bluuebunny/crossref_metadata_2025_split huggingface dataset:
Handheld Double Packer Equipment for Water Sampling and Hydraulic Measurements in Deep Boreholes
Authors: Laaksoharju Marcus , Ahonen Lasse , Blomqvist Runar 
Published: February 2007

AbstractThe need 10 characterize deep and shallow bedrock hydrogeologic conditions in remote terrain encouraged the development of an inexpensive, last, and easily transporrable double packer sampler. The principal objective was to combine water sampling and hydraulic measurement with the same equipment. Unconventional construction that does not create any large hydraulic pressure differences in the equipment allows light and inexpensive standard materials and components to be used. The low cost, lightweight equipment can thus be operated by a single person.The equipment is based on the principle of using soft, hydraulically expandable packers that isolate the required section of the borehole. The inflation and deflation of the packers is controlled by a single tube, through which the water sample is also withdrawn. The uppermost part of the tube branches into two tubes; the pumping action is generated by cyclic pressure pulses applied to one of these tubes.The equipment has mainly been used in narrow 1,8‐inch (46 mm) diameter boreholes down to a depth of about 3280 feet (1000 m); versions capable of operating in larger boreholes and with higher pump capacity have also been constructed. At one sampling site, the chemical composition of water from an isolated fracture zone was compared with open hole water at the same depth. The water from the fracture had a different chemical composition compared with the mixed water sample from the open hole. To collect representative ground water samples, double packers and long pumping limes are required.The equipment characterizes both the hydraulically conductive bedrock structures and the chemical compositions of bedrock ground water. Through comparison to K‐values and chemical constituents in other portions of the borehole, the collected data can be used to estimate transport pathways, aquifer yield, travel times, and ground water evolution. The range of hydraulic conductivity measured with the equipment in association with this research was 10‐10 to 10‐7 m/s.
Remediation of Dissolved BTEX Through Surface Application: A Prototype Field Investigation
Authors: O'Leary Katherine E. , Barker James F. , Gillham Robert W. 
Published: February 2007

AbstractThe feasibility of surface application for remediating monoaromatic hydrocarbons (benzene, toluene, ethylbenzene, and xylenes — termed BTEX as a croup) dissolved in ground water under field conditions was investigated at a site within Canadian Forces Base. Borden. Ontario. The surface area was 25 m2 and underlain by 3 to 3.5 m of unsaturated sands soil. For periods of at least 216 hours, between 43 and 72 cm/d of water containing BTEX at concentrations that averaged between 8 and 11 mg/L were continuously applied by drip irrigation. Nitrogen was added to the soil as a nutrient for the final third of the investigation.Before the applied water reached the water table. BTEX mass losses ranged from of to essentially KM) percent. Less than 6 percent of the BTEX mass losses could be attributed to volatilization from the unsaturated soil. The remaining BTEX mass losses were attributed to biodegradation, mostly in the top 50 cm of the soil, which contained more inorganic nitrogen and organic carbon than the deeper soil. Biodegradation rates increased with applied concentration, nitrogen addition, and exposure to BTEX. Benzene concentrations in ground water attained compliance with Canadian and American drinking water standards only after nitrogen application.
The Electromagnetic Borehole Flowmeter: Description and Application
Authors: Young Steven C. , Pearson Hubert S. 
Published: February 2007

AbstractBorehole flowmeters are downhole tools that measure axial flow in a well or borehole. Desirable flowmeter characteristics include low detection limit, a wide range of operation, accuracy, durability, reliable performance, and a small diameter and length. The recently developed electromagnetic (F.M) flowmeter has these trails. The first portion of this paper presents the MM flowmeter design, provides laboratory calibration data, and compares the performance characteristics of MM flowmeters 10 those of impeller and thermal pulse flowmeters. The second portion of the paper discusses applications of the MM flowmeter.
Feasibility Study of In‐Well Vapor Stripping Using Airlift Pumping
Authors: Gvirtzman Haim , Gonen Ori 
Published: February 2007

AbstractThis study tests the feasibility of an aquifer remediation concept proposed by Gvirtzman and Gorelick (1992) that involves the removal of volatile organic compounds (VOCs) dissolved in ground water. The principal is 10 inject air into a well, creating airlift pumping, which is used as a means of in‐well vapor stripping. The partially treated water is diverted away from the well and infiltrates back to the water table, thus allowing remediation of a larger aquifer volume.A remediation well prototype, constructed in a laboratory aquifer model, was used to demonstrate the processes involved. The removal rates of trichloroethylene, toluene, and chloroform were monitored using eight triple‐level observation wells. The continuous decrease of VOC concentrations during the short‐term experiment has yielded macroscopic evidence that the process offers some promise. It was found that the flow field in the saturated zone. involving the continuous water circulation between the pumping well and the recharging area, caused temporal and spatial variation in remediation efficiency.
Estimating the Horizontal Gradient in Heterogeneous, Unconfined Aquifers: Comparison of Three‐Point Schemes
Authors: Cole Bryce E. , Silliman Stephen E. 
Published: February 2007

