[Federal Register Volume 86, Number 138 (Thursday, July 22, 2021)]
[Proposed Rules]
[Pages 38643-38651]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-15464]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R05-OAR-2021-0256; FRL-8692-01-R5]


Air Plan Approval; Wisconsin; Attainment Plan for the Rhinelander 
SO2 Nonattainment Area

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve the State Implementation Plan (SIP) revision submitted by 
Wisconsin on March 29, 2021, which amends a SIP submission previously 
submitted to EPA on January 22, 2016 and supplemented on July 18, 2016, 
and November 29, 2016, for attaining the 1-hour sulfur dioxide 
(SO2) primary national ambient air quality standard (NAAQS) 
for the Rhinelander SO2 nonattainment area. This plan 
(herein referred to as Wisconsin's Rhinelander SO2 plan or 
plan) includes Wisconsin's attainment demonstration and other elements 
required under the Clean Air Act (CAA). In addition to an attainment 
demonstration, the plan addresses the requirement for meeting 
reasonable further progress (RFP) toward attainment of the NAAQS, 
reasonably available control measures and reasonably available control 
technology (RACM/RACT), and contingency measures. This action 
supplements a prior action which found that Wisconsin had satisfied 
emission inventory and new source review (NSR) requirements for this 
area, but had not met requirements for the elements proposed to be 
approved here. EPA is proposing to conclude that Wisconsin has 
appropriately demonstrated that the plan provisions provide for 
attainment of the 2010 1-hour primary SO2 NAAQS in the 
Rhinelander SO2 nonattainment area and that the plan meets 
the other applicable requirements under the CAA.

DATES: Comments must be received on or before August 23, 2021.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R05-
OAR-2021-0256 at http://www.regulations.gov, or via email to 
leslie.michael@epa.gov. 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: Abigail Teener, Environmental 
Engineer, Attainment Planning and Maintenance Section, Air Programs 
Branch (AR-18J), Environmental Protection Agency, Region 5, 77 West 
Jackson Boulevard, Chicago, Illinois 60604, (312) 353-7314, 
teener.abigail@epa.gov. The EPA Region 5 office is open from 8:30 a.m. 
to 4:30 p.m., Monday through Friday, excluding Federal holidays and 
facility closures due to COVID-19.

SUPPLEMENTARY INFORMATION: This SUPPLEMENTARY INFORMATION section is 
arranged as follows:

I. Why was Wisconsin required to submit an SO2 plan for 
the Rhinelander area?
II. Requirements for SO2 Nonattainment Area Plans
III. Attainment Demonstration and Longer Term Averaging
IV. Review of Modeled Attainment Plan
    A. Model Selection
    B. Simulation of Downwash
    C. Meteorological Data
    D. Emissions Data
    E. Emission Limits
    F. Background Concentrations
    G. Summary of Results
V. Review of Other Plan Requirements
    A. RACM/RACT
    B. Reasonable Further Progress (RFP)
    C. Contingency Measures
VI. What action is EPA taking?
VII. Incorporation by Reference
VIII. Statutory and Executive Order Reviews

I. Why was Wisconsin required to submit an SO2 plan for the Rhinelander 
area?

    On June 22, 2010, EPA promulgated a new 1-hour primary 
SO2 NAAQS of 75 parts per billion (ppb), which is met at an 
ambient air quality monitoring site when the 3-year average of the 
annual 99th percentile of daily maximum 1-

[[Page 38644]]

hour average concentrations does not exceed 75 ppb, as determined in 
accordance with appendix T of 40 CFR part 50. See 75 FR 35520, codified 
at 40 CFR 50.17(a)-(b). On August 5, 2013, EPA designated 29 areas of 
the country as nonattainment for the 2010 SO2 NAAQS, 
including the Rhinelander area within the State of Wisconsin. See 78 FR 
47191, codified at 40 CFR part 81, subpart C. These area designations 
were effective October 4, 2013. Section 191 of the CAA directs states 
to submit SIPs for areas designated as nonattainment for the 
SO2 NAAQS to EPA within 18 months of the effective date of 
the designation, i.e., by no later than April 4, 2015 in this case. 
These SIPs are required to demonstrate that their respective areas will 
attain the NAAQS as expeditiously as practicable, but no later than 5 
years from the effective date of designation, which is October 4, 2018.
    In response to the requirement for SO2 nonattainment 
plan submittals, Wisconsin submitted a nonattainment plan for the 
Rhinelander area on January 22, 2016, and supplemented it on July 18, 
2016, and November 29, 2016. On March 23, 2021,\1\ EPA partially 
approved and partially disapproved Wisconsin's Rhinelander 
SO2 plan as submitted and supplemented in 2016. EPA approved 
the base-year emissions inventory and affirmed that the new source 
review requirements for the area had previously been met.\2\ EPA also 
approved the SO2 emission limit for Ahlstrom-Munksj[ouml]'s 
Rhinelander facility (Ahlstrom-Munksj[ouml]) (formerly Expera Specialty 
Solutions LLC (Expera)) as SIP-strengthening. At that time, EPA 
disapproved the attainment demonstration, since the plan relied on 
credit for more stack height than is creditable under the regulations 
for good engineering practice (GEP) stack height. Additionally, EPA 
disapproved the plan for failing to meet the requirements for meeting 
RFP toward attainment of the NAAQS, RACM/RACT, emission limitations and 
control measures as necessary to attain the NAAQS, and contingency 
measures.
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    \1\ 86 FR 15418 (March 23, 2021).
    \2\ 79 FR 60064 (October 6, 2014).
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    Under sections 110(c) and 179(a)-(b) of the CAA, a disapproval in 
whole or in part of a state submittal initiates a Federal 
Implementation Plan (FIP) clock and sanctions clocks, respectively, 
which are terminated by an EPA rulemaking approving a revised plan. On 
March 29, 2021, Wisconsin submitted a permit containing a revised 
emission limit and supplemental information in order to remedy the 
plan's deficiencies specified in EPA's March 23, 2021 rulemaking, along 
with a request that EPA approve its revised plan for the Rhinelander 
area.
    The remainder of this action describes the requirements that 
SO2 nonattainment plans must meet in order to obtain EPA 
approval, provides a review of Wisconsin's revised plan with respect to 
these requirements, and describes EPA's proposed action on the plan.

