Explosive ordnance survey in Marburg

The historical aerial photograph analysis examines suitable photographs for indications relevant to explosive ordnance assessment. It is not the same as looking at individual street-level photographs. The findings must relate to the area in question; poor image quality, insufficient coverage or features that cannot be identified reliably limit the conclusions. The absence of an indication in a single image is not general evidence that a site is unaffected.

Where historical information remains incomplete, the necessary research and aerial photograph analysis are commissioned for the specific area. This includes the available site and land-use records, earlier statements and the question of which ground works are to be prepared. A commission might, for example, concern the assessment of an extension area not previously evaluated or the analysis of additional photographs. The technical assessment records what these establish and where the available historical record remains limited. Newly found documents are interpreted in relation to their original brief. For a site in Marburg suspected of explosive ordnance contamination, the next step is to establish which technical investigation can address the remaining questions under the actual site conditions.

A survey is planned on the basis of the defined task and the site conditions. Existing utilities, structural remains or other interference may affect interpretation. Selecting the suitable method and any additional steps requires a specialist decision. A historical photograph description does not in itself determine a particular survey method.

For method selection the investigation objective and required depth range are assessed against the local survey conditions. Ground composition, fill, metal utilities, installations and structural remains can limit interpretation. These limitations are documented with their locations; specialist planning determines the additional work required. For excavations, piled foundations, retaining structures or deep utility works, the proposed ground works are therefore described by location and depth. Any required deep survey or borehole clearance remains specific to that task. Preparation of access for investigations is also agreed with the specialists. If a survey point or foundation depth changes, existing results are compared with the revised plans.

Where areas or depths remain uninvestigated, these limitations must be taken into account in the next steps. A clearance plan can specify the measures and evidence required for the project. According to the DGUV FAQ, visual observation alone during excavation does not meet the state of the art. Particularly where areas are difficult to access, the proposed solution should be justified rather than adopting an unsuitable measure solely because of time pressure.

For tendering, research, technical investigation and any necessary further work are described with their respective purposes. State the available findings, affected areas and depths, and the reports and site plans required. Access, building entrances that remain in use and operational work windows are among the relevant conditions. For separate construction stages, establish when each area will be available and who will receive the results. Offers can then be compared against the same technical tasks and execution conditions. Subsequent site management receives details of the areas actually treated and the unresolved questions before the work that depends on them begins. Additional ground works or plan changes are assigned to the affected section and agreed as supplementary tasks.