Underground tunnelling work for the East West Metro corridor is likely to take 10 more months to be completed, as a key machine has been damaged beyond repair, an international expert committee appointed by the Kolkata Metro Rail Corporation (KMRC) said here on Friday.
Besides, the safety of the people living in dilapidated buildings - many of which were built over 120 years ago - in one part of the route is a cause for concern, said Leonard John Endicott, a geotechnical expert and head of the committee.
'The biggest challenge is that many buildings in the area are in poor condition. Our concern is the safety of the people,' he told newspersons here.
The tunnelling work, which was put on hold after one of the two tunnel boring machines (TBM) hit an aquifer on August 31 last year in Bowbazar area leading to severe ground subsidence and collapse of buildings, will recommence in full swing in a day or two, Endicott said.
With the TBM getting damaged beyond repair in the accident, the work will have to be completed with one TBM only. The working TBM has been moved a few rigs to check for all safety parameters put in place to ensure that there is no repeat of the previous incident.
'We are being supercautious,' Endicott said.
Prior to that accident at Bowbazar in central Kolkata, two TBMs were working parallelly, boring tunnels for the up and down lines of the East West Metro corridor.
'It will take around 5 months for the TBM to go up to Sealdah from Bowbazar. Thereafter, it will take three months for the TBM, which is a huge machine, to turn around.
'It will take another two months for the machine to dig on the other side and reach up to the point where the first TBM had cut the tunnel,' the geotechnical expert said.
He said the working TBM has been upgraded and it now has 50 per cent more capability to ensure that the ground holds during tunnelling work.
'Special measures have been taken to ensure that water does not seep into the tunnel,' he said adding that work will be stopped within 60 minutes of noticing any abnormality during tunnelling in the area.
The damaged TBM, which Endicott said is a 'write-off', will be dismantled and taken away from the underground shaft.
The Calcutta High Court had on February 11 allowed resumption of tunnel-boring work for the East West corridor.
Accepting a report by IIT-Madras, the court's division bench directed the KMRC, the executing agency for the project, to restart operations in Bowbazar, in consultation with the institute.
The bench comprising Chief Justice TBN Radhakrishnan and Justice Arijit Banerjee had in September last year ordered suspension of tunnelling work till further orders.
Three months later, the KMRC, in view of a report prepared by its expert committee, moved the court seeking its permission to resume operations.
On a prayer by an NGO to get the expert committee report vetted by an independent agency, the KMRC requested IIT-Madras to review its findings.
The institute, in its report, stated that tunnel- boring work could be resumed.
On February 13, the 4.88km-long first phase of the East-West Metro, connecting information technology hub of Sector V in Salt Lake with Yuva Bharati Krirangan stadium, got functional.
Inaugurating the service, Railway Minister Piyush Goyal had said the entire 16.5-km stretch of the corridor - from Sector V to Howrah Maidan - is likely to be ready in two years.
The East West Metro corridor was earlier scheduled to be completed by June, 2021.
