bluuebunny/crossref_metadata_2025 huggingface dataset:
The Sensitivity of Four Monitoring Well Sampling Systems to Low Concentrations of Three Volatile Organics
Authors: Schalla Ronald , Myers David A. , Simmons Mary Ann , Thomas John M. , Toste Antony P.
Published: February 2007

Four state‐of‐the‐art ground water sampling systems were analyzed to determine their reliability in providing representative samples of the volatile chlorinated hydrocarbons trichloroethylene (TCE), perchloroethylene (PCE), and 1,1,1‐trichloroethane (TCA) from a simulated monitoring well. The sampling systems studied represent four commonly used devices, including a stainless steel and Teflon® piston pump, a Teflon bailer, a Teflon bladder pump, and a PVC air‐lift pump.

Controlled laboratory sampling experiments were conducted in a tank and well test chamber designed to approximate field conditions. A well purging and sampling procedure was used in the test apparatus to determine the accuracy and precision of each device for detecting low concentrations of the compounds in ground water. The compounds selected are some of the most ubiquitous hazardous contaminants found in shallow aquifers near hazardous waste sites throughout the United States.

No significant statistical difference was found among the four sampling systems in detecting the compounds.
Hydrogen Peroxide Treatment of Septic Systems and Its Negative Effects on Shallow Ground Water
Authors: Bicki Thomas J.
Published: February 2007

Soil‐solution samplers and shallow ground water monitoring wells were utilized to monitor nitrate movement to ground water following H2O2 application to a clogged soil absorption system. Nitrate‐nitrogen concentrations in soil water and shallow ground water ranged from 29 to 67 mg/L and 9 to 22 mg/L, respectively, prior to H2O2 treatment. Mean nitrate‐nitrogen concentrations in soil water and ground water increased and ranged from 67 to 115 mg/L and 23 to 37 mg/L, respectively, one week after H2O2 application. Elevated concentrations of nitrate‐nitrogen above background persisted for several weeks following H2O2 treatment. The H2O2 treatment was unsuccessful in restoring the infiltrative capacity of a well‐structured soil. Application of H2O2 to the soil absorption system poses a threat of nitrate contamination of ground water and its usefulness should be fully evaluated before rehabilitation is attempted.
Statistical Issues and Problems in Ground Water Detection Monitoring at Hazardous Waste Facilities
Authors: McNichols Roger J. , Davis Charles B.
Published: February 2007

Ground water monitoring presents interesting statistical challenges, including controlling the risk of entering compliance monitoring, incorporating all modes of inherent variability into the statistical model on which tests are based, and taming the detection limit problem, all while maintaining demonstrable sensitivity to real contamination.

Some of these challenges exceed textbook statistics considerably, even when considered alone, and good solutions are scarce. When these challenges are combined, the task of developing good statistical procedures or good regulations can be formidable.

This article presents a number of realities of ground water monitoring that should be considered when developing statistical procedures. Recommendations made for addressing these realities include the following: (1) the false positive rate should be controlled on a facility‐wide basis, rather than per well or per parameter as required in the proposed regulation (40 CFR §264); (2) multiple comparisons with control procedures are preferable to analysis of variance (ANOVA) for controlling the overall false positive rate; (3) retests can be made an explicit part of the statistical procedure in order to increase power and decrease sensitivity to distribution shape assumptions; (4) commonly used simple methods of handling below detection limit data with parametric tests, including Cohen's procedure as implemented in the U.S. EPA's Technical Enforcement Guidance Document (TEGD), should probably be avoided; (5) the statistical properties of practical quantitation limits for non‐naturally occurring compounds should be studied carefully; and (6) so long as the facility‐wide false positive rate is controlled, better sensitivity to real contamination is obtained by monitoring fewer well‐chosen parameters at a smaller number of well‐chosen locations.

An evaluation of the proposed revised §264 regulation with respect to these realities reveals that it seems to be a definite improvement over the current regulation, but that it may be quite difficult to develop an adequate statistical plan within its constraints.
Contamination of the Sandstone Aquifer of Prince Edward Island, Canada by Aldicarb and Nitrogen Residues
Authors: Priddle M. W. , Jackson R.E. , Mutch J.P.
Published: February 2007

Prince Edward Island is wholly dependent upon ground water from a highly permeable fractured sandstone aquifer for all industrial, domestic, agricultural, and potable uses. The contamination of this aquifer by agricultural residues, principally aldicarb and nitrate, has caused concern among Islanders. Ground water quality was monitored between 1985 and 1988 beneath two potato fields to which aldicarb (Temik) was applied at planting once or twice between 1983 and 1986. In May of 1988,12 percent of 48 monitoring well samples exceeded the drinking water guideline of 9μg/L for total aldicarb. Furthermore 32 percent of all samples exceeded the nitrate guideline of 10 mg/L. Aldicarb persistence appears related to its application at planting when soil temperatures are low and recharge is high and to the inhibiting pH effect that ammonium (from fertilizers and soil organic nitrogen) oxidation has on its degradation. Therefore, based on the research of others, it is recommended that aldicarb be applied at plant emergence when degradation is more rapid and recharge is lower.
Availability and Content of Domestic Well Records in the United States
Authors: Ganley Mary C.
Published: February 2007

Ground water professionals within public and private sectors use well records as data sources. Both the availability and the technical content of domestic well records in the 50 states are of interest to them. Well record availability is dependent on legal requirements, filing systems, databases, and storage places. Forty‐six states have statewide regulations or other legal requirements for filing completion reports for domestic wells. Fifty‐one agencies across the country maintain domestic well records. Filing systems involve location, chronology, date, or number information. Thirty‐one of the 51 agencies maintain varying types of databases containing record information or data related to the records. Overall, records are kept in central offices in 43 states and in regional offices in three states.

