REPORT ON HYDROGEOPHYSICAL

INVESTIGATION AND ESTIMATE FOR 8″

BOREHOLE DRILLING/INSTALLATION

FOR

Free African Football Academy

(ASUTUARE, EAGLE CITY)

BY:
EVANS KOFI VAKPO

Contact: (+233) 245882183 / (+233) 202400128

evansvakpokofii@gmail.com Signature

(Evans Kofi Vakpo)

24th March, 2023

TABLE OF CONTENTS

Table of Contents
TABLE OF CONTENTS ..................................................................................................................... 2

CHAPTER ONE ................................................................................................................................... 3

1.1 Introduction..................................................................................................................................... 3

1.2 Objective ......................................................................................................................................... 3

1.3 The Location ................................................................................................................................... 4

Fig. 1: Site Location and Sketch and where the borehole is to be drilled (marked in blue) not drawn to
Scale...................................................................................................................................................... 4

1.3.1 Geology and Hydrogeology..................................................................................................... 4

Fig. 2: Geology of the study area showing the proposed drilling points on the red dot ....................... 5

2.1 PQWT S500 .............................................................................................................................. 5

2.2 Methodology for Borehole site selection ................................................................................... 6

2.3 Results ........................................................................................................................................ 6

2.3 Results Processing ...................................................................................................................... 7

3.1 Isoline Graphs ................................................................................................................................. 8

Fig. 4 Two-dimensional modelling result of Profile Curve and profile map on Line 12 for the
unprocessed data showing proposed drilling location (Ln.12 pt_24m) ........................................... 9

Fig. 5 Two-dimensional modelling result of Profile Curve and profile map on Line 12 for the
processed data showing alternative proposed drilling location (Ln.12 pt_15m) ........................... 10

4.1 Conclusion ............................................................................................................................... 11

4.2 Recommendation ..................................................................................................................... 11

Table 2.1 Ranked Station for drilling........................................................................................................ 11

5.0 Appendix 1 (Proposed borehole design) ............................................................................................. 12
Fig. 6: Proposed Borehole construction diagram. ..................................................................................... 12

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Table 1: Budget Estimate for One Borehole Drilling & Construction and Mechanization ............... Error!
Bookmark not defined.

CHAPTER ONE

1.1 Introduction
This reports the geophysical investigation which has been completed and the findings and
recommendations for the drilling presented herein. The objective of this stage was to use geophysical
equipment to detect weak zones namely fractures and weathered zones (aquifers) at depth at various
portions of the designated borehole sites where there is very high possibility of groundwater existence.

The investigation was carried out on 24th March, 2023. The study is to select suitable sites for borehole
drilling and construction for water supply within the property at Asutuare Eagle City in the Shai Osu
Doku District of the Greater Accra region-Ghana.

1.2 Objective
The main aim for carrying out this studies was to locate and identify potential groundwater zones for

subsequent exploitation by drilling in order to supply sustainable water for the Free African Football

Academy

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1.3 The Location

Fig. 1: Site Location and Sketch of Free African Football Academy Property where the
borehole is to be drilled (marked in blue) not drawn to Scale

1.3.1 Geology and Hydrogeology

The topography can be described as generally gently flat. Geologically, it is underlain by Gneisses from
Dahomeyan Supergroup. Composed of rocks such as garnet-amphibolite gneiss, Pyroxenite (+/-
chromite), Nepheline syenite gneiss (+/- carbonatite), quartzo-feldspathic gneiss and some biotite gneiss
(Fig. 2). The area is believed to have developed some secondary porosities and permeabilities through
weathering and fracturing. This geological formation is of great groundwater accumulation potential. Its

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groundwater occurrence and movement is related to the structural features such as weathering, fracturing
and jointing.

Fig. 2: Geology of the study area showing the proposed drilling points on the red dot

CHAPTER TWO
INSTRUMENTATION AND FIELD PROCEDURE
2.1 PQWT S500
This study was carried out using PQWT S500 geophysical equipment. This employs the electrical
resistivity method for its operation. It's use the natural electric field as electromagnetic field work source,

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based on the resistivity differences of underground rock, mineral or groundwater, measure the natural
electric field in the soil of N different components of electric frequency field. The method provides a direct
reading of apparent electrical resistivity of the earth and allows for rapid surveying to be done. The
equipment is a one-person portable system. The Sensor is energized at an audio frequency in order to give
rise to a time-varying magnetic field which subsequently induces currents in the ground. Secondary
magnetic fields are further generated by these currents which are detected together with the primary field
by the Host. It gives variable depths of exploration that ranges from 100m to 500 m. The method has been
a powerful technique to investigate subsurface electrical structures in various environments.

