Mumbai: BMC starts trenchless upgrade of drains to boost flood control

The Brihanmumbai Municipal Corporation BMC has initiated a major infrastructure upgrade to strengthen over a centuryold network of underground arch stormwater drains in the island city using geopolymer lining through trenchless technologyThe civic body said the intervention aims to significantly improve the structural integrity of Britishera drains while enhancing their capacity to discharge rainwater more efficiently during heavy downpours Officials estimate that the upgrade could extend the lifespan of these drains by at least 50 yearsFocus on ageing and vulnerable infrastructureMumbairsquos stormwater drainage systemmdashmuch of which dates back over 100 yearsmdashhas been under increasing strain due to rapid urbanisation and more frequent extreme rainfall events The cityrsquos geography bounded by the Arabian Sea and influenced by tidal conditions further complicates drainage especially during high tideAccording to civic data the island city alone has a 495kmlong stormwater drain network while the eastern and western suburbs account for an additional 63 km each In total Mumbairsquos arch and closed drain network spans 621 kmRoutine maintenance such as desilting is carried out annually However recent CCTV inspections conducted by the BMCrsquos operations and maintenance teams revealed widespread structural deterioration in several sections of the underground drainsThese include cracks in masonry displaced bricks damaged joints partial roof collapses and other defects that could compromise drainage efficiency during intense rainfallCCTV surveys flag urgent repairsBased on these findings 56 arch drains measuring a combined 235 km were identified as being in poor condition Of these 27 drains covering 1428 km have been prioritised for urgent rehabilitation under Phase 1 of the projectCurrently lining work is underway across stretches totalling around 14 kmSenior civic officials including Deputy Municipal Commissioner Infrastructure Girish Nikam and Chief Engineer Storm Water Drains Kalpana Raut recently inspected ongoing work near the Shantiniketan outfall close to the Shamal Das Gandhi Marg flyoverTrenchless technology to minimise disruptionThe BMC has opted for geopolymer lining using trenchless technologymdasha method that allows repairs to be carried out without largescale excavation This is expected to reduce disruptions to traffic and daily life in densely populated parts of south MumbaiThe technology was selected following consultations with experts from the Indian Institute of Technology Bombay and the Veermata Jijabai Technological Institute and subsequent recommendations by a Technical Advisory Committee in November 2022While widely used in countries such as the United States this marks the first largescale application of geopolymer trenchless lining for stormwater drains in IndiaAddressing flood risks amid extreme rainfallIn recent years Mumbai has witnessed episodes of intense rainfall with nearly 1000 mm recorded within a few days in some instances leading to widespread waterlogging in lowlying areasCivic officials said the upgraded lining will not only reinforce the structural stability of the drains but also improve internal flow characteristics enabling faster discharge of stormwaterSustainable and longterm solutionApart from durability the BMC has highlighted the environmental benefits of geopolymer materials which are considered more sustainable compared to conventional optionsWith Phase 1 focusing on the most vulnerable sections the project is expected to serve as a model for future upgrades across the cityrsquos ageing drainage network as Mumbai continues efforts to strengthen its flood mitigation infrastructure ahead of increasingly erratic monsoon patterns