
[Federal Register Volume 76, Number 67 (Thursday, April 7, 2011)]
[Proposed Rules]
[Pages 19292-19304]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-8330]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R10-OAR-2011-0003; FRL-9291-4]


Approval and Promulgation of Implementation Plans; Oregon; 
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 a portion of the State 
Implementation Plan (SIP) revision submitted by the State of Oregon 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

[[Page 19293]]

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 Oregon'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 May 9, 2011.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R10-
OAR-2011-0003, by one of the following methods:
    A. http://www.regulations.gov. Follow the on-line instructions for 
submitting comments.
    B. E-Mail: R10-Public_Comments@epa.gov.
    C. Mail: Donna Deneen, U.S. Environmental Protection Agency, Region 
10, 1200 Sixth Avenue, Suite 900, Mail Stop: AWT-107, Seattle, WA 
98101.
    D. Hand Delivery: U.S. Environmental Protection Agency, Region 10, 
Attn: Donna Deneen (AWT-107), 1200 Sixth Avenue, Suite 900, Seattle, 
Washington 98101, 9th Floor. Such deliveries are only accepted during 
normal hours of operation, and special arrangements should be made for 
deliveries of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-R10-OAR-
2011-0003. EPA's policy is that all comments received 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 information claimed to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Do not submit information that you 
consider to be CBI or otherwise protected through http://www.regulations.gov or e-mail. The http://www.regulations.gov Web site 
is an ``anonymous access'' system, which means EPA will not know your 
identity or contact information unless you provide it in the body of 
your comment. If you send an e-mail comment directly to EPA without 
going through http://www.regulations.gov, your e-mail address will be 
automatically captured and included as part of the comment that is 
placed in the public docket and made available on the Internet. If you 
submit an electronic comment, EPA recommends that you include your name 
and other contact information in the body of you comment and with any 
disk or CD-ROM you submit. 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. Electronic files should avoid 
the use of special characters, any form of encryption, and be free of 
any defects or viruses.
    Docket: All documents in the electronic docket are listed in the 
www.regulations.gov index. Although listed in the index, some 
information, i.e., CBI or other information whose disclosure is 
restricted by statute, is not publicly available. Certain other 
material, such as copyrighted material, is not placed on the Internet 
and will be publicly available only in hard copy form. Publicly 
available docket materials are available either electronically in 
http://www.regulations.gov or in hard copy during normal business hours 
at the Office of Air, Waste and Toxics, U.S. Environmental Protection 
Agency, Region 10, 1200 Sixth Avenue, Suite 900, Seattle, Washington 
98101.

FOR FURTHER INFORMATION CONTACT: Donna Deneen, (206) 553-6706 or 
deneen.donna@epa.gov.

SUPPLEMENTARY INFORMATION: Throughout this notice, the words ``we'', 
``us'', or ``our'' means the Environmental Protection Agency (EPA).

Table of Contents

I. What proposed action is EPA taking?
II. What is a SIP?
III. What is the background for this proposed action?
IV. What is the state process to submit these materials to EPA?
V. What is EPA's evaluation of the state's submission?
    A. EPA's 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 to 
Nonattainment
    B. EPA's Evaluation of Interference With Maintenance
    1. Oregon's 2010 Interstate Transport SIP
    2. Interference With Maintenance Evaluation for the 8-Hour Ozone 
NAAQS
    3. Interference With Maintenance Evaluation for the 1997 
PM2.5 NAAQS
    4. Conclusion Regarding Interference With Maintenance
VI. Proposed Action
VII. Statutory and Executive Order Reviews

I. What proposed action is EPA taking?

    EPA is proposing to approve a portion of Oregon's Interstate 
Transport State Implementation Plan (SIP) revision for the 1997 8-hour 
ozone and 1997 PM2.5 NAAQS submitted by the Oregon 
Department of Environmental Quality (ODEQ) on June 23, 2010.\1\ 
Specifically, we are proposing to approve the portion of the interstate 
transport SIP revision that addresses the following elements of CAA 
section 110(a)(2)(D)(i): (1) Significant contribution to nonattainment 
of these NAAQS in any other state; and (2) interference with 
maintenance of these NAAQS by any other state. EPA will address element 
(3), interference with any other state's required measures to prevent 
significant deterioration (PSD) of its air quality; and element (4), 
interference with any other state's required measures to protect 
visibility, in a separate action.\2\ 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 transmittal letters dated June 23, 2010, from Joni 
Hammond, Deputy Director, ODEQ, and December 23, 2010, from Dick 
Pedersen, Director, ODEQ, to Dennis McLerran, Regional 
Administrator, EPA Region 10.
    \2\ On March 8, 2011, EPA proposed to approve the Oregon 
interstate transport SIP provisions addressing interference with any 
other state's required measures to protect visibility. See 76 FR 
12651 (March 8, 2011).
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II. What is a SIP?

    Section 110(a) of the CAA requires each state to develop a plan 
that provides for the implementation, maintenance, and enforcement of 
the NAAQS. EPA establishes NAAQS under section 109 of the CAA. 
Currently, the NAAQS address six criteria pollutants: Carbon monoxide, 
nitrogen dioxide, ozone, lead, particulate matter, and sulfur dioxide.
    The plan developed by a state is referred to as the SIP. The 
content of the SIP is specified in section 110 of the CAA, other 
provisions of the CAA, and applicable regulations. SIPs can be 
extensive, containing state regulations or other enforceable measures 
and various types of supporting information, such as emissions 
inventories, monitoring networks, and modeling demonstrations.
    A primary purpose of the SIP is to provide the air pollution 
regulations, control strategies, and other means or techniques 
developed by the state to

[[Page 19294]]

ensure that the ambient air within that state meets the NAAQS. However, 
another important aspect of the SIP is to ensure that emissions from 
within the state do not have certain prohibited impacts upon the 
ambient air in other states through interstate transport of pollutants. 
This SIP requirement is specified in section 110(a)(2)(D). Pursuant to 
that provision, each state's SIP must contain provisions adequate to 
prevent emissions that significantly contribute to violations of the 
NAAQS in any other state, interfere with maintenance in any other 
state, interfere with any other state's required measures to prevent 
significant deterioration of its air quality, and interfere with any 
other state's required measures to protect visibility.
    States are required to update or revise SIPs under certain 
circumstances. One such circumstance is EPA's promulgation of a new or 
revised NAAQS. Each state must submit these revisions to EPA for 
approval and incorporation into the federally-enforceable SIP.

