Geotechnical investigation: define project questions, fieldwork and deliverables
Foundations, excavations and water management need information that a plot plan alone cannot provide. An investigation connects existing knowledge with the enquiries required for your project. The questions, necessary work and a report your designers can use determine the commission.
Start with the project decision
Identify the project and why investigation is needed. New construction, an extension with excavation and review of an existing uncertainty can raise different questions. An existing report may also be reviewed for a changed project.
You do not need to specify a soil class, foundation type or drilling depth yourself. Describe proposed work and known information. The specialist establishes the purpose and appropriate scope.
| Question | Clarify in the commission |
|---|---|
| Foundations | Information for proposed loads and components. |
| Excavation | Ground, water and neighbouring areas to consider. |
| Groundwater | Required hydrogeological work and interfaces. |
| Infiltration | Investigation suited to the proposed use. |
| Existing information | Suitability, missing data and additional enquiries. |
Use existing information first
Previous investigations, geological information, drawings and reports can help. Identify where and why they were prepared. Information from a neighbouring plot or another part of a project is not automatically transferable.
Drawings help establish affected areas, levels and interventions. If technical information is missing, the first commission should distinguish questions that can already be answered from information designers still need to supply.
Report known observations or previous uses without drawing your own diagnosis. Water, settlement or fill can justify further questions; their cause and significance need professional investigation.
Separate document review from field investigation
Reviewing existing data can identify a need for further investigations. Fieldwork, sampling and laboratory testing differ from reading an old report. Ask what work is proposed and what conclusions it supports.
Methods and investigation locations depend on the project and site. Access, existing services and restrictions also matter. Do not specify a fixed number or depth of boreholes as presumed proof of complete coverage.
Agree when results are needed and who coordinates them with design. Observations during construction or extended monitoring are not automatically part of a single investigation.
Address water, contamination and limitations separately
Geotechnical properties and contamination investigations answer different questions. A building pollutant survey is a further separate task. Define the disciplines and analyses included.
Registers and archives can support further enquiries. They do not provide blanket confirmation that a site is free from every contaminant. An entry also does not automatically mean every area requires remediation.
The report should identify investigation points, information and assumptions. Uncertainty can remain between points or after project changes. Investigation guarantees neither identical conditions everywhere nor a particular future construction solution.
Prepare fieldwork and hand over results
Access, space, surfaces, use and known restrictions matter on site. Professionals must check whether proposed work needs permission or further coordination. Water, transport routes and other infrastructure require local, project-specific enquiries.
Agree organisation, responsible firms, work-area protection and the condition after completion. Access and service information supports planning; it is not client certification that drilling or digging is safe.
The deliverable should answer your designers’ questions. Clarify the report, explanation, data and any coordination with the engineer. Design and construction of foundations or excavation support can be separate commissions.
Compare the complete investigation
One field service is different from a commission including interpretation and a report. Prices depend on existing information, access, investigation scope and required analysis.
Compare preparation, field team, equipment, samples, laboratory work, reporting and discussions. Clarify how additional investigations are identified and authorised before execution. Project changes may require further assessment.
Consider permission enquiries, travel, facilities, reinstatement, third-party work and VAT. A price per drilled metre does not automatically cover these items. It cannot establish a reliable national average for different complete commissions.
| Cost item | Clarify for comparison |
|---|---|
| Preparation | Document review and investigation programme. |
| Fieldwork | Equipment, people, access and organisation. |
| Samples and laboratory | Geotechnical testing or additional analyses. |
| Interpretation | Report, recommendations and explanation. |
| Additional work | Approval of further points, tests or support. |
| Total | Third-party work, reinstatement, expenses and VAT. |
Prepare the enquiry with the known project
A clear description is enough for initial discussions. Technical details can remain open; the investigation programme belongs to professional assessment.
- Project. Identify proposed work, location and affected areas.
- Questions. Describe the assessment and decision required.
- Information. Explain existing drawings, reports and observations.
- Site. Identify use, access and known restrictions.
- Deliverable. Clarify reporting, coordination and additional specialists.
Obtain usable information for design
Investigation should fit the next planning steps. Scope, conditions and handover need to be understandable before fieldwork.
- Explain the need. Summarise project, questions and information.
- Agree the scope. Clarify data review, possible fieldwork and local conditions.
- Compare quotes. Compare matching work and complete deliverables.
- Investigate and interpret. Carry out agreed work professionally and document limitations.
- Discuss results. Coordinate the report with design and identify additional needs.
Frequently asked questions
Do I need to know the method or drilling depth?
No. Describe the project and questions. Methods, locations and depths need professional planning for the site. A fixed number alone does not prove complete investigation.
Can an existing report be enough?
It can provide useful information. Have its locations and original project checked, along with any need for additional investigation after changes or missing data.
Does the investigation include a contamination report?
Not automatically. Ground behaviour, water, ground contamination and building pollutants are different tasks. Agree the disciplines and analyses expressly.
Are fieldwork permissions included?
That depends on the commission. Have local requirements checked and agree who handles enquiries or applications. A commission does not automatically authorise every borehole or intervention.
What does a geotechnical investigation cost?
Compare preparation, fieldwork, sampling, laboratory work, interpretation and reporting. Access, reinstatement, third-party work and VAT can affect the total. A drilling price alone is not a complete report price.
Does the report guarantee safe, uniform conditions everywhere?
No. It reflects the locations and information investigated. Assumptions and uncertainties should be visible. Changes or observations during construction can require further enquiries.
