Nebraska / Otoe County
Score 40 · elevated · #4 of 93 in NE
Crawl space moisture in Otoe County, NE
54% of Otoe County's soil falls in hydrologic group D or a dual D group: clays and high water tables that shed water slowly. Where a seasonal water table is reported — 70% of acres — it averages 2 ft below grade.
- 1Water table 2 ft
- 2Wet soils 6%
- 3Moisture score 40
- 4EPA radon zone 1
Reading the Otoe County soil survey
The score of 40 combines four parts, each from the USDA survey: wet drainage classes contribute 26.2 points of 100 on their own scale, group D soils 63.6, a shallow water table 48.6, and flooding 11.5; the weights are on the methodology page. The dominant hydrologic group is D (54% of acres): very slow infiltration, high runoff (clays, high water table).
At 2 ft the seasonal water table is usually below a crawl-space floor, but the 70% 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.
Otoe County against the rest of Nebraska
Otoe County ranks 4 of 93 Nebraska counties, 30 points above the state median of 10. That puts it in the wettest quarter of the state. Statewide, 9% of mapped soil is in the wet drainage classes; here it is 6%, below the state figure — the score here comes from heavy group D soils rather than drainage class alone. After moderately well drained, the next most common class is well drained at 33%.
Flooding. 0.4% of acres with a flooding class are rated frequent; 18.1% of acres with a flooding class are rated occasional; 1% of acres with a flooding class are rated rare. That is a large flood-prone share; a crawl space in the floodplain needs flood vents under most local floodplain ordinances, which is a separate rule from R408 and can rule out a fully sealed design. Ponding — water standing at the surface with nowhere to go — affects 17.5% of acres.
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. Otoe 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 Otoe County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area NE131; drainage covers 99% of 396,147 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.