53 Pa. Stat. § 5206
It shall be unlawful for any person, firm, association, or corporation to dig, mine, remove, or carry away the coal, rock, earth, or other minerals or materials forming the natural support of the surface, beneath the streets, avenues, thoroughfares, courts, alleys, places, and public highways of any municipal corporation within this Commonwealth, to such an extent and in such a manner as to thereby remove the necessary adequate support of the surface against subsidence, without having first placed, built, erected, and constructed sufficient adequate and permanent artificial support, in place and stead thereof, to maintain, uphold, and preserve the stability of the surface of said streets, avenues, thoroughfares, courts, alleys, places, and public highways.
53 P.S. § 5206