ALBERT

Notes: Site selection for ground-water production wells was made easier using a microgravity survey technique. The ground-water regime beneath the Carleton University campus is dominated by fracture flow associated with major faults. These faults are located within buried bedrock valleys where preferential erosion of the bedrock has occurred. A series of faults is inferred from bedrock topography and hydrogeological testing; however, the precise orientation of the faults is to a large extent uncertain. The bedrock surface is masked by fluvial, glacial, and glaciomarine overburden of variable thickness.High precision, small-scale microgravity profiling was carried out to identify the bedrock valleys. Gravity anomalies of up to 0.05 mgal correspond to valley depths ranging from 5 to 15 meters. The density contrast between overburden and limestone bedrock is estimated as 0.3 g/cm3. Forward modeling using a polygon technique suggests that the observed, corrected gravity profile is a smoothed reflection of the bedrock surface at depth.Based on the locations of the bedrock valleys, several faults were identified and four test wells were drilled as part of the development of Phase 2 of the Carleton Groundwater Energy Project. Three of these wells produced high yields, exceeding 60 I/sec, when converted to 12 inch diameter production wells. The fourth well also encountered a bedrock valley but with a slightly lower yield of water.The favorable drilling results have shown that small-scale microgravity profiling, in an area that is largely unsuitable for the detection of subsurface features using other geophysical techniques, is an effective method for imaging the bedrock surface. The positions of the faults, which are known to exist on the basis of stratigraphy, geophysical well log correlations, bedrock topography, and calcite-filled fractures exposed in outcrop or core, have been more accurately defined.

Notes: Di-n-butyl phthalate (DBP) was found to be transformed by microorganisms under aerobic and anaerobic conditions at 10° C in microcosms simulating the Canadian Forces Base (CFB) Borden subsurface environment. Biotransformation of DBP was observed under aerobic, nitrate-reducing, Fe(III)-reducing, and sulfate-reducing conditions. The biotransformation of DBP in the microcosms was significantly decreased as the redox potential was lowered, especially under sulfate-reducing conditions. However, other factors such as nutrient depletion and buildup of toxic intermediates could have affected the biotransformation rates. The highest DBP biotransformation rate (0.57 μg DBP.g sediment−1.day−1) was observed under aerobic conditions whereas the lowest rate (0.05 μg DBP.g sediment−1.day−1) was under sulfate-reducing conditions. Biotransformation of DBP at 10° C was significantly enhanced by the addition of 10 mM NaNO3 suggesting that both the addition of nitrate and high redox conditions favor its biotransformation in subsurface environments.

Notes: Lake Chad, a closed basin lake, is the only large surface-water body in the African Sahel. Future water resource development in the Chad Basin requires an understanding of the hydrogeology of the basin. In this paper we examine the hydraulic relationship between the lake and the phreatic aquifer of the Chad Formation. Electrical resistivity data from 30 surveys were combined with over 60 open well measurements to construct a water-table map of the southwestern quadrant of the lake. The map indicates that the Lake Chad water level is at a higher hydraulic level than the phreatic aquifer and that the ground-water flow is southwest, away from the lake. The average measured seepage rate into the phreatic aquifer in the southwestern and southern parts of the lake was 7.1 × 10−3 m/d (median = 1.3 × 10−3 m/d) which is about 21% of the annual water input to the lake. This measured seepage flux (9.96 × 109 m3/yr) can account for about 107% of the annual solute input to the lake. Solute transport model simulations indicate about 32% (15.3 × 109 m3/yr) of the input water and 152% (2.87 × 1012 g/yr) of the total solute input can be removed by ground-water recharge (seepage) from the lake. These results provide an explanation to account for the freshness of Lake Chad's water despite its surficial closed basin geologic setting: solutes delivered to the lake via surface-water inflow leave the lake via ground-water recharge. These results also indicate recharge from the lake (∼ 1010 m3/yr) represents an enormous amount of water available as a ground-water resource in the African Sahel.

Notes: Aqueous geochemical data from unconfined sand aquifers beneath two operating domestic septic systems are used to illustrate and evaluate a conceptual model of septic-system geochemistry. This model emphasizes the changing redox and alkalinity conditions in the septic system and the subsurface. The septic-tank effluents flow as distinct plumes downward through the unsaturated zones and then primarily laterally in the ground-water zones. The composition of the effluent was measured at several points in each system. At each site, the septic-tank effluent underwent aerobic oxidation in the unsaturated zone, which caused conversion of NH4+ to NO3−, organic C to CO2 and organic S to SCh42-. At the first site, calcium carbonate dissolution in the unsaturated zone buffered the acidity released by the redox reactions. In contrast, the second system was poorly buffered and the pH dropped from 6.7 to 4.9 as aerobic oxidation occurred. Below the water table a small amount of aerobic oxidation occurred at each site. Nitrate-N concentrations in the cores of both plumes were above 25 mg/1 as the plumes traveled from the septic systems. At the second site, the ground-water plume discharges to a river at the edge of the property. As the effluent flowed through the organic C-rich sediments of the river bed, NO3− disappeared and alkalinity increased, presumably due to denitrification. Differences in sediment composition at the two sites also led to different behaviors of Fe, Al, and possibly PO43-. The conceptual model offers an organized approach to interpreting the major geochemical trends observed in the two systems, which are determined mostly by the well-aerated unsaturated zones below the drain fields and the amount of buffering material present in the sediments.

Notes: Characterizing the extent and severity of ground-water contamination at waste sites is expensive and time-consuming. A probabilistic approach, based on the acceptance of uncertainty and a finite probability of making classification errors (contaminated relative to a regulatory threshold vs. uncontaminated), is presented as an alternative to traditional site characterization methodology. The approach utilizes geostatistical techniques to identify and model the spatial continuity of contamination at a site (variography) and to develop alternate plausible simulations of contamination fields (conditional simulation). Probabilistic summaries of many simulations provide tools for (a) estimating the range of plausible contaminant concentrations at unsampled locations, (b) identifying the locations of boundaries between contaminated and uncontaminated portions of the site and the degree of certainty in those locations, and (c) estimating the range of plausible values for total contaminant mass. The first paper in the series presents the geostatistical framework and illustrates the approach using synthetic data for a hypothetical site. The second paper presents an application of the proposed methodology to the probabilistic assessment of ground-water contamination at a site involving ground-water contamination by nitrate and herbicide in a shallow, unconfined alluvial aquifer in an agricultural area in eastern Oregon.

Notes: An analysis of the deformation of a homogeneous electrical field caused by a long, thin inclined bed, which is of considerable importance in the exploration of ground water and minerals, is presented using the Hilbert transform. The thickness of the bed and the inclination are expressed as a function of the abscissae of the points of intersection of the horizontal and vertical derivatives of the field. The procedure is illustrated with a theoretical example and substantiated with field examples from the fractured Crystalline Basement Complex in Burkina Faso, Africa, and Pre-Cambrian limestones of the Cuddappah Basin in Andhra Pradesh, India. The results derived from the analytical method are shown to agree well with the ground truth.

Notes: Eight Schlumberger soundings and four Wenner anisotropy measurements were conducted in the northwestern section of the Yucatan Peninsula for hydrogeological investigations of a karst aquifer. This system is influenced by a circular high permeability zone (Ring of Cenotes) probably related to the Chicxulub Impact Crater. Schlumberger soundings and Wenner anisotropy measurements show that the karst aquifer can be modeled as an electrically anisotropic medium. Anisotropy is related to preferential permeability directions channeling ground-water flow within the aquifer. Directions of maximum permeability were determined using Wenner anisotropy measurements. Electrical soundings were conducted at different sites near the Ring of Cenotes. Resistivity values decrease toward the Ring of Cenotes supporting the hypothesis that selected segments of the Ring have high permeability. Several soundings were conducted in order to study lateral permeability variations along the Ring. A high permeability section can be identified by low resistivity models and is related to a zone of high cenote density. A low permeability section of the Ring was found showing high resistivity models. This zone overlaps with an area of low cenote density. Electrical soundings were used to determine the depth of the fresh-water lens; the interface was detected along two profiles perpendicular and parallel to the Ring of Cenotes resulting in a depth that ranged from 18 m near the coast up to 110 m in the southeastern part of the study area. The predicted depths of the interface using electrical methods showed a good correlation with Ghyben-Herzberg and measured interface depths at some sites. Discrepancies between calculated and interpreted interface depths at two sites may be explained by horizontal-to-vertical permeability anisotropy.

Notes: The “pore tree” model of pore structure was originally developed for catalyst and sorbent grains to allow coupled reactions and diffusion into and out of nonpermeable porous media in the absence of convection through the media. The pore tree model is extended herein to describe the permeable pore structure which characterizes the subsurface transport of gas and water in soil, the dispersion of contaminants, and in situ remediation. The interconnectivity of the pore structure is obtained via a statistical determination of the “branches” that are common to several trees to allow convection and diffusion through the large scale (permeable) structure in addition to diffusion and reactions in the smaller scale (nonpermeable) structure. The extended pore tree model has successfully explained measurement errors in the permeability of soil due to the measurement scale size and has successfully predicted the bulk gaseous diffusivity in partially saturated soil as a function of a saturation scale size. The extended pore tree model provides an analytic description of the pore structure of soil upon which bulk transport, small scale diffusion, and coupled chemical reactions may be added to accurately describe contaminant transport and in situ remediation.

Notes: Two-dimensional, finite-difference, saturated, ground-water flow models such as MODFLOW can be useful in simulating “mise-a-la-masse” electrical flow through conductive porous media. A new technique for using an existing numerical code to develop an approximate solution for point source electrical flow is presented. Incorporating a change in variables from ground-water flow to electrical flow within the MODFLOW input file allows the ground-water flow code to model the effects of resistivity contrasts directly. By adjusting the input data as presented herein, spherical electrical flow through contaminated porous media can be approximated in two dimensions.

