Mailuu-Suu tailings problems and options for remediation

The area of the town of Mailuu Suu, Kyrgyzstan, is polluted by radionuclides and heavy metals in tailing dumps and heaps resulting from the historic exploitation of U-mines in the Mailuu Suu area in Kyrgyzstan. Radioactive substances are stored in 23 tailings and 13 mining debris heaps situated along the Mailuu Suu River. The objective of the EC-TACIS funded project is to evaluate and prepare measures to be taken by the authorities to reduce the radiological exposure of the population and to prevent environmental pollution by radionuclides and heavy metals in case of loss of tightness of dams and damage to dumps and heaps from mining and milling by land and mudslides and to propose sustainable remedial options, accepted by the public. The actual radiological situation is of no immediate concern for most of the population of Mailuu Suu. From the gamma radiation monitoring campaign (monitoring network in Mailuu Suu, Kara Agach and vicinity), it showed that the background radiation is 100–120 nSv/h. On the tailings radiation is on average twice background. The average outside and in-house radon concentration is 175 Bq/m³. In 3 of the houses monitored at Kara Agach the radon level is between the exemption limit for new (200 Bq/m³) and old (400 Bq/m³) houses. The concentration of uranium in the Mailuu Suu river water is far below the exemption limit for drinking water set in Kyrgyzstan. Additional dose from irrigation with Mailuu Suu river water is small in actual conditions (< 0.1 mSv/year). However, there is an important possibility that triggered by an eathquake or a landslide, (part of the) tailing(s) content may be directed to the river Mailuu Suu. Doses to the affected population may increase to multiple ten mSv per annum. Given the actual limited stability of Tailing N°3, the potental of such a disaster to occur isnon-neglegible. To impede the consequences of a potential disaster, under the TACIS project different remedial options are evaluated for Tailing 3 including in situ stabilisation and tailing translocation. Also more global remedial options for the Mailuu Suu River valley are studied (translocation of other tailings, tunnel to deviate river, partial protection of river from landslide blockage). It was proposed to acquire a phased approach in time performing urgent limited stabilisation options for Tailing 3, improve the stability of the Tailing 3 by COLMIX-columns in the medium term, while investigating and evaluating further two long-term remedial options: the translocation of the tailings and the long-right-bank river diversion tunnel.