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4L <br /> Project Descriptions AddanBrown <br /> FATE AND TRANSPORT EVALUATION OF ARSENIC AND NITRATE, SOUTH <br /> DAKOTA <br /> AdrianBrown was retained to provide an evaluation of the fate and transport of arsenic and nitrate from <br /> spent gold ore to establish appropriate compliance monitoring sites as well as enhancing production <br /> practices. Our evaluation included field, laboratory and computational components. <br /> Field investigations were conducted to determine the lithologies present beneath the disposal site and <br /> along the anticipated flow path to the regulatory point of compliance. Solids were recovered from drill <br /> holes for the purpose of future geochemical testing in the laboratory to determine the extent to which <br /> geochemical attenuation would influence the migration of arsenic and nitrate from the disposed spent <br /> ore. <br /> Laboratory investigations were performed to measure the specific adsorption of arsenic and nitrate on <br /> spent ore as well as on local lithologies that occur in the subsurface hydrologic flow path. Additionally, <br /> local soils,gravels and organic matter(forest floor duff)were evaluated for adsorption to identify <br /> potential materials to be used as engineering amendments to spent ore to slow the release of <br /> contaminants. Column tests were also performed to evaluate the release of arsenic and nitrate from <br /> spent ore for calibration and verification of subsequent numerical modeling. All laboratory <br /> investigations were performed by AdrianBrown geochemists in our geochemical lab facility. <br /> Ultimately,a numerical model of arsenic and nitrate release from spent ore was constructed that <br /> simulated the movement of these contaminants from the disposal site to the regulatory point of <br /> compliance. This computer-based model was used to guide engineering design for disposal and provide <br /> assurance that water resources would be protected. The result of the three-pronged investigation led to <br /> the issuance of a groundwater discharge permit for our client and assured their ability to continue their <br /> operation. <br />