A loaded stemming truck was being driven at low speed through a right hand turn to enter a drill pattern. As the stemming truck turned, it rolled onto its left hand side, resulting in the load of stemming spilling out and also injuring the passenger. The emergency response team was mobilised to provide medical assistance and secure the scene.
The investigation determined that there had been after-market modifications to the truck. Instead of a competent person re-calculating the truck's gross vehicle mass (GVM), the new GVM was estimated by the supplier, who was not the truck's original equipment manufacturer (OEM), based on a similar stemming truck used at another site.
At the time of the rollover, the loaded truck's mass was actually 4.5 tonnes overloaded despite being 2.1 tonnes less than the estimated GVM.
Note: GVM is the maximum permissible operating mass of a vehicle, and includes the chassis, body, fuel, accessories, driver, passengers and load.
Direct causes
- The GVM estimated by the supplier was 6.66 tonnes greater than the design GVM calculated by engineering consultants after the incident.
- The stemming truck had been overloaded as the GVM provided was incorrect.
Contributory causes
- Full operating manuals, drawings and engineering sign-off were not provided by the supplier of the modified stemming truck.
- The truck, which was hired, was not subjected to the same approvals process as purchased vehicles.