Backfilling and Grading Requirements

PURPOSE: This rule sets forth the requirements for backfilling and grading pursuant to sections 444.810, 444.855.2(3) and .3, RSMo. (1) General. (A) Timing of Backfilling and Grading. 1. Contour mining. Rough backfilling and grading shall follow coal removal by not more than sixty (60) days or one thousand five hundred (1500) linear feet. The director may grant additional time for rough backfilling and grading if the permittee can demonstrate, through a detailed written analysis under 10 CSR 40-6.050(8)(B)3., that additional time is necessary. 2. Open pit mining with thin overburden. Rough backfilling and grading shall occur in accordance with the time schedule approved in the permit and plan, on the basis of the materials submitted under 10 CSR 406.050(8)(B)3., which shall specifically establish in stated increments the period between removal of coal and completion of backfilling and grading. 3. Area strip mining. Rough backfilling and grading either shall be— A. Completed within one hundred eighty (180) days following coal removal and shall not be more than four (4) spoil ridges behind the pit being worked, the spoil from the active pit being considered the first ridge; or B. Not more than three (3) spoil ridges behind the pit being worked, the spoil from the active pit being considered the first ridge. If the pit becomes inactive for a period longer than thirty (30) days and an alternate schedule is not approved, the pit must be backfilled and graded within one hundred eighty (180) days of cessation of operations. 4. Either of the previous two (2) rough backfilling and grading schedules shall be applicable to all areas on a mine with the backfilling and grading schedule for each specific area identified in the permit; 5. Additional time, spoil ridges, or both, for rough backfilling and grading may be granted by the director if the permittee can demonstrate in a detailed written analysis, including specific schedules and plans, that additional time or spoil ridges is necessary. 6. Active areas such as roads, ramps, parking areas, stockpiles and boxcut spoil, which area is shown on an approved operations plan map, are not subject to the backfilling and grading time frames until they become inactive or unless they are part of a variance schedule. (B) Method for Backfilling and Grading. 1. Except as specifically exempted in this chapter, all disturbed areas shall be returned to their approximate original contour. All spoil shall be transported, backfilled, compacted (where advisable to ensure stability or to prevent leaching) and graded to eliminate all highwalls, spoil piles and depressions. 2. Backfilled material shall be placed to minimize adverse effects on groundwater, minimize off-site effects and to support the approved postmining land use. 3. The postmining graded slopes need not be of uniform slope. 4. Cut-and-fill terraces may be used only in those situations expressly identified in section (2) of this rule. (2) General Grading Requirements. (A) The final graded slopes shall not exceed in grade either the approximate premining slopes or any lesser slopes approved in the permit and plan based on consideration of soil, climate or other characteristics of the surrounding area. Postmining final graded slopes need not be uniform but shall approximate the general nature of the premining topography. The requirements of this section may be modified in the permit and plan where the surface mining activities are reaffecting previously mined lands that have not been restored to the standards of this chapter and sufficient spoil is not available to otherwise comply with this section. The person who conducts surface mining activities, at a minimum, shall— 1. Retain all overburden and spoil on the solid portion of existing or new benches; and 2. Backfill and grade to the most moderate slope possible, to eliminate the highwall which does not exceed either the angle of repose or a lesser slope as is necessary to achieve a minimum static safety factor of one and three-tenths (1.3). In all cases the highwall shall be eliminated. (B) On approval in the permit and plan in order to conserve soil moisture, ensure stability and control erosion on final graded slopes, cut-and-fill terraces may be allowed if the terraces are compatible with the approved postmining land use and are appropriate substitutes for construction of lower grades on the reclaimed lands. The terraces shall meet the following requirements: 1. The slope of the individual terrace bench shall not exceed twenty feet (20') unless specifically approved in the permit and plan as necessary for stability, erosion control or roads included in the approved postmining land use plan; 2. The vertical distance between terraces shall be as specified in the permit and plan, to prevent excessive erosion and to provide long-term stability; 3. The slope of the terrace outslope shall not exceed 1v:2h (50%). Outslopes which exceed 1v:2h (50%) may be approved, if they have a minimum static