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~ ~ ~t~~~ v <br />1 <br />OVERVIEW OF SAN LUIS PROBLEM <br />WITH SUGGESTED SOLUTIONS <br />APR 3 1992 <br />t <br /> <br />Mined Land <br />Reclamatlon ~~'~•~~••~ <br />In our industry, with today's regulations, we are obviously all still learning. <br />I say this as a presage to our discussions here in the hope that you will <br />understand that criticism is welcomed. <br />With your indulgence I shall write this memo in note form. <br />' A. THE SITUATION AT SAN LUIS <br />1 <br />1 <br />BEI believes that Battle Mountain Gold at San Luis (SL) has a two-fold <br />"cyanide" problem: <br />Excessive free cyanide <br />Excessive WAD cyanide <br />These two problems are both interconnected and separate. <br />1 <br /> <br />1 <br />1 <br /> <br /> <br />1 <br />1 <br /> <br />1 <br /> <br />In the interconnected sense the presence of this spec9fic WAD (Cu) <br />enhances considerably the toxicity of free cyanide. In a Separate sense <br />S.L. must lower its free cyanide levels because of potential bird-kill and <br />must lower its Cu WAD cyanide levels because of: <br />Enhancing free cyanide toxicity <br />Keeping its circuit clear <br />Meeting permit requirements <br />Problems Associated with Hiah CN Levels <br />a. Free CN <br />(1) That CN is toxic is well known. However, the lethal <br />levels of CN are, with many animal, not fully <br />understood partly because of animal specimen scarcity <br />and partly because the presence of other compounds has <br />a marked effect upon CN toxicity. Copper is an element <br />that enhances CN toxicity. The EPA guideline is that <br />less than 50 ppm free CN is safe for higher animals <br />including waterfowl. However, the pre ence of, for <br />example, copper will lower this 50 ppm ~o some other <br />unknown level. Firm levels of CN, Cu, etc., are <br />therefore not mandated because of the lack of knowledge, <br />so the best course of action is to drop free CN levels <br />to their lowest achievable. <br />A recent publication (last week) by the U.S. Department <br />of the Interior provides a very good overview of CN <br />toxicity and is attached hereto as Section 1. <br />Bf~ <br /> <br />