[Federal Register Volume 86, Number 202 (Friday, October 22, 2021)]
[Rules and Regulations]
[Pages 58581-58592]
[FR Doc No: 2021-22661]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2020-0425; FRL-8723-02-R9]

Approval of Air Quality Implementation Plans; California;
Sacramento Metro Area; 2008 8-Hour Ozone Nonattainment Area
Requirements

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA) is taking final
action to approve portions of two state implementation plan (SIP)
revisions submitted by the State of California to meet Clean Air Act
(CAA or ``Act'') requirements for the 2008 8-hour ozone national
ambient air quality standards (NAAQS or ``standards'') in the
Sacramento Metro ozone nonattainment area (``Sacramento Metro Area'').
These SIP revisions address the CAA nonattainment area requirements for
the 2008 ozone NAAQS, such as the requirements for an emissions
inventory, an attainment demonstration,

reasonable further progress, reasonably available control measures, and
contingency measures, and it establishes motor vehicle emissions
budgets. The EPA is taking final action to approve these revisions as
meeting all the applicable ozone nonattainment area requirements,
except for the State's contingency measures revision. The EPA is
deferring action on this revision related to contingency measures.

DATES: This rule will be effective on November 22, 2021.

ADDRESSES: The EPA has established a docket for this action under
Docket ID No. EPA-R09-OAR-2020-0425. All documents in the docket are
listed on the https://www.regulations.gov website. Although listed in
the index, some information is not publicly available, e.g.,
Confidential Business Information (CBI) or other information whose
disclosure is restricted by statute. Certain other material, such as
copyrighted material, is not placed on the internet and will be
publicly available only in hard copy form. Publicly available docket
materials are available through https://www.regulations.gov, or please
contact the person identified in the FOR FURTHER INFORMATION CONTACT
section for additional availability information. If you need assistance
in a language other than English or if you are a person with
disabilities who needs a reasonable accommodation at no cost to you,
please contact the person identified in the FOR FURTHER INFORMATION
CONTACT section.

FOR FURTHER INFORMATION CONTACT: Jerry Wamsley, Air Planning Office
(AIR-2), EPA Region IX, 75 Hawthorne Street, San Francisco, CA 94105,
(415) 947-4111 or [email protected].

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Summary of the Proposed Action
II. Public Comments and EPA Responses
    A. Review of Ozone Chemistry and NOX Substitution
Effects
    B. Response to Comments
III. Final Action
IV. Statutory and Executive Order Reviews

I. Summary of the Proposed Action

    On October 29, 2020, the EPA proposed to approve, under CAA section
110(k)(3), and to conditionally approve, under CAA section 110(k)(4),
portions of submittals from the State of California as revisions to the
California SIP for the Sacramento Metro ozone nonattainment area.\1\
The principal submittals are as follows: ``Sacramento Regional 2008
NAAQS 8-Hour Ozone Attainment Plan and Reasonable Further Progress
Plan,'' (``2017 Sacramento Regional Ozone Plan''); and the Sacramento
Metro portion of the California Air Resource Board's (CARB) ``2018
Updates to the California State Implementation Plan'' (``2018 SIP
Update'').\2\ In this notice, we refer to these submittals collectively
as the ``Sacramento Metro Area Ozone SIP'' or the ``Plan,'' and we
refer to our October 29, 2020 proposed action as the ``proposed rule.''
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    \1\ 85 FR 68509 (October 29, 2020).
    \2\ The State submitted the 2017 Sacramento Regional Ozone Plan
and the 2018 SIP Update on December 18, 2017, and December 5, 2018,
respectively. Our proposed rule provides our detailed review of CAA
procedural requirements related to these submissions.
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    The Sacramento Metro Area consists of Sacramento and Yolo counties
and portions of El Dorado, Placer, Solano, and Sutter counties.\3\
Several local air agencies have their jurisdictions within this area.
Sacramento County is under the jurisdiction of the Sacramento
Metropolitan Air Quality Management District (SMAQMD). Yolo County and
the eastern portion of Solano County are under the jurisdiction of the
Yolo-Solano AQMD (YSAQMD). The southern portion of Sutter County is
under the jurisdiction of the Feather River AQMD (FRAQMD). The western
portion of Placer County is under the jurisdiction of the Placer County
Air Pollution Control District (PCAPCD). Last, the western portion of
El Dorado County is under the jurisdiction of the El Dorado County AQMD
(EDCAQMD). In this action, we refer to these five districts
collectively as the ``Districts.'' Under California law, each air
district is responsible for adopting and implementing stationary source
rules, while CARB adopts and implements consumer products and mobile
source rules. The Districts' and State's rules are submitted to the EPA
by CARB.
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    \3\ For a precise description of the geographic boundaries of
the Sacramento Metro Area for the 2008 ozone standards, refer to 40
CFR 81.305. Specifically included portions are the eastern portion
of Solano County, the western portions of Placer and El Dorado
counties outside of the Lake Tahoe Basin, and the southern portion
of Sutter County.
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    In our proposed rule, we provided background information on the
ozone standards,\4\ area designations, related SIP revision
requirements under the CAA, and the EPA's implementing regulations for
the 2008 ozone standards, referred to as the 2008 Ozone SIP
Requirements Rule (``2008 Ozone SRR''). To summarize, the Sacramento
Metro Area is classified as Severe nonattainment for the 2008 ozone
standards; consequently, the Sacramento Metro Area Ozone SIP was
developed to address the CAA requirements for this Severe nonattainment
area in meeting the 2008 ozone NAAQS.
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    \4\ Ground-level ozone pollution is formed from the reaction of
volatile organic compounds (VOC) and oxides of nitrogen
(NOX) in the presence of sunlight. The 1-hour ozone NAAQS
is 0.12 parts per million (ppm) (one-hour average), the 1997 ozone
NAAQS is 0.08 ppm (eight-hour average), and the 2008 ozone NAAQS is
0.075 ppm (eight-hour average). CARB refers to reactive organic
gases (ROG) in some of its ozone-related submittals. The CAA and the
EPA's regulations refer to VOC, rather than ROG, but both terms
cover essentially the same set of gases. In this final rule, we use
the term VOC to refer to this set of gases.
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    In our proposed rule, we also discussed a decision issued by the
D.C. Circuit Court of Appeals in South Coast Air Quality Management
Dist. v. EPA (``South Coast II'') \5\ that vacated certain portions of
the EPA's 2008 Ozone SRR. The only aspect of the South Coast II
decision that affects this action is the vacatur of the provision in
the 2008 Ozone SRR that allowed states to use an alternative baseline
year for demonstrating reasonable further progress (RFP). To address
this decision, CARB, in the 2018 SIP Update, submitted an updated RFP
demonstration that relied on a 2011 baseline year, as required, along
with updated motor vehicle emissions budgets (MVEBs or ``budgets'')
associated with the new RFP milestone years.\6\
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    \5\ South Coast Air Quality Management Dist. v. EPA, 882 F.3d
1138 (D.C. Cir. 2018). The term ``South Coast II'' is used in
reference to the 2018 court decision to distinguish it from a
decision published in 2006 also referred to as ``South Coast.'' The
earlier decision involved a challenge to the EPA's Phase 1
implementation rule for the 1997 ozone NAAQS. South Coast Air
Quality Management Dist. v. EPA, 472 F.3d 882 (D.C. Cir. 2006).
    \6\ In a letter dated December 18, 2019, from Richard W. Corey,
Executive Officer, CARB, to Michael Stoker, Regional Administrator,
EPA Region 9, CARB requested withdrawal of the RFP demonstration
included in the 2017 Sacramento Regional Ozone Plan submitted
previously. The RFP demonstration in the 2018 SIP Update replaced
the demonstration in the 2017 Plan.
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    Within our proposed rule, we reviewed the various SIP elements
contained in the Sacramento Metro Area Ozone SIP, evaluated them for
compliance with CAA statutory and regulatory requirements, and
concluded that they met all applicable requirements, with the exception
of the contingency measures element, for which the EPA proposed
conditional approval. Below, we provide a summary review of our
proposed rule, by SIP element.
     We found that CARB and the Districts met all applicable
procedural requirements for public notice and hearing prior to the
adoption and submittal of the components of the Sacramento Metro Area
Ozone SIP, i.e.,

