[Federal Register Volume 76, Number 52 (Thursday, March 17, 2011)]
[Proposed Rules]
[Pages 14616-14626]
[FR Doc No: 2011-6302]

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

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2011-0046; FRL-9282-9]

Approval and Promulgation of Implementation Plans; State of
California; Interstate Transport of Pollution; Significant Contribution
to Nonattainment and Interference With Maintenance Requirements

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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

SUMMARY: EPA is proposing to approve the State Implementation Plan
(SIP) revision submitted by the State of California for the purpose of
addressing the interstate transport provisions of Clean Air Act (CAA)
section 110(a)(2)(D)(i)(I) for the 1997 8-hour ozone National Ambient
Air Quality Standards (NAAQS or standards) and the 1997 fine
particulate matter (PM2.5) NAAQS. Section 110(a)(2)(D)(i) of
the CAA requires that each state have adequate provisions to prohibit
air emissions from adversely affecting air quality in other states
through interstate transport. EPA is proposing to approve California's
SIP revision for the 1997 8-hour ozone and 1997 PM2.5 NAAQS
as meeting the requirements of CAA section 110(a)(2)(D)(i)(I) to
prohibit emissions that will contribute significantly to nonattainment
of the these standards in any other state and to prohibit emissions
that will interfere with maintenance of these standards by any other
state.

DATES: Written comments must be received on or before April 18, 2011.

ADDRESSES: Submit your comments, identified by Docket ID Number EPA-
R09-OAR-2011-0046, by one of the following methods:
    1. http://www.regulations.gov: Follow the on-line instructions for
submitting comments.

    2. E-mail<EMAIL_ADDRESS>    3. Fax:<PHONE_NUMBER>.
    4. Mail or deliver: Rory Mays (AIR-2), U.S. Environmental
Protection Agency, Region IX, 75 Hawthorne Street, San Francisco, CA
94105-3901. Deliveries are only accepted during the Regional Office's
normal hours of operation.
    Instructions: All comments will be included in the public docket
without change and may be made available online at http://www.regulations.gov, including any personal information provided,
unless the comment includes Confidential Business Information (CBI) or
other information whose disclosure is restricted by statute.
Information that you consider CBI or otherwise protected should be
clearly identified as such and should not be submitted through http://www.regulations.gov or e-mail. http://www.regulations.gov is an
anonymous access system, and EPA will not know your identity or contact
information unless you provide it in the body of your comment. If you
send e-mail directly to EPA, your e-mail address will be automatically
captured and included as part of the public comment. If EPA cannot read
your comment due to technical difficulties and cannot contact you for
clarification, EPA may not be able to consider your comment.
    Docket: The index to the docket for this action is available
electronically at http://www.regulations.gov and in hard copy at EPA
Region IX, 75 Hawthorne Street, San Francisco, California. While all
documents in the docket are listed in the index, some information may
be publicly available only at the hard copy location (e.g., copyrighted
material), and some may not be publicly available in either location
(e.g., CBI). To inspect the hard copy materials, please schedule an
appointment during normal business hours with the contact listed
directly below.

FOR FURTHER INFORMATION CONTACT: Rory Mays, Air Planning Office (AIR-
2), U.S. Environmental Protection Agency, Region IX,<PHONE_NUMBER>,
<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION: Throughout this document, the terms ``we,''
``us,'' and ``our'' refer to EPA.

Table of Contents

I. Background
II. What is the State process to submit these materials to EPA?
III. What is EPA's evaluation of the State's submission?
    A. Evaluation of Significant Contribution to Nonattainment
    1. Significant Contribution to Nonattainment Evaluation for the
1997 8-Hour Ozone NAAQS
    2. Significant Contribution to Nonattainment Evaluation for the
1997 PM2.5 NAAQS
    3. Conclusion Regarding Significant Contribution
    B. Evaluation of Interference With Maintenance
    1. Interfere With Maintenance Evaluation for the 1997 8-Hour
Ozone NAAQS
    2. Interfere With Maintenance Evaluation for the 1997
PM2.5 NAAQS
    3. Conclusion Regarding Interference With Maintenance
IV. Proposed Action
V. Statutory and Executive Order Reviews

I. Background

    On July 18, 1997, EPA promulgated new standards for 8-hour ozone
\1\ and fine particulate matter \2\ (PM2.5). This proposed
action is in response to the promulgation of these standards (the 1997
8-hour ozone NAAQS and 1997 PM2.5 NAAQS). This proposed
action does not address the requirements of the 2006 PM2.5
NAAQS or the 2008 8-hour ozone NAAQS; those standards will be addressed
in future actions.
---------------------------------------------------------------------------

    \1\ See 62 FR 38856. The level of the 1997 8-hour ozone NAAQS is
0.08 parts per million (ppm). 40 CFR 50.10. The 8-hour ozone
standard is met when the 3-year average of the annual 4th highest
daily maximum 8-hour ozone concentrations is 0.08 ppm or less (i.e.,
less than 0.085 ppm based on the rounding convention in 40 CFR part
50 Appendix I). This 3-year average is referred to as the ``design
value.''
    \2\ See 62 FR 38652. The level of the 1997 PM2.5
NAAQS are 15.0 micrograms per cubic meter ([mu]g/m\3\) (annual
arithmetic mean concentration) and 65 [mu]g/m\3\ (24-hour average
concentration). 40 CFR 50.7. The annual standard is met when the 3-
year average of the annual mean concentrations is 15.0 [mu]g/m\3\ or
less (i.e., less than 15.05 [mu]g/m\3\ based on the rounding
convention in 40 CFR part 50 Appendix N Section 4.3). The 24-hour
standard is met when the 3-year average annual 98th percentile of
24-hour concentrations is 65 [mu]g/m\3\ or less (i.e., less than
65.5 [mu]g/m\3\ based on the rounding convention in 40 CFR part 40
Appendix N Section 4.3). Id. These 3-year averages are referred to
as the annual PM2.5 and 24-hour PM2.5 ``design
values,'' respectively.
---------------------------------------------------------------------------

    Section 110(a)(1) of the CAA requires states to submit SIPs to
address a new or revised NAAQS within three years after promulgation of
such standards, or within such shorter period as EPA may prescribe.
Section 110(a)(2) lists the elements that such new SIPs must address,
as applicable, including section 110(a)(2)(D)(i) which pertains to
interstate transport of certain emissions. On August 15, 2006, EPA
issued a guidance memorandum that provides recommendations to states
for making submissions to meet the requirements of section
110(a)(2)(D)(i) for the 1997 8-hour ozone and 1997 PM2.5
standards (2006 Guidance).\3\
---------------------------------------------------------------------------

    \3\ Memorandum from William T. Harnett entitled ``Guidance for
State Implementation Plan (SIP) Submission to Meet Current
Outstanding Obligations Under Section 110(a)(2)(D)(i) for the 8-hour
ozone and PM2.5 National Ambient Air Quality Standards,''
August 15, 2006.
---------------------------------------------------------------------------

    The transport SIP provisions in section 110(a)(2)(D)(i) (also
called ``good neighbor'' provisions) require each state to submit a SIP
that prohibits emissions that adversely affect another state in the
ways contemplated in the statute. Section 110(a)(2)(D)(i) identifies
four distinct elements related to the evaluation of impacts of
interstate transport of air pollutants. In this rulemaking, EPA is
addressing the first two elements of this section. This proposed action
does not apply to the remaining two elements of CAA section
110(a)(2)(D)(i) regarding interference with measures required to
prevent significant deterioration of air quality or to protect
visibility in another state. We intend to evaluate and act upon the
2007 Transport SIP for purposes of these additional requirements of CAA
section 110(a)(2)(D)(i) in separate actions.
    The first element of section 110(a)(2)(D)(i) requires that a
state's SIP for a new or revised NAAQS must contain adequate measures
to prohibit emissions from sources within the state from
``contribut[ing] significantly to nonattainment'' of the NAAQS in
another state. The second element of CAA section 110(a)(2)(D)(i)
requires that a state's SIP must prohibit any source or other type of
emissions activity in the state from emitting pollutants that will
``interfere with maintenance'' of the applicable NAAQS in any other
state.
    The CAA does not specifically mandate how to determine significant
contribution to nonattainment or interference with maintenance.
Therefore, EPA has interpreted these terms in past regulatory actions,
such as the 1998 NOX SIP Call, in which EPA took action to
remediate emissions of nitrogen oxides (NOX) that
significantly contributed to nonattainment of, or interfered with
maintenance of, the then applicable ozone NAAQS through interstate
transport of NOX and the resulting ozone.\4\ The
NOX SIP Call was the mechanism through which EPA evaluated
whether or not the NOX emissions from sources in certain
states had such prohibited interstate impacts, and if they had such
impacts, required the states to adopt substantive SIP revisions to
eliminate the NOX emissions, whether through participation
in a regional cap and trade program or by other means.
---------------------------------------------------------------------------

    \4\ See 63 FR 57356 (October 27, 1998). EPA's general approach
to section 110(a)(2)(D) in the NOX SIP Call was upheld in
Michigan v. EPA, 663 (DC Cir. 2000), cert denied, 532 U.S. 904
(2001). However, EPA's approach to interference with maintenance in
the NOX SIP Call was not explicitly reviewed by the
court. See, North Carolina v. EPA, 531 F.3d 896, 907-09 (DC Cir.
2008).

