SOIL INVESTIGATIONS REPORT
PROPOSED FUEL TANKS INSTALLATION AT
ADAMUS RESOURCES LIMITED-NZEMA
IN THE WESTERN REGION
OF GHANA
Prepared for:
GHANA OIL CO. LTD
Prepared by:
JONAH & MICKSON LIMITED
April, 2021
PROPOSED TANKS INSTALLATION AT ADAMUS RESOURCES LIMITED IN NZEMA
TABLE OF CONTENT
Table of Contents
1.0 INTRODUCTION................................................................................................................................... 2
1.1 General................................................................................................................................................ 2
2.0 GEOLOGY AND TOPOGRAPHY OF THE SITE ........................................................................................ 3
2.1 Description of the Site ........................................................................................................................ 3
2.2 Scope of work...................................................................................................................................... 3
2.3 Geology of the Site.............................................................................................................................. 3
2.4 Seismic Activities of the Project Area ................................................................................................. 4
2.5 Climate of the Project Area................................................................................................................. 5
3.0 THE SITE INVESTIGATION .................................................................................................................... 6
3.1 Field Activities ..................................................................................................................................... 6
3.1.1 Test Pits............................................................................................................................................ 6
3.2 Laboratory Tests ................................................................................................................................. 6
4.0 GEOTECHNICAL PROPERTIES OF THE SOIL.......................................................................................... 7
4.1 Ground Conditions and Soil Characteristics of Project site ................................................................ 7
4.2 Strength Characteristics ...................................................................................................................... 7
4.3 Overburden bearing capacity.............................................................................................................. 8
5.0 DISCUSSION......................................................................................................................................... 9
5.1 Site Utilization ..................................................................................................................................... 9
5.2 Foundation Type and Depth of Placement ......................................................................................... 9
5.3 SEISMIC CONSIDERATIONS ................................................................................................................. 9
6.0 SUMMARY AND CONCLUSIONS ........................................................................................................ 10
6.1 Disclaimer.......................................................................................................................................... 11
APPENDIX A TEST PIT LOGS.....................................................................................................................13
APPENDIX B PHOTOS DCP TESTS AND TEST PITS ....................................................................................14
APPENDIX C: DCP AND TEST PIT POINTS................................................................................................. 16
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PROPOSED TANKS INSTALLATION AT ADAMUS RESOURCES LIMITED IN NZEMA
1.0 INTRODUCTION
1.1 General
The client, GHANA OIL CO. LIMITED proposes to construct Vertical Fuel Tanks at Adamus Resources
Limited site in Nzema, in the Western Region of Ghana. JONAH AND MICKSON LIMITED was
contracted to undertake geotechnical investigations for the proposed project.
The investigations involved excavation of test pits at two (2) locations at varying depth where the tanks
and other structures are proposed to be located and dynamic cone penetrometer tests at six (6) locations at
the proposed site.
The method employed for the investigations were in accordance with what is specified in BS 5930-(Site
investigations for Civil Engineering Projects).
This report presents the findings and recommendations of soil investigations carried out at the proposed
locations for the construction of the Tanks. The report also outlined the work carried out and discusses the
ground conditions revealed by the investigations at the project site and recommendations for the design of
the foundations for the tanks.
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PROPOSED TANKS INSTALLATION AT ADAMUS RESOURCES LIMITED IN NZEMA
2.0 GEOLOGY AND TOPOGRAPHY OF THE SITE
2.1 Description of the Site
The site can be found at Adamus Resources Limited Mining Site in Nzema, Western Region of Ghana.
The land is flat with an existing Fuel Station on it. The description of the site is based on the
consultant’s field reconnaissance and fieldwork.
2.2 Scope of work
As a prerequisite for site investigations to arrive at a proper geotechnical characterization of the site, as
well as arrive at the economic design of the foundations, the following main activities were undertaken:

Desktop study of the geology, seismic, and drainage condition of the area.

Determination of the geotechnical properties and strata thickness of the various underlying soils
strata likely to be encountered at the site during the soil investigation on which the foundation
structure is to be built.

