Document ID: EPA-R08-OAR-2017-0567-0001
Agency: epa
Document Type: Proposed Rule
Title: Air Quality State Implementation Plans; Approvals and Promulgations: Colorado; Attainment Demonstration for the 2008 8-Hour Ozone Standard for the Denver Metro/North Front Range Nonattainment Area, and Approval of Related Revisions
Posted Date: 2018-04-06T04:00Z

[Federal Register Volume 83, Number 67 (Friday, April 6, 2018)]
[Proposed Rules]
[Pages 14807-14826]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2018-06847]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2017-0567, FRL-9975-09--Region 8]

Promulgation of State Implementation Plan Revisions; Colorado; 
Attainment Demonstration for the 2008 8-Hour Ozone Standard for the 
Denver Metro/North Front Range Nonattainment Area, and Approval of 
Related Revisions

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: On May 31, 2017, the State of Colorado submitted State 
Implementation Plan (SIP) revisions related to attainment of the 2008 
8-hour ozone National Ambient Air Quality Standards (NAAQS) for the 
Denver Metro/North Front Range (DMNFR) Moderate nonattainment area by 
the applicable attainment date of July 20, 2018. The Environmental 
Protection Agency (EPA) proposes to approve the majority of the 
submittal, which includes an attainment demonstration, base and future 
year emission inventories, a reasonable further progress (RFP) 
demonstration, a reasonably available control measures (RACM) analysis, 
a motor vehicle inspection and maintenance (I/M) program in Colorado 
Regulation Number 11 (Reg. No. 11), a nonattainment new source review 
(NNSR) program, a contingency measures plan, 2017 motor vehicle 
emissions budgets (MVEBs) for transportation conformity, and revisions 
to Colorado Regulation Number 7 (Reg. No. 7). The EPA is also proposing 
to approve portions of the reasonably available control technology 
(RACT) analysis. Finally, the EPA proposes to approve revisions made to 
Colorado's Reg. No. 7 in a May 5, 2013 SIP submission. This action is 
being taken in accordance with the Clean Air Act (CAA).

DATES: Comments must be received on or before May 7, 2018.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R08-
OAR-2017-0567, at http://www.regulations.gov. Follow the online 
instructions for submitting comments. Once submitted, comments cannot 
be edited or removed from Regulations.gov. The EPA may publish any 
comment received to its public docket. Do not submit electronically any 
information you consider to be Confidential Business Information (CBI) 
or other information whose disclosure is restricted by statute. 
Multimedia submissions (audio, video, etc.) must be accompanied by a 
written comment. The written comment is considered the official comment 
and should include discussion of all points you wish to make. The EPA 
will generally not consider comments or comment contents located 
outside of the primary submission (i.e., on the web, cloud, or other 
file sharing system). For additional submission methods, the full EPA 
public comment policy, information about CBI or multimedia submissions, 
and general guidance on making effective comments, please visit http://www2.epa.gov/dockets/commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT: Abby Fulton, Air Program, U.S. 
Environmental Protection Agency (EPA), Region 8, Mail Code 8P-AR, 1595 
Wynkoop Street, Denver, Colorado 80202-1129, (303) 312-6563, 
[email protected].

SUPPLEMENTARY INFORMATION: 

I. What action is the Agency taking?

    As explained below, the EPA is proposing various actions on 
Colorado's proposed revisions to its SIP that it submitted to the EPA 
on May 5, 2013, and May 31, 2017. Specifically, we are proposing to 
approve Colorado's 2017 attainment demonstration for the 2008 8-hour 
ozone NAAQS. In addition, we propose to approve the MVEBs contained in 
the State's submittal. We also propose to approve all other aspects of 
the submittal, except for certain area source categories and major 
source RACT, which we will be acting on at a later date. We propose to 
approve the revisions to Colorado's Reg. 11 and 7, except for Section 
X.E of Reg. 7, which we will be acting on at a later date. We propose 
to approve the revisions to Colorado Reg. 7 Sections I, II, VI, VII, 
VIII, and IX from the State's May 5, 2013 submittal.
    The specific bases for our proposed actions and our analyses and 
findings are discussed in this proposed rulemaking. Technical 
information that we rely upon in this proposal is contained in the 
docket, available at http://www.regulations.gov, Docket No. EPA-R08-
OAR-2017-0567.

II. Background

    On March 12, 2008, the EPA revised both the primary and secondary 
NAAQS for ozone to a level of 0.075 parts per million (ppm) (based on 
the annual fourth-highest daily maximum 8-hour average concentration, 
averaged over 3 years) to provide increased protection of public health 
and the environment (73 FR 16436, March 27, 2008). The 2008 ozone NAAQS 
retains the same general form and averaging time as the 0.08 ppm NAAQS 
set in 1997, but is set at a more protective level. Specifically, the 
2008 8-hour ozone NAAQS is attained when the 3-year average of the 
annual fourth-highest daily maximum 8-hour average ambient air quality 
ozone concentrations is less than or equal to 0.075 ppm. See 40 CFR 
50.15.
    Effective July 20, 2012, the EPA designated as nonattainment any 
area that was violating the 2008 8-hour ozone NAAQS based on the three 
most

[[Page 14808]]

recent years (2008-2010) of air monitoring data (77 FR 30088, May 21, 
2012). With that rulemaking, the DMNFR area was designated 
nonattainment and classified as Marginal. Ozone nonattainment areas are 
classified based on the severity of their ozone levels. This is 
determined using the area's design value. The design value is the 3-
year average of the annual fourth highest daily maximum 8-hour average 
ozone concentration at a monitoring site. See 40 CFR part 50, Appendix 
I. The DMNFR nonattainment area includes Adams, Arapahoe, Boulder, 
Broomfield, Denver, Douglas and Jefferson Counties, and portions of 
Larimer and Weld Counties. See 40 CFR 81.306. Areas that were 
designated as Marginal nonattainment were required to attain the 2008 
8-hour ozone NAAQS no later than July 20, 2015, based on 2012-2014 
monitoring data.
    On May 4, 2016, the EPA published its determination that the DMNFR, 
among other areas, had failed to attain the 2008 8-hour ozone NAAQS by 
the attainment deadline, and that the DMNFR was accordingly 
reclassified to a Moderate ozone nonattainment area (81 FR 26697; see 
40 CFR 81.306). Moderate areas are required to attain the 2008 8-hour 
ozone NAAQS by no later than 6 years after the effective date of 
designation, which for the DMNFR nonattainment area is July 20, 2018. 
See 40 CFR 51.903.

III. Analysis of the State's Submission

    CAA Section 182, 42 U.S.C. 7511a, outlines SIP requirements 
applicable to ozone nonattainment areas in each classification 
category. Moderate area classification triggers additional state 
requirements established under the provisions of the EPA's ozone 
implementation rule for the 2008 8-hour ozone NAAQS. See 40 CFR part 
51, subpart AA. Examples of these requirements include submission of a 
modeling and attainment demonstration, RFP, RACT, and RACM. Moderate 
nonattainment areas had a submission deadline of January 1, 2017 for 
these SIP revisions (81 FR 26697, 26699, May 4, 2016).
    Colorado submitted revisions to its SIP to the EPA on May 31, 2017, 
to meet the requirements of a Moderate area classification for the 
DMNFR nonattainment area and attain the 2008 8-hour ozone NAAQS. 
Colorado's proposed SIP revisions consist of the parts listed below.
     8-Hour Ozone Attainment Plan (OAP), which includes 
monitoring information, emission inventories, an RFP demonstration, an 
attainment demonstration using photochemical grid modeling, a weight of 
evidence analysis, a RACT analysis, a RACM analysis, a motor vehicle 
emissions I/M program, NNSR program certification, contingency 
measures, and 2017 MVEBs for transportation conformity.
     Revisions to Reg. No. 7.
     Revisions to Reg. No. 11.
    The Reg. No. 7 revisions in the 2017 submission include rule 
revisions related to the Moderate ozone nonattainment classification 
and revisions that address the EPA's concerns with previous SIP 
submittals. In this action, we are also acting on Reg. No. 7 revisions 
from a May 5, 2013 SIP submission. Reg. No. 11 revisions remove 
``state-only'' references in Part A, regarding Larimer and Weld 
counties, thereby making the entire motor vehicle inspection and 
maintenance program federally enforceable.
    The provisions we propose to approve meet the requirements of the 
CAA and our regulations. The specific bases for our proposed actions 
and our analyses and findings are discussed in this proposed 
rulemaking. Technical information that we rely on in this proposal is 
contained in the docket, available at http://www.regulations.gov, 
Docket No. EPA-R08-OAR-2017-0567.

A. Procedural Requirements

    The CAA requires that states meet certain procedural requirements 
before submitting SIP revisions to the EPA. Specifically, section 
110(a)(2) of the CAA, 42 U.S.C. 7410(a)(2), requires that states adopt 
SIP revisions after reasonable notice and public hearing. For the May 
5, 2013 submittal, the Colorado Air Quality Control Commission (AQCC) 
provided notice in the Colorado Register on September 21, 2012, and 
held a public hearing on December 20, 2012. The Colorado AQCC adopted 
the SIP revisions on December 20, 2012. The SIP revisions became state-
effective on February 15, 2013. For the May 31, 2017 submission, the 
Colorado AQCC provided notice in the Colorado Register on July 29 and 
August 29, 2016 and held a public hearing on the SIP revisions on 
November 17, 2016. The Colorado AQCC adopted the SIP revisions on 
November 17, 2016. The SIP revisions became state-effective on January 
14, 2017. Colorado met the CAA's procedural requirements for reasonable 
notice and public hearing.

IV. EPA's Evaluation of Colorado's Submission

A. Monitoring

    Ozone monitoring data are used as a basis for photochemical grid 
modeling in the attainment demonstration. The EPA requirements for 
ambient monitoring are in 40 CFR part 58. Colorado collected ozone 
monitoring data in accordance with these requirements and with the 
EPA's ``Quality Assurance Handbook for Air Pollution Measurement 
Systems, Vol. II--Ambient Air Quality Monitoring Program''; \1\ the 
Colorado Air Pollution Control Division's (APCD) Quality Management 
Plan \2\ and Quality Assurance Project Plan; \3\ and Colorado's 
monitoring network plan.\4\
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    \1\ QA Handbook for Air Pollution Measurement Systems: ``Volume 
II: Ambient Air Quality Monitoring Program'' (EPA-454/B-13-003, May 
2013) (available in the docket). The current version of the Handbook 
is available at https://www3.epa.gov/ttn/amtic/files/ambient/pm25/qa/FinalHandbookDocument1_17.pdf (EPA-454/B-17-001, Jan. 2017).
    \2\ Colorado Department of Public Health and Environment, 
Quality Management Plan (March 2016), available in the docket.
    \3\ Colorado Department of Public Health and Environment, 
Quality Assurance Project Plan (July 2015), available in the docket.
    \4\ Annual Network Plans available at https://www.colorado.gov/airquality/tech_doc_repository.aspx.
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    The monitoring section of Colorado's OAP includes:
     Information on the location of ozone monitors in Colorado, 
from southern Metropolitan Denver to northern Fort Collins (including 
Rocky Mountain National Park);
     4th-maximum monitored 8-hour ozone values from 2006 
through 2015, including levels recorded above the 75 parts per billion 
(ppb) 2008 ozone NAAQS; \5\
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    \5\ OAP Table 3.
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     A description of the State's ambient air quality data 
assurance program; and
     Relevant 8-hour-average ozone monitoring data and recovery 
rates from 2006 through September 2015.

B. Emissions Inventories

1. Background
    CAA section 172(c)(3), 42 U.S.C. 7502(c)(3), requires that each SIP 
include a ``comprehensive, accurate, current inventory of actual 
emissions from all sources of the relevant pollutant or pollutants in 
[the] area.'' The accounting required by this section provides a ``base 
year'' inventory that serves as the starting point for attainment 
demonstration air quality modeling, for assessing RFP, and for 
determining the need for additional SIP control measures. An attainment 
year inventory is a projection of future emissions and is necessary to 
show the effectiveness of SIP control measures. Both the base year and 
attainment year inventories are necessary for

[[Page 14809]]

photochemical modeling to demonstrate attainment. Section D includes 
additional discussion on how these inventories are used in the 
attainment modeling.
    Colorado's DMNFR area attainment plan includes a 2011 base year 
inventory and a 2017 attainment year inventory. The inventories catalog 
NOX and VOC emissions, because these pollutants are 
precursors to ozone formation, across all source categories during a 
typical summer day, when ozone formation is pronounced. Carbon monoxide 
(CO) emissions are reported as well, because they also impact ozone 
chemistry.
    In our 2008 ozone NAAQS implementation rule, the EPA recommends 
using 2011 as the baseline year (80 FR 12264, 12272). In addition, 
analysis of meteorological conditions in the DMNFR area leads to the 
conclusion that the summer of 2011 was a ``typical'' ozone season from 
a meteorological standpoint. The modeling analysis uses a base year of 
2011 to develop the modeling inputs for the base year modeling analysis 
and model performance evaluation.
2. Evaluation
    The 2011 base year emissions inventory and the 2017 attainment year 
emissions inventory were developed using EPA-approved guidelines for 
stationary, mobile, and area emission sources. Stationary source 
emissions data for 2011 were self-reported to the State by individual 
sources; the State then used the submitted 2011 information to project 
stationary source emissions for 2017. On-road and non-road mobile 
source emissions were calculated using the EPA's MOVES2014 model 
combined with local activity inputs including vehicle miles traveled 
(VMT) and average speed data, as well as local fleet, age distribution, 
meteorology, and fuels information. Area sources include many 
categories of emissions. The EPA finds that these sources (including 
those in the oil and gas sector) were adequately accounted for in the 
emissions inventory. The methodology used to calculate emissions for 
each respective category followed relevant EPA guidance; \6\ \7\ as 
applicable, employed approved emission factors and National Emissions 
Inventory (NEI) data; and was sufficiently documented in the SIP and in 
the State's technical support documents (TSD).\8\
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    \6\ Emissions Inventory Guidance for Implementation of Ozone and 
Particulate Matter National Ambient Air Quality Standards (NAAQS) 
and Regional Haze Regulations, EPA-454/B-17-003, available at 
https://www.epa.gov/sites/production/files/2017-07/documents/ei_guidance_may_2017_final_rev.pdf (hereinafter referred to as 
``Emissions Inventory Guidance'') (July 2017).
    \7\ MOVES2014 and MOVES2014a Technical Guidance: Using MOVES to 
Prepare Emission Inventories for State Implementation Plans and 
Transportation Conformity, EPA-420-B-15-093, available at https://nepis.epa.gov/Exe/ZyPDF.cgi/P100NN9L.PDF?Dockey=P100NN9L.PDF 
(hereinafter referred to as ``MOVES Guidance'') (Nov. 2015).
    \8\ See Colorado OAP, TSD Part 1, 2011-2017 Mobile and Area 
Sources Emissions Inventory Development, p. 1202.
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    Projected future emissions in 2017 were based on anticipated 
growth, technological advancements, and expected emissions controls 
that were to be implemented by the 2017 ozone season. Table 1 shows the 
emissions by source category from the 2011 base year and 2017 
attainment year emission inventories.
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    \9\ Emissions in Table 1 are reflective of an average summer 
day.

