Mine tailings — practical experiences in filling up harbours

Abstract

Abstract In the port of Rotterdam, old harbours are being filled up to create new sites for industrial activities. Large quantities of materials are required for these projects. Because of the mechanical, environmental and economical advantages, mine tailings are therefore used. In the past some 1.000.000 tons of this natural, inorganic residue of coal mining was used in several filling up projects in the port of Rotterdam. The muncipality of Rotterdam has carried out an environmental impact assesment on the use of mine tailings. Conclusion was that the oxydation of the mineral pyrite is the critical aspect of the mine tailings. To prevent oxydation, it's only used below the groundwater table, in anoxic zones. In the laboratory various experiments have been carried out on the contents and leaching of components, according to the legislation and the licences. Besides, the oxydation of pyrite is controlled in the field. At one harbour site (Beatrixhaven) the oxydation of pyrite is being monitored by measuring the pH and redoxpotential with an in-situ cone. As the mine tailings are produced in coal mines in Germany, the environmental survey starts with sampling at the mine. In the meantime, the mine tailings are shipped to Rotterdam. At the site, the delivered material is then again sampled and examined. The mine tailings are put in the harbour and the results of the survey have to meet the standards. The conclusion of the paper, after several years of experience with the application of mine tailings, is that the use of mine tailings is environmentally safe and meet the standards. The boundary is to use this material only in an anoxic environment (below the groundwater table). The major bottle neck in the benificial use of mine tailings is the long time, required for a licence (6 months) for a waste material, compared to those of raw materials (few days).