III. What is the background for this proposed action?

    On July 18, 1997, EPA promulgated new standards for 8-hour ozone 
\3\ and fine particulate matter \4\ (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).
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    \3\ See 62 FR 38856. The level of the 1997 8-hour ozone NAAQS is 
0.08 parts per million (ppm). 40 CFR part 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.''
    \4\ See 62 FR 38652. The level of the 1997 PM2.5 
NAAQS are 15.0 [micro]g/m\3\ (annual arithmetic mean concentration) 
and 65 [micro]g/m\3\ (24-hour average concentration). 40 CFR part 
50.7. The annual standard is met when the 3-year average of the 
annual mean concentrations is 15.0 [micro]g/m\3\ or less (i.e., less 
than 15.05 [micro]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 [micro]g/m\3\ or less (i.e., less than 65.5 [micro]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).\5\
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    \5\ Memorandum from William T. Harnett entitled ``Guidance for 
State Implementation Plan (SIP) Submissions 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 interstate 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 subsection.
    The first element of section 110(a)(2)(D)(i)(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 that ``contribute 
significantly'' to nonattainment of the NAAQS in another state. The 
second element of CAA section 110(a)(2)(D)(i)(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.\6\ 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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    \6\ 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, 213 F.3d 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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    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.\7\ 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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    \7\ 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

[[Page 19295]]

Proposal, as discussed further below, this impact must be evaluated 
with respect to monitors showing a violation of the NAAQS.\8\ 
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 
violations of the 1997 8-hour ozone or 1997 PM2.5 NAAQS in 
another state.
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    \8\ 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.'' \9\ EPA did not make 
specific recommendations for how states should assess interference 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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    \9\ 2006 Guidance at 5.
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    In 2008, the U.S. Court of Appeals for the D.C. Circuit found that 
CAIR and the related CAIR federal implementation plans were 
unlawful.\10\ 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.'' \11\ EPA's approach, the court reasoned, would leave 
areas that are ``barely meeting attainment'' with ``no recourse'' to 
address upwind emissions sources.\12\ 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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    \10\ See North Carolina v. EPA, 531 F.3d 896 (DC Circuit 2008).
    \11\ 531 F.3d at 909.
    \12\ 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).\13\ 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 in the future, and areas that it predicts to be 
close to the level of these NAAQS in the future 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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    \13\ 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 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.\14\
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    \14\ 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 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.\15\ 
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 evaluating the Oregon submission.
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    \15\ 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.
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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

[[Page 19296]]

affects the contents of the required submission.'' \16\ 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.\17\ 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.\18\ 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 PM concentrations in any 
downwind state that would result from emissions from individual western 
states, such as Oregon.
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    \16\ 2006 Guidance at 4.
    \17\ Ibid. at 5.
    \18\ 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 significantly contribute to 
nonattainment or interfere with maintenance of the 1997 8-hour ozone 
and 1997 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 June 23, 2010, and December 23, 2010, the Oregon Department of 
Environmental Quality (ODEQ) submitted a SIP revision to update 
Oregon's infrastructure SIP for ozone and PM2.5. Included in 
this submittal was a SIP revision entitled ``Oregon SIP Infrastructure 
for Addressing the Interstate Transport of Ozone and Fine Particulate 
Matter'' to address the interstate transport SIP requirements of CAA 
section 110(a)(2)(D)(i) for the 1997 8-hour ozone and 1997 
PM2.5 NAAQS (2010 interstate transport SIP).\19\ ODEQ's June 
23, 2010, submittal includes public process documentation for the 2010 
interstate transport SIP submittal. In addition, the SIP revision 
includes documentation of a duly noticed public hearing held on 
December 22, 2009.
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    \19\ Oregon's submission addresses the interstate transport 
requirements of the 1997 PM2.5 NAAQS, the 1997 8-hour 
ozone NAAQS, the 2006 PM2.5 NAAQS, and the 2008 8-hour 
ozone NAAQS. In this action, EPA is only taking action with respect 
to CAA section 110(a)(2)(D)(i)(I) for the 1997 PM2.5 and 
1997 8-hour ozone NAAQS.
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    We find that the process followed by ODEQ in adopting the 2010 
interstate transport SIP complies with the procedural requirements for 
SIP revisions under CAA section 110 and EPA's implementing regulations.

V. What is EPA's evaluation of the state's submission?

A. EPA's Evaluation of Significant Contribution to Nonattainment

    This proposed approval evaluates 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 Oregon's 2010 interstate transport SIP, in which the State 
explains that based on meteorological and other characteristics in 
Oregon and in the surrounding areas, PM2.5 and ozone 
precursor emissions from Oregon sources do not significantly contribute 
to violations of the PM2.5 or ozone NAAQS in other 
states.\20\ In addition, EPA has supplemented the State's analysis with 
its own evaluation of the evidence, including a review of the nearest 
monitors in other states that are appropriate nonattainment receptors, 
in order to assess whether emissions sources in Oregon contribute 
significantly to nonattainment of the 1997 8-hour ozone and 
PM2.5 NAAQS in other states.
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    \20\ Oregon's submission makes this conclusion with respect to 
not only the 1997 PM 2.5 NAAQS and 1997 8-hour ozone NAAQS, but also 
the 2006 PM 2.5 NAAQS and the 2008 8-hour ozone NAAQS.
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    Finally, EPA has also reviewed recent ozone and PM2.5 
monitoring data for the states bordering Oregon to consider whether 
Oregon emissions could significantly contribute to violations of the 
1997 8-hour ozone or PM2.5 NAAQS in those states.
1. Significant Contribution to Nonattainment Evaluation for the 1997 8-
Hour Ozone NAAQS
    To address whether emissions from Oregon sources significantly 
contribute to nonattainment of the 8-hour ozone NAAQS in another state, 
the State argued in the 2010 interstate transport SIP that 
meteorological and other characteristics of the Pacific Northwest 
support a finding that emissions from Oregon sources do not 
significantly contribute to violations of the PM2.5 or ozone 
NAAQS in other states. Oregon pointed out that, in the Pacific 
Northwest, exceedances of the 8-hour ozone standard occur in the summer 
months, and during that season the prevailing winds \21\ are 
predominantly from the north to northwest and, consequently, preclude 
any significant influence from Oregon on Washington ozone nonattainment 
areas.\22\ While acknowledging the possibility that prevailing summer 
winds could result in some interstate transport of ozone forming 
emissions to western Idaho, Nevada and northern California, the State 
asserted in the 2010 interstate transport SIP that significant 
distances and topography (such as major mountain ranges that separate 
Oregon from California, Idaho and Nevada) would likely minimize the 
significance of these impacts on other states. Oregon gave as an 
example the largest major urban center in Oregon (the greater Portland 
area), which it estimated is 400 to 700 miles away from urban areas in 
western Idaho, Nevada, and northern California, and is separated by at 
least one major mountain range (the Cascades).
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    \21\ This north/northwest prevailing wind direction was derived 
from surface level winds and airport data and is not necessarily 
indicative of the prevailing wind direction of typical weather 
systems in the west.
    \22\ Note that there are currently no ozone nonattainment areas 
in Oregon or Washington.
---------------------------------------------------------------------------

