Topsoil Removal. Topsoil to be saved shall be removed after vegetation that could interfere with the use of the topsoil is cleared from the areas to be disturbed, but before any drilling, blasting, mining, or other surface disturbance. All topsoil shall be removed in a separate layer from the areas to be disturbed, unless use of substitute or supplemental materials is approved by the Bureau. If the topsoil is less than 6 inches, a separate layer shall be removed that includes all of the topsoil and the unconsolidated materials immediately below the topsoil to a minimum depth of 6 inches. If the Bureau determines that it is necessary or desirable, to ensure soil productivity consistent with the post-mining land use, then the Bureau may require removal of an additional layer (including portions of the “B” or “C” horizons) to be segregated and redistributed as subsoil. The maximum amount of topsoil that shall be saved shall be an amount sufficient to cover the areas to be revegetated to a depth of 4 feet. Selected overburden materials may be substituted for, or used as a supplement to, topsoil if the Bureau determines that the resulting soil medium is equal to or more suitable for sustaining revegetation than is the available topsoil and if the substitute material is the best available to support revegetation. This determination shall be based on analysis of the thickness of soil horizons, total depth, texture, percent coarse fragments, pH, and areal extent of the different kinds of soils. The Bureau may require other chemical and physical analyses, field-site trials, or greenhouse tests, if determined to be necessary or desirable to demonstrate the suitability of topsoil substitutes or supplements. If the removal of vegetative material, topsoil, or other materials may result in erosion which may cause air or water pollution: The size of the area from which topsoil is removed at any one time shall be limited; The surface soil layer shall be redistributed at a time when the physical and chemical properties of topsoil can be protected and erosion can be minimized; and Such other measures shall be taken as the Bureau may approve or require to control erosion. Topsoil Storage. Topsoil and topsoil substitutes removed under §A of this regulation shall be stockpiled only when it is impractical to promptly redistribute these materials on regraded areas. Protection measures shall be accomplished either by: An effective cover of non-noxious, quick-growing annual and perennial plants, seeded, or planted during the first normal period after removal for favorable planting conditions; or Other methods demonstrated to, and approved by, the Bureau to provide equal protection. Unless approved by the Bureau, stockpiled topsoil and other materials may not be moved until required for redistribution on a regraded area. Topsoil Redistribution. After final grading and before the replacement of topsoil and topsoil substitutes, regraded land shall be scarified or otherwise treated as required by the Bureau to eliminate slippage surfaces and to promote root penetration. Topsoil and other materials shall be redistributed in a manner that: Achieves an approximate uniform, stable thickness consistent with the approved postmining land uses, contours, and surface water drainage system; Prevents excess compaction of the topsoil; and Protects the topsoil from wind and water erosion before and after it is seeded and planted. Nutrients and Soil Amendments. Nutrients and soil amendments shall be applied to the initially redistributed material when necessary to establish the vegetative cover.