Technical map of the administrative district of Arnsberg, marking Arnsberg as a location for ordnance investigation and surveying by FONTANA-EOD

Explosive ordnance assessment in Siegen: Define investigation areas clearly

Which area needs investigation: the whole property, the excavation pit or individual utility trenches? For projects in Siegen, FONTANA-EOD supports the commissioned preparation of explosive ordnance investigation. We coordinate the task using site plans, proposed depths and groundworks. This makes it possible to establish later which area the investigation result covers.

Property and construction area

Mark proposed groundworks on the site plan.

Valid plan revision

Allocate application, construction plan and report clearly.

Additional groundworks

Clarify enlarged or relocated areas in advance.

Discuss investigation areasExplosive ordnance assessment in North Rhine-Westphalia
Assess the construction project

The specific intervention area forms the basis

An address or cadastral parcel number does not always describe the whole proposed work area. For your Siegen project, we compare the application area, actual investigation and current ground interventions. Different boundaries and additional areas remain visible so that further work required can be determined traceably.

Project references

Selected project examples

Project site

Connect the site with the specific construction task

Illustrative map of North Rhine-Westphalia with the state coat of arms, a tablet, a white FONTANA-EOD helmet and a notebook.

Use Siegen's map requirement for your own project

The City of Siegen requires the application area to be defined as a closed polygon. The local procedure involves the regulatory authority and state explosive ordnance disposal service. For your project, the resulting findings are checked against the interventions actually proposed. The application boundary does not replace subsequent evidence of the investigation carried out.

For site allocation, the address, cadastral parcel and a clear map extract are brought together. Proposed groundworks may differ from the property boundary. Therefore identify the excavation pit, foundations, utility trenches and additional work areas with their respective spatial reference. Clear names are used for several construction sections. If a subarea lies outside the previous boundary, it is shown explicitly during further coordination. A project in another municipality follows that municipality's own procedure. Further project locations are shown in the regional overview.

The overview of the Arnsberg administrative district provides further local information for the regional context of your construction project.

North Rhine-Westphalia
Local context

The application starts with a clearly outlined area

Maps and application area in the Siegen procedure

In the City of Siegen's online application, the intended investigation area must be outlined precisely on the map extract. The instructions specify a closed polygon for this purpose. Based on the documents, the Ordnungsamt first arranges an aerial photograph analysis. The explosive ordnance disposal service then communicates the results and recommended further approach.

The City of Siegen commemorates the severe destruction caused by the air raid of 16 December 1944. For present-day construction areas, development at that time and subsequent changes are considered with their actual spatial reference. Suitable historical aerial photographs, building records and earlier terrain plans are researched and assessed by specialists. Findings are assigned to the specific investigation task. The city's history supplies historical context; property documents and current construction plans determine the question still needing an answer for the intervention.

Distinguish application, investigation and new plans

Mark on the construction plan whether the whole property or only areas for the excavation pit, utilities and extensions are concerned. It must be possible to compare the investigation area applied for with the proposed groundworks. Only then can site management later identify whether a result applies to its work area.

Earlier buildings and present-day structures may occupy different areas. Where reconstruction, demolition, filling or other ground changes are documented, the earlier state is therefore compared with the current design. A larger excavation, additional retaining elements or a relocated connection may extend beyond the area previously considered. Such changes receive their own reference on the current site plan. Earlier documents retain their original task. Subsequent specialist planning and the competent authorities receive the same clearly identified current version.

Working together

Distinguish the tasks of client, designers and specialist contractor

Client and operator

The client describes the project and provides the available project records. The operator adds requirements for use, access and timing. A coordinating contact brings the parties together; individual tasks remain assigned to the named parties. Before commissioning, it is clearly recorded what information is missing, who will obtain it and what decision the result is intended to prepare.

Planning and construction management

The specialist designers describe areas, depths, construction methods and changes. Site management coordinates the planned sequence with the construction contractors and agreed specialist works. Results are assigned to the respective intervention. A technical plan change is communicated early enough for its effect on the survey task to be assessed before construction. Organisational construction stage boundaries remain distinguishable from technical survey boundaries.

Specialist company and competent bodies

The private explosive ordnance specialist carries out the agreed investigation and documentation work. Requirements and decisions of public authorities are addressed with the responsible bodies. The documents needed for a particular procedure depend on the location and project. The technical report describes the work carried out, including its documented area, depth and scope. Decisions reserved for public authorities are made by those authorities.

