Seattle Tunnel Partners (STP) will begin next week to create a 120-foot-deep pit, to remove and repair the front end of boring machine Bertha.
A camera has been installed alongside the Alaskan Way Viaduct, so the public can glimpse progress at the pit.
The giant drill is stranded along the downtown waterfront, and not expected to resume digging until next spring. The Washington State Department of Transportation (WSDOT) announced Thursday that environmental reviews for the pit are complete, and equipment is arriving at the site near South Main Street.
Utility lines will be relocated, and then concrete grout will be injected to stiffen the soil. This should make it easier for workers to drill downward. STP plans to install a ring of vertical, concrete columns, then scoop out soil from inside the ring. Once that’s done, Bertha will drive forward into the round pit.
Contractors will be building the walls until July and dig until September, before the disc-shaped front end is hoisted to street level. Then, STP and machine maker Hitachi Zosen will replace the main bearing and install new rubberized seals.