| The physical hydrogeology of till at a central Alberta site is described as part of a remediation research project at a decommissioned gas treatment site. Field investigations reveal seasonally dynamic groundwater flow in the upper 4 m of weathered, fractured till, but not below in unweathered, sparsely fractured till. The water budget is dominated by the vertical fluxes of precipitation (494 mm) and evapotranspiration (545--575 mm). Upward vertical hydraulic gradients of up to 2.5 are strongly indicative of perched water table conditions. Horizontal flow is not found to be important due to low horizontal hydraulic gradients, low permeability, and lack of geologic continuity.; To confirm field interpretations, numerical models of groundwater flow are created with FRAC3DVS, a finite-element simulator. Model calibration to water level measurements is achieved primarily through modification of the timing and magnitude of the net surface boundary flux, and the magnitudes of hydraulic conductivity and specific storage. Model validation and sensitivity analyses reveal the difficulties in modelling fractured domains with a continuum approach. |
