www.all4inc.com | Philadelphia | Atlanta | Houston | Washington DC

SO2 Data Requirements Rule Modeling Strategies

Mark Wenclawiak, CCM | mwenclawiak@all4inc.com | 678.460.0324

Amanda Essner | aessner@all4inc.com | 610.933.5246 x 129

January 13, 2016

Presented to the 96th Annual Meeting of the American Meteorological Society by All4 Inc.

2 Your environmental compliance is clearly our business.

Agenda

Driver for Air Dispersion Modeling Projects

• SO2 Data Requirements Rule (DRR)

• Characterize maximum 1-hour concentrations and attainment status with NAAQS through modeling or monitoring

2 Case Studies

• Model refinements for over-predictions during low wind stable conditions

• Flat terrain vs. complex terrain

• Effect of low wind options in different topography

• Options for compliance strategy

National Ambient Air Quality Standards Update

SO2 NAAQS and the DRR

4 Your environmental compliance is clearly our business.

August 21, 2015 (40 CFR Part 51, Subpart BB)

Applies to facilities that:

1. Emitted 2,000 tons per year (tpy) of actual SO2

emissions during most recent calendar year

2. Not located in a nonattainment area

3. “Hot spots” = know your neighbors

Affected facilities required to conduct modeling or install ambient monitor locations

U.S. EPA Technical Assistance Documents (TADs)

SO2 NAAQS and the DRR

Air Dispersion Modeling for SO2 DRR

6 Your environmental compliance is clearly our business.

AERMOD - U.S. EPA air dispersion model

Differences from modeling for permitting

• Representative meteorological data for most recent 3 years

• Actual emissions rates from last 3 years (hourly if possible) with actual stack heights

• Receptors placed only where an ambient monitor could actually be located

Air Dispersion Modeling

7 Your environmental compliance is clearly our business.

DRR Receptor Grid

8 Your environmental compliance is clearly our business.

Non-default/beta options available

• Agency approval

• Proposed changes to guidelines

ADJ_U* (friction velocity)

• AERMET – meteorological data preprocessor

• Adjusts u*, which is used to calculate mixing height and initial horizontal and vertical dispersion

Model Refinements

9 Your environmental compliance is clearly our business.

LowWind• Adjusts minimum value of sigma-v, the horizontal turbulence

variable, and changes use of meander algorithm

• LowWind1

Increases the minimum value of sigma-v from the default of 0.2 to 0.5 m/s, and also eliminates the horizontal meander algorithm

• LowWind2

Increases the minimum value of sigma-v from 0.2 to 0.3 m/s, and retains the horizontal meander algorithm with an upper limit of 0.95

• LowWind3

Increases the minimum value of sigma-v from 0.2 to 0.3 m/s, and uses the FASTALL approach to replicate the centerline concentration accounting for horizontal meander, but utilizes an effective sigma-y and eliminates upwind dispersion

Model Refinements

SO2 DRR Case Studies

11 Your environmental compliance is clearly our business.

Facility A:

• Chemical plant

• Relatively flat terrain in rural setting

Facility B:

• Cement plant

• Complex terrain in rural setting

Background

12 Your environmental compliance is clearly our business.

Run AERMOD for each facility, using:

• The same meteorological dataset (Control Case)

• The LOWWIND3 option

• The ADJ_U* option on the meteorological dataset

• Both the LOWWIND3 and ADJ_U* options

Compare ground level concentrations

Process

13 Your environmental compliance is clearly our business.

Facility A – Flat Terrain

14 Your environmental compliance is clearly our business.

Control Case – Facility A

4th High - 387 µg/m325 µg/m3

50 µg/m3

75 µg/m3

100 µg/m3

196 µg/m3

15 Your environmental compliance is clearly our business.

LOWWIND3 – Facility A

4th High - 383 µg/m3

(-1%)

25 µg/m3

50 µg/m3

75 µg/m3

100 µg/m3

196 µg/m3

16 Your environmental compliance is clearly our business.

ADJ_U* - Facility A

4th High - 359 µg/m3

(-7%)

25 µg/m3

50 µg/m3

75 µg/m3

100 µg/m3

196 µg/m3

17 Your environmental compliance is clearly our business.

LOWWIND3 & ADJ_U* - Facility A

4th High - 359 µg/m3

(-7%)

25 µg/m3

50 µg/m3

75 µg/m3

100 µg/m3

196 µg/m3

18 Your environmental compliance is clearly our business.

Facility B – Complex Terrain

Mountains

Mountains

19 Your environmental compliance is clearly our business.

Control Case – Facility B

4th High – 2,464 µg/m325 µg/m3

50 µg/m3

75 µg/m3

100 µg/m3

196 µg/m3

20 Your environmental compliance is clearly our business.

LOWWIND3 – Facility B

4th High – 1,681.0 µg/m3

(-32%)

25 µg/m3

50 µg/m3

75 µg/m3

100 µg/m3

196 µg/m3

21 Your environmental compliance is clearly our business.

ADJ_U* - Facility B

4th High – 982 µg/m3

(-60%)

25 µg/m3

50 µg/m3

75 µg/m3

100 µg/m3

196 µg/m3

22 Your environmental compliance is clearly our business.

LOWWIND3 & ADJ_U* - Facility B

4th High – 862 µg/m3

(-65%)

25 µg/m3

50 µg/m3

75 µg/m3

100 µg/m3

196 µg/m3

23 Your environmental compliance is clearly our business.

Flat Terrain

• LOWWIND3 decreases areal extent of higher concentrations; ADJ_U* reduces the maximum concentration the greatest extent

Complex Terrain

• Marked decrease of maximum concentration from both options, with ADJ_U* having the most impact

Utilize options to identify more realistic ground level concentrations and location of ambient monitor

• Cluster sources

Conclusions & Compliance Approach

www.all4inc.com | Philadelphia | Atlanta | Houston | Washington DC

Questions & Open Discussions

Mark Wenclawiak, CCM | mwenclawiak@all4inc.com | 678.460.0324

Amanda Essner | aessner@all4inc.com | 610.933.5246 x 129

January 13, 2016