ALBERT

Notes: For horizontal layering and plane horizontal impulsive wavefronts it is theoretically possible to get rid of multiple reflections by a feedback procedure which can easily be derived using raypath philosophy. To reduce the increase of noise inherent in the method the precise theoretical formulae are altered in such a manner that a practical application becomes possible. For this purpose the autocorrelation will be used.Application of the new process to a CRP section where the shot geophone distances in the field had not been long enough to attenuate multiple reflections effectively gave favourable results.

Notes: Two in situ measurements of stress wave velocity in a granodiorite massif were made. Firstly, the velocities close to the source were investigated (for elimination of the influence of cracks), and secondly, the velocities in different horizontal directions over a large area were studied from the viewpoint of their dependence on the crack system of the medium. A correlation between the mutual orientation of the cracks and the maximum or minimum values of the stress wave velocities was obtained.

Notes: The technique of linear digital filtering as developed for the direct interpretation of Schlumberger and Wenner soundings (Ghosh 1971) has been applied here for the derivation of the resistivity transform function from the field dipole measurements as the first step in directly interpreting dipole data. Filter coefficients for this transformation have been worked out for the radial-polar, perpendicular and parallel (30°) arrays of dipole sounding. The procedure combines speed with accuracy.

Notes: Dipole soundings are more sensitive to noise caused by lateral and superficial inhomogeneities than Schlumberger soundings. However, the former are preferable for deep explorations in view of the relatively short cables required. The simple solution of carrying out the field work by means of dipole spreads, and to transform the dipole resistivity diagrams into Schlumberger ones by means of proper formulae would be valid only for smooth and regular curves; but often, owing to the presence of lateral noises, the dipole data show a considerable scatter. For such cases a “continuous dipole sounding” method is proposed for which all successive dipoles are contiguous, so that all parts of the profiles are covered and interpolation is not necessary. Obviously the moving dipoles have lengths proportional to their distances, so that they appear equal in the usual bilogarithmic scale. It follows that only polar-dipole arrays may be used. The transition from a dipole to the corresponding Schlumberger apparent resistivity diagram requires an integration constant which is not unequivocally determined. Therefore, the solution is not unique, but all possible derived Schlumberger diagrams have a common part. Similarly, they have some common interpretative results, which may be referred to the original dipole diagram obtained in the field.A special measurement technique is required since the dipole-dipole voltages to be determined are noticeably smaller than the Schlumberger ones. This is true also because dipole soundings are used for great depths and for long distances between the two dipoles.

Notes: Basic requirements for a seismic reflection system using a moderate-power controlled source are discussed. General considerations and computer modelling show promise for geophysical prospecting, especially at low penetration and very high noise level. For many applications, ranging from mineral and water prospecting, to civil and military engineering, and even archeology, a relatively cheap, small and portable device of this kind might be more convenient than conventional explosive sources or sophisticated controlled sources of the vibroseis type. The use of a simple, low frequency periodic signal facilitates rapid data processing procedures and suggests that the mechanical generator will be very simple and cheap.

Notes: A method is described to transform a dipole sounding curve, obtained with any one of the common dipole arrays over a horizontally layered earth, to the form of a Schlumberger sounding curve. Starting from the general expression which relates the dipole apparent resistivity to the Schlumberger apparent resistivity and its derivative with respect to the spacing, it is possible with some approximations to derive an easy numerical computation procedure in order to perform the transformation. The applicability of the method is discussed briefly.

Notes: Approximate deconvolution by means of Wiener filters has become standard practice in seismic data-processing. It is well-known that addition of a certain percentage of noise energy to the autocorrelation of the signal wavelet leads to a filter that does not increase, or even reduces, the noise level on the seismogram. This noise addition will, in general, cause a minimum phase signal to become mixed phase. A technique is presented for the calculation of the optimum-lag shaping filter for a contaminated signal wavelet. The advantages of this method over the more conventional approach are that it needs less arithmetic operations and that it automatically gives the filter with the optimum combination of shaping performance and noise reduction.

Notes: A set of parabolae is defined to approximate the observed gravity profile for specifying the lateral density variation in a two dimensional causative body. This variation separates the “biased” as well as “unbiased” residual anomaly structure. The method may be directly incorporated into existing numerical and graphical techniques of interpretation for subsequent delineation of structural configuration. The simple relations derived by inspection of the observed gravity profile permit universal application of the technique and in particular for the determination of the size and shape of sub-shelf structures. The suitability of the method in various problems of two dimensional interpretation has been indicated through an illustration of the Godavari Basin (India).

Notes: Decomposition of IP discharge curve into a sum of exponentials yields more information than present practice does. Such a work was performed, as a beginning, by hand, plotting the ordinates on semi logarithimic paper. It gave, according to the cases, two or three exponentials, each with an amplitude Ai and the time constant τi.Three examples of ground prospection are given, the third of which shows an anomaly, unnoticed with present technique but obvious on a profile curve with A1/A2 in ordinates.A computer processing technique is described which yields directly the time constants τi by seeking a differential equation which the IP voltage satisfies; the order of the equation is set arbitrarily. On a practical prospection record with only two exponentials, the assumption that the differential equation does not depend on charge duration (everything else being equal) has been checked (the shape of the curves would depend on boundary conditions). The assumption roughly holds for charge durations from 5 seconds to 40 seconds. We hope that a larger number of exponentials will yield better results.〈section xml:id="abs1-2"〉〈title type="main"〉SommaireLa décomposition de la courbe de décharge en une somme d'exponentielles permet d'en tirer plus d'information que la pratique actuelle. Un tel travail a été fait, pour commencer, à la main en portant les ordonnées sur papier logarithmique; il a fourni, suivant les cas, deux ou trois exponentielles avec, pour chacune d'elles, le coefficient Ai et la constante de temps τi.On donne trois exemples de prospection sur le terrain, dont le dernier comporte une anomalie, inaperçue avec la technique actuelle, mais bien mise en évidence en traçant la courbe de A1/A2 le long du profil.On donne ensuite une technique de calcul sur ordinateur des τi, en recherchant l'équation différentielle à laquelle obéit la tension ΔVPP enregistrée, l'ordre de cette équation étant fixé arbitrairement. On a cherchéà vérifier sur un enregistrement de terrain, avec. deux exponentielles seulement, l'hypothèse suivant laquelle l'équation différentielle ne dépend pas de la durée de charge (toutes choses égales d'ailleurs). L'hypothèse se trouve grossièrement vérifiée pour les durées de charge allant de 5 secondes à 40 secondes, et nous espérons qu'un plus grand nombre d'exponentielles donnera de meilleurs résultats.

Notes: The conventional seismic technique is subject to a recording time following each transmission of energy, in which it is forbidden to release any new pulse. The recording time depends on the deepest reflection of interest, and is often 10 seconds or more in actual practice. To each transmission corresponds one record, i.e. a fixed amount of data which cannot be increased in a given time.Pulse coding allows us to go beyond this limit, by transmitting several times during the normal recording time. The procedure gives as many records as there are pulses, but they overlap, each event being repeated every time there is a pulse. It is possible to process the composite record back to its usual appearance with all events in their proper place if the time breaks are accurately known and make up a code such that the unavoidable noise generated by the process be kept, on the final section, below the ambient noise. The processing is quite similar to that of records made from vibrating sources, though faster in practice.The additional information can be devoted to a saving of time and money as the same profile may be recorded in a shorter time; or to an improvement of quality of the section due to a higher order of coverage, a multiplication of the ray paths and a closer sampling of the reflectors. It is also possible to record information in several planes at the same time, and to work out a 3-dimensional restitution, without loss of production.The process applies to all kinds of sources provided they can be triggered according to the code with sufficient accuracy. Depending on the source and conditions of implementation, the method benefits from other advantages such as better resolution, increased flexibility, and better coupling.Two different names have been given to the process, Sosie and Seiscode, which apply to slightly different parameters for the sequence of pulses. Sosie is more useful at sea, while the normal scope for Seiscode is onshore. Both names are trademarks for SNPA.

