Air Dispersion Modeling Guidelines for Arizona Air Quality Permits PREPARED BY: AIR QUALITY PERMIT SECTION AIR QUALITY DIVISION ARIZONA DEPARTMENT OF ENVIRONMENTAL QUALITY September 23, 2013 TABLE OF CONTENTS 1 INTRODUCTION.......................................................................................................... 1 1.1 Overview of Regulatory Modeling ........................................................................... 2 1.2 Purpose of an Air Quality Modeling Analysis .......................................................... 2 1.3 Authority for Modeling ............................................................................................. 3 1.4 Acceptable Models.................................................................................................... 3 1.5 Overview of Modeling Protocols and Checklists ..................................................... 4 1.6 Overview of Modeling Reports ................................................................................ 5 2 LEVELS OF MODELING ANALYSIS SOPHISTICATION .................................. 5 2.1 Screening Modeling .................................................................................................. 6 2.2 Refined Modeling ..................................................................................................... 7 3 MODELING ANALYSIS FEATURES ..................................................................... 10 3.1 Modeling Worst-Case Scenarios............................................................................. 10 3.1.1 Emissions Profiles ............................................................................................ 10 3.1.2 Load Analyses .................................................................................................. 11 3.1.3 Emission Caps .................................................................................................. 12 3.2 Modeling Emissions Inventory ............................................................................... 12 3.3 Types of Sources ..................................................................................................... 13 3.3.1 Point Sources ................................................................................................... 13 3.3.2 Volume Sources ............................................................................................... 14 3.3.3 Area Sources .................................................................................................... 15 3.3.4 Line Sources ..................................................................................................... 16 3.3.5 Road Emission Sources .................................................................................... 16 3.3.6 Flares ................................................................................................................ 17 3.3.7 Open Pit Sources .............................................................................................. 19 3.3.8 Pseudo Point / Non-Standard Point Source ..................................................... 19 3.3.9 Emission Point Collocation .............................................................................. 20 3.4 Ambient Air Boundary ........................................................................................... 20 3.4.1 Definition of General Public ............................................................................ 21 3.4.2 Public Access ................................................................................................... 21 3.4.3 Property without an Effective Fence or Other Physical Barriers ..................... 22 3.4.4 Leased Property ............................................................................................... 22 3.5 Modeling Coordinate Systems ................................................................................ 22 3.6 Receptor Networks.................................................................................................. 23 3.7 Rural/Urban Classification ...................................................................................... 24 3.8 Meteorological Data................................................................................................ 26 3.8.1 Meteorological Data Description and Rationale .............................................. 28 3.8.2 Meteorological Data Processing ...................................................................... 29 3.9 Building Downwash and GEP Stack Height .......................................................... 30 3.10 Background Concentrations .................................................................................. 31 3.11 Modeled Design Concentrations ........................................................................... 34 4 ADEQ PERMITTING JURISDICTION AND CLASSIFICATIONS ................... 36 4.1 Air Quality Permitting Jurisdiction in Arizona ....................................................... 36 4.2 Main ADEQ Permit Classifications ........................................................................ 37 5 MODELING REQUIREMENTS FOR NON-PSD SOURCES ............................... 40 i 6 MODELING REQUIREMENTS FOR PSD SOURCES ......................................... 40 6.1 NAAQS Analyses for Pollutants That Do Not Trigger PSD .................................. 40 6.2 Overview of PSD Modeling Procedures ................................................................. 41 6.2.1 NAAQS Modeling Inventory ........................................................................... 42 6.2.2 Increment Modeling Inventory ........................................................................ 43 6.2.3 Additional Impact Analyses ............................................................................. 46 6.2.4 Class I Area Impact Analyses .......................................................................... 47 7 SPECIAL MODELING ISSUES ................................................................................ 49 7.1 Modeling for 1-hour NO2........................................................................................ 49 7.1.1 Emission Rate .................................................................................................. 50 7.1.2 Significant Impact Level .................................................................................. 50 7.1.3 Three-tiered Approach for 1-hour NO2 Modeling ........................................... 51 7.1.4 Determining Background Concentrations ........................................................ 51 7.1.5 In-Stack NO2/NOX Ratio .................................................................................. 54 7.1.6 Treatment of Intermittent Sources ................................................................... 54 7.1.7 Modeling Demonstration with the 1-hour NO2 NAAQS ................................. 55 7.2 Modeling for 1-hour SO2 ........................................................................................ 57 7.2.1 Emission Rate .................................................................................................. 57 7.2.2 Significant Impact Level .................................................................................. 58 7.2.3 Determining Background Concentrations ........................................................ 58 7.2.4 Treatment of Intermittent Sources ................................................................... 59 7.2.5 Modeling Demonstration with the 1-hour SO2 NAAQS ................................. 59 7.3 Modeling for PM2.5 ................................................................................................. 60 7.3.1 Significant Monitoring Concentration and Significant Impact Levels ............ 61 7.3.2 Modeling Primary PM2.5 and Secondarily Formed PM2.5 ................................ 62 7.3.3 Emission Inventories ........................................................................................ 64 7.3.4 Background Concentration .............................................................................. 65 7.3.5 Comparison to the SIL ..................................................................................... 66 7.3.6 Modeling Demonstration with the PM2.5 NAAQS .......................................... 66 7.3.7 Modeling demonstration with the PM2.5 Increments ....................................... 67 7.4 Additional Considerations for Modeling Particulate Matter (PM) ......................... 68 7.4.1 Paired-Sums Approach .................................................................................... 68 7.4.2 Particle Deposition ........................................................................................... 69 7.5 Modeling for Lead (Pb) .......................................................................................... 69 7.6 Modeling for Open Burning/Open Detonation Sources ......................................... 70 7.6.1 Modeling OB/OD Operations with OBODM .................................................. 70 7.6.2 Modeling OB/OD Operations with AERMOD ................................................ 70 7.7 Modeling for Buoyant Line Sources ....................................................................... 71 7.8 Modeling for HAPS Sources - Learning Site Policy .............................................. 71 8 REFERENCES .......................................................................................................... 72 APPENDIX A: MODELING PROTOCOL ELEMENTS