Approval and Promulgation of Air Quality Implementation Plans; State of Colorado; Denver Revised Carbon Monoxide Maintenance Plan

Note: EPA no longer updates this information, but it may be useful as a reference or resource.

[Federal Register: September 16, 2004 (Volume 69, Number 179)]
[Rules and Regulations]
[Page 55752-55759]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr16se04-8]

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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[RME Docket Number R08-OAR-2004-CO-0001; FRL-7813-3]

Approval and Promulgation of Air Quality Implementation Plans;
State of Colorado; Denver Revised Carbon Monoxide Maintenance Plan

AGENCY: Environmental Protection Agency (EPA).
ACTION: Direct final rule.

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SUMMARY: EPA is taking direct final action approving a State
Implementation Plan (SIP) revision submitted by the State of Colorado.
On October 15, 2003, the Governor of Colorado submitted a revised
maintenance plan for the Denver-Boulder metropolitan (hereafter,
Denver) carbon monoxide (CO) maintenance area for the CO National
Ambient Air Quality Standard (NAAQS). The revised maintenance plan also
contained a revised transportation conformity budget for the year 2013.
In this action, EPA is approving the Denver CO revised maintenance plan
and revised transportation conformity budget. This action is being
taken under section 110 of the Clean Air Act.

DATES: This rule is effective on November 15, 2004 without further
notice, unless EPA receives adverse comment by October 18, 2004. If
adverse comment is received, EPA will publish a timely withdrawal of
the direct final rule in the Federal Register informing the public that
the rule will not take effect.

ADDRESSES: Submit your comments, identified by RME Docket Number R08-
OAR-2004-CO-0001, by one of the following methods:
? Federal eRulemaking Portal: http://www.regulations.gov.
Follow the on-line instructions for submitting comments.
? Agency Web site: http://docket.epa.gov/rmepub/index.jsp.
Regional Materials in EDOCKET (RME), EPA's electronic public docket and
comment system for regional actions, is EPA's preferred method for
receiving comments. Follow the on-line instructions for submitting
comments.
? E-mail: long.richard@epa.gov and russ.tim@epa.gov.
? Fax: (303) 312-6064 (please alert the individual listed in
the FOR FURTHER INFORMATION CONTACT if you are faxing comments).
? Mail: Richard R. Long, Director, Air and Radiation
Program, Environmental Protection Agency (EPA), Region 8, Mailcode 8P-
AR, 999 18th Street, Suite 300, Denver, Colorado 80202-2466.
? Hand Delivery: Richard R. Long, Director, Air and
Radiation Program, Environmental Protection Agency (EPA), Region 8,
Mailcode 8P-AR, 999 18th Street, Suite 300, Denver, Colorado 80202-
2466. Such deliveries are only accepted Monday through Friday, 8 a.m.
to 4:55 p.m., excluding Federal holidays. Special arrangements should
be made for deliveries of boxed information.
Instructions: Direct your comments to RME Docket Number R08-OAR-
2004-CO-0001. EPA's policy is that all comments received will be
included in the public docket without change and may be made available
at http://docket.epa.gov/rmepub/index.jsp, 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 EDOCKET,
regulations.gov, or e-mail. EPA's Regional Materials in EDOCKET and
federal regulations.gov Web site are ``anonymous access'' systems,
which means EPA will not know your identity or contact information
unless you provide it in the body of your comment. If you send an e-
mail comment directly to EPA, without going through EDOCKET or
regulations.gov, your e-mail address will be automatically captured and
included as part of the comment that is placed in the public docket and
made available on the Internet. If you submit an electronic comment,
EPA recommends that you include your name and other contact information
in the body of your comment and with any disk or CD-ROM you submit. If
EPA cannot read your comment due to technical difficulties and cannot
contact you for clarification, EPA may not be able to consider your
comment. Electronic files should avoid the use of special characters,
any form of encryption, and be free of any defects or viruses. For
additional information about EPA's public docket visit EDOCKET online
or see the Federal Register of May 31, 2002 (67 FR 38102). 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 Regional
Materials in EDOCKET index at http://docket.epa.gov/rmepub/index.jsp.
Although listed in the index, some information is not publicly
available, i.e., CBI or other information whose disclosure is
restricted by statute. Certain other material, such as copyrighted
material, is not placed on the Internet and will be publically
available only in hard copy form. Publicly available docket materials
are available either electronically in Regional Materials in EDOCKET or
in hard copy at the Air and Radiation Program, Environmental Protection
Agency (EPA), Region 8, 999 18th Street, Suite 300, Denver, Colorado
80202-2466. EPA requests that if at all possible, you contact the
individual listed in the FOR FURTHER INFORMATION CONTACT section to
view the hard copy of the docket. You may view the hard copy of the
docket Monday through Friday, 8 a.m. to 4 p.m., excluding Federal
holidays.

