NTSB: Shock Loading Caused Catastrophic Line Failure in Alaska ITB Grounding

An integrated tug and barge (ITB) operating in Alaska’s Prince William Sound suffered a complete connection failure when all four push lines parted during routine transit conditions, leading to a constructive total loss of the barge valued at $2.9 million, according to a National Transportation Safety Board investigation.

The incident occurred on January 11, 2025, at 0250 local time, when the Krystal Sea/Cordova Provider was transiting Prince William Sound. The four lines connecting the tug to the barge suddenly parted, causing the barge to uncouple from the tug. The freed barge drifted for approximately four hours before grounding on the coast of Axel Lind Island, Alaska at about 0635.

“The National Transportation Safety Board determines that the probable cause of the grounding of the barge Cordova Provider was due to shock loading that led to the parting of the push lines connecting the Cordova Provider to the tug Krystal Sea,” the NTSB concluded in its report.

The freight barge Cordova Provider, built in 1981 at Tacoma Boat Building, began as an oil recovery barge with an ice-strengthened hull for Alaskan operations. It was converted in 2005 to also carry freight, when it received a custom-designed notch on the stern to operate as part of an ITB with the tug Krystal Sea.

The tug Krystal Sea was purpose-built in 2005 at Western Towboat Duwamish Shipyard to fit the stern notch of the Cordova Provider. The connection system utilized three wedges fitting into recesses within the notch, along with four push lines—two each on port and starboard sides—that were tensioned by winches to secure the vessels together.

At the time of the incident, the ITB was operating in seas of 4-6 feet with approximately 35-knot winds on the vessel’s port quarter—conditions that investigators noted were routinely encountered on the vessel’s normal transit route between Whittier, Cordova, and Valdez.

The NTSB investigation revealed that five days before the casualty, the captain had visually inspected the four push lines and documented no deficiencies. A post-casualty inspection by a technician from a local industrial and maritime supply company determined that the lines were in fair condition with no visible defects, concluding that the lines and soft shackle parted due to exceeding their breaking strength.

Investigators believe that after the first push line parted due to shock loading, the remaining three lines experienced a cascading failure as they took up additional strain. However, the NTSB noted it was “undetermined how the first push line that parted was shock loaded” given that the ITB was operating in familiar conditions with properly rigged lines.

The incident resulted in no injuries or pollution, but the barge Cordova Provider, valued at $2.9 million, was declared a constructive total loss by the vessel’s owner.

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