The Ketelmeer: highly sophisticated remedial dredging
Type:
Presented during:
WODCON XVII: "Dredging in a Sensitive Environment" - 2004, Hamburg, Germany
Authors:
Hans F. Hardeman, Wytze van de Herberg, and Koos Spelt
Abstract: For years, a large section of European industry has discharged its wastewater into the catchment area of the river Rhine. The flow of the river transported millions of cubic metres of heavily contaminated sludge to its estuaries. One of those estuaries is the Dutch Ketelmeer. The Ketelmeer is an important link in the management system for fresh surface water and there are also plans for transforming part of it into a nature area. It was therefore inevitable that cleanup operations would be required for the bed of the lake. After the construction of a depot for dredged material, the major cleanup operation started in 2000. More than 7,000 samples were taken to establish a precise picture of the distribution of the contamination. In order to prevent the dredging and storage of clean material, this sampling and dredging operation had to be completed using extremely tight tolerances. Requirements for both horizontal and vertical positioning were extremely strict. Dredging and completion of the remediated areas had to be precise to within centimetres. Special remediation equipment was used but it was not permitted to move the material underwater and the dredging process was not allowed to result in additional contamination of the surface water. Despite these criteria, 6,000,000 m3 of heavily contaminated sediment with an average thickness of 0.60 m was removed within two years from the five-metre-deep lake bed and stored in a depot.
Keywords: Remediation, lake bed, lake-bed cleanup, environmental dredging, dGPS