Kolkata: The city’s Purple Line completed its first phase of underground tunnelling on Tuesday as tunnel boring machine (TBM) Divya broke through the wall of the under-construction Victoria Memorial station.A month ago, its sibling, TBM Durga, achieved the feat, covering the 1.7km distance below Kidderpore’s St Thomas’ School. Both TBMs will be relaunched one after the other from Victoria station to dig another 900m to Park Street, where the Joka-Esplanade corridor interfaces with the Blue Line or the North-South corridor.Cheering the Purple Line’s latest milestone, railway minister Ashwini Vaishnaw posted on X: “TBM Divya achieves breakthrough at the Purple Line of Kolkata Metro. Congratulations to the team.” A TBM “breakthrough” in a Metro project is the moment, when each of the giant 600MT mechanical moles, finishes digging a specific tunnel stretch underground and punches through into a designated station box.Soon after the breakthrough, Metro general manager Prem Sagar Gupta said, “We have managed to uneventfully build the first phase of both the Purple Line tunnels from Kidderpore to Victoria. The giant borers had to be negotiated below quite a few historic edifices, such as RCTC, St Stephen’s Church and high-rises (like Turf View), without any subsidence.” The GM spoke of teamwork, of personnel who ensured safe, systematic and efficient tunnelling while maintaining the highest standard of quality and safety, without disturbing traffic and normal activities in this densely populated part of the city. He said the 14km Joka-Esplanade corridor would be commissioned in Dec 2029. The Purple Line now operates along an 8km elevated stretch from Joka to Majerhat. The line will go underground beyond Mominpur for 5km till Esplanade.Divya’s breakthrough took place at noon as senior officials from Metro Railway, implementing agency Rail Vikas Nigam Ltd (RVNL) and contractors L&T looked on. “The successful breakthrough marks completion of the second tunnel from Kidderpore to Victoria and the first phase of Purple Line tunnelling, which started in July 2025,” Vipin Kumar, RVNL’s chief project manager, said.The tunnel borers, split in 11 parts and reassembled into their current selves, will be relaunched from the other side of the under-construction Victoria station three months later. They are expected to take another five months to dig to reach Park Street.The TBMs were launched from a 17m-deep shaft, built inside St Thomas’, Kidderpore. The 95m-long TBMs, each with a 6.6m outer diameter, were brought in March 2025 for assembling and lowering.The Purple Line, when completed, would be an important addition to the city’s expanding Metro network and would significantly improve connectivity to the central business district, the Metro GM said.
