Document ID: EPA-R08-OAR-2007-1032-0001
Agency: epa
Document Type: Proposed Rule
Title: Approval and Promulgation of State Implementation Plans: Colorado; Interstate Transport of Pollution Revisions for the 1997 8-hour Ozone NAAQS, etc.
Posted Date: 2010-03-31T04:00Z

[Federal Register: March 31, 2010 (Volume 75, Number 61)]
[Proposed Rules]               
[Page 16032-16037]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr31mr10-21]                         

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2007-1032; FRL-9131-4]

 
Approval and Promulgation of State Implementation Plans; State of 
Colorado; Interstate Transport of Pollution Revisions for the 1997 8-
Hour Ozone NAAQS: ``Significant Contribution to Nonattainment'' 
Requirement

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing partial 
approval of the State Implementation Plan (SIP) revisions ``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'' submitted by the State of Colorado on June 18, 
2009. The Colorado Interstate Transport SIP revisions submitted June 
18, 2009 address the requirements of Clean Air Act section 
110(a)(2)(D)(i)(I) for the 1997 8-hour ozone National Ambient Air 
Quality Standards (NAAQS). In this Federal Register action EPA proposes 
approval of the Colorado SIP sections that address the requirement of 
section 110(a)(2)(D)(i)(I) prohibiting a state's emissions from 
contributing significantly to any other state's nonattainment of the 
NAAQS. EPA will act at a later date on the Colorado Interstate 
Transport SIP sections that address the requirement prohibiting a 
state's emissions from interfering with any other state's maintenance 
of the NAAQS. This action is being taken under section 110 of the Clean 
Air Act.

DATES: Comments must be received on or before April 30, 2010.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R08-
OAR-2007-1032, by one of the following methods:
     http://www.regulations.gov. Follow the on-line 
instructions for submitting comments.
     E-mail: videtich.callie@epa.gov and 
mastrangelo.domenico@epa.gov.
     Fax: (303) 312-6064 (please alert the individual listed 
under 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.

[[Page 16033]]

     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-
2007-1032. 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 Information
III. What Action Is EPA Proposing?
IV. What Is the State Process To Submit These Materials to EPA?
V. EPA's Review and Technical Information
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:
    a. Identify the rulemaking by docket number and other identifying 
information (subject heading, Federal Register date and page number).
    b. 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.
    c. Explain why you agree or disagree; suggest alternatives and 
substitute language for your requested changes.
    d. Describe any assumptions and provide any technical information 
and/or data that you used.
    e. If you estimate potential costs or burdens, explain how you 
arrived at your estimate in sufficient detail to allow for it to be 
reproduced.
    f. Provide specific examples to illustrate your concerns, and 
suggest alternatives.
    g. Explain your views as clearly as possible, avoiding the use of 
profanity or personal threats.
    h. Make sure to submit your comments by the comment period deadline 
identified.

II. Background Information

    Section 110(a)(2)(D)(i) of the CAA requires that a state's SIP must 
contain adequate provisions prohibiting any source or other type of 
emissions activity within the state from emitting any air pollutant in 
amounts which will: (1) Contribute significantly to nonattainment of 
the NAAQS in any other state; (2) interfere with maintenance of the 
NAAQS by any other state; (3) interfere with any other state's required 
measures to prevent significant deterioration of air quality; or (4) 
interfere with any other state's required measures to protect 
visibility. On June 11, 2008, the State of Colorado submitted to EPA an 
Interstate Transport SIP addressing the interstate transport 
requirements of CAA section 110(a)(2)(D)(i) for the 1997 
PM2.5 and 8-hour ozone NAAQS. In response to EPA's concerns 
with the June 11, 2008 submittal, on December 30, 2008 the State 
adopted and on June 18, 2009 submitted a revised SIP addressing the 
requirements of elements (1) and (2) of section 110(a)(2)(D)(i) for the 
1997 8-hour ozone NAAQS. The State of Colorado is planning to submit in 
June 2010 further revisions addressing the requirements of elements (3) 
and (4) for the 1997 8-hour ozone NAAQS and the requirements of 
elements (1) through (4) for the 1997 PM2.5 NAAQS.

