Completion 5: Chicago Skyway Rehabilitation
Cost: $240 million

The 8-mi.-long Chicago Skyway was originally opened in 1958 and now handles more than 90,000 vehicles a day.

In the late 1990s, inspections revealed corrosion, warping or cracks in components, loads nearing design capacity and excessive maintenance costs.

The decision to rebuild was made. Plans included the reconstruction of all overpasses and viaducts, modifications to toll plazas and reconstruction of the roadway's southern end.

A retained earth system was installed that places a good deal of the originally elevated roadway on grade. About 1,700 lin. ft. of bridge deck was removed between 75th and 79th streets and about 3,000 lin. ft. at the 106th Street viaduct.

More than 4.5 million lbs. of structural steel were installed as part of the project. Replacements affected floor beams underneath the deck and perpendicular to the roadway, stringers that extend from the beams and parallel with the roadway and trusses.

The Skyway was temporarily shored and jacked so that most of the piers supporting the approximately 3.5 mi. of elevated structure were replaced.

Along with the pier replacement, old bridge decks were removed and new ones installed.

A new interchange was installed at 92nd Street. This included the construction of a retaining wall with caissons only 15 ft. from the Norfolk Southern railroad track.

New lanes were added to the 104th Street exit ramp and the 105th Street entrance ramp. An entrance ramp was added at 84th Street in case the existing one at 87th Street is eliminated in the future to allow for the widening of the toll plaza.

Other key project elements include the installation of 28 surveillance cameras, landscaping and the reduction of bridge structure.

The project is intended to upgrade the Skyway for 50 years. In October, a lease was signed with Spain's private Cintra Macquarie Consortium that will funnel $1.8 billion into Chicago.

Avoiding Traffic Woes

A primary objective was to have the least impact on traffic while also finishing the work with reasonable promptness.

One key project element to keep three lanes open was to use a zipper wall - concrete barriers linked with pins at project start.

In the morning when traffic headed downtown was heaviest, two westbound lanes and one eastbound lane was open. At noon, a specially equipped vehicle was driven through the zipper wall's full 15,000-ft. length to shift the wall so that two Indiana-bound lanes were open.

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