North Dakota / Grand Forks County
Score 42 · elevated · #8 of 53 in ND
Crawl space moisture in Grand Forks County, ND
63% of Grand Forks 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 — 93% of acres — it averages 2.5 ft below grade.
- 1Water table 2.5 ft
- 2Wet soils 63%
- 3Moisture score 42
- 4EPA radon zone 1
Reading the Grand Forks County soil survey
The score of 42 combines four parts, each from the USDA survey: wet drainage classes contribute 52.8 points of 100 on their own scale, group D soils 25.2, a shallow water table 57.4, and flooding 3.2; the weights are on the methodology page. The dominant hydrologic group is C (52% of acres): slow infiltration (clay layers).
At 2.5 ft the seasonal water table is usually below a crawl-space floor, but the 93% of acres that report one are by definition the wettest parts of the county; on those lots, a wet spring can bring water close to the footings.
Grand Forks County against the rest of North Dakota
Grand Forks County ranks 8 of 53 North Dakota counties, 18 points above the state median of 24. That puts it in the wettest quarter of the state. Statewide, 23% of mapped soil is in the wet drainage classes; here it is 63%, half again the state figure or more. After somewhat poorly drained, the next most common class is moderately well drained at 20%.
Flooding. 1.4% of acres with a flooding class are rated frequent; 3% of acres with a flooding class are rated occasional; 0% of acres with a flooding class are rated very 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 an elevated county the soil supplies more moisture than average, but a vented crawl space can work if the ground is covered: the code lets vent area drop from 1 sq ft per 150 to 1 per 1500 with a Class I vapor retarder on the ground, which is an admission of how much moisture comes from below. Grading, gutters and a ground cover usually decide whether a crawl space here stays dry before any decision about sealing it.
Radon. Grand Forks County is in EPA radon zone 1, the highest predicted potential. A sealed crawl space and a radon system share most of their parts — the liner, the sealed seams, a fan — so if you are encapsulating, test for radon first and design both together. EPA itself says the zone map is not a reason to skip testing in zones 2 and 3.
Near Grand Forks County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area ND035; drainage covers 98% of 921,700 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.