At the 40m high Möhne cyclopean masonry dam a bottom gallery was constructed by drill and blast methods in the 1970's.
At the 48m high Eder masonry dam a gallery was excavated by drill and blast and in 1991 – 1994 a total of 104 anchors, 65 to 75m long, were installed each with an ultimate tensile strength of 7.5MN.
Although it appeared to suffer only minor damage in the raid at the 69 m high Sorpe earthfill dam there was a sudden increase in leakage to 180 l/sec in January 1951 which was attributed to bomb damage to the concrete core. This required the drilling of 53,000 lin m of boreholes and the injection of 4,350 tonnes of cement grout. 1,700 tonnes of clay were also used in the repairs.
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