New I-90 bridge over Fox: How do you build in a river?

At dawn today, wind willing, two hoists will lift a 190,000-pound beam from a waiting truck on the Jane Addams Tollway and heave it onto columns rising about 40 feet above the Fox River in Elgin.

Two teams of ironworkers 170 feet apart will chatter on walkie talkies, calibrating the movement of the beam so it's in the right spot at the right time. Then, the process starts again, every morning until 24 beams that form the backbone of a fourth eastbound lane on the new Fox River bridge are ready for the concrete that will transform it into a road.

It's the kind of project that gets civil engineers all misty-eyed as they rhapsodize over fewer road joints and gantry systems. But if you're driving in one of the 101,300 cars and trucks scooting by per day, you will probably see little of this flurry of activity.

Unlike the razzle-dazzle, cranes-gone-wild construction show occurring elsewhere on I-290/Route 53 or the Elgin-O'Hare Expressway, much of the work on the new I-90 bridge occurs underneath the existing structure for now.

I said “bridge,” but it's actually plural. The Illinois tollway is rebuilding both eastbound and westbound bridges over the Fox for $95 million.

During a site tour last week, my first question was, “How do you build in a river?” The answer is “very carefully.”

For starters, crews used 6-foot augers to drill down to the bedrock below the Fox River, creating space for caissons, large chunks of concrete to anchor the bridge. The water's depth ranges from 3 to 10 feet.

On top of the caissons and into the water went sheets of steel, creating walls. Water was pumped out of the space and concrete went in to form massive piers.

Just south of the existing eastbound bridge, workers this month are installing beams on the piers for the extra lane and pouring concrete.

When the project is finished late in 2016, there will be four lanes in each direction of the Jane Addams.

The one visual everyone can see on the eastbound bridge is a gantry system that uses hoists to transport the beams, instead of cranes, which would have eaten up space.

The tollway intends to keep all lanes open during construction, which will involve some funky shifting for drivers in the future, although after two solid years of roadwork I doubt anything could faze Jane Addams drivers.

In 2015, once the new lane is complete, all traffic will move to the eastbound side of I-90, using shoulders and existing lanes.

That will give workers free rein to demolish and rebuild the westbound bridge. When that's done, you can expect vehicles to transfer over in 2016 so the remaining lanes can be demolished and the eastbound bridge completed.

So what's exciting engineers? Besides the gantry system, there's jubilation that modern road technology will allow for fewer joints in the new structures, meaning less chances for snow, ice and salt to seep in and break down the concrete.

“There's only going to be one joint in the middle of the bridge. Our goal is to minimize long-term maintenance,” said deputy chief of program implementation Peter Foernssler, who's overseeing the I-90 corridor. “We've struggled with this bridge — every five to 10 years we're out here repairing (it).”

Wonk alert: The tollway is working now with the Illinois Department of Transportation on test bridges including one on the Kishwaukee River near Rockford to see how far lengths between joints can go.

Fewer joints equal fewer piers. Fourteen piers support the eastbound bridge over the Fox River now. The new structure will have seven, which is good news for spawning fish who like a free flow of water when they're in the mood, experts say.

“We did more repair work on these piers in the last five years than any other piece of tollway infrastructure,” tollway Chief Engineer Paul Kovacs said.

“We're trying to build something that lasts for a long time and stay out of the customers' way.”

You should know

In the midst of Metra's uber fare increase last week, Pace quietly announced it had passed its budget without a change in ticket prices. Ridership is expected to reach 36 million in 2015 compared to 35.5 million this year. Pace estimates its paratransit service, which serves riders with disabilities, will grow by 5 percent for a total of 4.37 million trips.

Gridlock alert

Part of Wiley Road in Schaumburg near the Jane Addams Tollway will close this week for sewer work.

Make cents?

Never one for small plans, the Chicago Metropolitan Agency for Planning is recommending a “modest quarter-cent increase in the regional sales tax.” The move would generate $300 million a year for transportation and water system improvements plus open space acquisition, officials said. Stay tuned to see how this fares in the Illinois General Assembly. To learn more go to http://www.cmap.illinois.gov/.