Document ID: EPA-R08-OAR-2012-0346-0001
Agency: epa
Document Type: Proposed Rule
Title: Air Quality State Implementation Plans; Approvals and Promulgations: Colorado; Interstate Transport of Pollution for the 2006 24-Hour PM2.5 NAAQS
Posted Date: 2015-05-12T04:00Z

[Federal Register Volume 80, Number 91 (Tuesday, May 12, 2015)]
[Proposed Rules]
[Pages 27121-27127]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-11338]

=======================================================================
-----------------------------------------------------------------------

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2012-0346; FRL-9927-55-Region 8]

Approval and Promulgation of State Implementation Plans; State of 
Colorado; Interstate Transport of Pollution for the 2006 24-Hour 
PM[bdi2].[bdi5] NAAQS

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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

SUMMARY: Environmental Protection Agency (EPA) is proposing to approve 
a May 11, 2012 State Implementation Plan (SIP) submission from the 
State of Colorado that is intended to demonstrate that its SIP meets 
certain interstate transport requirements of the Clean Air Act (Act or 
CAA) for the 2006 fine particulate matter (PM2.5) National 
Ambient Air Quality Standards (NAAQS). This submission addresses the 
requirement that Colorado's SIP contain adequate provisions prohibiting 
air emissions that will have certain adverse air quality effects in 
other states. EPA is proposing to determine that Colorado's existing 
SIP contains adequate provisions to ensure that air emissions in 
Colorado do not significantly contribute to nonattainment or interfere 
with maintenance of the 2006 24-hour PM2.5 NAAQS in any 
other state, or interfere with another state's measures to prevent 
significant deterioration (PSD) of air quality or to protect 
visibility. EPA is also proposing to approve the portion of Colorado's 
submission that addresses the CAA requirement that SIPs contain 
adequate provisions related to interstate and international pollution 
abatement.

DATES: Comments must be received on or before June 11, 2015.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R08-
OAR-2012-0346, by one of the following methods:
     http://www.regulations.gov. Follow the on-line 
instructions for submitting comments.
     Email: clark.adam@epa.gov.
     Fax: (303) 312-6064 (please alert the individual listed in 
the FOR FURTHER INFORMATION CONTACT if you are faxing comments).
     Mail: Director, Air Program, Environmental Protection 
Agency (EPA), Region 8, Mail Code 8P-AR, 1595 Wynkoop Street, Denver, 
Colorado 80202-1129.
     Hand Delivery: Director, Air Program, Environmental 
Protection Agency (EPA), Region 8, Mail Code 8P-AR, 1595 Wynkoop 
Street, Denver, Colorado 80202-1129. Such deliveries are only accepted 
Monday through Friday, 8:00 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-
2012-0346. EPA's policy is that all comments received will be included 
in the public docket without change and may be made available online at 
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 www.regulations.gov or email. The 
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 email comment 
directly to EPA, without going through www.regulations.gov, your email 
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 
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 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

[[Page 27122]]

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, 8:00 a.m. to 4:00 p.m., excluding 
federal holidays.

FOR FURTHER INFORMATION CONTACT: Adam Clark, Air Program, U.S. 
Environmental Protection Agency, Region 8, Mailcode 8P-AR, 1595 
Wynkoop, Denver, Colorado 80202-1129, (303) 312-7104, 
clark.adam@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 initials CAIR mean or refer to the Clean Air Interstate 
Rule.
    (iii) The initials CSAPR mean or refer to the Cross-State Air 
Pollution Rule or ``Transport Rule.''
    (iv) The initials CDPHE mean or refer to the Colorado Department 
of Public Health and Environment.
    (v) The words State and Colorado mean the State of Colorado, 
unless the context indicates otherwise.
    (vi) The words EPA, we, us or our mean or refer to the United 
States Environmental Protection Agency.
    (vii) The initials NAAQS mean or refer to the National Ambient 
Air Quality Standards.
    (viii) The initials NNSR mean or refer to nonattainment New 
Source Review.
    (ix) The initials PM2.5 mean or refer to fine 
particulate matter.
    (x) The initials PSD mean or refer to Prevention of Significant 
Deterioration.
    (xi) The initials RAVI mean or refer to Reasonably Attributable 
Visibility Impairment.
    (xii) The initials SIP mean or refer to State Implementation 
Plan.
    (xiii) The initials TSD mean or refer to Technical Support 
Document.
    (xiv) The initials WRAP mean or refer to Western Regional Air 
Partnership.
    (xv) The initials [mu]g/m\3\ mean or refer to micrograms per 
cubic meter.

