By: Tim Bruns
Built in 1958, the I-90 Fox River Bridge a few years ago was suffering from deterioration on its beams. What’s more, the bridge deck was nearing the end of its useful lifespan, and the estimated cost of rehabilitating and widening the bridge was 76% the cost to replace it.
“We’ve been out there repairing [the bridge] on a regular basis since about 1984,” Greg Bedalov, executive director of the Illinois Tollway, told Roads & Bridges. “We take great pride in having zero structural deficiencies on any of our bridges, and we noted that four of the seven water piers were in critical condition.” This prompted the Illinois Tollway to replace the old bridge with two new side-by-side structures over the Fox River.
The Tollway decided to incorporate the bridge replacement project into its Move Illinois program as part of the Jane Addams Memorial Tollway (I-90) project, which consisted of rebuilding and widening 62 miles of the Jane Addams between Rockford and the I-90 Kennedy Expressway. For the bridge replacement, capacity on the two new structures would increase from six to eight lanes with full shoulders in both directions to accommodate the widened Jane Addams Tollway.
The design team on the Fox River Bridge came up with an innovative plan to rebuild the new substructure at the same time the existing structure was in place. “We directed the designer to maintain a focus on our customers,” Paul Kovacs, chief engineering officer for the Tollway, told Roads & Bridges. “So that means, how do we do this replacement such that we don’t impact them, or minimize the impact to them while we’re replacing it?”
The design team utilized special low-clearance equipment to build the new piers to work underneath the old bridge. “They got a lot of work done on the underside of the bridge without the public even knowing that it was going on,” Kovacs said. The team also designed the piers in a way that reduced their number by half. Fewer piers meant longer beams, but the team still managed to keep work going below the bridge.
There were four stages of construction in the original plan. The contractor proposed eliminating two longitudinal joints on the bridge by implementing an overhead gantry system to set the large, 7-ft deep, 100-ton beams into place. By reducing the joints and designing stainless steel into the structure, the team created a bridge with a deck meant to last over 80 years, far exceeding the typical 40- to 50-year range.
Fewer piers on the new structure also meant reducing environmental impact to the waterway and the forested fen below the bridge. The unique high-quality water resource is completely dependent on the groundwater, so to protect the area the team enclosed all the drainage to go directly into the fen instead of into the river.
Project: I-90 Fox River Bridge
Location: Elgin, Ill.
Owner: Illinois Tollway
Designer: Stanley Consultants
Contractor: Kenny-Kraemer, Joint Venture
Cost: $95 million
Length: Two, side-by-side 1,315-ft-long structures
Completion Date: Sept. 1, 2016
About The Author: Bruns is associate editor of Roads & Bridges.
