[Federal Register Volume 83, Number 126 (Friday, June 29, 2018)]
[Proposed Rules]
[Pages 30609-30622]
[FR Doc No: 2018-14097]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R04-OAR-2017-0626; FRL-9980-18-Region 4]

Air Plan Approval; Tennessee; Attainment Plan for Sullivan County
SO2 Nonattainment Area

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to
approve a State Implementation Plan (SIP) revision submitted by the
State of Tennessee, through the Tennessee Department of Environment and
Conservation (TDEC), to EPA on May 12, 2017, for attaining the 2010 1-
hour sulfur dioxide (SO2) primary national ambient air
quality standard (NAAQS) for the Sullivan County SO2
nonattainment area (hereafter referred to as the ``Sullivan County
Area'' or ``Area''). The Sullivan County Area is comprised of a portion
of Sullivan County in Tennessee surrounding the Eastman Chemical
Company (hereafter referred to as ``Eastman''). This plan (herein
called a ``nonattainment plan or SIP'' or ``attainment plan or SIP'')
includes Tennessee's attainment demonstration and other elements
required under the Clean Air Act (CAA or Act). In addition to an
attainment demonstration, the plan addresses the requirement for
meeting reasonable further progress (RFP) toward attainment of the
NAAQS, reasonably available control measures and reasonably available
control technology (RACM/RACT), base-year and projection-year emissions
inventories, enforceable emissions limitations and control measures,
and contingency measures. EPA proposes to conclude that Tennessee has
appropriately demonstrated that the plan's provisions provide for
attainment of the 2010 1-hour primary SO2 NAAQS in the
Sullivan County Area and that the plan meets the other applicable
requirements under the CAA.

DATES: Comments must be received on or before July 30, 2018.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R04-
OAR-2017-0626 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: D. Brad Akers, Air Regulatory
Management Section, Air Planning and Implementation Branch, Air,
Pesticides and Toxics Management Division, U.S. Environmental
Protection Agency, Region 4, 61 Forsyth Street SW, Atlanta, Georgia
30303-8960. Mr. Akers can be reached via telephone at<PHONE_NUMBER> or
via electronic mail at [email protected].

SUPPLEMENTARY INFORMATION:

I. Requirement for Tennessee to Submit an SO2 Attainment
Plan for the Sullivan County Area

II. Requirements for SO2 Attainment Plans
III. Attainment Demonstration and Longer Term Averaging
IV. Review of Attainment Plan Requirements
    A. Emissions Inventory
    B. Attainment Modeling Demonstration
    1. Model Selection
    2. Meteorological Data
    3. Emissions Data
    4. Emission Limits
    i. Enforceability
    ii. Longer Term Average Limits
    5. Background Concentration
    6. Analysis of Multi-Stack Limit
    7. Summary of Modeling Results
    C. RACM/RACT
    D. New Source Review (NSR)
    E. Reasonable Further Progress (RFP)
    F. Contingency Measures
V. Additional Elements of Tennessee's Submittal
VI. Incorporation by Reference
VII. EPA's Proposed Action
VIII. Statutory and Executive Orders

I. Requirement for Tennessee To Submit an SO2 Attainment Plan for the
Sullivan County Area

    On June 22, 2010, EPA promulgated a new 1-hour primary
SO2 NAAQS of 75 parts per billion (ppb), which is met at an
ambient air quality monitoring site when the 3-year average of the
annual 99th percentile of daily maximum 1-hour average concentrations
does not exceed 75 ppb, as determined in accordance with appendix T of
40 CFR part 50. See 75 FR 35520, codified at 40 CFR 50.17(a)-(b). On
August 5, 2013, EPA designated a first set of 29 areas of the country
as nonattainment for the 2010 SO2 NAAQS. See 78 FR 47191,
codified at 40 CFR part 81, subpart C. These designations included the
Sullivan County Area, which encompasses the primary SO2
emitting source Eastman and the nearby SO2 monitor (Air
Quality Site ID: 47-163-0007). These area designations were effective
October 4, 2013. Section 191(a) of the CAA directs states to submit
SIPs for areas designated as nonattainment for the SO2 NAAQS
to EPA within 18 months of the effective date of the designation, i.e.,
by no later than April 4, 2015 in this case. Under CAA section 192(a)
these SIPs are required to demonstrate that their respective areas will
attain the NAAQS as expeditiously as practicable, but no later than 5
years from the effective date of designation, which is October 4, 2018.
In addition, sections 110(a) and 172(c), as well as EPA regulations at
40 CFR part 51, set forth substantive elements each SIP must contain to
be approved by EPA.
    For the Sullivan County Area (and many other areas), EPA published
a notice on March 18, 2016, that Tennessee (and other pertinent states)
had failed to submit the required SO2 nonattainment plan by
this submittal deadline. See 81 FR 14736. This finding initiated a
deadline under CAA section 179(a) for the potential imposition of new
source review and highway funding sanctions. However, pursuant to
Tennessee's submittal of May 12, 2017, and EPA's subsequent letter
dated October 10, 2017, to Tennessee finding the submittal complete and
noting the termination of these sanctions deadlines, these sanctions
under section 179(a) will not be imposed as a result of Tennessee
having missed the April 4, 2015 deadline. Under CAA section 110(c), the
March 18, 2016 finding also triggered a requirement that EPA promulgate
a federal implementation plan (FIP) within two years of the finding
unless (a) the state has made the necessary complete submittal and (b)
EPA has approved the submittal as meeting applicable requirements.

II. Requirements for SO2 Attainment Plans

    To be approved by EPA, nonattainment areas must provide SIPs
meeting the applicable requirements of the CAA, and specifically CAA
sections 110(a), 172, 191 and 192 for SO2. EPA's regulations
governing nonattainment SIPs are set forth at 40 CFR part 51, with
specific procedural requirements and control strategy requirements
residing at subparts F and G, respectively. Soon after Congress enacted
the 1990 Amendments to the CAA, EPA issued comprehensive guidance on
SIPs, in a document entitled the ``General Preamble for the
Implementation of Title I of the Clean Air Act Amendments of 1990,''
published at 57 FR 13498 (April 16, 1992) (General Preamble). Among
other things, the General Preamble addressed SO2 SIPs and
fundamental principles for SIP control strategies. Id., at 13545-49,
13567-68. On April 23, 2014, EPA issued recommended guidance for
meeting the statutory requirements in SO2 SIPs under the
2010 revised NAAQS, in a document entitled, ``Guidance for 1-Hour
SO2 Nonattainment Area SIP Submissions,'' available at
https://www.epa.gov/sites/production/files/2016-06/documents/20140423guidance_nonattainment_sip.pdf (hereafter referred to as EPA's
April 2014 SO2 guidance or guidance). In this guidance EPA
described the statutory requirements for SO2 SIPs for
nonattainment areas, which includes: An accurate emissions inventory of
current emissions for all sources of SO2 within the
nonattainment area; an attainment demonstration; demonstration of RFP;
implementation of RACM (including RACT); new source review (NSR);
enforceable emissions limitations and control measures; and adequate
contingency measures for the affected area.
    For EPA to fully approve a SIP as meeting the requirements of CAA
sections 110, 172 and 191-192, and EPA's regulations at 40 CFR part 51,
the SIP for the affected area needs to demonstrate to EPA's
satisfaction that each of the aforementioned requirements have been
met. Under CAA sections 110(l) and 193, EPA may not approve a SIP that
would interfere with any applicable requirement concerning NAAQS
attainment and RFP, or any other applicable requirement, and no
requirement in effect (or required to be adopted by an order,
settlement, agreement, or plan in effect before November 15, 1990) in
any area which is a nonattainment area for any air pollutant, may be
modified in any manner unless it insures equivalent or greater emission
reductions of such air pollutant.

III. Attainment Demonstration and Longer Term Averaging

    CAA sections 172(c)(1) and (6) direct states with areas designated
as nonattainment to demonstrate that the submitted plan provides for
attainment of the NAAQS. 40 CFR part 51, subpart G further delineates
the control strategy requirements that SIPs must meet, and EPA has long
required that all SIPs and control strategies reflect four fundamental
principles of quantification, enforceability, replicability, and
accountability. General Preamble, at 13567-68. SO2
attainment plans must consist of two components: (1) Emission limits
and other control measures that assure implementation of permanent,
enforceable and necessary emission controls, and (2) a modeling
analysis which meets the requirements of 40 CFR part 51, appendix W
which demonstrates that these emission limits and control measures
provide for timely attainment of the primary SO2 NAAQS as
expeditiously as practicable, but by no later than the attainment date
for the affected area. In all cases, the emission limits and control
measures must be accompanied by appropriate methods and conditions to
determine compliance with the respective emission limits and control
measures and must be quantifiable (i.e., a specific amount of emission
reduction can be ascribed to the measures), fully-enforceable
(specifying clear, unambiguous and measurable requirements for which
compliance can be practicably determined), replicable (the procedures
for determining compliance are

