Kariba Dam wall rehabilitation to begin in 2017
Kariba dam can carry up to 65 billion cubic metres of water.
REHABILITATION work on the 55-year-old Kariba Dam is expected to commence in February 2017, the Financial Gazette’s Companies & Markets (C&M) has learnt.
Kariba Dam is managed by the Zambezi River Authority (ZRA) on behalf of the governments of Zimbabwe and Zambia and supplies water for power generation to two hydropower stations with a combined capacity of 1 830 megawatts (MW) of electricity.
The North bank power station is operated by ZESCO in Zambia and has an installed capacity of I 080 MW. The South bank power station is operated by the Zimbabwe Power Company (ZPC) in Zimbabwe and currently has an installed capacity of 750 MW. ZPC is however, expanding the power station to add 300 MW to the national grid.
ZRA chief executive officer, Munyaradzi Munodawafa, confirmed that the rehabilitation of the dam wall, which is estimated to cost about US$294 million, will start in February 2017.
The works, which include the re-shaping of the plunge pool to minimise a scouring of the dam’s foundations and the refurbishment of the spillways and associated infrastructure to improve the dam’s stability and operations, are expected to last six years.
Munodawafa told C&M last week: “Tenders for contractors to carry out works on the plunge pool closed last month. Tenders for the sluice gates were opened this month. Without functional sluices, the reservoir level cannot effectively be maintained.”
The rehabilitation project is part of the critical dam maintenance programme which involves geo-technical investigations in order to verify the geo-mechanical characteristics of the rock mass in terms of fracturing, weathering, alteration, hardness, abrasiveness, strength and deformability.
The plunge pool, which should act as a shock absorber for the dam wall’s foundations and surrounding river banks, is said to be eroding towards the dam wall with the possibility of undercutting the foundation of the wall.
This could damage or compromise the dam wall which could result in a potentially disastrous event for thousands of people living downstream of the Kariba Dam.
The dam wall had been compromised through many years by an erosion of the plunge pool, with the foundations chipped down to depths of up to 90 metres beyond permissible levels.
The erosion had under-cut and destabilised the wall, putting the entire wall structure at high risk of collapse.
The project is being funded by partners who include the World Bank, the African Development Bank, the European Union and the Swedish government, who are helping the governments of Zimbabwe and Zambia.
ZRA will provide US$19,2 million while AfDB and the European Union will inject US$75 million and US$100 million respectively into the project.
The WB and Swedish government have also expressed interest to support the project. It is understood that the WB will provide US$75 million while the Swedish government will inject US$20 million.
About US$80 million would be used for reshaping and stabilisation of the plunge pool, with the balance being used to rehabilitate the spillway’s upstream hydro-mechanical facility.
Apart from economic losses arising from the destruction of the hydro-power stations, a collapse of the Kariba Dam wall would generate a regional humanitarian crisis arising from flooding in Zimbabwe, Zambia, Malawi and Mozambique.
The dam which has a height of 128 metres, was designed by French engineer and inventor Andre Coyne and was built between 1956 and 1958 by an Italian consortium, Impresit Group.