The Siegen Ordnungsamt arranges state aerial photograph analysis using the application documents. The explosive ordnance disposal service of the Arnsberg district government assesses the findings and recommends further steps. Official measures are coordinated through this interface. Permissible private specialist work is agreed with its specific investigation and documentation scope. The application area, area actually addressed and findings required for the next construction work remain distinguishable. For project locations outside the city, local responsibility follows the actual project address. Any need for ordnance recovery is coordinated with the permissible task and the competent authorities.

Investigation task

Which specialist task comes next?

Clarify the area question before selecting the method

It must first be clear which area and intervention the investigation is to address. An unclear boundary cannot be made unambiguous afterwards even by a technically suitable method. The site plan and task are therefore considered together. This establishes the specific question for further specialist work.

Assess historical documents

Consider result scope and technical limitations

The area actually investigated is read together with the method and the findings it can achieve. A large application area does not demonstrate uniform investigation of all parts. Interference or excluded areas remain part of assessment. Before a private supplementary investigation, official determinations and the NRW prerequisites for the specific activity are also checked.

Compare investigation methods
Project types

Show each area with its own meaning

Illustration: two people review plans and documents at a table beside a construction vehicle.

Define the area applied for clearly

A closed boundary describes the area intended for processing. It is supplied with the underlying site plan and its revision. The cadastral parcel boundary may differ from it. Allocation should also be understandable to people not already familiar with the project from a site meeting.

Coordinate the sequence and tasks
Illustration: two people review plans and documents at a table beside a construction vehicle.

Identify the area actually addressed

The subsequent investigation scope may differ from the original application. Inaccessible positions, excluded areas or changed tasks are documented traceably. The application remains the initial document, while the report describes the work actually carried out. These two boundaries are deliberately distinguished and considered together for further construction planning.

Document findings and their limitations
Illustration: two people with a tablet beside a drawing table and a survey trolley on a construction site.

Add further interventions to the current plan

If new work areas, borehole positions or retaining elements are added, they are shown explicitly. A shared project name does not replace spatial allocation. Compare the new location with existing results and their depth information. Parts not covered receive their own specialist clarification before the affected works begin there.

Specialist services and investigation tasks
Preparation

Prepare the scope and commission together

Before commissioning, the investigation required, the specific status of the Siegen procedure and the task permissible for the project are determined. Describe the proposed intervention with its location, depth and findings required.

Establish what needs to be known before commissioning the work

First establish which decision the commission needs to support. Is the task an initial assessment of existing documents, an investigation of a specific area or examination of an anomaly that has already been assessed? These tasks require different evidence. A general wish for safety does not define an investigation that can be carried out. The enquiry therefore specifies the groundworks, location, depth and available findings. Suitable specialist work and the required reporting are then agreed on that basis.

Define the specialist task

Coordinate preparatory work with the investigation

Required access and survey conditions are clarified before the site visit. This may include keeping areas clear, obtaining service information and coordinating with other trades. The method and site determine which preparations are actually needed. Changes to the surface or additional groundworks are not undertaken unilaterally simply to prepare for a survey. Their sequence is agreed with the specialist designers and responsible parties.

Clarify preparatory work in the programme

Agree a clear scope and schedule

A realistic programme distinguishes technically resolved work from prerequisites that are still outstanding. If only part of a site will be accessible, the commission must take this into account. Handover and assessment of the results also need time in the construction programme. The schedule and effort are agreed once the scope, access and prerequisites are clear. This coordination brings together the specified scope, access, documents, site conditions and the date by which a decision is needed.

Discuss the scope and schedule
Tasks at the site

What the investigation plan must show

01

Property and work area

Assign the project to the property and mark the proposed groundworks. These may include interventions outside the building footprint. Explicitly identify the areas to be investigated; the project name alone does not describe the task.

02

Depth and reference elevation

State the proposed depth and its reference for each work activity. The site plan initially shows horizontal extent. Investigation planning additionally needs the type of groundworks and depth to be considered.

03

Plan date and version

Identify the valid plan revision and assign investigation documents to that version. If several drawings are supplied, it must be clear which one currently applies. Earlier designs and unresolved variants must be identified accordingly.

04

Areas still unresolved

Mark areas whose location or use remains undecided. Clarify their investigation needs once plans are established. A later summary must not present these areas unchecked as already investigated.

Project documents

Documents that establish the next step

Link maps to the associated letter

Keep the report, appendix and plan revision clearly together. A map without its associated findings may leave the technical scope unclear. Conversely, a short text without a map extract may not explain the location sufficiently. Documents are therefore handed over in full and linked to the respective relevant project version.

