May 24, 1990
 
 


MEMORANDUM 
 
SUBJECT:  Review of El Paso/Juarez Modeling Plan 
 
FROM:     Joseph A. Tikvart, Chief 
          Source Receptor Analysis Branch (MD-14) 
 
TO:       Gerald Fontenot, Chief 
          Air Programs Branch, Region VI (6T-A) 

     In response to your request, the Model Clearinghouse has reviewed the 
subject Air Modeling Plan.  It was our understanding that you wanted a 
coordinated review, i.e. one that reflects both regulatory and technical 
comments.  As such, we requested comments from CO, O3 and PM-10 personnel in 
the Air Quality Management Division (AQMD), as well as technical comments from
monitoring, emission inventory and modeling personnel in the Technical Support
Division.  Attached are the comments we received from these individuals. 
 
     Our impressions from these comments are as follows: 
 
          1.  While the design of the study does not seem to conflict with 
current regulatory requirements, the SIP process could be impacted by the 
proposed Clean Air Act Amendments (CAAA).  To the extent possible, the design
of the study should take into account the expected effects of these 
amendments. 
 
          2.  While the Urban Airshed Model (UAM) does seem appropriate for 
the area for all three pollutants, there are a number of concerns on the use 
of the model for CO and PM-10 because of the possible need to address specific
localized impacts, the manner in which the design concentration will be 
chosen, and the possible need to address secondary particulates.  Also, it was
pointed out that the wind field model to be based on wintertime meteorological
conditions may not be applicable to high summer O3 days. 
 
          3.  Most of the comments reflect concerns about the emission 
inventory (EI).  Our sense from the written comments is that the reviewers did
not have serious problems with the emissions inventory procedures.  It was
noted, however, that the EI requirements might need to be changed in the
future because of CAAA requirements and updated guidance.  Followup 
discussions with some individuals indicated that the biggest concern is a lack
of confidence that the end product (the EI) will be "good enough" to use in 
modeling.  This concern prompted one reviewer to suggest the use of a modeling
"fudge factor" to compensate for uncertainties in the EI.  While we do not  
 
necessarily agree with that idea, it may be necessary to qualitatively 
interpret the modeling results because of EI uncertainties. 
 
     In summary, the Model Clearinghouse does not have significant problems 
conceptually with the proposed study.  The attached comments should be 
reflected in a more detailed protocol, which we assume will be forthcoming at
some point in time.  If you have any questions, please contact Dean Wilson at
FTS 629-5683. 
 
Attachments 
 
cc:  R. Bauman 
     T. Helms 
     W. Hunt 
     W. Laxton 
     N. Meyer 
 
bcc: K. Baugues 
     T. Braverman 
     G. Dorosz 
     O. Gerald 
     T. Pace 
     S. Reinders 
     M. Smith 
     D. Wilson

     Regional Modeling Contact, Regions I-X (with copy of incoming 
memorandum and list of FY-90 Clearinghouse memoranda)