Proposed Rule2022-28158
Air Plan Approval; Illinois; Alton Township 2010 SO2 Attainment Plan
Primary source
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Published
December 30, 2022
Issuing agencies
Environmental Protection Agency
Abstract
The Environmental Protection Agency (EPA) is proposing to approve the State Implementation Plan (SIP) revision which Illinois submitted to EPA on December 31, 2018, for attaining the 2010 sulfur dioxide (SO<INF>2</INF>) primary national ambient air quality standard (NAAQS) for the Alton Township nonattainment area in Madison County. This plan (herein called a "nonattainment plan") includes Illinois' attainment demonstration and other elements required under the Clean Air Act (CAA), including 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 emission inventories, enforceable emission limitations and control measures, nonattainment new source review (NNSR), and contingency measures. EPA is proposing to approve Illinois' submission as a SIP revision for attaining the 2010 primary SO<INF>2</INF> NAAQS in the Alton township nonattainment area, finding that Illinois has adequately demonstrated that the plan provisions provide for attainment of NAAQS in the nonattainment area and that the plan meets the other applicable requirements under the CAA.
Full Text
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<title>Federal Register, Volume 87 Issue 250 (Friday, December 30, 2022)</title>
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[Federal Register Volume 87, Number 250 (Friday, December 30, 2022)]
[Proposed Rules]
[Pages 80509-80519]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2022-28158]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R05-OAR-2018-0841; FRL-10489-01-R5]
Air Plan Approval; Illinois; Alton Township 2010 SO2 Attainment
Plan
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
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SUMMARY: The Environmental Protection Agency (EPA) is proposing to
approve the State Implementation Plan (SIP) revision which Illinois
submitted to EPA on December 31, 2018, for attaining the 2010 sulfur
dioxide (SO<INF>2</INF>) primary national ambient air quality standard
(NAAQS) for the Alton Township nonattainment area in Madison County.
This plan (herein called a ``nonattainment plan'') includes Illinois'
attainment demonstration and other elements required under the Clean
Air Act (CAA), including 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 emission inventories, enforceable
emission limitations and control measures, nonattainment new source
review (NNSR), and contingency measures. EPA is proposing to approve
Illinois' submission as a SIP revision for attaining the 2010 primary
SO<INF>2</INF> NAAQS in the Alton township nonattainment area, finding
that Illinois has adequately demonstrated that the plan provisions
provide for attainment of NAAQS in the nonattainment area and that the
plan meets the other applicable requirements under the CAA.
DATES: Comments must be received on or before January 30, 2023.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R05-
OAR-2018-0841 at <a href="https://www.regulations.gov">https://www.regulations.gov</a>, or via email to
<a href="/cdn-cgi/l/email-protection#7b1a09091a55081a091a133b1e0b1a551c140d"><span class="__cf_email__" data-cfemail="71100303105f0210031019311401105f161e07">[email protected]</span></a>. For comments submitted at <a href="http://Regulations.gov">Regulations.gov</a>, follow
the
[[Page 80510]]
online instructions for submitting comments. Once submitted, comments
cannot be edited or removed from <a href="http://Regulations.gov">Regulations.gov</a>. 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 <a href="https://www2.epa.gov/dockets/commenting-epa-dockets">https://www2.epa.gov/dockets/commenting-epa-dockets</a>.
FOR FURTHER INFORMATION CONTACT: Andrew Lee, Physical Scientist,
Attainment Planning and Maintenance Section, Air Programs Branch (AR-
18J), Environmental Protection Agency, Region 5, 77 West Jackson
Boulevard, Chicago, Illinois 60604, (312) 353-7645,
<a href="/cdn-cgi/l/email-protection#6e020b0b400f000a1c0b19400d2e0b1e0f40090118"><span class="__cf_email__" data-cfemail="402c25256e212e243225376e23002530216e272f36">[email protected]</span></a>. The EPA Region 5 office is open from 8:30 a.m. to
4:30 p.m., Monday through Friday, excluding Federal holidays and
facility closures due to COVID-19.
SUPPLEMENTARY INFORMATION: Throughout this document whenever ``we,''
``us,'' or ``our'' is used, we mean EPA.
Table of Contents
I. Why was Illinois required to submit an SO<INF>2</INF> plan for
the Alton township area?
II. Requirements for SO<INF>2</INF> Nonattainment Area Plans
III. Attainment Demonstration and Longer-Term Averaging
IV. Review of Modeled Attainment Plan
A. Model Selection and General Model Inputs
B. Meteorological Data
C. Modeled Emissions Data
D. Emission Limits
E. Background Concentrations
F. Summary of Results
V. Review of Other Plan Requirements
A. Emissions Inventory
B. RACM/RACT and Emissions Limitations and Control Measures
C. New Source Review (NSR)
D. RFP
E. Contingency Measures
VI. EPA's Proposed Action
VII. Incorporation by Reference
VIII. Statutory and Executive Order Reviews
I. Why was Illinois required to submit an SO[bdi2] plan for the Alton
township area?
On June 22, 2010, EPA published a new 1-hour primary SO<INF>2</INF>
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). EPA has
promulgated designations for this standard in four rounds. Alton
Township, Illinois was designated nonattainment by EPA on June 30,
2016, as part of the Agency's Round 2 designations.
In the Round 2 designations, EPA designated areas including power
plants exceeding certain emissions criteria, specifically including the
Wood River power plant located in Wood River, Illinois. The modeling
that Illinois submitted in support of its Round 2 designations
recommendations included both the Wood River power plant and an
additional source, the Alton Steel, Inc. steel mill in Alton, Illinois
(Alton Steel). Alton Steel was included in the modeling analysis
because its SO<INF>2</INF> emissions showed the potential for creating
significant SO<INF>2</INF> concentration gradients within the modeling
domain. The modeling was done using the AERMOD air dispersion modeling
software utilizing data based on actual emissions from the Wood River
Power Station and Alton Steel.
The state found that the highest modeled NAAQS violations in the
area were almost entirely due to Alton Steel emissions and especially
occurred along or near Alton Steel's north fence line. The Alton Steel
facility consists of a melt shop and a rolling mill in which steel
scrap is melted (electric arc furnace), refined/alloyed (ladle
metallurgical furnace), and then cast/formed into blooms and slabs.
