As the lead design and supervision engineers for the rehabilitation and reconstruction of the Main Road (MR) 172 route between Helshoogte and the R45, in the Western Cape, consultancy firm SMEC managed to deliver a project that balanced environmental and heritage sensitivities with onerous technical requirements.

SMEC manager for roads and highways in the Western Cape Neil Slingers points out that road safety concerns on the stretch of road, which runs through the Wine- lands area towns of Johannesdal and Pniel towards Franschoek, prompted the Western Cape government (WCG) to appoint SMEC, known at the time as Vela VKE Consulting Engineers, to under- take the planning and design for the upgrading and reconstruction of this section of the MR172.

Slingers notes that what made this project unique is the area in which it is located. “The MR172 runs through an area that is environmentally sensitive and significant in terms of national heritage. As a result, input and approvals were required from the South African Heritage Resources Agency and the Western Cape Department of Environmental Affairs and Development Planning.”

The existing road’s location and design elements were influenced by the topography, terrain, built environment, land use and historic significance of the surrounds.

“Since inception, the project was an integrated one, whereby one part of the design could not be done in isolation of any other factor. Hence, the technical design could not be done in isolation of the environmental aspects, the heritage impacts and the social requirements,” explains Slingers.

Initially, the MR172 had a very narrow cross-section, with a 6 m carriageway consisting of 3 m lanes and a gravel shoulder that carried about 4 500 vehicles a day.

The preliminary design called for two 3.7 m lanes and two 2.5 m surfaced roads to be constructed; however, the intruding terrain and residential areas did not allow for the cross-section to be implemented. Instead, a compromise was reached – two 3.7 m lanes and 1.5 m sidewalks were constructed in the rural area.

In addition to the technical require- ments, SMEC had to take into considera- tion limitations presented by the topo- graphy, the neighbouring residential area and high traffic volumes during construction.

“At no given time during construction could the MR172 be closed to traffic, which dictated that the construction of roadworks and the laying of pipes crossing the MR172 occur in half-widths. High volumes of traffic resulted in the contractor being limited to not more than three 500 m road closures, at least 1 km apart, to ensure that the tail of preceding closure would not extend to the one behind it.”

Slingers says one of the project’s most significant challenges is that the contractor and supervision team had to construct pavement layers through the town of Pniel by means of in situ recycling. The road reserve was narrow and in many instances the existing houses, most of which were old and of heritage significance, were built on the reserve edge.
“Therefore, we had to plan accordingly to ensure that all the necessary precautions were taken to mitigate any damage to the structures as a result of the recycling,” he explains.

The project was completed with as little as possible of the existing vegetation being affected by the upgrade. “The road was realigned in the area stretching past Boschendal Wine Estate to preserve the trees and vegetation in this region and the unlined earth drain width was reduced so that the trees bordering the road were not affected,” Slingers explains.
For traffic-calming purposes and for aesthetic reasons, red shoulders were constructed to further enhance the design of the road.

In keeping with the vision of the project in terms of development, prior to going to tender and construction, an economic- impact assessment was carried out to identify how the surrounding communities of Pniel and Johannesdal could benefit from the project.

“The report investigated the use of local labour during construction, the development of black economic empowerment, the use of local suppliers and the training of local labour by placing locals in learnerships, as well as the development of new or current small to medium-sized enterprises.” He points out that the nature of the con- tract allowed for the implementation of these goals, as a large percentage of the work was labour orientated and not machine orientated.

“The R73-million project, which was successfully completed and handed over to the WCG at the end of February 2011, was a truly integral project where no one aspect was viewed in isolation of one another – a milestone project for all parties involved,” Slingers concludes.