INCA CONCRETE PRODUCTS
Written by Beth McKellar-Basset
The “Green” Approach to Paving
Why Permeable Paving
The recent heavy rains and floods in the country and notably the Western Cape have highlighted the im-
portance of keeping hard areas like driveways, roads and footpaths free of excess water to an absolute
minimum. Achieving this is often easier said than done but one area where almost every household and
commercial sector can help is in the use of permeable pavers. Hard areas are bad news in heavy rain be-
cause they cause storm water to run-off in volume and speed, and sweep pollution along with them. Wher-
ever rain can soak in, there is the opposite effect, it is slowed down and filtered through the earth.
A high percentage of our cities are covered by impermeable
surfaces: asphalt roadways and streets, parking lots, side-
walks, driveways, and rooftops. Instead of percolating into the
ground, the majority of rain lands on these impermeable sur-
faces and flows into storm water sewers, picking up a toxic
combination of pollutants like oils, faeces, pesticides, metals,
nutrients and sediments as it goes. As we continue to develop
our inner cities, the increase in storm water runoff is resulting in
downstream flooding, stream bank erosion, and excessive
strain on existing drainage facilities.
Ottery Road off the M5 in Cape Town
during the 2007 storms
In 2005/6 the City of Cape Town drew up the “Green Building Guidelines” for the construction industry and
one of the many greening principles that the building industry had to address was “permeable paving”.
South Africa is at least 20 years behind Europe, where this practice is the norm rather than the exception.
In Germany for example, they lay 20 million square metres of permeable paving per year in the domestic
and industrial sectors, which includes public roads and municipal parking areas. Due to urban densifica-
tion, many of their local councils, have levied a tax on estimated water run-off, which is why permeable
paving is finding increasing favour with the Europeans.
In essence, our cities are enormous catch basins, collecting polluted water and diverting it into waterways.
The age-old storm water systems, especially in the older cities like Cape Town are not only pushed to
their capacity during torrential rains but are also a major source of pollution. Recently storm water has
been directed into our rivers and streams in volumes that are much greater than historic levels, substan-
tially eroding stream beds and banks and flooding surrounding areas. To address these issues and at
great cost, municipalities typically widen channels and armour the banks with concrete, drastically disrupt-
ing the streams’ ecological value.
The “Green” approach, permeable paving, would treat as much storm water as possible on-site as the
natural biological processes in the soil would filter and break down run-off pollutants. Because permeable
pavements promote water infiltration this would reduce flooding and non-point source pollution, minimize
storm water infrastructure costs, and maximize groundwater recharge and the ecological value of streams
and other waterways.
A toxic combination of pesticides, metals, oils and sediments are rendering our riparian eco system uninhabitable.
INCA Concrete Products realised the world wide trend of permeable paving. They have researched
this market thoroughly and have travelled extensively internationally to determine the “best of breed”
products, designs and methodologies. The following innovative players are the leading influences in
the permeable paving market today;
1. Australasia. Both New Zealand and Australia are strong advocators and well established
users of the permeable paving systems and techniques. The renowned paving engineer,
Dr Brian Schackle of New South Wales University resides here and has played a major
role in the standards and practical implementation criteria. Dr Schackle has spent more
than a decade researching and developing the design and layering system of permeable
paving and has earned his reputation as one of the doyens of the industry. His design sys-
tems and methods are due to be launched in South Africa at the ICCX Conference in Sun
City in February 2008 followed by a national road show which will be sponsored by the
CMA (Cement Manufacturers Association).
2. The UK. Formpave Limited have over the past 12 years sponsored an ongoing pro-
gramme of research and development into permeable paving systems at a number of aca-
demic and independent institutions including Coventry University and Edinburgh University.
Every aspect of Formpave's permeable paving system has been independently tested and
verified - both in terms of pollution control properties and hydraulic and structural perform-
ance. The Formpave Stormwater Source Control System allows rain to infiltrate through a
permeable concrete block paved surface into a unique stone sub-base where it is cleaned,
by filtration and microbial action, before being released in a controlled manner into sewers
or water courses, or infiltrated directly into the sub-grade. The water can also be harvested
and used for non-potable purposes such as watering plants and flushing toilets.
Inca Concrete Products (Western Cape) and Concor Technicrete- (balance of the count
country), hold the block design and methodology rights to Aquaflow Permeable Paving
and Sustainable Urban Drainage Systems (SUDS) in South Africa. Formpave’s offer is
an affordable solution to the challenges of storm water disposal and treatment and
water conservation, re cycling and reuse.
Formpave have always shared the results of their research with the industry, and it is
this approach that has established them as the world leader in permeable paving solu
A cross section of a permeable paving layering design
3) Europe. European countries such as Germany and Austria are the stalwarts of this industry
and have more square metres of permeable paving than anywhere else in the world. One of the
reasons for this is that their many municipalities have established a maximum rate of peak dis-
charge (in cubic feet/second or liters/second) for specific storm sewers or bodies of water and a
tax is levied accordingly. These regulations vary in Europe, as rainfall amounts, geography,
climate, and land use development patterns vary widely.
