Birete Dam Project - Geological Investigation Summary

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BIRETE DAM PROJECT geological in/sstigation report
abstract
The geological investigation reoort covers the geological maopmg for the Birete Dam site and includes
a geological cross-section along the axis of the dam. 
Nine boreholes have been logged and the permeability tests are conducted in four holes. The foundation is assessed 
as competent for building the dam. Prospecting for construction materials vvas carried out and the test results are appended. Recommendations are included regarding the use of construction materials.- 2 -
TABLE OF CONTENTS
Item
ABSTRACT .......................................................................................... 1
TABLE OF CONTENTS ......................................................................  2
1.      Introduction........................................................................................... ’ 3
2.      Basin discription.....................................................................................  3
3.      Previous work........................................................................................  4
4.      General Geology of the Area.................................................................. 4
5.      Dam Site Geology..................................................................................  5
6.      Drillings .................................................................................................  6
7.      Permeability tests....................................................................................  7
8.      Construction materials............................................................................  8
9.      Recommendations .................................................................................10
10.       opc.xtv <©• 
,,       __- 3 -
1.   Introduction
The Birete Pam study was initiated by building material corooration in collaboration with the Ministry of Mines, Energy and Water Resources.
Engineers from Land and Water studies agency and geologist from the Ethiopian Institute of Geological Surveys closely investigated the Birete river basin to identify all the
possible dam and reservoir sites so that sufficient water will be stored. The investigation was not limited to the indicated requirement of water 2000m^/day for the cement plant but also considered other needs and uses of water inorder to have the optimum utilization of the water wmch could be stored in the reservoir.
2.   Basin Iiscnption
Birete river, is one of the tributaries of sodoble river which drains into Mugher river tributary of Blue Nile river The basin extends between latitudes 9° 25’N and 9° 29*N and longitudes 33° 03' F and 33° 20’E and covers an area of 33 square Kilometres. Birete river orginates near
"ajuturie village about 10km north of water-sned divide of Blue Nile and Awash rivers. The altitude in the catchement area varies from 2450-2670 metres above sea level and is characterized by undulating toDography gradually sloping to the north. The top soil which is a residual weathering product of the basalt, covers most of the catchement area and outcrops are rare. More than 95% of the area is an open grass land most cf which is used for agriculture and posture. Bera and Likimsa are the mam tributaries and join Birete river one kilometre south (upstream) of the dam site.- 4 -
3.  Previous Work
Reconnaissance geological map of the area has been prepared by D.H.Jebsen and M.J.Athearn, U.S. Department of State Agency International development in 19o3» Hydrogeophysical and geological investigations of the area were carried by Ethiopian Institute of Geological Surveys in 1978 and 1979 respectively. The preliminary Hydrogeo Physical study revealed that the under ground water potentiality is limited and the geological investigation indicated the geological condition 
of the Dam site and construction materials.
Pitting
Thirty four pits were dug along the two previously proposed dam axis designated as profile I-I and II-II in the geological report of December 1979- Profile I-rl is very close to the final dam axis. The average thickness of overburden in profile I-I for 16 pits is about 2.50 metres and in profile
II-II for twelve pits 2.90 metres.
4.     General Geology of rhe j;rea
The area is located in the central Ethiopian plateau series of basalts which consistsof the following stratigraphic successions.
a)   upoer basic volcanites
b)   ignimbrites
e) lower basic volcanites
The basic unit is predominant in Birete river basin and is underlain by thin createceous sandstone, limestone with gypsum, shale and marl intercalation at the base. The Triassic sandstone is exposed further north at the- 5 -
confluence of sodoble end Mugher river. Different leva
flows with poleasoil formation are o ^served in the dissected part of the plateau.
Along the bank of Birete river the rocks are not well
exposed and almost all the rocxs in the surrounding ridges
ere nighly weathered and altered. The deep weathering of
‘the basalt nas resulted in the formation of residual clays
2-to5metres thick.
