Howrah Bridge from Howrah train station, photo: vinay g via flickr.
This is too interesting and gross at the same time. The Guardian reports how the Howrah Bridge in Kolkata, India is now threatened, not by an excess of traffic, flooding or other environmental problems, but by an excess of spitting. Spitting out paan to be specific. It seems the popular Indian betel leaf, areca nut and slaked lime mixture does more than stain your teeth and the section of sidewalk or wall you spit it out onto. It also can structurally weaken metal bridges.
Key struts that support the girders of the bridge--one of the biggest such cantilever structures in the world--have already lost half their protective metal casing to the acids contained in paan.
"A safety audit is now being planned to find out the effect of constant spitting," one senior official told the Calcutta Telegraph. "The 6mm bases are now around 3mm each. If corrosion continues at such a rate, we would need to decommission the bridge for repairs."
Again, gross! Half-chewed mouthfuls of paan, spat out over the past 80 years, have eroded the metal casing on the bridge by half.
Though technically illegal to spit on the bridge, and though fines are given to offenders, the original article notes that a lack of manpower means most scofflaw spitters go unchallenged.
Now officially known as Rabindra Setu (renamed after someone I happen to think is one of the greatest writers of all time, Rabindranath Tagore), the Howrah Bridge was built between 1937 and 1943 and is 705 meters in length. It carries at least 80,000 vehicles and countless pedestrians over the Hooghly River each day.
More on Civil Infrastructure:
Bridges are for People: 7 Bridges That People Live and Work On
Wood Bridge in Netherlands As Strong As Steel and A Lot Prettier
Creative Financing: Putting Shops and Cafes Back on a London Bridge