```

[Federal Register: September 17, 2010 (Volume 75, Number 180)]
[Proposed Rules]               
[Page 56935-56942]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr17se10-25]                         

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

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2007-1035; FRL-9202-7]

 
Approval and Promulgation of State Implementation Plans; State of 
Colorado; Interstate Transport of Pollution Revisions for the 1997 8-
hour Ozone NAAQS: ``Interference With Maintenance'' Requirement

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed Rule.

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

SUMMARY: EPA is proposing to approve the ``State of Colorado 
Implementation Plan to Meet the Requirements of Clean Air Act section 
110(a)(2)(D)(i)(I)--Interstate Transport Regarding the 1997 8-Hour 
Ozone Standard'' addressing the ``interference with maintenance'' 
requirement of section 110(a)(2)(D)(i)(I). On June 18, 2009 the State 
of Colorado submitted an interstate transport State Implementation Plan 
(SIP) addressing the interstate transport requirements under section 
110(a)(2)(D)(i) of the Clean Air Act (CAA). In this action, EPA is 
proposing to approve the Colorado Interstate Transport SIP provisions 
that address the section 110(a)(2)(D)(i)(I) requirement prohibiting a 
state's emissions from interfering with maintenance of the 1997 8-hour 
ozone National Ambient Air Quality Standards (NAAQS) by any other 
state. This action is being taken under section 110 of the CAA.

DATES: Comments must be received on or before October 18, 2010.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R08-
OAR-2007-1035, by one of the following methods:
    http://www.regulations.gov. Follow the on-line 
instructions for submitting comments.
     E-mail: mastrangelo.domenico@epa.gov Fax: (303) 312-6064 (please alert the individual listed in 
the FOR FURTHER INFORMATION CONTACT if you are faxing comments).
     Mail: Callie Videtich, Director, Air Program, 
Environmental Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595 
Wynkoop Street, Denver, Colorado 80202-1129.
     Hand Delivery: Callie Videtich, Director, Air Program, 
Environmental Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595 
Wynkoop, Denver, Colorado 80202-1129. Such deliveries are only accepted 
Monday through Friday, 8 a.m. to 4:30 p.m., excluding Federal holidays. 
Special arrangements should be made for deliveries of boxed 
information.
    Instructions: Direct your comments to Docket ID No. EPA-R08-OAR-
2007-1035. 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 your 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. For additional instructions on submitting 
comments, go to Section I. General Information of the SUPPLEMENTARY 
INFORMATION section of this document.
    Docket: All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly-available docket materials are available either electronically 
in http://www.regulations.gov or in hard copy at the Air Program, 
Environmental Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595 
Wynkoop, Denver, Colorado 80202-1129. EPA requests that if at all 
possible, you contact the individual listed in the FOR FURTHER 
INFORMATION CONTACT section to view the hard copy of the docket. You 
may view the hard copy of the docket Monday through Friday, 8 a.m. to 4 
p.m., excluding Federal holidays.

FOR FURTHER INFORMATION CONTACT: Domenico Mastrangelo, Air Program, 
U.S. Environmental Protection Agency, Region 8, Mailcode 8P-AR, 1595 
Wynkoop, Denver, Colorado 80202-1129, (303) 312-6436, 
mastrangelo.domenico@epa.gov.

SUPPLEMENTARY INFORMATION: 

Definitions

    For the purpose of this document, we are giving meaning to certain 
words or initials as follows:
    (i) The words or initials Act or CAA mean or refer to the Clean Air 
Act, unless the context indicates otherwise.
    (ii) The words EPA, we, us or our mean or refer to the United 
States Environmental Protection Agency.
    (iii) The initials SIP mean or refer to State Implementation Plan.
    (iv) The words Colorado and State mean the State of Colorado.

Table of Contents

I. General Information
    What should I consider as I prepare my comments for EPA?
II. Background
III. What action is EPA proposing?
IV. What is the State process to submit these materials to EPA?

[[Page 56936]]

V. EPA's Review and Technical Information
    A. EPA's Evaluation of Interference with Maintenance
    B. Colorado Transport SIP
VI. Proposed Action
VII. Statutory and Executive Order Reviews

I. General Information

    What should I consider as I prepare my comments for EPA?
    1. Submitting CBI. Do not submit CBI to EPA through http://www.regulations.gov or e-mail. Clearly mark the part or all of the 
information that you claim to be CBI. For CBI information in a disk or 
CD ROM that you mail to EPA, mark the outside of the disk or CD ROM as 
CBI and then identify electronically within the disk or CD ROM the 
specific information that is claimed as CBI. In addition to one 
complete version of the comment that includes information claimed as 
CBI, a copy of the comment that does not contain the information 
claimed as CBI must be submitted for inclusion in the public docket. 
Information so marked will not be disclosed except in accordance with 
procedures set forth in 40 CFR part 2.
    2. Tips for Preparing Your Comments. When submitting comments, 
remember to:
    Identify the rulemaking by docket number and other identifying 
information (subject heading, Federal Register date and page number).
    Follow directions--The agency may ask you to respond to specific 
questions or organize comments by referencing a Code of Federal 
Regulations (CFR) part or section number.
    Explain why you agree or disagree; suggest alternatives and 
substitute language for your requested changes.
    Describe any assumptions and provide any technical information and/
or data that you used.
    If you estimate potential costs or burdens, explain how you arrived 
at your estimate in sufficient detail to allow for it to be reproduced.