                              Table 1--Emissions Inventory Data for Specific Source
                                           [Tons/avg. episode day] \9\
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                                                              2011                             2017
                  Description                  -----------------------------------------------------------------
                                                   VOC        NOX         CO        VOC        NOX         CO
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Oil and Gas Sources:
    Point Sources Subtotal....................       14.8       18.1       17.0       16.3       20.6       19.7
    Condensate Tanks Subtotal.................        216        1.1        2.3       78.7        0.6        2.3
    Area Sources Subtotal.....................       48.9       22.2       12.9       59.0       44.6       31.4
                                               -----------------------------------------------------------------
        Total.................................      279.7       41.4       32.2        154       65.8       53.4
                                               -----------------------------------------------------------------
Point Sources (EGU and Non-Oil and Gas):
    Electric Generating Units (EGUs)..........        0.7       39.7        3.6        0.4       19.2        2.9
    Point (Non-Oil and Gas)...................       25.9       21.0       14.1       28.0       20.9       14.4
                                               -----------------------------------------------------------------
        Total.................................       26.6       60.7       17.7       28.4       40.1       17.3
                                               -----------------------------------------------------------------
Area Sources (Non-Oil and Gas):
                                               -----------------------------------------------------------------
        Total.................................       60.6        0.0        1.4       67.5  .........        1.6
                                               -----------------------------------------------------------------
Non-Road Mobile Sources:
                                               -----------------------------------------------------------------
        Total.................................       58.2       75.9      800.2       44.3       54.9      759.7
                                               -----------------------------------------------------------------
On-Road Mobile Sources:
    Light-Duty Vehicles.......................       90.0      102.5      812.2       52.4       50.3      538.6
                                               -----------------------------------------------------------------
    Medium/Heavy-Duty Vehicles................        3.7       39.6       20.6        2.6       23.0       16.2
                                               -----------------------------------------------------------------
        Total.................................       93.7      142.1      832.8       55.0       73.3      554.8
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            Total Anthropogenic Emissions.....      518.8      320.1    1,684.3      349.2      234.1    1,386.8
                                               -----------------------------------------------------------------
            Total Biogenic Sources............      170.5        6.1       21.6      170.5        6.1       21.6
                                               -----------------------------------------------------------------

[[Page 14810]]

 
            Total Nonattainment Area Emissions      689.3      326.2    1,705.9      519.7      240.2    1,408.4
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    Details of Colorado's emissions inventory development are in 
Colorado's supporting TSD.\10\ The inventories in the SIP are based on 
the most current and accurate information available to the State and 
the Regional Air Quality Council (RAQC) at the time the SIP was being 
developed. Additionally, the inventories comprehensively address all 
source categories in the DMNFR nonattainment area, and were developed 
consistent with the relevant EPA inventory guidance. For these reasons, 
we propose to approve the 2011 baseline emissions inventory as meeting 
the requirements of CAA section 172(c)(3), 42 U.S.C. 7502(c)(3). The 
EPA also finds that the 2017 inventory, which will be used to meet RFP 
and attainment demonstration requirements, was developed consistent 
with relevant EPA Emissions Inventory Guidance and MOVES Guidance. 
Further discussion on RFP and attainment demonstration is provided in 
their respective sections.
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    \10\ See Colorado OAP, TSD Part 1, 2011-2017 Mobile and Area 
Sources Emissions Inventory Development, p. 1202.
    \10\ Emissions in Table 1 are reflective of an average summer 
day.
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C. Reasonable Further Progress Demonstration

1. Background
    Section 182(b)(1) of the CAA, 42 U.S.C. 7511a(b)(1), and the EPA's 
2008 Ozone Implementation Rule require each 8-hour ozone nonattainment 
area designated Moderate and above to submit an RFP demonstration for 
review and approval into its SIP that describes how the area will 
achieve actual VOC and NOX emissions reductions from a 
baseline emissions inventory. Section 182(b)(1), 42 U.S.C. 7511a(b)(1), 
which is part of the ozone-specific requirements of Subpart 2 of the 
CAA's nonattainment plan requirements, requires RFP to demonstrate a 
15% reduction in VOC emissions. This requirement applies before the 
more general Subpart 1 RFP requirements of CAA Section 172(c)(2), 42 
U.S.C. 7502(c)(2), which permits a combination of VOC and 
NOX emission reductions to show RFP. Colorado has not 
previously submitted a 15% RFP SIP under Section 182(b)(1). Therefore, 
on May 31, 2017, the State submitted an RFP demonstration showing VOC 
emission reductions greater than 15% within six years after the 2011 
base year inventory (between 2012-2017).
    RFP plans must also include an MVEB, which provides the allowable 
on-road mobile emissions an area can produce while still demonstrating 
RFP. The State's RFP submittal included MVEBs for the DMNFR area for 
the year 2017 (see Chapter 11 of the State's OAP). The MVEBs are 
discussed in detail in Section M of this notice.
2. Evaluation
    To demonstrate compliance with RFP requirements, the State compared 
its 2011 base year VOC emissions inventory against its projected 2017 
VOC emissions inventory and demonstrated that the projected milestone 
year inventory (2017) emissions of VOC will be at least 15% below the 
2011 base year inventory. Colorado projects a 32.7% reduction in VOC 
emissions from 2011-2017 (see OAP, Table 25 on page 4-21). As discussed 
above in section IV.B., the EPA reviewed the procedures Colorado used 
to develop its projected inventories and found them to be reasonable.

D. Photochemical Grid Modeling

1. Background
    Under the 2008 Ozone Implementation Rule, Moderate ozone 
nonattainment areas are required to demonstrate attainment using 
``photochemical modeling or another equivalent analytical method that 
is determined to be at least as effective. . . .'' 80 FR at 12268. The 
EPA explained that ``photochemical modeling is the most scientifically 
rigorous technique to determine NOX and/or VOC emissions 
reductions needed to show attainment of the NAAQS.'' Id. at 12269. 
Consistent with the 2015 Ozone Implementation Rule, the SIP includes 
photochemical grid modeling with supplemental analyses to demonstrate 
that the emissions control strategy leads to attainment of the NAAQS by 
2017. The modeling effort was led by the RAQC in coordination with the 
Colorado Department of Public Health and Environment (CDPHE). The RAQC 
first developed a modeling protocol \11\ that describes the model 
configuration, domain, input data, and analyses to be performed for the 
SIP. As described in the protocol, the RAQC selected summer 2011 for 
the attainment demonstration base case model simulation using the 2011 
base year emissions inventory. The modeling platform used the Weather 
Research and Forecasting Model (WRF) \12\ to simulate meteorological 
data fields, and the Comprehensive Air Quality Model with Extensions 
(CAMx) as the photochemical air quality model. The modeling platform 
used a high resolution 4-km grid for the State of Colorado, nested 
within a western U.S. 12-km grid and a 36-km North America CAMx 
simulation developed by the Western Air Quality Study.\13\ Day-specific 
boundary conditions for the 36-km CAMx simulation were derived from a 
2011 simulation of the MOZART model.\14\ The Sparse Matrix Operating 
Kernel Emissions (SMOKE) model \15\ was used to process emissions data, 
and the Model of Emissions of Gases and Aerosols from Nature (MEGAN) 
\16\ was

[[Page 14811]]

used to estimate biogenic emissions of VOC and NOX. The 
anthropogenic precursor emissions data were based on the 2011 NEI \17\ 
with updates in key source categories, including oil and gas 
emissions,\18\ mobile and area source emissions,\19\ and point source 
emissions.\20\ The EPA reviewed each of the modeling documents listed 
above and determined that the modeling is consistent with the 
recommendations in the relevant EPA guidance.\21\
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    \11\ ENVIRON International Corporation, User's Guide 
Comprehensive Air-quality Model with Extensions Version 6.2, 
available at http://www.camx.com/files/camxusersguide_v6-20.pdf 
(March 2015).
    \12\ Weather Research and Forecasting model web page available 
at https://www.mmm.ucar.edu/weather-research-and-forecasting-model.
    \13\ Adelman, Z., Shanker, U., Yang, and Morris, R., CAMx 
Photochemical Grid Model Draft Model Performance Evaluation 
Simulation Year 2011, available at http://vibe.cira.colostate.edu/wiki/Attachments/Modeling/3SAQS_Base11a_MPE_Final_18Jun2015.pdf 
(June 2015); Ramboll Environ, Attainment Demonstration Modeling for 
the Denver Metro/North Front Range 2017 8-Hour Ozone State 
Implementation Plan, Draft Modeling Protocol, Prepared for Regional 
Air Quality Council, available at https://raqc.egnyte.com/dl/gFls58KHSM/Model_Protocol_Denver_RAQC_2017SIPv4.pdf (Aug. 2015).
    \14\ Emmons, L. K., et al., Description and Evaluation of the 
Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4), 
Geosci. Model Dev., 3, 4367, 2010, 3, pp. 43-67 (Jan. 2010).
    \15\ UNC, SMOKE v3.6.5 User's Manual, University of North 
Carolina at Chapel Hill, Institute for the Environment, available at 
https://www.cmascenter.org/smoke/documentation/3.6.5/html/ (2015).
    \16\ Sakulyanontvittaya, T., G. Yarwood and A. Guenther. 2012. 
Improved Biogenic Emission Inventories across the West, ENVIRON 
International Corporation, available at https://www.wrapair2.org/pdf/WGA_BiogEmisInv_FinalReport_March20_2012.pdf (March 2012).
    \17\ 2011 NEI web page available at https://www.epa.gov/air-emissions-inventories/2011-national-emissions-inventory-nei-data.
    \18\ See Colorado OAP, TSD Part 1, 2011 and 2017 Oil and Gas 
Emissions Inventory Development, p. 1429.
    \19\ See Colorado OAP, TSD Part 1, 2011 and 2017 Mobile and Area 
Sources Emissions Inventory Development, p. 1202.
    \20\ See Colorado OAP, TSD Part 1, 2011 and 2017 Point Source 
Emissions Inventory Development, p. 1443.
    \21\ Draft Modeling Guidance for Demonstrating Attainment of Air 
Quality Goals for Ozone, PM2.5 and Regional Haze, EPA, 
available at https://www3.epa.gov/scram001/guidance/guide/Draft_O3-PM-RH_Modeling_Guidance-2014.pdf (Dec. 2014).
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2. Evaluation
    EPA guidance recommends that model performance be evaluated by 
comparing model-simulated concentrations to observed concentrations. 
Model performance evaluation is used to evaluate the model for 
historical ozone episodes in the base year and to assess the model's 
reliability in projecting future year ozone concentrations. Using 
meteorological and emissions data from a historical base period, ozone 
and other species concentrations predicted by the model are compared to 
monitored concentrations to evaluate model performance. EPA modeling 
guidance emphasizes the use of graphical and diagnostic evaluation 
techniques to ensure that the modeling captures the correct chemical 
regimes and emission sources causing high ozone. Consistent with the 
guidance, Colorado's model performance evaluation included a 
comprehensive suite of graphical and diagnostic evaluation techniques, 
such as time-series plots of modeled and observed ozone at key 
monitoring sites, spatial plots of ozone, tabulations of model bias and 
error metrics, and diagnostic model simulations using sensitivity and 
source apportionment techniques. The WRF and CAMx configuration and MPE 
are described in Ramboll Environ's 2011 base case modeling and model 
performance evaluation report,\22\ which used both quantitative (model 
performance statistics) and qualitative (graphical displays) MPE 
approaches. At the four key monitoring sites in the Denver 
nonattainment area, the model achieved typical performance goals for 
model bias and error. However, as to the Chatfield monitor, which had 
the highest ozone design value, the model was biased low for some days 
in May and June and biased high for some days in July and August. While 
the model achieved the performance goal, it failed to accurately 
simulate some of the days with the highest monitored ozone.\23\
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    \22\ Ramboll Environ, Denver Metro/North Front Range 2017 8-Hour 
Ozone State Implementation Plan: 2011 Base Case Modeling and Model 
Performance Evaluation, available at https://raqc.egnyte.com/dl/pxHfZAhquy/TSD_2011_BaseCaseModeling%26MPE.pdf (Sept. 2017).
    \23\ As discussed in EPA guidance, it is normal for an air 
quality model to have some under-prediction or over-prediction bias 
and error in modeled ozone because of uncertainties and errors in 
model input data. The relative response factor (RRF) approach that 
is recommended in the guidance and that is used in the State's SIP 
attainment demonstration is designed to correct for bias in the 
model predictions for ozone.
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    Because of concerns with model underestimates of ozone on some of 
the highest days at the Chatfield monitor and other monitoring sites, 
Colorado performed additional weight of evidence (WOE) analysis to 
assess model performance and the effect of model performance on the 
model attainment demonstration, as discussed in Sections E and F below.

E. Modeled Attainment Demonstration

    In the modeled attainment demonstration, emissions inventories are 
developed for the attainment year (here, 2017) that reflect emissions 
control measures adopted in the SIP as well as other emissions 
reductions expected to be achieved through federally enforceable 
national programs, such as reduced tailpipe emissions for mobile 
sources. The Colorado 2017 emissions inventory is described in the 
RAQC's model attainment demonstration report.\24\ The photochemical 
model is then used to simulate air quality using the projected 2017 
emissions. Because of the concerns with bias and error in the model 
performance discussed in the previous section, absolute model results 
are not used to evaluate attainment. Instead, the model is used in a 
relative sense by calculating the ratio of the model's future (here, 
2017) to base case (here, 2011) predictions at ozone monitors in the 
nonattainment area. We call these ratios ``Relative Response Factors'' 
(RRFs). Future ozone concentrations are then estimated at existing 
monitoring sites by multiplying the modeled RRF at locations near each 
monitor by the observation-based, monitor-specific, baseline design 
value. The resulting predicted future concentrations are then compared 
with the 2008 8-hour average ozone NAAQS of 75 ppb. If the predicted 
future concentrations of ozone are lower than 76 ppb at all monitors, 
attainment is demonstrated.\25\ The EPA's ``Model Attainment Test 
Software'' (MATS, Abt., 2014 \26\) is used to calculate RRFs and to 
perform the attainment demonstration.
---------------------------------------------------------------------------

    \24\ See Colorado OAP, TSD Part 2, Denver Metro/North Front 
Range 2017 8-Hour Ozone State Implementation Plan: 2017 Attainment 
Demonstration Modeling, p. 1564.
    \25\ In determining compliance with the NAAQS, ozone design 
values are truncated to integers. For example, a design value of 
75.9 ppb is truncated to 75 ppb. Accordingly, design values at or 
above 76.0 ppb are considered nonattainment. See p. 100, footnote 34 
of Draft Modeling Guidance for Demonstrating Attainment of Air 
Quality Goals for Ozone, PM2.5 and Regional Haze, EPA, 
available at https://www3.epa.gov/scram001/guidance/guide/Draft_O3-PM-RH_Modeling_Guidance-2014.pdf (Dec. 2014), and p. 41 of Guidance 
on the Use of Models and Other Analyses for Demonstrating Attainment 
of Air Quality Goals for Ozone, PM2.5, and Regional Haze, 
EPA-454/B-07-002, available at https://www3.epa.gov/ttn/scram/guidance/guide/final-03-pm-rh-guidance.pdf (April 2007).
    \26\ Abt Associates Inc., Modeled Attainment Test Software--
User's Manual. available at http://www.epa.gov/ttn/scram/guidance/guide/MATS_2-6-1_manual.pdf (April 2014).
---------------------------------------------------------------------------

    Table 2 summarizes Colorado's 2011 base case design values, the 
RRFs from the 2017 control measure case modeling, and the projected 
2017 future design values. Table 2 shows results for two different 
approaches for calculating the model RRF. EPA guidance recommends that 
the RRFs be calculated using the maximum modeled ozone in a 3x3 matrix 
of grid cells surrounding each monitor. The 3x3 matrix is used because 
of the possibility that errors in model inputs or physics can result in 
under predictions in the grid cell with the monitor, and because of the 
possibility that emissions point sources could be located close to the 
edges of grid cells, as discussed in more detail in the modeling 
guidance (EPA, 2014, pp. 102-103).
    Using the 3x3 RRFs, the maximum projected 8-hour ozone design 
values for the 2017 control measure case are 76 ppb at the Chatfield 
and the Rocky Flats North monitoring sites. Thus, the primary model 
attainment demonstration did not project NAAQS-attaining future design 
values (that is, less than 76 ppb) at all monitor sites. When the 
primary model attainment demonstration is close to but fails to attain 
the NAAQS, EPA guidance recommends that states consider whether it is 
appropriate to perform an attainment demonstration using a WOE 
demonstration. Colorado performed a

[[Page 14812]]

WOE attainment demonstration as described in Section F below.

