Cofferdam at Varthur Lake breached, villagers on alert

Residents and villagers around the Varthur Lake were in for a shock on Sunday, when they found the cofferdam at the waterbody breached.

A cofferdam is a bund created to channelise or control the flow of water. The BDA had created temporary dams to check and control the flow of water as part of the waste weir construction.

The locals and the Bangalore Development Authority (BDA) officials are now equally worried about the water flow downstream, and the potential damage to the surrounding areas, especially to the farmers and other local communities dependent on the lake.

A lot of farmers upstream in the north, south and western part of the Varthur Lake are also worried. They grow vegetables, greens, paddy and do horticulture as well.

“As the cofferdam is damaged, the flow of water downstream cannot be controlled. The water level in the lake is receding drastically. This will have an adverse impact on the lives of over 500 families, dependent on the lake for daily needs and livelihood”, Jagadish Reddy Nagappa, a Varthur resident, told DH.

The locals also pointed out the threat to the catchment area and the buffer zone of the lake. They explained that when the water level drops, because of the delay in the dam repair, the grass which is exposed in the catchment area and buffer zone will dry up and will be prone to fire.

Reacting to this, BDA Engineer Aravind said it is only a temporary breach and damage to the water weir. He added that 70% of the water weir work is completed and 30% is pending. This breach has increased the water flow downstream by 25%. However, according to Aravind, the issue will be addressed within two days.

“As the bund was created by sand and mud bags, it was weak. This is a common problem during such constructions. People should not be worried,” added Aravind.

What is a cofferdam?

A cofferdam is a small enclosure built upstream or downstream of a waterbody facilitating the construction of a dam. The cofferdam makes it easier for the engineers and the masonry workers to pump out water easily. This, in turn, makes it easier to carry out concrete work on the dam wall. Usually, a cofferdam is built using fabricated steel structures which can easily be dismantled soon after the civil work. Cofferdams are common at ports, oil rigs and naval bases where repair works of the dam walls or sluice gates are frequent.