[Federal Register Volume 82, Number 192 (Thursday, October 5, 2017)]
[Proposed Rules]
[Pages 46434-46444]
[FR Doc No: 2017-21371]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R05-OAR-2016-0138; FRL-9968-84-Region 5]

Air Plan Approval; Illinois; Nonattainment Plans for the Lemont
and Pekin SO2 Nonattainment Areas

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to
approve State Implementation Plan (SIP) revisions, which Illinois
submitted to EPA on March 2, 2016, and supplemented on August 8, 2016
and May 4, 2017, for attaining the 2010 1-hour sulfur dioxide
(SO2) national ambient air quality standard (NAAQS) for the
Lemont and Pekin areas. These revisions (herein called the
nonattainment plans or plans) include Illinois' attainment
demonstration and other elements required under Clean Air Act (CAA) for
the two areas. In addition to an attainment demonstration, the plans
address: The requirement for meeting reasonable further progress (RFP)
toward attainment of the NAAQS; reasonably available control measures
and reasonably available control technology (RACM/RACT); emission
inventories; and contingency measures. EPA further proposes to conclude
that Illinois has demonstrated that the plans' provisions provide for
attainment of the 2010 1-hour primary SO2 NAAQS in the
Lemont and Pekin areas by the attainment date of October 4, 2018.

DATES: Comments must be received on or before November 6, 2017.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R05-
OAR-2016-0138 at http://www.regulations.gov, or via email to
<EMAIL_ADDRESS>For comments submitted at Regulations.gov,
follow the online instructions for submitting comments. Once submitted,
comments cannot be edited or removed from Regulations.gov. For either
manner of submission, EPA may publish any comment received to its
public docket. Do not submit electronically any information you
consider to be Confidential Business Information (CBI) or other
information whose disclosure is restricted by statute. Multimedia
submissions (audio, video, etc.) must be accompanied by a written
comment. The written comment is considered the official comment and
should include discussion of all points you wish to make. EPA will
generally not consider comments or comment contents located outside of
the primary submission (i.e. on the web, cloud, or other file sharing
system). For additional submission methods, please contact the person
identified in the For Further Information Contact section. For the full
EPA public comment policy, information about CBI or multimedia
submissions, and general guidance on making effective comments, please
visit http://www2.epa.gov/dockets/commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT: John Summerhays, Environmental
Scientist, Attainment Planning and Maintenance Section, Air Programs
Branch (AR-18J), Environmental Protection Agency, Region 5, 77 West
Jackson Boulevard, Chicago, Illinois 60604,<PHONE_NUMBER>,
<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:
    This supplementary information section is arranged as follows:

I. Why was Illinois required to submit SO2 plans for the
Lemont and Pekin areas?
II. Requirements for SO2 Nonattainment Area Plans
III. Modeled Attainment Plans
IV. Review of Residual and Distillate Fuel Oil Sulfur Content Limits
V. Review of Other Plan Requirements
VI. EPA's Proposed Action
VII. Incorporation by Reference
VIII. Statutory and Executive Order Reviews

I. Why was Illinois required to submit SO2 plans for the
Lemont and Pekin areas?

    On June 22, 2010, EPA promulgated a new 1-hour primary
SO2 NAAQS of 75 parts per billion (ppb), which is met at an
ambient air quality monitoring site when the 3-year average of the
annual 99th percentile of 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, EPA designated a first set of 29 areas of the country as
nonattainment for the 2010 SO2 NAAQS, including the Lemont
and Pekin areas within Illinois. 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 (also referred to as nonattainment plans or
plans) for the SO2 NAAQS to EPA within 18 months of the
effective date of the designation, i.e., by no later than April 4,
2015, in this case. These plans are required to demonstrate that their
respective areas will attain the NAAQS as expeditiously as practicable,
but no later than five years from the effective date of designation,
which in this case is October 4, 2018.
    For a number of areas, EPA published notice on March 18, 2016, that
the pertinent states had failed to submit the required SO2
nonattainment plan by the 18-month submittal deadline. See 81 FR 14736.
However, because Illinois had submitted its SO2
nonattainment plans before that date, EPA did not make such a finding
with respect to the Lemont and Pekin areas.
    Illinois submitted nonattainment plans for the Lemont and Pekin
areas on March 2, 2016 and submitted supplemental information on August
8, 2016 and May 4, 2017.\1\ The remainder of this proposed rule
describes the requirements that nonattainment plans must meet in order
to obtain EPA approval, provides a review of the state's plan with
respect to these requirements, and describes EPA's proposed action on
the state's plans.
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    \1\ Illinois' final rule amended other state regulations that
are not part of Illinois' nonattainment plans for the 2010
SO2 NAAQS and were not submitted to EPA as part of this
action.
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II. Requirements for SO2 Nonattainment Area Plans

    Nonattainment plans must meet the applicable requirements of the
CAA, specifically CAA sections 172, 191 and 192. On April 23, 2014, EPA
issued guidance for meeting these statutory requirements, in a document
entitled, ``Guidance for 1-Hour SO2 Nonattainment Area SIP
Submissions,'' (2014 SO2 Guidance) available at https://www.epa.gov/sites/production/files/2016-06/documents/20140423guidance_nonattainment_sip.pdf. In the 2014 SO2
Guidance, EPA described the statutory requirements for a complete
nonattainment area SIP under the 2010 SO2 NAAQS, 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); a new source review (NSR) permit program; and adequate
contingency measures for the affected area.
    In order for EPA to fully approve a SIP as meeting the requirements
of CAA sections 172, 191 and 192, the SIP for the affected area must
demonstrate, to EPA's satisfaction, that each of the aforementioned
requirements are met. In addition, the SIP must meet the applicable
regulatory procedural and substantive requirements set forth in EPA's
regulations at 40 CFR part 51. Under CAA sections 110(l) and 193,

EPA may not approve a SIP that would interfere with any applicable
requirement concerning NAAQS attainment and RFP, or any other
applicable requirement, and no requirement in effect (or required to be
adopted by an order, settlement, agreement, or plan in effect before
November 15, 1990) in any area that 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.

A. Emissions Inventory

    As required under CAA section 172(c)(3), the state must develop and
submit a comprehensive, accurate and current inventory of actual
emissions from all sources of SO2 emissions in each
nonattainment area. This inventory should be consistent with EPA's most
recent emissions inventory data requirements as codified at 40 CFR part
51, subpart A. The emissions inventory serves as the foundation for
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; (2) assess the
expected improvement in air quality within the nonattainment area due
to the adoption and implementation of control measures; and ultimately
3) demonstrate that the adopted control measures provide for attainment
of the SO2 standard by the attainment date.

B. Attainment Plan

    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. SO2
nonattainment 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 that 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 SO2 NAAQS as
expeditiously as practicable, but by no later than the attainment date
for the affected area. The 2014 SO2 Guidance advises that
compliance deadlines for these emission limits should be by, or before,
January 1, 2017, in order to provide for air quality data at or below
the level of the standard for at least one full calendar year before
the attainment deadline. In cases where the necessary emission limits
have not previously been made a part of the SIP, or have not otherwise
become federally enforceable, the plan needs to include the necessary
enforceable limits in adopted form suitable for incorporation into the
SIP in order for it to be approved by EPA. 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 fully enforceable.
    The 2014 SO2 Guidance recommends that the emission
limits be expressed as short-term average limits not to exceed the
averaging time for the applicable NAAQS that the limit is intended to
help maintain (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 SO2 guidance, pp. 22 to
39. The guidance recommends that--should states utilize longer
averaging times for certain sources--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.
    The 2014 SO2 Guidance provides an extensive discussion
of EPA's rationale for concluding that appropriately set, comparably
stringent limitations based on averaging times as long as 30 days can
be found to provide for attainment of the 2010 SO2 NAAQS. In
evaluating this conclusion, 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, and 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 ppb. In a year with 365 days
of valid monitoring data, the 99th percentile would be the fourth
highest daily maximum 1-hour value. The 2010 SO2 NAAQS,
including this form of determining compliance with the standard, was
upheld by the U.S. Court of Appeals for the District of Columbia
Circuit in Nat'l Envt'l Dev. Ass'n's Clean Air Project v. EPA, 686 F.3d
803 (D.C. Cir. 2012). Because the standard has this form, a single
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 whether 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 EPA's review of how to determine
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 SO2 nonattainment plans 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., the emission rate at which an ``average
year'' \2\ shows only three, not four days with maximum hourly levels
exceeding 75 ppb) is labeled the ``critical emission value.'' The
modeling process for identifying the 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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    \2\ An ``average year'' is used to mean a year with average air
quality. While 40 CFR 50 appendix T provides for averaging three
years of 99th percentile daily maximum values (e.g., the fourth
highest maximum daily concentration in a year with 365 days with
valid data), this discussion and an example below uses a single
``average year'' in order to simplify the illustration of relevant
principles.
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    EPA recognizes that some sources have highly variable emissions due
to, for example, variations in fuel sulfur content and operating rate
that can make it extremely difficult, even with a well-designed control
strategy, to ensure in practice that emissions for any given hour do
not exceed the critical emission value. EPA also acknowledges the
concern that longer term emission limits may allow short periods with
emissions above the critical emissions value, which in turn would
create the possibility of a NAAQS exceedance occurring when it
otherwise would not if emissions were continuously controlled at the
level corresponding to the critical emission value. However, for
several reasons, EPA believes that the approach set forth in the 2014
SO2 Guidance addresses this concern. First,