   Table 2--Current Year Observed 8-Hour Ozone Design Values (DVB), Relative Response Factors (RRF) and Projected 8-Hour Ozone 2017 Future Case Design
                                                 Values (DVFs), From Table 3-1 in Ramboll Environ 2016b
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                             3x3 Grid array (4 km)            7x7 Grid array (4 km)
                                                                                       -----------------------------------------------------------------
                                                                             Base year               Future                           Future
                  Monitor                                County                (2011)                 year      Final                  year      Final
                                                                             DVB (ppb)     RRF       (2017)    2017 DVB     RRF       (2017)    2017 DVF
                                                                                                   DVF (ppb)   (ppb) **             DVF (ppb)   (ppb) **
                                                                                                       **                               **
--------------------------------------------------------------------------------------------------------------------------------------------------------
Chatfield..................................  Douglas.......................       80.7     0.9453       76.2         76     0.9391       75.7         75
Rocky Flats North..........................  Jefferson.....................       80.3     0.9493       76.2         76     0.9441       75.8         75
NREL.......................................  Jefferson.....................       78.7     0.9591       75.4         75     0.9442       74.3         74
Fort Collins West..........................  Larimer.......................       78.0     0.9179       71.5         71     0.9098       70.9         70
Highland...................................  Arapahoe......................       76.7     0.9517       72.9         72     0.9431       72.3         72
Welby......................................  Adams.........................       76.0     0.9512       72.2         72     0.9712       73.8         73
Welch......................................  Jefferson.....................       75.7     0.9538       72.2         72     0.9428       71.3         71
Rocky Mountain NP..........................  Larimer.......................       75.7     0.9464       71.6         71     0.9385       71.0         71
South Boulder Creek........................  Boulder.......................       74.7     0.9477       70.7         70     0.9445       70.5         70
Greeley/Weld Co. Tower.....................  Weld..........................       74.7     0.9422       70.3         70     0.9226       68.9         68
Aspen Park.................................  Jefferson.....................       74.5     0.9389       69.9         69     0.9370       69.8         69
Arvada.....................................  Jefferson.....................       74.0     0.9723       71.9         71     0.9495       70.2         70
Aurora East................................  Arapahoe......................       73.5     0.9373       68.8         68     0.9367       68.8         68
Carriage...................................  Denver........................       71.0     0.9695       68.8         68     0.9595       68.1         68
Rist Canyon................................  Larimer.......................       71.0     0.9248       65.6         65     0.9161       65.0         65
Fort Collins CSU...........................  Larimer.......................       68.7     0.9217       63.3         63     0.9096       62.4         62
DMAS NCore.................................  Denver........................       65.0     0.9697       63.0         63     0.9522       61.8         61
--------------------------------------------------------------------------------------------------------------------------------------------------------

F. Weight of Evidence Analysis

    As noted above, the primary model attainment demonstration 
predicted future design values of 76 ppb at two monitors (Rocky Flats 
North and Chatfield), and thus these two monitors are not projected to 
attain the 75 ppb NAAQS by 2017. EPA guidance recommends a WOE analysis 
in cases for which future design values are close to the NAAQS, using 
the following criteria for a WOE attainment demonstration:
     A fully-evaluated, high-quality modeling analysis that 
projects future values that are close to the NAAQS;
     A description of each of the individual supplemental 
analyses, preferably from multiple categories. Analyses that use well-
established analytical procedures and are grounded with sufficient data 
should be weighted higher; and
     A written description as to why the full set of evidence 
leads to a conclusive determination regarding the future attainment 
status of the area that differs from the results of the modeled 
attainment test alone.
    The WOE analysis can include monitoring and emissions inventory 
trend analysis; review of the conceptual model for ozone formation in 
the nonattainment area; additional modeling metrics; alternative 
attainment test methods; and assessment of the efficacy of SIP-approved 
regulations, state-only regulations, and voluntary control measures. 
Considering this information and applying the criteria described in the 
guidance, the WOE analysis is then used to assess whether the planned 
emissions reductions will result in attainment of the NAAQS at the 
monitors that modeled ozone future design values of 76 ppb or higher.
    As part of its WOE analysis, Colorado evaluated the model 
attainment demonstration using a 7x7 matrix of grid cells around each 
monitor site, because the model performed better in simulating the 2011 
period when monitored concentrations were compared to model results in 
the 7x7 matrix.\27\ This performance difference may be a result of 
challenges in accurately simulating meteorological data in Colorado's 
complex terrain combined with the use of a high resolution 4-km grid in 
the Colorado modeling platform. It is possible that small errors in 
wind speed or wind direction could result in model-simulated plumes 
being offset by more than 4 km from a monitoring site. When using a 7x7 
matrix of grid cells, the monitored concentration is compared to 
modeled concentrations up to 12 km from the monitor site to assess 
whether the model more accurately simulated the observed ozone in grid 
cells close to the monitor site. Table 2 shows that when the model 
attainment test is performed using the 7x7 matrix, all monitor sites 
are projected to attain the 75 ppb NAAQS.
---------------------------------------------------------------------------

    \27\ See Colorado OAP, TSD Part 2, Denver Metro/North Front 
Range 2008 Ozone Standard Moderate Area State Implementation Plan: 
Air Quality Technical Support Document (AQTSD), p. 1608.
---------------------------------------------------------------------------

    Colorado also evaluated high ozone days from 2009 to 2013 that were 
likely influenced by atypical activities such as wildfire or 
stratospheric intrusion, but were included in the calculation of the 
2011 baseline ozone design value (see Table 3; CDPHE, 2016d \28\). 
While Colorado did not submit formal demonstrations under the 
Exceptional Events Rule (40 CFR 50.14) for these days because they do 
not affect the attainment status, which is evaluated based on 2015-2017 
monitoring data, these days do affect the baseline design value and 
thus affect the model projected future design value for 2017. Table 4 
shows the revised 2011 baseline design value when the data likely 
influenced by atypical activities are excluded, and Table 4 also shows 
the results of the model attainment demonstration using both the 3x3 
and 7x7 matrices for calculating the model RRF. All future design 
values are below

[[Page 14813]]

the 75 ppb NAAQS using both approaches when data possibly influenced by 
atypical activities are excluded in the calculation of the 2011 design 
values.
---------------------------------------------------------------------------

    \28\ See Colorado OAP, TSD Part 2, Analyses in Support of 
Exceptional Event Flagging and Exclusion for the Weight of Evidence 
Analysis, p. 1662.
---------------------------------------------------------------------------

    The EPA concurs with Colorado's assessment that the model was 
properly configured, met EPA performance requirements, and was 
appropriately used in its application. The EPA finds that the WOE 
analysis supports a determination that the area will attain the 75 ppb 
ozone NAAQS by 2017.

Table 3--Ozone Monitoring Data Flagged as Exceptional Events and Excluded From the 2011 Baseline Design Value in
                                         the Weight of Evidence Analysis
                                        [Table 1 from CDPHE, 2016d] \29\
----------------------------------------------------------------------------------------------------------------
                                    8-hour ozone concentrations (ppb)              Exceptional event type
                              ----------------------------------------------------------------------------------
                                                                                              Wildfire smoke
             Date                           Rocky                  Fort    Stratospheric         influence
                               Chatfield    Flats       NREL     Collins       ozone     -----------------------
                                            North                  West      intrusion     Regional      Local
----------------------------------------------------------------------------------------------------------------
April 13, 2010...............         79  .........  .........  .........            x    ..........  ..........
April 14, 2010...............  .........  .........  .........         75            x    ..........  ..........
June 7, 2011.................         84  .........  .........  .........            x    ..........  ..........
May 15, 2012.................  .........  .........  .........         76  .............  ..........          x
June 17, 2012................  .........  .........  .........         77  .............  ..........          x
June 22, 2012................  .........        101         83         93  .............  ..........          x
July 4, 2012.................         96         92         95         76  .............          x   ..........
July 5, 2012.................  .........         88         81  .........  .............          x   ..........
August 9, 2012...............         98         84         88         86  .............          x   ..........
August 21, 2012..............         80         80         80  .........  .............          x   ..........
August 25, 2012..............  .........         80  .........  .........  .............          x   ..........
August 31, 2012..............  .........  .........  .........         80  .............          x   ..........
August 17, 2013..............  .........         86         84         87  .............          x   ..........
----------------------------------------------------------------------------------------------------------------

Table 4--Base Year (DVB) and 2017 Future Year (DVF) Ozone Design Values (ppb) at Key Ozone Monitors With Flagged Exceptional Event Days Removed From the
                                                                      2009-2013 DVB
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                         Exceptional events omitted 3x3   Exceptional events omitted 7x7
                                                                                               grid array (4 km)                grid array (4 km)
                                                                             Base year -----------------------------------------------------------------
                  Monitor                                County                (2011)                           Final                            Final
                                                                             DVB (ppb)     RRF      2017 DVF   2017 DVF     RRF      2017 DVF   2017 DVF
                                                                                                     (ppb)      (ppb)                 (ppb)      (ppb)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Chatfield..................................  Douglas.......................       78.7     0.9453       74.4         74     0.9391       73.9         73
Rocky Flats North..........................  Jefferson.....................       78.7     0.9493       74.7         74     0.9441       74.3         74
NREL.......................................  Jefferson.....................       77.7     0.9591       74.5         74     0.9442       73.4         73
Fort Collins West..........................  Larimer.......................       76.3     0.9179       70.0         70     0.9098       69.4         69
--------------------------------------------------------------------------------------------------------------------------------------------------------

G. Unmonitored Area Analysis
---------------------------------------------------------------------------

    \29\ CDPHE did not identify any exceptional events in 2009 in 
their weight of evidence analysis.
---------------------------------------------------------------------------

    The EPA guidance recommends that an ``unmonitored area analysis'' 
(UAA) be performed to examine ozone concentrations in unmonitored 
areas. The UAA is intended to be a means for identifying high ozone 
concentrations outside of traditionally monitored locations, 
particularly in nonattainment areas where modeling or other data 
analyses have indicated potential high concentration areas of ozone 
outside of the existing monitoring network. This review can help ensure 
that a control strategy leads to reductions in ozone at other locations 
that could have base case (and future) design values exceeding the 
NAAQS were a monitor deployed there. The UAA uses a combination of 
model output and ambient data to identify areas that might exceed the 
NAAQS but that are not currently monitored. Colorado used the MATS to 
perform the UAA and found estimated 2011 ozone DVBs in excess of 76 ppb 
to the south, west, and northwest of Denver, stretching to Fort Collins 
and then west of Fort Collins. Colorado also found that the projected 
DVFs for 2017 showed all areas have values below 76 ppb. The maximum 
2017 estimated design value was 75.9 ppb near the Jefferson/Boulder 
County border.

H. Reasonably Available Control Technology (RACT) Analysis

1. Background
    Section 172(c)(1) of the CAA, 42 U.S.C. 7502(c)(1), requires that 
SIPs for nonattainment areas ``provide for the implementation of all 
reasonably available control measures as expeditiously as practicable 
(including such reductions in emissions from existing sources in the 
area as may be obtained through the adoption, at a minimum, of 
reasonably available control technology).'' The EPA has defined RACT as 
the lowest emissions limitation that a particular source is capable of 
meeting by the application of control technology that is reasonably 
available, considering technological and economic feasibility (44 FR 
53761, Sep. 17, 1979).
    The EPA provides guidance concerning what types of controls could 
constitute RACT for a given source category by issuing Control 
Techniques Guidelines (CTG) and Alternative

[[Page 14814]]

Control Techniques (ACT) documents.\30\ States must submit a SIP 
revision requiring the implementation of RACT for each source category 
in the area for which the EPA has issued a CTG, and for any major 
source in the area not covered by a CTG.\31\
---------------------------------------------------------------------------

    \30\ See https://www.epa.gov/ozone-pollution/control-techniques-guidelines-and-alternative-control-techniques-documents-reducing 
(accessed Sep. 21, 2017) for a list of EPA-issued CTGs and ACTs.
    \31\ See CAA section 182(b)(2), 42 U.S.C. 7511a(b)(2)); see also 
Note, RACT Qs & As--Reasonably Available Control Technology (RACT): 
Questions and Answers, William Harnett, Director, Air Quality Policy 
Division, EPA (May 2006), available at https://www3.epa.gov/ttn/naaqs/aqmguide/collection/cp2/20060518_harnett_ract_q&a.pdf.
---------------------------------------------------------------------------

    For a Moderate, Serious, or Severe area a major stationary source 
is one that emits, or has the potential to emit, 100, 50, or 25 tons 
per year (tpy) or more, respectively, of VOCs or NOX (see 
CAA sections 182(b), 42 U.S.C. 7511a(b); 182(c), 42 U.S.C. 7511a(c); 
182(d), 42 U.S.C. 7511a(d); and 302(j), 42 U.S.C. 7602(j)). For the 
DMNFR Moderate nonattainment area, a major stationary source is one 
that emits, or has the potential to emit, 100 tpy or more of VOCs or 
NOX. RACT can be adopted in the form of emission limitations 
or ``work practice standards or other operation and maintenance 
requirements,'' as appropriate.\32\ The Division identified 51 major 
sources in the DMNFR area, operated by 32 companies. The EPA will be 
acting on Colorado's major stationary source RACT submission in a 
separate action. Colorado did not rely on any emission reductions from 
major stationary sources in their 2017 modeling analysis. The remainder 
of this section will address Colorado's RACT submission related to CTG 
sources.
---------------------------------------------------------------------------

    \32\ See Memorandum, ``Approval Options for Generic RACT Rules 
Submitted to Meet the non-CTG VOC RACT Requirement and Certain 
NOX RACT Requirements,'' Sally Shaver, Director, Air 
Quality Strategies & Standards Division, EPA (Nov. 7, 1996), 
available at https://www.epa.gov/sites/production/files/2016-08/documents/shavermemogenericract_7nov1996.pdf.
---------------------------------------------------------------------------