Notes: Two-layer type curves of apparent frequency effect for the Wenner configuration are presented. The formulation is based on the normal definition of frequency effect in terms of resistivities measured at different frequencies plus the definition of apparent resistivity over two horizontal layers as a function of first and second layer resistivities. The use of these type curves in the interpretation of multilayer apparent frequency-effect curves is described and some field examples are given.

Notes: In this paper properties of the discrete zero-phase time function are derived and compared with related properties of the discrete minimum-phase time function.The two-sided minimum-length signal is introduced and it is derived that, for any given amplitude spectrum, the two-sided minimum-length signal and the signal with zero-phase spectrum are identical signals. A comparison is made between the one-sided minimum-length signal (minimum-phase signal) and the two-sided minimum-length signal (zero-phase signal).A computational scheme is discussed which determines the zero-phase correspondent of a given signal.A method is proposed to compute zero-phase least-square inverse filters. The efficiency of minimum-phase and zero-phase least-square inverse filters is shown on signals with different phase properties.A criterion is derived which determines whether a symmetric time function has the zero-phase property. The close relationship with the minimum-phase criterion is discussed.Finally the relationship between signal length and resolving power is illustrated on numerical examples.

Notes: Empirical equalities derived from time domain induced polarization scale modelling with the gradient array over simple geometries, and from the potential field functions for equivalent simple charge configurations are similar. The function for the dyke like body is analogous to the magnetic case allowing both total and vertical magnetic field interpretation techniques to be applied to gradient array chargeability anomalies.

Notes: A checking method of digital multiple elimination and of deconvolution processing using computers and based on optical autocorrelation is first presented. Comparison between autocorrelograms before and after a single or several processing steps allows to estimate, on one hand, the strength of the deconvolution obtained, known by the study of the central parts which is in fact the signal autocorrelation, on the other hand, the multiple elimination given by the study of side parts of the autocorrelogram.Further, an optical deconvolution procedure, is presented. For this, it is supposed that the signal is known and optically reproduced in the same way as the one of a trace. This is achieved by sphero-cylindrical optics allowing trace to trace processing. Deconvolution is carried out in the spectral domain by inserting a filter in the Fourier plane of the optical unit, the transmission law of which expresses the Fourier transform of the antisignal. This filter device introduces a holographic technique called Fourier holography, in such a way phases as well as amplitudes are preserved.Several results are presented from a synthetic section and also from field sections.

Notes: The separation of regional from local gravity anomalies by means of the application of two-dimensional linear filters is analyzed. It was found that optimization of the filter in the least squares sense leads to filters that produce strong localized concentrations of the error, which may erroneously be interpreted as anomalies. For this reason the maximum absolute value of the error is a more important criterion for the quality of the filter than the root mean square error. This maximum absolute error is minimized by the minimax filter. Intermediate filters are derived which give a transition zone which comes appreciably closer to that of the optimal filter at only a small price in terms of increase of the maximum absolute error.

Notes: Cable feathering is defined as the angle between a line connecting the cable end points and the line of the seismic profile. It is shown that an average reflection point map is more accurate than a shot point location map for geologic interpretation. Geologic resolution is degraded by feathering and this degradation is a function of the number of channels recorded. Feathering in areas of dipping reflectors produces non-standard normal move-out because the depth points are not common, and the perpendicular distances to the reflecting surfaces vary among traces in the c.d.p. gather. An example of a profile shot across a large river is discussed.

Notes: First, we review briefly the principle of the method, the computation of theoretical curves for a layered earth, and the recording technique in use in our surveys.The case history deals with an area covered with overthrust nappes (marls of Miocene age), which had slid on a Triassic sole, obscuring the geological picture.The magnetotelluric survey followed those of gravity and aeromagnetics and preceded the seismic one from North to South, it displayed a shallow and gently dipping basin, a major fault system, and a deep basin with a thick resistive layer, often underlying a conducting one.The seismics, and later the drilling of a well East of the profile, confirmed these features; in particular, the thick resistive layer was revealed to be Jurassic; only its thickness had been slightly overestimated. This fact lead the people in charge of the operations to ask for a reinterpretation synthesis of magnetotellurics, seismics and gravity, the results of which are also presented.

Notes: Qureshi and Mula have suggested a computer method for the calculation of the shape of a two dimensional body from the gravity anomaly profile associated with it. The application of the method, however, was restricted to those bodies which have their top or base horizontal and end sides vertical. In this paper study has been made to investigate the possibility of eliminating the above mentioned restrictions and has arrived at the affirmative conclusion.

Notes: Consideration is given to the form of apparent resistivity sections obtained by varying electrode array position and spacing over two dimensional features.Since basic solutions exist for horizontally layered media and for vertical or dipping single interfaces, simple rules are proposed whereby these solutions can be directly combined to give solutions for more complex sections. Substantial approximations may be involved as the rules do not fully allow for interactions between the constituents.The range of error incurred in application of the rules is explored, with particular reference to the square array system of resistivity measurement. The two extremes- of orientation of the square array with respect to the line of section are separately considered in this survey.Within appropriate limits, the rules appear extendable to a wide variety of simple structures for which rigorous solutions would be formidable. The rules are finally discussed in relation to practical applications.

Notes: In modern oil exploration layers of prospective interest with rather simple structural features are often overlain by very complicated bodies as e.g. saltdomes or other kinds of diapirs, olistostromes, or front zones of overthrusted blankets. In all these cases normal reflection seismic investigations, where downgoing and upgoing rays are rather close to each other, mostly fail, either because no reflections from underneath the complicated bodies are obtained, or because a reliable migrated depth presentation becomes practically impossible due to the inhomogeneity of the overlying bodies.The undershooting technique avoids these difficulties by using ray paths which do not traverse the complicated bodies e.g. by shooting on one side of a saltdome and recording on the other side. On account of the large shot-geophone distances in this method special considerations and computer processes were developed concerning moveout corrections for common depth point stacking and migrated depth presentation.In many cases the location of the disturbing complicated bodies is known in advance. The shooting and recording program can then be adjusted to this knowledge and thereby kept to a minimum. If the location of the complicated bodies is unknown a more extended seismic program has to be carried out encompassing a great variety of shot-geophone distances. But in this case the approximate location of the complicated bodies can be deduced from the survey too.Results are presented in order to give an idea of the efficiency of the new seismic tool.

Notes: This paper describes the procedure for interpreting the apparent resistivity data measured with the two-electrode array directly with the help of kernel function. The calculation of kernel function from the observed resistivity curve is done by the method of decomposition. In the method of decomposition the resistivity curve is approximated by a sum of certain functions, whose choice is only restricted by the requirement that the contribution to the kernel function corresponding to them should be easily computable. A few such functions are classified. These, and the standard curves for corresponding kernel functions obtained by utilising an integral expression for two-electrode array expressing the kernel explicitly in terms of the apparent resistivity functions, are plotted on log-log scale. The determination of layer parameters, that is, the layer resistivities and thicknesses from the kernel function can be carried out by a method proposed by Pekeris (1940).

