The work is part of a $7.5 million project for the west Pasco water treatment plant and includes two 250-hoursepower pumps, each with a capacity of six million gallons a day. Shannon & Wilson provided construction observation of shoring (i.e., secant pile wall), microtunneling, and dewatering elements.

The project included: 

• An approximately 85-foot-deep secant pile shaft which will house 25 1/2 -foot-diameter wet well upon completion. The secant pile wall specifications require minimum 30-inch-diameter individual shafts overlapping such that a minimum eight-inch-thick wall is achieved within the overlap sections.
• A 48-inch diameter, approximately 227-foot-long intake pipeline extending beneath the Columbia River to the wet well.
• A screen structure over the intake pipeline within the Columbia River.
• A control building constructed over the secant pile shaft/wet well footprint.