thumbnail

Water Quality of Sand and Gravel Aquifers in McHenry County, Illinois, 2020 and Comparisons to Conditions in 2010

Scientific Investigations Report 2022-5110
Prepared in cooperation with McHenry County, Illinois
By: , , , and 
https://doi.org/10.3133/sir20225110

Links

Abstract

McHenry County, Illinois, obtains most of its drinking water from shallow sand and gravel aquifers (groundwater). To evaluate this groundwater resource, the U.S. Geological Survey, in cooperation with McHenry County, Illinois, collected water-quality samples from 41 of 42 monitoring wells in the McHenry County Groundwater Monitoring Network and 4 monitoring wells from the U.S. Geological Survey National Water-Quality Assessment Project. Additionally, a subset of 12 monitoring wells was sampled and analyzed for pharmaceuticals and wastewater indicator compounds (WICs), collectively referred to as “contaminants of emerging concern” (CECs). Results from this 2020 study were compared to the 2010 results to assess changes in groundwater quality. Statistical analyses and chloride-bromide ratio analyses also were completed to assess changes in water quality.

Health-based benchmarks were exceeded for arsenic (about 24 percent; 11 of 45 monitoring wells), sodium (40 percent, 18 of 45), and manganese (about 2 percent, 1 of 45). Aesthetically based benchmarks were exceeded for dissolved solids (about 29 percent, 13 of 45), chloride (about 4 percent, 2 of 45), iron (about 87 percent, 39 of 45), and manganese (about 29 percent, 13 of 45). CECs were detected at low or estimated concentrations in 8 of the 12 (about 67 percent) monitoring wells analyzed.

In addition to sampling the groundwater monitoring wells, three surface-water-quality monitoring sites also were sampled and analyzed for pharmaceuticals and WICs to provide a preliminary assessment of the presence of CECs in the surface waters. CECs were detected in all three of the surface-water-quality monitoring samples collected, and WICs were more prevalent and more frequently detected than pharmaceutical compounds. These results provided a cursory understanding of the presence of CECs in surface waters and do not constitute a robust analysis of sources, seasonality, range of concentrations, persistence, or effects.

The 2020 groundwater-quality results had measurements of field properties, and concentrations of major ions, trace metals, and nutrients that were consistent with 2010 results with statistically significant increases for calcium, magnesium, and silica, and decreases for aluminum, ammonia, arsenic, barium, bromide, calcium, molybdenum, phosphate, specific conductance, sulfate, and dissolved solids. Increases generally were detected in the intermediate and deep parts of the sand and gravel aquifer, and decreases were detected in the shallow parts of the sand and gravel aquifer. The mixed distribution of increases and decreases among the various constituents and aquifer-depth groups could be reflecting dissolution and mobility of some of the redox sensitive constituents and dilution of some constituents in the shallow aquifer depths. These changes may be attributed to a combination of stable population of the past decade (2010–20), land-use management practices, and the recent wet years of 2017 through 2019 causing a dilution of the major ions in the shallow parts of the aquifer.

Suggested Citation

Gahala, A.M., Gruhn, L.R., Murphy, J.C., and Matson, L.A., 2022, Water quality of sand and gravel aquifers in McHenry County, Illinois, 2020 and comparisons to conditions in 2010: U.S. Geological Survey Scientific Investigations Report 2022–5110, 53 p., https://doi.org/10.3133/sir20225110.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Methods of Study
  • 2020 Water Quality
  • Comparison to 2010 Water-Quality Results
  • Statistical Comparison
  • Comparison of Chloride to Bromide Ratios
  • Summary
  • References Cited
  • Appendix 1. Quality Assurance and Quality Control of Water-Quality Results
Publication type Report
Publication Subtype USGS Numbered Series
Title Water quality of sand and gravel aquifers in McHenry County, Illinois, 2020 and comparisons to conditions in 2010
Series title Scientific Investigations Report
Series number 2022-5110
DOI 10.3133/sir20225110
Year Published 2022
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Central Midwest Water Science Center
Description Report: viii, 53 p.; Data Release; Dataset
Country United States
State Illinois
County McHenry County
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details