A new-intrusive monitoring method to detect the local drop of wall stiffness of shafts and tunnels at hydro plants has been developped in Switzerland. The method is based on the waterhammer and the fluid-structure interaction phenomenon. An overview is presented here of the status of the ongoing work in this field, includes a short state-ot-the-art-review, a description of the physical scale model with some tests results, and a description of an in-situ measurement system which acquires pressure records from the shaft of a pumped-storage in the Swiss Alps.