It is also equipped with 10m MN standard measuring line and supports both MN electrode.

2.2 Methodology for Borehole site selection

The investigation consisted of office and field work. The office work covered the acquisition and study of
geological. The field work entails mainly the geophysical survey. Detailed terrain resistivity geophysical
method was employed in the survey to measure ground resistivity along and across the boundaries.

Before setting up the equipment for a geophysical survey (groundwater exploration), the terrain was
evaluated. Care was taken in order to avoid areas that are prohibited such as toilets and refuse dumps.
After demarcating suitable sites for the survey, the equipment was set up for use. The Host Android System
and the electrodes were connected. A 1m station interval was chosen for all the profiles. Both horizontal
and vertical measurements were taken at each position with the Host trailing the electrodes always.
Potential groundwater bearing sites were identified.
Two points were selected. Fracturing occurs at various depths. The various aquifer zones are characterized
with blue colours.

2.3 Results
The resistivity data acquired from the field represent a general study for the site under investigation.
Figure 2.1 is the apparent resistivity values of each traversed stations and their respective depths (0m
– 150m). Each profile line represents a traverse.

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Figure 3.1 Data of Resistivity profile conducted at Traverse line

2.3 Results Processing

The data collected by the instrument is processed by “Aidu Intelligent Data Processing Software”,
where the abscissa indicates the measuring point number, the ordinate indicates the depth. After the
collected data is processed by "field source correction" and "depth calculation" in "Aidu Intelligent
Data Processing Software", the depth data is saved, and then processed by SURFER9 ( contour map),
and the abnormality is reflected.

The resistivity data is interpreted in an Isoline graph (2D image) form which shows contour map plots
of depths versus stations traversed. The PQWT S500 electrical resistivity imaging method, because
of its high resolution in indicating different electrical resistivities of geological units, it is commonly
used in measuring the electrical structure of subsurface within several tens to hundred meters deep.

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 CHAPTER THREE

DATA ANALYSIS AND DISCUSSION

Interpretation of geophysical data such as Resistivity data normally requires a good knowledge of the
geology, hydrogeology and field experience in the area. The electrical resistivity of a rock is a measure
of its opposition to electric current flow through it. According to the resistivity theory, groundwater
shows the characteristics of low-resistance anomaly compared with surrounding rock. Any significant
flow of current in these subsurface materials is mainly due to the groundwater existence and its ionic
contents in the soil or fractures. A good contrast between the resistivity of fractured rocks and
undisturbed hard rocks would be observed if fractures were filled with groundwater. Fractured rocks
show lower resistivity while unfractured rocks show higher resistivity.

The electrical resistivity contrasts between lithological sequences in the subsurface are usually
adequate to enable the delineation of aquiferous or non-aquiferous layers. The resistivity data are
presented as profiles of depth against stations traversed in a contour map called Isoline graph.

3.1 Isoline Graphs

The resistivity and depth values obtained for all the three profile lines were presented in the Isoline
graphs to further aid in the delineation of the subsurface units (Figure 3.1). The orange area represents
unfractures rock while the deep blue and purple represents good aquiferous zones with the purple
being the best (lowest resistivity). The black lines show the hypothetical interface between the various
layers. The yellow to green areas suggest the transitions zones between saturated and unsaturated
zones.

Thus, we can find the contrasts at where resistivity changes from the main resistivity layers in the
resistivity image. This produces a subsurface map of the apparent resistivity distribution map.

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Fig. 4 Two-dimensional modelling result of Profile Curve and profile map on Line 12 for the
unprocessed data showing proposed drilling location (Ln.12 pt_24m)

9
Fig. 5 Two-dimensional modelling result of Profile Curve and profile map on Line 12 for the
processed data showing alternative proposed drilling location (Ln.12 pt_15m)

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4.0 CONCLUSION AND RECOMMENDATIONS
4.1 Conclusion
The goal of this work is to locate a point where groundwater potential is high using 2D resistivity
image. In order to recognize and identify geologic or water bearing features, the profiling data were
examined and analysed with the aim of delineating water bearing features for the selection of a target
station for borehole drilling. Aquiferous zones defined by weathering, fractures and shear zones were
the main targets for the resistivity survey. These areas are characterized by anomalous zones that have
purple and blues areas indicating a lower resistivity values when measurements are taken and plotted
on the Isoline graph.
The Isoline Graph and map of the area was successfully delineated sequence of subsurface lithologies.
The comparison between the image analysis models showed a clear correlation and therefore indicate
a high reliability of the result. The analysis suggests that the bedrock is MODERATELY fractured
from near surface to depth. Altogether, the application of the geophysical data was very useful in
delineating prospective aquifer zones to aid in the drilling of boreholes for the facility.

