[Federal Register Volume 85, Number 36 (Monday, February 24, 2020)]
[Proposed Rules]
[Pages 10350-10357]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-03507]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R05-OAR-2015-0700; FRL-10005-64-Region 5]
Air Plan Approval; Indiana; Attainment Plan for Sulfur Dioxide in
Southwest Indiana
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
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SUMMARY: The Environmental Protection Agency (EPA) is reproposing to
approve under the Clean Air Act an element of the State Implementation
Plan (SIP) revision for attaining the 1-hour sulfur dioxide
(SO2) primary national ambient air quality standard (NAAQS)
for the Southwest Indiana nonattainment area (including parts of
Daviess and Pike Counties), based on revised limits for the
Indianapolis Power and Light's Petersburg facility (IP&L-Petersburg)
that Indiana submitted on September 18, 2019. Indiana's revised limits
are based on the same dispersion modeling and the same 1-hour average
emission rates that EPA proposed to conclude would result in
attainment. However, the revised limits reflect revised calculations of
the degree of adjustment needed for the 30-day average limits to be
comparably stringent to 1-hour limits at the modeled emission rates.
EPA is soliciting additional comments that may arise from these
revisions.
DATES: Comments must be received on or before March 25, 2020.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R05-
OAR-2015-0700 at http://www.regulations.gov, or via email to
[email protected]. For comments submitted at Regulations.gov, follow
the
[[Page 10351]]
online instructions for submitting comments. Once submitted, comments
cannot be edited or removed from Regulations.gov. For either manner of
submission, EPA may publish any comment received to its public docket.
Do not submit electronically any information you consider to be
Confidential Business Information (CBI) or other information whose
disclosure is restricted by statute. Multimedia submissions (audio,
video, etc.) must be accompanied by a written comment. The written
comment is considered the official comment and should include
discussion of all points you wish to make. EPA will generally not
consider comments or comment contents located outside of the primary
submission (i.e., on the web, cloud, or other file sharing system). For
additional submission methods, please contact the person identified in
the FOR FURTHER INFORMATION CONTACT section. For the full EPA public
comment policy, information about CBI or multimedia submissions, and
general guidance on making effective comments, please visit http://www2.epa.gov/dockets/commenting-epa-dockets.
FOR FURTHER INFORMATION CONTACT: John Summerhays, Environmental
Scientist, Attainment Planning and Maintenance Section, Air Programs
Branch (AR-18J), Environmental Protection Agency, Region 5, 77 West
Jackson Boulevard, Chicago, Illinois 60604, (312) 886-6067,
[email protected].
SUPPLEMENTARY INFORMATION: Organization of this document. The following
outline is provided to aid in locating information in this preamble.
Table of Contents
I. History of Nonattainment Planning for SO2 in Southwest
Indiana
II. Indiana's Revisions to Limits for IP&L-Petersburg
III. EPA Guidance Regarding Data Handling for Calculating Longer
Term Average SO2 Emission Limits
IV. EPA's Evaluation of the IP&L-Petersburg Limit Revisions
V. EPA's Proposed Action
VI. Incorporation by Reference
VII. Statutory and Executive Order Reviews
I. History of Nonattainment Planning for SO2 in Southwest
Indiana
In 2013, in implementing its 2010 1-hour primary SO2
NAAQS of 75 parts per billion (ppb), EPA designated a first set of 29
areas of the country as nonattainment for this NAAQS, including the
Southwest Indiana area (defined to include portions of Daviess and Pike
Counties). See 78 FR 47191 (August 5, 2013), codified at 40 CFR part
81, subpart C. In response to the resulting Clean Air Act requirements
to adopt and submit to EPA a SIP demonstrating attainment of the NAAQS,
Indiana submitted nonattainment plans for this and for three other
areas on October 2, 2015. Indiana then submitted supplemental material
pertinent in part to Southwest Indiana on November 15, 2017.
On August 15, 2018, EPA published a proposed rule that proposed to
approve the SO2 nonattainment plans for the Southwest
Indiana, Indianapolis, and Terre Haute areas. (See 83 FR 40487.) EPA
received no comments addressing the Indianapolis and Terre Haute areas,
and EPA published a final rule regarding these two areas on March 22,
2019 (84 FR 10692). EPA also published separate actions regarding the
SO2 attainment plan for Morgan County, including a proposed
rule published on July 9, 2019 (at 84 FR 32672) and a final rule
published on September 23, 2019 (at 84 FR 49659). This rule therefore
does not address these three areas that were addressed in Indiana's
2015 submittal, and only addresses SO2 in Southwest Indiana.
Indiana's plan for SO2 in Southwest Indiana addresses a
number of Clean Air Act requirements that SO2 nonattainment
plans must meet in order to be approved by EPA, including requirements
for emission limits sufficient to provide for attainment, a modeling
demonstration that these limits in fact provide for attainment, and
requirements for an emissions inventory, reasonably available control,
reasonable further progress (RFP), and contingency measures.\1\
Emission limits were submitted in October 2015 for both IP&L-Petersburg
and the Frank E. Ratts facility. EPA's August 15, 2018 proposed action
on this rule addressed these requirements.