II. Requirements for SO2 Nonattainment Area Plans

    Nonattainment SIPs must meet the applicable requirements of the 
CAA, and specifically CAA sections 172, 191 and 192. EPA's regulations 
governing nonattainment SIPs are set forth at 40 CFR part 51, with 
specific procedural requirements and control strategy requirements 
residing at subparts F and G, respectively. Soon after Congress enacted 
the 1990 Amendments to the CAA, EPA issued comprehensive guidance on 
SIPs, in a document entitled the ``General Preamble for the 
Implementation of Title I of the Clean Air Act Amendments of 1990,'' 
published at 57 FR 13498 (April 16, 1992) (General Preamble). Among 
other things, the General Preamble addressed SO2 SIPs and 
fundamental principles for SIP control strategies. Id., at 13545-49, 
13567-68. On April 23, 2014, EPA issued recommended guidance for 
meeting the statutory requirements in SO2 SIPs, in a 
document entitled, ``Guidance for 1-Hour SO2 Nonattainment 
Area SIP Submissions,'' available at https://www.epa.gov/sites/production/files/2016-06/documents/20140423guidance_nonattainment_sip.pdf. In this guidance EPA described 
the statutory requirements for a complete nonattainment area SIP, which 
includes: An accurate emissions inventory of current emissions for all 
sources of SO2 within the nonattainment area; an attainment 
demonstration; demonstration of RFP; implementation of RACM (including 
RACT); NSR; emissions limitations and control measures as necessary to 
attain the NAAQS; and adequate contingency measures for the affected 
area. EPA already concluded in its March 23, 2021 rulemaking that 
Wisconsin has met the emissions inventory and NSR requirements.
    In order for EPA to fully approve a SIP as meeting the requirements 
of CAA sections 110, 172 and 191-192 and EPA's regulations at 40 CFR 
part 51, the SIP for the affected area needs to demonstrate to EPA's 
satisfaction that each of the aforementioned requirements have been 
met. Under CAA sections 110(l) and 193, EPA may not approve a SIP that 
would interfere with any applicable requirement concerning NAAQS 
attainment and RFP, or any other applicable requirement, and no 
requirement in effect (or required to be adopted by an order, 
settlement, agreement, or plan in effect before November 15, 1990) in 
any area which is a nonattainment area for any air pollutant, may be 
modified in any manner unless it ensures equivalent or greater emission 
reductions of such air pollutant.

III. Attainment Demonstration and Longer Term Averaging

    CAA section 172(c)(1) directs states with areas designated as 
nonattainment to demonstrate that the submitted plan provides for 
attainment of the NAAQS. 40 CFR part 51, subpart G, further delineates 
the control strategy requirements that SIPs must meet, and EPA has long 
required that all SIPs and control strategies reflect four fundamental 
principles of quantification, enforceability, replicability, and 
accountability. General Preamble at 13567-68. SO2 attainment 
plans must consist of two components: (1) Emission limits and other 
control measures that ensure implementation of permanent, enforceable 
and necessary emission controls, and (2) a modeling analysis which 
meets the requirements of 40 CFR part 51, appendix W, which 
demonstrates that these emission limits and control measures provide 
for timely attainment of the primary SO2 NAAQS as 
expeditiously as practicable, but by no later than the attainment date 
for the affected area. In all cases, the emission limits and control 
measures must be accompanied by appropriate methods and conditions to 
determine compliance with the respective emission limits and control 
measures and must be quantifiable (i.e., a specific amount of emission 
reduction can be ascribed to the measures), fully enforceable 
(specifying clear, unambiguous and measurable requirements for which 
compliance can be practicably determined), replicable (the procedures 
for determining compliance are sufficiently specific and non-subjective 
so that two independent entities applying the procedures would obtain 
the same result), and accountable (source specific limits must be 
permanent and must reflect the assumptions used in the SIP 
demonstrations).
    EPA's April 2014 guidance recommends that the emission limits be 
expressed as short-term average limits (e.g., addressing emissions 
averaged

[[Page 38645]]

over one or three hours), but also describes the option to utilize 
emission limits with longer averaging times of up to 30 days so long as 
the state meets various suggested criteria. See 2014 guidance, pp. 22 
to 39. The guidance recommends that, should states and sources utilize 
longer averaging times, the longer term average limit should be set at 
an adjusted level that reflects a stringency comparable to the 1-hour 
average limit at the critical emission value shown to provide for 
attainment that the plan otherwise would have set.
    The April 2014 guidance provides an extensive discussion of EPA's 
rationale for concluding that appropriately set comparably stringent 
limitations based on averaging times as long as 30 days can be found to 
provide for attainment of the 2010 SO2 NAAQS. In evaluating 
this option, EPA considered the nature of the standard, conducted 
detailed analyses of the impact of use of 30-day average limits on the 
prospects for attaining the standard, and carefully reviewed how best 
to achieve an appropriate balance among the various factors that 
warrant consideration in judging whether a state's plan provides for 
attainment. Id. at pp. 22 to 39. See also id. at appendices B, C, and 
D.
    As specified in 40 CFR 50.17(b), the 1-hour primary SO2 
NAAQS is met at an ambient air quality monitoring site when the 3-year 
average of the annual 99th percentile of daily maximum 1-hour 
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 in particular 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 how EPA judges 
whether such plans ``provide for attainment,'' based on modeling of 
projected allowable emissions and in light of the NAAQS' form for 
determining attainment at monitoring sites follows.
    For SO2 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., in an ``average year'' \3\ which shows three days with maximum 
hourly levels exceeding 75 ppb) is labeled the ``critical emission 
value.'' The modeling process for identifying this critical emissions 
value inherently considers the numerous variables that affect ambient 
concentrations of SO2, such as meteorological data, 
background concentrations, and topography. In the standard approach, 
the state would then provide for attainment by setting a continuously 
applicable 1-hour emission limit at this critical emission value.
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    \3\ An ``average year'' is used to mean a year with average air 
quality. While 40 CFR 50 appendix T provides for averaging three 
years of 99th percentile daily maximum values (e.g., the fourth 
highest maximum daily concentration in a year with 365 days with 
valid data), this discussion and an example below uses a single 
``average year'' in order to simplify the illustration of relevant 
principles.
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    EPA recognizes that some sources have highly variable emissions, 
for example due to variations in fuel sulfur content and operating 
rate, that can make it extremely difficult, even with a well-designed 
control strategy, to ensure in practice that emissions for any given 
hour do not exceed the critical emission value. EPA also acknowledges 
the concern that longer term emission limits can allow short periods 
with emissions above the ``critical emissions value,'' which, if 
coincident with meteorological conditions conducive to high 
SO2 concentrations, could in turn create the possibility of 
a NAAQS exceedance occurring on a day when an exceedance would not have 
occurred if emissions were continuously controlled at the level 
corresponding to the critical emission value. However, for several 
reasons, EPA believes that the approach recommended in its guidance 
document suitably addresses this concern. First, from a practical 
perspective, EPA expects the actual emission profile of a source 
subject to an appropriately set longer term average limit to be similar 
to the emission profile of a source subject to an analogous 1-hour 
average limit. EPA expects this similarity because it has recommended 
that the longer term average limit be set at a level that is comparably 
stringent to the otherwise applicable 1-hour limit (reflecting a 
downward adjustment from the critical emissions value) and that takes 
the source's emissions profile into account. As a result, EPA expects 
either form of emission limit to yield comparable air quality.
    Second, from a more theoretical perspective, EPA has compared the 
likely air quality with a source having maximum allowable emissions 
under an appropriately set longer term limit, as compared to the likely 
air quality with the source having maximum allowable emissions under 
the comparable 1-hour limit. In this comparison, in the 1-hour average 
limit scenario, the source is presumed at all times to emit at the 
critical emission level, and in the longer term average limit scenario, 
the source is presumed 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 1,000 pounds of SO2 per hour (lbs/hr), 
which results in air quality at the level of the NAAQS (i.e., results 
in a design value of 75 ppb). Suppose further that in an ``average 
year,'' these emissions cause the 5 highest maximum daily average 1-
hour concentrations to be 100 ppb, 90 ppb, 80 ppb, 75 ppb, and 70 ppb. 
Then suppose that the source becomes subject to a 30-day average 
emission limit of 700 lbs/hr. It is theoretically possible for a source 
meeting this limit to have emissions that occasionally exceed 1,000 
lbs/hr, but with a typical emissions profile emissions would much more 
commonly be between 600 and 800 lbs/hr. In this simplified example, 
assume a zero background concentration, which allows one to assume a 
linear relationship between emissions and air quality. (A nonzero

