BACKHOE OPERATOR WAS LOADING CRUDE CLAY TRUCKS OFF OF THE TOP SHELF (APPROX. 8 FEET) WHEN HE GOT THE BACKHOE TOO CLOSE TO THE EDGE AND THE MACHINE SLIPPED OFF ON THE RIGHT SIDE. WHEN ATTEMPTING TO RELOCATE THE BUCKET TO BETTER SUPPORT THE MACHINE, IT SLIPPED DOWN VERY SLOWLY APPROX. 1 FOOT AND THEN SLOWLY ROLLED OVER ONTO ITS RIGHT SIDE.