sufficiently specific and non-subjective so that two independent
entities applying the procedures would obtain the same result), and
accountable (source specific limits must be permanent and must reflect
the assumptions used in the SIP demonstrations).
    EPA's April 2014 SO2 guidance recommends that the
emission limits be expressed as short-term average limits (e.g.,
addressing emissions averaged over one or three hours), but also
describes the option to utilize emission limits with longer averaging
times of up to 30 days so long as the state meets various suggested
criteria. See EPA's April 2014 SO2 guidance, pp. 22 to 39.
The guidance recommends that--should states and sources utilize longer
averaging times--the longer term average limit should be set at an
adjusted level that reflects a stringency comparable to the 1-hour
average limit at the critical emission value (CEV) shown by modeling to
provide for attainment that the plan otherwise would have set.
    EPA's April 2014 SO2 guidance provides an extensive
discussion of EPA's rationale for concluding that appropriately set
comparably stringent limitations based on averaging times as long as 30
days can be found to provide for attainment of the 2010 SO2
NAAQS. In evaluating this option, EPA considered the nature of the
standard, conducted detailed analyses of the impact of use of 30-day
average limits on the prospects for attaining the standard, and
carefully reviewed how best to achieve an appropriate balance among the
various factors that warrant consideration in judging whether a state's
plan provides for attainment. Id. at pp. 22 to 39. See also id. at
Appendices B, C, and D.
    As specified in 40 CFR 50.17(b), the 1-hour primary SO2
NAAQS is met at an ambient air quality monitoring site when the 3-year
average of the annual 99th percentile of daily maximum 1-hour average
concentrations is less than or equal to 75 ppb. In a year with 365 days
of valid monitoring data, the 99th percentile would be the fourth
highest daily maximum 1-hour value. The 2010 SO2 NAAQS,
including this form of determining compliance with the standard, was
upheld by the U.S. Court of Appeals for the District of Columbia
Circuit in Nat'l Envt'l Dev. Ass'n's Clean Air Project v. EPA, 686 F.3d
803 (D.C. Cir. 2012). Because the standard has this form, a single
hourly exceedance of the 75-ppb level does not create a violation of
the standard. Instead, at issue is whether a source operating in
compliance with a properly set longer term average could cause hourly
exceedances of the NAAQS level, and if so the resulting frequency and
magnitude of such exceedances, and in particular whether EPA can have
reasonable confidence that a properly set longer term average limit
will provide that the 3-year average of the annual fourth highest daily
maximum 1-hour value will be at or below 75 ppb. A synopsis of how EPA
judges whether such plans ``provide for attainment,'' based on modeling
of projected allowable emissions and in light of the NAAQS's form for
determining attainment at monitoring sites, follows.
    For SO2 plans that are based on 1-hour emission limits,
the standard approach is to conduct modeling using fixed emission
rates. The maximum emission rate that would be modeled to result in
attainment (i.e., in an ``average year'' \1\ shows three, not four days
with maximum hourly levels exceeding 75 ppb) is labeled the ``critical
emission value.'' The modeling process for identifying this critical
emissions value inherently considers the numerous variables that affect
ambient concentrations of SO2, such as meteorological data,
background concentrations, and topography. In the standard approach,
the state would then provide for attainment by setting a continuously
applicable 1-hour emission limit at this critical emission value.
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    \1\ An ``average year'' is used to mean a year with average air
quality. While 40 CFR 50 appendix T provides for averaging three
years of 99th percentile daily maximum hourly values (e.g., the
fourth highest maximum daily hourly concentration in a year with 365
days with valid data), this discussion and an example below uses a
single ``average year'' to simplify the illustration of relevant
principles.
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    EPA recognizes that some sources have highly variable emissions,
for example due to variations in fuel sulfur content and operating
rate, that can make it extremely difficult, even with a well-designed
control strategy, to ensure in practice that emissions for any given
hour do not exceed the critical emission value. EPA also acknowledges
the concern that longer term emission limits can allow short periods
with emissions above the ``critical emissions value,'' which, if
coincident with meteorological conditions conducive to high
SO2 concentrations, could in turn create the possibility of
a NAAQS exceedance occurring on a day when an exceedance would not have
occurred if emissions were continuously controlled at the level
corresponding to the critical emission value. However, for several
reasons, EPA believes that the approach recommended in its guidance
document suitably addresses this concern. First, from a practical
perspective, EPA expects the actual emission profile of a source
subject to an appropriately set longer term average limit to be similar
to the emission profile of a source subject to an analogous 1-hour
average limit. EPA expects this similarity because it has recommended
that the longer term average limit be set at a level that is comparably
stringent to the otherwise applicable 1-hour limit (reflecting a
downward adjustment from the critical emissions value) and that takes
the source's emissions profile into account. As a result, EPA expects
either form of emission limit to yield comparable air quality.
    Second, from a more theoretical perspective, EPA has compared the
likely air quality with a source having maximum allowable emissions
under an appropriately set longer term limit, as compared to the likely
air quality with the source having maximum allowable emissions under
the comparable 1-hour limit. In this comparison, in the 1-hour average
limit scenario, the source is presumed at all times to emit at the
critical emission level, and in the longer term average limit scenario
the source is presumed to occasionally emit more than the critical
emission value but on average, and presumably at most times, to emit
well below the critical emission value. In an ``average year,''
compliance with the 1-hour limit is expected to result in three
exceedance days (i.e., three days with hourly values above 75 ppb) and
a fourth day with a maximum hourly value at 75 ppb. By comparison, with
the source complying with a longer term limit, it is possible that
additional exceedances would occur that would not occur in the 1-hour
limit scenario (if emissions exceed the critical emission value at
times when meteorology is conducive to poor air quality). However, this
comparison must also factor in the likelihood that exceedances that
would be expected in the 1-hour limit scenario would not occur in the
longer term limit scenario. This result arises because the longer term
limit requires lower emissions most of the time (because the limit is
set well below the critical emission value), so a source complying with
an appropriately set longer term limit is likely to have lower
emissions at critical times than would be the case if the source were
emitting as allowed with a 1-hour limit.
    As a hypothetical example to illustrate these points, suppose a
source that always emits 1,000 pounds of SO2 per hour, which
results in air quality at the level of the NAAQS (i.e., results in a
design value of 75 ppb). Suppose further that in an ``average year,''
these emissions cause the 5-highest maximum

daily average 1-hour concentrations to be 100 ppb, 90 ppb, 80 ppb, 75
ppb, and 70 ppb. Then suppose that the source becomes subject to a 30-
day average emission limit of 700 pounds per hour (lbs/hr). It is
theoretically possible for a source meeting this limit to have
emissions that occasionally exceed 1,000 pounds per hour, but with a
typical emissions profile, emissions would much more commonly be
between 600 and 800 lbs/hr. In this simplified example, assume a zero-
background concentration, which allows one to assume a linear
relationship between emissions and air quality. (A nonzero background
concentration would make the mathematics more difficult but would give
similar results.) Air quality will depend on what emissions happen on
what critical hours, but suppose that emissions at the relevant times
on these 5 days are 800 lbs/hr, 1,100 lbs/hr, 500 lbs/hr, 900 lbs/hr,
and 1,200 lbs/hr, respectively. (This is a conservative example because
the average of these emissions, 900 lbs/hr, is well over the 30-day
average emission limit.) These emissions would result in daily maximum
1-hour concentrations of 80 ppb, 99 ppb, 40 ppb, 67.5 ppb, and 84 ppb.
In this example, the fifth day would have an exceedance that would not
otherwise have occurred, but the third and fourth days would not have
exceedances that otherwise would have occurred. In this example, the
fourth highest maximum daily concentration under the 30-day average
would be 67.5 ppb.
    This simplified example illustrates the findings of a more
complicated statistical analysis that EPA conducted using a range of
scenarios using actual plant data. As described in Appendix B of EPA's
April 2014 SO2 guidance, EPA found that the requirement for
lower average emissions is highly likely to yield better air quality
than is required with a comparably stringent 1-hour limit. Based on
analyses described in appendix B of its 2014 guidance, EPA expects that
an emission profile with maximum allowable emissions under an
appropriately set comparably stringent 30-day average limit is likely
to have the net effect of having a lower number of exceedances and
better air quality than an emission profile with maximum allowable
emissions under a 1-hour emission limit at the critical emission value.
This result provides a compelling policy rationale for allowing the use
of a longer averaging period, in appropriate circumstances where the
facts indicate this result can be expected to occur.
    The question then becomes whether this approach--which is likely to
produce a lower number of overall exceedances even though it may
produce some unexpected exceedances above the critical emission value--
meets the requirements in sections 110(a)(1) and (2), 172(c)(1) and (6)
for SIPs to contain enforceable emissions limitations and other control
measures to ``provide for attainment'' of the NAAQS. For
SO2, as for other pollutants, it is generally impossible to
design a nonattainment plan in the present that will guarantee that
attainment will occur in the future. A variety of factors can cause a
well-designed attainment plan to fail and unexpectedly not result in
attainment, for example if meteorology occurs that is more conducive to
poor air quality than was anticipated in the plan. Therefore, in
determining whether a plan meets the requirement to provide for
attainment, EPA's task is commonly to judge not whether the plan
provides absolute certainty that attainment will in fact occur, but
rather whether the plan provides an adequate level of confidence of
prospective NAAQS attainment. From this perspective, in evaluating use
of a 30-day average limit, EPA must weigh the likely net effect on air
quality. Such an evaluation must consider the risk that occasions with
meteorology conducive to high concentrations will have elevated
emissions leading to exceedances that would not otherwise have
occurred, and must also weigh the likelihood that the requirement for
lower emissions on average will result in days not having exceedances
that would have been expected with emissions at the critical emissions
value. Additional policy considerations, such as in this case the
desirability of accommodating real world emissions variability without
significant risk of violations, are also appropriate factors for EPA to
weigh in judging whether a plan provides a reasonable degree of
confidence that the plan will lead to attainment. Based on these
considerations, especially given the high likelihood that a
continuously enforceable limit averaged over as long as 30 days,
determined in accordance with EPA's guidance, will result in
attainment, EPA believes as a general matter that such limits, if
appropriately determined, can reasonably be considered to provide for
attainment of the 2010 SO2 NAAQS.
    The April 2014 SO2 guidance offers specific
recommendations for determining an appropriate longer term average
limit. The recommended method starts with determination of the 1-hour
emission limit that would provide for attainment (i.e., the critical
emission value), and applies an adjustment factor to determine the
(lower) level of the longer term average emission limit that would be
estimated to have a degree of stringency comparable to the otherwise
necessary 1-hour emission limit. This method uses a database of
continuous emission data reflecting the type of control that the source
will be using to comply with the SIP emission limits, which (if
compliance requires new controls) may require use of an emission
database from another source. The recommended method involves using
these data to compute a complete set of emission averages, computed
according to the averaging time and averaging procedures of the
prospective emission limitation. In this recommended method, the ratio
of the 99th percentile among these long term averages to the 99th
percentile of the 1-hour values represents an adjustment factor that
may be multiplied by the candidate 1-hour emission limit to determine a
longer term average emission limit that may be considered comparably
stringent.\2\ The guidance also addresses a variety of related topics,
such as the potential utility of setting supplemental emission limits,
such as mass-based limits, to reduce the likelihood and/or magnitude of
elevated emission levels that might occur under the longer term
emission rate limit.
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    \2\ For example, if the critical emission value is 1,000 pounds
of SO2 per hour, and a suitable adjustment factor is
determined to be 70 percent, the recommended longer term average
limit would be 700 lbs/hr.
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    Preferred air quality models for use in regulatory applications are
described in Appendix A of EPA's Guideline on Air Quality Models (40
CFR part 51, appendix W). In 2005, EPA promulgated AERMOD as the
Agency's preferred near-field dispersion modeling for a wide range of
regulatory applications addressing stationary sources (for example in
estimating SO2 concentrations) in all types of terrain based
on extensive developmental and performance evaluation. Supplemental
guidance on modeling for purposes of demonstrating attainment of the
SO2 NAAQS is provided in appendix A to the April 2014
SO2 guidance document referenced above. Appendix A provides
extensive guidance on the modeling domain, the source inputs, assorted
types of meteorological data, and background concentrations.
Consistency with the recommendations in this guidance is generally
necessary for the attainment demonstration to offer

adequately reliable assurance that the plan provides for attainment.
    As stated previously, attainment demonstrations for the 2010 1-hour
primary SO2 NAAQS must demonstrate future attainment and
maintenance of the NAAQS in the entire area designated as nonattainment
(i.e., not just at the violating monitor) by using air quality
dispersion modeling (see appendix W to 40 CFR part 51) to show that the
mix of sources and enforceable control measures and emission rates in
an identified area will not lead to a violation of the SO2
NAAQS. For a short-term (i.e., 1-hour) standard, EPA believes that
dispersion modeling, using allowable emissions and addressing
stationary sources in the affected area (and in some cases sources
located outside the nonattainment area which may affect attainment in
the area) is technically appropriate, efficient and effective in
demonstrating attainment in nonattainment areas because it takes into
consideration combinations of meteorological and emission source
operating conditions that may contribute to peak ground-level
concentrations of SO2.
    The meteorological data used in the analysis should generally be
processed with the most recent version of AERMET. Estimated
concentrations should include ambient background concentrations, should
follow the form of the NAAQS, and should be calculated as described in
section <IP_ADDRESS> of the August 23, 2010 clarification memo on
``Applicability of appendix W Modeling Guidance for the 1-hr
SO2 National Ambient Air Quality Standard'' (U.S. EPA,
2010a).

