Castle Rock, CO Radon Levels

Q: What EPA Radon Zone is Castle Rock in?

Castle Rock is in Douglas County, EPA Zone 1.

Q: How much does radon mitigation cost in Castle Rock?

Radon mitigation typically costs between $800 and $2,000. Most standard systems fall in the $1,000-$1,500 range.

Check local Castle Rock radon levels and find certified testing and mitigation professionals to keep your home safe

Castle Rock, CO Radon Facts

EPA Radon Zone Zone 1 — High Risk > 4.0 pCi/L (Zone 1)

County Douglas County, CO

Zip Code 80104

This Denver Metro community in Douglas County sits along Colorado's Front Range where granite and sedimentary bedrock create EPA Zone 1 conditions with high radon potential. Castle Rock's rapid suburban growth has produced numerous subdivisions with full basements, foundation types that readily facilitate radon accumulation. Testing data for zip codes 80104, 80108, and 80109 is currently limited, making individual home testing crucial for all residents.

7.57

pCi/L area average

Above EPA Action Level

Douglas County average: 7.57 pCi/L, based on 7 user-submitted tests across 3 cities in the county. No homeowner readings have been submitted for Castle Rock itself yet, so this county figure is the closest available benchmark. The EPA recommends taking action at or above 4.0 pCi/L.

4.0 EPA

10+

Castle Rock, CO Radon Mitigation

Professional radon mitigation is the most effective way to permanently lower radon levels and protect your household.

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Radon Readings Near Castle Rock, CO

No homeowner tests have been submitted for Castle Rock yet. The closest cities with user-submitted radon data are shown below — explore them to gauge local conditions. Radon varies by home, so testing is the only way to know your level.

City	Distance	Avg User Level	Readings
Parker	8.7 mi	5.40 pCi/L	5
Sedalia	12.0 mi	20.00 pCi/L	1
Littleton	14.5 mi	6.00 pCi/L	2
Elizabeth	14.9 mi	5.67 pCi/L	3
Englewood	16.0 mi	11.00 pCi/L	2
Monument	20.3 mi	6.33 pCi/L	3
Aurora	21.8 mi	7.40 pCi/L	5
Morrison	22.2 mi	5.00 pCi/L	3

Douglas County Radon Profile

Douglas County falls in EPA Radon Zone 1, meaning the local uranium-bearing geology is predicted to drive average indoor radon screening levels above the EPA's 4 pCi/L action threshold. Homeowner-submitted tests from 3 cities in Douglas County average 7.57 pCi/L across 7 tests — above the EPA's 4 pCi/L action level, reinforcing the need for testing across the county. Since radon is the second leading cause of lung cancer nationally, the EPA urges every household in Douglas County to test, as levels can differ between neighboring homes.

Radon FAQ for Castle Rock, CO

What EPA Radon Zone is Castle Rock in?

Castle Rock and the 80104 zip code are in Douglas County, which has an EPA assigned Radon Zone of 1. A zone of 1 predicts an average indoor radon screening level greater than 4 pCi/L.

Why are radon readings shown from areas near Castle Rock?

No homeowner radon tests have been submitted for Castle Rock yet. Because radon is driven by regional soil and bedrock geology, readings from the closest cities—and the Douglas County average—are the best available indicator of local conditions until Castle Rock homeowners submit their own results. The EPA still recommends testing every individual home, since levels can vary significantly from house to house.

How much does radon mitigation cost in Castle Rock?

Radon mitigation in Castle Rock typically costs between $800 and $2,000. Most homes with standard basements can be mitigated with a sub-slab depressurization system in the $1,000–$1,500 range. Factors that can increase cost include complex foundations, crawl spaces, or very high radon levels.

Should I test for radon if I'm buying a home in Castle Rock?

Yes. Radon testing should be part of every home purchase. A short-term radon test is typically included as part of the home inspection process and costs $150–$250. If elevated levels are found, you can negotiate mitigation as part of the sale.