Improved Methods for Determining Soil-Atmosphere Flux Boundary Conditions at Mine Waste Repositories

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Successful operation and closure of mine waste repositories require accurate quantification of the surface water budget that controls the infiltration of meteoric water into the waste profile. The rate of net surface infiltration ultimately generates internal seepage with the release of potential leachates that may threaten downstream receptors. Recent field scale observations at both active and reclaimed mine sites in Canada, as well as international sites operated by Canadian companies, have shown current predictive models used to calculate infiltration rates for mine waste deposits such as waste rock dumps and tailings impoundments are unacceptable. For example, net infiltration rates determined directly on the basis of measured flow rates in the drainage collection ditches at Equity Silver mine in British Columbia have been found to be three fold greater than infiltration rates predicted using the current soil-atmosphere modelling methodology. The global objective of the research program proposed here is to investigate the reasons for these errors and to improve the existing soil-atmosphere methods currently available for estimating surface flux boundary conditions at mine waste repositories.****All of the research carried out by the applicant over the past six years has been in the area of mine waste management. The objective of the research programs has been to develop new technologies for improved mine waste management, closure and the reduction of long-term environmental liabilities. These objectives have been achieved through the training and innovation of highly qualified personnel.***The short-term goal of this application is to advance new techniques that provide precise measurements of field scale evaporative fluxes for improving soil-atmosphere flux boundary methods. The long-term objective of the research program will be to improve the capability of researchers and practitioners to observe, predict and design cover systems for mine tailings and waste rock impoundments. In addition, the long-term objective will be to continue training of HQPs, disseminate the results of the research into appropriate journals and conference proceedings, and finally to assist with the implementation of the research results into practice. The training of 1 MSc and 2 PhD students and Research Associate (½ time) is planned. The ultimate objective for developing and implementing the new techniques proposed here will be to improve the design and performance of mine waste repositories with respect to surface water management and the reduction of environmental liabilities.**