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Our role in the Lower Duwamish Waterway Superfund cleanup

King County’s Wastewater Treatment Division and its predecessor Metro have worked for more than 40 years to restore the Lower Duwamish Waterway. King County is helping to pay for and implement EPA’s Superfund cleanup plan.
This is a photo of a waterway that splits to the left and right of the photo. In the middle is a marina with sailboats. The left and right banks of the waterway are densely populated with industrial buildings and parking lots.
Here is where the Lower Duwamish Waterway meets the southern end of Harbor Island.  The Duwamish has a rich history as Seattle’s only river and it continues to serve as a place for tradition, culture, recreation, wildlife, and commerce.

King County is helping to pay for and implement EPA’s Superfund cleanup plan and also provides education and community support through Seattle & King County Public Health.


Before today’s pollution control practices were in place, all properties in a wide area discharged stormwater and wastewater into the waterway during heavy rains. The stormwater and sewage contained contaminants that settled into the sediment at the bottom of the river. The King County International Airport (Boeing Field), the County-run regional wastewater treatment system, and some leased County properties contributed to these releases. In 2000, the County started discussions on how to best address the pollution problems in the Lower Duwamish.

In 2001, the County, together with the City of Seattle, Port of Seattle, and Boeing, voluntarily signed an order with EPA to start the investigations to determine how best to clean up the waterway under the Superfund process. There are many other companies, businesses and local governments, known as “potentially responsible parties,” or PRPs, that also contributed to the historical pollution and will be part of the cleanup.

The County has worked for decades to restore the waterway by investing in habitat restoration, water quality improvement, pollution controls and sediment cleanups. These investments in pollution control and CSO reduction projects have successfully removed decades of contamination from some of the waterway's most contaminated areas. Read more about King County’s long-standing commitment to the Duwamish. 

Some of the challenges we face:

  • The impacts of the cleanup could have a big effect—positive or negative—on the region’s economic health. For more information read The Economics of Cleaning Up the Lower Duwamish Waterway.
  • The waterway receives inputs from 32 square miles of urban runoff and industrial drainage.
  • Water and sediment quality is affected by inputs from a 492 square mile watershed.
  • Some of the contamination found in the waterway comes from products commonly used by businesses and consumers, and can therefore still be found throughout our environment.
  • Some sources of contamination are still unidentified.
  • Other sources of contamination, including runoff and air deposition continue today.
  • Urban background levels of contamination will not allow the cleanup to fully achieve the cleanup's risk reduction goals.
  • The cleanup itself will affect local community, including historically underrepresented populations, for years.

Who pays the cleanup costs?

Under Superfund laws, cleanup costs are paid for by businesses and public agencies found by EPA to be responsible for the historical pollution. There are no federal funds to pay for Superfund cleanup.

King County and other public agencies will pass along their share of cleanup costs to the people who pay taxes and sewer utility bills. Private companies will need to factor cleanup costs into their business costs. It’s important to consider the impact cost will have on people in the region.

Protecting the environment, protecting jobs 

The Lower Duwamish cleanup should protect public health, the environment and our economy. Learn more about the cleanup’s potential impact on the region’s economy and the quality of life for people directly impacted by the cleanup activities.

When it comes to quality of life, environmental health and the economy are intertwined. Businesses are required to comply with strict environmental laws to keep our air and water clean so we can protect the natural resources our region is known for. Many businesses in the Duwamish corridor including manufacturing, shipping, and industrial plants are finding ways to reduce pollution, complete low impact development projects and increase wildlife habitat. 

A healthy environment supports a quality of life that attracts people, business and investment to our region. 

When it comes to cleaning up and protecting the Duwamish, King County’s goal is to make the Lower Duwamish the cleanest working river in the world. A successful cleanup will make the Lower Duwamish and area of choice for businesses. It can spur job creation in pollution cleanup, habitat restoration and other related “green collar” industries. King County and its partners encourage these kinds of local opportunities to strengthen our economy.

Who works in the Lower Duwamish?

The Lower Duwamish industrial area is a regional economic engine with more than 100,000 jobs and an annual economic output of $13.5 billion. Eight percent of King County’s jobs are located in the Lower Duwamish, along with one-quarter of all jobs associated with manufacturing, transportation and warehousing. The jobs generally pay above-average wages without requiring advanced education, making economic opportunity widely accessible.

Jobs in the Lower Duwamish depend on the area’s unique transportation and infrastructure framework that allows ready access to a major port, rail lines and airports. King County’s economic health depends on its ability to keep goods, services and people moving through this vital maritime port and transportation hub.

Will the Superfund cleanup work create jobs?

The Superfund cleanup work will likely create fewer than 1,000 seasonal jobs, most of these jobs will be based outside the Lower Duwamish Waterway area. Jobs associated with dredging will mostly be located outside the area at landfills where the dredged mud will be hauled. Habitat restoration following the cleanup will generate some construction and landscaping jobs.

The industries and businesses currently in the Duwamish industrial area will continue to be the primary source of jobs for the local community.

Additional reading

Equity and social justice

King County is prioritizing racial justice as part of our government work overall and implementation of our Equity and Social Justice (ESJ) Strategic Plan. We are intentionally leading with racial justice to confront the historical and racial inequities that continue to exist in our community and our organization. These racial inequities affect all of us and our ability to live well and thrive. Learn more about our commitment to racial justice.

For years, the communities in the Duwamish Valley have experienced documented inequities. King County conducted an independent Equity Impact Review (EIR) on the cleanup alternatives and provided it to EPA in its comments on selection the remedy. The EIR is a process and a tool used to identify, evaluate, and communicate the potential impact - both positive and negative - of a policy or program on equity. By looking at the outcomes of the alternatives using an equity lens, the EIR identifies project components that limit negative impacts on determinants of equity.

Additional links

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