Model Clearinghouse Information Storage and Retrieval System
Record Details

Issue:  Region VI is seeking concurrence from the Model 
Clearinghouse on an alternative modeling approach that uses a 
combination of the Buoyant Line and Point Source model (BLP) and the 
American Meteorological Society/Environmental Protection Agency 
Regulatory Model (AERMOD) to represent buoyant roofline sources from 
the Freeport-McMoran Incorporated (FMMI) copper smelter located in 
Miami, Arizona. This alternative modeling technique is being proposed 
by the Arizona Department of Environmental Quality (ADEQ) as a part 
of its 2010 1-hr SO2 National Ambient Air Quality Standard (NAAQS) 
State Implementation Plan (SIP) revision for the Miami, AZ 
Nonattainment Area.

C/H Response:  In this case-specific concurrence, the regulatory 
modeling of the buoyant roofline sources at the FMMI copper smelter using 
the preferred model, BLP, at the time of the SIP revision development 
by ADEQ resulted in excessively high SO2 concentration as compared to a 
network of monitoring data collected in proximity to the FMMI facility. 
The FMMI facility accounts for more than 99.9% of the SO2 emissions in 
the nonattainment area, which simplified the model performance comparison 
in this particular situation. Region 9 and the ADEQ provided a rational 
discussion of the SO2 monitors and appropriate placement with respect to 
the FMMI copper smelter for the comparative analysis. The network of SO2 
monitors then provided the needed case-specific basis for developing an 
alternative model technique that could reasonably satisfy the 
requirements of Section 3.2.2(b)(2) in the Guideline on Air Quality 
Models (40 FR Part 51, Appendix W), which states, “a statistical 
performance evaluation has been conducted using measured air quality 
data, and the results of that evaluation indicate the alternative model 
performs better for the given application than a comparable model in 
Appendix A.”

The alternative "BLP/AERMOD Hybrid Approach" was found to most closely 
predict concentrations at the monitor most indicative of buoyant 
roofline sources and was also within a factor of two at the second 
most important monitoring location. By comparison, the preferred model 
approach substantially over-predicted by more than a factor of 2 at 
both of these locations. A statistical analysis following the EPA’s 
Protocol for Determining the Best Performing Model, that compares the 
fractional bias and Composite Performance Measures (CPM), equally 
found that the BLP/AERMOD Hybrid Approach performs better than the 
preferred model approach in this case.

After thorough review of the Region 9 technical analysis and the 
additional supporting material that was included from the ADEQ, the 
Model Clearinghouse concurs with Region 9 on the approval of the 
ADEQ’s proposed BLP/AERMOD Hybrid Approach to represent buoyant 
roofline sources from the FMMI copper smelter located in Miami, 
Arizona. Through this concurrence, the Model Clearinghouse is not 
broadly endorsing the BLP/AERMOD Hybrid Approach for application in 
additional PSD permit or SIP compliance demonstrations without adequate 
justification and appropriate alternative model approval by the 
respective EPA Regional Office with Model Clearinghouse concurrence.

Memo:  Model Clearinghouse Review of a BLP/AERMOD Hybrid Alternative Model 
Approach for Modeling Buoyant Roofline Sources at the FMMI Copper Smelter 
in Miami, AZ
          Dated: March 26, 2018
          From:  George Bridgers, Model Clearinghouse Director
                   Air Quality Modeling Group, EPA
            To:  Rynda Kay, Physical Scientist
                   Air Quality Analysis Office, Air Division, EPA Region 9
                 Meredith Kurpius, Associate Director
                   Air Division, EPA Region 9

Memo:  Concurrence Request for Approval of Alternative Model: BLP/AERMOD Hybrid
Approach for Modeling Buoyant Roofline Sources at the FMMI’Copper Smelter
in Miami, AZ
          Dated: March 12, 2018
          From:  Rynda Kay, Physical Scientist
                   Air Quality Analysis Office, Air Division, EPA Region IX
                 Meredith Kurpius, Associate Director
                   Air Division, EPA Region IX
            To:  George Bridgers, Director of Model Clearinghouse
                   Air Quality Modeling Group, Office of Air Quality Planning and Standards

Memo:  Technical Memorandum - Additional Performance Evaluation of Dispersion 
Modeling Approaches Miami SO2 Nonattainment Area State Implementation Plan
          Dated: February 5, 2018

TSD Appendix:  Appendix C - Modeling Technical Support Document for the Miami
Sulfur Dioxide (SO2) Nonattainment AreaProposed Workaround Related to
Buoyant Line Source Implementation Issues in AERMOD
          Dated: March 8, 2017
          Submitted To: Environmental Protection Agency, Region 9
          Prepared By: Arizona Department of Environmental Quality, Air Quality Division
                         & Freeport-McMoRan Inc.