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Proposed Rule

Approval and Promulgation of Air Quality Implementation Plans; State of Montana Second 10-Year Carbon Monoxide Maintenance Plan for Great Falls

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Environmental Protection Agency (EPA).


Proposed rule.


The Environmental Protection Agency (EPA) is proposing approval of a State Implementation Plan (SIP) revision submitted by the State of Montana. On July 13, 2011, the Governor of Montana's designee submitted to EPA a second 10-year maintenance plan for the Great Falls area for the carbon monoxide (CO) National Ambient Air Quality Standard (NAAQS). This maintenance plan addresses maintenance of the CO NAAQS for a second 10-year period beyond the original redesignation. EPA is also proposing approval of an alternative monitoring strategy for the Great Falls CO maintenance area, which was submitted by the Governor's designee on June 22, 2012.


Comments must be received on or before December 31, 2014.


Submit your comments, identified by Docket ID No. EPA-R08-OAR-2012-0353, 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).Start Printed Page 71058
  • Mail: Director, Air Program, Environmental Protection Agency (EPA), Region 8, Mail Code 8P-AR, 1595 Wynkoop Street, Denver, Colorado 80202-1129.
  • Hand Delivery: Director, Air Program, EPA, Region 8, Mail Code 8P-AR, 1595 Wynkoop, 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-2012-0353. 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 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 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, EPA, Region 8, Mailcode 8P-AR, 1595 Wynkoop, 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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Adam Clark, Air Program, EPA, Region 8, Mailcode 8P-AR, 1595 Wynkoop, Denver, Colorado 80202-1129, (303) 312-7104,

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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 initials ADT mean or refer to Average Daily Traffic.

(iii) The initials CO mean or refer to carbon monoxide.

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

(v) The initials LMP mean or refer to Limited Maintenance Plan.

(vi) The initials MDEQ mean or refer to Montana Department of Environmental Quality.

(vii) The initials MVEB mean or refer to Motor Vehicle Emissions Budget.

(viii) The initials NAAQS mean or refer to the National Ambient Air Quality Standards.

(ix) The initials ppm mean or refer to parts per million.

(x) The initials RTP mean or refer to Regional Transportation Plan.

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

(xii) The initials TIP mean or refer to Transportation Improvement Plan.

(xiii) The words Montana and State mean or refer to the State of Montana.

I. General Information

What should I consider as I prepare my comments for EPA?

1. Submitting Confidential Business Information (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 on 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:

  • Identify the rulemaking by docket number and other identifying information (subject heading, Federal Register, date, and page number);
  • Follow directions and organize your comments;
  • Explain why you agree or disagree;
  • Suggest alternatives and substitute language for your requested changes;
  • Describe any assumptions and provide any technical information and/or data that you used;
  • If you estimate potential costs or burdens, explain how you arrived at your estimate in sufficient detail to allow for it to be reproduced;
  • Provide specific examples to illustrate your concerns and suggest alternatives;
  • Explain your views as clearly as possible, avoiding the use of profanity or personal threats; and
  • Make sure to submit your comments by the comment period deadline identified.

II. Background

A. Great Falls CO Maintenance Plan

Under the Clean Air Act (CAA) Amendments of 1990, the Great Falls area was designated as nonattainment and classified as a “not classified” CO area. This was because the area had been designated as nonattainment before November 15, 1990, but had not violated the CO NAAQS in 1988 and 1989 (56 FR 56694, November 6, 1991). On February 9, 2001, the Governor of Montana submitted to us a request to redesignate the Great Falls CO nonattainment area to attainment for the CO NAAQS. Along with this request, the Governor submitted a CAA section 175A(a) maintenance plan which demonstrated that the area would maintain the CO NAAQS for the first 10 years following our approval of the redesignation request. We approved the State's redesignation request and 10-year maintenance plan on May 9, 2002 (67 FR 31143).

