[Federal Register Volume 84, Number 147 (Wednesday, July 31, 2019)]
[Proposed Rules]
[Pages 37173-37187]
[FR Doc No: 2019-16070]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 52 and 81

[EPA-R04-OAR-2018-0552; FRL-9997-32-Region 4]

Air Plan Approval and Designation of Areas; FL; Redesignation of
the Hillsborough County 2010 1-Hour Sulfur Dioxide Nonattainment Area
to Attainment

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: In a letter dated June 7, 2018, the State of Florida, through
the Florida Department of Environmental Protection (FDEP), submitted a
request for the Environmental Protection Agency (EPA) to redesignate
the Hillsborough County sulfur dioxide (SO2) nonattainment
area (hereinafter referred to as the ``Hillsborough County Area'' or
``Area'') to attainment for the 2010 1-hour SO2 primary
national ambient air quality standard (NAAQS or standard) and to
approve an accompanying State Implementation Plan (SIP) revision
containing a maintenance plan for the Area. The submittal was received
by EPA on June 12, 2018. Through a letter dated April 16, 2019, FDEP
submitted a revision to the June 7, 2018, redesignation request and SIP
revision asking EPA to incorporate certain conditions into the SIP from
a recent permit revision applicable to the Tampa Electric Company--Big
Bend Station (Big Bend) power plant. The submission was received by EPA
on April 25, 2019. EPA is proposing to determine that the Hillsborough
County Area attained the 2010 1-hour SO2 NAAQS by its
applicable attainment date of October 4, 2018; to approve the SIP
revision containing the State's plan for maintaining attainment of the
2010 1-hour SO2 standard and to incorporate the maintenance
plan into the SIP; to redesignate the Hillsborough County Area to
attainment for the 2010 1-hour SO2 NAAQS; and to incorporate
into the SIP certain permitting conditions applicable to Big Bend,
including a condition that lowers the SO2 emissions cap and
a condition that restricts fuel use at two electric generating units to
natural gas.

DATES: Comments must be received on or before August 30, 2019.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R04-
OAR-2018-0552 at http://www.regulations.gov. Follow the online
instructions for submitting comments. Once submitted, comments cannot
be edited or removed from Regulations.gov. EPA may publish any comment
received to its public docket. Do not submit electronically any
information you consider to be Confidential Business Information (CBI)
or other information whose disclosure is restricted by statute.
Multimedia submissions (audio, video, etc.) must be accompanied by a
written comment. The written comment is considered the official comment
and should include discussion of all points you wish to make. EPA will
generally not consider comments or comment contents located outside of
the primary submission (i.e., on the web, cloud, or other file sharing
system). For additional submission methods, the full EPA public comment
policy, information about CBI or multimedia submissions, and general
guidance on making effective comments, please visit http://www2.epa.gov/dockets/commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT: Madolyn Sanchez, Air Regulatory
Management Section, Air Planning and Implementation Branch, Air and
Radiation Division, U.S. Environmental Protection Agency, Region 4, 61
Forsyth Street SW, Atlanta, Georgia 30303-8960. Ms. Sanchez may be
reached by phone at<PHONE_NUMBER> or via electronic mail at
<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:

I. What are the actions EPA is proposing to take?

    EPA is proposing to take the following four separate but related
actions: (1) To determine that the Hillsborough County Area attained
the 2010 1-hour SO2 NAAQS by its applicable attainment date
of October 4, 2018; (2) to approve Florida's maintenance plan for
maintaining the 2010 1-hour SO2 NAAQS in the Area and
incorporate it into the SIP; (3) to redesignate the Hillsborough County
Area to attainment for the 2010 1-hour SO2 NAAQS; and (4)
incorporate certain revised permitting conditions applicable to Big
Bend into the SIP, including a condition that lowers the SO2
emissions cap and a condition that limits fuel use to natural gas at
two electric generating units. The Hillsborough County Area is
comprised of the portion of Hillsborough County encompassed by the
polygon with the vertices using Universal Traverse Mercator (UTM)
coordinates in UTM zone 17 with datum NAD83 as follows: (1) Vertices-
UTM Easting (m) 358581, UTM Northing 3076066; (2) vertices-UTM Easting
(m) 355673, UTM Northing 3079275; (3) UTM Easting (m) 360300, UTM
Northing 3086380; (4) vertices-UTM Easting (m) 366850, UTM Northing
3086692; (5) vertices-UTM Easting (m) 368364, UTM Northing 3083760; and
(6) vertices-UTM Easting (m) 365708, UTM Northing 3079121. There is one
major point source of SO2 emissions within the Hillsborough
County Area--Mosaic Fertilizer, LLC Riverview facility (Mosaic).\1\ Big
Bend is located just outside of the Area and is the largest source of
SO2 within 25 km outside of the Area.
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    \1\ There are two smaller point sources within the Area--Ajax
Paving Industries, Inc. Plant No. 6 (Ajax) and Harsco Minerals
(Harsco). Cumulative SO2 emissions for these sources were
less than 6 tons and 1 ton according to Florida's annual operating
report for 2011 and 2015, respectively. See Table 5 below and
Appendix D in the June 7, 2018, submittal.
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    EPA is proposing to determine that the Hillsborough County Area
attained the 2010 1-hour SO2 NAAQS by its applicable
attainment date of October 4, 2018. EPA is also proposing to approve
Florida's SIP revision containing the maintenance plan for the
Hillsborough County Area in accordance with the requirements of section
175A of the Clean Air Act (CAA or Act). The maintenance plan submitted
with Florida's request for redesignation is intended to help keep the
Hillsborough County Area in attainment of the 2010 1-hour
SO2 NAAQS through the year 2032.
    EPA is also proposing to determine that the Hillsborough County
Area has met the requirements for redesignation under section
107(d)(3)(E) of the CAA. Accordingly, EPA is proposing to approve a
request to change the designation of the portion of Hillsborough County
that is designated nonattainment to attainment for the 2010 1-hour
SO2 NAAQS.
    Finally, EPA is proposing to incorporate certain revised permitting
conditions applicable to Big Bend into the Florida SIP.

II. Background

    On June 2, 2010, EPA revised the primary SO2 NAAQS,
establishing a new 1-hour SO2 standard of 75 parts per
billion (ppb). See 75 FR 35520 (June 22, 2010). Under EPA's regulations
at 40 CFR part 50, the 2010 1-hour SO2 NAAQS is met at a
monitoring site when the 3-year average of the annual 99th percentile
of daily maximum 1-hour average concentrations is less than

or equal to 75 ppb (based on the rounding convention in 40 CFR part 50,
appendix T). See 40 CFR 50.17. Ambient air quality monitoring data for
the 3-year period must meet a data completeness requirement. A year
meets data completeness requirements when all four quarters are
complete, and a quarter is complete when at least 75 percent of the
sampling days for each quarter have complete data. A sampling day has
complete data if 75 percent of the hourly concentration values,
including state-flagged data affected by exceptional events which have
been approved for exclusion by the Administrator, are reported.\2\
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    \2\ See 40 CFR part 50, Appendix T, section 3(b).
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    Upon promulgation of a new or revised NAAQS, the CAA requires EPA
to designate as nonattainment any area that does not meet (or that
contributes to ambient air quality in a nearby area that does not meet)
the NAAQS. EPA designated the Area as nonattainment for the 2010 1-hour
SO2 NAAQS, effective October 4, 2013, using 2009-2011
complete, quality assured, and certified ambient air quality data. See
78 FR 47191 (August 5, 2013). Under the CAA, nonattainment areas must
attain this NAAQS as expeditiously as practicable but not later than
five years after the October 4, 2013, effective date of the
designation. See CAA section 192(a). Therefore, the Hillsborough County
Area's applicable attainment date was no later than October 4, 2018.
    EPA's 2010 SO2 nonattainment designation for the Area
triggered an obligation for Florida to develop a nonattainment SIP
revision addressing certain requirements under CAA title I, part D,
subpart 1 (hereinafter ``Subpart 1'') and to submit that SIP revision
to EPA in accordance with the deadlines in title I, part D, subpart 5
(hereinafter ``Subpart 5''). Subpart 1 contains the general
requirements for nonattainment areas for criteria pollutants, including
requirements to develop a SIP that provides for the implementation of
reasonably available control measures (RACM), requires reasonable
further progress (RFP), includes base-year and attainment-year
emissions inventories, a SIP-approved nonattainment new source review
(NNSR) permitting program that accounts for growth in the area,
enforceable emissions limitations and other such control measures, and
provides for the implementation of contingency measures. This SIP
revision was due within 18 months following the October 4, 2013,
effective date of designation (i.e., April 4, 2015). See CAA section
191(a). Florida submitted a nonattainment SIP revision to EPA on April
3, 2015.
    On July 3, 2017 (82 FR 30749), EPA approved Florida's April 3,
2015, SO2 nonattainment SIP revision. This SIP revision
provided a modeled attainment demonstration and satisfied the required
nonattainment planning requirements mentioned above for the
Hillsborough County Area. The revision included a base year emissions
inventory, a modeling demonstration of attainment for the 2010
SO2 NAAQS, RACM/Reasonably Available Control Technology
(RACT), an RFP plan, NNSR permitting program, and contingency measures
for the Hillsborough County Area. As discussed in Sections V and VI,
below, the nonattainment SIP revision included permit conditions to
reduce SO2 emissions at Mosaic and Big Bend.
    As part of that action, EPA incorporated into the Florida SIP
specified SO2 emissions caps, compliance monitoring, and
recordkeeping and reporting requirements for emission units at Mosaic
(Permit No. 0570008-080-AC, issued on January 15, 2015) and Big Bend
(Permit No. 0570039-074-AC, issued on February 26, 2015). Florida based
its modeled attainment demonstration, submitted with its April 3, 2015,
nonattainment SIP revision, on these conditions. Big Bend has four
emission units (EUs 1 through 4), and Big Bend's permit placed an
SO2 emissions cap on all four units at 3,162 lb/hr on a 30-
day boiler operating day average. On December 14, 2018, Florida issued
a final air construction permit to Big Bend (Permit No. 0570039-120-AC)
that, among other things, restricts two units to the use of natural
gas; lowers the four-unit emissions cap from 3,162 lb/hr to 2,156 lb/
hr; and modifies monitoring and recordkeeping requirements for EUs 1
and 2.\3\ Florida's April 19, 2019, submittal requests that EPA
incorporate into the Florida SIP certain permit conditions established
in Permit No. 0570039-120-AC. Some of the identified conditions replace
specific conditions from Permit No. 0570039-074-AC that EPA approved
into the SIP for purposes demonstrating attainment of the
SO2 standard pursuant to the nonattainment requirements of
sections 172, 191, and 192 of the CAA.
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    \3\ Florida incorporated the conditions applicable to Big Bend
from Permit No. 0570039-120-AC into the facility's Title V operating
permit on February 8, 2019.
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III. What are the criteria for redesignation?

