Sound Transit approves $225 million contract increase on East Link I-90 light rail project

March 27, 2017 1:30 am
Sound Transit tested the track bridge at an engineering firm in Pueblo, Colorado. Courtesy of Sound Transit.
Sound Transit tested the track bridge at an engineering firm in Pueblo, Colorado. Courtesy of Sound Transit.

Citing the engineering and construction difficulty of the world’s first light rail line on a floating bridge, Sound Transit’s board approved on March 23 a $225 million contract increase for the I-90 bridge project.

The board voted unanimously to increase the contract with construction group Kiewit-Hoffman, exceeding the agency’s original engineering estimate of $486 million.

This leaves $147 million left in reserves for the Eastside line and a remaining budget of $20 million for other construction in the I-90 corridor, according to a Sound Transit staff report to the board’s capital committee.

The contract increase includes a 7 percent contingency for Kiewit if needed. To see the contract amendment, go to www.soundtransit.org/sites/default/files/Motion%20M2017-30.pdf.

To safely transition light rail vehicles from the I-90 land bridge to the floating bridge, engineers and designers had to consider a number of factors in planning and construction, including six different ranges of motion from Lake Washington: up and down, back and forth and side to side.

To come up with a solution, Sound Transit designed and tested a “track bridge.” The track bridge includes having the rails rest on a series of bearings and plates allowing them to move with changing lake levels and bridge movements. Sound Transit partnered with Parsons Brinckerhoff and Jesse Engineering of Tacoma to design and build two full-scale prototypes. The materials for the track bridges can be found “on the shelf,” eliminating the need for custom materials.

The two track bridge prototypes, along with two Link light rail vehicles, were shipped for testing to the Transportation Technology Center in Pueblo, Colo. Once there, Sound Transit was able to mimic the forces and movements the track bridges will experience during normal and extreme conditions.

After collecting more than 500 channels of data during each light rail vehicle pass, the track bridges passed all critical test criteria with the ability to provide safe and comfortable light rail operations at planned speeds up to 55 mph the maximum operating speed for Link light rail.

East Link, approved by voters in 2008 as part of the Sound Transit 2 measure, is expected to cost $3.7 billion and open for service in 2023.