Document ID: EPA-R06-OAR-2020-0434-0001
Agency: epa
Document Type: Proposed Rule
Title: TX229.01 Air Quality State Implementation Plans; Approvals and Promulgations: Texas; Clean Data Determination for the 2010 1-Hour Primary Sulfur Dioxide National Ambient Air Quality Standard; Anderson and Freestone Counties and Titus County Nonattainment Areas, Proposed rule, 7 pages.
Posted Date: 2020-09-25T04:00Z

[Federal Register Volume 85, Number 187 (Friday, September 25, 2020)]
[Proposed Rules]
[Pages 60407-60413]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-20958]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R06-OAR-2020-0434; FRL-10014-56-Region 6]

Approval of Texas Air Quality Plans; Clean Data Determination for 
the 2010 1-Hour Primary Sulfur Dioxide National Ambient Air Quality 
Standard; Anderson and Freestone Counties and Titus County 
Nonattainment Areas

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
determine that the Anderson and Freestone Counties and the Titus County 
nonattainment areas, in Texas, have attained the 2010 1-hour primary 
Sulfur Dioxide (SO2) National Ambient Air Quality Standard 
(NAAQS) per the EPA's Clean Data Policy. The primary sources of 
SO2 emissions in these counties have permanently shut down 
and as a result air quality in these areas is now meeting the NAAQS for 
SO2. This proposed determination is supported by monitoring 
data from within or near to the nonattainment areas, emissions data and 
an evaluation of previous modeling.

DATES: Comments must be received on or before October 26, 2020.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R06-
OAR-2020-0434, to https://www.regulations.gov. Follow the online 
instructions for submitting comments. Once submitted, comments cannot 
be edited or removed from Regulations.gov. The EPA may publish any 
comment received to its public docket. Do not submit electronically any 
information you consider to be Confidential Business Information (CBI) 
or other information whose disclosure is restricted by statute. 
Multimedia submissions (audio, video, etc.) must be accompanied by a 
written comment.
    The written comment is considered the official comment and should 
include discussion of all points you wish to make. The EPA will 
generally not consider comments or comment contents located outside of 
the primary submission (i.e., on the web, cloud, or other file sharing 
system). For additional submission methods, please contact Robert 
Imhoff, (214) 665-7262, Imhoff.Robert@epa.gov. For, the full EPA public 
comment policy, information about CBI or multimedia submissions, and 
general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.
    Docket: The index to the docket for this action is available 
electronically at www.regulations.gov. While all documents in the 
docket are listed in the index, some information may not be publicly 
available due to docket file size restrictions or content (e.g., CBI).

FOR FURTHER INFORMATION CONTACT: Robert Imhoff, EPA Region 6 Office, 
SO2 and Regional Haze Branch, (214) 665-7262, or by email at 
Imhoff.Robert@epa.gov. Out of an abundance of caution for members of 
the public and our staff, the EPA Region 6 office will be closed to the 
public to reduce the risk of transmitting COVID-19. We encourage the 
public to submit comments via https://www.regulations.gov, as there 
will be a delay in processing mail and no courier or hand deliveries 
will be accepted. Please call or email the contact listed above if you 
need alternative access to material indexed but not provided in the 
docket.

SUPPLEMENTARY INFORMATION:  Throughout this document ``we,'' ``us,'' 
and ``our'' refer to the EPA.

Table of Contents

I. What action is the EPA proposing?
II. What is the background of this action?
    A. Nonattainment Designation
    B. Clean Data Policy
    C. How does a nonattainment area achieve ``clean data'' for the 
2010 1-hour primary SO2 NAAQS?
    D. What information did Texas provide that demonstrates that the 
area attained the NAAQS?
    i. Primary Source Shutdowns
    ii. Monitoring Data
    E. What is the EPA's rationale for proposing this action?
III. What is the EPA's analysis?
    A. Modeling Data and Supplemental 2016-2019 Emissions 
Information Evaluation
    B. Ambient Air Quality Monitoring Data Evaluation
    C. EPA's Proposed Clean Data Determination
IV. What would be the effects of this action, if promulgated?
V. Statutory and Executive Order Reviews

I. What action is the EPA proposing?

    The EPA is proposing to determine that portions of Anderson and 
Freestone Counties and Titus County (hereby referred to as ``the 
nonattainment areas''), in Texas, have attained the 2010 1-hour primary 
SO2 NAAQS.\1\ This proposed determination of attainment is 
in response to a June 30, 2020 request from the state \2\ that the EPA 
consider information--including quality assured and certified ambient 
air monitoring data \3\ from the 2017-2019 monitoring period and the 
permanent and enforceable shutdown of the primary sources of 
SO2 emissions in these areas, Big Brown Power Plant (Big 
Brown) and Monticello Steam Electric Station (Monticello), that were 
the key contributors to the violations of the standard--which both 
support our proposed finding that the nonattainment areas have attained 
the 2010 1-hour primary SO2 NAAQS. The primary basis for the 
state's request is that the primary sources of SO2 emissions 
in these nonattainment areas have permanently shut down. These sources 
were located in rural areas with few other sources. EPA has reviewed 
the Texas Commission on Environmental Quality