Estimate the bearing capacities and settlement characteristics of the underlying soils for adequacy
in order to recommend appropriate foundation type

Recommend the type and depths to which the foundations of the Tanks could be safely placed.
2.3 Geology of the Site
According to the current geological map of Ghana, the project area is underlain by rocks of the Birimian
Supergroup, Sedimentary Basins. This series consists of Argillitic/Pelitic Sediment dominant, +/Kerogene (‘graphite’). The soil formation site generally consisted of sandy clay with small sized glasslike pebbles in matrix, reddish yellowish brown followed by silty sand fractured rock in the form of
cobbles. Rock outcrops are not visible at the project site.
The current investigations coupled with records from previous borings within the vicinity of the project
site confirm the presence of sedimentary rocks of the kerogene (graphite) type.
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PROPOSED TANKS INSTALLATION AT ADAMUS RESOURCES LIMITED IN NZEMA
Figure 1: Geological Map of the Project Area (Red Box showing the Project area)
2.4 Seismic Activities of the Project Area
Historical records going back to 1615 show that areas extending from just north of Kumasi to the Coast
can be subjected to seismic activity. However it was only in 1939 Accra Earthquake that Junner and Bates
at Ghana Geological Survey Dept. made field observations to enable a map of isoseismals to be drawn for
the whole country.
History of seismic activity in Ghana dates back to 1862. Most of the earthquakes in Ghana occur in the
western part of Accra at the junction of the two major fault systems namely, the Coastal boundary fault
and Akwapim fault zone. According to seismologist, most of the epicenters are located south of Weija in
Accra, suggesting that there is little activity north-eastward along the Akwapim range and westward along
the coastal boundary fault. Most earth tremors in Ghana are related to the level of activity of the faults.
The site area is seismically active. Also no known fault is located within the project area. However, in
1939 a major earthquake which flattened Accra with its attendant casualties was felt in Eastern Ghana and
Togo. The maximum intensity of the shocks was estimated to be 8 on the Richter scale. Many buildings
were greatly affected by this event, some cracked and others partly destroyed. No casualties were reported
for this event.
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PROPOSED TANKS INSTALLATION AT ADAMUS RESOURCES LIMITED IN NZEMA
Between 1987 and 1990, over eight events with magnitude ranging from 2.5 to 4 on the Rictcher scale
have occurred with epicenters in the Accra- Tema area; ( Kato, 1990).
Several minor shocks relevant to foundation designers are picked daily by seismic monitors.
Figure 2: Isoseismic Indication Map of Southern Ghana (Mawuli, A. 1999)
2.5 Climate of the Project Area
The project area experiences two climatic seasons in a year- the wet and dry seasons.
The wet seasons usually extends from middle of April to July and September to November. The main
season reaches its peak in May/June.
The minor season normally extends from late September to early November. The rainfall values ranges
between 1100mm to 2100mm. The degree of saturation of the ground during this period is almost 100%.
The Harmattan, a dry desert wind, blows from the northeast from December to March, lowering the
humidity and creating hot days and cool nights. In the south the effects of the harmattan are felt in
January.
In most areas the highest temperatures occur in March and the lowest in August. The period between
October and March is relatively dry. A value of 25o and 30o are recorded for the lowest and highest mean
temperatures.
The relative humidity is 75% in the afternoon and nearly 90% in the evenings and mornings.
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PROPOSED TANKS INSTALLATION AT ADAMUS RESOURCES LIMITED IN NZEMA
3.0 THE SITE INVESTIGATION
3.1 Field Activities
The field activities started and ended on 15th April, 2021.
The field works involved excavating test pits at two (2) locations at varying depth where the tanks are
proposed to be located and dynamic cone penetrometer tests at six (6) points selected by the consultant
and agreed by the client.
3.1.1 Test Pits
The test pits were done to varying depths from 3.2m to 3.5m. Dynamic Cone Penetrometer tests (DCPT)
were also carried out. These tests give a measure of the relative density of the formation and enable the
variation of the soil strength with depth to be evaluated. The depths at which the test pits were terminated
are given below:
Test Pit no (BH)
Completed Depth (m)
TP 1
TP 2
3.2
3.5
The hardness of the ground was the main criteria for the termination of the pits.
The soil profile in each hole was carefully logged and disturbed and undisturbed soil samples were
recovered from suitable depths in the boreholes for onward laboratory testing.
The boring logs and the DCPT results are presented at the appendix.
Bulk disturbed samples soils were recovered, preserved in airtight containers and labeled as the borehole
was advanced. The soil was sent to the laboratory for testing.
3.2 Laboratory Tests