The technical content of the records was evaluated for general, location, hydrogeology, and well construction information to assess the relative value of the records for use in national pesticide surveys. Technical information tabulated from the well records collected for this paper included nine items in a general category, 28 items in a well‐construction category, eight items in a hydrogeology category, and six items in a location category. Items in the general and location categories identified the well location and ownership. Construction category items include those describing well‐construction parameters such as grout, casing, and screen. Hydrogeology category items include static water level, aquifer media, and estimated yield. The three items always requested were owner's name, driller's name, and static water level. The three least‐requested items, ranging from 16 percent to 10 percent, were packers, drilling fluid, and geologic formation.
Assessing Arkansas Ground Water for Pesticides: Methodology and Findings
Authors: Cavalier T.C. , Lavy T.L. , Mattice J.D.
Published: February 2007

During 1985 to 1987, 119 wells, Springs and municipal drinking water supplies throughout Arkansas were monitored for the presence of pesticides. Pesticides selected for analysis included acifluorfen, alachlor, aldicarb, atrazine, benomyl, cyanazine, cypermethrin, 2,4‐D, dichlorprop, diuron, fenvalerate, fluometuron, hexazinone, linuron, metolachlor, permethrin, picloram, and propanil. Not every sample was analyzed for every pesticide. Overall, results indicated that the 18 herbicides, fungicides, and insecticides were not present in the ground water samples studied. (Note: Detectable concentrations of three herbicides – alachlor, atrazine, and metolachlor – were found in one irrigation well, at 5.5,5.8, and 6.9 μg/L, respectively. However, since previous and subsequent sampling failed to detect these compounds, their presence is attributed to a localized spill or handling error rather than agricultural application.)
Ground Water Remediation Using an Extraction, Treatment, and Recharge System
Authors: Thomsen Kurt O. , Chaudhry Majid A. , Dovantzis Kostas , Riesing Ronald R.
Published: February 2007

Ground water remediation of volatile organic compound (VOC) contamination at a site in Michigan was initiated as a result of a consent agreement between the Michigan Department of Natural Resources (MDNR) and the responsible party. Under the direction of the MDNR, the responsible party conducted a remedial investigation/feasibility study using federal guidelines to define the extent of contamination at the site and to select a response action for site remediation. The selected alternative included a combination of ground water extraction, treatment, and recharge, and soil flushing. The extraction system withdraws ground water from various depths in heavily contaminated areas. The ground water is treated using an air stripper. A spray distribution system spreads effluent from the stripper over a recharge basin constructed over the most contaminated areas. Additional contaminant removal is achieved by volatilization from the spray and percolation through the gravel bed. Recharge water moves downward through the contaminated soils, thus flushing residual soil contaminants. The initial operating data demonstrated that the system can effectively remove trichloroethylene (TCE) from ground water (approximately 95 percent overall removal efficiency). The annualized capital and operation and maintenance (O & M) costs of the remedial action were estimated for several operating periods (15, 20, and 30 years).
Economics of Sample Compositing as a Screening Tool in Ground Water Quality Monitoring
Authors: Rajagopal R. , Williams L.R.
Published: February 2007

Recent advances in high throughput/automated compositing with robotics/field‐screening methods offer seldom‐tapped opportunities for achieving cost‐reduction in ground water quality monitoring programs. An economic framework is presented in this paper for the evaluation of sample compositing as a screening tool in ground water quality monitoring. When the likelihood of occurrence of a contaminant in a well is very small, the use of sample compositing instead of routine exhaustive sampling will lead to reduction in analytical efforts. Such reduction will be maximum when there are no contaminated wells in the network. An N‐fold reduction will result when none of the wells in a network of N wells are contaminated. When 25 percent or more wells in a network are contaminated, the use of sample compositing will require, at the most, an additional 50 percent analytical effort compared to exhaustive sampling. A quantitative measure of the cost‐effectiveness of sample compositing as a screening tool is shown to be dependent on two factors: a ratio (f1) of laboratory analytical cost to that of well installation and field sampling costs and a ratio (f2) of the expected number of contaminated wells to that of the total number of wells in the network. Several useful mathematical results of primary interest are derived and illustrated with case examples in the paper. Selected areas for further research are also outlined.
The Organization and Operation of the Savannah River Plant's Groundwater Monitoring Program
Authors: Olson C.M. , Heffner J.D.
Published: February 2007

The Groundwater Monitoring Program at the Savannah River Plant currently consists of more than 700 wells at more than 70 sites, and growth is projected. The organization and operation of the program has been designed to support an active drilling program, the acquisition of a large amount of repetitive data, the generation of numerous reports, associated QA/QC controls, and provisions for additional growth. The design is centered around two key features—modular components and computer usage.

