Chennai’s monsoon preparedness is facing a preventable threat as waste dumped into sewer lines continues to cause blockages, even while the Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) carries out precautionary work across the city. The board has already desilted roughly 6,000 km of active sewer lines twice and is now undertaking a third round that will continue through the monsoon, DT Next reported, quoting a senior official.
The desilting work has covered about 1,70,000 manholes. Officials said the blockages are caused by clothes, diapers, sanitary napkins and other waste entering the sewer system. The problem is not confined to informal settlements, despite the frequent focus on those areas. The official said similar dumping takes place from high-rise apartments and housing board flats, creating blockages that can result in sewer overflows.
CMWSSB has also expanded its operational preparations. Of the city’s pumping stations, 423 are automated and connected to the Internet of Things. These stations are designed to switch on when water reaches a set level and switch off after levels fall, reducing dependence on workers being physically present during heavy rain.
The board plans to double water-sample testing during the rainy season to 1,800 samples, compared with 600 on normal days. Additional samples will be collected from Tamil Nadu Urban Habitat Development Board complexes. The testing is intended to help prevent waterborne diseases during a period when sewer overflows and stagnant water can increase public-health risks.
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’s experience during the 2021 and 2023 floods has prompted the board to raise the height of 20 pumping stations in low-lying areas and install generators at those locations.
Generators are on standby, diesel supplies have been procured for one to two months, and sandbags have been kept ready. The board has 740 machines available, including high-speed sewage suction vehicles. CMWSSB owns 600 of these machines, while 173 will be outsourced under the Annal Ambedkar Business Champion Scheme. Around 130 suction lorries will be brought from other districts and shared with the Greater Chennai Corporation.
Rainwater harvesting remains another part of the city’s preparedness. Structures at about 10 lakh of Chennai’s 12 lakh buildings are reported to be functioning, while the remaining two lakh require maintenance. Officials said roughly 90 per cent of rainwater harvesting structures in large houses, high-rises, hospitals and information-technology companies are functional, but smaller houses have lower compliance.
The third round of sewer-line desilting will continue through the monsoon, while pumping, equipment deployment, water testing and rainwater-harvesting maintenance will remain central to the authorities’ preparations.
