847_BOREHOLE_TECHNICAL_SPECIFICATIONS.pdf

TECHNICAL SPECIFICATIONS

1. DRILLING, INSTALLATION, DEVELOPMENT AND TEST PUMPING OF ONE

PRODUCTION BOREHOLE AND EQUIPPING IT WITH PERMANENT PUMPING

SYSTEM ALONG KIAMBU ROAD (RIDGE WAYS) NAIROBI ( FBO 847)– CLIENT:

AMERICAN EMBASSY, NAIROBI

The scope of the Works is to drill one production borehole, steel casing work, install, develop, test pump and equip it with a permanent pumping system. The site is located along Kiambu

Road, Ridge ways Estate, Nairobi. The borehole will be drilled to a depth determined during the geological measurement (about 350m). Installation will be with mild steel casings and screens.

The minimum hole diameter shall be 8".

All the materials and equipment installed within the permanent works shall be non-toxic and of high quality.

1.1 DRILLING SITE AND CONDITIONS

The Contractor shall drill the borehole at the exact location designated by the client through

Contract Officer Representative (COR). The “Project Area” (also defined as the “site”) is here defined as the area within the Warehouse compound (FBO 847) along Kiambu Road, Ridge ways Estate Nairobi.

While access is deemed to be convenient for heavy machinery, it will remain the Contractor's final responsibility to inspect the site and confirm the accessibility for his equipment prior to commencement of work.

The project area is situated in Nairobi Area. Geologically, the area is characterised by Tuffs, trachytes, phonolites, weathered tuffs, Athi Series and Lake Beds hence drilling conditions are considered to be moderate but owing to the anticipated deep drilling depth, the drilling equipment employed should have a capacity to drill successfully to the recommended depth and diameter.

Drilling conditions are not expected to be difficult, even though the Contractor should be prepared to deal with unstable, collapsing formations.

1.2 ENVIRONMENTAL PROTECTION OF THE SITE

Care must be taken in the handling and storage of all drilling fluids, oils, greases and fuel on site, to avoid any environmental degradation. The Contractor shall dispose of any toxic materials, drilling fluid and other additives, cuttings and discharged water in a manner approved by the

Employer or his Supervising Engineer so as not to create damage to public and private property.

1.3 WORKMANSHIP

The Contractor is expected to carry out all works as instructed by the client or his Supervising

Engineer in a thorough and workman-like manner, and up to international professional standards;

he shall carry out operations with the due efficiency and dispatch in accordance with the terms of the contract and to the satisfaction of the Supervising Engineer. For this purpose the Contractor shall use suitable machinery and gear, and supply efficient and experienced staff.

1.4 EQUIPMENT PROVIDED BY THE CONTRACTOR

All machinery, equipment and materials to carry out the drilling, installation, development, headworks construction, etc. as specified in BoQ, are to be mobilized to the site. The drilling rig should be capable of attaining a depth of over 330 metres at a minimum diameter of 8 inch, by means of direct rotary (with foam or biodegradable polymer) and/or air hammer techniques. No works shall be certified and no payment shall be made if the Contractor fails to reach the stipulated depth due to evident shortcomings directly related to his equipment, supplied materials, drilling consumables, personnel or applicable drilling techniques.

Test pumping equipment should be independent from the drilling rig. The test pump should be capable of providing at least a yield of 15 m3/hr at a head of about 200metres to avoid under-testing the borehole. Alternative test pumping plant is subject to approval from the Employer Supervising Engineer.

At the start of the contract, the Employer/ Supervising Engineer will verify the specifications and state of repair of all major items of plant. He shall have the right to order the removal and/or replacement of any plant, which in his opinion is insufficient or unsatisfactory.

1.5 SUPERVISION OF CONTRACT

The Contract is to be supervised by the Employer's representative or appointed Supervising

Engineer.

1.6 BOREHOLE DEPTH AND DIAMETER

The envisaged borehole depth is approximately 330 metres, while the drilling diameter should not be less than 203 mm.

The Contractor shall however drill to the total depth and at such diameter as will be instructed by the Client or the Supervising Engineer. No borehole will be acceptable if drilled to such depth and diameter other than instructed by the Employer or his appointed Engineer.

1.7 DRILLING METHOD

The Contractor is obliged to make exclusive use of rotary drilling with foam or biodegradable mud and/or the air hammer technique. Percussion drilling shall not be accepted. The Contractor shall submit a detailed account of his proposed drilling method, additives etc. for approval by the

Employer/ supervising engineer.

