Water, Sewage & Effluent September October 2018 | Page 20

Afriline Civils, discusses some of those
encountered.
Challenges
With a large section of the site bound
between Macassar Road and existing
residential areas, the working width
of the site was very limited, with
some of the pipes being installed at
depths of between seven and eight
metres deep, so ensuring adherence
to Health & Safety compliance posed
a challenge, says Reed. “The depth of
the excavations required that they be
battered, and staff had to work within
a ‘drag box’ at invert level to create
a safe working environment for our
staff.”
As the project took place in a
residential area, the local community,
children specifically, entered the
construction area unauthorised. “With
all the pipes and mounds of sand, for the
children, it’s a playground,” Kleynhans
noted. Coupled with this challenge, the
project experienced continuous theft
and vandalism of safety barriers, traffic
signs, plant, equipment, and materials,
Reed describes.
“We put up fences to prevent entry,
but in the morning, they were gone,”
Reed adds, necessitating full-time
security on the site for the duration of
the contract, as well as enlisting safety
marshals from the local community,
“which was more effective as they
know the people,” he points out.
Reed says that during the
excavations, while minor quantities
of rock were encountered, it was the
subsurface water that was a major
obstacle and challenge in the pipe
installation and chamber construction,
with the need to deal with water in the
trenches and structures (groundwater
and surface run-off).
“That the gradient of the pipeline
to be constructed was 0.76mm per
metre, made precision surveying and
installation of utmost importance,” he
adds. “Dealing with the crossing of
existing services such as high-voltage
overhead power lines, fibre optic
cables, water and sewer pipelines,
and constructing adjacent to these
services, also posed challenges,” he
observes.
While the project started during the
peak of the Cape drought, in November
2016, imposing water restrictions on the
project that also required dust control
in the Cape winds, Kleynhans believes
that the drier conditions made it easier
for pipe installation. He explains that
the groundwater is relatively high in
the area of the sewer installation, but
because of the drought, this was less
problematic during the installation. The
recent rains have since changed the
scenario, but the majority of pipe laying
has been completed.
Technical scope of work
Reed explains that as the main
contractor on the project, Afriline
Construction of DN 900 diameter pipeline, 8–9 metres deep, along the City of Cape Town waste yard in Macassar.
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Water Sewage & Effluent September/October 2018