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. A 30 m high m towards proposed powerhouse location. One perennial dam is proposed to get additional head. The power potential nala namely Watakul Nala at km 5.900 is crossing over the of this project is estimated to be of 45 MW with 110 m head tunnel alignment (Plate-II). The overhead cover is sufficient and 50 cumecs design discharge.The project components are all along the tunnel alignment but due to freezing and located within the Dras Volcanic Formation that mainly thawing, most of the joints are open in the area and remain comprises basalt and andesite in association with under snow cover for a maximum period. The area is highly geosynclinal sediments. The main subdivisions of Dras charged with water and due to shattered nature of
Volcanic Formation are as under [3, 5]. PLATE II GEOLOGICAL CROSS SECTION ALONG TENTATIVE ALIGNMENT OF HRT DRASS-SURU HYDRO-ELECTRIC PROJECT STAGE-II, KARGIL DISTRICT, J&K 1. Volcanic suite of rocks SCALE KM 1012KM INDEX 2. Pyroclastic materials V S77°E V V N77°W V V DRASS VOLCANICS 3. Differentiated ultramafite bodies within the Dras VVV TRACES OF JOINTS 4000 WATAKUL NALLA V Volcanics 3500 NOTE: 1. Bench mark has been taken from the V V J2 V J1 V Survey of India toposheet 3000 J1 J2 2. For section line A-B refer Plate-I V V V 4. Sediments of the geosynclinal belt. J2 V 2500 J3 J3 J3 V V J4 J4 V V J4 V 2000 V V V V J2 V J2 V By: Dr. Ajay Kumar, Geologist V V
ELEVATION IN METERS IN ELEVATION 1500 V N.K Nayak, Geologist B A The volcanic suite is mainly represented by basalt in the 87 654321 0 FS 2010-12 Dras valley and andesite in the Suru valley. Bedded flows of basaltic lava are conspicuously developed in this area. The Fig. 2. Geological cross section along tentative alignment of HRT Dras-Suru most common rock type of the volcanic suite is basalt which hydroelectric project stage-I
328 rocks, heavy seepage is anticipated in this section. J2 and J3 water which cannot irrigate the entire area, it is are also forming wedges of different sizes. The alignment of recommended to the project authority that the already the head race tunnel can be finalized at the DPR stage existing canals in the area may be charged from Suru river investigation of the project.The geotechnical appraisals are water by simply diverting the river water upstream of based on the reconnaissance survey of the area on 1:50,000 Pheruna village to meet the actual requirement of the area. scale. The detailed geotechnical investigation is very much C. Geotechnical Appraisal of Karkit Hydroelectric Project essential before taking up the project for construction. The proposed Karkit HEP is a run of the river scheme B. Geotechnical Appraisal of Dras-SuruLink HEP – II located 1 km downstream of confluence of Dras river and The proposed Dras-Suru link HEP is a run of the river Shingo river near Kargil (34°35’29.4 N: 76°00’12.4” E)and scheme. The proposed dam / barrage site (34° 24’ 48” N: a underground powerhouse near Harka Bahadur Memorial 75° 51’ 59” E) is relocated upstream of Dandal Middle (34°35’34.9” N : 76°06’40.6” E) upstream of the confluence School. The project envisages construction of low height of Shingo river and Suru river. The project envisages dam / barrage across Dras River and a underground construction of low height dam of 30 m across Shingo powerhouse (34° 25’ 28.5” N : 75° 58’ 25.7” E) at village River. After seeing the feasibility of the area, along both the Pheruna along Suru River (Plate-I). The total length of the abutments where competent rock which is hard, fresh and Head Race Tunnel will be 9.36 km (Plate – III). The power less jointed granite is exposed, the height of the dam has potential of this project is estimated to be of 70MW with been revised upto 60 m. The total length of the head race 150 m head and 50 cumecs design discharge. tunnel will be 11 km along the right bank of Shingo River (Plate-IV). The power potential of this project is estimated GEOLOGICAL CROSS SECTION ALONG TENTATIVE ALIGNMENT OF HRT DRASS- SURU HYDRO-ELECTRIC PROJECT STAGE-11, KARGIL DISTRICT,J&K SCALE 180 MW with 134 m head and 126 cumecs design KM 1 1 2 3KM discharge.
