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• Reversal of the existing hydraulic gradient is depicted schematically in Figures 6-lb and 6-]c. <br />Figure 6-lb shows the initial pumping conditions where the total extraction rate from the backfill <br />well field would be approximately 200 gpm. The effective dewatering rate would be 120 gpm <br />because rechazge to the backfill would continue at a rate of approximately 80 gpm. Fifteen feet <br />of saturated backfill contains approximately 33 x 106 gallons of water (assuming a specific yield <br />of 0.25 for the backfill). Assuming that the average rate of storage removal from the backfill is <br />150 gpm, the time required to lower the water table 15 feet is approximately 150 days. <br />After the water level elevation in the backfill decreases to approximately 8580 fr amsl, the <br />pumping rate would then be gradually decreased to about 110 gpm (Figure 6-lc), which is <br />estimated to be the steady-state rate of rechazge to the West Pit under the modified hydrologic <br />conditions. The long-term pumping rate will be slightly higher than the current recharge rate into <br />the West Pit to account for an increase in the hydraulic gradient (and flow) along the eastern <br />boundary of the West Pit where water from the Rito Seco alluvial aquifer flows into the pit and <br />to account for additional backflow from the Rito Seco. <br />• <br />6.1.2 Enhanced Evaporation <br />Enhanced evaporation is considered the optimum initial water management alternative for use <br />during the initial phase of water management. The enhanced evaporation will utilize high- <br />pressure snow-making equipment to produce minute water droplets. The enhanced evaporation <br />system will be contained on a geomembrane-lined facility comprised of either high density <br />polyethylene or PVC-membrane, depending on the estimated life of the lined facility. The <br />tazgeted goal would be total evaporation of the liquid during the summer months with <br />concomitant accumulation of dissolved constituents in solid or sludge form, which would be <br />disposed of according to applicable federal, state, and local regulations. <br />To maximize evaporation, a lined application basin would be constructed upgradient of a lined <br />collection pond. The collection pond would serve to collect and retain that portion of the water <br />not evaporated for recirculation through a secondary enhanced system. Non-evaporated volumes <br />would be continually re-circulated until the retained water is exhausted. <br />Battle Mountain Resources, /nc. <br />pa 1001671reponslmarchrpAtrl6w'vmrtgtmarch.doc 66 March 11, l999 <br />