With a growing population of about 710,000, Lake County has been identified as the highest priority area in need of high-quality 3-D mapping of glacial aquifers. The maps provide a context for decision-making related to the use of groundwater and other natural resources, identification of natural hazards, and creation of economic development opportunities.
PRI scientists examined and interpreted historical records and maps containing facts and observations about surface and subsurface geology. The resulting project output used 200 borings with geophysical logs and sediment cores, 400 downhole geophysical logs, 21 miles of geophysical lines (seismic, etc.), and 24,000 lithologic logs from drillers and engineers. The Illinois State Geological Survey obtained funding through matching grants from the USGS, as well as from Lake County. These data were interpreted and characterized through cutting-edge 3-D analysis.
Lake County planners now deploy digital 3-D geologic map layers for effective use with other digital information, such as land parcel, land-use zoning, and park and natural area boundary maps. This information has supported several water supply decisions in Lake County, including planning for additional water withdrawal from Lake Michigan. For planning purposes, dramatic changes in the geology over short distances have weakened stakeholders’ confidence in long-term reliance on groundwater for western Lake County communities. Information from 3-D geologic mapping explains why some communities have been unable to find suitable aquifers in areas near existing production wells. Because each additional allocation of Lake Michigan water for some Illinois communities affects the potential future use of that resource for other communities, geologic maps that show effective management of aquifers are essential to the long-term sustainability of both our groundwater and surface water.