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<br />Dr. James A. Pendleton <br />May 26, 1942 <br />Page 5 <br />used also will be recorded. Two liquid samples will be collected on a daily basis and <br />analyzed for total cyanide, WAD cyanide, and copper, during initial detoxification of the <br />liquid pools in the impoundment and shipped to an off-site laboratory for analyses. Splits <br />of samples collected will be analyzed for copper at the San Luis site. Copper is <br />considered an indicator parameter for WAD cyanide concentrations. As cyanide is <br />oxidized, copper ions will form hydroxides and precipitate; thereby reducing soluble <br />copper concentrations in the pool water. Copper data will provide a rapid assessment <br />of the effectiveness of the hydrogen peroxide destruction system. <br />Liquid samples will continue to be collected after the pools have been successfully <br />detoxified to monitor the performance of the continuous hydrogen peroxide destruction <br />system. Samples will be collected on a daily basis until sufficient data have been <br />generated to document the effectiveness of the continuous cyanide destruction system. <br />At this time, the sampling frequency will be reduced to bi-weekly. All Samples will be <br />collected and handled as set forth in Quality Assurance/Quality Control PY~otocols for the <br />Collection of Surface and Ground Water Quality Data San Luis Gold Phoject, Costilla <br />County, Colorado (John C. Halepaska and Associates, Inc., 1992). Off-site analytical <br />work will be completed by Core Laboratories, Inc., using methods approved by MLRD. <br />The installation and operation of the continuous hydrogen peroxide cyanide destruction <br />system is intended to be a short-term and an interim mitigation measur@. Ultimately, <br />BMR proposes to install an INCO cyanide detoxification process. Design work is <br />currently underway and as currently projected, a technical revision describing the <br />proposed system will be submitted to your offices by June 15, 1992. <br />SUMMARY <br />Hydrogen peroxide is widely used for the oxidation of free and WAD cyanide compounds <br />in mill effluent solutions, and the process is environmentally sound. Based on laboratory <br />work performed by FMC and Degussa, solutions in the tailings impoundment at the San <br />Luis site are considered to be highly amenable to WAD cyanide detoxification using <br />hydrogen peroxide. <br />As proposed, hydrogen peroxide will be added directly to the existing liquid pools in the <br />impoundment to immediately decrease WAD cyanide levels. At the same time, a <br />continuous hydrogen peroxide distribution system will be installed around the perimeter <br />of the impoundment in very close proximity to the tailings discharge line. The existing <br />CYTOX free cyanide destruction system would continue to be used in cogjunction with <br />the perimeter hydrogen peroxide system until an INCO system is whstructed and <br />functioning properly. A monitoring program including rapid reporting to MLRD, will <br />