The State Highways Department has planned to build a bed-level diaphragm wall across the Kollidam to check sand erosion, which could possibly weaken the new bridge across the river in the city.
A proposal to this effect has been sent to the government for approval, sources in the Department said. The move comes in the wake of apprehensions being expressed by a section of farmers and media over the visible sand erosion around a few pile caps of the new bridge on the riverbed.
The new bridge, modelled on the lines of the Napier Bridge in Chennai with bowstring arches, connects the Srirangam island, wedged between the Cauvery and the Coleroon, with the rest of the district on the northern side. It was declared open by late Chief Minister Jayalalithaa in February 2016. The bridge was built to replace the British-built steel girder bridge, which was declared a weak structure in 2005.
Highways department sources maintained that the diaphragm wall is proposed to be built only as a matter of abundant caution, primarily to allay the fears of the public. The pile foundation of the bridge runs up to 17 metres in depth and the structure is strong. The bridge will not be endangered if a portion of the pile foundation is exposed due to erosion of sand. “Though it was not technically necessary, a bed level diaphragm wall is proposed to be built as matter of precaution,” an officer said.
Apparently, the department does not want to take any chance as a portion of the adjacent abandoned bridge across the river, collapsed during heavy water flow in the river in August 2018. Some of the farmers’ organisations and activists have been alleging that this and the partial collapse of the regulator across the Kollidam river at Mukkombu were caused by rampant sand mining in the vicinity of the structures. Though there may not be an official sand quarry in the immediate vicinity of the bridge, illegal sand mining, especially by bullock cart operators, was rampant, they alleged.
Sources also indicated that the department was awaiting government clearance for demolishing the old steel bridge, built about 90 years ago, and also to replace a brick-arched structure that got washed away in the 1924 floods. A portion of the steel girder bridge collapsed on August 19 last year when about 1.5 lakh cusecs of water flowed in the river. Once the government approval was obtained, tenders would be called to demolish the structure, the sources said.
