Excavation Work On Kariba Dam Plunge Pool Complete - ZRA

The Zambezi River Authority (ZRA) has said the excavation of the plunge pool, a key component of the Plunge Pool reshaping sub-project of the Kariba Dam Rehabilitation Project (KDRP), has been completed.

In a statement issued on Tuesday, 26 December, ZRA said about 750 000 tonnes of rock have been excavated coupled with the stabilisation of 20 000m² of slopes using anchors and shot-crete. ZRA said:

The Zambezi River Authority (the Authority) is pleased to announce that excavation of the plunge pool, a key milestone in the Plunge Pool reshaping sub-project of the Kariba Dam Rehabilitation Project (KDRP), has been completed.

In total, about 300,100 m³ (about 750 000 tons) of rock have been excavated through meticulous drilling and controlled blasting, coupled with the stabilisation of 20,000 m² of slopes using anchors and shotcrete.

ZRA said the project is being financed through a grant from the European Union. It said:

The Plunge Pool Reshaping works contract, supervised by the Zambezi River Authority with Gruner Stucky (a Swiss company) as Engineer, is being financed through a grant from the European Union.

The National Authorising Office (NAO) of the European Development Fund under the Ministry of Finance and National Planning (Zambia) contracted the services of Razel-Bec (a French company) as the contractor who commenced works in May 2017.

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.

Of note is the fact that despite the high-risk nature of the project, no adverse environmental, health and safety standards have been violated, nor have fatalities recorded thus far.

ZRA said the final phase of the project will commence before the end of 2023 and the focus will be strengthening the geological fault zone that is located immediately downstream of the dam, among other things. It added:

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

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

The objective of the plunge pool excavation works was to widen and change the shape of the 80m plunge pool which was created by the immense pressure of the ejected water jets during spilling episodes.

This major milestone has been made possible through joint collaborative efforts between a resolute and hardworking team of experts from the Authority, the NAO, the contractor, subcontractors, co-financiers of the KDRP (the African Development Bank, the European Union, the Swedish Government and the World Bank) and, indeed, relentless commitment from exceptionally skilled project support staff.

ZRA said the target date for completion of the Plunge Pool Reshaping Project is by the end of the second quarter of 2024.

It also said to date, the overall project (including the Spillway Refurbishment sub-project) is about 80% complete.

The KDRP comprises three main components, namely, the Reshaping of the Plunge Pool, the Refurbishment of the Spillway Upstream Control Facility, and Institutional Strengthening, ZRA further explained.

It is anticipated that the project will close in 2025 upon completion of the spillway refurbishment sub-project.

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