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18 Jul 2017

Renishaw Hills engineers ‘think green’ to bridge Mandawe Wetland

Judi Davis (South Coast Herald) Picture: The once-dysfunctional Mandawe Wetland is being rehabilitated. (Photo: Mia Morison)

 

The team replaced an existing dirt road with a crossing that made the system functional again.

A project involving the successful bridging of an intricate wetland crossing has demonstrated how environmental considerations are a priority for engineers involved in the construction of Renishaw Hills.

This mature lifestyle village is situated within the South Coast’s ecologically-diverse Mpambanyoni Conservation Development and the responsible bridging of the Mandawe Wetland to allow access to Renishaw has been a challenge to the developers.

“However, the essence of our development has always been to enhance the natural area. With that in mind, we discussed and debated proposed solutions with reputable environmental consultants.

Thereafter, we appointed environmentally-conscious engineers to design a crossing to replace the existing dirt road, which would allow the wetland to function as intended,” said Phillip Barker, managing director of Renishaw Property Developments, a subsidiary of the Crookes Brothers group.

Renishaw Hills forms part of a long-term project undertaken by Renishaw Property Developments to develop parts of the Crookes Brothers’ Renishaw sugar cane estate for residential and commercial purposes.

A heron appreciates the efforts of the Renishaw Hills developers to enhance this mature lifestyle village’s natural areas. Photograph by Mia Morison

Of the 1 800 hectares that make up the Renishaw farm, 266 hectares have approval from the KwaZulu-Natal Department of Economic Development, Tourism and Environmental Affairs for mixed-use development.

All the approved development plans have made provision for a number of watercourse and wetland crossings, including the upgrade of the main road leading to Renishaw.

“For the past 150 years, the Mandawe River Valley has been cultivated for sugar cane but we have some of the area’s best conservationists working to return this area to its original coastal forest, grasslands and wetlands state,” Mr Barker said.

This restoration, which started in 2016, is being led by four experienced and highly respected members of the industry.
They are landscaper and botanist Elsa Pooley, Geoff Nichols, a leading KwaZulu-Natal expert on rehabilitation, project manager Gareth Hampson and horticulturist Amanda Maphumulo.

The restoration of the Mandawe Wetland was a major project that would be worked on for the next five to 10 years, according to Mr Barker.

The Mandawe River Valley, between the N2 and Mpambanyoni River, had originally been a wetland adjoining the Mpambanyoni River estuary, but it had not functioned as such for years.

Problems concerning this wetland had been exacerbated by cultivation and the construction of the N2 across the water course, he explained.

In June 2016, developers received approval from the department of environmental affairs for the development of the first phase of Renishaw Hills, which includes the main access road and wetland crossing. Construction began late last year and is nearing completion.

The approved Mandawe Wetland crossing structure includes a solid base of dump rock, fully wrapped in a high-strength, composite geotextile, specifically designed to allow water percolation, as well as a battery of 450mm diameter piped culverts.

Upon commencement of construction, however, it was discovered that the original box culvert was largely still intact, although the inlet had somewhat collapsed.
This inlet was reinstated and extended to the full width of the approved road that crosses the wetland, thereby significantly improving the hydraulic capacity of the stormwater controls associated with this road. This assisted in returning drainage of the Mandawe Wetland to a significantly more natural state.

“We are seeing some amazing progress with the environmental rehabilitation as the development continues, with natural fauna returning to the area,” said Mr Barker. “This is evidence that we are on the right track and will maintain this meticulous approach to ecological sustainability.”