Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 30553 

D. Federalism and Indian Tribal 

Governments 

A rule has implications for federalism 

under Executive Order 13132, 

Federalism, if it has a substantial direct 

effect on the States, on the relationship 

between the national government and 

the States, or on the distribution of 

power and responsibilities among the 

various levels of government. We have 

analyzed this rule under that Order and 

have determined that it is consistent 

with the fundamental federalism 

principles and preemption requirements 

described in Executive Order 13132. 

Also, this rule does not have tribal 

implications under Executive Order 

13175, Consultation and Coordination 

with Indian Tribal Governments, 

because it does not have a substantial 

direct effect on one or more Indian 

tribes, on the relationship between the 

Federal Government and Indian tribes, 

or on the distribution of power and 

responsibilities between the Federal 

Government and Indian tribes. If you 

believe this rule has implications for 

federalism or Indian tribes, please 

contact the person listed in the FOR

FURTHER INFORMATION CONTACT section. 

E. Unfunded Mandates Reform Act 

The Unfunded Mandates Reform Act 

of 1995 (2 U.S.C. 1531–1538) requires 

Federal agencies to assess the effects of 

their discretionary regulatory actions. In 

particular, the Act addresses actions 

that may result in the expenditure by a 

State, local, or tribal government, in the 

aggregate, or by the private sector of 

$100,000,000 (adjusted for inflation) or 

more in any one year. Though this rule 

will not result in such an expenditure, 

we do discuss the effects of this rule 

elsewhere in this preamble. 

F. Environment 

We have analyzed this rule under 

Department of Homeland Security 

Directive 023–01 and Commandant 

Instruction M16475.1D, which guide the 

Coast Guard in complying with the 

National Environmental Policy Act of 

1969(42 U.S.C. 4321–4370f), and have 

determined that this action is one of a 

category of actions that do not 

individually or cumulatively have a 

significant effect on the human 

environment. This rule involves a safety 

zone lasting approximately three hours 

that will prohibit entry within 350 feet 

of a break wall at Kentucky Dam Marina 

in Gilbertsville, KY. It is categorically 

excluded from further review under 

paragraph L60(a) of Appendix A, Table 

1 of DHS Instruction Manual 023–01– 

001–01, Rev. 01. A Record of 

Environmental Consideration 

supporting this determination is 

available in the docket where indicated 

under ADDRESSES. 

G. Protest Activities 

The Coast Guard respects the First 

Amendment rights of protesters. 

Protesters are asked to contact the 

person listed in the FOR FURTHER

INFORMATION CONTACT section to 

coordinate protest activities so that your 

message can be received without 

jeopardizing the safety or security of 

people, places or vessels. 

List of Subjects in 33 CFR Part 165 

Harbors, Marine safety, Navigation 

(water), Reporting and recordkeeping 

requirements, Security measures, 

Waterways. 

For the reasons discussed in the 

preamble, the Coast Guard amends 33 

CFR part 165 as follows: 

PART 165—REGULATED NAVIGATION 

AREAS AND LIMITED ACCESS AREAS 

■ 1. The authority citation for part 165 

continues to read as follows: 

Authority: 33 U.S.C. 1231; 50 U.S.C. 191; 

33 CFR 1.05–1, 6.04–1, 6.04–6, and 160.5; 

Department of Homeland Security Delegation 

No. 0170.1. 

■ 2. Add § 165.T08–0239 to read as 

follows: 

§ 165.T08–0239 Safety Zone; Tennessee 

River, Gilbertsville, KY. 

(a) Location. The following area is a 

safety zone: All navigable waters of the 

Tennessee River at mile marker (MM) 23 

within a 350-foot radius from the 

fireworks launch site on the Kentucky 

Dam Marina break wall in Gilbertsville, 

KY. 

(b) Effective date. This section is 

effective from 6:50 p.m. through 10:10 

p.m. on June 30, 2018. 

(c) Regulations. (1) In accordance with 

the general regulations in § 165.23 of 

this part, entry into this zone is 

prohibited unless authorized by the 

Captain of the Port Sector Ohio Valley 

(COTP) or a designated representative. 

(2) Persons or vessels desiring to enter 

into or pass through the zone must 

request permission from the COTP or a 

designated representative. They may be 

contacted on VHF–FM Channel 16 or by 

phone at 1–800–253–7465. 

(3) If permission is granted, all 

persons and vessels must transit at their 

slowest safe speed and comply with all 

lawful directions issued by the COTP or 

a designated representative. 

(d) Informational broadcasts. The 

COTP or a designated representative 

will inform the public through 

Broadcast Notice to Mariners (BNMs) of 

the enforcement period for the safety 

zone as well as the date and time of 

enforcement. 

Dated: June 19, 2018. 

M.B. Zamperini, 

Captain, U.S. Coast Guard, Captain of the 

Port Sector Ohio Valley. 

[FR Doc. 2018–14020 Filed 6–28–18; 8:45 am] 

BILLING CODE 9110–04–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R06–OAR–2017–0435; FRL–9979– 

15—Region 6] 

Approval and Promulgation of 

Implementation Plans; Arkansas; 

Revisions to Minor New Source Review 

Program 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Final rule. 

SUMMARY: Pursuant to the Federal Clean 

Air Act (CAA or the Act), the 

Environmental Protection Agency (EPA) 

is approving revisions to the Arkansas 

State Implementation Plan (SIP) minor 

New Source Review (NSR) program 

submitted on July 26, 2010, and March 

24, 2017, including supplemental 

information provided on November 30, 

2015, May 26, 2016, July 5, 2017, July 

27, 2017, and March 16, 2018. 

Specifically, we are proposing to 

approve revisions that revise the minor 

NSR permitting thresholds and de 

minimis levels, as well as, additional 

non-substantive revisions contained in 

those submittals. This final action is 

consistent with the requirements of 

section 110 of the CAA. 

DATES: This rule is effective on July 30, 

2018. 

ADDRESSES: The EPA has established a 

docket for this action under Docket ID 

No. EPA–R06–OAR–2017–0435. All 

documents in the docket are listed on 

the http://www.regulations.gov website. 

Although listed in the index, some 

information is not publicly available, 

e.g., Confidential Business Information 

or other information whose disclosure is 

restricted by statute. Certain other 

material, such as copyrighted material, 

is not placed on the internet and will be 

publicly available only in hard copy 

form. Publicly available docket 

materials are available either 

electronically through http://

www.regulations.gov or in hard copy at 

the EPA Region 6, 1445 Ross Avenue, 

Suite 700, Dallas, Texas 75202–2733. 


sradovich on DSK3GMQ082PROD with RULES
30554 Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 

1Air Application Instructions available online at: 

https://www.adeq.state.ar.us/downloads/ 

WebDatabases/Air/PermitData/ 

Forms%20and%20Instructions/ 

Form%20and%20Instructions/Air_Permit_

Application_Forms_Instructions.pdf. 

FOR FURTHER INFORMATION CONTACT: 

Ashley Mohr, 214–665–7289, 

mohr.ashley@epa.gov. 

SUPPLEMENTARY INFORMATION: 

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

and ‘‘our’’ means the EPA. 

I. Background 

The background for this action is 

discussed in detail in our September 18, 

2017 proposal (82 FR 43506). In that 

document we proposed to approve 

revisions to the Arkansas SIP submitted 

on July 26, 2010, and March 24, 2017, 

including supplemental information 

submitted on November 30, 2015, May 

26, 2016, July 5, 2017, July 27, 2017, 

and March 16, 2018. The revisions 

addressed in our proposal included 

revisions to the Arkansas minor NSR 

permitting thresholds and de minimis 

levels, as well as, additional revisions to 

the minor NSR provisions that are 

considered to be non-substantive. 

We received one set of comments on 

the proposal. The full text of the 

comment letter received during the 

public comment period, which closed 

on October 18, 2017, is included in the 

publicly posted docket associated with 

this action at www.regulations.gov. 

Below the EPA provides a summary of 

the comments received and 

corresponding responses. 

II. Response to Comments 

Comment: The commenter stated that 

the revised minor NSR rule fails to 

provide legally enforceable procedures 

to ensure new sources that could 

interfere with NAAQS attainment or 

maintenance or violate the control 

strategy won’t be allowed to construct. 

More specifically, they stated that the 

minor NSR program does not explain 

how ‘‘actual emissions’’ are to be 

determined for a new source with no 

operational history. To the extent that 

Arkansas Department of Environmental 

Quality (ADEQ) determined 

applicability for new sources based on 

projected actual emissions, then the rule 

could ultimately allow sources with 

emissions greater than the permitting 

thresholds to construct without a permit 

and without evaluation of air quality 

impacts by a new source 

underestimating emission factors and/or 

operating parameters and exceeding 

those projected emissions after its 

construction. Therefore, the commenter 

stated it is unclear what size of sources 

could ultimately end up exempt from 

Arkansas’ minor NSR program. The 

commenter claims that because of the 

noted deficiencies there is a problem 

with any attempt to determine whether 

the revised minor NSR rule’s 

applicability thresholds are set to the 

appropriate level to ensure the state 

meets the applicable federal 

requirements found in CAA section 

110(a)(2)(C) and 40 CFR 51.160(b). 

Response: This comment is not 

relevant to our current rulemaking. As 

shown in Section IV of the Technical 

Support Document that accompanied 

our proposed approval action, our 

rulemaking only addresses revisions to 

the permitting thresholds values 

contained in Reg. 19.401. The 

applicability determination for the 

minor NSR program and its reliance on 

‘‘actual emissions’’ was not revised by 

Arkansas as part of the July 26, 2010, or 

May 24, 2017 SIP revision submittals. 

Therefore, the applicability 

determination as originally SIPapproved October 16, 2000 (65 FR 

61103) remains unchanged, is not a part 

of this rulemaking, and any comment on 

it is not relevant to the current 

rulemaking. 

While the comments regarding the 

applicability determination basis are not 

relevant to this rulemaking, we will 

respond to the commenter’s assertion 

that any attempt to determine if the 

revised minor NSR permitting 

thresholds meet the referenced federal 

requirements is problematic. We do not 

agree with this statement. As outlined in 

our proposed rulemaking, we evaluated 

several analyses submitted by Arkansas 

in support of the revised thresholds, 

including an emissions inventory 

analysis, a monitoring trends analysis, 

and a modeling analysis. Based on our 

evaluation of those analyses along with 

the SIP revisions submittals 

documentation (found in the Technical 

Support Document (TSD)), we find that 

the proposed thresholds will meet 

applicable federal requirements and not 

interfere with NAAQS attainment or 

maintenance or violate the control 

strategy. As required by Reg. 19.401, a 

source with actual emissions greater 

than the applicability thresholds would 

be required to obtain a permit and is 

subject to enforcement action if the 

source fails to do so. The emissions 

from a new source to be compared with 

the permitting thresholds would be 

based on controlled emission factors 

and projected operations (hours of 

operation and/or amounts of material 

processed). This approach allows 

permitting applicability to be based on 

emissions that are close to actual 

emissions. The regulation specifically 

does not allow construction and 

operation of sources with actual 

emissions in excess of the thresholds, 

and any source that did underestimate 

their emissions and exceed the 

emissions thresholds would be in 

violation of the regulations and beyond 

the scope of the analyses conducted to 

demonstrate the regulation’s compliance 

with applicable federal requirements for 

minor NSR programs. 

Comment: The commenter stated that 

the rule exempting de minimis changes 

at existing sources from permitting fails 

to provide legally enforceable 

procedures to ensure that modified 

sources that could interfere with 

NAAQS attainment or maintenance or 

violate the control strategy won’t be 

allowed to construct. More specifically, 

they stated a physical change or change 

in the method of operation at a source 

with no existing permit has no existing 

‘‘permitted rates’’ to compare ‘‘proposed 

permitted rates’’ to, and the rule does 

not explain how applicability is 

determined in such cases and the rule 

does not clearly say that it applies only 

to sources with existing permits. In 

addition, the commenter stated that Reg. 

19 does not clearly require a permit 

application for de minimis changes. 

Therefore, they claim that de minimis 

exemptions rule does not meet the 

requirements of 40 CFR 51.160(a) of 

providing legally enforceable 

procedures. 

Response: We do not agree that the 

applicability of the de minimis changes 

rule to existing sources with no permits 

is unclear. The de minimis change 

provisions are found in paragraph C of 

Reg. 19.407 of Arkansas’ ‘‘Minor Source 

Review’’ regulation (Reg. 19, Chapter 4). 

Reg. 19.407 is titled ‘‘Permit 

Amendments’’ and as stated in our 

original 2000 approval of Reg. 19.407 

(65 FR 26795; finalized at 65 FR 61103), 

this section describes the procedures for 

amending a permit. Because Reg. 19.407 

describes permit amendments, 

including de minimis changes, these 

provisions are not applicable to a source 

that does not have a permit. Existing 

sources with no existing permit would 

be subject to the minor NSR permitting 

thresholds found in Reg. 19.401 under 

the ‘‘General Applicability’’ section to 

determine if the source was subject to 

minor NSR permitting requirements. In 

addition to the clarity provided in the 

rule itself, the current ‘‘Air Application 

Instructions for Registrations, Minor 

Source Permits, or Title V Permits’’ 

made available on ADEQ’s air 

permitting website also indicates that de 

minimis applications are for ‘‘small 

modifications to a permit.’’ (Pg. 5) 1 Page 

12 of the application instructions 

reiterates the applicability of the de 


sradovich on DSK3GMQ082PROD with RULES
Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 30555 

2See Pages 31–32 of the EPA’s Technical Support 

Document dated August 24, 2017, which discusses 

the air quality modeling analyses that were 

completed by ADEQ in support of the submitted 

SIP revisions. In addition to the TSD, additional 

details regarding the modeling analyses are located 

in the modeling report submitted as part of the 

March 24, 2017 SIP revisions submittal, which 

outlines modeling tools and techniques utilized by 

Arkansas along with the results from the modeling 

analyses. (ADEQ’s modeling report located in the 

‘‘ADEQ 2010 Minor NSR Permitting Thresholds and 

De Minimis Levels SIP Revision—Technical 

Support Document’’ dated November 2015,) 

3A RRF is the ratio of future case modeled 

concentrations to base case modeled 

concentrations, which is used to quantify the 

relative impacts of the emissions added to the 

model. In the photochemical modeling conducted 

by ADEQ, the base case modeled concentrations are 

taken from the 2015 modeling without the 

hypothetical sources added while the future case 

modeling results are taken from the 2015 modeling 

plus the 8 modeled hypothetical sources. Therefore, 

the RRFs calculated in this modeling analysis 

quantify the relative impacts from the additional 

emissions from the hypothetical sources that would 

be exempt from permitting based on the new 

thresholds/de minimis levels. 

4RRFs can be used to estimate FDVs, which are 

determined by applying the RRF ratios to monitored 

design values from the base year taken from 

ambient monitoring data. 

minimis rule and states that a de 

minimis application ‘‘applies to 

facilities having a current air permits 

[sic].’’ Much like the de minimis change 

provisions in the rule, it is clear based 

on ADEQ’s current air permit 

application guidance that the de 

minimis change rule only applies to 

existing permitted facilities and not new 

facilities. 

