City and SPU Agree on Pipe Repair Plan, Initial Inspection Begins

After several weeks of close coordination and analysis, the City of Mercer Island and Seattle Public Utilities (SPU) are planning for a repair to the 24-inch water pipe that has been out of service since April 3.

A traditional repair of the pipe is challenging due to the site conditions. The location of the leak is on a very steep slope, in a difficult area to access with no adjacent roadway. As a result, SPU has proposed a liner solution that will insert a flexible liner inside the existing pipeline, spanning a total of 1,100 feet.

This approach does not require excavation on the slope. Instead, the liner will be inserted through two access points to the east and west of the leak location. When the liner is installed, it will include a leak detection system to ensure a rapid response if there is ever a subsequent issue with the pipe. Geotechnical engineers from the City and SPU have been closely evaluating the stability of the slope in considering this repair option to ensure the community’s safety.

This week, staff from SPU and outside contractors completed the excavation of the west access point. This work allowed the contractor to complete the first of two video inspections of the 24-inch pipe. SPU and the City are currently reviewing the video to learn more about the cause of the leak.

Once the City completes its review of the design, video inspection, and site reports, the repair will be scheduled for construction in early July.

If you have questions about this project, please contact the City’s Customer Service Team at 206-275-7600.