The US National Transport Safety Board (NTSB) has issued an investigation into the flooding and sinking of a towing vessel off the coast of Puerto Rico highlighting unsecured openings as the cause.
Marine Investigation Report 22/12 details the NTSB’s investigation into the 2020 sinking of the towing vessel Proassist III near Puerto Yabucoa, Puerto Rico. The towing vessel was transiting northbound off the coast of Puerto Rico when its stern compartments began flooding. The three crewmembers on board were unable to pump out the water and eventually abandoned the vessel.
“Unsecured or open aft deck hatches were the probable cause of the sinking of the Proassist III, an NTSB report has found.
Unsecured or open aft deck hatches were the probable cause of the sinking of the Proassist III, an NTSB report has found.
No injuries were reported, but the vessel was declared a total loss at US$968,000.
Shortly after departing Laguna de las Mareas, Guayama, the Proassist III encountered worsening weather conditions and seas began washing on deck. More than two hours after their departure, the crew noticed the vessel was down by the stern and found about three feet (one metre) of water in the flanking rudder compartment. Roughly 40 minutes after the crew discovered the water and attempted to pump it off, the flanking rudder and steering rudder compartments were filled with water. A post loss examination of the vessel showed openings in the vessel’s watertight bulkheads and a lack of gaskets and securing mechanisms for flush hatches and door openings on the deck.
NTSB investigators did not find any hull structural defects that could have allowed for the significant flooding and concluded a cover for an aft deck opening must not have been in place. Recently implemented regulations for towing vessels required all openings to be secured when operating offshore. The regulations also require maintaining the watertight and structural integrity of the vessel.
Deficiencies found in the post loss examination of the Proassist III indicated that the vessel was not adequately maintained. The U.S. Coast Guard’s Concentrated Inspection Campaign found three other vessels owned by the Proassist III owner had hull and deck integrity issues, signalling the company did not have an effective maintenance program.
The NTSB determined the probable cause of the sinking of Proassist III was unsecured or open aft deck hatches, which resulted in the flooding of the vessel’s aft compartments from water on deck and progressive flooding to other compartments through openings in watertight bulkheads. Contributing to the flooding of the vessel was the owner’s lack of an effective hull inspection and maintenance program.
Over the past five years, the NTSB has investigated five casualties involving towing vessels whose weather decks and openings were in poor condition—leading to flooding and subsequent sinking.
