September 30, 2014 – A surprise encounter with telephone equipment buried beneath the Chicago River caused a delay of Riverwalk construction in July and required the State Street Bridge to be closed a second time.

In mid-July, a contractor was drilling a hole in the riverbed below the south leaf of the bridge, into which a caisson – a long tube filled with concrete to anchor the Riverwalk – was going to be lowered.

The contractor came in contact with an unmarked conduit, currently owned by AT&T, which contained telephone cables. According to Chicago Department of Transportation, there was no significant damage but construction was delayed while another hole was drilled several feet away.

The conduits “hadn’t been mapped before we had started drilling,” said Peter Scales, director of public affairs for CDOT, on Monday. “We didn’t think that they were there. And then we encountered them and essentially we had to stop…cut off that caisson where it was, fill it in, and…then re-drill another one. So that knocked us back another week or so.”

The bridge had been closed to traffic and raised since July 14 but on July 17, it reopened four days early with no official explanation at the time. The bridge was then closed again from August 13 to August 25 but three caissons, not just the one that had to be redone, were installed.

(Left) A caisson is installed underneath the raised State Street Bridge on July 14. (Click on image to view larger version.)

In Illinois, the Underground Utility Facilities Damage Prevention Act protects buried utilities from construction damage and requires any excavation to stop if there is evidence of an unmarked utility. The excavator calls a hotline to provide information that is passed on to the utility, which then marks the location of their buried facilities.

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