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\1\ As discussed in the notice of proposed rulemaking, 83 FR
40487, 40497 (Aug. 15, 2018), EPA already approved Indiana's
nonattainment new source review rules on October 7, 1994, with
subsequent amendments approved July 8, 2011. See 59 FR 51108 and 76
FR 40242. EPA explained that these rules provide for appropriate new
source review for SO2 sources undergoing construction or
major modification without the need for modification of the approved
rules. Therefore, EPA concluded that Indiana had satisfied
nonattainment new source review requirements previously for the
Southwest Indiana area and did not need to include any provisions to
address these requirements in its 2015 submittal.
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In response to the August 15, 2018 proposed rule, EPA received
comments on Indiana's 30-day average limits for IP&L-Petersburg, which
prompted Indiana to reevaluate these limits.\2\ This reevaluation led
Indiana to adopt a revised set of limits for IP&L-Petersburg,
incorporated in Commissioner's Order Number 2019-2, which Indiana
submitted to EPA on September 18, 2019. As explained below, these
revised limits are based on the same modeling that was used to derive
the limits in Indiana's October 2015 submittal and, thus, reflect the
same critical emission values that Indiana identified in its October
2015 submittal. However, as explained further below, Indiana
reevaluated the adjustment factor that it used to determine the 30-day
average emission limits for IP&L-Petersburg, which resulted in
calculation of a revised adjustment factor and therefore revised
emission limits. These limits were incorporated in Commissioner's Order
Number 2019-2, which was issued on July 31, 2019 and became effective
on August 18, 2019.
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\2\ EPA received no comments regarding the 1-hour limits for the
Frank E. Ratts facility.
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Indiana's October 2, 2015 submittal addresses reasonably available
control measures (RACM) and RFP by means of its adopted limits, so the
limit revisions implicitly affect these elements of the plan. However,
Indiana's recent submittal did not otherwise revise its plan with
respect to these elements, and EPA continues to believe that Indiana
has met these requirements. The primary focus of this proposed action
is to evaluate whether these revised limits, in conjunction with other
limits that Indiana submitted previously, provide for attainment of the
SO2 NAAQS in Southwest Indiana and continue to support EPA's
proposed conclusions regarding Indiana's satisfaction of the RACM and
RFP elements.
II. Indiana's Revisions to Limits for IP&L-Petersburg
Indiana's October 2015 submittal included two sets of limits for
IP&L-Petersburg, including one set using 1-hour average emission limits
and one set using 30-day average limits, with provisions for IP&L to
select which limits would apply. IP&L has requested that the 30-day
average limits apply, and IP&L's involvement in pursuing modified 30-
day average limits suggests that IP&L envisions continuing to be
subject to 30-day average limits. Nevertheless, Indiana requested that
EPA approve both the 1-hour limits in 326 IAC 7-4-15 and the 30-day
average limits in the commissioner's order, and EPA is reproposing
action accordingly.
Historically, EPA required states to establish short-term emission
limits at the level that modeling shows provides for NAAQS attainment,
a level known as the critical emission value, with averaging times of
limits expected to match the averaging time of the relevant NAAQS. EPA
guidance for SO2 nonattainment plans under the 2010 1-hour
NAAQS states that limits with
[[Page 10352]]
averaging times up to 30 days may, in appropriate circumstances,
provide a suitable basis for plans to ensure attainment of that NAAQS.
However, EPA recommends that, to serve this purpose, any such limit
should be designed to have comparable stringency to a 1-hour average
limit at the critical emission value. Appendix C of EPA's guidance
provides a recommended procedure for determining adjustment factors
which may be multiplied by the value of a candidate 1-hour limit to
estimate a longer term averaged limit that is presumptively comparably
stringent. This procedure uses a pertinent hourly emissions data set to
determine the 99th percentile among 1-hour average emission values, to
determine the 99th percentile among longer term averaged values, and to
calculate the ratio between these two 99th percentile values in order
to determine an adjustment factor to be applied in determining the
longer term average limit. This adjustment factor represents an
estimate of the change in stringency from applying the limit on a
longer term average basis rather than on a 1-hour basis, so that the
adjusted longer term limit is estimated to be comparably stringent to a
1-hour limit at the critical emission value. The guidance document
(including appendix C) provides extensive guidance on the data sets and
the calculation procedures that EPA advises be used in these
determinations.\3\
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\3\ This guidance, issued on April 23, 2014, entitled,
``Guidance for 1-Hour SO2 Nonattainment Area SIP
Submissions,'' is available at https://www.epa.gov/sites/production/files/2016-06/documents/20140423guidance_nonattainment_sip.pdf. This
guidance is discussed at length in the August 15, 2018 notice of
proposed rulemaking identified above.
