Studies and reports

We conduct a variety of studies, in collaboration with other agencies, to help us understand the sources and pathways of pollution to the Lower Duwamish Waterway.

Green River Loading Study

Goal: Quantify sediment and toxic chemical loads associated with upstream sources in the Green River to the Lower Duwamish Waterway (LDW). Focus is on high flow/high turbidity events that may contribute more to the annual loading than average flow conditions. These improved measurements will aid in assessing the potential for future re-contamination of remediated sediment in the Lower Duwamish Waterway.


  • Interagency Agreement with U.S. Geological Study
  • Expand on Ecology's Environmental Assessment Program 2009 study
  • Sampling of whole water, suspended sediment, and bulk sediments at locations upstream of the LDW
  • Chemical analysis will be performed on a full suite of chemicals
  • Analyze for both PCB Aroclors and congeners

Phase 3 Report and Appendix
2016 Progress Report and Data Tables
Phase 2 Report and Appendices
Phase 1 Report and Appendices

Green-Duwamish River Watershed PCB Congener Study


  1. Summarize issues and considerations when evaluating historical PCB congener and Aroclor data or when collecting new data
  2. Compile available PCB congener data in the Green-Duwamish watershed, including any available information on data quality



  • Sources of PCBs to the environment, including historical and inadvertent new sources, and the relationship between specific Aroclors and congeners to types of source material
  • Fate and transport of PCBs, including volatilization and dechlorination
  • Toxicity of PCBs, including dioxin-like PCBs
  • Relationship between Aroclor and congener data
  • Measurement of Aroclors and PCB congeners, including laboratory methods
  • Laboratory analysis and data comparability issues
  • Numerical standards/criteria under various state and federal regulations
  • PCB congener data collection and management considerations
  • Summary of available congener data, including sediment, surface water, stormwater, storm drain solids, air, tissue, soil, and groundwater
  • Data quality and comparability, available metadata, and data gaps

Phase 1 Report
Phase 2 Report
Groundwater Sampling for PCB Congeners and Aroclors
Otter Scat Data Report

Green-Duwamish Pollutant Loading Study

The Green-Duwamish Pollutant Loading Study (PLA) will identify sources of pollution in the Green-Duwamish watershed and strategies to reduce those sources. We're partnering with the U.S. Environmental Protection Agency (EPA) to conduct this multi-year project.

The PLA will provide information on:

  • What pollutants enter the river.
  • Where pollution comes from.
  • How much comes from different sources.

The information will help us develop strategies so the basin's water and sediments meet environmental quality standards.

Cement Kiln Dust (CKD) mapping project

Cement kiln dust (CKD) is a caustic substance that was used as fill material at many facilities that discharge to the LDW. This study mapped all known deposits of CKD in the LDW source control area and assessed whether CKD:

  • is a source of arsenic and other metals to the LDW,
  • mobilizes other contaminants in the leachate plume, or
  • poses a threat to workers who are exposed to the caustic leachate.

Cement Kiln Dust: Summary of Existing Information, Lower Duwamish Waterway