[Federal Register Volume 83, Number 26 (Wednesday, February 7, 2018)]
[Proposed Rules]
[Pages 5375-5399]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2018-02462]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2017-0177; FRL-9974-10-Region 9]


Approval and Promulgation of Air Quality State Implementation 
Plans; California; Interstate Transport Requirements for Ozone, Fine 
Particulate Matter, and Sulfur Dioxide

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve a State Implementation Plan (SIP) submission from the State of 
California regarding certain interstate transport requirements of the 
Clean Air Act (CAA or ``Act''). This submission addresses the 2008 
ozone national ambient air quality standards (NAAQS), the 2006 fine 
particulate matter (PM2.5) and 2012 PM2.5 NAAQS, 
and the 2010 sulfur dioxide (SO2) NAAQS. The interstate 
transport requirements under the CAA consist of several elements; this 
proposal pertains only to significant contribution to nonattainment and 
interference with maintenance of the NAAQS in other states. We are 
taking comments on this proposal and plan to follow with a final 
action.

DATES: Any comments must arrive by March 9, 2018.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2017-0177 at http://www.regulations.gov, or via email to Rory Mays 
at [email protected]. For comments submitted at Regulations.gov, follow 
the online instructions for submitting comments. Once submitted, 
comments cannot be edited or removed from Regulations.gov. For either 
manner of submission, 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, please contact the person 
identified in the FOR FURTHER INFORMATION CONTACT section. For the full 
EPA public comment policy, information about CBI or multimedia 
submissions, and general guidance on making effective comments, please 
visit https://www.epa.gov/dockets/commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT: Rory Mays, Air Planning Office (AIR-
2), EPA Region IX, (415) 972-3227, [email protected].

SUPPLEMENTARY INFORMATION: Throughout this document, ``we'', ``us'' and 
``our'' refer to the EPA.

Table of Contents

I. Background
    A. Interstate Transport
    B. California's Submission
II. Interstate Transport Evaluation
    A. The EPA's General Evaluation Approach
    B. Evaluation for the 2008 8-Hour Ozone NAAQS
    C. Evaluation for the 2006 PM2.5 and 2012 
PM2.5 NAAQS
    D. Evaluation for the 2010 1-hour SO2 NAAQS
III. Proposed Action
IV. Statutory and Executive Order Reviews

I. Background

    Section 110(a)(1) of the CAA requires states to submit SIPs meeting 
the applicable requirements of section 110(a)(2) within three years 
after promulgation of a new or revised NAAQS or within such shorter 
period as the EPA may prescribe. Section 110(a)(2) requires states to 
address structural SIP elements such as requirements for monitoring, 
basic program requirements, and legal authority that are designed to 
provide for implementation, maintenance, and enforcement of the NAAQS. 
The EPA refers to the SIP submissions required by these provisions as 
``infrastructure SIP'' submissions. Section 110(a) imposes the 
obligation upon states to make a SIP submission to the EPA for a new or 
revised NAAQS, but the contents of individual state submissions may 
vary depending upon the facts and circumstances. This proposed rule 
pertains to the infrastructure SIP requirements for interstate 
transport of air pollution.

A. Interstate Transport

    Section 110(a)(2)(D)(i) of the CAA requires SIPs to include 
provisions prohibiting any source or other type of emissions activity 
in one state from emitting any air pollutant in amounts that will 
contribute significantly to nonattainment, or interfere with 
maintenance, of the NAAQS, or interfere with measures required to 
prevent significant deterioration of air quality or to protect 
visibility in any other state. This proposed rule addresses the two 
requirements under section 110(a)(2)(D)(i)(I), which we refer to as 
prong 1 (significant contribution to nonattainment of the NAAQS in any 
other state) and prong 2 (interference with maintenance of the NAAQS in 
any other state).\1\ The EPA refers to SIP revisions addressing the 
requirements of section 110(a)(2)(D)(i)(I) as ``good

[[Page 5376]]

neighbor SIPs'' or ``interstate transport SIPs.''
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    \1\ The remaining interstate and international transport 
requirements of CAA section 110(a)(2)(D) for the 2008 ozone, 2006 
PM2.5, 2012 PM2.5, and 2010 SO2 
NAAQS for California have been addressed in prior State submissions 
and EPA rulemakings. 81 FR 18766 (April 1, 2016). Specifically, this 
includes the section 110(a)(2)(D)(i)(II) requirements relating to 
interference with measures required to be included in the applicable 
implementation plan for any other state under part C to prevent 
significant deterioration of air quality (prong 3) or to protect 
visibility (prong 4), and the section 110(a)(2)(D)(ii) requirements 
relating to interstate and international pollution abatement.
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    Each of the following NAAQS revisions triggered the requirement for 
states to submit infrastructure SIPs, including provisions to address 
interstate transport prongs 1 and 2. On September 21, 2006, the EPA 
revised the primary and secondary 24-hour NAAQS for PM2.5 to 
35 micrograms per cubic meter ([micro]g/m\3\) and retained the primary 
and secondary annual NAAQS for PM2.5 of 15.0 [micro]g/
m\3\.\2\ On March 12, 2008, the EPA revised the levels of the primary 
and secondary 8-hour ozone standards to 0.075 parts per million 
(ppm).\3\ On June 2, 2010, the EPA established a new primary 1-hour 
SO2 standard of 75 ppb.\4\ Finally, on December 14, 2012, 
the EPA revised the primary annual PM2.5 standard by 
lowering the level to 12.0 [mu]g/m\3\ and retained the secondary annual 
PM2.5 standard of 15.0 [micro]g/m\3\ and the primary and 
secondary 24-hour PM2.5 standards of 35 [mu]g/m\3\.\5\
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    \2\ 71 FR 61144 (October 17, 2006). Regarding the annual 
PM2.5 standards, we note that the EPA previously approved 
a California SIP submission for the 1997 PM2.5 NAAQS (and 
the 1997 ozone NAAQS) for interstate transport prongs 1 and 2. 76 FR 
34872 (June 15, 2011).
    \3\ 73 FR 16436 (March 27, 2008).
    \4\ 75 FR 35520 (June 22, 2010).
    \5\ 78 FR 3086 (January 15, 2013).
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    The EPA has issued several guidance documents and informational 
memos that inform the states' development and the EPA's evaluation of 
interstate transport SIPs for section 110(a)(2)(D)(i)(I). These include 
the following memos relating to the NAAQS at issue in this proposed 
rule:
     Information on interstate transport SIP requirements for 
the 2008 ozone NAAQS (``Ozone Transport Memo''),\6\
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    \6\ Memorandum from Stephen D. Page, Director, OAQPS, EPA, 
``Information on Interstate Transport ``Good Neighbor'' Provision 
for the 2008 Ozone National Ambient Air Quality Standards (NAAQS) 
under Clean Air Act (CAA) Section 110(a)(2)(D)(i)(I),'' January 22, 
2015.
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     Cross-State Air Pollution Rule (CSAPR) Update ozone 
transport modeling (``CSAPR Update Modeling''),\7\
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    \7\ The EPA updated its ozone transport modeling through the 
CSAPR Update rulemaking. 81 FR 74504 (October 26, 2016). The 
modeling results are found in the ``Ozone Transport Policy Analysis 
Final Rule TSD,'' EPA, August 2016, and an update to the affiliated 
final CSAPR Update ozone design value and contributions spreadsheet 
that includes additional analysis by EPA Region IX (``CSAPR Update 
Modeling Results and EPA Region IX Analysis'').
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     Supplemental information on interstate transport SIP 
requirements for the 2008 ozone NAAQS (``Supplemental Ozone Transport 
Memo''),\8\
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    \8\ Memorandum from Stephen D. Page, Director, OAQPS, EPA, 
``Supplemental Information on the Interstate Transport State 
Implementation Plan Submissions for the 2008 Ozone National Ambient 
Air Quality Standards under Clean Air Act Section 
110(a)(2)(D)(i)(I),'' October 27, 2017.
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     Guidance on infrastructure SIP requirements for the 2006 
PM2.5 NAAQS (``2006 PM2.5 NAAQS Transport 
Guidance''),\9\ and
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    \9\ Memorandum from William T. Harnett, Director, Air Quality 
Policy Division, OAQPS, EPA, ``Guidance on SIP Elements Required 
Under Sections 110(a)(1) and (2) for the 2006 24-Hour Fine 
Particulate Matter National Ambient Air Quality Standards,'' 
September 25, 2009.
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     Information on interstate transport SIP requirements for 
the 2012 PM2.5 NAAQS (``2012 PM2.5 NAAQS 
Transport Memo'').\10\
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    \10\ Memorandum from Stephen D. Page, Director, OAQPS, EPA, 
``Information on Interstate Transport `Good Neighbor' Provision for 
the 2012 Fine Particulate Matter National Ambient Air Quality 
Standards under Clean Air Act Section 110(a)(2)(D)(i)(I),'' March 
17, 2016.
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    For the 2006 PM2.5 and 2008 ozone NAAQS, the EPA 
previously found that California failed to submit the required SIP 
revisions addressing interstate transport prongs 1 and 2 by certain 
dates.\11\ Those actions triggered the obligation for the EPA to 
promulgate a federal implementation plan (FIP) for these requirements 
unless the State submits and the EPA approves a SIP submission that 
addresses the two prongs. As discussed further in this notice, the EPA 
proposes that California's interstate transport SIP submission 
adequately addresses these requirements for the 2006 PM2.5 
and 2008 ozone NAAQS, as well as the 2012 PM2.5 and 2010 
SO2 NAAQS, for which the EPA has not made a finding of 
failure to submit.
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    \11\ 79 FR 63536 (October 24, 2014) for the 2006 
PM2.5 NAAQS and 80 FR 39961 (July 13, 2015) for the 2008 
ozone NAAQS.
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B. California's Submission

    The California Air Resources Board (CARB) submitted the 
``California Infrastructure State Implementation Plan (SIP) Revision, 
Clean Air Act Section 110(a)(2)(D)'' on January 19, 2016 (``California 
Transport Plan'' or ``Plan'').\12\ We are proposing action on the 
California Transport Plan, which addresses interstate transport for the 
2008 ozone, 2006 PM2.5, 2012 PM2.5, and 2010 
SO2 NAAQS. We find that this submission meets the procedural 
requirements for public participation under CAA section 110(a)(2) and 
40 CFR 51.102.
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    \12\ Letter from Richard W. Corey, Executive Officer, CARB to 
Jared Blumenfeld, Regional Administrator, Region 9, EPA, January 19, 
2016.
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    The California Transport Plan outlines the CAA interstate transport 
requirements, describes the State's and, to some degree, the local air 
districts' emission limits and other control measures, and presents its 
methodology for analyzing ozone, PM2.5, and SO2 
transport and conclusions for each. It includes appendices with CARB's 
analysis for each of the NAAQS addressed in the SIP submission, 
PM2.5 data and graphics from selected Interagency Monitoring 
of Protected Visual Environments (IMPROVE) monitors \13\ near areas in 
other western states with elevated levels of ambient PM2.5, 
emissions data from the 70 facilities closest to each PM2.5 
receptor, and a list of CARB control measures for mobile sources of air 
pollution.
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    \13\ IMPROVE monitors are located in national parks and 
wilderness areas to monitor air pollutants that impair visibility.
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II. Interstate Transport Evaluation

A. The EPA's General Evaluation Approach

    We review the state's submission to see how it evaluates the 
transport of air pollution to other states for a given air pollutant, 
the types of information the state used in its analysis, how that 
analysis compares with prior EPA rulemaking, modeling, and guidance, 
and the conclusions drawn by the state. Taking stock of the state's 
submission, the EPA generally evaluates the interstate transport of a 
given pollutant through a stepwise process. The following discussion 
addresses the EPA's approach to evaluating interstate transport for 
regional pollutants such as ozone and PM2.5. Our evaluation 
approach for interstate transport of SO2 is described in 
section II.D.1 of this proposed rule.
    Typically, for assessing interstate transport for regional 
pollutants, such as PM2.5 or ozone, we first identify the 
areas that may have problems attaining or maintaining attainment of the 
NAAQS. We refer to regulatory monitors that are expected to exceed the 
NAAQS under average conditions as ``nonattainment receptors'' (i.e., 
not expected to attain) and those that may have difficulty maintaining 
the NAAQS as ``maintenance receptors.'' \14\ Such receptors may include 
regulatory monitors operated by states, tribes, or local air 
agencies.\15\
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    \14\ Regulatory monitoring sites are those that meet certain 
siting and data quality requirements such that they may be used as a 
basis for regulatory decisions with respect to a given NAAQS.
    \15\ In California, there are two federally-recognized tribes 
that operate regulatory monitors for ozone or PM2.5: The 
Morongo Band of Mission Indians operates a regulatory ozone monitor 
and the Pechanga Band of Luise[ntilde]o Indians operates regulatory 
monitors for both ozone and PM2.5.
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    In some cases, we have identified these receptors by modeling air 
quality in a future year that is relevant to CAA attainment deadlines 
for a given NAAQS. This type of modeling has been

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based on air quality data, emissions inventories, existing and planned 
air pollution control measures, and other information. For purposes of 
this proposed rule, such modeling is available for western states \16\ 
for the 2008 ozone and 2012 PM2.5 NAAQS; in each case the 
EPA modeled air quality in the 48 contiguous states of the continental 
U.S.\17\ When such modeling is not available, the EPA has considered 
available relevant information, including recent air quality data. An 
interstate transport SIP can rely on modeling when an appropriate 
technical analysis is available, but the EPA does not believe that 
modeling is necessarily required if other available information is 
sufficient to evaluate the presence or degree of interstate transport. 
Further, the EPA believes it is appropriate to identify areas that 
violate the NAAQS or have the potential to violate the NAAQS within a 
geographic scope that reflects the potential dispersion of certain air 
pollutants. In the context of this proposed rule, this concept applies 
to the 2006 PM2.5 NAAQS, where we focused on air quality 
data in 10 western states outside of California, and the 2010 
SO2 NAAQS, where we reviewed air quality data in the 
California's three neighboring states (i.e., Arizona, Nevada, and 
Oregon).\18\ Identifying such receptors or areas helps to focus 
analytical efforts by the states and the EPA on the areas where 
transported air pollution is more likely to adversely affect air 
quality.
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    \16\ For purposes of this proposed rule, ``western states'' 
refers to the states of Arizona, California, Colorado, Idaho, 
Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming.
    \17\ The methodology for the EPA's transport modeling for the 
2008 ozone and 2012 PM2.5 NAAQS is described in the CSAPR 
Update Rule (81 FR 74504, October 26, 2016) and the EPA's 2012 
PM2.5 NAAQS Transport Memo, respectively. For the 2008 
ozone NAAQS, 2017 is the attainment year for Moderate ozone 
nonattainment areas. For the 2012 PM2.5 NAAQS, 2021 is 
the attainment year for Moderate PM2.5 nonattainment 
areas. While the EPA's 2016 Transport Modeling projected 24-hour 
PM2.5 concentrations for 2017 and 2025, such data can be 
used to inform analyses of interstate transport in 2021. The 
California Transport Plan (pp. 16-17) also discusses the EPA's 
regulatory framework with respect to ozone transport.
    \18\ The transport of SO2 is more analogous to the 
transport of lead rather than regional pollutants like ozone and 
PM2.5 because its physical properties result in localized 
pollutant impacts very near the emissions source. For this reason, 
we have evaluated SO2 interstate transport for the three, 
large states that border California, rather than a larger geographic 
area. For further discussion of the physical properties of 
SO2 transport, please see the EPA's proposal on 
Connecticut's SO2 transport SIP. 82 FR 21351 at 21352 and 
21354 (May 8, 2017).
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    After identifying potential receptors, the EPA's second step for 
regional pollutants such as PM2.5 or ozone is to assess how 
much the upwind state of interest (i.e., California) may contribute to 
air pollution at each of the identified receptors or areas in other 
states. The EPA has conducted contribution modeling for the 2008 ozone 
NAAQS to estimate the amount of the projected average ozone design 
value at each receptor that will result from the emissions of each 
state within the continental U.S., and we have considered this modeling 
in this proposed rule. The EPA has typically compared that contribution 
amount (e.g., from California to Colorado) against an air quality 
threshold, selected based on the level and nature of the contribution 
from other states, as discussed in section II.B.2 of this proposed 
rule. We use this information to determine whether further analysis of 
the emission sources in a state is warranted (i.e., step 3). When the 
EPA assesses state-to-state contribution, if we conclude that the 
upwind state contributes only insignificant amounts to all 
nonattainment and maintenance receptors or areas in other states, the 
EPA may approve a submission that concludes that the submitting state 
does not significantly contribute to nonattainment, or interfere with 
maintenance, of the NAAQS in any other state.
    Third, if warranted based on step 2, the EPA analyzes emission 
sources in the upwind state, including emission levels, state and 
federal measures, and how well such sources are controlled. We also 
review whether the applicable control measures are included in the SIP, 
consistent with CAA section 110(a)(2)(D)(i). For example, for ozone, 
this analysis has generally focused on the emissions of nitrogen oxides 
(NOX), given that prior assessments of ozone control 
approaches concluded that a NOX control strategy would be 
most effective for reducing regional scale ozone transport,\19\ and on 
large stationary sources, such as electricity generating units (EGUs), 
given their historic potential to produce large, cost-effective 
emission reductions.\20\
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    \19\ For discussion of the effectiveness of control strategies 
for NOX and volatile organic compounds (VOCs), which are 
precursors to ozone, to reduce ozone levels in regional versus 
densely urbanized scales, respectively, please see the EPA's 
proposal for the Cross-State Air Pollution Rule (CSAPR). 75 FR 
45210, 45235-45236 (August 2, 2010).
    \20\ For background on the EPA's regulatory approach to 
interstate transport of ozone, beginning with the 1998 
NOX SIP Call and the 2005 Clean Air Interstate Rule, 
please see the EPA's CSAPR proposal. 75 FR 45210 at 45230-45232 
(August 2, 2010).
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    If contribution modeling is not available, we conduct a weight of 
evidence analysis. This analysis is based on a review of the state's 
submission and other available information, including air quality 
trends; topographical, geographical, and meteorological information; 
local emissions in downwind states and emissions from the upwind state; 
and existing and planned emission control measures in the state of 
interest. In CSAPR and for the 2012 PM2.5 NAAQS Transport 
Memo, the EPA did not calculate the portion of any downwind state's 
predicted PM2.5 concentrations that would result from 
emissions from individual western states, such as California. 
Accordingly, the EPA considers prong 1 and 2 submissions for states 
outside the geographic area analyzed to develop CSAPR and the 2012 
PM2.5 NAAQS Transport Memo to be appropriately evaluated 
using a weight of evidence analysis of the best available information, 
such as the information that EPA has recommended in the 2006 
PM2.5 NAAQS Transport Guidance and 2012 PM2.5 
NAAQS Transport Memo. For this proposed rule, we conducted weight of 
evidence analyses to determine whether the emissions from California 
significantly contribute to nonattainment, or interfere with 
maintenance, of the NAAQS at each of the identified receptors (for the 
2012 PM2.5 NAAQS) or identified areas (for the 2006 
PM2.5 NAAQS and 2010 SO2 NAAQS).\21\ For the 2012 
annual PM2.5 NAAQS, we consider both annual and 24-hour 
PM2.5 data because, in many cases, the annual average 
PM2.5 levels in the western U.S. are driven by an abundance 
of high 24-hour average PM2.5 levels in winter.
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    \21\ The California Transport Plan also includes such weight of 
evidence analyses, though not necessarily to the same set of 
receptors or areas identified in the EPA's analyses.
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    At this point of our analysis, if we conclude that the SIP contains 
adequate provisions to prohibit sources from emitting air pollutants 
that significantly contribute to nonattainment, or interfere with 
maintenance, of a given NAAQS in any other state, the EPA may approve a 
submission that concludes that the state has sufficient measures to 
prohibit significant contribution to nonattainment, or interference 
with maintenance, of the NAAQS in any other state.
    If the EPA concludes that that the SIP does not meet the CAA 
requirements, then the EPA must disapprove the state's submission with 
respect to that NAAQS, and the disapproval action triggers the 
obligation for the EPA to promulgate a FIP to address that deficiency. 
Following such a disapproval, the state has an opportunity to resolve 
any underlying

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deficiency in the SIP. If the state does not address the deficiency, 
then the CAA requires the EPA to issue a FIP to adequately prohibit 
such emissions. The EPA has promulgated FIPs via regional interstate 
transport rules across much of the eastern U.S. for the 1997 ozone, 
1997 PM2.5, and 2006 PM2.5 NAAQS (CSAPR) \22\ and 
for the 2008 ozone NAAQS (CSAPR Update).\23\ To date, no such FIP has 
been promulgated with respect to CAA transport prongs 1 and 2 in the 
western U.S., and we are not proposing any such FIP in this proposed 
rule.
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    \22\ 76 FR 48208 (August 8, 2011).
    \23\ 81 FR 74504 (October 26, 2016).
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B. Evaluation for the 2008 8-Hour Ozone NAAQS