The portion of the comment raised 

regarding permit application 

requirements for de minimis changes is 

not relevant to our current rulemaking. 

As shown in Section IV of the Technical 

Support Document that accompanied 

our proposed action, our rulemaking 

only addresses revisions related to de 

minimis changes that are found in Reg. 

19.407(C)(2)(a) and (b). Permit 

application requirements, which are 

found in Reg. 19.404, are currently SIPapproved and were not revised as part 

of the July 26, 2010, or May 24, 2017 SIP 

revision submittals under review in this 

rulemaking. Similarly, Reg. 19.407(C)(7) 

was not revised in the 2010 or 2017 SIP 

revision submittals. Therefore, the SIPapproved Reg. 19.404 and Reg. 

19.407(C)(7) provisions as most-recently 

approved on October 16, 2000 (65 FR 

61103) and April 12, 2007 (72 FR 

18394), respectively, remain unchanged 

and are not part of this rulemaking and 

any comment on those provisions is not 

relevant. 

Comment: The commenter claims that 

Arkansas has failed to adequately justify 

the basis for its revised emission 

thresholds for exempting new sources 

and de minimis changes from its minor 

NSR program. They state that 40 CFR 

51.160(e) requires states to identify the 

types and sizes of sources subject to its 

minor NSR program and to explain the 

basis for determining which facilities 

are subject to review. ADEQ’s 

justification for the emission thresholds 

adopted in its minor NSR program for 

Reg. 19, Chapter 4, was essentially that 

these tons per year thresholds were the 

same thresholds identified as ‘‘de 

minimis’’ under major NSR permitting 

programs. However, there has been no 

analysis with current modeling 

techniques that the major NSR 

significance levels are adequate to 

ensure a modified source won’t interfere 

with the attainment or maintenance of 

all of the various current NAAQS, 

which differ in stringency from the 

NAAQS applicable at the time the PSD 

significant emission rates were 

developed. The commenter also stated 

that the AERMOD (dispersion) modeling 

results, which they believe 

underestimate actual impacts, indicate 

that the pollutant concentrations 

resulting from the emissions exempt 

from permitting based on the revised 

thresholds are significantly higher than 

4% of the NAAQS, which was a 

threshold for the EPA’s analyses from 

1980, 1987, and 2008 for demonstrating 

that the significant emission levels were 

de minimis to the PSD program. 

Response: We do not agree with this 

comment. Although ADEQ did include 

the data referenced by the commenter in 

their initial 2010 SIP revision submittal, 

the basis for ADEQ’s findings regarding 

the appropriateness of the revised 

thresholds was different and they also 

provided additional analyses to 

demonstrate the scope of the exempt 

sources and modifications resulting 

from the revised minor NSR permitting 

thresholds and de minimis change 

levels and to demonstrate that the 

revised thresholds will not interfere 

with attainment or maintenance of the 

NAAQS. These analyses were included 

in their entirety in the March 24, 2017 

SIP revision submittal and included: (1) 

An emissions inventory analysis that 

determined the percentage of the total 

statewide emissions that were to be 

exempt under the revised minor NSR 

permitting thresholds and de minimis 

change levels; (2) a monitoring trends 

analysis that included a review of the 

current status of ambient air quality, as 

well as, the impacts of the revised 

thresholds on ambient concentration 

monitoring trends in the state of 

Arkansas; and (3) a modeling analysis 

that included photochemical and 

dispersion modeling analyses that 

evaluated the impacts of the revised 

thresholds through model predicted 

results. The air quality modeling 

analysis report included in Appendix D 

of the March 24, 2017 SIP submittal 

describes the modeling approach used 

by ADEQ as part of the demonstration 

showing that the revised minor NSR 

permitting thresholds and de minimis 

change levels will not adversely impact 

the current NAAQS. Based on our 

review of the modeling analysis, which 

did use current air quality modeling 

techniques, and the other analyses 

completed by ADEQ, we found that the 

impacts resulting from the revised 

minor NSR permitting thresholds and 

de minimis levels would not interfere 

with the state’s ability to maintain 

compliance with the NAAQS. 

As discussed in the Technical 

Support Document accompanying our 

proposed action, ADEQ conducted both 

regional scale photochemical modeling 

using CMAQ and local-scale dispersion 

modeling using AERMOD to examine 

the predicted impacts from sources or 

de minimis changes that would be 

exempt from minor NSR permitting 

based on the revised thresholds.2 ADEQ 

employed this combined modeling 

approach in an effort to look at both 

regional and local scale impacts from 

emissions equal to the revised 

thresholds for VOC, NOX, SO2, CO, 

PM10, and PM2.5. In both the regionaland local-scale modeling analyses, 

ADEQ modeled hypothetical sources 

with emissions equal to the minor NSR 

permitting and de minimis change 

thresholds and stack parameters set 

equal to median values based on the 

2011 National Emissions Inventory 

(NEI) for Arkansas sources. As part of 

photochemical modeling, the maximum 

CMAQ-derived impacts on daily 

maximum 8-hour ozone, 24-hour PM2.5,

annual average PM2.5, 1-hour NO2, 1- 

hour SO2, and 24-hour PM10 were 

calculated. The statewide maximum 

impacts for each day resulting from the 

hypothetical sources was added to the 

unmodified future year concentration 

for each day and grid cell. The resulting 

concentrations represented the worstcase ambient concentrations including 

impacts from the threshold emission 

increases at any location in Arkansas. 

These worst-case ambient 

concentrations were then used to 

calculate relative response factors 

(RRFs) to estimate future design values 

(FDVs) at both monitored and 

unmonitored locations throughout 

Arkansas.3 4 The FDVs were compared 

with FDVs without the thresholds 

increase impacts, as well as, the NAAQS 

in an effort to determine whether 

emissions increases less than the minor 

NSR thresholds would cause or 


sradovich on DSK3GMQ082PROD with RULES
30556 Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 

5As stated in our original SIP approval of Chapter 

4, ‘‘[a] minor source is any source which does not 

meet the requirements of a major source. The Act 

in section 302(j) defines the terms ‘‘major stationary 

source’’ and ‘‘major emitting facility’’ as ‘‘any 

stationary facility of source of air pollutants which 

directly emits, or has the potential to emit, one 

hundred tons per year of more of any air pollutant 

(including any major emitting facility or source of 

fugitive emissions of any such pollutant, as 

determined by rule by the Administrator).’’ 

contribute to NAAQS violations or 

potentially interfere with NAAQS 

maintenance. Similar to the regionalscale photochemical modeling, the 

hypothetical sources modeling in the 

near-field dispersion modeling analysis 

were modeled with emission rates equal 

to the minor NSR permitting thresholds 

and de minimis levels and stack 

parameters were set equal to median 

stack parameter based on the 2011 NEI 

data. The maximum AERMOD-derived 

impacts on daily maximum 1-hr NO2,

annual average NO2, daily maximum 1- 

hour SO2, daily maximum 1-hour CO, 

daily maximum 8-hour average CO, and 

24-hour average PM10 were calculated 

for each air quality control region. The 

daily AERMOD-derived concentrations 

were added to the CMAQ-derived 

concentrations for the same location, 

using the CMAQ values as 

‘‘background.’’ ADEQ stated that the 

values determined for the statewide 

daily maximum impacts are expected to 

represent the near-field concentrations 

assuming worst-case impacts from 

threshold emission increases at a range 

of locations through Arkansas. The daily 

maximum worst case AERMOD impacts 

were added to the unmodified future 

year concentration for each day and grid 

cell. The resulting concentrations 

represented the worst-case ambient 

concentrations including impacts from 

the threshold emission increases at any 

location in Arkansas. Similar to the 

CMAQ-only modeling analysis, the 

worse-case modeled impacts were used 

to calculate RRFs and FDVs. The 

calculated FDVs were compared with 

the original unmodified FDVs and the 

NAAQS in order to examine the 

potential impacts of the proposed minor 

NSR threshold emissions on NAAQS 

attainment and maintenance. The 

modeling conducted by Arkansas 

utilized current air quality modeling 

techniques to demonstrate that the 

predicted impacts resulting from 

emissions at or below the revised minor 

NSR permitting thresholds and de 

minimis change levels, which happen to 

be equal in magnitude to the major NSR 

significance levels, will not interfere 

with the attainment or maintenance of 

the NAAQS current in effect at the time 

of the analysis—including those that 

were not applicable at the time the PSD 

significant emission rates were 

developed. 

Further, the entirety of the additional 

analyses provided by ADEQ in the 

March 24, 2017 SIP revision submittal, 

including the NAAQS non-interference 

modeling demonstration, was the basis 

of the EPA’s finding that the revised 

thresholds were approvable. As such, a 

linkage to the PSD significant emission 

rate values and/or comparison of 

modeled impacts to percentage 

thresholds relied upon during the EPA’s 

development of the significant emission 

rates in 1980, 1987, and 2008 for the 

PSD program was not applicable to our 

proposed approval of the revised minor 

NSR permitting thresholds and de 

minimis levels. Elsewhere in this final 

rulemaking, we have addressed the 

comments specifically made regarding 

the modeling techniques used by 

Arkansas and restated our finding that 

those techniques were reasonable and 

appropriate for the NAAQS noninterference demonstration required by 

CAA section 110(l). 

Comment: The commenter stated that 

modified major sources exempted from 

major source permitting under the PSD 

program will also be exempt from minor 

source permitting under Arkansas’ de 

minimis changes rule and that the 

revised minor NSR program will not 

pick up the slack and ensure protection 

of the NAAQS as was intended when 

EPA promulgated the 2002 revisions to 

the major source NSR rules. 

Response: The commenter is incorrect 

that modifications to existing PSD major 

sources, which are exempt from PSD 

permitting, would be exempt from 

minor source permitting under the de 

minimis change rule. As discussed 

below, any change at an existing major 

NSR source (PSD source) is prohibited 

from using the de minimis change 

process because the de minimis change 

rule at Reg. 19.407(C) is located in 

Chapter 4 of Reg. 19, which does not 

apply to PSD sources or any 

modifications at those sources. 

The SIP-approved Arkansas NSR 

program is comprised of two types of 

review: ‘‘Minor Source Review’’ and 

‘‘Major Source Review’’. Arkansas 

operates a so-called ‘‘merged, one 

permit’’ system, which is divided into 

these two types of review based on 

whether a source is required to obtain 

a title V operating permit. As such, 

‘‘Minor Source Review’’, which is 

contained in Reg. 19, Chapter 4, applies 

only to those sources that are not subject 

to title V permitting and require only a 

title I NSR authorization.5 All sources 

that are subject to title V, which would 

include PSD sources, are subject to 

‘‘Major Source Review’’ under Reg. 26 

provisions incorporated by reference in 

Reg. 19, Chapter 11. Therefore, all 

permitting at PSD sources, including all 

modifications, would be subject to Reg. 

19, Chapter 11 ‘‘Major Source Review’’ 

under the Arkansas NSR permitting 

program and cannot use the de minimis 

change provisions, which are limited to 

‘‘Minor Source Review’’ in Chapter 4. 

Only those non-title V sources that are 

minor under the SIP-approved 

definition of minor source may qualify 

for the de minimis change exemption 

found in Reg. 19.407(C). As discussed in 

our proposed rulemaking and the 

accompanying TSD, the emissions 

inventory analysis for the de minimis 

changes found that the scope of changes 

expected to qualify for the de minimis 

change exemption is very small with 

emissions associated with those 

exempted changes making up a fraction 

of a percent of statewide emissions. The 

range of percentage of statewide 

emissions for the pollutants determined 

in the emissions inventory analysis for 

de minimis changes was 0.0005% to 

0.019%. At these levels it would require 

over 50 times the NOX emissions 

authorized in 2016 to approach 1% of 

the statewide emissions and over 300 

times the emissions for the other 

pollutants. 

The state did not rely solely on the 

emissions inventory analysis to 

demonstrate NAAQS compliance. This 

emissions inventory analysis was 

coupled with additional analyses 

specifically looking at ambient 

concentrations (monitoring trends 

analysis) and potential ambient impacts 

(modeling analysis) that were completed 

by ADEQ as part of the 110(l) 

demonstration. The results from the 

modeling analysis indicate that while 

the addition of the exempt emissions 

did result in slight increases in the 

model predicted impacts, it did not 

violate the NAAQS. As such, the 

modeling analysis portion of the 110(l) 

demonstration shows that revised minor 

NSR program will continue to ensure 

NAAQS protection. 

EPA’s intent at the time of 

promulgation of the 2002 revisions to 

the major source NSR rules is not 

relevant here. What is relevant here is 

the approvability of these revisions in 

the context of the current regulatory 

framework as promulgated. The 

commenter has not cited any ambiguous 

regulatory language in order to justify an 

examination of EPA’s intent. In the 

absence of any ambiguity in regulatory 

language it is not necessary to address 

EPA’s intent here as there is no dispute 

regarding interpretation on the 

applicable rules. 


sradovich on DSK3GMQ082PROD with RULES
Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 30557 

6Reg. 407(C)(2)(a) and (b) contain the de minimis 

change emissions and air quality impacts 

thresholds. 

Comment: The commenter stated that 

EPA has previously required minor NSR 

programs to use much smaller emission 

thresholds than the major modification 

significant impact levels and gave the 

example of the Montana minor NSR 

program includes a de minimis increase 

exemption threshold of 5 TPY, which 

was approved by EPA, after a 15 TPY 

threshold that was initially set by 

Montana was not approved by EPA into 

the SIP. 

Response: In the case of Montana, 

which was referenced by the 

commenter, the state did not provide an 

adequate demonstration to support the 

approval of the 15 TPY exemption 

threshold that was initially established 

by the state into the SIP. The state later 

revised the threshold to 5 TPY and 

submitted this threshold for SIP 

approval along with an analysis to show 

that the 5 TPY exemption would not 

interfere with NAAQS attainment or 

maintenance or violate the control 

strategy. Based on the revised submittal 

and supporting information, EPA 

approved the lower threshold of 5 TPY 

into the Montana SIP. Our proposed 

approval of the de minimis change 

levels in Arkansas does not contradict 

the previous Montana approval. In fact, 

our proposed approval mirrors the 

Montana SIP approval in that we 

requested analyses from Arkansas as 

part of the 110(l) demonstration for the 

revised de minimis change levels and 

our approval is based on those analyses 

as documented in the proposed 

rulemaking. Specifically, we found that 

Arkansas’ documentation adequately 

demonstrates that these revised 

thresholds will not interfere with 

NAAQS compliance. Our approval of 

one de minimis exemption threshold 

level in one state does not preclude the 

approval of a different threshold in 

another state. Each state’s universe of 

minor NSR sources, meteorology, and 

ambient air quality conditions are 

unique and influence the types of 

exemptions that would not interfere 

with the minor NSR program’s ability to 

meet the applicable federal 

requirements. 

