bluuebunny/crossref_metadata_2025 huggingface dataset:
Field‐Scale Investigation of Infiltration Into a Compacted Soil Liner
Authors: Panno Samuel V. , Herzog Beverly L. , Cartwright Keros , Rehfeldt Kenneth R. , Krapac Ivan G. , Hensel Bruce R.
Published: August 2005

Little field‐scale research has been done to evaluate the effectiveness of compacted soil barriers in retarding the movement of water and leachates. In response to this need, the Illinois State Geological Survey constructed and instrumented an experimental compacted soil liner. Infiltration of water into the liner has been monitored for two years. The objectives of this investigation were to determine whether a soil liner could be constructed to meet the U.S. EPA's requirement for a saturated hydraulic conductivity of less than or equal to 1.0×10−7 cm/s, to quantify the areal variability of the hydraulic properties of the liner, and to determine the transit time for water and tracers through the liner.

The liner measures 8 m×15 m×0.9 m and was designed and constructed to simulate compacted soil liners built at waste disposal facilities. The surface of the liner was flooded to form a pond on April 12, 1988. Since flooding, infiltration has been monitored with four large‐ring (LR) and 32 small‐ring (SR) infiltrometers, and a water‐balance (WB) method that accounted for total infiltration and evaporation. Ring‐infiltrometer and WB data were analyzed using cumulative‐infiltration curves to determine infiltration fluxes. The SR data are lognormally distributed, and the SR and LR data form two statistically distinct populations. Small‐ring data are nearly identical with WB data; because there is evidence of leakage in the LRs, the SR and WB data are considered more reliable.

Geostatistical analysis of the SR infiltration data revealed that the infiltration‐flux data were unstructured (random) at scales greater than 0.8 m. This analysis shows that it is possible to construct a compacted soil liner with a uniformly low saturated hydraulic conductivity, and that classical statistics should adequately estimate the mean infiltration flux of the liner and the associated uncertainty in that value.

Saturated hydraulic conductivity of the liner was estimated using Darcy's Law and the Green‐Ampt Approximation; the average values for these calculations, based on the first and second years of SR data, were 4.0×10−8 and 3.4×10−8 cm/s, respectively. Breakthrough of water at the liner's bottom is expected to occur approximately six years after the initial ponding of the liner.
Water Quality Response to the Partial Casing of a Well
Authors: Grundl Tim , Delwiche Jim
Published: August 2005

The computer model MODFLOW was used to model the water quality effects caused by casing off a contaminated layer in a well screened across multiple hydrogeologic units. Water produced from the contaminated layer is initially prevented from entering the well, but eventually a new concentration steady state is reached in which the contamination returns to the original level. The time needed for establishment of the new concentration steady state is primarily a function of aquifer conductivity and is essentially independent of aquitard conductivity. Under the modeled conditions, pressure steady state was reached in less than 100 days. Under the same conditions, concentration steady state was reached in less than 6000 days.
Results of Two Pumping Tests in Wisconsin Age Weathered Till in Iowa
Authors: Jones LaDon , Lemar Tracy , Tsai Chin‐Ta
Published: August 2005

Glacial till overlies many bedrock aquifers in Iowa, and a number of landfills and leaking underground storage tank sites are located in weathered and unweathered till. To investigate the potential for significant lateral ground‐water flow in Wisconsin age weathered loam till in Iowa, two 24‐hour pumping tests were performed in the shallow unconfined ground water present in the weathered till, a constant flowrate pumping test and a constant drawdown pumping test. The saturated thickness in the weathered till at the research site is less than 3 m, and choosing a constant flowrate sufficient for significant drawdown in the monitoring wells without dewatering the pumping well was difficult. In a low conductivity medium with a thin saturated thickness, the constant drawdown pumping test was found to be a more practical field technique. In the constant drawdown test, a chosen level of constant drawdown is maintained in the pumping well for the duration of pumping, and the flowrate decreases with time. The changing flowrate of the constant drawdown pumping test was approximated as a series of step decreases, and superposition of the Theis solution was used for simulation. Both types of pumping tests yielded similar parameter estimates for the weathered loam till region in Iowa, with an average bulk horizontal hydraulic conductivity of around 5×10‐4 cm/s and an average specific yield of about 0.032. Single well response (bail) tests produced comparable estimates for hydraulic conductivity, with a mean of 3×10‐4 cm/s. The results imply significant lateral ground‐water flow is possible, and the weathered till should not be considered a significant barrier to the lateral spread of shallow ground‐water contamination.
Straight‐Line Intercept Method in Aquifer Volume Calculations
Authors: Şen Zekâi , Sabtan Abdullah A.
Published: August 2005