Eight years after an area is redesignated to attainment, CAA section 175A(b) requires the state to submit a subsequent maintenance plan to EPA, Start Printed Page 71059covering a second 10-year period.[1] This second 10-year maintenance plan must demonstrate continued compliance with the NAAQS during this second 10-year period. To fulfill this requirement of the CAA, the Governor of Montana's designee submitted the second 10-year update of the Great Falls CO maintenance plan (hereafter; “revised Great Falls Maintenance Plan”) to us on July 13, 2011. With this action, we are proposing approval of the revised Great Falls Maintenance Plan.

The 8-hour CO NAAQS—9.0 parts per million (ppm)—is attained when such value is not exceeded more than once a year. 40 CFR 50.8(a)(1). The Great Falls area has attained the 8-hour CO NAAQS from 1988 to the present. In October 1995, EPA issued guidance that provided nonclassifiable CO nonattainment areas the option of using a less rigorous “limited maintenance plan” (LMP) option to demonstrate continued attainment and maintenance of the CO NAAQS.[2] According to this guidance, areas that can demonstrate design values (2nd highest max) at or below 7.65 ppm (85% of exceedance levels of the 8-hour CO NAAQS) for eight consecutive quarters qualify to use an LMP. The area qualified for and used EPA's LMP option for the first 10-year Great Falls CO maintenance plan (67 FR 31143, May 9, 2002). For the revised Great Falls Maintenance Plan the State again used the LMP option to demonstrate continued maintenance of the CO NAAQS in the Great Falls area. We have determined that the Great Falls area continues to qualify for the LMP option because the maximum design value for the most recent eight consecutive quarters with certified data at the time the State adopted the plan (years 2008 and 2009) was 1.6 ppm.[3]

B. Alternative CO Monitoring Strategy

Along with the revised Great Falls Maintenance Plan, the State submitted a CO maintenance plan for the Billings, Montana maintenance area, and an alternative strategy for monitoring continued attainment of the CO NAAQS in all of the State's CO maintenance areas on July 13, 2011.[4] The State submitted the alternative monitoring strategy to conserve resources by discontinuing the gaseous CO ambient monitors in both the Billings and Great Falls CO maintenance areas. In place of the gaseous ambient monitors, the State's alternative method relies on rolling 3-year Average Daily Traffic (ADT) vehicle counts collected from permanent automatic traffic recorders in each maintenance area. We commented on the State's “Alternative Monitoring Strategy,” and the State submitted to us a revised version of the strategy which incorporated our comments on June 22, 2012. The State's June 22, 2012 Alternative Monitoring Strategy replaced the version submitted on July 13, 2011.

III. EPA's Evaluation of Montana's Alternative Monitoring Strategy in Great Falls

Since 2002, no Great Falls CO monitor has registered a design value greater than 2.8 ppm, which is below one-third of the NAAQS.[5] Citing these consistently low monitor values, and expressing a desire to conserve monitoring resources, the State has requested to discontinue CO monitoring in Great Falls and instead use an alternative strategy for monitoring maintenance of the CO NAAQS.

The State's Alternative Monitoring Strategy utilizes ADT vehicle counts collected from permanent automatic traffic recorders in the Great Falls CO maintenance area to determine average monthly traffic during the traditional high CO concentration season of November through February. The State will compare the latest rolling 3-years of monthly ADT volumes to the 2008-2010 baseline ADT volumes (see Table 1) that correlate to the low CO monitored values during that period (see Table 2). Because mobile sources are the biggest driver of CO pollution, the Montana Department of Environmental Quality (MDEQ) reasoned that any significant increase in CO emissions would have to be accompanied by a significant increase in ADT.[6] EPA agrees with the State's reasoning.

Table 1—Traffic Volumes for Great Falls, Montana

[Rolling 2008-2010 ADT: November to February]

Month-YearGreat Falls (#A-033)
January 200834,123
February 200836,855
November 200835,675
December 200833,584
January 200933,820
February 200936,102
November 200937,110
December 200934,742
January 201034,371
February 201036,576
November 201034,164
December 201034,691

Table 2—8-Hour CO Design Values for Great Falls, Montana

Design value (ppm) 7Year

If the rolling 3-year ADT value is 25% higher than the average value of 35,151 from the 2008-2010 baseline period, the State will reestablish CO ambient monitoring in Great Falls the following high season (November-February). If the CO design value in that season has not increased from the baseline mean by an equal or greater rate at which ADT has increased, and the monitor values remain at or below 50% of the CO NAAQS (2nd max concentration ≤4.5 ppm), the monitor may again be removed and the ADT counts will continue to be relied upon to determine compliance with the NAAQS. This process will be repeated each time the rolling 3-year ADT increases by a factor of 25% (e.g. 50%, 75%) above the baseline 2008-2010 period, and the same analysis will be conducted to determine if the monitors can again be removed.

