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RESEARCH TRIANGLEPARK.NC27711 '.c o*

+'4( pR07t 6'‘ OFFICE OF October 6,1995 AIR OUALlTYPLANNING AND STANDARDS

SUBJECT: Limited Maintenance Plan Option for Nonclassifiable CO Nonattainment Areas

FROM: Joseph W. Paisie,Group Leader Integrated Policy and

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 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 EPA1s guidance regarding the .availabilityof 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 e in the context of notice and comment rulemaking egarding 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.WallaceLimited Maintenance Plan Option forNonclassifiable CO Nonattainment areas

1. Question:

What requirementsmust CO nonclassifiable areas,which are attaining the CO NAAQS with a design value that is significantlybelow theNAAQS,meet in o'rderto have an approvablemaintenance 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

(85percent of exceedance levels of the CO NAAQS) at the time of redesignation may choose to submit a less rigorous maintenance plan than was formerly required. This new option is being termed a limited maintenance plan. Nonclassifiable CO areas with designvalues greater than 7.65ppmwill continue to be subject to full maintenance plan requirements described in the September 4, 1992memorandum, "Proceduresfor Processing Requests to RedesignateAreas to Attainment,"from John Calcagni, former Director of the OAQPS Air Quality Management Division to the Regional Air DivisionDirectors.

The EPA now believes t#'at it is justifiable 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 85percent of exceedance levels of the ozone NAAQS. The EPA does not believe that the fullmaintenance 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 areasdo not have either a recent history of monitored violation of the CO NAAQS or a longprior history of monitored air quality problems. The EPA believes that the continued applicabilityof 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. 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 (2years of data) used to demonstrate attainment, must be at or below 7.65ppm (85 percent of exceedance levels of the ozoneNAAQS). Additionally, the designvalue for the
area must continue to be at or below 7.65ppm until the time of final EPA action on the redesignation. Themethod for calculatingdesign values ispresented in the June 18, 1990 memorandum, "Ozoneand Carbon Monoxide DesignValue CalculationslMfrom William G. Laxton, former Director of the OAQPS Technical Support Division to Regional Air Directors. The memorandum focuses 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 monitor's 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 Statemay select the limited maintenance plan option for the first 10-yearmaintenanceperiod under section 175A. If the design value for the area exceeds 7.65ppmprior 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, 1992memorandum.3. Question:

What elements must be contained in a section 175A maintenance plan for nonclassifiable4 CO areaswhich qualify for the limited maintenance plan option?

Answer: Following is a list of core provisions which shouldbe included in the limitedmaintenance plan for CO nonclassifiable areas. Any final EPA 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 redesignationand 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 EPA1smost 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 "typicalwinter day" emissions of CO. 1

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 (7.65ppmor 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 applicabilityof PSD requirements, any control measures already in the SIP, and Federal measures, shouldprovide adequate assurance of maintenance over the initial 10-year

'The EPA1 s current guidance on the preparation of emissions inventories for ozone areas is contained in the following documents: "Proceduresforthe Preparationof Emission Inventories forCarbonMonoxide and Precursorsof Ozone: Volume I" (EPA-450/4 - 91-016) 

### , llEmissionInventory Requirements for Ozone State Implementation Plans" (EPA-450/4-91-010),and "Procedures for Emission Inventory Preparation: Volume IV,Mobile Sources" (EPA450/4-81-026d)



## .maintenance period.

When EPA approves a limited maintenance plan, EPA is concluding that an emissions budget may be treated as essentiallynot constraining for the length of the maintenance period because it is unreasonable to expect that such an area will experience somuch growth in that period that a violation of the CO NAAQS would result.

MonitorinsNetwork/~erification of ContinuedAttainment

To verify the attainment status of the area over the maintenance period, themaintenance plan should contain provisions for continued operation of an appropriate, EPAapproved air qualitymonitoring 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.

Cont insencv Plan

Section 175A of the Act requires that a maintenance plan include contingency provisions, as necessary, to promptly correct any violation of the NAAQS that occurs after redesignation of th'earea. These contingency measures do not have to be fullyadopted at the time of redesignation. However, the contingency plan is considered to be an enforceablepart of the/S~~ and should ensure that the contingencymeasures 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 implementationof 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,anexceedance of the NAAQS. By taking early action, a Statemay be able toprevent any actual violation of the NAAQS and, therefore, eliminate anyneed on the part of EPA to redesignate an area back to nonattainment.

C e. ConformityDeterminat'ionsUnder Limited Maintenance Plans

The transportation conformity rule (58FR 62188; November 24, 19935 and the general conformity rule (58FR 63214;November 30, 1993) apply to nonattainment areas and maintenance areas operating under maintenance plans. Under either rule,one means of demonstrating conformity of Federal actions is to indicate that expected emissions from

### planned actions are consistent with the emissions budget for the area. Emissions budgets in limitedmaintenance plan
areas may be treated as essentially not constraining for the length of the initialmaintenance 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. In otherwords, 

### EPAwould be concluding that emissions need not be capped for the maintenance period. Therefore, in areas with approved limited maintenance plans, Federal actions requiring conformitydeterminationsunder the transportation conformityrule could be considered to satisfy the "budget testurequired 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 testNspecified in section 93.158(a)

### (5)(i)(A) 

### of the rule.