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Approval and Promulgation of Air Quality Implementation Plans; State of Colorado; Second Ten-Year PM10

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Environmental Protection Agency.


Direct final rule.


The Environmental Protection Agency (EPA) is taking final action approving State Implementation Plan (SIP) revisions submitted by the State of Colorado. On May 11, 2012, the designee of the Governor of Colorado submitted to EPA a revised maintenance plan for the Steamboat Springs area for the National Ambient Air Quality Standards (NAAQS) for particulate matter with an aerodynamic diameter less than or equal to 10 microns (PM10). The SIP was adopted by the State on December 15, 2011. As required by Clean Air Act (CAA) section 175A, this revised maintenance plan addresses maintenance of the PM10 standard for a second 10-year period beyond the area's original redesignation to attainment for the PM10 NAAQS. In addition, EPA is approving the revised maintenance plan's 2024 transportation conformity motor vehicle emissions budget (MVEB) for PM10. This action is being taken under sections 110 and 175A of the CAA.


This rule is effective on March 23, 2015 without further notice, unless EPA receives adverse comment by February 20, 2015. 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.


Submit your comments, identified by Docket ID No. EPA-R08-OAR-2013-0814, by one of the following methods:

  • Follow the on-line instructions for submitting comments.
  • Email:
  • Fax: (303) 312-6064 (please alert the individual listed in the FOR FURTHER INFORMATION CONTACT if you are faxing comments).
  • Mail: Carl Daly, Director, Air Program, U.S. Environmental Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595 Wynkoop Street, Denver, Colorado 80202-1129.
  • Hand Delivery: Carl Daly, Director, Air Program, U.S. Environmental Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595 Wynkoop Street, Denver, Colorado 80202-1129. Such deliveries are only accepted Monday through Friday, 8:00 a.m. to 4:30 p.m., excluding federal holidays. Special arrangements should be made for deliveries of boxed information.

Instructions: Direct your comments to Docket ID No. EPA-R08-OAR-2013-0814. EPA's policy is that all comments received will be included in the public docket without change and may be made available online at, 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 or email. The Web site is an “anonymous access” system, which means EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an email comment directly to EPA, without going through, your email address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the Internet. If you submit an electronic comment, EPA recommends that you include your name and other contact information in the body of your comment and with any disk or CD-ROM you submit. If EPA cannot read your comment due to technical difficulties and cannot contact Start Printed Page 2828you for clarification, EPA may not be able to consider your comment. Electronic files should avoid the use of special characters, any form of encryption, and be free of any defects or viruses. For additional instructions on submitting comments, go to Section I. General Information of the SUPPLEMENTARY INFORMATION section of this document.

Docket: All documents in the docket are listed in the 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 or in hard copy at the Air Program, U.S. Environmental Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595 Wynkoop Street, Denver, Colorado 80202-1129. EPA requests that if at all possible, you contact the individual listed in the FOR FURTHER INFORMATION CONTACT section to view the hard copy of the docket. You may view the hard copy of the docket Monday through Friday, 8:00 a.m. to 4:00 p.m., excluding federal holidays.

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Crystal Ostigaard, Air Program, U.S. Environmental Protection Agency, Region 8, Mailcode 8P-AR, 1595 Wynkoop Street, Denver, Colorado 80202-1129, (303) 312-6602,

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

(i) The words EPA, we, us or our mean or refer to the United States Environmental Protection Agency.

(ii) The words or initials Act or CAA mean or refer to the Clean Air Act, unless the context indicates otherwise.

(iii) The initials APCD mean or refer to the Colorado Air Pollution Control Division.

(iv) The initials AQCC mean or refer to the Colorado Air Quality Control Commission.

(v) The words Colorado and State mean or refer to the State of Colorado.

(vi) The initials MVEB mean or refer to motor vehicle emissions budget.

(vii) The initials NAAQS mean or refer to National Ambient Air Quality Standard.

(viii) The initials PM10 mean or refer to particulate matter with an aerodynamic diameter of less than or equal to 10 micrometers (coarse particulate matter).

(ix) The initials SIP mean or refer to State Implementation Plan.

(x) The initials TSD mean or refer to technical support document.

I. General Information

1. Submitting CBI. Do not submit CBI to EPA through or email. Clearly mark the part or all of the information that you claim to be CBI. For CBI information in a disk or CD ROM that you mail to EPA, mark the outside of the disk or CD ROM as CBI and then identify electronically within the disk or CD ROM the specific information that is claimed as CBI. In addition to one complete version of the comment that includes information claimed as CBI, a copy of the comment that does not contain the information claimed as CBI must be submitted for inclusion in the public docket. Information so marked will not be disclosed except in accordance with procedures set forth in 40 CFR part 2.

