Feasibility Analyses

Feasibility Analyses

Potential Project Applicability

The feasibility of using this dredging methodology at HOP depends on

numerous technical, economical, and social aspects. The feasibility analysis in

this report primarily addresses technical aspects as outlined in "Assessment of

Coastwide Louisiana Maintenance Dredging Capabilities under the Federal

Standard,"1 along with navigational safety aspects of this method.

The June 2002 flexible-dustpan dredging demonstration project illustrated

that the Beachbuilder or a similar dustpan dredge can work safely at the HOP and

move significant amounts of dredged material out of the channel and place this

material for the beneficial use of marsh creation/restoration. The dredged mate-

rial can be transferred long distances by pipeline over the existing dike, pasture-

land, and wetlands and directly discharged into shallow open-water areas without

need for re-handling or construction of disposal facilities. A dustpan dredge

would prove most efficient at the HOP working on the RDB side of the channel

(inside of the bend) where the shoaling tends to be the greatest and the dredge

can operate almost continuously while allowing passage of most deep-draft

vessel traffic. Working the RDB side also removes the dredge from a potential

collision hazard caused by a passing vessel that, if it were to lose propulsion

power and be pulled by the current toward Pass A Loutre, would drift into the

LDB side and possibly the dredge itself.

A flexible-discharge dustpan dredge would require self-propulsion capa-

bilities similar to the Beachbuilder during the demonstration (provided by

external tugs or with in-hull plant). The flexible-discharge floating hose allows

the dredge to move across the total width of the channel but limits its movement

up and down the channel (based on the total length of the floating hose). Move-

ment beyond this range requires interruption of dredging operations while the

hard point is moved and submerged line is added or removed (if only one hard

point and submerged line is used as in this demonstration). As a result, the dust-

pan discharge line configuration, as used in this demonstration, is most efficient

where continuous thick shoals are present and minimal movement of the hard

point is required. The dustpan dredge would not be as efficient in addressing spot

shoaling over long distances up and down the channel where frequent movement

of the hard point and associated pipeline would be required. Such conditions

would be more efficiently addressed using hopper dredges. The demonstration

Ibid.

Chapter 6

Feasibility Analyses