Document ID: EPA-R08-OAR-2007-0622-0001
Agency: epa
Document Type: Rule
Title: Approval and Promulgation of Air Quality Implementation Plans; State of Colorado; Revised Denver PM10 Maintenance Plan
Posted Date: 2007-11-06T05:00Z

[Federal Register: November 6, 2007 (Volume 72, Number 214)]
[Rules and Regulations]               
[Page 62571-62579]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr06no07-8]                         

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2007-0622; FRL-8490-6]

 
Approval and Promulgation of Air Quality Implementation Plans; 
State of Colorado; Revised Denver PM10 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 September 25, 2006, the Governor's designee submitted a revised plan 
for particulate matter with an aerodynamic diameter, less than or equal 
to 10 microns (PM10) for the Denver metropolitan area for the PM10 
National Ambient Air Quality Standard (NAAQS). This revised maintenance 
plan addresses maintenance of the PM10 standard for a second ten-year 
period beyond redesignation, extends the horizon years, and contains 
revised transportation conformity budgets. EPA is approving the removal 
of Regulation No. 11, ``Motor Vehicle Emissions Inspection Program'' 
from Denver's revised PM10 maintenance plan. In addition, EPA is 
approving a transportation budget trading protocol for estimating the 
PM10 and nitrogen oxides (NOx) for each conformity determination. This 
action is being taken under section 110 of the Clean Air Act.

DATES: This direct final rule is effective on January 7, 2008 without 
further notice, unless EPA receives adverse comment by December 6, 
2007. 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 Docket Number EPA-R08-

[[Page 62572]]

OAR-2007-0622, by one of the following methods:
     http://www.regulations.gov. Follow the on-line 

instructions for submitting comments.
     E-mail: videtich.callie@epa.gov and fiedler.kerri@epa.gov.

     Fax: (303) 312-6064 (please alert the individual listed in 
the FOR FURTHER INFORMATION CONTACT, if you are faxing comments).
     Mail: Callie A. Videtich, Director, Air and Radiation 
Program, Environmental Protection Agency (EPA), Region 8, Mailcode 8P-
AR, 1595 Wynkoop Street, Denver, Colorado 80202-1129.
     Hand Delivery: Callie A. Videtich, Director, Air and 
Radiation Program, Environmental Protection Agency (EPA), Region 8, 
Mailcode 8P-AR, 1595 Wynkoop Street, Denver, Colorado 80202-1129. Such 
deliveries are 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 Docket ID No. EPA-R08-OAR-
2007-XXXX. EPA's policy is that all comments received will be included 
in the public docket without change and may be made available at http://www.regulations.gov
, including any personal information provided, 

unless the comment includes information claimed to be Confidential 
Business Information (CBI) or other information whose disclosure is 
restricted by statute. Do not submit information that you consider to 
be CBI or otherwise protected through http://www.regulations.gov or e-mail. The http://www.regulations.gov Web site is an ``anonymous 

access'' system, which means EPA will not know your identity or contact 
information unless you provide it in the body of your comment. If you 
send an e-mail comment directly to EPA, without going through http://www.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 the 
EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm. 

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 http://www.regulations.gov
 index. Although listed in the index, some 

information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in http://www.regulations.gov or in hard copy at the Air and Radiation 

Program, Environmental Protection Agency (EPA), Region 8, 1595 Wynkoop 
Street, Denver, Colorado 80202-1129. EPA requests, if at all possible, 
that 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: Kerri Fiedler, Air and Radiation 
Program, Environmental Protection Agency (EPA), Region 8, Mailcode 8P-
AR, 1595 Wynkoop Street, Denver, Colorado 80202-1129, phone (303) 312-
6493, and e-mail at: fiedler.kerri@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 Denver's PM10 Maintenance Plan
V. EPA's Evaluation of the Transportation Conformity Requirements
VI. EPA's Approval of the Transportation Budget Trading Protocol
VII. EPA's Evaluation of the Regulation No. 11 Revisions
VIII. Consideration of Section 110(l) of the Clean Air Act
IX. Final Action
X. 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.
    (vi) PM10 means particulate matter with an aerodynamic diameter 
less than 10 microns.

I. General Information

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

    1. Submitting Confidential Business Information. Do not submit this 
information to EPA through http://www.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 mailed 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 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.

