Three-Dimensional Surface Geophysical Exploration of the 200-Series Tanks at the 241-C Tank Farm

A surface geophysical exploration (SGE) survey using direct current electrical resistivity was conducted within the C Tank Farm in the vicinity of the 200-Series tanks at the Hanford Site near Richland, Washington. This survey was the second successful SGE survey to utilize the Geotection(TM)-180 Resistivity Monitoring System which facilitated a much larger survey size and faster data acquisition rate. The primary objective of the C Tank Farm SGE survey was to provide geophysical data and subsurface imaging results to support the Phase 2 RCRA Facility Investigation, as outlined in the Phase 2 RCRA Facility Investigation / Corrective Measures work plan RPP-PLAN-39114

Improved Three-Dimensional Resistivity Data Acquisition Capabilities at the Hanford Site - 14146

The recent 3D electrical resistivity characterization at 241_U Tank Farm represents the first full-farm true 3D environmental resistivity deployment in the world. Technological and manufacturing developments by the vendor resulted in a data acquisition system that far surpasses the ability of the previous off-the-shelf systems. The new data acquisition system allows for 180 channels, which enables the full-farm 3D acquisition without the inaccuracies associated with combining multiple datasets. This ultimately leads to a more accurate model of the subsurface and a better understanding of moisture and contaminant distribution within the vadose zone. Additionally, advancements in electrical noise filters and increased output power resulted in better quality data than previously acquired at the site, reducing the amount of poor quality data by more than half. Ultimately, the new, improved system increased the speed of data acquisition and quality of the final results. The system allowed a reduction in field labor and field work duration to half the field budget estimates, resulting in a 25% reduction in overall project costs. The new resistivity data acquisition system represents technological advancements resulting in a greater quantity of data with decreased project costs

Spectral Induced Polarization Response to Nanoparticles in a Saturated Sand Matrix

Nanoparticles have grown in importance over the last decade with significant consumer and industrial applications. Yet, the behavior (fate and transport) of nanoparticles in the environment is virtually unknown. Research is needed to identify, characterize, and monitor nanomaterials in the subsurface. Here, we investigate the spectral induced polarization (SIP) response of nanometallic powders (nZVI, nAg, nTiO2, nZnO, and nCeO2) in porous geologic media. Our main objective is to determine the sensitivity of the SIP response (0.1-10,000Hz) to the presence of nanoparticles (metals and metal oxides) in porous media. The SIP response was tested under various conditions: increasing particle concentration under constant solution chemistry; varying solution molarity (0.0 M-1.0 M), and varying solution valence (+1, +2, +3 valence) under constant particle volume. We examine the results in terms of phase shift and resistance magnitude. Our data suggest that the oxide nanoparticles do not show SIP responses to increasing particle concentration, solution valence, and molarity, while the metallic particles show a clear response to increasing particle concentration, and frequency. Silver was the only material to show any significant response to increasing solution molarity, valence, and frequency. Because of the high propensity of the nanoparticles to form aggregates, they essentially behave as colloidal and clay particles allowing us to apply conventional SIP theory to our interpretation. We suggest that the oxidation state of the metals diminishes their SIP response consistent with more recent studies that have documented that polarization decreases with oxidation of metallic particles. We infer from our results that nanoparticle crystalline composition and aggregation effects control the SIP response of nanoparticles in porous media

Characterization and Potential Remediation Approaches for Vadose Zone Contamination at Hanford 241-SX Tank Farm

Unplanned releases of radioactive and hazardous wastes have occurred at the 241-SX Tank Farm on the U.S. Department of Energy Hanford Site in southeast Washington State. Interim and long-term mitigation efforts are currently under evaluation for 241-SX Tank Farm. Two contiguous interim surface barriers have been designed for deployment at 241-SX Tank Farm to reduce future moisture infiltration; however, construction of the surface barriers has been deferred to allow testing of alternative technologies for soil moisture reduction and possibly contaminant source term reduction. Previous tests performed by other organizations at the Hanford Site have demonstrated that: vadose zone desiccation using large diameter (greater than 4 inch) boreholes is feasible; under certain circumstances, mobile contaminants may be removed in addition to water vapor; and small diameter (approximately 2 inch) boreholes (such as those placed by the direct push hydraulic hammer) can be used to perform vapor extractions. Evaluation of the previous work combined with laboratory test results have led to the design of a field proof-of-principle test to remove water and possibly mobile contaminants at greater depths, using small boreholes placed with the direct push unit