Pore-Water Extraction Scale-Up Study for the SX Tank Farm.

摘要

Nitrate and technetium-99 (Tc-99) concentrations measured in the water condensate of soil gas extracted as part of earlier work at the U.S. Department of Energy's Hanford Site in southeastern Washington State suggest that pore water was extracted from the sediment and entrained in the exhausted soil gas. As a remedial approach, pore-water extraction offers the possibility of contaminant and water removal from the vadose zone, which may be beneficial in reducing the flux of vadose zone contaminants to the groundwater. Previous laboratory and modeling efforts examining pore-water extraction have focused on two implementation approaches: 1) application of negative pressure (vacuum) via soil-gas extraction at a well to induce coincident pore-water extraction; and 2) deployment of super-absorbent polymers in a well to extract water from the surrounding soil. In this study, laboratory experiments and numerical modeling were conducted to specifically examine pore-water extraction for sediment conditions relevant to the vadose zone beneath the SX Tank Farm at the Hanford Site. Available SX Tank Farm data were evaluated to generate a conceptual model of the subsurface in areas with elevated moisture and Tc-99 concentration. This conceptual model formed the basis to select materials for subsequent laboratory hydraulic property analyses, and for conducting numerical modeling to simulate a targeted application of pore-water extraction.