[Federal Register Volume 87, Number 216 (Wednesday, November 9, 2022)]
[Proposed Rules]
[Pages 67617-67634]
[FR Doc No: 2022-24075]

=======================================================================
-----------------------------------------------------------------------

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2022-0632; FRL-10362-01-R8]

Air Plan Approval; Colorado; Serious Attainment Plan Elements and
Related Revisions for the 2008 8-Hour Ozone Standard for the Denver
Metro/North Front Range Nonattainment Area

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

-----------------------------------------------------------------------

SUMMARY: On March 22, 2021, the State of Colorado submitted State
Implementation Plan (SIP) revisions related to attainment of the 2008
8-hour ozone National Ambient Air Quality Standards (NAAQS) for the
Denver Metro/North Front Range (DMNFR) Serious nonattainment area by
the applicable attainment date of July 20, 2021. The Environmental
Protection Agency (EPA) proposes to approve the majority of the
submittal, including base and future year emission inventories, a
reasonable further progress (RFP) demonstration, a reasonably available
control measures (RACM) analysis, a motor vehicle inspection and
maintenance (I/M) program, a nonattainment new source review (NNSR)
program, 2020 motor vehicle emissions budgets (MVEBs) and
transportation controls, a clean fuel fleet program, and revisions to
Colorado Air Quality Control Commission (Commission or AQCC)
regulations for the control of ozone via ozone precursors and control
of hydrocarbons via oil and gas emissions. The EPA is also proposing to
approve portions of the reasonably available control technology (RACT)
analyses and revisions from submissions made on May 13, 2020; May 18,
2021; and May 20, 2022. Finally, the EPA proposes to approve revisions
from submissions made on May 14, 2018, May 13, 2020, and May 20, 2022
that were conditionally approved on May 13, 2022. This action is being
taken in accordance with the Clean Air Act (CAA).

DATES: Written comments must be received on or before December 9, 2022.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R08-
OAR-2022-0632, to the Federal Rulemaking Portal: https://www.regulations.gov. Follow the online instructions for submitting
comments. Once submitted, comments cannot be edited or removed from
www.regulations.gov. The EPA may publish any comment received to its
public docket. Do not submit electronically any information you
consider to be Confidential Business Information (CBI) or other
information whose disclosure is restricted by statute. Multimedia
submissions (audio, video, etc.) must be accompanied by a written
comment. The written comment is considered the official comment and
should include discussion of all points you wish to make. The EPA will
generally not consider comments or comment contents located outside of
the primary submission (i.e., on the web, cloud, or other file sharing
system). For additional submission methods, the full EPA public comment
policy, information about CBI or multimedia submissions, and general
guidance on making effective comments, please visit http://www2.epa.gov/dockets/commenting-epa-dockets.
    Docket: All documents in the docket are listed in the
www.regulations.gov index. Although listed in the index, some
information is not publicly available, e.g., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, will be publicly available only in hard copy.
Publicly available docket materials are available electronically in
www.regulations.gov. To reduce the risk of COVID-19 transmission, for
this action we do not plan to offer hard copy review of the docket.
Please email or call the person listed in the FOR FURTHER INFORMATION
CONTACT section if you need to make alternative arrangements for access
to the docket.

FOR FURTHER INFORMATION CONTACT: Abby Fulton, Air and Radiation
Division, EPA, Region 8, Mailcode 8ARD-IO, 1595 Wynkoop Street, Denver,
Colorado 80202-1129, telephone number:<PHONE_NUMBER>, email address:
[email protected].

SUPPLEMENTARY INFORMATION: Throughout this document wherever ``we,''
``us,'' or ``our'' is used, we mean the EPA.
    The information presented in this document is organized as follows:

I. What action is EPA taking?
II. Background
III. Summary of the State's SIP Submittals
IV. Procedural Requirements
V. The EPA's Evaluation of Colorado's Submissions
    A. Emissions Inventories
    B. Reasonable Further Progress Demonstration
    C. Reasonably Available Control Technology (RACT) Analysis
    D. Reasonably Available Control Measures (RACM) Analysis
    E. Motor Vehicle Inspection and Maintenance Program (I/M)
Program
    F. Nonattainment New Source Review (NNSR)
    G. Motor Vehicle Emissions Budget (MVEB)/Transportation
Conformity
    H. Clean Fuel Fleet Program
    I. SIP Control Measures
VI. Proposed Action
VII. Consideration of Section 110(l) of the CAA
VIII. Environmental Justice Considerations
IX. Incorporation by Reference
X. Statutory and Executive Order Reviews

I. What action is EPA taking?

    As explained below, the EPA is proposing various actions on
Colorado's proposed SIP revisions that were submitted on May 13, 2020,
March 22, 2021, May 18, 2021, and May 20, 2022. Specifically, we are
proposing to approve portions of Colorado's Serious attainment plan for
the 2008 8-hour ozone NAAQS. In addition, we propose to approve the
MVEBs and revisions to Regulation Number 7 (Reg. 7) contained in the
State's submittal. We also propose to approve all other aspects of the
submittal, except for the RACT submission for certain sources and
enhanced monitoring, which we will be acting on at a later date, and
for the attainment demonstration and contingency measures. We are also
proposing to approve revisions to Colorado Regulation Number 21 (Reg.
21) from the State's May 13, 2020 submittal, and to Reg. 7 from the
State's May 18, 2021 submittal. Finally, we are proposing to approve
the Reg. 7 revisions from the State's May 14, 2018, May 13, 2020, and
May 20, 2022

submittals that were conditionally approved on May 13, 2022.\1\
---------------------------------------------------------------------------

    \1\ Final rule, Air Plan Conditional Approval; Colorado;
Revisions to Regulation Number 7 and Oil and Natural Gas RACT
Requirements for 2008 8-Hour Ozone Standard for the Denver Metro/
North Front Range Nonattainment Area, 87 FR 29228.
---------------------------------------------------------------------------

    The basis for our proposed action is discussed in this proposed
rulemaking. Technical information that we rely upon in this proposal is
in the docket, which is available at http://www.regulations.gov, Docket
No. EPA-R08-OAR-2022-0632.

II. Background

2008 8-Hour Ozone NAAQS Nonattainment

    On March 12, 2008, the EPA revised both the primary and secondary
NAAQS for ozone to a level of 0.075 parts per million (ppm) (based on
the annual fourth-highest daily maximum 8-hour average concentration,
averaged over 3 years), to provide increased protection of public
health and the environment.\2\ The 2008 ozone NAAQS retains the same
general form and averaging time as the 0.08 ppm NAAQS set in 1997, but
is set at a more protective level. Specifically, the 2008 8-hour ozone
NAAQS is attained when the 3-year average of the annual fourth-highest
daily maximum 8-hour average ambient air quality ozone concentrations
is less than or equal to 0.075 ppm.\3\ Effective July 20, 2012, the EPA
designated as nonattainment any area that was violating the 2008 8-hour
ozone NAAQS based on the three most recent years (2008-2010) of air
monitoring data.\4\ With that rulemaking, the Denver-Boulder-Greeley-
Ft. Collins-Loveland, Colorado area (Denver or DMNFR Area) area was
designated nonattainment and classified as Marginal.\5\ Ozone
nonattainment areas are classified based on the severity of their ozone
levels, as determined using the area's design value. The design value
is the 3-year average of the annual fourth highest daily maximum 8-hour
average ozone concentration at a monitoring site.\6\ Areas designated
as nonattainment at the Marginal classification level were required to
attain the 2008 8-hour ozone NAAQS no later than July 20, 2015, based
on 2012-2014 monitoring data.\7\
---------------------------------------------------------------------------

    \2\ Final rule, National Ambient Air Quality Standards for
Ozone, 73 FR 16436 (March 27, 2008). The EPA has since further
strengthened the ozone NAAQS, but the 2008 8-hour standard remains
in effect. See Final Rule, National Ambient Air Quality Standards
for Ozone, 80 FR 65292 (Oct. 26, 2015).
    \3\ 40 CFR 50.15(b).
    \4\ Final rule, Air Quality Designations for the 2008 Ozone
National Ambient Air Quality Standards, 77 FR 30088 (May 21, 2012).
    \5\ Id. at 30110. The nonattainment area includes Adams,
Arapahoe, Boulder, Broomfield, Denver, Douglas and Jefferson
Counties, and portions of Larimer and Weld Counties. See 40 CFR
81.306.
    \6\ 40 CFR part 50, appendix I.
    \7\ See 40 CFR 51.903.
---------------------------------------------------------------------------

    On May 4, 2016, the EPA published its determination that the Denver
Area, among other areas, had failed to attain the 2008 8-hour ozone
NAAQS by the attainment deadline, and that it was accordingly
reclassified to Moderate ozone nonattainment status.\8\ Colorado
submitted SIP revisions to the EPA on May 31, 2017 to meet the Denver
Area's requirements under the Moderate classification.\9\ The EPA took
final action on July 3, 2018, approving the majority of the May 31,
2017 submittal, but deferring action on portions of the submitted Reg.
7 RACT rules.\10\ On February 24, 2021, the EPA took final action
approving additional measures as addressing Colorado's RACT SIP
obligations for Moderate ozone nonattainment areas.\11\ Areas that were
designated as Moderate nonattainment were required to attain the 2008
8-hour ozone NAAQS no later than July 20, 2018, based on 2015-2017
monitoring data.\12\ On December 26, 2019, the EPA published its
determination that the Denver Area, among other areas, had failed to
attain the 2008 8-hour ozone NAAQS by the attainment deadline, and that
it was accordingly reclassified to Serious ozone nonattainment
status.\13\
---------------------------------------------------------------------------

    \8\ Final rule, Determinations of Attainment by the Attainment
Date, Extensions of the Attainment Date, and Reclassification of
Several Areas for the 2008 Ozone National Ambient Air Quality
Standards, 81 FR 26697 (May 4, 2016).
    \9\ CAA section 182, 42 U.S.C. 7511a, outlines SIP requirements
applicable to ozone nonattainment areas in each classification
category. Areas classified Moderate under the 2008 8-hour ozone
NAAQS had a submission deadline of January 1, 2017 for these SIP
revisions (81 FR 26699).
    \10\ Final rule, Approval and Promulgation of State
Implementation Plan Revisions; Colorado; Attainment Demonstration
for the 2008 8-Hour Ozone Standard for the Denver Metro/North Front
Range Nonattainment Area, and Approval of Related Revisions (83 FR
31068).
    \11\ Final rule, Approval and Promulgation of Implementation
Plans; Colorado; Revisions to Regulation Number 7 and RACT
Requirements for 2008 8-Hour Ozone Standard for the Denver Metro/
North Front Range Nonattainment Area, 86 FR 11125.
    \12\ See 40 CFR 51.903.
    \13\ Final rule, Finding of Failure To Attain and
Reclassification of Denver Area for the 2008 Ozone National Ambient
Air Quality Standard, 84 FR 70897 (Dec. 26, 2019); see 40 CFR
81.306.
---------------------------------------------------------------------------

III. Summary of the State's SIP Submittals

    We are proposing to take action on Colorado SIP submittals made on
five different dates:

May 14, 2018 Submittal

    This submittal contains amendments to Reg. 7, sections XII
(Volatile Organic Compound Emissions from Oil and Gas Operations) and
XVIII (Natural Gas-Actuated Pneumatic Controllers Associated with Oil
and Gas Operations) to meet RACT for oil and gas sources covered by the
EPA's 2016 Oil and Gas Control Techniques Guidelines (CTG).\14\ We
previously acted on all parts of this SIP submittal \15\ except for
revisions to Reg. 7, section XII.J.1., concerning centrifugal
compressors, as to which we proposed conditional approval. We are now
proposing approval of those revisions.
---------------------------------------------------------------------------

    \14\ Control Techniques Guidelines for the Oil and Natural Gas
Industry, EPA-453/B-16-001 (Oct. 2016).
    \15\ Final rule, Approval and Promulgation of Implementation
Plans; Colorado; Revisions to Regulation Number 7; Aerospace, Oil
and Gas, and Other RACT Requirements for the 2008 8-Hour Ozone
Standard for the Denver Metro/North Front Range Nonattainment Area,
86 FR 61071 (Nov. 5, 2021).
---------------------------------------------------------------------------

May 13, 2020 Submittals

    On this date the State submitted two SIP revisions. One of the
submittals includes a full reorganization of Reg. 7 into parts A-E,
amends oil and gas storage tank requirements, updates RACT requirements
for major sources of volatile organic compounds (VOC) and nitrogen
oxides (NOX) in the DMNFR Area, updates requirements for
gasoline transport truck testing and vapor control systems, and
contains typographical, grammatical, and formatting corrections
throughout. We previously acted on all parts of this SIP submittal \16\
except for revisions to Reg. 7, sections I.D., I.E, and I.F. concerning
storage tanks, and section I.J.1. concerning centrifugal compressors,
as to which we proposed conditional approval. We are now proposing
approval of those revisions.
---------------------------------------------------------------------------

    \16\ 86 FR 61071 (Nov. 5, 2021).
---------------------------------------------------------------------------

    The second submittal contains new Reg. 21 to limit the VOC content
in consumer products and in architectural and industrial maintenance
(AIM) coatings manufactured, distributed, or sold in the DMNFR Area.
Specifically, the Commission adopted VOC standards in the Ozone
Transport Commission (OTC) AIM coatings model rule phase 2 (2014) and
VOC standards in the OTC consumer products model rule phase 4 (2013).
Reg. 21 includes definitions, exemptions, labeling, and recordkeeping
provisions based on the OTC model rules.

