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Originally published May 15, 2013 at 9:41 PM | Page modified May 16, 2013 at 10:49 AM

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Curved rings for Seattle tunnel take shape at Pierce County factory

Concrete segments for the Highway 99 tunnel tube are providing 130 jobs at a new assembly line in Frederickson, near Tacoma.

Seattle Times transportation reporter

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FREDERICKSON, Pierce County — Like the statues of Easter Island, the wall segments of Seattle’s future deep-bore tunnel sit motionless in gray rows, across a vast lot.

They seem crude from afar, but each concrete arc is molded to precision, so that someday they can form a seamless, quake-resistant tube beneath downtown.

More than 14,000 tunnel segments are being built here in a new $20 million factory, providing more than 130 jobs, in an industrial zone surrounded by young firs and Scotch broom.

Contractor and government dignitaries gathered Wednesday to give speeches, munch green cookies shaped like the tunnel drill’s cutter head, and tour the plant.

“Our objective is to build legacy projects to the highest standard of quality and safety,” said Alejandro Canga, president of tunnel contractor Dragados West.

Workers and their machines are shaking, pouring, and baking the concrete along an indoor assembly line, called a carousel. Each segment is more than 6 feet wide and up to 19 feet long, and must be built to within 1/32 of an inch of specifications to fit properly.

The operation is quiet, except when a machine vibrates the slurry to remove air pockets that would weaken the arc.

“I’ve been working in this business for 30 years,” said Doug Myers, general manager for FPS EnCon Precast, which owns the segment plant. “The thing that makes this interesting to me, it’s just the level of technology.”

Geometry is the real star of this show.

Nine arcs plus a smaller keystone form a ring. Each ring is more than 6 feet deep and 56 feet in diameter. By bolting the segments into 1,450 rings behind the advancing drill, the underground crews in Seattle will build the 1.7-mile tube.

The amazing part is that using just one size of ring, engineers have designed a tunnel that curves.

This is because each ring is 2.65 inches narrower on the keystone side than the opposite side. By rotating each nonsymmetrical ring, Dragados can make the tunnel dive below the old Alaskan Way Viaduct, slither from the waterfront to below Pike Place Market, then come up for air while bending north toward Seattle Center.

The segments will be trucked from Frederickson to the tunnel’s launch pit in Sodo, and lowered 80 feet down by the pit’s white crane. A heavier red crane has been lowering the 41 parts of the giant drill, which arrived in April from Osaka, Japan.

The boring machine will begin grinding dirt in July, about one month behind the original goal. Still, the $2 billion tunnel is expected to open by the end of 2015 on schedule, said Chris Dixon, project manager for Seattle Tunnel Partners, led by Spanish giant Dragados and California-based Tutor-Perini.

Pierce County Executive Pat McCarthy described the segment-casting operation as proof her county is eager to recruit manufacturers. A new six-lane road runs past EnCon and other enterprises here.

“This tunnel should be stamped with the words, “Built in Pierce County,” she said. “It does my heart good to look at the sign behind us that says, ‘Now Hiring.’ ”

EnCon has about 25 jobs to fill, at starting wages ranging from $11 an hour for unskilled laborers, to $18-$20 for welders, said Myers. Applicants should visit the office, at the corner of Canyon Road East and 189th Street East.

The segment casting began in February and will last about 14 months. EnCon is looking for future casting jobs that can take advantage of what Myers called the nation’s most spacious segment assembly line.

Mike Lindblom: 206-515-5631 or mlindblom@seattletimes.com. On Twitter @mikelindblom

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