
[Federal Register Volume 76, Number 52 (Thursday, March 17, 2011)]
[Proposed Rules]
[Pages 14616-14626]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-6302]


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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.

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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.

[[Page 14617]]

    2. E-mail: mays.rory@epa.gov.
    3. Fax: 415-947-3579.
    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, (415) 972-3227, 
mays.rory@epa.gov.

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.
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    \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.
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    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\
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    \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.
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    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.
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    \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).

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[[Page 14618]]

    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.
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    \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).
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    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.
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    \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.
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    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.
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    \7\ 2006 Guidance at 5.
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    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.
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    \8\ See North Carolina v. EPA, 531 F.3d 896 (DC Circuit 2008).
    \9\ 531 F.3d at 909.
    \10\ Ibid.
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    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.
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    \11\ See 75 FR 45210 (August 2, 2010).
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    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

[[Page 14619]]

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

[[Page 14620]]

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\
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    \20\ 2007 State Strategy, Attachment A, page 20.
    \21\ Ibid.
    \22\ Ibid.
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    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.
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    \23\ See ibid. (quoting CAIR proposal, 69 FR 4566 at 4581, 
January 30, 2004).
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    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

[[Page 14621]]

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

[[Page 14622]]

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

[[Page 14623]]

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

[[Page 14624]]

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

[[Page 14625]]

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

[[Page 14626]]

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