[[Page 62573]]

II. What is the purpose of this action?

    In this action, we are approving the revised maintenance plan for 
the Denver PM10 attainment/maintenance area that is designed to keep 
the area in attainment for PM10 for a second ten-year period beyond the 
original redesignation. EPA is approving the removal of Regulation No. 
11, ``Motor Vehicle Emissions Inspection Program'' from Denver's 
revised PM10 maintenance plan. In addition, we are approving revised 
transportation conformity motor vehicle emissions budgets (MVEBs) and 
MVEB trading protocol.
    We approved the original PM10 redesignation to attainment and 
maintenance plan for the Denver area on September 16, 2002, (67 FR 
58335). In this revised maintenance plan, the State has updated the 
mobile source PM10 emissions with MOBILE6.2; updated the transportation 
projections and stationary source inventories; revised the MVEBs; 
applied a selected amount of the available safety margin to the 
transportation conformity MVEBs; established an MVEB trading protocol; 
and extended the horizon year to 2022. Colorado is also removing 
Regulation No. 11, ``Motor Vehicle Emissions Inspection Program'' from 
Denver's revised PM10 maintenance plan. We have determined that these 
changes are approvable as 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 State Implementation Plan (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 PM10 maintenance plan and Regulation No. 
11 on December 15, 2005. The AQCC adopted the revised PM10 maintenance 
plan and removal of Regulation No. 11 from Denver's revised PM10 
maintenance plan directly after the hearing. This SIP revision became 
State effective on March 2, 2006, and was submitted by the Governor's 
designee to us on September 25, 2006.
    We have evaluated 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. As required by section 
110(k)(1)(B) of the CAA, we reviewed these SIP materials for 
conformance with the completeness criteria in 40 CFR part 51, Appendix 
V, and determined that the submittal was administratively and 
technically complete. Our completeness determination was sent on 
February 21, 2007, through a letter from Robert E. Roberts, Regional 
Administrator, to Governor Bill Ritter.

IV. EPA's Evaluation of Denver's Revised PM10 Maintenance Plan

    EPA has reviewed the State's revised PM10 maintenance plan for the 
Denver attainment/maintenance area and finds approval is warranted. The 
following are the key aspects of these revisions along with our 
evaluation of each:
    A. The State has revised the Denver PM10 maintenance plan to 
include air quality data that show continuous attainment of the PM10 
NAAQS.
    As described in 40 CFR 50.6, the level of the national primary and 
secondary 24-hour ambient air quality standards for particulate matter 
is 150 micrograms per cubic meter ([mu]g/m\3\), 24-hour average 
concentration. The standards are attained when the expected number of 
days per calendar year with a 24-hour average concentration above 150 
[mu]g/m\3\, as determined in accordance with 40 CFR part 50, Appendix 
K, is equal to or less than one (1). The regulations in 40 CFR 50.6 
continue by stating that the levels of PM10 in the ambient air shall be 
measured by a reference method, based on appendix J, and designated in 
accordance with part 53 of this chapter, or an equivalent method.
    The original Denver PM10 maintenance plan, approved by EPA on 
September 16, 2002, relied on ambient air quality data from 1999 
through 2001. This revised Denver PM10 maintenance plan submitted 
September 25, 2006, relies on ambient air quality data from 2000 
through 2004. Further, we have reviewed ambient air quality data from 
2005 to 2006 and the Denver area shows continuous attainment of the 
PM10 NAAQS based on the most recent data archived in our Aerometric 
Information and Retrieval System (AIRS).
    B. Using the MOBILE6.2 emission factor model, the State updated the 
attainment year, projected years and the maintenance year emission 
inventories. The State updated the attainment year (2001), projected 
years (2009, 2010, 2015, 2020) and the maintenance year (2022) emission 
inventories for Denver's revised PM10 maintenance plan.
    Denver's revised PM10 maintenance plan submitted on September 25, 
2006, included comprehensive inventories of PM10 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 2001 attainment year 
inventory; a new estimated 2009 inventory; updated 2010, 2015, and 2020 
projected inventories; and the 2022 maintenance year projected 
inventory are documented in the revised maintenance plan in section B, 
``Emission Inventories'' and in the State's Technical Support Document 
(TSD). The State's submittal contains emission inventory information 
that was prepared in accordance with EPA guidance. Summary emission 
figures for primary and secondary (NOx and SO2) mobile sources and 
totals emissions from the 2001 attainment year and the projected years 
are provided in Table IV-1 below.

