Emp was coming down a 5 foot ladder (used to access haul truck eng compartment). While coming onto the ladder emp put their foot on the 3rd rung. Emp's foot was wet from having (a few minutes ago) gone to the truck for a tool. When emp's foot slipped (wet) the ladder leaned hard to one side and fell over. Emp fell 3 feet to the floor and fractured (hair line) right radius.