June 19, 2014
Private water wells contaminated with flood water can pose health risk; owners urged to take precautions before and after flooding
Recommendations for steps to protect wells and users' health now posted on MDH website
Heavy rains causing overland and flash flooding have put some Minnesota homeowners' private wells under water and threatens many others. The Minnesota Department of Health (MDH) is advising well owners that private water wells contaminated with flood water can pose a health risk. So it's important to take precautions to protect your well and your health before flooding, if possible, and take corrective actions if your well is flooded.
Under current conditions, flood waters could rise quickly and may be fast-moving in some areas. Well owners should not put themselves at risk trying to protect their wells when they should be seeking safety from floodwaters. Stay attuned to local conditions.
MDH recommends that well owners take the following steps if they think their well may become flooded:
- Store a supply of clean water before taking your well out of service.
- Disconnect the power supply for your well. If you need help, consult with a licensed well contractor or pump installer.
- If you have time, have a well contractor install a water-tight cap or cover on your well – temporarily replacing the regular vented well cap or seal.
- If you don't have time to have a professional install a watertight cap, clean off the outside of the well casing and cover the top of the well with a heavy-duty trash bag or some other form of heavy plastic sheeting. Secure the plastic covering with electrical tape or some other type of waterproof tape or strapping material. Do not use duct tape – it won't hold under flooding conditions.
- Be prepared to have your well disinfected and tested after the flood waters recede, if your well does become flooded. Installing a water-tight cap or securing a plastic covering won't eliminate the need for disinfection and testing, but it will help keep debris and sediment out of the well, and make the post-flood clean-up go more smoothly.
- If flood waters cover the top of the water well casing, water from your well should not be used for drinking or cooking until the floodwater recedes and the well is disinfected and tested. Until then, use bottled water for drinking, cooking, or brushing your teeth.
After the flood waters recede, if the water reached your well casing, assume your well is contaminated. You should take the following steps to make sure your well is safe:
- If your well was not protected prior to the flooding, have a professional well driller clean out any sediment and debris. Using your well pump to flush out the well could ruin the pump. A directory of licensed well contractors is available on the MDH website at: www.health.state.mn.us/divs/eh/wells/lwc/.
- Disinfect the well yourself or have a well contractor disinfect the well. Disinfect the well using a chlorine solution before having it tested. Detailed instructions are available at: www.health.state.mn.us/divs/eh/wells/waterquality/disinfection.html.
- After disinfecting the well and pumping out the chlorine solution, contact an MDH-certified testing laboratory about submitting a water sample. Tell the lab staff you need to have your well tested for coliform bacteria – or simply "bacteria." They will tell you what you need to do, and provide a bottle for the sample. To find a lab, contact your local health department, or go to: https://apps.health.state.mn.us/eldo/public/accreditedlabs/labsearch.seam.
- Be prepared to repeat the disinfection and testing process several times, if necessary, to ensure that your well is free of bacterial contamination.
- Don't drink water from your well until the lab has informed you that it is safe and free of bacterial contamination.
If flood water came within 50 feet of your well – but did not reach the wellhead:
- You may still want to have your water tested as a precaution.
- You should not need to disinfect your well before having it tested.
If flood water did not come within 50 feet of your well, you do not need to do anything and your well should be fine.
For more information about well safety and protecting your health during a flood, visit www.health.state.mn.us/divs/eh/emergency/natural/floods/.