Subansiri dam unsafe: experts committee

Report kept under wraps shows project plan ignores flood control and compromises on design, safety

By Anupam Chakravartty, Arnab Pratim Dutta
Published: Tuesday 12 March 2013

Turbines being transported for the Subansiri hydropower project (photo by Arnab Pratim Dutta)

A yet-to-be released report has raised the alarm on the controversial 2,000 MW Subansiri Lower Hydroelectric Power Project (SLP) in the Assam-Arunachal Pradesh border. The report by a technical experts' committee (TEC), which was submitted to the Planning Commission, has questioned the safety of the dam on the Subansiri river a tributary of the Brahmaputra. The project has been undertaken by the National Hydroelectric Power Corporation (NHPC).

The report was submitted to the Planning Commission in July last year but has not been made public. RTI queries filed by environmental activists with the Planning Commission went unheeded. Organisations opposing the dam have accused Assam government of keeping the report under the wraps.

Former bureaucrats with the ministry of water resources, C D Thatte and M S Reddy, authored the report in which they state that the present planning of the project ignores the flood control aspect of the dam besides compromising the dam's design and safety. The report was prepared after the former minister of environment Jairam Ramesh visited Assam  in September 2010 following consultations with various civil society groups. Thereafter, under the instructions of the prime ministers' office, the Planning Commission constituted the experts committee to recommend how NHPC could move forward with the construction.

imageNHPC has already completed about 50 per cent of the work. While the dam originally planned in Gerugamukh through the creation of Brahmaputra Board (BB) close to the present dam site at Assam-Arunachal border would have addressed the issue of recurring floods, NHPC informed the experts committee in 2011 that there are only “incidental benefits of flood protection”. The report further states that NHPC could not provide any details on flood control measures if waters are released to areas downstream of the dam.
NHPC in a press release  in January 2013 had claimed that it had set up a panel under the Central Water Commission to review the dam’s design and safety aspects.

Skewed priority

The authors have stated the project ignores the flood control aspect. Such a change in the priority, the report states, contravenes the 1980 Brahmaputra Board Act. “Transferring the work of Water Resources Department of Subansiri Basin from the Brahmaputra Board to the public and private sector contravenes the Brahmaputra Board Act. Planning through public and private sector to utilise water resources for the single purpose of hydropower development also contravenes the basic premise of the Act, namely flood control, other benefits including hydropower generation as incidental,” it states.

Meanwhile, the reports suggest an increased seismic threat level to the dam, which was earlier assessed by Indian Institute of Technology at Roorkee. Seismic threat level, also referred as peak ground acceleration, was ascertained at 0.38g which is a characteristic low intensity earthquake. However, the authors referring to the previous seismic activity witnessed in the region in 1950 and 1897, point out that this figure was revised to 0.50g, which is characteristic of moderate to strong earthquakes.
The report also suggests that the very foundation on which the dam rests, might be weak. “The sandstone, which really looks and behaves like a sand rock, on which the dam is founded, has all through the SLP planning considered very weak. Its adequacy and competence to support the concrete gravity dam is not established satisfactorily,” it states.

The Planning Commission had declined to make the report public in spite of RTI queries filed by environment activists Rohit Choudhary and Neeraj Vagholikar. Vagholikar says the government cannot refuse such requests because the Chief Information Commissioner (CIC) had passed an order that all reports have to be made public after they are submitted. He cited the case of Madhav Gadgil's report on the Western Ghats, which was made public by the Union environment ministry under order of CIC. 

What the experts recommend
Transferring the work of water resource department of Subansiri basin from the Brahmaputra Board to a public-private sector contravenes the Brahmaputra Board Act. Planning through public and private sector to utilize the water resources for the single purpose of hydropower development also contravenes the basic premise of the Act, namely flood control, other benefits including hydropower being incidental. The present planning for Subansiri Lower Hydroelectric Power Project (SLP) ignores the flood control aspect.

There is some uncertainty about the seismo-tectonic environment of the project. There is a case for considering increase the strength of the structure and revise peak ground acceleration from 0.38g to 0.5 g.

NHPC will have to take necessary action to put in place non-structural flood-proofing measures under emergency action plan (EAP). NHPC shall complete all studies in respect of dam break analysis and EAP and disaster management plan urgently and get them cleared by the Central Water Commission.

The government of Assam has to put in place non-structural flood proofing measures. Incremental costs will be contributed by the dam proponents.

Government of India may provide a guarantee that government of Assam should have the first charge on SLP power There is no reason for anybody to believe that the construction of SLP will adversely affect Majuli island flood control or management plans. Majuli bank erosion cannot be attributed to floods on account of Subansiri.

The agitation against SLP and demand for flood control are self-contradictory. There cannot be any flood control without a dam. It must be appreciated by the agitators that there could be no irrigation development without the storage dams.

Click on the links below to read the complete report of the technical experts committee
Part I
Part II


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