Environmental Dredging of a Chromium Contaminated Fjord in Valdemarsvik, Sweden
Type:
Presented during:
WODCON XX: "The Art of Dredging" - 2013, Brussels, Belgium
Authors:
Pensaert S, Nollet H, Rombaut E, Lepere X
Abstract: The sediments in Valdemarsviken are contaminated with chromium from earlier discharge of untreated wastewater from tannery operations. The remediation of Valdemarsviken is very important for the water quality in the Baltic Sea. Contaminated sediments in the inner part of Valdemarsviken must be dredged, dewatered, stabilized and placed as fill on land. Dredging of the sediments in these areas will affect the stability conditions along parts of the shores and require the stabilization of quays, shores and the landfill area by limecement columns. The dredging of contaminated sediments covers about 200,000 m³ spread over a 350,000 m² large area. During a detailed design phase, prior to the start of the works, the site conditions and sediments were monitored and investigated thoroughly. Lab scale tests were performed to verify that the chosen process for the dredging, dewatering and stabilization meet the set requirements as regards to strength of the backfilled stabilized sediments specified by the client. The dredging operation should meet as well the stringent environmental demands towards turbidity and the generation of spill. The sediments will be dredged by using a hydraulic excavator equipped with a level-cut clamshell bucket. The dredged sediments will be pumped to a continuous mixing unit where sediments will be stabilized with a binder based on cement.
Keywords: environmental dredging, soil reinforcement, stabilization of sediments, level-cut clamshell