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and topsoil inventory for Nucla East. Sufficient quantities of suitable quality topsoil <br /> are available to restore the disturbed areas to the desired postmine land uses. <br /> Following mining, approximately 1.0 feet, 1.5 feet, and 4.0 feet of suitable topsoil will <br /> be replaced over the dry pasture, irrigated pasture, and irrigated prime farmland <br /> (hayland) regraded spoil mediums, respectively (Table 21-4). This will include <br /> approximately 1.0 feet of first lift topsoil and about 3.0 feet of second lift subsoil for <br /> irrigated hayland areas. The three topsoil replacement areas are shown on Exhibit 21-3, <br /> Postmine Soil Replacement Depths - Nucla East (also see Exhibit 12-3, Operations Plan - <br /> Nucla East). <br /> Research over the last ten years has demonstrated that topsoil depths required for optimum <br /> production are related to the quality of the underlying spoil, with greater depths of good <br /> quality soil needed to restore production on poor quality spoil (U.S. Congress, 1986). <br /> Poor quality spoil material may require more than three feet of topsoil replacement <br /> whereas good quality spoil may need less than one foot. in North Dakota, the replacement <br /> of one foot of subsoil plus one foot of topsoil over good quality spoil materials is <br /> • recommended (Doll et al , 1984). Power et al ., (1976) and Barth and Martin (1982) <br /> demonstrated that three feet of topsoil was necessary for optimum production on sodic <br /> spoil. Barth and Martin, 1982, showed fine sandy loam topsoil depths for optimum <br /> production in southeastern Montana to be less than one foot for optimum perennial grass <br /> production on nonsaline, nonsodic silt loam spoil. Schuman and others (1980) found that <br /> native grass production on reclaimed spoil in Wyoming equaled forage production on an <br /> undisturbed native area when the topsoil thickness was 1.3 feet. In northwestern <br /> Colorado, McCinnies and Nicholas, 1982, demonstrated with field and greenhouse studies <br /> that vegetation stands, herbage yield, and root production all increased linearly as <br /> topsoil depths increased from 0 to 1.5 feet. <br /> DePuit, 1984, points out that optimum plant community composition and diversity for <br /> rangeland is often reached at shallower topsoil depths than what is required for maximum <br /> production. This phenomenon apparently exists at the Seneca Mine in northwestern Colorado <br /> where Pfannenstiel and Wendt (1985) demonstrated that 0.5 feet of topsoil applied to Wadge <br /> spoil in 1976 has produced a native looking sagebrush grassland community with a shrub <br /> density of 1,450 stems/acre. <br /> • <br /> A topsoil replacement depth of approximately 4.0 feet for hayland (prime farmland), 1.5 <br /> 21-30 Revised 08/19/88 <br />