FOR FURTHER INFORMATION CONTACT: Tim Russ, Air and Radiation Program,
Environmental Protection Agency

[[Page 55753]]

(EPA), Region 8, Mailcode 8P-AR, 999 18th Street, Suite 300, Denver,
Colorado 80202-2466, phone (303) 312-6479, and e-mail at:
russ.tim@epa.gov.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. General Information
II. What Is the Purpose of This Action?
III. What Is the State's Process To Submit These Materials to EPA?
IV. EPA's Evaluation of the Revised Maintenance Plan
V. EPA's Evaluation of the Transportation Conformity Requirements
VI. Consideration of Section 110(l) of the CAA
VII. Final Action
VIII. Statutory and Executive Order Reviews

Definitions

For the purpose of this document, we are giving meaning to certain
words or initials as follows:
(i) The words or initials Act or CAA mean or refer to the Clean Air
Act, unless the context indicates otherwise.
(ii) The words EPA, we, us or our mean or refer to the United
States Environmental Protection Agency.
(iii) The initials NAAQS mean National Ambient Air Quality
Standard.
(iv) The initials SIP mean or refer to State Implementation Plan.
(v) The word State means the State of Colorado, unless the context
indicates otherwise.

I. General Information

A. What Should I Consider as I Prepare My Comments for EPA?

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

II. What Is the Purpose of This Action?

In this action, we are approving a revised maintenance plan for the
Denver CO attainment/maintenance area, that is designed to keep the
area in attainment for CO through 2013, and we're also approving
revised transportation conformity motor vehicle emissions budgets
(MVEB). We approved the original CO redesignation to attainment and
maintenance plan for the Denver area on December 14, 2001 (see 66 FR
64751); our approval became effective on January 14, 2002.
The original Denver CO redesignation maintenance plan, approved on
December 14, 2001, utilized the then applicable EPA mobile sources
emission factor model, MOBILE5a. On January 18, 2002, we issued policy
guidance for States and local areas to use to develop SIP revisions
based on the new, updated version of the model, MOBILE6. The policy
guidance was entitled ``Policy Guidance on the Use of MOBILE6 for SIP
Development and Transportation Conformity'' (hereafter, January 18,
2002 MOBILE6 policy). On November 12, 2002, EPA's Office of
Transportation and Air Quality (OTAQ) issued an updated version of the
MOBILE6 model, called MOBILE6.2, and notified Federal, State, and local
agency users of this update. MOBILE6.2 contained additional updates for
air toxics and particulate matter. However, the CO emission factors
were essentially the same as in the MOBILE6 version of the model. The
State revised and updated the mobile sources CO emissions with
MOBILE6.2 for each of the three years assessed in the previously
approved maintenance plan (2001, 2006, and 2013), recalculated the CO
intersection levels using CAL3QHC, revised the MVEB, and also applied a
selected amount of the available safety margin to the transportation
conformity MVEB. We have determined that these changes are approvable
as further described below.

III. What Is the State's Process To Submit These Materials to EPA?

Section 110(k) of the CAA addresses our actions on submissions of
revisions to a SIP. The CAA requires States to observe certain
procedural requirements in developing SIP revisions for submittal to
us. Section 110(a)(2) of the CAA requires that each SIP revision be
adopted after reasonable notice and public hearing. This must occur
prior to the revision being submitted by a State to us.
The Colorado Air Quality Control Commission (AQCC) held a public
hearing for the revised Denver Carbon Monoxide (CO) Maintenance Plan on
June 19, 2003. The AQCC adopted the revised maintenance plan directly
after the hearing. This SIP revision became State effective on August
30, 2003, and was submitted by the Governor to us on October 15, 2003.
We have evaluated the Governor's submittal for the revised
maintenance plan and have determined that the State met the
requirements for reasonable notice and public hearing under section
110(a)(2) of the CAA. By operation of law under section 110(k)(1)(B) of
the CAA, the Governor's October 15, 2003, submittal became complete on
April 15, 2004.

IV. EPA's Evaluation of the Revised Maintenance Plan

EPA has reviewed the State's revised maintenance plan for the
Denver attainment/maintenance area and believes that approval is
warranted. The following are the key aspects of this revision along
with our evaluation of each:
(a) The State has revised the original Denver maintenance plan and
has provided air quality data that show continuous attainment of the CO
NAAQS.
As described in 40 CFR Sec. 50.8, the national primary ambient air
quality standard for carbon monoxide is 9 parts per million (10
milligrams per cubic meter) for an 8-hour average concentration not to
be exceeded more than once per year. 40 CFR Sec. 50.8 continues by
stating that the levels of CO in the ambient air shall be measured by a
reference method based on 40 CFR part 50, Appendix C and designated in
accordance with 40 CFR part 53 or an equivalent method designated in
accordance with 40 CFR part 53. The original Denver CO maintenance
plan,

[[Page 55754]]

approved by EPA on December 14, 2001, relied on ambient air quality
data from 1996 through 1999. The revised Denver CO maintenance plan,
submitted by the Governor on October 15, 2003, relies on ambient air
quality data from 2000, 2001, and 2002. Further, we have reviewed
ambient air quality data from 2003 and the first calendar quarter of
2004 and the Denver area shows continuous attainment of the CO NAAQS
from 2000 to present. All the above-referenced air quality data are
archived in our Aerometric Information and Retrieval System (AIRS).
(b) The State updated the attainment year (2001) and projected
years (2006 and 2013) emission inventories.
The revised maintenance plan that the Governor submitted on October
15, 2003, included comprehensive inventories of CO emissions for the
Denver area. These inventories include emissions from stationary point
sources, area sources, non-road mobile sources, and on-road mobile
sources. More detailed descriptions of the revised 2001 attainment year
inventory, the revised 2006 projected inventory, and the revised 2013
projected inventory are documented in the maintenance plan in section
C, and in the State's TSD. The State's submittal contains emission
inventory information that was prepared in accordance with EPA
guidance. Summary emission figures from the 2001 attainment year and
the projected years are provided in Table IV-1 below.

