The 1999 SMP evaluated remediation strategies for correcting hazards caused by contaminated sediments near seven King County combined sewer overflows (CSOs). These seven sites were identified when the Department of Ecology’s published its Confirmed and Suspected Contaminated Site List that first contained aquatic sites in the 90’s. The plan also addressed ways to evaluate and rank other areas of contamination that may be identified in the future.
The 2018 SMP Update identifies appropriate sediment management strategies adjacent to each remaining King County CSO outfall location. Sediment quality at other facilities is evaluated on a case-by-case basis in separate reports. This SMP update describes King County CSO discharge locations, summarizes ongoing and previously performed sediment cleanup work, and summarizes the results of CSO solids deposition modeling and existing sediment quality in the CSO discharge areas. This SMP update also evaluates alternative sediment cleanup options for the University Regulator Station (RS) Overflow area to incorporate potential cost implications of any cleanup required at the site into long-range planning.