2. Evaluation
1. CTG Source Category Sources Addressed in This Action
    As part of its May 31, 2017 submittal, the Division conducted a 
RACT analysis to demonstrate that the RACT requirements for CTG sources 
in the DMNFR 2008 8-hour ozone nonattainment area have been fulfilled. 
The Division conducted its RACT analysis for VOC and NOX by: 
(1) Identifying all categories of CTG and major non-CTG sources of VOC 
and NOX emissions within the DMNFR nonattainment area; (2) 
Listing the state regulation that implements or exceeds RACT 
requirements for that CTG or non-CTG category; (3) Detailing the basis 
for concluding that these regulations fulfill RACT through comparison 
with established RACT requirements described in the CTG guidance 
documents and rules developed by other state and local agencies; and 
(4) Submitting negative declarations when there are no CTG or major 
non-CTG sources within the DMNFR area.
    The EPA has reviewed Colorado's new and revised VOC rules for the 
source categories covered by the CTGs for the 2008 8-hour ozone NAAQS 
listed in Tables 5 and 6 and proposes to find that these rules are 
consistent with the control measures, definitions, recordkeeping, and 
test methods in these CTGs and applicable EPA RACT guidance.\33\ Tables 
5 and 6 contain a list of CTG source categories, EPA reference 
documents, and the corresponding sections of Reg. No. 7 that fulfill 
the applicable RACT requirements for EPA-issued CTGs.\34\ Colorado's 
Reg. No. 7, Control of Ozone Via Ozone Precursors and Control of 
Hydrocarbons Via Oil and Gas Emissions, contains SIP-approved 
provisions (see 76 FR 47443, Aug. 4, 2011) that meet RACT requirements 
for the source categories listed in Table 5. Reg. No. 7 also contains 
general RACT provisions for the CTG source category listed in Table 6. 
To meet RACT requirements for the source category in Table 6, Colorado 
submitted several changes to Reg. No. 7 for adoption into its SIP (see 
Section N of this notice).
---------------------------------------------------------------------------

    \33\ See https://www.epa.gov/ozone-pollution/ract-information.
    \34\ See The EPA's TSD for a full analysis of Colorado's rules 
as they relate to EPA guidelines and available technical 
information. We will be acting on the following CTG source 
categories in a future action: Metal Furniture Coatings, 2007; 
Miscellaneous Metal Products Coatings, 2008; Wood Furniture 
Manufacturing Operations, 1996; Industrial Cleaning Solvents, 2006; 
and Aerospace, 1997.
    \35\ EPA Control Techniques Guidelines and Alternative Control 
Techniques Documents for Reducing Ozone-Causing Emissions, https://www.epa.gov/ozone-pollution/control-techniques-guidelines-and-alternative-control-techniques-documents-reducing.
    \36\ The EPA published a final CTG on October 27, 2016 to reduce 
VOC emissions from the oil and gas industry (see 81 FR 74798 and 
https://www.epa.gov/sites/production/files/2016-10/documents/2016-ctg-oil-and-gas.pdf). The CTG gives states two years from the date 
of issuance to submit SIP revisions to address requirements of the 
oil and gas CTG. Therefore, Colorado did not submit a RACT analysis 
with their May 31, 2017 submission for this source category.

                            Table 5--SIP Approved Source Specific Rules Meeting RACT
----------------------------------------------------------------------------------------------------------------
                                        CTG reference                                        Chapter 7 sections
   Source category in DMNFR area        document \35\                Date of CTG              fulfilling RACT
----------------------------------------------------------------------------------------------------------------
Bulk Gasoline Plants..............  Control of Volatile    1977..........................  Sections V, VI, and
                                     Organic Emissions                                      XV.
                                     from Bulk Gasoline
                                     Plants.
Equipment Leaks from Natural Gas/   Control of Volatile    1983..........................  Sections V and XII.
 Gasoline Processing Plants.         Organic Compound
                                     Equipment Leaks from
                                     Natural Gas/Gasoline
                                     Processing Plants.
Leaks from Gasoline Tank Trucks     Control of Volatile    1978..........................  Sections V, VI, and
 and Vapor Collection Systems.       Organic Compound                                       XV.
                                     Leaks from Gasoline
                                     Tank Trucks and
                                     Vapor Collection
                                     Systems.
Leaks from Petroleum Refinery       Control of Volatile    1978..........................  Sections V and VIII.
 Equipment.                          Organic Compound
                                     Leaks from Petroleum
                                     Refinery Equipment.
Manufacture of Synthesized          Control of Volatile    1978..........................  Sections V, IX, and
 Pharmaceutical Products.            Organic Emissions                                      XIV.
                                     from Manufacture of
                                     Synthesized
                                     Pharmaceutical
                                     Products.
Oil and Natural Gas Industry \36\.  Control Techniques     2016..........................  Sections V, XII,
                                     Guidelines for the                                     XVII, and XVIII.
                                     Oil and Natural Gas
                                     Industry.
Paper, Film, and Foil Coatings....  Control Techniques     2007..........................  Sections V and IX.
                                     Guidelines for Film
                                     Coatings.

[[Page 14815]]

 
Petroleum Liquid Storage in         Control of Volatile    1978 (ACT 1994)...............  Sections V and VI.
 External Floating Roof Tanks.       Organic Emissions
                                     from Petroleum
                                     Liquid Storage in
                                     External Floating
                                     Roof Tanks.
Refinery Vacuum Producing Systems,  Control of Refinery    1977..........................  Sections V and VIII.
 Wastewater Separators, and          Vacuum Producing
 Process Unit Turnarounds.           Systems, Wastewater
                                     Separators, and
                                     Process Unit
                                     Turnarounds.
Solvent Metal Cleaning............  Control of Volatile    1977..........................  Sections V and X.
                                     Organic Emissions
                                     from Solvent Metal
                                     Cleaning.
Stage I Vapor Control Systems--     Design Criteria for    1975..........................  Sections V and VI.
 Gasoline Service Stations.          Stage I Vapor
                                     Control Systems--
                                     Gasoline Service
                                     Stations.
Storage of Petroleum Liquids in     Control of Volatile    1977..........................  Sections V and VI.
 Fixed Roof Tanks.                   Organic Emissions
                                     from Storage of
                                     Petroleum Liquids in
                                     Fixed-Roof Tanks.
Surface Coating of Cans...........  Control of Volatile    1977..........................  Sections V and IX.
                                     Organic Emissions
                                     from Existing
                                     Stationary Sources--
                                     Volume II: Surface
                                     Coating of Cans,
                                     Coils, Paper,
                                     Fabrics,
                                     Automobiles, and
                                     Light-Duty Trucks.
Surface Coating of Coils..........  Control of Volatile    1977..........................  Sections V and IX.
                                     Organic Emissions
                                     from Existing
                                     Stationary Sources--
                                     Volume II: Surface
                                     Coating of Cans,
                                     Coils, Paper,
                                     Fabrics,
                                     Automobiles, and
                                     Light-Duty Trucks.
Surface Coating of Metal Furniture  Control of Volatile    1977..........................  Section V and IX.
                                     Organic Emissions
                                     from Solvent Metal
                                     Cleaning.
Surface Coating of Miscellaneous    Control of Volatile    1978..........................  Sections V and IX.
 Metal Parts and Products.           Organic Emissions
                                     from Existing
                                     Stationary Sources--
                                     Volume VI: Surface
                                     Coating of
                                     Miscellaneous Metal
                                     Parts and Products.
Tank Truck Gasoline Loading         Control of             1997..........................  Section V, VI and XV.
 Terminals.                          Hydrocarbons from
                                     Tank Truck Gasoline
                                     Loading Terminals.
Use of Cutback Asphalt............  Control of Volatile    1977..........................  Sections V and XI.
                                     Organic Emissions
                                     from Use of Cutback
                                     Asphalt.
----------------------------------------------------------------------------------------------------------------

               Table 6--General Rules With Proposed SIP Revisions Meeting RACT for Source Category
----------------------------------------------------------------------------------------------------------------
                                                                                           Chapter 7 sections
     Source category in DMNFR area        CTG reference document       Date of CTG          fulfilling RACT
----------------------------------------------------------------------------------------------------------------
Lithographic Printing Materials and     Control Techniques                       2006  Sections V and XIII.
 Letterpress Printing Materials.         Guidelines for Offset
                                         Lithographic Printing
                                         and Letterpress Printing.
----------------------------------------------------------------------------------------------------------------

    The Division also reviewed four ACT VOC source categories to 
determine if additional VOC reductions could be achieved (see section 
6.2.4 of the OAP):
    1. Organic Waste Process Vents (EPA 1990, ACT);
    2. Bakery Ovens (EPA 1992, ACT);
    3. Industrial Wastewater Alternative Control Technology (EPA 1994, 
ACT); and
    4. Control of Volatile Organic Compound Emissions from Batch 
Processes (EPA 1994, ACT).
    These four categories were evaluated because they are not addressed 
by a CTG, federal consumer product rule, or directly by a New Source 
Performance Standard (NSPS) or National Emission Standard for Hazardous 
Air Pollutant (NESHAP) and are not included in a State source-specific 
RACT provision. Colorado found in its analysis that there are more 
recent NSPS and NESHAPs that cover the source categories, and that the 
State has incorporated by reference in Reg. No. 6 and implements. 
Additionally, Reg. No. 7 establishes work practices and disposal 
practices similar to the ACTs. Accordingly, Colorado did not identify 
any additional requirements to include in their RACT analysis through 
their review of the ACTs.
    We have reviewed the emission limitations and control requirements 
for the above source categories (Tables 5 and 6 in Reg. No. 7) and 
compared them against the EPA's CTG and ACT documents, available 
technical information, and guidelines. The emission limitations and 
control requirements in Reg. No. 7 for the above source categories are 
consistent with our guidance.
    Based on available information, we find that the corresponding 
sections in Reg. No. 7 provide for the lowest emission limitation 
through application of control techniques that are reasonably available 
considering technological and economic feasibility. For more 
information, see the EPA TSD prepared in conjunction with this action. 
Therefore, we propose to find that the control requirements for the 
source categories identified in Tables 5 and 6 are RACT for all 
affected sources in the DMNFR area under the 2008 8-hour ozone NAAQS.
I. Negative Declarations
    States are not required to adopt RACT limits for source categories 
for which no sources exist in a nonattainment area, and can submit a 
negative declaration to that effect. Colorado has reviewed its

[[Page 14816]]

emissions inventory and determined that there are no subject sources 
for source categories listed in Table 7 in the DMNFR area. We are also 
unaware of any such facilities operating in the DMNFR nonattainment 
area, and thus we propose to approve the negative declarations made for 
the source categories in Table 7 for the DMNFR area under the 2008 8-
hour ozone NAAQS.

       Table 7--Negative Declarations for CTG VOC Source Categories
------------------------------------------------------------------------
          Source category negative declarations for DMNFR area
-------------------------------------------------------------------------
Auto and Light-Duty Truck Assembly Coatings (2008).
Factory Surface Coating of Flat Wood Paneling.
Fiberglass Boat Manufacturing Materials (2008).
Flat Wood Paneling Coatings (2006).
Flexible Packaging Printing Materials (2006).
Fugitive Emissions from Synthetic Organic Chemical Polymer and Resin
 Manufacturing Equipment.
Graphic Arts--Rotogravure and Flexography.
Large Appliance Coatings (2007).
Large Petroleum Dry Cleaners.
Manufacture of High-Density Polyethylene, Polypropylene, and Polystyrene
 Resins.
Manufacture of Pneumatic Rubber Tires.
Miscellaneous Industrial Adhesives (2008).
Oil and Natural Gas Industry (2016).
Plastic Parts Coatings (2008).
SOCMI Air Oxidation Processes.
SOCMI Distillation and Reactor Processes.
Shipbuilding/repair.
Surface Coating for Insulation of Magnet Wire.
Surface Coating of Automobiles and Light-Duty Trucks.
Surface Coating of Fabrics.
Surface Coating of Large Appliances.
Surface Coating of Paper.
------------------------------------------------------------------------

I. Reasonably Available Control Measures (RACM) Analysis

1. Background
    With the attainment demonstration, Colorado submitted a 
demonstration that the DMNFR area has adopted all RACM necessary to 
demonstrate attainment as expeditiously as practicable, as required by 
CAA section 172(c)(1), 42 U.S.C. 7502(c)(1), and 40 CFR 51.912(d). The 
EPA interprets the CAA RACM provision to require a demonstration that: 
(1) The state has adopted all reasonable measures (including RACT) to 
meet RFP requirements and to demonstrate attainment as expeditiously as 
possible; and (2) no additional measures that are reasonably available 
will advance the attainment date or contribute to RFP for the area. 
States should consider all available measures, including those being 
implemented in other areas, but must adopt measures for an area only if 
those measures are economically and technologically feasible and will 
advance the attainment date or are necessary for RFP.
    The EPA provided guidance interpreting the RACM requirements of 
section 172(c)(1) in the General Preamble for Implementation of Title I 
of the CAA of 1990.\37\ The EPA explained that states should consider 
all potentially available measures to determine whether they are 
reasonably available for implementation in the area, and whether they 
will advance the attainment date. Id. Potentially available measures 
that would not advance the attainment date for an area are not 
considered RACM; likewise, states can reject potential RACM if adopting 
them would cause substantial widespread and long-term adverse impacts. 
Id. Local conditions, such as economics or implementation concerns, may 
also be considered. To allow the EPA to determine whether the RACM 
requirement has been satisfied, states should provide in the SIP 
submittals a discussion of whether measures ``within the arena of 
potentially reasonable measures'' are in fact reasonably available.\38\ 
If the measures are reasonably available, they must be adopted as RACM.
---------------------------------------------------------------------------

    \37\ General Preamble, 57 FR 13498, 13560 (April 16, 1992).
    \38\ ``Guidance on the Reasonably Available Control Measures 
(RACM) Requirement and Attainment Demonstration Submissions for 
Ozone Nonattainment Areas,'' John S. Seitz, Director, Office of Air 
Quality Planning and Standards, EPA (Nov. 30, 1999).
---------------------------------------------------------------------------

2. Evaluation
    To demonstrate that the area meets the RACM requirement, Colorado 
identified potentially available control measures with input from 
stakeholders and analyzed whether the measure would be considered a 
RACM measure. In 2011, the RAQC issued a Report to the Governor that 
identified and evaluated potential control strategies. Later in 2011, 
the RAQC and CDPHE evaluated control measures for all source categories 
that could be implemented over the next five years and included them in 
a report to the RAQC Board in November 2011. Since 2011, Colorado has 
adopted oil and gas regulations, implemented Clean Air--Clean Jobs Act 
\39\ controls through the Regional Haze SIP, and continued alternative 
fuels, transportation, and land use programs. In May 2015, the RAQC 
reconvened discussions with the CDPHE and other partners to review 
control strategies for the 2008 ozone SIP as well as future SIPs. Three 
subcommittees made up of RAQC Board members were assembled. Areas of 
analysis included stationary/areas sources, mobile sources/fuels, and 
transpiration/land use/pricing/outreach. Subcommittee meetings were 
open to the public, and stakeholders provided input on the topics 
discussed.
---------------------------------------------------------------------------

    \39\ Colo. Rev. Stat. Sec.  40-3.2-201 et seq.
---------------------------------------------------------------------------

