CPP is an air quality and wind engineering consulting firm that provides air permitting and advanced dispersion modeling services. They have expertise in AERMOD modeling, wind tunnel modeling, and other advanced analysis methods like equivalent building dimensions and emission variability processing. Using these advanced methods, CPP can help optimize clients' emission control equipment and stack heights to make projects compliant with permitting requirements in cases where initial modeling shows exceedances.

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. 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. 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. 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. • 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. 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. Standard AERMOD Modeling Process

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. 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. Basic Wind Tunnel Modeling Methodology
• Specify model operating conditions
• Construct scale model
• Install model in wind tunnel and
measure desired quantity

11. Measure Ground-level Concentrations
Tracer
from stack
Max ground-level concentrations measured versus x

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. 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. Wind Tunnel Modeling Conducted
1:240 Scale Model of Rhinelander Installed in Wind Tunnel

15. Advanced AERMOD Modeling Process

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. Advanced AERMOD Modeling

18. Case Study: Refinery A
3D Printed
Scale Model

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. Refinery Structures Upwind
Solid BPIP Structure Upwind
No Structures
WHY EBD Helped

21. AECOM (David Shea) Conducted Field Study
That Validated use of EBD – see AWMA 2007 papers

22. • Short, wide and long buildings
• Wide and narrow buildings
• Lattice structures
• Streamlined structures
Other Examples Where AERMOD Overpredicts

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. 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. 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. 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. 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. 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. 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?