GSI-CHQ-872
48-735 (1)
GEOLOGICAL SURVEY OF INDIA
A PRELIMINARY REPORT ON JAINTI RESERVOIR PROJECT, SANTAL
PARGANAS BIHAR.
By
K.R. RAGHU NANDAN,
Assistant Geologist,
Geological Survey of India.
May, 1962
GSI-CHQ-872
A PRELIMINARY REPORT ON JAINTI RESERVOIR PROJECT, SANTAL
PARGANAS BIHAR.
By
K. R. Raghu Nandan,
Geological Survey of India.
CONTENTS
Chapter
Title
ABSTRACT
Paragraphs
-
I.
INTRODUCTION
1-4
II.
PHYSIOGRAPHY, DRAINAGE, CLIMATE AND RAINFALL
5-8
III.
REGIONAL GEOLOGY
9 - 14
IV.
ENGINEERING DETAILS OF PROJECT
V.
SITE CONDITIONS, GEOLOGY AND PROBABLE
FOUNDATION CONDITION
VI.
DESCRIPTION OF ROCK TYPES
VII.
STRUCTURE FEATURE
26 - 27
VIII.
SEISMICITY OF THE AREA
28 - 30
IX.
MATERIALS OF CONSTRUCTION
31 - 33
X.
DISCUSSION ON THE FEASIBILITY OF DAM SITES AND
LOCATION OF SPILLWAY
34 - 40
XI.
MINERAL OCCURRENCE IN THE RESERVOIR AREA
41 - 44
XII.
CONCLUSIONS AND RECOMMENDATIONS
45 - 62
15
16 - 24
25
APPENDIX
I.
Engineering Details of Projects: Tatariatanr Dam on Joint.
II.
Raghunathpur Dam on Jain.
PLATES
I.
Geological map of Jainti Dam Site.
II.
Geology along Dam Alignment at Tatariatanr site.
III.
Probable Reservoir limit plotted on the geological map of the area.
GSI-CHQ-872
A PRELIMINARY REPORT ON JAINTI RESERVOIR PROJECT, SANTAL
PARGANAS BIHAR.
By
K. R. Raghu Nandan,
Geological Survey of India.
ABSTRACT
The two proposed dams across Jainti river are located at Tetariatanr or Dhakawa and at
Raghunathpur in the district of Santal Parganas, Bihar State. The former will be 7000 ft. (2123.6 m)
long and 66 ft. (20.11 m) high. The river bed at the dam site is mostly sand covered with a few rock
exposures of mica gneiss, amphibolite, quartz and pegmatite veins. It is suggested that the spillway be
confined to the river bed-in order to determine bed rock four drill holes 100 ft. or 30.48 in apart are
recommended. The reservoir at Tetariatanr will not submerge any workable coal seams and no serious
seepage problem is anticipated in the present coal workings, if the gaps are plugged by dykes and the
reservoir spread is kept a mile (1.6 km) away from the coal workings.
At the Dhakawa site rock outcrops extend from bank to bank and consist of banded granitegneiss and amphibolite. Geologically it is good but siting the dam here would necessitate building
another dam to harness. Baghdharu nadi which has a catchment of 24 sq. miles (62.16 sq.kms.).
Hence this is not favoured.
The proposed dam site at Raghunathpur will be 7400 ft. (2255 m) long and 72 ft. (21.94 m)
high. The river bed is rocky consisting of porphyritic augen gneiss intruded by dolerite. It is suggested
that the spillway be located in the river bed. Exploratory programme will be indicated as soon as
geological mapping is completed.
I. INTRODUCTION
Under instructions from the Superintending Geologist, Engineering Geology Section, Eastern
Region, and as per item No. 16, page 88 of Field Season Programme 1961-62. the author carried out
the geological investigation connected with the "Jainti Reservoir Project", Santal Parganas District,
Bihar, between the 10th and 20th May 1961. Thin project envisages the construction of two dams
across Jainti River, viz.,(i) a Lower dam at Tetariatanr (24°12': 86°41¾', 72 L/12) or alternatively at
Dhakawa (24°12¾' : 86°40¾ ') and (ii) an Upper dam at Raghunathpur (24°12½' : 86°32½').
2.
The present visit was undertaken to examine the geology and foundation conditions of dam-
site at Tetariatanr, Dhakawa and Raghunathpur. A geological map of the dam site at Tetariatanr was
2
GSI-CHQ-872
prepared on the block level survey map supplied by the Project Division (scale 1" – 2" or scale 2.54
cm = 60.96 m) by using tape and compass.
Location and access:
3.
The nearest railway station to the dam sites is Madhupur on the main line of Eastern Railway
and is about 175 miles (281.63 km) from Howrah. The dam site at Tetariatanr (24°12': 86°41¾'; Sheet
No. 72 L/12) is about 8 miles (12.87 km) south of Madhupur Town and is connected by Murrum
Road. The alternative site proposed at Dhakawa (24°12 ¾': 86°40 ¾ ') is more than a mile (1.61 km)
upstream of the Tetariatanr site and can be approached from Dhobna (24°13': 86°40½' village 5 miles
or 8.04 km from Madhupur ) by a fair weather road. The dam site near Raghunathpur (24°12½': 86°
32½ ') is about 14 miles (22.53 km) from Madhupur. A metalled road runs parallel to the MadhupurGiridih Branch railway line, upto Jagdishpur R. S. and from there a fair weather moorrum road 6
miles ( 9-65 km ) long connects the dam site with the last two miles (3-22 km) running through the
jungle.
