An Assessment of the American Meteorological Society/U.S. EPA Regulatory Model s (AERMOD) Accuracy: A Case Study

Transcription

1 An Assessment of the American Meteorological Society/U.S. EPA Regulatory Model s (AERMOD) Accuracy: A Case Study Association of Air Pollution Control Agencies (AAPCA) Third Annual Meeting - Raleigh, NC September 17, 2015 Keith Baugues Assistant Commissioner Office of Air Quality Indiana Department of Environmental Management 1

2 Introduction In December of 2010, the Indiana Department of Environmental Management (IDEM) was faced with modeling over 100 sources to establish sulfur dioxide (SO2) limits for the new 1-hour SO2 standard. We contacted Chet Wayland (OAQPS) and asked how accurate is AERMOD. His response was do a study and show us. This presentation and the full report are IDEM s response to that request. 2

3 Duke Energy s Gibson Plant was selected for the following reasons: 1) It is located such that it is not impacted by other nearby SO2 sources. 2) It has Continuous Emission Monitors (CEMs) on each of its stacks so that hourly SO2 emission rates are known. 3) It had four SO2 monitors surrounding the facility. 4) It has a three-level meteorological tower on-site taking numerous meteorological parameters. 3

4 Figure 1 4

5 Plan 1) Model using National Weather Service Data from Evansville (approximately 40 kilometers south of Gibson) and using on-site meteorological data. 2) Predict 1-hour concentrations at the four monitoring sites. 3) Compare predicted and measured SO2 levels. 5

6 Results Based on National Weather Service Data 6

7 Monitored Concentration (ppb) Figure 2 Modeled vs. Monitored SO2 Levels - Mt. Carmel Site (All Data) Modeled Concentrations (ppb) 7 KB s AAPCA Presentation September 17, Office of Air Quality/IDEM (ams)

8 Table 1 Results of Scenario 2 Analyses All Data Mt. Carmel East Coal Road Schrodt Total Range No. Percent No. Percent No. Percent No. Percent No. Percent < , , , , , , , , , , , , Total 8,196 8,344 8,333 8,302 33,175 8 KB s AAPCA Presentation September 17, 2015 Office of Air Quality/IDEM (ams

9 Monitored Concentration (ppb) Figure Modeled vs. Monitored Concentrations - Mt. Carmel Site EVV Met All Data Modeled Concentration (ppb) 9

10 Table 6 Hours Within Selected Ranges Scenario 2 All Data Mt. Carmel East Coal Road Schrodt Range Model Monitor Model Monitor Model Monitor Model Monitor ,822 8,134 8,049 8,298 7,735 8,234 8,153 8, Total 8,196 8,196 8,344 8,344 8,333 8,333 8,302 8,302 Above

11 Monitored Concentrations (ppb) Figure Modeled Concentrations vs. Monitored SO2 Levels Mt. Carmel Site (Non-zero Predictions Only) Modeled Concentrations (ppb) 11

12 Table 7 Results of Scenario 2 Analyses Non-zero Predictions Only Mt. Carmel East Coal Road Schrodt Total Range No. Percent No. Percent No. Percent No. Percent No. Percent < , , , , , , , , , , Total 3,395 3,240 3,469 3,404 13,508 12

13 Table 8 Comparison of Average Modeled/Monitored Ratios vs. Wind Speed Wind Speed Range Mt. Carmel East Coal Road Schrodt 0-1 m/s KB s AAPCA Presentation 06/24-27/2014 Office of Air Quality/IDEM (ams)

14 Table 9 Comparison of Median Modeled/Monitored Ratios vs. Wind Speed Wind Speed Range Mt. Carmel East Coal Road Schrodt 0-1 m/s

15 Table 10 Comparison of Average Modeled to Monitored Ratios vs. Wind Direction WD Range Mt. Carmel East Coal Road Schrodt

16 Comparisons Not in Time When compared in this fashion, the following overall statistics (ratios of modeled to monitored concentrations) are found: Ratio Mt. Carmel East Coal Road Schrodt Total Range Hours Percent Hours Percent Hours Percent Hours Percent Hours Percent < , , , , , , , , Total 3,395 3,240 3,469 3,404 13,508 16

17 Monitored Concentrations (ppb) Figure Modeled vs. Monitored Concentrations - Mt Carmel Site EVV Met Non-zero Predictions Only Modeled Concentrations (ppb) 17

18 Monitored Concentrations (ppb) Figure Modeled vs. Monitored Concentrations - Mt. Carmel Site EVV Met Predictions > 75 ppb Modeled Concentrations (ppb) 18

19 Monitored Concentrations (ppb) Figure Modeled vs. Monitored Concentrations Mt. Carmel Site EVV Met Concentrations > 75 Adjusted for Emission Rate Modeled Concentrations (ppb) 19

