bluuebunny/crossref_metadata_2025 huggingface dataset:
Tracer Test Analysis of Anisotropy in Hydraulic Conductivity of Granular Aquifers
Authors: Kenoyer Galen J.
Published: February 2007

A simple method of determining the anisotropy ratio of hydraulic conductivity in near‐surface granular aquifers using tracer test and piezometer measurements is presented. Depending on the length of time allowed, the test will yield anisotropy ratios that are representative of the distance traversed by the tracer during the test, up to tens of feet from the injection point for some systems. This method is illustrated with an application to a ground water flow system in northern Wisconsin.
Reliability of Chemical Analyses of Water Samples — The Experience of the UMTRA Project
Authors: Rice George , Brinkman James , Muller Dianna
Published: February 2007

Ground water quality investigations require reliable chemical analyses of water samples. Unfortunately, laboratory analytical results are often unreliable. The Uranium Mill Tailings Remedial Action (UMTRA) Project's solution to this problem was to establish a two‐phase quality assurance program for the analysis of water samples. In the first phase, eight laboratories analyzed three solutions of known composition. The analytical accuracy of each laboratory was ranked and three laboratories were awarded contracts. The second phase consists of on‐going monitoring of the reliability of the selected laboratories.

The following conclusions are based on two years of experience with the UMTRA Project's Quality Assurance Program:

• The reliability of laboratory analyses should not be taken for granted.

• Analytical reliability may be independent of the prices charged by laboratories.

• Quality assurance programs benefit both the customer and the laboratory.
Screened Auger Sampling: The Technique and Two Case Studies
Authors: Taylor Theodore W. , Serafini Michael C.
Published: February 2007

The screened auger is a laser‐slotted, hollow‐stem auger through which a representative sample of ground water is pumped from an aquifer and tested for water‐quality parameters by appropriate field‐screening methods. Screened auger sampling can be applied to ground water quality remedial investigations, providing:(1) a mechanism for determining a monitoring well's optimal screen placement in a contaminant plume; and (2) data to define the three‐dimensional configuration of the contaminant plume.

Screened auger sampling has provided an efficient method for investigating hexavalent chromium and volatile organic compound contamination in two sandy aquifers in Cadillac, Michigan. The aquifers approach 200 feet in thickness and more than 1 square mile in area. A series of screened auger borings and monitoring wells was installed, and ground water was collected at 10‐foot intervals as the boreholes were advanced to define the horizontal and vertical distribution of the contaminant plumes. The ability of the screened auger to obtain representative ground water samples was supported by the statistical comparison of field screening results and subsequent laboratory analysis of ground water from installed monitoring wells.
A Discrete Point Sampler for Ground Water Monitoring Wells
Authors: MacPherson James R. , Pankow James F.
Published: February 2007

A discrete point sampler has been developed that overcomes disadvantages inherent in several current small‐volume samplers. It is designed to obtain ground water samples after a well has been purged with a pump. It consists of a sample chamber, two ports, and a stopcock for withdrawing sample aliquots. After lowering the sampler into a well, sampling is initiated by pulling on a line that sequentially removes the plugs in the lower and the upper level ports. The sample chamber fills from the bottom port and vents air from the top port. The device is suitable for sampling for volatile organic compounds in ground waters that are not subject to spontaneous bubble degassing. The upper port is sufficiently far above the lower port that none of the water that is sampled is exposed to the vented air. The sample chamber fills in such a way that the water that is taken from the chamber for analysis is not exposed to the headspace in the chamber.
A New Continuous‐Sampling Wireline System for Acquisition of Uncontaminated, Minimally Disturbed Soil Samples
Authors: Clark Robert R.
Published: February 2007

A new wireline system has been developed to alternately full‐hole drill or continuously sample soil in a variety of soils. Those samples recovered by the system are complete, relatively undisturbed, and minimally affected by drilling fluids. The system, which includes an outer barrel, center‐bit insert tube and a spring‐retract‐sampler inner barrel, can be used with either a core or rotary‐type drill. The system's outer barrel and bit act as a casing advancer to prevent hole collapse in unstable soils. The outer barrel and bit remain in the hole while either the center‐bit‐insert tube or the soil‐sampler inner barrel are wirelined in and out of the outer barrel and drill rod column. When the center‐bit insert is wirelined into place, it combines with the outer barrel and bit to become a full‐hole drilling tool. When this center‐bit insert is replaced with the soil‐sampler inner barrel, the system is capable of continuous soil sampling to depths ranging from several hundred to several thousand feet. The spring of this soil‐sampler inner barrel is designed to extend the drive‐shoe some 6 to 8 inches ahead of the outer‐barrel bit and the circulating fluids. Therefore, the sample is not in continuous contact with the circulating fluids during the sampling process.

