(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.
Equipment