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CPP's Advanced Dispersion Modeling Services

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dispersion modeling requirements are more common in air permitting projects and in many cases become the bottleneck in permitting. Unlike any other consulting firm, CPP promotes cutting edge techniques which can alleviate excessive conservatism in permit modeling to a reasonable level that still protects public health. At CPP we start with the standard modeling techniques and apply the following advanced analysis tools, as needed, to optimize your permitting strategy:
• Analysis of BPIP output to verify if AERMOD is overpredicting,
• Screening tool to assess the benefit of refining the BPIP building dimensions inputs,
• Use of Equivalent Building Dimension (EBD) studies to correct building wake effects in AERMOD,
• Evaluation of background concentrations to determine a reasonable value to combine with predicted concentrations,
• Use of the Monte Carlo approach (i.e., EMVAP) to address sources with variable emissions,
• Use of the adjusted friction velocity (u-star) option in AERMET to address AERMOD’s overestimation during low wind stable hours,
• Site analysis to determine whether stacks taller than formula GEP stack heights are justified,
• Site specific wind tunnel modeling to determine GEP stack heights and Equivalent Building Dimensions,
• Site-specific wind erosion inputs, and
• Area and volume source enhancements.

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CPP's Advanced Dispersion Modeling Services

  1. 1. Air Permitting and Advanced Dispersion Modeling Services Ron Petersen, PhD, CCM Sergio Guerra, Ph.D. Cell: 970 690 1344 Cell: 612 584 9595 rpetersen@cppwind.com sguerra@cppwind.com CPP, Inc. 2400 Midpoint Drive, Suite 190 Fort Collins, CO 80525 www.cppwind.com @CPPWindExperts
  2. 2. Who We Are • An air quality and wind engineering consulting firm based in Fort Collins, CO • Founded in 1981 as a spin off from Colorado State University • Offices in Australia, San Francisco, Boston, New York City, Dubai, Singapore and Malaysia
  3. 3. What We Do • Air permitting and advanced dispersion modeling • Industrial wind tunnel modeling • Particle and snow deposition • Fume reentry • Cooling tower impacts • Expert testimony/forensics • Wind energy assessments • Pedestrian comfort • Structural and cladding wind loads • Natural ventilation/internal flows • Fire and smoke management
  4. 4. Why CPP for Permitting? We have the best solutions to your permitting problem using AERMOD and advanced analysis methods such as: Equivalent Building Dimensions, wind tunnel determined GEP stack heights, EMVAP, emission rate analysis, site specific background analysis, in-stack NO2/NOx ratio optimization. Using all the advanced analysis methods and tools available, CPP can help optimize emission control equipment and stack heights and in some cases make a no-go project work.
  5. 5. • NAAQS are more stringent • Initial modeling may show your project exceeds the Significant Impact Levels (SILs) >> will trigger requirement for a detailed Air Quality Impact Assessment • AERMOD modeling is likely to show non-compliance with NAAQS in many situations • AERMOD tends to overpredict in many cases Problem
  6. 6. Air Permitting • Completion of air permit applications to satisfy for Federal NSR, Title V and Local/state programs • Standard dispersion modeling (SIL, NAAQS, PSD Increment, Air Toxics, Odor, etc.) • Advanced Dispersion Modeling Solutions • Equivalent Building Dimension (EBD) Studies • Emission Variability Processor (EMVAP) • GEP stack height evaluations • Evaluation of background concentrations • Haul road characterization based on site specific dispersion coefficients • Fugitive dust emissions based on site-specific friction velocity • Adjusted friction velocity (u*) in AERMET
  7. 7. Standard AERMOD Modeling Process
  8. 8. Advanced Model Input Analysis Solutions • Emission Variability Processor (EMVAP) • Evaluation of background concentrations • Adjusted friction velocity (u*) in AERMET EM Magazine, December 2014 Guerra, S.A. “Innovative Dispersion Modeling Practices to Achieve a Reasonable Level of Conservatism in AERMOD Modeling Demonstrations.” EM Magazine, December 2014.
  9. 9. Advanced Wind Tunnel Modeling Solutions • Equivalent Building Dimension (EBD) studies • GEP stack height evaluations • Haul road characterization based on site specific dispersion coefficients • Fugitive dust emissions based on site-specific friction velocity