[[Page 60408]]

(TCEQ) submission, available monitoring data and past modeling to base 
our proposed finding that air quality in these nonattainment areas is 
now meeting the NAAQS for SO2. The EPA has made the 
monitoring data, permit information submitted by the state, and 
additional information developed by EPA to support this proposed action 
available in the docket to this rulemaking through www.regulations.gov 
(please contact the person identified in the FOR FURTHER INFORMATION 
CONTACT section of this preamble for more information).
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    \1\ In accordance with Appendix T to 40 CFR part 50, the 1-hour 
primary SO2 NAAQS is met at an ambient air quality 
monitoring site when the valid 1-hour primary standard design value 
is less than or equal to 75 parts per billion (ppb). 40 CFR 
50.17(b).
    \2\ June 30, 2020 Letter from Toby Baker, Executive Director of 
TCEQ to Ken McQueen, Regional Administrator of EPA Region 6, 
subject: ``Sulfur Dioxide Clean Data Determination Request for 
Portions of Freestone, Anderson, and Titus Counties in Texas'' 
included in the docket for this action.
    \3\ Monitoring data must be reported, quality assured, and 
certified in accordance with the requirements set forth in 40 CFR 
part 58.
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II. What is the background of this action?

A. Nonattainment Designation

    On June 22, 2010 (75 FR 35520), the EPA published a health-based 1-
hour primary SO2 NAAQS at 75 parts per billion (ppb). 
Following promulgation of a new or revised NAAQS, section 107(d) of the 
Clean Air Act (CAA) requires the EPA to designate any area that does 
not meet (or that contributes to ambient air quality in a nearby area 
that does not meet) the NAAQS as nonattainment.
    The process for designating areas following promulgation of a new 
or revised NAAQS is contained in CAA section 107(d) (42 U.S.C. 
7407(d)). After promulgation of a new or revised NAAQS, each governor 
or tribal leader has an opportunity to recommend air quality 
designations, including the appropriate boundaries for nonattainment 
areas, to the EPA (42 U.S.C. 7407(d)(1)(A)). The EPA considers these 
recommendations when fulfilling its duty to promulgate the formal area 
designations and boundaries for the new or revised NAAQS. By no later 
than 120 days prior to promulgating designations, the EPA is required 
to notify states, territories, and tribes, as appropriate, of any 
intended modifications to an area designation or boundary 
recommendation that the EPA deems necessary (42 U.S.C. 7407(d)(1)(B)).
    After invoking a 1-year extension of the deadlines to designate 
areas, as provided for in section 107(d)(1)(B) of the Act, the EPA 
published an initial round of SO2 designations for certain 
areas of the country on August 5, 2013 (referred to as ``Round 1'') (78 
FR 47191). Following the Round 1 designations, several groups filed 
lawsuits against the EPA alleging the agency had failed to perform a 
nondiscretionary duty under the CAA to designate all portions of the 
country by the June 2, 2013, statutory deadline. As a result of the 
lawsuits, the EPA entered into a March 2, 2015, Consent Decree \4\ 
which required the EPA to complete the remaining area designations by 
three specific deadlines known as Rounds 2, 3, and 4 according to the 
court-ordered schedule. To meet the Round 2 court-ordered deadline for 
the SO2 designations, the court order required the EPA to 
designate areas containing sources meeting certain criteria no later 
than July 2, 2016.\5\
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    \4\ Mar. 02, 2015 Consent Decree; Sierra Club and Natural 
Resources Defense Council v. EPA, Case No. 3:13-cv-3953-SI (N.D. 
Cal.).
    \5\ Areas with three years of monitoring data showing violations 
of the NAAQS and areas containing stationary sources that had not 
been announced for retirement and that according to the EPA's Air 
Markets Database emitted in 2012 either (i) more than 16,000 tons of 
SO2 or (ii) more than 2,600 tons of SO2 with 
an annual average emission rate of 0.45 pounds of SO2 per 
one million British thermal units (lbs SO2/mmBTU) or 
higher. Mar. 02, 2015 Consent Decree; Sierra Club and Natural 
Resources Defense Council, et al. v. EPA, Case No. 3:13-cv-03953-SI 
(N.D. Cal.).
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    For SO2 NAAQS designations, air agencies have the 
