Construction this week on the new Tacoma Narrows bridge:
After 10 months in the Tacoma Narrows, the Gig Harbor-side bridge caisson is in its final position in the sea floor. Dredging crews finished digging last week, with the bottom of the tower foundation 57 feet below the mud line on the sea floor.
Dredging on the Tacoma side caisson will start Monday or Tuesday. Crews will continue until the caisson is 62 feet below the mud line.
Roadwork: Drivers should watch for nightly single-lane closures from 9 p.m. to 8 a.m. on westbound Highway 16 and from 7 p.m. to 5 a.m. on eastbound lanes. Crews will be installing temporary drainage structures and working in the median on both sides of the bridge.
Anchorages: Crews will place steel reinforcement and forms, but do no concrete pours. Representatives of the state Department of Transportation and Tacoma Narrows Constructors will hold an open house Wednesday to talk about construction and the widening of Highway 16.
The open house will be from 6 to 8:30 p.m. at Wilson High School, 1202 N. Orchard St. in Tacoma. It also will feature a short 1940 film documenting the construction and collapse of Galloping Gertie.
Q. Since the caissons are hollow, what's going to keep them from sinking deeper when they put all the extra weight of the towers on top of them?
A. TNC will pour 25 feet of concrete in their bottoms to seal them in place.