Technical map view of the Münster administrative district with Münster marked for explosive ordnance investigation and surveys by FONTANA-EOD

Ordnance assessment in Marl: assess ground levels and fill

Which surface is the planned intervention depth measured from? For developers, specialist planners and site management in Marl, FONTANA-EOD reviews existing ground and elevation information within the commissioned scope and compares it with the planned groundworks. After filling or soil removal, old figures may differ from today's conditions. Send available surveys, older plans and intended intervention depths to coordinate the investigation task.

Present and earlier elevations

Record the survey date and reference.

Information on fill

Distinguish documented strata from unresolved information.

Depth of groundworks

State the elevation reference used on the plan.

Discuss ground and depth informationExplosive ordnance assessment in North Rhine-Westphalia
Assess the construction project

Use elevation information with its actual reference

After a ground level change, a depth beneath today's surface may describe a different volume from before. For your Marl project, we relate surveying, information on ground changes and planned ground interventions to one another. Unknown elevations or fill remain explicitly outstanding and are clarified before further decisions.

Project site

Connect the site with the specific construction task

Schematic map with a coat of arms, alongside a tablet, safety helmet and notebook.

Place Marl's ground information within the procedural context

Marl is in North Rhine-Westphalia, in the Recklinghausen district and the Münster administrative district. The local public order authority is supported by the state explosive ordnance disposal service at the Arnsberg District Government. For construction projects involving ground intervention, the town describes an application for aerial photograph analysis first. Where relevant findings arise, a further ordnance investigation is requested before construction starts. For excavation, infrastructure development or site remediation, identify the project area, planned ground interventions and actual ground conditions together. Specialist services are coordinated with this procedural status and the specific investigation task.

North Rhine-Westphalia
Local context

The Marl form expressly asks about ground level

Ground information in Marl's application

The application for operational ordnance disposal linked by Marl asks whether today's ground level matches the level in May 1945. Where it differs, information on post-war fill is required. The form warns that incorrect information on the thickness of this fill may impair ordnance location. The current application distinguishes surface detection from investigation of a suspected unexploded bomb location or an indication of suspected ordnance. The proposed measure and associated aerial photograph analysis file reference are stated. As an annex, Marl requires a cadastral or comparable map with visible plot boundaries, at least two legible street names and a clearly defined investigation area. Documents are therefore related to the same area for further work. The application also includes details of existing utilities, known contaminated land and planned site preparation.

Distinguish documented information from outstanding questions

Compile the information available on ground changes for your project accordingly. The form does not establish that your property contains fill or contamination. Use documented details for the area concerned and identify what is still unknown. The commemorative brochure on the old Brassert cemetery published on the town's website describes the air raid of 22 June 1943 on Chemische Werke Hüls and residential areas affected. For today's investigation planning, historical findings are assigned to the specific project area. Actual ground changes are additionally considered using available plans, surveys and other documents. Earlier surfaces and material placed or removed later are described with their respective temporal and spatial references.

Working together

Distinguish the tasks of client, designers and specialist contractor

Client and operator

The project owner describes the proposed work and provides the available project documents. The operator adds requirements for use, access and timing. A coordinating contact makes cooperation easier but does not automatically take on every other party's duties. Before commissioning, record clearly which information is missing, who will obtain it and which decision the result is intended to support.

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 scope. Official requirements and decisions are clarified with the competent authorities concerned. The documents needed for a particular procedure depend on the location and project. The technical report describes the specialist service performed; its conclusions are not presented unchecked as general authorisation for further groundworks or as an authority's decision.

Investigation task

Which specialist task comes next?

Derive the specialist question from the intervention and existing knowledge

Compare planned depth, elevation reference and existing ordnance documents. Information on fill is relevant but does not determine the method alone. Actual survey conditions and the investigation objective are also assessed. Ground information without evidence is not adopted as an established planning prerequisite.

Assess historical documents

Coordinate further clarification before preparatory groundworks

Missing strata or elevation information is addressed with the responsible parties. A proposed exploratory opening or soil removal for this may itself constitute ground intervention and needs the corresponding prerequisites. Preparation is therefore specifically agreed before execution. Private activities remain subject to the relevant North Rhine-Westphalia rules and the authorities' state of knowledge.

