ALBERT

Notes: An approximate method of interpretation of resistivity sounding is presented, which may be described as a very crude manner of application of the exact direct interpretation method. The accuracy of this method is fairly low, the errors being in the order of 25%. The method is very fast in application and well suited for application to multilayer cases. The main advantage of the method is that it is in close and clear relation to the exact theory.

Notes: Dip selective migration velocity determination calculates coherency of energy migrating into an output trace or ‘MVD-axis’ as a function of the three variables time, velocity, and dip. In doing so, it provides additional information, the dip information, relative to standard MVD.

Notes: It is well known that interval velocities can be determined from common-reflection-point moveout times. However, the mathematics becomes complicated in the general case of n homogeneous layers with curved interfaces dipping in three dimensions.In this paper the problem is solved by mathematical induction using the second power terms only of the Taylor series which represents the moveout time as a function of the coordinate differences between shot and geophone points. Moreover, the zero-offset reflection times of the nth interface in a certain area surrounding the point of interest have to be known. The n—I upper interfaces and interval velocities are known too on account of the mathematical induction method applied. Thus, the zero-offset reflection raypath of the nth interface can be supposed to be known down to the intersection with the (n—1)th interface.The method applied consists mainly in transforming the second power terms of the moveout time from one interface to the next one. This is accomplished by matrix algebra.Some special cases are discussed as e.g. uniform strike and small curvatures.

Notes: The least squares estimation procedures used in different disciplines can be classified in four categories:〈list xml:id="l1" style="custom"〉a. Wiener filtering,b. b. Autoregressive estimation,c. c. Kalman filtering,d. d. Recursive least squares estimation.The recursive least squares estimator is the time average form of the Kalman filter. Likewise, the autoregressive estimator is the time average form of the Wiener filter. Both the Kalman and the Wiener filters use ensemble averages and can basically be constructed without having a particular measurement realisation available.It follows that seismic deconvolution should be based either on autoregression theory or on recursive least squares estimation theory rather than on the normally used Wiener or Kalman theory. A consequence of this change is the need to apply significance tests on the filter coefficients.The recursive least squares estimation theory is particularly suitable for solving the time variant deconvolution problem.

Notes: A graphical interpretation method is presented by which separately the depth and the product of conductivity and thickness of a vertical plate-shaped conducting orebody can be determined. The method is based on the result of model experiments.

Notes: The Fourier transform of a square-shaped section of a magnetic survey, digitized in a square grid, forms a rectangular matrix of coefficients which can be condensed to a series of average amplitudes dependent only on their frequency and no longer on the direction of the respective partial waves. These average amplitudes together represent a spectrum which–when plotted in a semilogarithmic coordinate system (log amplitude versus frequency)–often shows straight segments which decrease with increasing frequency. By continuing the given field downwards these straight segments become horizontal at a certain depth, the so-called “white depth”. This white depth may be used as a first estimate for the depth of magnetic sources producing the respective part of the field. It is shown that the sources which correspond to such use of the white depth can be expected to be “randomly distributed with some positive autocorrelation”.As an example for such a depth estimation the interpretation of the aeromagnetic survey of NW-Germany by a relief in 8–16 km depth is given. The relief divides the subsurface in an upper nonmagnetic layer and a lower layer with magnetization M= 2 Am−1.

Notes: The combination of layer resistivity and thickness in the so-called Dar Zarrouk parameters S and T may be of direct use in aquifer protection studies and for the evaluation of hydrologic properties of aquifers.The protective capacity of a clayey aquifer overburden is proportional to its longitudinal unit conductance S which, in terms of aquifer protection, gets a dimension of time (e.g. infiltration time). Aquifer storage in fissured reservoirs may be determined from differential conductance measurements (ΔS). Combination of the expression for ΔS with an empirical expression for electric conduction in fissured media yields a simple formula for water content per unit surface area. Both principles and possible developments are illustrated for a set of carboniferous limestone basins.

Notes: The difficulty to use master curves as well as classical techniques for the determination of layer distribution (ei, ρi) from a resistivity sounding arises when the presumed number of layers exceeds five or six.The principle of the method proposed here is based on the identification of the resistivity transform. This principle was recently underlined by many authors. The resistivity transform can be easily derived from the experimental data by the application of Ghosh's linear filter, and another method for deriving the filter coefficientes is suggested.For a given theoretical resistivity transform corresponding to a given distribution of layers (thicknesses and resistivities) various criteria that measure the difference between this theoretical resistivity transform and an experimental one derived by the application of Ghosh's filter are given. A discussion of these criteria from a physical as well as a mathematical point of view follows.The proposed method is then exposed; it is based on a gradient method. The type of gradient method used is defined and justified physically as well as with numerical examples of identified master curves. The practical use for the method and experimental confrontation of identified field curves with drill holes are given. The cost as well as memory occupation and time of execution of the program on CDC 7600 computer is estimated.

Notes: The spectrum of a magnetic or a gravity anomaly due to a body of a given shape with either homogeneous magnetization or uniform density distribution can be expressed as a product of the Fourier transforms of the source geometry and the Green's function. The transform of the source geometry for any irregularly-shaped body can be accurately determined by representing the body as closely as possible by a number of prismatic bodies. The Green's function is not dependent upon the source geometry. So the analytical expression for its transform remains the same for all causative bodies. It is, therefore, not difficult to obtain the spectrum of an anomaly by multiplying the transform of the source geometry by that of the Green's function. Then the inverse of this spectrum, which yields the anomaly in the space domain, is calculated by using the Fast Fourier Transform algorithm. Many examples show the reliability and accuracy of the method for calculating potential field anomalies.

Notes: Several new features are described which facilitate an automatic, more meaningful, and more accurate interpretation of gravity anomalies associated with approximately two-dimensional mass distributions. These include a provision for fixed points on the bounds of a distribution, outward dipping boundaries, calculation of the gravity effect at individual elevations of stations, smoothing of models and end-corrections for distributions of limited strike length. It is possible to obtain distributions about a median plane; these distributions are sensitive to shape and allow estimates of optimum depths and minimum density contrasts for the anomalous masses.

Notes: The utility of electrical resistivity and magnetic measurements to locate suitable wellsites in hard-rock terrains intruded by dykes is illustrated. The example is taken from a highly hilly terrain of Karnataka State situated in the Western Ghat hills of Peninsular India. Electrical resistivity profiles and soundings, S.P., and total magnetic field measurements are discussed. Of the fifteen recommended sites, nine have been drilled, eight of which are reported to yield between 6–12 m3/hr (1500 to 3000 gals./hr), which is considered satisfactory in this region.

Notes: The relative time shift of CDP reflections, caused by long period statics, is treated as the result of a filtering process. The shape of the filter is that of a comb having the magnitude and spacing of its teeth determined by the CDP spread geometry. Convolution of a near surface anomaly with a comb filter representing the CDP spread geometry produces the same time fluctuations at CDP reflections (CDP statics) as the stacked traces across the anomaly. Conversely, the near surface time anomaly is given by the convolution of the CDP statics with the inverse of the comb filter. Provided that CDP statics can be separated from noise, dip, and residual normal moveout, it is pcissible to determine long period statics with a relative wavelength of between half a spreadlength and five spreadlengths.The object of this paper is to present the theory and practical applications of the method. Several examples based on synthetic and real data will also be discussed.

