[Federal Register Volume 82, Number 163 (Thursday, August 24, 2017)]
[Proposed Rules]
[Pages 40086-40103]
[FR Doc No: 2017-17736]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R07-OAR-2017-0416; FRL-9966-60-Region 7]

Approval of Iowa's Air Quality Implementation Plan; Muscatine
Sulfur Dioxide Nonattainment Area

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 the State
of Iowa (the state) submitted to the EPA on May 26, 2016, for attaining
the 1-hour sulfur dioxide (SO2) primary National Ambient Air
Quality Standard (NAAQS) for the Muscatine nonattainment area. This
plan (herein called a ``nonattainment plan'') includes the state's
attainment demonstration and other elements required under Clean Air
Act (CAA) sections 172, 191, and 192. In addition to an attainment
demonstration, the plan addresses the requirement for meeting
reasonable further progress (RFP) toward attainment of the NAAQS,
reasonably available control measures and reasonably available control
technology (RACM/RACT), base-year and projection-year emission
inventories, and contingency measures. The EPA proposes to conclude
that the state has appropriately demonstrated that the plan provisions
provide for attainment of the 2010 1-hour primary SO2 NAAQS
in the Muscatine nonattainment area by the applicable attainment date
and that the plan meets the other applicable requirements under CAA
sections 172, 191, and 192.

DATES: Comments must be received on or before September 25, 2017.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R07-
OAR-2017-0416 to https://www.regulations.gov. Follow the online
instructions for submitting comments. Once submitted, comments cannot
be edited or removed from Regulations.gov. The EPA may publish any
comment received to its public docket. Do not submit electronically any
information you consider to be Confidential Business Information (CBI)
or other information whose disclosure is restricted by statute.
Multimedia submissions (audio, video, etc.) must be accompanied by a
written comment. The written comment is considered the official comment
and should include discussion of all points you wish to make. The EPA
will generally not consider comments or comment contents located
outside of the primary submission (i.e., on the web, cloud, or other
file sharing system). For additional submission methods, the full EPA
public comment policy, information about CBI or multimedia submissions,
and general guidance on making effective comments, please visit https://www2.epa.gov/dockets/commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT: Tracey Casburn, Environmental
Protection Agency, Air Planning and Development Branch, 11201 Renner
Boulevard, Lenexa, Kansas 66219 at<PHONE_NUMBER>, or by email at
<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION: Throughout this document whenever ``we,''
``us,'' and ``our'' is used, we mean the EPA.
    Organization of this document. The following outline is provided to
aid in locating information in this preamble.

Table of Contents

I. Why was Iowa required to submit an SO2 plan for the
Muscatine area?
II. Requirements for SO2 Nonattainment Area Plans
III. Attainment Demonstration and Longer Term Averaging
IV. Review of Modeled Attainment Plan
    A. Model Selection
    B. Meteorological Data
    C. Emissions Data
    D. Emission Limits
    1. Enforceability
    2. Longer Term Averaging
    E. Background Concentrations
    F. Summary of Results
    1. Phase 1--Preliminary Analysis
    2. Phase 2--Control Strategy Development
V. Review of Other Plan Requirements
    A. Emissions Inventory and the Quantification of Emissions
    B. RACM/RACT

    C. Nonattainment New Source Review (NNSR)
    D. Reasonable Further Progress (RFP)
    E. Contingency Measures
VI. Additional Elements of the State's Submittal
    A. Compliance With Section 110(a)(2) of the CAA
    B. Equivalent Techniques
VII. EPA's Proposed Action
VIII. Incorporation by Reference
IX. Statutory and Executive Order Reviews

I. Why was Iowa required to submit an SO2 plan for the
Muscatine area?

    On June 22, 2010, the EPA promulgated a new 1-hour primary
SO2 NAAQS of 75 parts per billion (ppb), which is met at an
ambient air quality monitoring site when the 3-year average of the
annual 99th percentile of 1-hour daily maximum concentrations does not
exceed 75 ppb, as determined in accordance with appendix T of 40 CFR
part 50. See 75 FR 35520, codified at 40 CFR 50.17(a)-(b). On August 5,
2013, the EPA designated 29 areas of the country as nonattainment for
the 2010 SO2 NAAQS, including the Muscatine area in the
State of Iowa. See 78 FR 47191, codified at 40 CFR part 81, subpart C.
These area designations were effective October 4, 2013. Section 191 of
the CAA directs states to submit SIPs for areas designated as
nonattainment for the SO2 NAAQS to the EPA within 18 months
of the effective date of the designation, i.e., by no later than April
4, 2015. These SIPs must demonstrate that the respective areas will
attain the NAAQS as expeditiously as practicable, but no later than 5
years from the effective date of designation, which is October 4, 2018.
    On March 18, 2016, the EPA published an action that the State of
Iowa failed to submit the required SO2 nonattainment plan
for the Muscatine area by the SIP submittal deadline. See 81 FR 14736.
This finding initiated a deadline under CAA section 179(a) for the
potential imposition of new source and highway funding sanctions.
However, pursuant to Iowa's submittal of May 26, 2016, and the SIP
becoming complete by operation of law on November 26, 2016, the
sanctions under section 179(a) will not be imposed. Additionally, under
CAA section 110(c), the finding triggers a requirement that the EPA
promulgate a Federal Implementation Plan (FIP) within two years of the
finding unless, by that time (a) the state has made the necessary
complete submittal and (b) EPA has approved the submittal as meeting
applicable requirements. This FIP obligation will not apply if EPA
makes final the approval action proposed here by March 18, 2018.
    The remainder of this preamble describes the requirements that
nonattainment SIPs must meet in order to obtain EPA approval, provides
a review of the state's plan with respect to these requirements, and
describes the EPA's proposed action on the plan.

II. Requirements for SO2 Nonattainment Area Plans

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

III. Attainment Demonstration and Longer Term Averaging

    CAA 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 four fundamental
principles of quantification, enforceability, replicability, and
accountability. General Preamble, at 13567-68. SO2
attainment plans must consist of two components: (1) Emission limits
and other control measures that assure implementation of permanent,
enforceable and necessary emission controls, and (2) a modeling
analysis which meets the requirements of 40 CFR part 51, appendix W
which demonstrates that these emission limits and control measures
provide for timely attainment of the primary SO2 NAAQS as
expeditiously as practicable, but by no later than the attainment date
for the affected area. In all cases, the emission limits and control
measures must be accompanied by appropriate methods and conditions to
determine compliance with the respective emission limits and control
measures and must be quantifiable (i.e., a specific amount of emission
reduction can be ascribed to the measures), fully enforceable
(specifying clear, unambiguous and measureable 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).
    The 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 describes the option to
utilize emission limits with longer averaging times of up to 30 days so
long as the state meets various suggested criteria. See 2014 guidance,
pp. 22 to 39. The guidance recommends that--should states and sources
utilize longer averaging times--

