In addition to cleaning up flood damage, watching sump pumps and monitoring dikes, residents in the Fargo-Moorhead area must also deal with potential contamination of drinking water as the Red River crests this weekend. Contamination of drinking water after a flood is âÄúvery much a threat to public health,âÄù especially to people who draw their water from private wells, said Barbara Liukkonen , a coordinator at the University of MinnesotaâÄôs Water Resources Center. There are no private wells within the Fargo city limits, Miles Schacher , who works for the Cass Fargo Environmental Health division, said, but the city is continuously monitoring its water supply on the slim chance it becomes contaminated. Liukkonen said publicly controlled water supplies are usually safe because government agencies do a good job of proactively cleaning and monitoring the system. In case of contamination, she said the water supply can be shut off or residents can be warned to boil their water. But for people who draw water from a private well, encroaching floodwaters can contaminate the source with bacteria or parasites without the owner knowing. âÄúPrivate wells are a different thing,âÄù Liukkonen said. âÄúNobodyâÄôs really in charge of those.âÄù After the widespread flooding of the Red River in 1997, the Environmental Health Division tested about 500 samples from area wells, Schacher said, and found about 90 percent of the wells that had not been disinfected were contaminated in some way. Although there havenâÄôt been widespread problems with drinking water contamination due to the first crest of the Red River, the potential flooding of the Sheyenne River along with another expected crest of the Red River Friday or Saturday means a wider area will be affected by the flooding and there will be more potential for wells to be contaminated than after the first cresting, he said. A well can become contaminated when dirty flood water washes up over the wellâÄôs lid and leaks inside of the system. Flood waters can be contaminated with a variety of things, ranging from chemicals like automotive fluid and fertilizer to animal waste and other bacteria living in the ground. Although chemicals usually become diluted enough in the water to pose no threat to human health, infectious agents like parasites or bacteria found in waste can spill into wells and multiply, contaminating the water and making those who drink it sick. Liukkonen said diseases like hepatitis or dysentery can be spread through contaminated water, but the more common effects are nausea and diarrhea. Septic tanks are one possible source of contaminating waste, said Nick Haig, a septic specialist with the University Water Resources Center. Although septic tanks are required to be checked every few years for leaks, Haig said assuming all tanks are in compliance is âÄúnaive.âÄù When flood waters inundate a tank that isnâÄôt water tight, Haig said waste can escape and contaminate the flood waters. âÄúAny water that comes into a tank can also come out,âÄù he said. Disinfecting wells is a fairly simple task and Liukkonen recommended people disinfect their wells after a flood, even if theyâÄôre not sure itâÄôs been infected. All that is needed to clean a well is bleach, Liukkonen said. After pouring the bleach into the well, she said people should run all their faucets until they smell chlorine, after which they should shut off the water and avoid using it for at least eight hours. Until the well has been disinfected, residents can clean smaller batches of water by cooking it at a rolling boil for one minute, she said. After disinfecting, Schacher said residents can send in a sample of their well water to the Cass Fargo Environmental Health Division to see if they successfully cleaned their well.