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

    After promulgation of the 1997 8-hour ozone NAAQS and the 1997
PM2.5 NAAQS, EPA again recognized that regional transport
was a serious concern throughout the eastern United States and
therefore developed the 2005 Clean Air Interstate Rule (CAIR) to
address emissions of sulfur dioxide (SO2) and NOX
that exacerbate ambient ozone and PM2.5 levels in many
downwind areas through interstate transport.\5\ Within CAIR, EPA
interpreted the term ``interfere with maintenance'' as part of the
evaluation of whether or not the emissions of sources in certain states
had such impacts on areas that EPA determined would either be in
violation of the NAAQS, or would be in jeopardy of violating the NAAQS,
in a modeled future year unless action were taken by upwind states to
reduce SO2 and NOX emissions. Through CAIR, EPA
again required states that had such interstate impacts to adopt
substantive SIP revisions to eliminate the SO2 and
NOX emissions, whether through participation in a regional
cap and trade program or by other means.
---------------------------------------------------------------------------

    \5\ See ``Rule to Reduce Interstate Transport of Fine
Particulate Matter and Ozone (Clean Air Interstate Rule); Revisions
to Acid Rain Program; Revisions to the NOX SIP Call;
Final Rule,'' at 70 FR 25162 at 25263-69 (May 12, 2005).
---------------------------------------------------------------------------

    EPA's 2006 Guidance addressed CAA section 110(a)(2)(D)(i)
requirements for the 1997 8-hour ozone NAAQS and 1997 PM2.5
NAAQS. For those states subject to CAIR, EPA indicated that compliance
with CAIR would meet the two requirements of section 110(a)(2)(D)(i)(I)
for these NAAQS. For states outside of the CAIR region, the 2006
Guidance recommended various methods by which states might evaluate
whether or not their emissions significantly contribute to
nonattainment of the 1997 8-hour ozone or the 1997 PM2.5
NAAQS in another state. Among other methods, EPA recommended
consideration of available EPA modeling conducted in conjunction with
the CAIR, or in the absence of such EPA modeling, consideration of
other information such as the amount of emissions, the geographic
location of violating areas, meteorological data, or various other
forms of information that would be relevant to assessing the likelihood
of significant contribution to violations of the NAAQS in another
state.
    The assessment of significant contribution to nonattainment is not
restricted to impacts upon areas that are formally designated
nonattainment. Consistent with EPA's approach in CAIR and recently in
the Transport Rule Proposal, as discussed further below, this impact
must be evaluated with respect to monitors showing a violation of the
NAAQS.\6\ Furthermore, although relevant information other than
modeling may be considered in assessing the likelihood of significant
contribution to nonattainment of the 8-hour ozone or PM2.5
NAAQS in another state, EPA notes that no single piece of information
is by itself dispositive of the issue. Instead, the total weight of all
the evidence taken together is used to evaluate significant
contributions to nonattainment of the 1997 8-hour ozone or 1997
PM2.5 NAAQS in another state.
---------------------------------------------------------------------------

    \6\ See 63 FR 57371 (October 27, 1998), NOX SIP Call;
70 FR 25172 (May 12, 2005), CAIR; and 75 FR 45210 (August 2, 2010),
Transport Rule Proposal.
---------------------------------------------------------------------------

    As to the second element of section 110(a)(2)(D)(i), for states not
within the CAIR region, EPA recommended that states evaluate whether or
not emissions from their sources would ``interfere with maintenance''
in other states following the conceptual approach adopted by EPA in
CAIR. After recommending various types of information that could be
relevant for the technical analysis to support the SIP submission, such
as the amount of emissions and meteorological conditions in the state,
EPA further indicated that it would be appropriate for the state to
assess impacts of its emissions on other states using considerations
comparable to those used by EPA ``in evaluating significant
contribution to nonattainment in the CAIR.'' \7\ EPA did not make
specific recommendations for how states should assess interfere with
maintenance separately, and discussed the first two elements of section
110(a)(2)(D)(i) together without explicitly differentiating between
them.
---------------------------------------------------------------------------

    \7\ 2006 Guidance at 5.
---------------------------------------------------------------------------

    In 2008, the U.S. Court of Appeals for the DC Circuit found that
CAIR and the related CAIR federal implementation plans were
unlawful.\8\ Among other issues, the court held that EPA had not
correctly addressed the second element of section 110(a)(2)(D)(i)(I) in
CAIR and noted that ``EPA gave no independent significance to the
`interfere with maintenance' prong of section 110(a)(2)(D)(i)(I) to
separately identify upwind sources interfering with downwind
maintenance.'' \9\ EPA's approach, the court reasoned, would leave
areas that are ``barely meeting attainment'' with ``no recourse'' to
address upwind emissions sources.\10\ The court therefore concluded
that a plain language reading of the statute requires EPA to give
independent meaning to the interfere with maintenance requirement of
section 110(a)(2)(D)(i) and that the approach used by EPA in CAIR
failed to do so. In addition to affecting CAIR directly, the court's
decision in the North Carolina case indirectly affects EPA's
recommendations to states in the 2006 Guidance with respect to the
interfere with maintenance element of section 110(a)(2)(D)(i) because
the agency's guidance suggested that states use an approach comparable
to that used by EPA in CAIR.
---------------------------------------------------------------------------

    \8\ See North Carolina v. EPA, 531 F.3d 896 (DC Circuit 2008).
    \9\ 531 F.3d at 909.
    \10\ Ibid.
---------------------------------------------------------------------------

    To address the judicial remand of CAIR, EPA has recently proposed a
new rule to address interstate transport of air pollution pursuant to
section 110(a)(2)(D)(i), the ``Federal Implementation Plans to Reduce
Interstate Transport of Fine Particulate Matter and Ozone'' (Transport
Rule Proposal).\11\ As part of the Transport Rule Proposal, EPA
specifically reexamined the section 110(a)(2)(D)(i)(I) requirements
that emissions from sources in a state must not ``contribute
significantly to nonattainment'' or ``interfere with maintenance'' of
the 1997 8-hour ozone NAAQS and 1997 PM2.5 NAAQS in other
states. In the proposal, EPA developed an approach to identify areas
that it predicts to be violating the 1997 8-hour ozone and
PM2.5 NAAQS, and areas that it predicts to be close to the
level of these NAAQS and therefore at risk to become nonattainment
unless emissions from sources in other states are appropriately
controlled. This approach starts by identifying those specific
geographic areas for which further evaluation is appropriate, and
differentiates between areas where the concern is significant
contribution to nonattainment as opposed to interference with
maintenance.
---------------------------------------------------------------------------

    \11\ See 75 FR 45210 (August 2, 2010).
---------------------------------------------------------------------------

    As described in more detail below, EPA evaluated data from existing
monitors over three overlapping 3-year periods (i.e., 2003-2005, 2004-
2006, and 2005-2007), as well as air quality modeling data, in order to
determine which areas are predicted to be violating the 1997 8-hour
ozone and PM2.5 NAAQS in 2012, and which areas are predicted
potentially to have difficulty maintaining attainment as of that date.
In essence, if an area's projected data for 2012 indicates that it
would be violating the NAAQS based on the average of these three
overlapping periods, then this monitor location is appropriate for
comparison for purposes of the significant contribution to
nonattainment element of section 110(a)(2)(D)(i). If, however, an
area's projected data indicate that it would be violating the NAAQS
based on the

highest single period, but not over the average of the three periods,
then this monitor location is appropriate for comparison for purposes
of the interfere with maintenance element of the statute.\12\
---------------------------------------------------------------------------

