Insights into Contaminant Leaching Through An Intensive Field Monitoring Program

Risks to groundwater quality from mobile contaminants in the unsaturated zone associated with active or legacy mines present significant challenges for land managers and policy makers worldwide. Unsaturated zone flow processes are a dominant control on contaminant loading. However, the presence of unsaturated zone heterogeneity results in spatially and temporally variable flow pathways, due to capillary breaks and hydraulic barriers forming in various locations. This can result in the development of focused flow paths from where rapid contaminant transport to the water table may occur. In this study we designed an intensive monitoring program to attempt to characterise time-varying flow paths through a highly heterogeneous unsaturated zone through a dense network of combined soil moisture, electric conductivity and temperature probes. Estimations of surface fluxes and soil drainage along with observed water table response at a waste management site in Chalk River, Canada are presented providing insights into flow and transport processes.