US$294mln Kariba Dam-wall rehabilitation progresses

THE Kariba Dam-wall rehabilitation project is progressing well despite temporary disruptions caused by Covid-19 lockdowns, the Zambezi River Authority (ZRA) has said.

The rehabilitation project, which commenced in 2017, comprises the reshaping of the plunge pool and the refurbishment of the spillway gates.

The US$294 million project is being funded by the European Union, World Bank, African Development Bank, the government of Sweden, and the ZRA on behalf of the governments of Zambia and Zimbabwe, through a combination of grants and loans.

The authority, which manages the Kariba Dam on behalf of the Zimbabwean and Zambian governments, said expatriate staff who had traveled to their home countries on leave, were affected by international travel bans imposed due to Covid-19.

“This temporarily left some gaps in the smooth schedule of the operations, thus requiring very close supervision of potentially affected works. However, with the progressive easing of lockdowns under specified conditions, some of the affected team members have since returned,” the ZRA said in emailed responses.

“In order to stick to the set completion date, work has continued at the project site with strict adherence to health guidelines from both the World Health Organisation and the health authorities of the two contracting states. The contract implementation timeframe is scheduled as 48 months extending from the commencement date. This implies that completion of the works will be in January 2024.”

The ZRA said the re-shaping of the plunge pool would help minimise erosion which can undercut the dam foundations.

“The measures required to reshape the plunge pool include construction of a downstream cofferdam to enable the blasting and excavation of an estimated 300 000 m3 of rock from the downstream end and north and south bank sides of the pool in the dry.

“This will create a new pool profile that will improve energy dissipation and guide the spilling water in the downstream direction, away from the dam foundations avoiding backward erosion towards the dam foundations. The plunge pool reshaping works are being implemented by a civil engineering construction company known as Razel Bec (of France) and commenced in May 2017. The target date for completion of the works is December 2023,” it said.

On the spillway refurbishment works, the ZRA said the contractor was currently working on establishing the construction site facilities as well as the fabrication of the electro-mechanical equipment required for the execution of the works through specialist sub-contractors.

“The refurbishment of the built-in parts and replacement of the embedding concrete will require that the works are done in the dry.  In this regard, a buffer that separates the dam upstream water body from the spilling gate openings will need to be constructed and this is called a Coffer Dam.

The spillway refurbishment works contract is being implemented by a consortium of GE Hydro France with Freyssinet International and commenced in September 2019. The target date for completion of the works is December 2023.”

The rehabilitation works would ensure the dam’s longevity and long-term efficient operation.

“The overall development objective of the Kariba dam wall rehabilitation project is to address some major identified dam safety risks and thereby ensure the long-term safety and reliability of the Kariba Dam for power generation for the benefit of Zambia and Zimbabwe as well as the Southern African Region as a whole,” the authority said.

– New Ziana