BRIGHTWATER CONVEYANCE TUNNEL
King County, Washington
Brightwater Conveyance System consists of approximately 14 miles of pipeline built in underground tunnels. These tunnels range from 40 to 440 feet below the surface. Along some parts of the system there is only one pipe within each tunnel section. Other tunnel sections will have multiple pipes. Almost the entire Brightwater conveyance system was built using tunnel boring machines (TBMs). There were four construction staging areas, called portals, along the conveyance route where the TBMs were lowered into the ground, excavated material was removed, and personnel, materials and equipment entered and left the tunnel. This method of construction limited surface impacts along the conveyance route, since most of the construction activity was centered at the portals and the treatment plant site.
Approximately one mile of the system was built using micro-tunnel or surface cut-and-cover methods. Construction of the conveyance system was divided into different construction packages, each with its own construction schedule lasting from 2 to 4 years. The earliest conveyance construction work began in early 2006, though pre-construction activities such as clearing and demolition started earlier.
In addition, pipes, tunnels, pumps, flow and odor control facilities, and electrical and monitoring equipment were needed for the conveyance system. These were located at one of the four portals and became permanent after the construction was complete. Many of the facilities were below ground. EPC provided project controls, cost estimating and document control services on this project.