Geohydrology of the 218-W-5 Burial Ground, 200-West Area, Hanford Site

Construction a disposal facility for solid, mixed low-level radioactive and hazardous wastes at the Hanford Site in southeastern Washington State (Figure 1) is planned. A site-specific performance assessment for each new disposal facility to ensure that wastes will be isolated from the environment is required. To demonstrate the adequacy of the facility for isolating the wastes, computer codes are used to simulate the physical processes that could cause the waste to migrate to underground water supplies or to the land's surface. The purpose of this report is provide a compilation and interpretation of geologic and hydrologic data available use in the performance assessment modeling. A variety of data are needed to model flow and transport from a solid-waste burial trench. These data include soil water content, soil moisture potential, saturated and unsaturated hydraulic conductivity, and phase mineralogy of the soils and sediments within the vadose zone. The hydrologic data that are critical for quantifying the water storage and transport properties for unsaturated soils require a characterization of the heterogeneities of various soil layers and the moisture characteristic curves for these layers. Hydraulic properties and mineralogic data for the saturated sediments are also important for modelling the flow and transport ofmore » wastes in the unconfined aquifer. This report begins with a discussion of the procedures and methods used to gather data both in the field and in the laboratory. This is followed by a summary of the geology, including the stratigraphic framework, lithofacies, and mineralogic/geochemical characteristics of the suprabasalt sediments. The hydrology of the region of the site is discussed next. In this discussion, the characteristics of the uppermost aquifer(s), unsaturated zone, and the various hydrogeologic units are presented. 54 refs., 39 figs., 11 tabs.« less