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<br />3. Subsequent to the installation of CY'1'OX teclutulugy, BMG next <br />responded to the high cyanide levels by employing hydrogen pqeroxide <br />addition to the tailing ponds to oxidize the cyanide (w soluble tyariates, to <br />carbon dioxide, and to other products). <br />While hydrogen peroxide treatment of the pond waters did icunvert <br />cyanides to essentially nontoxic (ur at least less toxic forms ~uch as <br />cyanate), its primary action was on soluble free cyanide and thu, higher <br />than expected levels of metal-cyanide complexes remained in tf{e pond <br />waters, in deposited solids, and in the pore liquids in those deposited <br />solids. <br />4. In a final process addition to deal with the cyanide issue, BMG i~tstalled <br />the INCO sulfur dioxide system which aims to convert cyanide to nontoxic <br />products. <br />The INCO process has resulted in the deposition of a new class of . olids in <br />the tailings pond (primarily gypsum ur calcium sulfate) and this • dditiun <br />was not expected in the original permit documents. The INCO process <br />also relies on the presence of some level of copper to catalyze the <br />reactions and this element is a necessary additive to the pruces if nut <br />present in the ore in adequate amounts; any added copper, of coon e, exits <br />the [Hill and reports to the tailings impoundments in either dins Ived or <br />suspended solids form. <br />5. While not a variation in process chemistry between the original permit <br />application and approval and now, it is also noteworthy that the riginal <br />estimates of ore composition upon which the permit were bas d vary <br />somewhat from average "real" ore content being processed. <br />Variations in the content of the ore, particularly relative to I~vels of <br />accessory heavy metals and sulfide minerals, means that accumul• Lion of <br />these species in the tailing solids and waters is different than urjiginully <br />proposed. <br />Building upon this summary of factual operating history at the San Luis facili y, the <br />following questions relating to the pertinence of these issues to the question f adequacy of <br />the original permit and bonding to assure low risk of future danger or negativ impacts <br />when mining is completed and site reclamation is on-going can he proposed • pd answers <br />postulated: <br />DEH061693 <br /> <br />