USE OF GIS AND GEOLOGIC FRAMEWORK MODELS TO SUPPORT SITE EVALUATION AND SITE CHARACTERIZATION FOR A DEEP BOREHOLE FIELD TEST IN CRYSTALLINE ROCK

Options for disposal of spent nuclear fuel and other high-level radioactive waste are being evaluated through research supported by the DOE Used Fuel Disposition Campaign. In addition to more traditional mined geologic repositories, disposal options include disposal of certain types of radioactive waste in deep boreholes within crystalline basement rock. Understanding of the geologic environment for waste disposal is being supported by development of a Regional Geology GIS Database. In addition to data on the distribution of potential host rocks, the database also incorporates data pertaining to potential siting guidelines and issues, including data for geologic hazards, natural resources and cultural features.

A first step in the development of the deep borehole disposal concept is to drill a characterization borehole to a depth of 5 kilometers in suitable crystalline basement rock. In addition to testing the feasibility of drilling a stable and large-diameter borehole, geological, geophysical, hydrological, geochemical and geomechanical data will be collected from the borehole and will be used to assess the potential of using deep boreholes for long-term isolation of waste within a crystalline basement environment. In 2015, DOE initiated a request for proposals in order to obtain a site for a characterization borehole. Guidelines for a site include appropriate depth to basement, structural simplicity within the basement, low heat flow and low seismic activity. Proposals were evaluated with the support of the GIS database, which includes data for most of the specified guidelines.

Once a site is selected, the GIS database capability will be combined with a Geologic Framework Model (GFM) to represent existing geologic and geophysical data and to document new data from the borehole test. Existing data would include information from existing nearby boreholes, geophysical surveys, and hydrologic and geologic studies that would aid in understanding the regional and local geologic setting. The GFM would provide a tool for data management and visualization of data obtained from the field test. Data incorporated into the GFM would include stratigraphy, lithologic variations within crystalline basement, fracture data, as well as other data obtained from well logging and scientific tests.