Several stretches of Kolkata's roads that were subjected to patchwork repairs have suffered damage with the surface coming off following Tuesday's rain.
The surface of parts of Chittaranjan Avenue, EM Bypass, Park Circus connector, Harish Mukherjee Road, NSC Bose Road and Strand Road has peeled off within weeks of repairs.
Engineers said patchwork repairs could not be an alternative to thorough repairs.
A few weeks back, the Kolkata Municipal Corporation had carried out patchwork repairs on a number of stretches of Chittaranjan Avenue. By Wednesday, some of the stretches, including the one in front of MG Road Metro station and another near Girish Park, lost their top layer.
Similarly, the surface across stretches of EM Bypass where the KMDA had carried out patchwork repairs came off following Tuesday’s rain. The stretches include the approach to the Ruby rotary from the Parama flyover.
Civic engineers said the contract for patchwork repairs did not have a built-in guarantee period. The contractor will not be liable if cracks re-appear a day after repairs.
KMC officials said repairs would again be taken up once rain stopped. “We will ensure no puja committee has any complaint about potholed roads before the Puja,” said Ratan Dey, a member of the board of administrators of the Kolkata Municipal Corporation.
Engineers said many roads lacked proper compaction. A mixture of sand, stone chips, lime and gravel, which is usually used to build the sub-base, is not allowed to settle down. As a result, water tends to accumulate in uneven pockets and begins seeping in through the bituminous layer resulting in craters. When potholes are filled up in patchwork repairs, the strength of the existing material of the road and that of the one with which it has been repaired tend to vary. The variation results in poor bonding of materials.
“The variation is largely because not enough time is allowed for compaction of the surface. This lack of compaction of the sub-base also explains why we witness waterlogging,” said Partha Ghosh of the construction engineering department of Jadavpur University.
“The concept of patchwork repairs for bituminous surfaces is flawed. It only works for concrete surfaces because the two materials bond well.”