December 11, 1992


MEMORANDUM

SUBJECT:  Proposal for Resolving Part D Sulfur Dioxide
          State Implementation Plan Revision for
          Rhinelander, Wisconsin

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

TO:       Gary Gulezian, Chief
          Air Toxics and Radiation Branch, Region V (AT-18J)


     In response to your request, the Model Clearinghouse has reviewed your
latest proposal for resolving the emission limitations for the Rhinelander
Paper Company (RIPCO).  It is our understanding that the proposal would
allow RIPCO to essentially operate its cyclone boilers and stoker boilers
in more or less any combination provided that the total plant emissions
would not exceed the so-called "base case," approximately 26,948 pounds of
sulfur dioxide (SO2) per day.  This differs from previous proposals to the
Clearinghouse on this issue where the plant was prohibited from operating
any more than two stoker boilers in conjunction with the cyclone boiler. 
This mode of operation corresponded to the units that were operating on the
days of high observed concentration, thus forming a logical basis for the
rollback calculation.  

     Regarding the current proposal, the bottom line is that we are willing
to defer to your professional judgment that operating the plant as proposed
will not result in a violation of a National Ambient Air Quality Standard
(NAAQS).  However, as we indicate below, we do not believe that position
can be logically supported by dispersion modeling.  Also, given the
uncertainties in this case, we suggest that the plant be required to
conduct ambient monitoring, collect emissions data, and collect
meteorological data in the vicinity of the plant.  Such data would be used
to resolve the source-receptor relationships if another exceedance of the
NAAQS were observed.  Such data could also be used to support the
acceptability of any future plant expansion or different emission
configurations.

     Based on a review of our records on the RIPCO issue, it appears that
something similar to the current proposal was discussed between Region V
and the State back in 1988.  At that time the State suggested that various
combinations of boiler operating rates could be supported by modeling by
considering only the relative contribution of the various units, rather
than the absolute concentration.  In a May 9, 1988 letter from Region V to
the State, the Environmental Protection Agency (EPA) indicated that since
the model was underpredicting in the absolute sense, it should not be
relied upon in the relative sense either; thus, the State's position was
not supported by the modeling.

     In your current proposal, you indicate (last paragraph of your
November 9, 1992 memorandum) that it is supportable from dispersion
modeling results by examining the relative contribution of the cyclone and
stoker boilers.  Since the argument does not seem to be basically different
from that espoused by the State in 1988, and we have not seen any new
information that would refute the previous EPA position, we do not believe
that the current proposal can be supported by the modeling.

     However, as we indicated above, and setting aside the dispersion
modeling arguments, we would still be willing to defer to your professional
judgment that the NAAQS are not at risk with the proposed emission limits. 
Recognizing that rollback is an oversimplistic source-receptor analysis
technique, and especially so where multiple sources are involved, we
suggest that meteorological, ambient and emission data be collected in the
future such that any significant ambient events can be properly analyzed.

     If you have any questions please contact Dean Wilson at 919-541-5683.

cc:  G. Blais