Approval and Promulgation of Air Quality Implementation Plans; State of Colorado; Second Ten-Year PM10, 78797-78802 [2013-31110]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 78, Number 249 (Friday, December 27, 2013)]
[Proposed Rules]
[Pages 78797-78802]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2013-31110]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2011-0834; FRL-9904-90-Region 8]


Approval and Promulgation of Air Quality Implementation Plans; 
State of Colorado; Second Ten-Year PM10 Maintenance Plan for 
Pagosa Springs

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
partially approve and partially disapprove State Implementation Plan 
(SIP) revisions submitted by the State of Colorado. On March 31, 2010, 
the Governor of Colorado's designee submitted to EPA a revised 
maintenance plan for the Pagosa Springs area for the National Ambient 
Air Quality Standards (NAAQS) for particulate matter with an 
aerodynamic diameter less than or equal to 10 microns 
(PM10). The State adopted the revised maintenance plan on 
November 19, 2009. As required by Clean Air Act (CAA) section 175A(b), 
this revised maintenance plan addresses maintenance of the 
PM10 standard for a second 10-year period beyond the area's 
original redesignation to attainment for the PM10 NAAQS. EPA 
is proposing to approve the revised maintenance plan with the exception 
of one aspect of the plan's contingency measures. EPA's proposed 
approval includes the revised maintenance plan's 2021 transportation 
conformity motor vehicle emissions budget for PM10. In 
proposing to approve the revised maintenance plan, we are proposing to 
exclude from use in determining that Pagosa Springs continues to attain 
the PM10 NAAQS, exceedances of the PM10 NAAQS 
that were recorded at the Pagosa Springs PM10 monitor on 
March 22, 2009, April 3, 2009, April 5, 2010, April 28, 2010, April 29, 
2010, May 11, 2010, and May 22, 2010 because the exceedances meet the 
criteria for exceptional events caused by high wind natural events. 
This action is being taken under sections 110 and 175A of the CAA.

DATES: Written comments must be received on or before January 27, 2014.

ADDRESSES: Submit your comments, identified by Docket number EPA-R08-
OAR-2011-0834, by one of the following methods:
     https://www.regulations.gov. Follow the on-line 
instructions for submitting comments.
     Email: olson.kyle@epa.gov.
     Fax: (303) 312-6064 (please alert the individual listed in 
the FOR FURTHER INFORMATION CONTACT section if you are faxing 
comments).
     Mail: Carl Daly, Director, Air Program, Environmental 
Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595 Wynkoop Street, 
Denver, Colorado 80202-1129.
     Hand Delivery: Carl Daly, Director, Air Program, 
Environmental Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595 
Wynkoop Street, Denver, Colorado 80202-1129. Such deliveries are only 
accepted Monday through Friday, 8:00 a.m. to 4:30 p.m., excluding 
Federal holidays. Special arrangements should be made for deliveries of 
boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-R08-OAR-
2011-0834. EPA's policy is that all comments received will be included 
in the public docket without change and may be made available online at 
https://www.regulations.gov, including any personal information 
provided, unless the comment includes information claimed to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Do not submit information that you 
consider to be CBI or otherwise protected through https://www.regulations.gov or email. The https://www.regulations.gov Web site 
is an ``anonymous access'' system, which means EPA will not know your 
identity or contact information unless you provide it in the body of 
your comment. If you send an email comment directly to EPA, without 
going through https://www.regulations.gov, your email address will be 
automatically captured and included as part of the comment that is 
placed in the public docket and made available on the Internet. If you 
submit an electronic comment, EPA recommends that you include your name 
and other contact information in the body of your comment and with any 
disk or CD-ROM you submit. If EPA cannot read your comment due to 
technical difficulties and cannot contact you for clarification, EPA 
may not be able to consider your comment. Electronic files should avoid 
the use of special characters, any form of encryption, and be free of 
any defects or viruses. For additional instructions on submitting 
comments, go to Section I. General Information of the SUPPLEMENTARY 
INFORMATION section of this document.
    Docket: All documents in the docket are listed in the https://www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in https://www.regulations.gov or in hard copy at the Air Program, U.S. 
Environmental Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595 
Wynkoop Street, Denver, Colorado 80202-1129. EPA requests that if at 
all possible, you contact the individual listed in the FOR FURTHER 
INFORMATION CONTACT section to view the hard copy of the docket. You 
may view the hard copy of the docket Monday through Friday, 8:00 a.m. 
to 4:00 p.m., excluding Federal holidays.

