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<br />HEAP LEACH PADS <br />- The detoxifying of heaps, at the end of campaigns, is more Complicated than the <br />simple CN" reduction in ponds because of the laws governing ground-water <br />standards. <br />Levels of CN below D.2 ppm are mandated. In addition, the 1eve15 of e11 heavy <br />metals are equally mandated. Although the chemical processes described above for <br />ponds would no doubt work equally in heaps there are numerous pro69ems, such as: <br />i. Water Flushing - Availability of water <br /> Length of time needed <br />2. Hypochlorite and <br />Peroxlde - Genera]1y discouraged by the State <br /> Expensive <br /> In a number df sites heavy metal content is <br /> increased due to oxidation of the heap <br />3. S0~ - Expensive <br />4. Ferrous Sulphate - Increases heavy metal content of water through <br /> oxidation; increases Fe level beyond standards; <br /> reduce pH below 6 <br />5. Bacteria - Although cheap they take a long tirtle to reduce CN <br /> and cannot be guaranteed to succeed <br /> <br />