|This article was an excerpt from Maritime Reporter from September of 1986 - |
The dredge Chicago , said to be the world's largest and most powerful combination clamshell/dipper dredge, is scheduled for completion and assignment by the end of this year (1986) according to Great Lakes International., the vessel's owner. William L. Colnon, president of GLI, announced that when the Chicago is completed, it will provide unequaled capabilities and versatility for the dredging industry in both the clamshell and dipper modes.
In order to effectively utilize the unprecedented production capacity of the new dredge, two large split-hull, hopper dump barges have been designed are also presently under construction. This bold advancement in the bucket dredge field was based on a careful analysis of future dredging requirements, according to Mr. Colnon. The Chicago has been designed specifically for work in the ports of the U.S. including the deepening of proposed deep-water ports as well as in the ports of the rest of the world. The investment of $30 million in the new dredge and the two barges is the largest single appropriation in the company's 100-year history.
The first design criterion for the Chicago was to double the capability of any clamshell or dipper dredge in existence. The P&H model 5700 electric excavator was selected as the most efficient digging machine available for that purpose. The revolving unit, weighing nearly 100 tons is under construction at the Harnischfeger Corporation in Milwaukee, Wisconsin. The dredge will have a 50-cubic-yard clamshell bucket whereas the largest clamshell currently in operation uses only a 26-cubic-yard bucket.
The Chicago will develop a dipper hoist pull of 480,000 pounds at a line speed of 240 feet per minute, about twice that of the next largest dipper currently in operation anywhere in the world. In addition, the dredge has been designed to operate with a 27-cubic-foot dipper bucket, compared to the 14-cubic-yard dipper that is the biggest presently in use. Chicago's hull is being built by the Southern Shipbuilding Corportion in Slidell, Louisiana and it will be more than twice the size by volume of today's biggest clamshell and dipper dredges. The cross-sectional area of the new vessel's spuds (a measure of the ability to work in rough seas) will be 2.5 times that of similar existing dredges. Its total installed output of 8650 horsepower is almost 4 times greater than that of today's largest dipper and 7 times more than that available in clamshell dredges at Present.
The 2 new barges are being built by the Bay Shipbuilding Corporation in Sturgeon Bay, Wisconsin. With a 6,000 cubic-yard capacity, they are 1.5 times the size of the next largest barges of this type in use and have an overall length of 277 feet and beam of 63.5 feet. They will be towed by 5600 horsepower tugs of twin propeller, Cort nozzle designs. Working in either the clamshell or dipper mode, CHICAGO will provide a continuous operation, dredging the material and disposing of it without interruption, even if the disposal area is far removed from the dredge site. The exceptional dipper power also enables the dredge to excavate extremely difficult material that might otherwise have required blasting.