27938 Federal Register / Vol. 83, No. 116 / Friday, June 15, 2018 / Proposed Rules 

1See 75 FR 35520, codified at 40 CFR 50.17(a)– 

(b). 

2See 78 FR 47191, codified at 40 CFR part 81, 

subpart C. 

Agency views this as a noncontroversial 

submittal and anticipates no adverse 

comments. A detailed rationale for the 

approval is set forth in the direct final 

rule. If no adverse comments are 

received in response to this action, no 

further activity is contemplated. If EPA 

receives adverse comments relevant to 

this action, the direct final rule will be 

withdrawn and all public comments 

received will be addressed in a 

subsequent final rule based on this 

proposed rule. EPA will not institute a 

second comment period. Any parties 

interested in commenting on this action 

should do so at this time. 

DATES: Comments must be received in 

writing by July 16, 2018. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–R03– 

OAR–2018–0277 at http://

www.regulations.gov, or via email to 

spielberger.susan@epa.gov. For 

comments submitted at Regulations.gov, 

follow the online instructions for 

submitting comments. Once submitted, 

comments cannot be edited or removed 

from Regulations.gov. For either manner 

of submission, the EPA may publish any 

comment received to its public docket. 

Do not submit electronically any 

information you consider to be 

confidential business information (CBI) 

or other information whose disclosure is 

restricted by statute. Multimedia 

submissions (audio, video, etc.) must be 

accompanied by a written comment. 

The written comment is considered the 

official comment and should include 

discussion of all points you wish to 

make. EPA will generally not consider 

comments or comment contents located 

outside of the primary submission (i.e. 

on the web, cloud, or other file sharing 

system). For additional submission 

methods, please contact the person 

identified in the FOR FURTHER

INFORMATION CONTACT section. For the 

full EPA public comment policy, 

information about CBI or multimedia 

submissions, and general guidance on 

making effective comments, please visit 

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

commenting-epa-dockets. 

FOR FURTHER INFORMATION CONTACT: 

Brian Rehn, (215) 814–2176, or by email 

at rehn.brian@epa.gov. 

SUPPLEMENTARY INFORMATION: For 

further information on this action to 

remove requirements related to 

Pennsylvania Department of 

Environmental Protection (PADEP) 

requirements for a low RVP gasoline 

program in the Pittsburgh-Beaver Valley 

Area from the SIP, please see the 

information provided in the direct final 

action, with the same title, that is 

located in the ‘‘Rules and Regulations’’ 

section of this Federal Register 

publication. 

Dated: June 6, 2018. 

Cecil Rodrigues, 

Acting Regional Administrator, Region III. 

[FR Doc. 2018–12704 Filed 6–14–18; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R09–OAR–2017–0621; FRL–9979– 

49—Region 9] 

Approval and Promulgation of Air 

Quality Implementation Plans; Arizona; 

Nonattainment Plan for the Miami SO2

Nonattainment Area 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is proposing to approve 

an Arizona state implementation plan 

(SIP) revision for attaining the 1-hour 

sulfur dioxide (SO2) primary national 

ambient air quality standard (NAAQS or 

‘‘standard’’) for the Miami SO2

nonattainment area (NAA). This SIP 

revision (hereinafter called the ‘‘Miami 

SO2 Plan’’ or ‘‘Plan’’) includes Arizona’s 

attainment demonstration and other 

elements required under the Clean Air 

Act (CAA or ‘‘Act’’). In addition to an 

attainment demonstration, the Plan 

addresses the requirement for meeting 

reasonable further progress toward 

attainment of the NAAQS, reasonably 

available control measures and 

reasonably available control technology, 

base-year and projected emission 

inventories, enforceable emissions 

limitations and control measures, and 

contingency measures. The EPA 

proposes to conclude that Arizona has 

appropriately demonstrated that the 

Plan provides for attainment of the 2010 

1-hour primary SO2 NAAQS in the 

Miami SO2 NAA by the attainment date 

of October 4, 2018 and that the Plan 

meets the other applicable requirements 

under the CAA. 

DATES: Comments must be received on 

or before July 16, 2018. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–R09– 

OAR–2017–0621 at http://

www.regulations.gov. Follow the online 

instructions for submitting comments. 

Once submitted, comments cannot be 

edited or removed from Regulations.gov. 

The EPA may publish any comment 

received to its public docket. Do not 

submit electronically any information 

you consider to be Confidential 

Business Information (CBI) or other 

information whose disclosure is 

restricted by statute. Multimedia 

submissions (audio, video, etc.) must be 

accompanied by a written comment. 

The written comment is considered the 

official comment and should include 

discussion of all points you wish to 

make. The EPA will generally not 

consider comments or comment 

contents located outside of the primary 

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

other file sharing system). For 

additional submission methods, the full 

EPA public comment policy, 

information about CBI or multimedia 

submissions, and general guidance on 

making effective comments, please visit 

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

commenting-epa-dockets. 

FOR FURTHER INFORMATION CONTACT: 

Krishna Viswanathan, EPA, Region IX, 

Air Division, Air Planning Office, (520) 

999–7880 or viswanathan.krishna@

epa.gov. 

SUPPLEMENTARY INFORMATION: 

Throughout this document whenever, 

‘‘we,’’ ‘‘us,’’ or ‘‘our’’ is used, we mean 

the EPA. 

Table of Contents 

I. Why was Arizona required to submit a plan 

for the Miami SO2 NAA? 

II. Requirements for SO2 Nonattainment 

Plans 

III. Attainment Demonstration and LongerTerm Averaging 

IV. Review of Modeled Attainment 

Demonstration 

V. Review of Other Plan Requirements 

VI. Conformity 

VII. The EPA’s Proposed Action 

VIII. Statutory and Executive Order Reviews 

I. Why was Arizona required to submit 

a plan for the Miami SO2 NAA? 

On June 22, 2010, the EPA 

promulgated a new 1-hour primary SO2

NAAQS of 75 parts per billion (ppb). 

This standard is met at an ambient air 

quality monitoring site when the 3-year 

average of the annual 99th percentile of 

daily maximum 1-hour average 

concentrations does not exceed 75 ppb, 

as determined in accordance with 

appendix T of 40 CFR part 50.1 On 

August 5, 2013, the EPA designated a 

first set of 29 areas of the country as 

nonattainment for the 2010 SO2

NAAQS, including the Miami SO2 NAA 

within Arizona.2 These area 

designations became effective on 

October 4, 2013. Section 191 of the CAA 

directs states to submit SIPs for areas 


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3See 81 FR 14736. 

4Letters from Tim Franquist, ADEQ, to Alexis 

Strauss, EPA, dated March 8, 2017, and April 6, 

2017. Although the cover letter for the Miami SO2

Plan was dated March 8, 2017, the Plan was 

transmitted to the EPA on March 9, 2017. 

5Letters from Elizabeth Adams, EPA, to Tim 

Franquist, ADEQ, dated July 17, 2017, and 

September 26, 2017. 

6See 57 FR 13498 (April 16, 1992) (General 

Preamble). 

7 Id. at 13545–49, 13567–68. 

8See 57 FR at 13567–68 (April 16, 1992). 

9See 2014 SO2 Guidance, pages 22 to 39. 

designated as nonattainment for the SO2

NAAQS to the EPA within 18 months of 

the effective date of the designation, i.e., 

by no later than April 4, 2015, in this 

case (hereinafter called ‘‘plans’’ or 

‘‘nonattainment plans’’). Under CAA 

section 192, these plans are required to 

have measures that will help their 

respective areas attain the NAAQS as 

expeditiously as practicable, but no later 

than 5 years from the effective date of 

designation, which for the Miami SO2

NAA is October 4, 2018. 

For a number of areas, including the 

Miami SO2 NAA, the EPA published a 

document on March 18, 2016, finding 

that Arizona and other pertinent states 

had failed to submit the required SO2

nonattainment plan by the submittal 

deadline.3 This finding, which became 

effective on April 18, 2016, initiated a 

deadline under CAA section 179(a) for 

the potential imposition of new source 

review offset and highway funding 

sanctions. Additionally, under CAA 

section 110(c), the finding triggered a 

requirement that the EPA promulgate a 

federal implementation plan (FIP) 

within two years of the effective date of 

the finding unless by that time the State 

had made the necessary complete 

submittal and the EPA had approved the 

submittal as meeting applicable 

requirements. 

In response to the requirement for SO2

nonattainment plan submittals, the 

Arizona Department of Environmental 

Quality (ADEQ) submitted the Miami 

SO2 Plan on March 9, 2017, and 

submitted associated final rules on 

April 6, 2017.4 The EPA issued letters 

dated July 17, 2017, and September 26, 

2017, finding the submittals complete 

and halting the sanctions clock under 

CAA section 179(a).5

The remainder of this preamble 

describes the requirements that 

nonattainment plans must meet in order 

to obtain EPA approval, provides a 

review of the Miami SO2 Plan with 

respect to these requirements, and 

describes the EPA’s proposed action on 

the Plan. 