[[Page 38646]]

background concentration would make the mathematics more difficult but 
would give similar results.) Air quality will depend on what emissions 
happen on what critical hours, but suppose that emissions at the 
relevant times on these 5 days are 800 lbs/hr, 1,100 lbs/hr, 500 lbs/
hr, 900 lbs/hr, and 1,200 lbs/hr, respectively. (This is a conservative 
example because the average of these emissions, 900 lbs/hr, is well 
over the 30-day average emission limit.) These emissions would result 
in daily maximum 1-hour concentrations of 80 ppb, 99 ppb, 40 ppb, 67.5 
ppb, and 84 ppb. In this example, the fifth day would have an 
exceedance that would not otherwise have occurred (84 ppb under the 30-
day average limit compared to 70 ppb under the 1-hour limit). However, 
the third day would not have an exceedance that otherwise would have 
occurred (40 ppb under the 30-day average limit compared to 80 ppb 
under the 1-hour limit). The fourth day would have been below, rather 
than at, 75 ppb (67.5 ppb under the 30-day average limit compared to 75 
ppb under the 1-hour limit). In this example, the fourth highest 
maximum daily concentration under the 30-day average would be 67.5 ppb.
    This simplified example illustrates the findings of a more 
complicated statistical analysis that EPA conducted using a range of 
scenarios using actual plant data. As described in appendix B of EPA's 
April 2014 SO2 nonattainment planning guidance, EPA found 
that the requirement for lower average emissions is likely to yield as 
good air quality as is required with a comparably stringent 1-hour 
limit. Based on analyses described in appendix B of its 2014 guidance 
and similar subsequent work, EPA expects that emission profiles with 
maximum allowable emissions under an appropriately set comparably 
stringent 30-day average limit are likely to have the net effect of no 
more exceedances and as good air quality of an emission profile with 
maximum allowable emissions under a 1-hour emission limit at the 
critical emission value.\4\ This result provides a compelling policy 
rationale for allowing the use of a longer averaging period, in 
appropriate circumstances where the facts indicate this result can be 
expected to occur.
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    \4\ See also further analyses described in rulemaking on the 
SO2 nonattainment plan for Southwest Indiana. In response 
to comments expressing concern that the emission profiles analyzed 
for appendix B represented actual rather than allowable emissions, 
EPA conducted additional work formulating sample allowable emission 
profiles and analyzing the resulting air quality impact. This 
analysis provided further support for the conclusion that an 
appropriately set longer term average emission limit in appropriate 
circumstances can suitably provide for attainment. The rulemaking 
describing these further analyses was published on August 17, 2020, 
at 85 FR 49967, available at https://www.govinfo.gov/content/pkg/FR-2020-08-17/pdf/2020-16044.pdf. A more detailed description of these 
analyses is available in the docket for that action, specifically at 
https://www.regulations.gov/document?D=EPA-R05-OAR-2015-0700-0023.
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    The question then becomes whether this approach, which is likely to 
produce a lower number of overall exceedances even though it may 
produce some unexpected exceedances above the critical emission value, 
meets the requirement in section 110(a)(1) and 172(c)(1) for state 
implementation plans to ``provide for attainment'' of the NAAQS. For 
SO2, as for other pollutants, it is generally impossible to 
design a nonattainment plan in the present that will guarantee that 
attainment will occur in the future. A variety of factors can cause a 
well-designed attainment plan to fail and unexpectedly not result in 
attainment, for example if meteorology occurs that is more conducive to 
poor air quality than was anticipated in the plan. Therefore, in 
determining whether a plan meets the requirement to provide for 
attainment, EPA's task is commonly to judge not whether the plan 
provides absolute certainty that attainment will in fact occur, but 
rather whether the plan provides an adequate level of confidence of 
prospective NAAQS attainment. From this perspective, in evaluating use 
of a 30-day average limit, EPA must weigh the likely net effect on air 
quality. Such an evaluation must consider the risk that occasions with 
meteorology conducive to high concentrations will have elevated 
emissions leading to exceedances that would not otherwise have 
occurred, and must also weigh the likelihood that the requirement for 
lower emissions on average will result in days not having exceedances 
that would have been expected with emissions at the critical emissions 
value. Additional policy considerations, such as accommodating real 
world emissions variability without significant risk of violations, are 
also appropriate factors for EPA to weigh in judging whether a plan 
provides a reasonable degree of confidence that the plan will lead to 
attainment. Based on these considerations, EPA believes that a 
continuously enforceable limit averaged over as long as 30 days, if 
determined in accordance with EPA's guidance, can reasonably be 
considered to provide for attainment of the 2010 SO2 NAAQS.
    The April 2014 guidance offers specific recommendations for 
determining an appropriate longer term average limit. The recommended 
method starts with determination of the 1-hour emission limit that 
would provide for attainment (i.e., the critical emission value), then 
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 1-hour emission limit. This method uses a 
database of continuous emission data reflecting the type of control 
that the source will be using to comply with the SIP emission limits, 
which (if compliance requires new controls) may require use of an 
emission database from another source. The recommended method involves 
using these data to compute a complete set of emission averages, 
computed according to the averaging time and averaging procedures of 
the prospective emission limitation. In this recommended method, the 
ratio of the 99th percentile among these long term averages to the 99th 
percentile of the 1-hour values represents an adjustment factor that 
may be multiplied by the candidate 1-hour emission limit to determine a 
longer term average emission limit that may be considered comparably 
stringent.\5\ 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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    \5\ For example, if the critical emission value is 1,000 lbs/hr 
of SO2, and a suitable adjustment factor is determined to 
be 70 percent, the recommended longer term average limit would be 
700 lbs/hr.
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    Preferred air quality models for use in regulatory applications are 
described in appendix A of EPA's Guideline on Air Quality Models (40 
CFR part 51, appendix W). In 2005, EPA promulgated AERMOD as the 
Agency's preferred near-field dispersion modeling for a wide range of 
regulatory applications addressing stationary sources (for example in 
estimating SO2 concentrations) in all types of terrain based 
on extensive developmental and performance evaluation. Supplemental 
guidance on modeling for purposes of demonstrating attainment of the 
SO2 standard is provided in appendix A to the April 23, 2014 
SO2 nonattainment area SIP guidance document referenced 
above. Appendix A provides extensive guidance on the modeling domain, 
the source inputs, assorted types of meteorological data, and 
background concentrations. Consistency with the recommendations in this 
guidance is generally necessary for the attainment

