bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Aquifer Interconnection Resulting from Underground Coal Gasification
Authors: Stone Randolph , Raber Ellen , Winslow Alan M. 
Published: March 2006

ABSTRACTAn investigation was conducted to evaluate the effects of aquifer interconnection caused by the collapse of cavities formed in coal seams by two small underground coal gasification experiments in the Powder River Basin, Wyoming. The main objective of the work was to assess the magnitude and extent of changes in the ground‐water flow patterns near the sites of the two experiments. Hydraulic head measurements in the three affected aquifers were used to calibrate a steady‐state ground‐water flow model of the interconnection zone at each site. Flow modeling and field measurements show that water from one or both of the upper aquifers enters the collapse rubble and flows down to the lowest aquifer (the gasified coal seam) where it flows away from the collapse zones. The hydraulic conductivity of the collapse rubble is less than that of the aquifers and provides only a very moderately permeable interconnection between them. A marked reduction in the hydraulic conductivity of the gasified coal seam near the collapse zones causes restriction of flow in the seam, away from them. Changes in hydraulic head and flow patterns caused by aquifer interconnection extend generally only 200–300 ft (60–90 m) away from the experiment sites. Flow in the uppermost aquifer at one of the sites may be influenced as far as 400 ft (122 m) away. At both experiment sites, aquifer interconnection allows water from the uppermost (sand) aquifer, which contains the poorest quality water of the three aquifers, to enter one or both of the underlying coal aquifers.
AN APPLICATION OF GEOSTATISTICS TO DETERMINE REGIONAL GROUND‐WATER FLOW IN THE SAN ANDRES FORMATION, TEXAS AND NEW MEXICOa
Authors: Orr Elizabeth D. , Dutton Alan R. 
Published: March 2006

Abstract. The construction of a contour map of hydraulic head for ground water in the San Andres Formation in west Texas and eastern New Mexico is problematic due to variability in quality and distribution of data. The direction of regional ground‐water flow can be inferred from raw data only in the northern part of the study area where reliable drill‐stem tests and water‐level measurements make up most of the data. In the southern area, where unreliable and highly variable drill‐stem tests comprise the bulk of the data, variogram analysis and kriging successfully remove the effects of high measurement error. This allows the regional trend to be seen. However, kriged block estimates cannot be computed for a critical region with sparse data in the northeastern part of the study area. The most complete potentiometric surface can be contoured from hybrid data: kriged block estimates from the southern region, and original head measurements in the northern region.
Heat Convection in Warm Springs Valley, Virginia
Authors: Severini Anthony P. , Huntley David 
Published: March 2006

ABSTRACTWarm Springs Valley, located in northwestern Virginia, is characterized by the discharge of springs from cavernous limestone at temperatures up to 40°C, although the measured geothermal gradient is a normal 10°C/km. The area is therefore hypothesized to be an important example of a situation where thermal convection is sufficient to produce high‐temperature surface waters. A finite‐difference numerical model was constructed to simulate the simultaneous transport of heat and fluid under combined forced and free convection conditions. This model was used to test the hypothesized heat flow system for Warm Springs Valley.The results of the testing show that, within the hydrogeological constraints found at Warm Springs Valley, convection with a normal geothermal gradient is capable of producing 40°C hot springs. The conditions required a zone of enhanced vertical hydraulic conductivity in the area of ground‐water discharge and a deep zone of enhanced horizontal hydraulic conductivity. The enhanced zones are consistent with the geology found in the basin.
A CONSTANT DISCHARGE DEVICE FOR AQUIFER TESTS ON LARGE‐DIAMETER WELLS
Authors: Athavale R. N. , Singh V. S. , Subrahmanyam K. 
Published: March 2006

Abstract. The discharge in pumping tests conducted on large‐diameter wells declines with the fall of water level. This violates the basic requirement of pumping tests that the discharge should remain constant. A simple device to keep the discharge constant has therefore been developed. This device is also useful in keeping the discharge much lower than the rated capacity of the farmer's pump, and thus in increasing the total test period.The discharge from the farmer's pump is released in a barrel having a V‐notch at the top and an arrangement for returning a part of the discharge to the well. The return flow is gradually reduced through a control valve, and thus the net outflow is kept constant.This device has been used for conducting pumping tests on several dug wells.
Assessment of the Effectiveness of Barriers for the Retardation of Pollutant Migration
Authors: Knox Robert C. 
Published: March 2006