As the sample enters the soil‐sampler tube, those circulating fluids inside the tube are forced up and out through the inner barrel's fluid bypass. The result is a sample relatively free of contamination or washing by drilling fluids. Because the soil‐sampler tube comes in contact with the circulating fluid as it travels into sampling position, there is a film coating the recovered sample. Similarly, the fluid also coats either end of the sample. However, that film is easily scraped away before analysis. Should additional protection be required, a liner can be inserted inside the sampler tube. Sample contaminants can be totally eliminated through the use of filtered‐air circulation. In field use, negligible tearing or amalgamation of the samples has been experienced, because the soil‐sampler tube and retract‐spring are suspended from dual bearings, which prevent inner barrel rotation.
An Evaluation of Some Systems for Sampling Gas‐Charged Ground Water for Volatile Organic Analysis
Authors: Barker J.F. , Dickhout R.
Published: February 2007

Loss of volatile organics during sampling is a well‐recognized source of bias in ground water monitoring; sampling protocols attempt to minimize such loss. Such bias could be enhanced for ground water highly charged with dissolved gases such as methane. Such ground water was the object of this study. A positive‐displacement bladder pump, a momentum‐lift pump and a suction‐lift, peristaltic pump were employed in sampling both methane‐charged ground water for volatile aromatic hydrocarbons and a CO2‐charged reservoir water for volatile chlorinated hydrocarbons. In both cases, the suction‐lift pump produced samples with a significant negative bias (9 to 33 percent) relative to the other methods. Little difference between samples produced by the other pump Systems was noted at the field site, but in sampling the reservoir, the bladder pump produced samples that were 13 to 19 percent lower in halocarbon concentration than were samples from the momentum‐lift pump.

These negative biases are tentatively interpreted as losses due to volatilization during sampling. Slightly greater negative biases occur for compounds of higher volatility as estimated from their Henry's law constants. Additional studies appear to be warranted in order to adequately establish the scientific basis for recommending protocols for sampling ground water in which degassing could enhance the loss of volatile organics during sampling.
Comparison of Methods for Sampling Dissolved Nitrogen in a Fractured Carbonate‐Rock Aquifer
Authors: Lietman Patricia L. , Gerhart James M. , Wetzel Kim L.
Published: February 2007

As part of an agricultural non‐point‐source study in the Conestoga River head waters area in Pennsylvania, different methods for collecting ground water samples from a fractured carbonate‐rock aquifer were compared. Samples were collected from seven wells that had been cased to bedrock and drilled as open holes to the first significant water‐bearing zone. All samples were analyzed for specific conductance, dissolved oxygen, and dissolved‐nitrogen species. Water samples collected by a point sampler without pumping the well were compared to samples collected by a submersible pump and by a point sampler after pumping the well. Samples collected by using a point sampler, adjacent to major water‐bearing zones in an open borehole without pumping the well, were not statistically different from samples collected from the pump discharge or from point samples collected adjacent to major water‐bearing zones after pumping the well. Samples collected by using a point sampler without pumping the well at depths other than those adjacent to the water‐bearing zones did not give the same results as the other methods, especially when the water samples were collected from within the well casings. It was concluded that, for the wells at this site, sampling adjacent to major water‐bearing zones by using a point sampler without pumping the well provides samples that are as representative of aquifer conditions as samples collected from the pump discharge after reaching constant temperature and specific conductance, and by using a point sampler after pumping the well.
Should We Use a Well Foot (Sediment Trap) in Monitoring Wells?
Authors: Yu John K.
Published: February 2007

Traditionally, the water well contractor adds a section of blank casing to the bottom of the well screen in a production well. This practice has been carried over to ground water monitoring wells by some engineers and hydrogeologists, and is even recommended by the RCRA Technical Enforcement Guidance Document (TEGD). After examining the proclaimed advantages, it is the author's opinion that the well foot is not necessary for a monitoring well.
Screening of Ground Water Samples for Volatile Organic Compounds Using a Portable Gas Chromatograph
Authors: Buchmiller Robert C.
Published: February 2007

A portable gas chromatograph was used to screen 32 ground water samples for volatile organic compounds. Seven screened samples were positive; four of the seven samples had volatile organic substances identified by second‐column confirmation. Four of the seven positive, screened samples also tested positive in laboratory analyses of duplicate samples. No volatile organic compounds were detected in laboratory analyses of samples that headspace screening indicated to be negative. Samples that contained volatile organic compounds, as identified by laboratory analysis, and that contained a volatile organic compound present in a standard of selected compounds were correctly identified by using the portable gas chromatograph. Comparisons of screened‐sample data with laboratory data indicate the ability to detect selected volatile organic compounds at concentrations of about 1 microgram per liter in the headspace of water samples by use of a portable gas chromatograph.
In‐House Well Drilling Operations for a Ground Water Monitoring Program, Suffolk County, New York
Authors: Cary Steven V. , Markel Richard
Published: February 2007

All public agencies involved in ground water monitoring and protection face the requirement of obtaining well drilling services consistent with their needs. Most will rely on contracted drilling services, but a limited number of agencies having responsibilities for long‐term aquifer monitoring and the promulgation of monitoring standards may find that implementing an in‐house well drilling program is an effective approach to achieving their ground water protection goals.

