bluuebunny/crossref_metadata_2025 huggingface dataset:
Field Trapping of Subsurface Vapor Phase Petroleum Hydrocarbons
Authors: Moyer Ellen E. , Ostendorf David W. , Kampbell Don H. , Xie Yuefeng
Published: February 2007

Soil gas samples from intact soil cores were collected on adsorbents at a field site, then thermally desorbed and analyzed by laboratory gas chromatography (GC). Vertical concentration profiles of predominant vapor phase petroleum hydrocarbons under ambient conditions were obtained for the zone directly above the capillary fringe. Water and residual phase weathered aviation gasoline were present in this region of the profile.

The sampling, trapping, and GC methodology was effective in most respects. Reproducibility, trapping, and desorption efficiency were generally satisfactory, and different sorbent tubes gave similar results. A minor shortcoming of the method occurred with the most volatile compound, 2,3‐dimcthylbutane, which was poorly retained during several weeks of storage lime and was also poorly desorbed.

Vapor phase concentrations of predominant hydrocarbon compounds all increased with depth at one sampling location. At a more highly contaminated location, concentrations of highly volatile compounds increased with depth while concentrations of less volatile compounds remained constant or decreased, possibly indicating distillation effects. Scatier in the data was attributed to heterogeneities in water and residual phase distribution.
Contaminant Spread and Flushing in Fractured Rocks Near Oak Ridge, Tennessee
Authors: Shevenell L.A. , Moore G.K. , Dreier R.B.
Published: February 2007

Liquid wastes, including metals dissolved in nitric acid, were discharged into the S‐3 Ponds from 1951 to 1983. During this period, contaminants in ground water spread along shallow fracture flow paths toward nearby streams. Also, a high concentration of nitrate in one well at a depth of 110 to 240 in shows that some contaminants may have moved downdip because of differences in fluid density. Neutralization of the ponds in June 1983 caused a dramatic decrease in the contaminant concentrations of Bear Creek about three months later. Since then, the contaminant concentrations of Bear Creek have decreased at a first‐order exponential rate. This average rate, which is the same for both more reactive and less reactive constituents, can be interpreted to show that the contaminant reservoir consists of the unfractured rock matrix.

Flushing caused by the natural recharge and discharge of ground water is occurring at all locations, but contaminant concentrations are controlled by the relative rates of molecular diffusion from the rock matrix and advection along the fracture flow paths. Hushing has thus been most effective near the water table. If the exponential decrease in contaminant concentrations continues, water in Bear Creek will meet drinking water standards by 2012: regardless of any remedial action, contaminants will remain in the rocks for many years.
A Practical Approach to Evaluating Natural Attenuation of Contaminants in Ground Water
Authors: McAllister P.M. , Chiang C.Y.
Published: February 2007

The extent of natural attenuation is an important consideration in determining the most appropriate corrective action at sites where ground water quality has been impacted by releases of petroleum hydrocarbons or other chemicals. The objective of this study was to develop a practical approach that would evaluate natural attenuation based on easily obtained field data and field tested indicators of natural attenuation. The primary indicators that can he used to evaluate natural attenuation include plume characteristics and dissolved oxygen levels in ground water. Case studies of actual field sites show that plumes migrate more slowly than expected, reach a steady state, and decrease in extent and concentration when natural attenuation is occurring. Background dissolved oxygen levels greater than 1 to 2 mg/L and an inverse correlation between dissolved oxygen and contaminant levels have been identified through laboratory and field studies as key indicators of aerobic biodegradation. an important attenuation mechanism. Secondary indicators such as geochemical data, and more intensive methods such as contaminant mass balances, laboratory microcosm studies, and detailed ground water modeling can demonstrate natural attenuation as well. The recommended approach for evaluating natural attenuation is to design site assessment activities so that required data such as dissolved oxygen levels and historical plume flow path concentrations are obtained. With the necessary data, the primary indicators should be applied to evaluate natural attenuation. II the initial evaluation suggests that natural attenuation is a viable corrective action alternative, then a monitoring plan should be implemented to verify the extent of natural attenuation.
Surfactant‐Induced Reductions in Soil Hydraulic Conductivity
Authors: Allred Barry , Brown Glenn O.
Published: February 2007

Surfactant solutions are being proposed for in situ flushing of organic contaminants from soils and aquifers. The feasibility of surfactant additives in remediation may depend in large part on how these chemicals affect the hydraulic conductivity of the porous media. While there is evidence in the literature of conductivity loss during surfactant flushing (Miller et al. 1975; Nash et al. 1987), there has been little research on quantifying the process for unconsolidated sediments. Surfactant‐affected hydraulic conductivity reductions were measured in two soils (Teller loam and Daugherty sand). Testing was done with eight surfactants at a variety of concentrations (10‐5 to 10‐l mole/kg), surfactant mixtures, and added solution electrolytes. The Teller was also tested with its organic matter removed. Maximum hydraulic conductivity decreases were 47 percent for the sand and more than two orders of magnitude for the loam. Surfactant concentrations, surfactant mixtures, soil organic content, and added solution electrolytes all affected the degree of conductivity reduction. Results indicate that surfactant‐affected hydraulic conductivity losses should be considered prior to in situ remediation and may preclude surfactant use in some fine grain soils.
Effect of Concentration on Sorption of Dissolved Organics by PVC, PTFE, and Stainless Steel Well Casings
Authors: Parker Louise V. , Ranney Thomas A.
Published: February 2007

