The Kalighat bridge that connects Alipore and Kalighat over the Tolly’s Nullah has to be demolished, a government-appointed committee running a health check on bridges and flyovers has recommended.

The reason: the structure has suffered irreparable damage.

The committee, along with engineers of the urban development department, identified the 56-year-old bridge as the only one in south Calcutta that has to be replaced. Others can either be repaired or retrofitted with steel frames, according to the committee.

Some of the reasons why the Kalighat bridge has to be replaced:

• Its weight-bearing capacity is highly compromised
• Steel reinforcements are severely corroded
• The superstructure of the stands is damaged
• Acidic vapour from the waters of the Tolly’s Nullah beneath the bridge has corroded parts of the underbelly, making it vulnerable to even greater damage if heavy vehicles move on the bridge

The Kalighat bridge was among 15 bridges and flyovers — including Aurobin-

do Setu, Sealdah flyover, Bankim Setu, Ultadanga bridge, Ambedkar bridge, Dhakuria bridge and Sukanta Setu — which the committee had identified for an immediate health audit within months of the collapse of the Majerhat bridge in September 2018.

The government had set up the committee with six members, led by Amitabha Ghosal, a senior consultant on bridges and structures, to assess the condition of bridges and flyovers in the city.

Pedestrians and vehicles on the bridge.

A load test was carried out on the Kalighat bridge in July last year. In January this year, a height bar was installed on either end to prevent movement of heavy vehicles on the bridge.

The urban development department has, in principle, agreed to demolish the bridge and build a new one based on the committee’s recommendations.

Tenders will be floated in July and the committee will lay down specific conditions for bidders to qualify for the Kalighat project, a department official said.

Among various things, details of the last five projects executed by the bidding company and the time taken for completion will be taken into account, the official said.

“The cost of building a new structure will be Rs 12-15 crore. It is better to invest in a new structure rather than incur huge expenses periodically in maintaining the existing structure.”

The new bridge will be a steel girder structure. Most of the parts will be prefabricated. “We are looking at a two-year period to complete the construction of the bridge once a company is given the project,” the official said.

Traffic diversions will be challenging but not impossible since police successfully handled it when the bridge was shut down for load tests in July 2019.