Metropolitan Chicago Mapping Update

Lake County 3D

The ISGS has nearly completed a 3-D geologic model for Lake County, Illinois. Considering that Lake County has a population of more than 700,000 within 55 villages, towns, and cities and a mix of suburban, rural, agricultural, and unique natural areas, it has been a challenge to plan for long-term management and supply of water resources from both Lake Michigan-allocated surface water and groundwater from glacial deposits and carbonate and sandstone bedrock. Very detailed 3-D geologic information was developed based on data analyses from more than 200 exploration boreholes, 24,000 water-well and engineering borehole records, and several miles of geophysical transect data, which revealed the complex variability associated with glacial deposits. The ISGS has been able to explain why some communities have not been able to find suitable aquifer material even in areas near existing groundwater production wells. It is important to note that the geologic mapping has aided in decision making regarding the feasibility of additional water withdrawals from Lake Michigan (and the large associated costs) compared with the development of groundwater resources.

The ISGS has completed countywide 3-D hydrogeologic mapping in McHenry County, Illinois. The main objective was to build an interactive 3-D geologic map of the glacial deposits based on the geologic and hydrogeologic framework modified from previous studies. From this 3-D map, derivative 2-D maps were produced that depict new information on the thickness, sedimentology, and hydraulic characteristics of shallow sand and gravel aquifers. This project integrated new field exploration techniques, database standardization and refinement, and 3-D visualization and analyses.

The 3-D hydrogeologic mapping project of Kendall County includes county-scale mapping of the Quaternary sediments and most of the bedrock formations to support sustainable management of groundwater resources in this southwestern corner of metropolitan Chicago. The project, funded jointly by Kendall County and seven municipalities, included development of a 3-D map of aquifers and nonaquifers. One goal was to evaluate the potential for any previously unidentified sand and gravel aquifer resources within the Quaternary sediments. Although the mapping revealed no new sand and gravel aquifers, the project resulted in the compilation of a countywide 3-D geologic map that could be used as the basis for future groundwater management and land-use planning.