ASSESSMENT OF OPEN-WATER DISPOSAL

Framework for Dredged Material Management

May 2004

4.0 ASSESSMENT OF OPEN-WATER

DISPOSAL

This chapter describes the detailed assessment of open-water disposal including

testing and management options and control measures. The portion of the framework for

detailed assessment of open-water disposal alternatives is illustrated in Flowchart 3-2.

The paragraph numbers in the text are shown as appropriate in the flowchart. The

detailed assessment described in this chapter may be performed following a

determination of the need for such an assessment as described in Chapter 3.

4.1 Determination of Characteristics of Open-water Sites

A knowledge of site characteristics is necessary for assessments of potential

physical impacts and contaminant impacts. Information on site characteristics needed for

assessments may include the following:

Currents and wave climate.

Water depth and bathymetry.

Potential changes in circulation patterns or erosion patterns related to

refraction of waves around the disposal mound.

Bottom sediment physical characteristics including sediment grain-size

differences.

Sediment deposition versus erosion.

Salinity and temperature distributions.

Normal levels and fluctuations of background turbidity.

Chemical and biological characterization of the site and environs (e.g.,

relative abundance of various habitat types in the vicinity, relative adaptability

of the benthos to sediment deposition, presence of submerged aquatic

vegetation, and presence of unique, rare or endangered, or isolated

populations).

Potential for recolonization of the site.

Previous disposal operations.

Availability of suitable equipment for disposal at the site.

Ability to monitor the disposal site adequately for management decisions.

Technical capability to implement management options should they appear

desirable.

Ability to control placement of the material.

Volumetric capacity of the site.

Other site uses and potential conflicts with other activities (e.g., sport or

commercial fisheries, shipping lanes, and military use).

Established site management or monitoring requirements.

Public and regulatory acceptability to use of the site.