the longer term average limit should be set at an adjusted level that
reflects a stringency comparable to the 1-hour average limit at the
critical emission value shown to provide for attainment that the plan
otherwise would have set.
    The April 2014 guidance provides an extensive discussion of the
EPA's rationale for concluding that appropriately set comparably
stringent limitations based on averaging times as long as 30 days can
be found to provide for attainment of the 2010 SO2 NAAQS. In
evaluating this option, the EPA considered the nature of the standard,
conducted detailed analyses of the impact of use of 30-day average
limits on the prospects for attaining the standard, and carefully
reviewed how best to achieve an appropriate balance among the various
factors that warrant consideration in judging whether a state's plan
provides for attainment. Id. at pp. 22 to 39. See also id. at
Appendices B, C, and D.
    As specified in 40 CFR 50.17(b), the 1-hour primary SO2
NAAQS is met at an ambient air quality monitoring site when the 3-year
average of the annual 99th percentile of daily maximum 1-hour
concentrations is less than or equal to 75 parts per billion. In a year
with 365 days of valid monitoring data, the 99th percentile would be
the fourth highest daily maximum 1-hour value. The 2010 SO2
NAAQS, including this form of determining compliance with the standard,
was upheld by the U.S. Court of Appeals for the District of Columbia
Circuit in Nat'l Envt'l Dev. Ass'n's Clean Air Project v. EPA, 686 F.3d
803 (D.C. Cir. 2012). Because the standard has this form, a single
exceedance does not create a violation of the standard. Instead, at
issue is whether a source operating in compliance with a properly set
longer term average could cause exceedances, and if so the resulting
frequency and magnitude of such exceedances, and in particular whether
the EPA can have reasonable confidence that a properly set longer term
average limit will provide that the average fourth highest daily
maximum value will be at or below 75 ppb. A synopsis of how EPA judges
whether such plans ``provide for attainment,'' based on modeling of
projected allowable emissions and in light of the NAAQS' form for
determining attainment at monitoring sites, follows.
    For plans for SO2 based on 1-hour emission limits, the
standard approach is to conduct modeling using fixed emission rates.
The maximum emission rate that would be modeled to result in attainment
(i.e., in an ``average year'' \1\ shows three, not four days with
maximum hourly levels exceeding 75 ppb) is labeled the ``critical
emission value.'' The modeling process for identifying this critical
emissions value inherently considers the numerous variables that affect
ambient concentrations of SO2, such as meteorological data,
background concentrations, and topography. In the standard approach,
the state would then provide for attainment by setting a continuously
applicable 1-hour emission limit at this critical emission value.
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    \1\ An ``average year'' is used to mean a year with average air
quality. While 40 CFR 50 appendix T provides for averaging three
years of 99th percentile daily maximum 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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    The EPA recognizes that some sources have highly variable
emissions, for example due to variations in fuel sulfur content and
operating rate, that can make it extremely difficult, even with a well-
designed control strategy, to ensure in practice that emissions for any
given hour do not exceed the critical emission value. The EPA also
acknowledges the concern that longer term emission limits can allow
short periods with emissions above the ``critical emissions value,''
which, if coincident with meteorological conditions conducive to high
SO2 concentrations, could in turn create the possibility of
a NAAQS exceedance occurring on a day when an exceedance would not have
occurred if emissions were continuously controlled at the level
corresponding to the critical emission value. However, for several
reasons, the EPA believes that the approach recommended in its April
2014 guidance document suitably addresses this concern. First, from a
practical perspective, the EPA expects the actual emission profile of a
source subject to an appropriately set longer term average limit to be
similar to the emission profile of a source subject to an analogous 1-
hour average limit. The 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, the EPA expects either form of emission limit to yield
comparable air quality.
    Second, from a more theoretical perspective, the EPA has compared
the likely air quality with a source having maximum allowable emissions
under an appropriately set longer term limit, as compared to the likely
air quality with the source having maximum allowable emissions under
the comparable 1-hour limit. In this comparison, in the 1-hour average
limit scenario, the source is presumed at all times to emit at the
critical emission level, and in the longer term average limit scenario,
the source is presumed occasionally to emit more than the critical
emission value but on average, and presumably at most times, to emit
well below the critical emission value. In an ``average year,''
compliance with the 1-hour limit is expected to result in three
exceedance days (i.e., three days with hourly values above 75 ppb) and
a fourth day with a maximum hourly value at 75 ppb. By comparison, with
the source complying with a longer term limit, it is possible that
additional exceedances would occur that would not occur in the 1-hour
limit scenario (if emissions exceed the critical emission value at
times when meteorology is conducive to poor air quality). However, this
comparison must also factor in the likelihood that exceedances that
would be expected in the 1-hour limit scenario would not occur in the
longer term limit scenario. This result arises because the longer term
limit requires lower emissions most of the time (because the limit is
set well below the critical emission value), so a source complying with
an appropriately set longer term limit is likely to have lower
emissions at critical times than would be the case if the source were
emitting as allowed with a 1-hour limit.
    As a hypothetical example to illustrate these points, suppose a
source that always emits 1000 pounds of SO2 per hour, which
results in air quality at the level of the NAAQS (i.e., results in a
design value of 75 ppb). Suppose further that in an ``average year,''
these emissions cause the 5 highest maximum daily average 1-hour
concentrations to be 100 ppb, 90 ppb, 80 ppb, 75 ppb, and 70 ppb. Then
suppose that the source becomes subject to a 30-day average emission
limit of 700 pounds per hour. It is theoretically possible for a source
meeting this limit to have emissions that occasionally exceed 1000
pounds per hour, but with a typical emissions profile emissions would
much more commonly be between 600 and 800 pounds per hour. In this
simplified example, assume a zero background concentration, which
allows one to assume a linear relationship between emissions and air
quality. (A nonzero background concentration would make the mathematics
more difficult but would give similar results.) Air quality

will depend on what emissions happen on what critical hours, but
suppose that emissions at the relevant times on these 5 days are 800
pounds/hour, 1100 pounds per hour, 500 pounds per hour, 900 pounds per
hour, and 1200 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 and
fourth days would not have exceedances that otherwise would have
occurred. In this example, the fourth highest maximum daily
concentration under the 30-day average would be 67.5 ppb.
    This simplified example illustrates the findings of a more
complicated statistical analysis that EPA conducted using a range of
scenarios using actual plant data. As described in appendix B of EPA's
April 2014 SO2 nonattainment planning guidance, the 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 April 2014 guidance, the EPA expects that an emission profile with
maximum allowable emissions under an appropriately set comparably
stringent 30-day average limit is likely to have the net effect of
having a lower number of exceedances and better air quality than an
emission profile with maximum allowable emissions under a 1-hour
emission limit at the critical emission value. This result provides a
compelling policy rationale for allowing the use of a longer averaging
period, in appropriate circumstances where the facts indicate this
result can be expected to occur.
    The question then becomes whether this approach--which is likely to
produce a lower number of overall exceedances even though it may
produce some unexpected exceedances above the critical emission value--
meets the requirement in section 110(a)(1) and 172(c)(1) for state
implementation plans to ``provide for attainment'' of the NAAQS. For
SO2, as for other pollutants, it is generally impossible to
design a nonattainment plan in the present that will guarantee that
attainment will occur in the future. A variety of factors can cause a
well-designed attainment plan to fail and unexpectedly not result in
attainment, for example if meteorology occurs that is more conducive to
poor air quality than was anticipated in the plan. Therefore, in
determining whether a plan meets the requirement to provide for
attainment, the EPA's task is commonly to judge not whether the plan
provides absolute certainty that attainment will in fact occur, but
rather whether the plan provides an adequate level of confidence of
prospective NAAQS attainment. From this perspective, in evaluating use
of a 30-day average limit, EPA must weigh the likely net effect on air
quality. Such an evaluation must consider the risk that occasions with
meteorology conducive to high concentrations will have elevated
emissions leading to exceedances that would not otherwise have
occurred, and must also weigh the likelihood that the requirement for
lower emissions on average will result in days not having exceedances
that would have been expected with emissions at the critical emissions
value. Additional policy considerations, such as in this case the
desirability of accommodating real world emissions variability without
significant risk of violations, are also appropriate factors for the
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 the EPA's April 2014 guidance, will
result in attainment, the EPA believes as a general matter that such
limits, if appropriately determined, can reasonably be considered to
provide for attainment of the 2010 SO2 NAAQS.
    The April 2014 guidance offers specific recommendations for
determining an appropriate longer term average limit. The recommended
method starts with determination of the 1-hour emission limit that
would provide for attainment (i.e., the critical emission value), and
applies an adjustment factor to determine the (lower) level of the
longer term average emission limit that would be estimated to have a
stringency comparable to the otherwise necessary 1-hour emission limit.
This method uses a database of continuous emission data reflecting the
type of control that the source will be using to comply with the SIP
emission limits, which (if compliance requires new controls) may
require use of an emission database from another source. The
recommended method involves using these data to compute a complete set
of emission averages, computed according to the averaging time and
averaging procedures of the prospective emission limitation. In this
recommended method, the ratio of the 99th percentile among these long
term averages to the 99th percentile of the 1-hour values represents an
adjustment factor that may be multiplied by the candidate 1-hour
emission limit to determine a longer term average emission limit that
may be considered comparably stringent.\2\ The April 2014 guidance also
addresses a variety of related topics, such as the potential utility of
setting supplemental emission limits, such as mass-based limits, to
reduce the likelihood and/or magnitude of elevated emission levels that
might occur under the longer term emission rate limit.
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    \2\ For example, if the critical emission value is 1000 pounds
of SO2 per hour, and a suitable adjustment factor is
determined to be 70 percent, the recommended longer term average
limit would be 700 pounds per hour.
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    Preferred air quality models for use in regulatory applications are
described in appendix A of the EPA's Guideline on Air Quality Models
(40 CFR part 51, appendix W (appendix W)). In 2005, the EPA promulgated
the American Meteorological Society/Environmental Protection Agency
Regulatory Model (AERMOD) as the Agency's preferred near-field
dispersion modeling for a wide range of regulatory applications
addressing stationary sources (for example in estimating SO2
concentrations) in all types of terrain based on extensive
developmental and performance evaluation. Supplemental guidance on
modeling for purposes of demonstrating attainment of the SO2
standard is provided in appendix A to the April 2014 guidance. Appendix
A provides extensive guidance on the modeling domain, the source
inputs, assorted types of meteorological data, and background
concentrations. Consistency with the recommendations in this guidance
is generally necessary for the attainment demonstration to offer
adequately reliable assurance that the plan provides for attainment.
    As stated previously, attainment demonstrations for the 2010 1-hour
primary SO2 NAAQS must demonstrate future attainment and
maintenance of the NAAQS in the entire area designated as nonattainment
(i.e., not just at the violating monitor) by using air quality
dispersion modeling (see appendix W to 40 CFR part 51) to show that the
mix of sources and enforceable control measures and emission rates in
an identified area will not lead to a violation of the SO2
NAAQS. For a short-term (i.e., 1-hour) standard, the 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
SO2.
    The meteorological data used in the analysis should generally be
processed with the most recent version of AERMET. Estimated
concentrations should include ambient background concentrations, should
follow the form of the standard, and should be calculated as described
in section <IP_ADDRESS> of the August 23, 2010 clarification memo
``Applicability of Appendix W Modeling Guidance for the 1-hr
SO2 National Ambient Air Quality Standard'' (U. S. EPA,
2010a) (August 2010 1-hour SO2 clarification memo).

IV. Review of Modeled Attainment Plan

    The following discussion evaluates various features of the modeling
that Iowa used in its attainment demonstration.

