Mumbai: BMC plans to construct absorption pits for flooded city roads

As it prepares to concretise hundreds of kilometres of roads in the next three years to overcome the problem of potholes, the BMC plans to construct absorption pits on these roads to reduce waterlogging during heavy rain. Since concrete cannot soak water, sources in the civic body said, the pits will take some load off the stormwater drains and reduce waterlogging. They will also help recharge groundwater in the city.

The BMC has invited tenders worth Rs 5,800 crore to convert 400 km of asphalt roads into concrete thoroughfares. The absorption pits will come up during the concretisation of the roads. Absorption pits are usually built in the middle of a road, along with dividers, or at the edges, close to the pavements. These are closed porous chambers that allow water to seep into the ground.

"This is the first time BMC has decided to have absorption pits on roads. Not all rainwater falling on streets go into the drains. Some of it will be absorbed by the pits. These will also help reduce the load on the existing roadside drains. The move will not just help address waterlogging but also increase the groundwater level," said a BMC official.

Also read: Mumbai: More than half of city's roads to be under construction for next 3 years

Chandrakant Metkar, deputy chief engineer of the corporation's road department, said the pits will be created at regular intervals along the road. "The planning of these pits will be done according to the local geographical condition as well as the flooding issue at that particular spot or area," he said. Though accurate details about the soak pits will be known once the road designs are finalised, officials said, the gap between the two absorption pits is expected to be 300-350 metres. "The consultant will decide on the distance and other parameters for designing these pits," said Metkar.

Experts said the BMC will need to invest a lot of care and planning to make the absorption pits work. Sandeep Adhyapak, an expert on rainwater harvesting, said if the depth of the pits is kept at 2-3 feet, then they won't be useful. "Proper planning with help of experts needs to be done while constructing such pits. If implemented properly, the move will help reduce waterlogging to some extent," he said.

The soak pits do help recharge groundwater, said Adhyapak. At some places in Mumbai, people dig up to 500 feet to access groundwater, he said. "But if the new idea is not executed properly, citizens' money will go down the drain."

Mumbai and flooding

386: No. of flooding spots in the city
282: No. of spots where flood-control work has been done as per BMC
477: No. of dewatering pumps installed in the city which cost the BMC R25 crore

400 km
Length of roads that will be concretised in next three years