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Wednesday, 4 February 2026 by Oliver Fontana – Managing Director
How deep and borehole surveys reduce risks in deep groundworks
Deep and borehole surveys – investigating ordnance deeper in the ground
Deep-ground and borehole surveys investigate deeper areas where explosive ordnance is suspected. For deep excavations, drilling or foundations, the first step is to clarify which depths and areas are covered by existing documents and investigations.
Whether a borehole survey is suitable depends on factors including the suspected hazard, ground conditions, measurement conditions and proposed intervention. The investigation scope and limits of interpretation are defined and documented for each project.
Deep and borehole ground investigations
Borehole surveying is one option for investigating at depth
In ordnance work, deep surveying means investigating deeper parts of the ground. Borehole surveying is one way to do this, taking measurements at depth through boreholes. What the findings establish depends on the measurement principle, investigation geometry and site conditions. To clarify a project's requirements, FONTANA-EOD needs site and foundation plans, existing ordnance-related records, and details of the depth of the planned ground disturbance and existing structures.
What historical evidence means for deep surveying
Using historical evidence for the volume of ground involved
A deep investigation starts by defining what suspicion is to be investigated and in which area.
From historical context to the investigation objective
The air war, unexploded bombs, battlefield remnants or military uses may each prompt historical research. They do not lead to a general assumption about every property. What matters for planning is the evidence available for the affected area and the investigation task that can be justified from it. Provide existing assessments with their appendices and identified uncertainties.
Considering earlier ground surfaces
Present-day levels and earlier site conditions may differ. Filling, excavation and construction changes can make older records harder to relate to the site. Describe known changes and provide available level surveys and as-built plans. Specialist planners can then check which volume of ground the historical information and current works relate to.
Passing on the full existing evidence
An earlier report may contain historical assumptions, technical results and unresolved questions. For a new investigation at depth, these need to be read together. Its conclusion alone or a single map page is often insufficient. The handover should identify the report's underlying records and any later investigations or changes to the plans.
Terms, sources and professional assessment
Clarifying the suspicion, groundworks and survey conditions
What suspicion needs to be investigated?
Historical evidence and existing findings may indicate possible types of ordnance and their geographical relationship to the site. An unexplained survey signal is initially a finding, not a positively identified unexploded bomb. The investigation objective needs to be more specific than a general request for safety.
What intervention is planned?
Clearly describe the locations and depths of foundations, piles, excavations or utility sections. Depths need a vertical reference. If the plans change, check whether the existing investigation still covers the affected areas.
What can be measured under the site conditions?
Steel reinforcement, utilities, metal-containing fill and other sources of interference can affect measurements. Access, ground conditions and the characteristics of the object being sought help determine which method can provide usable data.
Bringing the probe closer to the area being investigated
Borehole magnetometry takes magnetic measurements inside a borehole. It records physical anomalies whose interpretation forms part of the professional assessment. A signal may also come from other ferromagnetic objects. The method does not provide a photograph of the ground and cannot identify an object from its signal alone.
The BFR KMR address the planning and execution of borehole magnetometry separately from other geophysical methods. Their specification concerns the search for unexploded bombs using particular gradiometers. It does not establish general suitability for every type of ammunition or every setting. The technical specification for borehole magnetometry describes the relationship between the investigation objective, site conditions and execution.
For clients, the central question is therefore not simply how deep drilling can go. Clarify which volume will be investigated, what can reliably be established and how areas that cannot be assessed because of interference will remain identifiable. The survey service page explains how to prepare a project-specific enquiry.
Defining an investigation at depth clearly for planning and assessment
The information should allow the design, completed investigation and report to be related to one another later.
Whether this access method is necessary and suitable needs professional justification. A surface investigation may be limited by the target size, depth or interfering structures. Conversely, a deep structure does not automatically justify the same borehole investigation in every case. The specific task determines what is needed.
Providing geometry and vertical references together
A position on a plan does not fully describe the required volume of ground. Provide the relevant plans, sections and depths with their vertical references. Identify whether a figure relates to the current ground surface, a planned excavation base or another reference. This prevents apparently identical depth figures from being used for different volumes of ground.
