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<br />MEMO to J. Stevens/J. Pendleton <br />January 26, 1996 -Santa Fe Groundwater Model <br />Page 2 <br /> <br />The average hydraulic conductivity (4.4 x 10~ cm/sec) provides a .32 ft/day seepage velocity <br />(118 ft/year) which would transport the contaminated fluid to the M-14 well in about 11.8 years. <br />BMRI's analyses are consistent with the requests of the Division. Noticeable variations in the <br />actual permeability data are indicative of the heterogeneous nature of the Santa Fe Formation <br />which, of course, will produce a wide range of fluid travel times. <br />If a leak occurred in the upper pond (a distance of about 2,050 feet from the M-14 monitoring <br />well), keeping all other assumptions constant, the travel times would still be relatively short (3.6 <br />years to 17.4 years). <br />BMRI believes that even if a leak occurred in the tailings facility, the contamin4ted fluid would <br />never reach the Santa Fe aquifer (see BMRI letter dated October 31, 1995 for sp¢cifics). <br />Because of the heterogenous nature of the sediments underlying the tailings facility, it is the <br />Division's position that any contaminant leak would pose a reasonable potential to adversely affect <br />the quality of groundwater in the Santa Fe aquifer and that BMRI must demonstrate, to the <br />satisfaction of the Division, that the existing and reasonably potential future uses of groundwater <br />are protected. <br />BMRI proposes to utilize the existing monitoring system (which includes three new wells; SF-1, <br />M-4R and M-15) to demonstrate to the Division that Santa Fe groundwater has not been adversely <br />affected by the mining operation. BMRI believes that an 8-year monitoring period after closure <br />is all that is warranted (see BMRI letter dated January 10, 1996). An 8-year monitoring period <br />after closure may be adequate to demonstrate to the satisfaction of the Division that the mine <br />operations did not adversely affect groundwater, given the short fluid travel times (based on the <br />above-noted parameters) and the near five years that have elapsed since the 1991 excursion. If <br />closure occurs in March of 1997 (current plans), monitoring would continue to 2005 which would <br />provide almost 14 years of continuous sampling. <br />I think the Division should seriously consider BMRI's 8-year after closure monitoring proposal. <br />Let's discuss. <br />M: \oe a\g~w \S W tiFe.jd <br />