On October 13, 2016, at 0108 local time, the articulated tug and barge (ATB) Nathan E Stewart/ DBL 55 ran aground on Edge Reef off Athlone Island in the Seaforth Channel near Bella Bella, British Columbia, Canada. At the time of the accident, Nathan E Stewart was en route to the Port of Vancouver, Canada, with the empty DBL 55.
Heavy Environmental Damages
None of the crewmembers were injured, but environmental damage occurred when about 29,000 gallons of fuel and lube oil were released. Damage to the vessel and barge was estimated at $12 million.
Vessel Departs for Ketchikan
The Nathan E Stewart routinely transited from petroleum facilities in the state of Washington and Vancouver, British Columbia, with the double-hull DBL 55 or one of the company’s other tank barges loaded with refined petroleum products to be delivered to various ports in Alaska. At 2110 on October 11th the vessel departed Ketchikan and began its southbound transit to Vancouver by way of the Inside Passage (via the approved voyage plan).
Early Change of Shifts
The second mate was on watch in the wheelhouse. He had been working shifts of 6 hours on, 6 hours off (including overnight work) while the ATB was unloading in port, but once under way, his schedule shifted to 4 hours on, 8 hours off. On October 12th at 2300, the 2nd mate relieved the captain of the watch- an hour earlier than his scheduled rotation time at 2400. Shortly before 0100, while making about 9 knots with the autopilot engaged, the ATB missed a turn at its next waypoint. About the same time, a tankerman on watched tried to radio the second mate but received no response. Moments later, the tankerman felt a “shuddering,” as the ATB ran aground. The Nathan E Stewart suffered extensive bottom damage, flooding and later sank. The DBL 55 had significant plating damage from its bow to its stern but none of its inner cargo tanks were compromised.
Sleep Deprived Second Mate
The second mate later admitted that he had fallen asleep. He said he was not taking any prescription medications, never been diagnosed with any sleep-related disorders, and felt that he was adequately rested during the 3 days preceding the accident. He said that on the underway watch rotation he would normally sleep from the time he completed his early morning watch at 0400 until 1115, and then again for a second period of rest around 1900 before awakening to assume the 2400–0400 watch. It is unknown whether frequent variation between the two watch-rotation schedules affected his circadian rhythm.
Preventive Protocol Ignored
He had, however, awakened and relieved the captain earlier than usual on the night of the accident and lost an hour of sleep during his second rest period. The company SMS required an additional watchstander in the wheelhouse when under way in pilotage waters (where the ATB was transiting at the time), but no evidence indicates that a second watchstander was ever present in the wheelhouse with the second mate. In addition, the ATB’s electronic chart system had an alarm function, which, if activated, would have sounded an alarm if the vessel went off-course. The second mate, who had the navigational watch, did not activate this function.
Probable Cause
The NTSB determined that the probable cause of the grounding of the articulated tug and barge Nathan E Stewart/DBL 55 was the second mate falling asleep while on watch. Contributing to the grounding was the ineffective implementation of the company’s safety management system procedures for watchstanding.
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Source: NTSB