1. State's Submission
    The California Transport Plan presents a weight of evidence 
analysis to assess whether emissions within the State contribute 
significantly to nonattainment or interfere with maintenance of the 
2008 ozone NAAQS in any other state. This analysis includes a review of 
the EPA's photochemical modeling data that were available at the time 
CARB developed its Plan (i.e., in the Ozone Transport Memo),\24\ air 
quality data, downwind receptor sites, and the science of interstate 
transport of air pollution in the western U.S. It focuses on potential 
contributions to receptors in the Denver, Colorado area (four 
receptors) and in Phoenix, Arizona (one receptor) based on the air 
pollution linkages identified in the EPA's modeling.\25\
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    \24\ 80 FR 46271 (August 4, 2015). This notice of data 
availability (NODA) for the EPA's updated ozone transport modeling 
data included the projected 2017 ozone design values at each 
regulatory ozone monitor in the 48 continental U.S. states and 
Washington, DC and the modeled linkages between upwind and downwind 
states. Based on input received in response to the NODA and through 
the EPA's CSAPR Update rulemaking, which was completed after the 
California Transport Plan submission of January 19, 2016, the EPA 
further updated the ozone transport modeling data. 81 FR 74504 
(October 26, 2016).
    \25\ California Transport Plan, pp. 15, 18-19.
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    CARB states that the EPA's Ozone Transport Memo considered an 
upwind state to be linked to a downwind state if the upwind state's 
projected contribution was over one percent of the NAAQS (i.e., one 
percent is a 0.75 ppb contribution to an 8-hour average ozone 
concentration).\26\ CARB also highlights a statement in the EPA's Ozone 
Transport Memo that ozone transport in western states should be 
evaluated on a case-by-case basis.\27\ The California Transport Plan 
contrasts ozone levels and emission sources in the eastern versus the 
western U.S. For states subject to CSAPR in the East, the Plan asserts 
that emissions from upwind states overwhelm downwind local emission 
contributions (i.e., local contributions are smaller than transported 
contributions by an average ratio of 1:2) and multiple upwind states 
affect a given downwind receptor. The Plan states that ozone levels in 
the West are primarily driven by local emissions (i.e., by an average 
ratio of 8:1), with a much smaller portion being attributed to 
interstate transport, and that western states have widespread complex 
terrain and are relatively larger on average than eastern states. The 
Plan describes this contrast in further detail by discussing modeling 
uncertainties.
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    \26\ Id., p. 18 and App. D, pp. D-3 to D-7.
    \27\ See Ozone Transport Memo, p. 4.
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    While acknowledging the possibility of some limited transport of 
ozone or its precursor pollutants, CARB believes that there are 
significant uncertainties in photochemical modeling of ozone transport 
in the western U.S.\28\ CARB summarizes certain comments it made in 
response to the EPA's August 2015 notice of data availability (NODA) 
regarding ozone transport modeling.\29\ Those comments discuss the 
challenge of modeling interstate transport of ozone in the western U.S. 
due to complex terrain, wildfire effects, and the limited monitoring 
data available to validate the modeling. CARB states that complex 
terrain can enhance vertical mixing of air, serve as a barrier to 
transported air pollution, enhance accumulation of local emissions in 
basins and valleys, and influence air flows up, down, and across 
valleys.\30\ Regarding wildfires, the Plan states that the size and 
number of wildfires in the western U.S. have significantly increased in 
recent decades and that wildfires can significantly increase ozone 
levels in adjacent and downwind areas. CARB asserts that the EPA's 
treatment of wildfire emissions in the Ozone Transport Memo modeling 
has the potential to overestimate ozone concentrations in 2017 and to 
underestimate the benefit of controlling anthropogenic emission 
sources.\31\ CARB states that further analysis would be required to 
quantify California's contribution with confidence.\32\
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    \28\ California Transport Plan, p. 15.
    \29\ Id., pp. 15-16. See also, comment letter from K. Magliano, 
Chief, Air Quality Planning and Science Division, CARB to the docket 
of the EPA's NODA. 80 FR 46271 (August 4, 2015).
    \30\ California Transport Plan, App. D, pp. D-1 to D-2.
    \31\ California Transport Plan, p. 24.
    \32\ Id.
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    Aside from the asserted modeling uncertainties, the Plan provides 
analyses of California's potential impacts and information regarding 
the Denver area and Phoenix receptors. For the Denver area 
nonattainment and maintenance receptors identified in the EPA's Ozone 
Transport Memo, CARB found it extremely unlikely that California 
emission sources would affect such receptors on high ozone days.\33\ 
CARB describes distance (more than 600 miles, or 1,000 kilometers (km), 
from California to Denver), topography (Denver is bounded by mountains 
to the west and south) and meteorology (local wind flow patterns driven 
by terrain and heat differentials) that would favor local ozone 
formation and includes trajectory analyses of ozone concentrations at 
the applicable receptors.\34\ This includes a description of the 
location and topography at each nonattainment monitor (Air Quality 
System (AQS) monitor ID 08-059-0006, Rocky Flats North; and 08-035-
0004, Chatfield State Park) and maintenance monitor (08-059-0011, 
National Renewable Energy Laboratory (NREL); and 08-005-0002, Highland 
Reservoir). CARB notes that the Chatfield nonattainment receptor and 
the NREL maintenance receptor are 300-800 feet higher than the 
elevation of Denver, away from sources whose emissions might scavenge 
ozone,\35\ and west-southwest of Denver--an area to which winds push 
emissions on days when meteorology is conducive to ozone formation.\36\
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    \33\ Id., pp. 23-24 and App. D, p. D-25.
    \34\ Id., App. D, pp. D-19 to D-31.
    \35\ Ozone scavenging refers to a process where a molecule such 
as nitric oxide strips an oxygen atom from ozone, thereby reducing 
the amount of ozone in the atmosphere. For example, ozone 
concentrations typically fall at night in urban areas due to 
scavenging of ozone by NOX and other compounds. 73 FR 
16436, 16490 (March 27, 2008).
    \36\ Id., p. D-23.
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    Regarding its trajectory analysis, CARB examined the potential for 
ozone or ozone precursor pollutants to travel from California to 
Colorado using the Hybrid Single Particle Lagrangian Integrated 
Trajectory model.\37\ CARB input ozone data from June and July in 2011 
and 2012 as the months with the most high-ozone days and identified 
only 11 of 447 back trajectories where pollution in the mixed layer of 
air in Colorado went back to the mixed layer in California. CARB then 
conducted forward trajectories for these 11 cases and found only one 
where pollution in California's mixed layer reached the mixed layer at 
a Colorado receptor. CARB concluded that the complex physical 
environment between California and Colorado limits the reproducibility 
of modeled transport of

[[Page 5379]]

air pollution. The Plan also describes a vertical cross-section profile 
from the back trajectories and states that the air at the surface (in 
California and/or Colorado) was almost always decoupled from the air 
higher in the atmosphere, thus limiting the effect of transported air 
pollution.
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    \37\ Id., pp. D-23 to D-25.
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    With respect to wildfires, CARB found an overall downward trend in 
ozone concentrations at the four Colorado receptors from 2003 to 2010 
followed by increases in 2011-2013, which coincide with large increases 
in the acreage of wildland burned per year in Colorado (e.g., about 
75,000 acres burned/year in 2009-2010 and about 190,000-255,000 acres 
burned/year in 2011-2013).\38\ CARB states that the EPA's Ozone 
Transport Memo modeling estimated 0.32-0.74 ppb of ozone was due to 
wildfire at the four Colorado receptors, but that this estimate was 
attributed only to ozone formed from the interaction of NOX 
and volatile organic compounds (VOCs) emitted by such wildfires, and 
not additional interactions of NOX and VOCs from wildfires 
with NOX and VOCs from anthropogenic sources. CARB asserts 
that this would underestimate the effect of wildfires on ozone levels 
in 2011-2013, which in turn meant that the EPA's modeling overestimated 
the predicted ozone concentrations at the Denver area receptors in 
2017.\39\ CARB states that this would affect both the weighted design 
values (of 2009-2013) used to identify 2017 nonattainment receptors and 
contributions thereto and the highest design value (e.g., 2011-2013) 
used to identify 2017 maintenance receptors and contributions 
thereto.\40\ CARB suggests that a case-by-case approach may be needed 
to adjust the weighting of years for base-year design values.
---------------------------------------------------------------------------

    \38\ Id., pp. D-26 to D-30.
    \39\ Id., pp. D-30 to D-31.
    \40\ For the primary and secondary ozone NAAQS, the design value 
at each site is the 3-year average annual fourth-highest daily 
maximum 8-hour average ozone concentration. 40 CFR part 50 App. I, 
section 3.
---------------------------------------------------------------------------

    CARB concludes that physical and chemical processes occurring over 
the complex terrain and the long distance from California to these 
receptors would significantly affect any air pollution traveling 
between the two states.\41\ Based on its analysis, CARB concludes that 
California does not significantly contribute to nonattainment, or 
interfere with maintenance, of the 2008 ozone NAAQS at the Denver area 
receptors.
---------------------------------------------------------------------------

    \41\ California Transport Plan, pp. D-31 to D-32.
---------------------------------------------------------------------------

    For the Phoenix, Arizona receptor, CARB states that, while the 
relatively shorter distance makes transport a possibility from southern 
California, high ozone days in Phoenix are predominantly driven by 
local contributions. CARB describes topography (e.g., Phoenix is in a 
large bowl), meteorology (e.g., monsoon rains in July and August reduce 
ozone levels, and highest ozone levels are observed in June), and a low 
correspondence between modeled and measured high ozone concentrations 
to support its assertion that high ozone days are driven by local 
contributions.\42\ CARB asserts that California does not interfere with 
maintenance of the 2008 ozone NAAQS at this maintenance receptor and 
that CARB's on-going control programs will ensure that California does 
not interfere with Phoenix maintaining the 2008 ozone NAAQS.
---------------------------------------------------------------------------

    \42\ Id., pp. D-13 to D-19.
---------------------------------------------------------------------------

    In addition, the California Transport Plan states that California 
has responded to each successive ozone NAAQS with increasingly 
stringent control measures and that CARB and other agencies' aggressive 
emission control programs will continue to benefit air quality in 
California and other states.\43\ The Plan states that CARB and local 
air districts implement comprehensive rules to address emissions from 
all source sectors.\44\ These programs and rules include measures on 
mobile sources, the State's largest emission source sector, local air 
district measures on stationary and area sources, and CARB regulations 
on consumer products. CARB states that the EPA's Ozone Transport Memo 
modeling takes into account many of California's existing measures and 
shows that California emission reductions from 2011 to 2017 are 445 
tons per day (tpd) of NOX and 277 tpd of reactive organic 
gases (ROG).\45\
---------------------------------------------------------------------------

    \43\ Id., pp. 15, 24-25.
    \44\ Id., pp. D-7 to D-9.
    \45\ CARB typically refers to reactive organic gases in its 
ozone-related submissions since VOCs in general can include both 
reactive and unreactive gases. However, since ROG and VOC 
inventories pertain to common chemical species (e.g., benzene, 
xylene, etc.) we refer to this set of gases as VOCs in this proposed 
rule.
---------------------------------------------------------------------------

    CARB highlights how its mobile source measures have often served as 
models for federal mobile source control elements and that California's 
legacy programs continue to provide current and future emission 
reductions from vehicles within California and elsewhere. Where 
California and federal rules have been harmonized, CARB has implemented 
rules to accelerate deployment of the cleanest available control 
technologies for heavy-duty trucks, buses, and construction equipment 
to achieve emission reductions more quickly. Appendix G of the 
California Transport Plan presents a list of regulatory actions taken 
since 1985 to reduce mobile source emissions. CARB also describes 
efforts underway to transition to near-zero vehicle emissions 
technologies and to review the state's goods movement (e.g., via the 
State's Sustainable Freight Action Plan, issued in July 2016). With 
respect to stationary and area emission sources, the California 
Transport Plan includes a table of 29 measures adopted by local air 
districts and approved into the California SIP by the EPA.\46\ CARB 
claims that these measures were not taken into account in the EPA's 
Ozone Transport Memo modeling.
---------------------------------------------------------------------------

    \46\ California Transport Plan App. D, Table D-2, pp. D-9 to D-
12.
---------------------------------------------------------------------------

    The Plan concludes that neither the EPA's modeling, given CARB's 
concerns about wildfire and model performance, nor CARB's weight of 
evidence analysis indicates that California significantly contributes 
to nonattainment, or interferes with maintenance, of the 2008 ozone 
NAAQS in any other state. Therefore, CARB concludes that California 
meets the requirements of CAA section 110(a)(2)(D)(i)(I) for the 2008 
ozone NAAQS.
2. Introduction to the EPA's Ozone Evaluation
    The EPA agrees with the conclusion that California meets the CAA 
requirements for interstate transport prongs 1 and 2 for the 2008 ozone 
NAAQS. However, our rationale differs from that presented in the 
California Transport Plan, as discussed below. First, we address CARB's 
assertions regarding ozone transport modeling uncertainties for 
identifying nonattainment and maintenance receptors in 2017 and 
linkages to California. We then discuss the EPA's CSAPR Update 
Modeling,\47\ which both decreased the number of receptors to which 
California is linked relative to the EPA's Ozone Transport Memo 
modeling and adjusted the estimates of California's contribution to 
each projected 2017 receptor. We also discuss the contrast that CARB 
draws between ozone transport in the eastern versus western U.S. These 
components are important to the first two steps of our evaluation: (1) 
To identify potential

[[Page 5380]]

nonattainment and maintenance receptors, and (2) to estimate interstate 
contributions to those receptors. Based on that analysis, we propose to 
find that California is not linked to any receptor in Arizona and 
linked only to maintenance receptors in the Denver area in Colorado.
---------------------------------------------------------------------------

    \47\ As noted previously, the EPA updated its ozone transport 
modeling through the CSAPR Update rulemaking. 81 FR 74504 (October 
26, 2016). The modeling results are found in the ``Ozone Transport 
Policy Analysis Final Rule TSD,'' EPA, August 2016, and an update to 
the affiliated final CSAPR Update ozone design value and 
contributions spreadsheet that includes additional analysis by EPA 
Region IX (``CSAPR Update Modeling Results and EPA Region 9 
Analysis'').
---------------------------------------------------------------------------

    With respect to California's linkage to those maintenance receptors 
in Denver, we then present a general assessment of the emission sources 
in California, including mobile and stationary emission sources. We 
propose to find that control measures in the California SIP for mobile 
sources, large EGUs, and large non-EGU sources (e.g., cement plants and 
oil refineries), adequately prohibit the emission of air pollution in 
amounts that will interfere with maintenance of the 2008 ozone NAAQS at 
the identified receptors in the Denver area.
    Given the role of regulatory monitoring data in the EPA's analysis 
of interstate transport, the regulatory monitoring performed by the 
Morongo Band of Mission Indians (Morongo) and the Pechanga Band of 
Luise[ntilde]o Indians (Pechanga), as well as comments from Morongo and 
Pechanga during the EPA's rulemaking on California's interstate 
transport SIP for the 1997 ozone and 1997 PM2.5 NAAQS,\48\ 
we have also considered transport to Morongo and Pechanga reservations. 
Based on our review of the ambient air quality data of Morongo and 
Pechanga and the emission control regimes of California's South Coast 
Air Quality Management District (AQMD) for stationary sources and of 
CARB for mobile sources, as described in the EPA's memo to the 
docket,\49\ the EPA proposes to find that California adequately 
prohibits the emission of air pollutants in amounts that will 
significantly contribute to nonattainment, or interfere with 
maintenance, of the 2008 ozone NAAQS in the Morongo or Pechanga 
reservations.
---------------------------------------------------------------------------

    \48\ 76 FR 34872 (June 15, 2011). In their comments, Morongo and 
Pechanga called for an analysis of any potential ozone or 
PM2.5 transport to their reservations and for 
consultation with the EPA.
    \49\ Memorandum from Rory Mays, Air Planning Office, Air 
Division, Region IX, EPA, ``Interstate Transport for the 2008 ozone, 
2006 PM2.5, 2012 PM2.5, and 2010 
SO2 NAAQS and the Morongo Band of Mission Indians and the 
Pechanga Band of Luise[ntilde]o Indians,'' January 2018.
---------------------------------------------------------------------------

3. Evaluation of CARB's Modeling Concerns
    The California Transport Plan asserts that uncertainty in the EPA's 
Ozone Transport Memo modeling derives from issues of complex terrain, 
wildfires, and model performance, and presents trajectory analyses to 
supplement these uncertainties. We consider each of these factors 
because they are important to the adequacy of the EPA's modeling data 
with respect to ozone transport in the western U.S.
    We agree with CARB that the terrain in the western U.S. is complex 
and can enhance vertical mixing of air, serve as a barrier to 
transported air pollution, enhance accumulation of local emissions in 
basins and valleys, and influence air flows up, down, and across 
valleys. It is also true that California is a long distance (about 
1,000 km) from the receptors identified in Colorado. The EPA used the 
CSAPR Update Modeling in a relative sense to project measured design 
values to 2017 and to quantify contributions from statewide 2017 
anthropogenic emissions of NOX and VOC on a broad regional 
basis.\50\ As such, it was important to use a large regional scale 
modeling domain to adequately capture multi-day regional transport of 
ozone and precursor pollutants over long distances. The EPA selected 
the Comprehensive Air Quality Model with Extensions to perform such 
modeling given its utility in regional photochemical dispersion 
modeling and in developing quantitative contributions for evaluation of 
the magnitude of ozone transport from upwind states. We believe the 
EPA's CSAPR Update Modeling adequately accounts for the complex terrain 
and distance.
---------------------------------------------------------------------------

    \50\ ``Cross State Air Pollution Update Rule--Response to 
Comments'' (CSAPR Update RTC), EPA, October 2016, p. 66.
---------------------------------------------------------------------------

    The EPA responded to CARB's comments regarding potential wildfire 
influences on modeling in our response to comments document for the 
CSAPR Update final rule (``CSAPR Update RTC'').\51\ We acknowledge that 
wildfires could influence downwind pollutant concentrations and that it 
is likely that wildfires would occur in 2017 and future years. However, 
there is no way to accurately forecast the timing, location, and extent 
of fires across a future three-year period that would be used to 
calculate ozone design values. In the EPA's CSAPR Update Modeling, the 
EPA held the meteorological data and the fire and biogenic emissions 
constant at base year levels in the future year modeling, as those 
emissions are highly[hyphen]correlated with the meteorological 
conditions in the base year.
---------------------------------------------------------------------------

    \51\ CSAPR Update RTC, pp. 25 and 27.
---------------------------------------------------------------------------

    Regarding model performance, CARB states that there are limited 
monitoring data available to validate the EPA's ozone transport 
modeling. We discuss our ozone transport modeling platform in section 
V.A of the CSAPR Update, including our model performance assessment 
using measured ozone concentrations.\52\ We compared the 8-hour daily 
maximum ozone concentrations during the May through September ``ozone 
season'' to the corresponding measured concentrations, generally 
following the approach described in the EPA's draft modeling guidance 
for ozone attainment.\53\ We found that the predicted 8-hour daily 
maximum ozone concentrations reflect the corresponding measured 
concentrations in the modeling domain in terms of magnitude, temporal 
fluctuations, and spatial differences. The ozone model performance 
results were within the range found in other recent peer-reviewed and 
regulatory applications. We note that any problem posed by imperfect 
model performance on individual days is expected to be reduced when 
using a relative approach (i.e., using base year data to project 
relative changes in a future year ozone design value), as was the case 
in the EPA's CSAPR Update Modeling. In brief, we disagree with CARB's 
perspective with respect to model performance.
---------------------------------------------------------------------------

    \52\ 81 FR 74504, 74526-74527 (October 26, 2016).
    \53\ ``Draft Modeling Guidance for Demonstrating Attainment of 
Air Quality Goals for Ozone, PM2.5, and Regional Haze,'' 
EPA, December 3, 2014.
---------------------------------------------------------------------------

    CARB states that the complex physical environment between 
California and Colorado limits the reproducibility of modeled transport 
of air pollution and that further analysis would be required to 
quantify California's contribution with confidence. We agree that such 
research could prove valuable, particularly with respect to 
implementing the more stringent 2015 ozone NAAQS.\54\ However, the 
prospect of future research does not itself undermine the technical 
adequacy of the EPA's current modeling for the 2008 ozone NAAQS.
---------------------------------------------------------------------------

    \54\ The EPA recently issued a NODA with our preliminary 
interstate transport data for the 2015 ozone NAAQS, which projects 
that California will have several nonattainment receptors, and 
California and Colorado will have several maintenance receptors, in 
2023. 82 FR 1733 (January 6, 2017).
---------------------------------------------------------------------------

    Having considered the effects of complex terrain, wildfires, and 
any model performance in the EPA's ozone transport modeling for ozone 
levels throughout the continental U.S. (i.e., not just the Denver area 
receptors), we assert the EPA's approach to forecasting interstate 
transport for the 2008 ozone NAAQS to be a reasonable means for 
identifying nonattainment and maintenance receptors and for estimating 
the state contributions to

[[Page 5381]]

those receptors. Thus, we turn to summarizing changes between the EPA's 
Ozone Transport Memo modeling and CSAPR Update Modeling results as they 
pertain to California's contribution to nonattainment and maintenance 
receptors in other states.
4. Identification of Receptors and Estimation of California 
Contribution
    The EPA noted in the CSAPR Update that there may be specific 
geographic factors in western states to consider in evaluating 
interstate transport and, given the near-term 2017 implementation 
timeframe, the EPA focused the CSAPR Update on eastern states.\55\ 
Consistent with our statements in the CSAPR Update and other transport 
actions in western states,\56\ the EPA intends to address western 
states on a case-by-case basis.
---------------------------------------------------------------------------

    \55\ 81 FR 74504, 74523 (October 26, 2016).
    \56\ See, e.g., the EPA's proposed rule on Arizona's interstate 
transport for the 2008 ozone NAAQS. 81 FR 15200 (March 22, 2016).
---------------------------------------------------------------------------

    As described in the California Transport Plan, the EPA's Ozone 
Transport Memo identified two nonattainment and two maintenance 
receptors in the Denver area and one maintenance receptor in Phoenix. 
Based on input received in response to our Ozone Transport Memo NODA 
and the CSAPR Update proposal, the EPA updated the ozone transport 
modeling to reflect the latest data and analysis (e.g., emission 
reductions from additional NOX control measures). In each 
modeling exercise, we used the same definition for nonattainment 
receptors: Regulatory ozone monitors where 2017 ozone design values are 
projected to exceed the 2008 ozone NAAQS based on the average design 
value of three overlapping periods (2009-2011, 2010-2012, and 2011-
2013) and where the monitor indicated nonattainment at the time of the 
analysis for the CSAPR Update. Similarly, we used the same CSAPR Update 
definition for maintenance receptors: Regulatory ozone monitors where 
2017 ozone design values do not exceed the NAAQS based on the projected 
average design values, but exceed the 2008 ozone NAAQS based on the 
projected maximum design value of any period within the three 
overlapping periods. In addition, monitoring sites that are projected 
to have average design values above the NAAQS but currently have 
measured design values below the NAAQS are also considered maintenance 
receptors.
    The EPA's CSAPR Update Modeling projects that for the western U.S. 
in 2017 (outside of California), there are no nonattainment receptors 
and only three maintenance receptors located in the Denver, Colorado 
area. Notably, that modeling projects that Phoenix, Arizona will not 
have any receptors.\57\ California emissions are projected to 
contribute above one percent of the 2008 ozone NAAQS at each of the 
three Denver area maintenance receptors, as shown in Table 1.
---------------------------------------------------------------------------

    \57\ The EPA's 2016 Ozone Transport Modeling projects that the 
2017 maximum base case design value in Maricopa County, Arizona (AQS 
ID 40-013-1004) will be 75.7 ppb (i.e., 0.0757 ppm), which is 
attaining the 2008 ozone NAAQS, per the data handling convention for 
computing 8-hour ozone averages (i.e., truncating digits to the 
right of the third decimal place of values presented in ppm). 40 CFR 
part 50, Appendix P, section 2.1.

