Government of India

Ministry of Environment & Forests


Telefax: 011-24360488                                                          


Date: January 5th 2011


Subject: Summary Record of 44th meeting of Expert Appraisal Committee on River Valley and Hydro Electric Projects constituted under the provisions of EIA Notification 2006

Kindly find enclosed the Minutes of the above mentioned meeting which was held on 11th November 2010 at Van Vigyan Bhawan, New Delhi under the Chairmanship of Shri Rakesh Nath, Chairman, EAC.


Comments, if any, may kindly be communicated immediately.



(Sanchita Jindal)

Additional Director

Encl: Minutes of the Meeting.   




Shri Rakesh Nath

Chairman, EAC

C-1/29, Bapa Nagar

New Delhi-110 003



Dr. A.K. Bhattacharya

Flat No. 805, Pocket-3

Akshardham Apartments

Sector-19, Dwarka

New Delhi-110 075



Dr. B.P. Das

717, Sahid Nagar


Orissa-751 007



Prof. Dulal Goswami

Quarter No. 2

Gauhati University


Assam-781 014



Dr. (Mrs.) Usha Bhat

C-68, Sector-40

Noida-201 301



Dr. Surendra Kumar Mishra

Department of Water Resources

Development & Management

Indian Institute of Technology

Roorkee-247 667



Dr. (Mrs.) Maitreyee Choudhary

Professor & Director

Central for Himalayan Studies

University of North-Bengal

P.O. North Bengal University

Raja Rammohunpur

District – Darjeeling-734 013



Prof. Arun Kumar

Department of Earth Sciences

Manipur University


Manipur-795 003



Prof. (Dr.) Dhananjai Mohan

Wildlife Institute of India

Dehradun-248 001





Central Inland Fisheries Research Institute


West Bengal-700 120



Chief Engineer (Hydrology)

Central Water Commission

Sewa Bhawan

R.K. Puran

New Delhi-110 066



Dr. S. Bhowmik

Member Secretary, EAC





Summary Record of 44th meeting of Expert Appraisal Committee on River Valley and Hydro Electric Projects constituted under the provisions of

EIA Notification 2006


            The Forty Fourth meeting of the Expert Appraisal Committee (EAC) on River Valley and Hydro Electric Projects was held on 11th December, 2010 at Van Vigyan Bhawan, New Delhi.  The meeting was chaired by Shri Rakesh Nath.  The list of participants is appended at Annexure I.

            After welcoming the participants, the agenda items were taken up for discussion.  Agenda item No. 2 for discussion with experts and officials of Government of Assam for Downstream Impact Study of the ongoing Subansiri Lower Hydroelectric Power Project at Gerukamukh was taken up first.  The following are the discussions and decisions taken during the meeting - 

Agenda item No. 2

Downstream Impact Study of the ongoing Subansiri Lower Hydroelectric Power Project at Gerukamukh – Discussion with Experts and Officials of Government of Assam.


            The Ministry of Environment & Forests had received reports on ‘Downstream Impact Study of the ongoing Subansiri Lower HEP at Gerukamukh’ conducted by an Expert Committee comprising of IIT Guwahati, University of Gauhati and Dibrugarh University and ‘House Committee Report of Legislative Assembly, Government of Assam’. These reports were discussed by the EAC on 7th October 2010; however, the discussions could not be completed.  The Principal Secretary to the Government of Assam, Power and Transport Departments has also sent a note on the concerns expressed by Government of Assam on this project.  Further the Professors of IIT Guwahati and other experts have represented to the Chairman of the EAC for giving a chance to present their view points. It was therefore, decided to discuss the matter with Government of Assam and Experts from IIT Guwahati, University of Gauhati, Dibrugarh University, IIT  Roorkee and NHPC.

