High Risk

ZIP Code 57430

Marshall County, South Dakota — Britton

Zone 1EPA Classification
>4Predicted pCi/L
0246810
>4pCi/L
Above EPA action level

What This Means

Marshall County, South Dakota is in EPA Radon Zone 1, the highest risk category. The EPA predicts average indoor radon levels greater than 4.0 pCi/L in this area — above the EPA action level. The EPA strongly recommends testing all homes in Zone 1 areas. If your home tests above 4.0 pCi/L, a radon mitigation system can reduce levels by up to 99%.

What You Should Do

1
Test your home immediately. Purchase a short-term radon test kit ($10–$30) or hire a certified professional. Place the test on the lowest livable level of your home.
2
If your test result is 4.0 pCi/L or higher, install a radon mitigation system. A qualified radon mitigator can install an active soil depressurization system for $800–$1,500, reducing levels by up to 99%.
3
Re-test within 24 hours of installation to confirm the system is working, then test again every 2 years to ensure continued effectiveness.

EPA Zone Details

ZIP Code57430
CountyMarshall
CityBritton
StateSouth Dakota (SD)
EPA Radon ZoneZone 1 — High
Predicted Indoor Radon>4 pCi/L

Source: EPA Map of Radon Zones

Radon & Your Basement in Marshall County

Marshall County is in EPA Zone 1, the highest risk category. Basements and ground-level rooms in this area are very likely to have elevated radon concentrations. If your home has a basement, it should be your first testing location.

Radon concentrations are typically highest in the lowest level of a home. However, radon does not stay confined to the basement — it migrates to upper floors through stairways, HVAC ducts, and gaps in flooring. Even if your basement is unfinished or rarely used, elevated radon there can affect the air quality on your main living floors. Always test on the lowest livable level.

Marshall County Radon Map

Counties colored by EPA radon zone. Red = Zone 1 (high), Orange = Zone 2 (moderate), Green = Zone 3 (low).

Check Another ZIP Code

Nearby ZIP Codes

57427 Bath, SD High 57428 Bowdle, SD High 57429 Spink, SD High 57432 Claremont, SD High 57433 Columbia, SD High

Frequently Asked Questions

What is the radon risk level for ZIP code 57430?

ZIP code 57430 is in Marshall County, South Dakota, which is classified as EPA Radon Zone 1 (high risk). The predicted average indoor radon level is >4 pCi/L.

Should I test for radon in 57430?

Yes. The EPA recommends testing all homes for radon regardless of zone. Since 57430 is in a high-risk Zone 1 area, testing is especially important.

What county is ZIP code 57430 in?

ZIP code 57430 is in Marshall County, South Dakota (SD).

Is it safe to live in ZIP code 57430?

ZIP code 57430 is in a high-risk EPA Zone 1 area. While this does not mean every home has dangerous radon levels, the probability is elevated. The EPA strongly recommends testing all homes in this zone. With proper mitigation, homes in high-risk areas can achieve safe radon levels.

Does radon in the basement affect upper floors in Marshall County?

Yes. Radon enters through the foundation and can migrate to upper floors through stairways, HVAC systems, and structural gaps. While concentrations are typically highest at the lowest level, upper floors in Marshall County homes can still have measurable radon. Always test on the lowest livable floor.

How much does radon mitigation cost in South Dakota?

In South Dakota, radon mitigation systems typically cost between $800 and $2,500 depending on home size, foundation type, and local labor rates. The most common system (sub-slab depressurization) averages $1,000-$1,500. The fan lasts 10-15 years and costs $150-$300 to replace. Some states offer financial assistance programs for radon mitigation.