EE's were in process of cleaning sumps and ponds along haul road with A35C Volvo articulating trucks. Stopped for lunch. After lunch injured EE backed truck from the area and traveled approx 110' backwards, striking a road berm that caused truck to roll over the embankment approx 24'. Transported to hospital. Diiagnosed with fractured ribs, clavicle, vertebra, punc lung.