Probe: Bank suction a factor when coke carrier struck police boatJan 23, 2014 03:57 PM
Courtesy U.S. Coast Guard
A damaged Boston Whaler is moored along the Black River after it was struck by the wayward coke carrier John D. Leitch, background.
The shipmaster’s failure to properly account for bank effect likely caused a bulk carrier to strike a moored police boat in Ohio’s Black River, the National Transportation Safety Board (NTSB) has determined.
The incident occurred Oct. 3, 2012, after the 730-foot John D. Leitch departed the Jonick Dock & Terminal in Lorain, Ohio. The Canadian-flagged ship, owned and operated by Algoma Central Corp., had been loaded with 25,877 metric tons of furnace coke at the terminal and was bound for Port Cartier, Quebec.
According to a marine accident brief filed by the NTSB, the outbound passage on the Black River — a 15-mile waterway maintained by the U.S. Army Corps of Engineers — required a series of turns to pass through a railroad lift bridge and under a highway bridge. When the master began a port turn near the highway span, trouble ensued.
“As the vessel’s bow cleared the bridge supports on the channel’s east side, the master noticed that the bow was not swinging to port as intended, so he applied more engine thrust and pitch to the vessel’s propeller but with no effect,” the NTSB stated. “The master had allowed the stern of the vessel to transit close enough to the west bank of the channel that the stern was influenced by bank suction.”
The accident location on the river’s east bank, near a bridge.
As a result, the stern was pulled toward the west bank and the vessel’s bow sheered to starboard, toward the east bank, where a Lorain County Sheriff’s Office boat was moored at Coast Guard Station Lorain. At 1912, the forward starboard bow of John D. Leitch “made slight contact” with a piling system and the unmanned police vessel, a 35-foot Boston Whaler, the NTSB reported.
Damage to the Boston Whaler exceeded $500,000. A manufacturer’s assessment determined that the aft port corner of the hull, inner liner and deck were crushed by the impact. The foam core “was sheared and unrepairable,” and a complete replacement of the hull was recommended, the NTSB said. Damage to John D. Leitch was limited to small scrapes along the forward starboard hull. The piling system sustained minor damage.
After the impact, the master of John D. Leitch maneuvered the ship to the retaining wall on the west bank of the river and moored. The master subsequently cooperated with local authorities and investigators from the Coast Guard, the accident brief stated.
The NTSB reported a controlling depth of 27 feet in that section of the channel at the time of the incident, 12 inches above the low-water level. John D. Leitch’s drafts after loading were recorded as 24 feet 3 inches forward, 24 feet 8 inches amidships, and 24 feet 10 inches aft. The river is about 260 feet wide at the site.
In a sidebar to its report, the NTSB describes bank effects and how they can influence the handling of a ship, particularly in shallow water.
“When a ship operates in an area with a shoal or shallow water near the channel edge, a positive (high) pressure area builds up off the bow near the shallow water and pushes the bow away from the shallow water or bank. This effect is known as bow cushion,” the report states. “As the water flow moves down the vessel’s side, a negative (low) pressure area builds up at the vessel’s stern and moves the stern toward the shallow water or bank. This effect is known as stern suction. Stern suction is stronger than bow cushion and requires constant corrective rudder and increased power to overcome.”
The five crewmembers aboard John D. Leitch — the master, first mate, third mate, AB and third engineer — were tested for alcohol and illegal drugs after the incident. All of the results were negative.