University Regulator Station Overflow Sediment Remediation Project

The University Regulator Station (RS) Overflow is identified as a site where cleanup may be necessary under the County's 2018 Sediment Management Plan. The plan evaluates remediation strategies for correcting hazards caused by contaminated sediments near King County combined sewer overflows (CSOs).

King County performed a preliminary evaluation of cleanup alternatives  for the University Regulator Station Overflow as a part of the 2018 Sediment Management Plan update. This will help King County incorporate the potential cost implications of any cleanup required at this site into our long-range planning.

King County is beginning a Green Stormwater Infrastructure (GSI) project that will install facilities to help control the overflow into Portage Bay through the University Regulator Station Overflow. The project team has been studying soil, groundwater, surface water flow, and street conditions in the project area to identify the best locations for facilities to be installed.

In this first phase of the project the County will consider what types of green stormwater infrastructure it should build, and where within the study area they should be installed. Some options include different types of bioretention and permeable pavement in alleys or streets.

GSI will be combined with storage to complete the CSO control project. Following GSI and before we design and construct the storage tank (planned to begin in 2022), King County will characterize and trace sources of contamination and reassess the potential for recontamination after cleanup. This information could be used to inform the development of a Cleanup Action Plan and a preferred cleanup alternative.  Modeling suggests that cleanup activities should not begin until the storage tank is constructed, to minimize recontamination potential. This assumption can be revisited following GSI completion and further source characterization.

University Regulator Station Overflow

The University Regulator Station discharges from the east side of Portage Bay. This overflow will be controlled by 2028 either through a joint King County-City of Seattle 5.23 million gallon storage tank that would also control three City of Seattle CSO sites or through a County project that would construct a 2.94 million gallon storage tank. In addition, King County will implement Green Stormwater Infrastructure in the basin to enhance CSO control.