The modular component concept is an organizational tool that gives one group responsibility for a specific portion of the program. This responsibility includes the operation of its segment and the coordination of operations with the other groups in the program.

Computers, the associated software programs, and a simple set of rules (the sampling guide) enables the program to accommodate large amounts of repetitive data in a timely, uniform manner. Feedback loops are included to ensure that new data are incorporated into future program decisions (new sample schedules and well locations). The highly automated system determines new sample schedules, collates/reviews incoming data, and generates various reports. Six reports are issued on a regular basis, from quarterly to annually, to ensure that the program is adequately documented.

The program has been in successful operation for more than a year and has accommodated the expected growth.
A Tracer Test for Detecting Cross Contamination Along a Monitoring Well Column
Authors: Meiri David
Published: February 2007

A tracer test was used to evaluate whether cross contamination exists along a monitoring well completed through a shallow ground water system in fractured clay and screened in a sand and gravel aquifer. The fractured clay is separated from the sand and gravel deposit by a layer of highly plastic unfractured clay. A natural vertical downward hydraulic gradient of approximately 0.5 exists between the shallow system and the sand and gravel aquifer. Ground water contamination was detected in an adjacent monitoring well screened in the fractured clay and in the monitoring well screened in the sand and gravel deposit. No ground water contamination was apparent in an intermediate well screened in the unfractured clay layer. A tracer of sodium bromide was injected into a shallow boring near the monitoring wells. The tracer was detected in the monitoring well in the sand and gravel aquifer after three to seven days. The bromide concentration continued to increase in this well with time while the concentration in the shallow boring declined. This trend of tracer concentration indicates the tracer has in fact migrated downward and possibly traveled along the well column.
Use of On‐Site High Performance Liquid Chromatography to Evaluate the Magnitude and Extent of Organic Contaminants in Aquifers
Authors: Goerlitz Donald F. , Franks Bernard J.
Published: February 2007

Scientists engaged in the appraisal of ground water contaminated by organic substances are faced with the problems of difficult sample collection and timely chemical analysis. High‐performance liquid chromatography was evaluated for on‐site determination of specific organic contaminants in ground water samples and was used at three study sites. Organic solutes were determined directly in water samples, with little or no preparation, and usually in less than an hour after collection. This information improved sampling efficiency and was useful in screening for subsequent laboratory analysis. On two occasions, on‐site analysis revealed that samples were undergoing rapid change, with major solutes being upgraded and alteration products being formed. In addition to sample stability, this technique proved valuable for monitoring other sampling factors such as compositional changes with respect to pumping, filtration, and cross contamination.
A Critique of the Hvorslev Method for Slug Test Analysis: The Fully Penetrating Well
Authors: Chirlin Gary R.
Published: February 2007

The Hvorslev (1951) method of slug test analysis addresses a variety of well and aquifer geometries, is easy to apply, and is widely used. Its underlying mathematical model assumes negligible compressive storage (aquifer water and matrix are incompressible, flow is quasi‐steady). The consequences of this assumption are explored here for the particular case of a well fully penetrating a confined, radially infinite, homogeneous, isotropic aquifer. The Cooper et al. (1967) model of this setting includes the effect of compressive storage and is otherwise identical to Hvorslev. Therefore, for this setting the performance of the Hvorslev method is gauged against that of the Cooper et al. model.

The original Hvorslev model is recast into conventional governing equations to facilitate the comparison with Cooper et al. The Hvorslev estimate of hydraulic conductivity for this setting is accurate only to within an order of magnitude, assuming no knowledge of the aquifer storage coefficient. Accuracy of the Hvorslev estimate depends on the normalized aquifer storage coefficient α, on the matching procedure used to fit the Hvorslev model, and on the analyst's choice for the Hvorslev effective radius re.

The Hvorslev model provides no physical basis for selecting re. Some insight is gained by viewing the constant head condition at radius re as an “infinite storage” at re. Flow from this discrete “storage” approximates the distributed storage of a compressible aquifer. By reference to Cooper et al. one can select a value of re, which leads to a correct Hvorslev estimate of hydraulic conductivity, given prior knowledge of the aquifer storage coefficient.

For an example aquifer, the Hvorslev and Cooper et al. models yield substantially different distributions of head within the aquifer.