4.
Acknowledgements: The author is grateful to Shri K. Prasad, Executive Engineer, Irrigation
and Project Division, Deoghar, for extending all facilities during the course of the investigation and
during his stay at Madhupur and Deoghar. The author wishes to convey his sincere thanks to Shri R.
K. Sundaram, Senior Geologist, Geological Survey of India, for giving valuable suggestions during
the preparation of this report.
II. PHYSIOGRAPHY, DRAINAGE, CLIMATE AND RAINFALL
5.
The country is generally flat, except for a few hillocks formed of the basic dykes. The area
around Raghunathpur is covered with jungle, while the country around Dhakawa and Tetariatanr is
thinly wooded with cultivated patches.
6.
The river Jainti which is a tributary of the Ajai river rises from thick wooded hills of
Hazaribagh district at an elevation of 1050' (320.04 m) above M. S. L. It flows towards south and then
towards east for about 8 miles (12.87 km) in the district of Santal Parganas and then joins Ajai near
Nawadih (24°9': 86°48½'; 72 L/16). The catchment area of the river at Tetariatanr - is 150 sq. miles
(388.50 sq. km). Near the dam sites the area is drain by a network of nalas and streams, the prominent
ones being Baghdharu nadi, Dilia and Patharjor, all of which join the Jainti.
7.
The area enjoys a very pleasant climate during winter and Madhupur town is a winter resort.
The summer between April to June is very oppressive due to the prevalent dry heat, like any other
parts of Bihar.
3
GSI-CHQ-872
The average annual rainfall* at the catchment area is 49.54" or 1.256 m (approximately), the
8.
maximum and minimum being 72.76" (1.85 m) and 34.78" or 0.87 m respectively. The available run
off from the catchment in an average year of rainfall is estimated to be at 16"(0.40 m).
III. REGIONAL GEOLOGY
T. W. F. Hughes1 (1870) was the first to describe an outlier of Lower Gondwana rocks in this
9.
area, which was later surveyed by P. K. Chatterjee2 (1936) and S. N. Puri3 (1952). P. K. Chatterjee
gave a description of the metamorphic rocks for the first time. According to the Puri the geological
sequence of rocks in this area is as follows:RECENT
Soil, Alluvium, and Laterite.
RAJMAHAL(?)
Dolerite and Mica Peridolite intrusives.
DAMUDAS
( BARAKARS ( KARHARBARI (?)
TALCHIR-----------------------------------------------------------------------------ARCHEANS
10.
Metamorphics
The metamorphics (Archean),include mica gneisses, banded granite gneisses, amphibolites
and basic granulites. These rocks are intensively traversed by pegmatite and quartz veins. Gneisses
and pegmatites vary in their trend from N.N.E.-S.S.W. to N. E – S. W. with varying amounts of dip
either towards east or west whereas the amphibolites and basic granulites vary in trend from N.W.S.E. to N.E. - S.W. with higher dips towards east.
11.
The Lower Gondwana outlier occupies an area of 24 sq. miles (62.16 so. km) of which coal
measures (Barakars) occupy 5 sq. miles (12.95 sq. km.). The coalfield in this region is named after the
river Jainti, by T. W. H. Hughes.
12.
A greater part of the area covered by the sedimentary formations is occupied by Talchir rocks
containing needle shales, sandstones and boulder bed at the bottom. S.N. Puri (1952) has identified a
formation probably belonging to Karharbari Stage (?) overlying the Talchirs. It consists of thick
felspathic sandstones with a few coaly shale seams and fireclay bands. Barakar rocks (which overlie
the doubtful Karharbari stage) include massive sandstones varying in texture from pebbly to gritty and
fine grained types. In the Jainti coalfield, the Barakars lie conformably on the Talchirs except along
the northern boundary where they have been brought in juxtaposition against the metamorphics due to
the boundary fault.
*
Rainfall data was supplied by the project authorities.
1
T. W. H. Hughes.- Mem. Geol. Surv. Ind. VII, pt. 2 1870.
2
P. K. Chatterjee, -Quart .Jour .Geo .Min . and Met. Soc. Ind. Vol: 8, P. 37 1936.
3
S. N. Puri - Report on Deoghar Coalfields., G.S.I. (unpublished report) 1952.
4
13.
GSI-CHQ-872
The northern boundary between the Gondwanas and metamorphics is faulted, while the
southern one is a natural boundary. The northern boundary fault has roughly E-W trend with throw
towards south and is itself cut in half by a N.W. fault. A few minor faults also occur within the
Gondwana rocks, (vide Plate I). Banskuppi area (24°11': 86°41') is a basin as the sandstones and the
coal seams dip towards the centre of the coalfield.
14.
