How to Drill a Borehole in Kenya

Before a borehole drilling rig arrives at your property, you need to establish your water requirements, confirm the site’s groundwater potential, identify a suitable drilling location, and obtain the required approvals.

After drilling, the contractor installs the casing and screens, places gravel pack around the screened sections, and installs a sanitary seal to protect the borehole from surface contamination. The contractor then develops the borehole and conducts a 24-hour pumping test to determine its yield, water levels, and recovery. The test results guide pump selection.

This step-by-step borehole drilling guide takes you through the process from site investigation to borehole commissioning. It explains what happens at each stage, why each stage is important, and what you need to know before moving to the next stage.

Determine Your Water Needs

Decide how you intend to use the water. A borehole serving a family home will have different water requirements from one supplying a farm, school, hotel, irrigation system, or factory.

Estimate your daily water demand and identify the activities that’ll use the water. Include domestic use, livestock, irrigation, commercial operations, or any other planned use. All this information helps us assess whether the borehole’s sustainable yield can meet your water demand.

The hydrogeological survey (see the next section) helps identify the groundwater potential and a suitable drilling location, while test pumping determines what the completed borehole can sustainably provide. If the sustainable yield falls below your water demand, you may need to adjust your usage, increase storage, or consider other water sources.

2. Conduct a Hydrogeological and Geophysical Survey

These two surveys, typically contained in one detailed report, help establish where groundwater is most likely to occur. A hydrogeological survey assesses the site’s geology and groundwater conditions, while a geophysical survey investigates the subsurface to identify formations that may contain groundwater.

We use the findings from both surveys to identify a suitable drilling location and recommend a target depth. The surveys help us make a more informed drilling decision instead of choosing a location at random.

However, neither survey guarantees that you will find water or that the borehole will produce a particular amount of water. The actual yield depends on the geological formations encountered during drilling and the results of the subsequent pumping test.

3. Get the Required Permits or Approvals

Get a Water Resources Authority (WRA) permit, WRUA (Water Resource Users Association) approval, and NEMA (National Environment Management Authority) approval. Depending on the county, you may also need county government approval.

Sure, you can handle the paperwork yourself, but the process can take time. We’ve seen authorities take up to 12 months to approve a borehole, much to the frustration of the landowner. A missing document or delayed follow-up can hold up the entire project.

We can help you handle the permit applications and follow up with the relevant authorities. We’ve built great working relationships with these entities over the years, and that really helps speed things up.

There’s also a hefty fine if you’re caught drilling without the required permits, so let’s do things right from the start and avoid trouble.

4. Drill the Borehole

We start by mobilizing resources, which entails transporting the drilling rig, technical team, casings, gravel, and other materials and equipment to the site. This mobilization often involves clearing the ground and preparing access so the rig can reach the exact drilling point identified in the hydrogeological and geophysical survey report.

Access matters because drilling rigs are extremely heavy machines. At the risk of sounding pessimistic, a lot of rigs have overturned while trying to reach difficult-to-access drilling locations. We make sure the ground and access route can support the rig before moving it into position.

Borehole Drilling Method

The drilling method used depends on the geological formation encountered at the site. We mostly use air drilling and mud drilling, but these aren’t the only ones. Other borehole sinking methods include percussion or cable–tool drilling and manual SHIPO drilling.

Air drilling:

uses compressed air to break and remove cuttings from the borehole. We commonly use it where drilling encounters hard, competent rock. This includes much of Kenya’s volcanic and hard-rock terrain, such as parts of Nakuru, Nairobi, Laikipia, Central Kenya, and other areas across the Rift Valley and highlands.

Mud drilling:

It uses drilling fluid to carry cuttings to the surface and stabilize the borehole walls. We use it where the formation is soft, loose, or likely to collapse during drilling. This method is useful when drilling through unconsolidated sediments, clay, sand, and loose alluvial deposits. These conditions occur in different parts of Kenya, especially in the coastal region.

Mud drilling costs more than air drilling because it requires additional materials, equipment, and handling. If the ground is suitable for air drilling, we use air drilling instead of paying the additional cost of mud drilling.

Percussion or cable-tool drilling:

This one uses a heavy bit that repeatedly strikes the formation to break it. It is an older drilling method and is generally slower than rotary drilling.

Manual drilling:

uses relatively simple, human-powered equipment and is suited to shallow groundwater in soft, unconsolidated formations. It is mainly used where mechanized drilling is unnecessary or impractical.

The actual drilling

Once the rig reaches the drilling point, we set it up and begin drilling through the geological formations. We record the formations encountered, the depth reached, and every water strike as we drill.

If we reach the target depth without encountering the expected water-bearing formation, we assess what we’ve encountered and decide whether to drill deeper or stop.

5. Install the Casing, Screens, Gravel Pack, Seal, and Cap

After drilling, we install the casing, which is a pipe placed inside the drilled borehole to support the borehole walls and provide a passage for the submersible pump. A common casing diameter is 6 inches, and we use mild steel or uPVC casings.

We install continuous casing through sections where groundwater should not enter the borehole, and slotted casing across the water-bearing sections. The slots allow groundwater to enter the borehole while keeping sand and other loose material out. We determine the position of the slotted sections from the formations and water strikes recorded during drilling.

We then place a gravel pack around the slotted sections. This is clean, selected gravel placed between the borehole wall and the slotted casing. The gravel allows groundwater to pass through while helping prevent sand and fine material from entering the borehole.

Next, we install a sanitary seal around the casing near the surface. The seal fills the space between the casing and the borehole wall and prevents contaminated surface water from flowing down into the borehole.

Finally, we cap the top of the casing to protect the borehole from dirt, debris, insects, and other contaminants entering through the opening.

The casings, slotted sections, gravel pack, sanitary seal, and cap must be installed correctly. Poor construction can allow sand into the borehole, reduce water production, damage the pump, or contaminate the water.

6. Borehole Development and Test Pumping

After constructing the borehole, we develop it to remove drilling fluids, sand, silt, and fine material left inside the borehole during drilling. We use methods such as airlifting and flushing to remove this material and clear the water-bearing sections so groundwater can enter the borehole properly.

After development, we do a 24-hour pumping test. We pump water from the borehole at a measured rate and monitor how the water level changes throughout the test.

Before pumping starts, we measure the static water level, which is the level of water in the borehole when it’s NOT being pumped. During pumping, we measure the pumping water level and record the amount of water being discharged. When pumping stops, we continue monitoring the borehole to see how quickly the water level recovers (recovery rate).

These numbers show how the borehole responds to sustained pumping and help determine its sustainable yield. Sustainable bore yield refers to the amount of water it can provide without being pumped beyond its capacity.

Another reason test pumping matters is that it gives us the information we need to choose the right submersible borehole pump and motor. Our pumping equipment technicians, who are engineers with strong technical expertise, use the borehole’s tested yield, water level, and your property’s water demand to select the appropriate equipment. This ensures the pump can supply the water you need without demanding more water from the borehole than it can sustainably produce.

7. Water Quality Analysis

We collect a water sample from the completed borehole and send it to an accredited laboratory for analysis. Sampling must be done correctly, as contamination introduced during collection can affect the results.

The lab analyzes the sample for the physical, chemical, and microbiological parameters required for the water’s intended use. The results reveal whether the water is suitable for its intended use. If treatment is necessary, the lab results tell us what impurities need removal before you can use the water for drinking, domestic purposes, livestock, irrigation, or other applications.

Clear water doesn’t necessarily mean safe water. Some contaminants can’t be detected by looking at, smelling, or tasting the water. We offer this extra service for absolutely FREE.