Watch Sound Transit build elevated light rail trackway

  Look for this video on the ST Facebook page
Photo courtesy Sound Transit

A new time-lapse video that compresses eight hours into three minutes offers a visually stunning answer for anyone who has wondered how a new section of elevated light rail trackway can go up so quickly.  

The video showcases construction of the aerial trackway for the future Angle Lake light rail station. Rather than the more typical bridge construction method of pouring concrete, crews are making shorter work of the 1.6-mile light rail extension between the airport and South 200th Street by using a long crane known as a gantry to lift and thread together 35-ton pre-cast concrete segments. 

The video is on the Sound Transit Facebook page - click the arrow in the photo with the first story.

The time-lapse footage (8 hours in 3 minutes) shows crews using the massive crane to lift and suspend the segments while they are connected with heavy-gauge steel cables and epoxy. Thirteen segments make up a span of trackway, and 1,166 segments are being cast for the job. Around 20 to 30 segments are cast each week in Enumclaw, loaded onto trucks and transported to the construction site. Sound Transit and contractor PCL Construction used precast segments to build the elevated trackway between Seattle and the airport.

Local residents can expect to see the same technology at work for the elevated sections of the Lynnwood Link through Shoreline.

Tracks will start as elevated heading north from Northgate Station and will be elevated again over freeway interchanges at NE 145th and NE 175th. Being elevated at these interchanges allows them to reduce the impacts to these very busy intersections by not disrupting them and having to rebuild them. 

Both the vehicle and pedestrian overpasses at NE 185th will probably be rebuilt but no designs have been created and no final decisions made.