ABSTRACTThe demand for‘Rolls‐Royce’ solutionsto the disposal of hazardous and radioactive wastes has seen a continuing move towards more sophisticated disposal concepts. If a disposal site for radioactive wastes meets the strict requirements laid down by Government departments it is difficult to see why there should be any impact to groundwater of concern to the water industry. Hazardous wastes are a much more significant problem, and the large size of many landfills, other pressures on groundwater quality and current EC directives are all contributing to a move away from the use of ‘dilute and disperse’ sites. It is argued that the long‐term performance of containment sites needs to be carefully evaluated over timescales of 2‐3 decades, as over such periods a correctly‐managed policy of ‘dilute and disperse’ may result in less of an overall impact to the environment than a policy of ‘con