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Revised 1/10/80 <br />• Section 780.21(c) Continued <br />The backfilled spoils aquifer will serve as the recharge area for <br />the undisturbed overburden aquifer down~ip fran the active mining <br />area. A water budget has been prepared to evaluate the recovery of <br />water levels in the spoils and the overburden aquifer. <br />Inflow to the spoils aquifer is estimated on page 780-182 as 1,330 <br />ao-ft/yr. Storage within the spoils aquifer is calculated as <br />follows: fran Table 108(a-f), Eclanan Park Overburden Calculations, <br />the sum of total pit volumes is 156 million yards. Due to swelling <br />of the overburden and average rock porosity of the unconsolidated <br />backfill the void space of the spoil aquifer will probably be about <br />• 328, making for 50 million yards or 31,000 ac-ft of available <br />storage. the water in the spoil aquifer will recharge the over- <br />burden aquifer, at a rate controlled by the permeability of the <br />overburden aquifer. Average permeability is given on page 779-42 <br />as 2.9gpd/ft'. the total recharge area of the boaccut highwall in <br />the Eckman Park mine area is 14,500 ft long and an average of 73 <br />feet thick, making for 1,060,000 ft'. Recharge to the overburden <br />aquifer should therefore be about 3 million 9Pd or 3,450 ac-ft/yr, <br />once the water level in the spoil a lifer rises sufficiently to <br />provide head on the overburden aquifer. In summary, with inflow to <br />the spoil aquifer of 1,330 ac-ft/yr, potential outflow to the <br />overburden aquifer of 3,450 ac-ft/yr, and storage capacity of <br />31,000 ac-ft within the spoils aquifer, the reclaimed mine area <br />780-182(a) <br />