Radon Mitigation in Southern Minnesota
Southern Minnesota is the state's hottest radon country. MDH county test data shows 48.6 percent of Olmsted County properties tested from 2010 to 2020 came in at or above the EPA action level, local health officials estimate roughly half of Winona County homes test elevated, and Olmsted, Blue Earth, and Winona counties all carry the EPA's Zone 1 rating.
The driver is under your feet: the southeast's karst bedrock and the deep glacial soils of the Minnesota River valley. We connect homeowners in Rochester, Mankato, Winona, and the surrounding towns with independent, MDH-licensed mitigation contractors who work these conditions every week.
The Highest Test Shares in the State
MDH publishes county-by-county radon results on its public data portal, and southern Minnesota counties consistently post some of the largest shares of tests at or above 4 pCi/L, led by figures like Olmsted County's 48.6 percent of properties tested from 2010 to 2020. When nearly every other house that tests comes back high, testing stops being optional due diligence and becomes the default first step of homeownership.
Source: MDH radon data portalKarst: Why the Southeast Tests So High
Southeastern Minnesota is the state's karst region: soluble limestone and dolomite bedrock close to the surface, dissolved over time into sinkholes, fractures, and underground conduits. The DNR's karst mapping, including its report on karst lands in Winona and Houston counties, documents how open this landscape is below ground. Fractured carbonate bedrock gives soil gas easy pathways, and the Prairie du Chien plateau east of Rochester is a textbook example.
Source: Minnesota DNR karst report GW-01River Towns, College Towns, Med City
The housing spans Winona's pre-1900 river town blocks with stone foundations, Mankato's bluff-top postwar neighborhoods full of walkouts, and Rochester's fast-growing subdivisions where anything permitted after June 1, 2009 carries a passive radon rough-in. Older stone basements take more sealing work, walkouts sometimes need a second suction point, and passive new builds convert to active systems with a fan. Licensed contractors in the region see all three weekly.
Source: Minnesota Rules 1303.2400Southern Minnesota Cities We Cover
Start with the service you need, Radon Mitigation or Real Estate Radon , or go deeper with the guide: Radon Levels by Minnesota County .
Verify Your Contractor's Minnesota Radon License
Before you hire anyone for radon work in Southern Minnesota, check their license. The Minnesota Radon Licensing Act, Minnesota Statutes section 144.4961, requires anyone who performs radon testing, mitigation, or laboratory analysis for compensation to be licensed by the Minnesota Department of Health, and every mitigation system installed under the law must carry an MDH system tag. A licensed professional expects the question. Three things to ask before you sign:
- Can I see your current MDH radon license, and is the company licensed too?
- Will the installed system carry the MDH system tag required under the licensing law?
- Will I get a written, itemized estimate and a follow-up radon test that confirms the system works?
Southern Minnesota Radon Questions
Why is southern Minnesota radon worse than the rest of the state?
Geology. The southeast sits on karst: fractured, soluble limestone and dolomite that gives radon-carrying soil gas easy paths toward foundations, as documented in DNR karst mapping. MDH county data reflects it, with Olmsted County posting 48.6 percent of tested properties at or above 4 pCi/L from 2010 to 2020.
Which southern Minnesota counties should test first?
All of them, per MDH guidance that every Minnesota home test regardless of location. That said, MDH county data and Zone 1 ratings for Olmsted, Blue Earth, and Winona counties mean a first-time tester in Rochester, Mankato, or Winona has close to a coin-flip chance of an elevated result.
Does karst mean my mitigation system needs to be different?
Not different in kind, but design matters. Fractured bedrock and variable soils can change how far a single suction point's pressure field reaches, which is one reason a licensed contractor diagnoses the sub-slab conditions before quoting. The system itself remains standard active sub-slab depressurization, verified by a follow-up test.
Get a Free Radon Mitigation Quote
Tell us about your home and get a free, no-obligation quote from an independent radon mitigation contractor licensed by the Minnesota Department of Health.
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