Quantitative comparisons here are restricted to a single setting. Hvorslev (1951) also addresses a number of other settings (partial penetration, no lower aquiclude). A companion paper, in preparation, will examine the significance of the incompressibility assumption for these other, more widely applied settings.
Planning Ground Water Monitoring Field Projects
Authors: Lister Kenneth H.
Published: February 2007

Project organization problems are not uncommon in ground water monitoring projects, particularly those which occur at sites remote from the office. Successful project management depends on coordination of the personnel, supplies, and equipment necessary to carry out each phase of the project. Procedures for planning and organizing field projects involving well installation, ground water sampling, and aquifer testing are outlined. Methods are suggested that will aid the Project Manager in planning and scheduling field work to make efficient use of personnel and material resources. Cautions are given regarding common pitfalls of projects involving operations at remote sites, and means of avoidance are enumerated. A checklist of commonly used field equipment and supplies is provided.
Application of Temperature and Electrical‐Conductivity Logging in Ground Water Monitoring
Authors: Michalski Andrew
Published: February 2007

Down‐hole temperature and electrical‐conductivity probes are attractive logging devices for use in monitoring wells, because they are readily available, relatively inexpensive, and allow for rapid measurements. Benefits of such logging are illustrated by examples from several small sites in complex hydrogeologic settings. Interpretation of the logs provided information on the effectiveness of well purging, aquifer heterogeneities and the rates of ground water movement, leaks and cross‐flows within wells, and locations of transmissive fractures in bedrock wells. Thus the logs offered an inexpensive means of acquiring valuable field information to supplement the geologic, potentiometric and chemical data collected during construction or subsequent investigation of the wells.
Modeling the Potential Effect of Additives on Enhancing the Solubility of Aromatic Solutes Contained in Gasoline
Authors: Mihelcic James R.
Published: February 2007

The potential effect of two common gasoline additives, ethanol and methyl tertiary‐butyl ether (MTBE), on enhancing the solubility of the aromatic solutes benzene, toluene, ethylbenzene, and o‐, m‐, and p‐xylene, was examined using a computer model, ARSOL. Aqueous solute systems containing cosolvents ethanol and MTBE at 0, 0.1, 1, and 4.3 percent were modeled for both ethanol and MTBE systems. Five‐ and 10‐percent ethanol systems were also modeled. Little solubility enhancement was predicted by modeling at cosolvent levels less than 1 percent. At cosolvent levels greater than 1 percent, predicted solute solubility increased curvilinearly with an increase in percent cosolvent; a 10 percent cosolvent system increased aromatic hydrocarbon solubility by approximately 100 percent. According to the model predictions, MTBE enhanced solute solubility more than ethanol, with enhancement by MTBE being approximately 10 percent greater than enhancement by ethanol at 4.3 percent cosolvent. Other concerns regarding gasoline additives are the observed reduction in partitioning of solutes to soils and sediments and the contamination of water supplies due to the high water solubility of the additives.
Organic Contamination of Ground Water at Gas Works Park, Seattle, Washington
Authors: Turney G.L. , Goerlitz D.F.
Published: February 2007

Gas Works Park, in Seattle, Washington, is located on the site of a coal and oil gasification plant that ceased operation in 1956. During operation, many types of wastes, including coal, tar, and oil, accumulated on‐site. The park soil is currently (1986) contaminated with compounds such as polynuclear aromatic hydrocarbons, volatile organic compounds, trace metals, and cyanide. Analyses of water samples from a network of observation wells in the park indicate that these compounds are also present in the ground water.

Polynuclear aromatic hydrocarbons and volatile organic compounds were identified in ground water samples in concentrations as large as 200 mg/L. Concentrations of organic compounds were largest where ground water was in contact with a non‐aqueous phase liquid in the soil. Where no non‐aqueous phase liquid was present, concentrations were much smaller, even if the ground water was in contact with contaminated soils. This condition is attributed to weathering processes in which soluble, low‐molecular‐weight organic compounds are preferentially dissolved from the non‐aqueous phase liquid into the ground water. Where no non‐aqueous phase liquid is present, only stained soils containing relatively insoluble, high‐molecular‐weight compounds remain. Concentrations of organic contaminants in the soils may still remain large.
Magnetic Surveying for Buried Metallic Objects
Authors: Barrows Larry , Rocchio Judith E.
Published: February 2007

Field tests were conducted to determine representative total‐intensity magnetic anomalies due to the presence of underground storage tanks and 55‐gallon steel drums. Three different drums were suspended from a non‐magnetic tripod and the underlying field surveyed with each drum in an upright and a flipped plus rotated orientation. At drum‐to‐sensor separations of 11 feet, the anomalies had peak values of around 50 gammas and half‐widths about equal to the drum‐to‐sensor separation. Remanent and induced magnetizations were comparable; crushing one of the drums significantly reduced both. A profile over a single underground storage tank had a 1000‐gamma anomaly, which was similar to the modeled anomaly due to an infinitely long cylinder horizontally magnetized perpendicular to its axis. A profile over two adjacent tanks had a smooth 350‐gamma single‐peak anomaly even though models of two tanks produced dual‐peaked anomalies. Demagnetization could explain why crushing a drum reduced its induced magnetization and why two adjacent tanks produced a single‐peak anomaly.