flexibility to characterize air quality using either appropriately 
sited ambient air quality monitors or using modeling of actual or 
allowable source emissions. The EPA issued the non-binding draft 
Monitoring Technical Assistance Document (TAD) and Modeling TAD \6\ 
recommending how air agencies should conduct such monitoring or 
modeling. The 1-hour primary SO2 standard is violated at an 
ambient air quality monitoring site (or in the case of dispersion 
modeling, at an ambient air quality receptor location) when the 3-year 
average of the annual 99th percentile of the daily maximum 1-hour 
average concentrations exceeds 75 ppb, as determined in accordance with 
appendix T of 40 CFR part 50. To determine model-based violations, the 
EPA believes that dispersion modeling is the appropriate tool, as 
discussed in the Modeling TAD. The TAD provides recommendations on how 
an air agency might appropriately and sufficiently model ambient air in 
proximity to an SO2 emission source to establish air quality 
data for comparison to the 2010 primary SO2 NAAQS for the 
purposes of designations.
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    \6\ Technical Assistance Documents for Implementing the 2010 
Sulfur Dioxide Standard, August 2016 and February 2016, https://www.epa.gov/so2-pollution/technical-assistance-documents-implementing-2010-sulfur-dioxide-standard.
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    In September 2015, Texas submitted updated recommendations for 
areas of the state where there were no monitors, including the above 
counties.\7\ Texas recommended ``unclassifiable/attainment'' 
designations for those areas and stated its position that ambient air 
monitoring data were the appropriate information for use in attainment 
and nonattainment designations.
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    \7\ https://www.regulations.gov/contentStreamer?documentId=EPA-HQ-OAR-2014-0464-0080&contentType=pdf.
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    On June 30, 2016, the EPA signed the final action designating 61 
additional areas for Round 2 (81 FR 45039, July 12, 2016). On November 
29, 2016, EPA supplemented its Round 2 designations by signing a 
supplemental final action that included nonattainment designations for 
portions of Freestone and Anderson Counties and Titus County (``Round 2 
Supplement'') (81 FR 89870, December 13, 2016). This action established 
an attainment date five years after the effective date for the areas 
designated as nonattainment for the 2010 SO2 NAAQS (i.e., by 
January 12, 2022). The state is required to submit a State 
Implementation Plan (SIP) for the nonattainment areas to the EPA that 
meets the requirements of CAA sections 110 and 172(c), and 191-192 
within 18 months following the January 12, 2017 effective date of 
designation (i.e., by July 12, 2018). The State of Texas has not yet 
submitted the Nonattainment Area Plan for the 2010 1-Hour Sulfur 
Dioxide National Ambient Air Quality Standard for these areas. 
Therefore, on August 10, 2020, EPA published a Finding of Failure to 
Submit (FFS) for Texas for these two nonattainment areas and one 
additional area. As a consequence of the FFS, Texas must submit a 
complete SIP for each area addressing the outstanding SIP requirements 
by February 10, 2022 (18 months from the effective date of the finding) 
or be subject to mandatory sanctions under the Clean Air Act. 
Additionally, Texas must submit and obtain EPA approval of its SIP by 
August 10, 2022 or EPA must promulgate a Federal Implementation Plan 
addressing any outstanding SIP requirements. As discussed in more 
detail below, if this proposed Clean Data Determination is finalized, 
certain nonattainment area SIP requirements for these two nonattainment 
areas are suspended as long as air quality continues to meet the 
standard.
    For the SO2 designations in the two Texas areas 
addressed in this action, the EPA considered the data available at the 
time of designations, including modeling submitted by Vistra Energy and 
the Sierra Club in March 2016. EPA found that the technical analysis 
provided by the Sierra Club demonstrated that in the Freestone and 
Anderson Counties area, Big Brown Steam Electric Station (``Big 
Brown'') and in the Titus County area, Monticello Steam Electric 
Station (``Monticello'') plants were the primary sources of 
SO2 emissions and the key contributors to the modeled 2010 
SO2 NAAQS