    \12\ A memorandum in the docket for this action provides the
information EPA used to identify monitors that are receptors for
evaluation of significant contribution or interference with
maintenance for certain states in the western United States. See
Memorandum from Brian Timin, EPA Office of Air Quality Planning and
Standards, ``Documentation of Future Year Ozone and Annual
PM2.5 Design Values for Monitors in Western States,''
August 23, 2010 (Timin Memo).
---------------------------------------------------------------------------

    By this method, EPA has identified those areas with monitors that
are appropriate ``nonattainment receptors'' or ``maintenance
receptors'' for evaluating whether the emissions from sources in
another state could significantly contribute to nonattainment in, or
interfere with maintenance in, that particular area. EPA believes that
this new approach for identifying areas that are predicted to be
nonattainment or to have difficulty maintaining the NAAQS is
appropriate to evaluate a state's submission in relation to the
elements of CAA section 110(a)(2)(D)(i)(I) pertaining to significant
contribution to nonattainment and interference with maintenance.\13\
EPA's 2006 Guidance did not provide this specific recommendation to
states, but in light of the court's decision on CAIR, EPA will itself
follow this approach in acting upon the California submission.\14\
---------------------------------------------------------------------------

    \13\ To begin this analysis, EPA first identifies all monitors
projected to be in nonattainment or, based on historic variability
in air quality, projected to have maintenance problems in 2012.
Monitors projected to be in nonattainment are those with future year
design values that violate the standard, based on the projection of
5-year weighted average concentrations. Monitors projected to have
maintenance problems are those at risk of not staying in attainment
because the air quality data is close enough to the level of the
1997 8-hour ozone and PM2.5 NAAQS that minor variations
in weather or emissions could result in violations of the NAAQS in
2012.
    \14\ By letter dated January 26, 2011, CARB acknowledged that
the 2008 remand of CAIR and EPA's Transport Rule Proposal would
affect EPA's review of the 2007 Transport SIP. The letter states
that based on EPA's findings in the Timin Memo regarding pollution
transport in the western states, ARB staff concludes that pollutants
from California do not contribute to nonattainment or maintenance
problems in other states. See letter dated January 26, 2011, from
Douglas Ito, Chief, Air Quality and Transportation Planning Branch,
CARB to Lisa Hanf, Chief, Air Planning Office, EPA Region 9.
---------------------------------------------------------------------------

    As explained in the 2006 Guidance, EPA does not believe that
section 110(a)(2)(D)(i) SIP submissions from all states necessarily
need to follow precisely the same analytical approach of CAIR. In the
2006 Guidance, EPA stated that: ``EPA believes that the contents of the
SIP submission required by section 110(a)(2)(D) may vary, depending
upon the facts and circumstances related to the specific NAAQS. In
particular, the data and analytical tools available at the time the
state develops and submits a SIP for a new or revised NAAQS necessarily
affects the contents of the required submission.'' \15\ EPA also
indicated in the 2006 Guidance that it did not anticipate that sources
in states outside the geographic area covered by CAIR were
significantly contributing to nonattainment, or interfering with
maintenance, in other states.\16\ As noted in the Transport Rule
Proposal, EPA continues to believe that the more widespread and serious
transport problems in the eastern United States are analytically
distinct.\17\ For the 1997 8-hour ozone and PM2.5 NAAQS, EPA
believes that nonattainment and maintenance problems in the western
United States are relatively local in nature with only limited impacts
from interstate transport. In the Transport Rule Proposal, EPA did not
calculate the portion of predicted ozone or PM2.5
concentrations in any downwind state that would result from emissions
from individual western states, such as California.
---------------------------------------------------------------------------

    \15\ 2006 Guidance at 4.
    \16\ Ibid. at 5.
    \17\ See Transport Rule Proposal, 75 FR 45210 at 45227 (August
2, 2010).
---------------------------------------------------------------------------

    Accordingly, EPA believes that section 110(a)(2)(D)(i) SIP
submissions for states outside the geographic area of the Transport
Rule Proposal may be evaluated using a ``weight of the evidence''
approach that takes into account the available relevant information,
such as that recommended by EPA in the 2006 Guidance for states outside
the area affected by CAIR. Such information may include, but is not
limited to, the amount of emissions in the state relevant to the NAAQS
in question, the meteorological conditions in the area, the distance
from the state to the nearest monitors in other states that are
appropriate receptors, or such other information as may be probative to
consider whether sources in the state may interfere with maintenance of
the 1997 8-hour ozone and PM2.5 NAAQS in other states. These
submissions can rely on modeling when acceptable modeling technical
analyses are available, but EPA does not believe that modeling is
necessarily required if other available information is sufficient to
evaluate the presence or degree of interstate transport in a given
situation.

II. What is the State process to submit these materials to EPA?

    CAA sections 110(a)(1) and (2) and section 110(l) require that
revisions to a SIP be adopted by the state after reasonable notice and
public hearing. EPA has promulgated specific procedural requirements
for SIP revisions in 40 CFR part 51, subpart F. These requirements
include publication of notices, by prominent advertisement in the
relevant geographic area, of a public hearing on the proposed
revisions, a public comment period of at least 30 days, and an
opportunity for a public hearing.
    On November 16, 2007, the California Air Resources Board (CARB)
submitted the ``Proposed State Strategy for California's 2007 State
Implementation Plan'' to attain the 1997 8-hour ozone and
PM2.5 NAAQS (2007 State Strategy).\18\ Appendix C of the
2007 State Strategy, as modified by Attachment A,\19\ contains
California's SIP revision to address the Transport SIP requirements of
CAA section 110(a)(2)(D)(i) for the 1997 8-hour ozone and
PM2.5 NAAQS (2007 Transport SIP). CARB's November 16, 2007
submittal includes public process documentation for the 2007 State
Strategy, including the 2007 Transport SIP. In addition, the SIP
revision includes documentation of a duly noticed public hearing held
on September 27, 2007 on the proposed 2007 State Strategy.
---------------------------------------------------------------------------

    \18\ See transmittal letter dated November 16, 2007, from James
N. Goldstene, Executive Officer, CARB, to Wayne Nastri, Regional
Administrator, EPA Region 9, with enclosures, and CARB Resolution
No. 07-28 (September 27, 2007).
    \19\ See ``Technical and Clarifying Modifications to April 26,
2007 Revised Draft Air Resources Board's Proposed State Strategy for
California's 2007 State Implementation Plan and May 7, 2007 Revised
Draft Appendices A through G,'' included as Attachment A to CARB's
Board Resolution 07-28 (September 27, 2007).
---------------------------------------------------------------------------

    We find that the process followed by CARB in adopting the 2007
Transport SIP complies with the procedural requirements for SIP
revisions under CAA section 110 and EPA's implementing regulations.

III. What is EPA's evaluation of the State's submission?

A. Evaluation of Significant Contribution to Nonattainment

    This proposed approval addresses the significant contribution to
nonattainment element of section 110(a)(2)(D)(i)(I) for the 1997 8-hour
ozone and 1997 PM2.5 NAAQS in several ways. It takes into
account California's 2007 Transport SIP, in which the state explains
that meteorological and other characteristics

