CHARACTERIZATION OF AN OLD MUNICIPAL LANDFILL (GRINDSTED, DENMARK) ASA GROUNDWATER POLLUTION SOURCE - LANDFILL HISTORY AND LEACHATE COMPOSITION

Investigations into the pollution of groundwater from old landfill hav e, in most cases, focused on delineating the pollution plume rather th an on the landfill as a source of groundwater pollution. Landfills oft en cover large areas and spatial variations in leachate composition wi thin the landfill may have great impact on the location of the main po llution plume in the downstream aquifer. The history of the Grindsted Landfill in Denmark was investigated using aerial photographs and inte rviews. On the basis of the aerial photographs, waste volume and age o f the different areas of the landfill were evaluated. A pronounced var iability in leachate composition was observed in the 31 leachate wells installed through the waste. The spatial variability was analysed by statistical methods, and a semivariogram model was able to describe th e variability both on small and large scale. The spatial variations in leachate composition are very important for locating the main source of the groundwater pollution and for selection of cost-effective remed ial action activities.