The tunneling work of East-West Metro in Bowbazar will remain suspended during the monsoon, officials of Kolkata Metro Rail Corporation (KMRC), implementing agency of the project, said on Friday.
This could lead to deferment of the deadline of the corridor, which once fully functional will link Sector V with Howrah Maidan.
Work on the underground corridor in Bowbazar had led to subsidence and cracks in a number of buildings in Durga Pituri Lane on May 11 and displacement of 150 people.
“We will not immediately remove the mass of concrete that was poured inside the shaft to plug underground leakage of water during the rainy season,” said N.C. Karmali, director (projects), KMRC.
“Additional safeguard will be taken around the shaft area through a process of deep grouting to prevent any untoward incident.”
A concrete mass of over 220 cubic metres and spanning 10 metres in length was used to plug water nearly 22 metres below the surface of Durga Pituri Lane when it started leaking on the night of May 11.
The idea was to arrest subsidence that caused cracks in the buildings.
Unless the mass is removed, the construction of another concrete structure to fill a yawning gap — in the form of a retrieval shaft between the two tunnels on the Sealdah-Howrah stretch — cannot be started, said engineers.
“While work at other sites will continue, it will remain suspended in Bowbazar for some time,” a senior KMRC official said. “We are figuring out the impact of the suspension on the final deadline of the project.”
After cracks surfaced in buildings in Durga Pituri Lane, Kolkata Municipal Corporation (KMC) engaged a team of experts from Jadavpur University (JU) to study the impact of soil subsidence in the area.
The team will submit a preliminary report shortly after assessing the area that has been affected by subsidence, the degree of tilt of some of the affected buildings, the nature of underground soil and the impact of water leakage from the shaft.
“The report will help identify the number of buildings that will require partial or complete demolition following the May 11 accident,” said a senior official of the KMC’s building department.
The KMRC, which has identified three buildings for partial demolition and started the work on one of them, has engaged IIT Roorkee for a technical study of the project, particularly in Bowbazar, which had witnessed an even bigger subsidence in 2019.
