A bituminous coat is being laid over several broken roads in the city without first scraping off the old layer, resulting in elevation of the roads beyond the ground floor of houses along them.
In many places, the roads were already higher than the properties along them. The new layer is further sinking the residences.
Every monsoon, water from the roads flows into the houses and inundates the ground floors. The Kolkata Municipal Corporation (KMC) repairs many broken roads during winter.
Two streets where a new layer was laid recently over the old layer are Balu Hakkak Lane and West Row Road in south Kolkata’s Beckbagan.
The owner of a shop on West Row Road said the top layer was laid recently. “Water from the road enters my store every monsoon,” he said.
A month ago, a fresh bituminous layer was laid over the old layer on Sarat Ghosh Garden Road in south Kolkata’s Kasba, sources said. In all these places, the current road height — after the new layer was laid — is between 3 and 4 inches higher than the oldest layer that can still be seen at the edges.
The overlaying without removing the old layer is mostly happening on sub-arterial roads and the ones connecting arterial roads.
Partha Pratim Biswas, a professor of construction engineering at Jadavpur University, said bonding between the new layer and the old layer is often not good enough when such overlaying takes place. The life of the new layer is considerably reduced when there is a lot of braking action on such roads.
Biswas said that in a city like Kolkata, where drivers brake and press the accelerator frequently, the top layer gets eroded faster if the bonding with the layer below is not good. The surface wears off faster because of the abrasive action of tyres.
Loose bonds between layers also leave open the possibility of sub-surface water penetration, leading to faster erosion of the top layer.
“When such a road gets waterlogged, the water will penetrate through the new and old layers and destroy the road,” he said.
A KMC official said that removing the top layer of a road was a costly task and the civic body did not have plans to remove the top layer of sub-arterial roads soon.
The KMC has embarked on a project where it is scraping off portions of some arterial roads like SN Banerjee Road or Ballygunge Circular Road that are undulated.
The uneven portions are scraped off and a new layer is laid to keep them at the same level as the surrounding sections.
This is being done after years of complaints that Calcutta’s arterial roads are undulated, which happens because of shoddy repair jobs, said engineers.
Similar scraping has not yet started on any sub-arterial road or other roads, said a KMC engineer.