Groundwater model parameter identification using a combination of cone-penetration tests and borehole data

In the framework of the disposal of short-lived low- and intermediate-level radioactive waste in a near-surface disposal facility in Dessel, Belgium, additional extensive site characterisation has been performed in 2008. Based on the interpretation of this new data, an update of the local groundwater flow model was performed. The information from the cone penetration tests interpretation and the hydraulic conductivity at different scales was combined into a new 3D hydrostratigraphical model (geometry of hydrogeological units). Model parameterisation was adapted according to the statistical analysis of the small-scale hydraulic conductivity measurements (on 100 cm³ core samples) and the pumping test results. Three alternative concepts were tested for the hydraulic conductivity field of the aquitard. Inverse modelling was then used to obtain large-scale effective parameter values for the different hydrogeological units. The obtained parameter values are then compared with hydraulic conductivity values obtained from lab and pumping tests. The performance of the original and the updated model are compared. The presented approach helped to decrease substantially the conceptual model uncertainty and improved the model calibration.