Introduction - The need for high-quality three-dimensional geologic information for groundwater and other environmental applications

The pressing need for high quality 3-D geological information on shallow deposits has become apparent since the 1960s as growing attention has been paid to environmental and land-use issues, particularly in urban and suburban areas (e.g., Larson and Hackett, 1965). After much emphasis since the 1970s on contaminated sites, attention is now shifting to regional groundwater systems, to ensure their long-term sustainable development (Sun and Johnson, 1994; Bradbury et al., 2000; Rivera et al., 2002). Geological reports and maps therefore are increasingly required by decision makers to provide a more rational basis to balance demands of sustainable groundwater use, mineral resource development, and safe burial of wastes.