GEOLOGIC MAPPING FOR GROUNDWATER APPLICATIONS IN KANE COUNTY, IL

Because water shortages are projected within the next 20 years, Kane County contracted with the Illinois State Geological Survey (ISGS) and Illinois State Water Survey (ISWS) to assess groundwater resources for the county and surrounding area. The ISGS will provide basic data on the geology of Kane County, produce maps of surficial geology, drift thickness, aquifer sensitivity and lithology, as well as develop a 3-D geologic model. The ISWS will use the resulting geologic maps and water level data to produce potentiometric surface maps of shallow aquifers and a regional groundwater flow model.

The ISGS has over 10,000 well log records for Kane County in its database, including 225 high quality logs. High quality well logs have detailed lithologic descriptions and often have sample sets and geophysical logs. These high quality wells are used as the framework for the geologic maps and 3-D geologic model. In addition to the high quality logs, one well log is selected per quarter section for inclusion in the model. The location of these wells is then field verified.

ArcGIS is used to create and display a series of data location maps, base maps, and digital orthophotos of the study area. Land surface elevations for each datum are obtained from a high-resolution digital elevation model. ISGS borings or geophysics are used to fill in areas with less reliable or absent well information. Driller’s logs are imported into RockWorks by translating the driller’s descriptions into a standard set of lithologies. RockWorks is then used to create a lithologic strip log for selected boreholes and exposures, which are compared to nearby high-accuracy records from described outcrops and key boreholes. Well-to well cross sections are then created and used to assign top and bottom surfaces for lithostratigraphic units. These individual surface models will be used in development of the 3-D model.