                        Table IV-1.--Summary of PM10 Emissions in Tons per Day for Denver
----------------------------------------------------------------------------------------------------------------
                                                        2001      2009      2010      2015      2020      2022
----------------------------------------------------------------------------------------------------------------
Primary PM10 Mobile Sources.........................      33.1      41.7      42.4      46.6      50.7      52.1
Total Primary PM10..................................      62.3        92      93.3      99.4     105.3     107.5
NOx Mobile Sources..................................     131.9      77.9      73.4      50.0      38.9      37.6
Total NOx...........................................     255.1     280.6     276.4     252.8     244.1     244.4
Mobile Source SO2...................................       4.9       0.8       0.5       0.6       0.7       0.7
Total SO2...........................................     101.3     181.8     181.7     182.4     183.5     184.9
----------------------------------------------------------------------------------------------------------------

[[Page 62574]]

    The State's approach follows EPA guidance on projected emissions 
and it is acceptable.\1\ Further information on these projected 
emissions may also be found in the State's TSD. The State estimated the 
emissions from vehicles using EPA's MOBILE6.2 model and the road dust 
emission factors derived from a Denver area road dust study conducted 
in 1989. These road dust factors were used to estimate emissions in the 
previous maintenance plan and original redesignation request. The 
MOBILE6.2 modeling information is contained in the State's TSD. Much of 
the modeling data, input-output files, fleet makeup, MOBILE6.2 input 
parameters, etc. is on a compact disc (CD), included with the docket 
for this action, and available from either EPA or the State. Other 
revisions to the mobile sources categories 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 estimates were extracted from DRCOG's 2030 Regional 
Transportation Plan of January, 2005. In summary, the revised 
maintenance plan and State TSD contains detailed emission inventory 
information, that were prepared in accordance with EPA guidance, and 
are acceptable to EPA.
---------------------------------------------------------------------------

    \1\ ``Procedures for Processing Requests to Redesignate Areas to 
Attainment,'' Policy Memo: J. Calcagni to Div. Air Directors, 
September 4, 1992.
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    C. The State revised the maintenance demonstration used in the 
original maintenance plan. The original Denver PM10 redesignation 
maintenance plan was approved by EPA on September 16, 2002. The State 
has revised and updated the maintenance plan for a second ten-year 
period beyond redesignation.
    The September 25, 2006 revised maintenance plan updated mobile 
source PM10 emissions with MOBILE6.2, assuming removal of Regulation 
No. 11, the vehicle I/M program, and used the most recent planning 
assumptions for the Denver metropolitan area from DRCOG's 2030 Regional 
Transportation Plan (RTP). The modeled domain-wide VMT estimate is 
presented in Chapter 4, Section B.1 of Denver's revised PM10 
maintenance plan and Table IV-2 below.

                                                            Table IV-2.--Estimated Daily VMT
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                Year                                       2001             2005             2015             2020             2030
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         49,783,121       53,208,574       65,722,110       71,484,844       82,081,684
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Chapter 2, Section D, of Denver's revised PM10 maintenance plan 
contains a discussion of the State's assessment of stationary source 
emissions. Stationary source inventories were updated including new 
sources permitted since the previously approved maintenance plan. The 
State estimates emissions for both major sources of primary PM10 and 
source of secondary NOx and SO2 emissions. We find the State's overall 
analysis of stationary sources of emissions acceptable.
    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 
Chapter 4, Section 1, Table 4-1 of Denver's revised PM10 maintenance 
plan, and a further discussion is presented in the State's TSD.

                                            Table IV-3.--Demographics
----------------------------------------------------------------------------------------------------------------
                   Year                         2001          2005          2015          2020          2030
----------------------------------------------------------------------------------------------------------------
Population................................     2,034,861     2,146,319     2,432,326     2,612,345     2,972,384
Households................................       812,273       868,183       994,133     1,074,706     1,235,853
Employment................................     1,171,970     1,122,934     1,434,530     1,533,233     1,730,639
----------------------------------------------------------------------------------------------------------------

    Based on the data provided in the submitted material, we have 
concluded that the revised maintenance demonstration is approvable.

