The US National Transportation Safety Board (NTSB) has issued a marine accident brief concluding that a man fell asleep at the wheel of tug Nathan E Stewart (IMO 8968210) while she was towing a barge through the Seaforth Channel on the central coast of British Columbia, causing it to run aground off Athlone Island, releasing 29,000 gallons of fuel and lube oil.
Damage to the tug and the barge was estimated at $12m.
The Nathan E. Stewart and the barge, the DBL 55, had departed from the Port of Vancouver on October 4th 2016 and arrived in Ketchikan, Alaska on October 11th. The articulated tug and barge (ATB) were operated by Kirby Offshore Marine. The pair discharged a cargo of jet fuel and gasoline and loaded 23,128 gallons of fuel oil into fuel tanks before setting course for the Port of Vancouver.
Once underway, the crew of the Nathan E Stewart/DBL 55 rotated watch duties at intervals of four hours on, eight hours off. On the night of October 12th the ATB’s second mate relieved the ship’s captain of his watch in the wheelhouse at 23:00, an hour earlier than his scheduled time. At a speed ranging between 8.4 and 9,3 knots, he took the vessel through Queen Charlotte Sound, making a preapproved course change at Salal Island.
The ATB had an electronic chart system (ECS), a navigational tool with a cross-track error alarm function that would sound an alarm if the vessel’s position veered to the right or the left of its path for the route it was taking. But that tool being was not in use at the time of the accident. With the second mate standing watch, the Nathan E Stewart missed a course change near Ivory Island at about 00:53 on October 13th.
A tankerman tried to reach the second mate via radio at around 01:00, but there was no response. He tried a second time and that too yielded no response. The tankerman then headed toward the wheelhouse, but felt a shuddering in the vessel along the way.
At the third attempt the tankerman reached the second mate, who informed him that the Nathan E Stewart had run aground at Edge Reef, a rocky area close to Athlone Island in the Seaforth Channel. The second mate would later admit he had fallen asleep — and confirm this detail with investigators.
At 02:40 crew members set up a hose to transfer diesel fuel from the Nathan E Stewart’s tanks to a cargo tank on the DBL 55. At 04:10 both crew members and first responders noticed diesel fuel in the water around the tug.
Crews tried to surround the spill with an oil containment boom, but winds and waves forced it open in parts. Meanwhile, the vessel was taking on water and the stern of the Nathan E. Stewart partially submerged at around 09:27. The tug separated from the barge at around 18:40 and was left partially sunk in about 28ft of water.
When the Nathan E Stewart was recovered on November 14th 2016, the tug’s bottom had extensive deformation which showed multiple penetrations in the hull plating.
Investigators determined a number of causes for the incident.
The main one was that the second mate had fallen asleep. He felt that he had had enough rest at the time, but it was determined that he missed an hour of sleep when he started early.
Another cause was that the vessel’s crew was not following its safety management system (SMS), which required a second watchperson in the wheelhouse with the second mate at the time. There was no evidence to indicate that a second watchstander was ever present on the bridge with the second mate.
Finally, if the ECS’s cross-track alarm function had been operating at the time, the ECS would have set off an alarm when the second mate missed the course change. It would have given the second mate time to make the change if it were being used, the report said.
2001-built, USA-flagged, 302 gt Nathan E Stewart is owned and managed by K-Sea Operating LLC of East Brunswick, New Jersey, USA.