Radon levels in Cass County, North Dakota
ModerateEPA Zone 1Predicted long-term basement average of 2.8 pCi/L (model estimate) across 23 ZIP codes - about 1.6× the US average of 1.8, close to the North Dakota average of 3.3. Ranked #51 of 53 North Dakota counties.
Test Cass County, ND - the EPA says "consider fixing" in this range
The predicted basement average here is 2.8 pCi/L, in the 2-4 pCi/L band where the EPA recommends considering mitigation. Plenty of individual homes in a moderate area test above 4. Start with a short-term test; if it comes back at 2 or higher, follow up with a long-term test or a continuous monitor.
Already tested at 4 pCi/L or higher? Find a certified mitigation professional (EPA). A mitigation system typically runs $800-$2,500 installed.
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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. How the numbers work.
2.8 ± 0.09
pCi/L predicted basement mean (model SD)
2.0 ± 0.07
pCi/L predicted upstairs (above-ground) mean
1.9-4.8
range of ZIP-level basement predictions in the county
What this means for Cass
The typical Cass County home is predicted in the 2-4 pCi/L band. The EPA's guidance for this range is to consider fixing, because there is no known safe level and roughly one home in several in a moderate area will test above 4.
Note that the EPA classifies Cass County as Zone 1 while the newer model predicts 2.8 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 North Dakota counties: Burleigh County (2.9), McKenzie County (3.0), Williams County (2.6), Ward County (2.5). The state's highest is Grand Forks County at 4.4 pCi/L.
ZIP codes in Cass County
Predicted basement and upstairs means by ZIP (model estimate). ZIPs whose land is mostly in this county.
| ZIP | Basement | Upstairs | Grade |
|---|---|---|---|
| 58103 | 2.8 ± 0.10 | 2.0 | Moderate |
| 58102 | 3.5 ± 0.09 | 2.3 | Moderate |
| 58104 | 1.9 ± 0.09 | 1.6 | Low |
| 58078 | 2.7 ± 0.08 | 1.9 | Moderate |
| 58047 | 3.4 ± 0.07 | 2.2 | Moderate |
| 58012 | 4.8 ± 0.10 | 2.8 | High |
| 58051 | 3.6 ± 0.07 | 2.3 | Moderate |
| 58042 | 3.2 ± 0.07 | 2.3 | Moderate |
| 58059 | 3.7 ± 0.07 | 2.2 | Moderate |
| 58005 | 3.5 ± 0.06 | 2.4 | Moderate |
| 58052 | 3.5 ± 0.06 | 2.0 | Moderate |
| 58079 | 3.7 ± 0.08 | 2.3 | Moderate |
| 58064 | 3.8 ± 0.06 | 2.3 | Moderate |
| 58021 | 4.0 ± 0.07 | 2.3 | High |
| 58006 | 3.4 ± 0.06 | 2.1 | Moderate |
| 58048 | 3.9 ± 0.06 | 2.3 | Moderate |
| 58031 | 3.7 ± 0.06 | 2.3 | Moderate |
| 58071 | 3.8 ± 0.06 | 2.3 | Moderate |
| 58011 | 3.9 ± 0.06 | 2.5 | Moderate |
| 58036 | 3.5 ± 0.06 | 2.2 | Moderate |
| 58004 | 3.9 ± 0.07 | 2.4 | Moderate |
| 58029 | 3.8 ± 0.07 | 2.1 | Moderate |
| 58007 | 3.6 ± 0.06 | 2.3 | 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.
Cass County radon questions
- Is radon high in Cass County, North Dakota?
- Moderate. The model predicts a long-term basement average of 2.8 pCi/L in Cass County (about 1.6× the US average of 1.8 and close to the North Dakota average of 3.3). That is in the 2-4 pCi/L range where the EPA recommends considering mitigation. Ranked 51 of 53 North Dakota counties.
- Should I test for radon in Cass County?
- Yes, soon. With a predicted average of 2.8 pCi/L and at least one ZIP predicted at 4.8, many homes in Cass County will test above the 4 pCi/L action level. Use a short-term kit first; if it reads 2 or higher, confirm with a long-term test or continuous monitor before deciding on mitigation.
- What does EPA Radon Zone 1 mean for Cass 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 2.8 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 Cass County?
- A standard active sub-slab depressurization system typically runs $800-$2,500 installed nationally; North Dakota 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.
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