King County Ballard Siphon Replacement Project

Seattle, Washington

Project Type

Civil, Wastewater, Water, Utilities, Siphon, Tunneling, Vertical Drilling, CM

SCL Project Role

Document Control Management, Scheduler

Project Description

King County Department of Natural Resources Wastewater Treatment Division plans to build a new 84-inch siphon pipe under Salmon Bay between the Ballard and Interbay areas of Seattle, WA. The new pipe replaces two 36-inch wooden stave pipes which have served the Ballard community since the 1930’s. The new siphon will be installed more than 120 feet underground and connect the Ballard Regulator Station at 5110 Shilshole Avenue Northwest in Ballard to the North Interceptor at West Commodore Way and 24th Avenue West intersection in Interbay. A Herrenknecht Vertical Shaft Machine (VSM) will be used to drill the launch shaft making this the first time this type of shaft technology will be used in North America. The Herrenknecht VSM robotically constructs tunnel shafts by precisely controlling the descent of the precast liner segments, allowing construction of deeper shafts without dewatering in high groundwater areas and without manned entry. The new pipe will accommodate extensive growth in north Seattle and will meet north Seattle’s wastewater conveyance needs through the end of the century.

Scope of Work

Collaborating with the prime on the 1st Vertical Tunnel Boring Machine in North America for Siphons, SCL was selected to provide project control services during the construction phase from startup to closeout. These included scheduling, scheduling analysis document control, data management and office administration services.