FOR FURTHER INFORMATION CONTACT: Kyle Olson, Air Program, U.S. 
Environmental Protection Agency, Region 8, Mailcode 8P-AR, 1595 Wynkoop 
Street, Denver, Colorado 80202-1129, (303) 312-6002, 
olson.kyle@epa.gov.

SUPPLEMENTARY INFORMATION: 

Definitions

    For the purpose of this document, we are giving meaning to certain 
words or initials as follows:

i. The words or initials Act or CAA mean or refer to the Clean Air 
Act, unless the context indicates otherwise.
ii. The initials APCD mean or refer to the Colorado Air Pollution 
Control Division.
iii. The initials AQCC mean or refer to the Colorado Air Quality 
Control Commission.

[[Page 78798]]

iv. The words CMB mean or refer to chemical mass balance.
v. The words Colorado and State mean or refer to the State of 
Colorado.
vi. The words EPA, we, us or our mean or refer to the United States 
Environmental Protection Agency.
vii. The initials MVEB mean or refer to motor vehicle emissions 
budget.
viii. The initials NAAQS mean or refer to National Ambient Air 
Quality Standard.
ix. The initials PM10 mean or refer to particulate matter with an 
aerodynamic diameter of less than or equal to 10 micrometers (coarse 
particulate matter).
x. The initials RTP mean or refer to the Regional Transportation 
Plan.
xi. The initials SIP mean or refer to State Implementation Plan.
xii. The initials TIP mean or refer to the Transportation 
Improvement Program.
xiii. The initials TSD mean or refer to technical support document.

Table of Contents

I. General Information
II. Background
III. What was the State's process?
IV. EPA's Evaluation of the Revised Pagosa Springs PM10 
Maintenance Plan
V. Proposed Action
VI. Statutory and Executive Order Reviews

