DEC (DEME Environmental Contractors) decontaminates heavily polluted fjord in Sweden
Antwerp, 23 January 2012 – DEC, the environmental branch of the Antwerp Dredging, Environmental and Marine Engineering (DEME) group, has just signed a contract to clean up the Valdemarsviken, Sweden’s only fjord and popular leisure area in the south-east of Sweden. A 30 million Euro contract was awarded to DEME Environmental Contractors (DEC) and involves removing and storing sediments contaminated with chromium and mercury. This will be an extremely delicate operation that must be carried out according to the highest possible environmental requirements.
The Valdemarsvik fjord stretches out over a distance of 12 km and ultimately runs into the Baltic Sea. It is a popular destination for boat trips, swimming, fishing and excursions to the Gryt archipelago. Further expansion of the tourism industry at this location is planned by the municipality. The bottom of the fjord, however, is heavily polluted with chromium and low levels of mercury, deposited as a result of industrial processes in one of Scandinavia’s largest tanneries between 1873 and 1960.
There is considerable contamination and chromium has been finding its way to the Baltic Sea for years on end. The polluted layers on the bottom of the fjord are up to 2 m deep.
The working environment is exceptional for two reasons. On the one hand, the slopes are very steep but, on the other, the surface sediment has an extremely loose structure. The combination of topography and low stability means that even moving a relatively low volume could lead to landslides.
DEME Environmental Contractors (DEC) will work with extreme caution and the very highest standards for limiting turbidity will be applied. The dredging itself must take place in an environmentally-friendly manner and, in this case, involves removing thin layers of the polluted sediment one after the other. The dredging zone encompasses 350,000 m². Calculations have shown that 400 tons of chromium must be removed and that this will reduce the spreading of chromium by 90 percent.
Before dredging commences, a range of soil improvement works, infrastructure and demolition works must take place. After dredging, dewatering and stabilising, the polluted sediments will be stored in a specially designed land fill nearby. Once filled, this will ultimately be sealed.
The remediation work in Valdemarsvik is scheduled to be completed before the end of 2015.
DEME Environmental Contractors (DEC) was founded in 2000, when the parent company DEME consolidated a series of environmental companies that had been set up during the 1980s. DEC has grown very quickly both in Belgium and abroad and has carried out important projects in various locations. These projects included the remediation of the site for the London Olympics; an innovative project for sludge recycling in the port of Antwerp, known as ‘Amoras’, and the remediation of former gas work sites in Dublin and Chesterfield. In Sweden, DEC has a head office in Malmö and has been active there since 2003, when a pioneering project began in Hultsfred. The sectional environmental dredger ‘Pixie’ was used to clean up two lakes contaminated with mercury. During Sweden's largest environmental remediation project EKA-Bengtsfors, DEC cleaned up mercury and dioxins from polluted soil. DEC also works at other locations in Sweden; over the past few years work has taken place in Stugsundsudden near Söderhamn (wood impregnation); Stenborgskanal in Gävle (gasworks); Fagervik in the municipality of Timra (sulphite factory).