Table IV-1.--Summary of CO Emissions in Tons per Day for Denver
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2001 2006 2013
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Point Sources................................................ *31.6 *25.6 *25.6
Area Sources................................................. 185.7 160.9 160.8
Non-Road Mobile Sources...................................... 55.9 57.7 61.4
On-Road Mobile Sources....................................... 1638 1614 1125
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Total.................................................... 1911 1858 1373
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* The reduction in point source emission figures, from the original maintenance plan, is due to the use of
actual emissions instead of allowable emissions for non-elevated sources.

We note in Table IV-1, the revised emission figures project
significant reductions in years 2006 and 2013 for point sources and
area sources. The majority of the projected area source reductions are
from the State's estimates for less woodburning in future years. We
believe this projection of less woodburning is reasonable. For point
sources, the original Denver CO maintenance plan used sources'
potential-to-emit (PTE) for 2001, but used projections of actual
emissions for the years 2006 and 2013. The revised maintenance plan now
uses actual point source emissions for 2001 and also projects actual
emissions from point sources in 2006 and 2013. The State's approach
follows EPA guidance on projected emissions and we believe it is
acceptable.\1\ Further information on these projected emissions may
also be found in Section 3 ``Non-Mobile Source Emission Inventory'' of
the State's TSD. The revised mobile source emissions show the largest
change from the original maintenance plan and this is primarily due to
the use of MOBILE6.2 instead of MOBILE5a. The MOBILE6.2 modeling
information is contained in the State's TSD in Chapter 2 and Appendix
C. Much of the modeling data, input-output files, fleet makeup,
MOBILE6.2 input parameters, etc. are on a compact disc (CD), included
with the docket for this action, and are available from either EPA or
the State. Other revisions to the mobile sources category were due to
revised vehicle miles traveled (VMT) estimates that were provided to
the State from the Denver Regional Council of Governments (DRCOG) which
is the metropolitan planning organization (MPO) for the Denver area.
The revised VMT were extracted from DRCOG's 2025 Regional
Transportation Plan of April, 2002. In summary, the revised maintenance
plan and State TSD contain detailed emission inventory information,
that was prepared in accordance with EPA guidance, and are acceptable
to EPA.
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\1\ ``Use of Actual Emissions in Maintenance Demonstrations for
Ozone and Carbon Monoxide (CO) Nonattainment Areas'', signed by D.
Kent Berry, Acting Director, Air Quality Management Division,
November 30, 1993.
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(c) The State revised the maintenance demonstration used in the
original Denver maintenance plan.
The original Denver CO redesignation maintenance plan, approved on
December 14, 2001, utilized the then applicable EPA mobile sources
emission factor model, MOBILE5a. On January 18, 2002, we issued policy
guidance for States and local areas to use to develop SIP revisions
using the new, updated version of the model, MOBILE6. The policy
guidance was entitled ``Policy Guidance on the Use of MOBILE6 for SIP
Development and Transportation Conformity'' (hereafter, January 18,
2002 MOBILE6 policy). Additional policy guidance regarding EPA's MOBILE
model was issued on November 12, 2002; this guidance notified Federal,
State, and local agencies that the updated MOBILE6.2 model was
available and was the recommended version of the model to be used. We
note that throughout the development of the revised Denver CO
maintenance plan, the State used the MOBILE6.2 model.
Our January 18, 2002, MOBILE6 policy allows areas to revise their
motor vehicle emission inventories and transportation conformity MVEBs
using the MOBILE6 model without needing to revise the entire SIP or
completing additional modeling if: (1) The SIP continues to demonstrate
attainment or maintenance when the MOBILE5-based motor vehicle emission
inventories are replaced with MOBILE6-based attainment and maintenance
year inventories and, (2) the State can document that the growth and
control strategy assumptions for non-motor vehicle emission sources
continue to be valid and minor updates do not change the overall
conclusion of the SIP. Our January 18, 2002 MOBILE6 policy also speaks
specifically to CO maintenance plans on page 10 of the policy. The
first paragraph on page 10 of the policy states ``* * * if a carbon
monoxide (CO) maintenance plan relied on either a relative or absolute
demonstration, the first criterion could be satisfied by documenting
that the relative emission reductions between the base year and the
maintenance year are the same or greater using MOBILE6 as compared to
MOBILE5.'' For clarity, a ``relative demonstration'' for maintenance is
based on the comparison of an attainment level of emissions to
projected future year emissions. Maintenance is demonstrated when the
projected future year emissions are at or