[[Page 16034]]

III. What Action Is EPA Proposing?

    EPA is proposing partial approval 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 submitted the 
December 30, 2008 SIP revision to EPA on June 18, 2009. In this Federal 
Register action EPA is proposing to approve only the language and 
demonstration that addresses element (1) of section 110(a)(2)(D)(i): 
Prohibition of significant contribution to nonattainment of the 1997 8-
hour ozone NAAQS in 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 a public hearing in December 2008 for the 
interstate transport SIP revision: ``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.'' The AQCC adopted this revision 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

    The interstate transport provisions at CAA section 110(a)(2)(D)(i), 
also referred to as the ``good neighbor'' provisions, require that each 
state's SIP contain adequate provisions prohibiting emissions that 
adversely affect any other state's air quality through interstate 
transport of air pollutants. As discussed in the Background Information 
section of this notice, a state's SIP must contain provisions that 
satisfy the four elements of section 110(a)(2)(D)(i). On August 15, 
2006, EPA issued guidance for SIP submissions addressing the 
requirements of section 110(a)(2)(D)(i) for the 1997 PM2.5 
and 8-hour ozone NAAQS.\1\ The portions of the Colorado Interstate 
Transport SIP revision that address element (1) of section 
110(a)(2)(D)(i) for the 1997 8-hour ozone NAAQS are consistent with 
EPA's 2006 guidance.
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    \1\ 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) (``2006 Guidance''). Available for review in EPA's 
January 14, 2010 docket document entitled: ``Relevant Guidance and 
Supporting Documentation for the Proposed Rulemaking Federal 
Register Action Docket ID  EPA-R08-OAR-2007-1032.
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    To demonstrate that emissions from Colorado do not contribute 
significantly to nonattainment of the 1997 8-hour ozone NAAQS in any 
other state, the Colorado Interstate Transport SIP relies on a 
combination of: (a) Modeling analysis done by the State as part of the 
attainment demonstration SIP for the Denver Metropolitan Area/North 
Front Range (DMA/NFR) nonattainment area for the 1997 8-hour ozone 
standard; (b) monitoring data gathered by states and reported to EPA in 
the Air Quality System (AQS) database; and (c) considerations of 
geographical and meteorological factors. In this action, EPA expands on 
the analysis of geographical and meteorological factors, and of ozone 
concentration levels reflecting AQS monitoring data.
    Section 110(a)(2)(D)(i) provides that EPA cannot approve a state's 
SIP for a new or revised NAAQS unless it contains adequate measures to 
prohibit emissions from sources within the state from contributing 
significantly to nonattainment of the NAAQS in another state. EPA's 
August 15, 2006 guidance to states concerning section 110(a)(2)(D)(i) 
recommended various methods by which states might evaluate whether or 
not its emissions significantly contribute to violations of the 1997 
ozone standards in another state. Among other methods, EPA recommended 
consideration of available EPA modeling conducted in conjunction with 
CAIR,\2\ 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, this impact must 
be evaluated with respect to any monitors showing a violation of the 
NAAQS (70 FR 25172, May 12, 2005, and 63 FR 57371, October 27, 1998). 
Furthermore, although relevant information other than modeling may be 
considered in assessing the likelihood of significant contribution to 
violations of the 1997 8-hour ozone standard in another state, EPA 
notes that no single piece of information in the following discussion 
is by itself dispositive of the issue. Instead, the total weight of all 
the evidence taken together supports the conclusion that emissions from 
Colorado sources are unlikely to contribute significantly to violations 
of the 1997 8-hour ozone standard in any other state.
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    \2\ In this action the expression ``CAIR'' refers to the final 
rule published in the May 12, 2005 Federal Register and entitled 
``Rule to Reduce Interstate Transport of Fine Particulate Matter and 
Ozone (Clean Air Interstate Rule); Revisions to Acid Rain Program; 
Revisions to NOX SIP Call; Final Rule'' (70 FR 25162).
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    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.\3\ EPA does 
not accept the State of Colorado Interstate Transport SIP assessment 
that these results

[[Page 16035]]

