NTSB: Downstreaming Caused Towboat Casualty
On Tuesday, the National Transportation Safety Board (NTSB) released its review of the sinking of the towboat Ricky J. Leboeuf, finding that the probable cause of the casualty was an "ill-advised decision to perform a downstreaming maneuver in high water conditions."
The San Jacinto River watershed received over five inches of rain on April 18, 2016, bringing the river's level to five feet above flood stage. The Coast Guard put out a warning about the dangerously high water velocities on the San Jacinto, and Kirby Inland Marine – the operator of the Leboeuf – forwarded this note to all of its vessels in the area. Kirby included an advisory restricting the use of "downstreaming," a maneuver in which a towboat heads upstream parallel to the barge, then makes a u-turn and heads downstream to the barge's stern, controlling speed by putting propulsion astern.
The crew of the Leboeuf received and discussed these instructions, and went over how the river conditions would affect operations.
The NTSB notes that downstreaming carries a significant risk during flood stage conditions: the towboat's flat bow must meet squarely with the barge's flat stern, or the boat runs the risk of being pushed sideways and coming to rest with one side against the barge. If this occurs, water can rise over the low freeboard of the towboat's upstream side, leading to rapid downflooding through ventilation louvers and open hatches.
The Coast Guard and the AWO studied this problem in 1997 and issued a set of best practices. When executing the maneuver in high current, towboat masters are advised to close hatches and keep crewmembers in a position where they can easily abandon ship. Like many operators, Kirby has adopted a stricter set of restrictions on downstreaming in certain conditions in its SMS, including a prohibition against its use without the port captain’s permission during periods of high river flow.
On the morning of April 19, the Leboeuf was dispatched to remove a barge from a fleeting area on the San Jacinto River. Her relief captain was in the wheelhouse with a steersman, and as the Leboeuf approached the barge, he mentioned the risk posed by the river conditions and took over the helm.
The relief captain brought the towboat upstream of the barge, then turned hard to port to return downstream and meet the barge's stern. However, he was unable to make contact squarely: the port push knee touched on the stern first, and the relief captain's efforts to correct the angle of contact were unsuccessful. Despite a series of attempts to square her up, the force of the current pushed the towboat's port side against the stern side of the barge fleet, and it began to heel her over to starboard. The water swiftly flooded over her starboard side, through two open hatches and into her interior compartments.
The relief captain sounded the general alarm. Two men were sleeping below, the captain and the senior tankerman, and both managed to get out the hatches on the port side before the Leboeuf capsized. The relief captain and the steersman managed to escape the wheelhouse. The deckhand, who had been forward on the bow, was last seen near the port push knee; his body was later recovered downriver.
The relief captain declined the Coast Guard and NTSB's requests for a debriefing, leaving the agencies unable to determine the exact logic he used in deciding to use the downstreaming maneuver. As the vessel was in good working condition and none of the crew tested positive for intoxicants, the NTSB concluded that the relief captain' decision was the probable cause of the capsize.