“Sorting out the environmental problems related to the site aren’t only important to Estonia but to all of the countries on the Baltic Sea,” said Tõnis Kaasik, the director of AS ÖkoSil. “It has been one of the European Union’s regional pilot projects. The financing scheme put together to resolve the issue is unique for involving so many different parties, and it sets a great example of cooperation to others.”
The project was launched in response to the environmental hazards the facility posed. Shoreline defences were erected from granite boulders as part of the remediation work in order to prevent erosion, thanks to which the tailings pond is protected against erosion from the sea and the effects of waves. Stability has been guaranteed using reinforced concrete buttresses on the sea-side of the pond and balanced dams at the right angles. In order to avoid pollution, a water re-routing system (with a wall built into the soil and deep drainage) was constructed to prevent waste from seeping into the sea. Surface water is now being routed past the tailings pond and ground water has been reduced to a level lower than that of the waste.
The tailings pond has been covered in a mixture of oil shale ash and various natural materials to a thickness of up to 13 metres. The use of layered covering was designed to provide the pond with the desired shape and a safe angle for its slopes. The final cover is made up of five different layers of soil, the most important of which is the lower, water-tight layer of clay. On top of this are different layers of soil performing various functions. The cover has been landscaped so as to avoid erosion and to achieve the optimum moisture regime. The cover is 2.1 metres thick and its construction involved 1.1 million m3 of different soils. The highest point of the hill with the cover in place is now 38 metres above sea level.
Design work on the covering and shaping of the tailings pond was carried out by the German company Wismut GmbH, that has extensive experience in planning and performance of similar remediation work in former mining regions in Germany.
The following threats to the environment have now been removed:
1. The covered facility looks like a grassy hill, which water cannot penetrate.
2. Radiation has been reduced to natural levels.
3. The chain of reinforced concrete buttresses constructed on the shore guarantees the stability of the dam, and shoreline defences have also been erected to combat the erosive effects of the elements.
“The Sillamäe uranium site has been one of the EU’s regional pilot projects,” Kaasik said. “Similar remediation projects have been carried out in Hungary, Slovenia, the Czech Republic and elsewhere in Central and Eastern Europe.”
One of the agencies behind the launch and organisation of the project was the Estonian Ministry of Environment.
The consultants on the project were Wismut GmbH, OÜ IPT Projektijuhtimine and
OÜ E-Konsult. Its contractors were AS Geotehnika Inseneribüroo G.I.B., AS Eesti Ehitus and AS Aspi. AS Silmet Grupp and the Port of Sillamäe acted as cooperation partners.
The total cost of remediation of the Sillamäe tailings pond was more than 21 million euros (330 million kroons). It was financed by the European Union’s Phare programme, the Nordic environmental fund NEFCO and the governments of Norway, Denmark, Finland and Sweden, in addition to Estonian funding from the state budget and through the Environmental Investment Centre.
Further costs were incurred by AS Silmet in reorganising its production processes.
On the 28th and 29th of October the international conference ‘From the past to the future – a retrospective on the Sillamäe tailings pond remediation project and the future possibilities of nuclear energy’ is being held by the Estonian Ministry of Environment and AS ÖkoSil at the Jõhvi Concert Hall.
The remediation of Sillamäe’s uranium tailings pond is the biggest environmental project of its kind ever undertaken in Estonia.
The facility was constructed in Sillamäe as a secret Soviet uranium plant in 1948. Uranium was produced at the site from mined Dictyonema shale between 1948 and 1953, after which it was produced using uranium ore imported from elsewhere in the Soviet Union and other Eastern bloc countries until 1977.
The Sillamäe radioactive waste storage facility is located on the western side of the town of Sillamäe in Ida-Viru County. At its closest point it lies just 30 metres from the shores of the Baltic Sea. The tailings pond covers an area of a little over 50 hectares. It contains 8 million m3 (12 million tonnes) of waste at a thickness of almost 20 metres.
The tailings pond contains toxic and hazardous waste from the processing of uranium ore – primarily residue from uranium, thorium and other radionucleides and heavy metals, as well as nitrogen compounds, acids and other chemicals. Oil shale ash from heating power station was also stored at the facility.
Preparations and design work on the remediation of the Sillamäe tailings pond began in 1997. One year later Estonian government and AS Silmet Grupp established a separate company for this purpose: AS ÖkoSil, specialising in environmental technology and waste management. Construction work lasted from 1998 to 2008.