For more than 15 years, the 72-year-old Harbor Lock on Lake Michigan in Chicago, USA, has been deteriorating. Leaks and breakdowns of the lock gates have stalled traffic several times. On average, more than 40,000 vessels, 900,000 passengers, and 200,000 tons of cargo pass through the gates of Chicago's Harbor Lock each year. The lock is opened and closed 11,500 times a year. Owned and operated by the US Army Corps of Engineers, the Harbor Lock has been restored, including the installation of new lock gates.
General Contractor James McHugh Construction is handling the project. Central Contractors Service of Chicago, a member of the ALL Erection & Crane Rental Corp. family of companies, was contracted to provide the lifting power to get the new gates in place. To get a crane to the jobsite out in the middle of the river necessitated a barge mount.
Central's team decided to use its 300-ton (272 tonne) capacity Manitowoc 4100W S-3 ringer crane rigged with a 140-foot (43 m) boom. The crane has a total picking radius of approximately 72 feet (22 m) and is outfitted with a capacity-enhancing ringer attachment. Central's team thought that the 4100W S-3 Ringer was the most economical crane for the job and would allow for better distribution of the point loading.
John Martello, Central Contractors Service general manager, says that the ringer was ideal in this application, with the crane on a barge. "When a crane must be mounted on a barge, the crane's load charts are decreased because of the lack of a reverse force; in other words, a barge is floating on water, not set on firm land," says Martello. "The relative instability of a floating platform has a negating effect on the load weight able to be picked. Adding a ringer and pedestals to a crane distributes loading over a larger area and can increase the lifting capacity dramatically. The ringer attachment on the 4100W was utilized to better spread the weight of the crane on the surface of the barge. Instead of all the weight of the crane being carried on just two tracks, the weight is distributed to 11 points. This allows point loads to be reduced."
The Manitowoc 4100W S-3 Ringer was erected on the barge at the Iroquois Landing dockside facility in Chicago. The new fabricated gates, with a total weight of 180,000 pounds (82 tonnes), were loaded up and the barge was towed by tugboat to Navy Pier, a trip of three hours. The lift and installation of the first gate took place on December 2, 2010, and the second gate was set a week later, on December 9. Both procedures were flawless.
Ken Derry, operator of the crane, said that the U.S. Army Corps of Engineers was impressed with the crane and the operation. "USACE required that the maximum list of the barge during the gate picks be no more than 2 percent," Derry explained. "The actual list during the pick was 0.00 percent. This number is amazing, considering the weight of the pick and its location on the water almost 90 feet [27 m] away from the crane."
The barge and crane were repositioned to set the final two gates in mid-January.