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Green-Duwamish River Watershed Quality Assessment

Green-Duwamish River Watershed Quality Assessment

Project overview Map of Green-Duwamish Watershed

The primary goal of this project is to develop analytical tools for evaluating current and future water quality issues in the Green-Duwamish River watershed, and to provide water quality information to a variety of programs, such as wastewater capital planning (including the Combined Sewer Overflow (CSO) program and habitat conservation planning), WRIA 9 salmon conservation planning, stormwater management efforts, and the Department of Ecology's TMDL (Total Maximum Daily Load).

The scope of work includes water quality and hydrologic monitoring, land use / land cover modeling, water quality and quantity modeling, and risk assessment.

The specific purposes of this project are:

  • To assess existing water quality conditions and future water quality conditions for selected parameters, and evaluate best management practices for achieving Washington State water quality standards in the Green-Duwamish Watershed.
  • To assess the 303(d) listed parameters of concern for the King County Wastewater Treatment Division (e.g., parameters that could influence future CSO permit requirements - fecal coliform/ E. coli, and metals), including the identification of sources of bacteria throughout the watershed.
  • To provide information to support the WTD Habitat Conservation Plan and WRIA 9 salmon conservation planning efforts, including information on water quality as a factor of decline for salmonids.
  • To provide technical information to the Department of Ecology to support development of TMDLs.
  • To create a working watershed model that can be used as a tool for regional water quality assessment and planning now and into the future.

Team members

As a multi-disciplinary project, the GD-WQA involves the work of a variety of Groups within WLRD's Science Unit, including: Map of Green-Duwamish Watershed
  • Risk
  • Freshwater
  • Hydrology
  • Groundwater
  • Watershed
  • Environmental Laboratory

In addition, supplemental services have been contracted for their expertise, including:

  • University of Washington
  • Portland State University
  • AQUA TERRA Consultants
  • Taylor Associates, Inc.
  • Herrera Environmental Consultants
  • Anchor Environmental, L.L.C.
  • Northwest Hydraulic Consultants
  • EVS Environment Consultants
  • Parametrix, Inc.
  • Pacific Northwest National Laboratory
  • Rhithron Associates, Inc.
  • Institute for Environmental Health

Finally, the GD-WQA Team strives to cooperate with the jurisdictions within the watershed through the WRIA 9 Technical Committee. This includes cooperating with the Washington State Department of Ecology and the U.S. Environmental Protection Agency as they develop the required TMDLs.

Project products


Green-Duwamish Watershed Water Quality Assessment . Scope of Work (442 KB Adobe Acrobat file)

Sampling analysis plans (SAP's)

Green-Duwamish Watershed Water Quality Assessment Comprehensive Monitoring Program. Sampling and Analysis Plan (886 KB Adobe Acrobat file)

Green-Duwamish River Watershed Water Quality Assessment (WQA) Microbial Source Tracking (MST) Sampling and Analysis Plan (532 KB Adobe Acrobat file)

Greater Lake Washington and Green-Duwamish River Watersheds Wadeable Freshwater Streams Benthic Macroinvertebrate Sampling and Analysis Plan (429 KB Adobe Acrobat file)

Green-Duwamish Watershed Endocrine Disrupting Compounds Survey. Sampling and Analysis Plan(557 KB Adobe Acrobat file)

Data reports

WRIA 9 Habitat Limiting Factors and Reconnaissance Assessment for Salmon Habitat Green-Duwamish and Central Puget Sound Watershed Water Resource Inventory Area (WRIA) 9. Chapter 1.2 Water Quality

Green-Duwamish Watershed Water Temperature Report June 2002 (831 KB Adobe Acrobat file)

Green-Duwamish Water Temperature Report for 2001-2003

Year 2003 Water Quality Data Report: Green-Duwamish Watershed Water Quality Assessment (3.79 MB Adobe Acrobat file)

2002 Macroinvertebrate Report

2003 Macroinvertebrate Report

Microbial Source Tracking Report

Water Quality Loadings Report


Watershed Modeling Needs Assessment, Modeling Strategy, and Model Recommendations for SWAMP and Green WQA Projects (3,010 KB Adobe Acrobat file)

Watershed Modeling Calibration Report (Adobe Acrobat files)

Green River CE-QUAL-W2 Project: A Hydrodynamic and Water Quality Study of the Green River (12.5 MB Adobe Acrobat)

Green River Model (CE-QUAL-W2) Data Summary (197 KB Adobe Acrobat file)

Green River Model (CE-QUAL-W2) Data Gap Memo (143 KB Adobe Acrobat file)

Green River Water Quality Model: Boundary Conditions and Model Setup (4.135 MB Adobe Acrobat file)

Riparian Shade Characterization Study (1.74 MB Adobe Acrobat file)

Detailed Project Plan for the Development of the Integrated Water Resource Modeling System (IWRMS) (1.53 MB Adobe Acrobat file)

Risk assessment

Risk Assessment (3.75 MB Adobe Acrobat file)