Amalendu Biswas, a retired government employee from Central Kolkata, was often forced to remember the office after a downpore because the lane in front of his house almost entered the waist-deep. He said that Muktaram Babu Street, Manikatala, Thana, MG Road, and Chittaranjan Avenue were flooded even after light rains.
“This scene was almost the same in some parts of Kolkata. Photos of boats in bodyguard lines in Alipore [housing police personnel] After being published after a heavy decline in every newspaper, “Biswas said.
The 150-year-old underground sewerage system of Kolkata has since changed a corner, which has overcome silt and neglect for silt and targeted restoration. There was hardly any water logging in July, even Kolkata received the second highest rainfall for the month since 2010. Mechanization has helped rapidly and more efficient will. The work starting in 2007-08 was extended in the last 10 years.
The Regional Meteorological Center (RMC) of the India Meteorological Department recorded about 669 mm of rainfall in July this, which is compared to the normal 371 mm. RWC chief HR Biswas said that there was at least three days of intense rainfall in July when Kolkata received more than 80 mm of rain within hours.
Large parts of Kolkata will be submerged after the first moderate (15 mm -64 mm) and heavy rainfall (64 mm -115 mm). Even after light rain (up to 15 mm), some pockets were performed.
A police constable said that despite the heavy rains in July, there is hardly any water logging in bodyguard lines. “Earlier, police personnel will need rubber boats to reach the office after a huge decline. After a huge decline now there is maximum ankle-deep water, but even it is rapidly again.”
British officer William Clarke designed the system between 1860 and 1875, the first such mechanism in Asia and the world’s third, rival London and Hamburg (Germany), to discharge rainwater up to 6 mm per hour.
Former Chief Engineer, former Chief Engineer of Kolkata Municipal Corporation (KMC), Nilangshu Bhusan Basu said Siltation reduced the hydraulic capacity of the sewer system. “The century old brickwork was in bad shape and was on the verge of collapse in many parts,” Basu said.
He said that the pumping stations were very old to handle the pressure. “Run-off-offs reaching sewers were increasing due to the destruction of the wetlands, which once worked as a sponge. Even the city’s outfall canal system was very quiet.”
KMC member-in-in-class Tarak Singh said that the civic body renewed the system by closing the sewer using a new machinery. He said that a complete overhaul was out of the question as it would cost years and thousands of crores. “We made a target intervention in weak and water logging-groce regions.”
Officials said that digging the entire system and laying new pipes was disqualified in a city with density of road spaces of more than 24,300 people in a city and about seven percent of the road space. The sewers were heavily filled with an obstruction of 70%-90%. There is hardly any disarray.
KMC Director General Satanu Kumar Ghosh said that he repaired the system. “The tunnels were rolled with a glass-rebellious polymer (GRP). It was smooth than the brick walls and ensured a sharp flow of water. The rapid flowing water would help to incite the sewer for a long time.”
The sewers were closed before repair. Singh said that about 36,500 mount silt was removed in 2014-15. “In 2024-25, it increased to 2,28,600 mounts. We removed the silt of about 184400 meters in 2020-21, when we removed [Covid] The epidemic was at its peak. In the last decade, KMC removed the silt of about 1.77 million meters to open the system, ”Singh said.
At least seven types of machines for removing silt, including street pit emptyer machines, jet cum suction machines and blow-vac machines, were used. Singh said that in 2004-05, the number of emptying street-pitting machines has increased from 15 to 15, jet-cum-clocks from seven to 63, and one to eight is empty. “Mechanization helped fast and efficient desilting.”
A KMC engineer said that water repair is required and reinforcement is dried out of the water. “The cleaning team then goes down after taking safety precautions. The machines are used to remove silt. Once the stretch is unlogged, the tunnels are repaired and their classic is groted to restore the size of their eggs.”
The engineer said that an egg -shaped tunnel helps maintain a good flow of water in dry weather. “GRP lines are then inserted to strengthen the tunnel.” He said that pumping stations were upgraded, and their number increased.
Jadavpur University School of Water Resource Engineering Professor Pankaj Kumar Roy called a huge work unloggy. “In some parts, the silt was rigid like the rock and had to be cut. The sewers were given a fresh strap of life by opening the sewer and strengthening them with the GRP.”
Above 5,000 crore was spent in the last 10 years on the project from KMC’s revenue, central and state government funds and an Asian Development Bank loan. Kolkata has about 2,800–3,000 km of underground sewerage and drainage systems, with new tunnels reinforced with concrete.
A former KMC engineer said that sewers should be declared an inheritance, called engineering Marvel, the most stretch with the British-era brickwork is still strong.
