NOTE: In light of the recent Midwest floods, this is the third in a series of safe flood recovery stories produced by the University of Nebraska Medical Center to assist people in their recovery efforts.
As the ravages of Nebraska’s catastrophic March flooding are experienced and assessed across the state, well owners in flooded areas are advised to test well water to verify if it’s safe to drink and inspect the well to identify any unseen damage.
Due to the wide range of contaminants associated with the flood - including animal and septic waste, animal carcasses, chemicals and fuel - water testing is key to identifying and treating potentially harmful microbiological elements of well water. Until testing is completed, bottled water is the safest source for drinking and cooking.
"Certainly, if a well was covered by flood water, it needs to be evaluated once flood waters recede," Professor Bruce Dvorak, Ph.D., at the University of Nebraska-Lincoln (UNL) College of Engineering said. "If there’s reason to believe that flood waters may have come within 100 feet of your well, it’s advised that you evaluate the well to identify any damage and test the water for contaminants."
In some instances, compromised wells will need to be cleared of debris deposited by the flood around and/or within the well. In addition to a well’s control box, breaker box, pressure switch, and pressure tank, the well casing may have been compromised by the presence of flood water or flood debris. Even if flood water didn’t engulf a well, a certified well installer has the necessary expertise to identify any well equipment or operation issues.
"Hire a licensed water well contractor to do this work," Dr. Dvorak said. "They know what to look for and how to repair any damage that occurred."
Washouts or significant loss of topsoil around the well may need to be addressed. A licensed water well contractor will quickly recognize these types of damage.
Becky Schuerman, UNL Extension associate for domestic water and wastewater management, recommends that even well owners who believe their well is functioning normally after flood waters recede should contact a Nebraska licensed water well contractor.
Before consuming any water from their well, they should at least have their water tested for total coliform and E.coli. Public drinking water sources are required to be tested regularly for these bacteria. Fecal coliform also may be a concern immediately following a major flood.
"Private drinking water safety is every bit as important as the safety of our public drinking water sources," Schuerman said. "We suggest following the EPA public water supply testing requirements. Contact a certified lab in Nebraska for the testing. Well owners will want to order a Quanti-tray test kit so their test results quantify the amount of coliform and E. coli present in the water. This testing costs about $17 at the State Public Health Environmental Laboratory."
If any nearby chemical facilities or warehoused supplies were breached by flood waters, well owners may want to conduct more extensive water testing to rule out any unusual contaminants.
"Your local Natural Resources District will be a good resource for identifying the potential for this type of contamination," Schuerman said. "Neighbors also may be able to provide information about chemical supplies suspected of entering the flood waters."
If there’s suspicion that well water is contaminated, the water should not be used for drinking, washing dishes, brushing teeth, washing or preparing food or making ice. Most bacteria are killed when water is brought to a rolling boil for at least one minute.
Shock chlorination is an inexpensive method used to disinfect a water system contaminated with bacteria. This process introduces high levels of chlorine into a water system. During the disinfection process, the water is not suitable for consumption or extended contact by either people or animals. Once the chlorine is introduced to the water system, the water should not be used for a minimum of eight hours, and preferably for 12 to 24 hours.
"If bacteria is found in the well water, lines running from the well to the home and outbuildings also should be treated," Schuerman said.
Before implementing shock chlorination, the integrity of the well must be restored to avoid contamination from sources such as animals, insects, debris or surface water. The well casing should be sanitarily sealed at the wellhead to prevent entrance of contaminants.
After the waiting period (8-24 hours), the well and water system must be flushed to clear it of residual chlorine. The water should be drained in an open field or low-lying ditch. Avoid the home septic system, since chlorine kills bacteria necessary to break down septic tank waste. The chlorinated water also will harm grasses and shrubs, so these areas should be avoided.
Inside a home, no more than 100 gallons of the chlorinated water should be flushed down the drain to the home’s septic system. Once the chlorine odor dissipates, the water should be safe to use.
"Make sure you have completely flushed your system of chlorine before testing again," Schuerman said. "Residual chlorine will interfere with obtaining accurate bacteriological test results."
Due to the serious nature of the March flood, well owners are encouraged to test water supplies again to ensure that no further contamination has occurred. A licensed water well contractor can help determine the need for follow-up testing.
"Wells drilled after 1988 were constructed under state water well construction standards and are less prone to contamination than older wells," Schuerman said. "The newest standards that went into effect in 2014 include the use of research-based grout layers to help stop well aquifer contamination. However, they’re likely to have a vent at the top that can be breached if it’s submerged. And there’s always the chance that rushing flood waters and/or debris might compromise the integrity of the wellhead."
Dr. Dvorak also is encouraging well owners to consider how to protect their well in the event of a future serious flooding incident.
"We would all like to think this is a once-in-a-lifetime event," Dr. Dvorak said. "However, we can’t rely on that. There are some basic steps that can help protect a well if another flood event threatens your property."
Disconnecting the well power supply can help protect pumps and screening on well vents can help keep flood debris from entering the well. A licensed water well contractor may be able to install a water-tight plug in the well or extend the vent to a level above potential flood water.
"If you anticipate a flood, you may consider using heavy duty plastic to cover the well head, securing it with waterproof tape to help minimize flood debris and sediment damage," Dr. Dvorak said. "Water-inflated flood barriers also may be an option for protecting a well."
Contact information for laboratories that are certified to do total coliform and E. coli testing for public water supply systems can be found here.
Additional details about restoring and maintaining a well in Nebraska following a flood are available here.