D. Monitoring Network and Verification of Continued Attainment

    Continued attainment of the PM10 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 E, ``Monitoring 
Network/Verification of Continued Attainment'' of the revised Denver 
PM10 maintenance plan. In this section, the State commits to continue 
operating the PM10 monitors in the Denver area, and to annually review 
the monitoring networks and make changes as appropriate.
    Also, in Section E, the State commits to track PM10 mobile source 
parameters and new and modified stationary source permits. Since 
regular revisions to the 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 VMT estimate and mobile source emissions projections used in 
the revised maintenance plan. This regional transportation process is 
conducted by DRCOG in coordination with the Regional Air Quality 
Council (RAQC), the State's Air Pollution Control Division (APCD), the 
AQCC, the Federal Highway Administration 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 and 
the previously revised 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

[[Page 62575]]

with a schedule for the development and implementation of such 
measures.
    As stated in Section F of the revised Denver PM10 maintenance plan, 
the contingency measures will be triggered by a violation of the PM10 
NAAQS. (However, the maintenance plan notes that an exceedance of the 
PM10 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 notification by the APCD that a violation of 
the PM10 NAAQS has occurred. The subcommittee will present 
recommendations within 120 days of notification and recommended 
contingency measures will be presented to the AQCC within 180 days of 
notification. The AQCC will then hold a public hearing to consider the 
recommended contingency measures, along with any other contingency 
measures that the AQCC believes may be appropriate to effectively 
address the violation of the PM10 NAAQS. The necessary contingency 
measures will be adopted and implemented within one (1) year after the 
violation occurs.
    The potential contingency measures that are identified in section 
F.1 of Denver's revised PM10 maintenance plan include: (1) 
Reinstatement of the enhanced I/M program in effect before January 10, 
2000; (2) required compliance with Regulation 12 concerning the diesel 
inspection/maintenance program; (3) compliance with Regulation 13 
concerning the oxygenated gasoline program; (4) permitting terms and 
limits that were included in stationary permits previously incorporated 
into the state implementation plan at 40 CFR 52.320(82); 62 FR 18716 
(April 17, 1997). In addition, the State lists potential contingency 
measures that would be evaluated for efficacy and suitability. These 
measures include, among others, increased street sweeping requirements, 
road paving requirements, wood burning restrictions, and retrofit 
programs for diesel engines.
    Based on the above, we find that the contingency measures provided 
in Denver's revised PM10 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 and previously revised maintenance plan.

F. Subsequent Maintenance Plan Revisions

    The previously approved maintenance plan addressed the period 1995 
through 2015 and demonstrated, in accordance with section 175A(a) of 
the CAA, that the PM10 standard will be maintained for the initial ten-
year period (through 2012). In accordance with section 175A(b), 
Colorado has submitted a revised maintenance plan within eight years 
after our approval of the original redesignation. The purpose of this 
revised maintenance plan is to provide for maintenance of the PM10 
standard for the additional ten years (through 2022) following the 
first ten-year period.
    Based on our review of the components of the revised Denver PM10 
maintenance plan, as discussed in items IV(A) through IV(F) above, we 
have concluded that the State has met the necessary requirements for us 
to fully approve the revised Denver PM10 maintenance plan. It is 
important to note that neither the maintenance plan nor the control 
measures relied upon in this maintenance plan will cease after the 
final maintenance year 2022. The maintenance plan and control measures 
relied upon in the maintenance plan will continue to be a part of 
Colorado's SIP, unless we approve their removal. The maintenance plan 
will remain in effect until it is revised and we approve the revision.

V. EPA's Evaluation of the Transportation Conformity Requirements

    One key provision of our conformity regulation requires a 
demonstration that emissions from the Long Range Transportation Plan 
and the Transportation Improvement Program (TIP) are consistent with 
the emissions budgets in the SIP (40 CFR 93.118 and 93.124). The 
emissions budgets are defined as the level of mobile source emissions 
relied upon in the attainment or maintenance demonstration to maintain 
compliance with the NAAQS in the non-attainment 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 motor vehicle emission budgets (MVEBs) 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).
    For transportation plan analysis years, after the last year of the 
maintenance plan, a conformity determination must show that emissions 
are less than or equal to the maintenance plan's MVEBs for the last 
year of the implementation plan. EPA's conformity regulation (40 CFR 
93.124) also allows the implementation plan to quantify explicitly the 
amount by which motor vehicle emissions could be higher while still 
demonstrating compliance with the maintenance requirement. The 
implementation plan can then allocate some or all of this additional 
safety margin to the emissions budgets for transportation conformity 
purposes.

