(a)(1) All nonbattery-powered electric equipment, including cables,
located within 50 feet from boreholes to be loaded with explosives or the
sites where sheathed explosive units are to be placed and fired shall be
deenergized or removed to at least 50 feet from these locations before
priming of explosives. Battery-powered equipment shall be removed to at
least 50 feet from these locations before priming of explosives.
(2) As an alternative to paragraph (a)(1) of this section,
electric equipment, including cables, need not be deenergized or removed if
located at least 25 feet from these locations provided stray current tests
conducted prior to priming the explosives detect stray currents of 0.05
ampere or less through a 1-ohm resistor.
(a)(2)(i) Tests shall be made at floor locations on the
perimeter, on energized equipment frames and on repaired areas of energized
cables within the area between 25 to 50 feet from the locations where the
explosives are to be primed.
(a)(2)(ii) Tests shall be conducted using a blasting multimeter
or other instrument specifically designed for such use.
(3) The blasting cable or detonator circuitry shall not
come in contact with energized electric equipment, including cables.
(b) Before loading boreholes with explosives, each borehole shall be
cleared and its depth and direction determined.
(c) No borehole drilled beyond the depth of cut coal shall be loaded
with explosives unless that portion of the borehole deeper than the cut is
tamped with noncombustible material.
(d) When two working faces are approaching each other, cutting,
drilling and blasting shall be done at only one working face at a time if
the two faces are within 25 feet of each other.
[35 FR 17890, Nov. 20, 1970, as amended at 56 FR 51616, Oct. 11, 1991]