Notes: Various Dix-type formulae are derived, which are useful to approximate travel time functions that can be observed while modeling the common depth point (CDP) technique for 3-D isovelocity layers of varying dip and strike. All formulae can be used to compute interval velocities and recover the depth model from surface measurements. They are established by making use of the concept of wavefront curvature. Many similarities with known formulae valid for the 2-D plane isovelocity layer case exist.

Notes: The main problem in seismic prospecting is to infer from the observed reflection response the distribution of density and seismic velocity with depth. This process is generally called the inversion of the reflection data.For plane waves propagating through plane parallel stratification, it can be shown that at any depth the ratio between the amplitude of the transmitted and reflected wave satisfies the Riccati equation. Based on this equation we have formulated an iterative inversion method, which is found to be suitable for numerical computations. We have applied this method on synthetic reflection data, and found that it provides a very fast and accurate inversion.

Notes: In-situ seismic measurements on shear waves propagation both in soft formations (clays) and in hard formations (calcareous rocks), using several field techniques did not result in clear S arrivals.Particular digital approaches were then used, based on spectral analysis of records, for the selection of the seismic events and the calculation of their propagation velocity.The actual application of these numerical procedures are described and to some records obtained using the “crosshole” field technique show that the suggested procedures are a substantial contribution to the identification of transverse waves.

Notes: A satisfactory approximation to the travel time of a reflected wave is achieved by finding a ray, which originates in the source and emerges close enough to the receiver. The reason for this is, that the actual travel time function can be approximated in every emergence point of the wave by a time function which is entirely defined by seismic parameters along the ray connecting the source with the point of emergence.

Notes: Laboratory studies of Bunter Sandstone specimens from Northwest Lancashire, Shropshire, West Cumberland, and the Vale of Clwyd have indicated that the parameters effective porosity, intergranular permeability, compressional wave velocity, formation resistivity factor, and effective matrix resistivity have significantly different distributions in each of these four regions. Regression analyses have shown that bivariate and trivariate expressions for the prediction of the two hydrological parameters from petrophysical data vary from region to region. It is concluded that, in quantitative geophysical investigations of these formations, each area must be investigated independently.For all four aquifers, and for both horizontally and vertically oriented specimens, effective porosity can be most reliably and readily estimated through a bivariate relationship involving formation resistivity factor. On the other hand, the best estimate of intergranular permeability from geophysical data is obtained through a trivariate expression involving both formation resistivity factor and effective matrix resistivity. The use of hydrogeophysical relationships to estimate hydrological parameters in situ is illustrated by reference to field examples.

Notes: A theoretical model is developed for predicting three important parameters of the pressure pulse radiated by an air-gun, namely the rise time, the amplitude of the initial pulse, and the period of the bubble pulse. A knowledge of these three parameters is essential for the efficient design of air-guns arrays.The prediction of the amplitude of the initial pulse is based on the assumption that the initial pulse is radiated by a spherical source with surface area equal to that of the air-gun ports and not by a spherical source with initial volume equal to that of the air-gun chamber, as has been assumed previously.A simple equation is obtained for predicting the period of the bubble pulsation, taking into account the effect of the air-gun body, boundaries such as the sea-surface and seabed and the presence of a number of identical air-guns placed at the same depth and fired simultaneously.

Notes: The manner in which boundary conditions are approximated and introduced into finite difference schemes may have an important influence on the stability and accuracy of the results. The standard von Neumann condition for stability applies only for points which are not in the vicinity of the boundaries. This stability condition does not take into consideration the effects caused by introducing the boundary conditions to the scheme.Working on elastic media with free stress boundary conditions we found that the boundary approximation gives rise to serious stability problems especially for regions with high Poisson's ratio. In order to detect these effects apriori and to analyse them, we have used a more elaborate procedure for checking the stability of the scheme which takes into consideration the boundary conditions. It is based on studying a locally spaced time propagating matrix which governs the time-space behavior of a small region of the grid which includes free surface points.By using this procedure a better insight into the nature of instability caused by the approximations to the boundary conditions was gained which led us to a new stable approximation for the free surface boundary conditions.

Notes: Mini-sosie consists in using a vibration-rammer as seismic source and changing the striking rate by varying the engine speed, resulting in a random impulse transmission. The recording instruments are made up of two seismic traces, two constant gain amplifiers and a two-channel sosie processor which performs the decoding in real time by using the actual transmission times supplied by a captor located on top of the vibration-rammer's plate. An idea of the possible penetration is given by the recording of a velocity survey. Other results obtained in seismic reflection and refraction are given.

Notes: The potential distribution and the wave propagation in a horizontally stratified earth is considered and the analogy of the mathematical expression for seismic transfer function, electromagnetic and electric kernel functions, and magnetotelluric input impedance is discussed. Although these specific functions are conveniently treated by a separate expression in each method, it is indicated that the function for seismic and electromagnetic methods is mathematically the same with a change in the physical meaning of the variables from one method to the other. Similarly, the identity of the mathematical expressions of the resistivity kernel function and magnetotelluric input impedance is noticed.In each method a specific geophysical function depends on the thickness and the physical properties of the various layers. Every specific function involves two interdependent fundamental functions, that is Pn and Qn, or Pn and P*n, having different physical meaning for different methods. Specific functions are expressible as a ratio Pn/Qn or P*n/Pn. Fundamental functions may be reduced to polynomials.The fundamental polynomials Q*n and P*n describing the horizontally stratified media are a system of polynomials orthogonal on the unit circle, of first and second order, respectively. The interpretation of geophysical problems corresponds to the identification of the parameters of a system of fundamental orthogonal polynomials. The theorems of orthogonal polynomials are applied to the solution of identification problems. A formula for calculating theoretical curves and direct resistivity interpretation is proposed for the case of arbitrary resistivity of the substratum.The basic equation for synthetic seismograms is reformulated in appendix A. In appendix B a method is indicated for the conversion of the seismic transfer function from arbitrary to perfectly reflective substratum.

Notes: A broken ore-vein is very common in nature. A small scale model of such a vein has been made by placing two thin metal sheets edge to edge with an air gap between them. The electromagnetic response of this model in a uniform oscillating magnetic field has been measured. The results show that (a) the response of the whole body is not the sum of responses of the constituent parts, (b) the response of the upper part is dominant by virtue of its proximity to the receiving coil and (c) the lower part has the effect of making the upper part appear nearer to the surface and poorer in conductance than it really is.

