Model Clearinghouse Information Storage and Retrieval System
Record Details

Issue:  Region X 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 ADJ_U* technique will be applied in a 
compliance demonstration for a PSD permit at the Donlin mine 
facility located on the western slopes of the Kuskokwin Mountains 
in the Yukon-Kuskokwin region of southwestern Alaska.

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 Donlin mine facility compliance 
demonstration performs better for the given application, i.e., 
surface mining operations, than the default regulatory version of 
AERMET and, therefore, is approvable per the second condition of 
Appendix W, Section 3.2.2.  We also concur with the decision to 
exclude the sigma-theta turbulence parameter when processing the 
site-specific meteorological data with the ADJ_U* Beta option and 
with the decision to not include any of the LOW_WIND Beta options 
in AERMOD for this alternative model approval. Finally, the Model 
Clearinghouse agrees with the use of the POINTCAP and POINTHOR 
Beta options for capped and horizontal releases in AERMOD for the 
Donlin mine facility compliance demonstration and further recommend 
their use as the best available options for all capped and 
horizontal stacks subject or not subject to downwash, consistent 
with our proposed revisions to Appendix W.

Memo:  Model Clearinghouse Review of the Use of the ADJ_U* Beta 
Option in the AERMET Meteorological Processor (Version 15181) 
for the Donlin Mine Compliance Demonstration
          Dated: February 10, 2016
          From:  George Bridgers, Model Clearinghouse Director
                   Air Quality Modeling Group, EPA
            To:  Janis Hastings, Acting Director
                   Office of Air, Waste, and Toxics, Region 10, EPA

Memo:  Model Clearinghouse Concurrence Request - Surface Friction 
Velocity (u*) Non-Default/Beta Option in AERMET Version 15181; 
Alternative Refined Model Demonstration
          Dated: December 1, 2015
          From:  Kate Kelly, Director
                   Office of Air, Waste, and Toxics, Region 10, EPA
            To:  Tyler Fox, Lead
                   Air Quality Modeling Group, EPA

Memo:  Supporting Documentation - Surface Friction Velocity (u*) 
Non-Default/Beta Option in AERMET Version 15181; Alternative 
Refined Model Demonstration
          Dated: December 1, 2015
          From:  Herman Wong, Region 10 Modeling Contact
                   Office of Air, Waste, and Toxics, Region 10, EPA
            To:  Alan Schuler, Engineer, P.E.
                   Alaska Department of Enviromental Conservation