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<br />"C T (? 1 199? <br />RESPONSES TO AGENCY CO!!![ENTB <br />SAN LIIIB RECLAMATION EVALIIATION <br />PREAMBLE <br />Many of the concerns expressed with the Reclamation Evaluation <br />prepared by Battle Mountain Resources (BMRI) dealt with the <br />same general issues. These issues can be defined as 1) the <br />tailings samples did not adequately represent the entire column <br />of tailings deposited in the facility; 2) the pore water in the <br />tailings was not adequately sampled; 3) the geochemi!cal test <br />program was not appropriate for the tailings material; and 4) <br />the geochemical test results indicated that the tailings were <br />materially different than the results presented in the approved <br />permit (i.e. that the tailings were acid generating). <br />Prior to reviewing responses to each question, BMRI believes <br />that it is important to address each of these major issues. <br />This preamble will form the basis of responses to many of the <br />specific questions raised regarding the reclamation report. <br />1.0 Thin Laver Tailings Deposition <br />Many of the comments indicated an incomplete understanding of <br />the thin layer deposition system. The concept of thin layer <br />deposition is to dewater the tailings as they are plaged. The <br />tailings are delivered to the disposal area as a slurry of <br />approximately 50$ water and 50~ solids. The tailings are <br />deposited in a rotating deposition network from the perimeter <br />of the disposal area (except along the embankments). As the <br />slurry flows through the disposal area, the tailings solids <br />settle out and the liquid portion is reclaimed and recycled. <br />Although the San Luis tailings have a limited size distribution <br />(see Figures 3.1 and 3.2 of the Reclamation Evaluation Report), <br />the coarser portions will settle first with the finer portions <br />traveling further from the discharge point before settling. <br />The settled solids form a low angle tailings beach (1 to 2$). <br />Generally, tailings are allowed to reach a depth of <br />approximately six inches in an area and then the deposition is <br />moved to another area, leaving the previous area to dry and <br />densify. <br />Dewatering is accomplished by evaporation and allowing the <br />water to run off the tailings beach into the pond. In <br />addition, there is an underdrain system which extends beneath <br />the entire facility immediately above the liner system. The <br />underdrain is designed to convey approximately 540 gpm~based on <br />expected flows during the first year of operations. As <br />discussed in the approved permit, the underdrain sizing will <br />limit the build up of phreatic surface or head on the liner <br />system to less than two feet or the thickness of the drainage <br />layer. This is considered the worst case since once the water <br />pool is -no longer in direct contact with the underdrain (i.e. <br />tailings deposition has occurred to separate the water pool <br />