EE STATED THAT HE WAS DESCENDING THE FIXED LADDER NEXT TO THE NO.3 DESLIME VIBRATOR, WHEN HIS FOOT SLIPPED OFF A RUNG OF THE LADDER, CAUSING HIMTO FALL APPROX 42 INCHES TO THE CONCRETE FLOOR OF THE PREP PLANT, AND LANDING ON HIS BACK. HE COMPLAINED OF PAIN TO HIS BACK AND NUMBNESS IN THE RIGHT FOOT.