I. General Information

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

II. Background

    The Pagosa Springs area was designated nonattainment for 
PM10 and classified as moderate by operation of law upon 
enactment of the CAA Amendments of 1990. See 56 FR 56694, 56705, 56736 
(November 6, 1991). EPA approved Colorado's nonattainment area SIP for 
the Pagosa Springs PM10 nonattainment area on May 19, 1994 
(59 FR 26126).
    On May 10, 2000, the Governor of Colorado submitted a request to 
EPA to redesignate the Pagosa Springs moderate PM10 
nonattainment area to attainment for the 1987 PM10 NAAQS. 
Along with this request, the State submitted a maintenance plan, which 
demonstrated that the area was expected to remain in attainment of the 
PM10 NAAQS through 2012. EPA approved the Pagosa Springs 
maintenance plan and redesignation to attainment on June 15, 2001 (66 
FR 32556).
    Eight years after an area is redesignated to attainment, CAA 
section 175A(b) requires the state to submit a subsequent maintenance 
plan to EPA, covering a second 10-year period.\1\ This second 10-year 
maintenance plan must demonstrate continued maintenance of the 
applicable NAAQS during this second 10-year period. To fulfill this 
requirement of the Act, the Governor of Colorado's designee submitted 
the second 10-year update of the PM10 maintenance plan to 
EPA on March 31, 2010 (hereafter, ``revised Pagosa Springs 
PM10 Maintenance Plan'').
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    \1\ In this case, the initial maintenance period described in 
CAA section 175A(a) was required to extend for at least 10 years 
after the redesignation to attainment, which was effective on August 
14, 2001. See 66 FR 32556. Therefore, the first maintenance plan was 
required to show maintenance through 2011. CAA section 175A(b) 
requires that the second 10-year maintenance plan maintain the NAAQS 
for ``10 years after the expiration of the 10-year period referred 
to in [section 175A(a)].'' Thus, for the Pagosa Springs area, the 
second 10-year period ends in 2021.
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    As described in 40 CFR 50.6, the level of the national primary and 
secondary 24-hour ambient air quality standards for PM10 is 
150 micrograms per cubic meter ([mu]g/m\3\). An area attains the 24-
hour PM10 standard when the expected number of days per 
calendar year with a 24-hour concentration in excess of the standard 
(referred to herein as ``exceedance''), as determined in accordance 
with 40 CFR part 50, appendix K, is equal to or less than one, averaged 
over a three-year period.\2\ See 40 CFR 50.6 and 40 CFR part 50, 
appendix K.
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    \2\ An exceedance is defined as a daily value that is above the 
level of the 24-hour standard, 150 [micro]g/m\3\, after rounding to 
the nearest 10 [micro]g/m\3\ (i.e., values ending in five or greater 
are to be rounded up). Thus, a recorded value of 154 [micro]g/m\3\ 
would not be an exceedance since it would be rounded to 150 
[micro]g/m\3\; whereas, a recorded value of 155 [micro]g/m\3\ would 
be an exceedance since it would be rounded to 160 [micro]g/m\3\. See 
40 CFR part 50, appendix K, section 1.0.
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    Table 1 below shows the maximum monitored 24-hour PM10 
values for the Pagosa Springs PM10 maintenance area for 1998 
through 2012, excluding seven values the State flagged as being caused 
by exceptional events. The table reflects that most of the values for 
the Pagosa Springs area were below the PM10 NAAQS of 150 
[mu]g/m\3\. In 2000 the area experienced an exceedance measured at 165 
[mu]g/m\3\, and in 2009 exceedances measured at 182 and 188 [mu]g/
m\3\.\3\ These exceedances did not cause a violation of the 
PM10 NAAQS.
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    \3\ The State flagged the exceedance of 188 [mu]g/m\3\ from 
April 25, 2009 as being caused by an exceptional event but, due to 
an administrative oversight, did not demonstrate that it was caused 
by an exceptional event by the June 30, 2012 regulatory deadline 
(see 40 CFR 50.14). Thus, EPA was unable to concur on the flag for 
that exceedance. In addition, it is thought that the exceedance of 
182 [mu]g/m\3\ was recorded during a regional dust storm on April 8, 
2009 but that the site operator mistakenly gave the filter a date of 
April 6, 2009. Since this supposition could not be proved, the State 
was unable to flag the April 6 exceedance of 182 [mu]g/m\3\.
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    40 CFR 50.1(j) defines an exceptional event as an event which 
affects air quality, is not reasonably controllable or preventable, is 
an event caused by human activity that is unlikely to recur at a 
particular location or a natural event, and is determined by the 
Administrator in accordance with 40 CFR 50.14 to be an exceptional 
event. Exceptional events do not include stagnation of air masses or 
meteorological inversions, meteorological events involving high 
temperatures or lack of precipitation, or air pollution relating to 
source noncompliance. 40 CFR 50.14(b) states that EPA shall exclude 
data from use in determinations of exceedances and NAAQS violations 
where a state demonstrates to EPA's satisfaction that an exceptional 
event caused a specific air pollution concentration in excess of one or 
more NAAQS at a particular air quality monitoring location and

[[Page 78799]]

otherwise satisfies the requirements of section 50.14.
    On March 29 and 30, 2012, the State submitted exceptional events 
packages for two exceedances of the PM10 NAAQS in Pagosa 
Springs that measured 255 [mu]g/m\3\ on March 22, 2009, and 225 [mu]g/
m\3\ on April 3, 2009. On June 28, 2013, the State submitted four 
exceptional events packages for five exceedances of the PM10 
NAAQS in Pagosa Springs that measured 349 [mu]g/m\3\ on April 5, 2010, 
181 [mu]g/m\3\ on April 28, 2010, 162 [mu]g/m\3\ on April 29, 2010, 200 
[mu]g/m\3\ on May 11, 2010, and 187 [mu]g/m\3\ on May 22, 2010. The 
Colorado Air Pollution Control Division (APCD) flagged these seven 
exceedances as exceptional events in EPA's Air Quality System, which is 
EPA's repository for ambient air quality data. EPA concurred on the 
APCD's flags in August, September, and November of 2013 because the 
State successfully demonstrated that the exceedances were caused by 
natural high wind exceptional events blowing desert dust from upwind 
natural desert areas of Arizona, Utah, New Mexico, and southwest 
Colorado into the Pagosa Springs area. Thus, we are proposing to 
exclude from use in determining that Pagosa Springs continues to attain 
the 24-hour PM10 NAAQS the exceedances of the 24-hour 
PM10 NAAQS that were recorded at the Pagosa Springs 
PM10 monitor on the seven dates listed above. See 40 CFR 
50.14(b) and (c)(2)(ii).

