Is Calaveras County, CA a radon risk area?

EPA places Calaveras County in Zone 2 - Moderate Potential — a predicted county-wide average indoor radon level between 2 and 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Nationally that's the 55th percentile for radon potential — Calaveras County outranks 55% of every county EPA has rated.

How Calaveras County compares

About 46,505 people live in Calaveras County, California, spread over 1,020.016 square miles. That works out to roughly 46 people per square mile. Rank 355 by population within its EPA zone puts Calaveras County at the 66th percentile among zone peers. Calaveras County falls in EPA Radon Region 9, one of 95 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

EPA's Zone 2 rating for Calaveras County sits below its own 4 pCi/L action level but above the national indoor average of about 1.3 pCi/L. Nothing about a Zone 2 label lowers the case for testing in Calaveras County — EPA recommends it in every zone, moderate included.

If Calaveras County tests above the action level

Nothing about Calaveras County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find California's state radon program

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

More on how this number was built

Calaveras County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.