1.8 SAMPLING

Representative, continuous samples (min. 200 grams) of the strata penetrated shall be collected for each 2 m interval and by whatever method is standard for the drilling technique in use and approved by the Supervising Engineer. The Contractor shall take every possible precaution to guard against sample contamination. Samples are not to be washed! The samples shall be put into suitable sample bags, labeled with the depth interval, and stored in a position where they will not be contaminated by site conditions or drilling operations. Any water struck level and estimated airlifted yield should be recorded on the sample bag with the corresponding geological log. Geological logging will be the responsibility of the Supervising Engineer.

1.9 TEMPORARY CASING

Installation and diameter of any temporary casing required for the construction of the borehole will be left to the Contractor so long as the finished product meets the specifications. Cost for supply, installation and removal of temporary casing shall be borne entirely by the

Contractor, should it not be included in his Method Related Charges. However, any casing left in the borehole, which is not retrievable, cannot be claimed by the Contractor.

1.10 WATER SUPPLY FOR DRILLING

The Contractor shall make his own arrangements for obtaining, storing, transporting and pumping of water, required for drilling purposes and for personal use by the drilling crew. The

Client, therefore will not pay for water supply, and it is assumed that all associated costs are covered in the quoted contract sum.

1.11 BOREHOLE DESIGN

Design of the borehole shall be made by the Supervising Engineer in consultation with the

Contractor after drilling is completed.

1.12 CASING AND SCREENS

Shallow aquifers down to a depth of approximately 180m or any other appropriate depth (based on water struck levels) as it may be decided by the supervising Engineer in conjunction with the contractor will be sealed off using plain casing and bentonite to avoid any hydraulic interference with the surrounding nearby boreholes with regard to WRMA regulations. Other aquifer zones shall be completely or partly lined with high quality 6" mild screens as it may be applicable.

The strength and wall-thickness of the 6" casings and screens should be sufficient to install the casing line to the desired depth. The Contractor shall be fully responsible for the quality and the proper installation of the casings and screens. The screen open area shall not be less than 5%, while the slots shall be uniform, and not wider than 1.5 mm. The casings and screens must be centralized in the borehole so that a minimum 1" (25 mm) annular space exists between the borehole wall and the casing.

1.13 VERTICALITY

If required by the Supervising Engineer the 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 Supervising Engineer, without additional payment. If the error cannot be corrected, then drilling shall cease and a new borehole will be drilled at a position nearby, indicated by the Supervising Engineer. The abandoned borehole shall be backfilled and/or capped by methods approved by the Supervising

Engineer. No payment will be made for the drilling and the sealing of abandoned boreholes, or for moving to the new site.

1.14 GRAVEL PACK

Suitable gravel-pack shall be supplied by the Contractor. Prior to delivery, samples of the gravel pack shall be analyzed for grain size and approved by the Supervising Engineer. Gravel should consist of washed, well-rounded particles of a uniform grading. The gravel shall contain not less than 90% siliceous material and contain no clay, shales, silt, fines, or excessive amounts of calcareous materials or crushed rock. In terms of grain size, 90% shall conform with the grading specified and the Contractor shall be required to submit samples of the material prior to installation for approval by the Supervising Engineer. Sufficient gravel-pack shall be installed to cover completely the uppermost screen, plus an additional length of not less than 15 m (to allow for settling).

The gravel-pack should be capped with a bentonite clay seal (minimum thickness 3 metres) 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.

1.15 SANITARY SEAL

To provide an effective seal to the entry of contaminants, the upper 3 meters of the borehole will be grouted using cement slurry 1.85 - 2.15 kg/liter. Grout is to be injected into the annulus between the casing and the wall of the hole, by a method to be approved by the Engineer.

1.16 YIELD ESTIMATES DURING DRILLING

When rotary-drilling method is used, either a water meter or a 90-degree V-notch flow measurement device or a drainpipe shall be permanently set up in an approved manner and level, so that continuous monitoring of airlift yields can be obtained. Average yields shall be read and rated every 3 meters of penetration and as otherwise directed by the Supervising Engineer, and recorded in the driller’s log. Care should be taken to ensure that the flow of water through the meter, over the V-notch or through the drainpipe is not impeded by debris.

