THE PROCESS AND COST OF BOREHOLE DRILLING IN KENYA
Kenya is classified as a water deficient country with less than 1000 cubic meters of renewable fresh water supply per capita. 80% of Kenya is classified as Arid and Semi-Arid (ASAL). This water deficiency problem is compounded by climate change that has seen rainfall patterns become increasingly unpredictable. In many parts of the country, it is becoming increasingly difficult to rely on rainfall for commercial and even subsistence production; rainfall when received is either too little or too much for meaningful commercial production. Furthermore, not much investment has been made in dams that would ensure that excessive water is harvested and stored for use during the dry season. This situation has forced many farmers to rely on borehole water for commercial crop and livestock production and other agricultural activities like value addition.
A borehole is a deep hole or shaft drilled into water bearing aquifers in the ground. An aquifer is an underground geological formation able to store and yield water. During drilling, one may come across several aquifers at different depths separated by impermeable layers.
This article is in reference to machine drilled boreholes and not hand drilled shallow wells.
Important considerations before drilling
Borehole drilling is an expensive undertaking. It is therefore important when planning to drill a borehole to get things right from the beginning. The following are important:
- Conduct a hydro-geological survey.
- Obtain requisite permits.
- Make sure that you are dealing with a reputable contractor.
- Engage on the basis of a written contract.
- Make sure that you fully understand the terms and conditions on the contract document.
FREQUENTLY ASKED QUESTIONS
- Is a borehole a good investment?
I always answer this question with a definite YES. A borehole can significantly increase your quality of life, your farming operations, the attractiveness and value of your property/agricultural land and your income. This is especially important in areas where water supply by the City or County Council is limited, unreliable or non-existent which is basically the situation in nearly all parts of Kenya.
Apart from allowing you to live comfortably and farm consistently, innovatively and profitably, a borehole offers other commercial opportunities such as direct sale of water to the neighboring community for domestic and commercial purposes and establishing a water purification and bottling business.
The initial cost of installing a borehole can be expensive but the return on investment and long term saving realized is worth it.
- How deep do I have to drill?
The depth of a borehole can only be determined through a hydro-geological survey. More on hydro-geological survey is covered in another part of this article.
- How much will it cost to drill, develop and equip the borehole?
Determination of cost is a multi stage process. The cost of drilling and casing depends on depth and nature of underlying rock formation. This cost can therefore only be quoted for after a hydro-geological survey has been done. Proper pump selection can only be done after a yield test has been done. Cost of equipping the borehole with a pump can therefore only be done after test pumping has been done. The practice however is to give an indicative cost to enable the client to plan financially. It must however be understood that the final cost may vary slightly from the indicative cost depending on actual findings on the ground. More on cost will be covered on another sections of this document.
- What if the driller does not find water?
This is a question that is perhaps most asked by those intending to drill boreholes. Many people expect that if the driller does not strike water then no payment should be made. However, it is important to appreciate that even with a well done hydro-geological survey, striking water still remains a probability. A hydro-geological survey however greatly increases the chances of striking water but there is usually a slight risk that one may not actually strike water.
Fortunately borehole drilling is a multi-stage process and the first step after the hydro-geological survey is to drill the borehole to the agreed depth. In the remote chance that the hole is found to be dry, the drilling contract should end at this point and the client should only pay for work done to this point which is equipment mobilization and drilling. All other costs that would have been incurred to develop the borehole to completion such as casing and test pumping should not be paid.
- What lifespan can be expected?
So long as recharge of the borehole from ground water does not exceed abstraction, you should always have constant flow of water for you and your future generations.
STEPS – THE DRILLING PROCESS
Borehole construction involves several steps:
- Hydrogeological survey.
- Permit acquisition.
- Casing, gravel packing and development.
- Test pumping.
- Water quality analysis.
- Equipping borehole with a pump.
The first step is to determine where the water is. A geological survey, done mostly using a combination of water dowsing and Vertical Electrical Sounding (VES), is done to identify aquifers and to give a geophysical indication of the underlying area. An aquifer as described earlier is an underground geological formation able to store and yield water.
The points identified through water dowsing are subjected to VES using a Resistivity meter, a device which pushes electrical currents through the ground and measures resistivity.
The data collected is then processed through a process called inversion and the output data obtained is then analyzed. The geologist will also rely on geophysical data of the environment in which the borehole is to be drilled including evaluation of the performance of neighboring boreholes.
Earth resistivity meter set-up in Kisamis by the Geology team
Before beginning the process of drilling, one requires a license from the Water Resources Authority (WRA) and a ‘No Objection’ letter from the local Water Resources Users Association (WRUA). WRA was first established under the Water Act 2002 as Water Resources Management Authority (WRMA) and later WRA under Section 11 of the Water Act 2016. It is the body charged with among other things, regulating the management and use of water resources in Kenya and receiving and processing permit applications for water abstraction, use and recharge.