A 40‐acre abandoned landfill was surveyed on a 50‐ by 100‐foot rectangular grid and along several detailed profiles. The observed field had broad positive and negative anomalies that were similar to modeled anomalies due to thickness variations in a layer of uniformly magnetized material. It was not comparable to the anomalies due to induced magnetization in multiple, randomly located, randomly sized, independent spheres, suggesting that demagnetization may have limited the effective susceptibility of the landfill material. A different 6‐acre site survey conducted on a 10‐ by 10‐foot grid was analyzed to determine the maximum station spacing and line separation that could have been used. Essentially, all of the anomalies at this site would have been resolved by a survey conducted on a 20‐ by 20‐foot grid and the larger anomalies would have been detected by a 50‐ by 50‐foot grid.
Complementary Investigative Techniques for Site Assessment with Low‐Level Contaminants
Authors: Byrnes Mark E. , Nelson R. Wayne , La Poe Robert G. , Lundquist Dennis E. , McNeill William
Published: February 2007

A remedial investigation (RI) was performed in an area downgradient from an abandoned missile silo at Vandenberg Air Force Base, California, as part of the United States Air Force Installation Restoration Program (IRP). A number of complementary investigative techniques were used to assure a reliable assessment of site contamination. These included the review of aerial photographs, the use of an organic vapor analyzer (OVA) and carbon adsorption/mass spectrometer (MS) method to conduct a soil‐gas survey; magnetic and electromagnetic geophysical surveys; bedrock permeability testing; and the chemical analysis of soil, sediment, surface water, and ground water samples. The results from this investigation revealed the presence of an undocumented landfill and a small trichloroethylene plume in ground water at concentrations ranging from 6.7 ppb to 31 ppb. The investigation also identified local ground water flow direction, provided strong evidence of the location of potential sources of contamination, and defined the downgradient extent of ground water contamination. Because the identified contaminants have not as yet reached the environmentally sensitive wetland at the base of the slope below this facility, there is still time to propose remedial alternatives that would serve to protect this environmentally sensitive area.
Factors Affecting Efficient Aquifer Restoration at In Situ Uranium Mine Sites
Authors: Osiensky James L. , Williams Roy E.
Published: February 2007

In situ mining of uranium typically requires the injection of a reactive leaching solution (lixiviant) such as sodium carbonate/bicarbonate, ammonium carbonate/bicarbonate, or sulfuric acid, and an oxidant such as hydrogen peroxide or oxygen into an ore‐bearing, confined aquifer. It also requires the environmental restoration of the source aquifer. The stratigraphy of sandstone uranium deposits typically consists of interbedded layers of poorly consolidated sands and clays and gravels deposited in fluvial or coastal environments. The parameters that influence the migration of lixiviant during mining and restoration in these environments include induced hydraulic gradients, hydrodynamic dispersion, heterogeneity, anisotropy, physicochemical reactions, leakage into and/or through confining layers, and convergence of flow lines due to partial well penetration.

The effectiveness of the various methods of aquifer restoration is sit ‐specific and is dependent upon the site hydrogeology and hydrogeochemistry, and the chemistry of the lixiviant. Each method of aquifer restoration has advantages and disadvantages. Selection of the most effective and economically feasible method requires detailed knowledge of the site‐specific hydrogeologic conditions.
A Practical Approach to the Design, Operation, and Monitoring of In Situ Soil‐Venting Systems
Authors: Johnson P.C. , Stanley C.C. , Kemblowski M.W. , Byers D.L. , Colthart J.D.
Published: February 2007

When operated properly, in situ soil venting or vapor extraction can be one of the most cost‐effective remediation processes for soils contaminated with gasoline, solvents, or other relatively, volatile compounds. The components of soil‐venting systems are typically off‐the‐shelf items, and the installation of wells and trenches can be done by reputable environmental firms. However, the design, operation, and monitoring of soil‐venting systems are not trivial. In fact, choosing whether or not venting should be applied at a given site is a difficult decision in itself. If one decides to utilize venting, design criteria involving the number of wells, well spacing, well location, well construction, and vapor treatment systems must be addressed. A series of questions must be addressed to decide if venting is appropriate at a given site and to design cost‐effective in situ soil‐venting systems. This series of steps and questions forms a “decision tree” process. The development of this approach is an attempt to identify the limitations of in situ soil venting, and subjects or behavior that are currently difficult to quantify and for which future study is needed.
Aqueous Surfactant Washing of Residual Oil Contamination from Sandy Soil
Authors: Ang Carolina C. , Abdul Abdul S.
Published: February 2007

