Feedback on the removal of the Kernansquillec dam

Abstract

Kernansquillec dam in French Britany has been demolished in 1996. It was a multiple arch dam, 75-year-old, 15 m high, with a reservoir capacity of 400 000 m3. Due to the poor condition of the dam, risks involved downstream, and lack of an operator after the end of the concession, the Prefet decided the dam demolition. Management of the sediments, representing 50% of the reservoir capacity was achieved without interrupting water intakes for domestic water supply and fishfarming, situated few hundred meters downstream from the dam. The solution combined: hydrodredging of 90 000 m3 of sediments to restore the old river bed in the reservoir; in situ consolidation of the rest of the sediments, by slowly lowering the reservoir water level; construction of four little rockfill weirs downstream from the dam, for water decantation at the end of emptying. Total cost of the operation was just over 1 MA, including 0,6 MA for sediment management.