[[Page 55755]]

below the attainment level. This method was applicable to CO
nonattainment areas classified as ``moderate'' with a design value of
less than 12.7 ppm. An ``absolute demonstration'' for maintenance is
based on modeling which shows that modeled CO emissions in future
projected years will be less than 9 ppm (the CO NAAQS). For CO
nonattainment areas, this requirement was applicable to areas
classified as ``moderate'' with a design value greater than 12.7 ppm
and to ``serious'' areas such as Denver.
As discussed above, the State prepared revised emission inventories
for the years 2001, 2006, and 2013 using MOBILE6.2. The results of
these calculations are presented in Table 8 ``Comparison of Attainment
Area Inventory Changes and Percent for Attainment, Interim &
Maintenance Years'' on page 16 of the revised Denver maintenance plan
and are also presented below in Table IV-2:

Table IV-2
[Figures are in tons per day of CO]
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Year 2001 2006 2013
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Previously Approved Denver 1083................... 1020................... 1041
Maintenance Plan (based on -5.8% from 2001........ -3.9% from 2001
MOBILE5a)*.
Revised Denver Maintenance Plan 1911................... 1858................... 1373
(based on MOBILE6.2)**. -2.8% from 2001........ -28.2% from 2001
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* As approved by EPA on December 14, 2001 (66 FR 64751).
** As submitted by the Governor on October 15, 2003.

Based on this information we have determined that the revised
maintenance plan meets the first criterion of our January 18, 2002
MOBILE6 policy for replacement of MOBILE5 emissions inventories and
MVEB with MOBILE6.2 emissions inventories and MVEB. Specifically, the
relative emissions reductions between the attainment year (2001) and
the maintenance year (2013) are greater using MOBILE6.2 (-28.2%) than
they were using MOBILE5 (-3.9%).
To address the second criterion of our January 18, 2002 MOBILE6
policy, the State documented that the growth and control strategy
assumptions for non-motor vehicle emission sources are still valid and
minor updates have not changed the overall conclusion of the SIP. The
State's analysis is contained in section C.2 of the revised maintenance
plan, entitled ``Methodology and Control Assumptions for Source
Categories'', in which the State evaluated updated planning information
from DRCOG, updated point source information, updated area and non-road
source information, and specific updated information for Denver
International Airport (DIA). We summarize the State's approach below.
For modeling of mobile sources emissions, the original maintenance
plan relied on planning data from the 2020 DRCOG plan. The revised
maintenance plan relies on data from the 2025 DRCOG plan. The changes
in the modeling domain-wide VMT are presented in section C.2.(a) of the
revised maintenance plan and Table IV-3 below:

Table IV-3
[Figures are in estimated Daily VMT]
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Year 2001 2006 2013
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Previously Approved Denver Maintenance Plan (based on MOBILE5a)* 58,156,000 66,760,000 77,187,000
Revised Denver Maintenance Plan (based on MOBILE6.2)**.......... 61,362,264 68,123,584 77,750,300
Percent change.................................................. +5.2 +2.0 +0.7
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* As approved by EPA on December 14, 2001 (66 FR 64751).
** As submitted by the Governor on October 15, 2003.

The comparison of daily VMT between the two maintenance plans, as
shown in Table IV-3 above, indicates a minor change in planning
assumptions.
Section C.2.(b) of the revised maintenance plan contains a
discussion of the State's assessment of point source emissions. The
State indicates that the prior analysis and growth assumptions used in
the original maintenance plan are still valid for the revised
maintenance plan. EPA notes that the State elected to base point source
emissions for 2001 on actual emissions and emissions for 2006 and 2013
on projected actual emissions. This methodology is acceptable to us.\2\
We also find the State's overall analysis of revised point source
emissions acceptable.
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\2\ ``Use of Actual Emissions in Maintenance Demonstrations for
Ozone and Carbon Monoxide (CO) Nonattainment Areas'', signed by D.
Kent Berry, Acting Director, Air Quality Management Division,
November 30, 1993.
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For the non-road and area source emissions, the State relied upon
updated demographic information from DRCOG. Several of the non-road and
area source emissions are dependent on demographic data as a surrogate
emission factor. DRCOG demographics are presented below from section
C.1 (Table 5 and Table 6) of the revised maintenance plan and a further
discussion is presented in the State's TSD.

[[Page 55756]]

Table IV-4
[Demographics]
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Year 2001 2006 2013
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Previously Approved Denver Maintenance Plan--Population*........ 2,364,000 2,616,000 2,889,000
Revised Denver Maintenance Plan--Population**................... 2,414,804 2,617,645 2,902,912
Percent change.................................................. +0.1 +0.1 +0.1
Previously Approved Denver Maintenance Plan--Households*........ 970,000 1,097,000 1,244,000
Revised Denver Maintenance Plan--Households**................... 957,780 1,050,166 1,172,902
Percent change.................................................. -1.3 -4.3 -5.7
Previously Approved Denver Maintenance Plan--Employment*........ 1,415,500 1,568,000 1,718,000
Revised Denver Maintenance Plan--Employment**................... 1,360,814 1,495,791 1,678,079
Percent change.................................................. -3.9 -4.6 -2.3
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* As approved by EPA on December 14, 2001 (66 FR 64751).
** As submitted by the Governor on October 15, 2003.

