Skip to content
RADON411

Locations and reports

Radon Levels in Skamania County, Washington

EPA puts Skamania County in Zone 1, its highest radon zone, and only 17 radon tests from it are on file with CDC (2020). Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    39.7%

    14.2 pts above WA

    Skamania
    39.7%
    Washington
    25.5%

    68 tests, 2008 to 2017

  • Median result

    2.9pCi/L

    Below action level

    Skamania
    2.9 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    68

    13th of 19 by tests

    Skamania
    68
    Spokane
    3,125

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    EPA predicts over 4 pCi/L indoors

  • Rank in Washington

    3 of 19

    Top quarter

    Skamania
    39.7%
    Pend Oreille
    63.2%

    By share, of 19 with 30+ tests

Read a result for Skamania County

Starts at Skamania County's median, 2.9 pCi/L

2.9pCi/L

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

EPA’s reading of 2.9 pCi/L

Between 2 and 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 between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Skamania County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Skamania County, At a glance

Skamania County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Skamania County in and predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county. That is one forecast for the whole county, not a reading of any address in it; homes above EPA's turn up in all three zones.

USGS geologic potential: Low across 76% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Skamania County, 2020

Share of reported tests at or above 4 pCi/L, by year, Skamania County
Share of reported tests at or above 4 pCi/L, by year, Skamania County
YearShare of reported tests at or above 4 pCi/L
201425.0%
201520.0%
201630.3%
201742.1%
201833.3%
201953.8%
202052.9%

2020: 52.9%. Across these years the share ran from 20.0% to 53.8%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

Only 17 tests were reported to CDC for Skamania County over 2020, 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: 2020. Measured data period: 2005 to 2020 (every CDC figure on file).

How to read these figures

Skamania County, Compared

Skamania County radon figures, compared

Calculated by Radon411

In Skamania County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (27 of 68) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 4.0 points higher. Across 39 Washington counties pooled together, 25.5% of tests reached that level, so Skamania County runs 14.2 points above its state.

The newest figure, in 2020, counts only 17 tests (52.9% at or above 4 pCi/L), too few to compare, so this reading uses the 68-test figure.

Of 5 neighbours with a figure, none reported a larger share at or above 4 pCi/L; the spread is 7.5% (Yakima County) to 33.1% (Multnomah County, OR). By share, Skamania County is 3rd of 19 Washington counties with 30 or more tests for the same period.

Half the tests came in under 2.9 pCi/L and half over it; the single highest reached 23.5 pCi/L. Below the action level, 21 tests (30.9%) came in under 2 pCi/L, against 56.7% statewide, and 20 tests (29.4%) fell between 2 and 4, against 17.8% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 39.7% share point the same way here. USGS geology rates 76% of the county's land low radon potential.

The busiest year on file was 2016, with 33 tests reported; the quietest, 2014, had 8.

Skamania County against Washington, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Skamania County
Skamania County6839.7%2.9 pCi/LThis county
Washington, pooled39 counties, pooled8,20125.5%Not pooled−14.2 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−4.0 points
Pend Oreille Countyhighest in the state3863.2%4.8 pCi/L+23.5 points
Snohomish Countylowest in the state2652.3%0.5 pCi/L−37.4 points
Klickitat County, WAborders it2941.4%2.2 pCi/L+1.7 points
Multnomah County, ORborders it12,33033.1%2.5 pCi/L−6.6 points
Hood River County, ORborders it13330.8%2.3 pCi/L−8.9 points
Clark County, WAborders it1,81425.1%1.8 pCi/L−14.6 points
Cowlitz County, WAborders it6211.3%1.1 pCi/L−28.4 points
Lewis County, WAborders it119.1%0.1 pCi/L−30.6 points
Yakima County, WAborders it807.5%0.7 pCi/L−32.2 points
Where Skamania County's reported results fell, 2008 to 2017, laboratory, beside Washington and the United States
ResultSkamania County testsSkamania County shareWashington shareU.S. shareAgainst Washington
Under 2 pCi/L2130.9%56.7%39.6%−25.8 points
2 to 4 pCi/L2029.4%17.8%24.7%+11.6 points
4 pCi/L and above2739.7%25.5%35.7%+14.2 points
Skamania County ranked among the 19 Washington counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Pend Oreille County1 of 193863.2%4.8 pCi/L
Spokane County2 of 193,12541.4%2.9 pCi/L
Skamania County3 of 196839.7%2.9 pCi/L
Stevens County4 of 1919636.2%2.3 pCi/L
Okanogan County5 of 194035.0%2.3 pCi/L
Clark County6 of 191,81425.1%1.8 pCi/L
Whitman County7 of 195822.4%1.5 pCi/L
Benton County8 of 1911319.5%2.0 pCi/L
Walla Walla County9 of 1912216.4%1.4 pCi/L
Chelan County10 of 194814.6%1.8 pCi/L
Cowlitz County11 of 196211.3%1.1 pCi/L
Skamania County radon tests by year, against Washington's pooled share
YearTestsAt or above 4 pCi/LMedianHighestWashington, pooledChange from the row before
20201752.9%4.9 pCi/L23.9 pCi/L19.0%−0.9 points
20192653.8%4.3 pCi/L136.6 pCi/L20.9%+20.5 points
20182133.3%3.2 pCi/L37.3 pCi/L16.1%−8.8 points
20171942.1%3.2 pCi/L17.8 pCi/L19.1%+11.8 points
20163330.3%2.8 pCi/L13.0 pCi/L16.6%+10.3 points
20152020.0%2.0 pCi/L7.8 pCi/L17.4%−5.0 points
2014825.0%2.7 pCi/L5.2 pCi/L15.0%First on file

