1-Hour SO2 NAAQSImplementation Modeling            Dan P. Dix23rd Virginia Environmental Symposium              April 11, ...
Agenda       Summary of NAAQS       NAAQS Implementation Updates       Dispersion Modeling Basics       NAAQS Modeling...
About ALL4       Environmental consulting firm       Founded 2002 – currently 30+ employees       Offices in Kimberton,...
National Ambient Air Quality Standards     (NAAQS)
NAAQS Background       “Backdrop” of the Clean Air Act       States design their SIPs and enforce and        implement t...
NAAQS Summary                  Averaging                             Historic    Revised NAAQS    Pollutant               ...
Attainment/Nonattainment Designations       U.S. EPA philosophy on the SO2 NAAQS        implementation process:        • ...
NAAQSImplementation   Updates
SO2 NAAQS Implementation       NAAQS Implementation Schedule:         • June 2011: Initial state nonattainment           ...
Implementation Update        Draft guidance for states to evaluate         designations using AERMOD was released on     ...
SO2 Maintenance SIP Submittals        U.S. EPA: Revising PSD/NNSR programs to include         new NAAQS is not sufficient...
SO2 NAAQS Implementation        State SIPs will be based on AERMOD dispersion         modeling for the following individu...
SO2 NAAQS Implementation        Legal challenges ongoing:          • Science behind NAAQS levels          • Approach of u...
SO2 NAAQS Implementation        What are other States doing?          • Maine - >100TPY Actual, Protocols due June 30, 20...
Dispersion Modeling Basics and Inputs
AERMOD Process      Hourly Wind Speed     Hourly Wind Direction       Hourly Ambient         Temperature      Land Use Pat...
Air Quality Modeling Steps     1. Emission Inventory     2. Meteorological Data        (AERMET/AERSURFACE)     3. Terrain ...
Emission Inventories        Short-term (1-hour) emission rates        Potential to be used as permit limits        Inte...
Meteorological Data19
Meteorological Data20
Meteorological Data        5 years of National Weather Service data        Minimum of 1 year of onsite data        Surf...
Terrain Data        “Ambient Air”           “that portion of the            atmosphere, external to            buildings...
Building Downwash23
Building Downwash24
NAAQS Modeling Demonstration   Approach
Full NAAQS Evaluation        Includes facility and other local facilities        Any modeled emission rates should be   ...
Local Sources        NAAQS evaluation must include sources         that result in a “significant concentration         gr...
NAAQS Modeling Strategy        Start with an evaluation of each individual         emission source        Each source wi...
NAAQS Modeling Strategy        Big picture factors that will drive ambient         concentrations for individual sources:...
Hypothetical Modeling Examples        Modeling of a hypothetical facility with the         following SO2 emission sources...
Hypothetical Facility Terrain31
“Process” SO2 Source        SO2 Emission Rate: 240 lb/hr (CEMS)        Stack Height: 290 feet        Stack Diameter: 16...
Process SO2 Source Impacts33
Process SO2 Source Impacts        Highest impacts in complex terrain far from         facility        Wind speed doesn’t...
Combustion SO2 Source        SO2 Emission Rate: 20 lb/hr (AP-42)        Stack Height: 60 feet        Stack Diameter: 2 ...
Combustion SO2 Source Impacts36
Combustion SO2 Source Impacts        Elevated concentrations are closer to the         facility        Building downwash...
Engine SO2 Source        SO2 Emission Rate: 3 lb/hr (Vendor)        Stack Height: 10 feet        Stack Diameter: 1.3 fe...
Engine SO2 Source Impacts39
Engine SO2 Source Impacts        Elevated ambient concentrations at the         facility fenceline for two reasons:      ...
Modeling Refinements        “Process” SO2 Emission Source:          • Stack height increase is technically and           ...
Process SO2 Source Impacts (Before)42
Process SO2 Source Impacts (After)43
Modeling Refinements        Combustion SO2 Emission Source:         • Stack height increase is technically and           ...
Combustion SO2 Source Impacts (Before)45
Combustion SO2 Source Impacts (After)46
Modeling Refinements        Engine SO2 Emission Source:         • Simplest fix is to change the stack           discharge...
Engine SO2 Source Impacts (Before)48
Engine SO2 Source Impacts (After)49
Cumulative Concentrations        The facility must cumulatively comply with         the NAAQS        Addressing each ind...
Modeling Strategies        Emissions Strategies         •   Actual Distribution of Emissions         •   Evaluate adequac...
