Olmsted County, Minnesota is underlain primarily by karsted limestone and relies entirely on groundwater supplies for its drinking water. Effective partnerships between scientists, local, state and federal governments and agencies, and interested citizens have been important in making good decisions that protect groundwater quality. In 1985, Olmsted County successfully worked with the Minnesota Geological Survey (MGS) to locate a site for a new landfill. Maps detailing bedrock geology, depth to bedrock, surficial geology, and groundwater sensitivity led to identification of a large bedrock valley filled with glacial drift as an appropriate site for the landfill. These same maps played an important role in the public education effort needed for public approval of the site. Since that time, the Olmsted County Geologic Atlas and subsequent GIS data-bases, containing these maps and others, have become a fundamental tools supporting planning, policy making, and public discussion. Continued collaboration between local government, the USGS, and the MGS have detailed the nature of groundwater movement in Olmsted county. This information has led to the identification of a particularly sensitive zone related to focused recharge of the drinking water aquifer. Discussion of strategies for balancing development pressure and water quality protection in this zone are currently underway, as are discussions of the location for expanded railway services across the county. The basic understanding of Olmsted County geology and hydrology developed by government officials, policy makers, and other stakeholders over the past two decades provides a strong foundation for discussing the details of these particular issues. Research collaborations, formal and informal educational materials and activities, media attention, informed public discussion, and the participation of scientists in the public process have been fundamental in establishing this understanding. A lasting lesson from these experiences is the importance of long-term dialog, collaboration, and public education in establishing a capacity for using geoscience effectively in public decision making.