What EPA's radon map says about Columbia County

Columbia County is mapped as Zone 2 - Moderate Potential by EPA — meaning the county-wide average indoor level is predicted between 2 and 4 pCi/L. That puts Columbia County in the 56th percentile nationally for radon potential — higher than 56% of the counties EPA has rated.

How Columbia County compares

About 58,113 people live in Columbia County, Wisconsin, spread over 765.6 square miles. That works out to roughly 76 people per square mile. Among counties sharing Columbia County's EPA zone, it outranks 70% of them by population. Geologically, Columbia County is grouped into EPA Region 5 alongside 523 other counties that share its rock and soil setting.

What this actually means for a house in Columbia County

Neither at the 4 pCi/L action level nor down at the roughly 1.3 pCi/L national indoor norm, Columbia County's Zone 2 prediction lands in the gap between the two. A county-wide moderate average, like Columbia County's, can still hide a specific house well above or below it — testing is what actually answers the question.

If Columbia County tests above the action level

Mitigation cost doesn't depend on Columbia 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 Wisconsin's state radon program

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

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.