The murky brown Big Sioux River consistently receives poor marks for itswater quality, but eastern South Dakota water systems near the river dont know if that pollution includes forever chemicals.
To find out, researchers from South Dakota Mines are testing for per- and polyfluoroalkyl substances (PFAS) at the behest of the East Dakota Water Development District.
The study will cost the district at least $100,000 to test 11 sites from northeast South Dakota to the Iowa border past Sioux Falls, including four more sample runs throughout 2025.
Ideally, well find nothing, and well have spent a lot of money to do that, said Jay Gilbertson, district manager. But right now, we dont know if there is PFAS in the river. Its hard to be proactive and plan if you dont have information.
Aseparate, federally funded projectthrough the South Dakota Department of Agriculture and Natural Resources was announced earlier this year to assess and clean up contaminated sites in South Dakota. Falls Park, quarry lake and a former rubble site just south of the Sioux Empire Fairgrounds in Sioux Falls are being tested for PFAS and other contaminants that pose risks to the Big Sioux River. The project is in the planning phase, and testing has not started yet.
The chemicals have been used in industry and consumer products since the 1940s and dont break down easily in the environment or in the human body. Research indicates PFAS exposure may be linked to negativedevelopmental and reproductive effects, and an increased risk of some cancers.
The federal governmentestablished new limitson some types of PFAS in drinking water earlier this year. Those limits apply specifically to treated drinking water. The limits do not apply to chemicals found in waterways.
Water treatment plants along the Big Sioux River can pull directly from the river or pull from underground wells near the river. Sioux Falls is the only water system that pulls water from the Big Sioux River, but the city rarely uses the river as a water source.
An ongoing study indicates that, under the right conditions, Big Sioux River water caninfiltratewells near the river.
Gilbertson saw water treatment plants in southeastern South Dakota along the Big Sioux River several years ago experience an influx of hard water in their systems. He said the culprit was Lake Poinsett, near Watertown, which began discharging water into the Big Sioux that seeped into underground wells used by some treatment plants downstream.
Thats why its better to go looking for it, Gilbertson said, so water treatment plants can prepare solutions before contamination becomes a crisis.
If PFAS is found in the Big Sioux River, the water district can inform public water suppliers, Gilbertson added.
Maybe we tell them, if they can, not to use the well thats so close to the river; reactivate one a little farther away, Gilbertson said. As a result, they might not technically have a problem and have to stop serving customers because they stopped using the water before it became a problem.
PFAS has been detectedin wells near Ellsworth Air Force Base at Box Elder, as well as Sioux Falls Regional Airport and its co-located Air National Guard base, where the chemicals were used in firefighting foam. The forever chemical has also been detected in wells at National Guard facilities near Custer and in Rapid City, and inthree private wellsin South Dakota.
Sioux Falls suspended 21 of its wells suspected of PFAS contamination after the detection. Since then, all raw water samples which can include the Big Sioux River at times have been tested for PFAS compounds, said Sioux Falls Water Superintendent Chris Myers in an emailed statement. The city has not detected PFAS in those sources.
But even if Sioux Falls doesnt find PFAS in river tests, that doesnt mean there isnt PFAS in the river: It just means its not immediately upstream, Gilbertson said.
It doesnt necessarily preclude it from the upper basin or below the city, he added.
Most recently, a preliminary sample ofMount Rushmore National Memorials drinking waterhad levels of PFAS more than two times higher than the new federal limit.
The South Dakota Association of Rural Water Systems is testing 40 rural water systems throughout the state for PFAS chemicals in cooperation with the EPA. Cities are also testing their water andsubmitting it to the EPA.
Lisa Kunza, associate professor in chemistry, biology and health sciences and director of the Center for Sustainable Solutions at South Dakota Mines in Rapid City, helped collect the initial Big Sioux River samples in September.
Kunza and her team research PFAS contamination impacts on water resources, agriculture and human health. Theyre looking for 40 PFAS compounds in the water. She said the initial test results could take a month to several months to get back from the lab.
About South Dakota Searchlight: We use our journalistic searchlight to illuminate critical issues facing South Dakota, dissect the decisions made by state leaders, and explain the consequences of their policies and the role of politics on South Dakotans.South Dakota Searchlight launched in 2022. Were an affiliate ofStates Newsroom, a national 501(c)(3) nonprofit supported by grants and a coalition of donors and readers. The staff of the Searchlight retains full editorial independence.
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