    The CAA provides the requirements for redesignating a nonattainment
area to attainment. Specifically, section 107(d)(3)(E) of the CAA
allows for redesignation provided that the following criteria are met:
(1) The Administrator determines that the area has attained the
applicable NAAQS; (2) the Administrator has fully approved the
applicable implementation plan for the area under section 110(k); (3)
the Administrator determines that the improvement in air quality is due
to permanent and enforceable reductions in emissions resulting from
implementation of the applicable SIP and applicable federal air
pollutant control regulations, and other permanent and enforceable
reductions; (4) the Administrator has fully approved a maintenance plan
for the area as meeting the requirements of section 175A; and (5) the
state containing such area has met all requirements applicable to the
area for purposes of redesignation under section 110 and part D of the
CAA.
    On April 16, 1992 (57 FR 13498), EPA provided guidance on
redesignations in the General Preamble for the Implementation of title
I of the CAA Amendments of 1990 and supplemented this guidance on April
28, 1992 (57 FR 18070). EPA has provided further guidance on processing
redesignation requests in the following documents:
    1. ``Procedures for Processing Requests to Redesignate Areas to
Attainment,'' Memorandum from John Calcagni, Director, Air Quality
Management Division, September 4, 1992 (hereinafter referred to as the
``Calcagni Memorandum'');
    2. ``State Implementation Plan (SIP) Actions Submitted in Response
to Clean Air Act (CAA) Deadlines,'' Memorandum from John Calcagni,
Director, Air Quality Management Division, October 28, 1992;
    3. ``Part D New Source Review (Part D NSR) Requirements for Areas
Requesting Redesignation to Attainment,'' Memorandum from Mary D.
Nichols, Assistant Administrator for Air and Radiation, October 14,
1994; and
    4. ``Guidance for 1-Hour SO2 Nonattainment Area SIP
Submissions,'' Memorandum from Stephen D. Page, April 23, 2014
(hereinafter referred to as the ``SO2 Nonattainment Area
Guidance'').
    EPA's SO2 Nonattainment Area Guidance discusses the CAA
requirements that air agencies need to address when implementing the
2010

SO2 NAAQS in areas designated as nonattainment for the
standard. The guidance includes recommendations for air agencies to
consider as they develop SIPs to satisfy the requirements of sections
110, 172, 175A, 191, and 192 of the CAA to show future attainment and
maintenance of the 2010 SO2 NAAQS. Additionally, the
SO2 nonattainment guidance provides recommendations for air
agencies to consider as they develop redesignation requests and
maintenance plans to satisfy the requirements of sections 107(d)(3)(E)
and 175A. If there are no air quality monitors located in the affected
area, or there are air quality monitors located in the area but
analyses show that none of the monitors are located in the area of
maximum concentration,\4\ then air quality dispersion modeling will
generally be needed to estimate SO2 concentrations in the
area.
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    \4\ See section VIII.A of the 2014 SO2 Nonattainment
Area Guidance.
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IV. Why is EPA proposing these actions?

    Through a letter dated June 7, 2018, FDEP submitted a request for
EPA to redesignate the Hillsborough County Area to attainment for the
2010 1-hour SO2 NAAQS and an associated SIP revision
containing a maintenance plan. Through a letter dated April 16, 2019,
FDEP submitted a revision to the June 7, 2018, redesignation request
and SIP revision asking EPA to incorporate certain conditions into the
SIP from a recent permit revision applicable to Big Bend. EPA's
evaluation indicates that the Hillsborough County Area meets the
requirements for redesignation as set forth in section 107(d)(3)(E),
including the maintenance plan requirements under section 175A of the
CAA. As a result of this evaluation, EPA is proposing to determine that
the Area has attained the 2010 1-hour SO2 NAAQS by its
attainment date of October 4, 2018, in accordance with section
179(c)(1) of the CAA, based upon air quality dispersion modeling
analyses.\5\ EPA is also proposing to approve Florida's maintenance
plan for maintaining the 2010 1-hour SO2 NAAQS in the Area
and incorporate it into the SIP, to redesignate the Hillsborough County
Area to attainment for the 2010 1-hour SO2 NAAQS, and to
incorporate certain conditions from the revised Big Bend permit into
the SIP because these conditions further reduce SO2
emissions.
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    \5\ Section 179(c)(1) reads as follows: ``As expeditiously as
practicable after the applicable attainment date for any
nonattainment area, but not later than 6 months after such date, the
Administrator shall determine, based on the area's air quality as of
the attainment date, whether the area attained the standard by that
date.''
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V. Operational Changes to Big Bend's Emission Units

    Florida's June 7, 2018, redesignation request and maintenance plan
for the Hillsborough County Area relies upon the State's model-based
attainment demonstration from its April 3, 2015, SO2
attainment SIP which EPA approved on July 3, 2017. EPA's approval
action incorporated into the Florida SIP a four-unit emissions cap of
3,162 lb/hr on a 30-day boiler operating day average and certain
compliance monitoring and recordkeeping and reporting parameters from
Permit No. 0570039-074-AC. Florida modeled the Big Bend emissions cap
along with the Mosaic SO2 emissions cap (and other Mosaic
permit conditions) to demonstrate attainment of the standard by the
attainment date. Florida established the Big Bend emissions cap to
demonstrate attainment of the SO2 standard based on a worst-
case operating scenario considering the physical design, heat input,
and emissions variability of each unit at Big Bend. To demonstrate
compliance with the four-unit cap, Permit No. 0570039-074-AC required
each unit to monitor SO2 emissions with a continuous
emission monitoring system (CEMS). The SO2 emissions cap
specified in that permit and the Mosaic permit conditions were the
basis for the model-based attainment demonstration in Florida's 2015
nonattainment SIP.
    On December 14, 2018, Florida issued a revised air construction
permit (Permit No. 0570039-120-AC) to Big Bend that lowers the four-
unit emissions cap from 3,162 lb/hr to 2,156 lb/hr; restricts EUs 1 and
2 to only burn natural gas; and since the amount of sulfur in natural
gas is negligible, authorizes the removal of the SO2 CEMS
for EUs 1 and 2 and requires monitoring for these two units in
accordance with the calculation method allowed for gas-fired acid rain
units in 40 CFR part 75 to demonstrate compliance with the lowered
emissions cap.\6\ EUs 1 and 2 share a stack and a flue gas
desulfurization (FGD) system to control SO2. Permit No.
0570039-074-AC required certified CEMS as the method of SO2
emissions monitoring and compliance for EUs 1 and 2. However, with the
restriction on EUs 1 and 2 to burn natural gas in the revised permit,
the new method of monitoring and compliance for EUs 1 and 2 utilizes
the protocol in 40 CFR part 75, Appendix D to determine the hourly
SO2 emission rate from each unit. EUs 3 and 4 continue to
certify compliance with the emissions cap through use of CEMS.
Therefore, Big Bend will demonstrate compliance of the lowered four-
unit emissions cap through a combination of 40 CFR part 75, Appendix D
(EUs 1 and 2) and SO2 CEMS data (EUs 3 and 4). As required
by 40 CFR part 75, Appendix D, section 2.1, Big Bend will measure and
record the hourly flow rate of natural gas combusted by EUs 1 and 2
with an in-line fuel flowmeter. The pounds-per-hour SO2
emission rates for each of these two units will then be calculated by
using the equation provided in 40 CFR part 75, Appendix D, section
3.3.1, along with the measured hourly natural gas flow rate to each
unit and the vendor certified sulfur content of the combusted natural
gas.
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    \6\ The permit also authorizes additional changes not applicable
to this proposed action, including removal of all coal and solid
fuels from the list of permitted fuels for EUs 1 and 2 so that the
units are no longer subject to the National Emission Standards for
Hazardous Air Pollutants for Coal- and Oil-Fired Electric Utility
Steam Generating Units in Subpart UUUUU in Title 40, Part 63 of the
Code of Federal Regulations (40 CFR 63) (also called the Mercury and
Air Toxic Standards (MATS) rule). EUs 008, 015, and 016 will be
removed because the units are not necessary for natural gas firing
operations. Additionally, this permit authorizes relocation of the
existing monitoring points for the nitrogen oxides, carbon dioxide,
and ammonia CEMS from the common stack for EUs 1 and 2 to the common
inlet duct of the flue gas desulfurization system for these two
units. This permit also removes other monitoring requirements for
other pollutants and removes the MATS conditions that are no longer
applicable because the permit exempts EUs 1 and 2 from MATS
requirements.
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    Florida's April 16, 2019, submittal requests that EPA incorporate
into the SIP certain conditions from Permit No. 0570039-120-AC. As
noted below, some of these conditions replace conditions that EPA
incorporated into the SIP from Permit No. 0570039-074-AC in the
Agency's July 3, 2017 action approving the State's nonattainment SIP.
The conditions identified for incorporation into the SIP from Permit
No. 0570039-120-AC are: (1) Section 2, Condition 4 (new)--describing
the 40 CFR part 75, Appendix D monitoring methodology and compliance
requirements for EUs 1 and 2; \7\ (2) the ``SO2 Emissions
Cap'' provision from Section 3, Condition 4 (replacement)--setting a
four-unit emissions cap of 2,156 lb/hr averaged over a 30-day boiler
operating day, requiring that EUs

1 and 2 demonstrate compliance with the cap by monitoring natural gas
fuel flow and following the procedures in Appendix D to 40 CFR 75 to
determine SO2 mass emissions, and requiring that EUs 3 and 4
demonstrate compliance with the cap through CEMS; \8\ (3) the
``SO2 CEMS'' provision from Section 3, Condition 4
(replacement)--requiring EUs 3 and 4 to use CEMS to demonstrate
compliance with the cap and to meet the quality assurance and quality
control requirements outlined in the facility's title V permit; \9\ and
(4) the ``Methods of Operation'' for Units 1 and 2 provision from
Section 3, Condition 6 (new)--restricting EUs 1 and 2 to burning only
natural gas from a federally regulated pipeline.\10\ As discussed in
section VI of this notice, Florida's April 19, 2019, submittal provides
even more air quality protection than the model-based attainment plan
approved by EPA.
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    \7\ The permit condition states that the permittee shall keep a
daily log of natural gas combusted at Units 1 and 2 and shall record
the sulfur content of the natural gas as provided by the fuel
supplier. The SO2 mass emissions calculated by following
procedures in Appendix D of 40 CFR 75 shall be averaged on a 30-
boiler operating day basis to demonstrate the contribution of Units
1 and 2 to the 4-unit SO2 cap. [Rule 62-4.070(3), F.A.C.
and Application No. 0570039-120-AC].
    \8\ This permit condition states that the combined emissions of
SO2 from all four-fossil fuel fired steam generating
units (EU 001-EU 004, combined) shall not exceed 2,156 lb/hour based
on a 30-boiler operating day rolling average. Units 1 and 2 shall
demonstrate compliance with the cap by monitoring the natural gas
fuel flow and following procedures in Appendix D of 40 CFR part 75
to determine SO2 mass emissions. For Units 3 and 4,
compliance with this SO2 emissions cap shall be
demonstrated by data collected from the existing SO2
CEMS. The new emissions cap applies at all times when these units
are operating including periods of startup and shutdown. [Rules 62-
4.070(1) and (3), and 62-4.080(1), F.A.C.; Hillsborough County
SO2 Maintenance SIP; and Application No. 0570039-120-AC].
In its April 16, 2019 submittal, Florida identifies this provision
as ``Section 3, Subsection B, Specific Condition 2''; however, it is
contained under the heading ``4. Permit Being Modified: Permit No.
0570039-096-AC'' in Section 3 of Permit No. 0570039-120-AC.
    \9\ This permit condition states that the permittee shall use
existing SO2 CEMS data to demonstrate continuous
compliance for Units 3 and 4 with the SO2 emissions cap
specified in Condition 2. The existing SO2 CEMS shall
continue to meet and follow the quality assurance and quality
control requirements outline in the facility's Title V air operation
permit. [Rules 62-4.070(1) and (3), and 62-4.080(1), F.A.C.;
SO2 Attainment SIP; and Application No. 0570039-120-AC].
In its April 16, 2019 submittal, Florida identifies this provision
as ``Section 3, Subsection B, Specific Condition 3; however, it is
contained under the heading ``4. Permit Being Modified: Permit No.
0570039-096-AC'' in Section 3 of Permit No. 0570039-120-AC.
    \10\ This permit condition states that Big Ben Units 1 and 2
shall fire only natural gas from a federally regulated pipeline. No
solid fuels shall be burned in these units. In its April 16, 2019
submittal, Florida identifies this provision as ``Section 3,
Subsection A, Specific Condition 3a''; however, it is contained
under the heading ``6. Permits Being Modified: Permit Nos. 0570039-
066-AC & 109-AC'' in Section 3 of Permit No. 0570039-120-AC.
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VI. What is EPA's analysis of the redesignation request and SIP
revision?

