Urvi, the tunnel-boring machine (TBM) digging the east-bound tunnel, is now lying below BB Ganguly Street, 500m from its destination, Sealdah Station.
Tunnelling has stopped since Friday as many labourers and supervisors, involved in operating the TBM, tested positive. Following this, 175 people employed with contractors ITD ITD Cementation, General Consultants and Kolkata Metro Rail Corporation (KMRC), the agency implementing the 16-km link between Howrah Maidan and Salt Lake’s Sector-V through the Hooghly riverbed, have undergone swab tests for Covid-19.
“Their reports will be made known by Wednesday, but under the current situation, tunnelling work will remain stalled for the next fortnight,” Manas Sarkar, MD, KMRC, said on Monday.
The TBM was scheduled to reach Sealdah by August. The latest disruption should delay this deadline to mid-September or later.
The 2.45km journey of the twin East-West Metro tunnels from Esplanade to Sealdah has been saddled with challenges. Not only did it mean digging below 700-plus century or more unstable buildings, but halfway into the zig-zag route, on August 31, last year, Urvi’s twin, Chundee, which was digging the west-bound tunnel, hit an aquifer. This had led to largescale subsidence that had buildings in Bowbazar falling like a pack of cards.
Tunnelling was stopped and resumed in February on Calcutta high court’s orders. As Chundee lay defunct 14m below Durga Pituri Lane off Bowbazar, Urvi took over the digging. But this TBM ran into the lockdown as it reached the cave-in zone (the 300 radius around the spot, where the tunnelling disaster happened last year).
Tunnelling resumed on June 19. Since then, Urvi has curved towards BB Ganguly Street negotiating another 40 shaky structures, which were already emptied after the August 31 accident. In fact, 27 other buildings that had either collapsed or damaged beyond repair had to be razed, making the cave-in zone turn into an open space.