Abstract: A method for assessing a wall of a depression, particularly a bore, in a workpiece. The method requires that a light beam in the depression is deflected so that at least two regions of the at least one wall portion are illuminated, and in that, by means of the at least two regions, reflected light is guided along the first axis out of the depression and is used outside the depression for determining the geometry and/or reflectivity of the at least one wall portion. The determination of the geometry or reflectivity is carried out interferometrically and/or wherein in each region for at least 250 pixels, at least one distance value and/or at least one intensity and/or reflectivity value is detected, and/or wherein the regions and/or the at least one light beam each has an area of at least 0.1 mm2.

Abstract: A method for the removal of water or aqueous liquids from the sump of an underground cavity, especially a cavern, is based on providing a process in which a water-miscible organic liquid is added to the sump, and then the mixture formed in this way is extracted from the cavity.