IV. Review of Attainment Plan Requirements

A. Emissions Inventory

    The emissions inventory and source emission rate data for an area
serve as the foundation for air quality modeling and other analyses
that enable states to: (1) Estimate the degree to which different
sources within a nonattainment area contribute to violations within the
affected area; and (2) assess the expected improvement in air quality
within the nonattainment area due to the adoption and implementation of
control measures. As noted above, the State must develop and submit to
EPA a comprehensive, accurate and current inventory of actual emissions
from all sources of SO2 emissions in each nonattainment
area, as well as any sources located outside the nonattainment area
which may affect attainment in the area. See CAA section 172(c)(3).
    The primary SO2-emitting point source located within the
Sullivan County Area is Eastman, which produces organic acids,
aldehydes, esters, polymers, cellulose esters, specialty plastics, and
acetate fibers. The facility also produces process steam and
electricity for most of the operations, including hazardous waste
combustion, and wastewater treatment. Eastman consists of three main
SO2 emitting sources comprised of three powerhouses that
include a total of 14 boilers and several smaller emitters:
     Powerhouse B-83 consists of Boilers 18-24, denoted B-18--
B-24, which fire coal to provide steam for facility operations. Each of
the seven emissions units has the following capacities: Boilers B-18--
B-20 are rated at 246 million British thermal units per hour (MMBtu/
hr); Boilers B-21--B-22 have a rated capacity of 249 MMBtu/hr; and
Boilers B-23--B-24 have a rated capacity of 501 MMBtu/hr. All seven B-
83 boilers have existing limits on SO2 emissions of 2.4 lbs/
MMBtu based on a 1-hour averaging period. Actual emissions from B-83
were 5,686 tons per year (tpy) in 2011.
     Powerhouse B-253 consists of units B-25--B-29 which fire
coal to provide steam for facility operations. Each emissions unit, B-
25--B-29 has a rated capacity of 655 MMBtu/hr and an existing limit on
SO2 emissions of 2.4 lbs/MMBtu based on a 24-hour averaging
period. The B-253 powerhouse is currently undergoing a multi-year
project to convert the power generation from the coal-fired boilers to
natural gas-fired boilers to comply with regional haze best available
retrofit technology (BART). See section IV.B.4.i for additional BART
discussion. The result will be that the emissions units B-25--B-29 will
fire only natural gas as repowered units start up and for all units no
later than the attainment date for the 1-hour SO2 NAAQS,
October 4, 2018.\3\ Actual emissions from B-253 were 14,897 tpy in
2011.
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    \3\ As mentioned elsewhere in this proposed action, four boilers
have converted to exclusive use of natural gas for fuel combustion
already. These repowered units have different heat capacities, and
the fuel content is such that the actual emissions of SO2
will always be much less than the formerly permitted rate.
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     Powerhouse B-325 consists of Boilers B-30 and B-31, which
fire coal to provide steam for facility operations. Boiler B-30 has a
rated capacity of 780 MMBtu/hr and an existing emission limit on
SO2 emissions of 317 lbs/hr based on a 30-day averaging
period, equivalent to 0.406 lbs/MMBtu. Boiler B-31 is rated at 880
MMBtu/hr and has an existing limit on SO2 emissions of 293
lbs/hr based on a 30-day averaging period, equivalent to 0.333 lbs/
MMBtu. Actual emissions from B-325 were 1,276 tpy in 2011.
     The B-248 unit consists of three hazardous waste
combustors, one liquid chemical waste incinerator and two rotary kilns
that can burn solid or liquid chemical waste, B-248-2, Vent A, and B-
248-1, Vents D and E, respectively. According to the attainment SIP
submitted by TDEC in May 2017, each of these units is subject to an
existing limit on SO2 emissions for an exhaust concentration
of 1,000 parts per million by volume SO2, equivalent to
1,109 tpy for B-248-2, Vent A, and 1,552 tpy each for 248-1, Vents D
and E. Actual emissions from B-248 were 7.3 tpy in 2011. On February 1,
2018, TDEC issued a revised title V permit (568496) that included
additional SO2 limits of 20 tpy for Vent A and 40 tpy for
Vents D and E, combined.
     Eastman has 31 other smaller emission units that provide
various services to other parts of the facility, and these units
account for 194.56 tpy of the allowable emissions across the facility.
Actual emissions from the remaining units were 40.9 tpy in 2011. For
more information on these miscellaneous units, see the May 12, 2017,
submittal.
    The emissions at units for Eastman were recorded either by using
data collected from CEMS or by material balances based on feed rates
and other parameters and are quality-assured by TDEC.\4\
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    \4\ As detailed in Section IV. of this proposed action, CEMS
will be installed for Powerhouse B-83. Therefore, all subsequent
emissions inventories and all compliance assessments will be based
on CEMS measurements.
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    The next largest SO2 source within the nonattainment
area is the EnviraGlass, LLC glass manufacturing facility
(EnviraGlass). SO2 emissions from EnviraGlass were 49.3 tons
in 2011, as determined from material balances. The EnviraGlass
Kingsport facility consists of one main SO2 emitter. The
glass melting furnace #1 (GMF-1) fires natural gas and No. 2 fuel oil.
The allowable permit limit for EnviraGlass of 39.6 lb/hr was included
in the attainment modeling.
    The next largest SO2 source in Sullivan County is
located just outside the Sullivan County Area boundary: Domtar Paper
Company, LLC, Kingsport Paper Mill (Domtar). Domtar produces pulp and
paper and is permitted to burn hog fuel, dry wood residue, engineered
fuel, wastewater treatment plant sludge, fuel oil, and natural gas.
SO2 emissions from this facility were 70.8 tons in 2011, as
determined from material balances.

The permitted allowable SO2 emissions limit for the main
SO2 emissions unit at Domtar, the HFB1-1 biomass boiler, was
included in the attainment modeling (264 lb/hr = 33.26 g/s). TDEC
determined that the other SO2 emissions units at Domtar did
not need to be explicitly modeled because of their smaller emissions
levels. Therefore, these sources were accounted for using the
background concentration discussed in section IV.B.5 of this notice.
    TDEC utilized EPA's 2011 National Emissions Inventory (NEI),
Version 2 as the starting point for compiling point source emissions
for the base year emissions inventory. The hazardous waste incinerators
at Eastman in B-248 were erroneously reported as 20 tpy each for B-248-
1 and B-248-2. TDEC corrected this information from the 2011 NEI with
information submitted by Eastman.\5\ EnviraGlass, formerly Heritage
Glass, did not report emissions for the 2011 NEI, so TDEC used
semiannual compliance reports pursuant to the title V operating permit
for the facility to determine emissions.
---------------------------------------------------------------------------

    \5\ For more information on this correction to the 2011 NEI,
Version 2 emissions, see Attachment A of Tennessee's May 12, 2017,
submittal.
---------------------------------------------------------------------------

    TDEC also used the 2011 NEI, Version 2 to obtain estimates of the
area and nonroad sources. For onroad mobile source emissions, TDEC
utilized EPA's Motor Vehicle Emissions Simulator (MOVES2014). A more
detailed discussion of the emissions inventory development for the
Sullivan County Area can be found in Tennessee's May 12, 2017,
submittal.
    Table 1 below shows the level of emissions, expressed in tpy, in
the Sullivan County Area for the 2011 base year by emissions source
category. The point source category includes all sources within the
nonattainment area.

                                        Table 1--2011 Base Year Emissions Inventory for the Sullivan County Area
                                                                          [tpy]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                Year                                      Point            Onroad          Nonroad            Area            Total
--------------------------------------------------------------------------------------------------------------------------------------------------------
2011...............................................................        21,956.5             1.62             0.16             10.6        21,968.88
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Domtar is not included in the base year inventory for the Sullivan
County Area because it is outside of the boundary of the nonattainment
area. However, TDEC evaluated 2011 emissions from this facility to
evaluate its impact on the area. Domtar's emissions were reported for
the 2011 NEI, but TDEC determined that emissions from HFB1-1, the
biomass boiler, were initially reported in error as 2.06 tons. Actual
emissions were determined from fuel usage data supplied by Domtar,
leading to 44.1 tpy SO2 emitted in 2011 from HFB1-1 and
total facility-wide emissions of 70.8 tpy.\6\
---------------------------------------------------------------------------

    \6\ For more information on this correction to the 2011 NEI,
Version 2 emissions, see Table 3-8 of the May 12, 2017, submittal.
---------------------------------------------------------------------------

