November, 14th, 1995, the Dutch trailer dredger “Spauwer” capsized during sandwinning operations on the “Kwintebank”, off the Belgian coast.
Four crewmembers survived for 11 hours in the upside down turned wreck, until rescued by Belgian navy divers. The skipper-owner died in the wheelhouse.
The wreck of the ship was salvaged on November, 26th, and delivered to the owner in Hansweert, the Netherlands one day later.
Trailer dredger "Spauwer", after salvage of the wreck.
The “Spauwer” was originally built as the “Vesta”, an incinerator ship, incinerating toxic waste in a designated area in the
The “Vesta” was rebuilt in a hopper dredger, under supervision of Germanischer Lloyd.
This rebuild included widening of the ship's hull, to increase stability.
The Dutch council for Shipping (“Raad voor de Scheepvaart”) investigated the accident; and came to some remarkable conclusions.
The “Spauwer” capsized –apparently- at the end of the loading process, and the Dutch Council for Shipping stated that:
What the Council did not mention, but –to my personal opinion- may have been contributory cause to the capsizing:
Stability is a crucial and underestimated point in the operation of trailer dredgers.
Particularly dangerous are:
What is always hammered home during the training of dredge officers is -when the dredger starts to capsize- to dump the cargo. (The skipper of the Spauwer did exactly that.)
While this is basically correct, yet another reflex should be trained:
During loading, a layer of water and soil is always on top of the loaded material.
By simply shutting down the dredgepumps, (even if that would mean that the dredgepumps would block with material), this layer quickly flows away through the overflow(s).
Since this layer is mostly quite large, and the effect of shuttingdown the dredgepumps immediately, the positive effect on stability is enough to avert capsizing, in most cases.
Most trailer dredgers have their suction pipes arranged in trunnion slide(s) in the hull. If a draghead gets stuck on the seabed, the resulting forces is applied to the bottom of the ship.
However: there are still some trailer dredgers around (see photo above), who have the connection ship-sucion pipe on deck. These are mostly found on ships converted into trailers.
This configuration may prove very dangerous when the suction head gets stuck on the bottom. The force applies much higher and may lead the ship to capsize.
Marc Van de Velde