Environmental Engineering Series Editors: U Forstner, R. J Murphy, W H Rulkens Dieter Vogelsang Environmental Geophysics A Practical Guide With 113 Figures Springer-Verlag Berlin Heidelberg New York London Paris Tokyo Hong Kong Barcelona Budapest Series Editors Prof. Dr. U. Forstner Arbeitsbereich Umweltschutztechnik Technische Universitat Hamburg-Harburg EiBendorfer StraBe 40 D-21073 Hamburg, Germany Prof. Robert 1. Murphy Dept. of Civil Engineering and Mechanics College of Engineering University of South Florida 4202 East Fowler Avenue, ENG 118 Tampa, FL 33620-5350, USA Prof. Dr. ir. W. H. Rulkens Wageningen Agricultural University Dept. of Environmental Technology Bomenweg 2, P.O. Box 8129 NL-6700 EV Wageningen, The Netherlands Author Professor Dr. rer. nat. Dieter Vogelsang KampstraBe 70 D-30629 Hannover Germany ISBN-13:978-3-642-85143-8 e-ISBN-13:978-3-642-85141-4 DOl: 10.1007/978-3-642-85141-4 CIP-data applied for This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in other ways, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag. Violations are liable for prosecution act under German Copyright Law. © Springer-Verlag Berlin Heidelberg 1995 Softcover reprint of the hardcover 1st edition 1995 The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence ofa specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Typesetting: Data-conversion by Fototsatz-Service Kohler OHG, Wiirzburg SPIN:I0085882 6113020-5432 I 0 -Printed on acid-free paper Preface Applied geophysics was developed to explore the raw materials required by civi lization. This book defines its new environmental task: to investigate the extent and nature of buried contaminated waste and leachates. It describes the possibil ities, advantages and shortcomings of geophysics in detail and in plain words, without referring to mathematical formulaes or scientific jargon. Environmental Geophysics may also serve as a simple introduction to geophysics for students inexperienced in mathematics. Firstly, geophysical methods are described. Later, more than 80 environmental case histories from the USA and abroad are discussed and documented with 113 figures. The last three chapters present the gist of the book through condensed, lucid tables for the hurried reader. This briefing comprises cost estimates for geo physical surveys and offers advice for the proper choice of methods and for the compilation of tenders. This book will enable engineers, scientists and lawyers to appreciate the great possibilities of geophysics in the assessment of environmental risks. This new branch of science allows continuous spatial coverage, considerable cost and time saving, is noninvasive and guarantees high standards of industrial safety. This American edition is based roughly on the second edition of Geophysik an Altlasten. The German book was completely revised and considerably enlarged to meet the high American standards and requirements. The author would like to thank Mrs. Barbara Eder for her help with the translation. Hannover, March 1994 Dieter Vogelsang Contents 1 Introduction 1.1 Targets.... 1.2 Fundamentals 1.3 Preconditions 1.4 Cooperation 2 2 Methods . . 5 2.1 Geomagnetic Methods. . . . . 5 2.1.1 Geomagnetic Ground Surveys. 5 2.1.2 Aeromagnetic Surveys 8 2.2 Geoelectric Methods ... 9 2.2.1 Direct-Current Methods. . 9 2.2.2 Electromagnetic Methods . 20 2.3 Seismic Methods 31 2.3.1 General ....... . 31 2.3.2 Seismic Refraction . . 32 2.3.3 Air-Acoustic Seismics . 35 2.3.4 Seismic Reflection 35 2.4 Gravity ..... . 39 2.5 Geothermometry 40 2.6 Well Logging .. 41 2.6.1 General ..... 41 2.6.2 Logging Methods 43 2.6.3 Percussion Probing 50 2.7 Radioactivity ... 51 2.8 Isotope Hydrology . 54 3 Case Histories . . . . . . . 57 3.1 Abandoned Hazardous Sites 57 3.1.1 Preconditions . . . . . . 57 3.1.2 Geomagnetics ....... . 57 3.1.3 Geoelectric DC Methods .. 65 3.1.4 Electromagnetic Methods (EM). 81 3.1.5 Seismics . 98 3.1.6 Gravity ............ . 105 VIII Contents 3.1.7 Geothermy. 106 3.1.8 Radiometry 110 3.2 New Disposal Sites 114 3.2.1 General ..... . 114 3.2.2 Horizontal Stratification 114 3.2.3 Steep Dipping Structures 119 3.2.4 Nuclear Repositories .. 127 4 Costs of Geophysical Surveys 131 4.1 Cost Structures . . . . . . . . 131 4.2 Comparison of Geophysical Expenditures 132 5 Briefing for Geophysical Surveys . 137 5.1 Areas of Application ....... . 137 5.2 Objectives and Limitations .... . 138 5.3 Planning and Execution ofInvestigations . 141 5.3.1 Choice of Methods .. 141 5.3.2 Necessary Experience ... . 143 5.3.3 Preparations ........ . 144 5.3.4 Evaluation and Interpretation 144 5.3.5 Follow-up Activities ..... 