    Provide specific examples to illustrate your concerns, and suggest 
alternatives.
    Explain your views as clearly as possible, avoiding the use of 
profanity or personal threats.
    Make sure to submit your comments by the comment period deadline 
identified.

II. Background

    On July 18, 1997, EPA promulgated new NAAQS for ozone and for fine 
particulate matter (PM2.5). This action is being taken in 
response to the promulgation of the 1997 8-hour ozone NAAQS. This 
action does not address the requirements for the 1997 or 2006 
PM2.5, or the 2008 8-hour ozone NAAQS; those standards will 
be addressed in later actions.
    Section 110(a)(1) of the CAA requires states to submit SIPs to 
address a new or revised NAAQS within 3 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 its ``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'' (2006 Guidance). EPA developed the 2006 Guidance to make 
recommendations to states for making submissions to meet the 
requirements of section 110(a)(2)(D)(i) for the 1997 8-hour ozone 
standards and the 1997 PM2.5 standards.
    As identified in the 2006 Guidance, the ``good neighbor'' 
provisions in section 110(a)(2)(D)(i) 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) contains four 
distinct requirements related to the impacts of interstate transport. 
The SIP must prevent sources in the state from emitting pollutants in 
amounts which will: (1) Contribute significantly to nonattainment of 
the NAAQS in other states; (2) interfere with maintenance of the NAAQS 
in other states; (3) interfere with provisions to prevent significant 
deterioration of air quality in other states; or (4) interfere with 
efforts to protect visibility in other states.
    On June 18, 2009, EPA received a SIP revision from the State of 
Colorado intended to address the requirements of section 
110(a)(2)(D)(i)(I) for the 1997 8-hour ozone standards. In this 
rulemaking, EPA is addressing only the requirements that pertain to 
preventing sources in Colorado from emitting pollutants that will 
interfere with maintenance of the 1997 8-hour ozone NAAQS by other 
states. In its submission, the State of Colorado indicated that its 
current SIP is adequate to prevent such interference. With this 
submission, the state intended to meet the recommendations of the 2006 
Guidance for SIP submissions to meet the second element of section 
110(a)(2)(D)(i) for the 1997 8-hour ozone standard.

III. What action is EPA proposing?

    EPA is proposing approval of a portion of the Colorado Interstate 
Transport of Air Pollution SIP addressing the requirements of CAA 
section 110(a)(2)(D)(i)(I) for the 1997 8-hour ozone NAAQS. On December 
30, 2008, the Colorado Air Quality Control Commission (AQCC) adopted 
the ``State of Colorado Implementation Plan to Meet the Requirements of 
the Clean Air Act Section 110(a)(2)(d)(i)(I)--Interstate Transport 
Regarding the 1997 8-Hour Ozone Standard'' (Colorado Interstate 
Transport SIP). Colorado submitted this SIP revision to EPA on June 18, 
2009. In this Federal Register action EPA is proposing to approve only 
the language and demonstration that, in this SIP revision, address the 
requirements of element (2), i.e., the prohibition of interference with 
maintenance of the 1997 8-hour ozone NAAQS by any other state.

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

    Section 110(k) of the CAA addresses EPA's rulemaking action on SIP 
submissions by states. The CAA requires states to observe certain 
procedural requirements in developing SIP revisions for submittal to 
EPA. Section 110(a)(2) of the CAA requires that each SIP revision be 
adopted after reasonable notice and public hearing. This must occur 
prior to the revision being submitted by a state to EPA.
    The Colorado AQCC held in early December 2008 a public hearing for 
the Colorado Interstate Transport SIP revision, adopted it on December 
30, 2008, and the State submitted it to EPA on June 18, 2009.
    On November 18, 2009, the AQCC provided EPA with an exact color 
duplicate of the SIP adopted by the AQCC on December 30, 2008 and 
included in the June 18, 2009 submittal to EPA. In the original 
submittal, AQCC provided a black and white copy. The SIP's color 
duplicate, available for review as part of the Docket, makes it easier 
to understand modeling results reported in several graphs that are part 
of the SIP technical demonstration.
    EPA has reviewed the submittal from the State of Colorado and has 
determined that the State met the requirements for reasonable notice 
and public hearing under section 110(a)(2) of the CAA.

V. EPA's Review and Technical Information

A. EPA's Evaluation of Interference With Maintenance

    The second element of 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

[[Page 56937]]

emitting pollutants that would ``interfere with maintenance'' of the 
applicable NAAQS by any other state. This term is not defined in the 
statute. Therefore, EPA has interpreted this term in past regulatory 
actions, such as the 1998 NOX SIP Call, in which EPA took 
action to eliminate emissions of NOX that significantly 
contributed to nonattainment, or interfered with maintenance of, the 
then applicable ozone NAAQS through interstate transport of 
NOX and the resulting ozone.\1\ 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.
---------------------------------------------------------------------------

    \1\ See, 63 FR 57356 (October 27, 1998). EPA's general approach 
to section 110(a)(2)(D) was upheld in Michigan v. EPA, 213 F.3d 663 
(D.C. 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 (D.C. Cir. 2008). Continued
---------------------------------------------------------------------------

    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 U.S. and therefore 
developed the 2005 Clean Air Interstate Rule (CAIR) to address 
emissions of SO2 and NOX that exacerbate ambient 
ozone and PM2.5 levels in many downwind areas through 
interstate transport.\2\ Within CAIR, EPA likewise 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.
