borehole siting is the evidence-led process used to select a defensible drilling point before a rig is mobilised. In Kenya, the process can combine site information, nearby borehole records, geology, topography, contamination risks, field reconnaissance and suitable geophysical measurements so the final target is based on more than convenience or guesswork.
Why borehole siting matters before drilling
borehole siting does not create groundwater and it cannot guarantee a successful borehole. Its purpose is to reduce avoidable uncertainty by identifying a drilling target that is supported by the available evidence. That distinction matters because underground conditions are only confirmed progressively through drilling, construction, development, test pumping and water-quality analysis.
A convenient open space is not automatically the right drilling point. The selected location must also consider access for the rig, nearby contamination risks, future buildings, drainage, power and pipe routes, the ability to protect the finished wellhead, and the practical location of storage and distribution equipment.
The wider professional assessment is described in our hydrogeological survey cost in Kenya guide. This article focuses specifically on how borehole siting turns that assessment into a recommended point on the ground.
Borehole siting starts with the project requirement
Before fieldwork begins, define why the borehole is being considered. A domestic property, farm, apartment block, school, hospital, hotel or industrial site can have different water-demand and operating requirements. The borehole siting professional needs the intended use because the project is not only about locating groundwater; it is about planning a usable water system.
- Record the site coordinates and land boundaries.
- State intended water uses and approximate daily demand.
- Identify planned buildings, roads, tanks and utilities.
- Note existing wells, boreholes, springs or drainage features nearby.
- Record known contamination risks such as sanitation facilities, waste areas or fuel storage.
- Describe rig access, gate width, slopes and overhead obstructions.
- Share any previous survey, drilling or water-quality records.
A clear brief helps borehole siting address the real site rather than producing a generic geophysical exercise disconnected from the eventual construction.
Borehole siting and desk study
Desk study is the first opportunity to build context before measurements are taken. Depending on the project and available information, the reviewer may consider regional and local geological information, existing groundwater records, topography, drainage, nearby boreholes, satellite or mapping information and previous reports.
Good borehole siting does not treat every source as equally reliable. A verified nearby drilling log can be more useful than an unverified depth quoted from memory. Likewise, a nearby successful borehole does not guarantee identical conditions on the subject property. Distance, structural geology, construction and aquifer conditions all matter.
The desk stage should produce questions for field verification. It may highlight possible geological structures, access issues or contamination constraints that need to be checked on site.
Field reconnaissance in borehole siting
The field visit connects maps and records with what actually exists on the property. The borehole siting professional can inspect topography, drainage, exposed rock where available, land use, access, existing water points, sanitation features and the proposed areas where drilling equipment could operate safely.
This is also the stage to identify practical conflicts. A geophysically interesting location may be unusable if a rig cannot access it, if a future building will cover the wellhead, or if surface contamination risks cannot be managed. Conversely, the easiest place for a rig may not be the strongest technical target.
Therefore, borehole siting is a trade-off between hydrogeological evidence and a constructible, protectable site. The final recommendation should explain that reasoning rather than simply placing a paint mark on the ground.
Geophysics in borehole siting
Geophysical methods can help investigate contrasts in the subsurface that may support hydrogeological interpretation. Electrical resistivity methods are commonly associated with groundwater investigations, but the measurements do not directly “see water” in a simple way. The response is influenced by geology, pore fluids, clay content, weathering and other subsurface properties.
That is why borehole siting should interpret geophysical measurements together with geological and field context. A low-resistivity feature, for example, is not automatically a productive aquifer. The survey design, electrode arrangement, line orientation, site conditions and interpretation all influence the quality of the conclusion.
Ask the consultant to explain the method used, measurement locations, quality limitations, interpretation and why the recommended point was selected over alternatives. Keep the original report for the driller and future owner.
What borehole siting cannot promise
borehole siting is risk reduction, not certainty. A responsible report should communicate uncertainty clearly. It may recommend a target depth range or identify interpreted structures, but drilling is the stage that physically confirms the sequence of materials and water strikes.
Be cautious with language that guarantees water, guarantees a particular yield or presents a geophysical reading as an exact underground map. Strong project planning uses the survey to make a better-informed drilling decision while retaining a contingency for geological uncertainty.
If you are budgeting the complete project, see 100 metre borehole cost in Kenya and borehole drilling cost per metre in Kenya.
Borehole siting and contamination risk
A drilling target should not be selected from groundwater potential alone. borehole siting must also consider how the finished source can be protected. Surface runoff, sanitation systems, waste areas, livestock facilities, chemical storage and other land uses can influence the risk environment.
