Calcutta: West Bengal chief minister Mamata Banerjee has pointed out an important thing that effects every state: It’s not that easy to repair old bridges and flyovers, because of the population living under them.

Chief minister Mamata Banerjee told reporters yesterday (6 September) that lifespan of several bridges in the city had “expired” but pleaded helplessness in carrying out repairs.

“We tried to repair the Sealdah flyover but there are markets below. No one is listening to us. No one is moving,” Mamata said. She was addressing a news conference on the Majerhat bridge collapse, in which the toll has gone up to 3.

Mamata said the Santragachhi flyover and the Ultadanga bridge were “weak” and that the Sealdah flyover, Dhakuria bridge, Belgachhia bridge, Chingrighata flyover and the Ultadanga flyover were among 20 whose lifespan had “expired”.

About the Sealdah flyover, she said: “I have asked the Calcutta Municipal Corporation and police to talk to the shop owners. They have to understand that they must make way for us to undertake the repairs. We would help them shift.”

Engineers of the Calcutta Metropolitan Development Authority (CMDA) hadtold local media that inspecting the Sealdah flyover from below was difficult because of the encroachments.

“Encroachment is rampant under the Sealdah flyover. That prevents regular inspection of the structure from below,” a CMDA engineer had said.

More than a thousand stalls and street vendors occupy the underbelly of the flyover. The market has the official name of Sisir Market. Under Bankim Setu in Howrah, fish markets and other encroachments impede inspection of a large stretch.

An official present at a meeting Mamata held at Nabanna on Thursday said encroachments under bridges and flyovers were discussed at length.

“There are encroachments under almost all bridges. All the ramps leading to Vidyasagar Setu have encroachments under them. It was decided that all encroachments under bridges and flyovers have to be removed,” the official said.

The encroachments make regular inspections and monitoring impossible.

The official said two elevated structures – the Ultadanga flyover that connects EM Bypass and VIP Road, and Aurobindo Setu that connects Ultadanga and Gauribari in north Calcutta – needed detailed study.

“There are visible signs of stress on both Aurobindo Setu and the Ultadanga flyover. We will now carry out a health audit of these bridges to determine their structural health so that remedial measures can be taken,” the official added.

Mamata said separate bridge inspection and monitoring cells will be formed by the public works department (PWD), CMDA and the irrigation department. All three are responsible for the maintenance of several bridges.

Earlier in the day, senior engineers and officials of CMDA and the urban development department held a meeting where they drew up a list of 48 bridges under their jurisdiction.

“We will conduct a health audit of all the flyovers in phases. The priority will be given to those structures where signs of stress are visible to the naked eye,” said an official who was present at the meeting.

Civil engineers this newspaper spoke to said every bridge was designed to take a certain amount of load over a certain period. Many of Calcutta’s bridges were built decades ago, when the traffic volume in the city was far less. Regular monitoring and maintenance is needed to keep the bridges safe, but this is rarely done.

A study, reported in April, by the railways’ consultancy arm ‘Rites’ had detected acute stress and diminished load-bearing capacity in the 43-year-old Aurobindo Setu, the bearings of which had not been changed although they were long past their lifespan.

An official who was part of the survey had then said the bearings of a flyover or bridge should be replaced every 10 to 15 years.