SPU to begin assessing sewer overflow at 24th Ave NW
In the week of Jan. 28, Seattle Public Utilities will begin assessing the combined sewer overflow area at the end of 24th Ave NW.
The overflow, NPDES 150, is one of the big problem spots in Ballard which gushes out sewage during a storm event. (We covered this more in detail in a cover story a couple of weeks ago.)
Turns out, the pipe is old. It's a 30-inch diameter wooden pipe which can't handle the combined volume of stormwater and sewage, allowing raw sewage to gush into Salmon Bay during storm events. the outfall pipe originally extended about 62 feet from sure, SPU said, but it's deteriorated so severely that now it only extends about ten feet.
In November, along with NPDES 151 (which shares the same overflow point), the pipe was responsible for spilling 3,350,000 gallons of sewer overflow into Salmon Bay.
Workers will be setting out to fix this problem by replacing the pipe. But first they have to do an environmental sampling and conduct a geotechnical investigation at the foot of 24th Ave NW. Workers will take boring samples from bay sediments and from the immediate upland area. That data will be used for the preliminary engineering of a project to replace the existing pipe and install a new manhole just upland from it.
Workers will start the week of Jan. 28 by marking underground utility locations. They will then take samples and testing Feb. 4–15, 8 a.m. to 6 p.m.
All work on the pipe will be in the public right-of-way, SPU said, and is currently scheduled for the summer of 2014.
Access to the pedestrian dock out onto Salmon Bay will remain open. Expect some increase in truck traffic, somewhat restricted pedestrian access and noise.
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