Brightwater drill repairs to begin soon

According to information released by the King County Waste Water Treatment Division, measures to reduce pressure deep underground will allow repairs on Brightwater’s idled tunnel boring machine to begin in earnest the last week of June.

The machine is now approximately 340 feet underground and more than 1.5 miles into a two-mile segment of tunnel being built between Kenmore and Bothell as part of the Brightwater project’s 13-mile tunnel.

Construction on this portion of the tunnel will be suspended for several months while workers repair a worn structural rim on the machine’s 17.5-foot-diameter cutter head. Because of the machine’s current location, repairing the machine in place is the only feasible option, according to the county.

To simplify repair work and enable crews to work under atmospheric pressure deep underground, the contractor will install six dewatering and monitoring wells in the access road adjoining the staff parking lot of Maywood Hills Elementary School, which is located near the intersection of 104th Avenue Northeast and Northeast 195th Street in Bothell.

Performing the work under atmospheric pressure eliminates the need for time consuming decompressions each time repair crew members surface and increases the efficiency of the repair process.

The county and its contractors stated they would be working closely with the Northshore School District, the city of Bothell, permitting agencies and affected community members to keep them informed about project plans and progress.

The 350-foot-long slurry machine is manufactured by German firm Herrenknecht.

More information about the Brightwater Project is available at

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