[[Page 38647]]

demonstration to offer adequately reliable assurance that the plan 
provides for attainment.
    As stated previously, attainment demonstrations for the 2010 1-hour 
primary SO2 NAAQS must demonstrate future attainment and 
maintenance of the NAAQS in the entire area designated as nonattainment 
(i.e., not just at the violating monitor). This is demonstrated by 
using air quality dispersion modeling (see appendix W to 40 CFR part 
51) that shows that the mix of sources, 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, should 
follow the form of the standard, and should be calculated as described 
in section 2.6.1.2 of the August 23, 2010 clarification memo on 
``Applicability of appendix W Modeling Guidance for the 1-hr 
SO2 National Ambient Air Quality Standard'' (U.S. EPA, 
2010a).

IV. Review of Modeled Attainment Plan

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

A. Model Selection

    Wisconsin's attainment demonstration used AERMOD, the preferred 
model for this application. Wisconsin's January 2016 submittal used 
version 15181 of this model, which was the most recent version at that 
time. However, the supplemental modeling that Wisconsin submitted in 
March 2021 used version 19191, which is the current regulatory version 
of AERMOD. EPA finds this selection appropriate.
    Wisconsin's receptor grid and modeling domain for the Rhinelander 
area followed the recommended approaches from EPA's Guideline on Air 
Quality Models (40 CFR part 51, appendix W). Receptor spacing for each 
modeled facility was every 25 meters out to a distance of 500 meters 
from each source, then every 50 meters to 1,000 meters, every 100 
meters out to 3 kilometers, every 250 meters out to 6 kilometers, and 
every 500 meters out to 10 kilometers.
    Wisconsin determined that the Rhinelander area should be modeled 
with rural dispersion coefficients, as Ahlstrom-Munksj[ouml] is 
surrounded by less than 50% of land classified as industrial, 
commercial, or dense residential within 3 kilometers, as recommended by 
EPA's Guideline on Air Quality Models. Therefore, EPA concurs with 
Wisconsin's determination that this area warrants being modeled with 
rural dispersion coefficients.

B. Simulation of Downwash

    Modeling of emissions from Ahlstrom-Munksj[ouml] has historically 
underpredicted concentrations measured at a nearby monitor. When winds 
blow from this facility toward the monitor, the emissions traverse a 
corner of the building. Under these circumstances, the building appears 
to cause enhanced eddies in the air flow, known as corner vortices, 
which in certain circumstances appear to result in a substantial 
enhancement of downwash of emissions to ground level and substantially 
greater concentrations than are modeled using the standard downwash 
algorithm in AERMOD.
    Recognizing these issues, the company contracted for a wind tunnel 
study, carried out by Cermak Peterka Petersen (CPP), to assess the 
magnitude of this effect and to support a more accurate assessment of 
downwash at this facility. This study supported the conclusion that the 
discrepancy between modeled and monitored SO2 concentrations 
were due to the corner vortex phenomenon, a phenomenon that is 
described in EPA's ``Guideline for Determination of Good Engineering 
Practice Stack Height (Technical Support Document for the Stack Height 
Regulations).'' \6\ The wind tunnel study showed that as the wind 
approaches the corner of the Ahlstrom-Munksj[ouml] building, vortices 
are created that act to increase the SO2 concentrations 
downwind of the building. Analysis of these results suggested that the 
influence of these corner vortices vary by wind speed. Ahlstrom-
Munksj[ouml]'s consultants, AECOM and CPP, developed an equation 
estimating a multiplier, varying by wind speed, by which to estimate 
the impact of downwash in this case, i.e., a multiplier by which to 
multiply concentrations estimated in absence of downwash to estimate 
concentrations reflecting the downwash induced by this facility. The 
wind tunnel study focused on concentrations in the direction with the 
most enhanced downwash but applied the same adjustment in all 
directions. Since there is less downwash in directions less influenced 
by corner vortices, EPA considers this approach conservative in 
maximizing estimated downwash effects on concentrations.
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    \6\ EPA-450/4-80-023R, June 1985.
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    Wisconsin's 2016 SIP submittal relied on modeling Ahlstrom-
Munksj[ouml] using a stack height of 90 meters. For this facility, the 
``formula good engineering practice (GEP) stack height'' computed 
according to the formula in EPA's stack height regulations (defined at 
40 CFR 51.100(ii)(2)(ii)) is 75 meters. EPA disapproved the 2016 
submittal because EPA's stack height regulations prohibit credit for a 
stack above formula GEP stack height unless the state meets 
requirements specified in those regulations for the level of control at 
the facility. Wisconsin's 2021 submittal meets EPA's stack height 
regulations by applying a limit demonstrated to provide attainment with 
a stack at the creditable height of 75 meters.
    The wind tunnel studies primarily simulated a stack with a height 
of 85 meters, with another run simulating a stack with a height of 90 
meters. These runs indicated the following equation to estimate the 
ratio of concentrations expected with the building as compared 
concentrations without the building:
[GRAPHIC] [TIFF OMITTED] TP22JY21.023


