Hot work near cardboard boxes caused riverboat fire, says NTSB

The US National Transportation Safety Board (NTSB) has decided that hot work near a pile of cardboard boxes caused a fire aboard passenger vessel Natchez, a Mississippi River riverboat which had its homeport in New Orleans.

The Natchez had begun a deep overhaul in January 2021 and was expected to return to regular passenger service in 2023. The work that was undertaken included extensive work on the boilers, generators and electrical system.

On May 3rd 2022 a crew of contractors came aboard to replace the ship’s main electrical panel. On the day in question preparation work was planned, cutting out the old panel with an acetylene torch. A marine fabrication contractor checked the space for fire hazards, and the vessel’s chief engineer had deckhands put a piece of sheet metal between the work area and an adjacent diesel generator, so that it would be protected from sparks. In addition a worker was tasked to take a fire watch, holding an extinguisher while the cutting proceeded.

The work crew then left at about 17:00. a diesel engine tech was in the space until 18:00. They all told NTSB that they saw nothing unusual before they departed.

However, nearly two hours later, at about 19:45, the security watchstander aboard Natchez saw smoke coming from the engine room. He called the emergency services and the New Orleans Fire Department responded quickly and put out the fire.

Most of the damage was limited to the area around the electrical panel, although there was minor damage in other areas of the engine room and some smoke damage in the decks above the fire. The total cost of repair came to about $1.5m. No injuries or pollution were reported.

An investigation by the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) found that, based on burn patterns, the fire began along the bulkhead, next to where the work was completed that day. The vessel operator provided the NTSB with photographs of the space from the day of the accident. These images showed that cardboard boxes and plastic containers had been stowed on wooden shelves about two to three feet away from where the hot work had been performed.

NTSB discovered during its investigation that the vessel owner and the contractor had no written policies for hot work safety, even those these are required by the US government agency Occupation Safety & Health Administration. The owner told the NTSB that it relied upon its contractors to have fire safety and hot work policies. The project superintendent said that he deemed the work site safe for hot work.

The safety regulations demand a 35ft distance between combustibles and hot work, or, if this is not possible, ensuring that the combustibles are well-covered and shielded with flameproof material. The superintendent and the welder who did the work told investigators that they were not aware of this requirement.

NTSB concluded that that it was likely a spark from the welding landed in the stack of cardboard boxes, causing the boxes to smoulder undetected for a considerable time before igniting.

The vessel was not required by regulation to have a fire detection system in place. The fixed firefighting system had been disabled during the overhaul. However, the NTSB did not identify these elements as contributing factors in the fire.