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2.3.2.3 Leachabili~ <br /> <br />The leachability of the tailings determined whether chemical species will be mobilized from the <br />tailings to groundwater and surface water. Tailings containing relatively insoluble minerals <br />species form a chemical environment which inhibits transport of any solutes leached, and ensures <br />the absence of any long-term impact from tailings disposal. <br />Leachability is assessed by sampling the tailings and subjecting the samples to accelerated <br />leaching in a chemical environment which simulates that which will occur in ntiture. <br />The United States EPA Method 1312 leach procedure was used to evaluate leachability of the <br />tailings material. This is an EPA prescribed protocol which is designed specifically for the <br />assessment of mining related wastes. It simulates the specific conditions which would occur <br />when rainfall leaches through a mine waste material. However, the liquid to solid ratio and the <br />agitated leaching make it a very conservative test as compared with the actual field conditions. <br />EPA Method 1312 leachability testing was performed on all unrinsed operational tailings samples <br />selected for geochemical testing. The unrinsed samples represent the max~mum potential <br />leachability for samples since rinsing would wash out some leachable species. <br />The leach procedure involves taking a known mass of the tailings and immersing this solid <br />material within a closed vessel that contains twenty times the volume of pH 5.0 t¢ 5.5 simulated <br />rainwater/snowmelt. The simulated rainwater is prepared by adding a mixture of 60% sulfuric <br />acid and 405'o nitric acid to deionized water until the pH decreases to the desired level. <br />The vessel is then agitated overnight and allowed to settle after agitation. The retulting solution <br />(known as the leachate or equilibrated fluid) is filtered and analyzed. In the EP~ Method 1312 <br />test procedure the leachate is analyzed for a range of eight metal species that~are of specific <br />concern to water quality. These are arsenic, barium, cadmium, chromium, lead, mercury, <br />selenium and silver. The concentrations of these species in the leachate arb compared to <br />Is <br />