Highway construction inside the tunnel moves north
This week, Seattle Tunnel Partners shifted gears and moved its road-building operation north for the final 3,000 feet of lower roadway inside the SR 99 tunnel.
Unlike the southbound (upper) roadway, which was built using concrete pours, the northbound (lower) roadway comes together one 22-ton panel at a time. The pre-made panels are trucked into the tunnel, lifted with a specialized crane and joined together to create a functioning highway.
This new time-lapse video shows how the road comes together:
STP installed the first 6,000 feet of lower roadway by hauling the panels from the south portal to a point roughly under Virginia Street and First Avenue. From there, they worked their way south, installing panels as they went. Following the recent completion of the upper roadway at the tunnel’s north end, crews can now deliver panels via the north portal and work south-to-north to finish the final 3,000 feet of lower roadway.
There’s still a lot work ahead before the tunnel is ready for traffic. STP must complete installation and testing of all the operational and safety systems that will make the tunnel function. You can follow the work on our tunnel progress tracker.