Laserfiche WebLink
the desired reduction in weak acid dissociable (WAD) cyanide complexes, specifically copper <br />cyanide complexes. The copper cyanide complexes formed from higher' than expected <br />concentrations of copper in the San Luis ore body. On March 31, 1992, the Colorado Mined <br />Land Reclamation Board (the Board) issued a Notice of Probable Violation to the San Luis <br />Mine. On April 23, 1992, the Board approved an Abatement Plan which included an interim <br />detoxification procedure and appropriate long-term detoxification procedures fpr the San Luis <br />facility. A three step approach was approved by the Board and followed by BI~iRI to meet the <br />abatement requirements. The three step approach is outlined below: <br />1. The use of Cytox (zinc ferrous sulfate) for the detoxification of Ifree cyanide in . <br />the tailings slurry as an interim method. <br />2. The use of hydrogen peroxide for the detoxification of free ~rtd weak acid <br />dissociable cyanide in the free water pool as an interim method. <br />3. The design, construction, and operation of an INCO S0~/Air Cyanide <br />Detoxification Circuit as a long-term detoxification system. <br />Each of these detoxification procedures is discussed in the following sections. <br />2.1.3 Interim Detoxification Methods <br />On April 7, 1992, the use of Cytox (zinc ferrous sulfate) as a supplemental treatment with the <br />AVR circuit was started. Zinc ferrous sulfate complexes the cyanide ions tb remove free <br />cyanide from solution. The resulting product is a ferrocyanide, an insoluble and stable <br />compound. Cytox was added to the tailings slurry before the tailings entered thl; AVR circuit. <br />Tailings deposition occurred only in the lower pond when the use of Cyto% began. The <br />maximum beach elevation of the lower pond at this time was 8,551. The upper fond remained <br />inactive during the Cytox use. Therefore, tailings in the upper pond had only been subjected <br />s <br />