bluuebunny/crossref_metadata_2025 huggingface dataset:
Cone Penetrometer Testing and Discrete‐Depth Ground Water SamplingL Techniques: A Cost‐Effective Method of Site Characterization in a Multiple‐Aquifer Setting
Authors: Zemo Dawn A. , Pierce Yvonne G. , Gallinatti John D.
Published: February 2007

Cone penetromcler testing (CPT). combined with discrete‐depth ground water sampling methods, can significantly reduce the time and expense required to characterize large sites that have multiple aquifers. Results from the screening site characterization can then be used to design and install a cost‐effective monitoring well network. At a site in northern California, it was necessary to characterize the stratigraphy and the distribution of volatile organic compounds (VC)Cs) to a depth of 80 feet within a ½‐mile‐by‐½‐mile residential and commercial area in a complex alluvial fan setting. To expedite characterization, a five‐week field screening program was implemented that consisted of a shallow ground water survey, CPT soundings and pore‐pressure measurements, and discrete‐depth ground water sampling. Based on continuous lithologic information provided by the CPT soundings, four predominantly coarse‐grained, water yielding stratigraphic packages were identified. Individual coarse‐grained units within each package are discontinuous, as they coalesce and pinch out in longitudinal and transverse directions. Seventy‐nine discrete‐depth ground water samples were collected using either shallow ground water survey techniques, the BAT Enviroprobe, or the QED HydroPunch I, depending on subsurface conditions.

Using results from these efforts, a 20‐well monitoring network was designed and installed to monitor critical points within each stratigraphic package. Good correlation was found for hydraulic head and chemical results between discrete‐depth screening data and monitoring well data. Understanding the vertical VOC distribution and concentrations produced substantial time and cost savings by minimizing the number of permanent monitoring wells and reducing the number of costly conductor casings that had to be installed. Additionally, significant long‐term cost savings will result from reduced sampling costs, because fewer wells comprise the monitoring network. We estimate these savings to be 50 percent for site characterization costs, 65 percent for site characterization time, and 60 percent for long term monitoring costs.
Low‐Cost On‐Site Treatment of Landfill Leachate Using Infiltration Beds: Preliminary Field Trial
Authors: Robertson W.D. , Murphy A.M. , Cherry J.A.
Published: February 2007

A small‐scale field experiment was carried out to demonstrate the effectiveness of using septic system ‐type infiltration beds for on‐site treatment of landfill leachate. Using an infiltration bed with a 3‐m‐thick vadose zone of medium sand, and loaded at a rate 01 18 cm/day, a treatment efficiency of >99 percent was obtained for Fe, 94 percent for NH4+, and 54 percent for dissolved organic carbon (DOC). Attenuation occurred during one‐ to two‐day residency in the aerobic vadose zone (pore gas O2 > 12 percent by volume) as a result of oxidation reactions that caused nitrification of NH4+, convened Fe2+ to Fe3+ allowing subsequent precipitation of sparingly soluble Fe oxyhydroxide minerals, and biodegraded DOC. Attenuation of an aerobically degradable trace volatile organic compound (dichlorobenzene) was also noted, although other less degradable compounds (trichloroethylene and tetrachloroethylene) persisted.

Fe mineral precipitation caused a discontinuous hardpan layer to occur in the zone immediately below the infiltration pipes. However, this layer did not become impermeable or continuous enough to significantly impede infiltration during the 82‐day experiment.

Advantages of this technology for leachate treatment are that it is low cost, it is simple to construct and operate. and treatment occurs on‐site, avoiding the cost of transporting leachate off‐site for treatment.
An Evaluation of Soil‐Gas Surveying for H2S for Locating Subsurface Hydrocarbon Contamination
Authors: Robbins Gary A. , McAninch Brian E. , Gavas Francis M. , Ellis Patricia M.
Published: February 2007

A soil‐gas survey was conducted at a gasoline service station and a former fire training facility to determine if surveying for hydrogen sulfide could be useful in locating nonaqueous phase hydrocarbon fuel in the subsurface. Relative; to total organic vapor, oxygen, and carbon dioxide distributions, detectable hydrogen sulfide concentrations were much more restricted to the suspected source vicinity at both sites. Appreciable levels of soil‐gas hydrogen sulfide. up to 600 Vppb. were observed in areas characterized by anaerobic or microaerophilic conditions having bulk oxygen levels below 4 percent. Based on the hydrogen sulfide distribution, nonaqueous phase hydrocarbon fuel was located at each site. These results suggest that soil‐gas surveying for hydrogen sulfide may help locale mobile or residual gasoline and other nonaqueous phase hydrocarbons in the subsurface.
Field Comparison of Analytical Results from Discrete‐Depth Ground Water Samplers
Authors: Zemo Dawn A. , Delfino Thomas A. , Gallinatti John D. , Baker Virgil A. , Hilpert Laurence R.
Published: February 2007

Discrete‐depth ground water samplers are used during environmental screening investigations to collect ground water samples in lieu of installing and sampling monitoring wells. Two of the most commonly used samplers are the BAT Enviroprobe and the QED HydroPunch I, which rely on differing sample collection mechanics. Although these devices have been on the market for several years, it was unknown what, if any, effect the differences would have on analytical results for ground water samples containing low to moderate concentrations of chlorinated volatile organic compounds (VOCs). This study investigated whether the discrete‐depth ground water sampler used introduces statistically significant differences in analytical results. Our goal was to provide a technical basis for allowing the two devices to be used interchangeably during screening investigations.

