Characterisation of landfills using a multidisciplinary approach

The Netherlands has about 3800 abandoned landfills with a total surface of about 9000 ha. As they are often located near urban areas and their influence extends into their surrounding environment they put pressure on available space. Most abandoned landfills were in use until the 1960s and 1970s. Their precise geometry and composition are often unknown. The same can be said about the internal processes and resulting short- and long-term risks of the landfills. As a result landfills are often poorly understood and only monitored by measuring surrounding groundwater composition. In order to gain a better understanding of landfills – especially of their outer boundaries and the lateral variation in composition – a multidisciplinary approach is used consisting of geophysical and chemical measurements to characterise landfills. The aim of this paper is to share experiences from two sites – an abandoned landfill at the Bergen site situated in the coastal realm of the Netherlands and a modern landfill situated at the Landgraaf site in inland, hilly terrain – with a clear focus on the geophysical results. For the considered case studies, continuous vertical electrical sounding and electromagnetic measurements appeared to be preferred geophysical techniques. In combination with chemical measurements they are suitable for detecting waste site boundaries and in addition provide information on the heterogeneity observed within the considered waste sites.