[en] This report describes modelling of the transport of solutes and colloids in an experimental system comprising an artificial dipole flow field in a water-conducting shear zone at Nagra's Grimsel Test Site (GTS) in the central Swiss Alps. The modelling work forms part of the Colloid and Radionuclide Retardation Project (CRR), which includes a series of field transport experiments and a supporting laboratory programme, as well as modelling studies. Four independent groups representing different organisations or research institutes have conducted the modelling, with each group employing its own modelling approach or approaches. Only the work conducted at the Paul Scherrer Institute (PSI) is described in the present report. The modelling approaches used in the present study may not be directly applicable to safety assessment problems and the direct implications of the results of this study for safety assessment are limited. It can, however, be said that the study has demonstrated the high degree of mobility of bentonite and other colloids in a system that is at least in some ways comparable to those of interest in safety assessment, and has shown that bentonite colloids can at least potentially affect the transport of some safety relevant radionuclides over longer temporal and spatial scales than those addressed here. (author)