bluuebunny/crossref_metadata_2025 huggingface dataset:
Chlorine‐36 Releases from the Savanniah River Site Nuclear Fuel Reprocessing Facilities
Authors: Beasley T. M. , EImore D. , Kubik P. W. , Sharma P.
Published: August 2005

Determinations of 36CI (T½= 301,000 a) in waters on and near the U.S. Department of Energy's Savannah River Site (SRS) in South Carolina reveal that nuclear fuel reprocessing activities there have released measurable amounts of this radionuclide to the environment. The natural atmospheric flux of 36CI at the latitude of SRS is 20‐25 atoms m‐2 sec‐1. Atmospheric releases of 36CI from SRS, within the site boundaries, have increased this flux by a factor of at least 10 to 20. Approximately 3×109 Becquerels (Bq) [84 millicuries (mCi)] of site‐derived 36 CI have been deposited within 200 km of the plant boundaries. By comparison, fallout of 36CI from nuclear weapons testing in the 1950s deposited twice this amount of activity in the same area. Surface‐water 36CI concentrations in on‐site streams represent about 0.01 percent of the Environmental Protection Agency (EPA) drinking‐water standard and therefore pose no health concern. At SRS and similar facilities, this additional source of 36CI should prove useful for validating ground‐water and atmospheric transport models.
Apparent Relative Retardation of Tritium and Bromide in Dolomite
Authors: Leap Darrell I.
Published: August 2005

In order to determine the suitability of bromide as a surrogate for tritium for ground‐water tracing in fractured and fissured dolomite, apparent relative retardation coefficients of bromide with respect to tritium were computed by the cumulative relative mass‐time method from breakthrough curves of both substances, when used simultaneously as tracers in a two‐well recirculating tracer test. Throughout the 33.78‐day test, relative retardation differences of only a few hundredths were detected for most of the testing time.

Tritium was less retarded in flow through highly transmissive openings than in more diffuse flow. Bromide was generally retarded relative to tritium except at the pumping well where the concentrations of both were diluted an order of magnitude below those in the monitoring wells, and tritium was retarded slightly more than bromide.

Apparent relative retardation was found to change with transmissivity, concentration, flow‐path length and time, but not enough to rule out bromide as a suitable surrogate for, or even better than, tritium in dolomite if the limitations of each tracer are known.
Saturated Mound Development on Sloping Clay Layers Due to a Finite Source: An Analytical Solutiona
Authors: Filley T. H.
Published: August 2005

Sloping clay layers beneath percolation ponds can cause infiltrating waste water to pond and move in directions not predicted by vertical infiltration equations. This paper presents a method for estimating the potential of percolation sumps located over sloping clay layers to interact with nearby ground‐water resources. The analytical solution developed is for steady‐state conditions and includes a procedure to estimate the time needed to reach steady state. The fundamental assumption used in the mathematical development requires that elevation‐head gradients be much larger than pressure‐head gradients. A method for testing the validity of this assumption is also included. An example calculation was performed for percolation sumps on the Naval Petroleum Reserves No. 1 in Elk Hills, California. That analysis shows that under the assumptions used, a sump exclusion zone on the Elk Hills is required to protect ground‐water resources within the adjacent San Joaquin Valley.
Optimal Design of Ground‐Water Capture Systems Using Segmental Velocity‐Direction Constraints
Authors: Ratzlaff Steven A. , Aral Mustafa M. , Al‐Khayyal Faiz
Published: August 2005

An effective means of containing contaminant plumes in regional aquifers is to regulate the ground‐water flow through extraction wells that are strategically located. In this paper, the best well locations and flow rates are determined using numerical ground‐water simulation and optimization techniques. As a first step in the analysis, the methodology utilizes a novel idea of delineating the capture zone by imposing segmental implicit velocity‐direction constraints as opposed to explicit and unilateral velocity‐direction constraints which have been proposed by others. The optimization problem that arises is a mixed‐integer linear program which is solved by standard branch and bound techniques. The overall procedure is illustrated on representative example problems.
VECTOR ‐ A Computer Program That Utilizes SURFER or GRAPHER to Plot a Vector Field
Authors: Lu Ning , Amter Steven
Published: August 2005

VECTOR is a Fortran 77 program that enables SURFER or GRAPHER to rapidly convert a two‐dimensional field of vectors into graphical form. SURFER and GRAPHER are both DOS format commercial graphics packages. The resulting graphical output can be plotted on‐screen or as hardcopy. Vector arrows and the size of the plot can be either manually or automatically scaled. For input, VECTOR requires only four pieces of data for each point: the x and y coordinates of the point and the x and y components of the vector's magnitude. VECTOR is an interactive program with defaults and on‐screen menus to simplify use.
Modeling Regional Ground‐Water Flow in Fulton County, Indiana: Using the Analytic Element Method
Authors: Haitjema Henk M.
Published: August 2005

In 1989, the Four County Landfill (FCL) in Fulton County, Indiana was closed by a federal judge because of regulatory violations and its threat to the environment. As part of the litigation, a ground‐water flow modeling study was performed on behalf of a group of concerned citizens. Time constraints and, even more importantly, budgetary constraints called for an approach which could be implemented quickly and would yield meaningful results without additional field data acquisition. The modeling was performed with the relatively new analytic element method.

