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www.cppwind.com www.cppwind.com Strategies to Deal with Monitored Exceedances When AERMOD Can’t be Used Ron Petersen, PhD, CCM Sergio Guerra, PhD Cell: 970 690 1344 Cell: 612 584 9595 [email protected] [email protected] CPP, Inc. 2400 Midpoint Drive, Suite 190 Fort Collins, CO 80525 www.cppwind.com @CPPWindExperts
33

Strategies to deal with monitored exceedances when AERMOD can’t be used

Jan 22, 2018

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Page 1: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Strategies to Deal with Monitored Exceedances When AERMOD Can’t be Used

Ron Petersen, PhD, CCM Sergio Guerra, PhD

Cell: 970 690 1344 Cell: 612 584 9595 [email protected] [email protected]

CPP, Inc.

2400 Midpoint Drive, Suite 190

Fort Collins, CO 80525

www.cppwind.com @CPPWindExperts

Page 2: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Overview • Monitored SO2 concentrations exceed the new 1-hour SO2

NAAQS at nearby Water Tower Monitor (WTM)

• Monitored design concentration is 151 ppb (2009-2011) relative to 75 ppb NAAQS; background is about 8 ppb

• For attainment, maximum hourly SO2 concentration needs to be reduced by at least 55%

• AERMOD is showing compliance at the monitoring station with predicted concentrations a factor of two lower than monitored

• Rhinelander Mill Boiler Stack S09 has been identified as the primary contributor

Page 3: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Rhinelander Mill and Monitor

Looking Northeast SO2 Monitor

Stack S09

Corner Vortex Problem

Page 4: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Rhinelander Mill and Critical Features

Cyclone Boiler(S09)

Stack Height

63 m

207 ft

Boiler

Building

38 m

125 ft

Looking South

Page 5: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Monitored SO2 Concentrations for 2009 Highest concentrations for wind speeds around 5 m/s for 200 degree wind direction (toward Water Tower monitor)

Page 6: Strategies to deal with monitored exceedances when AERMOD can’t be used

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AERMOD Corner Vortex Issue

• Current building wake equations do not account for corner vortex

• Corner vortex causes higher concentrations than currently predicted in AERMOD due to increased downdraft and plume rise suppression

• AERMOD and PRIME downwash model do not even have input for approach flow relative to building corners – model assumes flow toward broad side of buildings and is totally oblivious to corner effects

Page 7: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Corner Vortex Issues – EPA Research

Note increased effect for 45º approach flow

Page 8: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Possible Solutions • Reduce emission rate by 50% based on monitored

results >> not a good solution

• Extend stack to formula GEP stack height of 75 m plus emission control: how do you determine since AERMOD doesn’t work?

• Extend stack to actual GEP stack height plus emission control if needed: how to determine since AERMOD doesn’t work?

Page 9: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Issues for Consideration

• Two problems for consideration:

– The need to find a tool other than AERMOD to correlate reductions in SO2 emissions from the Mill to SO2 concentrations at the Water Tower monitor to show compliance with the 1-hour SO2 standard, and

– The need to develop a site-specific GEP stack height given the topography of the Mill and monitor and the excessive downwash caused by the corner vortex.

• Fluid modeling in a wind tunnel using HYWINMOD allows for correlation of mill emissions to monitor results, as well as development of site-specific GEP determination.

Page 10: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Overall Plan • Determine actual GEP stack height using wind

tunnel modeling

• Demonstrate compliance for final design configuration – HYWINMOD (CPP model utilizing output from wind tunnel +

AERMOD) >> complete but EPA approval pending

– AERMOD w/o downwash plus wind tunnel downwash factor >> likely approval soon

10

Page 11: Strategies to deal with monitored exceedances when AERMOD can’t be used

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GEP Study Plan • Test protocol developed and reviewed by WDNR and

EPA – tentatively approval received

• Constructed scale model (1:240) and setup

• Wind tunnel testing – documentation tests

• Wind tunnel testing – GEP stack height tests

– Tests with buildings present

– Tests without building present

• Specify the GEP stack height (40% and NAAQS test)

• Report submission and approval – January, 2015

11

Page 12: Strategies to deal with monitored exceedances when AERMOD can’t be used

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40 CFR 51.110 (ii) Defines GEP stack height to be the greater of:

• 65 meters;

• the formula height (Hb+1.5 L), or – For a 40 m cube, GEP = 100 m > 65 m!!!

• The height determined by a wind tunnel modeling study – Will 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

Page 13: Strategies to deal with monitored exceedances when AERMOD can’t be used

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GEP Stack Height Criteria for Wind Tunnel

• 40% maximum concentration difference with and without the buildings or terrain

• With buildings in Max Concentration must exceed NAAQS or PSD increment

• Easy test since approved wind tunnel method does not include plume buoyancy.