Because this study was based on field samples, it included several sources of potential variability. It was necessary to separate differences due to sampler type from variability due to sampling location, sample handling, and laboratory analytical error. To statistically evaluate these sources of variability, the experiment was arranged in a nested design. Sixteen ground water samples were collected from eight random locations within a 15‐foot by 15‐foot grid. The grid was located in an area where shallow ground water was believed to be uniformly affected by VOCs. The data were evaluated using analysis of variance.

This study indicates that when sampling for short‐chain. chlorinated aliphatic compounds such as trichloroethylene, spatial variability from sampling location (over even a relatively small area) exceeds the differences between the Enviroprobe and HydroPuneh I. Therefore, the two sampling devices can be used interchangeably without reducing the internal consistency of the resulting data. However, when sampling for chlorinated aromatics, the choice of sampling device max introduce significant differences in the analytical results.
The Hydraulic Effects of Lost Circulation and the Implications for Contaminant Migration During Drilling
Authors: Schilling Keith E.
Published: February 2007

The impact of lost circulation during rotary drilling near an existing monitoring well cluster was evaluated by periodic measurements of water levels and contaminant concentrations at the well cluster. Due to regulatory concerns, changes in water levels or VOC concentration in the well cluster during drilling would trigger monitoring well redevelopment. The borehole was drilled approximately 30 feet northeast of four nested monitoring wells that screen Devonian and Silurian carbonate bedrock at depths of 15, 60, 130, and 190 feet. Following complete circulation loss at depths of 177 and 1 S3 feet in the borehole, a rapid decrease in water levels was observed in the upper three monitoring wells. The water level in the well that was screened through the lost circulation zones increased slightly.

Decreasing water levels in formations located above the point of circulation loss appear to occur in response to a sudden decrease in borehole fluid pressure caused by the flow of drilling fluid into the formation. The relative contribution of contaminated formation water lo the borehole can be estimated by using the time‐drawdown relationship and estimates of transmissivity. At the point of circulation loss, significant dilution of contaminant concentrations occurs from the loss of drilling fluid into the contaminated zone. Contaminated formation water entering the borehole during periods of complete lost circulation may mobilize contaminants from upper lo lower formations. Lost circulation into a formation would be signaled by a water level increase in monitoring wells. The wells would subsequently require development to remove the volume of fluid lost to the formation, including both drilling fluid and contaminated formation water. Monitoring wells exhibiting declining water levels following lost circulation would not require development since drilling water has not entered the zones screened by these wells.
A Sophisticated Ground Water Analytical Tool
Authors: Tonjes David J. , Heil James H. , Black John A.
Published: February 2007

Stiff diagrams arc a multivariate method of analysis used to describe the chemical state of ground water. The use of Stiff diagrams to describe multiconstituent contamination sites, such as landfills, has distinct advantages over single constituent analyses. Problems associated with traditional Stiff diagram analyses, such as diagram attentuation, can be addressed by allowing the scale of the diagram to vary with the ionic strength of the analyzed sample. The use of these sliding scale Stiff diagrams reveals the chemical slate of the ground water over wide ranges of constituent concentrations and thus allows for sensitive and sophisticated depictions of complicated contamination sites in a fashion that is extremely difficult to replicate with single constituent analyses. This approach has possible applications for understanding and tracing the mixing and chemical changes in uncontaminated settings.
Geophysical Characterization of Smelting Wastes: A Case History
Authors: Ellefsen Karl J. , Bochicchio Regina M.
Published: February 2007

The thicknesses of slag piles at a smelling site in Midvale. Utah, were determined using geophysical methods; this information was needed to estimate the cost of removing or isolating slag that has the potential to contaminate ground water. From a small‐scale preliminary investigation that, included terrain‐conductivity profiling, low‐frequency resistivity measurements, and induction logging, the electrical resistivities of the slag and the underlying sediment were determined to be approximately 100 Ω‐m and 15 Ω‐m, respectively. Because electromagnetic measurements are affected by such significant contrasts, terrain‐conductivity profiling and time‐domain electromagnetic soundings were used to determine the thicknesses of the slag piles. Generally, the estimated thicknesses from both methods were consistent and geologically plausible. In some instances, reliable estimates of the thicknesses could not be obtained because, for example, the measurements were affected by buried metal objects.