    Colorado determined that all control measures necessary to 
demonstrate attainment are currently being implemented. Table 43 of 
Colorado's OAP lists control measures included in Colorado's SIP as 
they relate to the State's 2017 emissions inventory, photochemical 
modeling in the attainment demonstration, and weight of evidence 
analysis. As discussed in Chapter 7.3.2 of the OAP, the AQCC adopted 
modifications to Reg. No. 11 to incorporate the portions of Larimer and 
Weld Counties that are within the DMNFR nonattainment area into 
Colorado's I/M program. This change was submitted as a SIP revision and 
is being acted on in this action (see section J of this notice). 
Additionally, Chapter 7.3.5.1. describes SIP-strengthening revisions 
made to Colorado's oil and gas control program in Reg. No. 7 (see 
section N of this notice). These revisions include adoption of two 
``state-only'' provisions into the Ozone SIP, pertaining to (1) auto-
igniter requirements for combustion devices; and (2) audio, visual, and 
olfactory inspection of storage tanks and associated equipment.
    As part of the RACM analysis, CDPHE examined emission reduction 
measures (see Table 44 of the OAP) being implemented in the DMNFR area 
that are not included in the SIP modeling and emissions inventory 
because they are voluntary or difficult to quantify. Non-federally-
enforceable emission reduction measures were evaluated for stationary 
and mobile sources, lawn and garden, outreach and education, and the 
transportation system. Additionally, Colorado evaluated CAA 108(f), 42 
U.S.C. 7408(f) transportation measures (see Table 48 of the OAP) to 
determine whether sources have applied RACM.
    Emission measures that were evaluated but determined not to be RACM 
are discussed in Chapter 7.5 of the OAP. Colorado used the following 
criteria to determine whether measures were considered RACM:
     Necessary to demonstrate attainment;
     Technologically or economically feasible;
     Implemented successfully in other Moderate areas;

[[Page 14817]]

     Could be implemented by January 1, 2017; and
     Could qualify as SIP measures by being quantifiable, 
enforceable, permanent, and surplus.
    Emission reduction measures evaluated for RACM were broken into 
area sources, on-road mobile sources, non-road mobile sources, fuels, 
transportation, alternative transportation, and land use categories. 
Tables 50 and 51 of the OAP summarizes the measures evaluated and 
Colorado's RACM determination for each measure. Colorado also reviewed 
the EPA's Menu of Control Measures for NAAQS Implementation \40\ and 
voluntary and mandatory control measures in other ozone nonattainment 
areas. Table 53 of the OAP lists control measures identified, and 
indicates which measures were included in the State's RACM review. 
Although Colorado's analysis demonstrated that none of the additional 
measures identified met the criteria for RACM, the State plans to 
continue evaluating strategies in various areas including fuels, on- 
and off-road vehicles, and land use.
---------------------------------------------------------------------------

    \40\ The Menu of Control Measures gives state, local and tribal 
air agencies information on existing emissions reduction measures, 
as well as relevant information concerning the efficiency and cost 
effectiveness of the measures. Available at https://www.epa.gov/air-quality-implementation-plans/menu-control-measures-naaqs-implementation.
---------------------------------------------------------------------------

    In its analysis, Colorado evaluated all source categories that 
could contribute meaningful emission reductions, and identified and 
evaluated an extensive list of potential control measures. To determine 
reasonableness and availability, the State considered the time needed 
to develop and adopt regulations, and the time it would take to see the 
benefit from these measures. The EPA has reviewed the RACM analysis and 
finds that there are no additional RACM that would advance the Moderate 
area attainment date of 2018 for the DMNFR nonattainment area. 
Therefore, the EPA proposes to approve Colorado's Moderate area RACM 
SIP for the DMNFR Moderate nonattainment area.

J. Motor Vehicle Inspection and Maintenance Program (I/M) Program

1. Background
    As a Moderate ozone nonattainment area, Colorado is required to 
implement an I/M program. Colorado's Reg. No. 11 is entitled ``Motor 
Vehicle Emissions Inspection Program'' and addresses the implementation 
of the State's I/M program. Under Reg. No. 11 and state law (5 CCR 
1001-13), all eligible automobiles registered in the Automobile 
Inspection and Readjustment (AIR) program area (the current nine-county 
AIR program area is depicted in Chapter 8, Figure 27, page 8-3 of the 
OAP) are subject to periodic emissions inspection. Currently there is 
an exemption from emissions inspection requirements for the first seven 
model years. Thereafter, an On-Board-Diagnostics (OBD) vehicle computer 
inspection is conducted during the first two inspection cycles 
(vehicles 8 through 11 model years old). Vehicles older than 11 model 
years are given a dynamometer-based IM240 test for 1982 and newer 
light-duty gasoline vehicles \41\ and a two-speed idle test (TSI) \42\ 
for 1981 and older light-duty gasoline vehicles. To improve motorist 
convenience and reduce program implementation costs, the State also 
administers a remote sensing-based ``Clean Screen'' program component 
of the I/M program. Remote sensing is a method for measuring vehicle 
emissions, while simultaneously photographing the license plate, when a 
vehicle passes through infrared or ultraviolet beams of light. Owners 
of vehicles meeting the Clean Screen criteria are notified by the 
respective County Clerk that their vehicle has passed the motor vehicle 
inspection process and are exempt from their next regularly scheduled 
IM240 test.\43\
---------------------------------------------------------------------------

    \41\ See 40 CFR part 51, subpart S for a complete description of 
EPA's IM240 test. The IM240 test is essentially an enhanced motor 
vehicle emissions test to measure mass tailpipe emissions while the 
vehicle follows a computer generated driving cycle trace for 240 
seconds and while the vehicle is on a dynamometer.
    \42\ See 40 CFR part 51, subpart S for a complete description of 
EPA's two-speed idle test. The two-speed idle test essentially 
measures the mass tailpipe emissions of a stationary vehicle; one 
reading is at a normal idle of approximately 700 to 800 engine 
revolutions per minute (RPM) and one reading at 2,500 RPM.
    \43\ The Clean Screen program component of Reg. No. 11 was 
originally approved for implementation in the Denver area with the 
EPA's approval of the original Denver carbon monoxide (CO) 
redesignation to attainment and the related maintenance plan. See 66 
FR 64751 (Dec. 14, 2001). The Clean Screen criteria approved in 2001 
required two valid passing remote sensing readings, on different 
days or from different sensors and within a twelve-month period. 
Colorado revised Reg. No. 11 to expand the definition and 
requirements for a ``clean-screened vehicle'' to also include 
vehicles identified as low-emitting vehicles in the state-determined 
Low Emitting Index (LEI) that have one passing remote sensing 
reading, before the vehicle's registration renewal date. These 
improvements and other associated revisions to the Clean Screen 
program were approved by the EPA on October 21, 2016. 81 FR 72720.
---------------------------------------------------------------------------

2. Evaluation
    The AIR program and Reg. No. 11 were expanded into portions of 
Larimer and Weld counties in the Colorado 2009 Legislative session, 
with the passage of Senate Bill 09-003. The startup date of the I/M 
program in these two counties was November 1, 2010. The purpose of this 
expansion of the AIR program and Reg. No. 11 into portions of Larimer 
and Weld counties was to further reduce vehicle emissions of 
NOX and VOC ozone precursors in the 2008 8-hour ozone 
nonattainment area. The DMNFR was then only classified as a Marginal 
ozone nonattainment area, and an I/M program was not required in 
Larimer and Weld counties. Therefore, the State decided to make this 
portion of the I/M program, for these two counties, a ``State-only'' 
provision, and not to submit it as a SIP revision.
    With the reclassification of the DMNFR nonattainment area to 
Moderate for the 2008 8-hour ozone NAAQS, and in light of the 
associated CAA requirements, the State chose to submit the I/M program 
in Larimer and Weld counties into the federal SIP. Adding these 
requirements into the federal SIP required several minor revisions, 
which were adopted by the Colorado AQCC on November 17, 2016, and 
submitted to the EPA on May 31, 2017. These revisions involved changes 
to ``PART A: General Provisions, Area of Applicability, Schedules for 
Obtaining Certification of Emissions Control, Definitions, Exemptions, 
and Clean Screening/Remote Sensing.'' Specifically, definition number 
43 was modified to remove the notation that the ``North Front Range 
Area'' was a State-only program and not included in the SIP. In 
addition, Part A, section V, ``Expansion of The Enhanced Emissions 
Program to the North Front Range Area,'' was modified to remove the 
notation that the I/M program was only a State-only program for 
portions of Larimer and Weld counties and not part of the SIP. By 
making these changes to Part A of Reg. No. 11, and submitting them for 
approval by the EPA into the federal SIP, the State made the I/M 
program in portions of Larimer and Weld counties federally enforceable. 
Incorporating the formerly State-only portions of the I/M program into 
the SIP permitted Colorado to include the motor vehicle emissions 
reductions received from operation of the AIR program in these areas of 
Larimer and Weld counties in the DMNFR attainment demonstration.
    Based on our review and as discussed above, we propose approval of 
the submitted Reg. No. 11 SIP revisions.

[[Page 14818]]

K. Nonattainment New Source Review (NNSR)

1. Background
    As a Moderate ozone nonattainment area, Colorado is required to 
implement a nonattainment new source review (NNSR) program. Applicable 
NNSR requirements for ozone nonattainment areas are described in CAA 
section 182, 42 U.S.C. 7511a, and further defined in 40 CFR part 51, 
subpart I (Review of New Sources and Modifications). Under these 
requirements, new major sources and major modifications at existing 
sources must achieve the lowest achievable emission rate (LAER) and 
obtain emission offsets in an amount based on the specific ozone 
nonattainment classification. The emission offset ratio required for 
Moderate ozone nonattainment areas is 1.15 to 1. CAA section 182(b)(5), 
42 U.S.C. 7511a(b)(5).
2. Evaluation
    The Colorado SIP includes Regulation No. 3, Part D, Section V.A. 
(Concerning Major Stationary Source New Source Review and Prevention of 
Significant Deterioration, Requirements Applicable to Nonattainment 
Areas). This provision requires new major sources and major 
modifications at existing sources in the DMNFR area to comply with LAER 
and obtain emission offsets at the Moderate classification ratio of 
1.15 to 1. The EPA approved these provisions on January 25, 2016 (81 FR 
3963). In addition, in their OAP, Colorado recertified that the State's 
NNSR program is fully up to date with all requirements of the Marginal 
designation, including offset ratios of at least 1.1 to 1. Therefore, 
since the provisions in the Colorado SIP satisfy the CAA NNSR 
requirements for ozone nonattainment areas classified as Marginal and 
Moderate, we propose approval of this portion of the OAP.

L. Contingency Measures Plan

1. Background
    Nonattainment plan provisions must provide for the implementation 
of contingency measures. CAA section 172(c)(9), 42 U.S.C. 7502(c)(9). 
These are specific measures to provide additional emission reductions 
if a nonattainment area fails to make RFP, or to attain the NAAQS, by 
the applicable date. Contingency measures must take effect without 
further action by the state or the EPA. While the CAA does not specify 
the type of measures or quantity of emissions reductions required, the 
EPA has interpreted the CAA for purposes of the Ozone NAAQS to mean 
that contingency measures should provide additional emissions 
reductions of 3% of the adjusted base year inventory for the 
nonattainment area (or the state may implement contingency measures 
that achieve a lesser percentage that will make up the identified 
shortfall in RFP or attainment). Contingency measures may include 
federal measures and local measures already scheduled for 
implementation, as long as their emission reductions are in excess of 
those needed for attainment or to meet RFP in the nonattainment plan. 
The EPA interprets the CAA not to preclude a state from implementing 
such measures before they are triggered by a failure to meet RFP or 
failure to attain. For more information on contingency measures, see 
the General Preamble (57 FR at 13510) and the 2008 Ozone Implementation 
Rule (80 FR 12264, 12285).
2. Evaluation
    To meet the contingency measures requirement, the State identified 
specific measures that provide emissions reductions in excess of those 
needed for RFP and for attainment as contingency measures. See Chapter 
10, Tables 54 and 55 of the OAP. The submitted contingency measures 
consist of NOX reductions from two EGUs addressed in the 
Colorado Clean Air--Clean Jobs Act and previously adopted as part of 
the Colorado Regional Haze SIP. These two projects are: (1) The 
retirement of Valmont Unit 5, a 184 megawatt coal fired steam turbine 
located in Boulder County, and (2) switching the 352 MW coal fired 
steam turbine of Cherokee Unit 4 located in Adams County from coal to 
natural gas. The sources completed these projects by the end of 2017 
and they will result in an additional 11 tons per day of NOX 
reductions, equating to 3.4% of the 2011 base year NOX 
emissions inventory. Per EPA guidance for purposes of the Ozone NAAQS, 
contingency measures should achieve reductions of 3% of the baseline 
emissions inventory for the nonattainment area. The State's contingency 
measures therefore are consistent with Agency guidance, because they in 
fact result in more than 3% reductions over the relevant baseline. The 
purpose of the contingency measures is to provide for further emission 
reductions to make up the shortfall needed for RFP or for attainment, 
during the period in which the State and the EPA determine whether the 
nonattainment plan for the area needs further revision to achieve the 
NAAQS expeditiously.\44\
---------------------------------------------------------------------------

    \44\ See General Preamble, section III.A.3.c (57 FR 13498 at 
13511).
---------------------------------------------------------------------------

    The appropriateness of relying on already-implemented reductions to 
meet the contingency measures requirement has been addressed in two 
federal circuit court decisions. See Louisiana Environmental Action 
Network (LEAN) v. EPA, 382 F.3d 575, 586 (5th Cir. 2004), Bahr v. 
United States EPA, 836 F.3d 1218 (9th Cir. 2016), cert. denied, 199 L. 
Ed. 2d 525, 2018 U.S. LEXIS 58 (Jan. 8, 2018). The EPA believes that 
the language of section 172(c)(9) is ambiguous with respect to this 
issue, and that it is reasonable for the agency to interpret the 
statutory language to allow approval of already implemented measures as 
contingency measures, so long as they meet other parameters such as 
providing excess emissions reductions that the state has not relied 
upon to make RFP or for attainment in the nonattainment plan for the 
NAAQS at issue. Until the Bahr decision, under the EPA's longstanding 
interpretation of CAA section 172(c)(9), states could rely on control 
measures that were already implemented (so called ``early triggered'' 
contingency measures) as a valid means to meet the Act's contingency 
measures requirement. The Ninth Circuit decision in Bahr leaves a split 
among the federal circuit courts, with the Fifth Circuit upholding the 
Agency's interpretation of section 172(c)(9) to allow early triggered 
contingency measures and the Ninth Circuit rejecting that 
interpretation. The Tenth Circuit, in which Colorado is located, has 
not addressed the issue, nor has the Supreme Court or any other circuit 
court other than the Fifth and Ninth.
    Because there is a split in the federal circuits on this issue, the 
EPA expects that states located in circuits other than the Ninth may 
elect to rely on the EPA's longstanding interpretation of section 
172(c)(9) allowing early triggered measures to be approved as 
contingency measures, in appropriate circumstances. The EPA's recently 
revised Regional Consistency regulations pertaining to SIP provisions 
authorize the Agency to follow this interpretation of section 172(c)(9) 
in Circuits other than the Ninth. See 40 CFR part 56. To ensure that 
early triggered contingency measures appropriately satisfy all other 
relevant CAA requirements, the EPA will carefully review each such 
measure, and intends to consult with states considering such measures 
early in the nonattainment plan development process.