20 Results Based on On-site Meteorology 20

21 Monitored Concentrations (ppb) Figure Modeled vs. Monitored SO2 Levels - Mt. Carmel Site (All Data) On-site Meteorology Modeled Concentrations (ppb) KB s AAPCA Presentation September 17, 2015 Office of Air Quality/IDEM (ams) 21

22 Table 13 Results of Scenario 3 Analyses All Data Mt. Carmel East Coal Road Schrodt Total Range No. Percent No. Percent No. Percent No. Percent No. Percent < , , , , , , , , , , Total 8,214 8,360 8,349 8,319 33,242 22

23 Monitored Concentrations (ppb) Figure Modeled vs. Monitored Concentrations - Mt. Carmel Site On-site Met All Data Modeled Concentrations (ppb) 23

24 Table 18 Hours within Selected Ranges Scenario 3 All Data Mt. Carmel East Coal Road Schrodt Range Model Monitor Model Monitor Model Monitor Model Monitor ,791 8,150 8,052 8,314 7,773 8,247 8,146 8, Total 8,214 8,214 8,360 8,360 8,349 8,349 8,319 8,319 Above

25 Monitored Concentrations (ppb) Figure Modeled Concentrations vs. Monitored SO2 Levels Mt. Carmel Site (Non-zero Predictions Only) Modeled Concentrations (ppb) 25

26 Table 19 Results of Scenario 3 Analyses Non-zero Predictions Only Mt. Carmel East Coal Road Schrodt Total Range No. Percent No. Percent No. Percent No. Percent No. Percent < , , , , , , , Total 3,150 2,825 3,213 3,402 12,590 26

27 Table 20 Comparison of Average Modeled/Monitored Ratios vs. Wind Speed Wind Speed Range Mt. Carmel East Coal Road Schrodt 0-1 m/s Some persons would argue that using average values is inappropriate. Because the sample size of some categories may be small, one high ratio can overly impact the average. Table 21 shows the median ratios versus wind speed. The trends seen in the average data appear to be duplicated in the median data. 27

28 Table 21 Comparison of Median Modeled/Monitored Ratios vs. Wind Speed Wind Speed Range Mt. Carmel East Coal Road Schrodt 0-1 m/s

29 Table 22 Comparison of Average Modeled to Monitored Ratios vs. Wind Direction WD Range Mt. Carmel East Coal Road Schrodt

30 Table 24 Outlier Predictions Site Month Day Hour M/S WD Model Monitor Mt. Carmel Mt. Carmel Mt. Carmel Mt. Carmel Mt. Carmel Mt. Carmel Mt. Carmel Mt. Carmel Mt. Carmel Mt. Carmel Mt. Carmel East East East East East East East East East East East East East East East East East East East East East East Coal Road Coal Road Coal Road Coal Road Coal Road Coal Road Coal Road Coal Road Schrodt KB s AAPCA Presentation September 17, 2015 Office of Air Quality/IDEM (ams) 30

31 8 Figure 38 Modeled vs. Monitored Concentrations - Mt. Carmel Site On-site Met Non-zero Predictions Only Modeled Concentrations (ppb) 31

32 Comparisons Not in Time Ratio Mt. Carmel East Coal Road Schrodt Total Range Hours Percent Hours Percent Hours Percent Hours Percent Hours Percent < , , , , , , , Total 3,150 2,825 3,213 3,402 12,590 32

33 Monitored Concentrations (ppb) Figure Modeled vs. Monitored Concentrations On-site Data Predicted Values Greater Than 75 ppb - Mt. Carmel Site Modeled Concentration (ppb) 33

34 Monitored Concentrations (ppb) Figure Modeled vs. Monitored Concentrations - Mt. Carmel Site On-site Met - Concentration > 75 adjusted for emission rate Modeled Concentrations (ppb) 34 KB s AAPCA Presentation September 17, 2015 Office of Air Quality/IDEM (ams)

35 Overall Results Measured Hours Above 75 ppb 11 Predicted with NWS Data 450 Predicted with On-site Data

36 For Sulfur Dioxide (SO2) Prediction >75 ppb NWS Data 0.7% within a factor of two On-site Data 0% within a factor of two 51.0% over predicted % over predicted % over predicted % over predicted % over predicted

37 Comparison Not in Time Even using the U.S. EPA s methodology. AERMOD does not compare within a factor of two for predicted values of 75 ppb or greater. 37

38 Recommendations 1) Evaluate low wind speed performance of AERMOD. 2) Adjust concentrations for time to get from stack to monitor. 3) Consider use of a PUFF model. 38

39 Full report can be found at: 39

40 Contact Information Keith Baugues Assistant Commissioner Office of Air Quality (317)