Heavy flooding won’t only compromise structures and roadways — it can also breach wells, infecting drinking water with a “toxic brew” that can yield uncomfortable, and on rare occasions deathly, results for rural homeowners.

“The primary concern is bacteria contamination, particularly in the water levels overflow into the wells,” Minnesota Department of Health hydrologist Chris De Mattos said. “A flood water contains all kinds of organisms, and some of them are pathogenic — that means they can make you sick.”

Bacteria, such as viral hepatitis, E. coli, shigella and cryptosporidium, which most often derive from manure and sewage, are among the contaminants that can spill or leak into private wells, which are concentrated outside city limits countywide. Add pollutants picked up from farm fields, such as pesticides, and from flooded homes, such as cleaning products, gasoline and oil, and property owners can face health concerns deserving of immediate attention, well experts say.

“Flood waters can carry all sorts of things in them — solvents, ag chemicals, lawn chemicals, cleaners,” De Mattos said. “Anything you store in your basement and under your sink…”

According to De Mattos and Mower County Environmental Services Health Specialist Bill Buckley, old wells are particularly susceptible to contamination, even if waters haven’t capsized the top, because they can be infiltrated from below.

“They can get in more indirectly if you have old, poorly-constructed wells,” De Mattos said. “And there are a lot of those in the region.”

He added that old wells often suffer poor construction, shallow depths and thin casing, all of which may allow pollutants in. In addition, many old wells are also located in basements, according to Buckley, which, if flooded, also puts drinking water as risk, he said.

But property owners with newer wells don’t necessarily evade risk. Even the best wells can be breached by flood waters, particularly when high levels rise above well tops, they said.

“Even wells up to current code — the types of caps that are put over wells are excellent, but they still are vented,” De Mattos said. “They are not water tight.”

County and state departments recommend tests for anyone who’s had flooding within 50 feet of his or her water source or knows water has overcome the top.

“Any well that has had water over the top of it or around it or is located by a river that flooded should be tested,” Buckley said.

Until Thursday, Mower County Environmental Services is offering free testing for bacteria contamination, as authorized by county commissioners in years past. Bacteria and nitrate tests are $21 each otherwise.

According to De Mattos, a legislative study funded after flooding in Winona and Houston Counties last summer found that other types of contaminants — such as pesticides and solvents — typically don’t remain in drinking water long.

“The basic results from that is we found a low level of contaminants, but that was very short-lived,” he said. “And that’s essentially what we suspected.”

In 2004, which resulted in the largest flood in Austin’s history, Mower County tested about 140 wells; the state department also assisted.

This year, the health department has targeted their efforts in other regions, including Houston and Fillmore Counties, struck by several days of flooding mid-June. Mower County experienced the third-worst flood on record after thunderstorms June 11 saturated the region’s three main tributaries — Cedar River, Dobbins Creek and Turtle Creek — to crisis levels.

Buckley said experience has compelled many rural residents to seek testing for their wells, having been afflicted in the past.

“We’re certainly seeing an increase in the number of wells being tested, and they are related to flooding,” he said.

To request a test, residents must visit the environmental services office, at 1105 1/2 Eighth Ave. N.E., for a kit, which they take home and fill with a sample of their well water. The Mower County Office has a lab on site for the test, and can offer advice to affected property owners about well decontamination.

Most can clean wells themselves, though depending on the complexity of their pump system and other factors, may need to seek well contractors for the work. Costs can range between $50-$300, Buckley said.

De Mattos added that one can take measures to help prevent well contamination, though stated that such precautions provide no guarantees against infiltration.

“You certainly can do something — take a plastic bag, and tape it to the top of the well,” De Mattos said, recommending something thicker, such as a tarp or garbage bag.