The scenic 4.5 km stretch of coastal road between Muizenburg and Clovelly, one of only three routes linking the Cape Town metropolitan area with the far south, had last been re-surfaced in 1994 using a hot in-situ recycling method, which was designed to last approximately 10 years.
Knight Piésold was appointed by the City of Cape Town to rehabilitate the Main Road from Muizenberg to Clovelly in 2006 and the project was undertaken in three phases of which the Leighton Road, St. James to Kalk Bay Harbour Entrance section is Phase 2.
Several difficulties and complexities were experienced in laying the new 700 mm diameter ductile iron water main. Lack of sufficient space because of a multitude of existing services which to be kept alive for the full duration of the operation, and the fact that the road was constructed in half widths to maintain the flow of traffic, made it necessary in most cases to lay the new pipes in very close proximity to the old asbestos cement main.
In many instances, unknown services or banks of very hard Table Mountain sandstone were encountered. This necessitated the sudden making up of “specials” in the form of a series of bends which are obviously not “off the shelf” items, and innovative non-destructive blasting techniques such as “boulder busting” using an explosive cartridge inserted into a pre-drilled water-filled hole.
Bearing in mind that the far south of the Cape Peninsula is wholly independent on this pipe line for its water supply, any slight movement of the old joints could have resulted in absolute disaster, and many an anxious moment was shared by the site staff whenever this operation was carried out. It was therefore always a great relief to all involved when a “blasting” operation has been successfully completed. Fortunately, this has been the case in respect of both the phases that have been completed thus far and no serious mishaps have occurred.
Maintaining existing services and access to properties meant that the contractor has to ensure that all existing underground services, such as water, sewerage, electricity, telecommunications, and stormwater remained fully operational at all times. This required extremely careful work procedures to ensure that these fragile and essential services were not damaged.
In addition to the service mains under the road, care also had to be taken not to damage or disturb services to properties adjacent to the road. Maintenance of access to properties was also a major challenge that had to be dealt with. This was especially relevant in the busy Kalk Bay business district, which is a very popular tourist area with its many shops and restaurants.
2015 CESA AON Engineering Excellence Awards – Commendation in the category “Projects ranging in the value of R50m to R250m”