Notes: Results of a gravity survey conducted over Raniganj coalfield, one of the Gondwana basins of Damodar Valley in north-eastern part of India, are presented. The gravity field was separated into regional and residual components. The residual Bouguer anomaly map shows that the coalfield is characterized by a gravity low of about—32 mGal associated with Gondwana sediments. The deepest part of basin is found to be located near Asansole (23° 40’N, 86° 55’E), where the maximum thickness of sediments is estimated to be about 1.3 miles (2.08 km). The faults along the northern as well as the southern boundaries are found to be normal. The Gondwana sediments appear to continue eastward beneath alluvium and laterite of Bengal basin as far as 87° 25’E.

Notes: An offshore self-potential array, towed behind a small boat, has recorded anomalies of up to −300 mV. These anomalies were related to conductive onshore deposits, and appear to be caused by offshore extensions of the deposits. Along with locating onshore deposits and their offshore extensions, the system may be useful for locating offshore deposits with no onshore extension. The background noise level of the system typically is a few tenths of a millivolt, allowing reliable recording of one millivolt gradient anomalies under average sea conditions.

Notes: This paper is an experimental extension of the theoretical investigations by Roy (1975) on the relative performances of the Laterolog 7, normal and some other sondes in logging of resistive formations. Only infinitely resistive formations have been simulated and placed in a tank containing tap water (true resistivity 27 Ωm) as electrolyte—representing both the mud column and the adjacent formations.Two sets of laboratory results (Doll 1951, NN 1958, 1969), have been repeated and we find that, for both these sets, the performance of the normal device is by far the superior of the two. In addition, we have studied the effect of varying the spacings A1A2, O1O2 and AM of Laterolog 7, normal, and two new sondes—Laterolog 4 and modified unipole—for two bore hole diameters in each case. For formation thicknesses less than A1A2 or AM, the Laterolog 7 is unsuitable because its response is flat and close to the base-line value. The normal device is more diagnostic, although, in such a case, it registers a trough or a resistivity low even against a resistive formation.For bed thicknesses clearly greater than A1A2 or AM, the normal sonde is decidedly superior to Laterolog 7, since its anomalies are sharper and larger. When the formation thickness is equal to or only slightly larger than A1A2 or AM, Laterolog 7 is somewhat better as it records a readable positive deflection while the normal does not. However, one must remember that a single run of the conventional resistivity log includes two normals and a lateral at different spacings. Laterolog 4 and modified unipole can in many instances produce better logs than normal, other considerations apart.The results are consistent with our own theoretical predictions and experience in surface resistivity profiling. They do not, however, agree with the prevalent concepts on Laterolog 7 vis-a-vis normal sonde.

Notes: Refraction seismic and gravity investigations were executed to solve geological and hydrographical problems in recent strata: These loose sediments necessitated a special arrangement for the energy source in the seismic measurements, By the use of a falling weight the refracted wave could be registered from a depth of more than 30 m. Quaternary fluviatile sands are characterized by lower velocities than the Tertiary sediments. Even a marked velocity difference between different Tertiary formations could be observed. Sand-filled valleys in Tertiary clays give relatively important variations in the gravity field caused by the small differences of densities. Thus buried channels in a clay subsoil can be found by accurate gravity measurements.

Notes: An algorithm is presented for the direct interpretation of resistivity sounding data. The algorithm is based on the method of successive reductions to lower boundary plane of the resistivity transform function. A novel aspect of the algorithm is that error limits are assigned to the initial values of the resistivity transform, and these error limits are carried through in all the subsequent computations. The width of the error range is then used as the basis for assigning weight factors in the final computation of thicknesses and resistivities of the layers. The errors in the resistivity transform derived from the solution given by the algorithm are usually not more than twice as large as those in the original data.

Notes: From a gravity profile over a truncated horizontal plate, the horizontal derivative and, by means of the Hilbert Transform, the vertical derivative are obtained.When the horizontal derivative is plotted against the vertical derivative, the axis of symmetry of the resulting curve is inclined at the angle of dip of the face of the truncated plate. The depths to the upper and lower surfaces of the plate can be obtained uniquely from the symmetrical figure. Because of the derivatives being used, the method avoids the difficulties which arise from other methods of interpretation which depend upon a knowledge of the position of the origin of the gravity field data. The entire procedure for interpretation can be accommodated on a programmable calculator. An illustrative example is given.

Notes: A new device for resistivity logging has been developed with a doubly focussed system. It resembles a simplified double set of microlaterologs. The diagram of the log shows the formation resistivity factor of the sediments on the sea floor. The probe is trailed after the logging boat on a cable with at least two or four cores. The penetration of this log is better than 10 cm. The log is used for resistivity mapping, and it could be used for the exploration of heavy minerals and managese nodules.

Notes: The system of normal equations associated with the discrete Wiener filter is sometimes ill-conditioned. The purpose of this paper is to show that in such cases the solutions obtained vary drastically with the particular choice of an algorithm and of the computer used for its implementation.A review of the basic mathematical theory behind an ill-conditioned matrix is first presented. Numerical examples are then given to illustrate that the solutions of the normal equations are sensitive to the word length of a given computer. Finally, two possible remedies are described: (1) The well-known method of prewhitening and (2) the use of the conjugate-gradient algorithm for solving the normal equations.

Notes: Following up our recent study of an indirect procedure for the practical determination of the maximum frequency-effect, defined as fe = 1 − pρ∞/ρdc with ρ∞ the resistivity at infinite frequency, we show at first how, through the Laplace transform theory, ρ∞ can be related to stationary field vectors in the simple form of Ohm's law. Then applying the equation of continuity for stationary currents with a suitable set of boundary conditions, we derive the integral expression of the apparent resistivity at infinite frequency ρ∞,a in the case of a horizontally layered earth. Finally, from the definition of the maximum apparent frequency-effect, analytical expressions of feα are obtained for both Schlumberger and dipole arrays placed on the surface of the multi-layered earth section in the most general situation of vertical changes in induced polarization together with dc resistivity variations not at the same interfaces. Direct interpretation procedures are suggested for obtaining the layering parameters directly from the analysis of the sounding curves.

Notes: Claerbout's method has been implemented for the migration of stacked seismic data. A simplified description of the method is given together with an account of some of the practical programming problems and the types of inaccuracy encountered. Routine production results are considered to be comparable or superior to the results derived from alternative migration techniques. Particular advantages are 1) the possibility of using a detailed velocity model for the migration and 2) the preservation of the amplitude and character of the seismic events on the migrated time section.

Notes: An analysis is made of the propagation of the measuring error in the different stages of the interpretation by the linear filter and reducing method.This analysis leads to an understanding of the range of possible values of the layer parameters and of the nature of the relation between them.It is shown that this relation is not always adequately described by the equivalence expressions of Maillet.

