Minnesota / Koochiching County
Score 73 · high · #1 of 87 in MN
Crawl space moisture in Koochiching County, MN
91% of Koochiching County's mapped soil is somewhat poorly to very poorly drained, which means ground that stays wet near the surface for significant periods. Where a seasonal water table is reported — 97% of acres — it averages 0.2 ft below grade, shallow enough to reach a typical crawl-space footing.
- 1Water table 0.2 ft
- 2Wet soils 91%
- 3Moisture score 73
- 4EPA radon zone 2
Reading the Koochiching County soil survey
The score of 73 combines four parts, each from the USDA survey: wet drainage classes contribute 87.7 points of 100 on their own scale, group D soils 58.6, a shallow water table 93.4, and flooding 3.8; the weights are on the methodology page. The dominant hydrologic group is C/D (37% of acres): D when undrained, C when drained.
A water table under two feet is the single most important number here. A crawl-space floor is usually 18 to 36 inches below the joists and often below outside grade, so in a wet season groundwater can stand at or above the crawl-space floor across much of Koochiching County. Venting cannot fix that; it needs drainage — a perimeter drain to daylight or a sump — before any liner goes down.
Koochiching County against the rest of Minnesota
Koochiching County ranks 1 of 87 Minnesota counties, 26 points above the state median of 47. Only no other county in the state scores higher. Statewide, 55% of mapped soil is in the wet drainage classes; here it is 91%, half again the state figure or more. After very poorly drained, the next most common class is poorly drained at 17%.
Flooding. 3.7% of acres with a flooding class are rated frequent; 0.1% of acres with a flooding class are rated occasional; 0.2% of acres with a flooding class are rated rare. Flood-prone soils are a minority here, concentrated along streams; the score mostly reflects what happens between floods.
What it means for a crawl space here
In a high county, the model-code default of a vented crawl space over bare earth works against the soil: outside air brings humidity in all summer, and the ground underneath keeps supplying moisture from below. The R408 alternative — an unvented crawl space with a sealed vapor retarder lapped 6 inches and turned 6 inches up the stem wall, plus conditioned or exhaust air at 1 cfm per 50 sq ft or a dehumidifier — is built for exactly this. If the water table is shallow, drainage comes first.
Radon. EPA radon zone 2. The zone is a county-level prediction; EPA says elevated levels occur in every zone and every home should be tested.
Near Koochiching County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area MN625; drainage covers 98% of 2,002,582 mapped acres); EPA Map of Radon Zones, county table (June 2024 JSON); IRC R408.3 Unvented crawl space, as adopted in S.C. Code Regs. 8-1221 (LII). Checked 2026-10-23.