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Colorado, Mcginnies and Nicholas, 1982, demonstrated with field and greenhouse studies that <br />vegetation stands, herbage yield, and root production all increased linearly as topsoil depths increased <br />from 0 to 1.5 feet. Barth (1984) found that production of perennial grasses on bare spoil with no <br />adverse properties, was as great as when spoil was covered with soil of any thickness. <br />DePuit, 1984, points out that plant community composition and diversity for rangeland is often reached <br />at shallower topsoil depths than what is required for maximum production. This phenomenon <br />apparently exists at the Seneca Mine in northwestern Colorado where Pfannenstiel and Wendt (1985) <br />demonstrated that 0.5 feet of topsoil applied to Wadge spoil in 1976 has produced a native looking <br />sagebrush grassland community with a shrub density of 1,450 stems/acre. Proper topsoil handling <br />techniques used in combination with suitable spoil replacement and topsoil/spoil scarification, where <br />needed to reduce compaction, are more effective in reestablishing minesoil productivity than 50 years <br />of succession on poor quality minesoils (Schafer et al., 19791. <br />A mean topsoil replacement depth of approximately 1.3 feet over final graded spoil at Seneca II-W Mine <br />(North areal wiii be beneficial to establishing a good seedbed and rooting medium. This conclusion is <br />supported by the above referenced literature, premine soil survey (Tab 91, and vegetation inventories <br />(Tab 101, as well as on-site data from the Seneca H Mine. The anticipated loamy topsoil texture will <br />likely have favorable infiltration and water holding characteristics. Also, the spoil medium immediately <br />below the topsoil will typically have desirable chemical and physical characteristics for plant growth <br />including a loamy texture, low sodicity and salinity, and moderately low saturation percentage for <br />acceptable water holding characteristics, and no minor element toxicity problems (see Tab 6, Geology <br />and Overburden Assessment). <br />SCC has revised the approved traditional approach for topsoil replacement n the II-W South area, based <br />on requests made by the Division. In addition to areas on which the °standard' mean replacement <br />thickness of 1.7 feet will be employed, SCC will replace areas of both 'thicker° and `thinner' soils in <br />designated areas as shown on Exhibit 21-1A, Topsoil Replacement. SCC will place approximately 4.0 <br />feet of topsoil in the Aspen Establishment areas, approximately 2.5 feet along select postmining <br />drainages and in areas selected for Planting List 2, and 1.7 feet of topsoil on the remaining areas in II-W <br />South. <br />Maintenance and Testing Procedures. Prior to distribution of topsoil in the Lennox coal outcrop <br />sampling area shown on Exhibit 6-6, final graded areas (on which topsoil is to be applied) will be <br />sampled to confirm spoil suitability (see Tab 21, Overburden/Spoil Handling Plan for more detailsl. The <br />density and physical characteristics of the replaced topsoil and upper spoil will be observed.' Past <br />PR03 31 fievised 7/02 <br />