5.1.5 Data Requirements

5.1.5 Data Requirements

Data requirements for runoff evaluations include those pertaining to the

dredged material characteristics and should be obtained by sampling the

sediments to be dredged and testing them. The process described in Chapter 3

should identify the COCs for runoff quality evaluations. The dredged material

characterization data, the simplified laboratory runoff procedure (SLRP), and/or

the runoff simulator/lysimeter system (RSLS) tests described below provide the

remaining data required for prediction of the quality of the runoff. The CDF

surface area, slopes, and precipitation data for the region are also required. A

summary of the data requirements for runoff quality prediction is given in

Table 5-1.

Table 5-1

Summary of Data Requirements for Prediction of the Quality of

Runoff from Confined Dredged Material Disposal Areas

Data Required

Source of Data

Runoff total suspended solids concentration

Dissolved concentration of COC in runoff

Equilibrium Partitioning or SLRP or RSLS tests

Total concentration of COC in runoff

SLRP or RSLS tests

Fraction of COC in the total suspended solids in

SLRP or RSLS tests

runoff

CDF Surface Area

Site information

CDF Slope

Site information

Precipitation Data

National Weather Service

* This summary includes only those data required for runoff quality prediction. It is assumed that the

disposal area under consideration is designed for effective sedimentation and storage capacity to

handle effluent. Data requirements for such design or evaluation are found in EM 1110-2-5027

(HQUSACE 1987). The runoff evaluation assumes the worst case (direct discharge of runoff with no

retention time), so ponding effects are not considered in the evaluation of results.

5.1.6 CDF Design for Runoff Control

When the quality of the runoff from a CDF is of concern, the design,

operation, and management of the site is important. Because the runoff pathway

is of concern after filling and initial dewatering operations, CDF management for

runoff is different than for effluent. However, the storage time required for

effective sedimentation of TSS in runoff should be considered. Procedures

described in Engineer Manual 1110-2-2-5027 (HQUSACE 1987) for evaluating

TSS retention in CDF are generally applicable to runoff. These design procedures

determine the surface area and ponding depth required to achieve effective

sedimentation, the required containment volume for storage (including required

freeboard), and the proper sizing of weir structures.

Generally, a CDF designed for effective management of effluent would have

adequate storage capacity for managing precipitation runoff. However, as the

dredged material oxidizes and some contaminants become more soluble, simply

allowing time for settling may not be sufficient to reduce contaminants dissolved

in runoff.

5-4

Chapter 5

Surface Runoff After Disposal Operations