Hydraulic conductivity determination

Scholl M. A. and Christenson S. C. (1998) Spatial Variation in Hydraulic Conductivity Determined by Slug Tests in the Canadian River Alluvium near the Norman Laruifill, Norman, Oklahoma. US Geological Survey Water-Resources Investigations Report 97-4292, US Oklahoma City, OK. 

Atterberg-limit tests determine the water content influence in defining liquid, plastic, semisolid and solid states of fine-grained soils. Permeability tests may be carried out in the laboratory or in the field. Such tests are used to determine the hydraulic conductivity coefficient k. ... 

Physical properties involve tests of the physical index parameters of the materials. For spent foundry sand, these parameters include particle gradation, unit weight, specific density, moisture content, adsorption, hydraulic conductivity, clay content, plastic limit, and plastic index. These parameters determine the suitability of spent foundry sand for uses in potential applications. Typical physical properties of spent green foundry sand are listed in Table 4.5. 

It is obvious from Equation 14.14 that the most important parameter determining the volumetric air flow rate <2W is the intrinsic permeability K of soil. At this point it is important to stress the difference between water permeability (or hydraulic conductivity) k , air permeability ka, and intrinsic permeability K. In most cases, when permeability data are provided for a type of soil or geological formation, these data are based on hydraulic conductivity measurements and describe how easily the water can flow through this formation. However, the flow characteristic of a fluid depends greatly on its properties, e.g., density p and viscosity p. Equation 14.16 describes the relationship between permeability coefficient k and fluid properties p and p ... 

The investigators divided the collection units into a number of subunits, each subunit measuring 3 ft by 3 ft. A total of 250 different collection units underneath the soil liner were monitored independently to determine the rate of flow. The objective was to correlate the variability of the hydraulic conductivity of the liner with the molding water content of the soil and with the dry density of the compacted soil. 

The problem arises in determining from where a representative sample should be taken. Even if 25 samples were picked randomly in a grid pattern from that zone for 25 independent measures of hydraulic conductivity, it would be unclear how to arrive at a single representative measure. The flow through a 3-in. diameter specimen is much too small to mimic the patterns of fluid flow that occur in the field under similar conditions. 

The tests do not directly measure the hydraulic conductivity k of the soil. Instead they measure the infiltration rate / for the soil. Since hydraulic conductivity is the infiltration rate divided by the hydraulic gradient i (see equations in Figure 26.14), it is necessary to determine the hydraulic gradient before k can be calculated. The following equation (with terms defined in Figure 26.14) can be used to estimate the hydraulic gradient ... 

Chemical compatibility studies with hydraulic conductivity tests must be performed over a long enough period of time to determine the full effects of the waste liquid. Termination criteria include equal inflow and outflow of liquid, steady hydraulic conductivity, and influent/effluent equilibrium. At least two pore volumes of liquid must be passed through the soil to flush out the soil water and bring the waste leachate into the soil in significant quantities. Reasonable equilibrations of the influent and effluent liquids occur when the pH values of the waste influent and effluent liquids are similar and the key organic and inorganic ions are at full concentrations in the effluent liquid. 

It is often easy to measure the flux density, e.g., using a flowmeter, and then determine the hydraulic conductivity or diffusion coefficient by dividing the flux by the driving force. One of the most difficult problems is determining how to represent the driving force. The symbol V is called an operator, which signifies that some mathematical operation is to be performed upon whatever function follows. V means to take the gradient with respect to distance. For Darcy s law under saturated... 

Bouwer, H. and Rice, R. C., 1976, A Slug Test for Determining Hydraulic Conductivity of Unconfined Aquifers with Completely or Partially penetrating Wells Water Resources Research, Vol. 12, No. 13, pp. 423 438. 

The PHOSter II system is only applicable to contaminants that can be biologically degraded. In addition, it is only effective in settings where microbial activity is phosphorus limited. At sites with high contaminant concentrations, product recovery may be required during the initial treatment stage. Hydraulic conductivity and moisture content also determine the effectiveness of the PHOSter II technology. 

Both confined and unconfined conditions are simulated, where the hydraulic conductivity is 5 m/day and the initial saturated thickness is approximately 15.4 m for the unconfined aquifer. The transmissivity for confined conditions is 77 m2/day. The design problem is to contain the two plumes depicted on the figure, with the condition that remedial wells be located on site but not located in the building. The six candidate wells shown are used as potential pumping wells and the minimum total pumping from these wells must be determined such that the two plumes are captured. 