March 22, 2021 Submittal

    This submittal contains the State's Serious ozone attainment plan
and revisions to Reg. 7 to include RACT requirements in Colorado's
ozone SIP for 50 tons per year (tpy) major sources of VOC and/or
NOX. The Reg. 7 revisions include expansion of

categorical requirements to reduce VOC emissions related to wood
surface coatings in part C, section I.O., adding NOX
emission limits for turbines, boilers, and landfill or biogas engines
in part E, section II, and adding categorical requirements to reduce
VOC emissions related to foam manufacturing in part E, section V.
Typographical, grammatical, and formatting corrections were also made.

May 18, 2021 Submittal

    The state regulations included with this submittal contain mostly
state-only revisions that have not been submitted for inclusion in the
SIP. Portions of these regulations submitted as SIP revisions include
typographical, grammatical, and formatting corrections to the outline
of Reg. 7 and part E (combustion equipment at major source RACT).

May 20, 2022 Submittals

    On this date the State submitted three SIP revisions. One of the
submittals contains amendments that were mostly state-only and not
submitted as SIP revisions. The SIP revisions adopted by the AQCC on
Feb. 19, 2021 include updates to definitions in Reg. 7, part D, section
III (natural gas-actuated pneumatic controllers associated with oil and
gas operations).
    Another submittal contains amendments to Reg. 7 that establish
categorical RACT requirements for major sources of NOX and
certain CTG sources in the DMNFR Area. Specifically, on July 16, 2021
the AQCC adopted RACT requirements in part C, section I for
miscellaneous metal parts coatings and part E, section II RACT
requirements for process heaters at major sources of NOX
emissions. Typographical, grammatical, and formatting corrections were
also made.
    The third submittal contains revisions concerning RACT requirements
for oil and gas sources. Specifically, on Dec. 17, 2021 the AQCC
adopted revisions to Reg. 7, part D, section I for performance or
manufacturer testing for combustion equipment used to control emissions
from storage vessels and wet seal centrifugal compressors as to which
we proposed conditional approval. We are now proposing approval of
those revisions.

IV. Procedural Requirements

    The CAA requires that states meet certain procedural requirements
before submitting SIP revisions to the EPA, including the requirement
that states adopt SIP revisions after reasonable notice and public
hearing.\17\ For the May 14, 2018 submittal, the AQCC provided notice
in the Colorado Register on August 10, 2017 \18\ and held public
hearings on the revisions on October 19 and 20, 2017. The Commission
adopted the revisions on November 17, 2017. The revisions became state-
effective on December 30, 2017.
---------------------------------------------------------------------------

    \17\ CAA section 110(a)(2), 42 U.S.C. 7410(a)(2).
    \18\ 40 CR 15 available at https://www.sos.state.co.us/CCR/RegisterHome.do.
---------------------------------------------------------------------------

    For the May 13, 2020 (part D, oil and gas) submittal, the AQCC
provided notice in the Colorado Register on October 10, 2019 \19\ and
held public hearings on the revisions on December 17-19, 2019. The
Commission adopted the revisions on December 19, 2019. The revisions
became state-effective on February 14, 2020.
---------------------------------------------------------------------------

    \19\ 42 CR 19.
---------------------------------------------------------------------------

    For the May 13, 2020 (Reg. 21) submittal, the AQCC provided notice
in the Colorado Register on May 10, 2019 \20\ and held a public hearing
on the revisions on July 18, 2019. The Commission adopted the revisions
on November 17, 2016. The revisions became state-effective on September
14, 2019.
---------------------------------------------------------------------------

    \20\ 42 CR 9.
---------------------------------------------------------------------------

    For the March 22, 2021 submittal, the AQCC provided notice in the
Colorado Register on October 10, 2020 \21\ and held a public hearing on
the revisions on December 16, 2020. The Commission adopted the
revisions on December 18, 2020. The revisions became state-effective on
February 14, 2021.
---------------------------------------------------------------------------

    \21\ 43 CR 19.
---------------------------------------------------------------------------

    For the May 18, 2021 submittal, the AQCC provided notice in the
Colorado Register on July 10, 2020 \22\ and held a public hearing on
the revisions on September 17, 2020. The Commission adopted the
revisions on September 23, 2020. The revisions became state-effective
on November 14, 2020.
---------------------------------------------------------------------------

    \22\ 43 CR 13.
---------------------------------------------------------------------------

    For the May 20, 2022 submittal (part D, Definitions) the AQCC
provided notice in the Colorado Register on January 10, 2021 \23\ and
held a public hearing on the revisions on February 18, 2021. The
Commission adopted the revisions on February 18, 2021. The revisions
became state-effective on April 14, 2021.
---------------------------------------------------------------------------

    \23\ 44 CR 1.
---------------------------------------------------------------------------

    For the May 20, 2022 submittal (Misc. Metals and Process Heater)
the AQCC provided notice in the Colorado Register on May 10, 2021 \24\
and held a public hearing on the revisions on July 16, 2021. The
Commission adopted the revisions on July 16, 2021. The revisions became
state-effective on September 14, 2021.
---------------------------------------------------------------------------

    \24\ 44 CR 9.
---------------------------------------------------------------------------

    For the May 20, 2022 submittal (part D, Oil and Gas) the AQCC
provided notice in the Colorado Register on October 10, 2021 \25\ and
held a public hearing on the revisions on December 14, 2021. The
Commission adopted the revisions on December 17, 2021. The revisions
became state-effective on January 30, 2022.
---------------------------------------------------------------------------

    \25\ 44 CR 19.
---------------------------------------------------------------------------

    Accordingly, we propose to find that Colorado met the CAA's
procedural requirements for reasonable notice and public hearing.

V. The EPA's Evaluation of Colorado's Submissions

2008 Ozone Serious SIP Submittal

    CAA section 182 outlines SIP requirements applicable to ozone
nonattainment areas in each classification category. A Serious area
classification triggers requirements for state submissions described in
the EPA's regulations implementing the 2008 8-hour ozone NAAQS.\26\
Examples of these requirements include submission of a modeling and
attainment demonstration, RFP, an enhanced inspection and maintenance
program, RACT, and RACM. Serious nonattainment areas had a submission
deadline of August 3, 2020 for these SIP revisions.\27\
---------------------------------------------------------------------------

    \26\ See 40 CFR part 51, subpart AA.
    \27\ See 84 FR 70897 (Dec. 26, 2019).
---------------------------------------------------------------------------

    Colorado submitted SIP revisions to the EPA on March 22, 2021, to
meet the requirements of a Serious area classification for the DMNFR
Area. Colorado's proposed SIP revisions consist of the parts listed
below.
     8-Hour Ozone Attainment Plan (OAP), which includes
monitoring information, emission inventories, an RFP demonstration, an
attainment demonstration using photochemical grid modeling, a RACT
analysis, a RACM analysis, a motor vehicle emissions I/M program, NNSR
program certification, contingency measures, MVEBs for transportation
conformity, and a clean fuel fleet program.
     Revisions to Reg. 7.

A. Emissions Inventories

1. Background
    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.''
The accounting required by this section provides a ``base year''
inventory that serves as the starting point for

attainment demonstration air quality modeling, for assessing RFP, and
for determining the need for additional SIP control measures. An
attainment year inventory is a projection of future emissions and is
necessary to show the effectiveness of SIP control measures. Both the
base year and attainment year inventories are necessary for
photochemical modeling to demonstrate attainment. As previously noted,
we are not acting on the attainment modeling demonstration in this
action, but are evaluating Colorado's emission inventories for purposes
of meeting RFP requirements.
    Colorado's DMNFR Serious area attainment plan includes a 2011 base
year inventory, a 2017 milestone year inventory, and a 2020 attainment
year inventory. The inventories catalog NOX and VOC
emissions, because these pollutants are precursors to ozone formation,
across all source categories during a typical summer day, when ozone
formation is pronounced. The State developed an updated 2017
``milestone year'' emissions inventory for the Serious nonattainment
area. When initially developed for the Moderate area SIP, the 2017
inventory was calculated based on projected values. The 2017 inventory
approved as part of the Moderate area SIP has been updated for the
purposes of the Serious area SIP using data collected in 2017 \28\ and
methodologies as presented in chapter 3 of the OAP.
---------------------------------------------------------------------------

    \28\ Pursuant to 40 CFR 51.1110(b), the values in the submitted
2011 base year EI are actual ozone season day emissions.
---------------------------------------------------------------------------

2. Evaluation
    The 2011 base year inventory was included as part of the Moderate
area SIP submittal and approved as part of our July 3, 2018 action.\29\
As part of the Moderate area SIP, a projected 2017 attainment year
emissions inventory was developed and approved by the EPA on July 3,
2018.\30\ Due to the reclassification of the DMNFR to Serious
nonattainment for the 2008 ozone NAAQS, CDPHE prepared an updated 2017
emissions inventory based on currently available data in accordance
with the EPA's revised guidance on emissions inventory
developments.\31\ The updated 2017 emissions inventory was resubmitted
to meet the State's Serious area SIP requirements.\32\
---------------------------------------------------------------------------

    \29\ 83 FR 31068 (July 3, 2018).
    \30\ Id.
    \31\ See ``Emission Inventory Guidance for Implementation of
Ozone and Particulate Matter National Ambient Air Quality Standards
(NAAQS) and Regional Haze Regulations,'' EPA-454/B-17-002. Revised
May 2017.
    \32\ CAA section 182(c)(2)(B).
---------------------------------------------------------------------------

    The 2017 milestone year emissions inventories are in tons per
summer day and represent the most current available data, as of the
time of submission, for emissions estimates for an average episode day
during the peak summer ozone season of June through September. This
includes actual data for the oil and gas sector and stationary sources
in addition to newer data from updated regional transportation demand
models used by the two Metropolitan Planning Organizations in the DMNFR
Area.
    The 2020 inventory is in tons per summer day and represents
emissions estimates for an average episode day during the peak summer
ozone season (June through September). The 2020 inventory for VOC and
NOX accounts for emissions growth associated with changes in
population, fuel use, and economic activity as well as emissions
reductions associated with controls that were in place as SIP control
measures by the beginning of the 2020 summer ozone season. The EPA has
provided guidance on developing emission projections to be used with
models and other analyses for demonstrating attainment of air quality
goals for ozone.\33\
---------------------------------------------------------------------------

    \33\ Emissions Inventory Guidance for Implementation of Ozone
and Particulate Matter National Ambient Air Quality Standards
(NAAQS) and Regional Haze Regulations (May 2017) (``Emissions
Inventory Guidance''), available at https://www.epa.gov/sites/default/files/2017/07/documents/ei_guidance_may_2017_final_rev.pdf.
---------------------------------------------------------------------------

    The 2017 milestone year and 2020 attainment emission inventories
were developed using EPA-approved emissions models, methodology, and
guidelines for stationary, mobile, and area emission sources.
    The 2017 emissions inventories for power plants (also referred to
as electric generating units) and other point sources were developed
using Colorado Air Pollutant Emission Notice (APEN) reported data for
each year, as specified in Tables 16 and 17 of the OAP. Area sources
include many categories of emissions, such as coatings, household and
personal care products, pesticides, and sealants. The 2017 area source
emissions inventory is included in Table 18 of the OAP. The inventory
was based on the EPA's 2014 National Emissions Inventory (NEI) and was
derived from the 2014 NEI based on county population projections from
the Colorado State Demography Office. The EPA finds that these sources
(including those in the oil and gas sector) were adequately accounted
for in the emissions inventory. The methodology used to calculate
emissions for each respective category was consistent with
recommendations and explanations in relevant EPA guidance,\34\ employed
applicable approved emission factors and NEI data, and was sufficiently
documented in the SIP and in the State's technical support documents
(TSD).\35\
---------------------------------------------------------------------------

    \34\ Emissions Inventory Guidance; MOVES2014, MOVES2014a, and
MOVES2014b Technical Guidance: Using MOVES to Prepare Emission
Inventories for State Implementation Plans and Transportation
Conformity, EPA-420-B-18-039 (Aug. 2018) (``MOVES Guidance''),
available at https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100V7EY.pdf.
    \35\ See Colorado Serious SIP submittal, TSD for Mobile and Area
Sources Emissions Inventory Development. Available within the docket
for this action.
---------------------------------------------------------------------------

    Projected future emissions in 2020 were based on anticipated
growth, technological advancements, and expected emissions controls
that were to be implemented by the 2020 ozone season. The 2020 oil and
gas emission inventory was based on 2017 actual site-specific emissions
and 2018 APEN reported data, including technology and production and
projected 2020 emissions and production. The 2020 emissions inventory
for EGUs was developed based on Colorado APEN reported data for 2018
and is specified in Table 28 of the OAP. The future year inventory for
other point sources beyond EGUs is based on 2018 APEN data. The 2020
area source inventory is provided in Table 30 of the OAP and was grown
from the EPA's 2014 NEI based on county population projections from the
State Demography Office. Reductions from implementation of Colorado
AQCC Reg. 21 were then applied.\36\ On-road and non-road mobile source
emissions for the 2020 inventory were calculated using the EPA's
MOVES2014b \37\ model combined with local activity inputs including
vehicle miles traveled (VMT) and average speed data, as well as local
fleet, age distribution, meteorology, and fuels information. Table 34
of the OAP includes biogenic emissions as part of the overall 2020
future year emissions inventory.
---------------------------------------------------------------------------

    \36\ See section I. SIP Control Measures of this document for a
discussion of Reg. 21 controls.
    \37\ EPA's Motor Vehicle Emission Simulator (MOVES) is a state-
of-the-science emission modeling system that estimates emissions for
mobile sources at the national, county, and project level for
criteria air pollutants, greenhouse gases, and air toxics. See
https://www.epa.gov/moves.
---------------------------------------------------------------------------

    Table 1 shows the emissions by source category from the 2011 base
year, 2017 milestone year, and 2020 attainment year emission
inventories.

