New tech to fortify British era storm water drains, prevent floods

Experts say the technology will minimise excavation without disrupting traffic, phase 1 to be completed in 2027

MUMBAI: The Brihanmumbai Municipal Corporation (BMC) is reinforcing its 100-year-old underground storm water arch drains in Mumbai city and suburbs to increase its lifespan by at least 50 years, using a new technology that will improve water flow and speed up rainwater drainage during heavy spells of rain.

New tech to fortify British era storm water drains, prevent floods

The British-era drains will be fortified using geopolymer lining trenchless technology. Geo-polymer is a mineral-based chemical material made from aluminosilicate powders (such as fly ash or metakaolin) mixed with alkaline solution, which reacts chemically to form a ceramic-like solid structure. It is used to line the inside of the drain to prevent leaks and allows smooth flow of water.

Phase 1 of the project, at a cost of ₹535 crore, was commissioned in April 2023, following a survey by experts from IIT Bombay and VJTI the previous year. A technical survey meeting was held in November 2022, which approved the use of geopolymer lining trenchless technology to restore the damaged drains.

The survey revealed 56 storm water arch drains covering 23.58 kilometers were damaged, of which 27 arch drains spanning 14.28 kilometers were identified for urgent rehabilitation. This prompted the civic body to prioritise structural strengthening of the ageing underground network.

Work in the phase 1 however progressed at a snail’s pace from November 2023, but officials have said that it will be completed in November 2027. “We inspected the ongoing work on Saturday near Shantiketan storm water outfall at Shamaldas Gandhi Marg near Princess Street flyover to find that 50% of work is completed,” said Sunil D Rasal, deputy chief engineer from BMCs storm water drains (SWD) department.

The initiative is part of BMC’s broader effort to modernise Mumbai’s century-old storm water drainage infrastructure and reduce flooding risks during extreme rainfall. “The trenchless geopolymer lining technology enables repairs from within the drains, minimising excavation and avoiding major disruptions to roads and traffic in densely populated areas of the city,” said a civic official, adding that the technology was being used was being used for the first time in India, “though similar methods are widely used in USA”.

Mumbai’s storm water drainage system plays a crucial role in discharging rainwater into the Arabian Sea, with tidal conditions significantly influencing the outflow. Although regular desilting and maintenance are carried out, CCTV surveys revealed cracks, displaced bricks, damaged joints and roof collapses in several parts, necessitating urgent structural intervention.

The project comes at a time when Mumbai has been increasingly witnessing intense rainfall due to changing climate patterns, with nearly 1,000 mm of rain recorded within two to three days in recent years, leading to severe waterlogging and flooding in several parts.