II. Requirements for SO2

Nonattainment Plans 

Nonattainment plans for SO2 must 

meet the applicable requirements of the 

CAA, specifically CAA sections 110, 

172, 191 and 192. The EPA’s regulations 

governing nonattainment SIP 

submissions are set forth at 40 CFR part 

51, with specific procedural 

requirements and control strategy 

requirements residing at subparts F and 

G, respectively. Soon after Congress 

enacted the 1990 Amendments to the 

CAA, the EPA issued comprehensive 

guidance on SIP revisions in the 

‘‘General Preamble for the 

Implementation of Title I of the Clean 

Air Act Amendments of 1990.’’ 6 Among 

other things, the General Preamble 

addressed SO2 SIP submissions and 

fundamental principles for SIP control 

strategies.7 On April 23, 2014, the EPA 

issued recommended guidance for 

meeting the statutory requirements in 

SO2 SIP submissions, in a document 

entitled, ‘‘Guidance for 1-Hour SO2

Nonattainment Area SIP Submissions’’ 

(‘‘2014 SO2 Guidance’’). In the 2014 SO2

Guidance, the EPA described the 

statutory requirements for a complete 

nonattainment plan, which include: An 

accurate emissions inventory of current 

emissions for all sources of SO2 within 

the NAA; an attainment demonstration; 

demonstration of RFP; implementation 

of RACM (including RACT); new source 

review, enforceable emissions 

limitations and control measures, and 

adequate contingency measures for the 

affected area. 

For the EPA to fully approve a SIP 

revision as meeting the requirements of 

CAA sections 110, 172 and 191–192 and 

the EPA’s regulations at 40 CFR part 51, 

the plan for the affected area needs to 

demonstrate to the EPA’s satisfaction 

that each of the aforementioned 

requirements has been met. Under CAA 

section 110(l), the EPA may not approve 

a plan that would interfere with any 

applicable requirement concerning 

NAAQS attainment and RFP, or any 

other applicable requirement. Under 

CAA section 193, no requirement in 

effect (or required to be adopted by an 

order, settlement, agreement, or plan in 

effect before November 15, 1990) in any 

area that is a NAA for any air pollutant 

may be modified in any manner unless 

it insures equivalent or greater emission 

reductions of such air pollutant. 

III. Attainment Demonstration and 

Longer-Term Averaging 

Section 172(c)(1) and 172(c)(6) of the 

CAA direct states with areas designated 

as nonattainment to demonstrate that 

the submitted plan provides for 

attainment of the NAAQS. 40 CFR part 

51, subpart G further delineates the 

control strategy requirements that plans 

must meet, and the EPA has long 

required that all SIPs and control 

strategies reflect four fundamental 

principles of quantification, 

enforceability, replicability, and 

accountability.8 SO2 nonattainment 

plans must consist of two components: 

(1) Emission limits and other control 

measures that assure implementation of 

permanent, enforceable and necessary 

emission controls, and (2) a modeling 

analysis that meets the requirements of 

40 CFR part 51, appendix W and 

demonstrates that these emission limits 

and control measures provide for timely 

attainment of the primary SO2 NAAQS 

as expeditiously as practicable, but by 

no later than the attainment date for the 

affected area. In cases where the 

necessary emission limits have not 

previously been made a part of the 

state’s SIP, or have not otherwise 

become federally enforceable, the plan 

needs to include the necessary 

enforceable limits in adopted form 

suitable for incorporation into the SIP in 

order for the plan to be approved by the 

EPA. In all cases, the emission limits 

and control measures must be 

accompanied by appropriate methods 

and conditions to determine compliance 

with the respective emission limits and 

control measures and must be 

quantifiable (i.e., a specific amount of 

emission reduction can be ascribed to 

the measures), fully enforceable (i.e., 

specifying clear, unambiguous and 

measurable requirements for which 

compliance can be practicably 

determined), replicable (i.e., the 

procedures for determining compliance 

are sufficiently specific and nonsubjective so that two independent 

entities applying the procedures would 

obtain the same result), and accountable 

(i.e., source specific limits must be 

permanent and must reflect the 

assumptions used in the SIP 

demonstrations). 

The EPA’s 2014 SO2 Guidance 

recommends that the emission limits be 

expressed as short-term average limits 

not to exceed the averaging time for the 

applicable NAAQS that the limit is 

intended to help maintain (e.g., 

addressing emissions averaged over one 

or three hours), but it also describes the 

option to utilize emission limits with 

longer averaging times of up to 30 days 

as long as the state meets various 

suggested criteria.9 The 2014 SO2

Guidance recommends that—should 

states and sources utilize longer 

averaging times (such as 30 days)—the 

longer-term average limit should be set 

at an adjusted level that reflects a 


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10 Id. pages 22 to 39. See also id. at Appendices 

B and D. 

11An ‘‘average year’’ is used to mean a year with 

average air quality. While 40 CFR part 50, appendix 

T provides for averaging three years of 99th 

percentile daily maximum hourly values (e.g., the 

fourth highest maximum daily hourly concentration 

in a year with 365 days with valid data), this 

discussion and an example below uses a single 

‘‘average year’’ in order to simplify the illustration 

of relevant principles. 

12 Design values are the metrics (i.e., statistics) 

that are compared to the NAAQS levels to 

determine compliance. The design value for the 

primary 1-hour SO2 NAAQS is the 3-year average 

of annual 99th percentile daily maximum 1-hour 

values for a monitoring site, calculated as specified 

in 40 CFR part 50, appendix T, section 5. 

stringency comparable to the 1-hour 

average limit at the critical emission 

value shown to provide for attainment. 

The 2014 SO2 Guidance provides an 

extensive discussion of the EPA’s 

rationale for concluding that 

appropriately set, comparably stringent 

limitations based on averaging times as 

long as 30 days can be found to provide 

for attainment of the 2010 SO2 NAAQS. 

In evaluating this option, the EPA 

considered the nature of the standard, 

conducted detailed analyses of the 

impact of use of 30-day average limits 

on the prospects for attaining the 

standard, and carefully reviewed how 

best to achieve an appropriate balance 

among the various factors that warrant 

consideration in judging whether a 

state’s plan provides for attainment.10

As specified in 40 CFR 50.17(b), the 

1-hour primary SO2 NAAQS is met at an 

ambient air quality monitoring site 

when the 3-year average of the annual 

99th percentile of daily maximum 1- 

hour average concentrations is less than 

or equal to 75 ppb. In a year with 365 

days of valid monitoring data, the 99th 

percentile would be the fourth highest 

daily maximum 1-hour value. The 2010 

SO2 NAAQS, including this form of 

determining compliance with the 

standard, was upheld by the U.S. Court 

of Appeals for the District of Columbia 

Circuit in Nat’l Envt’l Dev. Ass’n’s Clean 

Air Project v. EPA, 686 F.3d 803 (D.C. 

Cir. 2012). Because the standard has this 

form, a single hourly exceedance does 

not create a violation of the standard. 

Instead, at issue is whether a source 

operating in compliance with a properly 

set longer-term average could cause 

hourly exceedances, and if so what the 

resulting frequency and magnitude of 

such exceedances would be, and in 

particular whether the EPA can have 

reasonable confidence that a properly 

set longer-term average limit will 

provide that the three-year average of 

the annual fourth highest daily 

maximum hourly value will be at or 

below 75 ppb. A synopsis of the EPA’s 

review of how to judge whether such 

plans ‘‘provide for attainment,’’ based 

on modeling of projected allowable 

emissions and in light of the NAAQS’ 

form for determining attainment at 

monitoring sites, follows. 

For SO2 plans based on 1-hour 

emission limits, the standard approach 

is to conduct modeling using fixed 

emission rates. The maximum emission 

rate that would be modeled to result in 

attainment (i.e., in an ‘‘average year’’ 11

shows three, not four days with 

maximum hourly levels exceeding 75 

ppb) is labeled the ‘‘critical emission 

value.’’ The modeling process for 

identifying this critical emissions value 

inherently considers the numerous 

variables that affect ambient 

concentrations of SO2, such as 

meteorological data, background 

concentrations, and topography. In the 

standard approach, the state would then 

provide for attainment by setting a 

continuously applicable 1-hour 

emission limit at this critical emission 

value. 

