bluuebunny/crossref_metadata_2025 huggingface dataset:
Migration of Petroleum Products Through Sandy Hydrogeologic Systems
Authors: Abdul Abdul S.
Published: February 2007

Laboratory column experiments were carried out to study the migration of petroleum products through a sandy porous medium. It was found that the oil pressure needed to displace water from the pores of the sand medium increased with depth below the top of the column. While oil under negative pressure displaced water through the variably unsaturated zone, a significant vertical column of oil was needed to displace water from the pores at the water table. These results indicate that oil penetration to and below the water table will occur only if the porous medium is highly conductive and the rate of oil leak is high. For small to moderate leak rates and hydraulic conductivities, oil would preferentially spread laterally through the zones above the water table. This process of spreading could serve as a natural barrier to severe aquifer contamination by petroleum products.

A simplified procedure was developed to give an order‐of‐magnitude estimate of the preferred subsurface migration pathways of leaked petroleum products. This procedure utilizes the main drainage and wetting curves for oil and water and the interfacial pressure between these two fluids. This approach could be useful in guiding exploratory investigations, reducing both the risk for further spreading of the contaminants and the investigative cost.
Evaluation of a Carbon Adsorption Method for Sampling Gasoline Vapors in the Subsurface
Authors: Wallingford Edward D. , DiGiano Francis A. , Miller Cass T.
Published: February 2007

Monitoring of the vapor phase has emerged as a very convenient method for detecting volatile organic contaminants in the subsurface. It can provide a reliable way of placing ground water monitoring and recovery wells. The most common method uses a driveable ground probe (DGP) to extract a vapor‐phase sample followed by direct injection of the vapor into a portable gas chromatograph (GC). However, many regional offices of regulatory agencies and consultants do not have ready access to such equipment. This research explores an alternative–the carbon adsorption method—in which the vapor is withdrawn by the DGP but concentrated on a small activated carbon trap (150mg). The carbon traps can be returned to a central laboratory for solvent extraction and GC analysis. This provides the advantages of increased sensitivity, reduction in field equipment and convenience of in‐lab analyses (multiple GC injections are possible). A simple DGP and carbon trap system was constructed and tested at a field site. Vapor‐phase concentrations of target compounds present in gasoline were mapped quite conveniently, ranging from 10,000μg/liter (vapor phase) to less than 10μg/L. These concentrations were also shown to decrease in the direction of the ground surface, as expected. Measurements of target compounds in soil showed that the vapor phase contributed a large fraction of the total contaminant burden where a non‐aqueous‐phase layer (NAPL) had been identified; as important, however, is the rather uniform contamination of the soil outside the NAPL region. Finally, the concentrations of target compounds in the vapor phase and ground water could be related in a manner roughly described by a simple equilibrium model, although exceptions were noted.
Small‐Scale Retrospective Ground Water Monitoring Studies for Agricultural Chemicals: Study Design and Site Selection
Authors: De Martinis James M.
Published: February 2007

A small‐scale retrospective ground water monitoring study is designed to determine if, after years of normal usage, an agricultural chemical has leached to ground water. These studies are conducted on actively planted fields in hydrogeologically vulnerable areas. Because the results of such studies may have larger ramifications for the particular agricultural chemical over much broader hydrogeologic and geographic areas, care must be exercised in selecting particular fields to be monitored and in establishing site‐specific ground water monitoring networks.

The U.S. Environmental Protection Agency, Office of Pesticide Programs, has established draft guidelines and suggested field protocols for such studies. These guidelines serve as a baseline for such studies, though many other hydrogeologic and agronomic factors play significant roles. Small‐scale retrospective studies are ordinarily broken into a series of tasks that lead to the selection of a suitable test site(s) by determining on a national scale where to monitor; meeting minimum hydrogeologic and agronomic criteria; and establishing a ground water monitoring program.

A detailed hydrogeologic vulnerability analysis is conducted in product use areas for the chemical being studied. A series of screening steps results in a subset of moderate‐ to high‐use counties that are underlain by permeable soils and vulnerable to ground water impacts from agricultural chemicals. Once these counties are determined, suitable test fields can be selected.

The individual site selection criteria can be exhaustive. However, these criteria in combination with one another are necessary to ensure that the selected sites will yield information as to whether or not the chemical has leached through the soil profile and the unsaturated zone to ground water. The following criteria are considered essential to a particular site: flat topography; “workable” field size; documented history of use of the chemical being monitored; avoidance of regional and farm‐specific point sources; typical irrigation and farm practices for the crop on which the chemical is applied; farmer cooperation; field accessibility; permeable soils and unsaturated zone; and shallow water table. There are also other hydrogeologic and agronomic parameters that need to be assessed prior to site selection.

