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Toxics Cleanup Program


Lower Duwamish Waterway
Source Control

What is source control?

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Illustration of potential pollution pathways.

Source control is the process of finding and then stopping or reducing releases of pollution to waterway sediments. The point of source control is to minimize the keep sediments from becoming polluted again after being cleaned up. Finding and controlling sources is difficult and even with aggressive source control, some recontamination may occur.

The near-term goal is to control sources sufficiently to allow active in‑waterway remediation to start, minimizing the likelihood that sediments will be recontaminated at levels that trigger additional active in-waterway remediation.

The long-term goal, after the sediment remedy is in place, is to minimize the risk of recontaminating sediments above the sediment cleanup standards established in the Record of Decision.

Source Control Strategy:

The Source Control Strategy describes the goals, priorities and process used to address source control work. The purpose of this document is to provide the framework and process for identifying source control issues and implementing effective controls for the Lower Duwamish Waterway. The basic source control strategy for the LDW site is to identify and manage sources of chemicals to site sediments in coordination with sediment cleanups.  

Source Control Work Group

Ecology leads the interagency Source Control Work Group (SCWG). The SCWG shares information, discusses strategy, develops action plans, implements source control measures, and tracks progress. The SCWG includes Ecology, the City of Seattle, King County, Port of Seattle, and EPA.

The table below shows each agency's role in the SCWG.

Ø Ecology: Lead for source control at properties that discharge directly to the waterway and for source control work at upland contaminated properties;

Ø City of Seattle: Lead for source control within their storm drain system;

Ø King County: Lead for source control for discharges to wastewater or combined wastewater and storm water systems;

Ø EPA: Lead for Boeing Plant 2, Terminal 117, Slip 4 sediments, and Rhone/Poulenc cleanup sites; provides technical assistance, source control coordination with EPA sediment investigation and cleanup activities.

Source Control Implementation Plans

As the lead agency for Source Control, Ecology has asked the city of Seattle, King County, and EPA to develop agency-specific implementation plans. The intent of the implementation plans is to set each agency’s priorities for source control for a near-term (5 years) and to establish long-term expectations for source control activities during and following construction of the in-waterway cleanup under the ROD. These plans will be considered part of the Source Control Strategy following their completion.

City of Seattle Implementation Plan

The land area around the Lower Duwamish Waterway (LDWW) is divided into 24 sub-basins (or source control areas) based on the pathways that storm runoff can take as it drains into the waterway.

Source Control Status Reports:

These reports summarize source control activities conducted by the Lower Duwamish Waterway (LDW) Source Control Work Group. They provide an overview of the LDW site, the strategy for controlling sources of pollutants to the LDW, the process for developing Source Control Action Plans (SCAPs), the methods and process for implementing the SCAPs, issues associated with permitted discharges, and a summary of source control actions during the period of the report. 

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This page last updated January 11, 2017