MDH urges private well owners in areas at risk of floods to take action to avoid contamination

As communities around the state prepare for spring flooding, Minnesota health officials are reminding private well owners and users of the importance of taking preventive action to reduce the possibility of their drinking water becoming contaminated by floodwaters.

Wells contaminated with floodwater pose a health risk, but the impact floodwaters have on wells and water quality are often not as visible as other flood damage. With that in mind, the Minnesota Department of Health (MDH) offers well users the following recommendations:

If your well is in a flood-prone area and you have time, consider contacting a licensed well contractor to check your well and make any necessary repairs or changes to help protect it from flooding. These changes may include repairing cracked or damaged casing, extending the well casing above the expected flood level or temporarily replacing the vented well cap with a watertight cap or cover. You should also make sure that grading allows water to flow away from your well.

If you think your well might become flooded, store a supply of clean water that will last for at least a few days. Shut off power to the well pump to avoid having floodwater pumped into your plumbing system or home. If you only have a little time before a flood, you can cover the well with a heavy plastic bag or sheeting and secure it with electrical tape. This won’t completely protect your well from contamination, but it will help reduce the amount of water and debris that could enter your well, making clean up easier.

If floodwater reached your well, assume your well is contaminated. Water from your well should not be used for drinking, cooking or brushing your teeth until the floodwater recedes and the following steps have been completed:

• Avoid electrical shock. Do not approach a flooded well until it has been completely disconnected from its power source.
• If floodwater covered your well or may have entered your well directly, have a licensed well contractor inspect the well, clean out sediment or debris and disinfect it. Using your well pump to remove sediment or debris could ruin the pump. A directory of licensed well contractors is available at: Licensed Well and Boring Contractor Directory.
• If floodwater reached your well but you are confident that floodwater did not enter the well, have a licensed well contractor disinfect your well or complete the disinfection yourself. Detailed instructions are available at Disinfecting Flooded Private Water Wells.
• After you or the licensed well contractor disinfects your well and pumps out the chlorine solution, contact your county health department or laboratory accredited by MDH to get your well tested. Tell them you need to have your well water tested for coliform bacteria. They will provide sampling instructions. Accredited Labs in Minnesota Accepting Samples from Private Well Owners (PDF).   
  • If your well water test comes back positive for coliform bacteria, repeat the disinfection and testing process. You may need to disinfect and test your well several times before your well is free of bacterial contamination.
  • Do not use the water from your well until the lab has informed you that it is safe and free of bacterial contamination.

If floodwater came within 50 feet of your well – but did not reach the well – MDH recommends that you have your well water tested for coliform bacteria as a precaution. You do not need to disinfect your well before having it tested. However, if the test comes back positive for bacteria, the well needs to be disinfected.

For well owners who need more information, please contact the Well Management Section at MDH at health.wells@state.mn.us or 651-201-4600 or 800-383-9808 or visit the Floods and Flood Precautions For Private Water Wells pages on the MDH website.

Media inquiries:
Doug Schultz
MDH Communications
651-201-4903
doug.schultz@state.mn.us