The influence of biofilm growth on the hydraulic properties of sediments and rocks will be investigated experimentally over scales from microscopic (10-10m) to macroscopic (102m). In addition, the effects of biofilms on the formation of fine oxide precipitates (FeO, OH, MnO.OH. etc.) and on the sorption behaviour of fluid transported trace impurities (U, Tc, Sr) will also be studied over these scales. These fundamental data will be obtained using a unique combination of experimental methods which will allow the results to be scaled up to field dimensions of distance and time, such that the results may be used by our industrial partners as input to field scale models of the migration of fluids and contaminants.