What EPA's radon map says about Tripp County

EPA's own radon map rates Tripp County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. Tripp County sits at the 36th percentile nationally for radon potential — above 36 of every 100 rated counties.

Where Tripp County sits nationally

About 5,717 people live in Tripp County, South Dakota, spread over 1,612.289 square miles. That works out to roughly 4 people per square mile. Among counties sharing Tripp County's EPA zone, it outranks 10% of them by population. EPA's geology-based Region 8 groups Tripp County with 290 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

Call it a middle case: above the 1.3 pCi/L most US homes average, below the 4 pCi/L line EPA uses to recommend mitigation — that's Tripp County's Zone 2 prediction. A county-wide moderate average, like Tripp County's, can still hide a specific house well above or below it — testing is what actually answers the question.

If Tripp County tests above the action level

Mitigation cost doesn't depend on Tripp 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

Tripp County's test kit answers today; a Airthings radon monitor keeps answering for Tripp County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 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. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.