            At the onset, Shri Sumeet Jerath, Principal Secretary, Power Department, Government of Assam apprised the Committee regarding the concerns of Government of Assam regarding safety and stability and downstream impact of the 2000 MW lower Subansiri Hydroelectric Project (SLHEP) of National Hydroelectric Power Corporation (NHPC).  He brought to the attention of the Committee the recommendations of the Study Report of the Expert Group constituted by Government of Assam. He also informed that the Chief Minister of Assam has taken up the matter with the Hon’ble Prime Minister on the following points –

(i)           Setting up a Technical Team consisting of Internationally acclaimed seismologist experts to examine the technical parameters for the safety and stability of the dam of the SLHEP by Government of India/NHPC.

(ii)       Setting up of a Steering Group by NHPC to advise them to initiate measures for flood and erosion control in the downstream areas.


(iii)      A comprehensive and cumulative river basin study by the Central Water Commission for studying cumulative impact on bio-diversity and the eco-system of the region due to the proposed hydel projects.


(iv)      Free power of 120 MW from the Subansiri instead of only 25 MW presently agreed.


(v)       Setting up of a North Eastern Water Resources Authority (NEWRA) for evolving a holistic and integrated water and hydel policy for the entire North Eastern Region.


            The Committee felt that it does not have any role on the above points and these may be taken up at the appropriate level with Government of India.  However, on item (iii) Ministry has already initiated a study, Terms of Reference of which were finalized by EAC during its last meeting.

            Shri M. Gogoi, Ex-Chairman, House Committee and MLA expressed his concern regarding downstream effects of the dam on population as well as ecological and biological diversity. He stressed the need for stopping the construction and reviewing all the parameters of the dam once again.  He also expressed the concern about the impact on flow of river and wide variation in flow due to peaking operation of the power project during lean months.

            Regarding safety and stability of the dam, Mr. Jerath expressed that the recommendations of the Expert Group need to be reviewed by the EAC.  Representatives of the Expert Group from IIT, Guwahati, Guwahati University and Dibrugarh University then presented the following recommendations, concerns and suggestions. Representatives of NHPC and Experts from IIT, Roorke provided explanations and their view point on these issues. 

Safety and Stability of the Dam


A.         Seismological Issues


(i)        The site specific seismic design parameter for peak ground acceleration (pga) value of 0.38g considered by NHPC is inadequate as the whole of the North East falls under Zone V – (very high damage risk zone) with probability of earthquakes of MSK IX or more.  Previously the earthquakes of 8.7 (Shillong earthquake) and 8.5 (Assam earthquake)on the Richter scale have been experienced.   In view of this, the design parameters need to be reconsidered to be at least 8.5 M at pga of 0.5g.


(ii)    The broad scale data provided by NHPC is shockingly lacking and there are gaps in the data.  A mega earthquake of 1947 has not been reported.  Therefore, lithologically and seismologically it needs deeper investigation, not only for lower but upper Subansiri too. A cumulative effect study should be conducted.


B.         Geological Issues


(iii)      The rocks in the foot hills are poorly cemented sand stone on which the dam would be constructed.  This also seems unstable even at pga of 0.38 g, especially for the surrounding ground. A fault along the Subansiri at about 2 Km downstream of the dam has also been inferred by GSI.  Therefore, the indications of recent tectonics in the area gives ample reason for giving a serious relook at the selection of the site for the dam.


(iv)      The Himalayan Foothills, south of MBT (Main Boundary Thrust) is not suitable for any mega hydro power project from the Geological, Tectonic and Seismological point of view.


C.         Design and Engineering Issues


(v)       The change of the height of the dam- a concrete gravity dam- was originally designed to be 133 m above the deepest foundation level including the foundation depth of 17 m. This has now been modified to 125 m by reducing the foundation depth to 9 meters. Therefore, the ratio of total dam height to the foundation is inadequate. This would make the dam highly vulnerable seismically especially when an earthquake of intensity 8.5 in the Richter scale has already occurred in that region in 1950.


(vi)      The maximum observed flood at Chouldhowaghat is 21, 230 cumecs on 11th July 1971 whereas NHPC has considered highest flood as 18,790 cumecs.


