NTSB: Anchor chain failure led to St. Thomas ship grounding

Inadequate scope on an anchor chain and its subsequent failure led to the 172’ cargo vessel Bonnie G going hard aground on a rock in the U.S. Virgin Islands Oct. 4, 2023, the National Transportation Safety Board reported Tuesday.

The Vanatu-flagged Bonnie G “was anchored, waiting out poor weather about 1 mile south of St. Thomas, U.S.V.I. Virgin Islands, when its anchor chain parted and the vessel began to drift toward land,” according to a summary from the NTSB.

As the captain tried to maneuver away from shore, the vessel grounded at around 3:30 a.m. With 12 people on board and concerned for their safety, the captain made plans to abandon the stranded vessel and called the Coast Guard to request rescue.

After securing the ship’s engines, the Bonnie G chief engineer saw water flooding into the midships space and returned to the main deck where the crew launched the ship’s life raft and rescue boat, according to the NTSB investigative report.

At 4:45 a.m. a 33’ Coast Guard special purpose craft with a crew of four launched from Charlotte Amalie Harbor, arriving at the scene 8 minutes later, and recovered all of the Bonnie G crew from the raft and rescue boat. They were transported safely to the dock at Crown Bay Marina with no injuries reported, according to the NTSB.

The Bonnie G remained stuck aground for several weeks until salvors could refloat it and tow it to a dock. At the time of the accident the ship was reported to carry up to 13,000 gals. of fuel but no pollution was reported, according to the Coast Guard.

 The vessel was declared a total constructive loss, valued at $1.5 million. In March 2024 the ship was scrapped in Colombia, according to the NTSB.

Built by Halter Marine, Lockport, La., in 1981 as an offshore supply vessel to service oil platforms in the Gulf of Mexico, it had several previous names, including Lone Wolf, Century, and Bella. In 2020 the vessel was acquired by Third Lady, LLC and underwent conversion into a cargo vessel, with widening of the stern ramp and moving the twin deck stacks to facilitate roll-on/roll-off cargo and maximize deck space.

The Bonnie G regularly transported cargo between Puerto Rico, St. Thomas, and St. Croix, with occasional stops in other U.S. Virgin Islands and British Virgin Islands (BVI) ports. The vessel was starting its weekly round-trip run.

After completing the port call in St. Thomas, the Bonnie G arrived in St. Croix around 7 a.m. on Oct. 3. By 2 p.m. cargo operations were complete, and the vessel was ready to depart, “loaded with six passenger vehicles; an industrial truck, trailer, and scissor lift; a refrigerated container full of fruits and vegetables; and an assortment of other cargoincluding medical supplies, scratch tickets, printer toner, magazines, books, whiskey,and beer,” the NTSB report notes.

In their detailed accident analysis, the safety board investigators wrote:

“Before departing St. Croix, the captain of the Bonnie G reviewed the weather forecast for the vessel’s intended route to St. Thomas. The winds were forecasted to be between 10–15 knots and gusting to 25 knots after midnight, by which time the crew expected to be tied up to the dock. When the vessel arrived in Crown Bay, the winds were higher than what had been forecasted.” 

“In addition, a loaded barge had broken free of its moorings and was partially blocking Bonnie G’s mooring location. Given the barge blocking the Bonnie G’s docking location and the worse than expected weather conditions, the captain decided to anchor the vessel until the weather improved.” 

Once in position within the anchorage, the Bonnie G captain deployed 135’ of anchor chain. That decision was apparently based on a falty assessment of the water depth being 23’ to 26’ when it was actually 68’ the investigators wrote. 

Based on that discovery, investigators found “the Bonnie G should have let out about 2.5–3.5 times more chain than was deployed,” they wrote. “Considering the water depth and windy conditions, the Bonnie G captain did not let out enough chain for a secure anchorage.” 

“When anchoring a vessel, a length of anchor chain that is five to seven times the water depth (scope, or ratio of anchor chain to water depth) should be used; even more anchor chain should be used in adverse weather,” the report said.

“The captain also did not use the available onboard navigational chart to identify a rock nearby, and when maneuvering after the anchor chain failed, he inadvertently steered directly onto the rock and grounded the vessel. As a result, the hull was breached just forward of the engine room.” 

“The forward watertight door in the engine room of the Bonnie G was open and not secured before the crew abandoned the vessel. Investigators determined that had the watertight door been shut as required, it is likely that progressive flooding of the engine room and aft spaces would not have occurred, limiting vessel damage.”

 “The NTSB determined the probable cause of the grounding was the inadequate scope of chain deployed when anchoring, which likely led to the anchor chain parting, and the captain not identifying a charted rock and steering the vessel onto it when attempting to maneuver to safe water.”

“When anchoring, mariners should review navigational charts and other sources of local information, such as the US Coast Pilot, to become familiar with nearby hazards,” the report said. “It is important to have this information available in heavy weather conditions, when there is heightened risk of drifting and crews may need to get a vessel underway on short notice.”