2. Tips for Preparing Your Comments. When submitting comments, remember to:

a. Identify the rulemaking by docket number and other identifying information (subject heading, Federal Register date and page number).

b. Follow directions—The agency may ask you to respond to specific questions or organize comments by referencing a Code of Federal Regulations (CFR) part or section number.

c. Explain why you agree or disagree; suggest alternatives and substitute language for your requested changes.

d. Describe any assumptions and provide any technical information and/or data that you used.

e. If you estimate potential costs or burdens, explain how you arrived at your estimate in sufficient detail to allow for it to be reproduced.

f. Provide specific examples to illustrate your concerns, and suggest alternatives.

g. Explain your views as clearly as possible, avoiding the use of profanity or personal threats.

h. Make sure to submit your comments by the comment period deadline identified.

II. Background

The Steamboat Springs area was designated unclassifiable for the 1987 PM10 NAAQS by operation of law upon enactment of the CAA Amendments of 1990. See 56 FR 56694, November 6, 1991. However, in January and February of 1991, the EPA notified the Governors of those States, including the State of Colorado, which recorded violations of the PM10 standard after January 1, 1989, that EPA believed that those areas should be redesignated as nonattainment for PM10. In the Federal Register published on April 22, 1991 (56 FR 16274), EPA identified those PM10 areas for which the EPA had notified the Governors of affected States that the area's PM10 designation should be revised to nonattainment. After notification, the Governor of each affected state was required to submit to EPA the redesignation he or she considered appropriate for each area. The EPA proceeded to redesignate to nonattainment 10 areas, including the Steamboat Springs area, for PM10 on December 21, 1993 (58 FR 67334). EPA fully approved Colorado's nonattainment area SIP for the Steamboat Springs area on December 31, 1997 (62 FR 68188).

On July 31, 2002, the Governor of Colorado submitted a request to EPA to redesignate the Steamboat Springs moderate PM10 nonattainment area to attainment for the 1987 PM10 NAAQS. Along with this request, the State submitted a maintenance plan, which demonstrated that the area would continue to attain the PM10 NAAQS through 2015. EPA approved the Steamboat Springs maintenance plan and redesignation to attainment on October 25, 2004 (69 FR 62210).

Eight years after an area is redesignated to attainment, CAA section 175A(b) requires the state to submit a subsequent maintenance plan to EPA, covering a second 10-year period.[1] This second 10-year maintenance plan must demonstrate continued maintenance of the applicable NAAQS during this second 10-year period. To fulfill this requirement of the Act, the Governor of Colorado's designee submitted the second 10-year update of the PM10 maintenance plan to EPA on May 11, 2012 (hereafter; “revised Steamboat Springs PM10 Maintenance Plan”).

As described in 40 CFR 50.6, the level of the national primary and secondary 24-hour ambient air quality standards for PM10 is 150 micrograms per cubic meter (μg/m[3] ). An area attains the 24-hour PM10 standard when the expected Start Printed Page 2829number of days per calendar year with a 24-hour concentration in excess of the standard (referred to herein as “exceedance”), as determined in accordance with 40 CFR part 50, appendix K, is equal to or less than one, averaged over a three-year period.[2] See 40 CFR 50.6 and 40 CFR part 50, appendix K.

Table 1 below shows the maximum monitored 24-hour PM10 values for the Steamboat Springs PM10 maintenance area for 2004-2014. The table reflects that the values for the Steamboat Springs area are well below the PM10 NAAQS standard of 150 μg/m3.

Table 1—Steamboat Springs PM10 Maximum 24-Hour Values

[Based on data from Routt County Court House site, AQS Identification Number 08-107-0003]

YearMaximum value (μg/m3)
2014* 84
* Preliminary 2014 Data only through September 17, 2014.

Table 2 below shows the estimated number of exceedances for the Steamboat Springs PM10 maintenance area for the three-year periods starting in 2004 and ending in 2014. The table reflects continuous attainment of the PM10 NAAQS.

Table 2—Steamboat Springs PM10 Estimated Exceedances

[Based on data from Routt County Court House site, AQS Identification Number 08-107-0003]

Design value period3-Year estimated number of exceedances
2012-2014* 0
* Preliminary 2014 Data only through September 17, 2014.

III. What was the State's process?

Section 110(a)(2) of the CAA requires that a state provide reasonable notice and public hearing before adopting a SIP revision and submitting it to EPA.