[[Page 38648]]


    The variable R is the ratio multiplier that is applied to the 
hourly emission rate file used in AERMOD. The Uairport and Umax values 
represent the actual hourly wind speed measured at the Rhinelander 
airport and the maximum wind speed, i.e., wind speed exceeded less than 
1% of the time, of 10.8 meters per second. The A and B parameters are 
best-fit coefficients. The A parameter, plus 1, represents the maximum 
multiplier that can be applied to the hourly emissions.
    While this equation was originally derived to assess the wind-
speed-dependent influence of downwash with a 90-meter stack, the 
influence of downwash for a 75-meter stack may be derived based on 
these same 85-meter and 90-meter results by using a best-fit 
coefficient (A) that is specific to a 75-meter stack. The best-fit 
coefficient was originally developed using wind tunnel data at an 85-
meter stack height. This coefficient was then adjusted using observed 
and predicted concentration ratios, from the wind tunnel information, 
to determine the appropriate coefficient for a 75-meter stack height. 
For a 75-meter stack, Wisconsin applied the above equation with a value 
of A of 0.826 and B of 0.174.
    Wisconsin did not modify any algorithms or computer code in AERMOD 
to reflect this enhancement of the influence of downwash. Instead, 
Wisconsin implemented this enhancement by using modified model inputs. 
Wisconsin first examined hourly wind speeds. Wisconsin computed hourly 
downwash multipliers based on the above equation. Ordinarily, Wisconsin 
would run AERMOD using a fixed emission rate reflecting the allowable 
emission rate, but in this case Wisconsin input an hourly varying 
emission rate in which each hour's input value equaled the fixed 
emission rate (reflecting the allowable emission rate) times that 
hour's downwash multiplier. For example, for an hour with a wind speed 
of 5 meters per second, for which the above equation gives a downwash 
multiplier of 1.564, the modeled emission rate for that hour reflected 
multiplication times 1.564. This multiplier gives the expected ratio of 
concentrations with the magnitude of downwash at this facility as 
compared to the concentrations expected if no downwash were occurring. 
Therefore, Wisconsin estimated hourly concentrations with Ahlstrom-
Munksj[ouml]-specific downwash by modeling the facility without 
downwash but incorporating the expected impact of downwash at this 
facility by increasing the emission rate modeled for each hour 
accordingly.
    EPA views Wisconsin's modeling as applying an alternate model under 
the terms of 40 CFR 51 appendix W section 3.2.2.b.2. Under the 
alternative model criteria discussed in section 3.2.2.b.2, it must be 
shown that the alternative model performs better for a given 
application than the recommended model, using a statistical analysis. 
The State of Wisconsin evaluated the performance of the alternative 
model from both a theoretical and a performance perspective. This 
information was included in the public notice which preceded Wisconsin 
finalizing its submittal. The Wisconsin analysis showed that the 
alternative model predicted a design value slightly above the monitored 
design value using the recent three years of monitoring data, 2017-
2019. The most recent three years reflect the impact of emissions 
exiting the 90-meter stack. Recent meteorological data, processed for 
modeling purposes, was not available. Consequently, the comparison was 
conducted using the full five years of meteorology applied for the 
attainment demonstration.
    Additional comparisons were conducted that examined, on a year-to-
year basis, how well the alternative model was performing compared to 
the regulatory version of the model and compared to monitoring data. 
That analysis only used emissions from boiler B26, which vents through 
Stack S09, when the boiler was actually operating, essentially non-
summer months for the years 2017-2019. This supplemental modeling was 
conducted using a grid focused on a 400-meter by 400-meter area around 
the monitor to the north of Ahlstrom-Munskj[ouml]. Again, 5 years of 
meteorological data (2011-2015) was used in the modeling.
    The model to monitor comparison used High 1st High concentrations, 
the average of the top 26 values, fractional bias, and 99th percentile 
values. The results of the comparison showed that the alternative model 
performed consistently better than the regulatory version, that is it 
predicted higher concentrations than the standard version of AERMOD. 
Additionally, the year-by-year comparisons to the monitored data showed 
that the alternative model produced underestimates for one year, 
overestimates for one year, and very similar estimates for the third 
year. There was considerable year-to-year variability, as one would 
expect. Consequently, the alternative model was viewed to be acceptable 
based on the theoretical aspects of its development, the superior 
performance compared to the recommended model, and the overall unbiased 
nature of the alternative model's predictions.
    Wisconsin's alternate model characterization was reviewed and 
concurred with on May 28, 2021 by EPA's Model Clearinghouse under EPA's 
Guideline on Air Quality Models criteria for alternate models. EPA 
Region 5's request for concurrence and EPA's Model Clearinghouse 
concurrence letters are included in the docket for this action.

C. Meteorological Data

    Wisconsin used Rhinelander-Oneida County Airport (KRHI) surface 
data and Green Bay, Wisconsin upper air data, years 2011-1015, for 
modeling the Rhinelander area. The surface station is located less than 
5 kilometers from Ahlstrom-Munksj[ouml] and is located in similar 
rolling terrain. Given the close proximity of the surface station and 
the similarity in surrounding terrain, EPA finds the use of the KRHI 
airport data, combined with the Green Bay upper air data to be 
appropriate, representative meteorological data sets for assessing 
dispersion at the facility.

D. Emissions Data

    Wisconsin included all point sources within 50 kilometers of 
Rhinelander in its modeling analysis. These sources included boilers 
B26 (sometimes coal fired) and B28 (natural gas and oil fired) at 
Ahlstrom-Munksj[ouml], the Kerry Inc. facility (formerly Red Arrow 
Foods), and the PCA facility. Wisconsin found that no other sources 
were close enough to cause significant concentration gradients. Boilers 
B20, B21, B22, and B23 at Ahlstrom-Munksj[ouml] were shut down in 2014, 
and their decommissioning is included in a federally enforceable 
permit, so they were not included in the modeling analysis. Wisconsin 
determined that boiler B26, which vents through stack S09, was 
primarily responsible for the Rhinelander area nonattainment 
designation, as the modeling results show that boiler B26 accounts for 
94-95 percent of the total SO2 concentration in the area 
depending on the boiler load. Therefore, boiler B26 was modeled at both 
minimum and maximum loads. The Kerry Inc. and PCA sources, as well as 
Ahlstrom-Munksj[ouml] boiler B28, were modeled at their current 
permitted maximum allowable SO2 emissions, as contained in 
federally enforceable permits.

