On August 27, 2016, about 8:26 a.m. EST, a railroad tank car sustained a 42-inch long crack in its tank shell shortly after being loaded with 178,400 pounds of liquefied compressed chlorine at a chlorine manufacturing plant in West Virginia. Over the next 2.5 hours, the entire 178,400-pound load of chlorine was released and formed a large vapor cloud that migrated south along the Ohio River valley. The railroad tank car, AXLX1702, built in June 1979 was a 17,388-gallon US Department of Transportation specification-105J500W tank car, also known as a class DOT-105 tank car, with a stenciled load limit of 178,400 pounds and a maximum gross rail load of 263,000 pounds.
By 8:15 a.m., the tank car was filled with its maximum authorized load of 178,400 pounds. After personnel removed the loading lines and sealed the valves and fittings, they used a Trackmobile® railcar mover to move the tank car forward at a walking pace about 30 to 40 yards north of the loading shed on track 10.4 The personnel set the handbrake and chocked the wheels. At 8:26 a.m., loading personnel heard a loud bang as AXLX1702 experienced a 42-inch long crack in the lower portion of the tank shell. Plant surveillance video showed a yellow-green chlorine vapor cloud quickly growing in the vicinity of the tank car. The tank car had not been offered into transportation at the time nor was it coupled to other railcars.