Notes: A six-channel wide-band digital system for magnetotelluric measurements is described The system is designed to operate in the frequency band 10-.0001 Hz. The recording is made on a 7 track tape in an IBM compatible 12 bit format. The amplitude and phase responses of the system and sample records are presented.

Notes: Several types of multichannel filters have been introduced in the past with the purpose of rejecting, in a seismic section, coherent noise having a slope different from that of the signal.These filters, generally, tend to introduce a certain amount of mixing and therefore the output trace shows increased horizontal coherence. This is due to the model on which these filters are based, since the hypothesis is posed that the reflectors are continuous. This may be dangerous since it could lead to mistaken interpretations, for example when small faults or breaks are made to disappear in the output section.Other problems that could arise in the application of multichannel filters after-stack are space-aliasing and high-pass filtering. The former occurs when coherent noise is rejected with apparent Velocity V and frequency fa=V/X, where X is the distance between traces. In this case, the signal also is distorted since it is rejected in the same frequency range. The high pass filtering effect occurs when the multichannel filter is designed to remove low coherent noise with high apparent velocity.In the paper a family of multichannel filters is presented based on a model of the seismic section such that minimum mixing effects appear. The filters are designed to give good results even in the case of low frequency and high velocity coherent noise.Some practical examples are shown.

Notes: Sub-bottom profilers achieve high resolution but limited penetration beneath the seabed. Marine seismic surveys with long streamers and conventional sources suffer from an incomplete CDP stack and an unnecessarily low signal frequency in the early part of the section. Consequently there is a depth interval over which the optimum resolution of the seismic reflection method is not achieved. This paper describes the design, conduct, and results of an experimental survey made to obtain high resolution sections (predominant frequency about 200 Hz) with reflection times up to one second in the northern North Sea. The prime motivation for the experiment was to assess the possibility of mapping a shallow gas sand which had been encountered by the drillers.The design concept of the survey was to keep all the benefits of conventional marine seismic data gathering and processing, but to reduce their dimensions and time scales by a factor of five to ten. The survey in 1972 recorded a total of twenty-four lines using twenty-four fold cover with 5 m spacing between the reflector points, and a separation of 50 m between adjacent lines. Multi-electrode sparkers were used with a shallow purpose-built twenty-four channel 240 m hydrophone streamer. The recording sample interval was 1 ms. The final sections, obtained after conventional data processing, were of good quality. The results of velocity analysis helped to distinguish primary and multiple energy. Reflections with large negative reflection coefficients were seen in some parts of the survey area, and these are thought to indicate thin gas sands.

Notes: This paper deals with a case study on the application of auto-correlation and spectral analysis methods to mineral assay data taken along seven drives and two winzes concerning the McTaggart's (West) lode of Kolar gold fields. The general model conceived in this study is: measured (estimated) ore grade at jth location =true value + error at jth location. Employing an auto-correlation function of the form C e- a |k| for signals, the respective contributions of signals and noise to the total logarithmic variances for the data along drives and winzes are analysed. Smoothed spectral density estimates and their 90% confidence limits are computed for the series of data.

Notes: Methods and typical case histories of EM and IP surveys are compared in order to check their compatibility for the investigation of large areas for base metal sulphides. It is demonstrated that the fast, low cost EM may miss sulphide concentrations which cause no reduction of apparent resistivity, or which act like horizontal slabs, where EM anomalies occur marginally. In such cases only IP can recognize the whole extent of the mineralization. The misleading role of graphite exists for both methods.The conclusion is that EM remains the only economical method to survey whole ore districts, but that the shortcomings should always be taken into account in the interpretation. They can be overcome by employing geological, geochemical or other geophysical indicators in selecting promising targets for follow-up IP. Even if less than 20% of the area is covered by the expensive IP, there is a fair chance that all sulphide bearing rocks will be found. Therefore, the question is not whether to apply EM or IP methods, but how to combine them best.

Notes: The paper deals with the prerequisites of application, specific peculiarities and methods of electrometric and thermometric investigations aimed at the solution of certain engineering-geological problems in offshore areas. Practical examples are supplied.

Notes: The voltage induced in a horizontal loop on a layered ground has been calculated for the case where the loop is excited by a step current and measurements are made during the off-cycle.The expressions derived for a uniform ground show that for large time t the induced voltage E(t) is approximately given by E(t)≃— (Ibαμ/20t) (σμ2/t)3/2 where σ is the conductivity of the ground, μ the permeability, b the loop radius, and I the amplitude of the current step. For small times the corresponding result is E(t)≃—Ibμ/2t.When the ground is composed of a number of layers a numerical procedure for calculating the induced voltage is described.The calculated responses of various multilayered structures show that at short times the induced voltage is asymptotic to that produced in the case of a uniform ground of conductivity equal to the top layer.Interference effects in the top layer can lead to anomalous decay curves which may result in the underestimation of the conductivity of a buried layer.

Notes: Marine geophysical work requires accurate navigation on a continuous basis. A repeatability of 150 m CEP (circular error probable) with sequential positioning of 15 m CEP is usually acceptable. Quoted figures for many presently available navigation systems yield nearly the required accuracy. In actual operations, however, such accuracies may not be achieved, and usually the performance actually realized cannot be determined for want of independent measurements for comparison. If more redundancy in navigation measurements were available on an integrated basis, the limitations of individual systems would no longer be so critical and the accuracy of measurements could be assessed in real time. Failures in navigation continue to occur. Such failures usually result from ignorance of the capabilities of the navigation system and limitations and consequent choice of a system which is not appropriate to the demands of a particular survey. The points to be covered in work standards are listed.

Notes: The acceptance of articles in Geophysical Prospecting is strictly based on the originality and relevance of the contents. In order to be published a paper has to satisfy additional requirements on its external form and on its style and language: it should be written preferably in English though articles in French and German are permitted. A paper should consist of (i) a title page, (ii) an abstract, (iii) the text, (iv) list of references, (v) captions to illustrations, if any, (vi) tables, if any, and (vii) illustrations, if any. These seven parts should be mailed together but be physically separable and should be prepared according to rules which are either based on printing necessities or on the editorial style of the Journal.Failure to comply with these rules may result in delay in further processing of the article. Since Geophysical Prospecting is edited with a minimal budget correspondence with authors is kept to a minimum.

Notes: Depths of investigation for normal (bipolar) and focusing (unipolar) linear electrode arrays have been computed following the method given earlier (Roy and Apparao 1971) both in homogeneous and layered earth. The focusing arrangement is found to be superior to normal arrangement both in regard to depth of investigation and zone of uniform depth of investigation. This analysis holds good in layered media too. Further, the depth of investigation increases with the increase in the length (2M) of the electrode and reaches a limit, 0.29L for normal and 0.50L for focusing, when the electrode attains an optimum length to satisfy the infinite condition. This optimum length of the electrode is six times the distance L of the observation point from the electrode for normal and about ten times for focusing. A contour diagram for contributions of individual ground elements to the total signal measured at the centre of focused system is also discussed.

