Air assets and a European Maritime Safety Agency satellite team will continue to monitor the area to ensure the long-term absence of oil spills.
No large-scale pollution is expected from the ConRo Grande America, which sank in in mid-March in the Bay of Biscay while en route from Hamburg to Casablanca, said Riaz Akhoune, spokesman for the French Atlantic Maritime Prefecture, earlier this week.
Patties of heavy fuel order may still wash ashore, Akhoune told 20 Minutes, and air assets will continue to monitor the site along with the European Maritime Safety Agency’s Cleanseanet satellite team to ensure the absence of oil spills.
“The shipowner will continue to watch his work and perhaps offer on-site treatment, but the main thing for us is that the pollution was treated downstream and the leaks from the wreckage were arrested,” Akhoune said via translation.
The Grimaldi Group-owned Grande America, which sank to a depth of 4,600 meters, was carrying about 2,200 tons of heavy fuel oil along with 2,210 vehicles and 365 containers, including 45 containers that had hazardous cargo. Six drifting containers were recovered, Jean-Louis Lozier said in early April.
“To date, we have been able to recover at sea several tens of tons of solid fuel oil in solid form, and several hundred tons of water polluted by hydrocarbons,” he said according to a translated article from 20 Minutes posted April 2. “These pollutants are landed in the port of La Rochelle to be treated by a specialized firm under contract with the shipowner.”
The French and Spanish ships chartered to pump the area have returned to port, Akhoune said.
Low intensity iridescence on the surface above the wreck remained in early April, but it disappeared under the natural effects of the sea and was not recoverable by a support vessel, according to the Prefecture.
Seabed survey and ocean exploration company Ocean Infinity, which conducted an inspection and operations program under contract with Grande American salvor Ardent, announced Tuesday it had finished work on the wreck site. The company used its fleet of autonomous underwater vehicles to locate the wreck and remotely operated underwater vehicles for the mission, which was conducted from the Island Pride.
The remote operated vehicles discovered the several slight oil leaks from the Grande America — which was upright and set straight on a sandy bottom with its rear part buried several meters — escaped through vents on some of the ship’s seawater ballasts from its fuel tanks, which explained the presence of low-density iridescence at the surface vertical to the wreck, the Prefecture said April 19 in a statement.
“It was therefore necessary to find a way to close these vents, with the robot that plugged the holes and screwed plates on top,” Akhoune said. “This is the first time that this type of operation is carried out with a robot at 4,600 meters deep, at least in the Atlantic. And then he stayed to check the tightness of the building.”
The Island Pride left the wreck area on April 19.