Kansas / Atchison County
Score 39 · moderate · #24 of 105 in KS
Crawl space moisture in Atchison County, KS
59% of Atchison 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 — 65% of acres — it averages 2.1 ft below grade.
- 1Water table 2.1 ft
- 2Wet soils 12%
- 3Moisture score 39
- 4EPA radon zone 1
Reading the Atchison County soil survey
The score of 39 combines four parts, each from the USDA survey: wet drainage classes contribute 27.4 points of 100 on their own scale, group D soils 64.4, a shallow water table 43.9, and flooding 9.5; the weights are on the methodology page. The dominant hydrologic group is D (52% of acres): very slow infiltration, high runoff (clays, high water table).
At 2.1 ft the seasonal water table is usually below a crawl-space floor, but the 65% 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.
Atchison County against the rest of Kansas
Atchison County ranks 24 of 105 Kansas counties, 26 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 12%. After moderately well drained, the next most common class is well drained at 30%.
Flooding. 2.6% of acres with a flooding class are rated frequent; 10.8% of acres with a flooding class are rated occasional; 2% 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 9.9% of acres.
What it means for a crawl space here
In a moderate county the soil record is mixed rather than uniformly wet, so conditions vary from lot to lot. Where the lot drains, the model-code default — a vented crawl space with 1 sq ft of net vent per 150 sq ft of floor, or 1 per 1500 with a Class I vapor retarder on the ground — is a reasonable starting point; where the sections above point to a shallow water table or flood-prone soil on your lot, plan as for an elevated county. Either way, check the site first: grading that falls away from the foundation, gutters and downspouts that discharge well clear of it, and a ground cover over bare earth. A wet crawl space in a moderate county points to one of those first.
Radon. Atchison 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 Atchison County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area KS005; drainage covers 99% of 278,400 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.