Butte County, SD: EPA's radon zone, explained

EPA's own radon map rates Butte County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. Nationally that's the 40th percentile for radon potential — Butte County outranks 40% of every county EPA has rated.

Butte County by the numbers

Butte County, South Dakota is home to about 10,891 people across 2,250.01 square miles. That works out to roughly 5 people per square mile. By population, Butte County is the 801st largest of every county sharing its EPA zone — the 22nd percentile by population within that zone. Geologically, Butte 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

Neither at the 4 pCi/L action level nor down at the roughly 1.3 pCi/L national indoor norm, Butte County's Zone 2 prediction lands in the gap between the two. A Zone 2 rating is a moderate county-wide average, not a guarantee about any one house in Butte County — testing is the only way to know an individual home's actual level.

If Butte County tests above the action level

For a Butte County homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.

Find South Dakota's state radon program

For Butte County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Butte County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.

Where Butte County's figures come from

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. Whatever zone Butte County carries, the zone explainer covers what it does and doesn't tell you about any one house.