    EPA has evaluated Tennessee's 2011 base year emissions inventory
for the Sullivan County Area and has made the preliminary determination
that this inventory was developed consistent with EPA's guidance.
Therefore, pursuant to section 172(c)(3), EPA is proposing to approve
Tennessee's 2011 base year emissions inventory for the Sullivan County
Area.
    The attainment demonstration also provides for a projected
attainment year inventory that includes estimated emissions for all
emission sources of SO2 which are determined to impact the
nonattainment area for the year in which the area is expected to attain
the standard. This inventory must address any future growth in the
Area. Growth means any potential increases in emissions of the
pollutant for which the Sullivan County Area is nonattainment
(SO2) due to the construction and operation of new major
sources, major modifications to existing sources, or increased minor
source activity. TDEC included a statement in its May 12, 2017
submittal declaring that the air agency assumes no growth of major
sources in the Sullivan County Area, and that minor source growth
should not significantly impact the Area. TDEC cites to its ``Growth
Policy'' found at Tennessee Air Pollution Control Regulations (TAPCR)
1200-03-09-.01(5), which includes the nonattainment new source review
(NNSR) program and the requirement for minor sources and minor
modifications proposing to construct in a nonattainment area to apply
BACT, approved into the SIP and last updated on July 30, 2012 (see 77
FR 44481). The NNSR program includes lowest achievable emissions rate,
offsets, and public hearing requirements for major stationary sources
and major modifications.
    TDEC provided a future year projected emissions inventory for all
known sources included in the 2011 base year inventory, discussed
above, that were determined to impact the Sullivan County Area. The
projected emissions are set to be accurate beyond October 1, 2018, when
the control strategy for the attainment demonstration will be fully
implemented. Therefore, as an annual future year inventory, the point
source portion is accurate beyond October 1, 2018, and would represent
an annual inventory for 2019 or beyond. The projected emissions in
Table 2 are estimated actual emissions, representing a 67.6 percent
reduction from the base year SO2 emissions. The point source
emissions were estimated by taking credit for the control strategy to
repower the boilers at B-253 and assuming actual emissions at other
Eastman units would remain the same as in 2011. Additionally,
EnviraGlass has not operated in recent years, and TDEC includes a
statement in its May 12, 2017 submittal that as of February 2017, the
source had not resumed its operations. Therefore, EnviraGlass emissions
were projected as zero tpy. If this source began operation again,
actual emissions would be much less than those from Eastman (~50 tpy),
and would be reported in future inventories.
    Per EPA's April 2014 SO2 guidance, the existing
allowable emissions limits and the new 30-day, combined emission limit
(see section IV.B.4) that TDEC is requesting EPA approve into the SIP,
were modeled to show attainment. These projected actual emissions
included in the future year inventory are less than the allowable
emission limits, and therefore offer a greater level of certainty that
the NAAQS will be protected under all operating scenarios. Emissions
estimates for onroad sources were re-estimated with MOVES2014. The
nonroad emissions were projected using national growth factors, and
area source emissions were scaled based on emission factors developed
using the Annual Energy Outlook 2014 for consumption and production
forecasts. Both categories were then apportioned to the nonattainment
area based on

population in the nonattainment area relative to that of Sullivan
County.\7\
---------------------------------------------------------------------------

    \7\ For more information, see Attachments A-D of the May 12,
2017, submittal.

                  Table 2--Projected 2018 SO2 Emissions Inventory for the Sullivan County Area
                                                      [tpy]
----------------------------------------------------------------------------------------------------------------
              Year                     Point          Onroad          Nonroad          Area            Total
----------------------------------------------------------------------------------------------------------------
2011............................        21,956.5            1.62            0.16            10.6       21,968.88
2019............................         7,104.5            0.64           0.006          10.521        7,115.67
----------------------------------------------------------------------------------------------------------------

B. Attainment Modeling Demonstration

    Eastman operates a large manufacturing facility in Kingsport that
includes major SO2 sources with the potential to emit
greater than 100 tons per year (tpy) of SO2. The
SO2 emissions come from three main boiler groups B-83, B-253
and B-325. Powerhouse B-253 serves five boilers (Boilers 25-29), each
with an individual stack, that provide steam and electricity to the
facility. Powerhouse B-325 serves two coal-fired boilers that vent to a
single stack (Boiler 30 and Boiler 31). Boiler 30 is equipped with a
spray dryer absorber and electrostatic precipitator to control
particulate matter and acid gases. Boiler 31 is equipped with a spray
dryer absorber and fabric filter to control particulate matter and acid
gases. Powerhouse B-83 serves seven boilers; five coal-fired boilers
(Boilers 18-22) venting to a single stack, and two coal-fired boilers
(Boilers 23 and 24) that also burn wastewater treatment sludge, venting
to a single stack.
    These boilers, along with three other backup natural gas-fired
boilers with minimal SO2 emissions (B-423), provide process
steam and most of the electrical power needed to supply Eastman's
operations. The combination of boilers and boiler operating loads at
any given time depends on manufacturing demands along with availability
of boilers, as each boiler has annual scheduled shutdowns. The
following discussion evaluates various features of the modeling that
Tennessee used in its attainment demonstration.
1. Model Selection
    Tennessee's attainment demonstration used AERMOD, the preferred
model for this application, and the associated pre-processor modeling
programs. The State used the 16216r version of AERMOD with regulatory
default options and urban dispersion coefficients.\8\ Receptor
elevations and hill heights required by AERMOD were determined using
the AERMAP terrain preprocessor version 11103. The meteorological data
was processed using AERMET version 16216 with the regulatory adjusted
U* option. The surface characteristics around the meteorological
surface station were determined using AERSURFACE version 13016 and
building downwash was assessed with the BPIP processor (version 04274).
EPA proposes to find these model selections appropriate for the
attainment demonstration.
---------------------------------------------------------------------------

    \8\ Tennessee and Eastman determined that urban dispersion
coefficients are appropriate for the modeling analysis based upon an
assessment of land use within a 3-kilometer radius of the Eastman
boiler stacks using the Auer technique contained in Section
<IP_ADDRESS>.b.i of 40 CFR part 51, appendix W. The analysis resulted in
52.4 percent of the area being classified as urban land use
categories, which is above the 50 percent criteria for using urban
dispersion coefficients. Additionally, Tennessee and Eastman
performed an analysis to estimate an effective population for the
urban option to account for the large industrial heat release at the
Eastman facility. The results of this analysis yield an effective
population of 200,000, which is approximately four times the
approximate 50,000 population of Kingsport, Tennessee. The complete
details of Tennessee and Eastman's analysis are discussed in Section
4.1 of Attachment G1, ``NAAQS Attainment Demonstration Modeling
Analysis,'' in Tennessee's final SIP submittal. EPA preliminarily
agrees that urban dispersion coefficients with an effective
population of 200,000 is appropriate for the modeling, and believes
the procedures to estimate the effective population are appropriate.
---------------------------------------------------------------------------

2. Meteorological Data
    The Sullivan County nonattainment area is in a wide valley
surrounded by complex terrain ridges. Eastman evaluated available
surface meteorological data in the area and determined that none of
nearby National Weather Surface (NWS) stations in area were
representative of the site-specific winds that occur in the
nonattainment area valley. Therefore, Eastman installed and operated a
site-specific 100-meter meteorological data tower and Doppler SODAR
system to collect profiles of meteorological data (wind speed, wind
direction, temperature). One year of site-specific data was collected
from April 1, 2012 through March 31, 2013.\9\ EPA has reviewed the
site-specific meteorological data and has preliminarily determined that
the data meets the quality assurance criteria and the 1-year of data is
appropriate for the modeling analysis. Site-specific turbulence
parameters (sigma-theta and sigma-w) were also collected. However, as
recommended in the December 2016 final revisions to the EPA's Guideline
on Air Quality Models, contained in 40 CFR part 51, appendix W
(Appendix W), since Eastman chose to use the adjusted U* (surface
friction velocity) regulatory option in AERMET, the site-specific
turbulence parameters were not used. The data from the 100-meter tower
and Doppler SODAR were merged with concurrent additional NWS surface
data parameters needed by AERMOD (e.g., cloud cover data) from the Tri-
City Regional Airport National Weather Station (13877) and upper air
data from Nashville, TN (13897).
---------------------------------------------------------------------------

    \9\ Pursuant to Section 8.4.2.e of 40 CFR part 51, appendix W,
if site-specific meteorology is used for the modeling analysis, at
least 1-year of site-specific data should be collected. The data
should meet the quality assurance criteria in EPA's 2000
``Meteorological Monitoring Guidance for Regulatory Modeling
Applications.'' Publication No. EPA-454/R-99-005. Office of Air
Quality Planning and Standards, Research Triangle Park, NC. (NTIS
No. PB 2001-103606).
---------------------------------------------------------------------------

    The surface roughness (zo), albedo (r), and Bowen ratio (Bo)
required surface parameters were determined for the area around the
site-specific meteorological surface station using AERSURFACE version
13016. Eastman processed the meteorological data and surface parameters
into AERMOD-ready files using AERMET version 16216 with the regulatory
adjusted U* option. Complete details of the meteorological data
collection and processing are available in sections 3.1-3.8 of
Attachment G1, ``NAAQS Attainment Demonstration Modeling Analysis,'' in
Tennessee's final SIP submittal. EPA preliminarily finds that the
meteorological data collection and processing is appropriate for the
modeled attainment demonstration.
3. Emissions Data
    The emission inputs to Tennessee's attainment demonstration
modeling reflect 1-hour emissions that correspond to allowable
emissions from sulfur dioxide emission units at the Eastman facility
and other nearby emissions sources located within and outside the

