Photo courtesy ALL Family of Companies

Mounted on a barge in the Chicago River, Manitowoc 888 RINGER can lift 660 tons.

A bright red Manitowoc 888 ring-type crane sitting on a barge in the Chicago River is playing a critical role in the construction of 150 North Riverside tower, whose site is sandwiched on a narrow, 380-ft-long spit of land between the river and a rail corridor.

For general contractor Clark Construction Group, Chicago, and subcontractor Chicago Steel Construction LLC, Merrillville, Ind., the challenge was to construct the foundation and lower floors while installing nearly 200 bulb-tee girders, weighing as much as 90,000 lb, to support the tower's new pedestrian plaza.

Due to its small footprint on the ground, the perimeter skin of the 1.2-million-sq-ft office building widens from its compact lower-floor footprint, ultimately rising to 54 stories upon completion in early 2017. Hemmed in by two elevated viaducts and an adjacent building, the site was simply too crowded to support a land-based crane with a reasonable reach.

"We realized we had the river at our doorstep," says Chris Phares, Clark project executive. "So, why not use it?"

In determining the right crane for the job, both distance and capacity were considered, as well as turning radius and the support barge's list and trim requirements. "From the river, we'd have to reach more than 250 feet for the heaviest pieces and 270 feet for lighter components," says Joe Jurasits, Chicago Steel project manager. "Because the railroad required a safety capacity of 50% over the heaviest pick, the crane would have to handle at least 130,000 pounds."

The calculus added up to the Manitowoc 888, with a 300-ft main boom and ring attachment, supplied by Central Contractors Service Inc., Crestwood, Ill. Constructed in 2001 and recently thoroughly refurbished, the crane, which has a 660-ton lifting capacity, would be mounted on a 99-ft-long, 132-ft-wide, 10-ft-tall, 31-unit modular barge system, introduced at CONEXPO 2014 by Poseidon Barge Corp., Ft. Wayne, Ind.

With riverfront space at a premium in downtown Chicago, the barge and crane were assembled in early April using a Manitowoc 2250 crane at a site three miles away. On Sunday morning, April 19, the unit was towed to the jobsite in a carefully synchronized procedure that required opening several Chicago River drawbridges and lowering the boom horizontally to squeeze beneath a vertical-lift structure.

Once anchored at the jobsite, the crane went to work installing the 150-ft-wide bulb tees during the four-hour, early-morning windows for construction allowed by Amtrak, as well modular structural steel-truss sections weighing up to 60,000 lb for the tower itself. Along with cutting by half the original two-month bulb-tee construction schedule, the barge-mounted crane provided the advantage of maneuverability, floating up and down the site as needed and shortening the picks.

At the same time, Jurasits notes, the project team has had to be aware of what's behind them on the busy shipping channel. "We're taking up about half of the width of the river with the barge, so there's been constant coordination with the city and the Coast Guard," he says.

The crane is expected to remain on the job until early July, when it will be used to assemble the tower crane that will construct 150 North Riverside's upper floors. That crane, in turn, will remove the 888's main boom to facilitate easier transport back to the disassembly yard.