Illinois provided suitable evidence that Wood River should be judged
not to contribute to the modeled violation as the facility was shut
down in 2016. As such, Illinois recommended the designation of
nonattainment for Alton Township to focus on the NAAQS violations
caused by Alton Steel.
The state's modeling in support of its designation recommendation
indicated that the predicted 99th percentile 1-hour average
concentration within the chosen modeling domain was 456.40 micrograms
per cubic meter ([mu]g/m\3\), or 174.2 ppb. This modeled concentration
included the background concentration of SO<INF>2</INF> and was based
on actual emissions from the facilities in the area. Illinois performed
a culpability analysis which demonstrated that only a small group of
receptors violated the 2010 SO<INF>2</INF> NAAQS, and these receptors
were primarily affected by emissions from Alton Steel, which were
greatly influenced by downwash. High concentrations near Alton Steel
were a consequence of building downwash combined with downward pointing
vents, and primarily occurred when winds were blowing from the
southwest, a direction that maximized the impact of the Alton Steel
building in causing downwash and downwash-influenced concentrations in
nearby ambient air locations.
On September 18, 2015, Illinois submitted its recommendations for
EPA to designate certain areas of the state as part of the Round 2
designations. In its submission, Illinois recommended that a portion of
Madison County be designated as nonattainment for the 2010
SO<INF>2</INF> NAAQS--specifically, a portion of southern Alton
Township. EPA, agreeing with Illinois' analysis of the area, concurred
with the state's proposed finding of nonattainment for Alton Township.
EPA published a final action designating the area as nonattainment on
July 12, 2016 (81 FR 45039), which became effective September 12, 2016.
In response to EPA's designation of the Alton Township area, Illinois
submitted an attainment plan on December 13, 2018, to EPA for approval.
Under CAA section 192(a), these plans are required to demonstrate that
their respective areas will attain the NAAQS as expeditiously as
practicable, but no later than five years from the effective date of
designation, which was September 12, 2021.
Unlike in the Round 2 designations modeling, the Alton Township
attainment demonstration does not include the Wood River Power Station
among the sources modeled. Wood River was excluded from the
nonattainment area because in November 2015, the facility owner
(Dynegy, Inc.) publicly announced that the power plant would be
closing, pending approval of the electrical transmission system
operator (Midcontinent Independent System Operator). The facility was
retired in June 2016 and ceased emitting SO<INF>2</INF> at that point,
and was demolished in February 2021.
[[Page 80511]]
II. Requirements for SO[bdi2] Nonattainment Area Plans
Nonattainment area SO<INF>2</INF> SIPs must meet the applicable
requirements of the CAA, and specifically CAA sections 110, 172, 191
and 192. EPA's regulations governing nonattainment area 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
SO<INF>2</INF> SIPs and fundamental principles for SIP control
strategies. Id. at 13545-49, 13567-68. On April 23, 2014, EPA issued
guidance and recommendations for meeting the statutory requirements in
SO<INF>2</INF> SIPs addressing the 2010 primary NAAQS, in a document
entitled, ``Guidance for 1-Hour SO<INF>2</INF> Nonattainment Area SIP
Submissions'' (April 2014 guidance), available at <a href="https://www.epa.gov/sites/production/files/2016-06/documents/20140423guidance_nonattainment_sip.pdf">https://www.epa.gov/sites/production/files/2016-06/documents/20140423guidance_nonattainment_sip.pdf</a>. In the April 2014 guidance, EPA
described the statutory requirements for a complete nonattainment area
SIP, which includes an accurate emissions inventory of current
emissions for all sources of SO<INF>2</INF> within the nonattainment
area; an attainment demonstration; enforceable emissions limitations
and control measures; demonstration of RFP; implementation of RACM
(including RACT); NNSR; and adequate contingency measures for the
affected area.
In order 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 ensures equivalent or greater emission
reductions of such air pollutant.
III. Attainment Demonstration and Longer-Term Averaging
CAA section 172(c)(1) directs 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 the four
fundamental principles of quantification, enforceability,
replicability, and accountability. See General Preamble, at 13567-68.
SO<INF>2</INF> 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 SO<INF>2</INF>
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 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 allows for emission limits
with longer averaging times of up to 30 days so long as the state meets
various suggested criteria. See April 2014 guidance, pp. 22 to 39. The
guidance recommends that, should states and sources utilize a longer-
term average limit, the limit should be set at an adjusted level that
reflects a stringency comparable to the 1-hour critical emission value
shown to provide for attainment that the plan otherwise could have set
as a 1-hour emission limit.
Illinois' plan applies 1-hour average emission limits to Alton
Steel. However, Illinois' plan also considers the impact of an
additional facility that is about 12 kilometers from Alton Steel,
namely Ameren's Portage des Sioux Power Center (``Sioux'' or ``Ameren-
Sioux'') in St. Charles County, Missouri, a facility that is subject to
a 24-hour block average limit. Therefore, EPA is providing the
following discussion of its rationale for approving the use of longer-
term average limits in plans designed to provide for attainment.
The April 2014 guidance provides an extensive discussion of EPA's
view that appropriately set comparably stringent limits based on
averaging times as long as 30 days can be found to provide for
attainment of the 2010 SO<INF>2</INF> NAAQS. In evaluating this option,
EPA considered the nature of the standard, conducted detailed analyses
of the impact of the 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. See id.; see also id. at appendices B, C and D.
As specified in 40 CFR 50.17(b), the 1-hour primary SO<INF>2</INF>
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 SO<INF>2</INF> 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
exceedance of the level of the NAAQS does not create a violation of the
standard. Instead, at issue is whether a source operating in compliance
with a properly set limit reflecting a longer-term average could cause
hourly exceedances of the NAAQS level, and if so the resulting
frequency and magnitude of such hourly 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 hourly value will be at or below 75 ppb.
The following is a synopsis of EPA's review of how to judge whether
such plans ``provide for
[[Page 80512]]
attainment,'' based on modeling of projected allowable emissions and in
light of the NAAQS' form for determining attainment at monitoring
sites.
For plans for SO<INF>2</INF> 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, over three consecutive years)
is labeled the ``critical emission value.'' The modeling process for
identifying this critical emission value inherently considers the
numerous variables that affect ambient concentrations of
SO<INF>2</INF>, 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. This is the approach Illinois
took for setting limits at Alton Steel.