Notes: None of the processes of estimation currently available is fully acceptable to the geophysicist. Firstly, they all assume that the variable, be it seismic reflection time, rms velocities, Bouguer anomaly, etc.… is random, amenable to pure statistical considerations, and the processes all disregard the relationships which link the values of the variable in the different points of the domain under investigation. Secondly, they do not provide the geophysicist with any guideline for smoothing his data, as smoothing and estimation are considered two separate operations. Thirdly, they fail to offer a valid criterion of estimation and a measure of the estimation error.The krigeage process overcomes the above mentioned difficulties. It synthesizes the structural or “geostatistical’ characteristics of the variable by using a function called the variogram (variances of the increases of the variable with respect to distance and direction). It smoothes the variable, when necessary, as a function of the “nugget effect’ (value at the origin of the experimental variogram). It yields an optimum estimation of the variable by minimizing the estimation error, and it computes a measure of the reliability of the estimation, the variance of krigeage.The process is demonstrated herein with three examples of variograms on seismic and gravity data and an example of contouring of velocities, reflection times and depths of a productive layer in an oil field, with detection and correction of irregular data, smoothing of velocities, migration of depth points, and display of estimation error.

Notes: Soils and aquifers can function as effective and economical filter systems for advanced treatment of conventionally treated sewage and other wastewater. The wastewater is applied to the land with low-rate or high-rate infiltration systems. Physical, chemical, and biological processes in the soil improve the quality of the wastewater as it percolates through the vadose zone and into the aquifer to become renovated water. The quality of the renovated water, however, often is not as good as that of the native ground water. To utilize the land for treatment of wastewater, without trading a problem of surface-water pollution for one of ground-water contamination, the spread of renovated water in the aquifer must be restricted. This can be accomplished by locating the system so that the renovated water drains naturally into a stream or other surface water, or by artificially removing renovated water from the aquifer with wells or drains at some distance from the application area. Examples are given of various systems that utilize these principles, and general design criteria are presented. Proper design involves analysis of underground-flow systems for various system geometries. Methods for measuring hydraulic conductivity, particularly in the vadose zone, are briefly reviewed.

Notes: Over the last few years rises in the nitrate content of ground water from wells and springs in the principal aquifers of the United Kingdom have been observed. In a number of cases the concentrations have exceeded the WHO lower recommended limit. In order to determine the reason for the rise, to assess whether it will continue and the eventual nitrate levels, the Water Research Centre has undertaken an extensive programme of drilling and sampling on the Chalk and Bunter Sandstone, and by August 1976, twenty-two sites had been examined. This work has established that high nitrate concentrations (peaks up to 60 mg/l NO3-N have been observed) are present in the unsaturated aquifers at fertilized arable/ley sites. At unfertilized grassland sites nitrate concentrations are low (less than 4 mg/l NO3-N) and below fertilized established grassland values are in the intermediate range. At one farm site near Winchester, models to predict the rate of movement of nitrate through the unsaturated and saturated Chalk have been developed. These suggest that the nitrate levels at this site will remain at an essentially constant value of about 4 mg/l NO3-N until the late 1970's when they will rise progressively to about 4 mg/l NO3-N. The models have been checked against tritium data and the approach is now being extended to other sites.

Notes: The chemical quality of water in many shallow and surficial aquifers exhibits cyclic fluctuations. These fluctuations are caused by the intermittent flushing of contaminants into the ground during recharge events. The contaminants may be natural or reflect man's activities, particularly waste disposal schemes.Over the past 12 years an oil-field brine contaminated aquifer in central Ohio has been monitored. Data from three closely-spaced wells tapping selected parts of the aquifer indicate that brine is flushed into the ground during recharge events and that each contaminated mass maintains much of its integrity as it sinks to the bottom of the aquifer and then migrates laterally to the adjacent river. The most concentrated mass that covers the largest area infiltrates during the spring recharge period, but less concentrated and smaller masses may occur any time rainfall is sufficient to overcome the soil-moisture deficiency.Because of the cyclic nature of recontamination events, care and common sense must be exercised in the extrapolation of quality data, particularly in regard to estimation of contaminant flushing rates.

Notes: A computer program, based on the Hantush inflection method and designed for “desk top” computers is presented. The method assumes a leaky, isotropic, homogeneous aquifer of infinite areal extent. The language employed is BASIC, an interactive language used on the Wang Model 2200 programmable calculator. The program can be easily adapted to FORTRAN IV for use on larger machines.

Notes: A study of the quality of ground water from 250 open wells in the coastal aquifer of Kaniti-Paravada near Visakhapatnam, India brings out the fact that the occurrence of highly brackish waters in certain localized pockets is due to the hydrogeological processes going on in the area and not due to the influence of the sea. The phenomenon is verified by determining standard ratios of tracing sea-water contamination like Ca/Mg, Cl/HCo3’and TA/TH. Conductivity and sodium adsorption ratio are also determined for finding out the alkali hazard, to supplement the observations.

Notes: A hydrochemical study is outlined which demonstrates the mixing of two different ground-water types in the Lincolnshire Limestone aquifer. The two water types consist of a modern recharge water and an ancient possibly connate water. The hydrochemistry of the “interface zone” between the two waters is discussed in detail. In the younger water a relationship between sulphate reduction and bicarbonate is illustrated approaching the “interface zone” and is considered to be related indirectly to the mixing. Carbon isotope content is shown to be radically different in the various ground waters and supports the mixing hypothesis.

Notes: Exact solution to the problem of unsteady drawdown in a leaky artesian aquifer due to a constant discharge nonpenetrating well is presented. Finiteness of the well radius and aquifer anisotropy are considered in formulating the problem. Solution is derived on the assumption that the flux entering the pumped well is uniformly distributed over the plane circular bottom of the well. The aquifer is considered to be finite in thickness, but of infinite lateral extent. The flow of ground water is assumed to be governed by Jacob's model of linear leakage. Laplace transformation technique is employed in the theoretical development. The drawdown function is numerically integrated in terms of dimensionless parameters of the flow system and the results are depicted in graphs.

Notes: The technical feasibility of storing energy in an aquifer is being investigated by Auburn University in a field experiment. Waste hot water from Alabama Power Company's Barry Steam Plant will be pumped into an artesian aquifer, stored, and recovered. The field data will be used by the U.S. Geological Survey to verify numerical models for the analysis of the transport of heat in an artesian aquifer system.

Notes: Environmental effects of feedlot location and related land disposal operations can be minimized if proper knowledge of hazardous conditions are known and appropriate protective steps taken. Common guidelines often do not apply because of differing physical characteristics of local areas.Analyses of various parameters within a soil profile beneath a feedlot revealed none of the chemical constituent present in high concentrations below the 23-foot depth. In areas where shallow ground water was less than 5 feet from the surface, the ground water was found to be affected by the feedlot. Other hazardous areas in feedlot location are flood-prone areas, areas of surface bedrock, and areas of excessive slope.For land disposal operations, loading rates and frequency of application of feedlot waste should be adjusted in accordance with soil permeability, depth to ground water, and irrigation practices to minimize detrimental effects on ground-water quality.

Notes: The successful design and operation of a ground-water monitoring and surveillance system are based on a stepwide process of obtaining hydrogeologic information.Because of the inherent uncertainty and inhomogeneity of natural hydrogeological systems, the true monitoring network cannot be specified before some basic knowledge about system configuration and dynamics is known.Forethought, planning and incorporation of design criteria as part of the initial phase of project management establishes the monitoring network strategy. Optimization of the monitoring network takes place through the completion of the following five phases: (1) preliminary network design and information gathering, (2) initial installation and testing, (3) completion and verification, (4) operational, and (5) project termination.Experience gained from monitoring the conditions at the University of Minnesota's chemical and special waste disposal site resulted in the design and optimization procedure. Concern for possible ground-water contamination led to analysis of surface and subsurface, physical and chemical conditions. Subsequently a monitoring system was established to meet project objectives. No degradation of the ground water was found during the five-year study.

