Borehole Drilling Processes and Procedures in Kenya

Environment Policy That Guides The Drilling Business

Environment Management and Co-ordination Act, 1999

This Act came into force on 14th January 2000. It aims at coordinating environmental protection activities in the country. In its preamble, the Act states that every person in Kenya has a right to a clean and healthy environment. According to section 58 of the Act (EMCA) No. 8 of 1999, second schedule 9 (i), and the environmental (Impact Assessment and Audit) Regulations, 2003, all new enterprises and projects must undergo Environmental Impact Assessment (EIA). The EIA study report is submitted to the National Environment Management Authority (NEMA) in the prescribed form.

 

Health And Safety Measures
The Occupational, Safety and Health Act, 2007
PART VII – Machinery safety

55. All plant, machinery and equipment whether fixed or mobile for use either at the workplace or as a workplace, shall only be used for work which they are designed for and be operated by a competent person.
56. (2) Every part of an electric generator, motor and rotary converter and every flywheel directly connected thereto shall be securely fenced.
57. (3) Every machine intended to be driven by mechanical or any other type of power shall be provided with an efficient starting and stopping appliance, the control of which shall be in such a position as to be readily and conveniently operated by the person operating the machine
(58) Suitable striking gear or other efficient mechanical appliances shall be provided and maintained and used to move driving-belts to and from fast and loose pulleys which form part of the transmission machinery and any such gear or appliances shall be so constructed, placed and maintained as to prevent the driving belt from creeping back on to the fast pulley.
59 (1) Every employer shall;
(a) be responsible for the safe condition of tools and equipment used by his employees, including tools and equipment which may be furnished by the employees
(b) ensure that no equipment or portable power tools shall be used in an environment that contains or is likely to contain flammable vapours or substances unless they are intrinsically safe for such environments
61 1) Where any machine in a workplace is a machine intended to be driven by mechanical power;
(c) every set-screw, bolt or key on any revolving shaft spindle, wheel or pinion shall be so sunk, encased or otherwise effectively guarded as to prevent danger, and,
(d) all spur and other toothed or friction gearing which does not require frequent adjustment while in motion shall be completely encased.

 

Sitting Of The Borehole (Hydro-Geologists/Site Investigations)
Geophysical Investigations Methods

i). Overview

A great variety of geophysical methods are available to assist in the assessment of geological subsurface conditions. The Water Resources Management Rules 2007 require that a section of the survey report is devoted to an explanation of the geophysical methodology used. The selected method is based on electrical resistivity, applying the principle of Ohm’s Law and detects vertical or lateral changes in ground resistivity. Since resistivity is a function of the state of weathering of the rock strata and is proportional to occurrence of interstitial water, the observed variations are used to determine the occurrence of water-bearing layers below ground level.

ii). Resistivity Method
a). Basic Principles

The electrical properties of rocks in the upper part of the earth’s crust are dependent upon the lithology, porosity, and the degree of pore space saturation and the salinity of the pore water. Saturated rocks have lower resistivity than unsaturated and dry rocks. The higher the porosity of the saturated rock the lower its resistivity, and the higher the salinity of the saturating fluids, the lower the resistivity. The presence of clays and conductive minerals also reduces the resistivity of the rock.

The resistivity of earth materials can be studied by measuring the electrical potential distribution produced at the earth’s surface by an electric current that is passed through the earth.
In conventional resistance, a specified current is injected into the ground using probes connected to a DC power source (Figure a). The resulting measured voltage is used to calculate the ground’s resistance to current flow by Ohm’s Law:
R = V/I, (1)
where R = resistance, V = voltage, and I = current
Resistance will vary depending on the distance and geometry between the probes so it is normalized with the addition of a geometric factor that converts the measurement to apparent resistivity, ρa, (expressed in ohm-meters):
ρa= 2π a V/I, (2)
for equally spaced galvanic electrodes (what is referred to as the Wenner array).

Figure a. Illustration of the theory behind field resistivity survey

There are two approaches to acquiring geo-electric resistivity data – either through a one-dimensional vertical electric sounding (VES) or horizontal electric profiling (HEP).

b) Horizontal electric profiling (HEP)

This is carried out to determine changes in electrical properties laterally with constant electrode spacing and interpreted as a continuous profile. The electrode spacing controls both the profiling depth and the resolution of the survey. The observed resistivity values are plotted on logarithmic paper and the graph obtained depicts lateral resistivity variation at constant depth. Geological structures such as faults, fractures, buried stream channels that may conduct groundwater, can be inferred.
c) Vertical electric sounding (VES)
This approach is used to investigate changes in ground layers below a fixed position. The array begins with small current and potential separation, which is increased gradually according to the selected array arrangement as described above. Half the length of the current electrode separation is theoretically the depth of investigation, if the Schlumberger array is used. However, due to effects of suppression, current scatter and damping factors, the effective depth of investigation is usually a fraction of the actual half-current electrode separation.

