Wisconsin Department of Natural Resources (WDNR) has concise guidance on flooded wells. See https://dnr.wi.gov/topic/wells/flood.html
Kevin Masarik, Groundwater Education Specialist, UW Extension/Stevens Point, provided 3 basic steps.
If the well or area around the well has been in contact with flood water:
- Stop using your well water for drinking and cooking
- Have your well and plumbing disinfected. The procedure for disinfecting a well is outlined in the DNR brochure “Bacteriological Contamination of Private Wells” or contact a licensed well driller or pump installer to perform a well disinfection.
- Only after obtaining a safe bacteria test from the disinfected well should you begin using your well water again for drinking and cooking
Even if the area directly around the well may not have been inundated, other signs that a well may have been compromised by heavy rains would include sudden changes in taste, color, odor or clarity of the well water. If any of these are observed protocol for flooded wells should also be followed.
Here is a list of labs certified to test for bacteria. Contact the lab first to obtain a sample test kit and instructions: https://dnr.wi.gov/topic/wells/documents/privatelabs.pdf