About 300 feet underground and six miles from Point Wells, a milestone is being reached: Tunneling for the Brightwater sewage-treatment plant is nearly complete.

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UNDERNEATH LAKE FOREST PARK — Down 300 feet underground where the wind never blows and the world is just 13 feet in diameter, encased in concrete, a milestone is being reached: Tunneling for the Brightwater sewage-treatment plant is nearly complete.

In all, four machines in four tunnel sections have been needed to complete the work. For the last piece, one machine traveling east from Point Wells is within 100 feet of meeting up with the tunnel bored from the west.

Concrete tunnel liner is erected behind the machines as they move forward, completing the tunnel section by section.

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It’s been an unusually challenging job. The tunnel is being mined not through rock, but through soft ground with variable soils.

“Foot to foot, day to day, you don’t know what you are going to encounter,” said Gregory Hauser, project manager for Jay Dee/Coluccio, one of the contractor teams on the job. And the tunnels in places are quite deep, burrowing as much as 425 feet down.

Workers also endure an otherworldly environment. For the last section where they are now working, it takes 40 minutes just to travel the six miles underground to reach the tunnel-boring machine. They travel on a tiny train pulling metal cars with open sides, rumbling ever farther into the earth, on bumpy temporary train tracks laid in the curved floor of the completed tunnel.

Working underground all day in dim fluorescent light, with air provided by a shaft from the surface, theirs is the life of miners who don’t see the sun. They work 10-hour shifts and make a base pay of about $32 an hour.

“Keep your hands inside the ride,” said Ken Rossi a foreman for EPC, a consultant on the Brightwater job, as he hopped on the train for a trip deep into the tunnel Tuesday.

Tunnel workers are a close-knit clan, he noted, with many intergenerational family teams of workers. Rossi followed his grandfather underground, starting out more than 30 years ago in coal mines in Colorado.

“It’s safer and cleaner than coal mining,” Rossi said, seemingly right at home as the train clack-clacked deeper into the gloom.

Tunneling is just one piece of the construction work required to complete the entire conveyance system to bring wastewater to the Brightwater plant, just north of Woodinville, and carry treated sewage to an outfall in Puget Sound. Construction of the conveyance system began in 2006, and the system is expected to be in use in August 2012.

The plant itself will begin treating wastewater in September, using existing pipelines to outfalls from King County’s other two wastewater-treatment plants, in Renton and at Westpoint, next to Seattle’s Discovery Park.

This project has had its share of drama. The westbound tunnel-boring machines ground to a halt at about Lake Forest Park. Construction on that portion of the tunnel was suspended in May 2009, when inspection revealed the machine was irretrievably crippled. Just why and who’s to blame will be disputed with the county by the contractor team Vinci, Parsons and Fronteir-Kemper in court. About $206 million in disputed costs will be litigated.

To get the project back on track, the county in April 2010 elected to hire the eastbound tunnel contractor, Jay Dee /Coluccio, to tunnel an additional two miles toward the stopped machine. Contractors are expected to “hole through” to the place where the machine broke down, connecting the two tunnels, by about Sept. 1.

Most of the stopped machine has been cut up and carted away, with its shell remaining to keep the tunnel’s shape. To complete the tunnel, contractors are freezing the soil around the shell of the stopped machine. Super-chilled brine is being pumped in 35 holes to a depth of 320 feet, basically encasing the shell in ice, Hauser said.

That keeps the ground from collapsing so workers can lay the last pieces of tunnel liner that will connect the two tunnels, completing the job.

“It’s exciting to see,” said Gunars Sreibers, project manager for the $1.8 billion project for King County.

The total length of the tunnel with all four pieces is 13 miles, from the Brightwater treatment plant to Point Wells. From there, an outfall pipe will extend one mile offshore, 600 feet deep, to release treated wastewater.

On a tour of the tunnel Tuesday to assess progress, Sreibers was pleased by how tightly and well the pieces of concrete in the tunnel fit together, a sign workers didn’t have to struggle to assemble the segments. “This is a major milestone for us,” he said. “We are on the verge of making that final connection, and completing the overall Brightwater system.”

The new plant will serve portions of King and Snohomish counties.

Lynda V. Mapes: 206-464-2736 or lmapes@seattletimes.com

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