May 23, 1994



MEMORANDUM

SUBJECT:  Calculating Good Engineering Practice (GEP) Stack       
          Height Due to Terrain Induced Downwash

FROM:     Joseph A. Tikvart, Chief
          Source Receptor Analysis Branch, TSD (MD-14)

TO;       Pamela Blakley, Air Emissions Expert
          RCRA Permitting Branch, WMD (HRPO-8J), Region V


     In response to your request to Dean Wilson, the Model
Clearinghouse has reviewed the March 22, 1994 memorandum from 
Dr. William Snyder to you concerning the wind tunnel modeling
study of the WTI Incinerator at East Liverpool.  You requested
that the memorandum be reviewed for consistent interpretation of
the appropriate regulations and procedures and whether Dr.
Snyder's recommendation stated in the memorandum is appropriate.

     We reviewed with Dr. Snyder the contents of his March 22,
1994 memorandum.  Overall we agree with Dr. Snyder's
interpretation of the procedures for calculating Good Engineering
Practice (GEP) stack height in elevated terrain as described in
the U.S Environmental Protection Agency's guideline for
determination of GEP stack height.  Also, we agree with his
assessment that following these procedures a significantly taller
GEP stack height at the WTI incinerator would likely not be
justified.  We understand that Dr. Snyder is proposing a wind
tunnel study to further assess the terrain effects on the WTI
incinerator stack.  He will accomplish this by comparing wind
tunnel data from a source with full terrain in place with a
similar source in flat terrain.  As Dr. Snyder noted in his
memorandum, large terrain effects are expected to be observed.

     If you have any additional questions or comments, please do
not hesitate to contact Dennis Doll at (919) 541-5693 or myself
at (919) 541-5562.


cc:  D. Doll
     J. Irwin
     S. Rothblatt (AR-18J)
     Dr. W. Snyder