The new method employs superposition of closed form analytic solutions, rather than a grid or element network, and proved an effective tool in answering some unresolved hydrogeological questions. The study results demonstrate substantially higher regional and local hydraulic conductivities than suggested by the landfill consultants, well‐connected upper and lower aquifer zones at the site, and potential ground‐water travel times from the landfill to the nearby Tippecanoe River of less than 15 years.
The Use and Performance of Collector Wells Within the Regolith Aquifer of Sri Lanka
Authors: Ball D. F. , Herbert R.
Published: August 2005

Thirty‐two collector wells were constructed from existing large‐diameter wells dug in weathered hard rock (regolith) areas of the northern Dry Zone of Sri Lanka. A collector well is constructed by drilling 30 m long horizontal adits from the base of the dug well so as to exploit the permeable layer of the regolith, which lies just above the zone of slightly weathered rock. Across the North‐Central Province of the island, the water table commonly lies within the regolith for most of the year enabling dug wells to yield water. The generally poor yield of these wells and the occasional dry well has resulted in this aquifer being largely neglected by developers with most recent efforts going into the construction of many slim boreholes.

The objectives of this work were: (1) to enhance the yields from suitable dug wells, (2) to observe the variation in yield improvement for wells with different constructions and in varying geologic and hydrogeologic environments, and (3) to monitor the performance of the converted wells throughout the dry season.

The project has demonstrated that, on average, the conversion of a dug well to a collector well more than doubles the yield of ground water and that these yields are sustainable throughout the dry season. Safe yields from these wells average an equivalent continuous yield of 60 m3/day, assuming a 100 day dry period.
Effects of Waste‐Water Irrigation on Aqueous Geochemistry Near Paris, Texas
Authors: Tedaldi Dante J. , Loehr Raymond C.
Published: August 2005

A comprehensive assessment of the environmental impact of a full‐scale, operating overland flow (OLF) land treatment system was made at the Campbell Soup (Texas), Inc. facility in Paris, Texas. The system treats over 16,000 m3/d of waste water and has been in operation for over 25 years. Field samples of soil, waste water, OLF runoff, and ground water collected during the study and detailed long‐term process records maintained by Campbell Soup were used as part of the evaluation. Geochemical data indicated that sulfate‐chloride facies were dominant for the ground water collected at the OLF site. Field data and calculations indicated that the evapotranspirative concentration of salts in the applied waste water would be insufficient to produce the measured concentrations in the ground water. A pattern of increasing ionic concentration over time (1968 to 1989) with small changes in ionic ratios suggested a trend toward the dissolution and concentration of naturally present minerals (such as gypsum and sodium chloride) in the slow moving ground water. Predictions made with the aid of MINTEQA2, a thermodynamic equilibrium model, indicated that precipitation of carbonates and simultaneous ion exchange on clays could represent a significant mechanism for the removal of calcium and magnesium from solution and the addition of sodium. The development of a slightly saline, semiconfined aquifer was strongly suggested by the ground‐water geochemical data, soil data, the estimated rate of infiltration, field hydraulic conductivity, MINTEQA2 model predictions and the magnitude of the volume of waste water applied.
Effects of Nutrient Management on Nitrate Levels in Ground Water Near Ephrata, Pennsylvania
Authors: Hall David W.
Published: August 2005

Effects of the implementation of nutrient management practices on ground‐water quality were studied at a 55‐acre farm in Lancaster County, Pennsylvania, from 1985‐90. After nutrient management practices were implemented at the site in October 1986, statistically significant decreases (Wilcoxon Mann‐Whitney test) in median nitrate concentrations in ground‐ water samples occurred at four of the five wells monitored. The largest decreases in nitrate concentration occurred in samples collected at the wells that had the largest nitrate concentrations prior to nutrient management. The decreases in median nitrate concentrations in ground‐water samples ranged from 8 to 32 percent of the median concentrations prior to nutrient management and corresponded to nitrogen application decreases of 39 to 67 percent in contributing areas that were defined upgradient of these wells.

Changes in nitrogen applications to the contributing areas of five water wells were correlated (Spearman rank‐sum test) with nitrate concentrations of the well water. Changes in ground‐water nitrate concentrations lagged behind the changes in applied‐nitrogen fertilizers (primarily manure) by approximately 4 to 19 months.
Pathline and Geochemical Evolution of Ground Water in a Regional Discharge Area, Red River Valley, North Dakota
Authors: Gerla Philip J.
Published: August 2005

