Counter-mining two historical naval mines discovered with the help of an autonomous underwater vehic

Counter-mining two historical mines discovered with the help ofan autonomous underwater vehicle

French Navy

Last updated: 2 October 2015 at 11:56

On September 24 and 27, a team of French clearance divers (Groupement des plongeurs démineurs, GPD) based in the Atlantic region neutralized one after the other two German naval mines from World War II off the coast of Plouguerneau. These munitions, each weighing one metric ton, were detected two weeks earlier a few hundred meters from the town's port by an autonomous underwater vehicle (AUV) currently being tested by France's Mediterranean and Atlantic GPD forces.

These mines were lifted from the seabed and then held in place at a depth of a dozen meters using air-filled balloons. They were then towed approximately four nautical miles further offshore away from inhabited areas. The divers then neutralized the devices in open water in order to protect as much as possible the underwater wildlife.

Three kilos

This is the amount of explosives placed on each of the mines to initialize their detonation. The priming system consisted of a detonator triggered by a diver and a 200-meter-long electrical wire connected to the explosive. The clearance divers carried out their work from the support, rescue and oil spill response vessel (BSAD) Argonaute and the clearance divers' base vessel (BBPD) Styx.

Maximum security

The French Maritime Prefecture for the Atlantic and the Plouguerneau mayor's office published local decrees to ensure the demining operations took place with the maximum security. Notably, all navigation was prohibited within a range of 1500 meters around the munitions as well as all water-based activities within a range of 3000 meters while the operations were ongoing.

Unmanned underwater vehicles: the future is underway

It was an A9, a French-made autonomous underwater vehicle currently being tested that enabled the detection of the two German mines. This vehicle was used in addition to a towed sonar array. The A9-M vehicle can be launched by two people in a semi-rigid craft. The Mediterranean and Atlantic GPD forces each have three.

Published on the web site Colsbleus.fr, September 2015

Sources: Marine Nationale

Rights: Ministère de la Défense

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