Comment: The commenter stated that 

the de minimis change rule contradicts 

with how applicability is determined 

under PSD permitting requirements and 

thus fails to ensure projects that should 

be required to obtain a PSD permit will 

not be instead considered a de minimis 

change under Reg. 19.407(C). They also 

state that EPA must disapprove the 

current submittal and require Arkansas 

to revise its de minimis rule and 

relevant definitions rule to clearly state 

that changes that are considered major 

modifications under the PSD permitting 

regulations cannot be considered as de 

minimis changes. Without such 

language clearly stated, the Arkansas 

minor NSR program could allow sources 

that would otherwise be subject to PSD 

permitting to improperly avoid major 

source PSD permitting requirements for 

a major modification. The commenter 

also states that EPA must disapprove the 

version of Reg. 19.407(C) currently 

approved into the SIP which EPA has 

reopened with this action to the extent 

the provisions could interfere with 

compliance with the PSD permitting 

regulations. 

Response: We agree with the 

commenter that changes that are 

considered major modifications under 

the PSD permitting regulations cannot 

be considered as de minimis changes. 

However, the commenter is incorrect 

that the revisions to the de minimis 

change provisions will interfere with 

proper implementation of the PSD 

permitting requirements. As previously 

stated in our responses, the de minimis 

change rules contained in Chapter 4 of 

Reg. 19 cannot be used for any changes 

at PSD sources/modifications. 

Therefore, our proposed approval of 

revisions to Chapter 4, including the de 

minimis change rule, will not impact 

PSD permitting implementation. 

Changes that are considered major 

would be subject to permitting under 

Reg. 26 is incorporated by reference in 

Chapter 11, which utilizes an actual-toprojected actual test for modifications to 

existing units and an actual-to-potential 

test for new units, are not exempted 

from the requirements of Chapter 11 by 

the provisions we are approving in this 

rulemaking. As noted in Section IV of 

the TSD, we are not taking action on any 

portion of Chapter 11 and the 

requirements of that chapter, which 

mainly incorporate by reference the 

requirements of the federal PSD 

program at 40 CFR 52.21, remain in 

effect. 

Regarding the commenter’s statement 

that EPA should take action to 

disapprove Reg. 19.407(C) as it is 

currently approved into the SIP, aside 

from the revisions to 407(C)(2)(a) and 

407(C)(2)(b) which are clearly annotated 

in Section IV of the TSD, the other 

portions of Reg. 19.407 are not being 

revised by our current rulemaking.6

Therefore, the other SIP-approved 

portions of Reg. 19.407 will remain 

unchanged by our rulemaking. As 

previously stated in our responses, any 

comment on provisions that are not 

being revised as part of our rulemaking 

is irrelevant to this action. Further, our 

current rulemaking does not reopen the 

current SIP-approved and unchanged 

provisions for any action, including 

disapproval. 

Comment: The commenter stated that 

because the minor NSR revisions could 

allow for increased deterioration in air 

quality over PSD baseline concentration 

the EPA cannot approve such a SIP 

revision without a demonstration that it 

will not cause or contribute to a 

violation of the applicable PSD 

increment. The commenter listed the 

following as chances for increased 

deterioration resulting from the SIP 

revision: (1) The minor NSR SIP 

revisions submitted by ADEQ allow for 

an increase in allowable emission rates 

to occur under the de minimis 

provisions of Reg. 19.407(C)(7); (2) Reg. 

19.417 allows sources currently holding 

permits pursuant to Reg. 19 but whose 

emissions are below the permitting 

thresholds to submit a registration 

request under Reg. 18.315, which is a 

state-only rule and not part of the SIP, 

and request that their permit containing 

federally enforceable requirements be 

terminated; and (3) to the extent ADEQ 

ensures compliance with the PSD 

increment as part of its minor NSR 

program, the relaxation in the sizes of 

sources and modifications subject to 

minor NSR permitting also could allow 

increased deterioration of air quality 

above baseline concentration. The 

commenter also stated that the modeling 

analysis provided by ADEQ to support 

approval of the minor NSR relaxations 

included violations of the Class I and 

Class II PM10 increments that were 

predicted due to the increased 

emissions thresholds that would exempt 

from minor NSR review under the 

proposed SIP revision, which indicates 

that an unpermitted source pursuant to 

the expanded exemptions from 

Arkansas’ minor NSR could cause an 

exceedance of the PM10 increment. The 

commenter also stated that pursuant to 

CAA section 110(l) and 40 CFR 

51.166(a)(2), EPA cannot approve a SIP 

submittal which admittedly allows a 

violation of the PSD increments. 

Response: We agree with the 

commenter that the revisions to the 

Arkansas minor NSR program do allow 

larger increases in allowable emissions 

to be authorized via the de minimis 

change rule by increasing the de 

minimis change thresholds. We also 

agree that the revisions allow currently 

permitted sources with emissions that 

fall between the old minor NSR 

permitting thresholds and the revised 

permitting thresholds to submit a 

registration under Reg. 18.315 and 

request that their Reg. 19 permit be 


sradovich on DSK3GMQ082PROD with RULES
30558 Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 

terminated. However, the applicable 

legal test for determining approvability 

of these revisions, which revise the 

minor NSR program so that it becomes 

less stringent, is the requirement of CAA 

section 110(l), EPA cannot approve a 

revision to the SIP if it interferes with 

applicable requirements of the Act. The 

PSD increment requirement found at 40 

CFR 51.166(a)(2) is inapplicable here 

because it is required to be met by a 

major source/major modification 

application, not a minor NSR permitting 

application. The major source/major 

modification application must show 

that the PSD increment is not violated 

and the applicant’s modeling must 

include the emissions from all of the 

nearby minor sources, as well as any 

other nearby major sources. If the major 

source/major modification modeling 

shows the PSD increment will be 

violated by the proposed construction/ 

modification, then the major source/ 

major modification must reduce its 

requested emissions or obtain 

reductions from the other sources 

impacting the increment. Because the 

burden of not violating the PSD 

increment is placed on the source 

subject to PSD, the PSD increment 

requirement does not apply to a minor 

NSR permitting SIP. As stated 

previously in our responses to the 

commenter, the PSD increment 

requirements are contained in the PSD 

rules under 40 CFR 51.166 and apply 

only to sources subject to PSD. They do 

not apply to minor sources. Therefore, 

an increment analysis would only be 

required to be completed as part of a 

PSD permitting action (Reg. 19, Chapter 

9) and would be a separate analysis than 

that completed as part of the NAAQS 

demonstration. Further, the air quality 

modeling that was conducted by 

Arkansas was conducted for NAAQS 

compliance demonstration purposes as 

part of the 110(l) non-interference 

demonstration. (See the March 24, 2017 

SIP Revision Submittal, Appendix D— 

Air Quality Modeling Analysis of Minor 

Source Permit Thresholds.) Because the 

PSD increment analysis and NAAQS 

analysis serve separate and distinct 

purposes, these analyses use different 

modeling approaches and often different 

model inputs. Therefore, a modeling 

demonstration conducted for NAAQS 

compliance cannot be relied upon to 

make a modeled PSD increment analysis 

determination, such as if a PSD 

increment violation exists. Therefore, 

we do not agree with the commenter 

that the NAAQS modeling indicates that 

the proposed SIP revision allows a 

violation of the PSD increments. We 

also do not agree that the modeled PM10

impacts exceed the referenced 

increments because the state’s modeling 

analysis did not include a PSD 

increment analysis for comparison with 

the PSD increments to determine if a 

predicted exceedance occurred. In 

addition, we reiterate that a PSD 

increment analysis is not necessary as 

part of a 110(l) analysis to support 

revisions to a minor NSR permitting 

program, since the federal PSD 

increment analysis requirement at 40 

CFR 51.166(a)(2) is not applicable to 

minor NSR programs. 

Comment: The commenter stated that 

a comparison of emissions that could be 

exempt from the relaxed minor NSR 

with total statewide emissions across 

the state of more than 53,000 square 

miles does not give any indication of 

whether the exempted emissions would 

interfere with attainment or 

maintenance of the NAAQS or 

increments. As such, the commenter 

stated that the emissions comparison 

analysis does not provide information 

relevant to whether the relaxations to 

Arkansas’ minor NSR program will 

interfere with attainment or 

maintenance of the NAAQS or any other 

CAA requirement. 

Response: We do not agree with the 

commenter that the emissions inventory 

analysis for the emissions exempt from 

minor NSR permitting based on the 

revised permitting thresholds does not 

provide information that is relevant to 

the 110(l) analysis. This analysis serves 

to determine the scope, or portion of 

emissions that would not undergo 

minor NSR permitting requirements 

relative to the statewide emissions. The 

approach to determine the scope is 

independent of the physical size of the 

state since the emissions inventory 

analysis was conducted to compare 

exempt emissions with the statewide 

emissions inventory. As detailed in our 

proposed rulemaking the scope of 

emissions anticipated to be exempt from 

minor NSR permitting by the revised 

permitting thresholds was minimal. The 

pollutant-based emissions inventory 

analysis showed that the scope of 

emissions exempt from permitting based 

on the revised permitting thresholds 

ranged from 0.006% to 0.125% of the 

total statewide emissions. This analysis 

clearly demonstrates that the magnitude 

of emissions that would be exempt from 

minor NSR permitting program makes 

up an extremely small portion of the 

statewide emissions. The state did not 

rely solely on the emissions inventory 

analysis to demonstrate NAAQS 

compliance. This emissions inventory 

analysis was coupled with additional 

analyses specifically looking at ambient 

concentrations (monitoring trends 

analysis) and potential ambient impacts 

(modeling analysis) that were completed 

by ADEQ as part of the 110(l) 

demonstration. The modeling trends 

analysis looked specifically at the 

current status of ambient air quality and 

the trends in ambient concentrations 

since the 2008 state adoption and ongoing implementation of the revised 

minor NSR permitting thresholds. The 

modeling analysis examined the 

potential impacts of the exempt 

emissions on ambient air quality via 

local and regional air quality modeling. 

(See the March 24, 2017 SIP Revisions 

Submittal Appendix C—2010 Minor 

NSR Permitting Thresholds and De 

Minimis Levels SIP Technical Support 

Document and Appendix D—Air 

Quality Modeling Analysis of Minor 

Source Permitting Thresholds. 

Monitoring analysis is discussed on 

pages 3–17 of Appendix C. Modeling 

analysis is discussed on pages 17–25 of 

Appendix C and pages 1–35 of 

Appendix D.) Regarding interference 

with increments, we previously 

responded regarding the nonapplicability of PSD increment 

requirements to the 110(l) analysis 

completed for this rulemaking. 

Comment: The commenter stated that 

ADEQ’s emissions analysis was 

incomplete because it analyzed sources 

with allowable emissions less than the 

emission thresholds of Reg. 19.401 

when the exemptions for new sources 

are not based on ‘‘allowable emissions,’’ 

but instead are based on ‘‘actual 

emissions.’’ The commenter also 

claimed the analysis was incomplete 

because it does not project total 

emissions that might be exempt from 

minor NSR in the future and instead 

reflects on sources that may request 

permits to be revoked because they are 

no longer subject to minor NSR 

permitting requirements found in Reg. 

19, Chapter 4. 

Response: We do not agree with the 

commenter that the emissions inventory 

analysis conducted for the permitting 

thresholds exemptions was incomplete. 

In their analysis, ADEQ compiled a 

complete list of all currently permitted 

minor NSR sources and determined 

which currently permitted sources 

would not be required to obtain a permit 

based on the revised permitting 

thresholds. It is important to note that 

this analysis included the review of all 

currently permitted facilities in the 

minor NSR program which spanned the 

entirety of the program—meaning all 

active minor NSR permits that had been 

issued by ADEQ. EPA originally SIPapproved the Arkansas construction 

permitting requirements in October 


sradovich on DSK3GMQ082PROD with RULES
Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 30559 

7EPA originally approved the Arkansas 

requirements for permitting the construction of new 

and modified sources, which were contained in the 

Regulation of Plan (ROP) Section 4—Permits, on 

October 5, 1976, effective November 4, 1976. (41 FR 

43904) EPA later approved the recodification of the 

permitting requirements for minor sources from 

ROP Section 4 into Regulation 19, Chapter 4— 

Minor Source Review on October 26, 2000, effective 

November 15, 2000. (65 FR 61103) 

8 Ibid. 

9The Springdale ozone monitor was the only 

exception and showed increased DVs since 2008. 

ADEQ did further evaluation of the Springdale 

monitor and determined that the increase in the 

monitored ozone DVs at this monitor are likely due 

to the increase in mobile emissions in the 

Fayetteville-Springdale-Rogers MSA as a result of 

rapid population growth in that area (population 

grew by over 65,000 people in the 2007–2014 

timeframe. The monitoring trends analysis included 

in the March 24, 2017 SIP submittal indicated that 

the 2012–2014 DV at the Springdale monitor was 

67 ppb (as compared with the 2008 and 2015 O3

NAAQS of 75 and 70 ppb, respectively). 

10EPA’s review of the monitoring and modeling 

analyses is detailed in Pages 27–33 of the Technical 

Support Document that accompanied our proposed 

rulemaking and if available in the docket. 

1976 (effective November 1976).7 This 

means that ADEQ looked at all minor 

NSR permits that had ever been issued 

and were still active. To determine the 

percentage of emissions exempt from 

permitting, the permitted emission rates 

were totaled for each pollutant and 

compared with the total emissions from 

the statewide emissions inventory. The 

state’s analysis based on the permitted 

allowable emissions is more 

conservative than the use of actual 

emissions for those permitted sources 

since they represent the maximum 

permit allowable emissions for the 

particular source. In most cases, the 

actual emissions would be less than the 

allowable emissions because of actual 

operations at less than maximum levels 

during a given calendar year and 

because of non-operational periods that 

may have taken place. If the state had 

further refined their analysis to 

determine the historical actual 

emissions emitted by the currently 

permitted sources which would not be 

required to be permitted under the new 

thresholds and compared the total 

actual emissions with the total 

statewide emissions inventory, the 

actual emissions would be expected to 

make up an even smaller fraction of the 

total statewide emissions. 

As stated above, Arkansas conducted 

the emissions review as a part of the 

110(l) demonstration to determine the 

scope of emissions that were previously 

subject to minor NSR permitting that 

would be exempt from permitting under 

the revised thresholds. As stated above, 

Arkansas reviewed their entire minor 

NSR permitting universe, which 

included all active permits that had 

historically been issued by ADEQ, to 

determine the currently permitted 

emissions that would be exempt from 

minor NSR permitting under the revised 

permitting thresholds.8 They found that 

the magnitude of currently permitted 

emissions that would be exempt from 

minor NSR permitting was a fraction of 

a percent of the total emissions in the 

statewide emissions inventory. (The 

range of calculated percentages by 

pollutant was 0.006% to 0.125%.) While 

emissions will be exempt in the future, 

the emissions inventory analysis shows 

the percentage of statewide emissions 

that were exempt from permitting for 

the entire minor NSR program based on 

the revised permitting thresholds 

indicates that the magnitude of 

emissions exempt from minor NSR 

permitting in the future will continue to 

make up a small fraction of the total 

statewide emissions. In addition, the 

state’s regulations require that a source 

exempt from minor NSR permitting 

based on the new revised permitting 

thresholds but with emissions greater 

than the previous thresholds obtain a 

registration in accordance with Reg. 