In this case study, we emphasize three principles that might help investigators at other smelter sites. First, a small‐scale preliminary investigation saves time and money because those geophysical methods that have the greatest likelihood of success can be determined. Second, when the results from several geophysical methods are consistent, the confidence in the interpretation increases. Third, geophysical characterization is not always successful. Nonetheless, because of its outstanding advantages, it should be used before other more expensive characterization methods arc tried.
Stratigraphic Trapping of Spilled Jet Fuel Beneath the Water Table
Authors: Vroblesky D. A. , Robertson J. F. , Rhodes L.C.
Published: February 2007

Environmental conditions and the initial attempt to recover JP‐4 jet fuel from a shallow aquifer at a tank farm in Hanahan, South Carolina, in 1975. allowed the jet fuel to become stratigraphically trapped below the water table. The trapped jet fuel remained an undetected source of dissolved hydrocarbon contamination in shallow ground water in the area for 17 years. The trapped jet fuel was located when a variety of chemical, hydrologic. geologic, and historical evidence led investigators to install and sample deeper wells. These findings emphasize the need to use an integrated approach lo evaluating the data when determining the extent of contamination and planning fuel recovery operations in a lithologically heterogeneous aquifer.
Uptake of Dissolved and Oil Phase Organic Chemicals by Bacteria
Authors: Mihelcic James R. , Pritschow Annette , Lueking Donald R.
Published: February 2007

Hydrophobic organic chemicals (HOCs) discharged into soil and ground water will partition into gaseous, aqueous, oil, and sorbed phases. Knowledge of how bacteria assimilate HOCs is important to individuals involved in evaluating intrinsic, or engineered, bioremediation. The majority of bacteria isolated from the subsurface are gram‐negative. The outer membrane of gram‐negative organisms acts as a selective barrier to many solutes, including hydrophobic chemicals. Thus, diffusional transport of a hydrophobic solute through the outer membrane may be the rate‐limiting step in biodegradation. Bacteria may also produce biosurfactants that can facilitate cell‐oil contact or assist solubilization of oil and sorbed phases.
Sampling of Agrochemicals for Environmental Assessment in Rice Paddies: Dry Tropical Wetlands, Costa Rica
Authors: Loaiciga Hugo A. , Robinson Timothy H.
Published: February 2007

This paper presents results from a preliminary sampling strategy developed to track agricultural contaminants found in surface and subsurface media and used commonly in rice paddy cultivation in the dry, tropical forest coastal region of Guanaeaste, Costa Rica. The emphasis is on the impact of eight indicator pesticides, five forms of nitrogen and phosphorus that are common nutrients found in fertilizers. After the field sampling strategy was developed, soil and water samples were collected twice: once during the beginning: of the wet season and once during the initiation of the dry season. Hydrological parameters, soil classifications, agricultural product toxicology, irrigation and drainage networks, cultivated areas, land ownership, and pristine environments have been studied, mapped, and entered into a database in order lo understand the spatial and temporal distribution of potential contaminants and their pending ecological degradation.

Alternative crops and agricultural practices are suggested to reduce or eliminate impacts on biological preserves. Database development and basin characteristics have been entered into a Geographic Information System (GIS) that is capable of fully integrating suggested site modeling. Field sampling results indicate that proposed rice paddy cultivation in a relatively undisturbed basin is likely lo have minimal impact on downstream biological preserves.
Planning Urban Growth in Ground Water Recharge Areas: Central Valley, Costa Rica
Authors: Rodriguez‐Estrada Hugo , Loaiciga Hugo A.
Published: February 2007

Nitrate levels in the ground water of the Central Valley of Costa Rica have increased in relation to the past. Previous studies determined that the unseweved sanitation systems in the recharge areas are the main source of nitrogen. Calculations are made in this study to estimate the maximum population density allowable without improved sewage systems in order to keep the nitrogen levels in ground water below the World Health Organization (WHO) criteria. Results were achieved employing a mass balance that involved the concentration and rate of domestic effluents and the flow rate in the aquifer, as well as an estimation of the effects caused by the agricultural activity. It was concluded that, in general terms, the population density must not exceed 45 inhabitants per hectare. Otherwise, sewage systems and treatment plants are necessary. These conclusions provide a basis for urban growth planning, which will protect ground water quality. The method used in this case should apply to similar situations.
Investigation of Ground Water Contamination by Fenamiphos and Atrazine in a Residential Area: Source and Distribution of Contamination
Authors: Appleyard Stephen J.
Published: February 2007

Ground water in a residential area of Perth. Western Australia, was contaminated with fenamiphos and atrazine. probably as a result of the storage and handling of these chemicals at a residential properly. Sampling of existing wells indicated that atrazine and fenamiphos concentrations in ground water beneath a neighboring property were 2000 μg/L and 1000 μg/L, respectively. Fenamiphos concentrations were sufficiently high to be toxic on prolonged skin contact, and contamination posed a public health threat to nearby residents with private wells. Management of the contamination problem included restricting ground water use in the area and using a recovery well to pump contaminated ground water.
The Application of a Statistical Trend Analysis Model to Ground Water Monitoring Data from Solid Waste Landfills
Authors: Lachance Amy D. , Stoline Michael R.
Published: February 2007

A statistical trend methodology is used to compare ground water quality between eight landfill sites in western Michigan as a case study. Monitoring data were collected over a 15‐year period on 36 parameters at an upgradient and downgradient well selected at each of the eight sites. This yielded a total of 576 monitoring data sets available for analysis. New trend and contamination indices are introduced that are used to compare ground water contamination between these eight sites. These indices are used to assess each landfill's relative potential for environmental harm.