in California and in the surrounding areas reduce the likelihood that
emissions from sources in California contribute significantly to
nonattainment of the 1997 8-hour ozone or PM2.5 NAAQS in any
downwind state. In addition, EPA has supplemented the state's analysis
with its own evaluation of the evidence to assess whether emissions
sources in California contribute significantly to nonattainment of the
1997 8-hour ozone or PM2.5 NAAQS in other states. First, EPA
has evaluated the potential for ozone transport from California to
specific locations identified in the Transport Rule Proposal by
reviewing ozone back-trajectory analyses and other relevant
information. Second, EPA has considered information in the Brian Timin
Memo, which provides projected future year ozone and annual
PM2.5 design values for monitors in the western U.S. based
on the air quality modeling carried out in support of the Transport
Rule Proposal. Finally, EPA has reviewed recent ozone and
PM2.5 monitoring data for the states bordering California to
consider whether California emissions could contribute to violations of
the 1997 8-hour ozone or PM2.5 NAAQS in those states. Based
on these analyses, we propose to conclude that emissions from
California do not contribute significantly to nonattainment in any
other state for the 1997 8-hour ozone or PM2.5 NAAQS,
consistent with the requirements of CAA section 110(a)(2)(D)(i)(I).
1. Significant Contribution to Nonattainment Evaluation for the 1997 8-
Hour Ozone NAAQS
    To address whether emissions from California sources significantly
contribute to nonattainment of the 1997 8-hour ozone NAAQS in another
state, California argued in the 2007 Transport SIP that meteorological
conditions within the State and its existing air pollution control
programs support a finding that emissions from California sources
``[do] not significantly affect nonattainment areas in other states.''
\20\ Specifically, the State's submittal argues that ozone episodes in
the southwestern U.S. are normally associated with meteorology that
results in stagnant conditions (i.e., not conducive to ozone transport)
and that, on occasion, those conditions are weakly impacted by
migrating low pressure systems over the Pacific Ocean that push air
high above the surface eastward.\21\ Even though acknowledging the
occasional possibility of ozone being transported over long distances,
the State asserted in the 2007 Transport SIP that California's existing
air quality programs (e.g., its motor vehicle emissions control
program, consumer product regulations, stationary source permit
programs, and other control measures) greatly reduce the likelihood
that emissions from California sources will contribute significantly to
nonattainment in any downwind state.\22\
---------------------------------------------------------------------------

    \20\ 2007 State Strategy, Attachment A, page 20.
    \21\ Ibid.
    \22\ Ibid.
---------------------------------------------------------------------------

    Also in support of its conclusion, the State's 2007 Transport SIP
references language in the preamble to CAIR citing EPA's own statement
that, given geography, meteorology, and topography in the western U.S.,
``PM2.5 and 8-hour ozone nonattainment problems are not
likely to be affected significantly by pollution transported across
[the western] states' boundaries.'' \23\ In sum, the State argues in
the 2007 Transport SIP that EPA's statement in the CAIR rulemaking with
respect to the likelihood of transport in western states, together with
the meteorological and other information provided in California's
submittal, support the finding that emissions from California sources
do not significantly affect nonattainment areas in other states.
---------------------------------------------------------------------------

    \23\ See ibid. (quoting CAIR proposal, 69 FR 4566 at 4581,
January 30, 2004).
---------------------------------------------------------------------------

    EPA does not agree with California's assessment in the 2007
Transport SIP that these factors alone demonstrate that emissions from
California sources do not contribute significantly to nonattainment of
the 1997 8-hour ozone NAAQS in other states. Therefore, EPA is
supplementing the State's submittal with additional information in
order to assess this issue more fully, and in light of more recent
information. As noted above, EPA is evaluating the 2007 Transport SIP
taking into account the methodologies and analyses developed in the
Transport Rule Proposal in response to the judicial remand of CAIR, as
well as EPA's projections of future air quality at monitors in western
states in the Timin Memo and preliminary air quality data from monitors
in the states bordering California.
    The Transport Rule Proposal includes an approach to determining
whether emissions from a state contribute significantly to
nonattainment of the 1997 8-hour ozone NAAQS in other states.
Specifically, EPA used existing monitoring data and modeling to project
future concentrations of ozone at monitors to identify areas that are
expected to be violating the 1997 8-hour ozone NAAQS in 2012, based on
the 5-year weighted average design value. We call these monitors
``nonattainment sites'' or ``nonattainment receptors.'' To identify the
states with emissions that may contribute significantly to ozone
nonattainment in other states, the Transport Rule Proposal models the
states' contributions to ambient ozone levels at these nonattainment
receptors.\24\ Because the Transport Rule Proposal does not model the
contribution of emissions from California (and other western states not
fully inside the Transport Rule Proposal's modeling domain) to 8-hour
ozone nonattainment receptors in other states, our assessment in this
proposed action relies on a weight of evidence approach that considers
relevant information from the Transport Rule Proposal pertaining to
states within its modeling domain and additional material such as back-
trajectory analyses, geographical and meteorological factors, EPA's
projections of future air quality at monitors in western states in the
Timin Memo, and EPA's Air Quality System (AQS) \25\ monitoring data.
Although each of the factors considered in the following analysis are
not in and of themselves determinative, consideration of these factors
together provides a reliable qualitative conclusion that emissions from
California sources are not likely to contribute significantly to
nonattainment of the 1997 8-hour ozone NAAQS at monitors in other
states.
---------------------------------------------------------------------------

    \24\ Transport Rule Proposal, 75 FR 45210 at 45253-45273.
    \25\ AQS is EPA's database repository of monitored ambient air
quality data. See http://www.epa.gov/ttn/airs/airsaqs/.
---------------------------------------------------------------------------

    Our analysis begins by assessing California's contribution to the
closest nonattainment receptors for the 1997 8-hour ozone standard. The
Transport Rule Proposal identifies, within its modeling domain
(consisting of 37 states east of the Rocky Mountains, and the District
of Columbia), 11 nonattainment receptors for the 1997 8-hour ozone
standard. Of these, the nonattainment receptors closest to California
are seven receptors in the Dallas-Fort Worth and Houston-Galveston-
Brazoria 8-hour ozone nonattainment areas in eastern Texas. The
remaining four nonattainment receptors for the 1997 8-hour ozone NAAQS
are in Louisiana, New York, and Pennsylvania.\26\
---------------------------------------------------------------------------

    \26\ See Transport Rule Proposal, Table IV.C-11, 75 FR 45210 at
45252.
---------------------------------------------------------------------------

    The nonattainment receptors in Dallas-Fort Worth and Houston-
Galveston-Brazoria areas are over 900 miles from the easternmost border
of California, and the monitors in Louisiana, New York, and
Pennsylvania

are significantly farther away. Although distance alone is not
determinative in the analysis of potential ozone transport, with
increasing distance there are greater opportunities for ozone and
NOX dispersion and/or removal from the atmosphere due to the
effect of winds or chemical sink processes. Moreover, the intervening
Rocky Mountains act as a natural barrier to air pollution transport.
These factors together support a conclusion that California sources do
not contribute significantly to nonattainment of the 1997 8-hour ozone
NAAQS in the nearest areas with nonattainment receptors identified in
the Transport Rule Proposal.
    In order to evaluate the potential impact of emissions from
California sources on the nonattainment receptors identified in the
Transport Rule Proposal, EPA evaluated air parcel pathways from
California to these monitoring sites. Specifically, EPA reviewed the
analysis of ozone transport by the Texas Commission on Environmental
Quality for each exceedance day in 2007, 2008, and 2009 for the seven
nonattainment receptors in the Dallas-Fort Worth and Houston-Galveston-
Brazoria 8-hour ozone nonattainment areas in eastern Texas.\27\
Exceedance days were identified using the AQS Database. Back-
trajectories \28\ were run for all of the days during the 2007-2009
period when ozone concentrations at these receptors exceeded the 1997
8-hour ozone NAAQS (i.e., monitored ozone concentrations were 85 parts
per billion (ppb) or above). These back-trajectory maps indicate that
air parcel pathways to nonattainment receptors in eastern Texas do not
originate in California.
---------------------------------------------------------------------------

    \27\ See Technical Support Document, California 2007 Transport
SIP, Evaluation of Significant Contribution to Nonattainment and
Interference with Maintenance for the 1997 8-hour Ozone NAAQS, U.S.
EPA Region 9, February 25, 2011.
    \28\ Trajectories for each monitor were run backwards in time
for 72 hours (three days), using a trajectory height at the starting
point of 1,500 meters above ground level.
---------------------------------------------------------------------------

    Because back-trajectory analysis results map pathways of air
parcels that may or may not transport pollutants, they cannot be
considered determinative as to the transport of ozone and its
precursors or the absence of such transport from California emission
sources. However, the fact that the air parcel trajectories do not
directly connect California to the nonattainment receptors in eastern
Texas strongly supports the conclusion that emissions of ozone and its
precursors from California are not likely to contribute significantly
to nonattainment of the 1997 8-hour ozone NAAQS at these receptors.
    To assist in the evaluation of the potential for ozone transport
among western states not included in the modeling domain for the
Transport Rule Proposal, EPA also developed an additional analysis in
the Timin Memo identifying monitors projected to record violations of
the 1997 8-hour ozone NAAQS within a modeling domain that includes the
western states.\29\ The Timin Memo identified numerous nonattainment
sites for the 1997 8-hour ozone NAAQS in southern and central
California.\30\ This analysis did not, however, identify any projected
nonattainment receptors for the 1997 8-hour ozone NAAQS in any other
western state. EPA's analysis for western states therefore supports our
proposal to conclude that California sources do not contribute
significantly to nonattainment of the 1997 8-hour ozone NAAQS in other
western states.
---------------------------------------------------------------------------

