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• samples taken from the lithologic units to be affected by mining (see Tab 6, Geology), a classification <br />system has been developed for these units with regard to handling during operation and reclamation <br />activities. A handling plan for those material classes identified by sampling as being potentially <br />deleterious to revegetafion or the ground water quality in either mining area has been developed and <br />is presented in Tab 21, Mine Soil Reconstruction. <br />It is not anticipated that Peabody will Vansfer ownership and use of any wells completed within the <br />Nucla Mine mining areas. Bore holes, shafts, wells, and auger holes will be cased and/or sealed <br />to prevent possible ground water depredation from mixing of waters of different quality within the <br />bore holes and acid or toxic surface runoff entering the bore holes. A specific plan for sealing of <br />bore holes, exploration holes, auger holes, wells, and shafts is presented in Tab 18, Hydrologic <br />Reclamation Plan. <br />Ground Water Quantity. Typical backfilling methods largely involve the use of dozers and scrapers <br />(see Tab 20, Backfilling and Grading). Studies by Rahn (1976) and VanVoast and Hedges (1975) <br />indicate that replaced spoil materials exhibit greater porosities and hydraulic conductivities because <br />of increased void values, regardless of how the spoil material is replaced in the pits. Spoil <br />replacement (backfilling) using methods outlined in Tab 20 (Backfilling and Grading) will ensure the <br />eventual resaturation of the disturbed areas (pits), minimizing the adverse effects of mining on <br />• ground water flow. The Nucla Mine mining area is located in a climate which generates less than <br />15 inches of precipitation annually. Evapotranspiration rates in the vicinity are relatively high (see <br />Tab 7, Hydrologic Description). Textural analyses performed on potential spoil materials generally <br />indicates that sandy clay loam materials will be replaced in the pits (see Tab 6, Geology). <br />Consequently, infilfration rates in reclaimed areas are expected to be slow to moderate. It follows <br />that contributions to spoil resaturation and subsequent recharge to surrounding aquifers from <br />precipitation will be slow. However, the upland and adjacent irrigation ditches and laterals will <br />eventually provide a more rapid source of recharge to spoils. Seepage from the irrigation network <br />has provided an artificial source of recharge to the undisturbed shallow ground water system. The <br />resaturation and recharge of replaced spoils will also be augmented by the irrigation. <br />Overburden and topsoil handling, reconditioning, and revegetation methods outlined in Tabs 21 <br />(Minesoil Reconstruction) and 22 (Revegetation Plan) will maximize the potential for establishing <br />reclaimed areas that will exhibit infiltration rates and capacities adequate for insuring at least <br />premining rates and capacities. Timely reseeding and mulching of redistributed topsoil will augment <br />the retention and eventual downward infiltration of soil moisture. Textures of topsoil material will <br />generally range from sandy loam to loam, and topsoil material will exhibit moderate infiltration rates. <br />Deep ripping of regraded spoil, followed by topsoil placement, chisel plowing, and disking will <br />improve the infiltration potential of the reclaimed medium. <br />• <br />i6-2 <br />