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Radon Levels in Tripp County, South Dakota

EPA puts Tripp County in Zone 2, its middle radon zone, and only 9 radon tests from it are on file with CDC (2008 to 2017, laboratory totals). Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

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  • Nearest county

    62.5%

    Brule County, 48 miles

    Brule
    62.5%
    SD
    58.8%

    Share at 4+ pCi/L, 32 tests, 2006 to 2015

  • Ground above low

    100.0%

    1.0 pts above SD

    Tripp
    100.0%
    SD
    99.0%

    Share of land USGS rates moderate or high potential

  • Tests reported

    9

    Too few for a share

    Tripp
    9
    Needed
    30

    2008 to 2017, laboratory

  • EPA radon zone

    Zone 2

    Moderate potential

    1. 1
    2. Zone 2
    3. 3

    1 highest, 3 lowest

    EPA predicts 2 to 4 pCi/L indoors

Read a result for Tripp County

Starts at EPA's action level

4.0pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 4.0 pCi/L

At or above 4 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 4 and aboveEPA says fix it

This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher.

Interpret this readingWhat a fix costs

The data

Tripp County, At a glance

Tripp County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Tripp County is a county: EPA's forecast for it as a whole is an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³). It describes no single address, and homes above EPA's are found in every zone, this one included.

USGS geologic potential: Moderate across 94% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Tripp County, 2008 to 2017, laboratory

CDC holds 9 reported tests for Tripp County over the 2008 to 2017 laboratory totals, with a median of 4.2 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Tripp County beside the counties around it is how this page reads it.

What these figures count

Only 9 tests were reported to CDC for Tripp County over 2008 to 2017 (laboratory totals), and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor this house.

Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).

How to read these figures

Tripp County, Compared

Tripp County radon figures, compared

Calculated by Radon411

CDC's largest figure for Tripp County rests on 9 tests over the 2008 to 2017 laboratory totals, 5 of them at or above 4 pCi/L, so each test moves its share by 11.1 points and no rank or comparison is drawn from it. Results reached as high as 11.6 pCi/L, with a middle value of 4.2 pCi/L.

The nearest counties with a figure are Brule County (48 miles away) at 62.5%, Hughes County (72 miles away) at 66.7% and Davison County (90 miles away) at 47.9%. Pooled across 63 South Dakota counties, 58.8% of reported tests reached that level; across every county in the country with a figure, 36.3%.

Statewide for the same period, Bon Homme County reported the highest share (79.5%) and Davison County the lowest (47.9%). EPA's 1993 map puts Tripp County in Zone 2, its middle label: a predicted county average between 2 and 4 pCi/L. USGS geology rates 94% of the county's land moderate radon potential.

South Dakota, the United States and the counties around Tripp County, 2006 to 2015, laboratory
AreaTestsAt or above 4 pCi/LMedian
South Dakota, pooled63 counties, pooled4,89358.8%Not pooled
United States, pooled2,669 counties, pooled1,805,52836.3%Not pooled
Bon Homme Countyhighest in the state3979.5%8.1 pCi/L
Davison Countylowest in the state7147.9%3.7 pCi/L
Lyman County, SDborders it5100.0%20.0 pCi/L
Gregory County, SDborders it1080.0%6.7 pCi/L
Keya Paha County, NEborders it1323.1%2.7 pCi/L
Cherry County, NEborders it224.5%1.9 pCi/L
The nearest South Dakota counties to Tripp County with 30 or more tests, 2006 to 2015, laboratory
CountyDistanceTestsAt or above 4 pCi/LMedian
Brule County48 mi3262.5%6.3 pCi/L
Hughes County72 mi3066.7%5.5 pCi/L
Davison County90 mi7147.9%3.7 pCi/L
Bon Homme County104 mi3979.5%8.1 pCi/L
Beadle County109 mi4663.0%5.6 pCi/L
Yankton County128 mi8066.3%5.4 pCi/L
Turner County138 mi4553.3%4.0 pCi/L
Kingsbury County139 mi3268.8%8.4 pCi/L
Tripp County ten-year laboratory totals, against South Dakota's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestSouth Dakota, pooledChange from the row before
2008 to 2017955.6%4.2 pCi/L11.6 pCi/L58.5%−1.5 points
2007 to 2016757.1%4.2 pCi/L11.6 pCi/L57.4%Level
2006 to 2015757.1%4.2 pCi/L11.6 pCi/L58.8%−2.9 points
2005 to 2014560.0%4.2 pCi/L11.6 pCi/L59.6%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period.

