How a 115-ton concrete beam cruises from Wisconsin to the Tri-State's Mile Long Bridge

How do you transport a 115-ton, 187-foot concrete beam from a Wisconsin manufacturer into Illinois along two major tollways sprawling with traffic and install it 50 feet above the ground on the Mile Long Bridge?

Very carefully, Illinois tollway engineers explain.

Last week, Illinois State Police began squiring concrete beams through the suburbs that will form the base for the deck of the new, expanded southbound Mile Long Bridge.

Although the title is singular, it refers to two separate structures on the Tri-State Tollway that date back to 1958 and carry about 150,000 vehicles daily.

  Illinois State Police escort a truck carrying a massive concrete beam to the Mile Long Bridge on the Tri-State Tollway, part of a $182.6 million replacement project. Brian Hill/

Workers completed a replacement northbound Mile Long Bridge in 2020 with five lanes, up from four, and wider shoulders that can accommodate transit and emergency vehicles when needed.

The beams are "very specialized and large, and they have to be delivered using special trucks and special bracing," acting Chief Engineering Officer Manar Nashif said. "It's a major operation. The trucks won't travel at full highway speeds, and we ask our customers for their patience and to heed the speed limits."

To move the behemoths, 10-foot wide, 14-axle heavy-load semitrailers and a police escort are required along the Jane Addams Tollway (I-90) and I-294 to the work site near Willow Springs. The project is part of a $4 billion Central Tri-State redo.

The Mile Long Bridge offers unique challenges for construction crews, spanning the Canadian National and BNSF railways, a UPS distribution center, 75th Street, the Des Plaines River, Illinois and Michigan Canal, and Chicago Sanitary and Ship Canal.

Adding to the complexities below are underground gas lines and a jet fuel line to O'Hare International Airport.

The new bridges have longer sections, or spans, and are supported by fewer piers, the sturdy vertical columns that hold up a structure. That means fewer bridge joints, which are usually the first to require repairs.

Two cranes and a gantry system are used to hoist beams that will form a base for the deck of a new southbound Mile Long Bridge on the Tri-State Tollway. Courtesy of Illinois tollway

The concrete beams will form the base for the bridge deck that vehicles will travel on. Two cranes and a gantry system assist in hoisting the beams to a permanent gig on the piers.

Space is limited for the engineering choreography, and that limits beam placement to five a day.

The tollway is keeping the original southbound bridge open while the adjoining replacement is built, as it did with the northbound ones.

Beam deliveries for 2021 will wrap up by Halloween and will occur between 4 a.m. and noon weekdays. Altogether, 250 concrete beams and 165 steel beams will be trucked to the southbound bridge before it's complete in 2022 at a cost of $182.6 million. The northbound version cost $184.6 million.

"This is going to provide a lot of congestion relief through this addition of lanes on the bridge," Nashif said.

Northbound bridge features include digital signs with traffic alerts and travels times, similar to those on I-90. The tollway is still finalizing plans for signage on the southbound structure, Nashif said.

<h3 class="leadin">Gridlock alert

Brace for delays in Algonquin starting today when IDOT crews clean and paint the Algonquin Road bridge over the Fox River. Drivers should expect lane closures and work should wrap up in mid-September.

<h3 class="leadin">One more thing

Lake County's Division of Transportation intends to offer an improved paratransit system serving riders with disabilities and is seeking feedback through Wednesday. "This new service would provide a borderless countywide transportation system for seniors and residents with disabilities to get to work, shopping, medical appointments and more," planners said. To learn more and participate in a survey, go to

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