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Water Quality Investigation of In-Situ Tailing Sand Deposits Under Natural Environmental Conditions


Tailing sands are abundant by-products of the phosphate ore beneficiation process, which are deposited as piles on undisturbed land, as piles over waste clay settling areas, and as fill in mine cuts. Tailing sand deposits from twelve locations, six each from pile and fill deposits, were identified and explored with geotechnical borings. At each location, a temporary monitoring well was installed and a sample of the ground water from the tailing sand deposit was obtained. Each sample was analyzed for primary and secondary drinking water standards. The water quality profiles of the fill and pile samples were compared. Ground water samples from tailing sand deposits met EPA and State of Florida primary and secondary drinking water standards for all but a few parameters. The main parameters that exceeded drinking water standards were iron and manganese, cations that commonly occur in natural ground water at  concentrations exceeding secondary drinking water standards. In a few samples, aluminum, antimony and cadmium exceeded drinking water standards, although the occurrence of these parameters was likely due to suspended clay in the samples. Ground water samples from tailing sand fill deposits had fewer exceedances of drinking water standards than samples from pile deposits (several of the piles were deposited over waste clay). Water quality differences among sites did not appear to be related to the age of the tailing sand deposits.