The following tests were performed on the disturbed and undisturbed soil samples recovered from the
boreholes:
-
Natural Moisture Content
Sieve Analysis
Atterberg Limit
Specific gravity
The tests were carried out in accordance with BS 1377 (1990).
Summary of laboratory test results are presented at the appendix.
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PROPOSED TANKS INSTALLATION AT ADAMUS RESOURCES LIMITED IN NZEMA
4.0 GEOTECHNICAL PROPERTIES OF THE SOIL
4.1 Ground Conditions and Soil Characteristics of Project site
Examination of the soils from the pits indicates that the site has a uniform sub-soil profile. The superficial
soils are mainly lateritic hardpan followed by silty sand with some clay binder. Beneath this is the silty
sandy coarse stones, scattered gravel with flaky rocks. The lines designating the interface between soil
strata on the boring logs represent approximate boundaries; transition between materials may be gradual
and different over the whole site. These soils have plasticity ranging between 6.0% and 10.0%. Logs of
the soil profile are presented in Appendix A. The summary of the properties of the soils as revealed by the
laboratory tests has been presented appendix D.
4.2 Strength Characteristics
The strength characteristics of the overburden granular soils may be evaluated by converting the unit
resistance of the ground into either allowable bearing capacity or standard penetration (N) blow-counts.
The dynamic cone penetration r, defined as the number of blows required for advancing the cone by
10cm, has been converted into allowable bearing capacities using the relationship
qa=30 r (kN/m2).
The probe results indicate the following minimum allowable bearing capacities for the soil at the site. The
DCP test results have been shown below:
Table 2: Bearing Capacity Estimation
BEARING CAPACITY KN/m2
DEPTH
DCP 1
DCP 2
DCP 3
DCP 4
DCP 5
DCP 6
0.1
180
390
360
540
540
420
0.2
210
390
540
630
630
420
0.3
180
630
840
630
840
540
0.4
150
540
810
630
1080
660
0.5
270
450
720
720
1290
780
0.6
510
360
750
930
1290
780
0.7
990
420
600
660
1170
750
0.8
1440
390
510
810
1230
720
0.9
1890
330
420
630
1200
750
1
300
420
840
1380
840
1.1
330
570
1020
1170
600
1.2
240
480
810
930
630
1.3
270
480
1110
870
570
1.4
390
600
960
840
720
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PROPOSED TANKS INSTALLATION AT ADAMUS RESOURCES LIMITED IN NZEMA
1.5
300
540
840
870
750
1.6
300
450
870
1110
870
1.7
240
600
810
1050
840
1.8
270
720
690
1230
990
1.9
300
840
660
1140
960
2
300
1020
1080
1080
960
2.1
390
1230
1140
1440
1050
2.2
390
1170
1140
1410
1110
2.3
330
1230
1080
1530
1170
2.4
360
1380
1500
1650
1170
2.5
390
1590
1830
1830
1170
2.6
390
1890
2100
1770
1140
2.7
330
2.8
390
2.9
690
3
1110
3.1
1350
3.2
1830
Undrained tri-axial test performed on few undisturbed soil samples with 1.5m-3.0m depths shows that the
cohesive strength ‘c’ values were very low ranging between 45KN/m2 and 70KN/m2 with the frictional
angle between 5.4°-9.7°. Generally the decomposed material has unit weight between 18.50-21.0KN/m3.
4.3 Overburden bearing capacity
The allowable bearing capacity for total permissible settlement of 50mm of the overburden soil for the
facility using the DCPT-N values were determined using Allowable bearing pressure on soils chart
(reproduced from Terzaghi, K. & Peck, R.B. (1996) Soil Mechanics in Engineering Practice, 3rd edn).
Summary of results is provided in table 2 above. Bearing Capacities of the ground ranged from about
150kN/m2 to 2100kN/m2. It is therefore being recommended that in the loading of the structures an
allowable bearing pressure of 300kN/m2 is not exceeded.
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PROPOSED TANKS INSTALLATION AT ADAMUS RESOURCES LIMITED IN NZEMA
5.0 DISCUSSION
5.1 Site Utilization
The subsoil investigation did not reveal any adverse condition that may render the site unsuitable for the
construction of the facility. The site could therefore be used for the proposed project.
5.2 Foundation Type and Depth of Placement
The overburden pressures increases with depth across the entire project site. The bearing pressure to be
used for the design of the foundations of structures for the facility can be found at table 2 above, at a
maximum settlement of 25mm. However, this consultant recommends that a bearing capacity of
300kN/m2 shall be used.
The absence of compressible strata at the subsurface indicates that neither total nor differential
settlements are expected to constitute a major foundation design problem. Settlement if any, will largely
keep pace with construction and that post construction settlement will be negligible.
5.3 SEISMIC CONSIDERATIONS
The project area is seismically active therefore it is necessary to consider a seismic factor in the design of
the facility and the foundations.
According to seismic zoning chart prepared by Amonoo-Neizer the seismic factor of 0g to 0.16g (where
g-acceleration due to gravity) for zone 3 may be considered for the design.
Table 3: Isoseismic classification of Southern Ghana
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PROPOSED TANKS INSTALLATION AT ADAMUS RESOURCES LIMITED IN NZEMA
6.0 SUMMARY AND CONCLUSIONS
Based on the results of the investigation,

