[Federal Register Volume 85, Number 114 (Friday, June 12, 2020)]
[Proposed Rules]
[Pages 35852-35874]
[FR Doc No: 2020-12499]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R03-OAR-2020-0157; FRL-10010-42-Region 3]

Air Plan Approval; Pennsylvania; Allegheny County Area Attainment
Plan for the 2012 Fine Particulate Matter National Ambient Air Quality
Standard

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to
approve elements of a state implementation plan (SIP) revision
submitted by the Pennsylvania Department of Environmental Protection
(PADEP) on behalf of the Allegheny County Health Department (ACHD) to
address Clean Air Act (CAA or ``the Act'') requirements for the 2012
annual fine particulate matter (PM2.5) national ambient air
quality standards (NAAQS or ``standards'') in the Allegheny County
Moderate PM2.5 nonattainment area (``Allegheny County
area''). The SIP revision contains the ``Attainment Demonstration for
the Allegheny County, PA PM2.5 Nonattainment Area, 2012
NAAQS,'' submitted on September 30, 2019 (also referred to as ``the
Allegheny County PM2.5 Plan'' or simply ``the plan''). EPA
is proposing to fully approve the following elements of the Allegheny
County PM2.5 Plan: The base year emissions inventory, the
particulate matter precursor contribution demonstration, the reasonably
available control measures/reasonably available control technology
(RACM/RACT) demonstration, the attainment demonstration, the air
quality modeling demonstration supporting attainment by the attainment
deadline, the reasonable further progress (RFP) demonstration, and the
a demonstration of interim quantitative milestones to ensure timely
attainment. EPA is proposing to conditionally approve the following
elements of this Allegheny County PM2.5 Plan SIP revision:
The contingency measures and the motor vehicle emission budget (MVEB)
elements of the plan. PADEP commits, on behalf of ACHD, to submit a
supplemental SIP revision to remedy those portions of the plan for
which EPA is proposing conditional approval within twelve months of
EPA's final conditional approval action. This action is being taken
under the CAA.

DATES: Written comments must be received on or before July 13, 2020.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R03-
OAR-2020-0157 at https://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 https://www.epa.gov/dockets/commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT: Brian Rehn, Planning & Implementation
Branch (3AD30), Air & Radiation Division, U.S. Environmental Protection
Agency, Region III, 1650 Arch Street, Philadelphia, Pennsylvania 19103.
The telephone number is<PHONE_NUMBER>. Mr. Rehn can also be reached
via electronic mail at<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION: Throughout this document, ``we,'' ``us,''
and ``our'' refer to EPA.

Table of Contents

I. Background
II. Clean Air Act Plan Requirements for Areas Designated Moderate
Nonattainment for the PM2.5 NAAQS
III. Review of the Allegheny County PM2.5 Plan
    A. Emissions Inventories for the Base Year and Attainment Year
    1. Requirements for Emissions Inventories
    2. Emissions Inventories in the Allegheny County
PM2.5 Plan
    3. EPA's Evaluation and Proposed Action on the Emission
Inventories
    B. Particulate Matter Precursor Demonstration
    1. PM2.5 Precursor Requirements
    2. Precursor Demonstration in the Allegheny County
PM2.5 Plan
    3. EPA's Evaluation and Proposed Action on the Precursor
Demonstration
    C. Reasonably Available Control Measures (RACM)/Reasonably
Available Control Technology (RACT)
    1. Requirements for RACM/RACT
    2. RACM Analysis in the Allegheny County PM2.5 Plan
    a. RACM Measures Evaluation
    3. RACT Analysis in the Allegheny County PM2.5 Plan
    a. RACT Measures Evaluation
    4. EPA's Evaluation and Proposed Action on RACM and RACT
    D. Air Quality Modeling
    1. Requirements for Air Quality Modeling
    2. Air Quality Modeling in the Allegheny County PM2.5
Plan
    3. EPA's Evaluation and Proposed Action on Modeling
    E. Attainment Demonstration
    1. Requirements for an Attainment Demonstration
    2. Attainment Demonstration in the Allegheny County
PM2.5 Plan
    3. EPA's Evaluation of ACHD's PM2.5 Attainment
Demonstration
    4. EPA's Proposed Action on the PM2.5 Attainment
Demonstration
    F. Reasonable Further Progress (RFP)
    1. Requirements for Ensuring Reasonable Further Progress
    2. RFP Demonstration in the Allegheny County PM2.5
Plan
    3. EPA's Evaluation of and Proposed Action on RFP
    G. Quantitative Milestone (QM) Demonstration
    1. Requirements for a QM Demonstration
    2. QM Demonstration in the Allegheny County PM2.5
Plan and 2019 QM Report
    a. Allegheny County Area QM Demonstration
    b. Allegheny County PM2.5 Area 2019 QM Report
    3. EPA's Evaluation and Proposed Action on the QM Demonstration
    H. Contingency Measures
    1. Requirements for Contingency Measures
    2. Contingency Measures in the Allegheny County PM2.5
Plan
    3. EPA's Evaluation and Proposed Action on Contingency Measures
    I. Transportation Conformity and MVEBs
    1. Requirements for Motor Vehicle Emission Budgets
    2. Motor Vehicle Emission Budgets in the Allegheny County
PM2.5 Attainment Plan
    3. EPA's Evaluation and Proposed Action on the Intended MVEB
IV. Summary of Proposed Action and Request for Public Comment
V. Statutory and Executive Order Reviews

I. Background

    Under section 109 of the CAA, EPA has established NAAQS for certain
pervasive air pollutants (referred to as ``criteria pollutants'') and
conducts periodic reviews of the NAAQS to determine whether they should
be revised or whether new NAAQS should be established. EPA sets the
NAAQS for criteria pollutants at levels required to protect public
health and welfare. ``Primary'' NAAQS are those determined by EPA as
requisite to protect human health, while ``secondary'' NAAQS are those
determined by EPA as requisite to protect the public welfare from any
known or anticipated adverse effects of the NAAQS pollutant.\1\
Particulate matter is one of the criteria pollutants for which EPA has
established health-based standards. The CAA requires states to submit
regulations that control particulate matter emissions.
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    \1\ See CAA section 109(b).
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    Particulate matter includes particles with diameters that are
generally 2.5 microns or smaller (referred to as PM2.5) and
particles with diameters that are generally 10 microns or smaller (or
PM10). Particulate matter has deleterious effects on the
environment, both to human health and to plants and wildlife. The
effects on human health include premature mortality, aggravation of
respiratory and cardiovascular disease, and decreased lung function.
Some individuals, such as older adults and people with lung or heart
disease, are particularly sensitive to PM2.5 exposure.
Impacts on the environment include impairment of visibility, as well as
damage to vegetation and ecosystems.\2\ Sources can directly emit
PM2.5 into the atmosphere, in the form of a solid or a
liquid particle (i.e., ``direct PM2.5'' or ``primary
PM2.5''). PM2.5 can also form as a result of
chemical reactions in the atmosphere of precursor pollutants emitted
from sources (i.e. ``secondary PM2.5''). Such secondary
PM2.5 precursor pollutants include nitrogen oxides
(NOX), sulfur dioxide (SO2), volatile organic
compounds (VOC), and ammonia.\3\
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    \2\ See 78 FR 3086, 3088 (January 15, 2013).
    \3\ See EPA, Air Quality Criteria for Particulate Matter, No.
EPA/600/P-99/002aF and EPA/600/P-99/002bF, October 2004.
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    On July 18, 1997, EPA revised the particulate matter NAAQS to
establish new primary and secondary annual and 24-hour standards for
PM2.5.\4\ The annual standard was set at 15.0 micrograms per
cubic meter ([micro]g/m\3\), based on a 3-year average of annual mean
PM2.5 concentrations. The 24-hour (daily) standard was set
at 65 [micro]g/m\3\ based on the 3-year average of the annual 98th
percentile values of 24-hour PM2.5 concentrations at each
population-oriented monitor within an area.\5\
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    \4\ 62 FR 38652 (July 18, 1997).
    \5\ In this action, EPA set primary and secondary standards at
the same level for both the 24-hour and the annual PM2.5
standards.
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    On October 17, 2006,\6\ EPA revisited the particulate matter NAAQS,
retaining the annual average PM2.5 NAAQS at 15 [mu]g/m\3\,
but revising the 24-hour PM2.5 NAAQS to 35 [micro]g/m\3\
(based on a 3-year average of the annual 98th percentile values of 24-
hour concentrations).\7\ On January 15, 2013, EPA finalized the 2012
PM2.5 NAAQS, which revised the annual standard to 12.0
[mu]g/m\3\ based on a 3-year average of annual mean PM2.5
concentrations, but retained the current 24-hour standard of 35
[micro]g/m\3\ based on a 3-year average of the 98th percentile of 24-
hour concentrations.\8\
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    \6\ See 71 FR 61144.
    \7\ Under 40 CFR part 50, the primary and secondary 2006 24-hour
PM2.5 NAAQS are attained when the annual arithmetic mean
concentration (as determined in accordance with 40 CFR part 50,
appendix N) is less than or equal to 35 [micro]g/m\3\ at all
relevant monitoring sites in the subject area, averaged over a 3-
year period.
    \8\ See 78 FR 3086.

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    Following promulgation of a new or revised NAAQS, EPA is required
by CAA section 107(d) to designate areas throughout the nation as
attaining or not attaining the NAAQS. EPA designated and classified the
Allegheny County area as ``Moderate'' nonattainment for the 2012 annual
PM2.5 standards based on ambient monitoring data that showed
the area was above 12.0 [micro]g/m\3\ for the 2011-2013 monitoring
period.\9\ Based on monitoring data for the 2011-2013 period, the
PM2.5 annual design values for the Liberty monitor [AIRS ID
42-00300064] were 13.4 [mu]g/m\3\.
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    \9\ See 80 FR 2206 (January 15, 2015).
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    The Allegheny County 2012 PM2.5 nonattainment area lies
in southwestern Pennsylvania and in 2018 had a population of 1,218,452
persons. Pittsburgh is the largest city in Allegheny County, which also
contains the Cities of Clairton, Duquesne, and McKeesport. In total,
the County has 130 self-governing municipalities. Allegheny County has
complex, mountainous terrain cut by numerous river valleys, which can
work to trap locally generated air pollutants. Within the County, some
river valleys lie at less than 720 feet in elevation above mean sea
level (MSL), while adjacent hilltops can be greater than 1250 feet--
with frequently large temperature differences between the hilltop and
valley floor (e.g. 2 to 7 [deg]F) during clear, light-wind, nighttime
conditions. The combination of higher elevation mountainous terrain and
river valleys, in conjunction with cool weather, traps locally
generated pollution and makes the area prone to atmospheric inversions
that impair PM2.5 dispersion, sometimes for multiple days,
particularly during winter. The Liberty monitor sits above the east
bank of the Monongahela River at an elevation of 1,100 feet,
immediately downwind of the highest emitting PM2.5
stationary source in the area, the U.S. Steel Clairton Coke Works,
which lies in the river valley at an elevation 300 feet below the
monitor. As a result, the monitored PM2.5 values at the
Liberty monitor are sometimes far higher than those of other monitors
in the surrounding region.
    ACHD has the primary responsibility for developing a plan to attain
the 2012 annual PM2.5 NAAQS in this area, working in
conjunction with the PADEP in preparing the Allegheny County
PM2.5 Plan. Under Pennsylvania law, authority for regulating
sources in the area is split between the County and Pennsylvania, with
ACHD having primary responsibility for regulating stationary sources in
the area.

