Radon over the EPA action level — the default Eden Prairie result.
Local first-test averages run 4.5 to 6.2 pCi/L, above the EPA 4.0 pCi/L action threshold. Eden Prairie is in EPA Zone 1 — the highest-risk classification — and premium-home airtightness only concentrates the gas. We measure on the EPA 48-hour continuous-monitor protocol and deliver hourly data, not just an average.
Zone 1 geology, Zone 1 results.
The EPA classifies Hennepin County as Zone 1 — the highest-risk radon zone in the federal map. Eden Prairie sits over glacial-till deposits with elevated uranium-decay activity, and the premium-tier housing stock is exceptionally airtight. The result is consistent: most basements test above the 4.0 pCi/L action level on first measurement. We have documented Bearpath, Cedar Forest, and Hennepin Village basements above 8 pCi/L, and a handful of finished-walkout basements above 12.
How radon enters the home.
Mitigation works because radon entry is concentrated at a small set of pathways. We document each one during inspection so the mitigation contractor can target it.
Slab cove joint
The seam between slab and footing is the largest concentrated entry path in most Eden Prairie basements. Soil gas is drawn through it by stack effect.
Open sump pit
Uncovered sump pits route soil gas directly into the conditioned space. Sealed lid plus mitigation tie-in is the standard correction.
Slab cracks
Settlement and shrinkage cracks in the basement slab. Smaller per-unit pathway than the cove, but cumulatively significant in older slabs.
Plumbing penetrations
Drain stack and supply-line pass-throughs in the slab. Often unsealed in the original pour. Caulk-grade urethane is a 30-minute fix.
Hollow-block walls
Concrete-block foundation walls are hollow-cored. Soil gas migrates through the cores and exits at the top course. Common in older Round Lake-area homes.
Stack-effect amplification
Tall premium homes with open staircases pull soil gas upward like a chimney. The basement reads moderate, the second-floor mechanical room reads high.
What the number means.
EPA action level is 4.0 pCi/L. Below that, monitoring; at or above, mitigation. The table is how we translate measured concentration into a recommended next step on the report.
| Measured concentration | EPA position | Severity | Recommendation |
|---|---|---|---|
| Below 2.0 pCi/L | Below action level | Monitor | Retest every 2 years |
| 2.0 – 3.9 pCi/L | Below action level | Monitor | Consider mitigation, retest annually |
| 4.0 – 7.9 pCi/L | At or above action level | Major | Mitigation recommended |
| 8.0 – 19.9 pCi/L | Well above action level | Critical | Mitigation, expedited |
| 20+ pCi/L | Far above action level | Critical | Mitigation immediately, exposure-time review |
Three steps. Calibrated, sealed, hour-by-hour.
Continuous monitor in the lowest livable level
Calibrated continuous radon monitor placed at breathing-zone height in the lowest livable level. Sealed-conditions protocol begins 12 hours before placement: windows and exterior doors closed except for normal entry/exit.
48-hour minimum, hourly logging
The instrument records hourly concentrations across the full test window. Hourly data lets us spot diurnal swings, ventilation changes, and any test-tampering signature.
Average plus hourly chart, plus action mapping
Same-evening report on retrieval day includes the calibrated 48-hour average, the hourly chart, EPA action-level interpretation, and a mitigation recommendation when concentrations warrant.
Add radon to your home inspection — or book it standalone.
Two-minute quote. EPA-protocol 48-hour test. Same-evening report on retrieval.