Long-Term Storage Capacity

Framework for Dredged Material Management

May 2004

dredged material. Procedures to evaluate the required surface area and volume during

active filling operations, to estimate effluent suspended solids concentrations, and to

design other features for CDFs are described in engineer manuals (USACE 1983, 1987

and in preparation). Expert systems for evaluation of initial storage capacity and solids

retention are described in Hayes and Schroeder (1992).

5.2.3 Long-Term Storage Capacity

In addition to initial capacity during active filling, an evaluation of long-term

storage capacity is required if a CDF is intended for use over multiple dredging cycles.

The long-term storage capacity of a given site is dependent on the material consolidation

and desiccation properties, climate, and operational conditions. Procedures to evaluate

long-term storage capacity of CDFs are provided in Engineer Manuals (USACE 1983,

1987 and in preparation). Expert systems for evaluation of long-term consolidation are

described in Schroeder et al. (2004).

5.2.4 Need for Management Actions

If the evaluation of direct physical impacts and evaluation of site capacity indicate

that the site is adequate, the remaining assessments can be conducted. If the evaluations

of direct physical impacts and site capacity indicate unacceptable impacts will result or

that site capacity is inadequate, management actions can be considered.

Management actions to minimize physical impacts of CDF construction may

include site management to reduce effluent solids discharge or dewatering of dredged

material between filling operations to extend capacity and reduce the need for a larger

site. Management actions are described in paragraph 5.4. If the management actions are

determined to be effective, the remaining assessments can then be conducted. If not, then

the confined-disposal alternative at the site under consideration should be eliminated.

5.3 Evaluation of Contaminant Pathways of Concern for CDFs

If the initial evaluation of sediment contamination described in paragraph 3.5.3

reveals that contaminants are not of concern for specific pathways, then no additional

contaminant testing is required for those pathways. However, if contaminants are of

concern, an analysis of appropriate pathways must be conducted that may include

possible testing.

5.3.1 Contaminant Pathways for CDFs

The possible migration pathways of contaminants from confined disposal

facilities in the upland environment are illustrated in Figure 5-1. These pathways include

effluent discharges to surface water during filling operations and subsequent settling and

dewatering, rainfall surface runoff, leachate into groundwater, volatilization to the

atmosphere, and direct uptake. Direct uptake includes plant uptake and subsequent

cycling through food webs and direct uptake by animal populations living in close