    The five redesignation criteria provided under CAA section
107(d)(3)(E) are discussed in greater detail for the Hillsborough
County Area in the following paragraphs.
    Criterion (1)--The Administrator determines that the area has
attained the NAAQS.
    For redesignating a nonattainment area to attainment, the CAA
requires EPA to determine that the area has attained the applicable
NAAQS (CAA section 107(d)(3)(E)(i)). As discussed in section VIII.A of
the SO2 Nonattainment Area Guidance, there are generally two
components needed to support an attainment determination for
SO2, which should be considered interdependently.\11\ The
first component relies on air quality monitoring data. For
SO2, any available monitoring data would need to indicate
that all monitors in the affected area are meeting the standard as
stated in 40 CFR 50.17 using data analysis procedures specified in 40
CFR part 50, Appendix T. The second component relies on air quality
modeling data. If there are no air quality monitors located in the
affected area, or there are air quality monitors located in the area,
but analyses show that none of the monitors are located in the area of
maximum concentration,\12\ then air quality dispersion modeling will
generally be needed to estimate SO2 concentrations in the
area. Such dispersion modeling should be conducted to estimate
SO2 concentrations throughout the nonattainment area using
actual emissions and meteorological information for the most recent
three calendar years. However, EPA may also make determinations of
attainment based on the modeling from the attainment demonstration for
the applicable SIP for the affected area, eliminating the need for
separate actuals-based modeling to support the determination that an
area is currently attaining. If the air agency has previously submitted
a modeled attainment demonstration using allowable emissions, no
further modeling is needed as long as the source characteristics are
still reasonably represented and so long as emissions are at or below
allowable levels. Where both monitoring and modeling information is
available, such as the case with the Hillsborough County Area, EPA will
consider both types of evidence.
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    \11\ SO2 is primarily a localized, source-specific
pollutant, and therefore, SO2 control measures are, by
definition, based on what is directly and quantifiably necessary to
attain the NAAQS.
    \12\ See section VIII.A of the SO2 Nonattainment Area
Guidance.
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    Florida's pre- and post-modification attainment demonstration
modeling indicates that the only ambient SO2 monitor in the
Area--the East Bay monitor (AQS ID: 12-057-0109)--is not cited in the
area of maximum concentration for both Mosaic and Big Bend, and
therefore, the clean monitoring data at the monitor does not on its own
demonstrate that the Area is currently attaining the 1-hour
SO2 NAAQS. For that reason, EPA's proposed approval of
Florida's redesignation and maintenance plan SIP for the Hillsborough
County Area is based on the modeled attainment demonstration that
includes permanent and enforceable SO2 controls and
emissions limits at Mosaic and Big Bend showing attainment of the 2010
SO2 standard by the statutory deadline. EPA approved the
attainment demonstration for the Area on July 3, 2017, and incorporated
the new allowable emission rates and control measures into the SIP,
making them permanent and enforceable. See 82 FR 30749. Florida's
redesignation request indicates that the control strategies were fully
implemented at Mosaic in November 2017 and at Big Bend in early 2016
(i.e., these sources are emitting SO2 at or below the SIP-
approved allowable emission levels). The revised conditions in Permit
No. 0570039-120-AC applicable to Big Bend became effective on December
14, 2018. If EPA approves these revised permit conditions into the SIP,
they will become permanent and enforceable measures. As discussed
below, EPA proposes to find that these permit revisions continue to
assure attainment because, among other things, they reduce the
SO2 emissions cap by approximately 32 percent. Details
regarding the control strategies and emissions reductions are provided
in the Criterion (3) section of this notice. Details regarding the
modeling analysis are discussed in the following paragraphs.

Florida's EPA-Approved Modeling Analysis

    Florida's modeling analysis was developed in accordance with EPA's
Guideline on Air Quality Models (Modeling Guidance) \13\ and the
SO2 Nonattainment Area Guidance and was prepared using EPA's
preferred dispersion modeling system--the American Meteorological
Society/Environmental Protection Agency Regulatory Model (AERMOD)--
consisting of the AERMOD (version 14134) \14\ model and multiple data
input

preprocessors as described below. FDEP used regulatory default options
and the rural land use designation in the AERMOD modeling.
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    \13\ See 40 CFR part 51 Appendix W (EPA's Guideline on Air
Quality Models) (January 17, 2017) located at https://www3.epa.gov/ttn/scram/appendix_w/2016/AppendixW_2017.pdf.
    \14\ Version 14134 of the AERMOD Modeling System was the current
EPA-recommended regulatory version at the time the modeling was
performed in 2014-2015, and therefore was appropriate for the
modeling analysis.
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    The pre-processors AERMET (version 14134) and AERMINUTE were used
to process five years (i.e., 2008-2012) of 1-minute meteorological data
from the Tampa National Weather Service Office (NWS) at the Tampa
International Airport, Tampa, Florida, surface level site, based on
FDEP's land use classifications, in combination with twice daily upper-
air meteorological information from the same site. The Tampa
International Airport is located approximately 20 km northwest from the
Hillsborough Area.
    The AERMOD pre-processor AERMAP (version 11103) was used to
generate terrain inputs for the receptors, based on a digital elevation
mapping database from the National Elevation Dataset developed by the
U.S. Geological Survey. FDEP used AERSURFACE to generate direction-
specific land-use surface characteristics for the modeling.
    The stack heights used in the modeling meet the Good Engineering
Practice stack height criteria and the Building Profile Input Program
for Plume Rise Model Enhancements was used to generate direction-
specific building downwash parameters. FDEP developed a Cartesian
receptor grid across the entire Area (extending up to 8.5 km from the
monitor), with 100 meter spacing in ambient air to ensure that maximum
concentrations are captured in the analysis.
    FDEP selected a background SO2 concentration based on
local SO2 monitoring data from the East Bay monitor for the
period January 2012 to December 2013. This background concentration
from the nearby ambient air monitor is used to account for
SO2 impacts from all sources that are not specifically
included in the AERMOD modeling analysis. The ambient monitoring data
was obtained from the Florida Air Monitoring and Assessment System. Due
to its close proximity to Mosaic and Big Bend, monitored concentrations
at this station are strongly influenced by emissions from both
facilities. As a result, and as allowed by EPA's Modeling Guideline,
the data was filtered to remove measurements where the wind direction
could transport pollutants from Mosaic and Big Bend to the monitor.
More specifically, the data was filtered to remove measurements where
hourly wind directions were between 275[deg] to 4[deg] or 153[deg] to
241[deg].
    EPA's SO2 Nonattainment Area Guidance provides a
procedure for establishing longer-term averaging times for
SO2 emission limits (up to a 30-day rolling averaging
time).\15\ In approving Florida's 2015 attainment demonstration, EPA
concluded that FDEP completed this analysis for both Mosaic and Big
Bend to derive a SIP emission limit with a block 24-hour longer-term
averaging time and a rolling 30-day longer-term averaging time,
respectively, that are comparatively stringent to the 1-hour limit. For
more details, see Florida's April 3, 2015, nonattainment SIP submittal
and EPA's final approval. See 82 FR 30749 (July 3, 2017).\16\
---------------------------------------------------------------------------

    \15\ FDEP followed EPA's SO2 Nonattainment Area
Guidance on procedures for establishing emissions limits with
averaging periods longer than 1 hour.
    \16\ Florida's nonattainment SIP submittal is located in Docket
No. EPA-R04-OAR-2015-0624.
---------------------------------------------------------------------------

    The results of Florida's attainment modeling are summarized in
Table 1. Table 1 presents the results from the six sets of AERMOD
modeling runs that were performed. The six modeling runs were the
result of using an uncontrolled, or pre-modification, scenario and five
different controlled, or post-modification, scenarios to account for
possible control strategies that involved two-unit and three-unit
emissions caps at Mosaic, in addition to individual emissions caps. The
model also included the 3,162 lbs/hr emissions cap at Big Bend. The
four Big Bend units were modeled at constant emissions rates derived by
distributing the emissions cap based on the relative maximum allowable
heat input for each unit. Maximum allowable permitted emissions caps
were used for the modeling demonstration. These emissions limits and
other control measures were established in construction permits issued
by FDEP. EPA incorporated the permit conditions necessary to
demonstrate modeled attainment into the Florida SIP via the approved
attainment plan making them permanent and enforceable. Florida
incorporated the conditions applicable to Big Bend from Permit No.
0570039-074-AC into the facility's Title V operating permit \17\ and
will incorporate the conditions for Mosaic into the next Title V
revision for that facility.
---------------------------------------------------------------------------

    \17\ See Title V Operating Permit No. 0570039-110-AV issued by
FDEP on November 7, 2017.
---------------------------------------------------------------------------

    As noted above, Florida's modeling presents five post-control
modeling runs, summarized in Table 1, which were used by FDEP to
identify the worst possible scenario of emissions distributions between
Mosaic's three sulfuric acid Emissions Units (EUs) 004-006. FDEP began
by evaluating maximum sulfuric acid production rates and catalyst
limitations, which resulted in a total SO2 emissions cap of
600 pounds per hour (lb/hr) for Mosaic EUs 004-006. This overall cap
was then scaled to a 24-hour limit, maintaining comparative stringency
with the 1-hour limit, following the procedures in the SO2
Nonattainment Guidance. The 24-hour emissions rate resulting from this
procedure is 577.8 lb/hr. FDEP rounded down the limit for an additional
buffer for the maximum modeled impact, resulting in a 24-hour limit of
575 lb/hr. FDEP then back-calculated to a 1-hour critical emission
value (CEV) emissions cap of 597 lb/hr. This three-unit emissions cap
was then modeled in several configurations to mimic variability in
emissions possible under the scenario of all three units operating
simultaneously. The different configurations were determined by
apportioning the emissions cap (597 lb/hr) based on each unit emitting
at its individual emissions limit with the remainder of the cap
distributed to the other two units based on their relative production
capacities. The highest impact is presented in Table 1 as the three-
unit emissions cap scenario.
    FDEP also evaluated two-unit emissions caps, which assumed that
only two of the three units were operating. The six possible two-unit
operating scenarios were evaluated in turn by modeling each unit
operating at its individual emission limit, while the remainder of the
597 lb/hr cap was distributed to the other operating unit. The highest
modeled impact is presented in Table 2 as the two-unit operating
scenario. For the three remaining scenarios, each sulfuric acid plant
was assumed to operate alone at its individual emissions cap. For all
of the modeling scenarios, the four Big Bend units were modeled at
constant emissions rates derived by distributing the 1-hour CEV
emissions cap \18\ based on the relative maximum allowable heat input
for each unit. The results for each of these scenarios are also
presented in Table 1. Table 1 shows that the maximum 1-hour average
across all five years of meteorological data (2008-2012) is less than
or equal to the 2010 1-hour SO2 NAAQS of 75 ppb for the five
post-control AERMOD modeling

runs. For more details, see Florida's April 3, 2015, nonattainment SIP
submittal.
---------------------------------------------------------------------------

    \18\ The details of Florida's procedures for developing the 1-
hour CEV and longer-term average emissions limits are provided in
its April 3, 2015, nonattainment SIP submittal.

