4.1.3 Regulatory Considerations

this case, but the influence of the filter media in retaining suspended particles and

adsorption of contaminants from the effluent discharge should be considered.

Dredged material may be placed in some CDFs by direct mechanical means

such as rehandling from barges or by truck. Although such filling operations

normally involve handling relatively little free water, there may still be an effluent

discharge. In addition, there may be ponded water in the CDF before filling

begins, especially for CDFs constructed in water. For the case of mechanical

filling, the effluent discharge involves the free water that is released during the

mechanical disposal operation or the existing pond water that is displaced by the

operation. Separate procedures are available in Tier II for mechanical filling.

However, no specific Tier III laboratory tests have been developed for the case of

direct mechanical disposal. The testing procedures described here for hydraulic

disposal may be used in the interim for the case of mechanical disposal and are

considered conservative for such evaluations.

4.1.3 Regulatory Considerations

As discussed in Chapter 1, CDF effluent is administratively defined as the

discharge of dredged or fill material into waters of the United States and is subject

to regulation under CWA Section 404. The fact that the effluent is nationwide

permitted at 33 CFR 330.5(16) does not relieve applicants from Corps of

Engineers permits, nor does it relieve the Corps when undertaking dredging

projects from ensuring that effluent does not violate applicable water quality

standards. Specifically, the nationwide permit requires that a water quality

certification be obtained from the appropriate agency, whether it be the State,

tribe, or EPA in some cases.

In those instances where the effluent receives CWA Section 401 Water

Quality Certification and there is no reason to believe that there will be

contaminants released from the effluent during the filling operation and

subsequent release of ponded water from CDF management, no further evaluation

of effluent is needed.

4.1.4 Mixing Zones

The evaluation of effluent discharges should consider the effects of mixing

and dispersion (Section 2.3.3). Mixing zones are normally defined by the State

regulatory agency as part of the CWA Section 401 Water Quality Certification

requirements. When effluent enters receiving waters, it is dispersed by natural

physical processes so that the concentration decreases spatially and temporally

beyond the point of entry. This phenomenon is important in determining the

potential for effects, because effects depend on both the concentration to which

organisms are exposed and the length of time for which they are exposed. Effects

are generally less at lower exposure concentrations or shorter exposure times, and

for each COC there are exposure time-concentration combinations below which

effects do not occur. The Federal regulations implementing Section 404(b)(1),

Clean Water Act (40 CFR 230), recognize this and explicitly provide for

4-3

Chapter 4

Effluent During Disposal Operations