---------------------------------------------------------------------------

    \2\ See, 70 FR 25162 (May 12, 2005).
---------------------------------------------------------------------------

    EPA's 2006 Guidance addressed section 110(a)(2)(D) 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 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.'' \3\ 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) together without 
explicitly differentiating between them.
---------------------------------------------------------------------------

    \3\ 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,'' 
Aug. 15, 2006, p. 5. (``2006 Guidance''). Available for review in 
EPA's September 15, 2010 docket document entitled: ``Relevant 
Guidance and Supporting Documentation for the Proposed Rulemaking 
Federal Register Action Docket ID  EPA-R08-OAR-2007-1035.''
---------------------------------------------------------------------------

    In 2008, however, the U.S. Court of Appeals for the DC Circuit 
found that CAIR and the related CAIR federal implementation plans were 
unlawful.\4\ 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. The court 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.'' \5\ EPA's approach, the court reasoned, would leave 
areas that are ``barely meeting attainment'' with ``no recourse'' to 
address upwind emissions sources.\6\ 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) and that the approach used by EPA in CAIR failed 
to do so.
---------------------------------------------------------------------------

    \4\ See, North Carolina v. EPA, 531 F.3d 896 (D.C. Cir. 2008).
    \5\ Id. at 909.
    \6\ Id.
---------------------------------------------------------------------------

    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)(I) because the agency's guidance 
suggested that states use an approach comparable to that used by EPA in 
CAIR. States such as Colorado developed and adopted their Interstate 
Transport SIPs not long after the Court's July 2008 decision, but well 
before EPA, in the Transport Rule Proposal (see below), was able to 
propose a new approach for the interference with maintenance element. 
Without recommendations from EPA, Colorado's SIP may not have 
sufficiently differentiated between the significant contribution to 
nonattainment and interference with maintenance elements of the 
statute, and relied in a general way on the difference between 
monitored concentrations and the 1997 8-hour ozone NAAQS to evaluate 
the impacts of State emissions on maintenance of the NAAQS in 
neighboring states. EPA believes that it is necessary to evaluate these 
state submissions 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, EPA believes it is necessary to use an updated 
approach to this issue and to supplement the technical analysis 
provided by the state in order to evaluate the submissions with respect 
to the interfere with maintenance element of section 110(a)(2)(D)(i).
    EPA has recently proposed a new rule to address interstate 
transport 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), in order to address the 
judicial remand of CAIR.\7\ As part of the Transport Rule Proposal, EPA 
specifically reexamined the section 110(a)(2)(D)(i) requirement that 
emissions from sources in a state must not ``interfere with 
maintenance'' of the 1997 8-hour ozone NAAQS and 1997 PM2.5 
NAAQS by other states. In the proposal, EPA developed an approach to 
identify areas that it predicts to be close to the level of the 1997 8-
hour ozone NAAQS and 1997 PM2.5 NAAQS in the future, and 
therefore at risk to become or continue to be nonattainment for these 
NAAQS unless emissions from sources in other states are appropriately 
controlled. This approach starts by identifying those specific 
geographic

[[Page 56938]]

areas for which further evaluation is appropriate, and differentiates 
between areas where the concern is with interference with maintenance, 
rather than with significant contribution to nonattainment.
---------------------------------------------------------------------------

    \7\ See ``Federal Implementation Plans to Reduce Interstate 
Transport of Fine Particulate Matter and Ozone,'' 75 FR 45210 
(August 2, 2010).
---------------------------------------------------------------------------

    As described in more detail below, EPA's analysis evaluates data 
from existing monitors over three overlapping three 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 with 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.
    By this method, EPA has identified those areas with monitors that 
are appropriate ``maintenance sites'' or maintenance ``receptors'' for 
evaluating whether the emissions from sources in another state could 
interfere with maintenance in that particular area. EPA then uses other 
analytical tools to examine the potential impacts of emissions from 
upwind states on these maintenance receptors in downwind states. EPA 
believes that this new approach for identifying those areas that are 
predicted to have maintenance problems is appropriate to evaluate the 
section 110(a)(2)(D)(i) SIP submission of a state for the interfere 
with maintenance element.\8\ 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 
Colorado submission.
---------------------------------------------------------------------------

    \8\ 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. 
These maintenance receptors are close to the level of the 1997 ozone 
and PM2.5 NAAQS such that minor variations in weather or 
emissions could result in violations of the NAAQS in 2012.
---------------------------------------------------------------------------

    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 as CAIR. In the 
2006 Guidance, EPA stated that: ``EPA believes that the contents of the 
SIP submission required by section 110(a)(2)(D)(i) 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.'' \9\ 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.\10\ 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. For the 1997 8-hour ozone NAAQS and the 1997 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.\11\ In the Transport Rule Proposal, 
EPA did not calculate interstate ozone or PM2.5 
contributions to or from western states.
---------------------------------------------------------------------------

    \9\ 2006 Guidance at 4.
    \10\ Id. at 5.
    \11\ See, Transport Rule Proposal, 75 FR 45210, 45277.
---------------------------------------------------------------------------

    Accordingly, EPA believes that section 110(a)(2)(D)(i) SIP 
submissions for states not evaluated in the Transport Rule Proposal may 
be evaluated using a ``weight of the evidence'' approach that takes 
into account 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 
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.

