Table 21. Five Common Types of Dredge Rigs 

 (Source: Reference 33) 



" Dipper Dredge— The dipper dredge is basically a power shovel mounted on a barge, 

 the barge (which serves as the work platform for the shovel) uses three spuds (two spuds 

 at the forward end and a single spud at the stern) to provide stability during dredging 

 operations. The dipper dredge is capable of excavating from 3 to 10 cubic yards of hard 

 material per cycle. It can remove blasted rock or loose boulders. The dredged material is 

 discharged within the reach of the dipper boom. The digging boom limits the depth of 

 excavation to not more than 60 feet. 



Ladder Dredge— The ladder dredge uses an endless chain of buckets for excavation. 

 The dredge is mounted on a barge which is stabilized by side cables during the dredging 

 operation. The ladder dredge is capable of excavating from 1 to 2 cubic yards of hard 

 material per bucket. It can remove blasted rock or loose boulders. The excavated material 

 is dumped from the buckets into chutes or onto belts and is discharged over the side of 

 the barge. The design of the ladder limits the depth of excavation to not more than 100 

 feet. 



Bucket Dredge— The bucket dredge is basically a crane mounted on a barge. The 

 bucket (clamshell, orange-peel, or dragline) can be changed to suit the job conditions 

 and material to be removed. The barge (which serves as the work platform for the crane) 

 uses either spuds or anchor lines to provide stability during dredging operations. The 

 bucket dredge is capable of excavating moderately stiff material in confined areas. It is 

 generally not used for large scale projects. The excavated material is dumped within the 

 reach of the boom. 



Pipeline Dredge— The pipeline dredge is the most versatile and widely used dredge. 

 It can handle large volumes of material in an economical fashion. Using a cutterhead the 

 dredge can excavate material ranging from light silts to heavy rock. It can pump the 

 dredged material through floating and shore discharge lines to remote disposal areas. 

 Pipeline dredges range in sizes (as measured by the diameter of the pump discharge) from 

 6 inches to 36 inches. The depth of excavation is limited to 60 feet. The rate of dredging 

 will decrease with (1) difficulty in digging, (2) increase in length of discharge pipe and 

 (3) increase in lift to discharge elevation. 



Hopper Dredge— The hopper dredge is a self-propelled vessel designed to dredge 

 material hydraulically, to load and retain dredge spoil in hoppers, and then to haul the 

 spoil to a disposal area or dump. Loading is accomplished by sucking the bottom material 

 through a drag-head into the hoppers while making a cut through the dredging area. 

 The quantity of volume pumped during a loading operation depends primarily upon the 

 character of the material and the amount of pumping time involved as well as the hopper 

 capacity and the pumping and propulsive capability of the dredge. The loaded dredge 

 proceeds to the disposal area where the dredge spoil is discharged through gates in the 

 bottom of the hoppers. " 



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