‘Forever chemicals’ found in deep wells in areas with porous bedrock

Synthetic chemicals that persist indefinitely in the environment have been detected in the water of several deep wells in parts of Iowa with porous bedrock, according to the Iowa Department of Natural Resources.

The department began in late 2021 to test community water supplies for perfluoroalkyl and polyfluoroalkyl substances — commonly known as PFAS or “forever chemicals.” In the latest round of testing, one of the chemicals was discovered in Osage drinking water in a concentration that exceeds a safety threshold that has been proposed by federal regulators.

The water came from a well that is 676 feet deep, and it contained PFOS — one of the most-studied PFAS — at the rate of 4.8 parts per trillion.

That exceeds the U.S. Environmental Protection Agency’s proposed maximum contaminant level of 4 parts per trillion. The agency has indicated that much tinier concentrations of PFAS pose health risks to humans, but current test methods are only capable of detection at about 2 parts per trillion.

The depth of the Osage well is noteworthy because most of the contaminated municipal water supplies in Iowa draw from rivers or much shallower wells, which are more susceptible to surface contamination.

That is the case in Camanche, which is poised to drill two new deep wells to replace its two shallow wells that environmental regulators say were likely contaminated by a nearby facility that has produced the chemicals.

Osage is located in an area of porous bedrock known as karst, which has the potential to accelerate the penetration of surface contaminants into the ground.

“That karst area is more vulnerable because of that fractured bedrock,” said Corey McCoid, supervisor of the department’s water supply operations. “With Osage, we have a specific reason (for testing). It was in the fire station. It’s an old well.”

Firefighting foam is a prominent source of PFOS contamination, and the Osage well is at the site of a former fire station.

It’s unclear how much of a role the geology of Osage has in the well’s contamination, but McCoid noted it is a very old well — drilled in 1912 — and could be contaminated via cracks in its casing.

McCoid said Osage is in the process of replacing the well with a new one.

Karst bedrock is most prevalent in northeast and east-central Iowa. Two other cities with the potential for that geological formation also have deeper wells with PFAS contamination, according to DNR testing.

A Buffalo well that is about 405 feet deep was found to have PFOA in a concentration of 3.1 parts per trillion. That is less than the maximum contaminant level of 4 parts per trillion that has been proposed by the EPA.

In Princeton, a well that is 455 feet deep well has a less-prominent PFAS chemical in a concentration of 8.3 parts per trillion. That chemical, PFBA, does not have a proposed maximum contaminant level.

Both of those wells are about 60 years old. Their locations in karst terrain do not automatically increase their risk for contamination, said David Cwiertny, director of the Center for Health Effects of Environmental Contamination at the University of Iowa. Some wells penetrate impermeable layers of clay or rock that can block contaminants from reaching the aquifer beneath.

“But I’m guessing that if (PFAS is) down there, it’s got to come from somewhere, and it’s likely gotta come from some sort of contamination that’s made its way into the ground, and karst just speeds that process up,” Cwiertny said.

Of the 36 water supplies the DNR sampled from March to June this year, nine had detectable amounts of various PFAS in their wells but didn’t exceed EPA health advisories.

They included the cities of: Atlantic, Carlisle, Mondamin, Sheldon, Silver City, Van Meter, Waukon and Waverly.

Osage was the only city in the latest round of testing with PFAS that exceeded a health advisory. It is among a dozen water supplies with recent test results that exceed an advisory.