Siegen's application instructions describe the precise outline as a closed polygon. Where several subareas exist, it must remain clear which proposed works relate to which area. Scale, extract and plan revision are stated for area comparison. The city also explains how to save the map extract for attachment to the online application. The file remains linked to the associated task description. If a boundary is changed later, the new outline is checked against the original application and existing result.

Spatially separate interventions have their subareas identified traceably within the same project revision. The legend explains which boundary belongs to the application, which area has already been investigated and where additional work is proposed. The respective reports remain accessible through these designations. Unclear overlaps are clarified before further technical assessment. If an outline changes, the earlier version also remains available with its work status. The parties can thus distinguish new plans from an investigation actually carried out.

Document differences in the result traceably

If the investigated area differs from the application, the location and reason for the change belong in the documentation. Site management can identify the limits of existing findings from this. Unaddressed areas are not concealed by a graphical summary. Their further treatment is coordinated on the basis of the knowledge actually available.

The result handover describes the scope actually addressed. Investigation boundaries, omitted positions and technical limitations are passed on with the maps. A short overview refers to the complete reports and already identifies important outstanding areas. Before the next construction phase, the current intervention is compared with this status. Site management can then establish which records belong to its work section. After clearance work, the clearance record with its scope, results and remaining limitations supplements these documents for the area actually addressed and defined on the site plan. Additional questions are assigned to the specialist task needed and the responsible parties before the groundworks concerned begin.

Construction sequence

Coordinate investigation and construction sections

Before submitting application documents

Show the proposed area traceably on the current site plan. Identify the proposed ground interventions and existing documents. Unclear boundaries or additional work areas are coordinated before further processing. The application should reflect the actual task rather than merely identify the location generally.

Coordinate the construction phase with us

Before passing on the investigation result

Compare the area shown in the report with the current construction plans. Mark relevant differences and outstanding areas. Site management receives the complete documents and associated limitations. A new plan revision does not become part of the report's investigated scope merely by being filed beside it.

Coordinate the construction phase with us
Method selection

Select methods according to the task and survey conditions

Historical records and aerial photographs

Historical aerial photograph assessment and other old records help place the basis for suspicion in its spatial context. The available images, their evidential value and the limits of the area considered matter. The absence of an identifiable indication must be distinguished from a technically surveyed ground area. The assessment is considered together with the planned intervention and other available findings. It can support the choice of a survey, but is not a measurement of the present-day subsurface or confirmation for all future works.

Understand aerial photograph assessment

Magnetometric survey

Magnetometric methods detect magnetic anomalies. Whether they can address the specific survey task depends, among other things, on the expected objects, ground conditions, interference and required survey area. Fences, utilities or existing structures may affect interpretation. A measurement signal is therefore not described as ordnance solely because of its strength. Method, interpretation and any further investigation are planned as a connected specialist task.

Understand the scope of magnetometry

Electromagnetic methods

Electromagnetic investigations can be suitable for particular metallic targets and site conditions. Their suitability must be explained for the task, rather than inferred simply from the availability of equipment. Interfering installations, accessible areas and the findings required must also be considered. Results are documented with their location and survey conditions. The specialist assessment determines whether a supplementary method is needed; this remains a project-specific decision.

Understand electromagnetic surveying

Ground-penetrating radar

Under suitable conditions, ground-penetrating radar can provide information about subsurface structures and reflections. Ground conditions, moisture, installations and the particular survey task affect interpretability. An anomaly is not automatically ordnance, and an area with no apparent anomalies is not general evidence for arbitrary depths. The specialist interpretation and its limits are documented with the instruction. A survey for another purpose is not adopted without checking as ordnance evidence.

GPR and limitations

Deep-ground and downhole surveys

For deeper groundworks, it may be necessary to establish whether a surface investigation can provide the required findings or another approach is needed. Preparation includes the location, depth, borehole layout and existing services. Creating access for the investigation must also be properly planned by specialists. A general depth figure or standard grid cannot replace that work. Findings remain limited to the areas actually investigated and the method used.

Prepare deep interventions

Survey during construction

If a necessary preliminary investigation cannot be completed, the specialists assess whether a planned approach during construction is suitable. This includes coordinated investigation, interpretation and communication of findings within the intended work sequence. Visual observation of excavated material is not an interchangeable substitute for a necessary survey. Site management needs a clear description of when specialist work will take place, how new findings will be handled and which areas remain unresolved.

