Document ID: EPA-R08-OAR-2011-0770-0056
Agency: epa
Document Type: Rule
Title: Air Quality State Implementation Plans; Approvals and Promulgations: Colorado; Regional Haze State Implementation Plan
Posted Date: 2015-05-26T04:00Z

[Federal Register Volume 80, Number 100 (Tuesday, May 26, 2015)]
[Rules and Regulations]
[Pages 29953-29959]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-12491]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2011-0770; FRL-9928-16-Region 8]

Approval and Promulgation of Implementation Plans; State of 
Colorado; Regional Haze State Implementation Plan

AGENCY: Environmental Protection Agency.

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA) is reissuing its 
final approval of the Colorado regional haze State Implementation Plan 
(SIP) revision submitted on May 25, 2011 with respect to the State's 
best available retrofit technology (BART) determination for the 
Comanche Generating Station (Comanche) near Pueblo, Colorado. EPA 
originally finalized its approval of the Colorado regional haze SIP on 
December 31, 2012. In response to a petition for review of that final 
action in the United States Court of Appeals for the Tenth Circuit, EPA 
successfully moved for a voluntary remand, without vacatur, to more 
adequately respond to public comments concerning Comanche. EPA is 
providing new responses to those comments in this rulemaking notice.

DATES: This final rule is effective on June 25, 2015.

ADDRESSES: EPA has established a docket for this action under Docket ID 
No. EPA-R08- OAR-2011-0770. All documents in the docket are listed on 
the www.regulations.gov index.

[[Page 29954]]

Although listed in the index, some information is not publicly 
available, e.g., Confidential Business Information (CBI) or other 
information whose disclosure is restricted by statute. Certain other 
material, such as copyrighted material, is not placed on the Internet 
and will be publicly available only in hard copy form. Publicly 
available docket materials are available either electronically through 
www.regulations.gov or in hard copy at the Air Program, Environmental 
Protection Agency (EPA), Region 8, 1595 Wynkoop Street, Denver, 
Colorado 80202-1129. EPA requests that if at all possible, you contact 
the person 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: Gail Fallon, Air Program, U.S. 
Environmental Protection Agency, Region 8, Mailcode 8P-AR, 1595 Wynkoop 
Street, Denver, Colorado 80202-1129, (303) 312-6281, 
fallon.gail@epa.gov.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Background
II. Public Comments and Revised EPA Responses
III. Final Action
IV. Incorporation by Reference
V. Statutory and Executive Order Reviews

I. Background

    On March 26, 2012, EPA proposed to approve the Colorado regional 
haze SIP as meeting the applicable requirements of Sections 169A and 
169B of the Clean Air Act (CAA) and EPA's implementing regulations at 
40 CFR 51.308-309 (Regional Haze Rule) and 40 CFR part 51, Appendix Y 
(Best Available Retrofit Technology (BART) Guidelines).\1\ Among the 
components of the SIP was a nitrogen oxides (NOX) BART 
determination for Units 1 and 2 at Comanche. As with several other 
facilities, the State submitted a BART analysis for Comanche that took 
into account the five factors required by section 169A(g)(2) of the 
CAA. The State determined that the existing emission controls at 
Comanche Units 1 and 2, low-NOX burners with over-fire air 
(LNB/OFA), are BART. EPA proposed to approve the State's NOX 
BART determination for Comanche.
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    \1\ 77 FR 18052.
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    EPA received several adverse comments on its proposed approval, 
including comments from WildEarth Guardians (Guardians) and the 
National Parks Conservation Association (NPCA). On December 31, 2012, 
EPA published a notice of its final approval of the Colorado regional 
haze SIP.\2\ That final action included an approval of the Comanche 
NOX BART determination.
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    \2\ 77 FR 76871.
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    On February 25, 2013, NPCA and Guardians filed petitions seeking 
the Tenth Circuit's review of EPA's final approval of the Colorado 
regional haze SIP.\3\ Guardians challenged EPA's approval of Colorado's 
BART determinations for Units 1 and 2 of the Craig Station; Units 1 and 
2 of the Comanche Station; and Boilers 4 and 5 of the Colorado Energy 
Nations Company (CENC), LLP facility at the Coors Brewery. Guardians 
also challenged EPA's approval of Colorado's reasonable progress 
determination for Craig Unit 3, and the deadlines for compliance with 
emission limits for the units at all three facilities. NPCA challenged 
only EPA's approval of Colorado's BART and reasonable progress 
determinations for Craig Units 1, 2, and 3. After the court 
consolidated the cases for review, EPA reached a settlement with NPCA 
and Guardians concerning their claims related to the Craig Station,\4\ 
and Guardians elected not to pursue its claims regarding CENC/Coors. 
Guardians' claims concerning the Comanche Station are still active. In 
response to these claims, EPA moved the court for a partial voluntary 
remand of its 2012 final approval without vacatur so as to provide a 
more detailed and complete response to some of the adverse comments on 
the proposed approval.\5\ The court granted EPA's motion.\6\
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    \3\ See WildEarth Guardians v. EPA, No. 13-9520 (10th Cir.) and 
National Parks Conservation Association v. EPA, No. 13-9525 (10th 
Cir.).
    \4\ See Proposed Settlement Agreement, 79 FR 47636 (Aug. 14, 
2014).
    \5\ See Respondents' Motion for Partial Voluntary Remand Without 
Vacatur and to Stay Briefing Schedule Pending Resolution of This 
Motion, filed Sep. 19, 2014 in WildEarth Guardians v. EPA, No. 13-
9520 (10th Cir.).
    \6\ See Order filed Oct. 6, 2014 in WildEarth Guardians v. EPA, 
No. 13-9520 (10th Cir.).
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II. Public Comments and Revised EPA Responses