Table of Contents

I. General Information
II. Background
    A. 2006 PM2.5 NAAQS and Interstate Transport
    B. Rules Addressing Interstate Transport for the 2006 
PM2.5 NAAQS
    C. EPA Guidance
III. Colorado's Submittal
IV. EPA's Evaluation
    A. Identification of Nonattainment and Maintenance Receptors
    B. Evaluation of Significant Contribution to Nonattainment
    C. Evaluation of Interference With Maintenance
    D. Evaluation of Interference With Measures to Prevent 
Significant Deterioration
    E. Evaluation of Interference With Measures to Protect 
Visibility
    F. Evaluation of CAA section 110(a)(2)(D)(ii) Requirements
V. Proposed Action
VI. Statutory and Executive Orders Review

I. General Information

What should I consider as I prepare my comments for EPA?

    1. Submitting Confidential Business Information (CBI). Do not 
submit CBI to EPA through www.regulations.gov or email. 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

A. 2006 PM2.5 NAAQS and Interstate Transport

    On September 21, 2006, EPA promulgated a final rule revising the 
1997 24-hour primary and secondary NAAQS for PM2.5 from 65 
micrograms per cubic meter ([mu]g/m\3\) to 35 [mu]g/m\3\ (October 17, 
2006, 71 FR 61144).
    Section 110(a)(1) of the CAA requires each state to submit to EPA, 
within three years (or such shorter period as the Administrator may 
prescribe) after the promulgation of a primary or secondary NAAQS or 
any revision thereof, a SIP that provides for the ``implementation, 
maintenance, and enforcement'' of such NAAQS. EPA refers to these 
specific submittals as ``infrastructure'' SIPs because they are 
intended to address basic structural SIP requirements for new or 
revised NAAQS. For the 2006 24-hour PM2.5 NAAQS, these 
infrastructure SIPs were due on September 21, 2009. CAA section 
110(a)(2) includes a list of specific elements that ``[e]ach such plan 
submission'' must meet.
    The interstate transport provisions in CAA section 110(a)(2)(D)(i) 
(also called ``good neighbor'' provisions) require each state to submit 
a SIP that prohibits emissions that will have certain adverse air 
quality effects in other states. CAA section 110(a)(2)(D)(i) identifies 
four distinct elements related to the impacts of air pollutants 
transported across state lines. The two elements under 
110(a)(2)(D)(i)(I) require SIPs to contain adequate provisions to 
prohibit any source or other type of emissions activity within the 
state from emitting air pollutants that will (element 1) contribute 
significantly to nonattainment in any other state with respect to any 
such national primary or secondary NAAQS, and (element 2) interfere 
with maintenance by any other state with respect to the same NAAQS. The 
two elements under 110(a)(2)(D)(i)(II) require SIPs to contain adequate 
provisions to prohibit emissions that will interfere with measures 
required to be included in the applicable implementation plan for any 
other state under part C (element 3) to prevent significant 
deterioration of air quality or (element 4) to protect visibility. In 
this action, EPA is addressing all four elements of CAA section 
110(a)(2)(D)(i).
    CAA section 110(a)(2)(D)(ii) requires that each SIP shall contain 
adequate provisions insuring compliance with applicable requirements of 
sections 126 and 115 (relating to interstate and international 
pollution abatement). EPA

[[Page 27123]]

is also addressing this requirement with regard to Colorado's SIP in 
this action.

B. Rules Addressing Interstate Transport for the 2006 PM2.5 NAAQS

    EPA has previously addressed the requirements of CAA section 
110(a)(2)(D)(i)(I) in past regulatory actions.\1\ Most recently, EPA 
published the final Cross State Air Pollution Rule (CSAPR or 
``Transport Rule'') to address CAA section 110(a)(2)(D)(i)(I) in the 
eastern portion of the United States with respect to the 2006 
PM2.5 NAAQS, the 1997 PM2.5 NAAQS, and the 1997 
8-hour ozone NAAQS (August 8, 2011, 76 FR 48208). CSAPR replaces the 
earlier Clean Air Interstate Rule (CAIR) which was judicially 
remanded.\2\ See North Carolina v. EPA, 531 F.3d 896 (D.C. Cir. 2008). 
On August 21, 2012, the U.S. Court of Appeals for the DC Circuit issued 
a decision vacating CSAPR, see EME Homer City Generation, L.P. v. 
E.P.A., 696 F.3d 7 (D.C. Cir. 2012), and ordering EPA to continue 
implementing CAIR in the interim. However, on April 29, 2014, the U.S. 
Supreme Court reversed and remanded the DC Circuit's ruling and upheld 
EPA's approach in CSAPR. EPA v. EME Homer City Generation, L.P., 134 S. 
Ct. 1584, 1610 (2014). After the U.S. Supreme Court decision, EPA filed 
a motion to lift the stay on CSAPR and asked the DC Circuit to toll 
CSAPR's compliance deadlines by three years. On October 23, 2014 the DC 
Circuit granted EPA's motion and lifted the stay on CSAPR. EME Homer 
City Generation, L.P. v. EPA, No. 11-1302 (D.C. Cir. Oct. 23, 2014), 
Order at 3. CSAPR began implementation on January 1, 2015 pursuant to 
the DC Circuit's directive lifting the stay. The State of Colorado was 
not covered by CSAPR, and EPA made no determinations in the rule 
regarding whether emissions from sources in Colorado significantly 
contribute to nonattainment or interfere with maintenance of the 2006 
24-hour PM2.5 NAAQS in another state.
---------------------------------------------------------------------------

