Environmental impact and remediation of uranium tailings and waste rock dumps at Mailuu Suu (Kyrgyzstan) 1

This paper describes the environmental situation in the former uranium mining and milling region of Mailuu Suu (Kyrgyzstan), the approach to environmental remediation of the waste facilities (tailings ponds and waste dumps) and the results achieved so far. It starts with an outline of the history of the environmental remediation project which has received international attention and is seen as pilot project for further remediation activities of former uranium mining and milling sites in the region. Apart from technical aspects, the paper draws conclusions with respect to the administrative environment, institutional capacity building and the local availability of resources needed to successfully implement a complex remediation project. The town of Mailuu Suu is located in the north-eastern part of the Fergana valley, in the valley of the Mailuu Suu river. The altitude of the area is between 900 and 1000 m a.s.l. The Mailuu Suu river reports to the Syr Darya river which, in turn, feeds lake Aral. Administratively, the area belongs to the Dzhalalabat province in the southern part of Kyrgyzstan, with a distance from the Uzbek border of around 25 km. Today, approximately 25,000 inhabitants live there, with a light bulb factory being the only employer of significance. In and around the town, uranium was mined and milled from the late 1940's to the 1960's. Most of the waste dumps and tailings ponds are located in the valleys of the Mailuu Suu river and its tributaries Kara Agach, Kulmen Sai und Aylampa Sai. Their proximity to the riverbeds, strong seasonal floods of rivers, steep slopes of a mountaineous landscape, landslides and a pronounced seismicity 5 add up in varying degrees to the structural instability of a large part of the waste facilities. The area, typically covered with grass, is over-grazed which adds to the landslide risk and further reduces the water retention potential of the soil, increasing the frequency and magnitude of floods. Under these conditions waste material with elevated natural radioactivity is eroded and transported towards the denser populated parts of the Fergana valley and, further on, across the border to Uzbekistan, adding a politically sensitive cross-border aspect to the problem. Investigation of the environmental and health impact of the uranium mining and milling wastes began after international attention had been drawn to the situation. Since then, numerous efforts have been undertaken to understand the environmental impact and develop appropriate remediation solutions, which have been financed by international organizations such as the European Commission's TACIS program and the World Bank. In the following sections, the various investigation and remediation approaches and the current status of the remediation works will be presented and discussed. Currently, the design of remedial measures has almost been completed, and implementation of the most urgent measures is in progress.