[[Page 60409]]

violations. A nonattainment area encompasses the area shown to be in 
violation of the standard and the principal source or sources that 
contributes to the violation. The analysis of the maximum impacts 
around Big Brown and around Monticello showed that Big Brown and 
Monticello were responsible for almost 100% of the impacts on the 
maximum modeled concentrations in each area, and therefore only these 
sources were included within the boundaries of the nonattainment areas. 
A complete description of the State recommendations and data considered 
in proposing and finalizing those designations are included in the 
Texas Intended TSD \8\ and Texas Final TSD \9\ from Round 2 that are 
also included in the docket to this proposed rulemaking.
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    \8\ https://www.epa.gov/sites/production/files/2016-03/documents/tx-epa-tsd-r2.pdf.
    \9\ https://www.epa.gov/sites/production/files/201611/documents/texas_4_deferred_luminant_tsd_final_docket.pdf.
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B. Clean Data Policy

    The EPA issued its ``Clean Data'' policy memoranda for 
SO2 and other NAAQS describing reduced attainment planning 
requirements for nonattainment areas that attain the NAAQS but have not 
yet been redesignated as attainment.10 11 When EPA considers 
a clean data determination for a designated SO2 NAAQS 
nonattainment area, the EPA determines whether an area has attained the 
NAAQS based on air quality monitoring data (when available) and air 
quality dispersion modeling information for the affected area as 
necessary.
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    \10\ Memorandum of December 14, 2004, from Steve Page, Director, 
EPA Office of Air Quality Planning and Standards to the EPA Air 
Division Directors, ``Clean Data Policy for the Fine Particle 
National Ambient Air Quality Standards.'' This document is available 
at: http://www.epa.gov/pmdesignations/guidance.htm.
    \11\ The memorandum of April 23, 2014, from Steve Page, 
Director, EPA Office of Air Quality Planning and Standards to the 
EPA Air Division Directors ``Guidance for 1-hr SO2 
Nonattainment Area SIP Submissions'' provides guidance for the 
application of the clean data policy to the 2010 1-hour primary 
SO2 NAAQS. This document is available at https://www.epa.gov/sites/production/files/2016-06/documents/20140423guidance_nonattainment_sip.pdf .
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    Additionally, the EPA has issued national rulemakings that have 
codified this policy for ozone and fine particulate matter 
(PM2.5) NAAQS.\12\ Under our Clean Data policy, the EPA has 
consistently interpreted the requirements of the CAA that are 
specifically designed to help an area achieve attainment, such as 
attainment demonstrations and implementation of reasonably available 
control measures (including reasonably available control technology), 
reasonable further progress (RFP) demonstrations, and contingency 
measures, to be suspended as long as air quality continues to meet the 
standard because requirements designed to achieve or plan for 
attainment are no longer necessary when an area is already meeting the 
standard. The nonattainment new source review and emissions inventory 
requirements are not suspended under a Clean Data Determination and 
must still be addressed for the nonattainment areas.
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    \12\ See, e.g., 81 FR 58010, 81 FR 58127-58129 (August 24, 2016) 
(promulgating 40 CFR 51.1015); 80 FR 12264, 80 FR 12296 
(promulgating 51.1118). See also 70 FR 1612, 70 FR 71664-46 
(November 29, 2005); 72 FR 20585, 72 FR 20603-20605 (April 25, 
2007).
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    In the memorandum of April 23, 2014, from Steve Page, Director, EPA 
Office of Air Quality Planning and Standards to the EPA Air Division 
Directors ``Guidance for 1-hr SO2 Nonattainment Area SIP 
Submissions'' (2014 SO2 Nonattainment Area Guidance), the 
EPA explained its intention to extend the Clean Data Policy to 1-hour 
SO2 nonattainment areas that show attainment of the 
SO2 standard. As noted therein, the legal bases set forth in 
the various guidance documents and regulations establishing the Clean 
Data Policy for other pollutants are equally pertinent to all 
NAAQS.\13\ This proposed determination is also consistent with prior 
actions of the EPA applying the Clean Data Policy to other 
nonattainment areas under the 2010 SO2 NAAQS.\14\
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    \13\ See court cases upholding the legal basis for the EPA's 
Clean Data Determination Policy, NRDC v. EPA, 571 F.3d at 1258-61 
(D.C. Cir. 2009); Sierra Club v. EPA, 99 F.3d 551 (10th Cir. 1996); 
Latino Issues Forum v. EPA, 315 Fed. App. 651, 652 (9th Cir. 2009).
    \14\ For example, see 82 FR 13227 (March 10, 2016) and 81 FR 
28718 (May 10, 2016).
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    A clean data determination is not a redesignation to attainment. 
For the EPA to redesignate a nonattainment area to attainment, the area 
must satisfy all of the statutory criteria for redesignation to 
attainment which, in addition to determining the area is in attainment, 
include a demonstration that the improvement in the area's air quality 
is due to permanent and enforceable emission reductions; have a fully 
approved SIP that meets all of the applicable requirements under CAA 
section 110 and CAA part D; and have a fully approved maintenance 
plan.\15\
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    \15\ Clean Air Act Section 107(d)(3)(E).
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C. How does a nonattainment area achieve ``clean data'' for the 2010 1-
hour primary SO2 NAAQS?

    Generally, the EPA relies on ambient air quality monitoring data 
alone in order to make determinations of attainment for areas 
designated nonattainment for a particular NAAQS. However, given the 
Agency's historical approach toward SO2, the source-specific 
nature of SO2 emissions, and the localized effect of those 
emissions the EPA has emphasized the use of additional sources of air 
quality information to determine attainment of the SO2 
NAAQS. In the preamble to the 2010 1-hour primary SO2 NAAQS 
rulemaking, the EPA stated that it did not expect to rely solely on 
monitored air quality data in all areas when determining if an area has 
attained the 2010 1-hour primary SO2 NAAQS (75 FR 35551).
    The 2014 SO2 Nonattainment Area Guidance states that in 
order for a nonattainment area that was designated based on modeling 
data to be determined as attaining the NAAQS, additional dispersion 
modeling may be required. The SO2 Modeling TAD states that 
for the purposes of modeling to characterize air quality for use in 
SO2 designations the EPA recommends using a minimum of the 
most recent three years of actual emissions data and concurrent 
meteorological data to allow the modeling to simulate what a monitor 
would observe. Additionally, the SO2 Modeling TAD indicates 
that it is acceptable to use allowable emission rates instead of actual 
emission rates. Although past actual emissions could have been higher 
than those under the most recent allowable rate, the SO2 
Modeling TAD reflects the EPA's belief that it is reasonable to account 
for any lower allowable limits currently in place when determining if 
an area is attaining the NAAQS. In addition, the SO2 
Modeling TAD indicates that, where an allowable emissions limit has 
been lowered during the relevant three-year period (such as through the 
implementation of emissions controls), the air agency may rely on the 
new limit in demonstrating that the modeled limit assures attainment. 
The EPA believes this kind of analysis is appropriate for both 
designations and clean data determinations, both of which use the 
analysis to determine whether the area is currently meeting the NAAQS.
    For areas designated based on air quality modeling alone and where 
the source determined to be the primary cause of the violation has been 
permanently shut down, a more streamlined analysis may be

[[Page 60410]]

appropriate. In this case, the relevant allowable emissions limit has 
been lowered to zero. The EPA believes that the permanent cessation of 
SO2 emissions from primary sources may be sufficient to 
determine that the area is attaining the NAAQS, if available 
monitoring, emissions and modeling data for the area also support the 
finding of attainment. As discussed elsewhere in this document, the 
Anderson and Freestone Counties and the Titus County nonattainment 
areas in Texas were designated based on available modeling data that 
characterized the area around the Big Brown and Monticello facilities 
using 2013-2015 emissions; these facilities have since been permanently 
shut down.

