Place

Seli River - Sierra Leone


Client

Ministry of Energy & Power - Republic of Sierra Leone


Year

1975 - 2015

Description for Bumbuna Hydropower (Sierra Leone)

The Bumbuna Hydroelectric Project (BHP) is the first power plant in the history of Sierra Leone for this purpose and is of considerable importance as it produces more than 50% of the country's total electricity.

This is one of our pet projects that we have faithfully followed for the past forty years notwithstandings several challenges, including in particular the interruption of activities (1996-2002) due to the civil war in Sierra Leone. From the first preliminary studies between 1970 and 1975, the plant was commissioned in 2009. SP has been responsible of the entire engineering.

The project site is located near Bumbuna Falls on the upper reaches of the Seli/Rokel river, about 200 km northeast of Freetown. The Seli River has a high flow rate in the wet season and a very much lower flow in the dry season, which is typical of the rivers of Sierra Leone.

The project was carried out by Studio Pietrangeli for the Government as part of a programme to implement electricity distribution in all urban and rural areas of the country: the exploitation of its reservoir has led to a significant improvement in the national energy situation with a generating plant of 50 MW*, in a country where the electricity supply - where present - was weak and inconsistent.

Bumbuna dam is an 88m high asphalt concrete faced rockfill structure with a crest length of 440m and a volume of approximately 2.5 million m3 of granitic rockfill. The upstream face is covered with an asphalt concrete membrane.

Two 31.6 m diameter morning glory type spillways have been constructed upstream of the dam, one on each abutment, which will discharge into the multipurpose tunnels. The spillways consist of reinforced concrete towers approximately 36 m high which continue as shafts until meeting the tunnels.

The two 9 m diameter, concrete and steel lined, multipurpose tunnels were constructed through both the left and right dam abutments, each with a length of approximately 620 m. Both tunnels are being used for diverting the Seli River around the dam site during construction.

During plant operation, the left tunnel is utilized as the primary spillway. The right tunnel functions as an auxiliary spillway and as a power tunnel when the radial gate installed at the downstream end of the tunnel is closed.

A surface powerhouse is located at the downstream toe of the rockfill dam. Penstocks and draft tubes have been installed for two generating units. Excavation has been made to allow future expansion for two additional units.

The design and engineering process was particularly long and complex, due to the various difficulties encountered during the design, financing, tendering and execution of the works, including the aforesaid civil war.

While the BHP will help to resolve the immediate supply shortages, a clear strategy is needed for the future expansion of power generation capability: the Bumbuna project can serve as a catalyst and model for the country to introduce it to sustainable development.

Main Features

  • Reservoir ( V = 410 Mm³ )
  • Bituminous Faced Rockfill dam ( BFRd, H = 88 m, V = 2.8 Mm³ )
  • No. 2 headrace tunnels ( L = 620 m, D = 9 m )
  • Shaft power house ( No. 2 Francis turbines, IP = 50 MW )
  • No. 2 step up transformers ( 13.8/161 kV )
  • Transmission line ( 161 kV, L = 205 km )
  • No. 2 substations with step-down transformers
 
Bumbuna Turbines
Intake tower Bumbuna
Bumbuna spiral case
Hydroelectric Engineering: Studio Pietranggeli hydroelectric engineers. Rockfill dam design firm in Sierra Leone, Africa - dams engineers
Hydroelectric engineers: Studio Pietrangeli hydroelectric consultants in Sierra Leone, Ethiopia, Africa and europe - rockfill dam consulting

Engineering Services

  • Prefeasibility and Feasibility studies
  • Final Design
  • Revision and Updating of Final Design
  • Supervision of Works
  • Emergency Preparedness Plan
  • Dam Operation and Maintenance
  • Monitoring and Assistance during Operation

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