II. Clean Air Act Plan Requirements for Areas Designated Moderate
Nonattainment for the PM2.5 NAAQS

    A January 4, 2013, U.S. Court of Appeals for the District of
Columbia Circuit decision \10\ stated that EPA must implement
PM2.5 NAAQS pursuant to title I, part D, subpart 4 of the
CAA, which contains provisions specifically concerning PM10
nonattainment areas. With respect to the statutory requirements for
attainment plans for the 2012 annual PM2.5 NAAQS, general
CAA nonattainment area planning requirements are found in part D,
subpart 1, and planning requirements specific to areas designated
Moderate for particulate matter are found in subpart 4 of part D.
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    \10\ Natural Resources Defense Council v. EPA, 706 F. 3d 428
(D.C. Cir. 2013).
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    EPA has a longstanding general guidance document interpreting the
1990 amendments to the CAA, referred to as the General Preamble for the
Implementation of title I of the Clean Air Act of 1990 (or the
``General Preamble'').\11\ The General Preamble addresses the
relationship between the requirements of CAA part D, subpart 1 and
subpart 4, and provides recommendations to states for meeting certain
statutory requirements for particulate matter attainment plans. As
explained in the General Preamble, requirements specific to Moderate
area attainment plan SIP submissions for particulate matter NAAQS are
set forth in subpart 4 of part D, title I of the CAA. However, such SIP
submissions must also meet the general attainment planning provisions
in subpart 1 of part D, title I of the CAA, to the extent these
provisions ``are not otherwise subsumed by, or integrally related to,''
the more specific subpart 4 requirements.\12\
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    \11\ See General Preamble, 57 FR 13498 (April 16, 1992).
    \12\ See 57 FR 13538, April 16, 1992.
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    To implement the PM2.5 NAAQS, EPA also promulgated the
``Fine Particulate Matter National Ambient Air Quality Standard: State
Implementation Plan Requirements; Final Rule'' (or the
``PM2.5 SIP Requirements Rule'').\13\ The PM2.5
SIP Requirements Rule provides additional regulatory requirements and
guidance applicable to attainment plan submissions for the
PM2.5 NAAQS, including the 2012 annual PM2.5
NAAQS that is the subject of this action. The PM2.5 SIP
Requirements Rule also clarifies how states should meet the statutory
SIP requirements that apply to areas designated nonattainment for any
PM2.5 NAAQS under both subparts 1 and 4.
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    \13\ See 81 FR 58010, August 24, 2016.
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    The CAA subpart 1 statutory requirements for attainment plans
include: (i) The section 172(c)(1) requirements for RACM/RACT and
attainment demonstrations; (ii) the section 172(c)(2) requirement to
demonstrate RFP; (iii) the section 172(c)(3) requirement for
preparation of emissions inventories; (iv) the section 172(c)(5)
requirements for adoption of a nonattainment new source review (NNSR)
permitting program; and (v) the section 172(c)(9) requirement to adopt
contingency measures.
    Requirements specific to Moderate PM2.5 nonattainment
areas under CAA subpart 4 include: (i) The section 189(a)(1)(A) and
189(e) NNSR permit program requirements; (ii) the section 189(a)(1)(B)
requirements for attainment demonstrations; (iii) the section
189(a)(1)(C) requirements for RACM; and (iv) the section 189(c)
requirements for RFP and QMs. Under CAA subpart 4, states with Moderate
PM2.5 nonattainment areas must provide for attainment in the
area as expeditiously as practicable (but no later than December 31,
2021) for the 2012 PM2.5 annual NAAQS. In addition, under
CAA subpart 4, direct PM2.5 (and all precursors to the
formation of PM2.5) are subject to control unless EPA
approves a demonstration from the state establishing that a given
precursor does not contribute significantly to PM2.5 levels
that exceed the PM2.5 NAAQS in the area.\14\
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    \14\ See 40 CFR 51.1006 and 51.1009.
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III. Review of the Allegheny County PM2.5 Plan

A. Emissions Inventories for the Base Year and Attainment Year

1. Requirements for Emissions Inventories
    CAA section 172(c)(3) requires that each SIP include a
``comprehensive, accurate, current inventory of actual emissions from
all sources of the relevant pollutant or pollutants in [the] area . .
.'' By requiring an accounting of actual emissions from all sources of
the relevant pollutants in the area, this section provides for the base
year inventory to include all emissions that contribute to the
formation of a particular NAAQS pollutant. For the 2012
PM2.5 NAAQS, this includes emissions of direct
PM2.5 as well as the main chemical precursors to the
formation of secondary PM2.5, including NOX,
SO2, VOCs, and ammonia (NH3). Primary
PM2.5 is comprised of both

condensable and filterable particulate matter components.
    EPA PM2.5 requirements rule establishes that ``the base
year inventory for the nonattainment area: (a) Be required to represent
one of the 3 years used for designations or another technically
appropriate year; (b) include actual emissions of all sources within
the nonattainment area; (c) be annual total or average-season-day
emissions in accordance with the NAAQS violation; (d) include direct
PM2.5 (filterable and condensable) as well as all scientific
PM2.5 precursors . . .'' \15\
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    \15\ 81 FR 58027-58033, August 24, 2016.
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    A state must include in its SIP submission documentation explaining
how the emissions data were calculated. In estimating mobile source
emissions, a state should use the latest emissions models and planning
assumptions available at the time it develops the SIP submission.\16\
States are also required to use EPA's ``Compilation of Air Pollutant
Emission Factors'' (AP-42) \17\ road dust method for calculating re-
entrained road dust emissions from paved roads.\18\ MOVES is EPA's
state-of-the-art tool for estimating emissions from on-road mobile
sources. At the time ACHD prepared the SIP, MOVES2014a was the latest
available version of the MOVES model, which included new data, emission
standards, and functional improvements and features over prior versions
of the model.\19\ EPA subsequently released an updated MOVES model
(MOVES2014b) in August 2018, which better estimates non-road mobile
emissions compared to MOVES2014a. However, MOVES2014b was not available
at the time ACHD began working on emission inventories in support of
this plan, and EPA does not consider MOVES2014b a new model for SIP and
transportation conformity purposes.\20\
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    \16\ See EPA's ``Policy Guidance on the Use of MOVES2014 for
State Implementation Plan Development, Transportation Conformity,
and Other Purposes,'' (EPA-420-B-14-008; July 2014), p. 6.
    \17\ EPA released an update to AP-42 in January 2011 that
revised the equation for estimating paved road dust emissions based
on an updated data regression that included new emission tests
results.
    \18\ See 76 FR 6328 (February 4, 2011).
    \19\ See EPA guidance document ``Policy Guidance on the Use of
MOVES2014 for State Implementation Plan Development, Transportation
Conformity, and Other Purposes'' (EPA-420-B-14-008; July 2014).
    \20\ See EPA guidance document ``EPA Releases MOVES2014b Mobile
Source Emissions Model: Questions and Answers,'' (EPA-420-F-18-014;
August 2018), available at: https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100V7H1.pdf.
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    In addition to the base year inventory submitted to meet the
requirements of CAA section 172(c)(3), the State must also submit
future ``baseline inventories'' for the projected attainment year and
each RFP milestone year, and any other year of significance for meeting
applicable CAA requirements.\21\ By ``baseline inventories'' (also
referred to as ``projected baseline inventories''), we mean projected
emissions inventories for future years that account for, among other
things, the ongoing effects of economic growth and adopted emissions
control requirements. The SIP submission should include documentation
to explain how the state calculated the emissions projections.
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    \21\ See 40 CFR 51.1007(a), 51.1008(b), and 51.1009(f). See also
U.S. EPA, ``Emissions Inventory Guidance for Implementation of Ozone
[and Particulate Matter] National Ambient Air Quality Standards
(NAAQS) and Regional Haze Regulations,'' available at: https://www.epa.gov/sites/production/files/2017-07/documents/ei_guidance_may_2017_final_rev.pdf.
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2. Emissions Inventories in the Allegheny County PM2.5 Plan
    The Allegheny County PM2.5 nonattainment area emissions
inventory has both small and medium city typical emission sources and
is home to several large industrial sources of PM2.5
pollution. The Monongahela River Valley contains the U.S. Steel
Corporation's Mon Valley Works, which includes the largest coke
manufacturing plant in the United States (the U.S. Steel Clairton Coke
Works) as well as the Irvin and Edgar Thomson steel works. The area is
also home (or nearby to) to several steel manufacturing facilities,
coal fired electric generating facilities, and other manufacturing and
industrial facilities.
    As specified by EPA's PM2.5 Implementation Rule,
pollutants inventoried for the Allegheny County PM2.5 area
include primary (direct) PM2.5 along with precursors
SO2, NOX, VOC, and NH3. Particulate
emissions are also transported into the Allegheny County area from
surrounding counties in southwestern Pennsylvania, as well as
surrounding, upwind states. EPA's Emissions Inventory Guidance for
PM2.5 specifies that PM10 should also be included
because PM10 emissions are often used as the basis for
calculating PM2.5.\22\
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    \22\ See U.S. EPA, ``Emissions Inventory Guidance for
Implementation of Ozone [and Particulate Matter] National Ambient
Air Quality Standards (NAAQS) and Regional Haze Regulations,''
available at: https://www.epa.gov/sites/production/files/2017-07/documents/ei_guidance_may_2017_final_rev.pdf
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    The 2021 inventory is a projection of the 2011 base year inventory,
which accounts for expected growth trends for each source category, as
well as emission reductions from adopted and implemented control
measures. This projection inventory also factors in stationary source
shutdowns occurring since the base year. Local projections were focused
on PM2.5 and precursor reductions from stationary point
source emissions, while regional projections were based on reductions
from all sectors as incorporated into the Mid-Atlantic Regional Air
Management Association (MARAMA) inventories. ACHD staff worked with
PADEP to develop the base year and projection emissions inventories for
the Allegheny County PM2.5 nonattainment area.
    The base 2011 and future projection 2021 emissions inventories for
the Allegheny County PM2.5 area used in this demonstration
are found in Section 4 (Emissions Inventories) of the Commonwealth's
September 30, 2019 SIP revision, with detailed emissions inventories
found in Appendix D (Emissions Inventories) of the SIP revision.
Documentation of the regional inventory development is included in
Appendix E (Emissions Inventory Documentation) of the SIP revision, and
emissions inputs used for the modeling are described in Section 5
(Modeling Demonstration) and Appendix F (Modeling Protocols). Table 1
provides a summary of the 2011 base year emission inventory for the
Allegheny County area in tons per year (tpy) of direct PM2.5
and PM2.5 precursors and also a summary of the 2021
projected emissions inventory.

