25 Pa. Code § 77.551
Noncoal surface mining activities may not be conducted closer than 500 feet to any point of either an active or abandoned underground mine except to the extent that the nature, timing and sequence of the operations that propose to mine closer than 500 feet to an active underground mine are jointly approved by the Department and the Mine Safety and Health Administration or by the Department in the case of an abandoned underground mine within 500 feet.
The provisions of this § 77.551 adopted March 16, 1990, effective March 17, 1990, 20 Pa.B. 1643.