Norwegian Mine Review
Years of Service
1987 to 1991
Norway has a history of mining sulphide ores dating many hundreds of years. In particular there were numerous underground massive sulphide mines that operated from the early 1900s through to the 1960s to 1980s. Acid generation from the tailings and mine wastes from these mines have released dissolved heavy metal loads, particularly copper and zinc as well as acidity to the receiving environment for several decades. In the mid 1980s the Norwegian Environmental Protection Agency started a program of mine site investigations and remediation directed specifically at both abandoned and operating massive sulphide mines. Dr. Andy Robertson was appointed by the Norwegian State Protection Agency to review the acid mine drainage conditions at 16 mines and advise on potential remediation measures.
Each of 16 Norwegian mines which had mined massive sulphide ores were visited, site reconnaissance studies completed, conceptual alternative remedial measures proposed and a preliminary cost estimate developed for the alternatives. Based on the results the Norwegian State Protection Agency pursued negotiations with the Norwegian Department of Mines, Mine Owners and local communities for the implementation of the appropriate remediation measures. Dr. Robertson continued to provide consulting review and advisory services to the Norwegian State Protection Agency and those responsible for the implementation of the remediation plans. A few of the remediation plans are described below:
- Kjoli Mine: This underground mine operated from the early 1900s to the 1940s. Ninety thousand m3 of rock waste with a 15% sulphur sulphide content was placed on scattered piles on the surface. Metals leaching from the mine and waste exceeded 2.4 tonnes of copper per year destroying a premier trout stream for 17 km. In 1981 the waste had been consolidated and a surface application of lime made in an attempt to control the acidic drainage. Disturbance of the pile resulted in increases in the metals leaching to over 10 tonnes of copper per year. An alternatives evaluation by Dr. Robertson resulted in the recommendation that the waste pile be re-shaped and covered with a geosynthetic membrane and till cover. This was installed in 1988 by the Norwegian Department of Mines resulting in a reduction of copper leaching to tenths of a tones per year. The pile is instrumental in determining long term oxygen entry and moisture conditions in the pile.
- Skorowas Mine: The Elkem mine was operated between 1952 and 1987 as an underground mine and produced a highly acid generating mine rock waste pile of approximately 450,000 m3 placed on the side of a hill above a small lake. An evaluation of alternatives by Dr. Robertson resulted in the selection of mine waste removal and re-location below final flooded water level in the lake as the most cost-effective long term acid generation control solution. The design of the re-location plan was done by Miljoplan of Norway, with Dr. Robertson providing review and technical guidance, for Elkem who performed the relocation in 1988. The re-location involved partial draining of the lake and the installation of a lake water lining system to control lake water pH and release during relocation. The submerged wastes were isolated by till covers and rip-rap protected. The final lake level was raised by constructing a dam to achieve a more efficient deposit. Instrumentation in the submerged rock waste and in the lake have demonstrated that lake water quality objectives have been achieved and long term collection and treatment of acid mine drainage from the mine wastes are no longer required.