Implications of AERMODon a

Chemical Plant

William B. JonesRoger P. Brower

Zephyr Environmental CorporationColumbia, Maryland

Presented at 100th Annual AWMA Conference and Exhibition

Pittsburgh, PA

June 26, 2007

Outline of PresentationOutline of PresentationOutline of PresentationOutline of Presentation

• Background on project

• Comparative Modeling– ISC3– AERMOD

• Conclusions

Background on ProjectBackground on ProjectBackground on ProjectBackground on Project

• Chemical plant in southwestern Louisiana

• Several permitting efforts required modeling over the past few years (modeling done with ISC3)

• November 9, 2006: AERMOD replaced ISC3 as preferred dispersion model

• Chemical plant was curious as to what effect going from ISC3 to AERMOD would have

Three projects examinedThree projects examinedThree projects examinedThree projects examined• Vinyl Acetate

– Modeling performed in 2005– In support of Title V application for Plant’s

polyethylene manufacturing complex

• Butadiene– Modeling performed in 2003– In support of revised Title V application for

Plant’s ethylene/styrene manufacturing complex

• PM10– Modeling performed in 2003– In support of “retroactive” PM10 NAAQS and

PSD Increment modeling

Comparative ModelingComparative ModelingVinyl AcetateVinyl Acetate

Comparative ModelingComparative ModelingVinyl AcetateVinyl Acetate

• Original ISC3 modeling– Initially only Plant sources, then offsite sources– Flat terrain (no receptor elevations)– Meteorological data from 2004 (Lake Charles surface

and upper air)

• AERMOD modeling– Plant sources only– Flat terrain (no receptor elevations)– Meteorological data from 2004 (Lake Charles surface

and upper air) processed using AERMET• Bowen Ratio, Albedo, and Surface Roughness Lengths

assumed constant for entire area

LDEQLDEQDefault Meteorological ValuesDefault Meteorological Values

LDEQLDEQDefault Meteorological ValuesDefault Meteorological Values

Taken from “Developing State-Wide Modeling Guidance for the Use of AERMOD, A Workgroup’s Experience” (Presented at 2005 Louisiana AWMA Fall Conference)

Comparative ModelingComparative ModelingVinyl Acetate: ISC3 ResultsVinyl Acetate: ISC3 Results

Comparative ModelingComparative ModelingVinyl Acetate: ISC3 ResultsVinyl Acetate: ISC3 Results

SourceHighest predicted 8-hr concentration (ug/m3)

203 202.63

BDRYER2 148.28

BDRYER3 36.93

BEXTRDR 36.50

BPELLET8 22.22

Comparative ModelingComparative ModelingVinyl Acetate: AERMOD ResultsVinyl Acetate: AERMOD Results

Comparative ModelingComparative ModelingVinyl Acetate: AERMOD ResultsVinyl Acetate: AERMOD Results

SourceHighest predicted 8-hr concentration (ug/m3)

203 350.53

BDRYER2 113.48

BDRYER3 89.01

BPELLET3 32.40

BPELLET4 31.90

Comparative ModelingComparative ModelingVinyl Acetate: Q-Q Plot, AERMOD and ISC3Vinyl Acetate: Q-Q Plot, AERMOD and ISC3

Comparative ModelingComparative ModelingVinyl Acetate: Q-Q Plot, AERMOD and ISC3Vinyl Acetate: Q-Q Plot, AERMOD and ISC3

Comparative ModelingComparative ModelingVinyl Acetate ObservationsVinyl Acetate Observations

Comparative ModelingComparative ModelingVinyl Acetate ObservationsVinyl Acetate Observations

• Highest contributing source is same with ISC3 and AERMOD

• Highest source-specific impacts for each model roughly the same

• AERMOD consistently over predicts relative to ISC3 (for highest 8-hr concentrations)

Comparative ModelingComparative ModelingButadieneButadiene

Comparative ModelingComparative ModelingButadieneButadiene

• Original ISC3 modeling– Initially only Plant sources, then offsite sources– Flat terrain (no receptor elevations)– Meteorological data from 2000 (Lake Charles surface

and upper air)

• AERMOD modeling– Plant sources only– Flat terrain (no receptor elevations)– Meteorological data from 2000 (Lake Charles surface

and upper air) processed using AERMET• Bowen Ratio, Albedo, and Surface Roughness Lengths

assumed constant for entire area

Comparative ModelingComparative ModelingButadiene: ISC3 ResultsButadiene: ISC3 Results

Comparative ModelingComparative ModelingButadiene: ISC3 ResultsButadiene: ISC3 Results

