Tests conducted to select the right quality of soil for the work

MADURAI: The Public Works Department has adopted new techniques to strengthen the bunds of tanks in which improvement work has been taken up under the Tamil Nadu Irrigated Agriculture Modernisation and Water Bodies Restoration and Management (IAMWARM).

In earlier works, the PWD took up desilting on tank beds closer to the bunds and just dumped the dug up loose soil on the bunds. “The strength of such bunds was good enough to withstand for only around five years,” PWD Executive Engineer Subramanian, said.

But in the World Bank-assisted project, soil suitability tests were conducted to select the right quality of soil to be used for bund strengthening work. “We went for soil that had more clay content. Besides, every layer of 25 cm of soil laid on the bund was compacted using heavy rollers,” he said.

The Kinnimangalam Keelakanmai tank in Usilampatti taluk, where the work is going on for nearly two months, has got a huge bund for over 700 metres. Earlier, the bunds were of 2.5 metres high with “cone edge” on top. But the height of the strengthened bund has been increased to 4.5 metres. Similarly, the bund top has been standardised to three-metre width.

Bund’s stability

“The base width of the bund has been increased from around 9 metres to a uniform 18 feet. The wider base and the compacted sides have increased the bund’s stability manifold. It will not require any kind of work for at least another 20 years,” Mr. Subramanian said. The PWD incurred huge expenditure for the time-to-time minor strengthening works taken up to prevent and plug breaches during floods, he added.

The tank is being desilted to increase its capacity by 20 per cent. Shutters in its two sluices will be repaired under the project.

The IAMWARM project will be carried out at a cost of Rs.39.06 crore in the Upper Gundar sub-basin and Therkkar sub-basin.