Notes: Dry washes or river beds are often used by southwestern communities to dispose of treated sewage effluent. Because many of these communities rely on ground water as a water supply, there is concern that this disposal practice may contaminate local aquifers. This has led to implementation of monitoring and tracing programs to quantify effluent and ground-water interactions and to development of efficient, easily used predictive models.The treated sewage effluent from the City of Tucson treatment plant has historically been used for irrigation and/or discharged to the normally dry Santa Cruz River. Numerous sampling programs have been undertaken to quantify the chemical quality, temperature, and microbiological activity of the ground water in the area near the Santa Cruz. Ground-water regions with high chloride and nitrate concentrations tend to be associated with areas irrigated with sewage effluent. Quality degradation due to channel recharge is not as evident because the effluent recharge is restricted by fine materials plugging the channel deposits. Recharging water tends to mound near the contact between the Recent and Fort Lowell formations spreading laterally more rapidly than downward.A new tracer, trichlorofluoromethane (trade name Freon 11, C13CF) with applications similar to environmental tritium is being evaluated. C13CF enters the hydro-logic cycle when it is partitioned between the gas and liquid phases during raindrop formation. C13CF in water samples is separated and quantitatively measured by a gas chromatograph with pulsed electron-capture detector.Preliminary Cl3CF analyses of ground water along the Santa Cruz do not correlate with nitrate values because mixing and increasing atmospheric Cl3CF concentrations were not accounted for. However, the presence of CI3CF in the ground water indicates recent recharge. Predictive modeling will be implemented using CI3CF and a finite-state mixing model.

Notes: Large well-field developments in the Mid-Gulf area have caused abnormal lowering of nearby lakes. A map showing the differential head between the surficial aquifer and the underlying limestone Floridan aquifer showed values ranging from 20 feet to zero at a location where the aquiclude is absent. Lake levels had been restored by pumping from limestone wells. From pumping data and analysis of recession limbs, lineal relations between recession rates and differential head appeared to exist. From these, leakance values and vertical permeabilities were determined, with the latter values for two distinctly different sites ranging from 2 × 10-2 to 200 gpd/sf.

Notes: The application of deicing salts is usually a highly successful strategy in improving driving conditions but the environmental impact of such actions may be a cause for concern. Since cheap, harmless and efficient alternatives to salt are not currently available it is suggested that moderation and regulation of salt applications are necessary if harmful side-effects of deicing salts are to be minimized.

Notes: Presented is an analysis of the hydrology and chemistry of the ground water of the Puna District, Hawaii, based on data from 16 drilled wells, ten test wells, two shafts and four exploratory thermal wells. Ground water occurs as (1) perched water located north of Mountain View; (2) dike water located along the east rift zone of Kilauea, and (3) basal water occurring throughout most of the district, except where dike water is present. The east rift zone serves as a barrier to ground-water movement, as demonstrated by the difference in basal water-table levels on the two sides of the rift zone. Salinity and temperature of the basal ground water varies greatly north and south of the rift zone due to differences in precipitation, sea-water intrusion, volcanic activity, flow rates, permeability, and discharge.Basal ground-water type is predominantly sodium chloride. Water samples taken from thermal test well no. 3 showed dissolved silica values two to three times higher than the 49 mg/l average for the rest of the island. Hydrologic and geologic conditions in and around Kilauea's east rift zone support the possibility of accumulations of superheated ground water. The mixing of waters of different composition at depth proved to be the most difficult problem encountered in estimating deep groundwater temperatures.

Notes: A method is presented for selecting ground-water flow paths by comparing modeled and measured hydraulic conductivity distributions. A flow chart is included which shows the steps followed in selecting the concept of groundwater flow which best fits measured hydrogeologic conditions.Both noneffluent and effluent stream conditions are evaluated using the method. Residual maps of hydraulic conductivity are used to show how modeled hydraulic conductivity may be as much as 300 times that expected when the wrong concept is used. Flow nets of modeled and measured data downstream from a flood-water-retarding structure are developed using the selected hydrogeologic conditions.Fitting hydraulic conductivity data results in a distribution of ground-water flow paths which better represent actual flow conditions. The method provides a unique means of calibrating a model in a pilot test area and applying it to geologically similar nearby watersheds. It is also useful for checking paths of subsurface flow where flow distribution is important as it is in the movement of chemical pollutants or nutrients from a source of recharge, such as a watershed impoundment, to downstream waters.

Notes: The value of the electrical resistivity method as a quantitative indicator of ground-water resistivity, porosity and effective matrix resistivity is examined through the equivalence of these parameters as manifested in the surface-measured resistivity of heterogeneous water-saturated sands. It is demonstrated that, where there are unknown variations in porosity, the mapping of groundwater resistivity is most feasible at lower salinities and where porosity is relatively high. Porosity can be determined most exactly at lower values and where groundwater salinity is relatively high. Both these approaches become less efficient as matrix conduction increases. The mapping of effective matrix resistivity is best effected at lower values where this parameter can be approximately monitored against moderate variations in both porosity and ground-water resistivity. In general, however, where there are unknown and pronounced variations in any two of these parameters, the geoelectrical determination of the third can be so ambiguous that the uncertainty in the estimated value of this parameter can exceed the total range of values encountered in an entire formation.

Notes: A classical battle between landowners desiring to protect their fresh ground water from pollution and oil companies needing a disposal zone for injection of oil-field brines developed in Texas County, Oklahoma.Initial studies showed that the disposal zone (Glorieta Formation) was in places only 500 feet below the bottom of the fresh-water aquifer (Ogallala Formation). Furthermore, solution/collapse features in the intervening formations plus numerous poorly plugged wells and exploration holes provided potential avenues of brine migration. The potential for pollution appeared very real. The landowners not only wanted to halt construction of new brine disposal wells, but also wanted all 33 existing disposal wells abandoned and plugged. Tempers flared and intermittent litigation continued for over two years.A more complete hydrogeologic analysis led to the following observations: (a) the potentiometric surface in the Glorieta is 100 to 400 feet below the water table in the Ogallala in areas where brine disposal is taking place; and (b) the transmissivities of the Glorieta and disposal rates are such that even pressure gradients around disposal wells are below the water level in the Ogallala. These hydrologic facts led to the conclusion that, even with a perfectly open conduit connecting the two formations, migration of disposal brine from the Glorieta into the fresh-water Ogallala would be impossible in the critical area because of pressure relationships.Techniques using “pressure bombs” and test injection data are presented by which transmissivity values in the Glorieta were estimated. Disposal well design and completion methods used by the oil companies were found to be inefficient and contributed to operational problems. Specific regulations were adopted regarding disposal wells to further assure that pollution of the Ogallala would not occur.As a result of all parties understanding the hydro-geologic factors, the oil companies are continuing to use the Glorieta as a disposal zone and the fearful landowners are assured that no real pollution hazard exists. This outcome assures full use of all natural resources–which is true conservationism. Ground-water technicians not only have a responsibility to use and protect ground-water resources, but also to assure that unnecessary cost burdens are not placed on other industries in the name of pollution prevention.