    \1\ See NOX SIP Call, 63 FR 57371 (October 27, 1998); 
Clean Air Interstate Rule (CAIR), 70 FR 25172 (May 12, 2005); and 
Transport Rule or Cross-State Air Pollution Rule, 76 FR 48208 
(August 8, 2011).
    \2\ CAIR addressed the 1997 annual and 24-hour PM2.5 
NAAQS, and the 1997 8-hour ozone NAAQS. It did not address the 2006 
24-hour PM2.5 NAAQS.
---------------------------------------------------------------------------

C. EPA Guidance

    On September 25, 2009, EPA issued a guidance memorandum that 
provides recommendations to states for making submissions to meet the 
requirements of CAA section 110(a)(2)(D)(i) for the 2006 
PM2.5 standards (``2006 PM2.5 NAAQS 
Infrastructure Guidance'' or ``Guidance'').\3\ With respect to element 
1 of CAA section 110(a)(2)(D)(i) to prohibit emissions that will 
contribute significantly to nonattainment of the NAAQS in any other 
state, the 2006 PM2.5 NAAQS Infrastructure Guidance advised 
states to include in their section 110(a)(2)(D)(i)(I) SIP submissions 
an adequate technical analysis to support their conclusions regarding 
interstate pollution transport, e.g., information concerning emissions 
in the state, meteorological conditions in the state and in potentially 
impacted states, monitored ambient pollutant concentrations in the 
state and in potentially impacted states, distances to the nearest 
areas not attaining the NAAQS in other states, and air quality 
modeling.\4\
---------------------------------------------------------------------------

    \3\ See Memorandum from William T. Harnett entitled ``Guidance 
on SIP Elements Required Under Sections 110(a)(1) and (2) for the 
2006 24-Hour Fine Particle (PM2.5) National Ambient Air 
Quality Standards (NAAQS),'' September 25, 2009, available at http://www.epa.gov/ttn/caaa/t1/memoranda/20090925_harnett_pm25_sip_110a12.pdf.
    \4\ The 2006 PM2.5 NAAQS Infrastructure Guidance 
stated that EPA was working on a new rule to replace CAIR that would 
address issues raised by the court in the North Carolina case and 
that would provide guidance to states in addressing the requirements 
related to interstate transport in CAA section 110(a)(2)(D)(i)(I) 
for the 2006 24-hour PM2.5 NAAQS. It also noted that 
states could not rely on the CAIR rule for section 
110(a)(2)(D)(i)(I) submissions for the 2006 24-hour PM2.5 
NAAQS because the CAIR rule did not address this NAAQS. See 2006 
PM2.5 NAAQS Infrastructure Guidance at 3.
---------------------------------------------------------------------------

    With respect to element 2 of CAA section 110(a)(2)(D)(i) to 
prohibit emissions that would interfere with maintenance of the NAAQS 
by any other state, the Guidance stated that SIP submissions must 
address this independent and distinct requirement of the statute and 
provide technical information appropriate to support the State's 
conclusions, and suggested consideration of the same technical 
information that would be appropriate for element 1 of this CAA 
requirement.
    In this action, EPA is proposing to use the conceptual approach to 
evaluating interstate pollution transport under CAA section 
110(a)(2)(D)(i)(I) that EPA explained in the 2006 PM2.5 
NAAQS Infrastructure Guidance and CSAPR. As such, we find that the CAA 
section 110(a)(2)(D)(i)(I) SIP submission from Colorado may be 
evaluated using a ``weight of evidence'' approach that takes into 
account available relevant information, including the factors 
recommended in the 2006 PM2.5 NAAQS Infrastructure Guidance. 
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.
    With respect to the requirements in section 110(a)(2)(D)(i)(II) 
which address elements 3 (PSD) and 4 (visibility), EPA most recently 
issued an infrastructure guidance memo on September 13, 2013 that 
included guidance on these two elements.\5\ For the purposes of this 
action, this memo will hereon be referred to as the ``2013 I-SIP 
Guidance.''
---------------------------------------------------------------------------

    \5\ See ``Guidance on Infrastructure State Implementation Plan 
(SIP) Elements under Clean Air Act Sections 110(a)(1) and (2)'' 
dated September 13, 2013, in the docket for this action.
---------------------------------------------------------------------------

