The National Transportation Safety Board has concluded an investigation right into a severe allision involving a tanker and a Navy gasoline pier at a base in South Carolina, and has decided that financial institution impact was the first trigger. 

On the afternoon of September 5, 2022, the product tanker Bow Triumph received underneath approach from a non-public petroleum terminal on the Cooper River, upstream of Joint Base Charleston. The river is a winding tidal waterway, with sharp bends and branching tributaries. With a docking pilot aboard and a harbor pilot on the conn, Bow Triumph received underneath approach at about 1530, headed for an additional product terminal a couple of miles downriver. The pilot had made this transit about 500 instances earlier than, together with voyages aboard the identical class of tanker, and had piloted greater than 10,000 ships over the course of his 30-year profession. 

The ship handed two bends with out problem. As the Triumph approached the third bend, the pilot maneuvered in the direction of the east financial institution (left descending financial institution), anticipating {that a} tidal present would push the ship in the direction of the west financial institution because it rounded the bend. Unbeknownst to the bridge staff, the ship was now transiting nearer to the east financial institution than any ship within the earlier yr, based mostly on AIS information.  

At 1600, the pilot started the flip to port. At first the ship responded correctly, however then the speed of flip stalled. The pilot elevated RPM to full forward and gave a sequence of escalating rudder instructions, culminating at a full Becker rudder angle of 90 levels (past the utmost potential on typical vessels). 

In the shut confines of the slender waterway, the state of affairs started to alter shortly. By 1601:24, it was evident that the heading had solely modified by two levels, and the vessel was not making the flip; as an alternative, it was headed for Naval Weapons Station Charleston’s Pier Bravo, a finger pier which protrudes at an angle out into the river. 

At this level, the pilot ordered the crew to drop anchor and put engines astern. Less than a minute later, at 1602:20, Bow Triumph’s bow allided with Pier B, destroying a 300-foot part of the wharf.

Bow Triumph sustained about $2.5 million in hull injury, and the pier part needed to be demolished and changed at  a price of $29 million. (This January, the bulker Hafnia Amessi hit the identical pier, inflicting greater than $3 million in injury.)

On drydocking, investigators seen that Bow Triumph was lacking her hull coating in a number of areas, a sign that she might have touched backside. The waterway is thought for fast shoaling, and a Corps survey in May 2022 discovered that sediment accumulation had diminished the water depth by greater than 10 toes. According to the NTSB, the survey that the pilot relied upon was from November 2021, 10 months earlier than the casualty voyage. 

Given the information, NTSB concluded that the ship skilled financial institution impact when it transited so near the east aspect of the channel and handed over the shoal. Bank impact happens when a vessel transits shut by a riverbank, shoal or canal financial institution, and creates a strain distinction between all sides of the ship. This hydrodynamic phenomenon can push the ship’s bow away and pull the ship’s stern in the direction of the financial institution, exerting a turning power – on this case, to starboard. The impact is stronger in shallow water and at greater speeds. The incoming tidal present would have added further turning power to the bow because the tanker exited the bend. 

“Transiting in the center of the channel is prudent to avoid the risks associated with bank effect,” concluded NTSB. “Pilots, masters, and other vessel operators should consider the risks in areas known for shoaling when planning transits.”