Protection of installations for potable water abstraction against hazardous environmental influences in bedrock media

Contaminated groundwater of abandoned hazardous sites are leading to significant ecological damages in the adjacent reservoirs. Especially explosive composites and their metabolites of armament industry are toxic. The direct vicinity of the abandoned defence industry site of Stadtallendorf (Hesse, Germany) to the water supply company of a great catchment area is a severe hazard for the water supply of the whole region. It is a prerequisite to determine the behaviour of flow and transport in the local aquifer to assess the status of the site. A sustainable protection of the reservoir is only feasible with predictions of a flow- and transport model of the local aquifer. Local geology includes bedrock media, faults and a diversified stratigraphy. To describe transport in the aquifers, one has to take into consideration interaction between advective transport in fractures and diffusion in porous bulk. Onsite investigations are carried out to make predictions of advection, dispersion and attributes of the fractures (strike, slip, hydraulic aperture, density, length). Laboratory tests reveal data concerning matrix diffusion and adsorptive character of the media. Also environmental dependent transformation rates are considered to assess natural attenuation processes. Bulkdiffusion has been identified as an important component of contaminant retardation. Porous bulk acts as a store of pollutants. Even after remediation of the site, diffusion controls the decrease of pollutant concentration in water. The determined parameters of the investigations are incorporated into a flow model and later on into a transport model.