The hydrogeologic and agronomic criteria are not always easily met. For example, the topography and shallow water‐table criteria could eliminate key agricultural areas in the United States where the agricultural chemical to be monitored may be used. However, the data generated during these field‐scale retrospective studies, when properly conducted, can provide information regarding whether or not a particular agricultural chemical has leached to ground water under worst‐case conditions.
Field Evaluation of a Slim‐Hole Borehole Induction Tool
Authors: Taylor Kendrick C. , Hess John W. , Mazzela Aldo
Published: February 2007

The Geonics EM‐39 borehole induction tool was field tested to evaluate its performance under controlled conditions. The effects of temperature changes and borehole fluids were found to be negligible under most conditions. The instrument can be calibrated in large bodies of water of known electrical conductivity. When properly calibrated, the ± 5 percent accuracy claimed by the manufacturer is obtainable. A geologic unit must be at least 4m thick for the electrical conductivity of the unit to be accurately measured. Geologic units thinner than 4m thick can be detected if the conductivity contrast to adjacent units is sufficiently large.
In Situ Bioreclamation: A Cost‐Effective Technology to Remediate Subsurface Organic Contamination
Authors: Wilson Scott B. , Brown Richard A.
Published: February 2007

In situ bioreclamation is a proven technology that cost‐effectively treats organic contamination in subsurface environments. As a remediation strategy, it reduces both the contamination dissolved in ground water, as well as residual soil‐bound contamination.

To maximize biodegradation, the technology is applied after conducting laboratory studies. Application of the technology involves infiltrating necessary nutrients to the contaminated subsurface.

Results of a specific case study indicate excellent performance with rapid cleanup of petroleum hydrocarbon contamination from soils and ground water.

Costs associated with in situ bioreclamation technology showed a savings of approximately 50 percent over simple pump‐and‐treat technology. Time frame for cleanup was shown to be approximately 30 percent of the projected time frame of simple pump‐and‐treat technology.
A Practical Approach to Shallow Petroleum Hydrocarbon Recovery
Authors: Hayes Douglas , Henry Evan C. , Testa Stephen M.
Published: February 2007

A practical pumping system for the recovery of free petroleum hydrocarbon product from shallow aquifers has been developed. The system is patterned after suction‐lift well point dewatering systems used in the construction industry. Pumping equipment consists of double‐diaphragm suction‐lift pumps manifolded to up to four recovery wells. Recovery wells are constructed with screens below the water table and sealed wellheads to enable vacuum‐assisted flow of fluids to the wells. Pumps utilized are pneumatically driven, can be pumped dry without damage, induce a vacuum on the wells when pumping dry, and provide delivery of pumped fluids to fluid separation and storage facilities. The system is effective in both low‐ and high‐permeability formations due to the wide range in available pumping rates afforded by the pumps.
Limitations of Monitoring Wells for the Detection and Quantification of Petroleum Products in Soils and Aquifers
Authors: Abdul Abdul S. , Kia Sheila F. , Gibson Thomas L.
Published: February 2007

Theoretical analysis and laboratory column experiments were carried out to investigate the conditions required for petroleum products (oil) to flow into a well installed through a sandy porous medium contaminated with the oil. The results indicated that oil would flow into a well only after a layer of “free oil” is formed in the adjacent porous medium. Because significant quantities of oil could be stored in the porous medium under the influence of capillary suction prior to the formation of the zone of free oil, the presence of oil in a well would indicate an advanced stage of oil contamination of the subsurface. While monitoring wells could be used to delineate the extent of the free‐oil plume and the plume of dissolved petroleum constituents, they are not useful for delineating the extent of capillary held oil.

The experimental results also indicated that the ratio of the oil‐layer thickness in the well to that in the porous medium is not a constant as is sometimes assumed in practice. Further, estimates of the oil thickness in the medium based on the oil thickness in wells and on capillary properties measured in the laboratory were sensitive to the values of the parameters used in these estimates. The measured thickness of the oil layer in a monitoring well alone may not yield reliable estimates of the amount of oil in the subsurface, and assuming that the oil‐thickness ratio is a constant can lead to inadequate site assessments and inappropriate remedial plans.
A Remedial Investigation of an Organically Polluted Outwash Aquifer
Authors: Jackson Richard E. , Patterson Ronald J.
Published: February 2007

A glacial outwash aquifer underlying the Gloucester Landfill near Ottawa, Canada, has become polluted with various organic chemicals following the disposal of laboratory solvents in shallow trenches immediately above the aquifer. Several remedial alternatives have been considered by the government of Canada. Impermeable barrier walls were rejected as being unsuitable given the permeable nature of the underlying bedrock. It appears improbable that pools of liquid organic chemicals (DNAPLs) exist within the aquifer, although ganglia are likely present. Therefore, much of the contaminant plume can be removed hydraulically over a period of five years by the operation of four purge wells discharging to an on‐site treatment plant from which the purified water is returned to the aquifer by recharge wells. The residual contamination is anticipated to be cleaned up by in situ biorestoration techniques currently under development.
Hydraulic Conductivity Measurements in the Unsaturated Zone Using Improved Well Analyses
Authors: Elrick D.E. , Reynolds W.D. , Tan K.A.
Published: February 2007

