Modeling to Understand Stormwater Management Efforts Portland Harbor Superfund Site Dawn Sanders City of Portland Bureau of Environmental Services September 16, 2010

Primary Contaminants  PCBs  Pesticides (e.g. DDT)  Dioxins and furans  PAHs  Heavy metals Portland Harbor

What I Will Cover  Background on Stormwater Drainage  Description of Modeling to Understand Stormwater Loading and In-water Fate and Transport  Preliminary Results and Conclusions  Cautionary Tales for Sustainable Stormwater Projects in Contaminated Areas

Portland Harbor Drainage  Total Stormwater acreage ~ 12,000  ~ 50% of total acreage drained by City system  City system drains ~ 30% of heavy industrial CSOs addressed by City CSO program

What Information is needed to Evaluate Recontamination? 1. Harbor-wide Loads: Infeasible to sample the >400 private and public outfalls in the Harbor Infeasible to sample the >400 private and public outfalls in the Harbor Most contaminants posing risk to the river not typically monitored in stormwater (e.g., banned chemicals) Most contaminants posing risk to the river not typically monitored in stormwater (e.g., banned chemicals) 2. Prediction of In-water Impacts: Understanding the fate and transport of all loads, including stormwater, is critical to determining overall sediment impacts Understanding the fate and transport of all loads, including stormwater, is critical to determining overall sediment impacts Bioaccumation in fish tissue from contaminated sediment Bioaccumation in fish tissue from contaminated sediment

In-river Models to Understand Stormwater Impacts

Routing of Chemicals in the River

Sources of Contaminants to Portland Harbor Water Column External pathways of pollutants  Upriver flows (advection)  Stormwater  Groundwater  Industrial wastewater (NPDES permits)  Riverbank erosion (not modeled)  Atmospheric (not modeled)  Overwater spills (not modeled) Internal pathways  Resuspension of contaminated sediment  Clean groundwater moving through contaminated sediment (porewater exchange)

Estimating Stormwater Loads  Land Use Approach 57% Parks & Open Space 33% Industrial 10% Residential, Commercial, and Major Transportation (highways/freeways)  Sediment Trap & Composite Stormwater Sampling  Loading rates developed for: Each each general land use Each each general land use Sites that have unique (higher) loading compared to typical land use Sites that have unique (higher) loading compared to typical land use  City Stormwater Model to estimate flows for each ½ segment

Stormwater Results: PCBs  PCBs found at every land use  Concentrations reflect findings from traditional stormwater monitoring of metals and PAHs Highest concentrations associated with current or historical industrial areas (48-9,900 µg/kg) Highest concentrations associated with current or historical industrial areas (48-9,900 µg/kg) Lowest concentrations associated with open space (4 µg/kg) Lowest concentrations associated with open space (4 µg/kg) Example: Storm Sediment Traps

Stormwater Loading by Land Use (based on Composite Water) Land UsePercent Acreage% PCB Loading (based on Geomean / Weighted Mean) Parks/Open Space - General57%0.04 / 0.02% Residential/Commercial - General8%0.6 / 1.0% Major Transportation - General2%1.0 / 0.8% Light Industry - General8%2.5 / 1.6% Heavy Industry - General25%26 / 50% Heavy Industry - Unique70 / 47% Example: PCB Loading Estimates for Stormwater Preliminary Model Results – Subject to Change

Example: Contributions from External and Internal Loads Preliminary Model Results – Subject to Change

Food Web Model – Bioaccumulation Predictions Chemical in Sediment Benthic Organisms Sediment Water Chemical in Water To be determined as part of recontamination analysis

Next Steps  Complete calibration of in-river models  Evaluate recontamination potential (impacts to sediment and fish tissue once sediment is cleaned up)  If recontamination is predicted, assess which additional sources are most controllable and the control mechanism

Considerations for Sustainable Stormwater Projects in Contaminated Areas (Part I)  Legacy contamination is often present in old industrial areas, even if current use looks benign  Sediment forebays should be considered to protect facilities in industrial areas  Infiltration of clean stormwater over areas with contaminated groundwater plumes can accelerate contaminants to receiving waters

Considerations for Sustainable Stormwater Projects in Contaminated Areas (Part II)  Typical pollutant load models using TSS as a surrogate can provide misleading results (not all TSS is equal)  Presumptive BMPs may not be protective of receiving waters when dealing with unusual contaminants, such as PCB and dioxin

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