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Remediation of Abandoned Mine Lands |
Thursday, October 2, 2008 : 2:00 p.m.
Stockpile Characterization and Hydrogeochemical Seepage Modeling for Mine Closure
These analyses show that sulfate, acidity, and other constituents are stored in waste piles in the form of jarosite and other sulfate minerals, which occur in significantly greater abundances in the stockpile materials as compared to fresh mine materials as a result of weathering, leaching and oxidation of pyrite. Static and kinetic testing results show that the potential for constituent release from leach ore and waste rock stockpile materials does not appear to be correlated with stockpile depth and age, but is a function of mine material type.
The weathering and leaching processes that can mobilize and redistribute constituents within the stockpiles and affect water quality and slope stability after closure were also investigated at these mines through hydrogeochemical modeling. The modeling results show that sulfate and other constituent concentrations and mass loading to surface and groundwater is highly dependent on material type, infiltration rates, and internal stockpile conditions which may be affected by the cover design. Stockpile slope and cover stability was also investigated. Acidic degradation stockpile slope stability and cover material is mitigated if alkaline materials are used in the cover design and reaction rates of minerals in the materials is slow.
Drummond Earley III, Ph.D., Daniel B. Stephens and Associates More than 20 years of technical experience in hydrogeochemistry and groundwater flow and multicomponent reactive transport modeling. Extensive experience in the field and laboratory characterization of geological fluids, materials, and minerals. Skills include risk assessment for feasibility assessment and the conceptual design of clean and industrial water management and processing systems. Projects primarily focused on mine waste assessment and reclamation, and watershed analysis including groundwater and soil remediation. More than nine years of experience as an environmental consultant in environmental project management and business development, state mining laws, Clean Water Act-TMDL regulations, and sustainable development of mineral resources.
Elizabeth A. Salvas, Daniel B. Stephens and Associates Ms. Salvas holds a B.S. degree in environmental geology and an M.S. degree in hydrology and has over nine years of experience in water resource investigations. Key areas of expertise include geochemical modeling, aqueous geochemistry, surface water hydrology, and water resource assessment and planning.
Neil Blandford, P.G., Daniel B. Stephens and Associates Mr. Blandford has 18 years of experience in numerical simulation of groundwater flow and contaminant transport, water rights analysis and water supply investigations, geostatistics and aquifer testing methods, wellhead protection area delineation and remediation well field design.