§ 880-X-10C-.36. Disposal Of Excess Spoil
(1) Spoil not required to achieve the approximate original contour within the area where overburden has been removed shall be transported and placed in a controlled manner in position for concurrent compaction and in such a way to assure mass stability and to prevent mass movement. Spoil shall be placed only in bonded and approved disposal areas within a permit area. The spoil shall be placed in an excess spoil fill in a controlled manner to ensure --
(a) That the adverse effects of leachate and surface runoff from the fill on surface or ground waters will be minimized;
(b) Stability of the fill; and
(c) That the land mass designated as the disposal area is suitable for reclamation and revegetation compatible with the natural surroundings.
(2) The fill and appurtenant structures shall be designed using recognized professional standards, and the design shall be certified by a qualified registered professional engineer, and approved by the State Regulatory Authority.
(3) The spoil shall be transported and placed in a controlled manner in horizontal lifts not exceeding 4 feet in thickness, concurrently compacted as necessary to ensure mass stability and prevent mass movement, covered with an approved material, and graded to allow surface and subsurface drainage to be compatible with the natural surroundings and attain a long-term static safety factor of 1.5. The Regulatory Authority may approve a design which incorporates placement of excess spoil in horizontal lifts other than 4-feet in thickness when it is demonstrated by the operator and certified by a qualified registered professional engineer that the design will ensure the stability of the fill and will meet all other applicable requirements.
(4) The fill shall be inspected for stability during construction by a qualified registered professional engineer or other qualified professional specialist who is under the direct supervision of the responsible qualified registered professional engineer. Both shall be experienced in the construction of earth and rockfill embankments. Inspections shall be made at least quarterly throughout construction and during the following critical construction periods:
(a) Removal of all organic material and topsoil,
(b) Placement of underdrains and protective filter systems,
(c) Installation of surface drainage systems,
(d) Placement and compaction of fill materials, and
The qualified registered professional engineer shall provide to the State Regulatory Authority a certified report within two weeks after each inspection that the fill has been constructed and maintained as specified in the design approved by the State Regulatory Authority. Certification on the underdrain system and protective filters shall be documented by color photographs taken during and after construction, but before the drain system is covered with spoil. If the underdrain system is constructed in phases, each phase shall be certified separately. Photographs shall be adequate in size and number to include enough terrain or other physical features of the site to provide a relative scale to the photographs. A copy of the inspection reports shall be retained at the minesite. Where excess durable rock spoil is placed in single or multiple lifts such that the underdrain system is constructed simultaneously with excess spoil placement by the natural segregation of dumped materials, in accordance with paragraph 18 of this Rule, color photographs shall be taken of the underdrain as the underdrain system is being formed.
(5) All vegetative and organic material shall be removed from the disposal area and the top soil shall be removed, segregated, and stored or replaced under Rules 880-X-10C-.07 - 880-X-10C-.11. If approved by the State Regulatory Authority, 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.
(6) Slope protection shall be provided to minimize surface erosion at the site. Diversion design shall conform with the requirements of Rule 880-X-10C-.-14. All disturbed areas, including diversion ditches that are not riprapped, shall be vegetated upon completion of construction.
(7) If the disposal area contains springs, natural or manmade water-courses, or wet-weather seeps, the fill design shall include diversions and underdrains as necessary to control erosion, prevent infiltration into the fill, and ensure stability. Diversions shall comply with Rule 880-X-10C-.14(f).
Underdrains shall consist of durable rock or pipe, be designed and constructed using current, prudent engineering practices and meet any design criteria established by the Regulatory Authority. The underdrain system shall be designed to carry the anticipated seepage of water due to rainfall away from the excess spoil fill and from seeps and springs in the foundation of the disposal area and shall be protected from piping and contamination by an adequate filter. Rock underdrains shall be constructed of durable, nonacid-, nontoxic-forming rock (e.g. natural sand and gravel, sandstone, limestone, or other durable rock) that does not slake in water or degrade to soil material, and which is free of coal, clay, or other nondurable material. Perforated pipe underdrains shall be corrosion resistant and shall have characteristics consistent with the long-term life of the fill.
(8) The disposal areas shall be located on the most moderately sloping and naturally stable areas available as approved by the State Regulatory Authority and shall be placed, where possible, upon or above, a natural terrace, bench, or berm, if such placement provides additional stability and prevents mass movement.
