Dredge mobility in working between dredging assignments

options would use the flexible floating hose, but for the shorter run, instead of

using submerged line connected after the hard point, pontoon-mounted floating

(steel) line could be used. This floating line could be connected to a spill barge

anchored with spuds or anchor/haul wires.

Dredge mobility in working between dredging assignments

This factor requires the dredge be capable of quickly moving between dredg-

ing assignments (generally less than 6 hr). The limiting factor in moving the

Beachbuilder (given the type of contract and demonstration project used) was

found to be relocation of the hard point by extending the submerged line. The

contractor estimated that with sufficient plant and pipe standing by, the 3,600-ft

extension of submerged line and relocation of the hard point would have been be

completed in 12 hr instead of 22.7 hr. Weeks Marine personnel also estimated

that a (planned) shorter extension (1,000 to 2,000 ft) would take 4 to 6 hr to

complete, and that a longer run (around 6,000 ft) would require about the same

12 hr as the 3,600-ft run because of the mechanics of how the extension is

accomplished.

For the demonstration at HOP, only one hard point/submerged line/shore line

was used as specified in the contract. In a (volume) unit price contract, it is con-

ceivable that the contractor might elect to construct more than one hard point/

submerged line/shore line setup. By doing so, when the dredge is finished at one

location, the floating hose could be immediately disconnected from that hard

point and moved to the next assignment. Once there, the floating hose would be

connected to the other hard point, allowing the dredge to maximize its effective

dredging time. Evaluation of the flexible-discharge dustpan dredge mobility

capabilities for this configuration is beyond the scope of this demonstration

report. When pumping through the 3,000-ft-long pipeline for overboard place-

ment projects, the use of pontoon-supported floating line could improve the

dredge's ability to move between assignments due to the higher degree of

"portability" of the entire pipeline. Or, similar to the 15,000-ft pumping config-

uration described above, separate hard point/submerged line or pontoon floating

line assemblies might be prepared and waiting for the dredge in different areas to

significantly reduce transfer times between assignments.

Dredging mobility in sailing between dredging regions

This factor requires the dredge be capable of quickly moving between dredg-

ing regions (generally less than 24 hr). In the Mississippi River these regions

include the HOP and Upper Southwest Pass, deep-draft crossings from Baton

Rouge to New Orleans, and lower jetty and bar channels; the Mississippi River-

gulf outlet bar channel; and the Calcasieu River bar channel. As discussed above,

for the 15,000-ft pumping capability, the limiting factor in moving the

Beachbuilder would be the movement of the submerged line and placement of

the shore line. The pipeline construction would be required prior to arrival of the

dredge. For the 3,000-ft pumping capability, the portability of taking the same

pontoon-mounted floating discharge line with the dredge may achieve the

mobility requirement, or having a different short line already assembled and

Chapter 6

Feasibility Analyses