SourceHighest predicted annual

concentration (ug/m3)

1296_D1 0.15047

WPT35_98 0.12538

12_96C 0.10160

WPT34_96 0.09661

1296_D2 0.09648

Comparative ModelingComparative ModelingButadiene: AERMOD ResultsButadiene: AERMOD Results

Comparative ModelingComparative ModelingButadiene: AERMOD ResultsButadiene: AERMOD Results

SourceHighest predicted annual

concentration (ug/m3)

5_89A_S1 1.20429

5_89A_S2 0.39604

WPT34_96 0.37479

5_89A_W1 0.28529

5_89A_S3 0.25612

Comparative ModelingComparative ModelingButadiene: Q-Q Plot, AERMOD and ISC3Butadiene: Q-Q Plot, AERMOD and ISC3

Comparative ModelingComparative ModelingButadiene: Q-Q Plot, AERMOD and ISC3Butadiene: Q-Q Plot, AERMOD and ISC3

Comparative ModelingComparative ModelingButadiene ObservationsButadiene Observations

Comparative ModelingComparative ModelingButadiene ObservationsButadiene Observations

• Major contributing sources in ISC3 are not consistent with those in AERMOD

• Highest source-specific impacts for AERMOD are higher (roughly an order of magnitude) than ISC3

• AERMOD consistently over predicts relative to ISC3 (for highest annual concentrations)

Comparative ModelingComparative ModelingPM10PM10

Comparative ModelingComparative ModelingPM10PM10

• Original ISC3 modeling– Initially only Plant sources, then offsite sources– 24-hr and Annual NAAQS and PSD Increment– Flat terrain (no receptor elevations)– Meteorological data from 1996-2000 (Lake Charles

surface and upper air)

• AERMOD modeling– Plant and offsite sources– 24-hr NAAQS only– Flat terrain (no receptor elevations)– Meteorological data from 1996-2000 (Lake Charles

surface and upper air) processed using AERMET• Bowen Ratio, Albedo, and Surface Roughness Lengths

assumed constant for entire area

Comparative ModelingComparative ModelingPM10: ISC3 Results (1996)PM10: ISC3 Results (1996)

Comparative ModelingComparative ModelingPM10: ISC3 Results (1996)PM10: ISC3 Results (1996)

Source

Highest second-high predicted 24-hr

concentration (ug/m3)

LC_COAL 44.01368

9_89 20.45634

FIRE_65 19.61712

CIT13_18 18.37893

8_89 16.53271

Comparative ModelingComparative ModelingPM10: AERMOD Results (1996)PM10: AERMOD Results (1996)

Comparative ModelingComparative ModelingPM10: AERMOD Results (1996)PM10: AERMOD Results (1996)

Source

Highest second-high predicted 24-hr

concentration (ug/m3)

LC_COAL 72.12283

FIRE_65 30.69010

STY20_90 23.74922

8_89 19.89097

9_89 18.35552

Comparative ModelingComparative ModelingPM10: Q-Q Plot, AERMOD and ISC3 (1996)PM10: Q-Q Plot, AERMOD and ISC3 (1996)

Comparative ModelingComparative ModelingPM10: Q-Q Plot, AERMOD and ISC3 (1996)PM10: Q-Q Plot, AERMOD and ISC3 (1996)

Comparative ModelingComparative ModelingPM10 ObservationsPM10 Observations

Comparative ModelingComparative ModelingPM10 ObservationsPM10 Observations

• Major contributing sources in ISC3 are consistent with those in AERMOD– The two Plant sources in the Top 5 for ISC3 and

AERMOD only had increases in their predicted 24-hr concentrations of 20% and 12% going from ISC3 to AERMOD (larger increases from offsite sources)

• Highest source-specific impacts for AERMOD are higher than ISC3

• AERMOD and ISC3 are consistent in lower concentrations (AERMOD sometimes slightly lower), but at higher concentrations AERMOD over predicts relative to ISC3 (for highest second-high concentrations)

ConclusionsConclusionsConclusionsConclusions

• Examined vinyl acetate, butadiene, and PM10 modeling

• AERMOD nearly always predicted higher concentrations than ISC3– For some lower PM10 concentrations

AERMOD slightly under predicted relative to ISC3

• Plant should exercise caution in future permitting efforts that involve updated previous dispersion modeling analyses

Contact InformationContact Information Contact InformationContact Information

Zephyr Environmental Corporation

10420 Little Patuxent Parkway, Suite 320

Columbia, Maryland 21044

Bill Jones

410-312-7910; bjones@zephyrenv.com

visit us at www.ZephyrEnv.com

and www.HazMatAcademy.com