The flow of ponded water into and through the unsaturated zone depends on both the saturated and unsaturated components of the hydraulic conductivity. Recent studies indicate that the ratio of the saturated (Kfs) to the unsaturated (φm) components (Kfs/φm=α*) of flow lies within prescribed bounds for most field soils, i.e., 1m−1≤α*≤ 100 m−1. In addition, the fact that the calculation of Kfs and φm is not strongly dependent on the choice of α*, suggests that a site estimation of α* leads to reasonable “best estimates” of Kfs and φm when using the constant head well permeameter technique. As a consequence, measurement of the steady flow rate using only one ponded head may be all that is necessary for many practical applications. Multiple head measurements or independent measurements of α* or φm can be used, however, to give more accurate estimates of Kfs if required.
Marketing Perspectives for the 1990s
Authors: Pierro W.J.
Published: February 2007

A recent survey sent to 500 environmental consulting firms across the United States has helped document specific promotional vehicles used within the environmental consulting industry, as well as highlighted a wide spectrum of attitudes toward adopting a formalized marketing function within a technically oriented firm. The population of study, from which a 22 percent response rate was received, consisted of scientific, engineering, and combination firms providing hydrogeologic, environmental assessment, natural resource, and hazardous waste management services. The study, conducted for a master's thesis in business administration, was supported in part by Hofstra University of Hempstead, New York.

The study indicated that consultants' resistance toward professional services marketing was directly proportional to the amount of referral work they received; that environmental consultants promote themselves significantly more often through commercial rather than non‐commercial vehicles; and that scientific firms were significantly more resistant to adopting a marketing function than engineering or combination scientific/engineering firms.
Field Methods for Measurement of Ground Water Redox Chemical Parameters
Authors: Walton‐Day Katherine , Macalady Donald L. , Brooks Myron H. , Tate Vernon T.
Published: February 2007

An inexpensive, versatile, and portable system is presented, which facilitates rapid field determinations of redox potentials, pH, conductivity, ferrous and total iron, nitrite, specific conductance, dissolved oxygen, and temperature. Accuracy is facilitated by on‐site measurements of most parameters using specially constructed flow‐through cells and, for several analyses, sealed reagent ampoules, which can be broken and developed inside a flowing stream of ground water. Coupled with laboratory analyses of more stable ground water parameters, this system can provide accurate and relatively inexpensive determinations of redox conditions in ground water.
Temporal Variations of Chlorinated Solvents in Abstraction Wells
Authors: Rivett Michael O. , Lerner David N. , Lloyd John W.
Published: February 2007

Data obtained during an organic water quality survey of abstraction (pumping) wells in the Triassic Sandstone Aquifer of Birmingham (U.K.) indicate that there are important variations of chlorinated solvent concentrations with time. Short‐term observation of solvent concentrations with elapsed pumping time indicates widely differing well responses; such observations are important in establishing good sampling protocols. Long‐term monitoring indicates that solvent concentrations, particularly trichloroethene, are often stable with time. When large solvent variations do occur, these are shown to be due to the variation in the abstraction history of the well or significant migration of solvent plumes during the monitoring period. The latter effect is particularly exemplified by rising trends in 1,1,1‐trichlroethane concentrations. The changes observed in solvent concentrations during long‐term monitoring of the Birmingham Aquifer are slow to occur, but often large.
Monitoring Ground Water for Pesticides at a Golf Course ‐ A Case Study on Cape Cod, Massachusetts
Authors: Horsley Scott W. , Moser John A.
Published: February 2007

The town of Yarmouth, Massachusetts, proposed to locate a new municipal golf course within a delineated area of recharge to public water‐supply wells. Two concerns of town officials were (1) hydrologic impacts upon downgradient wells; and (2) water‐quality impacts from fertilizers and pesticides. In response to these concerns, a thorough hydrogeologic investigation was made, fertilizer and pesticide management programs were recommended, and a ground water monitoring program was developed.

The golf course parcel was determined to be underlain by a sand and gravel aquifer composed primarily of glacial outwash. Water‐table maps confirmed that ground water flow was in the direction of several public water‐supply wells. A three‐dimensional finite‐difference flow model was used to determine the optimum location and pumping rates for irrigation wells. Potential nitrate‐nitrogen concentrations in the ground water were predicted to range from 5.0 to 7.9 milligrams per liter so slow‐release fertilizers were recommended.

With the assistance of the EPA Office of Pesticide Programs, the list of proposed pesticides was reviewed and sorted into three categories based on the known leachability, mobility, and toxicity characteristics of each compound. Specific recommendations were made as to pesticide selection and application rate using that classification.

A monitoring program was developed to provide an on‐going assessment of any effects on water quality related to the application of fertilizer or pesticide. The elements of the monitoring program include (1) specifications for monitoring wells and lysimeters, (2) a schedule for sampling and analysis, (3) specific concentrations of nitrates or pesticide compounds that require resampling and analysis, restriction of usage, or remedial action, and (4) regular reports to the Yarmouth Water Quality Advisory Committee and to the Yarmouth Water Department. In an effort to ensure the implementation of this program, a table of responsibilities was prepared, and a Memorandum of Understanding adopting the program was signed by the town agencies interested in water‐supply protection and the golf course operation.

