Recent Advances in Rock Engineering (RARE 2016) Pre-feasibility study of Dras – Suru link hydro- electric projects, Kargil District, Jammu&Kashmir Ajay Kumar N. K. Nayak Geological Survey of India (NR) Geological Survey of India (CHQ) Jammu & Kashmir Kolkata [email protected] Abstract:-The Jammu & Kashmir State Power harness the power potential of these rivers. JKSPDC Development Corporation (JKSPDC) is contemplating for approached CWC in this regard and CWC, in turn, construction of different run of the river schemes on Dras – requested Geological Survey of India for the preparation of Suru Rivers to harness the power potential of these rivers. The PFR of two hydro-electric projects across the Dras – Suru Pre-feasibility Stage geotechnical and geological investigation Rivers. The authors were deputed to undertake the of three hydroelectric projects across the Dras and Suru Rivers reconnaissance geological investigation in the Dras – Suru were carried out. These proposed projects, named as Dras- basins and Indus basin. The field investigations were carried Suru link HEP Stage-I, Dras-Suru link HEP Stage-II and out by the authors during August 2011 accompanied by the Karkit Hydro Electric Project, are all run of the river schemes. technical team of CWC and JKSPDC. The Dras-Suru link HEP Stage-I envisages construction of a low height dam near Dras Town across the Dras River II.GEOLOGY AND TECTONICS OF THE AREA downstream of the bridge connecting the road to Sanko with the Srinagar – Leh national highway and an underground The central portion of the Dras valley is occupied by the powerhouse near Dongchik village. The length of the proposed volcanic suit of rocks called Dras Volcanics (Plate – I), HRT is 8 km. and the estimated power potential is 45 MW with which have an intrusive contact with the hornblende-biotite 110 m head and 50 cumecs designed discharge. The Dras-Suru granite belonging to Ladakh Granitoid Complex in the north link HEP Stage-II envisages construction of a low height dam / and a thrusted contact (Sanku Thrust) with the slate-phyllite- barrage across Dras River upstream of Dandal village and an limestone sequence of Batal ≡ Phe Formation of Neo- underground powerhouse at village Pheruna along Suru River. Proterozoic age in the south [4]. The valley of Suru River The length of the HRT is 9.36 km. and the estimated power between Kargil and Sanku is also occupied mostly by the potential of the project is 70 MW with 150 m head and 50 Dras Volcanics with intrusive tongues of granites. The cumecs designed discharge. All the project components of these southern part of the volcanic belt towards Sanku has a two projects are located within Dras Volcanic Formation faulted contact with a group of highly folded and comprising mainly basalt and andesite in association with metamorphosed rocks resting over granitic gneiss.A geosynclinals sediments. The proposed Karkit Hydro Electric generalised regional geological / tectono stratigraphic Project envisages construction of a dam 1 km downstream of sequence worked out for Dras valley and Kargil – Sanku the confluence of Dras and Shingo Rivers with an underground powerhouse near Harka Bahadur Memorial upstream of the area has been given in Table – 1[3]. confluence of Shingo and Suru Rivers. The length of the HRT GEOLOGICAL MAP OF THE AREA DRASS- SURU LINK HYDRO-ELECTRIC PROJECT STAGE-II, is 11 km and the estimated power potential is 180 MW with KARGIL DISTRICT, J&K V V V V V V SCALE V V KM 1 .0 0 .5 0 1 .0 2. 0 3 .0 KM V V V A L V L V A V N 124 m head and 126 cumecs designed discharge. The project T V A V B V V V V IM V B INDEX V V V V V V V V V Quaternary components of this project are located within Ladakh 25 ° V V V V V V V V V V V V 25° V V V Drass Volcanic Formation V DRASS V 35 ° V V V V V V 25° V V A 56 ° V DR R V V 70° ASS IVE V Differentiated ultramafic Granitoid Complex comprising heterogeneous rock association V V 65° R 85° V V 35° V V V V 70° DA NDAI 85° V V V V V V V Intra trappian sediments 65° V V V 40° V 70 ° of granite, gabbro, basic dykes, meta-volcanics and meta- V 70° 50° V Batal=Phe Formation V V LAS V V 50° A V X R V V N V V ALLA B 75 ° V Dip and strike V V V V V V V V sediments. During the course of the Pre-feasibility geotechnical 65° V V V Sanku Thrust V V V 25° 25° 25° V 25° 25° V V V 30° V V V V V V V V investigation, one new project site was identified and height of 10° V 35° V V V Y V 40 ° 40° V V V V V V 75° By: Dr. Ajay Kumar, Geologist V 45° the dam in one project was suggested for enhancement based V N.K Nayak, Geologist V PHERANA V FS 2010-12 V 55° V V 30° V V 65° on the geotechnical considerations. This led to