Rehabilitation of Urft Dam - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 787

Figure 24.20 Inspection galleries, drainage and monitoring, cross-section (Wittke et al. 2012)
Even at the first impounding of the dam in 1905, wetness was observed at the down-
stream side, indicating seepage through the dam. This shows that the old drainage
system was not effective even from the very beginning. Reconstruction was therefore
inevitable.
In addition, monitoring devices for the calibration of the three-dimensional analysis
model and the long-term observation of the dam were installed (Figs. 24.5 and 24.20).
All rehabilitation works were carried out during operation, except from a short tem-
porary drawdown of the Obersee for sealing the bottom outlets. At the same time, the
cascade steps of the spillway and the dewatering conduits were renovated.
The most important rehabilitation measures were the excavation of the two inspection
galleries and the reconstruction of the drainage system.