18.315, which allows ADEQ to keep 

track of the sources exempt as a result 

of the new thresholds. In addition to the 

emissions inventory analysis, Arkansas 

provided additional analyses, both 

monitoring and modeling, to further 

show the limited potential impacts of 

the revised minor NSR permitting 

thresholds. The monitoring analysis 

examined statewide ambient air quality 

data since the adoption of the revised 

minor NSR permitting thresholds in 

2008 for CO, NOX, SO2, VOC, and PM10, 

including the examination of trends in 

design values (DVs). Since adoption of 

the revised thresholds, the DVs remain 

unchanged or show downward 

thresholds since the 2008 adoption of 

revised thresholds.9 The modeling 

analysis included regional-scale 

photochemical and local-scale air 

dispersion modeling to examine the 

potential impacts from emissions 

exempt from minor NSR permitting 

based on the revised thresholds. (See 

the March 24, 2017 SIP Revision 

Submittal, Appendix D—Air Quality 

Modeling Analysis of Minor Source 

Permit Thresholds.) As expected, both 

the regional and local modeling 

indicated some increases in model 

predicted concentration as a result of 

adding the exempt emissions into the 

modeled emissions inventory. However, 

for all pollutants and averaging period, 

the resulting ambient concentrations 

were less than the corresponding 

NAAQS. As stated in our proposed 

rulemaking, we find that the analyses 

submitted by Arkansas as part of the 

110(l) demonstration show that the 

revised thresholds will not interfere 

with attainment or maintenance of the 

NAAQS.10

Comment: The commenter stated that 

the emissions inventory analysis of the 

de minimis increases allowed (based on 

the 2016 de minimis approvals) is not 

persuasive because, the increased de 

minimis thresholds have not yet been 

approved as part of the SIP, and thus it 

is not reasonable to assume that all 

sources that might take advantage of this 

rule did take advantage of this rule in 

2016. The commenter also states that 

because the revised minor NSR 

permitting thresholds and de minimis 

levels have not been approved as part of 

the SIP, the state cannot infer anything 

in the monitoring trends analysis 

regarding the impacts of the revised 

minor NSR rules on air pollutant 

concentrations from reviewing past 

monitoring data and trends since it is 

likely that sources would be unwilling 

to rely on the revised values prior to SIP 

approval. 

Response: We do agree with the 

commenter’s claims that the SIP 

approval status of the revised minor 

NSR permitting thresholds and de 

minimis change levels impacts the 

validity or persuasiveness of the data 

included in the emissions inventory and 

monitoring trends analyses. While the 

revised de minimis change rule 

provisions are not approved into the 

current Arkansas SIP, they are adopted 

by the state into the state regulations 

and thereby state law. The CAA requires 

states to adopt, after reasonable notice 

and public hearings, revised regulations 

for submission to EPA as SIP revisions. 

(See CAA 110(a)(1)). Since adoption of 

the revised permitting thresholds and de 

minimis change levels into their states 

regulations, Arkansas has been 

implementing those revised levels 

through the issuance of Reg. 18 

registrations and de minimis change 

approvals. Lookback information 

regarding the historical de minimis 

change approvals was specifically cited 

in the emissions inventory analysis 

portion of the 110(l) demonstration. The 

calendar year (CY2016) de minimis 

change approvals included approval 

issued based on the revised thresholds 

that were adopted as state law December 

2008 (effective January 2009). ADEQ has 

subsequently provided more 

information regarding the number of 

Reg. 18 registrations (issued to those 

sources exempt from minor NSR 

permitting with emissions that fall 

within the old and revised permitting 


sradovich on DSK3GMQ082PROD with RULES
30560 Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 

11The number of Reg. 18 registrations submitted 

and de minimis change actions provided via emails 

received from Ms. Tricia Treece, ADEQ, on July 5, 

2017. 

12 Information regarding source inquiries to 

utilize SIP-approved thresholds instead of revised 

thresholds provided during telephone discussion 

between Ms. Ashley Mohr, EPA, and Mr. Thomas 

Rheaume and Ms. Tricia Treece, ADEQ, on March 

16, 2018. 

thresholds) submitted and de minimis 

change approvals issued since the 

adoption of the revised regulations. This 

additional lookback information clearly 

indicates that sources have been 

utilizing the revised thresholds—75 

registrations have been submitted since 

the permitting thresholds were revised 

and 476 de minimis change actions have 

taken place since 2010.11 Because state 

law requires that if a source used either 

the minor NSR permitting thresholds or 

de minimis changes levels to avoid 

minor NSR permitting the source must 

submit the required registration (in 

accordance with Reg. 19.417 and Reg. 

18.315) or obtain the required approval 

(in accordance with Reg. 19.407(C)(6)), 

a source not accounted for in the 

lookback information provided by 

ADEQ would have been, and still is, in 

violation of state law. Furthermore, 

ADEQ has indicated that since the 

adoption of the revised minor NSR 

permitting thresholds and de minimis 

change levels, they are not aware of any 

instance where a source has been 

unwilling to utilize the revised 

thresholds because of the status of the 

revisions with respect to the SIP.12

Based on the historical information 

provided, we find that the data included 

in the emissions inventory and 

monitoring trends analyses is valid and 

reflects the reality and do not agree with 

the commenter that nothing can be 

inferred from those analyses regarding 

the impacts of the revised minor NSR 

permitting thresholds and de minimis 

levels. Following adoption of the 

revised permitting thresholds and de 

minimis change levels in 2008, 

Arkansas began implementing the 

revised provisions (at the owner or 

operator’s own risk of federal 

enforcement) to exempt qualifying 

sources from minor NSR permitting 

requirements. The persuasiveness of 

data used in the monitoring trends 

analysis is not dependent on the SIP 

approval status. 

Comment: The commenter stated that 

the de minimis exemption is based on 

a comparison of allowable emissions 

increases, thus it could allow larger 

increases in actual emissions than the 

tpy emissions thresholds in Reg. 

19.407(C). Thus, the commenter states 

that any analysis, including the 

emissions inventory analysis, presented 

by ADEQ about the thresholds is not 

sufficient to ensure that the actual 

emissions increases allowed by the de 

minimis exemption will not threaten 

NAAQS attainment or maintenance or 

otherwise interfere with the control 

strategy. Similarly, the commenter also 

stated that the photochemical modeling 

also did not model the true increase in 

emissions that could be allowed—the 

actual emissions increases resulting 

from a de minimis change could be 

significantly higher than the de minimis 

levels and the actual emissions from a 

new source could exceed projected 

actuals that were used as a basis to 

exempt the source from permitting. 

Response: We do not agree with the 

commenter that the emissions inventory 

analysis and modeling analysis 

provided by ADEQ is not sufficient to 

support the proposed revisions to the de 

minimis change levels. Also, we do not 

agree with the commenters that the 

analysis provided by Arkansas did not 

model the true increase in emissions 

that could be allowed under Arkansas’ 

relaxed minor NSR program (i.e., those 

emissions exempt from minor NSR 

permitting requirements based on the 

revised permitting thresholds and de 

minimis change levels) under the 

revised minor NSR program. As stated 

in our proposed rulemaking, the de 

minimis change levels listed in Reg. 

19.407(C)(2)(a) are the maximum 

increases in permitted emission rates 

that can be exempt from minor NSR 

permitting requirements via the de 

minimis change rule. As such, to 

demonstrate that the proposed SIP 

revision resulting in revised de minimis 

change levels will not interfere with 

NAAQS compliance, it is reasonable 

that the 110(l) demonstration should 

evaluate the projected impacts resulting 

from the maximum emission increases 

allowed by the revised rule (i.e., the de 

minimis change levels). As documented 

in the modeling report submitted as part 

of the March 24, 2017 SIP revision 

submittal, Arkansas did follow this 

approach in their 110(l) demonstration 

and evaluated the impacts resulting 

from emission rates equal to the de 

minimis change levels. (See the March 

24, 2017 SIP Revision Submittal, 

Appendix D—Air Quality Modeling 

Analysis of Minor Source Permit 

Thresholds.) When a source seeks 

authorization for a proposed change at 

a facility via the de minimis change 

provision, they are requesting 

authorization specifically for the 

increase in the permitting emission 

rates. The previously permitted 

emission rates underwent a previous 

minor NSR permitting review and were 

demonstrated to be in compliance with 

the NAAQS. Evaluation of emissions 

accounted for in the pre-de minimis 

change permitted emission rates, which 

were previously authorized and 

evaluated for NAAQS compliance under 

an existing permit, are beyond the scope 

of the 110(l) analysis for the revised de 

minimis change levels. Therefore, a 

NAAQS demonstration associated with 

the potential impacts from a de minimis 

change should be based on the 

magnitude of increases in the permitted 

emission rates, which are being 

authorized via the de minimis change 

rule. With respect to the photochemical 

modeling, the purpose of the modeling 

analysis submitted by Arkansas was to 

demonstrate that those emissions 

exempt from permitting based on the 

revised thresholds would not cause a 

NAAQS violation. 

In the case of a new source that has 

actual emissions in excess of the minor 

NSR permitting thresholds without an 

issued permit authorizing those 

emissions, the source would be in 

violation of the minor NSR permitting 

requirements contained in Reg. 19, 

Chapter 4, and they could be subject to 

an enforcement action. For example, if 

a source was initially constructed as a 

seasonal source with emission below 

the de minimis levels, it is exempt from 

permitting. However, if the source’s 

actual emissions rise above those levels 

without first obtaining a permit, it 

would be in violation of minor NSR. It 

is reasonable (for the purposes of 

demonstrating compliance with 110(l)) 

to assume a new source would be 

required to obtain a permit to authorize 

the emissions and demonstrate they will 

not cause or contribute to a violation of 

a NAAQS if they have actual emissions 

above the minor NSR permitting 

thresholds. Therefore, the scenarios 

involving potentially violating sources 

are not a reasonable scenario to be 

included in an analysis conducted to 

support the minor NSR permitting 

thresholds. 

In the case of a de minimis change, 

the emissions exempt from minor NSR 

permitting by the de minimis change 

rule are the increases in the permitted 

emission rates. For the de minimis 

revisions to be approvable the analysis 

should demonstrate that the increases in 

the permitted emissions will not cause 

a NAAQS violation. By modeling the 

minor NSR permitting thresholds and 

de minimis change levels for each 

pollutant, Arkansas did evaluate the 

prospective impacts associated with the 

emission levels that could qualify for 

exemption from minor NSR permitting 

requirements under the revised rule. 


sradovich on DSK3GMQ082PROD with RULES
Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 30561 

Comment: The commenter stated that 

the analysis of the de minimis increases 

allowed (based on the 2016 de minimis 

approvals) is not persuasive because 

2016 only reflects one year of 

implementation and this rule will be in 

effect for the foreseeable future. 

Response: We do not agree with the 

commenter that the emissions inventory 

analysis for the de minimis changes is 

not persuasive because it is limited to 

2016. CY2016 provides a portion of time 

when the revised thresholds were being 

relied upon by owners and operators in 

Arkansas. The review of emissions 

associated with de minimis changes 

limited to CY2016 found that the 2016 

emissions inventory analysis shows the 

percentage of statewide emissions 

exempt by the de minimis change levels 

in the range of 0.0005 to 0.019%. While 

the analysis was limited to one calendar 

year, as discussed in our proposal, at 

these percentage levels it would require 

over 50 times the NOX emissions 

authorized in 2016 to approach 1% of 

the statewide emissions and over 300 

times the emissions for the other 

pollutants. In addition, this analysis 

conservatively did not account for any 

emissions decreases occurring as part of 

the approved de minimis changes. In 

addition, the analysis for 2016 was 

conservative in that it did not account 

for emissions decreases that did occur 

as part of the de minimis changes. We 

believe that additional analysis beyond 

one calendar year is unnecessary 

because the CY2016 data, that did not 

account for any associated emissions 

decreases, shows that exempt emissions 

makes up such a small fraction (much 

less than 1% for all pollutants) of the 

total statewide emissions. 

Comment: The commenter restates 

that a comparison of emissions that 

could be exempt from minor NSR 

permitting based on the revised de 

minimis change levels with total 

statewide emissions does not give any 

indication of whether the exempt 

emissions would interfere with 

attainment or maintenance of the 

NAAQS because of the various factors 

(such as: Stack parameters, operational 

stages, topography, and meteorology) 

that dictate ambient impacts. Because of 

the variability of these factors between 

sources, the commenter stated that the 

fact that two sources have similar 

annual emissions is not a rational basis 

to claim that they have similar ambient 

impacts. 

Response: We do agree with the 

commenter that a variety of factors may 

dictate ambient impacts, and that 

reliance on the state’s emissions 

inventory analysis does not demonstrate 

non-interference with the NAAQS. 

Instead, the emissions inventory 

analysis serves to determine the scope, 

or portion, of emissions that would not 

undergo minor NSR permitting based on 

the revised thresholds. However, the 

state did not only rely upon the 

emissions inventory analysis to 

demonstrate NAAQS compliance. The 

state addressed ambient concentrations 

and potential ambient impacts by 

looking specifically at the current status 

of ambient air quality, the historical 

ambient air quality trends since 

adoption in 2008 and the on-going 

implementation of the revised de 

minimis levels, and the potential 

impacts of the exempt emissions on 

ambient air quality via local dispersion 

(AERMOD) and regional photochemical 

(CMAQ) air quality modeling. As 

previously discussed in our responses, 

the monitoring analysis shows that 

since the adoption and implementation 

of the revised permitting thresholds and 

de minimis change levels the overall 

trends in DVs are either unchanged or 

decreasing. Meanwhile, the local and 

regional modeling analyses show that 

model predicted concentrations 

resulting from the addition of the 

emissions exempt from permitting 

remain less than the NAAQS. (See the 

March 24, 2017 SIP Revision Submittal, 

Appendix D—Air Quality Modeling 

Analysis of Minor Source Permit 

Thresholds.) While the emissions 

inventory analysis served to determine 

the scope, or portion of emissions that 

would not undergo minor NSR 

permitting requirements based on the 

revised de minimis change levels 

relative to the statewide emissions, the 

monitoring and modeling analyses 

completed as part of the 110(l) analysis 

accounted for the various factors cited 

by the commenter in evaluating the 

impacts of the revised de minimis 

levels. Specifically, the results from the 

air quality modeling analyses were 

impacted by the following factors, 

which are included as air quality model 

inputs: Emissions, stack parameters, 

topography and meteorology. 