Suffolk County, located on Long Island, New York, has been operating a well drilling program for 10 years, with three levels of drilling capability to meet the requirements of characterizing and monitoring an unconsolidated regional aquifer system. The program's cost and labor requirements are substantial, but this approach has provided uniformly high‐quality data and the hands‐on experience needed to test drilling innovations and produce monitoring regulations that are effective and feasible. If soundly organized and run, an agency‐directed drilling operation will be readily adaptable to changing needs and priorities. In Suffolk County, this has included emergency response and fuel‐spill monitoring. A successful program must also include a demonstrated geologic identification and well logging capability, close laboratory support, and an experienced hydrogeological or ground water engineering staff.

This approach may be suitable for other regional agencies based on their ground water conditions and water‐supply protection needs.
A Proposal to Use Chlorine‐36 for Monitoring the Movement of Radionuclides from Nuclear Explosions
Authors: Phillips Fred M. , Davis Stanley N. , Kubik Peter
Published: February 2007

Chlorine‐36 has been produced in large amounts by hundreds of nuclear explosions on the Nevada Test Site as well as 12 off‐site explosions at eight locations in five states. Continued monitoring of the redistribution of radionuclides by subsurface water is of concern in most of the areas affected by the detonations. Chlorine‐36 has the following advantages as a built‐in tracer for this redistribution: its mobility is equal to or greater than water, its long half‐life assures its continued usefulness over long periods, collection and storage of samples is simple, it is not subject to vapor transport at ordinary temperatures, its natural background is very low, and it does not form insoluble precipitates. Chlorine‐36 from the Gnome event near Carlsbad, New Mexico, illustrates how 36C1 can be used to help study the redistribution of radionuclides in the soil profile. Chlorine‐36 is also potentially useful as a tracer to study movement of contaminants around large nuclear reactor complexes and near respositories for radioactive waste.
Remote Data Collection and Control for Hydrogeologic Monitoring
Authors: Adomait Martin , Gillham Robert W.
Published: February 2007

A hydrogeologic field experiment, conducted at a research site some 125 miles (200km) from the home base, used commercially available computer controller technology for data collection and experimental control. A telephone line connected to the equipment facilitated the downloading of data, provided a means of remotely monitoring the operating performance, and made it possible to adjust the monitoring procedures.

This experiment demonstrated the benefits of a remotely controlled data acquisition system for a long‐term investigation. Identification of problems and the adjustment of the sampling algorithm by telephone reduced costly travel time. The considerable amount of data collected, the data evaluation techniques, and the continuous monitoring, provided a high degree of confidence in the results.
Preliminary Delineation of Contaminated Water‐Bearing Fractures Intersected by Open‐Hole Bedrock Wells
Authors: Williams John H. , Conger Randall W.
Published: February 2007

Contaminated water‐bearing fractures intersected by open‐hole bedrock wells were preliminarily delineated through a combination of geophysical logging, vertical‐flow measurements, and downhole water sampling as part of remedial site investigations in southeastern New York. The wells investigated range from 100 to 450 feet in depth, have only shallow surface casing, and intersect multiple water‐bearing zones. The distribution of water‐bearing zones that intersect the wells was determined from single‐point resistance, caliper, fluid‐resistivity, temperature, and acoustic‐televiewer logs. Measurable flow in the wells was downward from upper producing zones to lower receiving zones that are poorly connected in the aquifer and that differ in hydraulic head as a result of nearby pumping. A down hole sampler was used to collect discrete and composite water samples for analysis of volatile organic compounds from producing zones that are self‐purging as a result of flow in the wells.

The results obtained at two of the study sites are presented—the Spring Valley wellfield and the Mahopac business district. At the Spring Valley wellfield, a supply well completed in Mesozoic sandstone and conglomerate intersects water‐bearing zones at depths of 204 to 245 feet that produced contaminated water that was received by a zone at 278 feet. In the same well, a deeper zone at 345 feet produced uncontaminated water that was received by a zone at 403 feet. Correlation of information from the well, geophysical logs and drill cores from nearby monitoring wells, and bedrock outcrops indicates that most of the water‐bearing zones are bedding‐plane separations that probably provide pathways for contaminant transport in the bedrock aquifer for significant distances.

In the Mahopac business district, a deep test well completed in Precambrian gneiss intersected shallow waterbearing zones at 50 to 79 feet that produced contaminated water that was received by deep zones at 260 and 328 feet. The water‐bearing zones consist of single or closely spaced multiple fractures with dips of 5 to 50 degrees. By analogy with the results from this test well, deep open‐hole wells in the area may serve as “short circuits” in the ground water flow system and allow direct transport of contaminants to deeper zones in the fractured‐bedrock aquifer.

