NTSB: Slack Lines Allowed River Current to Pull Bulker Off the Dock
NTSB Report Finds Ship Accident on the Mississippi Caused by Loose Lines and Strong Currents
In March 2023, the National Transportation Safety Board (NTSB) completed an investigation into a ship accident involving the bulker Sirocco on the Lower Mississippi River. The investigation found that the accident occurred because the ship’s mooring winches couldn’t handle the strong river current, causing the ship to drift away and collide with another vessel, leading to over $5 million in damage.
What Happened
On March 24, 2023, the Sirocco arrived at an anchorage point on the Lower Mississippi River. The water level was very high, which triggered special safety measures at the Convent Marine Terminal (CMT), where the ship was scheduled to load cargo. These measures included using extra mooring lines and tugboats to keep the ship safely in place.
Two days later, Sirocco arrived at CMT and began unloading cargo. The crew tied up the ship with 16 mooring lines and used two tugboats to keep it steady. Everything seemed fine, but as the river current got stronger throughout the day, the mooring lines began to slacken, meaning they weren’t as tight as they should be. The ship’s port captain noticed this and instructed the crew to tighten the lines. However, he also noticed that the river level had fallen slightly, and told the ship’s master that the tugboats weren’t required anymore. This was a cost-saving measure since tugboats are expensive, and the shipowner would have to pay for them.
By 3 p.m., the master decided to release the tugboats, even though he and the second officer knew the river current was still strong. As the day wore on, the mooring lines continued to loosen, and the crew struggled to manage them while also handling other tasks related to loading cargo.
The Breakaway Incident
At around midnight on March 27, as cargo loading continued, the crew noticed that the ship’s bow had started to drift away from the dock. The lines were extremely tight, and the ship’s winches could no longer pull them back in. The river current, now running at over 4.5 knots, was overpowering the winches. The master immediately called for tugboat assistance and ordered the crew to drop the anchor. However, it was too late. The ship’s winches started sparking, and the Sirocco began drifting sideways down the river.
Two tugboats arrived to help, but they were limited in what they could do because of the ropes trailing behind the drifting ship. Despite the tugboats’ efforts, the strong current caused the Sirocco to collide with a barge moored at a nearby terminal. Fortunately, the workers on the barge evacuated in time to avoid injury. However, the barge was severely damaged and declared a total loss.
What Caused the Accident?
The NTSB determined that the accident happened because the ship’s bow drifted off the dock as it loaded cargo. This exposed more of the ship’s underwater hull to the strong river current, which created more tension than the ship’s winches could handle. The winches were designed to slip under heavy strain to prevent the ropes from snapping, but once they slipped, the ship drifted away from the dock.
The NTSB also noted that if the crew had let out more of the ship’s anchor chain, it might have held the ship in place. Using only one shot of anchor chain (a short length) wasn’t enough to stop the ship from drifting.
Safety Recommendations
The NTSB concluded the report with a safety recommendation for crews: as a ship loads cargo, especially at the bow, it’s important to keep mooring lines tight. As the ship gets heavier at the front, more of its hull is exposed to the water current, which can make it harder to stay in place. The crew should always make sure that slack is removed from the lines to prevent accidents like this from happening again.
In addition, the NTSB highlighted the importance of using enough anchor chain in strong currents. If the starboard anchor had been let out to a longer length, it could have helped keep the Sirocco in place and prevented the crash.
