SEATTLE - BRIGHTWATER
OWNER: King Country
LOCATION: Bothell, Washington
VALUE: $130 Million
This project is part of a $705 million wastewater conveyance system which will include an east tunnel, a central tunnel and a west tunnel. The east segment of the conveyance system consists of 14,050 feet of concrete segmentally-lined tunnel with an inside diameter of 16 feet 8 inches.
An Earth Pressure Balance Machine (EPBM) will be used to bore a tunnel approximately 18 feet in diameter to depths of up to 260 feet below the surface. The project lies near the north end of the Seattle Basin which is filled with Late Tertiary sedimentary rock and Quaternary sediments. The project includes excavating a 74-foot-deep shaft that will be used to launch the EPBM, installing four pipes in the tunnel ranging from 27 to 84 inches in diameter, and the installation of three fiber optic cables to monitor Brightwater facilities. The tunnel will then be backfilled with concrete.
The North Creek Connector will include a 2,400-foot-long microtunnel from the North Creek tunnel shaft to the existing pump station, and excavation of an 83-foot-deep double shaft for a new Brightwater system pump station.
The North Creek Portal includes a 74-foot-deep, 80 feet in diameter influent structure portal shaft with slurry diaphragm walls 130 feet deep, tremie slab, and final concrete wall lining. Also included is the excavation of a influent pump station approximately 83 feet deep, twin 84-foot diameter cells, with slurry diaphragm walls 160 feet deep and two connector tunnels approximately 40 feet long between the IS and IPS structure with 12 foot ID steel casing for the force mains and influent connection.
The treatment plant portal site includes an access portal approximately 40 feet deep with multiple pipes approximately 143 feet long.