Ground water in the Red River Valley region of North Dakota evolves from HCO3 to SO4 to Cl‐type water over a distance of less than 100 km. Pathline analysis of ground‐water flow in a transect across the valley combined with chemical equilibrium and mass balance relationships explain the processes responsible for the observed geochemical evolution. Prior geological studies have shown that the central Red River Valley is a discharge zone for regional ground‐water flow. Discharged waters are generated from different sources, processes, and pathlines. Closed surface drainage and small permeability provide Na‐HCO3 water for bedrock recharge on the western side of the transect. In contrast, greater recharge in shale outwash is characterized by Ca‐Mg‐HCO3 water. Both ultimately evolve to SO4 water with similar proportions of major cations. Upward flow through Paleozoic sediments into the Lower Cretaceous Inyan Kara Group consists of Na‐Cl water modified by downward leakage of SO4 water from Cretaceous shale and HCO3‐SO4 water from glacial sediments. Discharged ground water reveals chemical characteristics that suggest mixing of spatially varying proportions of local recharge and more evolved, deeper ground water. Mineral/ground‐water equilibria and estimation of mass transfer indicate that ground‐water composition is largely controlled by carbonate precipitation and dissolution, gypsum dissolution, and clay cation exchange.
An Evaluation of Flow Net Analysis for Aquifer Identification
Authors: Scott David M.
Published: August 2005

A computer‐assisted flow net analysis technique was developed and evaluated using a hypothetical heterogeneous aquifer with spatially variable recharge. Flow nets were derived and analyzed for cases with differing piezometric observation density and accuracy. Using a criterion to determine a best approximation to the observed piezometric surface, the transmissivity distributions implied by fitted surfaces were compared with the known true transmissivities. Where an optimum approximation to the piezometric surface was clearly defined, the resulting computed transmissivities compared favorably with the known values. With sparse or inaccurate observations, it became increasingly difficult to identify an optimum solution. The experiments illustrate some of the difficulties inherent in the ground‐water inverse problem and the flow net analysis method. Application of the method to real field cases has yet to be tested.
Prediction of Flow and Hydraulic Head Fields for Vertical Circulation Wells
Authors: Philip Ross D. , Walter Gary R.
Published: August 2005

A vertical circulation well is a well completed in two intervals with extraction induced in one interval and injection induced in the other, generating a circulating flow field near the well. A vertical circulation well may be used to remediate contaminated ground water by air stripping the extracted water and then reinjecting the clean water; by introducing oxygen and/or nutrients to the extracted water before reinjecting it, thereby stimulating the natural bioremediation of the water; or by injecting appropriate chemicals or microbes, effecting remediation of the circulated water. This paper summarizes an analytical technique for predicting the steady‐state hydraulic head and flow fields caused by the operation of multiple vertical circulation wells in a confined aquifer with a regional gradient. The method begins with the hydraulic head solution for a point sink in an infinite aquifer. The point sink is then integrated to derive the solution for a line sink. Linear superposition is applied to obtain the hydraulic head resulting from multiple line sinks and sources in a homogeneous confined aquifer. This solution is then differentiated to obtain the hydraulic head gradient and three‐dimensional velocity field. The velocity field is numerically integrated by an adaptive Runge‐Kutta scheme to obtain the pathlines of three‐dimensional flow.
Influence of Environmental Factors on Denitrification in Sediment Contaminated with JP‐4 Jet Fuel
Authors: Bradley Paul M. , Marjorie Aelion C. , Vroblesky Don A.
Published: August 2005

In 1975, the loss of approximately 83,000 gallons of JP‐4 grade jet fuel resulted in contamination of the shallow aquifer near North Charleston, South Carolina. To identify those factors likely to influence microbial activity under denitrifying conditions, we examined the fate of amended NO3, the effect of pH, NO3, and PO4 on denitrification, and the variability of denitrification in sediments collected at the site. Denitrification (N2O‐N production) accounted for 98% of the depletion of NO3‐N under anaerobic conditions. Both carbon mineralization and denitrification rates increased asymptotically with increasing NO3 to a maximum at approximately 1 mM NO3. Addition of up to 1 mM PO4 did not significantly increase N2O and CO2 production. Denitrification rates were at least 38% lower at pH = 4 than observed at pH = 7. Comparison of samples with differing degrees of hydrocarbon contamination indicated that at least a tenfold variation in sediment denitrification occurs at the North Charleston site.
Common Sense in Ground‐Water Protection and Management in the United States
Authors: LeGrand Harry E. , Rosen Lars
Published: August 2005

Interests in the development and protection of ground water have had unbalanced thrusts through the years, focusing on special types of problems that arise at a particular time. Massive funding and excessively rigid rules guided by bureaucratic procedures have resulted in excessive effort in some activities and neglect in others.

Of special importance are the needs for optimal use of existing experience and data and for strengthening the hydrogeologic experience at policy and regulatory levels. At hand are (1) great piles of hydrogeologic data, some unneeded, (2) widely varying background knowledge and varying experience of workers, and (3) types and ranges of uncertainties. To make optimal use of available data and knowledge, to handle uncertainties, and to properly integrate the hydrogeologic conditions with other factors, there should be risk‐based approaches in a decision analysis framework. Better balanced efforts toward future ground‐water protection and management can be realized by incorporating features of the suggested framework approach.
Optimal Orientation of Water‐Supply Boreholes in Fractured Aquifers
Authors: Banks David
Published: August 2005