Comment: The commenter stated that 

there are numerous other factors that 

came into play during the same 

timeframe that could cause pollutant 

concentrations to decrease in the 

timeframe right after the December 2008 

adoption of the minor NSR rule 

relaxations, including: The Great 

Recession began in 2007 and continued 

through 2009; natural gas prices 

dropped significantly and renewable 

sources of power generation became 

more competitive, reducing demand for 

coal-fired power plants which was 

replaced by gas turbines and 

renewables; various vehicle emission 

and liquid fuel standards came into 

effect; and less fuel efficient vehicles 

were replaced with more fuel efficient 

vehicles. The commenter stated that 

these factors make it very difficult for 

ADEQ to infer anything regarding the 

relaxations to its minor NSR program 

through the review of how air 

monitoring design values have changed 

over time. 

Response: We agree that the 

monitoring data reflects not only the 

impacts of the revised thresholds and de 

minimis levels, but other factors such as 

those cited by the commenter as well. 

However, the monitoring analysis does 

show that since Arkansas’ adoption in 

2008 and ongoing implementation of the 

revised values, the monitored ambient 

concentration data shows no NAAQS 

issues along with overall decreasing 

trends in DVs for some pollutants 

indicative of improved air quality since 

2008. The monitoring analysis 

submitted by Arkansas spanned eight 

years of ambient data (2007–2014, 

which includes and extends beyond the 

time period referenced as ‘‘the Great 

Recession’’ by the commenter). The 

8-year period covered in the ambient 

monitoring study is a reasonable and 

representative period of time to examine 

the impacts of the revised thresholds 

while also accounting for the variability 

in the other factors that may contribute 

to ambient concentrations. Further, we 

would like to point out that a NAAQS 

demonstration, including 

demonstrations of non-interference with 

attainment or maintenance of the 

NAAQS under section 110(l), should 

reflect ambient air quality as a whole, 

which would take into account the 

impacts on ambient concentrations 

resulting from the revised minor NSR 

regulations, as well as, the other factors 

mentioned by the commenter. As shown 

in the referenced monitoring analysis, 

the resulting ambient concentrations 

including the impacts from the minor 

NSR program revisions do not indicate 

NAAQS compliance issues. As stated in 

our proposal, the monitoring trends 

analysis is one part of the demonstration 

provided by Arkansas that supports the 

finding that the revised permitting 

thresholds and de minimis levels will 

not adversely impact NAAQS 

attainment or maintenance. In addition 

to the monitoring analysis, the modeling 

analysis is an important element of the 

NAAQS compliance demonstration and 

as discussed in our proposed 

rulemaking and previous responses, the 

modeling results indicate that the 

addition of the emissions exempt from 

minor NSR permitting requirements will 


sradovich on DSK3GMQ082PROD with RULES
30562 Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 

13EPA has set National Ambient Air Quality 

Standards for six principal pollutants, called 

criteria pollutants: Carbon Monoxide (CO), Lead 

(Pb), Nitrogen Dioxide (NO2), Ozone (O3), 

Particulate Matter (PM), and Sulfur Dioxide (SO2), 

as indicated in 40 CFR part 50 and appendices. 

14See 40 CFR part 58 and its appendices for 

federal requirements related to measuring ambient 

air quality and for reporting ambient air quality data 

and related information. 

15Arkansas’s initial statewide criteria pollutant 

modeling was conducted prior to 2015 using base 

case years of 2005 and 2008 and a future year of 

2015. The final modeling report detailing this initial 

modeling entitled ‘‘Criteria Pollutant Modeling 

Analysis for Arkansas’’ dated July 28, 2014 was 

included in the March 24, 2017 SIP revision 

submittal. Arkansas relied upon the 2015 modeling 

scenario from this statewide modeling as the 

baseline scenario in the minor NSR permitting 

thresholds and de minimis change levels modeling. 

They modified the 2015 emissions inventory to 

include the hypothetical source to represent the 

addition of emissions from a newly exempt 

emissions source based on the revised thresholds in 

order to examine the potential impacts and 

sensitivity of model predicted ambient 

concentrations to the exempt emissions. 

16A RRF is the ratio of future case modeled 

concentrations to base case modeled 

concentrations, which is used to quantify the 

relative impacts of the emissions added to the 

model. In the photochemical modeling conducted 

by ADEQ, the base case modeled concentrations are 

taken from the 2015 modeling without the 

hypothetical sources added while the future case 

modeling results are taken from the 2015 modeling 

plus the 8 modeled hypothetical sources. Therefore, 

the RRFs calculated in this modeling analysis 

quantify the relative impacts from the additional 

emissions from the hypothetical sources that would 

be exempt from permitting based on the new 

thresholds/de minimis levels. 

17RRFs can be used to estimate FDVs, which are 

determined by applying the RRF ratios to monitored 

design values from the base year taken from 

ambient monitoring data. 

18Arkansas applied the RRFs derived from the 

2015 baseline and 2015 baseline with hypothetical 

sources modeling analyses to calculated FDVs at all 

ambient monitoring locations for each pollutant. 

The difference between these FDVs represents the 

impacts from the hypothetical source emissions on 

ambient air quality. Appendix D of the March 24, 

2017 SIP revision submittal contains the details of 

this analysis including the calculated RRFs and 

FDVs. 

not interfere with NAAQS compliance. 

(See the March 24, 2017 SIP Revision 

Submittal, Appendix D—Air Quality 

Modeling Analysis of Minor Source 

Permit Thresholds.) 

Comment: The commenter stated that 

because the state does not have a 

monitoring network that covers all 

pollutants and all areas of the state 

where industrial sources are 

constructing and operating, a review of 

the monitoring data from Arkansas 

monitors provides an incomplete 

picture of the NAAQS attainment status 

around the state. 

Response: We do not agree that 

Arkansas’ submittal provided an 

incomplete picture of NAAQS 

attainment around the state. The 

ambient monitoring analysis was one 

part of the demonstration provided by 

the state to meet the 110(l) requirement. 

The monitoring trends analysis 

discussion included in Appendix C of 

the March 24, 2017 SIP revision 

submittal includes a figure showing the 

Arkansas Ambient Air Monitoring 

Network. This network includes 

ambient monitoring for the NAAQS 13 at 

monitoring sites located throughout the 

state in accordance with federal 

requirements.14 The State of Arkansas’ 

ambient air monitoring network is 

reviewed each year to ensure the air 

quality surveillance system continues to 

meet applicable requirements. The most 

recent review of the ambient air 

monitoring network for Arkansas, the 

2017 Annual Monitoring Network Plan, 

was reviewed and approved by EPA on 

October 3, 2017, as meeting the 

requirements of 40 CFR and its 

appendices. The analysis of the 

available monitoring data does provide 

valuable information about the current 

ambient air quality in the state, and the 

historical trends analysis of the data 

shows that since the adoption in 2008 

and the ongoing implementation of the 

revised exemption thresholds, ambient 

air quality has not been adversely 

impacted. In fact, as discussed in our 

proposed rulemaking, for several 

pollutants the ambient air quality has 

shown continued improvements since 

the state adoption and implementation 

of the revised thresholds. This 

information was supplemented by the 

additional analyses conducted by 

Arkansas, one of which specifically 

addresses the comment regarding the 

completeness of the picture of 

attainment status around the state. As 

discussed in our proposed rulemaking, 

Arkansas completed a modeling 

analysis to determine the potential 

impacts from sources exempt from 

permitting based on the revised minor 

NSR permitting thresholds and de 

minimis change levels, which included 

statewide modeling. (See the March 24, 

2017 SIP Revision Submittal, Appendix 

D—Air Quality Modeling Analysis of 

Minor Source Permit Thresholds.) 

Arkansas conducted photochemical 

modeling to support the revised 

thresholds based on a previous 

statewide modeling effort conducted for 

the 2008 base year and the 2008/2015 

future year scenarios. For the minor 

NSR thresholds analysis, the future year 

(2015) emissions inventory was 

modified to include eight hypothetical 

point sources that were distributed 

throughout the state’s Air Quality 

Control Regions. The emission rates for 

each of the hypothetical sources were 

set equal to the revised minor NSR 

permitting thresholds and de minimis 

levels. The statewide maximum impacts 

for each day resulting from the 

hypothetical sources was added to the 

unmodified future year concentration 

for each day and grid cell. The resulting 

concentrations represented the 

maximum ambient concentrations 

including impacts from the threshold 

emission increases at any location 

located throughout Arkansas. While the 

results from the photochemical 

modeling showed that while the 

addition of the hypothetical source 

emissions may increase the predicted 

concentrations within most grid cells, 

the calculated FDVs were still less than 

each of the NAAQS at each monitoring 

site. (See the March 24, 2017 SIP 

Revision Submittal, Appendix D—Air 

Quality Modeling Analysis of Minor 

Source Permit Thresholds.) 

Comment: The commenter stated that 

it is not appropriate to rely on a 

modeling assessment intended to 

estimate future pollutant concentrations 

out to 2015 to assess whether Arkansas’ 

relaxed minor NSR program will 

interfere with attainment or 

maintenance of the NAAQS. The 

commenter based their statement on the 

possibility that some of the rules that 

were relied on for the 2015 emission 

inventories could go away, the 

possibility of an economic boom in the 

state, the possibility of growth in a 

certain type of industry, or a 

combination of these events, which in 

turn could result in the approval of this 

SIP relaxation interfering with 

attainment or maintenance of the 

NAAQS in the future despite the CMAQ 

(photochemical) modeling predictions 

for 2015. 

Response: We do not agree with the 

commenter that the use of the future 

year (FY) modeling for 2015 is not 

appropriate.15 Arkansas submitted 

several analyses as part of the 110(l) 

demonstration, with the modeling 

assessment being one part of the 

demonstration submitted to support the 

proposed revisions to the Arkansas SIP. 

As such, our determination regarding 

the approvability of the SIP revisions 

relied on the combined demonstration 

and not just one element. Regarding the 

use of the future year modeling, 

Arkansas used this modeling in 

combination with the baseline modeling 

to determine RRFs both with and 

without the hypothetical exempt 

sources to calculate FDVs) 16 17 18 These 

FDVs were used to compare and 

contrast those DVs and determine the 

potential impacts of the exempt sources. 

This approach allowed for a quantitative 

comparison to determine what potential 

impacts would be expected from the 


sradovich on DSK3GMQ082PROD with RULES
Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 30563 

19The methodology used by Arkansas to develop 

the modeled future year 2015 emissions inventory 

is detailed in Section 3.6 of the ‘‘Criteria Pollutant 

Modeling Analysis for Arkansas’’ report provided in 

Appendix D of the March 24, 2017 SIP revision 

submittal. The 2015 emissions inventory was 

assumed equal to the 2014 emissions inventory 

with no further adjustments that were prepared 

based on as part of the EPA’s 2005-based platform, 

which included future year cases developed from 

it, that was used in the Final Transport Rule 

modeling (available at ftp://ftp.epa.gov/ 

EmisInventory/2005v4_2/). Arkansas did adjust the 

emissions inventory to include a new facility (AEP 

Service Corporations’ John W. Turk, Jr. facility 

located in southwestern Arkansas. 

additional emissions associated with 

sources and/or de minimis changes that 

would be exempt from minor NSR 

permitting requirements based on the 

revised thresholds. The quantitative 

comparison provided information 

regarding relative difference in impacts 

both with and without the newly 

exempt emissions compared with the 

NAAQS. When conducting future year 

modeling, informed assumptions must 

be made and some of these assumptions 

may differ from the actual real world 

conditions present when the future year 

becomes the present.19 However, it is 

important to note that the future year 

modeling approach was conducted in 

order to quantify the relative change in 

ambient concentrations resulting from 

the added potential impacts from the 

newly exempt sources using RRFs. 

Specifically, this analysis results in the 

calculation of FDVs both with and 

without the hypothetical source 

emissions and the difference between 

the FDVs represents the modeled 

predicted impacts from those emissions 

on ambient concentrations. The results 

of this quantitative comparison of 

ambient impacts with and without the 

newly exempt sources are not expected 

to deviate significantly, even with actual 

real world conditions potentially being 

different than the assumed modeled 

conditions, since the analysis focused 

on the relative impacts of the addition 

of the hypothetical source emissions. 

We believe that the future year 

modeling approach used by Arkansas 

that focused on the quantitative 

difference in the relative ambient 

impacts with and without the 

hypothetical sources is reasonable and 

informative for a 110(l) demonstration 

in that it specifically evaluated the 

impacts from newly exempt emissions 

based on revised minor NSR permitting 

thresholds and de minimis levels. The 

concerns raised by the commenter 

regarding the state’s ability to predict 

the exact conditions of a future year do 

not change our determination that this 

approach is reasonable. In fact, the 

inclusion of informed assumptions in a 

future year modeling analysis is not 

only reasonable, but also necessary, 

since neither we nor Arkansas can know 

with any certainty what emissions and/ 

or sources may change in the future. 

The inclusion of informed assumptions 

in the modeling analysis provides a 

reasonable estimate of future levels, 

given the inability to foresee the future. 

If ADEQ modified or removed any SIPapproved regulations (as relied upon to 

make these assumptions) and relax the 

SIP and render them substantially 

inadequate to attain or maintain the 

relevant NAAQ’s standard, EPA has the 

authority to publish a SIP call Federal 

Register notice requiring the state to 

adopt and submit a 110(l) justification 

for the relaxation. Regarding the 

commenter’s concern with potential 

boom in industrial growth, those 

sources seeking a construction permit, 

such as a PSD permit, would have to 

demonstrate NAAQS compliance as part 

of their permit application modeling. As 

such, we find that the state’s analysis 

based on future year photochemical 

modeling, along with the additional 

modeling, monitoring, and emissions 

inventory analyses, demonstrate that the 

revised thresholds are not expected to 

adversely impact the state’s ability to 

attain and maintain the NAAQS. 

Comment: The commenter stated that 

photochemical modeling submitted by 

Arkansas in support of the SIP revisions 

does not give a rational picture of the 

effect the SIP relaxations could have on 

air quality in Arkansas. The commenter 

stated that first, there could clearly be 

more than 8 sources, which was the 

number of sources included in the 

photochemical modeling, exempt from 

permitting under the revised minor NSR 

rules. The commenter also stated that 

the photochemical modeling did not 

model the worst case conditions such as 

terrain, stack height, stack temperature 

and velocity. 

Response: While we agree with the 

commenters that the potential number 

of exemptions resulting from the revised 

rule may not be limited to 8 sources, we 

do not agree with their assessment that 

the modeling analysis was limited to the 

impacts from only those 8 sources. 

