The major siphon project to replace a pair of 75-year-old sewer pipes that run under Salmon Bay is underway. The old wooden pipes convey about 60-million gallons of sewage to the West Point Treatment Plant near Discovery Park every day. According to Annie Kolb Nelson with the King County Wastewater Treatment Division, the pipes are at the end of their lifespan.
An update sent out this morning by Water Quality Manager Doug Marsano states, “King County contractors have been preparing the Shilshole Avenue Northwest (north) and West Commodore Way (south) work sites for construction since July, and will begin mobilizing equipment and personnel at both sites in August.” Crews will dig vertical shafts at each site and the “contractor will use a tunnel boring machine to dig the new siphon?s pipe corridor roughly 60 feet beneath Salmon Bay. The existing siphon will be cleaned out and relined during this project, and support equipment for the new pipe will be installed at the Ballard Regulator,” according to the update.
A look at the pedestrian detour. For a larger map, click here (.pdf)
During construction, the northern sidewalk on Shilshole Ave NW between 20th Ave NW and NW Dock Place will be closed and other traffic detours will be necessary along Shilshole Ave NW on the north end of the project and W. Commodore Way on the south side.
Crews will typically work from 7 a.m. to 5:30 p.m. Monday through Friday, until construction is complete in late 2013.
Click here for more information on this project.