Major faults are not observed in the vicinity of the Dam
site, however according to D.H.Jebsen and Murray J.Athearn one major fault is shown further north (downstream) from
the Dam site.
5• Dam Site leology
The dam site is situated about two to three kilometres
south west of the cement plant site, the area at the Dam
site and considerable areas down and upstream "f it were mapDed on the scale 1:2000.95$ of the mapped area is covered by soil, as a result of detailed geological study in the
tnree patches of basaltic out crops, the following joint direction and intensities were observed.
Ouxcrop
Str ike
Dip
Set
I
II
III
110-120°                40-55  ME      1
210-220°              vertical   to    4° 2
300-320°
290-310°
II
20 E 2
Spacing
15-25cm
15-30cm
15-50cm
22O°-23O°               —6
The width of tne columnar joint varies from few millimeters to eight millimetres on the surface which is probably due
to weathering. The joints are mainly filled by calcite
or clayey material as observed in the boreholes. Due to 
the scarcity of outcrops it was impossible to calculate
the coefficent of jointings.
6.   Drillings
In order to under—stand the exact nature of the dem site nine bore holes, were drilled along the dam axis, to 
a total of 173.43 linear meters, the cores were systematically logged. Bore logs are shown in aDpendix I. Field permeability tests were conducted in boreholes No 3»4,7 and 3. Results
of permeabilities at various locations appear in aopendix II. The subsurface features of the dam site were interpreted as to whether grouting is needed or not. Disturbed and undisturbed samples from the boreholes were submitted to the Building college and the physico-mechanical test results are shown in appendix III.
Thin      sections      of      the      core      sample      revealed      the      following 
minerallogical
composition
Phenocrysts
of
pl3gicclose,
ground mass
plagioclase
pyroxene
pyroxene and Augite 45%
40%
Accessory
othopy r oxer.e
magnetite (opaque)
According to the above mineralogical composition, the rock is augite basalt.- 7 -
As depicted in drawing No. SW 101 and cross-scction in figure I along the dam axis, the following information were deduced:
1.   The centre part of the valley is deeply weathered and consists from top to bottom of clay gravel and highly weathered basalt, the valley slopes (sides) arc cevered with clayey detrital materials and weathered basalts,
2.    At least two lava flows have taxen place within the drilled deoth (30 metre) and the paleosoil formation with indication of peat and silty clay stone suggests that the area was swampy before the last flow.
3.   As shown in the cross section along the Dam axis an average of about 2.50 metres depth of clayey material has to be stripped off.
4.   There is a confined shallow artesian ground water on the western terrace (left bank) of the river at and 
in the vicinity of Borehole No. 8 where the water was overflowing for several deys. The water encountered
in the other borehole and pits has no relation with it,
7.   Permeability tests
Permeability tests were carried out in four boreholes
(3»4,7  and 8) by pumping in test method where water
t
is forced into the section of borehole under tes4 through drill rods (pipe equiped with rubber packers). The interval of testing ani the pressure applied varied according to the materials under test. It depended on the compactness of the material under test to hold the packer tightly in the borehale and it also depended on the weight of the material above the length of holeundertest. The minimum pressure 2
and the maximum 2kg/cm*".
applied was 0.3 Kg/om
Pue to the physical condition of the material encountered at certain depths undertest, water pressure tests were
not performed at those depth intervals and are listed in tne following:
Borehole No
Interval
3
4
7
8
15.3-18.00m
0.00-14.00m
0•00—5•00m
0.00-4.00m
The permeability coefficient results are shown in appendix II
3. Construction Xatencls
a)   Bock
The exposed basalt at Liximsa river 500 metres south west of the dam site could be used for quarry. It covers an 
area of 3800 square metres and can be quarried with open pit to 10 metre depth. The other exposure of basalt is
700 metres north of the dam site. It can also be easily quarried to 10-12 metres depth.
b)   Clay
Three localities have been investigated in the vicinity 
of the dam site.
i)          Plant Site
In order to use the clay to be excaveted from the plant
site physico mechanical tests on the clay samples had been carried at the Building College but the clay type is art suitable for the construction of the dam. Test results- Q -
are attached na Appendix IV.
11) Kotena Creex
The clay Area near kotcha creek 1£ kilometre north east
of the 'lam site wc3 investigated ani was found to be
satisfactory as a core material for dem purpose. The borrow
area is designated as JA in the Irawing. Test results are
included as Appendix V. Relevant sample numbers are 118418 and 118078.
i 1 i )o Hud-mebey a
The clay occurrence near hud-gebeys is situated }km north 
west of the Dam site and could be used as cor6 material
for dam. This borrow area is designated a3 3B in the drawing. Relevant laboratory test results for this borrow area ere
