The third and final phase of the Chicago Riverwalk construction project was recently opened to the public on October 22, 2016.  This final phase extended the Riverwalk, located on the South side of the main branch of the Chicago River adjacent to Wacker Drive, from LaSalle Street to Lake Street putting the final leg on a continuous walkway from the heart of downtown to the lakefront. 

In order to create a continuous path, the project required a means for pedestrians to pass under the bridges.  Originally, the user's path would be impeded once they’d reach a bridge, at which point they’d have to use stairs to exit, cross the street, and re-access on the other side.  The Riverwalk project alleviated this issue by including an underbridge concrete path which spans over submerged piles within the existing river’s right of way. 

Utility Concrete Products was brought on to fabricate and supply the main precast structure for these paths, referred to as underbridge tubs.  Each underbridge required three precast sections, which resemble a concrete bathtub, to provide the necessary structure to pour cast-in-place (CIP) concrete and create a composite connection to complete the underbridge.  The tubs are 10’-0" wide x 4’-0" tall and varied in length from 38’-0" up to 86’-3 ¾” with the heaviest piece being at the LaSalle St. Bridge weighing in at nearly 164,000#. The longest tubs were poured with a precise camber that leveled out once the CIP concrete was poured within.  Poured with a High Strength High-Performance Concrete (HSHPC) mix, the tubs are designed to withstand the marine elements as they are constantly submerged in the Chicago River. 

Each tub is heavily reinforced with large diameter epoxy coated rebar spanning the longitudinal direction and was cast with either 6’-0" or 8’-0" diameter openings in the floor so that they could be installed on similar size piers in the field.  In these openings are massive ½” steel embed plates to connect to the piers. Further, a post installed neoprene seal provided a watertight seal between the precast and shafts once installed.

To transport the precast tubs to the jobsite, they were delivered to an auxiliary site along the river and loaded onto specially designed barges with the largest capacity crane in the Chicagoland area.  Once loaded onto the barges, the tub sections were welded together and floated up the South Branch of the Chicago River to the jobsite.  The barges positioned the tubs over previously drilled piers that they set on prior to being lowered to final elevation by a complex jacking system.  Once in place, the tubs were heavily reinforced and infilled with the HSHPC mix, which secured the tubs to the piers below and also created the final walking surface for the users.  Each underbridge was ultimately outfitted with a guardrail and a stainless steel canopy system to shield from runoff of the bridge decks above.  UCP is grateful to have been a part of such a high-profile project for the City of Chicago. 

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For the reconstruction of the Torrence Avenue Bridge spanning the Grand Calumet River, UCP provided 22 partial-depth precast approach slabs. The precast spans from the approach footing to the bridge abutment acting as a land bridge, which combats the issues seen with cast-on-grade applications, including settlement and cracking.  A 5" concrete wearing surface is poured in the field, which is tied to the precast through exposed, epoxy coated u-bar cast during the precast process.  The purpose of this project was to replace the existing bridge structure, as it was severely deteriorating. The new bridge will enhance safety, improve mobility of traffic, and reduce maintenance costs.  The use of precast for the approach slabs will decrease settling, providing a smooth transition for the driver from the roadway to the bridge deck.

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Interested in learning more about Precast Concrete?  Lunch and Learns with UCP are a great opportunity to stay up to date on new precast technologies and innovations while learning more about our products. 

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