That both the Gondwanas and metamorphics have been subjected to post -Gondwana igneous
activity is well manifested by the presence of several dolerite dykes. Besides the coal measures are
pierced by mica peridotites. The dolerite dykes can be traced for fairly long distances than mica
peridotites and the former show variation in their trend.
IV. ENGINEERING DETAILS OF PROJECT
15.
The two dams proposed across the river Jainti are mainly intended for irrigation of lands on
the right bank. The salient engineering features of the dams are given below. (Further details are given
in the Appendix).
(i) Lower Dam at Tetariatanr
Catchment area of the river (including that of at Raghunathpur)
150 sq. miles (388.50 sq. km)
Length of the dam
7000 ft. (2133.6 m)
Height of the dam
66 ft. (20.11 m)
A canal proposed on the right bank.
Total area of land to be irrigated
57,000 acres (23067 hectares)
Total area of land to be submerged
4,000 acres (1618 hectares)
Storage at F.R.S. (Reservoir capacity)
57,0000 ac.ft. (6920 hetare meter)
(ii) Upper Dam at Raghunathpur
Catchment area
61 sq. miles (158 sq. km).
Length of the dam
7400 ft. (2255.5 m)
Height of the dam
72 ft. (21.94 m)
A canal proposed on the right bank.
Total area to be irrigated
29,280 acres (11849 hectares)
Total area to be submerged
2000 acres (809.3 hectares)
Storage at F.R.S. (Reservoir capacity)
39.000 ac.ft. (4735 hectare meter).
5
GSI-CHQ-872
V. SITS CONDITIONS, GEOLOGY AND PROBABLE FOUNDATION
CONDITIONS
(A) TETARIATANR SITE
16.
Site conditions: On Both the banks, the dam axis runs on a sloping ground covered with
loose debris derived from the weathered pegmatites and gneisses . The river has an east-west course at
the site. The width of the river is about 500 ft. (152.4 m) and the river bed is sandy. A few rock
exposures are seen in the left and right bank of the river, where the cutcha road crosses the river.
17.
Geology: The rocks present at this site are dolerite, mica gneiss, amphibolite, pegmatitic and
quartz veins (vide Plate II). At the left abutment (R. L. 694), a dolerite dyke (marked by big boulders)
in observed trending N.W. and the rock is fresh and coarse grained. Mica gneisses are weathered on
the surface and are intensively increase by coarse-grained pegmatites. The strike direction of vein is N
20° E – S 20° W and the dip is at 25° towards N 70°. Amphibolites occur as small bands or lenses
within the gneiss striking N 50°- 60° W – S 50°- 60° E and dipping at 70° towards N 30°-40°. They
display various stages of migmatisation and the outcrops occurring a furlong (0.20 km) due E. S. E. of
Jhilra, exhibit good gneissic banding. Amphibolites are prominently exposed at the right bank of
Jainti particularly near its confluence with Baghdharu nadi. Both mica gneisses and amphibolites are
well jointed and the prominent Joint directions noticed in the exposures on either banks are as
follows:
Gneisses
(On left bank of Jainti)
(On right bank of Jainti)
(i)
N 60° E –S 60° W dipping vertical
(i)
N 15° E – S 15° W dipping at 82° towards
S 15° E.
(ii)
N 30° W – S 30° E dipping vertical
(ii)
N 70° W – S 70°, dipping 80° at-towards N
20° E.
Amphibolites
(A small lense within the gneisses, left bank)
(Right bank)
(i)
NW - SE, dipping 70° to NE
(i)
N 20° E – S 20° W dipping vertical
(ii)
N 60° E – S 60° W, dipping 60° to S 30° E
(ii)
N 55° E – S 55° W dipping vertical
Pegmatites containing crystals of mica are seen both on the left and right banks. The quartz
veins occurring ¼ mile (0.40 km) due E. S. E. of Tetariatanr exhibit close shear joints parallel to the
strike direction i.e. N-S and another vein, a furlong (0.20 km) to the north of Lutia ( i.e. on the left
bank) displays shear joints normal to the strike direction.
6
18.
GSI-CHQ-872
Probable foundation conditions: In the absence of any bore hole data it is rather difficult to
discuss on foundation conditions existing at this site. However the following features were observed
while geologically mapping the area along the proposed alignment. The river bed is mostly sandy
with a few outcrops on either banks. The sand cover may be fairly thick, and the sand is mostly fine to
medium grained, gravel beds being rather rare. Pegmatite and gneisses which occur on either banks
are< weathered and at places they are sheared. The abutments are mostly characterised by loose,
weathered, fragments of pegmatite often lying in a clayey matrix. It is observed from a well cutting at
the left abutment. (i .e. to the west of Lutia) that rocks are highly weathered even down to a depth of
20 ft.(6.10 m). Leases or bands of amphibolite occurring within the gneisses on both banks are at
places weathered to ferruginous lumps or nodules.
(B) DHAKAWA SITE
19.
Site conditions: The dam axis at this site runs on the left bank over a gradually sloping
ground, while on the right bank the ground rises sharply. Unlike the Tetariatanr site, the rock
exposures in the bed extend from bank to bank. The banks are covered with soil which is of reddish
brown colour and lateritic. The river has a width of about 400 ft. (121.92 m) at the site.
