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How Well is Your Water?

By Janet Andrew with notes provided by Julie Wiegel, Well Program Manager and the Illinois Department of Natural Resources

Nearly all of unincorporated areas Cook Counties are served by private wells that vary from approximately 40 feet to 780 feet deep.  Water is pumped out of these wells by tapping underground sources of drinkable water called aquifers. 

Water found in these underground aquifers is collected and recharged from rainfall and snowmelt and is filtered as precipitation seeps through layers of soil, sand, clay and rock.  The composition of soil as well as the quantity and the depth of the aquifer all contribute to the rate of recharge. 

As undeveloped areas are paved over with roads, driveways, buildings and parking lots, underground aquifers cannot recharge as easily as before.  About 80% of water that lands on a paved area will run off down the side of the road or into a storm sewer and be routed away from aquifers, diminishing the ability of these underground water resources to be replenished.

A simple table top model can help to illustrate how aquifers and groundwater are recharged and how pumping water from a well uses up groundwater resources.

In the diagram to the left, the tubes descending through the different layers of soil and sediment represent wells at various depths.  They are all recharged from the top as precipitation seeps into the ground and is filtered through the ground layers. 

Wells at shallower depths may experience higher concentrations of contamination since less filtering can take place before water is pumped out of the saturation layer. 

Wells at deeper depths may not recharge as quickly because water must travel a greater distance in order to reach the saturation layer.

As water is pumped out of a well, the water level within the well declines.  Since wells at similar depths will draw from the same saturation layer, as water is pumped from one well, water levels in other wells at the same or similar depth will also decline.

This very simply demonstrates why in times of severe drought, it is important that all well users that share an aquifer should be mindful of misuse and overuse of groundwater.

Unfortunately, groundwater can become contaminated by harmful chemicals, including household chemicals such as lawn care products, paints, and cleaners; agricultural fertilizers and pesticides; and oil. These chemicals can percolate down through the soil and rock and into the aquifer—and eventually your well and can pose a significant threat to human health. The measures that must be taken by well owners and operators to either protect or clean up contaminated aquifers are quite costly.  Here are a few easy steps you can take to help protect your well from contamination:

  • Don’t over-water your grass and gardens
    Fertilizers and pesticides can easily move through the ground into the aquifer.  If you use lawn chemicals, excess water will wash them straight into your groundwater before they can be absorbed by plant material. 

  • Don’t apply fertilizers or pesticides when it is windy or raining
    Chemicals can be quickly washed or blown away from the desired location and possibly into surface water.

  • Don’t use or store chemicals directly above your wellhead
    Consider the distance between potentially harmful chemicals and the water you use for drinking and cooking.

  • Don’t over-fertilize
    If your grass, trees and shrubs are growing normally and healthily without chemicals, don’t use them.

  • Inspect your well cap periodically for insect infestation (primarily earwigs) and make sure the cap is tightly bolted and not damaged.
    Earwigs will congregate in wet areas.  If your well is not sealed properly, carcasses of dead insects can get into your well and contaminate your water supply.

  • Make sure any landscaping is well maintained around the well casing and that the well cap is at least 8-inches above the ground.
    If you well cap becomes loose, grass clipping, twigs, leaves, insects or any thing that is nearby on the ground could easily get inside your well and contaminate your water.

When and how to test your well

The signs of drinking water contamination are not always obvious.  Contaminated water may not taste, smell or look any differently than safe drinking water.  What’s more, as a private well owner, YOU are your own regulatory agency!  You are responsible for the water your family drinks.

Homeowners should test their well annually for Coliform bacteria and nitrates.  Also, it’s it a good idea to test during the spring and summer following periods of heavy rainfall when fertilizer run-off can be a contamination factor.  A primary source of well contamination is from failed septic systems, so be sure to monitor and maintain your system properly.  If there is someone in your household who is pregnant, is a newborn or infant, or has a compromised immune system, you may wish to test more often than once per year.

A water test kit may be obtained from any state certified laboratory, but this location has been referred to Rolling Knolls Estates by the Cook County Health Department. 

Analytical Laboratories
5045 Shoreline Road
Lake Barrington
Open 10 a.m. to 5 p.m.

$35.00 price includes a sterile container for collecting a water sample, instructions, and lab fees for Coliform and nitrate tests.  You may pick up a test kit in person or call Analytical Labs to have one mailed to you.

To view other laboratories, visit this site:

Common Contaminants:
Coliform bacteria
Hydrogen Sulfide
Iron or Manganese
Sand, silt or clay
Minerals and heavy metals such as lead, mercury or arsenic

You may not need to test for all of these contaminants, but do order testing at a minimum for nitrates and Coliform bacteria. 

What to do if your well becomes contaminated

If you find that your water supply contains unsafe levels of any of these compounds, take corrective action immediately to stop further contamination before considering a treatment device.  Because water treatment can be costly, you may wish to investigate multiple options.   You may only need to disinfect your well, but if more drastic steps are required, a non-profit trade association, such as the Water Quality Association at 4151 Naperville Road in Lisle, may be able to recommend companies that sell treatment equipment.  Contact them at 630-505-0160 or at www.wqa.org.  Be wary of questionable claims from salespeople and do your research before buying!

You also may wish to consult with the Cook County Department of Health and perhaps also with your physician to interpret the results and formulate a mediation action plan.  Dave Rohboch at the Cook County Private Water Department may be able to help.  Call him at 708-492-2035.

The likelihood of experiencing negative health effects from water contaminants depends upon your general health, how long you have been exposed to the water, and how much the chemical is above or below the health advisory level.  You can obtain a health advisory summary from the U.S. EPA by contacting the Safe Drinking Water Hotline at 800-426-4791.  Additional helpful information can be found at www.epa.state.il.us/well-water.

Finding out more about your specific well in Rolling Knolls Estates

Every well drilled in Illinois between 1965 and 1992 has a Well Log Survey on file in the Illinois public records of the State Water Survey showing the depth and water quality from when the well was originally drilled.  This document can be a good baseline for measuring changes in your water quality over time.  To obtain a copy of your survey, contact Suzy Dodd at 217-333-2210.   Be prepared to give information on the exact location of your property, which can be found in your deed.  If you do not have your deed, contact your lending institution.  You will need the description of the property range, which means the “Quarter Section Code,” in order to request a copy of your well survey. 

If your property was built after 1992 and you do not have your original well survey, please contact the Cook County Health Department to request a copy.

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This site was last updated 03/25/06