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Indiana used this general approach to determine the 30-day average
limits adopted for purposes of its 2015 submittal. Based on historical
emissions data from a stack that vents controlled emissions from Unit 2
of IP&L-Petersburg, Indiana calculated an adjustment factor of 80
percent, leading Indiana to establish 30-day average limits at a level
that was 80 percent of 1-hour emission rates that were reflected in its
attainment demonstration modeling.
EPA's proposed rulemaking on Indiana's 2015 submittal elicited
public comments that, among other issues, addressed the suitability of
elements of the derivation of this adjustment factor. In response,
Indiana recalculated the adjustment factor to be applied in determining
the 30-day average limits for IP&L-Petersburg, and submitted these
revised calculations and the resulting adopted limits on September 18,
2019. Although this recalculation used the same data set as the
original submittal, namely the 2006 to 2010 emissions from the main
stack at IP&L-Petersburg Unit 2, Indiana used an edited data set
reflecting removal of a number of inappropriate zero entries (for hours
with no operation and, thus, no valid pound per million British Thermal
Unit (lb/MMBTU) value) and removal of selected hours with questionable
data. The revised calculations are provided in a spreadsheet that is
available in the docket for this action, along with spreadsheets
showing related EPA calculations described below.
Indiana's recalculated adjustment factor was 68 percent. That is,
Indiana's revised evaluation determined that the 30-day average limits
for IP&L-Petersburg should be 68 percent (reduced from 80 percent) of
the 1-hour average emissions limit indicated by the attainment
demonstration modeling. Indiana conducted no additional modeling, and
instead relied on the same critical emission values as were described
in its 2015 submittal. The revised limits are shown in Table 1, along
with the original limits. This table also shows the emission rates
(identified as critical emission rates, expressed in lbs/MMBTU) that
correspond (at maximum heat input) to the modeled critical emission
values.
Table 1--Revised Limits for IP&L-Petersburg
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Critical
Unit emission rate Revised limit Original limit
(lbs/MMBTU) (lbs/MMBTU) (lbs/MMBTU)
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Unit 1................................................. 0.15 0.10 0.12
Unit 2................................................. 0.15 0.10 0.12
Unit 3................................................. 0.37 0.25 0.29
Unit 4................................................. 0.35 0.24 0.28
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Indiana provided additional rationale for its selection of data for
performing these calculations. IP&L reports data for two emission
streams at Petersburg Unit 2, identified as main stack emissions and
bypass stack emissions. Indiana explained that the main stack vents
emissions that have been controlled by the unit's flue gas
desulfurization equipment, whereas the bypass stack vents emissions
that bypass such control. Therefore, Indiana explained, data on
emissions from the main stack \4\ provide the best representation of
the prospective variability of emissions that are controlled well
enough to meet the limits necessary to provide for attainment. Indiana
explained further that while its limits govern all emissions from each
unit (which is to say the sum of emissions from the main stack and from
the bypass stack at Unit 2, and similarly for the pair of stacks at
Unit 1), compliance with the adopted limits will require nearly
eliminating emissions that bypass the control system.
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\4\ Indiana refers to this stack as the ``FGD stack,'' i.e., the
stack venting emissions controlled by the flue gas desulfurization
system.
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In addition to the availability of a data set of controlled
emissions at Unit 2, Indiana also provided an additional rationale for
using data from Unit 2 to assess variability expected upon compliance
with SIP limits. Unit 1 has a similar setup as Unit 2, with separate
vents for controlled versus uncontrolled emissions. However, Indiana
explained that historic data from Unit 1 included a high fraction of
times when emissions exited through the bypass stack, so that the
resulting data set is both less robust and less predictive of effective
control equipment operation. Units 3 and 4 do not have separate vents
for controlled versus uncontrolled emissions, so data from these units
do not properly represent the variability of controlled emissions.
Units 3 and 4 only have single stacks, venting a combination of
controlled and uncontrolled emissions, so the historic data from these
units show variability that is dominated by variability in control
level, thus providing a poor data set for projecting the variability of
controlled emissions.
Indiana's October 2015 submittal included both mass limits (in
pounds per hour (lbs/hr)) and emission rate limits (lbs/MMBTU) for
IP&L-
[[Page 10353]]
Petersburg, and applied the same adjustment factor to the modeled 1-
hour values for these respective variables. EPA guidance provides for
separate calculations of adjustment factors for these separate limits,
which would reflect the different impact on stringency that can result
from expressing a mass limit versus an emission rate limit as a 30-day
average limit. Accordingly, Indiana reconsidered this feature of its
October 2015 submittal, with the result that the replacement 30-day
average limits for IP&L-Petersburg only include emission rate limits
(in lbs/MMBTU), based on a view that limits on emission rates alone
suffice, even at maximum heat inputs, to assure that the area will
attain the standard.