A. Denver MVEBs

    Section D of the revised Denver PM10 maintenance plan describes the 
applicable transportation conformity requirements and updated MVEBs for 
the revised maintenance plan. In addition to establishing MVEBs, the 
State establishes an emission budget trading protocol for trading 
between emissions budgets for primary PM10 and the PM10 precursor, NOx. 
Through this revised maintenance plan, the State has established a MVEB 
for 2015 through 2021 and 2022 and beyond. Specifically, the PM10 MVEBs 
are defined as 54 tons per day (TPD) of PM10 and 70 TPD of NOx for 
2015, and 55 TPD of PM10 and 56 TPD of NOx for 2022. The trading 
protocol will be explained more fully at a later point in this notice.
    Under our conformity rules, an MVEB is established for a given 
year, not for a range of years. This is because the MVEB reflects the 
inventory value for motor vehicle emissions in a given year, plus, 
potentially, any safety margin in that year. (We explain the concept of 
safety margin more fully below.) It is not possible to specify the same 
MVEB for a range of years absent specific analysis supporting the 
derivation of that budget for each year in the range. As a practical 
matter, this is not usually important because our conformity rules also 
say that an MVEB for a particular year applies for conformity analyses 
of emissions in that year and all subsequent years before the next 
budget year. See 40 CFR 93.118(b)(1)(ii), ``Emissions in years for 
which no motor vehicle emissions budget(s) are specifically established 
must be less than or equal to the motor vehicle emissions budget(s) 
established for the most recent prior year.'' Therefore, the ``2015 
through 2021'' and the ``2022 and beyond'' budgets were derived from 
the 2015 and 2022 inventory values, respectively, for on-road vehicle 
emissions and available safety margin.

[[Page 62576]]

Thus, we will refer to these as the 2015 and 2022 budgets in the 
remainder of this action.
    In addition, it is noted that the State had previously established 
MVEBs for 2006 for PM10 of 60 TPD, and 119.4 TPD for NOx for year 1998. 
These budgets will continue to be effective if the State should perform 
a conformity analysis for years prior to 2015, based on 40 CFR 
93.118(b)(1)(ii).
    The maintenance plan indicates that SO emissions from mobile 
sources are an insignificant contributor to secondary particulate 
formation in the Denver area (much less than 1 [mu]g/m3). 
This is evident by Table 4.3-2 Secondary Particulate Concentration 
Worksheet, found in the Colorado State Implementation Plan for PM10, 
Revised TSD. Therefore, an emission budget for SO2 is not established.
    The maintenance plan establishes regional budgets for the PM10 
modeling domain, which for technical modeling reasons, is less than the 
entire non-attainment area (as seen in the revised Denver PM10 
maintenance plan). All of the emission estimates and air quality 
modeling in the maintenance plan are based on this domain. Future 
conformity determinations shall also project future mobile source 
emission for this same domain, unless the geographic coverage of the 
budget is changed through a future SIP revision.
    As shown in the maintenance demonstration earlier in this plan, the 
2010, 2015, 2020, and 2022 regional emissions inventories for primary 
PM10 and PM10 precursors are below the level necessary to demonstrate 
continued maintenance of the PM10 standard (150 [mu]g/m3). 
As a result, EPA's conformity regulation (40 CFR 93.124) allows the 
implementation plan to quantify explicitly the amount by which motor 
vehicle emissions could be higher, while still demonstrating compliance 
with the maintenance requirement. The implementation plan can then 
allocate some or all of this additional ``safety margin'' to the 
emissions budget(s) for conformity purposes. The available safety 
margin in 2022 as shown in Table V-1 below is 4.7 [mu]g/m3. 
Expressed in tons per day, this is equivalent to 57.8 TPD of NOx 
emissions or 4.2 TPD of PM10, based on results and relationships 
established in the modeling analysis for 2001 as follows:
     Actual PM10 RAM inventory/averaged key receptor RAM PM10 
concentration

60.1 TPD PM10/68.0 [mu]g/m3 PM10 = 0.9 TPD PM10/[mu]g/
m3 PM10

     Actual NOx total inventory/NOx fraction of max. winter 
PM10 concentration (2001-2005)