The monitoring facilities were installed with minimal problems as part of the golf course construction tasks. However, implementation of the sampling and analysis part of the program was accomplished only after some difficulty and delay. The assistance of the State Pesticide Bureau, the University of Massachusetts Department of Entymology, and the Massachusetts Pesticide Laboratory was enlisted when budgetary problems threatened to prevent implementation. It is apparent from Yarmouth's experience that the mere preparation of a plan is not sufficient by itself. Consultants who prepare the plan should make every possible effort to include implementation in their scope of services.
Ground Water Contamination at Wood Treatment Facilities
Authors: Rosenfeld Jeffrey K. , Plumb Russell H.
Published: February 2007

Ground water contamination profiles from five wood treatment facilities across the country have been compared. The distributions of organic priority pollutants at the five sites are similar, with the most common contaminants being polynuclear aromatic hydrocarbons and phenolic compounds. These contaminants are the predominant constituents of creosote, which is a common wood preservative. Inorganic contaminants have also been detected at these sites, but their distributions are not uniform across all sites. The distributions of the organic priority pollutants at the five sites appear to differ from those at other hazardous waste sites. Suggested recommendations for choosing monitoring parameters for wood treatment facilities are presented.
An Analysis of Nitrate‐Nitrogen in Ground Water Beneath Unsewered Subdivisions
Authors: Tinker John R.
Published: February 2007

Water samples from private water supply wells in five unsewered subdivisions were tested for nitrate‐nitrogen to determine the possible impact of septic systems on ground water quality. Three subdivisions are located in Eau Claire County and two in LaCrosse County, Wisconsin.

The nitrate‐nitrogen concentrations in the wells were analyzed in relation to ground water flow direction, the location of septic systems within the subdivision, and the hydrogeologic and physical characteristics of the subdivisions. A comparison of three nitrogen mass balance models helped to identify the possible sources of nitrate‐nitrogen in the wells.

The results indicate that nitrogen from septic systems and lawn fertilizer cause nitrate‐nitrogen to increase in the ground water beneath the downgradient side of the subdivisions. In three of the five subdivisions the highest nitrate‐nitrogen value exceeds the drinking water standard of 10 mg/L.
The Effect of Latex Gloves and Nylon Cord on Ground Water Sample Quality
Authors: Canova Judy L. , Muthig Michael G.
Published: February 2007

Eighteen sites in South Carolina under investigation by the Superfund program were sampled to determine ambient ground water quality. Samples from 11 of 15 monitoring wells sampled with a bailer contained either caprolactam or Santowhite® (a registered trademark of the Monsanto Co.) or both organic compounds. A maximum of 540 μg/L of caprolactam and 780 μg/L of Santowhite was observed in the samples from the monitoring wells. None of the samples collected using dedicated submersible pumps at 28 other wells contained either compound.

Caprolactam is used in the manufacturing of nylon cord, and Santowhite is used as an antioxidant in latex gloves. Therefore, it was suspected that the nylon cord used to raise and lower the bailer and the latex gloves that were worn during sampling may have contributed the caprolactam and Santowhite to the sample.

An experiment using pH‐adjusted distilled water and private well water revealed that the nylon cord and the latex gloves may contribute contaminants to ground water samples. Research is needed into the potential for caprolactam and Santowhite to interfere with laboratory analyses in addition to the potential for absorption of contaminants by nylon cord. Until additional information is available, alternative materials or sampling techniques should be considered to minimize the potential impact of nylon cord and latex gloves on the quality of bailed samples.
A New Sampling System for Obtaining Relatively Undisturbed Samples of Unconsolidated Coarse Sand and Gravel
Authors: McElwee CD. , Butler J.J. , Healey J.M.
Published: February 2007

Geologic site characterization is an important issue that must be addressed if details of contaminant transport in the subsurface are to be understood and predicted. Ideally, the formation heterogeneities at a site must be characterized at several scales. This paper deals with the smallest practical scale: core samples with cross‐sectional dimensions of a few inches. Historically, there has been great difficulty in obtaining relatively undisturbed cores of Unconsolidated coarse sand and gravel. In this study, 23 wells were installed at a field site in the Kansas River alluvium with hollow‐stem auger techniques. Six of these wells were cored through about 30 feet of coarse sand and gravel at depths of 40 to 70 feet using various techniques. A modified Waterloo sampler was employed with good success, using drilling mud in the auger flights to control heave and help hold in the sample. However, the use of heavy drilling mud has disadvantages (for example, the potential to contaminate the aquifer and cores) and recovery without sample loss is difficult because the procedure is sensitive to vibration and other mechanical forces. Without the use of drilling mud, the modified Waterloo sampler design was unsatisfactory because of relatively low recovery. In order to address this limitation, new sampler designs were developed and field tested. The most promising design does not require drilling mud, achieves a high recovery, and is not as sensitive to vibration and mechanical forces during recovery. The new design incorporates an inflatable bladder, located in the drive shoe, which closes off the end of the sampler. The deflated rubber bladder lies behind a plastic sample liner as the core begins to enter the sampler. Near the end of the 5‐foot sample drive, a piston extension triggers a release mechanism and allows a 4‐inch retraction of the plastic liner, resulting in the bladder being in direct contact with the sediment. The bladder is then inflated from the surface with nitrogen gas, closing off the bottom of the sampler and allowing recovery with minimal opportunity for sediments to fall out. Using this sampler, we have been able to consistently achieve about 86 percent out of a possible 90 percent recovery (drive shoe loss is 0.5 feet out of 5 feet due to bladder length and placement). The remaining 4 percent loss is due to compaction, premature piston movement, or wall friction preventing material movement into the sampler. These cores have been evaluated in the laboratory for determination of hydraulic conductivity, porosity, density, and particle‐size fraction.
A Multilevel Ground Water Monitoring System for Casing Advance and Bedrock Drilling Methods
Authors: Boyle D.R.
Published: February 2007

