Brightwater Conveyance System
Location: Seattle, Washington
Owner: King County, Wastewater Treatment Division
Market: Wastewater
Construction Cost: $435 Million (Approximate)
Construction Start/End: 2006/2010 (Estimated)
Jacobs Associates’ Role: Final Design and Project Management in Joint Venture with MWH, Preliminary Design as Subconsultant to HDR, Engineering Support During Construction
Responding to rapid population growth in greater Seattle, King County conceived Brightwater as a major improvement to the regional sewerage treatment system. The project also will bring important environmental benefits, such as controlling untreated overflows into Lake Washington and Puget Sound, and recycling sewage into irrigation water.
The conveyance system portion of this project consists of 13 miles of new bored soft-ground tunnels. These tunnels will connect about 335 miles of existing sewage pipes to a new 36-million-gallons-per-day treatment plant. From the plant, treated wastewater will flow to a new outfall in Puget Sound. Tunnel construction, currently underway, employs four 14- to 20-foot diameter tunnel boring machines, launched and retrieved via deep shafts in glacial tills well below the water table.
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