Potential Project Applicability

project also illustrated that a flexible-discharge dustpan dredge and hopper

dredges can work safely together in the same channel reach.

Operational characteristics of this flexible-discharge dustpan dredge indicate

that it could effectively work in other reaches of the Mississippi River and in

other navigation channels in a long distance discharge configuration. Depending

on site-specific conditions, two discharge pipeline configurations might be pos-

sible. In the long distance discharge configuration as used in the demonstration,

the dustpan could work across the total width of the channel discharging to one

side across the dike. In this configuration, dredging would be interrupted peri-

odically for vessel traffic passage as the dredge would need to move when

working across the channel CL. As an alternative, the dustpan could work one-

half of the channel at a time discharging to that side across the dike. In this

configuration, vessel traffic could pass in the other half of the channel resulting

in fewer interruptions.

The results of this demonstration indicate that a flexible-discharge dustpan

dredge may be feasible for use in other reaches of the Mississippi River and in

other navigation types of dredging projects (with free-flowing relatively non-

cohesive material) such as construction and maintenance of sediment traps. Sedi-

ment traps are being considered for use in trapping and storing sediment upriver

of critical areas in navigation channels where shoaling occurs rapidly and can

impact vessel traffic. Sediment traps are also being considered for use at the

confluence of channels and downstream of critical shoaling areas. In these cases,

shoals that develop at the confluence of navigation channels or in other critical

areas can be managed by moving the sediment into the traps using technologies

such as the water injection dredge or SILT Wing excavator. This provides for

emergency shoal management involving small volumes of sediment without the

high costs associated with mobilization of traditional dredging equipment. The

traps are excavated when filled, often in association with other maintenance

dredging projects or during nonpeak dredging periods such that unit dredging

costs are lower.

If the flexible-dustpan dredge has a hull and winch anchoring system similar

to the Beachbuilder, then maintenance and specific beneficial use dredging in

more exposed (i.e., near coastal) project areas will be possible. The Beachbuilder

was designed for offshore beach renourishment projects on the east coast. Its

high freeboard and six-point anchor/winching system allow it to operate in

approximately 7-ft-high waves and ride out 10-ft-high waves (as per Weeks

Marine personnel). With this open-water operating capability, select projects

involving relatively free-flowing sediments located in more exposed sites could

be dredged by the flexible-discharge dustpan dredge.

Chapter 6

Feasibility Analyses