The chance of encountering a water‐bearing fracture when boring in a hard‐rock aquifer can be maximized by drilling a borehole at an optimal inclination from the vertical, and an optimal azimuth with respect to fracture orientation. This paper describes the process of calculating the optimal borehole orientation for two common fracture patterns (orthogonal and biaxial stress‐induced), and discusses the application of the technique to a general case. It is found that, in terrains with well‐developed, transmissive vertical fracture planes, significant advantages can be obtained by drilling at large angles to the vertical.
Analytical Estimation of Ground‐Water Flow Around Cutoff Walls and Into Interceptor Trenches
Authors: Ilyinsky N. B. , Kacimov A. R.
Published: August 2005

An impermeable boundary of the grout cutoff has been found that maximizes the seepage flow for a specified grouting volume. The shape of a trench has been defined that maximizes the quantity of fluid entering the ground‐water flow from the trench. The seepage characteristics of the grout cutoff and the trench which have arbitrary shapes are estimated in terms of the derived exact analytical solutions of variational problems.
Combined Mathematical Model of Flow in an Aquifer‐Horizontal Well System
Authors: Tarshish Michael
Published: August 2005

A mathematical model and calculation method were developed in this study for steady‐state flow in an aquifer‐horizontal well system under a water reservoir without the usual assumption about interface conditions that the specific discharge in the radial direction to the screen is constant along its axis.

A horizontal well (i.e. drain, gallery, or lateral) is represented as a linear sink with nonuniform intensity for description of a flow in an aquifer. Flow in the screen channels is described by taking into account energy losses and the momentum flux change along the well screen's axial orifice. Substantial errors are avoided by the use of the proposed model.

The mathematical model also can be used for the analysis of vertical wells.
Spreadsheet Modeling of Electrical Sounding Experiments
Authors: Sheriff Steven D.
Published: August 2005

Electrical resistivity sounding is useful for solving a variety of ground‐water problems. To model apparent resistivities for a specific model requires one to evaluate a convolution integral. This calculation, using linear filtering, is rapid and convenient with a commercial spreadsheet. In comparison to traditional programming languages, the high‐level language and built‐in screen graphics provided by the spreadsheet save much programming time.
Inverse Analytical Techniques Applied to Coincident Contaminant Distributions at Otis Air Force Base, Massachusetts
Authors: Ala Natalyn K. , Domenico Patrick A.
Published: August 2005

Inverse analytical techniques have been applied to six coincident plumes at Otis Air Force Base near Cape Cod, Massachusetts. The plumes contain chloride, boron, trichloroethene, tetrachloroethene, and biodegradable and nonbiodegradable detergents. Thus, a host of processes including physical, chemical, and biological, are presumed to be operative. The analytical technique is structured to solve several equations simultaneously and provides unique values for several unknowns which control the behavior of the contaminant plumes. The determined parameters include source strength and size, the advective position of the contaminant front for both retarded and unretarded constituents, dispersivities in x and y, and a reaction rate constant that describes decay, biodégradation, or chemical transformation. The obtained values for the transport parameters for the different constituents were reasonably similar, with the transverse dispersivity ranging from 1.2 to 2.7 m and the longitudinal dispersivity ranging from 6.1 to 7 m. The unretarded advective velocity of boron, chloride, and tetrachloroethene were quite similar (73, 78, and 65 m/yr) whereas tetrachloroethene had a velocity of 48 m/yr. Of special interest is the half‐life determination of the reactive constituents. The organic compounds trichloroethene and tetrachloroethene have half‐lives of 11 and 10 years, respectively, whereas the biodegradable detergent with linear alkyl sulfonate had a half‐life of 7.6 years. In all cases, this set of parameters captures the essence of the various plumes with a high degree of accuracy.
Exploration and Development of Ground Water from the Stone Forest Karst Aquifers of South China
Authors: Huntoon Peter W.
Published: August 2005

Stone forest aquifers are the most widely exploited sources for ground water in the vast south China karst belt. These aquifers occupy a thin epikarst zone that has been infilled with clastic sediments. The aquifers are characterized by large lateral permeabilities and small reservoir capacities owing to their thinness. The carbonate rocks which comprise the framework for the aquifers are usually buried under the karst plains and large karst depressions where development is desired.

The stone forest aquifer exploration procedure must first locate saturated zones. Second, those parts of the saturated zone having the greatest dissolution porosity must be identified because the infilled dissolution voids contain the water.

The best indicators of saturation include the combination of low topography and the presence of active karst features such as springs, karst windows (natural openings exposing the water table), and live surface streams. These elements are readily observed on intermediate scale (1:20,000) aerial photography.

The depth and degree of carbonate dissolution porosity is a function of several geologic and hydrologic factors including carbonate rock type, carbonate purity, fracture density, specific discharge, age of the circulation system, etc. These variables cannot be measured directly because the carbonate rocks are usually buried under a thin mantle of clastic sediments. However, if it is recognized that the ground‐water system has already exploited the most favorable geology and that dissolution is an ongoing process, a simple indirect method can be used to identify the areas having the greatest porosity. The presence of karst depressions and recent sinkholes are indicative of the most intensely karstified and hydraulically active parts of the epikarst zone. Mapping of these surface features from stereo aerial photography is a simple geomorphology exercise that can be used to directly identify the most favorable well sites.