Volume calculations in various aspects of ground‐water resources evaluation play a significant role. However, these calculations are made by different classical techniques, each of which employs the finite element concept. A common requirement in these techniques is the adaptation of a basic height—like contour interval. The accuracy of the estimated volume is influenced by the subjectivity on the part of the person doing the contouring on a specified contour interval. It is observed that there is a linear relationship between the contour interval and the estimated volume. The basic idea of this paper is to use a simple drawing procedure of a few points of different contour intervals versus the resulting volumes. A regression line is fitted through the scatter of these points. The best volume estimate corresponds to zero contour interval, i.e., the intercept of the straight line with the volume axis. This technique provides a common basis in that different researchers arrive at exactly the same conclusion for a given data set. The proposed method is verified by calculating the reservoir volume of a laboratory dam model with the known reservoir volume. It was found that the estimated volume was off by only 5% of the measured one. Further applications of the method are given for some observed data from the Floridan aquifer and a Black Hills dam reservoir.
Characterization of a Desert Aquitard— Hydrologic and Hydrochemical Considerations
Authors: Nativ Ronit , Nissim Ilan
Published: August 2005

The northern Negev desert has become a prime area for siting potentially contaminating facilities, including chemical industries and the Israeli national site for isolation and treatment of hazardous waste. The area is underlain by chalk formations having low matrix permeability. However, abundant fractures create preferential pathways for contaminant migration from the land surface to ground water in the chalk aquitard and, possibly, to adjacent aquifers. Geologic investigations preceding the construction of these industries assumed that the combination of the arid climate and low matrix permeability of the aquitard was sufficient to prevent any contaminant movement into its ground water. Solute transport through fractures and dissolution channels was never considered. However, contamination has been recently observed in the aquitard. Observations regarding the seasonal fluctuation of ground‐water levels, oxygen‐18 and deuterium composition, and the measurable tritium (0.3 to 15.9 TU) provide the basis for the following conclusions: (1) Ground‐water recharge by winter precipitation and runoff water occurs rapidly despite the regions's aridity and the low permeability of the overlying chalk matrix, (2) recharge occurs along fractures in all regions and is not restricted to hydrologically upgradient areas, and (3) recently recharged water is being mixed with the base flow of older water. Older ground water may flow along smaller, less developed fracture systems or through the porous matrix, whereas recent water probably moves along wider fractures or karst channels formed underneath ephemeral streams.
Relationships Between Saline Ground Water Soil, and Leaf Tissue Composition of the Phreatophyte Mezquite
Authors: García‐Carreño F. L. , Troyo‐Diéguez E. , Ochoa J. L.
Published: August 2005

The chemical and biochemical composition of leaf tissue from 24 mezquites (Prosopis articulata) was correlated with the ion content of soils and ground waters from six separate sites supporting plant growth. The peroxidase responses varied at different salinities; however, this enzyme activity decreased as the electrical conductivity of the ground water increased. Chlorophyll content of the leaves increased with the electrical conductivity (EC) of the well water, but the response was not statistically significant. The ion concentration (Ca++, Mg++, Na+, HCO3−, and Cl−), pH, and SAR (sodium adsorption ratio) in leaf tissue showed no correlation with their corresponding values for soil and ground water, confirming earlier reports on the ion‐exclusion mechanism of the mezquite root system. Likewise, low molecular weight metabolites such as glycerol, amino acids, and hexoses showed no correspondence with the salt content in ground waters. Of all the studied ions, chemical parameters, and biochemical compounds, EC in the ground water, leaves, and soil in the open field midway between mezquites, as well as peroxidase activity of foliar extracts showed the highest correlation with the salinity of ground water. The results of this research suggest that measuring EC and biochemical mezquite parameters may provide an alternative to drilling to evaluate ground‐water quality.
Unsaturated and Saturated Flow in Response to Pumping of an Unconfined Aquifer: Field Evidence of Delayed Drainage
Authors: Nwankwor G. I. , Gillham R. W. , van der Kamp G. , Akindunni F. F.
Published: August 2005

This paper revisits a long‐standing problem in aquifer analysis. In particular, it provides a physically consistent explanation of the characteristic time‐drawdown response of unconfined sand or gravel aquifers to pumping. It also provides a physical explanation for the low values of specific yield commonly obtained by type‐curve matching procedures. Tensiometers and piezometers distributed throughout the saturated thickness were used to monitor, in great detail, the hydraulic response of an unconfined sand aquifer to pumping. A gamma moisture gauge and core samples were also used to obtain measurements of water content in the region of the declining water table. The results showed the early period of time‐drawdown graphs to correspond with the period of increasing gradients. Excess storage of water was observed above the water table and was shown to be a necessary consequence of the vertical hydraulic gradients and the water‐content/pressurehead relationship for the aquifer material. The excess storage decreased during the period of decreasing vertical gradients. The period of delayed drawdown was shown to be the result of the decline in excess storage. Contrary to most of the recent literature, the results show that drainage processes above the water table have a very significant effect on the response of unconfined aquifers to pumping. The results indicate further that the normal methods of analyzing time‐drawdown curves for unconfined aquifers give excessively high values of storativity and values of specific yield that are unrealistically low.
Storage Coefficients and Vertical Hydraulic Conductivities in Aquitards Using Extensometer and Hydrograph Data
Authors: Cleveland Theodore G. , Bravo Rolando , Rogers Jerry R.
Published: August 2005

