Mega projects with a value greater than R1 billion
Zutari for Lower Thukela Bulk Water Supply Scheme
I
ncreasing demands from a growing
The R1.6 billion scheme consists of an
population, combined with periodic
abstraction works from the Lower Thukela
droughts that are increasing in
River, which needs to provide a steady
intensity, have left northern KwaZulu-
supply of water from the river throughout
Natal’s water supply vulnerable. The Lower Thukela Bulk Water Supply
the year, while also removing as much of the sediment load from the water as possible.
System was conceived decades ago but
The abstracted water is then pumped up to
was shelved as a scheme because it had not
the water treatment works.
been deemed necessary. However, with an
A weir was installed across the river to
PROJECT TEAM
Client: Umgeni Water Consulting engineer: Zutari (previously Aurecon) Contractors: Group Five, Stefanutti Stocks Coastal, Veolia Water Solutions, Esor Franki
surrounding communities. Sediment collected on-site is then processed to landfill.
impending drought in 2010, Umgeni Water
direct flow to the abstraction works, where
One of the key ecological functions of
needed to move quickly to implement
the water will continually scour the riverbed
the Thukela River is the transportation of
the scheme.
to maintain a channel to the abstraction
nutrient-rich sediment to the estuaries at
works. The removal of sediment is achieved
the mouth of the river. Zutari modelled
as it needed to be executed within a short
through a sequence of boulder, pebble,
the river chemistry and sediment loads to
timeframe in order to meet the client’s
gravel and sand traps.
demonstrate the optimum return flow of
The design of the scheme was challenging,
delivery commitments. It also needed to be
The water treatment works uses three
sediment from the works to the river in order
sufficiently robust so that the client would
stages of sedimentation to further remove
to maintain the ecological service of the river,
achieve a 95% assurance of supply to their
solid particles from the water. The water is
without impacting on the quality of the water
customers. This required an unconventional
then polished through rapid gravity sand
in the river.
design, considering the seasonal flooding of
filters and disinfected before being pumped
the river and the associated deterioration in
from the water treatment works to a 30 Mℓ
treated flow per day, with the option to readily
river water quality.
reservoir, from which it is distributed to the
upgrade it in the future to 110 Mℓ/day.
The scheme presently provides 55 Mℓ of
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 0
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