Implications of the New NAAQS
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Implications of the New NAAQS

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Implications of the New NAAQS Implications of the New NAAQS Presentation Transcript

  • Implications of the New NAAQS All4 Inc. Air Quality Training Seminar Montgomery, AL December 7, 2010 Colin T. McCall All4 Inc.
  • Agenda
    • NAAQS Background
    • Current NAAQS Revisions
    • NAAQS Implications and PSD Considerations
    • NAAQS Implementation Process
    • Example AERMOD Modeling
    • Planning Ahead
    • Conclusions
  • NAAQS Background
  • CAA- §109 National Ambient Air Quality Standards
    • 109(b) – the NAAQS
      • Primary standards: attainment and maintenance protect public health with adequate margin of safety
      • Secondary standards: protect public welfare
    • 109(d)(1) – timing
      • Every 5 years, “thorough” review of NAAQS
      • Revise as necessary
      • May also be done more frequently
  • CAA- §109 National Ambient Air Quality Standards
    • 109(d)(2) – Clean Air Scientist Advisory Committee (CASAC)
      • Appointed by U.S. EPA
      • 7 members: at least one physician, one member of the National Academy of Sciences, one representative of state air pollution control agencies
      • Review and recommend new NAAQS to EPA
  • 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
  • Current NAAQS Revisions
  • Current NAAQS Revisions
    • Lead
    • PM 2.5
    • CO
    • Ozone
    • NO 2 (Primary and Secondary)
    • SO 2 (Primary and Secondary)
  • NAAQS Summary Pollutant Averaging Period Historic NAAQS ( µ g/m 3 ) Revised NAAQS ( µ g/m 3 ) CO 1-Hour 10,000 10,000 8-Hour 40,000 40,000 Ozone 8-Hour 75 ppb 60 – 70 ppb (proposed) Pb 3-Month Rolling 1.5 0.15 PM 10 24-Hour 150 150 PM 2.5 24-Hour 65 35 Annual 15 15 NO 2 1-Hour N/A 188 Annual 100 100 SO 2 1-Hour N/A 196 3-Hour 1,300 1,300 24-hour 365 N/A Annual 80 N/A
  • Anticipated NAAQS Implementation Milestones Pollutant NAAQS Promulgation Date Designations Effective (approximate date) 110(a) SIPs Due (3 yrs after NAAQS promulgation) Attainment Demonstration Due Attainment Date PM 2.5 (2006) Sept 2006 Dec 2009 Sept 2009 Nov 2012 Nov 2014/2019 Pb Oct 2008 Nov 2010/2011 (extra time for new monitors) Oct 2011 June 2012/2013 Nov 2015/2016 NO 2 (primary) Jan 2010 Feb 2012 Jan 2013 Aug 2013 Feb 2017 SO 2 (primary) June 2010 July 2012 June 2013 Jan 2014 July 2017 Ozone Aug 2010 Aug 2011 (based on 2008-10 data) Aug 2013 Dec 2013 (to be proposed) Dec 2017 (Moderate) CO May 2011 June 2013 May 2014 Dec 2014 May 2018 PM 2.5 (2011) Oct 2011 Dec 2013 Oct 2014 Dec 2016 Dec 2018/2023 NO 2 /SO 2 Secondary March 2012 April 2014 March 2015 Oct 2015 N/A
  • New NAAQS Considerations
    • Historic NAAQS levels often not viewed as impacting day-to-day permitting.
    • New 1-Hour NAAQS levels are very stringent (example for SO 2 ):
      • SO 2 3-Hour to Annual Ratio: 16.25
      • SO 2 1-Hour to Annual Ratio: 2.45
    • It may be difficult to directly demonstrate compliance with the NAAQS.
  • NAAQS Implications and PSD Considerations
  • NAAQS Implications
    • NAAQS attainment status dictates air quality permitting requirements (PSD and BACT versus NNSR and LAER).
    • Traditionally, a direct NAAQS compliance demonstration has only been required as part of a PSD permitting project.
    • PSD NAAQS modeling is a two step process: (1) SIL Evaluation; (2) full NAAQS assessment.
  • PSD Permitting Considerations
    • Step 1 of a PSD NAAQS assessment is a significant impact level (SIL) analysis.
    • U.S. EPA has established interim SILs:
      • 24-Hour PM 2.5 SIL: 0.3 µg/m 3
      • 1-Hour NO 2 SIL: 7.5 µg/m 3
      • 1-Hour SO 2 SIL: 7.9 µg/m 3
    • Exceedance of the SILs will trigger a facility-wide NAAQS evaluation.
    • Consider short-term emissions increases.
  • Interacting with the NAAQS
    • Situations that call for facility-specific NAAQS evaluations:
      • Attainment/Nonattainment Designations (under the current U.S. EPA administration).
      • Major air permitting projects ( PSD vs. NNSR).
      • Discretionary requests by a state agency.
    • More stringent NAAQS levels will result in more stringent state developed emission limits, monitoring, etc.
  • NAAQS Implementation Process
  • Attainment/Nonattainment Designations
    • U.S. EPA philosophy on the SO 2 NAAQS implementation process:
      • Proposed NAAQS rule - designations based on ambient monitoring data
      • Final NAAQS rule - designations based primarily on air quality modeling data
    • Shift to reliance on air quality modeling will become a critical issue for individual facilities.
