King County’s Murray Combined Sewer Overflow (CSO) Control Project involved construction of a 1-million gallon underground storage tank across from Lowman Beach Park along Beach Drive Southwest in Seattle. The purpose of this 6,000 square foot tank is to prevent storm water and raw sewage from overflowing into Puget Sound during heavy rains. Working with general contractor, Shimmick Construction, Malcolm installed a 96-foot diameter vertical access shaft wet well to serve as the earth retention system for the massive tank, as well as the secondary structural wall for the actual tank structure. The access shaft was constructed of a compression ring system secant wall, consisting of 100 secant piles 98.5 feet deep.
This underground storage tank now works to monitor flows at the Murray Pump Station, and protects the public health, environment, and economy of millions of King County residents.