Arkansas submitted statewide modeling 

that accounted for cumulative impacts 

from the 8 hypothetical sources along 

with the emissions contained in the 

statewide emissions inventory. (See the 

March 24, 2017 SIP Revision Submittal, 

Appendix D—Air Quality Modeling 

Analysis of Minor Source Permit 

Thresholds.) The 8 modeled sources 

were distributed throughout the state’s 

Air Quality Control Regions. The 

modeling results showed the impacts of 

the addition of these eight hypothetical 

sources to the predicted ambient 

concentrations. In addition, the 

modeling extrapolated for the maximum 

modeled impacts from the hypothetical 

sources applied at each modeled grid 

cell throughout the state. In addition to 

examining the modeled impacts from 

these 8 hypothetical sources in their 

chosen locations in the Air Quality 

Control Regions, the modeling analysis 

conducted by Arkansas also looked at 

the impacts of sources with emissions 

equal to the revised thresholds 

throughout the state. This analysis was 

accomplished by determining the 

statewide maximum modeled impacts 

in the photochemical modeling for each 

day resulting from the hypothetical 

sources and adding those impacts to the 

unmodified future year concentration 

for each day and grid cell. This 

approach allowed the examination of 

the maximum predicted hypothetical 

source impacts combined at different 

geographic/topographic locations along 

with looking at those impacts combined 

with a variety of cumulative source 

inventory impacts throughout the state. 

It is impossible for the state to project 

each source that may be exempt under 

the revised rule and unreasonable to 

expect the inclusion of every potentially 

exempt source within an air quality 

modeling analysis. We determined that 

the approach used by Arkansas to 

include a number of hypothetical 

sources throughout the state and to 

examine the combined impacts of these 

sources with background emissions 

sources at each modeled grid cell in 

Arkansas provides information and a 

rational picture regarding the potential 

impacts of newly exempt emissions 

throughout the state. By modeling these 

8 hypothetical sources with emission 

rates equal to the revised thresholds, the 

state’s approach provided for the 

examination of the actual model 

predicted impacts at locations within 

each Air Quality Control Region from 

the maximum level of emissions that 

could be exempt from permitting for a 

source based on the revised minor NSR 

permitting thresholds and de minimis 

change levels. As a second step, the 

approach to apply the daily maximum 

modeled impacts from the hypothetical 

sources to each grid cell for each day in 

the modeled period provided for the 

examination of the impacts of the 

exempt emissions at each grid cell 

throughout the state. In the case of the 

minor NSR program revisions proposed 

by Arkansas, the state developed a 

110(l) demonstration comprised of air 

quality modeling, as well as an 

emissions inventory analysis and a 

monitoring trends analysis. As stated in 

our proposed rulemaking, we found in 


sradovich on DSK3GMQ082PROD with RULES
30564 Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 

20As discussed in Arkansas’s ‘‘2010 Minor NSR 

Permitting Thresholds and De Minimis Levels SIP 

Technical Support Document’’ (Appendix C to 

March 24, 2017 SIP revision submittal), the CMAQ 

photochemical modeling requires as input, hourly, 

gridded pollutant emissions from both 

anthropogenic and biogenic sources. 

combination that the modeling analysis 

along with the other analyses submitted 

by the state demonstrated that the 

proposed revisions would not interfere 

with NAAQS attainment or 

maintenance. Based on our review, we 

find the analysis conducted and the 

methods used to be appropriate and 

sufficient to support the proposed SIP 

revisions, especially for exemptions 

from minor NSR permitting 

requirements that are expected to make 

up fractional percentages (<1% for all 

pollutants) of the total emissions in the 

statewide emissions inventory—as 

documented in the state supplied 

emissions inventory analysis. 

Regarding the commenter’s statement 

regarding the modeling of worst-case 

conditions, we do not agree with the 

commenter. The modeling of the worst 

case conditions such as terrain, stack 

height, stack temperature and velocity is 

inappropriate for assessing whether the 

relaxed applicability to Arkansas’ minor 

NSR rule would violate the NAAQs. The 

hypothetical sources included in the 

110(l) demonstration modeling were 

meant to represent the exempt 

emissions that could occur from a 

variety of sources and were being 

modeled to examine the potential 

impacts from exempt emissions as part 

of the demonstration of non-interference 

with attainment or maintenance of the 

NAAQS under CAA section 110(l). 

Arkansas determined representative 

values to be used as model inputs for 

the hypothetical sources by reviewing 

real world stack parameters available 

through their emissions inventory data. 

Based on their review, the state chose 

the average stack conditions from the 

emissions inventory data as the 

representative inputs for the modeled 

hypothetical sources. As stated in the 

modeling report included in the March 

24, 2017 SIP revision submittal and in 

our proposed rulemaking, the state 

modeled the hypothetical sources with 

the maximum emissions exempt by the 

rule (i.e., emissions equal to the 

thresholds values), even though not all 

exempt sources would have those 

emissions levels. 

The use of the worst case conditions 

(as referenced by the commenter) is 

typically applied in modeling for an 

existing source or a proposed source of 

known type/size and location as part of 

a case-by-case NSR modeling analysis, 

such as a modeling analysis completed 

as part of a PSD permit action. In the 

case of the modeling analysis conducted 

by Arkansas to support the proposed 

SIP revisions, the state was examining 

the potential impacts of emissions 

exempt from minor NSR permitting by 

adding hypothetical exempt sources to 

represent those added emissions in the 

modeled emissions inventory. The 

modeling conducted by Arkansas as part 

of the 110(l) demonstration modeling 

serves a different purpose, and therefore 

is inherently different than PSD permit 

modeling. PSD permit modeling is 

conducted as part of the source analysis 

PSD requirement (40 CFR 51.21(k)) to 

examine the impacts from the 

construction or major modification of a 

specific, known PSD source where 

model inputs are based on the actual 

design and operational parameters of 

the emission points located at the 

source. That said, we do not agree that 

the modeling analysis conducted by 

Arkansas did not take terrain into 

account. As discussed previously in this 

response, at least one of the modeled 

hypothetical sources was located in 

each of the AQCRs. This allowed the 

examination of model predicted impacts 

across the different geographic and 

topographic areas in the state, including 

those areas in NW Arkansas with more 

elevated/complex terrain (1 source 

located in AQCR 17 and 2 sources 

located in AQCR 21), which are 

expected to have higher impacts. As 

discussed in our evaluation of the 

photochemical modeling conducted by 

Arkansas, the model predicted impacts 

from the hypothetical sources did not 

indicate any model predicted violations 

of the NAAQS for any pollutant or 

averaging period. The photochemical 

modeling approach was one element of 

the 110(l) demonstration provided by 

the state to support the proposed SIP 

revisions. The approaches used by 

Arkansas in their modeling 

demonstration to determine the 

potential impacts from the newly 

exempt emissions were reasonable and 

appropriate for 110(l) analysis being 

conducted to demonstrate noninterference, especially considering the 

small amounts of emissions expected to 

be exempt from minor NSR permitting 

based on the revised rule relative to the 

current statewide emissions. 

Comment: The commenter stated that 

the photochemical modeling gave no 

justification for where it located the 

sources within the state and it is not 

clear if the sources were located in areas 

where the source’s plume could cause 

high concentrations due to nearby 

elevated terrain or in areas where there 

are other significant sources of air 

pollutants to determine the cumulative 

impacts. 

Response: We do not agree with the 

commenter that no justification was 

provided for the location of the 

hypothetical sources within the 

photochemical modeling. Arkansas did 

state that they placed at least one source 

in each of their Air Quality Control 

Regions. They also stated that the 

sources were typically located in or near 

more urban areas of the state. A figure 

was included in the modeling report 

showing the location of the modeled 

sources relative to the populated areas 

in the state, which are also more likely 

to have larger ‘‘background’’ emissions 

within the modeled emissions 

inventory. (See the March 24, 2017 SIP 

Revision Submittal, Appendix C—2010 

Minor NSR Permitting Thresholds and 

De Minimis Levels SIP Technical 

Support Document, Figure 19.) The 

chosen locations allowed for the 

examination of impacts throughout the 

various regions of the state, focused on 

the more populated areas. As stated in 

our previous response, two of the 

modeled hypothetical sources were 

included in the areas in NW Arkansas 

with more elevated/complex terrain (1 

source located in AQCR 17 and 2 

sources located in AQCR 21). 

Additionally, the modeling approach 

used by the state in their 110(l) 

demonstration included a separate 

analysis to specifically examine the 

model predicted concentrations at each 

grid cell throughput the state when the 

maximum modeled impacts from the 

hypothetical sources were applied. This 

approach allowed the examination of 

the maximum hypothetical source 

impacts combined at different 

geographic locations along with looking 

at those impacts combined with a 

variety of cumulative source inventory 

impacts throughout the state. 

Comment: The commenter stated that 

the photochemical modeling did not 

attempt to take into account the 

cumulative impacts of exempt sources 

or modifications, and it did not include 

the possibility of multiple exempt 

sources locating nearby each other, nor 

did the modeling attempt to model more 

than one exemption at a single or 

multiple sources over time. 

Response: As discussed previously in 

our responses, we do not agree that 

cumulative impacts analysis was not 

conducted as part of the state’s 

modeling analysis. The photochemical 

modeling analysis combined the 

impacts from the hypothetical sources 

with the impacts of background 

emissions inventory sources via 

emissions inventory model inputs.20

Further, this cumulative impacts 

analysis was conducted in such a way 


sradovich on DSK3GMQ082PROD with RULES
Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 30565 

21Any emissions resulting from unplanned 

startup or shutdown activities or from 

malfunctions, and therefore not accounted for in the 

NSR permit authorization, would be considered 

violations of the SIP unless these emissions limits 

are reflected in a NSR SIP or a SIP rule. 

as to examine the maximum modeled 

impacts from the hypothetical sources 

with the impacts from the background 

emissions inventory sources at each grid 

cell in the state. Regarding the 

cumulative impacts from multiple 

exempt sources potentially located 

nearby each other, the modeling report 

included in the March 24, 2017 SIP 

revision submittal stated that ‘‘since the 

modeled impacts occur within or nearby 

the source location, cumulative effects 

from multiple sources in multiple grid 

cells are expected to be small.’’ Based 

on the 110(l) demonstration provided by 

Arkansas, which included modeling 

that looked at cumulative impacts from 

hypothetical exempt sources and the 

background emissions sources 

inventory, we do not find the revised 

thresholds to adversely impact the 

NAAQS. 

Comment: The commenter stated that 

there is no indication that the modeling 

took into account variability of emission 

rates over time to account for the very 

likely possibility that an exempt source 

could emit at higher rates over shorter 

periods of time rather than emitting at 

a consistent level. 

Response: It is unreasonable to expect 

the type of modeling conducted by 

Arkansas to examine the potential 

impacts of a small subset of minor 

sources that make up much less than 

1% of the total emissions in the 

statewide emissions inventory (less than 

or equal to 0.125% of the statewide 

emissions for minor NSR permitting 

thresholds; less than or equal to 0.019% 

of the statewide emissions for de 

minimis change levels) to include 

variable emissions modeling. The 

evaluation of impacts from variable 

emission rates is typically associated 

with modeling an existing source or a 

proposed source of known type/size and 

operation as part of a case-by-case NSR 

modeling analysis (such as the modeling 

conducted for PSD permitting). As 

stated in our previous responses, the 

modeling analysis conducted by 

Arkansas as part of the SIP revision 

submittal was completed as part of a 

110(l) demonstration for the purposes of 

determining the potential impacts of the 

revised missions exempt from minor 

NSR permitting by adding hypothetical 

exempt sources to represent those added 

emissions in the modeled emissions 

inventory. Modeling conducted as part 

of the 110(l) demonstration is conducted 

to determine whether a SIP revision will 

interfere with attainment or 

maintenance of the NAAQS, any 

required milestone, or any other 

requirement of the Act. Because the 

modeled sources were hypothetical in 

nature, source-specific information 

including emission rates and their 

potential variability, cannot be 

available, nor does it need to be. As 

stated in the modeling report included 

in the March 24, 2017 SIP revision 

submittal and in our proposed 

rulemaking, in the modeling analysis 

the hypothetical source emission rates 

were set equal to the revised minor NSR 

permitting thresholds and de minimis 

change levels to examine the potential 

impacts resulting from the newly 

exempt emissions. (See the March 24, 

2017 SIP Revision Submittal, Appendix 

D—Air Quality Modeling Analysis of 

Minor Source Permit Thresholds.) The 

approaches used by Arkansas in their 

modeling demonstration to determine 

the potential impacts from the newly 

exempt emissions were reasonable and 

appropriate for the type of analysis 

being conducted, especially considering 

the relatively small amount of emissions 

expected to be exempt from minor NSR 

permitting based on the revised rule 

compared to statewide emissions. 

Comment: The commenter stated that 

because presumably the same emission 

rates, stack parameters, and sources 

locations were modeled with AERMOD 

(dispersion model) as were modeled in 

the CMAQ photochemical modeling. 

Therefore, they stated that all of the 

prior comments raised with the CMAQ 

(photochemical) modeling also apply to 

the AERMOD (dispersion) modeling 

results. The commenter also stated that 

there is no indication that the air 

dispersion modeling accounted for 

impacts from startup, shutdown and 

malfunction emissions. 

Response: The comments raised on 

the CMAQ photochemical modeling 

were addressed above. Those responses 

would also apply to the AERMOD 

dispersion modeling, with some slight 

clarifications due to the inherent 

differences between photochemical and 

dispersion modeling analyses. We 

provide the following clarification 

related to the comments raised on 

cumulative impacts analyses since the 

CMAQ photochemical modeling and 

AERMOD dispersion modeling have 

different approaches to account for 

cumulative impacts because the models 

differ on how off-site background 

sources emissions inventories are 

represented and how impacts are 

determined. As discussed in the 

modeling report included in the March 

24, 2017 SIP revisions submittal, the 

CMAQ photochemical modeled 

concentrations/impacts from the 

background emissions inventory sources 

were included as background values in 

the AERMOD dispersion modeling and 

added to the AERMOD dispersion 

modeled concentrations from the 

hypothetical sources to determine 

cumulative impacts from the exempt 

emissions and the off-site emissions. 

(See the March 24, 2017 SIP Revision 

Submittal, Appendix D—Air Quality 

Modeling Analysis of Minor Source 

Permit Thresholds.) Although these 

approaches differ because of the nature 

of the modeling system used, both the 

CMAQ photochemical and AERMOD 

dispersion modeling analyses include 

the cumulative impacts of the 

hypothetical sources plus the 

background emissions inventory 

sources. 

Regarding the modeling of impacts 

from startup, shutdown and 

malfunction emissions, the evaluation 

of impacts from routine and/or 

predictable startup and shutdown 

emissions would be associated with 

modeling an existing source or a 

proposed source of known type/size and 

operation as part of a case-by-case NSR 

modeling analysis, such as PSD permit 

modeling.21 The routine and predictable 

startups and shutdowns are permitted 

emissions which are accounted for in 

the emissions inventory. As stated in 

our previous responses, the hypothetical 

sources included in the 110(l) 

demonstration modeling were meant to 

represent the exempt emissions that 

could occur from a variety of sources 

and were being modeled to examine the 

potential impacts from exempt 

emissions. Because the modeled sources 

were hypothetical in nature, 

information regarding source inputs 

including a small subset of their 

emissions such as source-specific 

startup, shutdown and malfunction 

emissions, was not available, nor should 

it be. Further, the emissions expected to 

be exempt from minor NSR permitting 

based on the revised permitting 

thresholds and de minimis levels made 

up much less than 1% of the total 

statewide emissions (less than or equal 

to 0.125% of the statewide emissions for 

minor NSR permitting thresholds; less 

than or equal to 0.019% of the statewide 

emissions for de minimis change levels) 

meaning that the startup, shutdown and 

malfunctions being a small subset of 

total emissions would make up an even 

smaller fraction of the statewide 

emissions. The commenter’s expectation 

for this type of analysis is unreasonable 

on the basis that these emissions make 

up such a small fraction of the statewide 

emissions (that is, a small subset of the 

total exempt emissions that are 


sradovich on DSK3GMQ082PROD with RULES
30566 Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 

22As stated in our original SIP approval of 

Chapter 4, ‘‘[a] minor source is any source which 

does not meet the requirements of a major source. 