  Table 1--Pagosa Springs PM10 Maximum 24-Hour Values (There Are Two 2001 Values Due to the Monitor Being Moved
  That Year From the Town Hall to High School Location) Based on Data From Town Hall and High School Monitoring
                                  Sites, AQS Identification Number 08-007-0001
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                                                                2nd Maximum
              Year                Maximum value ([mu]g/    concentration ([mu]g/          Monitoring site
                                          m\3\)                    m\3\)
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1998...........................                       66                       66  Town Hall.
1999...........................                      138                       82  Town Hall.
2000...........................                      165                       87  Town Hall.
2001...........................                      123                      121  Town Hall.
2001...........................                       66                       61  High School.
2002...........................                      107                       82  High School.
2003...........................                      123                      111  High School.
2004...........................                       79                       61  High School.
2005...........................                       82                       77  High School.
2006...........................                      122                       53  High School.
2007...........................                      102                       59  High School.
2008...........................                      149                       74  High School.
2009...........................                  \4\ 188                  \4\ 182  High School.
2010...........................                  \5\ 117                       73  High School.
2011...........................                      109                       81  High School.
2012...........................                      147                       93  High School.
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    Table 2 below shows the estimated number of exceedances for the 
Pagosa Springs PM10 maintenance area for the three-year 
periods of 1998 through 2000, 1999 through 2001, 2000 through 2002, 
2001 through 2003, 2002 through 2004, 2003 through 2005, 2004 through 
2006, 2005 through 2007, 2006 through 2008, 2007 through 2009, 2008 
through 2010, 2009 through 2011, and 2010 through 2012. To attain the 
standard, the three-year average number of expected exceedances (values 
greater than 150 [mu]g/m\3\) must be less than or equal to one. The 
table reflects continuous attainment of the PM10 NAAQS.
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    \4\ As noted above, it is believed that these two exceedances 
were impacted by regional dust storms in Pagosa Springs in 2009. 
Also, as noted above, exceedances that occurred on March 22 and 
April 3, 2009 were flagged by Colorado as exceptional events and 
received concurrence from EPA. Colorado also flagged a value of 100 
[mu]g/m\3\ that was recorded on March 29, 2009. A dust storm on that 
date caused one exceedance of the PM10 NAAQS elsewhere in 
western Colorado. However, the 100 [mu]g/m\3\ value in Pagosa 
Springs was not eligible for consideration under EPA's exceptional 
events rule because it was not an exceedance of the NAAQS. The 
highest two samples in 2009 not identified by Colorado to be 
impacted by regional dust storms were samples of 75 and 73 [mu]g/
m\3\.
    \5\ The 117 [mu]g/m\3\ value recorded on March 31, 2010 was 
flagged by Colorado as impacted by a regional dust storm. Since it 
was not an exceedance of the NAAQS, it was not eligible for 
consideration under EPA's exceptional events rule.

  Table 2--Pagosa Springs PM10 Estimated Exceedances Based on Data From
Town Hall and High School Monitoring Sites, AQS Identification Number 08-
                                007-0001
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                                                       3-Year estimated
                Design value period                       number of
                                                         exceedances
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1998-2000..........................................                 0
1999-2001..........................................                 0
2000-2002..........................................                 0.33
2001-2003..........................................                 0
2002-2004..........................................                 0
2003-2005..........................................                 0
2004-2006..........................................                 0
2005-2007..........................................                 0
2006-2008..........................................                 0
2007-2009..........................................                 0.7
2008-2010..........................................                 0.7
2009-2011..........................................                 0.7
2010-2012..........................................                 0
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III. What was the State's process?

    Section 110(a)(2) of the CAA requires that a state provide 
reasonable notice and public hearing before adopting a SIP revision and 
submitting it to EPA.
    The Colorado Air Quality Control Commission (AQCC) held a public 
hearing for the revised Pagosa Springs PM10 Maintenance Plan 
on November 19, 2009. The AQCC approved and adopted the revised Pagosa 
Springs PM10 Maintenance Plan during this hearing. The 
Governor's designee submitted the revised plan to EPA on March 31, 
2010.
    We have evaluated the revised maintenance plan and have determined 
that the State met the requirements for reasonable public notice and 
public hearing under section 110(a)(2) of the CAA. On September 30, 
2010, by operation of law under CAA section 110(k)(1)(B), the revised 
maintenance plan was deemed to have met the minimum ``completeness'' 
criteria found in 40 CFR part 51, appendix V.

