Kolkata Metro Starts ₹585 Crore Sustainability-Focused Renovation of Blue Line.

Kolkata Metro has launched a ₹585 crore modernisation project to upgrade air-conditioning and tunnel ventilation systems across 15 underground stations on the Blue Line, marking the first major overhaul of India’s oldest metro in its 41st year.

The project, covering the 16-km Belgachhia–Rabindra Sarobar section, aims to introduce energy-efficient tunnel ventilation (TVS) and environment control systems (ECS), enhancing comfort, safety, and sustainability for passengers. Metro Railway General Manager Subhransu Sekhar Mishra flagged off the initiative recently at a ceremony inside the Noapara station-cum-carshed, accompanied by a traditional puja.

“The project will save significant energy and groundwater. Work will be carried out in phases, covering five stations at a time, and will not disrupt metro operations,” Mishra said. The upgrade is expected to be completed in four years.

Asim Majumdar, Metro Railway’s Principal Chief Electrical Engineer, said the transition from water-cooled to air-cooled chillers will reduce 23,000 metric tonnes of carbon emissions annually and conserve around 18 crore litres of groundwater each year. Global bids were invited, and the contract was awarded to Shinryo Suvidha Engineers India, a subsidiary of Japanese firm Shinryo, to replace 30 out of 46 water-cooled chillers with energy-efficient air-cooled units.

Kolkata’s Blue Line was among the first tropical-climate metros in the world, alongside Hong Kong, to adopt air-conditioning. The original IIT-Kharagpur design from the 1970s used an open-loop water system requiring continuous water flow, later modified to a semi-closed system in 2011. The new upgrade further reduces energy waste by returning around 90% of cool air to air handling units (AHUs). The AC units will maintain a subsoil temperature of 28°C to protect essential microbial life in the tunnels.

The revamped tunnel ventilation system will also include automated fans that respond to temperature deviations and advanced smoke management to ensure passenger safety during emergencies. Non-AC rakes have been replaced by AC trains, necessitating the upgrade to maintain consistent cooling throughout the underground network.

The modernisation project is expected to significantly enhance the comfort, safety, and sustainability of Kolkata Metro’s Blue Line stations while preserving vital groundwater resources and reducing carbon emissions.