UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

                            REGION IV

                   345 COURTLAND STREET, N.E.
                     ATLANTA, GEORGIA 30365
                                
                           JUN 15 1993

4APT-AEB                    

Mr. Richard E. Grusnick, Chief
Air Division
Alabama Department of Environmental Management
1751 Congressman W.L. Dickinson Drive
Montgomery, Alabama 36130

RE:  BACT Applicability

Dear Mr. Grusnick:

This is to acknowledge receipt of your letter dated May 14, 1993,
which raised the issue of an apparent contradiction between EPA
guidance and the federal Prevention of Significant Deterioration
(PSD) regulations.  At issue is the January 18, 1990, letter from
Gerald Emison of EPA's Office of Air Quality Planning and Standards
(OAQPS) to Morton Sterling of the Detroit Edison Company concerning
a PSD applicability determination for Detroit Edison's Greenwood
Power Plant.  As pointed out in your letter, page 2 of Mr. Emison's
letter states that "BACT is applicable only to those emission units
at the source which undergo both a physical or operational change
and a significant net emissions increase" (emphasis added).  This
is in apparent conflict with the federal PSD regulations which
clearly state at 40 CFR SS52.21(j)(3):

     (j)  Control technology review
     (1)  ***   
     (2)  ***
     (3)  A major modification shall apply best available control
technology for each pollutant subject to regulation under the Act
for which it would result in a
     significant net emissions increase at the source.  This
requirement applies to each proposed emissions unit at which a net
emissions increase in the pollutant would occur as a result of a
physical change or change in the method of operation in the unit.

Gregg Worley of my staff raised this issue with Dennis Crumpler of
the New Source Review Section (NSRS), OAQPS.  It is our
understanding that for the applicability determination in question,
there was only one emissions unit involved; thus, a significant net
emissions increase from the unit would be




                               -2-

necessary to trigger PSD applicability.  More importantly, guidance
and/or interpretations do not supersede the actual regulation.  The
NSRS will make a determination as to whether a memorandum is
necessary to clarify the intent of the Emison letter.  In the
meantime, the interpretation of the regulation shared by your
agency and EPA is correct.

If you have any further questions on this issue, please contact
Gregg Worley of my staff at (404) 347-5014.

Sincerely yours,



Air Enforcement Branch
Air, Pesticides, and Toxics
Management Division

cc: Dennis Crumpler, OAQPS, NSRS