40 CFR 58.14(c) allows approval of requests to discontinue ambient monitors “on a case-by-case basis if discontinuance does not compromise data collection needed for implementation of a NAAQS and if the requirements of appendix D to 40 CFR Start Printed Page 71060part 58, if any, continue to be met.” EPA finds that the Alternative Monitoring Strategy meets the criteria of 40 CFR 58.14(c) for the Great Falls CO maintenance area. Given the long history of low CO concentrations in the Great Falls area, and the adequacy of the Alternative Monitoring Strategy at ensuring continued attainment of the CO NAAQS, EPA finds it appropriate to approve the State's request to discontinue the Great Falls monitor and use the Alternative Monitoring Strategy in its place.

IV. EPA's Evaluation of the Great Falls Second 10-Year CO Maintenance Plan

The following are the key elements of an LMP for CO: Emission Inventory, Maintenance Demonstration, Monitoring Network/Verification of Continued Attainment, Contingency Plan, and Conformity Determinations. Below, we describe our evaluation of each of these elements as it pertains to the revised Great Falls Maintenance Plan.

A. Emission Inventory

The revised Great Falls Maintenance Plan contains an emissions inventory for the base year 2009. The emission inventory is a list, by source, of the air contaminants directly emitted into the Great Falls CO maintenance area on a typical winter day in 2009.[8] The mobile sources data in the emission inventory in the July 13, 2011 submittal were developed using emissions modeling methods that EPA did not consider up-to-date. After consultation with EPA, the State then provided EPA with technical information to clarify and supplement the emissions inventory from the July 13, 2011 submittal.[9] This supplemental technical information utilized EPA-recommended mobile sources emissions modeling methods (MOVES2010b).[10] The Great Falls LMP and supplementary technical information contain detailed emission inventory information that was prepared in accordance with EPA guidance and is acceptable to EPA.[11]

B. Maintenance Demonstration

We consider the maintenance demonstration requirement to be satisfied for areas that qualify for and use the LMP option. As mentioned above, a maintenance area is qualified to use the LMP option if that area's maximum 8-hour CO design value for eight consecutive quarters does not exceed 7.65 ppm (85% of the CO NAAQS). EPA maintains that if an area begins the maintenance period with a design value no greater than 7.65 ppm, the applicability of prevention of significant deterioration requirements, the control measures already in the SIP, and federal measures should provide adequate assurance of maintenance over the 10-year maintenance period. Therefore, EPA does not require areas using the LMP option to project emissions over the maintenance period. Because CO design values in the Great Falls area are consistently well below the LMP threshold (See Table 2), the State has adequately demonstrated that the Great Falls area will maintain the CO NAAQS into the future.

C. Monitoring Network/Verification of Continued Attainment

In the revised Great Falls Maintenance Plan, the State commits to “continue to monitor CO using an instrumental method or a functionally equivalent monitoring methodology as approved by EPA.” As noted, EPA is proposing to approve the State's Alternative Monitoring Strategy for the Great Falls CO maintenance area as part of this action. Based on final approval of the Alternative Monitoring Strategy, we will have concluded that the strategy is adequate to verify continued attainment of the CO NAAQS in Great Falls.

D. Contingency Plan

Section 175A(d) of the CAA requires that a maintenance plan include contingency 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.

The Great Falls Maintenance Plan stated in section that the State will use an exceedance of the CO NAAQS as the trigger for adopting specific contingency measures for the Great Falls area. As noted, the Alternative Monitoring Strategy requires reinstitution of a CO monitor in Great Falls if traffic levels increase from the 2008-2010 baseline by a factor of 25%. Therefore, EPA finds that CO emissions in Great Falls are very unlikely to increase to the point of an exceedance without that exceedance being observed by a gaseous monitor.

