Transportation of Dredged Material

Framework for Dredged Material Management

May 2004

2.3 Transportation of Dredged Material

Transportation methods generally used to move dredged material include the

following: pipelines, barges or scows, and hopper dredges. Pipeline transport is the

method most commonly associated with cutterhead, dustpan, and other hydraulic

dredges. Dredged material may be directly transported by hydraulic dredges through

pipelines for distances of up to several miles, depending on a number of conditions.

Longer pipeline pumping distances are feasible with the addition of booster pumps, but

the cost of transport greatly increases. Barges and scows, used in conjunction with

mechanical dredges, have been one of the most widely used methods of transporting large

quantities of dredged material over long distances. Hopper dredges are capable of

transporting the material for long distances in a self-contained hopper. Hopper dredges

normally discharge the material from the bottom of the vessel by opening the hopper

doors; however, some hopper dredges are equipped to pump out the material from the

hopper much like a hydraulic pipeline dredge.

2.4 Placement or Disposal Operations

Selection of proper dredging and transport equipment and techniques must be

compatible with disposal site and management requirements. Three major alternatives are

available:

Open-water disposal.

Confined disposal.

Beneficial use.

Each of the major alternatives involves its own set of unique considerations, and selection

of a management alternative should be made based on environmental, technical, and

economic considerations.

2.4.1 Description of Open-Water Disposal

Open-water disposal is the placement of dredged material in rivers, lakes,

estuaries, or oceans via pipeline or release from hopper dredges or barges. Such disposal

may also involve appropriate management actions or controls such as capping. The

potential for environmental impacts is affected by the physical behavior of the open-

water discharge. Physical behavior is dependent on the type of dredging and disposal

operation used, the nature of the material (physical characteristics), and the

hydrodynamics of the disposal site.

Dredged material can be placed in open-water sites using direct pipeline

discharge, direct mechanical placement, or release from hopper dredges or scows. A

conceptual illustration of open-water disposal using the most common placement

techniques is shown in Figure 2-2.