This report examines sorption of low ppb levels of organic solutions by polytetra‐ fluoroethylene (PTFE), rigid polyvinyl chloride (PVC), and stainless steel 304 and 316 well casings. Nineteen organics were selected, including several munitions and chlorinated solvents. Compounds were selected to offer a range of physical properties, such as solubility in water, octanol/water partition coefficient, and molecular structure. When these results were compared with the results from a similar study conducted at ppm levels, the rate and extent of sorption by PTFE and PVC were the same as seen previously for almost all analytes. There were no losses of any compounds associated with stainless steel. At these low levels (ppm and ppb), the rate of diffusion within the polymer (PVC and PTFE) is independent of concentration. Only with PTFE are the rates rapid enough to be of concern when monitoring for some contaminants in ground water. Tetrachloroethylene was the compound PTFE sorbed the most rapidly. The study showed that PVC well casings are suitable for monitoring low levels (ppm and ppb) of organics.
Vertical Distribution and Partitioning of Chromium in a Glaciof luvial Aquifer
Authors: Nikolaidis Nikolaos P. , Robbins Gary A. , Scherer Michelle , McAninch Brian , Binkhorst Gordon , Asikainen Jay , Suib Steven L.
Published: February 2007

The vertical distribution and partitioning (between the solid and aqueous phase) of chromium in a glaciofluvial aquifer in northeastern Connecticut were assessed. Most of the chromium (99 percent of its mass) is bound to the soil. Retardation is primarily the result of binding to organic matter and adsorption to iron oxide coatings. However, other attenuation mechanisms also appear to be significant. If the degree of chromium binding observed here is representative of other chromium contaminated sites, pump‐and‐treat remediation will not remove the vast amount of chromium from the subsurface. However, most of the chromium may be immobile, and removal may not be required following the initial pumping to remove the mobile fraction. Further knowledge of the mechanisms that bind chromium to the soil, their reversibility, and their kinetics is essential to developing effective remediation strategies.
Evaluation of an Ultrafiltration Method for Surfactant Recovery and Reuse During In Situ Washing of Contaminated Sites: Laboratory and Field Studies
Authors: Ang Carolina C. , Abdul Abdul S.
Published: February 2007

Feasibility studies were conducted on the use of ultrafillration to recover surfactant from aqueous waste streams generated from the in situ surfactant washing of a site contaminated with poly‐chlorinated biphenyls (PCBs) and oils. A Romicon Model HF‐Lab‐5 ultrafiltration unit and three types of ultrafillration membranes (PM500, XM50, and CM50) were evaluated for their permeability to a nonionic surfactant previously selected for the in situ washing. Results from laboratory studies using the XM50 membrane cartridge showed that 78 percent of the surfactant passed through the membrane surface (permeate) and was recovered.

Two field‐pilot tests of the ultrafiltralion system were conducted using leachate containing a mixture of water, oils, PCBs, and surfactant that was collected from an in situ surfactant‐washing demonstration test. Forty‐six percent of the surfactant (mass) was recovered during the first field test using the XM50 membrane. The membrane retained 94 percent of the PCBs and 89 percent of the oils. The second field test showed that the PM500 membrane recovered 67 percent of the surfactant in the permeate and retained more than 90 percent and 83 percent of the PCBs and oils, respectively. This study indicates that a significant volume of a nonionic surfactant can be recovered from leachatc mixture containing PCBs and oils by ultrafillration. The recovered surfactant could be reused to improve the economic viability of in situ surfactant washing of contaminated sites.
A Conceptual Model of Field Behavior of Air Sparging and Its Implications for Application
Authors: Ahlfeld David P. , Dahmani Amine , Ji Wei
Published: February 2007

The basic physics of air flow through saturated porous media are reviewed and implications arc drawn for the practical application of air sparging. A conceptual model of the detailed behavior of an air sparging system is constructed using elements of multiphase flow theory and the results of recent experimental work. Implications of the conceptual model on air sparging topics are discussed. The meaning of radius of influence in the context of air sparging is found to be ambiguous. The hydrodynamic effects of air sparging such as mounding of ground water and flow impedance are explored. Limitations on rates of remediation and operational strategics for improving sparging effectiveness are examined.
The Application of Petroleum Hydrocarbon Fingerprint Characterization in Site Investigation and Remediation
Authors: Zemo Dawn A. , Bruya James E. , Graf Tom E.
Published: February 2007

Tremendous resources have been and continue to be spent investigating and remediating petroleum hydrocarbon compounds (PHCs) in soil and ground water. Investigating and planning a remedial strategy for sites affected by PHCs is often a challenging task because of the complex chemical nature of the PHCs. the complex regulatory environment related to PHC cleanup, and the use of analytical methods that provide quantitation but not identification of PHCs. From a technical standpoint, the PHC impacting soil and/or ground water is frequently inadequately characterised, both in identification as well as in is general properties (solubility, toxicity). From a regulatory standpoint, promulgated or recommended total petroleum hydrocarbon (TPH) cleanup levels generally relate to assumed properties of specific unweathered products and are inconsistent among different agencies and regions. This produces a prime situation for unwillingly spending more resources on investigation or remediation than may be necessary, especially when the PHC in the subsurface has different properties from unweathered products such as gasoline or diesel.