AbstractAt least two approaches may be used to estimate the horizontal components of the hydraulic gradient based on measured heads from three observation points. First, the gradient may be estimated by passing a plane through the measured heads (h‐method). Second, if the elevation of the base of the aquifer is known to be spatially constant, an estimate of the gradient may be obtained using the squares of the measured heads (h2‐ method). In the present study, these methods are examined in application to a heterogeneous system. Using Monte Carlo analysis, we demonstrate that the magnitude of the gradient estimated via the h‐method involved significant bias, which increased when the distance separating the wells increased. In contrast, bias in the estimated magnitude of the gradient based on the h2‐method decreased with increasing separation among the wells. Estimation variances for both the magnitude and orientation of the gradient also decreased with separation distance. The variance in the orientation was observed to remain relatively high, however, even at relatively large separations among the wells (e.g., 10 integral scales). These results are Interpreted as implying that the best estimate of the gradient for steady flow in an unconfined aquifer is derived from the h2‐ method with the wells separated by significant distances. These results also demonstrate the uncertainty inherent in estimating the gradient based on limited field data.
Using Vertical Circulation Wells for Partitioning Tracer Tests and Remediation of DNAPLs
Authors: Chen L. , Knox R. C. 
Published: February 2007

AbstractTwo different vertical circulation well (VCW) systems (Type A and Type B) were used to detect and subsequently remove tetrachloro‐ethylene (PCE) spilled in a three‐dimensional sand tank. The Type A system has one injection interval and one extraction interval. The Type B system has two injection intervals separated by an intermediate extraction interval. PCE was detected through partitioning tracer tests using ethanol and 2,2‐dimethyl‐3‐pentanol as the non‐partitioning and partitioning tracers, respectively. The concentration breakthrough curves for the tracers exhibited significant chromatographic separation due to partitioning of the 2,2‐dimethyl‐3‐pentanol into the PCE. Because of the unique streamline distribution generated by the VCW systems, injected solutions did not sweep through the entire contaminated pore volume, which resulted in less than 100 percent detection of the spilled PCE. However, multiple tests along the borehole of the well were used to delineate the vertical profile of PCE residual saturation. Three food‐ grade surfactants were used to remediate the spilled PCE. For surfactant‐enhanced solubilization, the PCE effluent concentrations for the VCW systems were approximately eight (Type A) and 13 (Type B) times higher than that of a pump‐and‐treat system using water alone. The VCW effluent concentrations are actually diluted because the extraction rate exceeds the injection rate. Removing the effects of dilution occurring in the borehole, the concentrations leaving the treatment zones around the VCW are found to be 32 (Type A) and 52 (Type B) times higher than using water alone. During surfactant‐enhanced mobilization, the Type A VCW system was unable to capture all of the PCE‐surfactant microemulsion as it migrated downward. The uncaptured PCE could have negative impacts on ground water quality due to its increased solubility. The Type B system was found to be hydraulically more efficient than the Type A system both in terms of overall PCE removal and capturing mobilized microemulsions.
Diffusion Samplers as an Inexpensive Approach to Monitoring VOCs in Ground Water
Authors: Vroblesky Don A. , Hyde W. Thomas 
Published: February 2007

AbstractDiffusion samplers installed in observation wells were found to be capable of yielding polyethylene to transmit other volatile compounds, such as benzene and toluene, indicates that the samplers can be used for a variety of volatile organic compounds. In wells at the study area, the volatile organic compound concentrations in water samples obtained using the samplers without prior purging were similar to concentrations in water samples obtained from the respective wells using traditional purging and sampling approaches. The low cost associated with this approach makes it a viable option for monitoring large observation‐well networks for volatile organic compounds.
Analysis of Nitrate‐Nitrogen Movement Near High‐Capacity Irrigation Wells
Authors: Chen Xunhong , Ayers Jerry F. , Gosselin David C. 
Published: February 2007

