The Itezhitezhi Dam, located about 300 km north-west of Lusaka, is essentially intended to control the flow of the Kafue River so that it can be used to better effect at the Kafue Gorge hydroelectric power plant located 400 km downstream, and thus increase electrical power production.
The Kafue River has flood flows greater than 2,000 m3/sec; for this reason, the program primarily called for the construction of two large diversion tunnels, each having an excavation cross-section of 190 m2, and measuring 500 m and 550 m long, respectively.
Next came construction of the upstream and downstream cofferdams, diversion of the river into the tunnels (July 1975), and removal of deposited material at the dam's foundation.
In the second half of 1975, installation of the dam embankment in the river bed began, which reached the crest in November 1976.
The design of the dam, which is a rock-filled type with an impermeable core of clayey laterite, was influenced by the seismic activity of the area, the inability to reach the excessively deep granite foundation, and the need to support the dam's core on clayey shale (mudstone). In addition to the main barrier, which is 1,500 m long and reaches a maximum height of 55 m, an auxiliary rock-filled dam was also built.
The system called for two types of spillway works:
- a main concrete spillway with three ports, with radial gates for both normal regulation of the river's flow and evacuation of overflow exceeding the reservoir's capacity;
- a relief dam (located on the left bank about 600 m from the spillway) to prevent the main dam from overflowing in the event of extremely exceptional flooding.
The structure was completed and delivered about eight months ahead of the initial schedule.
|MAIN TECHINCAL DATA:|
|Required surface excavation: 2,350,000 m3|
|Underground excavation: 200,000 m3|
|Total embankment volume: 8,500,000 m3|
|Total volume of concrete: 50,000 m3|