the 2017 Sacramento Regional Ozone Plan and the Sacramento Metro
portion of CARB's 2018 SIP Update.\7\
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    \7\ 85 FR 68509, 68511-68512.
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     We proposed to approve the base year emissions inventory
element in the 2017 Sacramento Regional Ozone Plan as meeting the
requirements of CAA sections 172(c)(3) and 182(a)(1) and 40 CFR 51.1115
for the 2008 ozone NAAQS. Based on our review, we proposed to find that
the future year baseline projections in the 2017 Sacramento Regional
Ozone Plan are properly supported by SIP-approved stationary and mobile
source measures.\8\
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    \8\ Id. at 68513-68515.
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     We proposed to approve the reasonably available control
measures (RACM) demonstration element in the 2017 Sacramento Regional
Ozone Plan as meeting the requirements of CAA section 172(c)(1) and 40
CFR 51.1112(c) for the 2008 ozone NAAQS. Based on our review of the
State and Districts' RACM analyses and the Districts' and CARB's
adopted rules, we proposed to find that there are, at this time, no
additional RACM that would further advance attainment of the 2008 ozone
NAAQS in the Sacramento Metro Area.\9\
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    \9\ Id. at 68516-68518.
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     We proposed to approve the attainment demonstration
element for the 2008 ozone NAAQS in the 2017 Sacramento Regional Ozone
Plan as meeting the requirements of CAA section 182(c)(2)(A) and 40 CFR
51.1108. In our review provided in the proposed rule, we observed that
the Plan followed the modeling procedures recommended in the EPA's
Modeling Guidance and showed excellent performance in simulating
observed ozone concentrations in the 2012 base year. Given the
extensive discussion of modeling procedures, tests, and performance
analyses called for in the modeling protocol, the good model
performance, and the model response to emissions changes consistent
with observations, we proposed to find that the modeling is adequate
for purposes of supporting the attainment demonstration.\10\
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    \10\ Id. at 68518-68523.
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     We proposed to approve the rate of progress (ROP)
demonstration element in the 2017 Sacramento Regional Ozone Plan as
meeting the requirements of CAA 182(b)(1) and 40 CFR 51.1110(a)(2) for
the 2008 ozone NAAQS.\11\ As noted in the proposed rule, in 2015, the
EPA approved a 15 percent ROP plan for the Sacramento Metro Area for
the 1-hour ozone NAAQS and 1997 8-hour ozone NAAQS.\12\
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    \11\ Id. at 68523-68525
    \12\ 80 FR 4795 (January 29, 2015).
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     We proposed to approve the RFP demonstration element in
Section V--SIP Elements for the Sacramento Metropolitan Area of the
2018 SIP Update (as clarified) as meeting the requirements of CAA
sections 172(c)(2), 182(b)(1), and 182(c)(2)(B), and 40 CFR
51.1110(a)(2)(ii) for the 2008 ozone NAAQS. We proposed to find that
CARB and the Districts used the most recent planning and activity
assumptions, emissions models, and methodologies in developing the RFP
baseline and milestone year emissions inventories. Also, we proposed to
find that the Districts and CARB used an appropriate calculation method
to demonstrate RFP. Lastly, we proposed to find that the Districts' use
of oxides of nitrogen (NOX) NAAQS substitution is warranted
and appropriately implemented based on the NOX-limited
conditions in the Sacramento Metro Area, and the area's greater
responsiveness to NOX emissions reductions relative to VOC
emissions reductions.\13\
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    \13\ 85 FR 68509, 68523-68525.
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     We proposed to approve the vehicle miles traveled (VMT)
emissions offset demonstration element in the 2017 Sacramento Regional
Ozone Plan as meeting the requirements of CAA section 182(d)(1)(A) and
40 CFR 51.1102 for the 2008 ozone NAAQS. Based on our review of revised
Sacramento Metro Area VMT emissions offset demonstration in the 2017
Sacramento Regional Ozone Plan, we proposed to find that CARB's
analysis is consistent with the August 2012 Guidance and with the
emissions and vehicle activity estimates found elsewhere in the 2017
Sacramento Regional Ozone Plan. Also, we proposed to find that CARB and
the Sacramento Area Council of Governments (SACOG) have adopted
sufficient transportation control strategies (TCSs) and transportation
control measures (TCMs) to offset the growth in emissions from growth
in VMT and vehicle trips in the Sacramento Metro Area for the purposes
of the 2008 ozone NAAQS.\14\
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    \14\ Id. at 68525-68527.
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     We proposed to approve the MVEBs in Section V--SIP
Elements for the Sacramento Metropolitan Area of the 2018 SIP Update
for the RFP milestone year of 2023, and the attainment year of 2024 and
find that these budgets are consistent with the RFP and attainment
demonstrations for the 2008 ozone NAAQS proposed for approval and the
budgets meet the other criteria in 40 CFR 93.118(e).\15\ We reviewed
the budgets in the Sacramento Metro Area Ozone SIP and proposed to find
that they are consistent with the attainment and RFP demonstrations for
which we proposed approval, are based on control measures that have
already been adopted and implemented, and meet all other applicable
statutory and regulatory requirements including the adequacy criteria
in 40 CFR 93.1118(e)(4) and (5).\16\
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    \15\ Table 9 in our proposed rule provides the VOC and
NOX emissions budgets that we proposed for approval.
    \16\ 85 FR 68509, 68529-68531.
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    We also proposed to make the following findings related to other
CAA requirements:
     The emissions statement element of the 2017 Sacramento
Regional Ozone Plan satisfies the requirements under CAA section
182(a)(3)(B) based on our prior approvals of the Districts' emission
statement rules; \17\
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    \17\ Id. at 68515-68516.
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     The enhanced vehicle inspection and maintenance program in
the Sacramento Metro Area meets the requirements of CAA section
182(c)(3) and 40 CFR 51.1102 for the 2008 ozone NAAQS; \18\
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    \18\ Id. at 68531.
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     The California SIP revision to opt out of the Federal
Clean Fuels Fleet Program meets the requirements of CAA sections
182(c)(4)(A) and 246 and 40 CFR 51.1102 for the 2008 ozone NAAQS with
respect to the Sacramento Metro Area; \19\ and,
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    \19\ Id.
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     The enhanced air quality monitoring in the Sacramento
Metro Area meets the requirements of CAA section 182(c)(1) and 40 CFR
51.1102 for the 2008 ozone NAAQS.\20\
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    \20\ Id. at 68531-68532.
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    Finally, under CAA section 110(k)(4), we proposed to approve
conditionally the contingency measures element of the Sacramento Metro
Area Ozone SIP as meeting the requirements of CAA sections 172(c)(9)
and 182(c)(9) for RFP and attainment contingency measures. Our proposed
approval was based on commitments by the Districts and CARB to
supplement the element through submission, as a SIP revision within one
year of our final conditional approval action, of new or revised rules
with more stringent requirements sufficient to produce near to one
year's RFP if an RFP milestone is not met, as well as continuing
emission reductions from State mobile source control measures.\21\
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    \21\ Id. at 68527-68529.
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    Please see our proposed rule and the docket for more information
concerning the background of this final action and

for a detailed discussion of the rationale for approval or conditional
approval of the above-listed elements of the Sacramento Metro Area
Ozone SIP.

II. Public Comments and EPA Responses

    The public comment period on the proposed rule opened on October
29, 2020, the date of its publication in the Federal Register, and
closed on November 30, 2020. During this period, the EPA received one
comment letter submitted by Air Law for All on behalf of the Center for
Biological Diversity and the Center for Environmental Health
(collectively referred to as ``CBD'' herein). Before we provide a
detailed summary of and response to each of these comments in Section
II.B, we provide a brief review of ozone chemistry and terminology as
it relates to our responses to comments concerning the Plan's use of
NOX substitution and the NOX-limited conditions
in the Sacramento Metro Area.

