Minnehaha County, South Dakota: drinking water report. Minnehaha County in southeastern South Dakota has about 198,000 residents, with Sioux Falls as the…
Minnehaha County in southeastern South Dakota has about 198,000 residents, with Sioux Falls as the largest city. The Lewis & Clark Regional Water System, Big Sioux River, and deep wells supply the area. Sioux Falls draws primarily from wells in the Big Sioux Aquifer and the Madison-Prairie du Chien aquifer system. The Big Sioux River watershed drains intensive agricultural land and receives discharges from meatpacking plants and other industries.
The Big Sioux River carries agricultural contamination from upstream. According to the South Dakota DENR's 2024 water quality report, nitrate at the Sioux Falls intake averaged 5.1 mg/L during spring – elevated but below the MCL. Atrazine detections are seasonal, peaking in May and June following spring planting.
Joe Foss Field (Sioux Falls Regional Airport) and the South Dakota Air National Guard have documented AFFF use. The South Dakota DENR's 2024 PFAS investigation found PFOS at 7 ppt in monitoring wells near the airport, below federal MCLs. Sioux Falls' deep well supply is naturally protected by clay layers that limit contamination migration from the surface.
Sioux Falls' deep aquifer supply provides a naturally well-protected water source. The city's treatment system handles the surface water inputs effectively. For most residents, the primary concern is aesthetic – high mineral content that affects taste.
Check your water for the latest results. For taste improvement, a carbon filter is typically sufficient. For additional protection against PFAS and other emerging contaminants, reverse osmosis goes further. Our water filter guide covers systems suited to Great Plains water. Pull your detailed report for trends, and visit our South Dakota page for statewide context.
Drinking water is one exposure route. These federal datasets also cover Minnehaha County, SD.
The EPA places Minnehaha County, SD in Zone 1 - the EPA's highest-risk category, where the predicted average indoor radon level is above 4 pCi/L. Zone maps predict an area's radon potential from geology and existing indoor readings; they say nothing about a specific house. Testing is the only way to know your own level.
44% of homes in Minnehaha County, SD were built before 1980, and 15% before 1950. Residential lead paint was banned in 1978, so housing age is the strongest available proxy for lead-paint exposure. This describes the county's housing stock, not any one home.
Modelled annual fine-particle pollution (PM2.5) in Minnehaha County, SD averages 5.3 µg/m³, within the EPA's annual standard of 9 µg/m³. These are CDC modelled county estimates rather than readings from a specific monitor.
How radon zones work · Air quality by county · Lead exposure guide