                                                 Table 1--2017 Ozone Maintenance Receptors in Colorado Based on the EPA's CSAPR Update Modeling
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                               Other
                                                                                       2017 base                                            states % of                               Number of
                                                                                          case      California    California  Contribution   2017 base     Colorado        All         states
                 AQS monitor ID                                 County                  maximum    contribution   % of 2008     by other        case     contribution   remaining   contributing
                                                                                         design        (ppb)     ozone NAAQS  states (ppb)    maximum        (ppb)       sources     over 1% of
                                                                                      value (ppb)                                  \a\         design                     (ppb)         NAAQS
                                                                                                                                               value
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
08-035-0004.....................................  Douglas...........................         77.6          1.18          1.6          7.29          9.4         26.10        41.90             3
08-059-0006.....................................  Jefferson.........................         78.2          1.96          2.6          7.16          9.2         21.16        47.17             2
08-059-0011.....................................  Jefferson.........................         78.0          0.79          1.1          7.29          9.3         29.32        38.13             4
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Contribution by other States includes contribution from states and tribes in the continental U.S., including California, that are outside of Colorado.

    The modeling shows that other states also contribute above one 
percent of the NAAQS to these maintenance receptors. The EPA found that 
the average interstate contribution to ozone concentrations from all 
states upwind of these receptors ranged from 9.2 to 9.4 percent of the 
projected ozone design values.\58\ Thus, the collective contribution of 
emissions from upwind states represent a considerable portion of the 
ozone concentrations at the maintenance receptors in the Denver area.
---------------------------------------------------------------------------

    \58\ CSAPR Update Modeling Results and EPA Region 9 Analysis.
---------------------------------------------------------------------------

    The EPA has historically found that the one percent threshold is 
appropriate for identifying interstate transport linkages for states 
collectively contributing to downwind ozone nonattainment or 
maintenance problems because that threshold captures a high percentage 
of the total pollution transport affecting downwind receptors.\59\ The 
EPA believes a contribution from an individual state equal to or above 
one percent of the NAAQS could be considered significant where the 
collective contribution of emissions from one or more upwind states is 
responsible for a considerable portion of the downwind air quality 
problem regardless of where the receptor is geographically located. In 
this case, combinations of two, three, or four states contribute 
greater than or equal to one percent of the 2008 ozone NAAQS at each of 
these three maintenance receptors, as shown in Table 1.
---------------------------------------------------------------------------

    \59\ See, e.g., 75 FR 45210, 45237 (August 2, 2010) and 76 FR 
48208, 48238 (August 8, 2011) (CSAPR proposed and final rules); and 
80 FR 75706, 75714 (December 3, 2015) and 81 FR 74504, 74518-74519 
(October 26, 2016) (CSAPR Update proposed and final rules). See 
also, e.g., 81 FR 15200, 15202-15203 (March 22, 2016) (proposed rule 
on Arizona transport SIP, including prongs 1 and 2 for the 2008 
ozone NAAQS); 81 FR 71991, 71992 (October 19, 2016) (final rule on 
Utah transport SIPs, including prong 2 for the 2008 ozone NAAQS); 
and 82 FR 9142, 9143 (February 3, 2017) (final rule on Wyoming 
transport SIPs, including prongs 1 and 2 for the 2008 ozone NAAQS).
---------------------------------------------------------------------------

    Regarding CARB's comparison of the average ratio of local to 
transported emissions in the East (1:2) versus the average ratio in the 
West (8:1), while we did not quantitatively evaluate the ratios 
presented in the California Transport Plan, we generally agree that 
there could be substantial differences in such average ratios. However, 
the value of comparing average ratios is somewhat limited given that 
states within a particular region could have a wide variation of 
contributions to other states. For example, the EPA's CSAPR Update 
Modeling indicates that, excluding Texas, states collectively 
contribute 9.4 percent to 16.2 percent of the projected 2017 base case 
maximum ozone design values at each of three maintenance receptors in 
Denton County (Dallas-Fort Worth area) and Harris County

[[Page 5382]]

(Houston), Texas.\60\ For each Texas receptor, two or three states each 
contribute over one percent of the NAAQS. In comparison, we find that 
two to four states each contribute over one percent of the NAAQS to 
each of the Colorado maintenance receptors, which is similar to the 
Texas scenario.
---------------------------------------------------------------------------

    \60\ CSAPR Update Modeling Results and EPA Region IX Analysis.
---------------------------------------------------------------------------

    Given these data and comparisons, the EPA is proposing that the one 
percent threshold is also appropriate as an air quality threshold to 
determine whether California is ``linked'' to the three maintenance 
receptors in the Denver area for the 2008 ozone NAAQS.
    The EPA is not necessarily determining that one percent of the 
NAAQS is always an appropriate threshold for identifying interstate 
transport linkages for all states in the West. For example, the EPA 
recently evaluated the impact of emissions from Arizona on two 
projected nonattainment receptors identified in California and 
concluded that, even though Arizona's modeled contribution was greater 
than one percent of the 2008 ozone NAAQS, Arizona did not significantly 
contribute to nonattainment, or interfere with maintenance, at those 
receptors.\61\ Accordingly, where the facts and circumstances support a 
different conclusion, the EPA has not always applied the one percent 
threshold to identify states that may significantly contribute to 
nonattainment, or interfere with maintenance, of the 2008 ozone NAAQS 
in other states.
---------------------------------------------------------------------------

    \61\ Final rule, 81 FR 31513 (May 19, 2016). See also proposed 
rule, 81 FR 15200, 15203 (March 22, 2016). The EPA evaluated the 
nature of the ozone nonattainment problem at the California 
receptors and determined that, unlike the receptors identified in 
the eastern U.S. and unlike the maintenance receptors in Colorado, 
only one state (Arizona) contributed above the one percent threshold 
to the California receptors and that the total contribution from all 
states linked to the receptors (2.5 to 4.4%) was negligible. 
Considering this information, along with emissions inventories and 
emissions projections showing Arizona emissions decreasing over 
time, the EPA determined that Arizona had satisfied the requirements 
of CAA section 110(a)(2)(D)(i)(I) with respect to the 2008 ozone 
NAAQS.
---------------------------------------------------------------------------

    Likewise, the EPA is not determining that because California 
contributes above the one percent threshold, it is necessarily making a 
significant contribution that warrants further reductions in emissions. 
As noted above, the one percent threshold identifies a state as 
``linked,'' prompting further inquiry into whether the contributions 
are significant and whether there are cost-effective controls that can 
be employed to reduce emissions (i.e., the third step in our 
evaluation).
    The EPA also notes that recent modeling shows that by the 2023 
ozone season the receptors identified in Denver are projected to be 
``clean,'' i.e., both the average and maximum design values are 
projected to be below the level of the 2008 ozone NAAQS.\62\
---------------------------------------------------------------------------

    \62\ Supplemental Ozone Transport Memo, Attachment A, pp. A-7 to 
A-8.
---------------------------------------------------------------------------

5. Evaluation of California Control Measures
    Based on the 2011 National Emissions Inventory (NEI) and the EPA's 
CSAPR Update Modeling, California's anthropogenic NOX 
emissions in 2011 were 1,944 tpd and its VOC emissions were 2,274 tpd. 
These emissions came from mobile sources (i.e., on-road motor vehicles, 
such as passenger cars, trucks, buses, and nonroad vehicles, such as 
construction equipment, locomotives, ships, and aircraft), stationary 
sources (e.g., EGU, non-EGU point, and oil and gas point and non-point 
sources), and area sources (e.g., residential wood combustion). Based 
on the EPA's CSAPR Update Modeling, California's anthropogenic 
NOX emissions in 2017 were projected to be 1,409 tpd (a 
decrease of 535 tpd, or 28 percent, from 2011), and its VOC emissions 
were projected to be 1,972 tpd (a decrease of 302 tpd, or 13 percent, 
from 2011). Table 2 shows the percentage of California NOX 
and VOC emissions that came from mobile, stationary, and area sources, 
based on the 2011 NEI and the 2017 emission projections.\63\
---------------------------------------------------------------------------

    \63\ Summary of 2017 projected California NOX and VOC 
emissions workbooks, EPA, included in the docket to this proposed 
rule as ``California--
2017ek_cb6v2_v6_11g_state_sector_totals.xlsx.'' We note that the EPA 
estimated that California's NOX and VOC emission 
reductions from 2011 to 2017 would be larger than the 445 tpd of 
NOX and 227 tpd of VOC emission reductions that the State 
projected in the California Transport Plan.

                    Table 2--California Emissions From the 2011 NEI and 2017 Projected Emissions From the EPA's CSAPR Update Modeling
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                NOX                                            VOCs
                                                         -----------------------------------------------------------------------------------------------
                                                            Mobile (%)    Stationary (%)     Area (%)       Mobile (%)    Stationary (%)     Area (%)
--------------------------------------------------------------------------------------------------------------------------------------------------------
2011 NEI Emissions (% of annual emissions)..............            78.4            11.2            10.4            34.8             6.5            58.7
2017 Projected Emissions (% of annual emissions)........            69.8            15.1            15.1            25.7             7.4            67.0
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Both NOX and VOCs are precursors to ozone but, as noted 
above, given that assessments of ozone control approaches concluded 
that a NOX control strategy would be most effective for 
reducing regional scale ozone transport, and consistent with the CSAPR 
Update and prior interstate transport rulemakings, we have focused our 
control measure review on sources of NOX.
    CARB identified numerous State mobile source measures and examples 
of local air district stationary measures that control NOX 
and VOCs emissions and have been approved into the California SIP, and 
CARB stated that these measures are part of how California addresses 
the CAA interstate transport requirements for the 2008 ozone NAAQS.\64\ 
Below, we discuss our evaluation of California's mobile source 
measures, for which CARB has unique authority under State law, and 
stationary source measures, which are adopted and implemented by 
California's 35 local air districts. For the latter, beyond the 
measures described in the California Transport Plan, we have also 
considered stationary source control measures for EGUs, consistent with 
the controls analysis for CSAPR, and examples of stationary source 
control measures for the largest non-EGU sources in the State.
---------------------------------------------------------------------------

    \64\ California Transport Plan, App. G (state measures) and App. 
D, pp. D-7 to D-12 (discussion of California emission control 
programs, including recent local measures).
---------------------------------------------------------------------------

    As noted above, the mobile source sector is the largest source of 
NOX in California and accounts for approximately 70 percent 
of the projected 2017 NOX emissions. As a general matter, 
the CAA assigns mobile source regulation to the EPA through

[[Page 5383]]

title II of the Act and, in so doing, preempts various types of state 
regulation of mobile sources.\65\ However, for certain types of mobile 
source emission standards, the State of California may request a waiver 
(for new motor vehicles and new motor vehicle engines) or authorization 
(for new and in-use nonroad engines and vehicles) for standards 
relating to the control of emissions and accompanying enforcement 
procedures, under CAA sections 209(b) and 209(e)(2), respectively.
---------------------------------------------------------------------------

    \65\ For further background on CAA title II authorities, 
including the waiver and authorization process, particularly as they 
apply to approval of CARB mobile source measures into the California 
SIP, please see the EPA's proposed and final rules approving 
numerous such measures. 80 FR 69915 (November 12, 2015) and 81 FR 
39424 (June 16, 2016).
---------------------------------------------------------------------------

    Pursuant to CAA section 209(b) and (e)(2), CARB has requested, and 
the EPA has approved, numerous waivers and authorizations over the 
years, allowing CARB to establish a comprehensive program to control 
and reduce mobile source emissions within the state. Once the 
underlying regulations establishing the mobile source emissions 
standards are waived or authorized by the EPA, CARB submits the 
regulations to the EPA as revisions to the California SIP. In recent 
years, the EPA has approved many such mobile source regulations as part 
of the California SIP, including regulations establishing standards and 
other requirements relating to emissions from cars, light- and medium-
duty trucks, heavy-duty trucks, commercial harbor craft, mobile cargo 
handling equipment, marine engines and boats, and off-highway 
recreational vehicles.\66\ To support and enhance these emissions 
standards, CARB has also established specific gasoline and diesel fuel 
requirements, and the California Bureau of Automotive Repair has 
established a vehicle emissions and inspection (i.e., ``smog check'') 
program.\67\
---------------------------------------------------------------------------

    \66\ 81 FR 39424 (June 16, 2016) and 82 FR 1446 (March 21, 
2017).
    \67\ 75 FR 26653 (May 12, 2010) (revisions to California on-road 
reformulated gasoline and diesel fuel regulations), and 75 FR 38023 
(July 1, 2010) (revisions to California motor vehicle inspection and 
maintenance program).
---------------------------------------------------------------------------

    Originally, CARB's mobile source control program focused on new 
engines and vehicles. The emissions reductions from increasingly 
stringent emissions standards for new engines and vehicles occur over 
time as new, cleaner vehicles replace old, more polluting models in a 
foreseeable process referred to as ``fleet turnover.'' In more recent 
years, CARB has recognized that emissions reductions from the mobile 
source sector due to fleet turnover would not occur quickly enough to 
meet attainment deadlines established under the CAA. As a result, CARB 
has expanded its program to address the emissions from in-use vehicles 
(referred to as the ``legacy'' fleet) by establishing, for example, 
retrofit or replacement requirements for certain types of heavy-duty 
trucks and certain fleets of nonroad equipment.\68\
---------------------------------------------------------------------------

    \68\ 77 FR 20308 (April 4, 2012) (EPA approval of in-use truck 
and bus regulation) and 81 FR 39424 (June 16, 2016) (EPA approval of 
in-use off-road diesel-fueled fleets regulation).
---------------------------------------------------------------------------

    With respect to stationary and area emission sources, the 
California Transport Plan states that local air districts implement 
comprehensive rules to address emissions from all sectors.\69\ The 
California SIP has hundreds of prohibitory rules that limit the 
emission of NOX and VOCs.\70\ Many of these rules were 
developed by local air districts to reduce ozone concentrations in the 
numerous areas that were designated nonattainment for the 1979 1-hour 
ozone and 1997 8-hour ozone NAAQS, including Severe (i.e., Coachella 
Valley, Sacramento Metro, and Western Mojave Desert for both NAAQS, and 
Ventura County for the 1-hour ozone NAAQS) and Extreme (i.e., Los 
Angeles-South Coast and San Joaquin Valley) nonattainment areas.\71\ 
Generally, the planning requirements associated with the numerous 
California ozone nonattainment areas, coupled with the increased 
control requirement stringency for areas classified Severe and above 
(e.g., lower major source thresholds and increasing permit offset 
ratios), have served to limit emissions of NOX and VOCs from 
California that might affect other states.
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    \69\ California Transport Plan, App. D, p. D-7.
    \70\ For VOCs, these include rules limiting emissions from the 
largest area, mobile, and stationary source categories such as 
consumer products, farming operations, architectural coatings/
solvents, off-road equipment, light-duty passenger vehicles, 
recreational boats, petroleum marketing, and coatings/process 
solvents.
    \71\ Based on 2010 U.S. Census data, the total population in the 
nonattainment areas for the 1997 ozone NAAQS was 34.7 million 
people, including 23.1 million people in areas classified severe or 
extreme. See https://www3.epa.gov/airquality/urbanair/sipstatus/reports/ca_areabypoll.html#ozone-8hr_1997_.
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    The California Transport Plan includes a table of 29 measures 
recently adopted by local air districts and approved into the 
California SIP by the EPA. These measures are representative of the 
wide array of NOX and VOC control measures employed by the 
local air districts. For example, Ventura County Air Pollution Control 
District (APCD) adopted rules limiting NOX emissions from 
boilers, water heaters, and process heaters, and Santa Barbara County 
APCD and South Coast AQMD adopted rules limiting NOX 
emissions from certain types of central furnaces and water heaters. San 
Joaquin Valley APCD adopted a rule to limit VOC emissions from 
composting operations, and Sacramento Metropolitan AQMD adopted a rule 
to limit VOC emissions from automotive and related equipment coatings 
and solvents.
    In addition to the numerous SIP-approved state and local 
regulations cited in the California Transport Plan, we also considered 
California's control measures for NOX emissions from EGUs, 
consistent with our approach for evaluating control measures in the 
CSAPR Update and other interstate transport rulemakings, and other 
large stationary sources in the state. For EGUs producing greater than 
25 megawatts of electricity, including non-fossil fuel EGUs, the state-
wide NOX emissions rate in California is projected to be 
0.0097 pounds of NOX per million British thermal units (lb/
MMBtu) in 2018.\72\ Thus, California ranks as the 47th lowest out of 
the 48 contiguous states and Washington, DC, for which the EPA 
performed power sector modeling in the context of the CSAPR Update.
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    \72\ Ranking of NOX emission rate by state and 
related spreadsheets, EPA, included in the docket to this proposed 
rule as ``5.15_OS_NOX_AQM_Base_Case RPE File CA analysis 
(2018 data).xlsx.''
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    Furthermore, considering facility-level emissions and operations, 
2016 emissions monitoring data indicate that 242 of the 244 EGUs in 
California that reported ozone season NOX emissions to EPA 
emitted NOX at rates less than or equal to 0.061 lb/
MMBtu.\73\ Two EGUs, Greenleaf One unit 1 and Redondo Beach unit 7, 
emitted at rates higher than 0.061 lb/MMBtu. Greenleaf One unit 1 
emitted less than 11 tons of NOX in the 2016 ozone season 
and is therefore unlikely to have significant cost-effective emission 
reduction opportunities. Applied Energy Services (AES) plans to retire 
its Redondo Beach units, including unit 7, no later than December 31, 
2019, to comply with California regulations on the use of cooling water 
in certain power plant operations.\74\ In aggregate, these

[[Page 5384]]

assessments indicate that California produces electricity very 
efficiently in terms of NOX emissions and is therefore 
unlikely to have significant, further NOX reductions 
available from the EGU sector at reasonable cost.
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    \73\ 2016 ozone season NOX emissions and heat rate 
data for California EGUs, EPA Air Markets Program Data, included in 
the docket to this rulemaking and entitled ``2016 AMPD Ozone Season 
NOX Emissions Heat Rate from California EGUs.xlsx.''
    \74\ ``Once-Through Cooling Phase-Out,'' California Energy 
Commission, last updated March 8, 2017, Table 3, p. 6. Available at 
http://www.energy.ca.gov/renewables/tracking_progress/documents/once_through_cooling.pdf. AES plans to retire Redondo Beach unit 7 
by December 31, 2019, and units 5, 6, and 8 by December 31, 2020.
---------------------------------------------------------------------------

    The largest collection of EGU facilities emitting over 100 tons per 
year (tpy) of NOX, per the 2011 NEI, are found in the San 
Joaquin Valley, Bay Area, and South Coast air districts.\75\ These 
sources are subject to district rules limiting NOX emissions 
that have been approved into the California SIP.\76\ At least two of 
these facilities in the San Joaquin Valley APCD have shut down since 
2011.\77\ Otherwise, the largest NOX-emitting EGU facility 
in 2011 was the ACE Cogeneration coal-fired power plant in Trona 
(Mojave Desert AQMD). It emitted 620 tpy of NOX and was the 
only EGU facility in California that emitted more than 250 tpy of 
NOX. However, as discussed in the ACE Cogeneration Company's 
2014 petition to the California Energy Commission to decommission this 
facility, the company had signed an agreement with Southern California 
Edison (the regional utility) to terminate operation of the facility in 
December 2014 and, in fact, ceased operation on October 2, 2014.\78\
---------------------------------------------------------------------------

