Modeling to Understand Modeling to Understand Stormwater Management EffortsStormwater Management Efforts

Portland Harbor Superfund SitePortland Harbor Superfund Site

Dawn SandersDawn Sanders

City of PortlandCity of Portland

Bureau of Environmental ServicesBureau of Environmental Services September 16, 2010September 16, 2010

Primary ContaminantsPrimary Contaminants PCBs PCBs Pesticides (e.g. DDT) Pesticides (e.g. DDT) Dioxins and furansDioxins and furans PAHsPAHs Heavy metalsHeavy metals

Portland HarborPortland Harbor

What I Will CoverWhat I Will Cover

Background on Stormwater DrainageBackground on Stormwater Drainage Description of Modeling to Understand Description of Modeling to Understand

Stormwater Loading and In-water Fate Stormwater Loading and In-water Fate and Transport and Transport

Preliminary Results and ConclusionsPreliminary Results and Conclusions Cautionary Tales for Sustainable Cautionary Tales for Sustainable

Stormwater Projects in Contaminated Stormwater Projects in Contaminated AreasAreas

Portland Harbor DrainagePortland Harbor Drainage

Total Stormwater Total Stormwater acreage ~ 12,000acreage ~ 12,000

~ 50% of total ~ 50% of total acreage drained by acreage drained by City systemCity system

City system drains ~ City system drains ~ 30% of heavy 30% of heavy industrialindustrial

CSOs addressed by City CSOs addressed by City CSO programCSO program

What Information is needed to What Information is needed to Evaluate Recontamination?Evaluate Recontamination?

1. Harbor-wide Loads1. Harbor-wide Loads: : Infeasible to sample the >400 private and public outfalls Infeasible to sample the >400 private and public outfalls

in the Harborin the Harbor

Most contaminants posing risk to the river not typically Most contaminants posing risk to the river not typically monitored in stormwater (e.g., banned chemicals)monitored in stormwater (e.g., banned chemicals)

2. Prediction of In-water Impacts:2. Prediction of In-water Impacts: Understanding the fate and transport of all loads, Understanding the fate and transport of all loads,

including stormwater, is critical to determining overall including stormwater, is critical to determining overall sediment impacts sediment impacts

Bioaccumation in fish tissue from contaminated Bioaccumation in fish tissue from contaminated sedimentsediment

In-river Models to Understand In-river Models to Understand Stormwater ImpactsStormwater Impacts

Routing of Chemicals in the RiverRouting of Chemicals in the River

Sources of Contaminants to Sources of Contaminants to Portland Harbor Water ColumnPortland Harbor Water Column

External pathways of pollutantsExternal pathways of pollutants Upriver flows (advection)Upriver flows (advection) Stormwater Stormwater GroundwaterGroundwater Industrial wastewater (NPDES permits)Industrial wastewater (NPDES permits) Riverbank erosion (not modeled)Riverbank erosion (not modeled) Atmospheric (not modeled)Atmospheric (not modeled) Overwater spills (not modeled)Overwater spills (not modeled)

Internal pathwaysInternal pathways Resuspension of contaminated sedimentResuspension of contaminated sediment Clean groundwater moving through contaminated Clean groundwater moving through contaminated

sediment (porewater exchange)sediment (porewater exchange)

Estimating Stormwater LoadsEstimating Stormwater Loads Land Use Approach

57% Parks & Open Space 33% Industrial 10% Residential, Commercial,

and Major Transportation (highways/freeways)

Sediment Trap & Composite Sediment Trap & Composite Stormwater SamplingStormwater Sampling

Loading rates developed for:Loading rates developed for: Each each general land useEach each general land use Sites that have unique (higher) Sites that have unique (higher)

loading compared to typical loading compared to typical land useland use

City Stormwater Model to City Stormwater Model to estimate flows for each ½ estimate flows for each ½ segmentsegment

Stormwater Results: PCBsStormwater Results: PCBs

PCBs found at every land usePCBs found at every land use Concentrations reflect findings from traditional Concentrations reflect findings from traditional

stormwater monitoring of metals and PAHsstormwater monitoring of metals and PAHs• Highest concentrations Highest concentrations

associated with current or associated with current or historical industrial areas historical industrial areas (48-9,900 µg/kg)(48-9,900 µg/kg)

• Lowest concentrations Lowest concentrations associated with open associated with open space (4 µg/kg)space (4 µg/kg)

Example: Storm Sediment TrapsExample: Storm Sediment Traps

Stormwater Loading by Land Use (based on Composite Water)

Land Use Percent Acreage % PCB Loading (based onGeomean / Weighted Mean)

Parks/Open Space - General 57% 0.04 / 0.02%

Residential/Commercial - General 8% 0.6 / 1.0%

Major Transportation - General 2% 1.0 / 0.8%

Light Industry - General 8% 2.5 / 1.6%

Heavy Industry - General 25% 26 / 50%

Heavy Industry - Unique 70 / 47%

Example: PCB Loading Estimates for StormwaterExample: PCB Loading Estimates for Stormwater

Preliminary Model Results – Subject to ChangePreliminary Model Results – Subject to Change

Example: Contributions from Example: Contributions from External and Internal LoadsExternal and Internal Loads

Preliminary Model Results – Subject to ChangePreliminary Model Results – Subject to Change

Food Web Model –Food Web Model –Bioaccumulation Predictions Bioaccumulation Predictions

Chemical in Chemical in SedimentSediment

Benthic Benthic OrganismsOrganismsSedimentSediment

WaterWater Chemical in Chemical in WaterWater

To be determined as part of recontamination analysisTo be determined as part of recontamination analysis

Next StepsNext Steps

Complete calibration of in-river modelsComplete calibration of in-river models Evaluate recontamination potential Evaluate recontamination potential

(impacts to sediment and fish tissue (impacts to sediment and fish tissue once sediment is cleaned up)once sediment is cleaned up)

If recontamination is predicted, assess If recontamination is predicted, assess which additional sources are most which additional sources are most controllable and the control controllable and the control mechanismmechanism

Considerations for Sustainable Stormwater Considerations for Sustainable Stormwater Projects in Contaminated Areas (Part I)Projects in Contaminated Areas (Part I)

Legacy contamination is often present in old Legacy contamination is often present in old industrial areas, even if current use looks industrial areas, even if current use looks benignbenign

Sediment forebays should be considered to Sediment forebays should be considered to protect facilities in industrial areas protect facilities in industrial areas

Infiltration of clean stormwater over areas with Infiltration of clean stormwater over areas with contaminated groundwater plumes can contaminated groundwater plumes can accelerate contaminants to receiving waters accelerate contaminants to receiving waters

Considerations for Sustainable Considerations for Sustainable Stormwater Projects in Contaminated Stormwater Projects in Contaminated

Areas (Part II)Areas (Part II)

Typical pollutant load Typical pollutant load models using TSS as a models using TSS as a surrogate can provide surrogate can provide misleading results (not all misleading results (not all TSS is equal)TSS is equal)

Presumptive BMPs may Presumptive BMPs may not be protective of not be protective of receiving waters when receiving waters when dealing with unusual dealing with unusual contaminants, such as contaminants, such as PCB and dioxinPCB and dioxin

0

100

200

300

400

500

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Total PCB congeners (µg/L)

TSS

(mg/

L)

To ConcludeTo Conclude

Know or characterize the area to be Know or characterize the area to be treated, including land use history, and treated, including land use history, and make appropriate actions to protect make appropriate actions to protect your facility and ensure stormwater your facility and ensure stormwater effluent is of acceptable qualityeffluent is of acceptable quality