Frequently asked questions
What is sediment?
Sediment is material deposited on the bottom of streams, rivers, lakes, and bays. Sediments can come from surface water runoff, a pipe, or from upstream locations where loose bottom material mixes with flowing water.
How do sediments get contaminated?
Contamination or pollutants in sediment can come from a variety of sources. Heavy metals (such as copper and zinc) and oils (polycyclic aromatic hydrocarbons) can come from automobiles. Other chemicals (such as PCBs) can come from industrial discharges that took place years ago or from yards and streets where people use chemicals (pesticides and fertilizers). Some pollutants found in sediment can date back to times when there wasn't wastewater treatment or containment of polluted discharges. Others are in the air and dust that get deposited on the ground and washed into our waterways.
In general, the pollutants come from all of us. Each person can contribute to the pollution found in sediments by many common things we do in living our daily lives.
Who regulates contaminated sediments in Washington?
Where are cleanup sites located?
The seven sites identified to data are located on the Seattle Waterfront in Elliott Bay or in the Duwamish Waterway.
Who is responsible for the cleanup?
King County has taken the responsibility to implement the clean ups identified in the Sediment Management Plan
. King County continually explores ways to partner with other agencies and projects that have interest in the clean up areas.
How much will the cleanups cost?
The current estimate to clean up sites King County has identified is $35 million dollars.
How are the cleanups paid for?
King County will pay for the clean ups under the Model Toxics Control Act (MTCA) program. Because a lot of the clean up entails historical contamination, there is a state fund
to cover ½ of the costs of clean up for municipalities.
How long does it take to clean up a site?
Sites that are manged by King County may generally take 2-3 years to clean up. Sites that fall under a federal or state clean up program may take longer
Are the sites monitored after the cleanup is completed?
Yes. King County monitors sites for at least 5 years to determine if any recontamination has occurred. Each site presents different circumstances, so monitoring periods may vary. Monitoring reports are available in the each of the projects' libraries
Are the CSOs controlled before the clean up can start?
Due to King County's industrial waste program, industrial wastewater is controlled in the combined sewer system and sent to West Point for treatment. Based on studies by King County and other groups, sites that have been cleaned up have a very low likelyhood of recontamination from CSOs. Since the CSO control program will take longer to implement, it is important to remove the historical contaminants like PCBs and mercury sooner rather than later.