Hydropower plant Heiterwang is a pumped storage facility operated by Elektrizitätswerke Reutte (EWR) in the Tyrolean Außerfern region. The power plant, which originally commenced operation in 1977, …

… is supplied by the upstream Rotlech water reservoir, which has a capacity of 1.3 million m³. As part of a project to bring the gate construction up to the latest technical standards required by the reservoir review committee, the gate was equipped with a second bottom outlet sluice gate. Three Austrian providers with a proven track record were contracted for the required work.

As for planning, EWR relied on the experience of the Linz-based subsidiary of the renowned planning office of BHM INGENIEURE Engineering & Consulting GmbH. BHM INGENIEURE specialises in interdisciplinary planning services for industrial, traffic and power plant operations, with a long list of successfully completed national and international projects to their name. Dipl.-Ing. Rudolf Kandler, who managed the project on behalf of BHM, describes the planning process: „First off, we had to work out a modification concept that would allow the turbine to be operated during the upgrade work.” „The concept called for the integration of a new the maximum storage level of the reservoir was slightly reduced,” adds Ing. Georg Hauser, Head of Production at EWR.

PROFESSIONALS AT WORK
The contract for the delivery and installation of the new gate and hydraulic system was awarded to Braun Maschinenfabrik GmbH from Vöcklabruck in Upper Austria. The gate consists of a pressure-tight steel enclosure, which had to be manufactured in and installed in several parts (i. e., the gate body and the hydraulic system) due to the required dimensions and the difficult installation conditions. Control of the gate is effected by means of an integrated hydraulic cylinder with a piston diameter of 300 mm and 2,780 mm of travel. Despite the difficult conditions, the specialists from Braun Maschinenfabrik managed to install the new components with technical perfection. As a prerequisite for installing the new sluice gate, the team first had to complete the demanding task of excavating more than 100 bottom outlet sluice gate into the existing downstream gate construction. To be able to install this new gate, it was necessary to carve out a cavern from the existing concrete dam. While the construction work was ongoing, cubic metres of concrete from the gate body. This was to create a cavern in the gravity dam to accommodate the second gate. The contract for this part of the project went to civil construction company Jäger Bau GmbH from Schruns in the Austrian province of Vorarlberg.

DAM CONSTRUCTION BROUGHT UP TO LATEST TECHNICAL STANDARDS
The main requirement with regard to the excavation work was the need to proceed carefully with the drilling, cutting and manual excavation work to ensure the required precision. The excavated material, which was partially steel reinforced, had to be disposed of through the 15 m bottom outlet, which was also used to bring in the new parts. This passageway, as well as an existing narrow inspection tunnel, were also used by technicians and installation engineers to get to and from the installation site. A key challenge in this project were the very limited spatial conditions under which the team had to complete the entire concrete and hydraulic steel construction work. In the end, a special telescopic handler vehicle was used to carry the around 20 tonnes of steelwork engineering equipment through the bottom outlet and set it up in its intended location with millimetre precision. In addition to the 2.7 m x 2.7 m gate section the Braun engineering team also installed the hydraulic power unit required for operating the gate. Equipped with redundant hydraulic pumps, the drive module works based on biodegradable oil and can be operated in parallel with the existing hydraulic power unit via multiway switching.

EXCELLENT COLLABORATION
Following completion of the heavy haulage and potting work in December 2014, the installation of the hydraulic and electrical components as well as the integration into the power plant’s control grid were completed in January of the following year. The final commissioning and handover of the new gate took place in March 2015 in the presence of representatives of the reservoir review committee and an expert on hydraulic steelwork engineering. Highlighting the excellent collaboration between the project partners, EWR’s company magazine described the project as a complete success. Rudolf Kandler from BHM INGENIEURE could not agree more. Like the contributing steelwork and construction engineering firms, BHM have added another successful project to their list of references.