The EPA recognizes that some sources 

have highly variable emissions due, for 

example, to variations in fuel sulfur 

content and operating rate, that can 

make it extremely difficult, even with a 

well-designed control strategy, to ensure 

in practice that emissions for any given 

hour do not exceed the critical emission 

value. The EPA also acknowledges the 

concern that longer-term emission limits 

can allow short periods with emissions 

above the critical emissions value, 

which, if coincident with 

meteorological conditions conducive to 

high SO2 concentrations, could in turn 

create the possibility of a NAAQS 

exceedance occurring on a day when an 

exceedance would not have occurred if 

emissions were continuously controlled 

at the level corresponding to the critical 

emission value. However, for several 

reasons, the EPA believes that the 

approach recommended in the 2014 SO2

Guidance suitably addresses this 

concern. First, from a practical 

perspective, the EPA expects the actual 

emission profile of a source subject to 

an appropriately set longer-term average 

limit to be similar to the emission 

profile of a source subject to an 

analogous 1-hour average limit. The 

EPA expects this similarity because it 

has recommended that the longer-term 

average limit be set at a level that is 

comparably stringent to the otherwise 

applicable 1-hour limit (reflecting a 

downward adjustment from the critical 

emissions value) and that takes the 

source’s emissions profile into account. 

As a result, the EPA expects either form 

of emission limit to yield comparable air 

quality. 

Second, from a more theoretical 

perspective, the EPA has compared the 

likely air quality with a source having 

maximum allowable emissions under an 

appropriately set longer-term limit, as 

compared to the likely air quality with 

the source having maximum allowable 

emissions under the comparable 1-hour 

limit. In this comparison, in the 1-houraverage-limit scenario, the source is 

presumed at all times to emit at the 

critical emission level, and in the 

longer-term average limit scenario, the 

source is presumed occasionally to emit 

more than the critical emission value 

but on average, and presumably at most 

times, to emit well below the critical 

emission value. In an ‘‘average year,’’ 

compliance with the 1-hour limit is 

expected to result in three exceedance 

days (i.e., three days with hourly values 

above 75 ppb) and a fourth day with a 

maximum hourly value at 75 ppb. By 

comparison, with the source complying 

with a longer-term limit, it is possible 

that additional exceedances would 

occur that would not occur in the 1- 

hour limit scenario (if emissions exceed 

the critical emission value at times 

when meteorology is conducive to poor 

air quality). However, this comparison 

must also factor in the likelihood that 

exceedances that would be expected in 

the 1-hour limit scenario would not 

occur in the longer-term limit scenario. 

This result arises because the longerterm limit requires lower emissions 

most of the time (because the limit is set 

well below the critical emission value). 

Therefore, a source complying with an 

appropriately set longer-term limit is 

likely to have lower emissions at critical 

times than would be the case if the 

source were emitting as allowed with a 

1-hour limit. 

The following hypothetical example 

illustrates the aforementioned points. 

Suppose there is a source that always 

emits 1000 pounds of SO2 per hour and 

these emissions result in air quality at 

the level of the NAAQS (i.e., a design 

value of 75 ppb).12 For this source, in 

an ‘‘average year’’, these emissions 

cause the five highest maximum daily 

average 1-hour concentrations to be 100 

ppb, 90 ppb, 80 ppb, 75 ppb, and 70 

ppb. Subsequently, the source becomes 

subject to a 30-day average emission 

limit of 700 (lb/hr). It is theoretically 

possible for a source meeting this limit 

to have emissions that occasionally 

exceed 1000 lb/hr, but with a typical 

emissions profile, emissions would 

much more commonly be between 600 

and 800 lb/hr. In this simplified 

example, assume a zero-background 

concentration, which allows one to 


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13A nonzero background concentration would 

make the mathematics more difficult but would 

give similar results. 

14For example, if the critical emission value is 

1000 pounds of SO2 per hour, and a suitable 

adjustment factor is determined to be 70 percent, 

the recommended longer-term average limit would 

be 700 pounds per hour. 

15The EPA published revisions to appendix W on 

January 17, 2017, 82 FR 5182. 

16 40 CFR 51.112(a)(1). 

17 40 CFR 51.112(a)(2); appendix W, section 3.2. 

assume a linear relationship between 

emissions and air quality.13 Air quality 

will depend on what emissions happen 

on what critical hours, but suppose that 

emissions at the relevant times on these 

five days are 800 lb/hr, 1100 lb/hr, 500 

lb/hr, 900 lb/hr, and 1200 lb/hr, 

respectively. (This is a conservative 

example because the average of these 

emissions, 900 lb/hr, is well over the 30- 

day average emission limit.) These 

emissions would result in daily 

maximum 1-hour concentrations of 80 

ppb, 99 ppb, 40 ppb, 67.5 ppb, and 84 

ppb. In this example, the fifth day 

would have an exceedance that would 

not otherwise have occurred, but the 

third and fourth days would not have 

exceedances that otherwise would have 

occurred. In this example, the fourth 

highest maximum daily concentration 

under the 30-day average would be 67.5 

ppb. 

This simplified example illustrates 

the findings of a more complicated 

statistical analysis that the EPA 

conducted using a range of scenarios 

using actual plant data. As described in 

Appendix B of the 2014 SO2 Guidance, 

the EPA found that the requirement for 

lower average emissions is highly likely 

to yield better air quality than is 

required with a comparably stringent 1- 

hour limit. Based on analyses described 

in appendix B of the 2014 SO2

Guidance, the EPA expects that an 

emission profile with maximum 

allowable emissions under an 

appropriately set comparably stringent 

30-day average limit is likely to have the 

net effect of having a lower number of 

exceedances and better air quality than 

an emission profile with maximum 

allowable emissions under a 1-hour 

emission limit at the critical emission 

value. 

The EPA must evaluate whether a 

longer-term average emission limit 

approach, which is likely to produce a 

net lower number of overall 

exceedances of 75 ppb even though it 

may produce some exceedances of 75 

ppb on occasions when emissions are 

above the critical emission value, meets 

the requirements in sections 110(a)(1) 

and 172(c)(1) and (6) for state 

implementation plans to ‘‘provide for 

attainment’’ of the NAAQS. For SO2, as 

for other pollutants, it is generally 

impossible to design a nonattainment 

plan in the present that will guarantee 

that attainment will occur in the future. 

A variety of factors can cause a welldesigned nonattainment plan to fail and 

unexpectedly not result in attainment 

(e.g., if meteorology occurs that is more 

conducive to poor air quality than was 

anticipated in the plan). Therefore, in 

determining whether a plan meets the 

requirement to provide for attainment, 

the EPA’s task is commonly to judge not 

whether the plan provides absolute 

certainty that attainment will in fact 

occur, but rather whether the plan 

provides an adequate level of 

confidence of prospective NAAQS 

attainment. From this perspective, in 

evaluating use of a 30-day average limit, 

the EPA must weigh the likely net effect 

on air quality. Such an evaluation must 

consider the risk that occasions with 

meteorology conducive to high 

concentrations will have elevated 

emissions leading to exceedances that 

would not otherwise have occurred, and 

it must also weigh the likelihood that 

the requirement for lower emissions on 

average will result in days not having 

exceedances that would have been 

expected with emissions at the critical 

emissions value. Additional policy 

considerations, such as in this case the 

desirability of accommodating realworld emissions variability without 

significant risk of violations, are also 

appropriate factors for the EPA to weigh 

in judging whether a plan provides a 

reasonable degree of confidence that the 

plan will lead to attainment. Based on 

these considerations, especially given 

the high likelihood that a continuously 

enforceable limit averaged over as long 

as 30 days, determined in accordance 

with the 2014 SO2 Guidance, will result 

in attainment, the EPA believes as a 

general matter that such limits, if 

appropriately determined, can 

reasonably be considered to provide for 

attainment of the 2010 SO2 NAAQS. 

The 2014 SO2 Guidance offers specific 

recommendations for determining an 

appropriate longer-term average limit. 

The recommended method starts with 

determination of the 1-hour emission 

limit that would provide for attainment 

(i.e., the critical emission value) and 

applies an adjustment factor to 

determine the (lower) level of the 

longer-term average emission limit that 

would be estimated to have a stringency 

comparable to the otherwise necessary 

1-hour emission limit. This method uses 

a database of continuous emission data 

reflecting the type of control that the 

source will be using to comply with the 

SIP emission limits, which may require 

use of an emission database from 

another source (e.g., if compliance 

requires new controls). The 

recommended method involves using 

these data to compute a complete set of 

emission averages, calculated according 

to the averaging time and averaging 

procedures of the prospective emission 

limitation. In this recommended 

method, the ratio of the 99th percentile 

among these long-term averages to the 

99th percentile of the 1-hour values 

represents an adjustment factor that may 

be multiplied by the candidate 1-hour 

emission limit to determine a longerterm average emission limit that may be 

considered comparably stringent.14 The 

guidance also addresses a variety of 

related topics, such as the potential 

utility of setting supplemental emission 

limits (e.g., mass-based limits) to reduce 

the likelihood and/or magnitude of 

elevated emission levels that might 

occur under the longer-term emission 

rate limit. 

