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Federal Register / Vol. 86, No. 139 / Friday, July 23, 2021 / Rules and Regulations
Management Section, Air Planning and Implementation Branch, Air and Radiation Division, U.S. Environmental Protection Agency, Region 4, 61 Forsyth Street SW, Atlanta, Georgia 303038960.
EPA requests that if at all possible, you contact the person listed in the FOR
FURTHER INFORMATION CONTACT section to schedule your inspection. The Regional Offices official hours of business are Monday through Friday 8:30 a.m. to 4:30 p.m., excluding Federal holidays.
FOR FURTHER INFORMATION CONTACT:
Sarah LaRocca, Air Regulatory Management Section, Air Planning and Implementation Branch, Air and Radiation Division, U.S. Environmental Protection Agency, Region 4, 61 Forsyth Street SW, Atlanta, Georgia 303038960.
The telephone number is 404 562
8994. Ms. LaRocca can also be reached via electronic mail at larocca.sara@
epa.gov.
SUPPLEMENTARY INFORMATION:

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I. Background In 1979, under section 109 of the Clean Air Act CAA or Act, EPA
established primary and secondary NAAQS for ozone at 0.12 parts per million ppm, averaged over a 1-hour period. See 44 FR 8202 February 8, 1979. On July 18, 1997, EPA revised the primary and secondary NAAQS for ozone to set the acceptable level of ozone in the ambient air at 0.08 ppm, averaged over an 8-hour period. See 62
FR 38856 July 18, 1997.1 EPA set the 8-hour ozone NAAQS based on scientific evidence demonstrating that ozone causes adverse health effects at lower concentrations and over longer periods of time than was understood when the pre-existing 1-hour ozone NAAQS was set. EPA determined that the 8-hour ozone NAAQS would be more protective of human health, especially children and adults who are active outdoors, and individuals with a pre-existing respiratory disease, such as asthma.
Following promulgation of a new or revised NAAQS, EPA is required by the CAA to designate areas throughout the nation as attaining or not attaining the NAAQS. On April 15, 2004, EPA
designated the Knoxville 1997 NAAQS
Area, which is comprised of Anderson, Blount, Knox, Jefferson, Loudon, and Sevier Counties in their entireties, and 1 In March 2008, EPA completed another review of the primary and secondary ozone NAAQS and tightened them further by lowering the level for both to 0.075 ppm. See 73 FR 16436 March 27, 2008. Additionally, in October 2015, EPA
completed a review of the primary and secondary ozone NAAQS and tightened them by lowering the level for both to 0.070 ppm. See 80 FR 65292
October 26, 2015.

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the portion of Cocke County that falls within the boundary of the Great Smoky Mountains National Park, as nonattainment for the 1997 8-hour ozone NAAQS, and the designation became effective on June 15, 2004. See 69 FR 23858 April 30, 2004. Similarly, on May 21, 2012, EPA designated areas as unclassifiable/attainment or nonattainment for the 2008 8-hour ozone NAAQS. EPA designated Blount and Knox Counties and the portion of Anderson County surrounding the TVA
Bull Run Fossil Plant as nonattainment for the 2008 8-hour ozone NAAQS and classified as a marginal nonattainment area hereinafter referred to as the Knoxville 2008 NAAQS Area. This designation became effective on July 20, 2012.2 In addition, on November 16, 2017, areas were designated for the 2015
8-hour ozone NAAQS. The Knoxville 1997 NAAQS Area 3 was designated attainment/unclassifiable for the 2015 8hour ozone NAAQS, with an effective date of January 16, 2018.4
A state may submit a request to redesignate a nonattainment area that is attaining a NAAQS to attainment, and, if the area has met other required criteria described in section 107d3E
of the CAA, EPA may approve the redesignation request.5 One of the criteria for redesignation is to have an approved maintenance plan under CAA
section 175A. The maintenance plan must demonstrate that the area will continue to maintain the NAAQS for the period extending ten years after redesignation, and it must contain such additional measures as necessary to ensure maintenance and such contingency provisions as necessary to assure that violations of the NAAQS
will be promptly corrected. Eight years after the effective date of redesignation, the state must also submit a second maintenance plan to ensure ongoing maintenance of the NAAQS for an additional ten years pursuant to CAA
section 175Ab i.e., ensuring maintenance for 20 years after redesignation.
EPA has published long-standing guidance for states on developing 77 FR 30088.
Knoxville 1997 NAAQS Area encompasses both the Knoxville Area and the Knoxville 2008 NAAQS Area.
4 See 82 FR 54232 November 16, 2017.
5 Section 107d3E of the CAA sets out the requirements for redesignating a nonattainment area to attainment. They include attainment of the NAAQS, full approval of the applicable SIP
pursuant to CAA section 110k, determination that improvement in air quality is a result of permanent and enforceable reductions in emissions, demonstration that the state has met all applicable section 110 and part D requirements, and a fully approved maintenance plan under CAA section 175A.

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maintenance plans.6 The Calcagni memo provides that states may generally demonstrate maintenance by either performing air quality modeling to show that the future mix of sources and emission rates will not cause a violation of the NAAQS or by showing that projected future emissions of a pollutant and its precursors will not exceed the level of emissions during a year when the area was attaining the NAAQS i.e., attainment year inventory. See Calcagni memo at page 9. EPA clarified in three subsequent guidance memos that certain areas could meet the CAA section 175A
requirement to provide for maintenance by showing that the area was unlikely to violate the NAAQS in the future, using information such as the areas design value 7 being significantly below the standard and the area having a historically stable design value.8 EPA
refers to a maintenance plan containing this streamlined demonstration as an LMP.
EPA has interpreted CAA section 175A as permitting the LMP option because section 175A of the Act does not define how areas may demonstrate maintenance, and in EPAs experience implementing the various NAAQS, areas that qualify for an LMP and have approved LMPs have rarely, if ever, experienced subsequent violations of the NAAQS. As noted in the LMP
guidance memoranda, states seeking an LMP must still submit the other maintenance plan elements outlined in the Calcagni memo, including: An attainment emissions inventory, provisions for the continued operation of the ambient air quality monitoring network, verification of continued attainment, and a contingency plan in the event of a future violation of the NAAQS. Moreover, a state seeking an LMP must still submit its section 175A
maintenance plan as a revision to its SIP, with all attendant notice and comment procedures. While the LMP
6 John Calcagni, Director, Air Quality Management Division, EPA Office of Air Quality Planning and Standards OAQPS, Procedures for Processing Requests to Redesignate Areas to Attainment, September 4, 1992 Calcagni memo.
7 The ozone design value for a monitoring site is the 3-year average of the annual fourth-highest daily maximum 8-hour average ozone concentrations.
The design value for an ozone area is the highest design value of any monitoring site in the area.
8 See Limited Maintenance Plan Option for Nonclassifiable Ozone Nonattainment Areas from Sally L. Shaver, OAQPS, dated November 16, 1994;
Limited Maintenance Plan Option for Nonclassifiable CO Nonattainment Areas from Joseph Paisie, OAQPS, dated October 6, 1995; and Limited Maintenance Plan Option for Moderate PM10 Nonattainment Areas from Lydia Wegman, OAQPS, dated August 9, 2001. Copies of these guidance memoranda can be found in the docket for this proposed rulemaking.

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