Model-Based Preliminary Assessment: A New Approach to Improve Tiered Decision-Making for Contaminated Land Management

Contamination of land and groundwater by organic chemicals, particularly non-aqueous phase liquids (NAPLs), is a widespread problem that severely impacts human health, the environment and the economy at many urban sites all over the world. Novel, efficient and sustainable. management strategies are urgently required to solve the existing problems at large-scale, so-called megasites. Usually a considerable number of potential management solutions exist at each of these sites. A detailed investigation of all these options, however, is not economically feasible which makes streamlining of the planning and decision process a mandatory requirement. Complexity of the situation at these sites (in terms of contamination extent, boundary conditions/limitations, stakeholders, etc.) has led to the proposal of tiered frameworks for site investigation, risk assessment and management, e.g. in United Kingdom and in the USA. Also, recent policies request an increased emphasis on modelling (e.g. EU Water Framework Directive). A methodological gap exists particularly with respect to preliminary assessment methodologies to support early decisions on prioritising hot spots and pre-selecting mitigation options to streamline the further planning process. To fill this gap, we propose a novel system dynamics modelling approach utilizing a multiple source-pathway-receptor concept. It quickly provides reasonable estimates of current and future risks, as well as of the costs of possible remediation (risk reduction) strategies for integration into the planning process. The large potential of preliminary assessment for contaminated land management will be shown for a pilot case study site in Germany.