III. Colorado's Submittal

    On May 11, 2012, the Colorado Department of Public Health and 
Environment (CDPHE) submitted an interstate transport SIP which 
concluded that Colorado meets all of the requirements of CAA section 
110(a)(2)(D)(i) for the 2006 24-hour PM2.5 NAAQS.\6\ In this 
submission, Colorado provided a thorough technical analysis for 
elements 1 and 2 of CAA section 110(a)(2)(D)(i) which concluded that 
the State did not contribute significantly to nonattainment or 
interfere with maintenance of the 2006 24-hour PM2.5 NAAQS 
in other states. The State based this conclusion on consideration of 
factors including distance, monitored attainment of the 2006 24-hour 
PM2.5 NAAQS in Colorado and downwind states, and modeling 
conducted by EPA.
---------------------------------------------------------------------------

    \6\ Colorado's SIP, dated May 11, 2012, is included in the 
docket for this action.
---------------------------------------------------------------------------

    To meet the element 3 (PSD) requirement of CAA section 
110(a)(2)(D)(i), the State referenced its existing PSD and 
nonattainment New Source Review (NNSR) permitting programs. To meet the 
element 4 (visibility) requirement of 110(a)(2)(D)(i), the State 
referenced and discussed its Reasonably Attributable Visibility 
Impairment (RAVI) program, Regional Haze SIP, and some emission 
reduction programs currently in the Colorado SIP that reduce visibility 
impairing pollutants.
    The State's May 11, 2012 interstate transport submission and June 
4, 2010 infrastructure SIP certification for the 2006 24-hour 
PM2.5 NAAQS both overlooked the requirements of CAA section 
110(a)(2)(D)(ii), which requires that each SIP shall contain adequate 
provisions insuring compliance with applicable requirements of sections 
126 and 115 (relating to interstate and international pollution 
abatement). The State submitted a clarification letter on March 12, 
2015, which explained that

[[Page 27124]]

the State had inadvertently left discussion of 110(a)(2)(D)(ii) out of 
the 2006 24-hour PM2.5 infrastructure certification.\7\ The 
State noted that in its four subsequent infrastructure submittals (for 
the 2008 Pb, 2008 Ozone, 2010 NO2 and 2010 SO2 
NAAQS), it had included the necessary demonstration that Colorado's SIP 
meets the requirements of 110(a)(2)(D)(ii). The State requested that 
the same demonstration used in all subsequent infrastructure submittals 
be applied to the 2006 24-hour PM2.5 certification submitted 
June 4, 2010.\8\
---------------------------------------------------------------------------

    \7\ Colorado's certification letter is available in the docket 
for this action.
    \8\ Colorado's 2006 PM2.5, 2008 Pb, 2008 Ozone, 2010 
NO2 and 2010 SO2 infrastructure certifications 
are available in the docket for this action.
---------------------------------------------------------------------------

IV. EPA's Evaluation

    To determine whether the CAA section 110(a)(2)(D)(i)(I) requirement 
is satisfied, EPA first determines whether a state's emissions 
contribute significantly to nonattainment or interfere with maintenance 
in other states. If a state is determined not to have such contribution 
or interference, then section 110(a)(2)(D)(i)(I) does not require any 
changes to that state's SIP.
    Consistent with the first step of EPA's approach in the 1998 
NOX SIP call, the 2005 CAIR, and the 2011 CSAPR, EPA 
evaluated impacts of emissions from Colorado with respect to specific 
monitors identified as having nonattainment and/or maintenance 
problems, which we refer to as ``receptors.'' To evaluate these 
impacts, and in the absence of relevant modeling of Colorado emissions, 
EPA examined factors suggested by the 2006 Guidance such as monitoring 
data, topography, and meteorology. EPA notes that no single piece of 
information is by itself dispositive of the issue. Instead, the total 
weight of all the evidence taken together is used to evaluate 
significant contributions to nonattainment or interference with 
maintenance of the 2006 24-hour PM2.5 NAAQS in another 
state.
    Our proposed approval takes into account the information provided 
in Colorado's 2012 Interstate Transport SIP. In addition, we are 
supplementing the evaluation of the State's submittal with a review of 
the monitors in other states that are appropriate ``nonattainment 
receptors'' or ``maintenance receptors,'' consistent with EPA's 
approach in the CSAPR, and additional relevant technical information to 
determine whether sources in Colorado contribute significantly to 
nonattainment or interfere with maintenance of the 2006 24-hour 
PM2.5 NAAQS in other states.
    Our Technical Support Document (TSD) contains a detailed evaluation 
and is available in the public docket for this rulemaking, which may be 
accessed online at www.regulations.gov, docket number EPA-R08-OAR-2012-
0346. Below, we provide a summary of our analysis.