1.17 DEVELOPMENT AND CLEANING OF THE BOREHOLE

Development and cleaning of the borehole shall be carried out by the Contractor upon completion of the drilling and installation of casing. 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 will probably be necessary.

The method proposed by the Contractor for development of boreholes shall be submitted to the

Supervising Engineer in writing for his approval. Development of the 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 Supervising

Engineer. Upon completion of development, any accumulation of material shall be removed from the bottom of the borehole by airlifting.

1.18 TEST PUMPING

The Contractor shall perform test pumping to establish well performance and yield of the borehole. A test pumping unit shall be provided for the testing of the drilled borehole, which should include a submersible pump with a minimum capacity of 15 m3/hr at a head of about 200 metres, a suitable control panel, generator, rising main, electrical connections, and all other ancillary equipment required to carry out the specified tests.

Standard test pumping will consist of a 4-hour step-drawdown test, followed by a constant discharge test for a period of 24 hours. The latter may be extended at the discretion of the

Supervising Engineer, e.g. if the water level has not stabilized after the 24 hours. The Contractor shall provide a suitable means of achieving and maintaining the rate of flows specified.

Before testing, the borehole will be subject to a short-term test (calibration) to establish the approximate yield/drawdown properties and to decide upon pumping rates for step-drawdown or continuous yield tests. Sufficient time shall be allowed for the recovery of water level in the borehole between each type of test. This shall be at the discretion of the Supervising Engineer.

Discharge measurements shall be made by using a flow meter or otherwise approved calibrated measuring device. During test pumping, the discharge water will be diverted in an appropriate manner over a distance of at least 50 m downslope from the wellhead. This condition may not be required when the pumped aquifer is confined.

During all testing operations, once the flow rate has been determined and preliminary adjustments made, the measured discharge rate shall be maintained within 15% of the required rate for the duration of the test. Persistent fluctuations beyond this tolerance will require abortion of the test, for which payment shall not be made.

When continuous pumping at a uniform rate is specified, failure of the operation for a period greater than one percent of the elapsed pumping time shall also require abortion of the test.

Any test, which is aborted due to the reasons above, shall be repeated after recovery of the water level. No payment shall be made for aborted tests or for standing time during water level recovery after aborted tests.

1.18a STEP DRAWDOWN TEST

At the discretion of the Supervising Engineer, the Contractor will conduct a step drawdown test of not less than four-hour duration. The well shall be pumped at a minimum of four separate discharge rates specified by the Supervising Engineer. Each step shall have duration of at least one hour.

The change from one pumping rate to the next shall be effected without stopping the pump by means of a gate valve in the discharge pipe, or by any other means to be approved by the

Supervising Engineer. The change from one step to the next shall take place in the shortest time possible. Water discharge measurements shall be taken at appropriate time intervals as instructed by the Supervising Engineer, while at the same time EC readings are to be taken.

1.18b CONSTANT DISCHARGE TEST

At the discretion of the Supervising Engineer, a constant discharge test will be carried out for a maximum pumping stage of 24 hours, followed by a maximum of 24 hours of recovery observations. The discharge rate shall be specified prior to the test. During the test, water level and discharge measurements shall be made at time intervals specified by the Supervising

Pumping test data shall be supplied to the Supervising Engineer from all pumping tests conducted at the borehole. These will show dates, water levels, discharge rates, electrical conductivity values, times of starting and stopping the pump, changes in discharge, weather, and other conditions that could affect the test data.

1.18 WATER LEVEL OBSERVATIONS

The Contractor shall supply appropriate electric contact water level gauges for measuring water levels in the borehole to the nearest 10 mm at pre-determined intervals. The length of the electrical dipper shall be capable of reaching a depth of 300 metres. Wellhead arrangements shall permit these gauges to be inserted and passed freely. Hereto the Contractor shall be required to install a dipping tube, minimum 3/4" inner diameter, lowered to approximately 2 metres above the pump intake or the anticipated maximum drawdown level.

Other methods for measuring water levels are subject to approval by the Supervising Engineer.

1.19 ELECTRICAL CONDUCTIVITY MEASUREMENTS

The Contractor shall have an operational EC-meter on site to take electrical conductivity readings whenever required during drilling, development and test pumping.

