INDUSTRY NEWS 8
PICP - A CASE FOR REGULAR PERFORMANCE TESTING AND MAINTENANCE Permeable interlocking concrete paving
celerates the blocking process. As yet,
systems (PICP) established a tentative
it would appear that there is no local
toehold on the South African landscape 13
installation which has been properly
years ago. The first known system was in-
maintained, although the PICP system
stalled in 2007 at The Reeds, a townhouse
at Cape Town’s Blue Route Mall comes
complex in Fairlands, Johannesburg.
close. The results were inevitable; apart
As with all PICP systems worldwide,
from new installations, no South African
the prime objective – then as now – was
PICP installation is known to be operat-
the prevention of flooding through the
ing optimally and some – such as the
controlled discharge of stormwater into
parking lot at Cape Town’s Grand Parade
municipal drainage systems. This was
– are totally blocked. Now 10 years old,
to be achieved by creating a surface
the parking lot was constructed shortly
which facilitated stormwater infiltra-
before the 2010 Fifa World Cup.
tion, rather than run-off, as found in traditional impermeable paved surfaces.
Working group
With the introduction of Cape Town’s
Fortunately, this situation has been
Management of Urban Stormwater Im-
identified as a major problem by the
pacts Policy in 2009, PICP was quickly
University of Cape Town (UCT), which
adopted by local stormwater profes-
is tackling it head-on. Over the past
sionals to reduce the negative impact
year, Neil Armitage, deputy director:
of impermeable surfaces on equatic
“Future Water” and a professor in UCT’s
Sustainable solutions
ecosystems.
Department of Civil Engineering, has
“This lack of information as to how regular
been conducting research which aims
maintenance affects the longevity of PICP
Gaining traction
to improve the sustained performance
systems has been identified as a limiting
Notwithstanding dozens of installations
of all South African permeable paving
factor in improving the wider use and ac-
countrywide, PICP still has some way to
installations. He is being assisted by a
ceptance of PCIP. My research is intended
go before it can claim fail-safe status.
working group of professionals and civil
to contribute to the limited source mate-
It is hard to find a single installation
engineering students at UCT and some
rial on infiltration capability and testing
without some design flaw. These include
of their findings have been discussed in
methods of permeable pavement systems
the use of dirty aggregates, inappropri-
previous issues of Precast .
in the South African context and thereby
(Above): Measuring a SWIFT test wetted area.
ate use of geotextiles, pavers with poor
In this issue we take a brief look at
to promote sustainable counter-solutions
interlocking properties and the use of
some research on PICP performance
to conventional pavement designs which,
sand as the filler between pavers.
testing and maintenance aspects un-
in turn, will play a role in solving SA’s cur-
Then there is maintenance. Many
dertaken by one of Armitage’s students,
rent water management and shortage
property-owners appear to be unaware
Cole Barnard, for a thesis which forms
problems,” writes Barnard.
that PICP systems require maintenance,
part of his BSc in civil engineering.
He tested infiltration rates on seven
but regular removal of sand and other
Barnard asser ts that because
sites in greater Cape Town. Some of
debris from between the pavers to
PICP technology is still relatively new,
them had not been previously tested,
prevent blocking is essential to their
maintenance requirements have yet
while others had test results data dat-
proper functioning.
to be categorically established across
ing back to 2017. Only two sites were
the full range of installation types and
tested in Johannesburg, as most sys-
conditions.
tems were located in gated communities
C ap e To w n f ac e s the addi tional problem of windblown sand, which ac-
with restricted access. Barnard’s research involved testing the infiltration rates using the ASTM Single Ring Infiltrometer – the American standard – and the Stormwater Infiltration Field Test (SWIFT) method modified from its original Australian use. Although the Single Ring Infiltrometer test, which measures actual infiltration
(Left): Water is discharged from a bucket during a SWIFT test.
PRECAST | ISSUE ONE | 2020
