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A 15-foot deep sinkhole appeared on 4th avenue in Chennai's Annanagar neighbourhood on Tuesday, leading to day long traffic disruptions in the area.
By-standers and shop owners who witnessed the road cave in told TNM that at around 8 am they heard a loud thud and the road in front of them staring sinking. A gaping hole had formed by then. āIn the morning when I came the road was fine. Then I heard a loud noise and I saw that a portion of the road was sinking in. Others too had gathered by then. We called the Chennai corporation and they came to check the sinkhole soon,ā Subburaju, a mechanic shop employee said.
Chennai Metrowater Supply and Sewage Board workers who inspected the sinkhole and began works to fill up the road stated that a manhole had sunk-in, leading to the crack in the road. The underground sewage collectio system which carries wastewater to a pumping station in the locality had collapsed with the lid of the manhole sinking in deep.
"We are still inspecting the reasons for the collapse of the manhole. This is a deep sewer or arch sewer which was constructed more than 30 years ago. We have to pull out the lid that has sunk in and see from which depth it has to be reconstructed, and if the sewer is partially collapsed or fully collapsed," Suresh Kumar, deputy area engineer from the CMWSSB told TNM.
The sewer is 18-feet deep. The lid has sunk down to 15 feet, Suresh Kumar added.
A probable reason for the sudden collapse of the system was the trench-less technology used by cable operators to lay their cables in the area.
"We found two or three cables that were inside the manhole. These are being laid by private operators without taking permission or receiving a go-ahead from the corporation. We have to remove all these cables and construct the sewer again. With this type of laying, the concrete slabs and soil start loosening up, leading to the caving in of the road" Suresh Kumar added.
Workers from the Chennai Metro Water Supply and Sewage Board have extracted the lid using a JCB and inspections on how the manhole collapsed are being undertaken.