Federal investigators believe the pilot of a small towboat became “overwhelmed” by strong currents before his tow struck a bridge guard pier in the Cumberland River.
The 700-hp Steve Plummer was pushing three loaded sand barges upriver against a 3-mph current on the morning of the incident, which occurred March 11, 2017, near downtown Nashville, Tenn. Two barges hit the upstream guard pier for the CSX Railroad Bridge located at mile 190.4.
No injuries were reported, but the two barges sustained more than $70,000 in damage. The guard pier was destroyed, requiring $1.7 million for a corrugated steel replacement that was installed about six months later.
In its accident report, the National Transportation Safety Board (NTSB) said vessel operator Pine Bluff Materials gave its pilots leeway when configuring tows, noting that tow sizes varied depending on river conditions, the weather and pilot preference. That said, the company has since limited tows to two barges when passing through the narrow CSX span.
“(The) probable cause of the Steve Plummer tow’s allision with the CSX Railroad Bridge was the pilot’s decision to tow three loaded barges during rising river conditions with swift currents, which overwhelmed his ability to maneuver the tow through the bridge,” the NTSB said.
Steve Plummer, a 50-foot, twin-screw pushboat built in 1966, left Pine Bluff Materials’ fleeting area at mile 184 pushing three barges in a single string. Its destination was the company’s sand yard eight and a half miles upriver at mile 192.5. The entire tow was 590 feet long by 35 feet wide.
The tow made about 3.5 mph (3 knots) against the 3-mph current. It reached the 693-foot swing bridge at about 1110, 40 minutes after departing the fleeting area. The bridge has guard piers upriver and downriver to protect the span when it’s open for vessels to pass through. The channel width on either side of the guard pier is 116 feet.
“As the Steve Plummer tow approached the bridge, the pilot positioned the tow to transit through the opening near the right descending bank; however, he noticed that the tow was being set toward the middle of the river,” the NTSB said. “He then tried to correct for the set by increasing speed and adjusting the rudders.”
The lead barge cleared the bridge and the upstream guard pier. But the second and third barges hit the upstream guard pier, which broke apart and collapsed. All three barges broke away and became pinned against the bridge.
According to the report, Steve Plummer ultimately reassembled the tow and brought the three barges to Pine Bluff’s sand facility. Barges H4128B and HMT316, the second and third in the string, each sustained damage from the incident requiring between $30,000 and $40,000 in repairs.
The 44-year-old pilot steering the tow was an experienced mariner credentialed as a master on the Western Rivers. For three months — the period since Pine Bluff acquired the company he had worked for previously — the pilot had made the same transit almost daily, with loaded and empty barges, through 10 bridges between the fleeting area and the company terminal, the NTSB said. The tow cleared five bridges on the morning of the incident before hitting the CSX bridge.
Investigators homed in on the pilot’s decision to push three loaded barges given the conditions. Although there are no regulatory mandates for a towboat to have a certain horsepower rating for each barge in tow, industry best practices usually assume 250 horsepower for each loaded barge on inland rivers. Pine Bluff noted its towboats occasionally push four barges in slack water conditions. One or two barges was common during high water.
“Based on these hp-to-barge ratios, the 700-hp Steve Plummer pushing three barges (carrying a total of 3,934 tons of cargo) was within the industry norm for an experienced operator,” the report said. “Although the Cumberland River was rising from recent rain, at the time of the accident the river was within its normal range.”
The NTSB also noted the pilot could have checked in with a more senior pilot for guidance on the upriver transit in fast water conditions. Although he did not do so, such a discussion was not required by company policy.
Pine Bluff Materials, based in Nashville, declined to comment on the NTSB findings.