Pioneering Water Infrastructure Solutions Across Kenya

What is the borehole drilling process in Kenya?

Borehole drilling process in Kenya involves several steps:

Step 1: Hydrogeological Survey

Hydrogeological survey is the first step and is done to determine where the water is. It establishes the location, soil formation and depth to which drilling will be done. The survey is often done using a combination of Vertical Electrical Sounding (VES) and water dowsing to identify aquifers as wells as a geophysical indication of the underneath area. The information obtained is analysed. Besides, the geologist will evaluate the performance of neighbouring boreholes before giving the final report.

Step 2: Permit Acquisition

Before the actual borehole drilling process commences, it is mandatory to acquire a license from the Water Resources Authority (WRA) as well as a “No Objection” letter from the local Water Resources Users Association (WRUA). For borehole drilling projects near public facilities such as school or market, an Environmental Impact Assessment should be conducted and the report submitted to the NEMA for approval.

Step 3: Actual Drilling

Borehole drilling is done using advanced well drilling machines also referred to as drilling  rigs. The rotary drilling method is the most common method of drilling boreholes in Kenya. Here, a drill bit is attached to a string of drill pipes that are interconnected into a drill string.  So, as the drill strings rotate, the drill bit grinds the soil and rocks beneath to create a hole of a specified diameter. The ground soil and rocks are flushed out of the hole as the drilling continues using drilling fluid or compressed air.

Step 4:Borehole Casing and Gravel Packing

Once the water is reached, the borehole is lined using steel or plastic pipes referred to as well casing. The purpose of casings is to strengthen the hole thus protecting it from collapse. Besides, the casings act as sanitary seals that keep the well safe from contamination risks.

Also, screens are installed in the water bearing sections to allow water to flow up the well while preventing small soil particles from entering. It is necessary to record drilling logs during the drilling process as it comes in handy in determining the ideal depth for borehole installation of screens and gravel packs.

The casing diameter is often smaller that the drilled hole. The annulus – space between the drilled hole and the casing is back filled with gravel. With the gravel in place, fine sand particles won’t enter the borehole through the screens. They also prevent the walls of the hole from collapsing onto the screen which may happened depending on the geology.

Step 5: Well Development

Well development is the act of cleaning out the silt and clay introduced during drilling. Well development is done by flushing which also increases the rate of water movement from the aquifer to the borehole.

Step 6: Test Pumping

Test pumping is usually done to determine amount of water that can be drawn from the borehole in the long term minus pumping the borehole dry. Therefore, abstraction from the borehole should never exceed natural refresh. 

Step 7: Pump Selection

When choosing a pump to deliver water from a borehole, electric submersible pumps are typically utilized. These pumps are designed to be fully submerged in water, featuring a hermetically sealed motor that is attached to the pump body. It is important to select a pump with the appropriate flow rate and head. The flow rate determines the volume of water the pump can deliver per unit of time, while the head refers to the vertical difference between the pump’s installation point and the highest point where water needs to be pumped. By carefully considering the flow rate and head requirements, you can make an informed decision when choosing a pump for your borehole.

Step 8: Water Quality Test

Water quality test is carried out in a credited laboratory to determine the suitability of the borehole water for domestic use, irrigation or any other use. While some boreholes yield pure neutral water, others may yield saline water which will need treatment before use.

Step 9: Borehole Equipping 

Borehole equipping involves installation of pumps. Solar submersible, electric submersible or diesel pumps may be installed in the borehole as per the expert advice. Equally, uPVC pipes or HDPE pipes are immersed into the borehole depending on the depth.

Step: Auxiliary Services

In Kenya, auxiliary services encompass optional extras such as pipe installation, plumbing, tank tower construction, tank installation, irrigation, and more. However, these auxiliary services are quoted separately from the main service, which may include the installation of a borehole water purifier for ensuring clean and safe drinking water.

What is Test Pumping a Borehole?

The process of test pumping entails connecting a test pump and pumping water from a specific time while monitoring particular variables. Monitoring the pumping rate during the test is crucial as it allows for dependable drawdown data to be gathered.

During the test pumping, the borehole water level should be measured using a lighting dipper or electric sounding. Testing is not only done for water yield but water levels as well. The three most common yield tests for borehole water include constant test, step test and recovery test.

In order to determine the constant discharge of a borehole, water is pumped at a constant discharge rate for a period of time that is proportional to the expected yield. The constant testing time can be from 8 to 48 hours or longer. The data gathered during this process is analysed and used to determine, assess and recommend the water yield of the borehole. Moreover, the data is used to determine the pump size and depth of its placement.

What is the Importance of Water Chemical Analysis?

Water chemical analysis is usually done to determine the suitability of the borehole water for drinking, livestock, irrigation or any other use. This is an important part of ensuring that the newly drilled borehole is a safe and reliable source of water. Moreover, the chemical analysis allows for proper address of any specific problems of the water from the borehole. 

The chemical analysis of water also helps to ensure that the water source is properly protected from potential contamination and that appropriate treatment is chosen. Most importantly, water chemical analysis helps in making informed decisions about the water and how to utilize it.

What is Borehole Equipping?

Borehole equipping the process that  involves pump installation with its accessories such as control panel, submersible and underground cables, galvanized pipes and main to the tank.

What are the timelines for drilling a borehole in Kenya?