B. Colorado Transport SIP

    To meet the requirements of section 110(a)(2)(D)(i)(I) for the 1997 
8-hour ozone standard, the State of Colorado developed and submitted to 
EPA on June 18, 2009 an Interstate Transport SIP that focused primarily 
on the ``significant contribution to nonattainment'' requirement of 
section 110(a)(2)(D)(i) and, as noted earlier, addressed only in a 
limited way the interference with maintenance requirement of section 
110(a)(2)(D)(i)(I). On June 3, 2010, EPA approved the Colorado 
Interstate Transport SIP provision that require that emissions from a 
state's sources do not significantly contribute to nonattainment of the 
1997 8-hour ozone NAAQS in any other state. To demonstrate that 
emissions from Colorado do not interfere with maintenance of the 1997 
8-hour ozone NAAQS in neighboring states, the Colorado Interstate 
Transport SIP uses results from Colorado's 2009 ``8-Hour Ozone 
Attainment Plan'' for the DMA/NFR nonattainment area, and a report from 
the Western States Air Resource (WESTAR) Council to underscore that: 
(a) Local anthropogenic ozone contribution to high ozone concentrations 
in Denver is only about 25%; and (b) on days of highest ozone 
concentrations (reflecting a design value of 84.9 ppb) in the DMA/NFR 
area, the projected design values decrease to 63 ppb or less for all 
downwind Colorado counties east of an imaginary north-south line 
approximately 70 miles east from Denver.\12\ EPA does not agree with 
the State of Colorado Interstate Transport SIP's assessment that these 
results demonstrate that ``the magnitude of ozone transport from 
Colorado to other states is too low to * * * interfere with maintenance 
by any other state with respect to the 0.08 ppm NAAQS'' as the sole 
basis for evaluating the state's interference.\13\ The limited 
contribution of local emissions to nonattainment in the DMA/NFR and the 
quick drop in ozone levels in the easternmost Colorado counties, in and 
by themselves do not exclude a potential for interference with 
maintenance of the 8-hour ozone NAAQS from Colorado emissions to 
downwind maintenance areas. Rather, as a reflection of emission levels, 
the relatively (to the 1997 8-hour ozone

[[Page 56939]]

NAAQS) moderate ozone concentrations in eastern Colorado and in 
neighboring states somewhat reduce the probability that State emissions 
interfere with maintenance of the NAAQS by these states.\14\
---------------------------------------------------------------------------

    \12\ Colorado Interstate Transport SIP, December 12, 2009, 
Figure 5 at 15. Note that the modeling analysis domain for the DMA/
NFR attainment plan was limited to the State's territory, and that 
the 70 mile distance represents the approximate distance from Denver 
to the western border of Morgan County, Colorado.
    \13\ Id. at 17.
    \14\ Similar evidence is provided by the substantial gap between 
the 1997 8-hour ozone standard and the design values at monitors in 
adjacent downwind states such as Kansas, New Mexico, Utah, and 
Wyoming. Id. at 7-8.
---------------------------------------------------------------------------

    EPA is evaluating the Colorado Interstate Transport SIP taking into 
account the methodologies and analysis results developed in the 
Transport Rule Proposal in response to the judicial remand of CAIR. As 
noted previously, the Transport Rule Proposal includes a new approach 
to determine whether emissions from a state interfere with maintenance 
of the 1997 8-hour ozone NAAQS and the 1997 PM2.5 NAAQS by 
other states. In this action, EPA is using a comparable approach to 
that of the Transport Rule Proposal in order to determine if emissions 
from Colorado sources interfere with maintenance of the 1997 8-hour 
ozone NAAQS by other states.
    To evaluate ambient impacts from upwind states to maintenance 
receptors, the Transport Rule Proposal evaluates, through air quality 
modeling of each state's emissions, the contribution from individual 
states to downwind maintenance receptors. States that contribute 
pollutant concentrations below the significance threshold for 
interference with maintenance, proposed at one percent of the NAAQS, 
are excluded from further analysis.\15\ For the 1997 8-hour ozone 
standard state contributions of 0.8 ppb and higher are considered above 
the threshold, while ozone contribution less than 0.8 ppb are below the 
threshold.
---------------------------------------------------------------------------

    \15\ Transport Rule Proposal, 75 FR 45210, 45254.
---------------------------------------------------------------------------

    In the Transport Rule Proposal, EPA projected future concentrations 
of ozone at monitors to identify areas that are expected to be out of 
attainment with NAAQS or to have difficulty maintaining compliance with 
the NAAQS in 2012. To determine the states that may cause interference 
at the maintenance receptors, the Transport Rule Proposal models the 
states' ozone contribution to these maintenance receptors. Because the 
Transport Rule Proposal does not model the contribution of emissions 
from Colorado (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 (such as identification of 
maintenance receptors and estimates of ozone contributions) from the 
Transport Rule Proposal pertaining to states within its modeling 
domain, and additional material such as geographical and meteorological 
factors, modeling analysis results from other studies, back trajectory 
analyses, and AQS monitoring data. While conclusions reached for each 
of the factors considered in the following analysis are not in and by 
themselves determinative, consideration of these factors together 
provides a reliable qualitative conclusion that emissions from Colorado 
are not likely to interfere with maintenance of the 1997 8-hour ozone 
NAAQS at monitors in other states.
    Our analysis begins by assessing Colorado's contribution to the 
closest maintenance 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) 16 maintenance receptors, among which the eight closest to 
Colorado are eight receptors in the Dallas Fort Worth (DFW) and 
Houston-Galveston-Brazoria (HGB) 8-hour ozone nonattainment areas.\16\
---------------------------------------------------------------------------

    \16\ The remaining eight maintenance-only sites are in a handful 
of East Coast states: Connecticut, Georgia, New York and 
Pennsylvania. See Table IV C-12, Transport Rule Proposal, at 45252-
253.
