UAS EVALUATION OF A 2020 DEBRIS FLOW THAT LED TO A FIERY TRAIN DERAILMENT IN PIKE COUNTY, KENTUCKY

On February 13, 2020 a CSX train transporting ethanol in tank cars was derailed about 7:00am when it struck a debris flow adjacent to the small community of Draffin in Pike County, Kentucky. The lead locomotive carrying two crew members plunged down an embankment and into Russell Fork, along with at least four tank cars, resulting in a chemical spill and fire in the river and on the river bank. The fire partially engulfed the lead locomotive and other rail cars. The two train crew members were trapped by the fire for some time, until being rescued by boat. In February, 2023, the authors, at the request of attorneys representing the train crew, evaluated the debris flow with regard to causation; in particular, involving possible relationships to bedrock structure and intense rainfall and flooding. Unmanned Aerial Systems (UASs) were employed to capture overlapping high resolution images of the site. The images were processed using Pix4D Mapper, resulting in digital point clouds and triangle mesh models of both the debris flow source area and the runout zone. CloudCompare software was then used to extract dip direction and dip angle values for bedrock geologic structure, including bedding planes and joint sets. The study concluded that near-vertical valley stress-relief joints served as the primary release surface and that water pressure within the joints from recent storms served as the triggering mechanism.