[en] 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 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% (water), 0.5%, 1.0%, or 2.0% aqueous surfactant solutions through the columns. The fifth column was washed intermittently with 28 pore volumes of a 1.0% surfactant solution. Water washed only 25.5% of the ATF from the column soil, while the 0.5%, 1%, and 2% surfactant solutions washed 55%, 60%, and 72.8% of the oil, respectively. In the case of water, the displacement of oil was the main washing mechanism, while all three mechanisms were operative during surfactant washing. Oil dispersion and solubilization were improved at higher surfactant concentrations. The column that was washed intermittently to pulse oil from dead end pores did not show a significant improvement over the column that was continuously washed with the same 1.0% surfactant solution. The results show promising potential for application in the field and will be further investigated in a two-dimensional model aquifer

[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] More than 200,000 gallons of automatic transmission fluid (ATF) leaked from an underground storage tank system and contaminated an area of about 64,000 ft² of a soil and ground water system. A pumping strategy for improved drainage and recovery of free oil was developed, tested in a laboratory model aquifer, and implemented (1) the oil recovery rate is carefully controlled to maximize the pumping rate while maintaining continuity between the oil layer in the soil and the recovery well, to avoid isolation of the oil in the subsurface; and (2) the rate of ground water pumping is controlled to maintain the depressed oil/water interface at its prepumped position. This approach prevents further spread of oil into the ground water, prevents reduction in the volume of recoverable oil due to residual retention, and maintains a gradient for oil flow toward the recovery well. In a model aquifer study, nearly 100% of the recoverable volume of ATF was pumped from the system, and about 56,000 gallons of the ATF has been recovered from the field site

[en] Retention of diesel fuel in soil material from the Borden aquifer was investigated for five particle-size fractions over the size range 75-500 micrometers and for different packing structures. Results show a variation in retention with pore structure, especially for small particle size. The variation was, however, nonuniform; retention increased with increasing porosity over some ranges of pore structure, whereas the reverse occurred over the ranges of pore structure. Also, depending upon pore structure, retention showed little variation or decreased with increasing particle size. The retention of diesel fuel was greater than the retention of water under similar packing conditions. The dependency of retention on fluid type and medium structural parameters agrees qualitatively with theoretical predictions for retention in porous media of uniform spherical particles, which can be explained based on the concept of capillary retention. 23 refs., 7 figs., 2 tabs

[en] This report presents an evaluation of the results of simulation studies of groundwater discharge to streams from abandoned uranium mill tailings and the effects of this discharge on the flux of contaminants to surface water systems. In particular, a discussion of the sensitivity of subsurface discharge to specific geometirc, climatic and hydrogeologic factors is presented. Simulations were carried out using a two-dimensional numerical finite-element unsaturated-saturated flow model. A total of twenty-six simulations were made. The first twenty-four of these considered a tailings medium with homogeneous and isotropic hydraulic properties and with textural properties similar to those of sandy geological materials. In addition, two simulations were carried out for tailings materials with hydraulic properties that are similar to those of silt-loam. The results indicated that the actual quantity of subsurface discharge depends on many factors including rainfall rate and duration, surface slope, and texture. However, for the medium-fine sand material, subsurface discharge was always a significant component of the total discharge. Within the context of uranium tailings management this implies that large quantities of contaminants from subsurface sources of medium-textured tailings can be expected to be discharged to streams during stormflow events. Therefore there is reason to suspect that untreated runoff from such tailings will contain significant concentrations of contaminants for long periods of time

[en] Highlights: ► An automatic alignment system was developed to process images of the laser beams. ► System uses processing to adjust a series of control loops until alignment criteria are satisfied. ► Monitored conditions are compared against nominal values with an off-normal alert. ► Automated health monitoring system trends off-normals with a large image history. - Abstract: The National Ignition Facility (NIF) is a high power laser system capable of supporting high-energy-density experimentation as a user facility for the next 30 years. In order to maximize the facility availability, preventive maintenance enhancements are being introduced into the system. An example of such an enhancement is a camera-based health monitoring system, integrated into the automated alignment system, which provides an opportunity to monitor trends in measurements such as average beam intensity, size of the beam, and pixel saturation. The monitoring system will generate alerts based on observed trends in measurements to allow scheduled pro-active maintenance before routine off-normal detection stops system operations requiring unscheduled intervention.