The State indicates that notification of an exceedance to EPA and to the local governments in the Great Falls area will occur within 60 days. Upon notification of a CO NAAQS exceedance, MDEQ and Cascade City/County Health Department (CCCHD) will recommend an appropriate contingency measure or measures that would be necessary to avoid a violation of the CO NAAQS standard. The necessary contingency measure(s) will then be proposed for local adoption. Finalization of the necessary contingency measures for local adoption will be completed within three months of the exceedance notification. Full implementation of the locally adopted contingency measure(s) will be achieved within one year after the recording of a CO NAAQS violation.

The potential contingency measures, identified in section of the Great Falls Maintenance Plan, include implementation of a mandatory oxygenated fuels program with local regulations in the Great Falls or Cascade County area for the winter months of November, December, and January, and establishing an episodic woodburning curtailment program. A more complete description of the triggering mechanism and these contingency measures can be found in section of the Great Falls Maintenance Plan.

We find that the contingency measures provided in the State's maintenance plan for Great Falls are sufficient and meet the requirements of section 175A(d) of the CAA.

E. Transportation Conformity

Transportation conformity is required by section 176(c) of the CAA. 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 (CAA 176(c)(B)). EPA's conformity rule provisions in 40 CFR part 93, Subpart A require that transportation plans, programs and projects conform to SIPs and establish the criteria and procedures for determining whether or not they demonstrate conformity. EPA's conformity rule provisions include requirements for a demonstration that emissions from the Regional Transportation Plan (RTP) and the Transportation Improvement Program (TIP) are consistent with the motor vehicle emission budget (MVEB) contained in the SIP revision (40 CFR 93.118 and 93.124). The MVEB is defined as the level of mobile source emissions relied upon in the attainment or maintenance demonstration to maintain compliance with the NAAQS Start Printed Page 71061in the nonattainment or maintenance area.[12]

Under the LMP policy, emissions budgets are treated as essentially not constraining for the length of the maintenance period. While EPA's LMP policy does not exempt an area from the need to affirm conformity, it explains that the area may demonstrate conformity without submitting a MVEB. This is because it is unreasonable to expect that an LMP area will experience so much growth in that period that a violation of the CO NAAQS would result.[13] Therefore, for the Great Falls CO maintenance area, all actions that require conformity determinations for CO under our conformity rule provisions are considered to have already satisfied the regional emissions analysis and “budget test” requirements in 40 CFR 93.118.

Since LMP areas are still maintenance areas, certain aspects of transportation conformity determinations are still required for transportation plans, programs and projects. Specifically, for such determinations, RTPs, TIPs and projects must still demonstrate that they are fiscally constrained (40 CFR 93.108) and must meet the criteria for consultation and Transportation Control Measure implementation in the conformity rule provisions (40 CFR 93.112 and 40 CFR 93.113, respectively). In addition, projects in LMP areas will still be required to meet the applicable criteria for CO hot spot analyses to satisfy “project level” conformity determinations (40 CFR 93.116 and 40 CFR 93.123) which must also incorporate the latest planning assumptions and models available (40 CFR 93.110 and 40 CFR 93.111 respectively).

In view of the CO LMP policy, the effect of this proposed approval will be to affirm our adequacy finding such that no regional emissions analyses for future transportation CO conformity determinations are required for the CO LMP period and beyond (as per EPA's CO LMP policy and 40 CFR 93.109(e)).

V. Proposed Action

EPA is proposing to approve the revised Great Falls Maintenance Plan submitted on July 13, 2011. This maintenance plan meets the applicable CAA requirements and EPA has determined it is sufficient to provide for maintenance of the CO NAAQS over the course of the second 10-year maintenance period out to 2022.

EPA is also proposing to approve the State's Alternative Monitoring Strategy for the Great Falls CO maintenance area. We do not propose to approve application of the Alternative Monitoring Strategy in other areas of Montana with this action, as the Alternative Monitoring Strategy must be considered on a case-by-case basis specific to the circumstances of each particular CO maintenance area rather than broadly.

