Video: Construction continues on Caldecott Tunnel fourth bore

This is a pretty nice little 3-minute news segment on the Caldecott Tunnel 4th Bore Project in the California Bay Area. Progress is slow, at only about 10-15 feet of progress per day, but work continues around the clock. The rock formations they are tunneling through have methane present, so the news segment focuses quite a bit on the issue and the safety precautions in place. [Source: via ASCE SmartBrief]