A. Identification of Nonattainment and Maintenance Receptors

    EPA evaluated data from existing monitors over three overlapping 3-
year periods (i.e., 2009-2011, 2010-2012, and 2011-2013) to determine 
which areas are expected to be violating the 2006 24-hour 
PM2.5 NAAQS and which areas might have difficulty 
maintaining attainment of the standard. If a monitoring site measured a 
violation of the 2006 24-hour PM2.5 NAAQS during the most 
recent 3-year period (2011-2013), then that monitor location was 
evaluated for purposes of the significant contribution to nonattainment 
(element 1) of section 110(a)(2)(D)(i). If, on the other hand, a 
monitoring site shows attainment of the 2006 24-hour PM2.5 
NAAQS during the most recent 3-year period (2011-2013) but a violation 
in at least one of the previous two 3-year periods (2010-2012 or 2009-
2011), then that monitor location was evaluated for purposes of the 
interfere with maintenance (element 2) of section 110(a)(2)(D)(i).
    This approach is similar to that used in the modeling done during 
the development of CSAPR, but differs in that it relies on monitoring 
data (rather than modeling) for the western states not included in the 
CSAPR modeling domain.\9\ By this method, EPA has identified those 
areas with monitors to be considered ``nonattainment receptors'' or 
``maintenance receptors'' for evaluating whether the emissions from 
sources in another state could significantly contribute to 
nonattainment in, or interfere with maintenance in, that particular 
area.
---------------------------------------------------------------------------

    \9\ As noted, the State of Colorado was not included in the 
CSAPR modeling domain.
---------------------------------------------------------------------------

    EPA continues to believe that the more widespread and serious 
transport problems in the eastern United States are analytically 
distinct. For the 2006 24-hour PM2.5 NAAQS, EPA believes 
that nonattainment and maintenance problems in the western United 
States are relatively local in nature with only limited impacts from 
interstate transport. In CSAPR, EPA did not calculate the portion of 
any downwind state's predicted PM2.5 concentrations that 
would result from emissions from individual western states, such as 
Colorado. Accordingly, EPA believes that section 110(a)(2)(D)(i)(I) SIP 
submissions for states outside the geographic area analyzed to develop 
CSAPR 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 Guidance. 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 as to whether sources in the state may contribute 
significantly to nonattainment or interfere with maintenance of the 
2006 24-hour PM2.5 NAAQS in other states. These submissions 
can rely on modeling when acceptable modeling technical analyses are 
available, but EPA does not believe that modeling is necessarily 
required if other available information is sufficient to evaluate the 
presence or degree of interstate transport in a given situation.

B. Evaluation of Significant Contribution to Nonattainment

    EPA reviewed technical information to evaluate the potential for 
Colorado emissions to contribute significantly to nonattainment of the 
2006 PM2.5 NAAQS at specified monitoring sites in the 
Western U.S.\10\ EPA first identified as ``nonattainment receptors'' 
all monitoring sites in the western states that had recorded 
PM2.5 design values above the level of the 2006 24-hour 
PM2.5 NAAQS (35 [mu]g/m3) during the years 2011-
2013.\11\ See Section III of our

[[Page 27125]]

TSD for more a more detailed description of EPA's methodology for 
selection of nonattainment receptors.
---------------------------------------------------------------------------

    \10\ EPA also considered potential PM2.5 transport 
from Colorado to the nearest nonattainment and maintenance receptors 
located in the eastern, midwestern and southern states covered by 
CSAPR and believes it is reasonable to conclude that, given the 
significant distance from Colorado to the nearest such receptor (in 
East St. Louis, IL) and the relatively insignificant amount of 
emissions from Colorado that could potentially be transported such a 
distance when compared to downwind states whose contribution was 
modeled for CSAPR, emissions from Colorado sources do not 
significantly contribute to nonattainment or interfere with 
maintenance of the 2006 24-hour PM2.5 NAAQS at this 
location. These same factors also support a finding that emissions 
from Colorado sources neither contribute significantly to 
nonattainment nor interfere with maintenance of the 2006 24-hour 
PM2.5 NAAQS at any location further east. See TSD at 
Section I.B.3.
    \11\ Because CAIR did not cover states in the Western United 
States, these data are not significantly impacted by the remanded 
CAIR and thus could be considered in this analysis. In contrast, 
recent air quality data in the eastern, midwestern and southern 
states are significantly impacted by reductions associated with CAIR 
and because CSAPR was developed to replace CAIR, EPA could not 
consider reductions associated with the CAIR in the base case 
transport analysis for those states. See 76 FR at 48223-24.
---------------------------------------------------------------------------