Modeling Strategies        Stack/Exhaust Strategies:         • Combined source exhausts         • Co-located exhaust poin...
Modeling Strategies        Temporal pairing approach        Plume transport time        Surrounding surface characteris...
Modeling Strategies        Use of PTE emissions and AERMOD can         over estimate concentrations        Know issues w...
Ambient SO2 Monitoring
Ambient SO2 Monitoring        What’s involved in conducting an ambient         SO2 Monitoring program?         • Who shou...
Ambient SO2 Monitoring        Who Should Consider?         • Facilities that have conducted modeling with           unfav...
Ambient SO2 Monitoring Equipment        Thermo 43i – Pulsed Fluorescence SO2         Analyzer        Thermo 146i – Multi...
Ambient SO2 Monitoring59
Ambient SO2 Monitoring        How do you decide where to site an         ambient SO2 monitor?          • Typically sighte...
Ambient SO2 Monitoring Pros        Pros         • Collection of monitoring data below the SO2           NAAQS.         • ...
Ambient SO2 Monitoring Cons        Cons         • Collection of monitoring data above the SO2           NAAQS.         • ...
Ambient SO2 Monitoring        Engineering          • $8K – $15K        Equipment Cost          • $75K – $100K        In...
Final Thoughts    States developing their modeling plans now    States will reach out to request information and/or mode...
Questions?         Dan Dix        ddix@all4inc.com       (610) 933-5246 x18      2393 Kimberton Road           PO Box 299 ...
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1-Hour SO2 NAAQS Implementation Modeling

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ALL4's Dan Dix presented at the 23rd Virginia Environmental Symposium about 1-Hour SO2 Implementation Modeling. Dan's presentation consisted of a summary of the NAAQS, an update on NAAQS implementation, NAAQS modeling demonstration approach, and a summary of ambient SO2 monitoring.

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  • Meteorologists – Affects everybody We are concerned you should concerned
  • Primary Secondary Column
  • Distinction between project requirment
  • State conducting modeling not modeling strategies.Why you should consider completing yourselves.SIP will include requirements and to change SIP requirement is very difficult. Not like change and TV permit limit.Deadline can slip but then Enviro Groups get involved.
  • States that are pushing back.
  • If States SIP fail to satisfy the SIP then EPA will likely implement a FIP
  • State doesn’t have these.
  • Limits on operating hours.
  • Receptor Spacing
  • Local Source Information. First strategy cut without local sources.
  • Figure out strategy. Maybe blinded by doing everything together.
  • Include – Top
  • NO PTE on an hourly basis. SIP Limit 500 ppm not realistic.
  • SODAR - Meteorological data
  • Similar. State does not complete this
  • Transition between Modeling and Monitoring.
  • Power, Secure Area
  • in preparing and obtaining agency approval for monitoring plan, installation, processing the data and interpreting the results.
  • Engineering includes sitting, plan development, regulatory correspondence, procurement of equipment States not setting up monitors.
  • Strategy!!!!!Timing!!
  • 1-Hour SO2 NAAQS Implementation Modeling

    1. 1. 1-Hour SO2 NAAQSImplementation Modeling Dan P. Dix23rd Virginia Environmental Symposium April 11, 2012
    2. 2. Agenda  Summary of NAAQS  NAAQS Implementation Updates  Dispersion Modeling Basics  NAAQS Modeling Demonstration Approach  Ambient SO2 Monitoring2
    3. 3. About ALL4  Environmental consulting firm  Founded 2002 – currently 30+ employees  Offices in Kimberton, PA and Columbus, GA  Specialize in air quality consulting: • Complex air permitting and strategy development • Air dispersion modeling • Ambient air quality monitoring  Dispersion modeling as a company-wide initiative  www.all4inc.com3
    4. 4. National Ambient Air Quality Standards (NAAQS)
    5. 5. NAAQS Background  “Backdrop” of the Clean Air Act  States design their SIPs and enforce and implement their regulations to meet the NAAQS  Air quality construction permit programs are designed around NAAQS compliance • PSD: Maintaining NAAQS attainment • NNSR: Getting into NAAQS attainment  NAAQS reevaluated every 5 years5
