More than 314,000 cubic yards of soil, clay and rock has been removed during excavation of the two tunnels, which run beneath San Pedro Mountain just south of Pacifica, Caltrans District 4 Director Bijan Sartipi said.
The tunnels are each 30 feet wide and about 4,200 feet long.
Crews are continuing to work on installing electrical systems, insulation and lining on the inner tunnel walls.
Work on the $342 million tunnel project began in 2007.