    \75\ 2011 NEI California emission inventory spreadsheet of 
stationary sources emitting over 100 tpy NOX (``2011 NEI 
CA NOX Spreadsheet''), included in the docket to this 
rulemaking and entitled ``AIR17025--2011 NEI NOX sources 
by CA air district--RIX Analysis.xlsx.'' The total emissions from 
such sources in 2011 were 686 tpd in San Joaquin Valley APCD (five 
facilities in Kern County), 474 tpd in Bay Area AQMD (four 
facilities in Contra Costa County), and 394 tpd in South Coast AQMD 
(one facility in each of Los Angeles, Riverside, and San Bernardino 
Counties).
    \76\ For San Joaquin Valley APCD, see, e.g., Rule 4301 (``Fuel 
Burning Equipment,'' amended December 17, 1992), 64 FR 26876 (May 
18, 1999); Rule 4352 (``Solid Fuel Fired Boilers,'' amended December 
15, 2011), 77 FR 66548 (November 6, 2012); Rule 4702 (``Internal 
Combustion Engines,'' amended November 14, 2013), 81 FR 24029 (April 
25, 2016); and Rule 4703 (``Stationary Gas Turbines,'' amended 
September 20, 2007) 74 FR 53888 (October 21, 2009). For Bay Area 
AQMD, see e.g., Regulation 9, Rule 11 (``Nitrogen Oxides and Carbon 
Monoxide from Electric Power Generating Steam Boilers,'' amended May 
17, 2000), 67 FR 35435 (May 20, 2002). For South Coast AQMD, see 
e.g., Regulation 20 series rules for the Regional Clean Air 
Incentives Market (RECLAIM) program. RECLAIM information is 
available at: http://www.aqmd.gov/home/programs/business/business-detail?title=reclaim.
    \77\ The Rio Bravo Jasmin and Rio Bravo Poso biomass plants in 
Bakersfield have closed and the San Joaquin Valley APCD has issued 
emission reduction credit certificates for doing so on January 19, 
2016. See http://www.valleyair.org/notices/Docs/2016/01-19-16_(S-
1153637)/S-1153637.pdf and http://www.valleyair.org/notices/Docs/2016/01-19-16_(S-1154416)/S-1154416.pdf, respectively.
    \78\ ``ACE Decommissioning Plan,'' ACE Cogeneration Company, 
November 25, 2014, p. 1-1.
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    To investigate the potential for further NOX emission 
reductions from EGUs, the EPA assessed the cost effectiveness of 
reducing NOX emissions from fossil fuel-fired EGUs in each 
of the 48 contiguous states by estimating the amount of NOX 
that would be emitted at certain levels of NOX control 
stringency, represented by uniform regional cost thresholds from $800 
per ton of NOX removed up to $6,400 per ton.\79\ The CSAPR 
Update finalized EGU emission budgets for 22 eastern states based on a 
cost threshold of $1,400 per ton since that level of cost-effective 
control would achieve sufficient reductions to partially address ozone 
transport in the eastern U.S. The NOX emission level for 
California is flat at 1,905 tons across the cost threshold scenarios 
until the $5,000 per ton scenario, where the California ozone season 
NOX emission level would be reduced to 1,810 tons. In other 
words, additional NOX reductions from EGUs in California 
would cost more than three times the amount that the EPA determined to 
be cost-effective to partially address ozone transport obligations in 
the eastern U.S. under the CSAPR Update.
---------------------------------------------------------------------------

    \79\ ``Ozone Transport Policy Analysis Final Rule TSD,'' U.S. 
EPA, August 2016, Table C-1, p. 15.
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    Non-EGU stationary sources emitted 6.7 times more NOX 
(61,074 tpy) than EGUs (9,159 tpy) in California, per the 2011 NEI, and 
largely fall under the regulatory authority of California's local air 
districts. Of these non-EGU stationary sources, 19 sources emitted over 
500 tpy of NOX, per the 2011 NEI.\80\ These sources (and the 
associated air districts) include: Six Portland cement plants (Kern 
County, Mojave Desert, and Bay Area),\81\ nine petroleum refineries 
(Bay Area and South Coast),\82\ and several other source types, 
including a mineral processing plant (Mojave Desert), a natural gas 
compressor station (Mojave Desert), a glass plant (San Joaquin 
Valley),\83\ and a calcined pet coke plant (Bay Area).\84\ These 19 
sources represent 67 percent of the NOX emissions from 
California stationary sources that emitted over 100 tpy in 2011 and 
represent 5.2 percent of the total 2011 NOX inventory for 
California. Overall, these sources are subject to rules that limit 
NOX emissions and have been approved into the California 
SIP, as cited in the various footnotes of this paragraph. In light of 
the overall control of such sources, for the small number of large non-
EGU sources that are either subject to NOX control measures 
that have not been submitted for approval into the California SIP, or 
fall outside the geographic jurisdiction of the applicable district 
rules, our analysis finds that further emission controls would be 
unlikely to reduce any potential impact on downwind states' air quality 
because such sources comprise no more than 0.8 percent of the total 
NOX emitted in California in 2011.\85\
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    \80\ 2011 NEI CA NOX Spreadsheet. Other sources in 
California emitting over 500 tpy of NOX include the Los 
Angeles, San Francisco, San Diego, and other airports and the U.S. 
Army National Training Center (Fort Irwin) and U.S. Marine Corps 
Twentynine Palms military bases, whose NOX emissions from 
aircraft are outside the regulatory authority of the State of 
California. Separately, we do not count two Southern California 
Edison substations in Antelope Valley AQMD among the sources listed 
as emitting more than 500 tpy NOX., as we believe their 
NOX emissions were recorded in error. They subsequently 
do not appear in the 2014 NEI California emission inventory 
spreadsheet of stationary sources emitting over 100 tpy 
NOX (``2014 NEI CA NOX Spreadsheet''), which 
is included in the docket to this rulemaking and entitled 
``AIR17025--2014 NEI NOX sources by CA air district--RIX 
Analysis.xlsx.''
    \81\ Kern County APCD Rule 425.3 (``Portland Cement Kilns 
(Oxides of Nitrogen),'' amended October 13, 1994), 64 FR 38832 (July 
20, 1999); Mojave Desert AQMD Rule 1161 (``Portland Cement Kilns,'' 
amended March 25, 2002), 68 FR 9015 (February 27, 2003); and Bay 
Area AQMD Regulation 9, Rule 13 (``Nitrogen Oxides, Particulate 
Matter, and Toxic Air Contaminants from Portland Cement 
Manufacturing,'' amended October 19, 2016). The latter has not been 
submitted by the Bay Area AQMD and CARB as a revision to the 
California SIP.
    \82\ Bay Area AQMD Regulation 9, Rule 10 (``Nitrogen oxides and 
Carbon Monoxide from Boilers, Steam Generators and Process Heaters 
in Petroleum Refineries,'' amended July 17, 2002), 73 FR 17897 
(April 2, 2008); and South Coast AQMD RECLAIM program, whose rules 
have been approved into the California SIP, as noted above.
    \83\ San Joaquin Valley Rule 4354 (``Glass Melting Furnaces,'' 
amended May 19, 2011). Notably, the parent company of the Pilkington 
North America, Inc. glass plant in Lathrop announced that the plant 
was to be closed by January 1, 2014. http://www.recordnet.com/article/20131113/A_BIZ/311130312. Consistent with closure, it does 
not appear in the 2014 NEI CA NOX Spreadsheet.
    \84\ Bay Area AQMD Regulation 9, Rule 10 (``Nitrogen Oxides and 
Carbon Monoxide from Boilers, Steam Generators, and Process Heaters 
in Petroleum Refineries'', amended July 17, 2002), 73 FR 17897 
(April 2, 2008). This rule applies to some (e.g., process heaters), 
but not all (e.g., the plant's coker unit), of the applicable 
calcined petroleum coke plant's equipment.
    \85\ 2011 NEI CA NOX Spreadsheet.
---------------------------------------------------------------------------

    On the strength of CARB and the local air districts' emission 
control programs, especially for mobile and stationary sources of 
NOX, we propose that the California SIP, as explained in the 
California Transport Plan and our evaluation above, adequately 
prohibits the emission of air pollutants in amounts that will 
significantly contribute to nonattainment, or interfere with 
maintenance, of the 2008 ozone NAAQS in any other state. We agree with 
CARB that California meets the requirements of CAA section

[[Page 5385]]

110(a)(2)(D)(i)(I) for the 2008 ozone NAAQS, but we differ as to the 
rationale for that conclusion. California's analysis relies primarily 
on its conclusion that the ozone transport linkages are uncertain and 
therefore no significant contribution of interference with maintenance 
has been demonstrated. The EPA's evaluation finds that the transport 
linkages are adequately quantified (and uncertainties sufficiently 
addressed) and that California's emission control programs adequately 
address the transport requirements.

C. Evaluation for the 2006 PM2.5 and 2012 PM2.5 NAAQS

1. State's Submission
    The California Transport Plan presents a weight of evidence 
analysis to assess whether the state contributes significantly to 
nonattainment or interferes with maintenance of the 2006 24-hour 
PM2.5 and 2012 annual PM2.5 NAAQS in any other 
state. This analysis includes a review of air quality data for 
California and other states, including daily 24-hour PM2.5 
concentrations at potential downwind receptors and PM2.5 
design value concentrations at IMPROVE monitoring sites; local 
emissions near, distance to, and changes in population and vehicle 
miles traveled (VMT) in areas near downwind receptors; California 
emissions and rules and regulations to reduce such emissions; and other 
information available from the EPA and other states' technical support 
documents (TSDs) for various CAA requirements.\86\
---------------------------------------------------------------------------

    \86\ California Transport Plan, pp. 11-12.
---------------------------------------------------------------------------

    Regarding air quality data, CARB reviewed PM2.5 design 
values in western states from the EPA's air trends website for three 
overlapping periods between 2010-2014.\87\ For the purpose of 
identifying potential receptors, CARB defined nonattainment receptors 
as monitors violating the 2006 24-hour PM2.5 NAAQS (35 
[micro]g/m\3\) or the 2012 annual PM2.5 NAAQS (12.0 
[micro]g/m\3\) in 2012-2014 and maintenance receptors as those that 
attained the NAAQS in that period, but violated the NAAQS in either of 
the two preceding periods (2010-2012 or 2011-2013).
---------------------------------------------------------------------------

    \87\ Id., p. 10. The EPA's air trends website is available at: 
https://www.epa.gov/air-trends.
---------------------------------------------------------------------------

    For the 24-hour PM2.5 standard, CARB identified 17 
nonattainment receptors, with design values ranging from 36-61 
[micro]g/m\3\, across the following five states listed by the 
receptors' counties: Arizona (Pinal), Idaho (Lemhi and Shoshone), 
Montana (Ravalli and Silver Bow), Oregon (Crook, Jackson, Lake, and 
Lane), and Utah (Box Elder, Cache, Davis, Salt Lake, and Utah).\88\ 
CARB also identified four maintenance receptors, with design values 
ranging from 36-39 [micro]g/m\3\ in either the 2010-2012 or 2011-2013 
periods, across three states listed by the receptors' counties: Montana 
(Lewis and Clark, and Missoula), Oregon (Klamath), and Utah (Weber).
---------------------------------------------------------------------------

    \88\ Id., p. 11, Tables III.1 and III.2.
---------------------------------------------------------------------------

    For the annual PM2.5 standard, CARB identified two 
nonattainment receptors (i.e., having design values over 12.0 [micro]g/
m\3\), with design values of 12.1 and 13.1 [micro]g/m\3\, respectively, 
and no maintenance receptors, in just one state listed by the 
receptors' counties: Idaho (Lemhi and Shoshone).
    The California Transport Plan discusses California emissions from 
mobile, stationary, and area sources and applicable regulatory 
programs. CARB highlights the authority granted by Congress in the 1970 
CAA for California to adopt mobile source emission control standards in 
certain situations. Within the California Health and Safety Code, CARB 
highlights the authority granted to CARB to adopt and implement 
controls on mobile sources and their fuels, as well as consumer 
products, and to the state's 35 local air districts to adopt and 
implement stationary and area source controls.\89\ For mobile sources, 
CARB states that it has adopted and implemented: ``fleet rules'' for 
heavy-duty trucks, buses, and construction equipment; light-duty 
vehicle and fuel regulations, such as the LEV III program and the 2012 
Advanced Clean Car regulation; and inspection and maintenance programs 
for light duty (i.e., smog check) and heavy-duty vehicles; among other 
measures. For stationary and area sources, CARB states that local air 
district rules, in combination, are among the most stringent in the 
U.S. and cover a wide range of sources such as refineries, 
manufacturing facilities, cement plants, refinishing operations, 
electricity generation and biomass facilities, boilers, and generators.
---------------------------------------------------------------------------

    \89\ Id., pp. 5-6. As noted in section II.B.1 of this proposed 
rule, Appendix G of the California Transport Plan presents a list of 
CARB regulatory actions taken since 1985 to reduction mobile source 
emissions.
---------------------------------------------------------------------------

    The California Transport Plan includes a sample list of State and 
local air district rules that have been approved into the California 
SIP and a graph of how California state-wide emissions of 
PM2.5, and PM2.5 precursor pollutants, such as 
NOX, VOC, and sulfur oxides (SOX), have decreased 
significantly from 2001 (~7,000 tpd) to 2011 (~4,300 tpd) and are 
expected to continue to decrease to 2021 (projected to be ~3,100 
tpd).\90\ For example, the list includes CARB regulations for heavy-
duty trucks and buses and light- and medium-duty vehicles, and air 
district regulations for open burning, agricultural burning, and 
fugitive dust as example of regulations that limit the emission of 
particulate matter. CARB states that these state and local programs 
have reduced and will continue to reduce the potential for California 
emissions to contribute to violations, or interfere with maintenance, 
of the federal standards.
---------------------------------------------------------------------------

    \90\ Id., pp. 7-9, Table II.1 and Figure II.1. CARB's analysis 
of California SO2 emissions in based on SOX 
because CARB estimates that SO2 comprises 97% of the 
state-wide SOX inventory. California Transport Plan, App. 
C, p. C-10.
---------------------------------------------------------------------------

    We have further summarized the California Transport Plan in terms 
of California's emissions and the State and local regulatory programs 
in sections II.B and II.D of this proposed rule. These sections 
describe CARB's statements with respect to NOX and VOC 
emissions (for the 2008 ozone NAAQS) and SOX emissions (for 
the 2010 SO2 NAAQS) and are relevant, as precursors to 
PM2.5, to interstate transport for the 2006 PM2.5 
and 2012 PM2.5 NAAQS. For example, CARB states that 
NOX and VOC emissions have been reduced by 445 tpd and 277 
tpd, respectively, from 2011 to 2017 due to California's regulatory 
programs.\91\ Similarly, from 2000 to 2015, CARB estimates that CARB 
and the air districts achieved the following SOX emission 
reductions: Stationary sources (59 percent), mobile sources (88 
percent), and area sources (33 percent).\92\
---------------------------------------------------------------------------

    \91\ Id., App. D, p. D-8.
    \92\ Id., App. C, p. C-3.
---------------------------------------------------------------------------

    Regarding assessment of the causes of the PM2.5 
concentrations at each receptor, CARB presents its analysis for each 
county or PM2.5 nonattainment area (e.g., the Salt Lake City 
nonattainment area for the 2006 PM2.5 NAAQS, which includes 
the receptors in Box Elder, Davis, and Salt Lake Counties). CARB's 
receptor analyses focus on local emission sources, the distance between 
California and each receptor, long-term PM2.5 trends and 
daily PM2.5 data (as opposed to design values), population, 
and VMT. These analyses appear in Appendix A of the California 
Transport Plan for the 2006 24-hour PM2.5 NAAQS and in 
Appendix B for the 2012 annual PM2.5 NAAQS. CARB includes 
additional analyses of air quality data at IMPROVE sites that are 
located between California and the receptor counties in Appendix E and 
uses these data as an indicator of whether elevated PM2.5 
levels are observed regionally. We discuss the

[[Page 5386]]

State's analysis of each receptor area in greater detail as part of our 
evaluation for each PM2.5 NAAQS, below.
    For the 2006 24-hour PM2.5 NAAQS, CARB relies in part on 
technical documents from applicable states and the EPA (e.g., TSDs for 
the 2006 PM2.5 NAAQS nonattainment area designations) in 
concluding that most exceedances at each nonattainment or maintenance 
receptor are due to emissions from local sources, especially during 
winter-time inversions.\93\ CARB further concludes that California 
emissions from stationary sources are subject to stringent limits for 
PM2.5 and its precursors, such as those for NOX 
and SOX, and that California has a long history of reducing 
emissions through motor vehicle and fuel standards. CARB also finds 
that monitors in western states generally have valid design values well 
below 35 [micro]g/m\3\, except for the 17 receptors identified in 
CARB's analysis. Based on these analyses, CARB states that California 
does not contribute to, or interfere with maintenance of, the 2006 
PM2.5 NAAQS in neighboring or nearby states.
---------------------------------------------------------------------------

    \93\ Id., p. 22.
---------------------------------------------------------------------------

    For the 2012 annual PM2.5 NAAQS, CARB draws similar 
conclusions as those for its 24-hour PM2.5 analyses: That 
most of the high, annual PM2.5 concentrations are due to 
local emissions, especially during winter-time inversions; that 
California's stationary and mobile sources are well regulated; and that 
monitors in western states generally have valid design values well 
below 12.0 [micro]g/m\3\, except for the two receptors identified in 
CARB's analysis.\94\ CARB concludes that California does not contribute 
to, or interfere with maintenance of, the 2012 PM2.5 NAAQS 
in neighboring or nearby states.
---------------------------------------------------------------------------

    \94\ Id., p. 22-23.
---------------------------------------------------------------------------

2. Introduction to the EPA's PM2.5 Evaluation
    The EPA agrees with CARB's conclusions that California meets the 
CAA requirements for interstate transport prongs 1 and 2 for the 2006 
PM2.5 and 2012 PM2.5 NAAQS, as discussed below. 
First, we discuss our evaluation of CARB's identification of 
nonattainment and maintenance receptors in western states based on data 
presented in the California Transport Plan as well as the EPA's 
analysis of 2009-2013 24-hour and annual PM2.5 design 
values. Based on this analysis, we present modified lists of such 
receptors (i.e., step one) that largely follow the lists of receptors 
in the California Transport Plan, as presented in Table 3 (for the 2006 
PM2.5 NAAQS) and Table 4 (for the 2012 PM2.5 
NAAQS) of this proposed rule. We include data on the most recent, valid 
design values (e.g., 2014-2016) for each receptor. We then discuss 
California emissions of PM2.5 and its precursors, 
California's regulations to limit such emissions, and the emission 
trends resulting from such regulations.
    Building on the identification of potential nonattainment and 
maintenance receptors and our discussion of California emissions, we 
present our own weight of evidence analysis for addressing the CAA 
requirements. This analysis affirms CARB's weight of evidence analysis 
for the 2006 24-hour PM2.5 and 2012 annual PM2.5 
NAAQS. Like the analytical approach used in the California Transport 
Plan, for each potential receptor area we summarize our analyses of air 
quality data at the applicable receptors, daily 24-hour 
PM2.5 concentrations at the receptors, PM2.5 
design value concentrations at IMPROVE monitoring sites,\95\ local 
emissions and other local factors, and California's emission control 
programs. We prepared a TSD containing our more detailed analysis of 
interstate transport for the 2006 24-hour PM2.5 NAAQS 
(``EPA's PM2.5 Transport TSD''), which is also relevant for 
our evaluation of the 2012 annual PM2.5 NAAQS, and it is 
included in the docket of this proposed rule.\96\
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    \95\ Air quality data from IMPROVE monitoring sites may provide 
an indication of rural background PM2.5 concentrations. 
Low PM2.5 concentrations at IMPROVE sites that coincide 
temporally with high PM2.5 concentrations at nearby 
PM2.5 receptors may indicate a relatively localized 
pollution impact, whereas high PM2.5 concentrations at 
IMPROVE sites may indicate a more regional pollution impact.
    \96\ ``EPA Evaluation of the California Interstate Transport 
Plan (2006 PM2.5 NAAQS), Technical Support Document,'' 
EPA, Region 9, January 2018.
---------------------------------------------------------------------------

    Given the role of regulatory monitoring data in the EPA's analysis 
of interstate transport, the PM2.5 regulatory monitoring 
performed by Pechanga, as well as comments from the Morongo and 
Pechanga during the EPA's rulemaking on California's interstate 
transport SIP for the 1997 ozone and 1997 PM2.5 NAAQS,\97\ 
we have also considered transport to the Morongo and Pechanga 
reservations. Based on our review of such ambient air quality data, as 
described in the EPA's memo to the docket referenced here,\98\ the EPA 
proposes to find that the 24-hour and annual PM2.5 design 
value concentrations at the Pechanga monitor and at monitors nearest to 
the Morongo reservation fall below the levels of the 2006 24-hour 
PM2.5 NAAQS and the 2012 annual PM2.5 NAAQS, and 
thus do not warrant further analysis with respect to interstate 
transport under CAA section 110(a)(2)(D)(i)(I) for any potential 
PM2.5 air quality impacts in the Morongo or Pechanga 
reservations.
---------------------------------------------------------------------------

    \97\ 76 FR 34872 (June 15, 2011). In their comments, Morongo and 
Pechanga called for an analysis of any potential ozone or 
PM2.5 transport to their reservations and for 
consultation with the EPA.
    \98\ Memorandum from Rory Mays, Air Planning Office, Air 
Division, Region XI, EPA, ``Interstate Transport for the 2008 ozone, 
2006 PM2.5, 2012 PM2.5, and 2010 
SO2 NAAQS and the Morongo Band of Mission Indians and the 
Pechanga Band of Luise[ntilde]o Indians,'' January 2018.
---------------------------------------------------------------------------