Many questions remain unanswered, but what is demonstrated here is that this type of methodology has the potential to be used to assess trends of ground water chemistry concentrations at landfill sues in a region. A specific purpose of such an assessment could be to provide a quantified basis for the prioritization of funds allocated for cleanup of contaminated landfill sites. Having a technical capability to reduce large amounts of ground water monitoring data to appropriate summaries, which then can be used to assess environmental contamination between several sites, could also have important economic and health implications in other settings. Hopefully this paper will encourage further development of such technologies for these purposes.
Inexpensive Electronic Water Level Recorders for Hydrologic Studies
Authors: Keenan R. , Dickerson J. , Gardner L. , Reeves H.
Published: February 2007

Hydrologic investigations typically involve the collection of water level measurements at discrete points in space and time. The high cost of commercial electronic recorders can be a burden. We have developed an inexpensive (∼$200) electronic water level recorder consisting of a Motorola microcontroller, a clock, memory, pressure transducers, and associated circuitry. The instrument is powered by a 6‐V battery. These devices, each capable of monitoring up to eight channels of analog input, are presently providing continuous monitoring of nested piezometers, tide gauges, and rain gauges in hydrologic studies at the Savannah River site and the North Inlet (South Carolina) Long‐Term Ecological Research (LTER) site. The instruments can be custom tailored to record water levels at any specified time interval, or whenever the water level changes by a specified amount, and can store up to 32,000 water level observations. These instruments have been used to conduct slug tests and can be configured to monitor observation wells for pumping tests. Simplicity of construction and availability of components offer hydrologists an inexpensive but reliable method of water level recording. Several examples of the use of this instrumentation in diverse hydrologic settings are described.
The Rehabilitation of Monitoring Wells Clogged by Calcite Precipitation and Drilling Mud
Authors: Kroening David E. , Snipes David S. , Brame Scott E. , Hodges Rex A. , Price Van , Temples Tom J.
Published: February 2007

Based on aquifer performance tests, 13 out of 15 wells situated at the Mixed Waste Disposal (MWD) area located at the Savannah River site. South Carolina, exhibited high skin factors and low well efficiencies indicative of severely damaged wells. The use of damaged wells in aquifer testing can lead to inaccurate determinations of aquifer properties, and such wells are unusable in future remediation programs. Moreover, damaged wells can go dry during purging, thus compromising sample collection. Pump tests, chemical analyses, and biological investigations revealed that the poor well performance at MWD was attributable to calcite precipitation on the well screen and drilling mud in the filter pack. The calcite problem resulted from improper well installation, and the drilling mud in the filter pack was due to inadequate well development.

Experimental rehabilitation procedures employed on two wells, MWD 5A and 1A, included acidification, swabbing, introduction of surfactants, and surging. Treatment of the wells substantially improved well yields, skin factors, and well efficiencies. Moreover, well rehabilitation was determined to be a reasonable alternative to drilling new wells at the MWD wellfield.
Cryogenic Drilling: A New Drilling Method for Environmental Remediation
Authors: Simon Rafael D. , Cooper George A.
Published: February 2007

Cryogenic drilling is a technique developed at the University of California (UC), Berkeley, for drilling in unstable sediments of environmental monitoring, for characterizing, and for remediation wells, The method uses standard air rotary drilling techniques, but with cold nitrogen rather than ambient air as the circulating fluid in order to freeze and stabilize the borehole wall. Several laboratory and full‐scale field tests have been performed. A.52‐foot‐deep (16 m) soil boring and 24 foot (7 m) monitoring well have been drilled as part of the Lawrence Berkeley Laboratory Site Characterization Project. Continued testing and refinement of the equipment and operational method are in progress. The method has been proposed for use as part of the Department of Energy (DOE) weapons site cleanup at locations with unstable sediments such as Hanford, Sandia, and Idaho National Engineering Laboratory (INEL).
Secondary Effects of Soil Venting and Potential Low‐Cost Enhancements
Authors: Walton John C. , Anker Charles B.
Published: February 2007

Soil venting, in addition to removing volatile organic compounds, has secondary effects on soil temprature and moisture content. A simple enthalpy balance model is used to illustrate the maganitude and direction of temperature and moisture content changes in the soil during ordinary venting and with several potential modifications to venting. Because of the importance of latent heat of vaporization, injection of warm, dry air into the substance is generally ineffective in heating the soil. In contrast, injection of humidified, slightly heated air is found to result in significant soil warming even at low flow rates. Soil warming is thought to be an important mechanism for enhancing remediation, particularly in the final or tail stage of cleanup where concentrations slowly decline wiht time. A variety of soil venting alternatives are simulated at hypothetical sites in Chicago, Illinois, and Tucson, Arizona, including simple humidification, humidification with solar heating, and venting under positive pressure. All there methods result in higher final soil temperatures than the control case of normal soil venting. Humidification of the input air at the rates applied does not result in significant change in average soil moisture content or saturation of the soil wtih water.
Analysis of Petroleum‐Contaminated Water by GC/FID with Direct Aqueous Injection
Authors: Potter Thomas L.
Published: February 2007

