Projects with a value between R50 million and R250 milion
Xhora Off-channel Dam Project by Hatch for Amathole District Municipality, Eastern Cape
PROJECT TEAM
Client: Amathole District Municipality Consulting Engineer: Hatch Contractor: Stefanutti Stocks/Mfuraa Consortium
T
he Xhora Water Supply Scheme was identified in a feasibility study that was completed in 2002. 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 in the Elliotdale District of Mbhashe Local Municipality, within the Amathole District Municipality. The Xhora Off-channel Dam is a 29.4 m high crest, 230 m long, zoned earth-fill embankment dam with a diversion culvert to allow for flood water during construction, outlet pipework, and a
25 m long ogee side-channel spillway on the right flank, with a 5 m wide trapezoidal spillway chute, widening to 9.5 m before entering the stilling basin. The stilling basin was designed and model tested by the University of Stellenbosch. project-specific density test method to
On completion of the dam, the river
of the dam, and the impact of siltation, it
be developed. Limited higher PI clay
diversion culvert was closed through the
was conceived as an off-channel storage
was imported.
installation of two sets of precast reinforced
To minimise the environmental impact
dam in a small section of the catchment.
The water stored in the dam is expensive,
concrete planks, with the void between
Water releases are provided to maintain
as a substantial portion is pumped from
the planks filled with mass concrete post-
the aquatic environment within the river
the Xhora River raw water abstraction weir
grouted through a tube manchette system.
channel downstream of the dam.
to the dam. It was therefore important to
The diversion culvert provides passage for
grout the rock below the dam to minimise
the two outlet pipes, a domestic supply
2 dam by the Department of Water and
leakage. In order to allow a higher first-
to the water treatment works, and for
Sanitation Dam Safety Office. The Stefanutti
stage grouting pressure, grouting was
emergency emptying of the dam, as well
Stocks/Mfuraa Consortium was appointed
undertaken through the imported clay
as making provision for environmental
as the contractor for the project.
cut-off. This allowed a significant increase
releases. A low-cost solution to abstract
in the pressure that could be specified for
water for domestic consumption was
the first stage of grouting.
implemented utilising a floating intake.
The dam is categorised as a category
Maximum use of the materials from the basin was made, which required a
C E S A A o n E n g i n e e r i n g E x c e l l e n c e Aw a r d s 2 0 2 1
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