also given in Aonendix V bearing sample Nos. 113417 and 118079
c)    Transition Materials
l) Weathered Bcsclt
ThG weathered basaltic rem at Biyo, area 7A and near the church at Mekoda, area 73 in the Jrawing DE 101, can be used as transition material.
ii)     Tumtu Sandstane
The friable sandstone which can be easily made into sand available at Tumtu, 14km soutn of the dem, can be used as n filter layer next to the impervious core.
j
iii)       bcdoblc Riv r Alluvial Deposit
lhe river send in the sodoblc valley has been investigated by pitting with an average depth of 2 metres. The sand is mixed with gravel, boulder and silty materials in the following proport ions.10
Boulder 50$, Gravel 30%, Sand 15$, Silt 5$. ^rain size analysis revealed that the material could be used as a transition material after processing but the sand proportion of the material which can be only obtained by screening is fine and is not considered suitable for making concrete.
9- Recommendations
a) Foundation
i)    Perusal of the bore logs shows that the bed rock would provide a suitable foundation for the dam. There is no serious weak spot in the foundation area. Localized thin peat layer is encountered at a depth of 30m below the foundation level. The dam is about 20.5m high and considering load dispersion for the deuth at which peat layer is encountered, its presence is not considered of
any serious consequence.
ii)     Permeability in the boreholes 3,4,7 and 8 shows that in hole No. 4 at depth 18.50m and in hole No.8 at depth 
-4 
22m, it is 6.96 x 10 and 5.42 x 10 cm per second 
—4
respectively. Artesian flow was also experienced in hole No. 3. In hole No. 4 permeability tests could not be conducted from 0 to 14m depth. In the light of the above information it 13 suggested that tne area between horizontal distance 240 to 310 from, tne left abutment should be provided with a single line grout curtain for a depth of
18 metres.
In case the physical potential for grouting is not available the area from the impervious core to the upstream toe of the dam could be provided with dental treatment and then the dentel treated area could be tied with a clay blanket
411
upstream. Tyin? of upstream clay blanket with the core
is not suggested in view of the very low shear parametres
of the clay available.
b) Materials
i) Clay material for core
Clay material has been tested in the Building College
laboratory. The facility for triaxial testing is not
available. The values of internal shear angle indicated 
are based on the direct shear tests.
Test results of clay samples from the plant area (Appendix IV) indicate internal shear angles of 3° and 5°• This material
is unsuitable for the clay core.
Test results of clay samples from Borrow area, Kotche creek (3A) and Hud-gebeye (33) appear in Appendix V and internal shear angle values show e large variation. Two samples
No. 113417 from 3B Borrow area and No. 113413 from 3A Borrow area were tested earlier. Since the sample No. 113417 
which had higher percentage of fines smaller than 2 microns and had higher liqul<. limit and plasticity index snowed higher internal friction angle compared to sample No. 118418 it was considered advisable to get new samples from the
two Borrow areas and run the tests again. The tests were repeated by a different engineer. The new results are higher in botn cases, a comparision is shown belowj—12 -
Sample
No
Borrow
area
L.L
P.I
Angle of
shearing resistance
Cohesion 
k/cm
unified soil
classification 
group symbol
113417
118418
3B
3A
70
64
43
36
23-0
15.0
0.10
0.16
CH
CH
118078
118079
3A
3B
76
75
49
46
26.5
26.0
CH
CH
Since the variation in tne results is so much it was considered advisable to use average values as given in table 8, chapter
V of the book, "Design of Small Dams by U.S. Bureau of Reclamation.” The following shear parametrcs were adopted for the design of Birete Dam Embankment.
Angle of internal friction, 0 = 15°
o
cohesion = 0.05 kg/cm
ii) Transition materiel
Grain size carves from area 7 A sample No 118077 and area 7B, sample No 118080 are shown in Appendix VI. Though it is not a well graded material and is deficient in finer fractions
it is considered that during transport and compaction it would produce finer fractions that would improve its quality as
a transition material. The material from tne area near the
church is considered better, it is
l   nearer Xo the dem Slte a so
and may be used.
iii)      Rock
Bock can be obtained, tor constructing the rock-fill zones, from too locations, one tree, 500 metres upstreen and the other13 -
700 metres downstream of the dem. The upstream location, though near, is within the reservoir area. Rock quarry from that site would expose all the joints, fissures etc., which
X can be a source of leakage from the reservoir, unless the
quarry area after the completion is properly dressed and 
is covered with a clay blanket. In view of the above it is recommended that the downstream location which is about 700 metres north of the dam site may be exploited as a reck quarryAPPENDIX II
FIELD ’EIxMLaBILITYComputation of Permeability Values
12
3
4
5
6
BH
No
Bore Hole
Depth
(M)