Notes: The authors generalize a method expounded in a previous paper (1971, Geoph. Prosp. 18, 786-799) to the case of a local conductivity σ(M) of the infinite medium satisfying the relation 〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR246:GPR_246_mu1"/〉 where the Ri's are the distances from the point M to n fixed points Si (i= 1,. n), k is a positive real constant and Ci, Cii are constants ensuring the condition α 〉 O.The sub-surface conductivity distributions (half-spaces) complying with (1) provide a wide variety of conducting structures, which can fit quite successfully the rather complicated distributions of conductivity occurring in natural ore bodies.An exact algebraic calculation of the apparent resistivity for these grounds, valid for any dc electrical prospecting devices (Wenner, Schlumberger, dipole, etc.) leads to a set of simultaneous linear equations, with a matrix which is invariant with respect to the position of the quadrupole being used. This greatly simplifies the numerical computation.We also present some examples of cross sections for the real and apparent resistivity obtained by this method.

Notes: Section migration after stack has been widely accepted by the industry. From a theoretical point of view, section migration before stack should provide superior results, the improvement warranting the drastically increased cost is not realized in most cases.There are a number of reasons that explain the discrepancy between actual and theoretically expected quality: Long period statics, refraction of rays, two-dimensional treatment of an actually three-dimensional problem.The section migration package subject to this paper allows(i) to take refraction into account,(ii) to discriminate against noise with a variety of statistical and geometrical criteria,(iii) to adapt processing time to problem complexity by a special process called SEMI-STACK.A number of examples will demonstrate the effects of section migration.

Notes: A seismic trace after application of suitable amplitude recovery may be treated as a stationary time-series. Such a trace, or a portion of it, is modelled by the expression 〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR627:GPR_627_mu1"/〉 where j represents trace number on the record, t is time, αj is a time delay, α (t) is the seismic wavelet, s(t) is the reflection impulse response of the ground and nj is uncorrelated noise. With the common assumption that s(t) is white, random, and stationary, estimates of the energy spectrum (or auto-correlation function) of the pulse α(t) are obtained by statistical analysis of the multitrace record. The time-domain pulse itself is then reconstituted under the assumption of minimum-phase. Three techniques for obtaining the phase spectrum have been evaluated: (A) use of the Hilbert transform, (B) Use of the z-transform, (C) a fast method based on inverting the least-squares inverse of the wavelets, i.e. inverting the normal time-domain deconvolution operator. Problems associated with these three methods are most acute when the z-transform of α(t) has zeroes on or near the unit circle. Such zeroes result from oversampling or from highly resonant wavelets. The behaviour of the three methods when the energy spectra are perturbed by measurement errors is studied. It is concluded that method (A) is the best of the three. Examples of reconstituted pulses are given which illustrate the variability from trace-to-trace, from shot-to-shot, and from one shot-point medium to another. There is reasonable agreement between the minimum-phase pulses obtained by this statistical analysis of operational records and those estimated from measurements close to the source. However, this comparison incorporates a “fudge-factor” since an allowance for absorption has to be made in order to attenuate the high frequencies present in the pulse measured close to the shot.

Notes: The implementation of a stacking filter involves the filtering of each trace with an individual filter and the subsequent summing of all outputs. The actual position of a trace in space as well as certain simultaneous shifts of traces and filter components in time do not influence the process. The resulting output is consequently invariant to various arbitrary coordinate transformations. For a certain useful class of ensembles of non-linear moveout arrival times for signals a particular transformation can be found which transforms a given ensemble into one consisting only of straight lines. It is thus possible to reduce, for instance, the analysis of a stacking filter designed for hyperbola-like moveout curves to the analysis of a velocity filter with linear moveout curves. As the (f—k) transform is a very useful concept to describe a velocity filter, it can consequently be applied to characterize a stacking filter in regard to its performance on input signals with non-linear moveout.

Notes: The technique of linear digital filtering developed for the computation of standard curves for conventional resistivity and electromagnetic depth soundings is applied to the determination of filter coefficients for the computation of dipole curves from the resistivity transform function by convolution. In designing the filter function from which the coefficients are derived, a sampling interval shorter than the one used in the earlier work on resistivity sounding is found to be necessary. The performance of the filter sets is tested and found to be highly accurate. The method is also simple and very fast in application.

Notes: A case history is presented for the exploration of barite with the electrical resistivity method. Altogether eight locations were recommended out of which six correspond to barite bodies. In the present case the gravity method, which is commonly used for the location of barite because of its high density contrast with the host rocks, has failed, perhaps due to small size of the ore bodies.

Notes: A correct derivation of rms, average and interval velocities from one another and from common depth point stacking velocities requires a clear understanding of the relationships between these velocities. We relate the average velocity to the rms velocity through a “heterogeneity factor” which is a quantity that gives a measure of the degree of velocity heterogeneity in the ground. The interval velocity is a quantity which varies according to the method of its derivation. The difference between rms and stacking velocities depends on the heterogeneity factor and on the length of the spread. Unless allowed for, this difference can reverse the advantages of long spreads and cause large errors in interval velocity determinations. It may be removed through a number of techniques. The accuracy of stacking velocities in the presence of random “noise” is independent of the heterogeneity factor. Relevant expressions can be broken down into simple formulae which give the accuracy quickly and with good precision.

Notes: Results obtained from a linear programming ground-water management model are tested against those obtained using numerical and electrical analog ground-water models. The optimal distributions of pumping and head as predicted by the management model are verified.An improved optimal solution could be obtained by reformulating the management model using different constraints or a finer grid spacing.

Notes: DuPage County, one of the major counties of the Chicago metropolitan area, obtains all of its water supply from ground-water resources. In 1972, pumpage was 56.6 mgd, 18 percent more than the combined potential yield of shallow aquifers and the practical sustained yield of deep aquifers. Total pumpage from shallow aquifers almost equals the potential yield. In some areas, yields of shallow wells have declined drastically as a result of excessively heavy pumpage. Pumpage from deep aquifers is more than double the practical sustained yield. Demands for water are projected to increase more than 250 percent by the year 2020. Alternative methods of developing supplies to meet the anticipated demands include artificial recharge of shallow and/or deep aquifers, mining of deep aquifers, increased diversion of water from Lake Michigan, demineralizing Mt. Simon sandstone water, and importation of underdeveloped surface or ground-water resources in north central and northwestern Illinois. Increased coordination of development programs becomes of greater importance as locally available supplies lose the capability to meet growing demands.

Notes: The alluvial aquifer underlying and adjacent to the Mojave River near Barstow, California, has been subjected to degradation from percolation of industrial and municipal wastes for more than 60 years. Effluents discharged to the aquifer have contained high concentrations of both organic (detergents, oil and grease, phenols, humic compounds, and others) and inorganic (chromium, chloride, phosphates, and others) substances. The concentration of dissolved organic carbon (DOC), as determined by a wet combustion technique, has been shown to be a definitive parameter in identifying ground water affected by waste disposal. DOC concentrations ranged from 0.1 to 0.8 milligram per liter in the nondegraded ground water and exceeded 6 milligrams per liter in the ground water affected by the waste discharge.The general distribution of DOC in the degraded ground water has been defined both areally and vertically. The vertical distribution of DOC and other constituents indicates that two plumes of degraded water occur at different depths. A comparison of the areal distribution of DOC and detergents (as MBAS) suggests that some organic compounds may have been adsorbed by the aquifer sediments.

Notes: Analytical data for 161 sampling sites indicate orthophosphate concentrations in ground water ranging from 0 to 1.7 mg/1. Ground water in about 50 percent of the county contains concentrations of 0.1 mg/1 or greater. In two areas aggregating 115 square miles, orthophosphate concentrations exceed 0.5 mg/1. Principal sources of phosphate in ground water in Hall County include: indigenous soil phosphate, municipal sewage effluent, commercial fertilizer, and feedlot wastes.

