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Nathpa-Jhakri project opening tomorrow
Rakesh Lohumi
Tribune News Service

Shimla, October 12
The huge cost and time overruns notwithstanding, the 1500-MW Nathpa-Jhakri project is an engineering marvel with several features unparalleled in the history of hydropower development.

The country’s largest hydroelectric project, the first phase of which is being inaugurated by Mr Anant G. Geete, Union Minister for Power, on October 14, boasts of the world’s largest underground desilting complex, Asia’s largest underground power house and one of the longest power tunnels in the world. The desilting arrangement comprises four chambers, each of which is half-a-kilometre (525 m ) long , 16.31 m wide and has a depth of a nine -storey high building (27.5 m). Similarly, the underground power house complex is housed in a cavern measuring 220m x 22m x 49m , big enough to house a 17-storeyed structure.

The execution of the project has been a big challenge for engineers as barring the diversion dam, all other works were underground. The enormity of the task could be judged from the fact that in all 58 lakh cubic metres of earth was excavated for the project which was equivalent to drilling a hole of 75 cm diameter across the globe. The excavated material could be spread into a 8 m wide and 12.5 cm thick carpet on the Great Wall of China.

In all 3.20 lakh tonnes of steel was used which was enough to lay a rail line along the quadrilateral connecting the four metropolis of the country. The 14 million bags of cement used in the project will be sufficient to provide a 75 cm-wide pavement around the earth. The 27.4 km-long headrace tunnel and 301 m-deep surge shaft are the other salient features of the project. Besides 250-MW capacity generating units were being installed for the first time in any project in the country.

The unique features of the project apart, the engineers had to struggle against the might of a vagrant weather god with flash floods causing extensive damage to the project thrice. In July 1993, a huge landslide at the dam site blocked the Satluj to form an artificial lake. It also buried the inlet portal of the diversion tunnel. Thereafter, a cloudburst in the catchment of the left bank tributaries of the Satluj caused heavy damage to the works in 1997. The worst came in August 2000 when unprecedented flash floods in the Satluj played havoc with the project. Machinery worth crores of rupees was washed away and the power house complex was inundated causing damage to the turbines which were under installation.

The engineers also encountered geological constraints in the form of highly unstable strata and gushing hot water with temperature ranging between 40°C to 66°C during tunnelling.

The project is being completed six years behind the original schedule of December 1998 and at more than double the original cost. It was estimated to cost Rs 4,336 crore but it is being completed at Rs 8657 crore. Besides natural calamities like cloudbursts and a landslide, the unending disputes between direct recruits of the Satluj Jal Vidyut Nigam and deputationists from the state electricity board, which led to frequent strikes, delayed the project.

The first of the six generating units, each of 250-MW capacity, will be inaugurated by Mr Geete and the remaining five will be commissioned in a phased manner up to July 2004.