Project in progress

Print edition : June 06, 1998

With fears of cracks in the Tehri dam structure set at rest, work on the ambitious project goes on.

PICTURES: M.LAKSHMANAN

THE Tehri multipurpose river valley project in Garhwal district of Uttar Pradesh has been the subject of much controversy ever since it was launched in 1972, and the latest round of controversy has involved news reports of cracks in the dam. These reports in May created a sensation, and they seemed to buttress the claims of the anti-dam movement. Supporters of the movement, led by the Tehri Bandh Virodhi Sangharsh Samiti, have been arguing against the construction of the dam, which they say is not safe since it is located in a seismologically active zone.

But it has turned out that the cracks that were reported have nothing to do with the dam itself, which is yet to come up. What has manifested itself is subsidence of the loose mass on the hillside and inside gate shaft number three leading to the head race tunnel. The subsidence was caused by heavy rain. Experts have set at rest apprehensions about the safety of the dam on this score.

Anti-dam activists led by environmentalist Sunderlal Bahuguna have consistently opposed the construction of the dam on grounds ranging from safety from the seismic point of view to the inadequacy of the rehabilitation package for those people who are displaced by the project. The C.H. Hanumantha Rao Committee which went into the rehabilitation package offered by the Tehri Hydro Development Corporation (THDC), submitted its report earlier this year. The committee made a set of recommendations revising its earlier rehabilitation package (Frontline, December 26, 1997). The key element in the recommendations relate to the definition of the 'family' for determining eligibility for rehabilitation. Married sons and unmarried children who have attained the age of majority were included in the definition of 'family' eligible for compensation. The recommendations of the Hanumantha Rao panel were reviewed by an inter-ministerial committee headed by M.C. Saxena, Secretary, Union Ministry for Rural Development. The committee submitted its report to the Government in March 1998.

An overview of the Tehri dam site.-

Another committee to review the seismic stability of the dam, set up by the Government following requests from Bahuguna, has just submitted its report. All the members of this committee were seismologists nominated by Bahuguna. The five-member committee, comprising V.K. Gaur, former Secretary to the Union Government, K.N. Khatri of the Wadia Institute of Himalayan Geology, Dehra Dun, N.C. Nigam, Vice-Chancellor, Roorkee University, Ramesh Chander of the Earth Sciences Department of Roorkee University, and R.N. Iyengar, Director, Central Building Research Institute, Roorkee, submitted two reports - one report authored by Nigam and the other by the other four scientists. Both the reports found that the dam was safe from the seismic point of view. The report said: "Based on a review of the reports made available to the Group and further studies conducted... on the behaviour of the idealised two dimensional model of the dam... the Group came to the conclusion that the present design of the dam is expected to be structurally safe to withstand the maximum credible earthquake during its economic life."

However, the scientists other than Nigam recommended that as a measure of abundant caution, a further three-dimensional non-linear analysis be done to ascertain seismic safety. Only a two-dimensional analysis has been done so far. Experts are of the view that a two-dimensional analysis invariably shows up much worse values than a three-dimensional analysis and therefore, if the dam is safe from a two-dimensional analysis, it ought to be even safer when a three-dimensional analysis is conducted.

However, Dr. Jaikrishna, president of the International Association of Earthquake Engineering, said: "A three-dimensional analysis is not only not feasible, it is not necessary either. The Tehri dam design conforms to the design on which dams all over the world are based. There are other dams which are located in much worse zones in terms of seismic activity such as the Beas, Bhakra and Ravi in India and Mangala dam in Pakistan which have faced no problems whatsoever in the last 40 years. The Barapani dam in Assam is located in a zone that is much more seismically active and it has not failed in the last 30 years. The only instance of any damage ever caused by an earthquake was in Japan in 1928 when the Ono dam cracked slightly. Even that was repaired."

Also, engineers point out that the Tehri dam is an earthfill dam which will be shaped like a hill. The river is S-shaped near the dam and a substantial portion of the water pressure will be borne not by the dam structure itself, but by the hillsides. They point out that even in the event of an earthquake, the structure might flatten out a little, unlike a concrete dam which will crack under the impact. Since there is a clearance of 10 metres above the maximum water level as against 0.5 m that is necessary, there is no scope for the water to overflow the dam. Dr. Jaikrishna says: "I doubt if the dam will ever be filled to capacity. After all, Bhakra was filled to capacity only once in 40 years."

Subsidence of loose mass on the hillside caused by heavy rain recently.-

The Tehri dam, at 840 m, will be the tallest dam in Asia and the fourth tallest earth-and-rockfill dam in the world. When completed, it is expected to produce 2400 MW of electricity and help irrigate the plains of Uttar Pradesh.

WHEN completed, the dam will submerge old Tehri town which is situated at a height of 650 m above mean sea level. The THDC has constructed a new township at a height of 1500 m to 2000 m above sea level. New Tehri Township (NTT) is a gleaming modern township with amenities such as schools, hospitals, post offices, playgrounds, shopping malls, cinema halls and modern housing. The Garhwal University will be relocated in its own complex in New Tehri Township.

Most of the buildings now remain unoccupied although the shopping complexes appeared to be doing brisk business thanks to a large floating population engaged in the construction and maintenance of the township. The shops are run by old Tehri townspeople who have taken possession of the sites, shops and houses offered to them at NTT but have not yet moved their families. S. Bisht, one of the shopkeepers, said: "We're waiting for others to move in. Business is brisk in old Tehri. I am running shops in both the places, but will move to NTT when everybody else does so."

A Russian geologist during a routine check of project structures.-

Old Tehri citizens are unlikely to move until the dam is complete, although the old town is congested and squalid, with its drains open and pigs roaming about on the streets. In 1997, when flood waters rose up to a level just a couple of feet below the bridge linking old Tehri town to nearby Champa, the settlements at the lower levels were evacuated. S.C. Sharma, General Manager of the THDC at the dam site, said: "Last year, the water level was 3,000 cumecs, but if it rises to its full potential of 4,000 cumecs, the entire township may have to be evacuated. We hope the Tehri citizens will not wait for such an eventuality before deciding to shift to NTT."

Citizens of Tehri have already been paid 90 per cent of the compensation due to them under the earlier rehabilitation package. The agreement was that they would be paid the remaining 10 per cent when they moved into NTT. However, with the rehabilitation package being revised on the recommendations of the Hanumantha Rao panel, the THDC will have to mobilise additional resources to implement the new package. A senior official of the THDC said: "As long as there is hope of revision in the rehabilitation package, the people are not going to move. It is this hope that the anti-dam activists are keeping alive. There is no assurance that once we implement this revised package there will not be further demands."

Work on the coffer dams in progress.-

The THDC has spent Rs.1,650 crores on the project up to March 1998. The estimated cost of Stage I of the project (1000 MW) is Rs.4,700 crores plus interest of Rs.750 crores during the construction stage. In Stage II, another dam at Koteshwar, 30 kilometres downstream, will be built. This and the pump storage power plant will cost Rs.1,200 crores plus interest during construction. The second stage has not been cleared by the Government. The cost of Stage I is being shared by the Union Government and the Government of Uttar Pradesh in a 60-40 ratio. The THDC has raised Rs.540 crores through external commercial borrowings from a Russian consortium and the loan has been guaranteed by the Union Government. The rest of the funds will come from budgetary support and suppliers' credit.

According to THDC officials, the cost escalation amounts to 10 per cent annually. Any further delays in construction may upset the cost-effectiveness of the project, they say.

Meanwhile, construction work goes on. If there are no further stoppages, the dam will be ready by the year 2002, according to THDC officials.

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