KENYA
In places where a borehole drilling machine is to be used, there is a need to first visit the proposed location of the borehole and determine the road conditions for accessibility of the drilling machine. The visit is done by the contractor who also receives other additional reserve locations by order of preference from the client.
Then two to three sites that are socially acceptable to the communities are selected within the proposed locations. Once they are selected a geological specialist checks the site and determines the feasibility of drilling a successful borehole in that location.
Once the site is selected the appropriate drilling method chosen. The contractor may use any drilling technique that he feels is able to achieve the depth and diameter required. The most preferred drilling method is rotary percussion.
The borehole should be drilled at least six meters below the water bearing layers that the contractor shall know whether the borehole should be abandoned or drilled deeper.
During drilling a sample of the strata penetrated is collected after every two meter’s drilled and stored in a place where they cannot be contaminated. Some of the water drilled is used by the drilling team in the campsite. How this water is obtained, stored and pumped is determined by the contractor.
The design of the borehole can either be open hole, protected borehole in collapsing rocks with a 10’’ Surface casing and will be cased with 6’’ Dia 4mm steel plain and screen pipes with artificial gravel pack. The choice is made by the supervisor of the whole construction with the help of the contractor.
Upvc Casings can also be installed but that will be done on the formation of the ground and water quantity.
Once the borehole is drilled and lined, a pump test is done. The 24Hrs pump test is used to access the volume of water the borehole can produce and the speed at which it is produced. Once this is done the water from the borehole is tested and the chemical and bacterial content is determined to show if the water is suitable for consumption.
After the test pumping is complete we shall know what kind of Submersible Pump that can be installed to the borehole. If the water quantity is low the recommended pump will be a small sized i.e. 2m 3 to 4m3 and if the water quantity is high the pump that will be recommended shall be from 5m3 to 10m3 or more.
Over head water tank can be installed its upon the client if he/she wants a steel tank, plastic tank or concrete tank.