A major milestone has been reached at the 140MW Tanahu hydropower project in Nepal with breakthrough of the 1.4km headrace tunnel achieved, meaning the project is now 50% complete.

The breakthrough was achieved on 31 March 2024. Contractor Tractebel was at the Tanahu headworks site to mark the occasion, in the presence of representatives from the Nepal Electricity Authority, the Ministry of Energy, local authorities, other contractors and project personnel.

Tractebel's team in Germany, collaborating with Canada's Manitoba Hydro International, is tasked with executing the contract for Tanahu Hydropower Limited. Their responsibilities include preparing tender documents, evaluating tenders, overseeing construction, checking designs, and providing advisory services throughout project operation and maintenance.

The first of the three construction packages (headworks; waterways, power plant, and hydromechanical works; and the 33-km transmission line) began in December 2018. The project is expected to be commissioned in 2026.

The Tanahu hydropower project is anticipated to generate approximately 1.1 terawatt-hours (TWh) of renewable energy, with an initial output of 586 gigawatt-hours (GWh) expected within the first decade. This significant contribution promises substantial benefits to both the people and economy of Nepal. The project is also poised to enhance the stability of the national grid while facilitating energy exports to neighboring countries like India, thereby furthering regional energy cooperation.

“Since the headrace tunnel is the only waterway between the reservoir and the underground powerhouse, resilience and serviceability are vital factors for the entire lifetime of the project,” said Renos Christakis, Senior Engineering Geologist with Tractebel in Germany. “For the last 29 months, the contractor’s designer, its engineering geologists and hundreds of workers, with the support and technical input of Tractebel and in particular its geologists, worked together and managed to excavate a large-span underground structure through challenging rock mass conditions; conditions that required excellent cooperation, mutual understanding, real-time support optimization techniques, diligent monitoring and above all, engineering integrity.”

Excavation and temporary support in dolomite, 50 metres before breakthrough