20.
Geology: The principal rock types exposed in the river bed and along banks at the site are
banded granite gneisses and amphibolites (often gneissic), occurring as alternate bands and along the
banks. The general strike direction varies between N 30° E – S 30° W and N 65° E – S 65° W with
dips towards E. S. E. or S.E. The amphibolites are often characterised by high dips of 70° - 80° while
the gneisses dip from 45° - 70°. These rocks are not so intensively traversed by pegmatites as
observed at Tetariatanr site. About a furlong (0.20 km) downstream of the alignment there is a narrow
patch of dark coloured, fine-grained basic granulite within the amphibolites, trending N 55° E – S 55°
W with a dip of 45° towards S 35° E. The banded granite gneisses and the amphibolites are well
jointed, the direction parallel to the foliation being more prominent and closely spaced.
Banded granite gneiss (on the left bank)
(i)
N 30° E – S 30° W , 55° dip towards S 60° E
(ii)
N 60° W – S 60° E , 80° dip towards N 30° E
Amphibolite (on the river bed)
(i)
N 55° E – S 55° W , 85° dip towards N 35° W
(ii)
N 20° W – S 20° E , 80° dip towards S 70° W
(iii)
N 50° W – S 50° E , 75° dip towards N 40° E
7
21.
GSI-CHQ-872
Probable foundation conditions: Along this alignment the rock is exposed in its entire
section. The rocks show prominent joints, particularly parallel to the foliation direction. The sand
cover in the river bed may not be thick and the sand is medium to coarse-grained, often containing
gravel. The rocks exposed at the site i.e. banded granite gneisses and amphibolites, are generally fresh
and hard. At the abutments, the gneisses are at places weathered. The banks are generally covered by
a reddish brown soil.
(C) RAGHUNATHPUR SITE
22.
Site conditions: The dam alignment connects the 800' (243.84 m) contour on either fide of
the river. The banks rise rather high above the river bed. The left bank is mostly-covered by jungle
suggesting a thick cover of soil the right bank rises gradually and is devoid of jungle. Rocks are well
exposed at the river bed. The river flows in a NE direction at the site along a narrow channel (width
about 300 ft or 91.44 m). Pot holes are observed in the rocks exposed in the river bed.
23.
Geology: Porphyritic, augen gneisses are exposed in the river bed, striking N 60° W – S 60° E
and dipping at 20° towards N 30° E. The rocks are nearly fresh and coarse grained, containing large
porphyroblasts of felspar. In the left bank, i.e. north of Raghunathpur quartzeo-felsnathic gneisses are
seen traversed by veins of graphic granite. Less than a furlong (0.20 km) downstream of the
alignment, a dolerite dyke, about 120 ft. (36.58 m) wide, traverses the augen gneisses trending N 55°
W – S 55° E. The dolerite being fine grained near its contact with the gneisses exhibites the chilled
effect clearly. It is dark in colour exhibites columnar jointing. The central portion of the dyke in
coarse grained and dark greyish in colour while the chilled margin exhibits basaltic texture under the
microscope. This permeation of the fine grained rock is also noticed along the joints in the gneiss. The
principal joint directions observed in gneisses and dolerites are:
Augen Gneiss (River bed)
(i)
N 55° W – S 55° S , vertical dip
(ii)
N 25° E – S 25° W , 75° dip towards N 65° W
Dolerite (North of Nuniad, left bank)
(i)
N 40° W – S 40° E, 75° dip towards N 50° E
(ii)
N 55° E – S 55° W, 20° dip towards S 35° E
(iii)
N 25° E – S 25° W, 45° dip towards S 65° E
24.
Probable foundation conditions: As mentioned earlier the river bed is rock marked by
exposures of porphyritic augen gneiss. Since the rock appears to be fresh and hard, it may be of
proper foundation grade for the location of a spillway. The small amount of sand seen in the river bed
8
GSI-CHQ-872
is coarse-grained and gravely. The banks are mostly covered by a brownish-yellow soil, often clayey
and the rock exposures seen at a few places are generally weathered. Two dolerite dykes seen at the
left abutment are fresh, hard and tough.
VI. DESCRIPTION OF ROCK TYPES
25.
The chief rock types occurring in the dam site areas are briefly described below.
(a)
Dolerites are dark coloured, coarse-grained though fine-grained types are not uncommon.
Under the microscope, they show tight interlocking arrangement of grains. They are simple dolerites
containing plagioclase, augite, magnetite and a little pyrite. The rocks are fresh and practically free
from alteration. Because of their fresh nature and texture, they may prove to be suitable for
construction purposes.
(b)
Gneisses are light coloured, generally fine to medium-grained, typically banded and with poor
to moderate interlocking arrangement of grains. Gneisses occurring in this area can be broadly
considered to be of three types - (i) Biotite gneiss, (ii) Banded granite gneiss and (iii) Porphyritic
augen gneiss. In the low lying areas gneisses are highly kaolinised. The common minerals present in
the gneisses include quartz muscovite biotite orthoclase, plagioclase (albite) and occasionally
hornblende.
