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Solution to AERMOD/PRIME PM10 Overpredictions for Extremely Short, Long and Wide Buildings

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The current formulation in AERMOD/PRIME is prone to downwash overestimations as documented by Petersen et al. Some of these overpredictions can be minimized by conducting a wind tunnel study to refine the building inputs used in AERMOD/PRIME for critical stacks and wind directions. Most of the wind tunnel studies conducted to date involve taller building structures of at least 20 meters in height. However, a recent wind tunnel study was conducted for the Basic American Foods, Blackfoot, Idaho facility, which has extremely short buildings (7 to 12 meters in height) with very long and wide footprints and many exhaust stacks which are less than 25 meters above ground
The wind tunnel study confirmed that AERMOD was vastly overstating downwash effects for certain critical wind directions. In some cases, AERMOD-predicted concentrations were almost four times higher without the wind tunnel refinements. This study indicates that the previously identified tendency of AERMOD to overpredict downwash using the traditional BPIP-derived building inputs also applies to sites with shorter buildings. Because shorter buildings with shorter stacks are common in many sources subject to the minor New Source Review program (such as most food and beverage and manufacturing facilities), AERMOD’s overpredictions may be causing significantly higher predicted concentrations for many industrial sources.
This paper describes the wind tunnel study performed for this site, presents the benefits obtained from these building input refinements, and reviews comments received on the project from regulatory agencies.

Published in: Engineering
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Solution to AERMOD/PRIME PM10 Overpredictions for Extremely Short, Long and Wide Buildings

  1. 1. Solution to AERMOD/PRIME Overpredictions for Extremely Short, Long, and Wide Buildings Guideline on Air Quality Models: The Changes Chapel Hill, NC Sergio A. Guerra, Ron Petersen; CPP Inc. Steve Nelson; Coal Creek Environmental John S. Kirkpatrick; Basic American Foods November 15, 2017 COAL CREEK ENVIRONMENTAL ASSOCIATES
  2. 2. BAF Customers
  3. 3. Basic American Foods (BAF) Overview • Family owned and operated since 1933 – Ongoing innovation (40+ patents) – Shelf-stable potatoes and beans • Food Service • Limited Retail – Hungry Jack • Facility Locations – Idaho • Blackfoot • Shelley • Rexburg – Washington • Moses Lake
  4. 4. BAF Blackfoot Facility
  5. 5. BAF Blackfoot Facility
  6. 6. Baseline Case (with BPIP values)
  7. 7. Permitting and Modeling Challenges • BAF is updating a PM10 compliance demonstration • No clear path to show needed reductions in PM10 impacts (needed 80% reduc8ons in impacts) ̵ Modeling op8ons exhausted ̵ No apparent treatment options (most of the PM10 is non-filterable material) ̵ Stack height increases unfeasible • Wind tunnel analysis of downwash appeared promising
  8. 8. BPIPPRM Derived Values Flow Wind BUILDHGT BUILDWID BUILDLEN Vector Direction Hb W L Hs/Hb W/Hb L/Hb (Deg.) (Deg.) (m) (m) (m) 10 190 7.92 61.66 35.92 2.1 7.8 4.5 20 200 7.92 62.29 44.07 2.1 7.9 5.6 180 360 7.92 59.22 26.93 2.1 7.5 3.4 StackEU_13BPIP DimensionsDiagnostic Aspect Ratio
  9. 9. Downwash Screening – Stack CXX
  10. 10. Downwash Screening – Stack EU_15
  11. 11. Equivalent Building Dimension Method for Downwash
  12. 12. Model Design and Construction • Obtain source/site data • Specify test wind speeds and directions • Compute model operating conditions • Construct scale model
  13. 13. Phase 1 Testing: Flakers
  14. 14. Phase 2 Testing: Dehydrators
  15. 15. Measure Ground-level Concentrations Data taken until good fit and max obtained Automated Max GL Concentration Mapper
  16. 16. Identify Wind Tunnel Determined EBD that Match Dispersion with Site Structures Present
  17. 17. Sample Result Plot
  18. 18. Baseline Case (with BPIP values)
  19. 19. WT EBD values for Flakers and Dehys Max PM10 H6H = 82 ug/m3
  20. 20. Dehy area Flaker area
  21. 21. Conclusions • EPA provided technical assistance to IDEQ in reviewing the EBD study • IDEQ has accepted the results of the EBD study • BAF has resubmitted the Alternate Compliance Plan using the EBD study results • This study demonstrated the applicability of EBD method to shorter buildings and stacks • Case study provides an opportunity to revisit the use of wind tunnel testing for regulatory purposes
  22. 22. Questions?

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