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King County to conduct in-water geotechnical work in Lake Washington’s East Channel


Boaters will see a barge, equipment and support crews on the north side of the I-90 Bridge for two or three days beginning Aug. 8, 2016, as King County’s North Mercer Island/Enatai Sewer Upgrade Project carries out geotechnical borings and underwater assessment in Lake Washington’s East Channel.


1603_NMercer-Enatai-rec-alternativeSummer boat traffic in Lake Washington’s East Channel will be a little tighter for two or three days in August as the King County Wastewater Treatment Division begins in-water work to replace aging pipeline running from Mercer Island to Bellevue.

King County is designing a project to replace about 14,000 feet of sewer pipeline extending from the North Mercer Pump Station at 7631 SE 22nd St. to the Sweyolocken Pump Station at 3100 Bellevue Way SE. Now in early design, the project is conducting field investigations on land and in water. Results from these investigations will inform project design.

Beginning Aug. 8, a geotechnical contractor will be performing borings in the East Channel of Lake Washington on the north side of the I-90 bridge. This work involves use of a 130- by 42-foot barge, equipment and divers.  Work hours will be from 7 a.m. to 7 p.m. and the barge will remain moored in place overnight. The barge will be launched and removed from Lake Washington from the Mercer Island boat launch. The boat launch will remain open, but delays of up to one hour may occur as the barge is launched and retrieved.

Work is expected to be complete within two or three days. The barge will be removed the last day of work if time allows, or the following day.

For more information about this important sewer upgrade project, visit

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 1.6 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.