Hydraulic Conductivity Estimation Using Low-Flow Purging Data Elaboration in Contaminated Sites (original) (raw)
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Arabian Journal of Geosciences, 2018
The groundwater exploitation requires the evaluation of groundwater potentiality of the aquifer, particularly from the various studies such as the study of its physical characteristics. A complete hydrodynamic study requires knowledge of the properties of the aquifer system: its characterizing configuration and structure, functions of the reservoir, and its behavior. The aquifer is a complex interaction of two main functions: the storativity function and the conductivity function. This research is an integral part of a long-term research development and of a short-term operation, typically for medium-and long-term exploration of groundwater resources. In order to achieve this target, a substantial number of well-developed methods of evaluating the hydric potential and statistic calculations are currently being established. It is generally accepted that the method of estimating hydraulic parameters such as hydraulic conductivity of the aquifer is a very effective way, in case it is correlated to the results of the physical properties characterizing this aquifer. The laboratory study has been realized on an adequate sample of the soil from the aquifer by using appropriate techniques, to define its properties such as particle size, porosity, and measurements. For this case study, the physical properties of the aquifer materials are based on analysis of the test results obtained from 18 samples of the soil aquifer material, weighing from 2500 to 3000 g each, with the total mass of about 50 kg. Resulting values of the hydraulic conductivity are quite similar; all of them meet the range of the hydraulic conductivity from medium to coarse sand (8.8 E-05 to 3.27 E-03 m/s), an average value of (1.5 E-3 m/s). Nevertheless, it is possible to show the linear relationship between hydraulic conductivity and other physical properties such as void ratio (e) and the effective diameter (d 10) of the aquifer material which its mean values are respectively 52% and 0.52 mm. The hydraulic conductivity of soil depends on a variety of physical factors, including porosity, particle size and distribution, shape of particles, and arrangement of particles. Thus, it is complicated to identify a method to estimate values of hydraulic conductivity yielding a priori reliable ranges of results, when they are compared with results obtained by other methods of in situ measurement and laboratory. However, this method of empirical expression based on the particle size we have used provides satisfactory results.
Hydraulic Conductivity Characterization Methods for Environmental Site Investigations
Hydraulic conductivity (K), a parameter that describes the ease with which water flows in the subsurface, is widely regarded as one of the most important hydrogeologic parameters for environmental site investigations. Mathematically, it is defined as the flow rate per unit area divided by the hydraulic gradient in the direction of flow. Many approaches have been developed to characterize K. These approaches can be grouped into two general categories based on how the K estimates are obtained: hydraulic methods that involve water or other fluid injection or extraction and the measurement of the induced pressure response, and indirect methods that rely on empirical correlations, often site-specific in nature, between K and other more readily evaluated formation properties (e.g., resistance to electric current). Because hydraulic methods can be directly related to the mathematical definition of K through Darcy's Law, K estimates obtained with those methods are generally considered to be more reliable than those obtained with indirect methods. As fluids of different composition pass through saturated porous medium, the properties of the composition of the fluid will influence hydraulic conductivity characterization. Traditional methods for in situ measurement of K include pumping tests and slug tests.
Determining Hydraulic Conductivity Using Pumping Data from Low-Flow Sampling
Ground Water, 2009
Hydraulic conductivity values computed using the steady-state discharge and drawdown attained while low-flow sampling were evaluated to determine if they were equivalent to those determined from slug testing. Based on testing 12 wells, it was found that the results were statistically equivalent. Conductivity values computed using low-flow sampling parameters were also evaluated as to their reproducibility in actual practice by analyzing consultant data for three wells sampled over three quarterly monitoring periods by four field technicians. The results were found to be reproducible within about a factor of 2 or better. Since the method is based on only one pair of parameters, diligence is required in attaining steady state and in accurately measuring the flow rate and drawdown. Conductivity values computed using this approach can enhance the use of low-flow data gathered in water quality sampling, avoid the need for slug testing in a subsequent phase of investigation, and help reduce the cost of characterizing sites when multilevel samplers are used. Given the practical range of discharge in low-flow sampling, the method was found to be applicable at conductivity values somewhat greater than 10−6 cm/s. Given the typical accuracy of water level meters and pressure transducers and a maximum discharge of 1 L/min, as mandated by regulatory guidance, the method has a calculated upper conductivity limit in the range of 10−3 to 10−2 cm/s.
Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis
Hydraulic conductivity determination plays an essential role in the investigation of groundwater flow regime which can then influence many field problems such as pumping capabilities in the area, transport of contaminant or heat and soil internal erosion. Numerous equations based on dimensional analysis or experimental measurements have been published since the end of the 19th century for the determination of hydraulic conductivity. However, not all of these formulae are applicable for every material and all of them bring some uncertainty in the value of hydraulic conductivity. This paper contains a description of experimental research carried out concerning the determination of hydraulic conductivity for four types of sand with different grain size distribution curves and variable porosity. Obtained values of hydraulic conductivity ranged from 1 × 10-4 to 4 × 10-3 according to the sample porosity. The series of experiments consisted of 160 separate tests conducted in order to obtai...
Academic Journals, 2011
Several empirical formulae were used to determine the hydraulic conductivity of aquifer materials in the Jimeta-Yola area. The results indicate that the best estimation of hydraulic conductivity is based on Terzaghi equation, followed by Kozeny-Carman, Hazen, Breyer and Slitcher equations, respectively. The mean values from these equations were 1508, 287.1, 213.3, 186.9 and 102.3 m/day. The estimated hydraulic conductivities from the different methods indicate the hydraulic conductivity of clean sand to gravelly materials. USBR method underestimated the hydraulic conductivity of the aquifer materials in the area. The method, indicate the hydraulic conductivity of fine sand.
Borehole flowmeter measurements obtained during pumping can be effective in determining profiles of hydraulic conductivity (K). Few tests have been reported on flowmeter in full-screened wells that penetrate unconsolidated aquifers. In this paper, we demonstrate the utility of the flowmeter technique in quantifying the spatial variability of K and in distinguishing hydrofacies in an unconsolidated heterogeneous aquifer that exhibits low to moderate K. Results indicate that: (1) comparison of K values obtained from flowmeter measurements and multilevel slug tests shows differences consistently below 10%, and (2) individual hydrofacies can be delineated based upon K contrasts.
1992
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Experimental methods to determine the hydraulic conductivity
E3S Web of Conferences, 2019
Hydraulic conductivity is one of the most variable and yet an essential parameter in environmental engineering, in estimation of contaminant travel time in soils and groundwater. Also, it is one of the most difficult parameters to determine, and directly affects the quantity of water that will flow. Hydraulic methods for estimation the hydraulic conductivity can be either laboratory methods or in-situ methods. This study presents five laboratory methods which can be used to estimate the hydraulic conductivity of soils: variable-head permeameter - Kamenski; simplified permeameter; constant-head Cromer permeameter, in two working configurations; constant-head permeameter connected to piezometric tubes and a variable-head permeameter. Although these methods require more labour than other available methods, e.g. the correlation methods, they are relatively fast and not expensive. For the porous material used in the experiments, the most accurate values of the hydraulic conductivities we...
Quali-quantitative considerations on low-flow well purging and sampling
Acque Sotterranee - Italian Journal of Groundwater
This article deals with both the main advantages and issues related to groundwater purging and sampling that are usually carried out through the so-called low-flow methodology or with the method based on the purging of 3-5 well volumes, which is still widely used in environmental monitoring. A review of the recent literature concerning the technical characteristics, innovations and modelling related to low-flow sampling is presented. The aim is to provide to the reader a broad overview on this specific field application and offer a new vision, which considers two aspects: 1. The qualitative aspect, relating to the representativeness of the sample taken through a correct purging of the monitoring well and the consequent correct interpretation of hydrochemical data; 2. The quantitative aspect, related to the possibility of using water level data during purging and low-flow sampling operations to estimate the soil horizontal hydraulic conductivity, without further investigations. Low-f...