(vii)     Inflow sediment deposition and Silt load management is also poor. 


D.        Downstream Issues


(viii)    The discharge from the project will be only about 6 cumec for about 18-20 hours a day when sufficient water will have to be stored, during the rest of the day, to get the desired momentum to run all or most of the eight machines (250 MW each).  The daily lowering and rising of water level in the downstream of the river can have serious ramification in the lives of all aquatic life and also in agriculture and navigation etc.


(ix)      A balancing tank pond (reservoir) at the downstream may be provided to take care of the peaking load.  The efficiency of this is proven world over.


E.         Physical, Ecological and Biodiversity issues


(x)       Life of about 308 bird species living on fish in the Subansiri River will be affected. Biodiversity will be lost and whole aquatic and terrestrial ecosystem will be destroyed.


(xi)      Resident population of 29 Dolphins and other fish will be affected, the river being their nursery and breeding ground. The Dolphins are at downstream of the dam at the confluence of Subansiri and Brahmaputra rivers. A minimum of 4-5 m depth of water needs to be maintained for Dolphins. The proposed 6 cumec water flow would be insufficient for fish survival.


(xii)     Physical, Chemical and Biological quality changes in water at downstream need to be studied.

             Chairman stated that the purpose of the meeting is to exchange technical information and have healthy discussions to remove some of the misgivings and to work out the best possible mitigating measures.  On the request of EAC,  NHPC had carried out an  exercise on scheduling of generation with a view to operate one machine round the clock throughout the year.  The exercise indicates that it is possible to operate one machine continuously, though at the cost of peaking power, to maintain the minimum flow, which could take care of downstream issues of Dolphins, fish and birds as well as the water quality issue, as the requisite flow and depth of water may be available.   He also informed that EAC has recently finalized Terms of Reference for cumulative Impact Assessment for Subansiri and Siang Basin to be conducted by Government of India.  It has been recommended by EAC that the report may be given in two phases.  The First Report may be a Rapid Assessment based on available secondary data and the second report may be a detailed one.

            The Chairman then requested NHPC to provide their point of view and explanation on each issue raised by the Expert Group of Govt. of Assam. NHPC felt that the study was instituted for the downstream effects of the Dam while the expert group has raised whole lot of issues. It was clarified by the EG that they have carried out the study as per the TORs given to them. The experts from NHPC informed the Committee that the contents of the preliminary report of the aforesaid expert group have already been discussed in detail with them and a field visit was undertaken by Dr. D.P. Duarah and Prof. S. Kalita of Gauhati University along with Prof. A.K. Jain of IIT Roorkee and NHPC officials regarding issues related to Geology, Geomorphology etc. A meeting of Professors of Earthquake Engineering Department, IIT Roorkee was arranged with the Members of the Expert Group at Guwahati regarding issue of seismicity. Besides, a visit to Bhakra Dam was also arranged for the Expert Group Members to compare Subansiri project as both are concrete gravity dams and are located south of MBT.  NHPC also expressed that they have requested the Ministry of Power to constitute the technical team and steering group as desired by Government of Assam.

