What EPA's radon map says about Minnehaha County

Minnehaha County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Rank it against the rest of the country and Minnehaha County lands in the 97th percentile for radon potential.

Where Minnehaha County sits nationally

About 208,639 people live in Minnehaha County, South Dakota, spread over 806.86 square miles. Population density there runs about 259 people per square mile. Among counties sharing Minnehaha County's EPA zone, it outranks 91% of them by population. Geologically, Minnehaha County is grouped into EPA Region 8 alongside 290 other counties that share its rock and soil setting.

Why the zone isn't the answer by itself

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Minnehaha County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. Being in Zone 1 raises the odds Minnehaha County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.

Testing and mitigation in Minnehaha County

Mitigation cost doesn't depend on Minnehaha County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find South Dakota's state radon program

Minnehaha County's test kit answers today; a Airthings radon monitor keeps answering for Minnehaha County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

More on how this number was built

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.