Job Description

PROJECT INFORMATION
Following geophysical borehole site investigations and Environmental Social Impact (ESIA) Assessment
conducted by Tawakal Consultant, a suitable location was identified and successfully drilled to a depth
of 194.7m. A submersible pump with a power of 11 kW was installed, resulting in a yield of 24 cubic
meters per hour. The borehole pumping test was conducted between 5 and 6 September 2024.
The Lafole borehole has experienced repeated pump failures caused by the accumulation of
sediments, mud, and fine sand. Typically, during operation, the borehole discharges heavy sediments
for about two hours. However, on 21 August 2025, it discharged sediments continuously for three
consecutive hours. This led to clogging of the pump’s intake screen and internal components,
ultimately causing pump failure. The borehole is drilled in a formation of very fine sand, which
infiltrates the borehole by bypassing the casing screen.
The following are the findings and observations made during technical assessments conducted at the
BH
• Sandy water discharge: The borehole has experienced repeated pump failures caused by the
accumulation of sediments, mud, and fine sand. On 21st August 2025, it discharged sediments
continuously for three consecutive hours. This led to clogging of the pump’s intake screen and
internal components, ultimately causing pump failure.
• Sediment Accumulation: Significant deposits of dark brown sediment were observed around the
borehole. This indicates that fine sediments have accumulated inside the well, reaching up to the
pump setting depth.
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• Pump Damage: According to the borehole caretaker, three submersible pumps have already been
replaced due to damage, mainly caused by the abrasive and corrosive nature of the water.
Conclusions have been drawn to the leading cause of borehole failure in the Lafole area is the
mismatch between the screen slot size and the size of the formation sand grains. The screen size of
0.5mm slots allowed fine sand to enter the boreholes, reducing well efficiency and damaging the
pumps. Fine sand intrusion caused frequent damage to electric submersible pumps, including
clogging, abrasion, and motor burnout. The current casing and screen, constructed from uPVC
material, are inadequately designed to retain fine sand particles. Consequently, sand passes through
the screen and fills the borehole. UPVC screens are ineffective in preventing fine sand intrusion. A
more suitable alternative is mild steel casing fitted with Johnson-type screens. These screens allow
higher flow rates while effectively blocking fine sand particles, ensuring efficient water infiltration and
sustainable operation.
Remedial rehabilitation options have been suggested and reviewed, and given the uncertainty and
complexity of the suggested rehabilitation options, like flushing out the BH, inserting smaller casings,
sealing off the fine sand section (158-194.7m), reducing the pump intake, installing a smaller capacity
pump. These may only offer a temporary solution, with the possibility of the sand intrusion recurring
after some time. Hence a long term sustainable solution is being sort.
The following recommendations are prescribed:
1. Drill a new BH near the existing one to a depth of 155m (to avoid reaching the fine sand
deposits, in line with the hydro-geological reports).
2. Install mild steel casings (plain and screens) with 10’’ internal diameter. The mild steel casing
(as compared to the PVC casings) will possibly provide strength and rigidity required in the
underground soil conditions of Lafoole area.
3. Use factory pre-packed stainless steel screens (Johnson type) with outer pre-pack gravel
engineered to retain the formation, with equivalent slot opening ≤ 0.25mm. Johnson-type
screens, are specifically designed to prevent fine sand intrusion and ensure long-term
functionality.
4. Provide a well-compacted, properly graded gravel pack matched to sieve analysis - special,
well-known gravel sourced from the Burhakaba area as it has clean, durable, and suitable for
groundwater filtration.
5. Complete rigorous development and sand-free acceptance testing before commissioning.
6. The pump design to be based on the tested yield, and the water demand needs. The test
pumping to be carried out using variable pumping rates and depths to provide a good basis to
determine the right pump sizing.
7. Retrieval/recovery of the pumping equipment (riser down pipes, down cable) – to be re-used
in the new BH.
8. Reconnection to the existing water supply network.
9. Drilling process to be supervised by an experienced and qualified Hydro-geologist.
2. OBJECTIVE OF THE ASSIGNMENT
The objective of the consulting services is to manage and supervise the drilling contract of one (1)
borehole located in Lafoole on a day-to-day basis on behalf of Concern Worldwide. The aim of the
supervisor is to support the client in contract supervision of the drilling works, and contract
management for the smooth execution acting as the on-site representative in making decisions for
the client. In addition, final certification and verification shall be carried out by the consultant. The
supervisor shall carry out quality control and ensure that Works are being carried out as provided for
in the contract. The drilling site supervisor shall supervise if the Contractor is following the terms,
conditions and specifications as provided for in the drilling contract and make amends only after
consulting with the client (Concern Worldwide) if different ground conditions are encountered that
were not envisaged.
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Boreholes are one of the best means of obtaining clean water in field conditions. However,
constructing, or repairing, boreholes requires specialized knowledge and technical expertise, much of
which can be gained from the standard literature; but field operations in remote areas or in difficult
conditions often require flexibility and imagination in avoiding and solving technical problems.
The supervisor will be able to take prompt decision, that no waiting time is incurred for the driller. The
