The US NTSB issued an investigation report on the collision and sinking of the towing vessel ‘Todd Brow’, in the Lower Mississippi River, in April 2017, which led to an estimated $1.5 million damage and a release of approximately 100 gallons of diesel fuel into the water.
The incident
At about 1530 local time on April 17, 2017, while attempting to maneuver a string of barges from a barge fleet on the right descending bank of the Lower Mississippi River near mile marker (mm) 940, about 4 miles from Columbus, Kentucky, the uninspected towing vessel Todd Brown collided with the lead barges moored downriver and sank. Before the sinking, all six crewmembers abandoned the vessel by climbing aboard the barges without reported injury. Approximately 100 gallons of diesel fuel were released during salvage operations but later recovered. Damage to the vessel was estimated at $1.5 million.
Analysis
As noted, in April 2017, the Mississippi River was rising to a historically high level due to excessive runoff from melting snow and recent rainstorms. On April 17, the day of the accident, the gauge at Cairo, Illinois, measured at about 36 feet, almost 4 feet higher than normal, and was expected to crest to 48.5 feet. As a result of the rising river, the current had also increased, reaching an estimated 8 mph by the time the accident occurred.
With the high water and increased current, debris such as tree trunks, limbs, and other accumulating litter collected from the shorelines and drifted downstream. A substantial amount of debris accumulated at the heads of the moored barge fleets due to the bends in the river. The barge fleets were secured by bridle and stern lines attached to large cement blocks buried in the ground on the river banks.
The accumulating debris led to an increased strain on the moorings, thus elevating the risk of the wires parting. In order to remove the debris, or “drift,” from the moored barges, fleet towboats such as the Todd Brown would perform “de-drifting” operations: maneuvered by one or more towboats, barges would be uncoupled from the remainder of the fleet and repositioned to allow the river current to flush the debris from their upstream end.
Probable cause
The National Transportation Safety Board determines that the probable cause of the collision and sinking of the uninspected towing vessel Todd Brown was the pilot’s underestimation of the effect of the river current on the barge string being maneuvered during a de-drifting operation.
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