In instances where the borehole is to be drilled near public facilities like a market or school, it is important to conduct an Environmental Impact Assessment. The report is then submitted to the National Environmental Management Authority (NEMA) for approval.
Drilling is done using specialized drilling equipment known as rigs. The most common method of drilling wells is the rotary drilling method. A drill bit is attached to a string of drill pipes interconnected into a drill string. As the drill string rotates, the drill bit grinds the soil and rocks underneath creating a hole with a specific diameter. Cuttings are flushed out of the hole as drilling proceeds using compressed air or drilling fluid.
It is important to create a log of the different types of soil encountered during drilling. Different soil types have different levels of permeability (ability to transmit water through it). Sand and gravel are very permeable, clay and loam are impermeable while mixed soil is semi permeable.
A rig in operation. Ace Intergrated Services drilling in Muranga. Notice the rotation of the drill string.
Casing and gravel packing
Once drilling is complete, the hole is lined using plastic or steel pipes known as well casing. Casings strengthen the hole protecting it from the risk of collapse. They also act as a sanitary seals keeping the well safe from contamination risks.
Screens are installed in the water bearing sections of the borehole. They allow water to flow into the well while preventing small particles from entering. It is important to record proper drilling logs during drilling as this will be useful in determining the correct depth for placement of screens and gravel packs.
The diameter of the casing is usually smaller than the drilled hole. The space between the drilled hole and the casing is known as annulus and is usually back filled with gravel. Gravel prevents fine sand particles from entering the borehole through the screens and may also serve to prevent the wall of the hole from collapsing onto the well screen which can sometimes happen depending on the geology.
This refers to the act of cleaning out the clay and silt introduced during the drilling process. Flushing increases the rate of water movement from the aquifer to the well. This can be done using compressed air (air jetting) or any other appropriate method available to the driller.
Yield Test (Test Pumping), Pump Selection and Installation
Test pumping, Yield test or aquifer test is done to determine how much water can be pumped from the borehole in the long term without affecting the yield or pumping the borehole dry. Abstraction from the borehole should not exceed natural recharge.
Test pumping involves installing a test pump and pumping the water for a given amount of time while monitoring certain variables. Control of the pumping rate during the test is important as it allows for reliable drawdown data to be collected.
During test pumping, the water level is measured using electric sounding or lighting dipper. It is very important to measure not just the yield but water levels as well. There are three common types of yield tests i.e. step test, constant test and recovery test.
To determine constant discharge, the borehole is pumped at a constant discharge rate over a period that is proportional to the expected yield. The constant testing period can from 8 to 48 hours or even longer.
The data collected during test pumping is analyzed and used to asses and recommend the yield of the borehole. This information is important in determining pump size and depth of placement.
Test pumping in Muranga. A yield of 8,500 liters per hour was realized.
Pump selection: A pump is needed to get water out of the well; electric submersible pumps are normally used. A submersible pump is a pump that can be fully submerged in water; the motor is hermetically sealed and close coupled to the body of the pump. It is important to obtain a pump with the right flow rate and head. The head is simply the vertical difference between the point the pump is positioned and the highest point where the water is supposed to be pumped.
Water Quality Test
Water quality test is important in determining whether the water is suitable for domestic, irrigation and industrial use. A water sample is collected and analyzed in an accredited laboratory.
|WHO DRINKING WATER GUIDELINES|
|Turbidity||NTU||5||Cloudiness of the water|
|Arsenic||mg AS/l||10||Bronchial disease|
|Lead||mg Pb/l||10||Toxicity in animals|
|Selenium||mg Se/l||10||Toxic in excess|
|Aluminum||mg Al/l||0.2||Soluble Al salts cause neuro-toxicity|
|Ammonium||mg NH3/l||1.5||Toxic in aquatic organisms|
|Boron||mg Bo/l||0.3||Toxic to plants in high concentrations|
|Calcium||mg Ca/l||NS||No Standard|
|Flouride||mg F/l||1.5||Dental and Skeletal Fluorosis|
|Iron||mg Fe/l||0.3||High concentrations toxic to children|
|Magnesium||mg Mg/l||0.1||May cause diarrhea in new users|
|Nitrates||mg NO3||11||Infant blue baby syndrome|
|Potassium||mg K/l||NS||No Standards|
|Sodium||mg Na/l||200||Chronic, long term toxicity|
|Sulphate||mg SO4/l||250||Taste, odour|
|Zinc||mg Zn/l||3||Toxicity in excess|
|Total coliform per 100ml||Nil||Contain disease causing pathogens|
|Fecal coliform per 100ml||Nil||Contain disease causing pathogens|
mg/L – Milligrams of dissolved solid in one liter of water.
