Drilling Procedure

Step 1: A Site Consultation/Basic feasibility study. After your initial contact we may arrange a site consultation. This may involve a representative of the drilling team and our survey team visiting site to establish the viability of the project and to understand the site conditions. From our site visit an initial idea of whether the water bearing aquifer will yield the quantity of water required will be established. Our visiting engineer will be happy to explain all the options to ensure that you get the correct system for your needs.

  • Siting Of The Borehole

The first decision is to determine where to drill. There are numerous ways in which we can go about deciding where to place the borehole on your property. We turn to hydro-geologists who make use of various geographical methods to probe beneath the surface. By employing these geophysical methods, hydro geologists are able to infer the subsurface geology of an area.

  • Acquiring the Statutory Documents/Drilling authorizations

After the siting has been done, the hydro geologist will need to do a report of the findings and have it submitted to the Water Resource Management Authority who will in turn evaluate it and give written authority to construct the borehole, without which, a borehole cannot be drilled.

An Environmentalist also needs to be contracted to carry out an E.I.A (Environmental Impact Assessment) of the project. This will facilitate the issuance of the NEMA license which is also a prerequisite in drilling.

Once the WRMA Groundwater Authorisation and NEMA license is received (after some 4-8 weeks), then borehole drilling is permitted and can duly commence. The authorization is valid for one year and can be readily renewed twice but not for a fourth year when the hydro-geological report will need review, qualification and re-issue, before further re-application for Groundwater Authorisation.

Step 2 - 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 we use at Indepth water services is known as “down-the-hole” air flush rotary method. A pneumatic hammer and drill 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.

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