CHANGING PIPE ON LEACH PAD. ROCKY SLOPE ON LEACH PAD CAUSED THE EE TO SLIP AND FALL BACKWARD, LANDING ON A SOFTBALL-SIZED ROCK AND CAUSING A LARGE BRUISE ON THE LEFT BUTTOCK. GIVEN PRESCRIPTION FOR PAIN PILLS AT ER; X-RAYS NEGATIVE. (DELAY IN FILING INJURY REPORT BECAUSE COMPANY THOUGHT ONLY 1X INJECTION FOR PAIN WAS GIVEN AT ER.)