When Dutch dredging contractor Martens en van Oord discovered ammunition in the material it was dredging the job was shut down and they had to find a solution.
They had been working to enlarge the Twentekanaal an important inland shipping channel in the east of Holland. The goals of the project are to enlarge the canal to accommodate larger ships and to provide extra capacity for water drainage.
Martens en van Oord is a medium-sized contractor specializing in infrastructural jobs.
The explosives found were identified as ammunition dating from the Second World War. After the war they had been dumped in large quantities into the canal especially near quaysides and at bridges. At once all backhoes and excavators were banned from the area as the explosive devices were not to be brought above the water surface for security reasons.
Martens contacted Damen Dredging Equipment to seek a solution. The two companies collaborated to design a a specialized suction mouth to attach to a DOP submersible dredge pump which in turn could be attached to the hydraulic excavator Dongeoord. The heavily-constructed suction mouth is provided with a grid and jetwater nozzles. The grid filters out the ammunition leaving it on the canal bed. The jetwater keeps the grid free and ensures free flow of the material.
The DOP3530LD submersible dredge pump to which the special head is directly attached is connected to the boom of the hydraulic excavator and pumps the dredged material through a discharge line over the pontoon to a heavy-duty funnel-shaped barge loader. Should any explosive manage to get through the grid and the dredge pump it is caught in the funnel and the barges can be filled without danger. The funnel has a hatch to empty it from below – dumping any debris back into the canal. The complete configuration has been patented by Martens en van Oord.
The suction mouth was designed built and delivered in two months along with the DOP pump complete with power pack hoses and other equipment. As of the first of January 2007 the configuration had been running for three months. The barges are filled continuously without any explosives being found.