E7-21611. Approval and Promulgation of Air Quality Implementation Plans; State of Colorado; Revised Denver PM10

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Direct final rule.

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-OAR-2007-0622, by one of the following methods:

• http://www.regulations.gov. Follow the on-line instructions for submitting comments.
• E-mail: [e-mail] and [e-mail].
• Fax: [phone] (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 [phone], and e-mail at: [e-mail].

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.

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 (μg/m³), 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 μg/m³, 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

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.

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 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. 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 μg/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 μg/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 μg/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 μg/m³ PM10 = 0.9 TPD PM10/μg/m³ PM10

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

255.1 TPD NOx/20.8 μg/m³ PM10 = 12.3 TPD NOx/μg/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 μg/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 Concentration	149.9 μg/m3	149.9 μg/m3
Maintenance Demonstration	145.2 μg/m3	145.2 μg/m3
Available “safety margin” ((micrograms/meter3)	4.7 μg/m3	4.7 μg/m3
Available “safety margin” (tons per day)	57.8 TPD *	4.2 TPD **
2022 Mobile Sources	37.6 TPD	52.1 TPD
2022 Mobile Source Budget with all Safety Margin Applied to NOx or PM10	95.4 TPD	56.3 TPD
* 1 μg/m3 = 12.3 TPD NOx.
** 1 μg/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 μg/m3	4.7 μg/m3
Allocate a portion of PM10 “safety margin”		−3.2 μg/m3
Remaining Safety Margin available to NOx	1.5 μg/m3
Available “safety margin” (tons per day)	18.5 TPD *	2.9 TPD **
Allocated Safety Margin (tons per day)	18.4 TPD	2.9 TPD
2022 Mobile Sources	37.6 TPD	52.1 TPD
2022 Mobile Sources Emissions Budgets	56 TPD	55 TPD
* 1 μg/m3 = 12.3 TPD NOx.
** 1 μg/m3 = 0.9 TPD PM10.

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

Year	NOx (TPD)	PM10 (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 Concentration	149.9 μg/m3	149.9 μg/m3
Maintenance Demonstration	137.5 μg/m3	137.5 μg/m3
Available “safety margin”	12.4 μg/m3	12.4 μg/m3
Allocate a portion of PM10 “Safety Margin”		−8.2 μg/m3
Remaining Safety Margin available to NOx	4.2 μg/m3
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 μg/m3 = 12.3 TPD NOx.
** 1 μg/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

Year	NOx (TPD)	PM10 (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 μg/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:

○ 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.

○ 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:

○ 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.

○ 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 be used to supplement the primary PM10 budget, in tons per day, for each required year of the conformity demonstration.

○ The increase in the NOx budget or primary PM10 budget that results from use of the applicable formula specified above, along with relevant calculations.

○ 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 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.

40 CFR part 52 is amended to read as follows:

PART 52—[AMENDED]

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

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

Subpart G—Colorado

2. Section 52.332 is amended by adding paragraph (p) to read as follows:

§ 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.

Footnotes

1.  “Procedures for Processing Requests to Redesignate Areas to Attainment,” Policy Memo: J. Calcagni to Div. Air Directors, September 4, 1992.