NTSB Identifies Cause of Bonnie G Accident
The NTSB has released its report on the grounding of the former OSV Bonnie G, which occurred on October 4, 2023, half a mile south of Cyril E. King Airport, St. Thomas, U.S. Virgin Islands. The agency determined that a broken anchor chain caused the Bonnie G to run aground during Tropical Storm Philippe and initiated a 26-day rescue journey at the height of hurricane season.
Originally delivered in 1981 by Halter Marine of Lockport, Louisiana as an offshore supply vessel, the 172-foot-long, Vanuatu-flagged vessel has had several names, including Lone Wolf, Century, and Bella. She was acquired by Third Lady, LLC in 2020. She was subsequently converted to a cargo ship, with the stern ramp extended and the double-deck funnel relocated to facilitate ro-ro loading and maximize deck space. She regularly transports cargo between Puerto Rico, St. Thomas, and St. Croix, with occasional stops at other ports in the U.S. Virgin Islands and the British Virgin Islands.
On October 4, 2023, the Bonnie G was anchored one mile south of St. Thomas waiting for severe weather to pass when her anchor chain broke and the ship began to drift toward land. When the captain attempted to steer the ship away from shore, the ship ran aground.
All 12 people on board were rescued by the U.S. Coast Guard. The Bonnie G lay aground for several weeks until rescuers refloated it and towed it to the dock. No injuries or pollution were reported. Structural damage to the vessel totaled approximately $1.5 million, according to reports.
Prior to leaving St. Croix, the ship’s captain, Bonnie G., checked the weather forecast for the ship’s planned route to St. Thomas. Winds were expected to be between 10 and 15 knots, with gusts up to 25 knots, after midnight, when the crew was moored to the dock. When the ship arrived at Crown Bay, the wind was stronger than expected. In addition, one of the convoys, which was loaded with cargo, broke away from its anchorage and partially blocked Bonnie G’s berth. With Bonnie G’s dock blocked by the convoy and weather conditions worse than expected, the captain decided to anchor the ship until the weather improved.
Once the vessel reached the inner anchorage position, the captain deployed 135 feet of anchor chain, which was likely based on an erroneous assessment of the water depth of 23 to 26 feet, when the actual water depth was 68 feet.
Investigators concluded that the missile fired by Pony G should have been 2.5 to 3.5 times larger than it actually was. Due to the water depth and wind conditions, Bonnie G’s captain did not release enough chain to safely anchor the vessel.
The report added: “When the vessel is anchored, a length of anchor chain 5 to 7 times the water depth (span, i.e. the ratio of anchor chain to water depth) should be used; in severe weather conditions, a greater number of anchor chains should be used.”
The captain had not used the ship’s nautical chart to identify nearby rocks, and while maneuvering the vessel after the anchor chain broke, he inadvertently struck the rocks directly, causing the vessel to run aground. As a result, the hull was penetrated directly forward of the engine room. Before the crew abandoned ship, the forward watertight door of the Bonnie G’s engine room was open and unlocked. Investigators determined that if the watertight door had been closed as required, the engine room and aft space would have been less likely to be gradually flooded, thereby limiting the damage to the ship.