An important aspect of any longer term average emission limit is
the set of data handling procedures to be used in determining
compliance. Indiana's commissioner's order makes no direct statement
regarding data handling procedures. However, the order states that the
``requirements of this Order are in addition to any less stringent
requirements applicable to [IP&L] pursuant to 326 IAC 7-4-15,''
implying that the state intends that compliance with the 30-day average
limits in the order is to be evaluated using the same procedures as
those for the 30-day average limits in the rule. Paragraph (d) of 326
IAC 7-4-15, which Indiana requests be incorporated into the SIP, states
that ``Compliance with [the 30-day average limits in the rule] shall be
determined by calculating the thirty (30) boiler operating day rolling
arithmetic average emission rate at the end of each boiler operating
day using all of the quality assured hourly average continuous emission
monitoring system data for the previous thirty (30) boiler operating
days.''
Indiana's submittal also includes a copy of the letter which
transmitted the commissioner's order to IP&L. This letter describes the
order as applying the data handling procedures of 326 IAC 7-4-15(d),
and notes further that the ``methodology is documented in IPL-
Petersburg's [compliance] assessment protocol, which follows
methodologies recommended in U.S. EPA's Mercury and Air Toxics Standard
(MATS) rule guidance and the U.S. EPA memorandum `Guidance for 1-Hour
SO2 Nonattainment Area SIP Submissions'.''
III. EPA Guidance Regarding Data Handling for Calculating Longer Term
Average SO2 Emission Limits
EPA's guidance on 1-hour SO2 nonattainment plans, issued
in April 2014, provides numerous detailed recommendations regarding
longer term average SO2 emission limits, including several
recommendations regarding data handling procedures.\5\ The guidance
states that the rule promulgating MATS provides a good prototype for
procedures for data handling. The guidance recommends the MATS approach
of only averaging data obtained during operating hours, so that the
compliance assessment focuses on how well emissions are controlled and
is not influenced by the fraction of time that the facility operates.
The guidance recommends that emission limits averaged over multiple
days be addressed by averaging emissions over the pertinent number of
operating days, as is done in MATS, which improves robustness of the
compliance determination by helping assure that the compliance
determination reflects an adequate set of data. The guidance recommends
determining compliance with limits on emission factors (e.g., limits on
pounds of emissions per megawatt-hour) by dividing total mass over the
30 operating days by the total electrical output during that period.
(The analogous approach for a limit expressed in pounds per MMBTU is to
divide total pounds of emissions over the averaging period by total
heat input in MMBTU during the period.) The guidance explains that this
approach effectively weights each hour's data point according to the
hour's emissions (more precisely, according to the hour's electrical
output or heat input), and thus better indicates the average rate of
emissions than, for example, computing an average of hourly average
emission rates.
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\5\ Guidance is cited in footnote 3 above. See especially page
32.
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Unfortunately, in this last respect, EPA's SO2
nonattainment planning guidance misrepresents the data handling
procedures in MATS. In fact, MATS, consistent with common practice,
determines compliance by averaging the pertinent hourly values, either
in pounds per megawatt or in pounds per MMBTU (reflecting the units of
the applicable limit). See 40 CFR 63.10021. On the other hand, while
EPA promulgated MATS as a national emission standard for hazardous air
pollutants (NESHAP) under Clean Air Act section 112, EPA also
simultaneously promulgated revisions to new source performance
standards (NSPS) under Clean Air Act section 111 with limits in which,
for facilities constructed, modified, or reconstructed after May 3,
2011, ``compliance . . . is determined by dividing the sum of the
SO2 . . . emissions for the 30 successive boiler operating
days by the sum of the [energy output] for the 30 successive boiler
operating days.'' See 40 CFR 60.48Da(d), promulgated on February 16,
2012, 77 FR 9304, 9454. Thus, while the substance of EPA's
recommendations was clear, the guidance was incorrect in its
description of the data handling procedures of MATS, and the guidance
should have cited the revisions to the NSPS for sources that began
construction, modification or reconstruction after May 3, 2011 as a
template for relevant data handling provisions, rather than the
procedures of MATS. The following section reviews Indiana's revised
submittal in light of this clarified guidance.
IV. EPA's Evaluation of the IP&L-Petersburg Limit Revisions
EPA conducted multiple analyses of the expected variability of
emissions at IP&L-Petersburg upon compliance with Indiana's limits.
These analyses inform EPA's judgment as to whether Indiana's revised
limits can be expected to be comparably stringent to 1-hour limits at
the critical emission values.
The first analysis used the data provided by Indiana but used a
different data handling procedure. Indiana's rule (326 IAC 7-4-15)
specifies that compliance with the 30-day average limits in the rule
shall be evaluated by determining the ``30 boiler operating day rolling
arithmetic average emission rate at the end of each boiler operating
day using all of the quality assured hourly average continuous emission
monitoring system data.'' This indicates that if, for example, a 30-
operating day period has 700 operating hours with valid data, the
compliance determination for that period would be based on the average
of those 700 hourly values.