Regarding seismological and geological issues, NHPC explained that the site specific earthquake design parameter studies have been carried out by the Department of Earthquake (DEQ), IIT Roorkee taking into account major earthquakes in the area.  The issue has been re-discussed with  Professors of Department of Earthquake Engineering, IIT, Roorkee, who, being involved with the regional geological studies of that area  are well conversant with the area, and have again confirmed that the maximum PGA value i.e. 0.38 g considered for design is adequate. Prof.  V.C. Thakur from Wadia Institute of Himalayan Geology (WIHG), Dehradun presented the details of earlier earthquakes and the justification for the PGA value. He informed the Committee that the basic Geological Frame Work map of the area has been well studied for last 30 years. The Oil and Natural Gas Commission (ONGC) has also conducted the geological studies in the area for oil exploration. Therefore, the area is very well known. Based on this, the Brahmaputra Board had selected the site.  Regarding location and disposition the Himalayan Frontal Thrust (HFT) is also notional. Tectonic contacts are fairly well marked and placed at the same site however, concealed. HFT is a linear feature at the junction of Himalayan front (Siwaliks) and alluviums all along the Himalayas from NW to NE. At Subsansiri Project site, HFT is found concealed under alluvium, however continuity of Siwalik outcrops are observed in Dirpai Nala, which is located about 5 km D/S of dam site.  As such, HFT can be placed either at this location or further Southwards of Dirpai Nala.  This location of HFT (5 km) is more or less in line of findings of GSI/Brahmaputra Board as mentioned in their Feasibility Report. Regarding apprehension of fault along Subansiri River, GSI in one of the photo-geological map (1:50,000) had indicated a lineament/fault along Subansiri River (2 Km downstream of Dam site).  There is no such fault noticed along Subansiri River neither by NHPC nor by WIHG during field surveys.  Moreover, GSI has not substantiated existence of this fault by any field evidence. Further, there is no trace of any fault at the foundation of dam site.  Foundation geological map (1:250 scale) of the area was given to Expert Group as well as the site was seen by the members of Expert Group during concreting at dam foundation. He further emphasized that Cartosat – II data has been analysed and there is no indication of river bed fault along Subansiri River.   They have analysed the earthquake cycles which repeats almost after 500 years, at least the larger ones. After analysing the past earthquakes, it is concluded that an earthquake of 8.5 on Richter scale is not possible in the present tectonic set up around project area. There is a standard methodology to study these and IIT Roorkee and NHPC arrived at a value of 7.5 Mag but 8.0 Mag has been taken as more conservative value. The same way a seismic horizontal co-efficient of 0.15 was arrived at and a 100% escalation has been taken. Thus enough margins have been kept and nowhere in the world, design values of higher magnitude have been used in dams. IIT Roorkee has studied the issue and has submitted a detailed report to NHPC. Moreover, all these issues have been looked into by the National Committee on Seismic Design Parameters (NCSDP) who has already approved the site specific earthquake design parameters. NHPC explained that a number of mega dams like Bhakra, Ranjitsagar, Pong Kalagarh, Mangla (Pakistan) etc. have been constructed south of MBT in Shivalik formation.

After detailed discussion, it was felt that the expert in dam design and seismology should have a separate meeting to narrow down their differences. It was decided to organize a separate meeting on 7th January, 2011 at New Delhi between concerned experts from IIT Roorkee, IIT Guwahati, Guwahati University, Dibrugarh University and NHPC.  It was also suggested by the Expert Group that experts from earthquake Engineering group from IIT Guwahati may also participate.  NHPC would also invite Prof. Arya in the meeting.  NHPC will coordinate and organize the meeting.

            For other issues like Safety and Stability of Dam, design flood, reservoir sediment management and downstream management etc. NHPC informed the Committee that they have adopted the following measures –

(i)       The Stability of dam has been ensured for all statutory load combinations by providing larger base width.

(ii)    Maximum base width for the dam is kept 170 m for 125m high dam (1.35 times of Dam height) whereas it is normally kept as 0.8 times of Dam height.  Foundation depth of Subansiri should not be compared with other dams as requisite bedrock has been obtained at higher alleviation i.e. 85 m than envisaged earlier.  It is not advisable to unnecessarily increase the depth of foundation when hard rock has been found and replace natural hard rock by concrete.  This point was appreciated by all the expert and EAC members.

(iii)       The dam has been designed for seismic parameters as approved by NCSDP.

(iv)      50 m deep concrete cut off wall with cumulative length of 370 m has been envisaged for the safety of Dam foundation.

(v)     Cumulatively about 6 km of drilling and 1.5 km of drifting has been carried out. Cut of wall and consolidation Grouting has been adopted and foundation has been encased.


(vi)      Concrete apron has been provided at the Toe of the Dam.


(vii)     Concrete cladding with cable anchors (30-35 m long) have been provided for stability of dam abutments.