    Oregon also pointed to its section 110 infrastructure SIP to show 
that ODEQ

[[Page 19297]]

has the ability to participate as needed in future studies on regional 
air pollution issues, or collaborate with other states if air quality 
concerns are identified that require a case-specific evaluation of 
interstate transport, and also ensures the legal mechanism for ODEQ to 
take action as needed to reduce emissions to help attain compliance 
with Federal NAAQS.
    Finally, the State explained that it consulted with air agencies in 
Washington, Idaho, Nevada, and California and other agencies to 
evaluate case-specific air quality problems that may involve regional 
transport of air pollution. These staff-level communications indicated 
no impacts on ozone concentrations in other states caused by transport 
from the State of Oregon. The State added that if any future violations 
of ozone standards occur, Oregon would work with other air agencies and 
EPA as necessary to evaluate the role of interstate air pollution 
transport. This consultation provided additional support for the 
state's view that emissions from Oregon sources do not significantly 
contribute to violations of the 1997 8-hour ozone NAAQS in other 
states.
    Based on the information provided in its 2010 interstate transport 
SIP, ODEQ concluded that emissions from air pollution sources in Oregon 
do not significantly contribute to nonattainment of the 1997 8-hour 
ozone NAAQS in other states.
    EPA does not necessarily agree that Oregon's methodology is 
adequate for purposes of a section 110(a)(2)(D)(i) analysis. Therefore, 
EPA is supplementing the State's submission with additional, and more 
recent, information in order to assess this issue more fully. As noted 
above, EPA is evaluating the State's 2010 interstate transport SIP 
taking into account methodologies and analyses for the identification 
of receptor monitors that was developed in the Transport Rule Proposal, 
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 Oregon. 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 Oregon do not 
contribute significantly to nonattainment of the 1997 8-hour ozone 
NAAQS at monitors in other states.
    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 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 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.\23\ Because the 
Transport Rule Proposal does not model the contribution of emissions 
from Oregon (nor 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 
geographical and meteorological factors, EPA's projections of future 
air quality at monitors in western states in the Timin Memo, and AQS 
monitoring data.
---------------------------------------------------------------------------

    \23\ Transport Rule Proposal, 75 FR 45210 at 45253-45273.
---------------------------------------------------------------------------

    Our analysis begins by assessing Oregon'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 Oregon 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.\24\
---------------------------------------------------------------------------

    \24\ See Transport Rule Proposal, Table IV.C-11, 75 FR 45210 at 
45252.
---------------------------------------------------------------------------

    The nonattainment receptors in Dallas-Fort Worth and Houston areas 
are over 1200 miles from the closest point on Oregon's border, and the 
receptors in Louisiana, New York, and Pennsylvania are significantly 
further 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 Oregon 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.
    To assist in the evaluation of the potential for ozone transport 
among western states, EPA also developed an additional analysis in the 
Timin Memo identifying monitors projected to record violations of the 
1997 8-hour ozone NAAQS in the western U.S. The Timin Memo identified 
predicted future nonattainment receptors for the 1997 8-hour ozone 
NAAQS in southern and central California. This analysis did not, 
however, identify any projected nonattainment receptors for the 1997 8-
hour ozone NAAQS in any other western state.\25\ The nonattainment 
receptor nearest to Oregon for the 1997 8-hour ozone NAAQS was 
identified as Nevada County, California. Nevada County is approximately 
170 miles south/southeast of the closest point on Oregon's border and 
on the other side of intervening mountain ranges that act as a natural 
barrier to air pollution transport. Although not determinative by 
themselves, distance and topography are not favorable to 8-hour ozone 
transport from Oregon to central California. In addition, prevailing 
winds in the west generally move from south-westerly, westerly, or 
north-westerly directions, as indicated by the typical movement of 
weather systems. Hence central and southern California are not in the 
predominant direction of winds from Oregon. Given the distance between 
Oregon's border and central and southern California nonattainment 
receptors, the intervening mountainous topography, and the general 
direction of transport winds in the Western U.S., it is reasonable to 
conclude that Oregon sources do not contribute significantly to 
nonattainment of the 1997 8-hour ozone NAAQS in Nevada County or to any 
more distant nonattainment receptors in California. EPA's analysis for 
western states therefore supports our proposal to conclude that Oregon 
sources do not contribute significantly to nonattainment of the 1997 8-
hour ozone NAAQS in any other state.
---------------------------------------------------------------------------

    \25\ See Timin Memo at Appendix B (``Base year 2003-2007 and 
Future Year 2012 8-Hour Average Ozone Design Values--Western 
States'').
---------------------------------------------------------------------------

    In addition to the information in the 2010 interstate transport SIP 
and EPA's projections of future air quality in the Transport Rule 
Proposal and in the

[[Page 19298]]

Timin Memo, EPA also evaluated preliminary air quality monitoring data 
for the areas in states bordering Oregon that are designated 
nonattainment for the 1997 8-hour ozone NAAQS. While 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 point of analysis. Two 
states bordering Oregon--California and Nevada--have areas currently 
designated nonattainment for the 1997 8-hour ozone standard. In 
California, the closest nonattainment area is Butte County, and in 
Nevada, the closest nonattainment area is the Las Vegas area in Clark 
County. 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 81.305 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 Air Quality System (AQS) database indicates that the 
8-hour ozone design values for Butte County and Las Vegas during this 
period were 82 and 74 ppb, respectively.\26\ We therefore believe it is 
reasonable to conclude that Oregon sources are not contributing 
significantly to nonattainment of the 1997 8-hour ozone NAAQS in Butte 
County, California or Clark County, Nevada. The closest nonattainment 
area to the Oregon border that had a design value above the 1997 8-hour 
ozone NAAQS for the 2007-2009 period was Nevada County, California. As 
noted above, given the distance between the Oregon border and Nevada 
County, the intervening mountainous topography, and the general 
direction of transport winds in the Western U.S., it is reasonable to 
conclude that Oregon sources do not contribute significantly to 
nonattainment in Nevada County or to any more distant central or 
southern California 1997 8-hour ozone nonattainment areas. There are no 
designated nonattainment areas in Idaho and Washington for the 1997 8-
hour ozone NAAQS. This is further support that Oregon sources do not 
contribute significantly to nonattainment of the 1997 8-hour ozone 
NAAQS in any other state.
---------------------------------------------------------------------------

    \26\ See EPA AQS, ``Preliminary Design Value Report,'' 2007-
2009, for Washington, Idaho, Nevada, and California.
---------------------------------------------------------------------------

