Maintenance work on the Kariba Dam is expected to commence by the end of this year at an estimated cost of US$220m. The funds will be used towards reshaping the plunge pool and installing new gates which have not been changed since the construction of the dam wall in the 1950s.
Engineers have identified three vital dam maintenance programmes to be undertaken temporarily while a lasting solution is sought. Major structural defects include the spillway, which is no longer bending and does not open automatically, owing to the expansion of the concrete on the walls and heavy accumulations of rust on the steel bars.
Major preventive engineering works to be undertaken immediately include the reshaping and stabilization of the dam’s plunge pool to limit scouring and erosion, which threaten to undermine the dam’s foundation and induce a collapse. The second phase will focus on the refurbishment of the spillway and involves redesigning works, fabrication works and the installation of a new emergency spillgate.
The dam also needs a new scaffold to prevent uncontrolled loss of water in the event of flood-gate failure, which engineers fear could result in water levels dropping below the minimum operational levels and lead to long-term inter-eruptions of power generation operations. The third and final phase involves the refurbishment of the upstream stop-beam guides and total replacement of secondary concrete structures to prevent failure during the operation of stop beams.
Collapse of Kariba dam wall would endanger the lives and livelihoods of more than 3.5 million people in Zimbabwe, Zambia and Mozambique.