                                Table 1--Maximum Modeled SO2 Impacts in the Hillsborough Area, Micrograms per Cubic Meter
                                                                          [ppb]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                Maximum predicted impact
          Model scenario               Averaging time     ------------------------------------    Background           Total             SO2 NAAQS
                                                                Mosaic           Big Bend
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pre-modification.................  1-hour................    425.50 (162.4)       0.82 (0.31)       20.40 (7.8)    446.72 (170.5)             196.4 (75)
Three-unit.......................  1-hour................     118.90 (45.4)      55.90 (21.3)       21.44 (8.2)     196.24 (74.9)
Two-unit.........................  1-hour................     123.59 (47.2)      52.22 (19.9)       18.83 (7.2)     194.65 (74.3)
EU 004 only......................  1-hour................       0.33 (0.12)     170.84 (65.2)       17.26 (6.6)     188.43 (71.9)
EU 005 only......................  1-hour................       0.25 (0.10)     170.84 (65.2)       17.26 (6.6)     188.35 (71.9)
EU 006 only......................  1-hour................       0.33 (0.12)     170.84 (65.2)       17.26 (6.6)     188.43 (71.9)
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The pre-control analysis resulted in a predicted impact of 170.5
ppb. The post-control analysis resulted in a worst-case predicted
impact of 74.9 ppb in the three-unit operating scenario. EPA determined
that the modeling results indicate sufficient reductions in air quality
impact with the implementation of the post-construction control plan
for Mosaic and Big Bend. The control measures that have been
implemented at the Mosaic and Big Bend are outlined in the Criterion
(3) section of this notice. The collective emission limit and related
compliance parameters have been incorporated into the SIP, making them
permanent and federally enforceable. More details on the pre-
construction and post-construction operations at the facilities are
included in Florida's nonattainment SIP submission and in EPA's
rulemaking on that submittal.\19\
---------------------------------------------------------------------------

    \19\ See 82 FR 30749 (July 3, 2017) (final rule), 81 FR 57522
(August 23, 2016) (proposed rule), and Florida's SIP submittal
located in Docket EPA-R04-OAR-2015-0624.
---------------------------------------------------------------------------

    On July 3, 2017, EPA approved the modeled attainment demonstration
described above and concluded that it is consistent with CAA
requirements, EPA's Modeling Guideline, and EPA's guidance for
SO2 attainment demonstration modeling. Florida's
redesignation request indicates that the control strategies were fully
implemented at Mosaic in November 2017 and at Big Bend in early 2016,
meaning that emissions are at or below the levels modeled in Florida's
attainment plan. Therefore, EPA proposes to find that air quality
modeling supports the conclusion that the Area has attained the 2010 1-
hour SO2 NAAQS and attained the standard by the applicable
deadline.

Effect of the Big Bend Permit Revisions on Florida's EPA-Approved
Modeling Analysis

    As discussed above, since the time that EPA approved Florida's
attainment demonstration modeling on July 3, 2017, Florida issued a
revised permit to Big Bend that restricts EUs 1 and 2 to only burning
natural gas; reduces the four-unit SO2 cap from 3,162 lb/hr
to 2,156 lb/hr (each on a 30-day average basis); and amends the method
for demonstrating compliance with the four-unit cap. Florida's April
19, 2019, submittal revises its pending June 7, 2018, redesignation
request and associated SIP revision for the Hillsborough County Area by
asking EPA to incorporate the aforementioned permit conditions into the
SIP. Florida's 2019 submittal states that its model-based attainment
demonstration (described above) is still valid for demonstrating
attainment in the Area. Florida's conclusion is based on the
approximate 32 percent reduction in the four-unit cap and the change in
stack parameters for the stack shared by EUs 1 and 2 due to the switch
to natural gas. According to the State, the plume flowrate, exit
velocity, and temperature for the stack shared by EUs 1 and 2 have all
increased. Florida's submittal also asserts that a faster flowrate and
velocity leaving the stack will lead to increased plume rise and that
the warmer temperatures will also increase plume rise. With increased
plume rise, pollutants will be able to disperse more before reaching
the ground and will lead to lower pollutant concentrations at the
surface. Therefore, Florida believes that the new stack parameters for
the shared stack of EUs 1 and 2, along with the reduced SO2
emissions cap, would lead to lower modeled concentrations.
    Florida's submittal also notes that the stack parameters for EUs 3
and 4 have not changed from the values used in the modeling
demonstration. The stack configuration for EUs 1 through 4, which have
stack heights of 150 meters, are spaced less than 120 meters apart and
are over 2 kilometers (km) from the Area, which according to the State,
leads to the stacks behaving as a single, distant point source for
receptors within the Area. The submittal also asserts that any
potential emissions scenario with the revised cap would be expected to
lead to decreased modeled concentrations due to the overall decrease in
emissions from the four EUs due to the revised four-unit SO2
cap.
    EPA proposes to agree with Florida's assessment and conclusion
regarding the effect of the revised Big Bend permit conditions on the
State's model-based attainment demonstration. EPA believes that
Florida's modeling, which showed that Big Bend's maximum impact was 87%
of the NAAQS at 170.84 [mu]g/m\3\ (see Table 1) and demonstrated
attainment of the 2010 SO2 NAAQS using a four-unit
SO2 cap of 3,162 lb/hr, is more conservative (in relation to
a demonstration relying on the lowered cap) and is still valid for
demonstrating attainment in the Area.

Monitoring Data

    For SO2, a location may be considered to be attaining
the 2010 1-hour SO2 NAAQS if it meets the NAAQS as
determined in accordance with 40 CFR 50.17 and Appendix T of part 50,
based on three complete, consecutive calendar years of quality-assured
air quality monitoring data. Specifically, to attain the NAAQS at each
monitoring site, the 3-year average of the annual 99th percentile
(fourth highest value) of 1-hour daily maximum concentrations measured
at each monitor within an area must be less than or equal to 75 ppb.
The data must be collected and quality-assured in accordance with 40
CFR part 58 and recorded in the EPA Air Quality System (AQS). The
monitors should have remained at the same

location for the duration of the monitoring period required for
demonstrating attainment.
    As discussed above, FDEP currently operates one ambient
SO2 monitor in the Area, the East Bay monitor. This monitor
is located approximately 1 km southeast of Mosaic and 7 km north of Big
Bend. The original nonattainment designation was based on the 2009-2011
design value of 103 ppb at this monitor. As shown in Table 2, the
design values at this monitor have decreased steadily since 2011.
---------------------------------------------------------------------------

    \20\ The 2017 data is available at https://www.epa.gov/outdoor-air-quality-data/monitor-values-report.
    \21\ The East Bay monitor did not collect a valid 2016-2018
design value due to incomplete data in 2018.

                          Table 2--Hillsborough County Area SO2 Monitored Design Values
                                                      [ppb]
----------------------------------------------------------------------------------------------------------------
                                2011-2013    2012-2014    2013-2015    2014-2016    2015-2017
 Monitoring station (AQS site     design       design       design       design       design    2016-2018 design
             ID)                  value        value        value        value      value \20\        value
----------------------------------------------------------------------------------------------------------------
East Bay (12-057-0109).......      93 ppb       79 ppb       66 ppb       66 ppb       60 ppb   Incomplete.\21\
----------------------------------------------------------------------------------------------------------------

    Quality-assured and certified ambient air monitoring data for the
2015-2017 period, the most recent 3-year period with complete data, are
attaining the 2010 1-hour SO2 NAAQS with a design value of
60 ppb. This design value is approximately 43 percent lower than the
2009-2011 design value and 40 percent lower than the NAAQS. Although
the 2016-2018 design value is invalid due to incomplete data in 2018,
EPA has no reason to believe that the 2016-2018 design value would have
been above the NAAQS if the monitor had complete data for 2018 given
the downward trend in emissions shown in Table 2 and a 2015-2017 design
value that is 40 percent lower than the NAAQS. Furthermore, since 2013,
the annual 99th percentile daily maximum 1-hour SO2
concentration has remained below the standard, and there have been no
1-hour values recorded above the level of the standard since late 2016.
EPA believes that the significant decrease in SO2
concentrations is due to the permanent and enforceable control measures
at Mosaic and Big Bend. Thus, the monitoring data also support the
conclusion that the Area has attained the standard.
    EPA is proposing to determine that the Area has attained the 2010
1-hour SO2 NAAQS based on the modeling analysis discussed
above which is not contradicted by monitoring data. Preliminary
monitoring data for the Area for 2019 indicates that the Area continues
to attain the standard and has not measured any exceedances of the 1-
hour SO2 standard.\22\ If, before EPA takes final action,
monitoring data or other evidence causes EPA to conclude that the Area
is not continuing to meet the standard, EPA will not go forward with
the redesignation. As discussed in more detail below, Florida has
committed to continue monitoring ambient SO2 concentrations
in this Area in accordance with 40 CFR part 58. Any future changes to
the state or local air monitoring station network in the Area will be
submitted to EPA for approval in Florida's annual ambient air
monitoring network plan, as required by 40 CFR 58.10.
---------------------------------------------------------------------------

    \22\ Preliminary 2019 data is available at https://www.epa.gov/outdoor-air-quality-data/monitor-values-report.
---------------------------------------------------------------------------

    Criterion (2)--The Administrator has fully approved the applicable
implementation plan for the area under section 110(k); and Criterion
(5)--Florida has met all applicable requirements under section 110 and
part D of title I of the CAA.
    For redesignating a nonattainment area to attainment, the CAA
requires EPA to determine that the state has met all applicable
requirements under section 110 and part D of title I of the CAA (CAA
section 107(d)(3)(E)(v)) and that the state has a fully-approved SIP
under section 110(k) for the area (CAA section 107(d)(3)(E)(ii)). EPA
proposes to find that Florida has met all applicable SIP requirements
for the Hillsborough County Area under section 110 of the CAA (general
SIP requirements) for purposes of redesignation. Additionally, EPA
proposes to find that the Florida SIP satisfies the criterion that it
meets applicable SIP requirements for purposes of redesignation under
part D of title I of the CAA in accordance with section
107(d)(3)(E)(v). Further, EPA proposes to determine that the SIP is
fully approved with respect to all requirements applicable for purposes
of redesignation in accordance with section 107(d)(3)(E)(ii). In making
these proposed determinations, EPA ascertained which requirements are
applicable to the Area and, if applicable, that they are fully approved
under section 110(k). SIPs must be fully approved only with respect to
requirements that were applicable prior to submittal of the complete
redesignation request.

