Tellus environment - Cartographier l'invisible pour agir

Securing drilling sites and survey pits

Published in Polluted land and soil

  • Client: ESID de Metz
  • Domaine: Sites & sols pollués
  • Moyens utilisés: Scan magnétique à l’aide du Grad 601 Bartington

In the context of the reconfiguration of the 128 Airbase, located in Frescaty near Metz, soil surveys are necessary for pollutants detection.

Theses surveys are to be done in a First World War “zone rouge” with severe pyrotechnic risk.

The issue lies in locating blank zones, without any targets in there, and securing 82 survey pits on a very disturbed area from a magnetic point of view (ballast, ferrous waste, etc.).


 

Methods and equipment

- Identification of zones with a 10 m x 10 m surface and decimetric scouting

- Magnetic scan with the Grad601 Bartington magnetometer

- Treatment with the patented software Magsalia

- Tomography drafting: a 3D decision-support tool

- Interpretation, identification and marking of survey pits

- Securing of the drilling site with a Foerster magnetometer

- 2 days-long measuring process

 

Results and customer benefits

An initial 2D cartography without any digital treatment had not provided satisfactory outcomes, because the targets seemed vague or not isolated.

Data analysis and the first digital treatment allow the characterisation of the zone and highlight the foundations of a Zeppelin hangar, which is not visible on the maps.

 

3D system: a securing decision-support tool

The Magsalia expert inversion system produces 3D tomographic pictures from the collected magnetic data. It is possible to dependably estimate the equivalent in pure iron of the magnetic targets. For the characterisation of these blank zones, we set up the threshold at 10 g of pure iron.

 

Valuable time saving for the client and the driller

In spite of the site’s magnetic saturation, 82 drilling points have been mapped in 4 days.

 

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