Is radon high in Dewey County, South Dakota?

Moderate. The model predicts a long-term basement average of 3.2 pCi/L in Dewey County (about 1.7× the US average of 1.8 and about 18% below the South Dakota average of 3.9). That is in the 2-4 pCi/L range where the EPA recommends considering mitigation. Ranked 53 of 66 South Dakota counties.

Should I test for radon in Dewey County?

Yes, soon. With a predicted average of 3.2 pCi/L, many homes in Dewey County will test above the 4 pCi/L action level. Use a short-term kit first; if it reads 2 or higher, confirm with a long-term test or continuous monitor before deciding on mitigation.

What does EPA Radon Zone 2 mean for Dewey County?

Zone 2 - moderate potential (2-4 pCi/L). The zone map dates from 1993 and classifies whole counties. The 2001-2021 model agrees with the zone here. Neither replaces a test of your own home.

How much does radon mitigation cost in Dewey County?

A standard active sub-slab depressurization system typically runs $800-$2,500 installed nationally; South Dakota quotes vary with foundation type (slab, crawlspace, basement), home size and local labor. Get two or three bids from certified mitigators listed by your state radon program or the EPA's find-a-professional page.

Radon levels in Dewey County, South Dakota

ModerateEPA Zone 2

Predicted long-term basement average of 3.2 pCi/L (model estimate) across 4 ZIP codes - about 1.7× the US average of 1.8, about 18% below the South Dakota average of 3.9. Ranked #53 of 66 South Dakota counties.

Test Dewey County, SD - the EPA says "consider fixing" in this range

The predicted basement average here is 3.2 pCi/L, in the 2-4 pCi/L band where the EPA recommends considering mitigation. Plenty of individual homes in a moderate area test above 4. Start with a short-term test; if it comes back at 2 or higher, follow up with a long-term test or a continuous monitor.

Get a short-term test kit →Or track it with a continuous monitor

Already tested at 4 pCi/L or higher? Find a certified mitigation professional (EPA). A mitigation system typically runs $800-$2,500 installed.

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Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. How the numbers work.

3.2 ± 0.06

pCi/L predicted basement mean (model SD)

2.0 ± 0.08

pCi/L predicted upstairs (above-ground) mean

2.5-3.7

range of ZIP-level basement predictions in the county

What this means for Dewey

The typical Dewey County home is predicted in the 2-4 pCi/L band. The EPA's guidance for this range is to consider fixing, because there is no known safe level and roughly one home in several in a moderate area will test above 4.

The 1993 EPA zone (2) and the 2001-2021 model agree for Dewey. County figures weight each ZIP by its 2010 Census population, so they describe where people live rather than empty land.

Comparable South Dakota counties: Minnehaha County (3.2), Corson County (3.1), Harding County (3.1), Tripp County (3.1). The state's highest is Jerauld County at 5.2 pCi/L.

ZIP codes in Dewey County

Predicted basement and upstairs means by ZIP (model estimate). ZIPs whose land is mostly in this county.

ZIP	Basement	Upstairs	Grade
57625	2.8 ± 0.06	2.0	Moderate
57601	3.7 ± 0.05	2.2	Moderate
57656	2.5 ± 0.07	1.4	Moderate
57630	3.6 ± 0.06	1.9	Moderate

If your test comes back at 4 pCi/L or higher

Mitigation is a routine job: a fan-driven pipe that vents soil gas from under the slab to above the roofline, typically $800-$2,500 installed (typical range; local quotes vary). Use certified professionals: EPA find-a-professional. Read the full mitigation guide.

Dewey County radon questions

Is radon high in Dewey County, South Dakota?: Moderate. The model predicts a long-term basement average of 3.2 pCi/L in Dewey County (about 1.7× the US average of 1.8 and about 18% below the South Dakota average of 3.9). That is in the 2-4 pCi/L range where the EPA recommends considering mitigation. Ranked 53 of 66 South Dakota counties.
Should I test for radon in Dewey County?: Yes, soon. With a predicted average of 3.2 pCi/L, many homes in Dewey County will test above the 4 pCi/L action level. Use a short-term kit first; if it reads 2 or higher, confirm with a long-term test or continuous monitor before deciding on mitigation.
What does EPA Radon Zone 2 mean for Dewey County?: Zone 2 - moderate potential (2-4 pCi/L). The zone map dates from 1993 and classifies whole counties. The 2001-2021 model agrees with the zone here. Neither replaces a test of your own home.
How much does radon mitigation cost in Dewey County?: A standard active sub-slab depressurization system typically runs $800-$2,500 installed nationally; South Dakota quotes vary with foundation type (slab, crawlspace, basement), home size and local labor. Get two or three bids from certified mitigators listed by your state radon program or the EPA's find-a-professional page.

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