Preferred air quality models for use in 

regulatory applications are described in 

appendix A of the EPA’s Guideline on 

Air Quality Models (40 CFR part 51, 

appendix W (‘‘appendix W’’)).15 In 

general, nonattainment SIP submissions 

must demonstrate the adequacy of the 

selected control strategy using the 

applicable air quality model designated 

in appendix W.16 However, where an air 

quality model specified in appendix W 

is inappropriate for the particular 

application, the model may be modified 

or another model substituted, if the EPA 

approves the modification or 

substitution.17 In 2005, the EPA 

promulgated the American 

Meteorological Society/Environmental 

Protection Agency Regulatory Model 

(AERMOD) as the Agency’s preferred 

near-field dispersion modeling for a 

wide range of regulatory applications 

addressing stationary sources (e.g., in 

estimating SO2 concentrations) in all 

types of terrain based on extensive 

developmental and performance 

evaluation. Supplemental guidance on 

modeling for purposes of demonstrating 

attainment of the SO2 standard is 

provided in appendix A to the 2014 SO2

Guidance. Appendix A provides 

extensive guidance on the modeling 

domain, the source inputs, assorted 

types of meteorological data, and 

background concentrations. Consistency 

with the recommendations in the 2014 

SO2 Guidance is generally necessary for 

the attainment demonstration to offer 

adequately reliable assurance that the 

plan provides for attainment. 

As stated previously, attainment 

demonstrations for the 2010 1-hour 


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27942 Federal Register / Vol. 83, No. 116 / Friday, June 15, 2018 / Proposed Rules 

18 ‘‘Applicability of Appendix W Modeling 

Guidance for the 1-hr SO2 National Ambient Air 

Quality Standard’’ (August 23, 2010). 

19See Appendix C to Miami SO2 Plan, ‘‘Modeling 

Technical Support Document for the Miami Sulfur 

Dioxide (SO2) Nonattainment Area’’ (Modeling 

TSD). 

20See letter from Farah Mohammadesmaeili, 

ADEQ, to Rynda Kay, EPA Region 9, dated March 

16, 2018. 

21The EPA has since approved AERMOD, with 

newly incorporated BLP algorithms, as the 

preferred model for buoyant line sources. See 82 FR 

5182. 

22 40 CFR 51.112(a)(2); Appendix W, section 3.2. 

23 Id. section 3.0(b). 

24Further details can be found in ‘‘Concurrence 

Request for Approval of Alternative Model: BLP/ 

AERMOD Hybrid Approach for Modeling Buoyant 

Roofline Sources at the FMMI Copper Smelter in 

Miami, AZ’’ (March 12, 2018). 

25 ‘‘Model Clearinghouse Review of a BLP/ 

AERMOD Hybrid Alternative Model Approach for 

Modeling Buoyant Roofline Sources at the FMMI 

Copper Smelter in Miami, AZ’’ (March 26, 2018). 

26See email from Farah Mohammadesmaeili, 

ADEQ, to Rynda Kay, EPA Region 9, dated March 

16, 2018. 

27 ‘‘EPA Meteorological Monitoring Guidance for 

Regulatory Modeling Applications.’’ Publication 

No. EPA–454/R–99–005 (February 2000). 

primary SO2 NAAQS must demonstrate 

future attainment and maintenance of 

the NAAQS in the entire area 

designated as nonattainment (i.e., not 

just at the violating monitor) by using 

air quality dispersion modeling (see 

appendix W) to show that the mix of 

sources and enforceable control 

measures and emission rates in an 

identified area will not lead to a 

violation of the SO2 NAAQS. For a 

short-term (i.e., 1-hour) standard, the 

EPA believes that dispersion modeling, 

using allowable emissions and 

addressing stationary sources in the 

affected area (and in some cases those 

sources located outside the NAA which 

may affect attainment in the area) is 

technically appropriate. This approach 

is also efficient and effective in 

demonstrating attainment in NAAs 

because it takes into consideration 

combinations of meteorological and 

source operating conditions that may 

contribute to peak ground-level 

concentrations of SO2.

The meteorological data used in the 

analysis should generally be processed 

with the most recent version of 

AERMET, which is the meteorological 

data preprocessor for AERMOD. 

Estimated concentrations should 

include ambient background 

concentrations, follow the form of the 

standard, and be calculated as described 

in the EPA’s August 23, 2010 

clarification memo.18

IV. Review of Modeled Attainment 

Demonstration 

The following discussion evaluates 

various features of the modeling that 

Arizona used in its attainment 

demonstration. 

A. Model Selection 

Arizona’s attainment demonstration 

used a combination of AERMOD and the 

Buoyant Line and Point Source model 

(BLP).19 The State used AERMOD 

version 14134 (‘‘v14134’’), the 

regulatory version at the time it 

conducted its nonattainment planning, 

for all emission sources except for those 

over the Freeport-McMoRan Miami 

Incorporated (FMMI) smelter (‘‘Miami 

Smelter’’ or ‘‘Smelter’’) building 

roofline. For AERMOD-only sources, the 

State used regulatory default options. To 

represent emissions from the Smelter 

roofline, the State used a combination of 

AERMOD v14134 and BLP (‘‘BLP/ 

AERMOD Hybrid Approach’’). BLP was 

used to estimate hourly final plume rise 

and sigma-z (a measure of vertical size 

of the plume), which were then used to 

define volume sources in AERMOD. The 

State later repeated the simulation using 

AERMOD version 16216r, the current 

regulatory version, and showed no 

difference in predicted annual 4th high 

daily SO2 hourly concentrations from 

the previous version.20

The copper smelting process produces 

large amounts of excess heat. Fugitive 

SO2 is released from the Miami Smelter 

building roofline at an elevated 

temperature and velocity, leading to 

enhanced plume rise. AERMOD v14134 

does not account for buoyant plume rise 

from line sources. At the time of 

preparation of the Miami SO2 Plan, BLP 

was identified in appendix W as the 

preferred model for representing 

buoyant line sources.21 As noted above, 

where an air quality model specified in 

appendix W is inappropriate for the 

particular application, the model may 

be modified or another model 

substituted if the EPA approves the 

modification or substitution.22

Appendix W also specifies that for all 

such approvals, the EPA regional office 

will coordinate and seek the 

concurrence of the EPA’s Model 

Clearinghouse.23 Arizona has sought 

approval to use the BLP/AERMOD 

Hybrid Approach under appendix W, 

paragraph 3.2.2(b), condition (2), which 

allows for use of an alternative model 

where ‘‘a statistical performance 

evaluation has been conducted using 

measured air quality data and the 

results of that evaluation indicate the 

alternative model performs better for the 

given application than a comparable 

model in appendix A.’’ The State 

provided a statistical performance 

evaluation using measured air quality 

data that demonstrates the alternative 

model performs better than the 

preferred model for this application. 

Additionally, the State provided 

technical justification for the validity of 

the approach for the meteorology and 

topography affecting this area. EPA 

Region 9 requested and received 

concurrence from the EPA’s Model 

Clearinghouse that the alternative model 

is appropriate for this particular 

application.24 25 For the reasons 

described in the concurrence 

documents, the EPA finds this selection 

appropriate and proposes to approve 

use of this alternative under 40 CFR 

51.112(a)(2). 

The modeling domain was centered 

on the Miami Smelter facility and 

extended to the edges of the Miami SO2

NAA. A grid spacing of 25 meters was 

used to resolve AERMOD model 

concentrations along the ambient air 

boundary surrounding the Smelter and 

increased toward the edges of the NAA. 

Receptors were excluded within the 

ambient air boundary, which is defined 

by the facility’s physical fence line, 

except in several segments where there 

is no fence and the State inspected and 

concluded steep topography precludes 

public access. We agree with the State’s 

conclusion that the model receptors 

placed by the State correspond to 

ambient air. 

