The tunneling work for the East-West Metro project, which aims to connect Howrah Maidan to Sector V via Sealdah, will resume in Bowbazar within a fortnight, after a gap of over four months, officials of the Kolkata Metro Rail Corporation (KMRC), the implementing agency for the 16.6 km project, said on Thursday.
In May KMRC had suspended the work of constructing an underground tunnel in Bowbazar in the wake of a fresh round of subsidence on Durga Pituri Lane following leakage of underground water.
The subsidence had resulted in cracks appearing in at least nine buildings on Durga Pituri Lane in Bowbazar, leaving 160 people displaced for the second time in less than three years.
“We will start the work of grouting the underground soil in Bowbazar within a fortnight,” N.C. Karmali, director (project) of KMRC told The Telegraph on Thursday.
“After observing the effectiveness of the grouting process we will start planning the removal of concrete that was laid to plug the water leakage in Bowbazar.”
Senior KMRC engineers said the act of grouting the underground soil would be carried out under supervision of experts in a step-by-step process, which would include drilling a hole through the concrete mass that has been laid, and the mixture, pumped into the soil under high pressure.
“The whole idea of this grouting is to make the lower base of the tunnel impervious to water so that there is no water inside the shaft,” said a senior KMRC official.
“It will take around one and a half months. It is a complex process since one doesn’t get to see what’s happening underground.”
There are two tunnels of the East-West metro and officials said the grouting work in Bowbazar would be aimed at strengthening the underground soil of the west-bound tunnel. Trains at Sealdah are now running on the eastbound tunnel.
Engineers said the work of grouting underground would be followed by the more challenging task of removing the concrete that was poured to stop water leakage underneath Durga Pituri Lane.
“We will have to remove around three metres thick layer of concrete from underground after the grouting work is successfully done,” the official said.
“The entire area of leakage was completely sealed with concrete to outlast this monsoon season and avoid further subsidence in the area.”