(9) Where the slope in the disposal area exceeds lv:2.8h (36 percent) or such lesser slope as may be designated by the Regulatory Authority based on local conditions, key way cuts (excavations to stable bedrock) or rock toe buttresses shall be constructed to stabilize the fill. Where the toe of the spoil rests on a down slope, stability analyses shall be performed in accordance with Rule 880-X-8F-.16 to determine the size of rock toe buttresses and key way cuts.
(10) The foundation and abutments of the fill shall be stable under all conditions of construction. Sufficient foundation investigations as well as any necessary laboratory testing of foundation materials shall be performed in order 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.
(11) The final configuration of the fill must be suitable for postmining landuses approved in accordance with Rule 880-X-10C-.66 except that no permanent impoundments shall be allowed on the completed fill. Small depressions may be allowed by the Regulatory Authority if they are needed to retain moisture, minimize erosion, create and enhance wildlife habitat or assist vegetation; and if they are not incompatible with stability of the fill.
(12) Terraces may be constructed on the outslope if required for control of erosion or for roads included in the approved postmining landuse plan. Terraces shall meet the following requirements:
(a) The slope of the outslope between terrace benches shall not be steeper than lv:2h (50 percent).
(b) To control surface runoff, each terrace bench shall be graded with a slope toward the embankment. Runoff shall be collected by a ditch along the intersection of each terrace bench and the outslope.
(c) Terrace ditches shall have a slope controlled such that erosive velocities are not produced.
(a) Excess spoil that is acid- or toxic-forming or combustible shall be adequately covered with nonacid, nontoxic and noncombustible material, or treated, to control the impact on surface and ground water in accordance with Rule 880-X-10C-.12, to prevent sustained combustion, and to minimize adverse effects on plant growth and the approved postmining land use.
(b) Coal processing waste may be disposed of in excess spoil fills if approved by the State Regulatory Authority and if such waste is --
1. Placed in accordance with Rule 880-X-10C-.40;
2. Demonstrated to be nontoxic-, nonacid-forming; and
3. Demonstrated to be consistent with the design stability of the fill.
(14) Excess spoil may be returned to underground mine workings, but only in accordance with a disposal program approved by the State Regulatory Authority and MSHA upon the basis of a plan submitted in accordance with Rule 880-X-8I-.16.
(a) The Regulatory Authority may approve the disposal of excess spoil through placement on pre-existing benches; provided, that all the standards set forth in paragraphs (1)-(14) of this Rule are met except as provided in this paragraph:
1. All spoil shall be placed on the solid portion of the pre-existing bench.
2. The fill shall be designed, using prudent engineering practices, to attain a long-term static factor of 1.3 for all portions of the fill.
3. The pre-existing bench shall be backfilled and graded to:
(i) Achieve the most moderate slope possible which does not exceed the angle of repose, and
(ii) Eliminate the highwall to the extent practicable.
(b) Disposal of excess spoil from an upper actively bench to a lower pre-existing bench by means of gravity transport may be approved by the State Regulatory Authority provided that:
1. The operator demonstrates that the spoil to be disposed of by gravity transport is not necessary for elimination of the highwall and return of the upper bench to approximate original contour;
2. The following conditions and performance standards in addition to the environmental performance standards of this part are met;
(i) Only spoil in excess of that necessary to eliminate the highwall and return the upper bench to the approximate original contour may be placed on the lower solid bench;
(ii) The gravity transport points are determined on a site-specific basis by the operator and approved by the Regulatory Authority as a part of the permit application to minimize hazards to health and safety and to ensure that damage will be minimized should spoil accidentally move downslope of the lower bench;
(iii) The excess spoil is placed only on solid portions of the lower pre-existing bench;
(iv) All excess spoil on the lower bench, including that spoil immediately below the gravity transport points and any pre-existing spoil that is disturbed, is rehandled and placed in a controlled manner to eliminate as much of the lower highwall as is practicable. Rehandling and placing of excess spoil on the lower solid bench shall consist of placing the excess spoil in horizontal lifts in a controlled manner, concurrently compacted as necessary to ensure mass stability and to prevent mass movement, and graded to allow surface and subsurface drainage to be compatible with the natural surroundings to ensure a long-term static safety factor of 1.3. Spoil placed on the bench prior to the current mining operation that is not disturbed need not be rehandled except to ensure stability of the fill;
(v) A safety berm is constructed on the solid portion of the lower bench prior to gravity transport of the excess spoil. Where there is insufficient material on the lower bench to construct a safety berm, only that amount of spoil necessary for the construction of the berm may be gravity transported to the lower bench prior to construction of the berm; and
(vi) The area of the lower bench used to facilitate the disposal of excess spoil is considered an affected area.