end result should be a cost-effective facility capable of supplying potable water for many years.The
drilling supervisor will use check lists for all major steps.
Therefore, Concern Worldwide is seeking the expertise of a Borehole Drilling Supervisor (BDS), who
will be responsible for delivering the above outputs.
3. MAIN RESPONSIBILITIES
Concern Worldwide intends to engage the services of a competent drilling supervisor to undertake
supervision of the drilling of one (1) borehole at the identified/georeferenced site, next to a collapsed
BH site at Lafoole. A production borehole shall be drilled in the recommended site or as may be
determined by the client and/or Engineer and instructed to the consultant. Drilling will be supervised
by a competent drilling supervisor. Supervision shall include geological logging of drilling samples,
reporting on daily progress, borehole design, design for installation of the borehole, supervision of
installation of borehole screens and casings, development and test pumping, sampling and analysis of
water quality, and quality control of all other work done by the Contractor. Full time availability of the
drilling consultant at the site is a must. Invoices submitted by the Contractor are to be certified by the
Consultant. The data acquired during drilling and testing shall be analysed and borehole completion
report prepared for the production borehole. While overall quality control of the works shall be done
by the consultant, attention shall be paid to the following issues pertaining to drilling, installation and
test pumping works.
General description to the role
The main responsibilities/tasks can be summarized as follows:
• Drilling supervision
• Preparation of Borehole completion reports for the borehole.
• Certification of contractor’s invoices
• Recommendation of production pump
5. SUPERVISER ACTIVITIES /TASKS
Details of these responsibilities/tasks are further detailed below.
5.1 Drilling supervision
5.1.1 Borehole Depth and Diameter
The supervisor shall give instructions on the total depth and at what diameter to drill. Should
collapsible formations be encountered, installation of telescopic casing shall be decided upon by the
Supervisor.
5.1.2 Drilling Method and Process
The supervisor shall approve or reject all drilling methods and/or any additives to be employed by the
Contractor. The site supervisor shall ensure that the contractor follows the standard drilling practice,
including making all necessary drilling records correctly and on the spot, and that he/she completes
the borehole according to the recommended well design.
• Examine tools, materials, plant and equipment, and approve or reject as appropriate on the
basis of the standards. Such instructions shall be provided to the contractor in writing.
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• Write instructions to the contractor relating to the management of the contract, the design
and development of the water source, or any other relevant matters as and when required.
All instructions issued by the drilling supervisor shall be in triplicate and shall be signed by site
representatives of both the contractor and site supervisor.
• Ensure that the contractor uses the correct drilling methods, equipment and tools for any site
to be drilled as specified. The supervisor shall approve all drilling methods and/or any
additives to be employed by the Contractor. Ensuring drilling to recommended depths and
diameter; the supervisor shall give instructions on the total depth and at what diameter to
drill. Should collapsible formations be encountered, installation of telescopic casing shall be
decided upon by the Supervisor.
5.1.3 Sampling
The supervisor shall ensure that representative samples are taken at specified intervals (three - metre)
of the strata penetrated and are put into suitable sample bags, labelled with the depth interval, and
stored in a position where they will not be contaminated by site conditions or drilling operations.
Geological logging will be the responsibility of the Supervisor
5.1.4 Yield estimates during drilling
The supervisor shall continuously monitor air lift yields will be made by the contractor and recorded
by the Supervisor. Ensure the borehole driller reads and rates average yields every
3 meters of penetration and as otherwise directed by the supervisor and recorded in the driller’s log.
5.1.5 Borehole design
Ensure borehole design is made by the drilling contractor after drilling completion. The design shall
ensure that aquifer zones are completely or partially lined with mild steel plain casing and stainlesssteel continuous slot screen as decided and approved by the Supervisor or as determined by the client
prior to award of the contract. Samples of the installation materials shall be tested by the drilling
Contractor. During installation, the supervisor will confirm that the screen open surface area is as
specified in the contract with a uniform slot size. In addition, the Supervisor will ensure that the casings
and screens are centralized in the borehole so as to leave a uniform annular space between the
borehole wall and the casing. Suitable centralizers should be provided to allow the casing and screen
to be set correctly in the centre of the drilled borehole.
5.1.6 Temporary Casings
In case the design was predetermined before the actual drilling, reconstruction of the well-design after
the drilling, or possible encountering unproductive well (dry) due to unforeseen variations in
hydrogeological conditions, the contractor shall be required to make consultations with the site
supervisor who, upon a sound technical judgment, for which he/she takes full responsibility, will
consult with the employer/client, then issue written approval and instructions to the contractor to go
ahead with the necessary changes. All the changes made shall be properly recorded and shall form
part of the driller’s log.
The supervisor shall direct installation and recommend the diameter of any temporary casing required
for the construction of the borehole based on formation penetrated. He shall ensure that the same