A. Review of Ozone Chemistry and NOX Substitution Effects

    As explained in the proposed rule, ground-level ozone pollution is
formed from the reaction of volatile organic compounds (VOCs) and
NOX in the presence of sunlight. When VOC is abundant
compared to NOX, i.e., when there is a high ratio of VOCs
relative to NOX (``VOC:NOX ratio''),
NOX is a limiting ingredient for ozone formation, and
reducing NOX emissions causes ozone to decrease. An area
with these conditions may be described as ``NOX-limited,''
which is the terminology used in this notice. Elsewhere,
``NOX-limited'' is sometimes used in a stronger, relative
sense to mean that NOX emissions reductions are more
effective than VOC reductions at reducing ozone, and an area may be
described as ``NOX-limited'' or ``VOC-limited'' as a
shorthand for whether NOX or VOC emissions reductions are
more effective at reducing the area's ozone design value.\22\ In
contrast, in a ``NOX-saturated'' area where NOX
is abundant compared to VOC, i.e., when there is a low
VOC:NOX ratio, ozone concentrations typically increase with
NOX emission reductions, that is, there is a
``NOX disbenefit.'' \23\ Between the NOX-limited
and NOX-saturated ozone chemistry regimes, there is an
intermediate ``transitional'' regime where ozone responds weakly to
NOX emissions reductions. Which one of these three chemical
regimes exists for an area can depend on the season, time of day, and
the area's location relative to a source of NOX emissions.
As one moves farther downwind from an urban center, ozone formation
tends to become more NOX-limited, as the VOC:NOX
ratio increases. While there are continued VOC emissions in rural
areas, there are fewer new NOX emissions from combustion
sources, and some NOX deposits out of the atmosphere (in the
form of HNO3); as a result, peak ozone hours and downwind
locations are more NOX-limited than non-peak hours and
upwind or central locations.\24\ When an area reduces NOX
emissions more than VOC emissions, the VOC:NOX ratio
increases and the area can transition from NOX-saturated to
NOX-limited conditions. In general, areas in the United
States have become more NOX-limited over time, though
NOX-saturated areas and seasons remain.\25\
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    \22\ For example, the Plan generally uses the term
``NOX-limited'' to mean that NOX emission
reductions in the Sacramento Metro Area are more effective than VOC
at decreasing ozone; e.g., 2017 Sacramento Regional Ozone Plan,
Appendix B-4, page B-146, Figure 13 (labeling as ``NOX-
limited'' the region of a typical ozone isopleth plot where
NOX reductions are more effective than VOC reductions).
    \23\ A NOX disbenefit can occur under NOX-
saturated conditions because enough NOX is present to
interfere with ozone formation via VOC. VOC radicals require the
hydroxyl radical (OH) to form, but OH is made unavailable when
NOX combines with it to form nitric acid
(HNO3), which then deposits out of the atmosphere. A
reduction in NOX emissions reduces this OH sink reaction,
increasing the OH available to form VOC radicals and ozone.
    \24\ Barbara J. Finlayson-Pitts and James N. Pitts Jr.,
``Tropospheric Air Pollution: Ozone, Airborne Toxics, Polycyclic
Aromatic Hydrocarbons, and Particles,'' Science, Vol. 276, May 16,
1997; EPA, U. S., Health Risk and Exposure Assessment for Ozone
Final Report. Office of Air Quality Planning and Standards: RTP, NC,
2014; EPA-452/R-14-004a, https://www.epa.gov/naaqs/ozone-o3-standards-risk-and-exposure-assessments-review-completed-2015.
    \25\ Wolff, G.T., Kahlbaum, D.F., & Heuss, J.M., 2013. ``The
vanishing ozone weekday/weekend effect,'' Journal of the Air & Waste
Management Association), 63(3), 292-299, https://doi.org/10.1080/10962247.2012.749312 Jin et al., 2017, ``Evaluating a space-based
indicator of surface ozone NOX VOC sensitivity over
midlatitude source regions and application to decadal trends,''
Journal of Geophysical Research: Atmospheres, 122,10,439 10,461.
https://doi.org/10.1002/2017JD026720; Sicard et al, 2020, ``Ozone
weekend effect in cities: Deep insights for urban air pollution
control,'' Environmental Research, 191, 110193. https://doi.org/10.1016/j.envres.2020.110193.
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    NOX is emitted primarily in the form of nitric oxide
(NO), which becomes nitrogen dioxide (NO2) as it converts or
``titrates'' ozone (O3) to regular oxygen (O2).
Therefore, the initial effect of a NOX emissions increase
can be to decrease ozone immediately downwind of a NOX
source, such as downtown metropolitan areas or a large fossil fuel
burning power plant.\26\ Farther downwind from the NOX
source, however, the NOX can increase ozone, via reactions
with VOC. Conversely, the initial effect of a NOX emissions
reduction, which is mainly a NO reduction, can be to increase ozone
immediately downwind from the NOX source because there is
less remaining NO to titrate ozone to oxygen. Because of this
phenomenon, it may be impossible for an area to be ``NOX-
limited'' at all locations, at least with respect to a given change in
NOX emissions occurring just upwind of a given location or
monitor. Titration can occur under any ozone chemistry regime whether
NOX-saturation, NOX-transitional, or
NOX-limited.
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    \26\ EPA, Health Risk and Exposure Assessment for Ozone Final
Report, 2-5.
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    To summarize, under certain conditions, NOX emissions
can reduce existing ozone concentrations in nearby downwind areas
through titration and can interfere with the formation of ozone in
NOX-saturated areas. Reducing NOX emissions can
lessen these effects and lead to ozone increases. Reducing
NOX by a larger amount can, however, change the ozone
chemistry from NOX-saturated to NOX-limited,
meaning that NOX emission reductions can again result in
reduced ozone. The overall effect of NOX emissions on an
area's ozone chemistry depends on the location's existing mix of ozone
and VOCs, as well as the location relative to the source of
NOX emissions.

B. Response to Comments

    Comment #1: CBD notes that CAA section 182(c)(2)(C) allows a state
to substitute NOX emissions reductions for the VOC
reductions otherwise required by CAA section 182(c)(2)(B)
(``NOX substitution'') if it demonstrates that the combined
VOC and NOX reductions ``would result in a reduction in
ozone concentrations at least equivalent'' to the reduction in ozone
concentrations achieved through VOC emissions reductions alone. CBD
argues that CAA section 182(c)(2)(C)'s use of the plural ``ozone
concentrations'' means that an equivalency demonstration at a single
monitoring site would be insufficient, and therefore asserts that
Congress intended the equivalence requirement to apply throughout the
nonattainment area. CBD interprets statements in the proposal that the
Sacramento Metro Area is NOX-limited to indicate that the
EPA agrees that equivalence must be demonstrated throughout the
nonattainment area and says that the EPA must confirm this
understanding in a final rule.

    Response to Comment #1: The EPA disagrees that CAA section
182(c)(2)(C)'s use of the term ``ozone concentrations'' warrants the
commenter's narrow interpretation that equivalence must be specifically
demonstrated throughout a nonattainment area. As an initial matter, we
note that the Act commonly uses the term ``concentrations'' to refer
generally to ambient pollution levels at one or more (but not
necessarily multiple) monitors or locations.\27\ Moreover, CAA section
182(c)(2)(C) grants the EPA discretion to define the conditions under
which NOX reductions may be substituted for or combined with
VOC reductions ``in order to maximize the reduction in ozone air
pollution'' and does not further specify the conditions that represent
an ``equivalent'' reduction in ozone; for instance, it does not require
a specific concentration test at every monitor or at specific locations
within an area. No such requirement appears in the Act's other
provisions governing the RFP demonstration, which define specific
percentage reductions aimed at ensuring timely attainment of the
NAAQS,\28\ or in the EPA's 1993 NOX Substitution Guidance,
which describes a recommended procedure for states to utilize
NOX substitution.\29\ We interpret CAA 182(c)(2)(C) and
these supporting authorities as properly reflecting Congress' intent to
allow NOX reductions to be considered within an RFP
demonstration so long as these reductions are at least as effective in
reducing ozone consistent with the area's demonstration of timely
attainment.\30\
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    \27\ E.g., CAA section 107(e)(2); CAA section 110(a)(5)(D).
    \28\ E.g., CAA 182(b)(1) and (c)(2)(B); see also CAA 171(1)
(defining RFP as ``such annual incremental reductions in emissions
of the relevant air pollutant as are required by this part or may
reasonably be required by the Administrator for the purpose of
ensuring attainment of the applicable national ambient air quality
standard by the applicable date'').
    \29\ NOX Substitution Guidance, Office of Air Quality
Planning and Standards, U.S. Environmental Protection Agency,
December 1993, available at https://archive.epa.gov/ttn/ozone/web/html/index-13.html.
    \30\ See id. at 8, (quoting H. Rept. No. 490, 101st Cong., 2d
Sess. 239 (1990)), (``NOX reductions may not be
substituted for VOC reductions in a manner that delays attainment of
the ozone standard or that results in lesser annual reductions in
ozone concentration than provided for in the attainment
demonstration.'').
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    Also, we disagree with the commenter's assertion that statements
from the proposed rule describing the Sacramento Metro Area as
NOX-limited convey the EPA's position that NOX
substitution requires a specific demonstration of equivalence
throughout all portions or monitors within a nonattainment area. As
described in our proposed rule and discussed further in our responses
below, NOX-limited conditions likely persist throughout the
Sacramento Metro Area, suggesting that NOX reductions will
generally be effective in reducing ozone concentrations; with these
statements, we intended no other suggestion regarding the demonstration
necessary to support NOX substitution. The EPA evaluates the
appropriateness of NOX substitution on a case-by-case
basis,\31\ considering the balance of available evidence to support the
efficacy of NOX reductions in reducing ambient ozone
concentrations as necessary for timely attainment, and consistent with
the requirements of CAA section 182(c)(2)(C).
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    \31\ NOX Substitution Guidance at 3 (``The EPA will
approve substitution proposals on a case-by-case basis. Generally
speaking, any reasonable substitution proposal will be approved.'');
also, id. at 1 (explaining that the Guidance's purpose is ``to
provide a procedure that can be applied to meet the post-1996
Section 182(c)(2)(B) RFP requirement as well as the Section
182(c)(2)(C) equivalency demonstration requirements'' (emphasis in
original).
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    In some areas, NOX emissions reductions may be needed
for attainment, even though it may not be possible to decrease ozone
concentrations simultaneously at all locations in the short term. For
example, in some NOX-limited areas, reducing NOX
emissions may represent the most effective or only approach to timely
attainment, but may nonetheless generate temporary ozone increases in
some locations due to NOX titration or local NOX-
saturated conditions. In these areas, we believe it is reasonable to
implement NOX reductions in lieu of some portion of the VOC
emissions reductions otherwise required for RFP as part of an area's
strategy for timely NAAQS attainment and notwithstanding limited short-
term increases, as an alternative to pursuing relatively ineffective
VOC controls. We discuss conditions for the Sacramento Metro Area in
detail below, including the relative importance and efficacy of
NOX reductions for attainment.
    Comment #2: CBD comments that the Plan's evidence is equivocal and
insufficient to show that NOX substitution will result in
equivalent reductions in ozone concentrations throughout the
nonattainment area. According to the commenter, the Plan's analysis of
the ``weekend effect'' in the years 2000-2014 shows a shift to more
NOX-saturated conditions in the Western and Central
subregions of the Sacramento Metro Area and more transitional
conditions in the Eastern region, and this is not inconsistent with the
independent study of conditions in the years 2001-2007 cited by the
EPA. CBD says that this evidence is insufficient for the EPA to
rationally conclude that the entire nonattainment area is currently
NOX-limited, and that, at most, it can only be concluded
that the Eastern region is still NOX-limited. Furthermore,
CBD says that the EPA must consider changes in NOX emissions
occuring by 2024, such as the replacement of natural gas power plants
by less NOX-emitting sources, to determine whether the
entire Sacramento Metro Area will be NOX-limited through
2024.
    The commenter characterizes the Plan's evidence as qualitative,
rather than quantitative. The commenter states that a qualitative
analysis does not address the possibility that NOX
reductions could change the characteristics of the area and argues that
the definition of the word ``equivalent'' as used in CAA section
182(c)(2)(C) requires a quantitative analysis, such as photochemical
grid modeling. The commenter notes that the Plan uses photochemical
grid modeling to analyze ozone sensitivity to NOX reductions
in the context of the attainment demonstration. CBD then states that
this modeling analysis is insufficient to support the Plan's conclusion
that the entire area is NOX-limited or to show equivalence
throughout the nonattainment area because the Plan includes one
isopleth diagram only for the Folsom monitoring site in the Eastern
subregion.\32\
---------------------------------------------------------------------------

