An international engineering firm commissioned to do a study of bridges and flyovers in Calcutta has put three of them on its red list, based on an assessment of long-term damage that warrants “immediate repair”.

The report submitted to the Calcutta Metropolitan Development Authority (CMDA) by AECOM, a Los Angeles-headquartered firm, details the extent of damage to the Sealdah, Chingrighata and Ultadanga flyovers in the absence of routine maintenance.

According to the report, the almost 37-year-old Sealdah flyover that has a bustling marketplace under it is in the worst condition among the three. “There are vertical cracks at the bottom of the pier shaft which might lead to serious compression failure and collapse,” it says.

Chief minister Mamata Banerjee had said after the Majerhat bridge collapsed on September 4 that several flyovers and bridges had exceeded their “lifespan” without periodic repairs. “We tried to repair the Sealdah flyover but there are markets below. No one is listening to us. No one is moving,” the chief minister told reporters.

A couple of days later, traders in the marketplace under the flyover and along its piers were told that they might need to temporarily relocate for civic engineers to carry out overdue inspections of the structure and commission repairs wherever required.

AECOM has said that the Sealdah flyover should get priority in repairs, followed by the Ultadanga and Chingrighata flyovers.

Structures in the “grey” category are Bankim Setu in Howrah, the Kalighat bridge, Bijon Setu that connects Kasba with Gariahat and Aurobindo Setu between Khanna and Ultadanga. The third category, marked yellow, includes the Ambedkar, Durgapur, Chetla and Dhakuria bridges.

An estimated 20 lakh people travel through Sealdah station every day, the majority of them using the market under the flyover to reach the terminal Sisir Market, the official name of the trade hub operating under the flyover, has about 930 shops. While some of these shops are licensed, many illegally occupy the remaining space below the flyover.

“Checking the underside of the flyover’s deck slab for damage is almost impossible as long as the stalls are occupied,” said an official of RITES, the public-sector consultancy that did a study of flyover around 18 months ago.

Sources in the CMDA said the government had entrusted AECOM to carry out a “confidential” study after the Majerhat bridge collapsed. The report, submitted a week ago, mentions how the survey was carried out, summarises the findings and makes recommendations.

On the Ultadanga flyover, a portion of which had suffered subsidence in March 2013, the report states: “Development of cracks (vertical and diagonal) in the concrete long girder might be due to inadequate strength of the girder to carry present traffic.”

The CMDA has set up a height bar at the entry to the Ultadanga flyover to prevent heavy vehicles from taking that route. But it has yet to do the same for the Chingrighata flyover, whose design has been officially termed “faulty”.

According to the report, the Chingrighata flyover suffers from “torsional distress” and “buckling of (the) steel griders is severe for a steel composite bridge that may lead to progressive failure”.

A senior CMDA official said the government had already prioritised repairs based on Aecom’s report. “We are drawing up a request for proposal ahead of putting out a tender for the repair of eight bridges.”

AECOM officials in Calcutta declined to comment on the report.

What the findings say

• Code red (needs immediate repair): Sealdah, Ultadanga and Chingrighata
  
• Code grey (should get priority once first three are repaired): Bankim Setu, Kalighat bridge, Bijon Setu and Aurobindo Setu
  
• Code yellow (requires repair but not an emergency): Ambedkar, Durgapur, Chetla and Dhakuria bridges