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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 values (e.g., the fourth
highest maximum daily concentration in a year with 365 days with
valid data), this discussion and an example below uses a single
``average year'' in order 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 emissions 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 SO<INF>2</INF>
concentrations, could in turn create the possibility of a NAAQS level
exceedance occurring on a day when an exceedance would not have
occurred if emissions were continuously controlled at the level
corresponding to the critical emissions 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 like
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 emissions 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 emissions level, and in the longer-term average limit
scenario, the source is presumed occasionally to emit more than the
critical emissions value but on average, and presumably at most times,
to emit well below the critical emissions value. In an ``average
year,'' compliance with the 1-hour limit is expected to result in three
exceedance days (i.e., three days with an hourly value 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 emissions 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 emissions 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 SO<INF>2</INF> 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. 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 pounds per hour. This
simplified example assumes 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 pounds per
hour, 1,100 pounds per hour, 500 pounds per hour, 900 pounds per hour,
and 1,200 pounds per hour, respectively. (This is a conservative
example because the average of these emissions, 900 pounds per hour, 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 day
would not have an exceedance that otherwise would have occurred, and
the fourth day would have been below, rather than at, 75 ppb. In this
example, the fourth highest maximum daily concentration under the 30-
day average would be 67.5 ppb.
This simplified example encapsulates 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 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 emissions
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 hourly exceedances of the NAAQS
level and better air quality than an emission profile with maximum
allowable emissions under a 1-hour emission limit at the critical
emissions value.\2\ This
[[Page 80513]]
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.
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\2\ See also further analyses described in rulemaking on the
SO<INF>2</INF> nonattainment plan for Southwest Indiana. In response
to comments expressing concern that the emissions profiles analyzed
for appendix B represented actual rather than allowable emissions,
EPA conducted additional work formulating sample allowable emission
profiles and analyzing the resulting air quality impact. These
analyses provided further support for the conclusion that an
appropriately set longer term average emission limit in appropriate
circumstances can suitably provide for attainment. The rulemaking
describing these further analyses was published on August 17, 2020,
at 85 FR 49967, available at <a href="https://www.govinfo.gov/content/pkg/FR-2020-08-17/pdf/2020-16044.pdf">https://www.govinfo.gov/content/pkg/FR-2020-08-17/pdf/2020-16044.pdf</a>. A more detailed description of these
analyses is available in the docket for that action, specifically at
<a href="https://www.regulations.gov/document?D=EPA-R05-OAR-2015-0700-0023">https://www.regulations.gov/document?D=EPA-R05-OAR-2015-0700-0023</a>.
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The question then becomes whether this approach--which is likely to
produce a lower number of overall hourly NAAQS level exceedances even
though it may produce some unexpected exceedances above the critical
emission value--meets the requirement in section 110(a)(1) and
172(c)(1) for state implementation plans to ``provide for attainment''
of the NAAQS. For SO<INF>2</INF>, 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 NAAQS level 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 hourly 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 NAAQS 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 SO<INF>2</INF> NAAQS.
The April 2014 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 emissions 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
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 emissions limit. 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.\3\ 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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\3\ For example, if the critical emission value is 1,000 pounds
of SO<INF>2</INF> per hour, and a suitable adjustment factor is
determined to be 70 percent, the recommended longer term average
limit would be 700 pounds per hour.
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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 SO<INF>2</INF> concentrations) in all types of terrain based
on extensive developmental and performance evaluation. Supplemental
guidance on modeling for purposes of demonstrating attainment of the
SO<INF>2</INF> standard is provided in appendix A to the April 2014
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 SO<INF>2</INF> 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 SO<INF>2</INF>
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 those
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 SO<INF>2</INF>.
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 standard, and should be calculated as described
in section 2.6.1.2 of the August 23, 2010, clarification memo on
``Applicability of Appendix W Modeling Guidance for the 1-hr
SO<INF>2</INF> National Ambient Air Quality Standard'' (U.S. EPA,
2010).
IV. Review of Modeled Attainment Plan
This section generally discusses EPA's evaluation of the modeled
attainment demonstration for Illinois' plan. A more detailed discussion
is also presented in a technical support document (TSD) contained in
the public docket for this proposed approval of Illinois' SIP.
A. Model Selection and General Model Inputs
As part of its SIP development process, Illinois used EPA's
regulatory dispersion model, AERMOD, to help determine the
SO<INF>2</INF> emission limit
[[Page 80514]]
revisions that would be needed to bring the Alton Township
nonattainment area into attainment of the 2010 SO<INF>2</INF> NAAQS.
For its 2018 Alton Township attainment plan, Illinois has relied upon
AERMOD Version 18081 and the companion AERMOD User Guide documentation
in developing this attainment demonstration. Regulatory default options
were specified in developing the attainment demonstration that are
consistent with established practices for use of AERMOD in determining
NAAQS compliance for SIP revisions. Included among those default
options are stack tip downwash, buoyancy induced dispersion, default
wind profile coefficients, default vertical potential temperature
gradients, and final plume rise. EPA finds these selections
appropriate.
This attainment demonstration uses a modeling domain that reflects
the geographic extent of emission sources included in the Round 2
modeling for the Wood River Power Plant. The most significant sources
addressed in the modeling for the area are the Alton Steel facility and
the Ameren-Sioux power center in Missouri about 13 kilometers west-
northwest of the nonattainment area. These two facilities are the
principal causes of the modeled violations in the area. Illinois
modeled several other, relatively minor sources within the area that
did not contribute significantly to the violation. Illinois performed a
culpability analysis to quantify the impacts of these various minor
sources to determine their contribution to the modeled violations. At
the highest concentrations the model estimated in the area, all other
sources combined, aside from Ameren-Sioux and Alton Steel, contributed
less than 2 [mu]g/m\3\ in total to the modeled violations. The way
these sources are modeled are discussed in detail below.
The receptor network encompasses the nonattainment area and
consists of discrete fence line receptors spaced at approximately 50-
meter intervals and a gridded receptor array with 100-meter interval
spacings. The receptor density is consistent with standard modeling
guidance for adequately capturing and resolving SO<INF>2</INF>
concentration maxima. See TSD pg. 3.
Selection of terrain data corresponds to the geographic area
represented by the Alton Township nonattainment area, as well as the
locations of facilities nearby that influence concentrations in the
area. U.S. Geological Survey (USGS) National Elevation Dataset (NED)
data were obtained in an appropriate format for use in AERMAP and used
for generating the necessary terrain inputs. Elevations from the NED
data were determined for all sources and structures, and both
elevations and representative hill heights were determined for
receptors.