                                                            Table 1--Emissions Inventory Data
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       2011                            2017                            2020
                       Description                       -----------------------------------------------------------------------------------------------
                                                                VOC             NOX             VOC             NOX             VOC             NOX
--------------------------------------------------------------------------------------------------------------------------------------------------------
Area (non-oil and gas) Total............................            60.6  ..............            65.3  ..............            54.6  ..............
                                                         -----------------------------------------------------------------------------------------------
    Non-Road Total......................................            58.2            75.9              44  ..............            44.3            39.1
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                   Oil and Gas Sources
--------------------------------------------------------------------------------------------------------------------------------------------------------
Area....................................................            48.9            22.2            43.6            38.1            54.5            34.4
Condensate/Oil Tanks....................................             216             1.1           107.7             1.4            50.2             0.6
Point...................................................            14.8            18.1              12            11.5            14.3            13.1
                                                         -----------------------------------------------------------------------------------------------
    Oil and Gas Total...................................           279.7            41.4           163.3            51.0           119.0            48.2
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         On-Road
--------------------------------------------------------------------------------------------------------------------------------------------------------
Light-Duty Vehicles.....................................            90.0           102.5            55.6            53.5            47.6            41.4
                                                         -----------------------------------------------------------------------------------------------
Medium/Heavy-Duty Vehicles..............................             3.7            39.6             2.0            14.9             1.8            13.3
                                                         -----------------------------------------------------------------------------------------------
    On-Road Total.......................................            93.7           142.1            57.6            68.4            49.4            54.7
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                      Point Sources
--------------------------------------------------------------------------------------------------------------------------------------------------------
                           EGU                                       0.7            39.7             0.3             9.4             0.4             4.6
Non-EGU.................................................            25.9            21.0            22.6            15.8            24.6            17.1
                                                         -----------------------------------------------------------------------------------------------
    Point Total.........................................            26.6            60.7  ..............  ..............              25            21.7
--------------------------------------------------------------------------------------------------------------------------------------------------------
        Total Anthropogenic Emissions...................           518.8             320           353.1           187.1           292.3           163.7
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Details of Colorado's emissions inventory development are in
Colorado's supporting TSD.\38\ The inventories in the SIP are based on
the most current and accurate information available to the State and
the Regional Air Quality Council (RAQC) at the time the SIP was being
developed. Additionally, the inventories comprehensively address source
categories in the DMNFR nonattainment area, and were developed
consistent with the relevant EPA inventory guidance. For these reasons,
we propose to approve the 2017 milestone inventory and the 2020
inventory, which will be used to meet RFP requirements.\39\ The
following section discusses RFP further.
---------------------------------------------------------------------------

    \38\ See Colorado Serious SIP submittal, TSD for Mobile and Area
Sources Emissions Inventory Development. Available within the docket
for this action.
    \39\ The EPA approved Colorado's 2011 base year inventory in our
July 3, 2018 action (83 FR 31068).
---------------------------------------------------------------------------

B. Reasonable Further Progress Demonstration

1. Background
    CAA section 182(b)(1) and the EPA's 2008 Ozone Implementation Rule
\40\ require each 8-hour ozone nonattainment area designated Moderate
and above to submit an RFP demonstration for review and approval into
its SIP that describes how the area will achieve actual VOC and
NOX emissions reductions from a baseline emissions
inventory. CAA section 182(b)(1), which is part of the ozone-specific
nonattainment plan requirements of subpart 2 of the CAA, requires RFP
to demonstrate a 15% reduction in VOC emissions. To satisfy the section
182(b)(1) RFP requirement, on May 31, 2017 Colorado submitted an RFP
demonstration showing VOC emission reductions greater than 15% over the
six years after the 2011 base year inventory (i.e., 2012-2017). The EPA
approved this 15% RFP SIP on July 3, 2018.\41\
---------------------------------------------------------------------------

    \40\ 80 FR 12264, 12266 (March 6, 2015).
    \41\ 83 FR 31068. The state's 15% RFP demonstration was also
sufficient to satisfy the more general CAA subpart 1 requirements of
CAA section 172(c)(2), which permits a combination of VOC and
NOX emission reductions to show RFP.
---------------------------------------------------------------------------

    As noted above, the CAA section 182(b)(1) requirement for a 15% RFP
demonstration applies to ozone nonattainment areas classified Moderate
and above. In addition, Serious ozone nonattainment areas are subject
to the CAA section 182(c)(2)(B) requirement to submit SIP revisions
showing a 9% reduction of VOC \42\ emissions over each consecutive
three-year period beginning six years after redesignation until the
attainment date. For the DMNFR Area, the redesignation date was July
20, 2012. Accordingly, the DMNFR Area was required to submit SIP
revisions showing that 9% reductions in ozone precursor emissions would
be achieved between January 1, 2018 and December 31, 2020.
2. Evaluation
    We reviewed the State's 9% RFP submittal for consistency with the
requirements of the CAA and EPA regulations and guidance. To
demonstrate compliance with RFP requirements, the State compared its
2017 milestone VOC inventory against its projected 2020 VOC emissions
inventory and demonstrated that the projected 2020 emissions of VOC
were at least 9% below the 2011 base year inventory. Colorado projected
an 11.7% reduction in VOC emissions from 2017-2020.\43\ As discussed in
section V.A. of this document, the EPA reviewed the procedures Colorado
used to develop its projected inventories and the State's submittal for
consistency with the requirements of the CAA and the EPA's regulations
and guidance and found them to be reasonable. We therefore

propose approval of Colorado's Serious-area RFP demonstration.
---------------------------------------------------------------------------

    \43\ See OAP, Table 35 on page 4-21. This projection has proven
to be correct. See the ``Denver Metro Area/North Front Range
Nonattainment Area Milestone Compliance Demonstration,'' March 31,
2021 and the EPA's 2020 milestone compliance demonstration adequacy
letter, July 6, 2021. Available in the docket for this action.
---------------------------------------------------------------------------

C. Reasonably Available Control Technology (RACT) Analysis

1. Background
    Section 172(c)(1) of the CAA requires that SIPs for nonattainment
areas ``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).'' The EPA has defined ``reasonably available
control technology'' (RACT) as ``[t]he lowest emissions limitation that
a particular source is capable of meeting by the application of control
technology that is reasonably available considering technological and
economic feasibility.'' \44\ The EPA provides guidance concerning what
types of controls may constitute RACT for a given source category by
issuing Control Techniques Guidelines (CTG) and Alternative Control
Techniques (ACT) documents.\45\ States must submit a SIP revision
requiring the implementation of RACT for each source category in the
area for which the EPA has issued a CTG, and for any major source in
the area not covered by a CTG.\46\
---------------------------------------------------------------------------

    \44\ General Preamble for Proposed Rulemaking on Approval of
Plan Revisions for Nonattainment Areas--Supplement (on Control
Techniques Guidelines), 44 FR 53761 (Sep. 17, 1979).
    \45\ See https://www.epa.gov/ground-level-ozone-pollution/control-techniques-guidelines-and-alternative-control-techniques for
a list of EPA-issued CTGs and ACTs.
    \46\ See CAA section 182(b)(2), 42 U.S.C. 7511a(b)(2)); see also
Note, RACT Qs & As--Reasonably Available Control Technology (RACT):
Questions and Answers, William Harnett, Director, Air Quality Policy
Division, EPA (May 2006), available at https://www.regulations.gov/document/EPA-R08-OAR-2020-0114/0008.
---------------------------------------------------------------------------

    For a Moderate, Serious, or Severe area a major stationary source
is one that emits, or has the potential to emit, 100, 50, or 25 tpy or
more, respectively, of VOCs or NOX.\47\ Accordingly, for the
DMNFR Serious nonattainment area, a major stationary source is one that
emits, or has the potential to emit, 50 tpy or more of VOCs or
NOX. RACT can be adopted in the form of emission limitations
or ``work practice standards or other operation and maintenance
requirements,'' as appropriate.\48\
---------------------------------------------------------------------------

    \47\ See CAA sections 182(b), 182(c), 182(d), 182(f)(1), and
302(j).
    \48\ See Memorandum, ``Approval Options for Generic RACT Rules
Submitted to Meet the non-CTG VOC RACT Requirement and Certain
NOX RACT Requirements,'' Sally Shaver, Director, Air
Quality Strategies & Standards Division, EPA (Nov. 7, 1996),
available at https://www.epa.gov/sites/production/files/2016-08/documents/shavermemogenericract_7nov1996.pdf.
---------------------------------------------------------------------------

    On reclassification to Serious status, the DMNFR Area was required
to implement RACT as expeditiously as practicable, but no later than
August 3, 2020 for RACT needed for demonstrating attainment and July
20, 2021 for RACT not needed for demonstrating attainment.\49\ The
Division conducted a series of analyses and rulemakings to address 2008
ozone Moderate and Serious RACT requirements.
---------------------------------------------------------------------------

    \49\ Final rule, Finding of Failure To Attain and
Reclassification of Denver Area for the 2008 Ozone National Ambient
Air Quality Standard, 84 FR 70897, 70900 (Dec. 26, 2019); see also
Final rule, Determination of Attainment Date, Extensions of the
Attainment Date, and Reclassification of Seceral Areas Classified as
Moderate for the 2008 Ozone National Ambient Air Quality Standards,
84 FR 44238 (Aug. 23, 2019).
---------------------------------------------------------------------------

    As part of its May 31, 2017 Moderate ozone attainment plan, the
Division conducted RACT analyses to demonstrate that the RACT
requirements for CTG and major sources in the DMNFR Area had been
fulfilled. The Division conducted these RACT analyses for VOC and
NOX by listing state regulations implementing or exceeding
RACT requirements for each CTG or non-CTG category at issue, and by
detailing the basis for concluding that these regulations fulfilled
RACT, through comparison with established RACT requirements described
in the CTG and ACT guidance documents and rules developed by other
state and local agencies. The EPA approved the majority of the State's
CTG RACT analysis on July 3, 2018.\50\
---------------------------------------------------------------------------

    \50\ See 83 FR 31068. A negative declaration as to RACT for
sources covered by the aerospace CTG was approved on November 5,
2021 (86 FR 61071). Colorado's RACT demonstrations for sources
covered by the industrial cleaning solvents, metal furniture
coatings (2007), and wood furniture CTGs were approved on February
24, 2021 (86 FR 11127); and the state's RACT demonstration for
sources covered by the oil and gas CTG was conditionally approved on
May 13, 2022 (87 FR 29228).
---------------------------------------------------------------------------

    In July 2018, the Commission adopted categorical RACT requirements
for combustion equipment at major sources under the Moderate
classification that the Commission had determined in 2016 were not
addressed by SIP RACT requirements. In November 2019, the Commission
adopted SIP requirements to include provisions that implement RACT for
major sources of VOC and NOX under the Serious
classification and for additional CTG VOC source categories in the
Area. Specifically, the Commission adopted categorical RACT
requirements for combustion equipment at major sources, major source
breweries, and wood furniture manufacturing, and addressed the EPA's
concerns with industrial cleaning solvent and metal furniture surface
coating requirements. The EPA approved these revisions on February 24,
2021.\51\
---------------------------------------------------------------------------

    \51\ 86 FR 11127.
---------------------------------------------------------------------------

    In December 2019, the Commission adopted additional RACT
requirements for major sources of VOC and NOX in the DMNFR
Area under the Serious classification, including expanded categorical
combustion equipment and new categorical general solvent use
requirements. The EPA approved the majority of these revisions on
November 5, 2021.\52\ The State re-reviewed its point source inventory
as part of the March 22, 2021 Serious OAP submittal to verify that non-
CTG major sources (50 tpy) of VOC or NOX emissions in the
DMNFR Area are subject to requirements that meet or exceed RACT.\53\
---------------------------------------------------------------------------

    \52\ Final rule, Approval and Promulgation of Implementation
Plans; Colorado; Revisions to Regulation Number 7; Aerospace, Oil
and Gas, and Other RACT Requirements for the 2008 8-Hour Ozone
Standard for the Denver Metro/North Front Range Nonattainment Area
86 FR 61071 (Nov. 5, 2021).
    \53\ See appendix 6-E of the OAP.
---------------------------------------------------------------------------

    The RACT submissions that we are now proposing to approve include
those that we have not previously acted on that are addressing RACT for
several non-CTG VOC and NOX sources and categories. We are
also proposing to convert to a full approval our previous conditional
approval of submissions made on May 14, 2018, May 13, 2020, and May 20,
2022, concerning RACT related to the Oil and Gas CTG.
2. Evaluation
    In preparing its RACT determinations, Colorado reviewed source
permits, consulted with Division permitting and enforcement staff
involved with each source, and consulted with the sources
themselves.\54\ Colorado also considered control strategies identified
in the CTGs, ACTs, RBLC, EPA's Menu of Control Measures, New Source
Performance Standards (NSPS), emission guidelines, National Emission
Standards for Hazardous Air Pollutants (NESHAP), and in Colorado's
regulations and determined that Colorado's major sources are currently
subject to federally enforceable emission limits or requirements
similar to measures described in these documents and regulations.\55\
In 2019, Colorado incorporated by reference some NSPS and NESHAP
requirements into its SIP and expanded the applicability of some

existing RACT requirements. A summary of our proposed action with
respect to each of these RACT categories follows.
---------------------------------------------------------------------------

    \54\ See Colorado's Technical Support Document for Reasonably
Available Control Technology for Major Sources, December 14, 2020.
Available within the docket.
    \55\ See id.

