You may have seen it before, and if you didn’t, you probably felt it, a manhole cover that is installed in the middle of the road, exactly where your wheels are heading, and wondered why on earth it could not have been placed two metres to the left on the sidewalk.
With these sewer covers posing safety risks for motorists, it may seem counterintuitive to put them on a busy street, but there is logic behind it.
According to the Joburg Roads Agency (JRA), the city allowed services to be laid within a road following the rapid expansion of infrastructure over the decades, as there is limited extra space for it to be done.
“Johannesburg is more than 100 years old. Back in the day when Johannesburg was laid out, no one would ever have thought that the City would expand as much as it has in the last decades. Thus in an area like the old CBD and even the old suburbs, road reserve sizing was limited to only what was required at that time. Since then, the City has significantly expanded, not only from a road capacity perspective but also from other requirements like stormwater management, technology, electricity, telecoms, water, sewer, fibre, to name a few,” said the JRA.
“Due to limited space, other alternatives had to be considered, roads got wider and wider, sidewalks got narrower, underground services expanded, therefore, the road reserve was optimized and we introduced services to be laid within the road.”
In modern times, when an area is developed, the JRA’s cross sections for a road reserve provide a plan for what underground service will be laid there, and more often than not, there are instances where a manhole would be required in the actual road specifically for stormwater, sewer, and water services as it is not always possible to place them only on sidewalks/road reserves due to the contours of the ground, as well as other existing services below the sidewalk’s surface.
There are two types of manhole lids; light-duty covers specifically designed for on-the-sidewalk applications, and heavy-duty covers which are firstly strong enough to carry any weight of any vehicle that uses a road and secondly will not flip up when a vehicle drives over it.
There are also fibre internet and electricity manholes that must be made waterproof, as well as sewer covers that require breathing space to ensure no build-up of methane gas.
Manholes do not accelerate road decay
Despite providing more gaps and crevices for water to seep into, manholes do not, in fact, accelerate road deterioration, said the JRA.
The cover frames are packed tightly into the road and the little bit of water that manages to seep in does not have a noticeably negative impact. The tar itself also contains chemicals like bitumen that prevent the corrosion of the metal frames.
“In most cases, the tar around the manhole gets damaged due to theft and vandalism of the steel frames and covers,” it said.
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