Air Quality Impacts Analysis

1. Air Quality Impacts Analysis Presented to: American Public Power Association APPA New Generation Meeting: Anticipating new permitting issues, IGCC Technology Options, Atmospheric Modeling, and Anticipating the Public’s Reaction Presented by: William B. JonesProject Manager Zephyr Environmental Corporation June 28, 2006

2. Outline of Presentation What is modeling and why do it? Types of models Typical modelinganalyses Recent modeling activity

3. What is Modeling? Running computer programs to predict air pollutant levels Dates back to 1930’s, looked at smoke from chimneys Different applications Complex terrain Long-range transport Photochemical

4. Why do Modeling? Relative to monitoring, it is Cheaper Faster More extensive Useful regulatory tool Developing control strategies Permitting of new/modified industrial facilities

5. Types of Models Screening SCREEN3 AERSCREEN (any day now) Refined ISC3 AERMOD CALPUFF

6. Features of Screening Models Quick and dirty Required inputs are limited Meteorological data Source data Terrain data Cursory structure downwash analysis Conservative (high) results

7. Features of Refined Models Required inputs can be substantial Preprocessed meteorological data Preprocessed terrain data Detailed structure downwash analysis

8. AERMOD Will become EPA’s official preferred model for most near-field industrial applications on December 9, 2006 Improvements over ISC3 Dispersion within Planetary Boundary Layer Characterization of meteorological conditions Terrain depiction

9. AERMOD is a steady-state model Straight line trajectory for plume Spatially constant meteorological conditions No “memory” of previous hour’s emissions

10. When should you use AERMOD? Most industrial applications When your situation involves Pollutant concentrations within tens of km of source Flat or complex terrain (but maybe not “complicated” terrain) Most NAAQS/PSD Increment analyses

11. Issues with AERMOD The input/output files may look the same as ISC… But it is much more labor-intensive than ISC AERMET AERMAP Computer runtimescan measure in days

12. CALPUFF Non-Steady-State model (Puff model)

13. CALPUFF ISC vs. CALPUFF animation here

14. CALPUFF Non-Steady-State model (Puff model) Source input requirements are more detailed than AERMOD Terrain input requirements are more detailed than AERMOD Meteorological data input requirements are quite substantial MM5 can be run for anywhere in the world

15. When should you use CALPUFF? Most long-range transport applications (i.e., greater than 50 km) Class I impact/visibility assessments Nearfield analyses involving significant terrain variations

16. Typical Modeling Analyses Class II Significance NAAQS PSD Increment Class I

17. Class II Analyses:Significance Modeling Consider only project in question (emissions increases and decreases) Compare against U.S. EPA significance levels If below, analysis is finished If above, proceed with more comprehensive NAAQS/PSD Increment analysis

18. Class II Analyses:NAAQS Modeling Comprehensive assessment of overall air quality Include all sources at your facility Include offsite sources Include representative ambient background pollutant concentrations

19. Class II Analyses:PSD Increment Modeling Include PSD Increment consuming and expanding sources at your facility Include PSD Increment consuming and expanding offsite sources No ambient background pollutant concentrations are included

20. Class I Areas

21. Areas within 300 km of Class I Area

22. Class I Analysis Class I PSD Increments Air Quality Related Values (AQRV’s) Visibility Acid deposition (sulfate and nitrate)

23. History of Class I Analyses 1993: Interagency Workgroup on Air Quality Modeling (IWAQM) formed, recommended CALPUFF 2000: Federal Land Manager’s Air Quality Related Values Workgroup (FLAG) was written to develop a more consistent approach for the FLMs to evaluate air pollution effects on their resources

24. History of Class I Analyses History has shown it’s easier to define what is not a problem vs. what is a problem Each case is different—for each facility, and each FLM

25. Current (typical) approach to assessment of visibility impairment Run CALPUFF with 3 years of met data Calculate 24-hr bext (visibility index) Compare bext against natural conditions If < 5%, FLM doesn’t object If between 5% and 10%, FLM may object If > 10%, FLM likely to object