A direct aqueous injection capillary gas chromatography/flame ionization (GC/FID) procedure for the analysis of petroleum‐contaminated water was developed and applied to seven water samples saturated with different petroleum products. Separation of C1 to C4 alcohols, C6 to C9 monoaromatics, MTBE, phenol, aniline, and other compounds, and the detection of BTEX compounds at concentrations at or below their maximum contaminant levels (MCLs) is reported. Among the test compounds analyzed, the only pair found to coelute were 1‐butanol and benzene. A method for confirmation of alcohols and polar compounds in the presence of dissolved petroleum hydrocarbons was also evaluated. In this case, water samples were analyzed before and after purging. Polar compounds were found to be significant components of the water soluble fractions of commercial petroleum products.
Micellar‐Enhanced Ultrafiltration and Air Stripping for Surfactant‐Contaminant Separation and Surfactant Reuse
Authors: Lipe K. Michelle , Sabatini David A. , Hasegawa Mark A. , Harwell Jeffrey H.
Published: February 2007

Micellar‐enhanced ultrafiltration (MELT) and air stripping were evaluated for surfactant‐contaminant separation and surfactant recovery. Two linear alkyl diphenyloxide disulfonate (DPDS) surfactants were evaluated with the contaminants naphthalene and trichloroethylene. A separation model developed from micellar partitioning principles showed a good correlation to batch MEUF studies, whereas flux analysis highlighted concentration polarization effects in relation to hydrophobe length. MEUF effectively concentrated the surfactant‐contaminant system (93 to 99 percent retention); however, this did not result in surfactant‐contaminant separation. Batch and continuous flow air stripping models were developed based upon air/water ratio, surfactant concentration, and Micellar partitioning; model predictions were validated by experimental data. Sensitivity analyses illustrated the decline in contaminant‐surfactant separation with increasing surfactant concentration (e.g., TCE removal efficiency declines from 83 percent to 37 percent as C‐16 DPDS concentration increases from 0 to 55 mM). This effect is greater for more hydrophobic contaminants (naphthalene vs. TCE) and surfactants with greater solubilization potential (C16‐DPDS vs. C‐12 DPDS). The resulting design equations can account for this effect and thus properly size air strippers to achieve the desired removal efficiency in the presence of surfactant micelles. Proper selection and design of surfactant‐contaminant separation and surfactant recovery systems are integral to optimizing surfactant‐enhanced subsurface remediation.
Performance of the In Situ Microcosm Technique for Measuring the Degradation of Organic Chemicals in Aquifers
Authors: Nielsen Per H. , Christensen Thomas H. , Albrechtsen Hans‐Jørgen , Gillham Robert W.
Published: February 2007

An in situ microcosm (ISM) consists of a stainless steel cylinder isolating about 2 L of the aquifer and is equipped with valves allowing for loading and sampling from the ground surface. During the last five years, this technique has been used frequently to study the degradation of organic chemicals in polluted and pristine aquifers representing different redox environments. The ISM technique has great potential for providing field‐relevant degradation potentials and rate constants, but care must be taken in using the equipment and interpreting the results. This paper provides details concerning the installation and operation of an ISM and presents experiences concerning data interpretation and monitoring of redox conditions.
Allocation of Environmental Remediation Funds Using Economic Risk‐Cost‐Benefit Analysis: A Case Study
Authors: James Bruce R. , Huff Dale D. , Trabalka John R. , Ketelle Richard H. , Rightmire Craig T.
Published: February 2007

Efficient allocation of remediation resources is a critical need throughout the nation. Economic risk‐cost‐benefit analysis is an important tool for meeting this need. This paper provides site engineers, geologists, and managers with a conceptual understanding of economic risk‐cost‐benefit analysis and shows how it can be applied, even in situations where existing data are sparse or poor in quality. An example analysis is applied to the remediation of radioactive waste at Oak Ridge National Laboratory, in which the cost‐effectiveness is compared for two remediation alternatives: containment of the waste or monitoring only. A data‐worth analysis is also carried out to estimate the maximum justifiable exploration budget and the cost‐effectiveness of two proposed data collection programs. Results indicate that the methodology has potential in making robust remediation decisions regarding certain types of questions.
Intercomparison of Waterborne222Rn Collection Methods: Professional Vs. Homeowner Collection
Authors: Field R. William , Kross Burton C.
Published: February 2007

An intercomparison between trained professional and homeowner water collection techniques was conducted to assess the validity of using both inexperienced homeowner water collectors and mail‐in return of point‐of‐use water samples. The findings indicate that homeowner‐collected water samples obtained at the point of use inside the home and professionally collected water samples collected at an outside tap are comparable, especially if confounders, such as air bubbles in the sampling vials, are minimized.
Effects of Process Control Changes on Aquifer Oxygenation Rates During In Situ Air Sparging in Homogeneous Aquifers
Authors: Rutherford Kyle W. , Johnson Paul C.
Published: February 2007

