A barge tow struck a mooring cell on the Ohio River last year after encountering a strong outdraft current above the McAlpine Dam during high-water conditions, the US National Transportation Safety Board (NTSB) said recently.
The towing vessel Queen City was transiting the Ohio River with 11 barges in tow when the tow struck the Vane Dike at the arrival point for the McAlpine Locks and Dam in Louisville, Kentucky, on March 28, 2023.
The tow broke apart, resulting in an estimated US$2 million in damages to the barges and cargo.
Investigators determined that the barge tow pilot did not effectively compensate for the strong outdraft current.
As Queen City transited through the centre span of the Clark Memorial Highway Bridge, the pilot attempted to move the tow west to enter the Portland Channel. However, the McAlpine Dam's outdraft current – current moving across the lock entrance toward the dam – pulled the vessel away from the channel entrance.
Shortly after passing through the bridge, the starboard side of the tow struck the Vane Dike mooring cell.
At the time of the contact, the height of the water at the McAlpine Locks measured about 17.5 feet (5.33 metres) and rising, indicating a period of "extreme high water/extreme high flow conditions," according to the Mississippi and Ohio Valley and Tributaries Waterways Action Plan.
"When towing vessel operators decide to steer through an area with strong outdrafts, they must steer a course to account for the set from the outdraft," the report said.
Queen City's pilot intended to steer into the entrance channel to the locks, knowing that an outdraft would set the tow toward the Vane Dike and the dam gates. Although the pilot attempted to steer the tow to the left, he did not anticipate the strength of the outdraft and its effect on the tow.
"High currents resulting from high water pose unique hazards for vessels transiting inland rivers," the report continued. "In addition, near dams, greater dam openings in high-water conditions lead to high flow rates, which can produce outdraft currents near the dam. Mariners should thoroughly assess the potential impact of outdraft currents when entering or exiting locking channels.
"Vessel horsepower and vessel handling should be carefully considered. Mariners should also consult available resources, such as Waterways Action Plans and company policies, when passage planning."
Marine Investigation Report 24-12 is available online here.