A method is presented to estimate elastic and inelastic specific storage and vertical hydraulic conductivities in aquitards in multilayered flow systems. Borehole extensometer records and ground‐water hydrographs from piezometers are used to construct plots of effective stress and deformation. Elastic and inelastic specific storage are estimated from the plots of effective stress and deformation during loading and unloading cycles. The elapsed loading time is estimated from the same plots and is used to calculate vertical hydraulic conductivity using Terzaghi's consolidation theory. The method is applied to three sites in Houston, Texas.
Relation Between Anisotropic Transmissivity and Azimuthal Resistivity Surveys in Shallow, Fractured, Carbonate Flow Systems
Authors: Ritzi Robert William , Andolsek Robert Henry
Published: August 2005

In an investigation of a near‐surface, fractured, carbonate ground‐water flow system, the axes of the apparent resistivity ellipse determined from an azimuthal resistivity survey were shown to coincide with both the ellipse of depression during an aquifer test, and the eigenvectors of the transmissivity tensor determined from the aquifer test analysis. Thus, for such relatively shallow, fractured flow regimes, azimuthal resistivity surveys may be a useful methodology for determining the principal directions of transmissivity prior to conducting anisotropic pumping tests, and thus aid in designing the emplacement of observation wells.
Comparison of Purge and Trap GC/MS and Purgeable Organic Chloride Analysis for Monitoring Volatile Chlorinated Hydrocarbons
Authors: Barber Larry B. , Michael Thurman E. , Takahashi Yoshi , Noriega Mary C.
Published: August 2005

A combined field and laboratory study was conducted to compare purge and trap gas chromatography/mass spectrometry (PT‐GC/MS) and purgeable organic chloride (POC1) analysis for measuring volatile chlorinated hydro‐carbons (VCH) in ground water. Distilled‐water spike and recovery experiments using 10 VCH indicate that at concentrations greater than 1 /ig/1 recovery is more than 80 percent for both methods with relative standard deviations of about 10 percent. Ground‐water samples were collected from a site on Cape Cod, Massachusetts, where a shallow unconfined aquifer has been contaminated by VCH, and were analyzed by both methods. Results for PT‐GC/MS and POC1 analysis of the ground‐water samples were not significantly different (alpha = 0.05, paired t‐test analysis) and indicated little bias between the two methods. Similar conclusions about concentrations and distributions of VCH in the ground‐water contamination plume were drawn from the two data sets. However, only PT‐GC/MS analysis identified the individual compounds present and determined their concentrations, which was necessary for toxicological and biogeochemical evaluation of the contaminated ground water. POC1 analysis was a complimentary method for use with PT‐GC/MS analysis for identifying samples with VCH concentrations below the detection limit or with high VCH concentrations that require dilution. Use of POC1 as a complimentary monitoring method for PT‐GC/MS can result in more efficient use of analytical resources.
Patterns and Rates of Ground‐Water Flow on Long Island, New York
Authors: Buxton Herbert T. , Modica Edward
Published: August 2005

Increased ground‐water contamination from human activities on Long Island has prompted studies to define the pattern and rate of ground‐water movement. A two‐dimensional, fine‐mesh, finite‐element model consisting of 11,969 nodes and 22,880 elements was constructed to represent ground‐water flow along a north‐south section through central Long Island. The model represents average hydrologic conditions within a corridor approximately 15 miles wide. The model solves discrete approximations of both the potential and stream functions. The resulting flownet depicts flow paths and defines the vertical distribution of flow within the section. Ground‐water flow rates decrease with depth. Sixty‐two percent of the water flows no deeper than the upper glacial (water‐table) aquifer, 38 percent enters the underlying Magothy aquifer, and only 3.1 percent enters the Lloyd aquifer. The limiting streamlines for flow to the Magothy and Lloyd aquifers indicate that aquifer recharge areas are narrow east‐west bands through the center of the island. The recharge area of the Magothy aquifer is only 5.4 miles wide; that of the Lloyd aquifer is less than 0.5 miles.

The distribution of ground‐water traveltime and a flownet are calculated from model results; both are useful in the investigation of contaminant transport or the chemical evolution of ground water within the flow system. A major discontinuity in traveltime occurs across the streamline which separates the flow subsystems of the two confined aquifers. Water that reaches the Lloyd aquifer attains traveltimes as high as 10,000 years, whereas water that has not penetrated deeper than the Magothy aquifer attains traveltimes of only 2,000 years. The finite‐element approach used in this study is particularly suited to ground‐water systems that have complex hydrostratigraphy and cross‐sectional symmetry.
Hydrogeologic Factors Affecting New Sinkhole Development in the Orlando Area, Florida
Authors: Wilson William L. , Beck Barry F.
Published: August 2005

