Once again, traffic is driving along the dam crest, electricity generation is running full-steam ahead, and lake Forggensee is filled with water. After a total construction time of only 16 months, during which all participants worked at maximum capacity, remediation of the Forggensee reservoir dam in Rosshaupten was successfully completed in July 2019. After completion of the new street along the dam crest (including walking and biking paths) and other construction projects, the Rosshaupten reservoir dam was re-opened on September 12 during a festive ceremony.
After welcoming the attending dignitaries, Dr. Klaus Engels, Director Operations Hydro Germany at Uniper, praised the extraordinarily fruitful and effective cooperation on the part of all those involved and expressed his thanks with regard to smooth completion of the demanding project. Dr. Rüdiger Detsch, Director of the Bavarian State Ministry of the Environment and Consumer Protection, drew attention to the special significance of lake Forggensee as the “Pearl of the Allgäu” and praised the work by Bauer Spezialtiefbau GmbH, who went above and beyond in this project.
Uniper Kraftwerke GmbH commissioned Bauer with execution of the 13,500 m² diaphragm wall to seal the dam. This project posed a particular challenge: the diaphragm wall could only be built from the very narrow 11-meter-wide dam crest. To make things more complicated, the crest was located unfavorably on the side of the dam rather than in the middle. The diaphragm wall, which is 1 m thick and 70 m deep, includes socketing into very hard rock and was executed in two steps. First, excavation of the upper 40 m of the dam body was carried out with the help of a diaphragm walling grab on a Bauer MC 64 duty-cycle crane. The remaining 30 m, beneath the actual dam body, was excavated using a trench cutter on an MC 96 duty-cycle crane. Bauer carried out the construction work for the diaphragm wall seven days a week in day and night shifts – in other words 24 hours a day.
During the ceremony, Prof. Thomas Bauer, Chairman of the Supervisory Board of the Bauer Group, praised the outstanding work by the entire construction team and thanked all the participants for their excellent cooperation. He expressed his pride in the fact that Bauer, after completing the Sylvenstein reservoir, had the chance to remediate yet another reservoir dam in Bavaria. District administrator Maria Rita Zinnecker also underlined lake Forggensee’s great importance to the region and ended her welcoming address with well wishes for the new dam seal, the entire region, and lake Forggensee itself.
Idyllically located near Neuschwanstein castle, in an area known as the “king’s nook” in Bavaria, lake Forggensee is fed by the Lech river and serves as both a local recreational area and a tourist destination. The fifth-largest lake in Bavaria and the largest reservoir in Germany in terms of area, it also generates electricity and provides flood control when the snow melt begins in the Alps. To prepare the power plant and the flood control for the future, the dam seal was renovated by Bauer Spezialtiefbau GmbH from March 2018 through April 2019.
Eckhart Rümmler, member of the Management Board at Uniper, specifically addressed the key role that hydropower plays as part of the energy mix and drew attention to the importance of workplace safety and the overall success of the project at the Rosshaupten reservoir dam.
Source: Bauer Group
Find more information about the project in:
Jäger, S. (2019): New Diaphragm Cut-off Wall for the Rosshaupten Dam. GeoResources Journal (3-2019), pp. 10–13. Online available: here