    Because geographic distance is a relevant factor in the assessment 
of potential pollution transport, EPA first reviewed information 
related to potential transport of PM2.5 pollution from 
Colorado to the nonattainment receptors in Utah, the only state 
bordering Colorado which contains such receptors. As detailed in our 
TSD, the following factors support a finding that emissions from 
Colorado do not significantly contribute to nonattainment of the 2006 
24-hour PM2.5 NAAQS in Utah: (1) Technical information, such 
as data from monitors in the vicinity of these nonattainment receptors, 
related to the nature of local emissions; (2) topographical 
considerations such as intervening mountain ranges which tend to create 
physical impediments for pollution transport; and (3) meteorological 
considerations such as prevailing winds. While none of these factors by 
itself would necessarily show non-contribution, when taken together in 
a weight-of-evidence assessment they are sufficient for EPA to 
determine that emissions from Colorado do not significantly contribute 
to nonattainment at the Utah receptors.
    EPA also evaluated potential PM2.5 transport to 
nonattainment receptors in the more distant western states of Idaho, 
Montana, California and Oregon. The following factors support a finding 
that emissions from Colorado do not significantly contribute to 
nonattainment of the 2006 24-hour PM2.5 NAAQS in any of 
these states: (1) The significant distance from Colorado to the 
nonattainment receptors in these states; (2) technical information, 
such as data from nearby monitors, related to the nature of local 
emissions; and (3) the presence of intervening mountain ranges, which 
tend to impede pollution transport.
    Based on our evaluation, we propose to conclude that emissions of 
direct PM2.5 and PM2.5 precursors from sources in 
the State of Colorado do not significantly contribute to nonattainment 
of the 2006 24-hour PM2.5 standards in any other state, that 
the existing SIP for the State of Colorado is adequate to satisfy the 
``significant contribution'' requirements of CAA section 
110(a)(2)(D)(i)(I) with respect to the 2006 24-hour PM2.5 
standards, and that the State of Colorado therefore does not need to 
adopt additional controls for purposes of implementing the 
``significant contribution to nonattainment'' requirement of 
110(a)(2)(D)(i)(I) with respect to that NAAQS at this time.

C. Evaluation of Interference With Maintenance

    We also reviewed technical information to evaluate the potential 
for Colorado emissions to interfere with maintenance of the 2006 24-
hour PM2.5 standards at specified monitoring sites in the 
Western U.S. EPA first identified as ``maintenance receptors'' all 
monitoring sites in the western states that had recorded 
PM2.5 design values above the level of the 2006 24-hour 
PM2.5 NAAQS (35 [mu]g/m\3\) during the 2009-2011 and/or 
2010-2012 periods but below this standard during the 2011-2013 period. 
See section III of our TSD for more information regarding EPA's 
methodology for selection of maintenance receptors. All of the 
maintenance receptors in the western states are located in California, 
Utah and Montana. EPA therefore evaluated the potential for transport 
of Colorado emissions to the maintenance receptors located in these 
states. As detailed in our TSD, the following factors support a finding 
that emissions from Colorado do not interfere with maintenance of the 
2006 24-hour PM2.5 NAAQS in those states: (1) Technical 
information, such as data from monitors near maintenance receptors, 
related to the nature of local emissions, and (2) the significant 
distance between Colorado and these maintenance receptors.
    Based on this evaluation, EPA proposes to conclude that emissions 
of direct PM2.5 and PM2.5 precursors from sources 
in the State of Colorado do not interfere with maintenance of the 2006 
24-hour PM2.5 standards in any other state, that the 
existing SIP for the State of Colorado is adequate to satisfy the 
``interfere with maintenance'' requirements of CAA section 
110(a)(2)(D)(i)(I), and that the State of Colorado therefore does not 
need to adopt additional controls for purposes of implementing the 
``interfere with maintenance'' requirements of section 
110(a)(2)(D)(i)(I) with respect to that NAAQS at this time.

D. Evaluation of Interference With Measures To Prevent Significant 
Deterioration

    With regard to the PSD portion of section 110(a)(2)(D)(i)(II), this 
requirement may be met by a state's confirmation in an infrastructure 
SIP submission that new major sources and major modifications in the 
state are subject to a comprehensive EPA-approved PSD permitting 
program in the SIP that applies to all regulated NSR pollutants and 
that satisfies the requirements of EPA's PSD implementation 
rule(s).\12\ On September 23, 2013, EPA approved CAA section 110(a)(2) 
elements (C) and (J) for Colorado's infrastructure SIP for the 2006 24-
hour PM2.5 NAAQS with respect to PSD requirements for all 
regulated pollutants (78 FR 58186). As discussed in detail in the 
proposed rulemaking for that final action, the concurrent approval of 
PSD-related revisions which incorporated the requirements of the 2008 
PM2.5 NSR Implementation Rule and certain requirements of 
the 2010 PM2.5 Increment Rule to the Colorado SIP action 
ensured that Colorado's SIP-approved PSD program meets current 
structural requirements for all regulated NSR pollutants.\13\
---------------------------------------------------------------------------

    \12\ See 2013 I-SIP Guidance.
    \13\ The proposed rulemaking was published May 23, 2013 (78 FR 
30830). As described in that proposed rulemaking, EPA did not 
approve certain portions of the State's incorporation of the 2010 
PM2.5 Increment Rule because these portions were 
ultimately removed from EPA's PSD regulations.
---------------------------------------------------------------------------

