Category:

Water Quality: Northeastern Illinois

Groundwater Quality

     Deep Bedrock Aquifers

Radium, Barium, and TDS
The most important water quality issues pertaining to deep bedrock (Cambrian-Ordovician) aquifers in northeastern Illinois are elevated levels of naturally occurring radium, barium, and total dissolved solids (TDS).

TDS concentrations generally increase from northwest to southeast across northeastern Illinois. Significant portions of Lake, Cook, and Will Counties have TDS concentrations above the secondary drinking water standard (500 milligrams per liter or mg/L), and TDS concentrations in the extreme southeastern part of the area are high enough to make the water unpotable without substantial treatment, which is uneconomical at this time.

Radium concentrations above the primary drinking water standard (5 pico curries per liter or pCi/L) are found in water pumped from the deep bedrock aquifers throughout northern Illinois, including all counties in the Chicago metropolitan area (Figure 1). Public water systems reduce radium concentrations by ion-exchange softening, lime softening, filtration, and/or by blending low-radium water from surface water sources or shallow aquifers.

Barium concentrations above the primary drinking water standard (1 mg/L) occur in water pumped from the deep bedrock aquifers in the northeastern part of the Chicago metropolitan area, in most of Kane and McHenry Counties and in parts of Cook and Lake Counties (Figure 2). Extremely high concentrations (>5 mg/L) occur in a significant part of this area. In addition to posing a health risk, barium can precipitate out of solution as the mineral barite in wells, resulting in reduced well productivity and high maintenance costs. Barium is removed from drinking water supplies by ion exchange softening and lime softening.

Based on pumping from aquifers in other parts of the world, it is possible that increased pumping from the deep bedrock aquifers beneath northeastern Illinois may increase levels of TDS, radium, and barium. Preliminary examination of historical data suggests that while TDS levels have not been increasing in wells open to deep bedrock aquifers in most of northeastern Illinois, levels may be increasing at some major pumping centers, including Joliet and Aurora1. Assessments of trends in radium and barium concentrations have not been done, and there is a lack of historical radium data.

Radium and Barium in the Ironton-Galesville Bedrock Aquifer in NE Illinois.

     Shallow Aquifers

Shallow Aquifers and Sources of Contamination
Population growth and development in northeastern Illinois place a heavy demand on water resources. Due to court-mandated limits on Lake Michigan withdrawals, and the fact that withdrawals from deep bedrock aquifers may be approaching their sustainable limits, shallow bedrock and overlying sand-and-gravel aquifers are expected to be an important source of additional water to meet the increased demand. A considerable amount of water (500 million gallons/day) has been estimated to be available in these shallow aquifers2.

Shallow aquifers, however, can be vulnerable to surface contamination, and there are many potential sources of contamination to shallow groundwater in urban and suburban areas, including landfills, sewage treatment plants, industrial effluents, atmospheric deposition, septic fields, gasoline storage tanks, and road runoff. The large list of potential contaminants includes various organic classes (e.g., petroleum compounds, solvents and pesticides), toxic metals (e.g., cadmium, lead and chromium), chloride, sulfate, nitrogen, and high total dissolved solids (TDS)3. Chloride concentrations have been increasing in many shallow wells in northeastern Illinois, primarily due to road salt runoff (Figure 4, Figure 5). Shallow groundwater quality was reported to be significantly worse in the urban eastern part of Kane County compared to the western rural part of that county4 (Figure 6).

Research is still required to determine the shallow groundwater quality in northeastern Illinois, especially in regions undergoing rapid urbanization, such as Kendall, Grundy, and parts of Kane, McHenry, and Will Counties. Information on water quality, along with geologic and land use information, will help water supply planners identify vulnerable aquifers and take steps to protect them.

Historical Changes in Shallow Groundwater in NE Illinois.

Surface Water Quality

     Fox River Basin

Emerging Contaminants in Surface Water and Groundwater - Fox River Basin
The rapidly urbanizing Fox River watershed is placing ever-increasing demands on available surface and groundwater resources. Studies are underway or have been proposed that primarily address water supply issues in this watershed. The impact of increased use, particularly of shallow groundwater, on the water quality in these aquifers and the Fox River is largely unknown.

Drawdown of the shallow aquifers likely will result in a decreasing contribution of groundwater discharge to the base flow of the Fox River, while the contribution to base flow of wastewater effluent increases. Consequently, base flows in the Fox River are expected to become increasingly dominated by wastewater effluents. Shallow aquifers similarly may become affected through their interconnections with streams. 

Resulting water quality impacts may include increased nutrients and algal biomass and reduced dissolved oxygen in surface waters, as well as increased concentrations of emerging contaminants in both surface and shallow ground waters.  This deteriorated water quality also may result in increased water treatment costs as new or improved treatment methods are mandated or otherwise become necessary.

References

1.    Kelly, W.R., and S. Meyer, 2005. Temporal changes in deep bedrock groundwater quality in northeastern Illinois. Illinois State Water Survey Contract Report 2005-05, Champaign, 40 p.

2.   Schicht, R.J., J.R. Adams, and J.B. Stall, 1976. Water Resources  Availability, Quality, and Cost in Northeastern Illinois. Illinois State Water Survey, Champaign, Report of Investigations 83.

3.   Kelly, W.R., and S.D. Wilson, 2003. Temporal changes in shallow groundwater quality in Northeastern Illinois. In Research on Agricultural Chemicals in Illinois Groundwater: Status and Future Directions XII, Proceedings of the Ninth Annual Illinois Groundwater Consortium Conference, Makanda, IL, April 22, 2003, http://www.siu.edu/orda/igc/proceedings/03/kelly.pdf.

4.   Kelly, W.R., 2005. Shallow Groundwater Quality Sampling in Kane County: October 2003. Illinois State Water Survey Contract Report 2005-07, Champaign, IL.

Surface Water – Groundwater Interactions

Also See: Water Quality