revision of After complied GSI map V V V aggregate power potential of these projects from 172 MW to V 305 MW, i.e. an addition of considerable 133 MW power Fig. 1. Geological map of Dras-Suru Link hydroelectric project Stage-II potential. Tectonically, the proposed Dras – Suru link HEP Stage-I, Keywords:- Pre-feasibility; Hydroelctric; powerhouse Stage-II and Kirkit HEP lie on the south-western edge of the Indus-Shyok Belt. This belt is sandwiched between I.INTRODUCTION Karakoram Belt in the north and Main Himalayan Belt in the The Jammu & Kashmir State Power Development south. It comprises Cretaceous and Tertiary sediments and Corporation (JKSPDC) is contemplating construction of associated mafic, intermediate and acid magmatic rocks with different run of the river schemes on Dras – Suru Rivers to imprints of Upper Palaeozoic and Early to Middle Mesozoic © 2016. The authors - Published by Atlantis Press 327 sediments in the Shyok Belt. Wakha, Pashkyum and Shyok is medium to fine grained, greenish coloured and highly Thrusts are the major tectonic planes from south to jointed in nature. Vescicles are also recorded at a few places north.Seismotectonically, the Projects are located in the in the basalt which are filled with calcite as secondary Trans-Himalayan Indus Suture Zone (ISZ) in Central Ladakh mineral, while andesite is greyish or greenish in colour falling in the Seismic Zone-IV and V of the Seismic having cryptocrystalline aggregate of feldspar and Zonation Map of India[1,2,4]. ferromagnesian minerals with little silica.Two small outcrops of volcanic agglomerate have been noticed on the TABLE – 1: GENERALISED REGIONAL GEOLOGY / TECTONO-STRATIGRAPHIC SEQUENCE. left bank of Bhimbat nala. These pyroclastic beds comprise fragments of limestone, basic rock and chert. Group Formation Lithology Age Glacial moraines, Differentiated ultramafite bodies are occurring at Pleistocene Quaternary scree and recent to Recent several places within the Dras Volcanics at Dras and alluvium Thasgam area. The ultramafite bodies constituting “Brown Hornblende-biotite Cretaceous Ladakh Granitoid Hill” are exposed along western slope of Tololing Hill and granite with dioritic to Complex enclaves Oligocene north of Gosan village. They mainly comprise -------------------------------------------------Intrusive------------------ monomineralic rock, Dunite, which is medium to coarse Basalt, Andesite, grained in texture, pale green in colour and greasy in luster Ultrabasics, Sangeluma Dras Cretaceous [3].There is widespread distribution of chert within volcanic intratrappean Group Volcanics to Eocene belt which is greyish, bluish and reddish in colour. sediments with Interbedded outcrops of limestone and shale occur within Orbitolina limestone. ------------------------------------------------Sanku Thrust-------------- the volcanics in Dras valley. It comprises alternate bands of Pyritiferous dark grey and purple shale, calcareous siltstone and orbitolina Batal ≡ slate, phyllite, limestone.These rock units are highly jointed with multiple Haimanta Neo- Phe crystalline limestone Group Proterozoic set of joints trending in all directions. Four set of joints Formation / marble and meta- recorded in area are tabulated below. basics TABLE-2: DETAILS OF JOINT SETS. III.GEOTECHNICAL APPRAISALS Dip & Sl. Spacing Continuity Strike of Remarks A. Geotechnical Appraisal of Dras-Suru Link HEP – I No. (in cm) (in m) Joint set Dras-Suru link HEP Stage – I is a run of the river N80W- Bedded flow joint, 50 – 200 Continuous scheme. This is a new project suggested by the authors 1 S80E / 65 smooth and tight. based on the current investigation. The project authorities SW N10W- Open at places filled did not have this proposal when they had approached the 10 – 100 20-25 2 S10E / with clay and grass GSI. The proposed dam site (34° 25’ 37” N : 75° 45’ 59” E) 30SW roots, slightly rough is located downstream of bridge on Dras river heading N25W- Open at places filled 10 – 100 20-25 towards Sanko in J&K. At this location Dras River is 3 S25E / 70 with clay and grass forming deep and narrow gorge of 40 m width. The project NE roots, slightly rough envisages construction of low height dam across Dras River N50E- Close Open at the surface, 4 S50W / 80 spaced Discontinuous and an underground powerhouse (34° 24’ 53” N : 75° 51’ rough. 12” E) near opposite to the village Dongchik (Plate – I). The NW total length of the Head Race Tunnel will be 8 km. The Along the head race tunnel (HRT) minimum cover is 50 water level at proposed dam site is 3080 m and at m at the intake point and maximum cover over HRT is 600 powerhouse site the tail water level is 3000 m.