Notes: Soil gas pump tests are commonly performed to identify important unsaturated zone parameters such as the effective gas permeability tensor and the influence of tight or leaky confining units. An interactive FORTRAN computer program called GASSOLVE has been developed for analyzing these tests under both transient and steady-state conditions. The code uses one of two general analytical solutions for radially symmetric gas flow to a well: the solution for transient compressible gas flow to a partially penetrating well in which the ground surface is open to the atmosphere; and the solution for transient compressible gas flow to a partially penetrating well bounded above by a leaky confining layer. Pump tests involving steady-state conditions, fully penetrating wells, or tight confining layers are considered as special cases of these solutions. The field gas pressure data from multiple observation wells are inverted using a multidimensional nonlinear optimization routine to provide a best fit of the data with the selected analytical solution.

Notes: The Yuma area has experienced agricultural development since the late 1890s and ground-water levels have risen over 70 feet due to recharge from heavy application of irrigation water, unlined canals and flooding along the Colorado and Gila Rivers. The resulting shallow water levels have seriously impacted residential areas and prime agricultural land.The Arizona Department of Water Resources in conjunction with Yuma County Flood Control District developed a regional three-dimensional ground-water flow model of the Yuma area. The purpose of the model is to assist local agencies in evaluating remedial water management alternatives to mitigate the shallow ground-water level problems.The model domain incorporates over 900 mi2 of Arizona, California, and Mexico and simulates ground-water pumpage, deep percolation from agricultural irrigation, evapotranspiration from phreatophytes and flow in 12 canals, 16 drains, and the Colorado and Gila Rivers. The model contains four layers with over 30,000 model cells ranging in size from 40 acres to 640 acres.Different model scenario simulations were conducted to evaluate the effectiveness of proposed water management alternatives on lowering ground-water levels within the northern portion of Yuma Valley. These scenarios include lining a portion of the East Main canal and pumping two drainage wells, lining the All-American canal, and simulating a decrease in deep percolation from agricultural irrigation on the Yuma Mesa and northern portion of Yuma Valley.

Notes: The first paper in this series (Rautman and Istok, 1996) presented a geostatistical framework for obtaining a probabilistic assessment of ground-water contamination. This paper presents the results of a case study that applies this framework to define the spatial extent and severity of nitrate and Dacthal (dimethyl tetrachloroterephthalate or DCPA, a herbicide) contamination in the unsaturated and saturated zones for a 150 km2 site near Ontario, Oregon. Sediment samples collected from 35 boreholes were used to compute vertical accumulations of nitrate and DCPA in the unsaturated zone. Measured nitrate and DCPA concentrations in ground-water samples collected from 42 wells were used to compute vertical accumulations of nitrate and DCPA in the saturated zone. Sample variograms were fit with nugget and spherical models to describe the pattern of spatial continuity of nitrate and DCPA concentrations and accumulations. Conditional, sequential Gaussian simulation was used to generate 100 simulations for each variable on a 0.5 × 0.5 km grid. Probabilistic summaries of these simulations were used to develop (a) maps showing the probability of contamination exceeding specified theshold values, (b) probability distributions for contaminant accumulation and concentration at unsampled locations, (c) probabilistic descriptions for the location of contaminant-plume boundaries, and (d) probability distributions for the total contaminated area and total contaminant mass. The results demonstrate that interpretations of site characterization data to determine the extent and magnitude of contamination at a site will vary depending upon the level of uncertainty that will be tolerated by the decision maker. This case study also illustrates the potential applicability and utility of the probabilistic approach for the interpretation of site characterization data and the design of future data collection activities.

Notes: The results of an extended analysis of the chloride breakthrough curves (BTCs) obtained from transport experiments on undisturbed soil monoliths previously reported by Sassner et al. (1994) are discussed. Parameter values for different forms of the advection-dispersion equation (ADE) were obtained by curve-fitting using the nonlinear least-squares optimization code CXTFIT developed by Parker and van Genuchten (1984). Good fits to the experimental BTCs from the individual soil monoliths were obtained for three different forms of the ADE, allowing for anion exclusion, immobile water, and both of these processes, respectively. Although the more complex forms of the ADE possess more flexibility to provide a slightly more refined fit to the individual breakthrough curves, larger uncertainty is associated with the fitted parameter values. Due to the limited amount of information manifested in the BTCs it is not possible on the basis of this information to distinguish which of the models is physically more meaningful. Furthermore, when more parameters are included in the optimization procedure, the resulting values are more uncertain. The same ADE models were also fitted with equally good results to a hypothetical large-scale BTC derived by flux-averaging the responses from the individual monoliths. However, regardless of the form of the ADE used, the resulting parameter values for the large-scale transport (i.e., not only the dispersivity value that is expected to increase) were inconsistent with the corresponding parameter values obtained for the individual BTCs. This supports previous indications that ADE models may not be accurate for predicting large-scale transport in heterogeneous soil systems corresponding to e.g. the scale of an agricultural field or a grid element in a numerical catchment model because model parameters are not determinable from independent measurements on a scale corresponding to a practical manageable core size or to standard intrumentation.

Notes: By employing the principle of superposition, we offer a semianalytical solution for a one-dimensional advective-dispersive solute transport equation under an arbitrary concentration boundary condition. The technique is applicable to many other existing analytical solutions of solute transport problems.

Notes: An experimental study was conducted to assess how ion exchange processes, which occur during subsurface transport of oilfield brines, manifest themselves on graphical water quality diagrams. Concentrated brine soil column studies indicated sodium in the brine solution is able to exchange for calcium and magnesium on the soil, thereby retarding transport of sodium relative to the average ground-water velocity and resulting in the development of a “hardness halo” at the leading edge of the brine plume. In this zone, calcium and magnesium concentrations exceed the values for both the brine and the fresh ground water. The hardness halo manifests itself as a characteristic deviation away from the mixing lines on the Piper diagram. Initially, the hardness halo causes concentrations to plot left of the fresh-water end member in the cationic triangle. Chloride domination in oilfield brine causes concentrations to plot in the lower right corner of the anionic triangle almost immediately. After the hardness halo passes through the column, the sampling results show a characteristic pattern of movement parallel to the mixing line in the cation triangle or along the (decreasing) hardness axis of the upper diamond of the Piper diagram. The laboratory results were similar to those exhibited by monitoring well samples taken at a field site involving oilfield brine contamination. The results of this study show the Piper diagram to be potentially useful for early detection of brine contamination episodes.

Notes: This note shows how to construct and perform a graphical type-curve analysis using a computer spreadsheet. Formulas are provided to generate the axis shifting behavior that is required for the graphical fit. Arbitrary match points are obtained by trial-and-error (or by closed form solution) for use in the calculation of aquifer hydraulic parameters. The analysis is illustrated using a leaky aquifer type curve and a confined aquifer type curve. Macro programming is not required, only data entry and the ability to use plotting features of a computer spreadsheet. The approach can be adapted for parameter estimation using any tabulated type curve.

Notes: Chlorinated organic solvents introduced to unlined lagoons at an industrial waste-water treatment plant in the Inner Piedmont of South Carolina resulted in ground-water contamination of a fractured-rock aquifer. Part of the ground-water contamination discharges to Little Rocky Creek, downgradient from the waste-water treatment plant. Passive vapor collectors were buried in the bottom sediment of the creek to locate areas where ground water contaminated with volatile organic compounds was discharging to the creek. High concentrations of volatile organic compounds (VOCs) were found in passive vapor collectors in an area where VOCs were known to be discharging from ground water to surface water. This area was also a site where very low frequency electromagnetic anomalies (interpreted as fracture zones) intersected the creek or converged near the creek. The data show that passive vapor collectors in bottom sediment of Little Rocky Creek provided information on the location of fractures that were discharging contaminated ground water to surface water.

Notes: Analytical equations are developed to model changes in porosity, specific surface area, and permeability caused by biomass accumulation in porous media. The proposed equations do not assume any specific pattern for microbial growth but instead are based on macroscopic estimates of average biomass concentrations. For porous media with a pore-size distribution index value (λ) equal to 3, the macroscopic model predictions of porosity, specific surface area, and permeability changes are in exact agreement with biofilm-model predictions. At other values of λ between 2 and 5, simulated porosity profiles are identical and relative specific surface area and permeability profiles show minor deviations. In comparison to biofilm-based models, the macroscopic models are relatively simple to implement and are computationally more efficient. Simulations of biologically reactive flow in a one-dimensional column show that the macroscopic and biofilm approach based transport codes predict almost identical porosity and permeability profiles. The macroscopic models are simple and useful tools for estimating changes in various porous media properties during bioremediation of contaminated aquifers.

Notes: A method is presented for determining steady-state capture zones in three dimensions around horizontal drains and vertical wells in homogeneous, anisotropic aquifers in a uniform flow field. Equations are presented for determining drawdown and velocity vector components in three dimensions around drains and wells. Using these equations, a second-order Runge-Kutta particle tracking algorithm is applied to trace streamlines in three dimensions. By tracking a large number of particles, it is possible to determine areas where capture occurs and areas where particles escape capture. The resulting 3D capture zones are diagrammed as both 2D (section view) plots and 3D plots.

Notes: A nonparametric statistical methodology based on kernel function estimation is developed for assessing the probability that a particular location in the aquifer has high or low conductivity using borehole information. The approach presented is an alternative to Indicator Kriging. Soils are classified through a binary indicator function defined as 0 for low and as 1 for a high conductivity soil. Estimates of the probability of occurrence of a high or low conductivity soil are made on a three-dimensional grid. Each such estimate is formed as a local weighted average of the indicator function values that lie within an averaging interval or bandwidth of the point of estimate. A different vertical bandwidth is chosen at each borehole log. Horizontal bandwidths are selected independently at each horizontal level. These bandwidths are chosen by cross validation. Observations closer to the point of estimate are weighted higher using a kernel or weight function. Unlike Kriging, the underlying stochastic process is not assumed to be stationary. An application using data from Lake Bonneville deposits in Davis County, Utah is presented.