VI. Statutory and Executive Orders Review

Under the CAA, the Administrator is required to approve a SIP submission that complies with the provisions of the Act and applicable federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, EPA's role is to approve state choices, provided that they meet the criteria of the CAA. Accordingly, this action merely proposes to approve state law as meeting federal requirements and does not impose additional requirements beyond those imposed by state law. For that reason, this action:

  • Is not a “significant regulatory action” subject to review by the Office of Management and Budget under Executive Order 12866 (58 FR 51735, October 4, 1993);
  • Does not impose an information collection burden under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
  • Is certified as not having a significant economic impact on a substantial number of small entities under the Regulatory Flexibility Act (5 U.S.C. 601 et seq.);
  • Does not contain any unfunded mandate or significantly or uniquely affect small governments, as described in the Unfunded Mandates Reform Act of 1995 (Public Law 104-4);
  • Does not have federalism implications as specified in Executive Order 13132 (64 FR 43255, August 10, 1999);
  • Is not an economically significant regulatory action based on health or safety risks subject to Executive Order 13045 (62 FR 19885, April 23, 1997);
  • Is not a significant regulatory action subject to Executive Order 13211 (66 FR 28355, May 22, 2001);
  • Is not subject to requirements of Section 12(d) of the National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 note) because application of those requirements would be inconsistent with the Clean Air Act; and
  • Does not provide EPA with the discretionary authority to address, as appropriate, disproportionate human health or environmental effects, using practicable and legally permissible methods, under Executive Order 12898 (59 FR 7629, February 16, 1994).

In addition, this rule does not have tribal implications as specified by Executive Order 13175 (65 FR 67249, November 9, 2000), because the SIP is not approved to apply in Indian country located in the State, and EPA notes that it will not impose substantial direct costs on tribal governments or preempt tribal law.

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List of Subjects in 40 CFR Part 52

  • Environmental protection
  • Air pollution control
  • Carbon monoxide
  • Intergovernmental relations
  • Reporting and recordkeeping requirements
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Authority: 42 U.S.C. 7401 et seq.

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Dated: November 10, 2014.

Shaun L. McGrath,

Regional Administrator, Region 8.

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1.  In this case, the initial maintenance period extended through 2012. Thus, the second 10-year period extends through 2022.

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2.  Memorandum “Limited Maintenance Plan Option for Nonclassifiable CO Nonattainment Areas” from Joseph W. Paisie, Group Leader, EPA Integrated Policy and Strategies Group, to Air Branch Chiefs, October 6, 1995.

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3.  See Table 2 below. Additionally, according to the LMP guidance, an area using the LMP option must continue to have a design value “at or below 7.65 ppm until the time of final EPA action on the redesignation.” Table 2, below, demonstrates that the area meets this requirement.

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4.  In addition to Great Falls and Billings, the Missoula, MT CO maintenance area was included in the July 13, 2011 Alternative Monitoring Strategy.

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5.  See Table 2 below. Design values were derived from the EPA AirData (​ airdata/) Web site.

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6.  See “Review of National Ambient Air Quality Standards for Carbon Monoxide,” 76 FR 54294, August 31, 2011.

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7.  Design values were derived from the EPA AirData (​airdata/​) Web site.

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8.  Violations of the CO NAAQS are most likely to occur on winter weekdays.

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9.  The supplemental technical information was sent to EPA on July 23, 2014, and is available in the docket for this action.

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10.  Motor Vehicle Emissions Simulator (MOVES) model; version 2010b.

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11.  “Procedures for Processing Requests to Redesignate Areas to Attainment,” from John Calcagni, September 4, 1992.

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12.  EPA's transportation conformity requirements and policy on MVEBs are found in the preamble to the November 24, 1993, transportation conformity rule (see 58 FR 62193-62196) and in the sections of 40 CFR part 93 referenced above.

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13.  Limited Maintenance Plan Guidance at 4. October 6, 1995.

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[FR Doc. 2014-28293 Filed 11-28-14; 8:45 am]