4.3.2 Tier II - Effluent Quality Screen - Equilibrium Partitioning

1. Information is sufficient to reach a decision. This is the case when WQS

exist for all COC and are met for all COC after consideration of mixing.

No further effluent evaluations are necessary.

2. Information is not sufficient to reach a decision. This is the case when

WQS are exceeded for one or more COC after consideration of mixing.

Conduct the effluent equilibrium partitioning screen (Section 4.3.2), and/

or if applicable WQS are not available or there is concern about

interactive effects, go to the Tier III toxicity evaluation.

4.3.2 Tier II - Effluent Quality Screen - Equilibrium Partitioning

The second Tier II evaluation for effluent is based on equilibrium partitioning

principles and conservative (i.e., err on the side of environmental protection)

application of design and operating principles for CDFs (Schroeder, Olin Estes,

and Palermo in preparation). The equilibrium partitioning screen is based on the

maximum COC concentrations that could possibly result from the dredged

material effluent, considering the concentrations of dredged material solids in the

ponded water and effluent, the bulk concentration of contaminants in the dredged

material, the initial mixing of effluent in receiving waters, and applicable WQS.

Separate procedures are available for evaluating effluent releases from both

mechanically dredged and hydraulically dredged or offloaded sediments.

The effluent equilibrium partitioning procedure utilizes an electronic

spreadsheet for the calculations. Project-specific information regarding the method

and rate of CDF filling and dredged material properties is entered in the

appropriate cells of the effluent tab of the spreadsheet. The evaluation uses these

data and default values for pertinent variables to calculate a predicted maximum

effluent concentration of contaminants. The results are compared to WQS. The

spreadsheet, along with documentation, can be downloaded as an Automated

Dredging and Disposal Alternatives Modeling System (ADDAMS) module from

the USACE DOTS website at www.wes.army.mil/el/dots. If desired, equations for

performing the calculations manually are also available (Schroeder, Olin-Estes,

and Palermo in preparation).

4.3.3 Tier II Effluent Decisions

After consideration of the Tier II effluent equilibrium partitioning evaluation,

one of the following conclusions is reached (Figure 4-2).

1. Information is sufficient to reach a decision regarding effluent quality. In

this case either:

a. WQS exist for all COC and are met for all COC after consideration of

mixing. No further effluent evaluations are necessary.

b. WQS are exceeded for one or more COC after consideration of

mixing, and information is sufficient such that management actions

should be considered. A decision to implement management actions

for effluent, such as operational modification or effluent treatment,

4-9

Chapter 4

Effluent During Disposal Operations