    We received adverse comments on our proposed approval of the 
Colorado regional haze SIP, including comments from Guardians related 
to our proposed approval of Colorado's BART determinations for Units 1 
and 2 at the Comanche Station. We are reissuing our final approval of 
the Colorado regional haze SIP with respect to Comanche to provide more 
detailed and clearer responses to the Comanche-related adverse 
comments. The responses below contain our complete, updated, and 
clarified responses to comments related to the Comanche NOX 
BART determination.
    Comment: The commenter argues that Comanche Units 1 and 2 are 
currently meeting lower NOX emission rates than the State's 
BART emission limits that EPA proposed to approve. The commenter cited 
the State's BART analysis, noting that currently Unit 1 is emitting at 
an average annual rate of 0.124 lb/MMBtu and Unit 2 is emitting at an 
average annual rate of 0.165 lb/MMBtu, and compares those rates to the 
Colorado BART limits: a 30-day emission rate of 0.20 lb/mmBtu, and a 
combined annual average emission rate of 0.15 lb/mmBtu. According to 
the commenter, allowing these units to emit more pollution than they 
currently emit does not represent BART and would not lead to visibility 
improvements, and nothing in the CAA or EPA's regulations suggests that 
it is appropriate for BART limits to include any such cushion. Further, 
the commenter alleges that that under the annual BART limits, 
NOX emissions will be allowed to increase by at least 14 
tons per year (tpy), and that the 30-day rolling average limits would 
allow Unit 1 to emit at least 40% more NOX than the baseline 
30-day rolling average peak and Unit 2 to emit 12% more NOX. 
The commenter claims that the data demonstrates that Unit 1 could meet 
a 30-day rolling average NOX emission limit of 0.15 lb/MMBtu 
and Unit 2 could meet a limit of 0.18 lb/MMBtu without any trouble, and 
that the BART limits should reflect what is achievable. Accordingly, 
the commenter asserts that EPA must disapprove Colorado's 
NOX BART determinations for Comanche Unit 1 and Unit 2 and 
adopt a FIP that establishes BART limits that represent actual emission 
reductions.\7\
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    \7\ Comments submitted by WildEarth Guardians (hereinafter 
referred to as ``Guardians' Comments'') at 5-6, EPA-R08-OAR-2011-
0770-0040 Attachment 2 (May 25, 2012).
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    Response: We disagree with this comment. The State set 
NOX BART emission limits for Comanche Units 1 and 2 
individually at a 30-day rolling average emission rate of 0.20 lb/MMBtu 
and a combined annual average emission rate of 0.15 lb/MMBtu. As EPA 
requested in our October 26, 2010 comment letter during the state 
public comment process, the State considered tightening the 30-day 
limits, but ultimately chose not to do so. In EPA's judgment, the State 
could have better explained the basis for the margin for compliance, 
but a more robust analysis

[[Page 29955]]

