EMPLOYEE WALKED ACROSS FILLED AREA. THE 15'HIGH FILLED AREA WAS SUPPORTED FROM THE BOTTOM WITH TIMBER & PLANK. AS HE WALKED ACROSS THE 2-3'WIDE FILLED SECTION IT GAVE WAY. EMPLOYEE FELL APX 15 ' & STRUCK A LANDING, FELL ANOTHER 20' & STRUCK ANOTHER LANDING, THEN FELL 20'.