EE WAS STEERING SCRAP CEMENT MIXER TO JUNK PILE. THE MIXER TRUCK WAS BEING PUSHED FROM BEHIND BY ANOTHER EE IN A 980G LOADER ON LEVEL GROUND AT LESS THAN 2 MPH. APPARENTLY THE RIGHT FRONT LOAD ER TIRE DIPPED INTO A SMALL SWALE ENOUGH THAT THE LOAD IN THE MIXER SHIFTED CAUSING THE MIXER TO ROLL OVER ON ITS SIDE. EE WAS EJECTED FROM THE CAB & RECEIVED A BRUISE ON HIS HEAD & A CUT ON