(a) Only noncombustible material shall be used for stemming
boreholes.
(b) Stemming materials other than water stemming bags shall be tamped
to fill the entire cross sectional area of the borehole.
(c) Stemming material shall contact the explosive cartridge nearest
the collar of the borehole.
(d) Each borehole 4 or more feet deep shall be stemmed for at least
24 inches.
(e) Each borehole less than 4 feet deep shall be stemmed for at least
half the depth of the borehole.
(f) When blasting off the solid in bituminous and lignite mines, only
pliable clay dummies shall be used for stemming.
(g) The diameter of a water stemming bag shall be within 1/4 of an
inch of the diameter of the drill bit used to drill the borehole.
(h) Water stemming bags shall be constructed of tear-resistant and
flame-resistant material and be capable of withstanding a 3-foot drop when
filled without rupturing or developing leaks.
