Fact Sheet 1

Boone County, Illinois

Subsequently, the Boone County Health Department and the Illinois Department of Public Health (IDPH) obtained water well samples over a number of years for numerous private wells in the subdivisions (Nordic Acres and Stonefield) on the north and south sides of Squaw Prairie Road near the Beaver Valley Road intersection. A number of private wells tested showed low-levels of VOCs. IDPH sent letters to individual well owners explaining the test results, any health implications, and advising residents about the use of their well water. A public meeting was held in1999 by IDPH and Boone County Health Department for the homeowners in the two subdivisions to respond to concerns about the contamination. The Illinois EPA began an investigation for a source of contamination in 2002.

During the entire study, 95 individual wells were tested, including wells outside of the two subdivisions where the contamination was found. Approximately one-third of all wells tested showed some contamination. About half of the wells tested in the two subdivisions where the contamination plume is located had detectable contamination. In six instances, residents were advised to use an alternative drinking water source. Others were advised to simply test their wells again in the future, while some showed no evidence of VOCs. In 2007, Illinois EPA expanded the investigation for a potential source of the contamination.

What has Illinois EPA learned recently about a source of the chemical contamination?

After several years of attempting to identify a source of contamination that is affecting the private wells, Illinois EPA concludes that it is unable to locate a specific source at this time. Most likely, the contamination occurred as a result of one or more incidents of dumping or spilling solvents in the past – perhaps thirty or more years ago. The location of the dumping is no longer apparent at the surface, since the chemicals evaporate or move downward through soil into groundwater over time. If further data becomes available in the future, Illinois EPA may again evaluate the situation as to a potential source.

What is being done to monitor this situation and prevent further public health exposure?

The Illinois Department of Public Health plans to continue monitoring the identified plume of contamination in the future by doing some limited testing at the peripheral edges of the plume. The Boone County Health Department has implemented well drilling code restrictions. The new restrictions will require drillers to go below the aquifer where contamination was found when installing private wells.

Where did Illinois EPA conduct testing most recently and what were the results of the testing?

Illinois EPA tested wells in May 2007 northeast of the two subdivisions in an attempt to find the source of contamination. Groundwater moves generally from northeast to southwest in this area. In addition to the new subdivision immediately northeast of Nordic Acres, Illinois EPA tested wells on Spring Creek Road, Town Hall Road and Beloit Road. None of the eleven private wells and one small community supply well tested in May 2007 showed any VOC contamination.

Does the contamination still represent a threat to area wells?

Low level VOC contamination may still be present in the groundwater underneath Nordic Acres and Stonefield Subdivisions, although it is likely diminishing over time. Recent testing showed no contamination in wells northeast of this location. The contamination seems to be isolated to a narrow area within the two subdivisions.

Should residents in the two subdivisions where contamination was found be concerned about their well water in the future?

Residents who live in Nordic Acres and Stonefield Subdivisions should continue to follow the advice from IDPH in individual letters about their well tests. If there was contamination in the past, residents should continue to test for it in the future. If a resident’s well showed no contamination in the past, he or she may want to test in the future to make sure that is still the case.

What about residents who have wells farther downgradient (in the direction of groundwater flow)?

Most residences south/southwest of the area of contamination are connected to the Belvidere Public Water Supply (PWS) system, which extends north on Beaver Valley Road, nearly to Squaw Prairie Road. The PWS is not affected by the area contamination. Homeowners with private wells along Beaver Valley Road, just south of Squaw Prairie Road may want to consider testing their wells to insure the contamination does not migrate into their water supplies.

Did the depths of the wells tested show any correlation to the contamination?

Illinois EPA did not find a correlation between depth of the well and contamination. Depths of the wells that were previously tested in the two subdivisions range from 90 to 175 feet deep. Records indicating well and well casing depths were not available for all addresses.

Well logs for the (newer) wells that were recently tested immediately northeast of the subdivisions in question, which did not have any contamination, were mainly in the same 165- to 175-foot deep range as wells previously tested. One was 296 feet deep. Other wells tested in May, along Town Hall Road and Beloit Road ranged from 100 to 135 feet deep, and did not show any contamination.

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