Comprehensive environmental and restoration project
The dredging of the Karlsaue is part of a comprehensive environment and restoration project aimed at preserving the pond landscape of this historic Kassel park for the long term. Over the decades, layers of sediment up to 80 centimetres thick have built up in the water. The Hesse State Building and Property Ageuthority (LBIH) estimates that a similar clean-up last took place in the early 1980s, prior to the Federal Horticultural Show.
Protection of flora and fauna
Before the suction dredger arrived and began work, the waters around Siebenbergen Island were cleared of fish. A total of around 260 fish, including eels, bream and pike, as well as around 860 mussels, were removed from the basin and released into the Fulda.
On-site extraction and treatment
In the course of the clean-up operation, the sludge is gently extracted from the riverbed using a floating dredger. The sludge-water mixture is then pumped through a pipe approximately 400 metres long to a mobile sludge dewatering plant on the edge of the Karlsaue. In preparation for disposal, the sludge is treated in three stages:
- Removal of coarse particles such as branches and stones
- Separation of sand
- Sludge dewatering in centrifugesn
Sludge disposal
All components are disposed of separately: the water separated from the sludge is returned to the basin via a second pipe. The treated sludge, with a residual moisture content of around 50 per cent, is professionally collected by BAUREKA Baustoff-Recycling GmbH and disposed of in a controlled manner at a landfill site in Lower Saxony. Due to its contamination from environmental pollutants such as tyre abrasion or de-icing salt, it can no longer be used for agricultural purposes, as was common practice in the past.
Project completion scheduled for the end of April
For BAUREKA, the project represents a logistical task spanning several weeks: the dewatered sediments must be continuously loaded, transported and professionally disposed of. In doing so, the company is making an important contribution to sustainable waterway restoration and the preservation of the historic Karlsaue park landscape. Work on the basin is scheduled to be completed by the end of April. Whether further water areas of the Karlsaue will subsequently be dredged also depends on future budgetary decisions by the State of Hesse.
Find out more about REMEX’s subsidiary BAUREKA and its activities in and around Kassel on the German website baureka.de
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