(c)
Pegmatites are light coloured, coarse-grained exhibiting typical graphic texture. Fine grained
types are also present. They essentially contain big crystals of orthoclase, mica (both muscovite and
biotite), quartz (at places rose variety) and occasionally tourmaline and garnet. It is common to find
broken fragments of weathered pegmatite strewn on the surface.
(d)
Amphibolites are massive, dark coloured, fine to medium-grained, and show preferred
orientation of amphibole crystals. Often they exhibit typical gneissic banding. The fresh rocks are
hard and tough, while the altered ones are brittle and crumble into thin fragments.
(e)
Granulite exposures are limited in occurrence (viz. near Dhakawa site and on the left bank of
Baohdhanu nadi) when compared to the other rocks. The rocks are dark coloured, fine-grained
showing typical granulitic texture.
VII. STRUCTURAL FEATURES
26.
The regional structural features are already dealt under paras 13 and 14. The gneisses appear
to have been folded to a syncline, the exposures at Tetariatanr site perhaps representing the eastern
limb of the fold with gentle dips and those at Dhakawa representing the western limb, with rather high
dips of 45° to 70°. A minor, plunging anticline (in banded gneisses) with a plunge of 20° towards N
25° E was observed a mile (1.61 km) N 35° E of Jhilua and close to the Railway line. The limbs of the
9
GSI-CHQ-872
anticline have also developed tension cracks.
27.
The pegmatite and quartz veins are often highly sheared and the gneisses at places show
abrupt change in their attitude. Some of the sheared quartz veins may represent fault zones. Other
minor features noticed include ptygmatic folds in gneisses and amphibolites, contortions of veins etc.
Amphibolites and gneisses are well jointed (see paras 19.22 and 25) and the strike of the joints are as
follows:(i) NW - SE (ii) WNW - ESE (iii) NNE - SSW (iv) N 60° E – S 60° W
VIII. SEISMICITY OF THE AREA
28.
It is recognized that the area itself is not seismically active, but feels the fringe effects of
earthquakes which originate in the seismic zone to the north.
29.
The area was affected by the great Bihar-Nepal Earthquake of 1934. The following effects
were noticed at Madhupur town which is in close proximity to the dam site. A preliminary-tremor for
15 seconds was followed by s violent shock for 70 seconds during which the ground oscillated N.W.S.E. with an estimated maximum amplitude of 4" (0.101 m) and a frequency of 100 cycles/minute,
which ended abruptly but was followed by tremors for another 100 seconds. A rumbling sound was
heard for 7 seconds at the beginning. A large number of buildings were cracked.*
30.
From the isoseismal map (with isoseismal lines based on Mercalli scale) for the above
earthquake prepared by the Geological Survey of India, it is seen that the Jainti dam sites fall within
the isoseismals 7 and 8 (but closer to 7). According to the McAdie modification of the Mercalli scale
the magnitude of acceleration is of the order of 500 mm/sec/sec which is equivalent to a seismic factor
of 0.06 g. However, for all the dams constructed by the D. V. C. in the neighbourhood of this area, a
factor of 0.1 g has been taken for design purposes and it is recommended that the same may be
followed in the design of the dams under construction.
IX. MATERIALS FOR CONSTRUCTION
31.
As the total quantity of materials required and full details of the type of dam are is not known
a broad indication of the construction material locally available is given below.
32.
(i) For Lower Dam at Tetariatanr
(a) Coarse aggregate and Rip Rap: A three mile (4-82 km) long dolerite dyke with an
average width of 50-75 ft. (15-24 m -22.86 m) starts near 754 and continues up to Jorama Halt
(24°12½': 86°42½') may supply enough material required for coarse-aggregates and rip-rap work.
*
Bihar-Nepal Earthquake of 1934 Mem. G.S.I. 1939, Vol. 73, P279.
10
GSI-CHQ-872
Also banded gneisses exposed near Dhakawa and ½ mile (0.80 km) to the south of Chaparia (24°13':
86°62') may be investigated to find out whether sufficient quantities of the material are available. It
should be remembered that if quarries are located very close to the river, difficulties due to subsurface water may have to be encountered. A small mound consisting of dark coloured, massive
amphibolite is available N 15° W of Sagarbhanga (24°11½': 86°41') and close to the right bank of
Baghdharu nadi.
(b) Fine aggregate: Sand occurring in the river bed at Tetariatanr is generally fine-grained
and micaceous. But sand of other grades are available further upstream and downstream of the
alignment. If required, sand from the bed of Baghdharu nadi at its confluence with Jainti, a furlong
(0.20 km) upstream may be used.
(c) Earth material ; Semi-impervious and impervious soils are present within half a mile or a
mile (0.80 - 1.60 km) lead from the dam site i.e. near Dhakawa, Jhilua and Lutia villages. The soil is
underlain by moorrum, followed downwards by in situ weathered rock. This weathered rock can be
used as semi-pervious fill. Borrow pits should be located as far as possible within the reservoir area
itself.