Notes: Beginning in February of 1974 and continuing to and through the start-up of the first generating unit at the Jim Bridger Power Plant on August 8, 1974, the authors were drilling monitoring holes, collecting water samples and evaluating water quality and ground-water levels at the project. During the course of this evaluation, considerable data was developed. Some unique and unusual problems were encountered and some of the results are interesting.As of this writing, there are over 25 water quality stations being monitored. Most of these stations are monitoring wells drilled into Tertiary or Cretaceous sedimentary rocks although some monitoring wells are drilled into recent stream alluvium. Also, there are surface-water monitoring sites on two major streams, the freshwater surge pond and the evaporation ponds that receive the blow-down water from the power plants' cooling towers.These waters were analyzed for at least 21 minerals and/or ions as well as pH, dissolved oxygen, turbidity, temperature and such exotics as phenols, hydrazine and ammonia.The indigenous water quality of the area is poor with total dissolved solids ranging to 15,000 mg/l and pH values from 7.3 to 12.3. pH values were found to vary as much as four points between two monitoring stations fifteen feet apart. This water quality is expected to be improved by the importation of relatively high-quality water from the Green River via a 41-mile pipeline.Graphs have been prepared showing some of the concentrations of the more important minerals and their relationship to human, cattle, sheep, crop and boiler tolerances. A water suitability chart also shows how the water quality in the various geologic units as well as the surface water relates to various limitations of water use.Seven of the nine toxic substances cited by the Public Health Service standards were analyzed. Of these, silver, arsenic, cadmium, hexavalent chromium and cyanide were not present in objectionable quantities. Lead, however, was excessive during some months at all well sites and two surface sites on a stream that parallels an interstate highway for more than 6 miles.The water quality was found to have a definite relationship to the geology. Similarly, the geologic conditions are expected to be the governing factor in the rate and direction of flow of subsurface water. This factor will be of major significance when the blow-down water in design concentrations of 30,500 mg/l TDS is discharged into the evaporation pond during the projected thirty-five-year life of the project.

Notes: The abundance and relative purity of ground water guarantees its increase in usage. In some localities, the content of iron and manganese in ground water is so high that these metals must be removed before the water can be used for drinking or industrial purposes.Iron occurs in two states of oxidation in nature–the divalent (ferrous) and trivalent (ferric) forms. The Vyredox method developed in Finland and used now also in Sweden and some other countries oxidizes the ferrous ion, which is soluble in water, to the ferric ion, which is insoluble, before the water enters the well.The Vyredox method achieves a high degree of oxidation in the strata around the well. The method makes use of iron-oxidizing bacteria and aeration wells. A number of aeration wells are placed in a ring around the supply well. Water is forced down the aeration wells but first it is degassed and then enriched with oxygen. The oxygen-rich water provides a suitable habitat for the iron-oxidizing bacteria which assist in the oxidation of ferrous iron. The process must be repeated at specific time intervals to avoid further increases of iron content.The process of precipitating iron in the aquifer has only a slight effect on aquifer permeability. Cloggage of the aquifer surrounding the well should not occur for a period many times longer than the life span of a typical well.

Notes: Data obtained from observation–well programs are used to determine (1) the effect of withdrawals on recharge and natural discharge conditions, (2) the hydraulic characteristics of ground–water systems, and (3) the extent and degree of confinement of aquifers. Wells in these programs can usefully be divided into three networks: (1) a hydrologic network which includes wells needed to determine the extent of aquifers and changes in storage, (2) a water–management network which includes wells needed to determine the effect of withdrawals and hydraulic characteristics, and (3) a baseline network which includes wells needed to determine the response of ground–water systems to natural changes such as those related to climate.

Notes: The drainage basin of Barbadoes Pond, Madbury and Dover, southeastern New Hampshire, was studied by seismic refraction and magnetic measurements as part of an interdisciplinary investigation. The purpose of the geophysical measurements was to provide boundary conditions (bedrock and water–table elevations) for a mathematical model of ground–water flow. The basin is intensively used for recreation, municipal water supply, and sand and gravel mining.Barbadoes Pond is a kettle lake lying in the middle of a broad, flat–topped sand and gravel hill (a “kame plain”). The plain is surrounded by marine clay at a lower elevation.A broad, deep, northwest–southwest trending trough underlies the plain according to seismic refraction measurements (45 lines) and water wells. The present form and location of the trough are attributed to glacial enlargement of a stream valley eroded along a bedrock shear zone. The bedrock topography and seismic velocity are directly related to erosion resistance of the vertically dipping metasedimentary bedrock. Magnetic anomalies are consistent with the seismic results.Water–table elevation correlates with bedrock elevation, not surface elevation. This is a consequence of highly permeable sand and gravel, the principal surfical materials. Apparently the pond is not hydraulically independent of nearby wells and a large reservoir.The results invite speculation that kame plains occur over bedrock troughs. Such a relationship, if generally true, would speed search for good well sites in this region of rapid population growth and industrial development.

Notes: In truly arid regions there is essentially no direct penetration of rainfall. Recharge to ground water is not only infrequent, but extremely localized, occurring only where surface runoff has been channelized or ponded. Over those vast desert areas covered by sparse xerophytic vegetation, the scant rainfall has little or no chance of becoming ground-water recharge. Such water is quickly dissipated by capillarity-assisted evaporation, or through rapid evapotranspiration by short-lived annuals. Where perennial xerophytes cover the ground surface, the extensive shallow root systems quickly utilize all of the rainfall stored in the soil. Beneath the infrequently moistened soil zone is the lower part of the vadose zone, extending to water tables which are usually at depths of tens to hundreds of feet. Almost always these vadose zones have moisture contents well below field capacity.Regardless of the cause, these dry vadose zones are capable of holding additional water, at least up to field capacity. And no water-carried pollutants can reach the water table from the ground surface until a pre-wetted path has been formed for the entire vertical distance. A practical use of this water-holding capacity can be made in the design of wastewater tailings ponds, with predictable safety and with great economic benefit. However, only in predictable geologic conditions, and in limited amounts can the use of this water-holding capacity be recommended. On the other hand, to make no use whatsoever of these great natural dry sponges would be an economic waste.

Notes: Individual subsurface liquid waste disposal has been cited as a source of ground-water contamination. Wastewater treatment systems using emergent marsh vegetation planted in a gravel substrate in a plastic-lined trench could be used to treat septic tank effluent. A pilot plant treating unchlorinated primary municipal effluent achieved the following reductions in mass: BOD5-77%; COD-71%; orthophosphate–35%; total phosphorus–37%; nitrate–22%; coliform bacteria–99.9%. While such treatment is possible only during the growing season, it could be useful at summer cottages, camping areas, resorts and roadside rest areas. Marsh treatment systems are inexpensive to operate and virtually automatic.