Notes: Vertical profiles of tritium and nitrate pore-water concentrations were determined to ∼8 m depth across two loess hillslopes. Mean recharge fluxes, estimated from chloride mass balance, are 5–10 times larger at the mid- and toe-slope positions than at the top-slope; the magnitudes of the values compare reasonably with results from other methods. The tritium and nitrate profiles exhibit multiple peaks which indicate that piston flow is not the sole flow process in this system. Results of a simple 1-D mixing model suggest that infiltration-exfiltration cycles in zones of plant root activity explain the shallow tritium peaks. Deeper peaks result from preferential vertical and/or lateral flow. The importance of these dispersive processes is underlined by great dilution of observed tritium concentrations, relative to expected concentrations assuming piston flow. In this setting, chloride is useful as a recharge estimator while tritium and nitrate serve as tracers of landscape-scale water movement.

Notes: Enthalpy and entropy of volatilization from dilute aqueous solutions for 26 volatile organic compounds (VOCs) have been determined using Henry's Law values reported in published literature. Based on the linearity of van't Hoff plots, for the temperature ranges common in soils, the differences in heat capacities of volatilization for reactants and products are very small for the VOCs studied.When volatile solutes such as VOCs are present in soil water, soil-gas concentration often nearly is in equilibrium with the dissolved solute. Setchinow salting coefficients are linearly related to dissolved partial molar volumes for halogenated aliphatic compounds. Based in part on approximations from this linear relationship, equilibrium deviations from Henry's Law behavior for dilute VOC concentrations due to capillary tension or the presence of ionic solutes are small for common soil conditions.Since gas/water partitioning of VOCs if temperature-sensitive and since annual soil moisture and temperature patterns vary geographically in documented fashion, geographically specific temporal patterns in soil-gas VOC concentrations are predictable in vadose zones containing dissolved VOCs. A U.S. map depicting these general soil-moisture and temperature patterns is provided. Gas concentrations in vadose zones containing dissolved VOCs tend to increase with increasing temperature and decreasing moisture content due to equilibrium partitioning effects.Diagrams useful for understanding the results of soil-gas surveys and the efficacy of various remediation options are provided. The effect of bubbles in VOC water-sample vials on aqueous concentrations is shown to be very small. The effect of head-space volume of soil samples on estimated soil-gas concentrations can be large.

Notes: Samana Cay, Bahamas, is a leading candidate among the sites proposed as the first landfall of Columbus in the New World. One main point of contention against this identification is that Samana lacks a feature matching the laguna observed by Columbus in the middle of his landfall island. However, this argument has failed to consider the paleogeographic aspects of the problem. A hydrogeologic computer model suggests the existence of a sizable surface-water feature in the medial interior of Samana Cay under conditions theorized to have been present when Columbus arrived in the Bahamas. This feature may correspond to the laguna described by Columbus.

Notes: Case histories of LNAPL contaminated sites indicate that LNAPL thicknesses in monitoring wells exhibit certain characteristic behaviors when related to water-table fluctuations. This paper investigates these behaviors using established theories for fluid saturataions in three-phase (air-LNAPL-water) porous media systems. A semianalytical model is developed to predict the LNAPL thickness in a monitoring well considering the effects of saturation hysteresis and air/LNAPL entrapment. Given the total LNAPL volume in the soil profile and the historical sequence of water-table elevations, the model predicts LNAPL thicknesses, based on the assumption of a succession of hydrostatic pressure distributions. For example simulations, the model indicates that the LNAPL thickness in a monitoring well can exhibit complex behaviors that are strongly dependent on the previous saturation history. While many of these predicted behaviors are consistent with field observations, some are not. This suggests that certain aspects of current theories pertaining to three-phase fluid saturations warrant further technical evaluation.

Notes: Combined optimization-simulation models for designing ground-water remediation systems generally focus on design strategies that use only one remedial technology, typically pumping. In practice, many field remediation programs use pumping along with one or more additional ground-water control technologies, such as drains, trenches, slurry walls, and low permeability caps. Simulated annealing provides a flexible optimization framework that can incorporate a number of different remedial technologies into the design process. Using simulated annealing, additional remedial technologies can be added to or subtracted from the optimization at any time. This flexibility can provide for remedial design evaluations that are more consistent with current field implementations. The use of simulated annealing is demonstrated by a series of hypothetical remediation design problems that incorporate four different remedial technologies. The computed optimal design solution depends on the relative costs of the remedial tools as specified by the cost function and on the effects that each tool has on the system behavior. A sensitivity analysis can reveal which costs are critical to the outcome of the optimization.

Notes: Surfactant mobility in unsaturated soil will impact the effectiveness and efficiency of using these compounds for in situ environmental remediation above the water table. For this reason, transient unsaturated column tests were used to study the influence of boundary conditions and soil attributes on anionic surfactant transport. In these tests, aqueous surfactant solutions were injected into the inlet of horizontally mounted soil columns. Two commercial anionic surfactants were used, an alkyl ether sulfate (AES) and a linear alkylbenzene sulfonate (LAS).The overall study was divided into two parts. First, boundary condition effects including injected surfactant solution concentration, initial moisture content, and surfactant application rate were investigated. Increasing the injection solution concentration increased anionic surfactant mobility in the column while changes in the initial soil moisture content and surfactant application rate had no significant impact. Second, the impacts of soil attributes such as texture, dominant exchangeable cation, and resident organic matter were measured. With respect to texture, mobility was found to be greater in a sandy soil as compared with two loamy soils. Both surfactants, especially LAS, were found to be more mobile in a Na+ dominated soil rather than one dominated by Ca−2.The absence of soil organic matter increased LAS mobility.

Notes: In volcanic areas, when two conditions are satisfied, there is a linear correlation between the range of negative self-potential (SP) anomalies and the thickness of the unsaturated zone measured in borings. The first condition is a high ratio between the resistivity of the unsaturated zone, and the resistivities of the substratum and the water-saturated zone. The second condition is the homogeneity of the unsaturated zone. From this relation, we develop the concept of a geophysical surface (SPS surface) calculated from SP and topographic data. Under these conditions, the SPS surface is both an equipotential SP surface and the interface between the unsaturated zone and the saturated medium below. Borehole logs for three field sites show that drainage courses and watersheds are located exactly on respectively the valleys and the ridge lines of the SPS surface.

Notes: This paper presents an approach to regional hydrological balance where the number and integrated discharge of springs are used to estimate recharge. This technique is applied to Spain, where approximately two-thirds of the country has an inventory of spring lithology and discharge (17,000 springs). The data are used to extrapolate results to the entire region and are compared to independent methods of estimating recharge. This is an informative use of commonly available information and it could be applied to other regions with a similar data base.From this sample, a distribution of the spring flow volume contribution in Spain is estimated (a) according to flow spring discharge, (b) as a limit of a lognormal distribution, which in our sample is simplified in a potential formula a(x) = 24,101.x −0.91. In this way it is calculated that the total flow volume of the springs is 14,877 hm3/yr. The study does not take into account seepage (diffuse discharge) draining to seas, rivers, or lakes but only water at the spring source. The most permeable lithological groups considered are the source of 94.2% of the total flow supplied by the springs. Limestone is especially significant, contributing 66.2%. The net recharge of precipitation to ground water varies widely according to lithologies. It reaches to 20.3% in limestones and drops to less than 1% for quartzites, slates, and plutonic rocks.

Notes: A series of ground-water flow and tracer experiments were performed on an undisturbed column of fractured clay-rich till, 0.5 m diameter by 0.5 m long, in a pressure-controlled cell. The measured hydraulic conductivity of the sample was 1.0 to 1.2 × 10–6 m/sec and the average hydraulic gradient during the tracer experiments ranged from 0.45 to 0.49. The experiments clearly show that ground-water flow and contaminant migration through the sample is primarily controlled by fractures and root holes. Tracer experiments using a solute (chloride), colloid-sized bacteriophage (PRD-1 and MS-2) and uncharged latex microspheres, indicated very fast transport rates of 4 to 360 m/day. These rates are similar to fracture flow velocities calculated on the basis of the measured bulk hydraulic conductivity of the column, and measured fracture spacing, using the cubic law for flow through parallel-walled fractures. Fracture aperture values calculated from the ground-water flow data (35 to 56 μxm) are of the same magnitude as values calculated from the breakthrough of tracers (13 to 120 μm). Aperture values calculated for fractures (1 to 94 μm) and root holes (2 to 188 μm), on the basis of measured immiscible creosote entry pressures, are also comparable with these values. The injected creosote, a DNAPL, penetrated most of the visible and a few invisible fractures and root holes, indicating that, for this till, fractures and root holes are important conduits for the transport of DNAPL's.

Notes: Detailed vertical sampling is useful in aquifers where vertical mixing is limited and steep vertical gradients in chemical concentrations are expected. Samples can be collected at closely spaced vertical intervals from nested wells with short screened intervals. However, this approach may not be appropriate in all situations. An easy-to-construct and easy-to-install multiport sampling well to collect ground-water samples from closely spaced vertical intervals was developed and tested. The multiport sampling well was designed to sample ground water from surficial sand-and-gravel aquifers. The device consists of multiple stainless-steel tubes within a polyvinyl chloride (PVC) protective casing. The tubes protrude through the wall of the PVC casing at the desired sampling depths. A peristaltic pump is used to collect ground-water samples from the sampling ports. The difference in hydraulic head between any two sampling ports can be measured with a vacuum pump and a modified manometer. The usefulness and versatility of this multiport well design was demonstrated at an agricultural research site near Princeton, Minnesota where sampling ports were installed to a maximum depth of about 12 m below land surface. Tracer experiments were conducted using potassium bromide to document the degree to which short-circuiting occurred between sampling ports. Samples were successfully collected for analysis of major cations and anions, nutrients, selected herbicides, isotopes, dissolved gases, and chlorofluorcarbon concentrations.

Notes: At the Fernald Environmental Management Project (FEMP) site in southwestern Ohio, sand and gravel lenses within till provide potential pathways for the flow of contamination into the underlying aquifer. These high-permeability lenses account for 22% of the volume of the till, have a complex arrangement, and are smaller in scale than the site. Even the relatively dense subsurface sampling program at the FEMP site is not adequate to determine facies interconnections with certainty. To delineate probable facies boundaries, a binary indicator random variable was used to represent the presence of high or low-permeability sediment. The 800 available lithologic logs that penetrate the till were coded with the binary system at 2 ft (0.6 m) intervals yielding 15,829 observations. These data were used to compute the declustered mean of indicator values in horizontal intervals, giving an estimate of the proportion of high-permeability sediment in each vertical zone. The areal correlation in specific zones was examined through indicator variograms, which had pronounced anisotropy. Three-dimensional indicator point kriging was used to produce maps of the probability of existence of high-permeability sediment. These maps were used in a preliminary analysis of sand body interconnectedness. Results indicate that portions of sand bodies are interconnected through the entire interval studied and that the areal extent of vertical interconnection is up to 1000 ft.

