[en] Efforts to sample representative, undisturbed distributions of uranium in ground water beneath the Fernald Environmental Management Project (FEMP) prompted the application of a novel technique that is less invasive in the monitoring well. Recent studies indicate that representative samples can and should be collected without prior well volume exchange purging or borehole evacuation. Field experiments conducted at the FEMP demonstrate that under specific sampling conditions in a well-defined 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 FEMP. Preliminary results obtained form the field experiments 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

[en] An in situ redox manipulation (ISRM) method for creating a permeable treatment zone in the subsurface has been developed at the laboratory bench and intermediate scales and deployed at the field scale for reduction/immobilization of chromate contamination. At other sites, the same redox technology is currently being tested for dechlorination of TCE. The reduced zone is created by injected reagents that reduce iron naturally present in the aquifer sediments from Fe(III) to surface-bound and structural Fe(II) species. Standard ground water wells are used, allowing treatment of contaminants too deep below the ground surface for conventional trench-and-fill technologies. A proof-of-principle field experiment was conducted in September 1995 at a chromate (hexavalent chromium) contaminated ground water site on the Hanford Site in Washington. The test created a 15 m diameter cylindrical treatment zone. The three phases of the test consisted of (1) injection of 77,000 L of buffered sodium dithionite solution in 17.1 hours, (2) reaction for 18.5 hours, and (3) withdrawal of 375,000 L in 83 hours. The withdrawal phase recovered 87% to 90% of the reaction products. Analysis of post-experimental sediment cores indicated that 60% to 100% of the available reactive iron in the treated zone was reduced. The longevity of the reduced zone is estimated between seven and 12 years based on the post-experiment core samples. Three and half years after the field test, the treatment zone remains anoxic, and hexavalent chromium levels have been reduced from 0.060 mg/L to below detection limits (0.008 mg/L). Additionally, no significant permeability changes have been detected during any phase of the experiment

[en] This report summarizes the initial results of subsurface remediation at Terminal 1, Kennedy International Airport, to remediate soil and ground water contaminated with Jet A fuel. The project was driven and constrained by the construction 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% of the removal resulted from biodegradation, 27% occurred as a result of liquid removal, and 11% resulted from the extraction of volatile organic compounds (VOCs)

[en] 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 be 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 in 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 method such as contaminant mass balances, laboratory microcosm studies, and detailed ground water modeling can demonstrate natural attenuation as well

[en] Current site assessment techniques do not always generate adequate information regarding the presence, type, or distribution of nonaqueous phase liquids (NAPLs) at sites with ground water contamination. Without this information, however, the design of remediation methods is uncertain, often resulting in costly and/or failed attempts to minimize risks associated with the contamination. In this work, it is proposed that a thorough multivariate analysis of data from ground water sampling efforts could improve one's overall understanding of these sites. Multivariate analyses can provide considerable insight into the contaminant source characteristics by elucidating correlations in ground water concentrations that identify recurring chemical patterns or signatures. These correlations are related to the type of NAPL and proximity to the contaminant source. Multivariate plots and a principal components analysis (PCA) are used to interpret ground water data from a manufactured gas plant site in Iowa contaminated with both gasoline and coal tar

[en] 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 f PHCs. From a technical standpoint, the PHC impacting soil and/or ground water is frequently inadequately characterized, both in identification as well as in its 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. 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

[en] Releases of petroleum products from leaking residential storage tanks are a growing problem in the state of New Jersey. Approximately two releases per day have been reported to the New Jersey Department of Environmental Protection. Product releases may cause aquifers to become contaminated, may effect surface water, or cause vapor problems inside households. As of 1992, there are no federal or state regulations pertaining to the maintenance and monitoring of residential petroleum storage tanks. Regulations are essential for protecting drinking water supplies. The regulations must address installation procedures, tank materials, monitoring, and tank location

[en] The generation and release of acidic drainage containing high concentrations of dissolved metals from decommissioned mine wastes is an environmental problem of international scale. A potential solution to many acid drainage problems is the installation of permeable reactive walls into aquifers affected by drainage water derived from mine waste materials. A permeable reactive wall installed into an aquifer impacted by low-quality mine drainage waters was installed in August 1995 at the Nickel Rim mine site near Sudbury, Ontario. The reactive mixture, containing organic matter, was designed to promote bacterially mediated sulfate reduction and subsequent metal sulfide precipitation. The reactive wall is installed to an average depth of 12 feet (3.6 m) and is 49 feet (15 m) long perpendicular to ground water flow. The wall thickness (flow path length) is 13 feet (4 m). Initial results, collected nine months after installation, indicate that sulfate reduction and metal sulfide precipitation is occurring. The reactive wall has effectively removed the capacity of the ground water to generate acidity on discharge to the surface. Calculations based on comparison to previously run laboratory column experiments indicate that the reactive wall has potential to remain effective for at least 15 years

[en] 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, hydrology, and contaminant. 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% by vapor extraction, 28% by bioventing, and 13% 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

[en] 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