The mean hydraulic conductivities for the aquifer sand determined using the two laboratory methods (constant-head and falling-head permeameters) were 5 10"4 m sec"1 and 2 1 O 4 m sec"1, respectively. The isotherm results showed that the sand had negligible sorption capacity for either chromate 01 PCE. 

Based on the assumption that much of the flow restriction was due to plugging of the upgradient barrier screen, the sand in the barrier frame annulus was removed and an attempt made to flush the screen with high-pressure water jets. Additional tracer tests conducted after the jetting showed that a hydraulic restriction was still present. Since the cause of the hydraulic restriction could not be unambiguously determined or ameliorated, the decision was made to replace the 14-40 SMZ with the higher hydraulic conductivity 8-14 SMZ, and at the same time to remove the 100-mesh screen from the barrier frame. 

Porosity and hydraulic conductivity are both properties of the porous medium. Hydraulic heads, and the hydraulic head gradient, may be determined by solving the equations of flow, with appropriate initial and boundary conditions [2]. 

The effects of aquifer anisotropy and heterogeneity on NAPL pool dissolution and associated average mass transfer coefficient have been examined by Vogler and Chrysikopoulos [44]. A two-dimensional numerical model was developed to determine the effect of aquifer anisotropy on the average mass transfer coefficient of a 1,1,2-trichloroethane (1,1,2-TCA) DNAPL pool formed on bedrock in a statistically anisotropic confined aquifer. Statistical anisotropy in the aquifer was introduced by representing the spatially variable hydraulic conductivity as a log-normally distributed random field described by an anisotropic exponential covariance function. 

For each hydraulic conductivity field generated, the associated variable hydraulic head field and groundwater velocity field were determined. Each variable hydraulic head field was evaluated numerically by solving the following steady state two-dimensional groundwater flow equation for a heterogeneous confined aquifer [50] ... 

The permeability coefficient (k) has the units of velocity, that is, distance/time. It is determined either in laboratory experiments or derived from pumping tests. Both methods are semiquantitative, but are still highly informative, as the values observed for common rocks span more than seven orders of magnitude. A variety of units are in use—m/day being a common one. The following are a few of the average permeability or hydraulic conductivity values floating around in the literature, expressed in m/day ... 

A closer look at the zone of lateral base flow (overflow). Overflowing water flows laterally by the critical angle. This angle is determined by the water viscosity, which in turn is dependent on the temperature and concentration of dissolved ions. Groundwater flows laterally toward the terminal base of drainage at a critical angle that is determined by the hydraulic conductivity, or permeability, of the rocks (k) the water viscosity, which depends on the temperature (7), and the concentration of dissolved ions (i) ... 

The dispersion phenomenon in the two humid soils (Pembroke and Uniontown) was evaluated through the use of an Imhoff cone test and a permeameter. The Imhoff cone is commonly used by engineers to determine settleable solids (see Chapter 9). The results of clay dispersion obtained by the Imhoff cone test are expressed as a dispersion index (percent of total clays in the soil sample dispersed), which is correlated with relative saturated hydraulic conductivity. This is shown in Figure 11.5. It demonstrates that each of the soils, depending on its clay content (Pembroke 59% Uniontown 20%), exhibits unique saturated hydraulic conductivity behavior with respect to the dispersion index. Also, in each of the soils, various mechanisms (different line slopes) appear to control saturated hydraulic conductivity. 

Under wet conditions and for young roots of desert succulents, Loveral1 is determined essentially only by Up° the root hydraulic conductivity... 

Results of experiments utilizing crushed rock and equilibration with waste solutions to determine sorption behavior cannot be extrapolated to actual aquifer conditions, even if B.E.T. surface area is known. This technique has been commonly used in the past to assess waste-storage-site safety. As the primary hydraulic conductivity decreases and secondary conductivity becomes more prominent, this methodology becomes less and less viable for input to modeling of waste transport. The method presented in this report should result in more realistic waste-transport modeling. 

Hanshaw B. B. and Back W. (1974) Determination of regional hydraulic conductivity through use of dating of groundwater. In Memoirs de I Association Internationale des Hydrogeologues. Montpellier, France, vol. 10, pp. 195-196. 

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