Seattle Public Utilities continues to asses stormwater runoff in Ballard.
Starting on Oct. 20 SPU will be replacing one of the combined sewage overflow pipes located west of the wooden pier at the end of 24th Avenue Northwest (NPDES 150).

The old pipe was constructed in the 1930’s and is one of the few outfall pipes that carry stormwater into Salmon Bay. A major problem is when it rains more than a tenth of an inch, stormwater mixes with raw sewage, overwhelming Ballard’s combined sewage system. 10 percent of the mix that spews into the Bay is raw sewage.

Project Manager Jerry Waldron shared details on the project.
“The Combined Sewer Overflow (CSO) Pipe, known as CSO Outfall 150, was installed in 1935 underneath the pedestrian pier at the dead end of 24th Avenue Northwest. It is a 30” wood-stave pipe that has deteriorated over time and its purpose is to release sewer overflows during heavy rain.”

Last November SPU reported that the outfall pipe originally extended about 62 feet from shore but has deteriorated to about ten feet. That same month Outfall pipe150 (which shares the same overflow point with pipe 151), the pipe was responsible for spilling 3,350,000 gallons of sewer overflow into Salmon Bay.
In 2013 Ballard accounted for over one-third of the entire city’s overflows. In addition, that same year year Ballard overflowed 58 times, totaling 14.9 million gallons of combined sewage.

“Seattle Public Utilities determined that the outfall no longer functions as designed and is not long enough to comply with the Department of Ecology’s NPDES Waste Discharge Permit. This project will replace the wood-stave pipe with a  30” high-density polyethylene (HDPE) pipe. The new pipe will be supported by piles in City right-of-way next to the pier.” 
 
Work will begin the week of October 20, 2014 and is expected to last four to five weeks. Normal work hours will be 7 a.m. to 6 p.m., Monday through Friday.
During the project there will be no boat or pedestrian access to the pier near Pacific Fisherman Shipyard. There will also be street closures, fewer parking areas available for automobiles. The scene is anticipated to be a controlled bedlam of noise, dirt, and vibration from pavement excavation and is scheduled for completion by December 31, 2014
The pipe is estimated to function for the next 60 years with cleaning and environmental impact assessments every five.

“The direct intent of this project is to comply with the Department of Ecology’s NPDES Waste Discharge Permit, rather than the EPA Consent Decree.”

Although the project is not specifically intended to prevent overflows, the pipe does need replacing to operate the way it is intended.

“Future projects that address the EPA Consent Decree typically provide storage or sewer pipe repairs to reduce the number of combined sewer overflow events into water bodies surrounding the City.”

The EPA Consent Decree stipulates having no more than one overflow per outfall pipe by 2025. To reach this goal, they are building raingardens in 2015 along streets in Ballard and eventually a stormwater storage facility near Salmon Bay. The facility will work like smaller underground vaults being used to manage stormwater. The vault would hold the flow until the storm passes and then meter it back into the sewer system to the treatment plant. Currently, SPU is testing soils to find places where such a facility could be built.
West Point Sewage Treatment Plant in Magnolia treats the water and it's transported there via Ballard Siphon, which was retrofitted earlier this year. WPSTP treats around 90 million gallons of sewage a day during the dry months, and up to 440 millions during the rain/storm season.