                 Table 2--Categories, Proposed Action, and Corresponding Sections of Submittals
----------------------------------------------------------------------------------------------------------------
               Category                    Proposed action               Location of RACT demonstration
----------------------------------------------------------------------------------------------------------------
Oil and gas..........................  Approval (converting     Technical Support Document for Reasonably
                                        previous conditional     Available Control Technology for the Oil and
                                        approval to full         Gas Industry, Dec. 17, 2021 (contained within
                                        approval).               the May 20, 2022 submittal).
Combustion equipment at major sources  Approval...............  Technical Support Document for Reasonably
                                                                 Available Control Technology for Major Sources,
                                                                 Dec. 14, 2020 (contained within the March 22,
                                                                 2021 submittal) and Technical Support Document
                                                                 for Reasonably Available Control Technology for
                                                                 Major Sources, July 16, 2021 (contained within
                                                                 the May 20, 2022 submittal).
Wood coating.........................  Approval...............  Technical Support Document for Reasonably
                                                                 Available Control Technology for Major Sources,
                                                                 Dec. 14, 2020 (contained within the March 22,
                                                                 2021 submittal).
Foam manufacturing...................  Approval...............  Technical Support Document for Reasonably
                                                                 Available Control Technology for Major Sources,
                                                                 Dec. 14, 2020 (contained within the March 22,
                                                                 2021 submittal).
----------------------------------------------------------------------------------------------------------------
Cited materials are contained within the docket for this action.

    We are proposing action on the RACT demonstrations for certain
additional VOC CTG, non-CTG VOC, and NOX sources and
categories. We have reviewed Colorado's new and revised VOC and
NOX rules for the categories covered by the CTGs, and for
major sources of non-CTG VOC and NOX sources for the 2008 8-
hour ozone NAAQS, and the demonstrations submitted by Colorado. Based
on this review we propose to find that these rules are consistent with
the control measures, definitions, recordkeeping, and test methods in
these CTGs and the CAA, and that they satisfy CAA RACT requirements for
the categories in question.\56\
---------------------------------------------------------------------------

    \56\ See https://www.epa.gov/ground-level-ozone-pollution/ract-information.
---------------------------------------------------------------------------

a. RACT for CTG Sources
    Table 3 contains the CTGs, EPA reference document, and the
corresponding sections of Reg. 7 that fulfill the applicable RACT
requirements for the EPA-issued CTGs. Colorado's Reg. 7 contains SIP
approved and submitted revisions (see section V.I. of this document);
we propose to find that these revisions meet RACT requirements for the
sources listed in Table 3.

   Table 3--Sources, EPA CTG Reference Document, and Corresponding Sections of Reg. 7 Proposed for Approval to
                                                  Fulfill RACT
----------------------------------------------------------------------------------------------------------------
                                                                                Reg. 7 sections
       Sources in the DMNFR area            CTG reference document        Date of CTG        fulfilling RACT
----------------------------------------------------------------------------------------------------------------
Oil and gas...........................  Control Techniques Guidelines             2016  part D, sections I, II,
                                         for the Oil and Natural Gas                     and III.
                                         Industry.
Miscellaneous Metal Coatings, Tables 2  Control Techniques Guidelines             2008  part C, section I.L.2.
 and 7 of the CTG.                       for Miscellaneous Metal and
                                         Plastic Parts Coatings.
----------------------------------------------------------------------------------------------------------------

    We have reviewed the emission limitations and control requirements
for the above sources and compared them against the EPA's CTG documents
and available technical information in CTG dockets. The EPA has also
evaluated the submitted rules and has determined that they are
consistent with the CAA, the EPA's regulations, and the EPA's policies.
Based on the information in the record, we propose to find that the
corresponding sections in Reg. 7 provide for the lowest emission
limitation through application of control techniques that are
reasonably available considering technological and economic
feasibility. Therefore, we propose to find that the control
requirements for oil and gas sources and certain miscellaneous metal
coatings are RACT for affected sources in the DMNFR Area under the 2008
8-hour ozone NAAQS.\57\
---------------------------------------------------------------------------

    \57\ For more information, see the EPA TSDs evaluating oil and
gas and miscellaneous metal coatings RACT. Available within the
docket for this action.
---------------------------------------------------------------------------

b. RACT for Non-CTG Major Sources
    In Colorado's TSDs for Reasonably Available Control Technology for
Major Sources, dated December 14, 2020,\58\ Colorado identified a list
of major non-CTG VOC and NOX sources in the DMNFR Area
subject to RACT requirements under a Serious classification. For major
VOC and NOX sources subject to nonattainment area RACT
review, Colorado used the construction permit thresholds established in
the State's Reg. 3 for determining which emission points to review.
Accordingly, emission points exceeding two tpy of VOC at a major VOC
source and five tpy of NOX at a major NOX source,
as reported on a source's APEN, and that were not part of the Moderate
RACT review, were evaluated. We have reviewed the State's March 22,
2021 and May 20, 2022 submittals and find its approach to including
these sources in the inventory acceptable. To satisfy the Serious RACT
SIP requirement to establish RACT for all existing major sources of VOC
and/or NOX in the DMNFR Area, the Commission incorporated by
reference NSPS limits for combustion turbines, expanded the combustion
equipment requirements for boilers, expanded wood furniture coating
requirements, and developed a new categorical rule for foam
manufacturing. These revisions were made based on a detailed review of
available information on major NOX

and VOC sources in the DMNFR Area, an examination of the EPA RACT/Best
Available Control Technology/Lowest Achievable Emission Rate
Clearinghouse for similar emission points, and consideration of CAA
section 182(b) RACT requirements for other ozone nonattainment areas.
Table 4 contains a list of non-CTG categories, the EPA's reference
documents, and the corresponding sections of Reg. 7 that are proposed
for approval in this action to fulfill RACT requirements (see section
V.I. of this document).\41\
---------------------------------------------------------------------------

    \58\ Contained within the March 22, 2021 submittal.

Table 4--Sources, EPA Reference Documents, and Corresponding Sections of
              Reg. 7 Proposed for Approval to Fulfill RACT
------------------------------------------------------------------------
                                  The EPA's reference
   Source in the DMNFR area     document or regulation   Reg. 7 sections
                                    (if applicable)      fulfilling RACT
------------------------------------------------------------------------
Combustion turbines...........  X Emissions from        part E, section
                                 Stationary Combustion   II.
                                 Turbines (EPA-453/3-
                                 91-026) (1991).
Process heaters...............  NOX Emissions from      part E, section
                                 Process Heaters (EPA-   II.
                                 453/R-93-034)(1993).
Combustion equipment            NOX Emissions from      part E, section
 requirements for boilers.       Industrial,             II.
                                 Commercial &
                                 Institutional Boilers
                                 (EPA-453/R-94-
                                 022)(1994).
Wood furniture coating          A Guide to the Wood     part C, section
 requirements.                   Furniture CTG and       I.O.
                                 NESHAP (EPA-453/R-97-
                                 002) (1997).
Foam manufacturing............  ......................  part E, section
                                                         V.
------------------------------------------------------------------------

    We have reviewed the emission limitations and control requirements
for the source categories in Table 4 and compared them to the EPA's
regulations, ACT documents, available technical information, and
guidelines. The EPA has also evaluated the submitted rules and has
determined that they are consistent with the CAA, the EPA's
regulations, and the EPA's policies. For more information, see the EPA
TSD prepared in conjunction with this action. Based on the information
in the record, we propose to find that the corresponding sections in
Reg. 7 provide for the lowest emission limitation through application
of control techniques that are reasonably available considering
technological and economic feasibility. Therefore, we propose to find
that the control requirements for the source categories identified in
Table 4 are RACT for all affected sources in the DMNFR Area under the
2008 8-hour ozone NAAQS.
c. Negative Declarations
    States are not required to adopt RACT limits for source categories
for which no sources exist in a nonattainment area, and can submit a
negative declaration to that effect. The EPA approved the majority of
the State's negative declarations on July 3, 2018.\59\ In its 2008
Serious OAP, Colorado reevaluated the CTGs and determined that it does
not have sources in the following CTG VOC categories or subject to the
potentially applicable CTG within the DMNFR Area that are listed in
Table 5. We are also unaware of any such facilities operating in the
Area, and thus we propose to approve the negative declarations made for
the CTG categories in Table 5 for the DMNFR Area under the 2008 8-hour
ozone NAAQS.
---------------------------------------------------------------------------

    \59\ See 83 FR 31068. A negative declaration for the aerospace
CTG was approved on November 5, 2021 (86 FR 61071).

          Table 5--Negative Declarations for CTG VOC Categories
------------------------------------------------------------------------

-------------------------------------------------------------------------
Auto and Light-Duty Truck Assembly Coatings (2008).
Coating Operations at Aerospace Manufacturing and Rework Operations
 (1994).
Factory Surface Coating of Flat Wood Paneling.
Fiberglass Boat Manufacturing Materials (2008).
Flat Wood Paneling Coatings (2006).
Flexible Packaging Printing Materials (2006).
Fugitive Emissions from Synthetic Organic Chemical Polymer and Resin
 Manufacturing Equipment (1984).
Graphic Arts--Rotogravure and Flexography (1978).
Large Appliance Coatings (2007).
Large Petroleum Dry Cleaners (1982).
Manufacture of High-Density Polyethylene, Polypropylene, and Polystyrene
 Resins.
Manufacture of Pneumatic Rubber Tires (1972).
Miscellaneous Industrial Adhesives (2008).
Plastic Parts Coatings, Tables 3, 4, 8, and 9 of the CTG (2008).
Synthetic Organic Chemical Manufacturing Air Oxidation Processes (1984).
Synthetic Organic Chemical Manufacturing Distillation and Reactor
 Processes (1993).
Surface Coating for Insulation of Magnet Wire (1977).
Shipbuilding/repair (1996).
Surface Coating of Automobiles and Light Duty Trucks (1977).
Surface Coating of Fabrics (1977).
Surface Coating of Large Appliances (1977).
Surface Coating of Paper (2007).
------------------------------------------------------------------------

D. Reasonably Available Control Measures (RACM) Analysis

1. Background
    CAA section 172(c)(1) of the CAA requires that states adopt ``all
reasonably available control measures [RACM] as expeditiously as
practicable.'' The EPA interprets the CAA RACM provision to require a
demonstration that: (1) The state has adopted all reasonable measures
(including RACT) to meet RFP requirements and to demonstrate attainment
as expeditiously as possible; and (2) no additional measures that are
reasonably available will advance the attainment date or contribute to
RFP for the area.\60\ States should consider all available measures,
including those being implemented in other areas, but must adopt
measures for an area only if those measures are economically and
technologically feasible and will advance the attainment date or are
necessary for RFP.\61\ Potentially available measures that would not
advance the attainment date for an area are not considered RACM;
likewise, states can reject potential RACM if adopting them would cause
substantial widespread and long-term adverse impacts.\62\ Local
conditions, such as economic or implementation concerns, may also be
considered. To allow the EPA to determine whether the RACM requirement
has been satisfied, states

should discuss in the SIP submittals whether measures ``within the
arena of potentially reasonable measures'' are in fact reasonably
available.\63\ If the measures are reasonably available, they must be
adopted as RACM.
---------------------------------------------------------------------------

    \60\ 40 CFR 51.912(d); Final Rule To Implement the 8-Hour Ozone
National Ambient Air Quality Standard--Phase 2, 70 FR 71612, 71659
(Nov. 29, 2005). See also General Preamble, State Implementation
Plans; General Preamble for the Implementation of title I of the
Clean Air Act Amendments of 1990, 57 FR 13498, 13560 (April 16,
1992).
    \61\ 80 FR 12264, 12282 (March 6, 2015).
    \62\ Id.
    \63\ ``Guidance on the Reasonably Available Control Measures
(RACM) Requirement and Attainment Demonstration Submissions for
Ozone Nonattainment Areas,'' John S. Seitz, Director, Office of Air
Quality Planning and Standards, EPA (Nov. 30, 1999).
---------------------------------------------------------------------------

