Geohydrology surrounding a potential high level nuclear waste repository in the Palo Duro Basin, Texas

The Palo Duro Basin of the Texas panhandle is being investigated as a potential high level nuclear waste repository site. Groundwater is the most likley mechanism for radionuclide movement, therefore, it is desirable to locate a repository in a hydrologic regime which is favorable for waste isolation and containment. The Palo Duro Basin consists of deep brine aquifers underlying a thick Permian age evaporite section. Overlying the Permian age evaporites are the Dockum and Ogallala fresh water aquifers. Observed potentiometric data in the principal aquifers indicate a potential for downward flow from the surficial aquifers to the deep brine aquifers. Groundwater movement in these deep aquifers is very slow. Modeling efforts indicate flow times of hundreds of thousands to over a million years for groundwater to reach the basin margins. Investigative methods have included drill-stem testing similar to oil field methodology, modified drill-stem testing with tools developed for low-permeability formations and long-term production tests similar to conventional water well pumping tests. Testing has generally indicated permeability of .1-10 millidarcies in the water transmitting units. 5 references, 6 figures, 1 table