Duwamish Waterway Programs
Introduction
Healthier today than it has been since the early 1900s, the Duwamish Waterway was neglected for decades. Thanks in part to work spearheaded by the King County Wastewater Treatment Division and its predecessor, the Municipality of Metropolitan Seattle (Metro), the Duwamish Waterway is running toward a brighter future.
The Duwamish was once a meandering river supporting rich agricultural land and a fertile delta. Since then, the Duwamish has been straightened, channeled, dredged, filled, transformed (external link), and used for urban and industrial waste disposal.
King County continues to improve water quality in the Lower Duwamish Waterway through actions such as reducing combined sewer overflows (CSOs), restoring habitats, sediment capping and cleanup, and controlling toxicants from industries and stormwater runoff.
King County also partners with other public and private agencies and organizations to tackle these environmental concerns in the Duwamish. One such partnership, the Lower Duwamish Waterway Group (external link), formed in 2000 to bring together King County, City of Seattle, Port of Seattle and Boeing Co.
Accomplishments
King County has been a partner and leader in planning and carrying out programs and projects to improve water quality in the Duwamish since the 1960s.
Sediment Remediation/Early Action | Source Control | CSO Reduction
Water Quality | Habitat Restoration | Construction
Sediment Remediation/Early Action
Source Control
CSO Reduction
- Systemwide efforts reduced CSO volumes from between 20 billion and 30 billion gallons per year to an average of 1.5 billion gallons per year.
- The frequency and volume of CSOs in the Duwamish vary at each of the 12 CSO locations – ranging from zero to 28 discharges per year and from zero discharge volume to 210 million gallons per year.
- King County Combined Sewer Overflow Water Quality Assessment Study for the Duwamish River and Elliott Bay monitors existing conditions of the Duwamish River and Elliott Bay with CSOs and the conditions of those water bodies if CSOs were eliminated.
Water Quality
- Dissolved oxygen levels have increased by a factor of 10 (from 1 milligram per liter to 10 mg/l).
- Fecal coliform counts (the amount of bacteria) have decreased by a factor of 100 (10,000 organisms/100 ml to below 100 organism/100 ml).
- Work on upstream issues with Auburn, Kent and the Muckleshoot Tribe is reducing pollution coming from agricultural runoff.
- King County’s Environmental Laboratory has collected and analyzed more than 2,000 samples to identify the type and level of pollutants in the water, sediment, and tissues (including samples from six of the CSO locations in the waterway) in the past 10 years.
- The Ambient Monitoring Program watches water quality in local water bodies including the Duwamish.
- King County and two dozen other local jurisdictions operate a water quality trouble call network to respond to and control events that affect water quality.
Habitat Restoration
- 6.2 acres and 1,900 feet of riparian stream restored on Hamm Creek.
- 17 acres of restored at Herring’s House/Seaboard Lumber.
- Intertidal habitat restored in the Turning Basin.
- 1.03 acres of restored at North Wind’s Weir and Cecil B. Moses Park.
Construction
- Untreated sewage and stormwater from cities along the Green/Duwamish River now send wastewater to the secondary treatment plants in Renton (completed in 1965) and at West Point in Seattle (completed in 1966).
- In the Forward Thrust (external link), Seattle and King County residents authorize bonds to sell $138 million for sewer and storm water improvements. About $1.4 million was spent in the lower Duwamish to separate sewers and improve drainage.
- The Hanford Separation Project reduced stormwater flow to the Diagonal Way storm drain by two-thirds.
- The Lander Separation Project provided storage of 1.4 million gallons during storms.
- The Renton effluent transfer system removed treated effluent form the Green River to a discharge off Duwamish Head that is 600 feet deep.
|
|
The Duwamish Waterway
is running toward
a brighter future.
News Releases
Aerial Photos
Click images for larger view. 
Duwamish Waterway,
looking south with First Avenue South bridge in foreground.
Duwamish Waterway,
looking north with First Avenue South bridge in lower right corner.
|
For questions about the Wastewater Treatment Division Web site, please send an