This initiative is expected to minimise run-off of rainwater and recharge the groundwater table

With drought, fears of water scarcity and a depleting groundwater table becoming part of our daily lexicon, the Bruhat Bengaluru Mahanagara Palike (BBMP) is now attempting to harness as much rainwater as possible. It has begun digging percolation pits in the drains of white-topped roads, which will help minimise the run-off of rainwater and recharge the groundwater table.

According to senior civic officials, the percolation pits were not part of the original design for the concrete roads. “However, we are now creating these pits even on roads where the work has been completed,” said a senior official.

The officials monitoring the white-topping told The Hindu that the depth of the pits are, on an average, four feet. Pre-cast rings of RCC (Reinforced Cement Concrete) are being laid. The size of the rings is dependant on the available width of the shoulder drains on either side of the road.

“The pits are being dug at the lowest point in the drain. They have basic filtration system comprising a layer of gravel and sand at the bottom, and a nylon net at the mouth on top. This will ensure that garbage doesn't clog the percolation pits,” the official said and added that the BBMP had now included percolation pits in the design.

The BBMP's move has been welcomed by civic activists.

S. Vishwanath, water conservationist and rainwater harvesting expert, pointed out that 100 sq.m. of roads have the potential to harvest 1 lakh litres of rainwater. “This is a phenomenal amount of water. However, the BBMP must test the rate of recharge and design the percolation pits/recharge wells accordingly,” he said.

He added that sand and gravel filtration may not be sufficient. “Apart from the net on top, the bottom of the pit must have a grill,” he said. He wants the BBMP to prioritise regular maintenance.

Footpaths to be better

Wide and obstruction-free pavements will be a feature on many of the roads where white-topping has been completed. According to senior officials of the BBMP, a presentation was made before the Chief Secretary recently.

On many stretches, the width of the footpath varies from 2.5 metres to 3.8 metres.

As per Indian Road Congress guidelines, the width should be at least 1.8 metres in residential areas and 2.5 metres in commercial areas.

Officials admitted to a delay in completion of work on 95 km taken up under Phase 1 of the project.

“We have completed work on around 40 km of roads. The work is being taken up on roads for which a green signal has been given by the traffic police,” an official said. Traffic police are wary of giving approval for taking up white-topping work on multiple stretches simultaneously, as it could compound the problem of congestion.

Meanwhile, white-topping will be carried out on 63 km of roads in Phase 2 of the project for which civil works have already been taken up.