Notes: Local ground-water pollution problems are often associated with disposal of sewage from remote recreational areas. Ground water in these areas is routinely used for domestic purposes without treatment. Sewage treatment facilities are often prohibitively expensive. Transporting sewage to municipal sewage treatment facilities is often equally costly, or adequate facilities are not available.A soil incorporation method was tested at two field sites in Michigan's Upper Peninsula to evaluate its impact on ground-water quality; Liquefied campground sewage was injected at 15 cm (6 in.) depths using a liquid manure system. Average dosage levels were 2.7 metric tons per hectare (1.2 ton/acre) of dry sewage solids. The application rate was equivalent to a fertilization rate of 116 kg/ha (104 Ib/a) of total nitrogen. Field tests were conducted on adjacent strips of Kalkaska sand soils in 1973, 1974, and 1975.Changes in ground-water quality in the zone immediately beneath the water table were evaluated by analyzing samples from randomly located wells. Test wells were located directly beneath the treated area and up to 30.5 m (100 ft.) away in the direction of ground-water flow. Nitrate levels in ground water at 3.6 m (12 ft.) depths were higher than control levels from the treated zone to the limit of the test well sampling. Levels of nitrate did not exceed the limits for potable water (10 mg/1 NO3-N). No fecal coliform organisms were detected in ground-water samples. Laboratory tests of the filtration capability of the A and B horizons indicated a high level of filtration of polio virus.Fertilization with sewage increased the biomass of native herbaceous vegetation by 410 percent. Nitrogen content of the treated vegetation was 63 percent above controls. Approximately 48 percent of the added nitrogen fertilizer was incorporated in herbaceous foliage at the end of the first growing season.Site selection guidelines for use by National Forests include remote location of incorporation sites, no potable-water sources within one-half mile downgradient from the site, infiltration rates between 5 and 25 inches per hour, slopes less than 5 percent, and dosage rates which will not exceed 50 kg/ha (56 lb/a) of mineralized nitrogen per year. Injection depths should provide complete soil coverage but sewage should be placed above the B horizon for maximum use of nutrients by plants.The soil incorporation method has been approved for selected sites by the Michigan Department of Natural Resources and the U.S. Environmental Protection Agency, with ground-water monitoring required at each site.

Notes: High concentrations of dissolved nitrate in the ground water in the Redlands, California, vicinity threaten public water supplies. Dissolved nitrate-nitrogen concentrations in water from wells, which frequently exceed 10 mg/1 (milligrams per litre), are attributed to the previous applications of large quantities of commercial nitrogen fertilizer on citrus crops. In a city of Redlands public water-supply well field, wells 1 and 2 normally produce water with dissolved nitrate-nitrogen concentrations of about 18 and 30 mg/1, respectively. Well 1 is a large-capacity well capable of yielding 3,700 gal/min (gallons per minute) [233 1/s (litres per second)] and is the major source of water in the well field.The very permeable unconfined alluvial aquifer is composed of sand, gravel, boulders, and discontinuous clayey deposits. Well 1 is 742 feet (226 metres) deep and is perforated throughout most of the zone of saturation. A major clayey interval from 425 to 480 feet (130 to 146 metres) effectively separates the aquifer into an upper and lower zone. Well 2 is 426 feet (130 metres) deep and is perforated throughout most of the upper zone of saturation. At the well field the static water level (February 1976) was 180 feet (55 metres) below land surface.Independent tests were made on wells 1 and 2 to evaluate aquifer characteristics and to determine the sources of the high-nitrate water. Chemical analyses of water collected from well 1 during the first 48-hour test showed an increase in dissolved nitrate-nitrogen from 4.1 mg/1 to a maximum of almost 20 mg/1. Dissolved nitrate-nitrogen concentrations during the 48-hour test of well 2 stayed constant at 30 mg/1. Interpretation of the chemical data and the results of previous studies indicate that the upper zone of saturation is the higher in concentration of dissolved nitrate.To reduce the concentration of dissolved nitrate in water from well 1, an inflatable packer was placed in the casing at 480 feet (146 metres) to coincide with the bottom of the clayey interval. The packer sealed off the upper part of the well and, as determined from a final test of well 1, reduced dissolved nitrate-nitrogen concentrations from 20 to 4 mg/1 while only reducing well yield from 3,700 to 2,600 gal/min (233 to 164 1/s).

Notes: Book Reveiwed in this articleWATER AND WATER USE TERMINOLOGY, by J. O. Veatch and C. R. HumphreysGROUND WATER STORAGE AND ARTIFICIAL RECHARGE, by the United Nations Department of Economic and Social Affairs, Natural Resources/Water Series No. 2

Notes: A method for collection and analysis of well cuttings samples to aid in ground-water resources evaluation of certain types of alluvial aquifers is described. The method standardizes collection procedures which minimize disruption of the drilling process and allows for easier laboratory interpretation. Analysis techniques for soils are adapted to differentiate between the formations encountered. Wet and dry colors, particle size analysis, acid reaction, plus examination of mineral constituents permits correlation of formation characteristics from wells constructed at different times and by different drillers. An example of the procedure for an area northwest of Tucson, Arizona is given.

Notes: An individual home waste nitrogen and phosphorus removal system was evaluated in the laboratory. The gravity flow system consisted of a 10 × 60 cm (4 × 24 in) vertical Plainfield sand column followed by a series of 8 × 32 cm (3 × 12 in) horizontal columns filled with calcite (CaCO3) or dolomite (Ca MgCO3). Nitrogen removal was attempted using a nitrification-denitrification system where methanol was used as an energy source and P removal was attempted using calcite and dolomite. Separate experiments running from 4 to 6 months were used to test various diameter calcite and dolomite. The phosphorus removal system was also the site of denitrification and hence was in an anaerobic environment. Nitrogen removal was successful with approximately 60–100% removal in a 1-day residence time after methanol addition. Increased denitrification rates were observed using smaller diameter filling materials but no differences were observed between equal-diameter calcite and dolomite. Phosphorus removal was successful initially but after approximately one month, the ability of the calcite or dolomite to sorb phosphorus was curtailed in a 3-day residence time. Results indicated that calcite was superior to dolomite and smaller diameter material was superior to larger diameter in removing phosphorus. However, it appeared that slime growth and organic anion competition covering the sorption sites on the calcite and dolomite prevented significant phosphorus removal after the first 2 to 3 months.

