Cleaning up the Lower Duwamish

Building on more than 50 years' work in the Duwamish

King County has invested more than $250 million to date and has committed an additional $170 million to pay for cleanups and related efforts that are returning the Duwamish to health.

When County studies in the 1980's identified pollution problems in the Duwamish and in Elliott Bay, King County and other agencies undertook the following to reduce pollution:

• Secondary wastewater treatment
• Rerouting plant discharges to deeper points of Puget Sound further offshore
• Sediment capping and cleanup of contaminated areas
• Controlling contamination from industries and stormwater runoff entering the Lower Duwamish Waterway
• Reducing combined sewer overflows (CSOs) to meet federal and state regulations

Due to these pollution-control efforts, temperature, dissolved oxygen, and fecal coliform bacteria readings improved. Lead and other heavy metals in the water from smokestacks, drains, and street runoff were drastically reduced; ammonia concentrations and garbage were reduced; and habitat has been restored along the river.

Reducing flow of pollutants into the waterway: Since 1958 Metro/King County has removed more than 22 billion gallons per year of wastewater and industrial process water from the Duwamish.

Reducing volume of CSOs: Since 1990, the County has decreased these overflows into the Duwamish by more than 90 percent. Five of the ten CSOs in the Duwamish are controlled, and planning for the next CSO control projects is to begin in 2012.

Contaminated sediment cleanup: The county cleaned up seven of most contaminated acres of river bed.

Source control: Partnered with other agencies in over 1000 business inspections, and other extensive sampling and investigation to find sources of pollution.

Sampling and monitoring metrics: More than a decade of sediment quality.

Habitat restoration -  restoring more than 25 acres of habitat along the waterway.

Partnerships