The heritage precinct, where Queen Elizabeth II presented the Queen Elizabeth II Cup in 1961, has been closely monitored throughout construction to safeguard its historic structures. The first tunnel boring machine (TBM), named Durga, began excavating the Esplanade-bound tunnel on 10 July 2025 and reached the RCTC area by late November after covering around 600 metres.
Rail Vikas Nigam Limited, which is implementing the 14-kilometre Joka–Esplanade Purple Line, installed advanced sensors on the heritage stands to detect even minimal ground settlement during tunnelling works.
Durga, which is 100 metres long, weighs 600 tonnes and has an outer diameter of 6.6 metres, now has a clear alignment towards the Victoria Memorial station. From there, it will continue tunnelling for about 900 metres up to Park Street.
The second TBM, Divya, which is excavating the parallel tunnel, has already reached Tolly’s Nullah and is expected to pass beneath the RCTC next month. Together, the two machines will complete around 1.7 kilometres of tunnelling between Kidderpore and Park Street.
Both TBMs were launched from a shaft at St Thomas’ Boys’ School in Kidderpore, measuring 37 metres in length, 22 metres in width and 17 metres in depth.
The Purple Line currently operates on an 8-kilometre elevated stretch between Joka and Majerhat. Once the underground section between Kidderpore and Park Street is completed, it is expected to significantly improve connectivity across central Kolkata while ensuring the preservation of the city’s historic landmarks.