255.1 TPD NOx/20.8 [mu]g/m3 PM10 = 12.3 TPD NOx/[mu]g/
m3 PM10

    The actual PM10 RAM inventory is derived by subtracting the 
Potential to Emit Point Sources from the Total Primary PM10 as seen in 
Table 4.2 (Primary and Secondary Emissions Inventory) found in the 
revised Denver PM10 maintenance plan. The averaged key receptor RAM 
PM10 concentration is estimated by using the RAM modeled concentrations 
from the 6th highest total concentrations above100 [mu]g/m3. 
The actual NOx inventory is found at Table 3.1-2 of the TSD, and the 
NOx fraction of maximum winter PM10 concentration (2001-2005) is found 
in Table 4.3-2 of the TSD.
    Allocation of all of the available safety margin to NOx results in 
mobile source emissions budgets of 95.4 TPD NOx and 52.1 TPD PM10. 
Conversely, allocation of the entire available safety margin to PM10 
results in mobile source emissions budgets of 37.6 TPD NOx and 56.3 TPD 
PM10, as illustrated in the following table:

          Table V-1.--2022 Available NOx or PM10 Safety Margin
------------------------------------------------------------------------
                                       NOx                  PM10
------------------------------------------------------------------------
Maximum Allowable             149.9 [mu]g/m3        149.9 [mu]g/m3
 Concentration.
Maintenance Demonstration...  145.2 [mu]g/m3        145.2 [mu]g/m3
Available ``safety margin''   4.7 [mu]g/m3          4.7 [mu]g/m3
 ((micrograms/meter3).
Available ``safety margin''   57.8 TPD *            4.2 TPD **
 (tons per day).
2022 Mobile Sources.........  37.6 TPD              52.1 TPD
2022 Mobile Source Budget     95.4 TPD              56.3 TPD
 with all Safety Margin
 Applied to NOx or PM10.
------------------------------------------------------------------------
* 1 [mu]g/m3 = 12.3 TPD NOx.
** 1 [mu]g/m3 = 0.9 TPD PM10.

    This maintenance plan allocates the entire safety margin to the 
motor vehicle emissions budget and allocates a portion of the available 
safety margin to PM10 and a portion to NOx as shown in Table V-2:

 Table V-2.--2022 Allocation of Available Safety Margin and Development
                   of Mobile Source Emissions Budgets
------------------------------------------------------------------------
                                       NOx                 PM10
------------------------------------------------------------------------
Available ``safety margin''....  4.7 [mu]g/m3     4.7 [mu]g/m3
Allocate a portion of PM10       ...............  -3.2 [mu]g/m3
 ``safety margin''.
Remaining Safety Margin          1.5 [mu]g/m3
 available to NOx.
Available ``safety margin''      18.5 TPD *       2.9 TPD **
 (tons per day).
Allocated Safety Margin (tons    18.4 TPD         2.9 TPD
 per day).
2022 Mobile Sources............  37.6 TPD         52.1 TPD
2022 Mobile Sources Emissions    56 TPD           55 TPD
 Budgets.
------------------------------------------------------------------------
* 1 [mu]g/m3 = 12.3 TPD NOx.
** 1 [mu]g/m3 = 0.9 TPD PM10.

[[Page 62577]]

    Therefore, the revised Denver PM10 maintenance plan establishes 
MVEBs for 2022, the final year of the maintenance plan as seen in Table 
V-3 below:

            Table V-3.--2022 Motor Vehicle Emissions Budgets
------------------------------------------------------------------------
                                                                 PM10
                      Year                        NOx  (TPD)     (TPD)
------------------------------------------------------------------------
2022............................................         56          55
------------------------------------------------------------------------

    The current 2015 motor vehicle emissions budgets were established 
in the previously approved maintenance plan using MOBILE5 and DRCOG 
transportation networks and data available at that time. As discussed 
previously, 2015 is an EPA approved budget year in the previously 
approved maintenance plan (September 16, 2002). The 2015 budgets will 
be revised in this maintenance plan, allocating a portion of available 
safety margin to both PM10 and NOx, and using the same methodology as 
the 2022 budgets. The analysis for allocating the safety margin is seen 
in Table V-4.

 Table V-4.--2015 Allocation of Available Safety Margin and Development
                   of Mobile Source Emissions Budgets
------------------------------------------------------------------------
                                       NOx                  PM10
------------------------------------------------------------------------
Maximum Allowable               149.9 [mu]g/m3     149.9 [mu]g/m3
 Concentration.
Maintenance Demonstration.....  137.5 [mu]g/m3     137.5 [mu]g/m3
Available ``safety margin''...  12.4 [mu]g/m3      12.4 [mu]g/m3
Allocate a portion of PM10      .................  -8.2 [mu]g/m3
 ``Safety Margin''.
Remaining Safety Margin         4.2 [mu]g/m3
 available to NOx.
Available ``safety margin''...  51.7 TPD           7.4 TPD **
Allocated ``safety margin''...  20.0 TPD           7.4 TPD
2015 Mobile Sources...........  50.0 TPD *         46.6 TPD
2015 MS Emissions Budget......  70.0 TPD           54 TPD
------------------------------------------------------------------------
* 1 [mu]g/m3 = 12.3 TPD NOx.
** 1 [mu]g/m3 = 0.9 TPD PM10.

