Model Clearinghouse Information Storage and Retrieval System
Record Details

Issue:  Region I is seeking concurrence from the Model 
Clearinghouse for the approval of an alternative modeling 
demonstration for the use of the beta adjusted surface friction 
velocity (ADJ_U*) modeling technique in the AERMET meteorological 
preprocessor.  The modeling demonstration, including the ADJ_U* 
technique will apply to the Response to Order on Title V Petition 
VI-2014-04 regarding the issuance of a proposed Title V Operating 
Permit TV-0053 for the Schiller Station energy generating facility 
(Schiller Station) located in Portsmouth, NH and also to commitments 
made by the New Hampshire Department of Environmental Services in 
its January 5,2016 submittal under the SO2 Data Requirements Rule.

C/H Response:  
The Model Clearinghouse concurs that a well-reasoned justification 
was thoroughly documented and demonstrates that the ADJ_U* Beta 
option in AERMET selected for the Schiller Station modeling 
demonstration performs better than the default regulatory version 
of AERMET for the given application, i.e., a tall stack located 
near complex terrain, where high modeled concentrations are likely 
to occur under low wind, stable conditions. While not an issue in 
this particular case, we continue to evaluate the potential that 
the use of the ADJ_U* Beta option in combination with site-specific 
meteorological data that includes the sigma-theta and/or sigma-w 
turbulence parameters may introduce a bias toward concentration 
underprediction and caution anyone considering the use of both the 
ADJ_U* Beta option and meteorological data that includes the 
derived sigma-theta and/or sigma-w turbulence parameters in 
regulatory applications without consultation and approval from the 
appropriate permitting authority and the respective EPA Regional 
Office.

Memo:  Model Clearinghouse Review of the Use of the ADJ_U* 
Beta Option in the AERMET Meteorological Processor (Version 15181) 
for the Schiller Station Modeling Demonstration
          Dated: April 29, 2016
          From:  George Bridgers, Model Clearinghouse Director
                   Air Quality Modeling Group, EPA
            To:  David Conroy, Chief
                   Air Programs Branch, Region 1, EPA

Memo:  Request to approve the use of the beta alternative 
formulation of surface friction velocity (u•) non-regulatory 
default option in AERMET version 15181; alternative refined 
model demonstration
          Dated: April 7, 2016
          From:  Leiran Biton, Physical Scientist
                   Air Permits, Toxics and Indoor Programs Unit
                   Air Programs Branch, Region 1, EPA
          Thru:  David Conroy, Chief
                   Air Programs Branch, Region 1, EPA
            To:  George Bridgers, Director of Model Clearinghouse
                   Air Quality Modeling Group, EPA