from a practical perspective, EPA expects the actual emission profile
of a source subject to an appropriately set longer term average limit
to be similar to the emission profile of a source subject to an
analogous 1-hour average limit. EPA expects this similarity because the
Agency has recommended that the longer term average limit be set at a
level that is comparably stringent to the otherwise applicable 1-hour
limit (reflecting a downward adjustment from the critical emissions
value) and that takes the source's emissions profile into account. As a
result, EPA expects either form of emission limit to yield comparable
air quality when the guidance is followed.
    Second, from a more theoretical perspective, EPA has compared the
likely air quality with a source having maximum allowable emissions
under an appropriately set longer term limit, as compared to the likely
air quality with the source having maximum allowable emissions under
the comparable 1-hour limit. In this comparison, in the 1-hour average
limit scenario, the source is presumed at all times to emit at the
critical emission level, and in the longer term average limit scenario,
the source is presumed 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 always emits 1000 pounds of SO2 per hour, which
causes air quality to be at the level of the NAAQS (i.e., causes a
design value of 75 ppb). Suppose further that in an ``average year,''
these emissions cause the five 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 on these 5 days are 800 pounds per 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
2014 SO2 Guidance, EPA found that the requirement for lower
average emissions is highly likely to yield better air quality than is
required with a comparably stringent 1-hour limit.
    Based on analyses described in appendix B of the 2014
SO2 Guidance, EPA has concluded 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.
    EPA must then evaluate 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, EPA's task is commonly to determine 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 the desirability of
accommodating real world emissions variability without significant risk
of violations as in this case, are also appropriate factors for EPA to
weigh in determining whether there is a reasonable degree of confidence
that the plan will lead to attainment. Based on these considerations,
especially given the high likelihood that a limit averaged over as long
as 30 days, determined in accordance with EPA's guidance, should result
in attainment, EPA believes as a general matter that such limits, if
appropriately determined, can reasonably be considered to provide for
attainment of the 2010 SO2 NAAQS.
    The 2014 SO2 Guidance offers specific recommendations
for determining an appropriate longer term average limit. The
recommended method starts with determination of the 1-hour emission
limit that would provide for attainment (i.e., the critical emission
value), and applies an adjustment factor to determine the (lower) level
of the longer term average emission limit that would be estimated to
have a 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, calculated 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.\3\ The guidance also addresses
a variety of related topics, such as the potential utility of setting
supplemental emission limits, such as mass-based limits, to reduce the
likelihood and/or magnitude of elevated emission levels that might
occur under the longer term emission rate limit.
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    \3\ For example, if the critical emission value is 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 EPA's Guideline on Air Quality Models (40
CFR part 51, appendix W).\4\ In 2005, EPA promulgated AERMOD as the
Agency's preferred near-field dispersion modeling for a wide range of
regulatory applications addressing stationary sources (including
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 2014
SO2 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.
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    \4\ EPA published revisions to the Guideline on Air Quality
Models on January 17, 2017.
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    As stated previously, attainment demonstrations for the 2010 1-hour
primary SO2 NAAQS must demonstrate future attainment and
maintenance of the NAAQS in the entire area designated as nonattainment
(i.e., not just at the violating monitor) by using air quality
dispersion modeling (see appendix W to 40 CFR part 51) to show that the
mix of sources and enforceable control measures and emission rates in
an identified area will not lead to a violation of the SO2
NAAQS. For a short-term (i.e., 1-hour) standard, EPA believes that
dispersion modeling, using allowable emissions and addressing
stationary sources in the affected area (and in some cases 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, follow
the form of the standard, and be calculated as described in section
<IP_ADDRESS> of the August 23, 2010, clarification memo on ``Applicability
of appendix W Modeling Guidance for the 1-hr SO2 National
Ambient Air Quality Standard'' (EPA, 2010).

C. RACM/RACT

    To be approved by EPA, the SIP must provide for attainment of the
standard based on SO2 emission reductions from control
measures that are permanent and enforceable.\5\ At a minimum, states
must consider all RACM and RACT measures that can be implemented in
light of the attainment needs for the affected area(s), and include all
necessary measures in order to attain the NAAQS.\6\ See ``General
Preamble for the Implementation of Title I of the Clean Air Act
Amendments of 1990; Proposed Rule,'' 57 FR 13498, 13547 (Apr. 16, 1992)
(``General Preamble'').
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    \5\ See section 110(a)(2)(A) of the CAA.
    \6\ Section 172(c)(1) of the CAA provides that ``Such plan shall
provide for the implementation of all reasonably available control
measures 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 reasonably available control
technology) and shall provide for attainment of the national primary
ambient air quality standards.''
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D. New Source Review (NSR)

    Part D of title I of the CAA prescribes the procedures and
conditions under which a new major stationary source or major
modification may obtain a preconstruction permit in an area designated
nonattainment for any criteria pollutant. The nonattainment NSR
permitting requirements in section 172(c)(5) and 173 of the CAA are
among ``the requirements of this part'' to be submitted to EPA as part
of a revised SIP for a nonattainment area within 18 months of the
effective date of a designation or redesignation to nonattainment. Air
agencies that already have a nonattainment NSR permitting program
applicable to areas previously designated nonattainment on the basis of
the previous SO2 NAAQS (annual, 24-hour or 3-hour averaging
periods) may be able to use that existing program to authorize the
construction and modification of major stationary sources of
SO2 that would locate in a new 2010 SO2
nonattainment area.\7\ However, because of the limited number of
nonattainment areas designated under the previous SO2 NAAQS,
and since nonattainment NSR rules in some states may not automatically
address areas designated nonattainment for newly promulgated air
quality standards, some air agencies may not have nonattainment NSR
rules that apply when new nonattainment areas for the 1-hour primary
SO2 standard are designated. In such cases, within 18 months
of designation, such agencies would need either to revise their
existing nonattainment NSR programs or to develop new programs to
enable the permitting of any major stationary source of SO2
locating in a nonattainment area under the 2010 SO2 NAAQS.
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    \7\ The annual and 24-hour primary SO2 NAAQS
generally will remain in effect for 1 year following the effective
date of the initial area designations for the new 1-hour 2010
SO2 NAAQS. However, the annual and/or 24-hour
SO2 NAAQS will remain in place for a longer period of
time for any current nonattainment area for the annual or 24-hour
SO2 NAAQS, and any area for which a state has not
fulfilled the requirements for a SIP call. See 40 CFR 50.4(e).
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E. RFP

    Section 171(1) of the CAA defines RFP as ``such annual incremental
reductions in emissions of the relevant air pollutant as are required
by part D or may reasonably be required by EPA for the purpose of
ensuring attainment of the applicable NAAQS by the applicable
attainment date.'' As EPA has previously explained, this definition is
most appropriate for pollutants that are emitted by numerous and
diverse sources, where the relationship between any individual source
and the overall air quality is not explicitly quantified, and where the
emission reductions necessary to attain the NAAQS are inventory-wide.
General Preamble, at 13547. EPA has also previously

explained that the definition is generally less pertinent to pollutants
like SO2 that usually have a limited number of sources
affecting areas of air quality that are relatively well defined, and
emissions control measures for such sources result in swift and
dramatic improvement in air quality. Id. For SO2, there is
usually a single ``step'' between pre-control nonattainment and post-
control attainment. Therefore, for SO2, with its discernible
relationship between emissions and air quality, and significant and
immediate air quality improvements, RFP is best construed as
``adherence to an ambitious compliance schedule.'' Id. This means that
the state must ensure that affected sources implement appropriate
control measures as expeditiously as practicable in order to ensure
attainment of the standard by the applicable attainment date.

F. Contingency Measures

    In accordance with section 172(c)(9) of the CAA, SO2
nonattainment plans must include contingency measures in order to
obtain EPA approval. These measures must be fully adopted and should
contain trigger mechanisms and an implementation schedule. In addition,
they should be included in the SIP as measures that will take effect
without further action by the state or EPA. Contingency measures are
implemented if RFP targets are not achieved, or if the nonattainment
area has not reached attainment by the applicable attainment date.
Where an area has already achieved attainment by the attainment date,
it has no need to rely on contingency measures to come into attainment
or to make further progress to attainment.
    EPA has explained that planning for SO2 poses special
considerations. SO2 control measures are based on what is
directly and quantifiably necessary to attain the NAAQS, and it would
be unlikely for an area to implement the necessary emissions control
yet fail to attain the NAAQS. General Preamble at 13547. Therefore, for
SO2 nonattainment plans, EPA guidance also observes that the
contingency measures requirement can be satisfied by the air agency
having a comprehensive program to identify sources of violations of the
SO2 NAAQS and to undertake an `aggressive' follow-up for
compliance and enforcement.'' Id. The 2014 SO2 Guidance
provides further explanation of the context in which such an approach
may be appropriate for addressing section 172(c)(9) contingency measure
requirements for SO2. This approach for meeting contingency
measure requirements does not preclude a state from requiring
additional contingency measures that are enforceable and appropriate
for a particular source or source category. General Preamble at 13547.

