(a) All explosives fired underground shall be confined in boreholes
except
(1) Sheathed explosives units and other explosive units
approved by MSHA for firing outside the confines of a borehole; and
(2) Shots fired in anthracite mines for battery starting
or for blasting coal overhangs. No person shall go inside a battery to start
the flow of material.
(b) Each borehole in coal for explosives shall be at least 24 inches
from any other borehole and from any free face, unless prohibited by the
thickness of the coal seam.
(c) Each borehole in rock for explosives shall be at least 18 inches
from any other borehole in rock, at least 24 inches from any other borehole
in coal, and at least 18 inches from any free face.
(d) No borehole that has contained explosives shall be used for
starting any other hole.
(e) When blasting slab rounds off the solid, opener holes shall not
be drilled beyond the rib line.
(f) When coal is cut for blasting, the coal shall be supported if
necessary to maintain the stability of the column of explosives in each
borehole.
