What EPA's radon map says about Wahkiakum County

EPA places Wahkiakum County in Zone 3 - Low Potential — a predicted county-wide average indoor radon level below 2 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Wahkiakum County sits at the 3rd percentile nationally for radon potential — above 3 of every 100 rated counties.

How Wahkiakum County compares

About 4,800 people live in Wahkiakum County, Washington, spread over 262.928 square miles. That works out to roughly 18 people per square mile. Among counties sharing Wahkiakum County's EPA zone, it outranks 8% of them by population. EPA's geology-based Region 10 groups Wahkiakum County with 141 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

At Zone 3, Wahkiakum County's predicted county average is under the national indoor average (~1.3 pCi/L) and well below EPA's 4 pCi/L action level — outdoor air nationally runs about 0.4 pCi/L for comparison. Low doesn't mean zero: EPA's own data shows homes in Zone 3 counties like Wahkiakum County testing above the action level often enough that skipping a test isn't the safe assumption.

If Wahkiakum County tests above the action level

Mitigation cost doesn't depend on Wahkiakum 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 Washington's state radon program

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

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.