III. Modeled Attainment Plans

    The following discussion evaluates various features of the modeling
and other elements of Illinois' nonattainment plans for the Lemont and
Pekin areas.

A. Model Selection

    Illinois' attainment demonstrations used AERMOD, the preferred
model for these applications. Illinois used version 14134 of this
model, using regulatory default mode, with no beta options. This
version of AERMOD was the recommended version at the time the state
conducted its nonattainment planning, and in any case the results of
this version are likely to be similar to those that more recent
versions would provide, so EPA finds use of this version of AERMOD to
be acceptable.
    Illinois performed an Auer's land use analysis which indicates that
the Lemont area is approximately 79 percent rural, and the Pekin area
is approximately 88 percent rural. A technical support document
provides figures, taken from Illinois' submittal, that show the land
use in the Lemont and Pekin areas, respectively, illustrating the areas
that are characterized as rural, not urban, in the Auer classification
system. EPA finds it appropriate to model these areas as rural areas.

B. Meteorological Data

    Illinois chose the Chicago O'Hare surface station (WBAN #94846) and
the Davenport, Iowa upper air station (WBAN #94982) as the most
representative meteorological stations for the Lemont area. Illinois
chose the Peoria surface station (WBAN #14842) and Lincoln upper air
station (WBAN #048233) as the most representative meteorological
stations for the Pekin area. These are the closest National Weather
Service surface stations to each respective area. The State determined
these stations to be the most representative for the respective
modeling domains. The upper air stations were chosen on the basis of
regional representativeness. EPA finds Illinois' choices of surface and
upper air meteorological stations appropriate based on: (1) The
suitability of meteorological data for the study area; and (2) the
actual similarity of surface conditions and surroundings at the
emissions source/receptor impact area compared to the locations of the
meteorological instrumentation towers.

C. Emissions Data

    Illinois chose to include emissions data from all permitted sources
within each modeling domain, which consists of a 50 kilometer radius
circumscribing an area centered on the violating monitor. Illinois
chose not to evaluate which sources would ``cause a significant
concentration gradient'' (40 CFR part 51, appendix W), because that
analysis would result in a greater modeling burden, along with
significant subjectivity. The inclusion of all permitted sources
assures that Illinois' modeled concentrations are conservative, in that
it adds impacts that may also be represented in the background
concentration.
    Except for the Powerton Generating Station (Powerton) located in
the Pekin area, the emission limits for newly limited sources, as
outlined in Illinois' attainment demonstration, correspond to the
revised sulfur limitations on a 1-hour basis and are found in 35
Illinois Administrative Code Part 214. The applicable emission limit
for Powerton is established on a 30-day average basis and is lower than
the modeled 1-hour attainment emission rate (the critical emission
value) by virtue of application of an adjustment factor determined and
applied in accordance with the 2014 SO2 Guidance.
    Specifically, as discussed further below, the 30-day average limit
is about 58 percent of the modeled 1-hour emission rate, or,
conversely, the modeled emission rate (the critical emission value) is
about 74 percent higher than the 30-day average limit. The emission
limits for sources in the Lemont area are all on a 1-hour average basis
and equal the modeled emissions rate. EPA finds Illinois' choice of
included sources and modeled emissions appropriate.

D. Emission Limits

    An important prerequisite for approval of an attainment plan is
that the emission limits that provide for attainment be fully
enforceable. The revised limits for significant contributing sources
are codified in Illinois' sulfur limitations rule at 35 Illinois
Administrative Code Part 214, Subpart AA, titled ``Requirements for
Certain SO2 Sources.'' The rules also include associated
monitoring, testing, and recordkeeping and reporting requirements. A
summary of the limits, showing the sum of the allowable hourly
emissions for each plant, is shown in Table 1. As shown in this table,
the emission limit for Powerton is

expressed as a 30-day average limit. Other limits in the rule are
expressed as 1-hour average limits. EPA's review of Illinois'
nonattainment plan addresses the use of these limits, both with respect
to the general suitability of using such limits in attainment
demonstrations, and whether Illinois has demonstrated that the
particular limits included in the plan provide for attainment.

          Table 1--Emission Limits in Submitted Illinois Rules
------------------------------------------------------------------------
                                     Sum of
                                    allowable       Averaging time for
            Facility                emissions             limits
                                  (pounds/hour)
------------------------------------------------------------------------
                Limits for Sources in or near Lemont Area
------------------------------------------------------------------------
Ingredion......................          175.91  1-hour.
Midwest Generation Joliet......          855.26  1-hour.
Midwest Generation Will County.        5,145.14  1-hour.
Owens Corning..................           82.78  1-hour.
Oxbow Midwest Calcining........          187.00  1-hour.
------------------------------------------------------------------------
                Limits for Sources in or near Lemont Area
------------------------------------------------------------------------
Aventine.......................           26.80  1-hour.
Illinois Power E.D. Edwards....           4,856  1-hour.
Midwest Generation Powerton....           3,452  30-day.
------------------------------------------------------------------------

    Illinois also modeled a number of other sources in its attainment
demonstration, basing allowable emissions on limits established in
state permits. EPA addresses the enforceability of the limits in the
plans and Illinois' use of a 30-day average emission limit for Powerton
below.
1. Enforceability
    In preparing its plans, Illinois adopted revisions to a previously
approved state regulation governing emissions of SO2. These
rule revisions were adopted by the Illinois Pollution Control Board
following established, appropriate public review procedures. In
addition, the rule revisions provide unambiguous, permanent emission
limits, expressed in pounds per hour of allowable SO2
emissions, that, if exceeded by a source, would be clear grounds for an
enforcement action.
    In comments to the state, Sierra Club requested that the rule being
adopted by Illinois ``incorporate enforceable restrictions for all
sources for which emissions reductions were included in the modeling
that demonstrated attainment.'' EPA's 2014 SO2 Guidance
addresses the need for enforceability of the limits necessary to
provide for attainment. The Guidance states, ``An approvable attainment
demonstration would . . . demonstrate that the emission limits in the
plan will suffice to provide for timely attainment . . . In cases where
the necessary emission limits have not previously been made a part of
the SIP, or have not otherwise become federally enforceable, the plan
needs to include the necessary enforceable limits in adopted form
suitable for incorporation into the SIP.'' See 2014 SO2
guidance, p. 9.
    The most significant sources in and near the designated
nonattainment areas are subject to new emission limits that Illinois
adopted as part of its part 214 rules. In particular, all of the
sources that needed to reduce emissions in order for the nonattainment
areas to attain the standard or that needed a reduced allowable
emission level in order for the areas to maintain attainment of the
standard are subject to limits adopted as part of the rule. Thus, the
sources that are most critical to the future success of the attainment
plans (including all of the significant units at these sources) are
subject to limitations adopted in Illinois' rule. Illinois did not
submit already federally enforceable permits for incorporation into the
SIP, even if the modeling showing future attainment accounted for such
limits. However, as previously discussed, all of the emission
reductions that Illinois identified as necessary to bring the Lemont
and Pekin areas into attainment are mandated by emission limits in the
rule. Those sources for which Illinois' modeled emissions were based on
federally enforceable limits already established in permits rather than
in the new rules are sources that are already required to meet emission
levels that should, combined with the new rule limits, provide for
attainment of the standard, so that no further emission reductions are
necessary for these sources in order for the SIP to provide for NAAQS
attainment.
    EPA reviewed the basis of the existing emission limits for the most
significant of those sources not needing to reduce emissions below
existing levels. In general, for these sources, the limits that
underlie the allowable emission levels that Illinois modeled were
established in federally enforceable construction permits. In some
cases, these permits were to authorize major modifications or major new
sources, in accordance with requirements for prevention of significant
deterioration (PSD). In other cases, notably for the refineries,
Illinois issued these limits in federally enforceable form in
accordance with a federal-state consent decree. For example, the limits
on emissions from the primary emission sources at CITGO, originally
established by consent decree, have been incorporated into PSD permit
number 05070003. The limits established in such permits are federally
enforceable. In accordance with EPA's guidance on the use of federally
enforceable limits, EPA finds that these limits are an appropriate
estimate of the maximum allowable emissions under the plans, and so EPA
finds that these limits represent an appropriate basis for modeling to
determine whether Illinois' nonattainment plan provides for attainment.
    Illinois has requested EPA to approve revisions to emission limits
for significant sources within the Pekin and Lemont areas in 35
Illinois Administrative Code part 214, as part of the SIP, and EPA
proposes to approve these new emission limits because they, in
combination with permit limits that are already federally enforceable,
provide adequate enforceability of the necessary emission limits for
the purposes of Illinois' nonattainment plans.

