VULNERABILITY ASSESSMENTS AT ILLINOIS NATURE PRESERVES – ASSESSING POTENTIAL FOR GROUNDWATER CONTAMINATION

In 1997, researchers at the Illinois State Geological Survey (ISGS) and Illinois State Water Survey (ISWS) published a novel technique to evaluate the potential risk from groundwater contamination at Illinois nature preserves. The site vulnerability assessment (SVA) process was developed to systematically evaluate a range of land use, hydrogeological, and geochemical information related to high-quality natural communities. Most Illinois nature preserves have limited data about groundwater quality and flow direction, which limits the ability of site owners and managers to assess if land use changes in the surrounding areas can impact the preserve. Information published in the 1997 report has been used for state designation of groundwater that contributes to a dedicated nature preserve as a Special Resource Ground Water as defined in the Illinois Administrative Code (Title 35, Part 620.230). Such a designation can provide an additional level of protection against destruction or degradation of nature preserves. Since 1995, more than 125,000 acres (~195 sq mi) at 32 sites in 13 counties have been designated as Special Resource (also known as Class III) Ground Water areas.

Since the 1997 report, more than 150 nature preserves have been added to the Illinois nature preserve system that require investigation. Updated screening identified an additional sixty-five nature preserves where vulnerability assessments were needed due to their sensitive hydrology and geology. The original paper-based method has recently been converted into an electronic-based method facilitated by data exploration and collection using ESRI applications ArcGIS Online, Survey123, and Field Maps. Past results yielded ~30% of sites ranked as moderate high to high vulnerability. Current investigations classified 48% of the twenty-nine completed sites as having a moderate to very high potential for groundwater contamination.

SVAs have proved useful for groundwater protection designations, impact assessments, Illinois Department of Natural Resources land acquisitions, local zoning considerations, and construction decisions. The data gathered from SVAs provides a baseline for understanding the shallow hydrogeology of a site, enabling site managers to implement better management practices and protect the sites in perpetuity.