When contamination has an impact on large areas

Megasite is the expression used for a large area with multiple contaminant sources related to (former) industrial activities, with a considerable impact on the environment, through groundwater, surface water and/or air migration. The dimensions of the area for which the megasite management strategy needs to be developed is determined by the sphere of influence of contaminant migration through these different pathways. In general these vary between 1-10 km.

Due to the complexity of megasites - related to site conditions, contaminant characteristics, organizations involved, regulatory aspects and considerable costs - an integrated risk-based management approach is recommended to manage the risks for the defined receptors (soil, groundwater, surface water and land users at the surface).

Megasites can be found in the (former) industrial areas of Europe. In the WELCOME project four typical megasites were included, namely:

• The chemical industrial area in the German city of Bitterfeld,
• The chemical plant in the Polish city of Tarnowskie Góry, and
• The heavily industrialized harbours of Rotterdam and Antwerp.