(viii)    The design flood of 37,500 cumec, as estimated by deterministic approach was cleared by CWC.


(ix)      The calculation for flood by probabilistic approach is less than the adopted design flood i.e. 37,500 cumecs which is safe even after considering 21,230 cumecs, a value suggested by the EG.


(x)       For management of inflow sediment deposition, Spillway crest has been provided at lower level. Reservoir shall be kept at lower levels in monsoon months so that incoming sediments are transported to downstream thereby maintaining the river regime close to the original natural condition.


(xi)      NHPC is prepared to operate one machine out of 8 machines of 250 MW capacity at 170 to 250 MW for 24 hrs to maintain a minimum discharge equivalent to natural discharge of about 300 cumecs in the river during lean period. Although, it will sacrifice peaking generation during lean season.    Regarding flood control, NHPC informed that during monsoon,   they propose to operate and maintain the reservoir at MDDL so as to provide flood cushion.  EAC felt that with this type of operation Subansiri HEP will help in providing some flood cushion which is better than ‘No Dam’ scenario.


Regarding strengthening of embankments, construction of Flood Shelters, installation of warning system/ communication network, green belt development, creation of Disaster Management cell, NHPC expressed that they are open to take suitable measures suggested by the Committee. Disaster Management Cell shall be established in association with the District Authorities. Regarding Fish conservation, NHPC shall create fish ponds in downstream areas to cater to the demands of locals for fisheries as per the study report of CIFRI. Training for development of various skills like handicrafts, fishery, improved agriculture practices, piggery etc. shall be given to the locals and awareness programmes to educate locales about benefits of the project shall be undertaken by NHPC under their CSR.


It was decided that NHPC shall –


            (i)        Install all weather stations and real time telemetric and data acquisition system for advance flood warning.


            (ii)       Install state-of-the–art monitoring and communication systems between the various components of the project, discharge sites and State Authorities in Assam which will operate round the clock.


            (iii)      Install Doppler Weather Station or have a tie-up with IMD.


            (iv)      Device Fool-proof mechanism for Disaster Management in consultation with District Authorities and submit a note to MoEF.


            (v)       Co-ordinate with the Govt. of Assam regarding location and type of warning systems.


            (vi)      Work out a conservation strategy for downstream aquatic life including                                 Dolphin.


            (vii)     Organize a meeting of experts on seismic design of the dam on 7.1.2011 at New Delhi as decided above.


(ix)      Carry out a model study for sedimentation of Subansiri reservoir based on the actual site data on silt load observed.  

(x)       Develop pattern of density current which is vital for prediction of sedimentation pattern as well as for procedure of flushing. 


                  NHPC agreed for all the above action points.


            Chairman thanked all the participants and hoped that this meeting has been useful in clearing some of the apprehensions and bridging the difference between the various experts.  All the participants thanked the Chairman for conducting the meeting in a harmonious atmosphere.


                  2.   Agenda Item No. 1


Acceptability of three season secondary data for preparation of downstream impact study of Lower Siang 2700 MW Hydro Electric Project in Arunachal Pradesh by Jaypee Arunachal Power Ltd.


            The additional TORs for downstream impact study of Lower Siang Hydro Electric Project in Arunachal Pradesh were given to the Project proponent M/S Jaypee Arunachal Power Ltd. on August 3, 2010. The project proponent has prepared the EIA report including downstream impact studies and has submitted to State Pollution Control Board for public hearing.  The Ministry received a number of representations demanding cancellation of the public hearing as data collected by the proponent is not as per the TORs given to the proponent for downstream impact study.  The proponent was to collect three season data for EIA/EMP however, they have submitted the EIA report based on the secondary data available with their consultant and other agencies.


            The Committee discussed the issue and found that data provided is insufficient and require more real time data, at least for one season for low levels.  Besides this, ground truthing is required.  The Committee further discussed some of the observations of Dr. Das who had visited the site.  The proponent was advised to include measures to take care for sudden variation in the river flow.  The study on fish needs to provide the type of fish available, their migration pattern and routes and restoration and mitigation programme.