Water
Lgss Q
/sec)
Water Loss (gPM)
Applied Pump      Press ure              9 Hn(Kg/cm")
Applied Pump      Press ure
Hi(PSI)
3
4
7
I
3
*
2.50-5.0
4.5 -7.2
7.20-10.40
10.40-13.05 13.05-15.30
15.80-18
18.0 -22.20
14-17.36
17.36-20.80
20.80-24.54 24.54-27.56 27.56-30.12
5.0 - 8.0
8-11.0
11.0 -15.0
4.0 - 7.0
7.0 -10.20
10-13
13-16
16-19
19-22
|       22-25
4.67x10"6
1.67x10"° 2.0 x10~5
1.33x1O"5
9 x 10"6
n
-
3.0 xio"5 4 x10“4
4.5 xIO"5 3.3 x10“? 4.67x10"°
5.67x1O~5 7.83x1O"5
-
1.57x1O"5
1.67x1O"5
3.33x1O"5
1,21x10-4
3.13xlO"5 8.33x10"° 3.03x1o"4
7.4x1O"2
2.64x1O"2
0.32
2.11
0.14
11
-
0.46
6.34
7.24X10"1 5.28x10"3 7.4 x10"2 8.98x10~1
1.24
*
2.48x10"1
2.64x10"1
5.28x10~1
1.92
4.97x10"1
1.32x10~1
4.81
I
I
0.5
0.8
1.0
1.2
1.3
I!
—
0.5
1.2
1.5
1.8
2.0
0.4
0.5
0.5
0.7
1.0
1.2
I        1.5
! 1.5
I 1.3 j
7.1
11.38
14.23
17.07
13.49
<1
7.1
17.07
21.33
25.60
28.45
5.69
7.1
7.1
9.96
14.23
*>7.07
21.33
21.33
18.49
----- ---------- -LComputation of Permeability Values
7
8
9
10              I       11
12
Applied
Pump Pressure
x 2.31 
Head 
of Water
(PSIx2.31)             H2
Feet of Water H
( ft)
Length of The column 
Tested L ( ft )
1 C =_l-logi
-r 277L        r for
L =- 10r
K=C  |
p
cm/sec
16.43
11.5
26.29                 22.15 32.87                 32.0
27.56
48.44
64.87
39.43
42.71
42.49          81.92
52.33
95.04
6.19x10-3
5.81x10"3
5.13x10"3
6.19X10-3
5.97x10" 3
1.66x1O"5
3.17x1O"6
2.53x1O"5
1.59x1O"4
8.79x10’6
n
It
11
-
-
-
8.2 8.86
10.5 8.69
9.02 11
-
-
—
16.43
10.04
26.47
11.06
5.25x1O-3
9.12x10 9
39.43
8.46
46.86
10.96
5.15x1O~3
6.96x1o"4
49.27
7.05
56.32
11.38
5.02x1o"3
6.45x1O-5
59.14
T.15
66.29
9.91
5.52x10-3
4.4 xIO-7
65.72
7.15
73.44
8.14
6.60x10“3
6.65x10**^
13.14
22.77
35.91
9.84
5.45x10-3
1.36x1O"4
16.43
32.81
49.24
9.84
5.45x1O"3
1.37X1O"4
16.43
7.71
24.14
9.84
5.45x10"3
5.6 x10~3
23.0
14.11
37.11
10.5
5.13x1O"3
3.65x1O-3
32.87
13.45
46.32
9.19
5.67x1O"3
6.46x10~3
39.43
15.26
54.69
9.84
5.59x10"3
1.96x1O"4
49.27
14.93
64.2
9.84
5.59x1o"3
4.33x10"'
49.27
12.8
62.09
9.84
5.59x1o"3
42.71
1.1 9x10" 5
9.68
52.39
9.84
5,59x1O“3
5.42x10"''PRESSUHS TEST
ETHIOPIAN BUILDING MATERIALS CORPORATION BIRETI DAM SITE - NEV’ MUDAER
BORE HOLE No. 3
DEPTH (M)
CONSUMPTION
From
To
Pump
Pressure
Kg/cm2
Start
End
h Water
Lose m3
1
2
3
4
5
6
2.50 m.
5.00 m.
0.3 kg/cm2
II
II
II
It
If
II
fl
II
II
fl
If
If
If
II
II
It
II
II
0.5 kg/cm2
1f
ff
4.50 m.
7•20 m.
0.6 kg/cm
2
fl
fl
ii
ii
II
II
If
ff
fl
n
n
if
ii
if
;i
0.3 kg/'cni
ii
fl
If
7.20 m.
10.40 m.
1.0 kg/cm2
II
If
II
tl
II
13.05 m.
If
ii
it
ii
10.40     m
1.2 kg/cm2
(I
n
fi
ii
i
II
It
”
11
IT
It
If
fl
13.05    m
II
II
tl
II
15.80 m.
tl
II
II
11
1.3 kg/cm2
II
II
tl
II
18.00     m.
II
II
22.20 m.
II
1.8 kg/cm2
If
If
.
230.5552
230.5578
230.5598
230.5612
230.5626
230.5640
230.5654
230.5668
230.5705
230.5717
230.5724
230.5729
230.5734
230.5739
230.5748
230.5753
230.8725
230.8800
230.8867
230.8927
230.8987
231.3315
231.8750
231.9157
231.9557
231.9957
232.1830
232.1875
232.1905
232,1932
232.1959
232.2905
232.2905
232 2905
230.5578
230.5598
230.5612
230.5626
230.5640
230.5654
230.5668
230.5682
230.5717
230.5724
230.5729
230.5734
230.5739
230.5748
230.5753
230.5758
230.8800
230.8867
230.8927
230.8987
230.9047
231.8750
231.9157
231.9557
231.9957
232.0357
232.1875
232.1905
232.1932
232.1959
232.1986
232.2905
232.2905
0.0026
0.0020
0.0014
0.0014
0.0014
0.0014
0.0014
0,0014
0.0012
0.0007
0.0005
0.0005
0.0005
0.0009
0.0005
0.0005
0.0075
0.0067
0.0060
0.0060
0.0060
0,0435
0.0405
0.0400
0.0400
0.0400
0.0045
0.0030
0.0027
0.0027 
0.0027
0.0000
0.0000
232.2905
0.0000PRESSURE TEST
ETHIOPIAN BUILDING MATERIALS CORPORATION BIRETI DAM SITE - NEV.' MUDaER
BORE HOLE No, 3
Start
TIME
-v .           Duration 511,1 (Min.;
DATE
Start Completed
'7           8
3:20
3:25 
3:30 
3:35 
3:40 
3:45 
3:50 
3:55
2:00 
2:05 
2:10
2:15
2:20 
2:25 
2:30 
2:35
2:50 
2:55 
3:00 
3:05 
3:10
3:40 
3:45 
3:50 
3:25 
3:30 
3:35 
3:40 
3:45 
3:50 
3:55 
4:00
2:05 
2:10 
2:15 
2:20 
2:25 
2:30 
2:35 
2:40
2:55 
3:00
3:05 
3:10 
3:15
3:45 
3:50 
3:55 
5
9 min.
10
27/8/80
ii
ii
ii
ii
ii
it
II
II
II
1!
11
II
11 _ 27/8/80 
«
ii
ii
n
11
11
it                                            11                                   11
5
min. n 
n n u n it
28/8/80
11
11
11
11
11
11
II
28/8/80
11
II
11
11
II
11
II
11
5
min.
11
II
11
11
29/8/80
II
II
11
It
29/8/80
11
II
11
II
5  min.
11
30/8/80
11
30/8/80
3:55 
4:00 
12:50 
12:55
1 :00 
1:05
1:10
4:00 
4:05 
12:55
1 :00 
1:05
1 :10 
1:15
11
11
(i 11
11
11
II
II
11
11
5  min.
I!
1/9/80
1/9/80 
II
n
ii
II
11
II
It
11
11
II
II
10:05 
10:1"
5  min.
ti
3/9/RO
11
11
3/9/30
10:15
10:10 
10:15 
10:20
ti
II
11
oo
REMARK
12
Hole   diameter   1.00   mm. H»3.40m.+0.3 kg/cm2
L = 2.50 m.
H=3.40m. -rO. 5kg/cm2
Hole diameter 100mm.
H=6.75m.+0.6kg/cm2
1 » 2.70 m.
H«6.75m. +0.8kg/cm2
Hole diameter 100mm.
L=9.75m.+1.Okg/cm~
1 3.20 m.
Hole     diameter     95mm, H’12.95m.+1,2kg/cm2
® 2.65 m.
Hole     diameter     85mm. H=15.95m.+1.3kg/cm2
L = 2.75 m.
Hole      diameter      75mm. H=21,95m.+1.3kg/cm2
L = 4.20 m. aep?i5-«
m.
i- th.
2/GROUND WATER LEVEL 1.18 .m
BORE HOLE No. 4
DTTPTM ('M'i
3
CONSUMPTION (M )
From
To
Rump
Pressure
Kg/cm2
Start
End
Water
Loss m3
1
2
3
4
5
6
14,00 m.
17.36 m.
’ ii
it
0.5 kg/cm2