                               Table 1--Base Year and Projected Attainment Year Emission Inventories for Allegheny County
                                                                     [Tons per year]
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                                                     PM2.5         PM2.5           PM2.5
                Allegheny County                    (total)    (filterable)    (condensable)     PM10         SO2         NOX         VOC         NH3
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                                    2011 Base Year Emission Inventory for Allegheny County, by Sector (Tons per Year)
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Point Sources...................................       2,503           1,338           1,164       2,987      13,460      11,128       1,169         207
Area Sources....................................       2,491           2,011             480       4,683       1,528       6,979      11,200         621
Non-road Mobile Sources.........................         361             361               0         378          11       3,921       3,780           5
Highway Mobile Sources..........................         450             450               0         984          78      13,259       7,383         304
Fires...........................................          24              24               0          29           2           5          64           4
Biogenic Sources................................           0               0               0           0           0         166       5,876           0
                                                 -------------------------------------------------------------------------------------------------------
    Total.......................................       5,829           4,185           1,644       9,061      15,080      35,460      29,972       1,141
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Point Sources...................................       2,256           1,256             999       2,722       5,921       7,928       1,534         202
Area Sources....................................       2,708           2,226             472       5,486       1,079       6,664      10,221         615
Non-road Mobile Sources.........................         234             234               0         248           5       2,212       2,752           6
Highway Mobile Sources..........................         266             266               0         722          31       5,708       3,479         209
Fires...........................................          24              24               0          29           2           5          64           4
Biogenic Sources................................           0               0               0           0           0         168       5,876           0
                                                 -------------------------------------------------------------------------------------------------------
    Total.......................................       5,488           4,007           1,471       9,207       7,039      22,684      23,926       1,037
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3. EPA's Evaluation and Proposed Action on the Emission Inventories
    The emission inventories in the Allegheny County area
PM2.5 plan are based on the most current and accurate
information available to PADEP and ACHD at the time the attainment plan
was developed and used the most recently available tools and planning
assumptions. The emission inventories in the attainment plan
comprehensively address all source categories in the Allegheny County
PM2.5 nonattainment area and were developed consistent with
EPA's emission inventory preparation guidance. The selection of 2011
for use as a base year emissions inventory is one of the three years
(2011-2013) used for purposes of designation of the area and the 2021
projection emissions inventory corresponds to the moderate area
attainment deadline, in accordance with EPA's SIP requirements rule.
The inventories model direct PM2.5 (including the filterable
and condensable components), as well as PM2.5 precursor
emissions. For these reasons, we are proposing to approve the 2011 base
year emissions inventory in the Allegheny County PM2.5 Plan
as meeting the requirements of CAA section 172(c)(3). We are also
proposing to find that the 2021 projected inventory in the plan is an
adequate basis for the determination of RACM, RFP, and for
demonstrating attainment in the Allegheny County PM2.5 Plan.
For further information on our review of the emission inventories
supporting this plan, refer to EPA's Technical Support Document (TSD)
for Emission Inventories prepared in support of this action, which is
available in the docket.

B. Particulate Matter Precursor Demonstration

1. PM2.5 Precursor Requirements
    The provisions of subpart 4 of part D, title I of the CAA do not
define the term ``precursor'' for purposes of PM2.5, nor
does subpart 4 explicitly require the control of any specifically
identified PM precursor. However, the definition of ``air pollutant''
in CAA section 302(g) ``includes any precursors to the formation of any
air pollutant, to the extent the Administrator has identified such
precursor or precursors for the particular purpose for which the term
`air pollutant' is used.''
    In the PM2.5 SIP Requirements Rule, EPA recognized that
treatment of PM2.5 precursors is an important issue in
developing a PM2.5 attainment plan.\23\ Therein, EPA
identified SO2, NOX, VOC, and NH3 as
precursors to formation of PM2.5. Accordingly, the
attainment plan requirements of subpart 4 apply to emissions of all
four precursor pollutants and direct PM2.5 from all types of
stationary, area, and mobile sources, except as otherwise provided in
the Act (e.g., in CAA section 189(e)).
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    \23\ See section III of EPA's PM2.5 SIP Requirements
Rule (81 FR 58017, August 24, 2016).
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    Section 189(e) of the CAA requires that the control requirements
for major stationary sources of direct PM10 (which includes
PM2.5) also apply to major stationary sources of
PM10 precursors, except where the Administrator determines
that such sources do not contribute significantly to PM10
levels that exceed the standard in the area. Section 189(e) contains
the only expressed exception to the control requirements under subpart
4 for sources of PM2.5 precursor emissions. Although section
189(e) explicitly addresses only major stationary sources, EPA
interprets the Act as authorizing it to also determine, under
appropriate circumstances, that regulation of specific PM2.5
precursors from other sources in a given nonattainment area is not
necessary.
    Under the PM2.5 SIP Requirements Rule, a state may elect
to submit to EPA a ``comprehensive precursor demonstration'' for a
specific nonattainment area to show that emissions of a particular
precursor from all existing sources located in the nonattainment area
do not contribute significantly to PM2.5 levels that exceed
the standard in the area.\24\ Such a comprehensive precursor
demonstration must include a concentration-based contribution analysis
(i.e., evaluation of the contribution of a particular precursor to
PM2.5 levels in the area) and may also include a
sensitivity-based contribution analysis (i.e., evaluation of the
sensitivity of PM2.5 levels in the area to a decrease in
emissions of the precursor). If EPA determines that the contribution of
the precursor to PM2.5 levels in the area is not significant
and approves the demonstration, the state is not required to control
emissions of the relevant precursor from existing sources in the
current attainment plan.\25\
---------------------------------------------------------------------------

    \24\ See 40 CFR 51.1006(a)(1).
    \25\ Id.
---------------------------------------------------------------------------

    EPA issued PM2.5 Precursor Demonstration Guidance
(``Precursor

Guidance'') to provide recommendations to states for conducting an
optional, comprehensive precursor demonstration as part of an
attainment plan SIP submission.\26\ Section 1.1.1 of the Precursor
Guidance describes the steps for performing a precursor demonstration.
First, a concentration-based analysis should be performed to determine
whether all emissions of the relevant precursor contribute
significantly to total PM2.5 concentrations. If the
concentration-based analysis does not support a finding of
insignificant contribution, then a sensitivity analysis may be
conducted to evaluate, through air quality modeling, the effect of
reducing emissions of the precursor (by a certain percentage) from
either all existing emission sources of the precursor or only existing
major stationary sources of the precursor, on PM2.5 levels
in the area.
---------------------------------------------------------------------------

    \26\ See EPA Office of Air Quality Planning and Standards,
``Fine Particulate Matter (PM2.5) Precursor Demonstration
Guidance,'' [EPA-454/R-19-004, May 30, 2019] https://www.epa.gov/pm-pollution/pm25-precursor-demonstration-guidance.
---------------------------------------------------------------------------

    Section 2.2 of the Precursor Guidance recommends the use of 0.2
[micro]g/m\3\ for the annual PM2.5 NAAQS and 1.5 [micro]g/
m\3\ for the 24-hour PM2.5 NAAQS as thresholds below which
ambient air quality impacts could be considered ``insignificant''
(i.e., impacts that do not ``contribute'' to PM2.5
concentrations that exceed the NAAQS). When considering whether a
precursor contributes significantly to PM2.5 levels which
exceed the NAAQS in the area, a state may also consider additional
factors based on the specific circumstances of the area. As to air
quality impacts that exceed the 0.2 [micro]g/m\3\ annual or 1.5
[micro]g/m\3\ 24-hour contribution thresholds, states may provide
additional support for a conclusion that a particular precursor does
not contribute significantly to ambient PM2.5 levels that
exceed the NAAQS. States may consider other information, such as the
amount by which the impacts exceed the recommended contribution
threshold; the severity of nonattainment at relevant monitors and/or
grid cell locations in the area; anticipated growth or loss of sources;
analyses of speciation data and precursor emission inventories; and air
quality trends.\27\
---------------------------------------------------------------------------

    \27\ Id. at p. 17.
---------------------------------------------------------------------------

2. Precursor Demonstration in the Allegheny County PM2.5
Plan
    The Allegheny County PM2.5 Plan includes a comprehensive
precursor demonstration, which evaluates the impact of the precursors
VOC and NH3 to nonattainment of the PM2.5 NAAQS
in Allegheny County. The concentration-based analysis indicates that
all precursors show ambient monitored levels above the thresholds for
significant contribution.\28\ Therefore, a sensitivity analysis was
performed using Comprehensive Air Quality Model with extensions
(CAMx).\29\ CAMx is a Eulerian photochemical grid model that simulates
a wide variety of inert and chemically active pollutants, including
ozone, particulate matter, inorganic and organic PM2.5/
PM10, and mercury and other toxics. For the sensitivity
analysis, a total of three CAMx runs were used to evaluate
PM2.5 sensitivity to reductions of NH3 and VOC
emissions in Allegheny County: A base case and two sensitivity-case
runs. For one sensitivity-case run, anthropogenic emissions of VOC in
Allegheny County were reduced by 50%. For the other sensitivity-case
run, anthropogenic emissions of NH3 were reduced by 50%. For
both runs, the 50% reductions were applied to both point and area
source anthropogenic emissions with all other emissions held constant.
EPA's Modeled Attainment Test Software (MATS) was then used to model
design values at monitoring sites in Allegheny County with and without
the 50% reduction in VOC and NH3. Table 2 shows the
projected annual and 24-hour reductions in PM2.5 design
values (DVs) at the monitoring sites in the nonattainment area based on
the reductions for VOC and NH3. Additional information
regarding the sensitivity analysis can be found in Appendix I.4
(Precursor Insignificance Demonstration) of the Allegheny County
PM2.5 Plan.
---------------------------------------------------------------------------

    \28\ For additional information on the concentration-based
analysis, see Appendix C of the Allegheny County PM2.5
Plan.
    \29\ CAMx is a photochemical grid model that simulates a wide
variety of inert and chemically active pollutants, including ozone,
particulate matter, inorganic and organic PM2.5/
PM10, and mercury and other toxics.

          Table 2--Sensitivity Test Reductions in Design Values (DVs) at Allegheny County Area Monitors
----------------------------------------------------------------------------------------------------------------
                                                           Annual basis                    24-hour basis
                                                 ---------------------------------------------------------------
                                                   Reduction in    Reduction in    Reduction in    Reduction in
       Monitoring Site               AQS ID         DV with 50%     DV with 50%     DV with 50%     DV with 50%
                                                     less VOC        less NH3        less VOC        less NH3
                                                    ([micro]g/      ([micro]g/      ([micro]g/      ([micro]g/
                                                       m\3\)           m\3\)           m\3\)           m\3\)
----------------------------------------------------------------------------------------------------------------
Avalon.......................        42-003-0002            0.01            0.20             0.0             0.1
Lawrenceville................        42-003-0008            0.00            0.23             0.0             0.0
Liberty......................        42-003-0064            0.00            0.15             0.0             0.8
South Fayette................        42-003-0067            0.00            0.10             0.0             0.1
North Park...................        42-003-0093            0.00            0.17             0.1             0.9
Harrison.....................        42-003-1008            0.00            0.13             0.0             0.0
North Braddock...............        42-003-1301            0.00            0.21             0.0             0.4
Clairton.....................        42-003-3007            0.00            0.13             0.0             0.0
----------------------------------------------------------------------------------------------------------------

    As can be seen in Table 2, the modeled decreases in design values
due to a 50% reduction in VOC and NH3 at the Liberty monitor
are both below the significance thresholds of 0.2 [micro]g/m\3\ for the
annual PM2.5 NAAQS and 1.5 [micro]g/m\3\ for the 24-hour
PM2.5 NAAQS. Therefore, ACHD determined that VOC and
NH3 are both insignificant contributors to nonattainment in
Allegheny County and excluded both precursors from additional analysis
in the Allegheny County PM2.5 Plan.
3. EPA's Evaluation and Proposed Action on the Precursor Demonstration
    EPA has reviewed the comprehensive precursor demonstration included
in the Allegheny County PM2.5 Plan and is proposing to find
that it meets the requirements of the PM2.5 SIP Requirements
Rule and EPA's Precursor Guidance. The comprehensive precursor
demonstration includes a sensitivity analysis that indicates that the
estimated impacts of a 50% reduction in point and area source
anthropogenic

emissions of VOC and NH3 are below the significance
thresholds of 0.2 [micro]g/m\3\ for the annual PM2.5 NAAQS
and 1.5 [micro]g/m\3\ for the 24-hour PM2.5 NAAQS at the
Liberty monitor, which has consistently been the highest reading
PM2.5 monitor in Allegheny County and the only monitor in
the County not meeting the 2012 annual PM2.5 NAAQS. Since
the estimated impacts at the Liberty monitor are below the significance
threshold, it can be concluded, for purposes of the precursor
demonstration, that the precursors VOC and NH3 do not
significantly contribute to nonattainment of the PM2.5 NAAQS
in Allegheny County. Therefore, pursuant to 40 CFR 51.1006, EPA is
proposing to find that Allegheny County is not required to control
emissions of VOC or NH3 from existing sources in the
Allegheny County PM2.5 Plan.