Accurately identifying the PHC and its nature, a process known as fingerprint characterization, is critical to the determination of appropriate regulatory goals and design of cost‐effective remedial approaches. This paper presents several case studies in which fingerprint characterization made a significant difference in the project outcome. In each instance the nature of the organic material was better understood, the regulatory cleanup levels were negotiated based on the nature of the material, and a remedial approach was implemented that differed significantly from and was generally less costly than what would have been required without fingerprint characterization data.
A Model for Determination of the Phase Distribution of Petroleum Hydrocarbons at Release Sites
Authors: Mott Henry V.
Published: February 2007

A model and computer‐based numeric approximation for computing the equilibrium distributions of contaminants at petroleum release sites is presented. A database of contaminant‐specific parameters, including solubility and organic‐carbon partitioning coefficient, is assembled. Applications and limitations of the model are discussed.
Micro‐Purge Low‐Flow Sampling of Uranium‐Contaminated Ground Water at the Fernald Environmental Management Project
Authors: Shanklin D.E. , Sidle W.C. , Ferguson M.E.
Published: February 2007

Efforts to sample representative, undisturbed distributions of uranium in ground water beneath the Fernald Environmemal Management Project (FEMP) prompted the application of a novel technique that is less invasive in the monitoring well. Recent studies (Kearl et al. 1992; Barcelona et al. 1994) indicate that representative samples can and should be collected without prior well volume exchange purging or borehole evacuation. Field experiments conducted at the FMMP demonstrate that under specific sampling conditions in a welldefined hydrogeologic system, representative ground water samples for a monitoring program can be obtained without removing the conventional three well volumes from the well. The assumption is made that indicator parameter equilibration may not be necessary to determine when to collect representative samples at the P'liMP. Preliminary results obtained from the field experiment suggest that this may be true. The technique employs low purge rates (< 1 L/min) with dedicated bladder pumps with inlets located in the screened interval of the well, while not disturbing the stagnant water column above the screened interval. If adopted, this technique, termed micro‐purge low‐flow sampling, will produce representative ground water samples, significantly reduce sampling costs, and minimize; waste water over the monitoring life cycle at the FEMP. This technique is well suited for sites that have been fully characterized and are undergoing long‐term monitoring.
Developing A National Drinking Water Regulation for Disinfection of Ground Water
Authors: Macler Bruce A.
Published: February 2007

The Safe Drinking Water Act directs EPA to promulgate requirements for disinfection of ground water‐based drinking water systems. The Ground‐ water Disinfection Rule regulatory workgroup, made up of representatives from EPA, the states, and other interested parties, is actively considering the issues for the wide range of elements necessary to ensure a regulation that will protect public health and can be feasibly implemented. This regulation is likely to require disinfection of ground water sources and systems found to be contaminated or vulnerable to contamination.
Tracer Test to Evaluate Dilution of Ground Water from Lost Circulation
Authors: Schilling Keith E. , Hoyle Blythe L.
Published: February 2007

Lost circulation, the inadvertent injection of drilling fluids into a highly permeable and/or fractured aquifer during rotary drilling, may result in collection of spurious information if the lost drilling fluids are not adequately purged before sampling the ground water. The purpose of this study was to determine whether removal of the volume of water lost during coring of a monitoring well in the carbonate Scotch Grove Formation (Silurian, east central Iowa) necessarily ensures collection of representative ground water samples. To monitor dilution of the ground water due to lost circulation, rhodamine dye was added to the drilling water and dye recovery was measured in samples collected during purging of five separate 5‐ to 10‐foot intervals.

Circulation loss occurred in all five intervals, ranging from nearly 200 gallons in the upper permeable portion of the Scotch Grove to 25 gallons in the less permeable Buck Creek Member below. When the volume of water purged from the upper three intervals corresponded to the volume of water lost during coring, the purge water still contained 11 to 20 percent dyed drilling water. As purging continued, the proportion of drilling water in the samples decreased slowly. After purging more than 200 gallons of water, 86 to 98 percent of the dyed drilling water was recovered from the five test intervals. Four traditionally measured water quality parameters‐pH, temperature, specific conductance, and dissolved oxygen — were less useful than the dye recovery for distinguishing drilling water from formation water in those zones in which the ground water quality was similar to the drilling water. These results indicate that the determination of the quantity of water to be purged prior to sampling must be based, at least in part, on aquifer lithology and hydraulic characteristics.
Monitoring Air Sparging Using Resistivity Tomography
Authors: Schima Susan , LaBrecque Douglas J. , Lundegard Paul D.
Published: February 2007

Air sparging is a relatively new technique for the remediation of ground water contaminated with petroleum hydrocarbons. In this technique, air is injected below the water table, beneath the contaminated soil. Remediation occurs by a combination of contaminant partitioning into the vapor phase and enhanced biodegradation. The air is usually removed by vacuum extraction in the vadose zone.

