2000-01-31_REVISION - M1988112 - Laserfiche WebLink

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Battle Mountain Resourc~ • January 31, 2000 Page 5 backfill materials were flushed rapidly. Thus, the hydraulic analysis conducted of flows in the vicinity of BF-1, in conjunction with the observed groundwater chemistry, would suggest that the lower range of S,. is the most representative value of S~ to use in calculating pore volume of the West Pit backfill material. Analysis of Recent Water Level A second hydraulic analysis was completed to refine the value of S~ to use in the calculation of pore volumes of the West Pit backYill material. Groundwater levels in the backtillcd West Pit are monitored continuously in BF-3, BF-4, BF-5, and BF-6. Results of the water level measurements indicate that the water level in the West Pit has declined in a ma~mer consistent with the conceptual hydrologic model presented in TR-26, i.e., water levels has declined i uniformly throughout the West Pit. The backfill wells have been pumped contintously at a rate of approximately 400 gallons per minute (gpm) since the beginning of January 2000 and water levels have dropped approximately 4 feet during that period of time (total Ovate- level decline since the inception of the TR-26 water management plan has been approximately 6.~ feet). These data were used to calculate a value for S,. of 0.22, which is less than the value of Sy. used in the estimates presented in TR-26, but is a value substantiated by field data. Revised Estimate of Backtill Flushing The information presented in previous sub-sections of [his technical memorand_tm have been used [o revise the calculation of estimated pore volumes required to flush secondary sulfate salts from the West Pit backfill. Table I lists the pertinent pore volume revisions :md shows the values initially calculated as part of TR-26. 3801 Auron:ation W'ay, Suite 100, For! Collins'. Colorado 80.i2.i Telephune (970) 223-9600 / F.<LY (970) 223-7171