Boreholes: What is a borehole?
A borehole is basicaly a hole that is drilled into the earth, from which water can be extracted. There are two basic types namely:
Sand boreholes are drilled in sandy areas usualy down to a maximum depth of about 40m.These holes are usualy high yeild holes and are ideal for production applications, such as farms , nurseries etc. These holes are usualy sleeved with 160mm PVC pipe to prevent the hole from collapsing and to allow for a solid structure inside wich the pump is inserted, down to the desired depth.
These boreholes cover the other side of the borehole spectrum.These holes are drilled anywhere from 30 to 300m, depending on the area in which they are situated.
In the case of these boreholes, a hole is drilled from the surface until the rock layer is met, using the "mud rotary technique".From this point on " percussion " drilling is used to drill into the rock to the depth required. Once this final depth is reached, the drilling rods are removedand a steel sleeve is inserted into the hole and hammeded into the rock to seal the hole and to prevevt the sand/clay from falling into the hole. Once this is done the hole can be cleaned and a capacity test can be performed on the hole to test the yeild performance. In some instances on in the case of old boreholes, it may be advisable to sleeve the hole with a PVC lining.Between the steel and pvc linings filter media is installed to filter the incoming water.