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The threshold levels are to be used as a guide in evaluating the suitability of a soil material for reclamation. An <br />evaluation should take into account the "total system". Interactive parameters may either nullify or verify the significance <br />of a potential problem. <br />2 The actual maximum acceptable salt level will depend on the plant species proposed in the revegetation plan and the <br />potential for upward salt movement. <br />3 Specific level depends upon clay mineralogy, soil texture, and saturation percentage according to Dollhopf et aL,1983. <br />'The specific percentage of clay or sand allowed will depend upon clay mineralogy, organic matter content, consistence, <br />soil lift, spoil characteristics, and size of sand fraction. <br />5 These values may vary depending upon the plant species proposed for revegetation in specific locations (e.g., a soil <br />with a high coarse fragment content throughout its profile may be completely salvaged if used for rangeland versus <br />cropland postmine land use). Prime farmland will not have >10% cobbles and boulders (3 inches mean diameter and <br />greater) and 15% coarse fraction (caught in a 2 millimeter sieve) by volume. The % volume is estimated visually. <br />6This value for selenium was chosen based on guidance from Dave Dearstyne of NRCS and recent data that other states <br />are using. Dave is currently working extensively (2008) with the Selenium Task Force on the western slope and is very <br />knowledgeable about this issue. He basically stated that there is no concern for selenium unless Mancos shale strata <br />is being placed near the surface. At the new Horizon #2 Mine, no Mancos shale is placed near the surface. Also, all tests <br />of selenium in the pre-mine soil survey of 1998 show all values less than 0.1 ppm. The suitability report of the Bench 1 <br />material used as subsoil on the previously backfilled portion of the Morgan property in early 2008 show <1 ppm in all <br />tests. Dave Dearstyne believes a threshold suitability level of 0.2 ppm in the Lift A material and 1.0 ppm in the Lift B <br />material is adequate. These are the levels proposed. <br />In cases where the Bench 1 material is used as the Lift B soil in prime farmland, it will meet the <br />specifications for Lift B, as outlined in Table 2.04.9-2. <br />The suitability evaluations, based on averages across the study area, were used for topsoil volume <br />determinations presented in the Topsoil Management Plan section of Section 2.05.4(2)(d), Topsoil <br />(Redistribution). The number of profiles on which these averages are based is noted in the Soil <br />Profile descriptions range of characteristics. The recommended topsoil salvage depths for each <br />map unit are weighted averages of each major component of the map unit (those listed in the map <br />unit name - for both associations and complexes) as well as major soil inclusions as presented <br />within the map units. <br />(Revised June 2008) 2.04.9-14