    We also evaluated ozone monitoring data from the 2007-2009 period 
from each of the ozone monitoring sites in Washington, Idaho, Nevada 
and California, to determine whether the ozone levels in any of these 
states violate the 1997 8-hour ozone NAAQS.\27\ We have identified no 
design values above the 1997 8-hour ozone NAAQS at any of the monitors 
in Washington, Idaho, or Nevada, nor any indication that emissions from 
Oregon sources contribute significantly to nonattainment of the 1997 8-
hour ozone NAAQS in these adjacent states. Although AQS data for 
California show 8-hour ozone design values above the 1997 NAAQS during 
the 2007-2009 period, the closest monitor to Oregon that has a 2007-
2009 8-hour ozone design value above the 1997 NAAQS is located in 
Nevada County. As noted above, given the distance between the Oregon 
border and Nevada County, the intervening mountainous topography, and 
the general direction of transport winds in the Western U.S., it is 
reasonable to conclude that Oregon sources do not contribute 
significantly to nonattainment in Nevada County or to any more distant 
central or southern California monitors. This is further support that 
Oregon sources do not contribute significantly to nonattainment of the 
1997 8-hour ozone NAAQS in any other state.
---------------------------------------------------------------------------

    \27\ Id.
---------------------------------------------------------------------------

    Finally, none of the ozone monitors in Oregon have themselves 
indicated a violation of the 1997 8-hour ozone NAAQS. The absence of 
violations in Oregon itself does not rule out the possibility of 
transport, but taken in conjunction with other relevant information, 
including the distance from Oregon to areas with design values above 
the 1997 8-hour ozone NAAQS and Pacific Northwest meteorology and 
topography, this fact helps to support the conclusion that there is no 
transport from Oregon resulting in significant contribution to 
nonattainment in another state. Distance per se is also not an obstacle 
to long range transport of ozone and its precursors, as discussed 
above. However, with increasing distance there are greater 
opportunities for ozone and NOX dispersion and removal from 
the atmosphere due to the effects of winds and chemical sink processes. 
In this context, the distance between Oregon sources and areas not 
meeting the 8-hour ozone standard reduces, but does not exclude, the 
possibility of significant contribution to nonattainment. Nevertheless, 
the absence of violations in Oregon combined with the total weight of 
all of the factors discussed above supports a conclusion that emissions 
from its sources do not significantly contribute to nonattainment in 
other states, in accordance with section 110(a)(2)(D)(i).
2. Significant Contribution to Nonattainment Evaluation for the 1997 
PM2.5 NAAQS
    To address whether emissions from sources in Oregon significantly 
contribute to nonattainment of the 1997 PM2.5 NAAQS in 
another state, the State argued in its 2010 interstate transport SIP 
that meteorological and other characteristics of any areas designated 
nonattainment for the 1997 PM2.5 NAAQS in the surrounding 
states of Washington, Idaho, Nevada, and California support a finding 
that emissions from Oregon sources do not significantly contribute to 
violations of the PM2.5 NAAQS or ozone NAAQS in other 
states. Oregon explained that the closest nonattainment areas in 
neighboring states are the Tacoma area (Pierce County) in Washington; 
the Chico area (portions of Butte County) in California, and the Cache 
Valley area in Southeast Idaho (portions of Cache County, Utah and 
Franklin County, Idaho).\28\ Oregon argues that the area of highest 
Oregon emission densities (Portland Metro area) is separated from these 
PM2.5 nonattainment areas by significant distances and major 
mountain ranges up to approximately 7000 feet. Oregon identifies one 
exception--the Portland-Vancouver metro area, which shares a common air 
shed between Oregon and Washington. Oregon, however, notes that both 
Portland and Vancouver are in attainment with the PM2.5 
NAAQS.
---------------------------------------------------------------------------

    \28\ Although the 2010 Interstate transport SIP identified these 
areas as PM2.5 nonattainment areas, they are all 2006 24-
hour PM2.5 nonattainment areas. There are no 1997 
PM2.5 nonattainment areas in Washington or Idaho, and the 
closest 1997 PM2.5 nonattainment area to Oregon is in 
California (San Joaquin County). Oregon asserts that its evaluation 
of more stringent 2006 24-hour PM2.5 NAAQS nonattainment 
areas is indicative of potential contribution to nonattainment of 
the less stringent 1997 PM2.5 NAAQS.
---------------------------------------------------------------------------

    Oregon described typical seasonal wind patterns during the winter 
when PM2.5 levels are the highest. It noted that wind speeds 
are typically variable with the majority of wind speeds occurring at 
less than 8 miles per hour, and a significant portion of low winds at 
less than 5 miles per hour. Oregon explained that these low wind speeds 
and air stagnation conditions do not lend themselves to long distance 
air pollution transport, and noted that the Portland area can 
experience high wind speeds in the winter travelling through the 
Columbia River Gorge east of Portland that are not conducive to the 
buildup of air pollution. Oregon concluded that general meteorology

[[Page 19299]]

supports the conclusion that high winter time PM2.5 levels 
in Pacific Northwest communities are typically dominated by local 
emission sources.
    Oregon also pointed to its section 110 infrastructure SIP to show 
that ODEQ has the ability to participate as needed in future studies on 
regional air pollution issues, or collaborate with other states if air 
quality concerns are identified that require a case-specific evaluation 
of interstate transport, and also ensures the legal mechanism for ODEQ 
to take action as needed to reduce emissions to help attain compliance 
with Federal NAAQS. Oregon stated that that high PM2.5 
levels that threaten the NAAQS are investigated as needed to identify 
contributing sources, including any potential role of interstate 
transport.
    Finally, the state explained that it had consulted with air 
agencies in Washington, Idaho, Nevada, and California and other 
agencies to evaluate case-specific air quality problems that may 
involve regional transport of air pollution. These staff-level 
communications indicated no impacts on PM2.5 concentrations 
in other states caused by transport from the state of Oregon, providing 
additional support for the state's view that emissions from Oregon 
sources do not significantly contribute to violations of the 1997 
PM2.5 NAAQS in other states.
    Based on this and other information provided in its 2010 interstate 
transport SIP, ODEQ concluded that emissions from air pollution sources 
in Oregon do not significantly contribute to nonattainment of the 1997 
PM2.5 NAAQS in other states.
    EPA does not necessarily agree that Oregon's methodology is 
adequate for purposes of a section 110(a)(2)(D)(i) analysis. Therefore, 
EPA is supplementing the State's submission with additional, and more 
recent, information in order to assess this issue more fully. As noted 
above, EPA is evaluating the 2010 interstate transport SIP taking into 
account methodologies and analyses for the identification of the 
receptor monitors that was developed in the Transport Rule Proposal, as 
well as EPA's projections of future air quality at monitors in western 
states in the Timin Memo, and air quality data from monitors in the 
states bordering Oregon. 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 Oregon do not contribute significantly 
to nonattainment of the PM2.5 NAAQS at monitors in other 
states.
    Specifically, we identified the nonattainment receptors for the 
1997 annual PM2.5 NAAQS closest to Oregon to evaluate 
whether emissions from Oregon sources contribute significantly to 
nonattainment of the 1997 PM2.5 NAAQS in any other 
state.\29\ For the 1997 annual PM2.5 NAAQS, the projected 
nonattainment receptors closest to Oregon that EPA identified from the 
modeling analyses conducted for the Transport Rule Proposal are all 
east of the Mississippi River.\30\ Given the significant distance 
between Oregon and these nonattainment receptors and the intervening 
mountainous terrain, we believe it is reasonable to conclude that 
Oregon sources do not significantly contribute to nonattainment of the 
1997 annual PM2.5 NAAQS in any of these areas.
---------------------------------------------------------------------------