ABSTRACTCurrently, one of the most popular methods of containing contaminated ground water is through use of subsurface impermeable barriers. These barriers can take one of three forms: slurry walls, grout curtains, or steel sheet piles. Successful operation of these barrier systems is dependent upon three basic criteria. First, the barrier must be truly impermeable and remain so over time even upon exposure to the contaminated ground water. Second, there must exist an underlying impermeable formation, at a reasonable depth, to which the barrier can be connected. Third, an adequate connection between the barrier and the underlying formation must be assured.This paper presents the results of the analysis of the movement of contaminated ground water under or through an imperfect barrier. The first phase of the analysis consists of the development of an analytical solution for the flow of ground water under a barrier and a simple numerical integration technique for developing concentration breakthrough curves. This simple solution algorithm was applied to the cases of variable recharge rates and lengths, variable depths of penetration of the barrier, and anisotropic soils. The second phase of the analysis involves applying a numerical solute transport model to analyze the performance of a barrier with and without the effects of hydrodynamic dispersion, and in the presence of a layered soil, and finally the performance of a fully penetrating but partially permeable barrier.
Aquifer Testing, Mathematical Modeling, and Regulatory Risk
Authors: Wang Ching‐Pi , Williams Roy E. 
Published: March 2006

ABSTRACTMathematical modeling founded on a strong field data base can be a valuable tool for the analysis of ground‐water contamination problems. The purposes of this paper are threefold: (1) we demonstrate the dilemma of a knowledgeable ground‐water quality regulator whose regulatory decision‐making process is confronted with the output of a mathematical model that is based on very limited field test data; (2) we demonstrate a method available to a knowledgeable regulator for assessing approximately a range of possible performances of a contaminated ground‐water recovery well field using a range of input data derived from a very limited data base; and (3) we present a strong case for presenting mathematical model outputs as ranges of values rather than as unique solutions. A range is determined by an examination of the level of sophistication of the field data base. Our experience with 12 field sites wherein ground‐water contamination has occurred has led us to conclude that field data are seldom, if ever, adequate to defend a unique solution from a mathematical model. Regulatory decisions generally can be reduced to minimization of risks based on the smallest range of model outputs that can be defended on the basis of the field data base. The more limited the field data base, the greater must be the range of defensible model outputs, and consequently, the greater the risk inherent in subsequent regulatory decisions. The knowledgeable regulator can assess the risks in the regulatory decision‐making process only if he is able to assess the extent to which the field data base for the mathematical model output reflects state‐of‐the‐art data collection and analysis technologies and methodologies. If an applicant for a permit or license submits a less than adequate data base and concomitantly a broad range of defensible model outputs, he inherently requests that the knowledgeable regulator accept a risk greater than that required if adequate aquifer testing techniques had been employed.
Ground‐Water Chemistry of Dibdiba Formation, North Kuwait
Authors: AI‐Ruwaih Fawzia 
Published: March 2006

ABSTRACTChemical studies have been carried out on a number of water wells from the Dibdiba Formation northeast of Kuwait. Water salinity of this formation ranges between 3,300 mg/l to 7,000 mg/l, increasing with depth. The water entrapped in Dibdiba Formation is mainly sodium chloride type which can be differentiated into three different groups according to the ranges of concentration of the main cations and anions. These groups are: (3331113) sodium chloride water type in which Cl > Na, group (3333113) sodium chloride water type in which Na > Cl. In both groups the sequence of dominant cations is Na > Ca > Mg. Group (3333111) sodium chloride water type has Na > Cl and the sequence of dominant cations is Na > Mg > Ca. Chemical ratios of Ca/Mg, Na/Cl, and C1/HCO3 were worked out for Dibdiba ground water. The ratio of Ca/Mg Dibdiba Formation ranges from 0.4 to 8.58, the ratio of Na/Cl ranges between 0.98 to 1.33, and the ratio of C1/HCO3 is 232.A plot of chemical analysis on a trilinear diagram shows that Dibdiba Formation ground‐water chemical properties are dominated by alkalies (Na > Ca) and strong acid (Cl > SO4). Water chemistry may reflect the history of the flow path, indicating regional flow as shown by increasing Na+, Cl‐, SO–4 and where Ca+, Mg+ achieve equilibrium.
Sources of Nitrate in Ground Water in a Sewered Housing Development, Central Long Island, New York
Authors: Flipse William J. , Katz Brian G. , Lindner Juli B. , Markel Richard 
Published: March 2006

