Kariba dam rehabilitation project, Zambia and Zimbabwe

4th October 2019

By: Sheila Barradas

Creamer Media Research Coordinator & Senior Deputy Editor

     

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Name of the Project
Kariba dam rehabilitation project (KDRP).

Location
Zambia and Zimbabwe.

Project Owner/s
The Zambezi River Authority (ZRA) operates, maintains and manages the Kariba dam on behalf of the governments of Zambia and Zimbabwe.

Project Description
After almost 60 years of serving the Southern Africa region, the Kariba dam requires rehabilitation to ensure its longevity.

The natural riverbed immediately downstream of the dam has eroded into an 80-m-deep plunge pool, as a result of routine heavy spillage of floodwater over the years. The erosion, instead of taking the expected downward trend, has also progressed towards the dam foundation, following a rock fault that had not been detected during the design and construction of the dam. Routine monitoring and the implementation of routine interventions, such as crevice underwater repairs and controlled spillage, have slowed the natural erosion. No significant changes to the plunge pool depth and shape have been recorded in the past 15 years.

The erosion has threatened to undercut and destabilise the foundations of the wall.

An analysis of the monitoring results by the ZRA has also shown continuous swelling of the wall concrete, owing to slow chemical reactions – alkaline aggregate reaction – over the years. This has affected the smooth and safe operation of the spillway gates. In the longer term, additional swelling could cause the spillway gates to jam. Failure to invest in the timely rehabilitation of the dam will result in the gradual deterioration of the key safety features associated with the structure.

Rehabilitation measures include:

• the design, fabrication and installation of an emergency gate and a new gantry to prevent the uncontrolled loss of water in the event of floodgate failure, which will result in water levels dropping to below the minimum operating levels and interrupt power production;

• the refurbishment of the upstream stop-beam guides and the replacement of secondary concrete to prevent failure during the operation of stop-beams; and

• reshaping the plunge pool downstream of the dam to limit scouring and erosion that could potentially undermine the dam foundations, leading to dam failure.

Potential Job Creation
The KDRP will create some job opportunities for skilled, semiskilled and general workers, particularly pertaining to the plunge pool reshaping.

Capital Expenditure
The total project cost was estimated at $294-million, which will be released in tranches spread over the duration of the project. The project is being funded by the European Union (EU), the World Bank, the African Development Bank (AfDB), the government of Sweden and the ZRA on behalf of the governments of Zambia and Zimbabwe.

Planned Start/End Date
The KDRP works, which started in earnest in 2017, will take eight years to complete. The plunge pool reshaping, which is estimated to take three years to complete, will be followed by the refurbishment of the spillway, which will take about five years to complete.

Latest Developments
The ZRA has awarded the $53.6-million contract for the rehabilitation of the Kariba dam spillway, a major component of the KDRP, to a consortium comprising GE Hydro France & Freyssinet International.

ZRA CE Munyaradzi Munodawafa has confirmed that, together with the plunge pool reshaping, “the refurbishment of the spillway will ensure the long-term safe operation of the Kariba dam for many more years, continued contribution to Zambia and Zimbabwe’s energy security and economic prosperity”.

The spillway will be refurbished over four years and is expected to be commissioned by the end of 2023.

The contractor started mobilising to site in September and will complete this process gradually over ten months.

The spillway refurbishment works are expected to generate a limited number of jobs for unskilled and semiskilled workers. However, the works will stimulate local businesses, given the influx of people into the area. 

The spillway works, like the plunge pool works, will not require the relocation of people from the project site or adversely affect water levels in the reservoir and fauna and flora in the dam area, Munodawafa has said.

The loan and grant financing committed to the KDRP project by the World Bank and the AfDB are primarily funding the spillway rehabilitation works and the supervision costs of the spillway refurbishment and plunge pool reshaping works contracts.

Key Contracts and Suppliers
EU (grant financing); World Bank and AfDB (loan and part grant financing); government of Sweden (grant financing) and Razel-BEC (plunge pool reshaping contractor); GE Hydro France & Freyssinet International (Kariba dam spillway contract).

On Budget and on Time?
The project is still on track to be completed in 2025.

Contact Details for Project Information
ZRA public relations and communications manager Elizabeth Karonga, tel +260 211 230551 or email karonga@zaraho.org.zm; info@zaraho.org.zm.

Edited by Creamer Media Reporter

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