Kariba Dam plunge pool rehab complete

BUSINESS REPORTER

The  rehabilitation of the Kariba Dam  plunge pool  has been  successfully completed, the Zambezi River Authority (ZRA)  has said.

It is anticipated that the rehabilitation efforts, which have involved the excavation of roughly 750 000 tonnes of rock, will add 60 years to the bridge’s lifespan. Apart from improving the safety and increasing the Dam’s lifespan, the project  has seen the reshaping of the plunge pool, which has increased its size, reducing the pressure the water spilling into the plunge pool exerts on the base of the pool thereby slowing the erosion of the natural rock floor.

The rehabilitation project was awarded to the French contractor Razel-Bec, under the supervision of ZRA, with technical assistance from the Swiss company Gruner Stucky.

The project, estimated to cost US$294m, is being funded by a combination of funds generated internally by the ZRA, which is jointly owned by the governments of Zimbabwe and Zambia, and amortized loans and grants from cooperating partners like the World Bank, African Development Bank, European Union, and Swedish International Development Agency.

The two parts of the rehabilitation project are the completed reshaping of the plunge pool downstream of the dam wall and the rehabilitation of the spillway, which includes replacing the secondary concrete and renovating the upstream stop-beam guides. As an extra safety measure, a new gantry and emergency gate will also be designed, fabricated, and installed.

The spillway consists of the six gates in the upper part of the concrete dam wall through which the ZRA releases water into the plunge pool to manage the reservoir water levels.

“While the excavation works are now 100% complete, the overall project is now 93% complete. In total, 550 000m3 of water (99% of the plunge pool volume) have been pumped out of the 80m deep plunge pool,” ZRA CEO, Munyaradzi Munodawafa said in a statement.

“As 2023 draws to a close, we commence the final phase of this extraordinary engineering marvel and remain focused on the upcoming challenges related to the strengthening of the geological fault zone that is located immediately downstream of the dam.

“This will be achieved through constructing a reinforced concrete slab that will cover the weak-rock zone to protect it from possible future erosion.”

He said no environmental, health and safety standards were violated despite the high-risk nature of the project.

“Upon completion of this concreting work, the plunge pool will be rewatered (re-filled with water). This refilling will not in any way affect river levels downstream,” he said.