The variability analysis provided by Indiana deviates from this
procedure by first calculating daily average emission rates and then
calculating averages of 30 operating days of daily averages. This
approach gives more weight to days with fewer operating hours than the
approach in 326 IAC 7-4-15. To evaluate the significance of this
difference, EPA calculated a set of 30-day average emission rates based
on the arithmetic average of all hourly emission rates. EPA's guidance
is to use the same data handling approach in the assessment of
variability as is provided in the state's compliance determination
procedures, in order best to determine the degree to which use of a
long term average limit affects stringency of the limit with those
compliance procedures. Nevertheless, EPA's analysis found that
[[Page 10354]]
the use of averaging procedures consistent with Indiana's compliance
determination procedures only modestly affected the resulting
adjustment factor; compared to IP&L's adjustment factor of 68 percent,
use of Indiana's compliance determination procedures using the same
data set yielded an adjustment factor of 68.2 percent.
IP&L explained that the data it used in its analysis are for the
``FGD stack,'' which corresponds to the monitoring site identified in
data reported to EPA as ``MS2S.'' However, the data reported to EPA for
these emissions differ from the emissions used by IP&L; for slightly
over the first three years, most of the data reported to EPA appear to
reflect approximately an 11 percent bias adjustment that is not
reflected in the data used by Indiana. Therefore, EPA conducted an
additional analysis of data reported to EPA for the MS2S monitoring
site. Despite the difference in magnitudes of the emissions in these
two data sets, the variability of emissions is similar, with EPA
suggesting an adjustment factor of 65.0 percent, modestly lower than
the 68.0 percent estimated by Indiana.
EPA also examined data reported to EPA for the main stack at Unit 1
for the same period examined by Indiana (2006 to 2010). EPA concurs
with Indiana that this is a less robust data set that appears less
representative of future controlled operations at this plant. The
adjustment factor calculated from data for this stack (62.2 percent) is
somewhat lower than the 68.0 percent adjustment factor that IP&L
calculated from Unit 2 main stack data, which may reflect what appears
to be comparatively unstable operation of control at Unit 1. Therefore,
these Unit 1 data are consistent with Indiana's view that the historic
data from the main stack at Unit 2 are the best predictors of
variability from the four units at IP&L-Petersburg upon compliance with
the limits.
EPA's general objective is to evaluate the degree of variability,
in particular the impact of variability on the stringency of an
emission limit expressed in this case as a 30-day average limit rather
than as a 1-hour limit. EPA seeks for this evaluation to be predictive
of the degree of variability that can be expected once the source is
complying with the control requirements of the SIP. The rules Indiana
submitted in October 2015 required compliance with the limits by
January 2017. Although Indiana's September 18, 2019 submittal imposes
slightly more stringent limits than its October 2, 2015 submittal, the
control measure in either case is the existing flue gas desulfurization
equipment, and EPA anticipates that the slight increase in control
efficiency needed to meet the new limits will not materially increase
the variability in emissions upon compliance with these limits.
Therefore, the data that are available for 2\1/2\ years starting
January 2017 provide a valuable indication of the likely degree of
emissions variability that can be expected to apply into the future
with compliance with the newer limits.
For these reasons, EPA analyzed the emissions data from January
2017 to June 2019 for each of the four units at IP&L-Petersburg. In
this analysis, for Units 1 and 2, in both cases EPA used the sum of
emissions from the main stack and from the bypass stack, reflecting the
fact that Indiana's limits govern total emissions from each unit. In
order to apply the same data handling procedures as are used to
determine compliance with the limits, EPA considered only days in which
the unit operated, EPA computed 30-operating-day averages ending at the
end of each operating day, and EPA computed the average emission rate
as an arithmetic average among the valid operating hour emission rate
data. Substitution data (conservative emission estimates derived
according to trading program requirements in cases where information
needed for a precise emission calculation was missing) appeared to be
rare and unlikely to affect results significantly, and so EPA's
analyses used a complete data set that reflected no deletion of any
substitution data.
EPA summarizes the results of these analyses in Table 2. Two
spreadsheets that are included in the docket, including one for 2006 to
2010 data and one for 2017 to 2019 data, show the data and the
calculations used in these analyses.
Table 2--Adjustment Factors for IP&L-Petersburg
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Analysis Resulting adjustment factor
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IP&L analysis, using Unit 2 Main 68.0 percent.
Stack data (2006-2010).
Using IP&L data with Indiana 68.2 percent.
compliance statistics.
Using EPA data (Unit 2 main stack, 65.0 percent.
2006-2010).
Using 2017--mid-2019 data......... Unit 1: 73.0 percent.
Unit 2: 57.6 percent.
