Residual pollution means an area or aquatic environment which has been polluted as a result of human activity in the past or hazardous substances which have been left unused in the environment and which may damage the health of the local people, as well as the wildlife.
Three sites will be cleaned of residual pollution:
- the territory of the former tyre factory in Kohta-Nõmme,
- the bed and banks of Erra River,
- the territory of the Pahnimäe asphaltic concrete factory.
Residual pollution was eliminated from the territory of the former tyre factory in Kohta-Nõmme in 2020. In total, 14,000 cubic metres of heavily polluted soil and 100 cubic metres of residual oil were removed. Polluted soil was extracted to the depth of two metres, up to the limestone layer. The most heavily polluted area was removed completely – there are no more semi-liquid oil residues on the ground. The works completed will improve the state of groundwater in the future and will help to improve the condition of Kohla and Purtse Rivers.
From the bed and banks of Erra River, the pitch which has been deposited on the bottom of Uhaku karst area will be removed in the extent of 1.5 km. The thickness of the pitch spots on Erra River ranges from 10–30 cm, reaching half a metre in some places. The estimated total volume of the pitch spots is 14,700 m³. It can be found as a separate layer as well as mixed into the soil on the riverbanks. The pitch will be removed with excavators and transported to a facility. After elimination of the pollution, the area will be fixed up, cleaned areas will be levelled, and the river habitats will be restored.
The soil of the Pahnimäe asphaltic concrete factory is polluted in four areas. Surveys show that the polluted soil layer reaches up to 7 m into the ground. As the soil is highly water-bearing and the groundwater low-lying, hazardous substances have spread deep into the ground with storm water. Based on a survey which was conducted in 2005, the estimated total volume of the polluted soil amounted to 21,300 m³. As the territory is in use, it is not possible to remove the soil. Thus, tests will be performed to identify the best technology for cleaning the soil which would not call for extraction of the soil. In the course of those operations, the appropriate technology for cleaning the entire site will be identified and used for cleaning 340 m³ of land.