Agree the approach during construction
Technical assessment

Which areas and conditions the investigation must cover

Assign aerial photograph analysis to the area

The historical aerial photograph analysis relates to the outline applied for and its associated explanations. A result for a neighbouring area does not automatically apply to your work area too. Where boundaries differ, it must be clarified which area was actually covered.

A result document is read with its associated map extract. The application, historical analysis and technical investigation carried out are distinguished according to their respective tasks. A written subject line or the same property address does not always suffice for spatial allocation. If documents use different extracts or plan revisions, common reference points are clarified. The comparison records which part of the proposed groundworks is already covered and which areas still require their own specialist work.

Check access and survey conditions

A survey must fit the investigation objective and site conditions. Buildings and metal installations can affect access and survey feasibility. The area drawn therefore determines neither the suitable method nor the investigation depth achievable.

The investigation area is described with access, installations and work areas actually reachable. Metal infrastructure, buildings or restricted vehicle access may affect method selection and findings. For a specific specialist question, ground conditions, target objects, depth and interference are therefore considered together. Investigation and specialist interpretation are prepared as a connected task. Areas with no or limited interpretability remain identifiable on the results plan. Additions required for them are determined from the knowledge actually available.

Assess enlarged or relocated interventions

If the intervention is enlarged or relocated, the clearance plan or investigation plan must be compared with the new construction plan. This requires assessing which results still apply and which questions remain outstanding. A changed line on a plan does not extend the scope of an earlier investigation.

For a relocated excavation pit, working spaces and retaining elements are also considered. The horizontal boundary is checked together with proposed depths and the elevation reference. New or deeper structural elements may require additional investigation. The comparison therefore identifies which existing findings remain usable and where current plans extend beyond them. Changes are coordinated with the specialist parties before the construction work concerned. An amended plan is clearly identified and handed over with all earlier reports.

Next steps

From the application to handover to site management

01

Initial contact and assessment of the evidence

At initial contact, describe the proposed groundworks and decision required. Application documents, explosive ordnance reports and official communications are compiled in full with maps. The local regulatory authority arranges the required aerial photograph analysis using the spatially defined documents. Where use or terrain information remains unresolved, supplementary historical records and images are researched and assessed by specialists. Available findings are assigned to the specific area and outstanding questions.

02

Coordinate areas and methods

The application area, work areas and proposed intervention depths are shown together. The suitable method is selected according to ground conditions, target objects, interference and accessibility. The state KBD's recommendation and further coordination required are considered. State measures and permissible private tasks retain their respective responsibilities. Preparatory work required and missing documents are clarified before execution. The parties use the same identified plan version for follow-up questions.

03

Investigate and assess results

The agreed survey or technically suitable supplementary supervision is carried out under its actual conditions. New trenches, foundations or further groundworks are coordinated before execution. Data and observations are assessed by specialists and assigned to the areas addressed. Assessment distinguishes usable results, anomalies and areas with limited interpretability. Differences from the application and original commission remain documented with their location and reason. Necessary additions are derived from the outstanding questions.

04

Document findings and prepare the subsequent decision

The results plan and report are handed over in full with technical information, limitations and relevant changes. Before the next construction work, site management compares the new intervention with the documented investigation scope. Outstanding areas and official steps required are assigned to the work section concerned. Changed boundaries, additional areas or different depths are checked separately before work there. Applicable existing results remain usable for the area they actually cover.

Documentation

Distinguish application areas from areas actually investigated

Document the area applied for and the area addressed together

The application states which area is to be assessed. The results report shows what was actually investigated or assessed. If part was inaccessible or a different boundary was addressed, this must be documented. A shared property designation must not conceal these differences.

Project responsibilities

The BFR Kampfmittelräumung provide technical guidance for planning and documentation. In North Rhine-Westphalia, the responsibilities of regulatory authorities and the limits of private work must be observed. Commissioned investigation and documentation by FONTANA-EOD do not replace an official decision about the project.

Working approach

How FONTANA-EOD works

Document the agreed specialist service clearly

We assess the planned groundworks against the available documents and their design revision. Before attending site, we agree with you what needs to be investigated, which areas are accessible and what findings are required. If the design or site conditions change, we check whether the agreed scope remains appropriate. The report states what was actually investigated and the limits of the findings. This allows designers and site management to see which findings they can use and where questions remain.

Discuss the investigation task

The task before the equipment

We first establish the investigation objective: which question must it answer? We then select a technically suitable method. The availability of a particular device or experience on a similar neighbouring site is not enough to justify the choice of method on its own.

