ASSESSMENT OF CONFINED (DIKED) DISPOSAL

Framework for Dredged Material Management

May 2004

5.0 ASSESSMENT OF CONFINED (DIKED)

DISPOSAL

This part of the report describes detailed assessments for alternatives involving

confined (diked) disposal facilities (hereinafter referred to as CDFs). In general, disposal

of dredged material in CDFs is regulated under the CWA. It is also important to note that

the CDF itself must comply with the Guidelines if it is sited in waters of the United

States. In addition, there may be other regulatory requirements under NEPA and other

applicable laws and regulations on a case-by-case basis.

CDFs differ in their geohydrology, sediment chemistry, carrier water removal,

contaminant release rates, and contaminant pathways affected. Therefore, the testing and

assessments required will vary somewhat accordingly, although the procedures are based

on similar scientific and engineering principles. The framework for assessing confined

disposal is illustrated in Flowchart 3-3. The detailed assessments described in this chapter

may be performed following a determination of the need for such assessments as

described in Chapter 3.

5.1 Determination of Characteristics of Confined Sites

Site specification for CDFs in many ways can be more complex than for open-

water sites. Real estate considerations are a major factor in determining the availability of

potential sites. Most navigation project authorizations require the local project sponsors

to provide the lands, easements, and rights of way for CDFs; some authorizations require

the sponsor to provide dikes and site management. CDFs therefore represent a substantial

economic investment on the part of the sponsor. In many instances, the sponsors will only

provide sites which meet short-term requirements, and additional sites may be required in

the future. Another consideration for CDF site specification is the fact that such sites are

normally visible to the public and are viewed as a competing interest for land use,

especially in coastal areas where there is intense pressure for both development and

preservation of lands.

A knowledge of CDF site characteristics is necessary for assessments of potential

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

assessments includes the following:

Available area and volumetric storage capacity to contain the material for the

required life of the site.

Real estate considerations.

Site configuration and access.

Proximity to sensitive ecological environments.