II
II
ti
II
11
«
If
n
ii
n
ii
"2
0.8 kg/cm
11
11
ii
it
ft
it
it
ii
17.36 m.
If
20.80 m.
II
11
II
II
II
II
11
II
11
11
II
11
11
11
11
1.0 kg/cm2
II
II
11
o
1.2 kg/cm
II
II
n
1!
20.80 m.
11
11
ii
II
11
11
1.5 kg/cm
n
ii
p
II
11
24.54 m.
24.54 m.
It
II
11
11
11
ri
n
27.54 m.
1.2 kg/cm2
II
11
11 
it
II
II
1.4 kg/cm2
11
11
II
II
27.56 m.
11
11
it
11
II
11
1.8 kg/cm
II                  2
11
II
30.12 m.
II -       ? 1.5 kg/cm"
11
If
II
fl
11
ii
11
11
ii
ii
ii
2.0 kg/cm, 2
11
II
224.9940
225.0038
225.0132
225.0222
225.0312
225.0402
225.0505
225.0605
225.0705
225.3710
225.4960
225.6170
225.7380
225.9240
226.0475
226.1700
226.2900
226.4100
226.5695
226.5808
216.5908
226.6008
226.6160
226.6313
226.6450
226.6587
226.6785
226.6790
226.6790
226.6795
226.6795
226.6802
£26.6809
226.6890
226.6915
226.6927
226.6939
226.6956
226.6970
226.6984
225.0038
225.0132
225.0222
225.0312
225.0402
225.0505
225.0605
225.0705
225.0805
225.4960
225.6170
225.7380
225.8590
226.0475
226.1700
226.2900
226.4100
226.5300
226.5808
226.5908
226.6008
226.6008
226.6313
226.6450
226.6587
226.6724
226.6790
226.6790
226.6790
226.6802
226.6790
226.6809
226.6816
226,6915
226.6927
226.6939
226.6951
226.6970
226.6984
226.6998
0.0098
0.0094
0.0090
0.0090
0.0090
0.0103
0.0100
0.0100
0.0100
0.1250
0.1210
0.1210
0.1210
0.1235
0.1225
0.1200
0.1200
0.1200
0.0113
0.0100
0.0100
0.0100
0.0153
0.0137
0.0137
0.0137
0.0005
0.0000
0.0000
0.0001
0.0000
0.00C1
0.0001
0.0025
0.0012
0.0012
0.0012
0.0014
0.0014
0.0014GROUITD WATER LEVEL 1.18 m
BORE HOLE No. 4
TIME
DATE
Start
End
Duration (min.
----------------------------———i REMARK
Start
Completed
11:30
11:35
11 :40
11 :45
11 :50
11:55
12:00
12:05
12:10
10:40
10:45
10:50
10:55
11105
11 :10
11 :15
11 :20
11 :25
4:15
4:20
4 :25
4:30
4:40
4:50
4:55
5 :00
2:20
2:25
2:30
2:40
2:35
2:45
2:50
9:25
9:30
9:35
9:40
9:50
9:55
10:00
11:35
11 :40
11:45
11:50
11:55
12:00
12:05
12:10
12:15
10:45
10:50
10:55
10:00
11 :10
11 :15
11 :20
11:25
11 :30
4:20
4:25
4:30
4:35
4:45
4:55
5:00
5:05
2:25
2:30
2:35
2:45
2:40
2:50
2:55
9:30
9:35
9:40
9:45
9:55
10:00 10:05
5 min.
5/7/80
5/7/80
fl
II
n
it
if
ti
n
ii
fl
II
11
11
II
11
II
11
fl
11
II
11
II
11
It
fl
Hole     diameter     85     mm. H=3.06m. +n. 5kg/cnr
L = 3.37 m.
p
H=3.Oom.+0.8kg/cm
5 min.
7/7/30
II
fl
7/7/80
II
II
II
11
11
ti
11
11
11
11
11
11
11
11
II
II
fl
11
fl
11
fl
11
5 min.
11
11
n
ii
H
8/7/80
n
ii
II
11
11
11
II
it
fl
8/7/80
It
If
ft
11
fl
fl
fl
5 min.
II
n
t:
it
ti
fi
9/7/80
II
It
fl
II
11
II
9/7/30
II
TI
11
1}
11
11
Hole diameter 85 mm. H a 2.58m.+1. Okg/cm^
L = 3.34 m.
H = 2.58m.+1.2kg/cm2
Hole dimeter •= 85mm, I = 2.15m.+1.2kg/cm^
1 = 3,74m.
• 2.15m.+1.5kg/cm^
Hole 0 3 85mm. 
H 3 2.18m.+1.4kg/cin
L = 3.02 m.
H=>2.18m. +1.8kg/cm2
o
5 min.
11
11
If
11
11
II
10/7/80 
11
10/7/80
II
fl
fl
Hole dimeter 385mm.
o
n
if
n
ii
ii
H = 2.1 8m. +1.5kg/cni
L = 2.56 m.
H»2.18m.-2.Okg/cm^
»7
I
 I
a9
10
- V
12BORE HOLE No. 7
DEPTH  CM)
CONSUMPTION (
«3)
From
To
Pump
Pressure
kg/cm-1
Starr
End
Watero
Loss nr
1
2
4
5
6
5.00 m.
8.00 m.
, 2
0.2 kg/cm
n
i>
n
it
n
ii
it
tt
it
ii
it
it
ii
it
it
ii
ii
it
it
11
II
n2
0.4 kg/cm
ii
n
it
8.00 m.
11.00 m.
11
n
0.3 kg/cin
n
n
n
n
ii
II
11
tl
It
0.5kg/cm
2
Ii
it
11
It
11.00 m.
11
II
It
11
It
II
II
II
15.00 m.
II
n
n
ii
it
ii
n
:t
0.8 kg/cm
- n i         /     2 1.0 kg/cm
227.1285
227.1433
227.1560
227.1690
227.1820
227.1980
227.2162
227.2340
227.2510
227.2680
227.3810
227.4045
227.4272
227.4495
227.4718
227.5025
227.5265
227.5502
227.5737
227.5972
227.8953
227.8957
227.8957
227.8957
227.8957
227.8960
227.3960
227.8960
227.8960
227.1433
227.1560
227.1690
227.1820
227.1950
227.2162
227.2340
227.2510
227.2680
227.2850
227.4045
227.4272
227.4495
227.4718
227.4941
227.5265
227.5502
227.5737
227.5972
227.6207
227.8957
227.8957
227.8957
227.8957
227.8960
227.8960
227.8960
227.3960
227.896(1
0.0148
0.0137
0.0130
0.0130
0.0130
0.0182
0.0178
0.0170
0.0170
0.0170
0.0235
0.022T
0.022?
0.0223
0.0223
0.0210
0.0237
0.0235
0.0235
0.0235
0.0004
0.0000
0.0000
0.0000
0.0003
0.0000
0.0000
0.0000
0.0000
"" "BORE HOLE No. 7
TIME
DATE
REMARK
Start
End
Duration
(min.)
Start
Completec
7
9:30 
9:35 
9:40 
9:45 
9:50 
10:00 
10:05 
10:10 
10:15 
10:20
8
9
10
29/7/80
11
29/7/80
12
9:35
9:40 
9:45
9:50
9:55 
10:05 
10:10
10:15 
10:20 
10:25
5  min.
11
11
Hole dianeter=l00mm2
n
n
it
ii
it
It
II
II
II
II
:t
ii
H = 6.94m.+0.2kg/cm
11
L = 3.00 m.
n
H = 6.94m.+0.4kg/cm
2
it
it
II
If
II
11
11
II
II
II
2:25
2:30
2:35 
'    2:40
2:45 
2:55 
3:00 
2:30
2:35
2:40
2:45
2:50 
3:00 
3:05 
5  min
1/8/80
1/8/80
n
it
it
ii
it
H
II
II
II
II
II
II
II
II
II
IIII
fl
Hole diameter® 1 00mm. g 
H = 10•00m.+0•3kg/cm
L = 3.00 m.
H = 10.00m.-t-0.5kg/cm 2
3:05 
3:10 
3:15
3:45 
3:50 
3:55 
it
it
ii
II
II
ft
It
II
II
5  min.
3/8/80 
II
3/8/80
n
II
II
11
II
Hole diameter-100mm.?
ii
H      =      12.25m.+0.8kg/cni
4 :00
it
L = 4.00 m.
4 :05
it
4 : 10
it
ii
ii
if
H = 12.25m.-rl .2kg/cnf
4 :15
4 :20
3:10 
3:15
3:20
3:50 
3:55 
4:00 
4:05 
4:10 
4:15 
4:20
4:25
11
11
11
II
II
II
II
IIBore Hole No
cn
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0
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O^T-iCOnW^r-       O O r- o »“ O O O •“
