September 4, 2017
The Mine Safety and Health Administration (MSHA) issued a Close Call Accident Alert after water overflowed a dam at an underground limestone operation. On August 22, 2017, after a heavy rainstorm, water overflowed a dam and went into a mine portal, partially blocking entries, including the primary escapeway. Luckily, no miners were injured.
MSHA offers the following Best Practices to help prevent this type of accident:
MSHA standards 30 CFR §§56/57.20010, which address retaining dams, state, “If failure of a water or silt retaining dam will create a hazard, it shall be of substantial construction and inspected at regular intervals.” “Substantial construction” includes adequately maintaining the dam to safely retain the material behind it, even during large storms. Ensuring adequate freeboard, the vertical distance between the lowest point on the dam crest and the pool elevation, is a part of this maintenance.