); 

• Does not contain any unfunded 

mandate or significantly or uniquely 

affect small governments, as described 

in the Unfunded Mandates Reform Act 

of 1995 (Pub. L. 104–4); 

• Does not have federalism 

implications as specified in Executive 

Order 13132 (64 FR 43255, August 10, 

1999); 

• Is not an economically significant 

regulatory action based on health or 

safety risks subject to Executive Order 

13045 (62 FR 19885, April 23, 1997); 

• Is not a significant regulatory action 

subject to Executive Order 13211 (66 FR 

28355, May 22, 2001); 

• Is not subject to requirements of 

section 12(d) of the National 

Technology Transfer and Advancement 

Act of 1995 (15 U.S.C. 272 note) because 

application of those requirements would 

be inconsistent with the CAA; and 

• Does not provide the EPA with the 

discretionary authority to address 

disproportionate human health or 

environmental effects with practical, 

appropriate, and legally permissible 

methods under Executive Order 12898 

(59 FR 7629, February 16, 1994). 

In addition, this proposed action does 

not have Tribal implications as 

specified by Executive Order 13175 (65 

FR 67249, November 9, 2000), because 

the SIP obligations discussed herein do 

not apply to Indian Tribes and thus this 

proposed action will not impose 

substantial direct costs on Tribal 

governments or preempt Tribal law. 

Nonetheless, the EPA intends to notify 

the Cocopah and Fort Yuma (Quechan) 

tribes, which have lands within the 

Yuma NAA. 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air 

pollution control, Incorporation by 

reference, Intergovernmental relations, 

Particulate Matter, Pollution. 

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

Dated: May 24, 2021. 

Deborah Jordan, 

Acting Regional Administrator, Region IX. 

[FR Doc. 2021–11395 Filed 5–28–21; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R03–OAR–2021–0017; FRL–10023– 

69–Region 3] 

Air Plan Approval; Maryland; Baltimore 

Area Base Year Inventory for the 2015 

Ozone National Ambient Air Quality 

Standards 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is proposing to approve a 

state implementation plan (SIP) revision 

submitted by the State of Maryland. 

This revision consists of the base year 

inventory for the Baltimore, Maryland 

marginal nonattainment area (Baltimore 

Area) for the 2015 ozone national 

ambient air quality standards (NAAQS). 

This action is being taken under the 

Clean Air Act (CAA). 

DATES: Written comments must be 

received on or before July 1, 2021. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–R03– 

OAR–2021–0017 at https://

www.regulations.gov, or via email to 

David.Talley@epa.gov. For comments 

submitted at Regulations.gov, follow the 

online instructions for submitting 

comments. Once submitted, comments 

cannot be edited or removed from 

Regulations.gov. For either manner of 

submission, EPA may publish any 

comment received to its public docket. 

Do not submit electronically any 

information you consider to be 

confidential business information (CBI) 

or other information whose disclosure is 

restricted by statute. Multimedia 

submissions (audio, video, etc.) must be 

accompanied by a written comment. 

The written comment is considered the 

official comment and should include 

discussion of all points you wish to 

make. EPA will generally not consider 

comments or comment contents located 

outside of the primary submission (i.e., 

on the web, cloud, or other file sharing 

system). For additional submission 

methods, please contact the person 

identified in the FOR FURTHER

INFORMATION CONTACT section. For the 

full EPA public comment policy, 

information about CBI or multimedia 

submissions, and general guidance on 

making effective comments, please visit 

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

commenting-epa-dockets. 

FOR FURTHER INFORMATION CONTACT: 

Serena Nichols, Planning & 

Implementation Branch (3AD30), Air & 

Radiation Division, U.S. Environmental 

Protection Agency, Region III, 1650 

Arch Street, Philadelphia, Pennsylvania 

19103. The telephone number is (215) 

814–2053. Ms. Nichols can also be 

reached via electronic mail at 

Nichols.Serena@epa.gov. 

SUPPLEMENTARY INFORMATION: On July 

30, 2020, the Maryland Department of 

the Environment (MDE), on behalf of the 

State of Maryland, submitted a revision 

to the Maryland SIP entitled, ‘‘2015 8- 

Hour Ozone NAAQS (0.070 ppm) 

Marginal Area State Implementation 

Plan for the Baltimore, MD 

Nonattainment Area, SIP #20–08.’’ This 

SIP revision, referred to in this 

rulemaking action as the ‘‘Baltimore 

base year inventory SIP,’’ addresses the 

base year inventory requirement for the 

2015 ozone NAAQS. 

I. Background 

On October 1, 2015, EPA strengthened 

the 8-hour ozone NAAQS, lowering the 

level of the NAAQS from 0.075 ppm 

parts per million (ppm) to 0.070 ppm. 

80 FR 65292 (October 26, 2015). 

Effective August 3, 2018, EPA 

designated the Baltimore Area, 

consisting of Anne Arundel, Baltimore, 

Carroll, Harford, and Howard Counties 

and the City of Baltimore, all in 

Maryland, as marginal nonattainment 

for the 2015 ozone NAAQS. 83 FR 

25776 (June 4, 2018). CAA section 

182(a)(1) requires ozone nonattainment 

areas classified as marginal or above to 

submit a comprehensive, accurate, 

current inventory of actual emissions 

from all emissions sources in the 

nonattainment area, known as a ‘‘base 

year inventory.’’ The Baltimore base 

year inventory SIP addresses a base year 

inventory requirement for the Baltimore 

Area. 

II. Summary of SIP Revision and EPA 

Analysis 

A. EPA’s Evaluation of the Baltimore 

Base Year Inventory SIP 

EPA’s review of Maryland’s base year 

inventory SIP for the Baltimore Area 

indicates that it meets the base year 

inventory requirements for the 2015 

ozone NAAQS. As required by 40 CFR 

51.1315(a), MDE selected 2017 for the 

base year inventory, which is consistent 

with the baseline year for the reasonable 

further progress (RFP) plan because it is 

the year of the most recent triennial 

inventory. MDE included actual ozone 

season emissions, pursuant to 40 CFR 

51.1315(c). 

EPA prepared a Technical Support 

Document (TSD) in support of this 

rulemaking. In that TSD, EPA reviewed 

the results, procedures, and 


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