    \29\ 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 Oregon's 2010 
Interstate 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.
    \30\ Specifically, the nonattainment receptors 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 PM2.5 transport among 
western states, EPA also relied on the additional analysis in the Timin 
Memo identifying monitors projected to record violations of the 1997 
annual PM2.5 NAAQS. The Timin Memo identified predicted 
future nonattainment receptors for the 1997 annual PM2.5 
NAAQS in southern and central California but did not identify predicted 
future nonattainment receptors for the 1997 annual PM2.5 
NAAQS in any other western state.\31\ For Oregon, the closest 
nonattainment receptor in California for the 1997 annual 
PM2.5 NAAQS was Fresno County. Fresno County is over 300 
miles south of the closest point on Oregon's border and is on the other 
side of intervening mountain ranges that act as a natural barrier to 
air pollution transport. Although not determinative by themselves, 
distance and topography are not favorable to PM2.5 transport 
from Oregon to central California. In addition, prevailing winds in the 
west generally move from south-westerly, westerly, or north-westerly 
directions, as indicated by the typical movement of weather systems. 
Hence central and southern California are not in the predominant 
direction of winds from Oregon. Given the distance between the Oregon 
border and central and southern California nonattainment receptors, the 
intervening mountainous topography, and the general westerly direction 
of transport winds in the Western U.S., EPA concludes that Oregon 
sources do not contribute significantly to nonattainment of the 1997 
annual PM2.5 NAAQS in Fresno County or to any more distant 
nonattainment receptors in California. EPA's analysis for western 
states therefore supports our proposal to conclude that Oregon sources 
do not contribute significantly to nonattainment of the 1997 annual 
PM2.5 NAAQS in any other state.
---------------------------------------------------------------------------

    \31\ See Timin Memo at Appendix B (``Base year 2003-2007 and 
Future Year 2012 8-Hour Average Ozone 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 km grid covering the continental U.S. 
east of the Rockies).\32\ Recent monitoring data in EPA's Air Quality 
System (2007-2009 design values) 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\,\33\ which is well below the 
level of the 1997 24-hour PM2.5 NAAQS of 65 [mu]g/m\3\. In 
California, 2007-2009 AQS data indicate that only one area, Kern 
County, has a design value above the level of the 1997 24-hour 
PM2.5 NAAQS. As discussed above, EPA believes that given the 
relatively long distance between the Oregon border and Kern County, the 
intervening mountainous topography, and the generally westerly 
direction of transport winds in the Western U.S., emissions from Oregon 
sources do not interfere with maintenance of the 1997 24-hour 
PM2.5 NAAQS in Kern County. These data and factors further 
support our proposed finding that Oregon sources do not significantly 
contribute to nonattainment of the 1997 24-hour PM2.5 NAAQS 
in any other state.
---------------------------------------------------------------------------

    \32\ 75 FR 45210 at 45249-45251 (August 2, 2010).
    \33\ 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/.
---------------------------------------------------------------------------

    In addition to the information in the 2010 interstate transport SIP 
and our review of the nearest nonattainment receptors identified from 
the modeling analyses conducted for the Transport Rule Proposal, EPA 
evaluated air quality data for the areas in states bordering Oregon 
that are designated nonattainment for the 1997 PM2.5

[[Page 19300]]

NAAQS. Although significant contribution must be measured not just 
against nonattainment areas but also against areas with monitors 
showing violations of the NAAQS, nonattainment areas are a convenient 
point of analysis.
    The closest 1997 PM2.5 nonattainment area in any state 
bordering Oregon is the San Joaquin Valley in California.\34\ This 
nonattainment area is located in central California and is over 250 
miles from the closest point on Oregon's border and on the other side 
of intervening mountain ranges that act as a natural barrier to air 
pollution transport. In addition, prevailing winds in the western U.S. 
generally move from south-westerly, westerly, or north-westerly 
directions, as indicated by the typical movement of weather systems. 
Hence, Joaquin Valley, California, is not in the predominant direction 
of winds from Oregon. Given the relatively long distance between Oregon 
and the San Joaquin Valley, the intervening mountainous topography, and 
the general direction of transport winds in the Western U.S., EPA 
believes that Oregon sources do not significantly contribute to 
nonattainment of the 1997 PM2.5 NAAQS in the San Joaquin 
Valley nonattainment area or to any more distant California 1997 
PM2.5 nonattainment areas. There are no areas in Idaho and 
Washington currently designated nonattainment for the 1997 
PM2.5 NAAQS. This is further support that Oregon sources do 
not contribute significantly to nonattainment of the 1997 
PM2.5 NAAQS in any other state.
---------------------------------------------------------------------------

    \34\ In 2005, EPA designated this area nonattainment for 
violations of the 1997 and annual PM2.5 NAAQS. 70 FR 944 
(January 5, 2005), and 40 CFR 81.305.
---------------------------------------------------------------------------

    Although not located in a state bordering Oregon, the closest 
designated nonattainment area to Oregon for the 1997 PM2.5 
NAAQS is Libby, in Lincoln County, Montana.\35\ In 2005, EPA designated 
this area nonattainment for the 1997 annual PM2.5 NAAQS. 70 
FR 944 (January 5, 2005) and 40 CFR 81.327. A number of factors provide 
evidence that Oregon emissions do not significantly contribute to past 
violations of the 1997 annual PM2.5 standards in Libby, 
Montana.
---------------------------------------------------------------------------

    \35\ Libby is in a narrow valley surrounded by mountains 4,000 
feet higher than the town. The Rocky Mountain Range to the west of 
Libby (and east of the Idaho border) reaches summit elevations of 
12,000 feet with most summit elevations between 6000 and 7000 feet 
that act as a barrier to air movement between Idaho and Montana.
---------------------------------------------------------------------------

    First, in the process of designating Libby nonattainment for both 
the 1997 PM2.5 NAAQS and the 2006 24-hour PM2.5 
NAAQS, EPA noted the predominantly local origins of PM2.5 
nonattainment in Libby.36 37 Residential wood-burning stoves 
during the winter-time, when frequent and persistent temperature 
inversions occurred, were specifically identified as a key source of PM 
emissions. The fact that nonattainment in a given area is primarily the 
result of local emissions sources does not, however, exclude the 
possibility of significant contribution to nonattainment from 
interstate transport. EPA believes that other evidence supports the 
conclusion that emissions from Oregon sources are not significantly 
contributing to violations in Libby, Montana.
---------------------------------------------------------------------------