A. Model Selection

    Iowa's attainment demonstration used the most current version of
AERMOD available during each phase of its analysis (i.e., the
determining sources culpable to nonattainment phase and the control
strategy phase). As previously stated, AERMOD is the preferred model
for this application. The final control strategy modeling analysis
utilized version 15181. The state asserts that all analyses were
conducted with EPA's regulatory default options and considering EPA's
guidance documents including the August 2010 1-hour SO2
clarification memo; the ``Additional Clarification Regarding
Application of Appendix W Modeling Guidance for the 1-hour
NO2 National Ambient Air Quality Standard'' memo (March 2011
1-hour NO2 clarification memo); and the December 2013
SO2 Modeling Technical Assistance Document (TAD).\3\ The
receptor grid was centered on the Musser Park monitor, and extended out
to the edges of the nonattainment area.\4\ Those portions of the fence
lines of the facilities being evaluated that fell outside of the
nonattainment area were omitted from the analysis. Finer grid spacing
of 50 meters was used to resolve modeled impacts around other nearby
individual facilities included in the analyses, but finer grid spacing
was applied only around sources within the confines of the
nonattainment area. Receptors were excluded from areas within the
property boundaries of each facility in the analysis. The most recent
version of AERMAP (11103) was used to import terrain and source
elevations from the National Elevation Dataset (NED). All building
downwash analyses were conducted using the most recent version (04274)
of EPA's Building Profile Input Program with Plume Rise Enhancements
(BPIP-Prime). EPA finds the selection and use of these inputs to
AERMOD, AERMAP and BPIP-Prime to be appropriate and in accordance with
appendix W and applicable EPA guidance, such as the TAD.\5\
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    \3\ SO2 NAAQS Designations Modeling Technical
Assistance Document, December 2013.
    \4\ The Musser Park monitor was the violating monitor utilized
during the designations process.
    \5\ The state utilized the December 2013 version of the modeling
TAD when completing its technical analysis. The modeling TAD has
been revised since then; the TAD was revised in February 2016 and
then again in August 2016.
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B. Meteorological Data

    Modeling for the Muscatine 1-hr SO2 nonattainment SIP
was conducted using the surface station and upper air data from the
Davenport airport, and used consecutive years from 2008-2012.\6\ This
represents the most recent, readily available 5-year period at the time
of the initial analysis per section <IP_ADDRESS> of 40 CFR part 51 appendix
W. The most current version of AERMET available during each phase of
the analysis was used. The final control strategy analysis utilized
data processed with AERMET version 14134. The state utilized AERMINUTE
to process 1-minute ASOS wind data to generate hourly average winds for
input to AERMET. EPA finds the selection and use of these inputs to
AERMET to be appropriate and in accordance with appendix W and
applicable EPA guidance, such as the TAD.
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    \6\ A detailed analysis to support the use of the Davenport
meteorological data from the Davenport airport was previously
approved by EPA for use in the PM2.5 Muscatine SIP
analysis. See 79 FR 46742. EPA finds use of the Davenport airport
site meteorological data to be appropriate for the 2010 1-hr
SO2 Muscatine SIP.
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C. Emissions Data

    The state utilized information from the technical support document
(TSD) it submitted to EPA during the nonattainment boundary
recommendations to inform which sources needed to be included in its
nonattainment SIP modeling.\7\ The nonattainment boundary analysis
demonstrated that industrial sources along the Mississippi River have a
role in causing or contributing to monitored exceedances at the Musser
Park monitor. Based on this analysis, all major sources of
SO2 emissions within the nonattainment area- Grain
Processing Corporation (GPC), Muscatine Power and Water (MPW), and
Monsanto- were included in the nonattainment SIP control strategy
analysis.
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    \7\ https://www.epa.gov/sulfur-dioxide-designations/so2-designations-round-1-iowa-state-recommendation-and-epa-response and
provided in the docket of this rulemaking.
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    As described in the state's nonattainment SIP, GPC is the largest
source of SO2 within the nonattainment area. GPC is a corn
wet milling facility that processes grain into industrial, beverage,
and fuel-grade ethanol, as well as a variety of grain based food
products, industrial products, and animal feeds. Early in the corn wet
milling process the grain is soaked (steeped) in large tanks where
sulfur containing compounds are added to the steep water to reduce
bacterial growth and help break down the kernels. The sulfur content in
the steep water is generally low but does lead to SO2
emissions from a variety of downstream processes. The state asserts
that 96 percent of the SO2 emissions at GPC is generated by
six coal-fired boilers.
    MPW is a municipal electric generating station. MPW produces steam
through the combustion of fossil fuels, generally coal, and uses the
steam to produce electricity. The largest sources of SO2
operated at MPW are three coal-fired boilers, Units 7, 8, and 9,
serving generators with nameplate capacities of 25, 937, and 175.5
megawatts (MW), respectively. An auxiliary boiler operated at MPW is
not capable of burning coal but has the potential to emit
SO2 when firing on distillate fuel oil.
    Monsanto is a manufacturer and formulator of herbicides for
agricultural use and also produces intermediates for herbicide
manufacturing and formulation. A coal-fired boiler (Boiler #8) used for
the production of on-site heat and power is the largest SO2
source at Monsanto.
    The state excluded four facilities located within the nonattainment
area from the its nonattainment SIP modeling analysis: HNI
Corporation--North Campus (HNI North); H.J. Heinz, L.P. (H.J. Heinz);
Union Tank Car Co. (Union Tank); and HNI Corporation--Central Campus
(HNI Central). As shown in the state's nonattainment SIP, the
cumulative actual emissions from these sources is relatively low; the
sources emitted a combined 0.14 tons of SO2 per year (tpy)
in 2011. See section V.A. Emissions Inventory in this

preamble for the 2011 emissions data from these sources. Additionally,
if the state were to consider the maximum fuel capacity of a source
like Heinz that has two boilers that burn natural gas, it is unlikely
that the SO2 emissions would be sufficient enough to cause a
significant concentration gradient. The TAD indicates that ``other''
sources in the area not causing significant concentration gradients in
the vicinity of the source(s) of interest, should be included in the
modeling via monitored background concentrations. The EPA agrees with
the state's recommendation that these facilities do not need to be
explicitly modeled and that they are adequately characterized in the
background SO2 concentrations. See section IV.E. Background
Concentrations in this preamble for more detailed information regarding
the determination of the background concentration.
    The state also evaluated several major sources of SO2
emissions located outside of the nonattainment area boundary-
MidAmerican Energy Louisa Generating Station (LGS), Gerdau Ameristeel
(Gerdau), SSAB and Linwood and Lafarge. Linwood and Lafarge, located in
Scott County, are approximately 20 km away from the nonattainment area.
The selection of the Davenport monitor to represent background likely
accounts for the emissions from Linwood and Lafarge.\8\ As such,
Linwood and Lafarge were excluded from further consideration. See
section IV.E. Background Concentrations in this preamble for additional
information.
---------------------------------------------------------------------------

    \8\ According to information provided by the state in its
nonattainment SIP, the Davenport monitor is located in Scott County,
approximately 11 km from Linwood and Lafarge, and likely accounts
for the emissions from Lafarge and Linwood.
---------------------------------------------------------------------------

    All included emission units were modeled using their actual stack
parameters and site layout. There were no stacks above formula GEP
(good engineering practice) height. There were stacks greater than 65
meters at GPC, MPW, and LGS and each of those stacks were adjacent to
tall buildings making the formula height taller than the actual stack
height. Therefore, each of those stacks were modeled at their actual
stack heights.
    Per EPA's April 2014 guidance, the use of allowable emissions and
the modeling of intermittent emissions (for sources such as emergency
generators and startup/shutdown emissions), for the purpose of modeling
for SO2 attainment demonstrations, should follow the
recommendations in EPA's March 2011 1-hour NO2 clarification
memo (even though it was specific to NO2). The state's
nonattainment SIP indicates that it addressed modeling intermittent
sources in according with EPA's March 2011 1-hour NO2
clarification memo, and as such all emission units that operate
intermittently (e.g., emergency engines and fire pumps) were excluded
from the analysis. Additionally, emission units that were limited to
burning a specific fuel occasionally were modeled at emission rates
that represent the fuel that is burned during normal operations. For
example, the two auxiliary boilers (EP2 and EP3) operated by LGS are
limited to burning fuel oil for no more than 48 hours per year. EP2 and
EP3 burn natural gas during normal operations therefore, EP2 and EP3
were modeled at emission rates associated with burning natural gas. EPA
agrees with the state that it is appropriate to exclude these
intermittent emissions (e.g., emergency engines and fire pumps) in the
analysis and modeling the fuel burned during normal operations, as it
is consistent with appendix W and the TAD.
    The state's nonattainment SIP acknowledges that, although
SO2 emissions in and near the nonattainment area are
principally attributable to point sources, a comprehensive emissions
inventory should include an assessment of the other source sectors. The
state asserted that it accomplished this by using estimates of air
emissions for the onroad, nonroad, and nonpoint (area) sources from
EPA's 2011 National Emissions Inventory (NEI) datasets. According to
the state's sector summary analyses using EPA's SCC (source
classification code) full detail data files from the 2011 NEI (version
2, dated March 4, 2015), approximately 2.64 tons of SO2 were
emitted by onroad mobile sources in all of Muscatine County (this
includes areas within and outside of the nonattainment area). Nonroad
mobile sources (which include non-road equipment, locomotives,
commercial marine vessels, and aircraft) contributed approximately 1.99
tpy of SO2. Again, that estimate includes nonroad mobile
sources across all of Muscatine County.
    The state asserts that nonpoint (area) SO2 emissions
were also relatively low, at approximately 18.73 tpy. Of that total,
roughly half (8.92 tons) was associated with emissions mostly from
prescribed fires. As with the mobile sectors, the nonpoint totals also
represent sums across all of Muscatine County. The EPA agrees with the
state's proposal that onroad, nonroad, and nonpoint sources in and near
the Muscatine nonattainment area are adequately represented by
background concentrations included in modeling analysis and that
further consideration of these sectors is unnecessary. See section
IV.E. Background Concentrations and section V. A. Emissions Inventory
in this preamble for more detailed information.