Notes: A new method is presented to determine the transmissivity and the storage coefficient from recovery data measured after a pumping period of an aquifer test. Previously available methods can determine the storage coefficient during the pumping period only or under restrictive conditions. This method requires observations from a minimum of two points (e.g., the pumping well and an observation well). For each time during recovery, the drawdowns observed in the two wells are first plotted with regard to the distance from the pumping well centrum, giving an intercept A and a slope B for each pair of data. The plot of A values with regard to time allows to calculate the transmissivity value, while the plot of B values versus time gives the storage coefficient value. The method is applied to two sets of field data, and the results obtained are close to those obtained using the classical methods (Theis or Jacob) applied to the drawdown data obtained during the pumping period. This method well determines transmissivity and storativity from recovery data obtained at short times after the completion of pumping, i.e., for times shorter than those which can be used by the Cooper-Jacob approximation.

Notes: Approaches to investigate possible recharge during a pumping test period are demonstrated by analyzing the pumping test data from the Nottingham aquifer, UK. The pumping lasted more than 200 days and the data for different observed periods are used to obtain aquifer parameters. If recharge is ignored, estimated transmissivities and storativities change progressively with the observation time. This indicates that a gradually added new source may be involved. Then the observed data in both pumping and recovery periods at one of the pumping sites are matched by the data calculated from the Theis equation. The match is very good except near the end of the recovery period. It shows that the real drawdown recovered more quickly than predicted by the model, indicating that the aquifer obtained extra recharge from other sources. The match between the observation and the model is improved by including a fixed-head boundary or leakage in the model. The recharge to the aquifer is estimated to be 19% and 34% of the pumpage at the end of pumping, depending on the method used. The real source of the additional recharge is not clear; it could be from the surface water in the unconfined area, the storage of the aquitard, the compaction of the aquitard, or a combination of the three. This requires further hydrogeological investigation.

Notes: The Clarendon Basin of south-central Jamaica has been recognized for its productive sugar cane industry since the late 1800s. Much of its success is attributed to rich alluvial soils, a year-round tropical climate and copious supplies of good quality irrigation water from a karstic limestone aquifer of Tertiary age. This aquifer extends throughout the northern part of the basin, but ends abruptly at the South Coast Fault, an east west feature that forms the northern boundary of a deep graben filled with alluvial sediments. These alluvial sediments are the only source of water for the area south of the fault (the Vere Plain). However, the sediments also lap onto the limestone to the north of the fault (the Clarendon Plain) and provide a supplementary ground-water source. By the early 1970s nearly 200 wells supplied irrigation water for over 20,000 hectares of land. As development increased, the salinity of the ground water increased. Consequently, many wells were closed down and several sugar plantations were abandoned. In the study presented here, major ion (Ca, Mg, Na, K, HCO3, Cl, SO4, and NO3), minor ion (F, Br, and I), and environmental isotope (δ18O,δD) hydrochemistry is used to resolve the hydrodynamics of ground-water flow in the basin and identify the source and mode of emplacement of the saline water.Oxygen and hydrogen isotope data confirm that while the major well production areas are located in lowland coastal areas, recharge originates almost exclusively as rainfall in the cooler elevated parts of the basin above 750 m (asl). Subsurface conduit flow brings this water to the limestone well fields, and any excess water is able to cross the South Coast Fault to feed the alluvial aquifer of the Vere Plain. The thin alluvial aquifer of the Clarendon Plain also receives limestone water but this water does not enter entirely by subsurface means. Instead data suggest that while some of the water can be attributed to natural upward vertical leakage in the northwest of the Clarendon Plain, the remainder can be attributed to the seepage of irrigation water drawn, at least in part, from wells developed in the underlying limestone.Saline ground waters affect all the aquifers of the basin and several potential sources have been proposed. Major and minor ion data point to a sea-water source, and a sea-water wedge extending beneath the thick alluvial aquifer of the Vere Plain is an obvious candidate for the source of salinity observed in wells from this aquifer. Closer examination of the chemical data reveals, however, that wells in the limestone and alluvial aquifers to the north of the South Coast Fault do not derive their salinity from this source location, and instead draw sea water from the east and west along the relatively permeable South Coast Fault zone. This water can move to limestone wells directly; wells in the alluvium of the Clarendon Plain, however, receive most of the saline water indirectly via leakage of irrigation water pumped initially from the limestone. Sea water drawn along the fault may also be the primary source of salinity in the aquifer of the Vere Plain but this cannot be confirmed on the basis of hydrochemical evidence alone.

Notes: The presence of dense nonaqueous phase liquids is one of the principal problems associated with current ground-water remediation efforts. Standard pump-and-treat methods are ineffective largely because of the low aqueous solubilities of DNAPL components. Surfactants can increase DNAPL solubility and hence have the potential for increasing the rate of DNAPL dissolution in pump-and-treat systems. To test the effectiveness of surfactants under field conditions, a controlled field test at Canadian Forces Base Borden was undertaken. Results indicate surfactant-enhanced aquifer remediation can rapidly remove the majority of DNAPL using simple modifications of a pump-and-treat system. As in all pump-and-treat systems, the efficiency is a function of the hydraulic conductivity. The persistence of high DNAPL concentrations at specific elevations within the aquifer throughout the test indicates that little vertical movement of DNAPL occurred as a result of the introduction of the surfactant. Since the test was stopped when small amounts of DNAPL still remained, the limit of removal was not investigated.

Notes: A numerical code which utilizes the boundary element method (BEM) for solving steady-state ground-water flow problems is illustrated. The paper concentrates on accuracy in studying the situations which are generally considered to involve some mathematical difficulty, such as zoned domains and flux discontinuities. A numerical BEM code is proposed, the main feature of which involves accurately calculating flux discontinuities using a structure particularly flexible in multizoned domains. Two examples are reported, the results of which are comparable with those available in the literature.

Notes: Ground-water chemistry data from wells are cokriged with ground conductivity measurements to quantitatively describe ground-water chemical quality at a site. The cokriged estimates are shown to be superior to both simple rescaling of ground conductivity by a linear regression model and to interpolation of ground-water chemistry data from wells using ordinary kriging. By extending the use of geophysical measurements in this way, significant cost savings in site assessment can be realized and the geophysics will have more data “worth.”

Notes: For compound mixtures or compounds with two or more differently sorbing isomers which are not analytically distinguished, combined sorption parameters determined in the laboratory are dependent upon the ratio of different compounds or isomers and upon experimental methods and conditions. The purpose of this paper is to mathematically examine the effects of these factors on sorption parameters calculated from batch (shake-flask) and continuous flow column sorption studies of compound or isomer mixtures. The analysis in this paper helps explain the apparent anomalies between batch and column sorption results in previously published studies of Rhodamine WT (RWT). In batch reactors, the solid: liquid ratio, Rs, has a major effect on batch sorption results. As Rs decreases, partitioning coefficients determined from batch results approach those determined from column results, which is contrary to the trend that may be anticipated for single component analytes. A single column sorption coefficient or retardation factor for multiple constituents does not accurately describe the transport of the individual compounds. The implications of the effects of experimental methods suggest that sorption parameters determined from batch studies for compound or isomer mixtures (e.g., BTEX, combined xylenes, and others) should be interpreted with care. Significant errors in prediction and description of contaminant transport can result if the presence of multiple compounds or isomers is not recognized or if batch or column data for compound or isomer mixtures are misinterpreted.

Notes: An analysis was conducted of multidimensional subsurface moisture flow in a hypothetical low-level radioactive waste disposal facility. The key design feature examined in the analysis was a sloping sand/gravel capillary barrier designed to route natural infiltration around a concrete vault. Three barrier slopes (1:25, 1:10, and 1:5) and three sand/gravel property combinations were considered. The slopes and material property combinations were selected to represent a range in barrier effectiveness. The porous media flow code used for this analysis was VAM3DCG, a three-dimensional, finite-element code which was able to use nonorthogonal grid discretizations and employed robust, efficient numerical techniques. Three-dimensional modeling demonstrated that flow in the hypothetical design exhibited cross-slope flow because of the pressure gradient produced in the third, cross-slope dimension. Barrier effectiveness was shown to be highly sensitive to the sand/ gravel material properties. Barrier slope was less important, especially for the effective material combinations. The presence of three-dimensional flow could be important in a performance assessment if the quantity of water predicted to breach the capillary barrier by a two-dimensional model were different from that predicted by a three-dimensional model. Comparative modeling demonstrated that a two-dimensional analysis resulted in underestimation of barrier effectiveness. For the considered design, two-dimensional modeling is a conservative, yet reasonable, approach in a performance assessment application.

Notes: Laguna Asososca, a large ground-water-fed volcanic crater, is an important source of municipal water supply for the city of Managua. In 1990, after 65 years of pumping at increasing rates from the crater, the gradient between the Laguna and the highly contaminated Lake Managua had potentially reversed, leading to a scenario where the Laguna was possibly drawing in contaminated ground water from Lake Managua and/or a highly contaminated aquifer below an industrial area located between the Laguna and Lake Managua. A drilling and sampling program undertaken between 1990 and 1992 found: (1) four synthetic organic chemicals in the Laguna (methylene chloride, chloroform, 1,3-dichlorobenzene and 1,4-dichlorobenzene), (2) numerous other synthetic organic chemicals near Laguna Asososca in the ground water below the industrial area, and (3) no evidence of Laguna Asososca drawing water from Lake Managua. It appears that the Laguna Asososca capture zone extended into the industrial area but not as far as Lake Managua. Ground-water flow modeling of the regional ground-water flow system was consistent with the field interpretation. Estimates of the relative mobilities of the synthetic organic chemicals indicated that the chemicals found in the water of Laguna Asososca likely represented the mobile leading edge of a contaminant plume emanating from the industrial area. The simplest and most effective solution to mitigate contamination of Laguna Asososca is to maintain its water level above that of Lake Managua by reducing its pumpage to about 50% of the 1990 rate.

