Redesign
However details regarding the redesign are available. The redesign calls for improvements in the pipe's lining as well as the addition of grouting around the penstock to reduce water flow between the penstock and the surrounding rock due to dynamic variation of the pipe diameter during operation (it expands due to water loading during operation then contracts when the load is removed, leaving a gap). The damaged section of the penstock was rerouted around the previous location to where new (undamaged) more stable rock is available. Construction on the redesigned penstock was completed in 2009. Redesign considerations include operational control of maximum agreed design limits under all conditions of assembly, design and service conditions (including water hammer pressure spikes).
Read more about this topic: Bieudron Hydroelectric Power Station