A roof fall was discovered at 4 main 2x #6 Hdg indersection. 18' x 18' x 12' high. The fall was 2,000' outby section. Area was bolted with 6' fully grouted and 6' super twists and 12' post tensioned bolts. A row of cribs were set along each rib. No ventilation or transportation was affected. No persons or machines were injured or trapped.