Distinguishing planned positions from positions actually investigated
Obstacles or access conditions may require changes during construction. Keep the originally planned position distinguishable from the position actually used. Clear identifiers connect the plan, work carried out and assessment. Document the change and its reason so that later participants can understand which planning question the available data addresses.
Keeping limitations with the results
For an area affected by interference or not investigated, explicitly record that it remains unresolved. Planning needs both the findings and the limits of what they establish. Record the area affected, the decision still needed and the relevant records. This makes the open question clear to the next contractor rather than losing it in a general summary. Missing or uninterpretable data must not be passed on as a finding with no anomalies.
What the investigation report establishes for your construction plans
A traceable report connects survey locations and vertical references with the method, data quality and professional interpretation. It needs to identify the areas investigated and any limitations. Gaps not investigated and data that cannot be interpreted because of interference must not silently be treated as having no anomalies.
Anomalous measurements may require further investigation. A finding with no anomalies applies within the investigation objective and what the survey could reliably establish. Neither the number of boreholes nor the greatest drilling depth replaces that assessment.
If the result is to support clearance of a construction section, the actual investigation scope needs to cover the planned works. The pages on Survey report and clearance record and the meaning of an ordnance clearance statement explain this handover.
Comparing existing surveys with the planned works at depth
A surface survey with no anomalous findings relates to its original objective and what it could actually establish. For deeper groundworks, compare the target object and required volume of ground with that scope. This identifies where existing results provide a sound basis and where further investigation is needed.
Where a base slab or other structures are present, assess access, interference and the investigation objective together. This determines the choice of a suitable method. A borehole investigation is an option where it can address the particular task at depth under the conditions present.
If depths change, new areas are added or the construction method changes, assess whether the existing results remain applicable. The BFR KMR describe the approach for federal government properties. Other projects are based on the applicable project specifications and requirements of the responsible authorities.
Keeping the terms used in commissioning and assessment distinct
A clear task description distinguishes suspicion, measurement, professional assessment and the evidence needed for the project.
Suspicion and suspected area
A suspicion concerns information requiring professional assessment. A suspected area connects that information to a defined location. For deep groundworks, also clarify the volume of ground and investigation objective. A general description of suspicion does not prescribe one standard survey method.
Distinguishing terms for suspected ordnance
Surveying
A survey investigates a defined volume of ground using a suitable technical method. The task specifies location, depth and the investigation objective. Ground conditions, structures, access for surveying and technical interference affect which methods are suitable.
Comparing technical investigation tasks
Clearance and recovery
Clearance concerns planned work on a defined area towards a specified objective. Recovery concerns an item that has been found, within the professionally planned approach. A survey anomaly is therefore first documented as a finding, together with the further clarification needed.
Understanding clearance and recovery
Clearance statements and documentation
When a statement is described as clearance, read it alongside the area, depth, method and limitations. The documentation connects these details to the commission and findings. For later planning, the statement's actual scope must remain clear.
Understanding the scope of the evidence
EOD and UXO
EOD stands for Explosive Ordnance Disposal and refers to specialist ordnance disposal work. UXO stands for Unexploded Ordnance: ordnance that has not detonated. Using these terms replaces neither a precise investigation task nor professional assessment of an individual survey anomaly.
Understanding EOD and ordnance disposal
KBD and local coordination
KBD stands for Kampfmittelbeseitigungsdienst, the ordnance disposal service. The responsible state and local authorities are involved according to the applicable procedure. When making an enquiry, provide existing correspondence, file references and details of previous contacts so that the private specialist service can be coordinated appropriately.
Distinguishing the responsibilities of those involved
BFR KMR and DGUV
The BFR KMR construction guidelines for ordnance clearance set out technical principles and requirements within their scope. DGUV refers to German Social Accident Insurance. When preparing the work, consider the relevant principles together with the specific task and site conditions.
Understanding the relevant guidance
Excavation supervision
Excavation monitoring accompanies suitable groundworks under defined conditions. It follows a professional decision about the particular task. A gap in the records no more prescribes this approach than a general mention of wartime damage nearby.