A detailed site characterization of the Alton Steel facility,
Ameren-Sioux power center, and pertinent other sources provided
dimensional and locational data for structures and stacks necessary for
addressing building-induced plume downwash. Stacks constructed to less
than good engineering practice (GEP) height and within the ``zone of
influence'' of a nearby structure have plumes that are potentially
subject to excessive downwash. Illinois used EPA's Building Profile
Input Program with PRIME algorithm (BPIPPRM, version 04274) to generate
direction-specific building parameters for modeling building wake
effects. The location and height of each stack and flare to be
evaluated, and the locations and heights of nearby structures, were
processed in BPIPPRM to produce the building parameters required by
AERMOD.
Most of the stacks modeled by Illinois are modeled at heights that
BPIPPRM considers to be at or below GEP height. However, two sources in
this analysis were modeled by Illinois with stacks above GEP height.
The stack at the Ameren-Sioux facility is constructed above GEP height
and was modeled by Illinois at actual height. Additionally, at WRB
Refining, several stacks have been constructed with heights above GEP
height and were modeled at the actual stack height and at full
potential to emit. WRB Refining, despite being modeled above GEP
height, is not considered a significant contributor to the violations
in the area. Illinois performed a culpability analysis and concluded
that WRB has a very low contribution, less than 1 [mu]g/m\3\ in all
modeled scenarios, to the modeled violations. As such, Illinois
modeling that facility at GEP height would change little about the
principal sources of SO<INF>2</INF> pollution in the area. Ameren-Sioux
was modeled at above GEP height and was determined to be a significant
contributor to the violations in the area. EPA has conducted
supplemental modeling to correct any deficiencies in Illinois's
modeling related to the characterization of emissions in the area. EPA
used Illinois' receptor grid, meteorological surface and upper air
stations, model settings, and some source parameters to develop the
modeling demonstration. EPA is relying on our supplemental modeling to
support the attainment plan and establish that the area is now modeling
attainment. See TSD pg. 6. More discussion on this topic is included in
the sections below.
B. Meteorological Data
Procedures for selecting and developing meteorological data have
been provided in the draft document ``Regional Meteorological Data
Processing Protocol, EPA Region 5 and States.'' \4\ This document
describes selection criteria for surface meteorological data that
address the representativeness of the meteorological data collection
site to the emission source/receptor impact area. There are two
specific criteria to be considered: (1) the suitability of
meteorological data for the study area, and (2) the similarity of
surface conditions and surroundings at the emission source/receptor
impact area compared to characteristics at the location of the
meteorological instrumentation tower.
---------------------------------------------------------------------------
\4\ Draft--Regional Meteorological Data Processing Protocol. EPA
Region 5 and States (August 2014), available in the docket for this
action.
---------------------------------------------------------------------------
In its 2018 submission, Illinois used the then-most recent five
years (2012-2016) of surface meteorological data from St. Louis,
Missouri (WBAN No. 13994, 28 kilometers to the southwest) and
coincident upper air data from Lincoln, Illinois (WBAN No. 4833, 157 km
to the northeast). These data were determined to be representative of
the NAA's airshed. These data, in combination with surface
characteristics data, were processed using AERSURFACE (version 13016)
to prepare the meteorological data for simulating the area's planetary
boundary layer turbulence structure. Illinois utilized AERMET (version
16216) to process the raw meteorological data. Illinois obtained
Automated Surface Observing Systems (ASOS) one-minute wind speed and
wind direction data for NWS surface stations and processed it using
AERMINUTE (version 15272). EPA utilized the meteorological data
processed by Illinois in its supplemental modeling. See TSD pg. 13.
The frequency and magnitude of wind speed and direction are defined
in terms of where the wind is blowing from, parsed out in sixteen 22.5-
degree wind sectors. The predominant wind direction during the five-
year period is from the south, occurring approximately 9.8% of the
time. The highest percentage wind speed range, occurring 34.5% of the
time, was in the 3.6-5.7 meters per second range.
C. Modeled Emissions Data
In its 2018 submittal, Illinois provided an analysis modeling other
[[Page 80515]]
SO<INF>2</INF> sources in the area, including GBC Metals, Olin
Corporation, National Maintenance & Repair, Alton Water Treatment
Facility, Conoco-Phillips Hartford Plant, Alton Memorial Hospital, St.
Anthony's Hospital, St. Claire's Hospital, the Charles E. Mahoney
Plant, WRB Refinery, and most notably including the Alton Steel
facility and the Ameren-Sioux facility. Data for detailed site
characterization (stack locations, fence line locations, building
dimensions, etc.) of these sources were gathered and/or generated to
support development of specific AERMOD inputs. Illinois used EPA's
Building Profile Input Program with PRIME algorithm (BPIPPRM, version
04274) to generate direction-specific building inputs for modeling
building wake effects within AERMOD. Building-induced plume downwash
was addressed for all stacks and flares. The flares, all of which are
located at WRB Refining, were modeled with adjusted release parameters
including fixed values for temperature, exit velocity, and modified
values for release height and diameter. Illinois relied upon the
AERSCREEN User's Guide \5\ to calculate the effective height and
diameter for modeling the flares. Following the submittal from
Illinois, EPA performed a supplemental modeling run to evaluate changes
in allowable emissions that occurred after Illinois submitted the
attainment plan and to correct any deficiencies in the emissions data
or source characterization that could potentially cause reduced
concentrations. See TSD p. 2.
---------------------------------------------------------------------------
\5\ AERSCREEN User's Guide. EPA-454/B-16-004. December 2016.
U.S. Environmental Protection Agency, Research Triangle Park, NC.
---------------------------------------------------------------------------
The most significant sources affecting the nonattainment area were
Alton Steel and the Ameren-Sioux facility in Missouri. While the
Ameren-Sioux facility is not in the nonattainment area, Illinois
modeled this facility due to its proximity to the nonattainment area
and its high SO<INF>2</INF> emissions, yielding an impact of up to
283.4 [mu]g/m\3\ on the air quality in the area. Illinois modeled
numerous minor point sources in the nonattainment area as well.
Illinois did not explicitly model emissions from non-point sources, for
example mobile emissions, incineration, agricultural field burning,
etc., in AERMOD but instead represented the impact of these sources via
monitored background data.