2. Longer Term Average Limits
    As noted above, the 2014 SO2 Guidance discusses the
option to establish limits with averaging times up to 30 days in length
that are comparably stringent to the 1-hour average limit that would
otherwise have been set, and recommends a detailed procedure for
determining such a comparably stringent limit. The Guidance also notes
that it might be appropriate to establish supplemental limits in order
to limit the magnitude and/or frequency of elevated emissions, as a
means of further reducing the likelihood of elevated emissions
occurring on those occasions when the meteorology is conducive to high
concentrations of SO2.
    Based on the variability of emissions at Powerton, Illinois opted
to set the emission limit for this facility on a 30-day average basis.
Illinois closely followed the recommendations of the 2014
SO2 Guidance in determining an appropriate level for this
limit. As a first step, Illinois conducted modeling which determined
that the 1-hour emission limit that would provide for attainment (the
critical emissions value) would be 6,000 pounds of SO2 per
hour. That is, Illinois conducted a series of modeling runs identifying
baseline allowable air quality (in absence of emission reductions),
evaluating the air quality consequences of feasible emission
reductions, and ultimately identifying a set of reduced allowable
emission levels that would provide for attainment. In this attaining
set of ``critical emission levels,'' the ``critical emission level''
for Powerton was 6,000 pounds per hour.
    Illinois then used a database of hourly SO2 emissions
data from a source comparable with Powerton to determine the historical
and expected future relationship between 1-hour and 30-day average
actual emission levels of a source using the control technology that
Powerton will employ. Illinois' submittal notes that Powerton
(presumably for purposes of satisfying the Mercury and Air Toxics
Standards) is expected to install ``a trona injection dry FGD system
for the control of SO2 emissions before 2017, so historical
data from the units at the source would not be appropriate'' as a basis
for determining the prospective relationship between 1-hour and 30-day
average emissions once the control is installed. See Illinois
submittal, Technical Support Document, page 9. ``As a substitute,
[Illinois used] a data set consisting of 42 months of emissions data
from the Potomac River Generating Station, located in Alexandria,
Virginia, [which] are similar to the Powerton units, and were operated
with trona injection systems during the time this data set was
created.'' Id. Using this data set, Illinois determined the 99th
percentile of the historical 1-hour values in this data set to be 1,107
pounds per hour and the 99th percentile of the historical 30-day
average values calculated from this data set to be 637 pounds per hour.
Illinois used the ratio between these two 99th percentile values (i.e.,
approximately 58 percent) as an adjustment factor to multiply by the
critical emissions value (the otherwise applicable 1-hour emission
limit) of 6,000 pounds per hour to determine a comparably stringent 30-
day average limit of 3,452 pounds per hour. This adjustment factor is
quite similar to, and slightly more conservative (i.e., it reflects a
more stringent long term limit) than, the average adjustment factor
discussed in EPA's 2014 SO2 Guidance for facilities using
dry scrubbers, an average adjustment factor of 63 percent. See appendix
D of EPA's 2014 Guidance.
    As noted above, EPA's 2014 SO2 Guidance notes the
benefit of supplementing long term average limits with additional
limits to reduce the likelihood and/or the magnitude of emission levels
above the 1-hour critical emission value. For this purpose, Illinois'
rules supplement the 30-day average limit for Powerton with a
requirement that emissions not exceed 6,000 pounds per hour more than 5
percent of the hours (as a 1-hour average) during any 30-day averaging
period. By constraining the likelihood of elevated emissions, and
thereby reducing the likelihood that elevated emissions will occur at
times when meteorology is conducive to high SO2
concentrations, this supplemental limit further strengthens the degree
of confidence that Illinois' plan for the Pekin area should result in
attainment.
    Based on a review of the state's submittal, the 3,452 pounds per
hour 30-day average limit for Powerton, supplemented with a limit on
the percentage of time that Powerton may exceed the 6,000 pounds per
hour critical emission value, provides a suitable alternative to
establishing a 6,000 pounds per hour 1-hour average emission limit for
this source. The state used a suitable database and then applied an
appropriate adjustment, yielding an emission limit that has comparable
stringency to the 1-hour average limit that the state determined would
otherwise have been necessary to provide for attainment. While the 30-
day average limit allows for occasions in which emissions are higher
than the level that would be allowed under 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. Further, the supplemental limit adopted by Illinois
ensures that elevated emissions will be infrequent. Thus, the 30-day
average limit of 3,452 pounds per hour as supplemented is comparably as
stringent as a 1-hour limit of 6,000 pounds per hour. Furthermore,
Illinois' modeling of 6,000 pounds per hour for Powerton is an
appropriate means of assessing whether the 30-day average limit of
3,452 pounds per hour plus supplemental limit provides for attainment.
    Based on EPA's review of this information, the 30-day average limit
for Powerton, in combination with other limitations in the state's plan
(most notably the limits summarized in Table 1 above), should provide
for attainment.

E. Background Concentrations

    Illinois used seasonally varying hourly background data. These
values were taken from an SO2 monitor in Oglesby, Illinois,
which is located approximately half way between the two areas. There
were 24 hourly values for each season, for a total of 96 monitored
concentration values. Each of these values represents a three-year
average (2011-2013) of the second highest hourly concentration for each
season.\8\ The values that Illinois determined range from 1.54 to 12.22
micrograms per cubic meter ([mu]g/m\3\). EPA has reviewed these
background concentrations and finds these values appropriate as
modeling inputs.
---------------------------------------------------------------------------

    \8\ Since this 3-year period has 1,096 days, and the data set
for each hour of the day is divided into four seasons of data sets,
the data set for the determination of each of the 96-hour and
season-specific background concentration includes a maximum of about
274 values. The selection of the second highest value is considered
to provide an appropriate degree of conservatism in determining the
background concentration for each hour and season. AERMOD then
reports results that reflect the addition of the appropriate
background value; for example, concentrations reported for an 8 a.m.
hour in springtime reflect the sum of the source impacts for that
hour plus the springtime 8 a.m. background concentration.
---------------------------------------------------------------------------

F. Review of Modeling Concerns Addressed by Illinois

    During preparation of its nonattainment plans, Illinois received
and responded to a number of comments by, among others, the Sierra Club
and the Environmental Law and Policy Center that EPA believes warrant
further review and explanation. Sierra Club noted that the
nonattainment plans provide only a relatively small margin of
attainment, and Sierra Club commented (among other comments)

that in this context, various types of emissions that Illinois does not
account for could result in these areas violating the standard. EPA has
reviewed the comments that Sierra Club provided to Illinois and the
response that Illinois provided in a document dated August 28, 2015.
(These comments and responses were included in Illinois' SIP submittal
and thus are available in the docket for this action).
    First, Sierra Club expressed concerns about emissions from modeled
sources that are not subject to Illinois Administrative Code section
214.603. Section 214.603 includes the following sources: Aventine
Renewable Energy; Illinois Power Holdings E.D. Edwards; Ingredion
Bedford Park; Midwest Generation Joliet; Midwest Generation Powerton;
Midwest Generation Will County; Owens Corning; and Oxbow Midwest
Calcining. Sierra Club commented that emissions from start-up,
shutdown, and malfunction that represent noncompliance could lead to a
violation of the NAAQS. Illinois responded that maximum allowable
emissions for the sources were used, and that these allowable emissions
are enforceable through emission limitations in other regulations or
permit conditions. EPA agrees with Illinois' response, finding that
while emissions above allowable levels may occasionally occur, excess
emissions that are prohibited by applicable requirements (whether they
are occurring during start-up, shutdown, or malfunctions or at other
times) need not be considered in evaluating whether a plan provides for
attainment. That is, if a plan requires emissions to be sufficiently
low to achieve attainment, EPA considers the plan to satisfy the
requirement to provide for attainment, and the possibility of
noncompliance that causes violations is an enforcement concern and not
an indication that the plan has failed to provide for attainment.
    Second, Sierra Club expressed concern regarding emissions from
minor sources. Sierra Club expressed particular concern about minor
sources being authorized by ``permits by rule'' that exempt the sources
from review of their impact on SO2 air quality. In
expressing this concern, Sierra Club did not identify any permits by
rule that had been issued or that were under consideration, or levels
of emissions that might arise from such authorizations that may cause
concern about maintaining attainment of the standard. Furthermore,
Sierra Club did not identify examples of source types that might be
minor enough to be authorized by a permit by rule and yet significant
enough to cause the potential for violations of the SO2
standard. Illinois responded that no such ``permits by rule'' exist
that exempt minor sources with SO2 emissions from review of
air quality impacts. Illinois further noted that, even in the
hypothetical situation that such a permit by rule existed, new minor
sources, and minor modifications at major sources, in general
contribute very little to SO2 ambient concentrations, but in
any case that Illinois conducts additional modeling in cases where the
potential for air quality problems exists. Illinois' minor source
permitting program provides adequate protection against minor sources
and minor modifications causing violations of the SO2
standard.
    Third, Sierra Club contended that while Illinois claims more than
99 percent emission reduction at many sources, presumably based on the
requirement that Illinois has now adopted rules requiring industrial
sources that burn diesel fuel or residual oil to burn ultra-low sulfur
fuel, these requirements cannot achieve the 99 percent reduction at
modeled sources that Illinois claimed. It appears that Illinois is
claiming that the rules reduced allowable emissions by more than 99
percent, while Sierra Club is asserting that there will be no such
percent reduction in actual emissions. Illinois responded that the
relevant issue is whether the emission level required by the rules is
an appropriate level consistent with attaining the standard, not the
percent reduction in relation to prior actual or allowable emissions.
That is, the percent reduction that results from Illinois' rules, and
whether it is calculated on the basis of actual or allowable emissions,
is not germane to the attainment demonstration, which is designed to
demonstrate that allowable emissions are sufficiently low to provide
for attainment. EPA agrees that, irrespective of the precise
relationship between current and required future emissions, i.e.,
irrespective of what emission reduction percentage the rule requires
relative to current emission levels, the rules require emissions to be
at levels that provide for attainment.
    Fourth, Sierra Club expressed concern that the flares modeled by
Illinois will have ``much higher'' emissions during routine operations,
such as flaring off gases during start-up, shutdown, and malfunction
events when compared to pilot emissions, and that Illinois did not
model these higher emission rates. Illinois responded that the flares
have limits on their allowable emissions (which apply at all times,
including during the events of concern to the Sierra Club), and the
flares were modeled at their maximum allowable emission rates. The most
significant flares in the Lemont area are at the CITGO and Exxon-Mobil
refineries; these flares were addressed in a consent decree,\9\ with
terms and conditions subsequently incorporated into federally
enforceable state permits requiring compliance with new source
performance standards. The most significant flare in the Pekin area, at
Aventine, is subject to emission limits in the state rules submitted in
Illinois' plan. As noted above, these emission limits are practically
enforceable, and the approach taken by Illinois in modeling maximum
allowable emission rates is consistent with EPA recommendations for
attainment demonstration modeling. EPA agrees with Illinois' rationale
and conclusions regarding Sierra Club's concerns about Illinois'
modeling analysis.
---------------------------------------------------------------------------

