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Mon, Dec 22, 2014




Updated Friday, November 23, 2012 at 08:57 PM

Work nearly complete on assembling Highway 99 tunnel drill

By Mike Lindblom
Seattle Times transportation reporter

Workers in Osaka, Japan, are almost done assembling the world-record, 57.5-foot diameter drill that will churn beneath downtown Seattle next year, to form the Highway 99 tunnel.

On Nov. 29, the giant cutter head will be hoisted and attached to the front of the cylindrical machine, longer than a football field. The team at Hitachi-Zosen will test the machine before the Washington State Department of Transportation formally accepts it at a ceremony in December.

Construction of the drill is on schedule, said Chris Dixon, project director for Seattle Tunnel Partners.

The drill will be dismantled into 41 sections and shipped to Seattle's Terminal 46 in March. Crews here will lower the parts into a huge pit in Sodo. Drilling of the two-mile tunnel is scheduled to start in June.

The first few months will be the trickiest, as the machine crawls through weak fill soil, then beneath the old Alaskan Way Viaduct and Pioneer Square's brick buildings. Hundreds of concrete pillars are being poured to create buried walls on either side of the machine's path, to reduce vibration risks nearby.

Breakthrough is scheduled at South Lake Union by October 2014, with traffic to use the four-lane toll tunnel by the start of 2016.

Some fiscal problems remain unsolved, notably the state's realization that tolls cannot fund as much of the project as once predicted. Also, downtown Seattle is too crowded to absorb the traffic that is expected to steer clear of the tunnel tolls, even if set at a range of $1 to $2.50. More fuel-tax money may be required to fund the project.

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

See more photos

Check out more of the work in Japan:

Workers in Osaka, Japan, are nearing completion on the assembly of the world-record 57.5-foot-diameter drill that will bore beneath downtown Seattle to create the Highway 99 tunnel.

The boring machine's cutter head has teeth on its eight spokes to grind through the soil and will be fitted with cutting tools on the face.

Workers at the Osaka, Japan, site are dwarfed by the rotary joint, which will spin the world's largest tunnel cutter head at about 3 rpm.


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