Compare investigation methods
Project types

Link today's ground levels and earlier information traceably

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

Record when the ground survey was taken

A survey describes conditions at the time it was taken. Material placed or removed later may change them. Identify known changes with their area and date. The older survey is retained as a document but is not used unchecked as a complete description of today's starting elevation. List the survey with its date and elevation system. State whether the plans already use the surveyed condition or show a ground profile only intended for the future. Specialists can then distinguish actual surveyed conditions from future construction plans. For a new survey, the older survey and documented change status remain assigned to the area affected.

Document findings and their limitations
Illustration: two people review plans and documents at a table beside a construction vehicle.

Identify different elevation references

A relative depth below ground level and an absolute elevation serve different purposes. Identify each reference so specialists can assign it unambiguously. Unclear or conflicting details are clarified before further assessment. An apparently identical figure does not necessarily describe the same subsurface volume. Plans clearly show starting elevations and intended final levels of ground interventions. This concerns excavation bottoms, utility trenches or starting points of planned boreholes, for example. Location labels and the document date accompany these details. Where several plan versions exist, identify which applies to the current investigation task.

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

Show areas with a different ground build-up

If existing documents describe different fill or ground changes, assign each affected area separately. A value from one area is not transferred unchecked to the whole property. Also identify where information is missing. Further investigation considers the actual information available and its spatial limits.

Specialist services and investigation tasks
Preparation

Prepare the scope and commission together

The following specialist topics explain possible investigation tasks. Which activity may be privately commissioned under the specific North Rhine-Westphalia procedure is clarified separately before an agreement.

Establish what needs to be known before commissioning the work

For the Marl commission, describe planned groundworks together with their reference elevation. After ground changes, a depth below today's surface and a depth from an older report may concern different volumes of ground. Provide existing surveys, ground level plans and earlier investigation results with their dates. Comparison determines whether information first needs clarification, additional areas need investigation or already assessed findings need further work. The enquiry identifies location, depth and the state of knowledge; the agreed result documents must later show this spatial relationship.

Define the specialist task

Coordinate preparatory work with the investigation

Before measurement, record the actual ground conditions on which plans are based and which working areas are accessible. Utility documents, site access and coordination with other trades are assigned to the investigation area required. The selected method determines specialist requirements for survey conditions and preparation. Placing or removing material may change the reference and is therefore agreed with the responsible parties beforehand. Preparatory breaking out and new investigation access are also planned by specialists; they are not undertaken independently merely to create favourable survey conditions.

Clarify preparatory work in the programme

Agree a clear scope and schedule

The date relates to an identified plan and ground-condition version and the areas actually accessible. If only individual areas can initially be investigated, the division remains clear in the service scope. Coordination considers fieldwork, interpretation and handover so the necessary construction decision rests on a traceable result. Costs and dates are agreed according to this scope and outstanding prerequisites. If the surface changes before execution, specialist planners receive the new details before the affected work to review the investigation commission.

Discuss the scope and schedule
Tasks at the site

What elevation and depth information is needed

01

Conditions when the survey was taken

State when the ground surface was surveyed and which condition the survey shows. If material was placed or removed afterwards, document the change. The older survey must then not be used unchecked as today's condition.

02

Documented earlier ground elevations

Assign older plans and reports to the correct area and date. Distinguish documented elevations from assumptions. If the earlier condition is unknown, identify this gap; an estimated value must not appear as confirmed information. State the origin of each figure used, such as an earlier survey, as-built plan or specialist report. Differing details are handed to the responsible specialists with their respective areas and revisions. Further clarification can then address the information actually missing. Necessary investigations or new exploratory openings are coordinated with the planned construction task and its safety prerequisites.

03

Depth and reference point of the construction work

For each planned depth, state what it is measured from. A depth beneath today's surface is distinct from an absolute elevation on the plan. Coordinate elevation references so plans and investigation describe the same volume.

04

Differences between parts of the site

Record where documents describe different ground or strata conditions for separate areas. Do not transfer a single value to the whole site without evidence. Show the differences on the plan so investigation planning can consider them.

Project documents

Documents that establish the next step

Preserve the origin and reliability of information

Older plans, surveys and other reports are compiled with their dates and issuers. Established information remains distinguishable from assumptions. Completing a form does not itself confirm the correctness of an unknown layer thickness. Outstanding questions are therefore identified during preparation and clarified with suitable specialists.

Hand over results with ground and planning status

The report and annexes must identify the elevation reference used. Site management receives this information with the results. After clearance work, the clearance record with the areas treated, scope and results is filed together with the associated location and elevation reference. The significance of later changes is checked before new ground interventions. A changed ground surface does not automatically extend or replace the documented investigation scope.