Current well construction practices in the south China karst belt involve both dug and drilled wells. Dug wells are preferred in many locations owing to both cost‐effectiveness associated with cheap labor and lack of available drilling equipment. The dug wells look and function identically to karst windows and thus conform to timeless water use traditions in the region.
Fresh‐Water/Sea‐Water Relationship Within a Ground‐Water Flow System, Northeastern Coast of the Yucatan Peninsula
Authors: Moore Yolanda H. , Stoessell Ronald K. , Easley Dale H.
Published: August 2005

Ground‐water velocities within fractures and boreholes, hydraulic heads, and depth profiles of conductivity were measured along a 70 km section of the northeastern coast of the Yucatan Peninsula, Mexico. Hydraulic heads ranged from 40 to 60 cm above mean sea level between 2 and 4 km from the coast. Fluid velocities estimated from point‐dilution tests, in the dual‐porosity rock in a borehole several kilometers from the coast, were 0.021 cm/sec in the fresh‐water lens and 0.082 cm/sec near a fracture in the underlying sea‐water zone. Velocities in large fractures increased from 1 cm/sec 10 kilometers inland to 12 cm/sec near discharge points along the coast. This increase is attributed to the decrease in thickness of the fresh‐water lens.

The thickness of the fresh‐water lens is approximately 40% less than the Ghyben‐Herzberg relation predicts for a static system, providing the potential to drive fresh water through fractures into the sea‐water zone below the halocline. Overall, the halocline appears to be in a steady‐state position due to the rapid flow of fresh water and brackish water towards the coast combined with rising sea water in corivectional flow.
Potentiometric and Aquifer Property Changes Above Subsiding Longwall Mine Panels, Illinois Basin Coalfield
Authors: Booth Colin J. , Spande Erik D.
Published: August 2005

This study examined the response of potentiometric levels and hydraulic properties to subsidence caused by a 725‐ft‐deep active longwall mine in southern Illinois. The overburden is mainly shale but includes a shallow sandstone aquifer, overlain by a shale aquitard, capped by thin drift. Pumping and packer tests indicate that subsidence fracturing increased the hydraulic conductivities of the sandstone aquifer by about an order of magnitude, and of certain horizons of the lower bedrock by several orders. The water table in the drift aquifer was unaffected by mining; however, heads in the bedrock units dropped sharply in response to subsidence, probably because tensional dilation of fractures increased storativities. The sandstone aquifer also displayed gradual potentiometric declines ahead of mining, and a rapid partial recovery afterwards. Depression of water levels and potentially higher well yields represent conflicting negative and positive aspects of the hydrologic impact of longwall mining.
Hydrogeological Decision Analysis: 3. Application to Design of a Ground‐Water Control System at an Open Pit Mine
Authors: Sperling Tony , Freeze R. Allan , Massmann Joel , Smith Leslie , James Bruce
Published: August 2005

Control of ground water plays an important part in operations at many open pit mines. Selection of an efficient and cost‐effective ground‐water control program is frequently complicated by the complex and somewhat uncertain hydrogeo‐logic environment found at most mine sites. This paper documents a case study of dewatering operations at Highland Valley Copper that shows how risk‐cost‐benefit analysis can be used to identify the best ground‐water control strategy to improve stability of pit walls under such conditions.

For each of a specified set of design alternatives, the analysis involves evaluation of an economic objective function, comprised of revenues, operating costs, and monetary risks associated with slope failure. The risk calculation requires an accurate estimate of the probability of slope failure on the pit wall. The calculation involves a coupled, steady‐state, saturated‐unsaturated, finite‐element ground‐water flow model and a limit equilibrium slope stability model. The coupled model is invoked in a conditional Monte Carlo simulation that is based on a geostatistical description of the level of uncertainty inherent in the available hydrogeological and geotechnical data.

Although the emphasis in this paper is on identifying the optimum slope angle and ground‐water control strategy for open pit mines, the framework is equally well‐suited to the analysis of design issues for any engineering projects in which the hydrogeological environment plays an important role.
Hydrograph Analysis in a Fractured Rock Terrane
Authors: Moore Gerald K.
Published: August 2005

A typical watershed near Oak Ridge, Tennessee is underlaid by a stormflow zone, which approximately corresponds with the root zone of vegetation, and by a ground‐water zone. Analysis of the streamflow hydrograph and water‐level hydrographs during the nongrowing season shows that discharge from the stormflow zone constitutes nearly all streamflow after the end of overland runoff but that discharge from the ground‐water zone is dominant after about 8–10 d (days) of recession. Simple equations that express the relationship between streamflow recession and storage depletion can be used to calculate average values of specific yield, transmissivity, and hydraulic conductivity in both the stormflow and ground‐water zones. The calculated values are reasonable and are nearly the same as those obtained by other methods.
Analysis of Ground‐Water Flow and Injection Fluid Transport in the Floridan Aquifer Near Pensacola, Florida
Authors: Ward David S. , Mercer James W. , August Lisa L.
Published: August 2005