Notes: Cutoff walls are becoming increasingly attractive options for the control of solute migration from long-term sources of contamination. The main advantage of low permeability enclosures is that they restrict advective transport of solutes away from the source. However, with high concentration source zones surrounded by cutoff walls, there exists the potential for notable mass fluxes outward due to diffusive transport. This paper shows, through the use of the steady-state flux equations, that there is an optimal range of hydraulic conductivities for barrier materials which permit the outward diffusive flux to be counter balanced by an inward advective and dispersive flux. This concept of designing optimum contaminant containment using an inward advective flux to counter the outward diffusive flux is valid for sealable joint sheet pile walls, bentonite-slurry walls and clay liners, but not synthetic membrane materials with extremely low hydraulic conductivities. The effective diffusion coefficient for the common chlorinated organic solvents such as TCE in water-saturated clayey materials is approximately 1 × 10−6 cm2/sec, resulting in an optimum hydraulic conductivity ranging from 1 × 10−6 to 1 × 10−8 cm/sec. This range in hydraulic conductivity is within the range of common barrier materials but not the lowest achievable. The steady-state concentration profile in a slurry cutoff wall can result in a substantial amount of contaminant mass stored within the wall which will need to be considered over the long term or dealt with during site remediation. Large inward advective fluxes reduce the total chemical mass stored within the low permeability barrier material.

Notes: Flow-through microcosms were constructed to conduct ecological experiments on aquifer organisms. The two 5-channel microcosms were simple to construct, were fed by an artesian spring, and maintained close to in situ temperature and O2 concentrations. They were used to test relative microbial colonization of three substrate sizes: silt (0.063 mm), sand (0.9 mm), and gravel (3 mm). After 96 days of incubation, O2 microelectrode measurements revealed the lowest O2 tension in the silt, the highest in the gravel, and intermediate values in the sand. Microbial activity (3[H]-thymidine incorporation) was greatest in the gravel, followed by sand and then silt. Denitrification was greatest in the silt, followed by sand and then gravel. Microbial activity may be greatest with the largest particle size because of increased water exchange through pores, and denitrification may be greatest with the smallest particle sizes because of the occurrence of anaerobic microzones.

Notes: On March 8 and 9, 1992, a thermal-infrared-multispectral scanner (TIMS) was flown over two military ordnance disposal facilities at the Edgewood Area of Aberdeen Proving Ground, Maryland. The data, collected by the National Aeronautics and Space Administration, in cooperation with the U.S. Army and the U.S. Geological Survey, were used to locate ground-water discharge zones in surface water. The images from the flight show areas where ground-water discharge is concentrated, as well as areas of diffuse discharge. Concentrated discharge is predominant in isolated or nearly isolated ponds and creeks in the study area. Diffuse discharge is found near parts of the shoreline where the study area meets the surrounding estuaries of the Chesapeake Bay and the Gunpowder River. The average temperature for surface water, measured directly in the field, and the average temperature, calculated from atmospherically corrected TIMS images, was 10.6° C (Celsius) at the first of two sites.Potentiometric surface maps of both field sites show discharge toward the nontidal marshes, the estuaries which surround the field sites, and creeks which drain into the estuaries. The average measured temperature of ground water at both sites was 10.7° C. The calculated temperature from the TIMS imagery at both sites where ground-water discharge is concentrated within a surface-water body is 10.4° C. In the estuaries which surround the field sites, field measurements of temperature were made resulting in an average temperature of 9.0° C. The average calculated TIMS temperature from the estuaries was 9.3° C. Along the shoreline at the first site and within 40 to 80 meters of the western and southern shores of the second site, water was 1° to 2° C warmer than water more than 80 meters away. This pattern of warmer water grading to cooler water in an offshore direction could result from diffuse ground-water discharge. Tonal differences in the TIMS imagery could indicate changes in surface-water temperatures. These tonal differences can be interpreted to delineate the location and extent of ground-water discharge to bodies of surface water.

Notes: The slug test is one of the most commonly used field methods for obtaining in situ estimates of hydraulic conductivity. Despite its prevalence, this method has received criticism from many quarters in the ground-water community. This criticism emphasizes the poor quality of the estimated parameters, a condition that is primarily a product of the somewhat casual approach that is often employed in slug tests. Recently, the Kansas Geological Survey (KGS) has pursued research directed at improving methods for the performance and analysis of slug tests. Based on extensive theoretical and field research, a series of guidelines have been proposed that should enable the quality of parameter estimates to be improved. The most significant of these guidelines are: (1) three or more slug tests should be performed at each well during a given test period; (2) two or more different initial displacements (H0) should be used at each well during a test period; (3) the method used to initiate a test should enable the slug to be introduced in a near-instantaneous manner and should allow a good estimate of Ho to be obtained; (4) data-acquisition equipment that enables a large quantity of high quality data to be collected should be employed; (5) if an estimate of the storage parameter is needed, an observation well other than the test well should be employed; (6) the method chosen for analysis of the slug-test data should be appropriate for site conditions; (7) use of pre-and post-analysis plots should be an integral component of the analysis procedure, and (8) appropriate well construction parameters should be employed. Data from slug tests performed at a number of KGS field sites demonstrate the importance of these guidelines.

Notes: It is a general belief that useful estimates of total dissolved solids concentrations of ground water cannot be made from borehole geophysical logs. A case study of estimating total dissolved solids concentration of ground water in the local area using the ratio method yielded estimates with an average error of less than 25 percent. The results do not support the hypothesis that useful estimates of total dissolved solids concentration cannot be made from borehole geophysical logs.The case study included a comparison of estimates of total dissolved solids concentration utilizing a resistivity of the mud input versus using resistivity of the mud filtrate input. Estimates made using resistivity of mud had a correlation coefficient of 0.97 whereas estimates using resistivity of mud filtrate had a correlation coefficient of only 0.27. The results from the case study suggest that at least in some cases the resistivity of the mud (Rm) may produce a better estimate of the resistivity of water (Rw) in the fully flushed zone than an estimate using the resistivity of the mud filtrate Rmf.The ratio method can be easily used to estimate ground-water resistivity and total dissolved solids concentration of the formation water based only on data from resistivity logs. The advantage of the method is that data on porosity, cementation exponent, temperature, and volume of clay are not required. The method, which has been used by the oil industry to crudely estimate water resistivity, is based in part on the ratio of the resistivity of a fully water-saturated formation to the resistivity of the fully flushed zone adjacent to the annulus in a mud-filled borehole. The method, which is very robust, requires only an estimate of the resistivity of a fully water-saturated formation from a deep looking induction or resistivity log, an estimate of the resistivity of the fully flushed zone from a microresistivity or short normal log, and a measurement of resistivity of the mud or mud filtrate and its temperature.

Notes: Surface application offers an inexpensive, noninvasive alternative to injection wells and infiltration galleries for in situ ground-water bioreniediation applications. The technology employs artificial recharge to create favorable hydraulic conditions for mixing and vertical transport of supplemental electron acceptor and nutrients. A test plot infdtration test and a conservative tracer test at Eglin Air Force Base, FL confirmed the potential for transporting solutes to the subsurface via recharging water. These experiments demonstrated both the mounding hydraulics and vertical solute transport that occurs in response to surface application. Modeling provided quantitative estimates of site-specific hydrogeologic and transport parameters. Experimental results also indicated that dilution may be a dominant attenuation mechanism associated with high surface application rates. The tests also served as the basis for the design of a pilot scale surface application system for delivery of nitrate to bioremediate a JP-4 contaminated aquifer at the Eglin site. Models calibrated to data from the infiltration experiment were scaled up for design of the pilot scale surface application system. Preliminary tracer results from the pilot scale experiment confirm that surface application can adequately deliver chemicals to the subsurface.

Notes: The results of a field experiment comparing water-quality constituents, specific conductance, geophysical measurements, and well-bore hydraulics in two long-screen wells and adjacent vertical clusters of short-screen wells show bias in ground-water data caused by well-bore flow in long-screen wells. The well screen acts as a conduit for vertical flow because it connects zones of different head and transmissivity, even in a relatively homogeneous, unconfined, sand and gravel aquifer where such zones are almost indistinguishable. Flow in the well bore redistributes water and solutes in the aquifer adjacent to the well, increasing the risk of bias in water-quality samples, failure of plume detection, and cross-contamination of the aquifer. At one site, downward flow from a contaminated zone redistributes solutes over the entire length of the long-screen well. At another site, upward flow from an uncontaminated zone masks the presence of a road salt plume.Borehole induction logs, conducted in a fully penetrating short-screen well, can provide a profile of solutes in the aquifer that is not attainable in long-screen wells. In this study, the induction-log profiles show close correlation with data from analyses of water-quality samples from the short-screen wells; however, both of these data sets differ markedly from the biased water-quality samples from the long-screen wells. Therefore, use of induction logs in fully cased wells for plume detection and accurate placement of short-screen wells is a viable alternative to use of long screen wells for water-quality sampling.

Notes: Ground-water flow models developed for the flow systems around Bass Lake and Nepco Lake, Wisconsin, show that models can be useful tools for estimating lake seepage rates. A two-dimensional profile model for Bass Lake illustrates that the ratio of horizontal to vertical hydraulic conductivity of the aquifer around the lake is related to both the magnitude of vertical hydraulic gradients near the lake and the distribution of seepage from the lake as a function of distance from shore. The model also shows that it is important to know the vertical hydraulic conductivity of littoral lake-bed sediments to estimate lake seepage rates.A three-dimensional model constructed for an unusual ground-water flow system around Nepco Lake provides a more realistic simulation of the flow system than does a comparable two-dimensional model. Both models were useful for identifying additional data that could be used to quantify the ground-water portion of the lake's water budget more accurately. It is suggested that a combination of two-and/or three-dimensional models could be used to estimate seepage rates at many lakes for which sufficient data exist.