    \29\ See fn. 12 above.
    \30\ See Timin Memo at Appendix B (``Base year 2003-2007 and
Future Year 2012 8-Hour Average Ozone Design Values--Western
States'').
---------------------------------------------------------------------------

    Finally, in addition to the information in the 2007 Transport SIP,
our review of air parcel pathways to the nearest nonattainment
receptors identified from the modeling analyses conducted for the
Transport Rule Proposal, and EPA's projections of future air quality in
the western states in the Timin Memo, EPA evaluated preliminary air
quality monitoring data for the areas in states bordering California
that are designated nonattainment for the 1997 8-hour ozone NAAQS.
Although significant contribution must be measured not just against
designated nonattainment areas but also against areas with monitors
showing violations of the NAAQS, nonattainment areas are a convenient
starting point for the analysis. The 2007 Transport SIP identifies two
areas in states bordering California that are currently designated
nonattainment for the 1997 8-hour ozone standard: The Las Vegas area in
Clark County, Nevada, and the Phoenix-Mesa area in Arizona. EPA
designated both of these areas as nonattainment for the 1997 8-hour
ozone standard in 2004. See 69 FR 23858 (April 30, 2004); 40 CFR 81.303
and 81.329. Both of these areas, however, have current design values
indicating attainment of the 1997 8-hour ozone NAAQS. Our review of
preliminary monitoring data for the 2007-2009 period available in EPA's
AQS Database indicates that the 8-hour ozone design values for Las
Vegas and Phoenix-Mesa during this period were 78 ppb and 76 ppb,
respectively.\31\ Thus, we believe it is reasonable to conclude that
California sources are not contributing significantly to nonattainment
of the 1997 8-hour ozone NAAQS in either the Las Vegas, Nevada or
Phoenix-Mesa, Arizona nonattainment areas. No other area in the states
bordering California (Oregon, Nevada, or Arizona) is currently
designated nonattainment for the 1997 8-hour ozone NAAQS.
---------------------------------------------------------------------------

    \31\ See U.S. EPA AQS, ``Preliminary Design Value Report,''
2007-2009, for Nevada, Arizona.
---------------------------------------------------------------------------

    As mentioned above, EPA considers not only significant contribution
to designated nonattainment areas, but also to areas with monitor
readings showing violations of the NAAQS. A review of the AQS
monitoring data for adjacent states shows that it is highly unlikely
that emissions from California contribute significantly to violations
of the 1997 8-hour ozone NAAQS in any downwind state. Specifically,
EPA's observed maximum design values at monitors in the western states
during the 2003-2007 period were generally well below the 1997 ozone
NAAQS (except in California), and the 2012 modeling results at these
western monitors (where a future year design value could be estimated)
show a downward trend in ozone.\32\
---------------------------------------------------------------------------

    \32\ See Timin Memo at Appendix B (``Base year 2003-2007 and
Future Year 2012 8-Hour Average Ozone Design Values--Western
States'').
---------------------------------------------------------------------------

    Additionally, we evaluated ozone monitoring data from the 2007-2009
period from each of the ozone monitoring sites in Oregon, Nevada, and
Arizona, to determine whether the ozone levels in any of these states
violate or potentially violate the 1997 8-hour ozone NAAQS.\33\ The
highest ozone design value at these monitoring sites during the 2007-
2009 period was 78 ppb (in the Las Vegas, Nevada area), and most
monitors recorded significantly lower ozone levels.\34\ We have found
no violations of the 1997 8-hour ozone NAAQS at any of the monitors in
states bordering California, nor any indication that emissions from
California sources contribute significantly to nonattainment of the
1997 8-hour ozone NAAQS in these adjacent states.
---------------------------------------------------------------------------

    \33\ See U.S. EPA AQS, ``Preliminary Design Value Report,''
2007-2009, for Oregon, Nevada, Arizona.
    \34\ Ibid.
---------------------------------------------------------------------------

    The fact that monitors in these nearby areas are not registering
violations of the NAAQS does not in itself conclusively establish that
emissions from California could not contribute in the aggregate to
violations in any other state. But this fact combined with our
evaluation of the nearest nonattainment receptors in

eastern Texas, taking into account distance, topographical barriers,
and typical meteorological conditions, supports California's conclusion
that emissions from its sources do not contribute significantly to
nonattainment of the 1997 8-hour ozone NAAQS in other states, in
accordance with section 110(a)(2)(D)(i)(I).
2. Significant Contribution to Nonattainment Evaluation for the 1997
PM2.5 NAAQS
    In its 2007 Transport SIP, California argues that distance to the
nearest designated PM2.5 nonattainment area, topographical
features and meteorology support a finding that California sources do
not significantly contribute to nonattainment of the 1997
PM2.5 NAAQS in another state. The 2007 Transport SIP also
references EPA's technical support document (TSD) for the
PM2.5 NAAQS nonattainment designations (PM2.5
Designations TSD),\35\ which identifies Libby, Montana (in Lincoln
County), as the area closest to California that is designated
nonattainment for the 1997 PM2.5 standards.\36\ As EPA noted
in the PM2.5 Designations TSD, PM2.5 in Libby is
predominantly local in origin (e.g., residential wood-burning stoves
during the winter time, when frequent and persistent temperature
inversions occur, were specifically identified as a key source of
particulate emissions in the area). Thus, California correctly noted
that EPA concluded that PM2.5 pollution in Libby is a
localized problem.\37\
---------------------------------------------------------------------------

    \35\ See Technical Support for State and Tribal Air Quality Fine
Particle (PM2.5) Designations, ``EPA 9-Factor Analyses
for Montana for the Designation of PM2.5 Nonattainment
Areas,'' Chapter 6.8.1, December 17, 2004.
    \36\ EPA designated this area as nonattainment for the 1997
PM2.5 NAAQS in 2005. 70 FR 944 (January 5, 2005) and 40
CFR 81.305.
    \37\ ``Factor 6'' of this 9-Factor Analysis describes the
meteorology in the Libby area as follows: ``Libby Montana is located
in the northwestern part of the state in a narrow north-south
oriented valley. The ridgetops surrounding Libby are approximately
4,000 feet higher than the town. There are no other towns or large
emissions sources immediately upwind, so transport of high
background concentrations into Libby is considered unlikely. The
highest PM2.5 concentrations in Libby generally occur
during the months of November through February. During the summer
months concentrations typically average less than half the level of
the annual PM2.5 NAAQS, while winter concentrations may
double the NAAQS. The much higher concentrations in winter are
related to stagnant weather conditions dominated by light winds and
strong temperature inversions. These meteorological conditions may
trap emissions within the valley for many days. No recent
meteorological data is available for Libby, however, data from
Kalispell, MT show calm wind conditions occur 35 percent of the time
in the winter months and only 15 percent of the time in the spring
and summer. Vertical temperature soundings at Great Falls in Western
MT also show a very high frequency of surface temperature inversions
in the winter.
    Due to the meteorology conditions in the town and surrounding
vicinity of Libby and due to the topographical features within
Lincoln County and more specifically around Libby, that create
stagnant weather conditions, EPA feels the adjacent counties do not
impact the PM2.5 monitor located at the Libby Courthouse
Annex and that the nonattainment problem is a localized
PM2.5 problem.'' PM2.5 Designations TSD at
Chapter 6.8.1.
---------------------------------------------------------------------------

    The fact that nonattainment in a given area is primarily the result
of local emissions sources does not exclude the possibility of
significant contribution to nonattainment from interstate transport.
This fact and other evidence, however, support the conclusion that
emissions from California sources are not significantly contributing to
violations in Libby, Montana. That area is more than 900 miles away
from California and is on the other side of the Sierra Nevada
Mountains, a 400-mile-long north-south range of mountains that act as a
natural barrier to air movement between California and Montana.\38\ In
addition, Libby is not in the predominant direction of winds from
California, as transport winds generally flow from west to east, and
not toward the north. Given the relatively long distance between
California and Libby, Montana, the intervening mountainous topography,
the localized nature of the PM2.5 nonattainment problem in
Libby, and the general west-to-east direction of transport winds across
California, EPA believes it is reasonable to conclude that California
sources do not contribute significantly to nonattainment of the 1997
PM2.5 NAAQS in Libby, Montana. We note also that preliminary
data available in EPA's AQS Database for the 2007-2009 period indicate
that the Libby, Montana nonattainment area is currently attaining the
1997 PM2.5 standards.\39\
---------------------------------------------------------------------------

