Plastic, solid waste and other discarded objects that float to the drainage pumping stations at the end of canals are a cause of concern with the monsoon just around the corner, officials of the state irrigation department and the Kolkata Municipal Corporation said after inspecting some canals on Monday.

Accumulation of silt, especially near the drainage pumping stations, was another issue flagged during the joint inspection.

How fast Calcutta’s roads drain water following a heavy spell of rain depends on the canals’ ability to take the water and channel it.

“I have asked the irrigation department engineers to desilt the stretch near the Chowbhaga drainage pumping station a little more. The desilting has been done, but a little more near the drainage pumping station will allow pumps to drain out water faster,” said Tarak Singh, the mayoral council member in charge of the sewerage and drainage department of the Kolkata Municipal Corporation (KMC).

Officials said the plastic menace was also something that had them worried.

The state irrigation department has started setting trash racks across the canals to stop floating materials from reaching the drainage pumping stations.

“If the floating materials clog the drainage pumping stations and slow down the pace of water draining out from the canals,” said an official of the state irrigation department.

The drainage pumping stations have high-power pumps that suck water out from the canal and drainage network downstream and throw the water into other channels through which the water is eventually taken out of Calcutta.

On Monday, the officials inspected four canals — Suti canal, Guniagachhi canal, Intercepting canal and Tollygunge-Panchannagram canal — that drain water out of the city’s southern fringes and southeast.

All the canals had large volumes of discarded objects floating on the surface.

The trash racks being built across the canals will have a mesh-like structure above the water that will block the floating materials from reaching the drainage pumping stations. Two foundations are being built on the two banks of the canal to hold together the mesh-like structure that will span from one bank to the other.

Monday’s inspection was part of the civic body’s preparations for the approaching monsoon, but it came when the Alipore weather office had already forecast heavy rain in the city.

KMC officials said they will deploy additional manpower to run the pumps, operate the penstock gates and monitor the waterlogging-prone areas from Wednesday to Saturday.

“Usually, we deploy these people from June 10 till the end of October. We are deploying them for four days because of the heavy rain forecast,” said an official.

The KMC runs 460 pumps in 82 drainage pumping stations.

Singh said the civic body had cleaned 20 lakh tonnes of silt from the city’s drainage network in the last ten years. “We have significantly increased the capacity of the drainage network,” he said.