Nathan E. Stewart (2016)

Classification

• Incident Type: Grounded
• Severity: High
• Tug involvement: yes
• Tug mechanism: N/A

The initiating event was a grounding, not a tug-specific capsize mechanism.

Vessel Details

Incident Details

Key facts

• Nathan E. Stewart and the empty tank barge DBL 55 grounded on Edge Reef at about 0106 on 13 October 2016.
• The fatigued second mate was alone on the bridge, fell asleep and missed the planned turn into Seaforth Channel.
• Navigational alarms were not used, and the tug had no bridge navigational watch alarm system.
• Repeated contact with the reef breached the tug's hull, causing flooding and an estimated 110,000-litre diesel release.
• All seven crew survived, although two were washed overboard during abandonment and recovered.
• The tug sank, separated from the barge and was removed 33 days later; DBL 55 was repaired and returned to service.

Narrative

The articulated tug-barge Nathan E. Stewart / DBL 55 departed Ketchikan, Alaska, at 2230 on 11 October 2016 for Vancouver with seven crew members. DBL 55 was an empty double-hulled tank barge. At 2300 on 12 October, the second mate took over the bridge watch from the master. His fitness for duty was not discussed, and the assistant tankerman assigned to the watch was occupied with rounds rather than stationed on the bridge.

At 0020 on 13 October, the second mate altered course toward Seaforth Channel. The ATB passed the next alteration point off Ivory Island without turning. The assistant tankerman called the bridge at about 0100 but received no response and started toward the wheelhouse. At approximately 0106, the ATB struck Edge Reef at 52°14.37′N, 128°23.08′W.

The master attempted to reverse off, causing the tug to pivot and repeatedly contact the seabed. He reported the grounding at 0111. Initial surveys found no obvious flooding or pollution, but rising seas increased the hull's movement against the reef. At 0407, the crew detected falling fuel-tank levels and began transferring fuel to the barge. By 0520, the tug was flooding and diesel was escaping.

Containment boom was deployed, but it parted at about 0630. Flooding caused loss of power at 0650, and portable pumps could not keep pace. At about 0900, the master ordered abandonment. A wave washed two crew members overboard; one climbed back aboard and the other was recovered by a rescue craft. By 0945, all seven crew members were safely aboard the Canadian Coast Guard vessel Bartlett.

The tug's stern remained suspended from the barge until the connection failed at about 1900. Nathan E. Stewart then sank and DBL 55 was towed clear. Spill control and salvage continued for 40 days. Responders removed about 119,000 litres of diesel oil and lubricants from the tug, while an estimated 110,000 litres entered the environment. The tug was raised on 14 November and removed 33 days after the grounding.

The TSB found that the second mate was fatigued, fell asleep and missed the course alteration. A 6-on, 6-off work schedule, disrupted and insufficient sleep, darkness, low stimulation and working alone increased the risk. Navigational alarms were not used, no bridge watch alarm was fitted, and the second watchkeeper was not on the bridge. The arrangement created a single point of failure during a confined-water transit.

Nathan E. Stewart sustained punctures near fuel tanks and the engine room and was declared a constructive total loss. DBL 55's outer hull was punctured, but its cargo tanks remained intact; the barge was repaired and returned to service.

Sequence of events

Contributing factors

Investigation

The Transportation Safety Board of Canada investigated the grounding and sinking in report M16P0378. It found that fatigue, a one-person bridge watch, unused navigation alarms and the absence of a bridge watch alarm directly contributed to the casualty. The report also identified broader risks associated with unmitigated 6-on, 6-off schedules, lack of fatigue-management training and incomplete multi-agency evaluation of major spill responses.

References

• TSB report M16P0378: Grounding and subsequent sinking of Nathan E. Stewart / DBL 55

Related

• Nathan E. Stewart
• Canada
• Transportation Safety Board of Canada
• Kirby Offshore Marine Operating LLC
• Tug Incident Classification
• Grounding
• Fatigue and Alertness
• Loss of Propulsion and Steering
• DBL 55

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