    6. 6. NAAQS Summary Averaging Historic Revised NAAQS Pollutant Primary/Secondary Period NAAQS (µg/m3) (µg/m3) 1-Hour Primary 40,000 10,000 CO 8-Hour Primary 10,000 40,000 Ozone 8-Hour Primary/Secondary 75 ppb Withdrawn Pb 3-Month Rolling Primary/Secondary 1.5 0.15 PM10 24-Hour Primary/Secondary 150 150 24-Hour Primary/Secondary 65 35 PM2.5 Annual Primary/Secondary 15 15 1-Hour Primary N/A 188 NO2 Annual Primary/Secondary 100 100 1-Hour Primary N/A 196 3-Hour Secondary 1,300 1,300 SO2 24-hour Primary 365 Revoked Annual Primary/Secondary 80 Revoked6
    7. 7. Attainment/Nonattainment Designations  U.S. EPA philosophy on the SO2 NAAQS implementation process: • Proposed NAAQS – designations based on ambient monitoring data • Final NAAQS – designations based primarily on air quality modeling data  Shift to reliance on air quality modeling will become a critical issue for individual facilities7
    8. 8. NAAQSImplementation Updates
    9. 9. SO2 NAAQS Implementation  NAAQS Implementation Schedule: • June 2011: Initial state nonattainment recommendations to U.S. EPA (most counties were “unclassifiable”) • June 2012: EPA to finalize attainment status (most states will still be “unclassifiable” or attainment) • June 2013: Maintenance SIP submittals including individual facility modeling to achieve compliance with the NAAQS • August 2017: Full NAAQS compliance in all areas9
    10. 10. Implementation Update  Draft guidance for states to evaluate designations using AERMOD was released on September 22, 2011  Most states are currently reviewing the U.S. EPA guidance and crafting their plans  States or facilities conducting modeling?  U.S. EPA indicated at 10th Conference on Air Quality Models that final guidance will not be released this year due to the scope of comments made.10
    11. 11. SO2 Maintenance SIP Submittals  U.S. EPA: Revising PSD/NNSR programs to include new NAAQS is not sufficient. Five components are required: • “Attainment Emission Inventory” • Maintenance Demonstration • Control Strategy • Contingency Plan • Verification of Continued Attainment  Maintenance SIP will list enforceable 1-hour emission limits (August 2017)11
    12. 12. SO2 NAAQS Implementation  State SIPs will be based on AERMOD dispersion modeling for the following individual facilities (by order of priority): • SO2 Actual Emissions > 100 tons per year • SO2 PTE > 100 tons per year • Smaller facilities “with a potential to cause or contribute” to a NAAQS violation  States are considering other options based on population12
    13. 13. SO2 NAAQS Implementation  Legal challenges ongoing: • Science behind NAAQS levels • Approach of using modeling  Under the current approach, if states don’t perform modeling, U.S. EPA will through Federal Implementation Plan (FIP)  Some states don’t have the resources to complete evaluations and don’t think U.S. EPA does either.13
    14. 14. SO2 NAAQS Implementation  What are other States doing? • Maine - >100TPY Actual, Protocols due June 30, 2012, and final analysis due December 31, 2012. • Lake Michigan Air Directors Consortium (LADCO) has developed Protocol for states to follow.  Wisconsin, Michigan, Minnesota, Indiana, and Illinois included.  >100 TPY PTE, facilities given option to complete themselves or have state complete.  Michigan were due December 31, 2011.  Minnesota completed March 12, 2012. • Nebraska – Power plants have joined to conduct modeling themselves and conducting tracer study. • Missouri – Facilities conducting modeling due by April 2012. • Connecticut - >15TPY PTE, conducted by State by July 2012.14
    15. 15. Dispersion Modeling Basics and Inputs
    16. 16. AERMOD Process Hourly Wind Speed Hourly Wind Direction Hourly Ambient Temperature Land Use Patterns Predicted Ground Level Topography Ambient Concentrations (µg/m3) Building Dimensions for all averaging times Stack Dimensions Exhaust Velocity Exhaust Temperature Emission Rates16
    17. 17. Air Quality Modeling Steps 1. Emission Inventory 2. Meteorological Data (AERMET/AERSURFACE) 3. Terrain Data (AERMAP) 4. Building Downwash (BPIPPRM)17
    18. 18. Emission Inventories  Short-term (1-hour) emission rates  Potential to be used as permit limits  Intermittent emission units (e.g., emergency generators, intermittent emission scenarios such as startup/shutdown operations or alternative fuels) • Latest guidance indicates following form of standard as guideline for what to include (i.e., 99th percentile (4th highest))  Stack characteristics (height, temperature, velocity, diameter, location)18
    19. 19. Meteorological Data19
    20. 20. Meteorological Data20