144 5.4 Combination of Geophysical Methods 146 5.5 Research and Development 146 6 Geophysical Tenders . 151 6.1 Procedures... 151 6.2 Call for Tenders 152 6.2.1 Preparation. 152 6.2.2 Field Work. 152 6.2.3 Evaluation . 152 7 List and Origin of Figures and Tables. 153 7.1 List of Figures . 153 7.2 List of Tables 159 8 References 161 9 Index ... 165 1 Introduction 1.1 Targets This book was written to show how geophysics might be applied to the solution of environmental problems. Investigations of ground water, soil and rocks are described the subject of air pollution is not addressed, however. Non-geophysicists who deal with environmental problems, like engineers, scientists of other faculties, lawyers and community personnel, are introduced to the application of geophysical methods. Complicated scientific elaborations and mathematical formulaes are omitted. To contribute to a better understanding of the practical feasibility and validity of these methods, many illustrated case histories are presented. Additionally, examples of tenders for geophysical surveys are included. Cost benefit analyses compare geophysics, drilling and probing programs and demon strate the economic advantages of using geophysical measurements to solve environmental problems. 1.2 Fundamentals Geophysical surveys of hazardous waste deposits are rarely published, since they contain the classified data of companies, government offices and corporations. Because of this, the high success rate of geophysical activities at contaminated sites is as of yet known only to insiders. Thanks to an intiative of the German state of Baden-Wuerttemberg, which allowed a comparison of the results of 60 geophysical surveys at eight model sites at hazardous waste dumps, essential high-quality information became available. Geophysical results published by scientists from Europe and America plus investigations carried out by the author have enlarged the scope of this book con siderably. 1.3 Preconditions Over the past 75 years or so, geophysical methods have been developed, mainly for the prospecting of deep-seated deposits of hydrocarbons and ores. During this time, many instruments have been constructed and extensive experience in evaluating and interpreting data has been accumulated. 2 1 Introduction To cope with increasing rates of consumption of raw materials, the geophysical exploration of the resources of fossil energy and ore has had to extend to greater depths. Geophysics has thus helped to satisfy the raw material needs of our high tech civilization. However, the task of controlling the disposal of the voluminous remnants of used raw materials is a new one for geophysics. It necessitates a completely new orientation. Now, the hitherto eliminated surface effects that have been suppressing the signals of deep-seated deposits have become a new subject of in vestigation. There is no need to develop completely new geophysical methods for the exploration of hazardous sites. The above mentioned instruments and experiences can be utilized fully. However, it is necessary to adapt the various methods to the new environmental problems. It is, for instance, necessary to layout very fine meshed grids, which allow high accuracy in shallow depths. Since geophysical evaluations depend strongly on the geological and hydro geological structures of the ground, it is necessary to consider these when any geological interpretation is derived from geophysical data. 1.4 Cooperation Difficulties and misunderstandings may arise between geophysicists and engineers due to the lack of mutual understanding. Good cooperation is essential, since engineers control and finance most geophysical surveys. The reason for this is mostly a different consideration of geophysical results. While engineers regard every figure as "absolute", geophysical data may be rela tive, though they are based on the exact sciences of mathematics and physics. This paradoxical phenomenon comes from the great variety and complexity of the physical properties of geophysical targets. Their physical parameters must often be smoothed and averaged before they can be treated by mathematical for mulaes. Table 1.1 elucidates this dilemma. Furthermore, advice is included that engineers should describe their environmental problems as exactly as possible, so that the most suitable array may be chosen. The geophysicist should, in return, inform the engineer precisely about the limitations and restrictions of geophysical interpretation and should point out the margins of error. Further misunderstandings may arise from the presentation of data. They should be readable and understandable, even for the geophysical layman. Most impressive are certainly three-dimensional colored maps or sections. They por tray many details, and make complicated issues understandable. Columns of numbers, pseudosections and contour maps are less comprehen sible. But it must be considered that a "beautiful" picture can rarely be used for reinterpretation or upgrading, since it is mostly impossible to obtain precise data from three-dimensional and/or color illustrations. 