Metro rail authorities in Kolkata are preparing to embark on a comprehensive ₹500 crore overhaul of the four-decade-old Blue Line tunnel between Tollygunge and Dum Dum, following serious structural concerns including subsidence, water seepage and platform damage. The programme will begin after reconstruction of the compromised Up platform at Kavi Subhash (New Garia) station.
Metro officials confirmed that a significant crack in the Dakshineswar-bound platform columns prompted suspension of services at New Garia as of 28 July. A demolition and rebuild contract worth ₹9.4 crore has been awarded to reconstruct the damaged section, with completion slated within nine months. The tender was kept deliberately under ₹10 crore to enable quicker procurement and avoid requiring Railway Board sanction. Once construction at Kavi Subhash is complete, officials plan to carry out tunnel-wide rehabilitation, targeting the entire 16.45 km underground stretch operational since 1995. A study by RITES is underway to structure the plan, including civil repair, track relaying, and upgrading signalling systems to increase operational speeds from the current reduced average of 55 km/h towards 80 km/h.
Metro Railway general manager highlighted critical subsidence in several tunnel sections, attributed to decades of wear and inadequate remediation. Expert assessments point to foundation issues and corrosion of support columns due to stray currents, exacerbated by heavy monsoon rains. Diaphragm wall leaks have also caused waterlogging and service disruptions in mid‑2025. The project will also include enhanced structural integrity measures at stations and pillars, more robust platform designs, and installation of modern signalling systems in line with contemporary safety norms. Metro officials emphasise that the 40-year-old infrastructure now demands proactive rehabilitation rather than periodic maintenance.
Commuter impact is expected, with truncated services on affected sections until rehabilitation is complete. The first phase of station reconstruction at New Garia is expected to be completed before Durga Puja; meanwhile, truncated service between Shahid Khudiram and Dakshineswar stations has been implemented. Shuttle bus services have begun along the 1.5 km corridor to mitigate commuter inconvenience. Railway sources say the repair timeline for the full tunnel overhaul could span three to four years given the scale and complexity, which includes coordination across civil, electrical, and signalling works.
The initiative aligns with Kolkata Metro’s sustainability and safety agenda, emphasising green corridor maintenance, long-term structural resilience and minimal disruption to commuters. As the city advances towards modern, equitable urban mobility, ageing infrastructure must be replaced or upgraded for safety and reliability. The overhaul marks a critical step in restoring public confidence in metro safety standards and long-term operational viability.
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