    \9\ For example, for CITGO, see Civil Action Number H-04-3883
entered January 26, 2005 in the Southern District of Texas.
---------------------------------------------------------------------------

    Finally, Sierra Club expressed concern regarding the impacts of
possible emission ``spikes'' at Powerton, i.e., occasions with elevated
emissions that would be permissible under the 3,452 pound per hour 30-
day average emission limit applicable to the facility. Sierra Club in
particular urged the adoption of supplemental limits to restrict the
magnitude and frequency of these emission spikes. As described earlier,
Illinois responded by adopting a supplemental limit requiring that no
more than 5 percent of the hours in any 30-day averaging period may
have emissions in excess of 6,000 pounds per hour, which is the modeled
critical emissions value. EPA believes this supplemental limit
appropriately addresses Sierra Club's concern.

G. Summary of Results

    The final dispersion modeling results submitted by Illinois show
design value concentrations of 190.9 and 196.2 [mu]g/m\3\ for the
Lemont and Pekin nonattainment areas, respectively. Both of these
design value concentrations are below 75 ppb, which corresponds to
196.4 [mu]g/m\3\, and therefore Illinois' modeling analysis
demonstrates attainment of the 2010 SO2 NAAQS for the Lemont
and Pekin areas. EPA has reviewed Illinois' attainment demonstrations,
agrees with Illinois' submitted results, and proposes to determine that
Illinois' plans provide for attainment of the 2010 primary
SO2 NAAQS in the Lemont and Pekin nonattainment areas.

IV. Review of Residual and Distillate Fuel Oil Sulfur Content Limits

    In conjunction with its adoption of SO2 emission limits
for major sources, Illinois adopted rule revisions to limit the sulfur
content of distillate and residual fuel oil combusted at stationary
sources throughout the state. Consistent with trends toward increasing
availability and use of lower sulfur oil of all kinds, these limits
were intended to assure that the considerable number of generally
smaller boilers that burn these fuels use fuels with relatively low
sulfur content. The new limits adopted by Illinois will help protect
air quality in the entire state, including the Lemont and Pekin
nonattainment areas. As a result, EPA proposes to approve these rule
amendments as part of the SIP.
    On and after January 1, 2017, the sulfur content of residual fuel
oil combusted at stationary sources will be limited to 1,000 parts per
million (ppm), and sulfur content of distillate fuel oil will be
limited to 15 ppm. These limits apply to facilities that exclusively
burn liquid fuel. These limits were adopted as part of Title 35 of
Illinois Administrative Code part 215 subparts B and D, in sections
214.121, 214.122, and 214.161. Section 214.121(b) sets these limits for
large sources (sources with actual heat input greater than 73.2
megawatts (MW)), and section 214.122(b) sets these limits for small
sources (sources with actual heat input smaller than, or equal to, 73.2
MW).
    Section 214.161(c) and (d) set exceptions from the sulfur content
limitations mentioned above for specific sources. Section 214.161(c)
lists exceptions for Midwest Generation Joliet, Powerton, Waukegan, and
Will County power stations or electric generating units (EGUs). These
sources must comply with the following limitations: (1) From January 1,
2016 through December 31, 2018, the sulfur content of all distillate
fuel oil purchased for use by the listed EGUs must not exceed 15 ppm;
(2) from January 1, 2017 through December 31, 2018, the sulfur content
of all distillate fuel oil used by the listed EGUs must not exceed 500
ppm; and (3) on and after January 1, 2019, the sulfur content of all
distillate fuel oil used by the listed EGUs must not exceed 15 ppm.
Section 214.161(d) sets an exception for Caterpillar Montgomery, and
sets the following limit: On and after January 1, 2016, the sulfur
content of all distillate fuel oil purchased for use by this source
must not exceed 15 ppm, and the sulfur content of all distillate fuel
oil used by this source must not exceed 500 ppm. These exemptions
provide the listed sources with additional time to burn existing stocks
of higher sulfur oils, but ultimately require these sources to meet the
same sulfur content limits as apply to other sources in the state.
    For the sources to which these alternate provisions apply that are
in or near the Lemont or Pekin areas, the attainment modeling reflects
the emissions that are allowable as of January 1, 2017, without regard
to the tighter limits that apply two years thereafter. Thus, Illinois'
modeling shows that these short term extensions of the deadline for
complying with the generally applicable oil sulfur content limits do
not prevent timely attainment. In addition, for the rest of the state,
these limits strengthen the SIP and help improve air quality. For these
reasons, EPA proposes to approve these rule amendments.
    In the rulemaking adopting the above elements of its Part 214
rules, Illinois also adopted revisions to Part 225 and 217. However,
Illinois' Lemont and Pekin nonattainment plans are not contingent on
any of the provisions of these parts of Illinois administrative code,
and these rules were not submitted as a part of this SIP revision
request. Thus, EPA is taking no action with respect to those revisions
as part of this action.

V. Review of Other Plan Requirements

A. Emissions Inventory

    The emissions inventory and source emission rate data for an area
serve as the foundation for air quality modeling and other analyses
that enable states to: (1) Estimate the degree to which different
sources within a nonattainment area contribute to violations within the
affected area; and (2) assess the expected improvement in air quality
within the nonattainment area due to the adoption and implementation of
control measures. As noted above, the state must develop and submit to
EPA a comprehensive, accurate and current inventory of actual emissions
from all sources of SO2 emissions in each nonattainment
area, as well as any sources located outside the nonattainment area
which may affect attainment in the area. See CAA section 172(c)(3).
    Illinois provided a comprehensive, accurate, and current inventory
of emissions of SO2 in and within 50 kilometers of the
Lemont and Pekin areas. By addressing sources to this distance from the
nonattainment areas, Illinois has developed a thorough list of the
sources with any potential to cause impacts that warrant including in
the areas' attainment modeling. Illinois' initial submittal provided
inventories of allowable emissions, and then Illinois supplemented this
information on May 4, 2017 with a submittal of inventories of actual
emissions.
    As noted above, these inventories addressed sources within 50
kilometers of the Lemont and Pekin nonattainment areas. These
inventories addressed 425 sources in and near Lemont and 48 sources in
and near Pekin. Once Illinois compiled its inventory of current
allowable emissions, Illinois conducted modeling to determine the
degree to which the applicable emission limitations allowed violations
of the SO2 air quality standard. Illinois then conducted a
series of additional modeling runs to determine a set of emission
limits that would provide for attainment. In accordance with EPA
guidance, Illinois' attainment demonstration is based on modeling using
allowable emissions to demonstrate that its plans provide for
attainment. This reflects Illinois' intent to ensure that emissions are
required to be sufficiently low as to achieve attainment, i.e., that
allowable emissions will not cause violations. Similarly, Illinois'
plans are designed to meet the other part D requirements on the basis
of allowable emissions, for example by setting allowable emissions at a
level that satisfy applicable requirements for RACT/RACM and RFP.
Illinois did not use actual emissions in this planning process.
Accordingly, Illinois initially provided an inventory of allowable
emissions, which served the needs of the pertinent nonattainment
planning requirements. Then, in its May 4, 2017, submittal, Illinois
also submitted a comprehensive, accurate, current inventory of actual
emissions. Tables 1 and 2 summarize actual emissions in 2014 for a
subset of these sources, namely those sources that have actual
SO2 emissions of at least 100 tons per year. Therefore,
Illinois has met the emission inventory requirement of CAA section
172(c)(3) for the Pekin and Lemont areas.