Sinkhole development affects approximately 15 percent of the land area of the world. Development of new sinkholes is extremely site‐specific, but general associations between new sinkhole development and hydrogeologic factors can be established for areas with adequate historical records of sinkhole development. In the Orlando area, east‐central Florida, at least 140 sinkholes have developed between 1961 and 1986. The Orlando area is situated on a thickly mantled karst area, and sinkholes form by cover collapse or, less commonly, cover subsidence. On the average, 11 new sinkholes collapse each year. The mean diameter is 30.8 feet and the mean depth is 15.5 feet. Eighty‐five percent of the new sinkholes occur in high recharge areas (10 to 15 inches/year) on slightly elevated, sandy ridges. Few or no sinkholes occur in discharge areas where net downward erosion of surficial sediment is very unlikely. Forty‐two percent of all new sinkholes occur during April and May when ground‐water levels are usually at seasonal low stands. When the potentiometric surface declines 5 feet below its mode, then more sinkholes than expected per unit time begin to occur. When the potentiometric surface declines 10 feet below its mode, then more than 10 times as many sinkholes as expected per unit time begin to occur. Management of ground‐water withdrawal to avoid drawdowns in excess of 5 feet in sinkhole‐prone areas will minimize new sinkhole development induced by man.
Chromatographic Evidence for Nonlinear Partitioning of Aromatic Compounds Between Petroleum and Water
Authors: Wise William R. , Robinson George C. , Bedient Philip B.
Published: August 2005

Chromatographic analysis of published laboratory data suggests that the observed tailing behavior of aromatics (benzene, toluene, ethylbenzene, and xylene) being leached from a residual‐petroleum phase into a flushing‐water phase is explicable using nonlinear (specifically favorable) partitioning relations in the absence of kinetic limitations. This result raises questions regarding the legitimacy of deducing kinetic limitations of interphase transfer based upon the assumption of linear partitioning.
In Situ Surfactant Washing of Polychlorinated Biphenyls and Oils from a Contaminated Site
Authors: Abdul A. S. , Gibson T. L. , Ang Carolina C. , Smith Julie C. , Sobczynski R. E.
Published: August 2005

Over the past four years, we have been developing an in situ surfactant‐washing method to decontaminate soil systems. This study addresses another major step in that development: a field test of the surfactant‐washing method at a site contaminated with polychlorinated biphenyls (PCBs) and oils. A test plot, 10‐ft diameter by 5‐ft deep, was selected in an area of high levels of contaminataion. The study involved applying a surfactant solution on the plot to wash the site material and carry the leachate down to the depressed water table, where it was collected by pumping a recovery well installed through the center of the plot. The leachate pumped to the surface was biotreated to degrade the oils and surfactant, and the PCBs were removed from the leachate by an activated carbon system. Soil cores from the test plot indicated concentrations of up to 6,223 mg/kg PCBs and 67,000 mg/kg oils. The test plot initially contained about 15 kg of PCBs and 157 kg of oils. The hydraulic response of the test plot to washing was monitored by measuring the water levels in wells around the test plot and the fluid pressure and saturation through the plot. These real‐time data were used to adjust the surfactant‐application rate to minimize lateral spread of the surfactant and leachate and the pumping rate to capture all the leachate by the recovery well. The response of contaminant concentrations in the test plot to washing and the performance of the leachate‐treatment system were also monitored during the test by collecting and analyzing samples from the recovery well and from the treatment system. An on‐site laboratory was used for these analyses. During the 70 days of the washing test, 5,375 gallons of a 0.75% aqueous surfactant solution was applied on the test plot at an average rate of 77 gal/day. During the same period, 10,981 gallons of leachate were recovered at an average rate of 157 gal/day. A total of 1.6 kg of PCBs and 16.9 kg of oils (about 10% of the initial mass) was washed from the test plot during the test. Maximum concentrations of 65 mg/1 PCBs and 709 mg/1 oils were measured in leachate samples. The leachate was adequately treated before it was discharged. These test results indicate that in situ surfactant washing is a promising candidate for the remediation of contaminated soil systems.
Modeling Transport in Transient Ground‐Water Flow: An Unacknowledged Approximation
Authors: Goode Daniel J.
Published: August 2005

Abstract. During unsteady or transient ground‐water flow, the fluid mass per unit volume of aquifer changes as the potentiometric head changes, and solute transport is affected by this change in fluid storage. Three widely applied numerical models of two‐dimensional transport partially account for the effects of transient flow by removing terms corresponding to the fluid continuity equation from the transport equation, resulting in a simpler governing equation. However, fluid‐storage terms remaining in the transport equation that change during transient flow are, in certain cases, held constant in time in these models. For the case of increasing heads, this approximation, which is unacknowledged in these models’documentation, leads to transport velocities that are too high, and increased concentration at fluid and solute sources. If heads are dropping in time, computed transport velocities are too low. Using parameters that somewhat exaggerate the effects of this approximation, an example numerical simulation indicates solute travel time error of about 14 percent but only minor errors due to incorrect dilution volume. For horizontal flow and transport models that assume fluid density is constant, the product of porosity and aquifer thickness changes in time: initial porosity times initial thickness plus the change in head times the storage coefficient. This formula reduces to the saturated thickness in unconfined aquifers if porosity is assumed to be constant and equal to specific yield. The computational cost of this more accurate representation is insignificant and is easily incorporated in numerical models of solute transport.
SUPRPUMP: An Interactive Program for Well Test Analysis and Design
Authors: Bohling Geoffrey C. , McElwee Carl D.
Published: August 2005

