Evacuation likely under weakened Tallah bridge
The state government wants to immediately evacuate the 200-odd people who live under the old and ailing Tallah bridge, sources in the government said.
The chief secretary has called a high-level meeting on Wednesday morning, just four days after he chaired a meeting on Friday to discuss the health of the bridge. Engineers of the state public works department (PWD) conducted an inspection on Saturday that Metro had reported.
“There are 200 people living under the bridge. It would be catastrophic if the bridge collapsed. We want to evacuate these people,” a senior state government official said. “Even if a concrete chunk falls, it could seriously injure people.”
The engineers who carried out the inspection were alarmed by the findings, which will be conveyed to the chief secretary at Wednesday’s meeting.
The bridge used to take about half of the city’s truckload till it was closed to heavy goods vehicles on Saturday.
Besides lorries, Matadors and buses, thousands of other vehicles take the bridge to reach the city from Barrackpore and Sodepur. It is a key link between Shyambazar and areas further north, including Chiria More, Sinthee and Dunlop, down BT Road and up to Barrackpore.
The Tallah bridge was built using the same technology as the Majerhat bridge, which collapsed in September last year. “There are strands of wires that hold the deck. The wires have become de-stressed. In lay language, it means the wires have started bending downwards. So reducing the load is one way of controlling the bending of the wires,” said a bridge engineer.
The railways and the PWD are jointly responsible for the maintenance of the 625m-long bridge. While the railways are the custodian of the 182m stretch above the tracks, the PWD looks after the rest.
The engineers have found that the concrete has become “very weak” and marks of de-stress of the strands have been noticed, officials said. The concrete has peeled off in many places and led to corrosion of the steel reinforcements.
The senior bridge engineer said “very weak” concrete meant it has lost the strength to bear heavy load. “The concrete could even crumble if the load on it becomes too heavy. So, load restriction is one of the preventive measures,” he said.
Just like in Majerhat bridge, layers of bitumen have been added to the deck of Tallah bridge since its inauguration in 1962, engineers said. “The bitumen has naturally added load to the structure.”
The weakened concrete had allowed air and water to penetrate into the concrete and corrode the steel reinforcements, further weakening the structure.
Senior PWD engineers, secretaries of various departments and officials of the Calcutta Municipal Corporation (CMC) would be present at Wednesday’s meeting.
PWD engineers said the bridge would have to be closed for a few days after Durga Puja for a load test to help assess how much load it can bear. The PWD has decided to install height bars at the northern and southern ends of the Tallah bridge to restrict movement of heavy vehicles on the structure.
The PWD on Tuesday issued a circular inviting tenders for the installation of the height bars. The nine-feet-high bars would be placed at the approaches to the bridge on either side to restrict movement of vehicles.
PWD engineers have consulted police officers and identified the spots where the bars would be placed.
The project cost has been pegged at Rs 26 lakh. The company that would take up the project can work only at night, the circular said. The state government will sign a three-year contract with the agency.