The Estonian waste depository is located near the town Sillamäe, on the shore of the Gulf of Finland. It occupies 50 hectares and the total amount of radioactive waste amount there is 12 million tons, half of which half originates from the enrichment of uranium.
Uranium mining and production in Sillamäe was started in 1947. It was a top secret industrial town then. Uranium beneficiation in the Sillamäe metallurgy factory was started in 1948. The technology was primitive, so, as a result, a large part of the uranium was left in solid waste. This production was found to be inefficient and the factory switched to other raw materials, but the uranium beneficiation process was stopped completely only in 1989.
However, the waste continued to flow to the Sillamäe depository – from 1950 to 1977, the uranium ore, more than four million tons, was obtained from Middle Asia and Eastern Europe. The estimated amount of elementary uranium in the U3O8 concentrate produced was almost 25 000 tons.
From 1971 to 1989, pre-processed uranium raw material was imported. The estimated amount of elementary uranium in the U3O8 concentrate produced was 74 000 tons. Additionally, from 1982 to 1989, 1350 tons of UO2, containing 40–80% uranium, was imported to Estonia.
The existence of such a site presents a significant environmental threat to both the coastal zone and the Gulf of Finland. Coastal erosion could affect the structural integrity of the waste depository site. In 1997, in order to protect the highest risk regions from flooding or erosion, preliminary coastal defences were constructed. In 1998, Estonia applied moreover for financial assistance from the EU and the other Baltic states in order to reduce the environmental risk posed by the site. The project included the complete covering of the site and the construction of a small channel to redirect rainwater directly into the sea and thus mitigating contaminated rainwater infiltration of the depository.