ABSTRACTNitrate concentrations in ground water on Long Island, New York, have increased markedly in the last 30 years. A significant amount of this increase has been attributed to lawn and garden fertilizers in addition to cesspool and septic‐tank discharges. The increase in nitrate concentration is of particular concern in the central and eastern part of the island, where ground water is the sole source of drinking water.Ground‐water samples were collected from 14 wells screened near the water table in the sewered Twelve Pines housing development constructed in Medford, Suffolk County, in 1970. Samples were collected during 1972–79 and analyzed for total ammonium, organic nitrogen, and nitrate.Statistical analyses indicate that concentrations of nitrate‐nitrogen in water from 10 of the wells increased significantly during 1972–79; those in water from the other four wells did not.Nitrogen loads were estimated to be 2,300 kg/yr from fertilizers, less than 80 kg/yr from irrigation water, 200 kg/yr from animals, and less than 670 kg/yr from precipitation. Leakage from sewers was considered negligible.Nitrate‐nitrogen isotope ratios also suggest that the greatest source of nitrogen is from cultivation sources (either mineralized soil nitrogen or fertilizers) rather than human or animal wastes.
Bedrock Depth Estimates from Ground Magnetometer Profiles
Authors: Birch F. S. 
Published: March 2006

ABSTRACTBedrock depths can be calculated readily from ground magnetic profiles using either Werner deconvolution or Fourier spectral analysis. For crystalline basement rocks of New England and eastern Canada, a vertical dike is a useful magnetic source model. Formulae for these methods are presented along with some practical guidelines for implementing them.Six field examples from metamorphic and igneous areas in New Hampshire show that bedrock depths from spectral analysis agree well with estimates from seismic refraction, from wells and from outcrops. The Werner estimates are much more variable but commonly bracket the others. At several of these sites, measurements by other geophysical methods would be impractical, more expensive, or restricted to certain times of the year.
Land Subsidence Near Oil and Gas Fields, Houston, Texasa
Authors: Holzer Thomas L. , Bluntzer Robert L. 
Published: March 2006

ABSTRACTSubsidence profiles across 29 oil and gas fields in the 12,200‐km2 Houston, Texas, regional subsidence area, which is caused by decline of ground‐water level, suggest that the contribution of petroleum withdrawal to local land subsidence is small. Despite large volumes of petroleum production, subsidence at most fields was not increased by oil and gas withdrawal. Local increases of subsidence were detected at only six fields—Alco‐Mag, Chocolate Bayou, Goose Creek, Hastings, Mykawa, and South Houston. With the exception of the 1‐m subsidence from 1917 to 1925 at Goose Creek, differential subsidence across oil and gas fields was smaller by a factor of two or more than subsidence caused by aquifer compaction. At four fields—Barbers Hill, Cedar Bayou, Humble, and Pierce Junction—subsidence was substantially less than in the surrounding area. Except for Cedar Bayou, these fields are associated with shallow salt domes that partly occupy the aquifer system; for the three fields, subsidence during the periods of record came to less than half the subsidence in the surrounding area.In addition to land subsidence, faults with an aggregate length of more than 240 km (150 mi) have offset the land surface in historical time. Natural geologic deformation, ground‐water pumping, and petroleum withdrawal have all been considered as potential causes of the historical offset across these faults. The minor amount of localized land subsidence associated with oil and gas fields, however, suggests that petroleum withdrawal is not a major cause of the historical faulting, at least by a differential compaction mechanism.
Field and Laboratory Analyses of Water from the Columbia Aquifer in Eastern Maryland
Authors: Bachman L. Joseph 
Published: March 2006

