UNITEDSTATES ENVIRONMENTALPROTECTIONAGENCY RESEARCHTRIANGLE PARK

. NC 2771'1

OFFICE OF October 6, 1995 AIR QUALITY PLANNING ANDSTANDARDS MEMORANDUM SUBJECT:
FROM:
TO: Limited Maintenance Plan Option for Nonclassifiable CO Nonattainment Areas

. .

# Joseph~- Paisie, Group Leader

# ~~ 

# ft Integrated Policy and

## Strategies~Gtoup (MD-15) 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 Air Division 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 eligibility of areas 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. Wallace Received : in theAirQual ityBranch', 10/6/95 Limited Maintenance Plan Option for Nonclassifiable CO Nonattainment areas
1. Question: 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 175A of the Act? Answer: Nonclassifiable CO nonattainment areas seeking redesignation to attainment whose design values are at or below 7

.65ppm (85 percent of exceedance levels of the CO NAAQS) at the time of redesignation may choose to submit a less rigorous maintenance plan than was formerly**re~ ire** **d.** 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 September 4, 1992 memorandum, 11Procedures for Processing Requests to Redesignate Areas to Attain ment," £rom John Calcagni, former Director of the OAQPS Air Quality Management Division to the Regional Air Division Directors. The EPA now believes that it is j' ustifiable and appropriate to apply a different set of maintenance plan requirements to a nonclassifiable CO nonattainment areas whose monitored air quality is equal to or less than 85 percent of exceedance

·levels of the 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 of control measures required by the Act for moderate and serious nonattainment areas. Also, these areas do not have either a recent histor¥ of monitored violation of the CO NAAQS or a long prior history of monitored air quality problems. The EPA believes that the continued applicability of prevention 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 of maintenance for these areas.·,_ 2 2. Question: Besides having a design value that is equal to or less than 85% of the CO NAAQS what other requirements are necessary for a

_ nonclassifiable 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 consecutive quarters (2 years of data) used to demonstrate

.attainment, must be at or below 7.65ppm (85

.percent of exceedance levels of the ozone NAAQS). Additionally, the design value for the area must continue to be at or below 7

.65ppm until the time of final EPA action on the redesignation. The method for calculating design valries is**pr~sented in** **th~** June 18, 1990 memorandum, "Ozone and Carbon Monoxide Design Value Calculations," from William G

. Laxton, former Director of the OAQPS Technical Support Division to Regional Air

·Directors. The memorandum foquses primarily on determining design values for nonattainment areas in order to classify the areas as 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 of a nonattainment area seeking redesignation to attainment, all monitors must be meeting the standard. To assess. whether a nonclassifiable area meets the applicability cutoff for the limited maintenance plan, a separate design value must be developed for every monitoring

·site. The highest of these design values is the design value for the whole area. If the area .design value'is ·at or below 7.65ppm, the State may select the limited maintenance plan option for the first 10-year maintenance period under section 175A. If the design value for the area exceeds 7.65ppm prior to 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 September 4, 1992 memorandum.·, 3 3. Question: What elements must be contained in a section 175A maintenance plan for nonclassifiable CO areas which qualify for**t~e** limi ted maintenance plan option? Answer: Following is a list of core provisions which should be included 

### in the limited maintenance plan for CO nonclassifiable areas. Any final**~PA** determination regarding the adequacy of a limited maintenance plan will be made following review of the plan submittal in light of the particular circumstances facing the area proposed for redesignation and based on all relevant available information.
a. Attainment Inventory**~** .. The State should develop an attainment emissions inventory to identify a level of emissions

-in the area which is sufficient to attain the NAAQS. This inventory should be consistent with EPA's most recent guidance1 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 of CO. b. Maintenance Demonstration The maintenance demonstration requirement is considered to be satisfied for nonclassifiable areas .if the monitoring data show that the area is meeting the air quality criteria for limited maintenance areas (7.65ppm or. 85% of the CO NAAQS)

. There is no requirement to project emissions over the maintenance period. The EPA

-believes if the area begins the maintenance period at or below 85 percent of exceedance levels, the air quality along with the continued applicability of PSD requirements, any control measures already in the SIP, and Federal measures, should provide

-

·adequate assurance of maintenance over the initial 10-year

1The 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-450/4-91-010) , and "Procedures for Emission Inventory Preparation: Volume IV, Mobile Sources" (EPA

450/4-8l-026d).4 maintenance period

. When EPA approves a limited maintenance plan, EPA is concluding that an emissions budget may be treated as essentially not constraining for the length of the maintenance period because it is unreasonable to expect that such an area will experience so much growth in that period that a violation of the 

## co NAAQS would result

. ·
c. Monitoring Network/Verification of Continued Attainment To verify the attainment status of:the area over the maintenance period, the maintenance plan should contain provisions for continued operation of an 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 175A of the Act requires that 

### a maintenance plan include contingency provisions, as necessary, to prom ptly correct any violation of the NAAQS that occurs after redesignation of the area. These contingency measures do not have to be fully adopted at the time of redesignation. However,

. the contingency plan is considered to be an**enforceabl~** part of the 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**dule** and procedure for adoption and implementation of the measures. The State should also identify specific indicators, or triggers, which will be used to determine when the contingency measures need to be implemented. While a violation of the NAAQS is an acceptable trigger, States may wish to choose a pre-violation action level as a trigger, such as an exceedance of the 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 of EPA to redesignate an area back to nonattainment.
e. Conformity Determinat 'ions Under·Limited 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 main-tenance areas operating under maintenance plans. Under ei ther rule, one means of demonstrating conf ormity of Federal actions is to indicate**th~t** expected· emissions from5 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 of the initial maintenance period because it is unreasonable to expect that such an area will experience so much growth**i~** that period that a violation of the 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 of the rule. · Similarly, in these areas, Federal actions subject to the general conformity rule could be considered to satisfy the "budget test" specified in section 93

. 158(a) (5} (i} (A} of the rule.