    Based on this analysis the revised Denver PM10 maintenance plan 
establishes MVEBs as seen in Table V-5 below for 2015. Upon the 
effective date of this approved maintenance plan, the previously 
approved budgets for 2015 will no longer apply.

            Table V-5.--2015 Motor Vehicle Emissions Budgets
------------------------------------------------------------------------
                                                                 PM10
                      Year                        NOx  (TPD)     (TPD)
------------------------------------------------------------------------
2015............................................         70          54
------------------------------------------------------------------------

VI. EPA's Approval of the Transportation Budget Trading Protocol

    This revised maintenance plan establishes these specific MVEBs. 
However, this plan is establishing a protocol for trading emissions, as 
allowed under 40 CFR 93.124(b), between the primary PM10 budget and the 
PM10 precursor NOx. Trading will allow for different pairs of PM10 and 
NOx budgets to demonstrate conformity while still resulting in the same 
PM10 concentrations and ensuring continued air quality with respect to 
PM10.
    The technical analysis presented above has shown a relationship 
between the concentration of PM10 and the emissions of NOx and primary 
PM10 as follows:

1 [mu]g/m3 PM10 = 12.3 TPD NOx = 0.9 TPD PM10

    This relationship can also be expressed as:

1.0 TPD PM10 = 13.6 TPD NOx

    In terms of trading emissions the State is indicating that if the 
PM10 budget is increased by 1 TPD the NOx budget should be reduced 13.6 
TPD in order to have no impact on the ambient PM10 concentration. 
Conversely, if the NOx budget is increased by 13.6 TPD the primary PM10 
budget will be reduced by 1 TPD. The State, as requested by EPA, in 
order to account for uncertainties in modeling and to provide 
additional assurance of continued maintenance of the PM10 NAAQS has 
incorporated a 10% safety factor to the PM10 and NOx trading ratio 
described above. The resulting ratios for use in trading of emissions 
are detailed in the trading protocol described below.
    The MPO is the entity responsible for demonstrating transportation 
conformity. This revised PM10 maintenance plan authorizes the MPO to 
follow the steps below in determining the conformity of the long range 
transportation plan. The trading protocol is as follows:
     Initially, a demonstration of conformity shall be made 
using the approved PM10 and NOx MVEBs.
     Prior to any emissions trading, the MPO shall consider 
implementing all reasonably available local control measures to reduce 
the PM10 or NOx emissions to meet the established budgets. If 
conformity cannot be demonstrated, the MPO shall express the need for 
trading through the normal interagency consultation and review process 
described in Colorado's Air Quality Regulation No. 10: Criteria for 
Analysis of Conformity, which includes regional, state, and federal air 
quality and transportation agencies.
     If trading of NOx for PM10 or PM10 for NOx is determined 
through consultation to be necessary to adjust emission budgets for 
purposes of demonstrating transportation conformity, it shall be 
allowed using the emission trading formulas as follows:
    [cir] For any trades necessary to increase a primary PM10 budget, 
15.0 TPD of NOx will be taken from the NOx budget to increase the 
primary PM10 budget by 1.0 TPD, a ratio of 15 to 1.
    [cir] For trades necessary to increase a NOx budget, 1.0 TPD of 
primary PM10 will be taken from the primary PM10 budget to increase the 
NOx budget by 12.0 TPD, a ratio of 1 to 12.
     The MPO shall include the following information in the 
transportation conformity determination:
    [cir] The budget for primary PM10 and NOx for each required year of 
the conformity demonstration, before trading allowed by this 
maintenance plan has been employed.
    [cir] The portion of the primary PM10 budget that will be used to 
supplement the NOx budget, or, in the alternative, the portion of the 
NOx budget that will

