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RULE 4 PERFORMANCE STANDARDS <br />4.06.4 Redistribution <br />After the final grading is completed, the topsoil will be reapplied as shown on the disturbed land areas <br />shown on the Topsoil Handling Map (Map 28 and 28A). Future topsoil redistribution will be done at an <br />average depth of eight (8) inches based on the volumetric analysis of available materials and areas as <br />presented in Rule 2.05. Historical replacement depths for reclaimed area units are tracked in the Annual <br />Report. <br />Where necessary, to prevent slippage surfaces and promote root penetration the spoil will be scarified by <br />ripping and/or rough grading. This practice will assure a solid bond between the spoil and reapplied <br />topsoil. To date, there is no evidence of topsoil slippage on reclaimed areas. A few small tension cracks <br />resulting from settling of fill and topsoil have occurred in a few areas within a year or two after <br />reclamation, but soon stabilize and begin to fill in. <br />Since all available topsoil existing on areas to be disturbed will be removed and reapplied, it will be fully <br />capable of supporting growth necessary for the proposed post -mining land use. Compaction will be <br />alleviated through chisel plowing. The method of topsoil replacement most often used at Colowyo, which <br />makes use of dozers, leaves the surface in a rough condition which minimizes wind and water erosion. <br />The use of a chisel plow following topsoil replacement and the construction of contour furrows at the <br />time of seeding or before will also aid in erosion control. <br />4.06.5 Reconditioning <br />Topsoil quality at Colowyo is excellent in terms of providing a suitable plant growth medium capable of <br />supporting the approved post -mining land use and the revegetation requirements of Section 4.15. Soil <br />testing has not indicated any deficiencies. Refer to Volume 3, Exhibit 10, Establishment of Native Shrubs <br />on Disturbed Lands in the Mountain Shrub Vegetation Type. This study was conducted on the Colowyo <br />Mine July 1975 through December 1979. Colowyo has the option to apply 50-70 pounds of phosphorus <br />per acre to all safely accessible reclaimed mine areas prior to chiseling and seeding. <br />4.07 Sealing of Drilled Holes and Underground Openings <br />4.07.1 General Requirement <br />Each exploration hole, or other bore hole well or other exposed underground opening encountered during <br />surface mining, will be cased, sealed,. plugged, or otherwise managed to meet the requirements of this <br />Section and described more fully in Section 2.05.4. <br />Holes used for surface blasting will not be included under the requirements of this Section. <br />4.07.2 Temporary Sealing <br />Each exploration hole or other drill or bore hole described in this Section will be protected, inspected and <br />maintained according to this Section. This performance is described more fully in Section 2.02 and 2.05.4 <br />of this application. <br />4.07.3 Permanent Sealing <br />Drilled holes no longer needed for monitoring or other approved uses will be backfilled and sealed as <br />described in this Section. This performance is described more fully in Sections 2.02 and 2.05.4 of this <br />application. <br />Rule 4 Performance Standards 4-26 Revision Date: 8/28/17 <br />Revision No.: TR -115 <br />