A. The Hillsborough County Area Has Met All Applicable Requirements
Under Section 110 and Part D of the CAA

1. General SIP Requirements
    General SIP elements and requirements are delineated in section
110(a)(2) of title I, part A of the CAA. These requirements include,
but are not limited to, the following: Submittal of a SIP that has been
adopted by the state after reasonable public notice and hearing;
provisions for establishment and operation of appropriate procedures
needed to monitor ambient air quality; implementation of a source
permit program; provisions for the implementation of part C
requirements (Prevention of Significant Deterioration (PSD)) and
provisions for the implementation of part D requirements (NNSR permit
programs); provisions for air pollution modeling; and provisions for
public and local agency participation in planning and emission control
rule development.
    Section 110(a)(2)(D) requires that SIPs contain certain measures to
prevent sources in a state from significantly contributing to air
quality problems in another state. To implement this provision, EPA has
required certain states to establish programs to address the interstate
transport of air pollutants. The section 110(a)(2)(D) requirements for
a state are not linked with a particular nonattainment area's
designation and classification in that state. EPA believes that the
requirements linked with a particular nonattainment area's designation
and classifications are the relevant measures to evaluate in reviewing
a redesignation request. The transport SIP submittal requirements,
where applicable, continue to apply to a state regardless of the
designation of any one particular area in the state. Thus, EPA does not
believe that the CAA's interstate

transport requirements should be construed to be applicable
requirements for purposes of redesignation.
    In addition, EPA interprets the other section 110(a)(2) elements
that are neither connected with nonattainment plan submissions nor
linked with an area's attainment status not to be ``applicable''
requirements for purposes of redesignation. The area will still be
subject to these requirements after the area is redesignated. The
section 110 and part D requirements which are linked with a particular
area's designation and classification are the relevant measures to
evaluate in reviewing a redesignation request. This approach is
consistent with EPA's existing policy on applicability (i.e., for
redesignations) of conformity and oxygenated fuels requirements, as
well as with section 184 ozone transport requirements. See Reading,
Pennsylvania, proposed and final rulemakings (61 FR 53174-53176,
October 10, 1996), (62 FR 24826, May 7, 2008); Cleveland-Akron-Loraine,
Ohio, final rulemaking (61 FR 20458, May 7, 1996); and Tampa, Florida,
final rulemaking at (60 FR 62748, December 7, 1995). See also the
discussion on this issue in the Cincinnati, Ohio, redesignation (65 FR
37890, June 19, 2000), and in the Pittsburgh, Pennsylvania,
redesignation (66 FR 50399, October 19, 2001). Nonetheless, EPA has
approved Florida's SIP revisions related to the section 110
requirements for the 2010 SO2 NAAQS, with the exception of
the interstate transport elements at section 110(a)(2)(D)(i)(I). See 81
FR 67179 (September 30, 2016).
2. Title I, Part D, Applicable SIP Requirements
    Subpart 1 of part D, comprised of CAA sections 171-179B, sets forth
the basic nonattainment requirements applicable to all nonattainment
areas. All areas that were designated nonattainment for the
SO2 NAAQS were designated under Subpart 1 of the CAA in
accordance with the deadlines in Subpart 5. For purposes of evaluating
this redesignation request, the applicable Subpart 1 SIP requirements
are contained in section 172(c)(1)-(9), section 176, and sections 191
and 192. A thorough discussion of the requirements contained in
sections 172(c) can be found in the General Preamble for Implementation
of Title I. See 57 FR 13498 (April 16, 1992).
a. Subpart 1 Section 172 Requirements
    Section 172 requires states with nonattainment areas to submit
plans providing for timely attainment and meeting a variety of other
requirements. As discussed in section V.A, above, EPA's longstanding
interpretation of the attainment-related nonattainment planning
requirements of section 172 is that once an area is attaining the
NAAQS, those requirements are not ``applicable'' for purposes of CAA
section 107(d)(3)(E)(ii) and therefore need not be approved into the
SIP before EPA can redesignate the area. In the 1992 General Preamble
for Implementation of Title I, EPA set forth its interpretation of
applicable requirements for purposes of evaluating redesignation
requests when an area is attaining a standard. See 57 FR 13498, 13564
(April 16, 1992). EPA noted that the requirements for RFP and other
measures designed to provide for attainment do not apply in evaluating
redesignation requests because those nonattainment planning
requirements ``have no meaning'' for an area that has already attained
the standard. Id. This interpretation was also set forth in the
Calcagni Memo.
    As discussed above, EPA previously approved Florida's nonattainment
SIP for the Hillsborough County Area. See 82 FR 30749 (July 3, 2017).
Among other things, the nonattainment SIP for the Area satisfied the
section 172(c)(1) requirements for RACT/RACM; 172(c)(2) requirements
related to RFP; 172(c)(3) requirements for a comprehensive and accurate
emissions inventory; 172(c)(6) requirements for enforceable control
measures necessary to provide attainment of the NAAQS by the attainment
date; and section 172(c)(9) requirements for contingency measures.
    Section 172(c)(4) requires the identification and quantification of
allowable emissions for major new and modified stationary sources to be
allowed in an area, and section 172(c)(5) requires source permits for
the construction and operation of new and modified major stationary
sources anywhere in the nonattainment area. EPA has a longstanding
interpretation that because NNSR is replaced by PSD upon redesignation,
nonattainment areas seeking redesignation to attainment need not have a
fully approved part D NNSR program in order to be redesignated. See
memorandum from Mary Nichols, Assistant Administrator for Air and
Radiation, dated October 14, 1994, entitled ``Part D New Source Review
Requirements for Areas Requesting Redesignation to Attainment.''
Florida currently has a fully-approved PSD and part D NNSR program in
place in Chapters 62-204, 62-210, and 62-212 of the Florida
Administrative Code. Florida's PSD program will become effective in the
Area upon redesignation to attainment.
    Section 172(c)(7) requires the SIP to meet the applicable
provisions of section 110(a)(2). As noted above, EPA believes that the
Florida's SIP meets the requirements of section 110(a)(2) applicable
for purposes of redesignation.
    Finally, Section 172(c)(8) allows a state to use equivalent
modeling, emission inventory, and planning procedures if such use is
requested by the state and approved by EPA. Florida has not requested
the use of equivalent techniques under section 172(c)(8).
    As mentioned above, EPA fully approved Florida's April 3, 2015,
nonattainment SIP for the Hillsborough County Area, including the
model-based attainment demonstration, and determined that the SIP
submission met the applicable nonattainment planning requirements of
sections 172 and 191-192 of the CAA demonstrating attainment of the
SO2 standard by the statutory deadline. This approval
included the specific SO2 emissions caps and compliance
monitoring established for the two SO2 point sources
impacting the Hillsborough County Area (Mosaic and Big Bend) and
included in the 2015 SIP revision.
b. Subpart 1 Section 176--Conformity Requirements
    Section 176(c) of the CAA requires states to establish criteria and
procedures to ensure that federally supported or funded projects
conform to the air quality planning goals in the applicable SIP. The
requirement to determine conformity applies to transportation plans,
programs, and projects that are developed, funded, or approved under
title 23 of the United States Code (U.S.C.) and the Federal Transit Act
(transportation conformity) as well as to all other federally supported
or funded projects (general conformity). State transportation
conformity SIP revisions must be consistent with federal conformity
regulations relating to consultation, enforcement, and enforceability
that EPA promulgated pursuant to its authority under the CAA.
    EPA believes that it is reasonable to interpret the conformity SIP
requirements \23\ as not applying for purposes of evaluating the
redesignation request under section 107(d) because

state conformity rules are still required after redesignation and
federal conformity rules apply where state rules have not been
approved. See Wall v. EPA, 265 F.3d 426 (upholding this interpretation)
(6th Cir. 2001); 60 FR 62748 (December 7, 1995). Furthermore, due to
the relatively small, and decreasing, amounts of sulfur in gasoline and
on-road diesel fuel, EPA's transportation conformity rules provide that
they do not apply to SO2 unless either the EPA Regional
Administrator or the director of the state air agency has found that
transportation-related emissions of SO2 as a precursor are a
significant contributor to a SO2 or fine particulate matter
(PM2.5) nonattainment problem, or if the SIP has established
an approved or adequate budget for such emissions as part of the RFP,
attainment, or maintenance strategy. See 40 CFR 93.102(b)(1), (2)(v);
SO2 Nonattainment Area Guidance. Neither of these conditions
have been met; therefore, EPA's transportation conformity rules do not
apply to SO2 for the Area. For these reasons, EPA proposes
to find that Florida has satisfied all applicable requirements for
purposes of redesignation of the Hillsborough County Area under section
110 and part D of title I of the CAA.
---------------------------------------------------------------------------

    \23\ CAA Section 176(c)(4)(E) requires states to submit
revisions to their SIPs to reflect certain federal criteria and
procedures for determining transportation conformity. Transportation
conformity SIPs are different from the motor vehicle emission
budgets that are established in control strategy SIPs and
maintenance plans.
---------------------------------------------------------------------------

B. The Hillsborough County Area Has a Fully Approved Applicable SIP
Under Section 110(k) of the CAA

    EPA has fully approved the applicable Florida SIP for the
Hillsborough County Area under section 110(k) of the CAA for purposes
of redesignation. EPA may rely on prior SIP approvals in approving a
redesignation request (see Calcagni Memorandum at p. 3, Southwestern
Pennsylvania Growth Alliance v. Browner, 144 F.3D 984, 989-90 (6th Cir.
1998); Wall, 265 F.3d 426) plus any additional measures it may approve
in conjunction with a redesignation action. See 68 FR 25426 (May 12,
2003) and citations therein. As mentioned above, EPA fully approved the
State's nonattainment SIP and approved Florida's SIP revisions related
to the section 110 requirements for the 2010 SO2 NAAQS, with
the exception of the interstate transport elements at section
110(a)(2)(D)(i)(I). See 82 FR 30749 (July 3, 2017) and 81 FR 67179
(September 30, 2016), respectively.
    As discussed above, EPA believes that the section 110 elements that
are neither connected with nonattainment plan submissions nor linked to
an area's nonattainment status are not applicable requirements for
purposes of redesignation.
    Criterion (3)--The air quality improvement in the Hillsborough
County Area is due to permanent and enforceable reductions in emissions
resulting from implementation of the SIP and applicable Federal air
pollution control regulations and other permanent and enforceable
reductions.
    For redesignating a nonattainment area to attainment, the CAA
requires EPA to determine that the air quality improvement in the area
is due to permanent and enforceable reductions in emissions resulting
from implementation of the SIP, applicable Federal air pollution
control regulations, and other permanent and enforceable reductions
(CAA section 107(d)(3)(E)(iii)). EPA proposes to determine that Florida
has demonstrated that the observed air quality improvement in the
Hillsborough County Area is due to permanent and enforceable reductions
in SO2 emissions resulting from implementation of the SIP,
including the SO2 control measures at Mosaic and Big Bend
incorporated therein.
    When EPA designated the Hillsborough County Area as a nonattainment
area for the 2010 1-hour SO2 NAAQS, EPA determined that
operations at Mosaic were the primary cause of the 2010 1-hour
SO2 NAAQS violations in the Area. See 78 FR 47191.\24\
However, Florida included the nearby Big Bend power plant in its model-
based attainment demonstration because it determined that Big Bend was
also a significant contributor to elevated concentrations within the
Area.\25\ Florida's April 3, 2015, nonattainment SIP revision was based
on this determination and successfully reduced ambient concentrations
below the 1-hour SO2 NAAQS by only requiring emissions
reductions at Mosaic and Big Bend.
---------------------------------------------------------------------------