A single‐hole multilevel sampling piezometer system (MLSPS) has been designed by the Geological Survey of Canada (GSC) to be installed using drilling systems that continuously core (e.g., Rotosonic) or continuously sample (e.g., hollow‐stem auger, Becker hammer) overburden and that have the flexibility of allowing additional coring (diamond drilling) or sampling (hammer drilling) of bedrock. The GSC‐MLSPS (under license to Solinst Canada Ltd.) uses a patented GSC dry injection system for accurate emplacement of filter packs and seals. This system permits (a) the use of variable screen lengths; (b) the complete evacuation of piezometers before introduction of new ground water (no bailing); (c) the use of a number of types of hydraulic tests (e.g., slug, withdrawal/recovery, vacuum, pressure‐pulse); (d) ground water sampling under a nitrogen atmosphere; (e) dissolved gas sampling; (f) a great deal of flexibility in the use of design materials; and (g) the elimination of bridging and collapse of filter packs and seals.
The Application of In Situ Air Sparging as an Innovative Soils and Ground Water Remediation Technology
Authors: Marley Michael C. , Hazebrouck David J. , Walsh Matthew T.
Published: February 2007

Vapor extraction (soil venting) has been demonstrated to be a successful and cost‐effective remediation technology for removing VOCs from the vadose (unsaturated) zone. However, in many cases, seasonal water table fluctuations, drawdown associated with pump‐and‐treat remediation techniques, and spills involving dense, non‐aqueous phase liquids (DNAPLS) create contaminated soil below the water table. Vapor extraction alone is not considered to be an optimal remediation technology to address this type of contamination.

An innovative approach to saturated zone remediation is the use of sparging (injection) wells to inject a hydrocarbon‐free gaseous medium (typically air) into the saturated zone below the areas of contamination. The contaminants dissolved in the ground water and sorbed onto soil particles partition into the advective air phase, effectively simulating an in situ air‐stripping system. The stripped contaminants are transported in the gas phase to the vadose zone, within the radius of influence of a vapor extraction and vapor treatment system.

In situ air sparging is a complex multifluid phase process, which has been applied successfully in Europe since the mid‐1980s. To date, site‐specific pilot tests have been used to design air‐sparging systems. Research is currently underway to develop better engineering design methodologies for the process. Major design parameters to be considered include contaminant type, gas injection pressures and flow rates, site geology, bubble size, injection interval (areal and vertical) and the equipment specifications. Correct design and operation of this technology has been demonstrated to achieve ground water cleanup of VOC contamination to low part‐per‐billion levels.
Case Histories of Shallow Time Domain Electromagnetics in Environmental Site Assessment
Authors: Hoekstra Pieter , Lahti Raye , Hild Jim , Bates C. Richard , Phillips David
Published: February 2007

Time domain electromagnetic (TDEM) soundings were utilized in site assessment studies for the purpose of accomplishing two objectives: (1) measuring the migration of brines from oil and gas field evaporation pits, and (2) mapping the continuity of clay strata. Both case histories are representative of common objectives in site assessment. The data for both examples were analyzed by one‐dimensional ridge regression inversions.

Both case histories illustrate that TDEM is an effective method for determining the lateral and vertical resistivity distribution (geoelectric section) of the subsurface in the depth range from about 5 m to 100 m, and it is known from other investigations that depths of investigations up to 2500 m can be achieved with TDEM.

Frequently, the lateral extent of contaminant plumes emanating from localized sources are of limited areal extent. The case history involving the use of TDEM to map a brine plume shows that a TDEM measurement has a relatively small zone of influence, so that meaningful information about the lateral and vertical extent of the plume can be obtained. Both case histories demonstrate the ability of TDEM to determine geoelectric sections below layers of low resistivity.
Evaluation of Visual Methods to Detect NAPL in Soil and Water
Authors: Cohen Robert M. , Bryda Anthony P. , Shaw Scott T. , Spalding Charles P.
Published: February 2007

Non‐aqueous phase liquids (NAPLs), such as chlorinated solvents and petroleum products, are present in the subsurface at numerous contamination sites in North America. Determination of NAPL presence should be an early investigation goal to guide site characterization and control efforts. Indirect methods for assessing NAPL presence rely on comparing measured chemical concentrations to effective solubility limits for ground water and to calculated equilibrium partitioning concentrations for soil. Under ideal conditions, NAPL presence can be identified by visual examination of soil or ground water samples. Direct visual detection may be difficult, however, where the NAPL is clear and colorless, present at low saturation, or distributed heterogeneously. There appears to be little documentation of practical, simple methods for direct identification of NAPL in soil or water.

