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<br />Review: "Ironclad Mill Tailings; Results of Cyanide Detox" <br />Memo to B. Keffelew, June 27, 1994 <br />Page 5 <br /> <br />d. Cadmium, chromium, lead, and selenium were not analyzed to proper detection <br />limits. <br />e. Copper exceeds water quality standards in 5 out of 6 samples. <br />f. All six mercury analyses exceed water quality limitations. <br />g. Molybdenum, though unregulated, appears high in all samples. This element may <br />be regulated before this mine is closed. CC&V are advised to keep hack of <br />developing regulations and be prepared with background information as the needs <br />may arise. <br />h. Four of six samples were not analyzed for manganese. <br />i. One of the samples showed a zinc exceedence. <br />10. All of the above discussion assumes that the water quality standards of concern are <br />surface water in Arequa Gulch (see CC&V letter to Mr. B. Keffelew, June 19, 1994, re: <br />Commitment Number 36, Underdrain Material, for the surface water standards.) <br />However, it cannot be assumed that Arequa Gulch water will not reach groundwater. <br />As groundwater, the Arequa Gulch water will probably be subject either to ambient <br />values or to drinking water standards. <br />Assuming that part of the Arequa Gulch water will recharge groundwater locally, the <br />results should include analyses for all of the metals regulated under drinking water <br />requirements. <br />11. The metals, chloride and pH need to be modeled in a manner similar to the cyanide. <br />The Division needs to have certain assurance that flooding of the underdrain either will <br />not occur, even accidentally, or that in the event of flooding the quantity of metal <br />chloride and cyanide and the pH level at groundwater and surface water compliance <br />points will meet water quality compliance criteria. <br />CONCLUSIONS <br />Overall, the Division concurs that modeling is an appropriate method for showing that the <br />Ironclad tailings, if weathered under worst case conditions, will not discharge non-compliant <br />waters. The model provided with the present submittal does not adequately demonstrate that the <br />tailings will be environmentally benign. The following are the primary problems with the model <br />as currently presented. <br />1. The fundamental assumption used in the cyanide model, that the tailings contain 51 mg/L <br />cyanide, was not substantiated. <br />