Hydrogeological-Geophysical Methods for Subsurface Site Characterization

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9628306 Yoram Rubin This project focuses on three issues that are critical to environmental management of contaminated sites: reducing cost, reducing risk, and increasing the effectiveness of subsurface remediation schemes. The significance of this proposal is that it addresses the issue of site characterization: not only that this issue is a very significant budget item in the site cleanup effort, but also it is now realized that accurate and reliable site characterization is the key to the success of any cleanup effort. Our objective is to develop the scientific basis and demonstrate methodologies for inexpensive high resolution imaging of natural heterogeneities and for relating these heterogeneities to the hydrogeologic parameters that control flow and contaminant transport--in effect, to develop methods for "imaging" hydrogeologic parameters. Our focus is to help establish the scientific basis for applying shallow geophysics to hydrogeological problems, through (a) feasibility studies, (b) sediment-rock physics, and (c) improvements in the procedures for co-interpretation of geophysical and hydrogeological data. An essential task will be to identify limitations, pitfalls, and uncertainties of these co-interpretation--i.e., to quantify the risks in applying shallow geophysics to hydrogeological site characterization. The proposal combines theoretical modeling, analysis of laboratory measurements, and integration techniques. Our approach is to use seismic and electromagnetic methods jointly to map the distribution to seismic velocity and attenuation and electrical conductivity in the the 3-D volume defined by a set of boreholes. In a rough sense, both velocity and conductivity depend on porosity and to a lesser extent on permeability, clay content, saturation and nature of pore fluid. Laboratory studies have shown these relationships in great detail and we now propose to refine these results to utilize them to interpret survey data in terms of map of the distribution of t he hydrogeologic properties. This proposal is an interdisciplinary study, since it integrates the fields of hydrogeology and geostatistics, geophysics, and rock physics. The team of researchers brings to this project a large collective experience in performing theoretical, field, and lab work. In response to cuts in the original budget, we reduced the scope of lab testing and the variety of geological setting that we shall investigate under Feasibility Studies. ??