bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface Geophysical Surveys of the Freshwater‐Saltwater Interface in a Coastal Area of Long Island, New York
Authors: McNew Elizabeth R. , Arav Sara 
Published: August 2005

AbstractThe North Fork of Long Island is a peninsula whose freshwater supply consists of several lenses of fresh ground water that are surrounded by saline ground water. A study to determine the thickness of one freshwater lens near the Village of Greenport used two surface‐geophysical techniques at several sites to provide ground‐conductivity data that were, in turn, used to estimate the depth to the freshwater‐saltwater interface. Surveys were made during the spring and fall of 1989. Wells drilled during 1989 provided some verification of geophysical interpretations.Geophysical‐data interpretations were based on conceptual models with two, three, and four conductivity layers; the three‐layer concept produced interpretations that best matched geophysical measurements at all sites. The surface geophysical techniques were successful in interpreting depth to saline ground water. Interpreted depths to the freshwater‐saltwater interface were compared to assess seasonal changes; the interpreted differences were small and within the range of error of the survey techniques.
Estimation of Free‐Hydrocarbon Recovery from Dual‐Pump Systems
Authors: Charbeneau Randall J. , Chiang Chen Y. 
Published: August 2005

AbstractFree‐product hydrocarbon which floats on the water table may be recovered using single‐pump and dual‐pump systems. The factors that affect the long‐term free‐product recovery using dual‐pump systems include the free‐product thickness as measured in monitoring wells, the ground‐water pumping rate, hydrocarbon density and viscosity, and the soil permeability. This paper presents a simple model for prediction of free‐product recovery using dual‐pump systems. The model predicts the long‐term rather than short‐term recovery rates, and lends itself to spreadsheet calculations on microcomputers. A particularly simple form arises for cases where the drawdown is small. An application for estimating recovery from a dual‐pump system is presented, and limitations of the model are summarized.
Observed and Simulated Movement of Bank‐Storage Water
Authors: Squillace Paul J. 
Published: August 2005

AbstractDetailed hydrologic and water‐chemistry data were collected that document the movement of bank‐storage water during March 7‐April 17, 1990, in an alluvial aquifer adjacent to the Cedar River, Iowa. Hydrologic data included 745 daily ground‐water‐level measurements from 27 observation wells. Water‐chemistry data indicate that bank‐storage water had smaller specific conductance and larger concentration of atrazine than ambient ground water. To quantify the movement of the bank‐storage water, a two‐dimensional ground‐water flow model was constructed, and the resulting calibrated model accurately simulated observed conditions. Analysis of water chemistry and model results indicate that a 2‐meter rise in the river stage caused bank‐storage water to move horizontally at least 30 meters into the aquifer and vertically about 4 meters below the river bottom, whereas the remaining 30 percent moved laterally through the riverbank. The model also showed that bank storage caused the ground‐water flux to the river to increase by a factor of five during the first three weeks of base flow after runoff and that it required about five weeks for bank‐storage water to discharge from the alluvial aquifer after the peak river stage. These results quantitatively demonstrate the importance of bank storage as a source of recharge to the alluvial aquifer and as a source of water to the river during early base‐flow conditions.
The Constant Displacement Scheme for Tracking Particles in Heterogeneous Aquifers
Authors: Wen Xian‐Huan , Gómez‐Hernández J. Jaime 
Published: August 2005

AbstractSimulation of mass transport by particle tracking or random walk in highly heterogeneous media may be inefficient from a computational point of view if the traditional constant time step scheme is used. A new scheme which adjusts automatically the time step for each particle according to the local pore velocity, so that each particle always travels a constant distance, is shown to be computationally faster for the same degree of accuracy than the constant time step method. Using the constant displacement scheme, transport calculations in a 2‐D aquifer model, with nature log‐transmissivity variance of 4, can be 8.6 times faster than using the constant time step scheme.
Feasibility of Bioremediation of a Ground Water Polluted with Alkylpyridines
Authors: Ronen Zeev , Bollag Jean‐Marc , Hsu Cheng‐Hsiung , Young James C. 
Published: August 2005

AbstractThe potential for bioremediation of ground water polluted with various alkylpyridines was investigated. Aerobic bacteria, indigenous to the ground‐water aquifer, were utilized for biodegradation of the various contaminants. Laboratory experiments demonstrated that biodegradation occurred only under aerobic and not under anaerobic conditions. Analysis of the ground water in the site indicated that levels of oxygen were below 1 mg/l. Thus, it is suggested that oxygen limitation prevented the biodegradation of pollutants in the aquifer. Phosphate amendment (5 mg/1) into slurries of contaminated sediment and ground water resulted in enhanced degradation rates.Columns filled with aquifer material and leached with contaminated ground water were used to simulate possible in situ bioremediation. Reduction in concentration of the different compounds in column effluents ranged between 40 and 80%, with 2,3‐, 2,6‐, and 3,5‐lutidine degrading at lower rates than other contaminants. In addition to in situ treatment, the potential of using aboveground systems for treatment was explored. A mixed culture capable of degrading 14 different alkylpyridines was isolated from the subsurface sediment. This culture was used to seed a two‐stage fixed film reactor. The reactor was fed with a mixture of organic acids and alkylpyridines that simulated the ground‐water composition. The reactors were very effective in removing the pollutants from the waste stream. The efficiency of alkylpyridine removal was between 98 and 100% and overall COD removal was 97%, when operating at a loading rate of 4.32 g COD/L‐h and hydraulic retention time of 3 h. These results imply that a combined approach which utilizes both in situ and aboveground treatments should be used for the bioremediation of polluted ground water.
Surface Application System for In Situ Ground‐Water Bioremediation: Site Characterization and Modeling
Authors: Sweed Howard G. , Bedient Philip B. , Hutchins Stephen R. 
Published: August 2005