Notes: A digital model of a buried channel aquifer contaminated by hydrocarbons is used to evaluate development alternatives. The response to ground-water pumping is critical because the hydrocarbons cause taste and odor problems. The source of contamination is an abandoned pit used to dispose of coal tar residues from an old coal-gas plant. The hydrocarbon residues overflowed the pit, migrated a short distance and seeped into flood plain soils. The downward movement of the hydrocarbons stopped at the water table but some dissolved into the ground water. Three general approaches taken to evaluate management alternatives include: (1) regulation of pumping of the city wells and of drawdown, and recovery periods are considered and the model stressed with various pumping rates and times; (2) construction of a pumping trough barrier is considered and a hypothetical control well is simulated; (3) new well field developments in various locations are considered. Results suggest that there is no way to prevent movement of contaminants to the well field. The only feasible solution is the removal of coal tar residues from the source area and construction of a pumping trough barrier.

Notes: Increased attention is being directed toward the investigation of tight zones in relation to the storage and disposal of hazardous wastes. Shut-in tests, slug tests, and pressure-slug tests are being used at the proposed Waste Isolation Pilot Plant site, located in southeastern New Mexico, to evaluate the fluid-transmitting properties of several zones above the proposed repository zone. Apparatus used to conduct these tests includes a pressure-transducer system connected to a recording device at the land surface. All three testing methods were used in various combinations to obtain values for the hydraulic properties of the test zones. Multiple testing on the same zone produced similar results. Transmissivities determined by these tests range from 0.00001 to 10 feet squared per day (.000001 to 1 meter squared per day).

Notes: Organic solvents, including 1,1,1-trichloroethane at concentrations up to 40,000 ppb, were detected in the Old Bridge aquifer under an industrial plant in South Brunswick Township, New Jersey. A hydrogeologic investigation defined the ground-water flow system and a plume of contamination which extended, at a concentration of at least 100 ppb, for a distance of about 1000 feet down-gradient of the plant. A contamination abatement system was designed and installed to prevent this plume from reaching a municipal well located about 2500 feet from the site. The system includes seven extraction wells and a water treatment facility. The locations of the extraction wells and their combined pumping rate were determined in part by a computer simulation of the aquifer, which was subsequently checked by a 20-day pumping test of the system. The on-site treatment facility uses two cooling towers in series to air-strip the volatile organics, and two infiltration ponds to return the treated water to the aquifer. The abatement system has been operating for about 10 months. Ground-water monitoring results show that the plume is now significantly smaller and less concentrated than before the abatement system was installed. It is projected that in several years the aquifer will be largely decontaminated.

Notes: Pumpage from shallow aquifers, primarily dolomite bedrock, in northeastern Illinois has exceeded estimates of ground-water recharge in extensive areas creating concern that ground-water recharge estimates are too low. Pumpage increased 92 percent during the period 1966-1978 and was 61.7 million gallons per day (2.33 × 108 liters/day) during 1978. During the period 1966-1979 water level declines exceeded 30 feet (9.14 meters) in some areas. Based on a ground-water budget study, it was determined that recharge estimates were in the right order of magnitude and pumpage in excess of recharge was balanced by water taken out of storage from the shallow aquifers. A specific yield of 0.017 was determined for the dolomite bedrock aquifer based on the ground-water budget study.

Notes: Thirty-three wells and two springs yielding high chloride water from granitic rocks define a northwesttrending lineament, which extends for 60 miles (100 km) along the western Sierra Nevada foothills of Fresno and Madera Counties. Geochemical evidence indicates that many of the constituents in this water are marine connate in origin. However, the connate water has been strongly diluted with meteoric water. The connate water is believed to have been derived from Paleozoic and early Mesozoic marine clastic rocks (now metamorphosed) in the Sierra Nevada. The lineament marks the location where marine connate water has migrated upward from these rocks along an eastward-dipping fault zone. A capping of granitic rocks has enhanced the persistence of this connate water for millions of years. The lineament may be structurally related to the Oakhurst-Fine Gold fault zone, which it parallels for approximately 15 miles (25 km). There is a remarkable correlation in the Oakhurst area between wells yielding high-chloride water and fracture trends determined from aerial photographs. High chloride ground water is present only in topographically low areas, where little flushing by meteoric water has been possible.

Notes: This is the second of two articles on calculator programs for inverse solutions of the Theis equation.Newton's method is used to develop an iteration formula for the determination of transmissivity and storage coefficient values from a combined Theissian expression that incorporates the information contained in two independent aquifer test data point sets.The algorithm is used in a polynomial-based program for Hewlett Packard HP 67/97 calculators that is designed to process data corresponding to the full practical range of Theis well function arguments and to accept measurements from one or two observation wells, or from entirely different tests of a given aquifer. Program modifications providing for series-based well function calculations are appended, and example calculations are shown.

Notes: The major water-bearing units in the Houston district are the Chicot and Evangeline aquifer systems. Both systems consist of discontinuous layers of unconsolidated sand (aquifers) separated by clay layers.Extensive pumping has caused large declines of potentiometric surfaces in and around Houston. The declines have caused both the compaction of clay layers, which has resulted in land-surface subsidence, and the movement of salt water towards Houston.During the early 1960's, an electric analog model of the district was made. The model simulated water-level declines; but more importantly, the model indicated that the available data and conceptual model of the hydrologic system, consisting of two aquifers, were not totally adequate to allow simulation of the ground-water systems.During the early 1970's, a second electric analog was built. The second model used new data and a conceptual model consisting of two aquifer systems simulated water-level declines quite accurately, but the model was unable to accurately simulate the spatial distribution of water yielded from clay storage.A digital model was then developed during 1979 to simulate the hydrology of the district. The digital model used five layers and accurately simulated the hydraulic heads in both aquifer systems and land-surface subsidence.

Notes: Marquardt algorithm has been used for estimating aquifer parameters from pump test data in nonleaky and leaky aquifers. It emerges from the study that in spite of poor initial estimates, the convergence is quick; and the residual square error, for the difference between the observed drawdowns and those calculated from parameters estimated using Marquardt algorithm and the known methods, is minimum in the case of Marquardt estimates.

Notes: The geochemistry of a very permeable ground-water system containing calcium sulfate was studied to determine the present rate of dissolution. An estimate was made of the chemical composition of water recharging the system and the difference between that estimate and the composition of the ground water in the system was used to determine the minimum amount of calcium sulfate being dissolved under existing hydrologic conditions. This result was used, with published data on rates of calcium-sulfate dissolution, to determine the effective surface area involved in solution processes. Results indicate that flow in this system is through large solution openings, which are growing larger at a rate of a few tens of millimeters per year.

Notes: Due to inexperience on the part of those assigned to purchase computer facilities for water resource tasks, a poor or unacceptable choice of equipment is often made. The political realities of introducing new computing equipment into a firm which has several departments which will vie for the use of that equipment must be faced.The size, complexity, and capabilities of the machine to be purchased as well as the software and personnel involved must be considered carefully in relation to the specific tasks at hand. The bidding process, demonstrations, and reference materials offer some assistance in deciding among the often confusing array of systems available on the market.

Notes: Enjebi Island on Enewetak Atoll has been the site of extensive hydrological, geological and geophysical studies. Tidal lag, tidal efficiency and water levels have been measured in 24 wells ranging in depth from one m to 90 m (3–290 ft). Hydraulic conductivity has been measured both on laboratory samples and by aquifer testing in the field. Theoretical ground-water tidal responses have been calculated using a model based on horizontal propagation of tidal signals. Comparison of field observations and model results indicates that the observed results are not consistent with horizontal tidal propagation and that the hydraulics of the system are probably controlled by vertical coupling between the unconsolidated surface aquifer and an underlying aquifer of more permeable limestone. Results from other islands of Enewetak, Bikini and Kwajelein Atolls are comparable, and suggest that vertical transport between layered aquifers is an important feature of atoll ground-water hydrology at least throughout the northern Marshall Islands.

Notes: In an investigation of the hydrogeology of bedrock valley fills in northeastern Wisconsin, it was determined that the yield and spatial distribution of glacial aquifers are controlled by bedrock topography and glacial geology. Lithologic control for identification and classification of aquifer units was obtained from several hundred drillers' logs calibrated by auger borings and interviews. Transmissivities of drift aquifers calculated from specific capacity tests using Jacob's equation agree well with estimates made from lithologic logs. Seismic refraction and gravity surveys were coupled with well log data to derive a bedrock elevation map. Vertical variability maps calculated from the lithologic logs show that bedrock topography strongly influences the distribution and character of glacial units, and clearly delineate the two glacial aquifer types present, valley and morainal units. Morainal units parallel the Late Wisconsin end moraine trends, while valley units are perpendicular to the moraines. The morainal units are small ice-contact features such as kames, fans, and deltas. The valley units are stream deposits and may have been deposited subglacially. Valley aquifers are the most productive units. Using lithologic and geophysical data, and statistical analysis, a predictive depositional model can be proposed. This conceptual model allows knowledge of bedrock topography to be coupled with glacial geology to predict the spatial distribution of glacial aquifers.

Notes: Few studies have been performed on the occurrence of enterovirus contamination of ground water. In this study, 99 ground-water samples were examined for the presence of enteroviruses, total bacteria, fecal coliforms, and fecal streptococci by standard methods. Enteroviruses were isolated from 20% of the samples. Viruses were isolated from 12 samples which contained no detectable fecal organisms per 100 ml. No statistical correlation between presence of virus and bacteriological indicators could be determined. The widespread failure of current bacteriological standards to indicate the presence of potentially pathogenic enteroviruses in ground water is an area of concern that requires more study.

Notes: Flow to wells in leaky artesian aquifers is intimately related to changes in aquitard storage, well storage capacity, and degree of well penetration. The manner and extent to which these and other factors affect water levels may be evaluated with aquifer test data. Families of type curves describe time-drawdown in the aquifer and aquitard under complex aquifer and well penetration conditions. Analysis of leaky artesian aquifer test data is possible with the array of equations derived largely in the 1950's through 1970's. Erroneous data analysis will result unless complicating factors are fully recognized and taken into account. A review of leaky artesian aquifer test evaluation methods is presented in this paper together with the field application of selected methods to foster greater use of current theories.

