oa Geophysical Characterization Of Mineral Waste Sites

Surface geophysical methods including electromagnetic conductivity,<br>spontaneous potential, seismic reflection and refraction, ground<br>penetrating radar (GPR), and magnetometry were evaluated at mineral<br>waste sites to characterize subsurface geology and hydrology.<br>Three metal mine waste sites were investigated: (1) an open pit<br>operation with extensive spoils and sub-ore grade materials<br>distributed over an area approximately one square mile; (2) a<br>typical mill waste dump site, a few acres in size; and (3) a small<br>mill waste tailings pond. At the open pit mine, four different<br>locations were investigated to determine pre-mining topography,<br>characterize the subsurface groundwater flowpaths, and design the<br>most efficient drilling program for monitor wells. Interpretation<br>of the geophysical surveys at the waste dump site provided a model<br>of the ground water conditions which was crucial to the development<br>of a remediation plan. Results of the geophysical surveys at the<br>tailings pond provided information on the thickness of tailings and<br>water channelling for subsequent modeling of the hydrology, in<br>addition to determining feasibility of new methods for<br>characterization of mine wastes. The work to date has emphasized<br>the need for a multi-disciplinary approach to the characterization<br>of mineral waste sites with geological, hydrological, and<br>historical input to determination of the best technical evaluation<br>of site conditions. An integrated approach using multiple<br>techniques provided a high degree of confidence in interpretation<br>of conditions that were relevant to design of drilling plans,<br>development of groundwater models, and remediation efforts.<br>Efforts at two mill tailings piles, and at the abandoned open pit<br>mine indicate that each investigation must necessarily be<br>considered an applied research study and that the best methods will<br>evolve from ongoing surveys.