A Borehole is mechanically drilled hole on the earth crust with the aim of exploiting the natural reserve of water that is deposited in an aquifer or water table or water bearing formation. Borehole remains one the readily alternative to pipe born water for domestic, industrial and homes; a borehole system comprises of the use of mechanical and electrical devices to draw the natural reserve of water to the surface for human use. All over the world borehole is one of the alternative source of water supply, in Nigeria about 60% of the total population depend on groundwater.

In this piece we will unravel the borehole drilling methods, borehole systems and installations, the maintenance approach for boreholes and other related information to unravel all you need to know about a borehole.


What to look out for before Starting a Borehole Drilling Project.

Borehole drilling is a project; a good project knowledge and management skill is required. Borehole Drilling is a capital and technical project, so should not be handled by amateurs. The following steps are to be followed to achieve a successful borehole project.

  1. Geophysical Survey: this gives the project a guide for budgeting and project execution. It’s dangerous to avoid survey and most dangerous not to follow the survey, however an extensive and concise survey should be conducted.
  2. Discuss the project details with the geologist: Some questions will help; what’s the scope, specifications and details should be discussed? Is the project industrial, community or domestic? What’s the expected usage capacity of the water reservoir?
  3. Accessibility: it’s not proper to mobilize to site and then the drill location is not accessible, the geologist have to visit site and make sure the drill point can be accessed by the drilling truck.



Borehole Drilling Methods

Depending on your area, different drill methods can be deployed. There are two general drill method which are dependent on the two basic types of formation (subsurface layers) that can be encountered while drilling:

  1. Mud drilling Method
  2. Air Drilling Method


  1. Mud Drilling Method: this method is applicable in sedimentary terrains; the general geology of the area informs the geologist the nature of terrain, however a geophysical survey gives the geologic information of the formation beneath the earth surface. With the use of water, chemicals and mud pits the job is done.
  2. Air Drilling Method: this method is applicable in a basement (igneous and metamorphic) terrains, also the general knowledge and survey report will inform this drill method. This drill method is achievable through use of an air compressor. These drill method is further divided by casing design: a) Full casing and b) hanging Casing.

The above casing design is largely dependent on the kid of rocks encountered while drilling, please contact a geologist for a better guidance.


Components of a Borehole System and their maintenance approach

Just like every system, a borehole have several components. All the components are linked and interconnected to function to provide the water needs of humans. These components are:

  1. Geological
  2. Mechanical
  3. Electrical
  4. Environmental

The clear understanding of these components, will guide in the maintenance of any borehole system. Below are clear explanation of the different components of a Borehole System.

  1. Geological: a borehole is sunk through the earth; which comprises of sequence of geological strata/layers. The clear knowledge of the geological formation is important in borehole maintenance. For instance, if a borehole produce dirty or colored water, knowledge of the regional geology of the area is needed to know if the dirty is insitu or environmental, this will advise the kind of maintenance approach to undertake; in situation like this it’s either the borehole undergo flushing, relining, treatment or all aforementioned.

A borehole needs a geological maintenance approach if you experience the following:

  • Brown/iron coloration of the water.
  • Particles e.g. Mica (silver shinning particles) in water.
  • Gravel dropping from a basement hanged borehole.
  • Collapse or mud infilling (depending the degree of collapse).


  • 2. Mechanical: this comprises the plumbing design and installation of the different components of the borehole mechanics. The submersible pump, pipping and reticulations are the main mechanical components of the Borehole. The mechanical systems brings forth the water from deep below the earth to the surface. A borehole needs a mechanical maintenance approach if you experience the following:
  • If your reservoir tank takes longer than normal to get filled.
  • If your reservoir tank never gets filled after pumping for hours.
  • If your pump stops working or floating switch stop functioning.


  • 3. Electrical: this comprises of all electrical design of the borehole from the submersible pump to control panel to the floating switch. This controls the pumping systems of the borehole. An electrical surge can destroy the pump and wires, so it’s advisable to use good wires and breakers before the panels to prevent power surge. A borehole needs an electrical maintenance approach if you experience the following:
  • If the overload in the control box trips off; then the wires or wiring system is faulty.
  • If the pump refuse working due to faulty wires.
  • If there was a power surge.


  • 4. Environmental: this comprises of the environmental factors that will affect or enhance the borehole system. Before drilling a borehole consider the following;
  • The drill point is at valley area or mountainous area? If the drill point is at valley area, make sure your wellhead is lifted up to about 50cm or 0.5m about the ground, well grouted and protected from flood.
  • Are there septic tanks around? How far are they? They should be about 30m or 100fts away. In cases these cannot be achieved, if the borehole is not domestic and not for consumption purposes a professional geologist should be sorted to develop a sustainability design applying all the environmental factors involved.

If all these are considered, the borehole system is expected to be free from smell and flooding if you experience any the following consult a professional geologist especially one specialized in Borehole systems (Hydrogeologist).


When is advisable to drill a borehole

There have been controversies on the time of the year when a borehole drilling project can be carried out, some school of thoughts believe drilling in raining season is not guaranteed while some are against. The FEAR is, not drilling to the aquiferous depth and unravel the water table; we will X-ray thoughts that should inform our decision.

  1. If a proper geologic survey is conducted to detect the aquiferous layers; the fear should be eliminated.  
  2. If a driller and a professional geologist work together with a well conducted survey and drill to the recommended depth; the fear should be eliminated.
  3. If you drill to the average depth of drill in the area. There must be existing serving borehole in the area, once same drill depths or more are achieved there is nothing to fear.

When the above listed conditions are meet the FEAR should be eliminated.

Borehole drilling is a scientific, technical and engineering project; clear understanding of the project is key.

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