Unit 3: 68.6 percent.
Unit 4: 70.4 percent.
Average: 67.4 percent.
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As noted above, Indiana used data from the stack at Unit 2 that
vents controlled emissions to determine an adjustment factor to apply
in determining 30-day average limits. Indiana has confirmed that these
limits govern the total of all emissions from the respective units; in
particular the limits for Units 1 and 2 govern the sum of emissions
from the main stack plus the emissions from the bypass stack for each
of these two units. The determination of an adjustment factor from just
the main stack data reflects a premise that the historic data for the
controlled emission stack is most indicative of the prospective
variability of all emissions once the control requirements of the SIP
are met. This premise in turn reflects an expectation that
implementation of the control strategy will result in (uncontrolled)
bypass stack emissions being minimal.
EPA used the available 2017 to 2019 data to test these premises.
For 2006 to 2010, according to data reported to EPA, bypass stack
emissions for the 5 years accounted for 89 percent of the total Unit 1
emissions and 30 percent of the total Unit 2 emissions. In contrast,
for 2017 to mid-2019, bypass stack emissions accounted for only 3
percent of emissions from Unit 1 and 0.2 percent of emissions from Unit
2.
In any case, the adjustment factors shown in Table 2 above for 2017
to mid-2019 are based on statistics for total emissions for each unit,
which for Units 1 and 2 reflect the sum of emissions from the main
stack plus emissions from the bypass stack. Thus, the results in Table
2 for recent emissions represent
[[Page 10355]]
the strongest evidence that the 2006 to 2010 data for the main stack at
Unit 2 provides a suitable projection of the degree of variability in
total emissions upon implementation of the SIP limits.
Since the methods recommended in appendix C of the guidance rely on
99th percentile values, the guidance recommends assuring that these
assessments be based on a robust data set. For this reason, the
guidance recommends using a data set with three to five years of data.
The post-control data being used here represent only 2\1/2\ years.
Therefore, EPA averaged the adjustment factors for the four units
(shown in Table 2) in order to improve the robustness of the analysis.
As shown in Table 2 above, the post-control data for the four units
at IP&L-Petersburg support an average adjustment factor of 67.4
percent, very close to the 68.0 percent adjustment factor applied by
Indiana.\6\ The similarity of these percentages support several
findings. First, the 2006 to 2010 data for the stack known as MS2S, the
stack that vents controlled emissions from Unit 2, provide a good
representation of the variability of emissions to be expected upon
implementation of the limits in Indiana's plan. Most plants do not have
separate vents for controlled versus uncontrolled emissions, but the
availability here of separate data for controlled versus uncontrolled
emissions results in the availability of a good representation of the
variability of emissions to be expected when the plan requires virtual
elimination of uncontrolled emissions. Second, the similarity of
percentages further supports Indiana's assertion that the controlled
emissions from Unit 2 provide a better forecast of emissions
variability for controlled emissions of all four units than would be
obtained from the controlled emissions from Unit 1. Finally, this
similarity supports a finding that the use of 2006 to 2010 data for the
controlled emission stack for Unit 2 provides a good basis for
estimating the degree of adjustment for determining 30-day average
limits at IP&L-Petersburg that are comparably stringent to the 1-hour
limits that would otherwise apply.
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\6\ The slightly lower adjustment factor suggests the
possibility that the limits Indiana adopted correspond to (are
comparably stringent to 1-hour limits at) slightly higher emission
rates than Indiana modeled. However, Indiana's attainment
demonstration (with a design value of 189.68 micrograms per cubic
meter) provides a sufficient attainment margin so that these
differences in adjustment factors would not alter the conclusion
that Indiana's limits provide for attainment.
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As noted in Section II, Indiana's rule provides for computing 30-
day average emission rates as an arithmetic average of the hourly lbs/
MMBTU values during operating hours. Notwithstanding the potential for
confusion regarding EPA's guidance on this point (as discussed above),
this approach differs from the recommendation in EPA's guidance to
compute 30-day average emission rates as the ratio between the 30-day
total emissions divided by the 30-day total heat input.
Therefore, EPA conducted additional evaluation, using the 2017 to
mid-2019 data from the four units at IP&L-Petersburg, to compare the
results of these two data handling approaches. This evaluation focused
on 99th percentile values of the 30-day average emission rates
calculated using these two approaches, in order to focus on periods
when compliance is most challenging. Table 3 shows the results of this
evaluation.
Table 3--Effect of Data Handling Approach on 99th Percentile 30-Day Average Emission Rates
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Arithmetic Total emissions/
Unit average (lbs/ total heat input Ratio (%)
MMBTU) (lbs/MMBTU)
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1...................................................... 0.097 0.088 110
2...................................................... 0.117 0.121 97
3...................................................... 0.214 0.219 98
4...................................................... 0.214 0.220 97
Average................................................ ................. ................. 100
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These results suggest several conclusions. First, the results of
these approaches, at least at times of most concern (i.e., times with
relatively high emissions), tend to be quite similar. Second, neither
approach is necessarily more conservative than the other. Third, the
variation in results across the four units lends some support to the
view that the arithmetic average approach gives slightly less stable
results, but the results are sufficiently similar that either approach
is a suitable approach for evaluating compliance.
