Excavated material

"Excavated material" refers to waste consisting mainly of rock and earth excavated during construction of infrastructure (tunnels, culverts etc.) and buildings.

Ecological evaluation

Hydraulic schemes such as widening watercourses, dredging reservoirs and draining flood protection systems also generate large quantities of this material. Finally, it can also be produced in large quantities during natural disasters (rockfalls, avalanches and landslides). Excavated material may be polluted, particularly if it is derived from excavations on industrial or old landfill sites.

Existing data

Very little data is available regarding the quantity of excavated material produced, as there is currently no legal basis which requires it to be monitored. However, by cross-checking various data sources it is possible to arrive at an estimate of 40 million cubic metres produced per annum in Switzerland, a volume approximately equivalent to 15 times that of the Great Pyramid of Giza. This means that excavated material represents the largest waste stream in Switzerland. Only a small percentage - 5 to 10% - is polluted. With the increase in underground buildings and transport infrastructure and the growing erosion in mountain regions, the quantity of excavated material is likely to be even higher in the future.

Treatment

If unpolluted, the great majority of this material is used for rehabilitation of gravel pits and other extraction sites, to reinstate the original geomorphology. A small proportion - again unpolluted - is recycled as gravel and reused on the actual construction site (e.g. to backfill excavations) or for landscaping features such as noise-abatement embankments, dikes and undulating parkland. The rest goes to landfill.

In some regions, however, the capacity for disposal to landfill and as gravel will be progressively reduced. Therefore more and more excavated material will have to be upgraded, preferably on the actual site where it is generated or nearby, to limit haulage. It is important to consider the question of excavated material during the planning phase of any major construction project.

Some projects in Switzerland prove that original and innovative solutions for upgrading this material do exist. These examples are described in a study by the University of Applied Sciences Rapperswil commissioned by the FOEN. Proposals for other possible methods of reuse are also defined in the study.