4.4.1 Tier III - Effluent Total Suspended Solids Evaluation

may require more detailed information prior to design of such actions.

If management actions are selected, no further effluent evaluation is

necessary.

2. Information is not sufficient to reach a decision, which includes cases

where:

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

mixing, and more detailed information is desired for a decision

regarding WQS.

b. There are no applicable WQS or there is concern about interactive

effects.

In either of these cases, further evaluation in Tier III, or management actions

as an alternative to further evaluation, should be considered. A decision to

implement management actions for effluent may require more detailed

information for design of such actions. If management actions are selected, no

further runoff evaluation is necessary.

In determining the potential level of concern regarding interactive effects, the

number and classes of COCs that may be exceeded and the relative degree of

exceedences should be considered. Interactive effects may be purely additive,

synergistic (the resulting effect is greater that the sum of the effects stemming

from individual COCs), or antagonistic (the resulting effect is less that the sum of

the effects stemming from individual COCs). WQS were developed for single

contaminants. Where several are present and are close to WQS, especially if they

are the same class of contaminants (metals, chlorinated organics, metal-organic

complexes, nonpolar organics, etc), interactive effects may be of concern.

4.4 Tier III Effluent Water Quality and Toxicity

Evaluations

If Tier III is entered from Tier II because there was not sufficient information

to make a decision about WQS, the evaluation of water quality should proceed as

described in Sections 4.4.1 through 4.4.5. If Tier III is entered from Tier II

because of the absence of applicable WQS or because of concern about interactive

effects, the evaluation of toxicity should proceed as described in Sections 4.4.6

through 4.4.8.

4.4.1 Tier III - Effluent Total Suspended Solids Evaluation

If Tier III is entered for WQS evaluation, TSS and/or turbidity should be

evaluated as a COC. A Long Tube Column Settling Test (LTCST) is conducted

for the Tier III evaluation of TSS in the effluent. The LTCST measures the

effluent TSS for anticipated ponding and operational conditions (Averett,

Palermo, and Wade 1988; Montgomery, Thackston, and Parker 1983; and

Palermo and Thackston 1988c). This test is conducted in an 8-inch diameter,

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Chapter 4

Effluent During Disposal Operations