2. Evaluation
    Colorado previously evaluated potentially available control
measures for RACM purposes with their 2008 Moderate ozone attainment
plan. The EPA approved the State's RACM analysis on July 3, 2018.\64\
The RAQC resumed RACM discussions with the CDPHE and other partners in
2018 when the DMNFR Area was reclassified to Serious, so as to identify
strategies that would help the Area attain by the 2020 ozone
season.\65\ Areas of analysis included stationary and area sources,
mobile sources and fuels, transportation, land use, pricing, and
outreach. Subcommittee meetings were open to the public, and
stakeholders provided input on the topics discussed.
---------------------------------------------------------------------------

    \64\ See 83 FR 31068.
    \65\ See p. 7-3 of the OAP.
---------------------------------------------------------------------------

    The State's RACM review took place in the context of a series of
state actions that had the effect of reducing emissions. Since the base
year of 2011, Colorado has adopted oil and gas regulations; \66\
implemented controls required under the State Clean Air Clean Jobs Act
\67\ through the Regional Haze SIP; and continued alternative
fuels,\68\ transportation,\69\ and land use programs.\70\ Additional
efforts include the ongoing work of the Statewide Hydrocarbon Emissions
Reduction Team and Pneumatics Task Force, and numerous bills aimed at
improving air quality.\71\
---------------------------------------------------------------------------

    \66\ Colorado Reg. 7, part D.
    \67\ Colo. Rev. Stat. section 40-3.2-201 et seq.
    \68\ E.g., fueling and charging station grants.
    \69\ E.g., Programs for improved public transit.
    \70\ E.g., example, Denver Regional Council of Governments
identified urban growth area.
    \71\ See p. 7-3 of the OAP.
---------------------------------------------------------------------------

    As part of the RACM analysis, CDPHE examined emission reduction
measures \72\ being implemented in the DMNFR Area that are not included
in the SIP modeling and emissions inventory because they are voluntary
or difficult to quantify. Non-federally enforceable emission reduction
measures were evaluated for stationary and mobile sources, lawn and
garden equipment, and the transportation system; outreach and education
were also evaluated as part of this analysis. Additionally, Colorado
evaluated CAA 108(f), transportation measures \73\ to determine whether
sources have applied RACM.
---------------------------------------------------------------------------

    \72\ See Table 48 of the OAP.
    \73\ See Table 52 of the OAP.
---------------------------------------------------------------------------

    After reviewing possible measures, Colorado determined that all
reasonably available control measures necessary to demonstrate
attainment are currently being implemented. Table 47 of Colorado's OAP
lists control measures included in Colorado's SIP as they relate to the
State's 2017 and 2020 emission inventories, photochemical modeling in
the attainment demonstration, and weight of evidence analysis.
    Emission measures that were evaluated but determined not to be RACM
are discussed in chapter 7.5 of the OAP. Colorado used the following
criteria to determine whether measures were considered RACM:
     Necessary to demonstrate attainment;
     Technologically or economically feasible;
     Implemented successfully in other Serious nonattainment
areas;
     Could be implemented by May 1, 2020; and
     Could qualify as SIP measures by being quantifiable,
enforceable, permanent, and surplus.
    Emission reduction measures evaluated for RACM were broken into
various categories: oil and gas, mobile source inspection and
maintenance, fuels, transportation, local government policies,
outreach, land use, and other. Table 54 of the OAP summarizes the
measures evaluated and Colorado's RACM determination for each measure.
Colorado also reviewed the EPA's Menu of Control Measures for NAAQS
Implementation \74\ and voluntary and mandatory control measures in
other ozone nonattainment areas. Table 55 of the OAP lists control
measures identified, and indicates which measures were included in the
State's RACM review. Although Colorado's analysis demonstrated that
none of the additional measures identified met the criteria for RACM,
the State plans to continue evaluating strategies in various areas,
including oil and gas, mobile source inspection and maintenance, fuels,
transportation, and local government policies, as described in Table 54
of the OAP.
---------------------------------------------------------------------------

    \74\ The Menu of Control Measures gives state, local and tribal
air agencies information on existing emissions reduction measures,
as well as relevant information concerning the efficiency and cost
effectiveness of the measures. Available at https://www.epa.gov/air-quality-implementation-plans/menu-control-measures-naaqs-implementation.
---------------------------------------------------------------------------

    In its analysis, Colorado evaluated all source categories that
could contribute meaningful emission reductions, and identified and
evaluated an extensive list of potential control measures. To determine
reasonableness and availability, the State considered the time needed
to develop and adopt regulations, and the time it would take to see the
benefit from these measures. The EPA has reviewed the RACM analysis and
finds that there are no additional RACM that would have advanced the
Serious area attainment date of 2021 for the DMNFR Area.\75\ Therefore,
the EPA proposes to approve Colorado's Serious area RACM analysis for
the DMNFR Serious nonattainment area.
---------------------------------------------------------------------------

    \75\ On October 7, 2022 the EPA finalized an action that among
other things reclassified the DMNFR Area to Severe nonattainment
status for the 2008 ozone NAAQS. See Final rule, Determinations of
Attainment by the Attainment Date, Extensions of the Attainment
Date, and Reclassification of Areas Classified as Serious for the
2008 Ozone National Ambient Air Quality Standards, 87 FR 60926.
Accordingly, the State of Colorado will be required to submit a
demonstration that the area will attain the Severe standard, and
other elements of a Severe SIP.
---------------------------------------------------------------------------

E. Motor Vehicle Inspection and Maintenance Program (I/M) Program

1. Background
    As a Serious ozone nonattainment area, pursuant to CAA section
182(c)(3), Colorado was required to implement an enhanced I/M program
in the DMNFR Area.\76\ Colorado's Regulation Number 11 (Reg. 11) is
titled ``Motor Vehicle Emissions Inspection Program,'' and addresses
the implementation of the State's I/M program.\77\ Under Reg. 11 and
other state law,\78\ all eligible automobiles registered in the
Automobile Inspection and Readjustment (AIR) program area \79\ are
subject to periodic emissions inspection. Currently there is an
exemption from emissions inspection requirements for the first seven
model years. Thereafter, an On-Board-Diagnostics (OBD) vehicle computer
inspection is conducted during the first two inspection cycles
(vehicles 8 through 11 model years old). Vehicles older than 11 model
years are given a dynamometer-based IM240 test for 1982 and newer
light-duty gasoline vehicles \80\ and a two-speed idle test

(TSI) \81\ for 1981 and older light-duty gasoline vehicles. To improve
motorist convenience and reduce program implementation costs, the State
also administers a remote sensing-based ``Clean Screen'' program
component of the I/M program. Remote sensing is a method for measuring
vehicle emissions, while simultaneously photographing the license
plate, when a vehicle passes through infrared or ultraviolet beams of
light. Owners of vehicles meeting the Clean Screen criteria are
notified by the respective County Clerk that their vehicle has passed
the motor vehicle inspection process and are exempt from their next
regularly scheduled program inspection.\82\
---------------------------------------------------------------------------

    \76\ 5 CCR 1001-13.
    \77\ The provisions which have been approved by the EPA into the
Colorado SIP via past rulemaking actions, including Reg. 11, are
publicly available at https://www.epa.gov/sips-co/epa-approved-statutes-and-regulations-colorado-sip.
    \78\ CO Rev Stat section 42-4-304 (2016).
    \79\ The current nine-county AIR program area is depicted in
chapter 8, figure 19, page 8-3 of the OAP.
    \80\ See 40 CFR part 51, subpart S for a complete description of
EPA's IM240 test. The IM240 test is essentially an enhanced motor
vehicle emissions test to measure mass tailpipe emissions while the
vehicle follows a computer-generated driving cycle trace for 240
seconds and while the vehicle is on a dynamometer.
    \81\ See 40 CFR part 51, subpart S for a complete description of
EPA's two-speed idle test. The two-speed idle test essentially
measures the mass tailpipe emissions of a stationary vehicle; one
reading is at a normal idle of approximately 700 to 800 engine
revolutions per minute (RPM) and one reading at 2,500 RPM.
    \82\ The Clean Screen program component of Reg. 11 was
originally approved for implementation in the Denver area with the
EPA's approval of the original Denver carbon monoxide (CO)
redesignation to attainment and the related maintenance plan. See 66
FR 64751 (Dec. 14, 2001). The Clean Screen criteria approved in 2001
required two valid passing remote sensing readings, on different
days or from different sensors and within the twelve-month period
prior to that vehicle's registration renewal date. Colorado revised
Reg. 11 to expand the definition and requirements for a ``clean-
screened vehicle'' to also include vehicles identified as low-
emitting vehicles in the state-determined Low Emitting Index (LEI)
that have one passing remote sensing reading, before the vehicle's
registration renewal date. These improvements and other associated
revisions to the Clean Screen program were approved by the EPA on
October 21, 2016 (81 FR 72720).
---------------------------------------------------------------------------

2. Evaluation
    The AIR program and Reg. 11 were expanded into portions of Larimer
and Weld counties as ``state only'' requirements in the Colorado 2009
Legislative session, with the passage of Senate Bill 09-003. The
startup date of the I/M program in these two counties was November 1,
2010. The purpose of this expansion of the AIR program and Reg. 11 into
portions of Larimer and Weld counties was to further reduce vehicle
emissions of NOX and VOC ozone precursors in the 2008 DMNFR
Area. With the reclassification of the DMNFR Area to Moderate for the
2008 8-hour ozone NAAQS, and in light of the associated CAA
requirements, the State chose to submit the I/M program in Larimer and
Weld counties into the SIP. Accordingly, as part of Moderate Area SIP
revisions for the 2008 8-hour ozone NAAQS, Colorado removed the
Larimer/Weld ``state-only'' designation in Reg. 11 and submitted a
revised Reg. 11 to the EPA, which was approved July 3, 2018.\83\
---------------------------------------------------------------------------

    \83\ 83 FR 31068.
---------------------------------------------------------------------------

    The most recent federally approved revisions to the Reg. 11
enhanced I/M program were adopted by the AQCC in May 2017. The
revisions consisted of:
     Inclusion of OBD I/M pass/fail results as a qualifying
consideration in the remote sensing clean screen low emitter index,
     Clarification of details of tailpipe and OBD inspection
procedures and OBD readiness criteria, and
     Establishing authority to fail vehicles exhibiting
evidence of OBD fraud.
    These revisions were approved by EPA on February 7, 2019.\84\
---------------------------------------------------------------------------

    \84\ 84 FR 2449. Colorado submitted the latest revisions to Reg.
11 to the EPA on May 16, 2022. The EPA will act on those revisions
in a separate action. Since these most recent changes to Reg. 11
were adopted by the State after the attainment date for Serious
areas under the 2008 ozone NAAQS, the revisions were not considered
when evaluating the adequacy of Colorado's enhanced I/M program in
the context of this current EPA action.
---------------------------------------------------------------------------

    On July 15, 2022, Colorado submitted supplemental modeling of the
State's I/M program for comparison against the applicable Enhanced I/M
performance standard requirements in 40 CFR part 51, subpart S.
Colorado used the latest approved version of the EPA's mobile source
emissions model, MOVES3.0.3 (released January 2022), for the
comparative analysis. Demonstration of program equivalency to the
enhanced I/M program standard was conducted in accordance with the
EPA's published I/M performance standard modeling guidance, MOVES3
technical guidance, and additional technical guidance from the EPA as
necessary.\85\
---------------------------------------------------------------------------

    \85\ See Performance Standard Modeling for New and Existing
Vehicle Inspection and Maintenance (I/M) Programs Using the MOVES
Mobile Source Emissions Model, EPA-420-B-14-006 (Jan. 2014),
available at http://nepis.epa.gov/Exe/ZyPdf.cgi?Dockey=P100HHMP.pdf;
MOVES3 Technical Guidance: Using MOVES to Prepare Emission
Inventories for State Implementation Plans and Transportation
Conformity, EPA-420-B-20-052 (Nov. 2020), available at https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P1010LY2.pdf.
---------------------------------------------------------------------------

    To demonstrate that the Colorado enhanced I/M program meets the
enhanced program performance standard described in 40 CFR 51.351(i),
the Colorado program must be modeled to show that, on the proper
analysis date, it obtains the same or lower emissions reductions as the
federal model enhanced program. The state program may provide
reductions of NAAQS relevant pollutants equivalent to the reductions
expected from the model program to within 0.02 grams per
mile for the area's total vehicle miles travelled on a July weekday in
the attainment date year. Colorado's supplemental demonstration shows
that the state's I/M program meets the applicable enhanced I/M
performance standard requirements for the 2008 ozone NAAQS.
    Based on our review and as discussed above we find that Colorado
has a Vehicle I/M Program that meets the performance standard for
Enhanced I/M, and we therefore propose approval of this portion of the
OAP.