The survey and construction planning should identify relevant separation and protection considerations for the actual site and applicable requirements. After drilling, sanitary headworks, appropriate sealing and drainage are part of protecting the source at the surface. See borehole headworks in Kenya for the completion stage.
Do not move a recommended point casually just because another location is easier for the rig. If a move is necessary, return the decision to the hydrogeological professional so the implications can be assessed.
Borehole siting and rig access
Access is a technical and commercial part of borehole siting. A drilling rig may require substantial working space, turning room and stable ground. A compressor, support vehicle, rods, casing and crew also need safe positioning. Overhead cables, narrow gates, steep slopes, weak bridges and wet ground can affect mobilisation.
Record access conditions during the survey rather than discovering them after the drilling crew arrives. If grading, tree trimming, temporary road improvement or other preparation is needed, make that visible in the project scope.
On developed properties, also consider long-term service access. The pump may eventually need to be removed, the headworks inspected, or the borehole rehabilitated. borehole siting should avoid creating a source that becomes impossible to maintain after new construction surrounds it.
How borehole siting connects to the drilling log
The drilling log is where the borehole siting interpretation meets physical evidence. As drilling advances, the contractor should record depth, formation changes, water strikes and construction decisions. These observations help the hydrogeological and drilling team understand whether the encountered conditions align with the pre-drilling interpretation.
The recommended survey point does not remove the need for competent decisions during drilling. If the formations differ materially from expectations, the method, depth or construction may need to change. Those changes should be documented rather than hidden in a final lump-sum invoice.
Keep the borehole siting report and drilling log together. Future technicians can then understand the original interpretation and what the rig actually found.
Borehole siting is only the first evidence stage
Even when drilling intersects groundwater, borehole siting has not yet answered the complete water-system question. The borehole still needs appropriate construction, development and performance testing. A water strike observed during drilling is not the same as a tested sustainable operating rate.
After completion, use controlled test pumping to measure discharge and water-level response. The borehole test pumping Kenya guide explains drawdown, recovery and why the results should guide pump selection.
In plain English, drawdown s is the difference between the pumping water level and the static water level measured from the same reference.
In plain English, specific capacity SC relates tested discharge Q to drawdown s. It is a performance measure taken after drilling, not a value that borehole siting can guarantee beforehand.
How to compare borehole siting quotations
| Quotation item | What to ask | Why it matters |
|---|---|---|
| Desk review | Which records and mapping sources will be reviewed? | Shows whether fieldwork is grounded in site context |
| Field reconnaissance | Will access, land use and contamination risks be recorded? | Connects the target to a constructible site |
| Geophysical method | What method and survey layout are proposed? | Allows the measurement approach to be understood |
| Interpretation | Who interprets the data and how are limitations stated? | Separates raw measurement from professional conclusion |
| Recommended point | Will coordinates and a marked location be provided? | Prevents ambiguity during mobilisation |
| Report | What maps, plots, conclusions and recommendations are included? | Creates a permanent project record |
A useful borehole siting quotation names the deliverables. Avoid comparing only one headline fee when one provider includes fieldwork and reporting while another offers a narrower service.
Worked example: choosing between two possible drilling points
Imagine a farm where two locations appear plausible after initial borehole siting. Point A has stronger interpreted subsurface evidence but difficult rig access and lies near a future building. Point B has slightly weaker interpreted evidence but safer access, better wellhead protection and a shorter route to the planned storage tank.
The decision should not be made by access alone or geophysics alone. The hydrogeological professional should weigh the evidence and explain whether Point B remains a defensible target or whether the stronger hydrogeological case at Point A justifies site preparation and a revised building layout.
This illustrates why borehole siting is a decision process rather than a single instrument reading.
| Illustrative siting factor | Relative review index |
|---|---|
| Hydrogeological evidence | 95 |
| Rig access | 80 |
| Protection and serviceability | 88 |
| Distribution practicality | 74 |
Features of our borehole siting service
| Feature | What it provides |
|---|---|
| Project brief | Water-use, site and access information before fieldwork |
| Desk evidence review | Available geological, groundwater and site context |
| Field reconnaissance | Ground truth for access, topography and risk features |
| Geophysical investigation | Subsurface measurements selected for the site question |
| Integrated interpretation | A conclusion that combines field and desk evidence |
| Recommended drilling point | Coordinates or a clearly marked target with stated reasoning |
| Written report | A permanent record for approvals, drilling and future reference |
Advantages of evidence-led borehole siting include:
- Better target selection than choosing a convenient open space alone.
- Visible uncertainty so the project retains realistic contingencies.