The methods presented can be used to investigate ground water flow and contamination in fractured‐bedrock aquifers in advance of more focused monitoring programs. The methods can be applied in existing open‐hole wells before test drilling and monitoring well installation to provide for efficient program design. The methods also can be used during the installation of monitoring wells to help determine completion depths and open intervals and to ensure that the wells are not serving as conduits for the flow of contaminated water.
Comparisons of Three Methods to Determine the Vertical Stratification of Pore Fluids
Authors: Taylor Kendrick , Hess John , Mazzella Aldo , Hayworth Joel
Published: February 2007

Three methods were used to investigate the possibility of vertical stratification of the pore fluid in an aquifer. The wells available for the study were fully screened and had a 5cm disturbed annulus around them. The first method used a pump with a straddle packer to isolate a short section of the secreened interval. A tracer test demonstrated that most of the pumped sample came from the well bore, presumably by piping through the disturbed. annulus. The second method used induction logs to measure the formation electrical conductivity as a function of depth. Due to the presence of clays and an inability to obtain porosity information, it was not possible to determine the pore fluid electrical conductivity using induction logs. A third method, dilution sampling, was developed that used a straddle packer to isolate a segment of the well screen. A tracer was injected into the packed‐off segment, and the tracer concentration in the well was monitored. The tracer was removed from the packed‐off segment by dilution and advection by ground water. When the tracer was completely removed from the packed‐off segment, the fluid in the segment was considered to be representative of the adjacent pore fluid. Only the dilution sampling method determined unambiguously that the pore fluid was not stratified.
Modeling Management Practice Effects on Pesticide Movement to Ground Water
Authors: Shoemaker L. L. , Magette W. L. , Shirmohammadi A.
Published: February 2007

The assessment of agricultural impacts on water quality are now being redirected to include both ground water and surface water. Mathematical models have enhanced the ability of scientists’to evaluate these impacts. A variety of public domain models are available that can aid in evaluating the effects of managerial activities on pesticide movement to ground water. However, the ideal non‐point source (NPS) pollution management model does not exist. Current models fail to adequately describe the transport of chemicals to ground water and, simultaneously, the effect of managerial practices on transport mechanisms. Much more work is necessary to develop a model that can describe water quality impacts of agricultural practices in a holistic framework that includes ground water and surface water concerns.
The Detection of Naturally Occurring BTX During a Hydrogeologic Investigation
Authors: Slaine David D. , Barker James F.
Published: February 2007

Benzene, toluene and xylenes (BTX) were detected in ground water during a contaminant hydrogeological investigation of a landfill site. The landfill site was situated on approximately 10m (33 ft) of clay and glacial till overburden soils, which were underlain by a shaly limestone bedrock. The top part of the bedrock was the regional aquifer in the study area. Initial thoughts were that the landfill was the source of the BTX. However, the BTX was detected in ground water a considerable distance from the known extent of the leachate plume. Subsequent detailed analysis of rock cores showed the BTX could be leached from bituminous layers of shale that were interbedded in limestone. Rock core testing included gas chromatograph (GC) analysis of organic free reagent water used for leaching tests, flame ionization detection on a solvent used for leaching tests and thermal desorption analysis of the solid rock. The naturally occurring BTX, along with the presence of brackish ground water in the shaly bedrock, made it difficult to identify ground water contamination emanating from the landfill. Thus, the presence of BTX should not be considered definitive evidence of ground water contamination in certain sedimentary rock aquifers.
A Method to Evaluate the Vertical Distribution of VOCs in Ground Water in a Single Borehole
Authors: Hoffman Fredric , Dresen Michael D.
Published: February 2007

Volatile organic compounds (VOCs) are present in multiple water‐bearing zones beneath and downgradient of Lawrence Livermore National Laboratory. This area is composed of interfingering unconsolidated alluvial sediments with hydraulic conductivities ranging over four orders of magnitude. The more permeable sediments exhibit moderate hydraulic interconnection horizontally and less interconnection vertically, and appear to consist largely of interconnected stream channel deposits. To optimize selection of monitoring well screened intervals in this complex environment, a technique that enables collection of saturated formation samples from each water‐bearing zone without contamination from other VOC‐containing zones was developed, tested, and implemented. The technique utilizes a wireline punch‐coring system that allows the drill bit to be replaced with a core barrel without removing the drill rod from the borehole. To help ensure that a sample from one water‐bearing zone is not contaminated by VOCs from another zone, the drilling fluid is replaced with new fluid before each sampling run. Overnight chemical analysis by gas chromatography enables field personnel to know the vertical distribution of VOCs as drilling proceeds. Since its first use in 1985, the technique has successfully characterized the presence or absence of VOCs in ground water in 123 of 140 wells, many with concentrations in ground water in the low parts‐per‐billion range. Our sampling technique is a cost‐effective and rapid method of evaluating the vertical distribution of VOCs in ground water in a complex hydrogeologic environment.
Differentiation of the Origins of BTX in Ground Water Using Multivariate Plots
Authors: Lesage S. , Lapcevic P. A.
Published: February 2007

