A group of five experts appointed by the Government of India to study the seismic safety of the 260.5m high Tehri dam has come to a divided conclusion.

While all five members of the group agreed that the dam design was seismically safe, four members have expressed a need for further studies to settle some of the crucial concerns.

The dam and the two stage 2000MW hydroelectric project, under construction in a highly seismically active region of Uttar Pradesh in northern India, has been mired in controversy since the project was first approved.

The seismic safety of the dam, located upstream of the densely populated Ganges Basin, has been studied by seismologists and has also been the target of protests by local citizen groups.

The protests were the focus of an international campaign led by environmental activist Sunderalal Bahuguna, who has called for a stoppage of the work pending a complete review of the project.

A hunger strike by Bahuguna in 1996 was successful in extracting a promise from the then Prime Minister of India, Deve Gowda, to appoint a committee to review the project.

This expert group was then set up by the central government in June 1996 and was headed by Professor Vinod K. Gaur, former director of the National Geophysical Research Institute.

In their report, the five member review committee, has stated that the present dam design was expected to be structurally safe to withstand the maximum credible earthquake (MCE) during the economic performance life of the dam-reservoir system.

They based their conclusion on the review of reports made available to them and the two studies conducted by the Department of Earthquake Engineering at the Roorkee University.

However, four out of the five members, including the committee’s leader, have recommended, that it is prudent to carry out some more studies. These were three dimensional non-linear analysis of the dam to evaluate its performance against MCE, and a simulated dam break analysis to ensure that the consequences were minimal in the unlikely event of an uncontrolled release of water.

The majority report stated that a number of crucial concerns could not be settled satisfactorily. These included the stability analysis of the dam under earthquake loading, and the dynamic response of the dam to the MCE in the longitudinal direction.
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