An Unusual Inspector Investigates Road Resealing
In Kruger National Park
This year routine maintenance of Kruger's 'tar' roads experienced a slight hitch, when an unexpected wildlife encounter occurred. An elephant objected to a heavy vehicle going to the sand stockpile on the side of the road. The driver stopped the truck, but the elephant was obviously feeling grumpy, and took out his frustration on the truck's cab. Coenie Coetzer, roads foreman for the Letaba district, says that this is the first time in his 24 years in the park that such an incident has occurred.
The Kruger National Park has about 900km of 'tar' roads, which are in fact sand seal roads, created with hot bitumen and sand. Unlike other roads, they contain no crushed stone. Every year, the park's routine maintenance programme tries to reseal about 70km of road. This March, it was the turn of the H9 between Phalaborwa and Letaba, with work starting where it was left off last year at about 30km from the Phalaborwa Gate. This resealing is now completed all the way to the Phalaborwa gate.
Coenie says the team reseals about 3.5km per day. Resealing involves first stockpiling sieved river sand, which must be free of silt. Then, hot bitumen is shipped into the park, with several tankers being necessary to ensure an uninterrupted supply. A coat of hot bitumen is sprayed on the old road surface. Immediately, a sand spreader that puts sand on top of the bitumen follows the tanker. A roller then compacts the surface, giving a finished thickness of about 6mm.
Cars can drive over the sand as soon as it has been rolled. If some sticky sand gets on the car, Coenie says it can easily be removed with either paraffin or car polish. Sand seal roads have a maintenance-free life of about 14-16 years, and the river sand eventually washes back into the rivers as the road degrades.
Although both black and smelly, bitumen and tar are actually different products. Bitumen is the residue created when crude oil is refined, while tar is made from coal. Tar contains cancer-causing hydrocarbon compounds that can leach into water, while bitumen is relatively inert and therefore much more environmentally-friendly. The next section of road due for its routine maintenance resealing is up near Punda Maria, and the team will be busy there in about a month's time.