are retrieved at the end of all drilling and installation activities. Where the contractor is unable to
retrieve the casings due to jamming, this shall be confirmed that it has no negative effect to the quality
of the water or the installation of the permanent designed borehole, and at no cost to the client.
5.1.7 Verticality
The Supervisor shall decide whether the Drilling Contractor will conduct a verticality test during and
after drilling by approved methods to demonstrate that the departure from the vertical does not
exceed 3 in 100 between ground level and the base of the borehole. If this departure is exceeded, the
Contractor shall make the necessary corrections to the approval of the Supervisor. If the error cannot
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be corrected, then drilling shall cease and a new borehole be drilled at a position nearby, indicated by
the Supervisor. The abandoned borehole shall be backfilled and/or capped by methods approved by
the Supervisor.
5.1.8 Gravel pack
The Supervisor shall ensure that suitable gravel pack is supplied by the Contractor. Prior to delivery,
samples of the gravel pack shall be analysed for grain size and approved by the Supervisor. Gravel
should consist of washed, well-rounded particles of a uniform grading. The gravel shall contain 90%
siliceous material and contain no clay, shales, silt, fines, excessive amounts of calcareous materials or
crushed rock.
In terms of grain size, 90% shall conform to the grading specified and the Contractor shall be required
to submit samples of the material prior to installation for approval by the Supervisor. Sufficient gravel
pack shall be installed to cover completely the uppermost screen, plus an additional 5 m length (to
allow for settling). A good supply of water should be introduced with the gravel to prevent bridging.
The pack should be capped with a clay seal to prevent contamination. The annular space above this
seal can be back filled with inert drill cuttings. The top three meters should be grouted with cement.
5.1.9 Sanitary Seal
To provide an effective seal to the entry of contaminants, the upper 10 meters of the borehole will be
grouted using a cement slurry injected into the annulus between the casing and the wall of the hole,
by a method to be approved by the Supervisor. Grouting ensures non entry of contaminants to the
well.
5.1.10 Water quality and electrical conductivity measurements
Carries out water quality analysis in conformity with specifications. Electrical conductivity (EC)
readings shall be carried out whenever required during drilling, development and test pumping. EC
measurements and readings shall be taken for each aquifer strike.
5.1.11 Development and cleaning of borehole
Development and cleaning of the borehole shall be carried out by the Contractor upon completion of
the drilling and installation of casing and screens. This will remove the native silts, clays and drilling
fluid residues deposited on the borehole wall and adjacent portions of the aquifer during the drilling
process.
• If organic drilling fluids are used, they shall be broken down chemically according to
manufacturer's recommendations before or during development. Cleaning shall be carried
out by airlift pumping, surging, backwashing or jetting. Clay disaggregation by means of
Sodium Hexametaphosphate ('Calgon') treatment might be necessary in some cases. The
Supervisor issue instructions to the contractor for such treatment.
• The method proposed by the Contractor for development of borehole shall be submitted to
the Supervisor in writing for his approval. Development of borehole shall be effective from
the depth at which water is encountered to the bottom of the borehole. Development shall
continue until water is completely free from fine particles, as to be decided by the Supervisor.
Upon completion of development, any accumulation of material shall be removed from the
bottom of the borehole by airlifting.
• The supervisor shall ensure that all native silts, clays and drilling fluid residues deposited on
the borehole wall and adjacent portions of the aquifer during the drilling process are removed.
Cleaning shall be procedural starting within the regions of first water strikes systematically
and bottom wise.
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5.1.2 Well Disinfection
The supervisor will ensure that disinfection of the borehole is carried out by the Contractor before
demobilization from the site. This shall be done by placing a chlorine solution into the well so that a
concentration of at least 50 mg/l of available chlorine existing in all parts of the borehole at static
conditions. All the borehole surfaces above the static water level shall be completely flushed with the
solution. The solution shall remain in the borehole a minimum of 2 hours before pumping the borehole
to waste.

Experiences and Qualifications

10.1 Qualifications and skills
• Minimum of High Diploma or Equivalent in Drilling or Water Supply or related technical field
(like Geology).
• Hands-on contract and day-to-day management of drilling contractors
• Demonstrated practical experience in the deep groundwater development from siting up to
drilling;
• Demonstrated excellent command of spoken and written English. Fluency in Somali is
requested; and
• Excellent interpersonal and diplomatic skills.
10.2 General professional experience
• At least 10 years demonstrated experience in the field of drilling deep boreholes and able to
provide evidence and contact references
10.3 Specific professional experience
• Minimum of 5 years conducting borehole drilling supervision in Somalia. The supervisor must
demonstrate that they have conducted at least three similar assignments in the last 3 years.
11 PAYMENT
A consultancy fee will be paid to the selected Borehole Drilling Supervisor upon completion of the
assignment and submission of time sheets and invoice approved by the Concern Worldwide WASH
and Construction Coordinator.
Any other allowance will be in line with the Concern Worldwide terms and conditions of the service
contract

Skills Required

Attachment

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