State Set To Study, Fill Big Dig Hole In Boston

Engineers will drill 100-foot deep holes next month around a huge empty space that opened up beneath a Big Dig tunnel to determine exactly how big it is, what caused it and how to fill it.

State Highway Administrator Frank DePaola said Thursday that despite the void several feet below the road surface, the tunnel remains safe.

He says by comparing new soil samples to samples taken during construction, officials will be able to determine how much cement grout to use to fill the hole.

Officials have said the hole was caused by the settling of 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.

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