The efficiency of remediation from air sparging is a function of the air flow pattern, although the distribution of the injected air is still poorly understood. Cross‐borehole resistivity surveys were performed at a former service station in Florence, Oregon, to address this unknown. The resistivity measurements were made using six wells, one of which was the sparge well. Data were collected over a two‐week period during and after several air injections, or sparge events. Resistivity images were calculated between wells using an algorithm that assumes axially symmetric structures. The movement of the injected air through time was defined by regions of large increases in resistivity, greater than 100 percent from the background. During early sparge times, air moved outward and upward from the injection point as it ascended to the unsaturated zone. At later sparge times, the air flow reached a somewhat stable cone‐shaped pattern radiating out and up from the injection point. Two days after sparging was discontinued, a residue of entrained air remained in the saturated zone, as indicated by a zone of 60 to 80 percent water saturation.
Risk‐Based Engineering Design for a Landfill Leachate Collection and Liner System
Authors: Murray Gordon B. , McBean Edward A. , Sykes Jonathan F.
Published: February 2007

A methodology is used to identify the tradeoffs between costs and exposure risk associated with landfill leachate collection and low permeable systems. The results are useful in demonstrating the point at which additional levels of sophistication in design of a leachate/liner system do not produce significant reductions of exposure risk. The case study application to the Durham Regional landfill demonstrates that clay liner hydraulic conductivity is the parameter with the largest influence on the risk of exceedance at the point of compliance. When the underlying clay is more permeable, there is a significant merit associated with use of a QA/QC program.
A Sample‐Freezing Drive Shoe for a Wire Line Piston Core Sampler
Authors: Murphy Fred , Herkelrath W. N.
Published: February 2007

Loss of fluids and samples during retrieval of cores of saturated, noncohesive sediments results in incorrect measures of fluid distributions and an inaccurate measure of the stratigraphic position of the sample. To reduce these errors, we developed a hollow drive shoe that freezes in place the lowest 3 inches (75 mm) of a 1.88‐inch‐diameter (48 mm), 5‐foot‐long (1.5 m) sediment sample taken using a commercial wire line piston core smapler. The end of the core is frozen by piping liquid carbon dioxide at ambient temperature through a steel tube from a bottle at the land surface to the drive shoe where it evaporates and expands, cooling the interior surface of the shoe to about ‐ 109°F (‐ 78°C). Freezing a core end takes about 10 minutes. The device was used to collect samples for a study of oil‐water‐air distributions, and for studies of water chemistry and microbial activity in unconsolidated sediments at the site of an oil spill near Bemidji, Minnesota. Before freezing was employed, samples of sandy sediments from near the water table sometimes flowed out of the core barrel as the sampler was withdrawn. Freezing the bottom of the core allowed for the retention of all material that entered the core barrel and lessened the redistribution of fluids within the core. The device is useful in the unsaturated and shallow saturated zones, but does not freeze cores well at depths greater than about 20 feet (6 m) below water, possibly because the feed tube plugs with dry ice with increased exhaust back‐pressure, or because sediment enters the annulus between the core barrel and the core barrel liner and blocks the exhaust.
In Situ Remediation of Jet A in Soil and Ground Water by High Vacuum, Dual Phase Extraction
Authors: Kirshner Marvin , Pressly Nicholas C. , Roth Robert J.
Published: February 2007

This report summarizes the initial results of subsurface remediation at Terminal 1, Kenneth International Airport, to remediate soil and ground water contaminated with Jet A fuel. The project was driven and constrained In the const ruction schedule of a major new terminal at the facility. The remediation system used a combination of ground water pumping, air injection, and soil vapor extraction. In the first five months of operation, the combined processes of dewatering, volatilization, and biodegradation removed a total of 36,689 pounds of total volatile and semivolatile organic jet fuel hydrocarbons from subsurface soil and ground water. The. results of this case study have shown that 62 percent of the removal resulted from biodegradation, 21 percent occurred as a result of liquid removal, and 11 percent resulted from the extraction of volatile organic compounds (VOC's).
Effect of Various Materials in Multilevel Samplers on Monitoring Commonly Occurring Agrichemicals in Ground Water
Authors: Papiernik Thomas D. , Widmer Sharon K. , Spalding Roy F.
Published: February 2007