26. But FLAG guidancemay be changing! John Vimont (NPS) spoke at Guideline on Air Quality Models Conference in Denver this past April Outlined proposed changes to visibility analysis methodology Different way of accounting for relative humidity Different way of comparing bext (98th percentile, or 8th high per year)

27. Examples of analyses required ofrecent coal-fired facilities Plum Point Energy Station: Osceola, Arkansas Comanche Generating Station: Pueblo, Colorado Duke Energy: Cliffside, NC Sandy Creek: McClennan County, TX City Public Service: San Antonio, TX

28. Plum Point Energy Station, Osceola, ARPermit issued August 20, 2003

29. Plum Point Energy Station, Osceola, ARClass I Visibility Analysis Ran CALPUFF, initially found light extinctions > 5% Developed water content adjustment to modify natural light extinction calculation • Re-ran CALPUFF, did not find light extinctions > 5%

30. Comanche Generating Station, Pueblo, COPermit issued July 5, 2005

31. Intermission Quick Class I Area Tour

32. Weminuche Wilderness, 1999

33. Weminuche Wilderness, 1999(Continental Divide)

34. Weminuche Wilderness, 1999(Neighbor near campsite)

35. Great Sand Dunes NP, 2002“The Summit”

36. Black Canyon of the Gunnison River NP(2002)

37. Comanche Generating Station, Pueblo, COClass I Analyses Performed Visibility Found change in light extinction to be less than 5% at all Class I areas, so acceptable Acid Deposition Sulfur deposition less than 0.005 kg/ha/yr (Deposition Analysis Threshold, or DAT) (western US value), so acceptable Class I PSD Increment PM10 impacts less than Class I significance level of 0.3 ug/m3

38. Comanche Generating Station, Pueblo, COAdditional Analysis: Acid Neutralizing Change U.S. Forest Service has established threshold of concern for acid deposition in Class I areas Considered three high altitude lakes in Class II areas Change in ANC resulting from PM10 and H2SO4 emissions evaluated Percent change found to be below threshold of 10%

39. Duke Energy, Cliffside, NCPermit Application submitted December 16, 2005

40. Duke Energy, Cliffside, NCPermit Application submitted December 16, 2005 Visibility NPS required speciation of PM10 emissions by light scattering properties (soils, elemental carbon, and organic aerosols) Acid Deposition Used DAT of 0.01 kg/ha/yr (eastern US value) Class I PSD Increment PM10 and NOx impacts less than Class I Significance Levels

41. Sandy Creek, McClennan County, TXUpdated application submitted March 10, 2005 Closest Class I area is Wichita Mountains Wilderness (Oklahoma), ~ 370 km away Did not have to examine any impacts on Class I areas

42. City Public Service, San Antonio, TXPermit issued January 2006 Closest Class I area is Big Bend National Park (Texas), ~ 440 km away TCEQ did not require any Class I analysis CPS assessed visibility and acid deposition at Big Bend and six other Class I areas (out to 870 km) Results Light extinction found to be < 5% at all Class I areas Sulfur and Nitrogen deposition found to be < DAT at all Class I areas

43. Summary Model selected based on Type of analysis being conducted Characteristics of region being modeled Class II (NAAQS and PSD Increment) analyses will typically use AERMOD More complicated than ISC was Class I analyses will typically use CALPUFF Reach of FLM is increasing Requirements of analysis are very fluid

44. Useful Modeling Links EPA’s SCRAM Website: www.epa.gov/scram001 IWAQM: www.epa.gov/scram001/7thconf/calpuff/phase2.pdf FLAG: www2.nature.nps.gov/air/Permits/flag/index.cfm CALPUFF:src.com/calpuff/calpuff1.htm PM2.5:www.epa.gov/ttn/caaa/t1/memoranda/pm25.pdf (John Seitz (OAQPS) 10/23/97 memo on using PM10 as surrogate for PM2.5 in PSD analyses)

45. Hopefully you’ve found this a “model” presentation Bill Jones 410.312.7910 bjones@zephyrenv.com