3. Identification of Receptors
    The EPA's 2012 PM2.5 NAAQS Transport Memo was released 
on March 17, 2016, and presented air quality modeling that identified 
potential nonattainment and maintenance receptors.\99\ The EPA's 
analysis used ambient PM2.5 data from 2009-2013, emissions 
inventory data from the 2011 NEI, photochemical modeling for a 2011 
base year and 2017 and 2025 future years, and other information to 
project annual PM2.5 design values for 2017 and 2025. As 
identified in the 2012 PM2.5 NAAQS Transport Memo, it may be 
appropriate to use this information to help evaluate projected air 
quality in 2021, which is the attainment deadline for 2012 
PM2.5 NAAQS nonattainment areas classified as Moderate. 
Because modeling results are only available for 2017 and 2025, one way 
to assess potential receptors for 2021 is to assume that receptors 
projected to have average and/or maximum design values above the NAAQS 
in both 2017 and 2025 are also likely to be either nonattainment or 
maintenance receptors in 2021. Similarly, it may be reasonable to 
assume that receptors that are projected to attain the NAAQS in both 
2017 and 2025 are not likely to have nonattainment or maintenance 
problems in 2021.
---------------------------------------------------------------------------

    \99\ 2012 PM2.5 NAAQS Transport Memo, Table 1, p. 5.
---------------------------------------------------------------------------

    Where available, we rely on this kind of modeling for interstate 
transport because it accounts for the effect of emission reductions 
from planned federal, state, and local measures, as well as input from 
state, local, industry, and community entities, to project where 
violations, or potential violations, of the NAAQS will occur. By 
aligning the overlapping design value periods (2009-2013) with the 2011 
NEI, we can establish an improved understanding of the relationship 
between emissions of PM2.5 and its precursors to ambient 
PM2.5 concentrations. We have also considered the recent 
2014-2016 design values at the potential nonattainment

[[Page 5387]]

and maintenance receptors identified in the EPA's 2012 PM2.5 
NAAQS Transport Memo.
    We note that CARB's adoption of the California Transport Plan on 
December 17, 2015, preceded the release of the EPA's 2012 
PM2.5 NAAQS Transport Memo. CARB analyzed the overlapping 
design value periods of 2010-2014, albeit without projecting those 
values forward. Given the utility of the EPA's modeling for the reasons 
described above, we have used the list of receptors from the EPA's 2012 
PM2.5 NAAQS Transport Memo as the primary basis for our 
evaluation, while also considering the differences in CARB's list of 
receptors. In addition, we present the 2014-2016 design value data at 
each identified receptor to indicate current air quality. The EPA's 
list of receptors for the 2012 PM2.5 NAAQS appears in Table 
4.
    For the 2006 PM2.5 NAAQS we have derived a list of 
receptors using 2009-2013 design values as the primary basis for our 
evaluation, while considering the differences in CARB's list of 
receptors, as well as the most recent, valid design values (2014-2016, 
where available). We selected this approach to provide a common base of 
ambient air quality and emissions information for PM2.5 for 
both the 24-hour and annual standards. Because neither the EPA nor CARB 
modeled future 24-hour PM2.5 design values, we use the same 
conceptual definition for 24-hour PM2.5 receptors from the 
California Transport Plan--nonattainment receptors are those that 
violate the 2006 24-hour PM2.5 NAAQS in the last of three 
overlapping design value periods (2011-2013); and maintenance receptors 
are those that attain the 2006 24-hour PM2.5 NAAQS in the 
latest period, but violate the standard in either of the preceding two 
design value periods (2009-2011 or 2010-2012). As with the annual 
standard, we also present the 2014-2016 24-hour PM2.5 design 
values at each identified receptor. The EPA's list of receptors for the 
2006 PM2.5 NAAQS appears in Table 3.\100\
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    \100\ Consistent with prior western interstate transport 
actions, we have excluded from this list the receptors in Ravalli, 
Montana (AQS ID 30-081-0007), Missoula, Montana (AQS ID 30-063-
0024), and Jackson, Oregon (AQS ID 41-029-0133) with design values 
that may have been affected by wildfires. See, e.g., 80 FR 9423 
(February 23, 2015), ``Technical Support Document--Idaho [SIP] and 
Interstate Transport Requirements for the 2006 24-hour 
[PM2.5 NAAQS],'' EPA, Region X, January 22, 2015, p. 12.

                                             Table 3--EPA List of Potential Nonattainment and Maintenance Receptors for the 2006 24-Hour PM2.5 NAAQS
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                                                               Most recent valid
                                                             Nonattainment area for                                                                                               design value
               State                         County           2006 PM2.5 NAAQS \a\       AQS ID      CARB receptor type (2010-2014 data)   EPA receptor type (2009-2013 data)   ([micro]g/m\3\)
                                                                                                                                                                                  (2014-2016,
                                                                                                                                                                                except as noted)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Arizona............................  Pinal.................  West Central Pinal....     04-021-3013  Nonattainment......................  (Nonattainment) \b\................                 30
Idaho..............................  Ada...................  ......................     16-001-0010  Not discussed......................  Nonattainment......................     19 (2008-2010)
Idaho..............................  Franklin..............  Logan.................     16-041-0001  Discussed with Cache County, Utah..  Nonattainment......................     46 (2008-2010)
Idaho..............................  Lemhi.................  ......................     16-059-0004  Nonattainment......................  Nonattainment......................                 41
Idaho..............................  Shoshone..............  West Silver Valley         16-079-0017  Nonattainment......................  Nonattainment......................                 39
                                                              (2012 PM2.5 NAAQS).
Montana............................  Silver Bow............  ......................     30-093-0005  Nonattainment......................  Nonattainment......................                 33
Oregon.............................  Crook.................  ......................     41-013-0100  Nonattainment......................  Nonattainment......................                 38
Oregon.............................  Lake..................  ......................     41-037-0001  Nonattainment......................  Nonattainment......................     56 (2013-2015)
Oregon.............................  Lane..................  Oakridge..............     41-039-2013  Nonattainment......................  Nonattainment......................                 31
Oregon.............................  Klamath...............  Klamath Falls.........     41-035-0004  Maintenance........................  Nonattainment......................                 27
Utah...............................  Box Elder.............  Salt Lake City........     49-003-0003  Nonattainment......................  Nonattainment......................                 31
Utah...............................  Cache.................  Logan.................     49-005-0004  Nonattainment......................  Nonattainment......................     45 (2013-2015)
Utah...............................  Salt Lake.............  Salt Lake City........     49-035-3006  Nonattainment......................  Nonattainment......................                 38
Utah...............................  Salt Lake.............  Salt Lake City........     49-035-3010  Nonattainment......................  Nonattainment......................                 42
Utah...............................  Utah..................  Provo.................     49-049-0002  Nonattainment......................  Nonattainment......................                 29
Utah...............................  Utah..................  Provo.................     49-049-4001  Nonattainment......................  Nonattainment......................     43 (2013-2015)
Utah...............................  Utah..................  Provo.................     49-049-5010  Nonattainment......................  Nonattainment......................                 27
Utah...............................  Weber.................  Salt Lake City........     49-057-0002  Maintenance........................  Nonattainment......................     37 (2013-2015)
Montana............................  Lewis and Clark.......  ......................     30-049-0026  Maintenance........................  Maintenance........................                 37
Utah...............................  Davis.................  Salt Lake City........     49-011-0004  Nonattainment......................  Maintenance........................                 34
Utah...............................  Weber.................  Salt Lake City........     49-057-1003  Not discussed......................  Maintenance........................     35 (2011-2013)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ A blank cell in the column for nonattainment area indicates that the monitor is not located in an area currently designated nonattainment for the 2006 PM2.5 NAAQS.
\b\ Although EPA's 2012 PM2.5 Transport Memo did not identify the Pinal County, Arizona monitor as either a nonattainment or maintenance receptor in the 2009-2013 data, we are evaluating it
  here as a nonattainment receptor because it was identified as such in the California Transport Plan.


                                  Table 4--EPA List of Potential Maintenance Receptors for the 2012 Annual PM2.5 NAAQS
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                        2014-2016 design
              State                       County          AQS site ID    CARB receptor type   EPA receptor type    EPA receptor type    value ([micro]g/
                                                                          (2012-2014 data)    (2017 projection)    (2025 projection)         m\3\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Idaho \a\........................  Shoshone...........     16-079-0017  Nonattainment (13.1  Maintenance (Avg.    Maintenance (Max.                 11.9
                                                                         [micro]g/m\3\).      12.43 [micro]g/      12.22 [micro]g/
                                                                                              m\3\).               m\3\).

[[Page 5388]]

 
Pennsylvania.....................  Allegheny..........     42-003-0064  Not discussed......  Maintenance (Max.    Attainment (Max.                  12.8
                                                                                              12.16 [micro]g/      11.65 [micro]g/
                                                                                              m\3\).               m\3\).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ CARB identified the monitor in Lemhi County, Idaho (AQS ID 16-059-0004) as a nonattainment receptor based on a 2012-2014 design value of 12.1
  [micro]g/m\3\. The EPA's modeling for the 2012 PM2.5 NAAQS Transport Memo projects this monitor to be attaining and maintaining the NAAQS in both 2017
  (maximum design value of 11.79 [micro]g/m\3\) and 2025 (maximum design value of 11.65 [micro]g/m\3\). Its 2014-2016 design value is 12.4 [micro]g/
  m\3\.

4. Evaluation of California Control Measures
    We discuss California's control measures before presenting our 
analysis for transport prongs 1 and 2 for each NAAQS because such 
discussion provides a common basis for evaluating the California 
emissions component of CARB's weight of evidence analysis. Also, for 
three precursors, we incorporate our evaluation of California's 
emissions and regulatory programs in sections II.B and II.D of this 
proposed rule for NOX and VOC (for the 2008 ozone NAAQS) and 
SOX (for the 2010 SO2 NAAQS), respectively, given 
their roles as precursors to ambient PM2.5.
    We agree with CARB's general conclusions: That California emissions 
from stationary sources are subject to stringent limits for 
PM2.5 and its precursors, such as those for NOX 
and SOX; that California has a long history of reducing 
emissions through motor vehicle and fuel standards; and that 
California's State and local measures will continue to reduce the 
potential for California emissions to contribute significantly to 
nonattainment, or interfere with maintenance, of the 2006 24-hour 
PM2.5 or 2012 annual PM2.5 NAAQS in any other 
state. This is based on our review of the state and local measures 
cited in the California Transport Plan that limit the emissions of 
PM2.5 and its precursor pollutants and of the applicable 
California emission trends, which are generally decreasing.
    For direct PM2.5 emissions, the California Transport 
Plan cites examples of State and local rules that limit the emission of 
particulate matter (PM), which includes direct PM2.5, and 
cites to the EPA actions approving such measures into the SIP.\101\ 
These include emission standards and test procedures for heavy-duty 
engines and vehicles, passenger cars, light duty trucks, and medium 
duty vehicles; in-use diesel standards for heavy-duty trucks, buses, 
drayage trucks, and off-road vehicles; and inspection and maintenance 
programs. We affirm that these measures limit the emission of PM and 
have been approved into the California SIP.\102\
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    \101\ California Transport Plan, p. 8.
    \102\ See, for example, 77 FR 20308 (April 4, 2012), approving 
Title 13 of the California Code of Regulations (CCR) section 2025, 
commonly referred to as CARB's Truck and Bus Rule, into the 
California SIP.
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    The California Transport Plan also includes examples of air 
district measures for area sources such as those for open burning in 
South Coast and Imperial County, agricultural burning in Sacramento 
Metro and Imperial County, fugitive dust in Mojave Desert, and 
agricultural sources in San Joaquin Valley. We similarly affirm that 
these measures limit the emission of PM and have been approved into the 
California SIP.\103\ More broadly, the California Transport Plan refers 
to control measures that apply to a range of pollutants emitted by 
refineries, manufacturing facilities, cement plants, refinishing 
operations, electricity generation and biomass facilities, boilers, and 
generators.\104\ As a general matter, we affirm that there are many 
SIP-approved rules for such sources that limit the emission of PM and 
its precursors.
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    \103\ See, for example, 66 FR 36170 (July 11, 2001), approving 
Imperial County APCD Rule 421 (``Open Burning,'' amended September 
14, 1999) into the California SIP.
    \104\ California Transport Plan, p. 6.
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    Per our review of the EPA's emissions trends data, from 2000 to 
2016, total statewide PM2.5 emissions, excluding wildfires 
and prescribed fires, decreased by 75 percent, resulting in 2016 
emissions of 99,016 tpy.\105\ As discussed in section II.B.5 of this 
proposed rule, we estimate that California emissions will be reduced 
from 2011 to 2017 by 535 tpd of NOX (28 percent decrease 
from 2011) and 302 tpd of VOC (13 percent decrease from 2011). On a 
longer timeline, from 2000 to 2016, California NOX and VOC 
emissions have decreased by 66 percent and 54 percent, respectively. 
For SO2, total statewide emissions have decreased by 75 
percent from 2000 to 2016. Thus, emissions of each of these pollutants 
has decreased substantially in response to California State and local 
control measures, as well as federal measures for sources outside 
California's regulatory authority.
---------------------------------------------------------------------------

    \105\ 1990-2016 emission inventory spreadsheets of statewide 
emission trends, included in the docket to this rulemaking and 
entitled ``1990-2016 State Tier 1 Annual Average Emission Trends--
RIX Analysis.xls.'' Additional emissions trends data are available 
at: https://www.epa.gov/air-emissions-inventories/air-pollutant-emissions-trends-data.
---------------------------------------------------------------------------

5. Evaluation for the 2006 24-Hour PM2.5 NAAQS
    We summarize our evaluation of the areas encompassing the 18 
nonattainment receptors identified in Table 3 and group them into three 
geographic bins (i.e., Arizona, the Northern Rocky Mountains, and Utah) 
based on the nature of the emission sources affecting the receptors. We 
then summarize our evaluation of the areas encompassing the three 
maintenance receptors identified in Table 3 and group them by the two 
relevant states. The EPA's PM2.5 Transport TSD in the docket 
for this proposed rule contains our more detailed analyses for 
interstate transport prongs 1 and 2.
i. Evaluation for Significant Contribution to Nonattainment (Prong 1)
    CARB discussed the Pinal County, Arizona receptor, which is known 
as the Cowtown monitor. This receptor is in the West Central Pinal 
PM2.5 nonattainment area, approximately 240 km east of the 
California border. The Cowtown area is surrounded by mountain ranges 
with open-ended valleys that could allow transport of air pollution 
from the west. The area's population has grown by 40 percent from 2005 
to 2014 and the VMT has grown by 10 percent between 2005 and 2011. Most 
of the exceedances of the 2006 24-hour PM2.5 NAAQS at the 
Cowtown monitor did not occur during high wind conditions, indicating 
that they were likely due to local rather than transported sources, 
particularly local feedlots and geologic soil, based on speciated 
ambient PM2.5 data. The 24-hour PM2.5 
concentrations at this receptor were the highest in Arizona, yet the 
PM2.5 monitor in Yuma, Arizona, along the California border, 
recorded

[[Page 5389]]

lower concentrations of 15-19 [micro]g/m\3\--well below 35 [micro]g/
m\3\.
    For the Northern Rocky Mountains, which herein includes 
nonattainment receptors in Idaho, Montana, Oregon, and the Cache County 
portion of Utah, we evaluated nine nonattainment receptors. The 
receptors in Idaho and Montana are 360-740 km from California while 
those in Oregon are 25-255 km from California. All nine are separated 
from California by various mountain ranges. Locally, the receptors are 
surrounded by mountains that in some cases rise several thousand feet 
above the mountain basins, forming a topographical barrier to 
PM2.5 transport and often trapping PM2.5 
pollution near the surface during wintertime temperature inversions. 
For example, the receptors in Franklin County, Idaho and Cache County, 
Utah are surrounded by the Wasatch-Cache, Bear River, Monte Cristo, and 
Wellsville mountain ranges that rise 3,000 to 5,000 feet above the 
valley floor. These areas tend to have small populations with VMT 
increases or decreases of 20 percent or less from 2005 to 2011.
    The highest 24-hour PM2.5 concentrations in each area 
are generally observed in winter, with certain receptors, representing 
counties in Idaho (Lemhi and Shoshone), Montana (Silver Bow), and 
Oregon (Lake and Lane), that appear to have been affected by wildfire 
in summer or fall. The PM2.5 concentrations at IMPROVE 
monitors nearest each of these receptors, including IMPROVE monitors 
between California and the receptors, were generally low when elevated 
PM2.5 concentrations were recorded at the receptors, in 
winter. Where available, limited chemical speciation and meteorological 
data during cold PM2.5 episodes indicate that transport of 
air pollution from the periphery of such areas is limited and that 
PM2.5 is formed from local emission sources through 
secondary formation of PM2.5. Residential wood burning, 
especially during winter inversions, is considered the primary 
contributor to 24-hour PM2.5 exceedances. Additional sources 
contributing to such exceedances vary by area and may include mobile 
sources and agricultural activities (e.g., open burning).
    For Utah, we evaluated seven nonattainment receptors that are 
either in the Salt Lake City or Provo nonattainment area for the 2006 
PM2.5 NAAQS. Both areas are valleys bordered to the east by 
the Wasatch Mountains, to the west by the Stansbury and Promontory 
Mountains and the Great Salt Lake for Salt Lake City, and by the 
Oquirrh Mountains and Utah Lake for Provo. While they are designated 
separately, the EPA has determined that the two areas share an airshed. 
These areas are about 700 km from the California border and separated 
from California by the Sierra Nevada mountain range and the Great 
Basin, a large area comprised of depressions and flats scattered 
between smaller mountain ranges in Nevada and Utah. Approximately 80 
percent of the population of Utah resides in the counties with 
nonattainment receptors identified in CARB's and the EPA's analyses, 
with county population increases ranging from 11-26 percent from 2005 
to 2014 and county VMT changes ranging from a 62 percent decrease in 
Weber County to a 116 percent increase in Box Elder County from 2005 to 
2011.
    The highest 24-hour PM2.5 concentrations in these two 
nonattainment areas primarily occur during winter, with occasional 
spikes in other seasons. IMPROVE monitors between California and the 
Salt Lake City and Provo nonattainment areas, including Bryce Canyon 
and Zion National Parks in Utah and Jarbidge Wilderness Area in Nevada, 
recorded their highest 24-hour PM2.5 concentrations in 
summer, and their concentrations were generally low when elevated 
PM2.5 concentrations were recorded at the Salt Lake City and 
Provo receptors, in winter.\106\ Most of the ambient PM2.5 
in the urban portions of these nonattainment areas is generated locally 
and trapped during winter inversions. Transport between the Salt Lake 
City and Provo areas can occur during these inversions, as there is a 
gap in the mountains separating these areas below their average 
inversion heights.
---------------------------------------------------------------------------

    \106\ States' contributions to the best and worst visibility 
days at IMPROVE monitors were modeled to address requirements of the 
EPA's regional haze rule. 64 FR 35714 (July 1, 1999), and later 
revised at 82 FR 3078 (January 10, 2017). The California Transport 
Plan notes that while the percentage of contributions from 
California are highest for the worst visibility days at these 
IMPROVE monitors, these days occurred during summer months and would 
not, therefore, affect winter exceedances at the receptors in Utah. 
California Transport Plan, p. A-54 and Appendix E.1. The modeling 
data are available at: http://vista.cira.colostate.edu/TSS/Results/HazePlanning.aspx.
---------------------------------------------------------------------------

    We have reviewed the information compiled and presented in the 
California Transport Plan, including distance of relevant receptors 
from California; intervening terrain; potential wildfire effects; 
chemical speciation data; local topography; the effect of local 
emission sources, particularly residential wood burning and, in certain 
cases, other sources (e.g., mobile sources, agricultural activities), 
on wintertime exceedances; and regional background levels represented 
by IMPROVE data. We have reviewed California's emissions and emission 
control programs for PM2.5 and its precursors, especially 
for NOX and SOX, and conclude that California has 
an extensive and effective program for limiting emissions of such 
pollutants. Thus, we propose that California will not significantly 
contribute to nonattainment of the 2006 24-hour PM2.5 NAAQS 
in any western state.
    The California Transport Plan did not evaluate PM2.5 
transport to states farther east than Montana, Wyoming, Colorado, and 
New Mexico. To evaluate the potential for transport of PM2.5 
and its precursors to states farther east, we have reviewed modeling 
data from the CSAPR and recent air quality data to identify the 
westernmost area in the East \107\ with a potential nonattainment 
receptor. We then compared California's likely contributions to those 
of states in the East that may significantly contribute to 
nonattainment at that receptor, considering several pieces of evidence.
---------------------------------------------------------------------------

    \107\ For purposes of the PM2.5 evaluation in this 
notice, ``the East'' refers to the 37 states and Washington, DC that 
lie east of the states of Montana, Wyoming, Colorado, and New 
Mexico. The EPA modeled the contribution of states within the East 
to each receptor for CSAPR, but did not model the contribution of 
any state further west, such as California.
---------------------------------------------------------------------------

    CSAPR identified nonattainment receptors for the 2006 
PM2.5 NAAQS in numerous eastern states using a 2012 base 
case and projected forward to 2014.\108\ The westernmost of these was 
in Madison County, Illinois (AQS ID 171191007), which is across the 
Mississippi River from St. Louis, Missouri. We looked at the 
westernmost of these states because its relative position with respect 
to California might help to determine whether the EPA should evaluate 
PM2.5 transport to any state farther east. In reviewing 
recent air quality data, including 2014-2016 24-hour PM2.5 
design values, very few of those receptors recorded ambient 24-hour 
PM2.5 concentrations above 35 [micro]g/m\3\ (e.g., Allegheny 
County (Pittsburgh), Pennsylvania).\109\ Notwithstanding, we further 
examined the Madison receptor as the westernmost potential 
nonattainment receptor in the East.
---------------------------------------------------------------------------

    \108\ 76 FR 48208 at 48242-48243 (August 8, 2011), Table V.D-5.
    \109\ EPA 2016 Design Value Reports, spreadsheet entitled 
``Table 6, Site DV History,'' July 14, 2017, available at: https://www.epa.gov/air-trends/air-quality-design-values#report. We note 
that data quality issues in Illinois and four counties in Florida 
prevent the calculation of valid design values for recent years.
---------------------------------------------------------------------------