Studies have shown that materials, such us polytetra‐fluoroethylene (PTFE), rigid polyvinyl chloride (rigid PVC). flexible polyvinyl chloride (flexible PVC), stainless steel (SS). low‐density polyethylene (LDPE), and high‐density polyethylene (HDPE), have the potential to influence certain analyte concentrations in ground water samples. The effects of HDPE, LDPE, PTFE, rigid PVC, and SS on aqueous concentrations of nitrate‐N, atrazine, deethylatrazine (DEA), and deisopropylatrazine (DIA) were evaluated in a field study A laboratory study was conducted to evaluate sorption of atrazine DEA, DIA, cyanazine, alachlor, metolachlor, and butachlor to PTFE, HDPE, and SS materials. Butachlor is rarely use in the United States, but was included because of its expected high sorptivity. No significant differences between HDPE, LDPE, PTFE, rigid PVC, and SS were determined for any of the analytes tested in the field study. In the laboratory study, sorption of DIA to PTFE and SS was significant at 2.6 × 10−5 and 4.1 × 10−5μg/m2 respectively. Sorption of DIAA to HDPE was not significantly > 0 sorption of all other compounds to HDPE, PTFE, and SS were also not significantly >0. Results of the two studies indicate that for these analytes (relatively polar or ionized compounds), representative ground water samples are not dependent on the materials used for multilevel sampler construction. When considering these compounds, it appears that the least expensive materials (HDPE, rigid PVC, and LDPE) are good choices for the construction of ground water monitoring wells.
Nickel and Chromium in Ground Water Samples as Influenced by Well Construction and Sampling Methods
Authors: Oakley D. , Korte N.E.
Published: February 2007

An investigation of elevated concentrations of nickel and chromium in certain ground water samples collected at Williams Air Force Base (AFB) indicated that type 304 stainless steel well materials are the source. Chloride in the ground water has apparently caused crevice corrosion of the stainless steel well screens installed during site characterization. An evaluation of site geochemistry suggested that chromium released from the well screen would precipitate, while nickel would remain dissolved. Thus, low‐flow purging and sampling significantly reduces the chromium found in the ground water samples because such sampling minimizes the collection of artificially entrained particulates. In contrast to chromium, nickel concentrations did not decrease during low‐flow purging and sampling, indicating that it is dissolved. Nickel and chromium concentrations are both low following high‐volume purging when turbidity levels are stabilized below 10 nephelometric turbidity units prior to sampling. In the latter case, chromium concentration is low because particulate collection is minimized, and nickel concentration is low because of increased dilution. Based on these results, it is recommended that elevated levels of nickel and chromium in ground water samples collected from stainless steel monitoring wells be carefully evaluated, because well materials may be the source. In addition, although low‐volume purging is increasingly becoming the sampling method of choice, high‐volume purging may be a useful means of determining whether the well materials influence nickel and chromium concentrations.
Ground Water Discharge of Agricultural Pesticides and Nutrients to Estuarine Surface Water
Authors: Gallagher Daniel L. , Dietrich Andrea M. , Reay William G. , Hayes Mary C. , Simmons George M.
Published: February 2007

This research investigated the transport of land‐applied nutrients and pesticides from unconfined aquifers to tidal surface waters of Virginia's coastal plain. Ground water, estuarine surface water, ground water discharge, upland soil, and offshore sediment samples were collected from May 1992 until February 1993 from four agricultural sites. Samples were analyzed for inorganic nitrogen and phosphorus and five pesticides: atrazine, cyanazine, alachlor, metolachlor, and carbofuran. Pesticides from aqueous samples were determined by liquid‐solid phase extraction followed by gas chromatography‐electron capture detection (GC‐ECD) and/or by pesticide‐specific immunoassay. Soil and sediment samples were analyzed by extraction and gas chromatography/mass spectrometry (GC/MS). Nutrient measurements indicated that fertilizer nitrogen was moving from the ground water to the surface water, and nitrogen fluxes across the sediment‐water interface were correlated with fresh water discharge rates. Mean nitrate‐N flux was 2.48 mg/m2hr, with a maximum value of 30.98 mg/m2hr. Pesticides were detected in more than half of the upland soil samples, in approximately 40 percent of the ground water samples, and in just under 20 percent of the seepage meter samples. Pesticides were not detected in any of the offshore sediment samples or surface water samples. Alachlor and metolachlor were detected in upland soil samples at concentrations ranging from 10 to almost 500 μg/kg. All five pesticides were found in ground water samples at concentrations generally below 1 μg/L, with alachlor, atrazine, and metolachlor most frequently found. Alachlor, atrazine, cyanazine, and metolachlor were detected in water discharging across the sediment‐water interface and entering estuarine waters at concentrations ranging from 0.05 to 0.5 μg/L. These levels were generally consistent with the amount of dilution due to the mixing of fresh ground water and saline pore waters prior to discharge across the sediment‐water interface. Based on all positive detections of pesticides in ground water discharge, which represented approximately 18 percent of all samples, average flux rates of cyanazine, metolachlor, alachlor, and atrazine were 0.32, 0.37, 0.80, and 1.12 μg/m2hr, respectively. These findings indicate that submarine ground water transport of both nutrients and pesticides does occur, and this transport route should be considered when implementing agricultural management practices. The levels of nitrogen transport to surface water appears significant. The overall levels of pesticide movement through ground water, although generally quite low, represent a transport route that is commonly neglected in watershed management.
Compatibility of NAPLs and Other Organic Compounds with Materials Used in Well Construction, Sampling, and Remediation
Authors: McCaulou Douglas R. , Jewett David G. , Huling Scott G.
Published: February 2007