S77°E N77°W INDEX V LASAR N-2 V V DRASS VOLCANICS GEOLOGICAL MAP OF KARKIT HYDRO ELECTRIC POWER PROJECT, V V V V J2 LASAR N-1 LEH DISTRICT, J&K J1 V TRACES OF JOINTS
V V J1 J1 J4 V V J3 V V J3 V NOTE: 1. Bench mark has been taken from the V J2 V V J3 J4 J1 V V Survey of India toposheet J2 2. For section line X-Y refer Plate-I J4 V J2 V V J2 V J4 J3
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SHINGO RIVE Fig. 3. Geological cross section along tentative alignment of HRT Dras-Suru R Medium to coarse grained foliated D leno granite, granodiorite, adamelite, CHHANIGUN GARKHUN GRANITOID DAM boitite granite with migmitite and enclave of diorite HARKA BAHAUR hydroelectric project stage-II A Mesocratic to malnocratic granite, diorite, HANNGOMAGRANITOID quartz diorite, granodiorite, quatrz niorite
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N U Volcanic Formation that mainly comprises basalt and G 4302 By: Dr. Ajay Kumar, Geologist N.K Nayak, Geologist KARGIL andesite in association with geosynclinal sediments. Since FS 2010-12 Dras – Suru Link HEP Stage – I & II are located in the same Fig. 4. Geological map of Karkith hydroelectric power project geological set up. The geological part for Stage – II refer under Stage – I to avoid reputation. Along the head race The project components are located within Ladakh tunnel (HRT) minimum cover is 100 m at the intake point Granitoid Complex (LGC). The valley appears to be narrow and maximum cover over HRT is 1650 m in its central and suitable for concrete structure. However, proper portion. Two perennial nalas namely Lasar nala-I at km assessment thickness of river borne material in the river bed, 2.650 and Lasar nala-II at km 3.850 are crossing over the stability of left abutment and topography of the site will tunnel alignment. The overhead cover is sufficient all along ultimately be the deciding factors in the finalization of the the tunnel alignment but due to freezing and thawing, most actual structure and type of the diversion structure.At the of the joints are open in the area. The area between km 2.5 TABLE-3: DETAILS OF JOINT SETS. and km 6 along HRT remains under snow cover throughout the year. The area is highly charged with water and due to Sl. Dip & Strike Spacing Continuity Remarks shattered nature of rocks, heavy seepage is anticipated in No. of Joint set (in cm) (in m) this section. J2 and J3 are also forming wedges of different N4°W-S4°E / Foliation joint, 1 50 – 200 Continuous sizes.The geotechnical appraisal is based on the 85° E smooth and tight. reconnaissance survey of the area on 1:50,000 scale. The Open at places detailed geotechnical investigation is very much essential N80°W-S80°E / 10 – 100 20-25 filled with clay before taking up the project in construction. 2 50° SW and grass roots,
It was also proposed to construct a canal from the tail slightly rough and water to irrigate the command area in the downstream of in dry condition. Pheruna village. After visiting site it has been assessed from Open at places N35°W-S35°E / the topography of the area that irrigation canal from tail 10 – 100 20-25 filled with clay 3 60° SW and grass roots, water is not feasible. Three set of canals at different contour levels already exist in the area. But these canals are not slightly rough and successful to meet the actual requirement of the area as they in dry condition. are fed by the snow melt water and remain dry for most part Close Discontinuo Open at the 4 E - W / 55° N of the year.Instead of constructing new canal from the tail spaced us surface, rough.
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TABLE - 4. A COMPARATIVE STATEMENT OF THE INITIALLY PROPOSED POWER POTENTIALS AND REVISED POWER POTENTIAL OF ALL THE PROJECTS. Length Location of Lithology Dam Average Location of Lithology Total Power of Sl. No River dam / exposed height discharge power exposed head potential tunnel barrage (Dam site) (m) (cumec) house (PH site) (m) (MW) (in km) Basic Basic 1 Dras Dras 30 50 8 Dongchik 100 40/45 volcanics volcanics Basic Basic 2 Dras Dandal Barrage 50 13 Pheruna 140 65/70 volcanics volcanics 1 km D/S of Harka Dras - confluence of 3 Granite 30 / 60 126 11 Bahadur Diorite 94 / 124 107 / 180 Shingo Dras & Memorial Shingo
GEOLOGICAL CROSS SECTION KARKITHYDRO-ELECTRIC PROJECT an 8 km long HRT has been proposed. The roughly LEH DISTRICT DISTRICT,J&K SCALE km1.0 0.5 0 1. 0 2. 0 3. 0 km calculated discharge in the Dras River at this location is
S88°E N88°W INDEX 50 cumecs and the power generation is estimated upto
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CHHANIGUND N 40 MW. All the components of this project are located in LADAKH GRANTOID
SHINGO N COMPLEX HANNGOMAGRANITOID 3000 the basic volcanic rocks of Dras Volcanic. The overall 2500 TRACES OF JOINTS
