A driver was killed when the ground under his haul truck collapsed as he dumped a load of sand at a mine. Investigators found that inadequate workplace examinations contributed to the incident.
U.S. Mine Safety and Health Administration (MSHA) investigators determined that the inadequate workplace examinations failed to reveal the hazard, leading to the fatal incident.
Customer sees haul truck upside down on stockpile
Darrell Huff was a haul truck operator for the Central Stone Company at the Huntington Plant CS01 surface limestone mine in Ralls County, Missouri.
On May 22, 2023, Huff started his shift by conducting a pre-operational inspection of his haul truck. By 6:13 a.m., he hauled the first of three loads of manufactured sand to the top of the mine’s stockpile, which was 42 feet high. As Huff and other haul truck operators dumped their loads at the top of the stockpile, a front-end loader loaded customer trucks at the base.
At 11:10 a.m., a customer who was picking up a load of sand at the mine saw Huff’s haul truck upside down on the side of the stockpile with sand still coming down the pile. The customer drove over and yelled to get Huff’s attention but received no response.
The customer called the mine’s scale operator to report the incident and two other employees reported to the stockpile to help. They checked Huff for vital signs but couldn’t detect any.
Emergency responders arrived at 11:35 a.m. and Huff was pronounced dead by the county coroner at 12:18 p.m.
Seat belt worked but wasn’t used
Investigators examined the haul truck and found no defects that would have contributed to the incident. The seat belt was functional, but Huff wasn’t wearing it at the time.
The main contributing factor to the incident was the method in which haul trucks dumped new material on the top of the stockpile.
Haul truck operators would drive up the access road built into the stockpile, back up to the berm and dump the load near or over the edge. Huff trained other haul truck drivers to dump loads back and forth, or left to right, on top of the stockpile. When dumping was done in this manner, it allowed a front-end loader to push the material up after the area was full.
However, Huff wasn’t following that method when the incident occurred. Instead, he dumped over the edge instead of filling in the area on top. The berm Huff backed up to shared an outside edge with the stockpile itself, which had become over-steepened. Further, the berm material was too narrow at its base to restrain a haul truck like it was supposed to because of the way the front-end loader had to push material up when trucks dumped over the edge.
Superintendent, drivers failed to point out hazard
Investigators learned that a mine superintendent had driven through the area prior to the incident and made no effort to correct the problem. MSHA determined that the mine operator failed to establish mining methods to ensure the stability of the dump site, which contributed to the collapse that caused Huff’s death.
To make matters worse, haul truck operators were required to conduct workplace examinations around the stockpile, but only at the end of their shifts. Examination records from previous shifts didn’t identify the hazard. That meant the hazardous condition never got called out from one shift to the next.
MSHA found that the lack of adequate workplace examinations contributed to the incident.
Mine developed new procedures for exams
Investigators identified four root causes that contributed to the incident, including:
- lack of seat belt use
- failure to ensure the stability of the dump site, and
- failure to ensure that haul truck operators dumped loads a safe distance from the edge of the stockpile.
The fourth root cause was the mine operator’s failure to conduct adequate workplace examinations. Following Huff’s death, the mine developed new written procedures for conducting workplace examinations around stockpiles and trained its haul truck operators on the new procedure.