This comparison of demographics between the two maintenance plans
indicates a minimal level of change. Therefore, the planning and growth
assumptions used in the original maintenance plan continue to be valid
for the revised maintenance plan.
As discussed above, the State has satisfactorily addressed the
requirements of our January 18, 2002 MOBILE6 policy for the
substitution of MOBILE6.2-based inventories and MVEB for MOBILE5 based
inventories and MVEB in the revised maintenance plan. The State has
also documented that the growth and control strategy assumptions for
non-motor vehicle emission sources remain valid and minor updates have
not changed the overall conclusions of the Denver CO maintenance plan
SIP element. We have concluded that the revised maintenance
demonstration is approvable.
(d) Monitoring Network and Verification of Continued Attainment
Continued attainment of the CO NAAQS in the Denver area depends, in
part, on the State's efforts to track indicators throughout the
maintenance period. This requirement is met in section F. ``Monitoring
Network/Verification of Continued Attainment'' of the revised Denver CO
maintenance plan. In section F., the State commits to continue
operating the CO monitors in the Denver area and to annually review
this monitoring network and make changes as appropriate.
Also, in section F., the State commits to track mobile sources' CO
emissions (which are the largest component of the inventories) through
the ongoing regional transportation planning process that is done by
DRCOG. Since revisions to Denver's transportation improvement programs
are prepared every two years, and must go through a transportation
conformity finding, the State will use this process to periodically
review the Vehicle Miles Traveled (VMT) and mobile source emissions
projections used in the maintenance plan. This regional transportation
process is conducted by DRCOG in coordination with the Denver Regional
Air Quality Council (RAQC), the State's Air Pollution Control Division
(APCD), the AQCC, and EPA.
Based on the above, we are approving these commitments as
satisfying the relevant requirements. We note that our final rulemaking
approval renders the State's commitments federally enforceable. These
commitments are also the same as those we approved in the original
maintenance plan.
(e) Contingency Plan
Section 175A(d) of the CAA requires that a maintenance plan include
contingency provisions. To meet this requirement, the State has
identified appropriate contingency measures along with a schedule for
the development and implementation of such measures.
As stated in section G of the revised maintenance plan, the
contingency measures for the Denver area will be triggered by a
violation of the CO NAAQS. (However, the maintenance plan does note
that an exceedance of the CO NAAQS may initiate a voluntary, local
process by the RAQC and APCD to identify and evaluate potential
contingency measures.)
The RAQC, in coordination with the APCD and AQCC, will initiate a
subcommittee process to begin evaluating potential contingency measures
no more than 60 days after being notified by the APCD that a violation
of the CO NAAQS has occurred. The subcommittee will present
recommendations to the RAQC within 120 days of notification and the
RAQC will present recommended contingency measures to the AQCC within
180 days of notification. The AQCC will then hold a public hearing to
consider the contingency measures recommended by the RAQC, along with
any other contingency measures that the AQCC believes may be
appropriate to effectively address the violation of the CO NAAQS. The
necessary contingency measures will be adopted and implemented within
one year after the violation occurs.
The potential contingency measures that are identified in section
G.1 of the revised Denver CO maintenance plan include: (1) A 3.1%
oxygenated fuels program from November 8th through February 7th, with a
2.0% oxygen content required from November 1st through November 7th,
(2) reinstatement of the enhanced I/M program in effect before January
10, 2000, and (3) Transportation Control Measures (TCM) such as
financial incentives for Ecopass, Auraria transit pass, and improved
traffic signalization.
Based on the above, we find that the contingency measures provided
in the State's revised Denver CO maintenance plan are sufficient and
meet the requirements of section 175A(d) of the CAA. We note the
contingency measures and methodology to implement them are the same as
those we approved in the original maintenance plan.
(f) Subsequent Maintenance Plan Revisions
In accordance with section 175A(b) of the CAA, Colorado has
committed to submit a revised maintenance plan eight years after our
approval of the original redesignation. This provision for revising the
maintenance plan is contained in section H of the revised Denver CO
maintenance plan. In section H, the State commits to submit a revised
maintenance plan by December, 2009 to correspond with our approval of
the original maintenance plan on December 14, 2001 (66 FR 64751).
Based on our review of the components of the revised Denver CO
maintenance plan, as discussed in items IV.(a) through IV.(f) above, we
have

[[Page 55757]]

concluded that the State has met the necessary requirements for us to
fully approve the revised Denver CO maintenance plan.

