30 CFR § 56.3130
Wall, bank, and slope stability.
Mining methods shall be used that will maintain wall, bank, and slope
stability in places where persons work or travel in performing their assigned
tasks. When benching is necessary, the width and height shall be based on the
type of equipment used for cleaning of benches or for scaling of walls,
banks, and slopes.
For further information: See MSHA's Program Policy Manual