For this study, a series of experiments was conducted to test the hypothesis that simple and inexpensive methods can be used to visually identify clear, colorless NAPL in soil and water samples. Specific methods evaluated include direct visual examination, ultraviolet (UV) fluorescence analysis, a soil‐water shake test, adding hydrophobic dye to the shake test, and centrifugation. Additionally, the utility of organic vapor analysis was examined as an NAPL screening tool.

Of the methods investigated, the hydrophobic dye methods, followed by UV fluorescence, offer the most simple, practical, and effective means for direct visual identification of clear, colorless NAPL in contaminated soil samples. These methods can be utilized in the field or in a lab with minimal time and material expense. For volatile NAPLs, analysis of organic vapors in soil sample headspace can be used to screen samples for further examination and, possibly, to infer NAPL presence. The NAPL in water experiments demonstrate that very small quantities of clear, colorless NAPL in water can be quickly identified by mixing in a tiny amount of hydrophobic dye.
Comparison of Downhole and Surface Sampling for the Determination of Volatile Organic Compounds (VOCs) in Ground Water
Authors: Rosen Michael E. , Pankow James F. , Gibs Jacob , Imbrigiotta Thomas E.
Published: February 2007

The relative precision and accuracy of sampling and analysis methods for the determination of trace concentrations of volatile organic compounds (VOCs) in ground water were compared. Samples were collected from a well containing nanogram‐per‐liter (ng/L) to microgram‐per‐liter (μg/L) levels of VOCs. A Keck helical rotor submersible pump was used to collect samples at the surface for analysis by purge and trap (P&T) and for analysis by adsorption/thermal desorption (ATD). Downhole samples were collected by passing water through an ATD cartridge. Although slight spontaneous bubble outgassing occurred when the water was brought to the surface, the relative precisions and comparabilities of the surface and downhole methods were generally found to be equivalent from a statistical point of view. A main conclusion of this study is that bringing sample water to the surface for placement in VOC vials (and subsequent analysis by P&T) can be done reliably under many circumstances. However, care must still be taken to prevent adsorption losses and cross contamination. Samples subject to strong bubble outgassing will need to be handled in a special fashion (e.g., by downhole ATD) to minimize volatilization losses. Additionally, the higher sensitivity of the ATD method allows lower detection limits than are possible with P&T. For example, several compounds present at the ng/L level could be determined with confidence by ATD, but not by P&T.
Organic Halogen Group Parameters as Indicators of Ground Water Contamination
Authors: Grøn Christian
Published: February 2007

A regional survey of Danish ground water demonstrated the presence of adsorbable organic halogens (AOX) in almost all of 142 wells (99 percent). Generally, the presence of AOX was not related to point or non‐point source contamination with halogenated organics. However, the AOX concentrations varied with the geology of the aquifers. Extractable organic halogens (EOX) and volatile organic halogens (VOX) were far less prevalent (detected in 4 percent of sampled wells) and the detection could, in most cases, be explained by contamination or chlorination of the wells. The VOX concentrations corresponded to the concentrations of identified, volatile contaminants. The study demonstrates the presence of a natural background level of AOX in the investigated aquifers. This must be considered in the interpretation of AOX results as an indicator of ground water contamination with haloorganics. Similar background levels of EOX or VOX were not delected.
Sampling of VOCs with the BAT Ground Water Sampling System
Authors: Mines Barry S. , Davidson John L. , Bloomquist David , Stauffer Thomas B.
Published: February 2007

In the BAT ground water sampling system, a stainless steel probe with a porous filter element is pushed vertically to the desired sampling depth. An evacuated glass sampling tube is then lowered down the penetration rods where it makes contact with the filter via a hypodermic needle and draws a pore fluid sample.

An investigation of the system was carried out at a number of sites contaminated by leaking underground gasoline storage tanks. Ground water samples obtained using the BAT system and adjacent monitoring wells were analyzed for volatile organic compounds (VOCs).

Because the BAT system is an in situ penetration device with a small filter length, it is possible to determine variations in contaminant concentration with depth. BAT samples in general exhibited higher recovery of VOCs than did bailer samples from adjacent monitoring wells screened over large intervals.

Much higher levels of VOCs were recovered when the probe was used with its 316 stainless steel filter than when using the high‐density polyethylene (HDPE) filter. Significant sorption apparently occurred on the latter filter.

