Chapman’s Peak Drive (CPD) is a spectacular coastal route located within the Table Mountain National Park, connecting Hout Bay and Noordhoek. The road is one of the major tourism attractions of the Cape due to its scenic relationship with the mountain looming overhead and the sea below. There are many picnic sites and hiking trails off the road.
Precariously positioned on steep mountain slopes exposed to the full force of the coastal elements, the road has often had to be closed (since it was opened in 1922) due to damage and tragic accidents. It was finally closed for several years in January 2000 until it could be made safe.
The construction works required for the reopening of CPD were a major undertaking comprising a range of activities, all with potential impacts to the natural, visual and historic environment:
- rock barring to remove rocks identified as unstable and bearing greater energies than the catch fences’ capacity;
- installation of catch fences above the road, located on the steep slopes within the National Park;
- construction of two concrete structures and a half-tunnel at critical areas of the road;
- slope stabilisation, above and below the road;
- geometric improvements, resurfacing of the road and repair to drainage systems, retaining walls and side walls;
- and upgrading the picnic sites and providing ablution facilities.
Entilini Concession, a special purpose company set up by Concor, Haw and Inglis and Marib, was the successful bidder which entered into a public private partnership with the provincial government of the Western Cape. A project management team was established and diverse stake holders, specialists and independent monitors were appointed
to ensure that the road engineering was carried out successfully and without detriment to the adjacent protected environment. Megan Anderson Landscape Architects (MALA) were appointed as the environmental managers for the project, overseeing aspects such as the visual impact of construction and the vital rehabilitation of the natural environment.
Environmental management of the CPD rehabilitation meant the challenge of managing a wide range of construction activities, some being used for the first time in South Africa and taking place within a narrow, confined site within a national park. This required a strong presence on site and working closely with the engineering design and construction joint ventures, as well as the independent environmental consultant and stake holders to ensure that the impacts were understood, comprehensive method statements were drawn up and approved, and the implementation monitored.
During the rock barring phase of construction, boulders identified as too large for the catch fences’ design capacity were dislodged, and the programming of works was structured to ensure that there was no threat to a pair of nesting Peregrine falcons. The chicks hatched successfully and were flying confidently prior to rock barring activities taking place in their vicinity.
Along with monitoring and mitigating impacts on the natural environment, the site has a high visual and heritage sensitivity, which could be detrimentally affected by the construction activities. The shotcreting of slopes, and repairs to barrier stone walls and retaining walls all required careful integration with the existing character of the route. Workshops with the stone mason teams ensured that the repairs and new walling to be built out of stone were integrated with the earlier stone walls that were probably built in the first half of the last century.
Various solutions were supplied for the range of activities on Chapman’s Peak. These included gabions, reno mattresses and double twist rockfall protection netting used as slope erosion control measures, retaining structures below the road level and gabions for storm water drainage channels as well as for retaining rock fall on top of the concrete canopy structures.
To add to the aesthetic appeal of the gabion installations, as well as to alleviate concerns about potential fading, a dark brown PVC coated mesh was especially designed for Chapman’s Peak. This blends in well with the surrounding natural rock and is UV resistant.
The technical reasons that determined the choice of gabion structure and hexagonal rock fall protection netting were:
- ability to absorb increased surcharge (due to rockfalls) without any sudden failure (good flexibility);
- ability to blend into the natural environment, encouraging the growth of vegetation inside the wall;
- the low technology involved (unskilled labour, no need for sophisticated equipment) resulting in economical cost of the structure;
- speed and ease of installation, especially once the gabions were pre-assembled and filled;
- ease of maintenance – should a gabion be damaged by impact from a falling rock, the unit can be easily removed and replaced; and
- prompt supply of readily available products manufactured in South Africa.
A wide variety of plant species were searched for and rescued or propagated from site and maintained in one of two nurseries established for the revegetation of Chapman’s Peak Drive
Search & rescue and plant propagation
Chapman’s Peak Drive was a monumental feat of construction carried out between 1915 and 1922. Repairs and realignments of the road took place along the route prior to the major rehabilitation work of 2002/2003. As a result, the natural environment has been substantially impacted upon and the reinstatement of the indigenous fynbos and vegetation to the disturbed areas was identified as a prime objective, both of the construction activities and the ongoing management of Chapman’s Peak Drive as a 30 year toll concession.
A survey carried out in 2002 identified rare and endemic species that could potentially be affected by construction activities, and indicated useful species for rehabilitation, particularly species that could be used for revegetating harsh environments such as the structures and gabions.
In order to protect the environmental integrity of the area, rehabilitation was carried out through the harvesting of seed, cuttings and rescued plants within the vicinity of the areas to be revegetated. Plant material was differentiated in terms of its origination on sandstone or granite slopes, as well as its different microclimate of Hout Bay or Noordhoek. Search and rescue of plants took place from areas disturbed by construction activities, such as the repair of ?ll slopes and changes to the geometric alignment of the road.
