University Link light rail project update - January/February 2013

February 19, 2013

Passing the torch on Capitol Hill

In mid-March JCM, Sound Transit’s tunnel construction contractor, will turn over the Capitol Hill Station site to Turner Construction Co. Turner is building the station that will serve riders when the line opens in 2016. Concrete is already being poured inside the station box.

See what the Capitol Hill Station will look like when it’s finished (.pdf, 136KB).

Innovative formwork "unfolding" at Capitol Hill Station

Beginning this month, Turner Construction will use an innovative and time-saving approach to build the concrete walls and floors of Capitol Hill Station. A collapsible steel truss system will be lowered into the shaft where it will expand like an accordion to create the framework for the station’s thick concrete walls and floors. After the concrete for each section is poured, the forms will be collapsed, moved along a rail system and positioned for the next 40-foot section. This cycle can be repeated every four to five days including the time needed to cure the concrete.

This unique approach, proposed by Turner Construction, takes less time than conventional framing and allows walls on both sides of the station box to be completed at the same time.

As with any large concrete pour, the temperature of the concrete must be controlled as it cures. To aid this process, Turner will install a PVC piping system within the formwork. Water that re-circulates through the pipes will cool the concrete and help maintain a constant curing temperature.

This process is not widely used in underground construction, but with its innovation and significant time saving advantages, it may become more common.

Excavation finished at "Cross Passage 17"

University Link tunnel

Thanks to the Montlake community for its patience during the construction of Cross Passage 17, which has been underway 100 feet below the surface since July, 2012.

Montlake neighbors, families and the Montlake Elementary School staff have endured the presence of large equipment, traffic and parking revisions, well drilling and other surface work for longer than anticipated.

What is Cross Passage 17?
Cross Passage 17 is one of 21 horizontal tunnels, 18-24 feet long and about 10 feet in diameter, that connect the two University Link tunnels running between downtown Seattle and Husky Stadium. Cross passages provide emergency access as well as entry and exit between tunnels for routine maintenance.

Building Cross Passage 17 became very challenging when the contractor encountered more water than originally anticipated. To stabilize the area for mining, it was necessary to remove water from the ground surrounding the tunnel to give crews a safe working environment. For more than six months, generator-powered pumps removed water from soils around the tunnels. Today, Cross Passage 17 is nearly complete and work has turned to finishing the U-Link tunnels, including installing concrete duct banks, walkways, light rail tracks, power and signaling supply lines, tunnel lighting and communications systems.

On the surface, crews recently removed equipment and restored streets. Landscaping will be completed soon in order to return the location at 20th and McGraw to its original condition.

Construction at a glance

  UW Capitol Hill
Demolition 100% 100%
Station Excavation 100% 100%
Tunnel construction - TBM mining 100% 100%
Tunnel Construction – Cross Passage Excavation and Lining 100% 100%
Station construction 55% 0%
Power Systems & Track 0% 0%

U-Link Overall 61.62%