[[Page 14819]]

    As shown in Table 55 of Colorado's OAP, the NOX 
reductions projected through 2018 are sufficient to meet the 
requirements for contingency measures, consistent with the EPA's 
interpretation of the CAA to allow approval of already implemented 
control measures as contingency measures in states outside the Ninth 
Circuit. Therefore, we propose approval of the contingency measure 
submitted by the state in the OAP.

M. Motor Vehicle Emissions Budget (MVEB)/Transportation Conformity

1. Background
    Transportation conformity is required by section 176(c) of the CAA, 
42 U.S.C. 7506. Conformity to a SIP means that transportation 
activities will not produce new air quality violations, worsen existing 
violations, or delay timely attainment of the NAAQS (CAA 176(c)(1)(B), 
42 U.S.C. 7506(c)(1)(B)). The EPA's conformity rule at 40 CFR part 93, 
subpart A requires that transportation plans, programs, and projects 
conform to SIPs, and establishes the criteria and procedures for 
determining whether or not they conform. The conformity rule requires a 
demonstration that emissions from the Metropolitan Planning 
Organization's (MPO) Regional Transportation Plan (RTP) and the 
Transportation Improvement Program (TIP) are consistent with the MVEB 
in the control strategy SIP revision or maintenance plan. 40 CFR 
93.101, 93.118, and 93.124. The MVEBs are defined as the portion 
allocated to mobile source emissions out of the total allowable 
emissions of a pollutant defined in the SIP for a certain date for the 
purpose of demonstrating attainment or maintenance of the NAAQS or for 
meeting reasonable further progress milestones.\45\
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    \45\ 40 CFR 93.101; see 40 CFR 93.118 and 93.124 for criteria 
and other requirements related to MVEBs. Further discussion of MVEBs 
is in the preamble to the transportation conformity rule. 58 FR 
62188, 62193-62196 (Nov. 24, 1993).
---------------------------------------------------------------------------

2. Evaluation
    Colorado derived the MVEBs for NOX and VOCs from its 
2017 DMNFR attainment demonstration, and defined the MVEBs in Chapter 
11, section 11.4 of the OAP.

                Table 8--2017 NOX and VOC MVEBs for DMNFR
------------------------------------------------------------------------
                                  2017 NOX emissions
      Area of applicability         (tons per day)    2017 VOC emissions
                                                        (tons per day)
------------------------------------------------------------------------
Northern Subarea................                  12                   8
Southern Subarea................                  61                  47
                                 ---------------------------------------
    Total Nonattainment Area....                  73                  55
------------------------------------------------------------------------

    These MVEBs are consistent with, and clearly related to, the 
emissions inventory and the control measures in the SIP; are consistent 
(when considered together with all other emissions sources) with 
attainment of the 2008 8-hour ozone NAAQS in 2017; and satisfy the 
minimum criteria at 40 CFR 93.118(e)(4). Therefore, we propose approval 
of the MVEBs as reflected in Table 8. This proposed approval applies to 
the Northern Subarea and Southern Subarea MVEBs as well as the Total 
Nonattainment Area MVEBs. The transportation conformity subareas are 
defined in Chapter 11, section 11.3 of the OAP and are listed below.
     The Northern Subarea is the area denoted by the ozone 
nonattainment area north of the Boulder County northern boundary and 
extended through southern Weld County to the Morgan County line. This 
area includes the North Front Range MPO's (NFRMPO) regional planning 
area as well as part of the Upper Front Range Transportation Planning 
Region (TPR) in Larimer and Weld counties.
     The Southern Subarea is the area denoted by the ozone 
nonattainment area south of the Boulder County northern boundary and 
extended through southern Weld County to the Morgan County line. This 
area includes the nonattainment portion of the Denver Regional Council 
of Governments (DRCOG) regional planning area and the southern Weld 
County portion of the Upper Front Range TPR.
     Both subareas are further described in the OAP in Figure 
29, ``8-hour Ozone Nonattainment Area Subareas.''
    In addition to proposing approval of the MVEBs, we also propose to 
approve the process described in Chapter 11, section 11.6 in the OAP 
for the use of the Total Nonattainment Area MVEBs or the subarea MVEBs 
for the respective MPOs to determine transportation conformity for 
their respective RTP. As described in section 11.6 of Colorado's OAP, 
the OAP identifies subarea MVEBs for DRCOG and the NFRMPO. These SIP-
identified subarea MVEBs allow either MPO to make independent 
conformity determinations for the applicable subarea MVEBs whose 
frequency and timing needs for conformity determinations differ. As 
noted in section 11.6, DRCOG and the NFRMPO may switch from using the 
Total Nonattainment Area MVEBs to using the subarea MVEBs for 
determining conformity. To switch to use of the subarea MVEBs (or to 
subsequently switch back to use of the Total Nonattainment Area MVEBs) 
DRCOG and the NFRMPO must use the process described in the DMNFR OAP in 
section 11.6 (see pages 11-5 and 11-6). This process of demonstrating 
transportation conformity to the total or subarea area MVEBs, as 
described in section 11.6 of the OAP, was previously approved by the 
EPA for the Denver Ozone Plan for the 1997 8-hour ozone NAAQS (76 FR 
47443, Aug. 5, 2011). Now, as to the 2008 8-hour standard, the EPA 
finds that this process remains consistent with the CAA and with 
applicable EPA regulations, and therefore proposes to approve it.

N. SIP Control Measures

1. Background
    This section describes revisions to Colorado Reg. No. 7 submitted 
as a part of the SIP, including emission control requirements for oil 
and gas operations, graphic arts and printing processes, stationary and 
portable engines, and other combustion equipment. The revisions also 
establish RACT requirements for emission points at major sources of VOC 
and NOX in the DMNFR area.

[[Page 14820]]

    Reg. No. 7 contains various requirements intended to reduce 
emissions of ozone precursors. These are in the form of specific 
emission limits applicable to various industries and general RACT 
requirements.\46\ The EPA approved the repeal and re-promulgation of 
Reg. No. 7 in 1981 (46 FR 16687, March 13, 1981) and has approved 
various revisions to parts of Reg. No. 7 over the years. In 2008, the 
EPA approved revisions to the control requirements for condensate 
storage tanks in Section XII (73 FR 8194, Feb. 13, 2008). The EPA later 
approved revisions to Reg. No. 7, Sections I through XI and Section 
XIII through XVI (76 FR 47443, Aug. 5, 2011). Most recently, the EPA 
approved Reg. No. 7 revisions to control emissions from rich burn 
reciprocating internal combustion engines in Section XVII.E.3.a (77 FR 
76871, Dec. 31, 2012).
---------------------------------------------------------------------------

    \46\ On October 20, 2016, the EPA issued final CTGs for existing 
sources in the oil and natural gas industry (see https://www.epa.gov/sites/production/files/2016-10/documents/2016-ctg-oil-and-gas.pdf). In accordance with the timing set forth in the CTG, 
Colorado has two years from this date (October 20, 2018) to submit 
SIP revisions to EPA to update RACT for this source category (see 
Memo: Implementing Reasonably Available Control Technology 
Requirements for Sources Covered by the 2016 Control Techniques 
Guidelines for the Oil and Natural Gas Industry, available within 
the docket for this action).
---------------------------------------------------------------------------

    Colorado submitted proposed revisions to Reg. No. 7 on May 5, 2013, 
and submitted revised Reg. No. 7 revisions with the OAP on May 31, 
2017. The 2017 revisions address EPA concerns about the May 5, 2013 
submittal regarding monitoring, recordkeeping, and reporting 
requirements in Sections XII.H.5 and XII.H.6 and other concerns in 
Sections XII.C.1.c, XII.C.1.d, XII.C.2.a.(ii)(B), XII.E.3, and XII.H.4. 
The May 31, 2017 submittal also includes changes to Reg. No. 7 
regarding RACT requirements for lithographic and letterpress printing, 
industrial cleaning solvents, and major sources of VOCs or 
NOX. Colorado made substantive revisions to certain limited 
parts of Reg. No. 7, particularly Sections X, XII, XIII, XVI and new 
Section XIX., and also made non-substantive revisions to numerous parts 
of the regulation. For ease of review, Colorado submitted the full text 
of Reg. No. 7 as a SIP revision (with the exception of provisions 
designated ``State Only''). The EPA is only seeking comment on 
Colorado's proposed substantive changes to the SIP-approved version of 
Reg. No. 7, which are described below. We are not seeking comment on 
incorporation into the SIP of the revised portions of the regulation 
that were previously approved into the SIP and have not been 
substantively modified by the State as part of this submission.
    As noted above, Colorado designated various parts of Reg. No. 7 
``State Only'' and in Section I.A.1.c indicated that sections 
designated State Only are not federally enforceable. The EPA concludes 
that provisions designated State Only have not been submitted for EPA 
approval, but for informational purposes. Hence, the EPA is not 
proposing to act on the portions of Reg. No. 7 designated State Only 
and this proposed rule does not discuss them further except as relevant 
to discussion of the portions of the regulation that Colorado intended 
to be federally enforceable.
2. Evaluation
a. Analysis of Reg. No. 7 Changes in May 5, 2013 Submittal
    The EPA proposes to approve the changes made to Section XII.D 
(currently SIP-approved Section XII.A.2) with Colorado's May 5, 2013 
submission.\47\
---------------------------------------------------------------------------

    \47\ All other sections of Reg. No. 7 addressed in the May 5, 
2013 submission have been superseded by the State's May 31, 2017 
submission. The EPA is not acting on the superseded earlier 
submissions.
---------------------------------------------------------------------------

(i) Section XII.D
    Section XII.D contains an introductory statement regarding the 
control requirements for atmospheric condensate storage tanks. The 
changes to current SIP-approved Section XII.A.2 are minor and do not 
change the substance of the corresponding EPA-approved provisions.
a. Section XII.D.2.a
    Section XII.D.2.a contains the system-wide control requirements for 
condensate storage tanks. Owners and operators of storage tanks that 
emit greater than two tons per year of actual uncontrolled VOCs are 
subject to the requirements in Section XII.D.2.a. The current SIP 
provides for a weekly 75% system-wide VOC reduction during the summer 
ozone season beginning May 1, 2007, and 78% beginning May 1, 2012. The 
revised section significantly increases the summer ozone season weekly 
VOC reduction requirements from the current EPA-approved requirements, 
to 85% beginning in 2010 (revised Section XII.D.2.a.(ix)) and 90% 
beginning May 1, 2011, and each year thereafter (revised Section 
XII.D.2.a.(x)). The revised Section XII.D.2.a provides more stringent 
emission reductions than the current SIP and therefore serves to 
strengthen the SIP.
b. Analysis by Section of Reg. No. 7 Changes in May 31, 2017 Submittal
(i) Sections I, II, VI, VII, VIII, and IX
    The changes in these sections are clerical \48\ in nature and do 
not affect the substance of the requirements. Therefore, we propose to 
approve the changes.
---------------------------------------------------------------------------

    \48\ When we describe changes as clerical in this proposed 
action, we are referring to changes like section renumbering, 
alphabetizing of definitions, minor grammatical and editorial 
revisions, and changes in capitalization.
---------------------------------------------------------------------------

(ii) Section X
    Section X. regulates VOC emissions from the use of cleaning 
solvents. We will be acting on Section X revisions in a future action.
(iii) Section XII
    Section XII contains emission control requirements for VOCs from 
oil and gas operations. The State originally reorganized Section XII 
and included additional control requirements for condensate tanks in 
their June 18, 2009 SIP submittal. The EPA disapproved revisions to 
Reg. No. 7, Section XII in our August 5, 2011 rulemaking (76 FR 47443) 
because of deficiencies in Colorado's proposed revisions (see 75 FR 
42355, July 21, 2010). The State once again submitted proposed 
revisions to Section XII with their May 31, 2017 submissions. Table 9 
outlines the reorganization/renumbering in Colorado's proposed 
revisions to Section XII:

 Table 9--Reorganization/Renumbering in Colorado's Proposed Revisions to
                               Section XII
------------------------------------------------------------------------
                                Corresponding EPA-
Proposed section XII numbering   approved section         Subject
                                  XII numbering
------------------------------------------------------------------------
XII.A.........................  XII.A............  Applicability.
XII.A.1.......................  XII.A............  Applicability.
XII.A.1.a through d.(ii)......  XII.A.1.a through  Applicability.
                                 c.
XII.A.2.......................  XII.D.4..........  Exception to
                                                    applicability of oil
                                                    refineries.

[[Page 14821]]

