February 22, 1990 
 
 
 
 
 
 
 
MEMORANDUM 
 
SUBJECT:  Approval of Equivalence Demonstration Plan 
          Integrated Intermediate Terrain Model 
 
FROM:     Joseph A. Tikvart, Chief 
          Source Receptor Analysis Branch (MD-14) 
 
TO:       Alan J. Cimorelli, Lead Meteorologist 
          Region III (3AM12) 
 
     In response to your request the Model Clearinghouse has reviewed the
UE&C protocol for demonstrating equivalence of the IGM with ISCST and
COMPLEX I, for application of this nonguideline model to a new source in
the Clover VA area.  Our understanding is that the IGM is designed to not
only reproduce ISCST and COMPLEX I estimates at receptors where these
models are applicable, but to also make the appropriate choice between
estimates of these two models in intermediate terrain (between stack height
and plume height).  This "appropriate choice" would be consistent with the
hour-by-hour choice described in your memorandum to me dated March 9, 1989
(which we subsequently concurred on). 
 
     It is our understanding that the equivalency demonstration proposed by
UE&C will consist of three parts:  1) the submission of evidence that care
was taken in the development of IGM to ensure that it indeed reproduces the
guideline model estimates and makes the proper choice in intermediate
terrain situations; 2) the submission of an equivalency demonstration
between the models (demonstrating that estimates are within 2%) for an
undefined subset of receptors for the Clover VA source and, 3) the
submission of evidence that the IGM made the appropriate choice between ISC
and COMPLEX I estimates for a very limited subset of sources, receptors and
time periods involved in the Clover analysis. 
 
     The Model Clearinghouse agrees in principle with the protocol
submitted by UE&C.  While we advise that more data points should be
included in the demonstration, especially in Part 3, we do understand that
the manual comparison practically limits this aspect.  We leave it to you,
when reviewing the data submitted pursuant to this protocol, to decide
whether enough data are included to provide confidence that proper
estimates are being made for the Clover source.  For other sources where
UE&C wishes to use the IGM, we believe that Parts 2 and 3 of the
equivalency demonstration should be repeated, at least until confidence and
familiarity with IGM can be established. 
     
          If you have any questions please contact Dean Wilson at 629- 
5683. 
 
cc:  D. Grano 
     D. deRoeck