The Estate - Development

The Wetland

The Wetland

The Island Estate’s wetland has since completion already proved to play a significant role in maintaining the excellent quality of the water in the Estate’s canal. The wetland makes provision for islands and walkways adding to the tranquil atmosphere,

The constructed wetland on the site consists of a shallow, lined excavation containing a bed of porous soil gravel in which emergent aquatic vegetation has been planted. A coarse stone layer with a depth of 0.7m was selected in this design aiming at polishing and reducing nutrient levels in the water.

The water-loving plants, which will eventually cover between 60-70% of the wetland, are already flourishing.

The wetland further consists of a series of water connecting dams with varying volumes of water acting
as cleaning filters for the canals. Water from the top canal is circulated through the artificial wetland,
at a rate of 400 litres per second while water from the bottom canal is pumped at 780 litres per second to
various outlet points in the top canals to prevent stagnation or dead spots in these areas. The water
quality is further improved by continuously blending it with borehole water and stormwater .

The blue-green bacteria growing in the Hartbeespoort Dam cannot establish itself in the canals because of
the growth environment created in them. The flow of water in the canals, preventing layer forming
(stratification) of the water, and the lowering of the phosphorus and nitrogen content of the water
contributes to a growth-restricted environment for the blue-green bacteria.

The management team is also monitoring the wetland closely and is especially happy about the number
of birds which have fallen in love with their new habitat.

Irrigation System

The irrigation system was designed by Gert Le Roux of Controlled Irrigation and uses the latest equipment in Nelson’s water conservation range. All the road verges are irrigated with the MP rotator and through a sophisticated variable speed pumping system, the pressure and flow operate optimally for water savings. The system was installed by Greenacres Landscapes in accordance with the LIA’s recommended set of standards. Due to the cooperation between the irrigation designers and contractors, the client has received a highly efficient, water saving irrigation system. The irrigation dams are situated in the service yard and are currently filled with borehole water. However once the estate is complete, they will be filled with water from sewerage works; the idea is to recycle water from sewerage to irrigation and minimise water use from the high yielding borehole. The pump installation consists of variable speed pumps with a filter system which is self-cleaning. When the need for water in the system increases, a second pump engages to increase delivery.

Environmental considerations

In all aspects of the project, the developers were mindful of the environment. When the canals were mapped out on the site, it was found that certain trees were “in the way” of their intended positions and approximately 160 of these were saved and transplanted into the park areas. They comprised mainly Celtis and Olea species, as well as some Acacias which could not be transplanted due to their very long roots. Aloe species found on the site were also saved and replanted.From an ecological point of view, the developers have ensured that water in the canals functions independently from the adjacent Hartebeespoort Dam as the canals have been constructed above the dam’s water level. The bi-directional lock system will be fully functional above the 80% level.

An artificial wetland has been created; this consists of a series of interconnecting dams with varying volumes of water acting as cleaning filters for the canals. Eventually, the wetland will be 60 - 70% covered with water-loving plants and reeds.

Residential and Marine Development

The Islands Estate, adjacent to Pecanwood at Hartebeespoort Dam, is a residential and marine development comprising different components: free-standing homes, an over fifties development, two further residential developments and a hotel. The latter two are still to be built in subsequent phases, and will be featured in a future issue of Landscape SA.

A key feature of the project is a system of canals – six kilometers of navigable water at various points in the estate, with islands and jetties to accommodate boats. The idea to develop the property as a marina was the culmination of many ideas by a creative development team. The land previously belonged to Dries Pretorius, whose family has owned it for the past 160 years. Whilst in the United Kingdom some years ago, he observed the operation of long boats in the canals and locks of the Thames, and this formed the starting point of his idea for The Islands Estate. The flatness of the site was also ideal for creating the dams and canals.

Project Team

Project Team

Developers: Andre Burger, Dries Pretorius, Roelf Burger
Project Managers: CPJ du Toit & Associates
Architects: Plan Studio Architects
Consulting Engineers: D& G Encotech
Civil & Structural Engineers: I M Ferreira & Associates
Landscape Design and Installation: Greenacres Landscapes

The success of the project was due to the high level of co-operation between everyone on the professional team, and the fact that the clients themselves were very ‘hands-on’, attending site and co-ordination meetings as well as regular ‘walkabouts.’ The developers’ vision has come to fruition and all involved agree that it was a privilege to take part in the project.

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