Structural integrity of well construction, sampling, and remediation materials may be compromised at many hazardous sites by nonaqueous phase liquids (NAPLs) and their dissolved constituents. A literature review of compatibility theory and qualitative field experiences are provided regarding the degradation and corrosion of materials in contact with NAPLs and organic compounds. A chemical compatibility table, compiled from several sources of compatibility testing results, is presented for 73 chemicals and 28 commonly used materials. Field experiences illustrate the compatibility problems of some of the common wastes and materials found at hazardous waste sites.
Synergistic Application of Four Remedial Techniques at an Industrial Site
Authors: Dasch Jean. M. , Abdul Abdul S. , Rai Devi N. , Gibson Thomas L. , Grosvenor Noel
Published: February 2007

The soil and ground water at a General Motors plant site were contaminated with petroleum products from leaking underground storage tanks. Based on the initial assessment, the site was complex from the standpoint of geology (clay layers), hydrology (a recharge zone with a perched water table), and contaminant (approximately 4800 gallons of mixed gasoline and oil). After a thorough study of remedial alternatives, a synergistic remedial approach was adopted including pump and treat, product removal, vapor extraction, and bioventing. The system was designed and implemented at the site through 22 dual‐extraction wells. Over a 21‐month period, 4400 gallons of gasoline and oil were removed from the system, including 59 percent by vapor extraction, 28 percent by bioventing, and 13 percent by pump and treat. Synergism between the various remedial methods was demonstrated clearly. Ground water pump and treat lowered the water table, allowing air to flow for vapor extraction. The vacuum applied for vapor extraction increased the ground water removal rate and the efficiency of pump and treat. The vapor extraction system also added oxygen to the soil to stimulate aerobic biodegradation.
Evaluation of Batch Leaching Procedures for Estimating Metal Mobility in Glaciated Soils
Authors: Lackovic Jeffrey A. , Nikolaidis Nikolaos P. , Chheda Pradeep , Carley Robert J. , Patton Elsie
Published: February 2007

Batch leaching methods have been used for several decades to estimate the potential release of contaminants from soils. Four batch leaching procedures (toxicity characteristic leaching procedure, synthetic precitation leaching procedure, deionized water leaching procedure, and California waste extraction test) were evaluated for their ability to realistically quantify the mobility of metals from previously contaminated glaciated soils. The study was conducted using soils from four different sites (three in Connecticut and one in Maine). The results of the batch leaching procedures were compared with a set of continuous column leaching experiments performed at two different flowrates and two influent pH values. The results suggested that the synthetic precipitation leaching procedure (SPLP) was more realistic than the toxicity characteristic leaching procedure (TCLP), but still a conservative leaching estimate for evaluating the potential for metal mobility in glaciated soils. This study suggests that using SPLP as a test for estimating metal cleanup levels will result in lower remediation costs relative to TCLP or waste extraction test (WET), but still maintain a high level of confidence in the protection of ground water quality.
Effect of Rigid PVC Bailer Contact on Detection of Pesticides in Water Samples
Authors: Schuh W.M. , Cline R.L. , Kosse M.J. , Sletton D.W.
Published: February 2007

A field experiment was conducted to examine the effect of short‐term (one minute) contact of pesticide‐laden water with a polyvinyl chloride (PVC) bailer on quantitative laboratory measurements of seven pesticide concentrations in distilled water samples subsequently decanted from the bailer. Pesticides were tested at two initial concentrations (low. based on current FPA maximum contaminant levels, or MCL: and high, based on a multiple of approximately lour times the MCL). Pesticide species included bromoxynil, diclofop‐m, dimethoate. MCPA, methyl parathion, propiconazole, and trifluralin. Dimethoate recoveries were poor for all treatments. For all other pesticides there was no systematic difference between pesticide concentrations measured before and after bailer contact. Effectiveness of bailer decontamination treatments consisting of distilled water rinse alone was related to water solubility (S) for each species. Distilled water samples decanted from a rigid PVC bailer following initial bailer contact with pesticide‐spiked water, and after the bailer had been cleaned with a single distilled water rinse, had measured pesticide concentrations of less than 2 percent of the pesticide concentration in the initial pesticide‐spiked water, regardless of S. A single distilled water rinse effectively removed all trace of contaminants having S> 500 mg/L. Multiple distilled water rinses, and multiple distilled water rinses followed by 15 bailings of a well, effectively removed all trace of contaminants having S> 50 mg/L. Below threshold S, cleaning effectiveness decreased as a power function of S.
Comparison of Fiberglass and Other Polymeric Well Casings, Part I: Susceptibility to Degradation by Chemicals
Authors: Ranney Thomas A. , Parker Louise V.
Published: February 2007