Abstract. We have developed a program which aids in the design and analysis of pumping tests and slug tests. In design mode, the program emphasizes calculation and plotting of the sensitivities of drawdown (or head) to well function parameters. In analysis mode, the program can analyze a given set of experimental data. For pumping tests, the program allows multiple observation wells and multiple variable‐rate pumping wells. The program is written in a modular fashion, allowing easy addition of well functions to the currently existing library. An example based on a hypothetical pumping test illustrates the utility of sensitivity analysis for well test design.
Analysis of Unsteady Flow to a Large‐Diameter Well Experiencing Well Loss
Authors: Chachadi A. G. , Mishra G. C.
Published: August 2005

Unsteady flow to a large‐diameter well in a confined aquifer experiencing well loss has been analyzed by the discrete kernel approach. The well storage reduces the well loss component and the well storage is effective in the beginning of pumping. The inefficiency of a well is overcome by increasing the well radius. The variation of specific drawdown in a large‐diameter well experiencing well loss with pumping rate is nonlinear. The nondimensional time drawdown graph at a large‐diameter well, in which the well loss component follows the Jacob's equation, is not unique but dependent on pumping rate.
Confining Unit Effects on Water Quality in the New Jersey Coastal Plain
Authors: Pucci Amleto A. , Ehlke Ted A. , Owens James P.
Published: August 2005

Sediment and pore‐water samples from Tertiary and Cretaceous strata in the New Jersey Coastal Plain were collected from cores from Freehold Township, Monmouth County; Howell Township, Monmouth County; and from Clayton Township, Gloucester County. These strata form a multilayered aquifer system in which upper units are marine origin and lower units are predominantly nonmarine.

Concentrations of major constituents in pore‐water samples from confining units and aquifers were highly variable: calcium (1.7–660 mg/I), magnesium (0.3–140 mg/l), sulfate (1.52200 mg/l), and dissolved inorganic carbon (9–290 mg/l); with large differences between marine confining units and aquifers. Where the aquifers are unconfined and oxic, well waters in the Potomac‐Raritan‐Magothy aquifer system in the northern Coastal Plain have higher concentrations of nitrate, chloride, and dissolved oxygen. In areas where the aquifer system is confined and anoxic, there are higher concentrations of sulfate and bicarbonate. Differences in bicarbonate concentrations between two wells (12 and 67 mg/l) along a regional flow path can be caused by mixing of water in a nonmarine aquifer with leached sulfate‐enriched, marine confining‐unit water, and subsequent reduction of sulfate.

Bacterially mediated organic carbon oxidation, iron reduction, and sulfate reduction, and ion‐exchange reactions may explain constituent variations. Bacteriological assays of core sections from the Howell and Clayton Township coreholes showed viable sulfate‐reducing bacteria as deep as 558 feet below land surface. Sediments from a depth of 210 feet showed populations of sulfate‐reducing bacteria of 103–l06 organisms per gram of soil.
Combined Mathematical Model of Flow in an Aquifer‐Vertical Well System
Authors: Tarshish Michael
Published: August 2005

A mathematical model and calculation method were developed for steady‐state flow in a confined aquifer‐vertical well system without the usual assumption that the specific discharge in the radial direction to the screen is constant along its axis.

A vertical well is represented as a linear sink located along the well axis with nonuniform inflow (specific discharges) 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 (vertical) orifice. Substantial errors are avoided by the use of the proposed model in calculations of drawdown‐well discharge function and maximum specific discharge to the screen which influences sand pumping, incrustation, and corrosion processes.
The Occurrence and Effect of Sulfate Reduction and Sulfide Oxidation on Coastal Limestone Dissolution in Yucatan Cenotes
Authors: Stoessell Ronald K. , Moore Yolanda H. , Coke James G.
Published: August 2005

Dissolution of carbonate minerals in the coastal halocline is taking place in the karst terrain along the northeastern coast of the Yucatan Peninsula. The dissolution is being accelerated in cenotes (sinkholes) where sulfate reduction and oxidation of the produced sulfide is occurring.

Hydrogen‐sulfide concentrations ranged from 0.06 to 4 mmolal within the halocline in two sinkholes. Relative to concentrations expected by conservative mixing, fluids with high hydrogen‐sulfide concentrations were correlated with low sulfate concentrations, high alkalinities, low pH values, and heavy sulfur isotope values for sulfate. Hydrogen‐sulfide concentrations were less than those predicted from sulfate reduction, calculated from deficiencies in measured sulfate concentrations, indicating mobility and loss of aqueous sulfide.

Fluids with low hydrogen‐sulfide concentrations were correlated with very high calcium concentrations, high strontium and sulfate concentrations, slightly elevated alkalinities, low pH values, and sea‐water sulfur isotope values for sulfate. Gypsum dissolution is supported by the sulfur isotopes as the major process producing high sulfate concentrations. However, oxidation of aqueous sulfide to sulfuric acid, resulting in carbonate‐mineral dissolution is needed to explain the calcium concentrations, low pH values, and only slightly elevated alkalinities.