    \36\ ``Technical Support for State and Tribal Air Quality Fine 
Particle (PM2.5) Designations,'' (for Montana) Chapter 6, 
pp. 347-352, December 2004.
    \37\ ``Technical Support for State and Tribal Air Quality Fine 
Particle (PM2.5) Designations,'' (for Montana) Chapter 
4.8.1, pp. 1-15, December 2008.
---------------------------------------------------------------------------

    Second, monitoring data from 1999 through 2009 from areas outside 
of Libby in Montana support a determination that Oregon does not 
significantly contribute to nonattainment in Libby. At all other sites 
in Montana, annual PM2.5 design value levels have remained 
below the 15 [mu]g/m\3\ nonattainment threshold. Annual 
PM2.5 design values for this period for most of these 
monitors remained at levels equal to, or less than, two-thirds of the 
1997 annual PM2.5 NAAQS. Even the three highest design 
values at these monitors were 20 percent below the level of the annual 
standard.\38\ The lower PM2.5 levels elsewhere in Montana 
are evidence that local sources, and not interstate transport, are key 
contributors to past nonattainment in Libby.
---------------------------------------------------------------------------

    \38\ In 2001, 2002 and 2006, design values for two monitors in 
Missoula County were 11.1, 11.4 and 11.8 [mu]g/m\3\. Computed from 
AQS monitoring data. 75 FR 16028 (March 31, 2010).
---------------------------------------------------------------------------

    Third, for 2007-2009, AQS data show that the annual 
PM2.5 design values for the Libby nonattainment area 
themselves fell below the levels of the NAAQS. This reduction has been 
attributed to an effective wood stove replacement program that 
decreased PM2.5 emissions by approximately 59 percent.\39\ 
In other words, even if emissions from Oregon sources were reaching 
Libby, they would not significantly contribute to violations of the 
1997 annual PM2.5 NAAQS because monitoring data demonstrate 
that Libby is not violating the 1997 annual PM2.5 NAAQS.
---------------------------------------------------------------------------

    \39\ State of Montana, Department of Environmental Quality, 
``State Implementation Plan-Libby Annual PM2.5 Control 
Plan,'' submitted to EPA April 1, 2008.
---------------------------------------------------------------------------

    Finally, EPA's conclusion that emissions from Oregon do not 
significantly contribute to nonattainment in Libby, Montana, is further 
supported by the analysis of monitors in the western United States.\40\ 
This analysis concludes that in 2012 the average annual 
PM2.5 design values in Lincoln County, Montana will be below 
the threshold for consideration as a nonattainment receptor. These 
factors together support a conclusion that Oregon sources do not 
contribute significantly to nonattainment of the 1997 annual 
PM2.5 NAAQS in the Libby 1997 PM2.5 nonattainment 
area.
---------------------------------------------------------------------------

    \40\ See Timin Memo at Appendix A (``Base year 2003-20007 and 
Future Year 2012 Annual Average PM2.5 Design Values--
Western States'').
---------------------------------------------------------------------------

    As mentioned above, EPA considers not only significant contribution 
to designated nonattainment areas, but also significant contribution to 
areas with monitors showing violations of the NAAQS. A review of the 
most recent three years (2007-2009) of monitoring data in AQS for the 
bordering states of Washington, Idaho, Nevada, and California shows 
that the only monitors with design values above the 1997 annual 
PM2.5 NAAQS are located in central and southern California. 
The county closest to the Oregon border that has a design value above 
the 1997 annual PM2.5 NAAQS is Kern County, California. Kern 
County is more than 400 miles from the closest point on Oregon's border 
and is on the other side of intervening mountain ranges that act as a 
natural barrier to air pollution transport. Although not determinative 
by themselves, distance and topography are not favorable to 
PM2.5 transport from Oregon to central California. In 
addition, prevailing winds in the west generally move from south-
westerly, westerly, or north-westerly directions, as indicated by the 
typical movement of weather systems. Hence Kern County, California is 
not in the predominant direction of winds from Oregon. Given the 
relatively long distance between the Oregon border and Kern County, the 
intervening mountainous topography, and the generally westerly 
direction of transport winds in the Western U.S., it is reasonable to 
conclude that Oregon sources do not significantly contribute to 
nonattainment of the 1997 PM2.5 NAAQS in Kern County or to 
any more distant monitors in California.
    As noted above no monitors in Washington, Idaho and Nevada or 
Northern California had design values above the 1997 annual 
PM2.5 NAAQS for the 2007-2009 period. The fact that monitors 
in these areas are not registering violations of the 1997 
PM2.5 NAAQS does not in itself conclusively establish that 
emissions from Oregon could not contribute in the aggregate to

[[Page 19301]]

violations in these areas. But this fact combined with our above 
evaluation of the nearest nonattainment receptors, nearest 
nonattainment areas, and nearest monitors with design values above the 
1997 annual PM2.5 NAAQS, supports a conclusion that Oregon 
sources do not significantly contribute to nonattainment of the 1997 
PM2.5 NAAQS in other states.
    Finally, none of the PM2.5 monitors in Oregon have 
themselves indicated a violation of the 1997 annual PM2.5 
NAAQS. The absence of violations in Oregon itself does not rule out the 
possibility of transport, but taken in conjunction with other relevant 
information, including the distance from Oregon to areas with design 
values above the 1997 annual PM2.5 NAAQS and Pacific 
Northwest meteorology and topography, this fact helps to support the 
conclusion that there is no transport from Oregon resulting in 
significant contribution to nonattainment in another state. Taking into 
account the total weight of all of the factors discussed above, EPA 
concludes that Oregon does not significantly contribute to the 1997 
annual PM2.5 NAAQS nonattainment in any other state.
3. Conclusion Regarding Significant Contribution to Nonattainment
    Based on the weight of evidence discussed above, including the 
location of the nearest projected nonattainment receptors, distance to 
the nearest designated PM2.5 nonattainment area, 
meteorology, topography, and recent air quality monitoring data, we 
propose to determine that Oregon's 2010 interstate transport SIP is 
adequate to ensure that emissions from Oregon 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 
Oregon's SIP includes the measures necessary to prevent such prohibited 
interstate transport impacts for these NAAQS.