In situ air sparging is used to remediate petroleum fuels and chlorinated solvents present as submerged contaminant source /ones and dissolved contaminant plumes, or to provide barriers to dissolved contaminant plume migration. Contaminant removal occurs through a combination of volatilization and aerobic biodegradation: thus, the performance at any given site depends on the contaminant and oxygen mass transfer rates induced by the air injection. It has been hypothesized that these rates are sensitive to changes in process flow conditions and site lithology, but no data is available to identify trends or the magnitude of the changes. In this work, oxygenation rates were measured for a range of air injection rates, ground water flow rates, and pulsing frequencies using a laboratory‐scale two‐dimensional physical model constructed to simulate a homogeneous hydrogeologic setting. Experiments were conducted with water having low chemical and biochemical oxygen demand. Results suggest the following: that there is an optimum air injection rate: advective How of ground water can be a significant factor when ground water velocities are > 0.3 m/d: and pulsing the air injection had little effect on the oxygenation rate relative lo the continuous air injection case.
History of the Sole Source Aquifer Program: A Community‐Based Approach for Protecting Aquifers Used for Drinking Water Supply
Authors: McCabe William J. , Job Charles A. , Simons John J. , Graves John S. , Terada Calvin J.
Published: February 2007

The Sole Source Aquifer Program has helped prevent contamination of many community drinking water supplies. If an aquifer supplies the sole or principal source of a community's drinking water, a local ground water user may petition the Environmental Protection Agency (EPA) under the Safe Drinking Water Act for its designation and protection as a “sole source aquifer.” Since 1974, residents and officials of 65 communities and multi‐community areas have petitioned and received assistance from the EPA to prevent contamination of their local ground water source of drinking water. This designation means that EPA may review federal financially assisted projects to determine if they would contaminate the aquifer and cause a public health hazard. If they could cause contamination, EPA can request that the project be modified or stopped. The significance of this program in terms of population served and funds affected has been substantial, indicating the Sole Source Aquifer Program has been an important local tool for protecting ground water used as a source of drinking water. Information is given on three different examples of sole source aquifer designations protected under this program: the New Jersey Coastal Plain Aquifer System, the Great Miami River Buried Valley Aquifer System (Ohio), and the Eastern Snake River Plain Aquifer (Idaho), serving populations of 543,000, 921,000, and 275,000, respectively. In all three examples, preventing ground water contamination through the Sole Source Aquifer Program has protected the community drinking water supply.
Field Evaluation of Ultrasonic Method for Assessing Well Seals
Authors: Yesiller Nazli , Benson Craig H. , Edil Tuncer B.
Published: February 2007

Field tests were conducted in three boreholes using an ultrasonic testing method to evaluate its ability to assess contact between the seal and riser (casing). The ultrasonic method is used inside the riser without disturbing the riser, seal, or formation soil. The risers were 50‐mm‐diameter (2‐inch) Schedule 40 steel pipes that are used for ground water monitoring wells. Different types of seals were placed around the risers and defects were purposely introduced in the seals to test the ultrasonic method. The ultrasonic response changed as the neat‐cement seals cured or hydration of the bentonite seals changed. When adequate moisture was not available, the bentonite seals deteriorated, losing contact with the riser. When adequate moisture was available, however, the seals swelled into contact with the riser. Both conditions were detected with the ultrasonic method. The method also detected the intentional defects, as well as defects that were not intended. The boreholes were excavated to compare results of the ultrasonic tests with the actual condition of the seals. The condition of the seals agreed well with the results of the ultrasonic tests.
Three‐Dimensional Experimental Testing of a Two‐Phase Flow‐Modeling Approach for Air Sparging
Authors: Hein Gretchen L. , Gierke John S. , Hutzler Neil J. , Falta Ronald W.
Published: February 2007

Air sparging has been used for several years as an in situ technique for removing volatile compounds from contaminated ground water, but few studies have been completed to quantify the extent of remediation. To gain knowledge of the air flow and water behavior around air injection wells, laboratory tests and model simulations were completed at three injection flow rates (62, 187, and 283 lpm) in a cylindrical reactor (diameter ‐ 1.2 m, depth = 0.65 m). Measurements of the air flux distribution were made across the surface of the reactor at 24 monitoring locations, six radial positions equally spaced along two orthogonal transects. Simulations using a multiphase flow model called T2VOC were completed for a homogeneous, axisymmetric configuration. Input parameters were independently measured soil properties. In all the experiments, about 75 percent of the flow injected exited the water table within 30 cm of the sparge well. Predictions with T2VOC showed the same. The averages of four flux measurements at a particular distance from the sparge well compare satisfactorily with T2VOC predictions. Measured flux values at a given radius varied by more than a factor of two, but the averages were consistent between experiments and agreed well with T2VOC simulations. The T2VOC prediction of the radial extent of sparging coincided with the distance out to which air flow from the sparge well could not be detected in the reactor. The sparging pattern was relatively unaffected by the air injection rate over the range of conditions studied. Changes in the injection rate resulted in nearly proportional changes in flux rates.
Analytical Model for Contaminant Mass Removal by Air Sparging
Authors: Rabideau Alan J. , Blayden James M.
Published: February 2007

