Remote control and autonomous underwater vehicles enable salvors to visualise the state of the sunken roro vessel
Under a contract with Houston-based marine salvage and emergency response company Ardent, Ocean Infinity used its autonomous underwater vehicles (AUVs) to conduct an urgent subsea search, inspection and operations project on the wreck of the roll-on/roll-off cargo vessel Grande America, which sank off the coast of France in the Bay of Biscay on 12 March 2019.
The ship was en route from Germany to Morocco when containers on the ship’s weather deck caught fire. The fire spread to other containers and led to the ship listing heavily and finally sinking. Italy’s Grimaldi Group reported that 2,210 vehicles and 365 containers were onboard on the ship.
In accordance with its antipollution plan, the Grimaldi Group initially dispatched the Boskalis-owned anchor-handling tug Union Lynx at the time of the accident to monitor any environmental damage and organise the recovery of any floating containers. Additionally, Grimaldi undertook an underwater survey of the wreck, located in 4,600 m of water, using a remotely operated vehicle (ROV) aboard France-based Ifremer’s multi-purpose research vessel Pourquoi Pas.
Under its contract with Ardent, Ocean Infinity used its AUVs to locate the wreck, and its ROVs undertook a programme of inspection and operations to determine the state of Grande America.
Last year, Ocean Infinity bought five Hugin AUVs from Kongsberg Maritime to enhance its fleet. Overall, the company has a fleet of six Hugin AUVs which are capable of operating in 6,000 m of water to collect high-resolution data at high speeds. For data collection, each AUV is equipped with:
- Side scan sonar.
- Multi-beam echosounder.
- Very low-frequency sonar (called a sub-bottom profiler).
- High-definition cameras
- Temperature sensors.
- Depth sensors.
High resolution interferometric synthetic aperture sonar (HISAS) generates high resolution range independent imagery and full swath bathymetry. Coupled with the other sensors on board, the Hugin AUVs produce a robust data set including HISAS imagery and bathymetry, EM2040 bathymetry, sub-bottom profiler data and colour photographs.
The mission was conducted from Ocean Infinity’s vessel Island Pride which had been in Gibraltar prior to the contract. Island Pride is a multi-purpose support vessel, with dynamic positioning class 2 capability based on a UT 737 CD design. The MPSV is owned by Island Offshore, which is majority owned by the Ulstein and Chouest families.
“At a depth of approximately 4,600 m, our data gathering technology was used to assess the state of the wreck”
“At a depth of approximately 4,600 m, our data gathering technology was used to assess the state of the wreck, and the high-quality imagery that we collected was pivotal in guiding our ROV team in executing the subsequent intervention,” says Ocean Infinity chief executive Oliver Plunkett.
“Emergency response, whether it’s a loss of assets, damaged infrastructure or where there is the potential for environmental impact, is a key part of Ocean Infinity’s offering,” says Mr Plunkett. He says the company maintains a fleet of three mobilised vessels, each with a complete set of the latest deepwater technology tools, deployed across the globe, to respond to such events.
In March, Ocean Infinity acquired a 25% interest in Guardian Geomatics.
“As with our AUV projects there are material gains in speed and efficiency using autonomous assets in scale to perform seabed surveys,” an Ocean Infinity spokesperson said. “We will also have materially fewer offshore man hours and fuel consumption is expected to be reduced, meaning our approach is not only faster and safer, but has a significantly reduced impact on the environment.”