Model Clearinghouse Information Storage and Retrieval System
Record Details

Issue:  Region VI is seeking concurrence from the Model 
Clearinghouse for the approval of an alternative modeling 
demonstration for the use of the beta Ambient Ratio Method 2 
(ARM2) Tier 2 NO2 modeling technique.  The ARM2 technique will be 
applied in an compliance demonstration for a PSD permit at 
the Sundrop Fuels Rapides Station Fuels Facility in Boyce, 
Louisiana.

C/H Response:  The Model Clearinghouse concurs with Region VI's 
position that ARM2 is an appropriate technique for modeling 
NO2 impacts from the Sundrop Fuels Rapides Station 
Fuels Facility project. We agree that the facility meets the 
requirements for the usage of ARM2 set forth in the 
September 30, 2014 EPA clarification memorandum. The ARM2 
technique can be used to model a variety of sources, provided 
that they meet certain minimum criteria to insure that the model 
results are appropriately conservative relative to a more 
refined Tier 3 technique (i.e., the Ozone Limiting Method, 
or OLM, and the Plume Volume Molar Ratio Method, or PVMRM). As 
noted in your memorandum, a review of the EPA’s NO2/NOX ISR 
Database was conducted to determine representative ISR from 
reported similar sources, where available. While representative 
ISR information was not available for all on-site sources, 
information was identified for most of the NOX sources. The 
average ratios of the identified representative ISRs were 
all less than 0.2 and maximum values less than 0.25, with the 
exception of the ISRs for natural gas fired reciprocating IC 
engine sources group. Based on the ISR information available 
and the types of on-site emission sources, we believe the 
minimum ambient NO2/NOX ratio of 0.50 is appropriately 
conservative for this proposed Sundrop Fuels facility project.

Memo:  Model Clearinghouse Review of the Use of the 
Ambient Ratio Method 2 (ARM2) Default AERMOD Option for the 
Sundrop Fuels Rapides Station Fuels Facility NO2 Ambient 
Impact Analysis
          Dated: August 1, 2016
          From:  George Bridgers, Model Clearinghouse Director
                   Air Quality Modeling Group, EPA
            To:  Jeffrey Robinson, Chief
                   Air Permits Section, Region 6, EPA
                 Ashley Mohr, Environmental Scientist
                   Air Permits Section, Region 6, EPA

Memo:  Concurrence Request - Approval of Ambient Ratio Method 2 
(ARM2) Default AERMOD Option for the Sundrop Fuels Louisiana 
LLC - Rapides Station Fuels Facility NO2 Ambient Impact 
Analysis
          Dated: August 1, 2016
          From:  Jeffrey Robinson, Chief
                   Air Permits Section, Region 6, EPA
            To:  George Bridgers, Director of Model Clearinghouse
                   Air Quality Modeling Group, EPA