  10. 10. Basic Wind Tunnel Modeling Methodology • Specify model operating conditions • Construct scale model • Install model in wind tunnel and measure desired quantity
  11. 11. Measure Ground-level Concentrations Tracer from stack Max ground-level concentrations measured versus x
  12. 12. GEP Stack Height • 40 CFR 51.110 (ii) Defines GEP stack height to be the greater of: • 65 meters; the formula height; or • The height determined by a wind tunnel modeling study – Can be taller than the formula!! • Up to 3.25 times the building height versus 2.5 for the formula • Typically 2 times the nearby terrain height
  13. 13. Real World Example – Rhinelander Mill SO2 Monitor Exceeds 1-hr SO2 NAAQS Stack AERMOD predicts 1-hr SO2 NAAQS met AERMOD predictions 50% of monitored value Corner Vortex Problem Formula GEP Height 75 m, Taller Stack Needed
  14. 14. Wind Tunnel Modeling Conducted 1:240 Scale Model of Rhinelander Installed in Wind Tunnel
  15. 15. Advanced AERMOD Modeling Process
  16. 16. • Equivalent Building Dimensions” (EBDs) are the dimensions (height, width, length and location) that are input into AERMOD in place of BPIP dimensions to more accurately predict building wake effects • Guidance originally developed when ISC was the preferred model – • EPA, 1994. Wind Tunnel Modeling Demonstration to Determine Equivalent Building Dimensions for the Cape Industries Facility, Wilmington, North Carolina. Joseph A. Tikvart Memorandum, dated July 25, 1994. U.S. Environmental Protection Agency, Research Triangle Park, NC • Determined using wind tunnel modeling • How does EBD Improve Accuracy? Watch video What is EBD?
  17. 17. Advanced AERMOD Modeling
  18. 18. Case Study: Refinery A 3D Printed Scale Model
  19. 19. Stack height: 45 m Structure height: 61 m Emission rate: 1 g/s Five years of met data Stack Building Input 1-hour 24-hour annual BPIP 23.21 5.51 0.37 Wind Tunnel EBD 7.72 2.36 0.11 Reduction Factor 3.01 2.33 3.51 Maximum Concentration Results AERMOD Results – Lattice Structure
  20. 20. Refinery Structures Upwind Solid BPIP Structure Upwind No Structures WHY EBD Helped
  21. 21. AECOM (David Shea) Conducted Field Study That Validated use of EBD – see AWMA 2007 papers
  22. 22. • Short, wide and long buildings • Wide and narrow buildings • Lattice structures • Streamlined structures Other Examples Where AERMOD Overpredicts
  23. 23. Stack S_288 From ALCOA EBD Study Stack height = 27 m Q = 1 g/s Building height = 17 m Building width/length > 200 m 5 years of meteorological data (Moline/Quad-City Airport 2000-2004 Building Input 1-hr 3-hr 24-hr annual BPIP 129.1 101.7 38.2 4.0 Wind Tunnel EBD 27.3 17.8 7.9 0.5 Decrease Factor 4.7 5.7 4.8 7.9 Maximum concentration (ug/m3 )
  24. 24. Stack height: 47 m Building height: 31 m Property line in Red Emission rate: 1 g/s AERMOD RESULTS Five years of met data AERMOD Building Dimension Inputs 1-hour 24-hour annual BPIP 15.19 8.20 0.89 Screening EBD Values 9.68 5.05 0.19 EBD values from wind tunnel study 3.99 1.88 0.18 AERMOD Maximum predicted concentration (μg/m3 ) Wide/narrow building
  25. 25. Typical AERMOD Predictions for Refinery Structures with BPIP and EBD Inputs 0.00 0.25 0.50 0.75 1.00 BPIP EBD Predicted Concentrations FACTOR of 2 to 3.5 reduction when EBD used Lattice Structures
  26. 26. 0.00 0.25 0.50 0.75 1.00 BPIP EBD Predicted Concentrations FACTOR of 4 to 8 reduction when EBD used Short building with a large foot print Typical AERMOD Predictions for Buildings with Large Footprint BPIP and EBD Inputs
  27. 27. 0.00 0.25 0.50 0.75 1.00 BPIP EBD Predicted Concentrations FACTOR of 2 to 5 reduction when EBD used Very Wide/Narrow Buildings Typical AERMOD Predictions for Very Wide/Narrow Buildings with BPIP and EBD
  28. 28. Summary We can bring best solution to for you permitting problem using AERMOD and advanced analysis methods such as Equivalent Building Dimensions, wind tunnel determined GEP stack heights, EMVAP, emission rate analysis, site specific background analysis, in-stack NO2/NOx ratio optimization. Using all the advanced analysis methods and tools available CPP can help optimize emission control, equipment, and stack heights and in some cases make a no-go project work.
  29. 29. Ron Petersen, PhD, CCM, FASHRAE Sergio Guerra, PhD rpetersen@cppwind.com sguerra@cppwind.com Mobile: + 970 690 1344 Mobile: + 612 584 9595 CPP, Inc. 2400 Midpoint Drive, Suite 190 Fort Collins, CO 80525 + 970 221 3371 www.cppwind.com @CPPWindExperts Questions?

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