C. Reasonably Available Control Measures (RACM)/Reasonably Available
Control Technology (RACT)

1. Requirements for RACM/RACT
    CAA section 172(c)(1) requires that each attainment plan ``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 ambient air quality
standards.'' Section 189(a)(1)(C) of the CAA requires that states with
areas classified as moderate nonattainment for PM2.5 have
attainment plan provisions to assure that RACM and RACT are implemented
no later than four years after designation of the area. EPA reads CAA
sections 172(c)(1) and 189(a)(1)(C) together to require that attainment
plans for moderate nonattainment areas must provide for the
implementation of RACM and RACT for existing sources of
PM2.5 and PM2.5 precursors in the nonattainment
area as expeditiously as practicable but no later than four years after
designation.\30\
---------------------------------------------------------------------------

    \30\ See 81 FR 58010 and 58034, August 24, 2016.
---------------------------------------------------------------------------

    The preamble to the PM2.5 SIP Requirements Rule defines
RACM as ``any technologically and economically feasible measure that
can be implemented in whole or in part within four years after the
effective date of designation of a PM2.5 nonattainment
area,'' including RACT.\31\ The preamble also recommends steps for
evaluating control measures as part of a RACM/RACT analysis.\32\ In
short, a RACM/RACT analysis is a process for states to identify
emission sources, evaluate potential emission controls, and impose
those control measures and technologies that are reasonable and
necessary to bring the area into attainment as expeditiously as
practicable, but no later than the statutory attainment date for the
area.
---------------------------------------------------------------------------

    \31\ See 81 FR 58010-58035 and 58043, August 24, 2016, as well
as 40 CFR 51.1009(a)(4)(i)(A).
    \32\ See 81 FR 58010-58035 and 58046, August 24, 2016.
---------------------------------------------------------------------------

    Pursuant to the preamble of the PM2.5 SIP Requirements
Rule, in the case of a moderate area that can demonstrate it can attain
by the statutory attainment date without implementing all reasonably
available control measures (i.e. RACM/RACT and additional reasonable
measures), the state would not be required to adopt certain otherwise
reasonable measures if the state demonstrates that collectively such
measures would not enable the area to attain the standard at least one
year earlier (i.e. ``advance the attainment date'' by one year).\33\
The attainment date for the Allegheny County nonattainment area is
December 31, 2021.
---------------------------------------------------------------------------

    \33\ See 81 FR 58018, August 24, 2016.
---------------------------------------------------------------------------

2. RACM Analysis in the Allegheny County PM2.5 Plan
    A summary of ACHD's RACM analysis is provided in Section 6 of the
Allegheny County PM2.5 Plan and a detailed analysis is
provided in Appendix J. Based on the insignificance findings for VOC
and NH3, ACHD did not evaluate options for the control of
VOC and NH3 in their RACM analysis. ACHD's RACM analysis
examines options for the control of primary PM2.5 and
precursors SO2 and NOX in the Allegheny County
nonattainment area for the following source categories: Area sources,
non-road mobile sources, on-road mobile sources, and some small point
sources.
    For each source category, ACHD evaluated RACM alternatives through
the following process: (1) Examine source category emissions in the
nonattainment area; (2) determine technologically feasible control
technologies or measures for each source category; and, (3) for each
technologically feasible control technology or measure, examine the
control efficiency by pollutant, the estimated emission reductions by
pollutant, the estimated cost per ton of pollutant reduced, and the
date by which the technology or measure could be reasonably
implemented.
a. RACM Measures Evaluation
    Table 3 lists the RACM measures in the Allegheny County
PM2.5 Plan. These measures are discussed in more detail in
Appendix J of the Allegheny County PM2.5 Plan, which is
located in the docket for this rulemaking.

                      Table 3--Summary of RACM Alternatives Evaluated for Allegheny County
----------------------------------------------------------------------------------------------------------------
                                          Existing controls/
        Source category group                  programs           RACM alternative(s)             Notes
----------------------------------------------------------------------------------------------------------------
Agriculture..........................  None...................  None identified........  Small source of
                                                                                emissions; mostly NH3
                                                                                emissions, NH3 is an
                                                                                insignificant
                                                                                precursor in the
                                                                                nonattainment area.
Commercial Cooking...................  None...................  1. Charbroiler           1. Small emission
                                                                 catalytic oxidizers      reductions county-
                                                                 for chain-driven         wide.
                                                                 broilers..              2. Full implementation
                                                                2. HEPA filters for       could take five years
                                                                 under-fired boilers..    from promulgation.
Cremation............................  None...................  None identified........  Small source of
                                                                                emissions county-wide;
                                                                                permit restrictions
                                                                                are BACT.
Fuel Combustion (Industrial and        Federal standards for    Low-NOX burners........  Full implementation
 Commercial).                           boilers and engines.                              could take five years
                                                                                from promulgation.
Fuel Combustion (Residential)........  Sulfur limit for home    None identified........  Small source of
                                        heating oil.                                      emissions compared to
                                                                                commercial and
                                                                                industrial fuel
                                                                                combustion.

Fuel Combustion (Residential Wood)...  1. Fireplace insert      1. Additional wood       1. Insignificant
                                        program.                 stove change-out         emission reductions.
                                       2. Prohibition of non-    program.                2. Reductions difficult
                                        phase 2 outdoor wood-   2. Education and          to quantify.
                                        fired boilers (OWBs)..   outreach on clean       3. Reductions and costs
                                       3. No outdoor burning     burning..                difficult to quantify;
                                        when Air Quality        3. Replacement of old     Significant PM2.5
                                        Action Days are          stoves when homes are    emission reductions
                                        predicted..              sold..                   unlikely within short
                                       4. Wood stove change-    4. OWB compliance for     to medium timeframe.
                                        out program..            pre-2011 units..        4. Insignificant
                                                                                emission reductions.
Fugitive Dust........................  Use of dust              Paving of all unpaved    Small emission
                                        suppressants.            roads countywide.        reductions county-
                                                                                wide.
Oil and Gas Exploration and            None...................  No feasible, cost        None.
 Production.                                                     effective options were
                                                                 identified.
Petroleum Storage....................  None...................  None identified........  VOC emissions only, VOC
                                                                                is an insignificant
                                                                                precursor in the
                                                                                nonattainment area.
Solvent Utilization..................  ACHD regulations.......  None identified........  VOC emissions only, VOC
                                                                                is an insignificant
                                                                                precursor in the
                                                                                nonattainment area.
Surface Coatings.....................  ACHD regulations.......  None identified........  VOC emissions only, VOC
                                                                                is an insignificant
                                                                                precursor in the
                                                                                nonattainment area.
Marine...............................  Federal standards;       1. Vessel repowering     1. High costs.
                                        towboat repowering       from Tier 0 to newer    2. Small emission
                                        project.                 engines.                 reductions.
                                                                2. Retrofit tugboats     3. Emission reductions
                                                                 with diesel              not quantified,
                                                                 particulate filters..    potential
                                                                3. Control idling......   insignificant emission
                                                                4. Pleasure craft         reductions.
                                                                 controls..              4. Emission reductions
                                                                                not quantified,
                                                                                potential
                                                                                insignificant emission
                                                                                reductions that are
                                                                                not cost effective.
Railroad.............................  Federal standards......  Replacement of older     High costs relative to
                                                                 engines to newer         emission reductions.
                                                                 engines.
Off-Highway Equipment (Gasoline).....  Rebate program for       Additional gas-for       Emission reductions not
                                        gasoline-fueled          electric exchange        quantified, potential
                                        equipment exchange.      programs.                insignificant emission
                                                                                reductions.
Off-Highway Equipment (Diesel).......  Federal Standards;       Retrofit construction    Small emission
                                        idling restrictions.     equipment with a         reductions county-
                                                                 diesel particulate       wide.
                                                                 filter (DPF).
Off-Highway Equipment (Other)........  None...................  None identified........  None.
Gasoline Refueling...................  Stage II vapor recovery  None identified........  VOC emissions only, VOC
                                        systems.                                          is an insignificant
                                                                                precursor in the
                                                                                nonattainment area.
Gasoline Vehicles (Light-Duty).......  Federal emission         Ridesharing program....  Reductions not
                                        standards; Inspection/                            quantified; light duty
                                        Maintenance (I/M)                                 gasoline vehicles show
                                        program.                                          large reductions
                                                                                through 2021 with
                                                                                current controls.
Gasoline Vehicles (Heavy-Duty).......  Federal emission         None...................  Small portion of the on-
                                        standards; idling                                 road mobile source
                                        restrictions.                                     inventory.
Diesel Refueling.....................  None...................  None identified........  VOC emissions only, VOC
                                                                                is an insignificant
                                                                                precursor in the
                                                                                nonattainment area.
Diesel Vehicles (Light-Duty).........  Federal emission         None identified........  Small portion of the on-
                                        standards; idling                                 road mobile source
                                        restrictions.                                     inventory.
Diesel Vehicles (Heavy Duty).........  Federal emission         (1) Additional diesel    (1) Small emission
                                        standards; idling        engine retrofits.        reductions county-
                                        restrictions.           (2) Replacement of        wide.
                                                                 public or private       (2) Small emission
                                                                 fleets ahead of normal   reductions county-
                                                                 schedule..               wide.
                                                                (3) Additional diesel    (3) Reductions not
                                                                 idling requirements..    quantified.
Compressed Natural Gas (CNG) Vehicles  None...................  None identified........  Small portion of the on-
 (Heavy Duty).                                                                            road mobile source
                                                                                inventory.
Ethanol E-85 Vehicles (Light-duty      None...................  None identified........  Small portion of the on-
 gasoline, capable of burning 85%                                                         road mobile source
 ethanol 15% gasoline blend).                                                             inventory.
Aggregate Processing.................  Rules in effect for      Require water sprays,    None.
                                        stone, sand, and         dust suppressants,
                                        gravel operations.       telescopic chutes, and
                                                                 baghouse/cyclone dust
                                                                 collectors.
----------------------------------------------------------------------------------------------------------------

3. RACT Analysis in the Allegheny County PM2.5 Plan
    Section 6 of the Allegheny County PM2.5 Plan also
includes a summary of ACHD's RACT analysis. ACHD's detailed analysis is
provided in Appendix J of the Allegheny County PM2.5 Plan.
    ACHD used the following methodology for their RACT analysis: (1)
Identify all current major stationary point sources of
PM2.5, SO2, or NOX in the Allegheny
County nonattainment area; (2) identify the different processes, or
process groups, for the applicable major source facilities and the
current controls for the processes; (3) identify potential RACT
alternatives for the process groups; and (4) evaluate the technological
and economic feasibility of any potential RACT alternatives.\34\
---------------------------------------------------------------------------

    \34\ An explanation of sources that were excluded from ACHD's
RACT analysis as well as the control technologies that were analyzed
are provided in Appendix J of the Allegheny County PM2.5
Plan.
---------------------------------------------------------------------------

a. RACT Measures Evaluation
    Table 4 summarizes the identified facilities and corresponding
findings from ACHD's RACT analysis for the Allegheny County
PM2.5 Plan. ACHD's complete RACT analysis is provided in
Appendix J of the Allegheny County PM2.5 Plan.