Sullivan County nonattainment area. Eastman's modeled emissions sources
include nine coal-fired boilers, five natural gas boilers that were
converted from coal-fired to natural gas-fired units, and a tail-gas
incineration unit. Although the limit on emissions from Eastman governs
the 30-day average sum of emissions from all nine coal-fired boilers,
Tennessee conducted modeling using a constant hourly rate (the 1,905
lb/hr 1-hour CEV), as recommended by EPA's April 2014 SO2
guidance. As discussed in more detail in section IV.B.6 below,
Tennessee has conducted 34 modeling runs using a full range of emission
distributions, to show that the limit ensures attainment, regardless of
how emissions are distributed among the various boilers within this
limit. In addition, Tennessee used the statistical procedures
recommended in Appendix C of EPA's guidance to establish an adjustment
factor that it applied to determine the limit it would otherwise have
set.
    Two additional SO2 emissions sources, EnviraGlass,
located within the nonattainment area, and Domtar Paper, located just
outside the nonattainment area, were also included in Tennessee's
attainment demonstration modeling, modeled at their hourly emission
limits. Additional details regarding the emissions units are included
in the Emissions Inventory, section IV.A., of this proposed rule and
section 2 of Attachment G1, ``NAAQS Attainment Demonstration Modeling
Analysis,'' in Tennessee's final SIP submittal. EPA proposes to find
that the emissions sources included in the modeling are appropriate for
the attainment demonstration. All other sources not explicitly included
in the modeling were addressed using the background concentration
discussed in section IV.B.5 of this notice.
4. Emission Limits
    An important prerequisite for approval of an attainment plan is
that the emission limits that provide for attainment be quantifiable,
fully enforceable, replicable, and accountable. See General Preamble at
13567-68. Some of the limits that Tennessee's plan relies on are
expressed as 30-day average limits. Therefore, part of the review of
Tennessee's attainment plan must address the use of these limits, both
with respect to the general suitability of using such limits for this
purpose and with respect to whether the limits included in the plan
have been suitably demonstrated to provide for attainment. The first
subsection that follows addresses the enforceability of the limits in
the plan, and the second subsection that follows addresses the
combined, 30-day emission limit for Boilers 18-24, 30 and 31. Sections
IV.B.6 and 7 discuss the modeling conducted to demonstrate that the
limit of combined emissions of these boilers suitably provides for
attainment.
i. Enforceability
    Section 172(c)(6) provides that emission limits and other control
measures in the attainment SIP shall be enforceable. Tennessee's
attainment SIP for the Sullivan County nonattainment area relies on
control measures and enforceable emission limits for Powerhouses B-253,
B-83 and B-325 (for more discussion on these boilers, please refer to
section IV.A above). These emission reduction measures were accounted
for in the attainment modeling for the Eastman facility which
demonstrates attainment for the 2010 NAAQS.
    Tennessee's control strategy for B-253 relies on compliance with
the State's Regional Haze SIP to install BART for SO2 and
other pollutants that impair visibility at Class I areas. TDEC's
original April 4, 2008, regional haze SIP identified B-253 (Boilers 25-
29) at Eastman Chemical as BART-eligible units.\10\ Tennessee
subsequently amended its regional haze SIP (May 14, 2012 and May 25,
2012) to establish BART requirements for Eastman including an
alternative BART option to repower (convert coal-fired boilers to
natural gas) Boilers 25-29 at B-253 by December 31, 2018.\11\ The
alternative BART measure became federally-enforceable through the
issuance of BART permit 066116H on May 9, 2012, and an amendment on May
22, 2012, which changed the conversion completion date to align with
the 1-hour SO2 NAAQS compliance deadline of October 4, 2018
(Condition 4(f)).\12\ Tennessee issued construction permit 966859F on
June 15, 2013, authorizing construction of the B-253 boilers conversion
to natural gas. Condition 6 of Permit 966859F establishes a natural gas
fuel restriction after conversion is complete for each boiler.
---------------------------------------------------------------------------

    \10\ A BART-eligible source is an emission source that has the
potential to emit 250 tons or more of a visibility-impairing
pollutant, was constructed between August 7, 1962 and August 7,
1977, and whose operations fall within one or more of 26 listed
source categories. The Clean Air Act requires BART for any BART-
eligible source that a State determines ``emits any air pollutant
which may reasonably be anticipated to cause or contribute to any
impairment of visibility in any such area.'' EPA finalized a limited
approval/limited disapproval of portions of Tennessee's April 4,
2008, regional haze SIP on April 24, 2012 (77 FR 24392). The April
4, 2008, SIP established the State's plan to comply with federal
requirements to ensure natural visibility conditions at Class I
areas by requiring affected sources to install BART for
SO2 and other visibility-impairing pollutants.
    \11\ Tennessee's initial Eastman BART determination required
Eastman to reduce SO2 emissions at Boilers 25-29 either
by 92 percent or comply with a limit of 0.20 lbs/MMBtu established
through the BART permit (066116H). EPA approved Eastman's BART
determination, the alternative BART option and permit 066116H on
November 27, 2012 (77 FR 70689).
    \12\ Condition 4(f) also prohibits operation of any B-253 boiler
not converted after the October 2018 SO2 NAAQS compliance
date until repowered to natural gas.
---------------------------------------------------------------------------

    In conjunction with the natural gas conversion control strategy at
B-253, Tennessee also established a 30-day combined SO2
emission limit for nine coal-fired boilers at B-83 (seven boilers) and
B-325 (two boilers) pursuant to EPA's April 2014 SO2
guidance on longer term average limits (see section IV.B.4.ii below).
Tennessee established a single, combined 30-day rolling average of
1,753 lbs/hr SO2 emission limit through Permit 070072F on
May 10, 2017, for Boilers 18-24 at B-83 and Boilers 30-31 at B-325.
Boilers 30 and 31 at B-325 also have existing individual SO2
emission limits of 317 lbs/hr and 293 lbs/hr, respectively, based on a
30-calendar day rolling average.\13\ Eastman must comply with the
combined 30-day limit for the 30-day period ending on October 31, 2018
\14\ and each 30-day period thereafter. Therefore, Eastman must begin
to comply with the new limit no later than October 2, 2018. Compliance
will be determined based on continuous emission monitoring system
(CEMS) data for all nine boilers. EPA provides additional details,
section IV.B.4.ii below, regarding how the combined 30-day
SO2 emission limit was derived. The enforceable emission
limit and compliance parameter ensure control measures will achieve the
necessary incremental SO2 emissions reductions necessary to
attain the NAAQS as expeditiously as practicable. Based on

the attainment modeling of B-253 repowering combined with the 30-day
SO2 emission limits for B-83 and B-325, the area is
projected to begin showing attaining monitoring design values.
---------------------------------------------------------------------------

    \13\ Established in construction Permit 955272F, Boiler 30 has a
317 lbs/hr 30-day SO2 limit and Boiler 31 has a 293 lbs/
hr 30-day SO2 limit, giving B-325 an allowable limit of
610 lbs/hr on a 30-day average.
    \14\ EPA's April 2014 SO2 guidance recommends that
attainment plans provide for compliance at least one calendar year
prior to the attainment deadline, to facilitate collection of air
quality monitoring data reflecting attainment plan implementation.
This air quality data would indicate whether the attainment plan is
in fact successfully providing for attainment. Nevertheless, the
guidance also notes that EPA has the discretion to approve plans
that are judged to provide for attainment by the statutory
attainment deadline, even if the monitoring data collected prior to
the attainment deadline are judged to indicate that that plan has
not yielded timely attainment. EPA believes that Tennessee's
attainment plan provides for attainment, notwithstanding the
possibility that subsequent review of available monitoring data may
support a conclusion that the plan did not in fact provide for
timely attainment.
---------------------------------------------------------------------------

    Tennessee's May 11, 2017, attainment SIP requests EPA approve into
the SIP the authorization for alternative BART repowering of Boilers
25-29 at B-253 at Condition 4(f) of Regional Haze permit 066116H \15\
(approved into Tennessee's regional haze SIP on November 12, 2012),
natural gas fuel restriction for Boilers 25-29 (after each natural gas
conversion) at Condition 6 of PSD construction permit 966859F, and the
30-day rolling single, combined SO2 emission limit of 1,753
lbs/hr for boilers at B-83 and B-325 at Conditions 1 through 4 \16\ of
permit 070072F, which also include compliance parameters (monitoring,
recordkeeping and reporting). The accountability of the SO2
emission limit is established through TDEC's inclusion in the
nonattainment SIP and in the attainment modeling demonstration to
ensure permanent and enforceable emission limitations as necessary to
provide for attainment of the 2010 SO2 NAAQS.
---------------------------------------------------------------------------

    \15\ EPA notes condition 4(f) was approved into Tennessee's SIP
on November 12, 2012 as part of the State's Regional Haze SIP. See77
FR 70689.
    \16\ In Tennessee's SO2 attainment SIP (page 33) the
state requested EPA approve Conditions 1-5 from Permit 070072F
however, EPA notes only four conditions were included in the final
issued permit.
---------------------------------------------------------------------------

ii. Longer Term Average Limits
    Tennessee has developed a single, combined emission limit of 1,753
lbs/hr of SO2 emissions on a 30-day average basis. This
emission limit applies to nine coal-fired boilers, which emit
SO2 from three separate stacks from powerhouses B-83 and B-
325. These nine coal-fired boilers help provide both steam and
electricity for the Eastman facility and Boilers 23 and 24 (at B-83)
also burn wastewater treatment sludge. Based on the unique,
interconnected operations and the steam demand for the Eastman
facility, Tennessee elected to establish a single, combined emission
limit governing the sum of emissions from these nine boilers. Tennessee
concluded that the NAAQS will be attained so long as total hourly
emissions from these nine boilers are at or below 1,905 lbs/hr.
Tennessee based this conclusion on a set of 34 modeling runs, which
encompassed several ``worst-case'' emissions scenarios. These scenarios
and the modeling results are described in detail in section IV.B.6 of
this notice. EPA ordinarily uses the term critical emissions value
(CEV) to mean the 1-hour emission rate for an individual stack that, in
combination with the other CEVs for other relevant stacks, the state
shows through proper modeling to yield attainment. However, in this
case, EPA is using the term CEV to mean the total emissions from all
nine Eastman coal-fired boilers emitting from three stacks that
Tennessee has shown to yield attainment, reflecting Tennessee's
approach of evaluating an appropriate limit on the sum of these
emissions.
    After establishment of this combined-source CEV, Tennessee used the
procedures recommended in Appendix C of EPA's April 2014 SO2
guidance to determine an adjustment factor with which to establish a
single, combined emission limit with a longer term averaging time (30-
day). Tennessee analyzed three years of historical hourly emissions
data (2013-2015) from the nine boilers in question. Tennessee used the
sum of emissions from the nine boilers in this analysis, determining a
99th percentile of the 1-hour total emissions values and a 99th
percentile of the 30-day average total emission values. The ratio of
these 99th percentile values yielded an adjustment factor of 0.92.
Multiplication of this adjustment factor times the collective CEV
yielded a 30-day average limit of 1,753 lbs/hr. EPA believes that
Tennessee, by following the approach recommended in Appendix C of the
April 2014 SO2 guidance, has justified a conclusion that
this 1,753 lbs/hour limit (governing the sum of emissions from the nine
boilers) may be considered comparably stringent to a 1-hour limit of
1,905 lbs/hr (again governing the sum of emissions from the nine
boilers). Since the emission limit being established for these nine
boilers is a single, combined limit, EPA believes it is appropriate for
the adjustment factor also to be computed based on the total combined
emissions from the nine boilers. Therefore, EPA proposes to agree that
the adjustment factor of 0.92 is appropriate in this case.
    EPA's April 2014 SO2 guidance further states, ``The
second important factor in assessing whether a longer term average
limit provides appropriate protection against NAAQS violations is
whether the source can be expected to comply with a longer term average
limit in a manner that minimizes the frequency of occasions with
elevated emissions and magnitude of emissions on those occasions.'' The
guidance advises that the establishment of supplemental limits to
provide direct constraints on the frequency and/or magnitude of
emissions exceeding the CEV can be valuable, but the guidance also
acknowledges the possibility that occasions of emissions exceeding the
CEV may be rare and modest in magnitude even without supplemental
enforceable limitations. Tennessee concluded that occasions of
emissions exceeding the critical emissions would be infrequent and
modest in magnitude even without adoption of supplemental limits. EPA
conducted its own evaluation of whether this element of the guidance is
satisfied, such that compliance with Tennessee's 30-day average
emission limit would provide adequate confidence that the area will
attain the standard.
    The historical emissions data do not provide a direct measure of
the frequency and magnitude of elevated emissions to expect once
Eastman complies with the 30-day limit. The historical Eastman
emissions data that Tennessee used is from a period in which emissions
frequently were higher than the new limit. During the 2013 to 2015
period, Eastman's total emissions exceeded the subsequently adopted
limit (1,753 lbs/hr) in approximately 32.4 percent of 30-day averages,
and exceeded the 1-hour CEV (1,905 lbs/hr) in approximately 21.5
percent of hours. Thus, Eastman will be required to make emission
reductions sufficient to comply with the new 30-day limit (1,753 lb/
hr), which would both eliminate the occasions of 30-day average
emissions above 1,753 lbs/hr and reduce the number and possibly
eliminate the occasions when 1-hour emission levels exceed 1,905 lbs/
hr. The question then is how frequently and with what associated
emission levels can 1-hour emissions levels be expected to exceed the
CEV once Eastman complies with the 30-day average limit.
    Since Tennessee has permitted a combined, multi-stack emission
limit (1,753 lb/hr) for the nine coal-fired boilers, there are multiple
compliance scenarios possible. Consequently, there is also a range of
frequencies that the hourly emissions can exceed the CEV while still
meeting the 30-day permit limit. To forecast the frequency and
magnitude of emissions of occasions with emissions above the CEV, EPA
asked Tennessee for information regarding how Eastman expects to comply
with the new limit. Tennessee responded \17\ that Eastman's compliance
strategy will likely be to modify the order of dispatch of the nine
boilers in question, dispatching Boilers 18 through 22 from Powerhouse
B-83 less often in the future, in particular by reducing the
dispatching of the smaller coal-fired boilers (Boilers 18, 19, and 20)
in favor