ABSTRACTField and laboratory analyses of pH, alkalinity, and specific conductance from water samples collected from the Columbia aquifer on the Delmarva Peninsula in eastern Maryland were compared to determine if laboratory analyses could be used for making regional water‐quality interpretations.On the basis of 170 field pH and specific conductance measurements, 165 laboratory pH and specific conductance measurements, and 86 field and 135 laboratory alkalinity measurements, a significant difference at the 0.1‐percent level was found between laboratory and field analyses of pH and specific conductance. No significant difference was found between laboratory and field analyses of alkalinity. In most samples, laboratory pH was greater than field pH, laboratory specific conductance was less than field specific conductance, and laboratory alkalinity was equally likely to be less than, the same as, or greater than field alkalinity.Kruskal‐Wallis tests of field and laboratory data grouped by north‐south and east‐west coordinates and by land use indicate that the difference between field and laboratory values is usually not enough to affect the outcome of the statistical tests. Thus, laboratory measurements of these constituents may be adequate for making certain regional water‐quality interpretations, although they may result in errors if used for geochemical interpretations.
Anisotropy in the Ironton and Galesville Sandstones Near a Thermal‐Energy‐Storage Well, St. Paul, Minnesota
Authors: Miller R. T. 
Published: March 2006

ABSTRACTThe U.S. Geological Survey is studying the potential for storage of heated water in a sandstone aquifer in St. Paul, Minnesota. The efficiency of the aquifer to store thermal energy is related, in part, to the hydrogeologic characteristics of the aquifer. The movement of heat away from the injection well is directly related to the anisotropy. Aquifer tests were conducted to determine the anisotropy near the heated‐water injection well. The maximum and minimum values of transmissivity along the principal directions of the hydraulic conductivity tensors of the Ironton and Galesville Sandstones in St. Paul, Minnesota are approximately 1,090 and 480 feet squared per day. The storage coefficient is 4.5 × 10−5. These values represent the average of four determinations of nonsteady flow to a well in an idealized infinite anisotropic aquifer. Analysis of the values of transmissivity and storage coefficient for hypothetical changes in location of two of the monitoring wells where depth‐deviation surveys were not available indicates that computed transmissivities vary less than 5 percent and storage coefficients vary less than ±6 percent.
Aquifer Studies Using Flow Simulations
Authors: Puri S. 
Published: March 2006

ABSTRACTFlow simulations supplemented resource evaluation studies of the Lower Greensand aquifer. The annual recharge has hitherto been considered to be the resource available for development although a large confined storage exists. Pumping is principally in urban areas but recent monitoring suggests that the aquifer may have suffered excessive drawdowns. Therefore, simulation studies were carried out to refine the annual recharge estimate, to define the past effects of pumping and to obtain an indication of future trends. Catchment water balance indicates average annual recharge of 28 × 106 m3. One‐dimensional (ID) ground‐water flow simulation suggests that regional abstractions affect outcrop‐water levels. The study showed that the aquifer reached a new equilibrium with the current pumping regime. An improved insight to the aquifer has permitted the formulation of strategies for future resource development.
Hydrogeologic Characteristics of Shallow Glacial Drift Aquifers in Dissected Till Plains (North‐Central Missouri)
Authors: Sharp John M. 
Published: March 2006

ABSTRACTThe dissected till plains physiographic province contains extensive areas of pre‐Illinoian drift in Kansas, Nebraska, Iowa, and Missouri. The drift is typically a clay‐rich, oxidized, and highly weathered till. In many areas of Missouri, this shallow drift represents the only readily available aquifer suitable for domestic and small agricultural users. There are, however, only few published data on the region's hydrogeology. Water budget analyses indicate that approximately 30% of mean annual rainfall is discharged by stream flow and 70% by evapotranspiration. The shallow drift flow systems are best considered unconfined, steady‐state systems. Each watershed corresponds roughly to a local ground‐water system. There is, typically, little hydraulic connection between the shallow drift systems and underlying strata. The drift hydraulic conductivity varies from approximately 1011 m/sec (laboratory tests) to 10−6 to 10−7 m/sec (field tests) when permeable sand lenses or joints are intersected. Ground‐water discharge is concentrated in the immediate vicinity of stream channels, and recharge is concentrated on nearly horizontal hillslope summits. The ground water is generally potable (averaging 455 mg/1 total dissolved solids), but may be high in iron or polluted locally by organic wastes.
Ammonium Ion, Humic Materials, and Trihalomethane Potential in Northeastern Kansas Ground Waters
Authors: Denne Jane E. , Hathaway Lawrence R. , McCool S. Patrick 
Published: March 2006