    \24\ See Final Technical Support Document, July 2013, Florida
First Round of Nonattainment Area Designations for the 2010
SO2 Primary NAAQS, Prepared by EPA Region 4. This
document is available at Docket ID: EPA-HQ-OAR-2012-0233-0307.
    \25\ FDEP modeled actual emissions at the time of area
designations which revealed contributing impacts throughout the
nonattainment area due to emissions from Big Bend. See 82 FR 30749
(July 3, 2017) and Docket ID: EPA-R04-OAR-2015-0623.
---------------------------------------------------------------------------

    Mosaic received an air construction permit \26\ on January 15,
2015, from FDEP requiring Mosaic to construct and implement
SO2 emission control measures and limitations, according to
a specific compliance schedule, necessary to ensure attainment of the
SO2 NAAQS as expeditiously as practicable. Mosaic produces
fertilizers, sulfuric acid, phosphoric acid, and fluoridation
ingredients and emits SO2 from three main emissions units--
sulfuric acid plants (SAPs) Nos. 7 (EU 004), 8 (EU 005) and 9 (EU 006).
See 82 FR 30749 (July 3, 2017). The air construction permit authorized
Mosaic to: Replace the vanadium catalyst (used to convert
SO2 to sulfuric trioxide) for each SAP (Nos. 7, 8, and 9)
with a more efficient catalyst for improved performance; \27\ increase
the stack height at each SAP; \28\ eliminate the use of fuel oil at the
plant except during periods of natural gas curtailment or disruption;
and comply with specific SO2 emissions caps for two-unit
(550 lb/hr) and three-unit (575 lb/hr) operating scenarios based on 24-
hour block averages as determined by continuous emission monitoring
system (CEMS) data.\29\ The new catalyst replacement converts more
SO2 for process purposes, allowing Mosaic to meet more
stringent emissions limits for these units. Allowable SO2
emissions (from SAPs 7-9 combined) were estimated to be reduced from
1,140 lb/hr (based on total individual unit emission limits) to a
maximum of 575 lb/hr, representing at least a 50 percent allowable
emissions decrease. The stack heights for all three sulfuric acid
plants were increased from 45.7 to 65 meters (213.5 feet); thus, the
new heights are fully creditable in accordance with EPA's stack height
regulations. EPA incorporated these new emissions limits, operating
parameters, compliance monitoring, and recordkeeping and reporting
requirements into the Florida SIP on July 3, 2017, making them
permanent and enforceable. See 82 FR 30749 (July 3, 2017). Florida's
redesignation request indicates that the control strategies were fully
implemented at the Mosaic facility in November 2017.
---------------------------------------------------------------------------

    \26\ See Air Construction Permit (No. 0570008-080-AC) issued by
FDEP on January 15, 2015, located in the docket for this proposed
action.
    \27\ Improvements in catalyst efficiency allow the units to meet
the multi-unit caps incorporated into the Florida SIP by converting
more SO2 emissions formed during the manufacturing
process to sulfuric acid, improving the efficiency of the
manufacturing process, and reducing SO2 emissions.
    \28\ A stack height increase can result in greater plume
dispersion across an area, minimizing stagnation and local impacts
from higher concentrations, primarily due to the avoidance of
building downwash effects. See EPA's June 1985 guidance document,
``Guideline for Determination of Good Engineering Practice Stack
Height (Technical Support Document for the Stack Height
Regulations),'' which can be found at: http://www3.epa.gov/scram001/guidance/guide/gep.pdf.
    \29\ SAPs 7, 8, and 9 are also subject to the existing,
individual SO2 emission limits that were previously
adopted into Florida's SIP (including SAP 7--400 lbs/hr, 24-hour
average; SAP 8--315 lbs/hr, 24-hour average; SAP 9--425 lbs/hr, 24-
hour average).

                                                       Table 3--Mosaic Facility SO2 Source Changes
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                      SO2 emission limit  (lb/hr) *                                 Stack height  (m)
                  Source                  --------------------------------------------------------------------------------------------------------------
                                             Previous    Individual             2-unit                        3-unit
--------------------------------------------------------------------------------------------------------------------------------------------------------
SAP 7....................................          400          400  Any two units cannot exceed   Combined emissions cannot           45.7         65.0
                                                                      550 combined.                 exceed 575.
SAP 8....................................          315          315  ............................  ...........................         45.7         65.0
SAP 9....................................          425          425  ............................  ...........................         45.7         65.0
                                                       -------------------------------------------------------------------------------------------------
No. 6 AP Plant...........................         40.2  Mosaic was required to cease burning of fuel oil at all units. This
                                                              essentially eliminated SO2 emissions from these five units.
                                                  No changes.
No. 5 Granulation Plant..................         20.1

No. 1 AFI Plant..........................         45.0

No. 2 AFI plant..........................         45.0

Auxiliary Boiler.........................         65.3

--------------------------------------------------------------------------------------------------------------------------------------------------------
 * All previous and new SO2 emission limits are 24-hour block averages.

    For Big Bend, FDEP issued Permit No. 0570039-074-AC on February 26,
2015, requiring the facility to comply with a SO2 emissions
cap of 3,162 lb/hr based on a 30-day rolling average for all four units
as determined by CEMS data.\30\ This involved replacing all existing
No. 2 fuel igniters and associated equipment to allow all four units to
fire natural gas during startup, shutdown, and flame stabilization.
These enhancements allowed Big Bend to meet the new combined unit
emissions cap beginning June 1, 2016. Big Bend's combined allowable
SO2 emissions were reduced from 6,587.6 lb/hr (based on
total individual unit emission limits) to 3,162 lb/hr, representing a
52 percent decrease in allowable emissions. EPA incorporated the
emissions cap, operating parameters, compliance monitoring, and
recordkeeping and reporting requirements into the Florida SIP on July
3, 2017, making them permanent and enforceable. See 82 FR 30749 (July
3, 2017). Florida's redesignation request indicates that the control
strategies were fully implemented at Big Bend in early 2016. FDEP
incorporated the permit conditions into Big Bend's title V operating
permit (No. 0570039-110-AV) \31\ on November 7, 2017.
---------------------------------------------------------------------------

    \30\ See Air Construction Permit 0570039-074-AC issued by FDEP
on February 26, 2015, located in the docket for this proposed
action.
    \31\ See Title V operating permit 0570039-110-AV issued by FDEP
on November 7, 2017, located in the docket for this proposed action.
---------------------------------------------------------------------------

    The nonattainment SIP submittal estimated base year 2011
SO2 emissions from Big Bend of 9,105.93 tons and from Mosaic
of 3,034.06 tons. Big Bend's previous allowable limit was 29,033.79
tons per year. Mosaic's previous allowable limit was 4,993.2 tons per
year. The attainment year maximum allowable emissions are 2,518.5 and
13,866 tons per year for Mosaic and Big Bend, respectively, a reduction
of approximately 50 percent. Actual SO2 emissions from
Mosaic and Big Bend decreased by 7,253 tons (approximately 54 percent)
from 2014 to 2017 \32\ which corresponds with the overall downward
trend in monitored daily maximum 1-hour ambient SO2
concentrations \33\ (with no values measured above the standard in
2017). The air quality improvement in the Hillsborough County Area is
due to permanent and enforceable reductions in SO2 emissions
resulting from these control measures incorporated into the SIP.
---------------------------------------------------------------------------

    \32\ See Figure 5 in Florida's June 7, 2018, submission.
    \33\ See Figure 2 in Florida's June 7, 2018, submission.
---------------------------------------------------------------------------

    As discussed above, Florida issued a revised permit to Big Bend
(Permit No. 0570039-120-AC) that restricts EUs 1 and 2 to only burning
natural gas; reduces the four-unit SO2 cap from 3,162 lb/hr
to 2,156 lb/hr (each on a 30-day average); and amends the method of
compliance for the revised four-unit cap. Table 4 summarizes the
changes in the SO2 emissions limits at Big Bend.

                                  Table 4--Big Bend SO2 Emissions Limit Changes
----------------------------------------------------------------------------------------------------------------
                                                             SO2 emissions limit  (lb/hr) *
                                      --------------------------------------------------------------------------
                Source                                                                Permit No. 0570039-120-AC
                                          Previous       Permit No. 0570039-074-AC     (effective December 14,
                                                         (effective June 1, 2016)               2018)
----------------------------------------------------------------------------------------------------------------
FFSG Unit 1..........................        1,009.25  Four-unit emissions cap of    Four-unit emissions cap of
                                                        3,162 (originally 6,587.6     2,165.
                                                        total).
FFSG Unit 2..........................          999.00
FFSG Unit 3..........................        1,028.75
FFSG Unit 4..........................        3,550.60
----------------------------------------------------------------------------------------------------------------
* All SO2 emission limits are 30-day rolling averages.

