Hydropower is an important source of renewable energy. Due to ageing infrastructure, more and more existing hydropower plants have to be refurbished and modernised. This includes a complete review of the design parameters as well as the change of specific parts. Investments should be targeted to improve the overall performance of hydropower plants and ensure a long lasting life extension. This paper presents the concept of the submerged wall as a local high point in the headrace tunnel, which can—in combination with the intake gates—replace existing penstock shutoff valves. Such a replacement was conducted for the hydropower plant Schneiderau in Austria, which also allowed us to prove the concept based on measurements including a simulated break of the penstock. The presented solution can help to reduce investment costs and also minimise maintenance efforts and therefore is an attractive option for classic penstock shutoff valves for comparable projects.

The construction site is located close to the Spullersee, one of the most impressive mountainsides in the Alps, and is part of the ÖBB Spullersee power station, which is used to generate green 16.7 Hz traction current. The Spullersee, a formerly natural mountain lake, is located over 1800 m a.s.l.in the municipality of Dalaas in Vorarlberg. After almost a century of generating electricity, essential parts of the plant have reached the end of service life, resulted in essential facility renewals as well as numerous operational optimizations in the last two years. In a first construction phase, a new access tunnel to the existing apparatus chamber had to be excavated before seasonal winter closure of the access road. For the winter construction phase, thousands of tons of building materials were stored on the construction site in order to replace the old system parts in the area of the lake‐side apparatus chamber after the Spullersee had been completely emptied. Due to high‐alpine location of the site in one of the snowiest regions in Austria, not just working in winter was challenging, but also access. In winter the site was achieved only by using a small cable car and a narrow footpath through the almost two‐kilometer‐long pipe tunnel. This was not everyone's cup of tea.