D. Emission Limits

    Section 172(c)(6) of the CAA requires that the state's
nonattainment plan include enforceable emission limitations, and such
other control measures, means or techniques (including economic
incentives such as fees, marketable permits, and auctions of emission
rights), as well as schedules and timetables for compliance, as may be
necessary or appropriate to provide for attainment of such standard in
such area by the applicable attainment date. See General Preamble at
13567-68.
    Part of the review of state's attainment plan must address the use
of these limits, both with respect to the general suitability of using
such limits for the purpose of meeting the requirements of CAA Sec.
172(c)(6) with respect to whether the particular limits included in the
plan have been suitably demonstrated to provide for attainment. The
first subsection that follows addresses the enforceability of the
limits in the plan, and the second subsection that follows addresses in
the limits in particular the longer term average limits (i.e., the 21-
day average limit for MPW).
1. Enforceability
    As specified in section 172(c)(6) and section 110(a)(2)(A) of the
CAA and 75 FR 35520, emission limitations, control measures and other
elements in the SIP must be enforceable by the state and EPA. Working
with GPC, MPW, and Monsanto the state developed an implementable
control strategy designed to ensure expeditious attainment of the 1-hr
SO2 NAAQS. The control strategy establishes source-specific
control measures that include more stringent SO2 emissions
limits, new control devices, and process changes. The state's
nonattainment SIP includes these control measures with specific
timetables for implementation, establishes minimum performance
criteria, and provides schedules for completing verification processes.
See section V. B. RACM/RACT in this preamble for additional
information. New air construction permits issued to GPC, MPW, and
Monsanto include emissions limits, timetables for compliance, and
enforcement criteria and are the enforceable documents included in the
state's nonattainment SIP that EPA is proposing to approve. As noted in
the nonattainment SIP, the

state has the authority to implement each of the permits. Each permit
includes notification, reporting, and recordkeeping requirements. The
facilities must, for example, notify the state when they initiate and
when they complete construction. Each permit also contains performance
testing (emissions testing) obligations with specific schedules,
methods, and frequencies for compliance. Each performance test must be
approved by the state and a testing protocol must be submitted to the
state in advance of the compliance demonstration. Results of the tests
must be submitted in writing to the state in the form of a
comprehensive report within six weeks of the completion of any testing.
Additionally, GPC, MPW, and Monsanto are major sources under the Title
V operating permit program and must submit semi-annual monitoring
reports by September 30 and March 31, and an annual compliance
certification by March 31, of each year. The state also inspects Title
V sources at a minimum of every two years. In summary, the state has a
comprehensive program to identify sources of violations and to
undertake follow-up for compliance and enforcement.
    As noted in the state's May 26, 2016, submittal letter, Iowa was
included in the agency's Response to Petition for Rulemaking;
Restatement and Update of EPA's SSM Policy Applicable to SIPs; Findings
of Substantial Inadequacy; and SIP Calls To Amend Provisions Applying
to Excess Emissions During Periods of Startup, Shutdown and Malfunction
(SSM SIP call) published June 12, 2015, (80 FR 33839). In the SSM SIP
call, subrule 567--Iowa Administrate Code (IAC) 24.1(1) was found to be
``substantially inadequate'' because it provides that excess emissions
during periods of startup and shutdown are not a violation of an
emission standard if good practices for minimizing emissions are
followed. Each construction permit the state requested be included in
the SIP apart if its control strategy contains SSM language from the
subrule that is subject to the SIP call (Condition 6 of each permit).
As such the state is requested that EPA not act on permit Condition 6
of the included permits. EPA agrees that it would not be appropriate to
approve Condition 6 of each permit into the SIP and propose the
condition's exclusion.
    EPA is proposing to determine that these control measures, and the
permits that contain them, satisfy CAA Sec.  110(a)(2)(A) and 172(c)(6)
requirements and 75 FR 35520. It should be noted that the emission
limit established for MPW in the control strategy of the state's
nonattainment plan relies on a pound/hour (lb/hr) limit expressed an
averaging time (e.g. as 21-day average) across multiple units.\9\ In
accordance with EPA policy, the 21-day average limit is set at a lower
level than the emission rate used in the attainment demonstration; the
relationship between these two values is discussed in more detail in
the following section.
---------------------------------------------------------------------------

    \9\ The MPW permit included as appendix C to the nonattainment
SIP specifies that compliance with the emission standard of 1153 lb/
hr of SO2 shall be demonstrated through the use a
Continuous Emissions Monitoring System (CEMS) and shall be
determined on a 21-day rolling average bases. The limit includes
startup, shutdown and malfunction emissions. Compliance with the
emission limit shall be demonstrated using the formula found in
Permit Condition 15.8. The emission limit became effective January
1, 2017.
---------------------------------------------------------------------------

2. Longer Term Averaging
    As discussed in the April 2014 guidance, and in section III.
Attainment Demonstration and Longer Term Averaging in this preamble,
EPA has recommended that averaging times in SIP emission limits should
not exceed the applicable NAAQS averaging time, in this case 1-hour,
however, EPA has acknowledged that a 1-hr emission rate limit may be
difficult to achieve at some facilities. As such EPA provided guidance
for establishing longer term averaging limits based on a supportable
downward adjustment of the critical emissions value. The critical
emissions value is the 1-hr averaged emission rate that dispersion
modeling predicts would attain the NAAQS.
    The control strategy included in the state's nonattainment SIP
allows MPW to meet a compliance formula based on a 21-day averaging
period across multiple units running alone or in combination. The
formula incorporates a weighting function derived from the modeling
results of the individual units (Units 7, 8 and 9), and downward
adjustments of the critical emissions values. A separate downward
adjustment was calculated for each unit using five years of unit-
specific CEMS data, 2010-2014; the state considered this data to be
representative of the boilers' operations into the future, and reflect
the fact that each unit is emitting from a separate stack. The 1-hour
emissions value of 1,153 lbs/hr used in the formula incorporates the
adjustment to a longer term limit according to the ratio of the 99th
percentile 21-day average emission rate to the 99th percentile 1-hr
emission rates from the CEMS data. Because the 1,153 lbs/hr value was
derived from all 3 units operating together additional model runs were
needed to ensure the formula was protective under other operating
scenarios, with combinations of one or two units operating. The formula
provides flexibility for MPW to run their three coal units alone or in
combination in such a way that the NAAQS will be protected at all
times. Because the units have different dispersion characteristics, the
formula weighs each unit's individual emissions such that the critical
modeled value in the formula is always protected.
    To determine the longer term average limit, the state determined
the individual variability of each unit from the 2010-2014 CEMS data as
described above. The variability value ratios of the 99th percentile
21-day average and 99th percentile hourly values were 0.71, 0.90, 0.63
for the three units respectively. The state determined a critical value
for each of these units individually using their respective variability
and stack characteristics. In the first modeling scenario (the ``All''
run) the state determined the hourly critical values for Units 7,8,9 as
250 lbs/hr, 1000 lbs/hr, and 120 lbs/hr respectively, so 1,370 lbs/hr
total from the 3 units. Applying the individual unit variability, the
equivalent 21 day limits would be 177.5 lbs/hr, 900.0 lbs/hr, and 75.6
lbs/hr respectively which when added together is 1,153 lbs/hr, the
value that becomes the basis of the compliance formula. The state then
modeled 7 combinations of emissions scenarios using the individual unit
stack characteristics that all demonstrated compliance with the NAAQS
and accounted for individual variability of each unit. These scenarios
consisted of 3 model runs where the individual units were operating
alone and 4 model runs with various combinations of units operating.
Each run had its own hourly critical modeled value demonstrating
compliance and these 7 runs formed the basis for the weights in the
formula to ensure 1,153 lbs/hr was always protective of all the
individual critical values modeled. This provided modeled emission
rates such that a weighted formula could be derived such that any
combination of emissions from the three individual units would always
be at or below the value of 1,153 lbs/hr as expressed in the formula.
Because the stacks have different dispersion characteristics and the
modeled scenarios have different critical emission values, the formula
derived contains different weights or multipliers for each unit's
actual hourly emissions, but the weights are such that no individual
unit operating alone or a combination of units will cause a NAAQS
violation as long as the formula criteria as expressed in the permit
are

met.\10\ Table 1 shows that during each operational scenario at MPW,
combined with the control strategies for GPC and Monsanto, the current
maximum allowable permitted emission rates from LGS, and background
concentrations, will result in attainment of the 1-hour SO2
NAAQS.
---------------------------------------------------------------------------

    \10\ The formula for MPW, as specified in their permit is as
follows:
    ``The owner or operator shall maintain a file of computations to
show the total hourly emission level for SO2. The owner
or operator shall use the total hourly SO2 emission rates
to calculate and record the average SO2 emission rate for
each calendar day. Effective January 1, 2017, the owner or operator
shall use the daily average SO2 emission rates to
demonstrate compliance with the 21-day rolling average as calculated
below: SO2 = 2.03*(Unit 7) + 0.84*(Unit 8) + 1.22*(Unit
9) Where, SO2 = total emissions, in pounds per hour, of
sulfur dioxide from Unit 7, Unit 8 and Unit 9
    Unit 7 = 24-hour average sulfur dioxide emission rate, lb/hr,
for Unit 7
    Unit 8 = 24-hour average sulfur dioxide emission rate, lb/hr,
for Unit 8
    Unit 9 = 24-hour average sulfur dioxide emission rate, lb/hr,
for Unit 9.