Page 14: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Example 1 • Kennecott Smelter

mid 80s

• 1200 ft stack justified as GEP using wind tunnel modeling

Page 15: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Example 2: • Titus Generating Station, Schuylkill River about 3 km south of

Reading, Pennsylvania

• 175 m stack height justified as GEP using wind tunnel

modeling, 1995

175m

100m

65m

Page 16: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Basic Wind Tunnel Modeling Methodology

•Specify model operating conditions

•Construct scale model (3D printing)

• Install model in wind tunnel and measure desired quantity

Page 17: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Source Parameters

Stack

Height

Source Source Above Exit Exit Volume Exit

Description ID Base Diameter Temp. Flow Rate Velocity

(m) (m) (K) (m3/s) (m/s)

S09 - Maximum Load S09 max 62.09 2.13 430.4 47.23 13.25

S09 - Nominal Load S09 nom 62.09 2.13 422.0 34.21 9.60

S09 - Minimum Load S09 Mmin 62.09 2.13 422.0 26.50 7.44

Page 18: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Wind Tunnel Testing 1:240 Scale Model Installed in Wind Tunnel

Page 19: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Measure Ground-level Concentrations

Tracer

from stack

Max ground-level concentrations measured versus x

Page 20: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Measure Ground-level Concentrations

Data taken until good fit and max

obtained Automated Max GL Concentration Mapper

Page 21: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Buildings in

Buildings out

Page 22: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Plume rise with and without the building

Buildings in

Buildings Out

CORNER VORTEX EFFECT

Page 23: Strategies to deal with monitored exceedances when AERMOD can’t be used

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All GEP Testing Results

Page 24: Strategies to deal with monitored exceedances when AERMOD can’t be used

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GL Concentration Profile W and W/O Buildings at 90 m GEP Stack Height

90 m stack height,

190 degree WD,

8 m/s wind speed

Page 25: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Final Result

Actual GEP = 90 m

Formula GEP = 75 m

Creditable GEP = 90 m > formula > 65 m

Page 26: Strategies to deal with monitored exceedances when AERMOD can’t be used

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NAAQS Compliance Demonstration Using HYWINMOD • Test protocol development and approval

• HYWINMOD validation

• Surface Roughness

– 0.49 m for Water Tower Direction

– 0.25 m for Airport

• Scale model setup and instrumentation

• Wind tunnel testing of final design configuration for S09

• HYWINMOD analysis to demonstrate compliance at monitor and at least 55% reduction in concentrations from baseline emission conditions

• Report submission – approval pending

Page 27: Strategies to deal with monitored exceedances when AERMOD can’t be used

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HYWINMOD • CPP developed a practical method where wind

tunnel modeling can be used to predict hourly concentrations for all stabilities and can account for plume buoyancy

• Previously validated against EPA database: Bowline Point

• Will account for corner vortex

Wind tunnel

predicted

concentration

(neutral)

Data post

processing

and

correction

Hourly concentrations

incl. plume buoyancy

for all stabilities

Page 28: Strategies to deal with monitored exceedances when AERMOD can’t be used

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HYWINMOD Validation Rhinelander Mill WT Monitor

HYWINMOD

AERMOD

”Raw” wind tunnel

prior to HYWINMOD

processing

Page 29: Strategies to deal with monitored exceedances when AERMOD can’t be used

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HYWINMOD Results

4th highest max daily SO2

concentration (μg/m3)

Description/Source Configuration

Maximum

Load

Scenario

Nominal

Load

Scenario

Minimum

Load

Scenario*

5-year

average

5-year

average

5-year

average

Supporting Information

1-hour NAAQS NAAQS 196.5 196.5 196.5

Water Tower Monitor SO2 Design Value

(2009-2011) Co,DV (WTM) 395.6 395.6 395.6

Estimate Design Value Based on

HYWINMOD Scaling Plus BG at 90 m

GEP Stack Height

Cp,DV

(WTM,GEP,S09)+

BG

136.8 152.4 195.7

% Emission Reduction Required -52% -34% 0%

Page 30: Strategies to deal with monitored exceedances when AERMOD can’t be used

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AERMOD Compliance Demonstration

• Run AERMOD w/o building downwash in approved manner

• Use wind tunnel determine downwash factor, R, to adjust emission rate

• R is a only a function of wind speed

R = 1 @ <= 2 m/s

R = 1.5 @ 10.8 m/s

Page 31: Strategies to deal with monitored exceedances when AERMOD can’t be used

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AERMOD Emission Factor to account for downwash

Page 32: Strategies to deal with monitored exceedances when AERMOD can’t be used

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AERMOD Compliance Demonstration

• Protocol prepared: reviewed and approved by agency

• Report submitted: approval should be forthcoming this month.

Page 33: Strategies to deal with monitored exceedances when AERMOD can’t be used

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Ron Petersen, PhD, CCM Sergio A. Guerra, PhD

[email protected] [email protected]

Mobile: +1 970 690 1344 Mobile: + 612 584 9595

CPP, Inc.

2400 Midpoint Drive, Suite 190

Fort Collins, CO 80525

+ 970 221 3371

www.cppwind.com @CPPWindExperts

Questions?