[en] Solubility and aqueous speciation calculations constitute the backbone of the assessment of radionuclide mobility under repository conditions. To this respect, geochemical codes and their associated databases have to be verified and quality assured prior to their use in Performance Assessment exercises. The main objective of this Blind Prediction Modelling (BPM) Exercise was to test the ability of the different geochemical tools (codes and databases) to predict the concentrations of trace metals in a well characterised natural system. In this respect, widely used geochemical codes and databases have been tested. Eight water samples, representative of the different boreholes studied during the El Berrocal Project were selected for this purpose. The four participating groups were provided with the information needed to perform the predictions. The type of information released was separated into two main groups: - Concentration of major ions in the selected groundwaters - Mineralogical analyses of the site. (Author)