Because the BAT sample tubes are sealed and remain a closed system, the in situ water pressure is maintained. No significant loss of VOCs was found in sampling tubes containing headspace. Samples from the upper tube in the cascaded setup with headspace recovered levels of VOCs as high, or in a few cases higher, than the lower, no‐headspace tubes.
Hydrocarbon Vapor Diffusion in Intact Core Sleeves
Authors: Ostendorf David W. , Moyer Ellen E. , Xie Yuefeng , Rajan R. V.
Published: February 2007

The diffusion of 2,2,4‐trimethylpentane (TMP) and 2,2,5‐trimethylhexane (TMH) vapors put of residually contaminated sandy soil from the U.S. Environmental Protection Agency (EPA) field research site at Traverse City, Michigan, was measured and modeled. The headspace of an intact core sleeve sample was swept with nitrogen gas to simulate the diffusive release of hydrocarbon vapors from residual aviation gasoline in and immediately above the capillary fringe to a soil‐venting air flow in the unsaturated zone. The resulting steady‐state profile was modeled using existing diffusivity and air porosity estimates in a balance of diffusive flux and a first order source term. The source strength, which was calibrated with the observed flux of 2,2,4‐TMP leaving the sleeve, varied with the residual gasoline remaining in the core, but was independent of the headspace sweep flow rate. This finding suggested that lower soil‐venting air flow rates were in principle as effective as higher air flow rates in venting LNAPL vapors from contaminated soils. The saturated vapor concentration ratio of 2,2,4‐TMP to 2,2,5‐TMH decreased from 6.6 to 3.5 over the duration of the experiments in an expression of distillation effects. The vertical profile model was tested against sample port data in four separate experiments for both species, yielding mean errors ranging from 0 to—24 percent in magnitude.
Single Well Tracer Tests in Aquifer Characterization
Authors: Hall Stephen H.
Published: February 2007

When the purpose of aquifer testing is to yield data for modeling aqueous mass transport, pumping tests and gradient measurement can only partially satisfy characterization requirements. Effective porosity, ground water flow velocity, and the vertical distribution of hydraulic conductivity within the aquifer are left as unknowns. Single well tracer methods, when added to the testing program, can be used to estimate these parameters. A drift, and pumpback test yields porosity and velocity, and point‐dilution testing yields depth‐discrete hydraulic information, A single emplacement of tracer into a test well is sufficient to conduct both tests. The tracer tests are facilitated by a simple method for injecting and evenly distributing the tracer solution into a wellbore, and by new ion‐selective electrode instrumentation, specifically designed for submersible service, for monitoring the concentration of tracers such as bromide.
Laboratory Study of Air Sparging: Air Flow Visualization
Authors: Ji Wei , Dahmani Amine , Ahlfeld David P. , Lin Jia Ding , Hill Edward
Published: February 2007

Laboratory flow visualization experiments, using glass beads as the porous medium, were conducted to study air sparging, an innovative technology for subsurface contaminant remediation. The purpose of these experiments was to observe how air flows through saturated porous media and to obtain a basic understanding of air plume formation and medium heterogeneity effects. The experiments indicate that air flow occurring in discrete, stable channels is the most probable flow behavior in medium to fine grained water saturated porous media and that medium heterogeneity plays an important role in the development of air channels. Several simulated scales of heterogeneities, from pore to field, have been studied. The results suggest that air channel formation is sensitive to the various scales of heterogeneities. Site‐specific hydrogeologic settings have to be carefully reviewed before air sparging is applied to remediate sites contaminated by volatile organic compounds.
An Overview of In Situ Air Sparging
Authors: Johnson R.L. , Johnson P.C. , McWhorter D.B. , Hinchee R.E. , Goodman I.
Published: February 2007

In situ air sparging (IAS) is becoming a widely used technology for remediating sites contaminated by volatile organic materials such as petroleum hydrocarbons. Published data indicate that the injection of air into subsurface water saturated areas coupled with soil vapor extraction (SVE) can increase removal rates in comparison to SVE alone for cases where hydrocarbons are distributed within the water saturated zone. However, the technology is still in its infancy and has not been subject to adequate research, nor have adequate monitoring methods been employed or even developed. Consequently, most IAS applications are designed, operated, and monitored based upon the experience of the individual practitioner.

The use of in situ air sparging poses risks not generally associated with most practiced remedial technologies: air injection can enhance the undesirable off‐site migration of vapors and ground water contamination plumes. Migration of previously immobile liquid hydrocarbons can also be induced. Thus, there is an added incentive to fully understand this technology prior to application.

This overview of the current state of the practice of air sparging is a review of available published literature, consultation with practitioners, a range of unpublished data reports, as well as theoretical considerations. Potential strengths and weaknesses of the technology are discussed and recommendations for future investigations are given.
Method for Determining the Age of Diesel Oil Spills in the Soil
Authors: Christensen Lars Bo , Larsen Thomas Hauerberg
Published: February 2007

This study evaluates the changes in the composition of diesel oil as a function of the time during which the oil has been present in the vadose zone. The study also develops a reliable method for determining the age of diesel oil in the subsurface soil environment at service stations, oil terminals, and similar locations where the diesel is protected from direct exposure to factors increasing the rate of microbial activity.