    21. 21. Meteorological Data  5 years of National Weather Service data  Minimum of 1 year of onsite data  Surface characteristics and topography surrounding the facility should be similar to (representative of) those surrounding the meteorological station  If no representative meteorological data are available, SO2 implementation guidance suggests possibility of using AERSCREEN (with agency approval)21
    22. 22. Terrain Data  “Ambient Air”  “that portion of the atmosphere, external to buildings, to which the general public has access” or “the air everywhere outside of a contiguous plant property to which public access is precluded by a fence or other effective physical barrier”22
    23. 23. Building Downwash23
    24. 24. Building Downwash24
    25. 25. NAAQS Modeling Demonstration Approach
    26. 26. Full NAAQS Evaluation  Includes facility and other local facilities  Any modeled emission rates should be acceptable as a 1-hour permit limit with the appropriate margin for compliance  Considerations for accounting for emissions during startup and shutdown  Emergency unit considerations26
    27. 27. Local Sources  NAAQS evaluation must include sources that result in a “significant concentration gradient” in the vicinity of the facility  Same emission rate considerations apply for local sources (although permit limit concerns wouldn’t apply)  State agency typically dictates which local sources to include in evaluation27
    28. 28. NAAQS Modeling Strategy  Start with an evaluation of each individual emission source  Each source will have different factors that drive resulting ambient concentrations  The cumulative ambient concentration from all sources (plus background) will be evaluated against the NAAQS  Evaluate each source against the NAAQS as a first step28
    29. 29. NAAQS Modeling Strategy  Big picture factors that will drive ambient concentrations for individual sources: • Elevated emission rates • Stack velocity (orientation of release and flowrate) • Stack temperature (plume buoyancy) • Stack height versus surrounding terrain • Surrounding buildings and structures (i.e., building downwash)29
    30. 30. Hypothetical Modeling Examples  Modeling of a hypothetical facility with the following SO2 emission sources: • Process SO2 source • Fuel oil combustion SO2 source • Backup engine source  NAAQS modeling evaluation is based on SO2 potential-to-emit30
    31. 31. Hypothetical Facility Terrain31
    32. 32. “Process” SO2 Source  SO2 Emission Rate: 240 lb/hr (CEMS)  Stack Height: 290 feet  Stack Diameter: 16.5 feet  Exhaust Temp: 350 °F  Exhaust Flow: 230,000 acfm  Elevated emission rate, buoyant source, tall stack (taller than the tallest buildings at the facility)32
    33. 33. Process SO2 Source Impacts33
    34. 34. Process SO2 Source Impacts  Highest impacts in complex terrain far from facility  Wind speed doesn’t match location of elevated concentrations  Impacts occur during periods of atmospheric stability and low mixing heights (typically early morning, low wind speed conditions)  High concentrations due partially to the limitations of the AERMOD dispersion model34
    35. 35. Combustion SO2 Source  SO2 Emission Rate: 20 lb/hr (AP-42)  Stack Height: 60 feet  Stack Diameter: 2 feet  Exhaust Temp: 225 °F  Exhaust Flow: 16,000 acfm  Buoyant source, short stack (shorter than the tallest buildings at the facility)35
    36. 36. Combustion SO2 Source Impacts36
    37. 37. Combustion SO2 Source Impacts  Elevated concentrations are closer to the facility  Building downwash effects have a noticeable impact on ambient concentrations37
    38. 38. Engine SO2 Source  SO2 Emission Rate: 3 lb/hr (Vendor)  Stack Height: 10 feet  Stack Diameter: 1.3 feet  Exhaust Temp: 935 °F  Exhaust Flow: Horizontal Discharge  Horizontal discharge, short stack38
    39. 39. Engine SO2 Source Impacts39
    40. 40. Engine SO2 Source Impacts  Elevated ambient concentrations at the facility fenceline for two reasons: • Low stack height (10 feet) • No plume buoyancy due to horizontal discharge  Ambient air considerations become very important (i.e., public access)40
    41. 41. Modeling Refinements  “Process” SO2 Emission Source: • Stack height increase is technically and economically infeasible • Raw materials are fixed due to product and consumer demand • Upgrades to the scrubber could achieve control: ~30% more control (~170 lb/hr)41
    42. 42. Process SO2 Source Impacts (Before)42
    43. 43. Process SO2 Source Impacts (After)43
