Award of Merit: Transportation

The Des Plaines Valley Bridge is a 6,600-ft-long overpass to carry six lanes of the Interstate 355 extension over the Des Plaines River Valley through Lemont, Ill., in southwest suburban Will County. There is about 1,400 ft of mainline paving on grade at the north end of the bridge and 400 ft of paving on grade at the south end.

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The substructure is made up of 34 piers, and each is comprised of four caissons, four concrete columns and a post-tensioned pier cap. It supports 250 simple span prestressed concrete beams, 360 spliced, post-tensioned beams and an 8-in.-thick deck.

The 6,600-ft-long bridge spans several obstacles, including the Des Plaines River, the Illinois & Michigan Canal, the Sanitary & Ship Canal and railroads. Between the obstacles the majority of the existing site was forest preserve and wetlands. The span also encompasses an 80-ft-deep natural gorge near the south abutment.

Accommodating the Environment

The wetlands are home to several creatures, including the endangered Hines Emerald Dragonfly, the Spotted Turtle and Blanding’s Turtle.

To minimize the impact on the wetlands, limits were imposed on how low the bridge could drape, how many piers could be built and the acreage of construction area that could be used. The height of the bridge was chosen based on the flight pattern of Emerald Dragonfly, and the decision to construct a post-tensioned segmental concrete bridge was the result of the limit on the number of piers.

A key issue was the was the method of erection and how to providing access. The decision was that each of the 612 girders would be erected with two crawler cranes, and a portion of the wetlands was removed and backfilled with stone to provide a working surface.

Managing the sizable precast girders was also a problem, and they were shipped on specially designed trucks. Just finding access was a challenge because the smallest beam was 90 ft and the longest was 170 ft, 6 in.

Once the beams were onsite, there was the headache of in arranging two cranes and the beams for erection. Indeed, some picks involved erecting over the Des Plaines River, the Sanitary & Ship canal and the railroads.

As a result, an island was built in the river and accessed by two temporary bridges, and a Manitowoc 2250 picked a beam while sitting on barge. Indeed, two picks involved backing the trucks carrying the beams to the edges of bluffs with one crane picking from the top of the hill and the other crane below.

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