AbstractAGalerkin finite‐element model coupled with a particle tracking routine was developed to analyze the flow and transport dynamics near a high‐capacity irrigation well. The model was used to compute the head distribution around the pumping well, to determine the area of influence, and to define ground water flowlines during short‐term pumping periods typical of those used to collect water quality samples from high‐capacity wells. In addition to hypothetical example results, the model was used to qualitatively analyze data obtained from pump‐and‐sample experiments conducted in an unconfined alluvial aquifer within the Platte River valley of south‐central Nebraska where nitrate‐nitrogen (NO3‐N) contamination is prevalent.Simulation results of both the hypothetical and field cases suggest that short‐term pumping events, impact a limited volume of aquifer. The area of influence and flowlines are affected by aquifer anisotropy, pumping rate, and well construction characteristics). Ground water above or below the screened intervals does not enter a partially penetrating well in anisotropic aquifers. In aquifers where NO3‐N concentration varies vertically and horizontally, waler quality samples from an irrigation, or other high‐capacity, well provide only limited information about ground water contamination. A numerical model is thus recommended for calculating the area of influence and determining flowlines around high‐capacity wells so that information derived from water quality samples collected at the wellhead can be better interpreted.
Field Observations of Tidal and Seasonal Variations in Ground Water Discharge to Tidal Estuarine Surface Water
Authors: Robinson Michael , Gallagher Dan , Reay William 
Published: February 2007

AbstractA field study of the tidal and seasonal variations in upland, shoreline, and nearshore hydrological processes associated with ground water discharge from the unconfined Columbia Aquifer was conducted. The study, performed along a tidal subestuary of the Chesapeake Bay, involved measurement of water table elevation, ground water discharge, potentiometric had differentials across the sediment‐water interface, and ground water salinity. Fresh ground water discharge rates calculated from the measured water table gradient using the Dupuit assumptions varied from 6.1 X 10‐3 to 3.8 X 10‐2 m3/day per m of shoreline during the study period, May 1994 to September 1995. Variation in discharge rates were associated with seasonal recharge patterns.Integrated total discharge rates based on seepage meter measurements decreased with distance offshore from a maximum of 3.3 L/m2 hr at the shoreline to 0.5 L/m2hr at 30 m offshore Maximum instantaneous discharge rates calculated from potentiometric head differentials were much higher than integrated discharge rates and ranged from 19.2 L/m2hr at 4.8 m offshore to 0.8 L/m2hr at 19.8 m offshore. Instantaneous discharge rates were inversely correlated to tidal elevation and fluctuated rapidly decreasing from 19.2 L/m2hr to 2.5 L/m2 hr during a several‐hour period.Seasonal variations in salinity patterns within the transition zone of the Columbia Aquifer were observed and indicated a dependence on fresh ground water discharge and surface water salinity/density gradient was observed within the transition zone. The gradient was created, in part, by the infiltration of surface water into tidally exposed sediments. Seasonal periods of low fresh ground water discharge and high surface water salinity were associate with intrusion of the surficial mixing zone landward while seasonal periods of high fresh ground water discharge and low surface water salinity were associated with a seaward movement of the mixing zone.
In Situ Vertical Circulation Column: Containment System for Small‐Scale DNAPL Field Experiments
Authors: Sorel Dominique , Cherry John A. , Lesage Suzanne 
Published: February 2007

AbstractThe in situ vertical circulation column (ISVCC) is a cylindrical containment system consisting of an instrumented steel cylinder used for experimental ground water studies in sandy aquifers. Vertical flow is imposed inside the ISVCC. Although vertical wells are an option, the ISVCC installed in the Borden Aquifer is instrumented with horizontal wells and monitoring ports to avoid creating vertical preferential flow paths. The cylinder was driven downward into the aquifer using a small backhoe equipped with a vibrating plate. The ISVCC penetrates the 2.3‐m‐thic sand aquifer and is keyed 20 cm into the underlying clay aquitard. The cylinder was installed inside a 2 m X 2 m steel sheet pile enclosure so that the enclosed segment of aquifer could be conveniently dewatered and then excavated to allow installation of the horizontal wells. The dispersivity of the column was comparable to literature values for long sand‐packed laboratory columns.Pure phase DNAPL (tetrachloroethene and 1,1,1‐trichloroethane) was slowly pumped into two ports in the center of the column. Following this DNAPL injection, an aqueous solution of vitamin B12 and reduced titanium was circulated through the column to promote degradation of the solvents. Processes observed in the ISVCC included DNAPL distribution, dissolution, and degradation, and geochemical evolution of the aquifer.The ISVCC provides a convenient means for testing in situ technologies in the experimental stage or for selection of proven technologies to find the most effective at a specific site. It is inexpensive, easy to install, and maximizes control over flow distribution in a heterogeneous aquifer. Its application will be restricted where low hydraulic conductivity beds are present in the aquifer.
Estimation of Biodegradation Rates Using Respiration Tests During In Situ Bioremediation of Weathered Diesel NAPL
Authors: Davis G.B. , Johnston C.D. , Patterson B.M. , Barber C. , Bennett M. 
Published: February 2007

