FALL APPROX 0-6'THICK, 40'LONG, 20'WIDE. FELL ON BELT & TRACK. NO BLOCKAGE OF VENT. NO INJURIES-DAMAGE TO BELTLINE- SECONDARY ESCAPEWAY- RE-ROUTED IN NEXT ENTRY BESIDE TRACK & BACK IN BELT WHI LE FALL WAS BEING CLEANED UP. SECONDARY ESCAPEWAY BACK IN BELT & TRACKING NOW.