Skagerak has modified and reinforced the needle dam at Dalsfos. The upgrading was carried out from November 2012 until July 2014.
The dam at Dalsfos was built in 1903 and is Norway’s first gravity dam made of concrete, with cut stone set in concrete on both the upstream and downstream sides. During the rehabilitation, the row of needle-like bars was filled in with solid concrete and the downstream side of the dam was faced in cut rock. The concrete on the upstream side was clad with false wooden bars to maintain the visual impression. To increase the dam’s stability, 28 rock anchors were installed that go through the dam and are fixed 12 metres into the bedrock below.
New flood diversion system
The row of wooden bars was removed because it does not meet the current safety requirements for flood diversion. It was replaced by a hydraulic sector gate, which, together with a similar gate from 1994, now makes up the dam’s flood diversion system.