Old pipeline led to soil erosion

Now that the GHMC is giving finishing touches to the new manhole pit atop a storm water pipeline near Model House where the road had caved in last week, it is time to learn certain cold truths. Firstly, the road collapse had nothing to do with the ongoing underground stormwater drain work taken up by the municipal corporation for more than a year now. In fact, a two-metre diameter pipeline laid a few months ago to prevent water logging remains unaffected by the incident which sent the traffic haywire. “We initially thought the storm water drain work could have led to the mishap but soon we realised that an old underground pipeline extending to the road median and its choked manhole led to the soil erosion,” explained Engineering-in-Chief R. Dhan Singh.

Once the leak point was identified with digging at different points and repair, the traffic police was allowed to let vehicles on one side of the road. With intermingling of sewer and storm water lines, there was continuous flow and the catch pit was filled with garbage and old tyres resulting in a reverse flow.

With layer upon layer of bitumen filled over the years on the road which is under R&B department, neither the manhole nor the pipeline was known to municipal officials till they dug more than five metres deep. Intermingling telephone lines and high tension power lines — three of them passing through the same space not only compounded the chock.

It also prevented faster repair work since power supply could not be cut as it was being supplied to VVIP areas. After suction machine removed the accumulated sewage, the flow was plugged near the manhole, concrete was poured and vehicles were also allowed on the other side too save for the pit spot.

Mr. Singh said this part would also be completed in a couple of days. It also gave a chance for GHMC to press the contractor to speed up the storm water drain work. “We have already issued notices and levied penalties too,” he said. The entire project entails laying another pipeline underneath and adjacent to the existing new one at a cost of Rs. 4.6 crore. It is part of the 4.10 km network connecting the Banjara surplus lake or the Jalagam Vengal Rao Park to Hussainsagar lake at an estimated cost of Rs. 29.28 crore.

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