[[Page 62578]]

be used to supplement the primary PM10 budget, in tons per day, for 
each required year of the conformity demonstration.
    [cir] The increase in the NOx budget or primary PM10 budget that 
results from use of the applicable formula specified above, along with 
relevant calculations.
    [cir] The resulting primary PM10 and NOx budgets, in tons per year, 
for each required year of the conformity demonstration, after the 
trading allowed by this maintenance plan has been employed.
     To demonstrate conformity, the MPO shall then compare 
projected emissions to the adjusted PM10 and NOx motor vehicle 
emissions budgets.
    Trades in either direction would be made on a case-by-case basis, 
decided for each plan/TIP conformity determination.
    Pursuant to section 40 CFR 93.118(e)(4) of EPA's transportation 
conformity rule, as amended, EPA must determine the adequacy of 
submitted MVEBs. EPA reviewed the Denver PM10 2022 budget for adequacy 
using the criteria in 40 CFR 93.118(e)(4), and determined that the 2022 
budget was adequate for conformity purposes. EPA's adequacy 
determination was made in a letter to the State on May 3, 2007, and was 
announced in the Federal Register on June 13, 2007 (72 FR 32646). As a 
result of this adequacy finding, the 2022 MVEB took effect for 
conformity determinations in the Denver area on June 28, 2007. However, 
we are not bound by that adequacy determination in acting on the 
maintenance plan. The 2022 and revised 2015 MVEBs are considered 
approved upon the effective date of this maintenance plan approval.

VII. EPA's Evaluation of the Regulation No. 11 Revisions

    Colorado's Regulation No. 11 is entitled, ``Motor Vehicle Emissions 
Inspection Program.'' In developing the revised Denver PM10 maintenance 
plan, the State conducted a comprehensive reevaluation of mobile source 
control programs with MOBILE6.2 and the latest transportation sets from 
DRCOG's 2030 Regional Transportation Plan. Based on these results, 
Colorado's Regulation No. 11 can be removed from the revised Denver 
PM10 maintenance plan effective December 31, 2007. This revised 
maintenance plan reflects the removal of Regulation No. 11 in that the 
mobile source PM10 emissions were calculated without the PM10 emissions 
reduction benefit of an inspection and maintenance (I/M) program 
starting January 1, 2008, and continuing through 2022. Even with the 
elimination of the I/M program from the revised Denver PM10 maintenance 
plan, beginning on January 1, 2008, the Denver area still meets EPA 
requirements to demonstrate maintenance of the PM10 standard through 
2022.
    We note that the removal of the I/M program from Denver's revised 
PM10 maintenance plan does not mean the I/M program is eliminated. The 
State relies on the I/M program in Denver's 1-hour ozone maintenance 
plan and Denver's 8-hour ozone Early Action Compact (EAC). Therefore, 
the motor vehicle I/M program will remain intact in the Denver-metro 
area. We have reviewed and are approving the removal of Regulation No. 
11 from the revised Denver PM10 maintenance plan.

VIII. Consideration of Section 110(l) of the Clean Air Act

    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. As stated above, the revised PM10 maintenance plan shows 
continuous attainment of the PM10 NAAQS since 2001 for Denver. The 
revised maintenance plan along with the removal of Regulation No. 11 
will not interfere with attainment, reasonable further progress, or any 
other applicable requirement of the CAA.

IX. Final Action

    In this action, EPA is approving the revised Denver PM10 
maintenance plan, that was submitted on September 25, 2006; the revised 
transportation conformity MVEBs for PM10 and PM10 precursor NOx for the 
years 2015 and 2022 for Denver; and the PM10 and PM10 precursor NOx, 
MVEB trading protocol and trading ratios. Furthermore, we are approving 
the removal of Regulation No. 11 (I/M) from the revised Denver PM10 
maintenance plan.
    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 January 7, 2008 without 
further notice unless the Agency receives adverse comments by December 
6, 2007. 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.

X. 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 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 (1) 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 
effect 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

[[Page 62579]]

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 January 7, 2008. 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, PM10, particulate 
matter, Intergovernmental relations, Reporting and recordkeeping 
requirements.

    Dated: October 22, 2007.
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 52.332 is amended by adding paragraph (p) to read as 
follows:

Sec.  52.332  Control strategy: Particulate matter.

* * * * *
    (p) Revisions to the Colorado State Implementation Plan, PM10 
Revised Maintenance Plan for Denver, as adopted by the Colorado Air 
Quality Control Commission on December 15, 2005, State effective on 
March 2, 2006, and submitted by the Governor's designee on September 
25, 2006. The revised maintenance plan satisfies all applicable 
requirements of the Clean Air Act.

 [FR Doc. E7-21611 Filed 11-5-07; 8:45 am]

BILLING CODE 6560-50-P