F. Nonattainment New Source Review (NNSR)

1. Background
    As a Serious ozone nonattainment area, Colorado was required to
implement an NNSR program. Applicable NNSR requirements for ozone
nonattainment areas are described in CAA section 182 and further
defined in 40 CFR part 51, subpart I (Review of New Sources and
Modifications). Under these requirements, new major sources and major
modifications at existing sources must achieve the lowest achievable
emission rate (LAER) and obtain emission offsets in an amount based on
the specific ozone nonattainment classification. The emission offset
ratio required for Serious ozone nonattainment areas is 1.2 to 1.\86\
---------------------------------------------------------------------------

    \86\ CAA section 182(c)(10).
---------------------------------------------------------------------------

2. Evaluation
    The Colorado SIP includes Regulation 3, part D, section V.A.
(Concerning Major Stationary Source New Source Review and Prevention of
Significant Deterioration, Requirements Applicable to Nonattainment
Areas).\87\ This provision requires new major sources and major
modifications at existing sources in the DMNFR Area to comply with LAER
and obtain emission offsets at the Serious classification ratio of 1.2
to 1. The EPA approved these provisions on January 25, 2016.\88\ Since
the provisions in the Colorado SIP satisfy the CAA NNSR requirements
for ozone nonattainment areas classified as Serious, we propose
approval of this portion of the OAP.
---------------------------------------------------------------------------

    \87\ The provisions which have been approved by the EPA into the
Colorado SIP via past rulemaking actions, including Regulation
Number 3, are publicly available at https://www.epa.gov/sips-co/epa-approved-statutes-and-regulations-colorado-sip.
    \88\ 81 FR 3963.

---------------------------------------------------------------------------

G. Motor Vehicle Emissions Budget (MVEB)/Transportation Conformity

1. Background
    Section 176(c) of the CAA establishes a requirement known as
``Transportation Conformity,'' under which federal agencies must ensure
that actions they support or fund will conform to the applicable SIP.
Conformity to a SIP means that transportation activities will not
produce new air quality violations, worsen existing violations, or
delay timely attainment of the NAAQS.\89\ The EPA's conformity rule at
40 CFR part 93, subpart A requires that transportation plans, programs,
and projects conform to SIPs, and establishes the criteria and
procedures for determining whether they conform. The conformity rule
requires a demonstration that emissions from the Metropolitan Planning
Organization's (MPO) Regional Transportation Plan (RTP) and the
Transportation Improvement Program (TIP) are consistent with the MVEB
in the control strategy SIP revision or maintenance plan.\90\ The MVEBs
are defined as the portion allocated to mobile source emissions out of
the total allowable emissions of a pollutant defined in the SIP for a
certain date for the purpose of demonstrating attainment or maintenance
of the NAAQS or for meeting RFP milestones.\91\
---------------------------------------------------------------------------

    \89\ CAA section 176(c)(1)(B).
    \90\ 40 CFR 93.101, 93.118, and 93.124.
    \91\ 40 CFR 93.101; see 40 CFR 93.118 and 93.124 for criteria
and other requirements related to MVEBs. Further discussion of MVEBs
is in the preamble to the transportation conformity rule. 58 FR
62188, 62193-62196 (Nov. 24, 1993).
---------------------------------------------------------------------------

    Additionally, CAA section 182(c)(5) requires that states, every
three years, submit a demonstration for Serious nonattainment areas
that current aggregate VMT, aggregate vehicle emissions, congestion
levels, and other relevant traffic-related and vehicle emissions-
related factors (collectively ``relevant parameters'') are consistent
with those used for the area's ozone attainment demonstration.
2. Evaluation
    Colorado derived the MVEBs for NOX and VOCs from its
2020 DMNFR Serious attainment demonstration, and defined the MVEBs in
chapter 11, section 11.2.1 of the OAP.

             Table 6--2020 NOX and VOC MVEBs for DMNFR Area
------------------------------------------------------------------------
                                             2020 NOX        2020 VOC
          Area of applicability              emissions       emissions
                                               (tpd)           (tpd)
------------------------------------------------------------------------
Northern Subarea........................             9.7             8.2
Southern Subarea........................              45            41.2
Total Nonattainment Area................            54.7            49.4
------------------------------------------------------------------------

    These MVEBs are consistent with, and clearly related to, the
emissions inventory and the control measures in the SIP, and satisfy
the criteria at 40 CFR 93.118(e)(4). Therefore, we propose approval of
the MVEBs as reflected in Table 6. This proposed approval applies to
the Northern Subarea and Southern Subarea MVEBs as well as the Total
Nonattainment Area MVEBs. The transportation conformity subareas are
defined in chapter 11, section 11.2 of the OAP and are listed below.
     The Northern Subarea is the area denoted by the ozone
nonattainment area north of the Boulder County northern boundary and
extended through southern Weld County to the Morgan County line. This
area includes the North Front Range MPO's (NFRMPO) regional planning
area as well as part of the Upper Front Range Transportation Planning
Region (TPR) in Larimer and Weld counties.
     The Southern Subarea is the area denoted by the ozone
nonattainment area south of the Boulder County northern boundary and
extended through southern Weld County to the Morgan County line. This
area includes the nonattainment portion of the Denver Regional Council
of Governments (DRCOG) regional planning area and the southern Weld
County portion of the Upper Front Range TPR.
     Both subareas are further described in the OAP in Figure
20, ``8-hour Ozone Nonattainment Area Subareas.''
    In addition to proposing approval of the MVEBs, we also propose to
approve the process described in chapter 11, section 11.2.3 in the OAP
for the use of the Total Nonattainment Area MVEBs or the subarea MVEBs
for the respective MPOs to determine transportation conformity for
their respective RTP. As described in section 11.2.3 of Colorado's OAP,
the OAP identifies subarea MVEBs for DRCOG and the NFRMPO. These SIP-
identified subarea MVEBs allow either MPO to make independent
conformity determinations for the applicable subarea MVEBs whose
frequency and timing needs for conformity determinations differ. As
noted in section 11.2.3, DRCOG and the NFRMPO may switch from using the
Total Nonattainment Area MVEBs to using the subarea MVEBs for
determining conformity. To switch to use of the subarea MVEBs (or to
subsequently switch back to use of the Total Nonattainment Area MVEBs)
DRCOG and the NFRMPO must use the process described in the DMNFR OAP in
section 11.2.3.\92\ This process of demonstrating transportation
conformity to the total or subarea area MVEBs, as described in section
11.2.3 of the OAP, was previously approved by the EPA for the Denver
Moderate Ozone Plan for the 2008 8-hour standard on July 3, 2018.\93\
Now, as to the Serious classification for the 2008 8-hour standard, the
EPA finds that this process remains consistent with the CAA and with
applicable EPA regulations, and therefore proposes to approve it.
---------------------------------------------------------------------------

    \92\ See pp. 11-5 and 11-6 of the OAP.
    \93\ 83 FR 31068.
---------------------------------------------------------------------------

    Regarding transportation control requirements, as described in
section 11.3 of the OAP, MVEBs are evaluated on a regular basis by the
MPOs through their conformity process. Based on the most recent
conformity determinations for the northern and the southern subregions,
Colorado's demonstration shows that both areas were meeting the current
emissions budgets established in the 2008 Moderate area Ozone SIP, and
that they are expected be able to meet the proposed budgets for the
2008 Serious area Ozone SIP in future conformity determinations. The
EPA finds that the transportation control measures as described in
section 11.3 of the OAP meet CAA requirements. We therefore propose to
approve this section of the OAP.

H. Clean Fuel Fleet Program

1. Background
    Sections 182(c)(4) and 241-246 of the CAA provide that states with
ozone nonattainment areas classified as Serious, Severe, or Extreme
must implement a federally enforceable program to require certain
centrally fueled fleet operators to include a specified percentage of
clean-fuel vehicles (CFV) in their new fleet purchases to reduce
emissions of ozone precursors, or else to engage in a state-managed
credit trading scheme with other fleet operators who purchase CFV in
excess to requirements. Section 182(c)(4) of the Act also allows states
subject to the clean-fuel fleet program requirements to develop
substitute programs to achieve equivalent reductions to those achieved
by the default program requirements for the covered nonattainment area,
and to submit them to the EPA for approval.\94\
---------------------------------------------------------------------------

    \94\ Final rule, Emission Standards for Clean-Fuel Vehicles and
Engines, Requirements for Clean-Fuel Vehicle Conversions, and
California Pilot Test Program, 59 FR 50042 (Sept. 30, 1994).
---------------------------------------------------------------------------

2. Evaluation
    In the OAP, Colorado cited an EPA determination \95\ that,
beginning with the 2007 model years, both the Tier 2 conventional
vehicle and engine standards and heavy-duty vehicle and engine
standards are either equivalent to or more stringent than the
applicable clean fuel vehicle program low emission vehicle (LEV)
standards. Table 59 of the OAP includes a clean fuel fleet emission
comparison demonstrating that Tier 2 and 2004 heavy-duty engine
standards are equivalent or more stringent than the Clean Fuel Fleet
standards and that the emission reductions from the federal standards
surpassed LEV emission reductions in 2004, when the federal standards
were implemented. Additionally, figure 23 of the OAP provides a
comparison of Tier 3 Motor Vehicle Emission and Fuel Standards program
that illustrates even larger emission reductions over CFV standards.
---------------------------------------------------------------------------

    \95\ See EPA Dear Manufacturer Letter CCD-05 (LDV/LDT/MDPV/HDV/
HDE/LD-FC), July 21, 2005, in the docket for this rulemaking.
---------------------------------------------------------------------------

    The EPA amended the Clean Fuel Fleet standards in 40 CFR part 88 in
2021 to address the fact that current emissions standards for engines
and vehicles are either more stringent than or equivalent to the Clean
Fuel Fleet standards.\96\ According to these amendments, all new fleet
purchases of vehicles and engines certified to current emission
standards are deemed to meet the Clean Fuel Fleet standards as Ultra
Low-Emission Vehicles.
---------------------------------------------------------------------------

    \96\ Final rule, Improvements for Heavy-Duty Engine and Vehicle
Test Procedures, and Other Technical Amendments 86 FR 34308 (June
29, 2021).
---------------------------------------------------------------------------

    Because 2004 model year Heavy Duty Diesel and Tier II and III
vehicle standards meet or exceed the CFV LEV standards, we propose to
find that Colorado meets the Federal Clean Fuel Fleet Program
requirements, and to approve that portion of the submittal that
addresses the requirements of section 182(c)(4) of the CAA.

I. SIP Control Measures

1. Background
    This section describes revisions to Colorado Regs. 7 and 21
submitted as a part of the SIP, including emission control requirements
for oil and gas operations; turbines, process heaters, and other
combustion equipment, foam manufacturing; architectural coatings and
consumer products. The revisions also establish RACT requirements for
emission points at certain CTGs and major sources of VOC and
NOX in the DMNFR Area.
    Colorado's Reg. 7, entitled ``Control of Ozone via Ozone Precursors
and Control of Hydrocarbons via Oil and Gas Emissions,'' contains
general RACT requirements as well as specific emission limits
applicable to various industries. The EPA approved the repeal and re-
promulgation of Reg. 7 in 1981,\97\ and has approved various revisions
to Reg. 7 over the years. In 2008, the EPA approved revisions to the
control requirements for condensate storage tanks in section XII,\98\
and later approved revisions to Reg. 7, sections I through XI and
sections XIII through XVI.\99\ The EPA also approved Reg. 7 revisions
to section XVII.E.3.a establishing control requirements for rich-burn
reciprocating internal combustion engines.\100\ In 2018 the EPA
approved Reg. 7 revisions in sections XII (VOC emissions from oil and
gas operations) and XIII (emission control requirements for VOC
emissions from graphic art and printing processes), as well as non-
substantive revisions to numerous other parts of the regulation.\101\
---------------------------------------------------------------------------

    \97\ Final rule, Colorado: Approval and Promulgation of State
Implementation Plans, 46 FR 16687 (March 13, 1981).
    \98\ Final rule, Approval and Promulgation of Air Quality
Implementation Plans; State of Colorado; Regulation No. 7, section
XII, Volatile Organic Compounds From Oil and Gas Operations, 73 FR
8194 (Feb. 13, 2008).
    \99\ Final rule, Approval and Promulgation of State
Implementation Plans; State of Colorado; Attainment Demonstration
for the 1997 8-Hour Ozone Standard, and Approval of Related
Revisions, 76 FR 47443 (Aug. 5, 2011).
    \100\ Final rule, Approval and Promulgation of Implementation
Plans; State of Colorado; Regional Haze State Implementation Plan,
77 FR 76871 (Dec. 31, 2012).
    \101\ See 83 FR 31068, 31071.
---------------------------------------------------------------------------

    In February 2021, the EPA approved Reg. 7 revisions in sections I
(Applicability), IX (Surface Coating Operations), X (Use of Cleaning
Solvents), XIII (Graphics Arts and Printing), XVI (Controls of
Emissions from Stationary and Portable Engines and Other Combustion
Equipment in the 8-Hour Ozone Control Area), and XIX (Control of
Emissions from Specific Major Sources of VOC and/or NOX in
the 8-hour Ozone Control Area). Revisions to incorporation by reference
dates to rules and reference methods in sections II, VI, VIII, IX, X,
XII, XIII, XVI and XVII were also approved, as well as non-substantive
revisions to numerous other parts of the regulation.\102\
---------------------------------------------------------------------------

    \102\ 86 FR 11125.
---------------------------------------------------------------------------

    In November 2021, the EPA approved submitted revisions to sections
II (general provisions), XII (Volatile Organic Compound Emissions from
Oil and Gas Operations), and XVIII (emissions from natural gas-actuated
pneumatic controllers located at or upstream of natural gas processing
plants) of Reg. 7 from State submissions in 2018 and 2019.\103\ From
the State's 2020 submission, the EPA approved revisions that fully
reorganized Reg. 7. into parts A-E; updated requirements for gasoline
transport trucks, bulk terminals, and service stations in part B; added
general solvent use requirements in part C, section II.F; and added
stationary internal combustion engine and flare RACT requirements for
major sources of VOC and/or NOX in the Denver Area in part
E. Revisions to incorporation by reference dates to rules, updates to
reference methods, and typographical, grammatical and formatting
corrections were made throughout Reg. 7. Additionally, the EPA
finalized approval of the State's negative declaration--(that is, its
statement that there are no covered sources in the DMNFR Area) as to
the aerospace CTG.
---------------------------------------------------------------------------