demonstrate that `` the magnitude of ozone transport from Colorado to 
other states is too low to significantly contribute to nonattainment in 
* * * any other state with respect to the 0.08 ppb NAAQS.'' \4\ 
Similarly, EPA does not accept the claim in Colorado's SIP that the 
absence of violations of the 8-hour ozone NAAQS in adjacent downwind 
states such as Kansas, Nebraska and Wyoming suffices to show that 
emissions from Colorado sources do not significantly affect farther 
downwind ozone nonattainment areas such as St. Louis.\5\ The relatively 
limited contribution of local emissions to nonattainment in the DMA/
NFR, the quick drop in ozone levels in the easternmost Colorado 
counties, and even the substantial gap between the 1997 NAAQS and 
design values in adjacent downwind states do not exclude a potential 
significant contribution from Colorado emissions to downwind 
nonattainment areas. However, as a reflection of emission levels, the 
relatively (to the 1997 8-hour ozone NAAQS) moderate ozone 
concentrations in eastern Colorado and in adjacent downwind states 
somewhat reduces the probability of significant ozone contribution from 
Colorado emission sources to considerably farther downwind 
nonattainment areas such as St. Louis, Missouri, and Chicago, Illinois.
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    \3\ See Figure 5, page 15 of the Interstate Transport SIP 
submitted June 18, 2009. It must be noted that the modeling analysis 
domain for the DMA/NFR attainment plan was limited to the State 
territory, and that the 70-mile distance represents the approximate 
distance from Denver to the western border of Morgan County.
    \4\ ``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,'' p. 17, 
December 12, 2009.
    \5\ Ibid., pp. 8-9.
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    In addition, significant contribution should be measured not just 
against nonattainment areas, but also against areas with monitors 
showing violations of the NAAQS. That said, nonattainment areas are a 
convenient starting point for EPA's analysis. For the 1997 8-hour ozone 
NAAQS, the St. Louis area and the Illinois and Wisconsin Counties along 
the southwestern shore of Lake Michigan (Illinois/Wisconsin area) are 
the designated downwind nonattainment areas closest to Colorado.\6\ 
EPA's evaluation of whether emissions from Colorado contribute 
significantly to ozone nonattainment in these areas relies on an 
examination of a variety of data and analysis that provide insight on 
ozone transport from Colorado to these two areas. Because EPA does not 
have detailed modeling for Colorado and nearby downwind states, our 
approach does not rely on a quantitative determination of Colorado's 
contribution, as EPA did for other states in its CAIR rulemaking, but 
on a weight-of-evidence analysis based on qualitative assessments and 
estimates of the relevant factors. While conclusions reached for each 
of the factors considered in the following analysis are not in and by 
themselves determinative, consideration of all of these factors 
provides a reliable qualitative conclusion on whether Colorado's 
emissions are likely to contribute significantly to nonattainment in 
the St. Louis and the Illinois/Wisconsin areas.
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    \6\ The Wisconsin nonattainment areas for the 1997 8-hour ozone 
standard include: Door, Kewaunee, Manitowoc, Sheboygan, Ozaukee, 
Washington, Milwaukee, Waukesha, Racine and Kenosha counties; the 
Chicago nonattainment area includes Cook County and several adjacent 
Illinois and Indiana counties (69 FR 23858, April 30, 2004).
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    The Illinois/Wisconsin nonattainment area is approximately 900 
miles east/northeast from the Colorado DMA/NFR area. Distance per se is 
not an obstacle to long range transport of ozone and/or its precursors, 
as discussed in the January 30, 2004 notice proposing CAIR (69 FR 
4599). NOx, the primary ozone precursor that was the object of the CAIR 
transport study, may be transported for long distances, contributing 
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 900-mile distance from Colorado sources of 
NOX emissions and the Illinois/Wisconsin area reduces, but 
does not exclude, the possibility of significant contribution to this 
area's nonattainment.
    Another transport factor is wind direction. For long range 
transport winds, a modeling analysis of ozone dispersion during the 
summer months (June to August) of the five-year period 1991-1995 shows 
that on high local ozone days the prevailing long range transport winds 
in States immediately to the east and north of Colorado (Kansas, 
Nebraska, South Dakota, Iowa, Minnesota, and North Dakota) had a 
southerly direction. On high regional ozone days, during the same 
period, regional transport winds in the same States were southwesterly, 
but with a westerly component so weak that a greater portion of 
NOX emissions from Colorado would likely remain 
significantly west of the Illinois/Wisconsin nonattainment area.\7\ To 
the extent that these results are representative of general ozone 
transport patterns not limited to the 1991-1995 period, the weak 
western component of long range transport winds during high ozone days 
in the States east and north of Colorado provides evidence that 
NOX emissions from Colorado are unlikely to contribute 
significantly to violations of the 1997 ozone NAAQS in the Illinois/
Wisconsin counties along the southwestern shores of Lake Michigan.
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    \7\ Ozone Transport Assessment Group (OTAG), Air Quality 
Analysis Workgroup: ``3.3 Climatology of Ozone Synoptic Scale 
Transport in the Eastern US,'' Figures 1(a) and 5(a), pp. 3, 6, 
January 11, 1998. High ozone days were days with ozone 
concentrations in the 90th percentile.
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    Additional circumstantial evidence supporting this conclusion is 
found in technical documentation developed in recent years by the 
States of Kansas and Wisconsin. To support its Interstate Transport 
SIP, the State of Kansas submitted to EPA Region 7 technical 
documentation that includes back trajectory analyses gauging the 
pathway of air masses impacting the Illinois/Wisconsin nonattainment 
area on the four days with highest ozone concentrations during each of 
the years 2005-2007. The back trajectory analyses in Appendix G of the 
technical support section show that, for the four days with the highest 
ozone readings, none of the pathways followed by air masses moving into 
the Chicago Metropolitan Statistical Area (MSA) or into several of the 
Wisconsin nonattainment counties came from Colorado. Since these back 
trajectories refer to the pathways of air masses and not specifically 
to ozone transport, the results of this analysis cannot be considered 
determinative as to the significant contribution of ozone or 
NOX from Colorado emissions to the nonattainment counties 
along the southwestern shores of Lake Michigan. However, the lack of 
any back trajectories from Colorado indicates that it is unlikely that 
NOX emissions from the State contribute significantly to the 
nonattainment of the Illinois/Wisconsin area.
    Further support is given by a recent attainment demonstration by 
the Wisconsin Department of Natural Resources (WDNR) for the 
nonattainment counties along the southwestern shores of Lake 
Michigan.\8\ The WDNR analysis identifies heavy industrial activity and 
dense urbanization as the major local contributors to the high ozone 
concentrations in the Indiana, Illinois and Wisconsin Counties along 
the southwestern shores of Lake Michigan. Between 40 and 60 percent of 
the maximum ozone concentrations in the Lake Michigan airshed is 
attributed to

