OPERATOR WAS HAVING A LOAD OF DIRT TO WASTE DUMPSITE AS HE COMPLETED DUMPING IS LOAD THE GROUND AT THE REAR OF THE TRUCK STRATED TO GIVE WAY.THETRUCK BEGAN TO SUDE BACKWARD AT THAT POINT THE OPERATOR JUMPED FROM THE CAB TO THE GROUND CAUSING INJURY TO HIS LEFT FOOT AND LOWER BACK. TRUCKSLID APPROX. 30 FT AND WAS STOPPED BY A DIRT BANK AND LOWER BACK. TRUCK SLID APPROX. 30 FT. AND