The Act in section 302(j) defines the terms ‘‘major 

stationary source’’ and ‘‘major emitting facility’’ as 

‘‘any stationary facility of source of air pollutants 

which directly emits, or has the potential to emit, 

one hundred tons per year of more of any air 

pollutant (including any major emitting facility or 

source of fugitive emissions of any such pollutant, 

as determined by rule by the Administrator).’’ ’’ 

anticipated to make up much less than 

1% of the statewide emissions). As 

stated in the modeling report included 

in the March 24, 2017 SIP revision 

submittal and in our proposed 

rulemaking, the hypothetical source 

emission rates were set equal to the 

revised minor NSR permitting 

thresholds and de minimis change 

levels to examine the potential impacts 

resulting from the newly exempt 

emissions. The approaches used by 

Arkansas in their modeling 

demonstration to determine the 

potential impacts from the newly 

exempt emissions were reasonable and 

appropriate for the type of analysis 

being conducted, especially considering 

the relatively small amount of emissions 

expected to be exempt from minor NSR 

permitting based on the revised rule 

compared to statewide emissions. 

Comment: The commenter stated that 

the dispersion modeling did not include 

the modeling of line sources and that 

fugitive PM10 emissions often cause 

increment and NAAQS violations. 

Therefore, the commenter claims that 

the AERMOD (dispersion) modeling 

does not reflect reasonable worst case 

impacts that could occur due to the 

sources and de minimis changes exempt 

from minor NSR based on the SIP 

revisions. 

Response: As discussed in our 

previous responses, the worst case 

impacts conditions (or potential worst 

case source type in the case of this 

comment) referenced by the commenter 

are typically associated with case-bycase NSR modeling of an existing source 

or a proposed source with known stack/ 

emission characteristics (such as, 

modeling associated with a PSD permit 

action). This would also be the case for 

the modeling of line sources mentioned 

by the commenter. The 110(l) 

demonstration modeling conducted by 

Arkansas in support of the SIP revisions 

has a different purpose and associated 

requirements than case-by-case NSR 

modeling. As discussed in our earlier 

response to the comment raised 

regarding worst case stack parameters, 

Arkansas relied on real world stack 

parameters available in their emissions 

inventory data to determine 

representative stack parameters to 

represent emissions newly exempt from 

minor NSR permitting via the inclusion 

of hypothetical sources in their 

modeling analyses. Specifically, they 

reviewed the stack parameters and 

determined the average stack parameters 

included as hypothetical point sources 

with emissions set equal to the minor 

NSR permitting thresholds and de 

minimis change levels. Because the 

modeled sources were hypothetical in 

nature, source-specific information 

including whether or not any portion of 

the emissions were fugitive in nature 

(such as road emissions) versus stack 

emissions, cannot be available, nor does 

it need to be. Modeling of hypothetical 

sources with emissions rates set equal to 

the revised minor NSR permitting and 

de minimis change thresholds ensures 

that the analysis accounts for the 

maximum amount of emissions that 

would be exempt from minor NSR 

permitting based on the revisions. The 

approaches used by Arkansas in their 

modeling demonstration and their 

reliance on representative stack 

parameters to determine the potential 

impacts from the newly exempt 

emissions were reasonable and 

appropriate for the type of analysis 

being conducted, especially considering 

the relatively small fraction of emissions 

expected to be exempt from minor NSR 

permitting based on the revised rule 

compared with statewide emissions. 

Comment: The commenter stated that 

the revised Arkansas NSR program 

conflicts with the requirements of 

section 110(2)(C). More specifically, the 

commenter stated that the de minimis 

change exemptions will exempt most if 

not all modifications at existing major 

stationary sources from minor NSR 

permitting. They indicate that this is in 

direct contrast with the intention for the 

new source review program required by 

CAA section 110(a)(2)(C) and 40 CFR 

51.160 to be a backstop on threats to 

attainment or maintenance of the 

NAAQS posed by new source growth 

that is not planned for in existing SIP 

rules. 

Response: We do not agree with the 

commenter that the de minimis 

exemptions will exempt most if not all 

modifications at existing major 

stationary sources from minor NSR 

permitting. As previously stated in our 

responses, the SIP-approved Arkansas 

NSR program is comprised of two types 

of review: ‘‘Minor Source Review’’ and 

‘‘Major Source Review’’. Arkansas 

operates a so-called ‘‘merged, one 

permit’’ system, which is divided into 

these two types of review based on 

whether a source is required to obtain 

a title V operating permit. As such, 

‘‘Minor Source Review’’, which is 

contained in Reg. 19, Chapter 4, applies 

only to those sources that are not subject 

to title V permitting and require only a 

title I minor NSR authorization.22 Any 

source that would be a major source for 

purposes of PSD review would also be 

a major source subject to title V 

permitting. Compare 40 CFR 52.21(b)(1) 

(establishing major source thresholds of 

100 and 250 tons per year) with Reg. 26, 

Chapter 2 (defining major sources to 

include, inter alia, any source with the 

potential to emit 100 tons per year). 

Therefore, any source subject to title V, 

which would include any new PSD 

major source and/or any modification to 

an existing PSD major source, cannot 

utilize the de minimis change 

exemption found at Reg. 19.407(C). 

Instead, all modifications at title V 

sources that are not be subject to Reg. 

19, Chapter 9 would instead be subject 

to the ‘‘Major Source Review’’ 

requirements found in Reg. 26 and 

incorporated by reference in Reg. 19, 

Chapter 11 and cannot use the de 

minimis change provisions, which are 

limited to ‘‘Minor Source Review’’ in 

Chapter 4 of Reg. 19. The revisions 

addressed in our proposed rulemaking 

are limited to ‘‘Minor Source Review’’ 

under Chapter 4 of Reg. 19 and do not 

impact ‘‘Major Source Review’’ in 

Chapter 11, which has already been 

approved into the SIP as part of 

Arkansas’ minor NSR program, most 

recent approval on March 4, 2015 (See 

80 FR 11573), and which contains the 

permitting requirement provisions 

applicable to the modifications not 

subject to Reg. 19, Chapter 9 at all title 

V sources, including all of the sources 

referenced by the commenter. 

Comment: The commenter stated that 

the NSR program required by CAA 

section 110(a)(2)(C) and 40 CFR 51.160 

is intended to be a backstop on threats 

to attainment or maintenance of the 

NAAQS posed by new sources growth 

that is not planned for in existing SIP 

rules. Because of the commenter’s 

assessment that NSR program is an 

important part of the SIP, they stated 

that EPA cannot approve exemptions 

from a minor NSR program unless it is 

shown that the exemptions are truly de 

minimis to the purposes of the program. 

Response: We agree that the NSR 

program is an important part of the SIP 

but this does not mean that under the 

CAA and the minor NSR SIP rules, EPA 

cannot approve exemptions from a 

minor NSR program. Consequently, 

what is relevant is whether or not the 

revisions to the Arkansas minor NSR 

program are approvable under the plain 

reading of the applicable statute and 

rules. There is no regulatory or statutory 


sradovich on DSK3GMQ082PROD with RULES
Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 30567 

23Alabama Power Company, et al., Petitioners,* 

v. Douglas M. Costle, As Administrator, 

Environmental Protection Agency, et al., 

Respondents,* Sierra Club, et al., Intervenors.*, 636 

F.2d 323 (D.C. Cir. 1980). 

prohibition that prohibits the types and/ 

or sizes of sources that could be exempt 

from the minor NSR program. In fact, 

the minor NSR SIP rules at 40 CFR 

51.160(e) only require that the minor 

NSR program include procedures that 

‘‘identify types and sizes of facilities, 

buildings, structures, or installations 

which will be subject to review under 

this section. [and] The plan must 

discuss the basis for determining which 

facilities will be subject to review.’’ 

These rules furthermore require that the 

plan must ensure that the issuance of 

minor NSR permits not result in a 

violation of the control strategy or 

interfere with the attainment or 

maintenance of a national standard. The 

CAA at section 110((a)(2)((C) requires 

regulation of the modification or 

construction of any stationary source 

within the area as necessary (emphasis 

added) to assure that the standards are 

achieved. As such, the CAA at section 

110((a)(2)(C) and the minor NSR SIP 

rules found at 40 CFR 51.160–165, as 

well as case law,23 allow exemptions 

from a minor NSR permitting program. 

In cases such as this, where the minor 

NSR SIP is being revised, the state must 

also demonstrate that the revisions meet 

the requirements of CAA section 110(l). 

Similar to the provisions of the Act and 

rules discussed above, section 110(l) 

requires that EPA cannot approve 

revisions to the Arkansas minor NSR 

SIP unless EPA finds that the changes 

would not interfere with any applicable 

requirement concerning attainment and 

reasonable further progress, as well as 

any other applicable statutory 

requirement. The clear reading of the 

Act and the EPA rules are that EPA can 

approve exemptions to the Arkansas 

minor NSR SIP program as long as it 

finds these exemptions will not interfere 

with attainment or maintenance of a 

NAAQS or other control strategy. 

Consistent with what is allowed, 

Arkansas has identified revised 

permitting thresholds and de minimis 

change levels to serve as the exemption 

thresholds for their minor NSR 

permitting program. To support the 

revised exemption thresholds, Arkansas 

provided analyses to define the scope of 

the exemptions and to demonstrate that 

these revised thresholds will not 

adversely impact NAAQS maintenance 

or attainment. The analyses, which were 

submitted as part of the March 24, 2017 

SIP revision submittal, included: (1) An 

emissions inventory analysis that 

determined the percentage of the 

statewide total emissions inventory that 

would be newly exempt by the revised 

thresholds; (2) a monitoring analysis 

that included a review of the current 

status of ambient air quality in the state 

along with a review of the trends in 

monitoring data since the state adopted 

and implemented the revised 

thresholds; and (3) a modeling analysis 

that examined the impacts of the 

exempt emissions on ambient 

concentrations. The analyses provided 

by Arkansas in the SIP revision 

submittals show that the minor NSR 

permitting exemptions resulting from 

the revised rule were limited in scope 

and comprised much less than 1% of 

the total emissions in the statewide 

emissions inventory and that the 

impacts from the newly exempt 

emissions would not adversely impact 

NAAQS maintenance or attainment, as 

part of their 110(l) demonstration. The 

EPA’s review of these analyses and our 

finding that the proposed SIP revisions 

were approvable were detailed in the 

proposed rulemaking and the Technical 

Support Document accompanying the 

rulemaking. 

Comment: The commenter stated that 

the results from the state’s AERMOD 

(dispersion) modeling show that the 

exemptions are not ‘‘de minimis.’’ The 

commenter also states that the EPA 

must not approve the revised program 

because it will interfere with the 

requirements that SIPs include 

programs to ensure that new and 

modified sources not be allowed to 

construct or modify if they would 

interfere with attainment or 

maintenance of the NAAQS. 

Response: Our proposed rulemaking 

specifically addressed the scope of the 

exemptions resulting from the revised 

minor NSR permitting thresholds and 

de minimis levels. As discussed in our 

proposal, Arkansas provided an analysis 

to quantify the amount of emissions that 

would be expected to be exempt from 

minor NSR permitting requirements 

relative to total emissions from the 

statewide emissions inventories. For all 

pollutants, the exempt emissions for 

both the permitting thresholds and de 

minimis levels made up a fraction of 1% 

of the statewide emissions. Therefore, 

we find that the scope of emissions 

expected to be exempt from minor NSR 

permitting as a result of the revised 

minor NSR program thresholds and de 

minimis change levels is extremely 

limited. Regarding the commenter’s 

claim that the revised program will 

interfere with NAAQS attainment or 

maintenance, the 110(l) demonstration 

submitted by Arkansas in support of the 

proposed revisions to the SIP 

specifically addressed the anticipated 

impacts on the NAAQS through both a 

review of the current status of ambient 

air quality in Arkansas and an 

evaluation the impacts of the revised 

thresholds on ambient air quality via air 

monitoring and air modeling data. As 

discussed in our proposed rulemaking, 

based on the ambient monitoring trend 

analysis, the implementation of the 

revised minor NSR permitting 

thresholds and de minimis levels 

following state adoption of the revisions 

in 2008 and ongoing implementation 

have not negatively impacted ambient 

air quality or interfered with the 

attainment of the NAAQS. In fact, for 

several pollutants the ambient air 

quality has shown continued 

improvements via decreases in 

monitored DVs during this period; and 

currently Arkansas does not have any 

areas classified as nonattainment for any 

NAAQS. Our proposal also summarized 

the air quality modeling results that 

Arkansas submitted as part of the SIP 

revisions. The modeling analysis 

included an evaluation of both 

statewide regional-scale 

(photochemical) and local-scale 

impacts. (See the March 24, 2017 SIP 

Revision Submittal, Appendix D—Air 

Quality Modeling Analysis of Minor 

Source Permit Thresholds.) The 

photochemical modeling was designed 

to specifically examine ozone and PM2.5, 

the model also simulates NO2, SO2, and 

PM10 so the results for those pollutants 

were also examined. The maximum 

photochemical modeling derived 

impacts including the hypothetical 

source emissions on daily maximum 8- 

hr ozone, 24-hr PM2.5, and annual 

average PM2.5 for any location in 

Arkansas was calculated. The maximum 

impacts including hypothetical source 

emissions on daily maximum 1-hr NO2

and SO2 and 24-hr average PM10 was 

also calculated. These maximum 

impacts were added to the baseline 

modeled predicted concentrations for 

each day and grid cell for the future year 

simulation. The resultant model 

predicted concentrations represented 

the future year concentrations assuming 

the worst-case impacts from the 

threshold emission increases at any 

location within the modeling grid. 

These model results were used in 

conjunction with the baseline modeling 

results to calculate the RRFs necessary 

to estimate FDVs. The FDVs were used 

to examine whether emission increases 

less than or equal to the revised 

thresholds will cause or contribute to a 

NAAQS violation or interfere with 

NAAQS maintenance. To further 

examine the potential near-field impacts 


sradovich on DSK3GMQ082PROD with RULES
30568 Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 

24For more detailed discussion regarding the 

regional-scale photochemical modeling results see 

Pages 29–31 of EPA’s Technical Support Document 

dated August 24, 2017, available in the electronic 

docket for this rulemaking. 

