pcbs total maximum daily loads san francisco bay fred hetzel sfb-rwqcb may 13, 2003
TRANSCRIPT
PCBs Total Maximum Daily Loads
San Francisco Bay
Fred HetzelSFB-RWQCBMay 13, 2003
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
PCBs Used in a Wide Range of Products
Closed applicationsCapacitors and transformersHeat transfer and hydraulic fluids
Open applicationsPlasticizersSurface coatings and paintsFlame retardantsInks and adhesivesPesticide extendersCarbonless duplicating paper
PCB Mass (kg)
3-5
Total 5,000-50,000
Active Layer 500-2,500Sediments
Compartment
Water
Large Mass of PCBs in the Bay
due to Past Activities
Link sources to endpoint
Pollutant fate, transport, and effects processes
Conceptual models
TMDL Linkage Analysis
Generic Conceptual Model of PCBs Fate and Movement in Aquatic
Systems
(USEPA)
Atmospheric Deposition
PointSources
UrbanRunoff
Spills &On-Land
ContaminatedSites
DeltaInflow
Non-UrbanRunoff &
Non-PointSources
SurfaceWaters
BiologicallyActive
SedimentLayer
BuriedSediment
Layer
Fish
Benthic Invertebrates
& Plants
Fish eatingWildlife
Benthic &Plant eating
Wildlife
Humans
Bioturbation, Scouring, Deposition & Resuspension,
Transport, Dredging
Degradation,Sorption & Desorption,
Diffusion
GoldenGate
Outflow
PCBs TMDLConceptual
Model
(Adapted from SETAC, 2002)
Atmospheric Deposition
PointSources
UrbanRunoff
Spills &On-Land
ContaminatedSites
DeltaInflow
Non-UrbanRunoff &
Non-PointSources
SurfaceWaters
BiologicallyActive
SedimentLayer
BuriedSediment
Layer
Bioturbation, Scouring, Deposition & Resuspension,
Transport, Dredging
Degradation,Sorption & Desorption,
Diffusion
GoldenGate
Outflow
Long Term Fate Model
SurfaceWaters
BiologicallyActive
SedimentLayer
BuriedSediment
Layer
Fish
Benthic Invertebrates
& Plants
Fish eatingWildlife
Benthic &Plant eating
Wildlife
Humans
Food Web Model
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
PCBs Sources to the Bay
Atmospheric deposition
In–Bay sediment “hot spots”
Dredging
Treated wastewater
Delta inflow
Urban runoff & on land “hot spots”
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
Limited Options for Reducing PCBs Loads
-7
32
1.9
34
12
-7
32
2
16
6
-7
32
0.142.0 1.4
-20
-10
0
10
20
30
40
Atmospheric Delta Municipal andIndustrial
Dischargers
Urban Runoff Dredged Material
Source Category
Ma
ss
(k
g)
Current Loads
Proposed Loads
Maximum Reductions
Margin of Safety
MOS incorporated implicitly in the implementation and monitoring plans
Adaptive management approach to implementation
Sediment PCBs Concentrations
Target = 2.5 parts per billion
Current ambient = 20-35 parts per billion
Near-shore ambient = higher ?
TMDL Target(s) and Implementation Action
Effort ($,time,…)
Objective
Target?
Target?
TMDL Adaptive Implementation
(NAS, 2001)
Immediate actionsHigh degree of certaintyFixed time period
Monitoring programAssess progress toward targetsRefine loading estimates
Studies (experiment ?) and model refinementValidate key assumptionsDetermine long term actionsResolve key uncertainties ?
Review targets, allocations, and implementation
PCB TMDL Implementation