WINDHOEK – The City of Windhoek (CoW) on Friday said preventative maintenance on the city’s roads should take place under ideal conditions, but this cannot happen due to financial constraints.
Municipal officials said the city receives approximately N$80 million a year to maintain the road network. Officials also estimate that about N$602 million is needed to resurface all of Windhoek’s 780km of tarred roads. The resurfacing should preferably take place every 10 years, which on average works out to about N$60 million a year in maintenance costs. The cost of preventative maintenance ranges from approximately N$334 000 per km for a 6.7mm single seal to N$1.2 million per km for a 35mm premix overlay. Roads are basically constructed with several foundation layers, depending on the volume and mass of the traffic it has to carry. This is then topped off with a waterproof sealing lafayette, commonly referred to as tar. “In cases where the upper foundation layers of the road has deformed, either due to the ingress of water or continuous heavy traffic, or needs to be strengthened, the material can be recycled and cement added to increase the strength and bitumen to increase reistance to water,” explained the city’s spokesperson, Joshua Amukugo. The cost to recycle the upper layer amounts to close to N$2 million per kilometre, after which a new surfacing layer still needs to be placed on top. Said Amukugo: “In cases where the road has been allowed to fail completely, the only option is to reconstruct it completely at a cost of at least N$5.3 million per kilometre.”
City of Windhoek engineers explained that as the roads age, the sealing layer dries out and eventually loses its elasticity and waterproofing properties. This distress can be seen as cracks on the road surface, as well as the aggregate loss from the surfacing seal. “When water penetrates into the upper foundation layers, the material starts to deform and distress can be seen as an uneven road surface and the formation of potholes. Continuous heavy traffic and overloaded vehicles place a tremendous amount of stress on the upper foundation layers and this distress can be seen as an uneven road surface,” Amukugo said.
City engineers added that the time permitted to resurface roads is a major problem. They explained that the work cannot be done when the road temperatures are below 15 degrees, which normally rules out the months from May to September. In addition, rainy weather severely restricts the work, which basically rules out the months from November to April, meaning there are effectively only two months out of the year when the work can be done. “The decision on what to do on which roads is based on visual assessments conducted on all the roads by a team of specialist engineers,” Amukugo further observed.
By Edgar Brandt