The Colorado Air Quality Control Commission (AQCC) held a public hearing for the revised Steamboat Springs PM10 Maintenance Plan on December 15, 2011. The AQCC approved and adopted the revised Steamboat Springs PM10 Maintenance Plan directly after the hearing. The Governor's designee submitted the revised plan to EPA on May 11, 2012.

We have evaluated the revised maintenance plan and have determined that the State met the requirements for reasonable public notice and public hearing under section 110(a)(2) of the CAA. On November 11, 2012, by operation of law under CAA section 110(k)(1)(B), the revised maintenance plan was deemed to have met the minimum “completeness” criteria found in 40 CFR part 51, appendix V.

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

The following are the key elements of a Maintenance Plan for PM10: Emission Inventory, Maintenance Demonstration, Monitoring Network/Verification of Continued Attainment, Contingency Plan, and MVEB for PM10. Below, we describe our evaluation of these elements as they pertain to the revised Steamboat Springs PM10 Maintenance Plan.

A. Emission Inventory

The revised Steamboat Springs PM10 Maintenance Plan includes three inventories of daily PM10 emissions for the Steamboat Springs area; they are for 2008, 2016 and 2024. The Air Pollution Control Division (APCD) developed these emission inventories using EPA-approved emissions modeling methods, and updated transportation information, demographics data, and reported actual emissions for point sources. Each emission inventory is a list, by source category, of the air contaminants directly emitted into the Steamboat Springs PM10 maintenance area. A more detailed description of the 2008 and 2024 inventories and information on model assumptions and parameters for each source category are contained in the State's PM10 Maintenance Plan Technical Support Document (TSD). Included in all the inventories are emissions data for: commercial cooking; construction; fuel combustion; highway vehicles; non-road vehicles; railroad; road dust; structure fires; woodburning; and point sources. We find that Colorado has prepared adequate emission inventories for the area.

B. Maintenance Demonstration

The revised Steamboat Springs PM10 Maintenance Plan uses emission roll-forward modeling to demonstrate maintenance of the 24-hour PM10 NAAQS through 2024. Using the 2008 and 2024 emissions inventories, the State first determined the projected growth in PM10 emissions from the 2008 base year to the 2024 maintenance year. The State estimated that emissions would increase from 5,095.9 pounds per day in 2008 to 7,308.8 pounds per day in 2024. This represents an increase of 43.4 percent.

The State then applied this percentage increase to the design day concentration of 99 μg/m3, which was the third highest 24-hour maximum PM10 value recorded in Steamboat Springs from 2008-2010. This resulted in an estimated maximum 24-hour PM10 concentration in 2024 of 142 μg/m3. This is below the 24-hour PM10 NAAQS of 150 μg/m3.

C. Monitoring Network/Verification of Continued Attainment

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

Based on the above, we are approving these commitments as satisfying the relevant requirements. These commitments are similar to those we approved in the original maintenance plan.

D. Contingency Plan

Section 175A(d) of the CAA requires that a maintenance plan include Start Printed Page 2830contingency provisions to promptly correct any violation of the NAAQS that occurs after redesignation of an area. 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 the revised Steamboat Springs PM10 Maintenance Plan, exceedances trigger one level of response and violations trigger another. If there is an exceedance, the APCD and local government staff will develop appropriate contingency measure(s) intended to prevent or correct a violation of the PM10 standard. The APCD and local government staff will consider relevant information about historical exceedances, meteorological conditions related to the exceedance(s), and the most recent estimates of growth and emissions, and whether the exceedance might be attributed to an exceptional event. The maintenance plan indicates that the State will generally notify EPA and local governments in the Steamboat Springs area within 30 days of the exceedance, but in no event later than 45 days. The process for exceedances will be completed within six months of the exceedance notification.

If a violation of the PM10 NAAQS has occurred, a public hearing process at the State and local level will begin. If the AQCC agrees that the implementation of local measures will prevent further exceedances or violations, the AQCC may endorse or approve the local measures without adopting State requirements. If, however, the AQCC finds locally adopted contingency measures to be inadequate, the AQCC will adopt State enforceable measures as deemed necessary to prevent additional exceedances or violations. The State commits to adopt and implement any necessary contingency measures within one year after a violation occurs. Any state enforceable measures that are adopted will become part of another revised maintenance plan, which will be submitted to the Colorado Legislature and the EPA for approval.

The State indentifies the following as potential contingency measures in the revised Steamboat Springs PM10 Maintenance Plan: (1) increased street sweeping requirements; (2) road paving requirements; (3) more stringent street sand specifications; (4) voluntary or mandatory woodburning curtailment; (5) bans on all woodburning; (6) expanded, mandatory use of alternative de-icers; (7) re-establishing new source review nonattainment area permitting requirements for stationary sources; (8) transportation control measures designed to reduce vehicle miles traveled; and (9) other emission control measures appropriate for the area based on the consideration of cost effectiveness, PM10 emission reduction potential, economic and social considerations, or other factors that the State deems appropriate.

