Kyshtym disaster

Only after the Chernobyl reactor explosion in 1986 did the Soviets begin to reduce the amount of waste poured into Lake Karachay.

An excerpt from the article 42 facts about Kyshtym disaster

They also began to backfill the lake. However, they did it very ineptly and explained it by lack of funding.

With the funding received from the West (the US and the EU) after the collapse of the USSR, the plan to backfill Lake Karachay was successfully implemented in 2016. Currently, there are about 60 million Ci of cesium and strontium in the former lake.