[[Page 78800]]

IV. EPA's Evaluation of the Revised Pagosa Springs PM10 
Maintenance Plan

    The following are the key elements of a maintenance plan for 
PM10: Emission Inventory, Maintenance Demonstration, 
Monitoring Network/Verification of Continued Attainment, Contingency 
Plan, and Transportation Conformity Requirements/Motor Vehicle Emission 
Budget for PM10. Below, we describe our evaluation of these 
elements as they pertain to the revised Pagosa Springs PM10 
Maintenance Plan.

A. Emission Inventory

    The revised Pagosa Springs PM10 Maintenance Plan 
includes three inventories of daily PM10 emissions for the 
Pagosa Springs area, one for 2007 as the base year, one interim 
inventory for 2015, and one inventory for 2021 as the maintenance year. 
The APCD developed these emission inventories using EPA-approved 
emissions modeling methods and updated transportation and demographics 
data. Each emission inventory lists estimated PM10 emissions 
for individual source categories within the Pagosa Springs 
PM10 maintenance area. A more detailed description of the 
2007, 2015 and 2021 inventories and information on model assumptions 
and parameters for each source category are contained in the State's 
PM10 maintenance plan Technical Support Document (TSD). The 
inventories include the following source categories: Commercial 
cooking, construction, fuel combustion, non-road, structure fires, wood 
burning, unpaved road dust, paved road dust, highway vehicles, and 
agriculture. We find that Colorado has prepared adequate emission 
inventories for the area.

B. Maintenance Demonstration

    The revised Pagosa Springs PM10 Maintenance Plan uses 
emission roll-forward modeling combined with chemical mass balance 
(CMB) analysis to demonstrate maintenance of the 24-hour 
PM10 NAAQS through 2021. The State's CMB analysis examined 
the chemical composition of material on filters from Pagosa Springs air 
quality monitors to determine the relative contribution from the 
following source categories: Geologic, burning, nitrate, sulfate, and 
unknown. The State collected CMB data on five days in 1994, 2006, and 
2008 when ambient PM10 concentrations exceeded 100 [mu]g/
m\3\. The State then averaged the data for the source categories to 
create a ``design day apportionment'' for each category, as follows: 
Geologic--79.0%; burning--7.3%; nitrate--1.0%; sulfate--1.6%; and 
unknown--11.1%. After subtracting background (8 [mu]g/m\3\) from the 
design day concentration (102 [mu]g/m\3\),\6\ the State applied the CMB 
apportionments to apportion the design day concentration by source 
category. For example, the State apportioned 74.3 [mu]g/m\3\ of a total 
of 94 [mu]g/m\3\ to the geologic source category (94 [mu]g/m\3\ x 0.790 
= 74.3 [mu]g/m\3\).
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    \6\ Based on EPA guidance, the State determined the design day 
concentration to be the third highest 24-hour maximum 
PM10 value recorded in the Pagosa Springs area from 2006-
2008. It was recorded in 2007.
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    Using assumptions about the inventory source categories that 
contributed to the CMB categories, the State applied the percent change 
in emissions for the relevant inventory source categories between 2007 
and 2021 to ``roll-forward'' the CMB apportionments to 2021. For 
example, the State determined that the inventory source categories of 
unpaved road dust, paved road dust, and highway vehicles contribute all 
of the geologic emissions accounted for in the CMB analysis. The 
State's inventories reflect that emissions from these source categories 
are estimated to grow by 54.9% between 2007 and 2021. Applying this 
growth factor, the State estimated that the 74.3 [mu]g/m\3\ of 
PM10 resulting from geologic materials would grow to 115.1 
[mu]g/m\3\ in 2021.
    Applying this methodology, the State projected a total 
concentration of PM10 in 2021 of 146.3 [mu]g/m\3\, which 
includes background. This value is below the PM10 NAAQS of 
150 [mu]g/m\3\ and, thus, is consistent with maintenance.
    To account for new data acquired since the submission of the 
State's Plan, we evaluated the 2010-2012 data in AQS to determine 
whether maintenance would be demonstrated using a more recent design 
value as a starting point. Excluding the exceedances in 2010 that were 
caused by high wind exceptional events, the third high concentration in 
2010-2012 was 109 [mu]g/m\3\, which was recorded on March 21, 2011. As 
noted, the State's emissions inventories contain emissions estimates 
for 2007, 2015, and 2021. An examination of these inventories reveals 
that total emissions in 2015 represent a point on a line of near linear 
growth from 2007 to 2021.
    Acknowledging that the State's analysis is complete, we used a 
simpler total emissions roll-forward analysis rather than the CMB-
apportioned analysis the State used in projecting 2006-2008 data in 
order to estimate emissions growth from 2011 to 2021 and ensure that 
growth in emissions would result in PM10 remaining below the 
NAAQS. We did this to evaluate future maintenance in light of the 
somewhat higher 2010-2012 design value, compared to the 2006-2008 
design value Colorado evaluated. The total emissions roll-forward 
approach produces a higher projected concentration than does the 
State's CMB-apportioned method. We first removed the 8 [mu]g/m\3\ 
background concentration from the 109 [mu]g/m\3\, which left 101 [mu]g/
m\3\. Next, relying on the linear growth in emissions, we estimated 
2011 emissions would grow 32.9 percent by 2021.\7\ Using this factor, 
we projected the 101 [mu]g/m\3\ from 2011 forward to 2021 to arrive at 
a concentration of 134.2 [mu]g/m\3\. We then added the 8 [mu]g/m\3\ of 
background to this value to predict a total concentration in 2021 of 
142.2 [mu]g/m\3\. This value is below the PM10 NAAQS of 150 
[mu]g/m\3\ and, thus, is consistent with maintenance.
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    \7\ Total emissions in 2007 were 184.3 tons/year, while total 
emissions were projected to be 236.1 tons/year in 2015 and 282.1 
tons/year in 2021; these values are nearly collinear. Updating the 
roll forward for growth from a 2011 monitored value to 2021 requires 
a projection of the growth in emissions from 2011 to 2021. Linear 
emissions growth from 2007 to 2011 is (282.1 tons/year--184.3 tons/
year)*(2011-2007)/(2021-2007), or 27.9 tons, bringing 2011 emissions 
to (184.3 + 27.9) = 212.2 tons. Growth from 2011 to 2021, therefore, 
is (282.1 tons/year--212.24 tons/year)/212.2 tons/year * 100% = 
32.9%.
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C. Monitoring Network/Verification of Continued Attainment