    \32\ An ``isopleth'' is a line connecting points having the same
value of a quantity, such as ozone concentration. Ozone isopleth
diagrams typically have a series of such lines to show the ozone
concentration for any combination of NOX and VOC
emissions, just as contour lines on a map show the elevation for any
combination of latitude and longitude.
---------------------------------------------------------------------------

    According to the commenter, approving NOX substitution
based on a demonstration of equivalence at only one monitor or
subregion is arbitrary for two reasons, even if it does not cause other
monitors to exceed the 2008 ozone NAAQS. First, it may cause, or
interfere with resolving, violations of the more protective 2015 ozone
NAAQS in NOX-saturated areas (which the commenter says would
violate CAA section 110(l)). Second, increased ozone levels, even below
the NAAQS, may still result in injury to public health and welfare.
    Response to Comment #2: The EPA disagrees that the Plan's evidence
is insufficient to support the use of NOX substitution under
CAA section 182(c)(2)(C). As discussed in our response to Comment 1,
use of NOX

substitution within an RFP demonstration does not require establishing
equivalent reductions in ozone concentrations throughout the
nonattainment area. As discussed in detail below, the Plan shows that,
overall, the area has transitioned from NOX-saturated to
NOX-limited as NOX emissions have declined, and
that NOX reductions are more effective than VOC reductions
on a percentage basis. Consistent with these conditions, the Sacramento
Metro Area has relied on, and continues to rely on, NOX
reductions to demonstrate attainment. While decreases in ozone
concentrations may have been delayed initially at some locations
because of the location-specific and complex behavior of NOX
in ozone formation, Sacramento Metro Area ozone design values have
shown a general downward trend at all monitors from 1990 to the
present, demonstrating that these locations have not experienced the
increased ozone design values of concern to the commenter, and that the
Plan demonstrates timely attainment of the NAAQS at all locations. For
these reasons and as addressed below, we find that the Plan provides
adequate evidence and justification for its use of NOX
substitution.
    As we discussed in the proposed rule and our accompanying technical
support document, the State concludes that NOX reductions
are more effective than VOC reductions throughout the Sacramento Metro
Area.\33\ The State supports this conclusion with modeling and
monitoring of weekday-weekend differences in ozone formation and
citations to published research papers that study these differences and
the response to NOX reductions in detail, as described
below. The State estimates weekday-weekend differences in ozone
concentrations using the Community Multiscale Air Quality (CMAQ)
photochemical model as part of the air quality model's performance
evaluation for the 2012 base year, in conjunction with the attainment
demonstration. As described in the Plan, in the early 2000's the
western region of the Sacramento Metro Area exhibited a ``weekend
effect,'' in which weekend ozone concentrations were higher despite
having lower NOX emissions, suggesting a NOX
disbenefit at that time.\34\ The modeling results in the Plan show that
the average daily maximum ozone concentrations at all monitoring sites
are higher on weekdays, indicating that maximum ozone concentrations
are lower when NOX emissions are lower, and that peak ozone
formation is NOX-limited, at all monitoring sites. This is
illustrated in Figure 14 from Appendix B-4 of the 2017 Sacramento
Regional Ozone Plan, which shows average modeled 2012 weekday-weekend
ozone concentrations above a 1:1 line, i.e., higher weekday
concentrations, for all monitoring sites in each subregion in the
nonattainment area (Western, Central, and Eastern).
---------------------------------------------------------------------------

    \33\ 85 FR 68509, 68520 (October 29, 2020); ``Modeling TSD--2017
Sacramento Regional Ozone Plan,'' September 14, 2020, Air and
Radiation Division, EPA Region IX, 25-26.
    \34\ 2017 Sacramento Regional Ozone Plan, Appendix B-4, B-148;
CARB Staff Report B-33.
---------------------------------------------------------------------------

    In addition, the modeled differences in ozone concentrations are
generally consistent with the monitored ambient concentrations.\35\
Monitored ozone concentrations included in the Plan for each year from
2000 to 2014 generally progressed from a NOX disbenefit,
i.e., higher weekend concentrations, to a NOX-limited or
transitional regime, i.e., weekend concentrations lower than or about
the same as weekday concentrations.\36\ The Eastern subregion has shown
higher concentration on weekdays than on weekends for the entire
period, i.e., no ``weekend effect''; this is evidence that ozone
formation is NOX-limited there. By 2014, the Western and
Central subregions of the Sacramento Metro Area show nearly identical
weekday and weekend concentrations, suggesting these areas had shifted
to a transitional regime by that time.\37\ For the Western subregion,
the Plan notes that the shift toward transitional conditions occurred
at ozone levels under 50 parts per billion (ppb), well below the 2008
ozone NAAQS of 75 ppb, meaning that these changes are not leading to
NAAQS exceedances. Indeed, monitoring sites in the Western subregion
have met the 75 ppb NAAQS from 2011 to the present day. Within the
Central subregion, ambient ozone data recorded for 2011-2014 show ozone
levels under 70 ppb.\38\
---------------------------------------------------------------------------

    \35\ 2017 Sacramento Regional Ozone Plan, Appendix B-4, B-149,
Figure 14. For sites appearing just above the 1:1 line, modeled
weekday ozone is higher by only a small amount.
    \36\ Id.
    \37\ Id. The commenter has interpreted the presence of points
below the 1:1 line as evidence of NOX-saturated ozone
formation, but that interpretation would be supported only by points
much farther below the line.
    \38\ 2017 Sacramento Regional Ozone Plan, Appendix B-4, B-148.
---------------------------------------------------------------------------

    The Plan suggests that the shift to a transitional regime could be
explained by natural year-to-year variability in biogenic VOC emissions
and in local meteorology.\39\ This is consistent with the relatively
low level of biogenic VOC emissions during 2011-2014,\40\ which would
decrease the VOC:NOX ratio and shift the atmosphere toward a
transitional ozone formation regime (though not necessarily all the way
to NOX saturation). VOC emissions have also decreased
steadily from 2000 to the present day,\41\ and biogenic VOC emissions
in the Sacramento Metro Area, while variable, are about ten times
higher than those from anthropogenic sources.\42\ Accordingly, the
shift to smaller differences in weekday-weekend ozone concentrations
seen in 2014 could be the result of natural variability in biogenic VOC
emissions that causes some locations to be transitional or
NOX-saturated on some days.
---------------------------------------------------------------------------

    \39\ Id.
    \40\ 2017 Sacramento Regional Ozone Plan Appendix B-2, B-31 and
B-34.
    \41\ CARB Staff Report, B-16.
    \42\ CARB Staff Report, B-7.
---------------------------------------------------------------------------

    The Plan also suggests variability in meteorology as a factor in
shifting ozone chemistry between NOX-limited and
NOX-disbenefit regimes.\43\ The Plan cites a research paper
that examined the effect of temperature and found that ``the average
O3 is higher on weekends than on weekdays only for the
lowest temperature days.'' \44\ Natural annual variability also applies
to the degree of pollutant carryover from one day to the next day; day-
to-day carryover can mix weekday and weekend pollutants, making
weekdays and weekends appear to be more similar. In addition, the
NOX emissions reductions that have occurred from 2000 to the
present day have decreased the difference between weekday and weekend
NOX emissions, which would also decrease the differences in
weekday and weekend ozone concentrations.
---------------------------------------------------------------------------

    \43\ 2017 Sacramento Regional Ozone Plan Appendix B-4, B-148.
    \44\ LaFranchi, B.W., Goldstein, A.H., and Cohen, R.C., 2011,
``Observations of the temperature dependent response of ozone to
NOX reductions in the Sacramento, CA urban plume,''
Atmospheric Chemistry and Physics, 11, 6945-6960, https://doi.org/10.5194/acp-11-6945-2011, 6954 (``LaFranchi et al. 2011'').
---------------------------------------------------------------------------