Illinois' SIP submittal describes an exploratory run that Illinois
conducted in order to define the air quality problem in the area and to
determine the most appropriate remedy. Notably, the baghouse at Alton
Steel was originally configured to emit out of downward pointing vents,
which Illinois modeled using the POINTHOR option in AERMOD to consider
the horizontally pointing vents. Based on the results of these runs in
which Alton Steel was the principal contributor to the highest modeled
violations, Illinois chose to mandate construction of a single vertical
unobstructed stack for this emission unit. Thus, Illinois' attainment
demonstration modeling represented this emission point (and all other
emission points) as a vertical unobstructed stack release. Flares were
modeled with adjusted release parameters, consistent with EPA's
guidance for modeling flares presented in the AERSCREEN User's
Guide.\6\ The adjusted parameters include fixed values for temperature
(1,273 degrees Kelvin) and exit velocity (20 meters/second) and
modified values for release height and diameter.
---------------------------------------------------------------------------
\6\ See supra n.5.
---------------------------------------------------------------------------
Ameren-Sioux operates two coal-fired boilers. Illinois modeled this
source using information provided by the Missouri Department of Natural
Resources. Illinois' modeling indicated that the limit on Ameren-Sioux
in Missouri's SIP of 4.8 lbs/MMBtu did not ensure attainment inside the
Alton nonattainment area. Illinois' modeling run evaluating the impact
of maximum allowable emissions from Ameren-Sioux also reflecting the
reconfigured ladle metallurgy facility (LMF) stack for Alton Steel
yielded a maximum predicted 99th percentile 1-hour average
concentration of 298.5 [mu]g/m\3\, and Illinois concluded that scaling
this result down to reflect a temporally representative operating rate
(either a 60th or a 70th percentile rate) for Ameren-Sioux would also
show violations.
EPA conducted a supplemental modeling run to correct deficiencies
in the characterization of emissions in Illinois's modeling. EPA
evaluated the estimated concentrations based on application of a new
limit of 7,342 lbs/hour averaged over a 24-hour block period on the
Ameren-Sioux facility published on November 16, 2022 (87 FR 68634). The
adopted new limit is substantially lower than the previous SIP limit of
4.8 lbs/MMBtu. Each of the facility's two boilers are rated to have a
maximum heat input capacity of 4,920 MMBtu/hr and when applied to the
former rate limit, add up to an effective rate of 47,232 lbs/hour on a
facility-wide basis. The newly adopted limit marks a significantly
reduced emission rate for the facility. EPA's supplemental modeling was
based on the modeling runs submitted by Illinois, which modeled maximum
uncontrolled emissions limits for all sources at the time but did not
consider the revised limit at Ameren-Sioux. EPA's supplemental model
run revised the modeled emissions for Ameren-Sioux to reflect the new
24-hour block limit and modeled the facility at GEP height.
The revised limit on Ameren-Sioux is on a 24-hour block average
basis. Much of EPA's 2014 guidance addresses the situation in which
modeling is used to determine the 1-hour critical emissions value used
to calculate a limit necessary to provide for attainment, in which an
adjustment factor is determined and applied to identify a reduced
longer-term average limit to correspond to the modeled 1-hour value.
The comparable stringency methodology provided in the guidance could
also be utilized to estimate a 1-hour emission rate that may be used in
a dispersion modeling run. Specifically, a preexisting longer-term
average limit can be divided by the appropriate adjustment factor to
determine an hourly modeled emission rate that is commensurate with the
longer-term limit. Application of an adjustment factor means modeling
this source using an hourly emission rate to which the 24-hour block
limit established in Missouri's SIP is comparably stringent.
In EPA's supplemental modeling run, the emissions from Boilers 1
and 2 were treated as merged for a combined emissions rate from Ameren-
Sioux. EPA's stack height regulations restrict the circumstances under
which plume merging is creditable. Under 40 CFR 51.100(hh), plume
merging is defined to be a prohibited dispersion technique except, in
the case of merging occurring after July 8, 1985, for cases in which
such merging is part of a change in operation at the facility that
includes the installation of pollution controls and is accompanied by a
net reduction in the allowable emissions of a pollutant. (See 40 CFR
51.100(hh)(2)(B)). The stack height regulations also note that this
exclusion from the definition of dispersion techniques shall apply only
to the emission limitation for the pollutant affected by such change in
operation. To reduce its SO<INF>2</INF> emissions, Ameren-Sioux began
operation of flue gas desulfurization of the emissions from Boilers 1
and 2 on November 15, 2010, and October 26, 2010, respectively. The
construction of the new stack to vent the emissions from these units
was part of the same project as installation of flue gas
desulfurization equipment. Although Missouri did not adjust its SIP
emission limit to reflect the reduction of allowable emissions
[[Page 80516]]
until several years after the installation of the pollution controls,
the merging accompanied the installation of controls and may also be
considered to accompany a net reduction in allowable emissions because
the initial request for credit for merging was accompanied by a limit
that required the net emission reduction that the Ameren-Sioux control
project achieved. See TSD at 5.
The final SO<INF>2</INF> emission rate modeled for the merged
Boilers 1 and 2 stack at Ameren-Sioux was 10,301.669 lbs/hr (1,297.988
g/s). Based on guidance from the 2014 U.S. EPA's SO<INF>2</INF> NAAQS
Designations Modeling Technical Assistance Document, a ratio of 1-hour
to 24-hour block average 99th percentile SO<INF>2</INF> emission rates
in lbs/hr were calculated using data collected from 2016-2020. This
resulted in an adjustment factor of 2,007 lbs/hr/2,816 lbs/hr = 0.7127.
When the adjustment factor of 0.7127 is applied to the 24-hour block
limit of 7,342 lbs/hr, a 1-hour emission rate to which the longer-term
limit would be comparably stringent to would be 10,301.669 lbs/hr. The
merged stack was modeled using the GEP stack height of 145.41 meters.
The other model inputs of EPA's supplemental run, i.e., receptor
grid, background concentrations, meteorological data, and list of
modeled sources, were consistent with the Illinois submitted modeling.
Stack heights for the merged two vents at Ameren-Sioux and two stacks
at WRB Refining were modified in the supplemental run to be consistent
with GEP stack heights. The supplemental run used version 21112 of
AERMOD. Results of these runs are described below.