33
For the Upper Dam at Raghunathpur:
(a) Coarse Aggregate and Rip rap: Fresh gneisses are available near the dam site. Also there
are a few dolerite dykes which can supply material for coarse aggregates. They are exposed (1) at left
bank of the Jainti river extends upto the river bed to the north of Nuniad; and (2) another dyke ½ a
mile (0.80 km) N.E. of Raghunathpur, amidst the jungle.
(b) Fine aggregate: Investigation by pits in grid pattern may be made to find the required
quantity of sand occurring in the river bed further upstream and downstream of the dam site i.e. to the
south of Raghunathpur where the river takes a V bend; and about a mile (1.60 km.) downstream of the
alignment where the nala coming from Goradih (24°12': 86°33') joins Jainti.
(c) Earth material: Semi-impervious and impervious soils are available within half a mile
(0.80 km.) lead from the dam site i.e. around Raghunathpur and Lalpur (24°12 ½' : 86°33') villages.
X. DISCUSSION ON THE FEASIBILITY OF DAM SITES
AND LOCATION OF SPILLWAY
A. LOWER DAM SITES
34.
Of the two alignments examined viz., one at Tetariatanr and other at Dhakawa, outcrops are
rather scarce at Tetariatanr site. There is little scope for selecting a site further downstream of the
present alignment as it would be very close to the railway line and the Jainti Collieries. The
11
GSI-CHQ-872
advantages and disadvantages of both the dam sites are summarized as follows:
35.
Dhakawa site: (a) Advantages:
(1)
The river bed is rocky and proper foundation grade may be reached at shallow depths, thus
minimising excavation and construction costs.
(2)
Spillway may be located in the river bed.
(b) Disadvantages:
(1) Construction of a dam at Dhakawa means loss of run off of Baghdharu nadi, which joins
Jainti a mile (1.61 km) downstream.
(2) Lesser storage capacity of reservoir at Dhakawa results in lesser irrigation potential, since
a net area of 54,000 acres (21853 hectares) cannot be irrigated.
(3) The above two factors necessitate the construction of another dam across Baghdharu nadi;
thereby requiring large quantities of construction material and execution of two dams against one and
also maintenance of two dams instead of one.
36.
Tetariatanr site : Advantages
(1) Construction of a dam here means tapping the 24 sq. miles (62.16 sq. km) catchment of
Baghdharu nadi.
(2) Enough storage, capacity of the reservoir for irrigating 51,600 acres (20882 hectares) of
land on the right bank.
(3) Since the run off of Baghdharu nadi is not lost at this site, only one dam has to be
constructed instead of two as at Dhakawa.
Disadvantages:
(1)
Sand cover may be slightly thicker.
(2)
Sound rock for spillway section may be slightly at deeper level than at Dhakawa site, resulting
in an increase in cost of construction.
37.
But this slight increase in cost will more than offset the disadvantages mentioned in case of
Dhakawa site. Hence it will be advantageous to have the darn located at Tetariatanr, than having two
dams one on Jainti at Dhakawa and another across Baghdharu nadi.
12
38.
GSI-CHQ-872
Location of spillway at Tetariatanr site: The site for the spillway at Tetariatanr has been
tentatively proposed to be located on the left bank, near Lutia village and the spill discharge conveyed
through the nala flowing in a N.W. direction to the E. of Lutia .joining Jainti about ½ mile (0.80 km)
downstream of the present alignment. The gneisses exposed on the flanks of the nala are weathered
and as such are likely to be badly eroded by the spilling waters eventually leading to the undermining
of the main spillway structure itself due to headword erosion. Examination of a dug well immediately
west of Jhilua also indicates that the rocks are highly weathered down to a depth of 20 ft. (6.096 m) or
even more. It is therefore doubtful whether sound rock will be available at shallow depths in the left
bank for founding the proposed spillway. Even if rock elevation at the proposed site for the spillway
prove to be more than in the river bed, the protective work necessary along the entire spill channel is
likely to be considerable. Besides, if the spill waters are conveyed through the nala as proposed, some
river training may also be necessary where the spill waters join the main river. Therefore, it will be
advisable to locate the spillway in the river bed.
B. UPPER DAM SITE AT RAGHUNATHPUR
39.
The proposed site appears to be geologically satisfactory as fresh, augen gneisses are exposed
in the river bed. Hence, proper foundation grade may be reached at fairly shallow depths; so that
spillway can be located at the river bed, since soil cover appears to be thick on the left bank.
40.
Spillway: In this site also the spillway can be located at the river bed itself as suitable rocks
are exposed. Hence it will not involve deep excavation for founding the spillway.
XI. MINERAL OCCURRENCE IN THE RESERVOIR AREA
41.
The F. R. L. of the proposed dam at Tetariatanr is R. L. 675. The probable limit of the
reservoir at F. R. L. is marked on the geological map (vide Plate III) and it can be seen that major part
of the reservoir lies within the metamorphics, except a small area occupied by Talchirs and Barakars
in the south. Though, no detailed study of' the metamorphic rocks occurring within the reservoir area
has been made, from available records* it is seen that economic mineral deposits are not known to
occur in this area. However some of the pegmatite veins are noticed to contain large crystals of mica
(e.g. west of Tetariatanr, a large crystal of mica 8" x 5" or 0.20 x 0.12 cm) Mr. T. M. Mahadevan of
the Geological Survey of India had collected a few lumps of Beryl (a mineral used in atomic energy)
near Makhanpur in the year 1949-50. Thus to avoid any false claims at a later date for submergence of
valuable mineral deposits by unscrupulous persons, it is recommended that a detailed study of the
pegmatite within the reservoir be made and a detailed geological map of the area prepared.