B. Meteorological Data 

Arizona conducted its modeling using 

three years of on-site surface 

meteorological data collected by FMMI 

between 2010 and 2013 at a 30.5-meter 

tower located approximately 0.32 

kilometer (km) southwest of the 

Smelter. The State provided annual 

audit reports for the monitoring station 

to document that the station’s 

installation and data collection were 

consistent with the EPA 

recommendations.26 27 Cloud cover and 

relative humidity were not measured at 

the onsite location and were taken from 

the National Weather Service (NWS) 

station at Safford Airport (Weather 

Bureau Army Navy (WBAN) 93084), 

which is 132 km to the southeast of the 

Smelter and representative of cloud 

cover and relative humidity to the 

Miami SO2 NAA. The State used upper 

air data from the NWS station in 

Tucson, Arizona (WBAN 23160), which 

is 146 km south of the Smelter. The 

State used AERMET v14134 to process 

meteorological data for use with 

AERMOD and the Meteorological 


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28See ‘‘FmmiReponseToEpaReview—20160721— 

Final w Signature.pdf’’ and ‘‘FMMI—EmissionsInventory—2015–07–13—Past-Actuals-UsingSulfur-Balance.xlsx.’’ 

29See Appendix K of Modeling TSD. 

30See Appendix E of Modeling TSD. 

31See Appendix I of Modeling TSD. 

32See 57 FR at 13567–68. 

33See CAA section 302(k)(defining ‘‘emission 

limit’’ to include ‘‘any requirement relating to the 

operation or maintenance of a source to assure 

continuous emission reduction.’’). 

Processor for Regulatory Models for use 

with BLP. 

The State used AERSURFACE version 

13016 using data from the onsite 

location and the NWS Safford site to 

estimate the surface characteristics (i.e., 

albedo, Bowen ratio, and surface 

roughness (zo)). The State estimated zo

values for 12 spatial sectors out to 1 km 

at a seasonal temporal resolution for dry 

conditions. We conclude that the State 

appropriately selected meteorological 

sites, properly processed meteorological 

data, and adequately estimated surface 

characteristics. 

The State used the Auer (1978) land 

use method, with land cover data from 

the United States Geological Survey 

National Land Cover Data 1992 

archives, to determine that the 3-km 

area around the Miami Smelter is 

composed of 97.3% rural land types. 

Therefore, the State selected rural 

dispersion coefficients for modeling. We 

agree with the State’s determination that 

the facility should be modeled as a rural 

source. 

C. Emissions Data 

Arizona completed a modeling 

emissions inventory for sources within 

the Miami SO2 NAA and a 50-km buffer 

zone extending from the NAA boundary 

based on 2009–2011 data. In 2011, the 

Miami Smelter emitted 2,545 tpy SO2, 

accounting for more than 99.5% of SO2

emissions in the NAA. Other SO2

sources in the NAA include the Carlota 

Copper Pinto Valley Mine (2011 SO2

emissions of 32 tpy) and the Freeport 

McMoRan Miami Mine Smelter (2011 

SO2 emissions of 7 tpy), located 13 km 

and 3.3 km southwest of the Miami 

Smelter, respectively. No other sources 

had 2011 SO2 emissions greater than 1 

tpy SO2 in the NAA. The ASARCO LLC 

(ASARCO) copper smelter is located 46 

km south of the Miami Smelter and had 

2011 SO2 emissions of 21,747 tpy. The 

two smelters are separated by large 

mountains, making these two airsheds 

distinct. The State modeled the 

ASARCO stack emissions and 

determined that the modeled 

concentrations from that source were 

negligible in the Miami SO2 NAA. The 

State determined that other than the 

Miami Smelter, no sources were drivers 

of nonattainment. The State also 

determined that no other sources have 

the potential to cause significant 

concentration gradients in the vicinity 

of the Miami SO2 NAA affected by the 

Miami Smelter. Additionally, the State 

determined that all nearby sources are 

sufficiently captured by background 

monitored concentrations. We agree 

with the State’s determination that only 

Miami Smelter emissions need to be 

included in the attainment modeling. 

FMMI is undertaking substantial 

upgrades to the Smelter that will reduce 

SO2 and other pollutant emissions (see 

section 4.3 of the Miami SO2 Plan). The 

State estimated post-upgrade maximum 

1-hour SO2 emissions and used those 

estimates to model all facility emission 

sources subject to additional control. 

The State provided a justification for the 

control efficiencies assumed in the 

adjustments, which we reviewed and 

agree are reasonable.28 The State also 

modeled additional sources within the 

Smelter complex, including intermittent 

emergency generators, smelter building 

leaks, slag storage area, and other small 

sources, which will not be subject to 

further control. These sources 

collectively account for an additional 8 

pounds per hour (lb/hr) of SO2

emissions, which we agree were 

appropriately calculated.29 The 

resulting hourly emission rates used in 

the attainment modeling are shown in 

Table 1. Together these emissions 

accounted for a facility-wide critical 

emission value of 393 lb/hr (rounded to 

nearest whole number). The facilitywide critical emission value was used to 

derive a single facility-wide 30-day 

average emission limit, as described in 

section IV.D below. 

TABLE 1—PROJECTED MAXIMUM

SMELTER SO2 EMISSIONS AFTER

ADDITIONAL CONTROLS

Source 

SO2

Emissions 

(lb/hr) 

Acid Plant Tail Gas Stack .... 3.2 

Vent Fume Stack .................. 13.0 

Aisle Scrubber Stack—Normal Operations .................. 14.3 

Aisle Scrubber Stack—Bypass Operations ................ 275.0 

Isa Roof Vent ........................ 31.8 

ELF Roof Vent ...................... 14.2 

Converter Roof Vent ............. 25.6 

Anode Roof Vent .................. 8.0 

Additional Sources ................ 8.0 

Total .................................. 393 

The State asserts that a single facilitywide emission limit will adequately 

regulate emissions from each Smelter 

source. The State provided an analysis 

of the Smelter’s emissions variability, 

which showed that, due to the batch 

nature of the smelting process, 

emissions are independent of one 

another and therefore do not peak at the 

same time. This analysis indicates that 

the collection of future maximum 

potential emission rates for each source 

listed in Table 1 is a conservative 

estimate of the worst-case emission 

distribution at the Smelter.30

Additionally, the State conducted a 

sensitivity analysis increasing the 

modeled emission rate of each source 

(except the bypass stack) by 21%, while 

proportionally decreasing the emission 

rate of the remaining sources so that 

total facility-wide emissions remained 

constant.31 The resulting modeled 

design values were within 1% of those 

predicted by the attainment modeling 

and all below the NAAQS. These 

analyses suggest that variations in the 

location of peak emissions will not 

affect attainment so that a facility-wide 

limit would be sufficiently protective. 

We agree with the State that a facilitywide emission limit is appropriate in 

this case. 

The State also adequately 

characterized source parameters for the 

emissions described above, as well as 

the Miami Smelter’s building layout and 

location in its modeling. Where 

appropriate, the AERMOD component 

Building Profile Input Program for 

Plume Rise Model Enhancements 

(BPIPPRM) was used to assist in 

addressing building downwash. 

D. Emission Limits 

An important prerequisite for 

approval of a nonattainment plan is that 

the emission limits that provide for 

attainment be quantifiable, fully 

enforceable, replicable, and 

accountable.32 The numeric emission 

limit on which Arizona’s Plan relies is 

expressed as a 30-day average limit. 

Therefore, part of the review of 

Arizona’s Plan must address the use of 

longer-term average limits, both with 

respect to the general suitability of using 

such limits for this purpose and with 

respect to whether the particular 

numeric emission limit included in the 

Plan has been suitably demonstrated to 

provide for attainment. The first 

subsection that follows addresses the 

enforceability of the limits in the Plan 

(including both the numeric 30-day 

emission limit as well as operation and 

maintenance requirements, which also 

constitute emission limits),33 and the 


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27944 Federal Register / Vol. 83, No. 116 / Friday, June 15, 2018 / Proposed Rules 

34 83 FR 13716. 

35 ‘‘Technical Support Document for the EPA’s 

Rulemaking for the Arizona State Implementation 

Plan; Arizona Administrative Code, Title 18, 

Chapter 2, Article 13, Part C—Miami, Arizona, 

Planning Area; R18–2–C1302—Limits on SO2

Emissions from the Miami Smelter’’ (March 2018) 

(Rule C1302 TSD). 

36See Appendix K of the Modeling TSD. 

second subsection that follows 

addresses the 30-day limit in particular. 

1. Enforceability 

The emission limits for the Miami 

Smelter are codified in the Arizona 

Administrative Code, Title 18, Chapter 

2, Article 13, Section R18–2–C1302 

(‘‘Rule C1302’’). After following proper 

public notice procedures, Rule C1302 

was adopted by the State of Arizona 

through a final rulemaking in the 

Arizona Administrative Register. To 

ensure that the regulatory document 

was consistent with procedures for 

incorporating by reference, the EPA 

subsequently requested that ADEQ 

provide the version of this regulation 

that was codified in the Arizona 

Administrative Code as a supplement to 

the original SIP revision. 