- Better mobilisation planning because access is reviewed before the rig moves.
- Better source protection because surface risks are considered early.
- Better records because the drilling point and reasoning are documented.
- Better coordination between hydrogeologist, driller, pump designer and owner.
Borehole siting pricing in Kenya
The price of borehole siting depends on location, travel, site size, available records, field method, number and length of survey lines, reporting scope and whether the service forms part of a broader hydrogeological assessment. A current site quotation is more useful than a universal number.
| Scope | Indicative price | What to confirm |
|---|---|---|
| Desk and reconnaissance review | $— | Site information, records, access and initial constraints |
| Geophysical field investigation | $— | Method, layout, measurements and field time |
| Integrated siting report | $— | Interpretation, target coordinates, limitations and recommendations |
| Full hydrogeological assessment | $— | Broader reporting and project-specific requirements |
Borehole siting for small residential plots
Small plots can be more constrained than large rural properties. Buildings, septic systems, roads, walls, overhead services and neighbours may leave only a few physically drillable areas. In these cases, borehole siting should identify constraints before promising that a particular corner is suitable.
Share the site plan and future development plan if available. The best location is one that is both technically defensible and practical to construct, protect and service over the life of the borehole.
Borehole siting for farms
Farm borehole siting may have more physical space, but the water-system requirement can be larger. The recommended point should be considered alongside irrigation demand, livestock use, storage location, solar-panel area, distribution distances and future expansion.
If irrigation is planned, the eventual decision depends on both tested yield and water quality. Use can borehole water be used for irrigation once that article is live to connect source evidence with the farm water balance.
Borehole siting for apartments, schools and institutions
Institutional and high-occupancy sites may place greater value on reliability, access for maintenance, source protection and storage reserve. borehole siting should therefore consider the full site master plan rather than only current open space.
Record expected peak demand and planned building phases. Even a strong borehole target can become operationally awkward if later construction blocks pump-removal access or places contamination risks around the wellhead.
What to give the drilling contractor after borehole siting
- The final borehole siting report.
- Recommended point coordinates or clear site marking.
- Relevant target-depth guidance and stated uncertainty.
- Site-access notes and agreed working area.
- Applicable approvals and project-specific conditions.
- Any known nearby borehole records relevant to planning.
- The required logging and documentation expectations.
The drilling contractor should not have to guess which of several field marks is the approved target. Keep one controlled copy of the report in the project file.
What happens if the recommended point must move?
A recommended borehole siting point may sometimes conflict with newly discovered site constraints. Do not simply move the rig a convenient distance and assume the same interpretation applies. Contact the survey professional, explain the constraint and ask whether an alternative point can be supported by the existing data or whether additional fieldwork is appropriate.
This preserves the chain of reasoning behind the target and reduces the risk of turning a surveyed project back into guesswork.
How to get started with borehole siting
- Send the site location or coordinates.
- Describe the intended water use and approximate demand.
- Share any site plan, previous survey or nearby borehole information you legitimately hold.
- Identify known access and contamination constraints.
- Arrange the appropriate hydrogeological and field assessment.
- Review the borehole siting report and limitations.
- Confirm the recommended point before rig mobilisation.
- Keep the report with drilling, testing and handover records.
Borehole siting FAQs
What is borehole siting?
Borehole siting is the process of selecting a defensible drilling target using site context, hydrogeological interpretation, field reconnaissance and appropriate subsurface investigation.
Does borehole siting guarantee water?
No. It reduces avoidable uncertainty but underground conditions are confirmed through drilling, construction, development and testing.
Is geophysics the same as borehole siting?
Geophysics can be one part of borehole siting. The final decision should integrate measurements with geology, site observations, records, access and source-protection considerations.
Can I choose the drilling point myself?
You can identify practical site constraints, but a project that requires professional hydrogeological assessment should use qualified interpretation rather than convenience alone.
What should a borehole siting report include?
It should clearly identify the site, methods, observations, interpretation, recommended point, limitations and relevant recommendations for the drilling stage.
Can the drilling point be moved after the survey?
A material move should be reviewed with the survey professional so the alternative location remains supported by evidence.
What comes after borehole siting?
After applicable approvals and mobilisation planning, drilling confirms subsurface conditions, followed by construction, development, test pumping, water-quality testing and system design.
Use borehole siting to make the drilling decision defensible
borehole siting is most useful when it produces a clear, documented reason for choosing one drilling point over another. Combine desk evidence, field reconnaissance and appropriate measurements, state uncertainty honestly, confirm practical access and source protection, then carry the report forward into drilling and testing.