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z                             z                             z                       -
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Pi
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•
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0= = = = = = = = = =
s
o
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•
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cnTime
Start
7
End
8
Duration
(Min)
9
Start
10
Comp.
11
Renark
12 ~
12:35
12:40
12:45
12:50 
12:55
1 :00
12:40
12:45
12:50
12:55
5 nun.
10/8/80
II
II
10/8/80
II
II
II
11
Hole 0 = 100 mni<
2
II
H     =     2.35 
m.     +     0.3     Kg/cm
II
II
fl
II
II
II
II
L = 3.00 ra.
1 lOO
II
1:05
II
II
II
II
II
II
II
0.5       Kg/cm
2
1 : 10 
1:15
1   :30 
1:35
H = 2.35 m.
1:15
1 :30
II
II
12:35
12:40
12:45 
12:50 
12:55
1  :00 
1 : 10 
1x15 
1 :20
1 :25
12:40
12:45
12:50
12:55
1 :00
1 :05
1:15 
’1:20
1 :25
1:30
11/8/80
11/8/80
Hole 0 = 100 mm.
ii
H
ii
ii
II
II
II
II
II
II
II
II
II
H     =     4.30 
m.     +     0.5   Kg/cm2
L = 3•20 m.
it
ii
ii
ii
ii
H = 4.30 m.
♦ 0.7
6:50
6:55 
7:00
7:05 
7:10
7:15
7:25
7:30
7:35 
7:40 
7:45
6:55 
7:00
7:05 
7:10
7:15 
7:20
7:30
7:35
7:40
7:45
7:50
II
II
II
•1
II
II
II
II
II
II
II
16/8/80
16/8/80
II
11
II
II
II
•I
II
II
II
It
It
It
II
II
II
II
It
II
It
It
Hole 0 s 1OO mm.
H      =      4.10      ra.      +      0.8      Kg/cm2 L = 2.80 m.
H = 4.65 m.
1.2 Kg/cm"'
1:10
1:15
1  :20 
1:25
1 :30
1 :40
1 :45
1 :50
1:15
1 :20
1 :25
1   :30 
1:35
1 :45
1   :50 
1:55
II
II
II
II
11
II
II
II
18/8/80
18/8/80
II
11
II
II
II
II
It
II
It
It
It
It
II
II
Hole 0 = 85 mm.
H = 4.65 m.
L = 3.00 m.
1.0 Kg/cm2
H = 4.65 m. +
12
.2 Kg/cmDenth (m)
Consumption (m )
From
To
Pump
Pressure
kg/cm2
Start
End
Water ~
Loss nr
1
2
3
4
5
6
16.00m.
II
19.00m.
1 .2 Kg/cm2
II
II
II
II
II
It
II
It
II
II
II
II
II
n
11
11
11
n
11
it
11
n
19.00m.
22.00m.
11
It
11
22.00m.
II
25.00m.
11
II
1.5
11
11
II
1.5
II
11
It
It
11
1.3
It
11
II
11
229.0170
229.0252
229.0324
229.0392
229.0452
229.0512
229.0635
229.0735
229.0829
229.0923
229.1907
229.1942
229.1972
229.2000
229.2025
229.2050
229.2260
229.3310
229.4270
229.5160
229.6070
229.0252
229.0324
229.0392
229.0452
229.0512
229.0572
229.0735
229.O829
229.0923
229.1017
229.1942
229.1972
229.2000
229.2025
229.2050
229.2075
229.3310
229.4270
229.5160
229.6070
229.6980
0.0082
0.0072
0.068,
0.0060
0.0060
0.0060
0.0100
0.0094
0.0094
0.0094
0.0035
0.0030
0.0028
0.0025
0.0025
O.Q025
0.1050
0.0960
0.0910
0.0910
0.0910
NOTE:
On bore holes Hl. 3,4,6 4 8 pox,,.ability tests performed at the following depths respectively. From 0.00 to 2.50 m., 0.00 to 14.00,.0.00 to 5^00 m.
and 0.00 to 4.00 n., due to softness of the over burden.
„ otTime
Date
Start
End
Duration 
(Min )
Start
Comp.
Remark
7
8
■9
10
1
12
10:35
10:40
10:45
10: 50
10:55
11:00
11:10
11:15
11 :20
11 :25
10:20
10:25
10:30
10:35
10:40
10:45
12:10
12:15
12:20
12:25
12:30
10:40
10:45
10:50
10:55
11:00
1 1 :05
11:15
11:20
11:25
11:30
10:25
10:30
10:35
10:40
1O;45
10:50
12:15
12:20
12:25
12:30
12:35
5 Min.
19/8/80
19/8/80
n
it
n
it
it
it
tt
ii
ii
It
II
tl
II
II
11
It
II
tt
11
11
II
II
II
II
11
II
11
Hole 0 = 85 ma.
H = 4.55 m. + 1.2 Kg/cm
L = 3.00 m.
H = 4.55 m. + 1.5 Kg/cm
2
it
n
w
ii
ii
it
20/8/80
20/8/80
II
11
It
11
11
It
11
II
II
II
Hole 0 = 85 mm.
H = 3.90 m. + 1.5 Kg/cm2
L = 3•00 m.
it
it
ti
ii
ii
21/8/80 
II
21/8/80
tl
11
II
11
II
Hole 0 = 85 mm.
H = 2.95 m. + 1.3 Kg/cm2
L = 3.00 m.
♦ water table struck at
24.20 m. depth which
resulted is the continous
rises of water to the
surface.APPENDIX III
BOREHOLES SAMPLES TEST RESULTSLocality Birete
B H No 3
Elevation 114 7
Q^alh ill BK.
To
From
Graphic log                 Description                 R e cover/ %
AAA
0-00
<2
2
8
AAA
VVV
V     VV
V       VV
VkV
VVV
V VV
Brownish block
c lay with weal he- red basalt frag
men Is
weathered joint ed basalt joint
spacing 0 5 3 5 cm and colclte
fill Ing s
9 30- 9 90 no
highly weathered
II
>
PPV
bosolt with block
silty clay
VVV
P_JK_K-
weathered vest
17 50
color jointed ba salt with clay,ths
joints ore filled
by colclte
jointed bosolt
30 55
wilhcalcite fit If
ngejolnt spocing
03- 40cmJBERETE
B H No 8
Elevation Ill i
italic
Graphic log
Descrption
Sticky brownish
block cloy
Remark
Recovery^
_________ I
3 340 und'Siur ted sample
AA
Brown silty clay with basalt fragm ente (5mm)
AA AA
A      A a; AA
A      AA AA
A      AA A      AA
s • * ©
a«o•
o O On
Sludge
weathered jointed
baeolt
Sludge        wlthcrushe d basalt
weathered jointed boealt joint spoci- mg 6cm filled by
c olc 11
Silty cloy ’’one greyish black m
colour
wuter wot over flowing the wel for several days
XX
XX
jointed boeoHjointl
spacing 2-8 mmLocality BERETE
B H No 9
Elevation 119 7
Septfi »n
Form To
r——  *
Gropbic log
— — — —J
—r 1            —1  r. water               •to tic         |
Description
•J
I
core
Recovw/’/o a ■trues
J
water                     Remark
level
---------------- - —k
------- 1
Grey sb biocl
Sticly cioy
AAA
2 SO IO 00
AA
- . IQ 50
*° 50 12 60
AAA
&AA
AAA
AAA
AAA
PPP
PPP
Dori brown iNty
cloy wiih basalt
frogmoflto
- Ailljt Clfljt A!O£
Clay with bosoit
f ragmsnts
♦
'2 60
Ant grained janlod basal! joi rtfs a ro fill
ed by caciti3 * 3 £ I
Ccriihiaie
No.
3    aodr«*«   • 
S.implv Nu.
7872
M7CA-7O9
c** *
u