    Although these plots of weekday-weekend ozone differences provide a
useful indicator, they are not a definitive description of the ozone
chemistry involved. The plots show only the resulting ozone
concentrations, not any ozone precursors or meteorology whose
interaction results in those concentrations. Furthermore, the weekday-
weekend plots show just a single point for each monitor-year
combination, the average over a year's summer days of daily maximum 8-
hour ozone concentrations, rather than a point for each day. Ozone
concentrations vary between the days of

a single year, not just between years. A data point near the 1:1 line
may indicate that weekday-weekend differences are small due to
transitional chemistry on every individual day. Alternatively, it could
indicate that positive differences balance out negative ones, due to a
mix of high-ozone NOX-limited days and low-ozone
NOX-saturated or transitional days. This would mean that
NOX-saturated days with lower ozone concentrations and less
regulatory and health significance would be masking NOX-
limited days with higher ozone concentrations and greater significance.
In the context of the analyses and evidence presented in the Plan, the
smaller weekday-weekend differences in ozone concentrations in 2014 do
not indicate a change in ozone chemistry that would suggest a control
strategy failure or an unknown phenomenon. As the State explains,
variability in biogenic VOC emissions and in meteorology provide an
explanation for some locations being transitional or NOX-
saturated on some days. We agree with the State that the weekday-
weekend analyses support the conclusion that ozone formation in the
Sacramento Metro Area is mainly in a NOX-limited regime,
with some periods in a NOX-transitional regime, and that
there is no disbenefit from NOX controls. Next, we review
and present additional research evidence from the Plan that further
supports our conclusion that the Sacramento Metro Area's ozone
chemistry is NOX-limited.
    To supplement the analysis of weekday-weekend conditions, the Plan
cites several research and analysis papers examining daily and hourly
concentrations of ozone, NOX, and VOC in the years prior to
2011, which support the conclusion that ozone formation in the
Sacramento area is currently NOX-limited. Two related papers
by Murphy et al., from 2006 and 2007, examine monitored data from 1998-
2002 for the Central and Eastern subregions of the Sacramento Metro
Area.\45\ As described in these papers, the ``weekend effect,'' i.e.,
conditions in which ozone concentrations are higher on weekends, was
observed for monitoring sites in the Sacramento Valley (corresponding
to the Central subregion).\46\ The researchers attributed this largely
to NOX titration from mobile source emissions in urban
Sacramento.\47\ For the Mountain Counties of the Eastern subregion, the
researchers found that weekday ozone concentrations were higher,
consistent with NOX-limited conditions.\48\ The researchers'
analysis suggests that under conditions of high concentrations of ozone
and precursors flowing in from other urban areas, NOX
emission reductions of 50 percent or more would be needed to guarantee
lower rates of ozone production in the Sacramento Valley portions
studied, corresponding to the Central and Eastern subregions.\49\ In
comparison to this prospective analysis, NOX emissions in
the Sacramento Metro Area have decreased by 58 percent between 2000 and
2015. Thus, the work of Murphy et. al., along with subsequent
NOX emissions reductions, suggest that the full Sacramento
Metro Area should currently be NOX-limited.
---------------------------------------------------------------------------

    \45\ Murphy, J.G., Day, D.A., Cleary, P.A., Wooldridge, P.J.,
Millet, D.B., Goldstein, A.H., and Cohen, R.C., 2007, ``The weekend
effect within and downwind of Sacramento--Part 1: Observations of
ozone, nitrogen oxides, and VOC reactivity,'' Atmos. Chem. Phys., 7,
5327-5339, https://doi.org/10.5194/acp-7-5327-2007 (``Murphy et al.
2007''); Murphy, J.G., Day, D.A., Cleary, P.A., Wooldridge, P.J.,
Millet, D.B., Goldstein, A.H., and Cohen, R.C., 2006, ``The weekend
effect within and downwind of Sacramento: Part 2. Observational
evidence for chemical and dynamical contributions,'' Atmos. Chem.
Phys. Discuss., 6, 11971-12019, https://doi.org/10.5194/acpd-6-11971-2006 (``Murphy et al. 2006'').
    \46\ Murphy et al., 2007 at 5332.
    \47\ Murphy et al., 2007 at 5336; Murphy et. al., 2006 at 11972.
    \48\ Murphy et al., 2007 at 5336.
    \49\ Murphy et al., 2006 at 11996.
---------------------------------------------------------------------------

    LaFranchi et al., 2011 examines monitored data from 2001-2007 for
the Central and Eastern subregions.\50\ These researchers found
NOX-saturated conditions in the urban core, but mainly at
lower temperatures and lower ozone concentrations, and determined that
NOX emissions reductions were effective at reducing maximum
ozone concentrations.\51\ The researchers also found no evidence that
NOX reductions have been detrimental to air quality. For
example, the researchers found that the 30 percent decrease in
NOX and other nitrogen photochemical products from 2001 to
2007 was ``extremely effective in reducing the exceedance probability
at all locations during the hottest days of the year'' when increases
in biogenic emissions result in more NOX-limited
conditions.\52\ Furthermore, the researchers note that:
---------------------------------------------------------------------------

    \50\ LaFranchi et al., 2011 at 6945-6960.
    \51\ Id. at 6954.
    \52\ Id.

    It has been argued . . . that NOX decreases cause
O3 increases in the center of cities and are more
detrimental to health because of the larger number of people who
live in the urban core as opposed to the surrounding suburbs and
rural regions. . . . We find that between 2001 and 2007, the average
O3 is higher on weekends than on weekdays only for the
lowest temperature days . . . well below the exceedance limit
[California 1-hour standard of 90 ppb], increases in O3
with decreasing NOX are not likely to lead to additional
exceedances. Thus, we find no evidence that implementation of
NOX emission controls has been detrimental to air
quality, by any policy-relevant metric.\53\
---------------------------------------------------------------------------

    \53\ Id. at 6954-6955.

    Since NOX emissions examined in the Plan and today are
now lower \54\ than during the periods examined in these research
papers, ozone formation is now expected to be within a more
NOX-limited regime. As a result, current conditions are
consistent with and fit the predictions in LaFranchi et al., that
NOX emissions reductions decrease ozone concentrations in
the Eastern subregion and more recently in the Central subregion; the
possible exception being when ozone levels are already low, i.e., well
below the 2008 NAAQS.
---------------------------------------------------------------------------

    \54\ Anthropogenic VOC emissions have also decreased, but
because biogenic emissions are so much greater, the overall effect
of the NOX and VOC reductions has been to increase the
VOC/NOX ratio, resulting in more NOX-limited
ozone chemistry.
---------------------------------------------------------------------------

    Overall, the State's evidence presented in the Plan suggests that
NOX reductions are more effective than VOC reductions at
decreasing ozone concentrations in the Sacramento Metro Area. For
example, LaFranchi et al., observe that ``the intensity of biogenic VOC
emissions have made NOX emission reductions more effective
than anthropogenic VOC emission reductions in the region, at least
downwind of Del Paso [i.e., within the Central and Eastern
subregions].'' \55\ The Plan's ozone isopleth diagram for the Folsom
monitor \56\ also provides strong evidence that NOX emission
reductions are more effective than VOC reductions. The State generated
this diagram using photochemical grid modeling to simulate various
combinations of NOX and VOC emissions reductions and
plotting the resulting ozone concentrations for the Folsom monitor, the
ambient ozone monitor with the highest ozone design value in the
Sacramento Metro Area. The diagram shows a nearly horizontal slope of
the isopleth lines, indicating that ozone formation in the Folsom area
is much more responsive to NOX emission reductions than to
VOC reductions.\57\ As discussed in the proposed rule for this action,
the EPA estimated from the ozone isopleth diagram in the Plan that
ozone formation is about 14 times as

sensitive to NOX reductions than to VOC reductions on a
percentage basis, and about 24 times as sensitive on a tons-per-year
basis.\58\ Because the Plan demonstrates a shift to NOX-
limited conditions throughout all subregions in the area through its
review of relevant research and includes additional modeling evidence
at the Folsom monitor to support the Plan's reliance on NOX
emissions reductions to achieve attainment, we disagree with CBD that
additional evidence is needed to support the use of NOX
substitution under CAA section 182(c)(2)(C).
---------------------------------------------------------------------------

    \55\ LaFranchi et al. 2011 at 6958. Id. at 6946-6947, which
notes that VOC reactivity is controlled primarily by biogenic
emissions, including the urban core. This suggests that reducing
anthropogenic VOC emissions may be relatively ineffective for
reducing ozone.
    \56\ 2017 Sacramento Regional Ozone Plan Appendix B-4, B-158,
Figure 16.
    \57\ Id.
    \58\ 85 FR 68509, 68522 (October 29, 2020).
---------------------------------------------------------------------------

    We also disagree with the commenter's assertion that our proposed
approval does not consider emissions changes through 2024. The Folsom
isopleth diagram that supports the Plan's comparison of pre-2015
monitored weekday-weekend data shows that NOX reductions are
far more effective than VOC emissions based on 2026 emissions and
including changes through and after 2024.\59\ Furthermore, the changes
in emissions through 2024 posited by the commenter would not alter the
EPA's conclusion that NOX substitution is appropriate.
Indeed, we anticipate that the replacement of NOX combustion
sources with wind and solar electricity generation, as well as
continuing mobile source NOX reductions through 2024 and
beyond, will make the Sacramento Metro Area even more NOX-
limited, thereby further strengthening the Plan's conclusions regarding
the efficacy of NOX emissions reductions compared to VOC
reductions.
---------------------------------------------------------------------------

    \59\ Plan Appendix B-4, B-158.
---------------------------------------------------------------------------