[[Page 16036]]

regional transport, occurring from emission sources located within a 
south-southwesterly arc spanning from 160 to 270 degrees (compass 
direction). Colorado's location at the western margins of this arc 
(Denver is approximately 260 degrees southwest of Chicago) 
substantially reduces the likelihood for NOX emissions from 
the State to contribute significantly to nonattainment in the Illinois/
Wisconsin area.\9\ Given the southerly orientation of regional 
transport winds in States east and north of Colorado, it is likely that 
Colorado ozone or NOX emissions would be heavily dispersed 
in a northward direction west of this nonattainment area.
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    \8\ Wisconsin Department of Natural Resources, ``Attainment 
Demonstration--The Wisconsin Counties of Kenosha, Racine, Milwaukee, 
Waukesha, Ozaukee, Washington, Sheboygan, Manitowoc and Door,'' 
September 2009.
    \9\ Ibid., p. 51.
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    Finally, by 2008, the 8-hour ozone design values for the Illinois 
and Wisconsin nonattainment counties along the shores of Lake Michigan 
fell below the level of the NAAQS, a reduction attributed to the 
implementation of State and Federal control measures since the 
designation of these counties as nonattainment in 2004. In other words, 
were there emissions from Colorado sources reaching the Illinois and 
Wisconsin counties along the western rim of Lake Michigan, they would 
no longer be significantly contributing to violations of the NAAQS in 
that area.\10\
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    \10\ Ibid.
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    The other nonattainment area, St. Louis and adjacent counties, is 
approximately 800 miles straight east from the Colorado DMA/NFR area. 
This substantial distance does not, in and by itself, exclude the 
possibility of significant contribution from Colorado's NOX 
emissions to nonattainment in the St. Louis area. However, it is also 
sufficient to provide many opportunities for ozone dispersion and 
removal from the atmosphere due to the effect of winds and chemical 
sink processes, and thus reduce the likelihood of significant 
contribution from Colorado to nonattainment in this area.
    The impact of wind direction on ozone transport from Colorado to 
the St. Louis area is gauged through the results of several findings. 
Kansas, immediately east of Colorado and west of Missouri, is 
characterized by strong southerly surface winds that match prevailing 
regional transport winds, which have a southerly orientation during 
days of elevated ozone concentration. Throughout 2005 its winds 
averaged daily speeds slightly over 9 mph.\11\ The OTAG modeling 
analysis referred to earlier shows that, during the five years from 
1991 to 1995, on high ozone days regional transport winds in Kansas and 
Missouri have a prevailing southerly orientation. To the extent that 
these results are representative of general ozone transport patterns 
not limited to the 1991-95 period, they indicate that ozone/
NOX emissions from Colorado reaching Kansas or Missouri were 
very likely to be redirected northward and away from the St. Louis 
area, thus lessening the likelihood for a significant ozone 
contribution to nonattainment from Colorado.
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    \11\ See the January 4, 2007 State of Kansas submittal to EPA of 
Interstate Transport SIP revisions, Document ID EPA-R07-
OAR-2007-0141-0003, pp. 6-7.
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    Results from other studies are consistent with these tentative 
conclusions. In a study published by OTAG in 1997, the St. Louis area 
showed higher ozone concentrations (70 as compared with 55 ppb) on days 
with winds from the south or the east than on days with winds from the 
west (the general direction from Colorado) or southwest.\12\ More 
recent back trajectory analyses gauging the pathway of air masses 
impacting St. Louis on days of high ozone allow similar conclusions. 
The State of Kansas' technical documentation supporting its Interstate 
Transport SIP (approved by EPA in March 2007) include back trajectory 
