Tools for groundwater protection planning: An example from McHenry County,Illinois, USA

This paper presents an approach for producing aquifer sensitivity maps from three-dimensional geologic maps, called stack-unit maps. Stack-unit maps d epict the succession of geologic materials to a given depth, and aquifer se nsitivity maps interpret the successions according to their ability to tran smit potential contaminants. Using McHenry County, Illinois, as a case stud y, stack-unit maps and an aquifer sensitivity assessment were made to help land-use planners, public health officials, consultants, developers, and th e public make informed decisions regarding land use. A map of aquifer sensi tivity is important for planning because the county is one of the fastest g rowing counties in the nation, and highly vulnerable sand and gravel aquife rs occur within 6 m of ground surface over 75% of its area. The aquifer sen sitivity map can provide guidance to regulators seeking optimal protection of groundwater resources where these resources are particularly vulnerable. In addition. the map can be used to help officials direct waste-disposal a nd industrial facilities and other sensitive land-use practices to areas wh ere the least damage is likely to occur, thereby reducing potential future liabilities.