Detailed Hydraulic Assessment Using a High-Resolution Piezocone Coupled to the GeoVIS

Abstract

Abstract : The Department of Defense (DoD) groundwater assessment and remediation projects require cost-effective methods for determining the direction and rate of groundwater and contaminant flow. Monitoring wells have typically been used to estimate these parameters. Understanding flow pathways, gradients, and contaminant flux is essential for proper remedial design, risk determination, and evaluation of remediation effectiveness. Available methods capable of providing the required level of resolution to evaluate site conditions in three dimensions include multilevel well installation networks, comprehensive soil sampling and laboratory analyses, or the use of tracer tests. These options can be cost-prohibitive, especially at sites where contamination may be aerially extensive or the site has complex hydrogeologic conditions. It is likely that decades and tens of billions of dollars will be required to clean up DoD sites using standard hydrogeologic assessment methods. Cost-effective, high-resolution alternatives are needed to reduce costs associated with site assessment. This project employs two innovative direct-push sensor probes (the high-resolution piezocone and GeoVIS) deployed with a standard cone penetrometer system for the purpose of determining direction and rate of groundwater flow in three dimensions. The key to determining direction and rate of flow (or seepage velocity ) is to understand the distribution of groundwater head, hydraulic gradient, soil porosity, and soil hydraulic conductivity. When coupled to the distribution of contaminant concentration, a contaminant flux estimate can be derived. The piezocone and GeoVIS are direct-push probes that are part of the DoD Site Characterization and Analysis Penetrometer System (SCAPS) suite of tools.