Countless lakes and woods are Sweden’s most important environmental asset. Nevertheless, the forestry industry – and the paper industry in particular – have severely contaminated the lake beds with unmonitored discharges and dumping, leading to unacceptable levels of mercury being present.
In this case, the sediment was located in two lakes near the City of Hultsfred.
In the summer of 2006, DEC, in a joint venture with sister company Dredging International, dredged 265,000 m³ of contaminated sediment utilising the “environmental dredging technique”, which prevents contaminated sediment from polluting surrounding waters during dredging.
After dredging, the sediment was pumped to a disposal site and a system of geotubes was used for dewatering the sediment. Geotubes, which have a diameter of a few meters and are 50 to 100 meters long, can be linked to a type of “stocking” made of geotextile.
Sludge is essentially encapsulated and protected from the surrounding soil. Water that comes from the dewatering process is then purified before discharge.
The project lasted three years because the harsh winters limited the operational period to eight months a year. The disposal site was covered over in the summer of 2007.