Inspired by a 2,500-year-old Persian technique, pontoon bridges are serving as a vital link between the Sangam and the 4,000-hectare 'akhada' areas, connecting 25 vibrant sectors at the Maha Kumbh.
More than 1,000 people worked at least 10 hours a day for over a year to construct pontoons for 30 bridges, claimed to be the largest such project till date.
Over 2,200 black floating iron capsules, weighing five tonnes each, have been used to construct the bridges for facilitating the movement of vehicles, pilgrims, sadhus and workers at the world's largest cultural-cum-spiritual event.
Each bridge, being called a floating marvel, can withstand up to five tonnes.
The bridges are serving as vital links between the Sangam and the akhada areas, said Mahakumbh Nagar Additional District Magistrate Vivek Chaturvedi.
"The bridges are an integral part of the Maha Kumbh, offering a low-maintenance solution for the vast crowds. However, their operation requires constant monitoring, ensuring the safety and the smooth movement of devotees round-the-clock. We have CCTV cameras on each bridge and the footage is constantly monitored through the Integrated Command and Control Centre," he told PTI.
"Each bridge underwent several tests before being deemed fit for use. They are designed in such a way that they can handle the passage of a large number of people simultaneously," he added.
The pontoon bridges were first used in 480 BC by Persian king Xerxes I during his invasion of Greece. These bridges were also used by the Zhou dynasty in China during the 11th century BC.
In India, the first pipa bridge was built in October 1874 over the Hooghly river between Howrah and Kolkata.
Designed by British engineer Sir Bradford Leslie, the bridge was supported by wooden pontoons.
Damaged by a cyclone, it was eventually dismantled in 1943. The Rabindra Setu, famously known as the Howrah Bridge, was constructed in its place.
Maha Kumbh, a mega-religious event, organised every 12 years, is being held in Prayagraj from January 13 and will continue for 45 days. More than seven crore pilgrims have so far taken a holy dip at the Sangam -- the confluence of the Ganga, Yamuna and the mythical Saraswati rivers.
Alok Kumar, an engineer from the public works department, explained that pipa bridges were temporary structures built with large hollow iron containers (pontoons) floating on the water surface.
These are commonly called "pipe ka pul" in Prayagraj.
"These bridges have been built to facilitate movement not only for the public but also the grand entry of 13 akhadas, chariots, elephants, horses and more than 1,000 vehicles during the Amrit Snan," Kumar said.
He said he was entrusted with the task of building pipa bridges in August 2023.
"To construct 30 pipa bridges, 2,213 pontoons were used -- the highest number ever. More than 1,000 workers, engineers and officials worked tirelessly, often for 14 hours a day. The construction of these bridges was completed last October and subsequently handed over to the mela administration," he said.
"The construction of 30 pipa bridges over the Ganga for the Maha Kumbh is the largest such project till date. After the fair's conclusion, these bridges will be dismantled and stored for future use at other locations," he added.
The hollow pontoons, made of strong iron sheets, are lowered into the river with the help of cranes. Girder beams are then placed on them and secured with nuts and bolts. Hydraulic machines are used to accurately position the pontoons.
Thick wooden planks, sandy soil and iron angles are used to further stabilise the bridges. Finally, checker plates are laid on the surface to ensure the bridge remains strong for the movement of pilgrims and vehicles.
"Each pontoon weighs about five tonnes, yet it floats. The secret lies in Archimedes' principle. When an object is submerged in water, it experiences an upward force equal to the weight of the water displaced by it. This principle helps the heavy pontoons stay float," Kumar said.
"The design of the bridges is such that they can withstand up to five tonnes of weight. If the weight exceeds this limit, there is a risk of the bridge being damaged or sinking. Therefore, crowd management is crucial," he added.
Uttar Pradesh government officials said construction of the 30 pipa bridges cost Rs 17.31 crore.
"The bridge from the Shri Nagvasuki Temple to Jhusi is the most expensive, costing Rs 1.13 crore. The Gangeshwar and the Bharadwaj bridges cost between Rs 50 lakh and Rs 89 lakh," a senior government official said.
"After the Maha Kumbh, these bridges will be disassembled and stored in safe locations. Some of the bridges will be stored in Sarainayat (Kenihar), Trivenipuram, and Parade Ground in Prayagraj. Others may be repurposed as temporary bridges in various districts of Uttar Pradesh," he added.
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