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October 6, 1995 MEMORANDUM SUBJECT: Limited Maintenance Plan Option for Nonclassifiable CONonattainment Areas FROM: Joseph W. Paisie, Group Leader Integrated Policy and Strategies Group (MD-15) TO: Air Branch Chiefs, Regions I

-X
On November 16, 1994, EPA issued guidance regarding a limited maintenance plan option for nonclassifiable ozone nonattainment areas in a memorandum from Sally L 

### Shaver, Director, Air Quality Strategies and Standards Division, to Regional 

### AirDivision Directors. EPA believes that such an option is also appropriate for nonclassifiable CO nonattainment areas and the following questions and answers set forth EPA's guidance regarding the availability of this option for such areas. As this is guidance, final and binding determinations regarding the eligibiliry ofareas for the limited maintenance plan option will only be made 

### in the context of notice and comment rulemaking actions regarding specific redesignation requests. If

### there are any questions concerning the limited maintenance plan option for nonclassifiable CO areas, please contact me at (919) 541-5556 or Larry 

### Wallace at (919) 541- 0906. Attachment
cc: E. Cummings, OMS K McLean, OGC C
. Oldham L. WallaceAQSSD:IPSG:LWALLACE:vwyatt:x5628:MD-12: 10-6-95 WALLACE: A:\JOE.ABC

### 1. Quest ion: 

### 1016195 Limited Maintenance Plan Option for Nonclassifiable CO Nonattainment areas

What requirements must CO nonclassifiable areas, which are attaining the CO NAAQS with a design value that is significantly below the NAAQS, meet in order to have an approvable maintenance plan under section l75A ofthe Act? Answer: Nonclassifiable CO nonattainment areas seeking redesignation to attainment whose design values are at or below 7.65ppm (85 percent ofexceedance levels ofthe CO NAAQS) at the time ofredesignation may choose to submit a Jess rigorous maintenance plan than was formerly required. This new option is being termed a limited maintenance plan. Nonclassifiable CO areas with design values greater than 7.65ppm will continue to be subject to full maintenance plan requirements described in the September4, 1992 memorandum, "Procedures for Processing Requests to Redesignate Areas to Attainment," from John Calcagni, former Director ofthe OAQPS Air Quality Management Division to the Regional Air Division Directors. The EPA now believes that it is justifiable and appropriate to apply a different setof maintenance plan requirements to a nonclassifiable CO nonattainment areas whose monitored air quality is equal to or less than 85 percent ofexceedance levels ofthe ozone NAAQS. The EPA does not believe that the full maintenance plan requirements need be applied to these areas because they have achieved air quality levels well below the standard without the application ofcontrol measures required by the Act for moderate and serious nonattainment areas. Also, these areas do not have either a recent history of monitored violation ofthe CO NAAQS or a long prior history ofmonitored air quality problems. The EPA believes that the continued applicability ofprevention of significant deterioration (PSD) requirements, any control measures already in the SIP, and Federal measures (such as the Federal motor vehicle control program) should provide adequate assurance ofmaintenance for these areas.2 2. Question: Besides having a design value that is equal to or less than 85% ofthe CO NAAQS what otherrequirements are necessary for a nonelassifiable CO nonattainment area to qualify for the limited maintenance plan option?
Answer: To qualify for the limited maintenance plan option, the CO design value for the area, based on the 8 consecutivequarters (2 years ofdata) used to demonstrate attainment, must be at or below 7.65ppm (85 percent ofexceedance levels ofthe ozone NAAQS). Additionally, the design value for the area must continue to be at orbelow 7.65ppm until the time of final EPA action on the redesignation. Themethod for calculating design values is presented in the June 18, 1990 memorandum, "Ozone and Carbon Monoxide Design Value Calculations," from William G. Laxton, former Director ofthe OAQPS Technical Support Division to Regional Air Directors. The memorandum focuses primarily on determining design values for nonattaioment areas in orderto classify the areas**a.~** moderate or serious for CO. Therefore, the document discusses determining the design value for an area based on the monitors which are exceeding the standard. In the case ofa nonat tainment area seeking redesignation to attainment, all monitors must be meeting the standard. To assess whether a nonclassifiable area meets the applicability cutofffor the limited maintenance plan, a separate design value must be developed for every monitoring site. The highest ofthese design values 

### is the design value for the whole area. Ifthe area design value is at or below 7.65ppm, the State may select the limited maintenance plan option for the first IO-year maintenance period under section 175A. 

### Ifthe design value for the area exceeds 7.65ppm priorto final EPA action on the redesignation, the area no longer qualifies for the limited maintenance plan and must instead submit a full maintenance plan, as indicated in the September4, 1992 memorandum
.

