NTSB cites hull fracture, extra fuel in sinking of Florida tugboat

Atlantic Raider

Atlantic Raider was assisting with a dredging project near Jacksonville, Fla., when the tugboat abruptly listed to port. The lean got worse over the next few minutes until the port quarter was under water.

The captain steered the tug into shallower water, where it grounded and partially sank at about 1545 on Oct. 28, 2016, according to a National Transportation Safety Board (NTSB) report. Roughly 2,000 gallons of fuel escaped from the tug, but no one was injured.

NTSB investigators determined the tug had a small crack at the stern that operator Gore Marine Transportation Co. and the vessel captain did not know existed.

According to the report, “the probable cause of the flooding of the Atlantic Raider was a stern hull fracture that allowed ingress of water into the rudder compartment and caused the vessel to sink by the port quarter.”

Flooding into the engine room from an open door on deck contributed to the sinking, the report said.

Roughly six hours before the incident, the 70-foot, 1,430-hp tug took on 10,000 gallons of fuel in addition to roughly 16,000 gallons already on board. The dredging project was in Blount Island Channel, within the St. Johns River in Jacksonville. There were three crewmembers on board.

The sudden port-side list developed at about 1530 while the tug was at a project staging area. At the time, the crew couldn’t figure out what was causing the list.

“(The captain) and the deck hand went to the engine room, observed no sign of flooding there, started the main engines and tried to correct the list by shifting fuel, without success,” the NTSB report said. “Water covered the stern and eventually began to flood the lower engine room through an open door on the vessel’s port side, aft on the main deck.”

Crew closed the open door after noticing the flooding and steered outside the channel to the west side of the waterway. The list reportedly got worse while getting underway to leave the channel.

“The captain told investigators that the vessel rolled to port about 45 degrees as it grounded and came to rest down by the port quarter,” the report said, adding that crew got off the vessel without incident. “Water continued to flood through open portholes on the port and starboard side of the main deck. In a short period of time, the engine room and most of the main deck were fully submerged.”

Authorities said there was an inch-thick layer of marine diesel around the partially sunken tug, and sheening was visible in the waterway for approximately three miles. The cleanup lasted three weeks, during which time an oil spill response company removed more than 36,000 gallons of oily water from the tug.

After salvage crews raised the tug and it was placed in dry dock, investigators found the 9.5-inch-long hull fracture, which was one-half-inch wide, along a stern weld seam. Another 1-inch hole was found on a corroded bulkhead leading to the No. 4 fuel tank, the report said.

The most recent hull maintenance work on the tug occurred more than two years before the incident.

It’s not clear how long the fracture existed, but Gore Marine officials told the NTSB that Atlantic Raider didn’t normally have 26,000 gallons of fuel on board. In that condition, the vessel’s draft was deeper than normal —  about 10.5 feet — putting the fracture right at the waterline.

“Water likely entered the rudder compartment through the hull fracture and increased the draft by the stern, which would have caused the flooding rate to increase,” the report said.

Gore Marine is based in Townsend, Ga. The company did not respond to a request for comment on the incident.

It wasn’t clear if the 51-year-old tug has returned to service. The NTSB report estimated damage from the incident at about $1 million.

By Professional Mariner Staff