would not have led it to reach a different conclusion as to the 
Comanche NOX BART limits. Further, if we were to disapprove 
the SIP and promulgate a FIP with lower emission limits, the actual 
emissions from Comanche would unlikely be significantly lower. We 
therefore decline to disapprove the NOX BART determination 
for Comanche.
    In our October 26, 2010 comment letter to the State, we asked 
Colorado to evaluate tightening Comanche's NOX limits. The 
State conducted that evaluation.\8\ Based on its experience, and after 
reviewing other state BART proposals, Colorado found that 30-day 
rolling average NOX emission rates could be expected to be 
up to approximately 15% higher than annual average emission rates. With 
this in mind, and also considering uncertainty regarding load 
fluctuations, cold-weather operating, startup, and increased cycling to 
back up renewable energy generation, the State concluded that a 0.20 
lb/MMBtu 30-day rolling average emission limit was appropriate for both 
units.
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    \8\ See Colorado Regional Haze Submittal, Appendix C (Technical 
Support Documents for BART Determination), BART Analysis of Control 
Options For Public Service Company--Comanche Station, Units 1 and 2, 
at 17-19 (EPA-R08-OAR-2011-0770-0013, PDF pages 312-14); see also 
Appendix C--Technical Support Documents for BART Determination (EPA-
R08-OAR-2011-0770-0017), Attachment 5: Public Service Company--
Comanche Station Units 1 and 2 Technical Analysis.
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    As a general matter, EPA finds it appropriate and reasonable to 
allow a margin for compliance in setting 30-day rolling average BART 
limits, and we have approved other state BART determinations that 
included such margins. The shorter 30-day averaging period results in 
higher variability in emissions because of load variation, startup, 
shutdown, and other factors. Accordingly, we have not generally 
required that 30-day rolling average emission limits be equal to the 
annual emission rates used for calculating cost-effectiveness. We find 
the State's application of a margin for compliance here consistent with 
that approach.
    The compliance margin included for the Comanche units is larger 
than we would generally expect. But we find that with respect to 
Comanche, the compliance margin is unlikely to lead to significant 
actual NOX emissions increases. After all, the lower 
Comanche emissions cited by the commenter occurred under permit limits 
identical to those the State selected as BART, and the commenter has 
provided no evidence that the facility will change its operations just 
because the State has adopted the permit limits as BART limits. 
Instead, emission rates are likely to remain near the baseline figures 
cited by the commenter, which as the commenter notes are below the BART 
limits. An occasional rise is possible in light of the uncertainties 
referred to above, which is the purpose of allowing a margin for 
compliance above the actual 30-day rolling average emissions levels. 
The commenter appeared to at least partly acknowledge this reality, 
stating that ``[w]e do not suggest that the State was required to set 
the emission limits exactly at the levels emitted.'' \9\ But none of 
these uncertainties suggests that there will be a consistent increase 
in emissions over the long term.
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    \9\ Guardians' Comments at 8.
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    As for annual average emission rates, Colorado found that in 2009, 
the annual average rate for both units combined was about 0.15 lb/
MMBtu. Colorado did not propose applying a margin of compliance to the 
2009 annual average rate, and set a limit at 0.15 lb/MMBtu. Because 
short-term emissions increases and decreases should average out over 
the course of any single year, we believe that setting the BART annual 
emission limit at about the annual emission rate from 2009 is 
reasonable, unless there is evidence that the source was not properly 
operated in 2009 or that annual average source operating conditions in 
2009 were unrepresentative of future operations. The commenter has not 
alleged that there is any such evidence. The commenter does assert that 
the 0.15 lb/MMBtu annual limit would allow an increase in actual 
emissions if both units operate at the BART limit. The potential 
emissions increase calculated by the commenter, however, would only be 
14 tons of NOX per year. A 14-ton increase is not 
significant when compared to the annual NOX emissions of 
approximately 3,860 tons from Comanche Units 1 and 2; it does not 
warrant disapproval and a subsequent FIP.\10\
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    \10\ Discussing state flexibility to exempt de minimis emission 
levels from a BART analysis, the BART Guidelines make a similar 
point: ``If a State were to undertake a BART analysis for emissions 
of less than 40 tons of SO2 or NOX . . . from 
a source, it is unlikely to result in anything but a trivial 
improvement in visibility. This is because reducing emissions at 
these levels would have little effect on regional emissions loadings 
or visibility impairment.'' 70 FR at 39117.
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    The commenter alleges, but does not support or quantify, a 
``likely'' further increase (beyond the claimed 14-ton increase) based 
on the potential for one unit to exceed 0.15 lb/MMBtu while the 
combined rate remains below that limit. This comment appears to be 
referring to a scenario in which the unit operating above 0.15 lb/MMBtu 
would have a higher heat input than the unit operating below 0.15 lb/
MMBtu, so that together they would still comply with the SIP's 0.15 lb/
MMBtu average emission rate limit while having higher emissions than if 
each unit were held to a limit of 0.15 lb/MMBtu. With the existing LNB/
OFA controls, though, neither unit can be operated at an emission rate 
much below its current emission rate, and so there is unlikely to be 
``room'' for the other unit to operate much higher while still meeting 
the combined emission limit. Also, the two units are subject to very 
similar physical limits on heat input.\11\ We therefore find that any 
additional emissions consistent with a 0.15 lb/MMBtu combined limit 
would be insignificant from a visibility standpoint. Further, we note 
that the annual NOX BART limit of 0.15 lb/MMBtu is below the 
average actual emissions of 0.16 lb/MMBtu for Units 1 and 2 between 
January and October 2010.\12\ Therefore, Colorado imposed an annual 
emission limit that was lower than the then most recent partial-year 
figures for Units 1 and 2.
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    \11\ See Colorado Regional Haze Submittal, Appendix C (Technical 
Support Documents for BART Determination), BART Analysis of Control 
Options For Public Service Company--Comanche Station, Units 1 and 2, 
at 2, Table 1: Comanche Units 1 and 2 Technical Information (EPA-
R08-OAR-2011-0770-0013, PDF page 297 (citing boiler ratings of 3,531 
MMBtu/hr for Unit 1 and 3,482 MMBtu/hr for Unit 2).
    \12\ January-October 2010 is the most recent annual average 
emission rate period discussed by Colorado in the regional haze SIP. 
See id. at 18 (PDF page 313).
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    The commenter also argues that the 30-day rolling average limits of 
0.20 lb/MMBtu would allow emission increases because the actual 30-day 
rolling average rates have consistently been below this number. Annual 
emissions are controlled by the SIP's limit of 0.15 lb/MMBtu for the 
average of the two unit's annual average emission rates, and would be 
so controlled even if there were no 30-day limits at all. The issue of 
whether the State and EPA correctly assessed how well the annual limit 
will control annual emissions was addressed above. Therefore, EPA 
understands that this comment regarding the 30-day limits of 0.20 lb/
MMBtu is meant to address the possibility that the emission rate of one 
or both units in 30-day periods may be higher than 0.15 lb/MMBtu, while 
the source could still comply with respect to the annual average limit 
by having lower emissions in other 30-day periods. EPA agrees that this 
is possible, but the State modeled the baseline visibility impact of 
the source assuming a constant emission rate of 0.20 lb/MMBtu, so the 
possibility has been fully considered.