D. What information did Texas provide that demonstrates that the area 
attained the NAAQS?

    TCEQ provided information related to primary sources of 
SO2, primary source shutdowns, and recent monitoring data. 
As noted by Texas, the Vistra Energy Power Plants Big Brown and 
Monticello were the only significant SO2 emission sources in 
the nonattainment areas. Texas also noted the resulting decrease of 
ambient SO2 concentrations after the shutdowns.
i. Primary Source Shutdowns
    As discussed above, for the SO2 designations in the two 
Texas areas addressed in this action, the EPA relied on modeling that 
demonstrated that the Big Brown and Monticello plants were the key 
contributors to the modeled 2010 SO2 NAAQS violations. Thus, 
the key factor in our proposed determination that the two areas are 
attaining the 2010 SO2 standard is the retirement of the two 
Vistra Energy facilities.
    Regarding the Anderson and Freestone Counties area, Vistra Energy 
permanently retired the Big Brown coal-fired steam electric generating 
Units 1 and 2 on February 12, 2018. Vistra Energy filed to void the Big 
Brown Title V permit, FOP 065, on May 24, 2018 and it was voided by 
TCEQ on August 29, 2018. A letter was submitted by Vistra Energy to 
TCEQ to void Big Brown's individual NSR permits (17891, 18744, 45420, 
53205, 54810, 56445, 56447, 83646, 83647, 85296, 94619, 95214, 96276, 
99047, 99050, 106862, 108990, 112207, and 148918). On March 29, 2018, 
TCEQ cancelled all new source review authorizations for Big Brown Units 
1 and 2 and certain other facilities, as requested by Vistra 
Energy.\16\ The remaining permits (17891, 18744, 56447, 106862, and 
112207) are material handling permits maintained while closure 
activities are completed, such as coal piles, silos, and conveyors.
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    \16\ See docket item number EPA-HQ-OAR-2014-0464-0455 for a list 
of Big Brown's voided NSR permits. Big Brown's voided operating 
permit is also located in Docket EPA-HQ-OAR-2014-0464.
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    Regarding the Titus County area, Vistra Energy permanently retired 
the Monticello coal-fired steam electric generating Units 1, 2, and 3 
on December 31, 2017. Vistra Energy filed to void the Monticello Title 
V permit, FOP 64, on May 23, 2018 and it was voided by TCEQ on August 
3, 2018. A letter was submitted by Vistra Energy to TCEQ to void 
individual NSR permits (2401, 26740, 45432, 54808, 56384, 71238, 85294, 
95215, 104897, 105738, 146220, 83645, and 83640) on February 9, 2018. 
On February 14, 2018, TCEQ cancelled all new source review 
authorizations for Monticello Units 1, 2, and 3 and certain other 
facilities, as requested by Vistra Energy.17 18 The 
remaining permits (146278, 2399, 140265, 137864, 56387, 54408, and 
104210) are material handling permits maintained while closure 
activities are completed, such as coal piles, silos, and conveyors.
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    \17\ For Monticello, see docket item number EPA-HQ-OAR-2014-
0464-0456 for a list of voided NSR permits, and docket item number 
EPA-HQ-OAR-2014-0464-0457 for the voided operating permit.
    \18\ Any remaining NSR or material handling permits for Big 
Brown and Monticello will only be maintained while the facilities 
complete closure activities related to coal piles, silos, conveyors, 
and other shutdown tasks.
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ii. Monitoring Data
    Texas provided recent monitoring data from the Fairfield FM 2570 
Ward Ranch monitor, located approximately three miles southwest of the 
Big Brown plant, and from the Cookville FM 4855 monitor, located 
approximately 12 miles to the east of the Monticello plant and source-
oriented to the still-operational Welsh power plant. The air quality 
data from these two monitors demonstrate a decrease in ambient 
SO2 concentrations (which Texas stated in their request is a 
result of the shutdowns of the Big Brown and Monticello plants) 
supporting EPA's proposed determination that these areas will continue 
to attain the SO2 NAAQS.
    In its 2017 annual monitoring network plan, Texas proposed 
SO2 monitoring sites in the Freestone/Anderson Counties and 
Titus County areas to assess air quality in the new SO2 
nonattainment areas involving Vistra Energy sources. Texas referred to 
the 2016 Sierra Club modeling analysis, among other information, to 
inform their proposed siting of the new monitors.\19\ The EPA approved 
the two monitoring sites.\20\
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    \19\ 2017 ANP, available in the docket for the action and at: 
https://www.tceq.texas.gov/assets/public/compliance/monops/air/annual_review/historical/2017-AMNP.pdf.
    \20\ EPA's approval of 2017 ANP, available in the docket for the 
action and at: https://www.tceq.texas.gov/assets/public/compliance/monops/air/annual_review/historical/EPA2017AMNP.pdf.
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Freestone/Anderson Counties Monitor Data
    Texas sited and began operating a monitor in the area of the Big 
Brown power plant (within the Freestone/Anderson Counties nonattainment 
area) on October 30, 2017. Though the Big Brown power plant shut down 
in February 2018, Texas continues to operate the monitor. EPA requires 
three calendar years of complete, quality assured, certified monitoring 
data to determine a design value, the measure of an area's air quality 
defined statistically by the form of the standard. For the 2010 one-
hour SO2 standard, the design value is the three-year 
average of the 4th-high annual daily maximum 1-hour average 
concentrations, representing the 99th percentile of annual daily 
maximum hourly average concentrations. A three-year period is used to 
smooth out variability in concentrations from year to year due to 
changes in source emission rates or to meteorological effects on 
dispersion. Texas stated that the monitor has a preliminary design 
value of 41 ppb based on the 99th percentile concentrations for 2017-
2019, compared to the standard of 75 ppb. We note that while this 
calculated design value is invalid due to insufficient information for 
2017, the data can be used as part of a weight of evidence analysis to 
support a determination of clean data. See the section below for EPA's 
analysis of the available monitor data.
Titus County Monitor Data
    For the Titus County nonattainment area, Texas did not install a 
monitor planned near the Monticello power plant once the retirement of 
the facility was announced for 2017. However, the TCEQ provided 
monitoring data from the Welsh monitor, (the Cookville FM 4855 monitor) 
also located in Titus county, approximately 16 km to the east of the 
nonattainment area surrounding the Monticello Power Plant. Unlike the 
Big Brown Monitor, the Welsh Monitor has 3 years of complete, certified 
monitoring data from the period of

