Kansas / Osage County
Score 45 · elevated · #17 of 105 in KS
Crawl space moisture in Osage County, KS
72% of Osage 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 — 83% of acres — it averages 1.9 ft below grade, shallow enough to reach a typical crawl-space footing.
- 1Water table 1.9 ft
- 2Wet soils 14%
- 3Moisture score 45
- 4EPA radon zone 2
Reading the Osage County soil survey
The score of 45 combines four parts, each from the USDA survey: wet drainage classes contribute 28.2 points of 100 on their own scale, group D soils 74.4, a shallow water table 58.5, and flooding 9; the weights are on the methodology page. The dominant hydrologic group is D (64% of acres): very slow infiltration, high runoff (clays, high water table).
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 Osage County. Venting cannot fix that; it needs drainage — a perimeter drain to daylight or a sump — before any liner goes down.
Osage County against the rest of Kansas
Osage County ranks 17 of 105 Kansas counties, 32 points above the state median of 13. That puts it in the wettest quarter of the state. Statewide, 8% of mapped soil is in the wet drainage classes; here it is 14%, half again the state figure or more. After moderately well drained, the next most common class is well drained at 31%.
Flooding. 4.7% of acres with a flooding class are rated frequent; 7% of acres with a flooding class are rated occasional; 0.8% 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. Ponding — water standing at the surface with nowhere to go — affects 2.3% 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. 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 Osage County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area KS139; drainage covers 97% of 460,608 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.