---------------------------------------------------------------------------

    Two of the three DFW area maintenance receptors are in Dallas 
County (Hinton Street and Dallas Executive Airport sites), and the 
third is in Tarrant County (Keller site).\17\ These monitors are at 
least 500 miles from Colorado.\18\ Distance by itself is not an 
obstacle to long range transport of ozone and/or its precursors. 
NOX, the primary ozone precursor that is the object of the 
Transport Rule Proposal, may be transported for long distances, and 
contribute significantly to high ozone concentrations in other states. 
However, with increasing distance there are greater opportunities for 
ozone or NOX dispersion and/or removal from the atmosphere 
due to the effect of winds or chemical sink processes. As a result, one 
may conclude that the approximately 500 miles from Colorado sources of 
X emissions to the DFW area maintenance receptors reduces, 
but does not exclude, the possibility that the Colorado emissions 
interfere with maintenance of the NAAQS at these receptors.
---------------------------------------------------------------------------

    \17\ The 500 mile estimate represents the approximate distance 
between Lamar, in the southeastern corner of Colorado, and Dallas, 
Texas. The monitors' Site ID Numbers are: Hinton, 48-113-0069; 
Executive Airport, 48-113-0087; and Keller, 48-439-2003. See id. For 
monitors' site names, see online TCQE web page at http://www.tceq.state.tx.us/cgi-bin/compliance/monops/site_info.pl.
    \18\ This distance underestimates the average distance covered 
by emissions from Colorado sources for at least two reasons: (a) 
Most Colorado sources are further north and/or west from the DFW 
area than Lamar; (b) 500 miles represents the distance along a 
straight pathway from Lamar to Dallas, Texas, as compared to the 
pathways full of twists and turns that often characterize the long 
range transport of air parcels.
---------------------------------------------------------------------------

    Because pollutant transport is linked to wind direction, we examine 
how frequently air masses from Colorado pass through or end in the DFW 
area that includes the maintenance receptors identified above. The 
State of Texas' 2007 attainment demonstration for the DFW area points 
out, without quantifying contributions, how heavily the area's ozone 
concentrations are affected by substantial transport from other areas. 
Average ozone background levels for DFW (reflecting concentrations 
contributed to the area by emissions from sources within Texas but 
outside the nonattainment area, and from sources outside Texas) are 
estimated to range between 44 and 61 ppb, with peak averages between 64 
and 68 ppb on days when 8-hour ozone concentrations exceed the 1997 
standard.\19\
---------------------------------------------------------------------------

    \19\ ``Dallas-Fort Worth Eight-Hour Ozone Nonattainment Area: 
Attainment Demonstration,'' TCEQ, May 23, 2007, p. i.
---------------------------------------------------------------------------

    To evaluate the impact of wind direction on ozone transport from 
Colorado to the DFW maintenance receptors, we rely on the results of 
two back trajectory studies, including a set of trajectories with end 
points at the maintenance receptors in the DFW area.\20\ EPA generated 
these trajectories using the HYSPLIT 4.9 online computer application, 
selecting the archived Eta Data Assimilation System (EDAS) 
meteorological data sets with the highest degree of resolution (40 
km).\21\ Back trajectories were run for the days of the 2005-2006 years 
in which ozone concentrations at these receptors exceeded the 1997 8-
hour NAAQS--i.e., monitored ozone concentrations were 85 ppb or above. 
Exceedance days were identified using the Air Quality System (AQS), 
EPA's repository of monitored ambient air quality data. At each 
monitor, trajectories were started at 22

[[Page 56940]]

Coordinated Universal Time (UTC), equivalent to 4 p.m. CST, and were 
run backwards in time for 72 hours (three days). The trajectory height 
at the starting point is 1500 meters above ground level. From the 
individual back trajectories, ``spider web'' maps were generated for 
all three monitors combined and for each monitor (Figure 1.1 and 
Figures 1.1.a through 1.1.c in Appendix A of EPA's TSD).\22\ These maps 
indicate that air parcel pathways from Colorado and ending at 
maintenance receptors in Dallas and Tarrant Counties are rare during 
the three days preceding ozone exceedances at these receptors. On only 
one day, of the 35 exceedance days at maintenance receptors in 2005-
2006, did the air mass pathway go through Colorado, and even in this 
one instance air parcels crossed the State along a short pathway 
through its northeast corner, before continuing on their southeastward 
course.\23\
---------------------------------------------------------------------------

    \20\ USEPA Region 8 mapped back trajectories using software and 
data files maintained by the National Oceanic and Atmospheric 
Administration (NOAA) Air Resource Laboratory (ARL).
    \21\ Draxler, R.R. and Rolph, G.D., HYSPLIT (HYbrid Single-
Particle Lagrangian Integrated Trajectory) Model (2010), available 
via NOAA ARL READY Web site, http://ready.arl.noaa.gov/HYSPLIT.php. 
NOAA Air Resources Laboratory, Silver Spring, MD. See also Rolph, 
G.D., Real-time Environmental Applications and Display sYstem 
(READY) Web site (2010), http://ready.arl.noaa.gov. NOAA Air 
Resources Laboratory, Silver Spring, MD.
