The fall of ground occurred at approximately 12:30pm in the 3920 SFW travel way area. The ground fall was approximately 6' in width 5' in length and 3' in depth. The drift is approximately 15' wide by 15' tall. It was determined that some roof bolts in the area had corroded over time and gave way. There were no injuries, equipment damage, change in ventilation, or entrapment.