Previous research has shown that the most commonly used well casing materials‐stainless steel. polyvinyl chloride (PVC). and polytetra‐fluoroethylene (PTFE)‐are not suited for all monitoring environments and applications. This study is part of a series of experiments that were conducted to determine the suitability of four other polymeric well casing materials‐acrylonitrile butadiene styrene (ABS), fluorinalcd ethylene propylene (FHP), fiberglass‐reinlorced epoxy (FRE), and fiberglass‐reinforced plastic (FRP)‐ for use in ground water monitoring wells. In these studies, these four materials were compared with two other commonly used polymeric well casings, PVC and PTFE. Part I of these studies examines the resistance of these materials to degradation by chemicals. Future reports will consider sorption and leaching of organic and metal contaminants.

In this study, the six materials were exposed to 28 neat organic compounds (including one acid) and to extremely acidic and alkaline aqueous solutions for up to 112 days. This was done to simulate the most aggressive environments to which monitoring well casings may be exposed. The casings were observed for changes in weight and signs of physical degradation (swelling, softening, deterioration, or dissolution).

The two fluorinated polymers (FEP and PTFE) were not degraded by any of the lest chemicals. Among the nonfluorinated products tested. FRE was the most inert. Three organic chemicals caused the glass fibers to separate. and two organic solvents caused weight gains exceeding 10 percent. ABS was the most readily degraded material tested. By the end of the study, only the acid and alkaline solutions had little effect on ABS. FRP was more severely degraded by the organic chemicals than FRH but was less affected than PVC. FRP and FRE. lost weight when exposed to the highly acidic conditions.
EPA's CLEANUP 2000: Reforms to the RCRA Corrective Action Program
Authors: Donovan Kevin
Published: February 2007

“EPA has initiated CLEANUP 2000, which includes a number of reforms to the RCRA Corrective Action Program to help increase the pace of cleanups.”
Identifying Synergy Between Remedial Strategies and Land Reuse
Authors: Nyer Evan K. , Graves Lawrence S.
Published: February 2007

“Today the environmental professional teams with the developer to use remedial technologies and approaches that complement planned land use and, conversely, use land in a fashion that accommodates environmental site conditions.”
In‐Line Measurement of Trichloroethylene Vapors Using Tin Dioxide Sensors
Authors: Heron G. , van Zutphen M. , Enfield C. G.
Published: February 2007

During thermally enhanced in situ remediation of soils and ground water, gas streams are generated with varying temperatures, moisture content, and organic compound concentrations. In this study, we evaluated the performance of tin dioxide sensors for measuring trichloroethylene (TCE) concentrations in gas streams from a thermally enhanced soil vapor extraction system. Temperature, pressure, moisture content, and vapor flow rates affected the resistivity of the sensors, and thus the signal. When fluctuations in these parameters were eliminated by condensing excess water and healing to a constant temperature prior to measurement, the sensors provided reliable in‐line measurement of TCE concentrations. Gas tracers such as methane were easily monitored in‐line, providing quick and inexpensive data on subsurface vapor flow velocities and direction.
Bioavailability of Hydrophobic Organic Contaminants: Effects and Implications of Sorption‐Related Mass Transfer on Bioremediation
Authors: Zhang Wei‐xian , Bouwer Edward J. , Ball William P.
Published: February 2007

The low bioavailability of hydrophobic organic compounds (HOCs) is one of the key sources of uncertainty in the implementation of in situ bioremediation. Bioavailability of HOCs in the subsurface is affected by sorption/desorption processes in two important ways. First, sorption causes high organic concentrations in microporous regions and impermeable zones to which bacterial access is obstructed. Second, because desorption and immobile zone diffusion must occur before biodegradation can proceed, the overall rate of bioremediation can be limited or even controlled by these mass transfer processes, not by the activity of the degrading microorganisms. Rate models that couple sorption/desorption—related mass transfer processes and biodegradation have been successfully applied to laboratory results and are beginning to offer some insight into the problem. Specifically, the influence of sorption on biodegradation is quantified here by defining a bioavailability factor, Bf. However, many questions remain and predictive modeling is elusive, especially in the context of complicated heterogeneous natural systems. Challenges facing environmental engineers are to develop a better understanding of these processes at both laboratory and field scales and ultimately to use such understanding toward the development of more effective and economical remediation technologies.
Sampling Trace‐Level Organic Solutes with Polymeric Tubing Part 2. Dynamic Studies
Authors: Parker Louise V. , Ranney Thomas A.
Published: February 2007

This is the second part of a study conducted to determine whether polymeric sampling tubing can affect organic analyte concentrations during a sampling event. In this part of the study, we looked for sorption and desorption of tricholoroethylene (TCE) and leaching of organic constituents in water pumped through five types of polymeric tubing. The materials tested were a rigid fluoropolymer, a flexible fluoropolymer, low‐density polyethylene (LDPE), and two plasticized polypropylene tubings. The effects of tubing length and flow rate were examined.