E. Emission Limits

    An important prerequisite for approval of an attainment plan is 
that

[[Page 38649]]

the emission limits that provide for attainment be quantifiable, fully 
enforceable, replicable, and accountable. See General Preamble at 
13567-68. The limit for Ahlstrom-Munksj[ouml] is expressed as a 24-hour 
average limit. Therefore, part of the review of Wisconsin's attainment 
plan must address the use of this limit, both with respect to the 
general suitability of using such limits for this purpose and with 
respect to whether the particular limits included in the plan have been 
suitably demonstrated to provide for attainment. The first subsection 
that follows addresses the enforceability of the limits in the plan, 
and the second subsection that follows addresses in particular the 24-
hour average limit.
1. Enforceability
    In preparing its plan, Wisconsin adopted a revision to a previously 
approved construction permit, Air Pollution Control Construction Permit 
Revision 15-DMM-128-R1, governing the Ahlstrom-Munksj[ouml] 
SO2 emissions. These permit revisions were adopted by 
Wisconsin following established, appropriate public review procedures. 
The revised permit limits boiler B26 emission rates to 2.38 pounds per 
million British Thermal Unit (lbs/MMBTU) on a 24-hour average basis. 
This limit is more stringent than the previously approved limit of 3.0 
lbs/MMBTU on a 24-hour average basis. The 3.0 lbs/MMBTU limit was 
included as part of Wisconsin's 2016 attainment demonstration that EPA 
disapproved in its March 23, 2021 rulemaking. In accordance with EPA 
policy, the 24-hour average limit is set at a lower level than the 
emission rate used in the attainment demonstration; the relationship 
between these two values is discussed in more detail in the following 
section. Additionally, the revised permit limits the maximum heat input 
to boiler B26 to 260 MMBTU/hour and requires that stack SO9 be a 
minimum of 75 meters (246 feet) above ground, as opposed to the 
previous boiler B26 limit of 300 MMBTU/hour and requirement that stack 
S09 be a minimum of 90 meters (296 feet) off the ground.\7\ The permit 
compliance date for Ahlstrom-Munksj[ouml] is December 31, 2021. EPA 
finds that this construction permit revision provides for permanent 
enforceability.
---------------------------------------------------------------------------

    \7\ For more discussion on stack height, see EPA's November 25, 
2020 proposed partial approval and partial disapproval (85 FR 
75273).
---------------------------------------------------------------------------

2. Longer Term Average Limits
    Ahlstrom-Munksj[ouml] requested a limit expressed as a 24-hour 
average limit in order to have a more robust limit, i.e., a limit based 
on more values that would be less prone to indicate noncompliance based 
on ordinary fluctuations in emissions. In accordance with EPA's April 
2014 guidance for SO2 nonattainment plans, Wisconsin 
therefore adjusted its limit, reducing the limit for purposes of 
assuring comparable stringency to the 1-hour limit that it otherwise 
would have adopted.
    Although compliance with this limit will be determined on the basis 
of continuous emissions monitoring system (CEMS) data, the facility 
does not have a sufficient historical record of CEMS data to be able to 
evaluate source-specific emissions variability for purposes of 
determining a source-specific factor by which to adjust the 1-hour 
limit for this source. Instead, Wisconsin determined its 24-hour 
average limit by applying one of the national average adjustment 
factors listed in appendix D of EPA's guidance. In particular, 
Wisconsin set its 24-hour average limit at 93 percent of the modeled 
emission rate, reflecting the national average adjustment factor that 
EPA found among facilities without emission control equipment. While 
the facility operates dry sorbent injection equipment to control 
hydrogen chloride (HCl) emissions so as to meet the maximum available 
control technology requirements for industrial boilers, HCl is 
generally much easier to control than SO2, and the 
information about the facility's sorbent usage provided in Wisconsin's 
submittal supports a conclusion that sorbent injection likely reduces 
SO2 emissions by less than one percent. Therefore, sorbent 
usage may be presumed to have very little impact on the variability of 
SO2 emissions at this facility, and the national average 
adjustment factor for facilities without control equipment is likely to 
provide the best estimate of the appropriate degree of adjustment to 
determine a 24-hour limit that is comparably stringent to the 1-hour 
limit that otherwise would have been established.
    Wisconsin set its limit at 2.38 lbs/MMBTU, corresponding to 93 
percent of the 2.56 lbs/MMBTU emission rate that Wisconsin modeled.\8\ 
Although appendix D of EPA's guidance reports average adjustment 
factors based on 99th percentile values among lbs/hr data rather than 
among lbs/MMBTU data, EPA generally finds that lbs/hr data show greater 
variability than lbs/MMBTU data, and so use of an adjustment factor 
determined from analysis of lbs/hr data is likely to yield a 
conservative (more stringent) result.
---------------------------------------------------------------------------

    \8\ To be precise, the emission rates that Wisconsin modeled 
reflected 2.56 lbs/MMBTU times the allowable operating rate of 260 
MMBTU/hour times the hour-specific downwash multiplier discussed 
above.
---------------------------------------------------------------------------

    The Ahlstrom-Munksj[ouml] 24-hour average SO2 emissions 
will be calculated by summing the emissions rates of each 1-hour 
operating period and dividing by the number of operating hours for that 
calendar day. Although EPA recommends that the average values be 
calculated by summing the total emissions and dividing by the total 
heat input for each day, this approach is infeasible for Ahlstrom-
Munksj[ouml]. Because Ahlstrom-Munksj[ouml] is using Method 19, 
calculating lbs/MMBTU SO2 concentration without evaluating 
either the mass or the heat input,\9\ the facility does not obtain the 
hourly mass or heat input values to support a calculation of daily 
total mass or daily total heat input. As the differences in results of 
the two approaches are expected to be minimal, EPA concurs with 
Wisconsin's approach.
---------------------------------------------------------------------------

    \9\ ``Method 19--Determination of Sulfur Dioxide Removal 
Efficiency and Particulate Matter, Sulfur Dioxide, and Nitrogen 
Oxide Emission Rates'' (40 CFR part 60, appendix A).
---------------------------------------------------------------------------

