Chennai has begun its third round of sewer desilting and monsoon preparations, but Metro Water officials say waste dumped into sewer lines remains a major risk to preventing overflows and water stagnation across the city.
The Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) has already desilted roughly 6,000 km of active sewer lines twice, covering about 1,70,000 manholes, according to a senior official quoted by DT Next. A third phase is now under way and will continue through the monsoon.
The official said blockages are caused by clothes, diapers, sanitary napkins and other waste entering the sewer network. While residents in informal settlements are frequently blamed for misusing the system, the problem also extends to high-rise apartments and Tamil Nadu Housing Board flats, where similar waste is dumped into sewers.
Of Chennai’s pumping stations, 423 are fitted with internet-of-things systems and automated controls. These pumps are designed to start when water reaches a predetermined level and stop once the level falls, reducing dependence on workers being physically present during heavy rain.
The board is also increasing water-quality monitoring to reduce the risk of waterborne disease. Officials said 1,800 samples will be tested during the rains, compared with 600 on normal days. Additional samples will be collected from Tamil Nadu Urban Habitat Development Board complexes.
Officials said infrastructure managed by the Greater Chennai Corporation can handle up to 20 cm of rainfall in a day, although rainfall intensity can vary sharply. The city experienced severe flooding in 2021 and 2023, after which the board raised the height of 20 pumping stations in low-lying areas and installed generators at those locations.
Generators are on standby, diesel stocks for one to two months have been procured, and sandbags have been kept ready. The board has identified 740 machines, including high-speed sewage suction vehicles, for monsoon operations. Of these, 600 are owned by Metro Water, while 173 are expected to be outsourced under the Annal Ambedkar Business Champion Scheme. Around 130 suction lorries will also be brought from other districts and shared with the Greater Chennai Corporation.
Rainwater harvesting is another preparedness concern. Structures are reported to be functional in about 10 lakh of Chennai’s 12 lakh buildings, while the remaining 2 lakh require maintenance. Officials said roughly 90 per cent of systems in large houses, high-rises, hospitals and information technology companies are working, but smaller homes have lower compliance.
The ongoing desilting, automated pumping, equipment deployment and additional health testing will continue through the monsoon, according to Metro Water officials.