 
XII.A.3.......................  None.............  Applicability for
                                                    natural gas-
                                                    processing plants
                                                    and certain natural
                                                    gas compressor
                                                    stations. Subject to
                                                    Section XII.G. and
                                                    XII.I.
XII.A.4.......................  None.............  Applicability for
                                                    certain glycol
                                                    natural gas
                                                    dehydrators, natural
                                                    gas compressor
                                                    stations, drip
                                                    stations, or gas
                                                    processing plants.
                                                    Only subject to
                                                    XII.B and XII.H.
XII.A.5.......................  XII.A.8..........  Exception to
                                                    applicability based
                                                    on uncontrolled
                                                    actual VOC emissions
                                                    threshold of 30 tons
                                                    per year.
XII.B.........................  None.............  Definitions specific
                                                    to section XII.
XII.B.1, 2, 3, 9, and 14......  XII.D.5, 8, 6, 1,  Definitions of
                                 and 9..            various terms.
XII.B.4, 5, 6, 7, 8, 10, 11,    None.............  Definitions of
 and 12.                                            various terms.
XII.C.........................  XII.D............  General provisions to
                                                    section XII.
XII.C.1.......................  None.............  General requirements
                                                    for air pollution
                                                    control equipment,
                                                    leaks.
XII.C.1.a.....................  XII.D.2.a........  General requirements
                                                    for operation/
                                                    maintenance of
                                                    control equipment.
XII.C.1.b.....................  XII.D.2.b........  General requirement
                                                    to minimize leakage
                                                    of VOCs.
XII.C.1.c.....................  XII.A.7 and        Air pollution
                                 XII.A.4.h.         control--equipment
                                                    control efficiency.
                                                    Failure to operate
                                                    and maintain control
                                                    equipment at
                                                    indicated locations
                                                    is a violation.
XII.C.1.d.....................  XII.D.2.c........  Requirements for
                                                    combustion devices.
XII.C.1.e.....................  None.............  State-only
                                                    requirements related
                                                    to combustion
                                                    devices.
XII.C.1.e.(iii)...............  None.............  Auto-igniter
                                                    requirements for
                                                    combustion devices.
XII.C.2 and XII.C.2.a.........  XII.D.3..........  Emission factors for
                                                    emission estimates.
XII.D.........................  XII.A.2..........  Emission control
                                                    requirements for
                                                    condensate tanks.
XII.D.2.a.(i) through (x).....  XII.A.2.a through  System-wide control
                                 h.                 requirements for
                                                    condensate storage
                                                    tanks.
XII.D.2.b.....................  XII.A.9..........  Alternative emission
                                                    control equipment.
XII.E.........................  XII.A.3..........  Monitoring.
XII.E.1.......................  None.............  Requirements for
                                                    control equipment
                                                    other than a
                                                    combustion device.
XII.E.2, XII.E.2.a and b......  XII.A.3.a and b..  Checks for combustion
                                                    devices.
XII.E.3.......................  XII.A.4.j........  Documentation of
                                                    inspections.
XII.E.3.a.-e..................  XII.A.3.c.-f.....  Requirements for the
                                                    weekly check.
XII.F.........................  XII.A.4 and        Recordkeeping and
                                 XII.A.5.           reporting
                                                    requirements.
XII.F.1 and 2.................  XII.A.10 and 11..  Marking of AIRS
                                                    numbers on tanks.
XII.F.3.......................  XII.A.4..........  Introductory language
                                                    for recordkeeping.
XII.F.3.a(i)..................  XII.A.4.a........  List of tanks and
                                                    production volumes.
XII.F.3.a(ii) and (iii).......  XII.A.4.b and c..  Listing of emission
                                                    factors and location
                                                    and control
                                                    efficiencies.
XII.F.3.a(iv).................  XII.A.4.d.i......  List weekly and
                                                    monthly production
                                                    values. Describes
                                                    how to determine the
                                                    averages.
XII.F.3.a(v)-(vii)............  XII.A.4.d.ii-iv..  List weekly and
                                                    monthly uncontrolled
                                                    actual and
                                                    controlled actual
                                                    emissions by tank
                                                    and system-wide.
                                                    List percent
                                                    reductions weekly
                                                    and monthly.
XII.F.3.a(viii)...............  XII.A.4.e........  Note any downtime and
                                                    account for it.
XII.F.3.a(ix)-(x).............  XII.A.4.f-g......  Maintaining and
                                                    mailing of
                                                    spreadsheet.
XII.F.3.b-d...................  XII.A.4.h-j......  Failure to have
                                                    control equipment as
                                                    indicated on spread
                                                    sheet is violation.
                                                    Retain spread sheets
                                                    for five years.
                                                    Maintain records of
                                                    inspections.
XII.F.4.......................  XII.A.5..........  Reporting for system-
                                                    wide requirements.
XII.F.4.a.....................  XII.A.5.a........  List tanks and
                                                    production volumes.
XII.F.4.b-c...................  XII.A.5.b-c......  List emission factor
                                                    and location and
                                                    control efficiency.
XII.F.4.d.....................  XII.A.5.d........  What different
                                                    reports must show
                                                    based on time of
                                                    year. Emissions from
                                                    individual tanks
                                                    must be included.
XII.F.4.e.....................  XII.A.5.e........  What different
                                                    reports must show
                                                    based on time of
                                                    year. Emissions
                                                    system-wide.
XII.F.4.f.....................  XII.A.5.f........  What different
                                                    reports must show
                                                    based on time of
                                                    year. Percent
                                                    reduction system-
                                                    wide.
XII.F.4.g.....................  XII.A.5.g........  Note shutdown of
                                                    control equipment
                                                    and account for same
                                                    in totals.
XII.F.4.h.....................  XII.A.5.h........  State whether
                                                    required reductions
                                                    were achieved.
XII.F.4.i.....................  XII.A.5.i........  Include any
                                                    information
                                                    requested by the
                                                    Division.
XII.F.4.j.....................  XII.A.5.j........  Retention period.
XII.F.4.k.....................  XII.A.5.k........  Additional reporting,
                                                    monthly reporting of
                                                    problems and
                                                    corrective actions.
XII.F.4.l.....................  XII.A.5.l........  Before ozone season,
                                                    identify tanks being
                                                    controlled to meet
                                                    system-wide control
                                                    requirements.
XII.F.5.......................  XII.A.6..........  Exemption from record-
                                                    keeping and
                                                    reporting
                                                    requirements for
                                                    natural gas
                                                    compressor stations
                                                    and drip stations
                                                    authorized to
                                                    operate pursuant to
                                                    a construction or
                                                    operating permit.
XII.G.........................  XII.B............  Requirements for gas
                                                    processing plants.
                                                    Introductory
                                                    statement.
XII.G.1.......................  XII.B.1..........  Part 60 leak
                                                    detection applies.
XII.G.2.......................  XII.B.2..........  Applicability of
                                                    control equipment.
XII.G.3.......................  XII.B.3..........  Compliance date for
                                                    existing plants.
XII.G.4.......................  XII.B.4..........  Compliance date for
                                                    new plants.

[[Page 14822]]

 
XII.H.1.......................  XII.C............  Requirements that
                                                    apply to vents from
                                                    gas-condensate-
                                                    glycol separators or
                                                    tanks on glycol
                                                    natural gas
                                                    dehydrators at an
                                                    oil and gas
                                                    exploration and
                                                    production
                                                    operation, natural
                                                    gas compressor
                                                    station, drip
                                                    station or gas-
                                                    processing plant.
XII.H.3.......................  XII.C............  Control requirements
                                                    application.
XII.H.3.b.....................  XII.C............  Control requirements
                                                    application.
XII.H.4.......................  None.............  Method for
                                                    calculating
                                                    emissions from
                                                    vents.
XII.H.5.......................  None.............  Monitoring and
                                                    recordkeeping
                                                    requirements for
                                                    glycol natural gas
                                                    dehydrators.
XII.H.6.......................  None.............  Reporting
                                                    requirements for
                                                    glycol natural gas
                                                    dehydrators.
XII.I.........................  .................  Natural gas
                                                    compressor and drip
                                                    station section XII
                                                    requirements
                                                    exemptions.
------------------------------------------------------------------------

    Section XII revises requirements for system-wide reductions in 
condensate storage tank VOC emissions. The current EPA-approved Section 
XII requires that uncontrolled actual condensate tank VOC emissions in 
the DMNFR area be reduced on a weekly basis during the summer ozone 
season by 75% system-wide beginning May 1, 2007, and 78% beginning May 
1, 2012. Revised Section XII (Section XII.D.2) requires an 81% system-
wide reduction in uncontrolled actual weekly condensate tank VOC 
emissions during the summer ozone season beginning May 1, 2009, an 85% 
reduction beginning May 1, 2010, and a 90% reduction beginning May 1, 
2011. Section XII proposed revisions also include combustion device 
auto-igniter requirements, a leak detection and repair (LDAR) program 
applicable to natural gas processing plants, and emission reductions 
from glycol natural gas dehydrators requirements. Below, we describe in 
detail Colorado's proposed revisions to Section XII and the basis for 
our proposed approval of such revisions.
a. Section XII.A
    Section XII.A defines the applicability of Section XII requirements 
and is consistent with the current EPA-approved applicability 
provisions in Section XII.
b. Section XII.B
    Section XII.B contains definitions specific to Section XII. The 
substance of the definitions in Sections XII.B.1, 2, 3, 9, 12, and 14 
is unchanged from the definitions contained in SIP approved Sections 
XII.D.1 and XII.D.5 through 9. The other definitions in revised Section 
XII.B define the following terms that are used in Section XII: Auto-
igniter, calendar week, condensate storage tank, downtime, existing, 
modified or modification, and new. The definitions are clear, 
straightforward, and accurate.
    The definition of existing is only pertinent to State-only 
provisions and thus has no meaning for our SIP action.
c. Section XII.C.1
    Section XII.C.1 contains general requirements for air pollution 
control equipment and prevention of leakage. Section XII.C.1.e includes 
a provision requiring all combustion devices installed on or after 
January 1, 2017, used to control emissions of VOCs to be equipped with 
an operational auto-igniter. This new provision strengthens Colorado's 
SIP. The remaining Section XII.C.1 revisions do not change the 
substance of the corresponding EPA-approved provisions.
d. Section XII.C.2
    Section XII.C.2 describes the emission factors to be used for 
estimating emissions and emissions reductions from condensate storage 
tanks under Section XII. In the current EPA-approved SIP (Sections 
XII.D.3.b and 3.b.i), the emission factors to be used are specified for 
condensate storage tanks at natural gas compressor stations, natural 
gas drip stations, and gas-condensate-glycol separators. In revised 
Sections XII.C.2.a.(ii) and a.(ii)(A), Colorado deleted the reference 
to gas-condensate-glycol separators. Revised Section XII.H still 
requires a 90 percent reduction in emissions at certain gas-condensate-
glycol separators. Emission calculation and monitoring and 
recordkeeping requirements established in XII.H.4, 5, and 6 provide for 
enforcement and compliance of emission reduction requirements in 
XII.H.1.
    At the EPA's request, Colorado deleted the EPA approval requirement 
in XII.C.2.a.(ii)(B). The EPA is not involved in formal approval of 
site-specific emission factors and the EPA was concerned with previous 
SIP-approved language in XII.D.b.3.ii, which allowed for default SIP 
approval if the EPA did not object within 30 days to a test method 
approved by the Division to determine an emission factor.
e. Section XII.D
    Section XII.D contains an introductory statement regarding the 
control requirements for atmospheric condensate storage tanks. The 
changes to current SIP-approved Section XII.A.2 are minor and do not 
change the substance of the corresponding EPA-approved provisions.
f. Section XII.D.2.a
    Section XII.D.2.a. contains the system-wide control requirements 
for condensate storage tanks and adds an introductory statement 
clarifying requirements for installing air pollution control equipment 
on condensate storage tanks to achieve reductions outlined in Sections 
XII.D.2.a.(i) through (x). The current SIP provides for a weekly 75% 
system-wide VOC reduction during the summer ozone season beginning May 
1, 2007, and 78% beginning May 1, 2012. The revised section 
significantly increases the summer ozone season weekly VOC reduction 
requirements from the current EPA-approved requirements, to 85% 
beginning in 2010 (revised Section XII.D.2.a.(ix)) and 90% beginning 
May 1, 2011, and each year thereafter (revised Section XII.D.2.a.(x)). 
The revised Section XII.D.2.a. provides more stringent emission 
reductions than the current SIP and therefore strengthens the SIP.
g. Section XII.D.2.b
    Section XII.D.2.b is a renumbered version of current EPA-approved 
Section XII.A.9. This section contains a process for approval of 
alternative emissions control equipment and pollution prevention 
devices and processes. Among other things, the section specifies 
requirements for public participation and EPA approval. Colorado did 
not change the substance

[[Page 14823]]

of this provision, but simply renumbered it from Section XII.A.9 to 
XII.D.2.b.
h. Section XII.E
    Section XII.E contains the monitoring requirements that are 
currently specified in EPA-approved Sections XII.A.3 and XII.A.4.j. 
Colorado retained the basic requirement for weekly inspections or 
monitoring. Colorado improved certain provisions. For example, under 
revised Section XII.E, an owner or operator must ensure not only that 
the control equipment is operating, but that it is operating properly. 
Revised Section XII.E.1 adds a requirement that owners or operators of 
control equipment other than a combustion device follow manufacturer's 
recommended maintenance and inspect the equipment to ensure proper 
maintenance and operation. Revised Section XII.E.3 (current XII.A.4.j) 
adds a requirement that the owner or operator document any corrective 
actions taken and the name of the individual performing the corrective 
actions resulting from a weekly inspection. Revised Sections XII.E.3.a 
through d. add the requirement that the owner or operator not only 
perform certain checks, but that the owner or operator document those 
checks. Revised Section XII.E.3.e adds a new requirement for owners or 
operators to conduct and document audio, visual, and olfactory 
inspections during liquids unloading events for tanks with uncontrolled 
actual emissions of VOCs equal to or greater than six tons per year. 
These provisions strengthen the SIP.
i. Section XII.F
    Section XII.F contains recordkeeping and reporting requirements 
that are currently in EPA-approved Sections XII.A.4 and XII.A.5. The 
recordkeeping requirements specify information that must be listed on a 
spreadsheet that owners/operators must maintain. Many of the provisions 
are identical to those in the current EPA approved SIP.
    In Sections XII.F.1 through 4, Colorado made a few substantive 
changes to the existing provisions. In revised Section XII.F.3, 
Colorado added a sentence requiring the owner or operator to track VOC 
reductions on a calendar weekly and calendar monthly basis to 
demonstrate compliance with system-wide VOC reduction requirements. 
Colorado also specified that owners/operators would need to use the 
Division-approved spreadsheet to track VOC emissions and reductions. 
These changes are reasonable and consistent with CAA requirements.
j. Section XII.F.3
    In revised Section XII.F.3.a(i), which requires the spreadsheet to 
list the condensate storage tanks subject to Section XII and the 
production volumes for each tank, Colorado specified that the 
spreadsheet must list monthly production volumes. Revised Section 
XII.F.3.a(iv) also requires the owner/operator to list the production 
volume for each tank as a weekly and monthly average based on the most 
recent measurement available and specifies the method for pro-rating 
that measurement over the weekly or monthly period.
    Revised Section XII.F.3.c requires owners/operators to retain a 
copy of each weekly and monthly spreadsheet for five years instead of 
the three years required by current EPA-approved Section XII.A.4.i. 
Revised Section XII.F.3.d requires owners/operators to maintain records 
of inspections required by Sections XII.C. and XII.E. for five years.
k. Section XII.F.4
    In revised Section XII.F.4, Colorado made minor changes to current 
EPA-approved reporting requirements. Revised Section XII.F.4.a requires 
the semiannual reports to list all condensate storage tanks subject to 
or used to comply with the system-wide reduction requirements, not just 
the tanks that are subject to such requirements. This reflects the 
change to the regulation that allows owners/operators to control tanks 
with emissions below the Air Pollutant Emission Notice (APEN) filing 
levels to meet the percent reduction requirement in Section XII.D.2. In 
revised Sections XII.F.4.d through f. Colorado clarified that the April 
30 reports must include the monthly emissions information and the 
November 30 reports must include the weekly emissions information. In 
revised Section XII.F.4.g, Colorado deleted the requirement in current 
EPA-approved Section XII.A.5.g that the owner/operator note in the 
report list ``the date the source believes the shutdown [of control 
equipment] occurred, including the basis for such belief.'' This 
deletion is reasonable because the owner/operator is not likely to be 
able to make an accurate estimate of the date the shutdown occurred, 
and, thus, the information is not likely to be meaningful in an 
enforcement context.
    In revised Section XII.F.4.h, Colorado clarified monthly versus 
weekly reporting requirements. In revised Section XII.F.4.j, Colorado 
increased the retention period for reports from 3 years to 5 years. 
These changes are consistent with CAA requirements.
l. Section XII.F.5
    Section XII.F.5 contains an exemption from Section XII's record-
keeping and reporting requirements for owners/operators of natural gas 
compressor stations (NGCSs) or natural gas drip stations (NGDSs) 
authorized to operate pursuant to a construction permit or Title V 
operating permit if certain conditions are met. In our August 5, 2011 
(76 FR 47443) proposed rulemaking, we expressed our concern with 
Colorado's removal of one of the conditions for this exemption 
contained in current EPA-approved Section XII.A.6. Colorado's current 
submission reinstates this exemption. Colorado therefore did not change 
the substance of this provision, but simply renumbered it from Section 
XII.A.6 to section XII.F.5, made minor typographical corrections, and 
updated section references.
m. Section XII.G
    Section XII.G specifies the control requirements applicable to gas 
processing plants and corresponds to current EPA-approved Section 
XII.B. The EPA-approved Section XII.B requires gas processing plants to 
meet the requirements in Section XII.B specifically applicable to such 
plants as well as the requirements in current EPA-approved Section 
XII.C, pertaining to certain still vents and vents from gas condensate-
glycol separators, and Section XVI, pertaining to emissions from 
stationary and portable engines. Revised Section XII.G requires gas 
processing plants to additionally comply with the requirements of 
revised Section XII.B, the definitions section, revised Sections 
XII.C.1.a and XII.C.1.b, which specify maintenance and design 
requirements for control equipment and the obligation to minimize 
leakage of VOCs to the atmosphere, and revised Section XII.H, which 
specifies control requirements for still vents and vents flash 
separators or flash tanks on glycol natural gas dehydrators located at 
oil and gas exploration and production operations, natural gas 
compressor stations, drip stations, or gas-processing plants. It 
appears that this change would strengthen the requirements applicable 
to gas-processing plants.
n. Section XII.G.1
    Section XII.G.1 specifies that NSPS leak detection and repair 
requirements apply regardless of the date of construction of the 
facility, and adds a reference to LDAR requirements in NSPS OOOO and 
OOOOa. Colorado made no substantive changes to this provision.

