The Alpbach stream rises at 1,584 metres above sea level (m.a.s.l.) in the upper section of the Erstfeld Valley. As it flows eastwards, and before it finally gushes into the river Reuss at 466 m.a.s.l., it has supplied up to 7,200 households with power since November 2020. A small hydropower plant was built on the Alpbach at Erstfeld in record time.
The use of hydropower in the canton of Uri dates back about one hundred years when the first attempts to dam the Fulensee lake were made. The issue of obtaining energy from the Alpbach stream was discussed on many occasions in past decades until EWA-energieUri AG finally managed to obtain definitive permission to build a run-of-river hydropower plant in 2018. A total of two and a half years passed between the first signature and generation of the first kilowatt. This was a masterly performance, achieved thanks to collaboration among 45 participating companies. One of these companies was Josef Muff AG, which was contracted to install the pressure pipe and carry out the construction work between January and November 2020. To generate power, the water is diverted at 730 m.a.s.l. in the Schopfen area and channelled via the new catchment into the pressure pipe, which is about one kilometre in length. Three turbines and a synchronous generator are installed in the power plant, located at a height of 484 m.a.s.l., so the region can be supplied with electricity generated from hydropower.
We manufactured the 1,000 m, DN 1400 steel pipe that carries the water through a new tunnel built for the power plant. The construction work on the pressure pipe was carried out in two major stages, for which the pipe sections had to be delivered individually in lengths of six and twelve metres. We engaged Wipfli AG as the haulage contractor. Thanks to their many years of experience and know-how, transportation of the pipes on the narrow mountain roads was handled smoothly and punctually, with no incidents. In the first phase of construction, the pipe was installed in the inclined shaft. The gradient here was at an angle of 53°, which did not make the work particularly easy. The pipe was gradually lowered into the shaft on two cable hoists after each pipe section was welded on. The longer section of the pressure pipe was completed in the second stage. For this 770 m length, the individual sections were lifted backwards over the entire distance and welded together directly in the tunnel. Delivery of the 12 m pipe sections called for good coordination and plenty of intuitive skill because there was not much room between the truck and the tunnel wall.
To protect the pressure pipe against rust and other damage, and to ensure a long service lifetime, it was treated with a special anti-corrosion product from TEKO Oberflächentechnik AG at the end of the process.
Josef Muff AG can look back on an outstanding and unique project that presented many challenges. It would not have been possible without know-how, precise time management, accurate planning and a high degree of coordination. Thanks are due to EWA-energieUri for awarding the contract and placing their trust in us.