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I UNITEDSTATESENVIRONMENTALPROTECTIONAGENCY OfficeofAirQualityPlanningandStandards \ ResearchTrianglePark, NorthCarolina27711 ! 

# NOV301993

MEMORANDUM

SUBJECT:

FROM:

TO: Use ofActual Emissions inMaintenance Demonstrations for Ozone and CarbonMonoxide (CO)**Nona~ta~nme/j_Areas**
D. Kent Berry, Acting Director

# j~~~)-~/~!J Air QualityManagement Division

## (MD-l£~ , - . Director, Air, Pesticides and Toxics Management Division, Regions I and IV Director, Air andWasteManagement Division, Region II Director, Air, Radiation and Toxics Division, Region III Director, Air and Radiation Division, RegionV Director, Air, Pesticides and Toxics Division, Region VI Director, Air andToxics Division, Regions VII, VIII, IX, and X

This memorandumprovides guidance onthe use of actual emissions in maintenance demonstrations for ozone and CO nonattainment areas seeking redesignation to attainment. This guidance supersedes previous Environmental Protection Agency (EPA) guidance set forth in the September 4, 1992 memorandum from John calcagni to Air Division Directors, "Procedures for Processing Requests to Redesignate Areas to Attainment" (redesignationpolicy), which required emission projections for these areas to be based on allowable emissions.

The EPAhas previously issued guidance on the use of actual emissions inprojecting emissions to meet the requirements for the 15 percent rate-of-progress plans for ozone nonattainment

areas. 1 For consistency, this memorandum extends the policy of using actual emissions to maintenance projections for ozone and CO areas, as well. This guidance is not intended to apply to emission projections in control programs for the other criteria pollutants (see discussion under "other Pollutants")

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. ISee Guidance for Growth Factors, Projections, and Control Strategies for the 15 PercentRate-of Progress Plans (EPA-452jR93-002, March 1993)." .......

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Ozone and CO Policy

Actual emissions from a source are the emissions based on the source's actual operating hours, production rates, and control equipment for the processes carried out at the source. Actual emissions take into consideration normal operating conditions as well as instances when deviations occur. For ozone and CO areas, the term allowable emissions refers to emissions estimates based on enforceable emission rates and actual production rates and hours.



# ,- consistentwith the earlier rate-of-progress plan guidance,

ozone and CO maintenanceprojections may be based on actual emissions for sources or source categories that are currently sUbjectto a regulation and that the state does not anticipate sUbjecting to additional regulation. Similarly, themaintenance projections may be based on actual emissions for sources or
source categories that are currently unregulated and are not expected to be subjectto·future regulation. (The state still has the option ofusing allowable emissions for these two cases.) However, for sources that are expected to be sUbject to additional regulation, the projections mustbe based on the new allowable emissions limits because the new actual emissions are not yetknown.

Upon approval ofa redesignationrequest and associated -maintenance plan by EPA, all future emissions calculations or

projections to implement other airquality requirements for an
area mustbe consistentwiththe maintenance demonstration (unless a more stringentrequirement applies). For example, if projected emissions from a sourceused in the maintenance demonstration are based on actual emissions, that source must use actual emissions in determining the credit available for emissions trading, innovative strategies, economic incentive plans, and emissions budgets.

Other Pollutants

Under the redesignationpolicy, emissions projections for particulatematter (PM-10), sulfur dioxide (S02), nitrogen dioxide, and lead (Pb) nonattainment areas are still required to follow current EPAmodeling guidance.2 Themodeling guidance requires that maximum allowable emission limits for major point

sources be used in demonstrating maintenance of short-term

2The EPA-approvedmodeling guidance may be found in the following documents: "Guideline onAir QualityModels (Revised)" (EPA-450/2-78-027R, JUly 1987) and "PM-10 SIP Development Guideline" (EPA-450/2-86-001, June 1987).**f'~"** 3

standards.3 It is necessary to continue the use ofmaximum allowable emissions when projecting emissions for these nonattainment areas because, in some cases, large point sources operating at full capacity could by themselves cause an exceedance ofthe applicable national ambient air quality standard. In contrast, large point sources are not likely to be dominant emission sources in inventories for ozone and CO nonattainment areas, and it is unlikely that the multitude of smaller sources would be'operating atmaximum capacity simUltaneously.

For further information regarding the use of actual and allowable emissions for maintenance demonstrations for ozone and CO areas, please contact Carla Oldham at (919) 541-3347. For information on projecting emissions for 802, PM-10, and Pb nonattainment areas, please contactRobin Dunkins at (919) 541- 5335.

cc: Air Branch Chief, Regions I-X John Cabaniss, OMS Mary Henigin, OAQPS Bob Kellam, TSD Rich Ossias, OGC John Rasnic, SSCD John seitz, OAQPS Ann Goode, OAR LydiaWegman, OAQPS

3Maximum allowable emissions are calculated using the enforceable (i.e., allowable) emission rate multiplied by the maximum operating capacity ofthat source at continuous operation (unless there are federally-enforceable limits on the hours of operation)

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