United States Office of Air Quality EPA-454/R-98-019 Environmental Protection Planning and Standards December 1998 Agency Research Triangle Park, NC 27711 AIR EPA INTERAGENCY WORKGROUP ON AIR QUALITY MODELING (IWAQM) PHASE 2 SUMMARY REPORT AND RECOMMENDATIONS FOR MODELING LONG RANGE TRANSPORT IMPACTS Air Q of ua ice li ff ty O Clean Air Pla s nn ard in nd g and Sta EPA-454/R-98-019 INTERAGENCY WORKGROUP ON AIR QUALITY MODELING (IWAQM) PHASE 2 SUMMARY REPORT AND RECOMMENDATIONS FOR MODELING LONG-RANGE TRANSPORT IMPACTS U.S. Environmental Protection Agency Air Quality Modeling Group (MD-14) Research Triangle Park, North Carolina 27711 National Park Service Air Resources Division Denver, Colorado 80225 USDA Forest Service Air Program Fort Collins, Colorado 80526 U.S. Fish and Wildlife Service Air Quality Branch Denver, Colorado 80225 December, 1998 NOTICE The information in this document has been reviewed in its entirety by the U.S. Environmental Protection Agency (EPA), and approved for publication as an EPA document. Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official EPA approval, endorsement, or recommendation. i PREFACE The Interagency Workgroup on Air Quality Modeling (IWAQM) was formed to provide a focus for development of technically sound recommendations regarding assessment of air pollutant source impacts on Federal Class I and Wilderness areas. Meetings were held with personnel from interested Federal agencies, viz. the Environmental Protection Agency, the U.S. Forest Service, the National Park Service, and the U.S. Fish and Wildlife Service. The purpose of these meetings was to review respective modeling programs, to develop an organizational framework, and to formulate reasonable objectives and plans that could be presented to management for support and commitment. The members prepared a memorandum of understanding (MOU) that incorporated the goals and objectives of the workgroup and obtained signatures of management officials in each participating agency. Even though no States are signatories, they did participate in IWAQM functions. This document is being released as a publication of the Environmental Protection Agency (EPA) in response to a request from the members of IWAQM. Members of the workgroup include representatives from the Environmental Protection Agency, the U.S. Forest Service, the National Park Service, and the U.S. Fish and Wildlife Service. The document includes IWAQM’s recommendations for modeling methods that might be used to estimate Prevention of Significant Deterioration air quality impacts and National Ambient Air Quality Standards (NAAQS) air quality impacts associated with long-range transport of pollutant emissions to Class I and Wilderness areas . The IWAQM recommends that the CALPUFF Lagrangian puff dispersion modeling system be used for characterization of the transport and dispersion. The recommendations of IWAQM contained in this document is considered technical guidance tailored for use in assessing air quality impacts associated with prevention of significant deterioration. ii ACKNOWLEDGMENTS The members of IWAQM acknowledge the special efforts by Mark Scruggs, John Notar and John Vimont of the National Park Service; Alan Cimorelli of the U.S. Environmental Protection Agency (EPA); John Irwin of the National Oceanic Atmospheric Administration (NOAA) Air Resources Laboratory; Richard Fisher and Bob Bachman of the U.S. Forest Service; Elwyn Rolofson of the U.S. Fish and Wildlife Service; Patrick Hanrahan of the State of Oregon, Department of Environmental Quality; and Kenneth McBee of the Commonwealth of Virginia, Department of Air Pollution Control for their input and suggestions on assembling this document and their subsequent review. In compiling the reviews of investigations completed that involved in some manner the CALMET/CALPUFF modeling system, various authors graciously provided access to their results and data, and have permitted IWAQM to cite directly from their reports and papers. The IWAQM gives special recognition and thanks to: Andrew Gray of SAI, Inc, John Sherwell of the Maryland Department of Natural Resources, O. Russ Bullock, Jr., Frank Binkowski, and Robin Dennis of the NOAA Air Resources Laboratory, David Strimaitis and Joesph Scire of Earth Tech Inc., Jim Paumier of Pacific Environmental Services Inc., Peter Eckhoff and C. Thomas Coulter of the EPA Office of Air Quality Planning and Standards. iii TABLE OF CONTENTS 1.0 INTRODUCTION .................................................. 1 2.0 MODELING RECOMMENDATIONS ................................... 6 2.1 Screening Analysis ........................................... 6 2.2 Refined Analysis ............................................. 