As if Darth Vader from the film Star Wars had landed in the port of Gorcum. The sound of a diver's breathing apparatus echoes over the water. His colleague on the deck of diving vessel Triton asks if everything is all right, when the diver is about to disappear into the depth.

The experts from ECG (Explosive Clearance Group) are searching the soil of the Vluchthaven on behalf of the contractor de Vries & van de Wiel. This is necessary, as the ground may still contain explosives from the Second World War. Therefore, this was mapped beforehand with the help of a sonar ship. It yielded seventeen suspected locations. Once the objects have been identified, de Vries & van de Wiel will start on the enormous dredging job.

That company is part of the DEME Group from Zwijndrecht in Belgium, a specialist in dredging work. Rijkswaterstaat hired it to do the job. ,,This work required the necessary preparation," says Harro van der Plas, process and environment manager of de Vries & van de Wiel. ,,We already started doing that at the end of 2015, beginning of 2016."

Rijkswaterstaat wanted to start earlier. But the tender took longer because the dredging of the Vluchthaven was eventually included in a larger maintenance contract", explains spokesperson Anneke Heinecke. For years, the Vluchthaven has been too shallow in some places for inland navigation. But the boatmen know those spots."

Van der Plas is standing on the bank near the landing stage for inland shipping. The diving vessel lies a few metres away. The divers only need to examine a relatively small area of the seabed here", he says.

Using a map, he shows exactly how big the area is. On it is a schematic illustration of the Vluchthaven. In the middle, several shades of blue can be seen. It turns red towards the banks. In the section where the De Merwede water sports association has its jetties, there are only shades of red. This section is also being dredged, but is not part of this job.

It is also coloured red at the jetty where barges carrying hazardous substances anchor. The map was made at the start of the work in early February. In the meantime, a great deal of dredging has already been carried out. It gives a good indication of how extensive this job is", says Van der Plas.

According to Heinecke, some 47,000 cubic metres of dredged material must be removed from the port. The cost of this work, including the search for unexploded explosives, has been estimated at 750,000 euros. An exact figure cannot be given because it is part of a larger project." At the Krinkelwinkel, the ship on which a crane operator is pulling the dredged material out of the water is moored. That is done with extreme precision," Van der Plas says. The crane operator can see on a screen in his crane what he is doing under water. Not literally, but schematically. That ensures that he can work with millimetre precision. A dredging job like this seems like just a matter of shovelling, but it is an art in itself and requires craftsmanship." The full dredgers go to a depot in Hollands Diep.

So before the crane operator can start dredging, the divers have first examined the bottom. They use detection equipment and, for larger areas, a grid that they sink. In this way, they can examine the section by section. They work with GPS coordinates, literally searching the bottom inch by inch. Visibility under water is variable. Particularly at the shore, the water is sometimes turbid.

The divers have now determined that fifteen suspicious objects do not pose a threat. Old bicycles, iron plates and an old sluice gate. That was in the corner where there used to be a lock gate depot. That was under water and when clearing it they apparently forgot about one."

It is the most remarkable find so far. Although it is not yet clear what the last two objects are. They lie in the middle of the channel and will not be examined by divers until this month or next month. If they also prove to be safe, dredging can continue and the job will be completed by the end of May. If the explosives are indeed present, then a different scenario will arise,' says Van der Plas. A lock gate lay in the corner where there used to be a lock gate depot. That was under water and while clearing it, they apparently forgot one.

Then the municipality of Gorinchem must take action. The municipality is legally obliged to report the find to the Explosives Clearing Service of the Ministry of Defence. These specialists will subsequently determine what needs to be done. There are scripts for that", says a municipality spokesperson.

Shipping must in any case take account of the dredging work in the Vluchthaven.

Skippers can't just barge into the port," Heinecke explains. Anyone who wants to moor there has to consult with our people at the Regional Traffic Centre in Dordrecht. Our messages to the shipping public also let them know that work is being carried out in the Vluchthaven."

In addition, there are two text signs at the Punt on the Merwede that warn shipping on the river about the work.

Members of the De Merwede water sports association also have to cross the 'work area' when they want to leave their harbour. Van der Plas: ,,They report in advance and get a signal when it is safe to pass. From Friday evening to Sunday inclusive, the dredging work will be stopped, so they can enter and leave the harbour freely.

On other days it has to be done by mutual agreement, with a view to safety. Our people also consult with each other all the time. This is necessary to ensure safety, not only for the divers but for everyone on the water. Not only for the divers, but for everyone on the water.

Source: AD, 15-04-2018