Pay-loaders and grinders will not be deployed to pull down the buildings in Bowbazar that are damaged beyond repair because of subsidence triggered by East-West Metro work.

Instead, a group of men on hydraulic lifts will go about the job, hitting the damaged walls with hammers and shovels, said officials of Kolkata Metro Rail Corporation, the implementing agency of the project.

The officials said manual demolition was the only option because pay-loaders and grinders cannot enter the narrow lanes of Bowbazar, where the affected buildings are located.

The width of the Bowbazar lanes where buildings have developed cracks vary between five and six feet. Some of them wind their way through densely populated neighbourhoods.

“The minimum wheelbase of a pay-loader is little above 10 feet. There is no way such huge engines can enter the affected lanes,” a KMRC official said.

“Under normal circumstances pay-loaders can pull down an old building, such as the ones Bowbazar is dotted with, in about three days. The manual demolition may continue for over a week.”

Yet another challenge is the condition of some of the buildings. Pulling down the balcony of one could put the terrace of another at risk. Ripping off a window could lead to the collapse of a wall of an adjoining kitchen.

“If we engage payloaders for demolition, different parts of damaged buildings might start falling off, putting the lives of labourers at risk,” said an engineer.

“Some of the buildings are century-old and in trying to rush through the demolition process, we might end up severely damaging adjoining houses that can otherwise be restored after thorough repair.”

A machine boring a tunnel for East-West Metro in Bowbazar hit a giant aquifer on August 31. Water from the aquifer entered the tunnel, triggering widespread subsidence.

Many buildings have been severely affected and hundreds of residents have been evacuated.

On Tuesday, a group of workers used a hydraulic lift to reach upper floors of a building at 11/1 Durga Pituri Lane — the worst-hit lane in Bowbazar — and kept hitting the walls with hammers and crowbars. Only six of the 27 rooms of the three-storey building are intact.

Engineers said the condition of the two adjoining buildings — 12 and 12/A Durga Pituri Lane — was equally bad. The one adjoining 12/A — 13 Durga Pituri Lane — was the first building that collapsed after cracks started appearing in Bowbazar buildings on September 1.

“If we demolish the buildings slowly, there are chances that labourers can collect some items that families have left behind and return them to owners,” said an official.

While dismantling continued, members of a team engaged in scanning buildings across Bowbazar entered some of the structures in the presence of residents and took pictures of the interiors.

“After inspecting the rooms, the engineers told me there was nothing to worry,” said Chandra Sekhar Chakrabarty, a resident of Durga Pituri Lane. “They told me there was some damage but that can be repaired and we can start living in the building once the repairs are over. They, however, did not give any timeline.”

After the inspection was over, KMRC officials said there was no immediate need to evacuate more families.

A senior official said the subsidence had not spread laterally over the past couple of days.

“It is a good sign that the subsidence is not spreading laterally and has been arrested,” said the official.

The official, however, added subsidence had not yet stopped within the affected zone, which has taken the shape of an ellipse.