    The revised four-unit emissions cap of 2,165 lb/hr proposed for
incorporation into the SIP represents a nearly 32 percent reduction
from the SIP-approved emissions cap. This lowered emissions cap will
become permanent and enforceable if EPA incorporates it into the SIP.
    Criterion (4)--The Hillsborough County Area has a fully approved
maintenance plan pursuant to section 175A of the CAA.
    For redesignating a nonattainment area to attainment, the CAA
requires EPA to determine that the area has a

fully approved maintenance plan pursuant to section 175A of the CAA.
See CAA section 107(d)(3)(E)(iv). In conjunction with its request to
redesignate the Hillsborough County Area to attainment for the 2010 1-
hour SO2 NAAQS, Florida submitted a SIP revision to provide
for the maintenance of the 2010 1-hour SO2 NAAQS for at
least 10 years after the effective date of redesignation to attainment.
EPA is proposing to determine that this maintenance plan meets the
requirements for approval under section 175A of the CAA.
a. What is required in a maintenance plan?
    Section 175A of the CAA sets forth the elements of a maintenance
plan for areas seeking redesignation from nonattainment to attainment.
Under section 175A, the plan must demonstrate continued attainment of
the applicable NAAQS for at least 10 years after the Administrator
approves a redesignation to attainment. Eight years after the
redesignation, the state must submit a revised maintenance plan
demonstrating that attainment will continue to be maintained for the 10
years following the initial 10-year period. To address the possibility
of future NAAQS violations, the maintenance plan must contain
contingency measures as EPA deems necessary to assure prompt correction
of any future 2010 1-hour SO2 violations. The Calcagni
Memorandum provides further guidance on the content of a maintenance
plan, explaining that a maintenance plan should address five
requirements: The attainment emissions inventory; maintenance
demonstration; monitoring; verification of continued attainment; and a
contingency plan. As is discussed more fully below, EPA is proposing to
determine that Florida's maintenance plan includes all the necessary
components and is thus proposing to approve it as a revision to the
Florida SIP.
b. Attainment Emissions Inventory
    An attainment inventory identifies a level of emissions in the Area
that is sufficient to attain the NAAQS. In its maintenance plan,
Florida used 2015 actual emissions data to represent the attainment
emissions inventory. As identified above, the 2015-2017 design value at
the East Bay monitor was below the NAAQS and there has not been a
monitored violation of the SO2 NAAQS at the monitor since
2014. SO2 emissions data from the Mosaic, Big Bend, Ajax,
and Harsco facilities,\34\ as included in Florida's required 2015
annual operating reports for all sources, are presented in Table 5.
Although Big Bend is located outside of the Area, Florida included it
in its model-based attainment demonstration because it determined that
it was a significant contributor to elevated concentrations within the
Area. The complete attainment emissions inventory for the Area and
relevant nearby stationary sources (i.e., Big Bend) is presented in
Table 6. Florida based area and non-road emissions for the Area on 2014
National Emissions Inventory (NEI) data for Hillsborough County because
the State is only required to develop these inventories on a triennial
period in accordance with the NEI and subpart A to 40 CFR part 51. The
2014 emissions for each category were projected to 2015 based on the
increase in the Hillsborough County population from 2014 to 2015, and
then allocated to the Area based on the Area's fraction of land area
within the county. The State estimated on-road emissions for the Area
with MOVES2014a, and similarly allocated to the Area based on the
Area's fraction of land area within the county.
---------------------------------------------------------------------------

    \34\ Ajax and Harsco are two smaller point sources within the
Area. See footnote 1 for additional information.

  Table 5--2015 SO2 Emissions Inventory for Big Bend, Mosaic, Ajax, and
                            Harsco Facilities
------------------------------------------------------------------------
                                                             2015 SO2
               EU ID                  Unit description       emissions
                                                              (tons)
------------------------------------------------------------------------
                     Big Bend Facility SO2 Emissions
------------------------------------------------------------------------
1.................................  Fossil Fuel Fired            1804.89
                                     Steam Generator
                                     Unit No. 1.
2.................................  Fossil Fuel Fired            1324.81
                                     Steam Generator
                                     Unit No. 2.
3.................................  Fossil Fuel Fired            1819.60
                                     Steam Generator
                                     Unit No. 3.
4.................................  Fossil Fuel Fired            2366.10
                                     Steam Generator
                                     Unit No. 4.
41................................  SCCT 4A: PWPS FT8-3             0.01
                                     SwiftPac CT/Gen
                                     Peaking Unit.
42................................  SCCT 4B: PWPS FT8-3             0.01
                                     SwiftPac CT/Gen
                                     Peaking Unit.
43................................  SCCT Black Start              0.0004
                                     Emergency Engine
                                     (1,495 HP).
44................................  Emergency Diesel              0.0003
                                     Generator (1,046
                                     HP).
45................................  Emergency Diesel              0.0003
                                     Generator and Fire
                                     Pump Diesel Engine.
51................................  Process Heaters (2-6          0.0007
                                     MMBtu/hour).
53................................  Units 1 & 2                  0.00005
                                     Emergency Diesel
                                     Generator (197 HP).
                                   -------------------------------------
    Total.........................  ....................         7315.42
------------------------------------------------------------------------
                      Mosaic Facility SO2 Emissions
------------------------------------------------------------------------
4.................................  No. 7 Sulfuric Acid           668.33
                                     Plant.
5.................................  No. 8 Sulfuric Acid           532.19
                                     Plant.
6.................................  No. 9 Sulfuric Acid           529.11
                                     Plant.
7.................................  No. 6 AP Plant......            0.02
55................................  No. 5 AP Plant......            0.04
63................................  Tank Nos. 1, 2, and                0
                                     3 for molten sulfur
                                     storage w/scrubber.
66................................  Sulfur Pit #7,                  0.02
                                     Molten Storage/
                                     Handling System.
67................................  Sulfur Pit #8,                  0.02
                                     Molten Storage/
                                     Handling System.
68................................  Sulfur Pit #9,                  0.02
                                     Molten Storage/
                                     Handling System.
74................................  Truck Loading                      0
                                     Station for Molten
                                     Sulfur w/common
                                     scrubber.
111...............................  Existing Emergency              0.13
                                     Stationary RICE <
                                     or equal to 500 HP.

112...............................  Auxiliary Boiler....           0.002
113...............................  Non-Emergency CI ICE            3.44
                                                         ---------------
    Total.........................  ....................         1733.32
------------------------------------------------------------------------
                       Ajax Facility SO2 Emissions
------------------------------------------------------------------------
5.................................  Diesel Engine and               0.05
                                     Power Generator for
                                     RAP Crusher.
6.................................  Drum Mix Asphalt                0.25
                                     Plant (400TPH).
                                                         ---------------
    Total.........................  ....................            0.30
------------------------------------------------------------------------
                      Harsco Facility SO2 Emissions
------------------------------------------------------------------------
1.................................  Fluid Bed Slag Dryer           0.004
    Total.........................  ....................           0.004
                                                         ---------------
        Total All Point Sources...  ....................        9,049.05
------------------------------------------------------------------------

                                      Table 6--2015 Attainment Emissions Inventory for the Hillsborough County Area
--------------------------------------------------------------------------------------------------------------------------------------------------------
                            Source Type                                   Point             Area           Non-Road         On-Road           Total
--------------------------------------------------------------------------------------------------------------------------------------------------------
2015 SO2 Emissions (tons)..........................................        9,049.05             8.80             0.16             1.86         9,059.87
--------------------------------------------------------------------------------------------------------------------------------------------------------

    For additional information regarding the development of the
attainment year inventory, please see Appendix D to Florida's June 7,
2018, submittal.
c. Maintenance Demonstration
    Maintenance of the SO2 standard is demonstrated either
by showing that future emissions will not exceed the level of the
attainment emissions inventory year or by modeling to show that the
future mix of sources and emission rates will not cause a violation of
the NAAQS.
    To evaluate maintenance through 2032 and satisfy the 10-year
interval required in CAA section 175A, Florida prepared projected
emissions inventories for 2020-2032. The emissions inventories are
composed of the following general source categories: point, area, non-
road mobile, and on-road mobile. The emissions inventories were
developed consistent with EPA guidance and are summarized in Table 7.
Florida compared the projected emissions for the final year of the
maintenance plan (2032) to the attainment emissions inventory year
(2015) and compared interim years to the attainment emissions inventory
year to demonstrate continued maintenance of the 2010 1-hour
SO2 standard. For additional information regarding the
development of the projected inventories, please see Appendix D to
Florida's June 7, 2018, SIP submittal.

                          Table 7--Projected Future Emissions Inventories for the Area
----------------------------------------------------------------------------------------------------------------
                                     Projected       Projected       Projected       Projected       Projected
                                     2020 SO2        2023 SO2        2026 SO2        2029 SO2        2032 SO2
           Source type               emissions       emissions       emissions       emissions       emissions
                                      (tons)          (tons)          (tons)          (tons)          (tons)
----------------------------------------------------------------------------------------------------------------
Point...........................        9,049.05        9,049.05        9,049.05        9,049.05        9,049.05
Area............................            9.53           10.01           10.47           10.91           11.31
Non-road........................            0.18            0.19            0.20            0.20            0.21
On-road.........................            0.74            0.71            0.69            0.67            0.66
                                 -------------------------------------------------------------------------------
    Total.......................        9,059.49        9,059.95        9,060.40        9,060.83        9,061.23
----------------------------------------------------------------------------------------------------------------

    In situations where local emissions are the primary contributor to
nonattainment, such as the Hillsborough County Area, if the future
projected emissions in the nonattainment area remain at or below the
baseline emissions in the nonattainment area, then the related ambient
air quality standards should not be exceeded in the future. Florida has
projected emissions as described previously, and these projections
indicate that emissions in the Hillsborough County Area will remain at
nearly the same levels as those in the attainment year inventory for
the duration of the maintenance plan. While these projections include a
small increase in area source and non-road emissions from 2020 to 2032
(1.81 tons), the increase is negligible when compared to the total
emissions inventory, and EPA does not believe that this projected
increase should cause an exceedance of the SO2 NAAQS through
2032. This belief is supported by the fact that Florida does not
anticipate any future development within the Area that could
potentially increase SO2 emissions and the fact that any
increases in actual emissions from

Mosaic or Big Bend are required to remain below the modeled emissions
that demonstrate attainment for the 1-hour SO2 NAAQS.
Furthermore, any potential future SO2 emissions sources that
may locate in or near the Area would be required to comply with the
FDEP's approved NSR permitting programs to ensure that the Area will
continue to meet the NAAQS. EPA also notes that the natural gas fuel
requirement for EUs 1 and 2 at Big Bend and the reduced four-unit
SO2 cap proposed for incorporation into the SIP are expected
to further reduce SO2 emissions beyond the levels projected
in Table 7.
    As discussed in the SO2 Nonattainment Area Guidance, an
approved attainment plan that relies on air quality dispersion modeling
using maximum allowable emissions, such as Florida's attainment plan
for the Area, can generally be expected to demonstrate that the
standard will be maintained for the requisite 10 years and beyond
without regard to any changes in operation rate of the pertinent
sources that do not involve increases in maximum allowable
emissions.\35\ EPA believes that the Area will continue to maintain the
standard at least through the year 2032 because the air quality
modeling in the approved attainment plan showed that the Area would
attain the standard based on the maximum allowable emissions limits at
Mosaic and Big Bend that are incorporated into the SIP, these sources
have fully implemented these permanent and enforceable measures, and
the emissions reductions from these measures are reflected in the
attaining design values for the Area. As discussed above, EPA believes
that the modeling in the attainment plan using the four-unit
SO2 cap of 3,162 lb/hr at Big Bend is more conservative (in
relation to a demonstration relying on the lowered cap) and is still
valid for demonstrating attainment in the Area.
---------------------------------------------------------------------------

