King County Wastewater Treatment Division (WTD) proposes to install Green Stormwater Infrastructure (GSI) facilities to the maximum extent practicable to reduce the gray infrastructure demands needed for full Combined Sewer Overflow (CSO) control at the University Regulator Station Overflow. RKI is serving as the Interagency Permitting Lead, responsible for planning and obtaining SDOT Street Improvement Permits and other required construction permits.

King County Wastewater Treatment Division is updating their Combined Sewer Overflow (CSO) Long-term Control Plan (LTCP). As GSI Lead, RKI was responsible for basin planning to integrate GSI techniques, such as roadway bioretention, permeable pavement, and green alleys, with conventional gray storage facilities to develop alternatives for reducing stormwater contributions to the combined system and reducing the required size of gray storage facilities to meet the regulatory control standard.

The County Council requested a report from Road Services Division staff describing the location and condition of the County’s drainage trunk system within major road rights-of-way in unincorporated areas, the estimated accuracy of the resultant database, an analysis of the data to assess risks and impacts, and a prioritized program for maintenance. As Project Manager, RKI oversaw the condition and risk assessment of several thousand regional drainage assets and authored a strategic business plan to direct near- and long-term maintenance, repair, and renewal priorities.

The West Duwamish Combined Sewer Overflow (CSO) Control Project will control CSOs for King County’s West Michigan and Terminal-115 basins to the Washington State regulatory requirement of one-event per year on a rolling 20-year average. As Design Team Manager, RKI led the GSI alternatives analysis to identify and compare various combinations of grey and green technologies to achieve the control strategy and help protect the Duwamish River and Puget Sound.