# - 3 3. Question: What elements must be contained in a section I75A maintenance plan for nonelassifiable CO areas which qualify for the limited maintenance plan option? Answer : Following is a list ofcore provisions which should be included in the limited maintenance plan for CO nonclassifiable areas. Any final EPA detennination regarding the adequacy of a limited maintenance plan will be made following review ofthe plan submittal in light oflheparticularcircumstances facing lhe areaproposed for redesignation and based on 

### all relevant available infonnation
.
a. Attainment Inventory The State should develop an attainment emissions inventory to identify a level of emissions in the area which is sufficient lo attain the NAAQS. This inventory should be consistent with EPA's most recent guidance 1 on emissions inventories for nonattainment areas available at the time and should represent emissions during the time period associated with the monitoring data showing attainment. The inventory should be based on actual "typical winter day" emissions ofCO. b. Maintenance Demonstcatjon The maintenance demonstration requirement is considered to be satisfied for nonclassifiable areas 

### ifthe monitoring data show that the area is meeting the air quality criteria for limited maintenance areas (7.65ppm or 85% ofthe CO NAAQS). There is no requirement to project emissions over the maintenance period
. The EPA believes ifthe area begins the maintenance period at or·below 85 percent ofexceedance levels, the air qunlity along with the continued applicabilit y ofPSD requirements, any control measures already in t he SIP, and Federal measures, should provide adequate assurance of maintenance over the initial 10

-year maintenance period. Whe n EPA approves a limited maintenance plan, EPA is concluding that an emissions budget may be treated as essentially not constraining for the length ofthe maintenance


### 'The EPA's current guidance on the preparation of emissions inventories for ozone areas is contained in the following documents : "Procedures for the Preparation of Emission Inventories for Carbon Monoxide and Precursors of Ozone: Volume I" (EPA-450/ 4

- 91-016), "Emission Inventory Requirements for Ozone State Implementation Plans" (EPA-450/4 -91-0 10), and "Procedures for Emission Inventory Preparation: Volume IV. Mobile Sources• (EPA-450/4-8 1

- 026d).4 

### period because 

### itis unreasonable to expect that such an area will experience so much growth in that period that a violation orthe CO NAAQS would result.
c. Monitoring NetworkNerification ofContinued Attainment To verify the attainment status ofthe area over the maintenance period, the maintenance plan should contain provisions for continued operation ofan appropriate, EPA-approved air quality monitoring network, in accordance with 40 CFR part 58. This is particularly important for areas using a limited maintenance plan because there will be no cap on emissions. d. Contingency Plan Section l75A ofthe Act requires that a maintenance plan include contingency provisions, as necessary, to promptly correct any violation ofthe NAAQS that occurs after redesignation ofthe area. These contingency measures do not have to be

### fully adopted at the time ofredcsignation. However, the contingency plan is considered to be an enforceable part ofthe SIP and should ensure that the contingency measures are adopted expeditiously once they are triggered by a specified event. The contingency plan should identify the measures to be promptly adopted and provide a schedule and procedure for adoption and implementation ofthe measures. The State should also identify specific indicators, ortriggers, which will be 

### used to determine when the contingency measures need to be implemented. While a violation ofthe NAAQS is an acceptable trigger, States may wish to choose a pre-violation action level as a trigger, such as an exceedance ofthe NAAQS. By taking early action, a State may be able to prevent any actual violation of the NAAQS and, therefore, eliminate any need on the part ofEPA to redesignate an area back to nonattainment.
e. Conformity DeteCIDinations UnderLimited Maintenance Plans The transportation conformity rule (58 FR 62188; November 24, 1993) and the general conformity rule (58 FR 63214; November 30, 1993) apply to nonattainment areas and maintenance areas operating under maintenance plans. Under either rule, one means of demonstrating conformity ofFederal actions is to indicate that expected emissions from planned actions are consistent with the emissions budget for the area. Emissions budgets in limited maintenance plan areas may be treated as essentially not constraining for the length ofthe initial maintenance period because it is unreasonable to expect that such an area will experience so much growth in that period that a violation ofthe CO NAAQS would result. 

### In other words, EPA would be concluding that emissions need not be capped for the maintenance period. Therefore, in areas with approved limited maintenance plans, Federal actions requiring conformity determinations under the transportation conformity rule could be considered to satisfy the "budget test" required 

### in sections 93.118, 93.119, and 93.120 ofthe rule. Similarly, in these areas, Federal actions subject to the general conformity rule could be considered to satisfy Lhe 

### "budget test"

### 5 specified in section 93.158(a)(5)(i)(A) ofthe rule.