2015 CSX train derailment in Maryville cause undetermined after investigation

Jun 07, 2023

The sudden failure of a wheel bearing appears to have triggered the disastrous July 2015 freight train derailment that forced the evacuation of 5,000 Blount County residents, according to federal investigators.

Why the bearing failed, however, remains undetermined, according to a recently released safety summary report from the Federal Railroad Administration.

The burned-off roller bearing caused the front axle to snap in half beneath a tanker car loaded with approximately 24,000 gallons of acrylonitrile, a toxic chemical used in plastics production. In turn, the car's steel wheels dug into the underside of the tank shell as the 57-car CSX train continued another 8.5 miles through the Maryville area before the larger wheel assembly gave way.

Friction created by the wheel punctured the tank and ignited the flammable chemical inside, sparking a fire that ultimately burned for 19 hours, sending poisonous gas into the air.

At least 87 people had to be treated at area hospitals, including 10 first-responders who were exposed to the noxious smoke. Thirty-six were admitted to the hospital. None had life-threatening issues, but were experiencing respiratory issues, skin irritation and nausea, according to hospital officials at the time.

Most had received urgent knocks at their doors between midnight and 6 a.m. by emergency workers who told them they should leave immediately. A shelter at Heritage High School, with American Red Cross workers, was set up and CSX provided bottled water to local schools while water testing took place.

CSX Transportation paid more than $3.5 million to residents and others immediately affected by the fire.

Federal investigators did not find any track conditions or actions by the train's crew that could have contributed to the derailment. Nor did they find any history of repairs to the tanker car's roller bearings or axles in CSX records.

Investigators also reviewed data from "hot box detectors" along the tracks, which can recognize overheating wheel components as a train passes by and alert the train's crew to any problems.

"The derailment occurred 17.8 miles from the last Hot Box detector it passed ... where no indication of overheating was recorded," the report states.

"The burned-off roller bearing overheated and failed suddenly without a gradual hearing process detectable by deployed Hot Box detectors."

The train was traveling from Cincinnati to Waycross, Georgia. It had 57 cars and two locomotives, and 27 cars carried hazardous chemicals: nine with acrylonitrile, 16 with propane and two with asphalt, Craig Camuso, CSX regional vice president for state government affairs, had said at the time.