analyses independent of their source regions (i.e., Colorado or 
Kansas.) The results show that for each of the 2005-2007 years, on the 
four days with the highest ozone readings the frequency of trajectory 
``contribution'' from Colorado to St. Louis was negligible. There is 
only one instance of a 500 meter trajectory from Colorado, while there 
were none for transport at 1500 meter of altitude.\13\ These findings, 
in combination with the other circumstantial evidence examined above, 
strengthen the conclusion that it is unlikely that emissions from 
Colorado sources contribute significantly to the nonattainment of the 
St. Louis area.
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    \12\ OTAG, ``Ozone as Function of Local Wind Speed and 
Direction: Evidence of Local and Regional Transport,'' p. 33, July 
26, 1997.
    \13\ Document ID EPA-R07-OAR-2007-0141-0003, Appendix 
G.
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    As mentioned above, EPA must consider not only significant 
contribution to nonattainment areas, but also to areas with monitors 
showing violations of the NAAQS. A review of the AQS monitoring data 
for adjacent downwind states shows that it is highly unlikely that 
emissions from Colorado contribute significantly to downwind areas that 
have monitors showing violations of the 1997 8-hour ozone NAAQS. 
Between 1999 and 2008 there were no violations of the 1997 8-hour ozone 
NAAQS at any of the monitors in adjacent downwind states, such as 
Kansas, Nebraska and Wyoming.
    Design values for the years 2005-2007 \14\ show that in adjacent 
downwind states such as Kansas, Nebraska, and Wyoming, there were no 
violations of the 1997 8-hour ozone NAAQS, and that in most counties 
ozone levels remained substantially below the NAAQS. In Kansas, the 
2007 design value for Trego County, the county with a monitoring 
station closest to Colorado, was 71 ppb, or 16 percent below the ozone 
NAAQS. The counties that had the highest design values are at or near 
the eastern edge of the state, about 400 miles from Colorado's eastern 
border, and their design values ranged from 76 ppb for Johnson and 
Sumner Counties to 77 ppb for Leavenworth and Wyandotte Counties. In 
Nebraska and Wyoming, the highest ozone design values did not exceed 69 
ppb in Douglas County, Nebraska and 72 ppb in Sublette County, Wyoming.
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    \14\ See Table 4, pages 7 and 8, of the Colorado Interstate 
Transport SIP.
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    The historical trend over the period 1998-2008 for the 1997 8-hour 
ozone design values in these states places the 2005-2007 data reviewed 
above in context. In Nebraska, ozone design values were consistently 
low throughout the period. In Wyoming, design values were also constant 
in most of the monitored areas, where ozone monitoring only began 
between 2003 and 2005. Kansas design values show a clear trend of 
declining ozone levels from the late 1990s to the most recent years. In 
Linn, Sedgwick, and Sumner Counties, design values decreased from highs 
ranging between 77 and 82 ppb during 2000-2003 to levels ranging 
between 66 and 75 ppb in 2006-2008.
    The data and weight of evidence analysis presented above support 
the conclusion 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 contribute significantly to 
nonattainment in any other state for the 1997 8-hour ozone NAAQS, 
consistently with the requirements of element (1) 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 ozone 
standard. Specifically, in this action EPA is proposing to approve only 
the language and demonstration that, in this SIP revision, address the 
requirements of element (1): Prohibition of significant

[[Page 16037]]

contribution to nonattainment of the 1997 8-hour ozone NAAQS in any 
other state. At a later date, EPA will act on the language and 
demonstration addressing element (2): prohibition of interference with 
maintenance 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: March 18, 2010.
Carol L. Campbell,
Acting Deputy Regional Administrator, Region 8.
[FR Doc. 2010-6893 Filed 3-30-10; 8:45 am]
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