Powering your borehole
Pumps can be powered using solar, generators or electricity. Electricity is convenient but in areas where there is no electric connection, one can opt for solar or generator as a source of power. Solar can be capital intensive initially but subsequently one gets access to power without recurring monthly bills. With a generator one has to consistently buy fuel, something that can be bothersome and costly. An ideal set up in my view is a set up that combines both electricity and solar allowing for change over when required. Ensure that you get strong solar panels that would generate power even during slightly cloudy days.
Solar panels positioned on top of a tank tower. The panels power the pump which subsequently pumps water into the tank. From the tank the water is distributed to the irrigation channels and the farm houses.
As mentioned earlier, borehole drilling, development and construction requires significant financial investment. The table below shows indicative costs for preliminary investigations, drilling and development of a borehole that is 200m deep.
|MOBILIZATION AND DRILLING OF 200M BOREHOLE – INDICATIVE COST|
|#||Item Description||Unit||QTY||Rate (Kshs)||Amount (Kshs)|
|A2.||Water Resources Authority||Lot||1||5,000||5,000|
|A3.||Water Resources Users Association||Lot||1||5,000||5,000|
|A4.||Follow -up and site visit facilitation||Lot||2||5,000||10,000|
|A5.||Environmental Impact Assessment||Lot||1||30,000||30,000|
|B1.||Mobilization and demobilization of all equipment, material and personnel to site||Ls||1||20,000||20,000|
|B2.||Erection and dismantling of drilling unit on site||Ls||1||20,000||20,000|
|C1.||Drilling at 254mm diameter||M||100||3,100||310,000|
|C2.||Drilling at 254mm diameter||M||100||3,200||320,000|
|D||Supply and installation of materials|
|D1.||Supply and instal surface casing, mild steel.||M||5||3,000||15,000|
|D2.||Supply and instal 6″ Steel casing||M||120||1,900||228,000|
|D3.||Supply of 6″ Steel screen casing||M||80||2,100||168,000|
|D4.||Supply of gravel pack||Ton||8||5,000||40,000|
|D5.||Supply of water for drilling||Ls||1||5000||5,000|
|E||Development and testing|
|E2.||Test Pumping constant Discharge||Hrs||24||2,150||51,600|
|E3.||Water rest level observation||Hrs||2||3,000||6,000|
|E4.||Grout Finish – Top||M||10||1,000||10,000|
|E5.||Water chemical analysis||L/s||1||7000||7,000|
|F||Preparation of borehole completion report and logging of samples at 2m intervals||Lot||1||5,000||5,000|
CARE, CONSERVATION AND SUSTAINABILITY
Access to ground water places a responsibility of care on the shoulders of the user. For the sake of future generations, it is important to jealously protect natural resources and the environment especially our water catchment areas. Boreholes can be complemented with rain water harvesting and storage.
Construct a proper well head that prevents contamination of the borehole. Contaminants in a farm set up can include fertilizers and hydro carbons such as diesel, petrol and engine oil.
Conservation and sustainability
Some conservation measures that can be adopted include:
- Use water conserving irrigation technologies. Drip irrigation technology and automatic irrigation systems that rely on moisture sensors to determine when to irrigate and how much water to apply can go a long water in ensuring proper utilization and conservation of water.
- Combine ground water utilization with other water sources such as rain water harvesting and storage.
- Adhere to regulations and recommendations in regards to ground water exploration and utilization.
YOU NEED A BOREHOLE, WHAT NEXT?
For as long as climate change and unpredictable rainfall patterns remain a problem, boreholes will continue to be a necessity in farming and other industries including real estate development, hospitality and manufacturing.
Lack of water can force one to reduce, suspend or stop production; loose tenants or property buyers and halt manufacturing. It would be unfortunate to have to cut back on your operations due to lack of water. Fortunately, we have the solution.
For more information or to contract us to start the process and work with you in getting your own borehole, please contact us on email@example.com or call +254721681943. CALL NOW and benefit from over ten years of experience in underground water exploration and abstraction.
The writer, Clifton Opala is the founder of Ace Intergrated Services, an Agricultural Services Firm offering end to end solutions to farmers. The firm specializes in Construction of Greenhouses, Shade structures & other Farm Structures; Irrigation Systems Design and Installation; Farm planning, establishment & Management; Ground water identification & Drilling and Farmer Training & Extension Services. The firm also has capacity to design and conduct Baseline and Impact Assessment Surveys for Agricultural Interventions.
P.O. Box 26619-00100 Nairobi