August 29, 2014 – The first of the under-bridge walkways will be delivered over the next week to the Chicago Riverwalk. The Chicago Department of Transportation was expecting delivery by now of the pre-fabricated walkway that will go under the Dearborn Street Bridge. They now say that will happen during the first week of September.

The walkway will be installed under the south leaf of the Dearborn bridge and connect the new Riverwalk from a stretch called Marina Plaza to a stretch called The Cove.

(Above) Aerial illustration of this area with the walkway in lower frame.

All of the caissons that will support these walkways, from the State Street Bridge west to LaSalle Street, will be installed by September 6, according to CDOT.

Three caissons have been installed underneath the State Street Bridge, requiring the bridge to be raised for days at a time, and one caisson was installed on the east side of the bridge this week.

(Left) Three bores sit on a construction barge east of the State Street Bridge on Wednesday. Inserted into a long steel tube called a caisson, a bore is used to dig a round hole – deep into the riverbed – into which concrete will be poured. (Click on image to view larger version.)

Workers get the day off on Labor Day. Then they will resume installing drainage structures and “chiller pipes,” thick insulated pipes that carry cold water. They will also pump water out of the new spaces between old and new river walls and pump concrete into the spaces, and build other wooden forms into which concrete will be poured.

• Previous story: State Street Bridge up through weekend
• More photos: Riverwalk construction