    The westernmost states that were linked (i.e., contributing over 
one

[[Page 5390]]

percent (0.35 [micro]g/m\3\) of the 2006 24-hour PM2.5 
NAAQS) to the Madison receptor in CSAPR were Kansas and Texas, which 
were each projected to contribute 0.37 [micro]g/m\3\ to this receptor 
and are about 385 km and 680 km, respectively, from this receptor.\110\ 
The other states situated along a similar western longitude, including 
North Dakota, South Dakota, Nebraska, and Oklahoma, were not linked to 
the receptor. Because Kansas and Texas were among the westernmost 
states analyzed within CSAPR, we compared their emissions with those of 
California. In the CSAPR 2014 base case, Kansas was projected to emit 
248,692 tpy of NOX and 117,050 tpy of SO2, and 
Texas was projected to emit 1,372,735 tpy of NOX and 704,311 
tpy of SO2.\111\
---------------------------------------------------------------------------

    \110\ ``Air Quality Modeling Final Rule [TSD]'' for the CSAPR 
final rule, EPA, June 2011, pp. D-11 to D-12.
    \111\ ``Emissions Inventory Final Rule [TSD]'' for the CSAPR 
final rule, EPA, June 28, 2011, Tables 7-1 and 7-2.
---------------------------------------------------------------------------

    By comparison, California is about 2,215 km from the Madison 
receptor and is separated from Illinois by the Rocky Mountains and the 
Great Plains. California's projected 2014 base case emissions were 
942,254 tpy of NOX and 119,268 tpy of SO2. Thus, 
California's NOX emissions were between those of Kansas (26 
percent of California's) and Texas (146 percent of California's) and 
its SO2 emissions were comparable to those of Kansas (98 
percent of California's) and much less than those of Texas (591 percent 
of California's). California is also much farther away (5.7 times the 
distance from Kansas to the receptor and 3.3 times the distance from 
Texas to the receptor).
    As summarized in section II.C.5 of this proposed rule, in response 
to California State and local control measures, as well as federal 
measures for sources outside California's regulatory authority, from 
2000 to 2016 California's total statewide emissions, excluding 
wildfires and prescribed fires, decreased by 75 percent for 
PM2.5, 66 percent for NOX, 54 percent for VOCs, 
and 75 percent for SO2. For NOX and VOCs, these 
reductions are consistent with the EPA's projection that California 
emissions will be reduced by 28 percent for NOX and 13 
percent for VOCs from 2011 to 2017. We reviewed the 24-hour 
PM2.5 design value history over the last decade for the 
Madison receptor and found that it has decreased from 39 [micro]g/m\3\ 
for 2005-2007 to 29 [micro]g/m\3\ for 2008-2010, with subsequent design 
values being invalid due to data quality issues.\112\
---------------------------------------------------------------------------

    \112\ EPA 2016 Design Value Reports, spreadsheet entitled 
``Table 6, Site DV History,'' July 14, 2017, available at: https://www.epa.gov/air-trends/air-quality-design-values#report.
---------------------------------------------------------------------------

    We conclude that California emission sources will not significantly 
contribute to nonattainment of the 2006 PM2.5 NAAQS at this 
site. This is based on the generally improved air quality in the East 
since the EPA's analysis in 2011 for CSAPR, which reduced the number of 
potential nonattainment receptors; the distance of the Madison County, 
Illinois receptor from California; intervening terrain; our analysis of 
the westernmost states linked to the Madison receptor and comparison of 
California emissions; the large reductions in emissions of 
PM2.5 and its precursors in California; and the trend of 
decreasing 24-hour PM2.5 concentrations at the Madison 
receptor. As the distance from California to the other potential 
eastern nonattainment receptors is even greater, the expected 
contribution from California to 24-hour PM2.5 concentrations 
at such receptors would be even smaller.
ii. Evaluation for Interference With Maintenance (Prong 2)
    The Lewis and Clark County maintenance receptor is in the Helena 
Valley of Montana and is surrounded by mountain ranges, including the 
Lewis Range to the north, the Absaroka Range to the south, and the 
Bitterroot Mountains to the west. It is about 800 km from the northeast 
corner of California, is separated from California by the Sierra 
Nevada, Blue, and Bitterroot mountain ranges, and its population has 
increased by 13 percent from 2005 to 2014 while its VMT has decreased 
by almost 60 percent. The highest 24-hour PM2.5 
concentrations generally occur in winter, consistent with the area's 
wintertime cold pool inversions, with lower concentrations in summer. 
The site has generally recorded 24-hour PM2.5 concentrations 
well below 35 [micro]g/m\3\, except for 2011 and 2012, which appear to 
have been affected by wildfire and whose corresponding design values 
(e.g., for 2009-2011, 2010-2012, and 2011-2013) exceeded the 2006 
PM2.5 NAAQS. During the months when exceedances were 
recorded at the Helena receptor, PM2.5 concentrations 
recorded at the IMPROVE monitor at the nearby Gate of the Mountains 
Wilderness Area were generally low. The EPA has concluded that 
emissions from residential wood burning were the largest source of 
PM2.5 emissions in the area.
    The Davis and Weber Counties maintenance receptors are in the 
northern part of the Salt Lake City nonattainment area for the 2006 
PM2.5 NAAQS. As noted above, this area is bordered to the 
east by the Wasatch Mountains and to the west by the Stansbury and 
Promontory Mountains and the Great Salt Lake. These receptors are about 
700 km from the California border and are separated from California by 
the Sierra Nevada mountain range and the Great Basin. The populations 
for Davis and Weber Counties, which are largely concentrated in the 
urban areas of the Wasatch Front, have increased by 23 percent and 14 
percent, respectively, from 2005 to 2014, while VMT has decreased by 23 
percent and 62 percent, respectively, from 2005 to 2011. Over the last 
decade, 24-hour PM2.5 concentrations have generally remained 
above the 2006 PM2.5 NAAQS and the highest concentrations 
primarily occur during winter, with occasional spikes in other seasons. 
Most of the ambient PM2.5 in the urban area is generated 
locally and trapped during winter inversions, with some transport to 
and from the adjacent Provo, Utah nonattainment area. IMPROVE monitors 
between California and Davis and Weber Counties, Utah, including Bryce 
Canyon and Zion National Parks in Utah and Jarbidge Wilderness Area in 
Nevada, recorded their highest 24-hour PM2.5 concentrations 
in summer, and were generally low when elevated PM2.5 
concentrations were recorded at the Davis and Weber Counties' 
receptors, in winter.
    We have reviewed the information compiled and presented in the 
California Transport Plan, including distance of these receptors from 
California; intervening terrain; potential wildfire effects; local 
topography; the effect of local emission sources on wintertime 
exceedances; and rural background levels represented by IMPROVE data. 
We have reviewed California's emissions and emission control programs 
for PM2.5, and its precursors, especially for NOX 
and SOX, and conclude that California has an extensive and 
effective program for limiting emissions of such pollutants. Thus, we 
propose that California will not interfere with maintenance of the 2006 
PM2.5 NAAQS in any western state.
    The California Transport Plan did not evaluate PM2.5 
transport to states farther east than Montana, Wyoming, Colorado, and 
New Mexico. As with our evaluation for prong 1, above, to evaluate the 
potential for transport of PM2.5 and its precursors to 
eastern states, we have reviewed modeling data from CSAPR and recent 
air quality data to identify the westernmost area in the east with a 
potential maintenance

[[Page 5391]]

receptor.\113\ We then compared California's likely contributions to 
those of states in the east that may interfere with maintenance at that 
receptor, considering several pieces of evidence.
---------------------------------------------------------------------------

    \113\ The EPA modeled the contribution of states within the East 
to each receptor for CSAPR, but did not model the contribution of 
any state further west, such as California.
---------------------------------------------------------------------------

    CSAPR identified maintenance receptors for the 2006 
PM2.5 NAAQS in numerous eastern states using a 2012 base 
case and projected forward to 2014.\114\ The westernmost of these was 
in Madison County, Illinois (AQS ID 171190023).\115\ As with our 
analysis for prong 1, we looked at the westernmost of these states 
because its relative position with respect to California might help to 
determine whether the EPA should evaluate PM2.5 transport to 
any state farther east. In reviewing recent air quality data, including 
2014-2016 24-hour PM2.5 design values, many of those 
receptors recorded ambient 24-hour PM2.5 concentrations 
consistently below 35 [micro]g/m\3\.\116\ Notwithstanding, we further 
examined this Madison receptor as the westernmost potential maintenance 
receptor in the East.
---------------------------------------------------------------------------

    \114\ 76 FR 48208 at 48243-48244 (August 8, 2011), Table V.D-6.
    \115\ Note that this monitor is distinct from the monitor 
discussed for prong 1 (AQS ID 171191007), although both are in 
Madison County, Illinois.
    \116\ EPA 2016 Design Value Reports, spreadsheet entitled 
``Table 6, Site DV History,'' July 14, 2017, available at: https://www.epa.gov/air-trends/air-quality-design-values#report. We note 
that data quality issues in Illinois and four counties in Florida 
prevent the calculation of valid design values for recent years.
---------------------------------------------------------------------------

    The westernmost states that were linked to this Madison receptor 
(i.e., contributing over one percent (0.35 [micro]g/m\3\) of the 2006 
24-hour PM2.5 NAAQS) were Iowa and Missouri, which each 
share a border with Illinois. Iowa was projected to contribute 0.40 
[micro]g/m\3\ and is about 220 km from this receptor, while Missouri 
was projected to contribute 3.71 [micro]g/m\3\ and is about 5 km from 
this receptor.\117\ The six states that were analyzed within CSAPR and 
are situated west of Iowa and Missouri, including North Dakota, South 
Dakota, Nebraska, Kansas, Oklahoma, and Texas, were not linked to the 
Madison receptor. As discussed in our evaluation for prong 1, above, we 
compared the 2014 base case NOX and SO2 emissions 
of Kansas and Texas to those of California. Because these states are 
not linked to the potential Madison maintenance receptor, and because 
California is even farther (about 2,215 km) from the receptor and is 
separated from this receptor by the Rocky Mountains and Great Plains, 
it would be even less likely for California to interfere with 
maintenance at this site than Kansas and Texas.
---------------------------------------------------------------------------

    \117\ ``Air Quality Modeling Final Rule [TSD]'' for the CSAPR 
final rule, EPA, June 2011, pp. D-13 to D-14.
---------------------------------------------------------------------------

    Furthermore, as summarized in the section II.C.5 of this proposed 
rule, in response to California and local control measures, as well as 
federal measures for sources outside California's regulatory authority, 
from 2000 to 2016 California's total statewide emissions, excluding 
wildfires and prescribed fires, decreased by 75 percent for 
PM2.5, 66 percent for NOX, 54 percent for VOCs, 
and 75 percent for SO2. For NOX and VOCs, these 
reductions are consistent with the EPA's projection that California 
emissions will be reduced by 28 percent for NOX and 13% for 
VOCs from 2011 to 2017.
    We conclude that California emission sources will not interfere 
with maintenance of the 2006 PM2.5 NAAQS at this site. This 
is based on the generally improved air quality in the East since the 
EPA's analysis in 2011 for CSAPR, which identified fewer potential 
maintenance receptors; the distance of the potential Madison County, 
Illinois maintenance receptor from California; intervening terrain; our 
analysis of the westernmost states linked, and not linked, to the 
Madison receptor and comparison of California emissions; and the large 
reductions in emissions of PM2.5 and its precursors in 
California. As the distance from California to the other potential 
eastern maintenance receptors is even greater, the expected 
contribution from California to 24-hour PM2.5 concentrations 
at such receptors would be even smaller. Thus, we propose that 
California will not interfere with maintenance of the 2006 
PM2.5 NAAQS in any state farther east than Montana, Wyoming, 
Colorado, and New Mexico.
6. Evaluation for the 2012 Annual PM2.5 NAAQS
    We agree with CARB that California does not significantly 
contribute to nonattainment, or interfere with maintenance, of the 2012 
annual PM2.5 NAAQS in any other state. However, there were 
some differences between the receptors identified by CARB and those 
identified by the EPA that affects which areas we evaluated for 
interstate transport. CARB identified two monitors in Idaho (Lemhi and 
Shoshone Counties) as nonattainment receptors, i.e., they exceeded the 
2012 PM2.5 NAAQS (12.0 [micro]g/m\3\) in the most recent 
period available at the time the SIP was developed (2012-2014). CARB 
looked to identify maintenance receptors as monitors that exceeded the 
standard in either the 2010-2012 or 2011-2013 design value periods, but 
not in 2012-2014, and found none.\118\ This method is consistent with 
past EPA practice for the 2006 PM2.5 NAAQS in the western 
U.S. because CARB adopted the California Transport Plan before the EPA 
released the 2012 PM2.5 NAAQS Transport Memo.
---------------------------------------------------------------------------

    \118\ California Transport Plan, App. B, p. B-2.
---------------------------------------------------------------------------

    As discussed above, the EPA's modeling used ambient 
PM2.5 data from 2009-2013, emissions inventory data from the 
2011 NEI, and other information to project annual PM2.5 
design values for 2017 and 2025. We rely on this modeling for the 2012 
PM2.5 NAAQS because it accounts for the effect of emission 
reductions from planned federal, state, and local measures, as well as 
input from state, local, industry, and community entities, to project 
where violations, or potential violations, of the NAAQS will occur. In 
other words, the modeling provides a more accurate accounting of the 
areas that warrant further analysis for interstate transport. In 
addition, where projected design values for 2017 and 2025 differ with 
respect to identification of receptors, we have evaluated what the 
projected air quality may be in 2021, as noted in section II.C.3 of 
this proposed rule.
    The EPA's 2012 PM2.5 NAAQS Transport Memo did not 
identify any potential nonattainment receptors outside of California 
for the 2012 annual PM2.5 NAAQS, but did identify a 
potential maintenance receptor in Shoshone County, Idaho and a 
potential maintenance receptor in Allegheny County, Pennsylvania. 
Accordingly, we have evaluated CARB's weight of evidence for Shoshone 
County as a maintenance receptor rather than a nonattainment receptor.
    For Lemhi County, the receptor was not identified in the EPA's 
modeling but was identified as a nonattainment receptor by CARB. Thus, 
while we have not included the Lemhi County monitor as either a 
nonattainment or maintenance receptor for the 2012 PM2.5 
NAAQS, we include discussion of Lemhi County alongside our discussion 
of Shoshone County, given their similar characteristics with respect to 
PM2.5 air pollution and its similar location relative to 
California. While we have not prepared a separate TSD for our 
evaluation of interstate transport for the 2012 PM2.5 NAAQS, 
we do rely, in part, on the information presented in the EPA's 
PM2.5 Transport TSD (for the 2006 24-hour PM2.5 
NAAQS) given the importance of generally higher winter PM2.5 
concentrations to the annual

[[Page 5392]]

concentrations, particularly at the Idaho receptors.
    In addition, we include our own weight of evidence analysis with 
respect to Allegheny County because the California Transport Plan did 
not evaluate PM2.5 transport to states farther east than 
Montana, Wyoming, Colorado, and New Mexico.
i. Evaluation for Interference With Maintenance (Prong 2)
    For Lemhi and Shoshone Counties, as described in our analysis for 
the 2006 24-hour PM2.5 NAAQS above, CARB notes that both 
counties are largely mountainous and the monitors are located in 
valleys that lie approximately 3,000 feet below surrounding mountain 
peaks, which limit the transport of air pollution.\119\ The receptors 
are about 610 and 685 km, respectively, from the northeast corner of 
California and are separated from California by the Sierra Nevada, 
Cascade, and Bitterroot mountain ranges. Both areas are rural with 
small, decreasing populations and decreasing VMT. The receptor in 
Shoshone County is within the West Silver Valley nonattainment area for 
the 2006 PM2.5 NAAQS.
---------------------------------------------------------------------------

    \119\ California Transport Plan, App. B.
---------------------------------------------------------------------------

    CARB states that the IMPROVE monitors at the Craters of the Moon 
National Park and Sawtooth National Forest in Idaho recorded single-
year annual PM2.5 concentrations that are well below the 
annual standard (i.e., in the range of 2-7 [micro]g/m\3\), that the 
highest 24-hour PM2.5 concentrations at these monitors are 
directly linked to western wildfires, and that weighted emission 
potential (WEP) analyses indicate that the worst visibility days are 
the result of more localized regional influences.\120\ CARB asserts 
that the IMPROVE data and WEP analyses indicate that even on the worst 
days, there are only minor impacts from California and that 
California's contributions occur most often during the days with the 
best visibility.
---------------------------------------------------------------------------

    \120\ Id., App. B, pp. B-4 to B-5.
---------------------------------------------------------------------------

    CARB notes that highest 24-hour PM2.5 concentrations are 
observed in winter, that the lowest concentrations are generally 
observed in summer, and that wildfire impacts occurred in August-
September 2012 when such concentrations exceeded 200 [micro]g/
m\3\.\121\ CARB states that residential wood burning, especially during 
winter inversions, is the primary contributor to exceedances of both 
the 24-hour and annual PM2.5 NAAQS at the Lemhi and Shoshone 
Counties monitors, aside from the 2012 wildfire effects. For the 
Shoshone receptor, motor vehicles were also identified as a primary 
contributor, as well as open burning and slash burning.
---------------------------------------------------------------------------

    \121\ Id., App. B, pp. B-7 to B-8 for Lemhi County and pp. B-10 
to B-11 for Shoshone County.
---------------------------------------------------------------------------

    We have reviewed the information compiled and presented in the 
California Transport Plan, including distance of these monitors from 
California; intervening terrain; wildfire effects; local topography; 
the effect of local emission sources on wintertime exceedances of the 
24-hour NAAQS and the effect of those exceedances on annual 
PM2.5 concentrations; and rural background levels 
represented by IMPROVE data. We have reviewed California's emissions 
and emission control programs for PM2.5, and its precursors, 
especially for NOX and SOX, and conclude that 
California has an extensive and effective program for limiting 
emissions of such pollutants. Thus, we propose that California will not 
interfere with maintenance of the 2012 PM2.5 NAAQS in Idaho 
or any other western state.
    To evaluate the potential for transport of PM2.5 and its 
precursors to Allegheny County, Pennsylvania, we first examined whether 
this monitor should in fact be a maintenance receptor given that the 
EPA's 2012 PM2.5 NAAQS Transport Memo indicates that the 
monitor is projected to exceed the annual PM2.5 standard of 
12.0 [micro]g/m\3\ in 2017, but be below it in 2025.\122\ Areas 
initially designated as Moderate nonattainment areas for the 2012 
PM2.5 NAAQS, such as Allegheny County, must attain the NAAQS 
by December 31, 2021. A simple linear interpolation between the 2017 
and 2025 projected design values leads to a projected 2021 average 
design value of 11.42 [mu]g/m\3\ and a 2021 maximum design value of 
11.91 [mu]g/m\3\, which are both below the 2012 PM2.5 NAAQS.
---------------------------------------------------------------------------

    \122\ 2012 PM2.5 NAAQS Transport Memo, Table A-3, p. 
7. Average design values, which represent nonattainment receptors, 
are projected to be 11.67 [micro]g/m\3\ in 2017 and 11.18 [micro]g/
m\3\ in 2025 at the Allegheny County receptor. Maximum design 
values, which represent maintenance receptors, are projected to be 
12.15 [micro]g/m\3\ in 2017 and 11.65 [micro]g/m\3\ in 2025.
---------------------------------------------------------------------------

    The Allegheny receptor is about 3,100 km from the California border 
and is separated from California by the Rocky Mountains, the Great 
Plains, and the Ohio Valley. Even with the generally westerly wind 
direction from California, this large distance and the intervening 
mountainous terrain serve as barriers to PM2.5 transport to 
Allegheny County. In EPA modeling for the 2006 PM2.5 NAAQS 
in the CSAPR final rule, the receptor in Allegheny County was linked to 
interference with maintenance from other states.\123\ While California 
was not analyzed in that modeling, some conclusions can be drawn from 
the results. First, Illinois was the most westward and distant state 
linked to the Allegheny receptor and it is about 650 km from the 
receptor, or about one-fifth of the distance from California to the 
receptor. Second, states farther west than Illinois, such as Arkansas, 
Iowa, Kansas, Missouri, Nebraska, Oklahoma, and Texas, were all 
included in the modeling and were not linked to Allegheny County, i.e., 
the contribution of these states to the Allegheny County receptor was 
below the one percent contribution threshold used in CSAPR for the 2006 
24-hour PM2.5 NAAQS. These states are each closer to 
Allegheny County than California and, in the case of Texas, emitted 
larger amounts of NOX and SO2.\124\
---------------------------------------------------------------------------

    \123\ 76 FR 48207, 48241 (August 8, 2011), Table V.D-3.
    \124\ ``Emissions Inventory Final Rule [TSD]'' for the CSAPR 
final rule, EPA, June 28, 2011, Tables 7-1 and 7-2. The 2014 (base 
case) total annual emissions for California and Texas were as 
follows: California (942,254 tpy NOX and 199,268 tpy 
SO2); Texas (1,372,735 tpy NOX and 704,311 tpy 
SO2).
---------------------------------------------------------------------------

    Consistent with our guidance, we have also considered additional 
information about emissions and air quality trends. As summarized in 
section II.C.5 of this proposed rule, in response to California State 
and local control measures, as well as federal measures for sources 
outside California's regulatory authority, from 2000 to 2016 
California's total statewide emissions, excluding wildfires and 
prescribed fires, decreased by 75 percent for PM2.5, 66 
percent for NOX, 54 percent for VOCs, and 75 percent for 
SO2. For NOX and VOCs, these reductions are 
consistent with the EPA's projection that California emissions will be 
reduced by 28 percent for NOX and 13 percent for VOCs from 
2011 to 2017. We reviewed the annual PM2.5 design value 
history over the last decade for the Allegheny receptor and found that 
it has decreased steadily from 19.8 [micro]g/m\3\ for 2005-2007 to 12.6 
[micro]g/m\3\ for 2013-2015, with a slight increase to 12.8 [micro]g/
m\3\ for 2016.\125\
---------------------------------------------------------------------------

    \125\ EPA 2016 Design Value Reports, spreadsheet entitled 
``Table 6, Site DV History,'' July 14, 2017, available at: https://www.epa.gov/air-trends/air-quality-design-values#report.
---------------------------------------------------------------------------

    We conclude that California emission sources will not interfere 
with maintenance of the 2012 PM2.5 NAAQS at this site. This 
is based on our interpolated projection that the Allegheny monitor will 
likely be attaining the annual PM2.5 NAAQS in 2021; the 
distance of this receptor from California; intervening terrain; the 
contribution modeling performed for

[[Page 5393]]

CSAPR; the large reductions in emissions of PM2.5 and its 
precursors in California; and the general trend of decreasing annual 
PM2.5 concentrations at the Allegheny receptor.
    Based on our analysis that there are no nonattainment receptors 
outside of California for the 2012 PM2.5 NAAQS, and our 
analysis presented above for the sole maintenance receptors in Idaho 
and Pennsylvania, we propose that California will not significantly 
contribute to nonattainment, or interfere with maintenance, of the 2012 
PM2.5 NAAQS in any other state.