Assessment requires the plan, survey and report together
The records explain the relationship between the original task and the documented findings.
The historical starting point
An existing assessment is read with its geographical reference and appendices. It helps formulate the investigation objective and is considered alongside the planned groundworks.
The investigation task at depth
Location, vertical reference and working space form the basis for technical coordination. Describe known structures and access conditions in the enquiry so that the task can be assessed for the actual site.
Preparing an investigation at depth
A traceable handover of results
Pass on a report with its maps, associated identifiers and clear limitations. All these elements are needed when comparing it with the construction plans. A depth or a count in isolation does not describe the volume investigated.
Responsibilities, qualifications and occupational safety
Drilling is itself a planned ground intervention
Records and utility locations
Preliminary works need an agreed basis, including utility and cable information and plans relevant to the site. Consider the ordnance question alongside existing technical infrastructure. A seemingly unobstructed drilling position is not sufficient evidence.
Responsibilities and execution
Investigation planning, drilling, surveying and assessment need to be technically coordinated. Check access and obstacles before work starts. Changes to the ground or deviations from the planned drilling positions must remain in the documentation.
Protecting the ground and surroundings
Preparation also needs to address ground conditions, subsequent land use and groundwater protection. Select the approach for the actual site. Independent test drilling by the project owner to investigate suspected ordnance is not an appropriate preparatory task.
Agreeing responsibilities before investigations begin
Assign responsibilities for planning, execution and assessment. Coordination also includes the prerequisites for the ground intervention itself.
Technical competence and responsible activities
The German Explosives Act distinguishes a company's permit, personal competence and responsibility. The First Ordinance to the Explosives Act (1. SprengV) covers technical knowledge and recognised training, among other matters. The evidence required relates to the actual relevant activity planned. Establish responsibility for planning, drilling, surveying and assessment before each relevant activity begins.
Risk assessment and technical guidance
The risk assessment addresses the planned works and their conditions. DGUV Information 201-027 covers risk assessment and protective measures in ordnance clearance. DGUV Rule 113-003 needs to be considered within its applicable scope and is not generally replaced by the Information document. The BFR KMR are used within their scope and alongside the applicable local requirements.
Finds and official hazard response
In Germany, stop work in the affected area if a possible item of ordnance is found. Do not touch or move it. Leave the area, keep your distance and keep others away without putting yourself at risk. Notify the police immediately on 110. The responsible authorities arrange the further response and involve the state ordnance disposal service according to local procedures. The business enquiry route is for planning and coordination, not for reporting an immediate find.
What needs to be clarified for your project
Determining the next professional decision from the starting conditions
Start with what is known and how the findings will be used.
The historical basis is still unclear
First relate the available information, earlier reports and historical records to the project. A justified investigation question is needed. Naming an instrument in the specification alone defines neither the basis for suspicion nor what the investigation needs to establish. If reliable historical evidence is missing, specify the archival research and historical aerial photograph assessment needed as separate specialist tasks. Their findings help justify the investigation objective and volume of ground involved.
Clarifying the historical basis for investigation
Existing results do not clearly cover the foundations
Compare the area investigated with the current design, including its levels and depths. Request missing appendices or clarification of uncertain references. This comparison establishes which decisions are already supported and which questions need further work.
Comparing existing results for separate areas
Existing structures limit survey conditions
Describe utilities, reinforcement and other structures together with survey access and the investigation objective. Specialist planning identifies an approach suitable for the actual conditions. A limitation at one location does not prescribe a general method for every other part of the site.
Choosing methods within technical limitations
The report leaves some areas unresolved
Further coordination addresses the areas specifically identified and the reason for each limitation. Retain existing results. State the decision still needed and its significance for the next works so that supplementary tasks can be commissioned appropriately.
Separating historical assessment, technical investigation and comparison of results
The three tasks may build on one another; their scope depends on the project's actual stage.
Assessing historical evidence for the groundworks
Bring earlier assessments and available historical records together with current site and foundation plans. Define the unresolved historical questions for professional assessment. A general account of the location does not by itself replace an existing technical survey.