    The EPA also disagrees that an equivalence demonstration requires a
quantitative analysis. Depending on the facts and circumstances of a
given nonattainment area, analytical information that establishes
equivalence may be quantitative or qualitative, or both. In this
instance, some of the evidence relied upon could be termed qualitative,
such as the shape of curves in the isopleth diagram.\60\ The Plan's
modeling and monitoring analyses, and the analyses used in the cited
research papers, are predominantly quantitative, with qualitative
aspects and some qualitative conclusions. Qualitative evidence can be
just as useful as quantitative evidence. For NOX
substitution to yield an equivalent ozone decrease, as required in CAA
section 182(c)(2)(C), a demonstration is adequate if it shows that
NOX reductions are more effective than VOC reductions--it
does not need to quantify an exact amount by which these reductions are
more effective.
---------------------------------------------------------------------------

    \60\ These curves are partly quantified by the proposed rule's
estimate that NOX emissions reductions are 14 times as
effective as VOC reductions.
---------------------------------------------------------------------------

    We also disagree with CBD's suggestion that the overall geographic
distribution of NOX and VOC emissions would be significantly
affected by realistic and incremental changes in these emissions.
Incremental changes resulting from the construction or closing of
NOX point sources would not affect the preponderance of
NOX emissions from mobile sources in the developed urban
area, when compared to the lower NOX emissions in suburban
and rural areas. These changes would also not significantly affect the
reverse pattern of relatively more VOC emissions (from biogenic
sources) in rural areas compared to urban areas. Such small changes in
overall NOX or VOC emissions would merely affect the degree
and amount by which NOX reductions are shown to be more
effective than VOC reductions. Consequently, the EPA's overall
conclusion that NOX substitution within the Plan meets the
requirements of CAA section 182(c)(2)(C) remains unchanged.
    Regarding CBD's concern that ambient ozone data from a single
monitoring site is inadequate to demonstrate equivalency, we agree that
this could be problematic in some circumstances but disagree that this
is a problem for the Sacramento Metro Area, for two reasons. First, as
discussed previously, in concluding that NOX emissions
reductions are more effective than VOC reductions at reducing ozone,
the State considered studies of ozone response at monitoring sites
throughout the nonattainment area as part of the Plan. Second, the Plan
demonstrates attainment at all monitoring sites, and its conclusion
that NOX reductions are more effective than VOC for the site
with the highest design value, i.e., the Folsom monitoring site, the
``controlling'' site for determining whether or not the NAAQS is
attained in the Sacramento Metro Area, therefore ensures that
NOX reductions will be effective in achieving ozone
reductions that will help the nonattainment area toward attainment in
all sub-regions. We anticipate that any increase in ozone
concentrations that might result from NOX emission
reductions would be only small, transient, and affect locations with
ozone concentrations well below the NAAQS. These ozone increases would
typically occur under low temperature conditions, with corresponding
low ozone concentrations well below the NAAQS, not at elevated ozone
concentrations that could affect public health or interfere with
attainment of the 2015 ozone NAAQS. As noted above, ambient ozone data
recorded in the Central subregion of the Sacramento Metro Area between
2011 and 2014 already show ozone levels under 70 ppb, the concentration
that the EPA has established as the 2015 ozone NAAQS.
    Concerning future air quality planning for the 2015 ozone NAAQS,
the State has requested that the EPA reclassify the Sacramento Metro
nonattainment area as a Serious nonattainment area, and the attainment
plan for Serious areas is not yet due. The EPA has proposed to require
that the State submit an attainment plan for the 2015 ozone NAAQS for
the Sacramento Metro Area by August 3, 2022.\61\ As proposed, this plan
will be required to demonstrate, through photochemical grid modeling
and other demonstrations, that all portions of the Sacramento Metro
Area will attain the 2015 NAAQS by no later than August 3, 2027. Based
on conditions in this area as described above and in the proposed rule
and the Plan, we anticipate that NOX reductions, including
those used to demonstrate attainment of the 2008 ozone NAAQS, will
remain a critical piece of the State's control strategy to meet the
2015 ozone NAAQS. Accordingly, we disagree with CBD's assertion that
the Plan's use of NOX substitution will interfere with
attainment of the newer and more stringent ozone standards in the
Sacramento Metro Area or violate CAA section 110(l).
---------------------------------------------------------------------------

    \61\ 86 FR 44677, 44678 (August 13, 2021).
---------------------------------------------------------------------------

    Comment #3: CBD states that an equivalence demonstration should be
as rigorous as an attainment demonstration; as such, an equivalence
demonstration should be based on photochemical modeling or another
equally rigorous technique. The commenter suggests that the State could
compare modeled relative response factors (RRFs) for each RFP milestone
year for the 3 percent per year VOC reductions to corresponding RRFs
from the control strategy, or the State could use ozone isopleth
diagrams together with conservative assumptions about the amount of
allowable NOX substitution. The commenter acknowledges that
section 182(c)(2)(C) does not explicitly prescribe the use of
photochemical grid modeling or an equally rigorous method and argues
that this does not mean that section 182(c)(2)(C) is worthy of a less
rigorous demonstration. The commenter argues that Congress added the
RFP provisions to the CAA in response to the EPA's failure to address
ozone pollution under

the general requirements for attainment demonstrations in subpart 1 of
the CAA. The commenter states that, in any case, it would be arbitrary
for the EPA to ignore the entire nonattainment area except for the
isopleths at the Folsom monitor and the Eastern region weekend effect
in assessing the equivalence demonstration.
    Response to Comment #3: The EPA disagrees that an equivalence
demonstration for purposes of CAA section 182(c)(2)(C) must be as
technically rigorous as a NAAQS attainment demonstration. As the
commenter notes, CAA section 182(c)(2)(C) does not require the use of
photochemical grid modeling to demonstrate the relative effectiveness
of NOX and VOC emissions reductions in reducing ozone
concentrations, whereas CAA section 182(c)(2)(A) explicitly requires
photochemical grid modeling or another equivalent analytical method as
part of the attainment demonstration. Instead, Congress provided the
EPA with discretion to evaluate state demonstrations supporting
NOX substitution, and to define the conditions under which
NOX substitution is appropriate ``in order to maximize the
reduction in ozone air pollution.'' \62\ We believe that this approach
reflects an appropriate balance in the level of analysis required for
demonstrating attainment by the attainment date, and for the supporting
evaluation of the relative effectiveness of potential measures and
reductions used to meet RFP milestones. Consequently, we disagree that
a NOX equivalence demonstration for RFP purposes must
reflect the same or equally rigorous analytical methods as used in the
attainment demonstration. As discussed previously, a qualitative
analysis may show that NOX reductions are more effective
than VOC reductions and be adequate for purposes of allowing
NOX substitution under section 182(c)(2)(C). As described
above, we proposed to approve the RFP demonstration and its use of
NOX substitution based on our analyses of the photochemical
modeling results included in the attainment demonstration and the
Folsom isopleth diagram, the other monitoring data from the Plan, and
the research papers and analyses cited within. Collectively, these
analyses and data show that NOX emissions reductions are
effective at reducing ozone throughout the Sacramento Metro Area and
are more effective than VOC reductions at bringing the area into
attainment of the NAAQS. Accordingly, we support the Plan's use of
NOX substitution.
---------------------------------------------------------------------------

    \62\ CAA section 182(c)(2)(C).
---------------------------------------------------------------------------

    Comment #4: CBD comments that the EPA has not demonstrated that the
approval of NOX substitution complies with Executive Order
12898, which expresses the EPA's obligation to identify and address
disproportionate impacts of its actions on minority populations and
low-income populations, i.e., environmental justice (EJ) communities.
The commenter asserts that because the EPA is not applying the
NOX Substitution Guidance in evaluating the Plan's use of
NOX substitution, it is exercising discretion, and should
use this discretion to require the State to demonstrate equivalence at
each monitoring site through photochemical modeling of the relevant
scenarios. Furthermore, the commenter says that because the record does
not support the EPA's conclusion that NOX substitution will
result in equivalent reductions in ozone concentrations throughout the
area, EJ communities may be disproportionately and adversely impacted
by the EPA's action by experiencing fewer reductions in ozone than
would be achieved through VOC reductions alone, or even ozone
increases. The commenter suggests that the EPA could exercise
discretion to disapprove the Plan on this basis, and that this
disapproval could result in the EPA issuing a Federal implementation
plan requiring additional emissions reductions to ensure equivalent
reductions in ozone concentrations. The commenter states that it is not
a sufficient response to say that approving the Plan will have no
adverse impact to EJ communities because it improves the status quo by
making State law federally enforceable. The commenter provides a map
generated using CalEnviroScreen, showing EJ communities concentrated in
the Central subregion where the commenter asserts that the Plan does
not demonstrate equivalence.
    Response to Comment #4: As explained in our previous responses, the
EPA and the State have determined that NOX reductions are
critical to the Sacramento Metro Area's attainment of the 2008 ozone
NAAQS and we anticipate that any localized increase in ozone
concentrations resulting from these NOX reductions would be
minor, transitory, and occur well below the limits established by the
NAAQS. Furthermore, we find that the Plan appropriately focuses on
ozone reductions in the regions subject to the highest ozone
concentrations, e.g., the eastern region and design value monitor at
Folsom, where adverse health impacts are most likely to occur. In this
context, we disagree that the use of NOX substitution is
inappropriate even if it may generate disproportionate reductions in
ozone concentrations within high ozone and NOX-limited
areas.
    Executive Order 12898, ``Federal Actions To Address Environmental
Justice in Minority Populations and Low-Income Populations,'' directs
Federal agencies to identify and address ``disproportionately high and
adverse human health or environmental effects'' of their actions on
minority populations and low-income populations to the greatest extent
practicable and permitted by law.\63\ Given our conclusion that the
Plan satisfies all applicable CAA requirements related to demonstrating
expeditious attainment of the ozone NAAQS, including the requirements
for RFP and NOX substitution,\64\ we have no basis to
conclude that this action will cause disproportionately high or adverse
human health or environmental effects on any population, including any
minority, low-income, or indigenous population. Under the CAA, the EPA
is required to approve a SIP submission that satisfies the requirements
of the Act and applicable Federal regulations,\65\ and Executive Order
12898 does not provide an independent basis for disapproving such a SIP
submission. The EPA remains committed, however, to working with CARB
and the local air districts in the Sacramento Metro Area to ensure that
the ozone attainment plans for this area satisfy CAA requirements for
attainment and RFP and thereby protect all populations in the area,
including minority, low-income, and indigenous populations, from
disproportionately high or adverse air pollution impacts.
---------------------------------------------------------------------------

