Even though this accident was caused by a derailment, we are stepping outside of our normal coverage zone by featuring this NTSB report on tank car structural integrity because it has received so much attention over the past few years. NTSB did not determine probable cause for the derailment and did not publish a brief or report.
The National Transportation Safety Board announced Thursday completion of its investigation to document the performance of DOT-117 rail tank cars involved in the Dec. 22, 2020, derailment near Custer, Washington.
The NTSB conducted a limited investigation of the accident, focused solely on the performance of the DOT-117 rail tank cars, as such, the NTSB did not determine probable cause for the derailment and did not publish a brief or report. The NTSB’s documentation of its investigation into the performance of tank cars is documented in a factual report.
No injuries were reported in connection with the derailment; however, 120 people were evacuated from a ½-mile radius around the accident site, and about 29,000 gallons of petroleum crude oil was discharged from three tank cars. The oil ignited and burned uncontrolled for two hours. Damage was estimated to exceed $1.5 million.
In its factual report the NTSB states nine of the 10 derailed tank cars were originally constructed to DOT-111A100WI specifications, with enhancements to the Association of American Railroads CPC-1232 industry standard for crude oil and ethanol service tank cars ordered after Oct. 1, 2011. The CPC-1232 tank cars were converted to DOT-117R100W in 2019.
NTSB investigators did not travel to Custer to examine the tank cars due to COVID-19 travel restrictions, however the investigators relied on close communication with the Federal Railroad Administration and the Washington State Utilities and Transportation Commission to collect derailment damage data.
“The NTSB’s intent for this investigation was to gain damage data from the DOT-117 rail tank cars involved in the derailment,” said Robert J. Hall, Director of the NTSB’s Office Railroad, Pipeline and Hazardous Materials Investigations. “Because our investigation was limited to data collection, we have not issued any findings or safety recommendations. The data we gathered in this investigation will assist us as we evaluate the performance of tank cars carrying flammable liquids involved in other rail accidents,” said Hall.
Ensure the Safe Shipment of Hazardous Materials was an item on the NTSB’s 2019 – 2020 Most Wanted List of Transportation Safety Improvements to highlight the need for the replacement of DOT-111 and CPC-1232 tank cars with the more robust DOT-117 design.