    \38\ See PM2.5 Designations TSD at Chapter 6.8.1.
    \39\ This data indicates the annual PM2.5 design
value for the Libby, Montana area during the 2007-2009 period was
12.2 [mu]g/m\3\. See U.S. EPA AQS, ``Preliminary Design Value
Report,'' 2007-2009, for Montana.
---------------------------------------------------------------------------

    EPA does not agree with California's assessment in the 2007
Transport SIP that these factors alone demonstrate that emissions from
California sources do not contribute significantly to nonattainment of
the 1997 PM2.5 NAAQS in any other states. Therefore, EPA is
supplementing the state's submission with additional information in
order to assess this issue more fully, and in light of more recent
information. As noted above, EPA is evaluating the 2007 Transport SIP
taking into account the methodologies and analyses developed in the
Transport Rule Proposal in response to the judicial remand of CAIR, as
well as EPA's projections of future air quality at monitors in western
states in the Timin Memo and preliminary air quality data from monitors
in the states bordering California.
    Specifically, we identified the nonattainment receptors for the
1997 annual PM2.5 NAAQS closest to California to evaluate
whether emissions from California sources contribute significantly to
nonattainment of the 1997 PM2.5 NAAQS in any other
state.\40\ For the 1997 annual PM2.5 NAAQS, the
nonattainment receptors closest to California that EPA identified from
the modeling analyses conducted for the Transport Rule Proposal are all
east of the Mississippi River.\41\ Given the significant distance
between California and these nonattainment receptors, and the
intervening mountainous terrain, we believe it is reasonable to
conclude that California sources do not contribute significantly to
nonattainment of the 1997 annual PM2.5 NAAQS in any of these
areas.
---------------------------------------------------------------------------

    \40\ For PM2.5, the Transport Rule Proposal
identified nonattainment receptors for the 1997 annual
PM2.5 NAAQS and the 2006 24-hour PM2.5 NAAQS.
See 75 FR 45210 at 45212. Because our proposal on California's 2007
Transport SIP addresses requirements of CAA section 110(a)(2)(D)(i)
only for purposes of the 1997 ozone and PM2.5 NAAQS, for
PM2.5 purposes we consider only the nonattainment
receptors for the 1997 annual PM2.5 NAAQS identified in
the Transport Rule Proposal.
    \41\ Specifically, the nonattainment sites for the 1997 annual
PM2.5 standard are located in Alabama, Georgia, Illinois,
Indiana, Kentucky, Michigan, Ohio, Pennsylvania, and West Virginia.
See Transport Rule Proposal, 75 FR 45210 at 45247-45248 (August 2,
2010).
---------------------------------------------------------------------------

    To address the potential for impacts on states not included in the
modeling domain for the Transport Rule Proposal, we also evaluated
whether there are monitors suitable for consideration as nonattainment
receptors in western states outside of the geographic area covered by
the Transport Rule Proposal. We note that EPA's analysis in the Timin
Memo for western states identified numerous nonattainment sites for the
1997 annual PM2.5 NAAQS in southern and central
California.\42\ This analysis did not, however, identify any projected
nonattainment receptors for the 1997 annual PM2.5 NAAQS in
any other western state. Thus, we believe it is reasonable to conclude
that California sources do not contribute significantly to
nonattainment of the 1997 PM2.5 NAAQS in other states.
---------------------------------------------------------------------------

    \42\ See Timin Memo at Appendix A (``Base year 2003-2007 and
Future Year 2012 Annual Average PM2.5 Design Values--
Western States'').
---------------------------------------------------------------------------

    The analysis for the Transport Rule Proposal did not identify any
nonattainment receptors for the 1997

24-hour PM2.5 NAAQS in the portions of the U.S. covered by
the Transport Rule Proposal modeling domain (i.e., the 12 kilometer
(km) grid covering the continental U.S. east of the Rockies).\43\
Recent monitoring data in EPA's Air Quality System (2007-2009 design
values that are under final EPA review) indicate that the highest 24-
hour PM2.5 design value in the 47 states of the continental
U.S. (excluding California) is 50 [mu]g/m\3\,\44\ which is well below
the level of the 1997 24-hour PM2.5 NAAQS of 65 [mu]g/m\3\.
This data further supports our proposed finding that California sources
do not contribute significantly to nonattainment of the 1997 24-hour
PM2.5 NAAQS in any other state.
---------------------------------------------------------------------------

    \43\ 75 FR 45210 at 45249-45251 (August 2, 2010).
    \44\ These values were recorded at monitors in Liberty-Clairton,
Pennsylvania and Provo, Utah. See http://epa.gov/airtrends/pdfs/PM2.5%202007-2009%20design%20value%20update.pdf. Data from EPA's Air
Quality System can be viewed at http://www.epa.gov/ttn/airs/airsaqs/.
---------------------------------------------------------------------------

    Finally, EPA evaluated PM2.5 air quality data for areas
in the states bordering California to determine whether California
sources might contribute significantly to violations of the 1997
PM2.5 NAAQS in these nearby areas. No areas in Oregon,
Nevada, or Arizona are currently designated nonattainment for the 1997
PM2.5 NAAQS. As mentioned above, however, EPA considers not
only significant contribution to designated nonattainment areas, but
also to areas with monitoring data showing violations of the NAAQS. A
review of the AQS monitoring data for adjacent states shows that it is
highly unlikely that emissions from California contribute significantly
to violations of the 1997 annual PM2.5 NAAQS in any downwind
state.
    Specifically, we reviewed preliminary PM2.5 monitoring
data for the 2007-2009 period available in EPA's AQS Database from all
PM2.5 monitoring sites in Oregon, Nevada, and Arizona, to
determine whether the PM2.5 design values in any of these
states potentially violate the 1997 annual PM2.5 NAAQS.\45\
During this period only one monitor in these adjoining states, the
``Cowtown'' monitor in Casa Grande, Arizona (monitor ID 04-021-3013),
has a PM2.5 design value exceeding the 1997 annual standard
of 15.0 [mu]g/m\3\.\46\ EPA has separately determined, however, that
this monitor is not suitable for determining compliance with the 1997
annual PM2.5 standard because the monitor functions as a
population-oriented microscale (i.e., localized hot spot) monitor.\47\
No other PM2.5 monitor in the three states bordering
California recorded a violation of the 1997 annual or 24-hour
PM2.5 NAAQS during the 2007-2009 period.\48\
---------------------------------------------------------------------------

    \45\ See U.S. EPA AQS, ``Preliminary Design Value Report,''
2007-2009, for Oregon, Nevada, and Arizona.
    \46\ The Cowtown monitor had a PM2.5 design value of
18.8 [mu]g/m\3\. See U.S. EPA AQS, ``Preliminary Design Value
Report,'' 2007-2009, for Arizona.
    \47\ See 76 FR 6056 (February 3, 2011); see also ``Technical
Support Document for Determination that the Cowtown Monitor is
Ineligible for Comparison with the Annual PM2.5 NAAQS,''
April 26, 2010.
    \48\ Our review of AQS data for the 2007-2009 period in the
three states bordering California indicated the highest valid annual
PM2.5 design value was 12.8 [mu]g/m\3\ (monitor ID 04-
023-0004 in Nogales, Arizona) and the highest valid 24-hour
PM2.5 design value was 47 [mu]g/m\3\ (monitor ID 41-035-
0004 in Klamath Falls, Oregon). See U.S. EPA AQS, ``Preliminary
Design Value Report,'' 2007-2009, for Oregon, Nevada, and Arizona.
---------------------------------------------------------------------------

    The fact that monitors in these nearby areas are not registering
violations of the 1997 PM2.5 NAAQS does not in itself
conclusively establish that emissions from California could not
contribute in the aggregate to violations in other states. But this
fact combined with our evaluation of the nearest nonattainment
receptors in states east of the Mississippi River, taking into account
distance, topographical barriers, and typical meteorological
conditions, supports California's conclusion on PM2.5
contribution for the 1997 NAAQS.
3. Conclusion Regarding Significant Contribution to Nonattainment
    Based on the weight of evidence discussed above, including the
location of the nearest projected nonattainment sites, distance to the
nearest designated PM2.5 nonattainment area, meteorology,
topography, and recent air quality monitoring data, we propose to
determine that California's 2007 Transport SIP is adequate to ensure
that emissions from California do not significantly contribute to
nonattainment in any other state for the 1997 8-hour ozone or 1997
PM2.5 NAAQS, consistent with the requirements of CAA section
110(a)(2)(D)(i)(I). Thus, we propose to determine that California's SIP
includes the measures necessary to prevent such prohibited interstate
transport impacts for these NAAQS.

