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KOSHKAR-ATA LAKE CASE STUDY: The hazardous legacy of an uranium mine

 

Koshkar-Ata is one of the largest industrial tailings in the world occupying an area of approximately 77 square kilometres. Located in a natural depression about 5 kilometres from the outskirts of the Kazakh town of Aktau and 8 kilometres from the shore of the Caspian Sea, the enormous dump is a serious environmental and health hazard. 

Before industrial activities started in the 1960s, the Koshkar-Ata hollow was a periodic lake rich in natural salt, making it unsuitable for farming. The discovery of vast uranium deposits in the deserts of western Kazakhstan lead to the establishment and rapid development of a uranium extraction and processing industry. At its peak in the 1980s Kazakhstan was producing more than one third of Soviet uranium, with more than 30 uranium mines. 

The Koshkar-Ata depression was chosen as a convenient location to accumulate radioactive and toxic waste from the chemical and hydrometallurgical complex in the newly-founded city of Shevchenko (now Aktau, with about 176,000 inhabitants). The complex produced, among others, uranium concentrate mostly for Soviet military purposes. Falling prices on the uranium market due to changes in military priorities, gradually decreasing uranium concentrations in the mines and the overall economic crisis in the post-Soviet world of the 1990s led to reduced output and ultimately complete stoppage of uranium milling in 1999. The lake is still used as a dumping ground for commercial and production waste, oil extraction sludge, etc.

In the years of uranium production, 356m tonnes of mining waste with a total radiation activity of 11,242 Curie were channelled into the Koshkar-Ata tailing pond. Uranium mill tailings with low to medium-level radioactivity account for almost 105m tonnes of the total. Significantly increased exposure rates at 80 to 150 micro roentgen per hour (µR/h) were measured in the southern part. 

Currently, about half of the tailing surface is covered with water from industrial operations. It is however estimated that the tailing pond will dry out within a few years due to high evaporation and the lack of water, with no more waste water flowing in from the shut-down factories. In the southern part of the hollow, a 12- to 14-square kilometre section is already exposed to the air. This part has the highest concentration of contaminants, covered with solid waste giving off high levels of radioactivity. Constantly swept by strong winds, there is a serious risk of pollutants being dispersed. Large amounts of phosphoric gypsum, a by-product of fertilizer production, were discharged into the lake. The gypsum has formed a crust on the surface, preventing dusting and the escape of radon. As a result, dispersal of dust-blown substances and radon emissions are limited, and local scientists conclude they do not currently constitute a health hazard.

The obsolete infrastructure from former uranium open-cast mines and processing facilities constitutes an additional risk of exposure to radioactive material. Among the industrial dumps and derelict industrial equipment there are several radiation hotspots exceeding 1,500 to 3,000 µR/h, as against natural radiation in Kazakhstan of 10 to 15 µR/h. The local population and temporary migrants from the neighbouring Uzbek Republic of Karakalpakia are illegally dismantling the infrastructure, to sell the scrap metal as a raw material for new construction. But potential customers are inclined to reject highly radioactive parts, and the sellers simply dispose of the material elsewhere in the countryside.

Aktau is also home to a nuclear power station, now shut down. Decommissioning of the fast-breeder reactor is under way, with extensive international support. Spent fuel is stored on-site, as are 1,000 tonnes of radioactive sodium. 

But radiation does not seem to be a major concern for the local authorities. They are more concerned that pollutants might migrate through groundwater and contaminate the Caspian Sea located just eight kilometres away. At present, there seems to be no hard evidence that pollutants have reached the Caspian Sea. According to recent monitoring data, elevated levels of contaminants in the groundwater as well as the soil are currently limited to a strip 2 to 4 kilometres wide around the lake. Contamination includes high concentrations of toxic metals (molybdenum, lead, manganese, strontium, etc.), rare-earth elements and radio nuclides. The situation is clearly precarious, as a rise in the level of groundwater could cause more widespread dispersal of pollutants.

Reclamation is costly (according to the Kazakh press estimates exceed 10bn tenge (€62m)) and the measures taken so far are only a temporary solution. To prevent pollutants from reaching the Caspian, with its rising water level, and delay the moment when the Koshkar-Ata will dry up, exposing the entire surface to the wind, millions of litres of water are being pumped into the tailing pond every year, at a cost of 5.5m tenge (about €34,000). At present annual total expenditure on the tailings deposit amounts to 300m tenge (€1.86m).

The concern expressed by local environmental authorities and the population about the state and future of the Koshkar-Ata lake will hopefully grow strong enough to induce longer-term rehabilitation of Koshkar-Ata. As mining worldwide is becoming attractive again with rising prices for resources, financing might become more realistic.