4.2 Recommendation
According to the resistivity theory, groundwater shows the characteristics of low-resistance anomaly
compared with surrounding rock. In Figure 4, the blue indicates the area of very low-resistance, the
light green and orange indicates the area of low-resistance; an anomalous zone where groundwater is
likely to exist. The stations with higher blue and blue extensions, which is most likely to be highly
weathered, fractured and saturated in view of its low apparent resistivity value, could contain
appreciable quantity of groundwater. Hence, it’s considered to be a good borehole drilling point. The
various stations are however ranked in order of the highest expected groundwater potential as shown
in Table 2. From the Table, station Pt_24m was considered the most suitable site for drilling and
expected overburden thickness believed to be 9-15m to saprolite before the fresh hard rock formation.
All the two points has equal groundwater potential if the client want to drill both.

Table 2.1 Ranked Station for drilling

Stations Ranks Minimum Drill depth Recommended
Depth Range
Pt_24m 1 75m 105m
Pt_15m 2 60m 105m

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5.0 Appendix 1 (Proposed borehole design)

WATER/ WELL DIAGRAM

ZONES WATER LEVEL m
Q (l/min)
0
Cement Grout

Back fill

Water Level 10

Screen uPVC

20

Gravels pack

30

Plain uPVC

40

Screen uPVC
50

60

70
botto Pl ug
Fig. 6: Proposed Borehole construction diagram.
The estimate for the drilling covers 8″ 100m borehole.

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Table 1: Budget Estimate for One 8″ Borehole Drilling & Construction and Installation
Cost
No: Item Unit Qty. Amount (Ghc)
(Ghc)
1 Geophysical Investigation L/S 1 1,200.00 Paid
1A Total of Geophysical Investigation Paid
2 Mobilization and demobilization L/S 1 1,600.00 1,600.00
2.A Total 1,600.00
3 Drilling&Construction of 8″ Borehole
3.1 8″ Bh Drilling (Soft formation) m 18 280.00 5,040.00
3.2 8″ Bh Drilling Hard rock formation) m 82 500.00 41,000.00
6″ Plain PVC supply & installation
3.3 m 27 780 21,060.00
6″
6″ Screen PVC supply &
3.4 m 6 800 4,800.00
installation
3.5 Gravel and Graveling/Cement L/S 75 25.00 1,875.00
3.A Total 73,775.00
Total for Drilling and Construction materials
3.AA 75,375.00
4.0 Pump Test
4.1 Constant test (Hrs) L/S 24 200.00 4,800.00
4.2 Recovery Test (Hrs) L/S 6 180.00 1,080.00
4A Total 5,880.00
5.0 Water quality
5.1 Physicochemical Test 1 350.00
L/S 450.00
5.2 Bacteriological Test 1 350.00
L/S 450.00
5.3 Disinfection of the borehole No 1 350.00
350.00
5.A Total 1,050.00
6.0 Pump Materials and Mechanization
3 Phase electrical submersible
6.1 1 13,200.00 13,200.00
pump (Head = 150m max) LS
6.2 Pump Accessories LS 1 3,560.00 3,560.00
6.3 Well Head Complete50mm 1 550.00
LS 550.00
Air Valve 50mm *Pressure
6.4 1 600.00
valve) LS 600.00
6.5 PE Pipe (50mm) Couplings No 4 320.00
80.00
PE Pipe PN 16, OD 50mm dia
6.6 m 100 3,200.00
rising main 100m 32.00
6.7 Filter and accessories No 1 350.00
350.00

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 6.8 Non return Valve 50mm No 1 290.00
290.00
6.9 Installation Kit No 1 200.00
200.00
6.1 Supporting Cable (metal) m 1 500.00
500.00
6.11 45⁰ Coupling 50mm (PE Elbow) No 4 480.00
120.00
6.12 Gate valve, nominal bore 50mm No 1 300.00
300.00
6.13 Sensor probe No 2 200.00
100.00
6.14 Sensor cable 1.5mm No 1 1,200.00
1,200.00
Installation Cable 2.5mm
6.15 No 1.5 4,800.00
(4x1mm, Turkey made) 3,200.00
6.16 Workmanship and T&T L/S 1 3,600.00 3,600.00
6.A Total 33,350.00
7 Grand Total 117,255.00

Note: The borehole will be fully lined (fully constructed) as shown above and installed up to the point not more
than 5m from the source (borehole) Connection to power source is not included in this estimate.
Mode of payment is by cash; 70% of the total cost before work start and the remaining 30% have to be paid when
the work reach 90% to its completion

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