This version is updated from the Dec. 7 print edition.
Regular sewer service for Magnolia residents will continue as normal as King County staff and contractors investigate a break in a county gravity sewer pipeline.
Located approximately 150 feet below the surface of the West Galer Street right-of-way, the broken pipe carries wastewater and stormwater to the Magnolia Wet Weather Storage Facility at Smith Cove when in service, to prevent combined sewer overflows from draining into Puget Sound during larger weather events.
Last week, county contractors began installing sensors to evaluate potential soil loss in the area of the break, in the Galer right-of-way between Northwest 28th Street and Magnolia Way West. In its most recent news release, the County said it has narrowed the location of the break to a 500-foot span of the 3,000-foot pipe.
Starting Wednesday (Dec. 7), contractors with the county will begin drilling holes approximately 130-feet deep to confirm the exact location of the break, with crews pumping grout into any areas of soil loss. During that work — which will occur between 9:00 a.m. and 3 p.m. on weekdays and until 5 p.m. on Saturdays through the end of the year — about 500 feet of the Galer eastbound traffic lane, sidewalk, and bike lane will close to traffic. The lane and sidewalk will reopen each day after work is completed, but steel plates that will cover active drill sites may extend into the bike lane.
Once that work is finished, a plan to repair the broken pipe will be developed. No timeline has been determined for those efforts.
The problem was first identified earlier this fall, when employees monitoring the storage facility determined that excess flows were not reaching the storage tank during the season’s first big storms. It was then found that there was soil blocking the pipe, and soil deposits in the underground diversion structures along 32nd Avenue West. When crews were removing soil from the pipe, they discovered pipe fragments, which indicated a break in the line.
While the pipe is being fixed, the system will operate as it did prior to the construction of the storage facility. In the event of a large storm that exceeds system capacity (an event which would make use of the pipe and storage facility), excess flows would continue south on 32nd Avenue West to the Magnolia Combined Sewer Overflow Outfall.
When the storage facility is online, the excess flows are diverted to a 1.5 million-gallon underground storage tank, and are later pumped out when there is more capacity in the system. After going online last December, the facility stored flows from January through March, when large storms stopped, and in that time there were no discharges into Puget Sound through the outfall. In comparison, untreated wastewater and stormwater was discharged into Puget Sound off of 32nd Avenue West in Magnolia more than 20 times in 2011 before the facility was constructed, resulting in more than 40 days in which the waters around the outfall would have been considered potentially unsafe for recreation.
For more information on the Magnolia Wet Weather Storage Facility, visit www.kingcounty.gov/environment/wtd/Construction/Seattle/SMagnoliaCSOStorage.aspx.