The open spaces beneath flyovers and bridges will be cleared of settlements and stalls and fenced off to prevent future “encroachments”, a state government official told The Telegraph on Saturday.

Most flyovers in the city currently have makeshift settlements or stalls beneath them, where residents cook over open flames. Stall owners and residents also hang belongings from bridge pillars.

Inspections of the undersides of the structures are often impossible, as access is blocked by these shops and settlements.

The Kolkata Metropolitan Development Authority (KMDA), custodian of several bridges and flyovers, has started erecting a fence under Ma Saradamani Setu near Taj Bengal.

It has floated tenders to demolish unauthorised structures and erect fencing under the Chetla bridge, Ambedkar bridge on EM Bypass, Chingrighata flyover, Bagmari bridge, Jibanananda Setu, and the slip bridge connecting VIP Road and EM Bypass, among others.

People have lived under the city’s flyovers for years, but the decision to evict them came after a fire in a settlement beneath the Durgapur bridge in New Alipore in December last year damaged the concrete of the structure.

On Friday, Calcutta’s mayor and state urban development minister Firhad Hakim said no one will be allowed to stay below flyovers and bridges.

Three departments of the government are custodians of most of the city’s flyovers and bridges — the KMDA, under the urban development department; the Hooghly River Bridge Commissioners (HRBC), under the transport department; and the public works department (PWD).

“The lifespan of the flyovers is decreasing. Heat from cooking fires is affecting the structures by causing the iron reinforcements to expand. During a fire, like the one under the Durgapur bridge, the expansion is significant. This weakens the reinforcements,” Hakim said.

“We have decided not to allow anyone to settle under the flyovers and bridges,” he added.

A government engineer said concrete and its reinforcements can withstand heat up to a certain temperature.

If the temperature exceeds the threshold, the reinforcements begin to weaken, the engineer said. “This can also happen gradually, as daily exposure to heat from cooking over several years causes the reinforcements to lose strength over time.”

During the fire under the Durgapur bridge, the temperature of the concrete rose significantly, reducing its moisture content and making the surface brittle, sources in the KMDA had said.

The KMDA had to carry out repairs under the bridge to fix the damage.

Chief minister Mamata Banerjee had expressed concern over the condition of the structure.

“The fire has affected the health of the Durgapur bridge. We have been forced to impose some restrictions and undertake extensive repairs, which will be costly. We sent a team for inspection, which said that the flames damaged the bridge,” Mamata had said.