Construction sequence

Coordinate investigation and construction sections

Before defining investigation scope

Compile the current survey, earlier ground information and planned ground interventions. Identify contradictions and assumptions without evidence. The outstanding question is assigned to the affected area. Further work can then be planned on traceable information without replacing missing values with unchecked estimates. The operational application states the applicant, ownership and measure requested. If the applicant does not own the property, the form requires the property owner's consent. Utility information is compared with the documents needed for the specific investigation. The application also describes the certificate concerning the presence of utilities provided after application. Its completion and necessary site briefing are coordinated with those responsible.

Coordinate the construction phase with us

After a change to the ground surface

Pass the area, date and type of change to the specialists involved. Existing plans and results are related to the new starting conditions. Necessary adjustments are clarified before further affected work. The actual documented scope is decisive, rather than an unchanged project name alone.

Coordinate the construction phase with us
Method selection

Select methods according to the task and survey conditions

Historical records and aerial photographs

Historical images and older documents for the Marl project are compiled with their dates and areas covered. They can locate indications of wartime impacts and former uses; availability and interpretability of the material remain decisive. Later fill or soil removal is additionally considered using suitable documents. Aerial photograph assessment is neither a present-day subsurface measurement nor measured evidence of layer thickness. Even without a discernible indication, the technical finding needed for current ground interventions must be clarified separately. Historical findings support method planning.

Understand aerial photograph assessment

Magnetometric survey

Magnetic methods detect magnetic anomalies. For an area with a changed ground surface, suitability is assessed against expected objects, ground conditions and the actual depth to investigate. Available information on fill and installations therefore belongs in preparation. Utilities, fences or existing structures can affect measurement and interpretation. An anomaly or its signal strength alone does not identify explosive ordnance. Specialist planning links measurement, assessment and further clarification to specific elevation and area references, rather than transferring results between areas documented differently.

Understand the scope of magnetometry

Electromagnetic methods

For electromagnetic investigations, suitability for metallic targets is justified under actual site conditions. Planning needs the ground interventions, accessible survey areas and available ground build-up information for each part of the site. Interfering installations are considered with their known locations. An instrument name does not replace this assignment. Survey conditions and results are documented so site management can trace the ground condition used. The need for a supplementary method follows from specialist assessment and the finding still missing for the intended groundworks.

Understand electromagnetic surveying

Ground-penetrating radar

Under suitable conditions, ground-penetrating radar can detect subsurface structures and reflections. Investigation planning considers ground conditions, moisture and installations with the information sought. Where ground levels change, also check which surface condition underlies an earlier radar report. An anomalous reflection is not yet identified ordnance; an unremarkable image does not evidence an arbitrary investigation depth. Results need specialist interpretation with their limits. A report prepared for other purposes is assessed against its original commission before its findings are used for the current ordnance question.

GPR and limitations

Deep-ground and downhole surveys

For a deeper ground intervention, first identify the starting elevation and ground condition from which the planned depth is measured. Specialist planners assess whether surface investigation is sufficient or a deep-ground or downhole survey is needed. Location, borehole layout and existing utilities are part of the basis, as is suitable creation of investigation access. A standard grid or general depth figure does not replace this planning. Results remain tied to the method actually used and volumes of ground covered. For boreholes, show starting elevation, location and intended depth reference together. Differences between the plans and actual starting point are clarified before the affected ground intervention. The ordnance investigation task and geotechnical question are assigned their respective evidence objectives.

Prepare deep interventions

Survey during construction

If part of the site cannot be fully investigated beforehand, specialists assess a suitable approach accompanying the planned work. The actual ground conditions and spatial finding still unresolved remain clear. Investigation is integrated into the construction sequence with interpretation and communication of findings. Visual observation during excavation alone does not replace a necessary survey. Site management receives a description of when specialist work takes place, how new findings are communicated and which areas are restricted or not yet assessed. A subsequent ground change is reported before further specialist use.

Agree the approach during construction
Technical assessment

Consider ground information when selecting and planning the method

Assign historical documents to today's area

The historical aerial photograph analysis and other documents are compared with current plans. A later ground change does not invalidate historical findings. However, clarify how the original information relates to today's area and elevations.

Select a survey method for the specific task

A survey is planned according to the investigation objective and local conditions. Information on fill is important but does not determine the method alone. Interference and access must also be assessed. A particular achievable investigation depth cannot be promised generally on this basis.

