The work and the technique: Gibe Hydroelectric Projects (I - II - III), Ethiopia
The Gibe Hydroelectric Projects were carried out by Salini Costruttori, now part of the Webuild Group: An integrated complex project to build three distinct hydro plants.
Gilgel Gibe I. The plant is made of a RCC dam, a bypass tunnel (with a 140 metre piezometric shaft) with the function of protecting the penstock connecting the reservoir with turbines, an underground power house (installed power 210 MW), a substation and complementary works.
Gilgel Gibe II. The plant is made of a concrete gravity dam (50 in height; 140 m crest length) that is connected to a pressurized tunnel - through which the 505 m gross head is created - measuring 26 km, Africa's longest and almost entirely excavated with a tunnel boring machine.
Gibe III. The hydroelectric plant is made of an RCC dam that is 246 m tall, has a crest length of 630 m and a total volume of 6,214,000 m3 of concrete. It also has an open powerhouse with 10 Francis turbines with a total installed power of 1,870 MW. The project also includes a 7-span spillway with radial gates and two halfway outlets; two adduction pressure tunnels, with a section lined in concrete with a diameter of 11 m and a total length of about 2 km, two intake structures; two shafts each approximately 126 m deep for the movement of the gates, two balancing shafts 140 m high and with an excavation diameter of 27 m, two pressure pipes with steel lining, inclusive of two vertical shafts about 110 m deep, and two collectors each with 5 lines; a 400 KV substation. The river diversion operations include diversion tunnels (a 3.2 km-long tunnel), an upstream cofferdam, about 600,000 m³ in volume, and a downstream cofferdam. In addition, the plant also forms a reservoir with a surface area of 200 km² and a storage capacity of 14 million cubic metersplant,