Notes: In areas of crystalline and basaltic rocks in India dug wells of large diameter may offer the only opportunity to test for the hydrologic characteristics of the shallow aquifers. Analysis of aquifer tests in these wells is difficult, however, if the volume of water stored in the wells contributes significantly to their discharge during the tests. In most dug wells, the time rate and spatial distribution of drawdowns in the aquifer, and the rate of change of head in the dug well are not predictable by the Theis equation or its semilog modifications. High rates of pumping result in difficulties due to the insensitivity of head distributions to drawdowns in the well.A review of current methods of analysis of aquifer tests in large-diameter wells indicates that most have serious theoretical and practical deficiencies. It is concluded that the methods of Papadopulos and Cooper (1967) and Papadopulos (1967) are the best available approaches, providing measurements of well volume can be made with sufficient accuracy. A consideration of aquifer tests in fractured rocks suggests that these tests can probably best be handled by treating the aquifer as an anisotropic porous medium on a macroscopic scale and utilizing observation wells.

Notes: To aid in determining the direction of ground-water flow after the effluent from the Lake George Village sewage treatment plant is discharged onto natural delta sand beds, resistivity studies were made in the soil (sand) in the vicinity of the recharge beds. Ground water having high dissolved solids is identified as producing lower resistivity readings. The sewage effluent has a higher dissolved solids content than the existing ground water in the area. The path of the recharged sewage effluent, as identified by lower resistivity readings, appears to flow in a northerly direction from the sewage treatment plant along Gage Road toward West Brook. Due to interferences, the resistivity studies could not show whether the high conductivity ground water flows into or under West Brook.

Notes: Practically all of the toxic chemical land disposal sites now in operation are equipped with only minimal and generally ineffectual monitoring systems, which seldom are capable of detecting even excessive surface-water and ground-water pollution from such sites. From monitoring data normally obtained, it is practically impossible to quantitatively evaluate the total toxic chemical buildup in contiguous soil, plant, and water environments or the vertical and horizontal migration patterns of pollutants through underlying earth materials. Monitoring facilities and procedures described in this paper are designed to provide that data required to effectively evaluate all of these parameters. These evaluations in turn should be most helpful in selecting the safest possible sites for hazardous waste disposal, and in developing ways and means to design, operate, and monitor such facilities that will assure minimal danger to public health from this particular waste disposal practice in the future.

Notes: Aquifers may serve as storage reservoirs, as treatment mediums, as discharge conduits, or in some combination of the various uses. If an aquifer serves as a conduit, the Darcy equation gives an accurate and simple solution for discharge provided the conduit is uniform; if nonuniform, the accuracy may be very poor unless special care is taken.Differential equations based on Darcy's equation and the equation of continuity give the steady-flow discharge rate for confined aquifers in which the cross-sectional area and permeability vary from point to point. For the general case the derived discharge expression is theoretically exact, whereas, for specific cases an approximate form can be used depending on the boundary conditions. Integration of the approximate form for a given aquifer length yields simplified solutions for discharge where the variation in cross-sectional area and/or permeability with distance in the direction of flow can be described by some mathematical expression.

Notes: Contemporary use patterns of land and water resources create conflicts between natural and human environments. These conflicts are generally not discussed as part of a classical approach to geologic education. This paper addresses the need to increase non-earth science training simultaneous with traditional training. The benefits to be gained will be welcomed by both students and their potential employers. One approach to suggested interdisciplinary water-resource education is discussed.

Notes: Low-rate or irrigation-type systems for land application of sewage effluent or similar wastewater are often used in humid areas because they have a small impact on the underlying ground water. In arid areas, low-rate systems cannot be used to produce renovated water for ground-water recharge, because the renovated water will have a much higher salt content than the effluent. Renovated water of relatively low salt content can only be produced with high-rate systems. Such systems, which require permeable soil, can also be used in humid areas to reduce the land requirements. To minimize the impact of high-rate systems on ground-water quality, the system should be managed to remove as much of the pollutants (particularly nitrogen and phosphorus) as possible from the wastewater as it seeps through the soil, and to restrict the spread of renovated wastewater in the ground-water basin. Nitrogen removal can be maximized by stimulating denitrification in the soil. Certain soils can store large quantities of phosphate. The spread of renovated water in the ground water can be controlled by intercepting the flow of renovated water with wells or drains for reuse or discharge into surface water. Techniques for predicting the underground flow system are presented.

Notes: Bore hole sampling of loose saturated sands and gravels forms a very important part of water well investigations. The materials are often difficult to sample and the adoption of adequate equipment and techniques can sorely tax the ingenuity of the driller.In some situations, the standard exploration sampling procedures can provide satisfactory information, while in others, it is necessary to resort to more precise techniques.A great variety of samplers have been designed including types such as open drive, piston drive, jet and extension flap samplers. No single sampler can cover the very wide range of material conditions and operational requirements which may be met during the drilling of water wells.In extreme circumstances, particularly for uncemented or poorly cemented gravels, it may be found necessary to stabilize the strata prior to sampling.

Notes: When the Lake George sewage treatment plant was put into operation in 1939, it was described as a “complete treatment” plant. This was because the treated effluent is discharged onto natural delta sand seepage beds which are “at least 25 feet deep.”Studies were made to determine the removal efficiency in the sand beds of coliforms, BOD, chlorides, and the nitrogen and phosphorus compounds.It was found that when beds were dosed, they were no longer saturated with water at 15 feet. Ten feet of sand were found to remove coliforms by 99% and BOD by 96%. However, nitrates, phosphates, and chlorides remained in significant concentrations after filtration through 10 feet of sand. Phosphate removal in an infrequently used sand bed was greater than in a continuously used bed.

Notes: At the Savannah River Plant near Aiken, South Carolina, as at other locations where there are chemical separations plants for the processing of nuclear fuels, the high-level radioactive wastes are stored in concrete and steel tanks buried just beneath the surface of the ground. This waste is of such activity and longevity that it cannot be dispersed into the environment, but it must be contained for periods of time extending at least into hundreds and perhaps thousands of years. One concept for the terminal containment of this waste is to store it in excavated chambers within the bedrock, which is covered by about 1000 feet of Coastal Plain sediments at the plantsite. As part of the safety evaluation of this concept, the geology and hydrology of both the Coastal Plain sediments and the bedrock have been studied. However, intensive investigation of bedrock waste storage has now been deferred pending more detailed evaluation of alternative concepts of waste storage and management.In the studies completed, a buried Triassic basin that might have potential for waste storage was discovered beneath the southern third of the plantsite. Investigation into the characteristics of this basin was started in 1971. This was not an engineering or design study but was aimed at understanding the geohydrology of the Triassic basin to determine its compatibility with the safe storage of waste.Seismic surveys, gravity and magnetic surveys, and the drilling of several exploratory wells indicate that the Triassic basin is about 30 miles long, 6 or more miles wide, and perhaps 5300 feet thick. One well penetrated the Triassic border, a second was in the center of the basin, and a third investigated an inferred intrabasin fault. The rock is predominantly mudstone of very low permeability with a few lenses of poorly sorted gritty sand. The water yield of all the exploratory wells is extremely low, and water-transmitting fractures are virtually nonexistent.In two wells within the basin, heads above land surface have been measured that cannot be explained by connection with a recharge area. Ten possible explanations have been evaluated: aquifer head, fossil head, tectonic compression, rapid loading and compaction of sediments, water derived from igneous intrusions, infiltration of gas, precipitation of minerals, phase changes, temperature increase, and osmotic membrane phenomena. Systematic evaluation, particularly of the time for dissipation of an elevated head to the head of its surroundings, eliminates most of these explanations. Those that remain as possible explanations are: tectonic compression, temperature increase, and osmotic membrane phenomena. It is not known at present whether the high head is general over the entire basin or only in segments of it.

