EE WAS OPERATING SKID STEER, CLEANING SPILLAGE FROM IN FRONT OF THE DUMP HOPPER. A EUCLID R-40 ARRIVED AT THE DUMP HOPPER TO DUMP. THE EUCLID R-40 DRIVER PULLED FORWARD AND STARTED TO BACK UP TO THE HOPPER. HE DID NOT SEE THE SKID STEER AND BACKED INTO IT, THROWING EE FORWARD AGAINST THE SAFETY BAR. DAMAGE TO SKID STEER WAS MINIMAL.