Damaged tunneling machine delays Brightwater opening

King County's Brightwater sewage-treatment plant, already behind schedule, will be delayed months more because one of four tunnel boring machines has been damaged, the Wastewater Treatment Division announced Friday.

About 60 employees were laid off by a tunneling contractor Thursday, and the contractor's tunneling machine will remain idle "for several months" while the contractor makes repairs 320 feet below ground level.

The $1.8 billion sewer plant, being built on Highway 9 in Snohomish County north of Woodinville, was expected to begin treating sewage in 2010 but its commissioning had been pushed back to September 2011 before this week's problem.

The damaged machine has been digging a two-mile segment of a 13-mile tunnel that will carry treated sewage from the plant to Puget Sound.

Brightwater Project Manager Gunars Sreibers said the joint-venture contractor, Vinci/Parsons/Frontier-Kemper/RCI, discovered "a significant amount of wear" on a structural rim on the 17 ½-foot-diameter machine that is boring its way from North Kenmore to North Creek in Bothell.

"The contractor really hasn't given us the detail in terms of the magnitude of the issue and how long it's going to take to repair it. That will happen next week," Sreibers said.

The machine was idled from December to March for maintenance and repairs, but the damage to its rim is new, Sreibers said. The used machine, known as BT-2, or "Helene," was rebuilt at German manufacturer Herrenknecht's factory.

Repairs are difficult so far underground because of high water pressure. Work on the face of the boring machines usually is done by divers working in a pressurized air pocket.

Divers can only work for a limited period and then must undergo lengthy decompression.

Sreibers said it isn't yet known whether the contractor will use the pressurized-diving method or will counteract water pressure by drilling wells to remove water from the work area.

Keith Ervin: 206-464-2105 or kervin@seattletimes.com