Keep limitations visible

Inaccessible areas and limited conclusions are identified. They do not disappear into a total area figure. Designers and site management can then decide specifically which areas still need attention and when a suitable survey becomes possible.

Clarify changes before intervening in the ground

A new location, additional depth or different construction method is compared with previous results. A familiar project name does not replace this comparison. Feedback is provided before the affected work so that an outstanding question can be included in the sequence.

Hand over the report and plan together

The technical conclusion remains connected to its location references and appendices. A brief summary helps orientation but does not replace the documented survey scope. This basis is retained even if site management or contractors change.

Understand the results

Use technical statements for the next decision

A cadastral parcel reference may cover several work areas

Different interventions with different depths and construction phases may be proposed on one property. These areas are allocated specifically for technical assessment. Shared ownership or cadastral reference does not extend an existing report. What matters remains the area and activity actually included in its task description and result.

Understand investigation reports and their limitations

Plan comparison needs the same reference

Different scales, extracts or unclear reference points make allocation more difficult. Use clearly identified versions and clarify differences before reaching a technical conclusion. A visually similar location is not always sufficient. Comparison should show traceably where proposed interventions and documented results match or diverge.

Understand the service scope
Design and findings

Documents for the next construction decision

Illustration: aerial photographs and maps on two screens and printed on a desk.

Historical evidence and the current design

Aerial photograph interpretation is related to the actual groundworks. Its purpose and geographical scope remain distinct from a technical investigation of the ground as it is today.

Understand aerial photograph assessment
Illustration: two people review plans and documents at a table beside a construction vehicle.

Specialist reports for site management

The findings, their locations and limitations are handed over together. This makes clear to those carrying out the work which area has been investigated and which task remains outstanding.

Assess investigation reports
Four people in orange high-visibility vests in front of two excavators on a construction site.
Person with a yellow survey cart on a footpath in front of a hedge.
Questions from planning

Questions about specifying areas for construction projects in Siegen

How is the investigation area drawn in the Siegen application?

The city requires a closed outline of the investigation area on the map extract, that is, a polygon. Follow the current online application instructions. The drawing must show the area you wish to have assessed. Prepare documents in good time before proposed groundworks so that analysis, further investigations required and preparatory work can be accommodated in the construction programme.

Must the investigation boundary match the property boundary?

Not necessarily. Proposed groundworks may concern only a subarea or several separate areas. Mark the property and intended investigation area so that both are clearly identifiable and match the commission described.

What happens if the building footprint moves?

Compare the new construction area with previous results and investigation boundaries. Further steps required depend on the change and applicable requirements. An older result does not automatically cover the relocated footprint. Method suitability depends on ground conditions, target objects, depth and interference. Subareas with no or limited interpretability remain documented with their boundaries.

Is a response sufficient without its associated site plan?

The area to which the response relates must be identifiable. Request the missing plan or clarify allocation with the parties involved. The address alone does not reliably show the area covered by the investigation. The process connects document assessment and required historical analysis with method selection, investigation or suitable supervision, assessment and documentation. Results are then checked against the next construction work and decisions still required.

How should a suspicious object be handled?

Stop work in the area concerned, neither touch nor move the object, and move away. Keep other people away. Siegen identifies the local regulatory authority as the reporting office and, outside its service hours, the emergency numbers 110 or 112. Follow official instructions.

What distinguishes the application area from the investigation area?

The application area describes the proposed work. The report documents which areas were actually investigated and the limitations or differences encountered. Complete reports and maps remain linked to the plan revision, location, depth and task of the documented investigation. A cadastral parcel may contain several areas requiring different work.

Which factors determine effort and costs?

Method, scope, depth, interference and accessibility determine the effort required. Preparatory works needed, separate subareas and supplementary investigations are considered in the specific procedure. The service agreement identifies the permissible specialist task and records required. The respective parties clarify who undertakes preparatory and accompanying works and how these are billed. State and private tasks are considered with their respective cost allocation.

How are additional work areas treated after an investigation?

They are marked on the current plan and checked against existing results. Missing findings and further steps required are clarified by specialists before the work concerned.

Project enquiry

Discuss investigation areas and construction plans together

Show areas clearly

Send the application boundary, investigation boundary and current intervention areas with a clear spatial reference. Add the project address, cadastral parcel, construction phase, timescale and decision sought. Alongside the outline, state proposed depths and the elevation reference. The sector overview explains typical interventions and the documents they require.

Keep plan revisions together

Attach reports and associated maps in full and describe later changes to the project. Identify the works approaching first and the contacts responsible for changes.

Project enquiry

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.

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