Multivariate plots were utilized to create fingerprints of aromatic hydrocarbon residues in ground water. The technique allows hydrogeologists to distinguish between residues of benzene, toluene, ethyl benzene, and total xylenes originating from ground water contact with petroleum in natural deposits and refined petroleum waste products. Examples were taken from deep‐well injection of refinery wastes, natural petroleum deposits, municipal and industrial landfill leachates, coal tar and creosote contaminated waters, and varnish industry contaminated ground water. The data were plotted from ASCII files generated through either Lotus 123™ or a database (The Manager™) report program, using a simple Fortran interactive program with Plot88™ subroutines.
Evaluating the Effectiveness of Ground Water Extraction Systems
Authors: Haley Jennifer L. , Hanson Bill , Enfield Carl , Glass John
Published: February 2007

The most common process for remediating contaminated ground water is extraction and treatment. Data from 19 on‐going and completed ground water extraction systems were collected and analyzed (U.S. EPA 1989b) to evaluate the effectiveness of this process in achieving cleanup concentration goals for ground water. This analysis indicated several trends including (1) containment of ground water plumes was usually achieved; (2) contaminant concentrations dropped significantly initially followed by a leveling out; (3) after the period of initial rapid decline, the continued decreases in concentration were usually slower than anticipated; and (4) certain data important to optimizing system design and operation had often not been collected during the site characterization phase.

Factors limiting the achievement of cleanup concentration goals fell into four basic categories: (1) hydrogeological factors, such as subsurface heterogeneity, low‐permeability units, and presence of fractures; (2) contaminant‐related factors, such as high sorption to soil and presence of non‐aqueous phases (dissolution from a separate non‐aqueous phase or partitioning of contaminants from the residual non‐aqueous phase); (3) continued migration from source areas and the size of the plume itself; and (4) system design factors, such as pumping rates, screened intervals, and extraction well locations.

The findings of this study indicate that ground water extraction is an effective method for preventing additional migration of contaminant plumes and achieving risk reduction. However, the findings indicate that in many situations, it may not be practicable to rely solely on ground water extraction and treatment to achieve health‐based cleanup concentrations throughout the contaminated zone and fulfill the primary goal of returning ground water to beneficial use.

This study suggests several recommendations (U.S. EPA 1989a) for improving ground water response actions including (1) actions to contain contaminant plumes should be initiated early; (2) data on vertical variation of hydraulic conductivity, distribution of the contaminant mass, and partitioning of contaminants to soil or a stationary phase in the saturated zone should generally be collected as part of the site characterization process; (3) remedial actions should be implemented in stages to better utilize information on aquifer response as the system is being designed and implemented; (4) remedial actions should be monitored and modified during operation to optimize system efficiency; and (5) methods to enhance extraction effectiveness and efficiency should be considered.
Impact of Recharge Through Residual Oil Upon Sampling of Underlying Ground Water
Authors: Wise William R. , Chang Chi‐Chung , Klopp Rick A. , Bedient Philip B.
Published: February 2007

At an aviation gasoline spill site in Traverse City, Michigan, historical records indicate a positive correlation between significant rainfall events and increased concentrations of slightly soluble organic compounds in the monitoring wells of the site. To investigate the recharge effect on ground water quality due to infiltrating, water percolating past residual oil and into the saturated zone, an in situ infiltration experiment was performed at the site. Sampling cones were set at various depths below a circular test area, 13 feet (4 meters) in diameter. Rainfall was simulated by sprinkling the test area at a rate sufficiently low to prevent runoff. The sampling cones for soil‐gas and ground water quality were installed in the unsaturated and saturated zones to observe the effects of the recharge process. At the time of the test, the water table was below the residual oil layer. The responses of the soil‐gas and ground water quality were monitored during the recharge and drainage periods, which resulted from the sprinkling.

Infiltrated water was determined to have transported organic constituents of the residual oil, specifically benzene, toluene, ethylbenzene, and ortho‐xylene (BTEX), into the ground water beneath the water table, elevating the aqueous concentrations of these constituents in the saturated zone. Soil‐gas concentrations of the organic compounds in the unsaturated zone increased with depth and time after the commencement of infiltration. Reaeration of the unconfined aquifer via the infiltrated water was observed. It is concluded that water quality measurements are directly coupled to recharge events for the sandy type of aquifer with an overlying oil phase, which was studied in this work. Ground water sampling strategies and data analysis need to reflect the effect of recharge from precipitation on shallow, unconfined aquifers where an oil phase may be present.
Computer Modeling of Scale Formation During Treatment of Ground Water in Air Strippers
Authors: Matisoff Gerald , Narquis Clifford
Published: February 2007

