Experts left baffled as rats eat away bridge

Kolkata: Even as the state government’s safety audit on the health of bridges and flyovers is complete, the old Dhakuria Bridge in south Kolkata that connects Jodhpur Park with Golpark is still giving them sleepless nights. More than 50 years old, the bridge is being weakened with rats gnawing at its base. It has sunk in sections leading to a carriageway that is extremely undulating.

“We have made a lot of efforts in the last six years to prevent the rats from removing the earth that supports this old bridge. In 2013, after RITES had conducted a study, we had pumped in cement mixture and mixed it with the earth. The process yielded fruits and for nearly four years, the rodents stayed away. But they have now come back,” state urban development minister Firhad Hakim said.

After discussion with experts on how to counter the problem, the government started to pump cement mixed with small glass pieces. “However, the hose pipe that is being used to put the mixture under the surface of the bridge is cracking due to pressure. We are discussing with experts and our engineers on how to solve this issue. It would have been handy if we had the ‘Pied Piper of Hamelin’,” the minister said.

He, however pointed out that the bridge, though old, had an advantage. “It is so solid that it will never collapse,” Mr Hakim said. An engineer of Kolkata Metropolitan Development Authority (KMDA), the custodian of the bridge said that if pieces of glass mixed with cement were mixed with the earth, rodents would stay away as they would get bruised trying to dig in. The bridge stands on inclining concrete walls filled with sand or earth, a technology that became obsolete decades ago.

“The pressure of traffic is very high and stopping the flow of traffic for repair will choke the entire south Kolkata,” a top traffic department official of Kolkata Police said. Experts are completely in the dark about why the bridge is infested with rats. The Chetla Bridge and the Durgapur Bridge in New Alipore are also very old and constructed in a similar fashion, but they do not have such problem. Some local residents believed that an open vat just adjacent to the bridge was attracting the rats. The civic body replaced it with a modern compactor station, in spite of which the problem persisted.