While Indiana's submittal (in the State's letter to the company
dated September 18, 2019) describes the commissioner's order as
applying the compliance methodology ``recommended'' in MATS, the
applicable compliance provisions (in 326 IAC 7-4-15(d)) provide for
averaging ``all of the quality assured hourly average . . . data,''
which would include data collected during startup and shutdown of the
units. Thus, Indiana's submittal does not raise questions as to whether
it is permissible to exclude data during startup and shutdown in an
attainment plan.
As noted above, EPA guidance recommends calculating adjustment
factors using data obtained according to the procedures used in
determining compliance. Since compliance with IP&L's 30-day average
limits is evaluated on the basis of an arithmetic average of operating
hour emission rates, the appropriate adjustment factors here are
calculated on that basis. For reasons discussed above, EPA believes
that Indiana has adopted limits that reflect suitable adjustments, such
that these limits are comparably stringent to the 1-hour limits that
Indiana's modeling has demonstrated would provide for attainment.
The August 2018 proposed rule observed that this facility, upon
complying with its 30-day average limits, can be expected to have only
a limited frequency and magnitude of hours with emissions exceeding the
critical emission value. Since the changes in Indiana's plan for IP&L-
Petersburg retain the same critical emission value but establish lower
30-day average emission limits, these changes can be expected to reduce
the frequency and magnitude of occasions when emissions exceed the
critical emission value.
Nevertheless, more pertinent data are now available to address this
question. EPA previously examined this question based on 2006 to 2010
data from the main stack at Unit 2, but EPA now has data for 2017 to
mid-2019 for all four
[[Page 10356]]
units, for a period when IP&L was required to meet limits similar to
the final limits. For this period, Units 1, 3, and 4 are complying with
the revised emission limits and are exceeding the critical emission
values (i.e., the modeled mass emissions in lbs/hour) for 0.9 percent,
0.1 percent, and 0.4 percent of the hours, respectively. Unit 2 is
exceeding its revised limit 17 percent of the time, while exceeding the
critical emission value 3 percent of the time.\7\ This suggests that
the necessary improvements in scrubber efficiency at Unit 2 would
likely yield a percentage of hours with emissions above the critical
emission value that is similar to the percentages found for the three
units that are already complying with limits.
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\7\ The exceedances of the new Unit 2 limit, while somewhat
frequent, are modest in magnitude; during this 2\1/2\-year period,
Unit 2 met the prior limit for all but one 30-day average period,
and a majority among the 30-day periods with averages above 0.10
lbs/MMBTU had average emission rates below 0.11 lbs/MMBTU.
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EPA proposed previously that Indiana's modeling provides an
appropriate estimation of the critical emission values that will
provide for attainment, and Indiana has made no changes that warrant
EPA revisiting that finding. Instead, Indiana has changed only its
calculation of an adjustment factor and, by applying the resulting
revised adjustment factor, determined and adopted a revised set of 30-
day average limits that EPA now judges to be comparably stringent to 1-
hour limits at the critical emission values. Accordingly, in this
proposed rule, EPA is soliciting comments on the revised adjustment
factor calculations, the resulting revisions in Indiana's plan, and
EPA's evaluation of these revisions. EPA is not soliciting additional
comments on Indiana's plan and EPA's evaluation of that plan other than
with respect to those elements of Indiana's plan and EPA's evaluation
that have changed since EPA's prior proposed rulemaking.
Indiana's September 18, 2019 submittal requests that EPA approve
326 IAC 7-4-15, including the 1-hour limits for IP&L-Petersburg, except
for the 30-day average limits for IP&L-Petersburg in that rule, and
approve the commissioner's order, which includes substitute 30-day
average limits. In seeking approval of both the rule and the
commissioner's order, Indiana seeks to allow IP&L to switch between 1-
hour limits in 326 IAC 7-4-15(a) and the 30-day average limits in the
commissioner's order. Indiana clarified that the 30-day average limits
in the commissioner's order are to be viewed as substitutes for the 30-
day average limits in 326 IAC 7-4-15(c), and that references to the
limits in subsection (c) in 326 IAC 7-4-15 should be understood as
references to the limits in the order. See email from Mark Derf to John
Summerhays dated November 19, 2019. Indiana further clarified that 326
IAC 7-4-15(e) thus provides terms under which IP&L may choose to switch
between being required to comply with the 30-day average limits in the
commissioner's order and being required to comply with the 1-hour
limits in 326 IAC 7-4-15(a). EPA is proposing action in accordance with
this interpretation.