25For more detailed discussion regarding the 

near-field dispersion modeling results see Pages 31– 

32 of the EPA’s Technical Support Document dated 

August 24, 2017, including Table V.5 which 

contains the maximum and average AERMOD 

concentrations both with and without the CMAQderived background concentrations that were 

determined in ADEQ’s nearfield hypothetical 

source analysis. 

26Air Application Instructions available online 

at: https://www.adeq.state.ar.us/downloads/ 

WebDatabases/Air/PermitData/ 

Forms%20and%20Instructions/ 

Form%20and%20Instructions/Air_Permit_

Application_Forms_Instructions.pdf. 

27See 82 FR 43508. 

from new or existing sources with 

emission increases less than or equal to 

the revised permitting and de minimis 

change thresholds, a dispersion 

modeling analysis was conducted. The 

dispersion model was applied for the 

same hypothetical sources used in the 

photochemical modeling with emissions 

set to the revised thresholds. The 

dispersion model was applied for one 

year for NOX, SO2, CO, and PM10. For 

each source location, daily 

concentrations (for the receptor with the 

maximum annual average value) taken 

from the dispersion modeling were 

added to the photochemical model 

-derived concentrations for that same 

location. In this manner, the 

photochemical modeling values were 

used as ‘‘background’’. The statewide 

daily maximum impact (maximum over 

all locations/AQCRs) obtained were 

expected to represent the near-field 

future-year concentrations assuming 

worst-case impacts from threshold 

emission increases at a range of 

locations throughout the state. Similar 

to the photochemical modeling, these 

maximum impacts were added to the 

baseline modeled predicted 

concentrations for each day and grid 

cell for the future year simulation. The 

resultant model predicted 

concentrations represented the future 

year concentrations assuming the worstcase impacts from the threshold 

emission increases at any location 

within the modeling grid. The resultant 

concentrations were used in 

conjunction with the baseline modeling 

results to calculate the RRFs necessary 

to estimate FDVs. Once again, the FDVs 

were used to examine if the emissions 

under the revised threshold values 

would cause/contribute to a NAAQS 

violation and/or interfere with NAAQS 

attainment. Both the photochemical and 

dispersion modeling results did show 

that the addition of exempt emissions 

via modeled hypothetical sources may 

result in some increases in ambient 

concentrations. However, as discussed 

in the TSD accompanying our proposed 

rulemaking, the FDVs calculated as part 

of the regional-scale modeling analysis 

that were based on the maximum 

modeled impacts from the hypothetical 

source were less than the NAAQS for 

each pollutant and averaging period.24

Similarly, the results from the near-field 

dispersion modeling also showed the 

modeled impacts from the hypothetical 

sources combined with background 

concentrations were all less than their 

corresponding NAAQS.25 Based on our 

evaluation of these analyses conducted 

by ADEQ to support the revised minor 

NSR permitting thresholds and de 

minimis levels, we find that the 

increased levels will not interfere with 

attainment or maintenance of the 

NAAQS. 

Comment: The commenter stated that 

EPA does not cite to the specific rule 

that states that ‘‘de minimis changes are 

still required to meet minor NSR 

requirements contained in Reg. 19, 

Chapter 4 including a demonstration 

that the proposed modification will not 

interfere with the NAAQS on a case-bycase basis’’ and that the EPA’s claim 

that this requirement remains is without 

merit. The commenter stated that EPA 

may be assuming that Reg. 19.402 

applies since a permit revision is 

implied by Reg. 19.407(C)(6), it is not 

clear that this requirement applies to 

what appears to be an administrative 

amendment to a source’s permit if it 

makes a de minimis change. The 

commenter also states that ADEQ made 

it clear that it does not plan to require 

or base any decision for de minimis 

changes on air quality modeling, and 

without conducting modeling, they will 

not be able to ensure that the proposed 

modification will not interfere with 

attainment or maintenance of a NAAQS 

on a case-by-case basis. So, the 

commenter stated that it is unlikely that 

ADEQ considered Reg. 19.402 as 

applying to de minimis permit changes. 

Response: We do not agree that our 

proposed rulemaking did not include a 

citation to the specific rule related to a 

case-by-case demonstration of noninterference with the NAAQS that is 

applicable to de minimis changes. We 

also do not agree that our statement that 

de minimis changes must still meet 

minor NSR requirements is without 

merit. Our position that de minimis 

changes must include a demonstration 

that the proposed modification will not 

interfere with the NAAQS on a case-bycase basis is based on the applicability 

of Reg. 19.405(A)(1) to these changes. 

Further, the provisions in the de 

minimis change rule indicate that de 

minimis changes include an application 

submittal/review process at Reg. 

19.407(C)(5) at it references applications 

for de minimis changes. In addition to 

the rule language, the current ‘‘Air 

Application Instructions for 

Registrations, Minor Source Permits, or 

Title V Permits’’ made available on 

ADEQ’s air permitting website indicate 

that the forms are to be used for de 

minimis changes.26 As such, we do not 

agree with the commenter that EPA 

assuming the de minimis changes 

include an application process without 

a basis. Further we do not agree with the 

commenter, that our proposed 

rulemaking did not clearly state the 

specific rule regarding the referenced 

technical review requirement to 

demonstrate NAAQS compliance for a 

de minimis change. In our proposed 

rulemaking, we specifically stated that 

the requirement found at Reg. 

19.405(A)(1) requires ADEQ must 

ensure as part of their technical review 

of de minimis change applications that 

the source will be modified to operate 

without interfering with NAAQS 

attainment or maintenance.27 The de 

minimis change rule found at Reg. 

19.407(C)(2) of the current Arkansas SIP 

exempts qualified proposed changes at 

an existing source from minor NSR 

permitting requirements, including 

public notice. The exemption only 

exempts the de minimis change from 

minor NSR permitting requirements and 

not all applicable minor NSR 

requirements. Therefore, the exemption 

does not exempt the change from the 

technical review requirements found at 

Reg. 19.405(A). Reg. 19.405(A) applies 

to the review of applications submitted 

under Chapter 4 of Reg. 19, where the 

de minimis change rule is located, and 

requires that on an application-byapplication basis ADEQ must ensure as 

part of their technical review that the 

source will be modified to operate 

without interfering with NAAQS 

attainment or maintenance. Our 

approval of the de minimis change level 

revisions does not revise or in any way 

change the applicability of the SIPapproved technical review requirements 

found in Reg. 19.405(A), or any other 

applicable minor NSR requirements, to 

de minimis changes. It is important to 

note that the Reg. 19.405(A) technical 

review requirements do not specify that 

modeling be completed to demonstrate 

that the source will be constructed/ 

modified without interfering with 

attainment or maintenance of the 

NAAQS. The EPA minor NSR SIP rules 

found in 40 CFR 51.160–165 do not 


sradovich on DSK3GMQ082PROD with RULES
Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 30569 

require modeling either. We do not 

agree with the commenter that without 

conducting modeling, ADEQ cannot 

ensure that a de minimis change will 

not interfere with attainment or 

maintenance of a NAAQS on a case-bycase basis. Case-by-case modeling, such 

as air dispersion modeling, is one of the 

methods that is commonly used to meet 

NAAQS requirements, but it is not the 

only method. Depending on the source 

and the proposed de minimis change, as 

part of their technical review ADEQ 

could alternatively utilize past modeling 

analyses, such as the statewide 

modeling that was included as part of 

the 110(l) demonstration in the March 

24, 2017 SIP revision submittal, or 

existing ambient monitoring data or 

emissions inventory data relevant to the 

proposed change to make a 

determination regarding NAAQS 

compliance. In addition, the SIPapproved provision found at Reg. 

19.407(C)(1)(b) specifies that ‘‘a 

proposed change to a facility will be 

considered De Minimis if: . . . the 

change will result in a trivial 

environmental impact.’’ Our rulemaking 

does not revise or in any way change 

this provision. 

Comment: The commenter stated that 

EPA has not evaluated whether the SIP 

revision satisfies CAA section 193. They 

state that because the revisions allow 

ADEQ to relax emission limits via de 

minimis changes and for previously 

permitting sources to terminate the 

existing permit and replace with a 

registration, EPA’s review should 

include an evaluation pursuant to CAA 

section 193 of whether these relaxations 

would allow for the relaxation of any 

control requirements in effect before 

November 15, 1990, in any 

nonattainment area, in which case 

equivalent or greater emissions 

reductions. 

Response: We do not agree with the 

commenter that this rulemaking is 

subject to CAA section 193. Section 193 

applies to nonattainment areas only and 

provides that ‘‘[n]o control requirement 

in effect, or required to be adopted by 

an order, settlement agreement, or plan 

in effect before the date of the 

enactment of the Clean Air Act 

Amendments of 1990 in area for any air 

pollutant may be modified after such 

enactment in any manner unless the 

modifications insures equivalent or 

greater emission reductions of such air 

pollutant.’’ The proposed rule does not 

change control requirements in 

nonattainment areas, of which Arkansas 

currently has none. Therefore, EPA did 

not address section 193 in the proposed 

approval action, since it does not apply. 

In the future, should an area become 

designated as nonattainment, Arkansas 

when developing the required 

nonattainment NSR permitting program 

would have to ensure that this program 

applied the Act’s thresholds, which 

might require Arkansas to revise its 

minor NSR SIP program. 

III. Final Action 

In this action, EPA is approving 

revisions to the minor NSR permitting 

program as submitted as revisions to the 

Arkansas SIP on July 26, 2010, and 

March 24, 2017, including supplemental 

information submitted on November 30, 

2015, May 26, 2016, July 5, 2017, July 

27, 2017, and March 16, 2018. Our 

approval includes the following 

revisions to the Arkansas SIP: 

• Revisions to Reg. 19.401 (submitted 

07/26/2010 and 03/24/2017); 

• Revisions to Reg. 19.407(C)(2)(a) 

and (b) (submitted 07/26/2010 and 

03/24/2017); and 

• Revisions to Reg. 19.417(A) and (B) 

(submitted 07/26/2010). 

As previously stated in our proposed 

rulemaking, this final action does not 

remove or modify the existing federal 

and state requirements that each NSR 

permit action issued by ADEQ include 

an analysis completed by the 

Department and their determination that 

the proposed construction or 

modification authorized by the permit 

action will not interfere with attainment 

or maintenance of a national ambient air 

quality standard. 

IV. Incorporation by Reference 

In this rule, the EPA is finalizing 

regulatory text that includes 

incorporation by reference. In 

accordance with requirements of 1 CFR 

51.5, the EPA is finalizing the 

incorporation by reference of the 

revisions to the Arkansas regulations as 

described in the Final Action section 

above. The EPA has made, and will 

continue to make, these materials 

generally available through 

www.regulations.gov and at the EPA 

Region 6 Office (please contact Ashley 

Mohr for more information). Therefore, 

these materials have been approved by 

EPA for inclusion in the SIP, have been 

incorporated by reference by EPA into 

that plan, are fully federally enforceable 

under sections 110 and 113 of the CAA 

as of the effective date of the final 

rulemaking of EPA’s approval, and will 

be incorporated by reference in the next 

update to the SIP compilation. 

V. Statutory and Executive Order 

Reviews 

Under the Clean Air Act, 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 Clean Air 

Act. Accordingly, this 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 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); 

• 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, 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 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 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 


sradovich on DSK3GMQ082PROD with RULES
30570 Federal Register / Vol. 83, No. 126 / Friday, June 29, 2018 / Rules and Regulations 

governments or preempt tribal law as 

specified by Executive Order 13175 (65 

FR 67249, November 9, 2000). 

The Congressional Review Act, 5 

U.S.C. 801 et seq., as added by the Small 

Business Regulatory Enforcement 

Fairness Act of 1996, generally provides 

that before a rule may take effect, the 

agency promulgating the rule must 

submit a rule report, which includes a 

copy of the rule, to each House of the 

Congress and to the Comptroller General 

of the United States. EPA will submit a 

report containing this action and other 

required information to the U.S. Senate, 

the U.S. House of Representatives, and 

the Comptroller General of the United 

States prior to publication of the rule in 

the Federal Register. A major rule 

cannot take effect until 60 days after it 

is published in the Federal Register. 

This action is not a ‘‘major rule’’ as 

defined by 5 U.S.C. 804(2). 

Under section 307(b)(1) of the Clean 

Air Act, petitions for judicial review of 

this action must be filed in the United 

States Court of Appeals for the 

appropriate circuit by August 28, 2018. 

Filing a petition for reconsideration by 

the Administrator of this final rule does 

not affect the finality of this action for 

the purposes of judicial review nor does 

it extend the time within which a 

petition for judicial review may be filed, 

and shall not postpone the effectiveness 

of such rule or action. This action may 

not be challenged later in proceedings to 

enforce its requirements. (See section 

307(b)(2).) 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air 

pollution control, Incorporation by 

reference, Lead, Nitrogen dioxide, 

Ozone, Particulate matter, Reporting 

and recordkeeping requirements, Sulfur 

oxides, Volatile organic compounds. 

Dated: June 20, 2018. 

Anne Idsal, 

Regional Administrator, Region 6. 

40 CFR part 52 is amended as follows: 

PART 52—APPROVAL AND 

PROMULGATION OF 

IMPLEMENTATION PLANS 

■ 1. The authority citation for part 52 

continues to read as follows: 

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

Subpart E—Arkansas 

■ 2. In § 52.170(c), the table titled ‘‘EPAApproved Regulations in the Arkansas 

SIP’’ is amended by: 

■ a. Revising entries for Reg. 19.401 and 

Reg. 19.407; and 

■ b. Adding an entry for Reg. 19.417 

immediately following the entry for Reg. 

19.413. 

The amendments read as follows: 

§ 52.170 Identification of plan. 

* * * * * 

(c) * * * 

EPA-APPROVED REGULATIONS IN THE ARKANSAS SIP 

State citation Title/subject 

State 

submittal/ 

effective 

date 

EPA approval date Explanation 

Regulation No. 19: Regulations of the Arkansas Plan of Implementation for Air Pollution Control 

*******

Chapter 4: Minor Source Review 

Reg. 19.401 .... General Applicability .... 03/24/17 6/29/2018, [Insert Federal Register 

citation].

Includes supplemental information provided on 

11/30/2015, 05/26/2016, 07/05/2017, and 

03/16/2018. 

* * * * * * * 

Reg. 19.407 .... Permit Amendments .... 03/24/17 6/29/2018, [Insert Federal Register 

citation].

Includes supplemental information provided on 

11/30/2015, 05/26/2016, 07/05/2017, 07/27/ 

2017, and 03/16/2018. 

* * * * * * * 

Reg. 19.417 .... Registration ................. 07/26/10 6/29/2018, [Insert Federal Register 

citation].

Includes supplemental information provided on 

11/30/2015, 05/26/2016, 07/05/2017, and 

03/16/2018. 

* * * * * * * 

* * * * * 

[FR Doc. 2018–13942 Filed 6–28–18; 8:45 am] 

BILLING CODE 6560–50–P 


sradovich on DSK3GMQ082PROD with RULES