GROUNDWATER PROTECTION - the link between EU acceptance criteria and sustainable landfill

EXECUTIVE SUMMARY: Terms as ‘landfill stability’ and ‘final storage quality’ are very often used in discussions about sustainable landfill and groundwater protection at landfills. Internationally accepted definitions of these terms are not available. Consequently there is also no shared notion of sustainable landfill. In a Dutch sustainable landfill project it was proposed that: ‘a landfill is stable when the undisturbed contents do no longer pose a threat to the environment in any way’. Clearly the potential threat does not only depend on the landfill but also on the environment. Especially the potential threat to the soil and groundwater depends on the local soil and groundwater conditions. The primary aim of the method used to establish the acceptance criteria for waste on landfills in the Annex II of the European Landfill Directive was to guarantee groundwater protection. This study indicates that progress in knowledge of landfill processes and geochemical modelling has enabled site specific long term emission predictions. The example in this study illustrates that ‘stable situation’ and ‘final storage quality’ are not aspects that can be defined entirely by means of absolute numbers. Acceptable emissions and limit values depend on the local situation. A rigid definition of leaching limit values does not always coincide with a realistic impact assessment. In order to end aftercare the landfill operator needs to prove to the competent authority that the landfill no longer poses a threat to the environment. A list of limit values can only achieve this if large (possibly unattainable) safety margins are introduced. This could result in unnecessary costs for society. Competent authorities and landfill operators could therefore benefit from a robust risk assessment method. Recent developments in British and German landfill regulations are very positive. They do provide more clarity concerning aftercare. The legislators have also realised that it is possible to actively reduce potential long-term emissions. The regulations provide possibilities for operators to apply measures to accelerate completion. Rather than making it redundant, these developments underline the need for a robust risk assessment method. Preferably that method takes the entire landfill (cell) into account instead of just individual waste batches. Moreover, the method should account for different soil and groundwater conditions as the site selection of landfills is an important aspect of sustainability. The approach used for the establishment of the acceptance criteria of the Annex II of the European Landfill Directive can provide a starting point for the development of a robust risk assessment method for groundwater aspects.