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DECEMBER • 2016
Construction
WORLD
62
SAVANNA CITY RESERVOIR
In the freedom era the developers wanted to be part of the process
of changing the housing landscape in South Africa.
It wanted to create affordable housing that would be attractive
to people from diverse cultural backgrounds. Its vision is of
creating an environment where people could experience real
quality of life in a safe, suburban space.
On final completion it will provide more than 18 000 new homes.
Aligning with its objective to build a sustainable city, Savanna
City’s water supply and distribution system has been designed
using the latest technology, aiming to limit water losses in the
system to 10%, which is a very ambitious target.
The reservoir is constructed using a ‘self-healing’ concrete. The
super-absorbent polymers in the concrete expand and fill the crack,
preventing any further loss. The concrete regains its liquid tightness
and impermeability, so that it remains durable, extending the
reservoir's lifetime and minimising maintenance and repair costs.
Water network sectorisation is a very effective method to create
a sustainable water system. In order to manage the water system
efficiently it is divided into manageable zones, making it possible
to monitor consumption of these zones independently. In addition,
current leak detection costs are reduced as repair work can be
focused in the high non-revenue water affected areas.
Pressure management also limits the potential damage of the
water related fittings and devices by reducing the maximum water
pressure in the zones from 9 bar to 5 bar, therefore increasing the
lifetime of the pipes and all related fittings and devices. Effective
sectorisation and pressure management can contribute largely to
the reduction of water losses.
The installation of pressure reducing valves (PRVs) within the
water distribution network is essential to relieve water pressure
on the pipes. The higher or lower the pressure, the higher or lower
Savanna City is one of the biggest developments of
its kind ever undertaken in South Africa. But sheer
size and return on investment were not the core
motivations behind the vision for Savanna City and
other developments.
the leakage. Valves can isolate incidents of pipe breakages and
contamination, and limit the risk to the surrounding system.
Savanna City opted for the use of automatic pressure reducing
valves. These valves that are installed at strategic points in the
network to control the water pressure, for example the PRVs will
automatically reduce the water pressure during off-peak times and
increase pressure at peak times.
The professional team is also investigating the possibility to
use the energy developed when the pressure is automatically
reduced to generate electricity through a mini turbine system. The
electricity developed, which could be regarded as 'clean' electricity,
will be utilised for community purposes.
Historically, the pipes used to distribute drinking water were
made of plastic, concrete or metal (e.g. galvanised iron or copper).
Poor quality pipes shorten the pipe lifetime and result in leaks,
bursts and corrosion.
Poor pipe quality may also facilitate the infiltration of chemicals
into the drinking water. Upon embarking on this mammoth project
Savanna City considered the size of pipes, the composition, the
properties and quality of the available materials and technology to
ensure an effective sustainable water system for the development,
and chose Orientated Polyvinyl Chloride (oPVC) pipes. oPVC, for
the main water distribution pipeline, is a world class technology
that adheres to international standards. It is manufactured
by realigning the PVC molecules through a process of biaxial
orientation, which enhances the material properties – around
twice the strength and ten times the impact resistance is achieved
compared to traditional PVC pipes.
oPVC pipes’ wall thickness can be reduced by up to 50% while
maintaining the same pressure as that of the traditional PVC
pipes. The result is that oPVC has a larger bore, offering greater
hydraulic capacity and is more material efficient compared to
other pipe options. It is also the most eco-friendly pipe system in
the world as it requires less energy to produce than conventional
PVC and other pipe materials. Considering the relative low weight,
oPVC pipes are strong and durable. It stays strong through a range
of temperatures, resulting in fewer burst pipes and is corrosion
resistant which makes it ideal for water infrastructure durability.
This initiative will have a major impact on how efficient
planning, technology and experience can be combined to develop
future sustainable cities.
Project information
• Company entering: Basil Read
• Client: Savanna City Developments on
behalf of Midvaal Local Municipality
• Start date: 4 May 2015
• End date: 30 September 2016
• Main contractor: Basil Read
• Project manager: Basil Read
• Quantity surveyor: Basil Read
• Consulting engineer: GIBB
• Subcontractor: Basil Read Civils
• Project value: R37 269 206
(excluding VAT)
Public Private Partnerships
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