    \63\ 59 FR 7629 (February 16, 1994).
    \64\ Our response to Comment #7 discusses our reasons for
deferring action on the State's contingency measures revision.
    \65\ CAA section 110(k); 40 CFR 52.02(a).
---------------------------------------------------------------------------

    Comment #5: CBD comments that the proposed rule fails to
acknowledge the EPA's NOX Substitution Guidance, and that
the EPA should explicitly disavow the guidance and its justifications.
The commenter says that there is no basis for this guidance and
suggests that the EPA's prior use of the guidance may have caused
increases in asthma, hospital and emergency room visits, and premature
mortality. An appendix to the comments provides numerous comments
directed at the NOX Substitution Guidance, asserting
generally that this guidance contradicts CAA section 182(c)(2)(C) by
recommending a procedure that fails to

demonstrate any equivalence between VOC and NOX reductions,
relies on incorrect policy assumptions, and gives legal justifications
that are without merit.
    Response to Comment #5: Our proposed approval of the Plan's use of
NOX substitution is compatible with the NOX
Substitution Guidance, which, while non-binding and not having the
force of regulation, provides a recommended procedure for substituting
NOX emission reductions for VOC reductions on a percentage
basis, consistent with a state's ozone attainment plan, control
strategy, modeled attainment demonstration, and RFP milestones and
requirements. The NOX Substitution Guidance specifies that
the EPA will review NOX substitution on a case-by-case basis
and will generally approve reasonable NOX substitution
proposals.\66\ As noted in our proposed rule and described above, our
approval of the State's reasonable use of NOX substitution
is supported by local conditions and needs as documented in the
modeling and analyses included in the Sacramento Metro Ozone SIP and is
consistent with the requirements in CAA section 182(c)(2)(C).\67\
---------------------------------------------------------------------------

    \66\ NOX Substitution Guidance at 3 (``The EPA will
approve substitution proposals on a case-by-case basis. Generally
speaking, any reasonable substitution proposal will be approved.'').
    \67\ See id. at 1 (recognizing that ``NOX controls
may effectively reduce ozone in many areas, and that the design of
strategies is more efficient when the characteristic properties
responsible for ozone formation and control are evaluated for each
area'').
---------------------------------------------------------------------------

    To be clear, our action on the Plan is not intended to disavow or
rescind any portion of the NOX Substitution Guidance.
Comments relating solely to the NOX Substitution Guidance
are outside the scope of this rulemaking action.
    Comment #6: CBD argues that, because the Plan does not meet the
requirements for RFP, the EPA cannot determine that the MVEBs are
allowable as a portion of the total allowable emissions for
demonstrating RFP. The commenter asserts that because there is no
measure of total allowable emissions for RFP in the absence of an
approvable plan, the EPA has no basis for approval of the MVEBs.
    Response to Comment #6: For the reasons described above in our
previous responses to comments, we have determined that the State's use
of NOX substitution is appropriate and adequately supported
within the Plan, consistent with the RFP and attainment demonstrations,
and that the Plan's RFP demonstration is approvable. Consequently, we
disagree with the commenter and their rationale suggesting that our
approval of the MVEBs is inappropriate.
    Comment #7: CBD challenges the EPA's proposed conditional approval
of the contingency measures as arbitrary and capricious and contrary to
law, based on CAA requirements and interpreting case law. The commenter
asserts that the EPA must disapprove the contingency measures.
    Response to Comment #7: As explained in the proposed rule, our
proposed conditional approval of the State's RFP and attainment
contingency measures was based on commitments from the State and
Districts in the context of additional emissions reductions in the RFP
milestone years and in the year following the attainment year.
Following publication of the proposed rule, the Ninth Circuit Court of
Appeals issued a decision in Association of Irritated Residents v. U.S.
Environmental Protection Agency, which remanded the EPA's conditional
approval of contingency measures for another California nonattainment
area.\68\ Based on this decision, we are not finalizing our proposed
conditional approval of the Plan's contingency measures at this time.
Consequently, CBD's comments on this issue are outside the scope of
this final action and we are not providing specific responses to these
comments.
---------------------------------------------------------------------------

    \68\ Association of Irritated Residents v. U.S. Environmental
Protection Agency, No. 19-71223 (9th Cir. Aug. 26, 2021).
---------------------------------------------------------------------------

III. Final Action

    For the reasons discussed in detail in the proposed rule and
summarized herein, under CAA section 110(k)(3), the EPA is taking final
action to approve as a revision to the California SIP the following
portions of the Sacramento Metro Area Ozone SIP, as provided within the
2017 Sacramento Regional Ozone Plan and the Sacramento Metro portion of
CARB's 2018 SIP Update:
     The base year emissions inventory element in the 2017
Sacramento Regional Ozone Plan meets the requirements of CAA sections
172(c)(3) and 182(a)(1) and 40 CFR 51.1115 for the 2008 ozone NAAQS;
     The RACM demonstration element in the 2017 Sacramento
Regional Ozone Plan meets the requirements of CAA section 172(c)(1) and
40 CFR 51.1112(c) for the 2008 ozone NAAQS;
     The attainment demonstration element for the 2008 ozone
NAAQS in the 2017 Sacramento Regional Ozone Plan meets the requirements
of CAA section 182(c)(2)(A) and 40 CFR 51.1108;
     The ROP demonstration element in the 2017 Sacramento
Regional Ozone Plan meets the requirements of CAA 182(b)(1) and 40 CFR
51.1110(a)(2) for the 2008 ozone NAAQS;
     The RFP demonstration element in Section V--SIP Elements
for the Sacramento Metropolitan Area of the 2018 SIP Update (as
clarified) meets the requirements of CAA sections 172(c)(2), 182(b)(1),
and 182(c)(2)(B), and 40 CFR 51.1110(a)(2)(ii) for the 2008 ozone
NAAQS;
     The VMT emissions offset demonstration element in the 2017
Sacramento Regional Ozone Plan meets the requirements of CAA section
182(d)(1)(A) and 40 CFR 51.1102 for the 2008 ozone NAAQS; and
     The motor vehicle emissions budgets in Section V--SIP
Elements for the Sacramento Metropolitan Area of the 2018 SIP Update
for the RFP milestone year of 2023, and the attainment year of 2024 are
consistent with the RFP and attainment demonstrations for the 2008
ozone NAAQS, and the budgets meet the other criteria in 40 CFR
93.118(e). In approving the budgets, we are also finding them adequate
for use in transportation conformity determinations, consistent with 40
CFR 93.118(f)(2).

 Table 1--Transportation Conformity Motor Vehicle Emissions Budgets for
            the 2008 Ozone NAAQS in the Sacramento Metro Area
                [Summer planning inventory, tons per day]
------------------------------------------------------------------------
               Budget year                      VOC             NOX
------------------------------------------------------------------------
2023....................................              15              22
2024....................................              15              21
------------------------------------------------------------------------
Source: 85 FR 68509; Id. at 68530, Table 9; and 2018 SIP Update, Table V-
  4.

    We also find that the:
     Emissions statement element of the 2017 Sacramento
Regional Ozone Plan satisfies the requirements under CAA section
182(a)(3)(B) based on our prior approval of the Districts' emissions
statement rules;
     Enhanced vehicle inspection and maintenance program in the
Sacramento Metro Area meets the requirements of CAA section 182(c)(3)
and 40 CFR 51.1102 for the 2008 ozone NAAQS;
     California SIP revision to opt out of the Federal Clean
Fuels Fleet Program meets the requirements of CAA sections 182(c)(4)(A)
and 246 and 40 CFR 51.1102 for the 2008 ozone NAAQS with respect to the
Sacramento Metro Area; and
     Enhanced monitoring in the Sacramento Metro Area meets the
requirements of CAA section 182(c)(1) and 40 CFR 51.1102 for the 2008
ozone NAAQS.
    To conclude, we are deferring final action on the contingency
measures element of the Sacramento Metro Area Ozone SIP as meeting the
requirements of CAA sections 172(c)(9) and 182(c)(9).