A laboratory study was conducted to determine the efficiency of different aqueous concentrations of an alcohol ethoxylate surfactant in washing residual levels of an oil [automatic transmission fluid (ATF)] from sandy soil. Five glass columns packed with the soil were prepared in a manner that simulated conditions leading to residual saturation in an actual oil leak. Each of four columns was washed continuously with 28 pore volumes of solution by pumping either 0.0 percent (water), 0.5 percent, 1.0 percent, or 2.0 percent aqueous surfactant solutions through the columns. The fifth column was washed intermittently with 28 pore volumes of a 1.0 percent surfactant solution. Water washed only 25.5 percent of the ATF from the column soil, while the 0.5 percent, 1 percent, and 2 percent surfactant solutions washed 55 percent, 60 percent, and 72.8 percent of the ATF, respectively. The distribution of the ATF remaining in the column after washing showed that the ATF removed by water was mainly from the outlet side of the column, while the ATF removed by the 2.0 percent surfactant solution was mainly from the inlet side of the column. This observation indicated that different mechanisms were involved; namely, the displacement of oil through the soil‐pore space, the dispersion of oil due to reduced surface tension, and the solubilization of oil by surfactant micelles. In the case of water, the displacement of oil was the main washing mechanism, while all three mechanisms were operative during surfactant washing. ATF dispersion and solubilization were improved at higher surfactant concentrations. The column that was washed intermittently to pulse ATF from dead end pores did not show a significant improvement over the column that was continuously washed with the same 1.0 percent surfactant solution. The results show promising potential for application in the field and will be further investigated in a two‐dimensional model aquifer.
The Development and Implementation of a Remedial Investigation Work Plan and Data Management System
Authors: Olson Clifford M.
Published: February 2007

The Pompton Lakes Works is a 580‐acre industrial facility in northern New Jersey that has manufactured explosives for more than 100 years. Waste from these operations was disposed of on‐site and a remedial investigation (RI) was initiated to determine the extent of contamination. A history of waste disposal, completed in 1989, identified 119 potential waste sites that vary in size from point sources to entire manufacturing operations of more than 40 acres. Before RI operations began, three issues had to be addressed. First is the length of the investigation and the need for consistency between the first and the last site investigated, second is the need to eliminate the investigative “stop and go” effects (delays for analysis, drillers, etc.) on the RI operations, and third is to report, in a useful manner, the massive amounts of RI data.

The solution to these issues involved the use of a sophisticated database management system developed concurrently with the RI work plan (RIWP) and designed around the RI goals. The RIWP addresses the first issue of consistency with two components, sample rules, and phased sampling. The sample rules dictate the analytes and the sample location (depending on previous results and on the phase). Phased sampling allows for incremental increases in work (depending on previous results) and is divided into two phases, exploratory that confirms the presence of contamination and characterization, with a variable number of rounds, that defines contaminant extent. These components are simple, easily applied, yet infinitely flexible to address changing conditions, and readily adapted to database management.

The database management system is the key to controlling a large RI; it eliminates the investigative “stop and go” and the problems associated with massive amounts of data. The system incorporates all investigative information (including digitized maps) into sample plans, chain‐of‐custodies, and reports. The reports may be either concurrent with RI work (i.e., a specific phase or round) or a summary report of the completed investigation at a waste site. The system allows a number of waste sites to be investigated simultaneously so that one person can manage a complex RI with a minimum of personnel, a maximum number of sites (in different phases or rounds), and issue timely reports that are crisp, concise, and informative.

Combining development of the RIWP with the database management system not only addressed the investigative aspects but also the operational and the reporting aspects too.
The Occurrence of Appendix IX Organic Constituents in Disposal Site Ground Water
Authors: Plumb R. H.
Published: February 2007

Monitoring data from 479 disposal site investigations were used to provide an initial estimate of the occurrence and distribution of 208 Appendix IX organic constituents in ground water. The most prevalent class of contaminants were the volatile organic compounds, which accounted for 84 percent of all the detectable events in the composite data set involving Appendix IX organic constituents. The abundance of the remaining subsets of Appendix IX organic constituents decreased in the following order: base/neutral compounds (8.6 percent), acid extractable compounds (3.5 percent), pesticides (3.0 percent), RCRA pesticides (0.6 percent), and non‐priority pollutants (0.25 percent). A total of 66 Appendix IX organic constituents, including one volatile compound, two pesticides, three base/neutral compounds, and 60 non‐priority pollutant compounds were not detected in any of the waste disposal site ground water monitoring records that were reviewed.

The current regulatory requirement to monitor for Appendix IX organic constituents is approximately four times more expensive than monitoring for conventional priority pollutants (volatile, base/neutral, acid extractable, and pesticide compounds). Because the non‐priority pollutant compounds account for an estimated 76 percent of the Appendix IX analytical costs but only 0.25 percent of the detectable events in disposal site ground water, it has been recommended that this class of compounds be deleted from routine monitoring programs. A scaling back of the current requirement to the conventional priority pollutants would still target more than 99 percent of the Appendix IX organic constituent occurrences in ground water and result in an analytical cost savings of approximately $2750 per sample or an estimated $51 million a year without significantly reducing the volume of useful organic monitoring data that would be generated to assess ground water conditions in the vicinity of waste disposal sites.
A Large‐Scale Retrospective Ground Water Monitoring Study for Metolachlor
Authors: Roux Paul H. , Balu K. , Bennett Rodney
Published: February 2007

A large‐scale retrospective ground water monitoring study'for metolachlor, 2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐ N‐(2‐methoxy‐l‐methylethyl) acetamide, was conducted. The study consisted of the collection and analysis of ground water samples from 240 existing wells (203 domestic farm wells and 37 monitoring wells) in selected areas of four states: the Dougherty Plains, Georgia; McLean County, Illinois; Floyd and Mitchell counties, Iowa; and the Central Sands area of Wisconsin. These locations were selected on the basis of high metolachlor use and hydrogeological vulnerability.