Liquid waste has been injected into a permeable part of the lower limestone of the Floridan aquifer since 1963, raising hydraulic head in the injection zone throughout a region of northwestern Florida. The injection zone consists of a moderately permeable limestone, hydraulically isolated from overlying aquifers by a thick layer of clay. The formation fluid is saline, but becomes fresher up dip, northward where the limestone crops out. Numerical simulations were performed at regional and local scales to assess the regional pressure increase, to analyze the movement of the 10,000 mg/1 total dissolved solids (TDS) isopleth (formation fluid) in the lower limestone of the Floridan aquifer, and to analyze the migration of the injection fluid, both historically and predictively, in the injection formation. This work is based largely on previous work by Merritt (1984), but uses the SWIFT code. Modifications to Merritt's work include increasing the hydraulic conductivity near the injection wells and using more recent injection rates; extensions include particle tracking and solute transport modeling. The simulations indicate that regional pressure increases should be much less than previously predicted. Using the new results, by the year 2033, the average movement of the 10,000 mg/1 TDS isopleth due to injection is expected to be approximately 2200 ft (671 m). Additionally, by the year 2033, the indiluted injection fluid (95% of injection concentration) should migrate to an approximate diameter of 2.1 mi (3.4 km) from the injection wells.
Field Determination of Geological/Chemical Properties of an Aquifer by Cone Penetrometry and Headspace Analysis
Authors: Chiang C. Y. , Loos K. R. , Klopp R. A.
Published: August 2005

The cone penetrometer with pore pressure measurements was first introduced in 1975. It is generally regarded in the geotechnical community as one of the most efficient tools for stratigraphic logging of soft soils. Recently, the conventional cone penetrometer has been coupled with a porous probe ground‐water sampler for environmental applications.

This coupled system was used to perform soil logging, collect ground‐water samples, and evaluate hydraulic conductivity in an effort to determine the extent and preferential flow pathway(s) of a soluble hydrocarbon plume in a Texas aquifer. Ground‐water samples collected by a porous probe sampler were analyzed for hydrocarbon content by a portable gas chromatograph with a photoionization detector (GC/PID) to characterize the extent of the soluble organic plume and provide a field evaluation of ground‐water quality. Aqueous concentrations of hydrocarbons calculated from vapor headspace measurements by this technique were in good agreement with direct concentration measurements obtained in the laboratory using standard EPA ground‐water analytical procedures. This field procedure makes it possible to efficiently use cone penetrometry equipment in less characterized areas allowing rapid delineation of volatile organic plumes by the headspace analysis.

Interpretation of the cone penetrometer test data located a buried channel on the site aligned in an east‐west depositional direction. To the north and south of the channel, the soils exhibited reduced hydraulic conductivity due to their respective soil type or depositional density. Analyses of ground‐water samples collected from the area confirmed that soluble hydrocarbon migration was following the more permeable channel. In addition, depth selective ground‐water sampling recorded sharp changes in the vertical concentration profiles indicating that macroscopic vertical dispersion may be negligible at this site.
Sea‐Water Intrusion in the Coastal Area of Laizhou Bay, China: 1. Distribution of Sea‐Water Intrusion and Its Hydrochemical Characteristics
Authors: Xue Yuqun , Wu Jichun , Liu Peimin , Wang Jianji , Jiang Qingbo , Shi Hongwen
Published: August 2005

Sea‐water intrusion was observed in China's coastal aquifers as early as the 1960s. At present, it covers an area of more than 580 km2, and is continuing to extend in the coastal area of Laizhou Bay. There is a wide transition zone of 1.5–6.0 km, in which both the simple mixing of local fresh water and sea water and the cation exchange can be recognized. In this paper, extensive chemical and head data sets in four dimensions relevant to the distribution of the sea‐water intrusion and ion exchange are presented.
Combined Use of Geoelectric Sounding and Profiling to Quantify Aquifer Protection Properties
Authors: Kalinski Robert J. , Kelly William E. , Bogardi Istvan
Published: August 2005

Evolving environmental regulations have increased the need for defining the protective properties of geologic layers. Of particular significance is the need for defining vertical times‐of‐travel (TOT) through aquitards located above municipal water supply wellfields. Surface geoelectrics provide an inexpensive field measurement method that can be used to quantitatively define protective properties. Protective layer longitudinal unit conductance squared (S2) can be theoretically related to TOT using material relationships between resistivity and hydraulic conductivity divided by porosity (K/n).

In an example presented for a municipal wellfield, it was possible to utilize a limited number of geoelectric soundings to establish relationships between S of a conductive protective layer and apparent resistivities measured at individual electrode spacings, providing a method to estimate S with profiling. In this case, longitudinal unit conductance (S) was the geoelectrically equivalent parameter of the protective layer. The use of combined sounding and profiling data in the wellfield area resulted in an overall reduction in the kriging estimation error of S for the protective clay layer and a larger area of coverage over what was obtained with soundings alone.
Designing a Nitrate Monitoring Program in a Heterogeneous, Carbonate Aquifer
Authors: Smith Ronald T. , Ritzi Robert W.
Published: August 2005