                        Table 4--Summary of RACT Analysis in Allegheny County PM2.5 Plan
----------------------------------------------------------------------------------------------------------------
                                                          Summary of
            Facility               Major  pollutants       facility            Controls          RACT Findings
----------------------------------------------------------------------------------------------------------------
Allegheny Energy Springdale.....  PM, NOX...........  Combined-cycle      Low NOX burners     Meets RACT
(now Springdale Energy).........                       turbine EGU,        (LNB), selective    requirements.
                                                       natural gas (NG)    catalytic
                                                       or fuel oil.        reduction (SCR).
ATI Allegheny Ludlum............  PM, SO2, NOX......  Specialty steel     Baghouses, ultra-   Meets RACT
                                                       facility.           low NOX burners     requirements.
                                                                           (ULNB), mist
                                                                           eliminators.
Bay Valley (now Riverbend)......  NOX...............  Food manufacturing  LNB, flue gas       Meets RACT
                                                       facility.           recirculation       requirements.
                                                                           (FGR); switched
                                                                           from coal to
                                                                           natural gas as
                                                                           fuel for all
                                                                           units.
Bellefield Boiler...............  NOX...............  Steam generation    LNB, FGR..........  Meets RACT
                                                       facility.                               requirements.
Energy Center Pittsburgh (North   NOX...............  District heating    LNB, drift          Meets RACT
 Shore).                                               and cooling plant.  eliminators.        requirements.
GenOn Brunot Island.............  PM, SO2, NOX......  Combined-cycle      Water injection     Meets RACT
                                                       turbine EGU, NG     with SCR, mist      requirements.
                                                       or fuel oil.        eliminators.
GenOn Cheswick..................  PM, SO2, NOX......  Coal-fired EGU....  FGD, LNB with       Meets RACT
                                                                           overfire air        requirements.
                                                                           (OFA), SCR, ESP.
Pittsburgh Allegheny County       NOX...............  Steam generation    NOX limits........  Meets RACT
 Thermal (PACT).                                       facility.                               requirements.
Universal Stainless.............  NOX...............  Specialty steel     LNB, baghouses....  Meets RACT
                                                       facility.                               requirements.
University of Pittsburgh--Main    NOX...............  Public university.  ULNB, FGR, low      Meets RACT
 Campus.                                                                   sulfur fuel oil.    requirements.
U.S. Steel Clairton.............  PM, SO2, NOX......  Metallurgical coke  Baghouses, baffles  Meets RACT
                                                       and by-products     (quench towers),    requirements.
                                                       facility.           coke oven gas
                                                                           (COG) grain
                                                                           limits,
                                                                           afterburners,
                                                                           visible emission
                                                                           (VE) restrictions.
USS Edgar Thomson...............  PM, SO2, NOX......  Iron and steel      Baghouses, COG      Meets RACT
                                                       making facility.    grain limits,       requirements.
                                                                           scrubbers, drift
                                                                           eliminators.
USS Irvin.......................  PM, SO2, NOX......  Secondary steel     COG grain limits,   Meets RACT
                                                       processing          scrubbers, mist     requirements.
                                                       facility.           eliminators.
----------------------------------------------------------------------------------------------------------------

4. EPA's Evaluation and Proposed Action on RACM and RACT
    ACHD has found that no economically or technologically feasible
controls (or combination thereof) in Allegheny County are needed to
show attainment by the attainment date of December 31, 2021 and that no
feasible controls (or combination thereof) will advance the attainment
date by one year or more (i.e. to December 31, 2020). The Allegheny
County PM2.5 Plan includes a modeling demonstration showing
that Allegheny County can attain the 2012 PM2.5 NAAQS by the
December 31, 2021 attainment date through the control strategy
described in the plan.
    EPA is proposing to approve ACHD's evaluation of RACM/RACT control
measures in the Allegheny County PM2.5 Plan. ACHD has
demonstrated in the plan that Allegheny County can attain the
PM2.5 NAAQS by the attainment date without implementing
RACM/RACT. Also, according to the Allegheny County PM2.5
Plan, the implementation of additional control measures will not
advance the attainment date in Allegheny County by one year or more.
Therefore, EPA is proposing to find that the Allegheny County
PM2.5 Plan satisfies the RACM/RACT requirements of title I,
part D, subpart 1 and subpart 4 of the CAA.

D. Air Quality Modeling

1. Requirements for Air Quality Modeling
    Section 189(a)(1)(B) of the CAA requires that a plan for a Moderate
PM2.5 nonattainment area include a demonstration (including
air quality modeling) that the plan will provide for attainment by the
applicable attainment date, or a demonstration that attainment by such
date is impracticable. An attainment demonstration must show that the
control measures in the plan are sufficient to attain the NAAQS by the
attainment date. The attainment demonstration predicts future ambient
concentrations for comparison to the NAAQS, making use of available

information on ambient concentrations, meteorology, and current and
projected emissions inventories, including the effect of control
measures in the plan. This information is typically used in conjunction
with a computer model of the atmosphere.
    EPA has provided additional modeling requirements and guidance for
modeling analyses in the ``Guideline on Air Quality Models''
(``Guideline'').\35\ Per the PM2.5 SIP Requirements Rule,
the attainment demonstration modeling guidance provides recommendations
that include: Developing a conceptual description of the problem to be
addressed; developing a modeling/analysis protocol; selecting an
appropriate model to support the demonstration; selecting appropriate
meteorological episodes or time periods to model; choosing an
appropriate area to model with appropriate horizontal/vertical
resolution; generating meteorological and air quality inputs to the air
quality model; generating emissions inputs to the air quality model;
and, evaluating performance of the air quality model. After these steps
are completed, the state can apply a model to simulate effects of
future year emissions and candidate control strategies.
---------------------------------------------------------------------------

    \35\ 40 CFR part 51 appendix W, ``Guideline on Air Quality
Models,'' 82 FR 5182, January 17, 2017; available at https://www.epa.gov/scram/clean-air-act-permit-modeling-guidance.
---------------------------------------------------------------------------

2. Air Quality Modeling in the Allegheny County PM2.5 Plan
    ACHD's September 30, 2019 PM2.5 SIP revision includes a
modeling demonstration showing that monitors in Allegheny County will
comply with both the 24-hour and the annual 2012 PM2.5
standards by December 31, 2021. The demonstration is based, in part, on
results from the CAMx analysis. The modeling analysis also includes a
local area analysis using the US EPA's AERMOD Gaussian dispersion model
to analyze the direct PM2.5 component for the Liberty
monitor, which has consistently been the highest reading
PM2.5 monitor in Allegheny County.
    The highest PM monitor readings in Allegheny County are generally
attributed to a combination of high localized industrial source
emissions with strong temperature inversions, which trap those locally
generated emissions within the major river valleys. Elevation
differences between the valley floors and surrounding terrain can be on
the order of 500 feet. Under ideal meteorological conditions (i.e.
light winds and clear night-time skies), Allegheny County has observed
temperature differences between hilltop and valley floor in the range
of 2 to 7 degrees Fahrenheit along with strong channeled flow within
the Monongahela River valley (``Mon Valley''). Strong temperature
inversions inhibit vertical mixing, trapping emissions emitted at near
ground-level within the valleys, contributing to episodes of poor air
quality.
    Given the topography of the area, which is marked by low mountains
and river valleys, and the resulting influence of that topography on
localized meteorological conditions and a propensity for atmospheric
inversions, ACHD developed their modeling analysis to consider these
localized conditions. Further, the modeling analysis needed to properly
account for both regional emission sources, and more importantly the
specific, localized impacts of several large industrial source
emissions that strongly contribute to episodes of poor air quality.
Further details related to development of the baseline and projected
year inventories can be found in appendices D and E of the
Commonwealth's September 30, 2019 SIP revision, which are available in
the docket for this rulemaking. The modeling protocols used for the
Commonwealth's analysis are found in Appendix F of the September 2019
SIP revision.
    Modeling for the Allegheny County area assesses regional impacts
from PM2.5 precursors and localized impacts from primary
PM2.5 sources. CAMx was utilized at fine grid resolution to
model both long-range transport and near-field impacts of most sources.
EPA's AERMOD Gaussian dispersion model was used for simulating
localized primary PM2.5 impacts at the Liberty monitor,
which has consistently recorded the highest monitor concentrations
since PM2.5 monitoring began in the area in the late 1990s.
    ACHD provided an extensive review of meteorological conditions in
Allegheny County over a five-year period from 2009 through 2013.\36\
The ACHD analysis involved a general review of inversions, winds,
temperature, and precipitation in general and its appropriateness for
the modeling demonstration. The modeling demonstration is indicative of
these meteorological conditions and the use of 2011 base year emissions
data is suitable to represent typical conditions over the five-year
(2009-2013) period examined--with the exception of one month (October
2011) that recorded severe inversions.
---------------------------------------------------------------------------

    \36\ See Appendix B of the September 30, 2019 SIP submittal
``Meteorological Analysis.''
---------------------------------------------------------------------------

    CAMx-ready emissions were prepared for the 2011 modeling base year
and projected 2021 attainment year and pre-processed for input to CAMx
using the Sparse Matrix Operator Kernel Emissions (SMOKE) model.\37\
CAMx was evaluated using ambient observational data from three
monitoring networks: EPA's Air Quality System (AQS) database; Federal
Reference Method (FRM) total PM2.5 mass; and the Chemical
Speciation Network (CSN) speciated PM2.5. The Atmospheric
Model Evaluation Tool (or AMET) was the primary software tool used to
compare observations and modeled values from the 1.333 kilometer (km)
domain in Allegheny County.\38\ ACHD found good agreement between
modeled and observed PM2.5 concentrations across Allegheny
County. The results of the model performance evaluations can be
referenced in Appendix G of the Commonwealth's September 30, 2019 SIP.
---------------------------------------------------------------------------

    \37\ See SMOKE model, at https://www.cmascenter.org/smoke/.
    \38\ See AMET software at: https://www.cmascenter.org/amet/.
---------------------------------------------------------------------------

    ACHD used MATS with the CAMx 2011 and 2021 modeling results to
obtain 2021 projected attainment year design value concentrations at
all of the FRM monitoring sites within the modeling domain. This
included some monitoring sites outside the Allegheny County
PM2.5 nonattainment area. Allegheny County's projected 2021
PM2.5 concentrations are summarized in Table 5 and include a
breakdown of each modeled PM2.5 component (2021 projected
value is the sum of all the PM2.5 components).

                         Table 5--Projected 2021 CAMx Modeled Values for the 2012 PM2.5 NAAQS for Allegheny County Area Monitors
                                                                [Based on a 1.33 km grid]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                          CAMx projected design value and PM2.5 modeled components  (1.333 km grid)
                                    --------------------------------------------------------------------------------------------------------------------
          Monitoring Site               Actual     Projected
                                      2016-18 DV    2021 DV        OPP           ED          NH4          OCmb         SO4          NO3          NaCl
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                     Allegheny County Area 24-Hour Design Values **
--------------------------------------------------------------------------------------------------------------------------------------------------------
Avalon.............................         20.2         21.4        0.606        0.965        2.191        9.064        3.258        3.564        0.150
Clairton...........................         18.7         21.4        0.869        3.542        1.882        7.753        4.464        0.828        0.038
Harrison...........................         20.0         20.7        0.870        1.348        1.809        8.807        4.917        0.862        0.055
Lawrenceville......................         18.4         20.4        1.000        0.996        1.855        8.723        4.334        1.480        0.087
Liberty............................         34.9         38.6        1.248        3.910        2.520       21.634        4.978        2.253        0.060
North Braddock.....................         24.5         23.4        1.178        2.564        2.353        8.304        4.577        2.403        0.096
North Park.........................         15.6         17.3        1.280        0.948        1.537        6.783        4.272        0.585        0.047
South Fayette......................         18.3         18.4        1.188        1.480        1.613        6.952        4.552        0.700        0.039
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                       Allegheny County Area Annual Design Values
--------------------------------------------------------------------------------------------------------------------------------------------------------
Avalon.............................          9.7         10.0        0.398        0.508        0.772        4.727        1.926        0.566        0.028
Clairton...........................          9.3          9.2        0.508        1.266        0.843        2.703        2.205        0.734        0.014
Harrison...........................          9.6          9.4        0.495        0.633        0.856        3.470        2.219        0.689        0.026
Lawrenceville......................          9.1          9.0        0.483        0.530        0.810        3.395        1.999        0.614        0.032
Liberty............................         12.6         12.5        0.618        1.509        1.058        4.637        2.795        0.937        0.017
North Braddock.....................         10.7         10.0        0.608        0.989        0.951        3.192        2.463        0.797        0.023
North Park.........................          7.8          7.6        0.593        0.478        0.743        2.219        1.908        0.560        0.026
South Fayette......................          8.3          8.5        0.579        0.636        0.774        2.844        2.071        0.592        0.020
--------------------------------------------------------------------------------------------------------------------------------------------------------
** 24-Hour Design values are rounded to nearest whole number so Avalon's projected 2021 24-hour design value is 21 [micro]g/m\3\
Blank = Salt and passive component held constant from base to future case, OPP = other primary PM2.5, EC = elemental carbon, NH4 = ammonium, OCmb =
  organic carbon mass (by) mass balance, SO4 = sulfate, NO3 = Nitrate, NaCl = ``salt''.