The project site could be rated as a competent and suitable for the proposed project.

The ground at the site is underlain by the lateritic hardpan followed by silty sand with some clay
binder. Beneath this is the silty sandy coarse stones, scattered gravel with flaky rocks. The
foundation of the proposed structures will be founded within the dense formation.

Isolated pad foundations could be adopted.

A bearing capacity of 300kN/m2 shall be used for the design of the isolated pad foundation which
shall be placed at a least depth of 1.8m from the ground level.

Mat foundations could also be adopted for the vertical tanks, where a bearing capacity of
250kN/m2 shall be used for the design and foundations placed at the least depth of 0.75m, after
the excavated foundations have been filled with crushed rocks and lateritic fill material and
compacted to 95% maximum dry density MDD.

A seismic gravity acceleration factor of 0.16g is proposed for the design of the
foundations to cater for seismic shocks.

Excavation shall be done without lateral support. This is because collapse of side wall is
not expected due to the level of densification of the soil.

Based on the moist nature of the soil and the soil chemistry, a likely reaction against
concrete and steel may be expected. The use of relatively dense/rich concrete mix for the
foundation structures with liberal cover to reinforcement shall be adhered to.
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PROPOSED TANKS INSTALLATION AT ADAMUS RESOURCES LIMITED IN NZEMA
6.1 Disclaimer
The recommendations given are based on conditions encountered during the field investigations.
There may be special conditions prevailing at the site, though unlikely, which may not have been
disclosed by the investigations. Such special conditions should they be discovered be brought to
the notice of the author of this report without delay.
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PROPOSED TANKS INSTALLATION AT ADAMUS RESOURCES LIMITED IN NZEMA
References:
1. Nayal, N.V
Foundation Design Manual for Practicing Engineers and Civil
Engineering Students, 4th Edition.
2. Khan,I.H
Text book of Geotechnical Engineering, 2nd Edition.
3. Som, N.N and Das,S.C Theory and Practice of Foundation Design
4. Braja M. Das
Principles of Geotechnical Engineering, 7th Edition.
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PROPOSED TANKS INSTALLATION AT ADAMUS RESOURCES LIMITED IN NZEMA
APPENDIX A TEST PIT LOGS
13
TP 1
PROJECT: PROPOSED VERTICAL TANKS INSTALLATION
Equipment & Methods
DCP
CLIENT:
Drilling
Progress
Water
return
