The tunnel that’s set to replace the Alaskan Way Viaduct is coming along beneath downtown, with the tunnel’s upper deck, which will eventually be a southbound roadway, complete. Much of lower deck, or northbound roadway, arrived in pieces back in November, and crews have been putting the panels together to make up the new road.
The 22-ton panels are brought into the tunnel and then joined together. This process is about 65 percent complete, with crews currently putting together the northern portion of the road. A time-lapse video, embedded above, shows how the process looks: trucks carry the panels in, then a specialized crane that fits into the tunnel lifts them into position. Then crews seal the panels together by pouring grout, letting it cure, then locking them together with steel cables.
The road, which 1.7 miles long, is made up of 1,152 panels in total. So far, 6,000 feet out of 9,270 have been completed.
In addition to the southbound roadway, the northbound walls and the tunnel’s corbels are also complete. Besides the northbound roadway, all that’s left to complete are some southbound walls, which are largely complete, and some work on the launch and disassembly pit.
Bertha the tunnel-boring machine officially finished the length of the two-mile tunnel, which will take cars past downtown along State Route 99, on April 4 of last year. That was a few years behind the original schedule, which estimated the tunnel would open in December 2015.
The new roadway is set to open in early 2019. After it opens, the aging Alaskan Way Viaduct will come down.