Lake Karachay

Lake Karachay is a small lake in Chelyabinsk Oblast, Russia, that became notorious in the mid-20th century as a dumping site for radioactive waste from the nearby Mayak production facility. The lake accumulated significant radiological contamination and is widely cited as one of the most polluted bodies of water on record.

Because of extensive contamination, the lake and surrounding area have been subject to remediation and containment efforts to limit further spread of radioactivity. The site remains subject to access controls and monitoring due to persistent contamination.

The lake’s contamination dates to the period when Mayak and associated nuclear facilities were expanding and used local water bodies for waste disposal. Public and scientific attention to the environmental and health impacts grew in subsequent decades, prompting containment work.

Lake Karachay is located near the closed town of Ozyorsk in Chelyabinsk Oblast, in the southern Ural foothills of Russia.

• Radiological hazard: The site is highly radioactive and entry is restricted; it is considered one of the most contaminated freshwater bodies in history due to mid-20th-century nuclear-waste disposal.
• Containment efforts: Remedial actions were taken in the late 20th century to reduce airborne dispersion, including partial infilling and containment measures.