In the Glarner Alpes, about 90 km south-east of Zurich (Switzerland), construction has begun at an altitude of 2,400mabove sea level on a 1,000MWhydro-power plant. The machine and the transfomer cavern are situated in Quintner limestone under 400–500m overburden. After the initial project design, their location had to be moved in accordance with the findings of additional geological investigations. Sensitivity analyses of rock mass parameters indicate also that the planned rock bolting system needs to be adapted.
The demand for sustainable power generation together with the accelerated retreat of glaciers and the predicted change of rainfall regimes urges Switzerland to economize its water resources. Underground pumped storage plants supply valuable peak electricity while minimizing the impact on the natural heritage and the water consumption. The power stations belonging to the Linth Limmern AG (KLL) in Glarus were built between 1957 and 1968. From a catchment area of 140 km2 they produce about 460 kWh per annum. By virtue of their pumping capability, however, their significance in providing peak-load energy across Switzerland is much greater.
A gravity dam will be built at lake Mutt to raise its current natural level of 2,446m to 2.474m a.s.l., thereby inceasing its storage capacity from 9 to 25 million m3. The newLimmern power station will be installed about 600m inside the mountain at approx. 1,700m a.s.l. at the foot of lake Limmern (Fig 1). Access to the underground caverns will be provided by cable car trough a 4 kmlong tunnel from Tierfehd, where an additional compensating basin is presently built to enable the machines to be used more flexibly for turbining or pumping and to improve the regulation of flow in the river Linth.