of greater operation of the larger boilers that are being converted to
burn natural gas.\18\ These smaller boilers are the oldest and least
efficient boilers of the nine and provide only low pressure steam to
the facility. EPA used this information provided by Tennessee and the
less efficient nature of these boilers and further analyzed the
historical (2013 to 2015) emissions. Given the order of preference in
boiler dispatch provided by Tennessee and efficiency considerations,
EPA expects that three boilers (B-18 to B-20) may be operated at
approximately 20 percent of their historical rates. This level of
operation for these boilers would yield compliance with the new limit
and allow Eastman to meet its steam generation needs. With that level
of operation of those boilers, the number of occasions of total plant
emissions exceeding the CEV was found to be 1.1 percent of the hours,
with these hours on average being 4.4 percent above the CEV.\19\ During
EPA's analyses, we found that the frequency of emissions over the CEV
could range from 1 to 10 percent of the time, depending on the
operational scenario used to comply with the 30-day limit. While EPA
acknowledges the uncertainty in forecasting the frequency of elevated
emissions and the magnitude of emissions on those occasions, based on
the information received from Tennessee and our own analysis, EPA
believes that emissions at Eastman are unlikely to exceed the CEV more
than a few percent of the hours, at levels generally only a modest
percent over the CEV. Compliance with the 30-day limit will be ensured
using a CEMS and appropriate monitoring, recordkeeping and reporting
requirements. Consequently, EPA proposes to conclude that the second
criterion for use of longer term average limits is satisfied, even
without supplemental limits to constrain the frequency and emissions
level of occasions when emissions exceed the CEV.
---------------------------------------------------------------------------

    \17\ See emails from TDEC to EPA Region 4 dated January 26 and
February 8, 2018.
    \18\ Tennessee's analysis in the February 8 email confirmed
that, under the new combined limit, there should be adequate
capacity available at natural gas boilers at B-253 and B-423,
without the need to revise existing permit limits for these
individual units.
    \19\ The email correspondence with TDEC and supporting
documentation (including Tennessee's spreadsheet data and EPA's
spreadsheet used for these calculations) are in the docket (ID: EPA-
R04-OAR-2017-0626) for this proposed rule.
---------------------------------------------------------------------------

    Based on a review of the State's submittal, EPA believes that the
single, combined 30-day average limit for the nine boilers in
Powerhouses B-83 and B-325, in conjunction with the existing individual
30-day average limits for Boilers B-30 and B-31, provides a suitable
alternative to establishing a 1-hour average emission limit for each
unit or for the collected units at this source. Further discussion of
Tennessee's modeling analysis of its set of limits, along with
discussion of pertinent considerations in applying the procedures of
Appendix C of EPA's guidance in determining appropriate longer term
limits, is provided in section IV.B.6 below. In summary, EPA believes
that the State has used a suitable data base in an appropriate manner
and has thereby applied an appropriate adjustment, yielding an emission
limit that has comparable stringency to the 1-hour average limit that
the State determined would otherwise have been necessary to provide for
attainment. While the 30-day average limit allows for occasions in
which emissions may be higher than the level that would be allowed with
the combined-unit 1-hour limit, the State's limit compensates by
requiring average emissions to be lower than the level that would
otherwise have been required by a 1-hour average limit. As described
above in this section, in section III and explained in more detail in
EPA's April 2014 SO2 guidance for nonattainment plans, EPA
believes that appropriately set longer term average limits provide a
reasonable basis by which nonattainment plans may provide for
attainment. Based on the general information provided in this guidance
document as well as the information in Tennessee's attainment SIP, EPA
proposes to find that the 30-day average limit for Eastman's nine
boilers in combination with other limitations in the State's plan will
provide for attainment of the NAAQS.
5. Background Concentration
    In accordance with section 8.3 of 40 CFR part 51, appendix W,
Tennessee's attainment demonstration addresses the impacts from all
SO2 emissions sources not explicitly included in the AERMOD
modeling analysis by adding representative background concentrations to
the impacts from the modeled sources. The State and Eastman chose to
use 2013-2015 ambient monitoring data from a sulfur dioxide monitor
located at Mammoth Cave National Park in Kentucky (AQS ID 21-061-0501)
to develop ``seasonal by hour of the day'' background concentrations.
The hourly concentrations range from 2.79 to 18.51 micrograms per cubic
meter ([micro]g/m\3\). The complete details of the background
concentrations are described in section 3.9 of Attachment G1 of the
Tennessee's Attainment Demonstration submittal. EPA preliminarily finds
use of the Mammoth Cave background data is appropriate for the
attainment modeling analysis.
6. Analysis of Multi-Stack Limit
    The use of a limit governing the sum of emissions from multiple
stacks, in lieu of individual limits for each stack, calls for a
demonstration that the worst-case distribution of these emissions
provides for attainment. To provide this demonstration, Tennessee
conducted thirty-four (34) AERMOD modeling runs using varying
combinations of boiler load and emissions scenarios for the nine coal-
fired boilers to verify that the modeling includes the worst-case
operational scenarios allowed under the single, thirty-day rolling
average, emissions limit of 1,753 lbs/hr for the nine coal-fired
boilers. The 34 modeling scenarios were performed to derive the single,
combined 1,905 lbs/hr CEV for the nine coal-fired boilers (two stacks
at the B-83 Powerhouse and one stack at the B-325 Powerhouse) that
results in modeled attainment of the NAAQS. As defined in EPA's April
2014 SO2 guidance, the CEV is the level of emissions that
results in modeled concentrations that are just below the level of the
NAAQS; as noted above, this term is being applied to the combination of
emissions from the nine coal-fired boilers referenced earlier in the
notice.
    With these 34 AERMOD modeling runs, Tennessee and Eastman evaluated
a wide range of future potential operational scenarios, considering
boiler steam load demands for Eastman's production processes and boiler
load-shifting that is projected to occur once the conversion of the
five coal-fired boilers at B-253 (Boilers 25-29) from burning coal to
natural gas is completed by October 2018. Based upon this evaluation,
34 operational scenarios were selected by Tennessee and Eastman for the
CEV modeling analysis. Four of these 34 operation scenarios reflected
all of the SO2 being emitted from a single stack, including
two scenarios where all of the 1,905 lbs/hr is released from one or the
other of the two B-83 stacks individually, one scenario where the B-325
stack emitted 726 lbs/hr \20\ (which is the one hour equivalent to the
current permitted, federally enforceable allowable

emissions limit for B-325), and one scenario where the B-325 stack
emitted 1,800 lbs/hr to simulate a B-325 worst-case emissions scenario.
The modeled predicted concentrations from the three single-stack
scenarios with permissible emission levels ranged from 89.08 [micro]g/
m\3\ to 182.7 [micro]g/m\3\; the scenario with B-325 emitting 1,800
lbs/hr, well above its permissible level, yielded an estimated highest
concentration of 190.8 [micro]g/m\3\. Nine modeling scenarios were
performed to evaluate emissions from various combinations when two of
the three stacks are in operation. For these scenarios, the 1,905 lbs/
hr CEV rate was divided between the two stacks in multiple combinations
to represent reasonable potential worst-case future operations. The
modeled predicted concentrations from the nine two-stack scenarios
range from 171.6 [micro]g/m\3\ to 190.5 [micro]g/m\3\, with the highest
value of 190.5 [micro]g/m\3\ resulting from a scenario when the Boilers
18-22 B-83 stack was emitting at the highest level near its maximum
capacity (1,039 lbs/hr), the Boilers 23-24 B-83 stack was emitting near
its average rate (866 lbs/hr), and Boilers 30-31 were not operating (0
lb/hr). Twenty-one modeling scenarios were performed to evaluate
simultaneous operation of all three stacks. As with the two-stack
scenarios, the 1,905 lbs/hr critical value emissions rate was divided
among the three stacks in multiple combinations to represent reasonable
potential worst-case future operations. The modeled predicted
concentrations from the twenty-one three-stack scenarios range from
186.0 [micro]g/m\3\ to 195.37 [micro]g/m\3\. The maximum model
predicted concentration from the three-stack scenarios, which is also
the maximum for all 34 scenarios, 195.37 [micro]g/m\3\, occurred in the
three-stack operational scenario that assumes the majority of the
emissions came from the Boilers 18-22 B-83 stack emitting near its
maximum capacity (1,133 lbs/hr), emissions were slightly below normal
from the Boilers 23-24 B-83 stack (719 lbs/hr), and emissions were low
from the B-325 stack (53 lbs/hr, as Boiler 30 was assumed to not be
operating and Boiler 31 operating under minimal load). Tables which
summarize the emissions and modeling input parameters for each of the
34 scenarios and additional details about the full range of scenarios
are contained in the State's modeling analysis in sections 7.11 and
7.12 of the State's Attainment Demonstration Submittal and section 5 of
Attachment G1, ``NAAQS Attainment Demonstration Modeling Analysis,'' in
Tennessee's final SIP submittal.
---------------------------------------------------------------------------