[[Page 60411]]

2017-2019, as it began operating in January 2017. The Welsh monitor was 
sited by Texas to characterize the SO2 concentrations from 
the Welsh Power Plant.
    The monitor at Welsh began reporting data to the EPA's Air Quality 
System (AQS) on January 1, 2017. The 2017-2019 design value for the 
most recent three years of complete, quality assured, and certified 
ambient air monitoring data is 28 ppb, 37% of the standard. This 
represents an upper limit for the estimated design value for the Titus 
County nonattainment area since the Welsh monitor includes the impacts 
from the nearby Welsh Power Plant. Concentrations in the nonattainment 
area, further from the Welsh plant, would be expected to be lower since 
there are no other large sources nearby. See the section below for 
EPA's analysis of the Welsh Monitor data as an indicator of air quality 
in the Titus nonattainment area.

E. What is the EPA's rationale for proposing this action?

    The EPA is proposing to issue a clean data determination for the 
Anderson and Freestone Counties and the Titus County nonattainment 
areas based on the shutdown of the sources in the nonattainment areas, 
and as supported by monitoring data from within or near to the 
nonattainment areas and an evaluation of previous modeling. A detailed 
analysis of the monitoring data is presented below. In addition, we 
consider below available modeling data and more recent emission 
inventory data for the areas as further support for our proposed 
determination, consistent with our Clean Data Policy, that the 
nonattainment areas are attaining the 2010 SO2 NAAQS.

III. What is the EPA's analysis?

A. Modeling Data and Supplemental 2016-2019 Emissions Information 
Evaluation

    In 2016, Sierra Club and Vistra Energy submitted modeling data for 
the then most recent three years (2013-2015). This modeling provided 
the basis for the two nonattainment designations as discussed earlier.
    In the 2016 designation action, EPA found that the Sierra Club's 
modeled source inventory was created in accordance with the 2014 
SO2 Nonattainment Area Guidance and the 2016 SO2 
Modeling TAD. Our analysis of the maximum impacts around Big Brown and 
around Monticello found that Big Brown and Monticello were responsible 
for almost 100% of the impacts on the maximum ambient concentration, 
and thus, it was appropriate for these sources to be the only sources 
explicitly modeled. EPA's boundaries for the nonattainment area 
encompassed the area shown to be in violation of the standard and the 
only sources within the boundaries of the nonattainment areas were the 
principal sources that contributed to the violation in each area, i.e., 
Big Brown and Monticello.
    We have evaluated this modeling to determine if there is any 
possibility the area would still be in nonattainment after the plant 
shutdowns. EPA also reviewed 2016-2019 emissions data from the Clean 
Air Markets Database (CAMD) and compared those emissions to the 
assumptions made in the 2013-2015 modeling demonstration. As shown in 
Table 1, beginning in the second quarter of 2018 both plants' emissions 
are omitted in CAMD, indicating no SO2 emissions due to the 
facility shutdowns. Overall, during the modeled period 2013-2015 Big 
Brown emitted 169,791 tons and Monticello emitted 63,230 tons of 
SO2. In the most recent three-year period, 2017-2019, they 
emitted 54,291 and 29,410 tons respectively, less than \1/2\ the 
average emission rates modeled. More importantly, both facilities no 
longer emit any SO2.

