Radon levels in Washington County, Minnesota
LowEPA Zone 1Predicted long-term basement average of 1.9 pCi/L (model estimate) across 15 ZIP codes - close to the US average of 1.8, about 22% below the Minnesota average of 2.4. Ranked #84 of 87 Minnesota counties.
Test Washington County, MN once anyway - radon varies house to house
The predicted basement average here is 1.9 pCi/L, below the EPA's 2 pCi/L "consider fixing" threshold. That's good news for the area - but the EPA still recommends every home be tested, because foundation cracks, soil pockets and ventilation make one house very different from its neighbor. One inexpensive kit settles it.
Monitor link goes to the Airthings store - use code RADONGRADE-10OFF at checkout for 10% off any Airthings monitor.
Affiliate links: we may earn a commission from Airthings or Amazon at no extra cost to you.
Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. Measured state test results are shown separately below, labeled with their source and years. How the numbers work.
1.9 ± 0.06
pCi/L predicted basement mean (model SD)
1.5 ± 0.06
pCi/L predicted upstairs (above-ground) mean
1.6-2.8
range of ZIP-level basement predictions in the county
Measured radon tests in Washington County (Minnesota Department of Health (MN Public Health Data Access), 2016-2025)
Actual results from home radon tests reported to the state, separate from the model estimate above. Coverage: 2016-2025.
- Measured mean
- 3.2 pCi/L
- Measured median
- 2.4 pCi/L
- Results ≥ 4 pCi/L
- 27.9%
- Results ≥ 2 pCi/L
- 61.4%
- Sample
- about 1,519 properties tested per year
| Figure | Model (predicted) | State tests (measured) |
|---|---|---|
| Mean, pCi/L | 1.9 basement | 3.2 |
| Share ≥ 4 pCi/L | not a model output | 27.9% |
The measured mean runs 1.3 pCi/L above the model because state test data is voluntary and skews toward basements, winter, and homeowners who already suspected a problem, while the model estimates the long-term average across all homes.
Source: Minnesota radon test results by county, Minnesota Department of Health (MN Public Health Data Access). Minnesota public data (Minn. Stat. ch. 13). Method and download.
Tested above 4 pCi/L? Get a mitigation quote from a certified local contractor
Typical mitigation runs $800-$2,500 and takes a day. Installers guarantee the system brings levels under 4 pCi/L. Tell us where you are in Washington County, MN and a certified mitigator will follow up - no obligation.
What this means for Washington
The typical Washington County home is predicted below 2 pCi/L, the lowest band. That is the best case an area can show - but it describes the average house, and the ZIP-level predictions within the county still span 1.6 to 2.8 pCi/L.
Note that the EPA classifies Washington County as Zone 1 while the newer model predicts 1.9 pCi/L. The zone map predates two decades of test data; where they disagree, we grade on the model but show both. County figures weight each ZIP by its 2010 Census population, so they describe where people live rather than empty land.
Comparable Minnesota counties: Lake County (1.9), St. Louis County (1.8), Lake of the Woods County (2.0), Isanti County (2.0). The state's highest is Rock County at 4.7 pCi/L.
ZIP codes in Washington County
Predicted basement and upstairs means by ZIP (model estimate). ZIPs whose land is mostly in this county.
| ZIP | Basement | Upstairs | Grade |
|---|---|---|---|
| 55125 | 1.6 ± 0.07 | 1.2 | Low |
| 55082 | 2.1 ± 0.06 | 1.8 | Moderate |
| 55016 | 2.2 ± 0.06 | 1.8 | Moderate |
| 55128 | 1.7 ± 0.07 | 1.3 | Low |
| 55038 | 1.5 ± 0.06 | 1.4 | Low |
| 55129 | 1.7 ± 0.07 | 1.4 | Low |
| 55042 | 1.9 ± 0.06 | 1.6 | Low |
| 55115 | 1.8 ± 0.06 | 1.4 | Low |
| 55071 | 2.7 ± 0.07 | 1.7 | Moderate |
| 55043 | 2.6 ± 0.08 | 1.8 | Moderate |
| 55003 | 2.3 ± 0.06 | 1.6 | Moderate |
| 55055 | 2.1 ± 0.05 | 1.6 | Moderate |
| 55073 | 2.4 ± 0.06 | 1.9 | Moderate |
| 55001 | 2.8 ± 0.06 | 2.1 | Moderate |
| 55047 | 2.3 ± 0.08 | 1.7 | Moderate |
If your test comes back at 4 pCi/L or higher
Mitigation is a routine job: a fan-driven pipe that vents soil gas from under the slab to above the roofline, typically $800-$2,500 installed (typical range; local quotes vary). Use certified professionals: EPA find-a-professional. Read the full mitigation guide.
Washington County radon questions
- Is radon high in Washington County, Minnesota?
- Low. The model predicts a long-term basement average of 1.9 pCi/L in Washington County (close to the US average of 1.8 and about 22% below the Minnesota average of 2.4). That is below the EPA's 2 pCi/L "consider fixing" threshold, though individual homes still vary. Ranked 84 of 87 Minnesota counties.
- What do actual radon tests show in Washington County?
- Minnesota Department of Health (MN Public Health Data Access) data covering 2016-2025 (about 1,519 properties tested per year) shows an average of 3.2 pCi/L, a median of 2.4, 27.9% of results at or above the 4 pCi/L action level, 61.4% at or above 2. These are voluntary home tests, so they skew toward basements and toward homes where radon was suspected; the model's predicted long-term basement average for the county is 1.9 pCi/L.
- Should I test for radon in Washington County?
- Yes, once. The EPA recommends testing every home regardless of area, and the model's ZIP-level predictions in Washington County already range from 1.6 to 2.8 pCi/L. A short-term kit costs little and settles the question for your house.
- What does EPA Radon Zone 1 mean for Washington County?
- Zone 1 - highest potential (predicted average > 4 pCi/L). The zone map dates from 1993 and classifies whole counties. The newer model's predicted average of 1.9 pCi/L does not line up with Zone 1, which is common - the EPA itself says high-radon homes exist in every zone. Neither replaces a test of your own home.
- How much does radon mitigation cost in Washington County?
- A standard active sub-slab depressurization system typically runs $800-$2,500 installed nationally; Minnesota quotes vary with foundation type (slab, crawlspace, basement), home size and local labor. Get two or three bids from certified mitigators listed by your state radon program or the EPA's find-a-professional page.
← All Minnesota counties · How to test · Radon in a home sale · Methodology