An analytical model was developed lo predict the removal of volatile organic compounds (VOCs) from ground water by air sparging (AS). The model treats the air sparging zone as a completely mixed reactor subject to the removal of dissolved contaminants by volatilization, advection, and first‐order decay Nonequilibrium desorption is approximated as a first‐order mass transfer process. The model reproduces the tailing and rebound behavior often observed at AS sites, and would normally require the estimation of three site‐specific parameters. Dimensional analysis demonstrates that predicted tailing can be interpreted in terms of kinetic desorption or diffusion of aqueous phase contaminants into discrete air channels. Related work is ongoing to test the model against field data.
Removal of Volatile Organic Compounds from Surfactant Solutions by Flash Vacuum Stripping in a Packed Column
Authors: Choori Umesh N. , Scamehorn John F. , O'Haver John H. , Harwell Jeffrey H.
Published: February 2007

Volatile organic compounds (VOCs) am be removed from contaminated ground water and subsurface media by surfaclant‐enhanced remediation processes. For the process to be economically competitive it is necessary to recover and reuse the surfactant from this concentrated solution. The VOC can be removed from this concentrated solution by flash vacuum stripping, leaving the surfactant solution for reuse. In this study, the flash vacuum stripping of trichloroethylene (TCE) from an anionic surfactant solution in a co‐current packed column was studied under rough vacuum conditions. The presence of surfactants lead to a reduction in the overall liquid phase volumetric mass transfer coefficient (MTC) of 40 to 95%. depending on flow rate and surfactant concentration at 50°C and 16 kPa. At liquid loading rates of less than 13 cm3/cm2min, the MTC of TCE decreases rapidly with an increase in liquid loading rate, and at liquid loading rates above that, the MTC decreases slightly with an increase in the liquid loading rate. This trend may have been due to foaming. At surfactant concentrations above the critical micelle concentration, the effect of surfactant concentration was not significant at liquid loading rates less than 13 cm3/cm2min. However, beyond that rate, the MTC of TCE decreased drastically with an increase in surfactant concentration. The MTC of TCE increased with an increase in temperature. A large pressure drop (3 to 4 kPa/m) was observed across the packed bed due to foaming.
Comparison of Fiberglass and Other Polymeric Well Casings Part II. Sorption and Leaching of Trace‐Level Organics
Authors: Ranney Thomas A. , Parker Louise V.
Published: February 2007

This paper contains the results of a laboratory study that was designed to compare sorption of low (mg/L) concentrations of 11 organic solutes by six polymeric materials (acrylonitrile butadiene styrene [ABS], fluorinated ethylene propylene [FEP], fiberglass‐reinforced epoxy [FRE] and fiberglass‐reinforced plastic [FRP], polyvinyl chloride [PVC], and poly‐tetrafluoroethylene [PTFE]).

During this six‐week study, ABS sorbed analytes much more rapidly and to a greater extent than did the other materials, and PVC and FRE sorbed analytes more slowly and to a lesser extent than the other materials tested.

As the study progressed, an increasing number of spurious peaks were found in the high performance liquid chromatography (HPLC) chromatograms of some of our samples, indicating that leaching of some consituents had occurred. By the end of the study, there were 11 additional peaks in the ABS samples, five in the FRP samples, and one in the FRE samples. Analysis by purge and trap gas chromatography/mass spectrometry (GC/MS) of those samples and of well water samples that were exposed to the casings for 500 hours revealed the identity of some of the leached constituents; acrylonitrile and styrene (components of ABS), chloroform and ethylbenzene (an intermediate in the production of styrene) from the ABS pipe, and toluene, 1,1,1‐trichloroethane, and ethylbenzene from the FRP casing.
Modeling of Plume Capture by Continuous, Low‐Permeability Barriers
Authors: Garon Kevin P. , Schultz Dale S. , Landis Richard C.
Published: February 2007

Modeling was performed to simulate ground water flow through reactive barriers of lower hydraulic conductivity than the surrounding aquifer to determine the plume capture widths. As a plume approaches such a barrier, it spreads laterally. Therefore, to intercept an entire plume, the barrier must be wider than the upgradient width of the undisturbed plume. The results indicate that, for practical values of barrier thickness and plume width, hydraulic conductivities ten‐fold less than that of the aquifer can be accommodated by making the width of the barrier approximately 20% greater than the upgradient width of the plume. Barrier hydraulic conductivities one‐hundred‐fold less than that of the aquifer may require barrier widths up to twice the width of the upgradient plume for plumes 100 feet wide (33 m) and as little as 1.1 times for plumes 1000 feet wide (325 m). The results presented here lend support to the view that novel emplacement methods that create zones of slightly lower hydraulic conductivity than the native aquifer may be viable alternatives to the excavation‐and‐backfill approaches which have thus far been used for installing permeable reactive barriers.
Characterization of a TCE DNAPL Zone in Alluvium by Partitioning Tracers
Authors: Young C. M. , Jackson R. E. , Jin M. , Londergan J. T. , Mariner P. E. , Pope G. A. , Anderson F. J. , Houk T.
Published: February 2007

