Lagoons at Villa Farm near Coventry, UK were used for the disposal of industrial liquid waste after 1967. The lagoons were unlined and a leachate plume developed in the underlying thin sand aquifer. As part of a research programme into controls on the migration of landfill leachate, a two-dimensional areal model describing the regional scale movement of chloride and phenol in the aquifer has been developed. Parameter ranges for advection, dispersion, degradation and adsorption have been established through model calibration, constrained by the results from previous laboratory studies. Linear representations of the adsorption and degradation processes are found to yield satisfactory results on the time and space scales adopted for the simulations. The model development has highlighted some important issues that have to be confronted when analysing the evolution of a plume based on short-term, late-time data. The uncertainty in the geometry of the aquifer on the simulated flow system has been examined using geostatistical methods.