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Limberg II pumped storage power plant

Facts and Figures
Company PORR Tunnelbau GmbH in a consortium
Principal VERBUND – Austrian Hydro Power
Location Kaprun - Austria
Type Power plant construction, Tunneling
Runtime 03.2006 - 10.2011

Even more power for Kaprun power plant.

Designed as a balancing and control power plant, the Limberg II pumped storage power plant was built in the area of the existing Glockner-Kaprun power plant. For this purpose, the two existing annual reservoirs of Mooserboden and Wasserfallboden were connected with a new headrace with a length of about 5,500m. The power plant consists of a tunnel and a pressure shaft inclined at about 45°, which opens via the distribution piping into the new power cavern. Both new machine sets with a capacity of 240MW each are located in this. The integration in the Wasserfallboden Reservoir was provided via a tailrace tunnel with a length of around 550m. The power plant construction site was safely made accessible for winter using a 5,500m long access tunnel to the Limberg Dam. In the underground construction of all facilities, the greatest possible consideration for nature and the ecological balance was placed in the foreground.

The 4,200m long headrace tunnel was largely driven through mechanically with an open hard rock tunnel boring machine whose break-out diameter was 7.03m. The headrace gallery of this tunnel consists of a 40cm thick unreinforced, in situ concrete inner shell, which connects to a 2.05m wide base segment. An open hard rock tunnel boring machine with an excavation diameter of 5.80m was also deployed for the break-out of the 770m long pressure shaft. The lining of this shaft occurs by means of steel armouring, the annular gap between break-out embrasure and armouring was filled with flowing concrete.

A 62m long, 25m wide and 43m high cavern was created inside the mountain for both machine sets – for this, a break-out of a total of 57,000m³ of rock occurred. Three chord lattice arches, three-layer reinforced sprayed concrete with 35cm thickness and a norm anchoring from 6m long SN, short for Store-Norfors, and 15m long long-term single rod anchors serve as break-out preventers. In the Mooserboden Reservoir, an inlet or outlet construction separates the two existing dams at around 2,000m above sea level.

The main challenge in this project arises from its very extensive and dense construction program. In particular, the large number of attack points, that lay partly in the high alpine area, put enormous demands on site planning and logistics.