Notes: Illinois aquifers furnish approximately 233 mgd (10.2 m3/s) of water to 677 public-water supplies outside the six-county area of northeastern Illinois. Ground water is usually obtained from sand-and-gravel deposits in the glacial drift or from limestone or sandstone formations in the underlying bedrock. The most favorable ground-water conditions are found in the northern third and the southern tip of the State, while, elsewhere, major aquifers are sand-and-gravel deposits of the Mississippi, Illinois, buried Mahomet, Wabash, Ohio, Kaskaskia, and Embarrass valleys.A brief review was made of data and information in the State Water Survey files for each public ground-water supply, and an assessment was given as adequate, marginal, or deficient, in terms of present demands. Twenty-four supplies were studied in greater detail, including calculations of aquifer sustained yields. The study indicated that 39 supplies were marginal and four were judged deficient in meeting current demands. The majority of the marginal and deficient supplies are located in the central third of the State; but so are most of the supplies (outside of north-eastern Illinois).The study represents the first of a three-part plan to: (1) define problem areas and determine priorities for studies in greater detail, (2) conduct regional studies, including test drilling, in problem areas to determine how great the water resource is, and (3) determine the water resource alternatives available to public ground-water supplies that are found to be inadequate.

Notes: An industrial waste liquid containing organonitrile compounds and nitrate ion has been injected into the lower limestone of the Floridan aquifer near Pensacola, Florida since June 1975. Chemical analyses of water from monitor wells and backflow from the injection well indicate that organic carbon compounds are converted to CO2 and nitrate is converted to N2. These transformations are caused by bacteria immediately after injection, and are virtually completed within 100 m of the injection well. The zone near the injection well behaves like an anaerobic filter with nitrate respiring bacteria dominating the microbial flora in this zone.Sodium thiocyanate contained in the waste is unaltered during passage through the injection zone and is used to detect the degree of mixing of injected waste liquid with native water at a monitor well 312 m (712 ft) from the injection well. The dispersivity of the injection zone was calculated to be 10 m (33 ft). Analyses of samples from the monitor well indicate 80 percent reduction in chemical oxygen demand and virtually complete loss of organonitriles and nitrate from the waste liquid during passage from the injection well to the monitor well. Bacterial densities were much lower at the monitor well than in backflow from the injection well.

Notes: Abstract. This investigation was to determine whether data on irrigation-well registration forms as reported by well drillers can be used in hydrologic studies. Transmissivity maps were prepared for Hamilton County, Nebraska using only specific capacity values computed from yield and drawdown data, as reported on irrigation well-registration forms. On one map each control point was the mean of the transmissivity values calculated for all wells in a section. On a second map each control point was the mean of the means for four contiguous sections sharing a common corner. The second map was similar to that of a previously prepared map based on control point values computed from specific capacities of selected wells, test hole logs, and geologic interpretations. These results suggest that reported registration data for a given area have a normal population distribution. In situations where individual data are unverified the data base can be treated as samples of a population where the mean of the means of several samples for adjacent areas is representative of actual field conditions.

Notes: A new method of testing anisotropic, inhomogeneous multiple aquifer systems developed by the author makes use of small diameter bore construction techniques and enables simultaneous testing of superposed aquifers and aquitards (aquicludes).Because of the low cost of the method the hydraulic properties of the multiple aquifer system can be determined at many sites distributed throughout the area of interest, enabling simulation of the local and regional ground-water flow conditions and other hydrological characteristics of the system.Since its development in 1964 the technique improved and was employed in ground-water investigations. Data and results from the inhomogeneous, anisotropic multiple aquifer system west of Melbourne are given.

Notes: Chemical and isotopic analyses were made of water from wells in and downgradient from a landfill to determine chemical and isotopic effects of generation and migration of leachate on ground water. The distribution and wide concentration range of oxygen and methane permit the delineation of an anaerobic zone, a regional oxygenated zone and an intermediate zone. The ratio of reduced nitrogen to nitrate indicates location of reducing fronts as the leachate migrates. The pH of the native ground water is low (≥5.0) primarily because of the low pH of rainfall and the lack of calcareous or other soluble minerals in the aquifer material. The pH is higher (∼6.6) in the leachate because of generation of carbon dioxide, ammonia, and methane. The native ground water has a low TDS (80 mg/l) while the leachate has an average TDS of 2800 mg/l and is primarily a NaHCO3 type water. Sulfate concentrations are extremely low and H2S was not detected.We suggest that a major source of cations may be their exchange from the clays by the ammonium generated in the leachate. High concentrations of Fe and Mn are attributed to a source in the refuse but more important to reduction of oxide cements and coatings resulting from degradation of organic matter. The main source of bicarbonate is from organic degradation with minimal CO2 from the soil zone. At one landfill site 52% of the total alkalinity is attributed to organic compounds, mainly organic acid anions. The δ13C of bicarbonate in the leachate is exceedingly heavy (+18.400/00) which results from fractionation during the formation of methane. The 10 per mil deuterium enrichment of water may be due to decomposition of deuterium-enriched compounds and bacterial processes that preferentially consume the lighter hydrogen isotope.

Notes: Rapid fissure flow has been recognised as an important factor in understanding the hydraulic behaviour of the Lincolnshire Limestone aquifer of eastern England. A study of the hydrogeology of a Lincolnshire Limestone spring-fed catchment enables three zones of discharge to be defined, based on their relative elevation along the valley floor. Comparison of the discharge characteristics of each zone reveals the existence of rapid ground-water flow associated with a discrete fissure system. Comparison of spring discharges and ground-water storage during a period of “high,”“low” and “typical” recharge enables a conceptual flow model of the aquifer to be constructed. A two-layered model is proposed, in which the secondary zone (upper unit) is characterised by higher transmissivity and lower storativity than the primary zone (lower unit). In addition, there is evidence of a rapid increase in transmissivity with water-table elevation in the secondary zone. The areal distribution of the secondary zone is associated with a net work dry valleys. The spatial distribution of the two zones is explained by geological structure, lithological variations and the post-glacial history of the area. A two-layered model is developed with these concepts in mind in order to simulate the spring discharges. Once proven, the model can be integreated with the regional hydrogeology and incorporated into existing digital models of the aquifer.

Notes: Abstract. An evaluation was made of the usefulness of the gamma-ray logger in delineating glacial-drift and bedrock stratigraphy in southwestern Ohio. The logger was useful in delineating gross stratigraphic units in a glacial outwash aquifer. The gamma log also provided a clearer indication of the clay content of sand and gravel units than did the driller's log.On the uplands, away from the valleys filled with glacial outwash, the logger could not be used to locate the thin, poorly-sorted, interstadial sand and gravel deposits between thicker till sheets. It could, however, be used to distinguish formational contacts in the upper Cincinnatian Series.

Notes: Injection of waste liquids into Florida's subsurface is physically feasible in many places but should be accompanied by monitoring of the waste-receiving aquifer system in addition to the injection facility. Monitoring of the interaction of factors including hydrogeologic conditions, well construction, waste volumes and characteristics, and potable-water sources is desirable to assure that fresh-water resources are not being adversely affected. An effective aquifer-system monitoring program includes on-site wells located close to an injection well and open to the next-higher permeable stratum, satellite wells located hundreds to several thousands of feet from an injection well and open to the receiving aquifer, and regional wells located miles from individual injection wells and open to the receiving aquifer. An extensive aquifer-system monitoring program associated with two waste-injection facilities near Pensacola, Florida, has provided data which have aided hydrologists to understand the aquifer system's response to the injection and, accordingly, to evaluate the potential for affecting the area's fresh-water resources.

Notes: Overexploitation of ground water in Krishni-Hindon interstream region (Lat. 29°05′N-29°29′N and Long. 77°19′E-77°32′E) in Uttar Pradesh, India, prompted us to carry out aquifer modeling studies. The area lies in Gangetic alluvial plain. The interconnections in the phreatic aquifer and the lower semiconfined aquifer led to the assumption of a single-story aquifer for which an R-C analog model was constructed.The input-output quantities in the model have been simulated using current/voltage generators and current sinks which are appropriately programmed in time-domain with the help of wave-form synthesizers for a realistic representation of the field system.The model study shows that the aquifer can sustain the present output rate of 200 mcm/year without much damage to the ground-water regime. In another scheme, an annual increase of 5% in exploitation rate, shows deleterious effects on the aquifer. Decreased rainfall/ droughts would worsen the situation.The influence of hydraulic connectivity between the aquifer and the Krishni-Hindon river system is quite significant. If the present exploitation rate were to continue for 20 years, the annual inflow to the aquifer from rivers is estimated to increase by about 36.0 mem.More hydrogeological data is required for further validation and refinement of the model.

Notes: Generally, the 208 planning approach is deficient in a number of ways. Its origin lies in Public Law 92-500, which focuses on protection of surface water and special uses of water for fish, wildlife, and recreation. Little ground water is used for these purposes. Nonpoint sources have not been defined in terms that have hydrogeologic significance. Local and State regulatory agencies have often been unsuccessful in controlling ground-water pollution, yet the 208 approach tends to disregard the reasons for this situation. The reasons for ground-water pollution in an area must be understood before meaningful control measures can be enacted. These include both technical and institutional problems.Planners are placed in the forefront of many 208 programs at the local level and often their backgrounds are inadequate in ground water. There is a great lack of ground-water professionals in regulatory agencies involved, particularly in the Southwest. This deficiency is paramount at high levels and in many regional offices of EPA. There are no provisions in the approach to insure that qualified ground-water geologists or hydrologists will be involved. Academic training in ground water is presently oriented toward ground-water development and not pollution. Lastly, public participation is greatly limited by the general lack of knowledge regarding ground water and its pollution.Successful 208 programs in terms of ground water have been enacted when ground-water professionals have had major roles. Changes are necessary in the academic training of ground-water geologists and hydrologists. The public must be educated concerning the long-term consequences of ground-water pollution. Lastly, ground-water professionals must assume the leadership in ground-water protection.