Nurseries were established in Hout Bay and Noordhoek to propagate and maintain the 130 000 cuttings and plants
rescued and propagated during the course of the project. Due to the wide range of habitat conditions on site, both natural and man-made, over 80 plant species were required for the rehabilitation of the mountain-side. Considering the large numbers of plant species, the project benefitted from a high success rate of propagated and rescued plant material.
The success of many species that are extremely sensitive to disturbance was excellent and a tribute to the skill of the landscape contractor. The fires of 1999 and 2000 also turned out to be of great advantage, as the relatively new growth on the mountainside meant that species such as Ericas and Leucadendrons were small enough to be successfully rescued and transplanted.
Removal and replacement of alien vegetation
There were several approaches to the control and eradication of invasive alien vegetation on Chapman’s Peak Drive.
The mature existing pine and gum trees form part of the heritage landscape of Hout Bay and offer an amenity at the picnic sites. As a result, these are scheduled for phased removal and this will take place during the course of the toll road concession, during which time indigenous trees will be established to replace these trees. Historically, kikuyu had been planted at the picnic sites and was spreading into the indigenous vegetation, and this was targeted for removal.
Kikuyu grass within the road reserve was sprayed with “Focus-Ultra”, a non-systemic herbicide which was applied by a registered pest control officer. The lay-by areas and picnic sites were then hydroseeded with Cynodon dactylon to replace the kikuyu, where grass was desirable. Port Jackson is particularly prevalent along Chapman’s Peak Drive.
Thabakholo Landscaping removed all alien vegetation within the road reserve and from the picnic sites and lay-by areas. Table Mountain National Parks personnel have cleared the alien vegetation from the surrounding areas of the park, ensuring a combined effort to manage invasive aliens. Alien vegetation removal within the private property
adjacent to Chapman’s Peak Drive in Noordhoek commenced this year, and will have a huge impact on enabling effective alien vegetation management for Chapman’s Peak Drive. Eradication of a wide variety of “garden escapees” and invasive vegetation will be an ongoing management challenge and an Alien Vegetation Register specific to Chapman’s Peak Drive has been compiled to facilitate their removal.
Stone catch walls have a dry-packed stone appearance which compliments the character of the scenic route Stone gabions used along the Noordhoek section of the route were packed to compliment the dry-packed stone walls One year after planting a good level of groundcover has been achieved, despite the artificial nature of the fill slope and disturbed natural water regimes.
Revegetation was undertaken by The Indigenous Vegetation Consultancy. Planting commenced on site in autumn and winter (May to August) 2004 to take advantage of the cooler, wetter conditions and ensure the best success rate for the revegetation.
Plants were hardened off prior to planting out to prepare them for the move from the sheltered nursery conditions to the exposed conditions on site. Material was planted at a density of 4 to 6 plants per m² and holes were organically fertigated and mulched. Species were replaced to their original locations wherever possible.
Due to the impact of construction activities on the water regime in certain areas, it was important to ensure that plants were accommodated within appropriate habitat conditions.
The following areas were prioritised for the initial phase of revegetation:
- fill slopes – original fill had to be removed and replaced to prevent the road from collapsing, resulting in slopes devoid of vegetation;
- drop zone area – original alignment of road at half-tunnel;
- concrete structures – roofs of concrete structures designed to be revegetated;
- stock pile sites and work areas – revegetate areas used for construction activities;
- cut off drains – replace planting disturbed by repairs to the cut off drains along the mountain side;
- catch fences – planting to rehabilitated disturbed areas and providing some screening at bases;
- picnic sites and lay-bys – planting to improve screening of new ablution facilities; improving the quality of indigenous vegetation on these areas, many of which were previously disturbed;
- general upgrading and improvement of indigenous vegetation in the road reserve.
The final stage of revegetation was hydroseeding these areas with a mix of indigenous seed. Two seed mixes were used, one for the Hout Bay section and one for the Noordhoek section of the road, using the seed collected in these two different areas.
The hydroseeding was particularly valuable to enable revegetation far beyond the road platform of the erosion slips below the road and the disturbed gullies above the road, where planting was not possible. Chapman’s Peak Drive will receive ongoing maintenance and revegetation over the course of the toll concession in order to upgrade the existing state of the natural environment. Improvements to the stability and visual impact of the original cut slopes have been targeted.
Erosion control and revegetation trials on the challenging clay slopes beyond the temporary toll plaza are currently being carried out and monitored.
Reflecting back one year later
The success of the search, rescue and propagation was followed by an extremely dry winter and one of Cape Town’s driest summers in many years. Water restrictions impacted on the irrigation of the newly planted areas, and limited permission to draw water from the Hout Bay river was granted under strict conditions.
However, despite the many challenges that have faced the rehabilitation of Chapman’s Peak Drive, the winter rains of 2005 have revitalised the revegetated areas and new growth is visible all along the site. This holds great promise for the future of Chapman’s Peak Drive.
Thabakholo’s maintenance period will end in August 2005, and maintenance will then cede to the operators, Entilni. MALA will continue to be involved in the environmental management and on-going rehabilitation of Chapman’s Peak Drive until 2008.
Text by Julia Goodwin. Photos by Julia Goodwin, Teresa Harwood and Megan Anderson, all of Megan Anderson Landscape Architects.
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