Subsection (A)(2) of Rule C1302 

(‘‘Effective Date’’) states that, ‘‘(e)xcept 

as otherwise provided, the provisions of 

this Section shall take effect on the later 

of the effective date of the 

Administrator’s action approving it as 

part of the state implementation plan or 

January 1, 2018.’’ Accordingly, the 

majority of the rule’s requirements will 

come into effect upon final approval by 

the EPA of the rule. We proposed to 

approve Rule C1302 into the Arizona 

SIP on March 30, 2018 34 and we intend 

to finalize action on the rule prior to 

taking final action on the Miami SO2

Plan. 

Rule C1302’s 30-day rolling average 

emission limit of 142.45 lbs/hr applies 

to emissions from the tail gas stack, vent 

fume stack, aisle scrubber stack, and 

bypass stack, as well as any fugitives 

that may come from the roofline of the 

smelter structure. To ensure that all 

emission sources subject to the facilitywide limit are accurately monitored and 

reported, the rule also requires that 

continuous monitoring systems be 

installed on each of the aforementioned 

stacks and at the roofline to measure 

fugitive emissions. In addition, under 

subsection (E)(8) of Rule C1302, FMMI 

is required to develop and implement a 

roofline fugitive emissions monitoring 

plan for review and approval by ADEQ 

and the EPA. Furthermore, FMMI is 

required to develop and submit for EPA 

review and approval an Operations & 

Maintenance plan for capture and 

control systems at the smelter to ensure 

that these systems are functioning 

properly and are adequately maintained 

in order to minimize fugitive emissions. 

The rule also includes provisions for 

determining compliance with the 

emission limit, and the necessary 

monitoring, recordkeeping, and 

reporting requirements to ensure that 

the regulation as a whole is enforceable. 

As noted above, the EPA proposed to 

approve this regulation into the Arizona 

SIP in a separate action. Further 

discussion on the enforceability for Rule 

C1302 is included in the Technical 

Support Document (TSD) for that 

action.35

In accordance with EPA guidance on 

the use of federally enforceable limits, 

we find that the limits in Rule C1302 

will be enforceable upon our approval 

of the rule, are supportive of attainment, 

and are suitable for inclusion into the 

Arizona SIP. We also find that the 30- 

day average limit is set at a lower level 

than the critical emission value used in 

the attainment demonstration; this 

relationship is discussed in detail in the 

following section. 

2. Longer-Term Average Limits 

The State modeled emissions from the 

Miami Smelter as described in Section 

IV.C of this notice to determine a 

facility-wide critical emission value of 

393 lb/hr. Arizona demonstrated that 

the Smelter’s ‘‘Additional Sources’’ 

listed in Table 1, which account for 8 

lb/hr, have a negligible contribution to 

the predicted design value 

concentration and asserted that these 

emissions need not be a part of the 

facility’s enforceable emission limit.36

As such, Arizona used an adjusted 

critical emission value of 385 lb/hr (i.e., 

393 lb/hr minus 8 lb/hr) in the 

calculation of the facility’s longer-term 

average limit. 

To derive a longer-term average 

emission limit, the State used hourly 

SO2 data collected using continuous 

emission monitors from May 2013 to 

October 2014, adjusted to account for 

facility upgrades and increased 

production capacity, as a representative 

emission distribution for the Smelter’s 

future configuration. The State summed 

the emissions from all point and fugitive 

sources, which yielded the hourly 

emissions data that provided for 

calculation of the 30-day average 

emission rates used to determine an 

appropriate adjustment factor. The 99th 

percentile of the 30-day and 1-hour SO2

emission rates were 102.4 lb/hr and 

276.7 lb/hr, respectively. The ratio of 

these two values (i.e., the computed 

adjustment factor) was 0.37. Compared 

to the national average adjustment 

factors (i.e., 0.63–0.79) estimated for 

Electrical Generating Units (EGUs) and 

listed in Table 1 of Appendix D of the 

2014 SO2 Guidance, the ratio reflects the 

high variability in Smelter emissions. 

Although the adjustment factor is out of 

the range derived for EGUs, this is 

expected, as smelters exhibit a greater 

range of variability due to feed and 

operational variability. In general, we 

expect operations with large variability 

to require bigger adjustments (lower 

adjustment factors) and result in lower 

longer-term average emissions limits 

relative to the 1-hour critical emission 

value. The adjustment factor was 

multiplied by the adjusted critical 

emission value (i.e., 385 lb/hr) to derive 

a longer-term 30-day average emission 

limit of 142.45 lb/hr. Based on a review 

of the State’s submittal, the EPA 

believes that the 30-day average limit for 

the Miami Smelter provides a justified 

alternative to establishing a 1-hour 

average emission limit for this source. 

The 2014 SO2 Guidance does not 

directly address the establishment of 

limits governing the sum of emissions 

from multiple units, and the it provides 

no specific recommendations for a 

methodology for determining 

appropriate adjustment factors for 

deriving comparably stringent longerterm limits in such cases. Nevertheless, 

the 2014 SO2 Guidance recommends 

computing adjustment factors based on 

emissions data that have been 

determined in accordance with the 

methods used to determine compliance 

with the limit. Therefore, in this case, it 

is appropriate to use facility total 

emissions data as the basis for a 

statistical analysis of the degree of 

adjustment warranted in determining a 

30-day facility-wide emission limit that 

is comparably stringent to the plant total 

1-hour emission limit that would 

otherwise have been set. 

The State has used an appropriate 

data base and the methodology specified 

in the 2014 SO2 Guidance to derive an 

emission limit that has comparable 

stringency to the 1-hour average limit 

that the State determined would 

otherwise have been necessary to 

provide for attainment. While the 30- 

day average limit allows occasions in 

which emissions may be higher than the 

level that would be allowed with the 

1-hour limit, the State’s limit 

compensates by requiring average 

emissions to be lower than the level that 

would otherwise have been required by 

a 1-hour average limit. For reasons 

described above and explained in more 

detail in the 2014 SO2 Guidance, the 

EPA finds that appropriately set longerterm average limits provide a reasonable 

basis by which nonattainment plans 


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37See CAA section 172(c)(3). 

may provide for attainment. Based on 

our review of this general information as 

well as the particular information in 

Arizona’s Plan, the EPA finds that the 

30 day-average limit will provide for 

attainment of the SO2 standard in the 

Miami SO2 NAA. 

E. Background Concentrations 

Arizona selected background SO2

concentrations using ambient air 

measurements recorded between 2009 

and 2013 during Smelter shutdown 

periods at the Jones Ranch (Air Quality 

System (AQS) ID: 04–007–0011), 

Townsite (AQS ID: 04–007–0012) and 

Ridgeline (AQS ID: 04–007–0009) 

monitors. The State calculated the 

5-year averages of the daily maximum 

99th percentile 1-hour average SO2

during Smelter shutdowns at each site, 

which were 8.1, 6.7, and 7.2 ppb, 

respectively. The State chose to use the 

Jones Ranch value of 8.1 ppb (21.2 

micrograms per cubic meter (mg/m3)) as 

background concentrations of SO2 to 

add to modeled design values. We agree 

that the State appropriately and 

conservatively calculated background 

concentrations. 

F. Summary of Results 

The EPA has reviewed Arizona’s 

submitted modeling supporting the 

attainment demonstration for the Miami 

SO2 NAA and has preliminarily 

determined that this modeling is 

consistent with CAA requirements, 

appendix W and the 2014 SO2

Guidance. The State’s modeling 

indicates that with a critical emission 

value of 393 lb/hr, the highest predicted 

99th percentile daily maximum 1-hour 

concentration within the Miami SO2

NAA would be 194.1 mg/m3, below the 

NAAQS level of 196.4 mg/m3 (75 ppb). 

This modeled concentration includes 

the background concentration of SO2 of 

21.2 mg/m3. The modeling indicates that 

the Smelter upgrades and resulting 30- 

day emission limit of 142.45 lb/hr are 

sufficient for the Miami SO2 NAA to 

attain the 2010 SO2 NAAQS. 

V. Review of Other Plan Requirements 

A. Emissions Inventory 

The emissions inventory and source 

emission rate data for an area serve as 

the foundation for air quality modeling 

and other analyses that enable states to 

estimate the degree to which different 

sources within a NAA contribute to 

violations within the affected area and 

assess the expected improvement in air 

quality within the NAA due to the 

adoption and implementation of control 

measures. As noted above, the state 

must develop and submit to the EPA a 

comprehensive, accurate and current 

inventory of actual emissions from all 

sources of SO2 emissions in each NAA, 

as well as any sources located outside 

the NAA which may affect attainment in 

the area.37

The base year inventory establishes a 

baseline that is used to evaluate 

emission reductions achieved by the 

control strategy and to assess reasonable 

further progress requirements. Arizona 

used 2011 as the base year for emission 

inventory preparation. At the time of 

preparation of the Plan, 2011 reflected 

the most recent triennial National 

Emission Inventory, supported the 

requirement for timeliness of data, and 

was also representative of a year with 

violations of the primary SO2 NAAQS. 