Notes: Ground-water contamination from uranium mining and milling results from the infiltration of mine, mill, and ion-exchange plant effluents containing elevated concentrations of radium, selenium, and nitrate. Available data indicate that radium concentrations in the discharge waters of a producing mine tend to increase substantially as the ore body is developed. Whereas natural background radium concentrations are generally about several picocuries/liter (pCi/l), 100 to 150 pCi/l appear in the effluents of operating mines. The discharge of such highly contaminated mine effluents to streams and seepage from tailings ponds, creates a long-lived source of ground-water contamination. Seepage of mill tailings at two active mills ranges from 126,000 to 491,000 m3/yr and, to date, has contributed an estimated 2400 Curies of uranium, radium, and thorium to the ground-water reservoir. The shallow aquifer in use and downgradient from another mill has been grossly contaminated with selenium, attributable to excessive seepage from a nearby tailings pond.Radium, selenium, nitrate and, to a lesser extent, uranium, are of most value as indicators of ground-water contamination. Gross alpha results are not consistent indicators of radium or uranium in water, although uranium does appear to be the principal contributor of alpha activity. Accurate radium-s226 analyses yield the most information for radiological evaluation of drinking water.To date, no adverse impacts on municipal groundwater supplies have been observed. However, industry-sponsored environmental monitoring programs are inadequately designed and implemented, and may not define the full, long-term impact of mining and milling operations on the ground-water quality of the study area.

Notes: Step-drawdown tests of a well in a dolomite aquifer in north-central Ohio, before and after it was enlarged from 10 to 12 inches (250 to 300 millimetres) in diameter, indicate changes in the well-loss constant, the exponent for turbulent flow, and the formation loss factor. The calculated difference in drawdown resulting from enlarging the well is of little practical importance at rates of 300 to 500 gallons per minute (19 to 31 litres per second), the range of rates at which the well is expected to be pumped, but for higher rates the decrease in drawdown and consequent reduction in power costs could be significant. For a pumping rate of 1,500 gallons per minute (95 litres per second), the decrease in drawdown would be 20.4 feet (6.2 metres).

Notes: Information from 675 water wells in and around Phelps County, Missouri shows that discrete areas of differing ground-water quality can be identified and mapped. The best quality ground water, as judged by its low nitrate content and coliform bacteria density, is found in areas of relatively little agricultural (pasture and livestock) land use. The poorest quality is found in areas of intensely developed karst and greater agricultural land use. The adverse effect of agricultural land use on ground-water quality is more severe in the intensely developed karst than in the less intensely developed. Rural population density and soil association variations have no readily discernible effects on ground-water quality. Nitrate content varies seasonally and in response to rainfall, and decreases with increasing well depth. Coliform bacteria density is positively correlated with nitrate content.

Notes: Fuel oil, underlying approximately four acres, was discovered floating on the water table beneath oil products' storage tanks. The oil, of unknown origin, originally was observed discharging to a river adjacent to the storage tank area from an abandoned clay tile. Approximately 35,000 gallons (132,500 liters) of oil were intercepted and contained prior to the field investigation by borings.Hantush's (1968) theory for the formation of a fresh-water lens in an unconfined saline aquifer was used to examine the decay of an oil lens resulting from a catastrophic oil spill at the site. The theory indicated that too much time had elapsed from the first detection of oil at the surface to the collection of subsurface information to make it feasible to speculate on the precise nature of the spill event–catastrophic or a slow leak. Application of the theory and consideration of the ground-water hydrology of the site did make it possible to identify the probable source area of the spill. Analysis of the flow system also assisted in the selection of the appropriate collection system to clean-up the spill.Subsequent to the boring program, an electrical resistivity survey was conducted to test the feasibility of delineating the extent of the subsurface oil by this method. Only modest success was achieved, apparently because of the thinness of the oil-bearing zone.

Notes: Because of increasingly stringent laws governing discharge of fluid wastes to surface waters, the alternative of discharge to the subsurface has become attractive. The physical-chemical processes that prevail in the subsurface are not well understood, but they are clearly not identical to processes of purification in surface waters. For example, in the subsurface the process of oxidation may be of little value in significantly reducing the concentration of discharged contaminants; in contrast, oxidation plays an important role in purifying surface waters. Eleven physical-chemical processes can be identified as having potential value for purifying wastes discharged to the subsurface, as follow: dilution, buffering of pH, precipitation by reaction, hydrolysis, oxidation or reduction, filtration, volatilization, biological assimilation, radioactive decay, membrane filtration, and sorption.Discharge to the vadose zone may be a safe means of disposal of wastes in arid regions. But it is necessary to carefully test the suitability of a particular site for a particular waste. Processes of purification in the vadose zone can be incorporated into a workable plan of discharge if adequate studies and safeguards are employed. Regulations governing subsurface discharge should take into account the physical-chemical processes that may act to purify the waste fluids. In one set of experiments, a soil from Sulfur Springs, New Mexico was capable of removing large quantities of dissolved molybdenum and copper from a synthetic mill water, and the soil was able to quantitatively retain the copper during subsequent leaching by fresh and metal-free mill waters. Such studies permit rational plans of discharge to be developed.

Notes: In 1973, the Suffolk County Department of Environmental Control in cooperation with Cornell University began a study on nitrogen (N) fertilization of potatoes and turfgrasses. The research and demonstration project has shown that current practices result in substantial N losses; and, in many cases, excessive use of N reduces crop yields and turf quality. Annual N losses of 50 lbs. per acre (55.5 kg-N/ha) are sufficient to cause a concentration in the aquifer's surface layer of 10 mg/1 nitrate-N (New York State Drinking Water Standard).The eastern portion of Long Island supports a productive agricultural industry whose main crop is potatoes. Ground-water surveys have shown that the aquifer system of this area is contaminated with nitrate nitrogen. The average potato grower applies 200 to 250 lb-N/a (222 to 278 kg-N/ha) at planting time; and depending upon a number of factors, N recovered in harvested tubers varies from 75 to 150 lb-N/a (83 to 167 kg-N/ha). Losses to the ground water could vary from 50 to 175 lb-N/a (55.5 to 194 kg-N/ha). The study has shown that the application of 150 lb-N/a (167 kg-N/ha) can still maintain maximum potato yields and keep the N loss to ground water below 50 lb-N/a (55.5 kg-N/ha) by improving nitrogen-use efficiency. This is done through splitting N applications so that one-third to one-half is applied at planting and the remainder is applied prior to the period of rapid crop growth and nutrient uptake. On-farm demonstration plots are being used to convince growers to reduce N rates and adopt more efficient application methods.The western portions of Long Island are highly urbanized and turfgrasses may be fertilized at rates up to 350 lb-N/a (389 kg-N/ha). Potential leaching losses are high for turfgrass as N is not recovered in harvested plant materials. Experiments are underway to establish rates of biomass N buildup under several fertilization regimes. Preliminary results indicate that N-use efficiency increases with more frequent but smaller N applications. Encouraging the use of low maintenance turf species appears to be the best long-term solution.

Notes: A preexisting network of 124 wells used for fire protection in the Town of Southampton, Long Island, New York, was monitored during a one-year period for groundwater levels and chloride concentrations. Water from 26 wells had chloride concentrations of 50 mg/l or greater and in 17 wells the chloride concentration exceeded 200 mg/l. Most of these wells are located in two densely populated areas. The possibility of widespread intrusion in one of these areas has not been previously documented. In addition, detailed water-table contour maps are presented for selected areas within the Town.