Leaching from Residues Used in Road Constructions – A System Analysis

When residues such as municipal solid waste incineration slag are used as construction materials they are commonly enclosed in a technical construction, which acts as a barrier. This will limit the exposure to water and the atmosphere and thereby delay the resulting leaching process. From a risk assessment perspective there is a great need to qualitative analyze the technical construction, its function, relevant emission scenarios and boundary conditions. The objective is to give a description of the processes and events that are crucial for assessing the leaching of contaminants from roads where residues are used as construction material. One method to describe a complex system is by using

interaction matrices

. The function of the system is broken down into a number of important components, properties and processes through a top-down approach. The method has successfully been used within rock engineering and nuclear waste disposal research, and is here employed on the use of residual materials in road constructions. Based on the analysis of the system it is concluded that a road ought to be treated as an integrated system instead of treating the system components and processes separately. The role of the road shoulders as water and gas vents remains as the most important mechanism governing emissions from roads where residues are used as an alternative unbound material.