TERMS OF REFERENCE FOR THE CONSTRUCTION OF SOLAR POWERED BOREHOLE DRILLING & EQUIPPING REF: DS4Y/srd/241106 - ToR
Tenders
- Impact Hub Harare
- Expires 29 Nov 2024
- Harare
- Full Time
Job Description
1.0 Introduction
As part of the Digital Skills 4 Youth project, Impact Hub Harare intends to drill a borehole
and equip it with solar powered pumping system in Tsholotsho Matabeleland North
Province.
The overall goal of the project is to improve access to safe water for the DS4Y Makerspace.
Impact Hub Harare therefore invites bids from reputable suppliers for the solar powered borehole drilling and equipping services.
2.0 Scope of works
The work comprises inter alia siting/hydro-geophysical surveys and drilling of boreholes at the above locations, inclusive of sustainable yield testing, water quality test, borehole equipping with solar powered pumps and water reticulation systems and security fencing as specified herein.
Duties and Responsibilities
3.0 Workmanship
a. The Contractor is expected to implement the project in accordance with acceptable
engineering practices, standards and codes.
b. All works shall be carried out by suitably qualified and experienced person(s) and must
comply with acceptable and good workmanship standards, paying particular attention
to structural integrity, alignment, squaring, plumbing and levelling of structures.
c. The Contractor shall provide and maintain, as far as is reasonably practicable, a working
environment that is safe, without risk to the health and safety of the community and
environment. The activities on site thereof shall be undertaken in such a manner as to
ensure, as far as practicable that persons who may be directly affected by the
activities are not thereby exposed to hazards to their health and safety.
d. The Contractor shall observe all construction procedures and liaise with the Client’s
representative and Rural Infrastructure Development Agency (RIDA) for relevant stage
approvals. Where work is to be covered or concealed, the Contractor shall not proceed
past that point until approval has been received.
e. The Contractor shall, upon receiving a contract instruction, cause the same to be made
good in a perfect and workmanlike manner at their own cost and in default thereof the
Client shall be entitled to cause it to be made good and to recover the cost thereof
from the Contractor or to deduct the same from amounts due to the Contractor.
DS4Y/srd/241106-ToR
4.0 General requirements
4.1 The Contractor shall deliver boreholes conforming to all the requirements for siting,
drilling, testing (to determine sustainable yields and water quality) and equipping of
the boreholes. Borehole water shall pass the minimum acceptable standard water
quality specifications (Portable Water ZWS 560:1997) for domestic use.
4.2 Dry holes and/or poor water quality yielding boreholes shall be replaced and tested by
the Contractor at no further cost to the Client. Therefore, bidders must include costs of
replacing unsuccessful boreholes emanating from poor water quality and/or dry holes
in their pricing.
4.3 The Contractor shall share the geo-physical survey results with the Client before drilling
operations. The Contractor shall also share the yield test results before equipping the
boreholes with pumps.
4.4 All materials shall be procured and supplied new by the Contractor unless otherwise
noted and all materials shall be approved by the Client or Client’s representative prior
to commencement of works.
4.5 Borehole location shall be identified in agreement with RIDA and in consultation with
the Client.
4.6 The Contractor shall inform the Client and RIDA or its representatives and make them
aware of every activity during the siting, drilling, testing and equipping process who
shall also be sensitized on basic upkeep, maintenance and repair of all the installed
infrastructure.
4.7 The borehole drilling Contractor, also responsible for the geo-physical surveys shall
generate a technical report stating all findings and justifications including those for
unsuccessful boreholes within a week after completion of each successful borehole. All
installations made shall be listed and shared with the Client.
Qualifications and Experience
5.0 Technical specifications
5.1 Borehole drilling
The Contractor shall on behalf of the client obtain the authority to drill from the Zimbabwe
National Water Authority (ZINWA) and quotations for drilling a wet hole and equipping
should include but not limited to the following specifications:
a. Suitable drilling methods shall be applied with no additional charges applicable
should the Contractor encounter loose, soft or hard formations.
b. Boreholes shall be drilled vertical and the casing shall be plumb. The Contractor
can be requested to perform a verticality test using approved methods and at
their own expense, if so required by the Client. Deviation from verticality shall not
DS4Y/srd/241106-ToR
c. d. exceed 20mm. All necessary corrections shall be subject to the Client’s approval. If
the error cannot be corrected, then drilling shall cease, and a new borehole shall be
drilled. The cost for making corrections or re-drilling shall be met by the Contractor.
During drilling, representative samples of soil shall be collected at every five meters
penetrated and when a change in the soil profile is encountered as well as at every
water strike.
The Contractor shall use temporary steel casing or class 16 UPVC casing in unstable
formations to stop collapses during drilling until a self-supporting geology is
reached. e. The Contractor shall drill boreholes to a minimum depth of 80 meters
with a minimum bit diameter of 165mm and cased to the bottom with 140mm class
10 UPVC casing and screen. Where drilling is envisaged to go beyond 80 meters
approval shall be sought from the Client or its representative in which case drilling
may be continued up to a maximum depth of 120m.
e. Full depth casing will then follow when final depth and promising blow yields have
been attained with slotted casing in the lower parts of the borehole and at water
strikes. This will then be followed by gravel packing and well development.
f. The screen shall be of the same class and standard as the plain casing. h. The
lower end of the casing shall be plugged by a Class 10 UPVC cap glued to the end.
g. The angular space between the casing/screen and the drilled borehole wall shall
be gravel packed using 6mm washed quarry. The top 6 meters shall be installed
with a grout sanitary seal to minimize direct seepage of surface water into the
borehole.