Notes: Many tube wells drilled for irrigation use fail prematurely because of poor well design, improper sized and placed gravel-pack material, and ineffective slotted-pipe screens. Well and gravel-pack design criteria and an improved slotted-pipe screen described in this paper offer promise of drastically reducing such failures. Properly designed tube wells equipped with this type of screen should have more than double the safe-yield and service-life capability of most irrigation tube wells now in use.In some countries large-diameter, low-capacity open wells always have been used to obtain irrigation water. Now, small-diameter, high-capacity tube wells are being constructed in the same aquifers. As extensive tube-well development occurs, the water table will drop, drying up many shallow open wells. In such instances, those who can afford the deeper, more expensive tube wells could gain almost exclusive use of the aquifer.Optimum development of surficial aquifers using both tube and open wells may have to be rigidly controlled to assure every farmer a fair share of available water. Such controls should be based on the potential safe yield capability of aquifers. A graphical procedure used in Illinois to obtain an estimate of this value for planning and initial development purposes is presented in this paper.

Notes: A mathematical model was developed and used to simulate the stream-aquifer system in the Arkansas River valley in southeastern Colorado, from Pueblo to the Colorado-Kansas State line. The model simulates the interrelations among ground water and surface water including reservoirs, losses, and transmountain diversions, utilizing various water-distribution rules. The model was used to analyze 24 water-management plans designed to reduce shortages in the irrigation supply. One management plan simulated salvage of water from phreatophyte evapotranspiration, different reservoir operation regulations, use of imported ground and surface water, a new reservoir, additional ground-water use, and application of excess streamflow. The resulting annual dependable supply was increased from 610,000 acre-feet to 870,000 acre-feet in relation to an annual demand of 1,100,000 acre-feet. The model can be used as a tool to analyze other water-management plans.

Notes: The technique for gridding of random data developed by Newton (1973) is useful in ground-water investigations. The method appears to have potential for both regional and local ground-water studies.The method as applied to the Wainwright area of Alberta shows that total dissolved solids content in glacial drift and at several depths in the bedrock is related to both the thickness and nature of the drift and to nature of the bedrock. Total dissolved solids in the ground water in areas of thick and coarse-grained drift are lower than in areas of thin and finer-grained drift. The dissolved solids content of the bedrock is lower where the bedrock is of nonmarine origin and where the overlying drift is thick. In areas where the bedrock is of marine origin and the glacial drift thin the total dissolved solids content of the ground water tends to rise.

Notes: The first three field reports were presented as part of a panel discussion entitled “Impact of Pollution Control Legislation on Ground-Water Management,” at the Ninth Biennial Conference on Ground Water, Francisco Torres Conference Center, Goleta, California, September 13-14, 1973.

Notes: The largest potential reservoir for the storage of potable water is in the unsaturated zone. Use of this space for the storage and retrieval of potable water is a multifaceted problem which requires application of the best talent from the scientific community.Artificial recharge has many similarities to liquidwaste disposal through deep wells. In both, the problem is to place liquid in a permeable lithologic unit at an economic rate, to predict movement and the chemical reactions and physical changes that take place while the liquid is in the reservoir. Differences between the two operations are principally in the type of fluid injected and the ultimate objective. In artificial recharge the objective is to store and retrieve water of good quality; in waste disposal the objective is to store permanently water of objectionable quality. In both artificial recharge and liquid-waste storage, the nature of the storage must be known, particularly that of the unsaturated zone. The techniques of investigation for recharge and waste disposal are generally the same.Water commonly is recharged by surface spreading through basins or by induced recharge from adjacent streams and lakes or through injection wells. Research in recharge through basins has been dominated by mathematical models based on idealized conditions and empirical relations, derived by experimental sequencing of recharge operations, and operational controls in the pretreatment of recharge water. Recharge by injection wells has been undertaken in a variety of hydrologic environments. In Israel efforts have been directed toward the analyses of diffusion and dispersion of the injected water. Much research in the United States has been directed toward the movement of bacteria and organic matter through an aquifer and toward the chemical modeling of changes in recharged water as it moves.Much more research is needed on the basic properties of aquifers, particularly in the unsaturated zone, and on all aspects of recharge-water quality. Research and the use of data produced are increasingly the responsibility of interdisciplinary teams which consider the geologic, hydraulic, and economic aspects of the system.

Notes: The Rio Salado catchment is located in the southern Atacama Desert. The area is distinctly arid and no ground-water reserves originating from local recharge exist. To obtain water for a new copper ore processing plant, brines are being utilized. The complex hydrogeology of the brines from their origin in the Andes to their emergence as springs in the vicinity of El Salado is described.The surface and ground-water discharges indicate that the long-term supply of brine will be adequate for the processing plant. A design for abstraction incorporating three filter drains with wooden pump-housings has been adopted to combat corrosion, incrustation and flood damage.

Notes: Electrical resistivity and thermal probe surveys were conducted in the vicinity of Morning Sun, Ohio, in an attempt to locate a buried glacial valley.The resistivity survey along six roughly parallel traverse lines was able to distinguish buried valley gravel from glacial till and Upper Ordovician limestone bedrock. A relative depth to bedrock contour map drawn from the resistivity data reveals two buried valleys east of Morning Sun, which coalesce under Morning Sun, then continue as one valley to its junction with the Four Mile Creek buried valley at the northeast corner of Acton Lake. The field data yield only a proposed location of the buried valley since test holes were not drilled for confirmation.The thermal probe, an electronic thermometer utilizing a thermistor at the end of an aluminum-tipped probe and a transistor-amplified bridge circuit, was employed in measuring near-surface temperatures at 4-foot depths along the same 6 traverse lines made in the resistivity survey. The thermal probe survey was unable to distinguish a summer low-temperature anomaly trend, indicative of a buried valley. The depth of the buried valley under the till overburden is 90 to 150 feet which is too deep to contact the summer segment of the annual wave; therefore, a near-surface low-temperature anomaly is not produced.

Notes: The development and application of mathematical models to simulate water quality behavior in ground-water basins is at a very youthful stage. There is still much to be learned and a great deal of experience to be gained. However, in the last few years, models have been developed to simulate conservative and some nonconservative constituents under both saturated and unsaturated soil conditions. In addition, models have been found to provide additional information for calibration of quantity models, to identify major data gaps and deficiencies, to be useful in the design of data collection programs and in the interpretation of collected data, to be valuable to watershed planners and managers through evaluation of alternative regulatory policies, physical facilities and management operational plans, and to point out where future research efforts are needed.

Notes: In recent years, the practice of artificially recharging wastewater such as storm runoff, sewage effluent, and various industrial wastes into the subsurface has become of growing importance in Hawaii. In 1970 the Kahului Development Company began construction of a collection basin and four deep injection wells for the disposal of storm runoff from a residential development in Kahului, Maui. This presented a unique opportunity to evaluate the response of a basaltic Ghyben-Herzberg aquifer to well injection, and to measure the rate of movement of injected water in the aquifer. The results of pumping and injection tests of one completed well and one test hole indicate that the finished injection wells should be able to transmit sediment-free water at rates in excess of 5500 gallons per minute per well. Observation well measurements indicate that injected water moves at a gross velocity of one foot per minute in the basalt aquifer in the vicinity of the injection wells.