3. Excess spoil shall not be allowed on the downslope below the upper bench except on designated gravity transport courses properly prepared according to Rule 880-X-10C-.07. Upon completion of the fill, no excess spoil shall be allowed to remain on the designated gravity transport course between the two benches and each transport course shall be reclaimed in accordance with the requirements of this part.
(16) Disposal of spoil in head-of-hollow and valley fills shall comply with paragraphs (1)-(14) of this Rule and the following:
(a) The top surface of the completed fill shall be graded such that the final slope after settlement will be toward properly designed drainage channels. Uncontrolled surface runoff from the top surface of the fill shall not be allowed to flow over the outslope of the fill.
(b) Runoff from areas above the fill and runoff from the surface of the fill shall be diverted into stabilized diversion channels designed to meet the requirements of Rule 880-X-10C-.14(f) and, in addition, to safely pass the runoff from a 100-year, 6-hour precipitation event.
(c) A rock-core chimney drain may be used in a head-of-hollow fill, instead of the underdrain and surface diversion system normally required, as long as the fill is not located in an area containing intermittent or perennial streams. A rock-core chimney drain may be used in a valley fill if the fill does not exceed 250,000 cubic yards of material and upstream drainage is diverted around the fill. The alternative rock-core chimney drain system shall be incorporated into the design and construction of the fill as follows:
1. The fill shall have, along with the vertical projection of the main buried stream channel or rill a vertical core of durable rock at least 16 feet thick which shall extend from the toe of the fill to the head of the fill and from the base of the fill to the surface of the fill. A system of lateral rock underdrains shall connect this rock core to each area of potential drainage or seepage in the disposal area. Rocks used in the rock core and underdrains shall meet the requirements of Paragraph (7).
2. A filter system to ensure the proper functioning of the rock core shall be designed and constructed using standard geotechnical engineering methods.
3. The grading may drain surface water away from the outslope of the fill and toward the rock core. The maximum slope of the top of the fill shall be lv:33h (3 percent). Instead of the requirements of Paragraph (11) of this Rule, a drainage pocket may be maintained at the head of the fill during and after construction, to intercept surface runoff and discharge the runoff through or over the rock drain, if stability of the rill is not impaired. In no case shall this pocket or sump have a potential for impounding more than 10,000 cubic feet of water. Terraces on the fill shall be graded with a 3 to 5 percent grade toward the fill and a 1 percent slope toward the rock core.
(17) In lieu of the requirements of Paragraph (16), the Regulatory Authority may approve alternate methods for disposal of hard rock spoil, including full placement by dumping a single lift, on a site specific basis, provided the services of a registered professional engineer experienced in the design and construction of earthen and rockfill embankments are utilized and provided the requirements of Paragraphs (1)-(14) are met except as modified in this paragraph. For this Section, hard rock spoil shall be defined as rockfill consisting of at least 80 percent by volume of non-acid, non-toxic forming sandstone, limestone, or other rocks that do not slake in water and will not degrade to soil material.
(a) Spoil is to be transported and placed in a specified and controlled manner which will ensure stability of the fill.
1. The method of spoil placement shall be designed to ensure mass stability and prevent mass movement in accordance with the additional requirements of this Section.
2. Loads of noncemented clay shale and/or clay spoil in the fill shall be mixed with hard rock spoil in a controlled manner to limit on a unit basis concentrations of noncemented clay shale and clay in the fill. Such materials shall comprise no more than 20 percent of the fill volume as determined by tests performed by a registered professional engineer and approved by the Regulatory Authority.
(b) A qualified registered professional engineer certifies that the design will ensure the stability of the fill and meet all other applicable requirements.
(c) The fill shall be designed to attain a minimum long term static safety factor of 1.5, and an earthquake safety factor of 1.1.
(d) The underdrain system may be constructed simultaneously with excess spoil placement by the natural segregation of dumped materials, provided the resulting underdrain system is capable of carrying anticipated seepage of water due to rainfall away from the excess spoil fill and from seeps and springs in the foundation of the disposal area the other requirements for drainage control are met.
(e) Surface water runoff from areas adjacent to and above the fill is not allowed to flow onto the fill and is diverted into stabilized diversion channels designed to meet the requirements of Rule 880-X-10C-.14(f) and to safely pass the runoff from a 100-year, 6-hour precipitation event.
Author:(Amended: Filed March 25, 1997; effective April 29, 1997.)
Statutory Authority: Code of Ala. 1975, §§ 9-16-71, 72, 73, 74, 75, 76, 80, 84, 90, 92, 97.
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