One of the first steps involves archaeological research as required by the Federal Highway Administration. This is required because the project's environmental review did not involve digging down from the surface.
To collect soil samples, crews will dig about 60 shafts to about 20 to 40 feet deep.
Transportation officials say they're not looking for anything in particular. They just want to make sure there isn't anything archaeologically sensitive in the area.
The Transportation Department's cultural resources manager, Steve Archer, says workers started boring probes Thursday. They are digging through an area of historic fill material.
The tunnel boring machine ground to a halt in early December 1,000 feet into the 1.7-mile Highway 99 tunnel that will replace the Alaskan Way Viaduct.