Located near Belfort (France), the Etueffont landfill was in operation from 1976 to 2002 for the disposal and storage of domestic waste produced by the area’s 47,650 inhabitants. The site is comprised of the original landfill site called the ‘‘old landfill,’’ in operation from 1976 to 1999, and a newer section known as the ‘‘new cell’’ which operated from 1999 to 2002. The objective of this study was to monitor over a four-year period the groundwater quality in the landfill’s surroundings along with its variations in chemical facies using the ion Cl- as an indicator of anthropogenic contamination in groundwater. The results illustrate the influence of the entire landfill site on the upper part of the groundwater layer. In addition, the leachate plume does not exceed the width of the storage zone and is no longer observed 250 m downstream. This demonstrates a weak transversal dispersion except toward the west where diverticulation of the mixture is guided by schistosity and fracturation.