Brightwater Conveyance System
This contract is part of a $705 million project that includes an east tunnel, a central tunnel and a west tunnel for the Brightwater treatment plant. The conveyance system will connect existing sewage collection pipes to the treatment plant and convey treated wastewater to an outfall and diffuser in Puget Sound.
Construction of the east combined tunnel consists of about 14,000 feet of concrete segmented lined tunnel with a minimum inside diameter of 16 feet 8 inches. A special tunnel-boring machine will be used to create the tunnel to depths of up to 260 feet.
Kenny/Shea/Traylor will excavate a 74-foot-deep shaft that will be used to launch the tunnel-boring machine, install four pipes in the tunnel ranging from 27 inches to 84 inches in diameter, and install three fiber-optic cables to monitor the Brightwater facilities. Once the pipes and cables are installed, the tunnel will be backfilled with concrete.
A 2,400-foot-long micro tunnel will extend from the North Creek tunnel shaft to the existing North Creek pump station.
There are four construction staging areas, called portals, along the conveyance route.
In addition to the tunnels and pipes, the conveyance system will include pump, flow and odor control facilities. These will be located at one of the four portals and will become permanent facilities after construction is complete.
The North Creek portal site involves: an influent structure (IS) portal shaft, which will be about 74 feet deep and 80 feet in diameter, with slurry diaphragm walls 130 feet deep; and an influent pump station (IPS) with twin 84-foot-diameter cells, with slurry diaphragm walls 160 feet deep and concrete wall lining.
Two 40-foot-long connector tunnels will be located between the IS and IPS structures. They will have 12-foot-diameter steel casing for force mains and for influent connections.
The treatment plant portal site includes an access portal about 40 feet deep and multiple pipes.
Address: North Creek portal site at the corner of Northeast 195th Street and North Creek Parkway in Bothell tunneling to the Brightwater Treatment Plant site at the intersection of SR-9 and SR-522 in Woodinville
Cost: $130.65 million (award amount)
Type of contract: Hard bid
Start of construction: Early 2006
Expected completion date: 2010
Owner: King County
Jacobs Civil, 600 108th Ave.