NTSB: Strong Outdraft Current Resulted In McAlpine Barge Accident

A strong outdraft current above the McAlpine Dam during high-water conditions led to the mv. Queen City’s tow hitting a mooring cell in March 2023, pinning three barges against the dam, the National Transportation Safety Board has determined.

The Queen City had 11 barges in tow March 28, 2023, when the tow struck the cell at the arrival point for McAlpine Locks and Dam in Louisville, Ky.

The tow broke apart, with six barges going through the lower dam gates and three becoming pinned against the lower dam, Ohio River Mile 606.8. One of the barges pinned against the dam was a tank barge loaded with 1,400 tons of liquid methanol.

“Due to the immediate threat to public safety associated with the flammability of methanol, air and water monitoring began, and the river was closed,” the NTSB report said. “A unified command was established that included local, state and federal agencies, as well as representatives of the vessel owner/operator.”

Air and water quality samples continued multiple times daily until the methanol was safely transferred and the tank barge removed on April 8 with no leaks ever detected.

The breakaway resulted in an estimated $1.98 million in damages to the barges and cargo, according to the NTSB. No one was injured, and no pollution was reported. The Queen City was not damaged. Nine barges received an estimated $1.475 million in damage, according to the report. Additionally, $500,000 in damage was from lost corn being transported as cargo in some of the barges.

“Investigators determined that the barge tow pilot did not effectively compensate for the strong outdraft current,” the NTSB said in a news release accompanying the report.

It added that as the Queen City transited downbound through the center span of the Clark Memorial Highway Bridge, the pilot attempted to move the tow west to enter the Portland Canal, but the current moving across the lock entrance toward the dam pulled the vessel away from the canal entrance.

“Shortly after passing through the bridge, the starboard side of the tow struck the Vane Dike mooring cell,” the NTSB said.

At the time of the contact at 2:24 a.m. Eastern time, the height of the water at the McAlpine Locks measured about 17.5 feet and rising, indicating a period of “extreme high water/extreme high flow fluctuations,” 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. “The Queen City 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.”

In its “lessons learned” segment of the report, the NTSB noted that high currents resulting from high water pose “unique hazards for vessels transiting the inland rivers.”

“In addition, near dams, greater dam openings in high-water conditions lead to high flow rates, which can produce outdraft currents near the dam,” the report continued. “Mariners should thoroughly assess the potential impact of outdraft currents when entering or exiting 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.”

The full report, labeled Marine Investigation Report 24-12, is available online at www.ntsb.gov/investigations/AccidentReports/Reports/MIR2412.pdf.