[[Page 29956]]

    For these reasons, we have determined that while the State could 
have better explained the basis for the margin for compliance it 
allowed, a more robust analysis would not have led it to reach a 
different conclusion as to the NOX emission limits for 
Comanche Units 1 and 2. In its next regional haze SIP, the State can 
review the longer history of emissions from Comanche that will be 
available then, and consider whether a downward adjustment in the 
emission limit is appropriate to ensure the best possible operation of 
the emission controls.
    Comment: The commenter asserts that the State failed to 
appropriately assess the cost of SCR, by assuming that SCR would 
achieve an emission rate of 0.07 lb/MMBtu on an annual average basis. 
But, according to the commenter, EPA has noted that SCR can achieve 
emission rates as low as 0.04 lb/MMBtu on an annual basis, and a 0.05 
lb/MMBtu emission rate on an annual average basis is a more appropriate 
benchmark from which to assess the cost-effectiveness of SCR. The 
commenter claims that because the State did not assess the cost-
effectiveness of SCR based on a rate of 0.05 lb/MMBtu, the State did 
not reasonably take into account the cost of compliance with SCR in 
accordance with the CAA. The commenter adds that although EPA and the 
State may claim that SCR would not be cost-effective in any case, there 
is no support for such an assertion, and without an adequate case-
specific cost analysis, there is no support for concluding that SCR is 
unreasonable, particularly for Unit 2.\13\
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    \13\ Guardians' Comments at 9.
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    Response: We disagree with this comment. We have reviewed the 
information in the administrative record for this action again, and we 
find that our previous conclusion is still correct. We agree that SCR 
can achieve annual NOX emission rates of 0.05 lb/MMBtu, and 
that ideally Colorado would have used this value when assessing the SCR 
control option.\14\ But if the State had done so, the marginally lower 
emissions would not have caused the State to reach a different 
conclusion as to what technology is BART.
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    \14\ Throughout this notice, our references to the use of SCR at 
Comanche incorporate the effects of LNB/OFA. Thus, when we discuss 
comparing the effects of SCR against the baseline, we are comparing 
SCR operating with LNB/OFA against the post-2009 baseline of LNB/OFA 
alone.
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    First, we note that the comment misstates the rate that Colorado 
actually used for the purpose of calculating cost-effectiveness. In the 
Comanche NOX BART analysis, the State assumed an annual 
emissions rate for SCR of 0.061 lb/MMBtu--not 0.07 lb/MMBtu.\15\ (The 
latter figure was the 30-day rolling average rate, not the annual 
average as the commenter contends.\16\) Therefore, the relevant 
comparison for the commenter's purpose would be between the 0.061 lb/
MMBtu annual average rate that the State used and the 0.05 lb/MMBtu 
annual average emission rate that the commenter prefers.
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    \15\ See Colorado Regional Haze Submittal, Appendix C (Technical 
Support Documents for BART Determination), BART Analysis of Control 
Options For Public Service Company--Comanche Station, Units 1 and 2, 
Tables 10 and 11, at 20-21 (R08-OAR-2011-0770-0013, PDF pages 315-
16; see also Technical Support Documents for BART Determination 
(EPA-R08-OAR-2011-0770-0017), Attachment: Public Service Company--
Cmanche Station, Units 1 and 2 Technical Analysis (.xls format 
spreadsheet file, tabs ``Comanche 1 NOX'' and ``Comanche 
2 NOX''). There is an inconsequential (approx. 0.33%) 
difference between the Unit 1 baseline numbers in these two parts of 
the record; the discussion in this rule uses the 1506 tpy figure 
from the State's technical analysis spreadsheet.
    \16\ Id.
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    Using the 0.061 lb/MMBtu annual average emission rate, Colorado 
estimated emissions of 740 tpy for Unit 1 and 869 tpy for Unit 2 with 
SCR.\17\ Based on those estimated emissions, the State calculated 
emission reductions of 770.4 tpy for Unit 1 and 1,480 tpy for Unit 2, 
compared to a baseline level of emissions measured in 2009 that 
reflected the installation of LNB/OFA controls.\18\ Based on these 
reductions, the State derived cost-effectiveness values for SCR of 
$15,920 per ton and $9,900 per ton for Units 1 and 2, respectively.\19\ 
It is a simple exercise to insert the annual average emission rate of 
0.05 lb/MMBtu into the State's technical analysis spreadsheet.\20\ 
Doing so, we can see that using the figure the commenter recommends 
would have produced estimated emission levels of about 609 tpy for Unit 
1 and 713 tpy for Unit 2 with SCR, which in turn give emission 
reductions of 897 tpy (Unit 1) and 1,636 tpy (Unit 2) compared to a 
2009 baseline level and cost-effectiveness values of $13,670 and $8,956 
per ton for Units 1 and 2, respectively.\21\ Considering that these 
adjusted cost-effectiveness values remain high and (as discussed below) 
the extent of the benefits associated with SCR remains low, we do not 
believe that the impact on the BART analysis would have led to a 
different conclusion if Colorado had used the more stringent emission 
rate. Therefore, we conclude that the State's use of 0.061 lb/MMBtu to 
evaluate the cost-effectiveness of SCR at Comanche is not grounds for 
disapproval.
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    \17\ Id.
    \18\ ``[T]he Division used years 2009 (annual averages and 30-
day rolling) for baseline emissions for reduction and cost 
calculations.'' Colorado Regional Haze Submittal, Appendix C 
(Technical Support Documents for BART Determination), BART Analysis 
of Control Options For Public Service Company--Comanche Station, 
Units 1 and 2, at 3 (R08-OAR-2011-0770-0013, PDF page 298); see also 
id., Table 2 (``PSCo Comanche Units 1 & 2 Baseline Emissions'').
    \19\ See Colorado Regional Haze Submittal, Appendix C (Technical 
Support Documents for BART Determination), BART Analysis of Control 
Options For Public Service Company--Comanche Station, Units 1 and 2, 
Tables 10-13, at 20-21 (R08-OAR-2011-0770-0013, PDF pages 315-16).
    \20\ See Technical Support Documents for BART Determination 
(EPA-R08-OAR-2011-0770-0017), Attachment: Public Service Company--
Comanche Station, Units 1 and 2 Technical Analysis (Excel 
spreadsheet file, tabs ``Comanche 1 NOX''and ``Comanche 2 
NOX'').
    \21\ For Unit 1, the State also calculated an incremental value 
to assess the cost-effectiveness of SCR over SNCR. Even after making 
the correction to an assumed annual average rate of 0.05 lb/MMBtu as 
described above, this value remains very high: $23,497 per ton.
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    Comment: The commenter states that Colorado appears to have 
overestimated the capital cost of SCR, in that the State's reliance on 
the CUECost model led to artificially inflated capital costs. According 
to the commenter, both EPA and the National Park Service (NPS) 
previously commented to the State that the State should have used EPA's 
Control Cost Manual, and both noted that the CUECost model relied upon 
by the State is not appropriate. The commenter argues that the State 
does not explain in the record why its use of CUECost was reasonable, 
particularly in light of the concerns expressed by EPA and the NPS.\22\
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    \22\ Guardians' Comments at 9.
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    Response: We agree that there were flaws in Colorado's approach to 
estimating the costs of SCR for the Comanche BART units, and that the 
CUECost model likely yielded an inflated cost estimate. In the 
referenced correspondence, EPA stated that ``the CUECost model yields 
high capital costs for the Comanche facility,'' and suggested that the 
capital costs calculated would have been approximately 50% lower if the 
CCM had been followed.\23\ But even if we reduce the capital cost 
estimates by that percentage, and also adjust the emission rate as 
discussed in the previous comment, we believe that the cost of SCR at 
Comanche would still be high compared to the visibility benefits, and