D. Emission Limits
A key element of Illinois' attainment plan is a change in Alton
Steel's LMF exhaust configuration from the four downward-angled vents
to a single 70-foot high, three-foot diameter stack with an
unobstructed (no rain cap), vertically directed exhaust stream, which
is represented in their final modeling. This change was mandated in
Illinois' Construction Permit #18020009. As required by the
construction permit, the SO<INF>2</INF> emissions of this furnace shall
not exceed 0.10 pound/ton of steel produced, 11.20 pounds per hour and
37.50 tons per year. The first two of these limits apply on an hourly
basis, such that Illinois' plan is designed to provide for attainment
based on emission limits for the primary source in the area that apply
every hour. Illinois is not relying on the limit on annual emissions to
provide for attainment.
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. The revised SO<INF>2</INF> emission SIP limit at Ameren-Sioux
is expressed as a 24-hour block average limit. Therefore, part of the
review of Illinois' attainment plan must address the use of these
limits, both with respect to the general suitability of using this
limit for this purpose and with respect to whether the particular
limits included in and/or credited by the plan have been suitably
demonstrated to provide for attainment. The first subsection that
follows addresses the enforceability of the limits in and/or credited
by the plan, and the second subsection that follows addresses the
credited 24-hour block limit.
1. Enforceability
The change to Alton Steel's LMF exhaust configuration from the four
downward-angled vents to a single 70-foot high, three-foot diameter
stack with an unobstructed (no rain cap), vertically directed exhaust
was mandated in Illinois Construction Permit #18020009, which is being
incorporated into Illinois' SIP in the present action. This permitting
action provides the federal enforceability supporting this portion of
the attainment demonstration element of the revised SIP. As required by
the construction permit, the SO<INF>2</INF> emissions of this furnace
shall not exceed 0.10 pound per ton of steel produced, 11.20 pounds per
hour and 37.50 tons per year. EPA considers these emission limits and
source configuration requirements, specified in Construction Permit
Number #18020009, to be suitably enforceable. The facility must submit
annual compliance certifications to ensure that the facility is
meetings its SIP limits. Additionally, the facility must submit a semi-
annual Monitoring Report to the Illinois EPA, Air Compliance Section,
summarizing required monitoring and identifying all instances of
deviation from the permit. Stack testing must be done to verify the
margin of compliance with the SO<INF>2</INF> limit.
For Ameren-Sioux, EPA has approved a more stringent 24-hour block
limit submitted by Missouri that is aimed at reducing the facility's
allowable emissions to levels that will allow the Alton nonattainment
area to be modeled in attainment.\7\ Ameren-Sioux will be subject to
the more restrictive limit of 7,342 lbs/hour of SO<INF>2</INF> averaged
over a 24-hour block period. Being a large coal fired EGU, the Ameren-
Sioux facility is required to monitor its release of SO<INF>2</INF> via
CEMS for other reasons such as the acid rain program and the Cross-
State Air Pollution Rule (CSAPR). This requirement also provides for a
means to measure compliance at the source to ensure that the facility
does not exceed its permanent and enforceable limit. To demonstrate
compliance, Ameren must calculate the calendar day 24-hour block
average emission for each unit subject to the facility wide emission
limit. Unit level emission rates will then be summed together to
determine a facility wide emission rate. Only valid operating hours
will be included in the calculations for the daily emission rates.
Valid operating hours include only hours that meet the primary
equipment hourly operating requirements of 40 CFR 75.10(d). For
example, if the source only meets 40 CFR 75.10(d) operational
requirements for one hour in a particular 24-hour block period, the
compliance with the emissions limit would be calculated by the total
emissions divided by the one hour of operation that meets 40 CFR
75.10(d). Therefore, any day with at least one hour that meets
operational requirements will have a calculated block average that will
be used to demonstrate compliance with the emissions limit. Hours when
the units are experiencing startup, shutdown, or malfunction conditions
will be used for the calculation if they meet the primary equipment
hourly operating requirements of 40 CFR 75.10(d).
---------------------------------------------------------------------------
\7\ See 87 FR 68634.
---------------------------------------------------------------------------
2. Longer-Term Average Limits
As noted above, while Illinois considered only the 1-hour average
limits it adopted for Alton Steel, EPA also considered the updated 24-
hour block limit approved into the Missouri SIP for the Ameren-Sioux
facility. Therefore, the hypothetical critical emissions value to which
Ameren-Sioux's 24-hour block average limit would be comparably
stringent, and that is used in the attainment modeling for the area,
would reflect an upward adjustment from the 7,342 lbs/hour averaged
over a 24-hour block period. EPA conducted a site-specific analysis of
variability at Ameren-Sioux using 2016-2020 CEMS data from EPA's Clean
Air Markets Division's MySQL database, which was the most up to date
information available at the time of analysis. EPA employed the method
detailed in our 2014 guidance and used the historic 1-hour 99th
percentile of SO<INF>2</INF> emissions against the 99th percentile 24-
hour block average to derive an appropriate adjustment factor.
[[Page 80517]]
EPA determined that the adjustment factor for the Ameren-Sioux facility
is 0.7127 and that it would be appropriate to apply this adjustment
factor to Ameren-Sioux's long term averaging limit in order to estimate
a 1-hour emission rate for modeling purposes. After applying the
adjustment factor, EPA determined that a 1-hour emission rate used for
modeling purposes would be 10,301.669 lbs/hour. EPA has determined
through our supplemental modeling that an hourly emissions rate of
10,301.669 lbs/hour is protective of the standard. As such, EPA
determines that Ameren-Sioux's updated limit of 7,342 lbs/hour will
provide for attainment in the nonattainment area.
E. Background Concentrations
The Illinois demonstration of modeled attainment of the 2010
SO<INF>2</INF> NAAQS is based upon the combined impacts of facility-
specific emission rates together with monitored background
concentrations integrated into the simulations. Regional sources not
explicitly modeled in AERMOD, but which are contributors to ambient
SO<INF>2</INF> loadings within the nonattainment area, are represented
via background monitoring data. In accordance with a ``Tier 2''
approach in EPA's guidance on background concentrations, Illinois
identified separate background values for each hour of the day for each
of the four seasons, for a total of 96 background values. Each of these
values represents a three-year average (2014-2016) of the second
highest hourly concentration for the applicable hour of the day for the
applicable season. The seasonal, hourly-averaged 2014-2016
SO<INF>2</INF> background values for the attainment demonstration were
developed from data collected at the East St. Louis monitor. See TSD at
13. These values range from 6.81 to 27.4 ppb, with an average value of
14.94 ppb.
