12 December 2001
DESIGN OF DREDGING PROJECTS
INTRODUCTION. Dredging is generally carried out either to increase the
depth of a body of water, or to replace, re-configure or mine for in situ sediments. It
may involve new construction (Capital dredging), such as excavation for harbors or
canals, the construction of stable bases for tunnels or reclamation of submerged land.
Maintenance dredging on the other hand is used for such purposes as maintaining
waterway utility and restoring the hydraulic efficiency of reservoirs. Section V-5-3 of the
CEM contains information on dredging. Additional extensive detailed information on
dredging project design can be found in the Handbook of Dredging Engineering by J.B.
Herbich; Dredging: A Handbook for Engineers by Bray, Bates and Land and the ASCE
Engineering Practice #80, "Report on Ship Channel Design (Herbich, 1992; Bray et al.,
1997; ASCE, 1993).
ACCOMPLISHMENT OF WORK. Government-owned dredges should be
used to the maximum extent consistent with economy. When the only suitable
dredging equipment is in private ownership, or when the workload exceeds the
capability of available government dredging facilities, private contractors may
accomplish dredging. Some of the factors to be considered in planning a dredging
Marine environment, including water depths, waves, tides, currents;
Nature and character of the sediments;
Dredged quantities and disposal areas;
Social, biological, regulatory and institutional factors;
Long term dredging and disposal problems.
More detailed information on dredging project implementation is found in Chapter 2 of
Dredging: A Handbook for Engineers (Bray, 1997).
TERMINOLOGY. Some common terminology is provided in the section
below. For additional information on this subject, refer to the Dredging Desk Reference
(Verna and Maciejewski, 1994).
Centrifugal Pump. A pump operated by centrifugal force, the force outward exerted by
a body moving in a curved path.
Clamshell. A dredging bucket made of two similar pieces hinged together at one end.
Drag Head. A device placed on the end of a suction pipe (connected to a dredge)
used for loosening or cutting away the bottom material that is to be dredged.