Texas Natural Resource Conservation Commission
         Austin                       Texas
                      Memorandum

To:  Manuel Aguirre, P.E., Permits and Enforcement Director,
     Permits Division Directors,
     Section Chiefs, 
     Permit Engineers, 
     Lucy Bartley and 
     Pam Taylor
From:  Lawrence Pewitt, P.E., Permits Program Director
Date:  May 17, 1993
Subject:  Prevention of Significant Deterioration (PSD)
          Modifications

Since receiving full PSD delegation on July 24, 1992 we have
been changing the modification number on PSD permits for all
PSD modifications, including minor modifications.  For
example:  PSD-TX-###M2 would become PSD-TX-###M3.  Prior to
full delegation, we only changed the modification number for
modifications to the PSD permit.  Because of the possibility
of the modification number becoming large very quickly,
especially for cases like Formosa where we have one PSD permit
for several TACB permits, we have decided to return to the
practice of only changing the PSD modification number when the
project is a major modification.  Therefore, when processing
projects which are only minor modifications to the PSD permit,
the modification number should not be changed.  Examples of
these types of projects include:  changes to the sampling or
monitoring conditions, amendments to the TACB permit which are
not above the PSD definition of a major modification,
amendments or revisions to the TACB permit which would lower
emissions of the pollutant for which the unit received a PSD
permit, etc.  EPA Region 6 (Stanley Spruiell) has no objection
to this policy.

Please begin implementing this policy immediately for all new
applications involving PSD.  It will be left up to the
engineer to decide what to do with currently pending
applications.  Keep in mind that it may be confusing to change
in mid-stream, especially if correspondence has already gone
out with the new number.