Surveys & assessments

The IGPA requires the Illinois EPA to conduct well site surveys. The program is organized on a priority basis so as to efficiently and effectively address areas of protective need. Each well site survey was required to consist of the following at a minimum:

• Summary description of the geographic area within a 1,000 foot radius around the wellhead;
• Topographic or other map of suitable scale of each well site denoting the location of the wellhead, the 1,000 foot radius around the wellhead, and the location of potential sources and potential routes of contamination within this zone;
• A summary listing of each potential source or potential route of contamination, including the name or identity and address of the facility, and a brief description of the nature of the facility; and
• A general geologic profile of the 1,000 foot radius around the wellhead, including depth and age of the well, construction of the casing, formations penetrated by the well and approximate thickness and extent of these formations. Upon completion the well site survey, the Agency provided reports which summarizes the results of the survey to the applicable county and municipality, regional planning committee, and the owner and operator of the community water supply well(s).

As a result, Illinois EPA has inventoried over 20,000 potential sources of groundwater contamination and has done the evaluation of the five elements described above for all of the community water supplies using groundwater. Currently, the Internet Geographic Information System can be used to map and query this information (name and type of business etc.) within delineated source water protection areas. For more information about this system visit the Source Water Assessment Protection page.

There are broad-based economic implications of groundwater contamination to companies, counties and municipalities. These potential problems could be eliminated or alleviated in the future if more preventive, proactive management strategies are developed and implemented. The Act established initial protection measures by establishing minimum setback zones, that prohibit new potentially threatening sources of contamination from locating within these sensitive areas. Additionally, the Act provided the authority for counties and municipalities to expand setback zones up to 1,000 feet from community water-supply wells. Although these setback zones provide a baseline of protection, without having detailed knowledge of the site-specific, hydrogeologic conditions in a community, it is likely that a significant portion of a groundwater resource utilized by a community water supply would benefit from regional groundwater protection.

The IGPA authorized counties and municipalities served by a community water supply to conduct Groundwater Protection Needs Assessments (GPNA). The intent of a GPNA is to provide a comprehensive evaluation of the groundwater protection measures necessary in order to assure a long-term supply of potable water that is not highly susceptible to contamination.

Although the IGPA authorizes counties and municipalities to perform needs assessments and identifies what should be done for such assessments, the IGPA does not provide a specific methodological approach to be followed. Four pilot GPNAs were conducted in Illinois in 1991. These pilot assessments were conducted in an effort to determine a technical basis for a GPNA methodology under a range of different settings and conditions. Additionally, these assessments also provided the basis for establishing a comprehensive groundwater protection program for each of these community supplies. Each of the pilot assessments were conducted under a different set of geologic and cultural conditions.

The Illinois EPA, the Illinois State Geological Survey (ISGS) and the Illinois State Water Survey (ISWS) developed and published a Guidance Document For Groundwater Protection Needs Assessments in 1995. This guidance has been used by many communities across the state to conduct GPNAs, and to develop local groundwater protection programs.

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