Update the plans for ground changes

The clearance plan or the investigation plan states elevation and depth references. If the ground surface changes before work, check whether the plans still fit. An earlier result plan does not apply to a different starting elevation without review.

Next steps

Prepare existing ground information for investigation

01

Compile surveys and older plans

Compile current survey records, older ground level plans and reports with their sources and dates. Keep conflicting information separate until clarified by specialists. Do not combine it unchecked into a single value. The initial project enquiry discusses the construction task, areas, depths and next decision needed. Alongside new buildings, demolition, connections and temporary construction stages are included. Known utilities and the respective current plan version are assigned.

02

Clarify missing elevation or strata information

Identify which elevation or strata information is missing and agree clarification with the specialists involved. Do not begin groundworks independently for this purpose. Before an exploratory opening or soil removal, the necessary hazard assessment must take place. Information, aerial photograph analyses and investigation reports are checked for plan version, spatial coverage, depth reference and outstanding questions relating to today's task. The scope actually documented is decisive. Missing or conflicting details are identified with their relationship to the planned ground intervention.

03

Supplement historical information

The required state aerial imagery analysis is initiated through the municipal procedure provided locally. If the available findings need supplementation, further historical research is carried out for the specific question. Available aerial imagery, maps and records of use are professionally analysed and related to the present-day construction site. The findings feed into further investigation planning.

04

Agree planned ground changes beforehand

For projects involving ground intervention, Marl describes aerial photograph analysis first and, where relevant findings arise, further investigations. Agree necessary site preparation with the responsible authorities. Planned material placement or removal belongs in this coordination beforehand. The specialist contractor selects the technically suitable approach according to the investigation objective, basis for suspected ordnance, ground build-up, interference and access. Preparatory services and permissible activity scope are clarified. Investigation areas and interfaces are coordinated with the construction sequence.

05

Investigate and assess results

Within the agreed and permissible scope, the defined areas or points are investigated using a suitable method. The data collected are recorded with location, depth reference and site conditions. Specialist personnel assess results and anomalies according to the investigation objective, method and interference. A measurement anomaly is not yet identified ordnance. Further clarification required and areas not adequately investigated are identified; local reporting procedures apply if ordnance is found.

06

Pass on result plans with their elevation reference

Hand the report and result plans to site management together. Documents must identify ground and planning status. Their documented scope is decisive for later groundworks; the property name alone is insufficient for assignment. Work performed and its specialist assessment are documented in a report with associated location drawings and plans. Methods, areas addressed, depth references and limits remain traceable. The client and designers compare this status with the next construction phase. Additional specialist work or official steps are identified before the ground interventions affected.

Documentation

Record elevation references and investigation limits in the report

Findings and their scope

A result can be used correctly later only if its area, depth and reference elevation remain identifiable. Where ground information was incomplete or available only for parts of the site, this limitation must be retained. A completed form does not establish that all its details have been confirmed through investigation. Keep the report with associated site plans and annexes. The document register identifies the issuer, date and plan version used. Information from earlier investigations is filed with the original investigation objective and documented limits. When passed on later, new designers also receive outstanding ground or strata questions. They can then assign the evidenced result status to the next construction phase.

Project responsibilities

FONTANA-EOD documents the commissioned investigation task and its results. The BFR Kampfmittelräumung provide specialist guidance; outside their direct scope, they are not a blanket local legal requirement. Official decisions and activities reserved under North Rhine-Westphalia law remain separate.

Working approach

How FONTANA-EOD works

Document the agreed specialist service clearly

For the Marl project, FONTANA-EOD links the agreed investigation scope to traceable ground and elevation information. Before execution, agree the information sought, accessible areas and result documents needed. For different parts of the site, documented conditions and missing information are identified separately. If the surface changes, its significance for the commission and results already available is checked. The report identifies the work actually performed and its limits. Site management then has a basis for relating the finding to the planned volume of ground and assigning further clarification needed.

Discuss the investigation task

The task before the equipment

Before selecting an instrument, establish which volume of ground is to be investigated and with what elevation reference. Specialist planners justify the method according to this objective and actual conditions. A comparable neighbouring site or an available instrument does not justify selection alone. Where ground information is missing, first record the basis still needed for the method decision.

Keep limitations visible

If parts of an area are inaccessible or can only be interpreted to a limited extent, identify them with their location and elevation reference. Site management can then distinguish areas actually addressed from outstanding tasks. A result from a well-documented part of the site is not transferred unchecked to an area with a different or unknown ground build-up. For the next section, agree what further clarification and access are needed.