            The proponent was advised to go for public hearing only after completion of collection of primary data as suggested above.


            The meeting ended with thanks to the Chair.


Annexure 1

List of Participants of 44th Expert Appraisal Committee Meeting for River Valley & Hydroelectric Projects held on 11th December 2010 in New Delhi


A.              Expert Appraisal Committee Members


1.                   1


Shri Rakesh Nath, Chairman



Dr. B. P. Das,  Vice-Chairman



Dr. A. K. Bhattacharya,  Member



Dr. (Mrs.) Usha Bhatt, Member



Prof. Arun Kumar, Member


6.                   6

Dr. D C Goswami, Member


7.                   7

Dr. Utpal Bhaumik, Member  


8.                   8

Shri N. K. Mathur , Member



B.               Ministry of Environment & Forests, New Delhi



Ms. Sanchita Jindal

Additional Director


10.               1

Dr. P. V. Subba Rao



C.               Representatives from Government of Assam and Expert Committee on Study on Downstream Impact of Lower Subansiri HEP


11.               1

Shri Sumit Jerath

Principle Secretary 

Department of Power & Transport

Government of Assam               


12.               1

Shri M. Gogoi

Ex-Chairman House Committee

MLA, Assam


13.               1

Shri G.K. Borua

MLA, Assam


14.               1

Shri N.C. Das

Secretary (WR)

Department of Water Resources

Govt. of Assam


15.               1

Shri H.M. Sharma

Resident, Engineering, ASEB

Govt. of Assam


16.               1

Shri R. Kapoor

Liaison Officer, ASEB

Govt. of Assam


17.               1

Shri J. Kalita


Gauhati University


18.               1

Shri A.K. Sharma


IIT Guwahati


19.               2

Dr. S.P. Biswas


Department of Life Sciences

Dibrugarh University



20.               2

Dr. J.N. Sarma

K.D.M. Chair Professor

Dibrugarh University

Assam-786 004


21.               2

Shri S. Kalitn


Environmental Science

Gauhati University


22.               2

Shri Abani Kumar Bhagbati

Gauhati University



23.               2

Shri B.P. Duarah

Associate Professor

Gauhati University



24.               2

Shri R.K. Gosami



D.              Representatives of NHPC and other Experts


25.               2

Dr. Gopal Dhawan

Executive Director (Geo Tech)


26.               2

Shri K.S. Nagaraja

Executive Director (D&E)


27.               2

Shri A.K. Sarkar

Executive Director (Planning)


28.               2

Shri Vipin Kumar

Chief (Environment)


29.               3

Shri P.K. Gupta

Chief Geology


30.               3

Ms Manjusha Mishra

Deputy Manager


31.               3

Shri Rajeev Baboota

Chief Engineer (Hydrology)


32.               3

Shri Anil Jain

Chief Engineer (Design )


33.               3

Shri Ratish Kumar

General Manager (E&M)


34.               3

Shri Rajesh Sharma

Chief  Engineer (E&M)


35.               3

Shri N.K. Mathur

Chief Geology


36.               3

Shri S.L. Kapil

Chief (Geophysics)


37.               3

Shri Anish Gauraha

Manager (E&M)


38.               3

Professor V.C. Thakur

Scientists Emeritus

Wadia Institute Himalayan Geology

Dehradun-248 001




Dr. B.K. Choudhuri

Wadia Institue of Himalayan Geology



40.               4

Professor Ashwani Kumar


Department of Earthquake

IIT Roorkee


41.               4

Dr. Manish Shrikhande

Associate Professor

Department of Earthquake Engineering,

IIT Roorkee




E.               Representatives from Lower Siang HEP


42.               4

Shri P.K. Alogh

Senior Vice President



43.               4

Shri Harish Aggarwal

General Manager



44.               4

Dr. Aman Sharma

CF (Env)
















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