NOTE: 1. Bench mark has been taken from the 2000 Survey of India toposheet rock quality is very good for the construction of HEP. 2. For section line A-B refer Plate-IV ELEVATION IN METERS ELEVATION IN METERS IN ELEVATION 1500 B 1098765 4321 0 By: Dr. Ajay Kumar, Geologist A N.K Nayak, Geologist Dras-Suru link HEP Stage - II is a run of the river FS 2010-12 schemeenvisaging construction of low height dam / Fig. 5. Geological cross section of Karkith hydroelectric power project barrage across Dras River near Dandal village and an proposed dam site, hornblende – biotite granite is exposed. underground powerhouse at village Pheruna along Suru Two sets of basic dykes are emplaced in the granite. River with a HRT of 9.36 km. The power potential of Whereas, the proposed underground power house site diorite this project is estimated to be of 70MW with 150 m head belonging to LGC is exposed which cuts across the HRT and 50 cumecs design discharge.The project components alignment in Chhanigund nala near Channigund village. are located within the Dras Volcanic Formation that mainly comprises basalt and andesite in association with These rock units are traversed by four set of joints. geosynclinal sediments.It was also proposed to construct These joint sets are forming the rock blocky in nature which a canal from the tail water to irrigate the command area requires minor treatment in the form of rock bolting and in the down stream of Pheruna village. But after site head ward excavation in the HRT and power house cavity assessment, it was recommended that instead of with fore polling method. The dip and strike of these joint constructing new canal from the tail water whose level is sets vary frequently due to circular nature of the joint pattern very low and inadequate to irrigate the entire area, the in granite terrain. Four set of joints recorded in the area are existing canal system in the area may be charged by tabulated below. diverting water of Suru River upstream of Pheruna which will serve the purpose better. The geotechnical appraisal is based on the reconnaissance survey of the area on 1:50,000 scale. The The proposed Karkit HEP is a run of the river scheme detailed geotechnical investigation is very much essential located 1 km downstream of confluence of Dras River before taking up the project for construction. and Shingo River near Kargil and an underground power house near Harka Bahadur Memorial.The project IV.CONSTRUCTION MATERIAL originally envisaged construction of low height dam of 30 m across Shingo River but after assessing the River terraces and shoals having sufficient quantity of feasibility of the area and studying both the abutments natural aggregate along the rivers Dras and Suru have been where good quality granites are exposed, revision of observed at a number of places in the vicinity of the project. height of the dam upto 60 m has been recommended.The Basic volcanic rock of massive and strong nature and project components are located within Ladakh Granitoid granites exposed along the banks of the Shingo and Suru Complex (LGC).The estimated power potential of this Rivers within the reasonable distance from the dam sites and project is 180 MW with 134 m head and 126 cumecs power house locations are the other prospective sources of design discharge. construction material. The proposed dam height of one projects and A comparative statement of the initially proposed power identification of one new site in addition keeping in view potentials and revised power potential of all the projects is the geotechnical considerations, the power potential of given in annexed table, Table-4 these projects were considerably revised. Earlier projected aggregate power potential of these projects V.CONCLUSION was 172 MW, considerably revised to 295 MW. Thus, as Dras-Suru link HEP Stage - Ia low height dam upto 30 a result of the modifications suggested during the m at this location and an underground power house with feasibility stage study of these projects a total 123 MW
330 power potential was added which is equivalent to Rs. 815.5 crore of yearly revenue (based on the current market rates of electricity, i.e. Rs 7.00 per unit). The geotechnical appraisals are based on the reconnaissance survey of the area on 1:50000 scale. The detailed geotechnical investigation is very much essential before taking up these projects for construction.
REFERENCES [1] India, Geological Survey (2005): Geology and mineral resourcesof the States of India Part X – Jammu & Kashmir, Misc. Pub. No. 30 2nd Edition (revised) [2] Narula, P. L. and Dasgupta, Sujit (2000): Seism tectonic atlas of India and its environs, GSI. [3] Sadhu M.L. Raina K.B. and Raina P.L.; Tirkey B (1973): Geology of parts of the Dras and Suru Valleys of Kargil Tehsil, Ladakh District Jammu & Kashmir State, Unpublished Report Geol. Surv. Ind. (F. S. 1972- 73) [4] Srikantia, S.V. and Razdan, M.L.(1980): Geology of part of Central Ladakh Himalaya with particular reference to Indus Tectonic Zone, Jour. Geol. Soc. India, 21 (II) PP. 523-545. [5] Wadia, D. N. (1937): The Cretaceous Volcanic series of Astor Desai, Kashmir, its intrusions. Rec. Geol. Surv. Ind, 72(2): 151-161
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