    Modeled 2021 PM2.5 design values for all monitors except
the Liberty monitor meet the revised 2012 PM2.5 NAAQS. All
monitors in Allegheny County meet the 24-hour PM2.5 NAAQS
using 2018 design values. Only the Liberty monitor is projected to
exceed the revised 2012 annual PM2.5 NAAQS in 2021, based on
the CAMx developed design values. Therefore, in accordance with EPA's
modeling guidance, ACHD undertook a more refined local area analysis to
better gauge emission control impacts for sources nearby the Liberty
monitor in southern Allegheny County and the effect of controlling
those sources on projected PM2.5 concentrations in the
Liberty monitor area. The Liberty monitor's location on elevated
terrain several miles downwind of the U.S. Steel Clairton Coke Works
complicates this analysis.
    As stated in EPA's ``Modeling Guidance for Demonstrating Air
Quality Goals for Ozone, PM2.5 and Regional Haze''
(``Modeling Guidance''), ``. . . there are numerous cases where local
source contributions may not be dominant but are a sizable contributor
to total annual average PM2.5 at this monitor. In these
cases, a more refined analysis of the contribution of local primary
PM2.5 sources to PM2.5 at the monitor(s) will
help explain the causes of nonattainment at and near the monitor and
may lead to more efficient ways to attain the NAAQS by controlling
emissions from local sources which may be important contributors to the
violating area.'' \39\ ACHD has done analysis of regional monitor
concentrations and demonstrated unique industrial source influences
using source apportionment modeling \40\ and concluded that the Liberty
monitor, ``shows a large contribution from carbon-rich industrial
sources, not present at the other sites, that contribute carbons as
well as primary sulfate and several trace elements.''
---------------------------------------------------------------------------

    \39\ EPA policy memo, Modeling Guidance for Demonstrating Air
Quality Goals for Ozone, PM2.5 and Regional Haze, from
Richard Wayland, dated November 29, 2018. See p. 134. Available at:
https://epa.gov/ttn/scram/guidance/guide/O3-PM-RH-Modeling_Guidance-2018.pdf.
    \40\ See Appendix C of the September 30, 2019 SIP Revision,
``Speciation and Source Apportionment Analysis.''
---------------------------------------------------------------------------

    EPA's Modeling Guidance allows the use of several tools to evaluate
contributions of local PM2.5 sources, such as Gaussian
dispersion modeling. While dispersion models may not be an appropriate
tool for determining secondary PM2.5 or ozone
concentrations, they work well for use in determining local primary
PM2.5 impacts.\41\ ACHD utilized EPA's AERMOD model to
conduct a local area analysis of the Liberty monitor area. The refined
Liberty local analysis modeling used AERMOD to further resolve the
impact of local area sources and meteorology beyond the CAMx analysis,
to generate the final modeled design values at the Liberty monitor.
This local area analysis shows that the Liberty monitor will attain by
attainment deadline.
---------------------------------------------------------------------------

    \41\ Modeling Guidance for Demonstrating Air Quality Goals for
Ozone, PM2.5 and Regional Haze, from Richard Wayland,
dated November 29, 2018, at p. 134.
---------------------------------------------------------------------------

    Finally, ACHD included additional information in its September 30,
2019 SIP revision constituting a ``weight of evidence'' demonstration
to support its modeling analysis, per EPA's Modeling guidance.\42\
ACHD's weight of evidence demonstration includes analysis of downward
PM2.5 monitoring trends at Allegheny County monitors, a
listing of permanent stationary source shutdowns (not reflected in the
modeling analysis), PM2.5 precursor reductions of
SO2 resulting from reductions in neighboring areas, emission
reductions due to population decrease projections, and emission
reductions due to voluntary programs (not included in the SIP). Also,
additional EGU deactivations in Pennsylvania and surrounding states
were announced after EGU forecasting was performed (based on 2015
data). These deactivations, which were not included in the air quality
modeling for this plan, will lead to further reductions of
PM2.5 precursor emissions that

potentially contribute PM2.5 emissions to Allegheny County.
Further information on recent planned EGU deactivations can be found in
Section 11.4 of the Allegheny County PM2.5 Plan.
---------------------------------------------------------------------------

    \42\ See pp. 169-171 of EPA's Modeling Guidance for
Demonstrating Air Quality Goals for Ozone, PM2.5 and
Regional Haze, which outlines several other analyses that could be
included in any attainment demonstration to help bolster results
from the primary modeling analysis. These could include additional
modeling analyses, analyses of trends in ambient air quality and
emissions, and additional emissions controls/reductions.
---------------------------------------------------------------------------

3. EPA's Evaluation and Proposed Action on Modeling
    EPA has reviewed the modeling demonstration prepared by ACHD for
the Allegheny County PM2.5 nonattainment area. EPA also
reviewed the supporting local area AERMOD dispersion model analysis
prepared by ACHD to assess the impact of sources closest to the Liberty
monitor. ACHD modeling protocols covering the Weather Research and
Forecasting (WRF) prognostic meteorological model, the CAMx modeling
domains and the AERMOD local area analysis all comport with EPA's
Modeling Guidance.\43\
---------------------------------------------------------------------------

    \43\ Ibid.
---------------------------------------------------------------------------

    With the exception of the Liberty monitor, the CAMx model projected
2021 PM2.5 design values for all monitors in Allegheny
County are projected to be below the NAAQS by the attainment deadline.
ACHD elected to conduct a refined local area assessment to further
assess the impact of several large nearby sources beyond the scope of
the CAMx modeling. The Allegheny County Plan contains ACHD's arguments
supporting its contention that the CAMx 1.333 km modeling analysis
could be overestimating projected 2021 PM2.5 concentrations
at the Liberty monitor.\44\ These CAMx modeling limitations cited
include: Limitations in CAMx's ability to properly characterize
concentration gradients across the 1.333 km grid cells, failure to use
the most up to date available stack test emissions data and stack test
emission calculations for several key sources in the area, improper
CAMx source characterizations, and improper source apportionment by
CAMx.
---------------------------------------------------------------------------

    \44\ See Appendix F.3 of the September 30, 2019 SIP revision.
---------------------------------------------------------------------------

    EPA proposes to agree with ACHD's assessment that these are
reasonable arguments to support use of a supplemental local area
analysis using AERMOD dispersion modeling to refine projected 2021
model concentrations at the Liberty monitor. Final projected 2021
values at the Liberty monitor using the local area analysis were 35
[micro]g/m\3\ (24-hour) and 12.0 [micro]g/m\3\ (annual), which
demonstrate attainment with the 2012 PM2.5 NAAQS.
    Given that the projected 2021 PM2.5 concentrations at
the Liberty monitor just meet the 2012 PM2.5 NAAQS, ACHD's
use of additional supporting information via a weight of evidence
demonstration is warranted. The Allegheny County Plan contains a
monitor value trends analysis showing statistically significant
downward trends at all of its PM2.5 monitoring sites,
including the Liberty monitor. EPA agrees with ACHD's contention that
the Pennsylvania Jersey Maryland Power Pool (PJM Interconnection, or
simply PJM) forecasts of electric generation for the last few years
have overestimated the actual amount of electric generation needed, and
as a result the projected regional PM2.5 precursor emissions
from the electric generation sector are likely overestimated.\45\
Electricity generation and demand reports from PJM indicate a decline
in coal-fired power plant operations and an increase in power
generation share from a rise in number and capacity of lower emission
producing, more efficient combined-cycle natural gas plants. This trend
is leading to significant reductions in regional emissions of
SO2, a precursor to PM2.5.\46\ It also appears
that the CAMx model overestimates projections for some monitor
locations in Allegheny County, as shown by the fact that actual
measured 2018 PM2.5 design values are already below forecast
2021 model projections. Allegheny County also documented additional
local emission reductions and source shutdowns which were not accounted
for in the projected emission inventories, along with other voluntary
programs that could lead to additional emission reductions. The
combination of these weight of evidence impacts should lead to
continued reductions in PM2.5 monitor concentrations in
Allegheny County.
---------------------------------------------------------------------------

    \45\ See Appendix K of the September 30, 2019 SIP revision.
    \46\ See Section 3, page 104, http://www.monitoringanalytics.com/reports/PJM_State_of_the_Market/2018.shtml.
---------------------------------------------------------------------------

    EPA believes ACHD's modeling demonstration shows that its projected
2021 PM2.5 design values will likely comply with the 2012
PM2.5 NAAQS--particularly since the actual 2018
PM2.5 design values at all monitoring sites in Allegheny
County (except the Liberty monitor) meet the 2012 PM2.5
NAAQS. Allegheny County's unmonitored area analysis attempts to more
accurately ensure attainment over the entire county and not just those
portions covered by the monitoring network. Given the results of ACHD's
CAMx modeling for the area, the refined AERMOD local area assessment,
and the additional emission reductions and other supporting arguments
from ACHD's weight of evidence demonstration, EPA supports ACHD's
finding that PM2.5 design values at the Liberty monitor will
meet the 2012 PM2.5 NAAQS by the December 31, 2021
attainment date.