1.4 Cooperation 3 Table 1.1. Assessment of geophysical results Engineers Geophysicists Absolutely unerring Ambiguous, several equivalent solutions possible All properties are exactly Properties can be determined only approximately expressed in measuring units No interpretation is neccessary Interpretation is essential Clear and correct description of problems .. Straightforward description of restrictions It is best to combine the beautiful with the exact: geophysical reports should contain the readable original data, perhaps on data carriers like PC discs or writ ten lists. Additionally, colored pseudo sections, 3D projections etc. should be included. Color has to be used with precaution: the nuances must agree with the data steps. Differences in colors are difficult to see in yellow or green, but provide good contrasts in red or blue. The introduction of colours means also the opening of an additional dimension for presentation; by colouring, one more set of data can be shown in a drawing. Depth data for engineers should be in meters or feet only. The tendency of geophysicists to divide the y-axes for the vertical extension in ms, ns, m V, nT or other physical units may be misleading because these units may be considered equivalent to depth measures in meters. If it is not possible to reveal the actual depth, the y-axes should not be marked at all. Naturally, the reason for this has to be mentioned. Overestimations of depth penetration may occur, especially in interpretations of electromagnetic or radar measurements. One should bear in mind that false depth declarations may cause expensive follow-up activities to fail. This may pro voke a general disregard of environmental geophysics. Further mishap may arise through wrong handling of pseudosections. In some cases, the metric scale at the surface (x-axis) was also used to determine the depth of sources. Accordingly, the follow-up drilling was full of surprises. To avoid this, pseudosections and similar presentations have to be described in detail to the client. A special warning not to measure depths by the meter should be included! Geophysical anomalies are created not only by natural or artificial structures, but also by human installations like cables or metal pipes, which produce un wanted disturbing anomalies. To avoid this, the area of investigation should be 4 1 Introduction Table 1.2. Presentation of geophysical results Medium Completeness Readability Follow-up Recollection evaluation possible tape, disc good difficult good bad tabled figures good difficult good small cross section acceptable good small good contour lines acceptable good small good 3D pictures small good not suitable excellent colouring enhanced enhanced not suitable excellent checked painstakingly by an electromagnetic cable/metal detector before geoelectric measurements commence. To eliminate "external" anomalies by calculation is not only very difficult, but often leads to wrong conclusions. If, for instance, a metal pipe crosses under a waste dump, it is preferable to leave the corresponding anomalies in the presen tation and show the pipe position in the maps. An additional obstacle is the meagre knowledge of geophysical methods by environmental experts. This may lead to the wrong approach: "Geophysics must be applied without any background information to find out whether it can really detect the wanted structures." It is much better to disclose all available informati on to the geophysicist in charge. This will enable him to plan and to evaluate the geophysical work much better and to overcome the ambiguity of some geo physical results. Most useful is the description of geological, hydrological and tectonical struc tures and of the materials that have been deposited in a dump. Geophysics should be employed within a loose frame: the width of the grid and of the measuring array should not be stipulated because all unexpected alterations of form, size and material content of the object, which come up during the survey, must be met with different directions of sections or a change of array.