    \103\ 86 FR 61071.
---------------------------------------------------------------------------

    Most recently, in May 2022, the EPA conditionally approved AQCC
regulations of ozone precursor and hydrocarbon emissions from oil and
gas operations in sections XII.J.1 of Reg. 7 from the State's May 14,
2018 submittal and part D, sections I.D., I.E., I.F., and I.J.1. of
Reg. 7 from the State's May 13, 2020 submission.\104\ Additionally, the
EPA conditionally approved Colorado's determination that Reg. 7, part D
satisfies RACT requirements for the

Colorado ozone SIP for the 2016 oil and natural gas CTG.
---------------------------------------------------------------------------

    \104\ 87 FR 29228 (May 13, 2022).
---------------------------------------------------------------------------

    Colorado submitted new regulation number 21 (Reg. 21) on May 13,
2020, and revised Reg. 7 revisions with the OAP on March 22, 2021, and
subsequent revisions on May 18, 2021 and May 20, 2022. The 2020
submittal includes new Reg. 21, which establishes VOC content limits in
architectural coatings and consumer products. The 2022 revisions in
Reg. 7, part C, section I.O and part E, sections II.A., III.B., and V.
address RACT for major sources with VOC and/or NOX emissions
equal to or greater than 50 tpy; specifically, for wood surface
coatings operations, boilers, turbines, process heaters, landfill gas
and biogas fired engines,\105\ and foam manufacturing. The 2021
submittals include revisions to Reg. 7, part D, sections I.E.3.,
I.J.1., and III.B to address oil and gas CTG requirements, and clerical
revisions in parts C, sections I.A., I.L., and E, sections II.A.
Colorado made substantive SIP revisions to Reg. 21 and certain limited
parts of Reg. 7, particularly part C, sections I.O. and I.L.; part D,
sections I.E.3. and I.J.1; and part E, sections, II.A.1.c., II.A.3.p,
II.A.4.b.(i), II.A.4.b.(iv), II.A.4.f., II.A.4.g, II.A.5.a.(iii),
II.A.5.b.(ii)(B), II.A.5.b.(ii)(B), II.A.5.b.(ii)(C)(4),
II.A.5.c.(i)(A), II.A.6.b.(viii)(E), and V. The State also made non-
substantive revisions to numerous parts of Reg. 7. For ease of review,
Colorado submitted the full text of Reg. 7 and Reg. 21 as a SIP
revision (with the exception of provisions designated ``State Only'').
The EPA is only seeking comment on Colorado's proposed substantive
changes to the SIP-approved version of Reg. 7, which are described
below. We are not seeking comment on incorporation into the SIP of the
revised portions of the regulation that were previously approved into
the SIP and have not been substantively modified by the State as part
of this submission.
---------------------------------------------------------------------------

    \105\ The EPA will be acting on the State's RACT determination
for landfill and biogas fired engines in a separate action.
---------------------------------------------------------------------------

    As noted above, Colorado designated various parts of Reg. 7 and
Reg. 21 ``State Only'' and in Reg. 7, section I.A.1.c and Reg. 21,
section I.A.2. indicated that sections designated State Only are not
federally enforceable. The EPA concludes that provisions designated
State Only have not been submitted for EPA approval, but for
informational purposes. Hence, the EPA is not proposing to act on the
portions of Regs. 7 or 21 designated State Only, and this proposed rule
does not discuss them further except as relevant to discussion of the
portions of the regulation that Colorado intended to be federally
enforceable.
2. Evaluation
a. Analysis of Reg. 21 Changes in May 13, 2020 Submittal
    The EPA proposes to approve the changes made to Reg. 21 with
Colorado's May 13, 2020 submission.
(i) Part A
    Part A of Reg. 21 establishes new rules for limiting VOC emissions
from consumer products as of May 1, 2020. ``Consumer products,'' as
defined in section VI.GG., ``means a chemically formulated product used
by household and institutional consumers including, but not limited to,
detergents; cleaning compounds; polishes; floor finishes; cosmetics;
personal care products; home, lawn, and garden products; disinfectants;
sanitizers; aerosol paints; automotive specialty products; and aerosol
adhesives. Consumer product does not include other paint products,
furniture coatings, or architectural coatings.'' \106\ Section I
contains the applicability requirements. The rules apply to people who
sell, supply, offer for sale, distribute for sale, or manufacture for
sale consumer products in the 8-hour ozone control area. Section I.B.
includes a number of exemptions from the requirements in section A,
such exemptions for consumer products that are manufactured in Colorado
solely for shipment and use outside of Colorado, and for consumer
products that have been granted an Innovative Product exemption, an
Alternative Control Plan (ACP), or a variance under the Variances
provisions by the California Air Resources Board (CARB).
---------------------------------------------------------------------------

    \106\ See p. 260 of the May 13, 2020 submittal.
---------------------------------------------------------------------------

    Table 1 in section II establishes VOC content limits for
manufacturing, selling, suppling, offering for sale, and distributing
consumer products. Additional standards in section II include labeling,
certification, and VOC limit applicability requirements for consumer
products. Section II.J. includes a list of chemicals that consumer
products cannot contain. Section II.K. includes a list of consumer
products that cannot contain trichloroethylene in a combined amount
greater than 0.01 percent by weight. Table 1 in Part A includes the VOC
content limits for consumer products manufactured on or after May 1,
2020.
    Section III of part A contains container labeling requirements,
including a requirement for clear display of dates that products were
manufactured or date codes representing the date of manufacture on
containers or packages; special purpose spray adhesive classification
requirements; and dilution ratios for non-aerosol floor wax strippers.
Sections III.E and F. include label display requirements for energized
electrical cleaner and zinc rich primers. Under section III.F aerosol
adhesives, adhesive removers, electronic cleaners, electrical cleaners,
energized electrical cleaners, and content products must include the
product category, applicable VOC standard for the product as a
percentage by weight, and the applicable substrate and/or application
for special purpose spray adhesives on labels.
    Section IV contains reporting requirements to demonstrate
compliance with the applicability and standards requirements in part A.
These include maintaining records necessary to demonstrate exemptions
under section I.B and of the para-dichlorobenzene content of solid air
freshener, insecticide, or toilet/urinal care consumer products.
Records must be maintained for a minimum of three years and made
available to the Division upon request. Section IV.D. includes a list
of information that must be reported to the Division within 90 days of
written notice. This information includes the names and contact
information of responsible parties, consumer product brand names for
each product label and category, Colorado sales in pounds per year, and
the net percent by weight of total product.
    Section V includes test methods that should be used to determine
compliance with the requirements in part A (CARB Method 310 or through
calculation of the VOC content from records of the amounts of
constituents used to make the product) and whether a product is a
liquid or solid (ASTM D4359-90(2000)e). Section VI contains a list of
definitions used throughout part A. We propose to find that the
provisions in part A are consistent with CAA requirements, and that
they strengthen the SIP. We therefore propose to approve the revisions
in part. A.
(ii) Part B
    Part B of Reg. 21 establishes new rules for limiting VOC emissions
from architectural or industrial maintenance (AIM) coatings as of May
1, 2020. Architectural coating, as defined in section VI.F., ``means a
coating to be applied to stationary structures or their appurtenances
at the site of installation, to portable buildings at the site of
installation, to pavements, or to curbs. Architectural coating does not
include

coatings applied in shop applications or to non-stationary structures
such as airplanes, ships, boats, railcars, and automobiles, as well as
adhesives.'' \107\ Industrial maintenance coatings, as defined in
section VI.DD., ``means a high performance architectural coating,
including primers, sealers, undercoaters, intermediate coats, and
topcoats, formulated for application to substrates, including floors,
and exposed to one or more of the following extreme environmental
conditions: immersion in water, wastewater, or chemical solutions
(aqueous and non-aqueous solutions), or chronic exposures of interior
surfaces to moisture condensation; acute or chronic exposure to
corrosive, caustic, or acidic agents, or to chemicals, chemical fumes,
or chemical mixtures or solutions; frequent exposure to temperatures
above 121[deg]C (250 [deg]F); frequent heavy abrasion, including
mechanical wear and scrubbing with industrial solvents, cleansers, or
scouring agents; or exterior exposure of metal structures and
structural components. Industrial maintenance coatings must be labeled
as specified in part B, section III.D.1.'' \108\
---------------------------------------------------------------------------

    \107\ See p. 282 of the May 13, 2020 submittal.
    \108\ See p. 285 of the May 13, 2020 submittal.
---------------------------------------------------------------------------

    Section I contains the applicability requirements. The rules apply
to people who sell, supply, offer for sale, distribute for sale, or
manufacture for sale AIM coatings in the 8-hour ozone control area.
Section I.B. includes a number of exemptions from the requirements in
section B including AIM coatings that are manufactured in Colorado
solely for shipment and use outside of Colorado; aerosol coating
products, and AIM coatings that are sold in containers with a volume of
one liter or less.
    Table 1 in section II establishes VOC content limits for
manufacturing, blending, suppling, selling, offering for sale, and
soliciting for application AIM coatings. Section III of part B includes
container labeling requirements including clearly displaying dates that
products were manufactured or date codes representing the date of
manufacture on containers, a statement of the manufacturer's
recommendation regarding thinning of the coating, and the VOC content
in grams per liter of coating. Section III.D. includes a list of
statements that should be displayed on container labels, such as ``for
industrial use only,'' ``for blocking stains,'' ``high gloss,'' and
``for metal substrates only.''
    Section IV contains a list of information that must be reported to
the Division within 180 days of written notice to demonstrate
compliance with part B requirements. This information includes the
names and mailing address of manufacturers, the names of the coatings
products as they appear on the labels and the application coating
categories, the VOC content in gram per liter as determined in
accordance with section V, and the density of the products in pounds
per gallon.
    Section V includes test methods that should be used to determine
compliance with the requirements in part B. Section V.A. describes the
process for determining the VOC content of a coating. Section VI.
contains a list of definitions used throughout part B. We propose to
find that the provisions in part B are consistent with CAA
requirements, and that they strengthen the SIP. We therefore propose to
approve the revisions in part B.
b. Analysis of Reg. 7 Changes in March 22, 2021 Submittal
    The EPA proposes to approve the following changes made to Reg. 7
with Colorado's March 22, 2021 submission.
(i) Part C, Section I
    Section I of part C contains rules for surface coating operations.
In this submittal, the Commission expanded Section I.O wood furniture
surface coating requirements to the surface coatings of other wood
products such as doors, door casings, and decorative wood accents. The
provisions apply to other wood products coating operations with
uncontrolled actual emissions greater than or equal to 50 tpy located
in the DMNFR Area. A detailed evaluation of section I is in the TSD for
this action. We propose to find that the provisions in part C are
consistent with CAA and RACT requirements, and that they strengthen the
SIP. We therefore propose to approve the revisions in part. C.
(ii) Part E, Section II
    Section II of part E contains rules for the control of emissions
from stationary and portable combustion equipment in the DMNFR Area.
The revisions in art E include RACT requirements for 50 tpy major
sources of VOC and/or NOX including a NOX
emission limit for boilers between 50 MMBtu/hr and 100 MMBtu/hr, a
NOX emission limit for landfill gas or biogas fired
engines,\109\ and NOX emission limits for combustion
turbines.
---------------------------------------------------------------------------

    \109\ The EPA will be acting on the State's RACT determination
for landfill and biogas fired engines in a sperate action.
---------------------------------------------------------------------------

