(Above) A crane on a construction barge west of the Dearborn Street Bridge holds the green mechanism at right that vibrates to push a steel caisson nearly 75 feet beneath the surface of the Chicago River. (Click on images to view larger versions.)
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Riverwalk caisson drilling starts, bridge closings announced
Text and photos by Steven Dahlman
June 7, 2014 – 75 feet long and six feet in diameter, the first Riverwalk caisson was pounded into the planet on Friday afternoon. It went down on the west side of the Dearborn Street Bridge, plunging through water and soil to bedrock.
(Left) Workers periodically inspect the caisson as it is pushed down.
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It is a step up from pile driving that had echoed through the riverfront since April. Smaller steel “H pile” beams were installed between State and LaSalle Streets to anchor the Riverwalk. Sheet piling was installed to form the new river wall. That work is now complete, according to the Chicago Department of Transportation.
In addition to installing the caissons, workers are now backfilling with crushed stone the areas between the old river wall and the new Riverwalk. As the aggregate goes in, water will come out. It will be filtered and returned to the Chicago River.
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(Above) Previously filled with light green water, the area at right is now filled with crushed stones. At left, construction barges and a tugboat owned by Jack Tanner Towing Company.
Under-bridge work will detour traffic
The Clark Street Bridge will be the first bridge raised and then closed to traffic for four days as caissons and the path under the bridge are installed.
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The bridge will close on Tuesday, June 10 at 7 a.m. and re-open on Friday, June 13 at 8 p.m., and then again the following Tuesday through Friday.
(Left) How traffic will be detoured around the Clark Street Bridge – vehicle traffic in orange and bicycles in green.
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After work underneath the Clark Street Bridge is complete, the Dearborn Street Bridge will be next and then the State Street Bridge after that.
