Illinois Groundwater Guide: Aquifers, Wells & Water Quality

Illinois’s Groundwater System

Groundwater is a vital resource in Illinois, serving both residential and agricultural needs. Understanding the state’s hydrogeological systems is essential for property owners relying on private wells.

The deep Cambrian-Ordovician aquifer system contains some of the most productive sandstones in the country, widely used in northern Illinois. Shallower glacial drift aquifers serve much of the state, while dolomite formations provide supplemental water.

The major aquifer systems in Illinois include:

• Cambrian-Ordovician aquifers (Ancell Group)
• Silurian-Devonian dolomite aquifers
• Glacial drift aquifers
• Illinois River alluvial aquifers

Each of these systems has different depths, yields, and water quality characteristics that affect well drilling costs and water treatment needs.

Well Water in Illinois

Majority of Illinois population served by public water systems, but groundwater supplies significant agricultural and some municipal water. This reliance on private wells is particularly important in rural communities where municipal water systems may not be available.

The average well depth in Illinois ranges from 300-500 feet, depending on the aquifer system accessed and local geology. Well drilling costs typically range from $12-$25 per foot, though this varies based on:

• Aquifer depth and geology in your specific location
• Soil and rock composition requiring different drilling techniques
• Well diameter and final depth required
• Local Illinois regulations and permit requirements
• Contractor experience and equipment availability

Common Water Quality Issues in Illinois

Illinois residents may encounter various groundwater quality challenges depending on geology and location:

• Radium in some deep well systems requiring treatment
• Naturally high sodium in deep aquifers
• Coliform bacteria in shallow wells
• Nitrate from agricultural sources

Regular water testing is essential for Illinois well owners. The state recommends testing at least annually for coliform bacteria and every three to five years for a comprehensive analysis including minerals, contaminants, and chemical parameters.

Illinois Well Regulations

All new wells in Illinois must comply with state regulations. Illinois Department of Natural Resources and IEPA regulate groundwater. Well drillers must be licensed and follow construction standards. ensures that:

• New wells meet minimum construction standards
• Proper well spacing protects other water users
• Contamination risks are minimized
• Well drillers possess appropriate training and licenses

Homeowners should always hire licensed groundwater contractors to ensure compliance with these regulations.

Drought & Climate Impacts on Illinois Groundwater

Illinois generally has adequate groundwater, though periodic droughts stress supplies. Climate change may affect recharge patterns and water availability. Groundwater conservation and sustainable management are increasingly important for long-term water security in Illinois.

Finding a Groundwater Contractor in Illinois

Groundwater World connects property owners with licensed groundwater contractors throughout Illinois. Whether you need:

• New well drilling for a new property
• Well rehabilitation or repair services
• Water quality testing and analysis
• Pump installation and maintenance
• Water treatment system design and installation

Our directory features qualified contractors experienced in Illinois’s unique geological conditions. Browse our complete directory of Illinois groundwater professionals to find the right contractor for your needs.