Table 2--Actual 2014 SO2 Emissions in Lemont Area Exceeding 100 Tons per
                                  Year
------------------------------------------------------------------------
                                                            Actual SO2
                       Source name                             (tpy)
------------------------------------------------------------------------
Midwest Generations--Joliet Station 29..................          12,800
Will County Generating Station..........................          10,478
Ingredion Incorporated Argo Plant.......................           1,671
Exxon Mobil Oil Corp....................................           1,562
Koppers Inc.............................................             867
CITGO Petroleum Corp....................................             346
Ardagh Glass Inc........................................             145
------------------------------------------------------------------------

 Table 3--Actual 2014 SO2 Emissions in Pekin Area Exceeding 100 Tons per
                                  Year
------------------------------------------------------------------------
                                                            Actual SO2
                       Source name                             (tpy)
------------------------------------------------------------------------
Midwest Generation LLC..................................          16,717
Illinois Power Resources Generating LLC--Edwards Energy            8,278
 Ctr....................................................
Aventine Renewable Energy, Inc..........................           7,292
Illinois Power Resources Generating LLC--Duck Creek                  240
 Energy.................................................
Keystone Steel & Wire Co................................             129
------------------------------------------------------------------------

B. RACM/RACT

    Illinois's plan reflects a number of strategies to reduce emissions
at various facilities. In the Lemont area, the Joliet power plant and
Unit 3 of the Will County power plant will cease burning coal and will
instead either burn natural gas or ultra-low sulfur diesel. In the
Pekin area, substantial emission reductions will result from conversion
of the Aventine facility switching from burning coal to burning natural
gas and from implementation of emission control equipment at the E.D.
Edwards and Powerton power plants. Both areas will also benefit from
statewide requirements for boilers burning fuel oil to burn low sulfur
fuel.
    In its August 8, 2016, supplemental submittal, Illinois explained
its rationale for concluding that the plans meet the RACM/RACT
requirement in accordance with EPA guidance. Specifically, following
EPA's interpretation that RACT and RACM reflect ``the level of
emissions control that is necessary to provide for expeditious
attainment of the NAAQS within a nonattainment area,'' Illinois noted
that its nonattainment plans require permanent and enforceable control
measures that provide for timely attainment. 35 Illinois Administrative
Code section 214.603 lists the appropriate source-specific
SO2 emission limits by unit, in pounds per hour. Therefore,
Illinois has satisfied the RACM/RACT requirements for the Lemont and
Pekin areas.

C. NSR

    EPA approved Illinois' nonattainment new source review rules on
December 17, 1992 (57 FR 59928); September 27, 1995 (60 FR 49780) and
May 13, 2003 (68 FR 25504). These rules provide for appropriate new
source review for SO2 sources undergoing construction or
major modification in the Lemont and Pekin areas without need for
modification of the approved rules. Although these rules predated
promulgation of the 2010 SO2 standards, these rules are
written in a manner such that new sources within areas that become
designated nonattainment for this new standard, such as the Lemont and
Pekin areas, become subject to these nonattainment new source review
requirements. Therefore, this requirement has been met for these areas.

D. RFP

    In its August 8, 2016, supplemental submittal, Illinois explained
its rationale for concluding that the plans met the requirement for RFP
in accordance with EPA guidance. Specifically, Illinois's rationale is
based on EPA guidance interpreting the RFP requirement being satisfied
for SO2 if the plan requires ``adherence to an ambitious
compliance schedule'' that ``implement[s] appropriate control measures
as expeditiously as practicable.'' Illinois noted that its
nonattainment plans provide for attainment as expeditiously as
practicable, i.e., by January 1, 2017, and finds that the plans thereby
satisfy the requirement for RFP. Therefore, Illinois has satisfied the
RFP requirements for the Lemont and Pekin areas.

E. Contingency Measures

    In its August 8, 2016, supplemental submittal, Illinois explained
its rationale for concluding that the plans met the requirement for
contingency measures in accordance with EPA guidance. Specifically,
Illinois relies on EPA's guidance, noting the special circumstances
that apply to SO2 (as discussed above), and explaining on
that basis why the contingency requirement in CAA section 172(c)(9) is
met for SO2 by having a comprehensive program to identify
sources of violations of the SO2 NAAQS and to undertake an
aggressive follow-up for compliance and enforcement of applicable
emissions limitations. Illinois stated that it has such an enforcement
program pursuant to Section 31 of the Illinois Environmental Protection
Act, identifying violators and taking prompt, appropriate enforcement
action, and concludes that Illinois' nonattainment plans satisfy
contingency measure requirements. Therefore, Illinois has satisfied the
contingency measure requirements for the Lemont and Pekin areas.

VI. EPA's Proposed Action

    EPA is proposing to approve Illinois' submission as a SIP revision,
which the state submitted to EPA on March 2, 2016, and supplemented on
August 8, 2016, and May 4, 2017, for attaining the 2010 1-hour
SO2 NAAQS for the Lemont and Pekin SO2
nonattainment areas.
    These SO2 nonattainment plans include Illinois'
attainment demonstration for the Lemont and Pekin SO2
nonattainment areas. These nonattainment plans also address
requirements for emission inventories, RACT/RACM, RFP, and contingency
measures. Illinois has previously addressed requirements regarding
nonattainment area new source review. EPA has determined that Illinois'
SO2

nonattainment plans meet the applicable requirements of CAA sections
172, 191, and 192. EPA is taking public comments for thirty days
following the publication of this proposed action in the Federal
Register. EPA will take all comments into consideration in our final
action.

VII. Incorporation by Reference

    In this rule, EPA is proposing to include in a final EPA rule
regulatory text that includes incorporation by reference. In accordance
with requirements of 1 CFR 51.5, EPA is proposing to incorporate by
reference Illinois Administrative Code, Title 35, Subtitle B, Chapter
I, Subchapter c, Part 214, Sections 214.121, 214.122, 214.161, 214.600,
214.601, 214.602, 214.603, 214.604, and 214.605, effective December 7,
2015. EPA has made, and will continue to make, these documents
generally available through www.regulations.gov, and/or at the EPA
Region 5 Office (please contact the person identified in the FOR
FURTHER INFORMATION CONTACT section of this preamble for more
information).

VIII. Statutory and Executive Order Reviews

    Under the CAA, the Administrator is required to approve a SIP
submission that complies with the provisions of the CAA and applicable
Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in
reviewing SIP submissions, EPA's role is to approve state choices,
provided that they meet the criteria of the CAA. Accordingly, this
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 Clean Air Act; and
     Does not provide EPA with the discretionary authority to
address, as appropriate, disproportionate human health or environmental
effects, using practicable and legally permissible methods, under
Executive Order 12898 (59 FR 7629, February 16, 1994).
    In addition, the SIP is not approved to apply on any Indian
reservation land or in any other area where EPA or an Indian tribe has
demonstrated that a tribe has jurisdiction. In those areas of Indian
country, the rule does not have tribal implications and will not impose
substantial direct costs on tribal governments or preempt tribal law as
specified by Executive Order 13175 (65 FR 67249, November 9, 2000).

List of Subjects in 40 CFR Part 52

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

    Dated: September 17, 2017.
Robert A. Kaplan,
Acting Regional Administrator, Region 5.
[FR Doc. 2017-21371 Filed 10-4-17; 8:45 am]
BILLING CODE 6560-50-P


 1 316b Phase II O& M Compliance Cost Estimation  Fixed & Variable O& M Plus Construction Downtime 5.0 Determining Fixed Versus Variable O& M Costs When developing the annual O& M cost estimates, the underlying assumption was that facilities were operating nearly continuously with the only downtime being periodic routine maintenance. This routine maintenance was assumed to be approximately four weeks per year. The economic model however, considers variations in capacity utilization. Lower capacity utilization factors result in additional generating unit shutdown that may result in reduced O& M costs. However, it is not valid to assume that intake technology O& M costs drop to zero during these additional shutdown periods. Even when the generating unit is shut down, there are some O& M costs incurred. To account for this, total annual O& M costs were divided into fixed and variable components. Fixed O& M costs include items that occur even when the unit is periodically shut down, and thus are assumed to occur year round. Variable O& M costs apply to items that are allocable based on estimated intake operating time. The general assumption behind the fixed and variable determination is that shutdown periods are relatively short ( on the order of several hours to several weeks).

5.1 Overall Approach The annual O& M cost estimates used in the cost models is the net O& M cost, which is the difference between the estimated baseline and compliance O& M costs. Therefore, the fixed/ variable proportions for each facility may vary depending on the mix of baseline and compliance technologies. In order to account for this complexity, EPA calculated the fixed and variable O& M costs separately for both the baseline technology and each compliance technology and then calculated the total net fixed and variable components for each facility/ intake.

