ENVIRONMENTAL AND ECONOMIC CONSIDERATIONS FOR MATERIALS SELECTION FOR MINERALIZED DULUTH COMPLEX WASTE REMEDIATIONFrancis D. Udoh
This paper evaluated materials as potential cover systems for mineralized Duluth Complex waste remediation, The methodology employed involved initially screening a large number of materials for their availability, cost, workability, expected hydraulic conductivity, and environmental ramifications. American Society for Testing and Materials (ASTM) soil testing standards were used to evaluate the physical properties of the materials in order to establish a barrier that would produce the highest soil density and lowest hydraulic conductivity when compacted at optimum moisture content. Based on the final evaluation of laboratory data, cost and any potential environmental problems which could result from the use of that material, glacial till, glacial till mixed with bentonite, and a 20 mil polyvinyl chloride (PVC) membrane were recommended for field evaluation. Fine tailings were eliminated since the hydraulic conductivity was greater than 2x10-' cm/sec, the maximum requirement of the Minnesota Pollution Control Agency (MPCA). Paint rock, although exhibited a suitable hydraulic conductivity, was eliminated due to possible environmental problems. The silty ciay from Aurora was also eliminated due to the high cost of delivering the material to the mine site. While these results are preliminary, such invaluable information can judiciously be brought to consolidate decisions on the selection of covers for future mineral stockpile capping projects.
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