Waste or valuable resource – a critical European review on re-using and managing tunnel excavation material

Re-use of excavated rock and soil from subsurface tunnelling has become an essential legal and technical factor in underground construction projects. European Union initiatives have caused an emergence of legal documents and technical guidelines for re-using excavated material. An improving situation towards a homogeneous European legislation is missing and site-specific re-use solutions are still favoured within the framework of national legislation. In this paper, we present a detailed review of legislation and technical concepts within the scope of re-using excavated rock and soil across Europe focusing on the Alpine countries. Austria, Switzerland and France prove to be role models in re-using excavating material whereas Italy is providing a limited amount of national solutions. Excavated rock and soil are still considered waste, which hampers legislation procedures and efficient technical re-use as a potential resource. National guidelines and recommendations bear huge potential to serve as a basis for a homogenisation of European legislation. Technical limitations imply physical and chemical characterisation of excavated rock and soil as well as their positioning in relation to inert waste thresholds, which requires a sophisticated material flow analysis. We introduce a material flow analysis concept installed on a tunnel boring machine managing on-line analyses, conditioning, separation and transport to consumers of excavated material resource-efficiently within a mutual European legal framework. A dedicated European authority is suggested to undertake responsibility for the material management and governing a technical database obliged to aim for maximum, efficient re-use and public awareness.