Postmining final graded slopes need not be uniform but shall approximate the general nature of the pre-mining topography. These requirements may be modified by the Bureau where the surface mining activities are reaffecting previously mined lands that have not been restored to these standards, and sufficient spoil is not available to otherwise comply with this chapter. The permittee shall, at a minimum: Retain all overburden and spoil on the solid portion of existing or new benches; and Backfill and grade to the most moderate slope possible to eliminate the highwall which does not exceed either the angle of repose or such lesser slope as is necessary to achieve a minimum long-term static safety factor of 1.5. In all cases the highwall shall be eliminated. On approval by the Bureau in order to conserve soil moisture, ensure stability, and control erosion on final graded slopes, cut and fill terraces may be allowed. The terraces shall be compatible with the approved postmining land use, and can be appropriate substitutes for construction of lower grades on the reclaimed lands. The terraces shall meet all of the following requirements: The width of the individual terrace bench may not exceed 20 feet, unless specifically approved by the Bureau as necessary for stability, erosion control, or roads included in the approved postmining land use plan. The vertical distance between terraces shall be as specified by the Bureau to prevent excessive erosion and to provide long-term stability. The slope of the terrace outslope may not exceed 2:1. Outslopes which exceed 2:1 may be approved, if they have a minimum static safety factor of 1.5, provide adequate control over erosion, and closely resemble the surface configuration of the land before mining. Highwalls may not be left as part of terraces. Small depressions may be constructed, if they: Are approved by the Bureau to minimize erosion, conserve soil moisture, create and enhance wildlife habitat, or promote vegetation; Do not restrict normal access; and Are approved, in writing, by the landowner. Preparation of final graded surfaces shall be conducted in a manner which minimizes erosion and provides a surface for replacement of topsoil which will minimize slippage. Spoil may be placed on the permit outside the mined-out area in non-steep slope areas to restore the approximate original contour by blending the spoil into the surrounding terrain if the following requirements are met: All vegetative and organic material shall be removed from the area; The topsoil on the area shall be removed, segregated, stored, and redistributed in accordance with COMAR 26.20.25.02; The spoil shall be backfilled and graded on the area in accordance with the requirements of this chapter.