The halocline may trap hydrogen sulfide that has been stripped from the underlying anoxic salt water. The halocline can act as a stable, physical boundary, holding some of the hydrogen sulfide until it is oxidized back to sulfuric acid through interaction with the overlying, oxygenated fresh water or through the activity of sulfide‐oxidizing bacteria.
Database Management System for a Ground‐Water Regime
Authors: Jin Menggui , Wu Beiyi , Zhang Binhai
Published: August 2005

This paper presents the structure and function of a database system for a ground‐water regime in the case study of Geermu, Qinghai Province, northwestern China. This database system was constructed by combining the Chinese dBASE3 with other computer languages, such as BASIC, FORTRAN, etc. It systematically organizes the hydrogeological data and information, and automatically stores, queries, and manipulates ground‐water observation and related data, including an analysis and forecast of the ground‐water regime and the generation of various report forms and related graphics or maps.
Retardation of Tritium and Cesium in Brine‐Saturated Mudstone, Halite, and Carbonate Porous Media
Authors: Voudrias Evangelos A. , Means Jeffrey L. , Kittel Jeffrey
Published: August 2005

Batch and column sorption/desorption experiments were conducted to quantify the retardation of tritium and cesium in brine‐saturated mudstone, halite, and carbonate rocks from Palo Duro Basin, Texas, one of the three sites originally nominated by the U.S. Department of Energy for construction of a civilian nuclear waste repository. Retardation factors (R) were determined using six different methods, including batch sorption equilibrium, fitting of two transport models, breakthrough area integration, and pore volume displacement at C/C0= 0.5, for both the sorption and desorption parts of the breakthrough curves. The breakthrough area integration method resulted in R values consistently lower than the other methods, which were in reasonable agreement. The data indicated very small retardation for cesium in all the media, except mudstone, which exhibited moderate retardation (R < 3.5). It was shown that the small extent of cesium retardation was most possibly caused by the strong competition for sorption sites of the components of the saturated brine, which were several orders of magnitude higher in concentration than cesium. Tritium breakthrough curves for all media tested were accurately simulated by the local equilibrium advection‐dispersion model (model I). With the exception of mudstone, cesium breakthrough curves were also adequately simulated by model I. The cesium breakthrough curve for mudstone exhibited considerable tailing on the desorption side of the curve, which was best described by the two‐site kinetic sorption model II. This was attributed to chemical nonequilibrium (two types of sorption sites). Predicted breakthrough curves for cesium using model I were in good to reasonable agreement with measured breakthrough curves.
Simulating Errors in Statistical Tests of Leachate‐lmpacted Ground‐Water Quality
Authors: Milke M. W. , Huitric R. L.
Published: August 2005

Data on 13 median leachate qualities at 56 landfills show a multivariate character, A simulation technique is used to include this multivariate character of leachate quality in assessing false negative error rates for statistical tests of ground‐water quality. Although the technique makes gross simplifying assumptions regarding the conservative mixing of leachate and ground water, the technique is more appropriate than traditional statistical methods for simulating false negative error rates that neglect correlations among water quality parameters. The technique is applied to the simple case of a control chart, intrawell statistical test of ground‐water contamination. Simulation results show that both the false positive and false negative errors of statistical tests can be reduced when tests include more parameters and a higher confidence level; thus, the technique can provide a “win‐win” situation for regulators and the regulated.
Air Sparging in Gate Wells in Cutoff Walls and Trenches for Control of Plumes of Volatile Organic Compounds (VOCs)
Authors: Pankow James F. , Johnson Richard L. , Cherry John A.
Published: August 2005

Volatile organic compounds (VOCs) can be stripped from ground water by sparging air into water in wells or in trenches. This well/trench sparging (“WTS”) can remove VOCs from plumes of contaminated ground water as that water passes across the sparge zone. With sparging in wells, cutoff walls will be needed to force the contaminated water through the “gate” wells. With in situ sparging (“ISS”), air is sparged directly into a contaminated aquifer. ISS may be useful in treating local zones of high contamination, but WTS is better suited for treating large plumes of contaminated ground water. Interest in sparging methods is growing because: (1) they do not remove water from the subsurface, and so difficult disposal issues are avoided and an increasingly valuable water resource is not depleted; and (2) the Darcy velocity v in many systems is low, and so only a relatively small volume of water must be treated per unit time.

The theoretical fractional efficiency of WTS is given by E = S/(l + S). The parameter S is named here as the “dimensionless sparge number,” with S = HRg/(RTyzv) where H (atm‐m3/mol) = Henry's Law constant for the compound of interest; Rg (m3/s, at 1 atm pressure) = gas sparging rate; R = gas constant (= 8.2 X 10˜5 m3‐atm/mol‐deg); T = temperature (K); yz (m2) = cross‐sectional area producing the water which is passing into the sparging zone; and v = Darcy velocity (m/s). E increases as S increases. E increases as H increases because the volatility of a compound goes up as its H increases. Plots for E in WTS are given vs. S as well as vs. some of the variables making up S.