    In the revised Pagosa Springs PM10 Maintenance Plan, the 
State commits to continue to operate an air quality monitoring network 
in accordance with 40 CFR part 58 and the EPA-approved Colorado 
Monitoring SIP Element to verify continued attainment of the 
PM10 NAAQS. This includes the continued operation of a 
PM10 monitor in the Pagosa Springs area, which the State 
will rely on to track PM10 emissions in the maintenance 
area. We are proposing to approve this commitment as satisfying the 
relevant requirements.

D. Contingency Plan

    Section 175A(d) of the CAA requires that a maintenance plan include 
contingency provisions to promptly correct any violation of the NAAQS 
that occurs after redesignation of an area. To meet this requirement 
the State has identified contingency measures along with a schedule for 
the development and implementation of such measures. The revised Pagosa 
Springs PM10 Maintenance Plan indicates that, upon 
notification of an exceedance of the PM10 NAAQS, the APCD 
and local government staff in the Pagosa Springs

[[Page 78801]]

area will develop appropriate contingency measures intended to prevent 
or correct a violation of the PM10 standard. According to 
the plan, notification to EPA and local governments of any exceedance 
will occur no later than 45 days and the process will be completed 
within six months of the notification. Upon a violation, a public 
hearing process at the State and local level will begin. The AQCC may 
endorse or approve local measures, or it may adopt State enforceable 
measures. The revised Pagosa Springs PM10 Maintenance Plan 
states that contingency measures will be adopted and fully implemented 
within one year of a violation.
    The State identifies the following as potential contingency 
measures in the revised Pagosa Springs PM10 Maintenance 
Plan: (1) Increased street sweeping requirements; (2) additional road 
paving requirements; (3) more stringent street sand specifications; (4) 
voluntary or mandatory coal and/or wood burning curtailment; (5) bans 
on all coal and/or wood burning; (6) expanded use of alternative de-
icers; (7) re-establishing new source review permitting requirements 
for stationary sources; (8) transportation control measures designed to 
reduce vehicle miles traveled; and (9) other emission control measures 
appropriate for the area based on the following considerations: cost 
effectiveness, PM10 emission reduction potential, economic 
and social concerns, and/or other factors.
    We find that the contingency measures provided in the revised 
Pagosa Springs PM10 Maintenance Plan are sufficient and meet 
the requirements of section 175A(d) of the CAA, with the exception of 
``voluntary coal and/or wood burning curtailment.'' While we have not 
required that potential contingency measures be effective without 
further action by the State, we interpret the CAA as requiring measures 
that will be enforceable. Voluntary measures may not be widely 
implemented and, thus, cannot be relied on to ensure prompt emission 
reductions to correct a violation. Thus, we are proposing to disapprove 
the listing of ``voluntary coal and/or wood burning curtailment'' as a 
potential contingency measure.

