Chennai Metro Water has begun its third round of monsoon preparations after desilting about 6,000 km of active sewer lines and nearly 1,70,000 manholes, while officials warn that waste dumped into sewers remains a major cause of blockages and overflows across the city.
The Chennai Metropolitan Water Supply and Sewerage Board, commonly known as Metro Water, has already completed two rounds of desilting ahead of the rains. The third phase is under way and will continue through the monsoon, according to a senior official quoted by DT Next.
The official said blockages are caused by clothes, diapers, sanitary napkins and other waste entering the sewer network. The problem is not restricted to informal settlements, despite the frequent focus on those areas. Similar waste is being dumped from high-rise apartment buildings and housing board flats, contributing to sewer overflow, the official said.
Metro Water is also relying on automation at pumping stations. Of the pumping stations in the city, 423 are IoT-based and automated. They are designed to switch on when water reaches a set level and stop once the level falls, allowing operations to continue even when workers are not present at the site.
The board plans to increase water-quality testing during the rainy season to reduce the risk of waterborne diseases. Sampling will rise to 1,800 during the rains, compared with 600 on normal days. Officials said additional samples would be collected from Tamil Nadu Urban Habitat Development Board complexes.
The city’s infrastructure managed by the Greater Chennai Corporation can handle rainfall of up to 20 cm a day, according to officials. However, the intensity of monsoon rainfall remains difficult to predict. The 2021 and 2023 floods exposed the pressure that extreme rainfall can place on drainage, pumping and sewage systems.
As part of its preparations, Metro Water has raised the height of 20 pumping stations in low-lying areas and installed generators at those locations. Other generators are on standby, while diesel supplies for one to two months and sandbags have been procured.
A total of 740 machines, including high-speed sewage suction vehicles, have been kept ready. Metro Water owns 600 of the machines, 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 unresolved part of the city’s monsoon readiness. Officials said systems in about 10 lakh of Chennai’s 12 lakh buildings were functioning, while the remaining two lakh required maintenance. Around 90 per cent of rainwater harvesting structures in large houses, high-rise buildings, hospitals and information technology companies were reported to be functional. Smaller houses, however, continued to show weaker compliance, officials said.
The preparations place responsibility on both the city’s public agencies and property owners. Sewer desilting, pumping capacity and emergency equipment can reduce the impact of heavy rain, but waste entering the network and poorly maintained rainwater harvesting systems can still undermine that infrastructure. Metro Water’s third desilting phase and increased sampling will continue through the monsoon.