Table 1--Quarterly Emissions From Big Brown and Monticello for 2013-2019
------------------------------------------------------------------------
                                                 Big Brown    Monticello
                                                    SO2          SO2
                    Quarter                      emissions    emissions
                                                   (tons)       (tons)
------------------------------------------------------------------------
2013 Q1.......................................       16,179        2,131
2013 Q2.......................................       14,603        7,358
2013 Q3.......................................       16,817       12,130
2013 Q4.......................................       14,895        2,778
2014 Q1.......................................       12,792        5,607
2014 Q2.......................................       13,119        3,683
2014 Q3.......................................       19,477       11,147
2014 Q4.......................................       12,072            2
2015 Q1.......................................       12,430            0
2015 Q2.......................................       11,677        4,205
2015 Q3.......................................       12,994        8,760
2015 Q4.......................................       12,737        5,430
2016 Q1.......................................        9,632        2,622
2016 Q2.......................................        7,369        3,853
2016 Q3.......................................       14,556       11,191
2016 Q4.......................................       10,913        7,293
2017 Q1.......................................        9,904        3,463
2017 Q2.......................................       10,244        8,558
2017 Q3.......................................       13,203        8,358
2017 Q4.......................................       14,282        9,030
2018 Q1.......................................        6,659            0
2018 Q2.......................................            0            0
2018 Q3.......................................            0            0
2018 Q4.......................................            0            0
2019 Q1.......................................            0            0
2019 Q2.......................................            0            0
2019 Q3.......................................            0            0
2019 Q4.......................................            0            0
------------------------------------------------------------------------

    The only emissions explicitly modeled were those from Big Brown and 
Monticello. The contributions from all other sources were represented 
in the model by an estimate of the background concentration. This is a 
technique in modeling to address smaller or more distant source 
contributions by examining monitoring data thought to be 
representative. These contributions were estimated to be small, 2 ppb 
for both areas. Review of 2017 National Emission Inventory data shows 
one additional SO2 emission source, Freestone Energy Center, 
within the Freestone/Anderson nonattainment area with total annual 
SO2 emissions of only 11.7 tons. There are no other 
SO2 emission sources in the Titus County nonattainment 
area.\21\
    The overall modeled concentrations at a receptor were computed by 
Equation 1.
    Equation 1. Equation representing the determination of total 
modeled total concentration at a receptor location.

Total Concentration = Concentration from Vistra Energy Source + 
Concentration from All Other Sources (background estimate 2 ppb)

    Because the Sierra Club sufficiently considered all significant 
sources of SO2 emissions for inclusion in the modeling 
demonstration, and these sources now have zero emissions, we do not 
believe that new modeling is required to determine attainment of the 
standard. Based on Equation 1, because the emissions from the Vistra 
Energy Sources are zero and their modeled concentrations would also be 
zero, the total concentration within the nonattainment area would be 
modeled as equal to the contribution from all other sources, or 
background. The modeled design value, in the absence of emissions from 
the Vistra Energy sources, if remodeled would then be equal to the 
concentrations from all other sources as represented by the background 
concentration of 2 ppb.

B. Ambient Air Quality Monitoring Data Evaluation

    According to the 2014 SO2 Nonattainment Area Guidance, 
to support a clean data determination based on monitoring data alone, 
the state needs to demonstrate that the area is meeting the standard 
based on three consecutive calendar years of complete and quality-
assured air quality monitoring data (consistent with 40 CFR part 58 
requirements). Neither nonattainment area contains a monitor with three 
complete years of monitoring data, but we believe that the available

[[Page 60412]]

monitoring data from the Big Brown and Welsh monitors do provide 
corroborating evidence that the source shutdowns have resulted in 
attainment. To further support our proposed determination, the EPA 
performed a detailed analysis of the SO2 concentrations 
monitored before and after the shutdowns.
    Data from the Big Brown monitor demonstrates a marked improvement 
in air quality in the nonattainment area due to the permanent 
retirement of the source as shown in Table 2. During the initial 107-
day period from the start of monitoring on October 31, 2017 to the 
shutdown of Big Brown on February 14, 2018, the 99th percentile 
concentration (the 1st high value for this shorter-than-one-year 
period) was 77.5 ppb, slightly above the standard. Post-shutdown, 321 
days were measured during 2018; during this period the 99th percentile 
concentration (the 3rd high value) was 14 ppb, 19% of the standard. The 
99th percentile concentration for 2019 (the 4th high value) is 5.8 ppb, 
8% of the standard. Preliminary monitoring data for the first quarter 
of 2020 gives a 99th percentile (the first-high value) of 7.6 ppb. The 
extremely low 99th percentile concentrations post-shutdown indicate 
that the monitored 99th percentile concentrations in the Freestone and 
Anderson County nonattainment area are now, and will continue to be, 
well below the NAAQS.
    As discussed previously, the Welsh Monitor provides a conservative 
estimate of possible concentrations in the Titus nonattainment area. 
Its design value is 28.0 ppb, in attainment of the standard, and 
supports the EPA's proposed determination that concentrations in the 
Titus County nonattainment area would also be in attainment. The 
shutdown of Monticello also reduced concentrations at the Welsh monitor 
when winds blew from the direction of Monticello (231[deg]-321[deg]). 
In 2017, prior to the shutdown, the maximum concentration from the 
direction of Monticello was 112.7 ppb. After the shutdown the maximum 
concentrations from that direction in 2018 and 2019 were 6.8 ppb and 6 
ppb respectively.
    Based on our analysis, the monitoring data from the Big Brown and 
Welsh DRR Monitors, before and after the major source shutdowns, 
support our proposed determination that both areas are now in 
attainment.