[[Page 29957]]

that Colorado's decision not to require SCR would still be reasonable.
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    \23\ Letter from Callie Videtich, EPA, to Paul Tourangeau, CDPHE 
(Oct. 26, 2010), at 8-9 (EPA-R08-OAR-2011-0770-0043, Attachment 19). 
EPA stated that using the CCM to assess SCR capital costs for the 
Comanche BART units yielded an estimate of approximately $120/kW, as 
opposed to the $247/kW (Unit 1) and $248/kW (Unit 2) derived from 
the CUECost model. Id. This ratio of dollars per kW results in a 
51.6% lower estimate.
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    Specifically, cutting the capital cost estimate by 51.6%, and using 
the more stringent 0.05 lb/MMBtu emission rate discussed in the 
previous comment, produces cost-effectiveness values of $9,319 and 
$6,481 per ton for employing SCR at Units 1 and 2, respectively.\24\ 
Thus, even after addressing both of the cost issues raised by the 
commenter, the cost-effectiveness values remain high. Also, as 
discussed below in response to another comment, we have concluded that 
the visibility benefits that would result from SCR are insufficient to 
justify these high costs. Accordingly, we do not believe that Colorado 
would have reached a different NOX BART conclusion if it had 
used the CCM in its analysis (as well as the more stringent emission 
rate discussed previously).
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    \24\ The 51.6% adjustment to capital cost can be made by 
multiplying the ``total capital costs'' figures on the State's 
technical analysis spreadsheet by 0.484. See Technical Support 
Documents for BART Determination (EPA-R08-OAR-2011-0770-0017), 
Attachment: Public Service Company--Comanche Station, Units 1 and 2 
Technical Analysis (.xls format spreadsheet file, tabs ``Comanche 1 
NOX'' and ``Comanche 2 NOX''). In addition to 
capital costs, the cost-effectiveness calculations incorporate 
operating and maintenance costs, which the commenter did not 
challenge.
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    In its SIP, the State explained that, in its view, SCR for 
NOX control would generally be reasonable if costs did not 
exceed $5,000 per ton of pollutant reduced, and if the controls 
provided a modeled visibility benefit of 0.50 deciviews (dv) or greater 
at the primary Class I Area affected.\25\ Considering the State's 
guidance, it is clear that making the adjustments that the commenter 
requests would not lead to a different outcome. Therefore, considering 
all the BART factors, we do not see a basis to conclude that using a 
lower capital cost estimate, combined with a 0.05 lb/MMBtu emission 
rate for SCR, would have led the State to reach a different conclusion 
or should lead us to disapprove the State's BART determination.
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    \25\ See Colorado Regional Haze Submittal at 52 (R08-OAR-2011-
0770-0013, PDF page 53).
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    Comment: The commenter states that Colorado and EPA may claim that, 
even if the costs were accurately assessed, the visibility benefits of 
SCR would not be significant, but that there is no support for this 
assertion. According to the commenter, it appears that Colorado's 
assessment of visibility improvements is based on an assumption that 
the proposed BART limits, which the commenter refers to as the ``do 
nothing'' BART limits, would actually improve visibility. But, the 
commenter claims, the proposed BART limits would allow increased 
emissions, and therefore would not improve visibility. On the other 
hand, states the commenter, SCR would appear to provide significant 
visibility improvements. The commenter argues that for Unit 2 this is 
especially significant because SCR was the only available technology 
analyzed for BART.\26\
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    \26\ Guardians' Comments at 9-10.
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    Response: We disagree with this comment. In relation to the high 
costs, the visibility benefits of SCR at Comanche are not sufficiently 
large to warrant disapproval of the State's BART determination. We 
would come to this conclusion regardless of whether the cost component 
of the BART analysis involved the State's original figures or the 
adjusted figures discussed above in response to previous comments. The 
State estimated that SCR would produce visibility improvements of 0.14 
dv (Unit 1) and 0.17 dv (Unit 2) as compared to the 2009 post-LNB/OFA 
baseline.\27\ This level of expected visibility improvement from SCR is 
insufficient to cause us to conclude that the State's BART 
determination is unreasonable.
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    \27\ See Colorado Regional Haze Submittal, Appendix C (Technical 
Support Documents for BART Determination), BART Analysis of Control 
Options For Public Service Company--Comanche Station, Units 1 and 2, 
Table 15, at 24 (R08-OAR-2011-0770-0013, PDF page 319). As discussed 
below, the table also includes information on improvements over the 
pre-control baseline; this information is illustrative and was not 
the basis for the BART determination or for our approval of the 
State's action.
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    As discussed above in response to a previous comment, we recognize 
that the State did not use the 0.05 lb/MMBtu emission rate that 
accurately represents the performance capabilities of SCR. Accordingly, 
it is reasonable to expect that the State would have estimated slightly 
greater visibility benefits from SCR if it had used the 0.05 lb/MMBtu 
rate. In EPA's judgment, however, the visibility benefits compared to 
the 2009 baseline would have remained modest. We note, for instance, 
that in the State's analysis of Comanche Unit 1, the difference in 
visibility benefit between selective non-catalytic reduction (SNCR) 
(with a NOX emission rate of 0.10 lb/MMBtu) and SCR (with a 
NOX emission rate of 0.07 lb/MMBtu) is only 0.03 dv.\28\ We 
conclude that the impact of a further reduction in emission rate to 
0.05 lb/MMBtu would be similarly small.\29\
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    \28\ What are labeled by the State as ``NOX emission 
rates'' (e.g., Table 15 of their analysis) are actually the 30-day 
emission limits. See Colorado Regional Haze Submittal, Appendix C 
(Technical Support Documents for BART Determination), BART Analysis 
of Control Options For Public Service Company--Comanche Station, 
Units 1 and 2, Table 15, at 24 (R08-OAR-2011-0770-0013, PDF page 
319). Actual 30-day emission rates have been lower. See id. at 18 
(PDF page 313).
    \29\ Thus, comparing the SNCR and SCR numbers, we see that a 
NOX emissions rate reduction from 0.10 to 0.07 lb/MMBtu 
is reflected in a visibility improvement from 0.11 to 0.14 dv. If we 
assume, for the purpose of conservatively estimating visibility 
improvements, that there is a linear relationship between emission 
reductions and visibility improvement, then further reducing the 
NOX emission rate from 0.07 to 0.05 lb/MMBtu might cause 
visibility improvements at Units 1 and 2 to increase from 0.14 and 
0.178 dv to approximately 0.16 and 0.198 dv. See Approval and 
Promulgation of Air Quality Implementation Plans; State of Florida; 
Regional Haze State Implementation Plan, 78 FR 53250, 53267 (Aug. 
29, 2013) (``[A]n assumption of a linear response to changes in 
emissions is a reasonable estimation and the simplified methodology 
used for these BART determinations likely provides conservative 
overestimates of visibility impact reductions.'').
---------------------------------------------------------------------------