    44. 44. Modeling Refinements  Combustion SO2 Emission Source: • Stack height increase is technically and economically infeasible • Fuel oil firing is desirable due to cost savings considerations • Raw materials to the source bring inherent scrubbing capacity: 50 to 65% based on previous studies • 50% inherent scrubbing brings emission rate to 10 lb/hr (justify through testing)44
    45. 45. Combustion SO2 Source Impacts (Before)45
    46. 46. Combustion SO2 Source Impacts (After)46
    47. 47. Modeling Refinements  Engine SO2 Emission Source: • Simplest fix is to change the stack discharge orientation from horizontal to vertical • No changes to the vendor-guaranteed emission rate of the engine47
    48. 48. Engine SO2 Source Impacts (Before)48
    49. 49. Engine SO2 Source Impacts (After)49
    50. 50. Cumulative Concentrations  The facility must cumulatively comply with the NAAQS  Addressing each individual source helps as a first cut  This scenario still exceeds the 1-hour NAAQS for SO2 when the sources are taken cumulatively  Haven’t even considered ambient background concentrations50
    51. 51. Modeling Strategies  Emissions Strategies • Actual Distribution of Emissions • Evaluate adequacy of emission limits • Evaluate emissions control options • Evaluate alternate fuels and fuel specifications • Evaluate alternate raw material  Facility Fence Line Strategies51
    52. 52. Modeling Strategies  Stack/Exhaust Strategies: • Combined source exhausts • Co-located exhaust points to increase buoyancy • Turn horizontal stacks vertical • Increase stack heights52
    53. 53. Modeling Strategies  Temporal pairing approach  Plume transport time  Surrounding surface characteristics  Wind speed monitor thresholds  Mechanical mixing height considerations  Alternative models (e.g., CALPUFF)53
    54. 54. Modeling Strategies  Use of PTE emissions and AERMOD can over estimate concentrations  Know issues with certain terrain and meteorological conditions  Consider Ambient SO2 Monitoring to compare to AERMOD results54
    55. 55. Ambient SO2 Monitoring
    56. 56. Ambient SO2 Monitoring  What’s involved in conducting an ambient SO2 Monitoring program? • Who should consider? • Equipment • Sighting Considerations • Pros/Cons • Cost56
    57. 57. Ambient SO2 Monitoring  Who Should Consider? • Facilities that have conducted modeling with unfavorable results, however:  Recommend conducting exploratory monitoring to assess conditions first.  If favorable work with state to develop a approved monitoring plan.  Who Should Not Consider? • Facilities that have conducted modeling with favorable results.57
    58. 58. Ambient SO2 Monitoring Equipment  Thermo 43i – Pulsed Fluorescence SO2 Analyzer  Thermo 146i – Multigas Calibrator  Thermo 111 – Zero Air Supply  Air Compressor  SO2 Calibration Cylinder Gas  Climate Controlled Shelter  Co-located Meteorological Tower58
    59. 59. Ambient SO2 Monitoring59
    60. 60. Ambient SO2 Monitoring  How do you decide where to site an ambient SO2 monitor? • Typically sighted using air dispersion modeling (i.e., AERMOD). • Should Consider multiple monitors if possible.  Up-wind, down-wind, and other “hot zones” (i.e., building downwash)60
    61. 61. Ambient SO2 Monitoring Pros  Pros • Collection of monitoring data below the SO2 NAAQS. • Monitoring data could be used to discount air quality modeling results. • Potentially avoid need for permit limits, pollution controls, fuel restrictions, or shutting down operations.61
    62. 62. Ambient SO2 Monitoring Cons  Cons • Collection of monitoring data above the SO2 NAAQS. • Potential changes to SO2 NAAQS SIP maintenance process. • Time involved. • Cost62
    63. 63. Ambient SO2 Monitoring  Engineering • $8K – $15K  Equipment Cost • $75K – $100K  Installation Cost • $25K – $50K  Operational Cost (Quarterly assurance, data collection and review) • $25K – $75K  Potential partnering opportunities with “neighbors” to split cost.63
    64. 64. Final Thoughts  States developing their modeling plans now  States will reach out to request information and/or modeling  Be involved with the SIP process: • Provide states with good information • Conduct your own modeling (either for the state or in parallel with the state)  Avoid surprises (new limits) at the end of the SIP process  Consider collection of ambient SO2 monitoring data64
    65. 65. Questions? Dan Dix ddix@all4inc.com (610) 933-5246 x18 2393 Kimberton Road PO Box 299 Kimberton, PA 19442 All4 Inc. www.all4inc.com www.enviroreview.com65

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