D. Evaluation for the 2010 1-Hour SO2 NAAQS

1. The EPA's SO2 Evaluation Approach
    As noted in section II.A of this proposed rule, the EPA first 
reviewed the California Transport Plan to assess how the State 
evaluated the transport of SO2 to other states, the types of 
information California used in its analysis, how that analysis compares 
with prior EPA rulemaking, modeling, and guidance, and the conclusions 
drawn by California. The EPA then conducted a weight of evidence 
analysis, including review of the State's submission and other 
available information, including air quality, emission sources, and 
emission trends in the states bordering California, and California's 
air quality, emissions sources, control measures, and emission trends.
    Although SO2 is emitted from a similar universe of point 
and nonpoint sources, interstate transport of SO2 is unlike 
the transport of PM2.5 or ozone because SO2 is 
not a regional pollutant and does not commonly contribute to widespread 
nonattainment over a large (and often multi-state) area. The transport 
of SO2 is more analogous to the transport of lead (Pb) 
because its physical properties result in localized pollutant impacts 
very near the emissions source. However, ambient concentrations of 
SO2 do not decrease as quickly with distance from the source 
as Pb because of the physical properties and release height of 
SO2. Emissions of SO2 travel farther and have 
wider ranging impacts than emissions of Pb but do not travel far enough 
to be treated in a manner similar to ozone or PM2.5. The 
approaches that the EPA has adopted for ozone or PM2.5 
transport are too regionally focused and the approach for Pb transport 
is too tightly circumscribed to the source. SO2 transport is 
therefore a unique case and requires a different approach. The EPA's 
evaluation of whether California has met its transport obligations was 
accomplished in several discrete steps, as described in section II.D.3 
of this proposed rule.
2. State's Submission
    The California Transport Plan presents a weight of evidence 
analysis to examine whether SO2 emissions from California 
adversely affect attainment or maintenance of the 2010 SO2 
NAAQS in other states. In contrast to its ozone and PM2.5 
analyses, CARB states that ambient SO2 is mainly derived 
from a single source or group of sources, that the highest 
concentrations are localized, and that the EPA has identified 
SO2 as a near-source pollutant.\126\ CARB finds that ambient 
SO2 monitoring in neighboring states (Arizona, Nevada, and 
Oregon) is limited and that, except for sites adjacent to large copper 
smelters in Arizona, 1-hour SO2 concentrations measured in 
these three states and California are well below the level of the 2010 
SO2 NAAQS, i.e., 75 ppb. Therefore, CARB's weight of 
evidence analysis focused on the location and emissions of facilities 
in California, Arizona, Nevada, and Oregon; the ambient SO2 
levels measured in each of these states; ambient SO2 trends 
in California; and the distance between facilities in California and 
the nearest state border.\127\ CARB concludes that California does not 
contribute to nonattainment, or interfere with maintenance, of the 2010 
SO2 NAAQS in neighboring states.\128\
---------------------------------------------------------------------------

    \126\ California Transport Plan, pp. 1, 12-13. CARB further 
explains that SO2 is a highly reactive gas and is 
deposited locally through wet and dry deposition processes. 
California Transport Plan, App. C, p. C-10.
    \127\ California Transport Plan, pp. 12-14.
    \128\ Id., p. 23.
---------------------------------------------------------------------------

    The California Transport Plan identified 31 facilities in 
California that emit more than 100 tpy of SOX, based on 
CARB's 2013 Facility Emissions Inventory.\129\ Of these, CARB explains 
that those emitting over 300 tpy of SOX are located more 
than 160 miles (257 km) from the nearest state border--well beyond the 
one- to two-mile radius within which CARB expects maximum 
SO2 concentrations to occur.\130\ These facilities include 
petroleum refineries in the Bay Area and South Coast air districts, and 
cement plants in the Bay Area and Kern County air districts. Of these, 
only two emitted more than 1,000 tpy: Shell Martinez Refinery (1,230 
tpy) and Phillips 66 Carbon Plant (1,242 tpy), a calcined petroleum 
coke plant, which are both located in Contra Costa County in the San 
Francisco Bay Area. CARB also notes that no facility in California 
emits more than the 2,000 tpy threshold required for characterization 
per the EPA's Data Requirements Rule for the 2010 SO2 NAAQS 
(``SO2 Data Requirements Rule'').\131\
---------------------------------------------------------------------------

    \129\ Id., App. C, p. C-6. CARB's Facility Emission Inventory is 
available at: http://www.arb.ca.gov/app/emsinv/facinfo/facinfo.php.
    \130\ Id., App. C, p. C-10. As noted previously in this proposed 
rule, CARB's analysis of California SO2 emissions in 
based on SOX because CARB estimates that SO2 
comprises 97% of the state-wide SOX inventory. California 
Transport Plan, App. C, p. C-1. The EPA notes that the presence of 
maximum SO2 concentrations within a narrow radius of a 
source does not automatically preclude the possibility of the source 
contributing to SO2 concentrations further afield.
    \131\ 80 FR 51052 (August 21, 2015). The EPA's SO2 
Data Requirements Rule required states to characterize air quality 
in areas around sources emitting over 2,000 tpy SO2 since 
the existing nationwide monitoring network had certain limitations 
and approximately two-thirds of the monitors were not located to 
characterize maximum 1-hour SO2 concentration impacts 
from emission sources. We also note that, while CARB found that no 
facility in California emitting more than 2,000 tpy SO2, 
there is a cluster of three sources in Contra Costa County that 
cumulatively emitted over this threshold and was subsequently 
characterized using monitoring. We have evaluated this cluster of 
sources as part of our SO2 interstate transport analysis.
---------------------------------------------------------------------------

    More broadly, CARB contrasts the larger SO2 emissions in 
the eastern U.S., which include electric generation facilities that 
emit in the tens to hundreds of thousands of tons of SO2, 
with the smaller SO2 emissions from California, where the 
largest facility emitted 1,242 tpy in 2013.\132\ CARB further explains 
that the latter source (the Phillips 66 Carbon Plant) is 587 miles (945 
km), 177 miles (285 km), and 361 miles (581 km) from the borders with 
Arizona, Nevada, and Oregon, respectively.\133\
---------------------------------------------------------------------------

    \132\ California Transport Plan, App. C, pp. C-1 to C-2.
    \133\ Id., App. C, p. C-4.
---------------------------------------------------------------------------

    Regarding ambient SO2 measurements, CARB found the 1-
hour SO2 design value concentrations in Arizona, Nevada, and 
Oregon to be well below 75 ppb, with two exceptions: Monitoring sites 
around two copper smelters in eastern Arizona (Gila and Pinal 
Counties). Overall, CARB states that Arizona operated nine 
SO2 monitors for the 2012-2014 period and those with 
complete data had 1-hour SO2 design values ranging from 6 to 
282 ppb, with violations of the 75 ppb standard occurring in the 
nonattainment areas surrounding the two copper smelters.\134\ CARB 
references Arizona's designations recommendation letter to the EPA, 
which noted that these smelters were the primary emission sources 
likely to contribute to the violations of the 2010 SO2 
NAAQS.\135\

[[Page 5394]]

CARB included 2014 design values of 6 ppb and 8 ppb at the two Nevada 
monitors \136\ and included the 2014 design value of 5 ppb for the 
Oregon SO2 monitoring site.
---------------------------------------------------------------------------

    \134\ Id., App. C, p. C-7.
    \135\ Id., App. C, p. C-6.
    \136\ Id., App. C, p. C-7.
---------------------------------------------------------------------------

    The California Transport Plan states that the 1-hour SO2 
design values for 2012-2014 at 34 regulatory monitors in California 
ranged from 1 to 39 ppb--well below the 2010 SO2 NAAQS.\137\ 
Based on data from these monitors and an additional 21 special purpose 
monitors operated by facilities in the Bay Area AQMD and South Coast 
AQMD, CARB recommended that California be designated attainment.\138\ 
Fifteen of the special purpose monitors are operated by refineries, as 
required by Bay Area AQMD operating permit regulations, and they 
recorded 2014 design values of 5 to 50 ppb. The remaining six special 
purpose monitors are operated by the Ports of Long Beach and Los 
Angeles, as part of the San Pedro Bay Clean Air Action Plan, and they 
recorded 2014 design values of 12 to 74 ppb.
---------------------------------------------------------------------------

    \137\ Id., p. 23.
    \138\ Id., App. C, pp. C-6 to C-7.
---------------------------------------------------------------------------

    CARB studied the trend of SO2 design values at 
regulatory SO2 monitors in California with a data record 
spanning 15 years, which included six sites each in the Bay Area and 
South Coast air districts.\139\ In 1990, 1-hour SO2 
concentrations ranged from 20 to 47 ppb and 13 to 47 ppb, respectively, 
for the Bay Area and South Coast air districts. By 2014, 1-hour 
SO2 concentrations ranged from 3 to 12 ppb and 5 to 14 ppb, 
respectively, and the design value at each district's highest 
concentration site had decreased by more than 1 ppb per year.
---------------------------------------------------------------------------

    \139\ Id., App. C, p. C-9.
---------------------------------------------------------------------------

    CARB asserts that the decline in SO2 concentrations at 
the highest sites in the State were the result of emission reductions 
achieved by California's control programs.\140\ From 2000 to 2015, CARB 
estimates that the following emission reductions were achieved: 
Stationary sources (59 percent), mobile sources (88 percent), and area 
sources (33 percent). CARB states that these reductions were achieved 
by improving emission controls and applying increasingly stringent 
permit requirements for stationary sources; lowering sulfur content 
requirements for diesel fuel for mobile sources, including on- and off-
road vehicles, railroad locomotives, and marine vessels; and reducing 
area source emissions through rules for residential fuel combustion and 
managed burning and disposal.\141\ CARB projected that in 2015, 
SO2 will be emitted in the following amounts: Stationary 
sources (54 tpd: 68 percent of statewide total), mobile sources (19 
tpd: 24 percent of total), and area sources (6 tpd: 8 percent of 
total). CARB states that California SOX emissions continue 
to decline and SO2 concentrations measured at regulatory 
monitoring site remain well below the 2010 SO2 NAAQS.\142\
---------------------------------------------------------------------------

    \140\ Id., App. C, p. C-3.
    \141\ For mobile sources, CARB gives examples of state 
regulations that have reduced SOX emissions in 
California, including the state's regulations for reformulated 
gasoline (13 CCR 2250-2297) and for the sulfur content of diesel 
fuel (13 CCR 2281). These have been approved into the California 
SIP. 60 FR 43379 (August 21, 1995) and 75 FR 26653 (May 12, 2010).
    \142\ California Transport Plan, App. C, p. C-4.
---------------------------------------------------------------------------

3. The EPA's SO2 Evaluation
    The EPA proposes to find that California meets the interstate 
transport requirements of CAA section 110(a)(2)(D)(i)(I) for the 2010 
SO2 NAAQS, as discussed below. First, we address the air 
quality, emission sources, and emission trends in the states bordering 
California, i.e., Arizona, Nevada, and Oregon. Then we discuss 
California's air quality, emissions sources, control measures, and 
emission trends with respect to interstate transport prong 1, followed 
by discussion of additional California air quality trends and emission 
trends with respect to interstate transport prong 2. Based on that 
analysis, we propose to find that California will not significantly 
contribute to nonattainment, or interfere with maintenance, of the 2010 
SO2 NAAQS in any other state.
    For the first step of our SO2 transport evaluation, we 
assessed the areas of Arizona, Nevada, and Oregon that may exceed or 
have the potential to exceed the 2010 SO2 NAAQS. Consistent 
with CARB's approach in the California Transport Plan, we focused on 
these three states given that the physical properties of SO2 
result in relatively localized pollutant impacts very near the 
emissions source. We selected the ``urban scale''--a spatial scale with 
dimensions from 4 to 50 kilometers (km) from point sources--given the 
usefulness of that range in assessing trends in both area-wide air 
quality and the effectiveness of large-scale pollution control 
strategies at such point sources.\143\ We reviewed the location of 
sources emitting more than 2,000 tpy (i.e., SO2 Data 
Requirements Rule sources) in these states and assessed whether there 
is any source in these states emitting more than 100 tpy of 
SO2 and located within 50 km of the California state border, 
because elevated levels of SO2, to which SO2 
emitted in California may have a downwind impact, are most likely to be 
found near such sources.
---------------------------------------------------------------------------

    \143\ For the definition of spatial scales for SO2, 
please see 40 CFR part 58, Appendix D, section 4.4 (``Sulfur Dioxide 
(SO2) Design Criteria''). For further discussion on how 
the EPA is applying these definitions with respect to interstate 
transport of SO2, see the EPA's proposal on Connecticut's 
SO2 transport SIP. 82 FR 21351, 21352, 21354 (May 8, 
2017).
---------------------------------------------------------------------------

    We reviewed the 2014 design value concentrations for Arizona, 
Nevada, and Oregon that were presented in the California Transport Plan 
and find them to be accurate. In addition, to assess how air quality 
has changed over time we also reviewed AQS data for the design value 
periods ending in years 2011 through 2016. We present the range of 
SO2 design values in Table 5 and specific SO2 
design values at selected monitoring sites in Table 6.\144\ We include 
California data for purposes of subsequent discussion in this proposed 
rule.
---------------------------------------------------------------------------

    \144\ 2011-2016 AQS Design Value Report, AMP480, June 12, 2017. 
The EPA's Air Quality System (AQS) contains ambient air pollution 
data collected by federal, state, local, and tribal air pollution 
control agencies from thousands of monitors. More information is 
available at: https://www.epa.gov/aqs. For a map of SO2 
monitors and emission sources in California and its bordering 
states, we have included a map in the docket of this rulemaking 
entitled ``DRR Sources, Monitoring Sites and 2014 NEI Facilities 
Emitting SO2 Within 50km of Region 9 States,'' September 
11, 2017.

               Table 5--Range of SO2 1-Hour Design Value Concentrations at Regulatory Monitors in Arizona, Nevada, Oregon, and California
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                Number of
                                                                 monitors    2009-2011    2010-2012    2011-2013    2012-2014    2013-2015    2014-2016
                          State/area                            with valid     Design       Design       Design       Design       Design       Design
                                                                  design       values       values       values       values       values       values
                                                                  values       (ppb)        (ppb)        (ppb)        (ppb)        (ppb)        (ppb)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Arizona (Hayden, Miami areas only)...........................          2-4      111-259      107-285      105-266      122-282      145-246      146-280

[[Page 5395]]

 
Arizona (excluding Hayden, Miami areas)......................          1-4            9            9          6-9          6-9          5-9          4-8
Nevada.......................................................          0-2          \a\          \a\          6-8          6-8          6-7          5-7
                                                                              (Invalid)    (Invalid)
Oregon.......................................................            1            9            7            6            5            4            3
California...................................................        19-28         2-17         2-25         2-36         1-39         1-20         1-18
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ SO2 design values are valid only when they meet the data completeness and/or data substitution test criteria codified at 40 CFR part 50, Appendix T,
  section 3.


                 Table 6--SO2 1-Hour Design Value Concentrations at Selected Regulatory Monitors in Arizona, Nevada, and California \a\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                             2009-2011    2010-2012    2011-2013    2012-2014    2013-2015    2014-2016
                                                                               Design       Design       Design       Design       Design       Design
                State/area                              AQS ID                 values       values       values       values       values       values
                                                                               (ppb)        (ppb)        (ppb)        (ppb)        (ppb)        (ppb)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Arizona/Phoenix...........................  04-013-9812...................  ...........  ...........            9            9            9            8
Nevada/Reno...............................  32-031-0016...................  ...........  ...........            6            6            6            5
Nevada/Las Vegas..........................  32-003-0540...................  ...........  ...........            8            8            7            7
California/Sacramento.....................  06-067-0006...................            2            2            2            3            5            7
California/Fresno.........................  06-019-0011...................  ...........  ...........  ...........            6            5            6
California/Trona (San Bernardino Co.).....  06-071-1234...................            9  ...........  ...........  ...........            8            6
California/Victorville (San Bernardino      06-071-0306...................            8            8            5            4           15           18
 Co.).
California/Rubidoux (Riverside Co.).......  06-065-8001...................            7            5            3            3            3            2
California/Calexico (Imperial Co.)........  06-025-0005...................            8            7  ...........  ...........  ...........            8
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ These monitors were selected as being the westernmost monitors in Arizona and Nevada (i.e., nearest to California), and easternmost monitors in
  northern, central, and southern California (i.e., nearest to Arizona or Nevada), with at least three valid 1-hour design values in the last six years.
  A blank cell in this table indicates that the data were invalid for the applicable design value period.

    These data were consistent with the assertion in the California 
Transport Plan that, except for Arizona's Hayden and Miami 
nonattainment areas, the 1-hour SO2 levels measured in 
Arizona, Nevada, and Oregon are 89-96 percent below 75 ppb. Thus, at 
the areas represented by these monitors, there were no violations of 
the 2010 SO2 NAAQS that indicate potential concern for 
interstate transport. Indeed, there have been slight decreases in 1-
hour SO2 levels at these monitors from already low 
concentrations.
    To date, the only areas that have been designated nonattainment in 
the states bordering California are the Hayden and Miami nonattainment 
areas in Arizona, respectively, based on 2009-2011 monitoring 
data.\145\ These nonattainment areas are approximately 325 km and 320 
km, respectively, from the California border, which is a large distance 
relative to the localized range of potential 1-hour SO2 
impacts from SO2 sources in California.
---------------------------------------------------------------------------

    \145\ 78 FR 47191 (August 5, 2013) and 83 FR 1098 (January 9, 
2018).
---------------------------------------------------------------------------

    Additional sources that were evaluated under the SO2 
Data Requirements Rule include six sources across Arizona (including 
the portion of the Navajo Nation geographically located in Arizona), 
Nevada, and Oregon, listed in Table 7. These sources range from 240-460 
km from California--a similarly large distance relative to the 
localized range of potential 1-hour SO2 impacts from 
SO2 sources in California.\146\
---------------------------------------------------------------------------

    \146\ For further discussion of the localized nature of 1-hour 
SO2 impacts, and the selection of air quality models to 
estimate SO2 concentrations around such sources, please 
see the draft ``SO2 NAAQS Designations Modeling Technical 
Assistance Document,'' EPA, August 2016, pp. 5-6, available at 
https://www.epa.gov/sites/production/files/2016-06/documents/so2modelingtad.pdf. We also note that the EPA recently designated 
areas surrounding these sources as Attainment/Unclassifiable or, in 
the case of the area near Navajo Generating Station, as 
Unclassifiable. 83 FR 1098 (January 9, 2018).