Partitioning interwell tracer tests (PITT) were used ID determine the spatial distribution and volume of residual trichloroethene (TCE) present in alluvium beneath the Portsmouth Gaseous Diffusion Plain in southern Ohio. Its first use at this site was in support of the design of a surfactant flood to remove the residual DNAPL (dense nonaqueous phase liquids) from the alluvial aquifer. The second application assessed the performance of the surfactant flood. The average DNAPL saturation in the first PITT was 0.1 to 0.2% in a swept pore volume of 4500 gallons (17.000 L). A second PITT was undertaken following the surfactant flood and yielded an average residual saturation of 0.06% in a swept pore volume of 3400 gallons (13.000 L), the reduction in pore volume being due to the confinement of the tracers to the lower sand and gravel unit of the alluvium. The design, operation, and analysis of the two PM Is provided strong evidence of a buried channel that controls the spatial distribution of the residual TCI: DNAPL in the basal sand and gravel aquifer and must be considered in the eventual full remediation of this aquifer.
Using Hydrochemical Fades to Delineate Ground Water Flowpaths in Fractured Shale
Authors: Schreiber M. E. , Moline G. R. , Bahr J. M.
Published: February 2007

Large differences in chemistry between sampling points separated In short vertical intervals are often observed in contaminant plumes in both granular and fractured aquifers. However, most regional models assume that such differences will be reduced by dispersive mixing during transport. At a field site located in a discharge area on the Oak Ridge Reservation, Tennessee, ground water flows along discrete flowpaths, as evidenced by the presence of four distinct water types—Ca‐HCO3, Ca‐Na‐HCO3, and Na‐Ca‐HCO3, and Na‐Ca‐HCO3‐S04—in samples collected from shallow (< 3D in) multilevel wells. The preservation of distinct chemical signatures suggests that ground water must he contained in discrete flow zones during much of its transport time. The chemical composition of the water types can be explained primarily by strata‐bound flow over varying flowpath lengths and secondarily by mixing of waters during cross‐formational flow in a discharge zone. The hydrochemical facies identified by correlation of water types between the boreholes indicate the general orientation of ground water How paths. These inferred flowpaths are oblique to the orientation of the measured hydraulic gradient and are more closely aligned with bedding and the calculated flow direction. Results of this study indicate that discrete multilevel sampling for analysis of major ions, in addition to information gathered from tracer tests, borehole flow tests. and visual core observations, can provide valuable information on flow directions and preferential flowpaths for contaminant transport.
Demonstrating Localized Intrinsic Biodegradation of Chlorinated Aliphatic Hydrocarbons Using Time Series Sampling
Authors: Schilling Keith E.
Published: February 2007

Localized intrinsic biodegradation of chlorinated aliphatic hydrocarbons (CAHs) was investigated by pumping from a monitoring well screened in a low conductivity carbonate mudstone. Two time series tests were conducted to assess the relative potential for intrinsic biodegradation in occur in the mudstone compared to the surrounding highly productive carbonate aquifer. Water samples were collected during pumping and analyzed for CAHs (tests 1 and 2). and water quality parameters (pH, specific conductance, dissolved oxygen, redox), election donors and acceptors, and biodegradation indicators (chloride, alkalinity) (test 2). During both lime series tests, concentrations of TCE breakdown products— DCE, vinyl chloride and ethane—decreased significantly after pumping 500 gallons of water from the well. During lest 2. concentrations of electron donors and acceptors and biodegradation indicators decreased, whereas dissolved oxygen and redox remained at low levels. Multiple lines of evidence demonstrated that that intrinsic bioremediation of CAHs is occurring in the mudstone, including: (1) presence of anaerobic conditions in the mudstone conducive for reductive dechlorination: (2) progression of electron acceptors and presence of methanogenic conditions; (3) available supply of electron donors in the mudstone: (4) occurrence of TCE breakdown products; and (5) increased chloride and alkalinity concentrations in the zone of active biodegradation.

Time series testing indicated that during the early stages of pumping, effluent consisted mainly of ground water derived from the mudstone unit. With continued pumping, an increasing percentage of effluent water was derived from the less contaminated, permeable carbonate units which bounded the mudstone layer. Differences in permeabilities between the carbonate aquifer and mudstone layer probably accounted for the varying degree of intrinsic biodegradation observed between the two systems. Future remedial efforts should consider avoiding ground water extraction from the mudstone and disturbing the intrinsic biodegradation processes that are reducing contaminant mass in the aquifer.
Comments on EPA Guidance for Ground Water Studies
Authors: Cohen Stuart
Published: February 2007

“The panel provided good, solid, interdisciplinary advice on a variety of challenging, state‐of‐the‐art issues.”
The Challenge of Ground Water Quality Monitoring
Authors: Anzzolin A. Roger , Siedlecki Mary , Lloyd Jennifer
Published: February 2007

“Valuable information pertaining to contaminant sources, contaminants, and ground water quality was derived using the state‐supplied data.”