Well/trench sparging (WTS) has the potential to become a useful treatment method for removing VOCs from contaminated ground‐water plumes. It is suited for use with most of the solvents and petroleum products which have caused extensive ground‐water contamination. The theory of the method is simple, and the theoretical removal efficiencies are predictable as well as adjustable.
Analytical Model for Estimation of Steady‐State Capture Zones of Pumping Wells in Confined and Unconfined Aquifers
Authors: Grubb Stuart
Published: August 2005

The analysis of capture zones of pumping wells is useful for designing pumping systems and wellhead protection programs. Using discharge potentials, equations are derived that can be applied to confined, unconfined, or combined confined and unconfined aquifers. The transient equations are transcendental and cannot be solved explicitly. However, infinite‐time (steady‐state) equations are presented which can be solved. They define an area in which, theoretically, all the water in the aquifer will eventually reach the pumping well, although the equations do not consider the effects of hydrodynamic dispersion. Equations for calculating the stagnation point, upgradient divide, and dividing streamline within the aquifer and an example problem are presented.
Testing Fournier's Method for Finding Water Table from Self‐Potential
Authors: Birch F. S.
Published: August 2005

Fournier's approximate method for relating self‐potential anomalies to water‐table elevation is satisfactory for five of the six sites where it has been tested in New Hampshire. At these sites water‐table elevations were determined independently from observation of surface‐water bodies and by seismic refraction at the times of the self‐potential surveys.

At three sites on drumlins formed of glacial till, the apparent coupling coefficients range from 0.95 to 4 mV/m whereas two surveys on sand and gravel deltas yield apparent coupling coefficients of −16 and −17 mV/m. At a third delta the apparent coupling coefficient suggests that the water table is in an underlying till rather than in the deltaic deposits.

Modeling of self‐potential anomalies using Fournier's method may permit isolation of anomalies caused by sources other than ground‐water flow as well as location of significant geological inhomogeneities. Because of nonuniqueness it is not possible to determine water‐table elevations from self‐potential surveys alone.
Multivariate Geostatistïcal Analysis of Ground‐Water Contamination: A Case History
Authors: Istok Jonathan D. , Smyth Jeffrey D. , Flint Alan L.
Published: August 2005

A case history is presented for the application of multivariate geostatistical methods to the problem of estimating pesticide concentrations in ground water from measured concentrations of nitrate and pesticide, when pesticide is under‐sampled. The shallow, poorly confined, sand and gravel aquifer underlying the lower Malheur River basin near Ontario, Oregon is contaminated by nitrate and metabolites of the herbicide Dacthal (dimethyl tetrachloroterephthalate) or DCPA. The results of extensive ground‐water sampling indicate that a significant positive correlation exists between measured nitrate and DCPA concentrations in the aquifer. This suggests that future sampling should include a large number of the less‐expensive nitrate analyses, and these data should be used to support the interpretation of fewer, more expensive DCPA analyses. Sample variograms were computed for nitrate and DCPA concentrations and were fit with isotropic, spherical variogram models with correlation ranges of 4 km. Incorporating measured nitrate concentrations in the DCPA estimates obtained by cokriging reduced estimation variances from 14 to 34%. A simple economic analysis demonstrated that for this aquifer, acquiring additional nitrate samples is a cost‐effective way to reduce estimation variances for DCPA.
Double Porosity Well Testing in the Fractured Carbonate Rocks of the Ozarks
Authors: McConnell Cary L.
Published: August 2005

The objective of this research was to determine a well test model which could be used for determining the hydraulic parameters of T and S in the complex fractured carbonates of the Ozarks of southern Missouri. Municipal water well testing in the Ozarks is performed on deep wells completed in confined fractured carbonate aquifers where all of the flow to the wellbore is through the fractures but most of the storage is in the matrix blocks. Observation wells are not used because of cost. The methodology uses double porosity well test analysis including the inner boundary conditions of skin and wellbore storage. Using this method, S and T are obtained as well as the storativity ratio, ω, and the block to fracture flow parameter λ. Because wellbore storage, skin, and storativity are interrelated, a computer simulation to find the final S was necessary. Derivative curve analysis provided a constraint in determining the correctness of the simulation results. Failure to use this well test method proved to result in storativities which are much too large. An example is presented.
Reservoir Characterization Applying High‐Resolution Seismic Profiling, Rabis Creek, Denmark
Authors: Olsen Henrik , Ploug Garsten , Nielsen Uffe , Sorensen Kurt
Published: August 2005

Onshore reflection seismics have been used to characterize the geometry and lithology of ground‐water reservoirs. The study was carried out as a seismic sequence and facies analysis along Rabis Creek in western Denmark. A1350 m long seismic section was produced on a presumed homogeneous outwash sand plain. High resolution data to a depth of 160 m (200 msec two‐way time) were obtained along most of this section, and reflections from more than 400 m in depth were obtained locally. The seismic data have been correlated with electrical resistivity logs. The reservoir is, in contrast to the expectations, highly heterogeneous, composed of three distinguishable seismic sequences of unconsolidated sediments. Layers down to 1.5 m thick were recognized in the seismic data. The study shows that onshore reflection seismics provide a unique possibility of 2‐D reservoir scale characterization of geological structures. Combined with seismic facies and sequence analysis, seismic profiling forms a strong hydrogeological tool that may supplement traditional boring and logging methods.
Assessing Public Exposure to Pesticide‐Contaminated Ground Water
Authors: Kastenberg William E. , Yeh H. C.
Published: August 2005

Long‐term exposure assessments regarding four commonly used pesticides are presented in this paper. Alachlor, aldicarb, lindane, and parathion have been detected in ground‐water monitoring wells. A multimedia transport model is employed to predict the long‐term fate of these chemicals in the environment. Concentrations in each environmental compartment are calculated and used to determine the dominant exposure pathways and hence dose rate.

