LARGE-SCALE AQUIFER SENSITIVITY MODEL

A 480-square-mile region within Will County, in northeastern Illinois, was used as a test region for the development of a methodology to map the sensitivity of aquifers to contamination. An aquifer sensitivity model was developed using a geographic information system (GIS) to ove rlay and combine several data layers. The components used for our mode l are: (1) depth to sand and gravel or bedrock, (2) thickness of the u ppermost sand and gravel aquifer, (3) glacial drift thickness, and (4) bedrock geology. The model is an improvement over many previous aquif er sensitivity models because it combines specific information on dept h to the uppermost aquifer with information on the thickness of the up permost sand and gravel aquifer. This county-wide model results in an aquifer sensitivity map that can be a useful tool for making land-use planning decisions regarding aquifer protection and management of grou ndwater resources.