Additional work in tunnel delays start of Reisseck II operation

8/2/2015Mühldorf, Reißeck

Supplementary sealing measures in the headrace tunnel lead to prolongation of the commissioning into spring 2016.

The startup of the new Reisseck II pumped storage plant will be prolonged by several months in order to improve the water tightness of the headrace tunnel, a requirement for decades-long unrestrictedly flexible operation. In standard operation, starting from spring 2016 Reisseck II will be able to provide an output of 430 Megawatts within seconds.

After a four-year construction period, VERBUND began the commissioning of the new pumped storage power plant in March 2015. In the process, water has already been conducted onto the turbines of Reisseck II, first test programmes executed and settings for the machines, each weighing more than 200 tons, undertaken in the mountain. In these tests, detailed pressure and leak tests were also carried out for the entire tunnel system. The assessment showed that in certain sections of the 2.7-kilometre-long headrace tunnel additional sealing measures are necessary in order to eliminate the need for improvements in the subsequent, decades-long operation of the power plant.

The headrace tunnel, with an internal diameter of 6.2 metres, forms the connection, equipped with concrete rings, between the Mühldorfer Lake on the Reisseck lake plateau at an altitude of 2,300 metres and the power plant cavern of Reisseck II in the Mühldorfer valley at an altitude of 1,600 metres. In this tunnel, 80 cubic metres of water per second will be conducted to the pump turbines at full capacity in order to thus generate electricity as needed. During pump operation, water will be pumped out of the lower basin through the same system back to the Mühldorfer lake and stored there.

Total investment in Reisseck II comes to 400 million euros

The additional sealing measures now required in subsections of the headrace tunnel are associated with the famously complex geological relationships in individual mountain sections which have accompanied the construction of the new power plant facility from the outset. Minimal fissures that exist deep in the mountain massif were first able to be established over the course of the pressure tests and documented to the centimetre through extensive boring into the surrounding rock. Although water losses from the tunnel were already accounted for in the planning of Reisseck II and represent no safety risk, nevertheless these would mean marked losses in the efficiency of the power plant facility over a long period of time. Additional sealing measures will therefore be undertaken in the coming months. The overall investment in the Reisseck II pumped storage power plant amounts to around 400 million euros.

With this, the commissioning programme of Reisseck II will be extended by some months. The start of regular operation will take place in spring 2016. From today's perspective, the expansion of the old Reisseck rail tunnel, planned for the coming winter, is also expected to be delayed because of this. The bus shuttle transport for tourists between the mountain station of the Reisseck railway on the Schoberboden and the lake plateau can only be resumed after the completion of work in the tunnel.