NTSB Determines Cause Of A Tank Vessel Striking A Pier In South Carolina

A tank vessel struck a pier at Joint Base Charleston’s Naval Weapons Station in South Carolina after a pilot allowed the vessel to get too close to a riverbank, the National Transportation Safety Board said Wednesday.

The 604-foot-long tanker Hafnia Amessi​ struck Naval Weapons Station Pier B while transiting the Cooper River on Jan. 14, 2024. A Charleston Branch Pilots Association pilot was navigating the vessel, which sustained damage to its side hull plating. The contact resulted in $8.1 million in damages to the vessel and pier. No pollution or injuries were reported.

​After making a right turn at a bend in the channel, the pilot began to favor the eastern side of the channel as the vessel approached the next bend, a left turn. During the maneuver, the tanker came closer to the riverbank, causing the vessel to experience bank effect—when a ship’s bow is pushed away from the bank and the stern is pulled toward the bank while transiting in confined waters.

The pilot’s subsequent rudder and engine orders could not overcome the bank effect, and the tanker could not complete the turn without striking the pier.

In addition to bank effect, the Hafnia Amessi was affected by the flood current when the vessel rounded the bend. As the tanker’s bow emerged from the shadow of the east bank, the current acted on the submerged portion of the vessel’s port bow—pushing it away from the bank and further working against the attempted turn.

The NTSB investigated another contact with Pier B in 2022 that was also caused by a pilot maneuvering a tank vessel, Bow Triumph, too close to the bank.

The Bow Triumph and Hafnia Amessi contacts demonstrate the risks associated with bank effect and current. If the Hafnia Amessi had approached the left turn in the relatively open water on its starboard side, the bank effect on the vessel’s port side would have been minimized, and the vessel would have been better positioned to handle the oncoming flood current.

As a result of the Bow Triumph and Hafnia Amessi contacts with Pier B, the Coast Guard Captain of the Port for Charleston issued orders requiring all vessels of 10,000 gross tons or more or with drafts exceeding 25 feet to “employ a tethered two-tug escort while transiting between Pier [B] and Snow Point.”

“Hydrodynamic forces reduce rudder effectiveness (squat and shallow water effect) and yaw the bow away from the closest bank and pull the stern in (bank effect),” the report said. “Shoaling can reduce the water depth in shallow waters, such as channels, below charted or expected, and therefore exacerbate the forces on a vessel. Bank effect can have an undesired effect on vessels, even for the most experienced ship handlers. Pilots, masters, and other vessel operators should consider the risks in areas known for shoaling when planning transits. Where appropriate, employ additional measures to mitigate the risk, including use of tugboats, reducing or increasing speed, and/or delaying the transit until more favorable conditions exist.”

For the full report, click https://www.ntsb.gov/investigations/AccidentReports/Reports/MIR2511.pdf

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