    Ahlstrom-Munksj[ouml] requested that Wisconsin specify compliance 
determination procedures for days with fewer hours of data (generally, 
days with fewer hours of operation) in order to ensure robust 
compliance determinations, specifically to ensure that compliance is 
determined on the basis of a minimum of 18 hours of data. For days with 
fewer than 24 but at least 18 hours of data, compliance will be 
determined by averaging the emissions rates from the hours of 
operation. For operating days with fewer than 18 hours of data, 
compliance will be determined by averaging all the values from that day 
along with all the values from the most recent day with at least 18 
hours of valid data. EPA supports the principle of ensuring that 
compliance with a long-term average limit should be based on a robust 
data set. Wisconsin's approach also is consistent with the principle 
that the facility shall be accountable for emissions at all times, 
i.e., that days with fewer hours of data shall not be disregarded but 
rather shall be included in a suitably constructed compliance 
determination. Therefore, EPA concludes that Wisconsin is using an 
appropriate approach for addressing days with fewer hours of data.
    Based on a review of the State's submittal, EPA believes that the 
24-hour-average limit for Boiler B26 at Ahlstrom-Munksj[ouml] provides 
a suitable alternative to establishing a 1-hour average emission limit 
for this source.

[[Page 38650]]

EPA finds that Wisconsin used an appropriate adjustment factor, 
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 24-average limit allows 
occasions in which emissions may be higher than the level that would be 
allowed with the 1-hour limit, the State's limit compensates by 
requiring average emissions to be lower than the level that would 
otherwise have been required by a 1-hour average limit. For the reasons 
described above and explained in more detail in EPA's April 2014 
guidance for SO2 nonattainment plans, EPA finds that 
appropriately set longer term average limits provide a reasonable basis 
by which nonattainment plans may provide for attainment. Based on its 
review of this general information as well as the particular 
information in Wisconsin's plan, EPA finds that the 24-hour-average 
limit for boiler B26 at Ahlstrom-Munksj[ouml] is a suitable alternative 
to establishing a 1-hour limit on emissions from this boiler.

F. Background Concentrations

    Wisconsin determined background concentrations for the Rhinelander 
area using 2013-2015 data from the Horicon (Dodge County) monitor, 
which is approximately 250 kilometers south of Rhinelander. The 
background concentration values that Wisconsin used varied by month and 
hour of the day and ranged from 1.40 micrograms per cubic meter ([mu]g/
m\3\) to 14.1 [mu]g/m\3\ with an average value of 4.87 [mu]g/m\3\. EPA 
agrees that the values from the Horicon monitor are representative for 
background concentration estimates.

G. Summary of Results

    Modeling for the Rhinelander Area in Wisconsin's March 2021 
submittal showed a design value of 74.8 ppb (195.8 [mu]g/m\3\). This 
resulted from modeling the Ahlstrom-Munksj[ouml] boiler B26 at maximum 
load, combined with all other area sources and including a background 
concentration. The run was conducted with emissions at 2.56 lbs/MMBTU, 
a level that corresponds in stringency to the 2.38 lbs/MMBTU 24-hour 
average emission limit that Wisconsin adopted and submitted and is more 
stringent than the previous 24-hour emission limit of 3.0 lbs/MMBTU. 
Therefore, EPA concludes that Wisconsin's plan provides for attainment 
in this area.

V. Review of Other Plan Requirements

A. RACM/RACT

    CAA section 172(c)(1) states that nonattainment plans shall provide 
for the implementation of all RACM as expeditiously as practicable 
(including such reductions in emissions from existing sources in the 
area as may be obtained through the adoption, at a minimum, of RACT) 
and shall provide for attainment of the national primary ambient air 
quality standards. CAA section 172(c)(6) requires plans to include 
enforceable emissions limitations, and such other control measures as 
may be necessary or appropriate to provide for attainment of the NAAQS. 
In its March 23, 2021 rulemaking, EPA disapproved Wisconsin's 2016 
attainment plan because the Ahlstrom-Munksj[ouml] emissions limits (3.0 
lbs/MMBTU 24-hour average SO2 limit and 300 MMBTU/hr 
operating limit) provided in the plan were not calculated in compliance 
with the stack height regulations. Therefore, the plan could not be 
considered to provide an appropriate attainment demonstration, and it 
did not demonstrate RACM/RACT or meet the requirement for necessary 
emissions limitations or control measures. Wisconsin's revised plan for 
attaining the 1-hour SO2 NAAQS in the Rhinelander area is 
based on a variety of measures, including more stringent SO2 
emissions and operating limits (2.38 lbs/MMBTU 24-hour average 
SO2 limit and 260 MMBTU/hr operating limit) for Ahlstrom-
Munksj[ouml], which were calculated in compliance with the stack height 
regulations. Wisconsin's plan requires compliance with these measures 
by December 31, 2021. Wisconsin has determined that these measures 
suffice to provide for attainment. EPA concurs and proposes to conclude 
that the State has satisfied the requirement in section 172(c)(1) and 
(6) to adopt and submit all RACM/RACT and emissions limitations or 
control measures as needed to attain the standards as expeditiously as 
practicable.

B. Reasonable Further Progress (RFP)

    In its March 23, 2021 rulemaking, EPA concluded that Wisconsin had 
not satisfied the requirement in section 172(c)(2) to provide for RFP 
toward attainment. Wisconsin's 2016 attainment plan did not demonstrate 
that the implementation of the control measures required under the plan 
were sufficient to provide for attainment of the NAAQS in the 
Rhinelander SO2 nonattainment area consistent with EPA 
requirements (in particular consistent with EPA stack height 
regulations). Therefore, a compliance schedule to implement those 
controls was not sufficient to provide for RFP. Wisconsin's revised 
plan requires compliance by December 31, 2021. Wisconsin concludes that 
this is an ambitious compliance schedule, as described in April 2014 
guidance for SO2 nonattainment plans, and concludes that 
this plan therefore provides for RFP in accordance with the approach to 
RFP described in EPA's 2014 guidance. EPA concurs and proposes to 
conclude that the plan provides for RFP.

