2019 floodwaters

2019 floodwaters cover a Saline County field at Grand Pass, near the Missouri River in north central Missouri.

Flooding across the Midwest this year presented heightened concerns about water well contamination.

After the floodwaters recede, one thing homeowners whose water supply comes from a private well should do is check the quality of the water, according to state and county officials. That is especially true if floodwater covered the above-ground portion of the well.

“A well over-topped with water has a lot bigger chance of being contaminated with bacteria,” said Steve Wilson, groundwater hydrologist with the Illinois State Water Survey. “If a well is in a flooded area where it’s over-topped, you shouldn’t drink the water until it’s been tested. If there’s something in it, you obviously need to disinfect the well.”

An older well may also be vulnerable, even if it was properly covered and sealed.

“Even though it may have a sanitary well cap, sometimes — if it’s been there a while — that rubber seal that fits there could get brittle. It’s possible it has cracks in it,” he said. “And it’s possible that it wasn’t sealed properly, or someone opened it up for whatever reason and didn’t get everything put back snug.”

Several communities in Jackson County, Illinois, whose 15-mile western border abuts the Mississippi River, were heavily flooded this year. Many residents have responded by having their water tested.

“We’re not flooded with requests, but we’ve had a few more than usual,” said Steve Williams, environmental health inspector with the Jackson County Health Department. “Not just in the bottoms, but people living in the flood fringe, near streams, may have had their wells over-topped.”

The department offers water tests at no charge for all residents with water wells on their property.

“They test for bacteria to make sure the water is safe to drink,” Williams said. “We can also do a field test for nitrates. If they’re concerned about water quality, we usually refer them to the Illinois Water Survey.”

Experts at a recent water quality conference in North Carolina said wells that have been over-topped with floodwater are five times more likely to be contaminated than those that were not flooded.

Wilson added homeowners whose wells have come into contact with floodwater sometimes hesitate to call authorities because they fear they will not be allowed to use the well anymore. That is a common misconception.

“Some people don’t want to call their local health department because they think they’re going to tell them they can’t drink their water. That’s not true,” Wilson said. “The health department doesn’t have the authority to tell anyone they can’t drink their water. They can certainly recommend you don’t.

“I had a well owner in Illinois who had very high arsenic and they had kids. But in the end, it’s up to the well owners themselves.”

At the very least, those who have concerns about contamination should boil their drinking water before determining the quality of the water source, he said.

“You can boil the water in between to be safe,” Wilson said. “Once you know it has bacteria, you want to disinfect it with shock chlorination. You put chlorinated water in your well because it kills bacteria. There’s a procedure for that. It’s a bone of contention, because different people give different advice. Sometimes drilling contractors don’t know the proper way to do it also. There are a lot of misconceptions.”

While wells over-topped with floodwater are at the highest risk for contamination, it’s possible tainted groundwater could also affect water quality in a home well.

“It could seep in if the well is not properly sealed,” Wilson said. “The well code in most states now requires you to put grout around the well. For a bored well, it’s 10 feet of film material before the large diameter of the well starts.

“… In certain geologies, or the well was put in before regulations took place, it may not have grout. I grew up in a household that had an old, hand-dug well. When it rained really hard, we had cloudy water. It’s especially likely those wells could be contaminated.”

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Nat Williams is Southern Illinois field editor, writing for Illinois Farmer Today, Iowa Farmer Today and Missouri Farmer Today.