Groundwater and Private Well Information

Test your well every 12 - 15 months.

As a private well owner, you are responsible for the quality of drinking water supplied to your home. On average, only 10% of well owners sample drinking water wells annually. At a minimum, a well should be sampled for bacteria and nitrate every 15 months. In karst areas of Calumet County, more frequent sampling is recommended.

What should I sample for?

  • Total Coliform Bacteria at least once a year.  A positive test may indicated something wrong with your well, including a unsealed well cap, crack in the casing or electrical conduit, or poor housekeeping practices around the well. 
  • Nitrate: should be sampled every 18 months if detectible levels are found with the first sample.  Nitrate is one of the most common contaminants found in private wells in Wisconsin.  
  • Metals Screen, including Arsenic: Sample every 5 years, more often for any metal that is elevated or found above safe drinking water standards.  

Where do I get a sample kit?

How to Sample Your Well

Here is a quick 5 minute video on how to sample your well for 3 common analyses: homeowners' package (includes the bacteria and nitrate test), metal's package, and the DACT screen.  The video was created by the UWSP Water & Environmental Analysis Lab.

Video: How to collect a Water Sample

Resources on Common Contaminants:


The Calumet County Groundwater Program Annual Report highlights results from the Annual Private Well Testing Day and takes a look at overall trends from wells that have participated in the County Well Testing Programs. 

Click for the latest on test results countywide!

Calumet County Groundwater Report Announcement

Online Private Well Class

Want to learn more about private wells? This free online class is a short series of weekly programming for homeowners on private wells. Visit the Private Well Class website to sign up and get started. This is highly recommended for residents that are new to owning a private well.  PrivateWellClass.org is a collaboration between the Illinois State Water Survey at the University of Illinois Urbana-Champaign and the Rural Community Assistance Partnership, with funding from the U.S. Environmental Protection Agency.

www.privatewellclass.org and 10 week online class geared towards private well owners


Groundwater in Karst Areas 

The karst areas of Calumet County are sensitive to groundwater contamination. The unique geology and soils present extreme challenges in protecting groundwater from surface contamination. The upper layer of bedrock is a type of rock that is easily dissolved by water. Sinkholes, disappearing streams, and caves are visible examples of places where bedrock is dissolved. Vertical and horizontal fractures (or cracks) that for from dissolution act similar to a network of pipes underground and can rapidly move water (in some cases, water can move 100 feet or more per day) from the surface to the underlying aquifer.

In some areas, the soil can be very shallow (0 to 40 inches thick) and/or can consist of light textured materials. Soil is important for protecting water quality because it naturally filters contaminants picked up by rainwaters and snowmelt before they reach groundwater. Where there is little soil or light textured soil, there is little to no natural filtering of contaminants. Pollution on the surface of the land can directly and quickly impact water underground, creating significant health concerns if the contaminants reach wells.

Calumet County's private well testing program is a voluntary program that has sampled over 1800 wells since 2005. With over 4000 samples to date, the results indicate that over 1/3 of wells do not meet safe drinking water standard requirements for bacteria and/or nitrate.

Susceptibility Map of the Silurian Aquifer

Aquifer Susceptibility.jpg

Helpful Links

Wisconsin Well Water Quality Viewer

Wisconsin Well Water 101 (PDF)

What's Wrong with my Well Water - resources to help identify problems based on symptoms

Water Health Series: Filtration Facts (PDF) - in-depth information on different treatment systems available.

Wisconsin DNR Groundwater Collaboration Workgroup – links to the workgroup commissions out of the Kewaunee County events

Final Report of the Workgroup (PDF)

Documents