    As stated in the 2013 I-SIP Guidance, in-state sources not subject 
to PSD for any one or more of the pollutants subject to regulation 
under the CAA because they are in a nonattainment area for a NAAQS 
related to those particular pollutants may also have the potential to 
interfere with PSD in an attainment or unclassifiable area of another 
state. One way a state may satisfy element 3 with respect to these 
sources is by citing an air agency's EPA-approved nonattainment NSR 
provisions addressing any pollutants for which the state has designated 
nonattainment areas. Colorado has a SIP-approved nonattainment NSR 
program which ensures regulation of major sources and major 
modifications in nonattainment areas.\14\ As Colorado's SIP meets 
structural PSD requirements for all regulated NSR pollutants, and 
contains a fully approved nonattainment NSR program, EPA is proposing 
to approve the infrastructure SIP submission as meeting the applicable 
requirements of element 3 of section 110(a)(2)(D)(i) for the 2006 24-
hour PM2.5 NAAQS.
---------------------------------------------------------------------------

    \14\ See Colorado Regulation No. 3, Part D, Section V, which was 
most recently approved by EPA in a final rulemaking dated February 
13, 2014 (79 FR 8632).
---------------------------------------------------------------------------

E. Evaluation of Interference With Measures To Protect Visibility

    To determine whether the CAA section 110(a)(2)(D)(i)(II) 
requirement for visibility protection is satisfied, the SIP must 
address the potential for

[[Page 27126]]

interference with visibility protection caused by the pollutant 
(including precursors) to which the new or revised NAAQS applies. 
PM2.5 is among the pollutants which could interfere with 
visibility protection.\15\ An approved regional haze SIP that fully 
meets the regional haze requirements in 40 CFR 51.308 satisfies the 
110(a)(2)(D)(i)(II) requirement for visibility protection as it ensures 
that emissions from the state will not interfere with measures required 
to be included in other state SIPs to protect visibility. In the 
absence of a fully approved regional haze SIP, a state can still make a 
demonstration that satisfies the visibility requirement section of 
110(a)(2)(D)(i)(II).\16\
---------------------------------------------------------------------------

    \15\ Section II.A.3 of Appendix Y to Part 51--Guidelines for 
BART Determinations Under the Regional Haze Rule and 40 CFR 
51.166(b)(i)(b).
    \16\ See 2013 I-SIP Guidance. EPA also approved the visibility 
requirement of 110(a)(2)(D)(i)(II) in a final rulemaking published 
April 20, 2011 (76 FR 22036) by a demonstration provided by the 
State that did not rely on the Colorado Regional Haze SIP.
---------------------------------------------------------------------------

    Colorado submitted a regional haze SIP to EPA on May 25, 2011. EPA 
approved Colorado's regional haze SIP on December 31, 2012 (77 FR 
76871). In early 2013, WildEarth Guardians and the National Parks 
Conservation Association (NPCA) filed separate petitions for 
reconsideration of certain aspects of EPA's approval of the Colorado's 
regional haze SIP.\17\ After these petitions were filed, a settlement 
agreement was entered into concerning the Craig Generating Station by 
the petitioners, EPA, CDPHE, and Tri-State Generation and Transmission 
Association, Inc., and filed with the court on July 10, 2014.\18\ In 
accordance with the settlement agreement, EPA requested and the court 
granted a voluntary remand to EPA of the portions of EPA's December 
2012 regional haze SIP approval that related to Craig Unit 1. Because 
of this remand, and because the additional controls at the Craig 
facility will be implemented through a revision to the Colorado 
regional haze SIP that EPA has not yet acted on, EPA cannot rely on 
this approval as automatically satisfying element 4.
---------------------------------------------------------------------------

    \17\ WildEarth Guardians filed its petition on February 25, 
2013, and NPCA filed its petition on March 1, 2013.
    \18\ This settlement agreement is included in the docket for 
this action; see also Proposed Settlement Agreement, 79 FR 47636 
(Aug. 14, 2014).
---------------------------------------------------------------------------

    EPA does, however, consider aspects of our approval of Colorado's 
regional haze SIP to be sufficient to satisfy this requirement. 
Specifically, EPA found that Colorado met its 40 CFR 51.308(d)(3)(ii) 
requirements to include in its regional haze SIP all measures necessary 
to: (1) Obtain its share of the emission reductions needed to meet the 
reasonable progress goals for any other state's Class I area to which 
Colorado causes or contributes to visibility impairment; and (2) ensure 
it has included all measures needed to achieve its apportionment of 
emission reduction obligations agreed upon through a regional planning 
process. Colorado participated in a regional planning process with 
Western Regional Air Partnership (WRAP). In the regional planning 
process, Colorado analyzed the WRAP modeling and determined that 
emissions from the State do not significantly impact other states' 
class I areas.\19\ Colorado accepted and incorporated the WRAP-
developed visibility modeling into its regional haze SIP, and the SIP 
included the controls assumed in the modeling. For these reasons, EPA 
determined that Colorado had satisfied the Regional Haze Rule 
requirements for consultation and had included controls in the SIP 
sufficient to address the relevant requirements related to impacts on 
Class I areas in other states. Therefore, we are proposing to approve 
the Colorado SIP as meeting the requirements of element 4 of CAA 
section 110(a)(2)(D)(i)(II) for the 2006 24-hour PM2.5 
NAAQS.
---------------------------------------------------------------------------

