Figure 1-1. Schematic of upland, nearshore, and island CDFs (after USACE/EPA 1992)

Figure 1-1 illustrates the various categories of CDFs. CDFs may be

constructed as upland sites, nearshore sites with part of the perimeter on shore and

part in water, or as island containment areas. CDFs also vary considerably in size,

dike type, and method of filling. The isolation of the dredged material from

adjacent waters and land during and following disposal distinguishes a CDF from

other forms of disposal such as unconfined upland, open water, wetland, or

contained aquatic disposal (CAD), which is a form of subaqueous confinement

with capping.

Figure 1-1. Schematic of upland, nearshore, and island CDFs (after USACE/EPA

1992)

A totally upland CDF would allow for all dredged material fill to be placed

above the water table. Over time, the material in an upland site will dry and

exhibit terrestrial conditions. CDFs constructed in water may become upland sites

once the fill reaches elevations above the mean high water elevation. A true

nearshore site will take advantage of the shoreline as a part of the containment

structure for the site, with in-water dikes or other containment structures required

only for the outer walls of the total enclosure. Island CDFs are similar to

nearshore CDFs, except that they are constructed totally in water with no direct

physical connection to the shore.

Dredged material in CDFs in any of the three types of locations (upland,

nearshore, and island) may constitute any of three types of habitats (aquatic,

wetland, and terrestrial). The resulting biogeochemical conditions determine

potential contaminant activity and receptors potentially at risk, and therefore, the

appropriate evaluative procedures.

Habitat

CDF Locations

Types

Biogeochemical Conditions

Upland, Nearshore, and

Aquatic

- Dredged material remains water-saturated, reduced,

Island

and anoxic

- Receptors are aquatic organisms and their predators

Wetland

- Dredged material remains water-saturated, reduced,

and anoxic

- Receptors are wetland organisms and their predators

Terrestrial

- Dredged material dries and oxidizes over time

- Receptors are terrestrial organisms and their predators

1-2

Chapter 1

Introduction