Submerged discharge - trdoer10048

a force that can be used to swing the end of the floating pipeline in an arc.

Such plates are commonly used in river dredging operations where mate-

rial is deposited in thin layers in areas adjacent to the dredged channel (El-

liot 1932). Such equipment can be used in capping operations to spread

thin layers of material over a large area, thereby gradually building up the

required capping thickness.

A device called a "sand box" (Figure 7) serves a similar function. This

device acts as a diffuser box with baffles and side boards to dissipate the

energy of the discharge. The bottom and sides of the box are constructed

as an open grid or with a pattern of holes so that the discharge is released

through the entire box. The box is mounted on the end of a spud barge so

that it can be swung about the spud using anchor lines (Sumeri 1989).

Figure 7. Spreader box or "sand box" for hydraulic pipeline discharge

Submerged discharge

If the placement of the contaminated sediment with surface discharge

results in unacceptable water column impacts, or if the anticipated degree

of spreading and water column dispersion for either the contaminated or

capping material is unacceptable, submerged discharge is a potential con-

trol measure.

In the case of contaminated dredged material, submerged discharge

serves to isolate the material from the water column during at least part of

its descent. This isolation can minimize potential chemical releases due

to water column dispersion and significantly reduce entrainment of site

water, thereby reducing bottom spread and the area and volume to be capped.

In the case of capping material, the use of submerged discharge provides

additional control and accuracy during placement, thereby potentially

reducing the volume of capping material required. Several equipment

Chapter 5 Equipment and Placement Techniques