B. Evaluation of Interference With Maintenance

    California's 2007 Transport SIP relies upon the recommendations in
EPA's 2006 Guidance and does not provide a specific analysis of the
interference with maintenance element of section 110(a)(2)(D)(i). Given
the court decision on CAIR in the interim, however, EPA believes that
it is necessary to evaluate the submission for section
110(a)(2)(D)(i)(I) in such a way as to assure that the interfere with
maintenance element of the statute is given independent meaning and is
appropriately evaluated using the types of information that EPA
recommended in the 2006 Guidance. To accomplish this, in this proposed
action, EPA has supplemented California's analysis with an approach
comparable to that of the Transport Rule Proposal in order to
adequately evaluate whether emissions from California sources interfere
with maintenance of these NAAQS in other states. As with the
significant contribution to nonattainment analysis, we have evaluated
the potential for transport of emissions from California sources to
specific locations identified in the Transport Rule Proposal, EPA's
projected future year ozone and PM2.5 design values in the
Timin Memo for monitors in the western U.S., and preliminary air
quality data from monitors in the states bordering California. Based on
these analyses, we propose to conclude that emissions from California
sources do not interfere with maintenance of the 1997 8-hour ozone
NAAQS or 1997 PM2.5 NAAQS in any other state, consistent
with the requirements of CAA section 110(a)(2)(D)(i)(I).
1. Interfere With Maintenance Evaluation for the 8-Hour Ozone NAAQS
    As discussed above, in the Transport Rule Proposal, EPA projected
future concentrations of ozone at monitors to identify areas that are
expected to be violating the NAAQS or to have difficulty maintaining
compliance with the NAAQS in 2012. For purposes of the interfere with
maintenance evaluation, EPA projected future concentrations of ozone at
monitors to identify areas that are expected to have a maximum design
value (based on a single 3-year period) that exceeds the 1997 8-hour
ozone NAAQS and by 2012. EPA anticipates that these ``maintenance
receptors'' or ``maintenance sites'' will have difficulty in
maintaining attainment of the NAAQS if there are adverse variations in
meteorology or emissions.
    To identify the states with emissions that may cause interference
with attainment of the NAAQS at the maintenance receptors, the
Transport Rule Proposal models the states' contributions to ambient
ozone levels at these maintenance receptors.\49\ Because the Transport
Rule Proposal does not model the contribution of emissions

from California (and other western states not fully inside the
Transport Rule Proposal's modeling domain) to 8-hour ozone maintenance
receptors in other states, our assessment relies on a weight of
evidence approach that considers relevant information from the
Transport Rule Proposal pertaining to states within its modeling domain
and additional information such as back-trajectory analyses,
geographical and meteorological factors, EPA's projections of future
air quality at monitors in western states in the Timin Memo, and AQS
monitoring data. Although each of the factors considered in the
following analysis is not in and of itself determinative, consideration
of these factors together provides a reliable qualitative conclusion
that emissions from California are not likely to interfere with
maintenance of the 1997 8-hour ozone NAAQS at monitors in other states.
---------------------------------------------------------------------------

    \49\ See Transport Rule Proposal, 75 FR 45210 at 45253-45273.
---------------------------------------------------------------------------

    Our analysis begins by assessing California's contribution to the
closest maintenance receptors for the 1997 8-hour ozone standard. The
Transport Rule Proposal identifies 16 maintenance receptors for the
1997 8-hour ozone standard within its modeling domain (consisting of 37
states east of the Rocky Mountains, and the District of Columbia). Of
these, the receptors closest to California are eight receptors in the
Dallas-Fort Worth and Houston-Galveston-Brazoria 8-hour ozone
nonattainment areas in eastern Texas. The remaining eight maintenance
sites are located in Connecticut, Georgia, New York and
Pennsylvania.\50\
---------------------------------------------------------------------------

    \50\ See Transport Rule Proposal, Table IV.C-12, 75 FR 45210 at
45252-45253.
---------------------------------------------------------------------------

    As discussed above in section III.A.1, the Dallas-Fort Worth and
Houston-Galveston-Brazoria areas are over 900 miles from the
easternmost border of California. The maintenance receptor monitors
located in Connecticut, Georgia, New York and Pennsylvania are
significantly farther away. Although distance alone is not
determinative in the analysis of potential ozone transport, with
increasing distance there are greater opportunities for ozone and
NOX dispersion and/or removal from the atmosphere.
    To evaluate further the potential for California emissions to
interfere with maintenance at the closest maintenance receptor
locations, EPA conducted an analysis of ozone transport for each
exceedance day in 2005 and 2006 for the eight maintenance receptors in
the Dallas-Fort Worth and Houston-Galveston-Brazoria 8-hour ozone
nonattainment areas in eastern Texas.\51\ Exceedance days were
identified using the AQS Database, EPA's repository of monitored
ambient air quality data. EPA ran back-trajectories \52\ for those days
during the 2005-2006 period when ozone concentrations at these
receptors exceeded the 1997 8-hour ozone NAAQS (i.e., monitored ozone
concentrations were 85 ppb or above). These back-trajectory maps
indicate that air parcel pathways to maintenance receptors in eastern
Texas do not originate in California.
---------------------------------------------------------------------------

    \51\ See Technical Support Document, California 2007 Transport
SIP, Evaluation of Significant Contribution to Nonattainment and
Interference with Maintenance for the 1997 8-hour Ozone NAAQS, U.S.
EPA Region 9, February 25, 2011.
    \52\ For each monitor, EPA ran the trajectories backwards in
time for 72 hours (three days), using a trajectory height at the
starting point of 1,500 meters above ground level.
---------------------------------------------------------------------------

    Because back-trajectory analysis results map pathways of air
parcels that may or may not transport pollutants, they cannot be
considered determinative as to the transport of ozone and its
precursors or the absence of such transport from California emission
sources. However, the fact that the air parcel trajectories do not
connect California directly to the maintenance receptors in eastern
Texas strongly supports the conclusion that emissions of ozone and its
precursors from California sources are not likely to interfere with
maintenance of the 1997 8-hour ozone NAAQS at these receptors. The
maintenance receptors for the 1997 ozone standard identified in the
Transport Rule Proposal are in similar locations relative to California
as are the nonattainment receptors discussed above in section III.A.1,
and the same considerations regarding distance, topography, and
meteorology therefore support our proposal to determine that emissions
from California sources do not interfere with maintenance at the
maintenance receptor sites. Thus, EPA believes it is reasonable to
conclude that California sources do not interfere with maintenance of
the 1997 8-hour ozone NAAQS in any other state.
    We note that EPA's analysis in the Timin Memo, for western states
not included in the modeling domain for the Transport Rule Proposal,
identified four maintenance sites for the 1997 8-hour ozone NAAQS in
southern and central California.\53\ This analysis did not, however,
identify any projected maintenance receptors for the 1997 8-hour ozone
NAAQS in any other western state. The absence of monitors even suitable
for comparison for this purpose indicates that emissions from
California sources do not have such an impact in western states. Thus,
EPA's analysis for western states also supports our proposal to
conclude that California sources do not interfere with maintenance of
the 1997 8-hour ozone NAAQS in other states.
---------------------------------------------------------------------------

    \53\ See Timin Memo at Appendix B (``Base year 2003-2007 and
Future Year 2012 8-Hour Average Ozone Design Values--Western
States'').
---------------------------------------------------------------------------

