Framework for Dredged Material Management
2.0 OVERVIEW OF DREDGING
OPERATIONS AND DREDGED MATERIAL
This section of the report is intended to provide a brief introduction and overview
of the dredging process, including types of dredges, transportation systems, and the
placement or disposal practices commonly used in navigation dredging projects.
References throughout this part provide more detailed discussion and explanation of
different kinds of dredges, transport equipment, and disposal practices.
The removal or excavation, transport, and placement of dredged sediments are the
primary components of the "dredging process." In design and implementation of any
dredging project, each part of the dredging process must be closely coordinated to ensure
a successful dredging operation.
The excavation process commonly referred to as "dredging" involves the removal
of sediment in its natural (new-work construction) or recently deposited (maintenance)
condition, either mechanically or hydraulically. After the sediment has been excavated, it
is transported from the dredging site to the placement site or disposal area. This transport
operation, in many cases, is accomplished by the dredge itself or by using additional
equipment such as barges, scows, and pipelines with booster pumps.
Once the dredged material has been collected and transported, the final step in the
dredging process is placement in either open-water, nearshore, or upland locations. The
choice of management alternatives involves a variety of factors related to the dredging
process including environmental acceptability, technical feasibility, and economic
feasibility of the chosen alternative.
2.2 Dredging Process Equipment and Techniques
Compatibility must exist between the dredging equipment and techniques used for
excavation and transport of the material and the management alternatives considered. The
types of equipment and methods used by both the USACE and private industry vary
considerably throughout the United States. The most commonly used dredges are
illustrated in Figure 2-1. Dredging equipment and dredging operations resist precise
categorization. As a result of specialization and tradition in the industry, numerous
descriptive, often overlapping, terms categorizing dredges have developed. For example,
dredges can be classified according to: the basic means of moving material (mechanical
or hydraulic); the device used for excavating sediments (clamshell, cutterhead, dustpan,
and plain suction); the type of pumping device used (centrifugal, pneumatic, or airlift);