r°
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MATERIALS research and testing department
FACULTY OF TECHNOLOGY
ADDlS ABABA UNIVERSITY
Addis Ababa
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Objects
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Sample No
7416
34494-495
MATERIALS
RESEARCH AND TESTING DEPARTMENT FACULTY OF TECHNOLOGY
ADDlS ABABA UNIVERSITY
Addis Aoaba
Client:                                 Ethiopian Building Materials Corporation, Addis Ababa.
Test Objects
Sampled by:
Dale Received
I ixaiiun.
Toi Specified by
Kind of tear
Remarks;
Soil Maples
Tbs olient (o/o Ato Bant eye mm Hails)
January 4* 19&0
Bireti - Now Huger
Ato Bantoyobun Hails
Attar bar g limits, grain else analysis, free-s^sll, shrinkage limit and. coapaotion (modified AAdHL)
TEST fihiSULTS
sample
No.
Cli earnp
ent's uraig
ls description
L.L.
%
P.L.
Pel.
*
t¥eo-swell
Shrinkage
limit
Optimum
moisture
content
- 34494
'
4-1
105
33
72
110
8.4
28.4
-495
B-l
115
30
85
125
7.8
28.5
Client s marking
1
sample description
A-l
B-l
3
Maxi aua
dry density
d (ic*-/d» )
1.49
1-52
Cohesion
C - xg/oB2
0.16
0.14
An le of anearing
a   reel stance
0 - (degrees)
3.0
5-5
For
<r*in i*lze distribution, please eee •nolobut• Ho. 1.
For mol
• ture-dangl^y. relationship curvet, please see enclosures No. 2 and. 3.
A «dle iv .
J *> Maroh 24, 1980
b
zz' <* 5 h v.
Tewocroe ?hilip
/mm
N i T GRAIN S»7E SCALt
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tERIALS RESEARCH AND TESTING DEPARTMENT
MAT E.
faculty of technology
ADDIS ABABA UNIVERSITY
Addis Ababa
Ju-ni-
fa Object- ;) «ptoi by:
d
put R-x‘‘« -
v
^iwn:
fa Specified by: Mr J of K-si.
r.jk'ks:
Ethiopian Building Materials Coin oration, Aodis Ataba.
Soil samples
The client (c/o Ate Banteyehun Haile)
April 15, 198C
New-Huger
Ato BanteyeLun Haile
Atterberg       limits,       grain       size       analysis,       free       swell,       specific       <jrav direct Ehear, shrinkage limit and compaction modified AAS'IO.
TEST RESULTS
Cl lent1 s     marking
Shrirxa e
1 e     Test
pit             Sample
L.L.        P.L.         P.I. £             > £
u                                 Free swell
K=.             Ho.              depth (m.)
limit
e*
5°
r.e;i7  1
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%
0-1.50
64           28 36
14.6
14.7
40
40
—
3 *M9 ' Ko,
^•17
ClientTs" marking___________ Test pit Sample
Ho.            depth (m. )
Cohesion
C-l.50
0-1.50
0.10
0.16
An^le of shearii$ 
resi stance {! - decrees
23.0 
15.0 
38.0
Specific eTavi ty
2.72 2.72
S^~giien_t ■ s marki ng
Not
1 18417
Test pit Sample
g                                 Ma ximum dry-density
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0-1.50
0-1.50
• d-kg/dm3
1.65
1.67
enclosures 1-2
Optimum moisture content
4
r
28.0 27.6
see enclosures 2-4.
ST
GU3t 27> 198q< .huujic Nu. 7768 Sample No. 37407-408
MATERIALS                research             and             testing             department
M
FACULTY OF TECHNOLOGY
ADDIS ABABA UNIVERSITY
Addis Ababa
. I Ethiopian Building Materials Corp., Addie Ababa.
Soil sample■
. J by r ^.ivco;
.j
The client (e/o Ato Bantey.hun Haile)
February 6, I98I
New Muger (Bireti)
specified by:        Ato Bantey.hun Haile
j ol Icm: rb:
Atterberg limits, grain siz. analysis, free swell and direst shear.
TEST RESULTS
Client’s marking
Sam die
No .  Pit No. Depth, o.
L.L.
$
P.L.
1>
P.I. Pree-
svell
1>
Angle of shearing
resistance
degrees
118078 . -                                              76        27        49        55
118079
75        29        46       50
26.5
26.0
for  tfrain size curve, please see enclosure No. 1.
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USS SIEVE SIZE ML SHE
FINE GRAINED
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TRANSITION MATERIALK.h. \ •
CABLE                 address
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TEL 44 70 30                   4
I
BUlLUir* :> <
b.H'ipk N-   J681o—619
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MATERIALS RESEARCH AND TESTING DEPARTMENT
FACULTY OF TECHNOLOGY
ADDIS ABABA UNIVERSITY
Addis Aoaba
Buildir.c Materials Corporation, Addis Ababa
1 .At Objects                        2 samples of coarto a _ yr elites
''.inipkd b)
4
The ellai (c/o Ato Aklilu Assefe)
Ihiic RcccivtJ
November 16, 19^0
1 ucjtion
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Test Specified by
Ato AkIiIu Assefa
kind of tvs'
Sieve analyses
in.ii ks
Te9T Results:
Sieve size (aSTO)
3i-
j”
2”
l 2-«- 1”
3/4"
2"
3/6* 
?’o. 4 
?o. 8 
ik .   16
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I
Sieve analyses" test results, ’■ (by Vei^bt)
Coarse a^gr^te ?o. llSof?
| After 4b-hrs+
As received 100
89 77 55 43 32 25 12
7 4
3 2 1 1
immersion and dryin L
100 96 86 69 57 41 31 15
8 5
4 3
2 1
Coarse a^greg-te No. 118080 AAfftteerr        4$-hrs* 
As received
immersion      and drying-
100 96 95 90 73 57 42 35 22 14
9 6 3 2
1
100 9y 98 93 76 54 40 24 15 10
3
2
•
according to ttie client’s request.
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RESEARCH ANO TESTING DEPARTMENT 
AODIS ABABA
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PERCENT FINER
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*1