    \22\ See back trajectory maps in Appendix A of the EPA's TSD 
supporting documentation in Docket ID No. EPA-R08-OAR-2007-1035.
    \23\ EPA's TSD is available for review as part of the supporting 
documentation for Docket ID N. EPA-R08-OAR-2007-1035.
---------------------------------------------------------------------------

    Back trajectory analysis results included in the May 23, 2007 DFW 
area Attainment Demonstration corroborate these conclusions. The 
analysis, also based on the HYSPLIT model, includes all days during the 
years 2001-2003, with trajectories of 48 hours (2 days) duration, 
heights of 100, 500 and 1300 meters, and start times of 20, 21 and 22 
UTC (2, 3, and 4 p.m. CST). The resulting density plots in Figure 3-1 
of the DFW attainment demonstration clearly show that during most of 
the ozone season, on high and low ozone days, air parcels from Colorado 
infrequently end in or pass through the DFW area.\24\
---------------------------------------------------------------------------

    \24\ Dallas-Fort Worth Attainment Demonstration, May 23, 2007, 
at 3-1 to 3-2.
---------------------------------------------------------------------------

    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 of the absence of such transport, from Colorado 
emissions. However, the rarity of air parcel trajectories from Colorado 
to the DFW area and to its maintenance receptors strongly support the 
conclusion that emissions of ozone and its precursors from Colorado are 
not likely to interfere with maintenance of the 1997 ozone NAAQS at 
these receptors.
    A final piece of evidence of a different type is found in a 
modeling analysis developed by EPA to assist the State of New Mexico in 
its assessment of ozone and PM2.5 transport from New Mexico 
to other states. This modeling analysis, part of the New Mexico 
Interstate Transport SIP submission of July 30, 2007, relies on data 
developed by the Central Regional Air Planning Association (CENRAP) 
that includes a 2002 third quarter CENRAP modeling dataset.\25\ It is 
based on a 36 km national grid that includes Colorado, and uses the 
ozone source apportionment tool (OSAT) to determine potential linkages 
between state emissions and downwind states.\26\ Modeling results 
indicate that at the height of the 2002 ozone season, the highest ozone 
contribution from Colorado emissions to the DFW monitors (including its 
maintenance receptors) averaged 0.4 ppb or less. That is well below the 
contribution threshold of 0.8 ppb, used in the proposed Transport Rule.
---------------------------------------------------------------------------

    \25\ ``New Mexico State Interstate Transport SIP,'' submitted to 
EPA July 30, 2007: Appendix D, Exhibit 9 Modeling Data and Report 
for New Mexico,'' at 2.
    \26\ For details on the model and on the analysis see: id.
---------------------------------------------------------------------------

    The other five Texas monitors identified by the Transport Rule 
Proposal as maintenance-only receptors in Texas are located in Harris 
County, which lies within the HGB nonattainment area. This area is at 
least 700 miles from Colorado.\27\ General considerations on the effect 
of distance on ozone transport from Colorado to the DFW area, discussed 
above, also apply to the potential for transport from Colorado to the 
maintenance receptors in the HGB area. The greater distance (by about 
one third) between Colorado and the HGB area increases the chance for 
dispersion of any Colorado ozone during its transport to HGB 
maintenance receptors, and increases the odds for air masses from 
Colorado to pick up greater quantities of ozone and/or precursors 
during their longer travel through emissions rich Texas. Again, these 
considerations reduce, but do not exclude, the possibility of emissions 
from Colorado interfering with maintenance of the 8-hour ozone NAAQS at 
the HGB maintenance receptors.
---------------------------------------------------------------------------

    \27\ The 700-mile estimate represents the approximate distance 
between Lamar, in the southeastern corner of Colorado, and Houston, 
Texas. The five monitoring sites' names (ID No.) are: Aldine (48-
201-0024), Northwest Harris (48-201-0029), Lynchburg Ferry (48-201-
1015), Clinton (48-201-1035), and Seabrook Friendship Park (48-201-
1050). The approximate 850-mile distance between Denver and Houston 
is intended to represent the distance to be covered by the emissions 
from Colorado to the five maintenance monitors. It is to be noted 
that the measured distance represents that of the straight (and 
shortest) path, which does not reflect the more circuitous paths 
followed by air parcels.
---------------------------------------------------------------------------

    A similar conclusion is suggested by the EPA back trajectories 
mapped for the HGB maintenance receptors. Using the same online HYSPLIT 
4.9 online computer application as for the DFW trajectories,\28\ EPA 
ran back trajectories from the HGB area maintenance receptors for all 
2005-2006 ozone exceedances days. The pathways of air parcels ending 
at, or passing through, these monitors when ozone concentrations 
reached levels of 85 ppb or higher are shown in Figure 2.1 of Appendix 
A in EPA's supporting documentation. At each monitor, trajectories 
started at 22 Coordinated Universal Time (UTC), equivalent to 4 p.m. 
CST, and ran backwards in time for 72 hours (three days), at 1500 
meters above ground level.\29\ Results show that air parcel pathways 
passing 1500 meters above the HGB maintenance receptors at 4 p.m. on 
exceedance days rarely came from Colorado. Figure 3 of the back 
trajectories report shows that only in one out of 53 exceedance days at 
the maintenance receptors did the air parcel's pathway go through 
Colorado. Even in this one instance, the pathway crossed Colorado for a 
very short distance through the State's northeast corner, before 
continuing on its southeastward course.\30\
---------------------------------------------------------------------------

    \28\ See note 24 above.
