Currently there are two proposed alternative locations for the new plant - either within the City of Edmonds or a site near Route 9 in Snohomish County north of the City of Woodinville. Alternate conveyance corridors have been developed for each site and have been included in the Draft Environmental Impact Statement (DEIS) Scoping Notice. As part of the siting process, two alternative outfall locations between Edmonds and Shoreline also have been identified.
Depending on the selected treatment plant site, the conveyance facilities will consist of between 12 and 20 miles of tunnel and micro-tunnel sections. The conveyance tunnels will vary in diameter from 6 to 14 feet to convey flows of up to 170 million-gallons-per day to the new Brightwater treatment plant. Conveyance facilities will also include surface pipes or micro-tunnels to connect existing King County interceptors to the new Brightwater conveyance system.
The predesign contract includes services for the completion of the environmental, permitting and corridor selection process from the DEIS through the Final Environmental Impact Statement (FEIS) and engineering predesign. Engineering services include up to 25 percent predesign for the selected land-based conveyance and marine outfall systems.
Source: HDR
