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Mercury Deposition and Risk Assessment Santee Cooper Pee Dee Generating Station Draft EIS

Mercury Deposition and Risk Assessment Santee Cooper Pee Dee Generating Station Draft EIS. Presentation by: Rick Gillam U.S. EPA Region 4 Modelers Workshop March 19, 2009. Acknowledgements. US Army Corps of Engineers Santee Cooper The LPA Group Trinity Consultants. Why Mercury?.

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Mercury Deposition and Risk Assessment Santee Cooper Pee Dee Generating Station Draft EIS

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  1. Mercury Deposition and Risk AssessmentSantee Cooper Pee Dee Generating Station Draft EIS Presentation by: Rick Gillam U.S. EPA Region 4 Modelers Workshop March 19, 2009

  2. Acknowledgements • US Army Corps of Engineers • Santee Cooper • The LPA Group • Trinity Consultants

  3. Why Mercury? • Relatively large amounts of mercury emitted from the proposed coal-fired boilers • Estimated emissions of 58 lb/yr from each of the 2 proposed boilers • Many waterbodies in the area of the proposed facility already under fish-consumption advisories for mercury contamination

  4. Mercury Risk Assessment • In the scoping phase of the NEPA assessment, EPA Region 4 recommended use of procedures in EPA’s Air Toxics Risk Assessment (ATRA) Reference Library to assess mercury • http://www.epa.gov/ttn/fera/risk_atra_main.html • ATRA references the methodology contained in EPA’s Human Health Risk Assessment Protocol (HHRAP) for Hazardous Waste Combustion Facilities for performing indirect exposure risk assessments • http://www.epa.gov/epawaste/hazard/tsd/td/combust/risk.htm

  5. Santee Cooper Draft Mercury Risk Assessment

  6. MERCURY CYCLE IN THE BIOSPHERE Hg0,Hg2+,Hg(p) Hg0 Hg0 Hg0 +O3Hg2+ Hg0 +? Hg0 Hg2+ Hg0 Hg0 Hg2+ (CH3)2Hg Hg2+,Hg(p) CH3Hg+ Image from: Dr. Jerry Keeler, University of Michigan

  7. AERMOD Screening Analysis • Modeled deposition to the entire Pee Dee River Basin • Out to 150 km from the proposed facility location • 1 km receptor spacing

  8. AERMOD Refined Analysis • Modeled impacts to the effective watershed area closer to the facility which had higher deposition impacts • Out to ~50 km from proposed facility location • 500 m receptor spacing

  9. Meteorology and Land Use • Used South Carolina’s 2002-2006 surface data set from the Columbia, SC met station and Greensboro, NC Upper Air data • Surface Parameters generated with AERSURFACE using the NLCD92 land-use data • AERMOD was run with both met site and project site land-use parameters • Project site parameters produced higher deposition rates and were used for the risk assessment

  10. AERMOD Mercury Deposition Inputs • Wet and Dry deposition of both divalent (Hg+2 or RGM) and elemental (Hg0) vapors were modeled • Also modeled particulate mercury deposition using AERMOD Method 2 • Mean particle diameter of 0.4 microns, with a mass fraction of 0.8 (80%) for particles in the PM2.5 size category

  11. Modeling Results

  12. Risk Assessment Results – Screening Analysis

  13. Risk Assessment Results – Refined Analysis

  14. Risk Assessment Results – Worst Case Scenario

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