V. EPA's Evaluation of the Transportation Conformity Requirements

One key provision of our conformity regulation requires a
demonstration that emissions from the transportation plan and
Transportation Improvement Program are consistent with the emissions
budget(s) in the SIP (40 CFR sections 93.118 and 93.124). The emissions
budget is defined as the level of mobile source emissions relied upon
in the attainment or maintenance demonstration to maintain compliance
with the NAAQS in the nonattainment or maintenance area. The rule's
requirements and EPA's policy on emissions budgets are found in the
preamble to the November 24, 1993, transportation conformity rule (58
FR 62193-96) and in the sections of the rule referenced above.
With respect to maintenance plans, our conformity regulation
requires that MVEB(s) must be established for the last year of the
maintenance plan and may be established for any other years deemed
appropriate (40 CFR 93.118).
Section E ( ``Carbon Monoxide Motor Vehicle Emissions Budget'') of
the maintenance plan describes the applicable transportation conformity
requirements and updated MVEB for the revised Denver CO maintenance
plan. The State has only established a MVEB for the last year of the
revised maintenance plan, 2013. Based on this choice, in order for a
positive conformity determination to be made, transportation plan
analyses for years after 2013 must show that motor vehicle emissions
will be less than or equal to the MVEB in 2013. Our conformity
regulation also allows the implementation plan (maintenance plan in
this case) to quantify explicitly the amount motor vehicle emissions
could be higher in 2013, while allowing a demonstration of maintenance
of the NAAQS (40 CFR 93.124). This process is known as allocating all
or a portion of the designated ``safety margin'' to the MVEB and is
further described in 40 CFR 93.124 and below.
In addition, our January 18, 2002 MOBILE6 policy states that `` * *
* regardless of the technique used for attainment or maintenance
demonstrations, a more rigorous assessment of the SIP's demonstration
may be necessary if a State decides to reallocate possible excess
emission reductions to the motor vehicle emissions budget safety
factor.'' Since the State decided to allocate available excess
emissions reductions in the revised maintenance plan to the 2013 MVEB,
we required a ``more rigorous assessment'' in order to ensure that even
with the allocation of ``safety margin'' to the 2013 MVEB, the revised
maintenance plan would continue to demonstrate maintenance. The ``more
rigorous assessment'' is described in section E.3 of the maintenance
plan, in the State's TSD, and below.
The original Denver CO maintenance plan, approved on December 14,
2001, contained a MVEB that was based on MOBILE5 and was 800 tons per
day of CO for the Denver attainment/maintenance area for the years 2002
and beyond. The State did not allocate any ``safety margin'' as none
was available for use. Section E.3 of the revised maintenance plan
states that the prior 800 tons per day MVEB is removed from the SIP and
is replaced by the new MVEB as described below.
In section E.3. of the revised maintenance plan, the State
indicates that the revised maintenance plan establishes a MVEB for 2013
and beyond and that this MVEB is applicable to the boundaries of the
Denver CO attainment/maintenance area. The revised maintenance plan
indicates there is a 28.2% reduction in CO emissions between the
attainment year of 2001 and the final maintenance year of 2013 (1911
tons per day in 2001 down to 1373 tons per day in 2013). As a result, a
``safety margin'' of CO emissions was identified. The ``safety margin''
and the allocation of these CO emissions is presented in Table 10 of
the revised maintenance plan and is reproduced in our Table V-1 below.

Table V-1.--Derivation of the MVEB for 2013 and Allocation of the
``Safety Margin''
------------------------------------------------------------------------
Tons per day
(TPD) of CO Explanation
------------------------------------------------------------------------
Total 2001 Attainment Year 1911 2001 Attainment year
Inventory CO Emissions. inventory from all
sources that
establishes the
attainment level of
emissions in the
attainment/maintenance
area.
Estimated 2013 Point and Area 248 Total estimated 2013
Emissions. emissions from point
and area sources.
Estimated 2013 Mobile Source 1125 Estimated 2013 mobile
Emissions. source emissions based
on MOBILE6.2 and State
control strategies.
Total 2013 Emission Inventory.. 1373 Total 2013 emissions
from all source
categories.
Potential 2013 ``Safety 1 538 This is the difference
Margin''. between the 2001 and
2013 total emission
inventories.
Allowable 2013 Mobile Source 1539 This is the total
Emissions. mobile source
emissions (after
subtracting 2013 point
and area emissions)
that would still
demonstrate
maintenance of the CO
NAAQS based on EPA's
recommended ``more
rigorous assessment.''
Avaiablle ``safety margin''.... 414 This is the difference
between the allowable
2013 mobile source
emissions (1539 TPD)
and the estimated 2013
mobile source
emissions (1125 TPD).
This is the ``safety
margin'' that may be
allocated to the MVEB.
Portion of the ``safety 19 This is the portion of
margin'' reserved. the ``safety margin''
that the State is
reserving to account
for point and area
source growth and
other modeling
uncertainties.
Amount of ``safety margin'' 395 This is the difference
allocated to the 2013 MVEB. between the available
``safety margin'' (414
TPD) and the reserved
``safety margin'' (19
TPD).
2013 and Beyond MVEB........... 1520 This is the 2013 MVEB
(1125 TPD from mobile
sources plus the
allocated ``safety
margin'' of 395 TPD).
------------------------------------------------------------------------
1 The State lists this value as 548 but it should be 538. This error
does not affect the State's calculation of the MVEB for 2013.

