A health check of five flyovers — including Gariahat, Park Street and AJC Bose Road flyovers — is under way, officials of the Hooghly River Bridge Commissioners (HRBC), the custodian of the structures, said.
Railways consultancy firm RITES has been hired by the HRBC to do the health study and submit a report on the repairs that are required and how to go ahead with them.
The Kidderpore flyover and the New Lockgate flyover in Cossipore are also undergoing health check-up that began in December.
The five flyovers were built in the 2000s.
An officer of Calcutta police said HRBC had sent them an application to allow RITES to conduct a radiography test, a non-destructive test and inspection of the expansion joints, among other procedures.
“We have started a health check of five flyovers in Calcutta, of which we are the custodian. We will conduct necessary repairs if required,” said Ajoy Kumar Dutta, the chief project manager of HRBC. Dutta, however, did not say when RITES would submit its report.
An engineer working with a private infrastructure company explained the tests that the HRBC has mentioned in its letter to the police.
A radiography test is like an X-ray that will detect any crack or porosity in the steel components of the flyover. In the non-destructive test, the sound waves generated after hammering a point in the flyover are tracked to understand whether the waves are rebounding normally or there are any defects inside the structure.
In the axle load survey, loaded vehicles are lined up along a flank to see whether the deflection occurring in the concrete and steel components are within safe limits. “The traffic-volume survey helps gauge if the flyover can take the volume of traffic that will use it after five or 10 years without any damage to the structure,” said the engineer.
The website of the HRBC mentions that the 3-km AJC Bose Road flyover was inaugurated in August 2003 and the 571-metre Gariahat flyover was opened in April 2002. The website does not mention the length and opening date of the Park Street, New Lockgate and the Kidderpore flyovers.
Sources in the Calcutta police’s traffic department said the Park Street flyover, which was inaugurated in 2005, would be approximately 500 metre long; the New Lockgate flyover, inaugurated in 2004, is about 700 metre long and Kidderpore flyover, inaugurated in 2007, about 500 metre in length.
Amitabha Ghosal, a bridge engineer who has been involved with construction and health audits of several elevated corridors, said it was good that the health check of the flyovers were being conducted. “Some basic health checks should be conducted every two years. It is good that the HRBC is doing the health check of all these structures.”
Though all these flyovers are less than 20 years old, it is still necessary to conduct health audits, said Ghosal.
Comprehensive health audits of flyovers were rarely done in the city earlier, admitted engineers who built flyovers in Calcutta and government officials. The collapse of the Vivekananda Road flyover in 2016 and the Majerhat bridge in 2018 jolted the government out of its slumber.
The state urban development department began a health check of several flyovers maintained by the Calcutta Metropolitan Development Authority (CMDA) from 2019. The CMDA will start repairs of Baghajatin and the Ultadanga flyovers soon, based on reports of the health audits.
The PWD, too, started health audits of some of its flyovers in Calcutta. The health audit of the Tallah bridge revealed its precarious condition and it was demolished. A new bridge is under construction now.
