30 CFR Part 57Public Domain
§ 57.22241 — Advance face boreholes (I-C mines)
Subpart T — Safety Standards for Methane in Metal and Nonmetal Mines
(a)Boreholes shall be drilled at least 25 feet in advance of a face whenever the work place is within—
(1)50 feet of a surveyed abandoned mine or abandoned workings which cannot be inspected; or
(2)200 feet of an unsurveyed abandoned mine or abandoned workings which cannot be inspected.
(b)Boreholes shall be drilled in such a manner to insure that the advancing face will not accidently break into an abandoned mine or abandoned working.
Public Domain: 30 CFR Part 57 (MSHA Safety and Health Standards — Underground Metal and Nonmetal Mines) is a U.S. government publication and is not subject to copyright. Text extracted from the official source ↗. Figures are served from the eCFR; if one does not load, use the link in its place.