Dr Söenke Borgwardt, a leading Landscape Architect and author of
several books and articles on permeable paving systems and best
management practices has been a major contributor to the industry in
Germany. He recently visited Cape Town as a keynote speaker at the
South Africa Housing Foundation Conference to deliver his message
on permeable paving with special attention to targeting the upgrade of
township developments. His message to the attendees was that the
wide range of benefits of permeable paving would alleviate the nega-
tive ecological effects, such as floods, overstressed drains, water pollu-
tion and the dropping of ground water level that we experience in our
Dr Söenke Borgwardt known as
country. Over and above the permeable paving methodology it is a “The Pope of Permeable Paving” in
low cost, long life concrete paving solution that can create employ- Germany, recently shared his vast
experience with delegates at the
ment opportunities because of the minimum skill and equipment re- South African Housing Foundation
quirements. Conference in Cape Town
Understanding the varieties of “Permeable Pavers”
To further understand permeable paving and its functionality, the following descriptions are useful.
1. Permeable paving is a paving system designed to infiltrate storm water for
the purpose of quality and /or quantity management.
2. Pervious paving is one type of permeable paving where a larger percentage of the surface is
permeable (e.g. grass block pavements and aggregate pavements)
3. Porous paving is one type of permeable paving where the entire surface of the pavement is
permeable (e.g. porous concrete pavements)
Inca recommend either the permeable pavers or the pervious pavers as standard practice. Po-
rous paving consists of cast-in–place asphalt or concrete, which is comprised of coarse aggre-
gates, and has earned a poor reputation due to the tendency to clog, resulting in non renewable
Permeable pavers that are designed to infiltrate stormwater for the purpose
of quality and / or quantity management.
Design and construction
Much of the design and construction is derived from experience with infiltration trench design,
which has been used for years as a way to reduce storm water runoff and recharge groundwater.
The structural design regarding the sub grade found on site, the materials and thickness of the
load –bearing base layers, the laying pattern of the paving blocks and the drainage surface are
all crucial for the long – term success of the paving project.
Permeable pavements should be designed by civil engineers, architects, or landscape architects
familiar with storm water management concepts. To maximize the effectiveness of permeable
paving, it should be used as part of the larger site design that utilizes a variety of techniques in
dealing with run-off such as swales, roof rainwater collection, catchments, and strategic land-
scaping with native vegetation. Inca have put a support team in place to assist professionals to
become more familiar with the favoured processes.
Functional considerations such as the cost of permeable paving can have a cost premium over
conventional paving. There may be additional unit costs if sub-surface reservoirs need to be in-
stalled. However, when installed as part of a good design, expensive storm water infrastructure
such as curbing, storm sewers and treatment facilities can be downsized or eliminated, creating
net savings. Over and above the savings, the following comparison should sway any concerned
developer or construction professional.
Recharges local aquifers
Reduces need for expensive storm water infrastructure
Large surface area allows pollutants to be broken down naturally
Contributes directly to a healthy river habitat
Removes water from site carrying with it a toxic combination of minerals and sediments
Requires expensive storm water infrastructure
Concentrates pollutants into waterways, where they cannot be completely broken down
Contributes indirectly to the destruction of river habitat.
Claremont Cape Town July 2007. Due to the lack of manpower available at the Cape Town City Council to
unclog the drains, residents were forced to pay enormous amounts of money to have the storm water drains
cleared by private companies. The damage to vehicles and homes was substantial enough to alert the public
that the storm water systems in the Cape can no longer bear the load in conditions such as this.
Inca Concrete Products invests in their customers
Inca Concrete Products have made a considerable investment in the permeable block machinery,
moulds and knowledge accumulation. They are geared to take on the vast South African perme-
able paving market however will remain in the forefront as a respected supplier in the conventional
paving arena. Of particular interest to all their customers -developers, pavers and local government
alike, Inca has recently become one of the largest Black Economic Empowered concrete product
providers in South Africa. Their message is very clear – they will continue to advance and improve
their offerings to their customers whilst remaining steadfast in their sound business ideologies and
The Aquaflow block is one of the
interlocking permeable pavers
that Inca Concrete Products of-
fer. It has the structural support
and stability of traditional con-
crete pavers, combined with the
environmental benefit of storm-
In every corner of the globe - on land and in water, in melting ice and
disappearing snow, during heat waves and droughts, in the eyes of
hurricanes and in the tears of refugees - the world is witnessing
mounting and undeniable evidence that nature’s cycles are profoundly
changing. I have found that, beyond death and taxes, there is at least
one indisputable fact: Not only does human-caused global warming
exist, but it is also growing more dangerous, and at a pace that has
now made it a planetary emergency.
AL GORE – an inconvenient truth 2006.
A MEMBER OF
Contact Deon van Vuuren on 082 9072171 or email email@example.com
Inca Concrete Products
Ryneveld Street Eerste Rivier
Phone : 021 904 1620 Fax : 021 904 3636
Website : www.incaconcrete.co.za