 

Borehole Drilling Process
Simply put, below is the recommended borehole drilling procedure:

i. A hydrogeological and geophysical survey is carried out by qualified hydro-geologist in order to understand the stratigraphy of the underlying aquifers, optimize the drill depths and prospect the presence of water and the anticipated yield of water within the project site. This is subsequently succeeded by compilation and documentation of the findings in a report that is later submitted to The Water Resources Authority for approval and issuance of a drilling authorization permit that approves of the client, in this case-the proponent, to drill the proposed borehole at the recommended site and depth.
ii. A NEMA lead expert carries out An Environmental Impact Assessment, compiles the findings in a report and finally submits the report to NEMA. Upon approval of this, the proponent is issued with a permit allowing him/her to implement the project taking the recommended mitigation measures to counter the negative impacts resulting from the project implementation.
iii. Both of the above outlined permits having been issued by the relevant authorities, the client can involve the services of a contractor to start drilling. Typically, a drilling may take 2-5 days depending on the type of formations encountered and the depth below ground level. Drilling also involves casing of the borehole and adding the gravel pack.
iv. This is followed by borehole development which is basically cleaning of the borehole.
v. Borehole test pumping is done to establish the yield and the long term sustainability of the facility.
vi. Water samples are taken for water quality analysis.
vii. Equipping of the borehole with an electric pump is done. The pump is connected to an electric system which is operated from the control panel at the surface.

Drillers may sink a borehole using a drilling rig or a hand-operated rig. The machinery and techniques to advance a borehole vary considerably according to manufacturer, geological conditions, and the intended purpose.

During the drilling, geological rock samples are to be collected progressively at a 2m interval and logged. The contractor records water struck and water rest levels. The contractor shall be held solely and entirely responsible for the completion and the safety of the works and shall indemnify the proponent against all claims that may arise as a result of carrying out the works. The project geologist may stop the drilling operations if in his own opinion sufficient water supply has been obtained or formation is unfavorable to drill further.

Drilling Procedure
1. Geological survey
This is an assessment of the geographical landscape and composition of the ground, which ascertains the location and depth at which the water drilling should take place.
2. Mobilization of drilling equipment
This is done once payment has been settled. Our drilling equipment is mobilized from our operations site to the drilling site.
3. Drilling and installations

Upon getting to the site, our rig locates the area identified by the hydro-geologist as suitable for drilling. The machine uses a rig and a hammer to penetrate the ground, and rods which further push the head of the drill towards the ground.
The penetration continues until the drill reaches the required depth. The drill usually passes through a water bearing formation as it drills. Casing of the borehole is usually done after the required depth is reached.
A borehole is usually cased with steel casings to prevent the walls of the borehole from collapsing and impurities from entering the borehole water.
A gravel pack is inserted on the lining of the casing to enable additional filtration of the borehole. A submersible motor is usually filled to pump the water from the borehole.

4. Testing
This is a chemical analysis of the borehole water to determine its suitability for use. This is usually a 24-hour process.
5. Securing the borehole
Top slabs are inserted and a cap is usually placed on the borehole.
6. Water collection
As per the client’s requests, we can also build a water tower and install steel/plastic tanks, along with the required piping.

Cost Of Water Drilling In Kenya

Our Business Development Unit personnel are highly professional and the cost of the borehole and breaks down the cost to enable you to understand the final quotation. Our prices are highly competitive in the market. Our team is well qualified in executing the job with diligence and in a timely manner. We strive to ensure that we exceed your expectations and leave with the best quality possible.
The cost of the borehole is dependent on many factors. Some of the factors put into consideration before issuing a customer with a quotation are:

1. Geology
The geology or rock formations are affect the amount of time and resources used in drilling the borehole. Some terrain might be too soft, causing the borehole walls to collapse in by itself – this creates difficulty in casing and removal of the borehole equipment.
On the other hand, some boreholes might contain hard rock, which takes a longer time to penetrate.
Our drillers are well-versed with all types of formations and employ various methodologies to overcome the various types of geologies. All these risks are factored into the cost of the borehole.
2. Location
The location/distance of the borehole from our operations site affects the cost of mobilizing the equipment to the site of the borehole.

3. Size of the borehole
Upon advice from a hydro-geologist who has done the initial survey, we work upon a recommended depth of how the borehole should be. This is usually charged in meters.
4. Cost of lining and packaging the borehole
We charge per meter to case the borehole, using either steel or plastic casing. The lining of the borehole is essential to prevent the walls from collapsing or impurities entering the water. We also insert a gravel pack along the sides of the casing to enable water filtration.
5. Pumping system
We install a submersible pumping system the type of the pump to be installed is determined by the depth of the borehole, the flow and pressure of water.
6. Water analysis

A chemical analysis is conducted on the water to assess the contents of the water. This gives an indication of the suitability to use. Some of our boreholes have had such pure contents that the water has been bottled for sale while numerous other boreholes are used for domestic purposes, construction or commercial purposes. Our detailed water analysis is an assessment to ensure that our customers have the right quality and quantity of water to serve their needs.