· .

r<>;- . I

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

Office of Air Quality Planning and Standards \

Research Triangle Park, North Carolina 27711 !

NOV 301993

MEMORANDUM

SUBJECT:

FROM:

TO:

Use of Actual Emissions in Maintenance Demonstrations

for Ozone and Carbon Monoxide (CO) Nona~ta~nme/j_Areas

D. Kent Berry, Acting Director j~~~)-~/~!J Air Quality Management Division (MD-l£~ , - .

Director, Air, Pesticides and Toxics

Management Division, Regions I and IV

Director, Air and Waste Management Division,

Region II

Director, Air, Radiation and Toxics Division,

Region III

Director, Air and Radiation Division,

Region V

Director, Air, Pesticides and Toxics Division,

Region VI

Director, Air and Toxics Division,

Regions VII, VIII, IX, and X

This memorandum provides guidance on the 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"

(redesignation policy), which required emission projections for

these areas to be based on allowable emissions.

The EPA has previously issued guidance on the use of actual

emissions in projecting 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") .

. ISee Guidance for Growth Factors, Projections, and Control

Strategies for the 15 Percent Rate-of Progress Plans (EPA-452jR93-002, March 1993).
" .......

2

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.

,-

consistent with the earlier rate-of-progress plan guidance,

ozone and CO maintenance projections may be based on actual

emissions for sources or source categories that are currently

sUbject to a regulation and that the state does not anticipate

sUbjecting to additional regulation. Similarly, the maintenance

projections may be based on actual emissions for sources or

source categories that are currently unregulated and are not

expected to be subject to·future regulation. (The state still

has the option of using allowable emissions for these two cases.)

However, for sources that are expected to be sUbject to

additional regulation, the projections must be based on the new

allowable emissions limits because the new actual emissions are

not yet known.

Upon approval of a redesignation request and associated

-maintenance plan by EPA, all future emissions calculations or

projections to implement other air quality requirements for an

area must be consistent with the maintenance demonstration

(unless a more stringent requirement applies). For example, if

projected emissions from a source used 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

particulate matter (PM-10), sulfur dioxide (S02), nitrogen

dioxide, and lead (Pb) nonattainment areas are still required to

follow current EPA modeling guidance. 2 The modeling guidance

requires that maximum allowable emission limits for major point

sources be used in demonstrating maintenance of short-term

2The EPA-approved modeling guidance may be found in the

following documents: "Guideline on Air Quality Models (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 of maximum

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 of the 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 at maximum 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 contact Robin 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

Lydia Wegman, OAQPS

3Maximum allowable emissions are calculated using the

enforceable (i.e., allowable) emission rate multiplied by the

maximum operating capacity of that source at continuous operation

(unless there are federally-enforceable limits on the hours of

operation) .