Clarifying the historical basis for work at depth
Planning a justified investigation at depth
Once the required volume of ground and investigation objective are defined, agree access and the method against the site conditions. The enquiry needs to cover geometry, vertical references, existing structures and available findings. The service page describes project-specific survey preparation.
Discussing investigation requirements at depth
Comparing existing reports with the plans
To use earlier findings, read the report, site plan, data references and limitations together. Identify the current plan revision and the decision the findings are intended to support. Keep unresolved or changed work areas distinguishable from areas already investigated.
Coordinating borehole positions and the required depth
Set out the proposed borehole positions or work areas with the depths of ground disturbance and their vertical references. Include a site plan, existing investigations, utility records and known access limitations. FONTANA-EOD will discuss the scope needed for the particular works at depth and any information still outstanding.
From the task description to a usable handover
Coordination brings the available information together step by step.
Defining the project question
Describe the decision that needs to be prepared for planning or construction.
Gathering the records
Provide existing findings with complete reports and appendices.
Defining the working space
Identify the location, depth, vertical reference and current plan revision.
Agree the site conditions
Tell us about existing structures, access, obstacles and relevant construction stages.
Define the technical scope
Agree the investigation required and how the results will be handed over.
Use the result for the specific project
Match the documented investigation volume to the work actually planned.
Prepare the commission from the current project information
A focused enquiry describes the outstanding task and the information already available.
Complete the preliminary investigation
Historical records and existing assessments are considered alongside the planned ground disturbance.
Add to the historical evidence
Commission a depth-specific investigation
For defined points or working volumes, provide the geometry, vertical datum, existing structures and investigation objective.
Agree the survey scope for deep ground disturbance
Reuse existing results
Compare the report and plans with the new design. Keep unclear spatial references and unresolved areas identifiable.
Compare the report with the current design
Send the documents for technical coordination
FONTANA-EOD will discuss the appropriate scope of services and any further information needed with you.
Describe deep ground disturbance by its actual geometry
The type of structure alone does not determine the investigation. Identify each working volume for the technical discussion.
Point foundations and individual work locations
Describe the location and depth of piles, wells or other individual ground disturbances. Include adjacent working areas and known obstacles in the plans. Evidence for another position must not be reused solely because the structure has a similar name.
Discuss depth-specific tasks at individual points
Retaining-wall alignments and linear structures
For an alignment, the actual width and depth of the ground disturbance matter as well as its route. Show changes to connections or individual sections in the current drawing revision. Investigation planning needs the required ground volume and known limitations along the route.
Plan linear ground disturbance with its depth
Excavations and changed foundation designs
An excavation can include different formation levels, deeper sections and working areas at the sides. Assign existing results to those areas. For new designs, explicitly check whether additional or differently positioned volumes are affected and what further technical clarification is needed. This applies to underground car parks and tunnel sections as well as new uses on industrial or redevelopment sites. Describe the ground volumes affected by the base level of the structure, retaining works, connections and preparatory utility works. For transport and infrastructure projects, also clearly distinguish the investigated section from the remaining existing structures.
Account for local requirements and project stages
Relate the technical task to the actual location and the coordination already completed.
Provide location-specific documents
Give the municipality, address and any local information already obtained. Include case references and the authorities or other bodies already involved. This places the private specialist service within the current project context, without adopting unverified procedural assumptions from another region.
Establish the project location and local coordination
Document separate working volumes individually
A project can cover different areas, levels and construction stages. Use clear identifiers and provide the associated plans together. This keeps results and limitations assigned to the correct area, even when several parties reuse the documents.
Documents and construction area
Explore the next technical question
Terms and their context
Read more about how suspected contamination, investigation and documented results relate to one another.
Surveying for the project
Describe the specific depth-related task and existing information so that the scope of services can be agreed.
Reports and subsequent decisions
Relate the scope of investigation and identifiable limitations to the current construction design.
Frequently asked questions
Are deep investigation and borehole surveying two separate methods?
