PCBs Total Maximum Daily Loads

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

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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

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Large Mass of PCBs in the Bay due to Past
Activities
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TMDL Linkage Analysis

• Link sources to endpoint
• Pollutant fate, transport, and effects processes
• Conceptual models

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Generic Conceptual Model of PCBs Fate and
Movement in Aquatic Systems
(USEPA)
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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
Biologically Active Sediment Layer
Benthic Plant eating Wildlife
Benthic Invertebrates Plants
Non-UrbanRunoff Non-Point Sources
Buried Sediment Layer
Humans
Degradation, Sorption Desorption, Diffusion
DeltaInflow
(Adapted from SETAC, 2002)
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Long Term Fate Model
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Food Web Model
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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

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PCBs Sources to the Bay

• Atmospheric deposition
• InBay sediment hot spots
• Dredging
• Treated wastewater
• Delta inflow
• Urban runoff on land hot spots

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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

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Limited Options for Reducing PCBs Loads
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Margin of Safety

• MOS incorporated implicitly in the implementation
  and monitoring plans
• Adaptive management approach to implementation

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Sediment PCBs Concentrations

• Target 2.5 parts per billion
• Current ambient 20-35 parts per billion
• Near-shore ambient higher ?

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TMDL Target(s) and Implementation Action
Objective
Effort (,time,)
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TMDL Adaptive Implementation
(NAS, 2001)
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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