    \35\ See SO2 Nonattainment Area Guidance at p.67.
---------------------------------------------------------------------------

d. Monitoring Network
    The East Bay monitor (12-057-0109) is the only SO2
monitor located within the Hillsborough County Area, and the 2010 1-
hour SO2 nonattainment designation was based on data
collected from 2009-2011 at this monitor. In its maintenance plan,
Florida has committed to continue operating an appropriate
SO2 monitoring network, consult with EPA prior to making any
changes to the existing network, and continue to quality assure the
monitoring data in accordance with 40 CFR part 58. Therefore, Florida
has addressed the requirement for monitoring. FDEP's monitoring network
plan was submitted on June 28, 2018, and approved by EPA on October 22,
2018.
e. Verification of Continued Attainment
    The State of Florida, through FDEP, has the legal authority to
enforce and implement all measures necessary to attain and maintain the
NAAQS. Section 403.061(35), Florida Statutes, authorizes the Department
to ``exercise the duties, powers, and responsibilities required of the
state under the federal Clean Air Act. This includes implementing and
enforcing all measures necessary to attain and maintain the NAAQS. In
addition, FDEP will use emissions data submitted by Mosaic and Big Bend
through annual operating reports to verify continued compliance with
the permitted emissions rates that were shown through the modeling
demonstration in the attainment plan to be sufficient to provide for
maintenance of the 2010 1-hour SO2 NAAQS throughout the
Area. Any increases in actual emissions from Mosaic or Big Bend must
remain below their permitted levels. Furthermore, any potential future
SO2 emissions sources that may locate in or near the Area
would be required to comply with FDEP's approved NSR permitting
programs to ensure that the Area will continue to meet the NAAQS. In
addition to assuring continued attainment in this manner, FDEP will
verify continued attainment through operation of the monitoring
network.
f. Contingency Measures in the Maintenance Plan
    Section 175A of the CAA requires that a maintenance plan include
such contingency measures as EPA deems necessary to assure that the
state will promptly correct a violation of the NAAQS that occurs after
redesignation. The maintenance plan should identify the contingency
measures to be adopted, a schedule and procedure for adoption and
implementation, and a time limit for action by the state. In cases
where attainment revolves around compliance of a single source or a
small set of sources with emissions limits shown to provide for
attainment, EPA interprets ``contingency measures'' to mean that the
state agency has a comprehensive program to identify sources of
violations of the SO2 NAAQS and to undertake aggressive
follow-up for compliance and enforcement, including expedited
procedures for establishing enforceable consent agreement pending the
adoption of revised SIPs.\36\ A state should also identify specific
indicators to be used to determine when the contingency measures need
to be implemented. The maintenance plan must include a requirement that
a state will implement all measures with respect to control of the
pollutant that were contained in the SIP before redesignation of the
area to attainment in accordance with section 175A(d).
---------------------------------------------------------------------------

    \36\ See SO2 Nonattainment Area Guidance at p.69.
---------------------------------------------------------------------------

    The contingency plan included in the maintenance plan contains
triggers to determine when contingency measures are needed and what
kind of measures should be used. Upon notification by the FDEP Office
of Air Monitoring that the East Bay monitor has registered
SO2 levels in excess of the standard for a fourth time
during a calendar year, FDEP will notify Mosaic and Big Bend of the
occurrence of the fourth high exceedance. Upon notification by FDEP of
a confirmed fourth high exceedance,\37\ Mosaic and Big Bend will,
without any further action by FDEP or EPA, undertake a full system
audit of all emissions units subject to control under the attainment
plan. Within 10 days of notification of the confirmed fourth high
exceedance, each source will independently submit a written system
audit report to FDEP summarizing all operating parameters of all
emissions units for four 10-day periods up to and including the dates
of the exceedances together with recommended provisional SO2
emission control strategies for each affected unit and evidence that
these control strategies have been deployed, as appropriate. Upon
receipt of the above-mentioned reports, FDEP will then begin a 30-day
evaluation of these reports to determine the cause of the exceedances,
followed by a 30-day consultation period with the sources to develop
and implement appropriate operational changes. At the end of the
consultation period, FDEP will mandate operational changes identified
by the written system audit to prevent any future violation of the
NAAQS. Any necessary changes would be implemented as soon as
practicable, with at least one implemented within 18-24 months of the
monitored violation, in order to bring the Area into attainment as
expeditiously as possible. These changes could include, but would not
be limited to:
---------------------------------------------------------------------------

    \37\ Confirmation of a fourth high exceedance over the
SO2 NAAQS would be made after quality assurance
activities are completed, but not necessarily with FDEP-certified
data.

---------------------------------------------------------------------------

     Fuel switching to reduce or eliminate the use of sulfur-
containing fuels; and
     physical or operational reduction of production capacity,
as appropriate.
    If a permit modification is necessary, the State would issue a
final permit in accordance to Sections 120 and 403 of the Florida
Statutes. Subsequently, Florida would submit any relevant permit change
to EPA as a source-specific SIP revision to make the change permanent
and enforceable. In addition to including these contingency measures in
the maintenance plan, Florida also stated that all existing control
measures will remain in effect after redesignation.
    EPA has preliminarily concluded that the maintenance plan
adequately addresses the five basic components of a maintenance plan:
The attainment emissions inventory; maintenance demonstration;
monitoring; verification of continued attainment; and a contingency
plan. Therefore, EPA proposes to determine that the maintenance plan
for the Area meets the requirements of section 175A of the CAA and
proposes to incorporate the maintenance plan into the Florida SIP.

VII. What is the effect of EPA's proposed actions?

    Approval of Florida's redesignation request would change the
designation of the portion of Hillsborough County that is within the
Hillsborough County Area, as found at 40 CFR part 81, section 81.310,
from nonattainment to attainment for the 2010 1-hour SO2
NAAQS. Approval of Florida's associated SIP revision would also
incorporate a plan for maintaining the 2010 1-hour SO2 NAAQS
in the Hillsborough County Area through 2032 into the SIP.
Incorporation of the Big Bend permit conditions discussed above from
Permit No. 0570039-120-AC into the SIP would make them permanent and
federally enforceable.

VIII. Incorporation by Reference

    EPA is proposing to include in a final EPA rule regulatory text
that includes incorporation by reference. In accordance with
requirements of 1 CFR 51.5, EPA is proposing to incorporate by
reference into Florida's SIP the following conditions from Permit No.
0570039-120-AC issued by FDEP to Big Bend with an effective date of
December 14, 2018: (1) Section 2, Condition 4; (2) the ``SO2
Emissions Cap'' provision from Section 3, Condition 4; \38\ (3) the
``SO2 CEMS'' provision from Section 3, Condition 4; \39\ and
(4) the ``Methods of Operation'' for Units 1 and 2 provision from
Section 3, Condition 6.\40\
---------------------------------------------------------------------------

    \38\ In its April 16, 2019 submittal, Florida identifies this
provision as ``Section 3, Subsection B, Specific Condition 2'';
however, it is contained under the heading ``4. Permit Being
Modified: Permit No. 0570039-096-AC'' in Section 3 of Permit No.
0570039-120-AC. See Section V of this notice for additional
information.
    \39\ In its April 16, 2019 submittal, Florida identifies this
provision as ``Section 3, Subsection B, Specific Condition 3;
however, it is contained under the heading ``4. Permit Being
Modified: Permit No. 0570039-096-AC'' in Section 3 of Permit No.
0570039-120-AC. See Section V of this notice for additional
information.
    \40\ In its April 16, 2019 submittal, Florida identifies this
provision as ``Section 3, Subsection A, Specific Condition 3a;
however, it is contained under the heading ``6. Permits Being
Modified: Permit Nos. 0570039-066-AC & 109-AC'' in Section 3 of
Permit No. 0570039-120-AC. See Section V of this notice for
additional information.
---------------------------------------------------------------------------

    EPA has made, and will continue to make, these materials generally
available through www.regulations.gov and at EPA Region 4 office
(please contact the person identified in the For Further Information
Contact section of this preamble for more information).

IX. Proposed Actions

    EPA is proposing to take four separate but related actions
regarding the redesignation request and associated SIP revision for the
Hillsborough County Area.
    First, EPA is proposing to determine that the Area attained the
2010 1-hour SO2 NAAQS by its attainment date of October 4,
2018. This determination is being proposed in accordance with section
179(c)(1) of the CAA.
    Second, EPA is proposing to approve the maintenance plan for the
Area and to incorporate it into the SIP. As described above, the
maintenance plan demonstrates that the Area will continue to maintain
the 2010 1-hour SO2 NAAQS through 2032.
    Third, EPA is proposing to approve Florida's request for
redesignation of the Area from nonattainment to attainment for the 2010
1-hour SO2 NAAQS.
    Fourth, EPA is proposing to incorporate into the SIP the
aforementioned permitting conditions applicable to Big Bend, including
a condition that lowers the SO2 emissions cap by
approximately 32 percent and a condition that restricts the fuel use at
two electric generating units to natural gas.
    If finalized, approval of the redesignation request for the
Hillsborough County Area would change the official designation of the
portion of Hillsborough County, Florida, encompassed by the polygon
with the vertices using UTM coordinates in UTM zone 17 with datum NAD83
as follows: (1) Vertices-UTM Easting (m) 358581, UTM Northing 3076066;
(2) vertices-UTM Easting (m) 355673, UTM Northing 3079275; (3) UTM
Easting (m) 360300, UTM Northing 3086380; (4) vertices-UTM Easting (m)
366850, UTM Northing 3086692; (5) vertices-UTM Easting (m) 368364, UTM
Northing 3083760; and (6) vertices-UTM Easting (m) 365708, UTM Northing
3079121, as found at 40 CFR part 81, from nonattainment to attainment
for the 2010 1-hour SO2 NAAQS.

X. Statutory and Executive Order Reviews

    Under the CAA, redesignation of an area to attainment and the
accompanying approval of a maintenance plan under section 107(d)(3)(E)
are actions that affect the status of a geographical area and do not
impose any additional regulatory requirements on sources beyond those
imposed by state law. A redesignation to attainment does not in and of
itself create any new requirements, but rather results in the
applicability of requirements contained in the CAA for areas that have
been redesignated to attainment. Moreover, the Administrator is
required to approve a SIP submission that complies with the provisions
of the Act and applicable Federal regulations. See 42 U.S.C. 7410(k);
40 CFR 52.02(a). Thus, in reviewing SIP submissions, EPA's role is to
approve state choices, provided that they meet the criteria of the CAA.
Accordingly, these proposed actions merely propose to approve state law
as meeting Federal requirements and do not impose additional
requirements beyond those imposed by state law. For this reason, these
proposed actions:
     Are not significant regulatory actions 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);
     Are not Executive Order 13771 (82 FR 9339, February 2,
2017) regulatory actions because these actions are not significant
regulatory actions under Executive Order 12866;
     Do not impose information collection burdens under the
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Are 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.);
     Do not contain any unfunded mandates or significantly or
uniquely affect small governments, as described in the Unfunded
Mandates Reform Act of 1995 (Pub. L. 104-4);

     Do not have Federalism implications as specified in
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Are not economically significant regulatory actions based
on health or safety risks subject to Executive Order 13045 (62 FR
19885, April 23, 1997);
     Are not significant regulatory actions subject to
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Are 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
     Will not have disproportionate human health or
environmental effects under Executive Order 12898 (59 FR 7629, February
16, 1994).
    These proposed actions do not 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, these
proposed actions do not have tribal implications as specified by
Executive Order 13175 (65 FR 67249, November 9, 2000), nor will they
impose substantial direct costs on tribal governments or preempt tribal
law.

List of Subjects

40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by
reference, Intergovernmental relations, Reporting and recordkeeping,
Sulfur dioxide.

40 CFR Part 81

    Environmental protection, Air pollution control, National parks,
Wilderness areas.

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

    Dated: July 18, 2019.
Mary S. Walker,
Regional Administrator, Region 4.
[FR Doc. 2019-16070 Filed 7-30-19; 8:45 am]
 BILLING CODE 6560-50-P