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t <br />Battle Mountain Resources <br />November 1, 2000 <br />Page 2 <br />2.1 TR-26 Pore Volume and Flushing Calculations <br />The estimation of pore volumes required to flush secondary sulfate salts from the Itackfilled West <br />Pit, as presented in the TR-26 document, was taken front the analysis presented in Appendix B of <br />the TR-15 Response Plan (hereafrer "Response Plan"). The geochemical analysis conducted as <br />part of the Response Plan was based on a combination of experimental data (from batch leaching <br />tests completed using materials representative of the backfill material placed in the West and Pink <br />Gneiss Pits) and initial concentration data obtained from the backfill groundwater monitoring well <br />BF-2. Results of the laboratory tests conducted on solids materials from the San Luis Mine were <br />presented in Appendix B of the TR-15 Response Plan and in Appendix B of TR-?6. The batch <br />leaching tests were developed specifically to address the potential for the backf II materials to <br />produce dissolved salts upon flushing by natural groundwater inflow to the backfilled West Pit. <br />Sulfate was chosen as the indicator parameter because secondary sulfate salts were the most likely <br />salts to form in response to the oxidation of sulfide minerals in the Precambrian bed: ock. <br />The general trend of the experimental data produced front the batch leach testing was consistent <br />with an aggregate geochemical process that yielded initially greater quantitie< of salts and <br />thereafter monotonically decayed to zero The conceptual description of the leaching process is <br />consistent with results from the geochemical testing that identified a limited amount of soluble <br />secondary sulfate salts associated with the backfill material. Tite flushing cltaracieristics of the <br />backfill materials were represented using a first order exponential decay equation of the form: <br />CP = Co exp(-~~) <br />where: C~ = the concentration at pore volumep <br />Co = the initial concentration at p = 0 <br />n = a parameter that determines the shape of the decay curve <br />p = the number of pore volumes that have passed throu;yh the backfill <br />material <br />2636 Midpoint Ur., Srute B, Fort Co/lirrs, Cu/orado SO.i2.i <br />Telephone (970) 454-7704 /FAX (970) 454-7759 <br />