52 Pa. Stat. § 70-238
Whenever a place is approaching inaccessible workings, the operator shall establish and clearly show on the map furnished the mine foreman a stopping distance not less than one hundred feet from the said inaccessible workings and such stopping point shall not be passed until after the coal company officials, the mining engineer and the mine inspector have agreed on the width of any such approaching place or places, the point at which test holes shall be started and the location of the test holes. The test holes shall not be less than twenty feet in advance of the working face with sufficient flank holes on each side of said place. No such stopping distance shall be less than one hundred feet from the said inaccessible abandoned workings, nor need it be greater than the distance calculated in accordance with the rule commonly used in the establishing of barrier pillars, namely, one per cent of the depth below drainage times the thickness of the coal seam plus thickness of seam times five, excepting in such cases where calculation in accordance with said rule establishes a stopping distance of less than one hundred feet. This act does not permit the driving of gangways, chambers or other excavations into barriers which are subjected to their maximum water pressure, as calculated in accordance with the rule here established, unless the said waterhead is reduced by pumping or other means. The term "mining engineer," as used in this act, shall mean the person who shall, in behalf of the operator, have charge or general supervision of the work of compiling the mine map.
52 P.S. § 70-238