Port of Rotterdam

ERDC TN-DOER-T1

February 2000

Port of Rotterdam. The Port of Rotterdam, The Netherlands, has developed a real-time manage-

ment program for dredge plants working in Rotterdam Harbor. The system includes real-time

monitoring of dredge operating systems, production rate, location, draghead settings, and bin

operations. It incorporates the latest survey data in an interactive computer-based system. The

system is operated from a central office in the Port that allows the Port managers to give real-time

directions to dredge operations. The Port enters into 5-year contracts with dredging companies. The

Port employs silt traps to increase efficiency and has performed extensive studies to identify

contaminated versus clean sediments. Clean sediments are placed back into the North Sea.

Contaminated sediments are placed in confined disposal sites. The system is completely integrated

with remote links to enable real-time review of dredging operations.

Belgium, Maritime Schelde Department. The Ministry of Flemish Community dredges approxi-

mately 80-100 million cubic meters annually from the River Schelde. Most of the material is placed

back into the river in several designated sites. To accomplish this massive dredging operation the

Ministry enters into maintenance contracts for 7 to 9 years. The contract requires simultaneous

deployment of five hopper dredges, three sweep beams, one oil skimmer, one cutterhead suction

dredge, one backhoe, and one bucket dredge. Payment is provided through bin measurement and

haul distance using an equation developed by the ministry.

To track the operations, the Ministry has developed a dredge information system that provides

real-time feedback on key performance parameters to determine how and what the dredge operator

is doing and where he is operating. Key performance parameters include location, depth of cut,

mixture concentration, and several other components of the operation. Weekly surveys are con-

ducted by the Ministry to determine assignments for the various dredges working for the Ministry

at that time. The information system is then employed to determine the compliance with the

prescribed program. The management and analyses of dredge operations are real-time and are

continuously updated by the Ministry. Current costs are estimated at $3.50 to $4.00/cubic meter

(U.S.).

Nearshore Shelf Placement: Rijkswaterstaat, the government agency in charge of navigation

channels in The Netherlands, has begun to utilize nearshore placement techniques using conven-

tional bottom-dump dredges to place material in the nearshore for beach nourishment. In 1998,

approximately half of all the material placed for beach nourishment was by nearshore placement.

Instead of building berms, the Rijkwaterstaat builds shelves of material nearshore, beginning at the

8-m contour. The dredges are equipped with doors that can be opened sequentially, usually bow to

stern, and in increments. From the 8-m contour the dredge begins to open its doors and reduces the

bottom elevation to approximately 5 m while reducing the draft of the dredge. As the dredge moves

closer to shore, it continues to open more of the bottom doors wider, releasing additional material

until it moves to the original 5-m contour. The dredge fills the site until the bottom between the

original 8-m and 5-m contour is filled to a depth of 5 m. One placement cycle takes between 6 to

12 minutes. If material must be placed in shallower water, the rainbow technique (a nozzle located

in the bow of the vessel used to spray the material up to 50 m closer to shore) is used. Studies of

the placement technique have shown that the sediment migrates shoreward and that it remains within

the littoral system.