     Table 2--99th Percentile 1-Hour Average in Parts per Billion (PPB) at the Welsh and Big Brown Monitors
                                                   [2017-2019]
----------------------------------------------------------------------------------------------------------------
            Monitor                 Site name          2017            2018            2019           Average
----------------------------------------------------------------------------------------------------------------
48-449-1078...................  Welsh...........            33.4            20.2            30.5          \1\ 28
48-161-1084...................  Big Brown.......        \2\ 77.5            39.4             5.8        \3\ 21.6
----------------------------------------------------------------------------------------------------------------
\1\ The 3-year average of the yearly 4th high of the complete and certified data from the Welsh monitor
  represents the design value for the monitor.
\2\ Includes only data beginning 10/30/2017.
\3\ Average is weighted by number of days included for each year.

C. EPA's Proposed Clean Data Determination

    The EPA acknowledges the permanent shut down of the Vistra Energy 
Big Brown and Monticello power plants and recognizes the corresponding 
relationship between the decrease in concentrations of SO2 
in the nonattainment areas and the cessation of emissions from the 
Vistra Power Plants. We have examined available monitoring and modeling 
data and propose to find that air quality in the nonattainment areas 
are now attaining the 1-hour SO2 standard.

IV. What would be the effects of this action, if promulgated?

    If this proposed determination is made final, the requirements for 
the state to submit an attainment demonstration, a reasonable further 
progress plan, contingency measures, and other planning SIP revisions 
related to attainment of the 2010 1-hour primary SO2 NAAQS 
such as reasonably available control measures and reasonably available 
control technology would be suspended until such time, if any, that the 
EPA subsequently determines, after notice-and-comment rulemaking in the 
Federal Register, that either area has violated the 2010 1-hour primary 
SO2 NAAQS. If this were to occur, the basis for the 
suspension of the specific SIP requirements would no longer exist, and 
the state would thereafter have to address the pertinent requirements. 
If finalized, a determination of attainment would not shield the area 
from other required actions, such as provisions to address pollution 
transport, which could require emission reductions at sources or other 
types of emission activities contributing significantly to 
nonattainment in other areas or states, or interfering with maintenance 
in those areas. The EPA has the authority to require emissions 
reductions as necessary and appropriate to deal with transported air 
pollution situations. See CAA sections 110(a)(2)(D), 110(a)(2)(A), and 
126.
    If, after considering any comments received on this proposal, the 
EPA finalizes a clean data determination for these areas, the state 
would still be subject to nonattainment area requirements, including 
nonattainment new source review and emission inventory requirements, 
until the area is redesignated to attainment.
    This proposed clean data determination is limited to a 
determination that the areas are attaining the 2010 1-hour primary 
SO2 NAAQS as evidenced by the state's monitoring data and 
the Sierra Club's modeling analysis; this proposed action, if 
finalized, would not constitute a redesignation to attainment under 
section 107(d)(3) of the CAA. The designation status of the 
nonattainment areas will remain nonattainment for the 2010 1-hour 
primary SO2 NAAQS until such time as the state submits 
approvable redesignation requests and maintenance plans, and the EPA 
takes final rulemaking action to determine that such submissions meet 
the CAA requirements for redesignation to attainment.

V. Statutory and Executive Order Reviews

    This action proposes to make a determination based on air quality 
monitoring data and modeling and would, if finalized, result in the 
suspension of certain Federal requirements and would not impose any 
additional requirements. For that reason, this proposed 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 this action is not

[[Page 60413]]

significant under Executive Order 12866.
     Does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have Federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Is not an economically significant regulatory action based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     Is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Is not subject to requirements of Section 12(d) of the 
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 
note) because application of those requirements would be inconsistent 
with the CAA; and
     Does not provide the EPA with the discretionary authority 
to address, as appropriate, disproportionate human health or 
environmental effects, using practicable and legally permissible 
methods, under Executive Order 12898 (59 FR 7629, February 16, 1994).
    In addition, this proposed action does not apply on any Indian 
reservation land or in any other area where the EPA or an Indian tribe 
has demonstrated that a tribe has jurisdiction. In those areas of 
Indian country, the rule does not have tribal implications and will not 
impose substantial direct costs on tribal governments or preempt tribal 
law as specified by Executive Order 13175 (65 FR 67249, November 9, 
2000).

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Sulfur dioxide, Attainment determination.

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

    Dated: September 17, 2020.
Kenley McQueen,
Regional Administrator, Region 6.
[FR Doc. 2020-20958 Filed 9-24-20; 8:45 am]
BILLING CODE 6560-50-P