  Table 1--Cumulative Modeling Results With Each MPW Operating Scenario
------------------------------------------------------------------------
                                            Cumulative      1-hour SO2
         MPW operating scenario            model result    NAAQS ([mu]g/
                                            ([mu]g/m3)          m3)
------------------------------------------------------------------------
All.....................................          182.76             196
U9 Off..................................          182.71  ..............
U8 Off..................................          183.66  ..............
U7 Off..................................          182.88  ..............
U7 Only.................................          183.96  ..............
U8 Only.................................          181.86  ..............
U9 Only.................................          187.78  ..............
------------------------------------------------------------------------

    Based on a review of the state's submittal, the EPA believes that
the 21-day average limit for MPW provides a suitable alternative to
establishing a 1-hour average emission limit for this source. The state
has used a suitable data base in an appropriate manner and has thereby
applied an appropriate adjustment, yielding an emission limit formula
that has comparable stringency to the 1-hour average limit that the
state determined would otherwise have been necessary to provide for
attainment. While the 21-day average limit allows occasions in which
emissions may be higher than the level that would be allowed with the
1-hour limit, the state's limit compensates by requiring average
emissions to be lower than the level that would otherwise have been
required by a 1-hour average limit. For reasons described above and
explained in more detail in EPA's April 2014 guidance, EPA finds that
appropriately set longer term average limits provide a reasonable basis
by which nonattainment plans may provide for attainment. Based on its
review of this general information as well as the particular
information in state's plan, the EPA finds that the 21-day average
limit formula for MPW in combination with other limitations in the
state's plan, will provide for attainment of the NAAQS.

E. Background Concentrations

    The state reviewed its statewide SO2 monitoring network
to determine an appropriate background monitoring location- the
Davenport SO2 monitoring site. As noted by the state, the
ideal background location chosen represents the contributions from all
sources not explicitly modeled. Because the monitoring locations in
Muscatine, IA are impacted significantly by sources that were included
in the modeling analysis, those monitors were eliminated as an option
to represent the background concentrations in the area. Of the
remaining monitor locations, two are situated adjacent to
industrialized areas (Cedar Rapids and Clinton), and, as such, would
likely be an overestimate of the concentrations caused by background
sources. The state determined that the Des Moines and Lake Sugema
monitors were impacted by less SO2 emissions than what would
be represented by the background for the Muscatine nonattainment area--
and, as such, would likely be an underestimation of the concentrations
of SO2 caused by background sources.\11\
---------------------------------------------------------------------------

    \11\ The Des Moines monitor is approximately 5 km from the
nearest SO2 source. The county emissions are
approximately 163 tpy. The Lake Sugema monitor is more than 10 km
away from the nearest SO2 source. The state's
nonattainment SIP indicates that are no reported major or minor
sources of SO2 emissions in the county.
---------------------------------------------------------------------------

    The state determined that the Davenport SO2 monitoring
location was appropriate for estimating background concentrations for
the following reasons: (1) The Davenport monitor is the nearest
location to the nonattainment area (other than those monitors located
in Muscatine already excluded); (2) the Davenport monitor is near a
moderately industrialized area, but is not situated adjacent to those
sources of emissions; (3) the Davenport monitor is in a county with a
moderate amount of SO2 emissions; and (4) using the
Davenport monitor is consistent with the meteorological data used for
the analysis. For these reasons the state believed that the Davenport
monitoring location could account for the sources screened out of the
control strategy such as emissions from natural sources, major and
minor point sources not included in the analysis, mobile (onroad and
nonroad) sources, and nonpoint sources.
    The state utilized temporally varying background concentrations by
hour and season from the Davenport SO2 monitoring location
to account for contributions to the predicted impacts from background
SO2 sources. To account for seasonal and diurnal variations
in the background levels, the state based the background concentration
on the average diurnal and seasonal concentration pattern observed at
the Davenport monitor during the years 2011-2013. For the years 2011-
2013, the 99th percentile monitor concentration was calculated for each
hour of the day by season and then averaged across the three years.\12\
---------------------------------------------------------------------------

    \12\ The EPA's SO2 National Ambient Air Quality
Standards Designations Modeling TAD describes an appropriate
methodology of calculating temporally varying background monitored
concentrations by hour of day and season (excluding periods when the
source in question is expected to impact the monitored
concentration). The methodology is to use the 99th percentile
concentration for each hour of the day by season and average across
3 years, excluding periods when the dominant source(s) are
influencing the monitored concentration (i.e., 99th percel1tile, or
4th highest, concentrations for hour l for January or winter, 99th
percentile concentrations for hour 2 for January or winter, etc.).
---------------------------------------------------------------------------

    The state also averaged the 2011-2013 design values for Cedar
Rapids, Davenport, Des Moines, and Lake Sugema to determine if that
number,

10.5 ppb, would be appropriate as background. The state called this the
Tier 1 value. The Tier 1 value of 10.5 ppb is higher than all but one
of the seasonal/diurnal concentrations. This shows that the use of the
Tier 1 value for all hours and seasons would have been too high to
represent the variable background concentrations. The EPA agrees with
the state's proposal that the method of using temporally varying
background monitor concentrations by hour and season from the Davenport
monitoring location, as it is calculated from the 99th percentile, is
appropriate.

F. Summary of Results

    The modeling analysis was conducted in two phases. The first phase
(Phase 1) of the analysis was a screening analysis to determine the
sources that needed to be included in the control strategy analysis.
The second phase (Phase 2) of the analysis was used to develop the
control strategy and included all significant sources identified in
Phase 1.
1. Phase 1--Preliminary Analysis
    This phase was accomplished by modeling actual emissions from GPC,
MPW, Monsanto, and LGS and allowable emissions from SSAB and Gerdau and
then determining the percentage of predicted NAAQS exceedances within
the nonattainment area to which each facility significantly
contributed. In this way, the state determined that GPC contributed to
100 percent of the NAAQS exceedances, MPW contributed to approximately
25 percent of the NAAQS exceedances, Monsanto contributed to
approximately 1 percent of the NAAQS exceedances, and LGS contributed
to approximately 5 percent of the NAAQS exceedances. Both SSAB and
Gerdau each modeled less than a 1 percent contribution to the NAAQS
exceedance days within the nonattainment area. Therefore, only GPC,
MPW, Monsanto and LGS were determined to have enough potential
contribution to NAAQS exceedances to be evaluated further.\13\
---------------------------------------------------------------------------

    \13\ The LGS facility is located immediately south of the
nonattainment area. During the designations process, this source was
shown to be insignificant during predicted exceedances at the Musser
Park monitor, but as it was possible that the source could cause a
concentration gradient in the vicinity of the southern portion of
the nonattainment area, it was included in the analysis.
---------------------------------------------------------------------------

    The state then further subdivided the sources by classifying the
significant contributors as either a primary or a secondary
contributor. If the facility's significant contribution to the
predicted NAAQS exceedance was greater than or equal to half of the
total concentration (minus background) it was considered a primary
contributor. If the facility's contribution was less than half of the
total concentration, but still more than the Significant Impact Level
(SIL) it was considered a secondary contributor.\14\
---------------------------------------------------------------------------

    \14\ Per EPA's August 23, 2010, ``Guidance Concerning the
Implementation of the 1-hour SO2 NAAQS for the Prevention
of Significant Deterioration Program'', the SIL is 3 ppb. The EPA
plans ``to undertake rulemaking to adopt a 1-hour SO2 SIL
value. However, until such time as a 1-hour SO2 SIL is
defined in the PSD regulations, we are providing an interim SIL of 3
ppb, which we intend to use as a screening tool for completing the
required air quality analyses for the new 1-hour SO2 SIL
NAAQS under the federal PSD program at 40 CFR 52.21. We are also
making the interim SIL available to States with EPA-approved
implementation plans containing a PSD program to use at their
discretion.'' The SIL remains an interim SIL until rulemaking is
complete.
---------------------------------------------------------------------------

    GPC was identified as a primary contributor to all predicted NAAQS
exceedances within the nonattainment area. GPC's max potential
contribution was estimated as 3,180 [micro]g/m\3\ (or approximately
1,223 ppb).\15\ GPC's contribution to the predicted NAAQS exceedance
was greater than or equal to half of the total concentration (minus
background) 100 percent of the time.
---------------------------------------------------------------------------

    \15\ To convert from [micro]g/m\3\ to ppb, the [micro]g/m\3\
value was divided by 2.6.
---------------------------------------------------------------------------