Date Completed:
GOIL
15/04/2021
15/04/2021
Ground Level:
Rock Quality
discontinu
ities
f
Cr
r
Core
run
Thick
ness
(m)
Depth
(m)
Orientation
vertical
Casing
Hole Diameter: 150mm
ADAMUS RESOURCES NZEMA Date Begun:
LOCATION:
description
O.D Level (m)
Legend
0.0
Firm to hard, moist, reddish brown,
yellowish brown, silty gravelly
SAND, hardpan noodles preserved
0.7
Firm, moist, dark, brownish, silty
SAND with clay binder
2.2
Dense, moist, dark brown, yellowish
brown, greyish brown silty sand,
fractured rocks in the form of
cobbles
3.2
End of Excavation
Remarks:
LEGEND:
Cr - Percentage Core Recovery
Ground water found at 3.0m
r - Rock Quality Designation
f - No of fracture per metre
Sheet 1 of 1
Logged by
THOMAS
Checked by
AUGUSTUS
TP 2
PROJECT: PROPOSED VERTICAL TANKS INSTALLATION
Equipment & Methods
DCP
CLIENT:
Drilling
Progress
Water
return
Date Completed:
GOIL
15/04/2021
15/04/2021
Ground Level:
Rock Quality
discontinu
ities
f
Cr
r
Core
run
Thick
ness
(m)
Depth
(m)
Orientation
vertical
Casing
Hole Diameter: 150mm
ADAMUS RESOURCES NZEMA Date Begun:
LOCATION:
description
O.D Level (m)
Legend
0.0
Hard, moist, dark, brownish,
yellowish brown, mottled gravelly
clay, cobbles/gravels in soil
0.7
Firm, moist, dark, brownish, mottled
silty SAND, coarse stones, scattered
gravels with rock flakes
1.7
Dense, moist, brownish, yellowish
brown, greyish brown silty sand,
fractured rocks in the form of
cobbles
3.5
End of Excavation
Remarks:
LEGEND:
Cr - Percentage Core Recovery
Ground water found at 3.0m
r - Rock Quality Designation
f - No of fracture per metre
Sheet 1 of 1
Logged by
THOMAS
Checked by
AUGUSTUS
PROPOSED TANKS INSTALLATION AT ADAMUS RESOURCES LIMITED IN NZEMA
APPENDIX B PHOTOS DCP TESTS AND TEST PITS
DCP TESTS
TEST PITS
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PROPOSED TANKS INSTALLATION AT ADAMUS RESOURCES LIMITED IN NZEMA
GOIL AND ADAMUS RESOURCES TEAM
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PROPOSED TANKS INSTALLATION AT ADAMUS RESOURCES LIMITED IN NZEMA
APPENDIX C: DCP AND TEST PIT POINTS
7M
TP1
1
3
24M
2
5M
57M
36M
6
35M
7M
5
4
8M
TP2
10M
10M
ENTRY
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PROPOSED TANKS INSTALLATION AT ADAMUS RESOURCES LIMITED IN NZEMA
APPENDIX D TEST RESULTS
17
project: PROPOSED VERTICAL TANKS INSTALLATION
client: GOIL
Location: ADAMUS RESOURCES LIMITED-NZEMA
Depth:
SUMMARY OF TESTS RESULTS
Test Pit
No.
No.1
No.2
Depth
(m)
2.2-3.2
1.7-3.5
Liquid
Limit
(%)
28
32
Plasticity
Index
(%)
10
12
Particle Size Distribution(%)
NMC
7
6
Clay
14
20
Silt
17
18
Sand
25
29
Specific
Gravity
Gravel
44
32
2.6
2.65