Concrete in Narmada dam = 22,500 km road

The concrete used to build the most controversial dam in the history of the country -- the Sardar Sarovar dam on river Narmada -- can lay a road that can encircle the equator.

Though mired in controversy, the construction of the dam is a mega task undertaken by the Sardar Sarovar Narmada Nigam Limited with the proposed construction of 1,210 metre-long, 146.50 metre-high and 124 metre-wide at base concrete gravity dam involving placement of about 73.20 lakh cubic meters of 'pre-cooled' concrete.

"This is the second largest dam in the world in terms of concrete used and it can lay a 22,500 km long concrete road which can encircle the equator," executive engineer of the project Ashok Gajjar told PTI. The Grand Kollig dam in the United States is the largest dam in the world in terms of concrete used.

The site chosen for construction of the reservoir in the Vindyachal mountain range is ideal to store a large volume of water in the reservoir, which can satisfy drinking water needs of people of the state, irrigation facility for Gujarat and two districts of Rajasthan, and can produce 1,450 mega watt of power, Gajjar said.

Speaking about the use of the pre-cooled concrete in the construction of the dam, the base of which is of the basalt rock, Gajjar said that without its use, it would have been very difficult to complete the

construction work of such a huge structure.

Gajjar said precooled concrete is used to avoid cracks in construction of dams due to exothermic reactions of large quantity of cement used in the construction every day.

"We have established an ice factory near the dam, which can produce 3 lakh kg of ice flakes per day for chilling the concrete and to prevent the development of cracks in the dam structure," said the executive engineer, who is overlooking the construction of the dam.

The SSNNL has brought a parallel motion cable crane from Germany, which can lay 5,000 cubic metre concrete per day. The crane helps in speeding up the construction work on the dam and was used for the first time in India by the SSNNL.

The dam will also have a service spillway with 23 gates having 60 feet by 55 feet size in the river bed and an auxiliary spillway with seven gates having 60 feet by 60 feet size for regulating flood of 30.70 lakh cusecs of water. The Sardar Sarovar dam has been constructed up to 119 meters so far.

Gajjar said once the monsoon recedes they will start the work to raise the height of the dam to 121.98 meter permission of which has been granted by the Narmada Control Authority. The construction of the dam will create reservoir having length of 214 km width of 1.60 km and gross storage capacity of 9,500 million cubic metre of water.