    As mentioned previously, the State explained that, in its view, SCR 
for NOX control will generally be reasonable when costs do 
not exceed $5,000 per ton of pollutant reduced, and when the controls 
provide a modeled visibility benefit of 0.50 dv or greater at the 
primary Class I Area affected.\30\ While we agree with the State that 
these guidance criteria should not be used as absolute determinants of 
BART outcomes, they are in general consistent with the decisions that 
other states and EPA have made when considering whether to require SCR 
as NOX BART, and generally reflect a reasonable balancing of 
the BART factors. In this case, we expect that even using the SCR 
emission rate requested by the commenter, the visibility improvement 
from SCR would fall well below the State's criteria. Judging these 
visibility improvements against the fairly high cost of SCR (again, 
even after adjustment to reflect the comments), we find that the 
State's decision not to impose SCR was reasonable.
---------------------------------------------------------------------------

    \30\ See Colorado Regional Haze Submittal at 52 (R08-OAR-2011-
0770-0013, PDF page 53).
---------------------------------------------------------------------------

    The commenter incorrectly asserted that the State's BART 
determination was based on the assumption that existing controls would 
improve visibility compared to current levels. Colorado did not claim 
that its BART emission limits would result in visibility benefits 
compared to current levels (that is, compared to the 2009 post-LNB/OFA 
emissions baseline). The State did note that the existing level of 
control provided benefits when compared to the 2004 baseline, which is 
true. But while Colorado referred to both a pre-LNB/OFA baseline and a 
2009 baseline when discussing visibility benefits, the State actually 
used only the 2009 baseline in calculating cost-effectiveness, and 
likewise relied on visibility benefits based on the 2009 baseline in 
making the BART determination for

[[Page 29958]]