    MPW, Monsanto and LGS were identified as secondary contributors.
MPW's max potential contribution was estimated as 107 [micro]g/m\3\ (or
approximately 41 ppb). MPW's contribution to the predicted NAAQS
exceedance was less than half of the total concentration, but still
more than SIL (minus background) 26 percent of the time. Monsanto's max
potential contribution was estimated as 28 [micro]g/m\3\ (or
approximately 11 ppb). Monsanto's contribution to the predicted NAAQS
exceedance was less than half of the total concentration, but still
more than SIL (minus background) less than 1 percent of the time. LGS's
maximum potential contribution was estimated as 59 [micro]g/m\3\ (or
approximately 22.7 ppb). LGS's contribution to the predicted NAAQS
exceedance was less than half of the total concentration, but still
more than SIL (minus background) 2 percent of the time. As such, only
GPC, MPW, Monsanto and LGS were included in the second phase of the
analysis.
2. Phase 2--Control Strategy Development
    Sources identified in Phase 1 (GPC, MPW, Monsanto, and LGS) as
being significant contributors were modeled at their maximum permitted
allowable emission rates. Using the process summarized below, more
restrictive maximum permitted emission rates were developed where
necessary to ensure modeled attainment.
    To start its Phase 2 analysis, the state provided GPC with a model
input file that included its emission units as well as the exceedance
receptors to which it contributed. The state's nonattainment SIP
submittal indicates that GPC reviewed the input data for accuracy and
then mitigated all modeled exceedances caused by the GPC facility
alone.
    The remaining facilities (MPW, Monsanto, and LGS) were then added
to the analysis with their maximum permitted allowable emission rates
and the cumulative impacts were determined across the entire
nonattainment area. According to the state's nonattainment SIP
submittal, the remaining predicted exceedances were then discussed with
Monsanto and MPW. As a result of those discussions, additional control
measures were developed for those facilities and are incorporated in
construction permits submitted as part of the SIP revision. See section
V.B. in this preamble for more information regarding the control
measures.
    Monsanto proposed to decrease the emission rate for Boiler 8 at its
facility to mitigate exceedances just north of its property. MPW
proposed multiple model scenarios with combined operation of Units 7,
8, and 9. Regardless of the operational scenario, the unit/units were
modeled at an equation cap of 1,153 lb/hr SO2. The model
results varied depending on which combination of boilers was running.
Each of the modeling scenarios (with background included) resulted in
concentrations below the 1-hour SO2 NAAQS. The highest
modeled SO2 concentration was 187.87 ug/m\3\ which included
the operation of just Unit 9 at MPW. See section IV.D.2. Longer Term
Averaging limits, in this preamble, for more discussion of the equation
used to determine compliance with the NAAQS for each MPW modeling
scenario.
    These results indicate that the controls established in the
construction permits for MPW, GPC and Monsanto result in attainment of
the NAAQS, and as such, additional controls were not necessary for LGS
in order for the area to attain. EPA agrees with the state's
determination that its control strategy analysis results in modeled
concentrations throughout the nonattainment area that are at or below
75 ppb/196.4 ug/m\3\. Based upon monitoring data discussed in section
V.B. RACM/RACT in this preamble, EPA expects that the Muscatine area
will attain by the attainment date, August 5, 2018.

V. Review of Other Plan Requirements

A. Emissions Inventory and the Quantification of Emissions

    Section 172(c)(3) of the CAA requires that the state's
nonattainment plan include a comprehensive, accurate, current inventory
of actual emissions from all sources of the relevant pollutant or
pollutants in such area, including such periodic revisions as the
Administrator may determine necessary to assure that the requirements
of this part are met. Section 172(c)(4) of the CAA requires that the
state's nonattainment plan expressly identify and quantify the
emissions, if any, of any such pollutant or pollutants which will be
allowed, in accordance with section 703(a)(1)(B) of the CAA, from the
construction and operation of major new or modified stationary sources
in each such area. The plan shall demonstrate to the satisfaction of
the Administrator that the emissions quantified for this purpose will
be consistent with the achievement of reasonable further progress and
will not interfere with attainment of the applicable National Ambient
Air Quality Standard by the applicable attainment date.
    The emissions inventory and source emission rate data for an area
serve as the foundation for air quality modeling and other analyses
that enable states to: (1) estimate the degree to which different
sources within a nonattainment area contribute to violations within the
affected area; and (2) assess the expected improvement in air quality
within the nonattainment area due to the adoption and implementation of
control measures. As noted above, the state must develop and submit to
EPA a comprehensive, accurate and current inventory of actual emissions
from all sources of SO2 emissions in each nonattainment
area, as well as any sources located outside the nonattainment area
which may affect attainment in the area. See the April 2014 guidance.
Additional emission inventory information was discussed in section IV.C
Emissions Data in this preamble. A brief summary is provided later in
this action.
    The base year inventory establishes a baseline that is used to
evaluate emissions reductions achieved by the control strategy and to
assess reasonable further progress requirements. The state's
nonattainment SIP noted that, at the time, the most recent and
available triennial inventory year was 2011 and the stated found that
it served as a suitable base year. Table 2 provides the 2011
SO2 emissions inventory data for sources within and outside
of the nonattainment the area (data have been rounded to the nearest
whole number).

       Table 2--Base Line Emission Inventory for the Muscatine, IA
                           Nonattainment Area
------------------------------------------------------------------------
                                                             2011 SO2
                                         Facility            emissions
                                                               (tpy)
------------------------------------------------------------------------
           Base Line Emissions Inventory for the Muscatine NAA
------------------------------------------------------------------------
Inside of the NAA..............  Grain Processing                 10,810
                                  Corporation.
                                 Muscatine Power and               2,374
                                  Water.
                                 Monsanto...............             537
                                 HNI Corp.--North Campus              <1
                                 HNI Corp.--Central                   <1
                                  Campus.
                                 H.J. Heinz L.P.........              <1
                                 Union Tank Car Co......              <1
Outside of the NAA.............  Louisa Generating                 7,304
                                  Station.
All of Muscatine County........  Onroad Mobile..........               3
                                 Nonroad Mobile.........               2
                                 Area Sources...........              10
                                 Fires..................               9
                                                         ---------------
    Total......................  .......................          21,049
------------------------------------------------------------------------

    Although not part of the state's discussion of its 2011 baseline
emissions inventory, the state's nonattainment SIP also provides 2013
SO2 data for Gerdau and SSAB in Muscatine County and Linwood
and Lafarge in Scott County. However, the state provided this as a sum
for the sources by county (e.g., the sum of Gerdau and SSAB was 254 tpy
and the sum of Linwood and Lafarge was 1,539 tpy). Gerdau and SSAB are
approximately 8-9 km away from the nonattainment boundary and Linwood
and Lafarge are approximately 20 km away from the nonattainment area
boundary.
    As already noted, the state's nonattainment SIP must identify and
quantify the emissions which will be allowed from the construction and
operation of major new or modified stationary sources in the area (see
CAA Sec.  172(c)(4)). The state must demonstrate that such emissions
will be consistent with RFP requirements and will not interfere with
attainment of the 1-hr SO2 NAAQS. These requirements are met
by the states preconstruction permitting program and implementation of
the Nonattainment New Source Review Rules (NNSR). See section C.
Nonattainment New Source Review in this preamble for more information.
    According to EPA's April 2014 SO2 guidance, the SIP
should also include a projected attainment year inventory that includes
estimated emissions for all emission sources of SO2 that
were determined to have an impact on the affected nonattainment area
for the year in which the area is expected to attain the standard,
consistent with the attainment demonstration. The inventory should
reflect projected emissions for the attainment year for all
SO2 sources in the nonattainment area. The state's
nonattainment SIP provided a projected inventory only for the
controlled sources, as provided in table 3. The inventory was developed
assuming each SO2 source operates 8,760 hours per year at
its permitted maximum allowable emission rate.\16\
---------------------------------------------------------------------------

    \16\ The projections don't consider operational, physical,
supply/demand, or other factors that typically curb actual emissions
to values below the maximum permitted allowable rate. There is
potential for the actual attainment-year emissions to be lower than
those in Table 2.

 Table 3--Projected Allowable Annual SO2 Emissions From Control Strategy
                                 Sources
------------------------------------------------------------------------
                                                               2018 SO2
                                                               emissions
                          Facility                               (tpy)

------------------------------------------------------------------------
           Projected 2018 Emissions for the Controlled Sources
------------------------------------------------------------------------
Grain Processing Corporation................................         167
Muscatine Power and Water...................................       5,051
Monsanto....................................................       1,196
------------------------------------------------------------------------

    The EPA is proposing to determine that the state has met the
requirements of CAA Sec.  172(c)(3) and 172(c)(4).

B. RACM/RACT

    CAA Sec.  172(c)(1) requires that the state's nonattainment plan
provide for the implementation of all RACM as expeditiously as
practicable (including such reductions in emissions from existing
sources in the area as may be obtained through the adoption, at a
minimum, of RACT) and shall provide for attainment of the NAAQS. The
state's plan for attaining the 1-hour SO2 NAAQS in the
Muscatine nonattainment area is based on a variety of control measures
at GPC, MPW and Monsanto. Those measures were included in the state's
nonattainment SIP as construction permits.\17\
---------------------------------------------------------------------------

    \17\ Appendix B, C and D of the state's nonattainment SIP
contain the Federally enforceable air construction permits that
define RACM/RACT requirements. The RACM/RACT limits taken to comply
with the NAAQS are specifically noted in each permit via footnotes
in the permits.
---------------------------------------------------------------------------

    To ensure the SO2 NAAQS is attained, GPC must install
additional scrubbers, comply with new and more stringent SO2
emission limits, and implement process modifications designed to ),
andreduce SO2 emissions across numerous downstream sources.
Table 4-1 of the state's nonattainment SIP lists all the sources
included in the control strategy, contains descriptions of the control
measures, and provides effective dates. Source specific permitted
allowable emission rates, compliance and monitoring obligations,
reporting and recordkeeping requirements, and implementation deadlines
(where not immediately effectively upon permit issuance) are detailed
in each construction permit included with the SIP submittal (appendix B
of the state's nonattainment plan). The GPC control strategy includes
measures at 52 emission points (EP) at the facility. In summary, those
measures include EP0001.0 (Power House Boilers 1-4 and 6-7) is subject
to a more stringent SO2 emission limit based on natural gas
combustion; EP546.0 is subject to a more stringent, source-specific
SO2 limit of .0034 lb/hr; a requirement to continue to add
sodium bisulfate to the steep water instead of sulfur dioxide in order
to reduce SO2 emissions from the steeping operations and
downstream processes; the establishment of source specific
SO2 emission limits at 43 EPs and the required installation
of scrubbers on EP015.0 (Germ Drier Nos. 1 and 2), EP097.0 (Germ Drier
No. 3), EP126.0 (Germ Drier No. 4), EP200N (Corn Steep Tank Nos. 1-30
and the North Wet Corn Drag), EP200S (Corn Steep Tank Nos. 31-62 and
the South Wet Corn Drag), and EP279.0 (Wet Milling Nos. 1-6). The state
expects the installation of the scrubbers to reduce SO2
emissions by up to 90 percent from those units.\18\
---------------------------------------------------------------------------