The least sorptive tubings, both initially and at equilibrium, were the fluoropolymers. However, in some instances the LDPE tubing had little effect on TCE concentrations. This was when a slow flow rate was used to sample relatively shallow wells (50 feet [15 m] or less) or when a faster flow rate (1 L/min) was used to sample wells that are less than 500 feet (152 m). Further testing is recommended using more sorptive analytes.

Using high performance liquid chromatography (HPLC), we were unable to detect any constituents leaching from any of the tubings used in these studies, even when a slow flow rate was used. However, desorption of sorbed analytes is a concern for all the tubings tested, including the rigid fluoropolymer.
Configuring Detection Wells Near Landfills
Authors: Hudak Paul F.
Published: February 2007

A graphical method was devised for designing contaminant detection monitoring networks in aquifers. The approach eliminates bias in detection efficiency among well pairs, thereby improving the overall efficiency of a ground water monitoring network. In the equidistant configurations derived by the graphical approach, all wells are located the same distance from a landfill, but the distance is measured parallel to ground water flow, Measured perpendicular to ground water flow, there is also an equal spacing between wells in an equidistant network. A simulation model was used to compare an equidistant network to a peripheral monitoring configuration, in which wells were spaced evenly along the downgradient boundaries of a landfill. The equidistant network yielded a 12.4% higher detection efficiency and also facilitated earlier release detection. In practice, the graphical approach that yields equidistant configurations can be used to identify candidate monitoring networks to detect potential releases from landfills.
A New Analytical Treatment of Airflow to Inlet Wells in Soil Vapor Extraction Systems
Authors: Ge Shemin
Published: February 2007

This paper provides a new analytical model of airflow to inlet wells in soil vapor extraction systems. It is based on a recent analytical solution of airflow to a single vapor extraction well by Bahr and Joss (1995), which updated the previous model of Baehr and Hult (1991). Baehr and Joss (1995) treated the air leakage through the surface as an air flux boundary condition, whereas Baehr and Hult (1991) approximated the leakage as a distributed source imposed in the governing airflow equation. The new analytical model shows significant improvement on air‐flow assessment over the previous model by Ge and Liao (1996), which could underestimate the efficiency of airflow to inlet wells by as much as 27% in a typical vapor extraction system.
Case History of a Large‐Scale Air Sparging/Soil Vapor Extraction System for Remediation of Chlorinated Volatile Organic Compounds in Ground Water
Authors: Gordon Matthew J.
Published: February 2007

A large‐scale air sparging/soil vapor extraction (AS/SVE) project constructed within coastal plain sediments in New Jersey has demonstrated substantial progress toward remediating ground water through removal of volatile organic compounds (VOCs). Potential concerns identified prior to project implementation regarding hydraulic mounding, reduction in hydraulic conductivity, development of air channels, and the absence of hydraulic containment were assessed and addressed through testing and operational features incorporated into the project. At the project site, AS/SVE has successfully reduced the presence of many VOCs to undetectable levels, while reducing the concentrations of the remaining VOCs by factors of two to 500. The physical agitation caused by air sparging, and incomplete transformation from sorbed and nonaqueous phases to the vapor phase, appears to temporarily increase VOC concentrations and/or mobility of dense nonaqueous phase liquids (DN APLs) within source areas at the project site, but this is addressed in terms of subsequent removal of VOCs by properly placed downgradient treatment lines and VOCs by properly placed downgradient treatment lines and DNAPL recovery wells. This case study identifies and evaluates project‐specific features and provides empirical data for potential comparison to other candidates AS/SVE sites.
RBCA Closure at DNAPL Sites
Authors: Sheahan Joseph W. , Ball Roy O. , Hahn Melinda W.
Published: February 2007

The closure of sites with identified or suspected DNAPL (dense nonaqueous phase liquids) under the requirements of the Resources Conservation and Recovery Act of 1976 (RCRA), or the Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA) has not been well defined. With respect to RCRA, the U.S. Environmental Protection Agency (EPA) has required that all contamination must be removed at closure such that no residual risk to human health or the environment remains. Therefore, even though many states administering the RCRA program have adopted or are considering Risk‐Based Corrective Action (RBCA) procedures (including the statistical methods described in SW‐846) for RCRA closure, the treatment of DNAPL is, at best, challenging.

The methodology for closure in CERCLA is described in “Risk Assessment Guidelines for Super‐fund (RAGS),” which requires that risks above the National Contingency Plan criteria must be remediated, preferably by on‐site or in situ destruction. Most risk‐based Brownfield or voluntary cleanup programs do not provide any explicit allowance for DNAPL. However, while the ASTM methodology for RBCA in E1739‐95 (ASTM 1995) does not explicitly treat the problem of DNAPL, a basic framework for DNAPL assessment is implicitly provided.

A uniform methodology for RBCA closure of VOC (volatile organic compounds) DNAPL sites can be used to achieve the program objectives of RCRA, CERCLA, and Brownfield or voluntary cleanup programs. The regulatory acceptance of the application of RBCA methods to DNAPL sites will require education and discussion, but the use of a uniform methodology should facilitate acceptance.