The wells selected were all screened in the uppermost aquifer, were relatively shallow, and were located close to fields where metolachlor has historically been used. Pesticide handling and storage practices on the farms where the wells were located were documented, and wells were selected to avoid obvious point sources. The wells selected for monitoring included drinking water, irrigation and monitoring wells. Monitoring was at quarterly intervals for a one‐year period.

Metolachlor was detected in 89 of 920 samples (9.7 percent) from 39 of 240 wells (16.3 percent) with a screening level (quantitation level) of 0.1 ppb. Ten out of 240 wells sampled (4.2 percent) showed detections in all sampling rounds.

Of the samples analyzed, 5.1 percent had detections in the range between 0.1 and 0.5 ppb. Thus, non‐detections plus detections below 0.5 ppb accounted for 95.4 percent of all samples, and detections below 0.5 ppb represented more than half of all the detections found in the study (47 out of 89 detections). In the 31 samples where metolachlor was detected above 1.0 ppb, every detection could be related to a known or suspected point source.

Based on the frequency and magnitude of metolachlor detections in this study, there appears to be no significant measurable field leaching of metolachlor to ground water under conditions of high product use and high ground water vulnerability. Instead, measurable detections of metolachlor, particularly those exceeding 1.0 ppb, appear to be associated with point sources.
Estimating Geohydrologic Properties from Borehole‐Geophysical Logs
Authors: Jorgensen Donald G.
Published: February 2007

Borehole‐geophysical logs can be used to estimate geohydrologic properties based on in situ measurement of rock and water properties. Estimates of properties of both formation and water, such as coefficient of diffusion, formation factor, cementation exponent, hydraulic conductivity, irreducible water content and specific yield can be assessed from borehole‐geophysical data and selected algorithms and graphs.

Water properties, such as resistivity, sodium chloride concentration, viscosity and density, can also be estimated using data from borehole‐geophysical logs. Water resistivity using the spontaneous‐potential method can be estimated if an empirical correction for fresh water is applied.

Estimates of formation properties, such as porosity and permeability, can also be made using borehole‐geophysical data.
Laboratory Demonstration of Hydrocarbon Migration in the Vadose Zone: Effectiveness of the U‐Tube Design for Underground Storage Tank Leak Detection Monitoring
Authors: Springer David S. , Keller Edward A. , Everett Lome G. , Eccles Lawrence A.
Published: February 2007

The experimental results derived from a laboratory model of gasoline migration from a simulated leaking underground storage tank (UST) demonstrate that the direction of migration through the simulated fill material is essentially straight down. Consequently, the U‐tube design for leak detection monitoring of USTs has limited utility because that design relies on the assumption that the path of migration of the leaked fluids will follow the surface of the tank to the bottom and be intercepted by the U‐tube below.
Survey of Rural Wells in Missouri for Pesticides and Nitrate
Authors: Sievers Dennis M. , Fulhage Charles D.
Published: February 2007

Two hundred and one rural wells were sampled in eight agricultural areas of Missouri. Samples were analyzed for 25 pesticides and nitrate. Forty‐three percent of the wells sampled had at least one pesticide detection. Thirteen percent of the wells had at least one detection ≧ 1 ppb and these concentrations were confirmed. Only one well exceeded U.S. EPA Health Advisory levels. Twenty‐two percent of the wells exceeded the U.S. EPA Drinking Water Standard for nitrate. Pesticide detections were most strongly correlated to well depth. Nitrate levels were primarily related to well depth, well construction methods, and well siting.
Procedures for Sampling Deep Subsurface Microbial Communities in Unconsolidated Sediments
Authors: Russell Brent F. , Phelps Tommy J. , Griffin William T. , Sargent Kenneth A.
Published: February 2007

A corehole sampling project utilizing a wireline coring system provided sediment samples for microbiological characterization from deep unconsolidated sediments. Sampling tools were developed or modified to minimize contamination during sample acquisition and to facilitate stringent decontamination requirements. Quality assurance procedures, including the use of tracers, were implemented to minimize and quantify contamination from drilling hardware, drilling fluids and sample processing. Tracers included microspheres, potassium bromide, rhodamine dye, and perfluorocarbons, which enabled the detection and measurement of 1mg of drilling fluid per kg of sediment. In addition, sample processing was performed on‐site in an anaerobic chamber to prevent exposure of the subsurface materials to atmospheric oxygen concentrations. Sediment samples were then disbursed to investigators at National Laboratories and universities funded through the Department of Energy Subsurface Science Microbiology Program for microbiological characterization. Results of these efforts demonstrated that representative subsurface samples were collected and disbursed.
Estimation of the Probability of Exceedance of Contaminant Concentrations
Authors: McBean Edward A. , Rovers Frank A.
Published: February 2007

