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State-of-the-Art of Phosphatic Clay Dewatering and Disposal Techniques. Volume 2 – A Technical Evaluation of Conventional Versus Developing Processes of Phosphatic Clay Disposal



The proper disposition of phosphatic clays is a problem which has been the subject of research and debated for years by phosphate producers, state and federal research agencies, regulatory authorities and environmentalists. To date, no “universal” solution exists for the ultimate disposal of phosphatic clays. This report examines the fundamental state of conventional clay disposal technology and reviews the technical progress of innovative alternatives. A total of 20 impoundment sites were investigated by the Bureau of Mines usinq geotechnical methods and laboratory analysis of cored samples. In addition, quasistatic cone penetrometer soundings were conducted to define clay and/or sand/clay interfaces en masse. Samples of the top, middle and bottom hole segments were obtained at each station for laboratory studies of clay densities, pore fluids, plasticity and mineralogical properties.

The results of this study support the continued use of initial clay settling impoundments but emphasizes the need of “in-line” systems to reduce the initial volumes of plant-generated phosphatic clays. The effective use of sand tailings is also encouraged to promote further consolidation of clays via self-weight stressing, sand/clay admixtures and/or surcharging sand caps.

FIPR Publication No. 02-017-021
State-of-the-Art of Phosphatic Clay Dewatering and Disposal Techniques. Volume 1 – A Review of Phosphatic Clay Dewatering Research. W. E. Pittman, Jr., and J. W. Sweeney, U. S. Bureau of Mines. September, 1983.