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Y2012-03 Enviromental accident at the Talvivaara mine in November 2012

A leak in gypsum pond No. 1 was noticed on 4 November 2012. At the time of the incident, the pond contained a total of some five million m3 of water with metal content and gypsum sediment. As a consequence of the accident, approximately 1.2 million m3 of environmentally hazardous water bearing metal content and sediment leaked out of the pond, around 240,000 m3 of which ended up outside the mine area.

The company initiated measures for finding the location of the leak and plugging it, and for limiting additional damage. In order to prevent water bearing metals from leaking outside the mine area, the company began building the Kortelampi safety dam. It also began the neutralisation of the water that had escaped from the gypsum pond and initiated monitoring of the environmental impact.

Construction of the leaking pond had been completed in spring 2008, and the authorities had approved the pond for commissioning in May 2008. Even prior to that date, in April 2008, the authorities had approved the use of the pond as temporary water storage for the purpose of starting the bioleaching process. A leak in the number one segment of the pond was detected for the first time in August 2008. The next leak in the same segment was detected in March 2010. In the case of all leaks that have occurred, the common denominator has been water stored in the pond.

The causes of the accident are the structure used in the gypsum pond and the use of the pond as water storage contrary to its proper purpose of use. The structure of the pond could not withstand the hydrostatic pressure of the water stored over the gypsum sediment; instead, the HDPE film tore and the water stored in the pond was able to escape. The two previous leaks in the pond probably led to the deterioration in the structures underneath the HDPE film, which is likely to have contributed to the creation of a new leak.

Prior to the November 2012 leak, raffinate, or an acidic metal sulphate solution, had been pumped into the gypsum pond, counter to the pond's original purpose of use, for a period of two months. This raffinate made the leaked water more hazardous to the environment.

The recommendation of the Safety Investigation Authority is that, in co-operation with the other actors, the Ministry of the Environment ensure through statutory means, if necessary, that the identification and prevention of and preparation for major industrial environmental accident risks be taken into consideration to a sufficient degree and in a uniform manner in the planning and implementation of activities by the authorities and companies. Additionally, the Ministry of
Employment and the Economy should co-operate with the Ministry of the Environment and the Ministry of the Interior in developing new forms of co-operation in the oversight of mining projects. This would enable the authorities to jointly handle the project, both when granting the environmental permit and during later stages of oversight, ensuring that no parts of the process have been left beyond the scope of oversight by the authorities. At the same time, the procedure whereby the granter of the environmental permit would also act as the permit overseer should be examined. Furthermore, the Ministry of the Interior should, in co-operation with other ministries, through legislative means if necessary, ensure that the overall leadership and competence is clear and practical in all serious incidents and accidents. Overall leadership is needed even in non urgent situations to ensure functioning cooperation, maintaining situational awareness and implementing communications.

Y2012-03 report (pdf, 4.8 Mt)

Published 3.2.2014