Drilling Of Two Boreholes In Ulyankulu Settlement, Kaliua District, Tabora Region 20 views0 applications

TERMS OF REFERENCE

“DRILLING OF TWO BOREHOLES IN ULYANKULU SETTLEMENT, KALIUA DISTRICT, TABORA REGION”

1. INTRODUCTION

Church World Service is a faith-based organization transforming communities around the globe through just and sustainable responses to hunger, poverty, displacement and disaster. Over 70 years CWS has been responding to the needs of refugees and other vulnerable persons in advancing protection and access to durable solutions. CWS has been working in the area of WASH in East Africa for the last 10+ years. CWS is officially registered as a non-governmental organization with the Government of Tanzania and has a main office in Dar es Salaam and two field offices in Kasulu and Ulyankulu.

CWS seeks to procure drilling services for two water boreholes with high yield among the ten tested points to provide water services to Ulyankulu settlement, Kaliua District Council in Tabora Region. The groundwater studies to earmark potential sites for drilling has been completed and sites identified. The prospective consultant will be handed over with a copy of such findings for the field use. Geological survey technique was used in identifying the visible surface geology of the area and its surrounding, including identification of topography, physical features, soil type, vegetation and drainage, rocky outcrops, strike/dip of rocks etc. CWS will supply the available information of the recommended drilling sites including hydro geological conditions.

1. Geology and hydrogeology

Geologically, the area belongs to the Tanzanian Archean Craton which comprises a series of elongate E to ESE trending outcrops of met sediments and metavolcanics which are intruded by post-orogenic granitoids. Main rock types include banded hematite, quartzite, sericite, talc, laterites, chlorite, corundum schists, hbl- orthogenesis, amphibolite’s and granites.

Groundwater occurrence in hard formation is largely limited to secondary features such as weathered zones, joints, fractured or faults. The potential of weathered zones depends on the degree and depth of saturation and associated fracturing. Correlation from geological logs for the few boreholes drilled at those mentioned area, the surveyed area show that superficial sand and clayey sands are present even at shallow depths. Thus, semi consolidated sand and weathered or fractured rocks are the expected aquifers in the surveyed area. However, the actual quality and quantity of water will be determined only after drilling.

1. Climate, Soil and Topography

The district is relatively homogeneous with gently undulating plains intersected by seasonally flooded valley bottom soil. The soils vary between red lateritic earth grey sand to silt hardpan and iron crust “mbuga”. Moreover, there are sandy clay loams and reddish colored soils on inter flute slopes that are saturated with water within 100cms of the surface during the growing season. The district receives rainfall of between 750mm and 950mm annually, falling between the months of October or November and December and a dry season from January to February or March and a second lower peak occurs in February or March and the rains then tail off in April or sometimes May.

2. Scope of Work

CWS seeks to procure drilling services for two water boreholes with high yield among the ten tested points to provide water services to Ulyankulu settlement, Kaliua District Council in Tabora Region. For this the Contractor shall provide all labour, transport, plant, tools, equipment and materials and appurtenances. The Contractor shall perform all Works necessary to satisfactorily locate sites for drilling, construct and complete successfully drilled boreholes including the cleaning and development of said boreholes, and MUST seal/cap boreholes to prevent the ingress of foreign materials in accordance with this specification and to any further details as may be ordered by the Client. The borehole depths will be dependent on local hydro-geological conditions at the site and recommendations made in feasibility study report. The boreholes will be drilled with a diameter not less than 171 mm for Down The Hole (DTH) and 216mm for mud drilling, completed in UPVC casing and screen of 98.8mm nominal diameter. The contractor shall ensure that standards regarding gravel pack, the screen intervals, yield test, well development, step draw down test in three steps and continue pump testing, sanitary sealing at the top of the borehole, installation of appropriate pump, completed the civil works and disinfection of the bore hole, chemical and biological water quality testing are strictly adhered to. The contractor shall also locate the completed borehole ready for human uses using geographical coordinates in addition to names of villages and number of beneficiaries. Here are the specific activities

1. Bore hole Drilling

The borehole drilling will be done under supervision of the Contractors Hydro geologist/Hydrogeology technician who will collect rock and water samples, record water strikes and drilling penetration rate and advice on final drilling depths, diameter and borehole design. The contractor ought to ensure that borehole logs are collected properly at 1.5m intervals as professionally required. The rig to be deployed must be capable of drilling to at least a depth of 25% beyond the recommended final depth at the final required diameter. Drilling method recommended is Down the Hole (DTH). The drilling diameter should be 8 inches and installed with uPVC pipes of 6’ up to the recommended depth.

1. Borehole construction.
2. The borehole should be drilled at a diameter of 6’’ from 10m to a recommended final depth starting with a diameter of 8’’, 10m deep for each borehole. The plain and screen casings to be used shall be of 6’’ diameter (unless directed otherwise).
3. Construction of the borehole will be undertaken in accordance with accepted practices and will be supervised by Church World Service (CWS and its partners)
4. The contractor will be required to state the type of polymer is going to use, and describe the means by which the selected fluid additive will be mixed.
5. Information concerning the borehole.

The contractor will supply a detailed borehole geo-log data, in which all the relevant information and drilling velocity, well casing and other well construction operations will be recorded. The contractor will also annotate all information pertaining to the appearance of water filtrations and aquifer, types of rock found and sampling details.

