Contractors building two segments of a 13-mile-long sewage conveyance tunnel near Seattle have devised plans to fix in place two stalled tunnel-boring machines that had been working in poor soils and high groundwater pressure.
The tunnel is a key portion of King County, Wash.’s $1.8-billion Brightwater wastewater treatment project. The rims of the cutter heads on the 17.5-ft-dia Herrenknecht slurry machines were damaged, allowing rock and boulders to get stuck, says Gunars Sreibers, King County project manager. The general contractor, the joint venture Vinci/Parsons RCI/Frontier-Kemper, first stopped tunneling in May and laid off about 160 employees. The second machine was idled in June.