Liftboat catastrophe

Fatalities in a Gulf of Mexico platform capsize could have been avoided if the crew and workers had been supplied with inexpensive lifesaving PLBs. 

In April 2021, the US-flagged liftboat SEACOR Power capsized seven miles off the coast of Louisiana, USA, in a severe thunderstorm. Eleven crew and eight offshore workers were aboard at the time. Search and rescue efforts — which were hampered by 40kn winds and 12ft seas — persisted throughout the night and into the next day. Six personnel were rescued and the bodies of six fatalities were recovered. The bodies of the seven other men were never found. The platform vessel, valued at $25m, was a total constructive loss.

Self-elevating vessels

A common sight in the relatively shallow waters of the Gulf of Mexico, liftboats are three- or four-legged self-propelled, self-elevating vessels used in the installation and maintenance of offshore infrastructure. After carrying equipment and personnel to a facility, they can elevate their hull clear of the water to provide a stable work platform. Apart from the expansive decks area, they are also usually equipped with an accommodation block, cranes and a helideck. 

White out

While enroute to the Mississippi Delta the 167ft by 103ft vessel was hit by a series of increasingly intense squalls as it proceeded at three knots using all four of its propulsion engines, each one driving a propeller. Within minutes it was engulfed in ‘white out’ conditions. They slowed the engines and decided to ‘soft tag’ the platform — a routine lowering of the legs until they just touch the seafloor in order to act as an anchor.  

As the legs were being lowered the vessel was steered into the wind to reduce its speed so that the leg pads wouldn’t be damaged when they connected with the seafloor.  

The vessel, however, quickly heeled over much more than expected and began rocking from side to side. At the same time, water started coming into the galley. When the angle of heel reached 5°, the captain took the wheel and throttles in an attempt to get the vessel back on track, while ordering everyone to don lifejackets. But the rate of heel increased until SEACOR Power capsized onto its starboard side, coming to rest in 50ft of water. 

The vessel eventually broke apart. The forward part of the hull, with the engine room, was recovered and brought ashore, along with portions of the legs. The remaining sections, including the accommodation block, sank to the seabed silt and could not be recovered.

Swept away

Nine of the 19 people onboard survived the initial capsizing. Of these, three were able to don lifejackets but were swept away by the seas. Two of those drifted more than four miles from the site of the incident after being in the water for two hours. 

The remaining six made their way onto the lower decks (four without lifejackets). Three of those were washed overboard but successfully rescued. The remaining three did not survive. 

Pre-accident photo of Seacor Power (left) in the lifted configuration, alongside an offshore platform. Credit: Seacor Marine

Hampered rescue

An accident investigation report by the USA’s National Transportation Safety Board (NTSB) found that the speed at which SEACOR Power capsized and the angle at which it came to rest made evacuating the structure difficult and dangerous. The high winds and challenging seas also hampered rescue efforts, as did underwater and overhead obstructions created by the liftboat’s upturned broken structure, which prevented surface and air resources getting close enough to rescue personnel straight from the wreck. Importantly, the investigators also found that none of the survivors were equipped with PLBs (personal locator beacons) or SENDs (satellite emergency notification devices). 

Report conclusions

The NTSB report concludes that the capsizing occurred when SEACOR Power was struck by conditions that exceeded its operational limits, causing a loss of stability. The weather forecast provided to the crew by the vessel’s operator on the morning of the incident was insufficient for weather-related decisions. The US Coast Guard’s local navigational telex site was also down at the time, which meant that the crew did not receive a Special Marine Warning outlining the severity of the incoming storm conditions. 

Although SEACOR Power met all required stability criteria, its trim at the time of the accident decreased its ability to resist a capsize after its turn to port, which, along with its speed through the water, shifting equipment and leg movement, induced the catastrophic motion.  

Safety recommendations

The NTSB has recommended that the US Coast Guard develops procedures to inform mariners in affected areas whenever there is an outage at a navigational broadcasting site, and that it modifies liftboat stability regulations to require even greater stability for all new liftboat vessels. The NTSB has also called on the US Coast Guard to ensure that all personnel employed on US-flagged vessels are provided with PLBs to enhance their chances of survival in a similar incident. 

Dennis O’Neill is a freelance journalist specialising in maritime.