Colby, WI Radon Levels

Q: What EPA Radon Zone is Colby in?

Colby is in Marathon County, EPA Zone 1.

Q: Why are radon readings shown from areas near Colby?

No homeowner radon tests have been submitted for Colby yet, so readings from the closest cities and the Marathon County average are used as the best available indicator of local conditions. The EPA recommends testing every individual home.

Q: How much does radon mitigation cost in Colby?

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

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

Colby, WI Radon Facts

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

County Marathon County, WI

Zip Code 54421

Nestled in central Wisconsin's Marathon County, Colby sits within EPA Zone 1 where glacial deposits over Precambrian bedrock create conditions highly favorable for radon accumulation. The community's housing includes older farmhouses and modern residential construction around 54421, most featuring basement foundations typical of Wisconsin homes. With limited local testing data available, homeowners should conduct radon assessments to determine if levels exceed EPA action thresholds common throughout this geological region.

9.50

pCi/L area average

Above EPA Action Level

Marathon County average: 9.50 pCi/L, based on 2 user-submitted tests across 2 cities in the county. No homeowner readings have been submitted for Colby 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+

Colby, WI 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 Colby, WI

No homeowner tests have been submitted for Colby 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
Stratford	15.1 mi	13.00 pCi/L	1
Medford	16.6 mi	7.50 pCi/L	2
Marshfield	18.5 mi	13.50 pCi/L	2
Mosinee	31.8 mi	6.00 pCi/L	1
Wisconsin Rapids	42.8 mi	4.50 pCi/L	2
Stevens Point	46.0 mi	6.00 pCi/L	3
Jim Falls	47.6 mi	5.00 pCi/L	1
Nekoosa	48.4 mi	6.00 pCi/L	1

Marathon County Radon Profile

Because of its underlying geology, Marathon County is mapped as EPA Radon Zone 1 — the most elevated classification — where predicted indoor screening averages exceed 4 pCi/L. Homeowner-submitted tests from 2 cities in Marathon County average 9.50 pCi/L across 2 tests — above the EPA's 4 pCi/L action level, reinforcing the need for testing across the county. As the second leading cause of lung cancer in the U.S., radon warrants testing in every Marathon County home regardless of zone or a neighbor's results.

Radon FAQ for Colby, WI

What EPA Radon Zone is Colby in?

Colby and the 54421 zip code are in Marathon 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 Colby?

No homeowner radon tests have been submitted for Colby yet. Because radon is driven by regional soil and bedrock geology, readings from the closest cities—and the Marathon County average—are the best available indicator of local conditions until Colby 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 Colby?

Radon mitigation in Colby 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 Colby?

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.