Clarify changes before intervening in the ground

New locations, greater depths or a different construction method are compared with existing results before the affected ground intervention. For fill or soil removal, also pass on the area, date and available elevation information. Specialist planners assess its significance for the investigation task. The process remains documented with the applicable plan version, even if the project name and property address remain unchanged.

Hand over the report and plan together

The report includes plans showing the ground conditions used, spatial references and respective limitations. A short summary can point to this basis but does not replace its documented scope. When site management or contractors change, complete documents and outstanding elevation or existing-condition questions are passed on together. The next specialist planners can then identify which details for the intended groundworks are already evidenced and which need clarification first.

Understand the results

Use technical statements for the next decision

An unknown value remains an outstanding question

If an earlier ground elevation is not evidenced, this uncertainty is explicitly passed on. A precise figure may appear clear but can create a false premise without a basis. Existing documents are therefore checked with their origin. Further treatment of the gap is agreed by specialists and within the necessary official context.

Understand investigation reports and their limitations

Elevation reference and investigation depth belong together

A depth figure becomes unambiguous only with its reference. The report should identify the surface or elevation to which the finding relates. For later construction plans, these details are compared with the new condition. A ground change alone establishes neither automatic continued applicability nor complete unusability of an earlier result.

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
Person in an orange high-visibility vest with a MALÅ survey cart on a meadow.
Person in a high-visibility vest in front of a marked construction area with piles of soil.
Questions from planning

Questions about ground changes for projects in Marl

When and why does Marl's application ask about post-war fill?

The form compares today's ground level with the level in May 1945. These details support investigation preparation. Incorrect fill information may impair ordnance location. Do not enter assumptions as established values. Before construction projects involving ground intervention, the town first provides for an aerial photograph analysis application through the public order office. Where relevant suspicions arise, the further ordnance investigation is requested before construction starts. Ground information is needed to prepare this specific measure.

What should I do if the earlier ground elevation is unknown?

Identify the missing information and provide existing plans and reports. Clarify with the responsible authorities and specialists how the gap should be addressed. An estimate without evidence does not replace this clarification.

Can later fill be covered by an earlier investigation?

Read the report to establish which areas and reference elevations were investigated. Compare the later change with this scope. This identifies outstanding questions. Neither a new investigation nor unchanged use of the older result is automatically correct.

May material simply be removed for preparation?

Clarify the groundworks and prerequisites with those responsible beforehand. Even soil removal intended only to facilitate a later investigation requires the necessary hazard assessment. Whether it is permissible and under what conditions must be defined for the specific area.

How should a suspicious object be handled?

Stop work, do not touch or move the object and leave the affected area. Keep other people away. Marl identifies the public order office and, outside office hours, the police on 110 or fire service on 112 as reporting contacts. Follow the authorities' instructions.

Why does the date of a ground survey matter?

Because the survey describes a particular condition. Later fill or soil removal may affect comparison with today's ground interventions and is therefore documented additionally.

May a known fill thickness be used for the entire property?

Only insofar as its spatial applicability is actually evidenced. Different areas and missing information are identified separately.

What determines the survey workload and costs?

The town describes aerial photograph analysis as generally free of charge. It identifies possible costs for specific suspected locations and difficult circumstances; preparatory, accompanying and follow-up work are considered separately. The operational application also describes additional costs, for example for specialist methods, water management or repeat visits. For current or former federal properties, clarify the intended administrative agreement with the explosive ordnance disposal service. Private specialist services are agreed according to area, depth, method, access, preparatory services, interpretation and documentation.

Project enquiry

Prepare your investigation in Marl

Provide elevations with their references

Send surveys and depth information with dates, starting elevations and clear spatial assignments. Assign each plan to the condition actually shown. For the initial project discussion, consider existing ordnance documents, the planned ground intervention and applicable ground and elevation status together. State which details are supported by documents and which still need clarification. Existing file references and the respective area affected help coordinate municipal processing and specialist preparation.

Identify ground changes

Mark documented fill, soil removal and unknown areas, as well as conflicting information not yet clarified. For a ground change, provide the area affected, type and date of the change, and existing surveys and reports with their elevation reference. Further specialist assessment follows from this. Also identify known contaminated land or contamination and existing protective planning. Necessary specialist protection documents are clarified with those responsible for the work actually planned. Agree the timing and scope of any preparation before commissioning it.

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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