An equipment operator died when the bank of the pit he was working from sloughed causing the excavator he was operating to topple into 25 feet of water.
U.S. Mine Safety and Health Administration (MSHA) investigators determined that the mining method used near the pit compromised ground stability and failure to perform adequate jobsite examinations caused the condition to go unnoticed.
Blasted limestone excavated from water-filled pit
Kenneth Wright was an equipment operator at the Florida Rock Industries Fort Pierce Mine in Saint Lucie County, Florida.
This surface mine employed miners to drill and blast limestone rock into an open, water-filled pit. Excavators were used to remove the rock from the water to a temporary stockpile on shore that front-end loaders would then transport to a crushing plant for processing.
On March 15, 2023, Wright and two other equipment operators began their shifts at 6 a.m. Wright was assigned to his usual duty, which was to operate an excavator to extract previously blasted limestone from the water-filled pit and stockpile it on the ground adjacent to the pit.
In order to do this, Wright had to operate the excavator from on top of the previously blasted loose rock on the edge of the bank adjacent to the pit.
Conditions too dangerous for search and rescue team to enter
After lunch, Wright returned to the excavator at 1 p.m. and resumed work. At about 1:15 p.m., the edge of the bank where Wright was working became unstable and the excavator toppled into the water-filled pit and quickly sank.
Another equipment operator witnessed the incident and drove the front-end loader he was operating over to check on Wright. He walked to the edge of the water but couldn’t see any part of the excavator and didn’t see Wright come to the surface. The other equipment operator also arrived on scene and he also couldn’t see the excavator or find Wright.
The two equipment operators called the scale clerk for help, leading to a 9-1-1 call at 1:15 p.m. The county search and rescue team responded but conditions in the murky waters of the pit were deemed too dangerous for divers to enter.
On March 16, 2023, the mine operator brought in an underwater recovery specialist contractor who was able to locate the cab of the excavator with a remotely operated vehicle. A diver went down into the pit’s waters, located the excavator, broke a window and recovered Wright from the cab.
Wright was pronounced dead from drowning at 6:10 p.m.
Previous incident should have led to changes in mining method
MSHA investigators determined that the mining method in use at the mine didn’t ensure that the material the excavator was operating on top of was stable.
The investigators discovered that an incident in 2022 resulted in too much material being removed from the pit bank, which caused the excavator to fall into the water at that time. The mine operator had to have the excavator removed from the waters of the pit.
That previous incident “should have been sufficient to put the mine operator on notice of the potential ground failure because of the mining method used,” according to MSHA. However, adequate changes in the mining method weren’t made to prevent recurrence.
Adequate exams would have caught dangerous condition
After Wright’s death, the excavator couldn’t be recovered from the pit, so investigators were unable to perform an inspection to see if it had any safety defects that may have contributed to the incident. However, Wright had been wearing a CO2-inflated flotation device around his waist and the excavator was equipped with a window breaking device but Wright didn’t seem to have activated either device.
MSHA found that workplace and ground condition examinations had been conducted on the day of the incident with no adverse safety conditions being identified.
A MultiBeam Hydrographic Survey taken during the MSHA investigation found that the bank where Wright was working had been undercut at some point during his shift. Investigators said that adequate examinations conducted as conditions changed would have identified the undercut bank that created the unstable ground.
Mine changed methods, developed new exam procedures
Ultimately, MSHA found that the mining method and the lack of adequate examinations were the two root causes of the fatal incident.
The mine operator has since developed new policies and mining methods that involved replacing the excavator with a dragline for use in the pit.
New procedures were also developed for conducting ground condition examinations as conditions warrant for the new mining method.