E. Transportation Conformity Requirements: Motor Vehicle Emission 
Budget for PM10

    Transportation conformity is required by section 176(c) of the CAA. 
EPA's conformity rule at 40 CFR part 93 requires that transportation 
plans, programs, and projects conform to SIPs and establishes the 
criteria and procedures for determining whether or not they conform. 
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. To effectuate its purpose, the 
conformity rule requires a demonstration that emissions from the 
Regional Transportation Plan (RTP) and the Transportation Improvement 
Program (TIP) are consistent with the motor vehicle emissions budget(s) 
(MVEB(s)) contained in a control strategy SIP revision or maintenance 
plan (40 CFR 93.101, 93.118, and 93.124). An MVEB is defined as the 
level of mobile source emissions of a pollutant relied upon in the 
attainment or maintenance demonstration to attain or maintain 
compliance with the NAAQS in the nonattainment or maintenance area. 
Further information concerning EPA's interpretations regarding MVEBs 
can be found in the preamble to EPA's November 24, 1993, transportation 
conformity rule (see 58 FR 62193-62196).
    The revised Pagosa Springs PM10 Maintenance Plan 
contains a single MVEB of 946 lbs/day of PM10 for the year 
2021, the maintenance year. Once the State submitted the revised plan 
with the 2021 MVEB to EPA for approval, 40 CFR 93.118 required that EPA 
determine whether the MVEB was adequate.
    Our criteria for determining whether a SIP's MVEB is adequate for 
conformity purposes are outlined in 40 CFR 93.118(e)(4), which was 
promulgated August 15, 1997 (see 62 FR 43780). Our process for 
determining adequacy is described in our July 1, 2004 Transportation 
Conformity Rule Amendments (see 69 FR 40004) and in relevant 
guidance.\8\ We used these resources in making our adequacy 
determination described below.
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    \8\ ``Companion Guidance for the July 1, 2004 Final 
Transportation Conformity Rule, Conformity Implementation in Multi-
Jurisdictional Nonattainment and Maintenance Areas for Existing and 
New Air Quality Standards'' (EPA420-B-04-012 July, 2004).
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    On November 22, 2010, EPA announced the availability of the revised 
Pagosa Springs PM10 Maintenance Plan, and the 
PM10 MVEB, on EPA's transportation conformity adequacy Web 
site. EPA solicited public comment on the MVEB, and the public comment 
period closed on December 22, 2010. We did not receive any comments. 
This information is available at EPA's conformity Web site: https://www.epa.gov/otaq/stateresources/transconf/reg8sips.htm#co
    By letter to the Colorado Department of Public Health and 
Environment dated March 17, 2011, EPA found that the revised Pagosa 
Springs PM10 Maintenance Plan and the 2021 PM10 
MVEB were adequate for transportation conformity purposes.\9\ However, 
we noted in our letter that the revised Pagosa Springs PM10 
Maintenance Plan did not discuss the PM10 MVEB for 2012 of 
7,486 lbs/day from the original PM10 maintenance plan that 
EPA approved in 2001 (see 66 FR 32556, June 15, 2001).
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    \9\ In a Federal Register notice dated August 2, 2011, we 
notified the public of our finding (see 76 FR 46288). This adequacy 
determination became effective on August 17, 2011.
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    According to 40 CFR 93.118(e)(1), the EPA-approved 2012 
PM10 MVEB must continue to be used for analysis years 2012 
through 2020 (as long as such years are within the timeframe of the 
transportation plan), unless the State elects to submit a SIP revision 
to revise the 2012 PM10 MVEB and EPA approves the SIP 
revision. The revised Pagosa Springs PM10 Maintenance Plan 
did not revise the previously-approved 2012 PM10 MVEB nor 
establish a new MVEB for 2012. Accordingly, the MVEB `` . . . for the 
most recent prior year . . . '' (i.e., 2012) from the original 
maintenance plan must continue to be used (see 40 CFR 93.118(b)(1)(ii) 
and (b)(2)(iv)).
    We note that there is a considerable difference between the 2021 
and 2012 budgets--946 lbs/day versus 7,486 lbs/day. This is largely an 
artifact of changes in the methods, models, and emission factors used 
to estimate mobile source emissions. The 2021 MVEB is consistent with 
the State's 2021 emissions inventory for vehicle exhaust and road dust, 
and, thus, is consistent with the State's maintenance demonstration for 
2021.
    The discrepancy between the 2012 and 2021 MVEBs is not a 
significant issue for several reasons. As a practical matter, the 2021 
MVEB of 946 lbs/day of PM10 would be controlling for any 
conformity determination involving the relevant years because 
conformity would have to be shown to both the 2012 MVEB and the 2021 
MVEB. Also, for any maintenance plan like the revised Pagosa Springs 
PM10 Maintenance Plan that only establishes a MVEB for the 
last year of the maintenance plan, 40 CFR 93.118(b)(2)(i) requires that 
the demonstration of consistency with the budget be accompanied by a 
qualitative finding that there are no factors that would cause or 
contribute to a new violation or exacerbate an existing violation in 
the years before the last year

