Capitol Hill Station Key Point for ST Tunnels by JOURNAL STAFF

August 31, 2010

Capitol Hill station key point for ST tunnels By JOURNAL STAFF

Photo courtesy of Sky-Pix, www.sky-pix.com [enlarge] The braces at the lower end of the site consist of struts to provide excavation support and support beams that help utilities span the opening.

JCM U-Link Joint Venture, the contractor on the Seattle light rail tunnel between Capitol Hill and Pine Street in downtown, has excavated approximately 25 percent of the Capitol Hill station box, Sound Transit officials say.

The public can monitor the project's progress on a web cam that Sound Transit launched earlier this month. A second cam is trained on the Husky Stadium light rail station. The cams can be accessed in the Projects & Plans section of soundtransit.org.

Ultimately, the Capitol Hill contractor will excavate around 100,000 cubic yards of material from the hole that will be approximately 80 feet deep, 540 feet long and 80 feet wide. As part of its $153.6 million contract, JCM is taking the spoils to different locations in the region.

JCM is made up of two Midwest companies — JayDee Contractors and Michaels Corp. — and Frank Collucio Construction of Seattle.

When the Capitol Hill excavation reaches the bottom of the station box, the contractor will pour a 10-foot-thick concrete slab, and a tunnel-boring machine will begin working on the first of the twin tunnels. The TBM is expected to excavate 40 feet a day. As it goes, the machine will place concrete rings that will form the exterior surface of the tunnel. Upon reaching Pine Street, the machine will be taken apart and transported back to the station, where it will be put back together to dig the second tunnel.

The length of the tunnels is just under three-quarters of a mile. Tunneling is expected to last through the end of 2012 with station construction starting in early 2013 and lasting two and a half years.

Sound Transit plans to ask state officials for permission to use the general contractor/construction manager construction method on the station, which Hewitt Architects is designing. If the state gives its OK, the request for proposals will go out next year.

The contractor on the 2.4 miles of tunnels between Husky Stadium and Capitol Hill is a joint venture of two Indiana-based companies, Frontier-Kemper Constructors and Traylor Bros. The JV bid $309.18 million. In early 2010, crews installed electrical infrastructure and now is prepping the site to start excavating the station box this fall. Tunnelling is scheduled to begin in mid-2011.

Construction of the Husky Stadium station, which LMN Architects is designing, is to start next year and last through 2014. Hoffman Construction Co., was hired to provide pre-construction services. Sound Transit will negotiate a general contractor/construction manager contract for the station with Hoffman.

The tunnelling work and stations are part of the $1.9 billion U Link, a 3.15-mile project between downtown and Husky Stadium. The line is scheduled to open in 2016. Northlink Transit Partners, formed by Jacobs Associates, Aecom and HNTB, is the U-Link designer.