    \29\ See Table 1, EPA's ``Back Trajectories Analysis 
Documentation,'' Table 1.
    \30\ The trajectory's path that ended at the Northwest Harris 
receptor on August 31, 2006, is almost the same as the one that on 
June 15, 2005 ended at the Keller receptor in Tarrant. This is 
likely to be a coincidence, or an indication about the pathways of 
air masses that go through eastern Colorado before ending in eastern 
Texas (DFW and HGB areas).
---------------------------------------------------------------------------

    Back trajectory analysis results from a 2009 report, ``Effects of 
Meteorology on Pollutant Trends'' report, corroborate these 
conclusions. The analysis uses HYSPLIT with EDAS meteorological 
datasets to plot 72-hour back trajectories centered in Houston, at 300 
meters height and for various times of the day. Trajectories are 
plotted for all days with available data between May 1 and October 31, 
2000-2007. A clustering algorithm built into HYSPLIT is used to group 
individual back trajectories into several classes based on shape and 
direction.\31\ Due to the greater number of days plotted, the six 
clusters of trajectories shown in Figures 6-17 to 6-22 include a much 
larger number of air parcel pathways than EPA's back

[[Page 56941]]

trajectory analysis referenced above, but still show similar results 
concerning trajectories from Colorado. Air parcels from Colorado to the 
Houston area are rare, as shown by the few trajectories from Colorado 
in cluster 3 (Figure 6-19) as compared with the total sample of 1416 
trajectories included in the six clusters. Figure 6-15 summarizes 
effectively the overall scarcity of wind pathways from Colorado, and 
from the west/lower northwest sector in general, to the HGB area. It 
shows the mean centerlines for the six identified clusters, and at 
their closest point to Colorado's borders the mean centerline (number 
3) is still at an estimated distance of approximately 200 miles.
---------------------------------------------------------------------------

    \31\ Dave Sullivan, ``Effects of Meteorology on Pollutant 
Trends,'' March 16, 2009, at 27-34. This report is available as one 
of the documents in EPA's TSD documentation, and may also be 
reviewed online at http://www.tceq.state.tx.us/assets/public/implementation/air/am/contracts/reports/da/5820586245FY0801-20090316-ut-met_effects_on_pollutant_trends.pdf.
---------------------------------------------------------------------------

    Again, back trajectories map pathways of air parcels that may or 
may not transport pollutants, and they cannot be considered 
determinative as to the transport of ozone and its precursors. However, 
the infrequency of air parcels trajectories from Colorado to the HGB 
area in general, and to its maintenance receptors in particular, 
strongly support the conclusion that ozone precursors' emissions and 
ozone from Colorado are not likely to interfere with maintenance of the 
1997 ozone NAAQS at these receptors.
    The EPA modeling analysis referenced earlier (concerning 
contribution from Colorado sources to the DFW area) includes 
information on the contribution of the State emissions to the HGB area 
as well. The 2002 modeled contribution from Colorado ozone emissions to 
the HGB area is estimated at 0.3 ppb or less. This fraction of the 
significant contribution threshold of 0.8 ppb, set in EPA's Transport 
Rule Proposal of August 2, 2010, strengthens our assessment that 
Colorado emissions are unlikely to interfere with maintenance of the 
1997 ozone NAAQS at the HGB maintenance receptors.\32\
---------------------------------------------------------------------------

    \32\ New Mexico State Interstate Transport SIP, 2007, Appendix 
D, at 52.
---------------------------------------------------------------------------

    As noted previously, eight of the 16 maintenance receptors 
identified within the modeling by the Transport Rule Proposal analysis 
are in a handful of East Coast states: Connecticut, Georgia, New York 
and Pennsylvania.\33\ The westernmost states ``linked'' by the 
Transport Rule Proposal to the eight maintenance receptors in these 
states include Indiana, Kentucky, Tennessee, and Alabama. None of the 
13 states west of these contributing states and east of Colorado (such 
as North and South Dakota and Nebraska) was found to contribute 
significantly to the maintenance receptors in the east.\34\ In 
addition, among the 13 non-contributing states closer than Colorado to 
the maintenance receptors in the east, there are states such as 
Illinois, Wisconsin, Iowa, Missouri, Arkansas, and Louisiana that in 
2005 had NOX emissions up to twice as high as Colorado's. 
Because the analysis for the Transport Rule Proposal found that these 
states with substantially larger NOX emissions than 
Colorado, and closer than Colorado to the maintenance receptors in the 
east, do not to contribute significantly to maintenance receptors in 
Connecticut, Georgia, New York and Pennsylvania, it is logical to 
conclude that it is quite unlikely for Colorado emissions to interfere 
with maintenance of the 1997 8-hour ozone NAAQS at these same 
receptors.
---------------------------------------------------------------------------

    \33\ Table IV C-12, Transport Rule, at 196-197.
    \34\ In addition to North Dakota, South Dakota and Nebraska, the 
13 states include: Kansas, Oklahoma, Minnesota, Iowa, Missouri, 
Arizona, Wisconsin, Michigan, Illinois, and Louisiana. Table IV-C-
21, Transport Rule Proposal, at 45269-70.