1. Casings and diameters.
2. The drilling of the borehole will be carried out according to the characteristics specified in this Tore and BOQ found in annex 1. The use of proper drilling tools, drive pipes, casing pipes with centralizers to ensure that the casing string is central within the hole, gravel packs and sanitary protection (seals) to isolate aquifers from other formations.
3. The contractor will supply all casings and screens of 6’’ diameter including plain casing and screens (annex 1).
4. Pump testing.

Development will be considered complete only when less than 15 ppm of suspended solids remains in the water. The test will consist of continuously pumping the borehole at the maximum yield (or at any other previously defined rate), according to the result of the drilling work. The duration of this pumping will be twenty four hours (24hrs). The measuring of the dynamic water levels will be performed according to the logarithmic time-scale schedule normally used for test pumping water from boreholes.

1. Borehole Protection.

The contractor will take maximum care to avoid the physical, chemical or bacteriological contamination of the borehole water, during the construction and after construction operations. In any case, where water is polluted due to the contractors neglect, he will be obliged to carry out all the necessary operations, at his own cost, in order to rectify such pollution of the borehole.

1. Well sterilization

Once the well has been completed and tested, the contractor will sterilize the well with a chlorine solution yielding at least 50 mg/litre of active chlorine in the borehole. The chlorine solution may be prepared for this purpose, by dissolving Calcium Hypo-chlorite, sodium Hypochlorite or gaseous Chlorine in water. The chlorine solution should stay in the well for at least four hours, at the specified concentration

1. Water samples

The contractor will take two (2) litre samples for laboratory analysis using United Republic of Tanzania recognized Laboratory, after completion of test pumping. One sample will be used for each of these tests; bacteriological, physical and chemical analysis, which should be collected in clean, sterilized properly, sealed and protected plastic containers. The samples so collected should reach the authorized Water Laboratory Technician, within six hours from the time of collection from the borehole.

3. IMPORTANT THINGS TO CONSIDER:

1. The contractor will evacuate all pumped water in such a way that no impoundments are produced at distances less than 200 metres from the borehole. The contractor will provide all necessary elements for this purpose which include provision of all necessary implements and pumping equipment i.e. weirs, pipes, gauges etc. for the proper measurement of discharge rates and water levels and disposal of extracts.
2. The contractor shall execute the drilling works in accordance with the relevant water Laws of the United Republic of Tanzania as they apply in all aspects of the operation including workmanship, quality of the equipment and materials.

iii. The contractor shall apply for the drilling permit from the respective authorities as stipulated in the Laws of United Republic of Tanzania and hand over two copies to CWS before commencement of work in field

1. The contract will apply for permission to enter in the settlements from the Ministry of Home affairs/ Refugees department and solely state personnel and number of days to be spent in the settlements

4. ABANDONED BOREHOLES.

1. If the contractor is not able to finish the drilling or has to abandon the borehole due to loss of tools, accidents or any unforeseeable circumstances, the contractor should remove the casings or drive pipes already in the hole and refill it with clay or concrete. All materials extracted from the hole, after refilling it will be the property of the contractor and all these costs will be to the contractor and not to CWS.
2. Payments agreed rate as per the bills of quantity supported by the contract will only be affected for a successful wells yielding at least 3m3/hr determined from pump testing for a minimum of 24 hrs.

iii. If a dry borehole is being drilled, (yielding less than 3m3/hr.), the contractor will have to drill a new boreholes at his own costs until successful

1. Qualification for the Services

CWS requires borehole drilling company to provide drilling and completion services. The service supplier shall be required to comply with all applicable Tanzania regulations, International Best Practice, and the highest level industry standards related to water well/borehole drilling and completion. The EOI submission should demonstrate the company’s ability to achieve such compliance. The interested companies MUST have the following equipment:

• Water well – borehole drilling rigs (complete with support trucks and equipment).
• Pump Testing equipment
• CCTV for inspection and down hole geophysical logging of boreholes.

The interested companies MUST have experience in:

• Solar submersible pumps, rising main and access for water-level monitoring and water-quality sampling
• Completion of borehole headwork’s and compound, flow meters, storage tanks, community water points fencing and gates.

Interested companies must meet below criteria:

• Must have the Hydro geologist/Hydrogeology technician who will collect rock and water samples, record water strikes and drilling penetration rate and advice on final drilling depths, diameter and borehole design
• Must be registered in Tanzania and majority owned Tanzania Company.
• Must possess all the requisite licenses and valid certifications for water well/borehole drilling and completion services.
• Must have been in operation for a period of not less than three years.
• Must possess an Environmental, Health and Safety Policy Statement & Quality Management.
• Must submit information to demonstrate their technical competency and relevant experience.

How to apply:

Interested companies that meet the above criteria should submit their Expression of Interest to [email protected] cc [email protected] , [email protected] by providing the following information:

• Brief summary of company background and experience in providing similar services
• Supporting documents for above criteria
• A comprehensive disclosure of qualifications and CVs of key personnel engaged on full-time basis, inclusive of organization structure and clear indication of the staff role in the firm;
• Description of at least three (3) similar assignments executed in the last three (3) years. Details to include the contract value, location, outline scope of work;
• Certified copies of firm’s registration certificate and other relevant certification and licenses and details of company directors/major shareholders.
• Certified copies of PIN/TIN and/or VAT registration and a current tax compliance certificate issued by TRA;
• Infrastructural capacity & financial capacity for the proposed service.