contec Systems for Environmental Protection: Fish Ladder at Mulde Barrier Lake, Germany

Mulde Barrier Lake in Saxony- Anhalt, north of Leipzig, is a former brown coal open pit mine that was flooded in 1975. After the closure of the Goitsche open pit mine, the Mulde River was redirected for a length of 9 km and a dam was built without considering the need for fish to transit the area.

In conjunction with a redevelopment in the former open pit area and the planned realization of the European Water Framework Directive, the decision was made to install a fish pass. The new fish pass, which was built as a double slurry wall, helps migrating fish get to the other side of the Mulde Weir.

Construction of the fish pass, designed using the waterproofing method, began in 2009. This method uses waterproof concrete which takes over both the waterproofing and load bearing functions. As waterproof structures cannot be concreted in a single step, concreting had to be carried out in sections using joints.

DSI Porta Westfalica developed the necessary joint details for this structure. By using bentonite coated waterstops – contaflexactiv – and contaseal polymer expanding seals as well as recostal forming units, the special requirements of the detailed design could be fulfilled completely.

During the construction of the dam’s trough structure, the impermeability of the joint between the old and the new structure was of utmost importance. A clamping flange type detail would not have been suitable for this project. In cooperation with DSI Porta Westfalica, a combination of contec “New to Existing” composite film for fresh concrete and bentonite filled geotextiles was developed and installed.

DSI Porta Westfalica supervised this project from the planning stages to its completion, and the company also provided the detailed plans necessary for construction.