The DOE National Laboratories have extensive environmental remediation and operations centers as well as research teams specializing in environmental problems. These organizations are concerned largely with pollution prevention, safe disposal of hazardous materials, polluted site identification and characterization, and cleanup of polluted sites. These organizations, and the private-industry subcontractors they hire, require state of the art tools and techniques for characterization and monitoring. Our research will contribute to this effort by providing descriptions of heterogeneities and scaling properties in the vadose and saturated zones with particular emphasis on flow and transport. This work will also provide an important link between some geophysical measurements and fluid transport characteristics.

The accurate characterization and remediation of contaminated subsurface environments requires the detailed knowledge of subsurface structures and flow paths. Enormous resources are invested in scoping and characterizing sites using core sampling, 3-D geophysical surveys, well tests, etc ... Unfortunately, much of the information acquired is lost to compromises and simplifications made in constructing numerical grids for the simulators used to predict flow and transport from the contaminated area to the accessible environment. In rocks and soils, the bulk geophysical and transport properties of the matrix and of fracture systems are determined by the juxtaposition of geometric features at many length scales. In the interest of computational efficiency, recognized heterogeneities are simplified, averaged out, or entirely ignored in spite of recent studies that recognize that: (1) Structural and lithologic heterogeneities exist on all scales in rocks. (2) Small heterogeneities influence, and can control the physical and chemical properties of rocks. In this work we propose a physically based approach for the description and treatment of heterogeneities, that highlights the use of laboratory equipment designed to measure the effect on physical properties of fine scale heterogeneities observed in rocks and soils. We then discuss the development of an integration methodology that uses these measurements to develop and upscale flow and transport models. Predictive simulations are 'calibrated' to the measured heterogeneity data, and subsequently upscaled in a way that is consistent with the transport physics and the efficient use of environmental geophysics. This methodology provides a more accurate interpretation and representation of the subsurface for both environmental engineering and remediation. We show through examples, (i) the important influence of even subtle heterogeneity in the interpreting of geophysical data, and (ii) how physically based upscaling can lead to a different and more accurate description of a heterogeneous system, when compared to a more traditional upscaling approach that combines averaging and the application of core-based models. This may be of particular significance in bio-remediation studies where the link between microorganism activity and mesoscale flow through geologic structures, resides in the integration of multiscale processes.

Heterogeneity and Scaling in Geologic Media: Applications to Transport in the Vadose and Saturated Zones Stephen Brown, Gregory Boitnott, and Martin Smith New England Research In rocks and soils, the bulk geophysical and transport properties of the matrix and of fracture systems are determined by the juxtaposition of geometric features at many length scales. For sedimentary materials the length scales are: the pore scale (irregularities in grain surface roughness and cementation), the scale of grain packing faults (and the resulting correlated porosity structures), the scale dominated by sorting or winnowing due to depositional processes, and the scale of geomorphology at the time of deposition. We are studying the heterogeneity and anisotropy in geometry, permeability, and geophysical response from the pore (microscopic), laboratory (mesoscopic), and backyard field (macroscopic) scales. In turn these data are being described and synthesized for development of mathematical models. Eventually, we will perform parameter studies to explore these models in the context of transport in the vadose and saturated zones. We have developed a multi-probe physical properties scanner which allows for the mapping of geophysical properties on a slabbed sample or core. This device allows for detailed study of heterogeneity at those length scales most difficult to quantify using standard field and laboratory practices. The measurement head consists of a variety of probes designed to make local measurements of various properties, including: gas permeability, acoustic velocities (compressional and shear), complex electrical impedance (4 electrode, wide frequency coverage), and ultrasonic reflection (ultrasonic impedance and permeability). We can thus routinely generate detailed geophysical maps of a particular sample. With the exception of the acoustic velocity, we are testing and modifying these probes as necessary for use on soil samples. As a baseline study we have been characterizing the heterogeneity of a bench-size Berea Sandstone block. Berea Sandstone has long been regarded as a laboratory standard in rock properties studies, owing to its uniformity and ''typical'' physical properties. We find that both permeability and velocity exhibit complex heterogeneity at the centimeter scale. While some correlation with the outcropping of the bedding is apparent, much of the heterogeneity is not clearly associated with visual features. We are developing software tools to examine simultaneously pixel by pixel correlations among geophysical measurements, transport properties, and visual (photographic) texture and the dependence of these correlations on measurement scale. We find that certain pairs of physical quantities, such as P velocity and permeability for example, are distinctly correlated with one another at certain scales, but less obviously at other scales. Preliminary analyses of the Berea Sandstone data show that by simultaneous consideration of several physical properties the data can be separated into clusters of like properties which can be considered distinct facies. Apparently, identification of these facies, which could represent a limited range of fluid permeability, may be made by making joint geophysical measurements. Given various physical models for the dependence of the geophysical and transport properties on pore size, we expect that these observed correlations will provide conditioning and constraints to inversions for stochastic models of the internal structure of a specimen. For the study of soil heterogeneity at a wide range of scales, we are focusing on a local glacial deposit. This deposit is a glacial kame terrace of fluvial origin with multi-scale sedimentary structures comprised of unconsolidated sands, clays, and gravels. There are also many joints and faults in the unconsolidated sediments, allowing study of these as potential fluid flow conduits or barriers. We have obtained undisturbed soil samples from this site, allowing detailed laboratory study using similar methods to those described for the sandstone block.

This textbook integrates classic principles of flow through porous media with recently developed stochastic analyses to provide new insight on subsurface hydrology. Importantly, each of the authors has extensive experience in both academia and the world of applied groundwater hydrology. The book not only presents theories but also emphasizes their underlying assumptions, limitations, and the potential pitfalls that may occur as a result of blind application of the theories as 'cookie-cutter' solutions. The book has been developed for advanced-level courses on groundwater fluid flow, hydraulics, and hydrogeology, in either civil and environmental engineering or geoscience departments. It is also a valuable reference text for researchers and professionals in civil and environmental engineering, geology, soil science, environmental science, and petroleum and mining engineering.

Capillary phenomena occur in both natural and human-made systems, from equilibria in the presence of solids (grains, walls, metal wires) to multiphase flows in heterogeneous and fractured porous media. This book, composed of two volumes, develops fluid mechanics approaches for two immiscible fluids (water/air or water/oil) in the presence of solids (tubes, joints, grains, porous media). Their hydrodynamics are typically dominated by capillarity and viscous dissipation. This first volume presents the basic concepts and investigates two-phase equilibria, before analyzing two-phase hydrodynamics in discrete and/or statistical systems (tubular pores, planar joints). It then studies flows in heterogeneous and stratified porous media, such as soils and rocks, based on Darcy’s law. This analysis includes unsaturated flow (Richards equation) and two-phase flow (Muskat equations). Overall, the two volumes contain basic physical concepts, theoretical analyses, field investigations and statistical and numerical approaches to capillary-driven equilibria and flows in heterogeneous systems

Over the past several decades, analyses of solute migration in aquifers have widely adopted the classical advection-dispersion equation. However, misunderstandings over advection-dispersion concepts, their relationship with the scales of heterogeneity, our observation and interest, and their ensemble mean nature have created furious debates about the concepts' validity. This book provides a unified and comprehensive overview and lucid explanations of the stochastic nature of solute transport processes at different scales. It also presents tools for analyzing solute transport and its uncertainty to meet our needs at different scales. Easy-to-understand physical explanations without complex mathematics make this book an invaluable resource for students, researchers, and professionals performing groundwater quality evaluations, management, and remediation.