*
Mineral Resources of Damodar Valley and Adjacent Region and their utilization for Industrial Development by V. R. R. Khedkar
13
42.
GSI-CHQ-872
The reservoir when formed above Tetariatanr, will not submerge coal deposits save for a
small patch of Barakars. A short description of the Jainti coalfield and the working area is given
below.
43.
Jainti coalfield is about 5 sq. miles (12.95 km) in extent. The coal mines, being worked at
present are situated to the east of Banskuppi. Of the two workable coal seams, it appears that the
upper one has already been worked out while the lower one known as Deoghar seam is being worked
at present. The coal is of poor quality (III grade, according to Coal Board classification). In one of the
Coal mines located on 650' contour, to the east of Banskuppi, dewatering was being carried out during
the time of the visit by the author. The third mine is near Madankatta east of the railway line. These
mines are situated more than a mile (1.61 km) downstream of the reservoir. To prevent any direct
submergence of the coal measures and colliery workings, two dykes may be constructed to the north
of Banskuppi.
44.
A point will arise that the reservoir may tend to raise the ground water level in the
surrounding area, Consequently in increasing the seepage of the underground coal workings. If by
plugging the gaps by dykes, the reservoir spread is kept a mile (1.61 km) away from the coal
workings, due to natural head loss along the path of percolation, the water table in the area near the
coal working may not rise appreciably to adversely affect mining. On the other hand, the construction
of a storage dam may prove to be helpful to the coal mines which are located near the Jainti river, in
that except during peak floods. The river will be nearly dry and seepage into the existing mines will
be much less than what it used to be before the formation of reservoir.
XII. CONCLUSIONS AND RECOMMENDATIONS
45.
The following are conclusions after a preliminary study of the geological conditions existing
at the site and recommendations pertinent to the design and construction of the dams.
46.
The dam site proposed at Tetariatanr is preferable to Dhakawa as 24 sq. miles (62.16 sq. km)
of catchment of Baghdharu nadi will be tapped and construction of two dams are avoided. The dam
site at Tetariatanr is recommended for further sub-surface explorations to assess the foundation
conditions.
47.
It has been mentioned under para 38 that the spillway for the Lower dam at Tetariatanr dam
should be located in the river bed, since it is doubtful whether sound rook will be available at a
shallow depths in the left bank as has been tentatively proposed.
48.
The upper dam site proposed at Raghunathpur appears to be geologically suitable, as fresh,
hard gneisses are exposed at the river bed and proper foundation grade may be reached at fairly
shallow depths. The spillway may also be located in the river bed. A scheme for further subsurface
14
GSI-CHQ-872
exploration at this site will be given after a large scale geological map is prepared.
49.
A schema for subsurface exploration for Tetariatanr dam site is outlined below to know the
foundation conditions for the location of spillway. Four drill holes (Nos. 1,2,3 and 4) at an interval of
100 ft. (30.48 m) in the river bed and two holes (Nos. 5 and 6) one on each bank near the river bed are
recommended. Their positions are indicated in plate II.
50.
The bore holes must be taken down to at least 30 ft. (9.14 m) into fresh rock, with a core
recovery of 70%. The cores from the bore holes must be properly preserved in strong core boxes and
the drilling record should be maintained properly, otherwise much of the valuable information about
the subsurface conditions existing at the site would be lost. The cores from the drill holes should be
logged by a geologist and cores should be tested for crushing strength.
51.
Water pressure tests should be conducted in all the drill holes and the records of leakage for
varying pressures must be maintained accurately. The object of this test is to obtain a qualitative
estimate of possible water losses in the reservoir and a concept of the amount and nature of grouting
that will be required.
52.
Test pits should be put clown along the earth section, at an interval of about 500 ft. (152.4 m)
and taken down to a depth of at least 10 ft. (3.05 m). Their positions are shown in plate II. The soil
from the pits should be sent to the soil laboratory for testing their physical properties. A few in situ
water tests may also be conducted to study the permeability of the material forming the earth dam
foundations.
53.
Though the area on which the dam sites are located is not seismically active, fringe effects are
felt when earthquake originates in the seismic zone to the north (see paras 29 and 30). As adopted in
the construction of dams by the D.V.C. in the adjoining areas, it would be presumably safer to
incorporate a seismic factor of 0.1 g in the design of dams under consideration.
54.
The sources for obtaining different types of construction material are broadly indicated under
Chapter IX, as the total quantity required and full details of the type of dam are not known.
55.
For coarse aggregates and rip-rap test pits or trenches should be put in the places mentioned in
paras 32 and 33 to get a rough idea of the reserve. The samples of rocks, viz., dolerite, banded gneiss
and amphibolite should be sent to the Alipore Testing House for the determination of physical
properties.
56.