Multilevel, double‐packer slug tests were performed in open core holes to characterize heterogeneity within a flat‐lying, fractured carbonate aquifer. Hydraulic conductivity was measured to vary by approximately three orders of magnitude in the vertical direction and by as much as two orders of magnitude in the horizontal direction. In general, hydraulic conductivity decreased with distance from the bedrock free‐surface, as the degree of fracturing decreased. The results of the multilevel slug tests provided the basis for hydraulic conductivity zonation within a two‐dimensional finite‐element model, which simulated nitrate transport in cross section. In simulation of steady‐state flow, several shallow, local ground‐water flow systems occurred with exit points that are consistent with springs observable in the field. Yearly rotating crops of corn and soybeans were simulated with nitrate source concentrations based on pore water measurements in the lower soil zones of the field site. The majority of simulated nitrate movement occurred within shallow, localized ground‐water flow systems, where much of the nitrate exited the system relatively soon after entering, without appreciable accumulation of nitrate through the years. Based on these results, a monitoring program with a relatively high spatial and temporal resolution in the shallow, localized ground‐water flow systems was required in order to characterize nitrate concentrations in the ground water. Regional water quality surveys that involve a random sampling of existing, widely spaced wells would likely miss detecting the locations and times of high nitrate concentrations in ground water.
Recovery Analysis from Pumping Tests with Stepped Discharge
Authors: Kawecki M. W.
Published: August 2005

Recovery analysis from pumping tests with varying discharge is well‐documented but in practice often wrongly considered to be impractical or even impossible. However, the Theis recovery method for constant rate tests is popular and widely used to determine aquifer transmissivity. The purpose of this paper is to review and promote determination of transmissivity by recovery analysis in tests in which the discharge is not steady but represented by a step function. The equations for a stepped discharge recovery method are presented in a simple form, highlighting the fact that it is a direct extension of the Theis recovery method with the same advantages and ease of application. It is demonstrated that the Theis recovery method cannot generally be used with an average discharge for varying rate tests. Recovery analysis should always be approached with the stepped discharge recovery method, which reduces to the Theis method if the discharge is constant. The stepped discharge recovery method is particularly useful for step tests and for analyzing data from the pumped well, and it should be standard practice to monitor the recovery in all pumping tests on single wells. It is also shown that a different storage coefficient during recovery than during pumping does not result in a shifted straight line in the recovery analysis but in a curve passing through the origin.
Use of Portable Oxygen and Carbon Dioxide Detectors to Screen Soil Gas for Subsurface Gasoline Contamination
Authors: Deyo Brendan G. , Robbins Gary A. , Binkhorst Gordon K.
Published: August 2005

The field screening of soil gas CO2 and O2 using portable instruments is shown to be useful for indirectly detecting and delineating subsurface gasoline contamination. Shallow (< 50 cm) soil gas surveys performed at a site of subsurface gasoline contamination in Connecticut indicated a good correlation between elevated CO2, depleted O2, and total hydrocarbon vapor anomalies. CO2 and O2 anomalies were also found to be spatially coincident with the area of known subsurface gasoline leakage. Soil gas CO2 levels ranged from 0.2 to 18.7 volume percent, whereas O2 levels ranged from 20.8 to 0.5 volume percent. The gases exhibited a nearly constant inverse correlation except near the source of contamination. In this area, CO2 generation from anaerobic degradation of hydrocarbons likely caused a decrease in the observed CO2 and O2 correlation. This suggests that the ratio of soil gas CO2 to O2 may be useful to delineate aerobic and anaerobic degradation zones, the latter being in the vicinity of highly contaminated areas. Periodic sampling of seven permanent soil gas probes over a 17‐month period indicated significant seasonal variations in CO2 and O2. When the soil was warmest during the summer, the CO2 reached a maximum and O2 reached a minimum. The opposite was observed during the winter when the soil achieved its minimum temperature. These observations most likely reflect changes in microbial acitivity in response to subsurface temperature variations. Further, hydrocarbon vapor levels were observed to decrease by several orders of magnitude to nondetectable levels during the winter months. Although CO2 and O2 anomalies were also diminished during the winter months, they were still readily detectable. These observations indicate that soil gas surveying for subsurface gasoline leakage may be enhanced by monitoring CO2 and O2.
Evaluating the Volume of Porous Medium Investigated During Slug Tests
Authors: Guyonnet D. , Mishra S. , McCord J.
Published: August 2005

This paper presents a methodology for quantifying the volume of porous medium investigated during a slug test in an unbounded porous medium, in the presence of a linear constant‐head or no‐flow boundary, and in the presence of a radial no‐flow boundary. For the unbounded case, type curves are generated for different values of the wellbore storage coefficient, which relate the distance travelled by a given pressure perturbation (1, 5, and 10% of the initial drawdown in the well), to dimensionless time. This distance is found to increase linearly on a log‐log plot until it reaches a maximum which is a function of the wellbore storage coefficient. The appropriate choice of dimensionless groups allows the different curves for each level of perturbation to be collapsed into one curve. Functional relationships offer an alternative to using the type curves graphically. For bounded systems, type curves relate the distance to the boundary to the time of 1 and 5% deviation from the unbounded response. Although these curves cannot be collapsed, the presented range of wellbore storage coefficients covers most practical situations. Developed relationships allow the estimation of the maximum distance travelled by the pressure perturbations in the unbounded case, and the maximum distance at which a linear constant‐head or no‐flow boundary, or a radial no‐flow boundary, still produces a given deviation in the pressure response measured at the well. An application shows that substantial error may result if the distance to a boundary is evaluated while neglecting storage in the well. Finally, application of the methodology developed for a linear no‐flow boundary to a real data set yields a realistic distance to the boundary and a far better match between simulated and measured data than if an unbounded system is considered. The type curves and relationships presented here should be applicable to slug test design and analysis.
Continuous Measurements of Ground‐Water Seepage Using an Automatic Seepage Meter
Authors: Taniguchi Makoto , Fukuo Yoshiaki
Published: August 2005