Arizona reviewed and compiled actual 

emissions of all sources of SO2 in the 

NAA in the 2011 base year emission 

inventory. In addition to developing an 

emission inventory of SO2 emission 

sources within the NAA, Arizona also 

provided an SO2 emission inventory for 

those emission sources within a 50 

kilometer buffer zone of the NAA. Table 

2 below summarizes 2011 base year SO2

emissions inventory data for the NAA, 

categorized by emission source type 

(rounded to the nearest whole number). 

TABLE 2—2011 BASE YEAR SO2 EMISSION INVENTORY FOR THE MIAMI SO2 NAA 

[Tons/year] 

Year Point source Nonpoint 

source 

Mobile source 

(onroad) 

Mobile source 

(non-road) Total 

2011 ..................................................................................... 2,583 13 2 >1 2,598 

As seen above, the majority of SO2

emissions in the 2011 base year 

inventory can be attributed to the point 

source category. Emissions for this 

category are provided in further detail 

in Table 3 below. 

TABLE 3—2011 BASE YEAR SO2 EMISSION INVENTORY

[Point sources] 

Point source Emissions 

(tons/year) 

Freeport McMoRan Miami Smelter ............................................................................................................................................... 2,545 

Freeport McMoRan Miami Mine .................................................................................................................................................... 7 

BHP Copper Pinto Valley Miami Unit ............................................................................................................................................ >1 

BHP Copper Pinto Valley Mine ..................................................................................................................................................... >1 

Carlota Copper Pinto Valley Mine ................................................................................................................................................. 31 

Total ........................................................................................................................................................................................ 2,583 

A projected attainment year emission 

inventory should also be included in the 

SIP submission according to the 2014 

SO2 Guidance. This emission inventory 

should include, in a manner consistent 

with the attainment demonstration, 

estimated emissions for all SO2

emission sources that were determined 

to have an impact on the affected NAA 

for the projected attainment year. Table 

4 below summarizes Arizona’s projected 

2018 SO2 emissions inventory data for 

the NAA, categorized by source type. 

2011 base year emissions, as well as the 

projected change between base year and 

projected year emissions, are also 

summarized below (rounded to nearest 

whole number). 


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38Miami SO2 Plan, Section 3.1.1, page 33. 

39 Id., page 84. 

TABLE 4—PROJECTED 2018 SO2 EMISSION INVENTORY FOR THE MIAMI SO2 NAA 

[Tons/year] 

Year Point source Nonpoint 

source 

Mobile source 

(onroad) 

Mobile source 

(non-road) Total 

2011 ..................................................................................... 2,583 13 2 >1 2,598 

2018 ..................................................................................... 685 13 2 >1 700 

Change ................................................................................. ¥1,898 0 0 0 ¥1,898 

As seen above, both the majority of 

SO2 emissions in the projected 2018 

emission inventory, as well as the 

majority of projected SO2 emission 

reductions, can be attributed to point 

sources. Emissions for this category are 

provided in further detail in Table 5 

below. 

TABLE 5—PROJECTED 2018 SO2 EMISSION INVENTORY

[Point sources] 

Point source 

2011 

Base year 

emissions 

(tons/year) 

2018 

Projected 

year emissions 

(tons/year) 

Change 

Freeport McMoRan Miami Smelter ............................................................................................. 2,545 660 ¥1,885 

Freeport McMoRan Miami Mine .................................................................................................. 7 8 1 

BHP Copper Pinto Valley Miami Unit .......................................................................................... >1 >1 0 

BHP Copper Pinto Valley Mine ................................................................................................... >1 14 13 

Carlota Copper Pinto Valley Mine ............................................................................................... 31 3 ¥28 

Total ...................................................................................................................................... 2,583 685 ¥1,898 

As seen above, the single largest 

decrease in emissions is attributed to 

the Miami Smelter. The projected 2018 

SO2 emissions for the Miami Smelter are 

consistent with allowable emission 

limits for the Miami Smelter that 

Arizona is requesting that the EPA 

approve into the SIP. For other point 

sources, projected 2018 SO2 emissions 

were determined by Arizona based on 

existing permit allowable SO2 limits or 

other federally enforceable SO2

emission limits. 

The EPA has evaluated Arizona’s 

2011 base year inventory and projected 

2018 emission inventory for the Miami 

SO2 NAA, and considers these 

inventories to have been developed 

consistent with EPA guidance. As a 

result, the EPA is proposing to 

determine that the Miami SO2 Plan 

meets the requirements of CAA Section 

172(c)(3) and (4) for the Miami SO2

NAA. 

B. Reasonably Available Control 

Measures and Reasonably Available 

Control Technology 

Arizona’s Plan for attaining the 1-hour 

SO2 NAAQS in the Miami SO2 NAA is 

based on implementation of controls at 

the Miami Smelter. ADEQ conducted a 

reasonably available control measures 

and reasonably available control 

technology (RACM/RACT) analysis in 

the Miami SO2 Plan, comparing the 

requirements at the Miami Smelter with 

controls in use at other large sources of 

SO2 to identify potentially available 

control measures, eliminating any 

measures that were not feasible at the 

Miami Smelter or not more stringent 

than those measures already being 

implemented. ADEQ then compared the 

proposed control measures for the 

Miami Smelter with the measures not 

eliminated in the first step of the 

RACM/RACT analysis, and concluded 

that the proposed control measures 

would be more stringent. We provide an 

assessment below of whether ADEQ’s 

RACM/RACT analysis is consistent with 

EPA guidance. 

The State’s RACM/RACT analysis can 

be found in section 4.4.3 of the Miami 

SO2 Plan. ADEQ compared SO2 controls 

at eight different facilities and found 

that all of these units used an acid plant 

to recover or reduce SO2 emissions. 

Some of these facilities also used acid 

absorption equipment (wet and dry 

scrubbers) to further control SO2. ADEQ 

also noted that enhanced capture 

systems (such as additional hooding, 

improved ventilation systems and 

enhanced ductwork) at the Miami 

Smelter would contribute to reducing 

uncontrolled fugitive emissions from 

the smelter structure. While enhanced 

capture does not inherently reduce SO2

emissions, these capture systems will 

route a greater amount of gas to control 

devices that do reduce SO2 emissions. 

The State concluded that upgrades to 

the acid plant, the installation of 

additional and improved scrubbers, and 

the installation of improved capture 

systems at the IsaSmelt furnace, electric 

furnace, converter department, and 

anode casting operations at the Miami 

Smelter constituted RACM/RACT and 

would allow the facility to meet the 

142.45 lb/hr emission limit and other 

requirements outlined in Rule C1302. 

As explained in the Rule C1302 TSD, 

we agree that Rule C1302 generally 

requires implementation of reasonable 

controls for the Miami Smelter. We also 

find that it was appropriate for Arizona 

to focus its RACM/RACT analysis solely 

on this source, given that the Miami 

Smelter accounted for more than 99.5 

percent of SO2 emissions in the NAA 

during the 2011 base year.38

As noted above, most of the 

requirements of Rule C1302 will become 

enforceable only after final approval of 

the rule by the EPA. However, the Plan 

itself provides that the owner or 

operator of the Miami Smelter will 

complete construction of the relevant 

control measures no later than January 

1, 2018, including steps that ADEQ will 

undertake if the owner or operator failed 

to complete construction by January 1, 

2018.39 On December 19, 2017, FMMI 

notified the EPA and ADEQ that it had 

completed construction of the SO2

capture and control system upgrades 


sradovich on DSK3GMQ082PROD with PROPOSALS
Federal Register / Vol. 83, No. 116 / Friday, June 15, 2018 / Proposed Rules 27947 

40Letter from Byron Belew, FMMI, to Alexis 

Strauss, EPA, and Timothy Franquist, ADEQ 

(December 19, 2017). 41 80 FR 67319 (November 2, 2015). 42 83 FR 19631 (May 4, 2018). 

43See 40 CFR 52.120(e), Table 3. 

44 77 FR 66398 (November 5, 2012). 

45 40 CFR 93.150 to 93.165. 

46 40 CFR 93.159(b). 

47See 58 FR 3776 (January 11, 1993). 

and had initiated associated 

commissioning activities.40

As explained above, we find that 

Arizona has demonstrated that 

implementation of the control measures 

required under the Plan are sufficient to 

provide for attainment of the NAAQS. 

