Extensive remedial works were undertaken between 1999 and 2001 to strengthen the dam wall. This work involved removing the top of the existing dam wall and drilling/blasting through the dam wall plus up to a further into the bedrock below. The top section of the wall was then rebuilt using reinforced concrete. Finally, permanent, re-stressable ground anchors were then installed through the formed and drilled holes from the crest to be stressed and grouted into the foundation rock. At time of completion, these were the largest capacity and longest permanent ground anchors ever installed in the world.