    \19\ See our proposed rulemaking on the Colorado regional haze 
SIP, 77 FR 18052, March 26, 2012.
---------------------------------------------------------------------------

F. Evaluation of CAA Section 110(a)(2)(D)(ii) Requirements

    As stated above, Colorado's May 11, 2012 interstate transport 
submission and June 4, 2010 infrastructure SIP certification for the 
2006 24-hour PM2.5 NAAQS both overlooked the requirements of 
CAA section 110(a)(2)(D)(ii). The State submitted a clarification 
letter on March 12, 2015, which explained that the State had 
inadvertently left discussion of 110(a)(2)(D)(ii) out of the 2006 24-
hour PM2.5 infrastructure certification, and referenced the 
four subsequent infrastructure submittals (for the 2008 Pb, 2008 Ozone, 
2010 NO2 and 2010 SO2 NAAQS) that included a 
demonstration that Colorado's SIP meets the requirements of 
110(a)(2)(D)(ii). The State requested that the same demonstration used 
in all subsequent infrastructure submittals be applied to the 2006 24-
hour PM2.5 certification submitted June 4, 2010.
    CAA section 110(a)(2)(D)(ii) requires that each SIP contain 
adequate provisions ensuring compliance with applicable requirements of 
CAA sections 126 and 115. Section 126(a) requires notification to 
affected, nearby states of major proposed new (or modified) sources. 
Sections 126(b) and (c) pertain to petitions by affected states to the 
Administrator regarding sources violating the ``interstate transport'' 
provisions of section 110(a)(2)(D)(i). Section 115 pertains to 
international transport of air pollution.
    As required by 40 CFR 51.166(q)(2)(iv), Colorado's SIP-approved PSD 
program requires notice to states whose lands may be affected by the 
emissions of sources subject to PSD.\20\ This suffices to meet the 
notice requirement of section 126(a).
---------------------------------------------------------------------------

    \20\ See Colorado Regulation 3, Part D. IV.A.1.
---------------------------------------------------------------------------

    Colorado has no pending obligations under sections 126(c) or 
115(b); therefore, its SIP currently meets the requirements of those 
sections. In summary, the SIP meets the requirements of CAA section 
110(a)(2)(D)(ii) for the 2006 PM2.5 NAAQS. Therefore, we are 
proposing to approve the Colorado SIP as meeting the requirements of 
element 4 of CAA section 110(a)(2)(D)(ii) for the 2006 24-hour 
PM2.5 NAAQS.

V. Proposed Action

    EPA is proposing to approve all four interstate transport elements 
of CAA Section 110(a)(2)(D)(i) from Colorado's May 11, 2012 submission. 
This proposed approval is based on EPA's finding that emissions from 
Colorado do not significantly contribute to nonattainment or interfere 
with maintenance of the 2006 24-hour PM2.5 NAAQS in any 
other state and that the existing Colorado SIP is, therefore, adequate 
to meet the requirements of CAA section 110(a)(2)(D)(i)(I) for the 2006 
24-hour PM2.5 NAAQS.
    EPA is proposing to approve the 110(a)(2)(D)(ii) portion of 
Colorado's submission, based on our finding that the State's existing 
SIP is adequate to meet the requirements of this element for the 2006 
24-hour PM2.5 NAAQS.

VI. Statutory and Executive Orders Review

    Under the CAA, 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 CAA. Accordingly, this 
action merely proposes to approve state law as meeting federal 
requirements and does not impose additional requirements beyond those 
imposed by state law. For that reason, this action:
     Is not a ``significant regulatory action'' subject to 
review by the Office of Management and Budget under

[[Page 27127]]

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 CAA; 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).
    The SIP is not approved to apply on any Indian reservation land or 
in any other area where EPA or an Indian tribe has demonstrated that a 
tribe has jurisdiction. In those areas of Indian country, the rule does 
not have tribal implications and will not impose substantial direct 
costs on tribal governments or preempt tribal law as specified by 
Executive Order 13175 (65 FR 67249, November 9, 2000).

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: April 29, 2015.
Shaun L. McGrath,
Regional Administrator, Region 8.
[FR Doc. 2015-11338 Filed 5-11-15; 8:45 am]
 BILLING CODE 6560-50-P