Tri County Materials found liable in Morenci mine fatality

Contributed Photo: This aerial view shows the Tri County Materials cement truck on its side after hitting a berm when its brakes failed.

By Jon Johnson

SAFFORD – The final fatality report from the Mine Safety and Health Administration regarding the Jan. 28 death of Monroe Caston Jr., 56, in a cement mixer crash at Freeport McMoRan’s Morenci Operations mine site listed Caston’s employer, Tri County Materials, a ready mix concrete supplier in Safford, liable for the crash.

At the time of the crash, the cement truck was loaded and driving down a ramp when the service brakes failed. The truck sped up quickly and passed its escort vehicle before it lost control on a curve, overturned, and slid into a berm.  

Another employee, David Butler, was a passenger in the Mack CV513 cement mixer truck and was severely injured. Neither occupant was wearing their seatbelts at the time of the crash.

According to the report, Tri County Materials “engaged in conduct constituting more than ordinary negligence in that the brake deficiencies were reported to the mine operator on January 20, 2022, and no effort was made to correct the hazardous condition.  This violation is an unwarrantable failure to comply with a mandatory standard.” The report lists three orders and three citations for Tri County Materials and reported that the company also failed to “remove defective equipment from service” and that “no effort was made to ensure that consistent, adequate pre-operational inspections were being conducted to correct hazardous conditions.” 

Contributed Photo: The investigation found the brakes on the truck were faulty.

The investigation found three of the four brakes on the cement truck were out of adjustment beyond retirement criteria, a rear drive axle had mismatching brake chambers, the brake shoes on the driver side were not properly positioned, one of the brake actuators had a leak, and five of the six braking components were worn beyond retirement criteria. 

In summation, the report concluded that Tri County did not maintain the braking systems in functional condition, did not conduct adequate pre-operational examinations, and did not ensure that all miners wore seat belts. 

“The accident occurred because the contractor that employed Caston and Butler, Tri County Materials Inc (Tri County), did not: 1) maintain braking systems in functional condition and did not remove equipment from service until defects that make continued operation hazardous were corrected, 2) conduct adequate pre-operational examinations on mobile equipment prior to operation, and 3) assure that miners wore seat belts,” the report states.

After the incident, Tri County took all of its trucks out of service and inspected the braking systems before putting them back and developed written criteria for removing defective equipment from service, a written SOP for pre-operational examinations of mobile equipment, and regarding seat belt use while all vehicles are in motion.  

Timeline of the incident

“On Jan. 28, 2022, Caston and Butler arrived at the Tri County equipment yard in Safford, Arizona at 4:30 a.m. to begin their shift.  Caston filled out a pre-operational examination record of the company number M14 cement mixer truck.  Caston drove this cement mixer truck to the Freeport-McMoRan Morenci Inc. mine in Morenci, Arizona with Butler, his passenger, who was in training as a cement mixer truck driver.

At 6:03 a.m., Caston and Butler arrived at the mine gate and proceeded to the concrete batch plant to await their first load.  At 7:21 a.m., Caston and Butler received their first load of ten cubic yards of concrete.  At 8:23 a.m., Caston and Butler hauled the concrete from the batch plant to the Shannon Booster Project work site.  At 8:35 a.m., the load of concrete was rejected by PVB Fabrications Inc because it was too wet.  After washing out the chute of the cement mixer truck, Caston and Butler drove the loaded vehicle down the Northwest Ramp to the batch plant to discard the rejected load of cement.  Caston and Butler were following an escort vehicle through the mine, which was driven by a Mixer Driver.

According to Butler, when Caston and Butler descended the Northwest Ramp, they lost the use of the service brakes on the cement mixer truck and the speed of the truck rapidly increased.  At 9:03 a.m., Caston and Butler passed their escort vehicle and a Caterpillar 793D Haul Truck driven by a Haul Truck Driver, who was also descending the Northwest Ramp.  Owen radioed that the cement truck had passed her and said the cement truck was traveling faster than the haul road speed limit.  As the cement mixer truck continued down the Northwest Ramp, it continued to accelerate, veered out of control on a curve, overturned on its side, and slid into a berm. 

At 9:09 a.m., the first person on the scene, a Water Truck Driver, called a “Mayday” on the radio to alert mine staff that a serious accident had occurred.  According to the Water Truck Driver’s interview, both miners were ejected from the truck.  At 9:12 a.m., a Haul Truck Driver, also trained as an Emergency Medical Technician (EMT), arrived on the scene and began administering first aid.  Shortly after, another trained EMT arrived on the scene.  The EMTs extricated Caston from the cab and moved him to a safe location to assess his injuries and began care.  At 9:23 a.m., the FMI Ambulance crew arrived on the scene and assumed care of Caston.  Then a second ambulance from Greenlee County arrived and assumed care of Butler.  Caston and Butler were transported by two ground ambulances to Gila Health Resources Clinic.  Butler was transported by ground, and Caston was airlifted, to the Banner University Medical Center in Tucson, Arizona where Caston was pronounced dead at 6:58 p.m.” – Source, United States Department of Labor Mine Safety and Health Administration fatality final report. 

The most previous fatal accident at the Morenci mine was on Sept. 15, 2021, when Cleveland Sloan, a 33-year-old contract welder with more than 10 years of mining experience, crawled into the confined space inside a stainless-steel pipe he was welding and died of asphyxiation due to the argon gas used in the welding process. Sloan was employed by PVB Fabrications, a contract fabrication service. MSHA issued a final report on this fatality in May.