December 4, 1991


MEMORANDUM

SUBJECT:  Proposal to Use a Non-Guideline Model to Satisfy
          Intermediate Terrain Policy in New Source Permitting
          (Pine State Power; Jay, Maine)

FROM:     Dean A. Wilson
          Techniques Evaluation Section, SRAB (MD-14)

          Dan deRoeck
          New Source Review Section, PPB (MD-15)

TO:       Ian Cohen, Regional Modeling Contact
          Technical Assistance Section, Region I

          Brian Hennessey
          Technical Assistance Section, Region I


     In response to your request, the Model Clearinghouse has
reviewed your proposal to accept the Pine State Power (PSP)
implementation of the intermediate terrain policy for their
forthcoming Prevention of Significant Deterioration permit.  We
have previously negotiated the technical and procedural details
of this issue through drafts of your request memorandum.  Thus we
are in agreement with your proposal.

     Over the last few weeks we have discussed a few additional
caveats to our agreement.  Here is our understanding of our
discussions, for the record.  We agreed that PSP's use of the
ISCMX model is, in general, limited to the stack configuration,
building dimensions and modeled background sources that were
included in the equivalency demonstration.  In that regard, we
understand that the State now wants to include another background
source, the James River Company, in the modeling but that source,
because of its source-receptor geometry, is not expected to
contribute to the design concentration.  Thus we have no problem
with its inclusion in the permit modeling.

     We also indicated that the Clearinghouse did not review the
fine details of the equivalency demonstration, e.g. whether the
correct wind speed profiles were used.  You agreed that this is
not expected of us and that the State/Region will be responsible
for that level of review, as appropriate.

     In summary, subject to the conditions stated in Section E of
your November, 6, 1991 memorandum, and to the above caveats, we
agree with your proposal to approve the equivalency demonstration
for PSP.

     If you have any questions, please contact us.

cc:  R. Lee