Given that these controls have already 

been installed and will be fully 

operational prior to October 4, 2018, we 

propose to conclude that the State has 

satisfied the requirement in section 

172(c)(1) and (6) to adopt and submit all 

RACM and emissions limitations and 

control measures as needed to attain the 

standards as expeditiously as 

practicable and the requirement in 

section 192(b) to provide for attainment 

by October 4, 2018. 

C. New Source Review 

On November 2, 2015, the EPA 

published a final limited approval and 

limited disapproval of revisions to 

ADEQ’s new source review (NSR) 

rules.41 On May 4, 2018, the EPA 

approved additional rule revisions to 

address many of the deficiencies 

identified in the 2015 action.42

Collectively these rule revisions will 

ensure that ADEQ’s rules provide for 

appropriate NSR for SO2 sources 

undergoing construction or major 

modification in the Miami SO2 NAA 

without need for further modification. 

Therefore, the EPA concludes that the 

NSR requirement has been met for this 

area. We note that Rule C1302 

subsection (I) indicates that the smelter 

emission limits contained in the rule 

shall be determined to be SO2 RACT for 

purposes of minor NSR requirements. 

This provision does not interfere with or 

adversely affect existing nonattainment 

NSR rules. 

D. Reasonable Further Progress 

In the Miami SO2 Plan, Arizona 

explained its rationale for concluding 

that the Plan meets the requirement for 

reasonable further progress (RFP) in 

accordance with EPA guidance. 

Specifically, Arizona’s rationale is based 

on EPA guidance interpreting the RFP 

requirement being satisfied for SO2 if 

the Plan requires ‘‘adherence to an 

ambitious compliance schedule’’ that 

‘‘implement[s] appropriate control 

measures as expeditiously as 

practicable.’’ Arizona noted that its Plan 

provides for attainment as expeditiously 

as practicable, i.e., by October 4, 2018, 

and finds that the Plan thereby satisfies 

the requirement for RFP. 

Arizona finds that the Miami SO2

Plan requires affected sources to 

implement appropriate control 

measures as expeditiously as practicable 

in order to ensure attainment of the 

standard by the applicable attainment 

date. Arizona concludes that the Plan 

therefore provides for RFP in 

accordance with the approach to RFP 

described in the 2014 SO2 Guidance. 

The EPA concurs and proposes to 

conclude that the Plan provides for RFP. 

E. Contingency Measures 

In the Miami SO2 Plan, Arizona 

explained its rationale for concluding 

that the Plan meets the requirement for 

contingency measures. Specifically, 

Arizona relies on the 2014 SO2

Guidance, which notes the special 

circumstances that apply to SO2 and 

explains on that basis why the 

contingency requirement in CAA 

section 172(c)(9) is met for SO2 by 

having a comprehensive program to 

identify sources of violations of the SO2

NAAQS and to undertake an aggressive 

follow-up for compliance and 

enforcement of applicable emissions 

limitations. Arizona stated that it has 

such an enforcement program pursuant 

to state law in Arizona Revised Statutes 

(ARS) sections 49–461, 49–402, 49–404 

and 49–406. Arizona also describes the 

process under State law to apply 

contingency measures for failure to 

make RFP and/or for failure to attain the 

SO2 NAAQS by the attainment date and 

concludes that Arizona’s Plan satisfies 

contingency measure requirements. The 

EPA concurs with this assessment. We 

note that the EPA has approved ARS 

49–402, 49–404, 49–406 and 49–461 

into the Arizona SIP.43 In addition, we 

have approved ARS 49–422(A) (‘‘Powers 

and Duties’’), which authorizes ADEQ to 

require sources of air contaminants to 

‘‘monitor, sample or perform other 

studies to quantify emissions of air 

contaminants or levels of air pollution 

that may reasonably be attributable to 

that source’’ for purposes of determining 

whether the source is in violation of a 

control requirement. We have also 

approved ARS 49–460 through 49–463, 

which authorize ADEQ to request 

compliance-related information from 

sources, to issue orders of abatement 

upon reasonable cause to believe a 

source has violated or is violating an air 

pollution control requirement, to 

establish injunctive relief, to establish 

civil penalties of up to $10,000 per day 

per violation, and to conduct criminal 

enforcement, as appropriate through the 

Attorney General.44 Therefore, we agree 

that the Arizona SIP establishes a 

comprehensive enforcement program, 

allowing for the identification of sources 

of SO2 NAAQS violations and 

aggressive compliance and enforcement 

follow-up. We propose to approve 

Arizona’s Plan as meeting the 

contingency measure requirement in 

this manner. 

VI. Conformity 

Generally, as set forth in section 

176(c) of the CAA, conformity requires 

that actions by federal agencies do not 

cause new air quality violations, worsen 

existing violations, or delay timely 

attainment of the relevant NAAQS. 

General conformity applies to federal 

actions, other than certain highway and 

transportation projects, if the action 

takes place in a nonattainment area or 

maintenance area (i.e., an area which 

submitted a maintenance plan that 

meets the requirements of section 175A 

of the CAA and has been redesignated 

to attainment) for ozone, particulate 

matter, nitrogen dioxide, carbon 

monoxide, lead, or SO2. The EPA’s 

General Conformity Rule establishes the 

criteria and procedures for determining 

if a federal action conforms to the SIP.45

With respect to the 2010 SO2 NAAQS, 

federal agencies are expected to 

continue to estimate emissions for 

conformity analyses in the same manner 

as they estimated emissions for 

conformity analyses under the previous 

NAAQS for SO2. The EPA’s General 

Conformity Rule includes the basic 

requirement that a federal agency’s 

general conformity analysis be based on 

the latest and most accurate emission 

estimation techniques available.46 When 

updated and improved emissions 

estimation techniques become available, 

the EPA expects the federal agency to 

use these techniques. 

Transportation conformity 

determinations are not required in SO2

nonattainment and maintenance areas. 

The EPA concluded in its 1993 

transportation conformity rule that 

highway and transit vehicles are not 

significant sources of SO2. Therefore, 

transportation plans, transportation 

improvement programs and projects are 

presumed to conform to applicable 

implementation plans for SO2.47

VII. The EPA’s Proposed Action 

The EPA is proposing to approve the 

Miami SO2 Plan, which includes 

Arizona’s attainment demonstration for 

the Miami SO2 NAA and addresses 

requirements for RFP, RACT/RACM, 


sradovich on DSK3GMQ082PROD with PROPOSALS
27948 Federal Register / Vol. 83, No. 116 / Friday, June 15, 2018 / Proposed Rules 

base-year and projected emission 

inventories, and contingency measures. 

The EPA proposes to determine that the 

Miami SO2 Plan meets applicable 

requirements of sections 110, 172, 191 

and 192 of the CAA for the 2010 SO2

NAAQS. 

The EPA is taking public comments 

for thirty days following the publication 

of this proposed action in the Federal 

Register. We will take all relevant 

comments into consideration in our 

final action. 

VIII. Statutory and Executive Order 

Reviews 

Under the CAA, the Administrator is 

required to approve a SIP submission 

that complies with the provisions of the 

Act and applicable Federal regulations. 

42 U.S.C. 7410(k); 40 CFR 52.02(a). 

Thus, in reviewing SIP submissions, the 

EPA’s role is to approve state choices, 

provided that they meet the criteria of 

the CAA. Accordingly, this proposed 

action merely approves state law as 

meeting Federal requirements and does 

not impose additional requirements 

beyond those imposed by state law. For 

that reason, this proposed action: 

• Is not a ‘‘significant regulatory 

action’’ subject to review by the Office 

of Management and Budget under 

Executive Order 12866 (58 FR 51735, 

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

January 21, 2011); 

• Is not an Executive Order 13771 (82 

FR 9339, February 2, 2017) regulatory 

action because SIP approvals are 

exempted under Executive Order 12866; 

• Does not impose an information 

collection burden under the provisions 

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, as 

appropriate, disproportionate human 

health or environmental effects, using 

practicable and legally permissible 

methods, under Executive Order 12898 

(59 FR 7629, February 16, 1994). 

In addition, 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. In those areas of 

Indian country, the rule does not have 

tribal implications and will not impose 

substantial direct costs on tribal 

governments or preempt tribal law as 

specified by Executive Order 13175 (65 

FR 67249, November 9, 2000). 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air 

pollution control, Incorporation by 

reference, Intergovernmental relations, 

Reporting and recordkeeping 

requirements, Sulfur oxides. 

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

Dated: June 4, 2018. 

Michael B. Stoker, 

Regional Administrator, EPA Region IX. 

[FR Doc. 2018–12913 Filed 6–14–18; 8:45 am] 

BILLING CODE 6560–50–P 


sradovich on DSK3GMQ082PROD with PROPOSALS