[[Page 14824]]

o. Section XII.G.2
    Section XII.G.2 is a renumbered and revised version of current EPA-
approved Section XII.B.2. This provision specifies the applicability 
threshold for installation of control equipment at gas processing 
plants and the efficiency requirement for the control equipment. The 
EPA approved current Section XII.B.2 on August 19, 2005 (70 FR 48652). 
In current EPA-approved Section XII.B.2, the requirement to install 
control equipment is triggered if condensate storage tank throughput 
exceeds ``APEN de minimis levels,'' as set in the State's Reg. No. 3, 
Part A, Section II.D. That regulation in turn specified that in 
attainment areas, the APEN requirement applied to sources with 
uncontrolled emissions of any criteria pollutant of less than two tons 
per year. For nonattainment areas, this de minimis threshold dropped to 
one ton per year. When the State submitted and the EPA approved section 
XII.B.2, the 8-hour ozone control area was still in attainment,\49\ and 
therefore the APEN de minimis level referenced in Section XII.B.2 was 
two tons per year.
---------------------------------------------------------------------------

    \49\ The 1997 8-hour ozone NAAQS nonattainment designation for 
the DMNFR became effective November 20, 2007 (72 FR 53952 and 53953, 
September 21, 2007).
---------------------------------------------------------------------------

    In 2008, along with renumbering section XII.B.2 to XII.G.2, 
Colorado revised the threshold in this provision to accurately reflect 
the original two-ton-per-year level.\50\ The two-ton threshold in 
revised Section XII.G.2, therefore, would capture the same tanks as 
were being captured at the time Section XII.B.2 was approved into the 
State's SIP, and would also provide clarity as to the SIP requirements 
by removing a cross-reference that is arguably ambiguous. We propose to 
find that the revised section XII.G.2 is approvable because it 
clarifies the applicability threshold for determining which condensate 
storage tanks are subject to control requirements.
---------------------------------------------------------------------------

    \50\ Colorado submitted this to the EPA as a SIP revision on 
July 18, 2009, but we disapproved the proposed revisions to section 
XII, including XII.G.2, with our August 11, 2011 rulemaking (76 FR 
47443). In our proposal, as to XII.G.2. we stated that our proposed 
disapproval rested in part on uncertainty about the effect of the 
change from ``APEN de minimis levels'' to ``greater than or equal to 
two tons per year,'' and in part on a revised control efficiency 
requirement that introduced a twelve-month averaging period. (75 FR 
42346, 42358, July 21, 2010). Colorado has since removed the twelve-
month averaging period, and as described in this notice we have 
concluded that the effect of the change to a specific two-ton-per-
year threshold has the effect of clarifying the SIP, not weakening 
it. Accordingly, we are proposing to find that this provision is 
approvable.
---------------------------------------------------------------------------

p. Section XII.G.3
    Section XII.G.3 specifies the compliance date for existing natural 
gas processing plants. Colorado did not change the substance of this 
provision.
q. Section XII.G.4
    Revised Section XII.G.4, which specifies the compliance date for 
new gas processing plants, adds a reference to Section XII.G. Colorado 
did not change the substance of this provision.
r. Section XII.H.1
    Section XII.H.1. specifies control requirements in current EPA-
approved Section XII.C. for still vents and vents from gas-condensate-
glycol separators on glycol natural gas dehydrators at oil and gas 
exploration and production operations, natural gas compressor stations, 
drip stations, or gas-processing plants. Colorado did not change the 
substance of this provision.
s. Section XII.H.3
    XII.H.3 specifies that control requirements in Sections XII.H.1 and 
2 apply where uncontrolled emissions of VOCs from glycol gas 
dehydrators are equal to or greater than one ton per year and the sum 
of actual uncontrolled emissions of VOCs from any single or grouping of 
glycol natural gas dehydrators at a single source is greater than 15 
tons per year. Revised Section XII.H clarifies current EPA-approved 
Section XII.C's applicability threshold for control requirements.
t. Section XII.H.4
    Section XII.H.4 adds a requirement for calculating emissions from 
still vents and vents from flash separators or flash tanks on glycol 
natural gas dehydrators to ensure the 90 percent VOC emission reduction 
requirements in XII.H.1 are achieved. This provision strengthens the 
SIP.
u. Section XII.H.5
    Section XII.H.5. adds monitoring and recordkeeping requirements for 
enforcement and compliance of emission reduction requirements in 
XII.H.1. XII.H.5.a requires owners and operators of natural gas 
dehydrators to check on a weekly basis that condensers and air 
pollution equipment control equipment are operating properly, and to 
document dates of inspections, problems observed, and descriptions and 
dates of corrective actions taken. XII.H.5.b requires owners and 
operators to check and document on a weekly basis that pilot lights on 
combustion devices are lit, that valves for piping gas to pilot lights 
are open, and to check for smoke. XII.H.5.c requires owners and 
operators to document any maintenance of the condenser or air pollution 
control equipment consistent with manufacturer specifications or good 
engineering practices, and XII.H.5.d requires owners or operators to 
retain records for a period of 5 years. Although there are requirements 
to check for and document any problems observed while inspecting 
condenser or air pollution control equipment, the State does not 
require any corrective action be taken to fix the problem. The EPA 
recommends the State add requirements for corrective action to be 
taken. However, even as is, the provision strengthens the SIP, and 
therefore the absence of a corrective action requirement within it does 
not form a basis for disapproval.
v. Section XII.H.6
    The reporting requirements included in section XII.H.6 support 
additional enforcement and compliance efforts in connection with the 
emission reduction requirements in XII.H.1. Under XII.H.6.a, owners or 
operators submit to the Division on a semiannual basis a list of glycol 
natural gas dehydrators subject to section XII.H, a list of condensers 
or air pollution control equipment used to control emissions of VOCs, 
and dates of inspections when condensers or air pollution control 
equipment was found not to be operating properly. This provision 
strengthens the SIP.
w. Section XII.I
    Section XII.I is entirely new. It adds an exemption from the 
otherwise applicable requirements of Section XII for an owner or 
operator of any natural gas compressor station or natural gas drip 
station, but only if the owner or operator applies control equipment 
designed to achieve a VOC control efficiency of at least 95% to each 
condensate storage tank or tank battery with uncontrolled VOC emissions 
greater than or equal to two tons per year and meets certain other 
requirements. This is more stringent than the system-wide requirement 
because it requires 95% control at each tank or tank battery over the 
threshold rather than a maximum of 90% control system-wide. 
Recordkeeping and reporting requirements in XII.I.4 provide for 
enforcement and compliance of emission reduction requirements in XII.I. 
This provision strengthens the SIP.
    Based on our analysis of Section XII changes, we find that 
revisions are clerical in nature, do not change the substance of 
currently approved SIP provisions, or are SIP strengthening provisions. 
The State has not yet submitted a RACT analysis for this

[[Page 14825]]

source category. Colorado has until October 27, 2018, to submit SIP 
revisions to address requirements of the EPA's oil and gas CTG 
published in 2016 (see footnote 37 of this notice). We therefore we 
propose approving the changes in Section XII.
(iv) Section XIII
    Section XIII regulates VOC emissions from graphic arts and printing 
processes.
a. Sections XIII.A
    Changes to Section XIII.A are clerical in nature and do not affect 
the substance of the requirements.
b. Section XIII.B
    Section XIII.B addresses VOC emissions from the use of fountain 
solutions, cleaning materials, and inks at lithographic and letterpress 
printing operations. XIII.B.1 includes general provisions of the rule 
including definitions, applicability, and work practice requirements, 
and VOC content limits for inks. Section XIII.B.2 outlines requirements 
for cleaning materials used at offset lithographic printing and 
letterpress printing operations and exempted materials and operations. 
Section XIII.B.3 contains requirements for the use of fountain 
solutions at offset lithographic printing operations, sheet-fed 
printing operations, and for non-heatset web printing. Section XIII.B.4 
sets forth control requirements for heatset web offset lithographic and 
heatset web letterpress printing operations. Requirements include 
reducing VOC emissions from heatset dryers thorough an emission control 
system with a control efficiency of 90% or greater and 95% or greater 
for control devices installed on or after January 1, 2017. Section 
XIII.B.4.d outlines exemptions from control requirements in Section 
XIII.B.4. Finally, XIII.B.5 \51\ contains monitoring, recordkeeping, 
and reporting requirements for compliance with VOC emission reduction 
requirements in XIII.B.4. We find that the provisions are consistent 
with CAA requirements and CTGs, and that they strengthen the SIP.
---------------------------------------------------------------------------

    \51\ Section XIII.B.5. contains a numbering error. The State has 
committed to correcting the errors in Section XIII.B.5.a. in a 
subsequent SIP revision which are currently numbered 
``XIII.E.5.a.,'' ``XIII.E.5.b.,'' and ``XIII.E.5.c.''
---------------------------------------------------------------------------

    Therefore, we propose to approve the changes in Section XIII.
(v) Section XVI
    Section XVI specifies emission control requirements for stationary 
and portable engines and other combustion equipment.
a. Section XVI.A.-XVI.C
    Revisions in Sections XVI.A through XVI.C make grammatical changes 
and update references to section numbers. Colorado did not change the 
substance of this provision.
b. Section XVI.D
    Section XVI.D. adds a combustion adjustment requirement for 
individual pieces of combustion equipment at major sources of 
NOX in Section XVI.D. The requirements in Section XVI.D 
apply to some equipment that is not subject to work practices under the 
NESHAPs that have uncontrolled actual NOX emissions equal to 
or greater than 5 tpy. Sections XVI.D.2.a-d include inspection and 
adjustment requirements for boilers, process heaters, duct burners, 
stationary combustion turbines, and stationary internal combustion 
engines. Section XVI.D.2.e requires owners and operators to operate and 
maintain equipment subject to Section XVI.D consistent with 
manufacturer's specifications or good engineering and maintenance 
practices. Section XVI.D.2.f outlines combustion adjustment frequency 
requirements and Section XVI.D.3 includes recordkeeping requirements 
for owners and operators when implementing combustion process 
adjustments. Section XVI.D.4 sets forth alternative options to the 
requirements in Sections XVI.D.2.a-e and XVI.D.3.a including conducting 
combustion process adjustments according to manufacturer's recommended 
procedures and schedules, or conducting tune-ups or adjustments 
according to schedules and procedures of applicable NSPS or NESHAPs. We 
find that the provisions in Section XVI.D are consistent with Clean Air 
Act requirements and CTGs, and that they strengthen the SIP.
    For the reasons previously explained, we propose to approve the 
changes in Section XVI.
(vi) Section XIX
    Section XIX establishes RACT requirements for emission points at 
major sources of VOC and NOX in the DMNFR area. We will be 
acting on Colorado's RACT demonstration for major sources and revisions 
to Section XIX in a future rulemaking.

V. Proposed Action

    We propose to approve the SIP submittal from the State of Colorado 
for the DMNFR ozone nonattainment area submitted on May 31, 2017. 
Specifically, we propose to approve the following:
     Attainment demonstration with weight of evidence analysis 
for the 2008 ozone NAAQS;
     Base and future year emissions inventories;
     RFP Demonstration;
     Demonstration of RACT for VOC CTG sources (except for the 
following CTG source categories as to which we are not taking any 
action at this time: Metal Furniture Coatings, 2007; Miscellaneous 
Metal Products Coatings, 2008; Wood Furniture Manufacturing Operations, 
1996; Industrial Cleaning Solvents, 2006; Aerospace, 1997; and Oil and 
Natural Gas Industry, 2016.);
     Demonstration of RACM implementation;
     Motor vehicle I/M program revisions in Colorado's Reg. No. 
11;
     NNSR program;
     Contingency measures plan;
     MVEBs; and
     Revisions to Colorado's Reg. No. 7 (except for revisions 
to Reg. No. 7, Section X pertaining to VOC controls of industrial 
cleaning solvents and Reg. No. 7, Section XIX revisions pertaining to 
RACT requirements for major sources as to which we are not taking any 
action).
    We also propose to approve SIP revisions to Reg. No. 7 submitted by 
the State on May 13, 2013, except for provisions that have been 
superseded by later submissions, as to which we are not taking any 
action. We propose these actions in accordance with section 110 and 
part D of the CAA.

VI. Incorporation by Reference

    In this rule, the EPA is proposing to include in a final EPA rule 
regulatory text that includes incorporation by reference. In accordance 
with requirements of 1 CFR 51.5, the EPA is proposing to incorporate by 
reference Colorado Regulation Number 11 pertaining to regulation of the 
State's motor vehicle emissions inspection program and Colorado 
Regulation Number 7 pertaining to regulation of sources of VOC and 
NOX emissions discussed in section IV., J. Motor Vehicle 
Inspection and Maintenance Program (I/M) Program and N. SIP Control 
Measures of this preamble. The EPA has made, and will continue to make, 
these materials generally available electronically through 
www.regulations.gov and in hard copy at the appropriate EPA office 
(please contact the person identified in the For Further Information 
Contact section of this preamble for more information).

[[Page 14826]]

VII. Statutory and Executive Order Reviews

    Under the Clean Air Act, the Administrator is required to approve a 
SIP submission that complies with the provisions of the Act and 
applicable federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). 
Thus, in reviewing SIP submissions, the 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 final action:
     Is not a significant regulatory action subject to review 
by the Office of Management and Budget under Executive Orders 12866 (58 
FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 2011);
     is not an Executive Order 13771 (82 FR 9339, February 2, 
2017) regulatory action because SIP approvals are exempted under 
Executive Order 12866;
     does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     is certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
     does not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
     does not have federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     is not an economically significant regulatory action based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
     is not subject to requirements of Section 12(d) of the 
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 
note) because application of those requirements would be inconsistent 
with the Clean Air Act; and
     does not provide the EPA with the discretionary authority 
to address, as appropriate, disproportionate human health or 
environmental effects, using practicable and legally permissible 
methods, under Executive Order 12898 (59 FR 7629, February 16, 1994).
    In addition, the SIP is not approved to apply on any Indian 
reservation land or in any other area where the 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, Carbon monoxide, 
Incorporation by reference, Intergovernmental relations, Greenhouse 
gases, Lead, Nitrogen dioxide, Ozone, Particulate matter, Reporting and 
recordkeeping requirements, Sulfur oxides, Volatile organic compounds.

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

    Dated: March 29, 2018
Douglas H. Benevento,
Regional Administrator, Region 8.
[FR Doc. 2018-06847 Filed 4-5-18; 8:45 am]
 BILLING CODE 6560-50-P