    \18\ The state's estimation of a 90 percent reduction in
SO2 emissions is based off of the control efficiency
readily achieved by the types of scrubbers being installed.
---------------------------------------------------------------------------

    While the scrubber installations will not be completed by January
1, 2017, the desired target date discussed in EPA's April 2014
guidance, the scrubbers will be operational as expeditiously as
practicable. Based on permitted requirements, three of the six new
scrubbers must be in operation no later than August 30, 2017, with the
final scrubber operational by March 31, 2018. The installation
timetable accommodates factors such as demolition and construction
schedules, structural modifications, ductwork design, and the addition
of scrubber water treatment capacity. The state asserts in its
nonattainment plan that the scrubber installation timeline will not
delay or prevent timely attainment of the 1-hr SO2 NAAQS.
    It should also be noted that, on July 14, 2015, GPC converted all
of its coal-fired boilers to natural gas. The state estimates that the
fuel switch will result in a 96 percent reduction in the facility's
total SO2 emissions. In terms of 2011 data, this fuel switch
eliminated 10,374 tons of SO2 emissions. The state believes,
and the EPA agrees, that the fuel conversion from coal to natural gas
in GPC's boilers has significantly reduced measured ambient
SO2 concentrations in Muscatine, as noted in Table 4. Based
on existing air quality improvements the state projects that monitored
attainment will be achieved by the attainment date. Appendix B of the
state's nonattainment SIP contains the Federally enforceable air
construction permits that define GPC's RACM/RACT requirements.

                                                                    Table 4--Air Monitoring Data From the Musser Park Monitor
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Design values (ppb)                     99th Percentile daily max 1-hr SO2 concentrations (ppb)
-------------------------------------------------------------------------------------------------------------------------------------
                                                                                -----------------------------------------------------------
              Monitor location                     1-hr SO2 NAAQS (ppb)         2011-2013     2012-2014     2013-2015     2014-2016     2011      2012      2013      2014      2015      2016
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Musser Park.................................  75............................          217           194           158           113       248       224       179       180       116        45
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    MPW is subject to several Federal programs that directly or
indirectly affect SO2 emissions, including the Acid Rain
provisions of title IV of the CAA, the Cross State Air Pollution Rule
(CSAPR), and the CAA section 112 Maximum Achievable Control Technology
regulations more commonly known as the Mercury and Air Toxics
Standards. However, the state did not rely on these Federal programs
alone to address SO2 emissions. Instead, as per the states
control strategy, MPW will comply with new SO2 emission
limits that provide for attainment of the NAAQS. The control measures,
described in table 4-2 of the state's nonattainment SIP, account for
seven possible operating scenarios involving the three coal-fired
boilers (Units 7, 8, and 9). Permit No. 74-A-175-S3, issued to the
facility in 2013, shows the SO2 emission limit for Units 7
and 8 was a combined maximum of 2,772 lb/hr. Permit No. 80-A-191-P2,
issued to the facility in 2013, shows the SO2 emission limit
for Unit 9 was 0.56 lb/MMBtu (a maximum daily average). Permit No. 80-
A-191-P4, issued to the facility in 2016 as part of the control
strategy of

the state's nonattainment SIP, shows the combined SO2
emissions from Units 7-9 must be less than 1,153 lbs/hr.
    The control strategy for MPW also addresses emission reductions
from EP60 (Auxiliary Boiler). A permit issued to the facility in 2013,
Permit No. 13-A-152, for the Auxiliary Boiler required that
SO2 emissions be limited to limited 0.44 lbs/MMBtu
(expressed as the average of 3 runs) when burning fuel oil, and to 500
ppm by volume when burning natural gas or propane.\19 20\ The permit
issued to the facility in 2016, as part of the control strategy, Permit
No. 13-A-152-S1, requires that the SO2 emissions be limited
to 0.45 lb/hr and that the sulfur content of the distillate fuel oil
combusted in the unit not exceed 15 ppm. Appendix C of the state's
nonattainment SIP contains the Federally enforceable air construction
permits that define MPW's RACM/RACT requirements. These permits are
effective January 1, 2017.
---------------------------------------------------------------------------

    \19\ The unit's 0.44 lbs/MMBtu emission rate is a Lowest
Achievable Emission Rate (LAER).
    \20\ The limit of 500 ppm by volume is from state rule.
---------------------------------------------------------------------------

    The control measures developed for Monsanto, described in table 4-3
of the state's nonattainment SIP, establish lower emission limits on
two sources--EP-195 (Boiler #8) and EP-234 (CAC Process Flare). The
Boiler #8 control strategy includes a more stringent SO2
emission limit. A 2007 permit issued to the facility Permit No. 82-A-
092-P9, limited the unit's SO2 emissions to 292.5 lb/hr. The
permit issued to the facility in 2015, Permit No. 82-A-092-P11, as part
of the control strategy, limits the unit's SO2 emissions to
273 lb/hr.\21\
---------------------------------------------------------------------------

    \21\ The unit also has a 1.95 lbs/MMBtu based on a 3-hr rolling
average limit is a Best Available Control Technology limit.
---------------------------------------------------------------------------

    The control strategy for the CAC Process Flare includes new
SO2 emission limit that restricts the unit's fuel use to
natural gas only. A 2012 permit issued to the facility, Permit No. 88-
A-001-S2, limited the unit's SO2 emissions to 500 ppm by
volume. The permit issued to the facility in 2015, Permit No. 88-A-001-
S3, as part of the control strategy, limits the unit to burning only
natural gas and the unit's SO2 emissions to 0.02 lb/hr.
Appendix D of the state's nonattainment SIP contains the Federally
enforceable air construction permits that define Monsanto's RACM/RACT
requirements. These permits are effective May 13, 2015.
    The state has determined that these measures suffice to provide for
attainment the attainment date, August 5, 2018. EPA concurs and
proposes to conclude that the state has satisfied the requirement in
CAA Sec.  172(c)(1) to adopt and submit all RACM as needed to attain
the standards as expeditiously as practicable.

C. Nonattainment New Source Review (NNSR)

    Section 172(c)(5) requires that the state's nonattainment plan
provisions shall require permits for the construction and operation of
new or modified major stationary sources anywhere in the nonattainment
area, in accordance with section CAA Sec.  173. EPA approved the
state's nonattainment new source review rules on May 15, 2014 (79 FR
27763). These rules provide for appropriate new source review for
SO2 sources undergoing construction or major modification in
the Muscatine nonattainment area without need for modification of the
approved rules. Therefore, EPA concludes that the requirements of CAA
Sec.  172(c)(5) have been met.

D. Reasonable Further Progress (RFP)

    Section 172(c)(2) requires that nonattainment plans include
provisions addressing reasonable further progress (RFP). Reasonable
further progress is defined in CAA Sec.  171(1) as: ``. . . such annual
incremental reductions in emissions of the relevant air pollutant as
are required by this part [part D] or may reasonably be required by the
Administrator for the purpose of ensuring attainment of the applicable
national ambient air quality standard by the applicable date.''
    As discussed in EPA's April 2014 guidance, this definition is most
appropriate for pollutants that are emitted by numerous and diverse
sources, where the relationship between any individual source and
overall air quality is not explicitly quantified, and where NAAQS
attainment requires inventory-wide emissions reductions. The
SO2 NAAQS presents special circumstances because there are
usually a limited number of well-defined sources affecting the area's
air quality and any emission control measures commonly result in swift
improvements that typically occur in one step. As noted in the state's
nonattainment SIP, the EPA has interpreted that RFP is best construed
as ``adherence to an ambitious compliance schedule'' in previous
rulemaking.\22\
---------------------------------------------------------------------------

    \22\ See 74 FR 13547 (April 16, 1992).
---------------------------------------------------------------------------

    As previously noted in section V.B. RACT/RACM, in this preamble,
the SO2 emission limits and application of control
technologies established for Monsanto (effective on May 13, 2015), MPW
(effective January 1, 2017) and for GPC occur on reasonable timelines.
    The state asserts that this plan requires that affected sources
implement appropriate control measures as expeditiously as practicable
in order to ensure attainment of the standard by the applicable
attainment date. The state concluded that its plan therefore provides
for RFP in accordance with the approach to RFP described in EPA's
guidance. EPA concurs and proposes to conclude that the plan provides
for RFP as required by CAA Sec.  172(c)(2).