[[Page 55758]]

As stated above, our January 18, 2002 MOBILE6 policy required a
``more rigorous assessment'' in order to ensure that even with the
allocation of ``safety margin'' emissions to the 2013 MVEB, the revised
maintenance plan would continue to demonstrate maintenance. We
determined that a ``more rigorous assessment'' for the revised Denver
CO maintenance plan would be an intersection modeling analysis similar
to that performed by the State for the original EPA-approved Denver CO
maintenance plan. The State's intersection analysis used a background
CO concentration combined with CAL3QHC intersection (``hot spot'')
modeling of the same six high-volume, high congestion intersections
that were analyzed for the original maintenance plan.
The background CO concentration for each intersection used the
second highest 8-hour maximum monitored value at a nearby CO ambient
air quality monitor for the time period of 2000 through 2002. The
CAL3QHC intersection modeling used 2013 MOBILE6.2 mobile sources
emissions and DRCOG projected traffic data. The background
concentration and results from the CAL3QHC modeling were them combined
for each intersection. If the resulting concentration was greater than
9 ppm (the CO NAAQS), the background concentration was reduced by the
necessary percentage to bring the total intersection value below 9 ppm.
This was necessary for only one case, the Foothills/Arapahoe
intersection in Boulder, where the initial background concentration was
4.3 ppm and the resulting intersection concentration was 9.27 ppm.
Since it is assumed that background concentrations are influenced
by regional emissions of CO, the State, in order to determine the
allowable regional emissions, reduced the base regional emissions (1911
tons per day in 2001) by the same percentage it had to reduce the
initial background concentration.
Specifically, the State applied a percentage reduction of about
6.5% to 4.3 ppm and 1911 tons per day to arrive at values of 4.02 ppm
and 1787 tons per day. To determine the available ``safety margin'',
the State then subtracted 1373 tons per day (the total 2013 emission
inventory) from 1787 tons per day to arrive at 414 tons per day. Of
this amount, the State ``reserved'' 19 tons per day. Thus, the State
applied 395 tons per day of the ``safety margin'' to the 2013 MVEB. The
2013 MVEB of 1520 tons per day results from the addition of the 2013
projected mobile source emissions (1125 tons per day) and the allocated
``safety margin'' (395 tons per day).
The State modeled the six intersections based on the MVEB of 1520
tons per day. The results are shown in Table 11 of the State's revised
maintenance plan and are reproduced in Table V-2 below.

Table V-2.--Intersection Modeling Results (in Parts Per Million) Using the Emissions Budget of 1520 Tons Per day
----------------------------------------------------------------------------------------------------------------
Background
Intersection (ppm) CAL3QHC (ppm) Total (ppm)
----------------------------------------------------------------------------------------------------------------
Broadway & Champa............................................... 5.00 1.47 6.47
Foothills & Arapahoe............................................ 3.98 4.97 8.95
1st & University................................................ 4.35 4.05 8.40
Hampden & University............................................ 3.52 4.83 8.35
Parker & Iliff.................................................. 3.52 3.29 6.81
Arapahoe & University........................................... 3.52 4.62 8.14
----------------------------------------------------------------------------------------------------------------

The modeling results presented in the revised Denver CO maintenance
plan and the State's TSD, and repeated in Table V-2 above, show that CO
concentrations are not estimated to exceed the 9.0 ppm 8-hour average
CO NAAQS for 2013. We have concluded that the State has satisfactorily
addressed the requirements of our January 18, 2002 MOBILE6 policy for a
more rigorous assessment of MVEBs and has also demonstrated maintenance
of the CO NAAQS while using a transportation conformity MVEB of 1520
tons per day for 2013. Therefore, we are approving the transportation
conformity MVEB of 1520 tons per day of CO, for the Denver attainment/
maintenance area, for 2013 and beyond.

VI. Consideration of Section 110(l) of the CAA

Section 110(l) of the CAA states that a SIP revision cannot be
approved if the revision would interfere with any applicable
requirement concerning attainment and reasonable further progress
towards attainment of a NAAQS or any other applicable requirement of
the CAA. The revised Denver CO maintenance plan will not interfere with
attainment, reasonable further progress, or any other applicable
requirement of the CAA.

VII. Final Action

In this action, EPA is approving the revised Denver CO maintenance
plan, that was submitted by the Governor on October 15, 2003, and we
are also approving the revised transportation conformity motor vehicle
emission budget for CO for the year 2013 and beyond.
EPA is publishing this rule without prior proposal because the
Agency views this as a noncontroversial amendment and anticipates no
adverse comments. However, in the ``Proposed Rules'' section of today's
Federal Register publication, EPA is publishing a separate document
that will serve as the proposal to approve the SIP revision if adverse
comments are filed. This rule will be effective November 15, 2004
without further notice unless the Agency receives adverse comments by
October 18, 2004. If the EPA receives adverse comments, EPA will
publish a timely withdrawal in the Federal Register informing the
public that the rule will not take effect. EPA will address all public
comments in a subsequent final rule based on the proposed rule. The EPA
will not institute a second comment period on this action. Any parties
interested in commenting must do so at this time. Please note that if
EPA receives adverse comment on an amendment, paragraph, or section of
this rule and if that provision may be severed from the remainder of
the rule, EPA may adopt as final those provisions of the rule that are
not the subject of an adverse comment.

