Floods & Water Wells

Important information for well owners whose wells are in or near flood area

Contaminated well water can make you sick. Never consume water from a well if there is any chance the well has been impacted by flood waters. You need to test your well water to determine if it is safe.

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Free Water Testing After Flooding

Find out more by contacting your local county environmental health sanitarian. Ask to participate in the Private Well Grants Program for water testing administered by Iowa Health and Human Services (HHS).

  • Test for coliform (bacteria) and fecal coliform (e.coli) to determine if additional well services like shock chlorination or well clean-out are needed to assist making the water coliform free.
    • Note: Giardia, cryptosporidium, and other parasites from sewage and feces are not detectable with bacteria and e.coli tests, but can cause severe illness. Please see this CDC germs webpage to learn more. If you suspect that your well has been contaminated with flood water, then ask your local county health department to contact the State Hygienic Laboratory to test for those specific parasites.
  • Test for nitrate as N. Then once each year unless near or above 10 mg/L as N, then twice each year is recommended.

If your well is positive for coliform (bacteria) and/or fecal coliform (e.coli), then you should take the following steps:

  1. Purge and shock chlorinate your well and water system
    1. Iowa's Private Well Grants Program can reimburse you up to $400 for this work. 
    2. Note: Giardia, cryptosporidium, and other parasites are not removed by shock chlorination. Please see this CDC germs webpage to learn more about treatment.
  2. Retest your well for bacteria, fecal coliform, and nitrate 7-10 days following shock chlorination (per Center for Disease Control guidelines).
  3. Repeat 1-2 until your well has zero coliform and fecal coliform.
  4. When nitrates near or above 10 mg/L as N, you should treat the consumable water used in the home. Information about treatment for private wells can be found on the Private Well Program webpage.

Why?

Floods can cause water quality problems with water supply wells - even if your well isn't directly in the flooded area. During a flood, the increased groundwater loading nearby a well can cause well contamination. Contaminated surface water can also leak into a well through defects in the well's casing or physically run over the top of the well and cause direct contamination of the aquifer.

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Common Contaminants in Flood Water

Flood water often contains infectious bacteria, viruses, agricultural or industrial chemicals, and other hazardous agents. Keep in mind that anything that is being stored in flooded areas has the potential to be part of the flood water. Because of this, consuming contaminated water can cause serious illness - especially in infants, individuals with compromised immune systems, and our elderly population. 

Water testing is the only way to know if your well is affected. Note that parasites which are often found in flood water are not detectable with standard bacteria and e.coli tests. If you suspect that your well has been contaminated with flood water, then ask your local county health department to contact the State Hygienic Laboratory to test for those specific parasites.

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