Kariba sluice gates rehabilitation ongoing

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KARIBA SLUICE GATES

rehabilitation ongoing

Kariba Dam rehabilitation works in progress

Situated in the Kariba Gorge of the Zambezi River basin between Zambia and Zimbabwe, the Kariba Dam provides hydroelectric power to both countries and has been in operation since 1960.

The double-curvature concrete arch dam has six sluice gates that release water into Lake Kariba. Over time, the concrete has expanded slightly, affecting their smooth operation. Potentially, this could cause these gates to jam in either the open or closed position.

As a countermeasure, the spillway gates are being refurbished one by one in a long-term project that commenced in 2019 and is scheduled for completion in 2025. The programme is being carried out by a consortium, comprising GE Hydro France and Freyssinet International, which was awarded the contract by the Zambezi River Authority.

Temporary cofferdams

Before works can begin, the contractors must first create a dry workspace at each gate so it can be refurbished. This entails building a small temporary cofferdam that clings to the dam wall on its lakeside. Experienced divers affix steel supporting members to the upstream face of the dam wall to allow the cofferdam to be put in place. Here, Pratley Putty was chosen as the best quick-setting solution.

“Pratley Putty is ideal for use underwater but can also fill, seal, build up and bond almost any rigid material,” notes Eldon Kruger, marketing director, Pratley.

A crane on the dam wall lowers the cofferdam pieces into place one by one. The water trapped between the cofferdam and the dam wall is then pumped out into the lake, creating the water-free space necessary for the refurbishment work.

In the final phase of the overall programme, a new self-motorised gantry crane will be installed that can place an emergency gate in position to close any of the sluice gates.