AbstractSurface 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.
Controls on 222Rn Variations in a Fractured Crystalline Rock Aquifer Evaluated Using Aquifer Tests and Geophysical Logging
Authors: Folger P. F. , Poeter E. , Wanty R. B. , Frishman D. , Day W. 
Published: August 2005

AbstractConcentrations of 222Rn in ground water may vary considerably within megascopically homogeneous rocks over relatively short distances. Calculations indicate that different hydraulic apertures of water‐bearing fractures may account for variations in dissolved 222Rn concentration measured in domestic water wells completed in fractured Pikes Peak Granite, assuming that all other factors influencing dissolved 222Rn concentrations are constant. Concentrations of dissolved 222Rn range from 124 to 840 kBq m‐3 [3,360 to 22,700 picocuries per liter (pCi L‐1)] within a 2.5 km2 well field. Aquifer tests show that transmissivities range from 0.072 to 160 m2 day‐1 within the well field. Acoustic televiewer and heat‐pulse flow meter logging of four wells reveals that, despite tens to hundreds of fractures that intersect each well, a single fracture supplies all the flow to three wells, and one fracture provides 65% of the flow to the fourth well. Aquifer tests indicate that two pairs of the four wells are hydraulically connected. Type‐curve interpretation of early‐time data from aquifer tests reveals classic half‐slope behavior on log‐log plots of drawdown versus time for two wells, suggesting linear flow to a single fracture. Drawdown versus time for the other two wells indicates radial or pseudo‐radial flow, which suggests a higher degree of fracture interconnectivity near those boreholes.Hydraulic apertures calculated using the cubic law are 0.024 and 0.038 cm for producing fractures in the first hydraulically connected well pair and 0.011 and 0.020 cm for flowing fractures in the second well pair. Assuming uniform distribution of 226Ra along fracture walls and long residence time of water relative to 222Rn decay, the ratio of fracture apertures should equal the inverse ratio of 222Rn concentration in each well. Assuming 50% error in hydraulic aperture estimation and 10% analytical uncertainty in 222Rn measurement, differences in 222Rn concentration between wells in the hydraulically connected pairs can be attributed solely to differences in hydraulic aperture. Different hydraulic apertures, however, do not explain different 222Rn concentrations between well pairs. Allowing for measurement error, a cubic meter of rock transfers from 1.3 to 20 times more 222Rn to ground water in the first pair of wells than in the second pair. Nonuniform distribution of 226Ra along fracture walls, heterogeneous emanating power in the rock‐water system, or short ground‐water residence time along the transmissive fracture network may account for the difference between well pairs.
Bias in Ground‐Water Data Caused by Well‐Bore Flow in Long‐Screen Wells
Authors: Church Peter E. , Granato Gregory E. 
Published: August 2005

AbstractThe 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.
Detection and Monitoring of Chlorinated Solvent Contamination by Thermal Neutron Logging
Authors: Endres Anthony L. , Greenhouse John P. 
Published: August 2005

AbstractThermal neutron logging is used to determine water content by measuring the elastic scattering due to hydrogen present in rocks and soils. The response of a thermal neutron device is also affected by the radiative capture of thermal neutrons by all elements. Chlorine has a large capture cross section in comparison to other elements usually found in aquifers; therefore, theory predicts that thermal neutron devices should respond to the presence of chlorinated solvents. Thermal neutron logging performed during a controlled release of perchloroethylene (PCE) confirmed that these methods can be used successfully to detect and monitor chlorinated solvents in the subsurface. To quantify the field results, a series of laboratory tests assessed the response of a neutron moisture probe used in the field experiments. These tests show that this device is very sensitive to the presence of chlorine and provide a basis for converting its response into an apparent PCE saturation. These saturation values compare favorably with PCE saturations obtained from core samples.
Modeling of Nitrogen Cycle and Nitrate Transfer in Regional Hydrogeologic Systems
Authors: Geng Q. Z. , Girard G. , Ledoux E. 
Published: August 2005