---------------------------------------------------------------------------

    To assist in the evaluation of whether states' emissions interfere 
with maintenance of the NAAQS in western states, EPA has developed, 
independent of the Transport Rule Proposal, a modeling analysis 
identifying monitors at risk for maintenance of the NAAQS within a 
modeling domain that includes the western states.\35\ The analysis 
presented in the memo, ``Documentation of Future Year Ozone and Annual 
PM2.5 Design Values for Western States'' (Western States 
Design Values), uses model results from the Transport Rule modeling 
Continental U.S. 36 km grid, which is coarser than the 12 km grid used 
in the Transport Rule, but does not necessarily yield less reliable 
results.\36\
---------------------------------------------------------------------------

    \35\ A memorandum in the docket for this action provides the 
information EPA used in order to identify monitors that are 
receptors for evaluation of interference with maintenance for 
certain states in the western United States. See, Memorandum from 
Brian Timin of EPA's Office of Air Quality Planning and Standards, 
Air Quality Modeling Group entitled ``Documentation of Future Year 
Ozone and Annual PM2.5 Design Values for Western States''
    ``Memorandum to Docket EPA-R08-OAR-2007-1035,'' EPA, August 23, 
2010.
    \36\ Id. at 5.
---------------------------------------------------------------------------

    EPA's modeling analysis of western states to determine the monitors 
that are at risk for maintenance of the 1997 8-hour ozone NAAQS 
identifies only four such maintenance receptors, and all four are in 
California, in Mercer, Placer, Riverside, and Sacramento Counties. 
Distance and topography are not favorable to ozone transport from 
Denver, which is approximately 750 miles east of the monitors in Placer 
and Sacramento Counties, and 850 miles northeast to a Riverside County 
monitor. In the absence of significant northwesterly regional transport 
winds, mountain ranges between Denver and the California maintenance 
receptors, such as the Rocky Mountains, the Wasatch and the Sierra 
Nevada, present large obstacles to ozone transport from Colorado to 
California. Thus, geography and topography reduce the likelihood of 
transport from Colorado to California's maintenance receptors.
    Prevailing wind orientation in fact strongly supports the 
conclusion that Colorado's emissions are unlikely to interfere with 
maintenance of the 1997 8-hour ozone standard in California. West of 
the Continental Divide the prevailing winds generally move from south-
westerly, westerly, or north-westerly directions, as indicated by the 
typical movement of weather systems. To further evaluate the direction 
of regional transport winds affecting the California maintenance 
receptors, we have plotted back trajectories starting at each 
maintenance receptor on high ozone days. High ozone days include the 
top one-third of the exceedance days (for the 1997 8-hour ozone NAAQS) 
registered at each monitor in 2005 and 2006. As shown by the 
trajectories mapped for all four maintenance receptors in Figure 3.1, 
Appendix A of EPA's supporting documentation, on high ozone days air 
parcels converge on the Mercer, Placer, Sacramento and Riverside 
monitors from the northwest, south and southeast, but there are no 
pathways from the east/northeast directions reaching even as far as the 
eastern Nevada border, let alone Colorado.
    For a large number of receptors in western states, EPA's modeling 
analysis could not calculate 2012 projected design values because these 
receptors did not have at least 5 days with base year concentrations 
equal to or greater than 70 ppb, as required by EPA's modeling 
guidance. However, the observed maximum design values at these sites in 
the 2003-2007 period were generally well below the 1997 ozone NAAQS. 
The highest (non-California \37\) site had a maximum design value of 77 
ppb. Additionally, the 2012 modeling results at western monitors (where 
a future year design value could be estimated, shows a

[[Page 56942]]

downward trend in ozone. There are no areas in the West where ozone is 
predicted to be higher in 2012 (without CAIR) compared to 2005. On 
these bases it is plausible to conclude that it is highly unlikely, but 
not impossible, for these monitors to be at risk for maintenance of the 
1997 8-hour ozone NAAQS.
---------------------------------------------------------------------------

    \37\ We are excluding the California monitors from this portion 
of our analysis because above we have already demonstrated that 
Colorado's emissions are unlikely to interfere with maintenance at 
the modeled California maintenance monitors in the northern, central 
and southern sections of the state. The factors we considered--
distance, topography, and wind orientation--apply equally to the un-
modeled monitors and make it plausible to conclude that the same 
demonstration is true for Colorado emissions' impact on California 
non-modeled monitors.
---------------------------------------------------------------------------

    In conclusion, the variety of data and the weight of evidence 
analysis presented in this section support the position of the Colorado 
Interstate Transport SIP (adopted into the State SIP on December 30, 
2008 and submitted to EPA June 18, 2009) that emissions from Colorado 
do not interfere with maintenance of the 1997 8-hour ozone NAAQS by any 
other state, consistent with the requirements of element (2) of CAA 
section 110(a)(2)(D)(i).

VI. Proposed Action

    EPA is proposing partial approval of the Colorado SIP to meet the 
requirements of Section 110(a)(2)(D)(i)(I) regarding the 1997 8-hour 
ozone standard. Specifically, in this action EPA is proposing to 
approve only the language and demonstration that address the 
requirements of element (2): Prohibition of interference with 
maintenance of the 1997 8-hour ozone NAAQS by any other state. EPA 
approved in a June 3, 2010 final action the language and demonstration 
addressing element (1): Prohibition of significant contribution to 
nonattainment of the 1997 8-hour ozone NAAQS in any other state.

VII. Statutory and Executive Order Review

    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 approves 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 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

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

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

    Dated: September 9, 2010.
Carol Rushin,
Acting Regional Administrator, Region 8.
[FR Doc. 2010-23294 Filed 9-16-10; 8:45 am]
BILLING CODE 6560-50-P
```