On January 8, 2022, about 9:49 a.m. local time, an eastbound BNSF Railway Company train, U JOENYF7 07A, derailed 37 tank cars at milepost 156.2 on the BNSF Railway Company Red River Division in Oklaunion, Texas. The train had 2 crewmembers on board and was composed of 2 head-end locomotives, 1 distributed power locomotive at the rear of the train, 2 buffer railcars, and 96 loaded US Department of Transportation specification 117J (DOT-117J) tank cars carrying denatured ethanol, a flammable liquid. The BNSF Railway Company estimated that 601,819 gallons of denatured ethanol released from 28 of the 37 derailed tank cars. The ethanol ignited and burned uncontrolled for about 4 hours, resulting in a pool fire. No injuries or evacuations were reported.
Because this was a hazardous materials investigation focused on the performance of the DOT-117J tank cars, we did not determine the probable cause of the derailment.
The majority of the ethanol released leaked from tank car service equipment (such as manway covers and bottom outlet valves) that remained intact during the derailment but sustained damage from the pool fire. We found that the gaskets used in the service equipment were made of materials that are vulnerable to damage when exposed to fire. Using gaskets made of more thermally resistant materials would likely increase the survival time of tank cars exposed to fire and reduce the severity of hazardous material releases.
We also found that when the Pipeline and Hazardous Materials Administration created the DOT-117 specification (which includes the DOT-117J specification) for non-pressure tank cars, it expanded existing thermal protection regulations for pressure tank cars to non-pressure tank cars with different designs.
Further, we found that a mechanical (non-thermal) breach of a tank car involved in the derailment occurred because of loading between underframe components and tank head material—an outcome that a specific federal regulation and an industry standard, the 85 percent rules, are intended to prevent. This load scenario likely occurred because several of the tank car’s welds exceeded the sizes specified in the design, which led to the tank head material being the weakest point in the load path and fracturing, releasing lading. Further, because there is not an industry standard for rejecting an oversized weld, the design size for each weld is effectively a minimum size, and that as-built tank cars may have oversized welds that may lead to tank fractures. Relatedly, we found that a design that complies with the 85 percent rules does not prevent fabrication of tank cars that may violate the rules because of oversized welds that make the tank cars more vulnerable to tank fractures in a derailment.
As a result of this investigation, we recommended that the Federal Railroad Administration and the Pipeline and Hazardous Materials Administration work together to develop and publish both benchmarks and thermal performance standards for gaskets used in tank cars transporting flammable liquids. We also recommended that the Pipeline and Hazardous Materials Administration revise the DOT-117 tank car specification to ensure that these tank cars use appropriate thermal protection systems, and that the Association of American Railroads update its certification process to ensure that tank cars comply with this revised specification.
We also recommended that the Association of American Railroads create an inspection standard in the Manual of Standards and Recommended Practices for rejecting oversized welds at key points on tank car underframes.