ABSTRACTGlacial buried‐valley aquifers serve as primary sources of potable ground water in northeastern Kansas. A long known problem, however, is that a large percentage of well waters in this region exceed the U.S. Environmental Protection Agency (EPA) limits for nitrate (NO−3). A detailed study of the hydrogeology and water quality of the buried valleys has confirmed the nitrate problem and led to a recognition that some well waters with low ( 5 mg/l) NO−3 concentrations have anomalous ( 0.5 mg/l) ammonium ion (NH+4) levels, with an NH+4 range from <0.1 to 4.8 mg/l. The extractable NH+4 concentrations in related glacial sediments range up to approximately 75 mg/kg, and the amounts generally increase from an average of 2 mg/kg in the topsoil downward to bedrock. Migration of brines from subjacent Permian or Pennsylvanian bedrock into the unconsolidated sediments locally may cause desorption of NH+4 and an increase in its levels in the associated ground waters. Numerous test holes drilled in the study area showed a black scum on the fluid and cuttings, which may be from buried humic materials. Recently measured total organic carbon (TOC) contents of the ground waters confirm a significant level in some areas, with a range from 0.1 to 2.4 mg/l as C. Chlorination of water with dissolved organics may lead to production of halogenated compounds. Two public‐water‐supply well waters contained total trihalomethane (TTHM) levels close to the maximum contaminant level (MCL) of 100 /μg/l in chlorinated samples quenched after one week. The presence of NH+4 inhibits the formation of THMs, but it also can give rise to odor and taste problems in the finished water. The inhibition of THM formation by NH+4 is achieved by reactions which compete with the organics for combination with chlorine. These reactions make maintaining appropriate chlorine residuals difficult and also may lead to production of undesirable side products. Present efforts to evaluate the regional water‐quality problems are focused in Nemaha County, Kansas.
A Comparative Study of Specific Yield Determinations for a Shallow Sand Aquifer
Authors: Nwankwor G. I. , Cherry J. A. , Gillham R. W. 
Published: March 2006

ABSTRACTUsing the type‐curve methods of Boulton (1963) and Neuman (1972), and comparisons, at various times, of the cumulative volume of water pumped to the volume of the water‐table drawdown cone (volume‐balance method), values of specific yield were obtained from pumping test data from numerous piezometers in an unconfined sand aquifer. The long‐term value of specific yield for the aquifer was determined from measurements of the laboratory drainage curve of the aquifer material.The volume‐balance method gave specific yield values of 0.02, 0.05, 0.12, 0.20, 0.23, and 0.25 at times of 0.25, 0.66, 10, 26, 45, and 65 hours, respectively, indicating a gradual increase in specific yield and an asymptotic approach to the long‐term value of 0.30 determined from the laboratory method. The type‐curve methods provided values of 0.07 and 0.08, which correspond to the volume‐balance values at early times, but which are less than one‐third of the value obtained from the laboratory method and from the volume‐balance method applied at the end of the pumping test (2.7 days). The type‐curve procedures therefore provide unrealistically low values of specific yield for application to problems concerning the long‐term yield characteristics of the aquifer.The observed trend towards increasing values of specific yield with increasing duration of pumping, and the vertical hydraulic head profiles that were measured during the pumping test indicate that both delayed drainage from above the water table and downward hydraulic gradients in the saturated zone can be important hydraulic effects contributing to the delayed‐drawdown segment that is characteristic of time‐drawdown graphs for unconfined aquifers.