16 Mar 2014 14:20pm
WINDHOEK, 16 MAR (NAMPA) - The City of Windhoek faces financial and climatic constraints for the maintenance of about 780 kilometres of surfaced roads and streets in the capital.
Speaking at a media briefing here on Friday, the City of Windhoeks Manager for Corporate Communication, Marketing, Tourism and Customer Care Joshua Amukugo said most of the roads in the City are aging and many have passed their original design life.
He said roads are constructed with several foundation layers, depending on the volume and mass of the traffic it has to carry, and are then topped off with tar.
Amukugo said the purpose of the tarred surface is to provide a smooth, waterproof and dustproof riding surface.
As the road ages, this sealing layer dries out and loses its elasticity and waterproofing properties. Distress can be seen as cracks on the road surface as well as aggregate in the surfacing seal and the road loses its skid resistance, he said.
The CoW manager noted that as the surfacing stone is polished, this leads to vehicles being unable to stop during wet weather.
He explained that when water penetrates the upper foundation layers, the material starts to deform and distress can be seen as an uneven road surface and the formation of potholes.
Amukugo said continuous heavy traffic and overloaded vehicles place a tremendous amount of stress on the upper foundation layer.
He further noted that under ideal conditions, preventative maintenance would be done on a regular basis to ensure the integrity of the waterproof seal, but this is basically impossible to do due to financial constraints.
Amukugo said the type of sealing layer to be placed on top of the surfaced roads depends on the type and volume of traffic, as well as whether there are a lot of turning movements, and the cost ranges from approximately N.dollars 334 000 per kilometre (km) for a 6.7 millimetre (mm) single seal to N.dollars 1,2 million per km for a 35mm premix overlay.
In cases where the upper foundation layers of the road has deformed due to 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 the resistance to water.
Amukugo said the cost of recycling the upper layer amounts to approximately N.dollars 1,9 million per kilometre, and then a new surfacing layer still needs to be placed on top of it.
He said 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.dollars 5.3 million per kilometre.
Amukugo further noted that the surfacing works cannot be done when the road temperatures are below 15 degrees Celsius and this normally rules out the months from May to September.
Rain weather severely restricts the work, but if you decide not do work while there is the possibility of rain, this would rule out the months from November to April. That would leave you with one to two months a year to do work, which is not achievable, he said.