Aldicarb is shown to move from the upper soil compartment, through the lower soil compartment, and accumulate at a rate which is several orders of magnitude greater than the other pesticides. Lindane moves faster to the biota compartment than the other pesticides. The dominant exposure pathway for aldicarb and alachlor is drinking water ingestion for both adults and children. For lindane and parathion, the dominant exposure pathway is biota ingestion for children and fish ingestion for adults. The methods presented in this paper can be used as screening tools for designing remediation, mitigation, or interdiction measures and can serve as a basis for evaluating risk management strategies.
Development of Transparent Porous Media with Permeabilities and Porosities Comparable to Soils, Aquifers, and Petroleum Reservoirs
Authors: Mannheimer R. J. , Oswald C. J.
Published: August 2005

Model porous media made from glass beads and matched refractive index liquids have made it possible to visualize displacement processes in heterogeneous porous media and to obtain in situ concentration profiles to validate flow codes. However, glass beads produce porous media that are translucent rather than transparent. Thus, these models cannot be used to observe 3‐D effects. Furthermore, the current necessity of using relatively large glass beads results in permeabilities that are several orders of magnitude larger than natural porous media. This paper describes a new approach for making transparent porous media by consolidating suspensions of amorphous silica in matched refractive index liquids. The resulting porous media can be made to have porosities and permeabilities comparable to a very wide range of soils and reservoir materials by the appropriate choice of particle size and/or consolidation pressure. Because these porous media are truly transparent and not merely translucent, relatively simple optical techniques can be used to map variations in porosity and to measure 3‐D flow processes.
Phase Diagrams to Optimize Surfactant Solutions for Oil and DNAPL Recovery in Aquifers
Authors: Martel Richard , Gelinas Pierre J. , Desnoyers Jacques E. , Masson Anne
Published: August 2005

Phase diagrams can be used to optimize the composition of surfactant solutions (cosurfactant/surfactant) designed for the recovery of DNAPLs at residual saturation in aquifer formations. The study also shows that the combination of cosurfactant (alcohol) and surfactant is more effective than the use of alcohols or surfactants separately. The suggested approach is based on miscible oil displacement using surfactant solutions at high concentrations. Most of the recent projects using surfactants for aquifer cleanup use low‐concentration solutions that promote immiscible oil displacement. The goal of the present study is to demonstrate the potential of optimized surfactant solutions to restore oil and DNAPL‐contaminated sites such as the one in Ville Mercier, Quebec (site contaminated with a mixture of petroleum and chlorinated solvents). The results show that alcohol/surfactant systems can be used to solubilize chlorinated solvents (TCE, PCE) and light oils (gasoline, diesel). For the dissolution of heavy and viscous oils (motor oil, ATF, creosote, Ville Mercier oil), an organic solvent must be added to the alcohol/surfactant system.
DERIV: A Computer Program for Calculating Pressure Derivatives for Use in Hydraulic Test Analysis
Authors: Spane F. A. , Wurstner S. K.
Published: August 2005

Hydrologie test analysis based on the derivative of pressure (i.e., rate of pressure change) with respect to the natural logarithm of time has been shown to significantly improve the diagnostic and quantitative analysis of slug and constant‐rate pumping tests. The improvement in test analysis is attributed to the sensitivity of the derivative to small variations in the pressure change that occurs during testing, which would otherwise be less obvious with standard pressure change versus time analysis. The sensitivity of the pressure derivative to pressure change facilitates its use in identifying the effects of wellbore storage, boundaries, and establishment of radial flow conditions on the test.

DERIV is a program for converting slug and pumping test data and associated type curves to derivative format. The program has features that permit the smoothing of noisy test data, accounts for pressure derivative end‐effects, and can be used to convert slug test data to equivalent pumping test responses. Test examples that demonstrate the use of pressure derivatives also are provided.
Estimation of Ground‐Water Mounding Beneath Septic Drain Fields
Authors: Finnemore E. John
Published: August 2005

Localized ground‐water mounding beneath larger on‐site sewage disposal fields (septic drain fields) can reduce and even eliminate the waste‐water treatment that occurs in the unsaturated soil zone. Such mounding was previously predicted for longer times by a procedure of uncertain accuracy and having a number of limitations. In this paper, a new procedure is developed on a stronger theoretical basis. The governing equation may be solved by four different methods. The new procedure considerably extends the time range of applicability, and no longer restricts the proportions of the rectangular disposal field. Errors in the previous methods approached 20% in some cases. Comparisons of different methods to reduce mound heights where they are critical indicate that the most effective method is to subdivide the disposal field into separated subareas.