The dam, in a river near Malmköping, south of Stockholm, raised water levels by one metre, forcing dirty water into the local water treatment works.
The Sörmland County Administrative Board has now given permission to Flen municipality to demolish the dam, but has warned that the beavers’ lodges must not be destroyed.
Olle Skantz, the municipality’s animal expert, said he feared that the beavers would be eager to reconstruct the dam immediately.