E. Contingency Measures

    Section 172(c)(9) of the CAA requires that the state's
nonattainment plan provide for the implementation of specific measures
to be undertaken if the area fails to make reasonable further progress,
or to attain the national primary ambient air quality standard by the
attainment date applicable under this part. Such measures shall be
included in the plan revision as contingency measures to take effect in
any such case without further action by the State or the Administrator.
    EPA's April 2014 guidance describes special features of
SO2 planning that influence the suitability of alternative
means of addressing the requirement in section 172(c)(9) for
contingency measures for SO2, such that in particular an
appropriate means of satisfying this requirement is for the state to
have a comprehensive enforcement program that identifies sources of
violations of the SO2 NAAQS and to undertake an aggressive
follow-up for compliance and enforcement.
    The state's nonattainment SIP provides that, after full
implementation of the control strategy, contingency measures will be
triggered if monitored ambient air quality records 1-hr SO2
NAAQS violation in the nonattainment area, or if the nonattainment area
fails to meet RFP. If triggered, the state will evaluate culpabilities
for the violation and will plan to complete the investigation within 3
months of the trigger. Where the investigation concludes unequivocally
that SO2 emissions from one of the three sources in the
control strategy is the cause of the recorded 1-hr SO2 NAAQS
violation or failure to achieve RFP, the state will conduct a
compliance evaluation and establish orders for the abatement or control
of air pollution or make changes to the GPC, MPW, or Monsanto
construction permits. Orders or construction permits will be issued
within approximately 9 months of completion of the investigation and
could include fuel switches, addition of

controls, curtailment of production, reducing boiler operating loads,
or other appropriate measures necessary to mitigate the violation.
    EPA proposes to approve the state's plan for meeting the
contingency measure requirement of CAA Sec.  172(c)(9).

VI. Additional Elements of the State's Submittal

A. Compliance With Section 110(a)(2) of the CAA

    Section 172(c)(7) of the CAA requires nonattainment SIPs to meet
the applicable provisions of CAA Sec.  110(a)(2). While the provisions
of 110(a)(2) address various topics, EPA's past determinations suggest
that only the Sec.  110(a)(2) criteria which are linked with a
particular area's designation and classification are relevant to Sec.
172(c)(7). This nonattainment SIP submittal satisfies all applicable
CAA Sec.  110(a)(2) criteria, as evidenced by the state's nonattainment
new source review program which addresses 110(a)(2)(I), the included
control strategy, and the associated emissions limits which are
relevant to 110(a)(2)(A). In addition, on July 26, 2013, Iowa submitted
to EPA an infrastructure SIP to demonstrate that the state has the
necessary plans, programs, and statutory authority to implement the
requirements of section 110 of the CAA as they pertain to the 2010 1-hr
SO2 NAAQS. EPA will take action on the state's
SO2 infrastructure SIP in a separate rulemaking. The EPA is
proposing to conclude that the state has meet the requirements of CAA
Sec.  172(c)(7).

B. Equivalent Techniques

    Section 172(c)(8) of the CAA states that upon application by any
state, the Administrator may allow the use of equivalent modeling,
emission inventory, and planning procedures, unless the Administrator
determines that the proposed techniques are, in the aggregate, less
effective than the methods specified by the Administrator.
    The state's nonattainment SIP indicates that it followed existing
regulations, guidance, and standard practices when conducting modeling,
preparing the emissions inventories, and implementing its planning
procedures. Therefore, the state did not use or request approval of
alternative or equivalent techniques as allowed under of the CAA and
the EPA is proposing to conclude that the state's nonattainment SIP
meets the requirements of CAA Sec.  172(c)(8).

VII. EPA's Proposed Action

    The EPA is proposing to approve the nonattainment SIP submission,
which the state submitted to EPA on May 26, 2016, for attaining the
2010 1-hour SO2 NAAQS for the Muscatine nonattainment area
and for meeting other nonattainment area planning requirements. This
SO2 attainment plan includes the state's attainment
demonstration for the Muscatine nonattainment area. The nonattainment
area plan also addresses requirements for RFP, RACT/RACM, base-year and
projection-year emission inventories, and contingency measures.
    The EPA has determined that the state's nonattainment plan meets
applicable requirements of the section 172 of the CAA (107(c)(1)
through (9). EPA's analysis is discussed in this proposed rulemaking.
    The EPA is taking public comments for thirty days following the
publication of this proposed action in the Federal Register. We will
take all comments into consideration in our final action.

VIII. 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 Iowa Regulations described in the amendments to 40 CFR
part 52 set forth below. EPA has made, and will continue to make, these
materials generally available through https://www.regulations.gov and/
or at the EPA Region 7 Office (please contact the person identified in
the For Further Information Contact section of this preamble for more
information).
    Therefore, these materials have been approved by EPA for inclusion
in the State implementation plan, have been incorporated by reference
by EPA into that plan, are fully Federally enforceable under sections
110 and 113 of the CAA as of the effective date of the final rulemaking
of EPA's approval, and will be incorporated by reference by the
Director of the Federal Register in the next update to the SIP
compilation.\23\
---------------------------------------------------------------------------

    \23\ 62 FR 27968 (May 22, 1997).
---------------------------------------------------------------------------

IX. Statutory and Executive Order Reviews

    Under the CAA, the Administrator is required to approve a SIP
submission that complies with the provisions of the Act and applicable
Federal regulations. 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
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 of Management and Budget under Executive Orders 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 CAA; and
     Does not provide EPA with the discretionary authority to
address, as appropriate, disproportionate human health or environmental
effects, using practicable and legally permissible methods, under
Executive Order 12898 (59 FR 7629, February 16, 1994).
    The SIP is not approved to apply on any Indian reservation land or
in any other area where EPA or an Indian tribe has demonstrated that a
tribe has jurisdiction. In those areas of Indian country, the rule does
not have tribal implications 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: August 9, 2017.
Edward H. Chu,
Acting Regional Administrator, Region 7.
    For the reasons stated in the preamble, EPA proposes to amend 40
CFR part 52 as set forth below:

Part 52--APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS

0
1. The authority citation for part 52 continues to read as follows:

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

Subpart Q--Iowa

0
2. Amend Sec.  52.820 by:
0
a. In the table in paragraph (d), adding entries ``(112)'' through
``(169)'' in numerical order; and
0
b. In the table in paragraph (e), adding an entry ``(47)'' in numerical
order.
    The additions read as follows:

Sec.  52.820  Identification of plan.

* * * * *
    (d)* * *

                                EPA-Approved Iowa Source-Specific Orders/Permits
----------------------------------------------------------------------------------------------------------------
                                                          State
         Name of source           Order/permit No.   effective date   EPA approval date        Explanation
----------------------------------------------------------------------------------------------------------------

                                                  * * * * * * *
(112) Grain Processing           Permit No. 95-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     374-S4.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(113) Grain Processing           Permit No. 15-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     078.                                publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(114) Grain Processing           Permit No. 79-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     194-S2.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(115) Grain Processing           Permit No. 71-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     067-S4.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(116) Grain Processing           Permit No. 75-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     087-S1.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(117) Grain Processing           Permit No. 72-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     199-S2.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(118) Grain Processing           Permit No. 74-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     014-S1.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(119) Grain Processing           Permit No. 74-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     015-S2.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(120) Grain Processing           Permit No. 75-A-            7/6/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     353-S2.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(121) Grain Processing           Permit No. 79-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     195-S2.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(122) Grain Processing           Permit No. 80-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     149-S5.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].

(123) Grain Processing           Permit No. 80-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     150-S5.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(124) Grain Processing           Permit No. 85-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     031-S2.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(125) Grain Processing           Permit No. 85-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     032-S2.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(126) Grain Processing           Permit No. 85-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     038-P1.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(127) Grain Processing           Permit No. 85-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     135-P1.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(128) Grain Processing           Permit No. 90-A-            7/6/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     111-S1.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(129) Grain Processing           Permit No. 91-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     068-S2.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(130) Grain Processing           Permit No. 93-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     110-P1.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(131) Grain Processing           Permit No. 92-A-            7/6/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     383-S2.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(132) Grain Processing           Permit No. 92-A-            7/6/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     385-S1.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(133) Grain Processing           Permit No. 94-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     055-S1.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(134) Grain Processing           Permit No. 94-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     061-S1.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(135) Grain Processing           Permit No. 02-A-            7/6/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     781-S2.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(136) Grain Processing           Permit No. 02-A-            7/6/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     782-S2.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].

(137) Grain Processing           Permit No. 09-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     482-S2.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(138) Grain Processing           Permit No. 10-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     563-S1.                             publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(139) Grain Processing           Permit No. 15-A-           3/25/16  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     200.                                publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(140) Grain Processing           Permit No. 15-A-           3/25/16  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     201.                                publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(141) Grain Processing           Permit No. 15-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     202.                                publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(142) Grain Processing           Permit No. 15-A-           2/15/16  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     203.                                publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(143) Grain Processing           Permit No. 15-A-           2/15/16  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     204.                                publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(144) Grain Processing           Permit No. 15-A-           2/15/16  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     205.                                publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(145) Grain Processing           Permit No. 15-A-           2/15/16  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     206.                                publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(146) Grain Processing           Permit No. 15-A-           2/15/16  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     207.                                publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(147) Grain Processing           Permit No. 15-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     208.                                publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(148) Grain Processing           Permit No. 15-A-          12/10/15  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     209.                                publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(149) Grain Processing           Permit No. 15-A-           2/15/16  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     480.                                publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of
                                                                      [Federal Register   the SIP; EPA-R07-OAR-
                                                                      citation].          2017-0416; FRL-XXXX-
                                                                                Region 7].
(150) Grain Processing           Permit No. 15-A-           2/15/16  [date of final      2010 1-hr SO2 NAAQ
 Corporation.                     481.                                publication in      Nonattainment Plan;
                                                                      the Federal         Condition 6 of the
                                                                      Register] and       permit is not part of