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<br /> <br />fluid have passed through the column, meet drin~Cing water <br />standards. However, there are quite a few exceptions. <br />Total cyanide continues to exceed the drink~ng water <br />standard after 3 pore volumes of flushing in most samples <br />even though the pre-op samples predicted this'~would be <br />within the standard. Sulfates, manganese, and TDS also <br />are quite high, and exceed the secondary drinking water <br />standards in contrast to the pre-op predictions. As <br />explained in the text, some of these condition are a <br />result of the additives used to control the c}~anide. <br />While this may be the case, they have still Chang d the <br />character of the leachate and make it more impe~tive <br />that the integrity of the containment syste be <br />maintained and monitored both during mining and <br />throughout an adequate reclamation period. A numb r of <br />metals for which there are drinking water standards ere <br />not tested. In particular, these include antim ny, <br />beryllium, thallium and aluminum. Maybe BMG can pro ide <br />us with some information on their feedstock indicating <br />whether these metals should be of any concern. <br />pg <br />36 Here BMG discusses the Divisions flow model for fluids <br />the tailings. BMG's points concerning porosi y <br />variations, degree of saturation and other aspects of th <br />tailings are correct. However, I'm not sure this reall <br />invalidates the Divisions findings. Some characteristic <br />would increase the flow rate while others would reduce, <br />it. The Division concluded that it would take 7.8 years <br />to complete one cycle of pore fluid through the tailings., <br />On page 37, BMG concludes that even using a 90 pcf <br />density and the corresponding 0.47 value of porosity {as <br />might be predicted to occur on the bottom of the <br />tailings) reduces the travel time by only 1.6 years. I <br />doubt if any of these calculations can be conducted this <br />precisely given the heterogeneity of the tailings. <br />38 At the top of the page, BMG indicates that the Divisions <br />modeling does not accurately predict the floe from the <br />tailings pond. Here a reasonable water balance might <br />help resolve a lot of the flow modeling uncertainties. <br />If we could quantify the amount of free fluid entering <br />the pond, approximate evaporation, and compare this with <br />the storage in the pond and pond discharges we may be <br />able to determine if there are gross discrepancies in the <br />modeling as suggested here, or if flows are reduced for <br />other reasons. <br />On this page BMG concludes "there is no model which can <br />accurately predict the time for movement of one pore <br />volume of water through the tailings". This is acc»--' <br />but only points out the need to make cc <br />assumptions in modeling used for regulatory puz <br />