safety factor of more than one and three-tenths (1.3), provide adequate control over erosion and closely resemble the surface configuration of the land prior to mining. In no case may highwalls be left as part of terraces; and 4. Culverts and underground rock drains shall be used on the terrace only when Surface Coal Mining and Related Activities approved in the permit and plan. (C) Small depressions may be constructed, if they— 1. Are approved in the permit and plan to minimize erosion, conserve soil moisture or promote vegetation; 2. Do not restrict normal access; and 3. Are not inappropriate substitutes for lower grades on the reclaimed lands. (D) All surface mining activities on slopes above twenty degrees (20°) or on lesser slopes that the permit and plan defines as steep slopes shall meet the provisions of 10 CSR 40-4.040. (E) All final grading, preparation of overburden before replacement of topsoil and placement of topsoil shall be done along the contour to minimize subsequent erosion and instability. If this grading, preparation, or placement along the contour is unnecessary or is hazardous to equipment operations, then grading, preparation or placement in a direction other than generally parallel to the contour may be used if approved in the permit and plan. In all cases, grading, preparation or placement shall be conducted in a manner which minimizes erosion and provides a surface for replacement of topsoil which will minimize slippage. (3) Covering Coal Seams, Combustible and Acid-Forming and Toxic-Forming Materials. (A) Cover. 1. Exposed coal seams, acid-forming and toxic-forming materials and combustible materials exposed, used or produced during mining shall be adequately covered with nontoxic and noncombustible material or treated, to control the impact on surface and ground water in accordance with 10 CSR 40-3.040, to prevent sustained combustion and to minimize adverse effects on plant growth and the approved postmining land use. Coal processing waste and noncoal waste shall be covered in accordance with 10 CSR 40-3.080. 2. Where necessary to protect against upward migration of salts, exposure to erosion, formation of acid or toxic seeps, to provide an adequate depth for plant growth or otherwise to meet local conditions, the permit and plan shall specify thicker amounts of cover using nontoxic material, or special compaction and isolation from groundwater contact. 3. Acid-forming or toxic-forming material, combustible materials and coal processing waste shall not be buried or stored in proximity to a drainage course so as to cause or pose a threat of water pollution. (B) Stabilization. Backfilled materials shall be selectively hauled or conveyed and compacted, wherever necessary, to prevent leaching of acid- and toxic-forming materials into surface or ground waters and wherever necessary to ensure stability of the backfilled materials. The method and design specifications of compacting material shall be approved in the permit and plan before acid- or toxicforming materials are covered. (4) Thin Overburden. (A) The provisions of this section apply only where there is insufficient spoil and other waste materials available from the entire permit area to restore the disturbed area to its approximate original contour. Insufficient spoil and other waste materials occur where the overburden thickness times the swell factor, plus the thickness of other available waste materials, is less than the combined thickness of the overburden and coal bed prior to removing the coal, so that after backfilling and grading the surface configuration of the reclaimed area would not: 1. Closely resemble the surface configuration of the land prior to mining; or 2. Blend into and complement the drainage pattern of the surrounding terrain. The provisions of this section apply only when surface mining activities cannot be carried out to comply with section (1) of this rule to achieve the approximate original contour. (B) In surface mining activities carried out continuously in the same limited pit area for more than one (1) year from the day coalremoval operations begin and where the volume of all available spoil and suitable waste materials over the mine plan area is demonstrated to be insufficient to achieve the approximate original contour of the lands disturbed, surface mining activities shall be conducted to meet, at a minimum, the following standards: 1. Haul or convey, backfill and grade, using all available spoil and suitable waste materials from the entire mine area, to attain the lowest practicable stable grade, to achieve a static safety factor of one and three-tenths (1.3), and to provide adequate drainage and long-term stability of the regraded areas and cover all acid- and toxic-forming materials; 2. Eliminate highwalls by grading or backfilling to stable slopes not exceeding 1v:2h (50%) or lesser slopes as may be specified in the permit and plan to reduce erosion, maintain the hydrologic balance or allow the approved postmining land use; 3. Haul or