Phase I and II Engineering for Mile Long Bridge Reconstruction

Move Illinois is a 15‐year, $14 billion capital program adopted by the Illinois State Toll Highway Authority (Illinois Tollway) to improve mobility, relieve congestion, reduce pollution, and increase connectivity across Northern Illinois. As part of the program, substantial improvements will be made to the existing tollway system, including the $4 billion, 22‐mile reconstruction of the Tri‐State Tollway (I‐94/I‐294), between 95th Street and Balmoral Avenue. Two large bridge projects form part of this initiative, and due to their complexity, the Illinois Tollway designated them as separate projects. Under a joint venture, Lochner is the lead design consultant for one of these complex bridge projects: the reconstruction of Mile Long Bridge.

Mile Long Bridge is a dual structure, comprised of 16 units, which are made up of 54 spans, and has a total length of 4,933 feet. The bridges carry the Tri‐State Tollway over an IC Railroad rail line with Amtrak and Metra use, the Illinois and Michigan Canal, two bike paths, the Chicago Sanitary and Ship Canal, the Metropolitan Water Reclamation District, the Des Plaines River, a BNSF rail yard, Santa Fe Drive, and the 75th Street interchange. Originally constructed in 1957, the bridge was widened in 1969 and again in 1993. The typical section for both structures now comprises four travel lanes with median and outside shoulders, providing an out‐to‐out width of 76.5 feet. From Span 45, the widths of both structures increase, to give out‐to‐out widths of 112 and 93 feet at the north abutment. The first eight spans fall in a horizontal curve, with a radius of 2,865 feet.

In the project’s first phase—the development of a project master plan—Lochner analyzed alternatives for the reconstruction, replacement, and/or widening of Mile Long Bridge, in liaison with the two master planning teams for the remainder of the I‐94/I‐294 corridor. Lochner led a comprehensive bridge type study, including the in‐depth structural inspection and analysis of the existing structure, the development of a bridge condition report, hydraulic and hydrological analyses, drainage analysis, and the development of type, size, and location (TSL) plans. The bridge type study helped determine the most appropriate type of structure to replace Mile Long Bridge. Lochner considered different structure types with different lane configurations and widths, including the reconstruction of the existing four lanes in each direction and the addition of a widened median shoulder to serve as a flex lane; reconstruction with an additional mainline lane; and reconstruction with an additional main line lane and flex lane. The chosen alternative was reconstruction with an additional main line lane and flex lane.

Mile Long Bridge is a high‐volume facility in an environmentally sensitive location, with limited available right of way. The potential impacts to the waterways, navigable channels, rail corridors, road facilities, utilities, and commercial activities beneath the structure, as well as to the huge numbers of Tollway users, are significant considerations in the bridge’s reconstruction. A particularly challenging area of the project is the I‐294/75th Street interchange at the north end of the bridge. For the realignment and widening of I‐294, the bridge deck will need to be widened to accommodate the reconstructed ramp. Lochner focused on the analysis of bridge structures and construction methods—such as accelerated bridge construction techniques—to minimize any impacts.

An additional project improvement at the south end of the bridge includes replacing the Tri‐State Tollway bridge over LaGrange Road. The design of this bridge included the development of TSL plans, roadway improvements, maintenance of traffic plans, and under‐bridge lighting.

In the second phase, Lochner is leading the production of final plans, specifications, and estimates. The development of comprehensive construction staging and maintenance of traffic plans to minimize disruption to traffic operations is a key task in this phase. Lochner is also assisting with utility and agency coordination. Key stakeholders include BNSF, IC Railroad, US Coast Guard, Illinois Department of Transportation, Village of Hodgkins, Metropolitan Water Reclamation District, and Forest Preserve District of Cook County.