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PCBs Total Maximum Daily Loads

PCBs Total Maximum Daily Loads

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PCBs Total Maximum Daily Loads

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  1. PCBs Total Maximum Daily Loads San Francisco Bay Fred Hetzel SFB-RWQCB May 13, 2003

  2. Polychlorinated Biphenyls (PCBs) Impairment of San Francisco Bay • PCBs on 303(d) list due to interim health advisory for fish consumption • U.S. EPA California Toxics Rule-Human health risk assessment for fish consumption sets a total PCBs criteria in water at 0.00017 µg/L

  3. PCBs Used in a Wide Range of Products • Closed applications • Capacitors and transformers • Heat transfer and hydraulic fluids • Open applications • Plasticizers • Surface coatings and paints • Flame retardants • Inks and adhesives • Pesticide extenders • Carbonless duplicating paper

  4. Large Mass of PCBs in the Bay due to Past Activities

  5. TMDL Linkage Analysis • Link sources to endpoint • Pollutant fate, transport, and effects processes • Conceptual models

  6. Generic Conceptual Model of PCBs Fate and Movement in Aquatic Systems (USEPA)

  7. Bioturbation, Scouring, Deposition & Resuspension, Transport, Dredging Atmospheric Deposition PCBs TMDLConceptual Model Golden Gate Outflow PointSources Surface Waters UrbanRunoff Fish eatingWildlife Fish Spills & On-LandContaminated Sites Benthic & Plant eating Wildlife Biologically Active Sediment Layer Benthic Invertebrates & Plants Non-UrbanRunoff &Non-Point Sources Buried Sediment Layer Humans Degradation, Sorption & Desorption, Diffusion DeltaInflow (Adapted from SETAC, 2002)

  8. Bioturbation, Scouring, Deposition & Resuspension, Transport, Dredging Atmospheric Deposition PointSources Golden Gate Outflow Surface Waters UrbanRunoff Spills & On-LandContaminated Sites Biologically Active Sediment Layer Non-UrbanRunoff &Non-Point Sources Buried Sediment Layer Degradation, Sorption & Desorption, Diffusion DeltaInflow Long Term Fate Model

  9. Surface Waters Fish eatingWildlife Fish Benthic & Plant eating Wildlife Biologically Active Sediment Layer Benthic Invertebrates & Plants Buried Sediment Layer Humans Food Web Model

  10. Proposed Numeric Targets for PCBs • Fish tissue = 23 parts per billion Based on human health risk assessment • Sediment = 2.5 parts per billion Based on generic bioaccumulation factors Not specific to San Francisco Bay

  11. PCBs Sources to the Bay • Atmospheric deposition • In–Bay sediment “hot spots” • Dredging • Treated wastewater • Delta inflow • Urban runoff & on land “hot spots”

  12. Proposed PCBs Allocations • Background and atmospheric deposition - 0 • Hot spots - Sediment target (phased approach) - Source investigations • Dredging - Sediment target (phased approach) - Source investigations • Treated effluent - Current mass • Run-off - Sediment target (phased approach) - Source investigations

  13. Limited Options for Reducing PCBs Loads

  14. Margin of Safety • MOS incorporated implicitly in the implementation and monitoring plans • Adaptive management approach to implementation

  15. Sediment PCBs Concentrations • Target = 2.5 parts per billion • Current ambient = 20-35 parts per billion • Near-shore ambient = higher ?

  16. Target? Target? TMDL Target(s) and Implementation Action Objective Effort ($,time,…)

  17. TMDL Adaptive Implementation (NAS, 2001)

  18. PCB TMDL Implementation • Immediate actions • High degree of certainty • Fixed time period • Monitoring program • Assess progress toward targets • Refine loading estimates • Studies (experiment ?) and model refinement • Validate key assumptions • Determine long term actions • Resolve key uncertainties ? • Review targets, allocations, and implementation