White topping: Concrete solution?

Proclaimed as the ultimate cure for the pot-holed Bengaluru roads, the massive white-topping project had everyone sit up and watch. But as a thick layer of concrete is being applied over the asphalt on roads across the city, a huge, unaddressed problem has surfaced: The increased road level has raised the potential for flooding. Will this be a serious miscalculation of design?

Triggering massive traffic jams, the project has indeed put motorists in misery. Yet, they have endured it in the hope that potholes would be a thing of the past. But what if it at the cost of flooding, where the rain water has just no way to drain out? This is exactly what road engineering experts are drawing attention to.

Design flaws

This design flaw is clearly evident on Mysuru Road near the KSRTC Satellite terminal. The 15-cm white-topping with only superficial milling of the existing bitumen layer has substantially raised the road level. A good five feet gap is left at the old level between the white-topped road and the footpath. Underneath the pavement runs the shoulder drain.

The challenge lies here. If this shoulder drain is not raised to the white-topped level and adequate openings made to let in water, the next rains could play havoc. Shopkeepers and commercial establishment owners along this critical arterial road now fear that the water could flood their properties.

Level variations

In New Guddadahalli on Mysuru Road, this fear has its basis in last year's floods. Recalls Vakil Singh, a shop owner, "Although the drain runs underneath at par with the road level here, the rainwater was overflowing like a river. Unless they sort out the road and drain levels with wide inlets, it will get worse after the next showers."

Planned execution of a complex work seems compromised in a hurry to finish the task before the elections. This is what Prakash K G, a petrol bunk manager near Nayandahalli feels about the project. "When they are spending such a lot of money, they should have had a good plan and design. It does not appear so, as properties on either side of the road are at a lower level and thus prone to floods," he says.

Thin, ultra-thin layers

Were these issues factored in before the white-topping design was finalized? Road and Transport Engineering expert M N Sreehari does not think so. "Current technology prefers a much thinner layer of white-topping over bitumen. The concrete layer could have been limited to 4-inch or 10-cm. The 10 to 12.5-cm layer being applied is a bit too thick. To ensure that the road level is not too high, the existing bitumen layer should have been milled entirely," he explains.

Unlike TenderSURE roads, the utility pipelines are not shifted underneath the pavement on white-topped roads. The alternative could be to shift these at least to the edges. Since this is not done on several stretches, a potential problem looms large. Civic agencies such as the Bangalore Water Supply and Sewerage Board (BWSSB) have notoriously dug up even TenderSURE roads. Doing so on white-topped roads could be disastrous.

Road-cutting issues

Road-cutting on white-topping is much worse than pot-holes on asphalted roads, say experts. "Even if water stagnates on concrete roads, pot-holes are not formed. But repairing a white-topped road after cutting it open is tough," says civic evangelist V Ravichander.

The BBMP, he says, should have opted for white-topping only at asphalted road intersections that are highly vulnerable to potholes. "Vehicles could then be evacuated faster from the junctions. The priority should be to re-imagine the entire project to ensure uniform road geometry and to think in terms of wider footpaths, cycling lanes and street furniture," he explains.

Footpath level

Besides the flooding risk, a key factor in the current white-hopping design is the level difference between the motorway and the footpath. "A good road is one where the footpath height is not more than six inches from the road. But on Koramangala 80 ft road, for instance, the gap between the road and footpath has almost disappeared. What is added is more than what is removed in a hurry."

Historically, many city roads have the shoulder drains near the property and not near the road. Retrofitting the white-topping method without a sound understanding of this complexity has now created problems of linkages. Civil engineering experts say the road should slope on either side so that rain water flows into openings leading to the drain near the road or the property. It has to be done now, when the concrete is mixed, and not later.

Palike assurance

The Palike, notes Sreehari, has not considered the available options of thin and ultra-thin white-topping. Adopting this could have save time and money. But the BBMP officials claim the increase in the surface level will not make much of a difference. Once the concretisation is completed, the gaps will be asphalted and the differences will disappear, says a senior Palike officer.

By all accounts, white-topping is an expensive project at Rs. 972.69 crore. The first phase covers 93.4 km of city roads while the second phase includes concretisation of another 150 kms. Promised are roads that can last upto 30 years. But whether road-users can endure flood-prone stretches for even a year is another question.