Test pits should be put in borrow areas in a grid pattern at an interval of 400 ft. (121.92 m).
The samples of the soil and highly disintegrated and weathered material below the horizon should be
collected at regular intervals and sent to the laboratory for testing their physical characters.
15
57.
GSI-CHQ-872
Sand in the river bed must be investigated in a similar way i.e. by putting pits in a grid pattern
and the samples should be tested for their suitability as fine aggregates.
58.
The river beds should be investigated in detail to know whether extensive deposits of gravel
are available. Gravel mounds occurring around Lutia village may also be investigated.
59.
The reservoir to be formed by the construction of Jainti dam at Tetariatanr would submerge
mostly the area covered by metamorphic rocks and only a small patch of Talchir and Barakar in the
south (vide Plate II).
60.
No economic mineral deposits have been recorded to occur in the reservoir area. But
numerous pegmatite exposures are observed in the area which may contain radioactive minerals.
Therefore to avoid any false claims at a later date for submergence of valuable mineral deposits by
unscrupulous persons, it is recommended that a detailed study of the pegmatites within the reservoir
be made and a geological map of the area prepared.
61.
It has also been mentioned that workable coal seams are not submerged by the reservoir (vide
para 42) and the mines are situated a mile (1.61 km) downstream of the reservoir.
62.
Therefore, no serious seepage problem is anticipated in the coal workings as due to natural
head loss along the path of percolation, the water table in the area near the coal workings may not rise
appreciably to adversely affect the mining.
Sd/- K.R. Raghu Nandan.
Engineering Geology Divn.,
Eastern Region,
Geological Survey of India,
5, Middleton Street,
Calcutta-16
16
GSI-CHQ-872
DISTRIBUTION LIST
1.
The Secy, to the Govt. of India, Ministry of Mines and Fuel, New Delhi.
2.
The Secy. Planning Commission, New Delhi.
3.
The Chairman, C. W. & P. C, New Delhi.
4.
Shri S.S. Kumar, Chairman, C. W. & P.O., New Delhi.
5.
The E-in-C, Army Headquarters, New Delhi.
6.
The Chief Engineer, Irrigation and Project Division, Patna, Bihar.
7.
The Executive Engineer, Irrigation and Project Division, Deoghar, Santal Parganas, Bihar.
8.
The Secy. To the Govt. of Bihar, Deptt. Of Industries and Corpn. ( Mines ) Patna.
APPENDIX - I
TETARIATANR DAM ON RIVER JAINTI
Location:
Lat 34°-12' North
Long., 86°- 41¾' East
Ref. to Toposheet - 72 L/12
Catchment Area (including catchment of Jainti at Raghunathpur)
150 Sq. miles (388.50 sq. km).
Maximum flood discharge
88000 cusecs. (2492 m3/sec)
Maximum rainfall in the catchment
72.76 inches. (1.85 m)
Minimum rainfall in the catchment
34.78 inches. (.98 m)
Average rainfall in the catchment
49.54 inches. (1.53 m)
Bed level
619.00 R. L.
D. S. S.
643.00 R. L.
F. R. S.
675.00 R. L.
Storage at D. S. S.
6700 ac. ft. (813.42 hectare meter)
Storage at F. R. S.
57000 ac. ft. 6920 hectare meter).
Crest of dam
685.00 R. L.
Length of dam
7000 ft. (2133.6 m)
Maximum height of dam from the beds
66 ft. (20.11 m)
Length of dyke :
(i)
1100 ft. (335.28 m)
(ii)
1300 ft. (396.24 m)
Gross command for the lower dam
1,05,000 acres. (42492 hectares)
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GSI-CHQ-872
Area irrigate
57,000 acres (23067 hectares)
Total cost
Rs. 2,48,26,080/-
Incident of cost per acre of kharif
Rs. 431/-
Sd/-Illegible
Executive Engineer,
Investigation & Project Division,
Deoghar
APPENDIX –II
RAGHUNATHPUR DAM ON RIVER JAINTI
Location -
Lat., 24°-12½' North
Long., 86°-32½' East
Ref. to Toposheet 72 L/12
Catchment Area
61 sq. miles (158. sq. km)
Maximum flood discharge
44000 cusecs. (1246 m3/sec.)
Maximum rainfall in the catchment
72.76 inches. (1.85 m)
Minimum rainfall in the catchment
34.78 inches. (0.98 m)
Average rainfall in the catchment
49.54 inches, (1.53 m)
Bed level
778.00 R. L.
D. S. S.
813.00 R. L.
F. R. S.
840.00 R. L.
Storage at D. S. S.
4600 ac. ft. (558.46 hectare meter)
Storage at F. R. S.
39000 ac. ft. (4735 hectare meter)
Crest of Dam
850.00 R. L.
Length of Dam
7400 ft. (2255.5 m)
Maximum height of dam
72 ft. (21.94 m)
Gross command
63,400 acres (25657 hectares)
Area irrigate
29,280 acres (11849 hectares)
Total cost
Rs. 1,60,96,000/-
Incidence of cost per acre of Kharif
Rs. 549/-
Sd/- illegible, 12.5.61,
Executive Engineer,
Investigation & Project Division
Deoghar.
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