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Considerable research has shown that the major control on the transport and fate of a pollutant as it moves through an aquifer is the spatial distribution of hydraulic conductivity. Although chemical and microbial processes play important roles, their influence cannot be understood without a detailed knowledge of the subsurface variations in hydraulic conductivity at a site. Many theories have been developed to quantify, in a generic sense, the influence of these variations using stochastic processes or fractal representations. It is increasingly apparent, however, that site-specific features of the hydraulic conductivity distribution (such as high conductivity zones) need to be quantified to reliably predict contaminant movement. Conventional hydraulic field techniques only provide information of a highly averaged nature or information restricted to the immediate vicinity of the test well. Therefore, development of new innovative methods to delineate the detailed hydraulic conductivity distribution at a given site should be a high priority. The research proposed here is directed at addressing this problem by developing techniques to map 3-D hydraulic conductivity distributions., The original document contains color images.

Since spatial changes in hydraulic conductivity are a major factor governing the transport and fate of a pollutant as it moves through an aquifer, we focus on the development of new innovative methods to delineate these spatial changes. The objective of the research proposed here is to build on our previous work to develop and improve field techniques for better definition of the three-dimensional spatial distribution of hydraulic conductivity by using hydraulic tomography coupled with high-resolution slug testing., The original document contains color images.

A typical method used to determine fluid behavior in a geologic matrix near a well is a pumping test Here a pump is installed into a well and groundwater is removed or injected while water levels in surrounding observation wells are monitored. Then the aquifer parameters can be estimated by monitoring changes in water levels at observation wells at some distance These types of tests are typically large in scale, (Schad and Teutsch, 1994) Another test is an interference test, which is a special pumping test where the pump discharge has a variable rate Interference tests are conducted by variable production or injection fluid (hydraulic head changes) at one well, and observing the changing pressure or hydraulic head with time and distance at other locations These tests are valued to estimate flow characteristics hi situ, but are measures of the aquifer material over large volumes also., KGS Open-File Report no. 2008-1

Since spatial changes in hydraulic conductivity are a major factor governing the transport and fate of a pollutant as it moves through an aquifer, we have focused on the development of new innovative methods to delineate these spatial changes The objective of the research proposed here is to build on our previous research to develop and improve field techniques for better definition of the three-dimensional spatial distribution of hydraulic conductivity by using hydraulic tomography coupled with high- resolution slug testing.

A considerable body of research has shown that the major control on the transport and fate of a pollutant as it moves through an aquifer is the spatial distribution of hydraulic conductivity. A number of theories have been developed to quantify, in a generic sense, the influence of the subsurface variations in hydraulic conductivity. It is becoming increasingly apparent, however, that site specific features of the hydraulic conductivity distribution (such as high conductivity zones) need to be quantified in order to reliably predict contaminant movement. Since spatial changes in hydraulic conductivity are a major factor governing the transport and fate of a pollutant as it moves through an aquifer, we have focused on the development of new innovative methods to delineate these spatial changes. The objective of the research proposed here is to build on our previous research to develop and improve field techniques for better definition of the three-dimensional spatial distribution of hydraulic conductivity by using hydraulic tomography coupled with high resolution slug testing. The research proposed here is directed at developing techniques with the ability to map 3-D hydraulic conductivity distributions., Prepared in cooperation with the Kansas Geological Survey, Lawrence, KS. The original document contains color images.

The purpose of this project was to evaluate promising methods for characterization of heterogeneities in hydraulic conductivity and to assess which are best for the prediction of contaminant movement in shallow alluvium. Although work is still ongoing, this research has produced results of considerable practical significance. A major field and theoretical emphasis was on slug tests. A general model for slug tests in partially penetrating wells was developed, the viability of conventional slug-tests methods in homogeneous and heterogeneous formations was assessed, and a general model for slug tests in formations of high hydraulic conductivity was proposed. A major product was a series of practical guidelines for slug tests, which should considerably improve the quality of parameter estimates obtained using this technique. An important theoretical accomplishment of this project was the development of a new approach for the characterization of spatial variations in flow properties based on the principles of tomography. A major field accomplishment was the design and performance of a large-scale induced gradient tracer test. Although data analysis/interpretation is ongoing, this experiment has clearly yielded an extremely detailed data set describing tracer movement in heterogeneous alluvium. Additional field and laboratory work has produced an excellent data set characterizing parameter variations at the core scale. Five articles have been published on this work and additional articles are under preparation.

The purpose of this project is to evaluate promising methodologies for characterization of heterogeneities in hydraulic conductivity. A major thrust of the first year of this project was an assessment of slug tests in heterogeneous formations. The theoretical components of this effort included the development of a time-continuous numerical model, a study of slug tests in layered aquifers, an examination of effective properties obtained from slug tests in the presence of well skins, and an examination of slug tests with observation wells. The field component emphasized multilevel slug tests. A prototype multilevel slug-test system was tested. Test results indicated that the tests are being affected by mechanisms not accounted for in the conventional theory. A series of experiments were carried out in order to clarify the mechanisms producing the observed behavior. These experiments served as the basis for the development of a new nonlinear model for the analysis of slug-test data. Additional field work included further hydraulic testing; a detailed aqueous geochemistry study; drilling and sampling activities; modification of the bladder sampler; laboratory analyses of cores; and a detailed seismic survey.