ALBERT

Description / Table of Contents: Contents: 1 Introduction. - 2 State of the Art. - 3 Research Studies. - 4 Groundwater Management. - 5 Conclusions and Recommendations.

Description / Table of Contents: PREFACE It is increasingly necessary to develop industrial and hydraulic engineering constructions under unfavourable geological or geotechnical conditions. Furthermore, it becomes more and more important to build effectively and economically and to find optimal solutions for a long-term steady function of the constructions. This emphatically demands exhaustive information on the structural situations and engineering parameters of local site assessments by areal investigations of the sites and the petrophysical parameters in situ. This requires, however, the use of geophysical techniques. During the last two or three decades international applied geophysics has systematically developed new possibilities for site investigations for the determination of petrophysical parameters in situ as well as for observation of the system building and site. As in "New techniques in engineering", geophysical methods make it possible to develop areal models of subsurface conditions of building sites, to quantify relevant engineering parameters in situ, as well as to analyze the longterm behaviour of the buildings, which are influenced by internal or external factors. With regard to the broad spectrum of applied geophysics, there are few methods, that especially favour application in engineering and groundwater studies. These methods are distinguished by a relatively simple measuring technique and good measuring progress, e.g. the geoelectrical self-potential method, the geoelectrical resistivity method as well as a newly developed devices for geothermic measurements. There exist numerous publications, broadly scattered in the technical literature, concerning the theoretical bases and applications of these methods, but until now, there have been only a few meetings to exchange experience and results on an international level. This was the aim of the symposium "Detection of Subsurface Flow Phenomena by Self-Potential/Geoelectrical and Thermometric Methods", held in Karlsruhe from 14-18 March 1988. An outstanding part of the symposioum was represented by the results of a research project, coordinated by the University of Karlsruhe (Department of Geology and Institute of Soil and Rock Mechanics) and the Federal Waterway Engineering and Research Institute (BAW), Karlsruhe. Regarding the subject "Experiments to ascertain the relations between hydraulic potentials in the underground and the geoelectrical and thermic potentials set off by these", the research work took four years. The project was sponsered by the Volkswagen Foundation/Hannover. The goal was to develop and test objective techniques for detecting leakages in dams, locating, demarcating and designating quantitatively inhomogeneous spheres in dams with the aim of detecting damage and subsurface flow phenomena as soon as possible. The symposium consisted of a three-day lecture meeting with about 40 papers and a summarizing respectively closing roundtable discussion, a visit to the laboratories and to the in situ constructions within the area of BAW developed in the frame of the research project. This included a technical excursion to the Rhine-Staustufe Iffezheim with its very impressive waterway constructions and an excursion to the Geophysical Observatory near Schiltach (Black Forest). The Observatory belongs to the Universities of Karlsruhe and Stuttgart. Approximately 80 scientists from 15 countries participated the symposium. They were welcomed by the Rector of the University, Professor Dr. A. Kunle and the representative of the Federal Ministry of Traffic, Dr. G. Schröder. Professor Dr. H. Hötzl elucidated the scientific problems and the economical importance of the project as a speaker of the research group. The following papers dealt with the fundamental aspects of geoelectrical and thermometric measurements, with the theory of these methods, the state and developing ter~dencies concerning devices, data acquisition, processing and interpretation as well as noise effects. It became clear that the solution of the complex scientific-technical problems of waterway constructions and environmental protection requires broad, interdisciplinary cooperation and international collaboration. Thus it would be possible to minimize the personnel, temporal and economic efforts. The intended cooperation of geoscientists, engineering geologists, building engineers and representatives of other disciplines make it possible, not only to exchange experiences and results relating to international problems unsolved until now, but also to determine new guidelines with regard to the scientific organization of further investigations. Thus in order to inform all interested parties of the main topics of the symposium and to advance international cooperation in the future, the present review includes a part of the papers and reports of the excursions recommended by the participants of the meeting, which have been divided into the following topics: - Introduction to engineering-geophysical problems and attempts at their solution; - Geoelectrical self-potential measurements; - Geoelectrical resistivity measurements; - Geothermic measurements; - Case histories; - Some topics of the roundtable discussion; - Reports concerning the excursions. The editors wish to thank very much all those, who contributed to the success of the symposium and to the publication of the present report. Finally they venture the note, that the authors theirselves are responsible for the content of their papers.

Description / Table of Contents: Abstract Within the framework of a current DFG (German Research Foundation) program natural attenuation processes of BTEX have been investigated in a Quaternary porous aquifer below a manufactured gas plant in Southwest Germany. Seasonal and regional variations of the BTEX plume have been registered since 1996 by detailed hydrochemical monitoring and frequent soil gas investigations. Taking into account that degradation of organic compounds results in O 2 decrease and CO 2 increase in soil air, the measured soil gas CO 2 -anomalies correspond quite well with the observed contamination pattern of the groundwater. Although soil-gas surveying is usually applicable to the most volatile organic compounds, at the test site only very low concentrations of VOCs have been detected in the soil gas above the contaminated groundwater. In order to understand the results of the field investigations, physical, chemical and microbial processes determining the VOC concentrations have been investigated in detail laboratory scale.

Description / Table of Contents: Sixteen countries took part in the European Coordination Program (COST Action 65), which dealt with hydrogeological aspects of groundwater protection in karstic terrains. Based on the experiences gained in these countries with large karst areas, efforts were undertaken to develop a uniform and transferable concept for the protection of karst groundwater resources. This protection program differentiates protection measures for groundwater resources as such, from those which are used for the abstration of drinking water. For the evaluation of required protection measures, a safety system is proposed that takes into consideration the concept of aquifer vulnerability and risk management.

Description / Table of Contents: While using CO 2 as gas tracer for estimating the pneumatic parameters of the unsaturated zone in the range of soil vapor extraction wells the recoveries often have been less than 70% of the originally injected tracer amount. To check the applicability of CO 2 for this purpose combined CO 2 -Helium gas tracer experiments were conducted. With the results of the experiments it was possible to show that in spite of different physical and chemical properties CO 2 and Helium behave quite similar in the unsaturated zone. Because CO 2 is easier to handle, it may be the preferable tracer.