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• There are 760.7 acres of land that are or will be disturbed by mining which will receive replaced soil from January 1, 1994 through 1998 (final reclamation year, Seneca 11 Mine, Exhibit 13-2, Reclamation Plan). As of December 31, 1993, there was 401.3 acre-feet of stockpiled soil and 176.8 acre-feet of soil remaining to be salvaged (Table 93.1). By dividing the number of acre-feet available soil (578.1) by the number of acres of projected disturbance (760.7), it is estimated 0.8 feet of suitable soil is available to be replaced. The average thickness of replaced soil is likely to exceed 0.8 feet as the stockpiled soil swells during redistribution. Field studies (1979) from Seneca II Mine indicate fine sandy loam, loam, and silt loam textured soil may shrink (compact) from 21 to 28 percent when stockpiled. Soil replaced from stockpi tes at Big Sky Coal Company's Big Sky Mine in southeastern Montana duri n9 1991 swelled 15.2 percent during replacement (BSCC, 1993). The soil replacement thickness (0.8 fee[), determined from [he annual soil balance, is identical to previous projected soil replacement thicknesses determined in 1992 and 1993 (0.8 feet). Soil Replacement iechnioue. The soil replacement area for [he 1993 field season is shown on Exhibit 93.1, 1993 Annual Reclamation Report Map. Historical soil replacement areas for • [he 1977 through 1992 field seasons are shown on Exhibit 92.4, Chronological Soil Replacement Map (PYCC, 1993). One reclamation Dl ock in the upper wadge area totalling 2.6 acres was reclaimed during 1993 using direct haul soil. Summary. The soil replacement thickness for the remaining permit terms was projected to be 1.0 feet (Permit C-80-005, Tab 9, Attachment 9-4). The balance completed above shows at leas[ 0.8 feet o! soil will be available to be replaced. Peabody suspects the difference between pre-disturbs nce projected and post-disturbance actual soil redistribution thickness is attributed to two important factors. First the density of soil in stockpiles has increased and caused an underestimation of soil that is stockpiled. The stockpiled soil will swell during redistribution. Second, the soil volume figure of 129.8 acre-feet provided for stockpile site Hx in November 1987 was apparently incorrect. About 11.5 at re-fee[ of soil was removed from [his pile during 1992. However, [he 1992 survey information indicates this pile decreased in volume by 51.9 acre-feet (Table 93.2). Peabody will continue to salvage, store, and replace soil as described and approved in Permit L-80-005. Peabody's soil scientist and reclamation supervisor will continue [o closely monitor soil handling activities a[ Seneca II, verifying scraper operators are • salvaging all viable soil materials and redistributing soil at the specified thickness. 7