Conceptual and computational models of contaminant transport in the subsurface are often hampered by an oversimplified or incomplete understanding of the hydrogeologic setting. While, much can be learned of the structure and stratigraphy of the subsurface environment through drilling and analysis of core material, this information is often obtained at great expense and provides only point source data on subsurface structure and hydrogeologic setting. The ERSP seeks to develop methods of site characterization that can dramatically aid the interpretation of subsurface hydrogeology and compliment information obtained from drilling. Non-invasive surface-deployed geophysical techniques that can provide data on subsurface structure and/or inferred groundwater flow properties at high resolution over large areas are of interest. The intent of this element is to foster the development of novel, high resolution geophysical techniques for subsurface research and/or deployment of current geophysical techniques in new ways to infer biogeochemical processes affecting contaminant transport across large areas.