[Federal Register Volume 69, Number 179 (Thursday, September 16, 2004)]
[Rules and Regulations]
[Pages 55752-55759]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-20793]


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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: [email protected] and [email protected].
     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: 
[email protected].

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
                                                              ------------------
    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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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
----------------------------------------------------------------------------------------------------------------
* 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.


0
40 CFR part 52 is amended to read as follows:

PART 52--[AMENDED]

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

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

Subpart G--Colorado

0
2. Section 52.349 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