    \20\ Established in PSD Permit 955272F, Boiler 30 has a 317 lbs/
hr 30-day SO2 limit and Boiler 31 has a 293 lbs/hr 30-day
SO2 limit, giving B-325 an allowable limit of 610 lbs/hr
on a 30-day average. For the purposes of modeling, Eastman
calculated an adjustment factor specific to the B-325 stack in
accordance with the methods of Appendix C of EPA's guidance. Eastman
calculated an adjustment factor of 0.84, which yielded a
corresponding one-hour emission rate of 726 lbs/hr.
---------------------------------------------------------------------------

    As noted earlier, in calculating the adjustment factor to multiply
times the collective CEV (the 1-hour sum of emissions providing for
attainment in the full range of distribution of the emissions) to
determine a comparably stringent collective 30-day emission limit,
Tennessee used statistics for the sum of emissions from all the stacks
governed by this limit. EPA's guidance does not expressly recommend how
to address comparable stringency for limits that address the sum of
emissions across multiple stacks. However, EPA's guidance at page 32
states:

    The selection of data handling procedures influences the longer
term averages that are computed and thus influences the relationship
between a 1-hour limit and a comparably stringent longer term
average limit. Therefore, . . . all analyses for determining
comparably stringent longer term average limits should then apply
those data handling procedures.

This suggests that the computation of adjustment factors for a limit
governing the sum of emissions from multiple stacks should be based on
statistical analysis of the variability of the sum of emissions from
the multiple stacks, irrespective of the variability of emissions from
the individual stacks. In the case of Eastman, while the facility
shifts load among its various boilers, resulting in relatively variable
emissions at any boiler, the total load is relatively steady, resulting
in only modest variability of total emissions. As a result, use of a
30-day limit makes less difference in the control measure needed to
meet the limit, and so less adjustment is needed to establish a 30-day
limit that is comparably stringent to the corresponding 1-hour limit.
Given the demonstration that the full range of potential distributions
of 1,905 lb/hr provides for attainment, EPA also believes that a 30-day
average limit of 1,753 lb/hr provides suitable assurance that
attainment would result under the full range of distribution of these
allowable emissions.
7. Summary of Modeling Results
    The AERMOD modeling analysis contained in Tennessee's Attainment
Demonstration submittal resulted in a maximum modeled design value of
195.37 [micro]g/m\3\, including the background concentration, which is
less than the 196.4 [micro]g/m\3\ (75 ppb) 1-hour sulfur dioxide NAAQS.
    EPA has evaluated the modeling procedures, inputs and results and
proposes to find that the results of the State's modeling analysis
demonstrate that there are no modeled violations of the NAAQS within
the nonattainment area when the combined emissions from the nine coal-
fired boilers are no greater that the 1,905 lbs/hr CEV. Additionally,
EPA proposes to find that the 34 modeling scenarios are adequate to
address the range of possible future operating scenarios of the boilers
at the Eastman facility and, therefore, support that the 1,905 lbs/hr
combined CEV is appropriate. Section IV.B.4.ii. of this notice explains
how Tennessee and Eastman developed the 1,753 lbs/hr 30-day rolling
average permit limit following the procedures in EPA's April 2014
SO2 guidance.

C. RACM/RACT

    CAA section 172(c)(1) requires that each attainment plan provide
for the implementation of all RACM as expeditiously as practicable
(including such reductions in emissions from existing sources in the
area as may be obtained through the adoption, at a minimum, of RACT)
and shall provide for attainment of the NAAQS. EPA interprets RACM,
including RACT, under section 172, as measures that a state determines
to be reasonably available and which contribute to attainment as
expeditiously as practicable for existing sources in the area.
    Tennessee's plan for attaining the 1-hour SO2 NAAQS in
the Sullivan County SO2 nonattainment area is based on
several measures, including repowering the B-253 boilers from coal to
natural gas operation. Tennessee's plan requires compliance with these
measures by October 1, 2018. This date is consistent with Tennessee's
Regional Haze SIP, which was amended on May 9, 2012. The amended SIP
allowed Eastman to implement BART no later than April 30, 2017, or an
alternative BART option (repowering of the boilers from coal to natural
gas) by December 31, 2018. The alternative BART option became federally
enforceable with the issuance of BART permit 066116H on May 9, 2012. A
prevention of significant deterioration (PSD) construction permit
(966859F), which authorizes construction for the boiler repowering, was
issued June 5, 2013. Condition 4(f) of permit 066116H requires the
repowering of B-253 to be completed no later than the compliance
deadline for the one-hour SO2 NAAQS. Also, Tennessee
evaluated B-325 Boiler 31, and determined that the spray dryer
absorber/fabric filter baghouse combination already in place
constitutes RACT, and that therefore no further analysis is required.
    Tennessee considered various other measures for the remaining B-83
and B-325 boilers. The State evaluated a range of measures to reduce
SO2 emissions,

including switching to low-sulfur coal, upgraded or additional control
equipment, conversion of existing coal-fired boilers to natural gas,
and replacing existing coal-fired boilers with natural gas boilers.
Tennessee determined that these other measures are not reasonable for a
variety reasons, including infeasibility and cost, and that they were
not needed to attain the NAAQS and would not advance the attainment
date. See Table 5-2 in the submittal for additional details on the
measures analyzed. In addition, Tennessee evaluated other operations at
Eastman as well as additional sources within and adjacent to the
nonattainment area and determined that no additional controls were
required as RACT.
    Tennessee has determined that repowering B-253 to natural gas
constitutes RACT and EPA proposes to concur with the state's RACT
analysis. Based on the attainment modeling, described herein, for the
B-253 control measures combined with the 30-day SO2 emission
limit for B-83 and B-325, the area is projected to show attainment of
the 1-hour SO2 standard. EPA believes the attainment plan
provides for attainment through the adoption and implementation of
Tennessee's RACT/RACM emission control strategy. Therefore, EPA
proposes to conclude that the state has satisfied the requirement in
section 172(c)(1) to adopt and submit all RACM as needed to attain the
standards as expeditiously as practicable.

D. New Source Review (NSR)

    Tennessee's SIP-approved NSR rules for nonattainment areas (NNSR)
are at TAPCR 1200-03-09-.01(5), last approved by EPA on July 30, 2012.
See 77 FR 44481. These rules provide for appropriate NSR for
SO2 sources undergoing construction or major modification in
the Sullivan County Area without need for modification of the approved
rules. Therefore, EPA proposes to conclude that this requirement is met
for this Area through Tennessee's existing NSR rules.

E. Reasonable Further Progress (RFP)

    The CAA section 172(c)(2) requires the SIP provide reasonable
further progress towards attainment of the applicable NAAQS. Regarding
part D nonattainment plans, section 171(1) of the CAA defines RFP as
the annual incremental reduction in emissions of the relevant pollutant
as are required for the purpose of ensuring attainment of the
applicable NAAQS by the applicable date. As discussed above,
Tennessee's 2008 regional haze SIP required Eastman implement BART at
B-253 (Boilers 25-29). The State revised its SIP to establish an
alternative BART option to repower/convert all five coal-fired boilers
at B-253 to natural gas units and changed the compliance deadline to
the 1-hour SO2 NAAQS attainment date or October 4, 2018.\21\
TDEC and Eastman indicated that the size and complexity of the
repowering required additional time to ensure the conversion was
technically feasible. Tennessee's control strategy to reduce
SO2 emission and attain the 2010 standard as expeditiously
as practicable include the repowering of the five coal-fired boilers at
B-253 and imposing an SO2 emission limit for the nine coal-
fired boilers for B-83 and B-325. Eastman established a repowering
timeline for B-253 listed in Table 3 below and in Tennessee'
SO2 attainment SIP.
---------------------------------------------------------------------------

    \21\ Tennessee's attainment SIP mistakenly states that the 1-
hour SO2 attainment date is October 5, 2018 instead of
October 4, 2018.

       Table 3--Estimated Compliance Schedule for B-253 Repowering
------------------------------------------------------------------------
           Boiler                Date \22\              Activity
------------------------------------------------------------------------
25..........................  1st              Complete; startup date
                               Quarter(Q1),     was April 23, 2014.
                               2014.
27..........................  1st and 2nd      Equipment mobilization,
                               Quarter in       six-week conversion and
                               2016.            demobilization; pre-
                                                outage construction
                                                conducted 4th quarter of
                                                2017 thru the 1st
                                                quarter in 2018.
                                               Conversion Complete--
                                                start-up date was April
                                                23, 2016.
28..........................  2nd and 3rd      Equipment mobilization,
                               Quarter in       six-week conversion and
                               2016.            demobilization; pre-
                                                outage construction
                                                conducted 4th quarter of
                                                2017 thru the 1st
                                                quarter in 2018.
                                               Conversion Complete--
                                                start-up date was
                                                October 2, 2016.
29..........................  1st and 2nd      Equipment mobilization,
                               Quarter in       six-week conversion and
                               2018.            demobilization; pre-
                                                outage construction
                                                conducted 4th quarter of
                                                2017 thru the 1st
                                                quarter in 2018.
                                               Conversion Complete--
                                                start-up date was March
                                                30, 2018.
26..........................  3rd Quarter in   Equipment mobilization,
                               2018.            six-week conversion and
                                                demobilization; pre-
                                                outage construction
                                                conducted 4th quarter of
                                                2017 thru the 1st
                                                quarter in 2018.
------------------------------------------------------------------------