B. EPA's Evaluation of Interference With Maintenance

    This proposed approval evaluates the interfere with maintenance 
element of section 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 Oregon's 2010 interstate transport SIP, in which the State 
explains that based on meteorological and other characteristics in 
Oregon and in the surrounding areas, PM2.5 and ozone 
precursor emissions do not interfere with maintenance of the 1997 8-
hour ozone or 1997 PM2.5 NAAQS in other states.\41\ In 
addition, EPA has supplemented the State's analysis with its own 
evaluation of the evidence, including a review of the nearest monitors 
in other states that are appropriate maintenance receptors, consistent 
with EPA's approach in the Transport Rule Proposal, in order to assess 
whether emissions sources in Oregon interfere with maintenance of the 
1997 8-hour ozone and PM2.5 NAAQS in other states.
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    \41\ Oregon's submission makes this conclusion with respect to 
not only the 1997 PM2.5 NAAQS and 1997 8-hour ozone 
NAAQS, but also the 2006 PM2.5 NAAQS and the 2008 8-hour 
ozone NAAQS.
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1. Oregon's 2010 Interstate Transport SIP
    To show that Oregon emissions, as controlled under its SIP, do not 
interfere with maintenance of the 1997 8-hour ozone NAAQS and 1997 
PM2.5 NAAQS in another state, Oregon's 2010 interstate 
transport SIP analyzed several types of factors to support its 
assertion. First, the State pointed to topography and meteorology for 
its evaluation, maintaining that high PM2.5 concentrations 
in adjacent states typically occur under winter conditions when air 
speeds are low and/or localized air inversions occur. Describing wind 
direction as being typically variable with the majority of wind speeds 
less than 8 miles per hour, and a significant portion of low winds less 
than 5 miles per hour, the state noted that these low wind speeds and 
air stagnation conditions do not lend them to long distance air 
pollution transport. The State indicated that there are occasional high 
8-hour ozone levels that occur in the summer months, but maintained 
that prevailing winds\42\ in Oregon are predominantly from the north to 
northwest.\43\ The state indicated that prevailing summer winds could 
theoretically result in some interstate transport of ozone forming 
emission from Oregon to western Idaho, Nevada and northern California. 
It also noted, however, that significant distances and topography (such 
as major mountain ranges that separate Oregon from California, Idaho, 
and Nevada) would likely minimize the significance of these impacts on 
other states. It pointed to, for example, the approximately 400 to 700 
miles distance between the largest major urban center in Oregon (the 
greater Portland area) and urban areas in western Idaho, Nevada, and 
northern California and at least one major mountain range between those 
areas.
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    \42\ This north/northwest prevailing wind direction was derived 
from surface level winds and airport data and is not necessarily 
indicative of the prevailing wind direction of typical weather 
systems in the west.
    \43\ There are currently no 1997 8-hour ozone nonattainment 
areas in Oregon or Washington.
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    Second, Oregon used AQS monitoring data for 2006-2008 from other 
states in its analysis. Oregon pointed out that both PM2.5 
and ozone design values in all counties adjacent to Oregon are below 
the PM2.5 and 8-hour ozone NAAQS. Oregon also consulted with 
each of the state air agencies for Washington, Idaho, Nevada, and 
California to get a sense of what the local air agencies believe are 
the likely causes of any air quality concerns for maintaining 
compliance with the PM2.5 and ozone NAAQS. Based on these 
consultations and the other information above, Oregon concluded that 
emissions from air pollution sources in Oregon do not interfere with 
the maintenance of the 8-hour ozone or PM2.5 NAAQS in other 
states.
    Oregon also relied on information about air stagnation conditions 
in other states to support its assertions that Oregon sources do not 
interfere with maintenance of the 1997 8-hour ozone NAAQS and 1997 
PM2.5 NAAQS in other states. Oregon noted that stagnant air 
conditions are associated with weak transport and that high 
PM2.5 concentrations in adjacent states typically occur 
under winter conditions when air speeds are low and/or localized air 
inversions occur. Oregon also pointed to examples of where it has 
collaborated with other states to demonstrate its ability and 
willingness to address problems involving interstate transport. 
Examples included the Portland-Vancouver 1-hour ozone attainment and 
maintenance plans, and Oregon's regional haze plan. Oregon described 
how in the mid-1990s and again in 2007, ODEQ collaborated with the 
Southwest Clean Air Agency (i.e., the State of Washington air agency 
with jurisdiction over Vancouver) to develop bi-state ozone attainment 
and maintenance plans with emission reduction strategies needed to 
attain and maintain compliance with federal ozone standards. In 2008-
09, ODEQ worked with the states of Washington, Idaho and California, as 
well as Federal Land Managers in developing Oregon's Regional Haze 
plan. Oregon described how under that plan ODEQ adopted several 
emission reduction strategies, including emission control requirements 
to reduce the interstate transport of haze forming emissions.
    Finally, Oregon pointed to its section 110 infrastructure SIP to 
show that ODEQ has the ability to participate as needed in future 
studies on regional air pollution issues, or collaborate with

[[Page 19302]]

other states if air quality concerns are identified that require a 
case-specific evaluation of interstate transport. Oregon added that its 
infrastructure SIP also ensures the legal mechanism for ODEQ to take 
action as needed to reduce emissions to help maintain compliance with 
federal NAAQS.
    EPA does not necessarily agree that Oregon's methodology is 
adequate for purposes of a section 110(a)(2)(D)(i) analysis. Therefore, 
EPA is supplementing the State's submission with additional, and more 
recent, information in order to assess this issue more fully. As noted 
above, EPA is evaluating the 2010 interstate transport SIP taking into 
account methodologies and analyses for the identification of the 
receptor monitors that was developed in the Transport Rule Proposal, 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 Oregon. 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 Oregon do not interfere with maintenance 
of the 1997 8-hour ozone and PM2.5 NAAQS at monitors in 
other states.
2. 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 interference 
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 EPA anticipates that by 2012 these maintenance 
receptors 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 maintenance of the NAAQS at maintenance receptors, the Transport 
Rule Proposal modeled the states' contributions to ambient ozone levels 
at these maintenance receptors.\44\ Because the Transport Rule Proposal 
did not identify the contribution of emissions from Oregon (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 
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 supports a reliable qualitative conclusion 
that emissions from Oregon do not interfere with maintenance of the 
1997 8-hour ozone NAAQS at monitors in other states.
---------------------------------------------------------------------------

    \44\ See Transport Rule Proposal, 75 FR 45210 at 45253-45273.
---------------------------------------------------------------------------

    Our analysis begins by assessing Oregon'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 Oregon are eight receptors in the 
Dallas-Fort Worth and Houston-Galveston-Brazoria 8-hour ozone 
nonattainment areas in eastern Texas. The remaining eight maintenance 
receptors are located in Connecticut, Georgia, New York and 
Pennsylvania.\45\
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    \45\ See Transport Rule Proposal, Table IV.C-12, 75 FR 45210 at 
45252-45253.
---------------------------------------------------------------------------

