Groundwater compressibility

Traditionally air sparging has been used as a groundwater remediation tool. Occasionally, however, it has been successfully used to remediate the vadose zone. In this application, the compressed air is injected through a well screen that is open to the VOC-contaminated area. The injection wells may be either vertical or horizontal (Figure 10.7). In this setting, the injected air is usually captured by a corresponding set of SVE wells (Figure 10.8). Properly spaced patterns of injection and recovery wells are necessary for efficient operation. 

The multistage in-well aerator is an inexpensive, low-maintenance device that simultaneously treats and extracts contaminated groundwater using only compressed air. Air stripping is based... 

The KGB technology consists of a combination of soil air venting with in situ groundwater stripping ( push-and-puU technique ). Clean compressed air is forced into a pressurized air distributor located between the capillary fringe and the aquifer base. The distributor s location depends on the vertical pollutant distribution. 

For ISSZT, a physical barrier, such as a slurry wall or vertical membrane barrier, is installed around the area of contamination to a depth that will be slightly below the future lowered groundwater level to limit the escape of air from the area. Existing clay or silt may serve as a cap for the system, otherwise a man-made cap is installed. Wells are installed into the soil to inject the low-pressure compressed air beneath the cap. As the air pressure increases, the groundwater is lowered. The injected air is prevented from escaping by the cap at the top, the barrier along the sides, and the water table at the bottom. 

Fig. 3.8 A fault has placed a high conducting aquifer against an igneous rock of low permeability. Water ascends along the fault zone, forming a line of springs. Only part of the faults are open and conduct groundwater flow others are clogged by compression and/or mineralization.

By introducing the appropriate expression for the hydraulic head, i.e. Equation 1.3 or 1.4, into Darcy s equation 1.8, it describes the flow for compressible and incompressible groundwater, respectively. The flow of compressible groundwater can thus be described by a more general form of Darcy s equation, in which the gradient of the groundwater potential is given by Equation 1.5... 

Hydrodynamic conditions in a basin may in part result from tectonic forces. Ge and Garven (1989) applied a numerical model of coupled tectonic- and gravity-induced flow to evaluate the relative importance of tectonic influence on groundwater pressure and flow in an otherwise gravity-induced flow system in a hypothetical foreland basin. Forbes et al. (1992) included an evaluation of lateral compression in their numerical reconstruction of the present-day pressure distribution in the Venture Field, Eastern Canada. 

All fractures generated by internal fluid overpressure are here referred to as hydrofractures. The fracture-generating fluid may be oil, gas, magma, groundwater, or geothermal water. Hydrofractures include dykes, inclined sheets, mineral veins, many joints, and the man-made hydraulic fractures that are used in the petroleum industry to increase the permeability of reservoir rocks. Hydrofractures are primarily extension fractures (Gudmundsson et al. 2001). The difference between the total fluid pressure in a hydrofracture and the normal stress, which for extension fractures is the minimum compressive principal stress, oj, is referred to as the fluid overpressure. 

R. Bond, S. Veerapaneni, I. Rackley, A. Ventimiglia, W. Pack, Reverse osmosis and vapour compression brine distillation to treat a shallow brackish groundwater in Las Vegas valley, in W.C. Lauer (Ed.), Desalination of Seawater and Brackish Water, AWWA, Denver, 2006, pp. 151—167. 

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