Brightwater Treatment Plant Marine Outfall

Project overview

Vanir provided extensive preconstruction services, full construction management and inspection for this design-build marine outfall project, which won eight industry awards. Vanir’s quality assurance and quality control support covered onshore and offshore work, plus off-site locations for pipe fabrication. The project was completed two years ahead of the contracted completion date and within budget.

The outfall begins as an 84-inch inside diameter (ID) steel pipe connecting onshore to conveyance tunnels that extend back 12 miles to the treatment plant. Shortly after leaving the shoreline, the 84-inch ID pipe branches at a steel wye to two, 5,000-linear-foot, 63-inch outside diameter high-density polyethylene (HDPE) lines. The HDPE pipe terminates at a water depth of 600 feet in Puget Sound, with the last 250 feet of each pipe being diffuser pipe.

The onshore and near shore pipe was installed in an open-cut trench, which was sheeted up to a water depth of 30 feet and unsheeted thereafter to -80 Mean Lower-Low Water. From 80 feet deep to the end of the line, the HDPE pipe was bottom laid. Over a 72-hour period, the two preassembled HDPE lines were floated into place and installed using controlled submergence by flooding the pipeline while it was under 60 tons of tension.

A project that was stellar from one end to the other and will certainly go into my career highlight reel. You folks made a huge contribution to that success and I thank you.

– Jeffrey Lundt, PE, Principal Wastewater Engineer, King County


2009 ENR – Best of the Best Heavy Civil Projects | APWA, Northwest Chapter – Project of the Year | Society of Civil Engineers Seattle Section – Structural Engineering Honor | 2009 Consulting Engineers of British Columbia – Award for Engineering Excellence | 2009 CMAA – National Project Achievement Award | NWCCC – Distinguished Project Award (Honorable Mention) | 2009 Northwest Construction Magazine–Best Civil Project | ACEC Washington – Engineering Excellence Gold Award

Woodway, Washington
King County Wastewater Treatment Division
Design-Build Engineer

Dayton & Knight

Design-Build Contractor

Triton Marine

Construction Cost
$29.8 Million
Start Date
Completion Date