During treatment to remove volatile organic compounds from contaminated ground water, inorganic scale sometimes precipitates in an air stripper tower. This leads to increased costs and down‐time associated with tower media replacement. In order to determine the kind, quantity, and rate of scale formation, the ground water from five locations in Florida was simulated using an aqueous equilibrium chemistry and flow process model. In all cases the pH of the outflow water is higher than that of the inflow water because of degassing of CO2. This often results in the precipitation of calcium carbonate. The addition of air to reduced ground water results in the oxidation of iron and the precipitation of ferric hydroxides. Model estimates of scale formation are about a factor of two to five too high. This indicates that the precipitation reactions do not reach equilibrium within the air stripper. Future work will require the inclusion of biological fouling and a kinetic expression to account for the observed non‐equilibrium.
The Utility of Multiple‐Completion Monitoring Wells for Describing a Solvent Plume
Authors: Korte N.E. , Kearl P.M.
Published: February 2007

At a study site in the midwestern United States, multiple‐completion wells demonstrated that a vertical hydraulic gradient was responsible for the contamination pattern exhibited by chlorinated solvent plumes. The typical pattern consisted of little or no contamination in the upper portion of the aquifer with concentrations increasing with depth. When ground water contamination was discovered in an unexpected portion of the site, water level elevations and contaminant distribution data obtained from multiple‐completion wells resulted in identification of the source location. The well eventually determined to be located in the source area displayed contaminant levels much higher in the upper zone of the aquifer — the opposite contamination pattern of other on‐site wells. Such results indicated that the spill had occurred near this location and that solvent residing along the capillary fringe was continuing to contaminate the aquifer.
The Disposable E‐Log
Authors: Greenhouse John P. , Pehme Peeter E.
Published: February 2007

A device was developed to make fine‐scale in situ measurements of formation and ground water conductivity at depths up to 10 meters in unconsolidated shallow aquifers. It consists of a casing that is left in place (“disposable”) and a probe that slides down the center of the casing making readings or taking water samples through screened slots. The device is inexpensive, designed to be jetted into place, and intended for use in monitoring situations where drilling rigs and wireline logs are impractical. It offers, in principle, 10cm resolution of the conductivities and the formation factor as a function of time.

Results from three of these units installed across a landfill plume near North Bay, Ontario, demonstrate the usefulness of these kinds of measurements in a monitoring study, and the problems that can be encountered in a highly contaminated environment.
Atrazine Used as a Tracer of Induced Recharge
Authors: Duncan Diana , Pederson Darryll T. , Shepherd Timothy R. , Can James D.
Published: February 2007

The city of Lincoln draws water from a well field along the banks of the Platte River in east‐central Nebraska. We have been able to follow the infusion of atrazine into this well field under induced recharge. Samples of water from the river, several monitoring wells and a production well were analyzed by GC/MS and solid phase extraction and found to change in concentration over the range 0.1 and 5.0 ppb of atrazine through the spring, summer, and fall 1989. Increases in the concentration of atrazine relating to precipitation events in the Platte River Basin were observable in the well water samples and ultimately in Lincoln municipal tap water. Atrazine from the river was seen to move via induced recharge and into well field ground water and away from the river at an observable rate. The concentration of atrazine in the river is dependent upon time of year and precipitation in the river basin.
Cascade Air Stripping: Techno‐Economic Evaluation of a New Ground Water Treatment Process
Authors: Nirmalakhandan N. , Peace G.L. , Shanbhag A.R. , Speece R.E.
Published: February 2007

A simple modification of the conventional air‐stripping process introduced as cascade air stripping is proposed for efficient and economical removal of semivolatile and low volatility contaminants from ground water. The technical feasibility and economic viability of this process are evaluated using field test results and cost model simulations. The field tests enabled the process model to be verified at various water flow rates ranging from 150 gpm to 400 gpm. The field study also demonstrated the feasibility of the proposed system at a near full‐scale level. Cost models were used to compare the proposed process to conventional air stripping and granular‐activated carbon adsorption in removing a range of contaminants. This analysis showed that the treatment cost (ø/1000 gal) of cascade air stripping is about 15 percent lower than conventional air stripping and about 40 percent lower than granular‐activated carbon adsorption.
Potential of Common Well Casing Materials to Influence Aqueous Metal Concentrations
Authors: Hewitt Alan D.
Published: February 2007

Static leaching and sorption laboratory studies were performed to assess the potential of polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), and two types of stainless steel (SS 304 and SS 316) well casing materials to influence metal concentrations in ground water solutions with low dissolved oxygen. Overall, PTFE was inert, whereas one or both stainless steels significantly altered the solution concentrations of Cd, Cr, Cu, Pb, Fe, and Ni. PVC was generally more reactive than PTFE, but did not significantly alter the solution metal concentrations as often, or as greatly, as either of the stainless casings.
Reversed Flow Test: A Borehole Logging Method for Estimating Pore Water Quality and Inflow Rates Along an Uncased Borehole Profile
Authors: Tellam J.H.
Published: February 2007

