Xhora Off Channel Dam

Xhora Off-Channel Storage Dam provides assurance of supply to the Xhora Water Supply Scheme

Amathole District Municipality | Elliotdale - Mbhashe Municipality, Eastern Cape, South Africa | 2008-2020

109 local people employed over the contract

R 5,2 million spent on local wages and local contractors

Earthworks volume
295 000 m3

Concrete volume
12 000 m3

Challenges

  • The Xhora Off-Channel Storage Dam provides assurance of supply to the Xhora Water Supply Scheme which is intended to provide potable water to 70 000 people
  • Environmental impacts on the surrounding rivers and streams were to be minimised
  • A shortage of suitable embankment materials required innovative solutions
  • The water in the dam was expensive as it was pumps so minimum leakage was required

Solutions

  • The Xhora offchannel dam provided the required assurance of supply with the minimum impact on the environment
  • The in stream flow requirements of both the stream below the off-channel storage dam and the Xhora River required care in the design of the raw water abstraction to provide for the maintenance of the low flows
  • Maximum use was made of the materials from the basin, which required a project specific density test method to be developed
  • To reduce leakage a low permeability grout curtain was required, which required an innovative approach

Highlights

  • The Xhora Off channel Dam now provides the assurance of water supply to 70 000 people who have never previously had potable water
  • This solution was able to minimise the environmental impacts of a new dam
  • To ensure a low permeability foundation, grouting of the shales and mudstones below the core to 2 lugeon reduced the dam leakage
  • A novel grouting approach was utilized to increase the grouting pressure

The project has been awarded a commendation in the Technical Excellence Project category at the SANRAL SAICE National Awards 2021 in South Africa.

Project numbers

R 112 million, excl VAT - Capital value of the project
25m long ogee side channel located on the right flank with a 5m wide trapezoidal spillway chute, widening to 9.5m before entering the stilling basin
A zoned earth fill embankment dam with a 29.4 high crest, 230 m long
Earthworks volume – 295 000 m3
Concrete volume 12 000 m3
Total length of grouting 3 500 m

Project services

Water

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