    Based on this projected timeline, Eastman intends to complete
conversion of B-253 by the 3rd quarter of 2018 just before the October
4, 2018 attainment date. At the time of this proposed rulemaking, four
of the five coal-fired boilers at B-253 (B-25, 27, 28, and 29) have
been converted, are fully operational and currently subject to the
natural gas fuel restriction established in Permit 966859F. According
to Eastman, this compliance schedule was the most practicable to meet
the BART requirements and attain the SO2 NAAQS to maintain
the necessary steam and electricity for manufacturing operations. This
is also due, in part, to the state required (Tennessee Code Section 68-
122-110) annual boiler safety inspection and maintenance of all 17
boilers at Eastman (including B-253) while ensuring necessary boiler
capacity to sustain facility operations.\23\ According to Eastman, to
complete the conversion of a boiler to natural gas the normal safety
inspection is extended to 6 weeks. Because of extended inspections and
boiler shutdowns in 2017, Eastman did not convert any boilers at B-253
in 2017. As indicated in Table 3, the final boiler (B-26) is scheduled
for conversion in the 3rd quarter of 2018.
---------------------------------------------------------------------------

    \22\ According to TDEC, Eastman did not schedule the conversion
of any boilers in 2015 or 2017 due to legally required annual boiler
safety inspections and maintenance to ensure facility steam and
electricity reliability. The necessary engineering work for the
conversion of Boilers 27 and 28 in 2016 was performed in 2015 and
2017 for Boilers 26 and 29. For additional information, please refer
to Tennessee's Attainment SIP Narrative located in the docket (ID:
EPA-R04-OAR-2017-0626).
    \23\ The Tennessee Boiler and Unfired Pressure Vessel inspection
law (Tennessee Code Section 68-122-110) requires annual inspection
and maintenance of Eastman's 17 power boilers. According to Eastman,
only one boiler at a time is taken off-line to ensure the necessary
steam and electricity reliability for manufacturing operations. The
duration of each inspection depends on the size and maintenance
cycle of the boiler components. Eastman has stated it takes 46-48 of
the 52 weeks to complete the scheduled inspections and boiler
maintenance. Eastman also indicated that it is not practicable for
the facility to schedule more than two extended inspections per
calendar year without potential risk meeting production demands.

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

    Tennessee's May 2017 attainment SIP also provides estimated
incremental emission reductions during the conversion of all five
boilers at B-253. Table 6-2 in TDEC's submittal \24\ provides for
projected change in actual emissions at Eastman over the duration of
the repowering at B-253 and post-control after the attainment date.
TDEC compared the pre-control emission rates for all boilers at B-83,
B-325 and B-253 for the period of April 1, 2012 through March 31, 2013
over the course of the conversion (interim years 2015 and 2017) to
post-control emissions (after October 4, 2018). Projected emission
reductions after the completion of B-253 conversion and compliance with
the SO2 emission limit for B-83 and B-325, are expected to
be 66 percent compared to pre-control levels (with estimated
incremental emission reductions of 11 percent and 39 percent in 2015
and 2017 respectively (after complete conversion of B-25 in 2014 and B-
27 and 28 in 2016). The average pre-control emissions from each B-253
boiler was 677 pounds per hour (or 2,965 tpy). TDEC estimates that each
boiler conversion will reduce emissions by 2,960 tpy.
---------------------------------------------------------------------------

    \24\ EPA notes the second note to Table 6-2 list 1,794 lbs/hr as
the combined 30-day average allowable emission rate for B-83 and B-
325 boilers, however, the correct emission rate is 1,753 lbs/hr.
---------------------------------------------------------------------------

    The control measures for attainment of the 2010 SO2
NAAQS included in the State's submittal have been modeled to achieve
attainment of the 1-hour SO2 NAAQS. The adoption of new
emissions limits, and compliance parameters and a natural gas
restriction (for repowered B-253 boilers) require these control
measures to achieve emissions reductions. Tennessee finds that the
attainment plan requires the affected sources to implement control
measures as expeditiously as practicable to ensure attainment of the 1-
hour standard and therefore concludes that the attainment plan provides
for RFP in accordance with the approach to RFP described in EPA's
guidance. EPA believes Tennessee's SIP provides for incremental
reduction in emissions to ensure reasonable further progress towards
attainment of the standard and therefore concurs and proposes to
preliminary conclude that the plan provides for RFP and therefore
satisfies the requirements of CAA section 172(c)(2).

F. Contingency Measures

    As noted above, EPA guidance describes special features of
SO2 planning that influence the suitability of alternative
means of addressing the requirement in section 172(c)(9) for
contingency measures for SO2, such that in particular an
appropriate means of satisfying this requirement is for the state to
have a comprehensive enforcement program that identifies sources of
violations of the SO2 NAAQS and to undertake an aggressive
follow-up for compliance and enforcement. Tennessee's plan provides for
satisfying the contingency measure requirement in this manner.
    Specifically, upon notification by Tennessee that a reference
monitor for the Area has registered four validated ambient
SO2 concentrations in excess of the NAAQS during calendar
years 2019 or 2020, or that a monitored SO2 NAAQS violation
based on the design value occurred during calendar years 2021 and
beyond, Eastman will, without any further action by Tennessee or EPA,
undertake a full system audit of all emission units subject to emission
limits under this plan and submit a written system audit report to
Tennessee within 30 days of the notification. Upon receipt of the
system audit report, Tennessee will immediately begin a 30-day
evaluation period to diagnose the cause of the monitored exceedance.
This evaluation will be followed by a 30-day consultation period with
Eastman to develop and implement operational changes necessary to
prevent future monitored violations of the NAAQS. These changes may
include fuel switching to reduce or eliminate the use of sulfur-
containing fuels, physical or operational reduction of production
capacity, or other changes as appropriate. If a permit modification is
deemed necessary, Tennessee would issue a final permit within the
statutory timeframes required in Tennessee Comprehensive Rules and
Regulations 1200-03-09, and any new emissions limits required by such a
permit would be submitted to EPA as a SIP revision. EPA concurs and
proposes to approve Tennessee's plan for meeting the contingency
measure requirement in this manner.

V. Additional Elements of Tennessee's Submittal

    To verify that the 30-day limit is resulting in continued
attainment of the 1-hour SO2 standard in the Sullivan County
area, Tennessee is establishing an additional safeguard within the
nonattainment area by upgrading its existing SO2 ambient air
monitoring network in the Sullivan County area. TDEC has committed to
deploy additional ambient air monitors within the nonattainment area
\25\ to characterize expected areas of maximum 1-hour SO2
concentrations near the Eastman Chemical Plant. The State intends to
designate the monitors as State/Local air monitoring stations in
accordance with 40 CFR part 58 and locate the monitors as close as
possible to the areas of expected maximum concentration. These monitors
will be submitted for approval by EPA as part of the state's annual
ambient air monitoring network plan.
---------------------------------------------------------------------------

    \25\ See email from TDEC to EPA Region 4, Air, Pesticides and
Toxic Management Division, Air Director Beverly Banister on June 6,
2018 included in the docket for this proposal (ID: EPA-R04-OAR-2017-
0626).
---------------------------------------------------------------------------

VI. 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 Tennessee's SIP a natural gas fuel restriction, a new
SO2 emission limit and specified compliance conditions
established in permits 966859F and 070072F for monitoring,
recordkeeping and reporting parameters for emissions units at Eastman
Chemical Company. Specifically, EPA is proposing to incorporate into
the Tennessee SIP, a new 1,753 lbs/hr 30-day SO2 emission
limit and operating, monitoring, recordkeeping and reporting parameters
all established at Conditions 1 thru 4 in Permit 070072F for Boilers
18-24 at B-83 and Boilers 30-31 at B-325 and, a natural gas fuel
restriction for Boilers 25-29 at B-253 (after each natural gas
conversion) established at Condition 6 in Permit 966859F. The
SO2 emission standards specified in each permit are the
basis for the SO2 attainment demonstration in the SIP. 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).

VII. EPA's Proposed Action

    EPA is proposing to approve Tennessee's SO2
nonattainment SIP submission, which the State submitted to EPA on May
11, 2017, for attaining the 2010 1-hour SO2 NAAQS for the
Sullivan County Area and for meeting other nonattainment area planning
requirements. EPA has preliminarily determined that Tennessee's
nonattainment SIP meets the applicable requirements of sections 110(a),
172, 191 and 192 of the CAA and regulatory requirements at 40 CFR part
51. This

SO2 nonattainment SIP includes Tennessee's attainment
demonstration for the Sullivan County Area and other nonattainment
requirements for a RFP, RACT/RACM, NNSR, base-year and projection-year
emission inventories, enforceable emission limits and compliance
parameters and contingency measures. Specifically, EPA is proposing to
approve into the Tennessee SIP, Eastman Chemical's enforceable
SO2 emission limit and compliance parameters (monitoring,
recordkeeping and reporting) from PSD construction permit 966859F
(condition 6) and Permit No. 070072F (conditions 1-4) (see section
IV.B.4.1).

VIII. Statutory and Executive Order Reviews

    Under the CAA, the Administrator is required to approve a SIP
submission that complies with the provisions of the Act and applicable
Federal regulations. 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. This action merely
proposes to approve state law as meeting Federal requirements and does
not impose additional requirements beyond those imposed by state law.
For that reason, this proposed action:
     Is not a significant regulatory action subject to review
by the Office of Management and Budget under Executive Orders 12866 (58
FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 2011);
     Is not an Executive Order 13771 (82 FR 9339, February 2,
2017) regulatory action because SIP approvals are exempted under
Executive Order 12866;
     Does not impose an information collection burden under the
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact
on a substantial number of small entities under the Regulatory
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or
uniquely affect small governments, as described in the Unfunded
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have Federalism implications as specified in
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Is not an economically significant regulatory action based
on health or safety risks subject to Executive Order 13045 (62 FR
19885, April 23, 1997);
     Is not a significant regulatory action subject to
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Is not subject to requirements of section 12(d) of the
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272
note) because application of those requirements would be inconsistent
with the CAA; and
     Does not provide EPA with the discretionary authority to
address, as appropriate, disproportionate human health or environmental
effects, using practicable and legally permissible methods, under
Executive Order 12898 (59 FR 7629, February 16, 1994).
    The SIP is not approved to apply on any Indian reservation land or
in any other area where EPA or an Indian tribe has demonstrated that a
tribe has jurisdiction. In those areas of Indian country, the rule does
not have tribal implications as specified by Executive Order 13175 (65
FR 67249, November 9, 2000), nor will it impose substantial direct
costs on tribal governments or preempt tribal law.

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by
Reference, Intergovernmental relations, Reporting and recordkeeping
requirements, Sulfur oxides.

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

    Dated: June 19, 2018.
Onis ``Trey'' Glenn, III,
Regional Administrator, Region 4.
[FR Doc. 2018-14097 Filed 6-28-18; 8:45 am]
 BILLING CODE 6560-50-P