There is often a need to estimate the variation in water quality and flow rate with depth in an aquifer given access only to an uncased borehole. In such situations, borehole logging techniques can be applied. This paper describes the Reversed Flow Test (RFT), a rarely used borehole logging method. The RFT is intended to provide information on pore water quality and inflow rates along the length of an uncased borehole profile. They are carried out by logging the conductivity of the borehole fluid under two pumping phases. During the first pumping phase the pump intake is located at the top of the borehole, and during the second the intake is located at the base. Provided the pumping rates are low and the system does not have marked lateral heterogeneity, stable conductivity profiles are often achieved within a relatively short time period. The data are interpreted to give estimates of electrical conductivity and inflow at each point in the profile. The test has been successfully carried out on a range of British aquifers, and four case histories are summarized here. In each case, the test was easily accomplished by two people in less than a day.
Progressive Packer/Zone Sampling Method for VOC Plume Delineation in Consolidated Aquifers
Authors: Laney Stephen E. , Enberg Charles A.
Published: February 2007

The progressive packer/zone sampling method was used to identify the bottom of a plume of volatile organic compounds (VOCs) in the parts‐per‐million (ppm) range using one well in each of three separate locations. The method involves progressively drilling a 20‐foot length of borehole through casing, setting an inflatable packer at the top of the drilled zone, purging the zone of three volumes of water using the airlift method, sampling the zone in situ through the packer string using a bailer, then repeating the procedure.

A plume consisting of chlorinated VOCs, alcohols, and vinyl chloride occurs in a low‐yielding fractured bedrock aquifer located in the Passaic Formation at a site in central New Jersey. The thickness of the plume in total VOC concentrations exceeding 1 ppm was determined using the progressive packer/zone sampling method to a depth of 200 feet. The first borehole was completed as a monitoring well in the “hottest” zone encountered during testing. Additional wells were then clustered with this exploratory well to delineate the plume in the parts‐per‐billion (ppb) range. Cross contamination from previously sampled zones was not a problem as long as total VOCs in the ppm range were targeted and the sample interval was properly purged.

Instead of using a multiple well cluster consisting of an indefinite number of wells to determine the bulk thickness of a plume at a specific location, information from one borehole may suffice during the exploratory phase. Costs to the client and cross contamination potential to the aquifer can be minimized by limiting the number of boreholes needed for vertical delineation.
Acquisition of Representative Ground Water Quality Samples for Metals
Authors: Puls Robert W. , Powell Robert M.
Published: February 2007

R.S. Kerr Environmental Research Laboratory (RSKERL) personnel have evaluated sampling procedures for the collection of representative, accurate, and reproducible ground water quality samples for metals for the past four years. Intensive sampling research at three different field sites has shown that the method by which samples are collected has a greater impact on sample quality, accuracy, and reproducibility than whether the samples are filtered or not. In particular, sample collection practices that induce artificially high levels of turbidity have been shown to have the greatest negative impacts on sample quality. Results indicated the ineffectiveness of bailers for collection of representative metal samples. Inconsistent operator usage together with excessive purging generally resulted in excessive turbidity (>100 NTUs) and large differences in filtered and unfiltered metal samples. The use of low flow rate purging and sampling consistently produced filtered and unfiltered samples that showed no significant differences in concentrations. Turbidity levels were generally less than 5 NTUs, even in fine‐textured glacial till. We recommend the use of low flow rates, during both purging and sampling, placement of the sampling intake at the desired sampling point, minimal disturbance of the stagnant water column above the screened interval, monitoring of water quality indicators during purging, minimization of atmospheric contact with samples, and collection of unfiltered samples for metal analyses to estimate total contaminant loading in the system. While additional time is spent due to use of low flow rates, this is compensated for by eliminating the need for filtration, decreased volume of contaminated purge water, and less resampling to address inconsistent data results.
Hydrogeological Investigation of Hydrocarbon Contamination of Ground Water in Albolote (Granada, Spain)
Authors: Cruz‐Sanjulián J. , Olías M. , del Valle M. , Rubio J.C.
Published: February 2007