Tripp County, Geology

The ground under Tripp County

Predicted

Most of the ground under Tripp County is one class on USGS's geologic map: 94.0% of its land is moderate radon potential, with 6.0% high. The map puts 77.9% of Tripp County in the area it calls Pierre Hills and 16.1% in Southern Plateaus, with one smaller area beside them. USGS gives the first a radon index of 10 and the second 11, both in the moderate band (9 to 11).

USGS's geologic areas under Tripp County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Pierre HillsPierre Shale and Fox Hills sandstone.Moderate1077.9%
Southern PlateausLate Tertiary continental sandstone.Moderate1116.1%
Missouri Coteau/James River Lowland/Coteau des PrairiesGlacial drift derived largely from Cretaceous marine shale.High146.0%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Tripp County beside the ground around it

South Dakota as a whole has more high-potential ground than Tripp County: 56.7% of its land, against 6.0% here. Of the 6 counties that border it, 3 have more high-potential ground, Lyman County the most at 55.7%.

Share of land by USGS radon potential: Tripp County, the 6 counties bordering it and South Dakota
AreaEPA zoneLow potentialModerate potentialHigh potential
Tripp CountyZone 2None94.0%6.0%
Keya Paha County, NEZone 2None92.2%7.8%
Gregory CountyZone 2None92.9%7.1%
Lyman CountyZone 1None44.3%55.7%
Todd CountyZone 232.8%67.2%None
Mellette CountyZone 2None100%None
Cherry County, NEZone 398.5%1.5%None
South Dakota66 counties, pooled by land areaVaries1.0%42.3%56.7%

The map rates the ground, not the air in any home.

Local help

Tripp County, Local resources

Radon testing and mitigation in Tripp County

What South Dakota's program says
Phone
1-800-438-3367

What it means

Tripp County, Questions

Questions about radon in Tripp County

Are radon levels high in Tripp County?

Over the 2008 to 2017 laboratory totals, 55.6% of the radon tests reported to CDC for Tripp County, South Dakota were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.2 pCi/L. Of the 8 nearest counties with a figure, within 139 miles, the share of tests at or above 4 pCi/L runs from 47.9% to 79.5%.

Which counties border Tripp County?

Tripp County borders 6 counties: Keya Paha County, NE, Gregory County, SD, Lyman County, SD, Todd County, SD, Mellette County, SD and Cherry County, NE.

Products

Tripp County, Products

Testing a home in Tripp County

No CDC figure names Tripp County; the nearest county with one, Brule County (48 miles away), reported 62.5% of its tests at or above 4 pCi/L over the 2006 to 2015 laboratory totals, the only reading nearby until a test of this home. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Tripp County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Tripp County homes, compared

Explore

Tripp County, Bordering counties

Counties bordering Tripp County

Calculated by Radon411

Tripp County, Cities and towns

Cities and towns in Tripp County

The Census Bureau estimates 5,708 residents in Tripp County for July 1, 2025, 102 more than in 2020 (+1.8%). Spread over its land, that is 3.5 people to the square mile. Winner alone is home to 2,969 of them, 52.0% of the total. Together its 3 incorporated places hold 58.9% of those residents; the other 41.1% live outside any of them. Reported testing is thin here: 9 tests over 2008 to 2017, or 1.6 for every 1,000 residents (2025 estimate), where South Dakota as a whole comes to 6.7.

From Winner to New Witten, CDC publishes no figure by town: each reads Tripp County's.

The cities and towns in Tripp County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Winner2,969+2.3%52.0%
Colome337+2.4%5.9%
New Witten55+1.9%1.0%

3 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).

Tripp County, Homes

Homes in Tripp County

Tripp County is a place of houses on their own lots: 78% of its 2,777 homes are detached single-family houses, against 67% across South Dakota. The homes are older than South Dakota's as a whole: half were built before 1963 (1979 for South Dakota), and 48% date from before 1960. 71% of occupied homes are lived in by their owner (South Dakota: 69%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Tripp County, South Dakota, 2019 to 2023
HomesTripp CountySouth Dakota
Housing units2,777402,364
Detached houses78%67%
In buildings of 5 or more6%16%
Mobile homes12%8%
Built before 196048%29%
Built since 200014%28%
Middle year built19631979
Owner-occupied71%69%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.