Italian contractor Salini Costruttori has been awarded the contract to construct the Gilgel Gibe II hydropower project in Ethiopia that includes a 25.8km headrace tunnel from the existing Gilgel Gibe dam.
Whilst negotiations with eligible consultants are ongoing for the project management and site supervision roles, Salini signed a contract agreement with the public Ethiopian Electric Power Corporation (EEPCO) in early May for construction of the 410MW scheme.
Construction is expected to get underway imminently, with a duration of 42 months programmed to the commissioning date.
Of the 25.8km headrace tunnel, 22km are expected to be excavated with a hard rock double shield TBM. The excavation diameter is 7m with a 6.3m i.d. hexagonal segmental lining being installed behind the shield. The 3.8km balance of the headrace tunnel will be excavated by conventional drill and blast methods. With the project having 470m of head, the headrace tunnel will transport 100m3/sec from the river intake to the top of the penstock.
Located to the southwest of Ethiopia’s capital of Addis Ababa, between the Gilgel Gibe and Omo rivers, the site is in the Ethiopian Highlands, near to the Rift Valley. Geology is characterised by volcanic and sedimentary rocks, typified as tuffs, basalts and rhyolites, which are frequently crossed by dolerite dykes.
This second phase of the Gilgel Gibe scheme is expected to cost US$458M and is being jointly financed by an Italian government (US$221M) loan, the European Investment Bank (US$123M loan), the Ethiopian government and Salini. Reports said the project has increased in importance to Ethiopia after the country’s other dam project at Gojeb ran into delays and technical problems. The importance is said to be illustrated by EEPCO’s project manager for Gilgel Gibe recently being appointed chairman of EEPCO.