Comanche.\31\ We have reviewed the visibility estimates and cost 
calculations that the State relied on when making its BART 
determination for Comanche and have confirmed that they were based on 
comparisons to the 2009 baseline.\32\
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    \31\ Colorado stated in the SIP that ``the Division used year[ ] 
2009 (annual averages and 30-day rolling) for baseline emissions for 
reduction and cost calculations.'' See Colorado Regional Haze 
Submittal, Appendix C (Technical Support Documents for BART 
Determination), BART Analysis of Control Options For Public Service 
Company--Comanche Station, Units 1 and 2, at 20-21, 24 (R08-OAR-
2011-0770-0013, PDF pages 315-16, 319); see also Appendix C--
Technical Support Documents for BART Determination (EPA-R08-OAR-
2011-0770-0017), Attachment 5: Public Service Company--Comanche 
Station Units 1 and 2 Technical Analysis. Likewise, the State's BART 
determination cites only the 0.14 dv and 0.17dv visibility 
improvement numbers derived from comparison to the 2009 baseline. 
See Colorado Regional Haze Submittal at 66 (R08-OAR-2011-0770-0013, 
PDF page 67).
    \32\ In replying to this comment and one other comment in the 
December 2012 final approval, we inadvertently made a confusing 
statement concerning the applicable baselines. In that notice, we 
stated that Colorado had ``assessed the benefit of control options 
relative to both the subject-to-BART baseline and to the 
installation of new low- NOX burners (LNB) [with over-
fire air] in 2007 and 2008.'' Further, we noted that ``relative to 
the subject-to-BART baseline, Colorado's BART selection (combustion 
controls), does in fact show visibility improvement.'' These 
statements appeared to suggest that it was appropriate for Colorado 
to use a 2009 baseline when evaluating the benefits of SNCR and SCR, 
but a 2004 (pre-LNB/OFA) baseline to evaluate the State's proposed 
BART option. That was not our intention. Our reference to the 2004 
subject-to-BART baseline--that is, to the emissions level before the 
installation of the LNB/OFA, which were required to comply with non-
BART CAA requirements--was merely an observation, by which we 
intended to show that the installation of those controls had 
produced real air quality improvements over previous levels. That 
illustration was not, however, intended to be part of our evaluation 
of the State's cost or visibility analyses.
---------------------------------------------------------------------------

    It was correct for the State to use the 2009 baseline for 
NOX emissions from Units 1 and 2 in the BART determination. 
The CAA requires that, in making BART determinations, states and EPA 
take into consideration ``any existing pollution control technology in 
use at the source.'' \33\ As we explained in detail in our final action 
on the Wyoming regional haze SIP, this consideration should generally 
incorporate controls into baseline emissions if the controls were 
installed to comply with CAA requirements other than the BART 
requirement.\34\ That is exactly what happened with respect to Comanche 
Units 1 and 2. The controls in question had been placed on these units 
to ``net out'' of Prevention of Significant Deterioration (PSD) review 
requirements for NOX and SO2 emissions from the 
new Unit 3.\35\ Therefore, it was appropriate for the State to use the 
2009 emissions baseline, which reflected the reductions achieved by 
LNB/OFA, in its BART analysis for Comanche.
---------------------------------------------------------------------------

    \33\ 42 U.S.C. 7491(g)(2).
    \34\ 79 FR 5032, 5104-05 (Jan. 30, 2014).
    \35\ See Colorado Regional Haze Submittal, Appendix C (Technical 
Support Documents for BART Determination), BART Analysis of Control 
Options For Public Service Company--Comanche Station, Units 1 and 2, 
at 1 (R08-OAR-2011-0770-0013, PDF page 1) (``As part of that [2004 
construction] project, PSCo proposed to install control devices on 
the existing units.''); see also Colorado Operating Permit # 
96OPPB133 (Comanche Station) (``. . . PSCo proposed to install 
NOX controls (low NOX burners with over-fire 
air) on both Units 1 and 2 . . . to `net-out' of Prevention of 
Significant Deterioration (PSD) review requirements for 
NOX and SO2''), posted at https://www.colorado.gov/pacific/cdphe/operating-permits-company-index.
---------------------------------------------------------------------------

    Finally, we addressed the assertion that the State's BART limits 
would lead to increased emissions in our response to a previous 
comment. The commenter has failed to offer any support for this claim, 
and we do not find any basis to conclude that increased emissions will 
result from the State's BART limits.
    For the above reasons, while we agree that SCR at Comanche Units 1 
and 2 would result in visibility improvements, we find that the State 
reasonably concluded that those visibility improvements would not be 
sufficient to justify the cost involved.
    Comment: The commenter states that it is unclear why Colorado 
rejected SNCR for Comanche Unit 1, particularly because the proposed 
BART limit for Unit 1 is less stringent than Unit 1's current actual 
emissions. Citing EPA figures, the commenter asserts that Unit 1 would 
meet a 30-day rolling average emission rate of 0.10 lb/MMBtu under an 
SNCR scenario. The commenter notes that the State found that the cost 
of $3,644 per ton of NOX reduced and the perceived ``low 
visibility improvement'' warranted a determination that SNCR was not 
reasonable for Unit 1. The commenter asserts, however, that this cost 
is squarely within the range of what Colorado considers to be cost-
effective.\36\
---------------------------------------------------------------------------

    \36\ Guardians' Comments at 10.
---------------------------------------------------------------------------