convey, backfill, grade and revegetate, in accordance with 10 CSR 403.120(1)–(7), to achieve an ecologically sound land use compatible with the prevailing use in unmined areas surrounding the mine plan area; and 4. Haul or convey, backfill and grade, to ensure impoundments are constructed only where— A. It has been demonstrated that all requirements of 10 CSR 40-3.040(1)–(16) have been met; and B. The impoundments have been approved in the permit and plan as suitable for the approved postmining land use as meeting the requirements of this chapter and all other applicable federal and state laws and regulations. (5) Thick Overburden. (A) The provisions of this section apply only where there is more than sufficient spoil and other waste materials available from the entire permit area to restore the disturbed area to its approximate original contour. More than sufficient spoil and other waste materials occur where the overburden thickness times the swell factor exceeds the combined thickness of the overburden and coal bed prior to removing the coal, so that after backfilling and grading the surface configuration of the reclaimed area would not: 1. Closely resemble the surface configuration of the land prior to mining; or 2. Blend into and complement the drainage pattern of the surrounding terrain. The provisions of this section apply only when surface mining activities cannot be carried out to comply with section (1) of this rule to achieve the approximate original contour. (B) In surface mining activities where the volume of spoil over the mine plan area is demonstrated to be more than sufficient to achieve the approximate original contour, surface mining activities shall be conducted to meet, at a minimum, the following standards: 1. Haul or convey, backfill and grade all spoil and wastes not required to achieve the approximate original contour of the mine plan area, to the lowest practicable grade, to achieve the static factor of safety of one and three-tenths (1.3) and cover all acid-forming and other toxic-forming materials; 2. Haul or convey, backfill and grade excess spoil and wastes only within the permit area and dispose of those materials in accordance with 10 CSR 40-3.060(1)–(4); 3. Haul or convey, backfill and grade excess spoil and wastes to maintain the hydrologic balance, in accordance with sections 10 CSR 40-3.040(1)–(17), and to provide longterm stability by preventing slides, erosion and water pollution; 4. Haul or convey, backfill, grade and revegetate wastes and excess spoil to achieve an ecologically sound land use approved in the permit and plan as compatible with the prevailing land uses in unmined areas surrounding the mine plan area; 5. Eliminate all highwalls and depressions by backfilling with spoil and suitable waste materials; and 6. Meet the revegetation requirements of 10 CSR 40-3.120(1)–(7) for all disturbed areas. (6) Regrading or Stabilizing Rills and Gullies. (A) When rills or gullies deeper than nine inches (9") form in areas that have been regraded and topsoiled, the rills and gullies shall be stabilized as soon as weather and soil conditions permit by use of temporary or permanent measures. Rills and gullies deeper than nine inches (9") which have formed prior to August 1 of any year and which either 1) disrupt the approved postmining land use or the reestablishment of the vegetative cover, or 2) cause or contribute to a violation of water quality standards for receiving streams shall be filled, graded and topsoiled by September 1 of each year and reseeded or replanted according to 10 CSR 40-3.120(1)– (7) as soon as weather and soil conditions permit, but no later than September 30 of each year. Rills and gullies of lesser depth which have formed prior to August 1 of any year must be permanently or temporarily stabilized as soon as weather and soil conditions permit and permanently repaired and topsoiled, if in a topsoiled area, by September 30 of each year if the rills and gullies disrupt the approved land use or the reestablishment of a vegetative cover or cause or contribute to a violation of water quality standards for receiving stream. (B) On areas that have been previously mined, the requirements for regrading or stabilizing rills and gullies pursuant to subsection (6)(A) apply after final grading and placement of topsoil or the best available topsoil substitute. AUTHORITY: sections 444.530 and 444.810, RSMo Supp. 1999.* Original rule filed Oct. 12, 1979, effective Feb. 11, 1980. Amended: Filed Dec. 10, 1980, effective April 11, 1981. Amended: Filed June 27, 1986, effective Jan. 12, 1987. Amended: Filed Aug. 14, 1986, effective Feb. 28, 1987. Amended: Filed Sept. 15, 1988, effective Jan. 15, 1989. Amended: Filed July 3, 1990, effective Nov. 30, 1990. Amended: Filed May 15, 1992, effective Jan. 15, 1993. Amended: Filed Sept. 15, 1994, effective April 30, 1995. Amended: Filed March 21, 2000, effective Oct. 30, 2000. *Original authority: 444.530, RSMo 1971 amended 1983, 1990, 1993, 1995; and 444.810,RSMo 1979, amended 1983, 1993, 1995.