The Svartliden Mine was the first integrated mine and treatment plant to be developed under the new Swedish Environment and Mining Acts. It was brought into production in March 2005 and the tailings (milled mine waste) have been disposed into a dam.
The mine is located between two environmentally sensitive rivers, Paubäcken and Örån, which are both Natura 2000 sites. Environmental concern is therefore essential when designing the future management of the tailings.
Three main alternatives for the tailings management are evaluated i.e. Backfilling of the underground mine, open pit disposal and raising the current dam to increase the capacity. Each alternatives has advantages and disadvantages regarding e.g. capacity, costs, needs for investment, environmental impact and remediation needs.
The main alternatives and combinations of them are compared with regard to the criteria defined above. Ramboll's role is to identify the optimal solution securing the environment, being flexible and economically advantageous for the company.
To optimize the tailings management, several aspects have to be considered. On one hand, economic aspects such as operational costs, investment needs, flexibility with regard to the production, and future maintaining and closure cost should be taken into account. On the other hand, risk of pollution release to the environment, health and security and impact on the landscape should be taken into account, even though their economic value is difficult to estimate.
To optimize water management at the site (and reduce drift costs) and reduce both environmental and working environmental risks, the use of thickened tailings and paste is investigated. Ramboll's geotechnical laboratory in Finland has been asked to develop recipes to add cement for tailings solidification and stabilisation. The solidified tailings might be used to allow the disposal of tailings in slopes and allow a more efficient use of the available volume for waste disposal. Further the solidified tailing could be used to consolidate the backfilled underground mine.
To reduce the costs of purchasing cement, the addition of ash, a residual product from biofuel incineration, is investigated. The use of ash is further environmentally beneficial, since a residual product is used instead of a material with an economic and environmental cost, solving two waste problems at the same time.
Ashes and slag
Ramboll Finland developed and has long experience in stabilisation and solidification techniques. They demonstrated in earlier studies that ashes and slag could be used to improve the economic and environmental viability of the method.
The use of residue products as alternative construction materials is a developing field. Ramboll and Luleå University of Technology are in cooperation assessing the potential use of different residual products for the remediation of mine waste. An understanding of how materials react with each other is necessary to assess the long term behaviour of the proposed solutions.