1996 Annual Environmental Conditions Report

Environmental Conditions of Illinois

Water Resources

For groundwater used by CWS wells withdrawing water from unconfined aquifers, a declining trend or no increases in groundwater exceedences will occur through the year 2005. The percentage of groundwater recharge areas (acres) with protection programs established or under development will increase 15 percent between 1995 and the year 2000. More sites monitoring shallow groundwater units will show improvement than will show degradation by 2000. Decreasing trend in significant releases to shallow groundwater at regulated non-LUST facilities over the next five years.

Nearly 36 percent of the state's population relies on groundwater for community drinking water supplies. The following figure illustrates a comparison of groundwater exceedences from data collected from Unconfined CWS Ambient Network Wells during 1993 to 1994 to what was collected during 1994 to 1995. The exceedences have been classified into Good, Threatened, and Poor ratings to represent the conditions. The percentage of exceedences that were rated as Good increased from 65 percent in 1993 to 1994 to 67 percent from samples collected during 1994 to 1995. In addition, the percentage of Threatened conditions decreased from 28 percent to 24 percent during this same period. However, there was a 2 percent increase (6.8 to 8.8 percent) in exceedences rated as Poor. The number of wells to be sampled also decreased during the 1994 to 1995 period due to wells that became inactive. Overall, there was net improvement in the conditions of groundwater utilized by unconfined CWS wells.

Unconfined CWS Ambient Groundwater Monitoring Network Results 1993-1995 Source Information Modified from O'Hearn and Schock Principal Aquifers of Illinois Map 1984 and State Boundary obtained from the ISGS. Groundwater Monitoring Results in Unconfined Ambient CWS Network Wells compiled by the Illinois EPA. Map compiled by the Illinois EPA Division of Public Water Supplies Groundwater Section No Detections Immunoassay Upward Trend Immunoassay No Trend Immunoassay Downward Trend Nitrate Upward Trend Nitrate No Trend Nitrate Downward Trend VOC Upward Trend VOC No Trend VOC Downward Trend State Boundary Principal Sand and Gravel Deposits Principal Shallow Bedrock Deposits Principal Deep Bedrock Deposits

The costs of dealing with contamination can be very high. Therefore, protection of this valuable resource is especially critical. There are 3,397 community water supply (CWS) wells using groundwater in Illinois. Approximately 2,429 are using aquifers that have natural geologic protection. These are referred to as confined aquifer system wells. Nine hundred and sixty-eight wells are using unconfined aquifers. These 968 wells are highly vulnerable to contamination due to the geologic conditions, and the potential sources of contamination that surround them. One million one hundred and twenty nine thousand persons in Illinois rely on these unconfined aquifers for their source of drinking water. The majority of CWS systems in Illinois are considered small systems. Thus, the population represented may appear insignificant in relation to the overall population in Illinois. However, the systems that supply small populations are often more negatively impacted by contamination than those systems that supply larger populations. Unlike larger water supplies, small supplies may not have experts on staff to solve water quality problems or the rate base from which to draw funds for corrections (such as new source development or expensive water treatment systems). Therefore, protecting these smaller systems can be critical.

Protecting the land surface areas around those wells (recharge areas) can help prevent contamination of the groundwater. Measuring the percentage of these highly vulnerable areas that have been protected indicated how well Illinois groundwater is being protected.

Baseline protection is associated with minimum setback zones to prevent contamination of the most vulnerable areas around the wellhead. Supplemental protection represents maximum setback zone protection. And, full protection indicates that the recharge area has been fully delineated, the potential source(s) of groundwater contamination identified and groundwater protection management is being implemented or is under development.

The Illinois EPA has made significant progress toward achieving the 15 percent goal by increasing the number of source water protection programs that are under development. The percent of source water protection programs under development increased from 4.81 percent in 1996 to 10.48 percent in 1997 (7,250 to 20,000 acres protected). The above figures show the acreage with recharge area protection under development and the progress made during 1996.

Additionally, the supplemental protection (maximum setback zones) increased from 1.89 percent in 1996 to 3.71 percent in 1997 (3,100 to 7,200 acres protected), as illustrated in the Progress Toward Goal Figure.

In 1997, the Illinois EPA plans to assess methods and indicators to measure the performance of certain facilities to achieve our environmental goals for groundwater conditions. The Agency will track its goal that more regulated sites will show improvement than degradation to shallow groundwater quality by year 2005 by assessing the performance of facility corrective measures. Site corrective measures will be assessed initially by developing baseline year 1997 concentrations for indicator parameters that represent groundwater contamination present at the site. As corrective measures progress, the indicator parameter concentrations will be graphed through time to show the improvement to groundwater quality.

The Illinois EPA will monitor progress towards its goal of a decreasing trend in significant releases to shallow groundwater by assessing the performance of facilities to maintain the ambient groundwater quality present at each facility. The assessment will compare groundwater conditions downgradient of the facility to the ambient or background quality for that facility. This will identify and rank facilities that are acting as a "point" source of contamination to ambient quality. Each identified impact will be ranked, based on a comparison to the state groundwater standards. Concentrations that exceed the groundwater standards and the facility ambient concentration will be ranked as significant, since the groundwater standards are accepted as being protective of human health and the environment.

Groundwater Evaluation System Pilot Study Area
	Facilities with ambient groundwater data American Bottoms Aquifer Facility was identified as having impacts to groundwater No impacts to groundwater