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SO2 Modeling

SO2 Modeling. SIP Steering Committee Meeting March 29, 2012. EPA’s Draft SIP and Modeling G uidance. In October 2011, EPA issued draft SIP and modeling guidance related to the 1-hour SO2 standard issued in June 2010

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SO2 Modeling

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  1. SO2 Modeling SIP Steering Committee Meeting March 29, 2012

  2. EPA’s Draft SIP and Modeling Guidance • In October 2011, EPA issued draft SIP and modeling guidance related to the 1-hour SO2 standard issued in June 2010 • EPA’s guidance addresses parameters for dispersion modeling of large sources of SO2 emissions • Refined dispersion modeling must be included in SO2 SIPs that states must submit to EPA in 2013

  3. What Sources Must Be Modeled? • NESCAUM states developed a draft dispersion modeling protocol consistent with EPA’s draft guidance; will serve as basis for states’ individual protocols • All NESCAUM states expecting to model emitters of 100 tons or more per year actual emissions as primary sources • Some variability among states as to emission thresholds to determine interactive sources

  4. MassDEP Draft Modeling Applicability Guidelines Primary Source Modeling • Required for any source that reported actual emissions >100 tons in one or more years during 2008-2010 • Modeling is of full potential or allowable emissions • A primary source must be placed at the center of its own modeling domain • Must include interactive sources in modeling

  5. MassDEP Draft Modeling Applicability Guidelines Interactive source modeling • Required for any source within 50 km of a primary source that reported actual emissions >40 tons in one or more years during 2008-2010 • Includes sources outside of Massachusetts with actual emissions >40 tons if within 50 km of MA primary source • MassDEP is collecting data from other states

  6. MassDEP Draft Modeling Applicability Guidelines Interactive source modeling • Interactive sources must be modeled at full potential or allowable emissions • Sources may be excluded from modeling if screening of the interactive facility demonstrates potential 1-hour SO2 impacts are not greater than 7.8 ug/m3 (3 ppb)   

  7. MassDEP Draft Modeling Applicability Guidelines Smaller interactive sources • Sources with reported emissions >20 tons per year (but <40 tons) generally not required to be modeled • However, may require modeling based on review of a number of factors: • is source is located in complex terrain • short stacks subject to building downwash • operating parameters • is source captured by background monitor

  8. MassDEP Draft Modeling Applicability Guidelines Emissions Data • Will use actual emissions reported by a source to MassDEP’s Air Registration System to determine if source meets threshold for primary and/or interactive sources • Emission data since 2005 will be reviewed as a check on representativeness of recent emissions • Will consider if changes in permit conditions, equipment, or operating parameters may cause future year emissions to vary significantly from reported emissions

  9. Next Steps • MassDEP developing a draft modeling protocol for EPA and stakeholder review • Preparing lists of primary and potential interactive sources and creating 50 km maps • Will schedule an SO2 stakeholder meeting in next 30 days or so • EPA still reviewing comments on its proposed modeling guidance; final EPA guidance date is uncertain

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