F. Summary of Results
Illinois evaluated many factors in their modeling runs to evaluate
measures needed to ensure attainment in the area. In their modeling
runs, Illinois indicated that the prior limit in Ameren-Sioux's
Missouri's SIP did not ensure attainment. Illinois determined that the
impact of maximum allowable emissions from Ameren-Sioux also reflecting
the reconfigured LMF stack for Alton Steel yielded a maximum predicted
99th percentile 1-hour average concentration of 298.5 [mu]g/m\3\, and
Illinois concluded that scaling this result down to reflect a
temporally representative operating rate (either a 60th or a 70th
percentile rate) would also show violations.
EPA concludes that Illinois' modeling is a suitable demonstration
that its requirements in the new permit for Alton Steel and all other
Illinois sources in the nonattainment area were properly addressed in
the attainment plan. EPA's supplemental modeling has demonstrated that
the updated 24-hour block limit for Ameren-Sioux of 7,342 lbs
SO<INF>2</INF>/hr and the revised limits at Alton Steel provide for
attainment. For reasons described above, EPA considers the limits
relied upon in this plan to be permanent and enforceable. EPA's
modeling suitably demonstrates that the Ameren-Sioux limit (in
combination with requirements for Alton Steel) provides for attainment.
As noted above, EPA conducted a supplementary modeling run to
evaluate the Ameren-Sioux facility subject to the updated 7,342 lbs
SO<INF>2</INF>/hr 24-hour block limit that is found in the Missouri
SIP. Since this limit is evaluated on a 24-hour block basis, EPA
applied a 71.27 percent adjustment factor, modeling a 1-hour emissions
rate of 10,300.666 lbs SO<INF>2</INF> per hour to which the 24-hour
block limit is comparably stringent. The modeled design value from
EPA's supplemental run was 196.2 [mu]g/m\3\, or 74.9 ppb. This run used
GEP stack heights, which for two facilities were slightly lower than
the heights Illinois modeled; a separate supplementary run without
these corrections yielded essentially identical results. These results
confirm Illinois' demonstration that with the applicability and
creditability of revised limits for Alton Steel and Ameren-Sioux,
Illinois' plan provides for attainment. EPA believes that this 24-hour
block average emission limit, in combination with the requirements for
Alton Steel, are suitable elements of a plan that appropriately
provides for attainment.
V. Review of Other Plan Requirements
A. Emissions Inventory
The Round 2 Wood River Study Area emission inventory was used as
the starting point for creating the Alton Township NAA modeling
inventory. A re-evaluation of sources was instituted, which reflected a
shift in modeling focus from Dynegy's Wood River Power Station to the
Alton Steel ``mini-mill.'' This re-evaluation was also driven by the
need to address allowable emissions (for the SIP revision) rather than
actual emissions (for an area designation recommendation).
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 prospects for attaining the standard
based on alternative 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 SO<INF>2</INF>
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).
Illinois provided a comprehensive, accurate, and current inventory
of emissions of SO<INF>2</INF> in and within 10 kilometers of the Alton
township area. Illinois additionally examined whether any large sources
beyond 10 kilometers of the nonattainment area might also have
significant air quality impacts in the area, resulting in the addition
of Ameren-Sioux to the inventory. By this means, Illinois has developed
a thorough list of the sources with any potential to cause impacts that
warrant including in the area's attainment modeling.
Illinois included the sources of WRB Refining Inc. (formerly named
ConocoPhillips), National Maintenance and Repair Inc., GBC Metals LLC
(d/b/a Olin Brass), Olin Corporation, Alton Water Treatment Facility,
ConocoPhillips Hartford Lubricant Plant, Alton Memorial Hospital, St.
Anthony's Hospital, St. Clare's Hospital, and Charles E. Mahoney
Company along with Alton Steel. The emission sources at Alton Steel, as
well as those for many of the modeled nearby Illinois facilities, do
not operate with variable loads but rather as ``on-off'' process
operations, with the notable exception of Ameren-Sioux. The emissions
inventory that Illinois submitted reflects actual emissions of these
sources.
[[Page 80518]]
Table 1--Alton Township NAA Modeling Inventory--Actual Alton Area 2017
SO2 Point Source Emissions
------------------------------------------------------------------------
Emission rate
Source description (tons per year)
------------------------------------------------------------------------
Alton Steel.......................................... 45.39
National Maintenance & Repair........................ 3.93
GBC Metals........................................... 0.64
Olin Corporation..................................... 0.12
Alton Water Treatment Facility....................... 2.40
Conoco Philips Hartford Lubricant Plant.............. 0.00
Ameren-Sioux Power Center............................ 2,722.267
Alton Memorial Hospital.............................. 0.15
St. Anthony's Hospital............................... 1.67
St. Clare's Hospital................................. 0.02
Charles E. Mahoney................................... 4.70
WRB.................................................. 1,494.59
Ardent Mills LLC..................................... 0.006
Bluff City Minerals ACQ LLC.......................... 0.04
Precor Refining Group Inc............................ 0.001
Linde LLC............................................ 0.005
Apex Oil Co Inc...................................... 0.014
Shell Oil Products US................................ 0.0012
Koch Fertilizer LLC.................................. 0.0042
------------------------------------------------------------------------
Table 2--Total SO2 Emissions
------------------------------------------------------------------------
Emissions (tons
Category per year)
------------------------------------------------------------------------
Non-EGU Point........................................ 1,559.34
EGU Point............................................ 2,722.267
Area................................................. 81.5196
On-Road Mobile....................................... 11.2065
Off-Road Mobile...................................... 41.8851
------------------
Total............................................ 4,415.9512
------------------------------------------------------------------------
B. RACM/RACT and Emissions Limitations and Control Measures
Section 172(c)(1) of the CAA requires states to adopt and submit
all RACM, including RACT, as needed to attain the standards as
expeditiously as practicable. Section 172(c)(6) requires the SIP to
contain enforceable emission limits and control measures necessary to
provide for timely attainment of the standard. Illinois has required
the principal contributor to the NAAQS violations, Alton Steel, to
build a stack aimed at reducing the facility's contribution to the
nonattainment area. Alton Steel built a stack to disperse emissions
more appropriately from their facility; this change, along with
establishment of suitable emission limits in their construction permit,
along with the proposed limit on Ameren-Sioux to be found in the
Missouri SIP, ensures that the area will attain the SO<INF>2</INF> air
quality standard. Consequently, consistent with EPA policy that
reasonable measures do not extend beyond a set of measures that provide
for attainment, Illinois asserts, and EPA concurs, that the state's
plan satisfies requirements for RACM/RACT.