We find that the contingency measures provided in the revised Steamboat Springs PM10 Maintenance Plan are sufficient and meet the requirements of section 175A(d) of the CAA.

E. Transportation Conformity Requirements: MVEB for PM10

Transportation conformity is required by section 176(c) of the CAA. EPA's conformity rule at 40 CFR 93 requires that transportation plans, programs, and projects conform to SIPs and establishes the criteria and procedures for determining whether or not they conform. Conformity to a SIP means that transportation activities will not produce new air quality violations, worsen existing violations, or delay timely attainment of the NAAQS. To effectuate its purpose, the conformity rule requires a demonstration that emissions from the Regional Transportation Plan and the Transportation Improvement Program are consistent with the MVEB(s) contained in a control strategy SIP revision or maintenance plan (40 CFR 93.101, 93.118, and 93.124). A MVEB is defined as the level of mobile source emissions of a pollutant relied upon in the attainment or maintenance demonstration to attain or maintain compliance with the NAAQS in the nonattainment or maintenance area. Further information concerning EPA's interpretations regarding MVEBs can be found in the preamble to EPA's November 24, 1993, transportation conformity rule (see 58 FR 62193—62196).

The revised Steamboat Springs PM10 Maintenance Plan contains a single MVEB of 1,103 lbs/day of PM10 for the year 2024, the maintenance year. Once the State submitted the revised plan with the 2024 MVEB to EPA for approval, 40 CFR 93.118 required that EPA determine whether the MVEB was adequate.

Our criteria for determining whether a SIP's MVEB is adequate for conformity purposes are outlined in 40 CFR 93.118(e)(4), which was promulgated August 15, 1997 (see 62 FR 43780). Our process for determining adequacy is described in our July 1, 2004 Transportation Conformity Rule Amendments (see 69 FR 40004) and in relevant guidance.[3] We used these resources in making our adequacy determination described below.

On November 15, 2013, EPA announced the availability of the revised Steamboat Springs PM10 Maintenance Plan, and the PM10 MVEB, on EPA's transportation conformity adequacy Web site. EPA solicited public comment on the MVEB, and the public comment period closed on December 16, 2013. We did not receive any comments. This information is available at EPA's conformity Web site:​otaq/​stateresources/​transconf/​currsips.htm#steam-spr-co.

By letter to the Colorado Department of Public Health and Environment dated January 23, 2014, EPA found that the revised Steamboat Springs PM10 Maintenance Plan and the 2024 PM10 MVEB were adequate for transportation conformity purposes.[4] However, we noted in our letter that the revised Steamboat Springs PM10 Maintenance Plan did not discuss the PM10 MVEB for 2015 of 21,773 lbs/day from the original PM10 maintenance plan that EPA approved in 2004 (see 69 FR 62210, October 25, 2004).

According to 40 CFR 93.118(e)(1), the EPA-approved 2015 PM10 MVEB must continue to be used for analysis years 2015 through 2023 (as long as such years are within the timeframe of the transportation plan), unless the State elects to submit a SIP revision to revise the 2015 PM10 MVEB and EPA approves the SIP revision. This is because the revised Steamboat Springs PM10 Maintenance Plan did not revise the previously approved 2015 PM10 MVEB nor establish a new MVEB for 2015. Accordingly, the MVEB “ . . . for the most recent prior year . . . ” (i.e., 2015) from the original maintenance plan must continue to be used (see 40 CFR 93.118(b)(1)(ii) and (b)(2)(iv)).

We note that there is a considerable difference between the 2024 and 2015 budgets—1,103 lbs/day versus 21,773 lbs/day. This is largely an artifact of changes in the methods, models, and emission factors used to estimate mobile source emissions. The 2024 MVEB is consistent with the State's 2024 emissions inventory for vehicle exhaust and road dust, and, thus, is consistent with the State's maintenance demonstration for 2024.Start Printed Page 2831

The discrepancy between the 2015 and 2024 MVEBs is not a significant issue for several reasons. As a practical matter, the 2024 MVEB of 1,103 lbs/day of PM10 would be controlling for any conformity determination involving the relevant years because conformity would have to be shown to both the 2015 MVEB and the 2024 MVEB. Also, for any maintenance plan, such as the revised Steamboat Springs PM10 Maintenance Plan, that only establishes a MVEB for the last year of the maintenance plan, 40 CFR 93.118(b)(2)(i) requires that the demonstration of consistency with the budget be accompanied by a qualitative finding that there are no factors that would cause or contribute to a new violation or exacerbate an existing violation in the years before the last year of the maintenance plan. Therefore, when a conformity determination is prepared which assesses conformity for the years before 2024, the 2024 MVEB and the underlying assumptions supporting it would have to be considered. Finally, 40 CFR 93.110 requires the use of the latest planning assumptions in conformity determinations. Thus, the most current motor vehicle and road dust emission factors would need to be used, and we expect the analysis would show greatly reduced PM10 motor vehicle and road dust emissions from those calculated in the first maintenance plan. In view of the above, EPA is approving the 2024 PM10 MVEB of 1,103 lbs/day.