    Section II.A.4.a.(iv) expands categorical boiler RACT requirements
for 50-100 MMBtu/hr boilers at 50 tpy major sources to comply with a
0.1 lb/MMBtu NOX emission limit. The owners or operators of
these boilers will continue to comply with the combustion process
adjustment, periodic performance testing, and recordkeeping
requirements in section II.
    Section II.A.4.b.(i)(A) was revised to reference NSPS KKKK
NOX emission limits for the turbines constructed before
February 18, 2005. These emission limits are included in Table 1 of
section II.A.4.b. Section II.A.4.b.(i)(A)(1) requires that turbines
with CEMS that are capable of operating in both combined and simple
cycle modes show compliance with a 30-day rolling average. Section
II.A.4.b.(iv) adds a new requirement for turbines, air pollution
control equipment, and monitoring equipment to be operated with good
air pollution control practices for minimizing emissions. Section
II.A.5.c.(i)(A) includes monitoring requirements for pre and post
February 18, 2005 turbines.
    A detailed evaluation of section II is in the TSD for this action.
We propose to find that the provisions in section II are consistent
with CAA and RACT requirements, and that they strengthen the SIP. We
therefore propose to approve the revisions in part E, section II.
(iii) Part E, Section V
    Section V of part E contains new rules for the control of emissions
from foam manufacturing in the DMNFR Area as of January 27, 2020. Foam
manufacturing operation, as defined in section V.A.3.e., ``means any
expanded polystyrene (EPS) production line, or portion of a production
line, which processes raw EPS bead into final molded EPS product.
Production line processes include, but are not limited to pre-
expansion, aging (pre-puff), and molding. The manufacturing process
ends after the product exits the EPS mold. `Foam manufacturing
operation' also means any production line processing methylene diphenyl
diisocyanate (MDI), resins, and various hardeners and thickeners into
foam products and which results in VOC emissions into the atmosphere.
The manufacturing process ends after the product exits the drying
tunnel.'' Section V.A.3. includes a list of definitions used in section
V.
    Section V.A.4. establishes emission limits for foam manufacturing
operations. Operators must limit VOC emissions from foam manufacturing
to 3.0 lbs per 100 lbs of total material processed, averaged monthly,
or must control VOC emissions from foam

manufacturing by 90%. Work practice requirements are set forth in
section V.A.5. and require that raw materials be stored in closed,
leak-free, labeled containers, and in a manner that minimizes
evaporation from open containers. Sections V.A.6., 7, and 8 contain
monitoring, recordkeeping, and reporting (MRR) requirements, including
MRR for performance testing to determine control efficiency of emission
control equipment, and requirements to keep records of the amounts of
raw material processed on a daily basis, total monthly VOC emissions,
and a manufacturer's guarantee of control equipment's emission control
efficiencies. Records must be maintained for five years and made
available to the Division upon request. Records of performance test
protocols for performance tests under Section V.A.6.b. must be
submitted to the Division for review at least thirty days before
testing.
    A detailed evaluation of section V is in the TSD for this action.
We propose to find that the provisions in section V are consistent with
CAA and RACT requirements, and that they strengthen the SIP. We
therefore propose to approve the revisions in part E, section V.
c. Analysis of Reg. 7 Changes in May 18, 2021 Submittal
    The majority of the changes to Reg. 7 from the May 18, 2021
submittal are state-only and therefore have not been submitted for
inclusion in the SIP. The SIP revisions from this submittal include
editorial revisions to the outline of the regulation and numbering
changes to part E, section I.D.4., SIP controls for existing natural
gas fired RICE. The revisions are clerical in nature and do not affect
the substance of the requirements. Therefore, we propose to approve the
changes.
d. Analysis of Reg. 7 Changes in May 20, 2022 Miscellaneous Metals and
Process Heaters Submittal
    The EPA proposes to approve the changes made to Reg. 7 with
Colorado's May 20, 2022 miscellaneous metals and process heaters
submittal.
(i) Part C, Section I
    Section I of part C contains rules for surface coating operations.
The Commission has previously adopted requirements for metal surface
coatings based on recommendations in EPA's Control of Volatile Organic
Emissions from Existing Stationary Sources--Volume VI: Surface Coating
of Miscellaneous Metal Parts and Products (1978), including VOC content
limits, work practices, and recordkeeping requirements. In 2008,
however, the EPA published a subsequent metal coating CTG, Control
Techniques Guidelines for Miscellaneous Metal and Plastic Parts
Coatings (Metal Coating CTG), which recommends expanding the coatings
VOC content limits from four to fifty, including work practices,
application methods, and recordkeeping. Therefore, in response to EPA's
concern with Colorado's existing metal parts coating requirements as
based on EPA's 1978 CTG, the Commission revised the metal surface
coating requirements in part C, section I to correspond to the
recommendations in the 2008 Metal Coating CTG.
    The revised section I.L., Manufactured Metal Parts and Metal
Products, applies to sources where actual emissions are greater than or
equal to 6.8 kilograms (15 lbs) per day and 1.4 kilograms (3 lbs) per
hour. Starting January 1, 2022, section I.L requirements applied to
metal parts and product surface coating units at facilities where total
actual VOC emissions from all metal parts and products surface coating
operations are greater than or equal to 2.7 tons per 12-month rolling
period, before consideration of controls.
    Revised section I.L.1.b. removes a number of exemptions for surface
coatings of various metal parts and products: automobiles and light-
duty trucks, metal cans, flat metal sheets and strips in the form of
rolls or coils, large appliances, magnet wire for use in electrical
machinery, and metal furniture. Section I.L.b.(iii) adds categories for
which section I.L. does not apply, including certain sources regulated
by NSPS and sources that must comply with other sections of the SIP.
Section I.L.2.b. includes new requirements for surface coating of
manufactured metal parts or metal products facilities and operations.
Section I.L.2.b.(i) requires that VOC emissions from coatings and
thinners be reduced with an emission control system having a control
efficiency of 90% or greater. Additionally, products must comply with
the VOC content limits established in Tables 1 and 2 of section
I.L.2.b. A number of new definitions were added to section I.L.1.c.
    Sections I.L.3. and I.L.4. include application methods and work
practice standards that owners and operators must use and follow. These
include the use of high-volume low-pressure spray, roller coat, and
airless spray; storing all VOC containing coatings, thinners, coating
related waste materials, cleaning materials, and used shop towels in
closed containers; and minimizing VOC emissions from cleaning of
application, storage, mixing, and conveying equipment by cleaning
equipment without atomizing the cleaning solvent and capturing spent
solvent in closed containers section I.L.5. contains recordkeeping
requirements to demonstrate compliance with section I.L. Records must
be maintained for a minimum of five years and made available to the
Division upon request.
    A detailed review of section I.L. is in the TSD for this action. We
propose to find that the provisions in section I.L. are consistent with
CAA requirements, represent RACT for the emission limits in Table 2
``Metal Parts and Products VOC Content Limits'' and Table 7 ``Metal
Parts and Products VOC Emission Rate Limits'' of the 2008 Miscellaneous
Metal Parts and Products CTG, and that they strengthen the SIP. We
therefore propose to approve the revisions in part C, section I.\110\
---------------------------------------------------------------------------

    \110\ In this action, we are not finalizing the State's
determination that RACT for the miscellaneous metal parts CTG has
been met, because Colorado has not adopted limits or negative
declarations for sources listed in Table 5, Pleasure Craft Surface
Coating VOC Content Limits or Table 6, Motor Vehicle Materials VOC
Content Limits of the CTG for Miscellaneous Metal and Plastic Parts
Coatings, EPA-453/R-08-003 (Sept. 2008). The State is actively
working on adopting RACT for these sources. Therefore, we will be
acting on these categories in a separate rulemaking.
---------------------------------------------------------------------------

(ii) Part E, Section II
    Section II of part E contains rules for the control of emissions
from stationary and portable combustion equipment in the 8-hour ozone
control area. The Commission revised this section of Reg. 7 to include
provisions in the SIP that require the implementation of RACT for
process heaters at major sources of NOX emissions.
NOX emission limits apply to natural gas-fired and refinery
gas-fired process heaters with a heat input rate greater than or equal
to 5 MMBtu/hr.
    Table 2 in section II.A.4.g. contains NOX emission
limits of 0.05 lb/MMBtu for natural gas fired and 0.1 lb/MMBtu for
refinery fuel gas fired process heaters with a heat input rate greater
than 5 MMBtu/hr. Section II.A.5.a. adds compliance dates for process
heaters subject to the section II.A.4.g. requirements. Continuous
emission monitoring in section II.A.5.b.(i), performance testing
requirements in section II.A.5.b.(ii) were expanded to include section
II.A.4.g. process heaters. Section II.A.6.b.(viii)(E) was added to
include combustion process adjustment requirements for process heaters.
    A detailed evaluation of section II is in the TSD for this action.
We propose to find that the provisions in section II

are consistent with CAA and RACT requirements, and that they strengthen
the SIP. We therefore propose to approve the revisions in part E,
section II.
e. Analysis of Reg. 7 Changes in May 20, 2022 Part D Definitions
Submittal
    The majority of the changes to Reg. 7 from the State's May 20, 2022
part D definitions submittal are state-only and therefore have not been
submitted for inclusion in the SIP. The SIP revisions from this
submittal include revisions to definitions included in Reg. 7, part D,
section III for natural gas-actuated pneumatic controllers associated
with oil and gas operations. The revisions to definitions associated
with pneumatic controllers reflect more accurate and appropriate
technical definitions and do not affect the substance of the
requirements. Therefore, we propose to approve the changes.
f. Analysis of Reg. 7 Changes in May 14, 2018, May 13, 2020, and May
20, 2022 Part D Oil and Gas Submittals
    In November 2021, the EPA approved the majority of revisions to
Colorado's regulations for oil and gas operations from State
submissions in 2018 and 2020 \111\ but deferred action on several
portions of the submittals because we determined that Colorado's SIP
revisions did not meet oil and gas CTG RACT requirements for testing
and monitoring requirements for combustion control devices for storage
vessels and centrifugal compressors. On October 20, 2021, Colorado
submitted a letter committing to adopt and submit specific revisions by
June 30, 2022. Specifically, the State committed to add requirements
for performance testing of certain combustion devices consistent with
the EPA's oil and gas CTG by using the same frequency, testing
protocol, and recordkeeping requirements that apply to storage vessels
and wet seal centrifugal compressors required to be controlled under
the EPA's oil and gas CTG (i.e., storage vessels that have the
potential for VOC emissions equal to or greater than 6 tpy). The EPA
issued a conditional approval of Reg. 7 revisions and the State's RACT
determination for the oil and gas CTG on May 13, 2022 \112\ based on
the commitment letter submitted by the APCD. An evaluation of Reg. 7
revisions from the State's May 14, 2018 and May 13, 2020 submittals and
October 20, 2021 commitment letter is in our February 17, 2022 proposed
rule.\113\
---------------------------------------------------------------------------

    \111\ 86 FR 61071.
    \112\ 87 FR 29228.
    \113\ Proposed rule, Air Plan Conditional Approval; Colorado;
Revisions to Regulation Number 7 and Oil and Natural Gas RACT
Requirements for 2008 8-Hour Ozone Standard for the Denver Metro/
North Front Range Nonattainment Area, 87 FR 8997.
---------------------------------------------------------------------------

    The revisions from the May 20, 2022 part D, Oil and Gas submittal
are consistent with the commitments in the letter \114\ and include
provisions for performance testing or demonstration of manufacturer
testing for combustion equipment used to control emissions from storage
vessels in section I.E.3. and wet seal centrifugal compressors in
section I.J.1.h. A detailed evaluation of section I is in our February
17, 2022 proposed rule and the associated TSD for that action.\115\ We
propose to find that the revisions in section I from the State's May
20, 2022 part D, Oil and Gas submittal are consistent with CAA and RACT
requirements, and that they strengthen the SIP. We also propose to find
that the State has adopted and submitted the specific revisions it has
committed to by June 30, 2022 and that the conditional approval will
now convert to full approval.
---------------------------------------------------------------------------

    \114\ See https://www.coloradosos.gov/CCR/eDocketDetails.do?trackingNum=2021-00594.
    \115\ See Technical Support Document for Proposed Action on the
Reasonably Available Control Technology Determination for Oil and
Gas CTG Sources Within Colorado's Denver Metro/North Front Range
Area 2008 Ozone State Implementation Plan, Air and Radiation
Program, U.S. EPA Region 8, January 2022, available within the
docket for this action.
---------------------------------------------------------------------------

VI. Proposed Action

    We propose to approve the majority of the OAP submittal from the
State of Colorado for the DMNFR Area submitted on March 22, 2021. (In
this rule we are not proposing any action on the submitted attainment
demonstration, enhanced monitoring, or contingency measures.)
Specifically, we propose to approve:
     Milestone and future year emissions inventories;
     RFP demonstration;
     Demonstration of RACT for oil and natural gas industry VOC
CTG sources;
     Demonstration of RACT for certain miscellaneous metal
parts coatings VOC CTG sources;
     Demonstration of RACT for certain VOC and NOX
non-CTG sources;
     Demonstration of RACM implementation;
     Motor vehicle I/M program;
     NNSR program; and
     MVEBs.
    We also propose to approve SIP revisions to Reg. 21 submitted by
the State on May 13, 2020 and to Reg. 7 submitted by the State on March
22, 2021, May 18, 2021, and May 20, 2022 as shown in Table 7. We are
proposing to approve Colorado's determination that the above rules
constitute RACT for the specific categories addressed in Tables 3 and
4. A comprehensive summary of the revisions in Colorado's Regs. 7 and
21 organized by the EPA's proposed rule action and submittal dates are
provided in the Table 7.

   Table 7--List of Colorado Revisions to Regs. 7 and 21 That the EPA
                           Proposes To Approve
------------------------------------------------------------------------
 Revised sections in May 14, 2018, May 13, 2020, March 22, 2021, and May
                20, 2022 submittals proposed for approval
-------------------------------------------------------------------------
May 14, 2018:
    Reg. 7, part D, section XII.J.1.
May 13, 2020, Oil and Gas Submittal:
    Reg. 7, part D, sections I.D.-D.3.a.(i), I.D.3.b.-b.(i),
     I.D.3.b.(ii), I.D.3.b.(v), I.D.3.b.(vii), I.D.3.b.(ix), I.D.4.-
     I.E.1.a., I.E.2.-.c.(ii), I.E.2.c.(iv)-c.(viii), I.F.-1.d.,
     I.F.1.g.-g.(xii), I.F.1.h.-F.2.a., I.F.2.c.-c.(vi), I.F.3.-3.a,
     I.F.3.c.-c.(i)(C), and I.J.1.-j. (renumbering).
May 13, 2020, Reg. 21 Submittal: