Boeing Creek Siphon Temporary Bypass Slope Stabilization

Owner: The Highlands Sewer District

Client: John Harris, Commissioner  |  The Highlands  |  Shoreline, WA

The District’s sewer system is located below the ground surface, except the inverted siphon, which extends over Boeing Creek at the north end of the District boundaries. Heavy rainfall in November and December 2007 saturated the soils in the Puget Sound region. Soil movement was noted and preliminary geotechnical engineering options were made in January 2008. CHS was asked to help prepare a Capital Facilities Plan, an Emergency Loan Application for Public Works Trust Fund and to oversee the alternative solutions for the project. CHS designed the temporary and final replacement for the existing sewer siphon which was constructed prior to the wet weather season. Rights-of-Entry were obtained from property owners along the proposed alignment. Two project alternatives were reviewed prior to construction of a wire-truss structure and spiral-nail layout designed to hold the slope in place along the south side of Boeing Creek. The project included the installation of a log crib wall adjacent to the Creek. CHS provided construction management support, project coordination and permits, including a Hydraulic Project Approval (HPA) by WDFW.

Public Works Emergency Loan
April 2008-December 2009
CHS Staff:
Scott Christensen, P.E., Principal-in-charge
Darrel Frame, P.E., Project Engineer

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