Analyses demonstrate that n‐alkanes are the dominant components of fresh diesel oil and isoprenoids the dominant components of degraded diesel oil. The analyses also show that the composition of fresh diesel oil produced in 1992 and that produced in 1974 is basically the same.

The difference in composition between fresh and degraded oil is the basis for defining a degradation ratio or rate of alteration in the composition of the diesel oil expressed in terms of a ratio between n‐alkanes and isoprenoids. At 12 test locations where the date of property damage was known, the C17/pristane ratio had by far the highest correlation factor (.89) with the residence time of the diesel based on the average degradation ratio for each location. Based on this high correlation factor, the C17/pristane ratio can be used to estimate the age of a diesel oil spill. The standard error of such an estimate is approximately two years.
Effects of Sample Isolation and Handling on the Recovery of Purgeable Organic Compounds
Authors: Gibs Jacob , Imbrigiotta Thomas E. , Ficken James H. , Pankow James F. , Rosen Michael E.
Published: February 2007

This report compares the recovery of purgeable organic compounds (POCs) obtained by using a downhole isobaric sampler developed by the U.S. Geological Survey, a helical‐rotor submersible pump, and a point source bailer to collect and isolate samples of ground water from three wells in Now York and New Jersey: the samples contained a total of 13 PCX's delectable at concentrations ranging from 0.5 μg/L to about 400 μg/L. This report also compares the effects of sample handling, specifically the differences in PCX concentration recovery when an isobaric sample container is filled at land surface vs. when it is filled downhole. and when samples art taken using a bailer with and without a bottom‐emptying device. These case studies are used to quantify the possible effects of different sample‐isolation find sample‐handling techniques on POC recovery.

The relative effectiveness of the three devices varied by site and by compound. Overall, the POC recoveries achieved by using the helical‐rotor submersible pump and the downlink isobaric sampler were not significantly different at the 95 percent confidence, level. POC recovery obtained by using the point source bailer was 11 percent lower overall. The downhole isobaric sampler results exhibited smaller coefficients of variation than did the helical‐rotor submersible pump or the point‐source bailer results. However, the differences between the coefficients of variation of the downhole isobaric sampler and those of the helical‐rotor submersible pump were not significant at the 95 percent confidence level. The nonsignificant smaller coefficient of variation of the downhole isobaric sampler apparently resulted from two fewer sample handling steps that exposed the sample water to ambient air. An independent experiment performed with a different downhole sampler at one of the wells used in this investigation produced a similar statistical result. Also, the POC recovery obtained by pouring sample water out the lop of a point source bailer into 40‐mL vials was S percent lower than that obtained by filling vials from a bailer with a bottom‐emptying device.
Ground Water Monitoring Statistics Update: Part I: Progress Since 1988
Authors: Davis Charles B. , McNichols Roger J.
Published: February 2007

Current federal ground water monitoring statistical regulation dates from the revised RCRA Subtitle C Final Rule of 1988. That rule was a considerable advance over previous RCRA statistical rules. However, two major problem areas remained: facility‐wide false positive rate (FWFPR) control and spatial variability. Progress has been made in the 1991 Subtitle D Final Rule and in guidance: the 1992 Addendum to Interim Final Guidance in particular includes a substantial conceptual advance toward resolving the FWFPR problem. Other areas of improvement include normality testing and distribution assumptions, dropping the four independent samples per monitoring period requirement, allowing a preliminary evaluation short of a 40 CFR Part 258 Appendix II assessment upon finding a statistically significant increase, and suggesting superior alternatives to analyses of variance (ANOVAs) and tests of proportions.

The problem of dealing with natural spatial variability remains. Although certain techniques listed in the regulations can control for inherent spatial variability and the performance standards require doing so “when necessary,” little attention has been paid to the ubiquity of such spatial variation. Moreover, regulatory traditions favoring upgradient‐downgradient comparisons often make control of natural spatial variation difficult and ineffective. With new. lined facilities easily implemented statistical solutions are available; however, dealing with the several existing solid waste facilities which will now be regulated under Subtitle D will present major challenges.

In short, the 1988 revision of the Subtitle C rules made it more possible to provide statistically sound monitoring programs, and there has been steady progress since then. Challenges remain, however. These vary from slate to slate, particularly with regard to controlling false positives and false negatives in the presence of natural spatial variability.
Field Comparison of Micropurging vs. Traditional Ground Water Sampling
Authors: Kearl Peter M. , Korte Nic E. , Stites Mike , Baker Joe
Published: February 2007

Micropurge sampling of ground water wells has been suggested as a possible replacement to traditional purge and sample methods. To compare methods, duplicate ground water samples were collected at two field sites using iraditional and micropurge methods. Samples were analyzed for selected organic and inorganic constituents, and the results were compared statistically. Analysis of the data using the nonparametric sign test indicates that within a 95 percent confidence interval, there was no significant difference between the two methods for the site contaminants and the majority of analytes. These analytical results were supported by visual observations with the colloidal borescope, which demonstrated impacts on the flow system in the well when using traditional sampling methods. Under selected circumstances, the results suggest replacing traditional sampling with micropurging based on reliability, cost, and waste minimization.