1.20 RECORDS

Daily activity records for the borehole shall be kept by the Contractor. The records shall contain the information as specified below.

i) Daily Record

- Site name

- Reference number of borehole

- Dates of reporting

- Names of foreman and driller

- Method of drilling

- Diameter of hole, and depth of changes in diameter

- Depth of hole at start and end of shift or working day

- Depth and size of casing at start and end of shift or working day

- Description of rocks drilled with depths of transitions encountered

- Depth at which water is struck

- Yield of air lifted water, when drilling or developing with air

- Time log showing rate of penetration in minutes per metre, type of bit, standby time due to breakdown

- Depth intervals at which each formation samples are taken

- Records of components and quantities used or added to the drilling fluid or air

- Water level at the start of each working day

- Electrical conductivity measurements

- Problems encountered during drilling

- Details on installation in the borehole (if any).

- Depth and description of well casing

- Depth and description of well screens

- Details of work to be invoiced at hourly rates (e.g. test pumping)

A copy of the daily drilling record shall be made available daily, including any other pertinent data as may be requested by the Employer or his Supervising Engineer.

ii) Borehole Completion Record

- As per standard borehole completion form.

- Detailed driller's log.

- Copy of standard chemical water quality test

- Borehole design and installation details (as-built drawing)

A copy of the Borehole Completion Record shall be made available to, and approved by the

Supervising Engineer on completion of the borehole. Three copies of these Records shall be forwarded to the Supervising Engineer for final submission to the Employer.

1.21 WATER SAMPLING

The borehole water will be sampled for both chemical and bacteriological lab analyses.

Water samples for testing the chemical water quality will be taken at the end of test pumping.

The Contractor shall keep on site a minimum of 5 suitable one-litre capacity water containers and shall collect and store water samples as directed by the Supervising Engineer. The

Contractor shall, within 24 hours from the sampling time, deliver the sample(s) to a recognized certified laboratory (such as the Government Chemist, or equivalent) for full chemical analysis.

Water Sample for bacteriological analyses shall be submitted to a recognized lab as above or any other appropriate lab within 6 hours after sampling. This sample will be taken after the borehole has been completely installed.

1.23 CAPPING THE BOREHOLE

During borehole construction, installation, development and test pumping, the Contractor shall use all reasonable measures to prevent entrance of foreign matter into the borehole. The

Contractor shall be responsible for any objectionable materials that may fall into the borehole and any effect it may have on water quality or quantity until completion of the works and acceptance by the Supervising Engineer or the Client.

1.24 ACCEPTANCE OF BOREHOLE

The borehole shall only be accepted by the client/Supervising Engineer upon satisfactory completion of all drilling operations, installation of casing and screens, development works, test pumping and wellhead construction.

1.25 LOSS OF EQUIPMENT

Any equipment lost down a borehole must be removed or the borehole will be considered a lost bore. A replacement borehole will have to be constructed and test pumped at the Contractor's expense.

1.26 LOST BORE

Should any incident to the plant, behaviour of the ground, jamming of the tools, or casing, or any other cause prevent the satisfactory completion of the works, a borehole shall be deemed to be lost. No payment shall be made for that bore or for any materials not recovered therefrom, nor for any time spent during drilling or while attempting to overcome problems. In addition, the borehole should be permanently sealed.

In the event of a lost bore, the Contractor shall construct a borehole immediately adjacent to the lost bore or at a site indicated by the Client/ Supervising Engineer. The option of declaring any bore lost shall rest with the Contractor, subject to the approval of the Supervising Engineer.

The abandoned hole shall be treated as follows:

a) The Contractor may salvage as much casing and screen from the initial borehole as possible and use it in a new borehole if not damaged, with the approval of the Supervising Engineer.

b) Salvaged material shall remain the property of the Contractor.

c) The borehole shall be backfilled to a level of 8 m bgl with inert material (e.g. drill cuttings), followed by a 6 m long plug of concrete, cement grout, or neat cement.

d) The upper 2 meters of borehole shall be backfilled with native topsoil. Sealing of the abandoned boreholes shall be done in such a manner as to avoid accidents and to prevent it from acting as a vertical conduit for transmitting contaminated surface or subsurface waters into the water bearing formations.

1.27 STANDBY TIME

Standby time is here defined as the time during which the whole of the drilling equipment and

Contractor's staff are available on site for the execution of the Contracted Works, while no operations can be carried out as a result of action or inaction by the Employer or his

Representative for a period longer than one working day (10 hours).

