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King County investigating damaged sewer pipe in Magnolia

Summary

King County is investigating a break in a pipe that carries combined wastewater and stormwater flows to the County’s Magnolia Wet Weather Storage Facility near Smith Cove in Seattle. A plan to repair the broken pipe will be developed once the exact location of the break is confirmed.

Story

Crews with the King County Wastewater Treatment Division are investigating a break in the gravity pipe that carries combined wastewater and stormwater flows to the County’s Magnolia Wet Weather Storage Facility, located near Smith Cove in Seattle.

Beginning Dec. 1, workers with ground monitoring equipment will be present along a portion of West Galer Street in south Magnolia to collect data on soil conditions in the area of the broken pipe.

The week of Dec. 5, King County’s contractor will mobilize a drill rig to address soil loss along the pipeline.  This work will result in one-lane traffic along a short portion of West Galer Street. A repair plan can be developed once this work is completed.

Operational since December 2015, the storage facility is designed to store mixed wastewater and stormwater during large storms to prevent combined sewer overflows (CSOs) into Puget Sound.

An underground structure on 32nd Avenue West diverts excess flows from the sewer system to a 3,000-foot-long pipe that leads to a 1.5 million gallon storage tank near Smith Cove.

The Wet Weather Facility operates during large storms, primarily during the fall and winter rainy season, and stored flows from January until this past March. Earlier this fall, King County employees monitoring the facility found that the pipe was not conveying excess flows to the storage tank during the season’s first big storms.

Further investigation revealed soil blocking the pipe and additional soil deposits in the underground diversion structures along 32nd Avenue West.

While removing soil from the pipe, crews discovered several pipe fragments, indicating a break in the line. At this time, the location of the broken pipe has been narrowed to a 500-foot stretch of the pipe along West Galer Street east of 28th Avenue West in south Magnolia. The pipe is located about 150 feet below the surface at this point.

Once the County addresses soil loss above the pipe, crews will continue cleaning soil from the pipe to locate the break, and then develop a repair plan. The County will keep the public up to date on findings, work activities, and progress.

King County has notified the Washington State Department of Ecology that the Wet Weather Storage Facility will not operate to control CSOs during the investigation and repairs.

The County’s sewer system will continue to provide service to the Magnolia community, operating as it did prior to the addition of the Wet Weather Storage Facility.

Additional information about the Magnolia Wet Weather Storage Facility is available at kingcounty.gov/environment/wtd/Construction/Seattle/SMagnoliaCSOStorage.

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People enjoy clean water and a healthy environment because of King County's wastewater treatment program. The county’s Wastewater Treatment Division protects public health and water quality by serving 17 cities, 17 local sewer districts and more than 1.7 million residents in King, Snohomish and Pierce counties. Formerly called Metro, the regional clean-water agency now operated by King County has been preventing water pollution for nearly 50 years.