Built with over 26,000 tonnes of steel over 70 years ago, the Howrah Bridge (officially renamed Rabindra Setu) is undeniably one of the most well-known landmarks in the city. But the 1500-ft.-long engineering marvel is threatened by the ubiquitous Indian habit of spitting — the acidic mix of gutka and saliva gnawing at the hangers that uphold its superstructure.
A Rs. 15 lakh project to provide fibre glass covers at the base of the hangers to protect them from the corrosive action of gutka-spitting commenced here on Thursday, officials of the Kolkata Port Trust told journalists.
The total load of the super-structure is transported to the deck slab of the bridge through these hangers. But water would seep through the junctions of the hangers and the deck corroding the cross girders below. To prevent this, covers had been provided at the base of the hangers in 2001, said A.K. Mehra, chief engineer of the Kolkata Port Trust.
“About five lakh pedestrians cross the bridge everyday and even if not all of them chew gutka or spit, the amount of drivel is significant,” Mr. Mehra said.
Following a survey, all the covers had been changed in 2007. Three years later in 2010, it was found that the 6-mm thick plates had been corroded to a 3-mm thickness, he added.
Various measures to counter the problem, including coating the plates with zinc oxide, failed to yield results.
“We had considered various other materials, including wood. But we thought that if we used fibre glass, it was not likely to be stolen as it has the least resale value. Additionally, fibre glass is washable and easier to keep clean,” Mr. Mehra said.
According to a traffic survey conducted by the Transport Department in 2007, more than one lakh vehicles ply on the Howrah Bridge on a weekday. This declines to over 95,000 vehicles on weekends.
Despite other bridges across the river, the Howrah remains the most popular because of its close proximity to the railway station, Mr. Mehra added.