C. Contingency Measures

    As noted above, EPA guidance describes special features of 
SO2 planning that influence the suitability of alternative 
means of addressing the requirement in section 172(c)(9) for 
contingency measures for SO2, such that in particular an 
appropriate means of satisfying this requirement is for the State to 
have a comprehensive enforcement program that identifies sources of 
violations of the SO2 NAAQS and to undertake an aggressive 
follow-up for compliance and enforcement. Wisconsin's plan provides for 
satisfying the contingency measure requirement in this manner.\10\ EPA 
concurs and proposes to approve Wisconsin's plan for meeting the 
contingency measure requirement in this manner.
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    \10\ Wisconsin Department of Natural Resources (WDNR) maintains 
an enforcement program to ensure compliance with SIP requirements. 
The Bureau of Air Management houses an active statewide compliance 
and enforcement team that works in all geographic regions of the 
State. WDNR refers actions as necessary to the Wisconsin Department 
of Justice with the involvement of WDNR. Wis. Stats. 285.83 and Wis. 
Stats. 285.87 provide WDNR with the authority to enforce violations 
and assess penalties, to ensure that required measures are 
ultimately implemented.
---------------------------------------------------------------------------

VI. What action is EPA taking?

    EPA is proposing to approve Wisconsin's SIP submission, which the 
State submitted to EPA on March 29, 2021 to supplement the prior SIP it 
had submitted on January 22, 2016 and supplemented on July 18, 2016, 
and November 29, 2016, for attaining the 2010 1-hour SO2 
NAAQS for the Rhinelander area and for meeting other nonattainment area 
planning requirements. This SO2 attainment plan includes 
Wisconsin's attainment demonstration for the Rhinelander area. The plan 
also addresses requirements for RFP, RACT/RACM, and contingency 
measures. EPA has previously concluded that Wisconsin has addressed the 
requirements for

[[Page 38651]]

emissions inventories for the Rhinelander area and nonattainment area 
NSR. EPA has determined that Wisconsin's Rhinelander SO2 
plan meets applicable requirements of section 172 of the CAA.
    Wisconsin's Rhinelander SO2 plan is based on the 
emissions limits specified in Air Pollution Control Construction Permit 
Revision 15-DMM-128-R1. Wisconsin seeks EPA to approve several elements 
of the permit, including the permit cover sheet, emissions limitations 
for Ahlstrom-Munksj[ouml] (Conditions A.3.a.(1)-(3)), compliance 
demonstration (Conditions A.3.b.(1)-(3)), reference test methods, 
recordkeeping and monitoring requirements (Conditions A.3.c.(1)-(5) and 
A.3.c.(7)-(9)), and the effective date (Condition YYY.1.a.(1)). 
Wisconsin did not seek approval of limits and test methods associated 
with oil sulfur content. Wisconsin stated that limits on the portion of 
emissions from oil are unnecessary to comply with the 24-hour 
SO2 emission limit and the boiler heat input limit, and 
attainment is ensured by limits on total emissions from boiler B26. EPA 
concurs with Wisconsin's rationale, and therefore EPA is proposing to 
approve these elements of the permit.
    Additionally, EPA is proposing to replace the previously approved 
consent and administrative orders (AM-94-38 and AM-15-01) governing the 
Ahlstrom-Munksj[ouml] emission limits \11\ with the elements of 
Wisconsin's Air Pollution Control Construction Permit Revision 15-DMM-
128-R1 specified above. This replacement would not be effective until 
December 31, 2021, which is the revised permit compliance date for 
Ahlstrom-Munksj[ouml]. Section 110(l) of the CAA states that EPA 
``shall not approve a revision of a plan if the revision would 
interfere with any applicable requirement . . .'' Since Permit 15-DMM-
128-R1 contains a more stringent SO2 limit for Ahlstrom-
Munksj[ouml] (2.38 lbs/MMBTU on a 24-hour average basis) than the 
previous orders (3.0 lbs/MMBTU on a 24-hour average basis), and since 
Wisconsin has demonstrated that the limit in Permit 15-DMM-128-R1 
provides for attainment without need for the limits in the prior 
orders, EPA concludes that Section 110(l) does not prohibit EPA from 
replacing the prior orders with the newer permit, and EPA is proposing 
to act in accordance with this Wisconsin request.
---------------------------------------------------------------------------

    \11\ Orders AM-94-38 and AM-15-01 were issued to the facility's 
prior owner, Expera, but the orders continued to limit the 
facility's emissions after it was acquired by Ahlstrom-Munksj[ouml].
---------------------------------------------------------------------------

    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 the final action. If this 
approval is finalized, it would terminate the sanctions clock started 
under CAA section 179 resulting from EPA's partial disapproval of the 
prior SIP, as well as EPA's duty to promulgate a FIP for the area under 
CAA section 110(c) that resulted from the previous partial disapproval.

VII. Incorporation by Reference

    In this rule, EPA is proposing to include in a final EPA rule 
regulatory text that includes incorporation by reference. In accordance 
with requirements of 1 CFR 51.5, EPA is proposing to incorporate by 
reference the specific portions of Wisconsin Air Pollution Control 
Construction Permit Revision 15-DMM-128-R1, effective December 31, 
2021, as described in section VI. above. EPA has made, and will 
continue to make, these documents generally available through 
www.regulations.gov and at the EPA Region 5 Office (please contact the 
person identified in the FOR FURTHER INFORMATION CONTACT section of 
this preamble for more information).
    Also in this document, as described in section VI, EPA is proposing 
to remove provisions of the EPA-Approved Wisconsin Source Specific 
Requirements from the Wisconsin State Implementation Plan, which is 
incorporated by reference in accordance with the requirements of 1 CFR 
part 51.

VIII. Statutory and Executive Order Reviews

    Under the CAA, the Administrator is required to approve a SIP 
submission that complies with the provisions of the CAA and applicable 
Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in 
reviewing SIP submissions, EPA's role is to approve state choices, 
provided that they meet the criteria of the CAA. Accordingly, this 
action merely approves state law as meeting Federal requirements and 
does not impose additional requirements beyond those imposed by state 
law. For that reason, this action:
     Is not a significant regulatory action subject to review 
by the Office of Management and Budget under Executive Orders 12866 (58 
FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 2011);
     Does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Is not an economically significant regulatory action based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     Is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Is not subject to requirements of Section 12(d) of the 
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 
note) because application of those requirements would be inconsistent 
with the CAA; and
     Does not provide EPA with the discretionary authority to 
address, as appropriate, disproportionate human health or environmental 
effects, using practicable and legally permissible methods, under 
Executive Order 12898 (59 FR 7629, February 16, 1994).
    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: July 13, 2021.
Cheryl Newton,
Acting Regional Administrator, Region 5.
[FR Doc. 2021-15464 Filed 7-21-21; 8:45 am]
BILLING CODE 6560-50-P