VIII. Statutory and Executive Order Reviews

Under Executive Order 12866 (58 FR 51735, October 4, 1993), this
action is not a ``significant regulatory action'' and therefore is not
subject to review by the Office of Management and Budget. For

[[Page 55759]]

this reason, this action is also not subject to Executive Order 13211,
``Actions Concerning Regulations That Significantly Affect Energy
Supply, Distribution, or Use'' (66 FR 28355, May 22, 2001). This action
merely approves state law as meeting Federal requirements and imposes
no additional requirements beyond those imposed by state law.
Accordingly, the Administrator certifies that this rule will not have a
significant economic impact on a substantial number of small entities
under the Regulatory Flexibility Act (5 U.S.C. 601 et seq.). Because
this rule approves pre-existing requirements under state law and does
not impose any additional enforceable duty beyond that required by
state law, it 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).
This rule also does not have tribal implications because it will
not have a substantial direct effect on one or more Indian tribes, on
the relationship between the Federal Government and Indian tribes, or
on the distribution of power and responsibilities between the Federal
Government and Indian tribes, as specified by Executive Order 13175
(65 FR 67249, November 9, 2000). This action also does not have federalism
implications because it does not have substantial direct effects on the
States, on the relationship between the national government and the
States, or on the distribution of power and responsibilities among the
various levels of government, as specified in Executive Order 13132
(64 FR 43255, August 10, 1999). This action merely approves a state rule
implementing a Federal standard, and does not alter the relationship or
the distribution of power and responsibilities established in the Clean
Air Act. This rule also is not subject to Executive Order 13045
``Protection of Children from Environmental Health Risks and Safety
Risks'' (62 FR 19885, April 23, 1997), because it is not economically
significant.
In reviewing SIP submissions, EPA's role is to approve State
choices, provided that they meet the criteria of the Clean Air Act. In
this context, in the absence of a prior existing requirement for the
State to use voluntary consensus standards (VCS), EPA has no authority
to disapprove a SIP submission for failure to use VCS. It would thus be
inconsistent with applicable law for EPA, when it reviews a SIP
submission, to use VCS in place of a SIP submission that otherwise
satisfies the provisions of the Clean Air Act. Thus, the requirements
of section 12(d) of the National Technology Transfer and Advancement
Act of 1995 (15 U.S.C. 272 note) do not apply. This rule does not
impose an information collection burden under the provisions of the
Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et seq.).
The Congressional Review Act, 5 U.S.C. section 801 et seq., as
added by the Small Business Regulatory Enforcement Fairness Act of
1996, generally provides that before a rule may take effect, the agency
promulgating the rule must submit a rule report, which includes a copy
of the rule, to each House of the Congress and to the Comptroller
General of the United States. EPA will submit a report containing this
rule and other required information to the U.S. Senate, the U.S. House
of Representatives, and the Comptroller General of the United States
prior to publication of the rule in the Federal Register. A major rule
cannot take effect until 60 days after it is published in the Federal
Register. This action is not a ``major rule'' as defined by 5 U.S.C.
section 804(2).
Under section 307(b)(1) of the Clean Air Act, petitions for
judicial review of this action must be filed in the United States Court
of Appeals for the appropriate circuit by November 15, 2004. Filing a
petition for reconsideration by the Administrator of this final rule
does not affect the finality of this rule for the purposes of judicial
review nor does it extend the time within which a petition for judicial
review may be filed, and shall not postpone the effectiveness of such
rule or action. This action may not be challenged later in proceedings
to enforce its requirements. (See section 307(b)(2).)

List of Subjects in 40 CFR Part 52

Environmental protection, Air pollution control, Carbon monoxide,
Intergovernmental relations, Reporting and recordkeeping requirements.

Dated: September 3, 2004.
Robert E. Roberts,
Regional Administrator, Region VIII.

? 40 CFR part 52 is amended to read as follows:

PART 52--[AMENDED]

? 1. The authority citation for part 52 continues to read as follows:

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

Subpart G--Colorado

? 2. Section 52.349 is amended by adding paragraph (i) to read as
follows:

Sec. 52.349 Control strategy: Carbon monoxide.

* * * * *
(i) Revisions to the Colorado State Implementation Plan, revised
Carbon Monoxide Maintenance Plan for Denver, as adopted by the Colorado
Air Quality Control Commission on June 19, 2003, State effective on
August 30, 2003, and submitted by the Governor on October 15, 2003.

[FR Doc. 04-20793 Filed 9-15-04; 8:45 am]
BILLING CODE 6560-50-P

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Approval and Promulgation of Air Quality Implementation Plans; State of Colorado; Denver Revised Carbon Monoxide Maintenance Plan

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