    As discussed above in section V.A.1, the Dallas-Fort Worth and 
Houston areas are over 1200 miles from the closest point on Oregon's 
border. The maintenance receptor monitors located in Connecticut, 
Georgia, New York and Pennsylvania are significantly further 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. Moreover, the intervening Rocky Mountains act as a 
natural barrier to air pollution transport. These factors together 
support a conclusion that emissions from Oregon sources do not 
interfere with maintenance of the 1997 8-hour ozone NAAQS in the 
nearest areas with monitors projected to violate the 1997 8-hour ozone 
NAAQS as part of the Transport Rule Proposal.
    EPA's analysis in the Timin Memo identified four maintenance 
receptors for the 1997 8-hour ozone NAAQS in southern and central 
California.\46\ The closest 8-hour ozone maintenance receptor to Oregon 
was in Placer County, California. Placer County is approximately 185 
miles south of the closest point on Oregon's border and is not in the 
predominant direction of transport winds. As noted earlier, prevailing 
winds generally move from south-westerly, westerly, or northwesterly 
directions, as indicated by the typical movement of weather systems. 
Given the relatively long distance between Oregon and central 
California, the intervening mountainous topography, and the general 
direction of west-to-east transport winds across Oregon, it is 
reasonable to conclude that Oregon sources do not interfere with 
maintenance of the 1997 8-hour ozone NAAQS in Placer County, 
California. It is also reasonable to conclude that emissions from 
sources in Oregon would not have such impacts at other identified 
maintenance receptor sites that are in central or southern California 
that are in the same direction and further away from the Oregon border. 
All of these factors taken together supports a conclusion that 
emissions from Oregon sources do not interfere with maintenance of the 
1997 8-hour ozone NAAQS in any other state.
---------------------------------------------------------------------------

    \46\ See Timin Memo at Appendix B (``Base year 2003-2007 and 
Future Year 2012 8-Hour Average Ozone Design Values--Western 
States'').
---------------------------------------------------------------------------

    Finally, none of the ozone monitors in Oregon have themselves 
indicated a violation of the 1997 8-hour ozone NAAQS. The absence of 
violations in Oregon itself does not rule out the possibility of 
transport, but taken in conjunction with other relevant information, 
including the distance from Oregon to areas with design values above 
the 1997 8-hour ozone NAAQS and Pacific Northwest meteorology and 
topography, this fact helps to support a conclusion that there is no 
transport from Oregon resulting in interference with maintenance in 
another state. Taking into account the total weight of all of the 
factors discussed above, EPA concludes that Oregon does not interfere 
with maintenance of the 1997 8-hour ozone NAAQS in any other state.
3. Interference With Maintenance Evaluation for the 1997 
PM2.5 NAAQS
    The Transport Rule Proposal identifies within its modeling domain 
16 predicted future maintenance receptors for the 1997 annual 
PM2.5 NAAQS. Of these, the closest to Oregon are receptors 
located in Harris County, Texas. Harris County, Texas, is over 1,400 
miles from the closest point on Oregon's border and on the other side 
of

[[Page 19303]]

the Rocky Mountains. Given the long distance and intervening 
mountainous topography between Oregon and this area, it is reasonable 
to conclude that there is a very low probability that Oregon sources 
interfere with maintenance in that area or at the other identified 
maintenance sites east of Harris County, Texas.\47\ EPA, therefore, 
concludes that Oregon sources do not interfere with maintenance of the 
1997 annual PM2.5 NAAQS in other states within the 
geographic region covered by the Transport Rule Proposal.
---------------------------------------------------------------------------

    \47\ Specifically, the remaining 15 maintenance sites for the 
1997 annual PM2.5 NAAQS are located in Kentucky, New 
York, Ohio, Pennsylvania, and West Virginia.
---------------------------------------------------------------------------

    EPA's analysis in the Timin Memo identified Los Angeles County, 
California, as the closest projected maintenance receptor to Oregon's 
border. Los Angeles County is located almost 500 miles south of the 
closest point on Oregon's border and is on the other side of 
intervening mountain ranges that act as a natural barrier to air 
pollution transport. Although not determinative by themselves, distance 
and topography are not favorable to PM2.5 transport from 
Oregon to central California. In addition, prevailing winds in the west 
generally move from south-westerly, westerly, or north-westerly 
directions, as indicated by the typical movement of weather systems. 
Given the relatively long distance between Oregon and Los Angeles 
County, the intervening mountainous topography, and the general 
westerly direction of transport winds in the Western U.S., it is 
reasonable to conclude that Oregon sources do not interfere with 
maintenance of the 1997 annual PM2.5 NAAQS in Los Angeles 
County or to any more distant maintenance receptors in central or 
southern California. EPA's analysis for the western states therefore 
supports our proposal to conclude that Oregon sources do not interfere 
with maintenance of the 1997 annual PM2.5 NAAQS in any other 
states. Based on all of these factors taken together, EPA further 
believes it is reasonable to conclude that Oregon emissions under the 
SIP 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.\48\ 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\.\49\ For California, AQS data indicate that only Kern 
County has a 24-hour design value above the level of the 1997 24-hour 
PM2.5 NAAQS. As discussed above, EPA believes that, based on 
the relatively long distance between the Oregon border and Kern County, 
the intervening mountainous topography, and the generally westerly 
direction of transport winds in the Western U.S., emissions from Oregon 
sources do not interfere with maintenance of the 1997 24-hour 
PM2.5 NAAQS in Kern County.
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    \48\ 75 FR 45210 at 45249-45251 (August 2, 2010). See also fn. 
39 and fn. 47.
    \49\ Data from EPA's Air Quality System can be viewed at http://www.epa.gov/ttn/airs/airsaqs/.
---------------------------------------------------------------------------

4. 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 Oregon's 2010 interstate 
transport SIP is adequate and that emissions from Oregon 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 
element (2) of CAA section 110(a)(2)(D)(i)(I). Thus, we propose to 
determine that Oregon's SIP contains adequate provisions necessary to 
prevent such prohibited interstate transport impacts for these NAAQS 
and does not require any additional measures for this purpose at this 
time.

VI. Proposed Action

    In light of the data and the weight of evidence analysis presented 
above, EPA is proposing to approve revisions to the Oregon SIP, 
submitted on June 23, 2010, and December 23, 2010, and concludes that 
for the 1997 8-hour ozone and 1997 PM2.5 NAAQS, air 
pollutant emissions from sources within Oregon do not either (1) 
significantly contribute to nonattainment of the NAAQS in any other 
state; or (2) interfere with maintenance of the NAAQS by any other 
state.
    As noted previously, EPA will address element (3) interference with 
any other state's required measures to prevent significant 
deterioration of its air quality and element (4), interference with any 
other state's required measures to protect visibility, in a separate 
action. EPA will also take action on the portion of Oregon's SIP that 
addresses the 2006 PM2.5 and 2008 8-hour ozone NAAQS in a 
separate action.

VII. 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 
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

[[Page 19304]]

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

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

    Dated: March 30, 2011.
Dennis J. McLerran,
Regional Administrator, Region 10.
[FR Doc. 2011-8330 Filed 4-6-11; 8:45 am]
BILLING CODE 6560-50-P