AbstractA model of the nitrogen cycle and nitrate leaching in soil, called MORELN, was developed to calculate the nitrate flux percolating from soils into aquifers. It uses a “coupled model,” which simulates both surface and subsurface flows. A third model, NEWSAM, is linked to the above models to simulate nitrate migration in an aquifer system. This methodology gives a quantitative global description of nitrate transfer, taking into account both leaching in soils and migration in aquifers. Three examples of application tested this methodology (especially the nitrate leaching code, MORELN) at different scales and with different emphases: (1) in a soil plot of several square meters; (2) in a small experimental basin of several square kilometers; and (3) in a regional hydrogeologic system of several hundred square kilometers. Satisfactory results were obtained for the simulation of nitrate leaching at the small scale. Major differences between the measured and simulated nitrate concentrations were observed in a regional aquifer, where the measured concentration does not spatially correlate and the larger spatial variability of the input data were averaged in the model.
LNAPL Thickness in Monitoring Wells Considering Hysteresis and Entrapment
Authors: Marinelli Fred , Durnford Deanna S. 
Published: August 2005

AbstractCase 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.
A Structured Approach for Calibrating Steady‐State Ground‐Water Flow Models
Authors: Yeh T.‐C. Jim , Mock Peter A. 
Published: August 2005

AbstractA structured approach for calibrating two‐dimensional, steady‐state ground‐water flow models is developed. The first step of the proposed approach is to replace the heterogeneous aquifer with an equivalent homogeneous one using the geometric mean of transmissivities. Then, boundary conditions are adjusted with the aid of a scatter gram to reduce bias of the simulated hydraulic head distribution of the equivalent homogeneous aquifer. After the bias is removed, the differences between the simulated mean hydraulic head and the observed hydraulic head, resulting from small‐scale heterogeneities, are then reduced by adjustment of local transmissivity values based on hydrological and geological information. The validity of the proposed procedure was tested for a hypothetical aquifer under idealized conditions and it was then applied to the Avra Valley in southern Arizona to demonstrate its utility in real world scenarios.
Multiphase Numerical Simulation of Air Sparging Performance
Authors: Lundegard Paul D. , Andersen Greg 
Published: August 2005

AbstractThe performance of air sparging systems, as measured by the predicted region of airflow, was investigated by conducting numerical simulations with a multiphase modeling program (TETRAD). The simulations employed standard two‐phase flow theory, and included pressure‐dependent calculations of the compressibility of water and air. Simulations tested the response of air sparging systems to variations in geological properties (intrinsic permeability and anisotropy of permeability) as well as different injection scenarios (depth, pressure, and rate of injection).Three stages of flow behavior are predicted following initiation of air injection. These are: (1) an initial transient period of growth in the lateral and vertical limits of airflow (expansion stage); (2) a second transient period of reduction in the lateral limits of airflow (collapse stage); and (3) a steady‐state stage, during which the system remains static as long as injection parameters do not change. In homogeneous media the geometry of the region of airflow changes from a teardrop‐or bell‐shaped configuration to a shape that is roughly conical during the expansion stage. During the collapse stage, air is preferentially diverted to established regions of high effective air permeability, and ground water resaturates the remainder of the original region of influence. For pilot testing it is important to realize that measurements of the lateral extent of airflow expansion and collapse stages can be misleading because they will differ from the limits established at steady‐state. The time required for a particular system to progress through the transient stages and establish steady‐state behavior can vary from hours to years, and is dependent on the permeability structure of the aquifer, injection depth, and injection rate. Under homogeneous conditions the maximum width of the region of airflow attained during the transient expansion stage was substantially greater than the width attained at steady‐state.The width of the steady‐state region of airflow is significantly affected by all the variables investigated, except injection depth, which appears to primarily influence the transient behavior. The simulations further show that the vertical permeability and anisotropy of the aquifer are very important variables, and warrant routine assessment during design of sparge systems. Simulation of heterogeneous media demonstrate that complex airflow patterns will occur as a result of air ponding beneath, and flow around, zones of low air permeability.
The Ratio Method of Estimating Water Resistivity and TDS from Resistivity Logs
Authors: Jorgensen Donald G. 
Published: August 2005

AbstractIt 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.
Application of Petroleum Geophysical Well Logging and Sampling Techniques for Evaluating Aquifer Characteristics
Authors: Temples Tom J. , Waddell Mike G. 
Published: August 2005

AbstractThe Hilton Head Island Test Well #1 was drilled to a depth of 3833 feet to evaluate the upper Cretaceous section as a potential ground‐water source for Hilton Head Island, South Carolina. The initial plan was to analyze continuous conventional cores. The interval to be analyzed extended from the top of the Eocene to the base of the Cretaceous (approximately 3500 feet). However, due to the high cost ($400,000), the decision was made to evaluate aquifer potential using advanced geophysical logs with sidewall cores for calibration.The logging suite consisted of a dual induction resistivity, spontaneous potential, compensated neutron, density log, gamma ray, spectral gamma, multipole array acoustic log, caliper, high resolution dipmeter, and a circumferential borehole imaging log. In addition to the wireline logs, 239 sidewall cores and 12 Formation Multi‐Test samples were obtained.The log, sidewall core, and FMT information were integrated into an interpretive package using computer generated logs and simple spreadsheets to calculate aquifer properties. Porosity, hydraulic conductivity, transmissivity, and lithologic data derived from this integrated analysis were then used to select screen zones. Water quality in relation to drinking water standards exceeded expectations. The information obtained from the integrated program allowed estimates to be made about the well's productivity without the expense of conventional coring, flow testing, and completion of the well.