    Finally, as discussed above in section III.A.1, EPA's observed
maximum design values at monitors in the western states during the
2003-2007 period were generally well below the 1997 ozone NAAQS, and
the 2012 modeling results at these western monitors (where a future
year design value could be estimated) show a downward trend in
ozone.\54\ Additionally, we evaluated ozone monitoring data from the
2007-2009 period from each of the ozone monitoring sites in Oregon,
Nevada, and Arizona, and found no violations of the 1997 8-hour ozone
NAAQS at any of these monitors during this period.\55\ The fact that
monitors in these nearby areas are not registering violations of the
NAAQS does not in itself conclusively establish that emissions from
California could not interfere with maintenance of the 1997 8-hour
ozone NAAQS in any other state. But this fact combined with our
evaluation of the nearest maintenance receptors in eastern Texas,
taking into account distance, topographical barriers, and typical
meteorological conditions, in addition to the back-trajectory analyses
conducted to evaluate air parcel pathways to eastern Texas, support our
proposal to conclude that California sources do not interfere with
maintenance of the 1997 8-hour ozone NAAQS in any other state.
---------------------------------------------------------------------------

    \54\ See Timin Memo at Appendix B (``Base year 2003-2007 and
Future Year 2012 8-Hour Average Ozone Design Values--Western
States'').
    \55\ See U.S. EPA AQS, ``Preliminary Design Value Report,''
2007-2009, for Oregon, Nevada, and Arizona.
---------------------------------------------------------------------------

2. Interfere With Maintenance Evaluation for the 1997 PM2.5
NAAQS
    The Transport Rule Proposal identifies, within its modeling domain,
16 maintenance receptors for the 1997 annual PM2.5 NAAQS. Of
these, the closest to California is one receptor located in the Harris
County PM2.5 nonattainment area in eastern Texas. The
remaining 15 maintenance receptors for the 1997 annual PM2.5
NAAQS are all located in states east of the Mississippi River.\56\
---------------------------------------------------------------------------

    \56\ Specifically, the remaining 15 maintenance sites for the
1997 annual PM2.5 NAAQS are located in Illinois,
Kentucky, New York, Ohio, Pennsylvania, and West Virginia.
---------------------------------------------------------------------------

    As discussed above in section III.A.1, the Dallas-Fort Worth and
Houston-

Galveston-Brazoria areas are over 900 miles from the easternmost border
of California, and states with maintenance receptors east of the
Mississippi River are even farther away. Because the maintenance
receptors for the 1997 PM2.5 standard identified in the
Transport Rule Proposal are in similar locations relative to California
as are the nonattainment receptors discussed above in sections III.A.1
and A.2, the same considerations regarding distance, topography, and
meteorology support our proposal to determine that emissions from
California sources do not interfere with maintenance at the maintenance
receptor sites. EPA therefore believes it is reasonable to conclude
that California sources do not interfere with maintenance of the 1997
PM2.5 NAAQS in any other state.
    We note that EPA's analysis in the Timin Memo, for western states
not included in the modeling domain for the Transport Rule Proposal,
identified numerous maintenance sites for the 1997 annual
PM2.5 NAAQS in southern and central California.\57\ This
analysis did not, however, identify any projected maintenance receptors
for the 1997 annual PM2.5 NAAQS in any other western state.
Thus, we believe it is reasonable to conclude that California sources
do not interfere with maintenance of the 1997 PM2.5 NAAQS in
other states.
---------------------------------------------------------------------------

    \57\ See Timin Memo at Appendix A (``Base year 2003-2007 and
Future Year 2012 Annual Average PM2.5 Design Values--
Western States'').
---------------------------------------------------------------------------

    Finally, as discussed above in section III.A.2, EPA reviewed
PM2.5 monitoring data for the 2007-2009 period from all
PM2.5 monitoring sites in states bordering California
(Oregon, Nevada, and Arizona) and found no violations of the 1997
annual PM2.5 standard. The fact that monitors in these
nearby areas are not registering violations of the NAAQS does not in
itself conclusively establish that emissions from California could not
interfere with maintenance of the 1997 annual PM2.5 NAAQS in
any other state. But this fact combined with our evaluation of the
nearest maintenance receptor in eastern Texas, taking into account
distance, topographical barriers, and typical meteorological
conditions, supports our proposal to conclude that California sources
do not interfere with maintenance of the 1997 PM2.5 NAAQS in
any other state.
    The analysis for the Transport Rule Proposal did not identify any
maintenance receptors for the 1997 24-hour PM2.5 NAAQS in
the portions of the U.S. covered by the Transport Rule Proposal
modeling domain.\58\ Recent monitoring data in EPA's AQS Database
(2007-2009 design values that are under final EPA review) indicate that
the highest 24-hour PM2.5 design value in the 47 states of
the continental U.S. (excluding California) is 50 [micro]g/m\3\, which
is well below the level of the 1997 24-hour PM2.5 NAAQS of
65 [micro]g/m\3\.\59\ This data further supports our proposed finding
that California emission sources do not interfere with maintenance of
the 1997 PM2.5 NAAQS in any other state.
---------------------------------------------------------------------------

    \58\ 75 FR 45210 at 45249-45251 (August 2, 2010). See also fn.
40 and fn. 48.
    \59\ Data from EPA's Air Quality System can be viewed at http://www.epa.gov/ttn/airs/airsaqs/.
---------------------------------------------------------------------------

3. Conclusion Regarding Interference With Maintenance
    Based on the weight of evidence, including the location of the
nearest projected maintenance sites, taking into account distance,
meteorology, topography, and recent air quality monitoring data, as
discussed above, we propose to determine that California's 2007
Transport SIP is adequate and that emissions from California do not
interfere with maintenance in any other state for the 1997 8-hour ozone
or 1997 PM2.5 NAAQS, consistent with the requirements of CAA
section 110(a)(2)(D)(I). Thus, we propose to determine that
California's SIP includes the measures necessary to prevent such
prohibited interstate transport impacts for these NAAQS.

IV. Proposed Action

    Under section 110(k) of the Clean Air Act, EPA is proposing to
approve the 2007 Transport SIP submitted by CARB on November 17, 2007,
as adequate to prohibit emissions from California sources that will
contribute significantly to nonattainment of the 1997 8-hour ozone or
1997 PM2.5 NAAQS in any other state, as required by CAA
section 110(a)(2)(D)(i)(I). EPA is also proposing to approve the 2007
Transport SIP as adequate to prohibit emissions from California sources
that will interfere with maintenance of these NAAQS by any other state,
as required by section 110(a)(2)(D)(i)(I). Accordingly, we propose to
find that the California SIP contains provisions adequate to prevent
significant contribution to nonattainment of, and interference with
maintenance of, these NAAQS and does not require any additional
measures for this purpose at this time. This proposed action does not
apply to the remaining two elements of CAA section 110(a)(2)(D)(i)
regarding interference with measures required to prevent significant
deterioration of air quality or to protect visibility in another state.
We intend to evaluate and act upon the 2007 Transport SIP for purposes
of these additional requirements of CAA section 110(a)(2)(D)(i) in
separate actions.
    EPA is soliciting public comments on this proposal and will accept
comments until the date noted in the ``DATES'' section above.

V. 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, EPA's role is to approve state
choices, provided that they meet the criteria of the Clean Air Act.
Accordingly, this 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 Order
12866 (58 FR 51735, October 4, 1993);
     Does not impose an information collection burden under the
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact
on a substantial number of small entities under the Regulatory
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or
uniquely affect small governments, as described in the Unfunded
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have Federalism implications as specified in
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Is not an economically significant regulatory action based
on health or safety risks subject to Executive Order 13045 (62 FR
19885, April 23, 1997);
     Is not a significant regulatory action subject to
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Is not subject to requirements of Section 12(d) of the
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272
note) because application of those requirements would be inconsistent
with the Clean Air Act; and
     Does not provide EPA with the discretionary authority to
address, as appropriate, disproportionate human health or environmental
effects, using

practicable and legally permissible methods, under Executive Order
12898 (59 FR 7629, February 16, 1994).
    In addition, this proposed rule does not have tribal implications
as specified by Executive Order 13175 (65 FR 67249, November 9, 2000),
because the SIP is not approved to apply in Indian country located in
the state, and EPA notes that it will not impose substantial direct
costs on tribal governments or preempt tribal law.

List of Subjects in 40 CFR Part 52

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

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

    Dated: March 11, 2011.
Jared Blumenfeld,
Regional Administrator, Region IX.
[FR Doc. 2011-6302 Filed 3-16-11; 8:45 am]
BILLING CODE 6560-50-P