                   Table 7--SO2 Data Requirements Rule Sources in States Bordering California
----------------------------------------------------------------------------------------------------------------
                                                                                    Approximate      2014 NEI
                                                                                    distance to       annual
                State/tribe                                Facility                 California       emissions
                                                                                       (km)            (tpy)
----------------------------------------------------------------------------------------------------------------
Arizona....................................  Tucson Electric Power--                         460         6,221.0
                                              Springerville Generating Station.
Arizona....................................  Arizona Electric Power Cooperative--            450         4,811.9
                                              Apache Generating Station.
Arizona....................................  Arizona Public Service--Cholla                  365         3,806.6
                                              Power Plant.
Navajo Nation..............................  Navajo Generating Station..........             360         5,665.6
Nevada.....................................  North Valmy Generating Station.....             240         7,429.9
Oregon.....................................  Portland General Electric Company--             400         7,438.6
                                              Boardman Power Plant.
----------------------------------------------------------------------------------------------------------------


[[Page 5396]]

    Based on the SO2 emissions data of the 2014 NEI, we did 
not find any source in Arizona, Nevada, or Oregon that emitted more 
than 100 tpy of SO2 and was located within 50 km of the 
California border.\147\ The closest source of this type is McCarran 
International Airport in Las Vegas, Nevada, which emitted 265.3 tpy of 
SO2 in 2014 and is located just over 50 km from the 
California border. More broadly, the statewide SO2 emissions 
from these three states have decreased substantially, per our review of 
the EPA's emissions trends data.\148\ From 2000 to 2016, total 
statewide SO2 emissions decreased by the following 
proportions, resulting in the total 2016 emissions listed for each 
state: Arizona (38 percent decrease to 8,298 tpy); Nevada (86 percent 
decrease to 8,729 tpy); and Oregon (90 percent decrease to 5,469 tpy).
---------------------------------------------------------------------------

    \147\ For a map of SO2 emission sources in states 
bordering California, and within California, please see ``DRR 
Sources, Monitoring Sites and 2014 NEI Facilities Emitting 
SO2 Within 50 km of Region 9 States,'' September 11, 
2017, in the docket for this rulemaking. The EPA also sought to 
assess more recent data for California sources emitting over 100 tpy 
of SO2 in the EPA's Emission Inventory System Gateway, 
available at: https://www.epa.gov/air-emissions-inventories/emissions-inventory-system-eis-gateway. Since data for all such 
sources were not available for years after 2014, we have relied on 
the data of the 2014 NEI.
    \148\ 1990-2016 emission inventory spreadsheets of statewide 
emission trends, included in the docket to this rulemaking and 
entitled ``1990-2016 State Tier 1 Annual Average Emission Trends--
RIX Analysis.xls.'' Additional emissions trends data are available 
at: https://www.epa.gov/air-emissions-inventories/air-pollutant-emissions-trends-data.
---------------------------------------------------------------------------

    In summary, we find that monitored 1-hour SO2 levels are 
generally well below 75 ppb; that sources emitting over 2,000 tpy of 
SO2 are located at a distance well beyond a 50-km buffer 
from California's borders where emissions from California sources might 
be expected to have downwind impacts on air quality; and that the 
downward SO2 emission trends in each state reduce the 
likelihood of SO2 nonattainment or maintenance issues 
appearing in the future.\149\ We now turn to our analyses of 
California's air quality and trends, emissions sources and trends, and 
control measures to assess whether California significantly contributes 
to nonattainment, or interferes with maintenance, of the 2010 
SO2 NAAQS in other states.
---------------------------------------------------------------------------

    \149\ This proposed approval of the California Transport Plan 
for the 2010 SO2 NAAQS under CAA section 
110(a)(2)(D)(i)(I) is based on the information contained in the 
administrative record for this action, and does not prejudge any 
other future EPA action that may make other determinations regarding 
California's air quality status. Any such future actions, such as 
area designations under any NAAQS, will be based on their own 
administrative records and the EPA's analyses of information that 
becomes available at those times. Future available information may 
include, and is not limited to, monitoring data and modeling 
analyses conducted pursuant to the SO2 EPAs Data 
Requirements Rule (80 FR 51052, August 21, 2015) and information 
submitted to the EPA by states, air agencies, and third party 
stakeholders such as citizen groups and industry representatives.
---------------------------------------------------------------------------

i. Evaluation for Significant Contribution to Nonattainment (Prong 1)
    The EPA reviewed ambient air quality data in California to see 
whether there were any monitoring sites, particularly near the 
California border, with elevated SO2 concentrations that 
might warrant further investigation with respect to interstate 
transport of SO2 from emission sources near any given 
monitor. Over the period of 2011 through 2016, CARB and local air 
districts operated 34-40 regulatory SO2 monitors, of which 
20-28 have data sufficient to produce valid 1-hour SO2 
design values.\150\ As described in the California Transport Plan, in 
2014 the monitors operating in California produced valid design values 
ranging from 1-39 ppb. As in our data review for Arizona, Nevada, and 
Oregon, we also reviewed AQS data for the design value periods ending 
in years 2011 through 2016 to assess how air quality has changed over 
time. Based on the data presented in Tables 5 and 6, above, we find 
that California's more extensive network of SO2 monitors 
indicate that 1-hour SO2 levels in California are 76-99 
percent below 75 ppb. The high design value of 39 ppb presented in the 
California Transport Plan for 2014 is the highest among the series of 
six design value periods, and the highest 2015 and 2016 design values 
were lower at 20 ppb and 18 ppb, respectively. Thus, these air quality 
data do not, by themselves, indicate any particular location that would 
warrant further investigation with respect to SO2 emission 
sources that might significantly contribute to nonattainment in the 
bordering states.
---------------------------------------------------------------------------

    \150\ 2011-2016 AQS Design Value Report, AMP480, June 12, 2017.
---------------------------------------------------------------------------

    While the 21 special purpose monitors operated by facilities in the 
Bay Area and South Coast air districts measured 1-hour SO2 
design values up to 50 ppb and 74 ppb, respectively, for 2012-2014, 
these concentrations are below the 2010 SO2 NAAQS of 75 ppb 
and represent air quality at locations that are over 200 km from the 
California border with other states. Based on SO2 air 
quality in California, we have not found any area that would warrant 
further investigation with respect to interstate transport of 
SO2. However, because the monitoring network is not 
necessarily designed to find all locations of high SO2 
concentrations, this observation indicates an absence of evidence of 
impact but is not sufficient evidence by itself of an absence of 
impact. We have therefore also conducted a source-oriented analysis.
    Regarding the largest sources of SO2 emissions in 
California, we agree with CARB that no individual facility emitted more 
than 2,000 tpy of SO2 in 2014. However, a cluster of three 
sources in or near Martinez, California, including the Shell petroleum 
refinery (1,369.0 tpy), the Tesoro petroleum refinery (647.8 tpy), and 
the Rhodia USA, Inc. chemical plant (382.7 tpy, now operated by Eco 
Services Operations Corp.), collectively emitted 2,399.5 tpy of 
SO2 in 2014.\151\ The air quality around this cluster of 
sources was characterized according to the monitoring pathway, under 
the requirements of the SO2 Data Requirements Rule.\152\
---------------------------------------------------------------------------

    \151\ 2014 NEI California emission inventory spreadsheet of 
stationary sources emitting over 100 tpy SO2 (``2014 NEI 
CA SO2 Spreadsheet''), included in the docket to this 
rulemaking and entitled ``AIR17025--2014 NEI SO2 sources 
by CA air district--RIX analysis.xlsx.'' We note that the emissions 
amounts differ slightly from CARB's 2013 Facility Emissions 
Inventory, though both underscore a similar magnitude of emissions 
(e.g., hundreds or thousands of tpy).
    \152\ Letter from Deborah Jordan, Acting Regional Administrator, 
Region IX, EPA to Governor Brown of California and affiliated TSD, 
Chapter 6 (California), section 3 (``Technical Analysis for the San 
Francisco Bay Area''). The SO2 Data Requirements Rule 
notes that clusters of multiple smaller sources in close proximity 
can cause as much impact as a single larger source and should be 
evaluated on a case-by-case basis, as was done for the cluster of 
sources in or near Martinez, California. 80 FR 51052, 51060-51062 
(August 21, 2015).
---------------------------------------------------------------------------

    The regulatory SO2 monitor near these sources is located 
at 521 Jones St. in Martinez (AQS ID 06-013-2001). The 1-hour 
SO2 design values at this monitor were 14 ppb for 2015 and 
13 ppb for 2016--below the 2010 SO2 NAAQS. As noted in the 
California Transport Plan, we find that these sources are a large 
distance from California's borders--approximately 700 km from Arizona, 
220 km from Nevada, and 440 km from Oregon, which is a large distance 
to these other states' borders relative to the localized range of 
potential 1-hour SO2 impacts from SO2 sources in 
California. Furthermore, these sources are subject to SO2 
emission limits under Bay Area AQMD Regulation 9, Rule 1, which has 
been approved into the California SIP.\153\
---------------------------------------------------------------------------

    \153\ Bay Area AQMD Regulation 9, Rule 1 (``Sulfur Dioxide,'' 
amended May 20, 1992), 64 FR 30396 (June 8, 1999). With respect to 
petroleum refineries, this rule includes limitations on ground level 
SO2 concentrations and a general emissions limitation, as 
well as specific emission limits for certain types of equipment.
---------------------------------------------------------------------------

    As further support of our proposal that California SO2 
emissions are

[[Page 5397]]

sufficiently low to avoid an ambient impact at downwind areas in 
violation of the good neighbor provision, California has reduced 
SO2 emissions from mobile and stationary sources, as 
described in the California Transport Plan, by adopting and 
implementing rules to limit the sulfur content of fuels. CARB mobile 
source rules have reduced SO2 emissions by limiting the 
sulfur content of Phase 2 and Phase 3 reformulated gasoline and of 
diesel fuel used statewide.\154\ Also, SO2 emission 
reductions from industrial sources in South Coast AQMD have been 
reduced by air district rules for fuels used at industrial sources such 
as power plants, refineries, landfills, and sewage digesters.\155\ Such 
measures will continue to limit the sulfur content of fuels that are 
combusted in California, thereby limiting SO2 emissions from 
mobile sources statewide and stationary sources in South Coast AQMD, 
where a large proportion of the biggest SO2 sources operate.
---------------------------------------------------------------------------

    \154\ 13 CCR 2262 (``The California Reformulated Gasoline Phase 
2 and Phase 3 Standards,'' amended December 24, 2002), 13 CCR 2262.3 
(``Compliance with the CaRFG Phase 2 and CaRFG Phase 3 Standards for 
Sulfur, Benzene, Aromatic Hydrocarbons, Olefins, T50 and T90,'' 
amended August 20, 2001), and 13 CCR 2281 (``Sulfur Content of 
Diesel,'' amended June 4, 1997), 75 FR 26653 (May 12, 2010).
    \155\ South Coast AQMD Regulation 4, Rule 431.1 (``Sulfur 
Content of Gaseous Fuels,'' amended June 12, 1998), 64 FR 67787 
(December 3, 1999) and Rule 431.2 (``Sulfur Content of Liquid 
Fuels,'' amended May 4, 1990), 64 FR 30396 (June 8, 1999).
---------------------------------------------------------------------------

    We agree with CARB that sources that emit more than 300 tpy are far 
from the California borders with Arizona, Nevada, and Oregon. CARB 
identified 10 stationary sources that emitted over 300 tpy of 
SO2 based on its 2013 Facility Emissions Inventory, and we 
identified 12 such stationary sources based on the 2014 NEI, most of 
which are located near the California coast in the Bay Area and South 
Coast air districts.\156\ As with the cluster of SO2 sources 
in the area of Martinez, California, most of these sources are subject 
to SO2 emission limits under air district rules of the Bay 
Area (petroleum refineries, calcined petroleum coke plant), Kern County 
(cement plant), and South Coast (petroleum refineries, calcined 
petroleum coke plant) that have been approved into the California 
SIP.\157\ One of these sources, the Lehigh Southwest Cement Company 
plant in Cupertino, is about 260 km from the nearest bordering state, 
Nevada, and emitted 854 tpy of SO2 in 2014, which is about 
3.5 percent of the total SO2 emitted in California in 2014. 
This source is subject to a Bay Area AQMD rule that limits 
NOX emissions but does not appear to be subject to rules 
limiting SO2 emissions. However, the facility's distance 
from Nevada and other states limit the potential for interstate 1-hour 
SO2 impacts from this source.
---------------------------------------------------------------------------

    \156\ 2014 NEI CA SO2 Spreadsheet. Other non-
stationary sources in California emitting over 300 tpy of 
SO2 include the Los Angeles and San Francisco airports, 
whose SO2 emissions from aircraft are outside the 
regulatory authority of the State of California.
    \157\ Bay Area AQMD Regulation 9, Rule 1 (``Sulfur Dioxide,'' 
amended May 20, 1992), 64 FR 30396 (June 8, 1999); Kern County APCD 
Rule 407 (``Sulfur Compounds,'' adopted April 18, 1972), 37 FR 19812 
(September 22, 1972); and South Coast AQMD, see e.g., Regulation 20 
series rules for the RECLAIM program. While the Kern County rule 
applicable to the California Portland Cement Company plant in 
Mojave, California is old, the facility is about 220 km from the 
nearest bordering state, Nevada.
---------------------------------------------------------------------------

    More broadly, there were no sources in 2014 that emitted over 100 
tpy of SO2 and were within 50 km of the state's border.\158\ 
Additionally, the statewide SO2 emissions from all sources 
in California have decreased substantially, as described in the 
California Transport Plan and per our review of the EPA's emissions 
trends data.\159\ From 2000 to 2016, total statewide SO2 
emissions, excluding wildfires and prescribed fires, decreased by 75 
percent resulting in 2016 statewide emissions of 21,422 tpy.
---------------------------------------------------------------------------

    \158\ Please see the map included in the docket of this 
rulemaking entitled ``DRR Sources, Monitoring Sites and 2014 NEI 
Facilities Emitting SO2 Within 50 km of Region 9 
States,'' September 11, 2017.
    \159\ 1990-2016 emission inventory spreadsheets of statewide 
emission trends, included in the docket to this rulemaking and 
entitled ``1990-2016 State Tier 1 Annual Average Emission Trends--
RIX Analysis.xls.'' Additional emissions trends data are available 
at: https://www.epa.gov/air-emissions-inventories/air-pollutant-emissions-trends-data.
---------------------------------------------------------------------------

    In conclusion, for interstate transport prong 1, we reviewed 
ambient SO2 monitoring data, SO2 emission sources 
and controls, including CARB measures for mobile sources and air 
district measures for large stationary sources, and emission trends in 
California. As for Arizona, Nevada, and Oregon, monitored 1-hour 
SO2 levels in California are low (most often below half the 
level of the 2010 SO2 NAAQS); the 29 SO2 sources 
in California that emit over 100 tpy of SO2 are located at a 
distance well beyond 50 km from California's borders, the distance 
where emissions from California sources might be expected to have 
downwind impacts on air quality in bordering states; and California's 
decreasing SO2 emission trend each reduce the likelihood of 
California emitting SO2 in amounts that would adversely 
affect other states in the future.
    Therefore, based on our analysis of SO2 air quality and 
emission sources in Arizona, Nevada, and Oregon and our analysis of 
SO2 air quality and emissions in California, we propose that 
California will not significantly contribute to nonattainment of the 
2010 SO2 NAAQS in any other state, per the requirements of 
CAA section 110(a)(2)(D)(i)(I).
ii. Evaluation for Interference With Maintenance (Prong 2)
    The EPA has reviewed the analysis presented in the California 
Transport Plan and has considered additional information on California 
air quality trends and emission trends to evaluate CARB's conclusion 
that California does not interfere with maintenance of the 2010 
SO2 NAAQS in other states. This evaluation builds on our 
evaluation of air quality and SO2 emission sources in 
Arizona, Nevada, and Oregon, and our evaluation for significant 
contribution to nonattainment (prong 1) based on the evidence that we 
reviewed (i.e., low ambient concentrations of SO2, large 
distance of SO2 sources from the California border, 
decreasing SO2 emissions, and the existence of SIP-approved 
California control measures).
    Complementing the 75 percent reduction in California SO2 
emissions from 2000 to 2015, we reviewed regional trends in the 99th 
percentile of the daily maximum 1-hour average SO2 
measurements, which are used to calculate 1-hour SO2 design 
values.\160\ For the western U.S. region, which includes California and 
Nevada, the mean of the 99th percentile ambient SO2 
concentrations decreased 46 percent from 2000 to 2015. For sources 
emitting over 300 tpy of SO2 based on a combination of the 
2014 NEI and the facilities identified in the California Transport 
Plan, we have also reviewed the trend of emissions from each such 
source at five year increments from 2000 thru 2015, as shown in Table 
8.\161\ Because the total SO2 emissions from these 
facilities have decreased substantially from 2000 to 2015, coupled with 
their distance from the California border and the generally low 
SO2 concentrations in bordering states, this trend further 
reduces the likelihood

[[Page 5398]]

of California emitting SO2 in amounts that would interfere 
with maintenance of the 2010 SO2 NAAQS in other states.
---------------------------------------------------------------------------

    \160\ 2000-2015 1-hour daily maximum SO2 air quality 
trend spreadsheet for California and Nevada, included in the docket 
to this rulemaking and entitled ``2000-2015 SO2 Trend in 
Western US (CA-NV).xlsx.'' These and other regional air quality data 
trends are available at: https://www.epa.gov/air-trends/sulfur-dioxide-trends.
    \161\ This table includes stationary sources that emitted more 
than 300 tpy of SO2 as identified in the 2014 NEI CA 
SO2 Spreadsheet plus two additional sources cited in the 
California Transport Plan, App. C, p. C-10 (i.e., California 
Portland Cement Co. and Solvay USA Inc, listed as Eco Services 
Operations Corp in the 2015 inventory). These data are from CARB's 
2013 Facility Emissions Inventory, available at: https://www.arb.ca.gov/app/emsinv/facinfo/facinfo.php.

                                Table 8--Emissions Trends for California Sources That Emitted Over 300 tpy of SO2 in 2014
--------------------------------------------------------------------------------------------------------------------------------------------------------
       CARB facility ID (2015)           Facility name (2015)     Air district (county)     2000 (tpy)      2005 (tpy)      2010 (tpy)      2015 (tpy)
--------------------------------------------------------------------------------------------------------------------------------------------------------
21360................................  Phillips 66 Carbon Plant  Bay Area (Contra Costa)           1,728           1,212           1,151           1,519
                                        (petroleum coke
                                        calciner).
11...................................  Shell Martinez Refinery.  Bay Area (Contra Costa)           2,556           1,670           1,208           1,093
17...................................  Lehigh Southwest Cement   Bay Area (Santa Clara).             473             310             492           1,058
                                        Company.
14628................................  Tesoro Refining and       Bay Area (Contra Costa)           5,423           2,646             470             962
                                        Marketing Co. LLC.
174655...............................  Tesoro Refining and       South Coast (Los                  1,705           1,221             594             503
                                        Marketing Co. LLC.        Angeles).
9....................................  California Portland       Kern County............           1,168           1,136           1,089             472
                                        Cement Co.
10...................................  Chevron Products Company  Bay Area (Contra Costa)           1,247           1,566             367             381
21359................................  Phillips 66 Company--San  Bay Area (Contra Costa)             705             407             414             365
                                        Francisco Refinery.
171109...............................  Phillips 66 Company/Los   South Coast (Los                    587             245             295             340
                                        Angeles Refinery.         Angeles).
800089...............................  ExxonMobil Oil            South Coast (Los                    725             574             353             333
                                        Corporation.              Angeles).
174591...............................  Tesoro Refining &         South Coast (Los                    408             178             240             329
                                        Marketing Co LLC,         Angeles).
                                        (petroleum coke
                                        calciner).
800030...............................  Chevron Products Co.....  South Coast (El                   1,006             396             425             300
                                                                  Segundo).
22789................................  Eco Services Operations   Bay Area (Contra Costa)             276             240             308             186
                                        Corp.
178639...............................  Eco Services Operations   South Coast (Los                    242             390             390              19
                                        LLC.                      Angeles).
                                                                                         ---------------------------------------------------------------
    Total............................  ........................  .......................          18,250          12,193           7,793           7,861
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Beyond this important subset of stationary sources, as discussed in 
our evaluation for significant contribution to maintenance herein, 
California has reduced SO2 emissions from mobile and 
stationary sources, as described in the California Transport Plan, by 
adopting and implementing rules to limit the sulfur content of fuels. 
These include CARB mobile source rules limiting the sulfur content of 
Phase 2 and Phase 3 reformulated gasoline and of diesel fuel used 
statewide, as well as air district rules limiting SO2 
emissions from industrial sources such as power plants, refineries, 
landfills, and sewage digesters.
    In conclusion, for interstate transport prong 2, we reviewed 
additional information on California air quality trends and emission 
trends, as well as the evidence considered for interstate transport 
prong 1. We find that from 2000 to 2015 both ambient SO2 
concentrations and SO2 emissions from California's largest 
stationary sources have decreased substantially; and that state and 
local measures to limit the sulfur content of fuels and limit 
SO2 emissions will continue to limit SO2 
emissions that might adversely affect other states. Accordingly, we 
propose that California SO2 emission sources will not 
interfere with maintenance of the 2010 SO2 NAAQS in any 
other state, per the requirements of CAA section 110(a)(2)(D)(i)(I).

III. Proposed Action

    We have reviewed the California Transport Plan for the 2008 ozone, 
2006 PM2.5, 2012 PM2.5, and 2010 SO2 
NAAQS using step-wise processes. Based on this review and additional 
analyses conducted by the EPA to verify and supplement the California 
Transport Plan, and consistent with CAA section 110(a)(2)(D)(i)(I) and 
EPA guidance with respect to interstate transport for these NAAQS, we 
propose that California will not significantly contribute to 
nonattainment, or interfere with maintenance, of the 2008 ozone, 2006 
PM2.5, 2012 PM2.5, and 2010 SO2 NAAQS 
in any other state. Accordingly, we propose to approve California's 
Transport SIP as satisfying the requirements of CAA section 
110(a)(2)(D)(i)(I) for these NAAQS.
    We will accept comments from the public on these proposals for the 
next 30 days and plan to follow with a final action. The deadline and 
instructions for submission of comments are provided in the ``Date'' 
and ``Addresses'' sections at the beginning of this proposed rule.

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 that they meet the criteria of the Clean Air Act. 
Accordingly, this proposed action merely proposes to approve state law 
as meeting federal requirements and does not impose additional 
requirements beyond those imposed by state law. For that reason, this 
proposed action:
     Is not a ``significant regulatory action'' subject to 
review by the Office of Management and Budget under Executive Orders 
12866 (58 FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 
2011);
     Is not an Executive Order 13771 (82 FR 9339, February 2, 
2017) regulatory action because SIP approvals are exempted under 
Executive Order 12866;
     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

[[Page 5399]]

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. In those areas of 
Indian country, the rule does not have tribal implications and will not 
impose substantial direct costs on tribal governments or preempt tribal 
law as specified by Executive Order 13175 (65 FR 67249, November 9, 
2000).

List of Subjects in 40 CFR Part 52

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

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

    Dated: January 26, 2018.
Alexis Strauss,
Acting Regional Administrator, Region IX.
[FR Doc. 2018-02462 Filed 2-6-18; 8:45 am]
 BILLING CODE 6560-50-P