EMPLOYEE WAS ATTEMPTING TO CLIMB DOWN FROM A 5TH WHEEL UTILITY TRAILER APPROX. 3'FROM THE GROUND SURFACE. HE PLACED HIS LEFT FOOT IN THE APPROPRIATE STEP & THEN PLACED HIS RT. FOOT ON TOP OF A PIPE RESULTING IN HIS RT. FOOT SLIPPING OFF PIPE & EE FALLING THE REMAINING 12""TO THE GROUND.