The drilling and construction of the borehole
Once the drilling authorization is obtained, the next phase is the actual drilling of the borehole. Many people are under the mistaken impression that when you simply drill, there is an immediate endless supply of water. There is a lot that needs to happen before this occurs. There are many drilling options available, but the general drilling method, a pneumatic hammer is operated at the end of the drill pipe and rapidly strikes the rock, while the drill pipe is slowly rotated. Shattered splinters of rock are removed from the borehole continuously by the air used to drive the hammer. This drilling process is noisy and can become dusty, muddy and very messy. Standard domestic boreholes are initially drilled at 215mm in diameter through topsoil and weathered overburden rock (the depth may vary depending on the actual level at which the most water is found). This facilitates the installation of steel casing of 153mm. Casing is usually only required through the unstable overburden. However, we recommend that all our boreholes be cased from top to bottom. The drillers will line the borehole with a slotted liner at lower levels to allow water to percolate and a solid liner near the surface to prevent migration of surface water into the well.
On satisfactory completion of the borehole construction works, we use the compressor to carry out physical development works using an air-lifting method with occasional addition of biodegradable polymer or as will have been specified in order to achieve the desired goals of producing clean sediment-free water and improving aquifer permeability. Chemical development depends on the basis of observations made during drilling by the Supervisor. Calgon (Sodium hexametaphosphate) used as a dispersing agent to break down clay and other soil types is injected and allowed to settle in. After a little while; we use the air compressor to clean out the borehole using the air-lifting method. A concrete slab is finally constructed at the well head to act as a sanitary seal and to give the borehole works a neat finishing as well. Its size and thickness is dependent on the nature of the soil around the borehole.
Photo courtesy of Pump Africa
Determining the yield of the borehole /Test pumping. The accurate yield of a borehole can only be determined by means of an aquifer test. This test involves installing a test pump and pumping the borehole for a period of time at a given rate, while recording the lowering of water level in the borehole. The maximum yield of a borehole is achieved by increasing the abstraction rate to a yield, resulting in the maximum drawdown of water in the pumping borehole.
Potable water test/Lab analyses A water sample is taken at the end of the aquifer testing for delivery to a credible laboratory. This will give you a breakdown of the chemical and bacterial parameters within the water, from this any additional water treatment equipment, if necessary can be recommended
Reports Submission Once construction is complete, the driller will issue a Borehole Completion Report with the Test Pumping Record and Water Quality Analysis. Then further application is made to WRMA to transform the Groundwater Authorization into Groundwater Abstraction License (at a fee).The license is valid for 4 years.