V. Final Action

We are approving the revised Steamboat Springs PM10 Maintenance Plan that was submitted to us on May 11, 2012. We are approving the revised maintenance plan because it demonstrates maintenance through 2024 as required by CAA section 175A(b), retains the control measures from the initial PM10 maintenance plan that EPA approved in October of 2004, and meets other CAA requirements for a section 175A maintenance plan. Our approval includes approval of the revised maintenance plan's 2024 transportation conformity MVEB for PM10 of 1,103 lbs/day.

VI. 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 or more Indian tribes, on the relationship between the Federal Government and Indian tribes, or on the distribution of power and responsibilities between the Federal Government and Indian tribes, as specified by Executive Order 13175 (65 FR 67249, November 9, 2000). This action also does not have Federalism implications because it does not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government, as specified in Executive Order 13132 (64 FR 43255, August 10, 1999). This action merely approves a state rule as meeting Federal requirements, and does not alter the relationship or the distribution of power and responsibilities established in the CAA. 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 CAA. 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 CAA. 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. 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. 804(2).

Under section 307(b)(1) of the CAA, petitions for judicial review of this action must be filed in the United States Court of Appeals for the appropriate circuit by March 23, 2015. Filing a petition for reconsideration by the Administrator of this final rule does not affect the finality of this action 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. Parties with objections to this direct final rule are encouraged to file a comment in response to the parallel notice of proposed rulemaking for this action published in the proposed rules section of today's Federal Register, rather than file an immediate petition for judicial review of this direct final rule, so that EPA can withdraw this direct final rule and address the comment in the proposed rulemaking. This action may not be challenged later in proceedings to enforce its requirements. (See CAA section 307(b)(2).)

Start List of Subjects

List of Subjects in 40 CFR Part 52

  • Environmental protection
  • Air pollution control
  • PM
End List of Subjects Start Authority

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

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Dated: December 17, 2014.

Shaun L. McGrath,

Regional Administrator.

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40 CFR part 52 is amended to read as follows:

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

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

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Subpart G—Colorado

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

End Amendment Part
Control strategy: Particulate matter.
* * * * *

(u) Revisions to the Colorado State Implementation Plan, PM10 Revised Maintenance Plan for Steamboat Springs, as adopted by the Colorado Air Quality Control Commission on December 15, 2011, State effective on January 30, 2012, and submitted by the Governor's designee on May 11, 2012. The revised maintenance plan satisfies all applicable requirements of the Clean Air Act.

End Supplemental Information


1.  In this case, the initial maintenance period described in CAA section 175A(a) was required to extend for at least 10 years after the redesignation to attainment, which was effective on November 24, 2004. See 69 FR 62210. So the first maintenance plan was required to show maintenance at least through 2014. CAA section 175A(b) requires that the second 10-year maintenance plan maintain the NAAQS for “10 years after the expiration of the 10-year period referred to in [section 175A(a)].” Thus, for the Steamboat Springs area, the second 10-year period ends 2024.

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2.  An exceedance is defined as a daily value that is above the level of the 24-hour standard, 150 µg/m3. , after rounding to the nearest 10 μg/m3. (i.e., values ending in five or greater are to be rounded up). Thus, a recorded value of 154 μg/m3. would not be an exceedance since it would be rounded to 150 μg/m3. ; whereas, a recorded value of 155 μg/m3. would be an exceedance since it would be rounded to 160 μg/m3. . See 40 CFR part 50, appendix K, section 1.0.

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3.  “Companion Guidance for the July 1, 2004 Final Transportation Conformity Rule, Conformity Implementation in Multi-Jurisdictional Nonattainment and Maintenance Areas for Existing and New Air Quality Standards” (EPA420-B-04-012 July, 2004).

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4.  In a Federal Register dated October 3, 2014, we notified the public of our finding (see 79 FR 59767). This adequacy determination became effective on October 20, 2014.

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[FR Doc. 2015-00780 Filed 1-20-15; 8:45 am]