In practical terms, mapping is carried out by flying a helicopter over the project area equipped with measuring instruments that send out electromagnetic signals in order to measure the ground resistivity. The measurements obtained constitute information that is used to interpret depth to bedrock and can say something about the type of rock and sediments in the area. Of particular interest is any indication of acidic rock types in the project area. This is information that Nye Veier and the contractors need in order to plan the construction of the new E18 and to avoid unpleasant surprises in the form of unforeseen ground conditions.
Investigations of ground conditions were formally carried out exclusively with the aid of a lot of time-consuming and expensive geotechnical drilling to uncover potential problem sites in the project area. Using helicopter scanning, the project area is mapped effectively, and 3D models of the ground conditions are produced. The contractors can therefore make informed decisions earlier in the project with fewer geotechnical drillings needed. Drilling is carried out where the data reveals potential problem areas or where there is still a considerable degree of uncertainty with regard to the geoscanning data. Meticulously planned drillings, along with the overall picture provided by EMerald Geomodelling’s models, will save Nye Veier both time and resources in the preparatory works for the new E18.
The helicopter-based scanning of the three stretches of road will take place at the end of February. The helicopter will fly in a planned grid, about 70 m above the ground and at a relatively low speed (60 kmph). A circular antenna is suspended beneath the helicopter 30 metres above the ground, and this sends electromagnetic signals towards the ground. Project manager for EMerald Geomodelling, Guro Huun Skurdal, emphasizes that the electromagnetic signals used are not harmful, to both people or to animals. The radiation people will be exposed to is no stronger than what you get from your own mobile phone. The only thing the public will notice is the noise of the helicopter while measuring is in progress.