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• Topsoil Replacement Depth <br />Approximately 1,057.9 acre-feet of suitable topsoil is available for <br />replacement over the life-of-mine (1986-1997) operation at Seneca II <br />Mine (Table 9-4-6). The disturbance area requiring topsoil replacement <br />totals 1,089.5 acres. By dividing the number of acre-feet available <br />topsoil (1,057.9) by the number of acres to be or that are disturbed <br />(1,089.5), it is estimated that approximately 1.0 feet of suitable <br />topsoil will be replaced. <br />The August 1986 topsoil replacement depth (1.0 feet) is equal to the <br />projected topsoil replacement depth determined in July 1984. There are <br />two reasons for the topsoil replacement depth remaining constant even <br />though topsoil salvage depths increased by 14.7 percent. <br />1. Topsoil replacement was completed for one pre-law haul road (16.4 <br />acres) and is proposed for two additional pre-law haul roads (34.5 <br />• acres) which are still being utilized. These areas (approximately <br />50.9 acres) were omitted in the July 1984 topsoil balance. This <br />modification accounts for 0.9 inches over the life-of-mine topsoil <br />replacement depth. <br />2. Topsoil replacement is proposed for Pond 004 (4.9 acres), Pond 007 <br />(1.8 acres) and an access loop road (1.5 acres) west of the Wadge <br />Impoundment. These areas (about 8.2 acres) were not included in <br />the July 1984 topsoil balance. This modification accounts for 0.1 <br />inches over the life-of-mine topsoil replacement depth. <br />Topsail Depth Requirements <br />Topsoil is generally beneficial for increasing infiltration, improving <br />seedbed and rooting mediums far germination and plant establishment, <br />enhancing nutrient cycling and serving as a source of seed, rhizomes and <br />• root cuttings that can promote species diversity. Topsoil depth <br />requirements on mined lands are site specific. The quality of topsoil <br />and spoil materials, climatic factors, seeded plant specie requirements <br />and concurrent reclamation practices all appear to influence the optimal <br />topsoil replacement depth fora specific mine site (Pinchak et al., <br />9-37 Revised 10/01/86 <br />