An automatic seepage meter using a heat pulse method was developed to obtain a continuous measurement of ground‐water seepage rates. According to calibrations of the automatic seepage meter fitted with a 50 cm diameter collection funnel, seepage rates from 2 X 10‐5 to 5 X 10‐4 cm/sec can be obtained by measuring the time when the temperature as measured by a thermistor peaks after applying a heat pulse. The automatic seepage meter was used to measure continuous seepage rates into Lake Biwa, Japan. The ground‐water seepage rate measured by the automatic seepage meter in Lake Biwa changed by six times within 12 hours. The automatic seepage meter is useful for surface‐/ground‐water studies, because a continuous seepage rate can be obtained without errors caused by the resistance of a collection bag to water flow.
A Comparative Study of Calculation Methods for Recharge of Rainfall Seepage to Ground Water in Plain Area
Authors: Liu Yong , Zhang Chun
Published: August 2005

Ground water in the plain area of China is recharged mostly with rainfall and to a lesser extent with surface water and nearby ground water. There are several methods for the calculation of recharge of rainfall seepage to ground water. The calculated values using different methods vary due to the accuracy of parameters and calculation methods chosen. A comparative study of methods used to calculate ground‐water recharge by rainfall seepage is made using the water‐balance method and the ground‐water regime analysis method applied to the plain area of China. The accuracy of the ground‐water regime analysis method is superior to that of the water‐balance method. The influential factors (lithology, depth to ground water, precipitation capacity, etc.) of ground‐water recharge by rainfall seepage and the accuracy of these factors are also discussed.
Vertical Heterogeneity in Horizontal Components of Specific Discharge: Case Study Analysisa
Authors: Ronen Daniel , Berkowitz Brian , Magaritz Mordeckai
Published: August 2005

Ground‐water management decisions are usually taken under uncertainty, since they depend on unknown parameters of the aquifer such as hydraulic conductivity and specific discharge. This study applies a number of analytical techniques to a case study in order to demonstrate the potential effect of vertical heterogeneity in the horizontal component of specific discharge on evaluating contaminant travel time in an aquifer. The modified point dilution technique developed by Ronen et al. (1986) is applied to study the vertical variability of the horizontal component of specific discharge in a deep unconfined sandy aquifer. This technique, used under natural flow conditions, employs a multilayer sampler, a tracer, and a mathematical diffusion model. Also analyzed are data from a very large unplanned tracer test where the “tracer”, sewage effluent with a high chloride content, was infiltrated into the aquifer for about 30 years. To date, based on available sedimentological evidence and pumping tests, the aquifer has been regarded as homogeneous. However, information from analysis of the tracer test data by two different flow models, and findings obtained by the modified point dilution technique, indicate the existence of zones of high hydraulic conductivity with specific discharges one order of magnitude higher than expected. As a consequence, chloride breakthrough in a pumping well downstream of effluent infiltration was detected after 10 years, at least 70 years earlier than could have been estimated from previously available data. The results demonstrate that consideration must be given to vertical heterogeneity when evaluating contaminant transport and show that detailed site‐specific field studies are needed in order to prevent or control aquifer contamination.
Effects of Pipe‐Outlet Terracing on Ground‐Water Quantity Near Churchtown, Pennsylvania
Authors: Hall David W.
Published: August 2005

Ground‐water quantity data were collected at a 22‐acre farm site near Churchtown, Pennsylvania, to determine if terracing changed the quantity of water recharging the aquifer. Double‐mass comparisons of water‐level data from six wells at the site were used to determine that the construction and operation of six pipe‐outlet terraces caused no statistically significant changes in the quantity of recharge to the carbonate aquifer. Analyses of water‐table altitude data from site wells indicate that terracing did not change mean annual water‐table altitudes at the site.
Model Calibration Techniques for Use with the Analytic Element Method
Authors: Power Barry F. , Barnes Randal
Published: August 2005

The combination of the analytic element method and a nonlinear parameter estimation technique forges a computationally efficient, information‐rich, and cost‐effective solution to the inverse ground‐water flow problem. The recommended model calibration method uses a nonlinear least‐squares objective, as quantified by misfitting the measured and modeled heads, and a modified Levenberg‐Marquardt algorithm. As detailed and demonstrated by a steady‐state regional aquifer model of Bemidji, Minnesota, automated calibration techniques make ground‐water modeling feasible for a wider variety of projects where tight budgets and a lack of tools may have previously made such modeling inappropriate.