IV. Statutory and Executive Order Reviews

    Under the Clean Air Act, the Administrator is required to approve a
SIP submission that complies with the provisions of the Act and
applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a).
Thus, in reviewing SIP submissions, the EPA's role is to approve state
choices provided they meet the criteria of the Clean Air Act.
Accordingly, this action merely approves state plans as meeting Federal
requirements and does not impose additional requirements beyond those
imposed by state law. For that reason, this action:
     Is not a ``significant regulatory action'' subject to
review by the Office of Management and Budget under Executive Orders
12866 (58 FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21,
2011);
     Does not impose an information collection burden under the
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact
on a substantial number of small entities under the Regulatory
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or
uniquely affect small governments, as described in the Unfunded
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have federalism implications as specified in
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Is not an economically significant regulatory action based
on health or safety risks subject to Executive Order 13045 (62 FR
19885, April 23, 1997);
     Is not a significant regulatory action subject to
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Is not subject to requirements of Section 12(d) of the
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272
note) because application of those requirements would be inconsistent
with the Clean Air Act; and
     Does not provide the EPA with the discretionary authority
to address disproportionate human health or environmental effects with
practical, appropriate, and legally permissible methods under Executive
Order 12898 (59 FR 7629, February 16, 1994).
    In addition, the SIP is not approved to apply on any Indian
reservation land or in any other area where the EPA or an Indian tribe
has demonstrated that a tribe has jurisdiction. Four Indian tribes have
areas of Indian country located within the boundaries of the Sacramento
Metro ozone nonattainment area. In those areas of Indian country, the
rule does not have tribal implications and will not impose substantial
direct costs on tribal governments or preempt tribal law as specified
by Executive Order 13175 (65 FR 67249, November 9, 2000).
    The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the
Small Business Regulatory Enforcement Fairness Act of 1996, generally
provides that before a rule may take effect, the agency promulgating
the rule must submit a rule report, which includes a copy of the rule,
to each House of the Congress and to the Comptroller General of the
United States. The EPA will submit a report containing this action and
other required information to the U.S. Senate, the U.S. House of
Representatives, and the Comptroller General of the United States prior
to publication of the rule in the Federal Register. A major rule cannot
take effect until 60 days after it is published in the Federal
Register. This action is not a ``major rule'' as defined by 5 U.S.C.
804(2).
    Under section 307(b)(1) of the Clean Air Act, petitions for
judicial review of this action must be filed in the United States Court
of Appeals for the appropriate circuit by December 21, 2021. Filing a
petition for reconsideration by the Administrator of this final rule
does not affect the finality of this action for the purposes of
judicial review nor does it extend the time within which a petition for
judicial review may be filed, and shall not postpone the effectiveness
of such rule or action. This action may not be challenged later in
proceedings to enforce its requirements. (See section 307(b)(2)).

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by
reference, Intergovernmental relations, Nitrogen dioxide, Ozone,
Reporting and recordkeeping requirements, Volatile organic compounds.

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

    Dated: October 9, 2021.
Deborah Jordan,
Acting Regional Administrator, Region IX.

    Chapter I, title 40 of the Code of Federal Regulations is amended
as follows:

PART 52--APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS

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

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

Subpart F--California

0
2. Section 52.220 is amended by adding paragraphs (c)(514)(ii)(A)(10)
and (c)(566) to read as follows:

Sec.  52.220  Identification of plan--in part.

* * * * *
    (c) * * *
    (514) * * *
    (ii) * * *
    (A) * * *
    (10) 2018 Updates to the California State Implementation Plan,
adopted on October 25, 2018, chapter V (``SIP Elements for the
Sacramento Metropolitan Area''), excluding section V.D (``Contingency
Measures''); and pages A-15 through A-18 of Appendix A (``Nonattainment
Area Inventories'').
* * * * *
    (566) The following plan was submitted on December 18, 2017 by the
Governor's designee.
    (i) [Reserved]
    (ii) Additional materials. (A) Sacramento Metropolitan Area 2008 8-
Hour Ozone National Ambient Air Quality Standard Planning Area.
    (1) Sacramento Regional 2008 NAAQS 8-Hour Ozone Attainment and
Reasonable Further Progress Plan, dated July 24, 2017, excluding the
following portions: Subchapter 7.9, ``Contingency Measures'';
subchapter 10.5, ``Proposed New Motor Vehicle Emissions Budgets''; and
chapter 12 (regarding reasonable further progress).

    (2) [Reserved]
    (B) [Reserved]

[FR Doc. 2021-22661 Filed 10-21-21; 8:45 am]
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[Federal Register: August 16, 2006 (Volume 71, Number 158)]
[Notices]
[Page 47210]
[DOCID:fr16au06-78]

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ENVIRONMENTAL PROTECTION AGENCY

[EPA-HQ-OPP-2005-0492; FRL-8086-4]

Oxytetracycline; Tolerance Reassessment Decision

AGENCY:  Environmental Protection Agency (EPA).

ACTION:  Notice.

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

SUMMARY:  This notice announces the availability of EPA's Tolerance
Reassessment Decision (TRED) for the pesticide oxytetracycline. The
Agency's risk assessments and other related documents also are
available in the oxytetracycline docket. Through the tolerance
reassessment program, EPA is ensuring that all pesticides meet current
health and food safety standards.

FOR FURTHER INFORMATION CONTACT:  Lance Wormell, Special Review and
Reregistration Division (7508P), Office of Pesticide Programs,
Environmental Protection Agency, 1200 Pennsylvania Ave., NW.,
Washington, DC 20460-0001; telephone number:<PHONE_NUMBER>; fax
number:<PHONE_NUMBER>; e-mail address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:

I. General Information

A. Does this Action Apply to Me?

    This action is directed to the public in general, and may be of
interest to a wide range of stakeholders including environmental, human
health, and agricultural advocates; the chemical industry; pesticide
users; and members of the public interested in the sale, distribution,
or use of pesticides. Since others also may be interested, the Agency
has not attempted to describe all the specific entities that may be
affected by this action. If you have any questions regarding the
applicability of this action to a particular entity, consult the person
listed under FOR FURTHER INFORMATION CONTACT.

B. How Can I Get Copies Of This Document and Other Related Information?

    1. Docket. EPA has established a docket for this action under
docket identification (ID) number EPA-HQ-OPP-2005-0492. Publicly
available docket materials are available either in the electronic
docket at http://www.regulations.gov, or, if only available in hard

copy, at the Office of Pesticide Programs (OPP) Regulatory Public
Docket in Rm. S-4400, One Potomac Yard (South Building), 2777 S.
Crystal Drive Arlington, VA. The hours of operation of this Docket
Facility are from 8:30 a.m. to 4 p.m., Monday through Friday, excluding
legal holidays. The Docket Facility telephone number is<PHONE_NUMBER>.
    2. Electronic access. You may access this Federal Register document
electronically through the EPA Internet under the ``Federal Register''
listings at http://www.epa.gov/fedrgstr.

II. Background

A. What Action is the Agency Taking?

     EPA has reassessed risks associated with use of the
oxytetracycline, reassessed two existing tolerances or legal residue
limits, and on June 30, 2006, reached a tolerance reassessment and risk
management decision. Oxytetracycline is an antibiotic pesticide used to
control bacteria, fungi, and mycoplasma-like organisms. The majority of
agricultural use of oxytetracycline is on pears. Other crops treated
include peaches, nectarines, and apples. Oxytetracycline use on apples
has been approved under emergency exemption (Section 18) provisions for
several years due to the lack of efficacious alternatives.
Oxytetracycline is also registered for use on forest trees and
ornamental trees, shrubs, and vines. There are no residential
pesticidal uses of oxytetracycline. Oxytetracycline is also registered
with FDA to treat infectious diseases in animals and humans and also as
a food additive to increase animal weight gain. The Agency is now
issuing a Report on Food Quality Protection Act (FQPA) Tolerance
Reassessment Progress and Risk Management Decision for Oxytetracycline,
known as a TRED, as well as related technical support documents.
    EPA must review tolerances and tolerance exemptions that were in
effect when FQPA was enacted in August 1996, to ensure that these
existing pesticide residue limits for food and feed commodities meet
the safety standard established by the new law. Tolerances are
considered reassessed once the safety finding has been made or a
revocation occurs. EPA has reviewed and made the requisite safety
finding for the Oxytetracycline tolerances included in this notice.
    EPA is applying the principles of public participation to all
pesticides undergoing reregistration and tolerance reassessment. The
Agency's Pesticide Tolerance Reassessment and Reregistration; Public
Participation Process, published in the Federal Register on May 14,
2004 (69 FR 26819) (FRL-7357-9), explains that in conducting these
programs, EPA is tailoring its public participation process to be
commensurate with the level of risk, extent of use, complexity of
issues, and degree of public concern associated with each pesticide.
Due to its uses, risks, and other factors, oxytetracycline was reviewed
through the modified 4-Phase public participation process. Through this
process, EPA worked extensively with stakeholders and the public to
reach the regulatory decisions for oxytetracycline.

B. What is the Agency's Authority for Taking this Action?

    Section 408(q) of the FFDCA, 21 U.S.C. 346a(q), requires EPA to
review tolerances and exemptions for pesticide residues in effect as of
August 2, 1996, to determine whether the tolerance or exemption meets
the requirements of section 408(b)(2) or (c)(2) of FFDCA. This review
is to be completed by August 3, 2006.

List of Subjects

    Environmental protection, Pesticides and pests.

    Dated: August 9, 2006.
 Debra Edwards,
Director, Special Review and Reregistration Division, Office of
Pesticide Programs.
[FR Doc. E6-13485 Filed 8-15-06; 8:45 am]

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