C. New Source Review (NSR)
EPA approved Illinois' nonattainment new source review rules on
December 17, 1992 (57 FR 59928); September 27, 1995 (60 FR 49780); and
May 13, 2003 (68 FR 25504). These rules provide for appropriate new
source review for SO<INF>2</INF> sources undergoing construction or
major modification in the Alton Township area without need for
modification of the approved rules. Although these rules predated
promulgation of the 2010 SO<INF>2</INF> standards, these rules are
written in a manner such that new sources within areas that become
designated nonattainment for this new standard, such as the Alton
Township area, become subject to these nonattainment new source review
requirements. Therefore, this requirement has been met for this area.
D. RFP
Section 172 of the CAA requires Illinois' Alton Township Attainment
Plan SIP to provide for reasonable further progress toward attainment.
For SO<INF>2</INF> SIPs, which address a small number of affected
sources, requiring expeditious compliance with attainment emission
limits can address the RFP requirement. Alton Steel was required to
complete its stack construction and meet its emission limits by
December 31, 2018. For Ameren-Sioux, a new limit was approved into the
Missouri SIP establishing a more stringent limit by establishing a
limit of 7,342 lbs/hour averaged over a 24-hour block period. EPA
approved Ameren-Sioux's new limit on November 16, 2022 (87 FR 68634)
and is permanent and enforceable. EPA concludes that the timely
requirements in the state's plan, including revised limits and
construction of a 70-foot-tall stack for the Alton Steel facility and
the SIP approved limit of Ameren-Sioux, represent implementation of
control measures as expeditiously as practicable. This plan shows that
Illinois can provide for attaining the standard. Accordingly, EPA
proposes to find that Illinois' plan provides for RFP.
E. Contingency Measures
Section 172 of the CAA requires that nonattainment plans include
additional measures which will take effect if an area fails to meet RFP
or fails to attain the standard by the attainment date. As noted above,
EPA guidance describes special features of SO<INF>2</INF> planning that
[[Page 80519]]
influence the suitability of alternative means of addressing the
requirement in section 172(c)(9) for contingency measures for
SO<INF>2</INF>. An appropriate means of satisfying this requirement is
for the state to have a comprehensive enforcement program that
identifies sources of violations of the SO<INF>2</INF> NAAQS and for
the state to undertake aggressive follow-up for compliance and
enforcement. Illinois' plan provides for satisfying the contingency
measure requirement in this manner for sources in the state. EPA
concurs and proposes to approve Illinois' plan for meeting the
contingency measure requirement in this manner.
VI. EPA's Proposed Action
EPA is proposing to approve Illinois' submission as a SIP revision,
which the state submitted to EPA on December 31, 2018, for attaining
the 2010 SO<INF>2</INF> NAAQS for the Alton Township nonattainment
area. As part of this action, EPA is proposing to incorporate Illinois'
Permit to Construct Number #18020009, applicable to Alton Steel, by
reference into the SIP. The permit requires that Alton Steel operates a
new LMF stack to replace the four downward facing vents on the
individual compartments on the LMF stack. The SO<INF>2</INF> emissions
from the LMF stack must not exceed 0.10 pound per ton of steel
produced, 11.20 pounds per hour, and 37.50 tons per year.
This SO<INF>2</INF> nonattainment plan includes Illinois'
attainment demonstration for the Alton township SO<INF>2</INF>
nonattainment area. Although Illinois did not explicitly model air
quality based on Ameren-Sioux's updated limit, Illinois provided
sufficient information and modeling to enable EPA to conduct
additionally necessary supplemental modeling to demonstrate that the
revised limit at the Alton Steel facility, that will drastically reduce
any contributions from Illinois to the violations modeled in the NAA,
and a lower limit imposed on Ameren-Sioux by Missouri would allow the
area to meet the standard. Therefore, EPA concludes that the modeling
in Illinois' plan, as supplemented by EPA, adequately demonstrates that
the control requirements that apply to relevant sources in and near the
area, including the revised 24-hour block SO<INF>2</INF> limit for
Ameren-Sioux, provide for attainment in the area. As previously
explained, EPA conducted a confirmatory model run explicitly applying
the more stringent limit at Ameren-Sioux, and factoring a historically
representative adjustment factor, showing more directly that the
measures in Illinois' plan as supplemented by this limit provide for
attainment. This nonattainment plan also addresses requirements for
emission inventories, RACT/RACM, RFP, and contingency measures.
Illinois has previously addressed requirements regarding nonattainment
area NSR. EPA has determined that Illinois' SO<INF>2</INF>
nonattainment plan meets the applicable requirements of CAA sections
172, 191, and 192. EPA is taking public comments for thirty days
following the publication of this proposed action in the Federal
Register. EPA will take these comments into consideration in our final
action.
VII. 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 the Illinois construction permit for Alton Steel, Inc.,
issued March 5, 2018, as described in section VI. of this preamble. EPA
has made, and will continue to make, these documents generally
available through <a href="http://www.regulations.gov">www.regulations.gov</a> 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).
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 CAA 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 CAA. Accordingly, this
action merely approves state law as meeting Federal requirements and
does not impose additional requirements beyond those imposed by state
law. For that reason, this action:
<bullet> 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);
<bullet> Does not impose an information collection burden under the
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
<bullet> 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.);
<bullet> 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);
<bullet> Does not have federalism implications as specified in
Executive Order 13132 (64 FR 43255, August 10, 1999);
<bullet> Is not an economically significant regulatory action based
on health or safety risks subject to Executive Order 13045 (62 FR
19885, April 23, 1997);
<bullet> Is not a significant regulatory action subject to
Executive Order 13211 (66 FR 28355, May 22, 2001);
<bullet> 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
<bullet> 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, Sulfur oxides.
Dated: December 21, 2022.
Debra Shore,
Regional Administrator, Region 5.
[FR Doc. 2022-28158 Filed 12-29-22; 8:45 am]
BILLING CODE 6560-50-P
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</html>Indexed from Federal Register on December 30, 2022.
This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.