Several alternative probability distributions for estimating the probability of exceedance of contaminant concentrations are examined for their appropriateness for developing inputs to risk assessments. The rationale is provided for using the log Pearson Type III distribution, a three‐parameter model, for estimation of the exceedance probabilities.
Spatial Moment Analysis for Mass Balance Calculations and Tracking Movement of a Subsurface Hydrocarbon Mound
Authors: Knox Robert C.
Published: February 2007

Leaking underground storage tanks are a proven source of subsurface hydrocarbon contamination. An improbable leak scenario supported by anomalous field data formed the basis of a major lawsuit filed against a tank installer. A simplified hydrocarbon mound migration model, coupled with basic mass balance calculations, showed the field data to be inconsistent with the purported leak scenario, and showed monitoring well tampering to be the source of hydrocarbon contamination. The method described is a simple yet efficient means of developing hydrocarbon mass estimates and mound migration projections. These values can also be valuable in siting injection/extraction locations and developing integrated in situ remediation technologies.
In Situ Electromigration as a Method for Removing Sulfate, Metals, and Other Contaminants from Ground Water
Authors: Runnells Donald D. , Wahli Catherine
Published: February 2007

Electromigration is proposed as an in situ method for preconcentrating contaminants in ground water prior to pumping and treating. In earlier investigations by the senior author and co‐workers, it was found that Cu in synthetic ground water migrated strongly to a Pt cathode and plated out as metallic copper. In the present study, carbon electrodes were inserted into a laboratory column of fine quartz sand that was saturated with a lower concentration of CuSO4 solution. A fixed potential of 2.5 V was applied, causing dissolved Cu and SO4 to accumulate strongly at the cathode and anode, respectively. Only minor plating‐out of Cu took place on the carbon electrodes. In addition to the use of carbon electrodes, the present research also investigated the effects of a lower concentration of metal, accumulation of SO4 adjacent to the anodes, adsorption of Cu on the sand, and competition by moving ground water.

At an imposed voltage of 2.5 V and in the presence of 65 mg/L of dissolved Cu and 96 mg/L of SO4 (0.001 M CuSO4 solution), electrolysis of water caused large changes in the pH and speciation of the aqueous components, as well as precipitation of solid Cu‐hydroxides. Significant retardation of Cu occurred in the presence of ground water flowing at an average intergranular velocity of 0.2 m/day, but only minor retardation at water velocities of 1.9 and 2.9 m/day.

Sulfate tends to migrate strongly to the anodes, suggesting that in situ electromigration may offer a useful new method for preconcentrating such highly soluble ions as SO4, NO3, and CI that are difficult to remove by conventional pump‐and‐treat methods. A number of potential problems exist that should be addressed in a field test.
Sampling for Purgeable Organic Compounds Using Positive‐Displacement Piston and Centrifugal Submersible Pumps: A Comparative Study
Authors: Knobel LeRoy L. , Mann Larry J.
Published: February 2007

Positive‐displacement piston pumps that minimize sample agitation have no apparent advantage over centrifugal submersible pumps when used to collect ground water samples for analysis of low concentrations of purge‐able organic compounds. Analytical uncertainties inherent in laboratory environments appear to influence analytical results of low‐concentration purgeable organic compound samples more than either pump type or sampling team. Centrifugal submersible pumps are at least equally efficient as positive‐displacement piston pumps in the recovery of carbon tetrachloride, 1,1,1‐trichloroethane, trichloroethylene, and chloroform after sampling and analytical influences are made constant.
Casing Leakage in Monitoring Wells: Detection, Confirmation, and Prevention
Authors: van der Kamp G. , Keller C.K.
Published: February 2007

A small but significant proportion of all existing monitoring wells may be affected by leakage through the casing, usually at joints. Casing leakage can render data obtained from a monitoring well unreliable. Anomalous water level, water quality, or isotope data from a particular well are an indication of possible leakage. The occurrence of a casing leak can be confirmed by means of a pressure test using water. The magnitude of the leakage flow can be estimated from the pressure test or from the observed head anomaly. Casing leaks can be largely prevented with adequate care during monitoring well installation, but the possibility that data may be affected by casing leaks should always be taken into account during hydrogeological investigations.
Dynamic Study of Common Well Screen Materials
Authors: Hewitt Alan D.
Published: February 2007

Experiments simulating the dynamics of compliance sampling via a monitoring well were performed to assess the effects of common well screen materials (rigid polyvinyl chloride, polytetrafluoroethylene, stainless steel 304. and stainless steel 316) on several metals and tri‐ chloroethylene (TCE) in ground water. This was achieved by using a continuous flow‐through chamber system capable of exposing monitoring well screens to ground water for periods ranging from 0.25 to 8 hours. The findings of this study are more representative than static laboratory experiments for assessing the potential effects well casing materials have on ground water samples. Under dynamic flow conditions stainless steel 304 and 316 screens were found to influence solution concentrations of Pb, Cd, Cr, Ni, and Fe, while ground water TCE concentrations were not affected by any of the materials tested.