5.2 Borehole yield test
a. To establish the borehole potential and estimate the sustainable yield, a yield test
shall be performed. The test shall include:
i. Step-drawdown test (SDT): 4 x 1-hour steps at constant discharge rates of
one half, three quarters, equal to, and one and half times the expected yield
respectively. ii. A Constant Discharge Test (CDT) shall be carried out for 2 hours
at a discharge rate advised by the SDT above and approved by the Client.
iii. Recovery test (RT): Allow water levels to recover until the water level returns to
at least 90% of the static water level or until at least 3 readings taken in
succession are identical as approved by the Client.
b. Water levels shall be measured every 30 seconds for the first 5 minutes, then every
minute until 15 minutes have elapsed, then every 5 minutes until the end of the
drawdown test. Pumping rates shall be measured at the beginning of pumping and
after every 20 minutes. Discharge rate shall be maintained within 10% of the
required rate for the duration of the test.
c. Successful boreholes (wet hole) shall be capable of delivering sustainable yields of
more than 0.75 litre per second or as shall be approved by the Client.
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5.3 Water quality tests
The Contractor shall be responsible for testing the quality of the borehole water at an
approved water testing laboratory. The Contractor shall collect water samples in approved
containers and take them to the laboratory at the end of the pumping test. Water quality
tests shall be performed to determine the biological, physical and chemical properties of
the water. The Contractor shall furnish the Client with the test results
5.4 Water pump installations and solar power connection
The Contractor shall supply and fit pumps and electrical system to the following guiding
specifications:
a. b. c. d. e. Installation of the solar powered systems shall be directed by the actual field data
obtained. The system shall run on Grundfos solar powered submersible pumps
with dry run sensor, motor, and controller (or of a similar approved brand) capable
of delivering a flow of 0.7 l/s at the ultimate water tank inlet level. Head losses shall
be considered for the whole system and at the maximum borehole depth.
The Contractor shall allow for power supply connections from an existing solar
system setup at the DS4Y hub.
A power distribution board equipped with a circuit breaker and pump drive shall be
secured as shall be directed by the Client. The Contractor shall provide a 1.2m x
16mm earth rod hammered into the ground as earthing to the system.
Armored cables and/or trunking shall be used on exposed surfaces.
All designs and installations shall be to the approval of the Client prior to fitting.
5.5 Water reticulation
a. b. c. d. e. f. The system shall be installed with a 50-gallon pressure tank, pressure switch, and
50mm ‘Elster Kent Helix’ water meter.
Supply and fix 2No. x 5000 Litre (Jojo or similar approved) plastic storage tanks with
float valves on 4m high steel galvanized and painted tank stand.
Tank stands shall be secured (bolted/encased) in minimum 800mm deep
concrete footings. The top platform members shall not cut through or cause
deformation to the water tanks. Guard rails shall be provided on the top platform.
A 75mm thick concrete apron shall be constructed under the tank stand with edges
extending 500mm from the tank stand legs and tucked 150mm into the ground. e.
All above ground water pipes shall be in galvanised iron.
Minimum cover (backfill) over underground pipes shall be 450mm. Pipes shall be
encased in galvanized pipes on river, trench or gully crossings. The galvanised
pipes shall be embedded in concrete on either side of such crossings.
2 x 20mm bib taps shall be connected to the water line from the tanks which shall
be in excess of 100m from the water storage tanks, end capped to allow future
connections. h. A 700mm wide apron and bund wall shall be constructed at each
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5.6 Concrete works
faucet point (see drawing). i. Rate for excavation for pipe works, pipe laying and
backfilling from pump to water storage tanks and from storage tanks to faucet
points shall be priced per meter. Allow 100m from pump to water storage tanks.
a. b. The ratio of cement: sand: stone for all concrete mixes shall be 2 bags of cement to
2 wheelbarrows of sand to 3 wheelbarrows of stone. All aggregates shall be free
from organic matter, clay and other impurities. The aggregates shall be from an
approved source. Stone aggregates shall have a nominal size of 19mm.
All concrete structures shall be cured for 7 days, starting 24 hours after pour
How to Apply
6.0 Suppliers’ Information Required
6.1 The suppliers should provide the following information and documents together
with their bids:
a. Current Tax Clearance Certificate
b. VAT Certificate
c. Certificate of Incorporation
d. List of the Company’s Directors
e. Lead time
f. Company Profile
g. Current/previous similar works - tenderers must list or attach records of ongoing
projects or those successfully undertaken in the past including 3 referral letters.
7.0 Tender/Bids Submission
7.1 Tender documents should be in sealed/closed envelope and addressed to
The Purchasing Committee
Impact Hub Harare
194 Baines Avenue
HARARE
OR send to the following e-mail address: procurement.harare@impacthub.net
7.2 Tender documents must be submitted before 13:00 hours on 29 November
2024.
7.3 Impact Hub Harare reserves the right to reject any or all submitted bids
