pcbs total maximum daily loads san francisco bay fred hetzel sfb-rwqcb may 13, 2003

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