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9/30/93 <br />Responses to Comments <br />San Luis Reclamation Evaluation Report <br />Page 6 <br />Finally, as part of the geotechnical test work for the first <br />embankment raise BMRI attempted to pull additional samples <br />using the BAT system. In one hole, attempts to collect a <br />sample were made at depths of 35', 40' and 45'. Due to the low <br />moisture content and permeability, sufficient water for <br />analysis could not be collected. <br />In short, the functioning of the thin layer deposition acts to <br />provide a dewatered, low permeability tailings which ajakes in- <br />situ fluid sample collection virtually impossible. This same <br />system will act to prevent the long term water movement and <br />make mobilization of entrained pore water virtually impossible. <br />Permeabilities such those measured in the deposited tailings <br />during the geotechnical investigation for the embankment raise <br />(low cm/sec) are equivalent to the typical permeabilities of <br />earthen liner/barrier systems and allow characterization of <br />this material as a soil liner effectively tens of feeit thick. <br />As discussed in Section 1.0, it is believed that permeabilities <br />for the lowermost tailings will continue to decrease throughout <br />the life of the operation under continued compactiion. In <br />p,r-effect the high cyanide tailings deposited will be c Aped by <br />u~L.! ~,,~~1 the ongoing deposition over the next four years. Th's has a <br />a, .-? substantial bearing on the potential for long tom water <br />,n~~ quality effects and the need for revision of the reclamation <br />plan. <br />Since a number of readers <br />water sample presented in tt <br />not collected deep enough it <br />collected additional pore ~ <br />m"` drilling program outlined <br />~~,e~ ~ ~t~', submitted for analyses and <br />xw r'~ completion. <br />7 <br />expressed a concern that the pore <br />e Reclamation Evaluation R port was <br />.to the AVR deposited taili gs, BMRI ~ ~r <br />ester samples during the vi ra core wO p,(,~r21 <br />above. The samples have been <br />the results will be presented upon <br />4.0 Geochemical Test Program <br />The geochemical test program utilized for evaluation of the San <br />Luis tailings for the Reclamation Report was the same program <br />utilized for testing the tailings in the approved permit <br />amendment. Abatement Requirement ~8 stated that "if the <br />chemical constituency of the tailings is different than the <br />original projections, the projected characterization of the <br />tailings as non-toxic and chemically inert is suspect." In <br />order to address this concern, the same geochemical program was <br />used to provide a basis for comparison. <br />