Not necessarily. Deep investigation describes the investigation of deeper ground. Borehole surveying is one way to carry out measurements below ground for that purpose. The measurement principle used must also be stated.
At what construction depth is borehole surveying always required?
There is no single depth that applies to every project. The suspected ordnance situation, possible target objects, construction design and the capabilities of existing investigations must be assessed together.
Can the probe identify every metal object as explosive ordnance?
No. Physical anomalies require specialist interpretation. Other metal objects or installed structures can cause signals or interfere with measurements. Suitability depends on the measurement principle and the specific task.
Is the maximum drilling depth enough to describe the result?
No. The measurement locations and vertical datum, methods, data quality, assessment and identifiable limitations must be clear. Only then can the investigated volume be compared with the planned ground disturbance.
Can an existing deep investigation be reused for a changed foundation design?
This must be checked against the documents. If new ground disturbance extends beyond the investigated area, goes deeper or takes place under different conditions, the earlier conclusion must not automatically be applied.
What determines the cost of a borehole survey?
The estimate depends on the required investigation volume, drilling access, ground conditions, utilities and other obstacles, as well as the planned data collection and analysis. Further investigation of anomalous areas or areas with limited measurability can change the scope. A well-founded enquiry therefore describes the existing information and the conclusion needed. Any preparatory work or official measures requiring separate allocation of responsibility are clarified for the project location.
What should I do if I find a possible item of ordnance?
Stop work in the affected area. Do not touch or move the object. Leave the area and keep your distance. Keep other people away without putting yourself at risk. In Germany, immediately call the police on 110 and follow their instructions. The competent authorities will arrange further identification and handling.
What information helps with the initial discussion before commissioning?
Provide the project location, current site and foundation plans, ground disturbance depths with a vertical datum, existing reports, and information about existing structures and access. Also state the decision that the investigation is intended to support. Discuss the requirements before the first planned ground disturbance. Official requirements are clarified with the authority responsible for the project location; technical investigation services are clarified with the specialist designer or contractor. Existing correspondence and case references help establish the context.
Records for your enquiry
Discuss borehole surveying for your project
Gather site and foundation plans, ground disturbance depths with a vertical datum, and existing explosive ordnance records. Also describe access and known utilities and installed structures. We use this information to assess with you the scope of investigation needed for the project.
FONTANA-EOD: +49 6843 9994997 · info@fontana-eod.de
Discuss the investigation needed
Clearance concept and investigation planning
Task
The investigation objective and the decision needed remain clearly stated.
Location
Planned and actual positions are clearly matched.
Elevation
Depths have a clear, shared reference datum.
Conditions
Existing structures, access and relevant interference are described.
Result
The assessment and its limitations are handed over together.
Updating the assessment
New designs are compared with the existing investigated volume.
Describe the depth-related task for an initial response
The clearer the question and the available evidence, the more precisely the required scope of services can be discussed.
Location, positions and depths
Give the address, region and land parcel. Include a current site plan showing the construction area, route, excavations and borehole positions. Add the ground disturbance depth with a vertical datum and any known differences between the current and proposed ground surface.
Existing documents and structures
Send historical records, aerial photograph assessments, previous investigation reports and utility plans with their appendices. State known installed structures, access conditions and requirements. Missing information or information that cannot be clearly assigned should remain identified as outstanding.
Project stage and the decision needed
Describe the project status, construction schedule and next stage of work. Explain which decision is to be supported, which authorities or other bodies are involved, and whether positions or depths have changed since earlier investigations.
Have your project assessed
Whether historical aerial photograph analysis, explosive ordnance surveying, surface surveying using GPR, magnetometry or TDEM, deep-ground surveys, downhole surveys, excavation supervision, area clearance or ordnance recovery is needed depends on the location, ground disturbance, depth, ground and existing documents. An early ordnance assessment provides clarity for tendering, programming, occupational safety and construction.
FONTANA-EOD combines its Section 7 SprengG licence, specialists holding Section 20 SprengG certificates of competence, suitable survey and clearance methods, and traceable documentation. Send the site plan, depth of ground disturbance, construction phase and existing documents for an initial technical assessment.