In the event of delays occurring for which the Contractor would be entitled to claim Standby

Time, the Contractor should notify the Supervising Engineer immediately in writing that such claims are becoming applicable.

1.28 CONSTRUCTION OF WELL HEAD COVER AND APRON

The Contractor shall on completion of the borehole cap the top with a mild steel blank flange, which shall incorporate a threaded nipple of 19 mm (3/4") diameter with cap, welded to the flange, to enable dipping access to the borehole. The blank flange shall be 300 to 400 mm above ground level and be bolted to a mild steel flange welded to a minimum of 2 m length of 10 to 12” mild steel casing coated internally and externally with non-toxic or bitumen or epoxy coating to the approval of the Supervising Engineer. This casing shall fit neatly over the borehole casing and be permanently grouted in at the time of completion of the borehole. Prior to, during and after the construction of the headwork, the Contractor must ensure that no debris whatsoever falls into the borehole.

Any additional/alternatives to the headworks completion may be determined after the borehole has been drilled/installed as it may be preferred by the Employer/Supervising Engineer.

1.29 WELL DISINFECTION

The Contractor before demobilization from the site shall carry out disinfection of the borehole(s).

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.

1.30 CLEARING THE SITE

On completion of the borehole the site must be left clean and free from all debris, hydrocarbons and waste, and all pits filled to the satisfaction of the Employer/ Supervising

Engineer. A site not delivered clean may render the borehole unacceptable.

2. PERMANENT PUMPING SYSTEM

From the test pumping data, a suitable submersible pump will be selected for permanent installation together with all other pumping plant accessories detailed in the BOQ or as it may be requested by the client. An appropriate control panel for the selected pump will also be installed.

All items to be installed should be subject to confirmation and approval by the Supervising

All items will be of high quality, and suitable to function properly in tropical conditions. Spare parts of the equipment to be supplied and installed shall as much as possible be available in

Kenya. The Contractor shall furnish the Supervising Engineer and the Employer of the addresses of the Suppliers of such spare parts.

The proper functioning of the installed pump will be tested by the Contractor or his

Representative in the presence of the client/Supervising Engineer.

3.0 COMPLETION CERTIFICATE

On satisfactory completion of the Works, the Employer through his Supervising Engineer shall issue a Completion Certificate within 14 days from acceptance and handing over. The Defects

Liability Period shall be effective from the signing date of the Completion Certificate. This will be expounded further in the conditions of the drilling contract document.

4.0 LIABILITY

The Contractor will be liable for all consequences resulting out of negligence or other misconduct on his part or on the part of his employees. The contractual liability of the Contractor shall terminate upon the final acceptance of the borehole and final demobilisation, but the

Contractor shall continue to be liable for any claims, damages, costs and awards arising from defective workmanship, negligence or misconduct or that of his employees.

4.1 DEFECTS LIABILITY PERIOD

The Contractor shall continue to be held liable for defective workmanship detected in the drilled borehole for a period of six months after completion of the borehole concerned. This represents the period during which the Employer or his appointed representative may instruct the

Contractor to execute such work of amendment or reconstruction and the repair of all defects or other faults for which the Contractor is deemed responsible, fair wear and tear excepted.

In case of default on the part of the Contractor in carrying out such instruction within a reasonable time, the Employer shall be entitled to employ and pay other persons to carry out the same and if such work is work which in the opinion of the Engineer, the Contractor was liable to do at his own cost under the Contract, then all costs consequent thereon or incidental thereto shall, after due consultation with the Employer and the Contractor, be determined by the

Engineer and shall be recoverable from the Contractor by the Employer, and may be deducted by the Employer from any monies due or to become due to the Contractor and the Engineer shall notify the Contractor accordingly, with a copy to the Employer.

If any defect or other fault in the works appears at any time prior to the end of the Defects

Liability Period, the Engineer may instruct the Contractor, with a copy to the Employer, to search under the directions of the Engineer for cause thereof. Unless such defect or other fault is one for which the Contractor is liable under the Contract, the Engineer shall, after due consultation with the Employer and the Contractor, determine the amount in respect of the costs of such search incurred by the Contractor, which shall be added to the Contract Price and shall notify the Contractor accordingly, with a copy to the Employer.

This provision is subject to the understanding that no third party attempts to rectify any operational problems that may occur in the borehole, the submersible pump or the control panel during this six months period.