In order to simplify the methodology ( i. e., avoid developing a whole new set of O& M cost equations), a single fixed O& M component cost factor was estimated for each technology application represented by a single O& M cost equation. To calculate fixed O& M factors, EPA first calculated fixed O& M cost factors for the range of data input values, using the assumptions described below, to develop the cost equation . For baseline technologies, EPA selected the lowest value in the range of fixed component factors for each technology application. The lowest value was chosen for baseline technologies to yield a high side net compliance costs for intermittently operating facilities. Similarly, for compliance technologies, EPA selected the highest value in the range of fixed component factors for each technology application, again, to provide a high side estimate.

For each O& M cost equation, a single value ( expressed either as a percentage or decimal value) representing the fixed component of O& M costs, is applied to each baseline and compliance technology O& M cost estimate for each facility. The variable O& M component is the difference between total O& M costs and the fixed O& M cost component. The fixed and variable cost components were then separately combined to derive the overall net fixed and overall net variable O& M costs for each facility/ intake.  2 .

5.2 Estimating the Fixed/ Variable O& M Cost Mix Depending on the technology, the O& M cost estimates may generally include components for labor, power, and materials. The cost breakdown assumes facility downtime will be relatively short ( hours to weeks). Thus, EPA assumes any periodic maintenance tasks, e. g., changing screens, changing nets, or inspection/ cleaning by divers) are performed regardless of plant operation, and therefore are considered fixed costs. Fixed costs associated with episodic cost components are allocated according to whether they would still occur even if the downtime coincided with the activity. For example, annual labor estimates for passive screens includes increased labor for several weeks during high debris episodes. This increased labor is considered a 100% variable component because it would not be performed if the system were not operating during this period. A discussion of the assumptions and rationale for each general component is described below.

Power Requirements In most cases, power costs are largely a variable cost. If there is a fixed power cost component, it will generally consists of low frequency, intermittent operations necessary to maintain equipment in working condition. For example, a 1% fixed factor for this component would equal roughly 1.0 hours of operation every four days for systems that normally operated continuously. Such a duration and frequency is considered as reasonable for most applications. For systems already operating intermittently, a factor that results in the equivalent of one hour of operation or one backwash every four days was used.

Labor Requirements Labor costs generally have one or more of the following components:

° Routine monitoring and maintenance ° Episodes requiring higher monitoring and maintenance ( high debris episodes) ° Equipment deployment and removal ° Periodic inspection/ cleaning by divers.

Routine Monitoring and Maintenance This component includes monitoring/ adjustment of the equipment operation, maintaining equipment ( repairs & preventive O& M), and cleaning. Of these the monitoring/ adjustment and cleaning components will drop significantly when the intakes are not operating. A range of 30% to 50% will be considered for the fixed component.

Episodes requiring higher monitoring and maintenance  3 This component is generally associated with equipment that is operating and will be assumed to be 100% variable.  4 Equipment deployment and removal This activity is generally seasonal in nature and assumed performed regardless of operation ( i. e., 100% fixed).

Equipment Replacement The component includes two factors: parts replacement due to wear and tear ( and varies with operation) and parts replacement due to corrosion ( and occurs regardless of operation). A range of 50% to 70% of these costs will be considered the fixed component.

Technology Specific Input Factors Traveling Screens To determine the range of calculated total O& M fixed factors, fixed O& M cost factors ( Table 5 1) were applied to individual O& M cost components for the various screen width values that were used to generate the O& M cost curves. As described earlier, the lowest value of this range was selected for the baseline O& M fixed cost factor and the highest of this range was selected as the compliance O& M fixed cost factor. Table 5 1 O& M Cost Component Fixed Factor Routine Labor Parts Replacement Equipment Power Equipment Deployment All Traveling Screens Without Fish Handling 0.5 0.7 0.05 1.0 All Traveling Screens With Fish Handling 0.3 0.5 0.01 1.0 Passive Screens The fixed O& M component was based on the following:

° Seasonal high debris period monitoring labor set equal to 0 hours ° Routine labor set at 50% of full time operation ° Back washes are performed once every four days ° Dive team costs for high debris were set at 50% of full time operation ° Dive team cost for new screens at existing offshore were set equal to 0 assuming no net additional diver costs over what was necessary for existing submerged intake without screens.  5 Velocity Caps Because the O& M cost for velocity caps was based on annual inspection and cleaning by divers, the entire velocity cap O& M cost is assumed to be fixed ( 100%).

Fish Barrier Nets Fish barrier net O& M costs are based on deployment and removal of the nets plus periodic replacement of net materials. As described above, EPA assumes seasonal deployment and removal is a 100% fixed O& M cost. EPA has assumed that the need for net maintenance and replacement is a due to its presence in the waterbody and should not vary with the intake operation. Therefore, entire fish barrier net O& M cost is assumed to be fixed ( 100%).

Recirculating Wet Cooling Towers Because the cooling tower O& M costs were derived using cost factors that estimate total O& M costs that are based on capital costs, a detailed analysis is not possible. However, using the pumping and fan energy requirements described in the Proposed Rule Development Document, EPA was able to estimate that the O& M energy component was under 50% of the total O& M cost. This energy requirement reduction, coupled with reductions in labor and parts replacement requirements, should result in a fixed cost factor of approximately 50%.

5.3 O& M Fixed Cost Factors Table 5 2 and 5 3 present the fixed O& M cost factors for baseline technologies and compliance technologies, respectively, derived using the above assumptions.  6 Technology Description Application Water Type Fixed Factor Traveling Screen With Fish Handling 10 Ft Screen Wells Freshwater 0.28 Traveling Screen With Fish Handling 25 Ft Screen Wells Freshwater 0.30 Traveling Screen With Fish Handling 50 Ft Screen Wells Freshwater 0.32 Traveling Screen With Fish Handling 75 Ft Screen Wells Freshwater 0.33 Traveling Screen With Fish Handling 10 Ft Screen Wells Saltwater 0.31 Traveling Screen With Fish Handling 25 Ft Screen Wells Saltwater 0.34 Traveling Screen With Fish Handling 50 Ft Screen Wells Saltwater 0.36 Traveling Screen With Fish Handling 75 Ft Screen Wells Saltwater 0.38 Traveling Screen Without Fish Handling 10 Ft Screen Wells Freshwater 0.45 Traveling Screen Without Fish Handling 25 Ft Screen Wells Freshwater 0.47 Traveling Screen Without Fish Handling 50 Ft Screen Wells Freshwater 0.48 Traveling Screen Without Fish Handling 75 Ft Screen Wells Freshwater 0.49 Traveling Screen Without Fish Handling 10 Ft Screen Wells Saltwater 0.49 Traveling Screen Without Fish Handling 25 Ft Screen Wells Saltwater 0.51 Traveling Screen Without Fish Handling 50 Ft Screen Wells Saltwater 0.53 Traveling Screen Without Fish Handling 75 Ft Screen Wells Saltwater 0.53 Table 5 2 Baseline Technology Fixed O& M Cost Factors  7 Technology Description Application Water Type Fixed Factor Add Fish Barrier Net Using Anchors and Bouys All Freshwater 1.0 Add Fish Barrier Net Using Pilings for Support 10 Ft Net Depth Saltwater 1.0 Add Fish Barrier Net Using Pilings for Support 20 Ft Net Depth Saltwater 1.0 Add Passive T screens to Existing Offshore Intake High Debris All 0.21 Add Passive T screens to Existing Offshore Intake Low Debris All 0.27 Relocate Intake Offshore with Passive T screens High Debris All 0.46 Relocate Intake Offshore with Passive T screens Low Debris All 0.56 Traveling Screen With Fish Handling and Fine Mesh 10 Ft Screen Wells Freshwater 0.38 Traveling Screen With Fish Handling and Fine Mesh 25 Ft Screen Wells Freshwater 0.35 Traveling Screen With Fish Handling and Fine Mesh 50 Ft Screen Wells Freshwater 0.37 Traveling Screen With Fish Handling and Fine Mesh 75 Ft Screen Wells Freshwater 0.39 Traveling Screen With Fish Handling and Fine Mesh 10 Ft Screen Wells Saltwater 0.41 Traveling Screen With Fish Handling and Fine Mesh 25 Ft Screen Wells Saltwater 0.38 Traveling Screen With Fish Handling and Fine Mesh 50 Ft Screen Wells Saltwater 0.40 Traveling Screen With Fish Handling and Fine Mesh 75 Ft Screen Wells Saltwater 0.41 Traveling Screen With Fish Handling 10 Ft Screen Wells Freshwater 0.40 Traveling Screen With Fish Handling 25 Ft Screen Wells Freshwater 0.42 Traveling Screen With Fish Handling 50 Ft Screen Wells Freshwater 0.42 Traveling Screen With Fish Handling 75 Ft Screen Wells Freshwater 0.42 Traveling Screen With Fish Handling 10 Ft Screen Wells Saltwater 0.42 Traveling Screen With Fish Handling 25 Ft Screen Wells Saltwater 0.43 Traveling Screen With Fish Handling 50 Ft Screen Wells Saltwater 0.44 Traveling Screen With Fish Handling 75 Ft Screen Wells Saltwater 0.44 Traveling Screen Dual Flow 10 Ft Screen Wells Freshwater 0.40 Traveling Screen Dual Flow 25 Ft Screen Wells Freshwater 0.40 Traveling Screen Dual Flow 50 Ft Screen Wells Freshwater 0.40 Traveling Screen Dual Flow 75 Ft Screen Wells Freshwater 0.40 Traveling Screen Dual Flow 10 Ft Screen Wells Saltwater 0.44 Traveling Screen Dual Flow 25 Ft Screen Wells Saltwater 0.44 Traveling Screen Dual Flow 50 Ft Screen Wells Saltwater 0.44 Traveling Screen Dual Flow 75 Ft Screen Wells Saltwater 0.44 Velocity Cap All All 1.0 Cooling Towers All All 0.5 Table 5 3 Compliance Technology Fixed O& M Cost Factors


UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

	OFFICE OF PREVENTION, PESTICIDE

	AND TOXIC SUBSTANCES

  SEQ CHAPTER \h \r 1 MEMORANDUM

Date:  August 19, 2008

SUBJECT:	d-Phenothrin (Sumithrin®):  Addendum to Residential Exposure
Assessment

PC Code:  069005	DP Barcode: 326931

Decision No.: 	Registration No.: 2596-150, 2596-151

Petition No.:  None	Regulatory Action: Reregistration

Assessment Type: ORE	Reregistration Case No.: 0426

TXR No.:  None	CAS No.: 026022-80-2

MRID No.:  None	40 CFR: NA

FROM:	Becky Daiss

Biologist

Reregistration Branch 4/HED (7509C)

THROUGH:	Susan Hummel

Branch Senior Scientist

Reregistration Branch 4/HED (7509C)

TO:		Jennifer Howenstine

Chemical Review Manager

		Reregistration Branch 3

		Special Review and Registration Division (7508C)

		       and

	Ann Sibold

Review Manager

Insecticide Branch

	Registration Division (7505C)

This is an addendum to the Health Effects Division’s (HED) July 2,
2008 assessment of residential exposure and risk for d-phenothrin (B.
Daiss, D326945).  This addendum provides a refined assessment of
residential exposure from use of d-Phenothrin as a spot on treatment for
dogs and puppies.  The probabilistic assessment conducted previously for
this scenario indicated risks of concern to toddlers from incidental
ingestion of residues on pets via hand-to-mouth activity.  This refined
assessment incorporates an incidental oral toxicity endpoint which was
derived using Benchmark Dose analysis.  Based on this refined analysis,
this pet treatment scenario does not present risks of concern.

Formulation and Use Pattern

The products assessed, EPA Reg. Nos. 2596-150 and 2596-151, are liquid
products containing 87.5% of the active ingredient d-Phenothrin.  These
products are applied to dogs and puppies to control fleas and ticks.
They are packaged and applied in varying amounts based on the weight of
the animal.  The products are applied by squeezing the contents out of
the tube from the dog’s shoulder blades along the back to the base of
the tail.

Toxicological Endpoint Selection

The endpoint used to conduct this assessment was derived using benchmark
dose (BMD) analysis.  Endpoints and levels of concern (LOCs) are
summarized below in Table 1.  The BMD analysis is provided in a separate
memorandum (B. Daiss, D326934, TXR0052377, 8/19/08).

Table 1. Summary of Toxicological Doses and Endpoints for d-Phenothrin
for Use in Non-Occupational Human Health Risk Assessments

Exposure/

Scenario	Point of Departure	Uncertainty/FQPA Safety Factors	 LOC for
Risk Assessment	Study and Toxicological Effects

Incidental Oral Short-Term (1-30 days) and

Intermediate-Term

(1-6 months)	BMDL10 = 100 mg/kg/day	UFA= 10 x

UFH= 10 x

FQPA SF= 10 x

UFDB 	Residential LOC for MOE = 1000	2-generation rat reproduction
study. The NOAEL is 1000 ppm (50 mg/kg/day).  The LOAEL is 3000 ppm (150
mg/kg/day) based on decreased body weight (4-6%) and increased liver
weight in F0 and F1 parental animals, and an increase in absolute and
relative spleen weight, and decreased absolute uterine weight in F1
adults and on decreased body weight gain during lactation of F2b pups,
and decreased litter size of F1b litters at day 1, decreased absolute
heart and kidney weight in F2b males, increased relative liver weight in
male and female F2b pups.

Dermal All Durations	Dermal toxicity systemic LOAEL = not established

21/28 Dermal toxicity study in rats dermal toxicity systemic LOAEL not
established up to 1000 mg/kg/day (HDT)

BMD10 = The dose associated with a 10% change of a biological effect.
BMDL10 = A lower one-sided confidence limit on the BMD10  UF =
uncertainty factor, FQPA SF = Special FQPA safety factor, NOAEL = no
observed adverse effect  level, LOAEL = lowest observed adverse effect
level, MOE = margin of exposure, LOC = level of concern, NA = Not
Applicable

Residential Exposure Assessment

	The exposure scenario assessed for this pet application is toddler
incidental ingestion of residues on pets via hand-to-mouth after pet
treatment.  HED conducted a probabilistic assessment using Cumulative
and Aggregate Risk Evaluation System (CARES® Version 3.0;   HYPERLINK
"http://cares.ilsi.org/"  http://cares.ilsi.org/ ), a publicly available
software program for this residential exposure scenario.  The
calculations and algorithms used to estimate exposure for the various
scenarios and routes are consistent with standard Agency practice for
residential pesticide exposure assessment.  The exposure scenario was
assessed using standard EPA algorithms for exposure estimation.
Distributional inputs were included in the probabilistic assessment
where possible.  The probabilistic assessment assumes postapplication
exposure occurs on the “day of application.”  Five thousand (5000)
product uses are assessed for each exposure scenario i.e., percentile
distributions for each scenario are generated from 5000 exposure
estimates.  A dermal exposure assessment for d-Phenothrin is not
required because dermal effects were not observed at the limit dose in
animal studies.

	Exposure Factor Distributions

	Inputs and distributions considered for the CARES assessment are
provided below.

Many of the non-phenothrin-specific distributional inputs are based on
EPA’s n-methyl Carbamate Revised Cumulative Risk Assessment (NMCCRA),
the most recent EPA publication using probabilistic methods and
distributional inputs for residential exposure assessment (EPA, 2007).

	Phenothrin-specific Factors

Residue Characteristics

•    Application Rate - 0.09 fl oz (2.6 mL)/ per 6000 cm2 (2230 mg
ai/animal)

•    Dissipation:  standard Agency practice for residential exposure
is to assess exposure on the “day of application”.  Therefore, use
of a 0.00001 day half-life in the CARES submission is consistent with
this practice because it is assuming no residue dissipation.

• 	Residue Transfer:  Point estimate of 2% described used in the
deterministic assessment.

	Use Pattern

• 	Indoor Monthly probability:  Equal use for each month of the year.
This assumption is acceptable, since these probabilities are irrelevant
when assessing “day of application” exposures.

• 	Day of Week probability:  Equal use for each day of the week.  This
assumption is acceptable, since these probabilities are irrelevant when
assessing “day of application” exposures.

• 	Annual Use: Ten (10) uses per year.  This value is irrelevant for
“day of application” exposure assessment.  [500 CARES individuals
are included in a model run.  A total of 5000 products (500 x 10) are
assessed.]

• 	Treatment Interval:  Thirty (30) day interval between treatments.
This value is irrelevant for “day of application” exposure
assessment.

• 	Co-occurrence Probability:  Set to zero.  Co-occurrence is
irrelevant for “day of application” exposures.

Non-Phenothrin-specific Factors

• 	Body Weight:  Correlated to randomly selected individual from the
specified subpopulation in the reference population.

• 	Exposure Duration (expressed as hours per day):  triangular
distribution (0.03, 0.108, 1.03).

• 	Hand-to-Mouth Exposure Factors (children only)

      -		Hand-to-Mouth Events: (expressed as contacts per hour)
Triangular distribution (1, 13, 26).

   	-  	Hand-to-Mouth Residue Transfer (i.e., saliva extraction factor)
(expressed as a percentage of hand residue):  Uniform distribution of
20% to 50%.

  	-  	Surface Area of Hand Mouthed (cm2):  Triangular distribution (1,
7, 20).

	Probabilistic Exposure and Risk Estimates

Results of the probabilistic CARES assessment for the pet
post-application incidental oral exposure scenario are presented in
Table 2.  Risks are presented in the form of Margins of Exposure (MOEs)
by percentile of exposure.  Based on this refined analysis, this pet
treatment scenario does not present risks of concern i.e., MOEs greater
than 1000 are seen at the 99.9th percentile.

Table 2: CARES Assessment – Sumithrin MOEs for Pet Care Spot-on
Children 1-2 years HTM Exposure – LOC/MOE = 1000

Percentile	Estimated LOC/MOE

99.9	1350

99.5	1700

99	2000

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