AbstractRespiration tests were carried out during a seven month bioremediation field trial to monitor biodegradation rates of weathered diesel non‐aqueous phase liquid (NAPL) contaminating a shallow sand aquifer. Multiple depth monitoring of oxygen concentrations and air‐filled porosity were carried out in nutrient amended and nonamended locations to assess the variability of degradation rate estimates calculated from respiration tests.The field trial consisted of periodic addition of nutrients (nitrogen and phosphorus) and aeration of a 100 m2 trial plot. During the bioremediation trial, aeration was stopped periodically, and decreases in gaseous oxygen concentrations were logged semi‐continuously using data loggers attached to recently developed in situ oxygen probes placed at multiple depths above and within a thin NAPL‐contaminated zone. Oxygen usage rate coefficients were determined by fitting zero‐and first‐order rate equations to the oxygen concentration reduction curves, although only zero‐order rates were used to calculate biodegradation rates. Air‐filled porosity estimates were found to vary by up to a factor of two between sites and at different times.NAPL degradation rates calculated from measured air‐filled porosity and oxygen usage rate coefficients ranged up to 69 mg kg‐1 day‐1. These rates are comparable to and higher than rates quoted in other studies, despite the high concentrations and weathered state of the NAPL at this test site. For nutrient‐amended sites within the trial plot, estimates of NAPL degradation rates were two to three times higher than estimates from nonamended sites. Rates also increased with depth.
Investigation and Remediation of a 1,2‐Dichloroethane Spill Part II: Documentation of Natural Attenuation
Authors: Lee Michael D. , Sehayek Lily , Sleep Brent E. , Vandell Terry D. 
Published: February 2007

AbstractA release of 1,2‐dichloroethane. also known as ethylene dichloride (EDC), resulted in shallow subsurface freephase contamination of a Gulf Coast site in the southern United States. The site stratigraphy consists primarily of a low permeability, surficial peat. silt, and clay zone underlain by fractured clay; a confined 12 in deep sand ground water flow zone; a confined 21 m deep fine sand zone of limited ground water flow, followed by a deep aquitard. The Gumbo clay and sandy clay aquitard below the release area overlies and protects the 61 m deep Upper Chicot Aquifer, which is a confined regional aquifer. An ongoing recovery and hydraulic containment program from the primary impacted and laterally and vertically restricted shallow 40‐foot sand zone has effectively recovered dense nonaqueous phase liquid (DNAPL) and contained dissolved phase EDC.Natural attenuation of EDC was demonstrated through (1) a laboratory microcosm study substantiating the ability of the native microbial population in the deeper aquifer lo degrade EDC under anaerobic environmental conditions found at the site. (2) field investigations showing reductions in EDC concentrations over time in many of the wells on site, and (3) an evaluation of the ground water for EDC and its degradation products and oilier geo‐chemical parameters such as dissolved oxygen, redox potential, and pH. Degradation products of EDC found in the field investigations included 2‐chloroeihanol, ethanol. ethene, and ethane. Dissolved EDC concentrations in selected wells between the first recorded samples and the fourth quarter of 1997 ranged from greater than 4% to 99% reductions. First‐order exponential decay half‐lives ranged from 0.21 to 4.2 years for wells showing decreases in FDC concentrations over time. Elevated methane concentrations indicated carbon dioxide to be the major terminal electron acceptor.
The Relative Merits of Monitoring and Domestic Wells for Ground Water Quality Investigations
Authors: Jones Joseph L. , Roberts Lonna M. 
Published: February 2007

AbstractThe results of two studios of the effect of agricultural hind use on shallow ground water quality indicate that monitoring wells may be a better choice than domestic wells for studies of pesticide occurrence or transport, or for use as early‐warning indicators of potential drinking water contamination. Because domestic wells represent the used resource, and because domestic well water may be affected by historical rather than current pesticide and land‐use practices, domestic wells would be the best choice for an investigation of drinking water quality. The key difference between the domestic and monitoring wells appears to be that the monitoring wells in this study were installed exclusively to sample the shallowest possible ground water. For these studies. 48 shallow domestic wells and 41 monitoring wells were located randomly within two land‐use settings (row crops and orchards) in an irrigated agricultural region of eastern Washington and sampled for 145 pesticides (including nine pesticide degradates) and common water quality indicators. Constructing and sampling monitoring wells required approximately four times the resources (including manpower and materials) as locating and sampling domestic wells. Sample collection and quality assurance procedures and analytical techniques were identical except that a portable submersible pump was required for monitoring wells. In both land‐use sellings, no significant difference in nitrate concentration was found between well types; however, the average number of pesticides detected per well was significantly higher (p<0.05) in the monitoring wells. A greater variety of pesticides was detected in monitoring wells: many were detected only in monitoring wells. More than 60% of detections of pesticides that were found only in domestic wells were of compounds that are no longer in use. These differences in ground water quality found in this studs relate lo the depth of the well and are apparently related lo the age of ground water in the two types of wells and the greater effects of sorption, degradation, dilution, and dispersion that accompany longer ground water residence times. The decision to invest resources in monitoring wells should be made in light of the study objective and should consider these differences in results from the two types of wells as well as the relative costs.