[[Page 78802]]

of the maintenance plan. Therefore, when a conformity determination is 
prepared which assesses conformity for the years before 2021, the 2021 
MVEB and the underlying assumptions supporting it would have to be 
considered. Finally, 40 CFR 93.110 requires the use of the latest 
planning assumptions in conformity determinations. Thus, the most 
current motor vehicle and road dust emission factors would need to be 
used, and we expect the analysis would show greatly reduced 
PM10 motor vehicle and road dust emissions from those 
calculated in the first maintenance plan. In view of the above, EPA is 
proposing to approve the 2021 PM10 MVEB of 946 lbs/day.

V. Proposed Action

    We are proposing to approve the revised Pagosa Springs 
PM10 Maintenance Plan that was submitted to us on March 31, 
2010, with one exception. We are proposing to disapprove the listing of 
``voluntary coal and/or wood burning curtailment'' as a potential 
contingency measure in section 5.F.3 of the revised Pagosa Springs 
PM10 Maintenance Plan. We are proposing to approve the 
remainder of the revised maintenance plan because it demonstrates 
maintenance through 2021 as required by CAA section 175A(b), retains 
the control measures from the initial PM10 maintenance plan 
that EPA approved on June 15, 2001, and meets other CAA requirements 
for a section 175A maintenance plan. We are proposing to exclude from 
use in determining that Pagosa Springs continues to attain the 24-hour 
PM10 NAAQS exceedances of the 24-hour PM10 NAAQS 
that were recorded at the Pagosa Springs PM10 monitor on 
March 22, 2009, April 3, 2009, April 5, 2010, April 28, 2010, April 29, 
2010, May 11, 2010, and May 22, 2010 because they meet the criteria for 
exceptional events caused by high wind natural events. We are also 
proposing to approve the revised maintenance plan's 2021 transportation 
conformity MVEB for PM10 of 946 lbs/day.

VI. Statutory and Executive Orders Review

    Under the CAA, the Administrator is required to approve a SIP 
submission that complies with the provisions of the Act and applicable 
federal regulations. 42 U.S.C. 7410(k), 40 CFR 52.02(a). Thus, in 
reviewing SIP submissions, EPA's role is to approve state choices, 
provided that they meet the criteria of the CAA. This proposed action 
merely proposes to approve state law as meeting federal requirements 
and does not propose to impose additional requirements beyond those 
imposed by state law. For that reason, this proposed action:
     Is not a ``significant regulatory action'' subject to 
review by the Office of Management and Budget under Executive Order 
12866 (58 FR 51735, October 4, 1993);
     does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 USC 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 USC 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 USC 272 
note) because application of those requirements would be inconsistent 
with the CAA; and,
     does not provide EPA with the discretionary authority to 
address, as appropriate, disproportionate human health or environmental 
effects, using practicable and legally permissible methods, under 
Executive Order 12898 (59 FR 7629, February 16, 1994).

In addition, this proposed action does not have tribal implications as 
specified by Executive Order 13175 (65 FR 67249, November 9, 2000), 
because the SIP would not be approved to apply in Indian country 
located in the state, and EPA notes that it will not impose substantial 
direct costs on tribal governments or preempt tribal law.

List of Subjects in 40 CFR Part 52

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

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

    Dated: December 16, 2013.
Shaun L. McGrath,
Regional Administrator, Region 8.
[FR Doc. 2013-31110 Filed 12-26-13; 8:45 am]
BILLING CODE 6560-50-P