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<br />Memo to Larrv Oehler 4 Mav 5, 1994 <br />deposited onto the drain blanket. Such a layer would act to retard <br />downward migration of interstitial fluids and to effectively "bleed" <br />the fluids into the drain blanket, thus minimizing development of head <br />on the liner. BMRI believes that decreasing flows to the collection <br />pond are an indication that this is, in fact, what has occurred. The <br />Division's view is that it would be extremely difficult to show that a <br />retarding layer of very low permeability tailing has developed, and <br />that there are a number of possible reasons for decreasing flows to the <br />collection pond other than decreased flow from the tails into the <br />drain, one of which would be inefficient conveyance of f:Luids in the <br />drain layer due to the use of low permeability materials for its <br />construction. It is also the Division's view, that in order to avoid <br />any potential concerns regarding the drainage blanket, BMRI should have <br />assured through verifiable sampling and analysis, that the drainage <br />materials were at least 1, and preferably 2 orders of magnitude more <br />permeable than the tailing, or should have installed are engineered <br />retarding layer on top of the drainage layer. <br />Since the level of knowledge regarding hydrostatic head applied to the \ <br />liner is such that a concern exists that excessive seepage may be <br />occurring, BMRI should be required to install angled monitoring wells <br />which will be screened in areas beneath the deepest part of the upper <br />and lower impoundments. These wells will have to be equipped to obtain <br />samples from unsaturated media. These wells should be completed as <br />close to the bottom of the impoundments as is possible, and should be <br />installed at the soonest opportunity, rather than as a proof for bond <br />release, in order that mitigation can be implemented immediately if a <br />contaminant plume exists. <br />Chemistry of Interstitial Fluids in the AVR Tails <br />In the BMRI letter dated November 30, 1993 it is stated: <br />BMRI is concerned by the Division's reference to high cyanide <br />fluids migrating through the tailings. Extensive fieald work and <br />laboratory analysis has been completed in conjunction with the <br />Reclamation Plan Evaluation for the tailings facility. None of <br />the testing indicates that high cyanide concentrations exist in <br />the AVR deposited tailings or in the tailings pore fluids. <br />Furthermore, the tailings underdrain system does not. indicate a <br />migration of high cyanide waters. The tailings disposal area <br />cyanide concentrations have been in complete compliance with <br />original permit limits for over a year. <br />It is the Division's view that the reason that none of the testing <br />indicates that high cyanide concentrations exist in the AVR deposited <br />tailings pore fluids is because these pore fluids, to the Division's <br />knowledge, have not been adequately sampled. The statement that the <br />tailings underdrain system does not indicate a migration of high <br />cyanide waters may not be accurate. The Division considers any cyanide <br />