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

Skamania County, Geology

The ground under Skamania County

Predicted

Most of the ground under Skamania County is one class on USGS's geologic map: 75.5% of its land is low radon potential, with 24.0% moderate. The map puts 75.5% of Skamania County in the area it calls Cascade Mountains and 24.0% in Columbia River Gorge. USGS gives the first a radon index of 6, in the low band (5 to 8), and the second 9, in the moderate band (9 to 11).

USGS's geologic areas under Skamania County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Cascade MountainsNorthern Cascade Mountains are Mesozoic metamorphic rocks intruded by Mesozoic and Tertiary granitic rocks. Southern Cascade Mountains are composed primarily of Tertiary and Holocene volcanic rocks.Low675.5%
Columbia River GorgeRiver and lacustrine delta deposits and volcanic debris flows.Moderate924.0%

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

Skamania County beside the ground around it

Across Washington 13.7% of the land is rated high; none of Skamania County's is. Of the 7 counties that border it, 5 have more moderate-potential ground, Klickitat County the most at 90.2%.

Share of land by USGS radon potential: Skamania County, the 7 counties bordering it and Washington
AreaEPA zoneLow potentialModerate potentialHigh potential
Skamania CountyZone 175.5%24.0%None
Clark CountyZone 126.0%70.9%None
Hood River County, ORZone 241.1%58.9%None
Cowlitz CountyZone 396.6%2.1%None
Multnomah County, ORZone 25.3%88.3%None
Lewis CountyZone 3100%NoneNone
Klickitat CountyZone 29.8%90.2%None
Yakima CountyZone 219.7%80.3%None
Washington38 counties, pooled by land areaVaries46.4%39.0%13.7%

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

Local help

Skamania County, Local resources

Radon testing and mitigation in Skamania County

What Washington's program says
Phone
360-236-3200
Email
doh.radon@doh.wa.gov

What it means

Skamania County, Questions

Questions about radon in Skamania County

Are radon levels high in Skamania County?

In 2020, 52.9% of the radon tests reported to CDC for Skamania County, Washington were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.9 pCi/L. Of 19 Washington counties with 30 or more tests for the same period, 2 reported a higher share; pooled, the state comes to 25.5%.

Which counties border Skamania County?

Skamania County borders 7 counties: Clark County, WA, Hood River County, OR, Cowlitz County, WA, Multnomah County, OR, Lewis County, WA, Klickitat County, WA and Yakima County, WA.

Products

Skamania County, Products

Testing a home in Skamania County

In Skamania County, 39.7% of 68 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 25.5% pooled across Washington. In Zone 1 the year-round level in Skamania County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.

Test kits and monitors3

See every kit and monitor

Skamania County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Skamania County

Explore

Skamania County, Bordering counties

Counties bordering Skamania County

Calculated by Radon411

Skamania County, Cities and towns

Cities and towns in Skamania County

Skamania County is growing: the Census Bureau puts it at 12,669 residents on July 1, 2025, up 5.2% from 12,038 in 2020. Spread over its land, that is 7.6 people to the square mile. No town dominates: Stevenson, the largest, has 1,596 residents, 12.6% of the total. Together its 2 incorporated places hold 23.8% of those residents; the other 76.2% live outside any of them. Testing is reported here more often than across the state: CDC's 68 reported tests for 2008 to 2017 come to 5.4 for every 1,000 residents (2025 estimate), against 1.0 for Washington.

From Stevenson to North Bonneville, CDC publishes no figure by town: each reads Skamania County's.

The cities and towns in Skamania County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Stevenson1,596+7.3%12.6%
North Bonneville1,415+1.3%11.2%

2 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).

Skamania County, Homes

Homes in Skamania County

Skamania County is a place of houses on their own lots: 78% of its 5,899 homes are detached single-family houses, against 62% across Washington. Half of its homes were built before 1984, close to Washington's 1984: 18% date from before 1960 and 26% from 2000 or later. Owners live in 81% of the occupied homes (Washington: 64%), so for most households a test and a fix are their own to order.

Homes in Skamania County, Washington, 2019 to 2023
HomesSkamania CountyWashington
Housing units5,8993,262,667
Detached houses78%62%
In buildings of 5 or more2%22%
Mobile homes14%6%
Built before 196018%21%
Built since 200026%28%
Middle year built19841984
Owner-occupied81%64%

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