9 2.2.1 Meteorology.......................................... 9 2.2.2 Chemistry........................................... 14 2.2.3 Dispersion .......................................... 15 2.3 Practicalities................................................ 16 2.3.1 Screening procedure uncertaintites ....................... 17 2.3.2 Refined modeling uncertainties .......................... 17 2.3.3 Secondary pollutant uncertainties ........................ 18 2.2.4 Technical oversight and review .......................... 19 3.0 TRANSFORMATIONS, VISIBILITY, AND DEPOSITION................... 20 3.1 Chemical Transformations..................................... 20 3.2 Visibility Analysis ............................................ 22 3.3 Deposition Calculations ...................................... 30 3.4 Assessing Air Quality Related Values - Background ................. 31 4.0 STUDIES AND FINDINGS ......................................... 33 4.1 MESOPUFF II Implementation Assessment ....................... 33 4.2 Revisions to CALMET and CALPUFF ............................ 44 4.3 Trajectory Comparisons....................................... 48 4.4 Constructing FDDA-MM Data Sets Assessment.................... 54 4.5 Regional Approach .......................................... 56 4.5.1 An Approach to Implementing a Class I Area Assessments . 57 4.6 Comparisons of CALPUFF with Tracer Field Data .................. 58 4.6.1 1975 Savannah River Laboratory Tracer Study .............. 58 4.6.2 1977 Idaho Falls Tracer Study ........................... 62 4.6.3 1980 Great Plains Tracer Study .......................... 67 4.6.4 1992 Project MOHAVE Tracer Study ...................... 73 4.7 Comparisons of CALPUFF With ISC3 ........................... 76 4.8 CALPUFF SCREEN.......................................... 83 4.8.1 Screening methodology ................................ 83 4.8.2 Year to year variability ................................. 87 4.8.3 SO2 concentrations ................................... 88 = 4.8.4 SO4 concentrations................................... 90 4.8.5 SO2 deposition ....................................... 91 = 4.8.6 SO4 deposition ....................................... 93 4.8.7 Old screen versus new screen estimates ................... 94 4.8.8 Findings and conclusions ............................... 96 iv 4.9 CALMET/CALPUFF Enhancements ............................. 97 4.9.1 Use of FDDA-MM data with CALMET ..................... 97 4.9.2 Use of CALMET to Develop Wind Fields................... 99 4.9.3 Kincaid SF62 and Lovett SO Comparisons ................. 104 5.0 CONCLUSIONS................................................. 111 6.0 REFERENCES ................................................. 113 APPENDIX A. CALMET RECOMMENDATIONS .......................... A-1 APPENDIX B. CALPUFF RECOMMENDATIONS .......................... B-1 APPENDIX C. COMPACT DISK DATA RESOURCES ...................... C-1 APPENDIX D. SIXTH MODELING CONFERENCE ........................ D-1 v LIST OF FIGURES Figure 1. Hygroscopic relative humidity adjustment factor f(RH)................ 27 Figure 2. Display of MESOPUFF II computational domain .................... 35 Figure 3. Display of ring source analysis computational domain ................ 40 Figure 4. Highest monthly concentrations................................. 42 Figure 5. 54-km and 18-km MM4 domains ................................ 46 Figure 6. Trajectories at 10 m on the 54 km grid............................ 49 Figure 7. Summary of CAPTEX trajectory results........................... 53 Figure 8. Savannah River Laboratory field experiment site .................... 59 Figure 9. Savannah River Laboratory December 10, 1976 results .............. 61 Figure 10. Idaho Falls field experiment site ............................... 63 Figure 11. Summary of Idaho Falls April 19, 1977 results ..................... 66 Figure 12. Great Plains field experiment site............................... 68 Figure 13. Summary of Great Plains 100 and 600 km July 8, 1980 results ........ 71 Figure 14. Summary of Great Plains 100 km July 11, 1980 results .............. 72 Figure 15. Project MOHAVE experimental site ............................. 74 Figure 16. Project MOHAVE results for Las Vegas Wash site ................. 75 Figure 17. Summary for Hour 62 of a CALPUFF simulation................... 79 Figure 18. CALPUFF and ISC comparisons for Medford, Oregon............... 81 Figure 19. Annual average CALPUFF and ISC comparisons .................. 82 Figure 20. Comparison of screening estimates of ambient sulfate concentrations . 95 Figure 21. Comparison of screening estimates of total sulfur deposition ......... 96 Figure 22. CALMET computational domain ................................ 98 Figure