OVERVIEW OF DREDGING OPERATIONS AND DREDGED MATERIAL MANAGEMENT ALTERNATIVES

Framework for Dredged Material Management

May 2004

2.0 OVERVIEW OF DREDGING

OPERATIONS AND DREDGED MATERIAL

MANAGEMENT ALTERNATIVES

2.1 General

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);