On a two day campaign the 'Vakimpak' device, which induces seismic waves in the ground, is operated in the HOAL catchment. At the device a drop weight is pulled up in a closed pipe and during the upwards movement vacuum is generated in this pipe. The weight later is dropped and forced by vacuum and gravity the weight falls down on a hard plastic plate and induces seismic waves in the ground. Geophones which are installed along a profile each 4 meters are registering the seismic waves which are later analysed.

With this method two seismic profiles are generated in the catchment. The main goal of the campaign is to determine the location of the hard rock layer or other layers below ground surface as a basis information for groundwater modelling and for further investigations.