West Duwamish Wet Weather Storage

Project description

King County will build a 1.25-million-gallon underground storage tank near the intersection of Southwest Michigan Street and Second Avenue Southwest to hold stormwater and wastewater that currently overflows into the Duwamish River during large storms. The water in the storage tank will then flow to the West Point Treatment Plant for treatment before it is safely released into Puget Sound. This storage tank will reduce overflows and pollution into the Duwamish River. The County will also build supporting infrastructure underneath West Marginal Way Southwest.

The project has recently reached the 90 per cent design milestone. At 90 per cent design, the project details are determined including equipment, architecture, landscaping, and contractor documents (design drawings and specifications). The project team is now focused on finalizing design details and preparing for construction, which will begin in 2025.