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Section 780.21 (b) Continued. <br />r1 <br />since no acid or toxic material has been found in the overburden, <br />and the use of natural materials helps to minimize disturbance to <br />the hydrologic balance. <br />Leaching within the mine plan area is unavoidable whenever water <br />infiltrates into spoil material. Leaching could be avoided by <br />insulating spoil against saturation, but this is not only impracti- <br />cable but would also prevent recharge of the aquifer adjacent to <br />the spoils. Once leaching has occurred, there is no practicable <br />technology currently available to decrease TDS concentrations. The <br />only method, therefore, to minimize the impacts of mining and <br />leaching on ground water quality is to minimize the amount of water <br />which can infiltrate spoils. <br />• <br />In order to decrease infiltration two types of spoil handling are <br />proposed within the permit area. One is to haul and dump over- <br />burden spoil directly into the previously mined area as mining <br />progresses. The second is utilize a temporary overburden stockpile <br />located in Section 2, TBN, R78W. The majority of this temporary <br />stockpile will remain in its present location until it is required <br />to backfill the final pit as explained in Section 780.11. In the <br />first case, the primary means of minimizing infiltration will be to <br />regrade, retopsoil, and revegetate the mined areas as soon as <br />possible following coal removal. According to Lusby and Toy (1976), <br />this should have a dramatic effect on minimizing the amount of <br />water entering the spoil material. Their studies show that the <br />infiltration rates of reclaimed land are lower than the same land <br />in the premined condition. A detailed discussion of reclamation <br />and revegetation as related to hydrology has been presented in this <br />Section under the sub-heading "Surface Water Quality Protection". <br />As a further means of minimizing water flaw through spoils, no <br />sedimentation ponds or other impoundments will be constructed on <br />top of mined areas or spoil. <br />780-104 <br />