GUWAHATI, Jan 28 � The safety of the Lower Subansiri Hydroelectric Power Project (LSHEP) being built by the National Hydroelectric Power Corporation (NHPC) is doubtful. It has a gap of eight metres between the natural hard rock and the foundation of its dam. This is quite contrary to the engineering norms, said consultant engineer J N Khataniar while talking to The Assam Tribune.
And now, in the face of popular apprehensions over the safety of the dam, the NHPC authorities have built one 50- metre deep and 80 centimetre thick concrete cut-off wall at the dam site to prevent seepage. They have also provided the dam wall with a 135 per cent base width of its maximum height to reduce the pressure of the stored water on the base.
Moreover, the power house being built by the NHPC is designed as an over ground one. The site was earlier stated to be not safe for such a power house by the Brahmaputra Board.
Initially, in 1983, the Brahmaputra Board had prepared the detailed project report (DPR) for the project in consultation with the Geological Survey of India (GSI) and the Central Water Commission (CWC). And the Board DPR had called for a rock-filled dam of 257-metre height from the deepest hard rock, suggesting that the height of the dam should be 240 metre from the riverbed.
But the NHPC has changed the dam type to a concrete gravity one with the height of 116 metres from the riverbed level and reduced the foundation depth to 9 metres from the river bed. This indicates that the heavy dam foundation is placed eight metres above the hard rock lying below the riverbed, Khataniar said.
But despite this, the NHPC has now been claiming that its DPR was approved by the Brahmaputra Board.
It is also not clear as to how the NHPC has addressed the issue of landslide in the area which is prone to severe landslide. Paragraph 137 of the geological report prepared by the Brahmaputra Board has mentioned the devastation caused by the land slid dam on the Subansiri following the August 15, 1950 earthquake, Khataniar said.
Khataniar has filed an RTI application with the Brahmaputra Board seeking information and observations of the Board on the above issues.
