UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
               Office of Air Quality Planning and Standards
               Research Triangle Park, North Carolina 27711

                             October 23, 1987





SUBJECT:  Review of WYNDvalley, Grid and Ventilated Valley Models

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

TO:       Robert B. Wilson, Regional Meteorologist
          Region X


     In response to your request the Model Clearinghouse has reviewed the
WYNDvalley and GRID models for application to PM10 SIP's in Oregon and
Washington.  Later, at the request of the Stagnation Work Group, we also
reviewed the Ventilated Valley Box model, which is being considered for
application in Region VIII.  In addition, we requested technical comments
on all three models by Meteorology (MD), ORD, personnel.  The MD comments,
provided by Bert Eskridge, are attached.

     Based primarily on the MD comments, it appears to us that only one of
the three models, WYNDvalley, has sufficient technical credibility to be
used for PM10 SIP's.  Moreover, it appears that this model will require
certain meteo-
rological input data/measurements to establish boundary conditions.  Any
application of WYNDvalley to PM10 SIP modeling should be accompanied by a
comparison between model estimates and air quality data.  (This is a
standard recommendation for any new model for which there has been limited
evaluation.)

     Upon receipt of this memorandum we recommend that you set up a
conference call with the Stagnation Work Group members to discuss these
findings and to propose future actions.

Attachments

cc:  R. Eskridge
     P. Hanrahan
     J. Notar
     D. Stonefield