Assessing the quality and availability of ground water and its vulnerability to contamination requires adequately characterizing the geologic, geophysical, and geochemical factors controlling subsurface fluid flow and contaminant dispersal. Although it is relatively easy to determine the average hydrologic properties of a rock mass or sediment, one of the greatest challenges to effective waste isolation lies in accurately characterizing hydrologic heterogeneity and preferential flow paths (for example, the one fracture, fault, or stream-channel deposit that may carry most of the contaminants). Also, predicting the long-term hydrologic behavior of aquifers and aquitards and the attenuation or degradation of toxic wastes requires an improved understanding of the physical, chemical, and biological processes controlling the evolution of hydrologic properties and fluid chemistry through time.
The GD will contribute geological, geophysical, and geochemical expertise to ground-water issues that are in the broad national interest; that is, issues that are regional to national in scale, pertain to Federal lands, or are expected to lead to fundamental advances in understanding the scientific basis for ground-water resource assessments and the mitigation and remediation of ground-water contamination. GD work will be conducted in close collaboration with the WRD's Toxic Substances Hydrology Program and their new Ground-Water Resources Program.
Basin-scale, nationally consistent maps showing the three-dimensional distribution of hydrogeologic properties.
The GD will generate these maps, using its expertise in surficial and bedrock geologic mapping, sedimentology, geophysical imaging, and other techniques, in support of ground-water resource development initiatives. Such maps will help define aquifer permeability structure and storage capacity, particularly in rapidly expanding urban and agricultural areas. These products will be developed in collaboration with the WRD and State and local agencies conducting hydrologic testing, computer modeling, and other activities.
Three-dimensional hydrogeologic maps and conceptual models of fluid flow and ground-water contamination associated with hazardous waste disposal sites and other sources.
These sources of potential contamination include high- and low-level nuclear waste, industrial chemical leaks, and saltwater intrusion. Creation of these maps and models will involve the same techniques and cooperators as the first product listed but will also incorporate GD expertise in neotectonic studies, borehole geophysics, rock mechanics, and geochemical investigations of fluid-rock interactions. These products will help define the heterogeneous permeability structure of critical aquifers and aquitards and the rates and pathways of contaminant transport.
Conduct geological mapping, geophysical imaging, geochemical testing, and borehole measurements in support of ground-water resource and contamination studies in critical areas.
Key parameters (or their proxies) to be determined include overall geologic structure; mineralogy and physical properties of rocks and sediments; nature, geometry, and hydrologic properties of fractures and faults; and the mechanisms and rates of chemical water-rock interactions.
Investigate the fundamental geologic factors controlling subsurface fluid flow in sedimentary basins and other deposits.
The GD will determine how depositional environment, diagenetic processes, and deformation affect permeability structure and storage capacity in highly porous, sediment-dominated hydrologic systems.
Conduct multidisciplinary research on the origin, development, and hydrologic properties of fracture and fault systems.
GD studies in a variety of geologic and tectonic environments will facilitate development of large-scale fluid flow models, especially where detailed in situ fracture data are lacking.
Conduct investigations to understand the links between geochemical, biological, and hydrogeologic processes.
These processes include mineral precipitation and dissolution reactions, permeability and fluid-pressure changes induced by earthquakes and volcanic eruptions, and biochemical interactions between microbes and mineral surfaces. Experimental, field, and theoretical studies will allow the GD to produce models showing the evolution of fluid permeability and water chemistry through time.