E. Attainment Demonstration

1. Requirements for an Attainment Demonstration
    CAA section 189(a)(1)(B) requires that each state in which a
Moderate PM2.5 nonattainment area is located submit an
attainment plan that includes, among other things, either a
demonstration (including air quality modeling) that the plan will
provide for attainment by the applicable attainment date, or a
demonstration that attainment by such date is impracticable. In
addition, CAA section 172(c)(1) generally requires, for each
nonattainment area, a plan that provides for the implementation of all
RACM and RACT as expeditiously as practicable and provides for
attainment of the NAAQS. EPA interprets these two provisions together
to require that an attainment demonstration for a Moderate
PM2.5 nonattainment area meet the following criteria: (1)
The attainment demonstration must show the projected attainment date
for the area that is as expeditious as practicable; (2) the attainment
demonstration must meet the requirements of 40 CFR part 51, appendix W
and must include inventory data, modeling results, and emission
reduction analyses on which the state has based its projected
attainment date; (3) the base year for the emissions inventory required
for the attainment demonstration must be one of the three years used
for designations or another technically appropriate inventory year; and
(4) the control strategies modeled as part of the attainment
demonstration must be consistent with the control strategy requirements
under 40 CFR 51.1009(a), including the requirements for RACM/RACT and
additional reasonable measures.\47\
---------------------------------------------------------------------------

    \47\ See EPA's PM2.5 Implementation Rule, at 40 CFR
51.1011(a).
---------------------------------------------------------------------------

    In addition, the attainment demonstration must provide for the
implementation of all control measures needed for attainment as
expeditiously as practicable, but no later than the beginning of the
year containing the applicable attainment date.\48\
---------------------------------------------------------------------------

    \48\ Id.
---------------------------------------------------------------------------

2. Attainment Demonstration in the Allegheny County PM2.5
Plan
    As explained in section III.D of this document, ACHD's
PM2.5 SIP includes a modeling demonstration, based on

modeling using currently implemented emission control measures, that
shows that monitors in Allegheny County, Pennsylvania will comply with
both the 24-hour and the annual PM2.5 standards by December
31, 2021. The modeling for the Allegheny County PM2.5
nonattainment area focuses on regional impacts from PM2.5
precursors and localized impacts from primary PM2.5 sources.
ACHD also conducted an unmonitored area analysis to better refine those
areas of Allegheny County further from the air monitor sites, as was
discussed earlier in section III.D of this document pertaining to the
modeling.
    The attainment plan includes a weight of evidence analysis to
further bolster the attainment demonstration. The plan shows reductions
in PM2.5 emissions and PM2.5 precursor emission
inventories between 2011 and 2021 as a result of implementation of
RACT/RACM, stationary source shutdowns (not reflected in the 2011
inventory), and from implemented state, local, and Federal emission
controls.
    ACHD contends that the results from their modeling analysis, as
well as its weight of evidence supplemental analysis, demonstrate that
all monitors in Allegheny County will attain the revised 2012 24-hour
and annual PM2.5 NAAQS by the statutory date (December 31,
2021).
3. EPA's Evaluation of ACHD's PM2.5 Attainment Demonstration
    EPA evaluated whether ACHD has adequately demonstrated that the
Allegheny County Area meets EPA requirements for demonstration of
attainment, as described here:
    a. The attainment demonstration must show the projected attainment
date for the area that is as expeditious as practicable.
    As discussed in section III.D of this preamble, EPA proposes to
find that the modeling demonstration and additional analysis in the
attainment plan show that the area will achieve the 2012
PM2.5 NAAQS by the attainment date. In its review of RACM
measures, ACHD found no additional measures that, if enacted, would
advance the attainment deadline earlier than the December 31, 2021
attainment deadline. Currently, 2018 PM2.5 design values at
all monitoring sites in Allegheny County except Liberty meet the 2012
PM2.5 NAAQS. Allegheny County's unmonitored area analysis
predicts attainment over the entire County. Given the results of the
refined local area analysis, ACHD's analysis of potential model
overestimations, and additional emission reductions identified as part
of the weight of evidence demonstration (that are not included in the
modeling demonstration), EPA concludes that attainment demonstration
modeling reasonably projects that all the monitors in the area will
meet the 2012 PM2.5 NAAQS by the 2021 projected attainment
date and that attainment prior to that date is not practicable.
    b. The attainment demonstration must meet the requirements of 40
CFR part 51, appendix W and must include inventory data, modeling
results, and emission reduction analyses on which the state has based
its projected attainment date;
    Based on our analysis of the attainment modeling demonstration in
section III.D of this document, EPA also proposes to conclude that the
attainment demonstration modeling includes appropriate modeling
analysis information complying with the requirements of 40 CFR part 51,
appendix W. Based on EPA's review of the supporting PM2.5
and PM2.5 precursor emission inventories (as described in
the emission inventory section of this action), EPA also proposes to
conclude that the plan includes appropriate emission inventory data to
meet the related EPA emission inventory requirements.
    c. The base year for the emissions inventory required for the
attainment demonstration must be one of the three years used for
designations or another technically appropriate inventory year; and
    ACHD selected 2011 as its base year for the emissions inventory
used for the attainment demonstration. Since 2011 is one of the three
years (i.e., 2011-2013) used for designation purposes, EPA finds that
this choice of base year for the attainment demonstration meets EPA
requirements.
    d. The control strategies modeled as part of the attainment
demonstration must be consistent with the control strategy requirements
under 40 CFR 51.1009(a), including the requirements for RACM/RACT and
additional reasonable measures.
    Based on our review of ACHD's attainment demonstration modeling,
EPA proposes to find that the air quality modeling meets the
requirements of 40 CFR 51.1011(a) and accounts for all technically and
economically feasible control measures for direct PM2.5 (as
well as PM2.5 precursor) emissions sources upon which PADEP
and ACHD have based their projected attainment date for the area. 40
CFR 51.1009(a) and 40 CFR 51.1011.
    As part of the RACT/RACM determination (in conjunction with the
accompanying weight of evidence demonstration emission reductions), EPA
proposes to conclude that the control strategies modeled as part of the
attainment demonstration are consistent with the control strategy
requirements under 40 CFR 51.1009(a), including the requirements for
RACM/RACT and additional reasonable measures. Based on the RACT/RACM
analysis and the additional weight of evidence demonstration for
PM2.5 and PM2.5 precursor emission reductions,
EPA believes the attainment modeling analysis shows that the projected
December 31, 2021 attainment date for the area is as expeditious as
practicable.
    e. The attainment demonstration must provide for the implementation
of all control measures needed for attainment as expeditiously as
practicable, but no later than the beginning of the year containing the
applicable attainment date.
    In Section 3 (Control Strategy) of the Allegheny County
PM2.5 Plan, ACHD sets out its attainment control strategy.
ACHD incorporated the controls described in Section 3 in the future
case 2021 emissions and modeling inventories for the attainment
demonstration. These controls include local source modifications, local
source shutdowns, and regional controls. ACHD states that the local
source modifications are Federally enforceable through ACHD
installation permits and operating permits. These local source
modifications are fully implemented, and the shutdowns all occurred
after the 2011 base year, but prior to the submittal of the plan. The
regional controls include various Federal control measures as well as
two Pennsylvania statewide measures related to sulfur limits for
commercial fuel oil and VOC limits for adhesives and sealants. These
regional measures are also fully implemented.
    EPA has evaluated ACHD's control strategy for attainment and found
that all control measures needed for attainment have been implemented
has expeditiously as practicable. The attainment date is December 31,
2021. These controls were all implemented prior to PADEP submitting the
September 30, 2019 SIP revision. Therefore, EPA concludes that the
control measures were implemented well before the beginning of the year
containing the applicable attainment date, 2021.
4. EPA's Proposed Action on the PM2.5 Attainment
Demonstration
    EPA proposes to conclude that the attainment demonstration for the
Allegheny County PM2.5 Plan meets the requirements for a
moderate area plan under CAA section 189(a)(1)(B), and

that this plan contains an approvable demonstration (including air
quality modeling) showing that the plan provides for attainment by the
applicable attainment date. EPA also proposes to conclude that this
plan meets CAA section 172(c)(1) requirements to provide for the
implementation of RACM and RACT as expeditiously as practicable and
provides for attainment of the NAAQS. By meeting these requirements,
EPA proposes to conclude that ACHD's plan for the Allegheny County
PM2.5 area meets applicable requirements for an approvable
attainment demonstration for a Moderate PM2.5 nonattainment
area.

F. Reasonable Further Progress (RFP)

1. Requirements for Ensuring Reasonable Further Progress
    CAA section 172(c)(2) states that all nonattainment area plans
shall demonstrate reasonable progress towards attainment. In addition,
CAA section 189(c) requires that all PM2.5 nonattainment
area SIPs include a QM demonstration, to be achieved every three years
until the area is redesignated to attainment and which demonstrate RFP,
as defined in CAA section 171(l). Section 171(l) 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
the Administrator for the purpose of ensuring attainment of the
applicable [NAAQS] by the applicable date.'' Neither subpart 1 nor
subpart 4 of part D, title I of the Act requires that a set percentage
of emissions reductions be achieved in any given year for purposes of
satisfying the RFP requirement. EPA's SIP requirements rule does not
require a specific RFP related inventory, but the attainment projected
inventory for the nonattainment area also may serve a purpose for
evaluation of RFP.\49\
---------------------------------------------------------------------------

    \49\ See EPA PM2.5 Implementation Rule. 81 FR 58029,
August 24, 2016.
---------------------------------------------------------------------------

    For purposes of the PM2.5 NAAQS, EPA has interpreted the
RFP requirement to require that nonattainment area plans show annual
incremental emission reductions sufficient to maintain generally linear
progress toward attainment by the applicable deadline.\50\ As discussed
in EPA guidance in the Addendum to the General Preamble (or ``the
Addendum''),\51\ requiring linear progress in reductions of direct
PM2.5 and any individual precursor in a PM2.5
plan may be appropriate in situations where: The pollutant is emitted
by a large number and range of sources; the relationship between any
individual source or source category and overall air quality is not
well known; a chemical transformation is involved (e.g., secondary
particulate significantly contributes to PM2.5 levels over
the standard); and/or the emission reductions necessary to attain the
PM2.5 standard are inventory-wide.\52\
---------------------------------------------------------------------------

    \50\ Addendum to the General Preamble at p. 42015. 59 FR 41998,
August 16, 1994.
    \51\ Id.
    \52\ Id.
---------------------------------------------------------------------------

    The Addendum indicates that requiring linear progress may be less
appropriate in other situations, such as: Where there are a limited
number of sources of direct PM2.5 or a precursor; where the
relationships between individual sources and air quality are relatively
well defined; and/or where the emission control systems utilized will
result in swift and dramatic emission reductions.
    In nonattainment areas characterized by any of these latter
conditions, RFP may be better represented as stepwise progress as
controls are implemented and achieve significant reductions soon
thereafter. For example, if an area's nonattainment problem can be
attributed to a few major sources, EPA guidance indicates that ``RFP
should be met by adherence to an ambitious compliance schedule, which
is likely to periodically yield significant emission reductions of
direct PM2.5 or a PM2.5 precursor.'' \53\ This
latter case is applicable to the Allegheny County Area, as the
violating monitor is impacted heavily by nearby major emission sources,
which are implementing controls in a stepwise fashion between the base
year and attainment deadline.
---------------------------------------------------------------------------

    \53\ Id at p. 42015.
---------------------------------------------------------------------------

    Where attainment is driven by regulatory compliance, the
PM2.5 attainment plan should include a detailed schedule for
compliance with regulations in the area and provide corresponding
annual emission reductions to be realized from each milestone in the
schedule.\54\ In reviewing an attainment plan under CAA subpart 4, EPA
considers whether the annual incremental emission reductions to be
achieved are reasonable in light of the statutory objective of timely
attainment. States should consider both cost-effectiveness and
pollution reduction effectiveness when developing implementation
schedules for its control measures and may implement measures that are
more effective at reducing PM2.5 earlier to provide greater
public health benefits.\55\
---------------------------------------------------------------------------

    \54\ Id. at p. 42016.
    \55\ Id.
---------------------------------------------------------------------------

    The PM2.5 SIP Requirements Rule establishes specific
regulatory requirements for purposes of satisfying the Act's RFP
requirements and provides related guidance in the preamble to the rule.
Specifically, under the PM2.5 SIP Requirements Rule, each
PM2.5 attainment plan must contain an RFP analysis that
includes, at minimum: (1) An implementation schedule for control
measures; (2) RFP projected emissions for direct PM2.5 and
all PM2.5 plan precursors for each applicable milestone
year, based on the anticipated control measure implementation schedule;
(3) a demonstration that the control strategy and implementation
schedule will achieve reasonable progress toward attainment between the
base year and the attainment year; and (4) a demonstration that by the
end of the calendar year for each milestone date for the area,
pollutant emissions will be at levels that reflect either generally
linear progress or stepwise progress in reducing emissions on an annual
basis between the base year and the attainment year.\56\ States should
estimate the RFP projected emissions for each milestone year by sector
on a pollutant-by-pollutant basis.\57\
---------------------------------------------------------------------------

