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I <br />Section 816. 102 (b) Continued. <br />cut-and-fill terraces may be allowed, if the terraces are compatible <br />with the approved postmining land use and are appropriate substitutes <br />for construction of lower grades on the reclaimed lands. The terraces <br />shall meet the following tequirements: <br />(1) The width of the individual terrace bench shall not exceed 20 feet, <br />unless specifically approved by the regulatory authority as necessary <br />for stability, erosion control, or roads included in the approved post- <br />mining land use plan. <br />(2) The vertical distance between terraces shall be as specified by the <br />regulatory authority, to prevent excessive erosion and to provide long- <br />term stability. <br />(3) The slope of the terrace outslope shall not exceed lv:2h (50 per- <br />cent). Outs lopes which exceed lv:2h (50 percent) may be approved, if <br />i they have a minimum static safety factor of more than 1.3, provide <br />adequate control over erosion, and closely resemble the surface configu- <br />ration of the land prior to mining. In no case may highwalls be left as <br />part of terraces. <br />(4) Culverts and underground rock drains shall be used on the terrace <br />only when approved by the regulatory authority. <br />As stated in Section 30 CFR 816.102 (a}, Kerr Coal's plan to re- <br />store an undulating topography which approximates premining grades <br />makes the use of cut and fill terraces unnecessary. <br />{c) Small depressions may be constructed, if they- <br />(1) Are approved by the regulatory authority to minimize erosion, <br />conserve soil moisture, or promote vegetation; <br />• <br />816-133 <br />