|(a) Underground Development Waste. Each plan shall contain descriptions, including appropriate maps and cross-section drawings of the proposed disposal methods and sites for placing underground development waste and excess spoil generated at surface areas affected by surface operations and facilities, according to §§12.531-12.534 of this title (relating to Disposal of Underground Development Waste and Excess Spoil: General Requirements, to Disposal of Underground Development Waste and Excess Spoil: Valley fills, to Disposal of Underground Development Waste and Excess Spoil: Head-of-Hollow Fills, and to Disposal of Underground Development Waste and Excess Spoil: Durable Rock Fills). Each plan shall describe the geotechnical investigation, design, construction, operation, maintenance and removal, if appropriate, of the structures and be prepared according to §12.153 of this title (relating to Disposal of Excess Spoil). (b) Return of Coal
Processing Waste to Abandoned Underground Workings. (1) Each plan shall describe the design, operation and maintenance of any proposed coal processing waste disposal facility, including flow diagrams and any other necessary drawings and maps, for the approval of the Commission and the Mine Safety and Health Administration under §12.541 of this title (relating to Coal Processing Waste: Return to Underground Workings). (2) Each plan shall describe the source and quality of waste to be stowed, area to be backfilled, percent of the mine void to be filled, method of constructing underground retaining walls, influence of the backfilling operation on active underground mine operations, surface area to be supported by the backfill, and the anticipated occurrence of surface effects following backfilling. (3) The applicant shall describe the source of the hydraulic transport mediums, method of dewatering the placed backfill,
retainment of water if released to surface streams, and the effect on the hydrologic regime. (4) The plan shall describe each permanent monitoring well to be located in the backfilled area, the stratum underlying the mined coal, and gradient from the backfilled area. (5) The requirements of paragraphs (1)-(4) of this subsection shall also apply to pneumatic backfilling operations, except where the operations are exempted by the Commission from requirements specifying hydrologic monitoring.