V. EPA's Proposed Action
EPA is proposing to conclude that, based on revised adjustment
factor calculations, the revised emission limits that Indiana has
adopted for IP&L-Petersburg are a suitable element of an approvable
plan for attaining the 2010 1-hour SO2 NAAQS for Southwest
Indiana. This action is a supplement to a prior proposed rule,
published August 15, 2018, at 83 FR 40487, which addressed the full
range of requirements that the SO2 nonattainment plan for
Southwest Indiana must meet.
EPA is not soliciting additional comments on the other elements of
Indiana's plan for Southwest Indiana, aside from any ramifications of
Indiana's revised emission limits for IP&L-Petersburg. In response to
comments received, Indiana has only revised its calculation of the
degree of adjustment needed for 30-day average limits at IP&L-
Petersburg to be comparably stringent to the 1-hour limits that would
otherwise be necessary, and has adopted the limits that this revised
calculation indicated to be warranted. Accordingly, EPA is only
soliciting comments on the revisions that Indiana made and EPA's
evaluation of these revisions. EPA acknowledges receipt of other
comments on Indiana's plan and EPA's August 2018 proposed action,
including comments on the general acceptability of 30-day average
limits. EPA plans to address those comments as part of final rulemaking
on Indiana's plan for SO2 in Southwest Indiana.
EPA's August 2018 proposed action specifies particular Indiana
rules that EPA proposed to incorporate by reference into the Indiana
SIP. Two of these rules (Title 326 Indiana Administrative Code Rules 7-
1.1-3 and 7-2-1 (326 IAC 7-1.1-3 and 7-2-1)) provide compliance
deadlines, reporting requirements and compliance determination
procedures not just for sources in Southwest Indiana but also for
sources in the Indianapolis, Terre Haute, and Morgan County areas. EPA
has already approved these rules as part of its action on the
Indianapolis and Terre Haute area plans, as published on March 22, 2019
at 84 FR 10692, and so no further action on these rules is necessary.
EPA also proposed to approve limitations for Pike County, in 326 IAC 7-
4-15, which includes limitations for IP&L-Petersburg and for the Frank
E. Ratts power plant. EPA continues to intend to approve most of this
rule, specifically paragraphs a, b, d, and e, incorporating the limits
for the Frank E. Ratts plant, the 1-hour limits for IP&L-Petersburg,
and associated compliance provisions into the SIP. The only portion of
326 IAC 7-4-15 that EPA is proposing not to take action on is paragraph
c, the paragraph with the prior 30-day average limits for IP&L-
Petersburg; as requested by Indiana, EPA is instead proposing to
approve the commissioner's order that Indiana submitted September 18,
2019, which EPA considers to provide substitute 30-day average limits
for the 30-day average limits in 326 IAC 7-4-15(c).
VI. Incorporation by Reference
In this rule, 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 Commissioner's Order Number 2019-2, effective August 18,
2019, and 326 IAC 7-4-15 Pike County sulfur dioxide emission
limitations (except for paragraph (c)), effective October 30, 2015. EPA
has made, and will continue to make, these documents generally
available through www.regulations.gov, and at the EPA Region 5 Office.
(Please contact the person identified in the FOR FURTHER INFORMATION
CONTACT section of this preamble for more information.)
VII. Statutory and Executive Order Reviews
Under the Clean Air Act, the Administrator is required to approve a
SIP submission that complies with the provisions of the Clean Air Act
and applicable Federal regulations. 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 Clean Air Act.
Accordingly, this proposed action merely approves state law as meeting
Federal requirements and does not impose additional requirements beyond
those imposed by state law. For that reason, this proposed action:
Is not a ``significant regulatory action'' subject to
review by the Office
[[Page 10357]]
of Management and Budget under Executive Order 12866 58 FR 51735,
October 4, 1993) and 13563 (76 FR 3821, January 21, 2011);
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 Clean Air Act; and
Does not provide EPA with the discretionary authority to
address, as appropriate, disproportionate human health or environmental
effects, using practicable and legally permissible methods, under
Executive Order 12898 (59 FR 7629, February 16, 1994).
In addition, the SIP is not approved to apply on any Indian
reservation land or in any other area where EPA or an Indian tribe has
demonstrated that a tribe has jurisdiction. In those areas of Indian
country, the rule does not have tribal implications and will not impose
substantial direct costs on tribal governments or preempt tribal law as
specified by Executive Order 13175 (65 FR 67249, November 9, 2000).
List of Subjects in 40 CFR Part 52
Environmental protection, Air pollution control, Incorporation by
Reference, Intergovernmental relations, Reporting and recordkeeping
requirements, Sulfur oxides.
Dated: February 10, 2020.
Kurt A. Thiede,
Regional Administrator, Region 5.
[FR Doc. 2020-03507 Filed 2-21-20; 8:45 am]
BILLING CODE 6560-50-P