Kolkata, Jul 10 (PTI) Tunnelling work for the Kolkata Metro's Purple Line began at Khidderpore on Thursday.

Tunnel boring machine (TBM), named Durga, started work at the shaft built on the St Thomas School campus following a brief ceremony.

It was attended by Metro Railway General Manager P Uday Kumar Reddy, officials of Rail Vikas Nigam Ltd (RVNL), which is implementing the project, and representatives of the Nepal Consulate, Ministry of Defence, CMRI Hospital, and St Thomas School, all of which gave land for the project.

The tunnel work began for the Khidderpore-Victoria Memorial section.

The Purple Line, which will connect Joka to Esplanade, is at present operational between Joka and Majherhat. The line is elevated till Mominpur, following which it will go underground.

The tunnelling work till Park Street is expected to be completed by the end of 2026, an official said.

"It is a historic day for the people of Kolkata as the TBM has started work," Reddy said.

The launching shaft is 37 metre long, 22 metre wide and 17 metre deep. The TBM, having a diameter of 6.63 metre and a length of 95 metre, was assembled in Chennai and brought to Kolkata in March.

Two TBMs will be used for the construction of the twin tunnels between Khidderpore and Park Street, beyond which tunnelling will be done by the conventional 'cut and cover' method till Esplanade, the official said.

At Esplanade in the heart of the city, the Purple Line will meet the Blue Line -- the country's first metro corridor, and the Green Line.

The Blue Line connects Dakshineswar to New Garia, while the Green Line or the East-West corridor links Howrah to Salt Lake with a section under the Hooghly river, because of which it is touted as the country's first underwater metro project.

To cater to the effects of high groundwater table and typical soft soil conditions, earth pressure balancing-type TBMs are being used to construct the Purple Line tunnels, the official said.

TBM Durga will bore the tunnel from Khidderpore to Victoria Memorial, a length of 1.70 km. It is expected to complete the work till Victoria Memorial by May 2026, he said. PTI SUS SOM

Public land allocation enables tunnelling start for Kolkata Metro Purple Line, advancing underground construction timeline. Tunnelling for the Purple Line began at Khidderpore using an earth pressure balancing TBM to construct the Khidderpore-Victoria Memorial underground segment; the project is implemented by a public executing agency after land contributions from multiple entities, with twin TBMs for parallel tunnels to Victoria Memorial and cut-and-cover methods beyond Park Street, and measures adopted to address high groundwater and soft soil conditions within the stated construction timeline.