The pumped storage hydro power station at Glarus is being expanded. One element of the project involves enlarging the capacity of the equalising reservoir in the valley.

To achieve this,WALO is working on providing a second equalising reservoir to the north of the current one.A channel linking them will allow water to move between the two so their levels correspond.
The existing terrain forms the east side of the reservoir while a dam is being raised on the west side of the new reservoir.
The crest of the dam will be 813 metres above sea level while the base of the reservoir will be 11 metres lower. The new reservoir is located within a groundwater protection zone which means the work has to meet a number of special requirements.

Once the profile of the new had been prepared by the excavation contractor, it was covered with a layer of filter ballast.A binding layer was then applied followed by a sealing layer and a coating of mastic which protects the reservoir lining against the elements and UV radiation.An asphalted road on the crest of the dam has also been built to allow access for operators and maintenance staff during the service life of the facility.