Notes: As water travels along the path of the hydrologic cycle, it changes from pure salt-free water suspended in the troposphere to ocean brines. Along the way, it progressively picks up salts in the atmosphere, on the earth's surface, through the soil medium and the unsaturated zone, and the saturated zone. Percolation of waste discharges and recycling of ground water through man's use add other complex factors. The process is indeed a water quality cycle. Thus, although water may be abundant, it may not all be fit for use. Understanding of the intricate processes that cause the change in the chemical composition of water is necessary to implement sound water quality management.(KEY TERMS: evapotranspiration; concentration; solution of minerals; carbon dioxide; ion exchange; biochemical reactions; dynamic cycle.)

Notes: . Prince George, B.C. required 15 mgd additional municipal water supply. A cost comparison led to the selection of the Nechako Aquifer ground-water supply instead of the Nechako River surface-water supply. A Fehlmann horizontal collector, consisting of a 16-inch diameter reinforced concrete caisson, 100 feet deep, with 1788 feet of 8-inch diameter polystyrene screen, projecting spoke-like at the bottom of the caisson, was installed. On test, the collector produced 15.3 mgd of clean, excellent quality water, with 6.7 feet drawdown under equilibrium conditions.

Notes: Four regional studies of the status of ground-water pollution problems in 26 States have been sponsored by the U.S. Environmental Protection Agency. These investigations involved comprehensive reviews of the literature and contacts with public officials and others involved in water supply, so that individual case histories of ground-water contamination problems could be evaluated. Septic tanks and cesspools, petroleum exploration and development, landfills, irrigation return flows, and surface discharges, impoundments, and spills are the principal sources leading to degradation of ground-water quality.Only a very small percentage of the instances of ground-water contamination that probably exist has been discovered to date, and almost all the reported cases were only discovered after a water-supply source had been noticeably affected by one or more pollutants. In the vast majority of cases inventoried, the problem has not been corrected and will become more troublesome in the future. A prime need in all four regions is a greater effort toward locating and evaluating as many additional cases of ground-water contamination as possible.

Notes: About 17 million families in the U. S. A. are served by septic tank and subsurface seepage systems. Rational design of these wastewater disposal systems includes three aspects. First the system must be hydraulically sound. This means that the flow regime and the storage and water carrying capacity of the receiving soil should be measured before design. A soil with a coefficient of permeability of less than 10-4 ft/min (5 × 10-5 cm/sec) suggests, for example, that the hydraulic capacity of the system governs the size of the subsurface leaching field. Seasonally high water tables or impervious strata may retard the flow and reduce the quantity of wastewater that can be carried away from the subsurface disposal area. In this case an elevated bed can be designed to increase the potential hydraulic gradient.The second consideration concerns the biological mat in leaching fields. Leaching fields can be designed with higher loadings in soils having a greater coefficient of permeability than 10-4 ft/min (5 × 10-5 cm/sec) if increased pretreatment is used. A mathematical relationship was developed for reducing the size of leaching fields for effluents with a BOD5 plus suspended solids less than 250 mg/1. Leaching fields were projected to operate indefinitely. Long-term loading rates for different soil permeabilities were plotted on a graph which can be used for sizing fields.The third design consideration concerns preservation of the ground-water quality. The travel of phosphate and nitrogen has been studied by others and by the authors. Concrete sand and silt with an unsaturated thickness of 1.5 feet (38.1 cm) still removed after 2 years of operation 30% of septic tank effluent phosphate and nitrogen. The effluent from the test soils had a concentration of about 13 mg/1 phosphate and 15 mg/1 nitrogen mostly in the NO-3— N form.

Notes: Alabama's solid waste management program has been commended repeatedly by the U.S. Environmental Protection Agency for establishing and operating throughout nearly all of the State effective, county-wide, Stateapproved, rural solid waste collection and disposal systems. The program is administered and regulated by the Division of Solid Waste and Vector Control of the Environmental Health Administration. Collection systems, sanitary landfills, and other parts of the program are rated by the regulatory agency; rating of landfills is used in enforcement. In 1974, 87.0 percent of the 67 counties in Alabama representing 97.0 percent of the total State population of 3,444,000 had total collection and disposal systems.The two greatest problems in the sanitary landfill program are disposal of hazardous industrial wastes and training of operators; other problems are noted. Current research throughout the nation on ground-water pollution related to sanitary landfills was reviewed to identify expected research results that will help solve the problems.

Notes: Two landfills, 27 and 41 years old, were studied and found to have plumes of leachate-contaminated ground water extending 10,600 and 5,000 ft (3,200 and 1,500 m), respectively, from the site of deposition in the upper glacial aquifer on Long Island, New York. The plumes sink to the bottom of the aquifer, which is 70 ft (21 m) below the water table at the 27-year old site and 170 ft (52 m) below at the 41-year old site. The aquifer has a hydraulic conductivity of 270 ft per day (80 m per day).

Notes: Over the past 30 years East Portland and central Multnomah County have metamorphosed from a rural-suburban to a locally urban community. Services, including community water and sewer have been extended to most of the area. However, a 30-square-mile (80 km2) area within central Multnomah County remains unsewered today. This area reportedly disposes of 8 to 10 mgd (34,400 m3/day to 38,000 m3/day) sewage via subsurface systems, i. e. cesspools, seepage beds, and drainfields. These methods of waste disposal have resulted in the degradation of the ground-water resource within the study area.Most of the developed area is located on a relatively level terrace made up of Pleistocene fluviolacustrine sediments. Partially cemented gravels of the Pliocene Troutdale Formation underlie the terrace deposits. Both of these units are generally excellent aquifers where saturated. The depth to water in the unsewered area ranges from about 100-200 feet (30 to 60 m) in the southern terraced area to less than 10 feet (3 m) in much of the northern area underlain by younger, floodplain, terraces adjacent to the Columbia River.Central Multnomah County is situated within a regional ground-water discharge zone. It receives ground-water recharge from the Cascade Mountains to the east and intermediate recharge from the Cascade foothills and other isolated hills bordering and within the study area. The major surface drains receiving ground water from the regional and intermediate flow systems are the Willamette, Clackamas, and Columbia Rivers.The fluviolacustrine terraces constitute a local recharge zone. The primary ground-water recharge source is infiltrating precipitation as evidenced by the paucity of natural surface drainage, although the area receives in excess of 40 inches (100 cm) of precipitation per year. However, due to development and its attendant reduction in area for infiltration, e.g. paving and building, there has been a decrease in natural recharge. The estimated 8 to 10 mgd (34,400 m3/day to 38,000 m3/day) of domestic waste which is disposed of via the subsurface is thus introduced as supplemental local recharge.Infiltrating precipitation and sewage effluent migrates downwards through the water table. The depth to which the local recharge can penetrate the water table is limited by its hydraulic potential and the vertical hydraulic conductivity of the substrata. Therefore, the NO3-N contaminated recharge is effectively buoyed up and migrates laterally along the upper portion of the water table to its eventual surface drain, Columbia Slough South Arm.Water samples from wells developing water in adjacent or upgradient sewered areas and/or from deeper aquifers within the unsewered area generally have NO3-N concentrations of less than 1 mg/1. Shallower wells and springs within the unsewered area and South Arm Slough, downgradient grom the unsewered area, had NO3-N concentrations ranging from 4.7 to 11.86 mg/1, with a mean value of 7.74 mg/1 in July 1974.

