§ 87.131. Disposal of excess spoil.
(a) Spoil not required to achieve the approximate original contour shall be transported and placed in designated disposal areas approved by the Department within the permit area. The disposal area shall be designed, constructed and maintained to ensure:
(1) That leachate and surface runoff from the fill will not degrade surface or groundwater or exceed the effluent limitations of § 87.102 (relating to hydrologic balance: effluent standards).
(2) The prevention of combustion.
(3) The stability of the fill.
(4) That the land mass designated as the disposal area is suitable for reclamation and revegetation compatible with the natural surroundings.
(b) The fill shall be designed using recognized professional standards, certified by a registered professional engineer, and approved by the Department.
(c) The excess spoil disposal fill shall be designed to attain a long-term static factor of safety of 1.5 and a seismic factor of safety of 1.1 based upon dataobtained from subsurface exploration, geotechnical testing, foundation design, fill design and accepted engineering analyses.
(d) Vegetative and organic materials shall be removed from the disposal area and the topsoil shall be removed, segregated and stored or replaced as provided in § § 87.96—87.100. If approved by the Department, organic material may be used as mulch or may be included in the topsoil to control erosion, promote growth of vegetation or increase the moisture retention of the soil.
(e) The excess spoil disposal area should be located in areas where groundwater discharge and surface water flows are minimal.
(f) The disposal areas shall be located on the most moderately sloping and naturally stable areas available as approved by the Department. If the placement provides additional stability and prevents mass movement, fill materials suitable for disposal shall be placed upon or above a natural terrace, bench or berm.
(g) The spoil shall be hauled or conveyed and placed in a controlled manner and concurrently compacted as approved by the Department in lifts no greater than 4 feet, or less if required by the Department as the design to:
(1) Achieve the densities designed to ensure mass stability.
(2) Prevent mass movement.
(3) Avoid contamination of the rock underdrain.
(4) Prevent formation of voids.
(h) The final configuration of the fill shall be suitable for postmining land uses approved in accordance with § 87.159 (relating to postmining land use), except that no depressions or impoundments may be allowed on the completed fill. The fill may not exceed the approximate elevation of the ridgeline.
(i) The top surface of the completed fill shall be graded so that the final slope after settlement will be no steeper than lv:20h-5.0% toward properly designed drainage channels in natural ground clay along the periphery of the fill. Surface runoff from the top surface of the fill may not be allowed to flow over the outslope of the fill.
(j) Terraces may be utilized to control erosion and enhance stability or for roads if approved by the Department and consistent with the approved postmining land use.
(k) When the slope in the disposal area exceeds lv:2.8h-36% or a lesser slope designated by the Department based on local conditions, keyway cuts (excavations to stable bedrock) or rock toe buttresses shall be constructed to stabilize the fill. When the toe of the spoil rests on a downslope, stability analyses shall be performed in accordance with § 87.79 (relating to disposal of excess spoil) to determine the size of rock toe buttresses and key way cuts.
(l) Surface water runoff from the areas adjacent to and above the fill may not be allowed to flow onto the fill and shall be diverted into stabilized channels which are designed to pass safely the peak runoff from a 100-year precipitation event. Diversion design shall comply with the requirements of § 87.105 (relating to hydrologic balance: diversions).
(m) Surface water runoff from the fill shall be diverted off the fill to properly designed channels which will pass safely the peak runoff from a 100-year precipitation event. Diversion design shall comply with the requirements of § 87.105.
(n) The fill shall be inspected for stability by a qualified registered professional engineer or other qualified professional specialist experienced in the construction of earth and rockfill embankments and working under the direction of a qualified registered professional engineer. These inspections shall occur at least quarterly throughout construction and during the following critical construction periods: removal of organic material and topsoil, placement of underdrainage systems, installation of surface drainage systems, placement and compaction of fill materials and revegetation. The qualified registered professional engineer shall provide to the Department a certified report within 2 weeks after each inspection that the fill has been constructed and maintained in accordance with the approved design, in accordance with the approved plan, and in accordance with all applicable performance standards and this chapter. The report shall include appearances of instability, structural weakness and other hazardous conditions. A copy of the report shall be retained at the minesite.
(o) Coal processing waste may be disposed of in the disposal area if the requirements of Chapter 90 (relating to coal refuse disposal) are met.
(p) If the disposal area contains springs, natural or manmade water courses, or wet-weather seeps, an underdrain system consisting of durable rock shall be constructed from the wet areas in a manner that prevents infiltration of the water into the spoil material. The underdrain system shall be protected by an adequate filter and ensure continued free drainage.
(q) An underdrain/subdrainage system for the fill shall be designed in accordance with the following:
(1) It shall include an underdrain system which will ensure free drainage of anticipated seepage from precipitation and from spring or wet-weather seeps and meet the following:
(i) Anticipated discharges from springs and seeps due to precipitation shall be based on records or field investigation, or both, to determine seasonal variation. The design of the underdrain system shall be based on maximum anticipated discharges.
(ii) Granular material used for the drainage system shall be nondegradable, nonacid- or toxic-forming rock free of clay, and consist of durable particles such as natural sands and gravels, sandstone, limestone or other durable rock which will not slake in water.
(2) An underdrain system shall be designed to be installed along with the natural drainage system; extend from toe to head of fill; and contain lateral drains to each area of potential drainage or seepage.
(3) A filter system to ensure the proper functioning of the rock underdrain system shall be designed and constructed using standard geotechnical engineering methods.
(r) The certified report required under subsection (n) shall include, as part of reporting on the underdrain/subdrainage system and filter system, color photographs taken during and after construction, but before the underdrains are covered with excess spoil. If the underdrain is constructed in phases, each phase shall be certified separately. Photographs shall be taken in adequate size and number with enough terrain or other physical features of the site shown to provide a relative scale to the photographs and to specifically and clearly identify the site.
(s) The foundation and abutments of the fill shall be stable under all conditions of construction and operation. Sufficient foundation investigation and laboratory testing of foundation materials shall be performed to determine the design requirements for stability of the foundation. Analyses of foundation conditions shall include the effect of underground mine workings, if any, upon the stability of the structure.
(t) Excess spoil may be returned to underground mine workings, but only in accordance with a disposal program approved by the Department and MSHA in accordance with Chapter 89 (relating to underground mining of coal and coal preparation facilities).
Authority The provisions of this § 87.131 amended under the Surface Mining Conservation and Reclamation Act (52 P. S. § § 1396.1—1396.19a); The Clean Streams Law (35 P. S. § § 691.1—691.1001); and section 1920-A of The Administrative Code of 1929 (71 P. S. § 510-20).
Source The provisions of this § 87.131 adopted December 19, 1980, 10 Pa.B. 4789, effective July 31, 1982, 12 Pa.B. 2382; amended July 30, 1982, 12 Pa.B. 2473, effective July 31, 1982, 12 Pa.B. 2382; amended June 15, 1990, 20 Pa.B. 3383, effective July 27, 1991, 21 Pa.B. 3316; amended December 11, 1992, effective December 12, 1992, 22 Pa.B. 5945; amended December 15, 1995, effective December 16, 1995, 25 Pa.B. 5821. Immediately preceding text appears at serial pages (198985) to (198988).
Cross References This section cited in 25 Pa. Code § 87.79 (relating to disposal of excess spoil); 25 Pa. Code § 87.141 (relating to backfilling and grading: general requirements); 25 Pa. Code § 87.174 (relating to steep slope operations); and 25 Pa. Code § 87.175 (relating to variance to contouring).
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