    Response: We find that the State's rejection of SNCR was reasonable 
based on its weighing of the BART factors. The State concluded that the 
cost of SNCR was not warranted given the relatively modest 0.11 dv 
visibility improvement that would result. Even if a control technology 
is cost-effective on a dollar per ton basis, a state may conclude that 
the control technology is not warranted based on a reasonable 
consideration of all five BART factors.
    Comment: The commenter states that Colorado's analysis indicates 
that SNCR would achieve greater emission reductions than an emission 
rate of 0.20 lb/MMBtu on a 30-day rolling average. According to the 
commenter, although the State asserts that the visibility improvement 
from SNCR would amount to 0.11 dv, it is unclear why such improvements 
are not reasonable or are insignificant, particularly given that the 
purpose of BART is to reduce or eliminate visibility impairment. The 
commenter argues that there is no explanation in the record supporting 
the State's assertion. Further, the commenter argues that it appears as 
if the State's assessment of visibility improvements is based on an 
incorrect assumption that the proposed BART limit would actually 
improve visibility. The commenter states that when compared to the real 
impacts of the State's proposed BART limit for Comanche Unit 1, SNCR 
appears to provide significant visibility improvements, because, as 
opposed to the proposed BART limit, SNCR would actually achieve 
improvements. Therefore, the commenter concludes, EPA must promulgate a 
FIP that establishes an appropriate NOX BART limit for 
Comanche Unit 1.\37\
---------------------------------------------------------------------------

    \37\ Guardians' Comments at 10.
---------------------------------------------------------------------------

    Response: The commenter is correct that the State predicted that 
SNCR would result in additional improvement in visibility over the 
control technology that the State selected as BART. However, this does 
not mean that the CAA or our regulations required the State to select 
SNCR as BART. For the reasons stated above, we find that it was 
reasonable for the State to reject SNCR based on consideration of all 
five BART factors. We agree that SNCR would result in visibility 
improvements, but as with SCR, we agree with the State's assessment 
that the visibility improvements were insufficient to justify the cost 
involved.
    Regarding the commenter's claim that the State's selected limits 
will lead to an increase in emissions, as discussed above in detail, 
the commenter has presented no evidence that any emissions increase 
will occur.

III. Final Action

    With respect to the Comanche Station, EPA is re-finalizing its 
approval of the Colorado regional haze SIP submitted on May 25, 2011. 
Because this re-finalization merely gives additional explanation in 
response to comments and does not alter any previous determinations, it 
does not affect any applicable SIP compliance deadlines. Our action is 
based on an evaluation of Colorado's regional haze SIP submittal for 
Comanche against the regional haze

[[Page 29959]]

requirements at 40 CFR 51.300-51.309 and CAA sections 169A and 169B. 
All general SIP requirements contained in CAA section 110, other 
provisions of the CAA, and our regulations applicable to this action 
were also evaluated. The purpose of this action is to ensure compliance 
with these requirements and to provide additional rationale to support 
our conclusions.

IV. Incorporation by Reference

    In this rule, the EPA is finalizing regulatory text that includes 
incorporation by reference. In accordance with requirements of 1 CFR 
51.5, the EPA is finalizing the incorporation by reference of Colorado 
revisions to its SIP to address the requirements of EPA's regional haze 
rule discussed in section III, Final Action, of this preamble. The EPA 
has made, and will continue to make, these documents generally 
available electronically through www.regulations.gov and/or in hard 
copy at the appropriate EPA office (see the ADDRESSES section of this 
preamble for more information).

V. Statutory and Executive Order Reviews

    Under the Clean Air Act, the Administrator is required to approve a 
SIP submission that complies with the provisions of the Act and 
applicable federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). 
Thus, in reviewing SIP submissions, EPA's role is to approve state 
choices, provided that they meet the criteria of the Clean Air Act. 
Accordingly, this action merely 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 this action does not involve the use of measurement or 
other standards; 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).
    The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the 
Small Business Regulatory Enforcement Fairness Act of 1996, generally 
provides that before a rule may take effect, the agency promulgating 
the rule must submit a rule report, which includes a copy of the rule, 
to each House of the Congress and to the Comptroller General of the 
United States. EPA will submit a report containing this action and 
other required information to the U.S. Senate, the U.S. House of 
Representatives, and the Comptroller General of the United States prior 
to publication of the rule in the Federal Register. A major rule cannot 
take effect until 60 days after it is published in the Federal 
Register. This action is not a ``major rule'' as defined by 5 U.S.C. 
804(2).
    Under section 307(b)(1) of the Clean Air Act, petitions for 
judicial review of this action must be filed in the United States Court 
of Appeals for the appropriate circuit by July 27, 2015. Filing a 
petition for reconsideration by the Administrator of this final rule 
does not affect the finality of this action for the purposes of 
judicial review nor does it extend the time within which a petition for 
judicial review may be filed, and shall not postpone the effectiveness 
of such rule or action. This action may not be challenged later in 
proceedings to enforce its requirements. See section 307(b)(2).

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental relations, Nitrogen dioxide, Particulate 
matter, Sulfur oxides.

    Dated: May 8, 2015.
Debra H. Thomas,
Acting Regional Administrator Region 8.

    40 CFR part 52 is amended as follows:

PART 52--APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS

0
1. The authority citation for Part 52 continues to read as follows:

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

Subpart G--Colorado

0
2. Section 52.320 is amended by revising paragraph (c)(124) 
introductory text to read as follows:

Sec.  52.320  Identification of plan.

* * * * *
    (c) * * *
    (124) On May 25, 2011 the State of Colorado submitted revisions to 
its State Implementation Plan to address the requirements of EPA's 
regional haze rule. On December 31, 2012, EPA issued a final rule 
approving this submittal and responding to public comments. On May 26, 
2015 EPA reissued the final rule with respect to the nitrogen oxides 
(NOX) best available retrofit technology (BART) 
determination for the Comanche Generating Station to provide additional 
responses to public comments.
* * * * *
[FR Doc. 2015-12491 Filed 5-22-15; 8:45 am]
BILLING CODE 6560-50-P