Sinkhole Opens up Beneath Boston Highway

Fri August 26, 2011 - Northeast Edition

BOSTON (AP) State transportation officials say a massive 4 ft. (1.2 m) deep hole has opened up about 9 ft. (2.7 m) below the road surface in a Big Dig tunnel in Boston, but poses no danger to drivers.

The roughly 190 ft. (58 m) long sinkhole that has filled with water was caused by settling of the clay around the tunnel.

During construction 11 years ago, contractors chemically froze the soil so it wouldn’t collapse as they dug the tunnel connecting the Massachusetts Turnpike with the Ted Williams Tunnel under train tracks.

Engineers expected settling, but it has happened faster than expected.

It’s expected to cost $15 million to fix the problem, but not until the ground finishes settling by 2014.

The $15 billion Big Dig highway project has been plagued by cost overruns and construction problems.