In July 1988, hydrocarbons were detected in wells in the urban area of Albolote, near Granada, Spain, near the border of the “Vega de Granada” alluvial aquifer. According to available hydrogeological data, the contamination was attributed to leaks in the underground pipelines of a nearby (300m) industrial factory, where the loss of 40,000 to 50,000 liters of gasoline had been detected some weeks before. A complete hydrogeological investigation was then undertaken, involving, among other techniques: (a) an inventory of the existing wells in the area; (b) the preparation of piezometric maps; (c) the application of electrical geophysical methods; (d) the drilling of piezometers and new pumping wells between the urbanized area and the leak point; (e) the improvement of the pluviometric and piezometric control by the installation of a pluviograph and several limnigraphs; (f) the sampling, initially daily and finally weekly, in a 20‐well observation network, also used for piezometric control; and (g) the geostatistical study of the analytical data. The contamination plume, extended in the direction of the flow lines, has a length of 500m and a width of less than 50m, and appears to have occurred mainly in a paleochannel. Hydrocarbons (1600 liters) were recovered by pumping and by using absorbent blankets, as well as by a gas and liquid suction method. Hydrocarbon concentrations have continuously decreased. However, sporadic increases, associated with rainfall, have been observed suggesting the presence of retained hydrocarbons in the unsaturated zone. The rate of decrease in hydrocarbon concentrations has currently slowed, particularly in the less affected zone. As a means of activating the cleaning up of the unsaturated zone, an artificial recharging method has been designed.
Planning of Soil‐Pore Water Sampling Campaigns Using Pesticide Transport Modeling
Authors: Banton O. , Lafranee P. , Martel R. , Villeneuve J.P.
Published: February 2007

Soil‐pore water sampling by suction lysimeters monitors the fate of soil contaminants as a function of depth and time. However, sampling campaigns must be planned to most effectively monitor the migration of contaminants with a minimum expenditure of resources. The vertical migration of pesticides was studied at two sites treated with systemic s‐triazine herbicides and equipped with suction lysimeters. The measured concentrations were compared with those calculated by a simulation model. This modeling was based on the processes that control the transport and fate of pesticide within the soil. The usefulness of such a tool was demonstrated by the good approximation obtained for pesticide concentrations and arrival times. Moreover, the significant spatial variability of concentrations observed justifies the use of a stochastic approach in modeling that takes into account the spatial variability of soil parameters. Also, the rapid transformation of herbicides observed in unsaturated soil zones demonstrates the importance of taking into account the sum of the toxic residues when evaluating the fate of s‐triazines in soil.
Mapping a Brine Plume Using Surface Geophysical Methods in Conjunction with Ground Water Quality Data
Authors: Chapman Melinda J. , Bair E. Scott
Published: February 2007

Oil field brine was applied to a gravel roadbed at an instrumented study site in Newark, Ohio, to simulate the use of brine as a deicer on roads in certain areas of Ohio. Brine was applied on a weekly basis eight times during the winter of 1988 as part of the deicing simulation. Eleven wells were installed at the site prior to brine application to permit collection of ground water quality samples. Surface geophysical methods — electrical resistivity and electromagnetic conductivity — were used to map the resulting brine plume. The accuracy of the methods was evaluated by comparing geophysical and ground water quality data. The presence of brine in ground water resulted in a decrease in resistivity and an increase in conductivity. Specific conductance measured in the field was used as a general indicator of the presence of the brine plume in ground water. Chloride concentration was an indicator of brine in the ground water. Results of the surface geophysical surveys correlated best with chloride and dissolved solids concentrations, and with specific conductance in ground water. The surface geophysical methods were found to be useful for qualitative interpretations of ground water quality changes resulting from the application of brine on roads.
Conceptual Model of Ground Water Flow in Fractured Siltstone Based on Analysis of Rock Cores, Borehole Geophysics, and Thin Sections
Authors: Merin Ira S.
Published: February 2007

The flow of ground water in flat‐lying sedimentary rocks of the Appalachian Plateau is significantly influenced by the vertical and horizontal distribution of vertical joints and horizontal bedding plane fractures. Although considerable published data document the geographic distribution of joints in outcrops in this region, few data have been published on the vertical distribution of joints and on the vertical and horizontal distribution of bedding plane fractures.

The vertical and horizontal distribution of bedding plane fractures at a site located in central New York was investigated by examination of borehole geophysical logs, continuous rock cores from boreholes drilled to a maximum depth of 175 feet, and rock outcrops. This investigation reveals that three zones of bedding plane fractures can be delineated based on the vertical distribution of horizontal fractures, and that the spacing between these horizontal fractures increases with depth. The occurrence of vertical joints is not noticeably influenced by depth. Because bedrock at this site consists of several hundred feet of relatively homogeneous, thin‐bedded, fractured siltstone (the Genesee Formation) having essentially no visible microscopic intergranular porosity, ground water flows exclusively through fractures. Caliper, density, temperature, and neutron logs indicate that submillimeter‐wide fractures serve as conduits that transmit ground water. Slug test data reveal that shallower wells exhibit hydraulic conductivities 10 to 100 times greater than those of deeper wells, confirming that increased (wider) fracture spacing at depth results in a lower permeability.

Because the spacing of horizontal fractures increases with depth, ground water flow in shallow bedrock is expected to be very different than that in deeper bedrock. Because both vertical joints and horizontal bedding plane fractures are conduits in shallow bedrock, flow might approximate equivalent porous media conditions. However, flow in deeper bedrock might approach fracture flow because bedding plane fractures are sparse and the principal conduits are only vertical joints. These differences can have important implications for modeling ground water flow.