A critical phase of tunneling under the busiest part of the city, which houses a number of heritage buildings, was completed today by the Kolkata Metro Rail Corporation, a Metro official said.
Starting from Howrah Maidan on the other side of the Hooghly, the west-bound line tunnel boring machine 'Prerna' reached Esplanade metro station covering a distance of 3.8 km after passing under the river, the official said.
The tunneling had begun at Howrah Maidan on April 21, 2016 and took 23 months to pass under the Hooghly river, wholesale business hub Burrabazar and several heritage buildings in Benoy Badal Dinesh Bagh also called the Dalhousie area to reach Esplanade in the heart of the city.
"Engineers and technicians from different countries joined hands with Indian experts to complete this task meticulously," the official said.
The tunnel crossing below the Hooghly is the first transportation tunnel in the country under any river, he said.
Beth El and Magen David synagogues, St Andrews church, Writers Buildings (the secretariat), Old Telegraph office and Raj Bhawan, Esplanade Mansion are some of the important buildings under which tunneling was done.
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"Necessary protective measures and continuous monitoring was adopted to avoid any impact on those structures," the official said.
The tunnel also passed under several dilapidated buildings in the Burrabazar area and measures like translocation of inhabitants were taken to ensure safety during the tunneling.
The 16.6 km-long East West Metro is scheduled to be completed by June 2021. It will have underground corridor of 10.8 km and the elevated section will be of 5.8 km, the official added.