Notes: A survey of waste-migration patterns from septic-tank/ tile-field systems surrounding Houghton Lake, Michigan indicates that sampling plans designed to detect and quantify waste migration in ground water should be predicated on the concept that the waste plume may be complex and that the plume may not follow regional, ground-water flow. The waste-migration plumes at Houghton Lake range from simple, multichemical plumes that move with regional flow to complex plumes that bifurcate, that show different migration patterns for different chemicals, and that move up the regional gradient for short distances. The complexity of these patterns is attributed to a combination of the following system properties: loading rate and recharge at the waste source, local hydrology, chemical-adsorption capacity of the soil, soil microbiology, regolith texture and fabric, and proximity to other waste sources. Based on the observed patterns, it is suggested that observation wells be placed so that an in-depth, 3-dimensional array of samples can be obtained. The wells should be of sufficient depth to insure that deep-moving plumes can be detected and, if the actual, vertical-migration pattern is of importance, the wells should allow collection of water samples at a number of depths. The waste-migration pattern should be monitored throughout the year in anticipation of vertical movement of the plume axis during periods of surface recharge. If more than one chemical is of interest, then it is unsafe to assume that an index chemical, such as chlorides, demonstrates the migration of the other chemicals and analyses must be run for the other chemicals.

Notes: Experiments are described which test the feasibility of diminishing the leachate production of sanitary landfills by using the roots of transpiring plants to dry the refuse and surrounding soil. Full-scale models of landfill cores were constructed and filled with typical municipal refuse in the early spring of 1973. Selected plant species such as slash pine, thorny elaeagnus, bristly locust, black locust, and two grasses were used to vegetate two landfill models, while a third was denied vegetation and used as a control. Intermediate term results have been positive from several viewpoints. The various species of selected plants have thrived, even though gas sampling indicated that the lower two-thirds of the landfill models quickly became anaerobic. Roots proliferated rapidly through the top 2 1/2 feet (76.2 cm.) of cover soil and first refuse layer. Following December 1973, all three lysimeters began producing leachate. However, the volume of leachate produced differed considerably depending on whether the particular lysimeter was vegetated or fallow. To date, the unvegetated control has produced 17.53 inches (44.53 cm.) while the two vegetated models have produced 8.59 inches (21.82 cm.) and 2.49 inches (6.32 cm.) respectively. The lysimeter producing the minimum leachate volume was vegetated with pine and thorny elaeagnus. The unvegetated bin produced the most dilute leachate. If one uses the chemical oxygen demand, the total Kjeldahl nitrogen, and the total solids as indices representative of the potency of leachate, then the leachate from the lysimeter containing pine and thorny elaeagnus was 1.97 times more concentrated than that from the fallow lysimeter. Thus one realizes a net improvement factor of 3.57 due to the presence of plants.

Notes: A generalized lumped parameter ground-water model is developed based on simultaneous water and solute balances for a phreatic aquifer. The basis for the lumped parameter approach is established by comparison with theoretical analyses of water and solute dynamics in a distributed aquifer model. The basic behavior of the model is characterized by two response times, one associated with the hydraulics and the other with the solute.The model is applied to simulate the impact of highway deicing salts on ground-water quality in eastern Massachusetts. The results, obtained by digital computer simulation, are found to be in reasonable agreement with observed trends over a 15-year period. The effects of various highway deicing alternatives are simulated and the dependence on the aquifer parameters is demonstrated.The application of this basin-wide modeling technique to the case of highway deicing salts demonstrates that this procedure can provide a reasonable basis for long-term evaluation of ground-water pollution. With adequate data on the inputs and aquifer parameters for a given locality, this general technique can be used to guide regulatory procedures and land use decisions which can be applied at the local, regional or State level to protect ground-water resources.

Notes: The function of a septic tank-soil absorption system is to purify the wastewater discharged from the home before reaching the ground water. However, failure often occurs in the soil absorption field. Failure can originate from two causes: (1) inadequate infiltration of effluent into the soil, due to soil clogging or an increase in loading which results in surfacing septic tank effluent, and (2) inadequate purification in the soil during percolation because of short travel times which can be due to presence of very permeable, shallow soils or to local overloading. Inadequate purification may result in pathogenic pollution of private well-water supplies.Failures of the second type can be prevented through proper design and operation of the soil absorption field. Studies have shown that 3 feet (90 cm) of unsaturated soil are adequate in purifying septic tank wastes with the exception of nitrogen removal. However, 4-inch (10 cm) diameter perforated drain pipe commonly used for distribution leads to local overloading near the point of inlet whereas other areas in the seepage system do not receive effluent at all. This leads to locally high flow rates of the waste through the soil reducing the soil's efficiency for pathogenic organism removal. Uniform distribution of the septic tank effluent over the entire soil absorption field is necessary to relieve this situation.One method by which uniform distribution can be achieved over a large area is through a pressurized system. By properly sizing the diameters of the pipes and the number and diameter of the orifices in the distribution laterals, the head losses across the orifices will be great enough to cause the entire network to fill before the liquid is applied to the soil. This system combines the advantages of dosing with uniform distribution.Three systems have been tested under laboratory and field conditions. The network is easy to manufacture and can be quickly sized. The design guidelines and results of laboratory and field testing are discussed.

Notes: Ground-water contamination resulting from hydrocarbon spills is a significant problem which has received little attention. Over two hundred spills to the ground have been investigated during the last two and a half years by the Ground Water Section of the Pennsylvania Department of Environmental Resources. Explosions, injuries, damaged water supplies and other serious consequences have forced the recognition that these cases are important. Since Federal regulations are unsatisfactory in preventing spills to the ground, it is clearly the responsibility of the State to develop meaningful controls.Hydrocarbon dispersion is essentially a shallow ground-water problem. The hydrogeologic characteristics at the spill site are critical in determining dispersion once the hydrocarbon has reached the water table. The hydrocarbon is largely contained on top of the water table. In unconsolidated deposits or in fill material, the shallow ground-water flow system and the direction of hydrocarbon dispersion will coincide. In sedimentary rocks the orientation of the rock becomes critical. When the dip is shallow enough to contain the water table, dispersion may either coincide with the major flow direction or may diverge from it where facies changes or significant changes in packing are encountered. Dispersion will parallel the strike of the rock in more steeply dipping rocks rather than the major ground-water flow direction. Lateral movement will be controlled by jointing and fracturing. Solution channels and fractures exert the major controlling influence on heavily cemented soluble limestones. In tightly cemented clastics, crystalline rocks and less soluble carbonates, contaminant flows on top of the water table in fractures. Hydrocarbons may be imprisoned where solution channels and fractures do not intercept other openings within the water-table plane.Recovery programs for most hydrocarbon spills are complex. Larger cases receive the greatest attention; however, smaller ones are actually more significant since they are more common. Recovery costs are expensive and complete removal is extremely time-consuming. Better maintenance and emergency response plans must be developed, even by small users. Federal and State governments must recognize the problem as being serious and must develop revolving product recovery funds to be used in ground-water cases. Lastly, ground-water spills must be handled by ground-water specialists. Experimentation by those who lack the proper qualifications can prove very costly.

Notes: When modelling the long-term behaviour of an aquifer, a resistance-capacitance model controlled by a mini digital computer can be used with advantage. A typical aquifer in eastern England, which is partly confined and partly unconfined is used as an example. The representation of recharge, river flow and pumpage is considered. A period of 100 years is modelled and typical results include the long-term behaviour over a number of years and the short-term response over a few days.