  • SO 2 NAAQS Monitoring Data
  • SO 2 NAAQS Implementation
    • NAAQS Implementation Schedule:
      • June 2011 : Initial state nonattainment recommendations to U.S. EPA (most counties will be “unclassifiable”)
      • June 2013 : State SIP submittals to achieve compliance with the NAAQS (including air quality modeling for individual facilities)
      • 2017 : Full NAAQS compliance in all areas
  • SO 2 NAAQS SIP Submittals
    • U.S. EPA: Revising PSD/NNSR programs to include new NAAQS is not sufficient. Five components are required:
      • “ Attainment Emissions Inventory”
      • Maintenance Demonstration
      • Control Strategy
      • Contingency Plan
      • Verification of Continued Attainment
  • SO 2 NAAQS Implementation
    • State SIPS will be based on AERMOD dispersion modeling for the following individual facilities (by order of priority):
      • SO 2 Actual Emissions > 100 tpy
      • SO 2 PTE > 100 tpy
      • Smaller facilities “with a potential to cause or contribute” to a NAAQS violation
    • Minor facilities may still have trouble.
  • Facility Specific NAAQS Evaluation
    • Modeling is based on potential-to-emit emission rates (not actual emissions).
    • Modeling must account for operating scenarios/loads that result in worst-case plume dispersion.
    • Must use representative meteorological data.
    • Ambient background data must be added to modeled concentrations.
  • Stringency of the NAAQS
    • Many facilities with any combination of the following may have difficulty modeling NAAQS compliance:
      • Elevated emission rates (fuel oil combustion, process SO 2 , etc.)
      • Low stack heights
      • Building downwash to any extent
      • Complex terrain
  • Example AERMOD Modeling
  • 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 step.
  • 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)
  • Hypothetical Modeling Example
    • Modeling of a hypothetical facility with the following SO 2 emission sources:
      • Process SO 2 source
      • Fuel oil combustion SO 2 source
      • Backup engine source
    • NAAQS modeling evaluation is based on SO 2 potential to emit.
  • “ Process” SO 2 Source
    • SO 2 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)
  • Process SO 2 Source Impacts
    • Highest impacts are in complex terrain far from the 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 model.
  • Combustion SO 2 Source
    • SO 2 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)
  • Combustion SO 2 Source Impacts
    • Elevated concentrations are closer to the facility.
    • Building downwash effects have a noticeable impact on ambient concentrations.
  • Engine SO 2 Source
    • SO 2 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 stack
  • Engine SO 2 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).
  • Modeling Refinements
    • “ Process” SO 2 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 of ~30% of the current uncontrolled emission rate (240 lb/hr to approximately 160 lb/hr).
  • Modeling Refinements
    • Combustion SO 2 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).
  • Modeling Refinements
    • Engine SO 2 Emission Source:
      • Simplest fix is to “turn up” the horizontal stack discharge.
      • No changes to the vendor guaranteed emission rate of the engine.
  • Cumulative Concentrations
    • The facility must cumulatively comply with the NAAQS level.
    • Addressing each individual source helps as a first cut.
    • This scenario still exceeds the 1-hour NAAQS level for SO 2 when the sources are taken cumulatively.
    • Haven’t even considered ambient background…..
  • Ambient Background Concentrations
    • NAAQS evaluation requires background concentrations to be added to modeled concentrations.
    • Example 1-hour attainment ambient concentrations:
      • NO 2 : 30 - 80 µg/m 3 (NAAQS: 188)
      • SO 2 : 50 - 100 µg/m 3 (NAAQS: 196)
  • Ambient Background Challenges
    • Availability of representative ambient monitoring data.
    • Monitor must be representative of the background concentrations at the facility.
    • Pre-construction monitoring may be required in the absence of representative ambient monitoring data.
    • Rural versus urban setting is important for availability and good data.
  • Ambient SO 2 Monitors
  • Ambient NO 2 Monitors
  • Ambient PM 2.5 Monitors
  • Ambient Background Challenges
    • Less room available for your facility to contribute to the NAAQS levels.
    • U.S. EPA “Tier 1” approach for combining modeled and monitored concentrations:
      • Combine 99 th percentile cumulative modeling concentration with peak hourly monitored concentration
  • Ambient Background Considerations 188 NO 2 1-hour Concentration (  g/m 3 ) 80 NAAQS Level Monitored Background Value 108  g/m 3 available for modeling
  • Temporal Pairing
    • New option for combining air quality modeling and ambient monitoring data.
    • Eliminates conservativeness of combining concentrations that occurred at different times.
    • U.S. EPA generally approves of the approach in recent guidance.
    • Specific evaluations need approval on a case-by-case basis (work with the state).
  • Temporal Pairing Example
  • Temporal Pairing Example
  • Temporal Pairing Example
  • Temporal Pairing Example
  • Planning Ahead
  • Planning Ahead
    • Emissions Strategies:
      • Evaluate adequacy of emission limits
      • Evaluate emissions control options
      • Evaluate alternate fuels and fuel specifications
    • Facility Fence Line Strategies
  • Planning Ahead
    • Stack/Exhaust Strategies:
      • Combined source exhausts
      • Co-located exhaust points to increase buoyancy
      • “ Turn up” horizontal stacks
      • Increase stack heights
  • Planning Ahead
    • Air Quality Modeling Strategies:
      • Temporal pairing approach
      • Plume transport time
      • Surrounding surface characteristics
      • Wind speed monitor thresholds
      • Mechanical mixing height considerations
      • Alternative models (CALPUFF, etc.)
      • Atmospheric chemistry options for NO 2
  • Conclusions
    • The new 1-hour NAAQS levels are so stringent that they will drive project feasibility and project design.
    • NAAQS will replace BACT as the most critical PSD permitting issue.
    • NAAQS modeling will be required even in the absence of new projects.
    • Plan early for new projects and for the SO 2 NAAQS implementation process.