Notes: It is herein submitted that the nearly universal phrase “shall not cause pollution of the ground waters and surface waters” written into the State regulations for waste disposal operations not only refutes a sound technical alternative, but is impractical, uneconomical and often unworkable.It is a fact that all ground waters are not created equal, as governed by certain irrefutable physical laws including the water budget equation and Darcy's Law which states that the quantity of ground water available is subject to wide variation from location to location. While an aquifer is a relative term, major, minor and nonaquifers can be identified within a given geographic area with respect to cost-effective ground-water resource development. Likewise, the natural quality of ground water is also a significant variable with certain parameters often exceeding drinking-water standards. The land application of wastes overlying the ground waters of an area should, therefore, also be subject to a certain degree of flexibility for prudent management of both the waste operation and the ground-water resources.Numerous investigations and empirical data can be cited to substantiate the fact that many wastes and their associated leachates can be safely assimilated into the environment with reliance on attenuation and controlled degradation of ground water by utilization of a mixing zone or zone of renovation with a specified distance from a disposal operation. As increased emphasis is placed on the land disposal/management of wastes/residuals and as the cost of these operations continue to mount, it is strongly recommended that controlled ground-water degradation be utilized in those areas where a “true” ground-water resource does not exist. Protection of such a “true” ground-water resource is obviously necessary as our demands for a potable water supply also continue to grow.

Notes: Ground-water computer models are, certainly, toys which provide intellectual stimulation. They can be useful tools for advancement of the ground-water profession, but I believe that they have been blown out of proportion and that this might cause irreparable damage to our profession.It is important to see where computer models fit into the ground-water problem-solving process. I believe that ground-water computer programs are simply a complicated “turn the crank” tool for making projections. They're one type of tool out of several which requires aquifer and confining bed characteristics to facilitate making projections. A second approach for making projections involves the direct extrapolation or manipulation of data which does not require transmissivity, storage coefficient, leakance, and other interpreted characteristics. Further, I believe that the collection and evaluation of data are of greater importance than the projection methods and/or tools in arriving at answers.Advantages of ground-water computer models include: speedy analyses once a program is working, ability to handle many parameters, and utilization of a large data base. The disadvantages include: use of computer models as end goals, tendency for misapplications, time-consuming setup, a waste of time and money in some cases, and diversion of human talent from useful ground-water work.

Notes: While it is true that waterborne diseases are still with us, and probably always will be, we cannot classify them as a current threat in the sense that they were 100 years ago. The discovery that chlorine would disinfect water supplies removed these diseases from a “current threat” category to the “historical lesson” category. We are not faced with unknowns which we are unable to attack. We have only to look at what others have done to protect themselves and follow the same or improved practices.If the record of waterborne outbreaks in public water supplies in this country from the end of World War II up to the present is examined, it will be found that all are caused by breakdowns in disinfection procedures or carelessness. The record is replete with statements such as “improper disinfection after repair,”“breakdown or lack of disinfecting equipment,”“back siphonage,” and other similar statements all pointing to failure to follow practices which the history of water treatment has shown to be necessary for protection against waterborne disease. Carelessness allows recurrence of disease outbreaks. If the lessons of history were followed, the conquest of waterborne disease transmission by public water systems could be complete.

Notes: The increasing use of ground water and its true role as a source of water supplies in the United States have sometimes been interpreted incorrectly. The total use of ground water has indeed increased tremendously during the last 20 years (by almost 80%), but so has the total use of water (over 70%). And ground water is still far from being a primary source of water supplies. In 1975, only 20% of the total amount of water withdrawn in the United States for various uses came from ground-water sources.Statistical analysis of ground-water data for the period 1950-1975 has shown that the ground-water usage is changing only very slowly. Relation of ground-water use to total water use expressed in percent was used as an indicator of changes of ground-water use patterns. This percentage has not changed significantly, and it has fluctuated around 19%. In 1975, only 6 States used more ground water than surface water for their water supplies, and in 23 States ground-water use was less than 10% of total use. Even more unfavorable is the magnitude of change in ratio of ground-water use relative to total water use. From 1955 to 1975 only 13 States show an increase in the ratio. In 28 States the ratio has decreased, and in 7 it has remained the same.

Notes: An objective view of the need for ground-water quality standards requires that an individual recognize the value that ground water contributes to the water supply needs of our nation. A vast number of people living in rural areas and a large number of communities are dependent upon ground water as their sole source of water for domestic, industrial, commercial, and agricultural needs.This large use and dependency upon ground water dictates that these resources are valuable and must be protected for both present day and future uses. There are many examples where present methods of disposal of wastes generated in America have not been satisfactory from an environmental standpoint, with an exception of projects where disposal sites have been properly designed, operated, and managed for protection of the ground water.One possible solution for ground-water protection is the establishment of ground-water quality standards. The purpose of such standards is to protect the public health and welfare and maintain the quality of ground waters in all usable aquifers for individual, public, industrial, and agricultural water supplies. A legal basis must exist and the prescribed steps must be followed as dictated by the rule making process. The primary aim of such standards is to prevent the degradation of ground waters such as they will not become a public health hazard or harm the users of the ground water.The backbone of such a standard rests on the completion of a hydrogeological study which is necessary to determine background water quality information, set up the monitoring program and outline sampling to determine when water quality changes are taking place and what is a significant change.

Notes: Half the population depends on ground water for domestic uses. Use is increasing 25 percent per decade. Ground water is generally used with little or no treatment.Some persons would transfer the discharge of our waste products from contaminated surface streams to the land and thus relatively clean ground waters.No standards exist that protect ground-water quality. Research necessary to give assurance that natural interaction of waste water and soils will remove, to acceptable levels, potentially harmful contaminants, organic and inorganic, that permeate today's waste streams and today's health concerns, has not been done.Success reports on land treatment of waste water have a not evaluated deterioration of ground water from organic contamination. Most waste waters contain synthetic organics in varying concentrations. EPA recommends their reduction in drinking water to the lowest possible level.Most instances of ground-water contamination have been discovered after drinking water is contaminated. Unless the public is willing to treat ground water as it does water from surface streams, greater control of land disposal practices must be exercised. Current practice does not indicate the necessary controls are contemplated or recognized. It follows that the widespread use of the land treatment alternative is, in reality, an accident waiting to happen.

Notes: The Nation's ground-water resources constitute a vast and often unprotected resource. The Environmental Protection Agency is about to launch a number of programs designed to protect what is, in many cases, a virtually non-renewable resource. Separate regulatory activities mandated under the Safe Drinking Water Act, the Resource Conservation and Recovery Act and the Clean Water Act must be carefully coordinated if they are to be effective.The current implementation efforts within the agency are being framed in view of our major principles which will be the focus of public comment in the months ahead. These principles are:First, the administration of the related programs will be a cooperative effort involving Federal, State and local governments, all of which must participate in formulating the program if it is to be effective.Second, the focus of the programs will be on the prevention of contamination rather than on its treatment at the point of withdrawal.Third, the applicable standards will be based primarily on technology rather than ambient ground-water quality considerations since the effects of discharges upon ambient quality are complex, difficult to predict, and of long duration.Fourth, there is a need to balance environmental protection, energy development and continued economic prosperity objectives so that the resulting programs fully protect public health while being realistically implementable.All of us—government, industry and citizens, through acts of commission or omission—have contributed to the potential problem. We must work together if we are to get on with the important task of protecting the quality of the Nation's ground-water resources.

Notes: An exact expression is derived for the optimal spacing between interfering wells in a rectangular well field in an ideal confined aquifer. A simple, practical method for determining the optimal spacing is presented. The optimal spacing is shown to be substantially different from the spacing determined by use of the Theis formulation. The economic savings resulting from use of the revised approach are evaluated and found to be considerable, especially when the number of wells is large and the transmissivity of the aquifer low.

Notes: Hydraulic conductivity studies of a consolidated pozzolanic material indicate that heat-shrinkable tubing can be utilized to encase cylinders for use in a permeameter. The materials required for encasement of a sample include: heat-shrinkable tubing, hose clamps, polyvinyl chloride discs, glass tubing, and an electric oven. The procedure requires that the assembled PVC discs, filters, shrinkable tubing, and sample be placed on a support stand in an electric oven for three to four minutes at a temperature between 450–500° F. Upon removal from the oven, hose clamps are placed around each PVC disc. The method has several advantages. It saves time and expenses over conventional methods such as pneumatic pressurized core holders or triaxial testing units and preserves the original interstitial bore spaces of the sample.

Notes: Six types of vegetation were established successfully on lysimeters containing sanitary landfill materials. The vegetation grew well with the roots penetrating several refuse layers within one year. Leachate analysis indicated that vegetation and evapotranspiration (ET) reduced leachate volume and increased the rate of refuse decomposition. This was accompanied by production of a more potent leachate and a substantial increase in cumulative chemical oxygen demand. Therefore, this study suggests more potential ground-water pollution in a shorter period of time when vegetation is planted on a landfill. The net effect of ET on the stabilization of any particular landfill will be the result of a complex interaction involving climate, vegetation, soil type, cover material, landfill geometry, and other variables. This makes extrapolation of our results to a particular field situation rather difficult.

Notes: The anisotropic, areal hydraulic conductivity of the Felix No. 2 coal (Eocene, Wasatch Formation) has been defined in a four-well pump test at a site in the Powder River Basin of northeastern Wyoming. The direction of maximum hydraulic conductivity of the subbituminous coal bed bears N59°E and is associated with a horizontal hydraulic conductivity of 0.27 m/day. The direction of minimum hydraulic conductivity bears N31°W and is associated with a horizontal hydraulic conductivity of 0.15 m/day. The direction of maximum hydraulic conductivity approximately corresponds to the trend of the prominent face cleat in the coal, while the direction of minimum hydraulic conductivity corresponds to the trend of the butt cleat. The cleat orientation appears related to the alignment of major structural features of the region. Prediction of the direction of both maximum and minimum horizontal hydraulic conductivity in near-horizontal coal beds appears possible. However, either the cleat orientation of the bed or the alignment of the controlling fold structure must be known or obtainable.