4.4.3 SETTLE Computer-Assisted Settling Data Analysis

calculation for prediction of the total concentration of contaminants in the effluent

can be made.

Comparisons of predicted concentrations based on laboratory tests with water

quality standards should also consider background concentrations in receiving

waters and the detection limits used in the tests. If background concentrations

exceed the standards, a specified percentage above background may be considered

in determining a dilution requirement (in this case, mixing to concentration

slightly above background, say 10 percent, would not be expected to result in

unacceptable adverse impacts). Considering predicted concentrations in effluent,

standards, background, and detection limits, a number of different cases may

apply in interpretation of the comparisons and dilution factor required. These

cases are illustrated in Figure 4-5 and are considered in the EFQUAL program

(Section 4.4.4).

Detailed procedures for conducing the EET and LTCST and calculations for

prediction of effluent quality are provided in Appendix B.

4.4.3 SETTLE Computer-Assisted Settling Data Analysis

The SETTLE application (Hayes and Schroeder 1992) of the Automated

Dredging and Disposal Alternatives Modeling System (ADDAMS) suite of

computer programs (Schroeder and Palermo 2000) provides a computer program

to assist users in the design of a CDF for solids retention and initial storage in

accordance with the design procedures in Engineer Manual 1110-2-5027 (HQ,

USACE 1987). SETTLE performs the necessary calculations for prediction of

effluent TSS concentrations for given CDF ponding and flow rate conditions, and

a relationship between CDF retention time and effluent TSS can be developed.

The laboratory column settling test is an integral part of these design procedures,

and the data from the LTCST are required in order to use this application. The

SETTLE application, along with documentation, is included in this manual as

Appendix E and can also be downloaded from the USACE DOTS website at

www.wes.army.mil/el/dots. If desired, manual data analysis procedures for CDF

design using the column settling test data are available (EM 1110-2-5027 (HQ,

USACE 1987); Appendix B Inland Testing Manual (EPA/USACE 1998; and

Palermo 1985a-d)).

4-13

Chapter 4

Effluent During Disposal Operations