Investigation of Surface Exploration Programs for Hydrological, Hydrogeological and Hydrogeochemical Issues in the Site Selection Procedure

Abstract

Abstract. The project “Investigation of Surface Exploration Programmes for Hydrological, Hydrogeological and Hydrogeochemical Issues in the Site Selection Procedure” summarizes the measurement methods that can be used for surface exploration of site regions and compares them with the measurement parameters as given in the Repository Site Selection Act (StandAG). Based on this, an orientation framework was developed that can support the evaluation of actual exploration programs. This project is limited to those measurement parameters that result from §§ 22–24 in conjunction with the Annexes 1–11 of the StandAG for the surface exploration of hydrological, hydrogeological and hydrogeochemical characteristics of site regions. In a first step, definitions of terms which are subject to interpretation were identified in the StandAG and advice was provided on how to deal with them and, in some cases, justified proposals for interpretation within the framework of this project were given. As a result, hydrological, hydrogeological and hydrogeochemical parameters were presented that were derived directly from the StandAG, as well as those that are not explicitly mentioned in the StandAG but are necessary for a detailed characterization of the rock formations in a site region. The next step was to identify measurement methods to be used for surface exploration of hydrological, hydrogeological and hydrogeochemical parameters. In particular, hydrogeologic and (borehole) geophysical methods were considered in the context of field measurements and laboratory investigations as well as field and laboratory tests for the determination of hydrogeochemical parameters. These measuring methods were described with respect to their measuring principle, the respective limits, the technical effort as well as the advantages and disadvantages of their application. Possible combinations with other measuring methods as well as a potential need for additional research and development for use in surface exploration programs were also presented. Considering the boundary conditions and dependencies for different rock types and necessary exploration depths, the measuring methods were assigned to the relevant parameters with respect to their applicability. In most cases, several methods are suitable for the determination of a specific parameter. Combining different physically independent methods can limit the range of variation of the measured variables and significantly increase the reliability of the results. The resulting compilation of measurement methods was used in the last step to establish an orientation framework. This framework contains the essential requirements for a complete documentation and quality assurance of the measurements and sampling and derives fundamental factors influencing the quality and quantity of the parameters. The orientation framework also refers to various factors that may influence the selection of suitable measuring methods for the surface exploration of the parameters as well as the determination of appropriate measuring network densities and measurement intervals. The measurement network densities selected at the beginning of the exploration are usually adjusted based on increasing knowledge of the site-specific geological conditions. This step-by-step procedure, which has proven successful in geological exploration programs, was also emphasized in the orientation framework, as it gradually increases the level of knowledge, the level of detail and thus the reliability of the measurement results.