Section 75.1319 - Weight of explosives permitted in boreholes in bituminous and lignite mines(a) The total weight of explosives loaded in any borehole in bituminous and lignite mines shall not exceed 3 pounds except when blasting solid rock in its natural deposit.(b) The total weight of explosives loaded in a borehole less than 6 feet deep in bituminous and lignite mines shall be reduced by 1/2 pound for each foot of borehole less than 6 feet.