Explosive ordnance surveys and EOD for construction projects

Historical aerial photograph analysis examines aerial photographs, maps, archives, previous uses and other sources for reliable evidence relating to the specific project area. It helps delineate an area of possible ordnance contamination, but does not replace a technical investigation of the present-day ground.

Its value lies in preparing the next steps: which parts of the site are affected, which target objects may be relevant, which works intersect the suspected area, and which explosive ordnance survey or clearance service may be appropriate in principle?

An aerial photograph shows conditions at the time it was taken. The report must therefore state when the images were taken, which parts of the present construction site can be identified and which other sources were used. Gaps and unclear areas remain explicitly identified; they are not automatically regarded as uncontaminated.

The historical evidence is compared with your current site plan. This shows whether a corridor, borehole location or excavation intersects an area with suspected ordnance. If the plans change, the comparison is repeated. The sources, drawing revision and limits of the assessment remain recorded in the report.

For projects with several construction phases, check whether the existing assessment covers the entire property or only part of it. Identical project names do not establish this. The site plan must show the assessed area and its investigation status. For further sections, the information or investigations still needed must be established.

Different geophysical methods are available for area-wide and near-surface investigations. Ground-penetrating radar (GPR), magnetometry and TDEM respond to different physical properties of the ground and of possible interfering or target objects.

The choice of method depends on target objects, depth, soil, moisture, sealed surfaces, utilities, reinforcement, scrap metal and accessibility. A surface survey is useful only if it can provide meaningful information about the intended ground disturbance under the conditions present.

In a surface survey, measurements are recorded with a spatial reference and then interpreted. The report shows where surveying took place, which method was used and what anomalies or limitations were identified. It must establish what conclusions can be drawn for the planned earthworks.

Open ground, paved routes and existing installations may create different survey conditions within the same site. For each part, it is assessed whether the selected method can answer the outstanding question. If further methods are needed, their purpose must be explained. A large number of instruments alone does not establish a good result.

Ask for a clear explanation of survey results and limitations. Areas that were not investigated, or could only be assessed to a limited extent because of interference, must remain identifiable in the report. The next investigation can then focus on these areas. An overview that omits such boundaries is insufficient to support a conclusion about the entire property.

For boreholes, piles, sheet piles and other deep ground disturbance, the relevant working space is investigated in three dimensions and at defined points. Investigation geometry, borehole diameter, target depth and safety distances must correspond to the subsequent construction method.

Casings, utilities, adjacent boreholes, geological layers and other interfering objects affect the measurements. A properly documented downhole survey therefore describes the conditions and limitations of the survey as well as its results.

The borehole schedule and site plan must match. The report should use the same point identifiers, coordinates and depths. Where there are several foundation or investigation points, each result can then be assigned to the correct point. The documentation must also describe the area around the point that was actually investigated.

If a borehole location is moved or a greater depth is planned, the existing investigation must be compared with the plans again. Proximity alone is insufficient. Pass on the revised site plan together with the earlier results so that the specialist contractor can assess whether supplementary work is needed.

Ground investigation and foundation design may use the same site plan while still specifying different ground disturbances. State the task for which the existing investigation was carried out. It can then be assessed whether it also covers the new task. A common project address does not replace this comparison.

Ordnance surveying during construction may be appropriate where advance investigations do not adequately cover the working space and the method is technically suitable for the planned ground disturbance. Before soil is removed in layers, technical surveying and a specialist decision take place; removal is then accompanied by an additional visual check. Before work begins, the work areas, equipment use, briefings, protective measures, hold points, procedures for a find and documentation must be defined and coordinated with site management to suit the actual construction sequence.

Before work begins, state the sequence and areas of excavation. Site management, the construction contractor and the ordnance specialist contractor agree the conditions for supervision. This includes how anomalies are reported and who initiates the next steps. These arrangements must be in place before the first excavation.

The documentation shows which earthworks were supervised and the areas and depths to which the result relates. Additional excavation areas or other changes are compared with the agreed commission. Areas not yet worked remain identifiable in the record so that the next construction phase starts from the correct information.

When handing over to another work crew, include the record and site plan. These must show where and to what depth the works were supervised and what remains outstanding. A verbal statement such as “The section was supervised” rarely contains all this information.

Where relevant anomalies or contaminated areas are identified, systematic area clearance involving exposure, identification and quality control may be necessary. The clearance objective, depth horizon, method, arrangements for making items available and handing them over, and documentation must be clearly defined in advance.

Ordnance recovery involves specialist handling of identified objects within the permitted scope of work. Technical supervision of explosive ordnance clearance requires an appropriate certificate of competence under Section 20 of the German Explosives Act (SprengG); the specific assigned tasks must fall within its scope.

An anomalous survey signal is not yet confirmed explosive ordnance. The point must first be relocated using the measurements and site plan and investigated by specialists. Only then can the object be assessed and the necessary next steps determined. A list of anomalies is therefore not a list of already identified ordnance.

Private clearance work and public-authority hazard response have different roles. Who handles an identified object next depends on the circumstances of the find, the object and local responsibilities. The responsible authorities decide on render-safe operations and further hazard response. The area worked and the handover must be recorded.

Each investigated suspect point needs an assigned result. The documentation must show what was done there and which questions remain open. When passing on information, identify the report and the point concerned. Site management can then assess the status without extending it to other areas or subsequent design changes.

An explosive ordnance assessment becomes useful for design and construction only when the starting conditions, investigated area, methods, data quality, findings and specialist conclusions are brought together clearly. Site plans, measurements, anomaly lists, field records and clearance records must be consistent.

The documentation also identifies areas that could not be investigated or could only be investigated to a limited extent. This shows which conclusions apply to which areas and depths and what supplementary action may be needed.

The anomaly list, site plan and record must use the same point identifiers. The list identifies anomalies, the plan shows their locations and the record describes the work performed. For every point worked, the documented result must be identifiable.

Hand over the full report with its appendices and limitations. The next design office or construction contractor needs these documents to use the results correctly. If the plans change, the earlier conclusions that remain applicable are assessed. A single result statement without its appendices cannot replace this comparison.

The report, site plan and lists must show the same revision status. Clearly identify supplemented or superseded versions. Designers and site management can then work with matching documents and assign queries to the correct section.