CORRECTION: The information in this article, originally published June 24, 2009, was corrected June 24, 2009. The article Wednesday incorrectly reported that without depressurization workers would have to wear diving suits. Wells will be dug to reduce underground water pressure around a damaged tunnel-boring machine on the Brightwater sewage-treatment plant project so workers can fix the machine without being subjected to high pressure.

Jun. 24--A second tunnel-boring machine for the Brightwater sewage-treatment plant has broken down, causing the layoff of 67 workers, King County officials said Tuesday.

King County wastewater officials said the westbound machine, nicknamed Rainier, has a problem with a part known as the cutterhead rim.

It's not as badly damaged as the eastbound boring machine, known as Helene, which broke down last month and caused the layoff of 60 people. Nonetheless, repairs to Rainier, also known as BT-3, are expected to take months, according to Brightwater Project Manager Gunars Sreibers.

Rainier has completed about two miles of its four-mile journey from Kenmore to the Ballinger Way portal in Shoreline, where it will meet up with a tunnel segment bored by a third machine.

Four tunnel segments are being dug.

Sreibers said the latest tunneling glitch won't necessarily delay startup and testing of the $1.8 billion Brightwater plant beyond the current target of mid-2011. Wastewater-treatment officials are exploring the feasibility of testing the plant before the tunnel is completed rather than after completion, as was originally planned.

When it's finished, the 13-mile tunnel will carry treated sewage from the new treatment plant in Snohomish County north of Woodinville to Puget Sound off Point Wells.

The first machine, Helene, also known as BT-2, will be repaired after several wells are drilled 340 feet. That will reduce water pressure from soil around the machine so workers can work under normal atmospheric pressure. County officials are negotiating an agreement with the Northshore School District that would allow the contractor to start drilling the wells from a parking-lot access road at Maywood Hills Elementary School in Bothell on Monday.

Until the tunneling contractor, Vinci/Parsons RCI/Frontier-Kemper, completes a plan for fixing Rainier, which is 330 feet below ground, it isn't known whether wells will be dug or divers will do those repairs.

The shutdown of the two machines has temporarily idled about half of the contractor's work force.

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

The information in this article, originally published June 24, 2009, was corrected June 24, 2009. The article Wednesday incorrectly reported that without depressurization workers would have to wear diving suits. Wells will be dug to reduce underground water pressure around a damaged tunnel-boring machine on the Brightwater sewage-treatment plant project so workers can fix the machine without being subjected to high pressure.

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