    \56\ 40 CFR 51.1012(a).
    \57\ See 81 FR 58010, 58056 (August 24, 2016).
---------------------------------------------------------------------------

2. RFP Demonstration in the Allegheny County PM2.5 Plan
    The RFP demonstration and QM demonstration methodology are detailed
in Section 7 of the Allegheny County PM2.5 Plan. ACHD
elected to try to show that nonattainment area emissions of direct
PM2.5 pollutants (and significant PM2.5 precursor
pollutants) decline from the base year to the attainment year, in a
generally linear manner.
    The Allegheny County Plan estimates that emissions of direct
PM2.5 will decline steadily from 2011 through 2021 and that
emissions of direct PM2.5 will generally remain below the
levels needed to show incremental, continuing progress toward
attainment. ACHD compiled RFP emissions inventories for the milestone
years of 2019 and 2022 using the base and projected inventories used in
the attainment demonstration. Milestone years are based on a schedule
of 4.5 and 7.5 years after designation (years 2019 and 2022,
respectively), as outlined in the PM2.5 Implementation Rule
for a moderate PM2.5 nonattainment area.\58\ Year 2019

emissions were calculated by linearly interpolating base year 2011 and
projected case 2021 emissions. Year 2022 emissions were held constant
from the projected 2021 case, as a conservative approach beyond the
expected attainment timeframe. In addition to direct PM2.5
emissions, the RFP demonstration includes PM2.5 precursor
emissions of SO2 and NOX. However, it does not
include VOC and NH3 emissions as PM2.5 precursors
because those emissions were shown to be insignificant for purposes of
the Allegheny County Plan. The direct PM2.5 emissions for
the baseline, milestone, and attainment years are shown in Table 6
(with PM2.5 broken down into filterable and condensable
components).\59\ The precursor emissions are shown in Tables 7 and 8.
---------------------------------------------------------------------------

    \58\ RFP milestones occur every three years, starting from the
due date of the SIP (i.e., 18 months after designation), or 4.5
years and 7.5 after designation in 2015. The second milestone of 7.5
years, although beyond the attainment date for a moderate area, is
included in the event the area (at a future date) is reclassified
from moderate to serious nonattainment.
    \59\ See corresponding Tables 7.1, 7.2, and 7.3 of
Pennsylvania's September 30, 2019 SIP revision.

                                                      Table 6--Direct PM2.5 RFP Emissions Inventory for Allegheny County, by Milestone Year
                                                                                [Tons/year]
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       Base year 2011                Milestone year 2019           Projected attainment 2021           Milestone year 2022
                                                             -----------------------------------------------------------------------------------------------------------------------------------
                            Year                                           PM2.5      PM2.5                 PM2.5      PM2.5                 PM2.5      PM2.5                 PM2.5      PM2.5
                                                                PM2.5     (filter)    (cond)     PM2.5     (filter)    (cond)     PM2.5     (filter)    (cond)     PM2.5     (filter)    (cond)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Point Sources...............................................     2,503      1,338      1,164      2,305      1,272      1,032      2,256      1,256        999      2,256      1,256        999
Area Sources................................................     2,491      2,011        480      2,665      2,183        473      2,708      2,226        472      2,708      2,226        472
Non-road Mobile Sources.....................................       361        361          0        259        259          0        234        234          0        234        234          0
On-road Mobile Sources......................................       450        450          0        303        303          0        266        266          0        266        266          0
Fires.......................................................        24         24          0         24         24          0         24         24          0         24         24          0
Biogenic....................................................         0          0          0          0          0          0          0          0          0          0          0          0
                                                             -----------------------------------------------------------------------------------------------------------------------------------
    Total...................................................     5,829      4,185      1,644      5,556      4,042      1,505      5,488      4,007      1,471      5,488      4,007      1,471
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

               Table 7--Allegheny County SO2 Precursor RFP Emissions Inventory, by Milestone Year
                                                   [Tons/year]
----------------------------------------------------------------------------------------------------------------
                                                                                Projected
                                                   Baseline 2011  Milestone 2019    attainment    Milestone 2022
                                                                                2021
----------------------------------------------------------------------------------------------------------------
Stationary Point Sources........................          13,460           7,429           5,921           5,921
Area Sources....................................           1,528           1,169           1,079           1,079
Non-road Mobile Sources.........................              11               6               5               5
On-road Mobile Sources..........................              78              41              31              31
Fires...........................................               2               2               2               2
Biogenic Sources................................               0               0               0               0
                                                 ---------------------------------------------------------------
    Total.......................................          15,080           8,647           7,039           7,039
----------------------------------------------------------------------------------------------------------------

                         Table 8--Allegheny County NOX Precursor RFP Emissions Inventory
                                                   [Tons/year]
----------------------------------------------------------------------------------------------------------------
                                                   Baseline 2011  Milestone 2019  Projected 2021  Milestone 2022
----------------------------------------------------------------------------------------------------------------
Stationary Point Sources........................          11,128           8,568           7,928           7,928
Area Sources....................................           6,979           6,727           6,664           6,664
Non-road Mobile Sources.........................           3,921           2,554           2,212           2,212
On-road Mobile Sources..........................          13,259           7,218           5,708           5,708
Fires...........................................               5               5               5               5
Biogenic Sources................................             166             166             166             166
                                                 ---------------------------------------------------------------
    Total.......................................          35,460          25,239          22,684          22,684
----------------------------------------------------------------------------------------------------------------

    Allegheny County then compared these RFP inventory projections
against the most currently available National Emissions Inventory (NEI)
data (i.e., 2017 for stationary point source and 2014 for mobile and
area emissions) to track the progress of their actual emissions against
their 2019 milestone year shown in Table 9.\60\
---------------------------------------------------------------------------

    \60\ See Table 7.4 of the September 30, 2019 SIP revision.

        Table 9--Allegheny County Composite Emissions Inventory, Based on Most Recent Available NEI Data
                                                   [Tons/year]
----------------------------------------------------------------------------------------------------------------
                                                  PM2.5 (filter)   PM2.5 (cond)
                                       PM2.5                                            SO2             NOX
----------------------------------------------------------------------------------------------------------------
Point Sources (2017 NEI)........           1,305             775             530           4,712           6,148
Area Sources (2014 NEI).........           2,646           2,174             473             481           8,687
Non-road Mobile Sources (2014                315             315               0               8           3,183
 NEI)...........................
On-road Mobile Sources (2014                 389             389               0              76          11,754
 NEI)...........................
Fires (2011 NEI)................              24              24               0               2               5
Biogenic Sources (2011 NEI).....               0               0               0               0             166
                                 -------------------------------------------------------------------------------
    Total.......................           4,679           3,677           1,003           5,279          29,943
----------------------------------------------------------------------------------------------------------------

    While the NEI dates do not directly correspond to the 2019 RFP
milestone year, the composite inventory shows that Allegheny County is
already meeting their projected PM2.5 and SO2
emissions. While NOX was not yet meeting the 2019 milestone
based on actual emissions data, additional NOX reductions
from mobile sources that occur after 2014 are expected to close the gap
between 2014 (when the latest mobile NEI data was available) and the
2019 projected NOX milestone.
    ACHD attempted to show that linear progress towards attainment is
being made by examining its monitoring data and its point source
emissions data for the period between the base and attainment years,
achieved by performing a linear regression on this data to show yearly
progress. Monitored concentrations are presented in Tables 10 and 11,
showing the annual and 24-hour PM2.5 design values,
respectively, for each Allegheny County site for years 2011 through
2018.\61\
---------------------------------------------------------------------------

    \61\ See Tables 7.5 and 7.6 in the September 30, 2019 SIP
revision.

               Table 10--Monitored Annual PM2.5 Design Values ([mu]g/m\3\) for Allegheny County Monitor Sites, With Linear Progress Rates
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                             Monitored annual design value ([mu]g/m\3\)                          Yearly
                                                      ----------------------------------------------------------------------------------------  rate of
                     Monitor site                                                                                linear
                                                          2011       2012       2013       2014       2015       2016       2017       2018     progress
--------------------------------------------------------------------------------------------------------------------------------------------------------
Liberty..............................................       15.0       14.8       13.4       13.0       12.6       12.8       13.0       12.6      -0.33
Avalon...............................................       14.7       13.4       11.4       10.6       10.6       10.4       10.2        9.7      -0.64
North Braddock.......................................       12.7       12.5       11.7       11.4       11.2       11.0       10.8       10.7      -0.30
Harrison.............................................       12.4       11.7       10.6       10.0        9.8        9.8        9.8        9.6      -0.38
Lawrenceville........................................       11.6       11.1       10.3       10.0        9.7        9.5        9.2        9.1      -0.35
Clairton.............................................       11.5       10.9        9.8        9.5        9.9        9.8        9.8        9.3      -0.24
South Fayette........................................       11.0       10.5        9.6        9.0        8.8        8.5        8.4        8.3      -0.39
North Park...........................................        9.7        9.4        8.8        8.5        8.5        8.2        8.2        7.8      -0.25
--------------------------------------------------------------------------------------------------------------------------------------------------------

                                       Table 11--Monitored 24-Hour PM2.5 Design Values, With Linear Progress Rates
                                                                      [[mu]g/m\3\]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                             Monitored 24-hour design value ([mu]g/m\3\)                         Linear
                                                      ----------------------------------------------------------------------------------------  progress
            Allegheny county monitor site                                                                                yearly
                                                          2011       2012       2013       2014       2015       2016       2017       2018       rate
--------------------------------------------------------------------------------------------------------------------------------------------------------
Liberty..............................................         44         43         37         35         33         36         37         35       -1.2
Avalon...............................................         34         29         25         22         23         22         21         20       -1.7
North Braddock.......................................         34         33         29         26         25         25         24         24       -1.5
Harrison.............................................         30         28         25         22         22         21         21         20       -1.4
Clairton.............................................         28         26         22         23         25         26         22         19       -0.8
Lawrenceville........................................         27         26         23         21         21         20         19         18       -1.3
South Fayette........................................         27         26         24         20         21         19         19         18       -1.3
North Park...........................................         25         23         19         17         18         18         17         16       -1.1
--------------------------------------------------------------------------------------------------------------------------------------------------------

    ACHD's analysis of historical monitored PM2.5 design
values shows that all sites in Allegheny County are achieving roughly
linear reductions from baseline case through the most recently
available monitor data. All sites are already below the NAAQS on both
annual and 24-hour bases, with the exception of the Liberty monitor
(for the annual PM2.5 NAAQS). Based on the linear annual
rate of 0.33 [mu]g/m\3\ improvement (for annual design values), ACHD
expects the Liberty monitor to achieve the annual NAAQS by 2021. Based
on the linear yearly rate of 1.2 [mu]g/m\3\ for 24-hour design values,
ACHD expects that the Liberty monitor will continue to achieve the 24-
hour standard.
    EPA's Implementation Rule requires attainment plans to provide an

implementation schedule containing regulatory implementation timeframes
showing progress towards attainment. However, ACHD did not present a
schedule, contending that because all control measures identified for
the Allegheny County Plan have already been implemented, and there are
no identified RACM/RACT or ``additional control measures'' to be
implemented, a schedule for implementation of controls is not
applicable to this SIP.
3. EPA's Evaluation of and Proposed Action on RFP
    For direct PM2.5, EPA agrees that ACHD has shown steady
progress towards measuring RFP for the 2012 PM2.5 NAAQS in
the Allegheny County area. ACHD has shown that the measures being
implemented in the area show ongoing progress towards achieving the
NAAQS.
    ACHD has established milestones for comparison of emissions and
monitored values corresponding to the milestone compliance
demonstration timeframes discussed in the QM and has demonstrated that