Summery

Project Overview

The geological investigation report covers the Birete Dam site including geological mapping, borehole logging, permeability tests, and assessment of construction materials. The foundation was found competent for dam construction.

Location: Birete River basin (tributary of Sodoble River), Ethiopia (Latitude: 9°25'-9°29'N, Longitude: 38°03'-38°20'E)

Purpose: Water storage (2000m³/day for cement plant plus other needs)

Key Findings

Geology

Area composed of Central Ethiopian Plateau basalts with stratigraphic succession:
- Upper basic volcanites
- Ignimbrites
- Lower basic volcanites
Deep weathering of basalt has created 2-5m thick residual clays
One major fault identified downstream from dam site
Joint directions and spacing documented at three outcrops

Drilling & Testing

Activity	Details
Boreholes	9 holes drilled (total 173.4 linear meters)
Permeability Tests	Conducted in 4 boreholes (Nos. 3, 4, 7, 8)
Core Recovery	Generally good (75-98%)
Notable Findings	Artesian groundwater encountered at BH No. 8 (overflowing for several days)

Construction Materials

Material	Source	Suitability
Rock (Basalt)	500m SW and 700m N of dam site	Suitable (recommend downstream quarry)
Clay (Core Material)	Kotcha Creek (3A) and Hud-gebeye (3B)	Suitable (shear angle 15-26.5°, cohesion 0.05-0.16 kg/cm²)
Transition Materials	Weathered basalt, Tumtu Sandstone, Sedoble River alluvium	Acceptable with processing

        Recommendations
        Foundation: Bedrock is suitable but grout curtain (18m depth) recommended between horizontal distance 240-310 from left abutment due to permeability findings
Materials:
                Use clay from Kotcha Creek (3A) and Hud-gebeye (3B) for core
Prefer downstream quarry (700m N) for rock to avoid reservoir leakage
Material near church (7B) recommended for transition zone

            
Design Parameters:
                Angle of internal friction (φ) = 15°
Cohesion = 0.05 kg/cm²

            

    

Appendices Summary

Appendix	Content
I	Borehole logs
II	Field permeability test results (detailed tables of test data)
III	Borehole sample test results (physical/mechanical properties)
IV	Clay test results (plant site - found unsuitable)
V	Clay test results (Kotcha Creek and Hud-gebeye)
VI	Transition material test results