Great Lakes Dredge & Dock Company services

Hopper Dredges are designed to vacuum material from the sea floor through drag arms that load the material into the hold of the vessel. The cargo of mud or sand can then be sailed to either an ocean disposal site where the material is dropped to the bottom through openings in the bottom of the hull, or alternatively an upland site such as a beach or reclamation where the material is pumped ashore by the ship.This method is most suited to the combined requirements to excavate loose material from open areas for delivery to a distant disposal location. These vessels are generally certified to sail in coastal or ocean waters and are suited for working in rougher sea conditions beyond those suitable for other dredging plant.

Cutter or Hydraulic dredges are floating platforms equipped with a rotating cutter that excavates the sea floor, feeding the loosened  material into a pipe and pump system that transports the material and water slurry up to typical distances of five miles. Transport distances can be extended by the addition of Booster pumps in the pipeline route.This method is most suited where the disposal location is within an economic direct pumping distance from the dredging location, typically no more than six miles. These dredges can pump a slurry of all types of material: mud, sand, clay and rock. The ability to dredge stiff or hard material is dependant on the size and weight of the dredging equipment and the installed power of the cutter, the ability to pump heavy material is dependant upon the installed power and size of the pumping systems.

Mechanical clamshell dredges are floating platforms that house a heavy duty cycle crane that uses a wire rope suspended bucket to excavate the sea bottom. The dredge locates itself in position during dredging operations by lowering retractable spud poles to the sea bottom. Excavated material is loaded into barges (scows) for transportation by tugs to a disposal area.This method is most suited to the excavation of loose materials in restrictive areas, working around obstacles and where disposal is beyond normal direct pumping distances. Generally dredged material will be disposed of in an ocean site being released from the barges through opening in the bottom of the hull. If the material is required to be disposed of in an upland site then a barge unloader may be used to pump material out of the barges.